Direct-reading type microwave interferometer

A microwave interferometer was developed and applied to the electron density measurement on a hybrid stellerator Tokamak device. The interferometer generates an output voltage proportional to the number of fringe shifts and also output pulses which indicate the change of electron density for the convenience of data processing, where the resolution is a quarter of fringe shift. The principle is based on the digitization of fringe shifts utilizing the phase detection of microwave signals with two-level modulation of source frequency. With this system and 70 GHz microwave source, a change of electron density as rapid as about 2 x 10 to the 13th power/cu cm in 1 ms was measured