Design, calibration, and performance of water diagnostics on the PBFA Z

Abstract

New voltage and current monitors have been designed and installed in the water transmission line sections of PBFA Z, which is now called Z. These monitors allow comparisons of machine operation with predictions, allow timing of the laser-triggered spark gaps to achieve the maximum energy output, and indicate pulse-power problems. The monitors also provide an accurate forward-going voltage for equivalent-circuit calculations. The bi-plate transmission line voltage monitors were designed using the ELECTRO code, which is a two-dimensional electrostatic field solver. Great care was taken to eliminate sharp edges and water-plastic-metal triple-point enhancements. The intermediate-store voltage monitors worked well at lower voltages but tended to give voltages that were too large at the highest Marx-bank charge voltages. This effect appears to be related to streamer formation that changes the effective size of the electrode and hence calibration at the highest voltages. We have also redesigned these probes to. Reduce peak fields. These probes were calibrated-in situ using a transmission-line pulser, and calibrated resistive dividers. With both the bi-plate and intermediate-store voltage monitors, the wave shapes agree well with those of the resistive dividers.