study materials for mit course [22.101] - applied nuclear physics

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1、22.101AppliedNuclearPhysics(Fall2004)Lecture1(9/8/04)BasicNuclearConcepts________________________________________________________________________References--P.MarmierandE.Sheldon,PhysicsofNucleiandParticles(AcademicPress,NewYork,1969),vol.1.__________________________________________________________

2、______________GeneralRemarks:ThissubjectdealswithfoundationalknowledgeforallstudentsinNED.Emphasisisonnuclearconcepts(asopposedtotraditionalnuclearphysics),especiallynuclearradiationsandtheirinteractionswithmatter.Wewillstudydifferenttypesofreactions,single-collisionphenomena(crosssections)andleave

3、theeffectsofmanycollisionstolatersubjects(22.105and22.106).Quantummechanicsisusedatalowerlevelthanin22.51and22.106.Nomenclature:AXdenotesanuclide,aspecificnucleuswithZnumberofprotons(Z=atomicznumber)andAnumberofnucleons(neutronsorprotons).SymbolofnucleusisX.Thereisaone-to-onecorrespondencebetweenZa

4、ndX,thusspecifyingbothisactuallyredundant(buthelpfulsinceonemaynotremembertheatomicnumberofalltheelements.ThenumberofneutronsNofthisnucleusisA–Z.Oftenitissufficientto235specifyonlyXandA,asinU,ifthenucleusisafamiliarone(uraniumiswellknowntohaveZ=92).SymbolAiscalledthemassnumbersinceknowingthenumbero

5、fnucleonsonehasanapproximateideaofwhatisthemassoftheparticularnucleus.233235238Thereexisturaniumnuclideswithdifferentmassnumbers,suchasU,U,andU;nuclideswiththesameZbutdifferentAarecalledisotopes.Bythesametoken,nuclideswiththesameAbutdifferentZarecalledisobars,andnuclideswithNbutdifferentZarecalledi

6、sotones.IsomersarenuclideswiththesameZandAindifferentexcitedstates.Weare,inprinciple,interestedinalltheelementsuptoZ=94(plutonium).Thereareabout20moreelementswhichareknown,mostwithveryshortlifetimes;theseareofinterestmostlytonuclearphysicistsandchemists,nottonuclearengineers.Whileeachelementcanhave

7、severalisotopesofsignificantabundance,notalltheelementsare1ofequalinteresttousinthisclass.Thenumberofnuclideswemightencounterinourstudiesisprobablylessthannomorethan20.Agreatdealisknownaboutthepropertiesofn