Because the output energy of the Prometheus was too low, I decided to passivate it. The chamber was vacuumed this morning, then Helium gas was filled into the chamber about 1 bar. A 16kV H.V. pulse was applied to the rail gap. After filling several mbar fluorine gas, the emission light was changed from white to red. In order to make the railgap firing at the peak time of transformer secondary, I changed the SRS DG-535 channel B timing, from B=A-1.58us to B=A-2.20us. This status has been kept for one hour, then I found a spark on the top 10k Ohm charging resistor. I had to stop passivation, and found the resistor broken. What caused this happened?
Later I replaced the broken resistor, and tried to passivate the Prometheus again. I also measure the Thyratron currents at different timing delays(158us, 190us, 220us).