1. MERLIN 3.0 only considers first order (dipole) modes. Kick is linearly proportional to offset. For offsets close to the axis this is a reasonable approximation. However, nearing the wall requires higher order modes to be considered. We have extended MERLIN to include these higher order modes, which are dependent on the trailing particles position and thus involve serious code extensions, up to a user specified number and compared with SLAC End Station A data. Higher Order Mode Implementation in MERLIN Simulation parameters: Bunch charge = 2e+10 Beam energy p0 = 1.19 GeV Horizontal Beta function = 3m Horizontal Bunch size = 0.36mm Vertical Beta function = 10m Vertical Bunch size = 0.16mm Longitudinal bunch size = 0.65 mm Aperture size = 38mm (impact parameter = 19mm)

2. Extending this to fifth order modes the curve is more pronounced Higher Order Mode Implementation in MERLIN Cont. Including the second order modes results in an increased kick near to the walls, as expected. and shows good agreement with SLAC ESA data. source: http://wwwconf.slac.stanford.edu/lc02/wg3/Onoprienko.pdf http://wwwconf.slac.stanford.edu/lc02/wg3/Onoprienko.pdf

3. Beam Parameters Charge: 2x10 10 e Energy: 250 GeV Mom. Spread: 0.1%  x : 50.5 m  y : 9.56 m  z : 2.04x10 -11 m  y : 6.13x10 -14 m Simulation Parameters 2mrad optics SR on Collimation on Vertical plane considered Offset at linac exit Wakefield modes Offset (  y ) RMS size (nm) 014.988 115.016 515.017 035.003 135.231 535.234 Corresponds to : - 1.1%  y growth for a 1  y offset. - 9.4%  y growth for a 3  y offset. Higher modes have a converging negligible (fraction of a %) effect. Vertical profile histograms with count vs displacement. No wakefields Wakefields present Difficult to see but, as expected, the profile broadens

4. Component Length Location # lost Quadrupole.QB1 1 879.913 47 Quadrupole.QB1 1 880.413 2 Drift.AB2 0.429 890.365 316 Drift.SP2 0.0086 890.794 539 Drift.SP4 0.0086 1088.04 72 Drift.SPEX 0.0356 1383.64 188 Initial gaussian bunch at end of linac/start of BDS with 1% flat halo extending to 18  x and 120  y. Tracked through ILC BDS optics with collimation depths given by Frank Jackson. Halo Tracking in MERLIN Curious effect (needs checking) of wakefields sometimes improving collimation by kicking out thhe higher amplitude particles.