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Interaction of High Energy Radiation with Matter Interaction of High Energy Radiation with Matter reviewreview
Two basic typesTwo basic types
ExcitationExcitation electrons move to a higher orbital shell electrons move to a higher orbital shell temporarilytemporarily
~70% of charged particle deposited ~70% of charged particle deposited energy leads to excitationenergy leads to excitationlasers, high-intensity sources of lasers, high-intensity sources of ultraviolet light, microwave transmitters ultraviolet light, microwave transmitters and other devices that produce high and other devices that produce high intensity radio-frequency radiation.intensity radio-frequency radiation.
IonizationIonizationelectrons absorb enough energy to be electrons absorb enough energy to be removed from orbit removed from orbit
Average energy deposited per ion pair Average energy deposited per ion pair produced ~34 eVproduced ~34 eV
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Ionizing Radiation classificationIonizing Radiation classification
• Directly IonizingDirectly Ionizing Non-penetratingNon-penetrating ChargedCharged Energy is transferred through electric (Coulombic) force Energy is transferred through electric (Coulombic) force
interactions with orbiting electronsinteractions with orbiting electrons
• Indirectly IonizingIndirectly Ionizing PenetratingPenetrating UnchargedUncharged Energy is absorbed (transferred) through collision with Energy is absorbed (transferred) through collision with
orbiting electronsorbiting electrons
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Ionization classificationIonization classification
Negatrons Negatrons ––
Positrons Positrons ++
Conversion Electrons Conversion Electrons ––
Auger electrons Auger electrons –– xβGamma rays and X-rays
γBeta particles
Indirectly Ionizing radiationNo electric chargePenetrating radiation
Directly Ionizing radiationElectric chargeNon-penetrating
pathrange rangepath
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Ionization and production of delta rays (secondary ionizations)
Further ionizations or excitations
Ionizations
(energy transfer)
Coulombic forces
Further ionizations or excitations
+
+
Charged Particles – non-penetratingCharged Particles – non-penetratinginteraction via the coulomb forces of attractioninteraction via the coulomb forces of attraction
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Charged Particles – non-penetratingCharged Particles – non-penetratinginteraction via the coulomb forces of attractioninteraction via the coulomb forces of attraction
.
Bremsstrahlung x-ray
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Photoelectric effectPhotoelectric effect uncharged x- and gamma-ray interaction via direct collisionuncharged x- and gamma-ray interaction via direct collision
Lack of charge permits passage of photon through matter without electrical interaction
Total energy is transferred to orbiting electrons through direct impact
Photon colliding with an orbiting electron in the K-shell
Knocking out an electron and creating a vacancy
Or alternatively energy is transferred to an auger electron
Vacancy filled by cascading electrons from higher orbits, creating Characteristic x-rays
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Compton scatteringCompton scattering
Partial energy transferred to orbiting electrons through Partial energy transferred to orbiting electrons through direct impact by an x- or gamma-raydirect impact by an x- or gamma-ray
x- or gamma-ray scatters and continues at a lower x- or gamma-ray scatters and continues at a lower energyenergy
Electron energy is the difference between the imparted Electron energy is the difference between the imparted x- or gamma-ray energy and the orbital binding energyx- or gamma-ray energy and the orbital binding energy