Scaling pulser output parameters for standard and dry brick configurations

Abstract

The building block of the linear transformer driver pulser, known as a brick, can be thought of as the smallest, independent unit from which the entire pulser is built. In a “standard” brick configuration, two capacitors and a spark-gap switch are connected in series and are oil insulated. Such a brick could be assembled, for example, from two 80-nF, 100-kV capacitors and a 200-kV spark-gap switch. A single brick in this configuration is capable of generating a current pulse with up to 50 kA of peak current and a rise time on the order of 100 ns, after the capacitors have been discharged at a combined output voltage of 200 kV (twice the bipolar charge voltage). By contrast, in a “dry” brick configuration, the two capacitors are placed in parallel and a multigap, multichannel “ball” switch follows them in series. The dry brick is epoxy insulated, and its slightly different configuration allows it to have a peak output current of up to 100 kA, after being discharged at a total output voltage of 100 kV (equal to the unipolar charge voltage). In this paper, we present how these two different brick topologies, either oil insulated (standard) or epoxy insulated (dry), affect a pulser’s output parameters, where the pulser has been constructed by connecting the outputs of N bricks together in parallel. We find that in many cases, the use of a dry brick configuration results in more current being delivered to the load. We also find that if the time to peak current is not a critical parameter for the experiment, then the lower charging voltage across the switch and the absence of insulating oil make the dry brick an excellent alternative to the standard brick, especially for smaller research laboratories with limited maintenance staff.