The construction of capacitive voltage divide for measuring ultrafast pulse voltage

Abstract

The problem of pulse voltage measurements in the nanoseconds range has become of great importance with ongoing problems related to the construction of pulse fusion generators as well as with simulations of electromagnetic pulses related to the atmospheric nuclear explosion. Ultrafast pulses in the nanoseconds range can be measured by the capacitive voltage divider. The problem that arises with ultrafast voltage occurrence is inductivity. Under conditions of the nanoseconds pulse increaserate, conductors of about few centimeters should be regarded as inductivity. Therefore, capacitive divider can be treated as an equivalent RLC circuit. The ohmic resistance R in that equivalent circuit originates from the characteristic impedance (either 50 Ω or 75 Ω) and, depending on its design, it can introduce an additional parasite inductivity. The aim of this paper is to consider and analyze the constructive solutions of capacitive voltage divider for measuring ultrafast voltage occurrence. Three types of capacitive divider will be constructed for that purpose. The high-voltage capacitor of each divider will be gas capacitor (in order to avoid both electrostatic and electrodynamic influence on measurement accuracy). The variations between divider types will be made for low-voltage capacitor. The designed low-voltage capacitors will be: 1-in the shape of 10 mica capacitors connected in a parallel with a discrete ending resistor of 50 Ω 2-in the form of gas trimmer capacitor with a discrete ending resistor of 50 Ω, and 3-the continual mica capacitor with waveguide resistor of 50 Ω (L=0). Ultrafast pulse response will be measured with dividers constructed in such manner, and will be compared with the corresponding response obtained from the numerical simulations.