2016/09/15 (Thursday)
| Status: LN2 in bath, turbopumping IVC overnight. No mixture in fridge, mixture cryocleaned twice yesterday. | |
| 0840 | Switch on leak detector |
| 0845 | MC(Cernox)/Sorb = 88/130 K. Turbo pressure = 2.5 nbar, IVC = 63 nbar. Better than Run 59 |
| Sorb temperature increasing slowly overnight, MC temperature decreasing | |
| 0855 | P2 (Trap 1, plus the pump line volume) = 20 mbar, contaminants from second cleaning last night. Pump this out with 4He pump. |
| 0905 | Start pumping on IVC with leak detector. After a few minutes leak signal falls to 100 pbarL/s. |
| 0910 | Stop pumping out Trap 1 and return trap to LN2 bath |
| 0915 | Open V13a, V12a+speedi, V1. This lets the mixture that's in the pump into both LN2 Cold Trap 1 and into the LHe cold trap (which is currently at LN2 temperature). IVC leak signal = 84 pbarL/s |
| 0920 | Turn on 3He pump to push mixture out of pump into trap and condenser line. G1/G2 = 480 mbar. Open V6 to 17% to clear out mixture from still pumping line. P1 falls from 800 to 7 μbar. Then close V6. |
| 0925 | Close V1, then open condenser speedivalve. This lets the small amount of mixture in the condenser line and LHe cold trap into the condenser. No change in leak signal, remains at around 83.5 pbarL/s. Slight increase in P1 (Still) from 7 to 9 μbar, may indicate that there is throughput. |
| 0930 | Close V12a+speedi, open V1. This lets the small amount of mixture in the G1 volume into the condenser. No change in leak signal. P1 (Still) pressure also stays flat. G1 falls from 510 to 350 mbar then falls more slowly, to 315 mbar after a few minutes. |
| 0935 | Close V13a, open V12a+speedi. This lets mixture from Trap 1 into condenser. G1 rises to 470 mbar. No change in leak signal (it's actually a bit smaller, 84 pbarL/s). P1 is rising very slowly, now at 12 μbar. |
| wait this is silly - I haven't opened the still gate valve. So we are not monitoring the still pressure on P1. | |
| 0940 | Open still gate valve. P1 immediately rises to 70 mbar. After a couple of minutes it rises above 500 mbar - this is above its range of accuracy. But it's a strong suggestion that there is throughput. |
| Meanwhile G1 (condenser) is falling at a rate of 5 mbar/min (currently at 455 mbar). Another indication of throughput, probably (could be just that the gas is cooling but likely it's throughput). | |
| 0945 | Open V13a. This lets mixture from pump outlet into condenser. G1 rises to 490 mbar. P1 (Still) = 1000 mbar (off scale). IVC leak = 82.5 pbarL/s. Nice. We seem to have fixed the leak from the condenser unit to the IVC. |
| 0955 | Close V13a and turn off 3He pump. This leaves some mix in the pump. We'll let the mixture already in the condenser and traps settle. G1 (condenser) = 470 mbar and is falling at about 5 mbar/min, so looks like there is still throughput. |
| 1010 | Begin blowing out LN2 from the cryostat. G3 = 430 mbar, kind of high, so adjust regulator to reduce this to 370 mbar. IVC leak = 81 pbarL/s. |
| note | We are using a modified LN2 blowout procedure. The Blow Out LN2 procedure has been rewritten. We no longer evacuate the helium gas line before pressurizing the main bath. Instead we put a blank at the end of the recovery line, then open the helium gas to the recovery line, then take off the blank to bleed the line with helium, then attach it to the top of the fridge to begin the blow out. |
| 1030 | IVC leak signal = 81 pbarL/s. |
| 1040 | G3 (main bath) starts to fall suddenly, blow out is almost finished. IVC leak signal = 80 pbarL/s, no leak seen. actually not sure whether the transfer tube was pushed all the way down |
| 1052 | Conducted electrical check. All looks good. PC ~10MΩ short to ground which was seen at room temp is now absent. |
| 1055 | No more LN2 is coming out of the rubber hose and it's mostly limp. Stop blowout. |
| 1100 | Put stopper on transfer stick. Start pumping out MB using scroll pump. Leak signal went up a little when we started pumping, to about 94 pbarL/s, then came down again. After 5 minutes P2 is down to 0.55 mbar so it looks like the MB is indeed empty. |
| 1110 | Stop pumping on MB. Flush MB with He gas. IVC leak rate remains stable, 84 pbarL/s. |
| 1125 | Fill LN2 cold trap bath |
| 1135 | G1 (condenser) is flat at 185 mbar. Close condenser valve. V1 and V12a+speedi are open - now open V13a and V9. This lets mix out of dump into LN2 Trap 1 and the LHe trap. G1/G2 → 745/675 mbar. |
| 1140 | Turn on 3He pump to push all of the mixture into the LN2 and LHe traps. G1/G2 → 765/695 mbar. |
| 1145 | Now that the mixture is a little cleaner, close V13a and open V5 to pump GHS contents to dump. |
| 1155 | Close V12a+speedi and V5, no longer pumping GHS to dump. Now open V6 to 13% to pump still contents to dump (still gate valve is open). Also open condenser valve and V1 to monitor condenser side pressure. G1 (condenser) = 7.6 mbar. P1 (still) has fallen to 26 μbar. |
| 1200 | Close still gate valve and open V3 to pump condenser contents to dump. When P1 falls to 100 μbar, open gate valve again. Now pumping both sides of fridge to dump. |
| Will use July 12 procedure to perform throughput test: |
- All mixture in dump, LN2 traps 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
| 1215 | Throughput looks good. G1 reaches maximum of 640 mbar before Step 3, then falls to minimum of 100 mbar, then rises at 50 mbar/min. Same as July 12. |
|---|---|
| 1230 | Open V12a+speedi and V3. Now mixture from dump is open to LN2 Trap 1 and both sides of the fridge. G1/G2 → 650/585 mbar. |
| 1300 | Remove LN2 transfer stick from MB and insert LHe transfer stick, close off end of LHe transfer stick. Pressurize MB again with helium gas, to 185 mbar overpressure on G3. Isolate MB, then open fully and reclose 1K Pot needle valve to flush it with helium. Then pump out 1K Pot through the speedivalve, to about 26 μbar. Close all valves and turn off scroll pump. |
| 1310 | Open the end of the LHe transfer stick for a couple of seconds to bleed the air out of it. Then open V1a to check the MB overpressure: currently G3 = 140 mbar. Close V1a again. |
| 1320 | IVC leak down to 81 pbarL/s. Turn off leak detector. |
| 1320 | MC (Cernox) = 87.4 K, has been slowly decreasing. Sorb = 139 K, has been rising since end of blowout. |
| 1414 | Commence LHe transfer (-1.0%). |
| 1415 | Add 46 μbar helium exchange gas to IVC. |
| 1445 | MC and Sorb both rose a bit when transfer began, now falling. G1/G2 slowly falling. MC(Cernox)/Sorb = 87.2/136.2 K, G1/G2 = 645/585 mbar |
| 1500 | MC(Cernox)/Sorb = 83.5/110.6 K, G1/G2 = 640/580 mbar, IVC = 14 μbar |
| 1515 | MC(Cernox)/Sorb = 78.0/81.6 K, G1/G2 = 625/570 mbar, IVC = 8.6 μbar |
| 1600 | MC(Cernox)/Sorb = 61.9/10.0 K, G1/G2 = 534/489 mbar, IVC = 1.6 μbar. LHe meter still shows -1.0%. 1K Pot thermometer falls into readable range. |
| 1610 | MC(Cernox)/Sorb/1K Pot = 58.6/6.0/4.8 K, G1/G2 = 513/469 mbar, IVC = 1.0 μbar. LHe meter still shows -1.0%. |
| 1635 | MC(Cernox)/Sorb/1K Pot = 52.2/5.5/4.37 K, G1/G2 = 494/451 mbar, IVC = 0.86 μbar. LHe meter = 0.1%. |
| 1755 | MC(Cernox)/1K Pot = 32.2/4.17 K, G1/G2 = 482/441 mbar, IVC = 0.63 μbar. LHe meter = 23.0%. |
| 1835 | MC(Cernox)/1K Pot = 24.3/4.13 K, G1/G2 = 475/435 mbar, IVC = 0.54 μbar. LHe meter = 55.6%. |
| 1905 | MC(Cernox)/1K Pot = 20.1/4.13 K, G1/G2 = 473/432 mbar, IVC = 0.54 μbar. LHe meter = 83.0%. |
| 1920 | Cease LHe transfer (93.2%). While undoing the transfer stick from the LHe storage dewar, it was discovered that the pressure release port had been open for the entire transfer. Perhaps this was the cause for the slow transfer. Or more probably it was just the slow cooldown. |
| 1922 | MC(Cernox)/1K Pot = 18.1/4.17 K, G1/G2 = 521/474 mbar, IVC = 0.86 μbar. |
| 1925 | Release pressure from Main Bath. Fill LN2 cold trap full. MC (Cernox) = 17.7K, but I have to go, so commence pumping out IVC exchange gas with turbopump. Pressure begins at 1.6E-3 mbar, but quickly drops to 1.4E-4 mbar. |