Effect of Resonant Magnetic Perturbation Field on Energetic Ion Behavior in the Large Helical Device

Abstract

A study of the resonant magnetic perturbation (RMP) effect on transit beam ion behavior is performed using the total neutron emission rate (S_n) measurement of the deuterium plasma in the Large Helical Device. We conducted no RMP field, one-half RMP field, and full RMP field discharges and compared S_n that reflects the global beam ion confinement information. It is determined that owing to the RMP field, S_n decreased by approximately 15 - 30%. Numerical calculations based on the classical confinement of beam ions were performed to investigate the bulk plasma parameter effect on S_n. The calculated S_n shows that the degradation of S_n by RMP is mainly caused by the degradation of the electron temperature owing to island formation which results in a shorter slowing down time of beam ions.