A magnetron pulsed modulator for microwave plasma interaction studies

An experimental system being developed in our laboratory, named “SYMPLE” (System for Microwave and Plasma Experiments), aims at investigation of nonlinear interaction of high power microwave (HPM) with over-dense plasma. The Phase-1 stage of the system involves interaction using a 3.1 MW, 3 GHz, pulsed (5μs) output from an S band magnetron. The time sequence of the experiment necessitates the HPM output in single pulse mode. In this context, use of conventionally available solid state modulators delivering pulses with high (100–200 Hz) repetition frequency are not suited for operations demanding single shot mode, repetitive pulses. In order to meet the specific requirement of wave-plasma interaction studies, a line type modulator which is simple, cost effective, rugged and easy to fabricate, is designed and developed. Low voltage tests up to 5 kV have been carried out across the dummy load, revealed attainment of pulses having ∼ 300ns fast rise time and 5 μs pulse width. An account of the design and development of the pulsed modulator and test results is presented here.