2015/02/25
| 0114 | Exchange gas has been pumped out for roughly four hours. External pressure sensor reads 5.4E-3 mbar (its default broken value), so we cannot be sure of the actual IVC pressure. Continue pumping on IVC as we add external pressure to He dewar to add liquid to the bath. Current mixing chamber temperature at 22 K, Sorb temperature at 15 K. Increase in Sorb temperature may be due to decreasing temperature gradient across fridge. |
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| 0159 | Finish LHe transfer (90.5%). Current mixing chamber temperature at 21 K. |
| 1255 | External pressure sensor on IVC reads 1.2E-8mbar. Isolate IVC. G1: .2mbar, G2: 629mbar, P1: 0.22mbar. |
| 1300 | Start 1K pot. 1K pot gets down to 1.64K. When commencing condensation procedure, G1 and P1 increase when opening cold trap 1 speedivalve. Pump to dump to condense what is assumed to be missing mixture. |
| 1320 | G1: 0.6mbar, P1: 0.5mbar, G2: 658mbar. Close V6. |
| 1330 | With 658mbar in G2, condense 350mbar of mixture leaving 308mbar in dump. Commence condensation procedure. 1K pot at 1.73K. |
| 1415 | Stop 1K pot to perform IVC leak check. Mixing chamber temperature at 11.55K. Note: Main bath is full of LHe so cryopumping will occur. Background leak rate of 2.7E-9 mbarL/s. |
| Open to IVC, leak rate drops to 1.5E-9 mbarL/s. Isolate IVC, and restart 1K pot. | |
| 1430 | Close V9 with 308mbar left in dump. |
| 1435 | With mixing chamber temperature at 2.14K, adjust 1K pot and commence circulation. |
| 1516 | Mixing chamber drops to 697mK and begins rising. |
| 1545 | Fill LN2 cold trap full. |
| 1556 | Mixing chamber temperature still increasing. Unplug 1st Fischer connector with 1K pot currently at 1.51K. Mixing chamber temperature begins dropping immediately and reaches 856mK before beginning to rise again. |
| Mixing Chamber (H35) Temperature: Cooldown and Oscillations |
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| 1600 | Plug in 1st Fischer connector and switch to Still thermometer. Still settles at 977mK (4.56kΩ) then begins rising. Shows similar oscillations as (usual) Mixing Chamber thermometer on 2nd Fischer connector, with minimums at ~700mK and maximums at 1.1K. |
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| Still Thermometer Measurement |
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| 1632 | Switch to Cold Plate thermometer. Temperature initially drops to 790mK (5.05kΩ) and then continues dropping to minimum of 746mK. Rises and reaches maximums <950mK. Overall, shows oscillations, but seems to have smaller magnitude than other thermometers. |
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| Cold Plate Thermometer Measurement |
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| 1652 | Switch to RuOx thermometer. Temperature initially reads to 1.05K (-4.44kΩ) and drops to 921mK(Temperature does not plot in DAQ graph, only resistance). Temperature briefly rises, but then drops 886mK. Shows similar oscillations as other thermometers. Eventually passes above 1.19K. At this point, unplugging both Fischer connectors for ~1 minute does not appear to have effect on temperature fluctuations. |
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| 1705 | Briefly switching to Cold Plate thermometer shows temperature of 754mK and oscillating within previous range mentioned. Appears “normal.” |
| 1708 | Switch back to RuOx thermometer. Currently at 1.242K and still rising. |
| 1713 | RuOx thermometer finally drops after reaching 1.261K (-4.1045kΩ) and begins oscillating as before. |
| 1718 | Switch back to (usual) Mixing Chamber thermometer on 2nd Fischer connector, which reads ~825mK and rising. Unplug 1st Fischer connector. Temperature reaches 922mK and begins falling. |
| 1721 | Reaches minimum of 821mK and rises. Continues oscillations as before. |
| 1744 | Temperature peaks at 1.247K and oscillates around that temperature. |
| 1746 | Unplug 2nd Fischer connector and plug in 1st Fischer connector. Read Cold Plate thermometer. |
| 1813 | Cold Plate more stable than previously at ~770mK. |
| 1814 | Switch to Mixing Chamber thermometer on 1st Fischer connector. Starts at 1.254K (-4.1115kΩ) and continues rising. |
| 1817 | Mixing Chamber temperature rises to 1.2566K (-4.1092kΩ) then drops to 1.255K before rising again. |
| 1818 | Temperature rises to 1.259K. Plug in 2nd Fischer connector. (Usual) Mixing Chamber thermometer reads ~820mK and rises to ~855mK in ~30 seconds. |
| Mixing Chamber (H35) and COld Plate Temperature |
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| 1821 | (Usual) Mixing Chamber temperature still rising to 890mK. |
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| 1822 | Continues rising. Now at 920mK. Unplug both Fischer connectors and wait to see if fridge cools down. |
| 1854 | Plug in 2nd Fischer connector. (Usual) Mixing Chamber thermometer reads 856mK and rapidly rises. |
| Mixing Chamber Thermometer (H35) |
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| 1900 | Still rising. Currently at 1.097K. |
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| 1920 | Leave overnight with 1st Fischer connector unplugged but 2nd Fischer connector plugged in. |