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

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3 Crest Phase is −4 deg 2 lengthattheundulatorvicinityischanged. Figure5.9:CTRsignalversustheSRFlinacoverallphase.Asthelinacphaseisvariedthebunch 1 performaninterferometricmeasurement.Inadditiontoprovidingtheenergyspectrumofthe 5.5TheMichelsonPolarizingInterferometer Onewayofaccessingthefrequencyspectrumofanelectronbunchlongitudinaldistributionisto radiationemitted,itcanalsogiveanestimateofthebunchlengthdirectlyfromtheinterferogram. 0 2 4 6 8 10 Suchestimatesmustbetakenwithcareaswewillseeinthefollowing.WeequippedtheIRFEL 5.5.1Overviewoftheexperimentalsetup SRF−Linac Gang Phase (RF−deg) acceleratorwithtwo\polarizing"MichelsoninterferometerbuiltbytheDepartmentofPhysicsand AstronomyoftheUniversityofGeorgia.Thelocationofthedevicesare: thatisparalleltothispreferreddirectionandtransmitsitsorthogonalcomponent. adichroicpolarizerthathasapreferreddirection.Itreectsthepolarizationoftheincomingeld Theadjective\polarizing"referstothenatureofthebeamsplitterusedintheinterferometer:itis thewigglerinsertionregion,tocheckthebunchlengthisadequatetogettheFELlasing. theinjectorfrontend,toverifythebunchingprocessintheinjectoriscorrect, Becauseelectronsinanacceleratorarerandomlydistributedfrombunchtobunch,autocorrelation ofradiationatwavelengthsmallerthanthebunchlengthwillnotprovideanyinformationonthe thanthebunchlength:thisistheregimeofcoherentemissionandthisinsuresbunch-to-bunch coherenceoftheradiation. IntheIRFEL,thisinterferometerisusedtomeasuretheautocorrelationfunctionofcoherent bunchstructure.Hencethewavelengthofobservationmustbechosentobecomparableorlarger Coherent Transition Radiation Signal (Volt)
1.5 1 correspondtothevarianceofveconsecutivemeasurements. transitionradiation(CTR)pulsesemittedastheelectronbunchespassthrougha0:8mthick, Figure5.10:CTRsignalversusbeamequivalenttransversespotsizepxy.Theerrorbars 0.5 0 0 0.5 1 1.5 2 Thewindowthicknessis4:826mm.Afterthewindow,aplano-convexlenswithafocallength ThebackwardCTRemittedfromthefoildirectlyshinesoutofthevacuumchamberthroughan andthereforeissomewhatmorediculttoanalyze. opticalwindowlocatedat90degwithrespecttothebeamtrajectory.Thisopticalwindowismade ofsinglecrystalquartzsothatitcantransmitfarinfraredradiationwithoutsignicantlosses. independentintheregionofinterestwhereastheCSRspectrumdependsonthefrequency(/!3=2) havepreviouslydiscussed,itwaspreferredtoCSRbecausetheTRpowerspectrumisfrequency and50:8mmdiameteraluminumfoil.ThoughtheuseofCTRisadestructivemeasurementaswe Equivalent Transverse Beam Size (mm) intheFIRdomainof125mmisusedtocollimatetheCTRbeamtoparallelrays(thelensis bywaterabsorptioninthemicrowaveregionofthespectrum.Inthepolarimetercomponentsare: twobeamsplitters,twoplanarmirrors,oneo-axisparabolicreector,andaGolaycelldetector: andtheinterferometercanbelledwithnitrogensothatthemeasurementisnotcontaminated approximatelylocated125mmfarfromthepointofemissiononthefoil).Thecollimatedbeamis senttotheMichelsonpolarimeterviaoneplanarmirrorM0(seeFig.5.11).Theopticalbeamline Thebeamsplittersaremadeofparalleltungstenwiresof20mdiameterspacedby50m. convertedtoenergyofthecurrent.Thelatteristhenconvertedtoheat,becauseofthesmall butsignicantelectricalresistanceofthewires.Hencetoobeytheboundaryconditionat spacesbetweenthewires,nocurrentcanowperpendiculartothem.Hencetheelectriceld componentperpendiculartothewiresproducenocurrentsandlosenoenergy,thereforeitis transmitted. thewires.Sucheldsproduceelectriccurrentsinthewires,andtheenergyoftheeldsis Beingmetallic,thetungstenwiresprovidehighconductivityforelectriceldsparallelto thewire,theeldparalleltothewiresisreected.However,becauseofthenon-conducting 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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(a) ceramic radiator beam x-wire be
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Page 123 and 124: Theequation5.8yields: f()=jZ+1 11Xn
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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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