Fast electron confinement during lower hybrid experiments in ASDEX

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