4P: Basic Phenomena

Computational Plasma Physics

Magnetic Fusion

High Energy Density Hydrodynamics

Basic Phenomena:

4P01: HF Conductivity of Parametrically Unstable Magnetized Plasma , V.G. Panchenko and Victor N. Pavlenko Institute for Nuclear research Prospect Nauki,47 03680 Kiev, Ukraine

4P02: Cross-field Diffusion in Magnetized Plasma due to Parametric Excitation of Convective Cells, Victor N.Pavlenko, V.G.Panchenko, Institute for Nuclear research Prospect Nauki,47 03680 Kiev, Ukraine

4P03: Simplified Algorithm of Electrostatic Fields Analysis Yu.Ya. Volkolupov, V.I. Chumakov, M.A. Ostrizhnoy, M.A. Krasnogolovets, T.A. Semenets Kharkov National University of Radioelectronics 14, Lenin av., Kharkov, Ukraine

4P04: Very Slowly Decaying Afterglow Plasma in Cryogenic Helium Gas Kazuo Minami, Yutaka Yamanishi and Takahiro Nakatani Graduate School of Science and Technology Niigata University, Niigata City, 950-2181 Japan

4P05: Plasma Formation and Electrical Breakdown in Water S. Katsuki*, F. Leipold, M. Laroussi, and K.H. Schoenbach Physical Electronic Research Institute, Old Dominion University Norfolk, VA 23529 * on leave from Kumamoto University, Kumamoto 860-8555, Japan

4P06: Kinetic Modeling of an Atmospheric Pressure Argon Plasma in Contact with a Floating Collector S. Coulombe¹, J.-L. Meunier¹ and M. Shoucri^{2 1}CRTP-Department of Chemical Engineering, McGill University, Montréal, Québec, Canada, H3A 2B2 ²IREQ, Varennes, Québec, Canada, J3X 1S1

4P07: Strong Correlations and Fast Electrons Distribution Function. O.G. Bakunin. Russian Research Center “Kurchatov Institute”,Moscow,Russia.

4P08: Properties of Plasmas Generated by a Single-turn Antenna at Lower-hybrid Frequency Saehoon Uhm, Han Sup Uhm*, and H.Y. Chang** Dept. of Physics, KAIST, Daejeon, Republic of Korea *Ajou University, Suwon, Republic of Korea **Dept. of Physics, KAIST, Daejeon, Republic of Korea

4P09: Effect of Magnetic Field on the Dynamics of Coulomb Cluster O. Ishihara,¹ T. Kamimura,² K. Hirose,² and N. Sato^{3 1}Faculty of Engineering, Yokohama National University, Yokohama 240-8501, Japan ²National Institute for Fusion Science, Toki, 509-5292, Japan ³Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan

4P10: Experimental Observation on Sheath and Magnetic Pre-sheath Over an Oblique Metallic Plate in Presence of Magnetic Field Bornali Singha^*, A. Sarma, and Joyanti Chutia. Plasma Physics Division, Institute of Advanced Study in Science and Technology, Khanapara, Guwahati-781022, Assam.

4P11: Electron Energy Distribution Function in a Helicon Discharge1 Shane Tysk, John Scharer, Kamran Akhtar, and Ben White University of Wisconsin – Madison Department of Electrical and Computer Engineering

4P12: Optical Emission, Electron Energy, Density, Wave Magnetic Field and Spectrum Measurements in a Helicon Plasma Source* J. Scharer, B. White, S. Tysk, E. Paller and K. Akhtar, Electrical and Computer Engineering Dept., Univ. of Wisconsin, Madison 53706

4P13: Finite Element Modeling of the Magnetic Reconnection Experiment (MRX) Richard Marchand, Jianyong Lu, Konstantin Kabin and Robert Rankin University of Alberta Department of Physics, Edmonton AB, T6G 2J1, Canada

4P14: Electron Heating Reduction in Inductively Coupled Plasma at Conditions of the Anomalous Skin Effect Yu. O. Tyshetskiy ¹, A.I. Smolyakov ¹, and V.A. Godyak ^{2 1} University of Saskatchewan 116 Science Place, Dept. of Physics and Engineering Physics, Saskatoon, SK, S7N 5E2, Canada ² OSRAM SYLVANIA 71 Cherry Hill Drive, Beverly, MA, 01915, USA

4P15: Eigenmodes of an Ion Plasma Sheath F. Detering, A.I. Smolyakov and I. Khabibrakhmanov University of Saskatchewan 116 Science Place Saskatoon, SK, S7N 5E2

4P16: Nonlocal Electron Hydrodynamics in Magnetized Plasmas. A.V. Brantov, V. Yu. Bychenkov¹, W. Rozmus, R. Sydora. and C.E. Capjack² Department of Physics,University of Alberta, Edmonton T6G 2J1, Alberta, Canada ¹. P. N. Lebedev Physics Institute, Russian Academy of Science, Moscow 117924, Russia ². Department of Computer and Electrical Engineering, University of Alberta, Edmonton, T6G 2V4, Alberta,Canada

4P17: Analytical Solution of the Relativistic Vlasov Equation and Thermal Transport Coefficients K. Bendib¹, N. Benyahia¹ and A. Bendib^{1 1} Laboratoire Electronique Quantique. Faculté des Sciences- Physique. USTHB BP 32 EL Alia, 16111 Bab Ezzouar Alger, Algérie.

Computational Plasma Physics:

4P18: Simulations of the Radiation-flow Within a Silica-aerogel Target Joysree B. Aubrey Los Alamos National Laboratory Los Alamos NM 87544

4P19: On the Elimination of Numerical Cerenkov Radiation Keith L. Cartwright, Andrew D. Greenwood, John W. Luginsland, and Ernest A. Baca Air Force Research Laboratory Directed Energy Directorate, Kirtland AFB, Albuquerque, NM 87117-5776

4P20: Modeling of Miniature Microwave Plasma Sources T.A. Grotjohn Electrical and Computer Eng., Michigan State University East Lansing, MI 48824

4P21: Numerical simulation of Corona Discharge Using Bidirectional Pulsed Voltage in Wire-cylinder Reactor Heung-Jin Ju, Hui-Dong Hwang, Jeong-Ho Park, *Kwang-Cheol Ko Dept. of Electrical Eng., Hanyang Univ., *Division of Electric and Computer Eng., Hanyang Univ. 17, Haengdang-dong, Seongdong-gu, Seoul, 133-791

4P22: Numerical Simulation of a Stationary 3D Direct Current Plasma Torch L. Klinger¹, J.B. Vos², K. Appert¹ and G. Barbezat^{3 1}Centre de recherches en physique des plasmas, EPFL, 1015 Lausanne, Switzerland ²CFS Engineering, PSE-B, 1015 Lausanne, Switzerland ³Sulzer-Metco AG, Rigackerstr. 16, 5610 Wohlen, Switzerland

4P23: A Finite Volume Scheme for the Two Fluid Plasma System J. Loverich, U. Shumlak University of Washington Aerospace and Energetics Research Program Box 352250 Seattle, WA 98195-2250

4P24: Asymptotic Analysis of Stability Transition in MHD Models M.A. Pinsky, V. Makhin University of Nevada, Reno Reno, NV, 89557

4P25: A Warm Fluid Model of Intense Laser-Plasma Interactions B.A. Shadwick,^*,† G.M. Tarkenton,^† and E.H. Erarey^{* *}Center for Beam Physics, LBNL Berkeley, CA 94720 ^†Institute for Advanced Physics Confier CO, 80433

4P26: Calculations of X-ray Yields in Annular Argon Gas Puff Experiments* P. Steen and S. Chantrenne Titan Pulsed Sciences Division, San Leandro, CA 94577 A. Wilson Avonia, San Diego, CA 92130 D. Bell DTRA, Alexandria, VA 22310

Magnetic Fusion and High Energy Density Hydrodynamics

4P27: Studies of Detached Plasma in the ULS Divertor Simulator K.J. Gibson, P.K. Browning, D.A. Forder, J. Hugill, M. Johnson and B. Mihaljcic Dept of Physics, UMIST PO Box 88, Manchester, M60 1QD

4P28: Design and Performance of a Current Transformer for Efficient Liner Implosions* James. C. Cochrane, Jr, Peter J. Turchi Los Alamos National Laboratory Los Alamos, New Mexico, USA

4P29: Z-pinch Implosing of Massive Copper Liners for Study of Phase Transitions in Carbon B.E. Fridman¹, I.P. Makarevich², A.D. Rakhel³, B.V.Rumyantsev^{4 1}D.V.Efremov Institute of Electrophysical Apparatus Sovetsky pr.,1, Metallostroy, St-Petersburg, 189631, Russia ²Institute of Problems of Electrophysics of RAS Dvortsovaya nab. 18, St-Petersburg, 191186, Russia ³High Energy Density Center, United Institute

4P30: Pulsed Discharge Characteristics of Spherically Convergent Beam Fusion Kunihito Yamauchi, Kazuki Ogasawara, Kunihiko Tomiyasu, Masato Watanabe, Akitoshi Okino and Eiki Hotta Department of Energy Sciences, Tokyo Institute of Technology Nagatsuta, Midori-ku, Yokohama, 226-8502, Japan

4P31: Optimization of Initial Gas Distributions in a Plasma Focus Discharge with a Pulsed Inlet of Gases N.I. Ajzatsky, A.N. Dovbnya, Eh. Yu. Khautiev, M.A. Krasnogolovets, V.I. Krauz, N.G. Reshetnyak, Yu. Ya. Volkolupov, V.V. Zakutin Scientific Research Complex “Accelerator”, National Science Center “Kharkov Institute of Physics and Technology” 1, Akademicheskaya St., 61108 Kharkov, Ukraine

4P32: Spall Experiments in Convergent Geometry Using the Atlas Pulsed Power Facility R.K. Keinigs, W.E. Anderson, F.L. Cochran, D. Oro, G. Rodriguez, M.A. Salazar, A.J.Taylor, D.L. Tonks, W.R.Thissell, A.K. Zurek Los Alamos National Laboratory Los Alamos, NM

4P33: The Inverse Z-Pinch as a Physics Test Bed, and, Possibly, a Target Plasma, for Magnetized Target Fusion (MTF) I. Lindemuth, R. Kirkpatrick, P. Sheehey, R. Siemon Los Alamos National Laboratory Los Alamos NM B. Bauer, V. Makhin, R. Presura, S. Fuelling University of Nevada

4P34: On possibility of Using Periodic Permanent Magnetic Structure to be Initial Energy Source for a Magneto-cumulative Generator Dong Zhiwei Wang Guirong Wang Yuzhi Institute of Applied Physics and Computational Mathematics P.O.Box 8009, Beijing 100088, P.R. China

4P35: Comparison of Z-pinch and Theta-pinch Drive for Implosion of Solid Liners Suitable for Compression of Field Reversed Configurations J.H. Degnan, P.J. Turchi, and R.E. Siemon (1) Air Force Research Laboratory, Directed Energy Directorate (1) Los Alamos National Laboratory

4P36: Extraordinary Phenomena of Micro Ball Lightning MATSUMOTO Taka-aki Department of Nuclear Engineering, Hokkaido University North 13, West 8, Sapporo 060-0813, JAPAN

Basic Phenomena:

4P01:

HF Conductivity of Parametrically Unstable Magnetized Plasma

V.G.Panchenko and Victor N.Pavlenko

Institute for Nuclear research

Prospect Nauki,47 03680 Kiev, Ukraine

The anomalous absorption of high-frequency (HF) pump wave in a nonequilibrium magnetized plasma was studied early on the basis of the kinetic theory of fluctuations [1,2]. The frequency bands in which the effective HF power dissipation mechanisms exist in a thermonuclear and space plasmas are the lower hybrid (LH) and upper hybrid (UH) regions [3,4].

In this report the HF power absorbed in the plasma is determined under the conditions characteristic of the parametric decay of the LH and UH wave into the secondary wave and low-frequency plasma oscillations ( ion-sound modes, convective cells, electron drift waves). It is shown that the anomalous absorption can be caused by scattering of charged particles from turbulent fluctuations of an electric field that is described by HF plasma conductivity.

We have calculated HF conductivity and the effective absorption lengths of pump energy. It is shown that for the thermonuclear plasma the effective absorption length is of the same scale as plasma dimension that ensures effective dissipation of the HF pump power.

References

[1] V.N.Pavlenko, V.G.Panchenko, S.M.Revenchuk, Sov.Phys.JETP, 1986,v.64, p.50.

[2] V.N.Pavlenko, V.G.Panchenko, L.Stenflo and H.Wilhelmsson, Physica Scripta, 1992, v.75, p.237.

[3] V.N.Pavlenko, V.G.Panchenko, I.N.Rosum, Proc. ICPP-1996, Nagoya, Japan, v.1, p. 262, 1996.

[4] V.N.Pavlenko, V.G.Panchenko, Plasma Phys.Reports, 1999, v.25, p. 288.

4P02:

Cross-field diffusion in magnetized plasma

due to parametric excitation of convective cells

Victor N.Pavlenko, V.G.Panchenko

Institute for Nuclear research

Prospect Nauki,47 03680 Kiev, Ukraine

Cross-field diffusion due to the convective cells in a magnetoactive uniform plasma has been of current interest in plasma physics [1-3].

In present report the diffusion in turbulent plasma under conditions of parametric interaction of lower hybrid waves with short-wavelength (, ) and long-wavelength (, ) convective cell modes is studied.

For the parametric decay of lower-hybrid pump wave into a daughter wave and the modified convective cells plasma diffusion coefficient is found.

Numerical calculations show that the diffusion term due to the pump wave is dominated in comparison with the diffusion which takes place in the plasma in the presence of the thermal fluctuations only.

The present results can be of interest for the investigation of anomalous transport processes in laboratory and space plasmas.

References

[1]. H.Okuda, Physics Fluids 1974, v.17, p.375

[2].P.K.Shukla, V.N.Pavlenko, V.G.Panchenko Plasma Phys. Control. Fusion 1991, v.33, p. 643.

[3].V.N.Pavlenko, V.G.Panchenko, S.A.Nazarenko, Plasma Phys.Cont.Fusion 2000, v.42, p.1187.

4P03:

Simplified Algorithm of Electrostatic Fields Analysis

Yu.Ya. Volkolupov, V.I. Chumakov, M.A. Ostrizhnoy, M.A. Krasnogolovets, T.A. Semenets

Kharkov National University of Radioelectronics

14, Lenin av., Kharkov, Ukraine

Algorithm of electrostatic field analysis formed by complex configuration electrode system is considered. The algorithm is based on Fourier transmission of electrode profile. The function of electrode profile is smoothed out with help of low–pass filter to produce equipotential line.

In dependently on distance between the equipotential line and the electrode the frequency response of low–pass filter is changed. Reducing of cut–off frequency of filter corresponds to increasing of distance.

With help of proposed algorithm to obtain equipotential line for electrostatic systems with electrode profile describer by unambiguous functions easily succeed. Typical examples are different inserts into waveguides and strip transmission lines.

4P04:

Very Slowly Decaying Afterglow Plasma

in Cryogenic Helium Gas

Kazuo Minami, Yutaka Yamanishi

and Takahiro Nakatani

Graduate School of Science and Technology

Niigata University, Niigata City, 950-2181 Japan

The purpose of the present experiment is to observe extremely slowly decaying cryogenic afterglow plasmas. It is well known that decay time of afterglow plasma in cryogenic helium gas is elongated by plasma production caused by collisions between metastable molecules. As a result, slow decay times on the order of a few msec were observed in cryogenic helium gas at 4.2 K [1]. The loss mechanism was electron-ion recombination, since they observed densities more than 10⁹ cm^-3. We try to measure a late afterglow period with low densities less than 10⁸ cm^-3 in cryogenic helium gas where the dominant loss mechanism is ambipolar diffusion. We fabricate a comparatively large stainless-steel cylindrical discharge vessel with diameter 16.6 cm and 9.1 cm in length that is a TE(011) mode cavity for 2.84 GHz with Q value larger than 1000. The diffusion length, 2.2 cm, of the present discharge vessel is much larger than those in the previous experiments on cryogenic afterglow plasmas [1][2]. The plasma is produced repeatedly between tungsten needle electrodes by high-voltage pulse of 15 kV, 600 A and duration 3 micro-sec. Gas pressure is varied from 0.06 to 3 Torr.

The plasma decay with time constant longer than 1 sec in cryogenic helium gas at 4.2 K is measured by an improved method of microwave interferometer. We can see very slowly fading fluorescent light with our naked eyes. The decay time is elongated by increasing power of CW microwave for observing the plasma parameters. Also, the decay time increases, if gas temperature is cooled below 4.2 K.

[1] J. F. Delpech and J. C. Gauthier, Phys. Rev. A6, 1932 (1972).

[2] P. D. Goldan and L. Goldstein, Phys. Rev. 138, 1A, A39 (1965).

4P05:

Plasma Formation and Electrical Breakdown in Water

S. Katsuki*, F. Leipold, M. Laroussi, and K.H. Schoenbach

Physical Electronic Research Institute, Old Dominion University

Norfolk, VA 23529

* on leave from Kumamoto University,

Kumamoto 860-8555, Japan

The temporal development of plasma formation in water with up to MV/cm pulsed electric fields applied was explored in a strongly inhomogeneous (wire-plane), and a semi- homogeneous (sphere–plane) electric field configuration. In the first case, by applying 120 kV voltage pulses to a tungsten wire with a diameter of 75 µm, and the second, plane electrode being 23 mm apart, an electric field of more than 2 MV/cm was generated at the wire surface. Replacing the wire with a 1.5 mm diameter sphere allowed us to study electrical breakdown in water in a quasi-homogenous electric field configuration. With submillimeter gaps and voltages of up to 30 kV, electric fields of up to MV/cm could be generated in this case. High-speed photography and an interferometric method were used to explore the temporal development of the discharges. The temporal resolution was, determined by a high-speed camera, on the order of one nanosecond.

For discharges between wire to plane electrodes, a large number of discharge channels emerge simultaneously from the wire electrode and propagate toward the plane electrode with a constant velocity of 32 mm/µs. This velocity is almost independent of the applied voltage. However, the number density of discharge channel is proportional to the applied voltage. The current flowing in each channel is on the order of amperes. The experimental results indicate that the plasma channel propagation is caused by the vaporization of water at the streamer head [1]. Electrical breakdown, characterized by a rapid increase in current, is observed when the first channel reaches the opposite electrode. The plasma formation in semi-homogeneous fields (sphere-plane electrodes) has so far studied by means of a Mach-Zehnder interferometer. At average electric fields of 400 kV/cm, approximately 100 mm wide striations have been observed which emerge from the surface of the spherical electrode, and propagate toward the plane electrode with the velocity of approximately 20 mm/ms. The striations seem to play a major role in streamer initiation, as indicated by the observation that early breakdown is related to geometrical distortions of the striations. Experiments to explore the physics of these striations are underway.

[1] S. Katsuki, H. Akiyama, A. Abou-Ghazala, and K.H. Schoenbach,

“Characteristic of streamer discharges between wire and plane electrodes in water,” to be published in IEEE Trans. Dielectr. Electr. Insulat, 2002.

This research has been supported by an AFOSR/DOD MURI grant on Compact, Portable Pulsed Power, administered through the University of New Mexico.

4P06:

Kinetic Modeling of an Atmospheric Pressure Argon Plasma in Contact with a Floating Collector

S. Coulombe¹, J.-L. Meunier¹ and M. Shoucri²

¹CRTP-Department of Chemical Engineering, McGill University, Montréal, Québec, Canada, H3A 2B2

²IREQ, Varennes, Québec, Canada, J3X 1S1

The problem of an atmospheric pressure argon plasma (T_edge=1 eV) in contact with a floating collector is considered through the framework of the kinetic Boltzmann equation in the x-v_x phase space, f_ion;e(x,v_x,ion;e). A BGK collision term where only weak deviations from the Maxwellian velocity distribution are allowed is considered for the electron equation. This collision term for the ion is more comprehensive and accounts for large potential deviations from the Maxwellian distribution. Due to the relatively low mean energies expected (<15 eV), only the momentum transfer collisions are considered. The normalized Boltzmann equations are solved self-consistently with Poisson’s equation using the method of fractional steps with cubic spline interpolation in the x-v_x space. 100 grid points in both the x and v_x spaces are used providing good solution stability and grid independence. Steady state solutions are obtained for normalized times w_p,iont>200. The results show that the sheath region extends about 25 Debye lengths from the floating collector surface and that the sheath voltage drop is ~6.5 V. The electron current density peaks at a distance of ~9 Debye lengths while the ion current remains essentially constant from the plasma edge to the collector up to a distance of ~9 Debye lengths, and then sharply drops to zero at the collector surface. Both currents at the collector are similar in magnitude giving rise to a zero collection current. The electron velocity distribution remains very close to a Maxwellian throughout the x-space while the ion distribution shows a smooth transition from a Maxwellian at the plasma edge to a distribution showing strong ion accelerations towards negative velocities near the collector surface. In the close vicinity of the collector surface, the ion velocity distribution peaks near -0.8C_s (C_s=(kT_edge/m_ion)^1/2). Further work is in progress to extend the kinetic model to include a thermionic electron beam and aims at a kinetic description of the cathode region of high-pressure arc discharges.

4P07:

Strong Correlations and Fast Electrons Distribution Function.

O.G. Bakunin. Russian Research Center

“Kurchatov Institute”,Moscow,Russia.

Modern technology often use discharges with strong nonequilibrium plasma. The electron distribution function can differ from Maxvellian one. For instance this is nonequilibrium discharge with high pressure. There are a lot of fast electrons. Distribution function became directly connected with correlations. Here kinetic equation of diffusive form does not apply. Classical kinetic equation are described only conditions near to equilibrium.

This work offers to use ideas anomalous diffusion in phase-space. The correlation properties describe by correlations of velocities of emitting particles: . We offer to use functional equation for probability collision instead of kinetic equation:

.

Usually : . In these case we use ballistic electrons with “memory” effects: . Distribution function become direct connected with correlations. In classical theory Kubo-Mory of transfer is necessary to get nondivergences integral: .In considering case we can use event “power function”. The information about kinetics and correlations properties are containing in one functional equation. It was received solution this equation in form Levy function:

.

The solution of this form can not to be get with help asymptotic methods of kinetic theory. Asymptotics of solution have scale-invariant character . This indicate on fractal properties phase-space.

4P08:

Properties of Plasmas Generated by a Single-turn Antenna

at Lower-hybrid Frequency

Saehoon Uhm, Han Sup Uhm*, and H. Y. Chang**

Dept. of Physics, KAIST, Daejeon, Republic of Korea

*Ajou University, Suwon, Republic of Korea

**Dept. of Physics, KAIST, Daejeon, Republic of Korea

A theoretical model of the plasmas generated by a sheath-helix antenna is developed for axisymmetric perturbations. The system configuration consists of a cylindrical plasma column inside a dielectric tube of radius R_c. The eigenvalue equation is obtained and the eigenfunction is identified as the Bessel function J₀(x) of the first kind of order zero. The radial wave numbers ξ and η for the eigenfunction are described in terms of the rf frequency and plasma density. A full dispersion relation is analytically obtained, including the influence of finite plasma size. It is shown from the dispersion relation that the radial mode number ξ approaches infinity at the lower-hybrid frequency, exhibiting a resonance condition. Meanwhile, the radial wave number η approaches 3.83/R_c at the lower-hybrid frequency. A cross-sectional view of the light emission in experiment indicates that the helicon-plasma density at the lower-hybrid frequency has a hollow profile. The azimuthal component E_θ(r) of the perturbed electric field observed experimentally is very similar to the theoretical model of J₁(3.83r/R_c) at the lower-hybrid frequency. The emission peak coincides with the radial location of the strongest electric-field intensity.

4P09:

Effect of Magnetic Field on the Dynamics of

Coulomb Cluster

O. Ishihara,¹ T. Kamimura,² K. Hirose,² and N. Sato³

¹Faculty of Engineering, Yokohama National University, Yokohama 240-8501, Japan

²National Institute for Fusion Science, Toki, 509-5292, Japan

³Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan

A Coulomb cluster has been observed to levitate in the low temperature plasma device by the balance of the sheath electric and the gravitational forces acting on the cluster. Motivated by the observation of rotation of the cluster in the presence of magnetic field[1], we have studied the dynamics of the Coulomb cluster by a particle simulation [2] as well by an analytical model. Our preliminary result was presented earlier[3]. Here we study the effect of the magnetic field on the dynamics of the Coulomb cluster in detail. We consider a Hamiltonian

,

where m and Q are a mass and a charge of a dust particulate, K is a constant to define a confining potential, g is a gravitational acceleration, is a Coulomb potential

produced by the j-th dust particulates in the cluster. The equations of motion reveal the rotational motion of the dust particulates in the cluster. We also study the effect of the ion flow which was considered to be responsible for the spinning rotation of individual dust particulates[4].

This work was supported by a Grant-in-Aid for Scientific Research (C) from Japan Society for the Promotion of Science.

[1] N. Sato, G. Uchida, T. Kaneko, S. Shimizu, and S. Iizuka, Phys. Plasmas 8, 1786 (2001).

[2] O. Ishihara, T. Kamimura, K. Hirose, and N. Sato, Second Workshop on Fine Particle Plasmas (National Institute for Fusion Science, Toki, Japan, December 19-20, 2001).

[3]T. Kamimura, K. Hirose, G. Uchida, S. Iizuka, and N. Sato, International Toki Conference on Potential and Structure in Plasmas (Toki, Japan, December, 2000).

[4]O. Ishihara and N. Sato, IEEE Trans. Plasma Sci. 29, 179 (2001).

4P10:

Experimental Observation on Sheath and Magnetic Pre-sheath Over an Oblique Metallic Plate in Presence of Magnetic Field

Bornali Singha^*, A. Sarma, and Joyanti Chutia.

Plasma Physics Division,

Institute of Advanced Study in Science and Technology,

Khanapara, Guwahati-781022, Assam.

Experimental observation on sheath and magnetic pre-sheath over an oblique metallic plate in presence of a magnetic field has been performed. The plate has been deployed in the plasma environment making some finite angle with the externally applied magnetic field. Studies have been carried out for various angles, magnetic field gradients and plate-biasing voltages as well. The analyses reveal that the magnetic pre-sheath thickness increases while the angle is varied from minimum to maximum; whereas the reverse happens in case of the sheath thickness. Furthermore, measurements of the sheath widths with increasing magnetic field strengths and the plate biasing voltages have been done which imply that sheath width enhances with increasing both the parameters. The electron temperature in the bulk plasma region is also evaluated for all the plasma conditions so as to find out its influence on the characteristic behavior of the sheath formation.

4P11:

Electron Energy Distribution Function in a Helicon Discharge¹

Shane Tysk, John Scharer, Kamran Akhtar, and Ben White

University of Wisconsin – Madison

Department of Electrical and Computer Engineering

A miniature, fast time response, gridded energy analyzer (GEA) is designed and constructed to measure the electron energy distribution function (EEDF) in a helicon plasma and compare with density, wave magnetic field, and Ar II optical emission results. These plasmas demonstrate an ionization efficiency greater than would be expected for their typical 3 eV electron temperature. The enhanced ionization effects may be partially explained by elevated quantities of high temperature electrons in the 20-50 eV range. Energy analyzer measurements of the EEDF can provide a more complete picture of helicon plasma source properties in different regimes. The helicon experimental facility at the University of Wisconsin operates with parameters of B= 0.2-1 kG, T=3 eV, and n=10^11-13 cm^-3. The plasma is created in a 10 cm diameter tube at Argon pressures in the 2-100 mTorr range with a half-turn double-helix antenna and a 6 ms pulsed 0.8-3 kW 10-30 MHz RF power source. The gridded energy analyzer consists of three grids and a collector plate in a 2.5 cm diameter stainless steel enclosure mounted on a movable rod. The enclosure is mounted at the end of a bend in the rod that allows the energy analyzer to scan the plasma radially. The grid surfaces are at all times perpendicular to the magnetic field. The entrance grid is a 500 lines per inch (lpi) Cu mesh biased at the plasma potential. The next grid is a 200 lpi Cu mesh repeller grid biased at a high positive potential to repel ions. The final grid is a 200 lpi Cu mesh with a swept variable negative bias to selectively repel electrons below a particular energy. The final part is the solid Cu collector plate biased at a high positive potential to collect electrons and emitted secondaries and repel ions. The fast time response is accomplished by restricting the distance between the entrance grid and the collector plate to 0.2 cm. The fast time response is necessary to correlate the data with the 10-30 MHz RF wave. The optical measurements count photons arising from Ar II emission and correlate photons in 10 bins corresponding to ~35° of phase of the RF wave (7 ns). The energy analyzer is capable of discriminating ~15° of phase of the wave (3 ns). Initial results and comparison of the time variation of the electron energy distribution with AR II optical emission for a wide range of coupled plasma powers, magnetic field intensities, and neutral pressures to clarify the mechanisms for ionization and plasma production.

¹This work is primarily supported by Air Force Office of Scientific Research Grants (F49620-00-1-0181) in cooperation with the Defense Department Research and Engineering Air Plasma Multi University Research Initiative Program. It is also supported in part by NSF Grant ECS-9905948.

4P12:

Optical Emission, Electron Energy, Density, Wave Magnetic Field and Spectrum Measurements in a Helicon Plasma Source*

J. Scharer, B. White, S. Tysk, E. Paller and K. Akhtar

Electrical and Computer Engineering Dept.

Univ. of Wisconsin, Madison 53706

Measurements and analysis of optical emission, electron energy analyzer, Langmuir and magnetic probe and wave spectra are presented for a wide range of helicon plasma source conditions. Helicon plasma source characteristics at lower argon neutral pressures of 2-6 mTorr at both low(200 G) and high(1.2 kG) magnetic field strengths and at high pressures(100 mTorr)are presented for a wide range of radiofrequency input powers. Plasma densities in the range of 10¹¹-10¹³/cm³ are obtained in the UW helicon facility which utilizes a double half-turn helix. Observations of Ar II emission, its modulation and correlation with the rf phase are presented in both time and spatial domains for a variety of plasma conditions. The emission spectrum measured by optical probes either internal or external to the 10 cm diameter Pyrex cylinder plasma is compared with wave magnetic and plasma density as well as miniaturized electron energy analyzer measurements. In addition, both low frequency, fundamental, sideband and harmonic components of the rf wave are measured and analyzed to obtain a comprehensive picture of the helicon source operation for a variety of conditions. Network analyzer measurements, AntenaII wave modeling and wave-particle ionization models are used to analyze the properties of the plasma source.

*This research is supported by NSF Grant ECS-9905948 and by AFOSR Grant F49620-00-1-0181.

4P13:

Finite element modeling of the Magnetic Reconnection Experiment (MRX)

Richard Marchand, Jianyong Lu, Konstantin Kabin and Robert Rankin

University of Alberta

Department of Physics, Edmonton AB, T6G 2J1, Canada

The Magnetic Reconnection Experiment (Hsu, et al. Phys. Plasmas, Vol, 8, pp. 1916-1928 (2001)) is modeled using a two dimensional finite element code. MRX is a laboratory experiment designed to study magnetic reconnection under well diagnosed controlled conditions. While of a much smaller scale than the magnetosphere, this experiment allows a direct analysis of several fundamental physical phenomena occurring in magnetic reconnection, including plasma transport and heating. In the simulations, the equilibrium and transport equations are discretized with finite elements on an unstructured triangular mesh. The equilibrium is obtained from solving the Grad-Shafranov equation. Plasma transport and magnetic reconnection are modeled in a resistive MHD approximation. Specifically, we solve for a reduced set of Maxwell equations, as well as for the conservation of particles, momentum and energy for electrons and ions. Preliminary results are presented for finite helicity, as well as for zero helicity reconnection.

4P14:

Electron Heating Reduction in Inductively Coupled Plasma

at Conditions of the Anomalous Skin Effect

Yu. O. Tyshetskiy ¹, A.I. Smolyakov ¹, and V.A. Godyak ²

¹ University of Saskatchewan

116 Science Place, Dept. of Physics and Engineering Physics,

Saskatoon, SK, S7N 5E2, Canada

² OSRAM SYLVANIA

71 Cherry Hill Drive, Beverly, MA, 01915, USA

A simple analytic model of electron heating in inductively coupled plasma (ICP) at the condition of anomalous skin effect (nonlocal regime) has been developed. The model assumes an exponential rf field decay and takes into account both, collisional and electron thermal effects and thus is applicable for an arbitrary degree of collisionality. Simple expressions are obtained for the spatial profile and integral power absorption of rf power in ICP. Negative power absorption regions have been found for a given exponential profile of the electric field in plasma and are shown to be similar to those found in experiment and calculation with a self-consistent electric field distribution. Thus, the negative power absorption is associated with thermal dispersion of the rf electron current, rather than with the non-monotonic profile of the rf electric field typical for anomalous skin effect. The results obtained from an approximate model are compared with experimental data and with the results of a self-consistent model, showing in both cases a reasonable agreement. A new effect of electron heating reduction in ICP due to electron thermal motion has been predicted in this model. It has been demonstrated that at low driving frequencies accounting for electron thermal motion results in a reduction of the integral rf power absorption in ICP compared with the purely collisional (ohmic) heating for the same electron-atom collision frequency. The reduction of electron heating, found in our simple analytical approach with the exponential rf electric field, has been confirmed in a model with the self-consistent profile of the rf electric field.

4P15:

Eigenmodes of an Ion Plasma Sheath

F. Detering, A.I. Smolyakov and I. Khabibrakhmanov

University of Saskatchewan

116 Science Place

Saskatoon, SK, S7N 5E2

We investigate the structure and stability of transverse (in the sheath plane) eigenmodes of a collisionless ion sheath occurring at the plasma boundary. An ion sheath represents a particular example of nonlinear ion-sound waves, which, in general include solitons and periodic waves structures. All these nonlinear waves can be found by formulating plasma equations in a form of the oscillator eigenvalue problem in a generic nonlinear potential (Sagdeev potential). Solitons and periodic waves correspond to trapped (localized) states, while the sheath solution is an untrapped state with the local maximum as the wall. To investigate the transverse stability and eigenmodes of the sheath solution we employ a method previously used to study transverse oscillations of solitons (e.g. within the Kadomtsev-Petviashvili equation). We have generalized this technique for the sheath solution. We have obtained the dispersion relation for transverse oscillations and found stable eigenmodes with a frequency lower than the ion plasma frequency.

4P16:

Nonlocal Electron Hydrodynamics in Magnetized Plasmas.

A.V. Brantov, V. Yu. Bychenkov¹, W. Rozmus, R. Sydora.

and C. E. Capjack²

Department of Physics,University of Alberta,

Edmonton T6G 2J1, Alberta, Canada

¹. P. N. Lebedev Physics Institute, Russian Academy of Science, Moscow 117924, Russia

². Department of Computer and Electrical Engineering, University of Alberta, Edmonton,T6G 2V4, Alberta,Canada

A system of nonlocal electron-transport equations for small perturbations in a fully ionized magnetized plasma is derived as a generalization of the nonlocal theory of unmagnetized plasmas [V. Yu. Bychenkov et al., Phys. Rev. Lett. 75, 4405 (1995); A. V. Brantov et al., JETP 84, 716 (1996)]. The Fourier components of the electron flux are found in an explicit form for quasi-static conditions in the limit k_^r < 1 and k_|| l_ei< 1. These are expressed in terms of the longitudinal, oblique, and transversal components of the generalized force (where k - wave number, r - Larmour radius and l_ei -electron mean free path). All the transport coefficients are calculated as a function of wave number. The interplay between nonlocality and particle magnetization makes the effect of heat flux suppression across a magnetic field less pronounced than found in the conventional local case. The equations of nonlocal hydrodynamics for small perturbations in magnetized plasmas are formulated and the dispersion relation for magnetized ion acoustic waves (IAW) is derived. The dependence of IAW damping on the magnetic field strength is investigated for weakly collisional plasmas.

4P17:

Analytical Solution of the Relativistic Vlasov Equation

and Thermal Transport Coefficients

K. Bendib¹, N. Benyahia¹ and A. Bendib¹

¹ Laboratoire Electronique Quantique. Faculté des Sciences- Physique. USTHB

BP 32 EL Alia, 16111 Bab Ezzouar Alger, Algérie.

An analytic solution of the perturbed relativistic Vlasov equation with the use of the projection operators [1] is presented. The explicit expression of the quasistatic distribution function has been derived. The collisioneless thermal transport coefficient, namely the thermal conductivity and the temperature anisotropy are deduced in whole temperature regime. It is shown that for ultrarelativistic plasmas, the thermal transport is less efficient than for the nonrelativistic one. Whereas, the relativistic effects increase the temperature anisotropy.

[1] K. Bendib and A. Bendib, Phys. Plasmas 6, 1500 (1999).

Computational Plasma Physics:

4P18:

Simulations of the Radiation-flow Within a Silica-aerogel Target

Joysree B. Aubrey

Los Alamos National Laboratory

Los Alamos NM 87544

The interaction of a silica-aerogel target with a source of soft x-rays is calculated using two-dimensional Lagrangian and Eulerian codes. The radiation is generated by a z-pinch contained within a vacuum hohlraum at Sandia National Laboratories in Albuquerque, NM. The source has been well-characterized using both experiments and simulations. Burn-through foils are used to shield the targets during the implosion phase of the pinch, generation of x-rays and equilibration of the radiation within the hohlraum. The impact of the foils on the experiments that are fielded is still under study. One of the issues under consideration in the present work is the effect of the radiation on the immediate environment of the target (including the burn-through foil). Parameter studies on the target itself have been done using different radiation-flow models. The effects of uncertainties in EOS’s and opacities are presented as well.

4P19:

On the Elimination of Numerical Cerenkov Radiation

Keith L. Cartwright, Andrew D. Greenwood, John

W. Luginsland, and Ernest A. Baca

Air Force Research Laboratory

Directed Energy Directorate, Kirtland AFB, Albuquerque, NM 87117-5776

Particle in cell (PIC) simulations are a useful tool in modeling plasma in physical devices. The Yee finite difference time domain (FDTD) method is commonly used in PIC simulations to model the electromagnetic fields. However, in the Yee FDTD method, poorly resolved waves, at frequencies near the grid’s cut off frequency, travel slower than the physical speed of light. These slowly traveling poorly resolved waves are not a problem in many simulations because the physics of interest are at much lower frequencies. However, when high-energy particles are present, the particles may travel faster than the numerical speed of their own radiation, leading to non-physical, numerical Cerenkov radiation. Due to non-linear interaction between the particles and the fields, the numerical Cerenkov radiation couples into the frequency band of physical interest and corrupts the PIC simulation. There are two methods of mitigating the effects of the numerical Cerenkov radiation. The computational stencil used to approximate the curl operator can be altered to improve the high frequency physics, or a filtering scheme can be introduced to attenuate the waves that cause the numerical Cerenkov radiation. Altering the computational stencil is more physically accurate but is difficult to implement while maintaining charge conservation in the code. Thus, filtering is more commonly used. Two previously published filters by Godfrey and Friedman are analyzed and compared to ideally desired filter properties.

4P20:

Modeling of Miniature Microwave Plasma Sources

T.A. Grotjohn

Electrical and Computer Eng., Michigan State University

East Lansing, MI 48824

Recently, interest in the development of systems on a chip, MEMS and their related microsystem applications, has suggested the possibility of numerous applications for miniature plasma sources. Accordingly, this investigation is devoted to developing models that improve the understanding of small microwave plasma sources. Methods of creating and controlling miniature microwave discharges that operate with low input power levels are being investigated. One aspect of this investigation is a numerical modeling effort on small microwave plasma sources that create plasmas with sizes in the range of submillimeter to a few millimeters. Microwave plasma systems based on microstripline structures [1] and monopole antenna structures[2] are being experimental constructed and measured, as well as, being modeled. The modeling work is the objective of this paper.

As described in [1,2] both bounded and unbounded microwave discharge systems are being studied. The modeling effort uses either one- and two-dimensional self-consistent solutions of Maxwell equations and the plasma discharge equations to solve for the discharge behavior. This model was initially developed for larger discharge systems [3] and is applied to the miniature microwave discharges in this study. The plasma discharge equations solved include the particle and energy balance equations, as well as, the electron Boltzmann equation.

Miniature microwave discharge experimental data and modeling results are generated across a range of input parameters, including pressure variation from below 0.1 Torr to 50 Torr, input power at 2.45 GHz from one watt to 100 watts, and a variety of gases including argon and hydrogen. Microwave plasmas of various sizes (volumes) and aspect ratios are studied. The experimental and modeling results are used to identify the operating regime necessary to excite and maintain stable, miniature microwave plasmas.

[1] The paper/abstract by Wijaya, Zuo, Grotjohn and Asmussen at this conference.

[2] The paper/abstract by Zuo, Grotjohn, and Asmussen at this conference.

[3]K. Hassouni, T. A. Grotjohn and A. Gicquel, J. Appl. Phys., 86, 134, 1999

Work supported by National Science Foundation, NSF-DMI-0078480.

4P21:

Numerical Simulation of Corona Discharge Using Bidirectional Pulsed Voltage in Wire-cylinder Reactor

Heung-Jin Ju, Hui-Dong Hwang, Jeong-Ho Park, *Kwang-Cheol Ko

Dept. of Electrical Eng., Hanyang Univ., *Division of Electric and Computer Eng., Hanyang Univ. 17, Haengdang-dong, Seongdong-gu, Seoul, 133-791, Korea

In 2-Dimensional wire-cylinder reactor, the influence of electric field and charged particle density is simulated. Poisson equation for the electric field and continuity equation was calculated to find out the temporal evolution of streamer corona using FEM-FCT method. Also the temporal distribution of radicals was calculated using Runge-Kutta method. A bidirectional pulsed voltage was applied to remove the noxious flue-gas efficiently.

4P22:

Numerical Simulation of a Stationary 3D Direct Current Plasma Torch

L. Klinger¹, J.B. Vos², K. Appert¹ and G. Barbezat³

¹Centre de recherches en physique des plasmas, EPFL, 1015 Lausanne, Switzerland

²CFS Engineering, PSE-B, 1015 Lausanne, Switzerland

³Sulzer-Metco AG, Rigackerstr. 16, 5610 Wohlen, Switzerland

Electric arcs used in plasma torches are found in many practical applications, such as thermal spraying or waste treatment. To get a better understanding of phenomena occuring inside a torch, a number of numerical studies first considered mainly 2D configurations [1]. In recent years, the increased available computer power allowed researchers to progress towards simulations of electric arcs in fully 3D configurations, such as arcs in a cross-flow [2] or DC plasma torches [3].

A 3D code was developed, starting from a Navier-Stokes CFD code [4] implementing the finite volume method, to which a Poisson equation for the electrical potential was added. The fluid and electric parts are linked through ohmic heating and Lorentz force source terms and electric conductivity, which depends on the state of the fluid. The code was first tested for arcs in a cross-flow in a simple geometry as described in the experimental study of Benenson et al. [5]. Results were consistent with similar simulations by Kelkar et al. [2].

Here we present simulations of an arc in the geometry of a Sulzer-Metco F4 torch operated in steady-mode conditions (600 A, 30 SLPM argon). Early runs revealed numerical problems originating in the evaluation of gradients not present in [4]. Recently we have found a second-order method for gradient evaluations based on an isoparametric transformation that retains its accuracy even on highly distorted meshes. Steady state computational solutions for the F4 torch using this new method will be presented.

References

[1] J.-M. Bauchire, J.-J. Gonzalez and A. Gleizes, Journal de Physique III, 7(4), 829-837, 1997.

[2] M. Kelkar and J. Heberlein, J. Phys. D: Appl. Phys., 33, 2172-2182, 2000.

[3] H.-P. Li and X. Chen, J. Phys. D: Appl. Phys., 34, L99-L102, 2001

[4] J. B. Vos, A. W. Rizzi, A. Corjon, E. Chaput and E. Soinne, Sciences Meeting & Exhibit, Reno, NV, January 1998

[5] D. M. Benenson and A. A. Cenkner, Journal of Heat Transfer, pp. 276-284, 1970.

4P23:

A Finite Volume Scheme for the Two Fluid Plasma System

J. Loverich, U. Shumlak

University of Washington

Aerospace and Energetics Research Program

Box 352250, Seattle, WA 98195-2250

In this paper we present our work on a numerical one-dimensional two fluid plasma solver. We take the collisionless, non-relativistic system of equations consisting of ion continuity, ion momentum, ion energy, combined with electron continuity, electron momentum and electron energy, coupled with the full electrodynamic Maxwell’s equations. The algorithm is a first-order time, second-order space finite volume formulation of a Roe-type approximate Riemann solver and uses flux limiters for good shock resolution without spurious oscillations. We address the issue of stiffness introduced by the speed of light and the stiffness associated with the strong coupling of the source terms in the hyperbolic system. Both explicit and implicit schemes are developed and the advantages of the implicit scheme are discussed. It is shown how the algorithm may be extended to multiple dimensions. The algorithm is tested on various numerical and physical problems including electrostatic and electromagnetic two fluid plasma waves and shock problems comparing the two fluid results to the MHD results.

4P24:

Asymptotic Analysis of Stability Transition in MHD Models

M.A. Pinsky, V. Makhin

University of Nevada, Reno

Reno, NV, 89557

Mathematical models of plasma instabilities, such as dense z-pinches, are often described by systems of nonlinear PDEs with fast varying coefficients, which involve numerous uncertainties in equation parameters, boundary and initial conditions. Instabilities and high dimension of these models may amplify uncertainties and result in unpredictability of simulations, which mirrors unpredictability of real systems. This has two important aspects. One is that underling dynamics may exhibit extreme sensitivity to variation of their parameters, initial and boundary conditions, which has been studied in the context of bifurcation phenomena and deterministic chaos. The second is combinatorial complexity of evaluating all model combinations that arise from possible variations in assumptions, parameters and initial data which prohibits direct evaluation of model uncertainties. Thus, it is important to understand and quantify the limits of predictability of full system simulation in terms of the uncertainties, inherent structure of the model and its components, and the length of the observation interval, and to develop computational approaches minimizing the effect of uncertainties and reducing simulation time while preserving and controlling the accuracy of obtained results.

In this paper we outline an asymptotic approach leading to derivation of simplified models of initial complex systems with fast varying coefficients. Each of these simplified models intend to provide to a certain degree inner averaging of individual elaborated simulations of the initial system and present more robust and practically significant results then individual computation events. Stability transition describing by these simplified models could be interpret as bifurcation phenomena developed due to variation of parameters in systems with constant or slowly varying coefficients which lead to deep classification of complex unstable behavior induced by fast varying parameters.

4P25:

A Warm Fluid Model of Intense Laser-Plasma Interactions

B.A. Shadwick,^*,† G.M. Tarkenton,^† and E.H. Erarey^*

^*Center for Beam Physics, LBNL

Berkeley, CA 94720

^†Institute for Advanced Physics

Confier CO, 80433

Much of the physics relevant to understanding the interaction of intense laser pulses with underdense plasmas is contained in the Vlasov–Maxwell equations. In limited, specialized cases, analytical progress can be made towards solving the Vlasov equation, but in full generality, the Vlasov–Maxwell system is considered to be intractable to analytic solution. Fluid models (both warm and cold) represent a significant simplification over full kinetic treatments of plasma dynamics while retaining enough physics to be qualitatively and quantitatively useful approximation. For the configurations of interest to us (namely, those associated with advanced accelerator concepts), the bulk motion of the plasma is relativistic and the fractional spread in momentum is typically very small. This regime is in contrast to the usual regime of relativistic thermodynamics¹ where the momentum spread is assumed to very large (i.e., high temperature). Following up on our previous work on modeling intense laser-plasma interactions with cold fluids², we are exploring warm fluid models. These models represent the next level in a hierarchy of complexity beyond the cold fluid approximation. With only a modest increase in computation effort, warm fluids incorporate effects that are relevant to a variety of technologically interesting cases. We present a derivation of the relativistic warm fluid from a kinetic (i.e. Vlasov) perspective and expand on the connection with the usual relativistic thermodynamic approach. We will provide examples in both one and two dimension and discuss experimental parameters where these effects are believed to be important.

¹S. R. de Groot, W. A. van Leeuwen and Ch. G. van Weert, Relativistic Kinetic Theory: Principles and Applications, North-Holland (1980).

²B.A.Shadwick, G. M. Tarkenton, E.H. Esarey, and W.P. Leemans, “Fluid Modeling of Intense Laser-Plasma Interactions,” in Advanced Accelerator Concepts, P. Colestock and S. Kelley editors, AIP Conf. Proc. 569 (AIP, NY 2001), pg. 154.

4P26:

Calculations of X-ray Yields in Annular Argon Gas Puff Experiments*

P. Steen and S. Chantrenne

Titan Pulsed Sciences Division, San Leandro, CA 94577

A. Wilson

B.

Avonia, San Diego, CA 92130

C. Bell

D.

DTRA, Alexandria, VA 22310

We have compared the measured yield and timing of x-ray pulses in Double Eagle 2D radiation-MHD calculations performed using MACH2. For the twin shell masses involved, the plasma was treated as optically thin to the K-shell radiation and two collisional radiative (CR) models were used to assess their ability to predict output. We found that calculations of both timing and yield of radiation above 1 keV gave reasonably accurate agreement with measurements if (1) the spatial resolution of the plasma during the peak compression and radiation output pulse was adequate and (2) the magnetic field gradients near the plasma-vacuum interface during implosion were sufficiently accurate. For an Eulerian code such as MACH2, such calculations, while possible, are not always straightforward to carry out. Practical values of the pseudo-vacuum resistivity in the absence of special treatment, may lead to compressed plasma densities that are too low and temperatures that are too high, resulting in radiative yield predictions that fall below measured values. We discuss differences in the spectra calculated using the two CR models and compare them with experimental data.

_______________________

*Work supported by the Defense Threat Reduction Agency.

Magnetic Fusion and High Energy Density Hydrodynamics

4P27:

Studies of Detached Plasma in the ULS Divertor Simulator

K.J. Gibson, P.K. Browning, D.A. Forder, J. Hugill, M. Johnson and B. Mihaljcic

Dept of Physics, UMIST

PO Box 88, Manchester, M60 1QD

We report on experimental and modelling studies of “detached “ plasma operation in the UMIST Linear System (ULS) divertor simulator. The ULS is a device designed to study a range of edge plasma physics issues relevant to tokamak gas target divertors and is capable of producing steady-state plasmas with electron densities and temperatures in the range 10¹⁷ – 10¹⁹ m^-3 and 2 – 15 eV respectively; this plasma is made to flow into a separate gas target chamber into which a variety of gases can be introduced. Previous studies of detached plasmas in the ULS have centred on the interaction between hydrogen plasma and low pressure (< 10 mTorr) neutral hydrogen gas and have identified aregime in which molecular activated recombination processes appear to be the dominant plasma loss mechanism (MG Rusbridge et al, Plas. Phys. Cont. Fus. 42, 588 (2000)).

Here we report on further studies in which the upstream plasma parameters are varied such that three-body and radiative electron-ion recombination (EIR) of hydrogen plasmas can be dominant. Spectroscopic and Langmuir probes data have demonstrated the resulting highly non-equilibrium distribution of excited neutral states resulting from these recombining plasmas. Evidence of hysteresis is found in the transition between the two modes (EIR and MAR) of recombination.

Initial modelling of the recombination region in the target chamber is being undertaken using simplified one-dimensional electron energy balance and continuity equations (Krasheninnikov et al, Phys. Plas. 4, 1644 (1997)). We determine the factors that govern the threshold between MAR and EIR dominant detached regimes in terms of the upstream plasma parameters. We discuss the significance of these results for future divertor simulator research.

4P28:

Design and Performance of a Current Transformer for Efficient Liner Implosions*

James. C. Cochrane, Jr, Peter J. Turchi

Los Alamos National Laboratory

Los Alamos, New Mexico, USA

Proton radiography offers several advantages in the analysis of convergent geometry hydrodynamic experiments when compared to the more usual flash x-ray radiography and laser shadowgraphy. However, such an experiment must be fielded at the proton beam line source. This requirement places severe constraints on the size and thus the efficiency of an electrical pulsed power driver. Turchi suggested using a current transformer with a minimum inductance toroidal secondary, with the inner wall of the toroid as the liner. Work is presented showing the design and performance of such a small (~18cm diameter) current transformer capable of delivering over 5MA to a 4g, 2.4 cm radius, liner. Such a liner will be accelerated to over 4km/sec before impacting a target at a radius of 0.5cm. These parameters are similar to experiments done on the Pegasus pulsed power facility using a large capacitor bank with a total system inductance of 28-34nH, depending on load geometry. The system presented here is able to achieve this performance with a compact, portable, capacitor bank storing 250kJ at 100kV. The entire pulsed power driver consist of 3 Marxed pairs of Atlas capacitors connected via a fuse to the current transformer/liner, all mounted on a portable platform.

*Work performed under the auspices University of California, for the NNSI under contract W-7405-Eng-36

4P29:

Z-pinch Implosing of Massive Copper Liners

for Study of Phase Transitions in Carbon

B.E. Fridman¹, I.P. Makarevich², A.D. Rakhel³, B.V. Rumyantsev⁴

¹D.V.Efremov Institute of Electrophysical Apparatus

Sovetsky pr.,1, Metallostroy, St-Petersburg, 189631, Russia

²Institute of Problems of Electrophysics of RAS

Dvortsovaya nab. 18, St-Petersburg, 191186, Russia

³High Energy Density Center, United Institute

for High Temperature of RAS

Izhorskaya, 13/19, Moscow, 127412, Russia

A.F.Ioffe

Physic Technical Institute of RAS

Polytechnicheskaya 26, St-Petersburg, 194021, Russia

The experimental set-up on z-pinch implosion is described. In the set-up a cylindrical copper tube (liner) having wall with 1¸3 mm thickness is accelerated by electrodynamic forces arising when pulsed electrical current of 2¸4 MA magnitude is passed through the liner in the longitudinal direction. Inside the liner the steel tube with smaller diameter is placed. The steel tube is filled by graphite or contained graphite substance. In the experiments the inner surface of liner achieved a velocity of about 1 km/s. The graphite inside steel tube is exposed to shock loading when the liner impacts this tube. As a result the pressure inside steel tube achieves about 30 GPa; the temperature increases also. Under this conditions the graphite may undergo phase transitions, including the graphite-diamond phase transition. In our experiments we have received up to 4% of yellow crystalline carbon. The results of X-ray diffraction analysis of carbon exposed to shock loading, as well as the electron microscope photographs of crystallites are presented. The limitations on the electrical current magnitude and the liner velocity achieved in the experiments are considered.

This work was executed in Institute of Problems of Electrophysics of RAS and supported by the Russian Foundation for Basic Research under project number 01-02-17243.

4P30:

Pulsed Discharge Characteristics of

Spherically Convergent Beam Fusion

Kunihito Yamauchi, Kazuki Ogasawara, Kunihiko Tomiyasu, Masato Watanabe

Akitoshi Okino and Eiki Hotta

Department of Energy Sciences, Tokyo Institute of Technology

Nagatsuta, Midori-ku, Yokohama, 226-8502, Japan

Previous studies of spherically convergent beam fusion (SCBF) indicate that it has a potential applicable to a portable neutron source. However, some problems remain for the practical uses. Although high neutron output needs a discharge with high voltage and current, it is difficult to get a power supply with sufficient capacity. Moreover, such a discharge leads to overheating of the cathode. Recently, pulsed SCBF has been studied in order to overcome these problems and to be applied to some applications, which require pulsed neutron output, such as landmine identification. However, the pulsed discharge of SCBF has not been studied detailedly. In this study, experimental results of pulsed discharge of SCBF will be presented. An experimental device is made of 45-cm diameter, 31-cm high stainless steel cylindrical chamber, in which a spherical mesh-type anode of 30-cm diameter is installed. An open spherical grid cathode of 7-cm diameter, which is made of 1.2-mm diameter stainless steel wire, is set at the center of the spherical anode. The system is maintained at a constant pressure of 1-15 mTorr by feeding deuterium gas. An electric pulse is generated by a discharge of a capacitor charged by a power supply through a high voltage transistor switch, and is added to a dc discharge with small voltage and current powered by another power supply. Pulsed discharge characteristics were measured with changing charging voltage of capacitor, gas pressure, dc discharge current, etc.

4P31:

Optimization of Initial Gas Distributions in a Plasma-Focus Discharge

with a Pulsed Inlet of Gases

N.I. Ajzatsky, A.N. Dovbnya, Eh.Yu. Khautiev, M.A. Krasnogolovets, V.I. Krauz,

N.G. Reshetnyak, Yu. Ya. Volkolupov, V.V. Zakutin

Scientific Research Complex “Accelerator”,

National Science Center “Kharkov Institute of Physics and Technology”

1, Akademicheskaya St., 61108 Kharkov, Ukraine

The paper reports the data on emission/dynamic characteristics of the plasma-focus discharge versus the gas distribution profile in the discharge volume. The noniniform initial gas distributions with the operating gas having a lower density near the insulator and a higher density in the region of plasma focus (PF) formation were obtained by means of a pulsed inlet of gas to the discharge volume. This mad e it possible to increase the electrical strength of the electrode spacing. At optimum conditions, regimes were attained to give a neutron yield of ~1.5_10 10 neutrons/discharge, which was well reproduced from discharge to discharge and was comparable with the scaling value for the power suply energies W ~ 40 kJ used in these experiments. An intense generation of hard X-ray radiation was also observed in this case. Experiments were made to investigate the conditions for generation of intense ion and electron beams at the PF, and also to determine their principal parameters. It is found that the energy spectrum of operating gas (deuterium) ions accelerated at the PF is discrete in character: in the energy range between 0.03 and 1 MeV a sequence of nearly monoenergetic ion bunches is registered. The average energy of the basic part of electrons in the beam ranges between 30 and 50 keV.

4P32:

Spall Experiments in Convergent Geometry Using the Atlas Pulsed Power Facility

R.K. Keinigs, W.E. Anderson, F.L. Cochran, D. Oro, G. Rodriguez,

M.A. Salazar, A.J. Taylor, D.L. Tonks, W.R. Thissell, A.K. Zurek

Los Alamos National Laboratory

Los Alamos, NM

The first spall experiments conducted on the twenty-four megajoule capacitor bank, Atlas, are described. These experiments are intended to determine whether there are qualitative differences between spall phenomena in convergent and planar geometries. It is well known that spall, which arises as a result of intersecting release waves putting a material into tension, is a function of shock amplitude, shape, and duration. However, quantifying differences is difficult, and often the best one can do is to obtain the “spall strength” of the material. This important parameter is inferred from laser interferometry measurements (VISAR) of the “pull back” velocity of the free surface of a shocked sample. Principally, planar experiments are performed one of three ways: using a gas gun to launch a free-flying sabot into the target, employing a laser driven mini-flyer, or using high explosives to launch the shock wave. In the case of Atlas, the flyer is a cylindrically imploding metal liner, driven by the magnetic pressure produced by the bank current. After impact of the liner with the target the magnetic pressure continues to accelerate the liner / target assembly radially inward. This continued acceleration combined with converging geometry differentiates these spall experiments from those conducted in planar geometry. VISAR will be used to measure the free surface velocity of a shocked aluminum target, and the signature will be used to infer the spall strength and compare this with that obtained from gas gun experiments. Comparisons of the VISAR signals obtained on Atlas experiments with gas gun signals will be used to provide insight into the effects of convergence on spall phenomena. Axial radiography will also be fielded to determine the location of the spalled material layer, and correlate this with the VISAR.

4P33:

The Inverse Z-Pinch as a Physics Test Bed, and, Possibly, a Target Plasma,

for Magnetized Target Fusion (MTF)

I. Lindemuth, R. Kirkpatrick, P. Sheehey, R. Siemon

Los Alamos National Laboratory

Los Alamos NM

B. Bauer, V. Makhin, R. Presura, S. Fuelling

University of Nevada

Reno NV

From an overall fusion system perspective, the possibility of compressing a magnetized target plasma with beta greater than unity by a magnetically driven imploding liner, or other target pusher driver, appears very exciting [1]. This approach, known as Magnetized Target Fusion (MTF), operates in a density regime that is intermediate between the twelve orders of magnitude in density that separate MFE and ICF [1,2]. Even if plasma transport is Bohm-like, the MTF parameter space appears accessible with existing drivers [1], i.e., MTF does not require a major financial investment in driver technology.

The confinement directly by material walls and the thermal transport of magnetized, high-beta plasma in the MTF regime has been studied only a little, theoretically [3], computationally [4,5], and experimentally [5,6]. We are computationally evaluating, using the well-benchmarked two-dimensional radiation-MHD code MHRDR, and other tools as appropriate, the inverse z-pinch as an experimental test bed to study MTF transport and confinement. Existing facilities being considered include the 2-terawatt Zebra generator at the Nevada Terawatt Facility, the Colt capacitor bank at LANL, and the Atlas capacitor bank (23 MJ, 30 MA) at LANL.

According to MHRDR, the plasma is expected to evolve into a near-equilibrium. Thin sheaths next to the outer cylinder and end walls contain steep temperature and density gradients [3,4]. The plasma should take microseconds to cool, even in the presence of considerable convection. This cooling rate is much slower than would result if free-streaming losses of ions or unmagnetized-electron conduction losses were present. Experimental verification and understanding of the energy transport in this simple wall-confined plasma would provide increased confidence in the design of integrated liner-on-plasma experiments.

We are also evaluating the inverse z-pinch as an MTF target plasma for integrated liner-on-plasma experiments.

[1] R. Siemon et al., Proc. ITC-12 (2001); R. Siemon, I. Lindemuth, K. Schoenberg Comm. Plas. Phys. Cont. Fusion 18, 363 (1999).

[2] I. Lindemuth, R. Kirkpatrick, Nuc. Fus. 23, 263 (1983).

[3] G. Vekshtein, Rev. Plas. Phys. 15, Consultants Bureau (1990).

[4] I. Lindemuth et al., Phys. Fluids 21, 1723 (1978).

[5] I. Lindemuth et al., Phys. Rev. Lett. 75, 1953 (1995).

[6] B. Feinberg, Plas. Phys. and Contr. Fusion 18, 265 (1976).

LA-UR-02-0081

4P34:

Comparison of Z-pinch and Theta-pinch Drive for Implosion of Solid Liners Suitable for Compression of Field Reversed Configurations

J.H. Degnan, P.J. Turchi, and R.E. Siemon (1)

Air Force Research Laboratory, Directed Energy Directorate

(1) Los Alamos National Laboratory

A comparison of Z-pinch and Theta-pinch driven implosions of metal shells (solid liners) is presented. The liners are Al, 30 cm long, 10 cm outer diameter, and ~ 0.1 cm thick. The circuit parameters are those of the 1300 microfarad Shiva Star capacitor bank, operated at ~80 kilovolts charge. The initial inductance used for this study is 35 to 44 nanohenries. The series resistance includes a safety fuse (2.125 cm2 cross section, 0.94 meter long, Al using a glass bead quench medium) and an external resistance of approximately a milliohm.

Both schemes are feasible, and they have different advantages for compression of magnetized plasmas to Magnetized Target Fusion (1) conditions. The Z-pinch approach has already demonstrated at least 35% conversion efficiency from stored electrical energy (4.4 megajoules) to implosion kinetic energy (1.5 megajoules), with good implosion behavior and symmetry, and at least 13 times radial convergence of the liner inner surface (2). The Theta-pinch approach has potential advantages for purer and easier injection of Field Reversed Configurations, easier diagnostic access, and may be more easily operated repetitively. Its calculated conversion efficiency is ~25%, or ~70% that of the Z-pinch driven approach.

This work is supported by DOE-OFES.

(1) K.F.Schoenberg, R.E. Siemon et al, LA-UR-98-2413, 1998

(2) J.H.Degnan et al, IEEE Transactions on Plasma Science 29, p.93-98 (2001).

4P35:

On Possibility of Using Periodic Permanent Magnetic Structure to be Initial Energy Source for a Magneto-cumulative Generator

Dong Zhiwei, Wang Guirong, Wang Yuzhi

Institute of Applied Physics and Computational Mathematics

P.O.Box 8009, Beijing 100088, P.R.China

In a lot of single-shot applications and experiments at remote locations where magneto-cumulative generator provide the most practicable power, it is impracticable to use a capacitor bank to be the initial energy source. Gdovnina，V.V. et al [1] has used a permanent magnets to be the initial energy source to drive a magneto-cumulative generator, but the energy density stored in a single permanent magnet is very low. In this paper the possibility of using periodic permanent magnetic structure to be initial energy source of magneto-cumulative generator is analyzed numerically. It is concluded that 1kJ initial energy can be provided to magneto-cumulative generator by the periodic-ring permanent magnetic structure which weights less than 30kg and the outside radius less than 30cm, and some relative technical problems are also considered.

References

[1] Gdovnina，V.V. et al , Megagauss and Mega-power pulse Technology and Applications, Sarov(Arzamas-16): VNIEF, 1996, PP333-335

4P36:

Extraordinary Phenomena of Micro Ball Lightning

MATSUMOTO Taka-aki

Department of Nuclear Engineering, Hokkaido University

North 13, West 8, Sapporo 060-0813, JAPAN

e-mail: mtmt@qe.eng.hokudai.ac.jp

Recently, a special state of atomic cluster (called itonic cluster or micro Ball Lightning (BL)) was discovered during experiments of electrolysis or underwater spark discharge (USD). A new kind of nuclear reactions (called Electro-Nuclear Reactions (ENRs)) including nuclear collapse (Electro-Nuclear Collapse (ENC)) could occur in the clusters (1). Furthermore, it was found that earthquake and volcanic eruption could be caused by a large scale of explosive ENC. This fact enabled us not only to predict the occurrence of earthquake and volcanic eruption (2) but also to open the door of controlling them to avoid severe damages to human society.

Here, as an environmental application of high energy accelerators, a proposal will be made to control earthquake and volcanic eruption by using high energy itonic clusters. The following subjects will be described:

a. mechanisms of formation of itonic clusters

USD experimental observations will be shown,

b. mechanisms of acceleration of itonic clusters

c. mechanisms of earthquake and volcanic eruption caused by ENC

micro BL emerged during those phenomena will be compared with the experimental ones, and

d. principles of controlling earthquake and volcanic eruption

methods of using micro BL or itonic clusters of positrons will be proposed.

(1) T. Matsumoto, "Steps to the Discovery of Electro-Nuclear Collapse," book, private publication, (2001). Books will be distributed to attendees at the conference place.

(2) T. Matsumoto, "A Theory of Predicting Earthquake by Micro Ball Lightning," ISBL'01, to be published (2001).