Dear All,
We did liquid helium transfer for our Varian Mercury 300M spectrometer
on last Friday, and later we found that no lock signal was detected, and
no proton signal either. We examined the magnet field by an iron key and
a magnetic stir bar tied to a string. All these show that we lost magnet
field.
At the beginning of transfer, we observed the pressure rapidly reached
2 psi, and then a plume popped up from both vent tubes on nmr magnet
dewar. We quickly opened the vent valve on liquid helium dewar, and then
pressure went back to 0, and the plume disappeared. The whole process
only last a few seconds, and no trouble happened again in the following
transfer.
We thought that plume might be caused by blockage in transfer line by
liquid air, not by magnet quench, because it didn't last very long. And,
helium level was 40~50% before transfer (and became 100% after
transfer), usually quench happens when level is much lower than that.
However, our magnet field was unfortunately lost after helium transfer.
My questions are: has anyone experienced this kind of "weird quench"?
is it a real magnet quench or just blockage of transfer line? and, does
anybody know any companies other than the manufacturer can re-energize
the magnet field?
Thanks,
--
Chuanzhong Wang
Department of Chemistry and Biochemistry
University of Regina
3737 Wascana Parkway
Regina, Saskatchewan
CANADA S4S 0A2
Phone: (306)585-4275
Email: chuanzhong.wang_at_uregina.ca
Received on Tue Dec 23 2008 - 05:24:25 MST