Diagnosing fast electron diffusion by electron cyclotron radiation
The problem of the radial diffusion of fast electrons in tokamak plasmas and its impact on electron cyclotron diagnostics is investigated. A three-dimensional Fokker-Planck code has been developed describing the evolution of the electron distribution function due to the action of Coulomb collisions, DC electric fields, RF heating and radial diffusion induced by turbulent magnetic fields. In ohmic plasmas, non-Maxwellian distributions are generated by the radial diffusion process in the pressure gradient region. It is shown that vertical electron cyclotron emission or transmission measurements on non-central chords yield, in principle, detailed information on the structure of the superthermal electron distribution. This effect can be used to investigate the radial structure and properties of the turbulent fields. In lower hybrid current drive plasmas, the possibility of diagnosing fast electron diffusion by electron cyclotron emission (ECE) in the equatorial plane at large toroidal angles and frequencies between the first and second harmonic is analysed and discussed.
Bibliographic Reference: Article: Plasma Physics and Controlled Fusion, Vol. 35 (1993) pp. 1541-1551
Record Number: 199311544 / Last updated on: 1994-11-28
Original language: en
Available languages: en