I would like to thank everyone for their helpful advice. I have included a
summary of the responses received. Fortunately, I have found another room for
the 300 MHz system. Thank you once again.
Cathy Lester
Summary
Cathy Lester-CC wrote:
> Dear colleagues,
>
> We are in the process of expanding our NMR lab and need to relocate our
> wide-bore (89mm) 300 MHz spectrometer. The only room that seems to be available
> is next to a freight elevator. We can place the magnet a distance of 18' from
> this elevator. I know this isn't a great idea, but in theory the elevator
> should be well outside of the 5 gauss line (which is 7.5'). I was wondering if
> I could receive some advice on this move. Does anyone have experience regarding
> magnets in close proximity of elevators? If I receive enough information, I may
> be able to lobby for a better room.
>
If solution-state experiments are to be performed, we would recommend
keeping the magnet outside the 1 Gauss line. On a 300/89 Oxford magnet the
1 Gauss line is 15.3'. Since you are at the limit of acceptable distance,
we would expect that any demanding cancellation experiment, would yield poor
results.
Read your group e-mail and wanted to add some two cents. There are two
issues regarding elevators, moving ferrous materials and electrical current.
Many elevators use large DC currents which, as you know, generate magnetic
fields. Your magnet needs to be a minimum of 30' from an elevator for
primarily electrical reasons, in our experience. Hope this helps!
I would not place your WideBore 300 that close to an elevator. The counter
weights and the elevator box itself will still effect your shims. If you
only perform routine solids you may not notice much difference but if you
want to do high resolution you may have a difficult time especially with
sensitive experiments (e.g.; NOE difference spectra). Slight changes in the
environment (A/C turning off/on, storm passing through, heavy metal objects
passing by) affect difference spectra so subtractions are trash. If you
will be running long experiments (2D or 3D), the change in shims may affect
the resolution enough to ruin the experiment. 18 feet is too close to an
elevator.
We have a 250 narrow-bore Oxford magnet. There are two elevators which are about
14' away from the magnet. We have about 80 NMR users on that instrument.
Elevators are bad news, no matter how close they are to the magnet. Best
case in point was the original work Bruker did on the digital lock in
Germany with an elevated train out side the building. The extra noise
(variation in the lock) will reduce the shim quality and overall spectral
quality, especially with a large bore magnet. It would be interesting if you
were to post the responses to your message for other to read.
be aware that not only the added iron of the supports for the elevator
but the movement of the elevator car plus the current field produced
when the elevator starts up. These items should be investigated somehow.
It depends on what you use the magnet for. If you are doing high
resolution type of measurements, you may experience fluctuations of the B0
field and/or shims to cause concern. On the other hand if you use this
magnet mainly for solid state or other applications where the highest
resolution/stability is not a major factor, then you may have no problem.
So make your own judgement based on what you use the instrument for. Wide
bore (89mm) magnets tend to experience more disturbances from external
sources than their narrow bore counterparts, because of their wider realm of
influence!
Not much help, but our wide-bore (89mm) 300 MHz MSL is twice as
far from a freight elevator and doesn't seem to mind.
We have a standard bore 400 Mhz Bruker DPX positioned about 5.5
metres from the chemistry department service elevator , we assumed
that we could get away with this.
Generally speaking we can for experiments / samples that don't
require extremely good resolution / lock stability. I can usually see
a slight 'kick' in the lock level every time someone uses the
elevator - it's a minor inconvenience unless some large lumps of
metal are being moved. For experiments like NOESY's I try to set them
running at the end of the day when there's less traffic in the
building - one researcher insisted on ( and got !) the elevator switched
off for a whole weekend whilst running an important experiment.
My preference would be to get as far away from elevators as possible
-but space restrictions here meant making the best of a bad job.
Hope this is useful info for you.
Have no direct experience with elevators in our lab, but some with
NMRFAM. They have (but about to move) a 500 that is about the same
distance from an elevator; when ever the elevator move, you can see
it directly on the lock. 2D data show the resulting, expected,
F1 noise. 5 gauss is defintely no the place you want to think
about for elevators; maybe 1 gauss. My memory suggests 25 feet,
from install manuals, but of course the distance would have to
be dependent on magnet type and strength.
Received on Wed Jun 07 2000 - 09:41:34 MST