2018/03/01 (Thursday)
| Status: IVC pumping out overnight. Mixture has been cryocleaned. Fridge pumped out and fridge lines open to LN2 Trap 1 overnight. | |
| 0720 | IVC pumping pressure = 74 nbar, IVC = 7.4 μbar with pump valved out for 5 minutes |
| 0725 | Fill LN2 cold trap bath |
| 0730 | Pump IVC with Leak Detector: 12 pbarL/s |
| 0730 | Let mixture into fridge through Trap 1. 3He pump off, V9, V13a, V12a+speedi, V3, V1, condenser & still valves all open No increase in LD, has fallen to 7.2 pbarL/s. |
| 0735 | Pump out main bath below 1 mbar (actually down to 0.15 mbar). |
| 0740 | Pressurize main bath with He to 205 mbar above 1atm on G3. |
| note: He gas is left in the Vent volume, the auxiliary right volume, the auxiliary left (G3) volume, and the P2 volume (pump inlet). | |
| 0745 | Let 5.4 mbar He exchange gas into IVC |
| 0755 | Begin LN2 transfer. |
| 0755 | MC(Cernox) = 294.9 K, Sorb = >249 K (max), IVC = 5.4 mbar, G1 (fridge) = 601 mbar, Level resistor = 1.056 kΩ. |
| 0800 | MC(Cernox) = 293.6 K, Sorb = >249 K (max), IVC = 5.4 mbar, G1 (fridge) = 600 mbar, Level resistor = 1.079 kΩ. |
| Start measuring the detector resistance: DIB1 qIbias to QET D return, which is 1 bias resistor plus the resistance of the detector from the top surface to the bottom | |
| 0815 | MC(Cernox) = 276.5 K, Sorb = >249 K (max), IVC = 4.0 mbar, G1 (fridge) = 599 mbar, Level resistor = 1.154 kΩ. DIB1 QIbias-pD = 25.4 nS. |
| 0830 | MC(Cernox) = 237.5 K, Sorb = >249 K (max), IVC = 3.0 mbar, G1 (fridge) = 598 mbar, Level resistor = 1.275 kΩ. DIB1 QIbias-pD = 25.4 nS. |
| 0845 | MC(Cernox) = 193.6 K, Sorb = >249 K (max), IVC = 2.5 mbar, G1 (fridge) = 597 mbar, Level resistor = 1.333 kΩ. DIB1 QIbias-pD = 25.4 nS. |
| 0900 | MC(Cernox) = 169.1 K, Sorb = 200.4 K, IVC = 2.2 mbar, G1 (fridge) = 596 mbar, Level resistor = 1.337 kΩ. DIB1 QIbias-pD = 25.4 nS. |
| 0915 | MC(Cernox) = 149.5 K, Sorb = 161.2 K, IVC = 2.2 mbar, G1 (fridge) = 595 mbar, Level resistor = 1.337 kΩ. DIB1 QIbias-pD = 25.4 nS. |
| 0915 | Stop LN2 transfer |
| 1000 | MC(Cernox) = 113.9 K, Sorb = 122.6 K, IVC = 1.9 mbar, G1 (fridge) = 596 mbar, Level resistor = 1.315 kΩ. DIB1 QIbias-pD = 25.4 nS. |
| 1030 | MC(Cernox) = 101.2 K, Sorb = 119.0 K, IVC = 1.9 mbar, G1 (fridge) = 597 mbar. DIB1 QIbias-pD = 25.4 nS. |
| 1040 | Mini-throughput check: close off Trap 1 and V3. Only V1, condenser speedivalve, still gate valve, and V9 open. Turn on 3He pump, then open V6 to 12.8%. This pumps mix out of the still side and we can see if the pressure goes down on the condenser side. G1 (condenser) is not falling! Crap. Still (P1) fell all the way to 0.022 mbar but condenser is just stuck. |
| 1050 | Pump mixture out of fridge and Cold Trap 1 to dump. |
| Throughput test procedure, Cold Trap 2: |
- All mixture in dump, LN2 traps cold, condenser & still valves open (3He pump on - optional)
- Open V9, V13b, V12b+speedivalve, V3. Wait for G1 to be close to G2.
- Close V12b+speedivalve and V3, open V1
- monitor G1
| 1100 | Perform mixture throughput test at MC = 93.4 K using above procedure. Let G1 rise to 580 mbar before Step 3, then it falls to 31 mbar, seems to be stuck. Throughput less than 0.5 mbar/min. |
|---|---|
| 1225 | Watching for about an hour, throughput is not zero - it's about 3.5mbar/60min = 0.058 mbar/min. Pretty much the same as zero. |
| 1225 | Pump mixture back to dump |
| 1235 | MC(Cernox) = 80.0 K, Sorb = 118.1 K, IVC = 1.6 mbar, DIB1 QIbias-pD = 25.4 nS. |
| 1240 | Perform mixture throughput test at MC = 79.8 K using same procedure as before. Let G1 rise to 580 mbar before Step 3, then it falls to 34 mbar, rising very slowly. Throughput ~ 0.06 mbar/min again. |
| 1255 | Turn off 3He pump, open both sides of fridge to Trap 2, leaving mixture in fridge for now. |
| 1305 | Begin blowing out LN2 from main bath. G3 = 537 mbar. Adjust He cylinder regulator. G3 settles at 465 mbar. |
| 1340 | G3 falls, looks like it's almost finished |
| 1350 | G3 = 156 mbar. Stop pressurizing main bath. |
| 1425 | Let two hose-lengths of He gas into cryostat vacuum jacket. |
| 1431 | Do 78K electrical check. DIB1 is okay, but DIB2 has issues. SQUID bias B/ret is open, SQUID bias D/ret is high (1.9MΩ vs ~1.5kΩ), Feedback Coils B and D to returns are both open, QETB→ret is open (but B returns are interconnected at 50Ω). Most notable problem for this run is that there seems to be a ~40MΩ short somewhere between DIB2 QI feedback resistor and ground and a ~1MΩ short from GND to QI Src/Drain, but open from QI Src/Drain to GND. This indicates a ~1MΩ short somewhere between DIB2 QI feedback resistor and FET ground. This is the central charge channel on the detector. :( |
| 1435 | Pump mixture out of Trap 1 and fridge to dump |
| 1445 | MC(Cernox) = 81.7 K, Sorb = 143.7 K, Cryostat surface = 16.8 C, IVC = 1.6 mbar |
| 1500 | MC(Cernox) = 86.0 K, Sorb = 159.7 K, Cryostat surface = 15.9 C, IVC = 1.9 mbar |
| 1510 | Pumped fridge lines down to 0.019 mbar on P1, 1.9 mbar on G1. Isolate fridge to do another cryocleaning. |
| 1515 | MC(Cernox) = 91.6 K, Sorb = 177.5 K, Cryostat surface = 15.5 C, IVC = 1.9 mbar |
| 1515 | Start cryocleaning mixture through Trap 2, V6 = 12.8% |
| 1520 | Increase V6→12.9% to reestablish flow. |
| 1525 | Increase V6→13.0% to reestablish flow. |
| 1530 | MC(Cernox) = 97.6 K, Sorb = 193.7 K, Cryostat surface = 15.2 C, IVC = 2.2 mbar |
| 1535 | Increase V6→13.1% to reestablish flow. |
| 1550 | MC(Cernox) = 105.9 K, Sorb = 213.8 K, Cryostat surface = 15.2 C, IVC = 2.2 mbar |
| 1600 | MC(Cernox) = 110.0 K, Sorb = 222.6 K, Cryostat surface = 15.2 C, IVC = 2.5 mbar |
| 1605 | We checked the DIB2 qI feedback short about 10 minutes ago and it was still there. But checking now (at 112 K), it seems to have disappeared. So if it is temperature dependent the critical temperature is around 110 K. The Chassis to qI Drain or Source right now is around 0.4 nS. These are lower on qO, around 0.1 nS. |
| 1615 | At 117 K, it looks like the Chassis to qI Drain or Source resistance is around 0.1 nS. So now it's as good as qO. |
| 1630 | Stop cryocleaning, pump mixture back to dump. |
| 1630 | MC(Cernox) = 121.9 K, Sorb = 245.7 K, Cryostat surface = 15.6 C, IVC = 2.5 mbar Newton's Law of Cooling/Warming suggests that we will hit 0 Celsius between 7:50 and 8:40 tomorrow morning |
| 1640 | Remove Trap 2 from LN2 bath to let it warm up. Turn off 3He pump. |
| 1705 | MC(Cernox) = 134.9 K, Sorb = >249 K, Cryostat surface = 15.8 C, IVC = 3.0 mbar Newton's Law of Cooling/Warming suggests that we will hit 0 Celsius between 7:45 and 8:20 tomorrow morning |