Design and Construction of the LEIR Injection Septa Borburgh J Balhan B Bobbio P Carlier E Crescenti M Hourican M Masson T Müller T Prost A 2005 The Low Energy Ion Ring (LEIR) transforms long pulses from Linac 3 into high brilliance ion bunches for LHC by means of multi-turn injection, electron cooling and accumulation. The LEIR injection comprises a magnetic DC septum followed by an inclined electrostatic septum. The electrostatic septum has been newly designed and built. The magnetic septum is mainly recovered from the former LEAR machine, but required a new vacuum chamber. Dynamic vacua in the 10-12 mbar range are required, which are hard to achieve due to the high desorption rate of ions lost on the surface. A new interlock and displacement control system has also been developed. The major technical challenges to meet the magnetic, electrical and vacuum requirements will be discussed. research-article

Reliability Analysis of the LHC Beam Dumping System Filippini Roberto Carlier Etienne Ducimetière Laurent Goddard Brennan Uythoven Jan 2005 The design of the Beam Dumping System of the Large Hadron Collider at CERN is aimed at ensuring a safe beam extraction and deposition under all circumstances. The system includes redundancy and continuous surveillance for most of its parts. Extensive diagnostics after each beam dumping action will be performed to reduce the risk of a faulty operation upon the subsequent dump trigger. Calculations of the system’s safety and availability are presented for the beam dumping kickers and septa magnets. research-article

Reliability Assessment of the LHC Machine Protection System Filippini Roberto Dehning Bernd Guaglio Gianluca Rodriguez-Mateos Felix Schmidt R Todd Benjamin Uythoven Jan Vergara-Fernández Antonio Zerlauth Markus 2005 A large number of complex systems will be involved in ensuring a safe operation of the CERN Large Hadron Collider, such as beam dumping and collimation, beam loss and position monitors, quench protection, powering interlock and beam interlock system. The latter will monitor the status of all other systems and trigger the beam abort if necessary. While the overall system is expected to provide an extremely high level of protection, none of the involved components should unduly impede machine operation by creating physically unfounded dump requests or beam inhibit signals. This paper investigates the resulting trade-off between safety and availability and provides quantitative results for the most critical protection elements. research-article

Aperture Studies of the SPS to LHC Transfer Lines Goddard Brennan Kain Verena Schmid Riccardo Wenninger Jörg 2005 The SPS to LHC transfer lines TI 2 and TI 8 are each several km in length and use magnets with small apertures. An aperture model for the lines has been developed in MADX format, with a full description of all installed vacuum elements and the possibility to interpolate at any length interval. This model has been used with tolerances and errors to simulate the expected line aperture available for the beam. The model features and simulation results are presented, with derived aperture limits. The results from aperture measurements made during the TI 8 beam commissioning in 2004 are presented and compared to expectations. research-article

Expected Emittance Growth and Beam Tail Repopulation from Errors at Injection into the LHC Goddard Brennan Burkhardt Helmut Kain Verena Risselada Thys 2005 The preservation of the transverse emittance of the proton beam at injection into the LHC is crucial for luminosity performance. The population of the beam tails is also important for beam losses and collimation. The transfer and injection process is particularly critical in this respect, and several effects can contribute to the expected emittance increase and tail repopulation, like optical and geometrical mismatch, injection offsets and coupling, etc. The various effects are described, together with the tolerance limits on the parameters, and the expected contributions evaluated analytically where possible. The emittance growth and tail distributions are also simulated numerically using realistic errors. The implications for the tolerances on the matching of the transfer lines are discussed. research-article

Aperture and Field Constraints for the Vacuum System in the LHC Injection Septa Henrist Bernard CERN Jiménez J M CERN Lacroix Jean Michel CERN Sgobba Stefano CERN Gyr Marcel CERN 2005 Each beam arriving from the SPS has to pass through five injection septum magnets before being kicked onto the LHC orbit. The injection layout implies that the vacuum chambers for the two circulating beams pass through the septum magnet yokes at a flange distance from the chamber of the beam to be injected. Specially designed vacuum chambers and interconnections provide the required straightness and alignment precision, thus optimising the aperture for both the circulating and injected beams, without affecting the quality of the magnetic dipole field seen by the injected beam. The circulating beams are shielded against the magnetic stray field by using µ-metal chambers with a thickness of 0.9 mm to avoid saturation of the µ-metal (0.8 T), coated with copper (0.4 mm) for impedance reasons and NEG for pumping and electron cloud purposes. A 2 mm gap between the iron yoke and the µ-metal chamber allows an in-situ bake-out at 200°C, based on a polyimide/stainless steel/polyimide sandwich structure with an overall thickness of 0.2 mm. The constraints are described and the resulting vacuum system design, the apertures and the residual stray field are presented in this paper. research-article

Commissioning of the LHC Beam Transfer Line TI 8 Uythoven Jan Arduini Gianluigi Goddard Brennan Jacquet Delphine Kain Verena Lamont Mike Mertens Volker Spinks Alan Wenninger Jörg 2005 The first of the two LHC transfer lines was commissioned in autumn 2004. Beam reached an absorber block located some 2.5 km downstream of the SPS extraction point at the first shot, without the need of any threading. The hardware preparation and commissioning phase will be summarised, followed by a description of the beam tests and their results regarding optics and other line parameters, including the experience gained with beam instrumentation, the control system and the machine protection equipment. research-article

Beam Tests of a New Digital Beam Control System for the CERN LEIR Accelerator Angoletta Maria Elena Bento Joao Blas Alfred De Long Joseph Findlay Alan Matuszkiewicz Pawel Pedersen Flemming Salom-Sarasqueta Angela 2005 The Low Energy Ion Ring (LEIR) is a major component in the Large Hadron Collider ion injector chain. We have been developing an all-digital beam control and cavity servo system for the RF acceleration in LEIR. The system is housed by VME motherboards that may hold various daughter boards. Fast tasks are executed in Field Programmable Gate Arrays (FPGAs), slower tasks and communication with the software layer above are achieved in Digital Signal Processors (DSPs). We describe a simplified system prototype, which we tested with low intensity beams on the CERN PS Booster (PSB). The aim was to verify the combined DSP+FPGA architecture and the feedback loop dynamics. An additional goal was to deploy and validate novel software concepts, such as reference-functions and timings generation, and user-selectable digital data acquisition. research-article

The Leir RF System Paoluzzi Mauro M Garoby Roland Haase Matthias Maesen Pierre Ohmori Chihiro Rossi Carlo 2005 The lead-lead physics program of LHC relies on major changes of the CERN ion injector chain. In this framework, the conversion of LEAR (low energy antiproton ring) into the Low Energy Ion Ring (LEIR) is central and implies a new accelerating system covering a wide frequency range (0.35 - 5 MHz) with a moderate voltage (4 kV). For this purpose two new wide-bandwidth cavities, loaded with Finemet® magnetic alloy cores, have been built in collaboration with KEK. Two 60 kW RF power amplifiers have also been built and the RF systems are now installed in the LEIR ring. They individually cover the whole frequency range without tuning and allow multi-harmonic operation. The design has been guided by need of safety margins, reliability and ease of maintenance. Some design aspects are presented as well as the performance achieved. The lead-lead physics program of LHC relies on major changes of the CERN ion injector chain. In this framework, the conversion of LEAR (low energy antiproton ring) into the Low Energy Ion Ring (LEIR) is central and implies a new accelerating system covering a wide frequency range (0.35 - 5 MHz,) with a moderate voltage (4 kV). For this purpose two new wide-bandwidth cavities, loaded with Finemet® magnetic alloy cores, have been built in collaboration with KEK. Two 60 kW RF power amplifiers have also been built and the RF systems are now installed in the LEIR ring. They individually cover the whole frequency range without tuning and allow multi-harmonic operation. The design has been guided by need of safety margins, reliability and ease of maintenance. Some design aspects are presented as well as the performance achieved. research-article

Protection against Accidental Beam Losses at the LHC Wenninger Jörg Schmidt R 2005 Protection of the LHC against uncontrolled beam losses is of prime importance due to the very high stored beam energy. For nominal beam intensities, each of the two 7 TeV/c proton beams has a stored energy of 360 MJ threatening to damage accelerator equipment. At injection a number of passive beam absorbers must be correctly positioned and specific procedures have been proposed to ensure safe injection of high intensity. The LHC beam dump block being the only LHC element that can safety absorb the full LHC beam, it is essential that the beams are extracted unto the dump block in case of emergency. The failure time constants extend from 100 microseconds to few seconds depending on the equipment. Failures must be detected at a sufficiently early stage and transmitted to the beam interlock system that triggers the beam dumping system. To ensure safe operation the machine protection system uses a variety of systems to detect such failures. The strategy for protection of the LHC will be illustrated, with emphasis on new developments and studies that aim for an increased redundancy of the protection system. research-article

Beam Stability of the LHC Beam Transfer Line TI8 Wenninger Jörg Goddard Brennan Kain Verena Uythoven Jan 2005 Injection of beam into the LHC at 450 GeV/c proceeds over two 2.7 km long transfer lines from the SPS. The small aperture of the LHC at injection imposes tight constraints on the stability of the beam transfer. The first transfer line TI 8 was commissioned in the fall of 2004 with low intensity beam. Since the beam position monitor signal fluctuations were dominated by noise with low intensity beam, the beam stability could not be obtained from a simple comparison of consecutive trajectories. Instead model independent analysis (MIA) techniques as well as scraping on collimators were used to estimate the intrinsic stability of the transfer line. This paper presents the analysis methods and the resulting stability estimates. research-article

Material Damage Test with 450GeV LHC-type beam Kain V Ramillon J Schmidt R Vorderwinkler K Wenninger J 2005 The design of LHC protection elements is based on assumptions on damage levels, which are derived from simulations. A dedicated experiment was prepared and carried out to cross-check the validity of this approach by trying to damage material in a controlled way with beam. The impact of a 450 GeV beam extracted from the SPS on a specially designed high-Z target with a simple geometry, comprising several typical materials used for LHC equipment, was simulated. The beam intensities for the test were chosen to exceed the damage limits of parts of the target. Results of the simulations are presented and compared with test results. research-article

A Large Diameter Entrance Window for the LHC Beam Dump Line Presland Andrew Goddard Brennan Jiménez J M Ramos D Veness Raymond 2005 The graphite LHC beam dump block TDE has to absorb the full LHC beam intensity at 7 TeV. The TDE vessel will be filled with inert gas at atmospheric pressure, and requires a large diameter entrance window for vacuum separation from the beam dumping transfer line. The swept LHC beam must traverse this window without damage for regular operation of the beam dump dilution system. For dilution failures, the entrance window must survive most of the accident cases, and must not fail catastrophically in the event of damage. The conceptual design of the entrance window is presented, together with the load conditions and performance criteria. The FLUKA energy deposition simulations and ANSYS stress calculations are described, and the results discussed. research-article

The Performance of the New TCDQ System in the LHC Beam Dumping Region Presland Andrew Goddard Brennan Weterings Wim 2005 The superconducting quadrupole magnet Q4 and other downstream LHC machine elements risk destruction in the event of a beam dump that is not synchronised with the abort gap. In order to protect these elements, a single sided mobile graphite diluter block TCDQ, in combination with a two-sided secondary collimator TCS and iron shield TCDQM, will be installed in front of Q4. This protection system should also intercept spurious particles in the beam abort gap to prevent quenches from occurring during regular beam aborts, and must also intercept the particles from the secondary halo during low beam lifetime without provoking quenches. The conceptual design of the TCDQ system is briefly presented, with the load conditions and performance criteria. The FLUKA simulations are described results discussed in the context of the expected performance levels for LHC operation. research-article

Energy Deposition Studies for the Betatron Cleaning Insertion (IR7) of LHC Santana-Leitner Mario Assmann R W Ferrari Alfredo Magistris Matteo Tsoulou A Vlachoudis Vasilis 2005 Two insertions (IR3, IR7) of the Large Hadron Collider (LHC) are dedicated to beam cleaning with the design goals of absorbing part of the primary beam halo and of the secondary radiation. The tertiary halo which escapes the collimation system in IR7 may heat the cold magnets at unacceptable levels, if no additional absorber is used. In order to assess the energy deposition in sensitive components, extensive simulations were run with the Monte Carlo cascade code FLUKA. The straight section and the dispersion suppressors (DS) of IR7 were fully implemented. A modular approach in the geometry definition and an extensive use of user-written programs allowed the implementation of all magnets and collimators with high precision, including flanges, steel supports and magnetic field. This paper provides the number and location of additional absorbers needed to keep the energy deposition in the coils of the magnets below the quenching limit. research-article

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Optics Studies of the LHC Beam Transfer Line TI 8 Arduini Gianluigi Goddard B Jacquet D Kain V Lamont M Mertens V Uythoven J Wenninger J 2005 The optics of the newly commissioned LHC beam transfer line TI 8 was studied with beam trajectories, dispersion and profile measurements. Steering magnet response measurements were used to analyze the quality of the steering magnets and of the beam position monitors. A simultaneous fit of the quadrupole strengths was used to search for setting or calibration errors. Residual coupling between the planes was evaluated using high statistics samples of trajectories. Initial conditions for the optics at the entrance of the transfer line were reconstructed from beam profile measurements with Optical Transition Radiation monitors. The paper presents the various analysis methods and their errors. The expected emittance growth arising from optical mismatch into the LHC is evaluated. research-article

Effect of Lattice and Electron Distribution in Electron-Cloud Instability Simulations for the CERN SPS and LHC Benedetto Elena Arduini Gianluigi Feng Bing Franchetti Giuliano Ghalam Ali F Katsouleas Thomas C Ohmi Kazuhito Roncarolo Federico Rumolo Giovanni Zimmermann Frank 2005 Several simulation codes have been adapted so as to model the single-bunch electron-cloud instability including a realistic variation of the optical functions with longitudinal position. In addition, the electron cloud is typically not uniformly distributed around the ring, as frequently assumed, but it is mainly concentrated in certain regions with specific features, e.g., regions which give rise to strong multipacting or suffer from large synchrotron radiation flux. Particularly, electrons in a dipole magnet are forced to follow the vertical field lines and, depending on the bunch intensity, they may populate two vertical stripes, symmetrically located on either side of the beam. In this paper, we present simulation results for the CERN SPS and LHC, which can be compared with measurements or analytical predictions. research-article

Collimation in the Transfer Lines to the LHC Burkhardt Helmut Goddard Brennan Kadi Yacine Kain Verena Risselada Thys Weterings Wim 2005 Injection intensities for the LHC are over an order of magnitude above damage level. The TI 2 and TI 8 transfer lines between the SPS and LHC are each about 2.5 km long and comprise many active elements running in pulsed mode. The collimation system in the transfer lines is designed to dilute the beam energy sufficiently in case of accidental beam loss or mis-steered beam. A system using three collimator families spaced by 60 degrees in phase advance, both in the horizontal and the vertical plane has been chosen. We discuss the reasons for this choice, the layout and, the expected performance of the system in terms of maximum amplitudes and energy deposition. research-article

Optics Flexibility and Matching at LHC Injection Burkhardt Helmut Brüning Oliver Sim Goddard Brennan Kain Verena Mertens Volker Risselada Thys Verdier Andre 2005 An excellent match between the SPS, the several kilometres long transfer lines and the LHC will be required to minimise emittance blow-up at injection. Several optics changes in the SPS and the LHC injection insertions had to be accommodated in the design phase. The new 3-phase collimation system in the transfer lines results in additional phase advance constraints. It will be important to maintain some tuning range for the LHC commissioning phase and to accommodate possible further optics changes. We analyse the requirements, the constraints, the current status and options to enhance the optics flexibility. research-article

Measurements of the LHC Collimator Impedance with Beam in the SPS Burkhardt Helmut Arduini Gianluigi Assmann R W Caspers Friedhelm Gasior Marek Grudiev Alexei Rhodri-Jones Owain Kroyer Tom Redaelli Stefano Robert-Demolaize Guillaume Roncarolo Federico Schulte Daniel Steinhagen Ralph J Wenninger Jörg Zimmermann Frank 2005 The transverse impedance of the LHC collimators will likely dominate the overall transverse impedance in the LHC at high energies and potentially limit the maximum intensity. A prototype collimator was recently tested in the SPS. Small, but significant tune shifts depending on the collimator position have been observed using different independent high resolution tune measurement methods. In addition trapped modes predicted from numerical simulation at the ends of the collimator jaws have been identified by bench measurement techniques as well as with the beam. We present a description of the measurements and an analysis of the results. research-article

Luminosity Limit from Bound-Free Pair Production in the LHC Jowett John M Bruce Roderik Gilardoni S S 2005 The luminosity of the LHC as a lead-ion collider is known to be limited by the large cross-sections for electromagnetic processes in ultra-peripheral collisions. In particular, the process of bound-free e-e+ pair production creates secondary beams of Pb81+ ions emerging from the collision points and impinging on the vacuum envelope inside superconducting magnets. New Monte-Carlo simulations, exploiting recent implementations of the physics of ion interactions with matter, are helping us to quantify the relationships among luminosity, energy deposition in the magnet coils a view to predicting and alleviating the quench limit on luminosity. research-article

Exploring a Nonlinear Collimation System for the LHC Resta Javier Assmann R W Faus-Golfe Angeles Redaelli Stefano Robert-Demolaize Guillaume Schulte Daniel Zimmermann Frank 2005 We explore the adaptation of a nonlinear collimation system, as previously developed for linear colliders, to LHC betatron cleaning. A possible nonlinear system for LHC consists of a horizontal and vertical primary collimator located in between a pair of skew sextupoles. We discuss the modified LHC optics, the need for and optimum placement of secondary absorbers, and the simulated cleaning efficiency. research-article

Detecting Impacts of Proton Beams on the LHC Collimators With Vibration and Sound Measurements Redaelli Stefano Aberle Oliver Assmann R W Masi Alessandro Spiezia Giovanni 2005 The 360 MJ stored energy of the 7 TeV LHC beams can seriously damage the beam line elements in case of accidental beam losses. Notably, the collimators will sit at 6 to 7 sigmas from the beam centre (1.2 to 1.4 mm) and will be hit and possibly damaged in case of failures, with a consequent degradation of the cleaning performance of the overall collimation system. The experience from operating machines shows that an a-posteriori identification of the damaged collimators from the observed performance degradation is extremely challenging. Collimator tests with beam at the SPS have shown that the impact of 450 GeV proton beams at intensities from 1010to 3x1013 could be detected by measuring sound and vibrations induced by the impacting beams. research-article

Experiments on LHC Long-Range Beam-Beam Compensation and Crossing Schemes at the CERN SPS in 2004 Zimmermann Frank Koutchouk Jean-Pierre Papaphilippou Yannis Roncarolo Federico Sen Tanaji Shiltsev Vladimir Wenninger Jörg 2005 Experiments with two prototype long-range beam-beam compensators (current-carrying wires) during the 2004 CERN SPS run explored the efficiency of a proposed long-range beam-beam compensation for the LHC. In addition, the SPS compensators were also used to 'simulate' the effect of different planes of crossing at two LHC interaction points. We present the experimental results and compare them with computer simulations. research-article

Coherent Beam-Beam Modes in the Cern Large Hadron Collider (LHC) for Multiple Bunches, Different Collision Schemes and Machine Symmetries Herr Werner Pieloni T 2005 In the LHC almost 3000 bunches in each beam will collide near several experimental regions and experience head-on as well as long range beam-beam interactions. In addition to single bunch phenomena, coherent bunch oscillations can be excited. Due to the irregular filling pattern and the unsymmetric collision scheme, a large number of possible modes must be expected, with possible consequences for beam measurements. To study these effects, a simulation program was developped which allows to evaluate the interaction of many bunches. It is flexible enough to easily implement any possible bunch configuration and collision schedule and also to study the effect of machine imperfections such as optical asymmetries. First results will be presented and future developments are discussed. research-article

A Collimation Scheme for Ions Changing Charge State in the LEIR Ring Pasternak Jaroslaw Bal Cathelijne Carli Christian Chanel Michel Mahner Edgar 2005 Avalanche-like pressure rise and an associated decrease of the beam life-time, caused by (i) beam loss due to charge exchange interactions with rest gas molecules and (ii) electron capture from the electron beam of the electron cooler and (iii) ion impact induced outgassing, is a potential limitation for heavy ion accelerators. The vacuum system of the LEIR ring as to be upgraded to reach the dynamical vacuum pressure in the low 10-12 Torr range necessary to reach design performance. A collimation system to intercept lost ions by absorber blocks made of low beam-induced outgassing material will be installed. This paper reviews the collimation scheme and simulations of beam loss patterns around the ring. research-article

Electron Cloud Measurements in the SPS in 2004 Schulte Daniel Arduini Gianluigi Baglin Vincent Jiménez J M Zimmermann Frank 2005 Novel measurements of the electron cloud have been performed in the SPS in 2004. The LHC beam in the SPS consists of a number of short bunch trains. By varying the distance between these trains it is possible to test the survival of the electrons after the bunch passage. In this paper, results from simulations and experiments are compared. research-article

Ions for LHC Maury Stephan CERN Angoletta Maria Elena Baggiolini Vito Beuret Andre Blas Alfred Borburgh Jan Braun Hans Heinrich Carli Christian Chanel Michel Fowler Tony Gilardoni S S Gourber-Pace Marine Hancock Steven Hill Charles E Hourican Michael Jowett John M Kahle Karsten Kuchler Detlef Mahner Edgar Manglunki Django Martini Michel Paoluzzi Mauro M Pasternak Jaroslaw Pedersen Flemming Raich Uli Rossi Carlo Royer Jean Pierre Schindl Karlheinz Scrivens Richard Sermeus Luc Shaposhnikova Elena Tranquille Gerard Vretenar Maurizio Zickler Thomas 2005 The first phase of the heavy ion physics program at the LHC aims to provide lead-lead collisions at energies of 5.5 TeV per colliding nucleon pair and ion-ion luminosity of 1027 cm-2s-1. The transformation of CERN’s ion injector complex (Linac3-LEIR-PS-SPS) presents a number of beam physics and engineering challenges, which are described in this paper. In the LHC itself, there are fundamental performance limitations due to various beam loss mechanisms. To study these without risk of damage there will be an initial period of operation with a reduced number of nominal intensity bunches. While reducing the work required to commission the LHC with ions in 2008, this will still enable early physics discoveries. research-article

Photon-Nucleon Collider based on LHC and CLIC Ciftci Abbas K Ankara U. Schulte Daniel CERN Zimmermann Frank CERN Aksakal Husnu Ankara U. 2005 We describe the scheme of a photon-nucleon collider where high energy photons generated by Compton backscattering off a CLIC electron beam, at either 75 GeV or 1.5 TeV are collided with protons or ions stored in LHC. Different design constraints for such a collider are discussed and achievable luminosity performance is estimated. INTNOTELHECPUBL

LHC Collimation Assmann R W Aberle Oliver Arduini Gianluigi Baishev Igor S Holzer Eva Barbara Bertarelli Alessandro Braun Hans Heinrich CERN Brugger Markus Burkhardt Helmut Calatroni Sergio Caspers Friedhelm Chiaveri Enrico Dallocchio Alessandro Dehning Bernd Ferrari Alfredo Gasior Marek Grudiev Alexei Jeanneret Jean Bernard Kadi Yacine Kurochkin Igor Losito Roberto Magistris Matteo Masi Alessandro Mayer Manfred Jímenez José Miguel Perret Roger Rathjen Christian Redaelli Stefano Robert-Demolaize Guillaume Roesler Stefan Santana-Leitner Mario Schulte Daniel Sievers Peter Spiezia Giovanni Tsoulou A Vincke Helmut H Vlachoudis Vasilis Wenninger Jörg 2005 The problem of collimation and beam cleaning is one of the most challenging aspects of the LHC project. A collimation system must be designed, built, installed and commissioned with parameters that extend the present state-of-the-art by 2-3 orders of magnitude. Problems include robustness, cleaning efficiency, impedance and operational aspects. A strong design effort has been performed at CERN over the last two years. The adopted phased approach is described. Robust and precisely controllable collimators have been designed. Several LHC prototype collimators have been built and tested with the highest beam intensities that are presently available at CERN. The successful beam tests are presented, including beam-based setup procedures, a 2 MJ robustness test and measurements of the collimator-induced impedance. Finally, an outlook is presented on the challenges that are ahead in the coming years. research-article

Protection Level during Extraction, Transfer and Injection into the LHC Kain Verena Goddard Brennan Schmidt Rüdiger Wenninger Jörg 2005 ailures during the LHC transfer and injection process cannot be excluded and beam loss with the foreseen intensities and energies will cause serious equipment damage. Consequences of equipment failures such as kicker erratics, power converter faults, etc. are investigated by means of a Monte Carlo based on MAD-X tracking with a full aperture model of the transfer line and the injection region. Geometrical and optical mismatch, orbit tolerances, mechanical tolerances for settings of protection elements, power converter ripples, misalignment of elements, etc. are all taken into account. The required performance of the protection system is discussed. The overall protection level for the LHC and the transfer lines during injection is presented. research-article

Beam based Alignment of the LHC Transfer Line Collimators Kain Verena Burkhardt Helmut Goddard Brennan Redaelli Stefano 2005 At LHC injection energy the aperture available in the transfer lines and in the LHC is small and the intensities of the injected beams are an order of magnitude above the damage level. The setting of protection elements such as the transfer line collimators is therefore very critical; mechanical and optical tolerances must be taken into account to define the nominal setting. Being able to measure and control the collinearity of the collimator jaws with the beam relaxes the requirement on the settings considerably. A method to measure angular misalignment of the collimator jaws in the transfer line based on a transmission measurement is discussed. Simulations have been made and a test of principle has been carried out during the 2004 commissioning of the transfer line TI 8. research-article