Non-proportionality of GAGG:Ce scintillators down to 50 eV electron equivalent by application of alpha particle excitation

In this manuscript we present the non-proportionality characteristics of the GAGG:Ce scintillators in very low energy range -down to 50 electron equivalent (eVee) - using alpha particle probing technique. The response of the GAGG:Ce crystals, with various Al/Ga ratio, to alpha particles in the energy range from 1.5 MeV up to 8.8 MeV, were studied in relation to that of gamma rays. As the initial energy of the alpha particle is defined, it is easily possible to transform its energy to velocity. Then, basing on the alpha particle velocity, we calculated the energy of an electron, which would have the same velocity as the alpha particle. It allows to obtain a non-proportionality characteristics of GAGG:Ce crystals down to about 50 eV of electron equivalent energy, significantly lower that achievable with the standard gamma ray sources. It is particularly important that for each crystal type significant difference of the non-proportionality pattern is observed in such low energy range. The calculation provides new data and methods of scintillation non-proportionality characterization down to a very low energy region with good precision, superior to this obtained with monochromatic synchrotron X-rays.