Wenninger, J.

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.
MOPLT017	Beam Commissioning of the SPS LSS4 Extraction and the TT40 Transfer Line	569
	B. Goddard, P. Collier, M. Lamont, V. Mertens, K. Sigerud, J.A. Uythoven, J. Wenninger CERN, Geneva
	The new fast extraction system in LSS4 of the SPS and the transfer line TT40 were installed between 2000 and 2003, and commissioned with beam in late 2003. The extraction system and transfer line will serve both the anti-clockwise ring of the Large Hadron Collider (LHC), and the long baseline neutrino (CNGS) facility. The layout and functionality of the main elements are briefly explained, including the various hardware subsystems and the controls system. The safety procedures, test objectives and results of the system commissioning with beam are described, together with the test methodology. Conclusions are drawn concerning the performance of the system elements, agreement between predicted and expected activation levels and test efficiency and procedures. The test results are also briefly discussed in the context of future LHC beam commissioning activities.
MOPLT018	Aperture and Delivery Precision of the LHC Injection System	572
	B. Goddard, M. Gyr, J.-B. Jeanneret, V. Kain, M. Lamont, V. Maire, V. Mertens, J. Wenninger CERN, Geneva
	The main LHC injection elements in interaction regions 2 and 8 comprise the injection septa (MSI), the injection kicker (MKI), together with three families of passive protection devices (TDI, TCDD and TCLI). The apertures of the injection septa for the injected and two circulating beams are detailed with a new enlarged vacuum chamber and final septum alignment. The circulating beam aperture of the TDI is detailed with a new TDI support design and modified vacuum tank alignment. A modified TCDD shape is also presented and the implications for the aperture and protection level discussed. The various errors in the SPS, the transfer lines and the injection system, which contribute to injection errors, are analysed, and the expected performance of the system is derived, in terms of the expected delivery precision of the injected beam.
MOPLT024	Flexibility, Tolerances, and Beam-Based Tuning of the CLIC Damping Ring	590
	M. Korostelev, J. Wenninger, F. Zimmermann CERN, Geneva
	The present design of the CLIC damping ring can easily accommodate anticipated CLIC parameter changes. Realistic misalignments of magnets and monitors increase the equilibrium emittance. In simulations we study both the sensitivity to magnet displacements and the emittance recovery achieved by orbit correction, dispersion-free steering and coupling compensation.
MOPLT034	Possible Causes and Consequences of Serious Failures of the LHC Machine Protection System	620
	J.A. Uythoven, R. Filippini, B. Goddard, M. Gyr, V. Kain, R. Schmidt, J. Wenninger CERN, Geneva
	The LHC machine protection systems, including the beam dumping system, are designed to ensure that failures leading to serious damage to the LHC during its lifetime are extremely unlikely. These kind of failures have to date been considered as being ?beyond the design case?, for instance requiring a combination of equipment failure and surveillance failure. However, they need to be evaluated to determine the required safety levels of the protection systems. A second objective is to understand if measures can and should be taken to further reduce the probability of such failures, or to minimise their impact. This paper considers various serious failure modes of the different machine protection systems. The probable consequences and possible ameliorating measures of the worst-case scenarios are discussed. The particular case of having a stored beam with an unavailable beam dumping system is mentioned, together with possible actions to be taken in such an event.
TUXLH01	Machine Protection Issues and Strategies for the LHC	88
	R. Schmidt, J. Wenninger CERN, Geneva
	For nominal beam parameters at 7 TeV/c, each of the two LHC proton beams has a stored energy of 350 MJ threatening to damage accelerator equipment in case of uncontrolled beam loss. Since the beam dump blocks are the only element of the LHC that can withstand the impact of the full beam, it is essential for the protection of the LHC that the beams are properly extracted onto the dump blocks in case of emergency. The time constants for failures leading to beam loss extend from 100 microseconds to few seconds. Several protection systems are designed to ensure safe operation, such as beam instrumentation, collimators and absorbers, and magnet protection. Failures must be detected at a sufficiently early stage and transmitted to the beam interlock system that triggers the beam dumping system. The strategy for the protection of the LHC will be illustrated starting from some typical failures.
	Video of talk
	Transparencies
WEPLT006	Expected Performance and Beam-based Optimization of the LHC Collimation System	1825
	R.W. Assmann, E.B. Holzer, J.-B. Jeanneret, V. Kain, S. Redaelli, G. Robert-Demolaize, J. Wenninger CERN, Geneva
	The cleaning efficiency requirements in the LHC are 2-3 orders of magnitude beyond the requirements at other super-conducting circular colliders. The achievable ideal cleaning efficiency in the LHC is presented and the deteriorating effects of various physics processes and imperfections are discussed in detail for the improved LHC collimation system. The longitudinal distribution of proton losses downstream of the betatron cleaning system are evaluated with a realistic aperture model of the LHC. The results from simplified tracking studies are compared to simulations with complete physics and error models. Possibilities for beam-based optimization of collimator settings are described.
WEPLT045	Experiments on LHC Long-range Beam-beam Compensation in the CERN SPS	1933
	F. Zimmermann, J.-P. Koutchouk, J. Wenninger CERN, Geneva
	Long-range beam-beam collisions may limit the dynamic aperture and the beam lifetime in storage-ring colliders. Their effect can be compensated by a current-carrying wire mounted parallel to the beam. A compensation scheme based on this principle has been proposed for the Large Hadron Collider (LHC). To demonstrate its viability, a prototype wire was installed at the CERN SPS in 2002. First successful machine experiments explored the dependence of beam loss, beam size, and beam lifetime on the beam-wire distance and on the wire excitation. They appear to confirm the predicted effect of the long-range collisions on the beam dynamics. In 2004, two further wires will become available, by which we can explicitly demonstrate the compensation, study pertinent tolerances, and also compare the respective merits of different beam-beam crossing schemes for several interaction points.
THPLT016	LHC Orbit Feedback Tests at the SPS	2496
	J. Wenninger, J. Andersson, L.K. Jensen, R.O. Jones, M. Lamont, R. Steinhagen CERN, Geneva
	The real-time orbit feedback system foreseen for the LHC will be an essential component for reliable and safe machine operation. A test setup including a number of beam position monitors equipped with the LHC acquisition and readout system have been installed in the SPS ring to perform prototyping work on such an orbit feedback. A closed loop digital feedback was implemented and tested with LHC beams on the SPS during the 2003 machine run. The feedback loop was tested successfully at up to 100 Hz. The performance of the feedback loop and of its constituents will be described.