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

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6.5.1EmittanceMeasurement Arstexperimentconsistedinvaryingthebunchlengthattheundulatorlocationandmeasuring interaction,ifthosearepresent.Afullyself-consistentcode,writtenbyR.LiofJeersonLab[70], implementedinparmelawefoundthatatsuchpointtheemittanceincreasescomparedtothecase intheundulatorvicinity(asinferredfromthemaximumCTRsignal).Fromasimplisticmodel whereCSRisnotincludedinthecalculationisapproximately10%.Atthetimeofthemeasurement weoperatedthegunwithaverypoorphotocathodeandcouldnotextractmorethat20pCcharge perbunch,atoolowchargetounambiguouslymeasurepotentialeectsfromCSRbunchself ingure6.21.Theemittanceseemstogothroughamaximumforaminimumbunchlength thehorizontalemittanceafterthedecompressorchicane.Atypicalplotobtainedispresented ranfor60pCandanominalemittanceofapproximately7mm-mradyieldeda20%increasein emittance13. Wealsoattemptedtocomparethetransversehorizontalemittancebeforeandafterthearc1.Inthe casecorrespondingtothenominaloperationofthelinac,whichcorrespondstoaminimumbunch lengthintheundulatorvicinity,noemittancegrowthwasobservedwithintheerrorbars(transverse horizontalemittancesmeasuredwereapproximately18mm-mradnormalizedat38MeV). 22 20 18 Before Arc 16 14 Unfortunatelynoparametricstudyhasbeencompletedtothepresentdate Figure6.21:TransverseHorizontalemittanceandtotalpowerCTRsignalmeasuredasafunction ofthelinacgangphase. 13R.Li,privatecommunication,thisincreasewasnoticedtobeverydependentontheopticallatticesetup. 12 10 bunch length CTR signal 8 4 6 8 10 12 14 16 18 20 Linac Phase (RF−deg) Horizontal Norm. Emittance (mm−mrad)
Inthesecondseriesofrun,wewereabletoextracthighchargeperbunchfromthephotocathode (typically60pC)butwewereneverabletoestablishsucientlylowtransverseemittanceinthe 6.5.2EnergySpreadMeasurement IRFEL14toprovidealowenoughsignal-to-noisetoseedenitivelyapotentialemittancegrowth hadremovedalltransverseeectsoftransportfromtheviewerimages,somethingthatneedstobe donetobesureonlyenergyspreadisbeingobservedontheviewers.However,forafewselectcases atthearcexit.Inthecaseofenergyspread,itwasgenerallydiculttoconvinceourselvesthatwe correspondingtoshortbunchlengthsclosetotheundulator,webelievewehavegooddata,and whichindicatestheenergyspreadincreasebetweenthecompressorchicanemidpointandthearc1 exitshouldbeoftheorderof5%15. withintheresolutionofthesemeasurements,theyshownoincreaseinenergyspreadaspicturedin gure6.22.ThisresultisconsistentwithsimulationperformedwiththeJLabselfconsistentcode −0.01 0 0.01 −0.01 0 0.01 −0.01 0 0.01 −0.01 0 0.01 0.5 energyspread(nounits)].Thebottomplotpresentsthermsrelativeenergyspreadcomputedfrom 0.4 thedistributions. Figure6.22:Energydistributionmeasuredalongthebeamline,atthechicanemidpoint(A)and (B)andentranceofthearcs(C)and(D)[thehorizontalaxisoftheseplotrepresenttherelative 0.3 14thereasonisstillnotunderstoodatthepresenttime 15R.Li,privatecommunication 0.2 0.1 0 0 20 40 60 80 Distance from the cryomodule exit (meters) δ (%) Energy Distrib. (A) (B) (C) (D)
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HighBrightnessElectronBeamDiagnosti
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eratedupto48MeVpriortothelasingsyst
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IthanktheCEBAFmachineoperators,with
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3.4MeasurementoftheLongitudinalResp
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5.6ZerophasingTechniqueforBunchLeng
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ListofTables 3.2Comparisonofcoecien
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ListofFigures 1.1Comparisonoftheexp
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3.11Momentumcompactionandnonlinearm
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4.18Overviewofthephasespacesampling
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5.16Interferogrammeasuredfordierent
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6.10Comparisonofthermstransversehor
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Chapter1 UVdomainandareplannedtogen
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space-chargeinthelowenergyregime,an
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!Vjitsthevelocity,and!Xjisthepositi
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equation boundarybetweenvacuumandam
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10 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.
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1.0 0.8 0.6 0.4 0.2 E=10 MeV E=42 M
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00000000000000000000000000000000000
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harmonicwithproperchoiceoftheKvalue
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Bu(rms)0.28T ParameterValueUnit Nu
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2.7TheJeersonLabIRproject usedasexp
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Study TheFELdriveraccelerator:Latti
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ParameterValue x -0.178 x(m) 8.331
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Thepurposeofmeasuringthetransverser
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computedusingthelatticeset-upuseddu
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etatronexcitationaspicturedingure3.
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∆ x (mm), Corrector 0F00H ∆ x (
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1 0.5 0 spreadoftheparticlewassetto
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2 1 −5 −3 −1 1 3 5 k (m q −
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Experimentallythecalibrationcoecien
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tioned.FromthetransferfunctioninFig
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Pickup Experiment #2 #3 #4 Simulati
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Fromthesebothmeasurementitispossibl
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. . . . . . . . . . . . . . . . . .
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10 5 Sext. ON Figure3.20:Eectofthes
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spaceabeamthatconsistsofNparticles,
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Asforthegeometricemittanceonecanden
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(a) ceramic radiator beam x-wire be
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and validundertheassumptionofaunifo
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1000 900 800 700 Figure4.4:Steadyst
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Fraction of Beam enclosed within (%
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5 2 2 3 4 5 6 7 8 9 10 0 10 5 2 Foi
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Actuator Inserts Foil and Mirror CI
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shortterm,touseasbeamdensitymonitor
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Alongwiththeseimplementedoperations
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whereiistheerrorontheithbeamsizemea
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Let'sassumethethinlensapproximation
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obtainedviathestatisticalanalysis.T
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20 18 16 . 14 . 12 . Figure4.14:Rel
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100 10 −3 10 −2 10 −1 10 that
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multislits mask (copper) Aluminum F
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TheReductionoftheSpaceChargeconditi
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. . . . . . . . . . . . . . . . . .
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Table4.7:Typicalsystematicerroronem
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180 8 160 6 Figure4.22:Anexampleof2
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4.0 3.5 3.0 2.5 Figure4.24:Emittanc
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Characterization LongitudinalPhaseS
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concentrateonthebeamparametersinthe
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1.1 1 mrad 0.9 5 mrad mainlyduetoth
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Population Population 100000 90000
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Theequation5.8yields: f()=jZ+1 11Xn
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presentanoutlineofthisproofbelow,an
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contrastintheCEBAFmachine,varyingas
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1.5 1 correspondtothevarianceofveco
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Ε’ 2 B Mirror M 2 Ε2 Polarizer
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Page 159 and 160: BeamDynamicsStudies Chapter6 undula
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Page 169 and 170: ε x (mm−mrad) Nominal 6 4 2 cryo
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Page 187 and 188: Conclusion Chapter7 Therecirculator
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Page 201 and 202: Initialization MAIN Stop INPUT DECK
Page 203 and 204: C.0.6TheDispersionRelationsfor^S(!)
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