On May 30 Aaron, Chad and I removed the empty LP FEBIAD target from the SHC into the anteroom to attempt to find out the source of the cathode short observed online. The behaviour online was that a connection of several hundred ohms was preventing the cathode from being biased. The resistance was still enough to allow us to run in anode mode, which is what we did. I am not sure where the cathode short came from but there was significant sparking on this module when ops conditioned it (destroyed the gmov of the COIL power supply and the electronics for anode/cathode switching) and we have seen this cause cathode shorts before. The shorted behaviour did not go away when the target was cooled down, so I assume it was permanent damage to one of the insulators. This would be either the support insulator, the trident insulator, the gas line insulator or one of the tube retainer insulators.

Since the target didn't see protons, we decided to take it out of the hot cell and disassemble it to find which insulator was broken. Unfortunately, it appeared totally fine outside of the hot cell, no shorts could be found. We disassembled it anyway to look for issues but all we saw was a heat mark on the copper plates covering the coil, underneat the target (see attachment). We even shook the target quite a bit, and didn't produce a short.

Maybe there was a trace created on one insulator by the sparking, which oxidized when exposed to air and became insulating again? We didn't see anything obvious on the insulators, but I'm not sure if we would expect to.

No conclusions from this work.