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Loading, absorption, and Fokker-Planck calculations for upcoming ICRF experiments on ATF

Description: ICRF experiments on ATF at the 100-kW level are planned for the current 1989 operating period. These plans include the 2..omega../sub cH/ regime at f/sub RF/ = 28.88 MHz, D(H) at 14.44 MHz, and /sup 4/He(/sup 3/He) and D(/sup 3/He) at 9.63 MHz. ECH target plasmas have n/sub eO/ /approx lt/ 0.15 /times/ 10/sup 20/ m/sup /minus/3/ and B = 0.95 T. The density and temperature profiles obtained are broader than those from 1988, owing to recent field error corrections. The values used for target-plasma parameters in the calculations were taken from initial 1989 ATF data. Loading and absorption calculations have been performed using the 3D RF heating code ORION with a helically symmetric equilibrium, and Fokker-Planck calculations were performed using the steady-state code RFTRANS with two velocity dimensions and one spatial dimension. 6 refs., 3 figs.
Date: January 1, 1989
Creator: Shepard, T.D.; Carter, M.D.; Goulding, R.H. & Kwon, M.
Partner: UNT Libraries Government Documents Department

X-ray diagnostics of hohlraum plasma flow

Description: In this study we use spectroscopy and x-ray imaging to investigate the macroscopic plasma flow in mm-sized laser-produced hohlraum plasmas. By using multiple diagnostics to triangulate the emission on a single experiment, we can pinpoint the position of dopants placed inside the hohlraum. X-ray emission from the foil has been used in the past to measure electron temperature. Here we analyze the spatial movement of dopant plasmas for comparison to hydrodynamic calculations.
Date: May 13, 1996
Creator: Back, C.A.; Glenzer, S.H.; Landen, O.L.; MacGowan, B.J. & Shepard, T.D.
Partner: UNT Libraries Government Documents Department

Determination of ICRF antenna fields in the vicinity of a 3-D Faraday shield structure

Description: A three-dimensional (3-D) magnetostatic analysis developed at Oak Ridge National Laboratory has been used to calculate the electromagnetic transmission properties of representative Faraday shield designs. The analysis uses the long-wavelength approximation to obtain a 3-D Laplace solution for the magnetic scalar potential over one poloidal period of the Faraday shield, from which the complete magnetic field distribution may be obtained. Once the magnetic field distributions in the presence and absence of a Faraday shield are known, the flux transmission coefficient can be found, as well as any change in the distributed inductance of the current strap. The disturbed capacitance of the strap can be found from an analogous 3-D electrostatic calculation, enabling the phase velocity of the slow-wave structure to be determined. Power dissipation in the shield may be estimated by equating the surface current on a perfect conductor with the surface magnetic field and using the surface current in conjunction with the finite conductivities of the shield materials to obtain the power distribution to eddy current heating. 4 refs., 5 figs., 1 tab.
Date: January 1, 1989
Creator: Ryan, P.M.; Rothe, K.E.; Whealton, J.H. & Shepard, T.D.
Partner: UNT Libraries Government Documents Department

Wall conditioning in ATF (Advanced Toroidal Facility)

Description: Techniques for cleaning and conditioning the vacuum vessel of the Advanced Toroidal Facility (ATF) and its internal components are described. The vacuum vessel cleaning technique combines baking to 150/degree/C and glow discharges with hydrogen gas. Chromium gettering is used to further condition the system. The major internal components are the anodized aluminium baffles in the Thomson scattering system, a graphite-shielded ICRF antenna, two graphite limiters, and a diagnostic graphite plate. Three independent heating systems are used to bake some of the major components of the system. The major characteristics used for assessing cleanliness and conditioning progress are the maximum pressure attained during bakeout, the result of gas analysis, and relevant plasma parameters (e.g., time to radiative decay). Details of the various cleaning and conditioning procedures and results are presented. 5 refs., 8 figs., 3 tabs.
Date: January 1, 1989
Creator: Langley, R.A.; Clark, T.L.; Glowienka, J.C.; Goulding, R.H.; Mioduszewski, P.K.; Rasmussen, D.A. et al.
Partner: UNT Libraries Government Documents Department

Recent results on cleaning and conditioning the ATF vacuum system

Description: Techniques for cleaning and conditioning the vacuum vessel of the Advanced Toroidal Facility (ATF) and its internal components are described. The vacuum vessel cleaning technique combines baking to 150/degree/C and glow discharges with hydrogen gas. Chromium gettering is used to further condition the system. The major internal components are the anodized aluminum baffles in the Thomson scattering system, a graphite-shielded ICRF antenna, two graphite limiters, and a diagnostic graphite plate. Three independent heating systems are used to bake some of the major components of the system. The major characteristics used for assessing cleanliness and conditioning progress are the maximum pressure attained during bakeout, the results of gas analysis, and relevant plasma parameters (e.g., time to radiative decay). Details of the various cleaning and conditioning procedures and results are presented. 5 refs., 8 figs., 3 tabs.
Date: January 1, 1989
Creator: Langley, R.A.; Clark, T.L.; Glowienka, J.C.; Goulding, R.H.; Mioduszewski, P.K.; Rasmussen, D.A. et al.
Partner: UNT Libraries Government Documents Department

Fast-wave ICRF minority-regime heating experiments on the Tore Supra tokamak

Description: Up to 4 MW of rf power at 57 MHz has been coupled to Ohmic target plasmas during the first ICRF heating experiments on Tore Supra. A total of 12 MW of rf power will ultimately be available from six tetrode amplifiers and will be coupled to the plasmas using three ORNL/CEA-designed resonant double-loop antennas. During these first experiments, two antennas were used, with one or two energized at a time. The antenna loading with plasma was observed to be well over an order of magnitude greater than that without plasma. In addition, one kilo-electron-volt of electron heating, significant minority nonthermal ions, and significant increases in diamagnetic stored energy were observed. A comparison of in-phase and out-of-phase antenna operation showed the same increase in stored energy, less radiated power, and a larger drop in loop voltage for out-of-phase operation. Confinement scaling agrees with the ITER scaling law. 2 refs., 5 figs.
Date: January 1, 1991
Creator: Shepard, T.D.; Haste, G.R.; Baity, F.W. (Oak Ridge National Lab., TN (United States)); Agarici, G.; Beaumont, B.; Becoulet, A. et al.
Partner: UNT Libraries Government Documents Department

Studies of plasma performance and transport in the advanced toroidal facility (ATF)

Description: An overview of recent ATF experimental results and program plans is presented, with emphasis on the role of magnetic configuration controls in transport studies. The ATF operating space is bounded by a density limit that effectively sets a limit on the energy confinement time {tau}{sub E}. Although this limit is not solely due to impurities, it has recently been raised by improved cleanliness following titanium gettering. This has led to collapse-free neutral beam injection (NBI) discharges with global {tau}{sub E} {approx} 16 ms. Preliminary experiments show that stored energy and bootstrap current are sensitive to details of the magnetic configuration. 13 refs., 8 figs.
Date: January 1, 1989
Creator: Neilson, G.H.; Bigelow, T.S.; Carreras, B.A.; Colchin, R.J.; Crume, E.C.; Dunlap, J.L. et al.
Partner: UNT Libraries Government Documents Department