Hi Eurenio,
what you describe has nothing to do with ice formation on the helium meter
but is merely something quite commonly observed during helium refills - the
helium splashes out of the transfer line directly onto the level detector,
which is in direct vicinity to the opening through which the helium is
injected into the magnet. You can experiment a bit with the direction the
flame diverter sprays to - try to keep it away from the detector which may
help a little with this effect.
The only notable exception are magnets whose helium level meter (supercon wire)
is far away from the refill port - for example essentially all Magnex/Varian/Agilent
magnets whose detector is "buried" inside the magnet. Because in these it is
impossible to replace the detector they all have two meters the helium display
can choose from.
Speaking of which - anyone who has such a magnet should observe the display
during refill mode - it should do a reading only of one of the two meters
- not both (they can be selected individually). If both are selected the helium
consumption is unnecessarily a tiny bit higher as each readout consumes some
helium (as it will do the same two readouts every 6 hours or so in normal mode).
Cheers
Bert
> Am 27.06.2025 um 15:35 schrieb Eugenio Alvarado via groups.io:
>
> Hi,
> We have a similar experience with an old Inova 400 and Oxford magnet.
> In our case, the helium level is read properly in slow mode, but when
> switched to fast mode it immediately jumps to 100% and stays there until
> the next day even after switching back to normal mode. So it is useless
> during a helium refill.
>
> Regards,
> Eugenio
>
> Eugenio Alvarado, Ph.D.
> NMR Facility Director
> Chemistry Department, room 3500.
> University of Michigan
> 930 N. University Ave.,
> Ann Arbor, MI 48109-1055.
> Voice: (734)-764-9924
> On 6/27/25 8:44 AM, foglein via groups.io wrote:
>> I've been lurking on this group for many years, but I believe this is
>> my first time asking a question.
>> We have an Oxford AS400 magnet as part of a Varian Mercuryplus system.
>> Starting with the last helium refill in April 2025, the helium level probe
>> no longer reads an accurate liquid helium level. When switched on for a
>> nitrogen fill, the helium level initially reads ~91-94%, and switching
>> to the 'fast' rate doesn't register a lower reading, which would be more
>> accurate to the actual level inside the magnet. Using historical data, I
>> am performing a helium refill today, so there is no fear of quenching.
>> Reading through the manual, I could not find a procedure for rectifying
>> this issue. I would appreciate anyone's recommendations for resolving this
>> issue, especially if you have experienced this issue yourself, and how
>> you resolved it.
>> Thanks in advance,
>> Jon
>>
>> --
>> Mr. Jonathan Foglein
>> Instrument Coordinator/
>> Chemical Hygiene Officer
>> Rowan University
>> Department of Chemistry & Biochemistry
>> Science Hall, Room 345
>> 201 Mullica Hill Road
>> Glassboro, NJ 08028
>>
>> Phone: 856-256-5456
>> Email: foglein_at_rowan.edu <mailto:foglein_at_rowan.edu>
>
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Received on Sat Jun 28 2025 - 06:06:10 MST