A high energy beta source would create such a gamma spectrum. Depending on the instrument and configuration, the x-ray peak would probably only be visible if the source is surrounded by lead or some other heavy metal. X-ray peaks would not necessarily be seen from steel encapsulation nor from similar or lighter atomic weight materials. If the source is a pure beta emitter, then a HPGe spectrum in the lab will look the same.
If the count-rate is excessive, the spectrum could look like you describe. I would also check the operability with a check source. Electronic noise could also create such a spectrum.
After checking out the instrument operability, I would suggest looking at a good spectrum taken at a low count-rate and comparing it to a good background spectrum. An approximate maximum beta energy can be determined (typically within a few hundred keV) and the possible isotopes can be narrowed down (but usually not identified).
There are also people on this list who are familiar all kinds of sources. You might try posting a description of the source to this list.
Brian Keele
Date: Thu, 01 Nov 2001 12:08:09 -0600
From: "Perrero, Daren" <
Perrero@IDNS.STATE.IL.US>
Subject: Spectral Analysis
This is definitely not my strong suite so any help here is appreciated. The
situation involves a field test using a portable MCA. Field readings give
dose rates of approximately 100 mr/h near contact and 10 mr/h at a foot from
a discrete source with no markings. However a limited time (approx 5 min)
NaI spectra out to 2.5 MeV does not show a discernible peak. What type of
nuclide could be producing these readings? If a beta emitter was here
wouldn't there at least be an x-ray peak produced from the cap!
sule material?
Eventually a lab quality spectra will be obtained and the mystery solved but
it would be nice to have some idea (or at least a couple of good guesses) of
what's being transported before it gets to the lab.
Daren Perrero
Health Physicist
Illinois Department of Nuclear Safety
(217) 785-9929
perrero@idns.state.il.us