2020/07/16 (Thursday)
- Lab in-person: Matt
- Virtual partner: Nick/Derek
| 1115 | Matt Fritts body temperature = 97.7 F |
|---|---|
| 1110 | Matt arrives in lab |
| 1115 | Check contents of warm LN2 Trap 1: 11.7 mbar. Pump out with scroll pump. |
| 1115 | Turbo on IVC = 14 nbar. Better than yesterday. |
| 1140 | Check contents of warm LN2 Trap 2: 4.6 mbar. Pump out with scroll pump. |
| Probably should do one more cryocleaning, hopefully will still have time for LN2 transfer | |
| 1150 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.3% |
| 1155 | Increase V6 → 12.5% to restart flow |
| 1200 | Increase V6 → 12.8% to restart flow |
| 1210 | Increase V6 → 12.9% to speed up flow |
| 1240 | Stop cleaning through Trap 1 after 50 min. G2 flow pressure was 550-715 mbar. Pump mixture to dump. Removed 8.0 mbar. (Didn't check this until Aug 17, one month later.) |
| 1230 | Tape plastic over stripline elbow and KF flange, in hopes of limiting helium that leaks in during transfers.  |
| 1255 | Check fridge pressures: LHe trap/Condenser/Still = 11.1/0.9/0.39 mbar. Pump out with scroll pump. |
| Throughput test procedure, Cold Trap 2: |
- All mixture in dump, LN2 trap 2 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
| 1310 | Perform mixture throughput test at MC = 300 K using above procedure with 3He pump on. Let G1 rise to 550 mbar before Step 3, then it falls to 40 mbar and starts to rise. Throughput = 5.9 mbar/min. |
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| 1315 | Pump mixture out of fridge and cold LN2 Trap 2 to dump. |
| 1320 | 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. |
| 1330 | Close off scroll pump, then pressurize bath and 1K Pot (both sides) to about 0.5 bar with helium. Then pump it out again with scroll pump to < 1 mbar. |
| 1335 | Close off scroll pump, then pressurize bath and 1K Pot (both sides) to about 0.5 bar with helium. Then pump it out again with scroll pump to < 1 mbar. |
| 1345 | Pressurize main bath and 1K Pot (both sides) with helium to 350 mbar +1atm on G3, then close 1K Pot speedivalve and needle valve. |
| 1345 | Turbo on IVC = 19 nbar. With turbo valved out for a few minutes, IVC = 540 nbar. |
| 1350 | Let 6.3 mbar He exchange gas into IVC. (Usually we do 5.4 mbar but this will do.) |
| 1355 | As on 2020 Feb 17, we will flow mixture through the fridge during LN2 cooldown. Let mixture from dump through cold LN2 Trap 2 to fridge, both sides. Then we'll isolate the sides and circulate with V6 open partially and mix open to dump. V9, V13b, V12b+speedi, V1, Condenser speedi, Still gate valves open, 3He pump on. Now open V6 to 12.8%. |
| 1400 | P1 falls to <1 mbar |
| 1400 | Try closing V12b+speedi. G1 falls as it should, showing we have throughput. Falls at 10 mbar/min. Open V12b+speedi again. |
| 1405 | Circulation pressures settling to G2/G1/P1 = 646/714/0.75 mbar |
| 1410 | Trouble starting Omni_Logger vi because Fridge Computer no longer recognizes the external link to Linux. Instead sending logged data to c:\K100\K100log. |
| 1410 | MC(Cernox) = 296.7 K, Sorb = >249 K (max), IVC = 6.3 mbar, G2/G1/P1 (circulation) = 644/715/2.6 mbar, Level resistor = 0.997 kΩ |
| 1415 | Begin LN2 transfer. |
| 1425 | MC(Cernox) = 295.8 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) = 643/714/5.0 mbar, Level resistor = 1.098 kΩ |
| 1437 | MC(Cernox) = 280.0 K, Sorb = >249 K (max), IVC = 4.0 mbar, G2/G1/P1 (circulation) = 642/713/9.0 mbar, Level resistor = 1.187 kΩ |
| 1439 | Close V12b+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 13.9 mbar/min. Open V12b+speedivalve again. |
| 1450 | MC(Cernox) = 243.3 K, Sorb = >249 K (max), IVC = 3.0 mbar, G2/G1/P1 (circulation) = 642/711/32.0 mbar, Level resistor = 1.295 kΩ |
| 1459 | MC(Cernox) = 218.5 K, Sorb = >249 K (max), IVC = 2.5 mbar, G2/G1/P1 (circulation) = 642/710/160.0 mbar, Level resistor = 1.326 kΩ |
| 1500 | Close V12b+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 22.3 mbar/min. Open V12b+speedivalve again. |
| 1515 | MC(Cernox) = 184.6 K, Sorb = 242.4 K, IVC = 2.5 mbar, G2/G1/P1 (circulation) = 641/707/(off scale) mbar, Level resistor = 1.345 kΩ |
| 1530 | MC(Cernox) = 162.7 K, Sorb = 187.1 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) = 638/703/(off scale) mbar, Level resistor = 1.350 kΩ |
| 1531 | Close V12b+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 39.2 mbar/min. Open V12b+speedivalve again. |
| 1535 | It looks like maybe we are out of LN2. I noticed the level resistor fell a bit, and then noticed the flow of gas out of the fridge exhaust port was low. I think it's full enough anyway. |
| 1535 | Stop LN2 transfer. Pull out Level Resistor and put ping-pong ball on MB exhaust port. |
| 1546 | MC(Cernox) = 145.5 K, Sorb = 154.3 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) = 633/697/(off scale) mbar |
| 1547 | Close V12b+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 46.4 mbar/min. Open V12b+speedivalve again. |
| 1600 | MC(Cernox) = 134.4 K, Sorb = 140.8 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 628/690/(off scale) mbar |
| 1621 | MC(Cernox) = 120.9 K, Sorb = 131.5 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) = 619/677/(off scale) mbar |
| 1622 | Close V12b+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 47.5 mbar/min. Open V12b+speedivalve again. |
| 1630 | Matt leaves lab |
| 1703 | MC(Cernox) = 102.2 K, Sorb = 127 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 594/653/(off scale) mbar |
| 1707 | Close V12b for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 37.0 mbar/min. Open V12b again. (done remotely so speedivalve not used.) |
| The lower throughput here could be concerning, but it may be because I did not close the speedivalve - maybe we're seeing the leak through V12b. | |
| 1734 | MC(Cernox) = 93.5 K, Sorb = 126.4 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 583/640/(off scale) mbar |
| 1736 | Close V12b for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 30.8 mbar/min. Open V12b again. |
| This is more concerning - throughput seems to be falling with repeated measurements using only V12b. Are we seeing a blockage slowly form? | |
| 1811 | MC(Cernox) = 86.7 K, Sorb = 126.0 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 572/627/(off scale) mbar |
| 1812 | Close V12b for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 23.3 mbar/min. Open V12b again. |
| yeah, looks kinda bad… well I guess we'll see tomorrow. … actually back in October we saw it fall off like this on LN2 day too - but it had good throughput the next day. So maybe it will be OK. |
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| 1815 | Close V6 and stop circulation pump. |
| 1910 | Matt Fritts body temperature = 98.6 F |