I specifically mentioned BC-400 to the Bicron engineer, as it's the stuff I have on hand, and specifically mentioned not using the BC-720, as it is considerably less efficient (see previous posts). Other plastic scintillators besides BC-400 will work, but it (or an equivalent from some other manufacturer) is the easiest material to get hold of. I don't know the availability situation in Italy, but Don Orie is sitting on a ton of the stuff in New Mexico...
If you pick up a scintillator/PMT combination on the used market or from Ebay, it's likely to be an NaI scintillator rather than plastic. These are commonly used for gamma detection and spectroscopy, as the relatively high atomic number of the constituent materials in the crystal aids in gamma absorbtion (other crystals like CsI and BGO are better for gamma absorbtion, but far less common and with lower light output). Having said that, NaI scintillators are pretty awful for neutron detection for the very same reason, as the neutrons scatter from the heavy nuclei with little energy loss. You want a material with a high hydrogen content to get the proton recoil effect, hence organic plastics. Pure organic compounds like anthracene and stilbene are good neutron detector scintillators as well, but crystals of these materials are hard to grow in large size, and can be orientation sensitive. Nothing beats the cheapness and convenience of a hunk of plastic... The plastic scintillators are generally rated in terms of the percentage of light output compared to pure anthracene. You can find out more at the Bicron web site.
Created on Tuesday, May 08, 2001 12:11 PM EDT by Richard L. Hester