RE: Random Number Generators

[tcmay@got.net (Timothy C. May)]

At 11:40 PM 1/17/96, Kurt Buff (Volt Comp) wrote:
>If you're going to work with hardware to get really random numbers, why not
>go to the back of any of several PC-type magazines, and order the radiation
>detector board that someone is hawking? Can't really do any better than
>that, can you? Counting cosmic ray hits and noting their time differentials
                         ^^^^^^^^^^^^^^^
>should be just what the doctor ordered, right?

Almost all of the counts in simple radiation detectors are from earthly
sources, not from cosmic rays. For Geiger tube counters (not very common
these days), the main counts are for gamma rays and for beta particles (if
a beta window is included). For solid-state detectors, most of the counts
are still betas and gammas, even though solid-state detectors (e.g., PIN
diodes) are certainly _capable_ of detecting alpha particles. The reason is
that alphas are very nonpenetrating, so alpha detectors for intentional use
must have extremley thin (and hence fragile and expensive) windows or
protective layers. Basically, it makes little sense to count alphas when a
rough radioactivity measurement is sought, as with cheap detectors.

Solid state detectors specially set up with alpha sources in proximity to
the detector are possible, but are a specialty item.

RNGs based on thermal noise and natural radioactivity have been discussed
on our list at least a dozen times (multiple posts each time), so I suggest
further research be done there.

--Tim May


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