Diagnosis of superthermal electrons using cyclotron radiation
Selective electron-cyclotron emission and absorption by fast electron tails are discussed using the concepts of momentum-space spectra and collective resonance velocity. This is defined from the maximum of the emission and absorption profiles in the momentum space for a system of electrons and represents the counterpart of the one-particle resonance velocity. It is shown that the collective resonance is sensitive to the superthermal momentum distribution and is therefore a useful parameter in the diagnosis of the fast electron tail. A simple relation between the collective resonance and the emission and absorption coefficients for propagation normal to the magnetic field is found. This theoretical framework is used for a new diagnostic method based on the localized (in phase space) perturbation of the electron tail by an electron-cyclotron wave and emission and transmission of radiation at higher harmonics. A numerical application is presented for the case of a lower-hybrid sustained tail, using the appropriate Fokker-Planck and ray-tracing codes.
Bibliographic Reference: Report: EUR-CEA-FC-1989 EN (1989)
Availability: Available from CEA, Département de Recherches sur la Fusion Contrôlée, Saint-Paul-lez-Durance (FR)
Record Number: 198911045 / Last updated on: 1994-12-01
Original language: en
Available languages: en