Microwave breakdown of air at low pressure with a 5 ns, 35 GHz pulse

This research was inspired by the need for a microwave source powerful enough to lead to enhancement in the air breakdown volume, when synchronized in time and space with a small region of pre-ionized air created with an intense laser pulse. We used the compact and portable RADAN pulser that drives a backward wave oscillator to produce microwaves for this purpose. The microwave pulse duration and power are 5 ns and 2 MW, respectively. The frequency of operation is 35 GHz. It is well known that air breakdown at atmospheric pressure requires an electric field amplitude of 30 kV/cm. Thus, an ouput power of 2 MW simply radiated in air does not have sufficient electric field to assist in air breakdown. For this reason, a parabolic dish was used to focus the microwaves into a small spot, thereby enhancing the electric field.