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2016/10/13 (Thursday)

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Status: LN2 transferred yesterday, in bath overnight. LN2 cold traps empty and cold.
0835 Remove Cf source from the IVC and return source to safe
0840 MC(Cernox) = 77 K and flat, IVC = 1.4 mbar. Sorb = 121 K, slowly increasing
0845 Begin scroll pumping, then turbo pumping, IVC
0850 Turbo pump = 54 nbar, IVC = 460 nbar
0910 Turbo pump = 14 nbar, IVC = 120 nbar
0915 77K electrical check with the following issues:
  • DIB3 qI feedback to chassis has high leakage, 26 nS
  • DIB4 SQUID bias B to return has high and somewhat unstable resistance, 90 kΩ (normal is 1-2 kΩ). Unfortunately this is a Side 1 channel, TES1.
    This is SQUET ST-3-10, last used on G106a DIB2 in Run 59

Also cross-channel checks:

DIB1 QET A-B-C = 700-900 kΩ, A,B,C-D = 0.4-0.7 nS. Note that pA,B,C are Side 1, pD is Side 2.
DIB3 QET B-C = 0.7 nS. Note pB is Side 2, pC is Side 1.
DIB4 QET C-D = 1300 kΩ, C,D-B = 0.4 nS. Note that pB is Side 1, pC,D are Side 2.
0920 Try pumping IVC with LD, signal is >500 pbarL/s, pretty high. Go back to turbopumping.
0945 Turbo pump = 8.6 nbar, IVC = 86 nbar
1010 Turbo pump = 7.4 nbar, IVC = 63 nbar
1020 Isolate turbopump, and switch to leak checker. Background leak rate stabilizes at 290 pbarL/s. Getting better. Switch back to pumping with turbopump.
1050 Turbo pump = 7.4 nbar, IVC = 86 nbar. Switch to leak checker. Background leak rate stabilizes at 190 pbarL/s. Switch back to pumping with turbopump.
1135 Switch to leak checker. Background leak rate stabilizes at 140 pbarL/s. Isolate leak checker to check IVC pressure. IVC = 74 nbar. Switch back to pumping with turbopump.
1213 Turbo pump = 6.3 nbar, IVC = 100 nbar. Switch to leak checker. Background leak rate stabilizes at 120 pbarL/s. Switch back to pumping with turbopump.
1254 Begin taking test series of data with signal generator on DCRC55 to look for trace glitches.
1305 Background leak rate = 99 pbarL/s. We just gotta do it. Commence LN2 blowout.
1310 Use blown out LN2 to fill LN2 cold trap full.
1400 Commence cryocleaning mixture through cold trap 1 in preparation for throughput test.
1405 LN2 blowout finished. Let hose thaw, and cease He gas flow through IGH. Leak rate dropped to 85 pbarL/s during blowout. No sign of leak.
1410 Pump and flush main bath with He gas.
1430 Cease cryocleaning mixture. Pump mix to dump.
1445 Pump out and backfill 1K Pot with He gas.
Will use July 12 procedure to perform throughput test:
  1. All mixture in dump, LN2 traps cold, condenser & still valves open (3He pump on - optional)
  2. Open V9, V13a, V12a+speedivalve, V3. Wait for G1 to be close to G2.
  3. Close V12a+speedivalve and V3, open V1
  4. monitor G1
1450 Throughput looks good. G1 reaches maximum of 660 mbar before Step 3, then falls to minimum of 105 mbar, then rises at 57 mbar/min. Same as Sept 15th. Leak rate drops from 77 pbarL/s to 76 pbarL/s during throughput test. No sign of leak from fridge lines.
1455 Pump mixture back to dump in preparation for cold trap cleaning.
1510 Commence LHe transfer (-1.0%). Open He recovery lines.
1515 Fill IVC with 4.6E-2 mbar of He exchange gas.
1520 Commence cryocleaning mixture through cold trap 1.
1600 MC(Cernox)/Sorb = 70/92 K
1630 MC(Cernox)/Sorb/1K Pot = 57/8.2/6.7 K, IVC = 7.4 μbar, MB = 8%
1700 MC(Cernox)/Sorb/1K Pot = 45/7.0/5.5 K, IVC = 6.3 μbar, MB = 2.5%. Previous bath level was maybe a spurious reading. 1K Pot and Sorb temperatures reached minima but then bounced back a bit higher, not sure whether that's related.
1730 MC(Cernox)/Sorb/1K Pot = 33/5.7/4.6 K, IVC = 1.4 μbar, MB = 33%
1755 Cease cryocleaning mix. Pump to dump.
1816 Had to switch He gas cylinder. Will order another new one tomorrow. Bath level at 66.4%.
1830 Cease LHe transfer (61.3%). The dewar must have run out of liquid just as I reintroduced He gas, so I mistook the lowering level for temporary boil off.
1835 MC (Cernox) = 12K. IVC = 630 nbar. Commence turbopumping on IVC.
Place Cf source on side of fridge at detector height.

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