Dear AMMRL members:
For the past 3 Helium fills (400 MHz) we couldn't get a complete fill.
After sighting liquid helium out of the transfer line I insert short stem
into magnet. A steady flow of helium gas plume from magnet slowed
considerably after some 20 minutes or so. We used to stop at the point
when the fill slowed. Last time I determined to wait as long as it takes
to fill the magnet. I tried to increase the flow of gas & raised and
lowered the transfer line into the Dewar to increase the fill rate. After 2
hours I gave up and stopped. The fill was only 73%.
As per the height chart on the Dewar, I had about 30L Helium to begin
with, but after I finished I had nothing.
I wonder whether I lost some Helium liquid from magnet because I
filled for a long time. How do we know if the Dewar is empty during a
fill?
We use to take only 30 minutes for a fill, but I was concerned about
low fills for the past 3 times and that's why I tried for a long time.
Wonder if there is a problem with the transfer line, or it is simply the
Dewar from our suppliers. Are there any extra fittings to assure a
smooth helium fill.
Appreciate your suggestions.
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Dr. Gopal subramaniam
Department of Chemistry & Biochemistry
Queens College, CUNY
Flushing, NY 11367
Tel: (718)-997-4123 FAX: (718)-997-5531
Received on Fri Mar 19 2004 - 12:45:11 MST