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THP101

The MERLIN Simulations Program: New features used in studies of the LHC Collimation System . THP101. R.J . Barlow, R. Appleby, J. Molson, H.L. Owen, A. M. Toader. Particle Loss Maps . Collimator Scattering Process: Pomeron exchange. Abstract.

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THP101

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  1. The MERLIN Simulations Program: New features used in studies of the LHC Collimation System THP101 R.J. Barlow, R. Appleby, J. Molson, H.L. Owen, A. M. Toader Particle Loss Maps Collimator Scattering Process: Pomeron exchange Abstract The collimation system of the LHC will be critical to its success, as the halo of high energy (7 TeV) particles must be removed in such a way that they do not deposit energy in the superconducting magnets which would quench them, or showers in the experiments. We study the properties of the LHC collimation system as predicted by the Merlin and Sixtrack/K2 simulation packages, and compare their predictions for efficiency and halo production, and the pattern of beam losses. The sophisticated system includes many collimators, serving different purposes. Both programs include energy loss and multiple Coulomb scattering as well as losses through nuclear scattering. The MERLIN code also includes the effects of wakefields. We compare the results and draw conclusions on the performance that can be achieved. Snapshot of Particle Tracking with MERLIN around the LHC ring Introduction MERLIN is a particle tracking code that we have enhanced to be able to take advantage of multicore CPUs and computer clusters. This gives a manyfold increase in speed, tracking millions of particles element by element over hundred of turns. The LHC Collimators are designed to remove halo particles so that they do not impinge onto either detectors or other vulnerable regions of the storage ring.  It is crucial to model them accurately, including the simulation of protons scattering at very small t, which can survive several turns before being lost. The physics of such soft processes at high energies are well described by recent Pomeron exchange models, which describe the data from ISR to Tevatron energies. This is the relevant region for the LHC, where the protons involved collide with a fix target at \sqrt(s)= 81GeV and 118GeV for 3.5 and 7 TeV beams.  We incorporate the elastic and quasi-elastic diffractive cross sections  for low momentum transfer (0.0001<t<0.01GeV2) into tracking code MERLIN, and use it to simulate the maps of the beam halo lost in the collimators. The scattering routines track the protons through some length of a given material having them interacting with the proper cross-sections. Top left: xyreal space bunch distribution through a tilted collimator. Top right: x & y phase space after the collimator showing the scattered particles. Bottom left and right: TWISS parameters at the collimator Acknowledgements: We like to thank Prof. Sandy Donnachie for providing us with theoretical framework of the Pomeron exchange implemented in MERLIN. www.cockcroft.ac.uk www.manchester.ac.uk

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