  This paper presents the results of an experimental study of a new hybrid
plasmatron scheme, which was used to realize a gas discharge at atmospheric
pressure supported by continuous focused submillimeter radiation with a
frequency of 263 GHz. The implemented design allowed organizing a
self-consistent interaction between submillimeter radiation and the
supercritical plasma in a localized area both in terms of gas flow and
electrodynamic. It is experimentally shown that the gas discharge absorbs up to
80% of the introduced submillimeter radiation power. The hybrid subterahertz
plasmatron as an effective reactor for non-equilibrium plasma chemical
processes was tested for the atmospheric nitrogen fixation.
