Applications of the gas discharge sustained by the powerful radiation of THz gyrotrons

The terahertz frequency range currently remains the least studied from the point of view of gas-discharge physics. Recent progress in its mastering is associated, first of all, with the creation of powerful sources of terahertz radiation - gyrotrons. Nevertheless, the discharge sustained by the powerful radiation of the terahertz frequency range is of interest not only from the fundamental point of view (because of its lack of knowledge), but also from the applied one. This paper presents results of investigations aimed at studying the point-like THz discharge as a source of vacuum ultraviolet radiation and at research of CW THz plasma torch existing at atmospheric pressure and therefore having promising applications in various fields: plasma medicine, plasma chemistry, material processing etc. It is shown that it is possible to create a point-like plasma in an inhomogeneous gas flow with the density above the cut-off one (4.10(15) cm(-3) for 0.67 THz). It has been demonstrated that such plasma is an effective source of VUV and EUV radiation. Investigations of the atmospheric plasma torch, sustained by CW sub-terahertz radiation (1 kW @ 0.26 THz), demonstrated the possibility of the creation dense non-equilibrium plasma (2.10(15) cm(-3)) with electron temperature in the range from 1 to 2 eV.