Non-linear microwave coupling experiments and simulations*

Non-linear wave coupling and other instabilities can develop in plasma perturbed by powerful EM waves. These effects can arise in microwave interactions in fusion plasma, cool plasma, radio propagation in ionospheric and magnetospheric plasma and laser-plasma interactions. Understanding these dynamics can provide useful mechanisms to introduce energy into plasma, to manipulate plasma conditions or to mitigate undesirable consequences induced by such parametric instabilities. Cool plasmas with critical frequencies in the low microwave range are relatively stable and relatively easier to diagnose. We are therefore undertaking experiments and simulations to study dynamics of microwave beams propagating in such plasma. A recently commissioned inductively coupled plasma is used for the experiments. It is driven by a two powerful microwave signals, one generated by a magnetron oscillator at a fixed tone, the other by a frequency flexible TWT amplifier. The strength of the non-linear sidebands caused by Raman interaction in the plasma is studied as a function of the plasma density. Important parts of the electrodynamic are simulated by the particle-in-cell method.