Afterglow in LSO and its possible effect on energy resolution

LSO is known to exhibit afterglow for approximately 24 h following exposure to intense room light. We find that LSO also exhibits afterglow following activation by gamma rays in normal scintillation counting. This scintillation afterglow is characterized by an exponential decay time constant of 50 min and an absolute light yield, relative to the fast scintillation component, of 1.7. Unless special attention is paid to the afterglow signal in designing the data acquisition electronics used with LSO, the gamma ray energy resolution of the spectroscopy system can he ruined by baseline shifts occurring during the acquisition of an energy spectrum. With proper provisions to handle these predictable baseline shifts, LSO is a promising new scintillator for fast counting gamma ray spectroscopy.