A Multiple-Probe Microwave System for Plasma Studies

This paper describes a fast-acting microwave diagnostic system which was developed for use with non-repetitive plasmas, such as those in shock tubes and pulsed discharges, and which has proved useful in a wide variety of experimental configurations. The system may be used for either reflection or transmission measurements and gives a polar display of phase and amplitude in conjunction with timing marks. Some of the principal features are wide dynamic range, expansion of high attenuation regions of the display, and a presentation of data which is readily assessed visually. The system has been used at microwave frequencies of 9.2 kMc, 9.7 kMc, 23.5 kMc, and 34.5 kMc, with sampling periods from 0.1 msec to 0.1 μsec at 50% duty cycles.