2019/04/09 (Tuesday)

Previous Day

Results:

• DIB1pD and DIB4pA SQUID and Feedback are now reading open. These are the channels that were biased (they are not Side1 channels). (DIB1pD was biased before modifying the HV board, DIB3pA has been biased throughout because that's the one connected to the electrode.) So it looks like we may have fried the phonon components in those channels.
  • This pattern did not repeat on DIB3 - we had DIB3pA,B,D biased originally too, but there's no change to on the SQUID and Feedback status on these channels. (pA SQUID is open but that was true before the run started.)
• No issues seen in DIB3pC (this is connected to Side1pA, which became nonoperational after our first high-leakage test). As Nick determined from SQUID tuning, it looks like the problem on this channel must be either at the TES or (more likely) at the input coil. We can't measure whether there's an open on the input coil/TES branch at the breakout box because they are shorted by the shunt resistor, so we'll have to wait until we deinstall to check these components.

Discussion:

It looks like the way we are applying HV has definite problems in terms of leakage in the SQUETs and damage to SQUET components. Since all three DIBs have readout Side1 channels, we can't avoid biasing some elements of a SQUET and grounding others, if we run the HV through the SQUET. Nick suggests an alternative: use a stripline diverter board at the SQUET end, disconnect the HV wire(s) from the SQUET at the board, and route the HV wire(s) to an unused tower face, plugging in directly at the SQUET socket in the tower. At the top of the tower use a wire to route this to the electrode.

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