FW: Scintillation Spectroscopy

["Clement, Christopher" <clementc@aecl.ca>]

> ----------
> From: 	Huffman, Dale
> Sent: 	March 25, 1999 4:50 PM
> To: 	Clement, Christopher
> Subject: 	RE: Scintillation Spectroscopy
> 
> We observed this phenomenon as well during a particularly hot and humid
> time in the summer, before all of our heating/cooling systems were in
> place and took measures to fix it, which worked.  Also, another incident
> occured where "peak splitting" was observed caused by a ground loop
> between the detector and the steel housing for the lead castle.  We found
> the grounding problem by continuity testing.  That is why our dewar is now
> on the rubber mat and several things are wrapped in electrical tape, e.g.
> the inner lead ring nearest the detector head.
> 
> ----------
> From: 	Clement, Christopher
> Sent: 	25-Mar-99 1:42 PM
> To: 	Huffman, Dale
> Subject: 	FW: Scintillation Spectroscopy
> 
> 
> 
> ----------
> From: 	Bill Kendall[SMTP:KENDALL@nucusa.com]
> Reply To: 	radsafe@romulus.ehs.uiuc.edu
> Sent: 	March 25, 1999 2:41 PM
> To: 	Multiple recipients of list
> Subject: 	RE: Scintillation Spectroscopy
> 
> Another possibility is that the high voltage on the PMT is very high in
> which case the tube becomes very sensitive to changes in barometric
> pressure
> and the calibration shifts as you reported.
> 
> Of course, both temperature and pressure and other effects could be the
> culprit.
> 
> Bill Kendall
> kendall@nucuasa.com
> 
> -----Original Message-----
> From: Tom Gwise [mailto:gwise@SLAC.Stanford.EDU]
> Sent: Thursday, March 25, 1999 10:16 AM
> To: Multiple recipients of list
> Subject: Re: Question
> 
> 
> I believe the problem you describe is caused by temperature changes over
> the count time. I use a system almost identical to yours and I have had
> the
> same problem. Try to stabilize the temperature of the electronics. I would
> be interested in knowing how you resolve your problem. Please contact me
> at
> the address below if you would like to discuss my experiences with this
> system.
> 
> Tom
> 
> >Dear Colleagues!
> >Could somebody make clear for me the following question?
> >I am Dr.Yuriy B. Nabyvanets from National Yang Ming University, Taipei,
> >Taiwan. I investigate the contents of radionuclides (Cs-137 and gamma
> >emitting radionuclides from Th-232 series) in soil. I use the EG&G ORTEC
> >Nomad Plus Portable Spectroscopy System, HPGe Coaxial Detector System
> >(GEM Series) and Gamma Vision Software for gamma spectrum analysis.
> >About two months I had not any problems with my device and it worked
> >perfectly. But approximately 2 weeks ago I got some problems. As the
> >contents of radionuclides in soil samples rather low, I need 8 hours to
> >measure each sample.  And here approximately in 5 hours of measurements
> >I have become to notice that the spectrum of samples begins to change.
> >It means, that near to, for example, peak of K-40 (from the left side to
> >the region of low energies) occurs the second and third peaks. That
> >occurs also for peak of Cs-137 but in this case shift goes to the region
> >of high energies. It seems, that during measurements  energy calibration
> >varies. I check energy calibration every day and really peak of Cs-137
> >>from standard source changes location on a spectrum. The difference
> >sometimes reaches 10 KeV.
> >So, what the possible reason of this phenomenon? I hope for your help.
> >Sincerely  Yuriy B. Nabyvanets
> >************************************************************************
> >The RADSAFE Frequently Asked Questions list, archives and subscription
> >information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
> 
> 
> Thomas Gwise
> Operational Health Physics
> Stanford Linear Accelerator Center
> PO Box 4349     MS 84
> Stanford, CA 94309
> 650-926-4172
> 
> 
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> The RADSAFE Frequently Asked Questions list, archives and subscription
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> 
> 
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