2022/07/29 (Friday)
- Lab in-personnel: Giulia, Matt
| Status | Run 76 in progress |
|---|---|
| Setup | Cables 2/3/1 → diverter/nothing/nothing → Side2-readout HV CONN 1/3/2 → HV 1(L)/2(R) → DCRC50(3)/DCRC55(1), DCRC33(2)→HV control, NaI trigger signal → DCRCX(4) Lead/poly shield fully assembled. Boron-filled socks covering NaI detectors. PuBe behind lead wall on West side of lead/poly shield. |
| Fridge failure four days ago, looks like an impedance blockage. Yesterday at 110 K the impedance blockage was gone. Pumping out cryostat vacuum jacket. Cryocleaned mixture twice yesterday. | |
| 0950 | Start cryocleaning mixture through LN2 Cold Trap 2, V6 = 12.3%. But, somehow mistakenly V13a was also opened, and V12a was opened partially. So some mixture is in warm LN2 Trap 1 (luckily it was pumped out yesterday) |
| 1005 | Close V12a and V13a. This traps some mixture in warm LN2 Trap 1. We'll want to pump that out at the end of the cleaning. |
| 1010 | MC = 162 K |
| 1040 | Increase V6 → 12.7% to restart flow |
| 1115 | Stop cleaning through Trap 2 after 85 min. G2 flow pressure was 550-630 mbar. Pump mixture to dump. Removed 6.0(5.0) mbar. |
| 1115 | Turbo on Cryostat Vacuum Jacket = 25 nbar. With Turbo valved out for 1 minute CVJ = 250 nbar |
| 1120 | Pump LN2 Trap 1 to dump (we mistakenly let some mixture into this trap too) |
| 1130 | Stop pumping CVJ |
| 1130 | Check pressure in IVC: 14 mbar |
| 1130 | Start pumping out IVC with Scroll pump. At < 0.1 mbar switch to Turbo pump |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 trap 2 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
| 1140 | Perform mixture throughput test at MC = 164 K using above procedure with 3He pump on. Let G1 rise to 553 mbar before Step 3, then it falls to 48 mbar and starts to rise. Throughput = 15.1 mbar/min. |
|---|---|
| It's difficult to say whether this is normal or somewhat low, since we only have benchmarks at 77K and 300K. But it seems pretty good. Higher than 300K standard, ~ 6 mbar/min | |
| 1145 | Check pressure in 1K Pot: off scale on P2, 0.06 atm on mechanical gauge. Pump out with Scroll Pump |
| 1155 | With 1K Pot speedivalve and needle valve closed, pump on Main Bath with scroll pump. Once P2 < 2 mbar, open 1K Pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 1 mbar on P2. |
| 1200 | 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. |
| 1205 | 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. |
| 1210 | Pressurize main bath and 1K Pot (both sides) with helium to 310 mbar+1atm on G3, then close 1K Pot speedivalve and needle valve. |
| 1245 | Check contents of warm LN2 Trap 2: base pressure 1.6 mbar, trap pressure 7.6 mbar. Pump out with Scroll pump. Final pressure 2.6 mbar. |
| 1305 | As on 2022 Mar 18, we will flow mixture through the fridge during LN2 cooldown. Let mixture from dump through cold LN2 Trap 1 to fridge, both sides. Then 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. Open V6 to 12.6%. |
| 1315 | P1(Condenser) → 0.40 mbar. |
| 1315 | Try closing V12a speedivalve. G1 falls as it should, showing we have throughput. Falls at 24.8 mbar/min. Open V12a speedivalve again. |
| 1320 | Turbo on IVC = 46 nbar. With Turbo valved out for 1 minute, IVC = 400 nbar. |
| 1320 | Let 5.4 mbar He exchange gas into IVC. (note this is what we put in at 300K, so since we're at 164 K this is significantly more gas.) |
| 1325 | MC(Cernox) = 164.7 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) = 668/737/0.7 mbar, Level resistor = 1.042 kΩ. |
| 1335 | Begin LN2 transfer. Dewar is low so it will probably run out. |
| 1350 | MC(Cernox) = 163.1 K, Sorb = >249 K (max), IVC = 4.6 mbar, G2/G1/P1 (circulation) = 669/735/2.8 mbar, Level resistor = 1.310 kΩ. |
| 1405 | MC(Cernox) = 141.1 K, Sorb = 220 K, IVC = 3.0 mbar, G2/G1/P1 (circulation) = 669/735/5.0 mbar, Level resistor = 1.270 kΩ. |
| 1405 | LN2 Dewar is empty, need to refill it. Transfer paused. |
| 1420 | MC(Cernox) = 125.2 K, Sorb = 186 K, IVC = 3.0 mbar, G2/G1/P1 (circulation) = 669/734/9.0 mbar, Level resistor = 1.277 kΩ. |
| 1430 | Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 47.7 mbar/min. Open V12a speedivalve again. |
| This throughput looks about right for this temperature. | |
| 1520 | MC(Cernox) = 94.5 K, Sorb = 138 K, IVC = 2.5 mbar, G2/G1/P1 (circulation) = 666/732/off-scale mbar, Level resistor = 1.247 kΩ. |
| 1525 | LN2 Dewar is refilled. Restart LN2 transfer. |
| 1530 | MC(Cernox) = 92.6 K, Sorb = 138 K, IVC = 2.5 mbar, G2/G1/P1 (circulation) = 666/732/off-scale mbar, Level resistor = 1.354 kΩ. |
| Level resistor is high, is transfer already finished? MC is lower than when we stopped last time, Sorb is a little higher. We've only been transferring for about 30 minutes, but of course much less will have boiled off than usual. | |
| 1540 | MC(Cernox) = 90.3 K, Sorb = 133 K, IVC = 2.5 mbar, G2/G1/P1 (circulation) = 665/731/off-scale mbar, Level resistor = 1.354 kΩ. |
| 1540 | Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 57.7 mbar/min. Open V12a speedivalve again. |
| 1545 | Stop LN2 transfer. Close LN2 Dewar valves. Pull out Level Resistor and put stopper in port. Put ping-pong ball on MB exhaust port. |
| 1545 | Close V6 and turn off 3He pump. |