BDSIM simulations/results: Synchrotron Radiation and Muons

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BDSIM simulations/results Synchrotron Radiation
and Muons
MDI Workshop SLAC January 6th 2005
Grahame Blair Royal Holloway, Univ of London

• Motivation and History
• Tracking results
• Synchrotron Radiation
• Tracking of Halo
• Muons
• News from EUROTeV
• Future plans/Summary

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BDS Simulation
Collimation Precision Diagnostics Design Muons Ha
lo Neutrons SR Laser-wires
Full simulations
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Motivation and History

• Work dates back several years.
• Grew out of initial plans to include Geant
  processes in Merlin.
• Then fast tracking incorporated into Geant4.
• Now a stand-alone approach and an alternative
  tracking code.
• All Geant4 processes included automatically
• Multiple scattering
• Bremsstrahlung
• New processes modified (eg new SR, muons,
  laser-wire ).
• Team at RHUL
• Ilya Agapov - Optics design, beam diagnostics
• John Carter - SR, beam diagnostics, IR layout
• GB - Collimation, muons, backgrounds
• Chafik Driouichi - Laser-wire design

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Overview of Approach
Beam-lines are built up out of modular
accelerator components
Full simulation of em showers
All secondaries tracked
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Synchrotron Radiation
Generator of H. Burkhardt Implemented for all
components Based on local curvature Individual
photons from individual parents
Primaries and secondaries tracked
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SR within beampipe

• J. Carter currently building IR model and
  simulation.
• Interface to Guinea-Pig format for SR of
  disrupted beam (track reflections back to IR)
• Implements low-energy G4 package

Axes scales are m
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Add any detector IR as a BDSIM object Ideal for
MDI studies For various detectors
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SR Absorption along ILC BDS
GeV/m
IP
z (m)
Exit of Linac
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ILC Beam Halo
GeV/m
Collimation efficiency studies are easy.
z (m)
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Muon Showers

• Increase statistics for Bethe-Heitler by forcing

The muons are in addition to the
electrons (doesnt conserve energy) correct
spectra via track weighting
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250 GeV electron on 1m iron
e
?s
500 GeV electron on 1m iron
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TESLA Muon Trajectories
Concrete tunnel 2m radius
BDS
No offset from centre
View from top
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ILC Muons at IP
Assume 10-3 Halo bunch ie 2.107 halo es per
bunch Nµ per e 1.4 10-5 , for 500 GeV e-
(Bethe-Heitler only) Adding a cut on initial
energy gt100 GeV (reduces number of tracked muons
by a factor of 30 without affecting greatly the
final results - preliminary)
Muon spoilers have now been implemented in BDSIM
as iron cylinders. An optional toroidal
magnetic field is also included Including no
spoilers and muon creation at z1532, Gives
approximately 144 muons per bunch at
IR. (Assuming Concrete tunnel of 2m radius.)
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Muon Rates at IP
Muon spoilers
9m
18m
Linac
IP
624
1532
1981
Sp1
Sp2
Initial z (m) Sp1 (Field/T) Sp2 (Field/T) Rel Flux
1532 1.0
1532 0 0.7
1532 1 0.7
624 0.5
624 0 0 0.2
624 1 1 0.2
624 1 -1 0.1
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For H. Burkhardt (CERN)
Halo and Tail Generation (HTGEN) Part of
Workpackage WP6 on Integrated Luminosity
Performance Studies study of potential sources
of halo and tail generation development of
analytic models of halo where appropriate
estimation of halo population development of
code modules for halo and tail generation
simulation studies of halo and tail generation
explore possibilities for benchmarking
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There is some (limited) experience from other
machines halo / tails can be a serious
performance limitation whenever seriously
attempted halo / tails can be quantitatively
understood and their production or effects be
minimized First steps establish a list of all
possible candidate processes collect all
existing information and codes work plan
priorities, what is missing, which framework(s)
up-do-date web based list of processes,
literature and code references as a very first
attempt see http//hbu.home.cern.ch/hbu/HTGEN.ht
ml close collaboration with related activities
and in particular COLSIM and the whole of WP6
(Integrated Luminosity Performance Studies)
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Candidate Processes Particle processes Beam
Gas elastic scattering inelastic scattering,
bremsstrahlung Ion or electron-cloud
effects Intrabeam scattering Touschek
scattering Synchrotron radiation (coherent and
incoherent) Scattering off thermal photons
Optics related Mismatch Coupling Dispersion No
n-linearities Various, equipment related,
collective Noise and vibration Dark
currents Space charge effects close to
source Wake-fields
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Summary/Future Plans

• Accurate accelerator tracking within Geant4
  achieved.
• Some optimisation still possible.
• Code management and public release planned (I.
  Agapov).

• The code is already at the status of an
  alternative tracking code.
• New processes SR, Laser-wire, Muon generation
• Serious studies of collimation efficiency are
  now underway
• Neutron studies will need some work to gain
  efficiency

• G4 studies will set the scale for detailed
  BDS/MDI design.
• Need to ensure accurate physics models low
  energy gammas,
• neutrons, multiple reflections of SR etc.
• Will need to improve weighting models etc. for
  efficiency
• BDIR simulation is a significant part of
  EUROTeV.