Lecture20 - ENU 4612C/5615C Nuclear Radiation Detection and...

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ENU 4612C/5615C Nuclear Radiation Detection and Instrumentation Lecture 20 Photomultiplier Tubes and Photodiodes
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Photomultiplier Tube (PMT) Glass Vacuum Envelope Photocathode Multiplying Structure Anode light e
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Photocathode e ν h W h E e = light) (blue 3 eV h eV 2 to 1.5 function) work (surface W
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Typical Photocathode Quantum Efficiency glass end-window quartz end- window Q.E. 0.2 0.3 0.4 0.5 0.6 λ (μm) 0 0.1 0.2 4 3 2.5 2 eV h ν photons incident of no. emitted rons photoelect of no. Efficiency Quantum =
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Common Photocathodes
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Photocathode Response and Scintillator Emission Spectra A good match is important to maximize quantum efficiency
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Electron Transit – Photocathode to first Dynode photocathode focusing electrodes first dynode second dynode third dynode focusing electrodes
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Secondary Electron Emission e - e secondary V factor tion multiplica e primary incident emitted e secondary of no. - - = δ
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Electron Multiplication GaP(Cs) Sb Cs 3 PRIMARY ELECTRON ENERGY (eV) SECONDARY ELECTRON EMISSION ( δ )
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Multiple Stages N Gain stages N" " δ = 7 10 10 5 Gain 10 N 5, : Example = = = PHOTOCATHODE ANODE DYNODES 0 V 1 V 2 V 3 V 4 V 5 V 6 V 7 V
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PM Tube – Wiring Diagram (Negative High Voltage) PHOTOCATHODE ANODE -HV Typically 1000 to 2500 V DYNODE OUT FOCUS
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(Positive High Voltage) PHOTOCATHODE ANODE +HV DYNODE OUT FOCUS
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Lecture20 - ENU 4612C/5615C Nuclear Radiation Detection and...

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