In United Kingdoms, a very simple structure was developed
by S.R. Wylie et al. [63]: the Microwave Plasma Jet (MPJ).
The plasma cavity consists of a rectangular wave guide section
that ends at a copper plate acting as a short circuit. The gas
nozzle is situated inside the cavity directly above an aperture in
the wave guide, one-quarter wavelength from the short circuit,
where the maximum electric field is produced. This system can
work either at 2.45 GHz or at 896 MHz [64] (this latter
wavelength limits the electromagnetic radiation, in spite of the
wave guide aperture).