Interpretation of quasi-periodic frequency sweeping in electron cyclotron emission of nonequilibrium mirror-confined plasma sustained by high-power microwaves

Abstract

In [Viktorov M E et al. 2016 Eur. Phys. Lett. 116 55001] we reported on chirping frequency patterns that have been observed in the electron cyclotron emission from strongly nonequilibrium plasma confined in a table-top mirror magnetic trap. These patterns were interpreted qualitatively as the first experimental evidence for so-called "holes and clumps" mechanism acting at such high frequencies (1-10 GHz). In the present paper, we prove this statement on a more rigorous basis, considering the formation of nonlinear phase space structures in proximity of the wave-particle resonances within the framework of the Berk-Breizman theory adopted for a kinetically unstable mirror-confined plasma.

Electron-cyclotron heating and kinetic instabilities of a mirror-confined plasma: the quasilinear theory revised

“…This case is most suitable for the ion-cyclotron problem in which ω b and ωc ≈ ω c are of the same order [47]. Separated bounce resonances in the electron-cyclotron range are possible only under very specific conditions [48,49]. Electrons are usually characterized by ω b ≪ ωc ∼ ω and many overlapped nω b -harmonics.…”

“…In the electroncyclotron range, this mechanism works only under very specific conditions for a small population of extremely fast electrons. Thus, this problem is mainly of fundamental interest [49].…”

Observation of rapid frequency chirping instabilities driven by runaway electrons in a tokamak

“…Rising tones, falling tones, and relatively steady 'hiss' are all observed under different circumstances [3]. In the laboratory, energetic electrons drive rising tones in the Terrella experiment [4] and both rising and falling tones in magn etic mirror [5][6][7] and linear [8,9] devices. In fusion devices, fast-ion driven chirping instabilities are extremely common in a wide variety of frequency bands [10,11].…”

Addendum: Electron-cyclotron heating and kinetic instabilities of a mirror-confined plasma: the quasilinear theory revised (2020 Plasma Phys. Control. Fusion 62 065005)

“…and the conjugate phase of the bounce motion ϕ, see, e. g. [2]. Once we know E(I || , I ⊥ ), a straightforward calculation results in…”