Investigation of microwave plasmas produced in a mirror machine using ordinary-mode polarization

This paper presents results of plasma production in a mirror machine with t he microwaves being coupled from a side port, in the ordinary-mode polariza tion. In this method of coupling, contamination due to the launching antenn a is avoided; also, there is very little window degradation since plasma bo mbardment on the side port is negligible. The coupling of the microwaves to the plasma in this method relies on the existence of certain surface waves that exist at low values of the magnetic field (below that for electron cy clotron resonance) and have a dominant E-z component. The existence of such surface waves is predicted by a recent theory (Ganguli A et al 1998 Phys. Plasmas 5 1178). The plasma characterization at microwave power levels of a bout 200 W, indicates moderately overdense plasmas (density approximate to 10(11) cm(-3)), with fairly uniform radial and axial profiles. From the dat a, the mechanism of plasma production and confinement in the mirror has bee n analysed. To gain insight into the nature of the waves in the plasma-load ed waveguide, the wavelengths of the waves within the plasma and the radial profiles of the wave electric field were measured. The results are compare d with the theory of Ganguli er al for wave identification.