scintillators hoda bagheri spring 2010. light emission scintillators scintillation mechanism ...
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ScintillatorsScintillators
HodaHoda BagheriBagheri
Spring 2010Spring 2010
Light emissionLight emission ScintillatorsScintillators Scintillation mechanismScintillation mechanism PhotomultiplayerPhotomultiplayer
light emissionlight emission
(1) thermal radiation----black-body (1) thermal radiation----black-body radiation, etc.radiation, etc. (2) braking radiation(2) braking radiation (3) Cherenkov radiation(3) Cherenkov radiation (4) luminescence---usually in the (4) luminescence---usually in the visible, UV, IR range visible, UV, IR range
Luminescence excited by Luminescence excited by different external energiesdifferent external energies::
photo-luminescene---by UV photons, etc.photo-luminescene---by UV photons, etc. radio---by radiation like X-, radio---by radiation like X-, ,rays,rays, etc. , etc. cathode- ---by electron beam,cathode- ---by electron beam, electro----by electric field, (examples: LED)electro----by electric field, (examples: LED)
Scintillation ~ Scintillation ~ Fluoarescence due to Fluoarescence due to
radiationradiation
Scintillators:Scintillators:
Inorganic: Inorganic: crystals,crystals, ceramics, ceramics, glasses, glasses, noble liquid, noble liquid, noble gassesnoble gasses
Organic: crystalsOrganic: crystals, liquid, plastic, liquid, plastic
ScintillationScintillation mechanism 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)
ScintillationScintillation mechanism mechanism
Scintillation mechanism in organic Scintillation mechanism in organic scintillatorsscintillators
Radiative transition of electrons
Main characteristicsMain characteristics
1. Quenching1. Quenching
(1) Thermal quenching
(2 )impurity quenching
(3 )concentration quenchin
Main characteristicsMain characteristics
2. Decay2. Decay
(2 )Afterglow due to metasatble states or traps
(1 )Natural afterglow-
I(t) = I(0) exp(-t/) = (Pnr + Pr)-1
Main characteristicsMain characteristics
3. Particle discrimination3. Particle discrimination
Possible for some inorganicand most of organic scintillators.
Particle discriminationParticle discrimination
Comparison betwee inorganic and organic scintillators
Photomultiplier tubePhotomultiplier tube
Gain ~ 106 - 107
Gain ~ 106 - 107
Thanks