TLDR: TBHT voltage too high and rising too quickly with TGHT current - voltage limited. TGHT power supply tripped breakers somehow. ITE:EL not outputting voltage.

 

A short between feedthroughs A and P developed at the end of the p2n run in this module, and was fixed by Chad prying apart the lines in the source tray with a long teflon bar. We did not take the containment box off to fix it properly for reasons of time and also potential damage to the containment box. This seemed to fix it and David measured around 13MOhms between A-P when the module was installed in ITE. To make sure we could recover if the short reappeared during the run, David did not connect the P/Q feedthrough to HV common on the module top as usual, but it was connected in the electrical room. I also unhooked the busbar from the coil power supply.

When trying to start the TGHT ramp up, it was discovered that ITE:TGHT had a fault in its readback circuit, which was showing negative voltages. Not sure how this happened, since the power supply was not used for the previous p2n run, maybe an HV spark? This supply was replaced with the spare (SN 1161-9894).

When TGHT and TBHT were able to be ramped up, we found that the tube heater voltage was increasing too much with the target current. Normally the rate of increase is about 0.0004 V per amp on TGHT. This time it was 0.004 V/A. This was causing the TBHT to be voltage limited, which I thought could be related to the AP short. So I re-wired it such that the P feedthrough (#7 in the electrical room) was disconnected from everything except it was tied to feedthrough A (#1) using a 100 Ohm resistor. This should prevent it from floating and also prevent current from going through. See documentation in the Target Records folder (https://documents.triumf.ca/docushare/dsweb/Get/Document-204373/July272021_ITETM4_electricalissues.pdf).

During the subsequent ramp up, the TGHT power supply tripped the breakers when it was at 500A, 8V. The cause of this is still uncertain, and the TBHT voltage issue persisted after the wiring change. In the interest of time we decided to stay conservative on the currents used and continue to run like this. It may also be possible that the copper block which is supposed to reference TBHT negative to HV common is not attached.