Confinement of fusion alpha-particles in JET hollow current equilibrium

Abstract

The effect of a toroidal current hole on the first orbit (FO) loss and on the collisional loss of alpha particles in JET is investigated. Numerical results of predictive three-dimensional Fokker–Planck modelling of the distribution function of D–T fusion alphas in hollow current JET discharges are presented. If the current hole region is kept reasonably small, it induces only a moderate increase of FO losses as well as of the collisional loss of fast alphas. The current hole effect is shown to be qualitatively equivalent to a reduction of the total plasma current I. Hence, the alpha confinement degradation by the current hole profiles can be compensated by enlarging I.