Hi Jim,
We have 22 or so magnets here in Utah, 12 supercons here in the
Chemistry building at 4620 feet altitude, 3 more supercons at
upper campus at 5000 feet, and 3 more at BYU, about 4900 feet,
and 3 more at Research Park, maybe at 5200 feet.
And if we have high boiloff, it (usually) means a weather front
is approaching... the speed of the gradient is the main factor
and they are fairly common and dramatic here. I really don't worry
about high boiloff unless it last longer that a day, especially
if several other magnets are also high.
As for high altitude,
All our magnets have very low field drift - much less than Oxford/
Varian spec. My personal theory is that LHe is colder here at this
altitude, just a bit below 4.2K, and the magnets like it better. One
of our very early 400 MHz Oxfords has not drifted measurably since
it was first energized in 1983; still same Z0 and the same basic
shims. Our newest 600 MHz widebore (installed last month) drifts
at 0.7 1H Hz per hour, well below the Oxford spec of 12.
Cheers, for what it's worth,
- Dennis
73, KK7SB
//
// Dennis Edwards
// edwards_at_chem.utah.edu
// (801) 581-4208
// (801) 949-2973 Cell
// (801) 581-8433 FAX
// UofUtah NMR Service
//
http://www.chem.utah.edu/staff/edwards/
// Servicing 7.9 GHz of NMR
//
> Date: Fri, 17 Oct 2003 09:24:20 -0400
> From: jim breeyear <jbreeyea_at_uvm.edu>
> To: ammrl <ammrl_at_chemnmr.colorado.edu>
> Subject: boil-off
> X-UUCD-MailScanner: Found to be clean
>
> Thanks to all for the comments and experiences with atmospheric
> pressure changes and boil-off.
> Pressure gradients arent usually that rapid or deep here in Vt.
> Curious, does anyone run a supercon at 5000 feet or higher. Mabye in
> Colorado?
>
> --
> My primary website: http://www.uvm.edu/~jbreeyea
> My alternate website: http://users.adelphia.net/~w1hrm/
> University of Vermont
> Chemistry Dept.
> website: http://www.uvm.edu/~jbreeyea
> voice: 802-656-0196
> fax: 802-656-8705
>
>
Received on Fri Oct 17 2003 - 14:42:09 MST