ATFIntrabeamScatteringResultsATF束内散射的结果

ATFIntrabeamScatteringResultsATF束内散射的结果第1页/共37页3/17/2023ComparisonMeasurements

NumericalComparisonwithSAD

ComparisonwithSimulationandTheoryDR2003,Jan.27atDaresbury第2页/共37页MeasurementsDR2003,Jan.27atDaresburySRInterferometerLaserWireinthering第3页/共37页MeasurementsEnergySpreadbyScreenMonitorattheExtractionLineBunchLengthbyStreakCameraintheRing第4页/共37页NumericalComparisonwithSADDR2003,Jan.27atDaresbury第5页/共37页NumericalComparisonwithSADDR2003,Jan.27atDaresbury第6页/共37页ComparisonwithSimulationandTheoryDR2003,Jan.27atDaresbury第7页/共37页ComparisonwithSimulationandTheory第8页/共37页SummaryVerticaldispersiononly,with(h)rms=5.6mmandey0=4.0pm(Solid).Couplingdominatedwithk=0.33%(dashes).Couplingdominatedwithk=1.2%,withtheCoulomblogartificiallyincreasedbyafactor1.75(dotdash).SameasEx.2butassumingeymeasurementerror,i.e.adding0.9%ofthemeasured(andsplined)extothecalculatedey(thedots).Followingismysuggestion(intention).Rejecttheartificialincrease.Beamorbittuning,dispersionandcouplingcorrectionhavetodoprecisely.BeamSizeMeasurementhastodoquicklyandprecisely.Improvedtoolswillbepreparedwithin3months.DR2003,Jan.27atDaresbury第9页/共37页NovelElectron-BeamDiagnostic(LaserWire)

atStCatherine’sCollege,Oxford,England

JunjiUrakawa,KEK,Japan,July10th20031.DevelopmentoflaserwirebeamprofilemonitorbasedonstableComptonscatteringinaFabry-Perotopticalcavity.(0.1mm(rms)positionstability,5mm(rms)beamcollision.)2.Futuredevelopment3.ConclusionUltra-lowemittanceelectronbeamisgoodforyou.第10页/共37页IntroductiontolaserwiremotivationLinearCollidersrequirenm-sizebeamsDampingringsproduceultralowemittancebeamsATFexperimentatKEKtodemonstratelowemittancebeamproductiondevelophandling/monitoringtechniquesstudybeamdynamics(lowemittance,multi-bunch)ATFdampingring1.1×10-9[mrad](horizontalemit.)~100[mm]0.5×10-11[mrad](verticalemit.)~7[mm]beamenergy:1.28GeVintensity:1.2×1010[e/bunch]numberofbunches:single/multi(2~20bunches)(2.8nsspacing)needreliablebeamsizemonitors第11页/共37页Introductionprincipleoflaserwiremonitorthinphotontarget(laserwire)transverselyplacedonthebeamorbitscanacrosstheelectronbeam“count”ComptonscatteredphotonsCWlaserwirewithopticalcavityenhancelaserpower(highmirrorreflectance⇔highpowergain)controllaserwaistsizelaseron/offforbackgroundsubtractionImportantissueshighintensitysmallwaistsize第12页/共37页reliablebeamsizemonitorinDampingringnon-invasivemethoddirectmeasurementofthebeamsizedispersionnegligible(straightsection)multi-bunchbeam(timingdetectionofgammarays)workatalmostzerocurrentIntroductionfeatureothermonitorsSRinterferometer(arc)X-raySRmonitor(arc)wirescanner(ext)OTR/ODR(ext)第13页/共37页Experimentalsetup1.laserwire2.detectorandcollimator3.datatakingsystem第14页/共37页Chambersystemreplacedin2002summershutdowncavitymodule第15页/共37页Opticswholesystemmountedonmovabletablemovablebothvertical/horizontaltablepositionismonitoredbylaserpositionsensor第16页/共37页Laserwiresetuphorizontalwireverticalwire第17页/共37页CavityresonanceFabry-Perothighpowergain⇔narrowresonancepowerinsidecavity第18页/共37页Cavitycontrolfeedbackcontroltransmissionintensity=referencevoltage<0.1nmresolutionservosystemcontrolcavitylengthpiezoactuatormonolithicelastichinge第19页/共37页Opticalcavityandlaserlaserspecificationcavityspecificationhorizontalwire(verticalmeasurement)verticalwire(horizontalmeasurement)mirrorfront99.1%99.8%reflectanceend99.9%99.9%mirrorcurvature20mm20mmfinesse6201700powergain6601300size(rms)5.67±0.1μm14.7±0.2μmRayleighrange760μm5100μmwavelength532nmCWpower300mWlinewidth<10kHz(1msec)LightWaveSeries142diode-pumpedsolidstatelaserCWfreq.doubledYAGlaser第20页/共37页LaserpowermodulationLaser-ON:Laser-OFF:

113Hzsinusoidalmodulationbackgroundsubtractionbackground~10kHzLaser-ON/Laser-OFFmeasurementmodulateintra-cavitypower(cavitylengthmodulation)30%(time)85%ofpower(average)30%(time)7.5%ofpower(average)第21页/共37页DetectorComptonscattering28.6MeV(maxgammaenergy)23.0MeV(0.2mradscatteringangle)gammaraydetector[70mm×70mm×300mm]CsI(pure)crystal2”photo-multipliertimeresolutionPMTsignalleadingedge0.56nsecresolution(signalenergyregion)enoughtoseparate2.8nsspacingbunches第22页/共37页ComptonscatteringsignalEnergyspectrumsignal/background=4/1(verticalbeamsizemeasurement)energywindow(15MeV–25MeV)“counting”methodnoeventpile-up(10kHzrate/2MHzringrevolution)energygateandleadingedgedetectionbunchidentificationbygammaraysignaltiming第23页/共37页Signalprocessing20beamprofiles(multi-bunch)atthesametimesinglebunchemittance(Mar2003)bunchIDbyhittiming(bunchmarker)laserON/OFFcountrate第24页/共37页Datatakingaligncollimatorsbeambasedalignmentforcollimatorslocalorbitbumpatlaserwirepositionifneededscanning1roundtripfor1profileautomaticscanvertical10sec.for1positionmove10micron(6sec.)6min.for1scanerrordominatedbyorbitdrifthorizontal30secfor1positionmove50micron(10sec.)15min.for1scanerrordominatedbystatisticsvertical“baddata”第25页/共37页Laserwaistmeasurementlongitudinallaserprofilelaserwiresize=5.67±0.1μm(laserdivergencemethod)laserwiresize=5.46±0.2μm(fittingfromfocusscan)smallwaistsize⇔smallRayleighlengthchangex-positionandconfirmlaserprofilelaserhasparabolicshape第26页/共37页AdditionaldatadispersionmeasurementbylaserwireitselfchangeRingRFscanbeambylaserwiremeasurethebeampositionshiftverticaldispersion=2.0mm(almostnegligible)horizontaldispersion=2.0mm(negligible)betafunctionattwocollisionpointsforverticalmeasurementβx=9.81m,βy=4.32mforhorizontalmeasurementβx=7.83m,βy=4.90m第27页/共37页Beamdampingmeasurementbeamsizemeasurementasafunctionofstoragetimestudydetectorresponseafterbeaminjection第28页/共37页HorizontalEmittanceVerticalEmittanceRecentResultswithcalculatedvaluesonintra-beamscatteringandpureinductiveimpedanceBunchLengthEnergySpread第29页/共37页FutureplanHowtoimproveresolution?beamsize:5.5[mm]⇔laserwaistsize:5.6[mm]closetotheresolutionlimitpossibilitiesstrongerfocusingfinetuningofcavitylengthsensitivetomirrorgeometriesshorterRayleighlengthshorterwavelengthhighqualitymirrorhighpower/stablelaserusehighertransversemode第30页/共37页TwinpeakslaserwireuseTEM01resonancemodeintheopticalcavityasalaserwirefactor2~3resolutionimprovementinsensitiveforbeamorbitdriftscanfreegoodresolutionforsmallbeamsize第31页/共37页HighermoderesonancesmisalignedlaserinjectionmodedegenerationTEM01/10mirrordistortiontosplitthesemodesmirrordistortion↓higherordermoderesonateinthecavitytransmittedlightprofilesofeachmode第32页/共37页HighermodetestexperimentstablerealizationofhigherordermodesTEM00TEM01TEM02第33页/共37页ConclusionUltra-lowemittanceelectronbeamisgoodforyou.Ultra-shortbunchedbeamsaregoodformyfutureR&D.Nowwearegoingtodonano-beamorbithandlingwithinternationalcollaboration.Sub-nanometerandsub-100fsecondbeamwillberealizedinthefuture.Beamdiagnosticsforabovebeamarenecessary.Ideaofsuchdiagnosticsexists.However,presenttechnologiesarenotmature.So,wecontinueR&Dwithchallengingspiritforfuturelinearcolliderproject.

第34页/共37页Installationof5wire-scannersintoATFLinacImprovementoftemperaturecontrol