Bob Carr, Mike Seely and I showed up this morning to do the cooldown. The outside plumbing had been switched back to hydrogen (for the 2nd time) and the line between MV28 and the ballast tank was pumped and backfilled with helium (last week). Starting pressure was ~23 psig.
BUT, we had no wireless network signal in Hall C, because they upgraded our wireless network hardware yesterday, and the work was not finished. On top of that, the accelerator EPICS_CA_ADDR_LIST IP addresses had changed since we last ran and although we could read almost all of our epics variables, we couldn't write/change any. SO we could monitor but not change anything. Needless to say these two independent problems took awhile to track down. By noon, with help from Mike Memory on the wireless network problem and Matt Bickely on the IP problem, we had both problems fixed. Whew...
So, the pump and purge procedure was completed around 11:15. This was procedure A and B from the gas handling users guide.
Although I was nervous to start the cooldown while both deaf and dumb down there, we did anyway, since there appeared to be a fallback solution for the main IP problem that was preventing us from communicating to the target. SO we started. It went well, we started the transition to cold return around 13:40. We took 15 minutes to go from about 25% to 15% where all the action occurs. This was much faster than we normally do it, because cryo (Pete) has asked us to go faster to avoid letting the cold return piping warm up. We think going too fast generates a large thermal bump which can (has in the past) tripped the ESR. We did get a whopper of a thermal bump sent back to the ESR this time, the 15K supply temp shot up to 27K and did not recover back to the nominal 14 or 15K for 6 minutes. We thought this was cuz we went so fast.
Talking afterwards with Pete, he thinks it is because we went too slow, which surprised us because we normally try to take 45-60 minutes to do this in order to minimize the thermal bump to just 1 or 2K. Which is what we get if we take an hour. He advocates going to 30% in a single step next time, and then only taking 1 minute to close it the rest of the way. So next time we will do it this way and then sit down together with him to pick whichever method is best for the ESR.
OK, now back to the cooldown. By the way, we cooled down HYDROGEN.
Conditions at the end of the cool down are: pt3=11.6 psig, 19.00K +- 0.03K on our PID thermometer gt2 (tpi). 130W on the heater (heater power is now being calculated from V^2/R instead of I*V because we still have the whacky current readout from the power supply). The pump tach is noisy as hell, but the frequency meter in the hall is reading a steady 30.3 +- 0.05 Hz. The JT is at 27%. The target is in the out-of-beam position. The flyswatter is in the NOT IN position (ie, out). MV12 is closed, PV12 open, we are completely ready, and out of the hall.
Remaining problems: the electronics room is too hot and we are getting
temperature alarms from up there. It is very hot outside today (95F),
fans are on, but we are calling people to see if the situation can be
improved. Second, we are not reading the SMS vacuum or the beam current.
We think this is connected to the epics IP changes on the accelerator
side, and we need to get this into the IOC somehow, which we do not have
the passwords to do. Steve is working with the IOC on call (Sue is on
vacation) to try and resolve this. Rebooting... fixed vacuum, but still
working on the beam current.