Single-layer and multilayer composite scintillators based on organic molecular crystalline grains

Recently, we proposed the technology of production of the new type of organic scintillation materials those are effective detectors of fast neutrons and have no technological limitation on the area of their input window. They are organic composite scintillators those contain crystalline grains of stilbene (C 14 H 12 ) or p-terphenyl (C 18 H 14 ) doped by 1,4-diphenyl-1,3-butadiene, i.e. hydrogen bearing materials. It is shown that the composite scintillation material based on the grains of an organic single crystal can be obtained even if the stage of single crystal growth is eliminated. In both cases (with and without crystal growth) it light yield can be about 90% of light yield of a single crystal, which was used to obtain the scintillation grains. The composite scintillators show the stable characteristics exposed to air during one year. The scintillation signal decreases with increase of light scattering inside composite scintillator. It is advisably to use the composite scintillators with thickness up to 20-25 mm even for fast neutron detection. Single-layer composite scintillators based on grains of stilbene and doped p-terphenyl crystals are very effective detectors of alpha particles, which can be useful in the application where it is necessary to define the coordinates of points of alpha particle detection. If one takes the efficiency of alpha particles detection by a thin single crystal as 100% then the relative efficiency for a single-layer composite scintillator is about 70%. If we take into account that scintillation grains fill about 70% of detector surface and about 30% is filling by a gel then we have to accept that a single-layer composite scintillator is a very effective detector of alpha particles.