Improvement of beam-heated limiter discharges by continuous pellet fueling in Doublet III
Conference
·
OSTI ID:6533529
A centrifuge pellet injector was employed to produce and maintaun high-density peaked profiles with low edge recycling in the Doublet III (DIII) tokamak. Whereas gas-fueled limiter discharges are characterized by high edge recycling and poor confinement during neutral beam injection, the pellet-fueled limiter discharges exhibit low edge recycling and energy confinement that is similar to diverted H-mode discharges (P-mode). In comparison to gas-fueled discharges, which have a n/sub e/ (0) approx. 1.0 x 10/sup 14/ cm/sup -3/ and tau/sub E/ approx. 45 ms, the values for pellet fueling were increased to n/sub e/ (0) approx. 2.0 x 10/sup 14/ cm/sup -3/ amd tau/sub E/ approx. 70 ms at 2.4 MW of beam heating. The neutron production rate was increased from 1 x 10/sup 11/ s/sup -1/ to 1 x 10/sup 12/ s/sup -1/. A technique of interrupting the neutral beam injectors just prior to injecting each pellet resulted in reduced edge ablation and a further enhancement in energy confinement for a peak beam power of 3.2 MW at a 53% duty cycle. Pellet fueling of divertor H-mode plasmas was also studied. In this case, the confinement times are not dramatically improved, but high-density discharges can be produced while maintaining the H-mode.
- Research Organization:
- Japan Atomic Energy Research Inst., Tokai, Ibaraki; Oak Ridge National Lab., TN (USA); GA Technologies, Inc., San Diego, CA (USA)
- DOE Contract Number:
- AT03-80SF11512; AC05-84OR21400
- OSTI ID:
- 6533529
- Report Number(s):
- CONF-840910-14; ON: DE85001855
- Country of Publication:
- United States
- Language:
- English
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