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Re: FAQ - Neutron-detection videos - another one

Posted: Mon Nov 23, 2009 8:42 am
by DaveC
Carl -

These are quite good. You have a clear and unhurried style of explaining that's very easy to follow.

These make a very useful addition to all the basic information that's on the site.

Thanks for taking the effort to organize them and putting them up for all to see.

Dave Cooper

Re: FAQ - Neutron-detection videos - another one

Posted: Mon Nov 23, 2009 4:21 pm
by Richard Hull
More superb work by a superb researcher and and sharer of good info.

Another three or four atta' boys for Carl.

Richard Hull

Re: FAQ - Neutron-detection videos

Posted: Tue Nov 24, 2009 8:42 pm
by hjerald1
Interesting videos Carl. Thanks for posing them.
Your radiomanganese clip reminds me of an anecdote from the 1980s when I was doing neutron activation analysis of some geological samples using the U of Utah research reactor. I was handling the irradiated polyethylene sample capsules and transferring them into the gamma ray spectrometer with my bare hands. Perhaps not the optimal technique but then those were the good old days.

Re: FAQ - Neutron-detection videos

Posted: Mon Feb 01, 2010 10:03 pm
by Steven Sesselmann

I am trying to replicate the setup that you are doing on the video. I have the identical He3 tube with a Cremat charge sensitive preamp, but unfortunately I don't have a hot gamma source or a sealed neutron source.

I have the He3 tube connected to the preamp, and set to 1500V, and the output from the preamp plugged into my oscilloscope, and I get absolutely nothing but a straight line.

Can this be right?

Shouldn't I at least get some slight background clicks?

The amp seems to work, because if I just move my finger close to the HV connection the scope immediately shows a strong signal.

So my question....Is it likely that the tube is dead, or is this normal?

A tiny neutron source would have been terrific.


Re: FAQ - Neutron-detection videos

Posted: Mon Feb 01, 2010 10:10 pm
by Doug Coulter
You should at least see some big ones from cosmic rays....something isn't right.

Re: FAQ - Neutron-detection videos

Posted: Tue Feb 02, 2010 6:40 pm
by Richard Hull
Not a lot to go on here except the preamp seems to be on.

What is the value and voltage standoff of the input capacitor?

The tube might be dead if it is surplus. Does it have a pressure indication on the label?
What about a voltage range or figure on the label?

You sort of have to have at least a nice hot piece of U ore!

I hope your scope is a DSO so that you can single shot capture any large cosmics. If not, then you might miss them on an old analog scope in auto roll mode.

Richard Hull

Re: FAQ - Neutron-detection videos

Posted: Wed Feb 12, 2014 4:31 pm
by Richard Hull
Polyethylene is the overall best moderator for the amateur and a, "right on its butt", second would be Paraffin wax which is much easier to obtain, but is a fire hazard in the amounts needed. There is no nearby third choice compared to these two.

You should really strive for the P.E. at a local plastics distributor. Some vendors are happy to sell, at low cost, odd ball cutoff chunks that are no longer of much value. thiese can be stacked and mounded up to make all manner of useful and efficient neutron ovens, caves and howitzers.

Richard Hull