2019/03/05 (Tuesday)

Previous Day

Status:	Mixture has been cryocleaned several times a few days ago. Tower has been installed and IVC turbo pumping overnight. Need to clean mixture again and leak check IVC.
0955	Tighten IVC bottom screws one more time.
1000	Turbo on IVC = 40 nbar. IVC = 2200 nbar with pump valved out. Kinda high maybe. Compare e.g. 20190304 in Run 68, overnight reached 16 nbar pumping, 340 nbar not pumping. Could be slow pumpout due to taping up more holes.
1015	Put leak detector on IVC. Background = 3.4 pbarL/s. That's nice and low.
1025	Leak detector = 4.1 pbarL/s.
1030	Leak check top of fridge and IVC. No leaks seen.
1035	Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.7%
1040	Increase V6→13.0% to restart flow
1110	Raise main bath
1040	Increase V6→13.1% to speed up flow
1135	Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 570-860 mbar. Pump mixture to dump. Removed 7.0 mbar
1205	Start cryocleaning mixture through LN2 Cold Trap 2, V6 = 12.4%
1210	Increase V6→12.9% to restart flow
1250	Increase V6→13.0% to speed up flow
1305	Stop cleaning through Trap 2 after 60 min. G2 flow pressure was 570-660 mbar. Pump mixture to dump. Removed 16.2 mbar
1320	Trap 1 is warm. Check contents: 8.5-1.5 = 7.0 mbar on G1. Pump out with scroll pump.
1335	Check pressure in condenser line (includes LHe cold trap) at G1 by opening V1. 206 mbar. That's pretty high. Had this been looked at since the end of the last run? Check that all the KF flanges are tight. Pump out with scroll pump.
1340	Check pressure in fridge at condenser side on G1 by opening condenser valve and V1. About 1 mbar. Check pressure in fridge at still side on P1 by opening still gate valve: about 0.83 mbar. Pump out both sides with scroll pump.
1355	Open dump to both sides of fridge lines via LN2 cold trap 1.
1400	With 1K Pot speedivalve and needle valve closed, pump on Main bath with scroll pump. Once P2 < 100 mbar, open 1K pot speedivalve and needle valve (5 turns) to pump out 1K pot volume.
1410	P2 < 1 mbar, close V1A, 1K Pot speedivalve. (Don't have to pump out lines up to 4He gas line.) Close off scroll pump. Flush MB and 1K pot with 0.4 bar of 4He gas.
1415	Do another pump and flush. Again, with 1K Pot speedivalve and needle valve closed, pump on Main bath with scroll pump. Once P2 < 100 mbar, open 1K pot speedivalve and needle valve (5 turns) to pump out 1K pot volume.
1420	P2 < 1 mbar, close off scroll pump. Pressurize MB and 1K pot (both speedivalve and needle valve open) with 175 mbar (above 1 atm) of 4He gas. Close 1K Pot needle valve and speedivalve.
1440	Turbo on IVC = 34 nbar. IVC = 1600 nbar with pump valved out. Improved since this morning.
1450	Let 6.3 mbar He exchange gas into IVC (a little high, usual target is 5.4 mbar).
1450	MC(Cernox) = 297.1 K, Sorb = >249 K (max), IVC = 6.3 mbar, G1 (fridge) = 606 mbar, Level resistor = 0.984 kΩ
1505	Begin LN2 transfer
1515	MC(Cernox) = 296.8 K, Sorb = >249 K (max), IVC = 6.3 mbar, G1 (fridge) = 605 mbar, Level resistor = 0.985 kΩ
1530	MC(Cernox) = 291.2 K, Sorb = >249 K (max), IVC = 5.4 mbar, G1 (fridge) = 604 mbar, Level resistor = 1.001 kΩ
1545	MC(Cernox) = 274.8 K, Sorb = >249 K (max), IVC = 4.6 mbar, G1 (fridge) = 604 mbar, Level resistor = 1.004 kΩ
1600	MC(Cernox) = 255.2 K, Sorb = >249 K (max), IVC = 4.0 mbar, G1 (fridge) = 603.8 mbar, Level resistor = 1.018 kΩ
1615	MC(Cernox) = 228.7 K, Sorb = >249 K (max), IVC = 3.4 mbar, G1 (fridge) = 603.0 mbar, Level resistor = 1.056 kΩ
1730	MC(Cernox) = 128.6 K, Sorb = 171.3 K, IVC = 2.2 mbar, G1 (fridge) = 599.0 mbar, Level resistor = 1.270 kΩ
1740	Cease LN2 transfer and put ping pong ball on main bath port.

HPGe Measurements

1100	Setting up to make measurements of HPGe sensitivity as a function of source position. The point of this measurement is to characterize the active detector volume. Built a lead castle with a slot to produce a thin sheet of flux. The source will go in the lead slot and we'll roll the detector around on a wooden cart to illuminate different regions of it.

1300	Set up associated HPGe electronics as described here. Tried slowly turning up the HV bias to the recommended 3.5kV, but the current drawn from the HV supply spikes when approaching 2.2kV and the supply disables itself. Tried waiting ~30 min and repeating, but that did not help. Even so, we are able to see pulses and take spectra using the EasyMCA when biased at 2kV.

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