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in subjects: "Plasma Sheath"

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Incomplete relaxation and finite beta plasmas

The treatment of plasma relaxation presented in this paper is a natural generalization of the earlier treatment of Taylor and yields predictions of finite beta plasma confinement. The analysis yields predictions for global reversed-field pinch (RFP) parameters such as ..beta../sub theta/, F, and theta. In qualitative accordance with the experimental evidence that RFP discharges have a cool outer region of high resistivity, we present a plasma model which permits vanishing wall values of pressur… more

Date: January 1, 1980

Creator: Turner, L. & Christiansen, J.P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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In-situ impurity measurements in PDX Edge plasma

The surface analysis station of PDX combines several surface analysis techniques (AES, XPS, SIMS) for in-situ measurement of impurity fluxes in the edge-plasma. The major impurities deposited on a sample surface during nondiverted PDX discharges are oxygen, titanium (limiter material) and chlorine. The impurity fluxes measured at different radial positions decreased by a factor of ten from the plasma edge to the wall. The sample surface collecting the impurity ions is located behind a circular … more

Date: July 1, 1980

Creator: Staib, P.; Dylla, H.F. & Rossnagel, S.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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MHD stability of torsatrons using the average method

The stability of torsatrons is studied using the average method, or stellarator expansion. Attention is focused upon the Advanced Toroidal Fusion Device (ATF), an l = 2, 12 field period, moderate aspect ratio configuration which, through a combination of shear and toroidally induced magnetic well, is stable to ideal modes. Using the vertical field (VF) coil system of ATF it is possible to enhance this stability by shaping the plasma to control the rotational transform. The VF coils are also use… more

Date: January 1, 1985

Creator: Holmes, J. A.; Carreras, B. A.; Charlton, L. A.; Garcia, L.; Hender, T. C.; Hicks, H. R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Self-consistent calculations of edge temperature and self-sputtering of the limiter surface for tokamak fusion reactors

Self-sputtering and edge temperature estimates have been made for a tokamak fusion reactor with a normal incidence boundary using models for the power balance, plasma sheath, charge state, and sputtering coefficients. Both structural materials and low-Z coatings have been examined. From the self-sputtering standpoint, some materials will work only at very low edge temperatures; these will require a high recycling rate and a high radiation fraction.

Date: May 1, 1980

Creator: Brooks, J. N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Analysis of electron transport in the plasma of thermionic converters

Electron transport coefficients of a gaseous ensemble are expressed analytically as function of density, and are expressed analytically as function of temperature up to an unknown function which has to be evaluated for each specific electron-neutral atom cross section. In order to complete the analytical temperature dependence one may introduce a polynomial expansion of the function or one may derive the temperature dependence of a set of coefficients, numbering thirteen for a third approximati… more

Date: March 1, 1980

Creator: Stoenescu, M.L. & Heinicke, P.H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Remarks on the clump theory

Further details are provided of a soon-to-be published dialog (Phys. Fluids 29 (July, 1986)) which discussed the role of the small scales in fluid clump theory. It is argued that the approximation of the clump lifetime which is compatible with exponentially rapid separation of adjacent orbits is inappropriate for the description of the dynamically important large scales. Various other remarks are made relating to the analytic treatment of strong drift-wave-like turbulence.

Date: July 1, 1986

Creator: Krommes, John A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Fundamentals of interruption in vacuum. Eleventh progress report

During the past three months effort has concentrated on formulating a method to predict the enhancement of electrode surface field and power input occasioned by the presence of a projection on the electrode surface, during the ion sheath development period which attends the scavenging a contact gap following current interruption in vacuum. In addition, experimental evidence has been obtained to support the theory, postulated earlier, of a turn-around interval for electrons left in the gap, whic… more

Date: February 28, 1981

Creator: Greenwood, A. N. & Sullivan, J. S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Characterization of the TEXTOR plasma edge using deposition probe techniques

Carbon and single crystal silicon passive deposition probes were used to measure the characteristics of the plasma edge region of the TEXTOR tokamak. Analysis of the probes was done by Rutherford backscattering for impurities and nuclear reaction analysis and elastic recoil detection for hydrogen isotopes. Plasma fluxes and energies in the edge were measured using probe techniques. The principal impurities in the plasma edge were determined and their behavior as a function of time and position … more

Date: October 1, 1983

Creator: Zuhr, R.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Multigroup calculations of low energy neutral transport in tokamak plasmas

Multigroup discrete ordinates methods avoid many of the approximations that have been used in previous neutral transport analyses. Of particular interest are the neutral profiles generated as an integral part of larger plasma system simulation codes. To determine the appropriateness of utilizing a particular multigroup code, ANISN, for this purpose, results are compared with the neutral transport module of the Duchs code. For a typical TFTR plasma, predicted neutral densities differ by a maximu… more

Date: September 1, 1977

Creator: Gilligan, J. G.; Gralnick, S. L.; Price, W. G. Jr. & Kammash, T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Sawtooth oscillations in the flux of runaway electrons to the PLT limiter

Increased fluxes of runaway electrons at the PLT limiter are observed in the few milliseconds following internal disruptions. These fluxes have an inverted (outside) sawtooth character. The time for the flux to reach a maximum after the disruption has been studied as a function of the plasma parameters for thousands of PLT discharges. One interpretation is that this delay represents the time for a perturbation to the runaway electron population to travel from the q = 1 region to the plasma boun… more

Date: March 1, 1982

Creator: Barnes, C.W. & Strachan, J.D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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ALT-I Pump Limiter Experiments With ICRF Heating on TEXTOR. Revision.

The ALT-I (Advanced Limiter Test-I) was installed on TEXTOR to benchmark the ability of a pump limiter as an efficient particle collector and to determine the physics of pump limiter operation. Experiments continue to show its capability of removing particles from the plasma edge under different operating conditions. In this paper we report first experimental results using ALT-I in conjunction with high power ICRF heating. The particle removal rate increases as the edge flux and density increas… more

Date: May 1, 1986

Creator: Leung, W. K.; Goebel, D. M.; Conn, R. W.; Dippel, K. H.; Finken, K. H. & Thomas, G. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Model calculations for the explosive generator-driven dense plasma focus

A models was developed to aid in the design and interpretation of explosive generator-driven dense plasma focus experiments. Several models were investigated, but the one presented here employs a plane sheath propagating along the barrel of a Mather-type gun, entraining a constant fraction of the swept-up gas and carrying the return current between the electrodes. The motion of the sheath is determined from the momentum equation using the integrated magnetic force on the sheath. The solutions a… more

Date: February 1, 1982

Creator: Brownell, J. & Landshoff, R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Near-surface sputtered particle transport for an oblique incidence magnetic field plasma

Near-surface sputtered particle transport has been analyzed numerically using models of sputtering, sheath parameters, and impurity collisions with a background D-T plasma. Tungsten and carbon sputtering was examined, for tokamak divertor plasma conditions. Redeposited ion parameters computed include the charge state, transit time, energy and angle of incidence. A regime of operation for finite self-sputtering of tungsten has been identified. This regime is broader than previous estimates. Resu… more

Date: November 1, 1989

Creator: Brooks, J. N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Plasma particle and energy reflection at a wall with an obliquely incident magnetic field

The particle and energy reflection coefficients are calculated for a plasma incident at a wall with an obliquely incident magnetic field. The salient result of these calculations is that the reflection coefficients can approach unity when the magnetic field is incident at grazing angles. This reflection of particles and energy will be an important process in determining the particle and energy balance in the edge plasma.

Date: July 1, 1985

Creator: Knize, R.J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Phenomenological model for H-mode

A phenomenological model has been developed to clarify the role of the boundary configuration in the heat transport of the H-mode regime. We assume that the dominant mechanism of heat loss at the edge of the plasma is convection and that the diffusion coefficient (D/sub edge/) at the edge of the plasma increases rapidly with plasma pressure, but drops to a low value when the temperature exceeds a certain threshold value. When particle refueling takes place without time delay, as in the case of … more

Date: August 1, 1985

Creator: Ohyabu, N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Physics of laser fusion. Vol. I. Theory of the coronal plasma in laser-fusion targets

This monograph deals with the physics of the coronal region in laser fusion targets. The corona consists of hot plasma which has been evaporated from the initially solid target during laser heating. It is in the corona that the laser light is absorbed by the target, and the resulting thermal energy is conducted toward cold high-density regions, where ablation occurs. The topics to be discussed are theoretical mechanisms for laser light absorption and reflection, hot-electron production, and the… more

Date: December 1, 1981

Creator: Max, C.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Materials erosion and redeposition studies at the PISCES-facility: net erosion under redeposition

Simultaneous erosion and redeposition of copper and 304 stainless steel under controlled and continuous plasma (D,He,Ar) bombardment has been investigated in the PISCES-facility, which generates typical edge-plasma conditions of magnetic fusion devices. The plasma bombardment conditions are: incident ion flux in the range from 10/sup 17/ to 10/sup 18/ ions/sec/cm/sup 2/, ion bombarding energy of 100 eV, electron temperature in the range from 5 to 15 eV, plasma density in the range from 10/sup 1… more

Date: May 1, 1986

Creator: Hirooka, Y.; Goebel, D. M.; Conn, R. W.; Leung, W. K. & Campbell, G. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Kinetic solution of the sheath region in a fusion reactor

The sheath region in a fusion reactor is studied with a one-dimensional kinetic code. The sheath potential, heat transmission, and sputtering of the boundary are all quite sensitive to electron re-emission. The expected heat and particle fluxes in future fusion reactors leads to a prediction of keV-edge temperatures.

Date: December 1, 1979

Creator: Brooks, J. N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Extraction induced emittance growth for negative ion sources

Nonlinear emittance growth produced by ion extraction is considered by a 3-D analysis in a Vlasov-Poisson-Boltzmann formulation. Phenomena considered include: presheath effects, including electron depletion, electron sheath accumulation (for large transverse magnetic fields), nonlinear sheath fields (obtained by a self-consistent solution with an assumed quasi-equilibrium positive ion distribution and at least one Vlasov distribution), nonlinear fringe fields produced by the accelerator-extract… more

Date: January 1, 1989

Creator: Whealton, J. H.; Meszaros, P. S.; Raridon, R. I. & Rothe, K. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Plasma injection and atomic physics models for use in particle simulation codes

Models of plasma injection (creation) and charged/neutral atomic physics which are suitable for incorporation into particle simulation codes are described. Both planar and distributed source injection models are considered. Results obtained from planar injection into a collisionless plasma-sheath region are presented. The atomic physics package simulates the charge exchange and impact ionization interactions which occur between charged particles and neutral atoms in a partially-ionized plasma. … more

Date: June 12, 1991

Creator: Procassini, R.J. (Lawrence Livermore National Lab., CA (USA) California Univ., Berkeley, CA (USA). Electronics Research Lab.)

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Electron heating and static sheath enhancement in front of energized rf antennas

An analytic model has been developed to describe the increased plasma potential and acceleration of ions in the vicinity of an ICRF Faraday shield. This model gives an estimate for the electron distribution function using a heating model with decorrelation caused by reflection of the electrons from the static sheath at the point where a magnetic field line intersects a grounded wall. The loss rate of the electrons from the system can be calculated from this distribution function. The expected s… more

Date: January 1, 1989

Creator: Carter, M. D.; Batchelor, D. B. & Jaeger, E. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Theoretical view of the plasma focus

The present theory of the plasma focus device is discussed. Experiments at low pressure clearly show a disruption of the current sheath and the formation of energetic electron and ion beams in a turbulent medium. Possible directions for calculations to explain this conversion of magnetic energy into charged particle beams are indicated.

Date: February 1, 1980

Creator: Maxon, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Transport of molecular impurities at the edge of tokamaks

The transport of molecules at the plasma edge in tokamaks is discussed in order to compare how light impurities enter the plasma if they are released either in atomic or molecular forms. Differences in their transport arise because of the dissimilarities between the atomic and molecular reactions with the bulk of the plasma. It is found that recycling to the walls is more efficient for the light impurities released in molecular form, but, also, that a substantial fraction of those atoms which o… more

Date: November 1, 1981

Creator: Langer, W. D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Physics of Plasma-Based Ion Implantation&Deposition (PBIID)and High Power Impulse Magnetron Sputtering (HIPIMS): A Comparison

The emerging technology of High Power Impulse MagnetronSputtering (HIPIMS) has much in common with the more establishedtechnology of Plasma Based Ion Implantation&Deposition (PBIID):both use pulsed plasmas, the pulsed sheath periodically evolves andcollapses, the plasma-sheath system interacts with the pulse-drivingpower supply, the plasma parameters are affected by the power dissipated,surface atoms are sputtered and secondary electrons are emitted, etc.Therefore, both fields of science and te… more

Date: August 28, 2007

Creator: Anders, Andre

Item Type: Article

Partner: UNT Libraries Government Documents Department