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

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tectorconsistsofagas-lledcellenclosedbytwomembranes.Theincomingradiationisabsorbed IntheearlystageoftheIRFELcommissioning,theexperimentalsetupdescribedingure5.12was usedtoimagetheCTRbeamemissionsourceproducedbytheelectronbeamasitpassesthrough analuminumfoilontoaGolaycelldetector.TheGolaycell(seeFig.5.7(A))isathermaldetector withanearlyuniformenergyresponsefromtheultravioletuptothemicrowaveregion.Thede- 5.4ObservationofCoherentTransitionRadiation overabroadrangeofwavelengths.Theabsorbedradiationheatsthegaswhichinturnincreases chosensothatthecorrespondingsurfaceimpedanceyieldsthemaximumabsorptionofradiation thepressureinsidethecellanddistortsthesecond(exible)membrane.Thedistortionissensedby aphotodetectorcellthatdetectsalightbeamreectedfromthemembrane.Thiseectisamplied bytwolargegridsarrangedsothatinitially,i.e.whennoradiationisdetected,thelinesofonegrid areimagedonthespaceofthesecondgridresultinginnolightdetectionbythephotodetector. byathinaluminumlayerdepositedonthe\input"membrane.Thealuminumlmthicknessis Whenthemembraneisdistorted,theimageoftherstgridshifts,allowingsignicantlymorelight toreachthephotodetector.Thisgridsystemisinfactamechanicalmeansofenhancingtheeect workstationcommunicatingtothecontrolsystem. factor10usingasimpleoperationalamplierlocatedintheacceleratortunnelenclosure,thenthe signalisbroughtintheservicebuildinglocatedupstairsthetunnelwhereitisshapedusinganoise ofsmalldisplacementsofthemembrane.Theoutputanalogsignalfromthephotodetectorinthe samplerateequaltothebeammacropulserepetitionrate.Thedigitalsignalisbroadcastviaa VMEinput/outputcontroller(IOC)totheEthernetnetworksothatitcanbeaccessedfromany GolaycellsetupiselectronicallyprocessedasdescribedinFig.5.7(B):First,itisampliedbya lter.Afterward,itisfedintoaAnalogtoDigitalConverter(ADC)whereitisdigitized,ata Itispossibletoverifythenonlinearityoftheradiationversusthebunchchargeaspicturedin Figure5.7:SimpliedschematicsofaGolaycell(A)andtheassociatedsignalacquisitionelectronics(B). pronouncedcomparedtotheonemeasuredintheCEBAFaccelerator[20]forexample.Thisis gure5.8.ThequadraticdependenceoftheCTRsignalversusthechargeperbunchisnotvery 0000000 1111111 0000000 1111111 000000 111111 0000000 1111111 bi-convex lenses 000000 111111 0000000 1111111 000000 111111 light emitting diode 0000000 1111111 000000 111111 LED 000000 111111 Grid 0000000 1111111000 111 grid 0000000 1111111 0000000 1111111 photodiode Photodiode detector 000 111 000 111 0000000 1111111000 111 0000000 1111111 Detector 0000000 1111111 bi-convex lenses (A) 000 111 000 111 0000000 1111111 000 111 0000000 1111111 000 111 0000000 1111111 refecting membrane 000 111 0000000 1111111 000 111 0000000 1111111 000 111 0000000 1111111 000 111 0000 1111 000 111 0000 1111 000 111 000 111 absorbing Reflecting Membrane adjustable 000000 111111 adjustable length 000000 1111110000 1111 000000 1111110000 1111 gas cell length 0000 1111 0000 1111 0000 1111 Absorbing Membrane 00 110 00 11 00 11 000 111 00 1100 11 00 11 00 11 00 11 00 11 00 11 00 11 00 1100 11 00 11 00 11 00 11 0000000 0000 1111 0000 1111 000 111 membrane 1 0000 1111 000 111 0000 1111 000 111 1 1 Golay 1 Cell Output 1 1 1 1 Gas Cell 01 01 01 01 ADC 01 input 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 Amplification System Electronic Filter (B)
contrastintheCEBAFmachine,varyingaslitapertureopeninginachoppercavityvariesthe chargeperbunch.Forallthepracticalslitsopenings,thebeamisneverspace-chargedominated andsotheslitopeningdoesnotsignicantlyaectthebunchingprocess. duetothemethodweusetovarythecharge:weusearotationalpolarizertoattenuateorincrease thedrivelaserpoweronthephotocathodethatalsosignicantlyaectsthebeamdynamicsinthe machine(especiallyinthelowenergyregionwherethebeamdynamicsisstronglydependent,via spacechargeforces,onthecharge).Thereforevaryingthechargealsoaectsthebunchlength, andthereforetheCTRsignalsinceitisdependentonboththechargeandthebunchlength.By Figure5.9depictsthedependenceoftheCTRsignalversustheoverallphaseofthemainlinac: 4.0 3.5 3.0 2.5 perbunchischangedbyvaryingtheintensityofthephotocathodedrivelaser.Thecirclesare 2.0 1.5 1.0 ergy,is4degandtheexpectedphaseformaximumbunching(i.e.minimumbunchlength)is Figure5.8:Scalingofcoherenttransitionradiationpowerversuschargeperbunch.Thecharge theexperimentaldatapointandthedashlineistheresultofaquadraticinterpolationofthe 0.5 approximately6degwhichisingoodagreementwiththephasevalueforwhichthemaximumCTR signalisobservedingure5.9('6:3deg). experimentalpoint. duringthisexperimentthemachinesettingswerekeptconstantandonlythelinac\gang"phase4 wasvaried.Themaximumaccelerationphase,determinedexperimentallybymaximizingtheen- 0.0 0 10 20 30 40 50 60 70 80 90 100 AlastexperimentconsistedofvaryingthebeamspotsizeontheTRradiatorandeachtime Charge per Bunch (pC) recordingtheCTRsignal.Thevariationofthissignalversustheequivalentbeamradiuswedene aspxyispresentedingure5.10.Atthispointitisdiculttotellwhetherthedecreaseoftotal otherradio-frequencyelementsintheIRFEL(seeAppendixD) powerdetectedisduetothespatialortheangularBFF. 4the\gangphase"knoballowstoshiftalltheacceleratingcavitiesinthelinacbythesamephasecomparetothe CTR Signal (Volts)
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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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Page 121 and 122: Population Population 100000 90000
Page 123 and 124: Theequation5.8yields: f()=jZ+1 11Xn
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Page 159 and 160: BeamDynamicsStudies Chapter6 undula
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EnergySpread(%) BunchLength(mm) Par
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15 Effect of RMS energy Spread 10 F
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6.4.4BunchSelfInteractionviaCoheren
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100 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0
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Inthesecondseriesofrun,wewereableto
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Conclusion Chapter7 Therecirculator
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[2]Y.Shibata,T.Takahashi,T.Kanai,K.
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[29]J.-C.Denard,C.Bochetta,G.Traomb
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[65]B.C.Yunn,\ImpedancesintheIRFEL"
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TEM:transverseelectricmagnetic. TOF
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B.2Anoteonspacecharge Wedenetheslop
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B.3.3PARMELA FeaturesofJeersonLabVe
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Initialization MAIN Stop INPUT DECK
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C.0.6TheDispersionRelationsfor^S(!)
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have: Howeveritshouldbenotedthatweh
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FigureD.1:OverviewoftheRF-controlsy
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