On nonlinear effects in electron-cyclotron resonance plasma heating by microwave radiation

Abstract

Possible nonlinear effects in electron-cyclotron plasma production and heating by microwave radiation are analyzed. They include nonlinear regimes of electron acceleration in strong microwave fields under cyclotron resonance conditions, nonstationary regimes of microwave beam self-focusing, and some parametric processes. Presented results may be of importance for predictions of plasma response to electron-cyclotron resonance (ECR) heating or preionization by powerful radiation.

Positive and negative effective mass of classical particles in oscillatory and static fields

“…IV C), all the three equilibria are stable here (Fig. 3), unlike for a one-dimensional (1D) nonlinear oscillator [60], as well as in contrast to the 3D cyclotron resonance in a quasi-static field [56] or any wave with a parallel refraction index n || other than unity [61,62,63,64]. The difference from Refs.…”

Anomalous phenomena in ECRH experiments at toroidal devices and low-threshold parametric decay instabilities

“…The analysis performed at fusion relevant parameters for the planned ECRH experiments in JET predicts the threshold of the absolute PDI in the range of 100 kW being approximately four orders of magnitude lower than that predicted by the standard theory [1] - [3] and an order of magnitude lower than the threshold of the fast convective PDI. Nevertheless, at low plasma density and temperature the growth rate of this instability appears to be too small to make the instability important for the energy budget.…”

“…Parametric decay instabilities (PDI) leading to anomalous reflection and/or absorption of microwave power are believed to be deeply suppressed in tokamak megawatt power level electron cyclotron (EC) resonance fundamental harmonic ordinary mode and 2 nd harmonic extraordinary mode heating experiments utilizing gyrotrons [1] - [3]. Therefore the wave propagation and absorption in these experiments are thought to be well described by linear theory and thus predictable in detail.…”

On possibility of low-threshold two-plasmon decay instability in 2ndharmonic ECRH experiments at toroidal devices

“…As having been revealed by theoretical analysis a couple of decades ago [1] - [3] parametric decay instabilities (PDI) which may accompany ECR fundamental harmonic ordinary (O) mode and 2 nd harmonic extraordinary (X) mode heating experiments are believed to be deeply suppressed by convective losses of daughter waves both along the magnetic field and in radial direction. Thus, the EC wave propagation and absorption are thought to be well described by linear theory and predictable in detail.…”