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

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

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

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

Charged Particles – non-penetratingCharged Particles – non-penetratinginteraction via the coulomb forces of attractioninteraction via the coulomb forces of attraction

.

Bremsstrahlung x-ray

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

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