放射物理-chapter1-2综述课件

ＴＨＥＰＨＹＳＩＣＳＯＦＲＡＤＩＯＬＯＧＹＢＡＳＩＣＣＯＮＣＥＰＴＳＰＡＲＴTWOBMECollegeShermansheenAtomsMatteriscomposedbyatomsStructureofAtoms nucleus----radius10-14m

electronsclouds----radii10-10mAtomicnumber:Znumberofelectrons chemicalpropertiesConstitutionprotonsneutronsQ:Howtoknowthestructureofthenucleus?Q:Propertiesofprotonsandneutrons:chargeandmassmassnumber:A

protons+neutrons

neutrons=A-ZNucleusnucleonIsotopedefinition:Atomscomposedofnucleiwiththesamenumberofprotonsbutdifferentnumberofneutronsarecalledisotopes.

stableorunstable;disintegrationandradioactive;

NucleusAtomicMassCarbonmassnumber12 representedbyANotationforatomicspecies

subscripts-Zandsuperscripts-AIsotopeofHydrogen,Helium,Cobalt

HydrogenZ=1111012123StableStableRadioactiveProtonDeuteronHydrogenDeuteriumTritiumHeliumZ=232He42He52He62He82He222221234634568StableStableRadioactiveRadioactiveRadioactiveAlphaElementalparticles

p—proton1.007277,+1

Theprotonisthenucleusofthehydrogenatom.Thehydrogenatomconsistsof1protoninthenucleusand1externalelectron.Themassoftheneutralatomis1.007277+0.000548=1.007825massunits.Theprotonisoneofthefundamentalbuildingblocksofallnuclei.Beamsofprotonsarebeingusedinradiotherapy.

Elementalparticlesn—neutron1.008665,0

Theneutronistheotherfundamentalbuildingblockofallnuclei.Neutronshavenearlythesamemassasprotons.Sincetheneutronsisanunchargedparticleitishardtostopanddifficulttodetect.Beamsofneutronsarebeingusedinradiotherapy.

Elementalparticles

e-β-0.000548,-1Theelectronhasaverysmallmasscomparedwiththeproton.Electronsaboundinnature.Everyatomcontainselectronsoutsidethenucleus.Theelectroniseasilydetected.Itissometimescalledanegatronorbetaparticleandrepresentedbye,e-orβ-.Beamsofhighenergyelectronsareextensivelyusedinradiotherapy.Elementalparticles

e+β+0.000548,+1Thepositronhasthesamemassasanelectronbutcarriesapositivecharge.Positronsexistinnatureonlywhiletheyareinmotion.Aslowlymovingorstationarypositronquicklycombineswithanelectrontoformaburstofradiationintheformoftwogammarays(seebelow).Positronsarerepresentedbye+,orβ+andreferredtoasbetaplusparticlesTheyareusedinnuclearmedicine.Elementalparticles

Hv

γ

,0,0Strictlyspeaking,thephotonisnotaparticle,butabundleofenergywhichtravelsatthespeedoflight(3×108ms-1).Inmanyinteractionsitactsmuchlikeaparticle.Photonsarereferredtoalmostinterchangeablyasquantaorgammaraysandarerepresentedsymbolicallybyhν

orγ.Beamsofphotonsaccountforthemajorpartofexternalbeamradiotherapy.

Elementalparticlesneutrinoνe

~,0Theneutrinoisaverysmallparticlewithpracticallynomassandnocharge.Forthisreason,ithasbeenverydifficulttodetectexperimentally.Itsinteractionwithprotonstoformneutronsandpositronsaccordingtothereactionνe+p→n+β+hasbeenobserved.Theneutrinowasintroducedoriginallyfromtheoreticalconsiderationstohelpexplainbetadecay.Elementalparticles

Mumesons,μ+

,μ-

,207m0,+1or-1

Mumesonsmaybeeitherpositivelyornegativelychargedandhaveamass207timesthemassoftheelectron.Theyareproducedindirectlybytheinteractionofveryhighenergyparticleswithmatter.Theparticlesareunstableanddecayspontaneouslyintoelectronsandneutrinosaccordingtothereactionsμ+→e++2νμ-→e-+2νThemeanlifeoftheparticlesis2.15×10-6sec.ElementalparticlesPimesonsπ+273m0+1π-273m0-1π0265m00Pimesonsmayhaveapositiveanegativechargeormaybeneutral.Theyareproducedbythebombardmentofmatterwithhighenergyprotonsorphotons.Thechargedπmesonsdecayintomumesonsandneutrinosaccordingtoπ+→μ++νπ-→μ-+νwithameanlifeof2.5×10-8s.Theneutralπ0mesondecaysinto2photonsπ0→hν1+hν2withameanlifeof10-15seconds.Beamsofnegativeπmesonsarebeingusedinradiotherapy.

Elementalparticlesp—proton1.007277,+1n—neutron1.008665,0

e-β-0.000548,-1

e+β+0.000548,+1

Hνγ0,0

νe

~,0

Mumesons207m0,+1or-1Pimesons273m0,+1or-1265m00

ExtranuclearstructureArrangementofplanetaryelectronsoutsidethenucleusTheoutermostorbitChemicalpropertiesandvalencerepeat inertgas:He,Ne,…alkalineelements:lithium,sodium,…Extranuclearstructure—

chemicalpropertiesAtomicEnergylevelsOpticalradiationandXradiationNuclearEnergylevelsGammarayQuantumnatureofradiationQuantumorPhotonbundleofenergyEnergyofaPhotonForadiagnosticX-rayGenerator,wavelength10pm,1photon:QuantumnatureofradiationImportantequation

Wavelengthandenergy

QuantumnatureandcontinuousradiationElectromagneticSpectrumFrequency(Hz)WavelengthPhotonEnergyProperties1.0×1053.0×10103km0.01m413peV124μeVRadiowavesrangingfromlongwavesthroughthebroadcastband,toshortwavesandtoultrashortwavesinradar.Thesewavesareproducedbyelectricaloscillationsanddetectedbyelectronicequipment.Theywillpassthroughnonconductinglayersofmaterialsbutarereflectedbyelectricalconductors.ElectromagneticSpectrumFrequency(Hz)WavelengthPhotonEnergyProperties3.0×10123.0×1014100μm1μm12.4meV1.24eVInfraredradiations.Theseareproducedbymolecularvibrationandtheexcitationoftheouterelectronsoftheatom.Theyaregeneratedbyheatinstores,radiators,etcetera,andcanbedetectedbyheatdevicesandfilms.Mostsolidmaterialsareopaquetoinfraredradiations.ElectromagneticSpectrumFrequency(Hz)WavelengthPhotonEnergyProperties4.3×10147.5×1014700nm400nm1.77eV3.1eV

Visiblelightrangingfromredthroughyellow,greenandbluetoviolet.Producedbytheexcitationoftheouterelectronsofanatom.Generatedinlampsandingastubesbyelectricaldischarge.Detectedbyfilms,byphotoelectriccells,andbytheeye.Transmittedbymaterialssuchasglass.ElectromagneticSpectrumFrequency(Hz)WavelengthPhotonEnergyProperties7.5×10143.0×1016400nm10nm3.1eV124eVUltravioletlight.Producedbytheexcitationofouterelectronsintheatom.Detectedbyfilms,Geigercounters,andionizationchambers.Produceserythematicoftheskin;killsbacteriaandisanagentintheproductionofvitaminD.ElectromagneticSpectrumFrequency(Hz)WavelengthPhotonEnergyProperties3.0×10163.0×101810nm100pm124eV12.4keVSoftxrays.Producedbytheexcitationoftheinnerelectronsofanatom.Detectedbyfilms,Geigercounters,andionizationchambers.Havetheabilitytopenetrateverythinlayersofmaterial.Oflittlevalueinradiologybecauseoftheirlimitedpowerofpenetration.3.0×10183.0×1019100pm10pm12.4keV124keVDiagnosticxraysandsuperficialtherapy.ElectromagneticSpectrumFrequency(Hz)WavelengthPhotonEnergyProperties3.0×10193.0×102010pm1pm124keV1.24MeVDeeptherapyxraysandgammaraysfromradiumdecayproducts.3.0×1021100fm12.4MeVRadiationfromasmallbetatronorlinearaccelerator.3.0×102210fm124MeVRadiationfromalargelinearaccelerator.3.0×10231fm1.24GeVProducedintheoperationoflargeprotonsynchrotronsorlinearaccelerators.ElectromagneticSpectrumFrequency(Hz)WavelengthPhotonEnergyProperties1.0×1053.0×10103km0.01m413peV124μeVRadiowavesrangingfromlongwavesthroughthebroadcastband,toshortwavesandtoultrashortwavesinradar.Thesewavesareproducedbyelectricaloscillationsanddetectedbyelectronicequipment.Theywillpassthroughnonconductinglayersofmaterialsbutarereflectedbyelectricalconductors.3.0×10123.0×1014100μm1μm12.4meV1.24eVInfraredradiations.Theseareproducedbymolecularvibrationandtheexcitationoftheouterelectronsoftheatom.Theyaregeneratedbyheatinstores,radiators,etcetera,andcanbedetectedbyheatdevicesandfilms.Mostsolidmaterialsareopaquetoinfraredradiations.4.3×10147.5×1014700nm400nm1.77eV3.1eVVisiblelightrangingfromredthroughyellow,greenandbluetoviolet.Producedbytheexcitationoftheouterelectronsofanatom.Generatedinlampsandingastubesbyelectricaldischarge.Detectedbyfilms,byphotoelectriccells,andbytheeye.Transmittedbymaterialssuchasglass.7.5×10143.0×1016400nm10nm3.1eV124eVUltravioletlight.Producedbytheexcitationofouterelectronsintheatom.Detectedbyfilms,Geigercounters,andionizationchambers.Produceserythematicoftheskin;killsbacteriaandisanagentintheproductionofvitaminD.3.0×10163.0×101810nm100pm124eV12.4keVSoftxrays.Producedbytheexcitationoftheinnerelectronsofanatom.Detected