2015/05/18 (Monday)

0854	MC = 78 mK, G1/G2 = 307/293 mbar, Still = 0.23 mbar (at 4 mW). These are rather high, so fridge has not returned to the previous base. 1K Pot = 1.71 K / 20 mbar (normal)
1025	Put all mix into circulation through V14, removed still heat. Does not improve base. Still P falls no lower than 0.28 mbar
1120	Try one-shot mode. Took a look at still thermometer: 2.5 K !!! This must be wrong. No other temperatures or pressures are consistent with this.
1134	In one-shot mode MC minimizes at 35 mK when G2 (dump) ~ 16 mbar. Then MC begins to get warmer.
1211	Back to normal circulation with all mix returned to circulation.
1240	MC/Tower minimize at 74/106 mK, G1/G2 fall to 273/261 mbar. Still down to 0.28 mbar, continues to read 2.5 K. 1K Pot normal. Cold plate cools from 384 down to 365 mK.
1314	Went back to one-shot briefly but then stopped. But fridge went quickly down to closer to normal.
1332	Return all mix to circulation again. MC oscillating in the 50s (mK), G1/G2 = 166/157 mbar, Still = 1.02 K / 0.12 mbar. All back to normal! Still thermometer reading properly again! (?)
1335	Apply 4 mW to still again.
1402	MC/Tower = 52/66 mK, G1/G2 = 201/190 mbar, Still = 4 mW / 1.07 K / 0.16 mbar, 1K Pot = 1.72 K / 22 mbar, Cold plat = 9.50 kΩ / 306 mK , MC sensor = -38.89 kΩ / 69 mK, Main bath = 58.8 %. Everything back to normal! Actually tower/MC difference somewhat smaller.

Comment: there seems to have been a temporary problem with the fridge, elevating the base temp and all circulation pressures by about 50%. Still thermometer read much higher than the still pressure (P1) would suggest - reading 2.5 K but logically should be no more than 1.2 K. But it seems to have fixed itself. It should also be noted that while it was bad, and while the fridge warmed to 8 K over the weekend, there were powered DCRCs in DIB1 and DIB2, at whatever settings they were left at. The fixing of the fridge corresponded roughly to powering down the DCRCs, but it wasn't clear that this was what fixed it.

1203	Fixed DCRC31 communication problem: Learned from Sten that the MAC addresses of DCRC31 and DCRC33 were set to the same value, which was probably the source of the communication problem with DCRC31 when it was sharing the switch with DCRC33. We were able to check this with a “set” command: sure enough both 31 and 33 had MAC addresses of 00.80.55.ee.00.04. 50 and X were the same except for the last two digits: 06 and 05 respectively. So we changed 31's last two digits to 03 so that they were all different. The change was persistent after power cycling 31, and now there is no communication problem with 31.

1203

Fixed DCRC31 communication problem: Learned from Sten that the MAC addresses of DCRC31 and DCRC33 were set to the same value, which was probably the source of the communication problem with DCRC31 when it was sharing the switch with DCRC33. We were able to check this with a “set” command: sure enough both 31 and 33 had MAC addresses of 00.80.55.ee.00.04. 50 and X were the same except for the last two digits: 06 and 05 respectively. So we changed 31's last two digits to 03 so that they were all different. The change was persistent after power cycling 31, and now there is no communication problem with 31.

1431	Set up DCRC33 on DIB2. Zap SQUIDs, set SQUID lockpoints.
1510	Measuring transition temperatures (TCs) of DIB2 TESs by sending 10 mVpp / 100 Hz triangle waves down the four QET lines, setting channels to non-inverting polarity and feedback signal source. At base temp triangle waveforms appear in all four channels; heat MC until these forms begin to distort, and heat further until triangle waveforms return.
1522	The tower-MC temperature difference seems smaller now than earlier in the run, so remeasure it today with a heating run:

MC temperature	Tower temperature
53.5 mK	67.9 mK
60 mK	71 mK
72 mK	82.5 mK
84 mK	91 mK
89 mK	97 mK
100 mK	105 mK
107 mK	114 mK

Tc measurements for DIB2 (DCRC33) - temperatures at MC / inferred temperatures at Tower
	Temperature range in which waveform is distorted
Channel	During heating	During cooling
A	94-99 mK / 101-105 mK	89-93 mK / 96-100 mK
B	104-110 mK / 110-116 mK	100-104 mK / 106-110 mK
C	90-95 mK / 97-102 mK	86-90 mK / 93-97 mK
D	106-111 mK / 112-117 mK	107-101 mK / 107-113 mK

Note: this is the second time we measured the DIB2 Tc's - compare with 2015/05/08. For the previous measurement the tower temperatures were inferred from the cooling power test done on the same day. For this test the tower temperatures were inferred from today's cooling power test; the tower-MC temperature difference is rather smaller now. The two Tc measurements agree well when you use the corrected tower temperatures, but not so well if you use the measured MC temperatures. This suggests that the crystal is much closer to the tower thermometer temperature than the MC temperature.

1610	Set up to redo charge breakdown study: plug DCRC31 into DIB1. Set SQUID lockpoints:

DIB1 DCRC31	SQUID Bias [uA]	Lockpoint [mV]	Modulation Depth [Vpp]
A	80.08	4.86	.412
B	85.94	3.41	.501
C	78.13	3.11	.503
D	80.08	2.53	.426

1630	Occasionally the interference pattern appears, even before raising charge biases. Observations: ~110 kHz, strongly saturated on DIB1 Qi, around 2 Vpp on DIB1 Qo, and around 0.2 Vpp on both Qi and Qo.
1650	While attempting to set charge biases, tower gets very warm: 200 mK (MC rises to 65 mK).
1655	Turned off FETs on both DIBs. Turn off all QET biases and charge biases. The tower stays hot, 200 mK.
1659	Power off the DCRCs: tower cools down immediately to base.
1709	Fill LN trap Dewar.