Effect of Magnetohydrodynamic Perturbations on the Orbit Lossof Alpha Particles in Tokamak Plasma

We investigate the orbit loss of alpha particles under helical magnetic perturbation in a tokamak. The results show that low-frequency and low-mode number magnetic perturbation can cause stochastic loss of alpha particles. This effect is significant for those particles close to the boundary between the transit zone and the trapped zone. The particle loss is sensitive to the phase of the magnetic perturbation, indicating the modulation of the particle loss with respect to magnetic perturbation. It is also found that the precession of the particle banana orbit can even further enhance the particle loss.