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gamma spectroscopy, computing HP



Frazier Bronson (of Canberra) gave a paper at the 99 HPS meeting that
represents a fundamental new approach to doing gamma spectroscopy.  Rather
constraining sample geometries to those for which you have approximate
standards he demonstrated that with the proper characterization of the
detector the counting efficiency for any geometry and sample constituency
can be computed (via MCNP).  Hence the lab can do away with multiple
standards and use only one or two for Q.A.

But more importantly you can optimize the sample geometry for every size
and type of sample that you have without having to worry if you have a
specific std for that combination (which folks rarely have anyway, e.g.,
assuming epoxy is the same as soil or water).

Various pieces of this has been done in the past but he demonstrated the
practicality of doing the whole thing now (or maybe tomorrow).

I'm posting this not as a commercial ad, but as food for thought.  This
approach raises lots of questions about proper Q.A., traceability, new
kinds of samples, sample geometries, and sample preparation.  And as noted
by a questioner at the meeting it raises questions on how standards are
written, i.e., the need to write them so these techniques can be used.  And
this approach ties in directly to the efforts of national reference labs
towards getting away from 'artifact standards', i.e., sources, and
depending more directly on processes that relate to fundamental standards
(and hence require less direct support from the national labs).

While the current code is just for gamma spectroscopy one can envision
other types of counting.  In a sort-of-related paper folks at Los Alamos
presented results on neutron detectors optimized for a rem-response using
MCNP (I am drooling for their 5 lb rem equivalent instrument!).  At least
two others papers at the meeting gave practical applications of this
computing technology.  This is just another example of how computing will
be encroaching into the HP world and eventually will impact almost everyone.


Disclaimer:  the above are the personal musings of the author, and do not
represent any past, present, or future position of NIST, the U.S. government,
or anyone else who might think that they are in a position of authority. 
Lester Slaback, Jr.  [Lester.Slaback@NIST.GOV] 
NBSR Health Physics 
Center for Neutron Research 
NIST
100 Bureau Dr.  STOP 3543 
Gaithersburg, MD  20899-3543 
301 975-5810 voice
301 921-9847 fax
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