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Laser-plasma interaction experiments at laser wavelengths of 1. 064. mu. m, 0. 532. mu. m, and 0. 355. mu. m

Description: The effect of laser wavelength on laser-plasma coupling is one of the critical issues facing the laser driven inertial confinement community. The advantages of using lasers with output wavelength less than 1 ..mu..m, such as enhanced absorption and hydrodynamic efficiency, reduction in parametric instabilities and corresponding suprathermal electron generation, have long been predicted theoretically.
Date: January 1, 1982
Creator: Campbell, E. M.; Mead, W. C. & Turner, R. E.
Partner: UNT Libraries Government Documents Department
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Recent US target-physics-related research in heavy-ion inertial fusion: simulations for tamped targets and for disk experiments in accelerator test facilities

Description: Within the last few years, there have also appeared in the Heavy-Ion Fusion literature several studies of targets which have outer tampers. One-dimensional simulations indicate higher target gains with a judicious amount of tamping. But for these targets, a full investigation has not been carried through in regards to conservative criteria for fluid instabilities as well as reasonable imperfections in target fabrication and illumination symmetry which all affect target ignition and burn. Compar… more
Date: June 24, 1982
Creator: Mark, J.W.K.
Partner: UNT Libraries Government Documents Department
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Optical-scattering measurements from 1. 06-. mu. m, 0. 53-. mu. m, and 0. 35-. mu. m laser-heated disk targets

Description: A discussion is presented on scattered light measurements relevant to three of the important parametric instabilities which occur in high intensity laser plasma interactions: stimulated Brillouin scattering (SBS), the two plasmon decay instability (2-..omega../sub pe/), and stimulated Raman scattering (SRS). Most of these experiments were carried out on the ARGUS facility. Its configuration is described for the multiple wavelength experiments, all of which were conducted with one beam illuminat… more
Date: January 1, 1982
Creator: Turner, R. E.; Campbell, E. M.; Phillion, D. W.; Mead, W. C.; Ze, F.; Max, C. et al.
Partner: UNT Libraries Government Documents Department
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Observation of tilt asymmetries in field-reversed configurations

Description: In recent years, part of the experimental effort on the FRX-C/LSM device has been devoted to understanding why good FRC confinement is observed only in a narrow window of the operating parameter space (fill pressures less than 5 mtorr and bias fields less than 0.8--0.9 kG). The transition from good to bad confinement has been shown for some time to correlate with strong axial shocks, suggesting a formation or stability problem. More recently, FRC magnetic asymmetries have been observed whenever… more
Date: January 1, 1989
Creator: Tuszewski, M.; Barnes, D. C.; Klingner, P. & Ng, Chun
Partner: UNT Libraries Government Documents Department
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Enhanced lower hybrid penetration via intense multi-microsecond pulses

Description: Applying lower-hybrid power in short, intense pulses can overcome Landau damping, allowing penetration into the core of reactor-grade plasmas. We present theoretical description of the absorption which accounts for transient collisional effects as well as nonlinear broadening of the resonant plateau. We show results from ray-tracing calculations which include the nonlinear absorption. We also derive the conditions required for pump depletion by parametric instabilities, and assess density deple… more
Date: January 1, 1991
Creator: Cohen, R. H.; Rognlien, T. D. (Lawrence Livermore National Lab., CA (United States)); Bonoli, P. T. & Porkolab, M. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center)
Partner: UNT Libraries Government Documents Department
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ICRF heating on TFTR

Description: The objectives of the ICRF heating program on TFTR are discussed along with a summary of the progress made to date towards achieving those goals. A more detailed analysis of experimental observations of ICRF sawtooth stabilization is given along with a comparison of the data to a theoretical model based on energetic ion stabilization of m=1 kink instabilities. A qualitative correlation is observed between the experimental observations and model predictions, but further development of the theory… more
Date: January 1, 1991
Creator: Phillips, C. K.; Fredrickson, E.; Hammett, G.; Hosea, J.; McGuire, K.; Stevens, J. et al.
Partner: UNT Libraries Government Documents Department
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Experimental studies of field-reversed-configuration (FRC) confinement in FRX-C

Description: A primary purpose of the large bore (0.5 m dia.) FRX-C field-reversed theta pinch experiment is to study the scaling of plasma particle containment time, tau/sub N/, with major radius, R, of the field-reversed configuration (FRC). At 20 mtorr fill pressure the FRX-C plasma parameters, anti n approx. 4 x 10/sup 15/ c/sup -3/, T/sub e/ approx. 100 eV, T/sub i/ approx. 150 eV, are comparable to those obtained in the smaller bore (0.25 m dia.) FRX-B device. Under these conditions, the present measu… more
Date: January 1, 1982
Creator: Siemon, R. E.; Armstrong, W. T. & Bartsch, R. R.
Partner: UNT Libraries Government Documents Department
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Electrostatically driven plasma hydrodynamic instability. I. The failure of vacuum-insulated, long wavelength laser fusion pellets

Description: Longer wavelength (e.g., lambda = 10.5 ..mu..m) laser radiation generates relatively large fluxes of superthermal electrons that penetrate and preheat the cores of such pellets at early times in their implosion history, precluding their efficient subsequent compression. It has been proposed to separate the outermost shell of such pellets (onto which the laser light is directed) from its inner regions by a vacuum layer, thereby ''insulating'' these inner portions from superthermal electron degra… more
Date: October 1, 1977
Creator: Levermore, C. D.; Caflisch, R. E. & Wood, L. L.
Partner: UNT Libraries Government Documents Department
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MHD stability of torsatrons using the average method

Description: 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.
Partner: UNT Libraries Government Documents Department
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Design and operation of the multipulse Thomson scattering diagnostic on DIII-D

Description: This paper describes the design and operation of a 40 spatial channel Thomson scattering system that uses multiple 20 Hz Nd:YAG lasers to measure the electron temperature and density profiles periodically throughout an entire plasma discharge. As many as eight lasers may be fired alternately for an average measurement frequency of 160 Hz, or they may be fired in rapid succession (< 10 kHz), producing a burst of pulses for measuring transient events. The high spatial resolution (1.3 cm) and wide… more
Date: March 1, 1992
Creator: Carlstrom, T. N.; Campbell, G. L.; DeBoo, J. C.; Evanko, R.; Greenfield, C. M.; Haskovec, J. et al.
Partner: UNT Libraries Government Documents Department
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Optimization and control of the plasma shape and current profile in noncircular cross-section tokamaks

Description: High-..beta.. equilibria which are stable to all ideal MHD modes are found by optimizing the plasma shape and current profile for doublets, up-down asymmetric dees, and symmetric dees. The ideal MHD stability of these equilibria for low toroidal mode number n is analyzed with a global MHD stability code, GATO. The stability to high-n modes is analyzed with a localized ballooning code, BLOON. The attainment of high ..beta.. is facilitated by an automated optimization search on shape and current … more
Date: June 1, 1980
Creator: Moore, R. W.; Bernard, L. C.; Chan, V. S.; Davidson, R. H.; Dobrott, D. R.; Helton, F. J. et al.
Partner: UNT Libraries Government Documents Department
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Control of ash accumulation by induced-fishbones

Description: Thermal alphas will accumulate in the ignited long pulse tokamak. Ash accumulation results in fuel dilution, reduced power output, increase in Z{sub eff}, and increased synchrotron losses. Recent Baldur' simulations of the ITER show that the ash accumulation is a distinct possibility for high ash recycling case, inevitably leading to burn quench. So, some means of ash is highly desirable. To this end, several control schemes have been looked at. Given the uncertainty in transport information es… more
Date: January 1, 1989
Creator: Varadarajan, V. & Miley, G.H.
Partner: UNT Libraries Government Documents Department
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Heating by the Raman instability

Description: Computer simulations are presented of the reflection and heating due to stimulated Raman backscatter of intense laser light in large regions of underdense plasma. The heated electron distribution is found to be approximately a Maxwellian of temperature (m/sub e//2)v/sub p//sup 2/, where v/sub p/ is the phase velocity of the electron plasma wave. A simple model of the reflection is presented. Raman may cause a pre-heat problem with large laser fusion reactor targets.
Date: April 11, 1980
Creator: Estabrook, K.G. & Kruer, W.L.
Partner: UNT Libraries Government Documents Department
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Application of an array processor to the analysis of magnetic data for the Doublet III tokamak

Description: Discussed herein is a fast computational technique employing the Floating Point Systems AP-190L array processor to analyze magnetic data for the Doublet III tokamak, a fusion research device. Interpretation of the experimental data requires the repeated solution of a free-boundary nonlinear partial differential equation, which describes the magnetohydrodynamic (MHD) equilibrium of the plasma. For this particular application, we have found that the array processor is only 1.4 and 3.5 times slowe… more
Date: August 1980
Creator: Wang, T. S. & Saito, M. T.
Partner: UNT Libraries Government Documents Department
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Pattern formation by shock processes

Description: Shock waves in condensed media often produce and leave behind periodic patterns and textures. These patterns have been observed both in real time and in postmortem examination. In many cases the patterns can be related to analogous Pattern-forming mechanisms in classical fluid dynamics, such as the Rayleigh-Taylor and Helmholtz instabilities. In other cases, the textures arise from peculiarities in the dynamic stress state immediately behind the leading edge of the shock wave. Periodic waves in… more
Date: January 1, 1983
Creator: Shaner, J.W.
Partner: UNT Libraries Government Documents Department
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Final analysis of the engineering data on the scyllac feedback stabilization experiment

Description: The feedback stabilization system consists of four basic components: plasma position detectors, a signal processor or mode analyzer driven by the position detector signals, power amplifiers which are driven by the mode analyzer, and feedback load coils driven by the power amplifiers. A short description of each of the four components of the system is presented. The location of the components in the experiment is shown.
Date: January 1, 1977
Creator: Kutac, K. J.; Kewish, R. W.; Miller, G. & Gribble, R. F.
Partner: UNT Libraries Government Documents Department
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Resistive G-modes and ballooning

Description: A unified theory of the linear stability of the Roberts and Taylor type of resistive interchange and ballooning is presented. The effects of both parallel and perpendicular viscosity as well as of finite shear and finite ..beta.. are included in a MHD treatment of the problem. Kinetic effects are also studied. The hybrid kinetic model with Vlasov ions and guiding center electrons has been appropriately generalized to allow for electron-ion collisions. The geometry is that of a plane slab with m… more
Date: January 1, 1980
Creator: Dagazian, R.Y.; Mondt, J.P. & Paris, R.B.
Partner: UNT Libraries Government Documents Department
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Plasma confinement experiments in the TMX tandem mirror. Paper IAEA-CN-38/F-1

Description: Results from the new Tandem Mirror Experiment (TMX) are described. Tandem-mirror density and potential profiles are produced using end-plug neutral-beam injection and central-cell gas-fueling. TMX parameters are near those predicted theoretically. The end-plug electron temperature is higher than in the comparably sized single-mirror 2XIIB. Axial confinement of the finite-beta central-cell plasma is improved by the end plugs by as much as a factor of 9. In TMX, end-plug microinstability limits c… more
Date: May 22, 1980
Creator: Simonen, T. C.; Anderson, C. A. & Casper, T. A.
Partner: UNT Libraries Government Documents Department
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Effects of fueling profiles on plasma transport

Description: The effects of cold particle fueling profiles on particle and energy transport in an ignition sized tokamak plasma are investigated in this study with a one-dimensional, multifluid transport model. A density gradient driven trapped particle microinstability model for plasma transport is used to demonstrate potential effects of fueling profiles on ignition requirements. Important criteria for the development of improved transport models under the conditions of shallow particle fueling profiles a… more
Date: January 1, 1977
Creator: Houlberg, W. A.; Mense, A. T.; Attenberger, S. E. & Milora, S. L.
Partner: UNT Libraries Government Documents Department
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Physics of mirror systems

Description: In recent years the emphasis in research on the magnetic mirror approach to fusion has been shifted to address what are essentially economically-motivated issues. The introduction of the Tandem Mirror idea solved in principal the problem of low Q (low fusion power gain) of mirror-based fusion systems. In order to optimize the tandem mirror idea from an economic standpoint, some important improvements have been suggested. These improvements include the thermal barrier idea of Baldwin and Logan a… more
Date: May 1, 1982
Creator: Post, Richard F.
Partner: UNT Libraries Government Documents Department
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Optical diagnostics on dense Z-pinch plasmas

Description: A novel point-diffraction'' interferometer has been implemented on the Los Alamos Solid Fiber Z-Pinch experiment. The laser beam is split into two legs after passing through the plasma. The reference leg is filtered with a pin-hole aperture and recombined with the other leg to form an interferogram. This allows compact mounting of the optics and relative ease of alignment. The Z-Pinch experiment employs a pulsed-power generator that delivers up to 700 KA with a 100ns rise-time through a fiber o… more
Date: January 1, 1992
Creator: Riley, R.A. Jr.; Lovberg, R.H.; Shlachter, J.S. & Scudder, D.W.
Partner: UNT Libraries Government Documents Department
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Heat transfer modelling of first walls subject to plasma disruption

Description: A brief description of the plasma disruption problem and potential thermal consequences to the first wall is given. Thermal models reviewed include: a) melting of a solid with melt layer in place; b) melting of a solid with complete removal of melt (ablation); c) melting/vaporization of a solid; and d) vaporization of a solid but no phase change affecting the temperature profile.
Date: January 1, 1981
Creator: Fillo, J.A. & Makowitz, H.
Partner: UNT Libraries Government Documents Department
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