Response of Some Scintillation Crystals to Heavy Particles

The dependence of the response of anthracene, stilbene, and sodium iodide crystals in a scintillation detector on the type and energy of charged particles incident on the crystal has been investigated. Electrons with energies from 500 ev to 624 kev, deuterons and molecular hydrogen ions with energies of 1 to 11 Mev, protons of 1 to 5 Mev, and alpha-particles of 4 to 21 Mev were employed. With the exception of protons and deuterons in sodium iodide, which gave a linear response over the entire energy region investigated, plots of pulse height vs energy for heavy particles gave a nonlinear relation for low energies tending toward linearity with increasing particle energy. Electrons in anthracene and stilbene show a nonlinear response below 100 kev, while the sodium iodide curve is linear above 1000 ev. The response of anthracene, whose behavior may be typical of organic crystals, has been compared for different ionizing radiations by considering the variation of the specific energy loss. Both electrons and heavy particles seem to show regions of linear response which start at quite different values of dE/dx. As the specific energy loss increases the response becomes nonlinear, with the ultimate saturation of the specific fluorescence for large values of dE/dx.