Investigation of Runaway Electrons Pitch Angle Scattering in HT-7 Tokamak

The fast pitch angle scattering (FPAS) of runaway electrons will happen if the anomalous Doppler resonance occurs in low density plasmas, while the normal pitch angle scattering (NPAS) will happen if the anomalous Doppler resonance occurs in high density plasmas with the same plasma current. The runaway electron behaviors during FPAS and NPAS plasmas were investigated. It is found that, in FPAS and NPAS plasmas, the synchrocyclotron emission of the runaway electrons increases because of the increase of the pitch angle of the runaway electrons. Therefore, the energy of runaway electrons decreases. The FPAS and NPAS have more effective influence on high energy runaway electrons than low energy ones.