2018/04/19 (Thursday) · UMN CDMS Wiki archive

	Status: Warming up from 77K because leak from bath to IVC discovered. Mixture cleaned several times. Pumped on cryostat jacket overnight.
0906	MC(Cernox) = 264.7 K. Turbo pumping pressure = 8.6 nbar; cryostat vacuum jacket = 120 nbar with pump valved out.
1000	Drop main bath. It's kind of chilly, frosting up a little, so we put the plastic bag over it.
1005	Check warm LN2 Trap 1: 4.4 mbar. Pump out with scroll pump.

Cryocleaning log
date	trap	duration (minutes)	contaminants removed (mbar)
Apr 6	1	70	9.5
Apr 6	2	70	6.6
Apr 6	1	70	11.0
Apr 6-7	2	overnight, no circ, dump exposed to trap	12.8
Apr 7-9	1	overnight, no circ, pump exposed to trap	6.8
Apr 9	2	70	8.9
Apr 9	1	60	9.0
Apr 10	2	90	10.5
Apr 10	1	70	8.5
Apr 10	2	75	6.6
Apr 10	1	70	1.9
Apr 11	2	75	2.7
Apr 11	1	75	14.4
Apr 11	2	70	4.5
Apr 11	1	70	6.4
Apr 12	2	70	4.7
Apr 12	1	135	3.3
Apr 16	2	95	4.0
Apr 16	1	60	14.7
Apr 18	2	70	4.2
Apr 18	1	75	4.4

1235	Tighten screws of upper two seals of IVC. They can be tightened a little.
1240	Remove lower piece of IVC to redo seal.
1345	IVC screws mostly tightened. Begin pumping IVC with scroll pump.
1400	Start pumping IVC with turbo pump
1430	Turbo = 220 nbar. IVC = 14 μbar with pump valved out for 5 minutes.
1430	Start leak detector on IVC. Background about 22 pbarL/s.
1435	Squirt-test, no leak seen at IVC indium seals. Around 20 pbarL/s increase when squirting around the stripline tube elbow, particularly the KF flange just before the elbow.
1455	Check pressure in fridge lines: <0.3 mbar. Pump out with scroll pump.
1530	Raise main bath
1535	Check pressure in 1K Pot: P2 = 24 mbar. Pump out with scroll pump.
1545	Turbo = 86 nbar. IVC = 12 μbar with pump valved out for 5 minutes.
1600	Pump out main bath with scroll pump to <1 mbar on P2.
1605	With leak detector on IVC, let mixture from pump outlet through Trap 2 into fridge lines, both sides. Leak steady at 22 pbarL/s. So no leak from circulation lines to IVC.
1610	Pressurize main bath with helium to 323 mbar above 1atm on G3. After fully pressurized, IVC leak signal begins to slowly rise, 22→35 pbarL/s. Probably leaking out the top of the bath.
1610	Open v9 so that mixture in dump is also open to Trap 2 and fridge.
1615	Let 5.4 mbar He exchange gas into IVC
1615	Begin transferring LN2
1615	MC(Cernox) = 289.5 K, Sorb = >249 K (max), IVC = 5.4 mbar, G1 (fridge) = 594 mbar, Level resistor = 0.989 kΩ.
1620	Pause transfer out of concern that the hose might be clogged with ice. Let it warm up and dry out.
1630	Restart LN2 transfer
1635	Again transfer seems slow somehow. Dewar was just filled and is frosty, maybe it needs to be warmed up at the valve and dried out. Stop transfer again to warm things up.
1645	Restart LN2 transfer
1700	Dewar valve is completely open but LN2 transfer seems very slow. (We filled the cold trap bath with it earlier, so it worked ok then.) Hose is getting stiff and frosting up, and Tower temperature is slowly falling, but level resistor reading hasn't budged yet.
1700	MC(Cernox) = 285.2 K, Sorb = >249 K (max), IVC = 5.4 mbar, G1 (fridge) = 596 mbar, Level resistor = 0.992 kΩ.
1710	MC(Cernox) = 282.8 K, Sorb = >249 K (max), IVC = 4.6 mbar, G1 (fridge) = 596 mbar, Level resistor = 0.999 kΩ.
1715	MC(Cernox) = 280.0 K, Sorb = >249 K (max), IVC = 4.6 mbar, G1 (fridge) = 596 mbar, Level resistor = 1.003 kΩ.
1720	MC(Cernox) = 276.6 K, Sorb = >249 K (max), IVC = 4.6 mbar, G1 (fridge) = 596 mbar, Level resistor = 1.006 kΩ.
1725	MC(Cernox) = 271.5 K, Sorb = >249 K (max), IVC = 4.6 mbar, G1 (fridge) = 596 mbar, Level resistor = 1.010 kΩ.
1745	MC(Cernox) = 246.4 K, Sorb = >249 K (max), IVC = 3.4 mbar, G1 (fridge) = 596 mbar, Level resistor = 1.024 kΩ.
1810	MC(Cernox) = 210.2 K, Sorb = >249 K (max), IVC = 3.0 mbar, G1 (fridge) = 596 mbar, Level resistor = 1.052 kΩ.
1830	MC(Cernox) = 183.9 K, Level resistor = 1.092 kΩ.
1900	MC(Cernox) = 144.7 K, Level resistor = 1.206 kΩ.
1930	MC(Cernox) = 118.4 K, Level resistor = 1.280 kΩ.
1945	MC(Cernox) = 109.7 K, Level resistor = 1.300 kΩ.
2000	MC(Cernox) = 102.7 K, Level resistor = 1.312 kΩ.
2015	MC(Cernox) = 97.1 K, Level resistor = 1.320 kΩ.
2030	MC(Cernox) = 92.4 K, Level resistor = 1.325 kΩ.
2045	MC(Cernox) = 89.0 K, Level resistor = 1.329 kΩ.
2100	MC(Cernox) = 86.1 K, Level resistor = 1.332 kΩ.
2115	MC(Cernox) = 83.9 K, Level resistor = 1.334 kΩ.
2130	MC(Cernox) = 82.2 K, Level resistor = 1.334 kΩ.
2145	MC(Cernox) = 80.9 K, Level resistor = 1.335 kΩ.
2200	MC(Cernox) = 79.9 K, Level resistor = 1.336 kΩ.
2315	MC(Cernox) = 77.8 K, Sorb = 119.2 K, IVC = 1.4 mbar, G1 (fridge) = 589 mbar, Level resistor = 1.337 kΩ.
2317	Stop LN2 transfer. Put ping pong ball on main bath outlet.