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

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15<br />

Effect of RMS energy Spread<br />

10<br />

Figure6.17:Emittancegrowthduetochromaticaberrationversusthemomentumspread<strong>and</strong><br />

5<br />

bendssystem)cancoupletothetransverseplane<strong>and</strong>yieldemittancedegradation.Thelinearized energyosetofthebeam.<br />

Effect of Energy Centroid Offset<br />

equationofmotionofanelectroninabend,assumingnoexternalfocusing<strong>and</strong>nocouplingbetween thetwotransversephasespaces,forthebendingplane(thex-x'planeinthecaseoftheIRFEL) is[59]: haveshowthatitisverysmallforourbeamparameters.Infactallthebeamlinecomponentshave beenspeciedinsuchawaythatthetotallongitudinallossfactoriswithinsomeimpedancebudget sothatthepotentialbeamdegradationisverysmall[65]. Inthissectionwewouldliketoshowhowenergyspreadgeneratedinadispersiveregion(i.e.a<br />

0<br />

0 0.5 1 1.5<br />

δ (%)<br />

radiusofcurvatureofthetrajectory<strong>and</strong>istherelativeenergyosetw.r.t.thereferenceorbit. wheresisthelongitudinalpositionreferredw.r.t.theentranceofthebendingsystem,xisthe Let'sassume,forsimplicity,thatthemechanismgeneratesanenergyspreadthatisonlydependent onthecurvilinearcoordinates10,i.e.=(0)+(s).Undersuchanassumption,thelatter equationtakestheform: d2x<br />

10generallyspeakingthemechanismisalsodependentontime,foracompletetreatmentsee[69]<br />

d2x ds2+x2x=(0)+(s)<br />

∆ε/ε (%)<br />

ds2+x2x=x (6.22)<br />

x (6.23)

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