Re: Efficiency Determination

[Bob Flood <bflood@SLAC.Stanford.EDU>]

At 11:24 AM 11/26/96 -0600, you wrote:
>
>Yesterday the above method gave me a 30.6% efficiency for P-32.
>
Of course, efficiency depends on the detector used, source construction
(especially self-absorption in the source materials), and the
source-detector geometry. However, one can generally estimate that almost
every beta from a high energy source like P-32 that is emitted toward the
detector will be detected. This means that the solid angle defined by the
source and detector, expressed as a fraction of full 4pi geometry should be
pretty close to the observed efficiency. This makes a useful "sanity check"
for one's measurements.

Like Mr. Dunn, I recommend purchasing calibration sources with
documentation of the known activities. This sort of pedigree will eliminate
a lot of questions and arguing with auditors and inspectors about the
accuracy of efficiency calibrations using home-made sources.


Bob Flood
Stanford Linear Accelerator Center
(415) 926-3793     bflood@slac.stanford.edu
Unless otherwise noted, all opinions are mine alone.