Dear Friends
I have been of the naive view so far that, when we either do a low
or a high temperature experiment, the shim currents should not change
that much on the RT shim coils. I am driven by the thinking that the
shim current boards basically are constant current sources such that,
even when the load resistance changes, as it will when the temperature
of the shim coil is far away from the ambient, they should be able to
regulate for the load change and maintain the current at the constant
value. Is this an erroneous understanding on my part? As long as the
current is constant, then the shim field values should also be constant.
I did hear a student complain about the need to change the shim
values very much when he was trying to get back to room temperature
after a low temperature data collection. He was working around -120
deg. C.
I will be obliged for your valued ideas on this.
sincerely
rajan
--
*_______________________________
Rajan K Paranji, Ph.D.
*NMR Facility Manager
Department of Chemistry
Room 65, Bagley Hall
Univeristy of Washington
*Seattle, WA 98105
ph: 206 685 2581
fax: 206 685 8665
email: paranji_at_chem.washington.edu
___________________________________*
Received on Mon Nov 24 2003 - 08:27:52 MST