2020/09/17 (Thursday)
- Lab in-person: Matt
- Virtual partner: Michael, Pramod, Derek
| Setup | Run 73. DIB 1/3/4 → Stripline 43/48/41 → pi-filters 1/2/3 → Cable 3/1/2 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1)-master; DCRC33(2) → HV control. DCRCs off. Lead/poly shield erected (4 lead walls, 2 poly walls). |
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| Status: | Warming up to deal with cryo problems: 1K Pot partial blockage, helium in IVC. Currently pumping out Cryostat Vacuum Jacket. 1K Pot and fridge valves closed. Mixture has been cryocleaned 3 times. |
| 0940 | MC(Cernox) = 253.6 K. It's clear that the warming slowed after we started pumping out the cryostat vacuum jacket. |
| 1015 | Matt Fritts body temperature 97.0 F |
| 1045 | Matt enters lab |
| 1055 | Turbo on Cryostat Vacuum Jacket: 0.22 ubar. With Turbo valve out for 1 minute, CVJ = 0.12 mbar. This is strange an a little concerning. This is not much lower than what we saw in the CVJ last night. There doesn't seem to be any leak in the pumping line - closing the CVJ valve, the Turbo pressure falls to 19 nbar. |
| 1115 | Check pressure in IVC: 4.6 mbar |
| 1120 | Insert lab thermometer into MB, 31.5“ down from port, near 1K Pot level. |
| 1125 | Check contents of warm LN2 Trap 1: 10.0 mbar. Pump out with Scroll Pump. |
| 1130 | Lab thermometer in MB at 1K Pot level = -13.2 C = 260.0 K. MC(Cernox) = 254.9 K |
| 1135 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.7% |
| 1140 | Increase V6 → 12.9% to restart flow |
| 1150 | Increase V6 → 13.0% to speed up flow |
| 1200 | Increase V6 → 13.1% to speed up flow |
| 1220 | Increase V6 → 13.2% to speed up flow |
| 1235 | Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 575-760 mbar. Pump mixture to dump. Removed 9.6 mbar. |
| 1155 | Let some additional helium into IVC, hoping to warm the fridge more. IVC → 40 mbar. |
| 1200 | With 1K Pot speedivalve and needle valve closed, pump on Main bath with scroll pump. Once P2 < 100 mbar, open 1K pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 1 mbar on P2. |
| 1215 | Close off scroll pump, then pressurize bath and 1K Pot (both sides) to about 0.75 bar with helium. After 10 minutes, pump it out again with scroll pump to < 1 mbar. |
| Close 1K Pot needle valve completely then open it 5 turns again. The idea is to crush any ice in there. Apparently Nicholas Llewelyn in the Goldman lab had a similar issue with his pot after using a Praxair Dewar, and was able to crush the blockage and get his pot working again. | |
| 1240 | Close off scroll pump, then pressurize bath and 1K Pot (both sides) to about 1 bar with helium. Close and reopen needle valve. After 5 minutes, pump it out again with scroll pump to < 1 mbar. |
| 1315 | Pressurize main bath and 1K Pot (both sides) with helium to 330 mbar +1atm on G3, then close 1K Pot speedivalve and needle valve. |
| 1315 | Insert lab thermometer into MB again, 31.5” down from port, near 1K Pot level. This depressurizes the MB of course. |
| 1325 | Lab thermometer in MB at 1K Pot level = -12.1 C = 261.1 K. MC(Cernox) = 256.1 K. So each of these has risen about 1 K in the last 2 hours. |
| 1340 | Check contents of warm LN2 Trap 1: 9.6 mbar. Pump out with Scroll Pump. |
| 1350 | Check fridge pressures: LHe trap/Condenser/Still = 3.4/0.0/0.046 mbar. Pump out with scroll pump. |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 trap 1 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
| 1400 | Perform mixture throughput test at MC = 257 K using above procedure with 3He pump on. Let G1 rise to 560 mbar before Step 3, then it falls to 39 mbar and starts to rise. Throughput = 8.0 mbar/min. |
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| 1410 | Pump mixture out of fridge and cold LN2 Trap 1 to dump. |
| Let's purge and flush MB and Pot again | |
| 1415 | With 1K Pot speedivalve and needle valve closed, pump on Main bath with scroll pump. Once P2 < 100 mbar, open 1K pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 1 mbar on P2. |
| 1450 | Perform a sort of 1K Pot throughput test (at MC = 257 K). Close needle valve then pump out 1K Pot, isolated from MB. Fill MB to about 1 atm helium. Then pump out 1K Pot, then stop pumping and watch the pressure rise at P2. Then repeat, but after stopping pumping open the needle valve a certain amount. Measured the amount of time to rise from 0.5 mbar to 3.0 mbar. At needle valve = 0/10/20°, risetime = 100/55/17 seconds. 0/10/20° → 1.5/2.7/8.8 mbar/min |
| 1505 | With 1K Pot speedivalve and needle valve closed, pump on Main bath with scroll pump. Once P2 < 1 mbar, open 1K pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 1 mbar on P2. |
| 1510 | Pressurize main bath and 1K Pot (both sides) with helium to 350 mbar +1atm on G3, then close 1K Pot speedivalve and needle valve. |
| 1515 | IVC = 16 mbar, down from the 40 mbar we raised it to earlier. |
| 1515 | Pump out IVC with Scroll Pump, then Turbo Pump, for a few minutes. Get IVC down to 54 ubar (Turbo valved out). |
| 1520 | Let 5.4 mbar He exchange gas into IVC. |
| 1525 | As on 2020 July 16, we will flow mixture through the fridge during LN2 cooldown. Let mixture from dump through cold LN2 Trap 1 to fridge, both sides. Then we'll isolate the sides and circulate with V6 open partially and mix open to dump. V9, V13a, V12a+speedi, V1, Condenser speedi, Still gate valves open, 3He pump on. Now open V6 to 12.8%. |
| 1525 | MC(Cernox) = 257.5 K |
| 1530 | P1 falls to <1 mbar |
| 1530 | Try closing V12a + speedi. G1 falls as it should, showing we have throughput. Falls at 14 mbar/min. Open V12a+speedi again. Note: tried just closing V12a via LabVIEW - this didn't cause G1 to fall. So I guess we can't test this remotely. (It worked remotely last time using Trap 2.) |
| 1535 | Circulation pressures settling to G2/G1/P1 = 677/754/1.6 mbar |
| 1540 | MC(Cernox) = 257.8 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) = 676/754/2.6 mbar, Level resistor = 1.005 kΩ |
| 1545 | Begin LN2 transfer. |
| 1555 | MC(Cernox) = 257.2 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) = 674/753/5.5 mbar, Level resistor = 1.121 kΩ |
| 1625 | MC(Cernox) = 204.3 K, Sorb = >249 K (max), IVC = 2.5 mbar, G2/G1/P1 (circulation) = 672/748/max mbar, Level resistor = 1.306 kΩ |
| 1625 | Close V12a speedivalve (not V12a itself) for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 25.6 mbar/min. Open V12a speedivalve again. |
| 1635 | MC(Cernox) = 182.6 K, Sorb = >249 K (max), IVC = 2.5 mbar, G2/G1/P1 (circulation) = 671/746/max mbar, Level resistor = 1.330 kΩ |
| 1640 | MC(Cernox) = 172.4 K, Sorb = 236.9 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) = 670/744/max mbar, Level resistor = 1.336 kΩ |
| 1650 | MC(Cernox) = 160.0 K, Sorb = 205.4 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) = 667/742/max mbar, Level resistor = 1.303 kΩ |
| LN2 Dewar is empty I think. Exhaust is weak, Level resistor is falling, and red indicator on LN2 Dewar is a little below halfway mark. Hopefully we've transferred enough. | |
| 1650 | Close V12a speedivalve (not V12a itself) for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 38.2 mbar/min. Open V12a speedivalve again. |
| 1705 | MC(Cernox) = 145.3 K, Sorb = 175.2 K (max), IVC = 2.2 mbar, G2/G1/P1 (circulation) = 662/736/max mbar, Level resistor = 1.295 kΩ |
| 1705 | Stop LN2 transfer. Pull out Level Resistor and put ping-pong ball on MB exhaust port. |
| 1715 | Try closing V12a from LabVIEW vi. Now it does cause G1 to fall. So it looks like throughput checks will work remotely. NO - see below |
| 1715 | MC(Cernox) = 136.9 K, Sorb = 161.1 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 658/730/max mbar. |
| 1715 | Close V12a for 2 minutes to assess throughput. But G1 only falls for about 30 seconds, then flattens. Closing the speedivalve works. So we do seem to have a problem with V12a. |
| 1720 | MC(Cernox) = 132.1 K, Sorb = 154.4 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 652/724/max mbar. |
| 1720 | Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 48.3 mbar/min. Open V12a speedivalve again. |
| 1735 | Matt leaves lab |
| 1820 | MC(Cernox) = 102.1 K, Sorb = 131.4 K (max), IVC = 1.6 mbar, G2/G1/P1 (circulation) = 619/689/max mbar. |
| 1920 | MC(Cernox) = 88.2 K, Sorb = 128.7 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 596/663/max mbar. |
| 1940 | Matt Fritts body temperature = 96.6 F |
| 1945 | MC(Cernox) = 84.8 K, Sorb = 128.5 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 589/655/max mbar. |
| 1945 | Close V6 and stop circulation pump. |