Monte Carlo simulation study of ICRF minority heating in the Large Helical Device

Abstract

A Monte Carlo simulation code is developed for ion cyclotron range of frequencies (ICRF) hearing in helical systems, which takes into account finite beta effects, complicated orbits of high energetic particles, Coulomb collisions and interactions between particles and the applied waves. The code is used to investigate ICRF minority heating in the Large Helical Device (LHD). The configuration of the magnetic fields changes significantly due to finite beta effects in the LHD. The resonance layer position is found to be crucial to the heating efficiency as the plasma beta increases. When the strength of the resonance magnetic field is set to the value at the magnetic axis, a higher heat efficiency is obtained and no clear difference of the heat efficiency due to finite beta effects is found in the high ICRF wave power region. However, the radial profile of the power transferred to majority ions and electrons from minority ions changes because of the deformation of the trapped particle orbits due to the finite beta effects. The heat efficiency is improved if the radial electric field, Er, is positive (Er is directed radially outward) and it is also improved by supplying 3He minority ions rather than proton minority ions