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Gamma Rays Detection: Scintillator Detectors and Silicon Photomultipliers

Learn about the detection of gamma rays, the most energetic electromagnetic radiation, through scintillator detectors and silicon photomultipliers. Discover the history of gamma rays and their interaction with matter.

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Gamma Rays Detection: Scintillator Detectors and Silicon Photomultipliers

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  1. Gamma RaysDetectionLNF – 14.2.18 | INSPYRE schoolDanilo Domenici

  2. What are the Gamma Rays? Gamma Rays (or γ rays) are the most energetic electromagnetic radiation It consists of photons of the highest energy (> 1 MeV)

  3. A bit of history γ rays have been discovered in 1900 in the Radium element In 1903 Ernest Rutherford dubbed the 3 radioactive decays as α rays, β rays and γ rays a neutron of the nucleus becomes a proton and a β particle (electron) is emitted together with a neutrino an α particle (2 neutrons and 2 protons) is emitted by the nucleus a γ photon is emitted by the nucleus the atomic number is decreased by 2 and the mass number is decreased by 4 the atomic number is decreased by 1 and the mass number is the same the atomic number and the mass number are the same

  4. Some exemples sometimes the 3 decays happens in a sequence called «radiocative chain»

  5. One more example: Cesium 137 the energy of the emitted radiation is equal to the difference of mass between initial and final nuclei according to E = mc2

  6. How we detect gamma rays? gamma is an ionizing radiation interacting in matter in 3 possible ways medium energy (100 keV – 1022 keV) Compton scattering high energy (> 1022 keV) pair production low energy (< 100 keV) photoelectric effect all these processes increase with the Atomic Number Z of the material

  7. Then how we detect free electrons? there are a lot of particle detectors: based on gas (Geiger counter), on semiconductors (Silicon detectors) We will use the scintillators

  8. Scintillator materials Scintillators are materials having the property of emitting visible light (mostly blue) when hit by ionizing particles through the fluorescence process There are several materials with this property (and others are being invented) NaI(Tl) - CsI(Tl) - BaF2 - BGO PbWO4 - LYSO - YAP – Polistirene https://crystalclear.web.cern.ch/crystalclear/scintillators.html

  9. Scintillator detectors In order to build a scintillator detector we need to assemble: a scintillator block a photosensor incoming gamma ray scintillator gamma ray absorbed light emitted photosensor detect light electric signal output

  10. A complete detection set-up

  11. Silicon Photomultipliers or SiPM invented at the beginning of 2000 to replace the old vacuum Photomultipliers Tubes (PMT) SiPM are solid-state photon sensitive micro-device on a Silicon substrate typical 5x5 mm2 sensor is made of a matrix of thousands of single photo-diodes with micrometric dimensions an avalanche inside the Silicon amplifies the signal

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