Dear AMMRLers,
[[[ the original email: One question posed by one faculty here at
Princeton is whether it would be possible to place an EPR (a Bruker EMX
model, 1.5T) close to the NMR's 300 and 400. We are particularly
interested in knowing if the scanning field would interfere with NMR
operation. Does anyone have any experience with this situation? ]]]
Many thanks to this wonderful list and to other helpful people, in
particular to Chris Rithner, Chuck Hanson, Robert J. Dick, Razvan
Teodorescu, Alexei Tyryshkin, David G. Bray, Guy Daelen, Jeff Simpson,
Jeff Walton, Manfred Philipp, Piotr Dobrowolski, Ralph Flachsbart, and Dave Scott.
Here is the compilation of the emails exchanged with the EPR
Spectroscopist at Princeton, with the Bruker EPR staff, and
received from AMMRL. I interpreted the question as a very specific
situation; as it turns out from a recent request, it is not as rare as I
initially thought, and I decided to post a summary to the list.
To answer the question about EPR field sweeping: the major problem seems
to run the NMRs unlocked, which is rarely the case with the 300/400. And even
in this scenario, the EPR run could be planned until the unlocked NMR run
is finished.
The position of the EPR magnet is surely a constraint. It will depend on
how heavy the magnet is, and how far it is positioned with respect to the
NMRs. The magnet weighs > 1,000 lbs, and our NMR shims will be affected,
and will need adjustments. I am sure that our cryo shims will be okay, but
the RTs will change. I've also received one NMR/EPR lab design, the
Bruker's facility planning manual, and other related info. Let me know if
you want them to be emailed to you.
Once more, thanks to all,
Carlos
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Carlos R. N. Pacheco, Ph.D. - NMR Spectroscopist
Princeton University/Chemistry
Frick Lab, Washington Road
Princeton, NJ 08544-1009
Phone: (609)258-1633; Fax: (609)258-6746
E-mail: cpacheco_at_Princeton.edu; http://www.princeton.edu/~nmr
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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(Princeton) I would personally vote for having all the EPR spectrometers,
including the new EMX, at one place or at least at close locations. This
way it will be easier to track them and to maintain as necessary. Also many parts,
including resonators and cryostats, are shared among the spectrometers and
moving them all the way to Frick and then back to Hoyt is certainly not a
good idea. There is a room next to B10 which is currently empty. I think
it was used as a photo lab. I do not know if Department has any plans for
this room, but this would be an ideal location for the new EMX
spectrometer.
------------------------------------------------------------------------
(Princeton) I do not know the answer: I guess each magnet has its "5
gauss" line and it should be documented somewhere. I do not have this number but can
assume that people at Bruker might know it. Another concern is a scanning
magnetic field which might have much stronger effect and require a longer
distance to not affect NMR field. I can imagine that the final answer will
depend also on pickup characteristics and dimensions of the
superconducting coils in your NMR magnet and its position with respect to
the scanning electromagnet, e.g. along or perpendicular to the magnet
axis. I would recommend contacting Ralph Weber or Bob Dick: they might
have already the experience.
------------------------------------------------------------------------
- At Lehman College we have an old Varian E-line ESR
spectrometer within at about 15 feet of the can of a new Bruker 300 MHz
machine. We have experienced no problems.
------------------------------------------------------------------------
-- Our EMX (weaker electromagnet) is about 15 feet from an
unshielded 500 MHz NMR. We have no problem with interference. Below is the
blurb from the web.
The DCIF houses a recently modernized Bruker EMX spectrometer outfitted
with 13" magnets, an ER 4102ST cavity and a newly upgraded Gunn diode
microwave source producing X-band (8-10 GHz) radiation. Optional
accessories include Q-band (35 GHz) and W-band (94 GHz) bridges, and a
cryo-cooled cavity for low temperature experiments. A recent acquisition
is the purchase of a recently developed high-sensitivity cavity. The
instrument is controlled with a Widows 2K based Intel Pentium III Process
Chemists running the Bruker Win-EPR Acquisition software. The Bruker
Win-EPR and
SimFonia software packages are also available for off-line data
processing.
------------------------------------------------------------------------
- When I was at MIT we sited a Bruker EMX EPR (probably about the
same as yours) within about 15-20' of a 500 magnet. There is so much iron
in the EPR magnet that all the field lines stayed within the EPR magnet
(the magnet weighed about 5040 lbs, as I recall). Check the weight of
your EPR magnet to determine if you have the same amount of iron to keep
the flux lines away from your NMR magnet. If you don't know the weight of
the magnet, just look at it and decide if it's one of those ones that is
only about 3' tall or one of the ones that is closer to 5' tall. If it is
5' tall, then it is the heavy one and you should be fine.
------------------------------------------------------------------------
- We keep our EMX outside the 2G line off-axis and "as far away as
possible" on axis. We did the experiment years ago and found that the EPR would
cause a field bounce on the NMR (unlocked). Not a big concern for routine
NMR but of more concern for experiments that run unlocked and possibly
(don't know for sure) experiments that are quite sensitive to little t1
noise induced by magnet instability, e.g., noesy and roesy.
------------------------------------------------------------------------
- About 10 years ago we had an epr within 12 feet of a 400.
Scanning the field didn't have any effect when the 400 was locked, but did
shift the unlocked spectrum. This subject came up in ammrl (probably pre
archive), and I posted the following. Can't repeat the measurement
because the epr moved to make room for another magnet. Its 200 yards away
now.
Couldn't resist Charlie's challenge...........
The center or our ER-200D magnet is 3.9M from the center of our 400MHz/52
DRX. Running unlocked and increasing CF on the ER-200 (X Band 9GHZ) from
40 to 4540 gauss did increase the acetone resonance (10% CHCL3 in
d6-acetone) by 0.93Hz. Three measurements at each field, bounced the epr
twice, 0.12Hz/point. An intermediate value (2040 gauss) increased the
acetone resonance by .33Hz (one measurement). Running locked, there was no
difference (0Hz) between low and high field. This surprised me because the
fields are orthogonal, but guess that those vectors still add :).
Fortunately?? our epr isn't used very often :(, we're usually locked, and
its a really heavy piece of metal with nowhere else to go.
------------------------------------------------
- I don't think it will. This is an electromagnet (if not disregard
this) which means the stray fields will be contained within the yoke.
You should keep it outside the 5 Gauss line and as far away as is
practical, but that is because it's a huge hunk of iron, not because
the sweep. Depending on how close you put it, you NMR shim files may not
be useful any more, and if real close, possibly the cryo shim may need to
be redone.
------------------------------------------------
I think the Magnet that is coming with your EMX spectrometer has a 6" pole
face and with the PS that comes with it only goes to 6 kG. This means the
5 G line does not extend much farther than the magnet. Attached is the
magnetic field map of a 10" magnet, a much bigger magnet.
----------------------------------------
A facility planning manual is included below for your use. I have also
included a magnetic field map.
----------------------------
1500 lbs if it is the 6" magnet. I don't know about the effect on the
shims.
---------------------------------------------------------------------------------
We had a MSL400 close to EPR, 4 meters between the magnets; no problem the
external field of an iron magnet is very small.
---------------------------------------------------------------------------------
I talked with Ralph Weber by phone yesterday and also about the problem of
having scanning magnet close to the NMR magnets. Later on Ralph sent me
the info (see his message below and also files attached) of how it has
been arranged in one facility. Ralph was suggesting to contact to Bob Dick
(sorry do not remember his email but will find out and send it to you
later) for all the details since he is a person in charge for planning the
facilities.
##################################################
> The EPR will indeed put out changing magnetic stray fields during
ramping-up and down. Depending on the proximity and orientation of the
systems, depending on the type of NMR magnets (shielded vs. non-shielded,
and brand name) and depending on the presence and quality of the NMR lock,
these small field changes - in the order of a few mG to tens of mG - may
or may not be harmful.
>
> We did some measurements in Bldg 1 many years ago prior to the
installation of a 500WB US NMR and of a EPR machine at BU Medical School
(Jim Hamilton).
>
> At BU they ended up with the two systems sited as shown attached.
Please notice the EPR magnet orientation versus the location of the NMR
magnet. I recall this was chosen to minimize the magnetic stray fields
produced by the EPR magnet at the NMR magnet location.
------------------------
Our Bruker ESP 300E is located about 6 yards from 400 MHz Bruker ARX and
is in another room. Both instruments can be quite busy. We have never
noticed any interference. I have no idea how close can it be.maybe Bruker
can tell you.
Received on Mon Nov 28 2005 - 19:59:24 MST