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 Blair Royal Holloway, Univ of London MDI Workshop SLAC January 6 th 2005

BDS Simulation ~km Collimation Precision Diagnostics Design Muons Halo Neutrons SR Laser-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 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

Overview of Approach Beam-lines are built up out of modular accelerator components Full simulation of em showers All secondaries tracked

Synchrotron Radiation Generator of H. Burkhardt Implemented for all components Based on local curvature Individual 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 studies For various detectors

SR Absorption along ILC BDS GeV/m Exit of Linac IP z (m)

ILC Beam Halo GeV/m z (m) Collimation efficiency studies are easy.

Muon Showers Increase 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: Halo bunch; ie halo e’s per bunch N μ per e ~ , 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 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 z=1532, Gives approximately 144 muons per bunch at IR. (Assuming Concrete tunnel of 2m radius.)

Muon Rates at IP Linac IP m18m Initial z (m)Sp1 (Field/T)Sp2 (Field/T)Rel Flux Muon spoilers Sp1Sp2

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 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 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 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 Non-linearities Various, equipment related, collective Noise and vibration Dark currents Space charge effects close to source Wake-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.