Excitation characteristics of sideband wave in a radio frequency stabilized simple mirror plasma

Abstract

A nonlinearly excited sideband wave due to a magnetohydrodynamic interchange mode is observed in a radio frequency (t-f)-produced simple mirror plasma, and its excitation is discussed. The measured amplitude of the sideband wave field is compared with the theoretical value showing the agreement in order of magnitude, but the radial distribution is different. As the rfcurrent of the production source is changed, the sideband excitation level varies and this variation is explained by the density fluctuation and the difference of the dispersion relations between pump and sideband waves. Using the difference of the dispersion relations, it would be possible to suppress the sideband excitation and to reduce its destabilizing contribution.

Influence of rf waves on interchange modes in HANBIT mirror plasmas

“…Although the wave structures of high frequency waves were not directly measured (due to lack of diagnostics), the occurrence of two sideband peaks in figure 9(b) suggests the excitation of sideband waves owing to the nonlinear coupling of the waves involved. The Fourier amplitude of the lower sideband wave is usually stronger than that of the higher one, which agrees with previous observations [14,15]. A dramatic change of density fluctuations, when the plasma undergoes stability transition, can be seen in power modulation experiments.…”

“…Rather, the efficacy of the SBC process on the interchange stability has been observed to be weaker than theoretical predictions [14]. An experimental study was also reported on the excitation characteristics of sideband waves and their destabilizing influence (when γ > 10) on the interchange stability in the HIEI tandem mirror [15].…”

A theoretical analysis of the effects of radio frequency waves on interchange stability in mirror plasmas

“…An experimental study on the excitation characteristics of SBWs and their impact on the interchange stability has also been reported in the HIEI mirror device. 13 In the present work, we address a theory of the rf stabilization of interchange modes in mirror plasmas. A two-fluid cold plasma model taking particle collisions into account is utilized in this study.…”