2017/01/18 (Wednesday)
| Status: LN2 transfer yesterday, turbopumping IVC overnight. Small leak at top of stripline tube. LN2 traps clean. Mixture is in dump, fridge evacuated. | |
| 0905 | MC(Cernox) = 83 K, Sorb = 141 K, Turbopump = 3.0 nbar |
| 0915 | Begin cryocleaning mixture through Trap 2 |
| 0930 | Begin pumping on IVC with leak detector, valve out turbo pump. Leak reads around 250 pbarL/s. Worse than last run, even though we pumped out all night this time and last time we only pumped out a few hours. |
| 0940 | Perform electrical check at 83 K. Issues: |
- On DIB4, there appears to be a 60 nS (15 MΩ) short to chassis from the qInner wire between the feedback resistor, coupling capacitor, and FET gate. This could be either in the side coax or the FET card. (symptoms: chassis→qIfeedback = 15 nS, chassis→qIsource = 60 nS, chassis→qIdrain = 50 nS, qIfeedback→chassis = 18 nS, qIdrain→chassis = 0.1 nS, qIsource→chassis = 0.1 nS.
- On DIB3 there is a 26 nS short to chassis from qIfeedback
- On DIB1, LED1 seems to leak in the reverse direction at 309 kΩ. (This was seen at the detector tests too)
- cross-channel checks yield confusing results. Not sure whether I should trust measurements of conductivity through silicon at 83 K
| 1050 | Leak background = 250 pbarL/s Begin blowing out LN2 from main bath |
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| 1105 | Stop cryocleaning mixture, pump mixture back 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
| 1125 | Not good. Throughput is flat, < 0.1 mbar/min. G1 reached maximum 640 mbar before Step 3, then fell to minimum of 37 mbar. On Oct 13 last run, we got 57 mbar/min. |
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| No significant increase in leak signal either from LN2 blowout or from throughput test | |
| 1155 | Pump mixture back to dump. |
| 1155 | Remove LHe trap from bath to allow it to warm up. Maybe this trap was dirty. We'll try pumping it out. |
| 1200 | LN2 blowout seems to be finished. Leak signal has risen to 290 pbarL/s |
| 1230 | LHe cold trap is warm. Open v1. G1 rises from 1.8 to 5.9 mbar. So there was some stuff in there. |
| 1240 | Pump out LHe cold trap with scroll pump, through V1, V2, V7, V2a, V5a. Closed vent speedivalve and V4a first to isolate pumping lines from bath pressurization. |
| 1300 | Try throughput test again. Not good. G1 reaches max 640 mbar after step 3, then falls to 43 mbar minimum. Throughput < 0.1 mbar/min |
| 1310 | Pump out main bath with scroll pump. After about 8 minutes it falls below 1 mbar so it seems to be empty. |
| 1325 | Fill main bath with N2 gas |
| 1340 | Remove LN2 Trap 2 from bath to let it warm up |
| 1340 | Let 1.2 mbar He exchange gas into IVC. MC(Cernox) goes up from 83 K to 84.2 K and rising. Sorb goes up from 153 K to 163 K and rising. |
| 1345 | Pump mixture out of Trap 1 and fridge (condenser and still) back to dump. Dump(G2) = 796.9 mbar. Close V9 and turn off 3He pump. |
| 1400 | Let two tube-lengths of He gas into main bath vacuum jacket |
| 1445 | MC(Cernox) = 97 K, Sorb = 205 K, IVC = 1.6 mbar |
| 1545 | MC(Cernox) = 118 K, Sorb = max, >249 K, IVC = 2.2 mbar |
| at the current rate fridge will be room temperature by midnight. But probably the warming will slow down. By Newton's Law of Cooling (warming), at 8:45 am the MC should be at 274 K, just above freezing. |
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| 1630 | MC(Cernox) = 136 K, IVC = 2.5 mbar |