High Brightness Electron Beam Diagnostics and their ... - CASA
High Brightness Electron Beam Diagnostics and their ... - CASA
High Brightness Electron Beam Diagnostics and their ... - CASA
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Chapter1<br />
UVdomain<strong>and</strong>areplannedtogenerateXrays.Theyhavefoundmanyapplicationsranging positron)accelerators.Suchlightsourceshaveproventobecapableofgeneratingphotonindeep Introduction<br />
fromfundamentalsciences(biology,crystallography,etc...)toindustrialapplications(e.g.nanoelectronics). Thegenericcongurationconsistsof,e.g.,anelectronbeamacceleratorthatgenerates<strong>and</strong>prepares (i.e.accelerates,bunches<strong>and</strong>transverselyshapes)theelectronbeambeforesendingitinaperiodic magneticeldcreatedbyanundulatormagnetwhichcausestheelectronstooscillatetransver- Inrecentyears,therehasbeenagrowinginterestincoherentlightsourcesdrivenbyelectron(or<br />
sally.Asanelectronbunchoscillates,itcreatesa(spontaneous)synchrotronradiationpulsethat lightsources:thestoragering<strong>and</strong>thefree-electronlaser(FEL).Intheformercase,theparticle mirrorsitscharacteristics(i.ebunchlength,shape,..).Twoschemesaregenerallyusedforsuch beamisstoredinaring<strong>and</strong>periodicallygoesthroughanundulatormagnet,whileinthelatter casethebeamisgeneratedbyalinac<strong>and</strong>passesthoughtheundulatoronce.Thefree-electron producehighbrightnessphotonbeamcomparedtostoragering.Furthermorebrightnessofstorage ringtendstoworsenatlowenergy,duetoTouschekintra-beamcollision,<strong>and</strong>highenergybecause oftheimportanceofquantumuctuations.Inaresonator-basedFELtheundulatormagnetis laserhasgeneratedmuchmoreinterestedintherecentyearsbecauseof<strong>their</strong>unequaledabilityto<br />
oftheincoherentsynchrotronemission.ThislattertypeofFELisespeciallysuitedtogenerate neousradiationcreatedviasynchrotronemission.InaSASE(selfampliedspontaneousemission) FEL,theundulatorismadelongenoughsothatlasingarise\naturally"fromselfamplication ultra-shortwavelength(e.g.X-rays)coherentlightsinceforsuchwavelengthsamirrormightnot quitesimilartoconventionallaser,the\free"electronsactsasmediumthatampliesasponta- coherentlysuperimposedtotheformerphotonpulse.InsuchanoscillatorFELthemechanismis insertedbetweentwomirrorswhichconstitutesaresonantopticalcavitythatrecirculatesthepho-<br />
beavailabletherebypreventingtheresonatorconguration.AmainfeatureoftheFEL-basedlight tonpulsecoincidentlywiththenextincomingelectronbunch.Itideallygeneratesaphotonpulse<br />
electronbeam. Generallythedriveracceleratorconsistsinroomtemperaturecavitiesthatdonotallowsimultane- sourceis<strong>their</strong>abilitytoprovidelaserlightoveracontinuoustunablerangeofwavelength,thatcan besubstantial,byvaryingthemagnetostaticeldoftheundulatorortheenergyoftheincoming 1