  We study deep trapping states in Ce3+-doped garnet crystals with the
composition (Lu,Y,Gd)3(Ga,Al)5O12, recently shown as having remarkably high
light yield. We use thermally stimulated luminescence (TSL) technique above
room temperature and determine the composition Gd3Ga3Al2O12 as the host showing
the lowest concentration of traps. This host consistently manifest very low
afterglow comparable to that of the standard BGO crystal. We also perform TSL
glow peak analysis based on the initial rise technique to evaluate trap depth
and other characteristics associated with TSL peaks.
