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

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structure(A)withparticlepushingnumericalsimulation(B).
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beamaxis.Suchhypothesishasbeeninferredfromotherobservationsduringthecommissioning
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ourdesiretoobtainamorerealisticmodeloftheIRFELelectronbeamtransport,weincludedthe Figure6.7:Comparisonofthetransversebeamdensitymeasuredattheexitoftheaccelerating
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misalignmentinparmelaandgetemittancevaluesclosertowhatweexperimentallymeasured. misalignmentcurvewasgeneratedbysteeringthebeamby50mradupstreamthecryomodule.In oftheinjectorincludinganoxiousorbitthatcouldnotbestraightened3out.Inthegure6.8,the
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EnergySpread
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Horizontal Axis (mm)
Horizontal Axis (mm)
measurementofthermshorizontalbeamsizegivesaccesstothequantity: Theenergyspreadcanbeestimatedbymeasuringthehorizontalbeamproleatthehighdispersion OTR(seegure6.1).Atthislocationthedispersioniscomputedtobe'42cmandthereforea
thehighdispersionOTRdensitymonitor.Fromtheseimageswecomputethermsvaluesforthe thislatterstatementisindeedalsoveriedvianumericalsimulationusingthecodeparmela.In Usingtheroutinelymeasuredrmshorizontalemittance(~"x'5-6mm-mradandbetafunction gure6.9wepresenttheeectofthebuncherelectriceldonthebeamOTRimagerecordedon x5m)wededucethatthedispersivecontributiontothebeamhorizontalsizeisdominant, x=sx~"x+EE2 (6.14)
horizontal(energyaxis)projectionandcomparetheirvalueswiththeoneexpectedfromnumerical simulationingure6.10.Theagreementisseentobereasonable,i.e.within30%,exceptforlarge bunchervoltage,thoughinthisrangewebelievethebeamwasscrapingonthebeamlinevacuum chamberupstreamthelocationofthemeasurement. 3Unfortunatelybecauseoftimeconstraintsthisproblemwasnotaddressed
Vertical Axis (mm)