Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Homemade neutron detector? (Am-Be source)
Date: Jan 26, 1:42 pm
Poster: Jim Lux

On Jan 26, 1:42 pm, Jim Lux wrote:

>Now to what our good friend Jim Lux was talking about with the Am241-Be source idea. Sorry Charlie, been there, done that.
> I have four nice very old industrial smoke detector Am241 strips of 15uc each! I put all four together and then covered them with finely powered elemental Be .9999 pure.

I believe the commercial sources use a very (!) thin foil of Be.

> Lets do the math.
> A 1 curie Am241-Be source made by Isotope Products is warranted to produce 2.2X10e5 neuts per second.(got th' data sheet)

That 1 curie is 37E9 alphas/second from the Am241. So, the overall efficiency of the commercial source is 6E-6.. It seems the cross section of the reaction is quite low (which is what I thought)...

Interesting, too.. I haven't done the "plausibility analysis" of the radioactive boyscout story, but as I recall, this guy tried using the Am241 from 100 scrap (presumably consumer) smoke detectors.. So he had 100 uC. He claimed he was getting neutron activation (I sort of doubt it based on the above calculations).. Once he got some radium, though... How many curies (i.e. grams) of radium are on a typical clock dial (or, more to the point, how much radium was in the paint)? milligrams? micrograms? I wouldn't think it would need much, and, of course, the Ra is somewhat expensive, so they wouldn't have been too profligate with the stuff.

a reference I found says that the dose rate from the minute hand on a clock was 1 mR/hr. A bit tricky to extrapolate back to how much Radium there is in the paint, though.