Analysis and Process of B-Dot Waveforms in a High-Current Injector

A B-dot was used for measuring cathode emission current in the injector of a linear induction electron accelerator. The measured current waveforms in commissioning were different from our initial expectation. This could well be explained by that the measured current waveform was the sum of actual emission current and displacement current. The displacement current could be derived by the measured diode voltage and the calculated diode capacitance. The actual emission current waveform was then obtained by subtracting the displacement current from the measured waveform. The pure displacement current waveform was also measured by the B-dot, while there was no emission from a thermionic cathode. The calculated and measured displacement current waveforms were well consistent with each other. The B-dot's sensitivity factor calibrated by comparing the aforementioned two waveforms was equal to our theoretical estimate within an error range. The obvious displacement current may also exist in the similar pulsed power facilities, which contain high-voltage and fast pulses. It can be processed by the same methods discussed in this paper.