2019/09/25 (Wednesday)
| Status: Started 1K Pot yesterday. Can't cool below 3 K, probably because of leak into IVC. | |
| 0920 | MC(Cernox)/Tower/Sorb = 3.16/3.5/4.0 K, G1(fridge) = 307 mbar, 1K Pot = 1.91 K / 45 mbar |
| 0920 | Turbo on IVC = 250 nbar. IVC = 16 μbar with pump valved out Leave pump valve closed to see if if creeps up. |
| 0925 | Fill LN2 cold trap |
| 0950 | IVC = 40 μbar |
| 0950 | MB = 39.6% |
| 1015 | IVC = 86 μbar |
| let's stop the 1K Pot and let the fridge warm back up to 4K | |
| 1020 | Close 1K Pot needle valve. 1K Pot pressure falls, temperature rises. Fridge pressure starts rising. Tower temperature is not responding as quickly. |
| 1025 | 1K Pot = 4.03 K / 0.36 mbar. Close 1K Pot speedivalve, leaving it essentially empty. Switch 4He pump outlet to Exhaust, close 1K Pot recovery system valve, turn off 4He pump. |
| 1030 | Tower → 4.1 K. G1(fridge) → 481 mbar. |
| 1030 | IVC = 120 μbar start pumping out IVC with turbo pump again. |
| 1100 | Tower/1K Pot/Sorb = 4.23/4.66/5.7 K, G1(fridge) = 523 mbar |
| 1145 | Tower/1K Pot/Sorb = 4.28/4.64/5.7 K, G1(fridge) = 531 mbar |
| 1145 | Put leak detector on IVC and valve out turbo pump. |
| 1145 | IVC = 3.1e-2 mbarL/s. |
| 1145 | Start pumping mixture from fridge to dump/Trap1. Condenser & Still valves, V1, V3 open, 3He pump on, V6 open to 12.8%, V13a & V9 open. When P1 starts falling open V6 further. |
| 1150 | IVC = 3.7e-2 mbarL/s. G1/P1 (fridge) = 2.6/0.6 mbar. |
| 1150 | IVC = 4.7e-2 mbarL/s. G1/P1 (fridge) = 1.3/0.04 mbar. |
| 1215 | IVC = 5.7e-2 mbarL/s. G1/P1 (fridge) = 1.2/0.02 mbar. |
| 1225 | IVC = 6.0e-2 mbarL/s. G1/P1 (fridge) = 1.4/0.017 mbar. |
| so again, looks like pumping out the fridge does not cause the IVC leak signal to decrease. So there's no leak from fridge to IVC. Must be from main bath to IVC. | |
| 1235 | Stop pumping out fridge, close Still and Condenser valves and V1. Pump cold LN2 Trap 1 contents to dump. |
| 1240 | Stop leak checking IVC and start pumping it out with the turbo pump again. |
| 1330 | Check DIB3 Feedback A at breakout box : 10 kOhm. The others read about 1.2 kOhm. This channel first showed problems at 77K, where it was reading 1.4 MOhm while the others read around 10 kOhm. |
|---|---|
| 1342 | Let's look at some SQUIDs at 4.25 K. Connect DIB1 to DCRC1, power it up and start MIDAS programs and zap DIB1 SQUIDs. |
| 1426 | DIB1PA SQUID is not responding to any changes in SQUID bias. Not sure what's wrong with it. Other channels look fine on this DIB. Stop SQUID tuning and shut down programs and DCRC. |
| 1434 | Check DIB1 PA SQUID bias / Feedback coil = 113 Ω / 1.26kΩ at the breakout box, similar to other channels. Maybe it's a DCRC issue? |
| 1435 | Connect DIB2 to DCRC1, power it up and start MIDAS programs and zap DIB2 SQUIDs. |
| 1440 | Again DIB2PA SQUID is not responding, but other channels look fine, this is probably a DCRC issue. Maybe it can't latch the test signal to PA FB or QET? It also looks like DCRC1 PB QET can't disconnect from the test signal. If the test signal is turned on, it shows up at the PB QET bias. |
| 1453 | Power down DCRC1. Disable DCRC1 and enable DCRC3 in ODB. Connect DCRC50 (aka DCRC3) to DIB1, start up programs, and zap DIB1 SQUIDs. Looks like DCRC3 can't connect a test signal to any channel. |
| 1534 | Power down DCRC3. Disable DCRC3 and enable DCRC4 in ODB. Connect DCRCX (aka DCRC4) to DIB1, start up programs, and zap DIB1 SQUIDs. All channels look good when using this DCRC. SQUID bias settings for DIB1 PB,PC,PD are similar when using DCRCs 55 and X, but the lockpoints are quite different. |
| Channel | DCRC | SQUID Bias | Modulation Depth (Vpp) | Lockpoint (V) |
|---|---|---|---|---|
| DIB1PA | 55 | - | - | - |
| DIB1PB | 55 | -68 | 0.127 | -2.6 |
| DIB1PC | 55 | -65 | 0.13 | -3.5 |
| DIB1PD | 55 | -84 | 0.146 | -2.3 |
| DIB1PA | X | -64 | 0.144 | -5.1 |
| DIB1PB | X | -68 | 0.134 | -4 |
| DIB1PC | X | -67 | 0.139 | -4.9 |
| DIB1PD | X | -85 | 0.149 | -5 |
| DIB2PA | 55 | - | - | - |
| DIB2PB | 55 | -83 | 0.144 | -2.2 |
| DIB2PC | 55 | -82 | 0.141 | -3.2 |
| DIB2PD | 55 | -85 | 0.17 | -1.9 |
| 1605 | Stop programs and power down DCRC. |
|---|---|
| 1628 | Turn on DCRC X attached to DIB2. Zap the squids |
| Channel | DCRC | SQUID Bias | Modulation Depth (Vpp) | Lockpoint (V) |
|---|---|---|---|---|
| DIB2PA | X | -95 | 0.164 | -4.5 |
| DIB2PB | X | -84 | 0.147 | -3.6 |
| DIB2PC | X | -91 | 0.178 | -5.1 |
| DIB2PD | X | -90 | 0.19 | -5 |
| 1651 | Power down DCRC X. Switch connection to DIB3, power on DCRC and zap squids. |
|---|
| Channel | DCRC | SQUID Bias | Modulation Depth (Vpp) | Lockpoint (V) |
|---|---|---|---|---|
| DIB3PA | X | -80 | 0.14 | -4.5 |
| DIB3PB | X | -65 | 0.148 | -3.6 |
| DIB3PC | X | -75 | 0.154 | -4.3 |
| DIB3PD | X | -75 | 0.104 | -4 |
| 1710 | DIB3PA was the channel that was reading a high feedback resistance at a low temperature electrical check, the channel appears to be working fine which is a good sign. |
|---|---|
| 1715 | Power down DCRC X. |