YSO, LSO, GSO and LGSO. A study of energy resolution and nonproportionality.

We have studied the nonproportionality and intrinsic energy resolution of cerium doped YSO, GSO, LSO and LGSO crystals. While LSO and YSO have similar light output, GSO and LGSO have ca. 70% and 20% lower light output than LSO, respectively. YSO, a compound containing fairly light elements, was expected to have proportional light output vs. energy, like YAP:Ce. Surprisingly it has almost the same nonproportional as LSO and GSO. The nonproportionality of YSO is followed by large values of intrinsic energy resolution. The comparison of the nonproportionality of YSO-LSO and YAP-LuAP pairs indicates that high proportionality is connected with the structure of the crystal and not with the presence of light elements. To our knowledge, this is the first study of nonproportionality and intrinsic resolution for LGSO.