[Hallb-engineering] Sniffer detector Dewar frozen
christo at jlab.org
Fri Aug 21 04:20:15 EDT 2009
At 10 pm last night the detector Dewar on the sniffer attempted to fill
but completely emptied the 50 l dewar while trying. The 50 l Dewar was
half full. I tried to remove the top hat with sensors to manually fill
it but it was stuck. There is a block of ice inside of the detector
Dewar holding the sensors! The same problem occurred last week but I
didn't have to remove the top hat at that time so didn't notice the ice.
Has anyone had this problem before? The only thing different now is that
the foam pad under the drip tray (below the top hat) is not installed. I
assumed (perhaps wrongly) that this was a only used as a spacer to keep
the old sensor away from the bottom of the Dewar. Could this be causing
it to condense more and drain water into the detector Dewar?
I ran through the remaining GN2 that was down there in an unsuccessful
attempt to thaw the ice and liberate the top hat. There is no more GN2
in the racks upstairs. I've ordered 3 more bottles. It may take all
weekend or longer to thaw the ice unless I'm successful chipping at it
with a needle tool. In the mean time I'll try to think of a way to
insulate the space between the bottom of the top hat and the top of the
Dewar. Maybe a soft foam donut.
More information about the Hallb-engineering