2019/03/06 (Wednesday)
| Status: | Transferred LN2 yesterday |
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| 0830 | MC(Cernox) = 78.1 K, Sorb = 137 K, IVC = 1.6 mbar, G1 (fridge) = 602 mbar, Level resistor removed last night. |
| 0835 | Start pumping out IVC |
| 0845 | Turbo on IVC: 10 nbar |
| 0900 | Perform electrical check, looks OK. Some issues that weren't seen at 300 K: 1) DIB3 Feedback D/return is too high, 700 kΩ (s/b 8 kΩ). Lots of problems with this SQUET, luckily pC is the only active channel and it's OK 2) DIB4 qI, short to chassis: feedback→chassis 22 nS, chassis→source-or-drain 2 MΩ. This was seen last run too. No problems with any relevant channels. |
| 0910 | Something is wrong with the leak detector. With port blanked, background signal is >100 pbarL/s, usually less than 1. When trying to calibrate it doesn't seem to pump down all the way. Tried opening it to IVC while it was running - this was a mistake, IVC pressure spiked up a couple of orders of magnitude briefly. Hopefully not too much contamination. After a couple of minutes IVC is back down to 40 nbar, but it had been below 10 nbar. Try turning leak detector off and back on. |
| 0925 | Turbo on IVC: 8.6 nbar. So it has recovered it seems. |
| 0930 | Reboot of leak detector failed. Display says: Error (41) TMP frequency is too low! Possible causes: * Frequency converter is faulty * Turbomolecular pump is faulty so maybe the turbo pump in the LD has died. |
| 0935 | Hit the Restart button and get another error: Error (56) P1 > 10 mbar after runup Possible causes: * Forepump is faulty * Valve V1 didn't open so maybe it's the forepump instead |
| 0940 | The shared Alcatel leak detector is available - bring it into the lab and warm it up. |
| 1015 | Alcatel leak detector seems not to be working either. Won't pump down, stays in “roughing” mode. |
| 1030 | After a restart the Alcatel LD seems to be working. |
| 1030 | Alcatel LD on IVC = 120 nbar (10 times higher than when our turbo is pumping on it. |
| 1030 | Alcatel LD = 5400 pbarL/s, slowly rising to some stable value. |
| 1035 | 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. P1 (still) falls to 6 mbar after a few minutes. G1 (condenser) falls, from 603 mbar to 440 mbar in 5 minutes, and continues to fall. Good, looks like we have throughput. |
| 1040 | Close V6, turn off 3He pump. Open trap 1 valves and V3 to let mix into fridge lines through trap 1. |
| 1045 | Begin blowing out LN2. Main bath (G3) = 440 mbar above 1atm. Alcatel Leak detector on IVC = 4500 pbarL/s |
| 1050 | Alcatel LD = 4200 pbarL/s. Main bath = 451 mbar. |
| 1055 | Alcatel LD = 4000 pbarL/s. Main bath = 444 mbar. |
| 1100 | Alcatel LD = 4000 pbarL/s. Main bath = 320 mbar and falling. |
| 1105 | Alcatel LD = 3800 pbarL/s. Main bath = 155 mbar. Stop pressurizing main bath. |
| 1110 | Pump mixture to dump, so we can clean out warm LN2 Trap 2, still dirty from the last cryocleaning. |
| 1110 | Start pumping out main bath with scroll pump. LD = 3600 pbarL/s. Takes 11 minutes to fall to 1 mbar. |
| 1125 | Trap 2 is warm. Check contents: 17.7-1.5 = 16.2 mbar on G1 (surprisingly high). Pump out with scroll pump. |
| 1135 | Let mixture back in to both sides of the fridge through LN2 Cold Trap 1 |
| 1135 | Alcatel LD = 3100 pbarL/s. |
| 1145 | Pressurize MB with helium to 380 mbar above 1 atm. Open 1K Pot speedivalve and needle valve (2 full turns) to repressurize pot as well. Notice MB pressure falls about 5 mbar. Close 1K Pot valves again. |
| 1145 | Alcatel LD = 3000 pbarL/s. IVC pressure while pumping = 86 nbar. |
| 1150 | Let 63 μbar He exchange gas into IVC. |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 trap 1 cold, condenser & still valves open (3He pump on - optional)
- Open V9, V13a, V12a+speedivalve, V3. Wait for G1 to be close to G2.
- Close V12a+speedivalve and V3, open V1
- monitor G1
| 1200 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 565 mbar before Step 3, then it falls to 68 mbar and starts to rise. Throughput = 35.7 mbar/min. |
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| 1215 | Let mixture back into fridge, both sides open to LN2 Trap 1 and dump, 3He pump off. |
| 1230 | Begin initial LHe transfer |
| 1240 | MC(Cernox) = 81.9 K, Sorb = 156 K, IVC = 74 μbar, G1(fridge) = 603.8 mbar. G3(MB) = 460 mbar. |
| 1245 | MC(Cernox) = 82.3 K, Sorb = 154 K, IVC = 46 μbar, G1(fridge) = 602.7 mbar. G3(MB) = 430 mbar. |
| 1250 | Transfer pressure on G3 started around 460 mbar, then gradually fell to around 360 mbar. Turn the Dewar Heater on to 4 PSIg. Transfer pressure climbed to 530 mbar after a few minutes and recovery meter was spinning fast, so turn it off again. |
| 1255 | Transfer pressure on G3 has fallen to 340 mbar (around 2 PSI on Main Bath gauge). Turn Dewar Heater on again to 4 PSIg. Pressure is not rising as quickly this time so we'll leave it on for a while. |
| 1300 | MC(Cernox) = 77.3 K, Sorb = 129 K, IVC = 19 μbar, G1(fridge) = 591.9 mbar. G3(MB) = 385 mbar. |
| 1320 | MC(Cernox) = 62.3 K, Sorb = 72 K, IVC = 14 μbar, G1(fridge) = 520.2 mbar. G3(MB) = 457 mbar. (MB gauge = 2.9 PSI, Storage Dewar gauge = 4.2 PSI.) |
| 1330 | MC(Cernox) = 56.6 K, Sorb = 38 K, IVC = 12 μbar, G1(fridge) = 472.9 mbar. G3(MB) = 418 mbar. (Storage Dewar gauge = 4.5 PSI.) |
| 1350 | MC(Cernox) = 47.5 K, Sorb = 7.4 K, IVC = 10 μbar, G1(fridge) = 459.2 mbar. G3(MB) = 376 mbar. MB = 55.7% |
| this is one of those times when the IVC pressure seems to be falling too fast. I think we concluded before that this was because the gauge got dirty. | |
| 1350 | Increase resistance range on bridge to 2.00 kΩ, so that the Cernox thermometer doesn't saturate and make us miss the pumpout point (10 K) |
| 1400 | MC(Cernox) = 40.7 K, Sorb = 7.0 K, IVC = 8.6 μbar, G1(fridge) = 456.3 mbar. G3(MB) = 363 mbar. MB = 79.3% |
| 1405 | MC(Cernox) = 38.9 K, Sorb = 7.0 K, IVC = 8.6 μbar, G1(fridge) = 455.2 mbar. G3(MB) = 360 mbar. |
| 1410 | End LHe transfer @ MB = 88.0% |
| 1435 | MC(Cernox) = 23.9 K, Sorb = 6.2 K, IVC = 7.4 μbar, G1(fridge) = 501.4 mbar. |
| 1450 | MC(Cernox) = 19.8 K, Sorb = 6.0 K, IVC = 7.4 μbar |
| 1500 | MC(Cernox) = 17.5 K, Sorb = 5.9 K, IVC = 6.3 μbar |
| 1510 | MC(Cernox) = 14.8 K, Sorb = 5.7 K, IVC = 6.3 μbar |
| 1522 | MC(Cernox) = 11.9 K, Sorb = 5.6 K, IVC = 1.6 μbar IVC falling fast, let's start pumping |
| 1523 | Start pumping out IVC with turbo |
| 1615 | MC(Cernox) = 10.4 K, Sorb/1K Pot = 6.4/5.1 K, Turbo on IVC = 2.5 nbar, G1(fridge) = 538 mbar. |
| Note temperature is creeping up. Last time it fell to 4K. So maybe I started pumping out too soon. Tomorrow it may be hard to cool to 1K. |
HPGe Measurement
| 1100 | Set up HPGe detector with HVbias=1.85 kV. Bias was unstable above this level. Took 1000s background spectrum using EasyMCA in this manner. |
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| 1125 | Remove 133Ba source from safe and place in lead castle. |
| 1130 | Take 1000s Ba data with source slot aimed at z=8“ and source at r=16” from the center of the HPGe detector. Hint of 356 keV line. |
| 1150 | Take 1000s Ba data with source slot aimed at z=6“ and source at r=16” from the center of the HPGe detector. Strong 356 keV line, maybe 80keV also. |
| 1150 | Take 1000s Ba data with source slot aimed at z=4“ and source at r=16” from the center of the HPGe detector. No clear Ba lines. |
| 1240 | Take 1000s Ba data with source slot aimed at z=5“ and source at r=16” from the center of the HPGe detector. No clear Ba lines. Detector may have been moved. Should repeat. |
| 1315 | Take 1000s Ba data with source slot aimed at z=7“ and source at r=16” from the center of the HPGe detector. Lines are back. |
| 1345 | Take 1000s Ba data with source slot aimed at z=7.5“ and source at r=16” from the center of the HPGe detector. Lines present. |
| 1430 | Take 1000s Ba data with source slot aimed at z=5.5“ and source at r=16” from the center of the HPGe detector. Some lines. |
| 1510 | Take 1000s Ba data with source slot aimed at z=5“ and source at r=16” from the center of the HPGe detector. |