shimming AMX500
Nick E Burlinson (nick@unixg.ubc.ca)
Tue, 6 May 1997 16:25:31 -0700 (PDT)
Dear BUMMER's
When after a probe switch, we were not able to return to even marginal
resolution after entering the previous shim set and many hours of
tweeking the shims, we decided to clean the
magnet bore. The room temp shims were removed,everything cleaned
thoroughly,magnet bore,shims,sample intro tube etc. Our normal probe (
grad inverse BB ) was placed back in and after shimming for four days we
could still not get the lineshape sample down under 20 hz at the top of
the c13 sat. peaks.
We decided to look at the cryoshims. A nonspin water sample ( all shims =
zero) has a halfheight linewidth of 150 hz but more surprisingly the peak
has a "foot" on the right side of the base that is ~ 1500 hz long! Has
anyone had cryoshims this bad and still able to remove the inhomogen.
with the room temp. shims on an AMX500 Bruker magnet.
Regards,
Nick Burlinson
NMR Service Lab
Chemistry Dept
Univ. British Columbia
Vancouver B.C.
Canada
email nick@unixg.ubc.ca