1. Cryo Update Alan Bross MICE Tracker Phone Meeting September 8, 2006

2. Status  Essentially all the parts have arrived  We are still having problems with the brazing of the studs u Cracking of the invar envelop has caused leaks to develop u “Work-in-Progress”  It was decided to reassemble the system with the new cassette (112), MICE cassette #3 and reassemble but this time try to flow the indium ribbons that sits between the copper thermal links and the VLPC cassette invar envelop and do not attempt stud brazing for now. The flow was accomplished with heat from a heat gun and/or iron using a dummy cassette in the cassette space. u This process yielding promising results (visually) s Good apparent contact between the thermal link and the invar u It was decided to proceed to full assembly and then cooldown

3. Cooldown  From Russ u The cryostat now appears to be as cold as it is going to get. u I am a bit puzzled by the temperatures. u The upper thermal link is running a few Kelvin warmer and with more gradient than previous operations. s T4(stage 1) = 49.2 K and T3 (near envelope) = 58.6 K. The delta T across the link is 9.3 K now versus 7.6 K in Jan. 06 and 6.7 K in April 05. The temperature gradient indicates that the upper link is taking out 20% more heat (watts) than previous operating periods. –This is usually a GOOD sign! u The lower thermal link temperatures are 1.7 Kelvin warmer but have the same gradient as previous operations. s T1(stage 2) = 7.12 K and T2 (near envelope) = 7.26 K. The delta T = 0.14 K. For comparison in April 05, T1 = 5.27 K and T2 = 5.40 K. In Jan. 06, T1=5.40 K and T2 = 5.54 K.  7k is too warm for good operation (will be worse @ 60Hz)

4. Cooldown II

5. Cooldown III Won’t Make It

6. Next Step  READ OUT CASSETTE TEMPERATURES!  Maybe this will help illuminate what is going on  Possible problems include u Bad thermal link to the cryo-cooler head u Cryo-cooler malfunction u High heat leak in new cassette (112) u Bolts loosened u ????  This will not speed things up  And So It Goes