Lower hybrid wave absorption study to improve the calculation of energy confinement time in EAST

Abstract

The auxiliary heating power absorption of 2.45 GHz and 4.6 GHz lower hybrid (LH) waves in EAST is analysed in order to improve the determination of the energy confinement time. The LH power absorption coefficient is obtained by using the time derivative of the total stored energy including the plasma kinetic energy and the poloidal magnetic field energy. Results on EAST have shown that, for both frequencies, the fraction of LH power absorbed in the plasma bulk decreases with the increase in the plasma density, and with the decrease in the toroidal magnetic field. Scaling laws for the density dependence of the LH absorption coefficient at different fields and frequencies have been statistically obtained. Comparison of the confinement improvement factor H89 obtained with these new scaling laws against those assuming an absorption coefficient equal to the launched k//wave spectrum directivity is made.