Hi Wendy,
could you maybe try to find a way to upload a picture of that curious bottom
flange modification you mentioned? I have never seen anything like it and
it doesn't sound logical to me…
Normally, all Oxford magnets should have either a full (red) drop-off plate
mounted to the bottom plate or - at the very least - have a (also red!) pop-off
plate/valve at the bottom of the black vacuum valve (in this case, the valve
piston is hollow and will allow any overpressure to be vented through it).
If the bottom of the valve is black then it doesn't have any venting valve.
Maybe send a picture of the underside of the vacuum valve as well?
Seconding every word Bob wrote below otherwise!
Cheers
Bert
> Am 14.08.2024 um 18:25 schrieb Bob Berno <bberno_at_mcmaster.ca>:
>
> Hello Wendy,
>
> Years ago when we had a magnet that we suspected might quench, I was advised
> to remove not only the room temperature probe, but also the shim stack.
> If/when the magnet quenches, the bore of the magnet will get extremely cold,
> leading to considerable ice/condensation buildup. This is especially true
> when the quench leads to a loss of vacuum in the magnet can.
>
> Whether or not the bottom flange blows out when the magnet quenches, I would
> not want to subject the probe to the extreme temperature drop and resultant
> condensation. So I would definitely warm up and remove the cryoprobe.
>
> If you would still like to make periodic measurements, then you could do so
> with a room temperature probe.
>
> If you also remove the shim stack, then you won't be able to take any NMR
> measurements. It's up to you to determine if being able to take measurements
> is worth the risk to the shim stack electronics.
> NOTE: If you do decide to remove the shim stack, be sure to power down the
> shim controller - a.k.a. the BSMS rack - before doing so.
>
> For me, I would be inclined to leave the shim stack in, and load an RT probe.
> That way you can continue to monitor how the magnet is doing.
>
> Good luck,
> Bob.
>
> On 2024-08-14 11:32 a.m., Wendy Breyer via groups.io wrote:
>>
>>
>> Thanks, everyone, for the suggestions. I'm currently working through them
>> but I have some questions for those of you who may have had an old Oxford
>> magnet quench:
>>
>> Our magnet was retrofitted with special bolts at the magnet flange. I a m
>> not 100% certain but I believe this was done to allow the bottom plate of
>> the magnet to drop in the case of over-pressurization as would be expected
>> in a quench. I'm a bit concerned for our newish cryoprobe that is currently
>> installed... if the bottom plate drops, how forceful is it? Will it damage
>> the cryoprobe? Should I remove the cryoprobe ASAP because of the possibility
>> of damage? Unfortunately I have no idea how likely a quench is and how
>> forceful the dropped plate will be... Any advice or experience would be welcome!
>>
>> Thanks again,
>>
>> Wendy
>
> -- Dr. Bob Berno Manager, NMR Facility McMaster University, ABB-156 1280
> Main St. West Hamilton, ON L8S 4M1 T: 905-525-9140 x24158 or x24686
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