Collimation Baseline Configuration and Collimation Studies Frank Jackson ASTeC Daresbury Laboratory.

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Collimation Baseline Configuration and Collimation Studies Frank Jackson ASTeC Daresbury Laboratory
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Collimation Baseline Configuration Document

Transcript of Collimation Baseline Configuration and Collimation Studies Frank Jackson ASTeC Daresbury Laboratory.

  • Collimation Baseline Configuration and Collimation StudiesFrank JacksonASTeC Daresbury Laboratory

  • ContentsBaseline Configuration DocumentCollimation Studies

  • Collimation Baseline Configuration Document

  • What Happened at SnowmassCollimation and Background Session of WG4 (Beam Delivery System)1Summaries by N. Mokhov (FERMILAB), F. Jackson (Daresbury), and A. Sugiyama (Saga)Additional talks by K. Buesser (DESY) and J. Carter (RHUL)Baseline Configuration Document (BCD) outline plan2N. Mokhov and F. Jackson nominated as authors of collimation sectionBCD to be completed end 2005First draft3 was provided for Global Design Effort (GDE) meeting on Sep 22

  • BCD Collimation ContentStates baseline design, alternatives to baseline, answers to GDE Snowmass questions, existing and future R&D,BaselineAdopt NLC BDS scheme (2-phase betatron upstream of energy collimation)Survivable spoilers/absorbers and protection collimatorsOctupole tail foldingAlternativesConsumable spoilersGDE question: Order of energy and betatron collimation?Betatron, then energy, as in NLC.TESLA design had opposite order but lower collimation efficiency

  • BCD Collimation Content Existing R&DCollimator survivabilitySpoilers can survive 2 bunches at 250 GeV, 1 bunch at 500 GeVCollimation DepthsEvaluated with linear calculations and simulationsSpoiler gaps < 1mm in both planes, but larger than NLCDynamic Heat LoadNeed to thicken protection collimators (x3) to increase quad lifetimes for 0.1% beam haloCollimation EfficiencyHalo tracking simulations show reasonable efficiency, poorer than NLCMuon Attenuation at Detector Muon spoiler simulations demonstrate effective design ~ 2.2 muons per 150 bunches

  • BCD Collimation Content. Future R&D Design of fast extraction system to match spoiler survival limitWakefield effects yet to be studied in detail for current designsWakefield measurements planned at SLAC. Optics optimisation for best halo removal efficiencyReduction of radiation loads on beamline components.Octupole tail-folding principle to be (re-)studied.Muon background tolerances in detector to be evaluated.Simulation benchmarking, code repositories

  • Collimation Studies: - Preliminary Optimisation- Wakefield Effects

  • Collimation Optics OptimisationA BCD future R&D topicCurrent efficiency of collimation system could be improved in 20 mrad and 2 mrad decks20 mrad deck is the most optimisedLast couple of weeks started to look at optics optimisation of 20 mrad deck

  • Measuring Collimation EfficiencyHalo-tracking with STRUCT been used in pastChose MERLIN tracking code for recent studiesCan examine primary beam halo just like STRUCT (secondaries not included)Primary beam halo is sufficient for first-order optimisation of collimation systemEasiest and quickest for me to use!

  • MERLIN and STRUCT BenchmarkFor 20 mrad BDS, collimation depth = 9.6x, 74.0yUse identical end-of-linac halo 10K particles, dp = 1%

    Halo population at FD is 4% lower in MERLIN than in STRUCTGood enough agreement to use MERLIN for these studies

    Snowmass ResultsMerlin Results

  • Real Optics PerformanceSnowmass performance used tight energy spoiler (10 sigx, 74 sigy) effectively as additional beta spoilerBETACOLFD optics more realistically studied by halo tracking with open energy spoiler (dE = 1.5 % in x, fully open in y)

    Y-collimation not perfect even with dp=0%Y-spoilers not at perfect phase w.r.t. FD. SP4-IP phase advance is 2.34 (units of 2). Phase advance should be 0 or /2 (modulo ).


  • MAD OptimisationUsed Mark Woodleys decks and optimisation routines.Vary matching section quadrupole strengths and drift spaceAdjust x and y phase advances SP4-IP to 2.75 (effectively /2)

    Need to optimise optics bandwidth at same time as varying phases Difficult problem to solve by MAD tweaking


  • Wakefield EffectsILC Technical Review Committee studied NLC wakefield effects of collimators Calculated jitter amplification factors at FD phase position jitter at IP

    Ay = 1.20 considered too large, equivalent to y/y ~ 20% for 1.y of incoming jitterWhat is situation for ILC BDS design?

    (nb1) n.y of incoming jitter at collimators additional Ay.n.y jitter at IP(nb2) Dispersion at collimators also converted to addtional IP jitter by A

  • Jitter Amplification for 20 mrad deckUsed MATLAB code provided by P. Tenenbaum ILC-FF9 deck with apertures from A. Drozhdins halo tracking study (BDIR, RHUL June 2005) SP2,4,SPEX = TiOpened SPEX (dp = 0.3% aperture), assuming we can optimise optics to allow this

    NLC had five betatron spoilers-absorber pairs and small spoiler apertures (0.2mm-0.3mm)ILC has two sp-ab pairs and larger apertures (0.5mm-1.0mm)But what about protection collimators and SR masks as sources of jitter?

    y/y ~ 5.5%

    ILC 20 mrad BDSAxAyA0.14 (0.15 in NLC)0.59 (1.20 in NLC)0.09 (0.07 in NLC)

  • Protection CollimatorsGood secondary absorption achieved for ILC deck by tightening PCs (nominal aperture 5mm)

    Some PC apertures < 1mm !A. Drozhdin, BDIR meeting, RHUL 2005

  • Jitter Amplification for 20 mrad deck, incl. PCs

    PC8,9 and SR masks contribute significantly to Ay. They are at non-zero dispersion points, so also contribute to A

    SR masks have large apertures, but are at large beta-function location (A ), and are exactly in phase with FD

    ILC 20 mrad BDS, with PCsAxAyA0.28 (0.14 no PC)1.28 (0.59 no PC)0.88 (0.09 no PC)

  • ConclusionsCan we achieve NLC-like collimation efficiency, even with wider PCs and SPEX?If so, wakefield situation much improvedOctupole tail folding should be (re)studied Effect of SR masks should not be ignored in wakefield calculations.

    ILC collimators aperture, length and material. CP


    spoiler, AB





    photon mask, PC

    protection collimators. Version ILCFF9.

    June 21, 2005