2019/05/18 (Saturday)
| Status | Blockage found, 4th attempt. Warming up. Cryostat vacuum jacket and IVC pumped out. Mix open to cold trap 1 overnight. |
|---|---|
| Setup | DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2 |
| 0945 | MC(Cernox)/Sorb = 260/>249 K. |
|---|---|
| 0950 | Pump mix to dump. Removed 5.4 mbar from Trap 1 overnight passive cleaning. |
| 1013 | Take trap 1 out of LN2 dewar to warm up. With 3He pump on and v9 open, G2 = 733.5 mbar in dump. |
| 1105 | LN2 Trap 1 is room temp. Check contents: 5.4-0.0 = 5.4 mbar on G1. Pump out with 4He pump from both sides of the trap by opening both V2 and V11A. |
| 1115 | Put trap 1 back in LN2 bath. Top off LN2 bath. |
| 1120 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.4% |
| 1130 | Increase V6→13.1% to restart flow. G2 runs away too fast, reaching 980 mbar before closing V6→12.0% |
| 1140 | Try to establish flow by slowly increasing V6. Now at V6=13.1% no flow, but at V6=13.2% G2 runs up really fast again, reaching 850 mbar before closing V6→0%. Let's start from scratch. |
| 1142 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.4% |
| 1147 | Slowly open V6 by 0.1% every 10 seconds to V6→12.9% to establish flow. Seems to be behaving now, but G2 still seemed to respond a little sluggishly (~10 s) to changing V6. |
| 1215 | Increase V6→13.0% to restart flow. |
| 1242 | Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 580-640 mbar during the main cleaning, and 580-980 mbar when initially trying to get flow established. Pump mixture to dump. Removed 5.9 mbar. |
| 1300 | Remove trap 1 from LN2 bath to warm. With 3He pump on and v9 open, G2 = 728.8 mbar in dump. |
| 1335 | LN2 Trap 1 is room temp. Check contents: 5.9-0.0 = 5.9 mbar on G1. Pump out with 4He pump from both sides of the trap by opening both V2 and V11A. |
| 1350 | Let's try to get to LN2 temp again this afternoon. |
| 1355 | Check pressure in condenser line (includes LHe cold trap) at G1 by opening V1. 0.7-0.4 = 0.3 mbar. Check pressure in fridge at condenser side on G1 by opening condenser valve. 1.0-0.7=0.3 mbar. Check pressure in fridge at still side on P1 by opening still gate valve: P1=0.02 mbar. Pump out both sides of fridge with scroll pump. |
| 1405 | G1/P1 = 0.9/0.032 mbar and flat. P1 is a little higher than before we started pumping like this, but this seems to be as flat as it will go with the scroll pump. |
| 1411 | Open dump to both sides of fridge lines via LN2 cold trap 1. |
| 1420 | 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. |
| 1430 | P2 < 1 mbar, close V1A, 1K Pot speedivalve. Open V5A, V2A, and the vent speedivalve evacuate the clear hose leading to the He gas line. Close off scroll pump. Flush MB and 1K pot with 0.24 bar (above 1 atm) of 4He gas. |
| 1433 | Do another pump and flush. Again, 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. |
| 1438 | P2 < 1 mbar, close off scroll pump. Pressurize MB and 1K pot (both speedivalve and needle valve open) with 180 mbar (above 1 atm) of 4He gas. Close 1K Pot needle valve and speedivalve. |
| 1440 | Turbo on IVC = 12 nbar. IVC = 340 nbar with pump valved out. |
| 1443 | Let 6.3 mbar He exchange gas into IVC (a little high, usual target is 5.4 mbar). |
| 1445 | MC(Cernox) = 261.7 K, Sorb = >249 K (max), IVC = 6.3 mbar, G1 (fridge) = 618 mbar, Level resistor = 0.996 kΩ |
| 1447 | Begin LN2 transfer. |
| 1455 | MC(Cernox) = 263.1 K, Sorb = >249 K (max), IVC = 6.3 mbar, G1 (fridge) = 618.3 mbar, Level resistor = 0.999 kΩ. DIB4 pD SQUID = 3.046 kΩ. |
| 1500 | We want to try periodic throughput tests while cooling down. We'll follow the standard throughput test procedure, so we first need all the mix in the dump. Close V12A + speedivalve and open V5 to pump mix from both sides of fridge to dump open to cold trap 1 |
| 1508 | G1/P1 = 2.4/2.2 mbar and flattening out. Close V1 and V5 |
| 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
| 1512 | Perform mixture throughput test at MC = 260 K using above procedure with 3He pump on. Let G1 rise to 575 mbar before Step 3, then it falls to 45 mbar, then rises. Throughput ~ 7.4 mbar/min. |
|---|---|
| 1515 | Open V12A +speedivalve and V3 to again expose mix to both sides of fridge via trap 1. |
| 1520 | MC(Cernox) = 251.7 K, Sorb = >249 K (max), IVC = 4.6 mbar, G1 (fridge) = 618.3 mbar, Level resistor = 1.018 kΩ. DIB4 pD SQUID = 2.631 kΩ. |
| 1525 | Let's try to get some mix to flow through the fridge as we cool. Open V6→12.4%. Then close V3. Now we have the circulation pump pulling at the Still side, it's output is open to the dump via V9 and cold trap 1. Cold trap 1 is open to the condenser side. |
| 1530 | G1/G2 = 620.4/574.2 mbar and flat. |
| 1530 | MC(Cernox) = 239.5 K, Sorb = >249 K (max), IVC = 4.0 mbar, G1 (fridge) = 620.4 mbar (new procedure), Level resistor = 1.027 kΩ. DIB4 pD SQUID = 2.407 kΩ. |
| 1533 | Try to start some flow by closing V13A and opening V6 a few clicks to V6→12.8%, where G2 starts to rise a little bit. Reopen V13A. Hopefully this will slowly draw mix through the fridge as we cool. |
| 1535 | G1/G2 = 664/617 mbar and rising slowly. |
| 1538 | DIB4 pD SQUID is bouncing all over the place, anywhere from 2-50 kΩ. Using manual kΩ range on Fluke 87V. |
| 1544 | G1/G2 = 675/626 mbar and starting to flatten out. Close V12A speedivalve and watch G1. G1 decreases at ~ 9.8 mbar/min and G2 remains flat. I think this indicates throughput? Reopen V12A speedivalve. |
| 1545 | MC(Cernox) = 217.6 K, Sorb = >249 K (max), IVC = 3.4 mbar, G1 (fridge) = 674.8 mbar (new procedure), Level resistor = 1.048 kΩ. DIB4 pD SQUID = 2.05 kΩ. |
| 1550 | G1/G2 = 674/626 mbar and flat. |
| 1555 | Close V12A speedivalve for a minute, then re-open it. G1 decreases at ~ 11.3 mbar/min and G2 remains flat. |
| 1600 | MC(Cernox) = 196.2 K, Sorb = >249 K (max), IVC = 3.0 mbar, G1 (fridge) = 672.4 mbar (new procedure), Level resistor = 1.084 kΩ. DIB4 pD SQUID = 2.2 kΩ, unstable. |
| 1610 | Close V12A speedivalve for a minute, then re-open it. G1 decreases at ~ 13.6 mbar/min and G2 remains flat. |
| 1615 | MC(Cernox) = 174.1 K, Sorb = >249 K (max), IVC = 3.0 mbar, G1 (fridge) = 670.4 mbar (new procedure), Level resistor = 1.120 kΩ. DIB4 pD SQUID = 1.8 kΩ |
| 1625 | Close V12A speedivalve for a minute, then re-open it. G1 decreases at ~ 15.9 mbar/min and G2 remains flat. |
| 1640 | Close V12A speedivalve for a minute, then re-open it. G1 decreases at ~ 19.1 mbar/min and G2 remains flat. |
| 1645 | MC(Cernox) = 136.8 K, Sorb = 235.4 K, IVC = 2.2 mbar, G1 (fridge) = 664.4 mbar (new procedure), Level resistor = 1.242 kΩ. DIB4 pD SQUID = 5.3 kΩ, unstable |
| 1655 | Close V12A speedivalve for a minute, then re-open it. G1 decreases at ~ 22.4 mbar/min and G2 remains flat. |
| 1700 | MC(Cernox) = 124.6 K, Sorb = 194.6 K, IVC = 2.2 mbar, G1 (fridge) = 660.6 mbar (new procedure), Level resistor = 1.278 kΩ. DIB4 pD SQUID = 4.0 kΩ, unstable |
| 1710 | Close V12A speedivalve for a minute, then re-open it. G1 decreases at ~ 24.3 mbar/min and G2 remains flat. |
| 1715 | MC(Cernox) = 115.2 K, Sorb = 166.6 K, IVC = 2.2 mbar, G1 (fridge) = 656.0 mbar (new procedure), Level resistor = 1.299 kΩ. DIB4 pD SQUID = 1.7 kΩ, unstable |
| 1718 | Let's try another throughput test. Close V6. Then close V12A + speedivalve and open V3 and V5 to pump out fridge lines from both sides to dump. |
| 1730 | G1/P1 = 2.1/3.2 mbar, Close V1 and V5 |
| 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
| 1735 | Perform mixture throughput test at MC = 115 K using above procedure with 3He pump on. Let G1 rise to 563 mbar before Step 3, then it falls to 67 mbar, then rises. Throughput = 33.7 mbar/min. Huzzah! |
|---|---|
| 1740 | Open V12A + speedivalve and V3. So we have V9, V13A, V12A + speedivalve, V1, and V3 open. This opens the dump to both sides of the fridge via cold trap 1. |
| 1740 | Cease LN2 transfer and put ping pong ball on main bath port |
| 1745 | MC(Cernox) = 102.3 K, Sorb = 138.7 K, IVC = 1.9 mbar, G1 (fridge) = 611.9 mbar, Level resistor = 1.28 kΩ. DIB4 pD SQUID = 1.43 kΩ |