Topic/Type: 3. Other, Oral
S. Heuraux1, E. Z. Gusakov3, A. Yu Popov3, F. da Silva2, M. Irzak3
1 IJL, UMR-CNRS 7198, UHP, BP70239, F-54506 VANDOEUVRE CEDEX, France #
2 Associa??o EURATOM/IST, Instituto de Plasmas e Fus?o Nuclear, Lisboa, Portugal
3 Ioffe Institute, Politekhnicheskaya 26, 194021 St.Petersburg, Russia
The simulations done are focused on the role of the resonance induced by density fluctuations in the plasma. A first part will be devoted to the possibilities to create such resonance in plasma by using coherent density fluctuations, which satisfy the Bragg backscattering condition. We show that the phase fluctuations are amplified by a factor equal to the square of the amplification factor of the probing wave. If these resonances are localised we have shown that corresponds to a selection of the radial wavenumber and an enhanced scattering for this wavenumber range. This phenomenon has been observed for 1-D and 2-D cases.
In turbulent plasma such resonances exist and a ratio of resonant case is determined for a given threshold of the amplified local probing wave. This ratio in the studied conditions is of the order of 15% where the phase variations are amplified by a factor of two. The behaviour can explain some phase jumps obtained from the reflectometry signal. A statistical treatment shows that the average value of the reflectometer signal can be described by a scattering photons equation, which permits to describe the average value of the probing wave intensity and compared to simulations.