Roesler, S.

Paper	Title	Page
MOPLT005	An Improved Collimation System for the LHC	536
	R.W. Assmann, O. Aberle, A. Bertarelli, H.-H. Braun, M. Brugger, L. Bruno, O.S. Brüning, S. Calatroni, E. Chiaveri, B. Dehning, A. Ferrari, B. Goddard, E.B. Holzer, J.-B. Jeanneret, J.M. Jimenez, V. Kain, M. Lamont, M. Mayer, E. Métral, R. Perret, S. Redaelli, T. Risselada, G. Robert-Demolaize, S. Roesler, F. Ruggiero, R. Schmidt, D. Schulte, P. Sievers, V. Vlachoudis, L. Vos, G. Vossenberg, J. Wenninger CERN, Geneva I.L. Ajguirei, I. Baishev, I.L. Kurochkin IHEP Protvino, Protvino, Moscow Region D. Kaltchev TRIUMF, Vancouver H. Tsutsui SHI, Tokyo
	The LHC design parameters extend the maximum stored beam energy 2-3 orders of magnitude beyond present experience. The handling of the high-intensity LHC beams in a super-conducting environment requires a high-robustness collimation system with unprecedented cleaning efficiency. For gap closures down to 2mm no beam instabilities may be induced from the collimator impedance. A difficult trade-off between collimator robustness, cleaning efficiency and collimator impedance is encountered. The conflicting LHC requirements are resolved with a phased approach, relying on low Z collimators for maximum robustness and hybrid metallic collimators for maximum performance. Efficiency is further enhanced with an additional cleaning close to the insertion triplets. The machine layouts have been adapted to the new requirements. The LHC collimation hardware is presently under design and has entered into the prototyping and early testing phase. Plans for collimator tests with beam are presented.
WEOBCH01	Performance Requirements for Monitoring Pulsed, Mixed Radiation Fields around High-energy Acclerators	147
	D. Forkel-Wirth, S.M. Mayer, H.G. Menzel, A. Muller, T. Otto, M. Pangallo, D. Perrin, M. Rettig, S. Roesler, L. Scibile, H. Vincke CERN, Geneva C. Theis TUG/ITP, Graz
	Radiation protection survey around CERN's High Energy Accelerators represents a major technical and physical challenge due to the pulsed and complexity of the mixed radiation fields. The fields are composed of hadrons, leptons and photons ranging in energy from fractions of eV to several 10 GeV. In preparation of the implementation of a Radiation Monitoring System for the Environment and Safety (RAMSES) of the future Large Hadron Collider (LHC) and its injectors comprehensive studies were performed to evaluate the suitability of different existing monitors for this task. Different ionization chambers were exposed to short, high-intensity radiation pulses and their saturation levels for high dose rates determined. Limiting factors such as recombination effects and the capacity of the electronics to process a high number of charges within very short time were studied in detail. These results are being used to optimize the design of the read-out electronics. In additional studies, the response of two different types of ionization chambers to high-energy radiation was investigated by measurements in the mixed radiation fields of the CERN EU high-energy Reference Field (CERF) facility. The results of the experiments agreed well with calculations, clearly demonstrating that modern Monte-Carlo simulation techniques can be used to design radiation monitors and to optimize their performance.
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