A proton recoil neutron detector can be made by dispersing 1.5g of ZnS(Ag) phosphor in 10g of lucite, forming a cylinder of 1" dia by 5/8" height. The cylinder is then coupled to a PMT with appropriate light and magnetic shielding. This type of detector is known as a Hornyak button, and is described in the Price book on nuclear radiation detection. Calibration would be a problem, but the manufacturing process seems straightforward. If the phosphor can be located on the open market, this might be a nice go/no go detector for the financially challenged. I see no reason why the process could not be used to make a relatively large area detector. The thickness would remain constant at 5/8" to reduce gamma sensitivity. Also, a thick detector would not result in much efficiency gain due to light scattering, as I suspect the ZnS/plastic combo is somewhat cloudy.
The Bicron BC-270 proton recoil detector appears to be a variant on this basic concept, with the phosphor forming a screen to maximize light output to the PMT(the recoil protons have a short range in the phosphor). A fair shot at a home-made BC-270 might be made by solvent bonding two lucite cylinders together with a thin layer of phosphor in between. The proton recoil layer would be about 5/8" thick as in the Hornyak button, while the cylinder on the other side would be shaped to couple with the PMT of one's choice. Neither lucite cylinder would be doped with scintiilator, so that the light production from the ZnS phosphor would be dominant. This thin layer of light producing material makes the BC-270 very insensitive to gamma radiation, as most of the energetic photons will pass through without depositing energy in the thin ZnS screen.
Food for thought and grounds for further research...
Richard Hester
Created on Saturday, January 13, 2001 10:30 PM EDT by Richard L. Hester