How is energy deposited in the interaction with matter of each of the following? photons, electrons,...

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Physics

How is energy deposited in the interaction with matter of eachof the following? photons, electrons, alphas, neutrons. Is the fullenergy of the radiation deposited? If not, where does the rest go?Is the energy deposited with high linear energy transfer or lowlinear energy transfer? Is the radiation track sparse or dense?

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The behavior of photons in matter is completely different fromthat of charged particles In particular the photons lack of anelectric charge makes impossible the many inelastic collision withatomic electrons socharacteristic of charged particlesFor this kind of radiation the most important mechanism ofinteraction areaPhotoelectriceffectbCompton and RayleighscatteringcPair productionAs consequence of such kind of interactions a photon thatinteracts with the target is completely removed from the incidentbeam in other words a beam of photons that cross a medium is notdegraded in energy but only attenuated in intensity Moreover dueto the smallest cross section of all this kind of reactionsxrayor ray are many times more penetrating than charged particlesThe attenuation of the incident beam is exponential with thethickness of the absorbing medium and can be expressed by thefollowing relationIx I0 exp xlwhere l is the linear attenuation coefficientI0 is the incident beam intensity and x the thickness Thelinear attenuation coefficient is related to the cumulative crosssection by the relationl A totwhere A is the number of atoms per unit of mass andtot is the total cross section The total or cumulativecross section tot is the sum of all the cross sections ofthe interactions mentioned above A plot of this quantity is shownin Figure 16 where the different components have beenhighlightedIn photoelectric absorption a photon disappears being absorbedby an atomic electron The process results in ionization bysubsequent ejection of the electron from the atom The energy ofthe liberated electron is the difference between the photon energyand the energy needed to extract the electron from the atom iethe binding energy of the electron The recoil momentum is absorbedby the nucleus to which the ejected electron was bound If theresulting photoelectron has sufficiently enough of kinetic energyit may be a source of a secondary ionization occurring along itstrajectory and in the case of the semiconductor material it maycreate further eh pairs If the electron does not leave thedetector the deposited energy corresponds to the energy possessedby the incident photon This feature of the photoelectric effectallows calibrating the gain of the detector chained with itsreadout system if the energy required to create a single eh pairis known The range R of the electron having the kinetic energy Eis of the order of some micrometers as given by the followequationRum 408 103 x EkeV 15Thus the cloud of generated charge is confined close to thephoton absorption point The clear image See Answer

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