1. Measurement Birk’s constant and Ligth Yield Light Yield is the number of optical photons emitted when 1 MeV energy deposited in the scintillaotr γ γ'γ' Free electron Compton scattering Light Yield

2. Mean free path 1.Compton scattering : γ’ + e 2.Photo electric effect : e 3.Pair production : e + e > 1MeV γ scintillator Measurement Birk’s constant and Ligth Yield atomic number _ _ _ + Energy loss of electron

3. LS Measurement Birk’s constant and Ligth Yield Birk’s model L : Light Yield S : Proportional Constant E : Kinetic Energy Of Electron dE/dx : Collision Stopping Power High Energy level (E ≥ 100KeV) kB : Birk’s Constant Low Energy level (E ≤ 100KeV)

4. Measurement Birk’s constant and Ligth Yield Kinetic Energy of Electron Scintillation response photon LS θ PMT Ge-Detector (measure γ’ energy) Compton Scattering e Mesured Kinetic Energy of Electron

5. Measurement Birk’s constant and Ligth Yield MeV Light yield Ratio [a.u.] kB = 1.16645e-02cm/MeV ± 3.23713e-04 kB = 1.242155e-02cm/MeV ± 4.97911e-04 MeV Light yield Ratio [a.u.] Birk’s Constant of GdLSBirk’s Constant of LS