Re: 4pi steradians

[Michael Kay <makay@teleport.com>]

Sorry, I missed the empty subject line.

Michael

Michael Kay wrote:

> As best I can remember, 4pi steradians is the total solid angle surrounding
> a point in space. The surface described by 4pi is a sphere. This
> nomenclature was used extensively in the days of gas-flow proportional
> counters. Those with a hemispherical counting chamber over the source were
> referred to as 2pi counters because they had an active volume of 1/2 of a
> sphere which is 4pi. There were some 4pi counters where the sample was
> suspended in some sort of manner and had active detection volume on both
> sides to make an approximation of a sphere. Samples were as thin as
> possible, and mounted on very thin backings.
>
> If the sample was actually part of the volume, like C-14 made into CO2 and
> introduced into the sealed counting chamber, that was very close to an
> absolute 4pi geometry.
>
> Hope this is of some help.
>
> Michael A. Kay, ScD, CHMM
> makay@teleport.com
>
> Mike Dupray wrote:
>
> > Does anybody know what a 4pi steridian cross section looks like?
> > Michael R. Dupray
> > Senior Staff Health Physics Technician
> > General Atomics
> > 619-455-3561
> > FAX 619-455-3465
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