COMPARISON OF TIME-DEPENDENT SIMULATIONS WITH EXPERIMENTS IN ION-CYCLOTRON HEATED PLASMAS

Comparisons between time dependent simulations and experiments in ion cyclotron heated plasmas in the JET tokamak have been made. A time dep endent code, PION-T, has been used to simulate the heating. The scenar io that has been analysed is minority heating of hydrogen in a deuteri um plasma. Two measured quantities have been compared with the calcula tions, namely the anisotropic plasma energy content and the 2.4 MeV ne utron 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 m odel for taking the finite width of drift orbits into account is emplo yed. The zero banana width calculations yield good agreement between m easurements and calculations for relatively low power levels only. How ever, 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 h armonic absorption by the deuterium is simulated and agreement is foun d provided the hydrogen concentration, for which no reliable measureme nts are available, is suitably chosen. Finally, by studying the rapid changes in fast ion energy content in connection with sawtooth instabi lities, it is found that about 40% of the fast ions are expelled outsi de the q = 1 surface and that prompt losses are negligible.