[Hallb-engineering] torus cooldown

[David Kashy]

The Torus and Buffer dewar have been cooled. It went quite well.
Please check for dripping water in the hall as the cooldown lines warm 
up. They should be melting now as we are fully on cold return for both 
systems.

Also we need to check the final flows once the system has stabilized 
because I'm not convinced the distribution vacuums are as good as they 
were in the past...

Cryo is using our pressure sensor PI1028 to control the back pressure 
regulation valve EV6721B to keep constant back pressure. At present this 
signal is very noisy. Hopefully it will stabilize when the magnet is 
full of liquid. Please keep an eye on this too. We may need to find a spare.

Thanks
Dave