Re: Genie PC Question

[Judd Sills <sillsj@GAT.COM>]

At 10:08 AM 4/17/97 -0500, you wrote:
>Radsafers,
>
>I recently setup a HPGe Spec system using GeniePC as the program to perform
>gamma spectrometry analysis.  The problem that I am running into is that
>when I perform a Nuclide Identification Report of a gamma spectrum, it will
>list activities for both energies of a nuclide. 
>
>For example, Co-60 has two energies of 1173.22 keV and 1332.49 keV.  Genie
>PC will show an activity for the 1173.22 keV peak as 2.86E-1 uCi/g and for
>1332.49 keV as 2.855E-1 uCi/g.
>
>Does anyone have any suggestions on how to fix that (if there is a way) or
>which activity do you use to make a report.  I setting up this equipment
>mostly for NORM analysis.
>
>Thanks for your help,
>
>Jason
>
>----------------------------------------------------------------------------
>-------
>Jason Armstrong
>Sr. Radiation Physicist
>Halliburton Technology Center
>PO Drawer 1431, Mail Stop 0454
>Duncan, OK  73533
>(405) 251-2205
>jarmstrong@halnet.com
>
>
As a user of this system, my general approach is to carefully
review the Peak Search report looking at the %Error that is reported
for each peak for multi-peak isotopes, considering what the relative
abundances of those peaks are (e.g., generally the higher the yield
of a peak, the better the quantification will be from that peak),
whether there are other possible isotopes that have peaks at the same
energies as others (for example, Eu-152, Eu-154, and Co-57 all have their
primary peaks near 123 KeV, so if these are all possible in the spectra,
you should consider alternative peaks for quantification to avoid inter-
ferences between the isotopes at this energy), the FWHM of the peaks (if
the FWHM is broad, such as greater than about 2.25 for your setup, I would
consider the peak to include a potential for poor fit), the background
reported
for the various peaks that you can choose from (the higher the background
the higher the LLD), whether any of the peaks might be near the compton edge 
(higher background and more difficulty in peak identification), etc.

The Genie-PC system printout is customizable to a great extent to your
desires, and this is discussed in their user manuals.  Canberra also provides
very good customer technical support to customers (free if you are on an
annual software support agreement), so don't be afraid to call them.  They
also have a website at http://www.Canberra.com/ .  Their website includes
technical papers and email support.  Canberra also has an extensive user
training program with classes on all aspects of the Genie PC system.  If
this sounds like an advertisement for Canberra, it isn't...trust me, I am
only a user of the system, not a stockholder or employee :)

I would recommend that you sit down and consider the isotopes that you
are interested in being able to quantify and develop a reproducible
scheme for review of the MCA peak identification print-out.  Kocher's
Decay Tables are an excellent reference when performing this planning,
and "appear" to have been used by Canberra in developing their decay
tables also.  I have developed a series of decay energy tables specific
to my own situation that involves longer lived fission products and
naturally occurring isotopes that aid me greatly during spectra review.
I would recommend that you do the same to standardize your approach
for consistent results.

For the case of Co-60, both peaks that you mentioned have 100% abundance
and are well off the compton edge, so they are good clean peaks.  They will
also yield very similar % error values, so choosing one over the other
shouldn't be a problem.  Look at the backgrounds for the two peaks to make
sure that nothing looks excessively high or low so as to affect the reported
concentration/activity values.  If everything is equal, and errors are
matched,
I would suggest that you go with the higher reported activity for
conservatism.

Best regards.  If you need assistance, you may call or write me directly.
Judd M. Sills, CHP           |   Office: (619)455-2049
General Atomics, Room 01-166C|      Fax: (619)455-3181
3550 General Atomics Court   |   E-Mail:  sillsj@gat.com
San Diego, CA  92121         |