Numerical Investigation Of A New Icrf Heating Scenario In D-T Plasma On Cfetr

For a fusion device, plasma pre-heating is required before the self-sustaining burning-state reactions of deuterium (D) and tritium (T) commence. Plasma heating with waves in the ion-cyclotron range of frequencies (ICRF) is effective in tokamaks. A new three-ion ICRF heating scheme for plasmas in the Chinese Fusion Engineering Test Reactor (CFETR) that require an increase in the bulk ion temperature via heating the lithium impurities in the D-T plasmas, was studied numerically. Our simulations show that the radio-frequency wave power is strongly absorbed by very few Li-7 ions with concentrations of 0.01%-0.2% in a suitable mixture of D-T plasmas, the enhanced minority ion heating is related to that the Li-7 fundamental resonance layer is very close to the two mode conversion layers. In adjusting the mixtures over a wide range of composition, an oscillatory behaviour in the Li-7 absorption efficiency arises because of interference. Moreover, from estimates of the Li-7 ion tail energy, most of the tail energy of the minority ions is found to be transferred to background ions via collisions. Compared with the routine (He-3)-D-T scheme, the ICRF power is absorbed more effectively by the Li-7 ions in the (Li-7)-D-T heating scenario, and after the Fokker-Planck equations were solved, a large fraction of bulk ion heating was evident in the (Li-7)-D-T heating scenario. The new three-ion scenario may therefore be an attractive proposition for bulk ion heating during the activated phase of the reactor.