At 05:07 PM 10/6/2012, mix...@bigpond.com wrote:
AFAIK fast neutrons are detected by the fact that they occasionally
break a C12
nucleus into 3 alpha particles. It is the three alpha particles that produce
three cone shaped tracks in the CR39, with a common origin. Note that only
charged particles create tracks, because the tracks are formed from chemical
changes in the CR39 caused by the CR39 molecules being ionized, and only
energetic photons and charged particles cause ionization (not neutral
particles).
The triple tracks are pretty distinct; however, the routine usage of
SSNTDs for neutron detection looks for proton tracks, created by
proton knock-on from hydrogen-containing materials. In the SPAWAR
triple-track report, the hydrogen would be in the CR-39 material itself.
SSNTDs, like CR-39 and LR-115, can also be used to detect slow
neutrons by using a boron-10 (n,alpha) converter screen. However,
while I have some boron-10 material, slow neutrons are not expected
from codeposition experiments.
Of course, fast neutrons weren't expected either....
These materials are not sensitive to "energetic photons," i.e., gamma rays.
