Resistor divider for high voltage pulse measurement in vacuum

A resistor divider has been designed for voltage measurement of diode load for 1 MV/100 kA fast linear transformer driver(LTD). The divider is designed with two stages. The primary stage is a column of alternating annular metal grading rings and tapered insulators enclosing a resistive solution of sodium thiosulfate. A middle electrode is connected to the secondary voltage dividing stage. There is a 4 k resistor in series with the 50 input impedance of the attenuator or oscilloscope. The equivalent circuit of the divider which includes distributed capacitance and inductance has been calculated. It indicates that the high frequency limit of the divider is about 200 MHz. The divider has been calibrated in-situ using a P6015A probe and a high voltage pulser. The calibration ratio is 5 400∶1. The voltage of diode load reaches 1.08 MV when the charging voltage of LTD stage is 85 kV respectively, according with the simulation of LTD.