Broadening of electron cyclotron power deposition and driven current profiles caused by dissipative diffractive propagation

Abstract

Improvements of the Electron Cyclotron Resonance Heating (ECRH) and Current Drive (ECCD) predictions are important issues to design and control the high-performance fusion plasmas in future devices, where those should play a more important role as an actuator than in devices to date. The newly developed EC-prediction package based on the quasioptical ray tracing code PARADE revealed in JT-60SA that (i) radial profiles of both EC power deposition and driven current are broadened and (ii) the net driven current is increased by few kA/MW, in comparison with conventional predictions due to the dissipative diffractive propagation (DDP). The mechanism of DDP is as follows; EC wave beam obliquely passing through the resonant surface is dissipated non- uniformly on its beam cross section, so that the beam trajectory shifts gradually and thus the resonant position also shifts, resulting in the broadened power deposition profile. This novel ECCD and ECRH prediction package based on PARADE is applicable not only to JT-60SA but other existing devices and even, future devices.