Discharge created by a propagative wave in presence of a static magnetic field

This report deals with the study of a low pressure argon microwave discharge (5 to 100 m Tor), created and sustained by a propagative wave with a fixed frequency (390 MHz), in presence of an axial static magnetic field (up to 550 Gs). To understand the discharge sustaining conditions. The microwave energy distribution has to be determined. For that purpose, the wave propagation has to be studied. Therefore, the wave characteristics are first of all computed, and their evolutions with the plasma frequency and the magnetic field are described, for a fixed wave frequency. The characteristics are: the 'phase relations', giving the wave number and the wave attenuation due to the electron-neutral collisions, as functions of the electron density. - The radial distribution of the electromagnetic energy. It is shown that, according to the values of the electron density and the magnetic field, the wave is either a surface or a volume one. Secondly, the results of the experimental discharge study are presented. The measure of the wave number enables the electron density diagnostic. With the help of a theoretical description of the plasma column, this diagnostic leads to the discharge characteristics the effective electron-neutral collision frequency, the power needed to maintain an electron and the effective electric field. At a fixed pressure, the effective electric field is a decreasing function of the magnetic field. This behaviour is explained in a theoretical way taking into account the reduction, due to magnetic field, of the electron losses by diffusion to the tube walls. (author)