In reply to Jones Beene's message of Sun, 7 Oct 2012 07:32:37 -0700: Hi Jones, [snip] >Robin > >The cross-section for alpha emission from carbon is way too small for the >explanation you suggest. > >Wiki sez: in the radiation detection application, CR-39 material is exposed >to proton recoils caused by incident neutrons. The proton recoils cause ion >tracks, which are enlarged by an etching process in a caustic solution of >sodium hydroxide. The enlarged ion tracks are counted under a microscope >(commonly 200x), and the number of ion tracks is proportional to the amount >of incident neutron radiation.
While what you say is true, a track created by a single proton is not necessarily indicative of neutrons, as the track could be caused by any reaction producing a proton, or any charged particle for that matter. However the triple track created by the C12 breakup is strongly indicative of fast neutrons. > > >-----Original Message----- >From: [email protected] > >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). > >Regards, > >Robin van Spaandonk > >http://rvanspaa.freehostia.com/project.html > > Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
