On Fri, 3 Nov 1995, Timothy C. May wrote:
I'd say they make poor sources. Far too large. A smaller source has better access to the detector without adding much to the overall background the user is exposed to. (I'm not saying low-level uranium or thorium sources are much of a hazard, but the fluence presented at the detector is very low for such an extended source.)
It depends on the detector type (alpha, beta, gamma, neutrino?), but high count rates can be obtained in a variety of ways. (Don't get too high a count rate, or the dead time characteristics of the pulse-height analyzers will introduce spurious correlations that decrease entropy--I mention this to show that even radiation detector sources of entropy have non-random issues to take into account.)
Gotta watch yourself around the physicist.... Most of the sources I mentioned are fairly anemic, however the Coleman lantern mantles are pretty good beta emitters. I can get count rates approaching 1000 cpm on a tired GM tube detector with a beta window of unknown thickness. Brad D.