drift rates revisited

Eric Enwall (eric-enwall@uoknor.edu)
Wed, 24 Jan 1996 15:40:00 -0800

I asked some time ago for information on drift rates for 600 magnets
(trying to decide what to spec) and promised a summary. I received only 3
responses. I thought there were a lot of these beasties up and running in
the membership, but maybe folks are not permitted to talk about them. In
any case the responses were for rates of 7.5, 4 and 0.6 Hz/hr. I did not
specify and am assuming that all reports were for proton signals.

One respondent emphasized that a simple drift spec is probably not adequate
for really protecting onself. It is possible to have one or more supercon
shim coils drifting as well as the main coil and this can make a magnet
nearly useless (e.g. if lineshape deteriorates enough in 12 hours.) My only
personal experience with this was in conjunction with a main field drift so
the one spec covered both. This is not necessarily so as my correspondent
described. At that point (my understanding is that,) they were at the mercy
of the vendor who indeed did attempt to solve the problem.

Thanks again to those folks who sent information.

--
Eric-Enwall@uoknor.edu
Department of Chemistry and Biochemistry, University of Oklahoma, Norman
Campus.  Norman Oklahoma 73019-0370
(405) 325-7571   (405) 325-2843  fax (405) 325-6111