He fill

Graham, Lachlan (Lachlan.Graham@dbce.csiro.au)
Sat, 23 Mar 96 16:27:00 PST

Dear Colleagues,
We attempted a He fill on our BC 24/40 magnet last week but unfortunately
lost the helium or it did not collect satisfactorily. Bruker recommends 500
l for a coold down. Our vacuum in the OVC is ok at about 5x10^-7 torr when
we filled the nitrogen tank.
My questions are:
1. Is the 500 l He recommended by Bruker realistic.
2. Is a liquid nitrogen precool possible. I'm a bit concerned about getting
it out before putting the He. Possibly we could use room temp He gas to
blow it out and raise the temperature of the He tank a some degrees above
the boiling point of N2 to get rid of it.
3. Any hints or experiences of others with horizontal magnets would be
appreciated.

Thank you,
L.J.W. Graham