Breakdown of t-decalin and cyclohexane in divergent fields

Breakdown voltage of trans-decalin and cyclohexane was measured at various pressures. After degassing the liquid by freeze-pump thaw cycles, it was transferred in vacuum to the test cell containing the electrodes, and the cell was sealed with argon or ammonia gas at a certain pressure. In trans-decalin, the breakdown voltage ratio for argon as compared to that for ammonia was 1.2-1.3; that is, ammonia could reduce the breakdown voltage. At the tail of the voltage pulse, back discharge light was found in the liquid for the ammonia atmosphere. The spectrum of the light included emission peaks at 550 nm of the ammonia molecule, which means that ammonia ions produced by the pulse were located near the point tip and recombined with electrons injected from the tip. In cyclohexane, the breakdown voltage ratio was 1.05-1.1. Breakdown velocities estimated from time lag measurement at 1 mm gap were 50-120 m/s, depending on the applied voltage