bdsim simulations/results: synchrotron radiation and muons motivation and history tracking results...
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BDSIM simulations/results: Synchrotron Radiation and Muons
• Motivation and History• Tracking results• Synchrotron Radiation• Tracking of Halo• Muons• News from EUROTeV• Future plans/Summary
Grahame BlairRoyal Holloway, Univ of London
MDI Workshop SLAC
January 6th 2005
BDS Simulation
~km
CollimationPrecision DiagnosticsDesign
MuonsHaloNeutronsSRLaser-wires …
Full simulations
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 scatteringBremsstrahlung …
• New processes modified (eg new SR, muons, laser-wire ).
Team at RHUL:Ilya Agapov - Optics design, beam diagnosticsJohn Carter - SR, beam diagnostics, IR layoutGB - Collimation, muons, backgroundsChafik Driouichi - Laser-wire design
Overview of Approach
Beam-lines are built up out ofmodular accelerator components
Full simulationof em showers
All secondariestracked
Synchrotron Radiation
Generator of H. BurkhardtImplemented for all componentsBased on local curvatureIndividual photons from individual parents
Primaries and secondaries tracked
SR within beampipe
Axes scales are m
•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
IR
Add any detector IR as a BDSIM object
Ideal for MDI studiesFor various detectors
SR Absorption along ILC BDSG
eV/m
Exit of Linac IPz (m)
ILC Beam HaloG
eV/m
z (m)
Collimation efficiencystudies are easy.
Muon ShowersIncrease statistics for Bethe-Heitler by forcing The muons are in addition to the electrons(doesn’t conserve energy)correct spectra via track weighting:
250 GeV electron on 1m iron
500 GeV electron on 1m iron
e ’s
TESLA: Muon Trajectories
BDS
Concrete tunnel 2m radius
No offset from centre
View from top
ILC: Muons at IP
Assume: 10-3 Halo bunch; ie 2.107 halo e’s per bunch Nμ per e ~ 1.4 10-5 , for 500 GeV e- (Bethe-Heitler only)
Adding a cut on initial energy >100 GeV (reduces number of tracked muons by a factor of ~30 withoutaffecting 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 z=1532,Gives approximately 144 muons per bunch at IR.
(Assuming Concrete tunnel of 2m radius.)
Muon Rates at IP
Linac IP624 15329m 18m
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
1981
Muon spoilers
Sp1 Sp2
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
For H. Burkhardt (CERN)
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 minimizedFirst 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 referencesas a very first attempt see
http://hbu.home.cern.ch/hbu/HTGEN.html
close collaboration with related activities and in particular COLSIM and the whole of WP6 (Integrated Luminosity Performance Studies)
Candidate Processes• Particle processes
Beam Gas elastic scatteringinelastic scattering, bremsstrahlungIon or electron-cloud effectsIntrabeam scatteringTouschek scatteringSynchrotron radiation (coherent and incoherent)Scattering off thermal photons
• Optics relatedMismatchCouplingDispersionNon-linearities
• Various, equipment related, collectiveNoise and vibrationDark currentsSpace charge effects close to sourceWake-fields
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.