Alpha heating and isotopic mass effects in JET plasmas with sawteeth

摘要

The alpha heating experiment in the Joint European Torus (JET) 1997 DTE1 campaign is re-examined. Several effects correlated with tritium content and thermal hydrogenic isotopic mass < A > weaken the conclusion that alpha heating was clearly observed. These effects delayed the occurrence of significant sawtooth crashes allowing the electron and ion temperatures T_e and T_i, to achieve higher values. Under otherwise equal circumstances T_e and T_i were typically higher for discharges with higher < A >, and significant scaling of T_i, T_e, and total stored energy with < A > were observed. The higher T_i led to increased ion-electron heating rates with magnitudes comparable to those computed for alpha electron heating. Rates of other heating/loss processes also had comparable magnitudes. Simulations of T_e assuming the observed scaling of T_i are qualitatively consistent with the measured profiles, without invoking alpha heating.