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T

Tim Auton

Jan 1, 1970
0
[magnetism and stuff]

You've probably most seen it before, but all this talk of huge magnets
brought to mind the most useful application we have yet found for
magnetic fields. I am referring, of course, to the levitation of
frogs.

http://www.hfml.sci.kun.nl/froglev.html


Tim
 
T

Terry Given

Jan 1, 1970
0
John Larkin said:
NMR is cool. You plop some water in a magnetic field and you get a
high-Q resonance that's precisely related to mag field strength, at
something like 4.3 KHz per gauss; the ratio is sort of a basic
property of the universe. Since we can measure this proton resonance
to 1 part in 1e9 or better, and since we can now measure frequency to
parts in something like 1e14, some pretty fine measurements can be
made. But, as I noted, this works best with high-field magnets which
are complex and very highly stressed, so aren't as stable as
lower-current stuff.

Here's a cute little magnet, complete with spiral staircase:

http://www.varianinc.com/cgi-bin/nav?products/nmr/spectromet/inova/900/index
&cid=KPJKJJLFN

This drifts less than 10 Hz/hour at 900 MHz, which is about 0.3 PPM
per day. You leave all your credit cards down the hall when you visit
this puppy.


John

yeeha, 21T - now thats what I call a magnet. I have looked at a couple of
SMES UPS (american superconductor? cant recall), but they were "only" around
10T

thanks
Terry
 
W

Watson A.Name \Watt Sun - the Dark Remover\

Jan 1, 1970
0
Terry Given wrote:

[snip]
yeeha, 21T - now thats what I call a magnet. I have looked at a couple of
SMES UPS (american superconductor? cant recall), but they were "only" around
10T

It's probably not a good idea to be near this with a pacemaker, either.
 
R

Rich Grise

Jan 1, 1970
0
I had a scan once - I actually don't know if it was NMR or CT, but it had
a real-time display that I could see. It was pretty freakin' cool watching
the contours of my organs as I trundled through the ring. At one point, the
tech went and did something in the control room for a few minutes, and I
was just lying there, but the monitor was still on. It was kinda fun rolling
my stomach and watching my organs move around.

Barium Sulfate suspension makes a great lubricant, by the way.

Cheers!
Rich
 
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