Re: survey sensitivity

[Lester.Slaback@nist.gov]

Mr. Reed asks.....
A visiting technician used a GM pancake probe with a planar correction
factor of 50 beta dpm/100cm^2 per cpm, a RATE METER without digital
integrating capability and scale divisions of 20 cpm in a background of
~40 cpm, WOULD YOU QUESTION a report of "<1,250 beta dpm/100cm^2" for a
STATIC (i.e., NON-scanning) survey?  (Assume the period of measurement is
adequate for the instrument to "fully" respond.)

I'm not convinced that <25 ncpm (i.e., only 1.25 scale divisions) can be
discerned or quantified with the above conditions/technique and that a
report of "<1,250 beta dpm/100cm^2" is not PROVEN by the survey.  Can
anyone relate contrary experience or empirical studies?  Please opine.

Craig Reed
East Tennessee Technology Park (K-25) RADCON
e77@ornl.gov
***********************

1. Most of our instruments have 50 div for the full scale.
At 20 cpm/div this instrument would be on a 1000 cpm full scale. Why not
the 100 cpm scale?

2. <in my opinion> no unless the instrument has a very long time constant.

3. Michelle Johnson (PNL) gave an excellent paper on survey sensitivity at
the Feb 98 midyear meeting, but it is not in the proceedings.  PNL will be
publishing a report.  Her email is supposedly ml.johnson@PNL.GOV, but my
mail bounced. -- 
the above are the personal musing of the author,
and do not represent any past, current, or future
position of NIST, the U.S. Government, or anyone else
who might think that they are in a position of authority.
NBSR Health Physics
NIST
Gaithersburg, MD 20899
301 975-5810
-----------------------------------------------------------
Lester.Slaback@nist.gov
-----------------------------------------------------------

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 -- End of forwarded message
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-- 
the above are the personal musing of the author,
and do not represent any past, current, or future
position of NIST, the U.S. Government, or anyone else
who might think that they are in a position of authority.
NBSR Health Physics
NIST
Gaithersburg, MD 20899
301 975-5810
-----------------------------------------------------------
Lester.Slaback@nist.gov
-----------------------------------------------------------