Effects of the trapping effect on LHCD in tokamak

Abstract

A Fokker-Planck study is carried out for tokamak lower hybrid current drive (LHCD)by considering the wave absorption in the presence of trapping effect situation. This Fokker-Planck code is developed based on FASTFP, and is suitable for various auxiliary heating and current drive situations. The energy loss mechanism through anomalous transport is modeled by using a suitable loss term. In the h eating phase, the electron distribution deviates clearly from the Maxwellian, an d this results in nonlinear absorption characteristics. As an electrostatic forc e, the lower hybrid wave makes the trapped electrons untrapped, and the wave los ses its energy,which cuts down the LHCD efficiency 30%.