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Re: relativity labs



I don't know of a source of "cheap" NaI detectors. If you find one, then
getting a Na-22 source gets you a positron emitter from whence you get
annihilation gammas. Good source of discussion about matter being
converted into "energy" and the fact that conservation of momentum
precludes the creation of one photon. Students seem to get a thrill
about annihilation and enjoy references to the starship Enterprise's
warp drives.

Another fun thing to do with NaI detectors is to wait until an
almost-dead-white-male (e.g. me) gets a thallium stress test. The
patient gets so hot that a NaI detector is saturated if held too close
and the spectrum is distorted due to pile up. One must back off some
distance to see that the isotope used emits just one strong peak.

Tim Sullivan
sullivan@kenyon.edu

Ben Crowell wrote:

Does anyone know of any good relativity labs for an
introductory course? Jackson refers to a lab with a
NaI detector to verify the relativistic energy-
momentum relationship, but I haven't yet made the
pilgrimage to the closest school that has the
journal it's described in. Other possibilities
that occur to me include observing pair production
by cosmic rays in a cloud chamber, or doing something
with GPS (GPS requires general relativity
corrections). Ideally I'd like something affordable
that could be done hands-on by six lab groups,
each with their own equipment, but I realize that's
asking a lot.

On a related note, has anyone bought and maintained
a NaI detector for undergraduate use? Can they
be gotten cheap via surplus? Is there
cheap ADC/histogramming software and
hardware for PC-compatibles?