ANALYSIS OF BURN STABILIZATION OF IGNITED D-T TOKAMAK PLASMAS ALLOWING FOR RADIAL MOTION

The possibility of passive and active burn stabilization of ignited de uterium-tritium (D-T) tokamak plasmas allowing for radial motion is st udied by using a zero-dimensional transport model. Analyses are based on a linear stability method and a nonlinear dynamic simulation. The r esults are principally given for a self-ignited International Thermonu clear Experimental Reactor (ITER)-grade plasma. The radial motion has a stabilizing effect in a plasma with ITER89 scaling. It is impractica l, however, to expect the radial motion to passively stabilize the bur ning plasma. A compression-decompression scheme based on regulation of the vertical field sufficiently stabilizes the plasma with ITER89 sca ling. This control scheme requires some space for radial motion. The r adial space requirement needed to manage a certain temperature perturb ation is typically written as deltaR/R0 almost-equal-to 0.6deltaT/T0. The allowable magnitude of temperature perturbation is within only 0.5 % for deltaR = 2 cm. The extra space requirement would be the most sev ere problem in this control scheme. If the fraction GT of alpha-partic le power loss due to field ripple is significant, the requirement on r adial space might be considerably relaxed. Preliminary calculations ha ve shown that deltaR/R0 almost-equal-to 0.3deltaT/T0 might be achievab le for GT = 20%.