changes observed here can be removed by replacing components, other sources may be unavoidable. In particular, the development and evolution of transient spark discharge dynamically loads supplies like SGTTs. For example, growing a long leader-like structure effectively loads the supply with $\sim$ 3 pF per meter of length.[@raizer] Unfortunately, no reproducible trend was observed that could be attributed to spark discharge, likely because of a larger variability in component effects.

This electrical loading from spark discharge is one potential obstacle to future research with Tesla transformers towards the laser guiding of long sparks, because their output capacitance is typically small ($\sim$20–50 pF). Unfortunately, the effects of such discharge loading on Tesla transformers have not been extensively studied (see supplementary material).

In summary, a Marx generator was modified to mimic a Tesla transformer, producing similar output and spark discharge. This apparatus tolerated larger changes in its circuit parameters than is expected for Tesla transformers. Thus, such supplies may be attractive alternatives to Tesla transformers in research with the production, control, and laser guiding of spark discharges.

Supplementary Material {#supplementary-material .unnumbered}
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See supplementary material for additional apparatus, analysis, and spark discharge details (including video).

I am grateful to Tanya Zelevinsky and 