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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densityprole,byactingontheotherthreeparametersitispossibletoreducethebeamcurrent withoutaectingonthephasespacedistribution.Naturallythefactwehavetouseareduced beamcurrentduringthemeasurementofthebeamparameterimpactsontheFELoperation<strong>and</strong> subsequentexperiments.Thereforesuchameasurementisinvasive.AswehaveseeninChapter2,<br />
Intensity (a.u)<br />
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109 4<br />
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Figure4.12:Rawdatabeamprole(topgraph)<strong>and</strong>beamproleafterprocessing(background whichalsosynchronouslygeneratea5Vrectangularpulsewhosewidth<strong>and</strong>repetitionratearethe replicaofthemacropulse.Suchsignalcalledthe\beamsync"isavailablefromthecontrolsystem totriggerdataacquisitionsystems. Inthepresentcase,wetriggertheimageprocessingboardtograbonlythevideoframethatcon- atarepetitionrateupto74:85MHz.Allthebeamstructureisgeneratedbyamasteroscillator subtracted,ghostpulsecontributionremoved,...).<br />
tainsthebeamimage.Forsuchapurposeweusethefollowingsetup:the\beamsync"isdelayed by0:435msbeforebeingsenttothe\externaltrigger"inputoftheimageprocessingboard.The eachmacropulsecontainsbunches(whosechargecanbearbitraryvariedfrom0pCto135pC6)<br />
SomeprimaryoperationsonthisdatastreamcanbedirectlyperformedbytheCPUoftheimage processingboardinrealtime[39].Suchoperationsincludethecalculationof: delayissetsothatthedigitizeristriggeredatthenextincomingpulse. Thedigitizeddatastreamattheimageboardoutputconsistsofa660484arraymatrix,I(x;y). 6Intheresultspresentedinthisreportthemaximumchargeusedisapproximately60pC<br />
Intensity (a.u)
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