impedance and instability in high intensity accelerator

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1、ImpedanceandInstabilityinHighIntensityAcceleratorIHEP黄良生Tel:15210902194E-mail:huangls@ihep.ac.cn1OutlineIntroductionofimpedanceandinstabilityTheprocessofinstabilitystudyStudyoninstabilityinCSNS/RCSImpedanceandinstabilityestimationResistivewallinstabilityImpedancemeasurementImpedanceandinst

2、abilityestimationinHIAF/ABR2Introduction-Impedance

3、

4、/⊥•Wakefield(wakefunction)WmandImpedance.•Broadbandimpedanceandnarrowbandimpedance,Q.•Component:spacecharge,resistivewall,kicker,cavity,bellow,collimator,pump.•Studymethod:-Theoreticalcalculationforstandardstructure-Simulationbysoftware:ABCI,MAF

5、IA,CST,HFSS.-Measurement.3Introduction-instabilityGeneralprocess:F→Z/Wy∆v=(Re(∆v),Im(∆v))Perturbationmethod:Vlasovequation4Introduction-instability•HighintensityinstabilityincludesSpacechargeeffect,Robinsoninstability,Resistivewalltransverseinstability,beamloadingMicrowaveinstability,(high-order)

6、head-tailinstability,Interbeamscatter,Coupledbunchinstability,E-cloud(e-p)instability,Fastbeamioninstability,Iontrapping,Dusteffect.•Spacechargeeffect:5Introduction-instability•Robinsoninstability*γ<γω>hω,Criterion:tR0γ>γω

7、lity(stronghead-taileffect,turbulentinstability,modelcouplinginstability)Criterion:<27Introduction-instability•Head-tailinstability/high-orderhead-tailinstabilityξ>0n=0,ηCriterion:ξ<0n≥1.ηThehead-tailinstabilityisseriousinlargemachine,suchasLHC,mainringinJ-PARC.8Introduction-instability•Coupledbu

8、nchinstability•E-cloud(e-p)instabilityTheelectroncomesfromsecondaryelectronyield,strippinginjection,ionizationofresidualgas,andinteractionbetweenbeamswithvacuumpipe.Criterion:Highvacuum,Solenoidfield,TiN.92.Theprocessofinstability-step1Whatproblemisinteresting?-Collide:Luminosity.i,e.BEPCII:

9、Z//

10、/n

11、<1Ω-SNS/CSNS:beamloss.<1w/m.-Microwaveinstability-impedancethreshold.Instabilityestimationandgivethemaininstability-Spacechargetuneshift,Microwaveinstability,resistivewalltransverseinstability,e-p,multiplebunchinst