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: Neutron Detection
Date: Oct 09, 11:09 pm
Poster: Richard Hester

On Oct 09, 11:09 pm, Richard Hester wrote:

The unfortunate thing about a cloud chamber is that a gaseous target would not intercept very many neutrons, just from density considerations alone. The efficiency would be worse than the best scintillators, which already aren't that hot.
An exception might be a gas such as diborane or BF3, which would have a good cross section for thermal neutron absorbtion (the chamber would require a moderator like a chunk of paraffin). Using the setup described as a conventional thermal neutron detector would be easier than trying to contrive a cloud chamber. It may also be difficult to get a cloud chamber going with reactive gases such as these, and I would not want to be caught in the same room with large quantities of said materials without elaborate safeguards, if at all. Both gases are poisonous and reactive, and diborane burns on contact with air. The scintillators sound like the best of a bad lot.

One possibility that gives me the crawlies thinking about it, but may just work, is to use a small quantity of depleted uranium as a neutron multiplier. This might increase the overall level of neutrons, but also may muddy the count because of the variable yield of neutrons per fission. Also the physical setup of the detector might be difficult if the neutron pattern from the fissions is isotropic. I would envision a chunk of uranium surrounded by the scintillator material, with a light pipe or several PMTs. Sounds like a pain in the tail... Also, it would only work if the fission cross section were significant at the energy level of the neutrons from the D-D reaction, and the background raditaion from the uranium did not mask what you were looking for.
Food for thought...
Richard Hester

>How about using a cloud chamber to discern neutron production from a Fusor?
>It may not offer a good measurement, but could a cloud chamber be used to at least verify neutron production? Could it be shielded?
>Scott Little details his very interesting cloud chamber here: