Collimation Wakefield Simulations

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Collimation Wakefield Simulations. Carl Beard ASTeC Daresbury Laboratory. Computer Simulations of Spoiler designs. Codes being developed to measure the impedance of vessels ECHO2D, MWStudio, HFSS, GDFIDL Calculation errors due to small angle of taper Off axis measurements. 1mm. 1m. - PowerPoint PPT Presentation

Text of Collimation Wakefield Simulations

  • Collimation Wakefield SimulationsCarl BeardASTeC Daresbury Laboratory

  • Computer Simulations of Spoiler designs1mm1mCodes being developed to measure the impedance of vesselsECHO2D, MWStudio, HFSS, GDFIDLCalculation errors due to small angle of taper Off axis measurementsuser defined pulse possibleThe length of the structure and the frequency make simulation time very long

  • MAFIAMAFIA3D Time domain simulations allow the possibility of TDR simulationsMany benchmarks with measurement and code have validated results (SNS, CEBAF).Limited to below 30 GHz due to memory constraints.Particle-in-cellDiagonal filled cells (though mesh Many benchmarks have also unvalidated the code

  • Meshing solutionsQuadratic mesh yields fast results but poor resolutionDiagonal mesh cells do allow tapers to be accurately meshed, however shallow angles lead to poor aspect ratios

  • Time Vs accuracyCoarse meshFast run-timeLow accuracyFine meshSlow run-timeGood accuracyFinding the balance

  • Microwave StudioSame solver as MAFIAImproved meshing (PBA)Still limited to below 30 GHzEarly days

  • GDFIDL3D Finite difference time domain codeLossy materials are allowed for calculations of resistive wall wakefield.Particle-in-cell CapabilityBunch lengths could lead to lengthy simulation timeSome verifiaction with Real tests up to 120 GHz

    Synergy with LC-ABD Cavity BPM Energy SpectrometryGDFIDL SimulationsBench tests with Impedance Test ApparatusBeam testsCluster license purchased, to be hosted at UCL.

  • Other codesHFSSFrequency domain solverOver large bandwidths sharp resonance's could be overlooked.Tetrahedral meshing MAGICMAFIA-esqueNo diagonal cells, so stepped geometry guaranteedECHO-2D 3D??Only 2D FDTD version workingInitial discussions suggested that bunch lengths were too demandingUnprovenCST Solver (again) Availability ?????

  • Bench Test TDR and Transmission impedance measurements Current apparatus provides ~ 25ps pulsewaveform analysis provides loss parameterCritical issue:Pulse speed!Time ~ LC bunch sz ~1 ps10 ps fastest pulse time availableVNA ~6GHzAbove 10 GHz Signal-to-noise ratio is too low~1.7m

  • Test Rig

  • Test Rig 2Matching PartsLaunch coneTest Vessels

  • Impedance Rig 3Tektronics 7854 TDR Scope6 GHz NA S-parameter test set

  • Purpose of the testFollowing the last meeting in February there was a recommendation that the test gear should NOT be used for spoiler design

    BenefitsExperimental expertiseBenchmarkingLow frequency verification of designsImprove the understanding of the physicsBy scaling at 100ps, 50ps, 25ps and 10ps, extrapolate for 1ps

    TimescaleImpedance

    Top hat function Gaussian signal User defined

    Difficult above 10 GHz due to mesh sizes for time-domain simulations.Vector network analyser available up to 6 GHz however the ILC parameters require measurements up to 300 GHz.

    Impulse forming network produces near gaussian pulse

    10 ps problems associated with scaling