Hi Ammrlers
A few weeks back I posted a question about our Oxford 600 MHz magnet
that after 6 months was showing splitting of the lineshape sample during
unlocked drift tests.
I'd like to thank everyone for their responses, which were plenty.
For anyone interested a I have a brief summary of the responses below
(very brief) anyone further interested in all the responses can email me
for these.
Basically most people suggested that this effect was environmental
ranging from changes in temperature, pressure etc, to a faulty
electronic manostat (a very common suggestion), to magnetic DC pulses
from a copy machine.
I should have initially stressed that we had tried to exhaust all these
possibilities, including the installation of a weather station from
Varian.
Richard Shoemaker mentioned that they had noticed a steady, monotonic
drift in Z1 and drift in other shims as well. We had also noticed such a
feature and I guess this is what has tempted Oxford to com e back and
quench the magnet or recycle the shims. Alternatively, it was suggested
that after a period (of up to 6 months) this effect will settle down and
disappear.
For those interested Oxford are here now and are about halfway through
an elaborate shim cycle that involves cycling 5 of the shims with 53
steps. In total this is going to take about 35 hours and I am searching
for various types of narcotics to keep the poor guy from going mad...
Once again thanks for all your responses. For anyone interested I can
update how the magnet behaves after this major shim overhaul.
Cheers
Mike
--
Mike Osborne
Iric-Institut de Recherche en Immunovirologie et Cancérologie
Université de Montréal
2950 Chemin Polytechnique
Pavillon Marcelle-Coutu
Bureau S2-122
Montreal, Quebec, H3T 1J4
michael.osborne_at_umontreal.ca
Ph: (514) 343 6111 ext. 0534(NMR)/ 0595(Office)/ 0610(Wet lab)
Fax: (514) 343 7379
Received on Thu Jun 02 2005 - 16:54:54 MST