Hi,
During last several weeks something bad has been happening to our
Oxford/Spectrospin 300 MHz magnet. 1-5 times a day helium flow from the
magnet undergoes abrupt increases from 0.15 (normal readings) to more than 1.0
scfh. Then it drops to 0.4-0.5 scfh and remains stable at elevated level for
several hours. After that it returns to normal level. If I close the output of
the helium flow meter with a finger for a moment (probably creating some
excessive pressure), the elevated flow immediately returns to normal level and
remains normal for hours.
The nitrogen flow hasn't shown any dramatic changes compared to old good
times.
I replaced the helium flowmeter - it did not help. I disconnected the helium
level meter - same result. The room temperature remains constant (20C).
I would appreciate any ideas.
Alex
______________________________________________________________________
Alex Kitaygorodskiy Tel. 864-656-0611
Director, NMR Facility Fax 864-656-6613
Clemson University Alex_Kitaygorodskiy@quickmail.clemson.edu
Clemson, SC 29634-1905