2016/12/19 (Monday)
| Status: fridge at room temperature. Some helium has been added to the IVC. Turbo pumping main bath vacuum jacket overnight. 1K Pot needle valve is open. Mixture has been pumped out of LN2 trap, traps are at room temperature, still need to be pumped out. Mixture is in dump, fridge evacuated. | |
| 0825 | Turbo pump = 34 nbar, Main Bath vacuum jacket = 1.4 μbar. Stop pumping out main bath vacuum jacket. |
| 0845 | For some reason G1 has risen to 138 mbar overnight. Where is this leaking from? Could be Trap 2 - I checked the speedivalve from Trap 2 and it wasn't completely snug although it seemed essentially closed. Is it mixture?? Open v9 and turn on pump to push mixture into dump, get a reading… reads 770 mbar. |
| 0855 | G2 (Dump) = 771.5 mbar, Pbarometric = 30.35 inHg, Dump pressure (adjusted) = 786.1 mbar. G2 is still creeping up though |
| 1015 | G2 (Dump) = 779.5 mbar, Pbarometric = 30.33 inHg, Dump pressure (adjusted) = 793.4 mbar. This is about 4 mbar smaller than yesterday's dump measurement. It's possible that the leak to the G1 volume is from the mixture, not certain. If so then v4 or v5 would probably have to be leaky. |
| Looking carefully at G1, it seems its rate of increase got a little higher at around 8:40, i.e. when I started pumping from the pump to the dump. This would have pushed more gas into the dump, so it would support the idea that v4 (which connects the dump to the G1 volume) is leaking. On the other hand it is surprising that this makes much difference, because the dump pressure probably didn't change much. | |
| We'll do the most cautious thing: cool a LN2 trap, let the G1 gas into it to trap the air out of it, then pump remainder to dump. | |
| 1200 | Put Trap 1 in LN2 trap Dewar and fill bath with LN2 |
| 1223 | Lower MB into pit, close 1K needle valve. |
| 1235 | Open V12a+speedivalve to let the G1 gas into LN2 Cold Trap 1 (which is cold). Pressure falls very low, 147 mbar to 1.7 mbar. That's a hint that the G1 gas is air, not mixture. But we'd need to check the relative volume of the trap to the G1 section to be sure, maybe it's just the expansion of the gas. |
| 1240 | Open V5 to pump Trap 1 and G1 volume to dump. G1 falls to 0.5 mbar so at least some gas is being pulled out. But G2(dump) is not increasing noticeably. |
| 1250 | Erect mini clean room around fridge |
| 1300 | G2 has not increased, it has actually gone down (that's probably just variation in barometric pressure). So if there was mixture in the G1 volume, there wasn't much. Probably it was mostly air. If so, it either leaked in from the room or from the cold trap (whose speedivalve wasn't completely tight as I mentioned) - let's hope the latter. |
| 1305 | Stop pumping from Trap1/G1 to dump: close v12a+speedivalve and v5. G2(dump) = 779.9 mbar. Close v9, then turn off 3He pump. Then remove Trap 1 from LN2 bath to let it warm up. |
| 1323 | Fill IVC with ~1mbar N2. |
| 1330 | Use the HP LCR Meter to try to measure inductance of TES loop through breakout box. Use DIB1pA and connect to QET/QET return. Not sure the results make sense… Below are results in two measurement modes, parallel and series, showing the L and R results as a function of frequency setting. |
| LCR measurements for DCRC1pA | ||
|---|---|---|
| Parallel | ||
| f [kHz] | L [μH] | G [mS] |
| 40 | 7800 | 9.7 |
| 100 | 1500 | 9.4 |
| 200 | 540 | 8.6 |
| 400 | 380 | 8 |
| 1000 | -85 | 5.4 |
| 2000 | -17.9 | 9.7 |
| 4000 | 2.7 | 22.5 |
| 10000 | 1.75 | -0.9 |
| Series | ||
| f [kHz] | L [μH] | R [Ω] |
| 10 | 25 | 101 |
| 20 | 23 | 102 |
| 40 | 21 | 102 |
| 100 | 18.4 | 106 |
| 200 | 15.5 | 113 |
| 400 | 6.4 | 123 |
Since most of the voltage drop is across the shunt resistor it's hard to understand whether these measurements are meaningful. The resistance is roughly correct in both modes if you consider it to be the resistance of the stripline wires.
| 1345 | Open IVC, begin removing 4K stage |
|---|---|
| 1355 | 50 minutes after closing v5, G1 has drifted up to 3.3 mbar. Yesterday in the same amount of time G1 drifted up to 15 mbar. So it's not going up so fast. Maybe it really was that the Trap 2 speedivalve wasn't closed tightly enough. |
| 1405 | Si HV#4 (S101) detector arrives. No accelerometer included. Shipping vessel pressure gauge reads 8.2 PSI. (Note vessel is still very cold from its journey.) |