Effect of Magnetic Field Distortion on Alpha-Particle Losses in Stellarators

The influence of weak distortion of a stellarator field on fast alpha-particle losses is considered. The analysis is carried out with the simplest example of a ripple-like distortion and shows that due to specific resonances this distortion (even of very small amplitude) can result in a rapid loss of high-energy particles and in the formation of a “loss cone” in the alpha-particle phase space.