2021/10/25 (Monday) · UMN CDMS Wiki archive

Status	Run 75 prep.
	All mixture is in dump. Fridge isolated. 1K Pot isolated. LN2 Trap 2 still has contaminants in it. MB in pit, clean tent erected. Cryostat vacuum jacket (CVJ) pumped out. IVC open. Tower removed.
	Did Tower electrical check on Friday. One of the Tower wires we were going to use for the Goldman thermometer (Face4 pin13) seems to be shorted to chassis.
1140	Decided we can shift the second plug from the interposer (which has two purple wires and two black wires) 2 pins over, and thus avoid the shorted tower wire. So instead of none/therm+/none/therm-/therm- → 9/10/11/12/13 → purple/purple/none/black/black, it will be none/therm+/none/therm-/therm- → 11/12/13/14/15 → purple/purple/none/black/black. This uses pins 12,14,15 none of which have shorts. New connections to Tower 30mK sockets shown below:
1145	Do quick electrical check at Tower 4K sockets.

	Looks good.
1150	Plug in a SQUET at Face3 with the interposer board attached. Check that connectors plug into Face 4 easily - no problem. Connection shown below:
1155	Perform accessory electrical check at the interposer pins, referring to stripline pin number table. All connections good, no shorts. Remove SQUET and interposer from Tower.
1450	Perform a Tower Electrical Check, making sure values are the same as on Friday. Table below is copy of Friday with the exceptions of 1) changes to accessory wiring mentioned above 2) on Face 2 for opposite side interchannel resistance changed to pA-pC, correction from Friday.

Run 75 Tower Electrical Checkout
Device	Label	Unit	Value
Face5pA	Side1pE	Ω	336.2
Face5pB	Side1pB	Ω	140.7
Face5pC	Side1pD	Ω	416.4
Face5pD	Side2pE	Ω	321.2
Face5pA-pB	same side inter	kΩ	1.285
Face5pA-pD	opp side inter	kΩ	2.619
Face5LED1	pin-to-chassis	Ω/V	0.754M/1.068
Face5LED2	pin-to-chassis	Ω/V	205k/ 1.043
Face5pA-chassis		nS	0.1

Face3pA	Side2pC	Ω	376.4
Face3pB	Side2pF	Ω	515.4
Face3pC	Side1pC	Ω	435
Face3pD	Side1pF	Ω	500.9
Face3pA-pB	same side inter	kΩ	1.76
Face3pA-pD	opp side inter	kΩ	2.68

Face2pA	Side2pB	Ω	140.7
Face2pB	Side2pA	Ω	87.1
Face2pC	Side1pA	Ω	100.9
Face2pD	Side2pD	Ω	389
Face2pA-pB	same side inter	kΩ	0.749
Face2pA-pC	opp side inter	kΩ	1.958

Face4 1-2	coil1	kΩ	7.65
Face4 3-4	coil2	kΩ	7.47
Face4 6-chassis	near endstop	kΩ	5.756
Face4 7-chassis	far endstop	kΩ	22.76
Face4 5-12	therm+	Ω	66.9
Face4 14-15	therm-	Ω	65.7
Face4 12-14	therm	kΩ	2.103
Face4 1,3,5-chassis		nS	0.1, 0.1, 0.1

1400	Double-bag Tower and place in anteroom.
1430	Move Tower into fridge clean tent and begin installation. Raise Tower with scissor jack. Be careful to orient tower as it is raised so that pins at the DIBs don't hit the lip of the 30mK can. Remove temporary tape holding thermometer wire to outer edge of 30mK adapter. Quick electrical check after tower attached to 30mK can. Tower Thermometer reads OK. Detector channels not shorted to chassis. Motor coils OK. Goldman thermometer OK, not shorted.
1500	Put cap on bottom hole of Tower.
1530	Finish bolts attaching 30mK adapter to 30mK can and torque them.
	Contemplating the SQUET situation. In recent runs with HV prototype detectors we've used SQUETs that have some bad phonon channels, but in a combination so that all Side1 channels had good SQUET components. And those channels specifically have Rshunt reduced from 20 mOhm to 6.7 mOhm. We also have three good unmodified SQUETs used for iZIP runs. We seem to have four SQUETs with all good channel, 2 with maybe all good channels but suspected problems. If we want to read out 12 channels in this run we'll want to modify more shunt resistances. There's a worry about modifying them if we want to switch them back later, because the bond pads on the SQUID chips are already pretty full of bond stubs. Double-bonds make it a double-problem (but this reduces parasitic resistance). To go from 20 to 6.7 requires adding a bond - going back just requires removing a bond.