2020/09/16 (Wednesday)
- Lab in-person: Matt
- Virtual partner: Zach
| Setup | Run 73. DIB 1/3/4 → Stripline 43/48/41 → pi-filters 1/2/3 → Cable 3/1/2 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1)-master; DCRC33(2) → HV control. DCRCs off. Lead/poly shield erected (4 lead walls, 2 poly walls). |
|---|---|
| Status: | Warming up to deal with cryo problems: 1K Pot partial blockage, helium in IVC. Softened vacuum in cryostat jacket, mixture in dump, traps clean. MC/Still Heaters on @ 20/30 mW. 1K Pot and fridge valves closed. Main Bath boiled off, disconnected from recovery. |
| 1040 | MC(Cernox) = 220 K. Main Bath (G3) = 297 mbar+1atm |
todo:
- cryoclean mixture
- retape plastic covering over stripline elbow
- some time late in the day, start pumping out cryostat vacuum jacket
Plan is to begin cooling again tomorrow (LN2 transfer).
| 1200 | Matt arrives in lab |
|---|---|
| 1220 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.7% |
| 1225 | Increase V6 → 12.9% to restart flow |
| 1230 | Increase V6 → 13.0% to speed up flow |
| 1300 | Increase V6 → 13.1% to restart flow |
| 1310 | Increase V6 → 13.2% to speed up flow |
| 1320 | Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 580-840 mbar. Pump mixture to dump. Removed 3.9 mbar. Note: accidentally let a little out of this trap at 13:45, so this may be artificially low. |
| 1225 | Add duct tape to plastic covering stripline elbow to improve seal. (This is intended to reduce the amount of helium leaking in during a transfer.) |
| 1255 | Turn off MC and Still Heaters, we'll see if it makes any difference with the heating. 15 minutes later, looks like the rate of warming is unchanged. I'll leave the heaters off. |
| 1300 | MC(Cernox) = 225 K. The rate of warming toward room temperature implies tau=31 hours. This suggests that at 11 pm the MC will reach 243.8 K. Not as warm as we'd want, but presumably the 1K Pot is warmer. |
| 1345 | Screwed up while trying to start a second cryocleaning - let some mixture into Trap 1, which is now not in the bath. Pump that back to dump. Trap 1 is still sorta cold… Put Trap 1 back into bath while pumping it to dump. |
| 1355 | Start cryocleaning mixture through LN2 Cold Trap 2, V6 = 13.1% |
| 1400 | Increase V6 → 13.3% to restart flow |
| 1415 | Increase V6 → 13.4% to speed up flow |
| 1500 | Stop cleaning through Trap 2 after 65 min. G2 flow pressure was 595-775 mbar. Pump mixture to dump. Removed 32.5 mbar. |
| 1400 | Attempting to measure temperature near the 1K Pot. Inserted the lab thermometer probe into the LN2 transfer stick. The 1K Pot is about 31.5“ down from the port. Insert the stick to position the thermometer near the 1K Pot. Allow several minutes for temperature to stabilize. |
| 1410 | At a depth of 31.5” from the port (near the 1K Pot), lab thermometer reads -32.3 C = 241 K. MC reads 228 K, so at this point in the bath the temperature is 13 degrees warmer. But the 1K Pot in the IVC may be colder than this. |
| 1415 | Try moving the thermometer up 5“, to depth 26.5” below port. |
| 1410 | At a depth of 26.5“ from the port (5” higher than before), lab thermometer reads -30.0 C = 243 K. Let's suppose this same gradient exists in the IVC. The 1K Pot is 12.4“ higher than the MC. Then the 1K Pot would be about 5.7 K warmer then the MC. |
| 1430 | Matt leaves lab |
| 1500 | Matt Fritts body temperature = 97.7 F |
| 2120 | Matt enters lab |
| 2130 | MC(Cernox) = 241.6 K |
| 2130 | Check contents of warm LN2 Trap 1: 3.9 mbar. Pump out with Scroll Pump. Note: some gas was accidentally let out of this trap earlier so probably the amount of contaminants removed during the cleaning was higher. |
| 2145 | Lab thermometer is inserted into MB, 31.5” down from port (near 1K Pot): reads -20.6 C = 252.6 K. MC = 242.3 K. Difference 10.3 K, smaller difference than earlier. |
| 2145 | Check contents of warm LN2 Trap 2: 32.5 mbar. Pump out with Scroll Pump |
| 2240 | Check pressure in Cryostat Vacuum Jacket: 0.14 mbar. Start pumping out CVJ with Scroll Pump, then Turbo Pump. |
| 2240 | MC(Cernox) = 244.0 K. Lab thermometer in MB near 1K Pot = -19.0 C = 254.2 K |
| 2235 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.6% |
| 2245 | Increase V6 → 13.1% to restart flow |
| 2430 | Stop cleaning through Trap 1 after 115 min (though the flow probably stopped earlier than that). G2 flow pressure was 580-910 mbar. Pump mixture to dump. Removed 10.0 mbar. |