Observation of Burning Plasma Dynamics in DIII-D

The key power balance building blocks of a burning plasma have been simulated in DIII-D using Xenon (Xe) and Krypton (Kr) for Tungsten (W)-like core radiation, feedback controlled NBI and/or ECH for α-heating, and independently controlled plasma β_N using NBI. A new algorithm was designed and demonstrated, capable of simulating any desired fraction of fusion α-power P_α, using real-time measurements of T_i and n_e, a T_i-shifted fusion reactivity to reproduce the T_i dependence of <σv> at DIII-D T_i levels, and controlling NBI and/or ECH power input. At DIII-D’s ITER baseline plasma core T_e≈2-3 keV, Xe and Kr radiate at a similar rate as W radiates at the T_e≈20 keV expected in ITER and an FPP. Using W-equivalent radiators Kr and Xe in DIII-D ITER baseline plasmas, the core radiated fraction is similar to f_rad≈30% expected in ITER, and experiments have observed non-linear oscillations coupling density, temperature and radiation. These oscillations have been reproduced with a simple coupled model that includes W-equivalent radiation and input-power feedback consistent with the experiment. This coupled model reproduces the oscillations and the interplay of the simulated P_α with the background plasma. These experiments establish a test-bed for simulating fusion burn dynamics and testing burn control techniques needed for long pulse high fusion gain Q≧10 experiments in ITER and future FPPs.