Microwave interferometer for steady-state plasmas

Standard single frequency, "fringe-counting," microwave interferometers are of limited use for steady-state plasma experiments. We have constructed a swept frequency microwave interferometer, similar to a classic zebra-stripe interferometer, optimized for electron density measurements in steady-stat e plasma experiments. The key element in the system is a frequency doubled YIG oscillator capable of sweeping from 20 to 40 GHz. As the source frequen cy is swept, the sum of the reference and plasma leg signals exhibits a ser ies of beats. Both the frequency shift and phase shift of the beat pattern due to the addition of plasma in one leg of the interferometer is used to d etermine the line-integrated electron density. (C) 2001 American Institute of Physics.