Excitation of half-integer up-shifted decay channel and quasi-mode in plasma edge for high power electron Bernstein wave heating scenario

Abstract

Electron Bernstein waves (EBW) consist of promising tools in driving localized off-axis current needed for sustained operation as well as effective selective heating scenarios in advanced over dense fusion plasmas like spherical tori and stellarators by applying high power radio frequency waves within the range of Megawatts. Here some serious non-linear effects like parametric decay modes are highly expect-able which have been extensively studied theoretically and experimentally. In general, the decay of an EBW depends on the ratio of the incident frequency and electron cyclotron frequency. At ratios less than two, parametric decay leads to a lower hybrid wave (or an ion Bernstein wave) and EBWs at a lower frequency. For ratios more than two, the daughter waves constitute either an electron cyclotron quasi-mode and another EBW or an ion wave and EBW. However, in contrast with these decay patterns, the excitation of an unusual up-shifted frequency decay channel for the ratio less than two is demonstrated in this study which is totally different as to its generation and persistence. It is shown that this mode varies from the conventional parametric decay channels which necessarily satisfy the matching conditions in frequency and wave-vector. Moreover, the excitation of some less-known local non-propagating quasi-modes (virtual modes) through weak-turbulence theory and their contributions to energy leakage from conversion process leading the reduction in conversion efficiency is assessed.

Excitation of electron Bernstein waves by beating of two cosh-Gaussian laser beams in a collisional plasma

“…The parametric instability channel is a good process for heating by electron Bernstein waves in quasi-mode plasma. In this process, the ratio of high power radio frequency to the electron cyclotron frequency give an analogy for decay of either electron Bernstein waves or ion Bernstein waves [28]. In the Prototype Material Plasma Exposure eXperiment device, a scheme of electron Bernstein wave heating scenario is presented by using 28 GHz microwave frequency injection [29].…”

Electron Bernstein wave aided heating of collisional nanocluster plasma by nonlinear interactions of two super-Gaussian laser beams

“…Over the last few years, beat wave excitation and heating of plasma as well as nanocluster plasma has been a particular field of interest due to its diverse applications in current drive experiments, terahertz radiation generation, acceleration of charge particles and diagnostics [1][2][3][4][5][6][7][8]. Although earlier studies of plasma excitations have been performed by several groups [9][10][11][12], a cluster adds new quantities to so called surface plasmons that enhance the excitation efficiency [13].…”