1. Scintillators Hoda Bagheri Spring 2010

2.  Light emission  Scintillators  Scintillation mechanism  Photomultiplayer

3. light emission (1) thermal radiation----black-body radiation, etc. (1) thermal radiation----black-body radiation, etc. (2) braking radiation (2) braking radiation (3) Cherenkov radiation (3) Cherenkov radiation (4) luminescence---usually in the visible, UV, IR range (4) luminescence---usually in the visible, UV, IR range

4. Luminescence excited by different external energies:  photo-luminescene---by UV photons, etc.  radio---by radiation like X-, ,rays, etc.  cathode- ---by electron beam,  electro----by electric field, (examples: LED)

5. Scintillation ~ Fluoarescence due to radiation

6. Scintillators: Inorganic: crystals, ceramics, glasses, ceramics, glasses, noble liquid, noble gasses  Organic: crystals , liquid, plastic

7. Scintillation mechanism Four types of luminescence in inorganic scintillators (1) Exciton luminescence: BGO, … (2) Dopant luminescence: GSO:Ce, … (3) Charge-transfer luminescence (4) CVL (Core-valence luminescence, Cross luminescence)

8. Scintillation mechanism  Scintillation mechanism in organic scintillators Radiative transition of  electrons

9. Main characteristics  1. Quenching (1) Thermal quenching (2) impurity quenching (3) concentration quenchin

10. Main characteristics  2. Decay (2) Afterglow due to metasatble states or traps (1) Natural afterglow- I(t) = I(0) exp(-t/  )  = (Pnr + Pr)-1

11. Main characteristics  3. Particle discrimination Possible for some inorganic and most of organic scintillators.

12. Particle discrimination

13. Comparison betwee inorganic and organic scintillators

14. Photomultiplier tube Gain ~ 106 - 107

15. Thanks