Hi,
I'm not sure just what is going on. Today a user on our R2D2 magnet
was running a long low temp experiment, and after a few hours he
noticed a plume at the LN2 stack. Both LN2 and LHe were boiling off
at a greatly increased rate, though the LHe was quite a bit lower.
This didn't seem to be a quench, given the relatively lower LHe
boiloff, but the outer can was cold, and it was clear that something
is seriously wrong.
The only thing I could think of to do was to hook up a pump to the
dewar vacuum line and try to pump it down, though I would expect
that a softening of the vacuum would affect the LHe more than the
LN2. So far it has had no effect, though it has been running under
an hour at this point. We still have a magnet, but at these boiloff
rates it won't last very long.
Any ideas of what may have happened, and if there is any course of
action I should follow (aside from just letting it quench)?
(If nothing else this demonstrates the well-known rule that bad
things usually happen on Friday.)
Steve
--
Steve Philson philson_at_nmr.chem.umn.edu
Director NMR Lab 612-626-0297
Chemistry Dept. University of Minnesota
Received on Fri Nov 14 2003 - 17:18:35 MST