**4. Conclusions**

In view of the low-energy explosion foil detonation system's requirements for the integration technology of high-voltage switches and the technical overload resistance technology, a magnetron sputtering coater is used to sputter copper film on the surface of the substrate. The thickness is 4.0 μm, the radius of the main electrode is 4 mm, the trigger electrode is 0.6 mm and 0.8 mm, and the main gaps are 0.8 mm, 1.0 mm, 1.2 mm mm, 1.8 mm, 2.0 mm, 2.2 mm, and 2.6 mm. Copper foil three-electrode planar spark gap high voltage switches are designed and manufactured, and the static self-breakdown characteristics, dynamic operating characteristics, and discharge life characteristics of the three-electrode planar spark gap high voltage switch based on copper foil are studied in this paper. The test results show that with the increase of the main electrode gap from 0.8 mm to 2.6 mm, the self-breakdown voltage of the planar spark gap switch increases, and the working voltage also increases. When the main electrode gap is a maximum of 2.6 mm, the self-breakdown voltage of the switch can reach 3480 V, which indicates that the maximum operating voltage of the switch is 3480 V. Under the condition of charging voltage of 2.0 kV, with the increase of the main electrode gap from 0.8 mm to 2.6 mm, the minimum trigger voltage value of the planar spark gap switch increases from 677 V to 1783 V (*a* = 0.6 mm), and from 685 V to 1766 V (*a* = 0.8 mm), the switch-on times are 16 ns, 22 ns, 28 ns, 48 ns, 64 ns, 77 ns, 93 ns (*a* = 0.6 mm), and 26 ns, 34 ns, 51 ns, 67 ns, 81 ns, 102 ns (*a* = 0.6 mm). With the increase of the main electrode gap, the maximum static operating voltage of the three-electrode planar spark gap high voltage switch increased. When the same width of trigger electrode was used, the minimum trigger voltage increased, with the increase of the main electrode gap. When the same width of the trigger electrode was used, the minimum trigger voltage decreased. When the switch had the same parameters, the trigger voltage was inversely proportional to the working voltage. When the same width of the trigger electrode was used, with the increase of the gap between main electrodes, the conduction time of the switch was longer, and the peak current of the discharging circuit

decreased. The dynamic impedance and inductive reactance of the switch increase with the increase of the gap between the two main electrodes, and decrease with the increase of the width of the trigger electrode.

**Author Contributions:** Conceptualization, K.H., Q.J. and E.C.; methodology, K.H. and W.Z.; software, P.D. and K.H.; validation, K.H. and W.Z.; formal analysis, W.Z. and Q.J.; investigation, K.H., Q.J. and E.C.; resources, E.C. and K.H.; data curation, K.H., W.Z. and Q.J.; writing—original draft preparation, K.H., W.Z. and Q.J.; writing—review and editing, K.H., W.Z. and Q.J.; visualization, P.D. and K.H.; supervision, Q.J. and E.C.; project administration, Q.J. and E.C.; funding acquisition, K.H. and W.Z. All authors have read and agreed to the published version of the manuscript.

**Funding:** We appreciate the funding support from the National Natural Science Foundation of China (Grant No. 22105025 and Grant No. 52022013). Thanks for the support from the China Postdoctoral Science Foundation (Grant No. 2021M690376).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.
