[3dem] Re: Slowly varying magnetic field

[Vladan Lucic]

It was a shaker in the room above the microscope that caused us some headache.

Vladan

On Thursday 04 June 2009 22:13:00 Ron Milligan wrote:
> I recall from years ago that those plug-in transformers that deliver
> low voltage for small electronics were a problem...
>
> Ron
>
> On Jun 4, 2009, at 12:57 PM, Amedee des Georges wrote:
> > Dear John,
> >
> > We have similar problems on our F30 here in New York, even though
> > our room is shielded and has an active field compensation system. We
> > haven't been able to find where the problem come from yet. If
> > anybody has had that problem and has solved it, we are also
> > interested in hearing about it.
> >
> > Amedee
> >
> >
> >
> >
> > Amedee des Georges
> > Howard Hughes Medical Institute
> > Columbia University Medical Center
> > Black Building Room 2-221
> > 630 West 168th Street
> > New York, NY 10032-3702
> > ad2720 at columbia.edu
> > Phone: 212-305-9524
> > Fax: 212-305-9500
> >
> > On Jun 4, 2009, at 3:00 PM, 3dem-request at ncmir.ucsd.edu wrote:
> >> Today's Topics:
> >>
> >>   1. Slowly varying magnetic fields (John Rubinstein, U of T)
> >>   2. Re: Slowly varying magnetic fields (Henning Stahlberg)
> >>
> >> From: "John Rubinstein, U of T" <john.rubinstein at utoronto.ca>
> >> Date: June 3, 2009 3:23:23 PM EDT
> >> To: 3dem at ncmir.ucsd.edu
> >> Subject: [3dem] Slowly varying magnetic fields
> >>
> >>
> >> Dear Colleagues,
> >>
> >> We recently identified a slow varying magnetic field (e.g. changes
> >> on the time scale of ~1 second) in our microscope room.  Looking at
> >> our FEI engineer's EMF meter, the minimal 60 Hz AC fields in the
> >> room appear to be carried on a (much larger) background that
> >> resembles the rising and falling of an ocean surface (but less
> >> regular).  This pattern would be quite pretty to look at if the
> >> fields did not cause random displacement of our electron beam of up
> >> to  ~5 mm on the phosphor screen at 600 kx magnification (Tecnai
> >> F20 operating at 200 kV).  These fields were not present 2 years
> >> ago when we installed the microscope.  We are not near any
> >> elevators and our room is on the 3rd floor so we know we are far
> >> from any subway tracks.  These "DC" fields are strongest as you go
> >> up in our room, but are stronger in our room than in the room above
> >> ours.  The only ductwork and wires in our ceiling are those we put
> >> in for our air conditioner and dehumidifier and the fields persist
> >> with this equipment turned off.  Naturally, I am concerned that
> >> something has changed far away in the building causing these
> >> effects and that the fields are being transmitted to our room via
> >> metal beams or rebar.
> >>
> >> Has anybody come across this sort of problem before, identified the
> >> source of the fields, and/or solved the problem in some way?  Any
> >> insight from experience would be greatly appreciated.
> >>
> >> Best regards,
> >> John
> >>
> >> --
> >> John Rubinstein
> >> Molecular Structure and Function Program
> >> The Hospital for Sick Children
> >> 555 University Avenue, Rm. 3330
> >> Toronto, ON
> >> Canada
> >> M5G 1X8
> >> Tel: (+001) 416-813-7255
> >> Fax: (+001) 416-813-5022
> >> www.sickkids.ca/research/rubinstein
> >>
> >>
> >>
> >>
> >>
> >>
> >> From: Henning Stahlberg <henning.stahlberg at unibas.ch>
> >> Date: June 3, 2009 3:33:36 PM EDT
> >> To: "John Rubinstein, U of T" <john.rubinstein at utoronto.ca>,
> >> 3dem at ncmir.ucsd.edu Subject: Re: [3dem] Slowly varying magnetic fields
> >>
> >>
> >> Hi John,
> >>
> >> Do you have NMR or MRI machines nearby?
> >>
> >> Henning.
> >>
> >>
> >> ___________________________________________________
> >>
> >> Henning Stahlberg
> >> Center for Cellular Imaging and Nanoanalytics (C-CINA)
> >> Structural Biology and Biophysics, Biozentrum,
> >> WRO-1058, Mattenstrasse 26
> >> University Basel, CH-4058 Basel, Switzerland
> >> Tel: +41 - 61 - 387 32 62 (office)
> >> Tel: +41 - 61 - 387 32 27 (administrative assistant)
> >> Fax: +41 - 61 - 387 39 86
> >> mailto:Henning.Stahlberg at unibas.ch
> >> Skype:henningstahlberg
> >> http://stahlberglab.org
> >> http://2dx.org
> >> ___________________________________________________
> >>
> >> On Jun 3, 2009, at 9:23 PM, John Rubinstein, U of T wrote:
> >>> Dear Colleagues,
> >>>
> >>> We recently identified a slow varying magnetic field (e.g. changes
> >>> on the time scale of ~1 second) in our microscope room.  Looking
> >>> at our FEI engineer's EMF meter, the minimal 60 Hz AC fields in
> >>> the room appear to be carried on a (much larger) background that
> >>> resembles the rising and falling of an ocean surface (but less
> >>> regular).  This pattern would be quite pretty to look at if the
> >>> fields did not cause random displacement of our electron beam of
> >>> up to  ~5 mm on the phosphor screen at 600 kx magnification
> >>> (Tecnai F20 operating at 200 kV).  These fields were not present 2
> >>> years ago when we installed the microscope.  We are not near any
> >>> elevators and our room is on the 3rd floor so we know we are far
> >>> from any subway tracks.  These "DC" fields are strongest as you go
> >>> up in our room, but are stronger in our room than in the room
> >>> above ours.  The only ductwork and wires in our ceiling are those
> >>> we put in for our air conditioner and dehumidifier and the fields
> >>> persist with this equipment turned off.  Naturally, I am concerned
> >>> that something has changed far away in the building causing these
> >>> effects and that the fields are being transmitted to our room via
> >>> metal beams or rebar.
> >>>
> >>> Has anybody come across this sort of problem before, identified
> >>> the source of the fields, and/or solved the problem in some way?
> >>> Any insight from experience would be greatly appreciated.
> >>>
> >>> Best regards,
> >>> John
> >>>
> >>> --
> >>> John Rubinstein
> >>> Molecular Structure and Function Program
> >>> The Hospital for Sick Children
> >>> 555 University Avenue, Rm. 3330
> >>> Toronto, ON
> >>> Canada
> >>> M5G 1X8
> >>> Tel: (+001) 416-813-7255
> >>> Fax: (+001) 416-813-5022
> >>> www.sickkids.ca/research/rubinstein
> >>>
> >>>
> >>> _______________________________________________
> >>> 3dem mailing list
> >>> 3dem at ncmir.ucsd.edu
> >>> https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem
> >>
> >> _______________________________________________
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> >
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