The diagnostic from August (the 8th) have shown that there was very poor electrical contact between the feed-through and the anode. During the week (27th of August-> 1rst of september), we replaced the gold-wires glued with sivler epoxy (Epotek 21D) with regular SnPb weldings. After three iterations (including the super-sonic bath) the system was tested with RF successfully, and set up under vacuum. The HV test showed again clear limit with the feedthrough above 1100 V:
- The front side of the MCP can stand up to 2.6 kV; micro discharge is seen around 1.3 kV at 1Hz. The origin and location is unknow.
- The rear side of the MCP can stand up to 1.1 kV; above this there is a high load of the oscilloscope
- The anode can stand up to 1.4 kV; above this there is a regular "clac-clac" noise in the experimental room
The first attempt to use the MCPs like they were, was obviously not a good idea: high current , dicharge, and almost no nice signal. During, the cleaning of the ceramic holders 4 odd things were pointed out:
- the Cu ring where very much oxyde
- the Cu ring for the grid where at a floating potential,
- the electric holder for HV where very close to the MCPs, and potentially could induce short circuit
- the front MCP was "burned" on the side probably due to a discharge...
I swap the front and read MCP, remove the dusts with Helium, and try to remove the burned part on the MCP. Then wait 72 hours !