Physics and application of gas discharge in millimeter wave beams

The microwave discharge produced in gases by millimeter wave radiation in wave beams is characterized by high plasma density, and wave beams allow one to control the form and size of plasma maintained both in free space and near surfaces of various materials. This paper reviews the results of studying dense plasmas in microwave discharges, which are produced in four and two crossing wave beams by continuous wave radiation of a gyrotron at frequencies of 30 GHz and 28 GHz, respectively. The results of using such discharges for advancing the technique of chemical vapor deposition of diamond films are described. Furthermore, new results on discharge characteristics at extreme values of power density up to 1000-1500 W cm−3 and the homoepitaxial growth of diamond under these conditions are presented.