2020/07/17 (Friday)
- Lab in-person: Matt
- Virtual partner: Pramod/Derek
| 0845 | Matt Fritts body temperature = 97.3 F |
|---|---|
| Status | LN2 transfer yesterday. Beginning Run 73 cooldown. |
| 0850 | Notice V12b was left closed, open it now |
| 0850 | MC(Cernox) = 77.2 K, Sorb = 128.3 K, IVC = 1.6 mbar, G2/G1 = 549/603 mbar |
| 0850 | Turn on 3He pump and open V6 to 12.8%, reestablishing circulation like yesterday. G2/G1/P1 → 649/711/0.9 and settle. |
| 0855 | Close V12b for 2 minutes to assess throughput. G1 falls at 61.2 mbar/min, good. Much better than last night. Reopen V12b. |
| 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
| Note: performing remotely, so skipping the speedivalve. | |
| 0910 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 520 mbar before Step 3, then it falls to 52 mbar, then rises. Throughput = 39.9 mbar/min. A little lower than last time, 2020 Oct 18 |
| 0955 | Matt arrives in lab |
| 0955 | Start pumping out IVC with Scroll Pump |
| 1000 | Switch to pumping IVC with Turbo Pump |
| 1035 | Perform electrical checks on all 3 DIBs. |
| 77K electrical checkout | |
|---|---|
| DIB4 + accessories | SQUID D is OK, last time read too high. Feedback A reads low, 1kΩ, normal 9-13kΩ, but this channel not used. |
| DIB1 | As seen before, SQUID and Feedback D are both open. This channel is not used so not a problem for this setup. At first QET A/B/C had shorts to chassis, around 1 MΩ. On second measurement this went away - all connected channels show about 5 nS to chassis. |
| DIB3 | All OK |
| 1105 | Turbo on IVC = 14 nbar. Leak signal on IVC with turbo pumping: 410 pbarL/s. With turbo valved out: 2200 pbarL/s. Switch back to pumping IVC with turbo. |
|---|---|
| 1140 | IVC = 2000 pbarL/s. |
| 1150 | Begin blowing out LN2. Main bath (G3) = 569 mbar above 1atm. |
| 1150 | IVC = 2100 pbarL/s, MB = 567 mbar+1atm |
| 1200 | IVC = 2000 pbarL/s, MB = 534 mbar+1atm |
| 1215 | IVC = 1900 pbarL/s, MB = <300 mbar+1atm and falling, looks like almost all the LN2 has been blown out. |
| 1220 | IVC = 1900 pbarL/s, MB = 160 mbar+1atm and leveling out. Stop pressurizing MB. |
| 1228 | Start pumping out main bath with scroll pump. Takes 10 minutes to fall to 1 mbar. |
| 1245 | Pressurize MB with helium to 210 mbar above 1 atm. |
| 1250 | Isolate MB by closing V1a. Pump out line to the G3 volume with Scroll Pump. Isolate pump, then open 1K Pot speedivalve to check pressure: about 0.08 bar. Then pump out 1K Pot (needle valve closed) with Scroll Pump to 0.03 mbar on P2. Then close 1K Pot speedivalve. Open V1a again to monitor bath pressure. |
| 1315 | IVC = 1600 pbarL/s. Switch to Turbo Pump on IVC. |
| 1320 | Turbo on IVC = 46 nbar. With Turbo valve out for a minute, IVC = 0.12 ubar |
| 1320 | Let 63 μbar He exchange gas into IVC. |
| 1325 | Open mixture to both sides of the fridge and cold LN2 Trap 2. |
| 1325 | Fill LN2 cold trap bath. |
| 1330 | MC(Cernox) = 77.4 K, Sorb = 138 K, IVC = 63 μbar, G1(fridge) = 595.6 mbar. G3(MB) = 147 mbar+1atm. |
| 1335 | Begin initial LHe transfer |
Note: I did the transfer as a one-person job using the new hangers:
- Insert short piece of transfer line in MB
- Attach telescoping extender to long piece, then hang long piece from the two aluminum hooks on the gray pipe. Tilt the extender to the left and hook it to the fridge shield or something to get it out of the way
- Roll in the storage Dewar
- Standing on the stool in front of the Dewar, raise the extender so that the top of the long piece goes between the gray pipe and copper pipe, which will disconnect it from the near hook, but keep the further end on the far hook. Position the extender above the Dewar port and lower it in. Open the Dewar port valve. The long piece should now be supported by the Dewar port and the far hook.
- Walk over to the ladder behind the Dewar and ascend to take the long piece off the far hook and carefully lower it to rest on the fridge stand.
- When the plume appears, connect the long piece to the short piece as usual to begin the transfer.
| 1335 | MC(Cernox) = 78.1 K, Sorb = 143 K, IVC = 63 μbar, G1(fridge) = 595.2 mbar. G3(MB) = 550 mbar+1atm. |
|---|---|
| 1345 | Set Range on LakeShore bridge to 2.0 kΩ, so that Cernox thermometer readout doesn't peg. |
| 1345 | MC(Cernox) = 78.2 K, Sorb = 141 K, IVC = 63 μbar, G1(fridge) = 594.5 mbar. G3(MB) = 420 mbar+1atm. |
| 1355 | Turn on heater on 250L Dewar to 4 PSIG. This causes the MB pressure to rise. |
| 1400 | MC(Cernox) = 74.4 K, Sorb = 116 K, IVC = 25 μbar, G1(fridge) = 585.7 mbar. G3(MB) = 350 mbar+1atm. |
| 1415 | MC(Cernox) = 62.9 K, Sorb = 65.5 K, IVC = 12 μbar, G1(fridge) = 522.5 mbar. G3(MB) = 454 mbar+1atm. MB = 1.0% |
| 1430 | MC(Cernox) = 54.6 K, Sorb = 9.5 K, IVC = 8.6 μbar, G1(fridge) = 459.8 mbar. G3(MB) = 417 mbar+1atm. MB = 23.6% |
| shortly after this, 1K Pot temperature falls below the 7K max value | |
| 1440 | MC(Cernox) = 49.5 K, Sorb = 7.4 K, 1K Pot = 5.90 K, IVC = 8.6 μbar, G1(fridge) = 452.7 mbar. G3(MB) = 401 mbar+1atm. MB = 46.1% |
| 1450 | MC(Cernox) = 44.5 K, Sorb = 7.2 K, 1K Pot = 5.78 K, IVC = 7.4 μbar, G1(fridge) = 449.2 mbar. G3(MB) = 409 mbar+1atm. MB = 69.0% |
| 1500 | MC(Cernox) = 39.3 K, Sorb = 7.0 K, 1K Pot = 5.65 K, IVC = 7.4 μbar, G1(fridge) = 447.6 mbar. G3(MB) = 408 mbar+1atm. MB = 90.2% |
| 1503 | Finish LHe transfer. MB = 89.3% |
| 1520 | MC(Cernox) = 28.0 K, Sorb = 6.3 K, 1K Pot = 5.07 K, IVC = 6.3 μbar, G1(fridge) = 490.0 mbar. G3(MB) = 167 mbar+1atm. |
| 1535 | MC(Cernox) = 20.0 K, Sorb = 6.0 K, 1K Pot = 4.81 K, IVC = 4.0 μbar, G1(fridge) = 494.1 mbar. G3(MB) = 155 mbar+1atm. |
| 1545 | MC(Cernox) = 16.1 K, Sorb = 5.8 K, 1K Pot = 4.65 K, IVC = 3.4 μbar, G1(fridge) = 498.7 mbar. G3(MB) = 143 mbar+1atm. |
| 1600 | MC(Cernox) = 12.4 K, Sorb = 5.6 K, 1K Pot = 4.49 K, IVC = 2.5 μbar, G1(fridge) = 503.9 mbar. G3(MB) = 132 mbar+1atm. |
| 1600 | MB = 83.9% |
| 1608 | MC(Cernox) = 10.0 K, Sorb = 5.5 K, 1K Pot = 4.39 K, IVC = 2.2 μbar, G1(fridge) = 509.6 mbar. G3(MB) = 135 mbar+1atm. Start pumping out IVC with Turbo pump. |
| 1615 | MC(Cernox)/Sorb/1K Pot = 7.2/5.5/4.40 K |
| 1615 | Matt leaves lab. |
| 1710 | Matt Fritts body temperature = 98.0 F |
| 1715 | MC(Cernox)/Sorb/1K Pot = 5.72/6.3/4.99 K |
| 1715 | Turn off 3He pump |