Comparative Analysis of Gas Insulation Within a Simulated Helical Flux Compression Generator Geometry Using Air, Sf6, and Novec 4710

In order to gain a deeper understanding of how well Novec ${ }^{\text{TM }} 4710 (\mathrm{C}_{3} ~\mathrm{F}_{7} \text{CN})$ would work as a substitute for sulfur hexafluoride $(\text{SF}_{6})$ in helical flux compression generator (HFCG) applications, a comparative analysis was made between the relative dielectric breakdown properties of air, $\text{SF}_{6}$, and Novec 4710 under the extreme conditions encountered in an HFCG. An experimental apparatus that emulated a helical FCG geometry was developed to allow the measurement of a time-resolved gas resistance using biased wire probes inserted into the device. After initiation, the expanding armature causes interplay between the advancing shocked gas region, armature, and the biased wire probes on the microsecond time scale. This leads to eventual dielectric breakdown on a nanosecond time scale. Incorporating piezoelectric pins, shorting pins, and fiber optic time-of-arrival sensors enabled precise tracking of the armature's position and the shock layer's progression, providing a measure of shock layer thickness at critical points. The spatial relationship between the shocked gas region, armature, and wire probes at the moment of breakdown was used to evaluate the relative performance of the different gases. The results demonstrate that Novec ${ }^{\text{TM }}$ 4710s performance closely aligns with $\text{SF}_{6}$, indicating it may be a viable alternative to $\text{SF}_{6}$ in HFCG applications.