2015/05/11 (Monday)
| 0825 | MC at 280 mK, G1/G2 = 215 mbar, Still = 0 mW / 0.130 mbar. Opening V14 for brief periods to let more mix in. |
|---|---|
| Note: | No mixture was removed from fridge yesterday. So probably the relief valve kicked in and let some mix into the dump. This valve releases mixture from the circulation lines to the dump if the differential pressure between them exceeds 500 mbar. |
| 1040 | Fill LN2 cold trap full. |
| 1100 | All mix in fridge. MC temperature around 56 mK and oscillating at ± 6 mK. Apply 4 mW to still. This causes MC temperature to stabilize, as before. |
| 1110 | MC/Tower = 53/69 mK, G1/G2 = 293/282 mbar. Still = 4 mW / 1.10 K / 0.19 mbar. 1K Pot = 1.73 K / 22 mbar. Cold plate = 9.50 kΩ / 306 mK. MC sensor = -36.23 kΩ. Main bath 26.4%. |
Lock DIB1 SQUIDs using DCRC33 (because I want to do Tc measurements and thought there may be some problem using DCRC50):
| DIB1 DCRC33 | SQUID Bias [uA] | Lockpoint [mV] | Modulation Depth [Vpp] |
|---|---|---|---|
| A | 80.08 | 5.35 | .404 |
| B | 80 | 3.70 | .438 |
| C | 72 | 4.28 | .448 |
| D | 82.03 | 3.89 | .446 |
| 1420 | We tried plugging the grounding plug into the DIB2 socket, and saw interference patterns in DIB1 and increasing temperature at the MC. We removed the plug but the effect continued. We turned off the FET (wr 30 0000) then turned it back on (wr 30 0800) which fixed both problems. |
|---|---|
| 1425 | Found approximate QET biases by adjusting them and watching for good (and frequent) phonon pulses. |
| Approx. QET biases for DIB1 (DCRC33) | |
|---|---|
| Channel | QET bias (μA) |
| A | -139 |
| B | -139 |
| C | -129.4 |
| D | -129.5 |
| 1435 | Interference pattern returns for no reason. Resetting FET helps but not immediately. Starting to suspect the issue is with DIB1 or corresponding SQUET/stripline, not with DCRC50 (which is what we suspected on Friday). |
|---|---|
| 1440 | Drop QET biases back to 0 μA |
| 1441 | Measuring transition temperatures (TCs) of DIB1 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. |
| Tc measurements for DIB1 (DCRC33) - temperatures at MC / inferred temperatures at Tower | ||
|---|---|---|
| Temperature range in which waveform is distorted | ||
| Channel | During heating | During cooling |
| A | 100-105 mK / 110-115 mK | 98-103 mK / 108-113 mK |
| B | 96-97 mK / 107-108 mK | 93-95 mK / 104-106 mK |
| C | 97-102 mK / 108-112 mK | 94-100 mK / 105-110 mK |
| D | 101-105 mK / 111-115 mK | 99-102 mK / 109-112 mK |
| 1537 | Move DCRC33 to DIB3. Zap SQUIDs. Lock SQUIDs, then find Tc's as before. |
|---|
| DIB3 DCRC33 | SQUID Bias [uA] | Lockpoint [mV] | Modulation Depth [Vpp] |
|---|---|---|---|
| A | 82.04 | 5.93 | .446 |
| B | 86.94 | 4.28 | .484 |
| C | 89.85 | 3.41 | .519 |
| D | 89.85 | 3.31 | .522 |
| Tc measurements for DIB3 (DCRC33) - temperatures at MC / inferred temperatures at Tower | ||
|---|---|---|
| Temperature range in which waveform is distorted | ||
| Channel | During heating | During cooling |
| A | 82-85 mK / 95-96 mK | 78-81 mK / 91-94 mK |
| B | 100-103 mK / 110-113 mK | 98-100 mK / 108-110 mK |
| C | 92-98 mK / 103-108 mK | 88-94 mK / 100-105 mK |
| D | 85-88 mK / 97-100 mK | 81-84 mK / 94-96 mK |
| 1620 | Commence LHe transfer (17.2%). |
|---|---|
| 1725 | Cease LHe transfer (90.5%). |
| 1750 | Running Ib-Is routine on DIB3 with DCRC33. This time we are stepping through QET biases starting at 0 and ending at -400 uA. The curves look better than the ones taken last week. |