acceptance & scraping

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Acceptance & Scraping. Chris Rogers Analysis PC 04-05-06. Overview. Why it isnt easy to place a constraint on detector apertures General view on the acceptance of the cooling channel A better - but still not perfect - requirement on the measurement of high emittance particles Implications. - PowerPoint PPT Presentation


  • Acceptance & ScrapingChris RogersAnalysis PC04-05-06

  • OverviewWhy it isnt easy to place a constraint on detector aperturesGeneral view on the acceptance of the cooling channelA better - but still not perfect - requirement on the measurement of high emittance particlesImplications

  • Effect of Losing MuonsWhat is the effect of losing muons?How does it effect emittance measurementIs the standard criterion (0.999 efficiency) sufficient?Quantify the argument that losing signal muons (because the TOF is too small) at larger amplitude will bias the measurement moreHow does a mis-measurement effect the measurement of cooling channel efficiency?Surely muons on the edge of the beam will never make it into an accelerating structure anywayConsider the acceptance measurement (number of muons within a certain acceptance)

  • Effect on Emittance MeasurementMeasured x variance (meas ) is related to true x variance, (true ) from rejected signal by:Nmeasmeas = Ntruetrue - NrsrsRef: Analysis PC Aug 19 2005N is number of muonsrs is Rejected signalAssume that the scraping aperture is at > 2sx and 2spxThen after some algebra emittance e is given byemeas >~ etrue [1 - (22-1) Nrs/Ntrue]Losing signal at high emittance will bias the measurement moreThis means that for a 1e-3 emittance requirement the efficiency requirement is much tougher than 0.999More like 0.9995-0.9998The emittance measurement is very sensitive to transmission

  • Beam DependenceBut the number of muons at high amplitude is very beam dependentDifferent beams will have very different tailsIt is not satisfactory to place a requirement on detector size based on such a quantityThe beam I use today will give a completely different requirement than the beam I use tomorrowReally, we want to use these muons to demonstrate that we understand the acceptance of MICEScraping is an important effect in a Neutrino Factory cooling channel

  • Scraping in a Neutrino FactoryIn a Neutrino Factory cooling channel, scraping is a first order effect on transmission into an accelerator acceptanceTypical input emittances ~ 12 p transverse (FS2A) vs scraping aperture ~ 20 pWe should be aiming to measure it to the same high precision as we aim to measure emittanceFS2FS2Z (m)Z (m)nmEmittancee//etrans

  • ScrapingThere is a closed region in phase space that is not scrapedI want to measure the size of this regionIt is independent of the particular beam going through MICEAperture 1TransportAperture 2Aperture 1TransportAperture 2xpx

  • HaloConsider hard edge acceleratorKill muons that touch the wallsNo RF or liquid HydrogenIn a realistic accelerator, there will be some region beyond the scraping regionA reasonable constraint is that we should be able to measure all muons that make it through the hard-edged cooling channelTo get a more serious constraint, need to understand the reduction in cooling channel transmission quantitativelySoft edgedHard edged

  • Apertures under investigationThree apertures in MICE that are under investigationTOF IIDiffuserTracker helium windowTOF IIDiffuserTracker Window

  • Physical Model842430304023015150630No absorbers or windowsHard edge -Kill muons that scrape100014941334150200Tracker AFCAFCAFCTracker RFCCRFCC

  • BeamsConsider two sets of particlesPhase space filling beam10 pi beamPhase space fillingPlace muons on a grid in x, pxMuons at x = 0, 10, 20 and px = 0, 10, 20, Add spread in either Lcan or pz10 pi gaussian beam, 25 MeV rms energy spreadCuts at 190
  • Max Radius vs z - Lcan spreadThis is a scatter plot of muons travelling down the cooling channelVertical lines come because I am only sampling the beam occasionallyDrawn a line for the maximum radius of the beamThis is using the beam with a spread in LcanradiuszRadius of MICE acceptance vs z

  • Max Radius vs z - Pz spreadRepeat the exercise but now use a spread in PzMax. radiusz

  • Max Radius vs z - 10 p beamRepeat the exercise but now use a full 10 p beamMax r @ diffuser = 0.128Max r @ window 1 = 0.136Max r @ window 2 = 0.121Max r @ TOFII = 0.273Max. radiusz

  • W Lau,CM 14

  • Gaussian 10 pi beam at DiffuserA significant number of tracks outside of 10 cm radiusNote some of these tracks also pass through the diffuser mechanism itselfIt may be possible to arrange the beamline to run in a less focussed mode with higher energyTry to punch muons through the diffuser mechanism to populate these tailsDiffuserRadius

  • Absorber window Thickness as a function of R (M Green)

  • R at tracker windowsNo tracks pass through the edge of the windowsBut the window gets increasingly thick towards the edgesWhat effect does this have on emittance?UpstreamZ~-4.6 mDownstreamZ~+4.6m

  • R at solenoid endThe downstream solenoid ends at z=6.011This is the downstream end of the last coilBut the high amplitude tracks are cut in the trackerDont strike the tracker endrrZ=6.111Z=6.211

  • x at TOFThe edge of the beam lies beyond the tof half widthWhile this doesnt look so bad, if I choose to use a different beam it may well get worseWithout materials so this is really a minimumIt may be possible to make the TOF larger than the Ckov and sacrifice some PID in these regionsTo avoid a very large Ckov

  • SummaryI would be happier if the TOF could be biggerIt may be possible to compromise by leaving the calorimeter smaller and losing PID on the fringeWhile tracks miss the tracker window, I am slightly nervous about the thickness towards the edgeI would be happier if the diffuser could be bigger