Comparison of time dependent simulations with experiments in ion cyclotron heated plasmas

Abstract

Comparisons between time dependent simulations and experiments in ion cyclotron heated plasmas in the JET tokamak have been made. A time dependent code, PION-T, has been used to simulate the heating. The scenario that has been analysed is minority heating of hydrogen in a deuterium plasma. Two measured quantities have been compared with the calculations, namely the anisotropic plasma energy content and the 2.4 MeV neutron flux from (D,D) reactions. Two versions of the PION-T code have been used, one with zero banana width and one in which a simplified model for taking the finite width of drift orbits into account is employed. The zero banana width calculations yield good agreement between measurements and calculations for relatively low power levels only. However, with the second version of the code, taking the finite width of the drift orbits into account, good agreement can also be obtained for higher power levels. The non-thermal neutron yield caused by second harmonic absorption by the deuterium is simulated and agreement is found provided the hydrogen concentration, for which no reliable measurements are available, is suitably chosen. Finally, by studying the rapid changes in fast ion energy content in connection with sawtooth instabilities, it is found that about 40% of the fast ions are expelled outside the q=1 surface and that prompt losses are negligible