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Light Output Uniformity for CsI(Tl) as supplied by manufacturers… - PowerPoint PPT Presentation


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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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slide1

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

slide2

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

slide3

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

slide4

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

slide5

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