Hi,
Thanks to everyone who offered suggestions as to what could be causing the
shims to go bad on our 40-year-old Oxford magnet.
Clemens Anklin and Dee Hua Huang both suggested that the problem could be
uneven flow out the exhaust ports on the Nitrogen can in the magnet.
Clemens noted that the uneven flow through the ports could tilt the Nitrogen
can which, in turn, could tilt the Helium can through the spacer rods.
This could result in a slight (but noticeable) change in magnet homogenization.
Dee Hua described the set-up he used on similar magnets to maintain a slight,
equal positive pressure on all three Nitrogen ports. After I enacted
his suggestions, the 3D shim values have held (2.5 weeks so far).
If anyone is still working with a ~40 year old Oxford magnet, please feel free
to contact me for details on the this very inexpensive fix.
Thanks again, especially Drs. Anklin and Huang!
Wendy
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Received on Mon Sep 16 2024 - 10:12:56 MST