Ruth -
I haven't worked around R2D2 magnets for some time (an
understatement.!!), but the next thing that occurred to me is to
wonder if one of the RT shims or Z0 circuit is going into some sort
of oscillation, generating noise similar to a speaker coil, in the
bore. Verify by switching off the shims if possible (not just in
software), or switching off the console the next tiime you hear it.
Good luck.
- Alan Olson
At 5:55 PM -0500 12/11/03, Ruth Nalliah wrote:
>Yesterday after a nitrogen fill, and today during the first part of
>a helium fill, I noticed a strange hissing sound which appeared to
>be coming from our R2D2 magnet of our Varian Gemini 200 MHz
>instrument. It was a hissing sound with almost a reverberation,
>like either wind blowing through a tunnel or LN2 when it's just been
>put into a warm lab dewar. No plumes were coming from the stacks.
>My first instinct was to look around and see if it could be coming
>from the air handlers instead. Each time the "blowing" sound lasted
>probably less than a minute.
>
>In both cases, a follow-up check after the fact showed that helium
>and nitrogen boiloff rates were normal. Air flow to the spinner and
>the spinner rate was normal (after the fact). The lock signal was
>normal. The instrument does not have VT capability installed.
>
>The instrument (1990's vintage) was installed here in June by a
>Varian representative.
>
>Has anyone else heard this type of sound coming from their magnet?
>
>Ruth
>
>Ruth E. Nalliah, Ph.D.
>Huntington College
>Huntington, Indiana
>(260)359-4203
><mailto:rnalliah_at_huntington.edu>rnalliah_at_huntington.edu
>
--
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From Alan Olson, Instrument Engineer
National Institutes of Health, NINDS
MRI Research Facility
10 CENTER DR, Room B1D-69, MSC 1060
Bethesda, Maryland 20892-1060
Phone: 301 496 8139, FAX: 301 402 0119
e-mail: awo_at_helix.nih.gov, olsoncna_at_adelphia.net(Alan)
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Received on Fri Dec 12 2003 - 13:16:21 MST