Neutral beam current drive scaling in DIII-D
Neutral beam current drive scaling experiments have been carried out on the DIII-D tokamak at General Atomics. These experiments were performed using up to 10 MW of 80 keV hydrogen beams. Previous current drive experiments on DIII-D have demonstrated beam driven currents up to 340 kA. In the experiments reported here we achieved beam driven currents of at least 500 kA, and have obtained operation with record values of poloidal beta (epsilon..beta../sub p/ = 1.4). The beam driven current reported here is obtained from the total plasma current by subtracting an estimate of the residual Ohmic current determined from the measured loop voltage. In this report we discuss the scaling of the current drive efficiency with plasma conditions. Using hydrogen neutral beams, we find the current drive efficiency is similar in Deuterium and Helium target plasmas. Experiments have been performed with plasma electron temperatures up to T/sub e/ = 3 keV, and densities in the range 2 /times/ 10/sup 19/m/sup /minus/3/ < n/sub e/ < 4 /times/ 10/sup 19/m/sup /minus/3/. The current drive efficiency (nIR/P) is observed to scale linearly with the energy confinement time on DIII-D to a maximum of 0.05 /times/ 10/sup 20/m/sup /minus/2/ A/W. The measured efficiency is consistent with a 0-D theoretical model. In addition to comparison with this simple model, detailed analysis of several shots using the time dependent transport code ONETWO is discussed. This analysis indicates that bootstrap current contributes approximately 10--20% of the the total current. Our estimates of this effect are somewhat uncertain due to limited measurements of the radial profile of the density and temperatures. 4 refs., 1 fig., 1 tab.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48; AC03-84ER51044
- OSTI ID:
- 6392634
- Report Number(s):
- UCRL-99938; CONF-890302-2; ON: DE89005639; TRN: 89-006908
- Resource Relation:
- Conference: 16. European conference on controlled fusion and plasma physics, Venice, Italy, 13 Mar 1989; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DOUBLET-3 DEVICE
NEUTRAL ATOM BEAM INJECTION
CONFINEMENT TIME
EFFICIENCY
ELECTRON TEMPERATURE
PLASMA DENSITY
PLASMA HEATING
SCALING LAWS
BEAM INJECTION
CLOSED PLASMA DEVICES
HEATING
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
700101* - Fusion Energy- Plasma Research- Confinement
Heating
& Production