Investigations of the influence of Am-241 photons on the measured alpha particle response of luminescent materials

Abstract Americium-241 isotope is used frequently for investigations of luminescent detectors and materials as a source of alpha particles, but it emits also gamma-rays (59.4 keV), what may have influence on the measured signal. The goal of the present work was to perform systematic investigations of the impact of the emitted photons on the measured TL/OSL response for a wide range of various luminescent materials. The obtained results confirmed the importance of this issue for part of the compounds. The contribution of photons to the total luminescent signal was found to range from a negligible level (BeO and LiF:Mg,Ti) up to 15% (e.g. LuAG, Lu2O3). Most of the measured values roughly follow a simple trend line, when plotted versus (μ/ρ)enρh. Some materials however, like LiF:Mg,Cu,P and Al2O3:C, do not fit into that trend, which may be explained by the dependence of their relative luminescent efficiency on ionization density. The effect of 241Am gamma-rays is of particular importance when samples of more complex, layered structure are investigated. For some samples of epitaxial crystalline layers grown on single crystal substrates, it was found that nearly entire (up to 96%) signal was generated by photons, not alpha particles.