1. Collimator design and short range wakefields
Adriana Bungau
Christmas meeting
Manchester

2. Collimator Design and Material Damage
Aim: design the optimal spoilers for the ILC ( geometry and material specification)
Project: collaboration between Birmingham Univ, Manchester Univ, Daresbury Laboratory,
SLAC and RAL
Geant4 simulations in Manchester
Collimator design - two types of spoilers: a full metal spoiler and a combinations of metal and graphite
Three materials used: Ti4Al6V, Copper, Aluminium
Beam was sent through the collimator at 2 depths: 2mm and 10 mm from the top
Decision of the best spoiler candidate was based on:
- instantaneous temperature rise
- outgoing particle multiplicities
- energy spectra of outgoing particles
The best spoiler candidate was Ti alloy with graphite
Results were cross-checked with Fluka and EGS4 - passed on at RAL for ANSYS studies
EUROTeV reports and EPAC papers:
Geant4 Simulations of Energy Deposition in ILC spoilers - A.Bungau, R.Barlow, N.Watson, EUROTeV Report
Shower simulations, comparison of FLUKA, GEANT4 and EGS4 - L.Fernandez, A.Bungau, L.Keller, R.Barlow, N.Watson, EUROTeV-Report

3. Wakefield simulations with Merlin
Current situation:
mathematical formalism for incorporating higher order mode wakefields (R.Barlow)
formalism implemented in the Merlin code
SLAC beam tests simulated (good agreement between analytical calculations and
experiment
so far, only simple beamlines were studied (ie. Drift, Collimator, Drift)
EPAC paper:
“Simulation of High Order Short Range Wakefields” - R.Barlow, A. Bungau, EUROTeV-Report
Studies are now extended to the ILC-BDS beamline - emittance growth due to wakefields and luminosity loss

4. Wakefield Measurements at SLAC-ESA
Motivation:
to optimize the collimator design by studying various ways of minimising wakefield effects while achieving the required performance for halo removal
Collaboration between SLAC, Birmingham, Lancaster, Manchester, Daresbury
Commissioning: Jan (4 old collimators) - Successful
Physics: first run: Apr/May second run: July (8 new collimators – CCLRC)
Experimental tests
- tested 8 collimators fabricated at RAL
- inserted collimators in beam path (x mover), moved collimator vertically (y mover),measured
centroid kick to beam via BPMs
- analysed kick angle vs collimator position (good runs as also bad runs)
EUROTeV reports and EPAC papers:
"Test Beam Studies at SLAC End Station A for the International Linear Collider" -M.Woods et all, EUROTeV-Report , SLAC-PUB-11988
"Direct Measurement of Geometric and Resistive Wakefields in Tapered Collimators for the International Linear Collider" - N.Watson et all, EUROTeV-Report , SLAC-PUB-12029

5. Plans for 2007 Colimator damage:
beam tests for material damage (SLAC, CERN ?)
Wakefield simulations:
studies for the ILC_BDS collimators with higher order modes
implement Gdfidl predictions in Merlin
Experimental tests at ESA:
next run: March 2007 with 8 new collimators
BPM reprocessing on the Manchester cluster
data analysis finished for 2006 and also for 2007
data comparison with the first 8 collimators used in 2006
Particle Accelerator Conference, June 2007-New Mexico abstracts