Session RP1 - Poster Session VIII.
POSTER session, Thursday afternoon, October 30
Fran Hill Southeast Exhibit Hall, ACC
The eigen surface modes of magnetically confined plasma column can be excited during the ion cyclotron resonance heating (ICRH) in stellarators plasma. These modes can be localized in a narrow region at the plasma edge. Therefore the essential part of the ICRH power will be absorbed at the plasma edge without the effective plasma heating in the center. Due to this reason the ICRH system has to avoid operating in the range of the parameters which provide a high probability of the surface mode excitation. As an example, the eigen surface modes of LHD have been studied to estimate the penetration depth of wave field into plasma column and calculate their radial distribution. The calculations have been carried out for the nonuniform radial density and temperature profiles. The eigen wavelength of the surface perturbations at harmonics of the cyclotron frequency are reported. The dependence of the eigen wavelength on the plasma density gradient has been studied.