FAST-ELECTRON CONFINEMENT DURING LOWER-HYBRID EXPERIMENTS IN ASDEX

A detailed analysis is presented of experimental data on the energy co ntent in the fast electron population created by lower hybrid waves in the ASDEX tokamak and it is shown that in most circumstances direct l osses due to diffusion of these electrons can be neglected. The value of the fast electron diffusion coefficient is inferred from die time b ehaviour of hard X ray emission during power modulation experiments. I t turns out that fast electrons are better confined than thermal elect rons. This experimental result is compared with a theoretical predicti on based on transport driven by electrostatic or magnetic turbulence.