Progress toward fully noninductive discharge operation in DIII-D using off-axis neutral beam injection
- General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States)
- Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, California 94550-9234 (United States)
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
- Columbia University, 116th St and Broadway, New York, New York 10027 (United States)
- University of California, Irvine, University Dr., Irvine, California 92697 (United States)
- University of California, Los Angeles, PO Box 957099, Los Angeles, California 90095-7099 (United States)
- FAR-TECH, Inc., 10350 Science Center Dr., San Diego, California 92121-1136 (United States)
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451 (United States)
The initial experiments on off-axis neutral beam injection into high noninductive current fraction (f{sub NI}), high normalized pressure (β{sub N}) discharges in DIII-D [J. L. Luxon, Fusion Sci. Technol. 48, 828 (2005)] have demonstrated changes in the plasma profiles that increase the limits to plasma pressure from ideal low-n instabilities. The current profile is broadened and the minimum value of the safety factor (q{sub min}) can be maintained above 2 where the profile of the thermal component of the plasma pressure is found to be broader. The off-axis neutral beam injection results in a broadening of the fast-ion pressure profile. Confinement of the thermal component of the plasma is consistent with the IPB98(y,2) scaling, but global confinement with q{sub min}>2 is below the ITER-89P scaling, apparently as a result of enhanced transport of fast ions. A 0-D model is used to examine the parameter space for f{sub NI}=1 operation and project the requirements for high performance steady-state discharges. Fully noninductive solutions are found with 4<β{sub N}<5 and bootstrap current fraction near 0.5 for a weak shear safety factor profile. A 1-D model is used to show that a f{sub NI}=1 discharge at the top of this range of β{sub N} that is predicted stable to n=1, 2, and 3 ideal MHD instabilities is accessible through further broadening of the current and pressure profiles with off-axis neutral beam injection and electron cyclotron current drive.
- OSTI ID:
- 22220605
- Journal Information:
- Physics of Plasmas, Vol. 20, Issue 9; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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