Experimental characterization of air breakdown plasma utilizing a 1.5MW, 110GHz gyrotron

Summary form only given. We present the latest results of the MIT microwave-frequency air breakdown experiment. The experiment utilizes a 1.5 MW, 110 GHz gyrotron producing 3 μs pulses. The beam is focused to a peak intensity of 5 MW/cm². At atmospheric pressure, the plasma forms a two-dimensional array of filaments oriented along the electric field lines^{1, 2}. The filaments smoothly transition to a largely structureless plasma at low pressures, e.g. 100 Torr. Recent experimental results include spectroscopic and interferometric measurements of electron number density and plasma temperature. Measurements make use of a high resolution spectrometer and a two-wavelength interferometer operating at 632.8 nm and 532 nm. Electron density and plasma temperature measurements are essential for comparison with numerical simulations of breakdown plasma formation. The status of the experiment will be presented as well as recent experimental results and plans for future work.