EFDA-JET-PR(03)01
Confinement of Fusion Alpha-Particles in JET Hollow Current Equilibrium
The effect of a toroidal current hole on the first orbit loss and on the collisional loss of alpha particles in JET is investigated. Numerical results of predictive 3D 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 first orbit 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 hollow current profiles can be compensated by enlarging I.