Emission spectra of Yb:YAG with Yb

3+

doping level from 5% to 30% at room temperature and(97 K) were characterized by cathodoluminescence spectra and the results showed the strongest emission peak is at 335~350 nm at room temperature which attributes to charge transfer luminescence(CT→F

7/2

) and shifted to shorter wavelength with decreasing temperature.Scintillation properties of Yb:YAG with different Yb

3+

doping level were studied by measuring relative light output and decay time of Yb:YAG crystal.Measurements of relative light output and temperature dependence have been performed with α excitations and the results showed light output is related to Yb

3+

doping level and crystal quality and the maximum achieved at low temperature for 5% Yb:YAG.The decay time and temperature dependence were measured by

22

Na excitation.The decay time of Yb:YAG crystal with different Yb

3+

doping level at room temperature is less than 50ns and it is monotonically decreasing with increase of temperature above the temperature where maximum of light output achieved

and decay time is monotonically decreasing with decrease of temperature below that temperature.Quenching temperature of Yb:YAG crystal at which the emission intensity has dropped to half of its maximum was determined.The relative light output and quenching temperature of Yb:YAG crystal with different Yb

3+

doping level are different.Relative light output decreases with the increase of Yb

3+

concentrations

while quenching temperature increases with increase of Yb

3+

concentration.5% Yb:YAG crystal has maximum relative light output and the lowest quenching temperature.We conclude from our measurements that Yb:YAG crystal should be possible for application in medical imaging at low temperature.