Inductive and helicon plasma for non-linear microwave coupling experiments

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 preparing experiments to study dynamics of microwave beams propagating in such plasma. A recently commissioned plasma source operating in the inductive/helicon mode has a transverse diameter of 1m and length of 3m. In inductive mode it operates in He and Ar gas with pressures in the range of 10^-3 mbar – 10^-1 mbar with plasma frequency in the range a few hundred MHz and bulk temperatures of <1eV (a tenuous hotter population is also present) when driven by a 10-200W RF source at 14MHz with appropriate matching. This plasma environment is well suited to studying non-linear wave coupling with readily available 10GHz microwave sources. Progress on this experiment will be reported.