Hi,
We have a ground-floor laboratory housing an actively-shielded 500 and an
800 MHz magnet. The pumped 800 is inside a vector shield.
The university will be constructing a steel and glass 'penthouse' on our
roof that will house air intake motors to augment the supply to the
building. This will involve lifting materials (steel beams, motors etc)
onto the roof above us, the construction, and eventually motors running.
As well, major demolition will be taking place in the adjacent laboratory
to remove some large metal beams and gut the room prior to making it into
a conventional chemistry lab.
The NMR lab is very well isolated from vibration by a thick floor that
housed paper milling equipment back in the day, and both magnets are on
anti-vibration legs. We have several concerns regarding the construction
and eventual running of the ventilation system.
One concern is whether the equipment once installed will have any
ill-effect on our day to day operation (lots of 3D biomolecular
experiments). Our feeling is probably not, there is basically a full story
between the top of the magnets and the existing roof, and in theory the
5-gauss limit of the 800 is well below the ceiling level. (This will be
measured).
More likely to pose some problems is the demolition and construction phase
of the project. I didn't manage to turn up too much previous
commentary. (if there is a good summary I've missed please let me know).
The main question is whether we can continue to collect reasonable data
during the construction, or will we have periods when it just isn't worth
running anything. There will be a crane lifting materials onto the roof
(this would be a matter of days) but then the time to construct the
penthouse (a few months).
The second potential for disruption is the demolition in the neighbouring
lab. The 5-gauss line of the 800 extends several feet into this room.
Movement of heavy equipment in that room I think will have some effect on
us. But this will not take too long.
The university also is considering installing iron sheets on the roof
above the 800 to be sure there is no stray field extending above into the
equipment room, and also along the wall where the 5-gauss line intrudes
into the neighbouring room. The question here is what the effect might be
on the 800 shims. Would we need to redo any cryoshims, or just reshim the
non-conducting ones to compensate. Do we need to worry about edge effects
depending on the size of the iron sheet?
We will be making sure that we minimize the ingress of metallic particles
by having double-door/clean-room style entrances erected.
Thanks for any input!
Tara
*********************************************
Dr. Tara Sprules
Quebec/Eastern Canada High Field NMR Facility
www.nmrlab.mcgill.ca
phone: (514) 398-1721
fax: (514) 398-8254
3420 University St., Rm 023
McGill University
Montreal, QC, H3A 2A7
*********************************************
Received on Mon Jan 27 2014 - 10:49:48 MST