Updated on 2022/05/26

写真a

 
MATSUNAGA, Yasushi
 
Affiliation
Affiliated organization, Research Innovation Center
Job title
Professor

Concurrent Post

  • Faculty of Law   School of Law

  • Faculty of Science and Engineering   Graduate School of Advanced Science and Engineering

Education

  • 1997.03
    -
     

    Waseda University   Graduate School of Science and Engineering  

  •  
    -
    1995

    Waseda University   Graduate School, Division of Science and Engineering   Pure and applied physics  

  •  
    -
    1988

    Waseda university   Faculty of Science and Engineering   Applied physics  

Degree

  • Waseda University, Japan   PhD

Research Experience

  • 2021.01
    -
    Now

    Waseda University

  • 2019.06
    -
    2020.12

    Waseda University

  • 2013.04
    -
    2019.05

    Waseda University   Center for Research Strategy

  • 2009.04
    -
    2012.03

    Waseda University   Center for Research Strategy

  • 2008.04
    -
    2009.03

    Waseda University   Institute for Nanoscience and Nanotechnology

  • 2002.04
    -
    2008.09

    Toho University   Faculty of Science

  • 2004.04
    -
    2008.03

    Waseda University   School of Science and Engineering

  • 2001.04
    -
    2005.03

    The University of Electro-Communications   Faculty of Electro-Communications

  • 2001.04
    -
    2004.03

    Waseda University   Advanced Research Institute for Science and Engineering

  • 1998.04
    -
    2004.03

    Waseda University   School of Science and Engineering

  • 1998.04
    -
    2001.03

    日本学術振興会   特別研究員(PD)

  • 1995.04
    -
    1998.03

    Waseda University   School of Science and Engineering

  • 1994.04
    -
    1995.05

    Waseda University   Honjo Senior High School

  • 1990.04
    -
    1992.03

    (株)東芝   ULSI研究所   研究員

▼display all

Professional Memberships

  •  
     
     

    日本物理学会

 

Research Areas

  • Fundamental plasma

  • Nanostructural physics

Research Interests

  • プラズマ理工学

Papers

  • A Landau mode in current-carrying carbon nanotube and effects on electrical breakdown

    Y. Matsunaga, T. Hatori, T. Kato

    J. Appl. Phys.   103   104301  2008.04

  • Evaluation of optimum sheath electric field and minimum catalyst interval for selective production of metallic carbon nanotubes

    Y Matsunaga, T Hatori, T Kato

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS   45 ( 3A ) 1877 - 1879  2006.03

     View Summary

    We estimate the optimum electric field at the sheath edge and the minimum interval among nanotubes to promote the growth of armchair-type nanotubes (metallic character) as a function of the nanotube length. On the basis of the electric charge distribution in a nanotube and the optimum electric field E-1(*) at the tip of a nanotube evaluated using the Huckel-Poisson method, we calculate the structure of the electric field lines outside a nanotube in the sheath region. As the nanotube length increases, E-1(*) decreases. To maintain the chemical activity at the tip, the sheath electric field must be decreased. We show the decreasing rate of the sheath electric field with respect to the nanotube length.

  • Evaluation of optimum sheath electric field for selective production of metallic carbon nanotubes

    Yasushi Matsunaga, Tadatsugu Hatori, Tomokazu Kato

    THIRD 21COE SYMPOSIUM: ASTROPHYSICS AS INTERDISCIPLINARY SCIENCE   31   187 - +  2006

     View Summary

    We estimate the optimum electric field at the sheath edge and the minimum interval among the nanotubes to promote the growth of armchair-type nanotubes (metallic character) as a function of the tube length. On the basis of the electric charge distribution in a nanotube and the optimum electric filed E*(1) at the tip of a nanotube evaluated using the Huckel-Poisson method, we calculate the structure of the electric field lines outside a nanotube in the sheath region. As the tube length increases, the E*(1) decreases. To maintain the chemical activity at the tip, the sheath electric field must be decreased. We show the decreasing rate of the sheath field to the tube length.

    DOI

  • Selective production of metallic carbon nanotubes

    Y. Matsunaga, T. Hatori, T. Kato

    Proc. ICPP2004, ccsd-0000198     1 - 9  2004.10

  • Selective production of armchair-type carbon nanotubes

    Y Matsunaga, T Kato, T Hatori

    JOURNAL OF APPLIED PHYSICS   95 ( 12 ) 8149 - 8154  2004.06

     View Summary

    The controllability and promotion of the production of metallic nanotubes by imposing an external electric field are examined based on a numerical simulation. The electronic states of the pi electrons are described by the Huckel method and their electric interactions are self-consistently taken into account through the Poisson equation. The frontier electron density at both ends of the nanotubes with open ends is evaluated. For armchair tubes, the frontier electron density at both ends becomes a maximum near the electric field of 1 V/nm. The ratio of the frontier density of the armchair tubes to zigzag tubes is 3:1 near this electric field. The frontier density for zigzag tubes shows a maximum in the absence of an external electric field, while, by imposing an electric field, the frontier density decreases. The optimal intensity of a direct current electric field to efficiently make metallic nanotubes is determined. (C) 2004 American Institute of Physics.

    DOI

  • Evaluation of improved efficiency with a diamond coating for a plasma display panel electrode

    Y Matsunaga, T Kato, T Hatori, S Hashiguchi

    JOURNAL OF APPLIED PHYSICS   93 ( 9 ) 5043 - 5052  2003.05

     View Summary

    Application of diamond to electrode coating of a plasma display panel (PDP) is evaluated, since we expect diamond to emit much secondary electron due to the Auger neutralization induced by Xe ions. In a conventional magnesium oxide-xenon (MgO/Xe) system, the most abundant Xe+ produced in the discharge does not effectively cause the secondary electron emission, because the condition of the Auger neutralization is not satisfied. In order to increase the efficiency of ultraviolet (UV) radiation, being especially important for engineering, we should avoid such inefficiency. Under suitable conditions in diamond/Xe system the Auger neutralization can occur. Further, if the electron affinity chi is negative, i.e., negative electron affinity (NEA), the condition of the Auger neutralization in diamond/Xe system is sufficiently satisfied. First, we calculate the coefficients of the secondary electron emission on diamond of clean surface or of hydrogenated surface where the dangling bonds are terminated, on the basis of the Hagstrum model. If the NEA with the electron affinity chi=-0.5 is realized, the high ion-induced secondary electron coefficients such as gamma(Xe)=0.25 and gamma(Ne)=0.32 are obtained. Next, we carry out a one-dimensional fluid simulation of the electric discharge in which the two secondary electron emission coefficients of Ne and Xe obtained theoretically are set. Results are presented with changing the sustaining voltage, the fraction of Xe, and the duration of the zero-voltage phase. For 10%Xe mixture, it is shown that the efficiency of UV radiation in the diamond coating increases two times higher than that in the MgO coating. An unnecessarily spontaneous breakdown during the zero-voltage phase, which is peculiar to high secondary electron emission materials, is observed. A mechanism of the breakdown is discussed and means to suppress it are proposed. Taking the zero-voltage phase short and increasing the fraction of Xe up to 50%, in comparison with MgO, a maximum improvement of 3.5 times in the efficiency of UV radiation can be performed. The high secondary electron emission due to Xe ion brings about a decrease in the sustaining voltage, and the sustaining voltage can be further lowered by shortening the duration of the zero-voltage phase. The operation with an increase of Xe fraction becomes attainable. The feasibility of the high performance operation on the ac type PDP by utilizing the materials including diamond with high secondary electron emission for Xe is quantitatively shown. (C) 2003 American Institute of Physics.

    DOI

  • Kinetic simulation of an ion acoustic wave with charge exchange process in direct current discharge plasma

    Y Matsunaga, T Hatori, T Kato

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 10 ) 2445 - 2455  2002.10

     View Summary

    A charge exchange model is set and its simulation results are compared to those of previous friction model in the lower current branch of a discharge plasma. A remarkable delocalization of a high frequency mode is found in the charge exchange model. When the mean free path of the charge exchange is larger than the system size, the effective temperature is lower than that of the friction model. However, with a decrease of the mean free path, the temperatures of the two models are inverted. Although the bifurcations of the fundamental mode described in previous paper are similarly reproduced, a parameter range has shifted and it is difficult to observe the ponderomotive effect in the charge exchange model. Simulation results are discussed from the view point of the second moments of the distribution function in both velocity and coordinate spaces. It is found that the effects due to the ponderomotive force and previously pointed-out sheath condition are concealed under the diffusion defined by the second moment of the displacement of scattered particles.

    DOI

  • 直流放電におけるイオン音波の分岐とカオス

    松永康

    J. Plasma Fusion Research   77   1199 - 1204  2001.12

  • Kinetic simulation of nonlinear phenomena of an ion acoustic wave in gas discharge plasma with convective scheme

    Y Matsunaga, T Hatori, T Kato

    PHYSICS OF PLASMAS   8 ( 3 ) 1057 - 1069  2001.03

     View Summary

    Nonlinear phenomena of the ion acoustic wave in a negatively charged plasma-sheath system are observed in the simulation with a convective scheme described by a two-dimensional phase space, and are theoretically analyzed. Subharmonics of a fundamental mode are excited and show the bifurcation phenomena when the intensity of the ion source relating to the ionization is increased. A reversed electric field from the cathode to anode reveals that the ponderomotive force due to a high frequency mode pushes the ions toward the cathode. A nonlinear coupling of two modes through the ponderomotive force is a key idea to construct the model. Nonlinear dynamical model equations involving the coupling of the two modes and an interaction of the sheath with the two modes, i.e., two nonlinear effects, are proposed. The period-doubling bifurcations of the fundamental mode are examined by using the same growth rates with the flow velocity as in our previously published linear theory. (C) 2001 American Institute of Physics.

  • Kinetic Kinetic Simulation of Ion Acoustic Wave with Charge Exchange Process in DC Discharge Plasma

    Y. Matsunaga, T. Hatori, T. Kato

    ICPP-2000 Proceedings   1   53 - 56  2000.10

  • Kinetic simulation on ion acoustic wave in gas discharge plasma with convective scheme

    Y Matsunaga, T Hatori, T Kato

    PHYSICS OF PLASMAS   7 ( 3 ) 784 - 794  2000.03

     View Summary

    In a one-dimensional plasma-sheath system representing a concave quasistationary electric potential typical of a negatively charged system, oscillations of ion are simulated by the aid of a convective scheme useful for weakly ionized plasma, and are theoretically investigated. The frequency spectra of the ion current through a cathode reveal to us that two modes of ion acoustic waves are dominant; a high and a low frequency mode. By deriving a linear differential equation with a dissipation and an ion flow, and taking for granted the sheath width and the distribution of ion flow velocity, the dispersion relation for a finite length system can be calculated. The simulation results, such as the reinforcement of the low frequency mode and the suppression of the high frequency mode, are satisfactorily corroborated by the linear theory. The instabilities of the waves are caused by the asymmetry of boundary conditions and by the dissipative effect. (C) 2000 American Institute of Physics. [S1070-664X(00)00603-0].

  • Kinetic simulation on nonlinear phenomenon of ion acoustic wave in gas discharge plasma with convective scheme

    Y Matsunaga, T Hatori, T Kato

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   ( 138 ) 726 - 727  2000

     View Summary

    Ion oscillations in a one dimensional plasma-sheath system are simulated by the aid of the convective scheme, combining the kinetic equation with the Poisson equation. The frequency spectra of the ion current through a cathode reveal to us that two modes of ion acoustic wave are dominant; a high frequency mode and the fundamental mode. By using a linearized differential equation the appearance of the two modes is corroborated. As the nonlinear phenomena on the fundamental mode, excitation of sub-harmonics is observed if the gas pressure concerned with ionization is changed. A model equation of nonlinear oscillation including the ponderomotive force term caused by the high frequency mode is introduced, and sub-harmonics and period-doubling bifurcations are shown by using the growth rate with the flow velocity obtained in our linear theory.

  • Kinetic Simulation on Ion Acoustic Wave in Gas Discharge Plasma with Convective Scheme

    Y. Matsunaga, T. Hatori, T. Kato

    J. Plasma and Fusion Research Series   2   451 - 454  1999.12

  • Kinetic Simulation on Nonlinear Oscillation in Gas Discharge Plasma with Convective Scheme

    Y. Matsunaga, T. Hatori, T. Kato

    1998 ICPP Contrib. Papers   22c   2403 - 2406  1998.07

  • プラズマ・シース系のエネルギー輸送と密度遷移現象

    松永康, 加藤鞆一

    Research Report NIFS-PROC   32   28 - 37  1997.04

  • Analysis of hysteresis characteristics and low frequency oscillation in gas discharge plasma

    Y Matsunaga, T Kato

    ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2   63   674 - 677  1997

     View Summary

    Hysteresis of gas discharge plasma and nonlinear oscillation of low frequency, caused by the trapped ion, are analyzed. Mainly, the hysteresis and emergence of multiple-steady states are discussed by a simple model of chemical-reaction system. It is shown that a function describing the energy balance has three different real roots. The condition for plural roots depends on the ratio of the bulk energy increase to the surface energy loss of plasma. The criterion contains the non-thermodynamic variables such as conductivity and surface quantities. Examination of stabilities of three-obtained solutions by using linear analysis of differential equations manifests that a root represents a saddle point and other two roots represent stable points.

  • Analysis of hysteresis characteristics and low frequency oscillation in gas discharge plasma

    Y Matsunaga, T Kato

    ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2   1   674 - 677  1997

     View Summary

    Hysteresis of gas discharge plasma and nonlinear oscillation of low frequency, caused by the trapped ion, are analyzed. Mainly, the hysteresis and emergence of multiple-steady states are discussed by a simple model of chemical-reaction system. It is shown that a function describing the energy balance has three different real roots. The condition for plural roots depends on the ratio of the bulk energy increase to the surface energy loss of plasma. The criterion contains the non-thermodynamic variables such as conductivity and surface quantities. Examination of stabilities of three-obtained solutions by using linear analysis of differential equations manifests that a root represents a saddle point and other two roots represent stable points.

  • Simple model analysis of hysteresis phenomenon of gas discharge plasma

    Y Matsunaga, T Kato

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   66 ( 1 ) 115 - 119  1997.01

     View Summary

    The hysteresis and multiple-steady states of gas discharge plasma are analysed by a simple model of chemical-reaction system. In our analysis the emergence of multiple-steady states is explained by using a fact that a function describing the energy balance has three different real roots. The condition that the function has three roots depends on the ratio of the bulk energy increase to the surface energy loss of plasma. The criterion of taking place of the jump between two steady states is examined in a similar manner to order-disorder transition. The critical parameter contains the non-thermodynamic variables such as conductivity and surface quantities. Stabilities of three obtained solutions are discussed by using linear analysis of differential equations and we find that a root represents a saddle point and other two roots represent stable points. The first step to explain the hysteresis phenomenon in Ar gas discharge plasma is found.

  • 放電プラズマのヒステリシス特性の解析

    松永康, 加藤鞆一

    Research Report NIFS-PROC   27   55 - 67  1996.09

  • 放電プラズマのヒステリシスと低周波振動

    松永康, 加藤鞆一

    NIFS-PROC/核融合科学研究所   22   39 - 46  1995.04

  • 放電プラズマの非線形現象の解析

    松永康, 加藤鞆一

    Research Report NIFS-PROC   16   1 - 7  1994.04

  • Analysis of Nonlinear Oscillation in Gas Discharge

    Yasushi Matsunaga, Tomokazu Kato

    Journal of the Physical Society of Japan   63 ( 12 ) 4396 - 4405  1994  [Refereed]

     View Summary

    Nonlinear oscillation that indicates chaotic behavior at low frequency in a gas discharge plasma is investigated by analytic and numerical solutions. The electric field in plasma is determined through the Poisson equation by assuming charge distribution: ions distribute spatially uniform, beam electrons from hot cathode are described by an exponentially decreasing distribution, and plasma electrons are in thermal equilibrium and described by the Boltzmann distribution. The electrostatic potential that is obtained analytically by using linear approximation contains the Debye shielding effect. Low frequency motion of the ions in this electric field is calculated numerically. Period-doubling bifurcation and chaotic oscillation are obtained for a region of parameters and they agree with the experimental results qualitatively. © 1994, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

    DOI

  • LINEAR RESPONSE THEORY REFORMULATED FROM THE CHAOTIC DYNAMICS

    N SAITO, Y MATSUNAGA

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   58 ( 9 ) 3089 - 3105  1989.09

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Books and Other Publications

  • 電磁気学II

    松永康, 徳永旻

    森北出版株式会社  2011.07 ISBN: 9784627158610

  • 電磁気学I

    牧野哲, 松永康, 徳永旻

    森北出版株式会社  2010.03 ISBN: 9784627158511

  • Physics of Self-Organization Systems

    edited by Shin'ichi Ishiwata, Yasushi Matsunaga

    World Scientific Publishing Co. Pte. Ltd.  2008.03 ISBN: 9789812793362

Industrial Property Rights

  • AC型プラグマディスプレイパネル

    松永 康, 羽鳥 尹承, 加藤 鞆一, 橋口 征四郎

    Patent

Awards

  • 日本学術振興会 科学研究費・第1段審査「模範となる審査意見を付していただいた審査委員」表彰

    2010.10  

Research Projects

  • A theoretical study and simulation on current-limit of carbon nanotubes

    Project Year :

    2005
    -
    2006
     

     View Summary

    At the first half, we estimated the optimum electric field at the sheath edge and the minimum interval among nanotubes to promote the growth of armchair-type nanotubes(metallic character) as a function of the nanotube length. On the basis of the electric charge distribution in a nanotube and the optimum electric field at the tip of a nanotube evaluated using the Huckel-Poisson method, we calculated the structure of the electric field lines outside a nanotube in the sheath region. To maintain the chemical activity at the tip, the sheath electric field must be decreased. We showed the decreasing rate of the sheath electric field with respect to the nanotube length.
    On the basis of the Landau quantization, the bound state is discussed, which includes the finite length effect, induced-magnetic field, and electric field in a current-carrying nanotube. Using a slab model and evaluating the matching of the wave function in the radial direction, the authors obtained the conditions of a Landau mode in which the momentum in the axial direction is reversed in the outer side and inner side of the nanotube shell. The mode arises over a threshold electric current and influences more long tubes t

  • A theoretical study and simulation on current-limit of carbon nanotubes

     View Summary

    At the first half, we estimated the optimum electric field at the sheath edge and the minimum interval among nanotubes to promote the growth of armchair-type nanotubes(metallic character) as a function of the nanotube length. On the basis of the electric charge distribution in a nanotube and the optimum electric field at the tip of a nanotube evaluated using the Huckel-Poisson method, we calculated the structure of the electric field lines outside a nanotube in the sheath region. To maintain the chemical activity at the tip, the sheath electric field must be decreased. We showed the decreasing rate of the sheath electric field with respect to the nanotube length.On the basis of the Landau quantization, the bound state is discussed, which includes the finite length effect, induced-magnetic field, and electric field in a current-carrying nanotube. Using a slab model and evaluating the matching of the wave function in the radial direction, the authors obtained the conditions of a Landau mode in which the momentum in the axial direction is reversed in the outer side and inner side of the nanotube shell. The mode arises over a threshold electric current and influences more long tubes th

Presentations

  • 早稲田大学の研究力強化の取組

    松永康  [Invited]

    第4回URAシンポジウム/第6回RA研究会  文部科学省「リサーチ・アドミニストレーターを育成・ 確保するシステムの整備」事業採択機関/RA協議会設立準備委員会 (主幹校:北海道大学)

    Presentation date: 2014.09

  • 研究評価先進国イギリスに学ぶ〜研究評価にどう向き合うか〜

    第6回エルゼビア研究戦略セミナー 

    Presentation date: 2013.06

  • 研究力調査・分析

    文部科学省「リサ-チ・アトドミニストレ-タ-を育成・確保するシステムの整備」(研修・教育プログラムの作成)事業 試行的研修会 

    Presentation date: 2013.03

  • リサーチ・アドミニストレーター研修・教育プログラムの策定

    第2回リサーチアドミニストレーターシンポジウム 大学の研究力強化におけるURAの担うべき役割 

    Presentation date: 2013.03

  • リサーチ・アドミニストレーター(URA)導入の動向と早稲田大学の取り組み

    岡山大学URAキックオフシンポジウム〜新たな研究の展開を目指して〜 

    Presentation date: 2012.09

  • 日本におけるリサーチ・アドミニストレーター(URA)導入の動向と早稲田大学の取り組み

    第5回エルゼビア研究戦略セミナー 

    Presentation date: 2012.06

  • リサーチ・アドミニストレーター研修・教育プログラムの設計と早稲田大学の取り組み

    北海道大学「リサーチ・アドミニストレーター入門セミナーFY2012」 

    Presentation date: 2012.02

  • URAと大学等研究戦略との関わり 早稲田大学における研究戦略とアドミニストレーション

    第3回 リサーチアドミニストレーション研究会 

    Presentation date: 2011.12

  • 早稲田大学における理工系大学院教育改革の実績と展望

    第3回COCN(産業競争力懇談会)「グローバルなリーダー人材の育成と活用研究会」 

    Presentation date: 2011.09

  • 大学ランキングの分析 THE vs. QS

    第一回RU11(学術研究懇談会)大学ランキング検討会 

    Presentation date: 2010.10

  • Micro and Nanotechnology at Waseda University - Nanotechnology and MEMS in Organic Devices, and Study of Fullerene -

    Hannover Messe 

    Presentation date: 2009.04

  • A new Landau mode in current-carrying carbon nanotubes

    The 5th COE symposium on Physics of self-organization systems: Toward Next Generation Physics, Tokyo 

    Presentation date: 2007.09

  • Evaluation of limit current caused by self-magnetic field in carbon nanotubes

    The 4th COE symposium on Physics of self-organization systems, Tokyo 

    Presentation date: 2006.09

  • Selective production of metallic carbon nanotubes and evaluation of limit current

    The 3rd COE symposium on Physics of self-organization systems, Tokyo 

    Presentation date: 2005.09

  • Selective production of metallic carbon nanotubes by the sheath field

    The 2nd COE symposium on Physics of self-organization systems, Tokyo 

    Presentation date: 2004.12

  • Selective production of metallic carbon nanotubes

    12th International Congress on Plasma Physics (IPP2004), Nice 

    Presentation date: 2004.10

  • Kinetic Kinetic Simulation of Ion Acoustic Wave with Charge Exchange Process in DC Discharge Plasma

    ICPP-2000, Quebec 

    Presentation date: 2000.10

  • Kinetic Kinetic Simulation of Ion Acoustic Wave with Charge Exchange Process in DC Discharge Plasma

    The 5th International Conference on Computational Physics 

    Presentation date: 2000.05

  • Kinetic Simulation on Ion Acoustic Wave in Gas Discharge Plasma with Convective Scheme

    9th International Toki Conference on Plasma Physics and Controlled Nuclear Fusion, Toki 

    Presentation date: 1999.12

  • Kinetic Simulation on Nonlinear Oscillation in Gas Discharge Plasma with Convective Scheme

    1998 International Conference on Plasma Physics, Prague 

    Presentation date: 1998.06

  • Analysis of Hysteresis Characteristics and Low Frequency Oscillation in Gas Discharge Plasma

    1996 International Conference on Plasma Physics, Nagoya 

    Presentation date: 1996.09

▼display all

Specific Research

  • プラズマ及びシースを含む系での非線形現象の解明

    1997  

     View Summary

    熱電子陰極を用いたプラズマの電流電圧特性はヒステリシスを描き、低周期倍化現象、カオス的振動現象が観測される。駆動系の振動のモデルとして、弱電離状態での非線形ポテンシャル中のイオンの運動に注目して数値解析を行い、パラメータ励振とポテンシャルの非対称性が原因で、カオス的振動が起こることを説明した。更に、放電特性の解析を行い、エネルギー変化と密度変化を結合させる多重定常状態モデルを提案した。 上述の理論的研究によりプラズマ周辺の物理量を更に詳しく考察する必要性が生じ、より近似を上げるため自己無撞着な計算手法が要求された。そこで、弱電離プラズマに有用な新しいカイネティック・シミュレーション技法であるCS(Convective Scheme)法を、カオス的振動現象に適用し、スキーム自体を検討しつつ、振動現象を再考することにした。以前の研究では一つのイオンの運動に注目して解析を進めたが、CS法を用いることによって系外へ流れ出るイオン電流をカイネティックステージで自己無撞着にシミュレートすることが可能となる。プラズマ中の電子はボルツマン分布とし、イオンの運動をCS法を用いポアッソンの式とカイネティック方程式を連立させ、差分近似法を用い各時間ステップごとに解いた。まず、定常解が下に凸型の電位分布と上に凸型の電位分布に落ちつくことを確認した。これは実験でも観測され、我々の理論でも裏付けされている電位分布である。次に陰極の電位等のパラメータを変化させることにより、下に凸型の電位分布での振動電流を得た。このモードの振動数と波数を議論した結果、イオン音波と系内のイオンの往復運動が関与する低周波が観測されていることがわかった。 このようにCS法によってイオン波の基礎的な振動モードをシミュレートする事に成功した。更にこの低周波振動は散逸を導入すると強調されることがわかったので、現在この線スペクトルの発生機構とモードの結合を集中的に議論している。

  • 放電プラズマの非線形現象の解明

    1996  

     View Summary

     放電プラズマの電流電圧特性は、一定の条件下で遷移現象を示しS型のヒステリシス曲線を描く事が多い。そして特定のパラメータ値では、自励系、駆動系、いずれも電流不安定性に関するカオスが報告されており、更に駆動系では低周期倍化現象が観測されている。 この駆動系の非線形振動のモデルとして、弱電離状態での非線形ポテンシャル中のイオンの運動に注目して数値解析を行い、パラメータ励振とポテンシャルの非対称性が原因で、カオス的振動が起こることを説明した。理論的に導入した静電ポテンシャルは、デバイ遮蔽の影響を残しているためプラズマ内部には陰極からの電位変動が伝わらず、通常の強制振動モデルとは異なる特徴を持つ。また周辺の電位よりプラズマ電位が低い静電ポテンシャルのプロファイルは実験的にも支持される。 次に、遷移を起こす放電特性の解析として、エネルギー変化(温度変化)と密度変化を結合させる多重定常状態モデルを提案した。エネルギー変化としては、ジュール熱、中性粒子との衝突によるエネルギー散逸、電離による散逸、プラズマから周辺への散逸を考慮した。反応方程式は以前から検討している自己触媒型(ロジスティック型)を用いた。電離係数の温度依存性をアレニウス型にすると、多重定常状態が存在すること、その条件は主にジュール熱の生成と周辺へ散逸する係数の比に依存すること等がわかった。このモデルで重要な量は周辺への散逸係数(熱伝導係数)と周辺プラズマの温度であり、現象を熱力学の概念だけでとらえるのではなく、散逸系のエネルギーバランスの問題と解釈すべきことを示している。従って、プラズマ・シース物理に固有の問題の可能性が高い。なお、弱電離プラズマの場合は熱伝導係数が密度に依存するので、モデル適用の制限が必要である。プラズマ・シース系の非線形現象は、核融合プラズマ、プロセスプラズマでも注目されている分野であり、この結果は大変示唆に富んでいる。

 

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Committee Memberships

  • 2021.05
    -
    2021.06

    文部科学省  研究インテグリティの確保に係る調査分析業務に関する技術審査

  • 2019.07
    -
    2021.06

    日本学術振興会  特別研究員等審査会専門委員

  • 2021.03
    -
    2021.04

    文部科学省  大学等における産学連携等実施状況に関する調査技術審査委員

  • 2020.10
    -
    2021.01

    金沢大学  文科省令和2年科学技術人材養成等委託事業 「URAの認定制度の実施制度の実施にむけた調査・検証」における 認定試行に係る検証役

  • 2016.12
    -
    2017.03

    日本学術振興会  科学研究費委員会専門委員

  • 2016.08
    -
    2016.12

    文部科学省  「産学連携等実施状況調査の効率的・効果的な運用実現に向けた調査」に関する技術審査専門委員

  • 2015.11
    -
    2016.03

    文部科学省 科学技術・学術政策局  「研究開発評価に関わる人材の現状と育成に関する調査・分析」検討委員会委員

  • 2015.08
     
     

    文部科学省科学技術・学術政策局産業・地域支援課  「リサーチ・アドミニストレーター業務の自立的運営に向けた調査・分析」技術審査専門員

  • 2015.05
     
     

    文部科学省科学技術・学術政策局産業連携・地域支援課  「我が国大学の研究経営システム確立に向けた国内外動向に関する基礎的調査」技術審査専門員

  • 2014.12
    -
    2015.03

    筑波大学  筑波大学URA整備事業外部評価委員会委員

  • 2014.08
     
     

    文部科学省科学技術・学術政策局産業連携・地域支援課  「産学連携等実施状況調査深化のための調査分析」技術審査専門員

  • 2013.02
    -
    2014.03

    京都大学  学術研究支援室評価委員会

  • 2008.12
    -
    2010.03

    日本学術振興会  科学研究費委員会専門委員

  • 2010
    -
     

    学術研究懇談会(RU11)  リサーチ・アドミニストレーター委員会 委員

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