Assmann, R. W.

Paper	Title	Page
MOPAN081	The LHC Collimator Controls Architecture - Design and Beam Tests	344
	S. Redaelli, R. W. Assmann, P. Gander, M. Jonker, M. Lamont, R. Losito, A. Masi, M. Sobczak CERN, Geneva
	The LHC collimation system will require simultaneous management by the LHC control system of more than 500 jaw positioning mechanisms in order to ensure the required beam cleaning and machine protection performance in all machine phases, from injection at 450~GeV to collision at 7~TeV. Each jaw position is a critical parameter for the machine safety which could cause a beam dump. In this paper, the architecture of the LHC collimator controls is presented. The basic design to face the accurate and real-time control of the LHC collimators and the interfaces to the other components of LHC Software Application and control infrastructures are described. The full controls architecture has been tested off-line in dedicated test benches, and in the real accelerator environment in the CERN SPS during beam tests with a full scale collimator prototype. The results and the lessons learned are presented.
TUZAC03	LHC Machine Protection	878
	R. Schmidt, R. W. Assmann, E. Carlier, B. Dehning, R. Denz, B. Goddard, E. B. Holzer, V. Kain, B. Puccio, B. Todd, J. A. Uythoven, J. Wenninger, M. Zerlauth CERN, Geneva
	This paper addresses the imposing challenges of the LHC Machine Protection System.
	Slides
TUPAN087	Scenarios for Beam Commissioning of the LHC Collimation System	1577
	C. Bracco, R. W. Assmann, C. Bracco, S. Redaelli, G. Robert-Demolaize CERN, Geneva
	A complex system of collimators has been designed to protect the superconducting LHC magnets against quench and damage from the high intensity proton beams. The considerable number of collimators and the resulting number of degrees of freedom for their set-up requires a well prepared commissioning strategy. Efficiency studies for various implementations of the LHC collimation system have been performed, taking into account the evolution in optics and beam intensity according to the LHC commissioning schedule. This paper explains the present plans for the set-up sequence of collimators and discusses the relevant tolerances induced from the collimation system for the first years of the LHC operation.
TUPAN100	Performance Reach of the	1613
	G. Robert-Demolaize, R. W. Assmann, C. Bracco, S. Redaelli, Th. Weiler CERN, Geneva
	State-of-the-art tracking tools have been developed for detailed LHC collimation and beam loss studies. This includes full chromatic treatment of both beam lines and error models. This paper reviews the main results on the performance reach of the multi-stage LHC collimation system that is being installed in the LHC. Limitations on the allowed proton loss rates and the stored intensity can be derived from the comparison of local losses with estimated quench limits for the superconducting magnets. The origins of the cleaning-related performance limitations are presented and possible improvements are discussed.
TUPAN107	Beam Loss Response Measurements with an LHC Prototype Collimator in the SPS	1622
	Th. Weiler, G. Arduini, R. W. Assmann, C. Bracco, H.-H. Braun, B. Dehning, P. Gander, E. B. Holzer, M. Jonker, R. Losito, A. Masi, L. Ponce, S. Redaelli, G. Robert-Demolaize, M. Sobczak, J. Wenninger CERN, Geneva
	Beam tests with an LHC prototype collimator were performed at the SPS in autumn 2006. Applying a new collimator control system many new beam measurements were performed. This contribution presents results on collimator-induced beam loss measurements and their applications to beam-based alignment of collimators and measurements of the beam size and position. Interesting features of the recorded beam loss signals are illustrated and possible impacts for LHC operation are discussed. The measured loss distributions around the full SPS ring are analyzed and compared with simulations.
TUPAN108	LHC Collimation System Hardware Commissioning	1625
	Th. Weiler, O. Aberle, R. W. Assmann, R. Chamizo, Y. Kadi, J. Lettry, S. Redaelli CERN, Geneva
	The stored energy and intensity of the LHC beam exceed the damage level of the machine and the quench level of the magnets by far. Therefore a robust and reliable collimation system is required which prevents the quenching of the magnets during regular operation and protects the accelerator components from damage in the event of beam loss. To assure that the installed collimators will protect the machine and permit the required performance of the collider, an appropriate hardware commissioning has to be implemented. In this contribution we describe the procedures for the hardware commissioning of the LHC collimation system. These procedures will establish the required precision and reliability of collimator movements and settings before the start of beam operation.
WEOAC03	Transverse Impedance of LHC Collimators	2003
	E. Metral, G. Arduini, R. W. Assmann, A. Boccardi, T. Bohl, C. Bracco, F. Caspers, M. Gasior, O. R. Jones, K. K. Kasinski, T. Kroyer, S. Redaelli, G. Robert-Demolaize, G. Rumolo, R. J. Steinhagen, Th. Weiler, F. Zimmermann CERN, Geneva F. Roncarolo UMAN, Manchester B. Salvant EPFL, Lausanne
	The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
	Slides
THPAN072	A Concept for the LHC Luminosity Upgrade Based on Strong Beta* Reduction Combined with a Minimized Geometrical Luminosity Loss Factor	3387
	E. Todesco, R. W. Assmann, J.-P. Koutchouk, E. Metral, G. Sterbini, F. Zimmermann, R. de Maria CERN, Geneva
	A significant increase of the LHC beam current touches physics limits as collective effects, electron-cloud, heat load, collimation and machine protection. We propose an upgrade scheme mainly based on a stronger focusing, with a beta* of 10 cm, requiring a triplet quadrupole aperture of around 130 mm. The performance is further improved if the triplet is based on the Nb3Sn technology. In the present baseline, this beta* reduction provides a negligible luminosity increase: this approach requires a drastic action to minimize the crossing angle, while the beam separation at the long-range encounters has to be increased. This is provided by an early separation scheme made of small dipoles inside the detectors. Optionally, a small angle crab cavity scheme may totally suppress the residual crossing angle. The quadrupole aperture is calculated to allow a larger gap for the collimator, suppressing their impedance limitation. This concept offers high performance while significantly reducing the risks associated to a beam current increase; it opens as well new issues that deserve further studies, such as the dipole integration in the detector, and the correction of the triplet aberrations.