Into darkness: From high density quenching to near-infrared scintillators

In many aspects measurement of the α/β ratio has advantages over other methods. It provides higher precision and higher density of excitation than is available with Compton or photoelectric effect electrons. It has been shown that the α/β ratio follows the same trends and patterns as previously found for nonproportionality of electron/ gamma photon response. The α/β ratio also correlates with intrinsic energy resolution measured with 10 keV gamma photons. Materials with high α/β ratio have high intrinsic energy resolution at high density of excitation. The same trend is observed for 662 keV gamma photons with exception of alkali halides and ZnSe:Te. We have found that alkali halides have lowintensity of quenching and performbetter than LaBr3:Ce and LaCl3:Ce at high density excitation (with α particles or 10 keV electrons). The superiority of LaBr3:Ce and LaCl3:Ce over alkali halides probably comes not from high resistivity to high density quenching, but from lack of a low density quenching which is responsible for the "hump" in an electron/gamma nonproportionality curve. We can conclude, that halide-based scintillators are the most promising for discovering new highly proportional materials.