Design and Testing of a Current and Voltage Monitor for HIFX,

A kiloampere, pulse-current monitor and a megavolt, pulse-voltage monitor was built to characterize the performance of field-emission diodes on HDLs pulse electron accelerator HIFX. The monitors were calibrated under kilovolt-pulse conditions, using a specially developed coaxial circuit, and tested by making time-synchronized current and voltage measurements on a hemisphere-plane diode. The measured diode current and voltage pulses are consistent with waveform and bremsstrahlung output expectations for the accelerator. The initial anode-cathode gap impedances obtained from these measurements are in reasonable agreement with the gap impedance calculated from the Langmuir-Child three-halves power law for space charge limited diodes. These findings indicate that the monitors are capable of measuring pulsed current and voltage waveforms with sufficient amplitude and timing accuracy to be useful in future field-emission diode studies. The monitors can provide a better understanding of those diode parameters that control electron energy and bremsstrahlung angular distribution. This understanding should permit the design of pulsed bremsstrahlung diodes that are capable of producing photons and electrons with greater or more desirable energies and spatial distributions. Author