Hi,
today we had a quench of a 26 year old 250 MHz oxford magnet.
After the quench helium evaporated for about 3 hours, the nitrogen can was empty, after refilling the nitrogen started immediately to evaporate.
This strongly looks like a vacuum break, which would be no special event for a 26 year old magnet.
Nevertheless there is an interesting observation, I am not able to understand.
Until friday last week the helium level was 60%. Until that time everything was as usual including the known evaporation rate. But beginning from
Friday .... no, no ... no increased helium consumption, that would be too easy. ;-)
Beginning from last friday, the measured helium level showed nearly no change. And yes, the sensor seems to be fine.
After the quench it shows 2%.
Knowing an explanation of this behaviour wouldn't change the world, nevertheless I would be very curious to get an idea, what happened.
I am able to add an old observation about 15 and 10 years ago. About 15 years ago I observed an
increase of the weekly helium consumption from 4 to 7% and 10 years ago this behaviour became reverted.
I think about some frozen oxygen/nitrogen diffusing through a not 100% perfect sealing. But thats only an idea.
Please excuse my somewhat questionable english.
Greetings
Rainer
Received on Tue Feb 11 2014 - 11:06:28 MST