Alan,

yours is a good point. But also remember that, even if a surface is 90 percent
reflective, then after only two reflections, the photon has an 81 percent chance
of reaching the PMT. After 3 reflections, the probability becomes 0.9 x 0.9 x
0.9 = about 72 percent, and so on. So unless the geometry of the reflector is
very well-designed, a lot of photons get lost. My real question about this
process centers on whether or not the photon emission is random in its
orientation. Or does the scintillator material emit along some kind of
preference to the angle at which the nuclear particle strikes it. In other
words, if you do NOT have a reflector in the design, does it matter at what
angle the radiation hits the scintillator material?

thanks,
Mark


--- In GeigerCounterEnthusiasts@yahoogroups.com, "Alan R. Betz" <arbetz@...>
wrote:
>
>
> >
> > Photomultiplier tubes can detect some of these photons, but of
> > course most of the photons shoot off in directions away from the
> > photomultiplier and are never detected.
> >
>
>
>
>
>
> Not quite true. Scintillators are usually surrounded by a reflective
> surface to
> correct this problem. For example, see the structure of any of the Harshaw
> hermetically sealed NaI (Tl) scintillation crystals.
> Regards, Alan
>