放射物理-chapter1-2综述课件

TWOTWOBME College Sherman sheenAtomsMatter is composed by atomsStructure of Atomsnucleus-radius 10-14melectrons clouds-radii 10-10mAtomic number:Z number of electrons chemical propertiesConstitution protons neutronsQ:How to know the structure of the nucleus?Q:Properties of protons and neutrons:charge and massmass number:A protons+neutrons neutrons=A-ZNucleusnucleonIsotope definition:Atoms composed of nuclei with the same number of protons but different number of neutrons are called isotopes.stable or unstable;disintegration and radioactive;NucleusAtomic MassCarbon mass number 12 represented by ANotation for atomic species subscripts-Z and superscripts-AIsotope of Hydrogen,Helium,Cobalt HydrogenZ=1111012123StableStableRadioactiveProtonDeuteronHydrogenDeuteriumTritiumHeliumZ=232He42He52He62He82He222221234634568StableStableRadioactiveRadioactiveRadioactiveAlphaElemental particles pproton 1.007277,+1 The proton is the nucleus of the hydrogen atom.The hydrogen atom consists of 1 proton in the nucleus and 1 external electron.The mass of the neutral atom is 1.007277+0.000548=1.007825 mass units.The proton is one of the fundamental building blocks of all nuclei.Beams of protons are being used in radiotherapy.Elemental particlesnneutron 1.008665,0 The neutron is the other fundamental building block of all nuclei.Neutrons have nearly the same mass as protons.Since the neutrons is an uncharged particle it is hard to stop and difficult to detect.Beams of neutrons are being used in radiotherapy.Elemental particles e-0.000548,-1The electron has a very small mass compared with the proton.Electrons abound in nature.Every atom contains electrons outside the nucleus.The electron is easily detected.It is sometimes called a negatron or beta particle and represented by e,e-or-.Beams of high energy electrons are extensively used in radiotherapy.Elemental particles e+0.000548,+1The positron has the same mass as an electron but carries a positive charge.Positrons exist in nature only while they are in motion.A slowly moving or stationary positron quickly combines with an electron to form a burst of radiation in the form of two gamma rays(see below).Positrons are represented by e+,or+and referred to as beta plus particles They are used in nuclear medicine.Elemental particles Hv ,0,0Strictly speaking,the photon is not a particle,but a bundle of energy which travels at the speed of light(3108ms-1).In many interactions it acts much like a particle.Photons are referred to almost interchangeably as quanta or gamma rays and are represented symbolically by h or.Beams of photons account for the major part of external beam radiotherapy.Elemental particlesneutrino e ,0The neutrino is a very small particle with practically no mass and no charge.For this reason,it has been very difficult to detect experimentally.Its interaction with protons to form neutrons and positrons according to the reactione+p n+has been observed.The neutrino was introduced originally from theoretical considerations to help explain beta decay.Elemental particles Mu mesons,+,-,207m0 ,+1 or-1 Mu mesons may be either positively or negatively charged and have a mass 207 times the mass of the electron.They are produced indirectly by the interaction of very high energy particles with matter.The particles are unstable and decay spontaneously into electrons and neutrinos according to the reactions+e+2-e-+2The mean life of the particles is 2.1510-6 sec.Elemental particlesPi mesons +273 m0 +1 -273 m0 -1 0 265 m0 0Pi mesons may have a positive a negative charge or may be neutral.They are produced by the bombardment of matter with high energy protons or photons.The charged mesons decay into mu mesons and neutrinos according to+-+with a mean life of 2.510-8 s.The neutral 0 meson decays into 2 photons0 h1+h2with a mean life of 10-15 seconds.Beams of negative mesons are being used in radiotherapy.Elemental particles pproton 1.007277,+1 nneutron 1.008665,0 e-0.000548,-1 e+0.000548,+1 H 0,0 e ,0 Mu mesons 207m0 ,+1 or-1 Pi mesons 273m0 ,+1 or-1 265m0 0 Extranuclear structureArrangement of planetary electrons outside the nucleusThe outermost orbitChemical properties and valence repeatinert gas:He,Ne,alkaline elements:lithium,sodium,Extranuclear structurechemical propertiesAtomic Energy levelsOptical radiation and X radiationNuclear Energy levelsGamma rayQuantum nature of radiationQuantum or Photon bundle of energy Energy of a PhotonFor a diagnostic X-ray Generator,wavelength 10pm,1 photon:Quantum nature of radiationImportant equation Wavelength and energy Quantum nature and continuous radiation Electromagnetic SpectrumFrequency(Hz)WavelengthPhotonEnergyProperties1.01053.01010103 km0.01 m413 peV124 eV Radio waves ranging from long waves through the broadcast band,to short waves and to ultra short waves in radar.These waves are produced by electrical oscillations and detected by electronic equipment.They will pass through nonconducting layers of materials but are reflected by electrical conductors.Electromagnetic SpectrumFrequency(Hz)WavelengthPhotonEnergyProperties3.01001012123.03.010101414100 m1 m12.4 meV1.24 eVInfrared radiations.These are produced by molecular vibration and the excitation of the outer electrons of the atom.They are generated by heat in stores,radiators,et cetera,and can be detected by heat devices and films.Most solid materials are opaque to infrared radiations.Electromagnetic SpectrumFrequency(Hz)WavelengthPhotonEnergyProperties4.31031014147.57.510101414700 nm400 nm1.77 eV3.1 eV Visible light ranging from red through yellow,green and blue to violet.Produced by the excitation of the outer electrons of an atom.Generated in lamps and in gas tubes by electrical discharge.Detected by films,by photoelectric cells,and by the eye.Transmitted by materials such as glass.Electromagnetic SpectrumFrequency(Hz)WavelengthPhotonEnergyProperties7.51051014143.0103.0101616400 nm10 nm3.1 eV124 eV Ultraviolet light.Produced by the excitation of outer electrons in the atom.Detected by films,Geiger counters,and ionization chambers.Produces erythematic of the skin;kills bacteria and is an agent in the production of vitamin D.Electromagnetic SpectrumFrequency(Hz)WavelengthPhotonEnergyProperties3.01001016163.0103.010181810 nm100 pm124 eV12.4 keVSoft x rays.Produced by the excitation of the inner electrons of an atom.Detected by films,Geiger counters,and ionization chambers.Have the ability to penetrate very thin layers of material.Of little value in radiology because of their limited power of penetration.3.01001018183.0103.0101919100 pm10 pm12.4 keV124 keVDiagnostic x rays and superficial therapy.Electromagnetic SpectrumFrequency(Hz)WavelengthPhotonEnergyProperties3.01001019193.0103.010202010 pm1 pm124 keV1.24 MeVDeep therapy x rays and gamma rays from radium decay products.3.0100102121100 fm12.4 MeVRadiation from a small betatron or linear accelerator.3.010010222210 fm124 MeVRadiation from a large linear accelerator.3.01001023231 fm1.24 GeVProduced in the operation of large proton synchrotrons or linear accelerators.Electromagnetic SpectrumFrequency(Hz)WavelengthPhotonEnergyProperties1.01053.010103 km0.01 m413 peV124 eVRadio waves ranging from long waves through the broadcast band,to short waves and to ultra short waves in radar.These waves are produced by electrical oscillations and detected by electronic equipment.They will pass through nonconducting layers of materials but are reflected by electrical conductors.3.010123.01014100 m1 m12.4 meV1.24 eVInfrared radiations.These are produced by molecular vibration and the excitation of the outer electrons of the atom.They are generated by heat in stores,radiators,et cetera,and can be detected by heat devices and films.Most solid materials are o p a q u e t o i n f r a r e d r a d i a t i o n s.4.310147.51014700 nm400 nm1.77 eV3.1 eVVisible light ranging from red through yellow,green and blue to violet.Produced by the excitation of the outer electrons of an atom.Generated in lamps and in gas tubes by electrical discharge.Detected by films,by photoelectric cells,and by the eye.Transmitted bymaterials such as glass.7.510143.01016400 nm10 nm3.1 eV124 eVUltraviolet light.Produced by the excitation of outer electrons in the atom.Detected by films,Geiger counters,and ionization chambers.Produces erythematic of the skin;kills bacteria and is an agent in the production of vitamin D.3.010163.0101810 nm100 pm124 eV12.4 keVSoft x rays.Produced by the excitation of the inner electrons of an atom.Detected by films,Geiger counters,and ionization chambers.Have the ability to penetrate very thin layers of material.Of little value in radiology because of their limited power of penetration.3.010183.01019100 pm10 pm12.4 keV124 keVDiagnostic x rays and superficial therapy.3.010193.0102010 pm1 pm124 keV1.24 MeVDeep therapy x rays and gamma rays from radium decay products.3.01021100 fm12.4 MeVRadiation from a small betatron or linear accelerator.3.0102210 fm124 MeVRadiation from a large linear accelerator.3.010231 fm1.24 GeVProduced in the operation of large proton synchrotrons or linear accelerators.Electromagnetic SpectrumBinding energy K radiation,BE:70000ev L radiation,BE:11000ev M radiation,BE:2500evRadiation of energy from an atomRadiation of energy from an atomsummaryAtomsThe NucleusElemental ParticlesExtranuclear StructuresAtomic Energy LevelsNuclear Energy LevelsElectromagnetic RadiationQuantum Nature of RadiationThe Electromagnetic SpectrumRadiation of Energy from an Atom