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Recent beam probe measurements on EBT, TMX, and RENTOR

Description: It is noted that beam probe systems can provide accurate, reliable measurments of plasma space potential and nf(T/sub e/). Over some temperature range, at least, it should be possible to separate n and T/sub e/ by measuring the multiple ionization reaction products. It is also an ideal diagnostic for studying fluctuations since it provides a simultaneous measurement of phi and nf(T/sub e/) from the same point in the plasma and the measurements are continuous in time. Measurements can be made qu… more
Date: June 1, 1980
Creator: Hickok, R. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Electron energy distributions, vibrational population distributions, and negative-ion concentrations in hydrogen discharges

Description: We consider the negative ion concentrations in hydrogen discharges caused by electron excitation and dissociative attachment processes. The principal formation and destruction processes are discussed for electron densities in the range 10/sup 8/ to 10/sup 13/ electrons cm/sup -3/. Expressions are developed for calculating the high energy portion of the electron energy distribution in the discharge; using these energy distributions the electron excitation rates are evaluated. At low densities, t… more
Date: June 28, 1982
Creator: Hiskes, J.R. & Karo, A.M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Plasma boundary layer and magnetopause layer of the earth's magnetosphere

Description: IMP 6 observations of the plasma boundary layer (PBL) and magnetopause layer (MPL) of the earth's magnetosphere indicate that plasma in the low-latitude portion of the PBL is supplied primarily by direct transport of magnetosheath plasma across the MPL and that this transport process is relatively widespread over the entire sunward magnetospheric boundary.
Date: June 1, 1979
Creator: Eastman, T.E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Improved numerical grid generation techniques for the B2 edge plasma code

Description: Techniques used to generate grids for edge fluid codes such as B2 from numerically computed equilibria are discussed. Fully orthogonal, numerically derived grids closely resembling analytically prescribed meshes can be obtained. But, the details of the poloidal field can vary, yielding significantly different plasma parameters in the simulations. The magnitude of these differences is consistent with the predictions of an analytic model of the scrape-off layer. Both numerical and analytic grids … more
Date: June 1, 1992
Creator: Stotler, D. P. & Coster, D. P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Current-drive experiments on the PLT Tokamak

Description: Lower hybrid current-drive experiments have been carried out on the PLT Tokamak. Steady currents up to 175 kA have been maintained for three seconds and 400 kA for 0.3 sec by the rf power alone. The principal current carrier appears to be a high energy (approx. 100 keV) electron tail, concentrated in the central 20 to 40 cm diameter core of the 80-cm PLT discharge. Effective current drive is observed only for anti n/sub e/ less than or equal to 8 x 10/sup 12/ cm/sup -3/. This limitation may be … more
Date: June 1, 1983
Creator: Jobes, F.; Bernabei, S.; Efthimion, P.; Hooke, W.; Hosea, J.; Mazzucato, E. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Electron-Cloud Build-up in the FNAL Main Injector

Description: We present a summary on ongoing simulation results for the electron-cloud buildup in the context of the proposed FNAL Main Injector (MI) intensity upgrade [1] in a fieldfree region at the location of the RFA electron detector [2]. By combining our simulated results for the electron flux at the vacuum chamber wall with the corresponding measurements obtained with the RFA we infer that the peak secondary electron yield (SEY) {delta}{sub max} is {approx}> 1.4, and the average electron density i… more
Date: June 4, 2007
Creator: Furman, M. A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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VORPAL simulations relevant to coherent electron cooling

Description: Coherent electron cooling (CEC) [1] combines the best features of electron cooling and stochastic cooling, via free-electron laser technology [2], to offer the possibility of cooling high-energy hadron beams with order-of-magnitude shorter cooling times. Many technical difficulties must be resolved via full-scale 3D simulations, before the CEC concept can be validated experimentally. VORPAL is the ideal code for simulating the modulator and kicker regions, where the electron and hadron beams wi… more
Date: June 23, 2008
Creator: Bell, G.; Bruhwiler, D.; Sobol, A.; Ben-Zvi, Ilan; Litvinenko, V. & Derbenev, Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Studies of Impurity Assimilation During Massive Argon Gas Injection in DIII-D

Description: Fast shutdown of discharges using massive gas injection (MGI) is a promising technique for reducing tokamak wall damage during disruptions [1]. An outstanding concern, however, is the generation of runaway electrons (RE) during the shutdown. Although RE formation observed during MGI in present-day experiments is quite small (typically <1% of the main plasma current I{sub p} in DIII-D), it is thought that even this small RE current could be amplified to significant levels in reactor-scale tok… more
Date: June 27, 2007
Creator: Hollmann, E.; Jernigan, T.; Parks, P.; Baylor, L.; Boedo, J.; Combs, S. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Determination of the electron velocity distribution from the soft and hard x-ray emission during lower-hybrid current drive on PLT

Description: During lower-hybrid heating in low-density-tokamak discharges, a nonMaxwellian tail of high-energy electrons is formed. This tail carries the plasma current. Utilizing the fact that relativistic electrons emit bremsstrahlung predominantly in the forward direction, we investigate the shape of the electron distribution by measuring the dependence of the x-ray emission on the angle between the magnetic field and the line of sight. The experimental data indicate that the distribution function is pr… more
Date: June 1, 1983
Creator: Von Goeler, S.; Stevens, J. & Karney, C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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X-ray analysis of nonMaxwellian distributions (current drive)

Description: The plasma bremsstrahlung emission is utilized to determine the shape of the electron velocity distribution in situations where it deviates strongly from a Maxwellian distribution. The instrumentation used to measure the hard x-ray emission is briefly discussed. Model calculations show that polarization measurements give best results for unrelativistic tails with tail temperatures T/sub b/ < 50 keV, whereas measurements of the angular distribution of the x-ray emission based on the forward scat… more
Date: June 1, 1983
Creator: Von Goeler, S.; Stevens, J. & Stodiek, W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Evaluation of potential runaway generation in large-tokamak disruptions

Description: A detailed evaluation of various potential mechanisms for the generation of strong runaway beams during disruptions of largetokamak devices, including TFTR, JET, DIIID and ITER, is performed based on typical operating parameters of these devices and the presently accepted disruption model. The main results include: (1) In the existing devices, the evaporative preicer'' process by itself can lead to sizable runaway beams in disruptions of high-current-medium-to-low-ne discharges. In ITER, such r… more
Date: June 1, 1993
Creator: Fleischmann, H. H. & Zweben, S. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Boundary conditions for OH, L, and H-mode simulations

Description: A method for prescribing appropriate boundary conditions for predictive simulations using flux-surface-averaged plasma transport codes is described. The model makes use of the present theoretical understanding of L and H-mode transport mechanisms and is consistent with trends in existing data. It is calibrated against an ASDEX experiment and used to predict the edge behavior in CIT. 14 refs., 7 figs.
Date: June 1, 1988
Creator: Singer, C. E.; Bateman, G. & Stotler, D. P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Influence of MHD effects and edge conditions on ITER helium ash accumulation and sustained ignition

Description: Dilution of reacting species by build-up of helium ash and its effect on ignition in the ITER tokamak have been studies in a series of simulations with the one-dimensional BALDUR transport code. Thermal diffusivities, obtained from ITER scaling laws and with radial variations observed in JET, gave {tau}{sub E} {approx} 2--4 sec. Refueling of deuterium and tritium maintained constant electron density, while carbon recycling was 100% and the helium ash recycling was varied from 1.0 to 0.5. Includ… more
Date: June 1, 1990
Creator: Redi, M.H. & Cohen, S.A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Improved numerical grid generation techniques for the B2 edge plasma code

Description: Techniques used to generate grids for edge fluid codes such as B2 from numerically computed equilibria are discussed. Fully orthogonal, numerically derived grids closely resembling analytically prescribed meshes can be obtained. But, the details of the poloidal field can vary, yielding significantly different plasma parameters in the simulations. The magnitude of these differences is consistent with the predictions of an analytic model of the scrape-off layer. Both numerical and analytic grids … more
Date: June 1, 1992
Creator: Stotler, D. P. & Coster, D. P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Ion cyclotron range of frequency heating on the Tokamak Fusion Test Reactor

Description: The complete ion cyclotron range of frequency (ICRF) heating system for the Tokamak Fusion Test Reactor (TFTR), consisting of four antennas and six generators designed to deliver 12.5 MW to the TFTR plasma, has now been installed. Recently a series of experiments has been conducted to explore the effect of ICRF heating on the performance of low recycling, Supershot plasmas in minority and non-resonant electron heating regimes. The addition of up to 7.4 MW of ICRF power to full size (R {approxim… more
Date: June 1, 1993
Creator: Taylor, G.; Bell, M. G.; Biglari, H.; Bitter, M.; Bretz, N. L.; Budny, R. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Microwave reflectometry for ICRF coupling studies on TFTR

Description: A dual-frequency differential-phase reflectometer has been developed for use in ICRF power coupling studies on TFTR. This system has been optimized for measurements of the electron density profile in the edge-gradient region, where density fluctuations are large. Initial proof-of-principle measurements demonstrate that this is an effective way to measure the electron density profile in the plasma-edge region. A new reflectometer launcher is presently being installed on the center axis of the ba… more
Date: June 1, 1993
Creator: Wilgen, J. B.; Bigelow, T. S.; Batchelor, D. B.; Hoffman, D. J.; Murakami, M.; Rasmussen, D. A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Differential phase reflectometry for edge profile measurements on TFTR

Description: Edge electron density profile measurements, including the scrape-off layer, have been made during ICRF heating with the two-frequency differential phase reflectometer installed in an ICRF antenna on TFTR. This system probes the plasma using the extraordinary mode with two signals swept from 90 to 118 GHz while maintaining a fixed difference frequency of 125 MHz. The extraordinary mode is used to obtain density profiles in the range of 1 {times} 10{sup 11} to 3 {times} 10{sup 13} cm{sup {minus}3… more
Date: June 1, 1994
Creator: Hanson, G. R.; Wilgen, J. B.; Bigelow, T. S.; England, A. C.; Murakami, M.; Rasmussen, D. A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A CO{sub 2} laser polarimeter for measurement of plasma current profile in Alcator C-Mod

Description: A multichannel infrared polarimeter system for measurement of the plasma current profile in Alcator C-Mod has been designed, constructed, and tested. The system utilizes a cw CO{sub 2}, laser at a wavelength of 10.6 {mu}m. An electro-optic polarization-modulation technique has been used to achieve the high sensitivity required for the measurement. The recent results of the measurements as well as the feasibility of its application on ITER are presented.
Date: June 1, 1994
Creator: Ma, C. H.; Hutchinson, D. P.; Richards, R. K.; Irby, J. & Luke, T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Nano Catalysts for Diesel Engine Emission Remediation

Description: The objective of this project was to develop durable zeolite nanocatalysts with broader operating temperature windows to treat diesel engine emissions to enable diesel engine based equipment and vehicles to meet future regulatory requirements. A second objective was to improve hydrothermal durability of zeolite catalysts to at least 675 C. The results presented in this report show that we have successfully achieved both objectives. Since it is accepted that the first step in NO{sub x} conversio… more
Date: June 1, 2012
Creator: Narula, Chaitanya Kumar; Yang, Xiaofan; Debusk, Melanie Moses; Mullins, David R; Mahurin, Shannon Mark & Wu, Zili
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Superthermal electron distribution measurements from polarized electron cyclotron emission

Description: Measurements of the superthermal electron distribution can be made by observing the polarized electron cyclotron emission. The emission is viewed along a constant magnetic field surface. This simplifies the resonance condition and gives a direct correlation between emission frequency and kinetic energy of the emitting electron. A transformation technique is formulated which determines the anisotropy of the distribution and number density of superthermals at each energy measured. The steady-stat… more
Date: June 1, 1988
Creator: Luce, T. C.; Efthimion, P. C. & Fisch, N. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Towards scalable electronic structure calculations for alloys

Description: A new approach to calculating the properties of large systems within the local density approximation (LDA) that offers the promise of scalability on massively parallel supercomputers is outlined. The electronic structure problem is formulated in real space using multiple scattering theory. The standard LDA algorithm is divided into two parts. Firstly, finding the self-consistent field (SCF) electron density, Secondly, calculating the energy corresponding to the SCF density. We show, at least fo… more
Date: June 1, 1994
Creator: Stocks, G. M.; Nicholson, D. M. C.; Wang, Y.; Shelton, W. A.; Szotek, Z. & Temmermann, W. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Evaluation of potential runaway generation in large-tokamak disruptions

Description: A detailed evaluation of various potential mechanisms for the generation of strong runaway beams during disruptions of largetokamak devices, including TFTR, JET, DIIID and ITER, is performed based on typical operating parameters of these devices and the presently accepted disruption model. The main results include: (1) In the existing devices, the evaporative ``preicer`` process by itself can lead to sizable runaway beams in disruptions of high-current-medium-to-low-ne discharges. In ITER, such… more
Date: June 1, 1993
Creator: Fleischmann, H. H. & Zweben, S. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Analysis of High-Te Plasmas Heated by HHFW in NSTX

Description: The implementation in TRANSP of a recent version of TORIC capable of calculating power deposition for HHFW conditions is used to analyze NSTX plasma under different operating conditions. The power deposition profile into the electrons is obtained for high-Te conditions - Te ≤ 5keV - obtained in He and D plasmas with ITB. HHFW heating of NBI-induced H-mode plasmas is discussed. At the RF onset the RF power is divided evenly between the electrons and the fast particles, but as the latter thermali… more
Date: June 26, 2009
Creator: LeBlanc, P.; Bell, R. E.; Bonoli, P.; Hosea, J. C.; Mazzucato, E.; Phillips, C. K. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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