Wednesday, March 6, 2013

Avoiding False Gamma Negatives

The experiment[1] I'll be working on this summer involves using a sodium iodide scintillator to detect gamma rays with an energy of around  318 keV emitted from the interior of a liquid helium cryostat.  In the event that a null result is achieved, (no gamma rays detected), I want to make sure that it's related to the phenomena we're researching and not due to our equipment.  To that end, one of my first experiments will be to place a gamma ray source in the cryostat.  Measurements will be taken using the scintillator to make sure that gammas of the expected energy can in fact penetrate the cryostat.

I found an excellent web site for deciding on a gamma ray source.  You can search gamma sources based on energy, half life, intensity and number of (spectral?) lines.  It turned up cesium 137 which looks like a good fit.  It emits a 283 keV gamma ray and it's used in academia and the oilfield, (see the cool truck below).  Being right in the middle of the oilfield here in TX, hopefully it will be easy to get a sample.



References:
1.  Proposal
https://docs.google.com/file/d/0B30APQ2sxrAYSWR5bkdwdFF3d28/edit?usp=sharing

2.  Gamma Sources
http://atom.kaeri.re.kr/cgi-bin/readgam?xmin=279.20&xmax=340.00&h=365&i=2&l=50

3.  Cesium 137
http://en.wikipedia.org/wiki/Cesium_137


Picture of the Day:
From 3/6/13



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