High Brightness Electron Beam Diagnostics and their ... - CASA

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Emittance (mm−rad)
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un-normalizedrmsemittance,the-function,theparameter. Figure4.15:Monte-Carlosimulationof200emittancemeasurements.Theplots(fromtop)arethe
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β (meters)
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α (no units)
ticledynamics.IntheInjectiontransferline,thebeamenergyisapproximately10MeVinthisTheenvelopettingtechniqueexposedintheprevioussectionreliesonthevalidityofsinglepar- beamspotsizeversusthequadrupoleexcitation. 4.5MeasurementofEmittanceintheInjectionTransferLine
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0 25 50 75 100 125 150 175 200
regime,thespacechargecollectiveforce(i.e.Coulombianrepulsionbetweenelectroninthebunch)
Measurement Number
envelope.Inanycasetheenvelopettingaredicultforcharacterizing,e.g.measuringemittance, aresignicantthebeamenvelopemustbedescribedwithadierentialequation:theSachererrms envelopeequation[37].Propagationofthebeamthroughamagneticelementthenrequiresthe usingthesingleparticleformalismbasedontransfermatrix.Inthecasewherespacechargeforces integrationofthisequation;generallyspeakingthisintegrationhastobeperformedusingnumericalmethodsbutinsomecaseonecanuseperturbativetheorytondgoodapproximationofthe aresignicantfora60pCchargeperbunch.Therefore,thebeamenvelopecannotbepropagated
trace-spacedensity. samplingtechniques[36].Thislattertypeofmeasurementcanalsobeusedtodirectlymeasurethe ofsuchspace-charge-dominatedbeam.Analternativemethodisbasedonthesocalledphasespace tures4.18.Thebeamletgeneratedbyeachapertureretainsthetransversetemperatureofthe beam.Itisdriftedthroughafreespaceuptoabeamprolemonitor.Thedriftlengthischosenso
Thetechniqueconsistsofinterceptingthespace-charge-dominatedbeambyaseriesofaper