© 2020 Society for Radiological Protection. Published on behalf of SRP by IOP Publishing Limited. All rights reserved. The lunar surface is directly and continuously exposed to Galactic Cosmic ray (GCR) particles and Solar energetic particles (SEPs) due to the lack of atmosphere and lunar magnetic field. These charged particles interact with the lunar surface materials producing secondary radiations such as neutrons and gamma rays. In a departure from precise GCR and SEP data, we estimated the effective dose equivalent at the lunar surface and in a lunar lava tube in this paper by using PHITS, a Monte Carlo simulation tool. The effective dose equivalent due to GCR particles at the lunar surface reached 416.0 mSv yr-1 and that due to SEPs reached 2190 mSv/event. On the other hand, the vertical hole of the lava tube provides significant radiation protection. The exposure by GCR particles at the bottom of the vertical hole with a depth of 43 m was found to be below 30 mSv yr-1 while inside a horizontal lava tube, the value was less than 1 mSv yr-1 which is the reference value for human exposure on the Earth. We expect that the lunar holes will be useful components in the practical design of a lunar base to reduce radiation risk and to expand mission terms.

© 2019 Elsevier B.V. Electron multiplication in high-pressure pure xenon was studied in the 0.5–3.0 MPa pressure range using a cylindrical proportional counter. The electron multiplication factor and the first Townsend ionization coefficient were determined, thus expanding collective knowledge beyond the previous studies, which were limited to 1.0 MPa. The measured electron multiplication factor falls between 15 and 2400 for the investigated pressure range. The density-reduced first Townsend ionization coefficient in this work is larger than that obtained for low-pressure xenon. In addition, the density-reduced first Townsend ionization coefficient was found to be density dependent. It was also found that the energy resolution deteriorates with increasing pressure. However, when the electron multiplication factor is several hundred, the energy resolution in high-pressure pure xenon was found to be better than that in commonly used xenon-based gas mixtures.

© 2019 authors. In this paper, we present the analysis and results of a direct measurement of the cosmic-ray proton spectrum with the CALET instrument onboard the International Space Station, including the detailed assessment of systematic uncertainties. The observation period used in this analysis is from October 13, 2015 to August 31, 2018 (1054 days). We have achieved the very wide energy range necessary to carry out measurements of the spectrum from 50 GeV to 10 TeV covering, for the first time in space, with a single instrument the whole energy interval previously investigated in most cases in separate subranges by magnetic spectrometers (BESS-TeV, PAMELA, and AMS-02) and calorimetric instruments (ATIC, CREAM, and NUCLEON). The observed spectrum is consistent with AMS-02 but extends to nearly an order of magnitude higher energy, showing a very smooth transition of the power-law spectral index from-2.81±0.03 (50-500 GeV) neglecting solar modulation effects (or-2.87±0.06 including solar modulation effects in the lower energy region) to-2.56±0.04 (1-10 TeV), thereby confirming the existence of spectral hardening and providing evidence of a deviation from a single power law by more than 3σ.

This paper proposes and develops a saliency map suitable for the wide angle fovea (WAF) sensor. The saliency map is well-known as a computational method inspired from the human cognitive vision processing. This bottom-up processing method is often available for finding a target, which should be paid attention to, automatically from the arbitrary scene. However, it is not necessarily sufficient to use the existing saliency sap directly with the W A F sensor. Usually, we utilize the W A F sensor by combining different-level image processing tasks using its high spatial resolution central field of view (FOV) or its wide-angle F O V cooperatively, because the W A F sensor does not provide with a uniform resolution input image. When we apply the saliency map for the input image by the W A F sensor, we need to take into account unique properties of this biologically-inspired special vision sensor. Therefore, we design a novel saliency map model which is more suitable for the W A F sensor. After configuration of this specific saliency map, some verification experiments were implemented to enhance advantages of our proposed saliency map for the W A F sensor, i.e., W A F saliency map.

© 2018. The American Astronomical Society. All rights reserved. We present the results of searches for gamma-ray counterparts of the LIGO/Virgo gravitational wave events using CALorimetric Electron Telescope (CALET) observations. The main instrument of CALET, CALorimeter (CAL), observes gamma-rays from ∼1 GeV up to 10 TeV with a field of view (FOV) of nearly 2 sr. In addition, the CALET gamma-ray burst monitor views ∼3 sr and ∼2π sr of the sky in the 7 keV-1 MeV and the 40 keV-20 MeV bands, respectively, by using two different crystal scintillators. The CALET observations on the International Space Station started in 2015 October, and here we report analyses of events associated with the following gravitational wave events: GW151226, GW170104, GW170608, GW170814, and GW170817. Although only upper limits on gamma-ray emission are obtained, they correspond to a luminosity of 1049 ∼ 1053 erg s-1 in the GeV energy band depending on the distance and the assumed time duration of each event, which is approximately on the order of luminosity of typical short gamma-ray bursts. This implies that there will be a favorable opportunity to detect high-energy gamma-ray emission in further observations if additional gravitational wave events with favorable geometry will occur within our FOV. We also show the sensitivity of CALET for gamma-ray transient events, which is on the order of 10-7 erg cm-2 s-1 for an observation of 100 s in duration.

In this study we describe the distribution of iron on the Moon as obtained by the Kaguya high energy resolution gamma-ray spectrometer (KGRS). We achieved for the first time the identification of iron based on the fast neutron flux obtained by the KGRS. The iron distribution obtained by KGRS is compared to that of the Lunar Prospector Gamma-Ray Spectrometer (LP GRS), showing that the FeO distributions observed by KGRS and LP GRS, in general, are in good agreement. Furthermore, we compare the iron content data obtained by KGRS and LP GRS to spectral reflectance measurements of the Clementine, Kaguya and Chandrayaan-1 spacecraft as well as those inferred from returned samples. We found differences in FeO concentration and distribution in areas of moderate abundance (6–15 wt%) of the South Pole-Aitken basin, Mare Orientale, and around the crater Tycho crater. It implies that high concentrations of FeO at Mare Ingenii in the South Pole-Aitken basin and Mare Orientale are due to the presence of mare basalts, whereas the enriched FeO content in the central depression of the South Pole-Aitken basin and the Tycho crater indicates the presence of mafic materials such as impact melt breccia.

© 2018 American Physical Society. Extended results on the cosmic-ray electron + positron spectrum from 11 GeV to 4.8 TeV are presented based on observations with the Calorimetric Electron Telescope (CALET) on the International Space Station utilizing the data up to November 2017. The analysis uses the full detector acceptance at high energies, approximately doubling the statistics compared to the previous result. CALET is an all-calorimetric instrument with a total thickness of 30 X0 at normal incidence and fine imaging capability, designed to achieve large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum in the region below 1 TeV shows good agreement with Alpha Magnetic Spectrometer (AMS-02) data. In the energy region below ∼300 GeV, CALET's spectral index is found to be consistent with the AMS-02, Fermi Large Area Telescope (Fermi-LAT), and Dark Matter Particle Explorer (DAMPE), while from 300 to 600 GeV the spectrum is significantly softer than the spectra from the latter two experiments. The absolute flux of CALET is consistent with other experiments at around a few tens of GeV. However, it is lower than those of DAMPE and Fermi-LAT with the difference increasing up to several hundred GeV. The observed energy spectrum above ∼1 TeV suggests a flux suppression consistent within the errors with the results of DAMPE, while CALET does not observe any significant evidence for a narrow spectral feature in the energy region around 1.4 TeV. Our measured all-electron flux, including statistical errors and a detailed breakdown of the systematic errors, is tabulated in the Supplemental Material in order to allow more refined spectral analyses based on our data.

The authors have developed the wide angle fovea (WAF) telescope. This development was originally motivated from our mind to assist the ranger to save the people floating on the sea. Cruel Tsunami disasters often cause such miserable situations. An objective lens part of this special telescope was formerly developed using the Advanced WAF (AdWAF) model, by which we can design a distribution of the lens curve very flexibly. This special-made objective lens has an enough wide field of view, and thus it can keep a moving target as being always inside field of view. In addition, it can observe the target more in detail because its central field of view has higher magnification than the conventional telescope. Yes, this telescope is inspired from a smart function of the human eye to improve its availability. This special-made objective lens achieves not only wide-angle surveillance and but also detailed observation on the same time. Moreover, a special-made eyepiece lens part is also designed for users to observe environments with a more immersive feeling. This eyepiece utilizes a broader area on the human retina for the WAF telescope image projection. Indeed, the developed telescope has 22 aspherical surfaces of all 28 surfaces by using economy plastic lenses.

© 2017 Published by the American Physical Society. First results of a cosmic-ray electron and positron spectrum from 10 GeV to 3 TeV is presented based upon observations with the CALET instrument on the International Space Station starting in October, 2015. Nearly a half million electron and positron events are included in the analysis. CALET is an all-calorimetric instrument with total vertical thickness of 30 X0 and a fine imaging capability designed to achieve a large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum over 30 GeV can be fit with a single power law with a spectral index of -3.152±0.016 (stat+syst). Possible structure observed above 100 GeV requires further investigation with increased statistics and refined data analysis.

The elemental composition and its distribution on planetary surface provide important constraints on the origin and evolution of the planetary body. The nuclear spectrometer consisting of a neutron spectrometer and a gamma-ray spectrometer obtains elemental compositions by remote sensing. Especially, the neutron spectrometer is able to determine the hydrogen concentration, a piece of information that plays an important role in thermal history of the planets. In this work, numerical and experimental studies on the neutron spectrometer for micro-satellite application were conducted. It is found that background count rate of neutron produced from micro-satellite is very small, which enables to obtain successful results in short time observation. The neutron spectrometer combining a lithium-6 glass scintillator with a boron loaded plastic scintillator was used to be able to detect neutrons in different energy ranges. It was experimentally confirmed that the neutron signals from these scintillators were successfully discriminated by the difference of scintillation decay time between two detectors. The measurement of neutron count rates of two scintillators is found to determine hydrogen concentration on the planetary surfaces in the future missions.

The elemental composition on planetary surface provides us an essential information to improve geological and geochemical understanding of planets. An active X-ray spectrometer (AXS) was developed and proposed as one of the mission payloads to perform in-situ X-ray fluorescence analysis. The AXS consists of multiple pyroelectric X-ray generators (PXGs) and a silicon drift detector (SDD). Although the PXG is light in weight and low in electric consumption, the limited X-ray intensity and reproducibility hamper obtaining the elemental composition by short time observation. This is attributed mainly to the less known mechanism of X-ray and electron emission by the pyroelectric crystal. In this study, we observed the crystal surface during X-ray emission as a function of the distance between the crystal top and a Cu target. Two types of light emission derived from the electric discharge were observed. The dependence of light emission on the distance was found to be related with the physical mechanism of pyroelectric X-ray emission. The study provides clues to obtain high intensity and reproducible X-rays emission. The experimental results and discussion are presented in this paper.

© 2016 Elsevier B.V. We have studied the performance of a newly-commercialized CR-39 plastic nuclear track detector (PNTD), “TechnoTrak”, in energetic heavy ion measurements. The advantages of TechnoTrak are derived from its use of a purified CR-39 monomer to improve surface quality combined with an antioxidant to improve sensitivity to low-linear-energy-transfer (LET) particles. We irradiated these detectors with various heavy ions (from protons to krypton) with various energies (30–500 MeV/u) at the heavy ion accelerator facilities in the National Institute of Radiological Sciences (NIRS). The surface roughness after chemical etching was improved to be 59% of that of the conventional high-sensitivity CR-39 detector (HARZLAS/TD-1). The detectable dynamic range of LET was found to be 3.5–600 keV/μm. The LET and charge resolutions for three ions tested ranged from 5.1% to 1.5% and 0.14 to 0.22 c.u. (charge unit), respectively, in the LET range of 17–230 keV/μm, which represents an improvement over conventional products (HARZLAS/TD-1 and BARYOTRAK). A correction factor for the angular dependence was determined for correcting the LET spectrum in an isotropic radiation field. We have demonstrated the potential of TechnoTrak, with its two key features of high surface quality and high sensitivity to low-LET particles, to improve automatic analysis protocols in radiation dosimetry and various other radiological applications.

Extra length and large sized bubble detectors (BD) of Type T-15 have been irradiated with 500 MeV/u Fe-56 ions at HIMAC accelerator in the National Institute of Radiological Sciences (NIRS), Chiba, Japan. Linear tracks composed of regular arrays of tiny bubbles are visible by the naked eyes. The total length of each track is longer than 4.2 cm. In each track there are commonly more than 24 bubbles. The gap distance (or called pitch distance) between two neighboring bubbles in a track has been measured and analyzed, which reflects the distance between the two invisible superheated droplets that form the visible bubbles. The gap distance is related to the volume ratio of the superheated liquid (Freon-115) droplets to the whole sensitive volume of the detector and to the sizes of the droplets of the superheated liquid. A technique has been developed to deduce the average diameter of superheated droplets and to derive the number of the droplets in unit volume of the detector. A method to calibrate bubble detectors with high-energy heavy ions at accelerators is advanced, which is similar to that of calibration of solid state nuclear track detectors (SSNTD) at accelerators. Feasible ranges of the percentage volume of superheated liquid being 10(-4)-10(-1), droplet diameter 1-10(3) mu m, and droplet number density 1-10(11) cm(-3) in bubble detectors are outlined according to the experiences of the authors. These techniques and method will facilitate the development and applications of bubble detectors. (C) 2015 Elsevier Ltd. All rights reserved.

© Published under licence by IOP Publishing Ltd. The CALorimetric Electron Telescope (CALET) is a space experiment, currently under development by Japan in collaboration with Italy and the United States, which will measure the flux of cosmic-ray electrons (and positrons) up to 20 TeV energy, of gamma rays up to 10 TeV, of nuclei with Z from 1 to 40 up to 1 PeV energy, and will detect gamma-ray bursts in the 7 keV to 20 MeV energy range during a 5 year mission. These measurements are essential to investigate possible nearby astrophysical sources of high energy electrons, study the details of galactic particle propagation and search for dark matter signatures. The main detector of CALET, the Calorimeter, consists of a module to identify the particle charge, followed by a thin imaging calorimeter (3 radiation lengths) with tungsten plates interleaving scintillating fibre planes, and a thick energy measuring calorimeter (27 radiation lengths) composed of lead tungstate logs. The Calorimeter has the depth, imaging capabilities and energy resolution necessary for excellent separation between hadrons, electrons and gamma rays. The instrument is currently being prepared for launch (expected in 2015) to the International Space Station ISS, for installation on the Japanese Experiment Module - Exposure Facility (JEM-EF).

The Active X-ray Spectrometer (AXS) is considered as one of the scientific payload candidates for a future Japanese mission, SELENE-2. The AXS consists of pyroelectric X-ray generators and a Silicon Drift Detector to conduct X-Ray Fluorescence spectroscopy (XRF) on the Moon to measure major elements: Mg, Al, Si, Ca, Ti, and Fe; minor elements: Na, K, F, S, Cr and Mn; and the trace element Ni depending on their concentration. Some factors such as roughness, grain size and porosity of sample, and the geometry of X-ray incidence, emission and energy will affect the XRF measurements precision. Basic studies on the XRF are required to develop the AXS. In this study, fused samples were used to make homogeneous samples free from the effect of grain size and porosity. Experimental and numerical studies on the XRF were conducted to evaluate the effects from incidence and emission angles and surface roughness. Angle geometry and surface roughness will be optimized for the design of the AXS on future missions from the results of the experiment and the numerical simulation. (C) 2015 Elsevier B.V. All rights reserved.

The CALorimetric Electron Telescope (CALET) is a space experiment, currently under development by Japan in collaboration with Italy and the United States, which will measure the flux of cosmic-ray electrons (and positrons) up to 20 TeV energy, of gamma rays up to 10 TeV, of nuclei with Z from 1 to 40 up to 1 PeV energy, and will detect gamma-ray bursts in the 7 keV to 20 MeV energy range during a 5 year mission. These measurements are essential to investigate possible nearby astrophysical sources of high energy electrons, study the details of galactic particle propagation and search for dark matter signatures. The main detector of CALET, the Calorimeter, consists of a module to identify the particle charge, followed by a thin imaging calorimeter (3 radiation lengths) with tungsten plates interleaving scintillating fibre planes, and a thick energy measuring calorimeter (27 radiation lengths) composed of lead tungstate logs. The Calorimeter has the depth, imaging capabilities and energy resolution necessary for excellent separation between hadrons, electrons and gamma rays. The instrument is currently being prepared for launch (expected in 2015) to the International Space Station ISS, for installation on the Japanese Experiment Module - Exposure Facility (JEM-EF).

© 2014 Elsevier B.V. The CALorimetric Electron Telescope (CALET) space experiment, currently under development by Japan in collaboration with Italy and the United States, will measure the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma rays to 10 TeV and nuclei with Z=1 to 40 up to 1,000 TeV during a two-year mission on the International Space Station (ISS), extendable to five years. These measurements are essential to search for dark matter signatures, investigate the mechanism of cosmic-ray acceleration and propagation in the Galaxy and discover possible astrophysical sources of high-energy electrons nearby the Earth. The instrument consists of two layers of segmented plastic scintillators for the cosmic-ray charge identification (CHD), a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 radiation length thick lead-tungstate calorimeter (TASC). CALET has sufficient depth, imaging capabilities and excellent energy resolution to allow for a clear separation between hadrons and electrons and between charged particles and gamma rays. The instrument will be launched to the ISS within 2014 Japanese Fiscal Year (by the end of March 2015) and installed on the Japanese Experiment Module-Exposed Facility (JEM-EF). In this paper, we will review the status and main science goals of the mission and describe the instrument configuration and performance.

The Ag+-doped phosphate glass which is commonly employed as the radiophotoluminscence (RPL) dosimeter has been applied as a nuclear track etch detector. The glass is etchable in the NaOH solutions and forms clear nuclear etch pit. The etching performances and track parameters vary as a function of the concentration of NaOH solution. The most sensitive normality was confirmed to be 7 N. The track response is controllable with NaOH concentration at the range of Z*/beta >= 80 (Z*: effective charge, beta: velocity). The charge spectroscopic resolution for Xe (Z*/beta = 107) was found to be 0.23 cu (charge unit), which would allow to identify individual nuclear charge of ultra heavy nuclei around Actinides in the cosmic rays. The Ag+-doped phosphate glass would be a promising detector for high Z spectroscopy for cosmic ray and nuclear physics fields and has the potential to operate not only RPL dosimeter but also nuclear track etch detector. (C) 2014 Elsevier Ltd. All rights reserved.

Depth dependency of neutrons produced by cosmic rays (CRs) in the lunar subsurface was estimated using the three-dimensional Monte Carlo particle and heavy ion transport simulation code, PHITS, incorporating the latest high energy nuclear data, JENDL/HE-2007. The PHITS simulations of equilibrium neutron density profiles in the lunar subsurface were compared with the measurement by Apollo 17 Lunar Neutron Probe Experiment (LNPE). Our calculations reproduced the LNPE data except for the 350-400 mg/cm(2) region under the improved condition using the CR spectra model based on the latest observations, well-tested nuclear interaction models with systematic cross section data, and JENDL/HE-2007. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.

This paper presents a developed experimental system using an eye-tracking device, by which we can control displayed visual stimuli flexibly like visual trick. Using this system, comparisons between two faces with different expressions are experimented in a specific condition as one face is always forced to display as in the subject's central field of view, while another face is always displayed in his/her peripheral field of view. The results have proved that ability of discriminate faces in the peripheral field of view is quite poor. In addition, the experimental results indicate how we could live our daily lives more peacefully.

Wide-Angle Fovea Vision Sensor (WAFVS) system was designed and developed being inspired from advantages of the human eye's functions. This system is characterized by its space-variant data acquisition property, i.e., the WAFVS captures a 120-degree wide-angle input image in which its resolution (or magnification) changes like the human visual acuity. As well-known, the human visual acuity is the highest at its central field of view (FOV) and decreases rapidly towards its peripheral FOV. Thus, using the WAFVS, we can observe a target in detail by its central field of view while observing the whole of environment by its wide field of view. In addition, by controlling a view direction of the WAFVS, this WAFVS system gets visual information from the environment more in detail by smaller data amount. Hence, the WAFVS achieves a better performance of data transmission and data storage. One of severe problems in remote control of rovers, UAVs, and satellites is of a pay-load. In this point of view, the authors think that the WAFVS is suitable for the planetary exploring rover because it was originally developed for multi-purpose use of a single vision sensor. This paper describes the multi-purpose use of the WAFVS system, i.e., the following tasks: (1) observing the environment displayed to the operator for the remote navigation of the rover, (2) recording images of important scenes by changing a view direction of the WAFVS, and (3) monitoring if the instruments on the rover work well or not. Moreover, this paper experiments and discusses on how to display images to the operator when an eye-tracking device is applied as a target coordinate input device. Accuracy index, i.e., a measurement error of a target, is defined in order to evaluate performance of a combination among the vision sensor, the coordinate input device and the image display method.

There exists a well-known visual illusion with respect to color propagation. That is, a human subject confuses a color in the subject's peripheral field of view (FOV) as another color in the central FOV (with a shape of circular disk) spreads into the peripheral FOV or as a color in the peripheral FOV erodes another color in the central FOV (also with a shape of circular disk) when he/she keeps gazing at a specific color visual stimulus in his/her central FOV for more than several seconds. In this paper, the authors experiment this illusion using multiple naive subjects in conditions of the visual stimuli as the central or peripheral colors and the disk size change. This paper has proposed a rate of propagation as a criterion and has analyzed and discussed the illusion using it.

Large-sized bubble detectors with microscopic droplets of superheated liquids of dichlorodifluoromethane (Freon-12), dichlorotetrafluoroethane (Freon-114), tetrafluoroethane (Freon-134a), and mixture of Freon-12 and Freon-114, respectively, were irradiated with 150 MeV/amu helium ions at the HIMAC accelerator in NIRS, Chiba, Japan. Distributions of bubbles produced by the helium ions have been studied in each type of the detectors. The origin of the bubbles has been investigated. The detection efficiency of each type of the bubble detectors for helium ions with respect to the energy of the ions has been obtained. The phenomenon of bubble occurrence and its possible applications to the determination of He intensity from accelerators, research of track formation mechanism, energy loss straggling and neutron detection in the space and at higher altitude are discussed. © 2012 Elsevier Ltd. All rights reserved.

An active X-ray spectrometer (AXS) is now being developed as a payload candidate for the rover on SELENE-2, the next Japanese lunar exploration mission. The AXS will determine the chemical compositions of lunar rocks and regolith around the landing site. The surface of lunar rock samples will be ground using a rock abrasion tool. Thus, fundamental studies on the X-ray fluorescence analysis for lunar rocks and regolith are required to design and develop the AXS. In this study, we have investigated the X-ray fluorescence analysis in order to evaluate the effects of surface roughness of samples and the angle of incident and emergent X-rays. It was found that the fluorescent X-ray yield for low energy X-rays, i.e. the light elements, decreases at rough surface samples. This effect of surface roughness becomes small for smooth surface samples. It was also found that the fluorescent X-ray yield depends on the incident angle, which is attributed to the fact that the X-ray fluorescence occurs closer to the sample surface at larger incident angles. Since the emergent X-rays are affected by the detection geometry and surface roughness, the incident angle effect also depends on the above conditions.

High-pressure xenon is an attractive medium for radiation detection in that the time projection chambers can be constructed by combined measurements of charge and light signals. The electron transport properties are essential information for developing and operating high-pressure xenon detectors. In this paper, our recent experimental results of electron diffusion coefficients in high-pressure xenon are presented. We measured the longitudinal diffusion coefficient of electrons under external applied electric fields in high-pressure xenon, ranging from 0.17 to 5.0 MPa in pressure at room temperature. A significant pressure dependence was found in the density-normalized longitudinal diffusion coefficient for low electric field region. We compared the longitudinal diffusion coefficient with the transverse one at a pressure of 1.0 MPa, and obtained the difference between both the diffusion coefficients. The longitudinal diffusion was found to become smaller than the transverse one when increasing the external electric field. © 2012 IOP Publishing Ltd and Sissa Medialab srl.

Using Geographic Information Systems (GIS), we performed comparative analysis among stratigraphic information and the Kaguya (SELENE) GRS data of the similar to 2500-km-diameter South Pole-Aitken (SPA) basin and its surroundings. Results indicate that the surface rock materials (including ancient crater materials, mare basalts, and possible SPA impact melt) are average to slightly elevated in K and Th with respect to the rest of the Moon. Also, this study demonstrates that K and Th have not significantly changed since the formation of SPA. The elemental signatures of the impact basin of Fe, Ti, Si, o through time include evidence for resurfacing by ejecta materials and late-stage volcanism. The oldest surfaces of SPA are found to be oxygen-depleted during the heavy bombardment period relative to later stages of geologic development, followed by both an increase in silicon and oxygen, possibly due to ejecta sourced from outside of SPA, and subsequent modification due to mare basaltic volcanism, which increased iron and titanium within SPA. The influence of the distinct geologic history of SPA and surroundings on the mineralogic and elemental abundances is evident as shown in our investigation. (c) 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.

Measurements of the mobility and longitudinal diffusion coefficient of electrons under external electric fields were performed in high-density gaseous xenon at room temperature. The xenon density and reduced electric field ranges were from 2.55 x 10(20) to 1.73 x 10(21) cm(-3) and from 0.027 to 0.19 Td, respectively. The electron transport parameters of the density-normalized mobility, density-normalized longitudinal diffusion coefficient, and the ratio of the longitudinal diffusion coefficient to the mobility were found to increase with increasing density for reduced electric fields at around 0.04 Td. This result indicates the density-dependent variation of the effective momentum-transfer cross section for electron-atom scattering. It was also found that the density-dependent variations are different depending on the electron transport parameters, which can be attributed to the difference in parameter sensitivity to the momentum-transfer cross section. (C) 2012 The Japan Society of Applied Physics

The first unambiguous global distribution of Ca on the Moon has been revealed by the Kaguya Gamma-Ray Spectrometer. The observation of the 3737 key gamma rays from Ca-40 with a high energy resolution Ge detector, corrected for fast neutrons, improved greatly our confidence in these remote sensing data. While the derived Ca abundance generally confirms the mare-highland dichotomy, we found that the eastern mare regions such as Crisium, Nectaris, and Fecunditatis exhibit unexpected high Ca abundances. This may be explained by regional concentrations of high-Ca clinopyroxene. Our Ca map also shows that the lowest CaO abundance found in the returned samples (similar to 8 wt%) may actually be common in Oceanus Procellarum, suggesting the possible sampling bias of Apollo and Luna missions. These observational results on Ca serve as a complementary criterion for better characterization of mare regions on the Moon. (C) 2012 Elsevier B.V. All rights reserved.

To approach basic scientific questions on the origin and evolution of planetary bodies such as planets, their satellites and asteroids, one needs data on their chemical composition. The measurements of gamma-rays, X-rays and neutrons emitted from their surface materials provide information on abundances of major elements and naturally radioactive gamma-ray emitters. Neutron spectroscopy can provide sensitive maps of hydrogen- and carbon-containing compounds, even if buried, and can uniquely identify layers of carbon-dioxide frost. Nuclear spectroscopy, as a means of compositional analysis, has been applied via orbital and lander spacecraft to extraterrestrial planetary bodies: the Moon, Venus, Mars, Mercury and asteroids. The knowledge of their chemical abundances, especially concerning the Moon and Mars, has greatly increased in recent years. This paper describes the principle of nuclear spectroscopy, nuclear planetary instruments carried on planetary missions so far, and the nature of observational results and findings of the Moon and Mars, recently obtained by nuclear spectroscopy.

As a feasibility study, gas chromatography-mass spectrometry (GC-MS) and matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) have been applied to analyze etch products of CR-39 plastic (one of the most frequently used solid states nuclear track detector) for the understanding of track formation and etching mechanisms by heavy ion irradiation. The etch products of irradiated CR-39 dissolved in sodium hydroxide solution (NaOH) contain radiation-induced fragments. For the GC-MS analysis, we found peaks of diethylene glycol (DEG) and a small but a definitive peak of ethylene glycol (EG) in the etch products from CR-39 irradiated by 60 MeV N ion beams. The etch products of unitradiated CR-39 showed a clear peak of DEG, but no other significant peaks were found. DEG is known to be released from the CR-39 molecule as a fragment by alkaline hydrolysis reaction of the polymer. We postulate that EG was formed as a result of the breaking of the ether bond (C-O-C) of the DEG part of the CR-39 polymer by the irradiation. The mass distribution of polyallylalcohol was obtained from the etch products from irradiated and unirradiated CR-39 samples by MALDI-MS analysis. Polyallylalcohol, with the repeating mass interval of m/z = 58 Da (dalton) between m/z = 800 and 3500, was expected to be produced from CR-39 by alkaline hydrolysis. We used IAA as a matrix to assist the ionization of organic analyte in MALDI-MS analysis and found that peaks from IAA covered mass spectrum in the lower m/z region making difficult to identify CR-39 fragment peaks which were also be seen in the same region. The mass spectrometry analysis using GC-MS and MALDI-MS will be powerful tools to investigate the radiation-induced polymeric fragments and helping to understand the track formation mechanism in CR-39 by heavy ions. (C) 2011 Elsevier B.V. All rights reserved.

Kaguya gamma-ray spectrometer measured thorium (Th) distribution on the lunar farside with the highest sensitivity among past gamma-ray remote sensing missions. The newly obtained Th map has revealed that two regions near the equator on the farside have the lowest Th abundances. We found that the variation of the Th abundance perfectly correlates with the crustal thickness in the farside and the southern nearside, and it could be a result of the crystallization of the lunar magma ocean. (C) 2012 Elsevier B.V. All rights reserved.

The longitudinal diffusion coefficient of electrons and the ratio of the longitudinal diffusion coefficient to the mobility of electrons were measured for the first time in high-density gaseous xenon in the extensive density range of 4.19 x 10(19)-4.82 x 10(20) cm(-3). The density dependence of the longitudinal diffusion coefficient was observed in the reduced electric field range of 0.025-0.055 Td. (c) 2012 The Japan Society of Applied Physics

The characteristics of charge amplification in high-pressure xenon were studied using a cylindrical proportional counter. The investigated pressure range was from 0.5 to 3.0 MPa, which is higher than previous studies. The charge amplification factor was obtained between 15 and 2.4 × 103 for investigated pressure. The first Townsend ionization coefficient was determined from the measured charge amplification factors. As a result, the ratio of α/N at higher pressures seems to increase for the same reduced electric field, which was observed approximately above 2.0 MPa. Consequently, α/N cannot apparently be represented as a function of reduced electric field only. It was found that a proportional counter is worked at weaker reduced electric field at higher pressures. This fact results in the complexity of electron avalanche processes and the deterioration of the energy resolution The non-uniformity of the anode wire would also be a cause of fluctuation of charge amplification particularly at high pressures. The energy resolution was observed to become worse with increasing pressure, which is attributed to above reasons. Nevertheless, the energy resolution in pure xenon is found to be superior to that in xenon-based gas mixtures at high pressure and several hundreds of the charge amplification factor. Further considerations about the first Townsend ionization coefficient in high-pressure xenon will be made in the future, together with the charge amplification in liquid xenon It may also be interesting to compare the behavior of charge amplification in cylindrical proportional counters at high pressure with parallel plate chambers at low pressure at the same reduced electric field. That will be important for better understanding of the mechanism of charge amplification in cylindrical geometry, or non-uniform electric field conditions.

The two-step etching method using PEW (Potassium hydroxide + Ethanol + Water) and NaOH solutions was applied to the control of the response of CR-39 plastic nuclear track detectors for the measurement of high LET (linear energy transfer) particles. CR-39 detectors were exposed to several heavy ion beams covering the LET infinity H2O range of 30-750 key/mu m from HIMAC (Heavy Ion Medical Accelerator in Chiba) at NIRS (National Institute of Radiological Sciences), Japan. The detectors were pre-etched in PEW solutions with 3 different ethanol concentrations at the temperature of 70 degrees C for 30-60 min. Then, the detectors were post-etched in 7N NaOH solution at the same temperature for 4-28 h. We found that the response curves and the detection thresholds of the detectors smoothly shifted to higher LET regions as the ethanol concentration increases in PEW solution. (C) 2011 Elsevier Ltd. All rights reserved.

The responses of a piezoelectric lead zirconate titanate (PZT) element to hypervelocity collisions were experimentally studied. In this study, the particles of masses ranging from 0.3 to 10 fg were made to collide with PZT at velocities between 20 and 96 km/s. The amplitude and the corresponding rise time of the single-pulse output signals that were produced in the piezoelectric PZT element were measured to determine the possible collision states. The results revealed an apparently multimodal output; three classes were assumed to be involved in the pulse formation mechanism. The amplitude and rise time were sensitive to the collision velocity. The multimodal behavior implied that the PZT-based cosmic dust detectors should be calibrated according to the class they belong to. (C) 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.

The charge resolution (delta Z) for heavy ions (nuclear charge: Z < 40) of 0.1-1 GeV/n energy in CR-39 plastic nuclear track detector (PNTD) and its dependence on etching time, and on projectile Z and energy were investigated and optimized as part of an effort to make precise measurements of projectile charge-changing cross sections. Two types of CR-39 PNTD, HARZLAS TD-1 and BARYOTRAK, were exposed to heavy ion beams with seven values of Z behind thick targets to produce projectile fragments. Following chemical etching (7 N NaOH at 70 degrees C) for varying etch times, delta Z of the projectiles was determined for each detector type. A strong dependence of delta Z on the amount of bulk etch (B) was seen. It was also observed that delta Z can be remarkably improved with longer etching time as a function of B(-1/2), in accordance with the trend seen in other types of track detector such as glass nuclear track detector. However, for B >= 60 mu m (30 h etching), saturation occurs and there is no further improvement in delta Z. Analysis of the correlations between projectile Z, energy, detector response, and fluctuation of the response make it possible to develop a model to predict the delta Z for projectiles of given Z and energy. The predicted and measured values of delta Z show good agreement within 10%. We conclude that 4 <= Z <= 30 at intermediate energy can be identified with good delta Z in these detectors. The predictive model will be used in designing future cross section measurement experiments. (C) 2011 Elsevier B.V. All rights reserved.

Variations of particle fluxes during a moderate magnetic storm on August 30-31, 2004 are analyzed in this paper using measurements on low-orbit polar satellites CORONAS-F and SERVIS-1. The Earth's radiation belts were filled at this time by enhanced flux of energetic particles accelerated a month ago during magnetic storms on July 23-27. The analysis has shown that even during a moderate magnetic storm a set of several adiabatic and non-adiabatic processes is observed, which leads to acceleration or release of particles and acts selectively depending on the energy range and charge of particles. © 2011 Pleiades Publishing, Ltd.

The CALorimetric Electron Telescope (CALET) mission is being developed as a standard payload for the Exposure Facility of the Japanese Experiment Module (JEM/EF) on the International Space Station (ISS). The instrument consists of a segmented plastic scintillator charge measuring module, an imaging calorimeter consisting of 8 scintillating fiber planes with a total of 3 radiation lengths of tungsten plates interleaved with the fiber planes, and a total absorption calorimeter consisting of crossed PWO logs with a total depth of 27 radiation lengths. The major scientific objectives for CALET are to search for nearby cosmic ray sources and dark matter by carrying out a precise measurement of the electron spectrum (1 GeV - 20 TeV) and observing gamma rays (10 GeV - 10 TeV). CALET has a unique capability to observe electrons and gamma rays in the TeV region since the hadron rejection power is larger than 105 and the energy resolution better than ∼2 % above 100 GeV. CALET has also the capability to measure cosmic ray H, He and heavy nuclei up to 1000 TeV. The instrument will also monitor solar activity and search for gamma ray transients. The phase B study has started, aimed at a launch in 2013 by H-II Transfer Vehicle (HTV) for a 5 year observation period on JEM/EF.

The neutron production from alpha particles in galactic cosmic rays (GCR) in the lunar subsurface has not been estimated with reliable precision despite its importance for lunar nuclear spectroscopy and space dosimetry. Here, we report our estimation of neutron production from GCR nuclei (protons and alpha particles) with the Particle and Heavy Ion Transport code System (PHITS), which includes several heavy ion interaction models. PHITS simulations of the equilibrium neutron density profiles in the lunar subsurface are compared with experimental data obtained in the Apollo 17 Lunar Neutron Probe Experiment. Our calculations successfully reproduced the data within an experimental error of 15%. Our estimation of neutron production from GCR nuclei, estimated by scaling that from protons by a factor of 1.27, is in good agreement within an error of 1% with the calculations using two different alpha particle interaction models in PHITS during a period of average activity of the solar cycle. However, we show that the factor depends on the incident GCR spectrum model used in the simulation. Therefore, we conclude that the use of heavy ion interaction models is important for estimating neutron production in the lunar subsurface.

The Kaguya gamma-ray spectrometer (KGRS) has great potential to precisely determine the absolute abundances of natural radioactive elements K, Th and U on the lunar surface because of its excellent spectroscopic performance. In order to achieve the best performance of the KGRS, it is important to know the spatial response function (SRF) that describes the directional sensitivity of the KGRS. The SRF is derived by a series of Monte Carlo simulations of gamma-ray transport in the sensor of the KGRS using the full-fledged simulation model of the KGRS, and is studied in detail. In this paper, the method for deriving absolute abundance of natural radioactive elements based on the SRF is described for the analysis of KGRS data, which is also applicable to any gamma-ray remote sensings. In the preliminary analysis of KGRS data, we determined the absolute abundances of K and Th on the lunar surface without using any previous knowledge of chemical information gained from Apollo samples, lunar meteorites and/or previous lunar remote sensings. The results are compared with the previous measurements and the difference and the correspondence are discussed. Future detailed analysis of KGRS data will provide new and more precise maps of K, Th and U on the lunar surface.

A radiation detector based on the piezoelectric effect, which is fabricated using lead zirconate titanate (PZT), has been investigated by irradiating it with a 400 MeV/n xenon (Xe) beam. To estimate quantitatively the electric charge appearing on the PZT detector, the detector made of PZT without poling was used in this study. It was found that the sensitivity of the detector without poling was reduced by similar to 1/20 compared with that of the detector with poling within the limits of the experimental conditions. (C) 2010 The Japan Society of Applied Physics

The Kaguya Gamma-Ray Spectrometer uniquely identified uranium gamma-ray lines from the Moon with a superior energy resolution of similar to 1%. A global lunar map of uranium distribution is derived for the first time. It was found that uranium abundances vary up to 2 ppm with an average of similar to 0.3 ppm, while the average thorium abundance was similar to 1.2 ppm. From these analyses, significant variation in U/Th ratio was found in the farside of the Moon that had not been reported by previous observations or in lunar materials. Our observations suggest that the lunar highland is not as uniform as has been long considered. Citation: Yamashita, N., et al. (2010), Uraniumon theMoon: Global distribution and U/Th ratio, Geophys. Res. Lett., 37, L10201, doi:10.1029/2010GL043061.

The detector characteristics of piezoelectric lead zirconate titanate (PZT) were studied by directly irradiating a multilayered PZT detector with 400 MeV/n xenon ions. An extracted beam was processed with a rotating slit. Thus, passed through similar to 10(3) xenon ions were available for 50 to 250 mu s. The effect of polarization on the output signal was discussed, and the optimal electrode configuration was determined. The output signal appeared as an isolated pulse whose amplitude was qualitatively understood by the Bethe-Bloch formula. However, the calculated and the observed values differed depending on the rotation speed of the slit. A process that can explain the differences is presented here. The output signal appearing beyond the range of 400 MeV/n xenon ion beam was discussed. The sensitivity was compared with that obtained with hypervelocity collision of dust. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3373383]

The characteristics of radiation detector fabricated by stacking some piezoelectric lead zirconate titanate (PZT) elements were studied by irradiating it with a 400 MeV/n xenon (Xe) beam. Comparing between observed results from the detector and calculation results using Bethe-Bloch formula, it was found that the amplitude of the output voltage observed was dependent on the amount of ionization energy loss of Xe ion with PZT. (C) 2010 Elsevier Ltd. All rights reserved.

The processes of penetration, trapping, and acceleration of solar protons in the Earth's magneto-sphere during magnetic storms in November 2004 and January 2005 are studied based on the energetic particle measurements on the CORONAS-F and SERVIS-1 satellites. Acceleration of protons by 1-2 orders of magnitude was observed after trapping of solar protons with an energy of 1-15 MeV during the recovery phase of the magnetic storm of November 7-8, 2004. This acceleration was accompanied by an earthward shift of the particle flux maximum for several days, during which the series of magnetic storms continued. The process of relativistic electron acceleration proceeded simultaneously and according to a similar scenario including acceleration of protons. At the end of this period, the intensification was terminated by the process of precipitation, and a new proton belt split with the formation of two maximums at L ~ 2 and 3. In the January 2005 series of moderate storms, solar protons were trapped at L = 3. 7 during the storm of January 17-18. However, during the magnetic storm of January 21, these particles fell in the zone of quasi-trapping, or precipitated into the atmosphere, or died in the magnetosheath. At the same time, the belts that were formed in November at L ~ 2 and 3 remained unchanged. Transformations of the proton (and electron) belts during strong magnetic storms change the intensity and structure of belts for a long time. Thus, the consequences of changes during the July 2004 storm did not disappear until November disturbances. © Pleiades Publishing, Ltd., 2010.

The neutron production from galactic cosmic ray (GCR) protons and alpha particles in the lunar subsurface was estimated using the three-dimensional Monte Carlo simulation code PHITS, together with GCR input spectra based on the BESS measurements. The PHITS simulations of equilibrium neutron density profiles in the lunar subsurface were compared with experimental data by Apollo 17 Lunar Neutron Probe Experiment. By use of accurate spectra and nuclear interaction models, our calculations successfully reproduced the data within the experimental error at the shallower region than 300 g/cm(2). However, our calculation was up to 30% higher in the deeper region.

The high precision Gamma-Ray Spectrometer (GRS) was carried on the first Japan's large-scale lunar orbiter, SELENE (KAGUYA). The GRS employed a Ge detector with high energy resolution. Since the regular observation by the KAGUYA GRS started on December 14, 2007, gamma-ray data had been accumulated over the Moon. Many elements were identified: O, Mg, Al, Si, K, Ca, Ti, Fe, Th and U. The regular GRS observation at 100 km altitude let us create global distribution maps of chemical abundances on the lunar surface, which showed considerable regional variations. Special operations were conducted in December 2008 in order to measure background gamma rays from materials of the spacecraft body and the GRS detector itself, and to anneal the Ge crystal for about two days at 85 ± 5 degrees Celsius in order to recover the resolution of the Ge crystal that had been degraded due to radiation damage in space. Its energy resolution was improved to the level at the initial phase of the mission. Results from the special operations and regular observation of the Moon are described.

The neutron production from galactic cosmic ray (GCR) protons and alpha particles in the lunar subsurface was estimated using the three-dimensional Monte Carlo simulation code PHITS. The PHITS simulations of equilibrium neutron density profiles in the lunar subsurface were compared with experimental data by the Apollo 17 Lunar Neutron Probe Experiment. By use of the latest GCR spectra based on BESS measurements and well benchmarked nuclear interaction models, our calculations well reproduced the data within the experimental error of 15% (measurement) + 30% (systematic) at the region shallower than 300 g/cm(2). However, our calculation showed 10-20% higher values in the deeper region.(1 2)

The time profile of recombination luminescence of dense xenon gas irradiated by an alpha-particle was absolutely measured in the density range of 0.027-0.112 g/cm(3) with the aim to investigate the intensities of recombination luminescence at zero electric field. It was found that the number of scintillation photons due to the recombination luminescence increases with xenon density up to around 0.05 g/cm(3), and then becomes nearly constant (= 2.32 x 10(5) photons for an alpha-particle with 5.49 MeV). The probability of recombination between electrons and ions at zero electric field is about 88% in the density range of 0.05-0.112 g/cm(3). it was also found that the percentage of slow component (similar to sub-milliseconds) in the recombination luminescence decreases with density from 73% to 33% in the density range from 0.027 to 0.112 g/cm(3). (C) 2009 Elsevier B.V. All rights reserved.

The high precision gamma-ray spectrometer (GRS) onboard the Japanese lunar explorer, SELENE (KAGUYA) consists of a large Ge crystal as the main detector and massive BGO and plastic scintillators as anticoincidence detectors. After a series of initial health checks, it started regular observation officially on December 21, 2007. Energy spectra of lunar gamma rays were obtained by GRS with very good energy resolution being 0.6% at 1.46MeV over the lunar surface. Many peaks of gamma rays from major elements and natural radioactive elements in the lunar surface have been observed. Individual gamma-ray lines emitted from the lunar surface have been identified. Here, we report the initial results obtained practically during the period from December 14, 2007 to February 17, 2008. Global maps of K and Th gamma-ray intensities are reported using count rates in several energy bands.

The characteristics of a detector fabricated using piezoelectric lead zirconate titanate (PZT) were studied by irradiating it with a 400 MeV/n xenon (Xe) beam while changing the beam flux intensity. The largest output signal was observed from the detector when the beam power per unit time was estimated to be largest. It was also found that the sensitivity per Xe ion of the detector seemed to be higher with decreasing the amount of the Xe ion flux within the limits of the experimental conditions. (C) 2009 Elsevier B.V. All rights reserved.

The characteristics of a radiation detector fabricated with stacks of piezoelectric lead zirconate titanate (PZT) elements were studied by irradiation with a 400 MeV/n xenon (Xe) beam. The detector was designed to monitor the output voltage formed on the surface of each element. Three additional PZT elements were placed in front of the detector to increase the thickness of the PZT target. It seemed that the individual output voltage observed at a position beyond the range was dependent on the amount of strain generated by the ionization loss energy of Xe ions within the range.

It is necessary to develop a track detector with higher detection threshold and high charge resolution for ultra heavy cosmic ray observation. The track registration sensitivity in CR-39 track detector etched by PEW (Potassium-Ethanol-Water) solution was verified using heavy ion beams at the HIMAC accelerator. It was found that PEW solution makes effectively to desensitize the track registration sensitivity in CR-39 detector. Its detection threshold of Z*/beta is successfully raised to be Z*/beta = 39 by using PEW solution with the concentration of ethanol of 45 wt%. However this produces a "fuzzy track". A two-step process of etching involving a post-etch with 7 mol/l sodium hydroxide solution produced very clear track edges and remarkably improves the charge resolution for heavy ions. (C) 2009 Elsevier Ltd. All rights reserved.

A new copolymer of CR-39 and DAP resin was developed for the selective detection of ultra heavy nuclei in galactic cosmic rays. The track registration sensitivity for heavy ions with various Z(+)/beta was verified for copolymers mixing CR-39 (BARYOTRAK) with various concentrations of DAP using heavy ion beams at the HIMAC accelerator. In order to realize sufficient polymerization of CR-39/DAP copolymer, the optimum fabricating method was also verified by modifying the concentration of the initiator and temperature-time curing cycle for the copolymerization. CR-39 (BARYOTRAK) used for the base material of copolymerization has many advantages: 1) high uniformity of detector response, 2) extremely clear surface condition after etching, and 3) excellent charge and mass resolutions for heavy ions. The surface condition of the copolymer after etching is remarkably improved by using the BARYOTRAK monomer and its track registration sensitivity is controllable by changing the DAP concentration. However the detection threshold of the CR-39 (BARYOTRAK)/DAP copolymer is not yet satisfactory. (C) 2009 Elsevier Ltd. All rights reserved.

Lunar-based measurement of galactic cosmic ray (GCR) nuclei with a high precision is a challenging approach in cosmic ray research for the coming 20 years. This approach focuses to measure the elemental composition of Pt- and Pb-groups, actinide and possibly trans-uranic nuclei of Pu and Cm. The observation covers a wide range of scientific themes including the study on the origin of GCR nuclei, the characteristic time, heating and acceleration mechanism of GCR particles. A large-scaled particle telescope is required in order to measure those nuclides with high precision. Solid state nuclear track detectors (SSTDs) with a geometric factor of about 1000 m(2)sr allow us to measure them easily. Fluorescent nuclear track detector such as Al(2)O(3) doped with C and Mg is the best candidate at present among SSTDs for a lunar-based experiment which is currently the focus of an international program of scientific investigation. A permanent sunshine region near crater at lunar polar region is thought to be an excellent site. A two-year-exposure by the large-scaled telescope would result in the detection of about 30,000 actinides in GCRs. (C) 2009 Elsevier Ltd. All rights reserved.

The average numbers of scintillation photons and electrons produced by an a-particle with 5.49 MeV were determined in high-density xenon gas in the density range of 0.03-0.12 g/cm(3). No significant density dependence was observed for the number of excited atoms or liberated electrons. The average energies expended per excited atom (W x-value) and liberated electron (W-value) were found to be 34.1 +/- 2.4 and 20.9 +/- 0.4 eV, respectively. It was also found that some liberated electrons escape from recombination at zero electric field. (C) 2009 The Japan Society of Applied Physics

We experimentally determined the suitable conditions of temperature and air pressure for measuring charge and mass compositions of heavy cosmic rays using CR-39 track detectors during long-duration, high-altitude balloon flights. The experiments were carried out utilizing Fe ion beams from Heavy Ion Medical Accelerator (HIMAC). Changes in the track registration sensitivity with temperature were studied at temperatures between 213 and 293 K. The charge and mass shifts around Fe ions are possibly 0.11 cu (charge unit) and 0.47 amu (atomic mass unit) at the temperature deviation between 227 and 243 K at balloon altitude. Decrease in track registration sensitivity as air pressure decreases has been observed between 13 Pa and 27 kPa. The charge and mass shifts around Fe ions are inferred to be 0.02 cu and 0.09 amu, respectively, when pressure varies between 20 and 27 kPa. During balloon flight, air pressure drops below this; therefore, care must be taken to keep the temperature and air pressure of CR-39 detectors within acceptable limits. (C) 2009 Elsevier B.V. All rights reserved.

The characteristics of a radiation detector fabricated with stacks of piezoelectric lead zirconate titanate (PZT) elements were studied by irradiating it with a 400 MeV/n xenon (Xe) beam for various beam pulse durations. This detector is referred to as the multilayered detector (MD). To understand the production mechanism behind the output voltage obtained from the MD, measurement of the spatial distribution of the output signals generated in the MD was attempted. It was found that the amplitude observed was dependent on the number of Xe ions per unit time and the amount of ionization loss energy of Xe ions in PZT.

A cosmic dust monitor for use onboard a spacecraft is currently being developed using a piezoelectric lead zirconate titanate element (PZT). Its characteristics of the PZT sensor is studied by ground-based laboratory impact experiments using hypervelocity particles supplied by a Van de Graaff accelerator. The output signals obtained from the sensor just after the impact appeared to have a waveform that was explicitly related to the particle's impact velocity. For velocities less than similar to 6 km/s, the signal showed an oscillation pattern and the amplitude was proportional to the momentum of the impacting particle. For higher velocities, the signal gradually changed to a single waveform. The rise time of this single waveform was proportional to the particle's velocity for velocities above similar to 6 km/s. The present paper reports on results for the low velocity case and especially discusses the effect of an outer coating of the sensor with a paint, which is used to reduce heating by solar radiation. (C) 2009 COSPAR. Published by Elsevier Ltd. All rights reserved.

It is a case study of a chain of three magnetic storms with a special attention to the particle dynamics based on CORONAS-F and SERVIS-1 low altitude satellite measurements. Solar proton penetration inside the polar cap and inner magnetosphere and dynamics at different phases of the magnetic storms was studied. We found, that solar protons were captured to the inner radiation belt at the recovery phase of the first and the second magnetic storms and additionally accelerated during the last one. No evidence of sudden commencement (SC) particle injection was found. Enhanced solar proton belt intensity with small pitch angles decreased slowly during satellite orbits for 30 days until the next magnetic storm. Then in 20-30 h we registered strong precipitation of these protons followed by the trapped proton flux dropout. Intensity decrease was more pronounced at lower altitudes and higher particle energies. (C) 2008 COSPAR. Published by Elsevier Ltd. All rights reserved.

A cosmic dust detector for installation on a satellite is currently being developed using piezoelectric lead zirconate titanate (PZT), which can possess both functions of the collector and the transducer. The characteristics of the PZT detector have been studied by bombarding it with hypervelocity particles supplied by a Van de Graaff accelerator. The front surface of the detector used in this study was covered with a white paint to reduce any increase in the temperature due to the solar radiation. There was a linear relationship between the rise time of the signal produced by the detector and the particle's velocities. which were above 10 km/s on impact. This implies that individual particle velocities on impact can be inferred through the empirical formula derived from the data obtained from the PZT detector. (C) 2008 Elsevier Ltd. All rights reserved.

A cosmic dust detector is currently being developed using a piezoelectric lead zirconate titanate (PZT) element. The characteristics of the multilayered detector (MD), which was composed of one hundred PZT disks, were investigated by bombarding it with hypervelocity iron particles supplied by a Van de Graaff accelerator. It was confirmed that there was a linear relationship between the signal amplitude observed from MD and the momentum of the particles. As compared with the single-layered detector (SD) that was composed of one PZT disk, it was found that the sensitivity of MD was similar to 3 times higher than that of SD within the limits of the experimental conditions. (C) 2008 COSPAR. Published by Elsevier Ltd. All rights reserved.

月周回探査機かぐやは約1年半にわたる観測を終え、2009年6月にその使命を完了した。かぐやに搭載されたガンマ線分光計（KGRS）は月面から放出されるガンマ線を測定することにより月表層物質の元素組成分布を調べることを目的とした観測装置である。月面から放出されるガンマ線の強度は月面の元素組成と密接に関係しているため、高精度のガンマ線分光を行なうことにより、月面の元素濃度を決定することができる。KGRSは月探査に初めてGe検出器を採用したことにより、これまでにない高い精度で月面元素濃度分布を調べることが可能となった。本講演ではガンマ線分光法の概略を紹介した上で、KGRSの観測、データ解析法、さらに解析結果を用いた最新の研究成果について報告する。

We analyze the spectra measured by the Gamma Ray Spectrometer (GRS) on board the SELENE satellite orbiting the Moon. The spectra consist in 8192 energy channels ranging from 0 to 12 MeV and exhibiting lines of interest (O, Mg, Al, Si, Ti, Ca, Fe, K, Th, and U) superposed on a continuum. We have also analysed the data with various multivariate techniques, one of them being the Independent Component Analysis. We have used the JADE algorithm for our analysis that we focused in the energy range from 750 to 3000 keV. We identify at least three meaningful components. The first one is correlated to the Thorium map. The corresponding correlation coefficient spectrum exhibits the lines of Thorium, Potassium and Uranium. The second component is clearly correlated with the Iron as shown on its corresponding spectrum. Finally the third component seems to be related to the altitude of the spacecraft. This work shows that maps of elements such as iron will be available with the GRS data by a purely statistical analysis.

The high precision gamma-ray spectrometer (GRS) is carried on the first Japan's large- scaled lunar explorer, SELENE (KAGUYA), successfully launched by the H-IIA rocket on Sep. 14, 2007. The GRS consists of a large Ge crystal as a main detector and massive bismuth germanate crystals and a plastic scintillator as anticoincidence detectors. After a series of initial health check of the GRS, it started a regular observation on December 21, 2007. Energy spectra including many clear peaks of major elements and trace elements on the lunar surface have been measured by the GRS. Global measurement of thorium counting rate on the lunar surface is presented. The region showing the highest count rate of thorium extends from Kepler to Fra Mauro region in the Procellarum. And Apennine Bench and Aristillus region and the northwestern region of Mare Imbrium are high in thorium count rate. Second high count rate region is located in the South Pole-Aitken basin of the farside. Arago and Compton/Belkovich craters are also enriched in thorium. The initial results observed by GRS during the period from Dec. 21, 2007 to Feb. 17, 2008 is reviewed. © 2009 The Physical Society of Japan.

The lunar surface is directly exposed to galactic cosmic rays (GCRs) and solar energetic particles (SEPs) because of the lack of atmosphere and magnetic field on the Moon. These charged particles successively interact with the lunar material and then produce secondary radiations as neutrons and gamma rays. The annual ambient dose equivalent on the lunar surface is estimated about 840 mSv/yr during the quiet period at the solar activity minimum. Particularly, GCR heavy component largely contributes by about 80% to the annual dose equivalents. The ambient dose equivalents of SEPs are also calculated for two transient solar particles events on October 28th in 2003 and January 20th 2005. The SEP protons take the largest contribution of about 90% to the dose, while the heavy components of SEPs do not contribute so much unlike GCRs. The ambient dose equivalent due to the SEP event on 2003 exceeds 2 Sv on the lunar surface. It is clear, however, that an aluminum shield with a thickness of 10 g/cm2 effectively reduces the dose to 0.1% of total because the solar event has a soft energy spectrum. © 2009 The Physical Society of Japan.

Imaging of 7 rays with 1 ~ 5 MeV with a xenon time projection chamber (Xe-TPC) has been simulated with the GEANT4 code. The clear image of a 7-ray source was obtained using the Xe-TPC. The dependence of angular resolution and imaging efficiency on xenon density were also investigated over the density range from 0.06 to 0.18 g/cm3. It was found that a Xe-TPC is promising for imaging of high-energy 7-rays (~ 5 MeV) on planetary surface. © 2009 The Physical Society of Japan.

The observation of energetic particles trapped in the magnetosphere has made clear that narrow spikes of these particles as observed at L~1.6 are causally generated by the precipitation of particles trapped in the inner radiation belt. Furthermore, the occurrence frequency of these spikes is well correlated with the local time as coincident with the radio power transmitted from a VLF station located in west Australia, NWC. The results suggest that narrow spikes observed at L~1.6 are mainly caused by the radio power from VLF transmitter, NWC located in Australia. © 2009 The Physical Society of Japan.

The sun is quite variable in time. When the solar activity is numerated by counting sunspots in number, there exists a so-called eleven year periodicity on the relative sunspot numbers, although this periodicity varies from about 7 to 13 years. The total relative sunspot numbers for respective solar cycles have been increasing almost monotonically for more than 100 years since 1882. This long-term variation as seen on these numbers may have been causally associated with the decrease of the rotation speed at the equator of the sun which has been endured throughout those years since 1882. This long-term increase of the solar activity necessarily introduces its associated increase of the intensity of magnetic field originated from the sun in the inner heliosphere. The intensification of this field seems to strongly influence the behavior of galactic cosmic rays deep in the inner heliosphere and thus indirectly influences the sun - climate condition since the terrestrial climate may be highly dependent in the long-term decrease of the cosmic ray influx into the earth's atmosphere. © 2009 The Physical Society of Japan.

A large scale observation program of ultra heavy nuclei (Z&gt
30) in galactic cosmic rays (UH- GCRs) is planned with the use of solid-state track detectors (SSTD) such as CR-39 plastic and BP-1 glass on the International Space Station and on board long-duration balloon flights. The handling of SSTDs usually requires a large number of year x person to scan and analyze the etch pits produced on the detector. It is due to the manual or semi-automatic analysis using a conventional optical microscope system. We plan to use a cosmic ray telescope with a large exposure area of 20 m2 made of the SSTD stacks. Detector handling will be more difficult as compared with before. A major problem for such a large scale experiment is how to quickly and precisely analyze the etch pit obtained over a short period. We have developed a new microscope system, the HSP-1000, for high speed image acquisition that uses a line sensor camera in place of a traditional CCD camera. Continuous, automatic focusing of the microscope is achieved by means of an optical pick-up system that provides fast feedback for control of distance between the objective and the image surface. As a result of continuous stage motion and continuous focusing, we have attained image acquisition speeds that are 50 - 100 times faster than conventional CCD-based microscope systems. In this paper, we present the current status of developments of the high speed microscopic measurement system, fully automated plate changing system and estimations of analyzing time for large scale observations of ultra heavy nuclei. © 2009 The Physical Society of Japan.

The lunar surface is directly exposed to galactic cosmic rays (GCRs) and solar energetic particles (SEPs) because of the lack of atmosphere and magnetic field on the Moon. These charged particles successively interact with the lunar material and then produce secondary radiations as neutrons and gamma rays. The annual ambient dose equivalent on the lunar surface is estimated about 840 mSv/yr during the quiet period at the solar activity minimum. Particularly, GCR heavy component largely contributes by about 80% to the annual dose equivalents. The ambient dose equivalents of SEPs are also calculated for two transient solar particles events on October 28th in 2003 and January 20th 2005. The SEP protons take the largest contribution of about 90% to the dose, while the heavy components of SEPs do not contribute so much unlike GCRs. The ambient dose equivalent due to the SEP event on 2003 exceeds 2 Sv on the lunar surface. It is clear, however, that an aluminum shield with a thickness of 10 g/cm2 effectively reduces the dose to 0.1% of total because the solar event has a soft energy spectrum. © 2009 The Physical Society of Japan.

The Japanese lunar explorer SELENE was launched from Tanegashima Space Center on September 14, 2007. It consists of a main orbiter KAGUYA at 100 km altitude and two daughter satellites (relay satellite OKINA and VRAD satellite OUNA) with 14 scientific instruments. The high precision gamma-ray spectrometer (GRS) on KAGUYA measures 200 keV - 12 MeV gamma rays to determine the elemental composition of the lunar surface. The GRS is composed of a large Ge crystal as a main detector and massive bismuth germinate (BGO) crystals and a plastic scintillator as anticoincidence detectors. The Ge detector is cooled by a Stirling cryocooler below 90 K during the observation. After successful launch of the spacecraft and initial checkouts, the GRS started the nominal observation on December 21, 2007, and the temperatures and counting rates of the GRS were confirmed to be stable. Energy spectra of gamma rays with a good energy resolution are being obtained over the lunar surface, which will allow us to make global maps of the elemental abundances of the Moon soon. © 2009 The Physical Society of Japan.

The high precision gamma-ray spectrometer (GRS) is carried on the first Japan's large- scaled lunar explorer, SELENE (KAGUYA), successfully launched by the H-IIA rocket on Sep. 14, 2007. The GRS consists of a large Ge crystal as a main detector and massive bismuth germanate crystals and a plastic scintillator as anticoincidence detectors. After a series of initial health check of the GRS, it started a regular observation on December 21, 2007. Energy spectra including many clear peaks of major elements and trace elements on the lunar surface have been measured by the GRS. Global measurement of thorium counting rate on the lunar surface is presented. The region showing the highest count rate of thorium extends from Kepler to Fra Mauro region in the Procellarum. And Apennine Bench and Aristillus region and the northwestern region of Mare Imbrium are high in thorium count rate. Second high count rate region is located in the South Pole-Aitken basin of the farside. Arago and Compton/Belkovich craters are also enriched in thorium. The initial results observed by GRS during the period from Dec. 21, 2007 to Feb. 17, 2008 is reviewed. © 2009 The Physical Society of Japan.

The origin of galactic cosmic rays (GCRs) nuclei is still unknown. Precise observation of ultra heavy GCRs would be an important step in resolving their origin including the remaining problems in cosmic ray astrophysics. A program to observe UH nuclei in GCRs is proposed which involves the use of a high performance solid-state track detector on board a long-duration balloon. The program focuses measuring the elemental and isotopic compositions of UH nuclei up to the actinides. The observation of nuclear composition covers a wide range of scientific themes including studies of nucleosynthesis in cosmic ray sources, chemical evolution of galactic material, the characteristic time of cosmic rays, and heating and acceleration mechanisms of cosmic ray particles. © 2009 The Physical Society of Japan.

The temperature recorded immediately after hypervelocity collision of microparticles comprising iron and nickel with a silver-coated piezoelectric plate was analyzed using photomultipliers of different spectral response characteristics. The conversion rate between the velocity and temperature is estimated to be similar to 900 K/km/s in the velocity range of 10-40 km/s. This rate is greater than that reported earlier. c 2008 American Institute of Physics. [DOI: 10.1063/1.3013313]

A radiation detector composed of fourteen lead zirconate titanate (PZT) disks was studied by directly irradiating it using a 400 MeV/n xenon beam while changing the beam intensity and beam pulse duration. The results obtained indicated that the sensitivity of the detector per xenon ion was explicitly dependent on the beam pulse duration. Comparing the sensitivity among PZT detectors with one, fourteen and one hundred layers, it was also found that the sensitivity of the fourteen-layered detector was highest under the experimental conditions. (C) 2008 Elsevier B.V. All rights reserved.

Electron drift velocities in He-3 and He-4 gases were measured at 0.1 MPa and we compared the results ill He-3 and He-4 under the electric field strength normalized by the number density of helium gas, E/N, from 0.04 to 1.0 Td. This is the first experimental confirmation of the fact that the electron drift velocity in He-3 gas is larger than in He-4 gas. The difference in the electron drift velocities is attributed to the difference in the atomic masses of He-3 and He-4.

We have developed an automated scanning system for handling a large number of nuclear track etched detectors (NTEDs). The system consists of a magazine station for sample storage, a robotic sample loader, a high-speed wide-area digital imaging microscope device (modified HSP-1000) and PitFit software for analyzing etch pits. We investigated the performance of the system using CR-39 plastic NTED samples exposed to high-energy heavy ions and fast neutrons. When applying the system to fast neutron dosimetry, the typical scanning speed was about 100 samples/day with a scan area of 4 cm(2)/sample. The neutron doses obtained from a fully automatic measurement agreed closely with those from a semi-automatic measurement. These results indicate the feasibility of fully automatic scanning of CR-39 personal neutron dosimeters. The system is also expected to be applicable to future large-scale experiments using CR-39 plastic and BP-1 glass NTEDs for observing ultraheavy galactic cosmic rays with high mass resolution. (C) 2008 Elsevier B.V. All rights reserved.

A new method to trace heavy ion trajectories in a stack consisting of interleaved CR-39 plastic nuclear track detectors and target material layers was developed and tested for use in the measurement of projectile charge changing cross-sections of heavy ion fragmentation reactions. A high speed imaging microscope with sophisticated track analysis software was utilized to extract the charge information from multiple ion tracks belonging to a single fragmentation event. The systematic error of trajectory tracing was verified for the measurement system. In order to verify the validity of system, the projectile total charge changing cross-sections for Fe ions on carbon target was estimated and compared with previous experiments at initial beam energy of 1GeV/n. The result is in good agreement with results obtained by other investigators. This method allows precise and fast measurement of the projectile charge changing cross-section with higher statistics on a level compatible to that of silicon spectrometer measurements. (C) 2008 Elsevier Ltd. All rights reserved.

Observation of trans-iron nuclei in galactic cosmic rays (Z >= 30) requires a high performance cosmic ray detector telescope with a large exposure area because of their extremely low fluxes. A solid-state track detector such as CR-39 has the advantage of easy extension of exposure area, but it is necessary to raise the Z/beta detection threshold in order to suppress background tracks produced by galactic cosmic rays with Z/beta< 30. The track registration sensitivity and detection threshold for heavy ions with various Z*/beta were verified by using track detectors of copolymers of CR-39 and DAP (diallyl phthalate) with various DAP concentration. We found that it is possible to control the Z*/beta detection threshold of copolymers by changing DAP concentration. In order to detect heavy ions with Z*/beta >= 30. the optimum DAP concentration was found to be approximately 50%. (C) 2008 Elsevier Ltd. All rights reserved.

The high precision gamma-ray spectrometer (GRS) is scheduled to be launched on the lunar polar orbiter of the SELENE mission in 2007. The GRS consists of a large Ge crystal as it main detector and massive bismuth germanate crystals as an anticoincidence detector. A Stirling cryocooler was adopted in cooling the Ge detector. The flight model of SELENE GRS has been completed and an energy resolution of 3.0 keV (FWHM) at 1.332 MeV has been achieved. The spectrometer aims to observe nuclear line gamma rays emitted from the lunar surface in a wide energy range from 100 keV to 12 MeV for one year and more to obtain chemical composition on the entire lunar surface. The gamma-ray data enable us to study lunar geoscience problems including crust and mantle composition, and volatile reservoirs at polar regions. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

The propagation of transverse waves generated acoustically in a piezoelectric element by colliding it with hypervelocity microparticles was studied. The propagation times were measured by a set of multiple electrodes on the surface of the element. The coordinates that the particles struck were determined by combining the propagation times and the velocity of the waves. By using the position-sensitive element, significant deviations between the prior indicated and actually measured orbits were observed. The potential of the present element as part of a steering system is discussed. [DOI: 10.1143/JJAP.47.3772]

A cosmic dust detector for use onboard a satellite is currently being developed by using piezoelectric lead zirconate titanate (PZT). The characteristics of the PZT detector have been studied by bombarding it with hypervelocity iron (Fe) particles supplied by a Van de Graaff accelerator. One central electrode and four peripheral electrodes were placed on the front surface of the PZT detector to measure the impact positions of the incident Fe particles. It was demonstrated that the point of impact on the PZT detector could be identified by using information on the time at which the first peak of the output signal obtained from each electrode appeared. (C) 2008 American Institute of Physics.

Energy resolution measurements of ultraviolet-sensitive windowless silicon p-i-n photodiodes were carried out with alpha rays. A resolution of 12.6 keV in full width at half maximum for 5.486 MeV was achieved. The ultraviolet-sensitive silicon p-i-n photodiodes were found to be suitable to alpha-ray spectrometry.

The feasibility of using piezoelectric lead zirconate titanate (PZT) elements as a radiation detector was examined. We tried to observe the pressure wave excited by irradiating liquid ethanol (C2H5OH) with a 400 MeV/n xenon (Xe) beam using an array of PZT elements, while changing the position of beam irradiation. The elements were designed to obtain two independent electric signals in order to estimate the beam position in one direction on a two-dimensional plane. The time at which the peak of the output signal appeared differed between the two signals obtained from one element under limited experimental conditions. This suggests that the trajectory of the Xe beam may be determined in three-dimensional space with an improved array of the PZT elements. (C) 2007 Elsevier B.V. All rights reserved.

日本初の大型月探査衛星「かぐや」に搭載されたガンマ線分光計（GRS）は，これまでの月探査に比べて高いエネルギー分解能を有する．「かぐや」搭載GRSの最初の2ヶ月間の観測により，O，Mg，Al，Si，K，Ca，Ti，Fe，ThおよびU由来のガンマ線を検出することができた．これらの元素のうちK，ThおよびUについて月面ガンマ線強度分布地図を作成することができた．今後様々な補正を行なうことにより，月面濃度分布地図を作成する．

Ambient dose equivalent on the lunar surface is estimated as contribution from galactic cosmic rays, secondary neutrons and gamma rays from the lunar surface. Since the cosmic ray flux on the lunar surface varies with the phase of the solar activity, radiation doses on the surface are calculated of the three cases of this activity; the maximum, the minimum and the average. To estimate the doses of the secondary particles, Monte Carlo simulation library Geant4 is applied. As a result, total annual dose equivalent of about 225 mSv/yr on the lunar surface is expected during the quiet time of solar activity. The dose of neutrons and gamma rays reaches to 50 mSv/yr and 2 mSv/yr, respectively. In particular, fast neutrons have the largest contribution to the total neutron dose. The dependency of total neutron dose for mare and highland region of the Moon is small on the lunar surface as comparing with that for solar activity.

Fluxes of gamma rays emitted from the lunar surface consisting from ferroan anorthosite with various concentration of water (H2O) were calculated with Geant4. They are useful to the current and future lunar missions for the projects to search for the existence of water in the lunar polar regions with a gamma-ray spectrometer. The result thus obtained indicates that the flux of gamma-rays with 2223 keV due to the reactions H-1(n, gamma)D-2 has a monotonous dependence on the concentration of H2O from 0.1 to 20 wt% and the flux of 4934 keV gamma-rays due to the reactions Si-28(n, gamma)Si-29 is remarkably correlated with the abundance of H2O. The variation of these gamma-ray fluxes dependent on the concentration of H2O is also discussed with the neutron density profile in the lunar subsurface.

We are developing the CALorimetric Electron Telescope, CALET, mission for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. Major scientific objectives are to search for the nearby cosmic ray sources and dark matter by carrying out a precise measurement of the electrons in 1 GeV - 20 TeV and gamma rays in 20 MeV - several 10 TeV. CALET has a unique capability to observe electrons and gamma rays over 1 TeV since the hadron rejection power can be larger than 105 and the energy resolution better than a few % over 100 GeV. The detector consists of an imaging calorimeter with scintillating fibers and tungsten plates and a total absorption calorimeter with BGO scintillators. CALET has also a capability to measure cosmic ray H, He and heavy ions up to 1000 TeV. It also will have a function to monitor solar activity and gamma ray transients. The phase A study has started on a schedule of launch in 2013 by H-II Transfer Vehicle (HTV) for 5 year observation.

The CALorimetric Electron Telescope, CALET, is a new Space Observatory being developed for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. Major scientific objectives are to search for nearby cosmic ray sources and dark matter by carrying out a precise measurement of the electron spectrum from 10's of GeV - 10 TeV and of gamma rays in the range 20 MeV - several TeV. CALET has a unique capability to observe electrons and gamma-rays over 1 TeV, with a hadron rejection power better than 105 and an energy resolution of a few % beyond 100 GeV. Moreover, CALET will follow PAMELA, GLAST and other experiments and can both extend and refine the observations made by those missions. The main instrument, to be described, consists of an imaging calorimeter combined with a total absorption calorimeter. With auxiliary detectors, the CALET Observatory will also monitor solar activity and study gamma-ray bursts. The phase A/B study is underway for a proposed 2013 launch on the H-II Transfer Vehicle (HTV) for 3- 5 years of observation on JEM-EF.

A cosmic dust detector using piezoelectric lead zirconate titanate (PZT) is currently being developed for use onboard a spacecraft for the BepiColombo mission. The characteristics of the PZT detector were studied by carrying out hypervelocity impact measurements with iron particles supplied by a Van de Graaff accelerator. The measurements with particle velocities of less than 5 km/s showed a linear relationship between the output voltages obtained froth the detector and the particle momenta. This linear relationship obtained was almost independent

The detector characteristics of a pentagonal element were studied by colliding it with hypervelocity micro-particles. A charge-sensitive amplifier was developed for the element of its capacitance similar to 10 nF. The output amplitudes were expressed as a linear function of the momentum at collision. Empirical formulas obtained from on-ground experiments could be used for the calibration of the detector. The pentagonal element was potential to measure the momentum during collision from the output amplitude. A set of electrodes on the surface was used to confirm the measurement of the coordinates at collision. A possible application of this pentagonal element on a real-time dust detector was discussed. (C) 2008 Published by Elsevier Ltd on behalf of COSPAR.

On the lunar surface, every human being would be exposed to galactic cosmic rays (GCRs) and their secondary products such as gamma rays and neutrons. For the human activity on the lunar surface in the future, it is important to estimate the effect of these particles on radiation doses. The annual ambient dose equivalent on the lunar surface was estimated on the basis of the latest observational data of GCRs. It is found that the annual ambient dose equivalent amount to about 570 mSv/yr during the intermediate period between the maximum and the minimum phases of the solar activity. This amount of dose is mainly produced from primary components of GCRs heavier than proton and helium nuclei. The annual ambient dose equivalent due to iron nuclei during this period is about 130 mSv/yr, more than 20% of the total dose on the lunar surface. Moreover, the dose due to these neutrons among the secondary particles reaches 50 mSv/yr, suggesting that the dose due to neutrons must be considered from the viewpoint of the human activity on the lunar surface.

We obtained the properties of the gas amplification in pure Xe gas up to 1.0 MPa. It is found that the first Townsend ionization coefficient becomes larger in highly-purified Xe gas. The energy resolution slightly deteriorates with increasing gas pressure, but it is possible to make the gas pressure higher with keeping the energy resolution constant when the gas gain is under approximately 500. In the future work, we will attempt to improve the energy resolution of the Xe proportional counter. The energy resolution we obtained is worse compared with the limit of the energy resolution from statistics of the gas amplification process determined through the Fano factor and the parameter of the variance of gas amplification for one electron. Therefore, it remains possible of improving the energy resolution. Furthermore, we will study the properties of the gas amplification in pure Xe gas at the higher gas pressure. The study will furnish the basic data to develop the high-energy-resolution gamma-ray spectrometer at the energy of above 100 keV.

The high-precision gamma-ray spectrometer (GRS) on the lunar polar orbiter SELENE is designed to measure 200 keV-12 MeV gamma rays in order to determine elemental compositions of the lunar surface. The GRS consists of a large germanium (Ge) crystal as a main detector and a massive bismuth germanate crystal and a plastic scintillator as anticoincidence detectors. The Ge detector is cooled by a Stirling cryocooler with its compressor attached to a passive radiator facing the cold space. The cooling system maintains the Ge detector below 90 K during the observation. The flight model of the GRS has achieved an energy resolution of 3.0 keV (FWHM) at 1333 keV. Energy spectra obtained by the GRS will show sharp gamma-ray lines whose energies identify the elements and whose intensities determine the concentrations of the elements, permitting global mapping of the elemental abundances in the sub-surface of the Moon. The elemental maps obtained by the GRS with such high-energy resolution enable us to study lunar geoscience problems.

Assuming different abundances of the Apollo lunar soil samples and the average spectrum of galactic cosmic ray protons, energy spectra of neutrons and gamma rays and emission rates of gamma-ray lines from major elements have been estimated by using the reviewed Monte Carlo simulation library Geant4 and nuclear data. Previously, such libraries were not able to reproduce gamma-ray lines properly for the planetary application. Results clearly show that the emission rate of gamma rays heavily depends not only on the chemical abundance but also neutron flux within the lunar subsurface. While the intensities of gamma-ray lines are mostly proportional to elemental abundances, the intensity per unit elemental abundance can vary. Such a complex correlation is attributed to the change in neutron flux within the lunar subsurface and petrological restriction of elemental variation.

The capability of the CR-39 track detector for isotope identification was verified using Fe-56 and Fe-55 beams from the heavy ion accelerator HIMAC at NIRS. A CR-39 stack was exposed to 56Fe and 55Fe beams with the energies of 460 MeV/nucleon. Drastic improvements in the accuracies of microscopic image analysis and detector thickness measurement enabled us to identify those iron isotopes with high mass resolution using the CR-39 track detector. As a consequence of the reduction of systematic errors, the mass resolution for iron isotopes in the CR-39 detector was obtained to be 0.22 +/- 0.03 amu in ruts. The mass resolution newly obtained by the CR-39 detector was compared with the former result and found to be 66% better than the former value of mass resolution as a result of reducing the systematic errors of mass dispersion. Moreover, the ultimate mass resolution of the CR-39 detector was estimated by calculation using those experimental results. As a consequence of reducing the random error, it is expected that the mass resolution for iron isotopes can ultimately approach to similar to 0.10 amu in the CR-39 detector.

Radiation detectors composed of lead-zirconate-titanate (PZT) were studied by directly irradiating them with a 400 MeV/n xenon beam. Fourier analysis revealed that frequency components of the output signal obtained from the detectors explicitly depended on the beam pulse duration. The sensitivity of the multilayered detector was discussed in comparison with that of a single-layered detector. (c) 2007 Elsevier B.V. All rights reserved.

A pressure wave excited by irradiating liquid chloroform (CHCl3) with a 400 MeV/n xenon (Xe) beam was observed using a detector composed of piezoelectric lead-zirconate-titanate (PZT) elements. The acoustic signals were examined for various beam pulse durations. The amplitude obtained in the first cycle was inversely proportional to the beam pulse duration. It was also found that the time at which the peak in the first cycle appeared was dependent on the location at which each element was set. This suggests that the position at which the Xe beam stops in CHCl3 may be precisely determined with the PZT detector. (c) 2007 Elsevier B.V. All rights reserved.

New optical system with an optical displacement sensor has been developed to measure the local thickness of CR-39 track detector. It can be applied to measure locally the thicknesses of whole detector area for making a map of the amount of bulk etch. The accuracy of the thicknesses measurement was found to be +/- 0.2 mu m using CR-39 detector. This accuracy is one order of magnitude higher than that of conventional methods, such as the Micrometer method, and is comparable to that of track size measurement under the optical microscope. It will also greatly improve the charge and mass resolutions of CR-39 detector that we can apply to measure galactic cosmic rays (GCRs) nuclei, especially the trans-iron nuclei (Z >= 30) in GCRs. (c) 2007 Elsevier B.V. All rights reserved.

The characteristics of piezoelectric lead-zirconate-titan ate (PZT) detectors were studied by directly irradiating them with a 400MeV/n Xe beam. The sensitivity of a multilayered detector was discussed in comparison with that of a monolayered detector. It was found that the sensitivity of the detectors depended on their structure.

Acoustic signals were observed with a lead-zirconate-titanate (PZT) element. that was directly irradiated with a 368 MeV/n xenon beam. Using an array comprising PZT elements, the energy loss in the PZT was studied. These elements are sensitive to an energy deposit of 100 nJ. A series of values of output voltage vs. integrated thickness of PZT was represented along a line similar to the ionization loss calculated by the Bethe-Bloch formula. The induced voltage was attributed to several processes-ionization, thermal, elastic, and piezoelectric processes. This study describes the possible applications of the PZT element as an active medium for calorimeters and a monitor for hypervelocity impact of space dust. (c) 2006 Elsevier B.V. All rights reserved.

We have obtained the ratio of the transverse diffusion coefficient to the mobility of electrons multiplied by the elementary charge, in Xe and Xe + H-2 under electric fields at a higher pressure of 1 MPa in comparison with those in preceding experiments. The results show that the density effect (nonlinear effect) of the ratio in both pure Xe and Xe + H-2 is <= 15% below 1 MPa over the reduced electric field range from 0.08 to 0.6 x 10(-17) V cm(2). We also found that the diffusion of an electron swarm is suppressed by adding trace amount of hydrogen to high-pressure xenon gas. We discuss the application of Xe + H-2 gas to a new gamma-ray camera.

The scintillation response to an alpha source (Am-241) and the ionization yield in pure gaseous xenon and its mixtures with 0.2-2% of methane were measured at a pressure of 26 atm and different values of reduced electric field E/N. Both light and ionization yields in xenon were shown to decrease with increasing percentage of methane.

Bombardment experiments with thick targets made of each of Al and Fe were performed using 230 MeV/nucleon helium and 210 MeV proton beams. The energies and intensities of prompt gamma rays emitted by inelastic nuclear scattering of energetic neutrons were measured by a high-purity Ge detector. This work presents the first experimental results concerning the emission of prompt gamma rays from thick targets anticipated by helium component in galactic cosmic rays, since no foregoing work related to this one has been done. It is concluded that helium has the capability of prompt gamma ray line emission through the inelastic nuclear reaction of neutrons with target material by a factor of 3.5 on average in comparison with proton. As regards the lunar and planetary nuclear spectroscopy, a consideration is given on the role of helium particles to the total production of gamma rays emitted from a planetary surface.

The acoustic signals generated by bombarding 400 MeV/n xenon ions in water were studied using an array of piezoelectric lead-zirconate-titanate elements. The observed signal was reduced to a bipolar form through Fourier analysis. The output voltage corresponded to the amount of energy deposit in water, and it tailed off beyond the range of 400 MeV/n xenon in water. This magnitude was explained qualitatively as cumulative processes. Its behavior was consistent with the calculations based on the Bethe-Bloch formula. Possible applications of this detector to radiology and heavily doped radiation detectors are described. (c) 2006 Elsevier B.V. All rights reserved.

Using Geant4 Monte Carlo simulation code, background gamma rays for Gamma Ray Spectrometer onboard SELENE were estimated. Gamma ray emissions from the spacecraft body by leakage neutrons from the Moon and GCR protons were calculated as well as ones from the Moon. It is found that a BGO background reduction system works so well that the background gamma rays produced from the spacecraft body is small in the energy spectrum to be observed by the spectrometer in SELENE.

A comparison between the abundances of major elements on the Moon determined by Lunar Prospector gamma ray spectrometer and those in returned lunar samples is performed. Lunar Prospector shows higher Mg and Al content and lower Si content in western maria in comparison with the lunar sample collection. Lunar Prospector overestimated the Mg content by about 20%. There are no elemental anomalies at the lunar poles: this is additional evidence for the presence of polar lunar hydrogen. Using Mg, Fe, and Al abundances, petrologic maps containing information about the abundances of ferroan anorthosites, mare basalts, and Mg-rich rocks are derived. This approach is useful for searching for cryptomaria and Mg-rich rocks deposits on the lunar surface. A search is implemented for rare rock types (dunites and pyroclastic deposits). Ca-rich, Al-low small-area anomalies are detected in the far side highlands. (C) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

The SELENE-B, a lunar landing mission, has been studied in Japan, where a scientific investigation plan is proposed using a robotic rover and a static lander. The main theme to be investigated is to clarify the lunar origin and evolution, especially for early crustal formation process probably from the ancient magma ocean. The highest priority is placed on a direct in situ geology at a crater central peak, "a window to the interior", where subcrustal materials are exposed and directly accessed without drilling. As a preliminary study was introduced by Sasaki et al. [Sasaki, S., Kubota, T., Okada, T. et al, Scientific exploration of lunar surface using a rover in Japanse future lunar mission. Adv. Space Res. 30, 1921-1926, 2002.], the rover and lander are jointly used, where detailed analyses of the samples collected by the rover are conducted at the lander. Primary scientific instruments are a multi-band stereo imager, a gamma-ray spectrometer, and a sampling tool on the rover, and a multi-spectral telescopic imager, a sampling system, and a sample analysis package with an X-ray spectrometer/diffractometer, a multi-band microscope as well as a sample cleaning and grinding device on the lander. (C) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

The isotope identification with the solid-state track detector (SSTD) newly developed for the observation of heavy cosmic ray particles was performed using Fe-56 and Fe-55 ions with 460 MeV/nucleon. Mass resolution for iron isotope was thus improved to similar to 0.20 amu in rms. The high speed automatic system of microscope analyzer was also developed to scan and analyze tracks formed by heavy ions in SSTD. The combination of isotope telescope consisting of SSTD with the high speed scanning system enables us to realize a large-scaled observation for trans-iron galactic cosmic rays (GCRs).

A new gamma-ray imaging camera based on High-pressure Xe Time-Projection-Chamber (HPXe-TPC) allows us to simultaneously determine arrival direction and its energy of individual incident gamma rays. HPXe-TPC is a promising y-ray detector for planetary science which provides means of global mapping of elemental composition in planetary surface as the remote sensing spectrometer. The simulation study by Geant4 and numerical calculation show that the angular resolution is mostly affected by multiple scattering of the recoil electron, and position resolution of electrodes of TPC. It is found that the angular resolution is 9 degrees (50%) at 2 MeV for gamma rays. The feasibility of HPXe-TPC is discussed as a y-ray imaging camera for future planetary mission. (C) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

We summarize the present R&D status of high-pressure xenon time projection chamber (HPXe-TPC) which is a new gamma-ray camera for planetary science mission.

A precise measurement of elemental abundances of galactic cosmic rays from charges Z = 20 to 34 was made by TIGER balloon experiment. Using the various path lengths in the atmosphere between 4 and 16 g/cm(2) from the TIGER flight data, we derived the attenuation length of iron nuclei with the energy above 2.5 GeV/n in the atmosphere. As the result, we obtained the attenuation length of 15.5 +/- 0.6 g/cm(2) which is consistent with previous results of balloon measurements.

The helium isotopes were observed by Heavy Ion Telescope (HIT) onboard the TSUBASA satellite from March, 2002 to September, 2003 in the geostationary transfer orbit The mass resolution of the HIT instrument is similar to 0.25 amu in energy range 20 divided by 43 MeV/nucleon for helium isotopes. Helium data in the quiet periods were analyzed to obtain the spatial and temporal variation of fluxes of helium isotopes, He-3 and He-4. From this analysis, the enhancement of He-3 flux as compared with He-4 one in low L-value was found. Both of the helium fluxes strongly fluctuated in their L-distributions in each period.

We analyze preliminary Lunar Prospector gamma-ray spectrometer data. Al-Mg and Fe-Mg petrologic maps of the Moon show that Mg-rich rocks are located in Mare Frigoris, the South Pole Aitken basin, and in some cryptomaria. Analysis of distances of Lunar Prospector pixels from three end-member plane in Mg-Al-Fe space reveals existence of Ca-rich, Al-low small-area anomalies in the farside highlands. An Mg-Th-Fe petrologic technique can be used for estimation of abundances of ferroan anorthosites, mare basalts, KREEP basalts, and Mg-rich rocks. (c) 2005 Elsevier Ltd. All rights reserved.

The gamma-ray spectrometer (GRS) of Japanese lunar polar orbiter SELENE uses a Ge detector for the first time on a lunar mission. This spectrometer will observe lunar gamma rays for I year or more to determine chemical composition over the entire lunar surface. For cooling the Ge detector, we adopted a Stirling cryocooler. The SELENE GRS flight model was completed and an energy resolution of 3.0 keV (FWHM) at 1.33 MeV was achieved. This paper describes the details of the detector-cryogenic system and its performance. (c) 2005 Elsevier B.V. All rights reserved.

Ferroelectric lead zirconate titanate (PZT) elements were studied by directly bombarding them with hypervelocity silver particles. The mass and velocity of these hypervelocity silver particles ranged from 1 to 80 pg and 2 to 6 km/s, respectively. This report examines the pulsed signals observed immediately after collision. The first cycle of the pulse is discussed because the information on impact is presumably recorded on the wave form. The experimental data were analyzed using the wave form that was generated immediately after collision. Consequently, the following conclusions were made: (1) the sensitivity of the element is independent of the thickness of element, (2) the pulse height is proportional to the particle momentum over the measured range, and (3) the wave form is not explicitly related to the velocity of the particles at the time of collision. The potential of a single PZT element acts as a real-time detector for hypervelocity microparticles is discussed. (c) 2005 American Institute of Physics.

Referring to the observed results on the source composition of galactic cosmic rays, a possible mechanism for the formation of this composition is proposed by taking into account the fractionation of elements in dust grains formed in the interstellar molecular clouds. These dust grains become enriched with the elements whose condensation temperature is higher than about 1000K. Most of these nuclei enhanced in the source composition axe identified as heavy and ultra-heavy ones, which must have been synthesized in the r-process initiated with the explosions of type II supernovae in the OB-association. The dust grains in the superbubble are later ionized and then accelerated through their interactions with shock waves of supershell formed from multiple explosions of nearby supernovae. This may mean that cosmic rays axe significantly generated from the dust grains drifting in the local interstellar space.

A response from piezoelectric lead-zirconate-titanate elements was investigated by bombarding them with hypervelocity iron particles. The observed signal form was clearly dependent on the particle velocity during collisions. The signal form exhibited oscillations for particle velocities less than 6 km/s, whereas it changed drastically into a solitary pulse above 20 km/s. This behavior was exclusively classified based on the velocity. The rise time of the solitary pulse in the output form had a good correlation with the velocity at impact. The change in the form was discussed in terms of elastic and plastic states by regarding Young's modulus as a criterion between both states. It is proposed that a single piezoelectric element has the potential to detect the velocity of particles in space. (c) 2005 American Institute of Physics.

Hypervelocity collisions of microparticles with a lead-zirconate-titanate piezoelectric element are examined. The waveforms thus obtained depend on the velocities during collision, and are classified into three categories. In particular, the first cycle of the signal observed immediately after collision is essential to obtain information on the impact. In each category, experimental formulas that are functions of the impact velocity are established based on experimental data. It is concluded that a single piezoelectric element can potentially measure the velocity and/or momentum of hypervelocity microparticles in real time. In the abovementioned context, the new dust detectors are described.

Piezoelectric lead-zirconate-titanate (PZT) elements were Studied by directly bombarding hypervelocity silver and iron particles in the velocity range of 2-63 km/s. This report focuses on the concept of "immediately after collision". This concept was realized in the leading part of a pulsed signal that exhibited no effects due to reflection. The signal form was discussed from the viewpoint that information on impact was recorded by the waveform. The results indicated that the output amplitude was independent of the thickness of a PZT element, and that the waveform was explicitly related to the velocity at collision. Further, it appeared as an oscillating form at velocities less than 6 km/s. As the velocity increased, it gradually changed to a solitary pulse. The rise time of the single solitary waveform was linearly related to velocities above 6 km/s. The potential of a single PZT element is discussed as a real-time detector for hypervelocity microparticles. (c) 2005 Published by Elsevier Ltd on behalf of COSPAR.

We have verified the capability of a CR-39 track detector for isotope identification using iron beam from the heavy-ion accelerator of HIMAC at NIRS. The same CR-39 stack was independently exposed to Fe-56 and Fe-55 ions with an energy of 460 MeV/nucleon. Mass resolutions for Fe-56 and Fe-55 ions were determined to be 0.28 +/- 0.12 amu and 0.28 +/- 0.11 amu in rms, respectively. A detailed analysis of the sources of the mass dispersion in the present mass identification experiment showed that significant errors were caused in the measurements of the surface position and the thickness of CR-39 sheets. By eliminating these errors as much as possible, the mass resolution is expected to be improved to similar to0.20 amu.

Scintillation and ionization yields in xenon gas for 5.49 MeV alpha-particles were measured in the range of pressure from 0.35 to 3.7 MPa and the electric field strength (E) over the number density of xenon atoms (N), E/N from 0 to 5 x 10(-18) V cm(2). When our data are normalized at the data point measured by Saito et a]., the number of scintillation photons is 2.3 x 10(5) while the number of ionization electrons is 2.0 x 10(5) at 2.6 MPa and at 3.7 x 10(-18) V cm(2). The scintillation and ionization yields of xenon doped with 0.2% hydrogen, High-Pressure Xenon gas[H-2-0.2%], at 2.6 MPa was also measured. Scintillation yield of the Xe-H-2 mixture gas is 80% as high as that of pure xenon. It is found that the scintillation yield is luminous enough to generate a trigger pulse of the high-pressure xenon time projection chamber, which is expected as a promising MeV Compton gamma-ray camera. (C) 2004 Elsevier B.V. All rights reserved.

We constructed a parallel plate drift chamber for measuring the ratio of the transverse diffusion coefficient D, to the mobility It of electrons multiplied by the elementary charge e, eD(t)/mu, which is called the transverse characteristic energy, in high-pressure xenon gas. The characteristic energies of electrons in Xe were obtained at a high pressure of 1.0MPa and the reduced electric field, E/N, from 0.77 to 7.7 x 10(-18) V-cm 2, where E denotes an electric field and N the number density of Xe atoms. At the same E/N, our results agreed well with the data at pressures from 107 to 193 kPa previously obtained by Koizumi et al. [J. Phys. B 19 (1986) 2331]. The characteristic energies of electrons in Xe were found to be constant as a function of E/N from a low pressure to 1.0 MPa.

High-pressure xenon time projection chamber (HPXe-TPC) is a sophisticated detector, which can determine not only an energy of gamma ray but also its arrival direction by using Compton scattering. Diffusion of electrons and scintillation yield in Xe and Xe+H2 mixture have been investigated to realize a HPXe-TPC. The transverse characteristic energy of electrons in Xe+H2 mixture (H2 0.44%) was reduced to about 40% against that of pure Xe at 1.0 MPa. Scintillation yields by alpha-particles ( 241Am) in Xe+H2 mixture (H2 0.23-5.7%) at 2.6 MPa were obtained as a function of E/N. The scintillation yields in Xe+H 2 mixture at 2.6 MPa and at E/N =0.3×10-17Vcm 2 were luminous enough to generate a trigger signal of a HPXe-TPC. It is found that doping hydrogen into xenon is effective to prevent the degradation of angular resolution of a HPXe-TPC. © 2004 IEEE.

Scintillation light and formation yields in pure xenon and xenon doped with various concentration of methane (0.2-2%) have been measured as a function of the reduced electric field (E/N) from 0 to 4×10-18Vcm 2 at a pressure of 2.6 MPa. The measurements of photons and electrons have been made in gaseous xenon excited by 241Am alpha particles. High purity xenon was used to fill a high-pressure xenon chamber equipped with MgF2 window coupled to a photomultiplier tube (PMT). The scintillation light in xenon-methane mixture is observed to decrease as the concentration of methane increases. © 2004 IEEE.

High-pressure xenon time projection chamber (HPXe-TPC) is a sophisticated detector, which can determine not only an energy of gamma ray but also its arrival direction by using Compton scattering. Diffusion of electrons and scintillation yield in Xe and Xe+H-2 mixture have been investigated to realize a HPXe-TPC. The transverse characteristic energy of electrons in Xe+H-2 mixture (H-2 0.44%) was reduced to about 40% against that of pure Xe at 1.0 MPa. Scintillation yields by alpha-particles (Am-241) in Xe+H-2 mixture (H-2 0.23 similar to 5.7%) at 2.6 MPa were obtained as a function of E/N. The scintillation yields in Xe+H-2 mixture at 2.6 MPa and at E/N =0.3 x 10(-17) Vcm(2) were luminous enough to generate a trigger signal of a HPXe-TPC. It is found that doping hydrogen into xenon is effective to prevent the degradation of angular resolution of a HPXe-TPC.

Scintillation light and ionization yields in pure xenon and xenon doped with various concentration of methane (0.2-2%) have been measured as a function of the reduced electric field (E/N) from 0 to 4x10(-18)Vcm(2) at a pressure of 2.6 MPa. The measurements of photons and electrons have been made in gaseous xenon excited by Am-241 alpha particles. High purity xenon was used to fill a high-pressure xenon chamber equipped with MgF2 window coupled to a photomultiplier tube (PMT). The scintillation light in xenon-methane mixture is observed to decrease as the concentration of methane increases.

Piezoelectric lead-zirconate-titanate was studied by bombarding with silver particles in the mass range from 2 to 100 pg, and the velocity range from 2 to 8 km/s. Output signals were uniquely identified on impact. It was found that incident energies above 100 nJ were measured unambiguously by a single lead-zirconate-titanate element. The detector characteristics were studied with respect to incident particle energy, angular dependence and size effects. Even though we have still unknown processes inherent in this detection method, the piezoelectric element has a potential as a real-time detector, if it is well calibrated. (C) 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

Results of observations of the Moon at 3.6 cm at Kashima (Japan) and at 6.2 cm and 3.56 cm at Simeiz (Ukraine) are presented. There is no evidence of the influence of the Leonid meteor shower on the lunar radio flux. The search for impact-produced radio flashes was also unsuccessful. Future study of seismic activity of the Moon by Lunar-A and Selene spacecrafts is discussed.

A lead-zirconate-titanate (PZT) element was studied by bombarding silver particles in the mass range from I to 100 pg, and the velocity from 2 to 6 km/s. Output signals were uniquely identified on impact and characterized by Fourier analysis. It was found that incident energies above 100 nJ were uniquely determined by a single PZT element. We discussed its potential as a real-time detector for space dust and debris.

Characteristics of lead-zirconate-titanate (PZT) elements were studied by directly irradiating them with a 400 MeV/n Xe beam. The elements were sensitive to 10(4) Xe ions and their output amplitudes were proportional to the beam intensity. An ensemble of those output amplitudes displayed a Bragg-curve-like response towards the range of 400 MeV/n Xe ion. We discuss the potential of PZT elements as a radiation detector and their application to high-intensity and high-energy detectors.

次世代の月惑星着陸探査をになうピンポイント軟着陸や自律制御ローバ技術などの実証を目指して、月着陸実験セレーネB計画が工学試験ミッションとして提案されているが、月クレータの中央丘に露出する深部物質を採取し、その場で分析する地質探査が検討されている。本報告ではその観測機器候補の検討について述べる。このミッションではランダからの分光撮像やローバでの多色撮像で路頭の特徴を調べ、また採取試料の選定を行う。ガンマ線分光により、ローバ走行経路に沿った放射線元素濃度の分布を調査する。採取した試料を顕微撮像やＸ線蛍光・回折等の分析を行うが、表面に付着した塵の除去や切断、研削を行うことで試料内部の組織まで調べることを目標にする。観測機器のシステム構成案についても考察した結果を述べる。

The presence of volatiles near the lunar poles is considered. The chemical composition of a lunar atmosphere temporarily produced by comet impact is analyzed during the day and night. C-rich and long-period comets are insufficient sources of water ice on the Moon. O-rich short-period comets deliver significant amounts of H2O, CO2, SO2, and S to the Moon. An observable amount of polar hydrogen can be delivered to the Moon by a single impact of an O-rich short-period comet with diameter of 5 km in the form of water ice. The areas where CO2 and SO2 ices are stable against a thermal sublimation are estimated to be 300 and 1500 km2, respectively. If water ice exists in the 2cm top regolith layer, CO2 and SO2 ices can be stable in the coldest parts of permanently shaded craters. The delivery rate of elemental sulfur near the poles is estimated to be 106 g yr-1. The sulfur content is estimated to be as high as 1 wt % in the polar regions. The SELENE gamma-ray spectrometer can detect sulfur polar caps on the Moon if the sulfur content is higher than 1 wt %. This instrument can check the presence of hydrogen and minerals with the unusual chemical composition at the lunar poles.

Piezoelectric PZT elements were studied by directly irradiating a 400 MeV/n Xe beam. The elements were sensitive to the number of 10(4) Xe ions and their output amplitudes were proportional to the beam intensity, that is, the total energy deposited within the element. An ensemble of the output amplitudes behaved like the Bragg curve towards the end of the range. We discuss its potential as a radiation detector and its application to high intensity and high energy detectors.

Drift velocities of electrons in a mixture of Xe (20 atm)-He (3 atm) were measured using a cylindrical high-pressure xenon chamber. The drift velocities were found to be greater than 3 x 10(5) cm/s above the reduced electric field of 2.0 x 10(-18) V.cm(2) at room temperature, which are close to those in Xe-H-2 (0.3%). The mixture of He gas into high-pressure xenon improved the resolving time of detectors because it increased the electron drift velocities. This implies that a high-pressure xenon chamber mixed with He-3 instead of He gas operates as a gamma-ray detector sensitive to thermal neutrons.

To help understand planetary gamma-ray spectra, the energies and intensities of gamma rays produced by energetic particles interacting in thick targets were simulated experimentally and numerically. Using the accelerator at RIKEN, thick targets of iron, granite, and gabbro were exposed to 180 or 210 MeV proton beam, and characteristic gamma rays emitted from the targets were measured by Ge detectors. The experimental results were compared with the values calculated by Geant4. The relative intensities of gamma-ray lines from the iron target in the experiment were consistent with those in the calculation within the error of similar to5%. As for stone targets, strong inconsistencies were observed. Further improvement in the calculation code and cross section files, as well as experimental resemblance to space missions are indispensable for gamma-ray spectroscopy. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

The electron and ion spectrometer (EIS) is one of the fourteen instruments onboard the Nozomi spacecraft, a Mars orbiter, launched on July 4, 1998. EIS consists of two kinds of telescopes (TOF-E and DeltaE-E telescopes) designed to measure the fluxes of electrons and ions in the energy range from similar to40 keV to a few MeV. The DeltaE-E telescopes are used to measure electrons and protons, while the TOF-E telescope is mainly used to measure He, CNO-group, NeMgSi-group, and Fe-group. In this paper, (a) the objectives of this experiment, (b) the details of the instrument and (c) initial results of the observation in interplanetary space are described. (C) 2001 Elsevier Science B.V. All rights reserved.

The electron and ion spectrometer (EIS) is one of the fourteen instruments onboard the Nozomi spacecraft, a Mars orbiter, launched on July 4, 1998. EIS consists of two kinds of telescopes (TOF-E and DeltaE-E telescopes) designed to measure the fluxes of electrons and ions in the energy range from similar to40 keV to a few MeV. The DeltaE-E telescopes are used to measure electrons and protons, while the TOF-E telescope is mainly used to measure He, CNO-group, NeMgSi-group, and Fe-group. In this paper, (a) the objectives of this experiment, (b) the details of the instrument and (c) initial results of the observation in interplanetary space are described. (C) 2001 Elsevier Science B.V. All rights reserved.

Detector characteristics of disk-shaped piezoceramic elements were studied by irradiating silver and carbon microparticles. A mass of particles ranged from 0.01 to 100pg, and whose velocity from 2 to 20km/s. We observed characteristic pulse signals when the particles were collided with the element. Carbon projectiles generated a bipolar-type sharp peak, whereas silver projectiles did not show such a distinct form. For silver, the pulse amplitude increased with increasing the particle energy. A possible application to a realtime detector of micrometeoroid and space debris is discussed.

The electron and ion spectrometer (EIS) is one of the fourteen instruments onboard the Nozomi spacecraft, a Mars orbiter, launched on July 4, 1998. EIS consists of two kinds of telescopes (TOF E and ΔE E telescopes) designed to measure the fluxes of electrons and ions in the energy range from ∼40 keV to a few MeV. The ΔE-E telescopes are used to measure electrons and protons, while the TOF-E telescope is mainly used to measure He, CNO-group, NeMgSi-group, and Fe-group. In this paper, (a) the objectives of this experiment, (b) the details of the instrument and (c) initial results of the observation in interplanetary space are described. © 2001 Elsevier Science B.V. All rights reserved.

The Japanese lunar polar orbiter SELENE carries a gamma-ray spectrometer which uses a high-purity Ge detector cooled to 80-90 K by a Stirling mechanical cooler. The Gamma-Ray Spectrometer (GRS) consists of a large volume n-type Ge detector (252 cc) as the main detector and bismuth-germanate (BGO) and plastic scintillators as an active shielding. The engineering model still maintains excellent energy resolution even after severe vibration testing. The Gamma-Ray Spectrometer will globally map of the Moon for the major elements of O, Mg, Al, Si, Ti, Fe, etc. and natural radioisotopes of K, Th and U with a high precision. The energy resolution of the GRS is such that it would identify prompt gamma-ray line from hydrogen and the location and the amount of ice, if it exists at the polar regions. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Storm-related magnetospheric oxygen bursts were observed in the dayside magnetosheath during the coronal mass ejection on January 10, 1997. These singly charged oxygen ion events exhibited a clear antisunward flow. The oxygen ions are associated with a strong negative interplanetary magnetosheath field (IMF). The average B-z was almost - 50 nT, and the field projection in the x - y plane (GSE) was nearly constant in the Sun/dawn sector forming an angle of 45 degrees relative to the Earth-Sun axis. The magnetopause was identified as a rotational discontinuity by using the principal axis analysis (PAA) method. The three-dimensional polar versus azimuthal angle distribution of the oxygen ions showed that the oxygen flow has a north to south velocity component. The observations suggest that the dayside reconnection process is generally steady. The energy dispersion can be explained with the time-of-flight (TOF) effect assuming oxygen ions are escaping from the magnetosphere along the reconnected field lines. The lack of hydrogen and helium ions during the observed oxygen bursts can be explained, as only oxygen ions are resupplied by the gradient drift in the inner magnetosphere because of their larger bounce periods with respect to hydrogen and helium ions. Therefore only oxygen ions are observed continuously in the magnetosheath. The estimated oxygen escape rate amounts to 0.61 x 10(23) ions/s, about 33% of the input rate of the ring current. The observations imply that the stormtime ring current is asymmetric. A large amount of ring current oxygen ions escape from the magnetosphere into the magnetosheath.

Five large events of solar energetic particles (SEP) during three years from 1993 to 1995 have been observed by high energy particle (HEP) instruments onboard GEOTAIL spacecraft. The composition of energetic ions, their energy spectra and time profiles of ion intensity were measured for the SEP events. Three SEP events observed on Feb. 15, 1993, Mar. 4, 1993 and Oct. 20, 1994, are enriched in Fe ions (> 10 MeV/n). The enhancement of Fe ions was observed at the onset time of SEP events (Mar. 4, 1993 and Oct. 20, 1994). The onset of the SEP events seems to have a feature with "impulsive" and "gradual" characteristics. This indicates a mixture of different seed populations and acceleration processes operating in these events.

A scintillating fiber camera for three-dimensional imaging was newly developed for radiation dosimetry in spacecraft. The camera consists of a scintillating fiber stack, an image intensifier unit and photomultipliers for triggering events. The scintillating fiber stack has 100 scintillating fiber layers. The layers are alternatively stacked up to be perpendicular to each other. The stack is coupled to a two-stage image intensifier and then coupled to a CCD camera for the track readout. Each fiber layer consists of 100 scintillating fibers and the fiber stack composed of 100 layers leads us to a sensitive volume of 50×50×50 mm3. Each fiber has a cross-section of 0.5×0.5 mm2. It is found that the camera has the capability to clearly identify charged particles, neutrons and γ-rays by observing individual three-dimensional images of those tracks. The threshold energy for identification of neutrons and γ-rays is 5-10 MeV for recoil proton energy when the coincidence signals from 2 photomultipliers are used as triggers and is expected to be 2-3 MeV when the triggers from either photomultiplier are used. The whole energy region for neutron dosimetry will be covered by the combination with the Bonner spheres for the energy region lower than approximately 10 MeV.

The Gamma Ray Spectrometer (GRS) will be onboard the Japanese lunar polar orbiter SELENE, to be launched in 2004, to obtain the information of element abundance on the entire lunar surface. GRS consists of a high-purity Ge detector as a main detector, which is an n-type Ge crystal with a high detection efficiency of 60 % encapsulated in an aluminum canister. In addition, BGO and plastic scintillators are employed for an anti-coincidence shield and for suppression of Compton photons and energetic ion backgrounds. GRS will be the first gamma ray spectrometer employing a Ge detector for the lunar mission. GRS adopted a Stirling cycle refrigerator, whose cooling capacity is 2.0 W at 80 K. The mechanical vibration from the cryosystem to the Ge detector is effectively reduced by the dual opposed pistons in the compressor and the flexible thermo-coupling link between the two components. An excellent energy resolution of &lt
3 keV at 1.33 MeV has been achieved in the prototype- model of GRS.

We have investigated the relationship between solar wind speeds and the energetic proton intensity associated with corotating interaction regions (CIR) observed at 1 AU during 1973 - 1995 using NSSDC Data. The speed-difference between the high-speed solar wind and the slow-speed solar wind, which forms CIR at outer heliosphere, shows a good correlation with the peak intensity of 1 - 2 MeV protons during the solar quiet periods. The speed-difference is probably related to the shock strength of the reverse shock of the CIR formed beyond - 1 AU. We have also found the solar activity dependence of the correlation between these quantities in CIR events during the period between 1973 and 1995. The intensity of CIR particles during the solar active periods is higher than that during the quiet periods, suggesting that the density of seed particles in CIR events during the solar active periods is larger than that during the solar quiet period. (C) 2000 COSPAR. Published by Elsevier Science Ltd.

The development of Gamma-Ray Spectrometer (GRS) is reviewed. Japanese lunar polar orbiter SELENE carries Gamma-Ray Spectrometer (GRS) which uses a high purity Ge detector cooled down to 80-90 K by a Stirling mechanical cooler for the first time in the lunar mission. GRS consists of n-type Ge detector as a main detector and EGO and plastic scintillators as an active shielding detector. The 250 cc Ge-detector is encapsulated in the aluminum canister. Its excellent energy resolution (< 3 keV in fwhm for K-40 gamma-ray line) is attained for engineering model even after severe vibration tests were made. GRS will provide the global mapping for major elements of O, Mg, Al, Si, Ti, Fe, etc. and natural radioactive elements of K, Th and U with a high precision. GRS has such an excellent energy resolution that it would identify prompt gamma-ray line from hydrogen, if there exists water ice at the surface of the lunar polar regions.

The existence of water ice at polar regions of the Moon is important not only in scientific interests but also utilizing lunar resource for the future exploration. The Clementine over the Moon reported the signature of lunar ice deposited in permanently shaded regions in the South Pole region. Recently, the neutron spectrometer onboard Lunar Prospector found dips in counting rate of epi-thermal neutrons corresponding to polar regions, which indicates the presence of water ice with high probability. However, after the one and half year mission of Lunar Prospector, the controlled crash of the spacecraft into a crater of the south pole region showed no observable signature of water ice. Gamma-Ray Spectrometer (GRS) with high sensitivity and energy resolution will be bearded on the Japanese lunar orbiter SELENE. It has an sufficient capability to detect the prompt gamma-ray line from hydrogen of water ice between the strong peaks of Si and Al lines. The GRS would make the first time detection of water ice deposited at lunar poles, and determine the locations and the amount of water ice on the surface, if it is exposed at polar regions of the Moon.

A new type of Real-time Radiation Monitoring Device, RRMD-III, consisting of three double-sided silicon strip detectors (DSSDs) has been constructed and used onboard the Space Shuttle mission STS-84. The Space Shuttle cruised at an altitude of 300-400 km and an inclination angle of 51.6 degrees for 221.3 h. RRMD-III succeeded in measuring the linear energy transfer (LET) distribution over the range of 0.2-600 keV/mu m for 178 h. The obtained LET distribution of particles was investigated in detail by classifying it into galactic cosmic ray (GCR) particles and trapped protons in the South Atlantic Anomaly (SAA region. The result shows that GCR particles contribute 60% to the total dose equivalent. The total absorbed dose rate during the mission was 0.516 mGy/day, the effective quality factor was 1.81 by ICRP-Pub.26, and the dose equivalent rate was 0.935 mSv/day. The average absorbed dose rates are 0.120 mu Gy/min for GCR particles and 4.80 mu Gy/min for trapped protons. The effective quality factors are 3.16 for GCR particles and 1.19 for trapped protons. RRMD-III data were also compared with the data of the tissue equivalent proportional counter (TEPC), proving that RRMD-III is a reliable device for deriving the true-LET distribution in real time for evaluating space radiation. (C) 1999 Elsevier Science B.V. All rights reserved.

The measurement of the directional distribution of incident particles was made by using the Realtime Radiation Monitoring Device (RRMD)-III placed inside the Space Shuttle STS-84 cruised at an altitude of 400 km and an inclination angle of 51.6 degrees, which are the same as the cruising orbit of the International Space Station (ISS). The directional distributions of incident particles were evaluated over the observed linear energy transfer (LET) range (1-100 keV/mu m). The pitch angle distribution is also obtained using the geomagnetic model of IGRF-95. The result is roughly in good agreement with the distribution obtained by the VF1-MIN anisotropy model calculation within the present experimental errors, if the shielding distribution is assumed to be uniform.

The energy loss distributions of heavy ions (Z less than or equal to 8) with high energies (2 MeV/u-50 MeV/u) in thick silicon detectors with uniform thickness have been measured in a wide range of fractional energy loss, Delta E/E-0, where Delta E is the energy loss and E-0 is the initial energy of incident ions. The measured distributions of energetic He, Li, Be, B and C ions are in good agreement with those predicted from Livingston-Bethe's theory when Delta E/E-0 < 0.2. However, the distributions for large fractional energy lasses Delta E/E-0 > 0.2, which are much wider than those expected from the theory, are approximately expressed by Stoquert's method considering the effect of velocity decrease into Livingston-Bethe's theory. In the previous experiment of the energy loss of heavy ions from K to Fe in thick Si detectors, Hasebe et al. obtained consistent results for heavier elements. By conbining the results in the previous and this works, it is concluded that the straggling in energy loss of heavy ions from roton to Fe with energies from about 5 MeV/u to a few hundred MeV/u in thick Si-absorber is explained by Stoquert's method.

In order to measure time correlation of primary cosmic rays, a network observation of extensive air showers started in Japan. The network as Large Area Air Shower (LAAS) group consists of nine air-shower-stations (seven institutes and 26,000 km(2)) using the Global Positioning system (GPS). We propose an analytical procedure to extract time-limited fractal structure from time series of arrival time intervals of successive air showers and present the results of the analysis by using the network data.

The measurement of the directional distribution of incident particles was made by using the Real time Radiation Monitoring Device (RRMD)-III placed inside the Space Shuttle STS-84 cruised at an altitude of 400 km and an inclination angle of 51.6°, which are the same as the cruising orbit of the International Space Station (ISS). The directional distributions of incident particles were evaluated over the observed linear energy transfer (LET) range (1-100 keV/μm). The pitch angle distribution is also obtained using the geomagnetic model of IGRF-95. The result is roughly in good agreement with the distribution obtained by the VF1-MIN anisotropy model calculation within the present experimental errors, if the shielding distribution is assumed to be uniform. Copyright 1999 by the American Geophysical Union.

The energy spectra (40 to 300 MeV/n) of galactic cosmic ray particles (C, N, O, Ne, Mg, Si, and Fe) observed by the HEP-HI silicon detector telescope onboard the GEOTAIL satellite were investigated over the period from January 1993 to May 1996, from the viewpoint of solar modulation. From the GEOTAIL data and those of relativistic heavy particles observed by HEAO-3, the modulation potential phi was obtained by using a solution of the Fokker-Plank equation with the "force-field" approximation. In the equation the diffusion coefficient was used as adjustable parameter, under the assumptions of a fixed velocity of solar wind (400 km/sec) and the radius of the heliosphere of 50 AU. The time variation of the modulation potential thus obtained is compared with that obtained from the CLIMAX neutron monitor. A reasonable correlation between both time variations is found when five months delay is applied to the results obtained by the HEP-HI telescope. (C) 1999 COSPAR. Published by Elsevier Science Ltd.

Long-term decrease events in the intensity of galactic cosmic rays have been investigated using solar wind parameters. We investigated distinct long-term decreases in 1993/94 near the solar minimum phase. In this period, the corotating interaction regions were observed over half a year. Recurrent increases of the solar wind speed were observed during this time period, forming corotating interaction regions. Simultaneously recurrent energetic proton events and recurrent decrease of galactic cosmic rays are measured. The baseline counts of neutron monitors was well anti-correlated with the peak speed of solar wind. It is suggested that long-lasting enhancements of solar wind velocity or corotating interaction regions formed by them can produce, the long-term decrease in the galactic cosmic ray intensity. (C)1999 COSPAR. Published by Elsevier Science Ltd.

The energy spectra (40 to 300 MeV/n) of galactic cosmic ray particles (C, N, O, Ne, Mg, Si, and Fe) observed by the HEP-HI silicon detector telescope onboard the GEOTAIL satellite were investigated over the period from January 1993 to May 1996, from the viewpoint of solar modulation. From the GEOTAIL data and those of relativistic heavy particles observed by HEAO-3, the modulation potential φ was obtained by using a solution of the Fokker-Plank equation with the "force-field" approximation. In the equation the diffusion coefficient was used as adjustable parameter, under the assumptions of a fixed velocity of solar wind (400km/sec) and the radius of the heliosphere of 50AU. The time variation of the modulation potential thus obtained is compared with that obtained from the CLIMAX neutron monitor. A reasonable correlation between both time variations is found when five months delay is applied to the results obtained by the HEP-HI telescope. ©1999 COSPAR. Published by Elsevier Science Ltd.

We review the current status of the development of Gamma-Ray Spectrometer (GRS) for the Lunar mission SELENE. The GRS instrument will measure gamma-rays in the energy range from 100 keV to 9 MeV. The instrument is a high-purity Ge detector surrounded by EGO and plastic scintillators which are operated as an anticoincidence shield, and is cooled by a Stirling cycle cryocooler. The primary objective is to provide global maps of the lunar composition. Measurements are anticipated for Fe, Ti, U, Th, K, Si, Mg, Al, O, Ca and Na over the entire lunar surface. The abundance of water ice in the permanently shaded craters at both the lunar poles will be measured with this instrument. (C) 1999 COSPAR. Published by Elsevier Science Ltd.

A series of corotating energetic helium events with 3-5 MeV/n has been observed by the HEP telescopes onboard the GEOTAIL satellite at 1AU from October 1993 to August 1994. We have examined the relationship between solar wind (SW) speeds observed at 1AU and the intensity of He in the series of the corotating interaction region (CIR) events. The speed difference of the high-speed SW from slow-speed SW; which forms a CIR in the outer heliosphere, shows a reasonable correlation with the peak intensity of He at 3-5 MeV/n. The speed difference of those SWs is considered to be related to the shock strength which develops in a CIR at a distance from the Sun. Such a correlation between energetic ions associated with CIRs and SW speed has not been shown so far for the events during the period of 1978-1986. We have also investigated the dependence of the relation between the CIR ion events and the SW speeds during the period between 1978 and 1995 which corresponds to the high solar active phase of Solar Cycle 22. There is a good correlation between the SW speed and the peak intensity of CIR energetic ions in the quiet phase of solar activity, but not in the active phase.

The real-time measurement of radiation environment was made with an improved real-time radiation monitoring device (RRMD)-II onboard Space Shuttle STS-79 (S/MM#4: 4th Shuttle MIR Mission, at an inclination angle of 51.6 degrees and an altitude of 250-400km) for 199 h during 17-25 September, 1996. The observation of the detector covered the linear energy transfer (LET) range of 3.5-6000 keV/mu m. The Shuttle orbital profile in this mission was equivalent to that of the currently planned Space Station, and provided an opportunity to investigate variations in count rate and dose equivalent rate depending on altitude, longitude: and latitude in detail. Particle count rate and dose equivalent rate were mapped geographically during the mission. Based on the map of count rate, an analysis was made by dividing whole region into three regions: South Atlantic Anomaly (SAA) region, high latitude region and other regions. The averaged absorbed dose rate during the mission was 39.3 mu Gy/day for a LET range of 3.5-6000 keV/mu m. The corresponding average dose equivalent rates during the mission are estimated to be 293 mu Sv/day with quality actors from International Commission on Radiological Protection (ICRP)-Pub. 60 and 270 mu Sv/day with quality factors from ICRP-Pub. 26. The effective quality factors for ICRP-Pub. 60 and 26 are 7.45 and 6.88, respectively. From the present data for particles of LET > 3.5keV/mu m, we conclude that the average dose equivalent rate is dominated by the contribution of galactic cosmic ray (GCR) particles. The dose-detector depth dependence was also investigated.

The Geotail high-energy particle instruments have observed cosmic-ray particles in the energy range from 3 MeV n(-1) to 150 MeV n(-1) at 1 AU during the period 1992 September-1995 August. A remarkable enhancement of anomalous cosmic-ray (ACR) N, O, Ne, and C is observed during the period. A measurable enhancement of the sulfur flux below about 20 MeV n(-1) was observed. This is the first evidence showing the existence of sulfur in the anomalous component. The flux increase of anomalous sulfur, with a first ionization potential (FIP) of 10.4 eV, is smaller than that of ACR carbon with an FIP of 11.3 eV and much smaller than those of high-FIP elements, which suggests that the fractions of neutral carbon and sulfur atoms are significantly low in the very local interstellar medium.

The composition and energy spectra of anomalous cosmic-rays (ACRs) in the energies 6 - 200 MeV/n have been measured during the period from September 1992 to August 1995 using the High Energy Particle instrument onboard the GEOTAIL satellite orbiting at 1 AU. A remarkable enhancement of ACR N, O, Ne and Ar is observed during the period. A flux enhancement of anomalous argon at 1 AU is confirmed by the GEOTAIL satellite. The first possible evidence for the emergence of a measurable sulfur component in ACR below about 20 MeV/n is found, The flux increase of anomalous sulfur with 10.4 eV FIP is smaller than that of ACR carbon with 11.3 eV FIP, and much smaller than those of high FIP elements, which suggests that the fraction of neutral carbon and sulfur atoms is significantly lower in the very local interstellar medium. (C) 1997 COSPAR.

A new telescope consisting of three two-dimensional position-sensitive silicon detectors which can measure the Linear energy transfer (LET) distribution over the range from 0.2 to 400 keV/mu m has been developed as a real-time radiation monitor in manned spacecraft. First, the principle of LET measurement and its design method are described. Second, suitable electronic parameters for the LET measurement are experimentally determined. Finally, the telescope performance is investigated by using relativistic heavy ions. The first in-flight test of this type of telescope on the US Space Shuttle (STS-84) is scheduled for May, 1997.

Space radiation dosimetry measurements have been made on board the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called ''Real-time Radiation Monitoring Device (RRMD)'' utilizing silicon semi-conductor detectors and others are conventional detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. Using the RRMD detector, the first attempt of real-time monitoring of space radiation has been achieved successfully for a continuous period of 251.3 h, giving the temporal variations of LET distribution, particle count rates, and rates of absorbed dose and dose equivalent. The RRMD results indicate that a clear enhancement of the number of trapped particles is seen at the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent, while some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions for galactic cosmic ray particles (GCRs). Therefore, the main contribution to dose equivalent is seen to be due to GCRs in this low altitude mission (300 km). Also, the dose equivalent rates obtained by TLDs and CR-39 ranged from 146.9 to 165.2 mu Sv/day and the average quality factors from 1.45 to 1.57 depending on the locations and directions of detectors inside the Space-lab at this highly protected orbit fdr space radiation with a small inclination (28.5 degrees) and a low altitude (300 km). The LET distributions obtained by two different detectors, RRMD and CR-39, are in good agreement in the region of 15-200 keV/mm and difference of these distributions in the regions of LET < 15 keV/mm and LET > 200 keV/mm can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks. Copyright (C) 1996 Elsevier Science Ltd

We present the global distributions of trapped He (4.8-37 MeV) fluxes in the low altitude region under quiet-time conditions (|Dst| &lt
30 nT) of geomagnetic activity. Observations were obtained by the OHZORA satellite during 1984-1987 in the altitude of350-850km. We have compared the global distributions of He fluxes with those for trapped electrons and protons at the same altitudes. Auroral zones observed from energetic He are not so prominent as compared with those from electron and proton fluxes. It is found that the anomalous distributions of He fluxes are localized at the South Atlantic Anomaly, while the anomalous distributions of electron and proton fluxes are clearly seen to extend from South Atlantic region to Southern Anomaly. Further, the L-distributions of trapped He fluxes are also examined during quiet-time conditions. It is found that the distributions for lower energies (4.8-13MeV) have two peaks at L =~ 1.4 and ~ 2.7, while the distribution for higher energies (13-37 MeV) has a single peak at L ~ 1.5 and does not have the peak at L =~ 2.7.

The real time monitoring of environmental radiation in the Space-Lab of STS-65 (IML-2: inclination 28.5 degrees, altitude 300 km) has been achieved successfully through the flight by a new silicon detector telescope called ''Real time Radiation Monitoring Device'' (RRMD). It consists of two 2-dimensional position sensitive silicon detectors and six diode type silicon detectors. In this monitoring, the temporal variation of rates of particle flux, together with the dose equivalent and the LET distribution at three locations in the Space-Lab, were reasonably given in real time. The LET distribution obtained by the RRMD and CR-39 track detectors measured at the same location is in good agreement except at the highest LET region >200 keV/mu m and the lowest LET region <5 keV/mu m.

We analysis the low energy ions data obtained by Geotail HEP experiment associate with a interplanetary shock. The energy spectra at downstream from the shock is somewhat different from former researchs and have small humps in low energy regions (< 100keV). We find that this feature is explicable in the model of particle acceleration at oblique shock.

We observed a Fermi acceleration event at a passage of a fairly strong quasi-perpendicular interplanetary shock. Gradual exponential increase of the flux levels, which are typical of interplanetary shock acceleration events, were observed both for ions (> 40 keV) and electrons (> several tens of eV) several hours before the shock arrival. Accelerated electrons showed a power-law type energy spectrum, which was significantly softer than what the standard Fermi theory predicts. We attribute this spectral softening to the effect of upstream free escape boundary.

A new observation of low energy cosmic ray particles with the energies from 4 to 120 MeV/n by the HEP instrument onboard the GEOTAIL satellite orbiting at 1 AU shows a remarkable enhancement of aItomalous cosmic ray (ACR) N, O and Ne in the period September 1992 - December 1993 before approaching to the solar minimum in solar cycle 22. The ACR fluxes obtained by the GEOTAIL. observation are in good agreement with the results earlier obtained from the SAMPEX satellite [Mewaldt et al. 1993a,b]. The ACR carbon is also evident though the C enhancement is small compared with those of N, O and Ne. We confirm the new SAMPEX finding that the ACR fluxes have recovered more rapidly in 1992-1993 than in previous solar cycles and find this tendency continues to the end of 1993.

A method of determination of charge and energy for energetic particles penetrating (not stopping) a multilayer silicon DELTAE x E telescope with a finite thickness (12 mm) is examined in the energy region up to several hundreds of MeV/nucleon. From the results of the accelerator experiment, an energy resolution sigma(E) of 1.2% in rms and a charge resolution sigma(Z) of 0.11 charge unit in rms for Fe-group nuclei with energies between 190 and 230 MeV/nucleon are obtained. For lighter elements such as hydrogens and helium ions, an energy resolution sigma(E) of 2.9% is obtained in the energy region between 33 and 42 MeV/nucleon and even their individual isotopes are separated. Also, the energy dependences of these resolutions suggest that this method can be utilized for particles with energies about two times larger than that corresponding to the range of telescope thickness for the evaluation of the space radiation effects even under the limitations of weight, size, and electric power supply.

The instruments for the HEP (High Energy Particle) experiments of the GEOTAIL mission, launched in July 1992, consist of 5 spectrometers (LD, BD, MI-1, MI-2 and HI). The LD (Low energy particle Detector) and the BD (Burst Detector) are mainly used to measure electrons, protons, helium and oxygen ions which reflect plasma dynamics in the magnetotail region. On the other hand, MI-1, MI-2 (Medium energy Isotope telescope-1, -2) and HI (High energy Isotope telescope) are used to measure the isotope abundance of solar flare particles and cosmic ray particles which reflect physical conditions of interplanetary space and origin of these particles. In this paper, the objectives of these experiments, the details of the instruments and preliminary results from the observation in the magnetotail are given. The preliminary results obtained by the LD and BD show that a highly collimated beam of energetic particles appear in the plasma sheet just after the substorm onset and that directional distribution of particles can be radically different for different energies. In the MI and HI telescopes, details a remarkable enhancement of anomalous cosmic ray components (N, O) in the quiet time of solar activity is reported, as well as the element composition of galactic cosmic rays.

The energy loss straggling of heavy charged particles with relatively high energies passing through thick uniform Si detectors (1.0 mm-9.2 mm) has been studied in a wide range of the ratio Delta E/E(0) where Delta E is the energy loss and E(0) is the initial energy of the incident particles. The experimental results are compared with those predicted by straggling theories. It suggests that the measured distributions are in good agreement with those predicted from the Bohr's or Livingston-Bethe's theories when Delta E/E(0)<0.3 where the distributions are to be Gaussian-symmetric, However, the distributions for larger energy losses deviate from those expected from the theories. It is found that the experimental data are approximately expressed by the modified Stoquert's theory when the ratio Delta E/E(0)>0.3.

A new approach using the Green function instead of the method of Fourier expansion is presented to determine the position-charge relationship for radiation detectors employing a charge division on the resistive anode bordered by an additional resistive line. The resistive anode with a polygonal shape is considered as a general case. Theoretical consideration shows that the position of radiation incidence in the position-sensitive detectors is represented in the integral form containing the Green function if the total charge generated in the detector is assumed to be collected over an infinite time. Anodes with the geometries of a triangle, square, circle or spherical triangle are described as practical shapes. It is shown that, when the shape of the anode is (spherical) triangular or square, the relationship between the position and charge is determined by a harmonic function obtained from a simple geometric consideration.

Using 5-in.-diameter Si(Li) detectors with a detector thickness of 1, 2 and 3 mm combined with 62 mm X 62 mm position-sensitive Si detectors, an excellent isotope telescope has been constructed for the Geotail mission. The performance of the telescope and the individual detectors has been investigated using Fe-56 beams with energies between 430 and 696 MeV/n. The nonuniformity of the detector thickness as measured by exposing the detectors to a monochromatic Fe beam is 0.44% for 1 mm thick detectors, 0.54% for 2 mm thick detectors and 0.15% for 3 mm thick detectors. The secondary isotopes of Al through Fe produced by 430 MeV/n Fe-56 in a polyethylene target were clearly resolved by the telescope. The measured mass resolution for Si, Ca and Mn were 0.36 amu, 0.42 amu and 0.44 amu in FWHM, respectively. The telescope has the following two key features: an excellent resolution (better than 0.5 amu) and an exceptionally high sensitivity (SOMEGA = 43 cm2sr) for a broad range of species from He through Ni with energies between 2.4 and 210 MeV/n.

The spatial and temporal features of the peak proton flux detected near the equator in the integral energy channel of 0.64-35 MeV by S-1 telescope on board the EXOS-C mission were studied for a period of three years (1984-86). The equatorial zone (+/-30-degrees geomagnetic latitude) proton data obtained for the angle between the telescope axis and the magnetic field direction in the range of 50-degrees-130-degrees and at the peak efficiency of the instrument, were sorted out from a study of the orientation of the telescope axis and calculation of the response function of the telescope. The data, after freed from the major influence of the South Atlantic Anomaly, and subsequently analyzed, revealed some new results contrary to the earlier observation (MORITZ, 1972) in the altitude range of 350 to 850 km. The spatial distribution shows that the global profile of the peak proton flux is aligned with the profile of the minimum magnetic field, and, the peak proton population straddles the minimum magnetic field equator with a full-width-at-half-maximum of about 19-degrees. Also, the pitch angle distribution of the equatorial proton population is found to have the anisotropy index in the range 7 to 10. Further, the proton flux shows altitude, L, and longitude dependences. The flux increases as h1.43 and L4.25-7.50 (corresponding to different equatorial pitch angles). Besides, in the longitude range 180-degrees < phi < 300-degrees, the flux is significantly larger than that in the range 100-degrees < phi < 180-degrees. The fact of L independence of low energy (< 5 MeV) protons, and the strong L dependence (L81) of high energy (> 5 MeV) protons, has been used to infer the presence of a major low energy component and a minor high energy component. In the study of temporal features, comparison of absolute fluxes during two solar epochs shows that the proton flux during the solar minimum in 1984-86 was, at least, 40 times less than that during the solar maximum condition in 1982, possibly, due to lesser amount of hydrogen escape to the exosphere during the minimum condition, and thereby causing less precipitation of low energy particles in the equatorial atmosphere.

A Heavy Ion cosmic ray Telescope (HIT) has been scheduled to be launched into the synchronous orbit in 1993 aiming to observe elemental and isotopic composition of solar energetic particles and galactic cosmic rays. In this paper, we report the results of accelerator beam experiments of a prototype model of HIT. The telescope consists of two dimensional Position Sensitive Detectors (PSDs) and energy loss detectors (PIN type and Li-drifted type). The mass resolution was 1.1 amu in FWHM for 110 MeV/n pure iron (Fe-56) beam. By exposing HIT to beams consisting of various nuclides produced by the projectile fragmentation process in a reaction induced by Fe-56 beam, we confirmed that the secondary elements from 16S to 25Mn were clearly separated and that also the isotopes were separated for each elements lighter than 22Ti. The observed mass resolution was 0.57 amu, 0.66 amu and 0.82 amu in FWHM for 18Ar, 20Ca and 22Ti, respectively. We can conclude that the HIT has good prospects of enough ability for our current purpose in space observation.