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.