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Light Output Uniformity of Long CsI(Tl) crystals - the “bottle-neck” for gamma and proton spectroscopy. Light Output Uniformity for CsI(Tl) as supplied by manufacturers…. …and Energy Resolution for gammas, measured by a APD ( 5x5), when irradiating the whole crystal volume…. *. source.
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Light Output Uniformity of Long CsI(Tl) crystals -the “bottle-neck” for gamma and proton spectroscopy Light Output Uniformity for CsI(Tl) as supplied by manufacturers… …and Energy Resolution for gammas, measured by a APD ( 5x5), when irradiating the whole crystal volume… * source L=110 mm CsI(Tl), L=110 mm 20x20 Lund-Dubna, VC_2007_12_13
Straggling and Nonlinearity for Protons and Gammas due to dL/L Effect of crystal Light Output nonuniformity ( a)- 5%, b)-10% on the Light collected by Photodetector. Calculated for Protons. For Gammas – the picture looks similar, but with energy scaled by factor 1/4 - 1/5 . Conclusion – dLO/LO must be less than 1% along the length of crystal Lund-Dubna, VC_2007_12_13
Test with highly uniform in Light Output Crystal , L=110 mm, dL/L <0.7% CsI(Tl) – 20x20 – 110 – 23x23 mm**3 Irradiated for 110 mm distance… Photodetectors: PD – 10x10 mm**2 APD – 5x5 mm**2 / <M>=40 APD – 10x10 mm**2 / <M>=50 Our data… compare APD of 5x5 and 10x10 mm**2 !!!! Published data, 10x10x10 mm**3 CsI(Tl)+ 10x10 APD !!! Lund-Dubna, VC_2007_12_13
Effect of VM200 ( ESR) Light Guide reflector on Light collection and Energy Resolution • - Active area of APD = Active area of LightGuide, 10x10 mm**2. S_APD/S_LG =1.0 • - Active area of APD = 0.25 of Active area of Light Guide, 5x5 mm**2. • S_APD/S_LG =0.25 • Light Collection coefficient, • L(5x5)/L(10x10) = 0.65, due to the VM2000 • (ESR) reflector, covering an extra surface • By using an APD of 10x10 mm**2 we can gain around 12% in the energy resolution as compared with the APD of 5x5 mm**2 a) b) Lund-Dubna, VC_2007_12_13
Some Conclusions and Plans for Future R&D • Light Output uniformity for Long crystals is more important than the active area of the APD • For the highly uniform in L.O. crystals we can get almost ideal Energy Resolution • New groups must be involved in the Uniformity Problem for real Califa geometries • Plans for nearest future: • Light Uniformity adjustment for the real CALIFA crystal geometry • Tests with APD’s, PMT’s / like R7400U-3, 20 – insensitive to magnetic field • To mount CsI(Tl) “demonstrator” for bench and in-beam tests Lund-Dubna, VC_2007_12_13
