High Brightness Electron Beam Diagnostics and their ... - CASA
High Brightness Electron Beam Diagnostics and their ... - CASA
High Brightness Electron Beam Diagnostics and their ... - CASA
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Experimentallythecalibrationcoecientsarestoredinsoftware,thevoltageVoutisdigitizedby Inthissectionwewillonlyconsidermeasurementperformedbythepickupcavities2,3,<strong>and</strong>4, Inthedriveracceleratorfourcavitieshavebeeninstalled;<strong>their</strong>locationsareshowningure3.12. anADCcard,<strong>and</strong>adataanalysisprogramdirectlyoutputtheTOFinunitofRF-deg(1RF-Deg is556mat1.497GHz).<br />
frequencyof60Hz). amacropulsethatconsistsof4675electronbunches(thecharacteristicsofthemacropulseusedfor themeasurementare:awidthof250sec,amicro-bunchfrequencyof18:7MHz<strong>and</strong>amacropulse themeasurementfromthecavity#1requiringsomedeeperanalysisasweshallseeinchapter6. Itisworthnotingthatcontrarytowhatwehaveimplicitlyassumedinthepreviousdiscussion goodenoughsignalovernoiseinthetimeofightmeasurement,thecavitysignalcorrespondsto themeasurementisnotasinglebunchmeasurement.Becauseoftheneededsignaltoachieve Toexpeditethemeasurements,thequantityvaried(i.e.laserphaseforhinjoutitransfermap<br />
<strong>and</strong>cavitygradientforhinjoutitransfermap),isindeedmodulatedwithafrequencyof60Hz Figure3.12:LocationofthepickupcavitiesalongthetransportlineintheFELdriveraccelerator. (seeagaing.3.13).Themodulationisperformedwithatriangularwaveformgeneratedbya cavitygradient).Thechoiceofatriangularmodulationwasdonetouniformlypopulatethetransfer map.Moreoversinusoidalmodulationisalsoplanned(butwasnotusedduringtheworkreported G.KratfortheCEBAFinjector[22]atJeersonLab. 3.4.4Simulationofhinjoutitransfermap hereafter)inordertousetheTchebytchev-polynomial-basedanalysisthathasbeendevelopedby functiongeneratorusedtovarytheproperquantity(phaseofthephoto-cathodedrivelaseror<br />
Asaforementionedthemeasurementofphase-phasetransfermapprovideimportantinformationon howthebunchingprocessisperforming<strong>and</strong>cangivesomeinsightsonthebunchlength.Because themapismeasuredbetweenthephotocathode<strong>and</strong>thepickupcavities(seeg.3.12for<strong>their</strong>locations),wecannotusest<strong>and</strong>ardsingledynamicsrelativisticcodessuchasTLieordimadbutneed touseparticletrackingcodesuchasparmelawhichincludenonrelativisticeectssuchasphase Weusetheparmelacodetogenerateuniformmacroparticledistributionoveragivenextentin<br />
slippageeectsinacceleratingcavities.Thetechniquewehaveusedtocomparemeasurementwith numericalsimulationisasfollows.<br />
Pickup #2 Pickup #1<br />
Pickup #3 Pickup #4<br />
Gun