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Ion acoustic wave studies near the presheath/sheath boundary in a weakly collisional argon/xenon plasma

Lutfi Oksuz et al 2008 Plasma Sources Sci. Technol. 17 015012 (5pp)   doi:10.1088/0963-0252/17/1/015012

Lutfi Oksuz¹, Dongsoo Lee and Noah Hershkowitz
Department of Engineering Physics, University of Wisconsin at Madison, Madison, WI 53706, USA
¹ Present address: Department of Physics, Suleyman Demirel University, Isparta 32260, Turkey.
E-mail: oksuz@fef.sdu.edu.tr

Ion acoustic wave (IAW) phase velocities are measured near the sheath/presheath boundary in a weakly collisional argon/xenon plasma. Wave profiles versus position are measured using a boxcar averager with a gate width of 30 ns and CW excitation at 50 or 75 kHz. Variable gate delays allow measurement of details of the wave close to the boundary. It is shown that the phase velocity at the presheath/sheath boundary is approximately twice the phase velocity in the bulk plasma for both argon and argon/xenon plasmas, in agreement with a recent calculation (Lee D et al 2007 Phys. Rev. Lett. 99 155004). This result indicates each ion's drift velocity at the boundary is equal to the IAW phase velocity in the bulk plasma.

Print publication: Issue 1 (February 2008)
Received 28 August 2007, in final form 11 October 2007
Published 19 December 2007

Diode lasers have proved to be a valuable light source for laser-induced fluorescence (LIF) measurements for plasma science since the early 1990s, and they have recently improved the state of the art of measuring ion flow from ion velocity distribution functions (ivdfs) at the sheath–presheath boundary in single and multiple ion species plasmas. In the case of a low temperature two ion species plasma (ArI + HeI), we were the first to show experimentally that ion species may reach the sheath edge flowing at a very different speed than that expected from the single species Bohm Criterion (ArII ions exceed the individual Bohm flow speed by almost a factor of 2 at the sheath edge). Simulation results are found to agree. Diode laser technology relevant to LIF measurements in multiple ion species plasmas is discussed with the aim of addressing outstanding problems in sheath formation in such plasmas.

Keywords: Plasma sheath; Plasma diagnostics; Plasma spectroscopy
 

Contrib. Plasma Phys. 46, No. 1-2, 3 – 191 (2006) / DOI 10.1002/ctpp.200610001

Plasma Edge Physics with B2-Eirene

The paper presents the basic equations for the plasma transport and the basic models for the neutral transport. This defines the basic ingredients for the SOLPS (Scrape-Off Layer Plasma Simulator) code package. A first level of understanding is approached for pure hydrogenic plasmas based both on simple models and simulations with B2-Eirene neglecting drifts and currents. The influence of neutral transport on the different operation regimes is here the main topic. This will finish with time-dependent phenomena for the pure plasma, so-called Edge Localised Modes (ELMs). Then, the influence of impurities on the SOL plasma is discussed. For the understanding of impurity physics in the SOL one needs a rather complex combination of different aspects. The impurity production process has to be understood, then the effects of impurities in terms of radiation losses have to be included and finally impurity transport is necessary. This will be introduced with rising complexity starting with simple estimates, analysing then the detailed parallel force balance and the flow pattern of impurities. Using this, impurity compression and radiation instabilities will be studied. This part ends, combining all the elements introduced before, with specific, detailed results from different machines. Then, the effect of drifts and currents is introduced and their consequences presented. Finally, some work on deriving scaling laws for the anomalous turbulent transport based on automatic edge transport code fitting procedures will be described.

Japanese Journal of Applied Physics
Vol. 45, No. 7, 2006, pp. 5945-5950
URL : http://jjap.ipap.jp/link?JJAP/45/5945/
DOI : 10.1143/JJAP.45.5945

Yong-Sup Choi^*, Hyun-Jong Woo, Kyu-Sun Chung^**, Myoung-Jae Lee, David Zimmerman¹ and Roger McWilliams¹

Electric Probe Applications Laboratory (ePAL), Hanyang University, Seoul 133-791, Korea
¹Department of Physics and Astronomy, University of California, Irvine, CA 92697, U.S.A.

(Received March 16, 2005; revised September 19, 2005; accepted February 23, 2006; published online July 7, 2006)

Abstract:

Plasma flow velocity was measured by Mach probe (MP) and laser-induced fluorescence (LIF) methods in unmagnetized plasmas with supersonic ion beams. Since the ion gyro-radius was much larger than the probe radius, unmagnetized Mach probe theory was used to determine plasma flow in argon RF plasma with a weak magnetic field (<200 G). In order to determine flow velocities, the Mach probe is calibrated via LIF in the absence of the ion beam, where existing probe theories may be valid although they use different geometries (sphere and plane) and analyzing tools [particle-in-cell (PIC) and kinetic models]. For the comparison of the average plasma flow velocities by MP and LIF, the supersonic ion beam velocity was measured by LIF and then incorporated into a simple formula for average plasma velocity with provisions for background plasma density and beam-corrected electron temperature (T_e) measured by a triple probe.

Keywords:

plasma flow velocity, Mach probe, triple probe, laser induced fluorescence, LIF, unmagnetized plasma.

^*Present address: Production Engineering Center, Samsung SDI Co., Ltd., Suwon, Gyeonggi 575, Korea.
^**Corresponding author: E-mail address: kschung@hanyang.ac.kr

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References:

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F. Allais^a, , J.P. Matte^{a, ,} , F. Alouani-Bibi^a, C.G. Kim^a, D.P. Stotler^b and T.D. Rognlien<sup>c

a</sup>INRS-Énergie, Matériaux et Télécommunications, 1650 boul. Lionel Boulet, Varennes, Québec, Canada J3X 1S2
^bPrinceton Plasma Physics Laboratory, Princeton, NJ, USA
^cLawrence Livermore National Laboratory, Livermore, CA, USA
 

Abstract

Diode lasers have proved to be a valuable light source for laser-induced fluorescence (LIF) measurements for plasma science since the early 1990s, and they have recently improved the state of the art of measuring ion flow from ion velocity distribution functions (ivdfs) at the sheath–presheath boundary in single and multiple ion species plasmas. In the case of a low temperature two ion species plasma (ArI + HeI), we were the first to show experimentally that ion species may reach the sheath edge flowing at a very different speed than that expected from the single species Bohm Criterion (ArII ions exceed the individual Bohm flow speed by almost a factor of 2 at the sheath edge). Simulation results are found to agree. Diode laser technology relevant to LIF measurements in multiple ion species plasmas is discussed with the aim of addressing outstanding problems in sheath formation in such plasmas.

W Fundamenski 2005 Plasma Phys. Control. Fusion 47 R163-R208   doi:10.1088/0741-3335/47/11/R01

http://www.iop.org/EJ/abstract/0741-3335/47/11/R01/

http://ej.iop.org/links/rTqyxnIWm/SnTZP6Wg2xGkAZxsav5vpA/psst5_1_022.pdf

Scrape-off layer physics: an introduction (to be published)

Ralf Schneider,

Max-Planck-Institut f¨ur Plasmaphysik, EURATOM association, Garching, Germany

http://www.ipp-garching.mpg.de/~dpc/rfs.pdf

C. Constantin, C. A. Back, K. B. Fournier, G. Gregori, O. L. Landen, S. H. Glenzer, and E. L. Dewald

Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550

M. C. Miller

Los Alamos National Laboratory, Los Alamos, New Mexico 87545

(Received 11 November 2004; accepted 8 April 2005; published online 6 June 2005)

A laser-driven supersonic ionization wave propagating through a millimeter-scale plasma of subcritical density up to 2–3  keV electron temperatures was observed. Propagation velocities initially ten times the sound speed were measured by means of time-resolved x-ray imaging diagnostics. The measured ionization wave trajectory is modeled analytically and by a two-dimensional radiation-hydrodynamics code. The comparison to the modeling suggests that nonlocal heat transport effects may contribute to the attenuation of the heat-wave propagation. ©2005 American Institute of Physics

L Oksuz et al 2005 Plasma Sources Sci. Technol. 14 201-208

Plasma, presheath, collisional sheath and collisionless sheath potential profiles in weakly ionized, weakly collisional plasma

L Oksuz¹ and N Hershkowitz
Department of Engineering Physics, University of Wisconsin-Madison, USA

¹ Current address: Plasma Research Laboratory, Dublin City University, Dublin, Republic of Ireland.

Received 30 September 2003
Published 7 February 2005
Print publication: Issue 1 (February 2005)

This paper appears in: Plasma Science, IEEE Transactions on
Publication Date: April 2005
Volume: 33,  Issue: 2, Part 2
On page(s): 631- 636
ISSN: 0093-3813
INSPEC Accession Number: 8398049
Digital Object Identifier: 10.1109/TPS.2005.844608
Posted online: 2005-04-18 09:10:46.0
 

G. Gregori, S. H. Glenzer, J. Knight, C. Niemann, D. Price, D. H. Froula, M. J. Edwards, and R. P. J. Town

Lawrence Livermore National Laboratory, University of California, P.O. Box 808, California 94551, USA

A. Brantov and W. Rozmus

Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2J1

Volume 44, Issue 4 , Pages 352 - 360

Published Online: 8 Jun 2004

Copyright © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

^*Correspondence to G. Fussmann, Humboldt-Universität zu Berlin, Institut für Physik Experimentelle Plasmaphysik, Germany

Simulation of the Edge Plasma in Tokamaks

D. P.? Coster, Max-Planck-Institut f?smaphysik,? EURATOM Association,? Garching,? Germany.
X.? Bonnin, Max-Planck-Institut f?smaphysik,? EURATOM Association,? Greifswald,? Germany.
B.? Braams, Courant Institute,? New York University,? New York,? USA.
D.? Reiter, Institut f?smaphysik, FZ J?? EURATOM Association,? J?? Germany.
R.? Schneider, Max-Planck-Institut f?smaphysik,? EURATOM Association,? Greifswald,? Germany.
ASDEX Upgrade Team? ,
 

Received? June 26, 2003; accepted?August 7, 2003.
 

Simulation of the Edge Plasma in Tokamaks

W Arter 1995 Rep. Prog. Phys. 58 1-59

Numerical simulation of magnetic fusion plasmas

W Arter
Culham Lab., AEA Technol., Abingdon, UK
Print publication: Issue 1 (January 1995)

     Lastly, it is worth noting that Fokker-Planck codes have been written to model inertial confinement fusion experiments, e.g. Andrade et al (1981), and at least one such (FPl) has then been used to model tokamak edge plasmas (Abou-Assaleh et al 1990).  The computational details are not directly relevant to this review, but the physical results from FPl are interesting, since they suggest that the heat transport is not well modelled by corresponding fluid codes. A comparison with results obtained using particle methods (section 3.6) would be of interest.

. . ."

S. A. Uryupin, S. Kato, and K. Mima

Institute of Laser Engineering, Osaka University, Suita, Osaka 565, Japan

(Received 23 June 1994; accepted 12 April 1995)

The self-similar distribution of electrons is found for a nonuniform underdense plasma that is heated by an intensive laser field. The distribution function is flat-topped for the low-energy electrons. And in the high-energy region, it has a well-pronounced high-energy tail. It is also found how the electron heat flux and the absorption coefficient depend upon both the ratios of electron mean-free path to the inhomogeneity scale of effective temperature and of the oscillation velocity to the thermal velocity. The actual shapes of electron energy distribution, the heat flux limitation, and the electromagnetic radiation absorption rate are given, both for a currentless plasma and for a plasma with a finite electric current. ©1995 American Institute of Physics.

F. Vidal and J. P. Matte

Institut National de la Recherche Scientifique—Energie et Matériaux, 1650 Montée Ste. Julie, CP 1020, Varennes, Québec J3X 1S2, Canada

M. Casanova and O. Larroche

Commissariat à l'Energie Atomique, Centre d'Etudes de Limeil-Valenton, 94195 Villeneuve St. Georges Cedex, France

(Received 7 November 1994; accepted 4 January 1995)

Electron heat flow was computed in the context of a steadily propagating shock wave. Two problems were studied: a Mach 8 shock in hydrogen, simulated with an ion kinetic code, and a Mach 5 shock in lithium, simulated with an Eulerian hydrodynamic code. The electron heat flow was calculated with Spitzer–Härm classical conductivity, with and without a flux limit, and several nonlocal electron heat flow formulas published in the literature. To evaluate these, the shock's density, velocity, and ion temperature profiles were fixed, and the electron temperature and heat flow were compared to those computed by an electron kinetic code. There were quantitative differences between the electron temperature profiles calculated with the various formulas. For the Mach 8 shock in hydrogen, the best agreement with the kinetic simulation was obtained with the Epperlein–Short delocalization formula [Phys. Fluids B 4, 2211 and 4190 (1992)], and the Luciani–Mora–Bendib formula [Phys. Rev. Lett. 55, 2421 (1985)] gave good agreement. For the Mach 5 shock in lithium, both of these gave good agreement. The earlier Luciani–Mora–Virmont formula [Phys. Rev. Lett. 51, 1664 (1983)] gave fair agreement, while that of San Martin et al. [Phys. Fluids B 4, 3579 (1992); 5, 1485 (1993)] was even further off than the classical Spitzer–Härm [Phys. Rev. 89, 977 (1953)] formula for thermal conduction. To assess the effect of nonlocal electron heat flow on the shock's hydrodynamics and ion kinetics, each of the two problems was done with two different electron heat flow models: the classical Spitzer–Härm local heat conductivity, and the Epperlein–Short nonlocal electron heat-flow formula. In spite of the somewhat different electron temperature profiles, the effect on the shock dynamics was not important. ©1995 American Institute of Physics.

J. M. Liu and J. S. De Groot

Plasma Research Group, Department of Applied Science, University of California, Davis, California 95616

J. P. Matte and T. W. Johnston

INRS-Énergie et Matériaux, C.P. 1020, Varennes, Québec, J3X 1S2 Canada

R. P. Drake

Plasma Physics Research Institute, Lawrence Livermore National Laboratory, L-418, P.O. Box 808, Livermore, California 94551

(Received 8 March 1994; accepted 14 July 1994)

Measurements are presented of electron heat transport with non-Maxwellian (flattopped) distributions due to inverse bremsstrahlung absorption of intense microwaves in the University of California at Davis Aurora II device [Rogers et al., Phys. Fluids B 1, 741 (1989)]. The plasma is created by pulsed discharge in a cylindrical vacuum chamber with surface magnets arranged to create a density gradient. The ionization fraction (~1%) is high enough that charged particle collisions are strongly dominant in the afterglow plasma. A short microwave pulse (~2 µs) heats a region of the afterglow plasma (n_e/n_cr0.5) creating a steep axial (L_T~1–10_ei) temperature gradient. Langmuir probes are used to measure the relaxation of the heat front after the microwave pulse. Time and space resolved measurements show that the isotropic component of the electron velocity distribution is flat topped (~exp[–(v/v_m)^m], m2) in agreement with Fokker–Planck calculations using the measured density profile. Classical heat transport theory is not valid both because the isotropic component of the electron velocity distribution is flattopped and the temperature gradients are very steep. Physics of Plasmas is copyrighted by The American Institute of Physics.

D. S. Montgomery¹, O. L. Landen^1,3, R. P. Drake^2,3, K. G. Estabrook¹, H. A. Baldis¹, S. H. Batha², K. S. Bradley³, and R. J. Procassini¹
 

¹Lawrence Livermore National Laboratory, Livermore, California 94551
 

²Plasma Physics Research Institute, University of California Davis and Lawrence Livermore National Laboratory, Livermore, California 94551

³Department of Applied Science, University of California Davis, Davis, California 95616
 

Received 31 August 1992

Time-resolved, 2D images of x-ray emission from thin, laser-irradiated titanium foils are presented. The foils are irradiated with 0.35 µm light at intensities of 1 x 10¹⁵ W/cm² which produces a plasma with electron densities <= 10²² cm^-3 and electron temperature of 3-4 keV. X-ray emission that is characteristic of the thermal heat front is observed to propagate radially outward from the heated region. Comparison of these measurements with 2D hydrodynamic simulations of the experiment suggests the radial heat flux to be about 3% of the free-streaming heat flux.

©1994 The American Physical Society

URL: http://link.aps.org/abstract/PRL/v73/p2055

Boris N. Chichkov, Yoshiaki Kato, Hartmut Ruhl, and Sergey A. Uryupin

Theoretical Quantum Electronics, Technical University Darmstadt, Hochschulstrasse 4A, Darmstadt, Germany

Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565, Japan

P. N. Lebedev Physics Institute, Leninsky prospect 53, Moscow, Russia
 

Received 8 February 1994

The temporal evolutions of the electron distribution function and the electric field in a dense, hot, multiply charged plasma due to the presence of a sharp temperature gradient from one side (plasma–cold matter contact) and a sharp density gradient from the other side (plasma-vacuum boundary) are studied. The prospects for x-ray lasing in such a plasma are discussed. The analogy with a p-n junction semiconductor laser is emphasized.

©1994 The American Physical Society

URL: http://link.aps.org/abstract/PRA/v50/p2691

J. M. Liu, J. S. De Groot, J. P. Matte, T. W. Johnston, and R. P. Drake

Plasma Research Group, Department of Applied Science, University of California, Davis, California 95616

Institut National de la Recherche Scientifique Energie et Matériaux, C.P. 1020, Varennes, Québec, Canada J3X 1S2

Plasma Physics Research Institute, Lawrence Livermore National Laboratory, L-418, P.O. Box 808, Livermore, California 94551
 

Received 15 December 1993

Non-Maxwellian (flattopped) electron velocity distributions resulting from inverse bremsstrahlung of intense microwaves are measured directly for the first time in experiments performed on the UCD AURORA II device. The experiments are performed in the afterglow of a pulsed discharge plasma that is moderately collisional and sufficiently ionized (~1%) that Coulomb collisions are dominant. Langmuir probe measurements indicate that the isotropic component of the electron velocity distribution is non-Maxwellian in very good agreement with electron kinetic (Fokker-Planck) simulations.

©1994 The American Physical Society

URL: http://link.aps.org/abstract/PRL/v72/p2717
DOI: 10.1103/PhysRevLett.72.2717
PACS: 52.50.Gj, 52.25.-b, 52.50.Jm, 52.65.+z

Ann W. Morgenthaler and Peter L. Hagelstein

Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 38-280, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139

(Received 22 June 1992; accepted 15 January 1993)

Cartesian velocity moments of the Boltzmann equation are evaluated using modal solutions to the spherical harmonic oscillator as a basis set. The nonlinear collision matrix describing the interaction between any two modes is evaluated analytically for the Landau collision operator, and matrix elements describing collisions between identical particles are calculated for some pairs of azimuthally symmetric modes. First-order linear transport coefficients calculated directly from collision matrix elements are shown to agree exactly with previously published results; coefficients of thermal conductivity and viscosity are computed much more accurately by trivially extending this calculation. Relaxation times for self-collisions in a two-dimensional linearized plasma are also computed, indicating that the plasma equilibrates in roughly one to ten times the Spitzer self-collision time. The results obtained in this paper are useful for both analytic and numerical simulations of nonequilibrium plasmas and an explicit six-moment model for a one-component azimuthally symmetric plasma is given. Physics of Fluids B: Plasma Physics is copyrighted by The American Institute of Physics.

J A Meyer et al 1992 Plasma Sources Sci. Technol. 1 147-150

Measurements of the presheath in an electron cyclotron resonance etching device

J A Meyer, G -H Kim, M J Goeckner and N Hershkowitz
Eng. Res. Center for Plasma-Aided Manuf., Wisconsin Univ., Madison, WI, USA
Print publication: Issue 3 (August 1992)

Juan R. Sanmartín and J. Ramírez

E.T.S.I. Aeronáuticos, Universidad Politécnica, 28040 Madrid, Spain

R. Fernández-Feria

E.T.S.I. Industriales, Universidad de Sevilla, 41012 Sevilla, Spain

F. Minotti

Laboratorio de Física del Plasma, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina

A single, nonlocal expression for the electron heat flux, which closely reproduces known results at high and low ion charge number Z, and ``exact'' results for the local limit at all Z, is derived by solving the kinetic equation in a narrow, tail-energy range. The solution involves asymptotic expansions of Bessel functions of large argument, and (Z-dependent) order above or below it, corresponding to the possible parabolic or hyperbolic character of the kinetic equation; velocity space diffusion in self-scattering is treated similarly to isotropic thermalization of tail energies in large Z analyses. The scale length H characterizing nonlocal effects varies with Z, suggesting an equal dependence of any ad hoc flux limiter. The model is valid for all H above the mean-free path for thermal electrons. Physics of Fluids B: Plasma Physics is copyrighted by The American Institute of Physics.

J. H. Rogers, J. S. De Groot, and D. Q. Hwang

University of California Davis and Lawrence Livermore National Laboratory, L-794 Livermore, California 94550

Several methods for estimating the plasma potential and density using cylindrical Langmuir probes are compared to the self-consistent solutions of the Vlasov–Poisson equations calculated by Laframboise (J. G. Laframboise, Ph. D. dissertation, University of Toronto, 1966). Measurements are made during the decay of a magnetic-field-free plasma in which the mean-free path of the electron is shorter than the dimensions of the vacuum vessel (the electrons, therefore, have a Maxwellian velocity distribution). The measurements are made in a parameter range in which exact analytical solutions do not exist for the ion and electron saturation currents, 0.5R/_De5, where R is the probe radius and _De is the electron Debye length (kT_e/4ne²)^1/2. An iterative procedure is used to fit the data at probe voltages both above and below the plasma potential while constraining the curves to be continuous at the plasma potential. The measured curves could be represented extremely well by the numerical results. It is therefore assumed that the plasma parameters used to fit the numerical results to the measurements are correct. The systematic errors which result from using several analysis techniques which assume R/_De1 are also presented, and it is shown that empirical corrections to these errors can be described which compensate for the finite probe radius. Review of Scientific Instruments is copyrighted by The American Institute of Physics.

A. Zigler, P. G. Burkhalter, and D. J. Nagel

Naval Research Laboratory, Washington, DC 20375

M. D. Rosen

Lawrence Livermore Laboratory, Livermore, California 94550

K. Boyer, G. Gibson, T. S. Luk, A. McPherson, and C. K. Rhodes

University of Illinois at Chicago, P. O. Box 4348, Chicago, Illinois 60680

The energy penetration depth characteristic of the interaction of intense subpicosecond (~600 fs) ultraviolet (248 nm) laser radiation with solid density material has been experimentally determined. This was accomplished by using a series of ultraviolet transmitting targets consisting of a fused silica (SiO₂) substrate coated with an 80–600 nm layer of MgF₂. The measurement of He-like and H-like Si and Mg lines, as a function of MgF₂ thickness, enabled the determination of the energy penetration depth. It was found that this depth falls in the range of 250–300 nm for a laser intensity of ~3×10¹⁶ W/cm². Based on numerical simulations, it is estimated that solid density material to a depth of ~250 nm is heated to an electron temperature of ~500 eV.

Applied Physics Letters is copyrighted by The American Institute of Physics.

R. Marchand, J. P. Matte, and K. Parbhakar

INRS-ENERGIE, CP 1020, Varennes, Quebec J3X 1S2, Canada

Electron kinetics is considered in a plasma in which the distribution of ion charge stages is far from the coronal equilibrium. In rapidly ionizing plasmas, radiative cooling and ionization are found to cause the electron distribution to deviate significantly from a Maxwellian. The relevance of such distribution functions to divertor plasmas near the neutralizer plate is discussed. Physics of Fluids B: Plasma Physics is copyrighted by The American Institute of Physics

Октябрь 1991 г. Том 161, № 10

УСПЕХИ ФИЗИЧЕСКИХ НАУК

ИЗ ТЕКУЩЕЙ ЛИТЕРАТУРЫ

533.9

СОВРЕМЕННОЕ СОСТОЯНИЕ ИССЛЕДОВАНИЙ

ПО ФИЗИКЕ ВЗАИМОДЕЙСТВИЯ

МОЩНОГО ЛАЗЕРНОГО ИЗЛУЧЕНИЯ

С ВЫСОКОТЕМПЕРАТУРНОЙ ПЛАЗМОЙ

В. Т. Тихончук

(Физический институт им. П.Н. Лебедева АН СССР)

http://data.ufn.ru//ufn91/ufn91_10/129.pdf

D. Ress and L. J. Suter

Lawrence Livermore National Laboratory, P. O. Box 808, L-473, Livermore, California 94550

E. F. Gabl and B. H. Failor

KMS Fusion, Inc., 700 KMS Place, P. O. Box 1567, Ann Arbor, Michigan 48106

The lasnex computer code [Comments Plasma Phys. Controlled Fusion 2, 51 (1975)] was used in the design and analysis of an experimental study of laser-driven plasma blowoff from gold disks. In the study, several temporal profiles of 0.53 mm laser illumination were used, including square pulses, picket pulse trains, and pulses with graduated leading edges. Preliminary modeling suggested diagnostic techniques [time- and space-resolved imaging of M-band x-ray emission and time- and space-averaged measurements of high-energy (3.5–20 keV) x-ray spectra] that complemented diagnostics already used in such experiments (four-frame holographic imaging to determine the electron-density profile in the underdense corona plasma). In this article, the lasnex results are analyzed and are compared with the measured plasma electron-density profiles and with time- and space-averaged measurements of the corona temperature. The simulation tracks the observed electron-density profiles fairly well during the early portions of the laser drive, during which the spatial profiles are approximately self-similar, but overestimates the electron density in the later, steady-state segment of the profile. For the corona electron temperature, simulation and experiment agree to within the experimental accuracy of ±20%. Physics of Fluids B: Plasma Physics is copyrighted by The American Institute of Physics.

F. Minotti and C. Ferro Fontán

Laboratorio de F ísica del Plasma, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. I, 1428 Buenos Aires, Argentina

(

An analytic solution to the problem of nonlocal heat transport in plasmas by electrons whose range is not short compared to the temperature scale length is presented. The formalism extends the results of Albritton et al. [Phys. Rev. Lett. 57, 1887 (1986)] to an arbitrary ionization state Z. This simple transport scheme is checked against recent experiments in the AURORA device [Phys. Fluids B 1, 741 (1989)]. The agreement, both for the measured cold electron temperature profile and the plasma potential, is very good and comparable to the result of full kinetic calculations. Physics of Fluids B: Plasma Physics is copyrighted by The American Institute of Physics.

"ACKNOWLEDGEMENTS

  . . .   This dissertation has been greatly enhanced by the efforts of Z. Abou-Assaleh,  J.P. Matte, and T.W. Johnston who are responsible for the Fokker-Planck International calculations.

 . . ."

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