Development of a Plasma Diagnostics System Using an Impulse Waveform Voltage

A new application using an electric impulse signal has been developed for electron density profile measurements in the Large Helical Device (LHD). Using an impulse waveform voltage, which has broadband frequency components, we constructed an ultrashort pulsed radar reflectometer with 28 channels in X-, Ka-, and U-band frequency components. The effect of the bandwidth of an inline band-pass filter was investigated, and was optimized. For a multiple-channel and multiple-frequency band system, a new switching technique and multiplexer were developed. Using the Abel inversion method, the reconstructed electron density profile was obtained from the delay time as a function of the probing frequency. Good agreement with other diagnostics was obtained