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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tectorconsistsofagas-lledcellenclosedbytwomembranes.Theincomingradiationisabsorbed IntheearlystageoftheIRFELcommissioning,theexperimentalsetupdescribedingure5.12was usedtoimagetheCTRbeamemissionsourceproducedbytheelectronbeamasitpassesthrough analuminumfoilontoaGolaycelldetector.TheGolaycell(seeFig.5.7(A))isathermaldetector withanearlyuniformenergyresponsefromtheultravioletuptothemicrowaveregion.Thede- 5.4ObservationofCoherentTransitionRadiation<br />
overabroadrangeofwavelengths.Theabsorbedradiationheatsthegaswhichinturnincreases chosensothatthecorrespondingsurfaceimpedanceyieldsthemaximumabsorptionofradiation thepressureinsidethecell<strong>and</strong>distortsthesecond(exible)membrane.Thedistortionissensedby aphotodetectorcellthatdetectsalightbeamreectedfromthemembrane.Thiseectisamplied bytwolargegridsarrangedsothatinitially,i.e.whennoradiationisdetected,thelinesofonegrid areimagedonthespaceofthesecondgridresultinginnolightdetectionbythephotodetector. byathinaluminumlayerdepositedonthe\input"membrane.Thealuminumlmthicknessis Whenthemembraneisdistorted,theimageoftherstgridshifts,allowingsignicantlymorelight toreachthephotodetector.Thisgridsystemisinfactamechanicalmeansofenhancingtheeect<br />
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<br />
Figure5.7:SimpliedschematicsofaGolaycell(A)<strong>and</strong>theassociatedsignalacquisitionelectronics(B). pronouncedcomparedtotheonemeasuredintheCEBAFaccelerator[20]forexample.Thisis<br />
gure5.8.ThequadraticdependenceoftheCTRsignalversusthechargeperbunchisnotvery<br />
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01 01 01 01 Amplification System <strong>Electron</strong>ic Filter<br />
(B)