On Thu, 8 Oct 1998, Dave VanHorn wrote:

> >anyway, I like the idea of getting the stars into the picture very much
> ;)  >How much for a Geiger tube for weak alpha ? I'm looking for
> something that >gives 10-30 clicks per minute for background. There
> aren't any on sale >here.
>
> For alpha, it's a large area diode, you won't be seeing any stellar
> alphas, they can't make it through the soup.  Gamma is what you're
> thinking of.. Electronics Goldmine had a small tube for sale (and a
> cheap counter kit)  What background rate you see is up for grabs
> though.

Last time I looked, there were NO Geigers on sale w/o data sheet, which
data sheet contains a plot of integrated clicks per dose (one curve for
each flavor of radiation, sometimes a fourth one for X) and another with
current/voltage curve for operating point setting. Geigers being what they
are, I strongly believe that there must be data sheets available
somewhere.

> I suppose an old propane lamp mantle in the box would give it enough
> background.

They're made with CeO, not ThO, as far as i know, and CeO can be had from
cigarette ashes ;) Do you smoke ? <g>

> OOOH!  Radioactive Ping-Pong balls!  Just dope each one with a
> binary-encoded brew of seven isotopes, and use a differential counter
> to tell which rad-bits are on.  128 unique codes possible.
> The balls would be cheap, but the detector could be a bit pricey.

I think that you would have to be patient to make out the profile for a
low enough radiation level, so as not to harm anyone. You'd also need a
lead-lined pit to quiet the background. Then, the croupier would be
accused of substituting balls in the pit...

Peter