EFDA-JET-CP(02)02/28
Influence of Safety Factor Profiles on Fast Ion Confinement in JET
Aim of this paper is to perform calculations of fusion alpha loss in optimised shear scenarios in JET [1-2] associated with the hollow current profiles [2, 3]. Such scenarios trigger internal transport barriers at lower input power and render a high fusion performance in JET [1], and are considered to be an attractive avenue for the nearest JET research program. We examine here the effect of the toroidal current hole [2] in the central plasma region on both the first orbit (FO) loss as well as on the collisional loss of alphas [4,5]. The collisional loss of alphas is mainly due to scattering into the loss-cone in velocity space (i.e. pitch-angle scattering of marginally circulating counter-going alphas into unconfined (fat) bananas and due to neoclassical (NC) radial transport.