Well, I see Rich is at work today...
Subject: Inova 500 (28 channel shims) homogeneity changes, lock level
and lineshape spontaneously vary greatly over span of minutes.
Tried so far:
Homogeneity comes and goes no matter whether PFG is hooked up or not.
RT shim supply fans are fine.
Anti-vibration table is steady.
Non-spinning doesn't fix anything.
Swapping Z0/Z1 board doesn't change anything.
Cleaning and re-inserting all the RT shim boards didn't help.
Evaluating on Sunday when bldg was empty (no human activity) didn't
help. (I was happy that the Provost saw me leaving work at 5 PM
yesterday. Nice to be seen by The Boss when you're working Sunday.)
What's next? After the Z0/Z1 board (slot 0) we have shim DAC boards
2, 3, 4, and 5 bearing respectively 6, 8, 8, and 4 gradients each.
Maybe one gradient DAC/register is misbehaving and pulling Z1 and Z2
way out of whack? Shim power supply?
I am out of ideas.
Bill
William C. Stevens, Ph.D. Director
Nuclear Magnetic Resonance Facility
Southern Illinois University
Carbondale, IL 62901-4405
618-453-6498 voice -6408 fax 521-9892 cell
http://opie.nmr.siu.edu
Received on Mon Jul 03 2006 - 17:58:35 MST