turns out all wires broke between 4K and 600mK solder pads - all still intact between 600mK and 30mK

Existing wires are actually similar to motor wires (copper-clad NbTi), but the copper is etched away between solder pads leaving only superconductor

Copper is a bad idea in terms of heat leak

Replaced the wires with manganin, a low-thermal-conductivity wire often used in cryo

but this has disadvantages - the resistance of one wire between 4K and 600mK is almost 1 Ohm. Unsuitable for phonon readout - but this tower face has other problems so we don't use it for phonon channels.

Resistances between channels are smaller. Biggest difference is between Side1 channels (note Side1 was the HV side when the HV mishap occurred)

Possibly potential differences occurred between channels, causing arcing between nearby rails and creating conducting paths

It's conceivable that when leakage is significant, ordinary biasing doesn't quite bias all channels equally. Then eventually maybe more leakage starts occurring between Side1 channels

This wouldn't really explain why biasing Side2 also seemed to show extra leakage above ~ 100V. But the leakage looked a little different.

Likely the leakage problem is at the detector itself (rather than SQUETs or DIBs or something). Possibly detector “surgery” could help, but it would probably be hard to know where to do it.

Potentially we could swap out chips to get four good ones on a SQUET. But you can't wirebond them too often, the bond pads get covered

Bonder in Hanany lab (note: Vlad Pribiag is currently in charge of the bonder) needs repairs

Paul Crowell hooked us up with the Ke Wang lab, they have their own bonder. Wei Ren let us use it under supervision.