Hybrid Scenario Development in DIII-D

Experiments in the DIII-D tokamak have demonstrated the ability to sustain ELMing H-mode discharges with high beta and good confinement quality under stationary conditions. These experiments have shown the ability to sustain normalized fusion performance (in terms of βNH89P /q952) at or above that projected for Qfus = 10 operation in the International Thermonuclear Experimental Reactor (ITER) design over a wide range in operating parameters. In the best cases, operation is maintained at the free boundary, n = 1 stability limit. Confinement is found to be better than standard H-mode confinement scalings over a wide range in operation space, and experimentally measured transport is consistent with predictions from the GLF23 transport code. Projections using the standard ITER H-mode scaling laws based on these discharges indicate that Qfus = 5 can be maintained for >5400 s in ITER at q95 = 4.5 while Qfus = 40 can be obtained for ∼2400 s at q95 = 3.2. These projected performance levels further validate the ITER design and suggest that long-pulse, high neutron fluence operation as well as very high fusion gain operation may be possible in next-generation tokamaks