engBarnes, M JFowler, TRavida, GRodriguez, IToral, FDesign, Manufacturing and Testing of the CTF3 Tail Clipper KickerAccelerators and Storage RingsCERN-ATS-2010-163CLIC-Note-852The goal of the present CLIC Test Facility (CTF3) is to demonstrate the technical feasibility of specific key issues of the CLIC scheme. The extracted drive beam from the combiner ring (CR), a pulse of 35 A magnitude and 140 ns duration, is sent to the new CLic EXperimental area (CLEX). A Tail Clipper (TC) kicker is required, in the CR to CLEX transfer line, to allow the duration of the beam pulse to be adjusted: the unwanted bunches are kicked into a collimator. The TC must have a fast field rise-time, of not more than 5 ns, in order to minimize uncontrolled beam loss. Striplines are used for the TC: to establish the required fields, the applied pulse wave front must fully propagate along the striplines. To reduce the wave front propagation time, the overall length of the stripline assembly is sub-divided into 4 sections. The TC has been designed with the aid of detailed numerical modelling: the stripline cross-section and coaxial-to-stripline transitions were carefully optimized using a 3D code. The results of simulations and the measured behaviour of the striplines are presented; in addition measured current pulses are shown.2010-06-01http://cds.cern.ch/record/1280679http://cds.cern.ch/record/1280679oai:cds.cern.ch:1280679 engSchoerling, DAms, ABernhard, AKarppinen, MMaccaferri, RPeiffer, PRossmanith, RFirst Magnetic Tests of a Superconducting Damping Wiggler for the CLIC Damping RingsAccelerators and Storage RingsCERN-ATS-2010-162CLIC-Note-853Each of the proposed CLIC electron and positron damping rings will be equipped with 76 wigglers. The length of each wiggler is 2 m, the period length lambda 40 to 50 mm, and the beam-stay-clear gap 13 mm. The minimum required mid-plane field B0 is 2.5 T, that can only be obtained with superconducting technologies. In order to demonstrate the feasibility of such a wiggler, a short model with a period length of 40mm was built and successfully tested at CERN. The measured mid-plane field was 2 T at 4.2K and 2.5 T at 1.9 K in the center of a 16mm gap. The currents were 730 and 910 A, respectively. To fulfill the field specification for the CLIC damping rings at 4.2 K it is planned to replace the Nb-Ti wire with a Nb$_{3}$Sn wire.2010-06-01http://cds.cern.ch/record/1280677http://cds.cern.ch/record/1280677oai:cds.cern.ch:1280677 engBarnes, M JDucimetière, LUythoven, JCLIC Pre-damping and Damping Ring Kickers: Initial Ideas to Achieve Stability RequirementsAccelerators and Storage RingsCERN-ATS-2010-161CLIC-Note-854The Compact Linear Collider (CLIC) study is exploring the scheme for an electron-positron collider with high luminosity (1034-1035 cm-2s-1) and a nominal centre-of mass energy of 3 TeV: CLIC would complement LHC physics in the multi-TeV range. The CLIC design relies on the presence of Pre-Damping Rings (PDR) and Damping Rings (DR) to achieve the very low emittance, through synchrotron radiation, needed for the luminosity requirements of CLIC. In order to limit the beam emittance blow-up due to oscillations the combined flat top ripple and droop of the field pulse, for the DR extraction kickers, must be less than 0.02 %. In addition, the allowed beam coupling impedance is also very low: a few Ohms longitudinally and a few MW/m transversally. This paper discusses initial ideas for achieving the demanding requirements for the PDR and DR kickers.2010-06-01http://cds.cern.ch/record/1280467http://cds.cern.ch/record/1280467oai:cds.cern.ch:1280467 engTodesco, EAquilina, NAuchmann, BBottura, LBuzio, MChritin, RDeferne, GDeniau, LFiscarelli, LHagen, PGarcia Perez, JGiovannozzi, MLamont, MMontenero, GMuller, GPereira, MRedaelli, SRemondino, VSammut, NSchmidt, FSteinhagen, RStrzelczyk, MTomas, RVenturini Delsolaro, WWenninger, JWolf, RThe Magnetic Model of the LHC in the Early Phase of Beam CommissioningAccelerators and Storage RingsCERN-ATS-2010-154The relation between field and current in each family of the Large Hadron Collider magnets is modelled with a set of empirical equations (FiDeL) whose free parameters are fit on magnetic measurements. They take into account residual magnetization, persistent currents, hysteresis, saturation, decay and snapback during initial part of the ramp. Here we give a first summary of the reconstruction of the magnetic field properties based on the beam observables (orbit, tune, coupling, chromaticity) and a comparison with the expectations. The most critical issues for the machine performance in terms of knowledge of the relation magnetic field vs current are pointed out.2010-06-01http://cds.cern.ch/record/1277918http://cds.cern.ch/record/1277918oai:cds.cern.ch:1277918 engPerin, AVan Weelderen, RClaudet, SOperational Experience with the LHC Superconducting Links and Evaluation of Possible Cryogenic Schemes for Future Remote Powering of Superconducting MagnetsAccelerators and Storage RingsCERN-ATS-2010-152In the LHC, a large number of superconducting magnets are powered remotely by 5 superconducting links at distances of 70 up to 520 m. This innovation allowed choosing more convenient locations for installing the electrical feedboxes and their related equipment. The consolidations performed after the first commissioning campaign and the operational experience with the superconducting links over a period of several months are presented. Based on the successful application of superconducting links in the LHC, such devices can be envisaged for powering future accelerator magnets. Several possible cryogenic configurations for future superconducting links are presented with their respective figures of merit from the cryogenic and practical implementation point of view.2010-06-01http://cds.cern.ch/record/1277916http://cds.cern.ch/record/1277916oai:cds.cern.ch:1277916 engWalckiers, LArpaia, PBottura, LBuzio, MDunkel, OFiscarelli, LMontenero, GGarcia Perez, JTodesco, EMeasurement and Scaling Laws of the Sextupole Component in the LHC Dipole MagnetsAccelerators and Storage RingsCERN-ATS-2010-149One of the main requirements for the magnet operation of the Large Hadron Collider at CERN is the correction of the dynamic multipole errors produced. In particular, integrated sextupole errors in the main dipoles must be kept well below 0.1 units to ensure acceptable chromaticity. The feed-forward control of the LHC magnets is based on the Field Description for the LHC (FiDeL), a semi-empirical mathematical model capable of forecasting the magnet’s behaviours in order to suitably power the corrector scheme. Measurement campaign were recently undertaken to validate the model making use of a novel Fast rotating-coil Magnetic Measurement Equipment (FAME), able to detect superconductor decay and snapback transient with unprecedented accuracy and temporal resolution. We discuss in this paper the test setup and some measurement results confirming the FiDeL model.2010-06-01http://cds.cern.ch/record/1277912http://cds.cern.ch/record/1277912oai:cds.cern.ch:1277912 engBertinelli, FCatalan Lasheras, NFessia, PGarion, CMathot, SPerin, AScheuerlein, CSgobba, Sten Kat, HTock, J PVerweij, AWillering, GTowards a Consolidation of LHC Superconducting Splices for 7 TeV OperationAccelerators and Storage RingsCERN-ATS-2010-144Following the analysis of the September 2008 LHC incident, the assembly process and the quality assurance of the main 13 kA interconnection splices were improved, with new measurement and diagnostics methods introduced. During the 2008-2009 shutdown ~5% of these 10 000 splices were newly assembled with these improvements implemented, but essentially maintaining the original design. It is known today that a limiting factor towards 7 TeV operation is the normal conducting resistance of ~15% of the original main 13 kA interconnection splices, associated to the electrical continuity of the copper stabiliser. A “Splices Task Force” has been set up at CERN to evaluate the need for, develop and test design improvements and prepare the implementation of a consolidation campaign. Important issues of splice design, process choice, resources and time requirements are considered.2010-06-01http://cds.cern.ch/record/1277711http://cds.cern.ch/record/1277711oai:cds.cern.ch:1277711 engSauerwein, CWilliams, L RCaspers, FDalin, J MHaemmerle, VTiseanu, ITock, J PMobile CT-System for In-situ Inspection in the LHC at CERNEngineeringAccelerators and Storage RingsCERN-ATS-2010-194CERN-ATS-2010-143For the inspection of certain critical elements of the LHC machine a mobile computed tomography system has been developed and built. This instrument has to satisfy stringent space, volume and weight requirements in order to be transportable and usable to any interconnection location in the LHC tunnel. Particular regions of interest in the interconnection zones between adjacent magnets are the plug in modules (PIM), the soldered splices in the superconducting bus-bars and the interior of the quench diode container. This system permits detailed inspection of these regions without needing to break the insulation vacuum. Limited access for the x-ray tube and the detector required the development of a special type of partial tomography, together with suitable reconstruction techniques for 3 D volume generation from radiographic projections. The layout of the complete machine, the limited angle tomography, as well as a number of radiographic and tomographic inspection results is presented.2010-05-30http://cds.cern.ch/record/1277708http://cds.cern.ch/record/1277708oai:cds.cern.ch:1287897 engBuzio, MBeaumont, AGalbraith, PGolluccio, GGiloteaux, DGilardoni, SPetrone, CWalckiers, LDevelopment of Upgraded Magnetic Instrumentation for CERN Real-Time Reference Field Measurement SystemsAccelerators and Storage RingsCERN-ATS-2010-142The control of five of the accelerators in the CERN injector chain (PS, PS Booster, SPS, LEIR and AD) is based upon real-time measurements in a reference magnet. These so-called “B-train” systems include a field marker to signal the achievement of a given field value, complemented by one or more pick-up coils to integrate flux changes. Recently, some concerns were raised about long-term reliability and performance improvements, in terms of both resolution and operational flexibility, for these systems. This paper reports the status of three related R&D activities, namely: the development of a novel dynamic NMR field marker for the PS; a campaign aimed at the detailed measurement of the magnetic state of a PS main magnet; and the design of a standardized electronic signal acquisition and conditioning system.2010-06-01http://cds.cern.ch/record/1277706http://cds.cern.ch/record/1277706oai:cds.cern.ch:1277706 engBarnes, M JDucimetière, LGoddard, BHessler, CMertens, VUythoven, JBeam-Based Measurement of the Waveform of the LHC Injection KickersAccelerators and Storage RingsCERN-ATS-2010-141Proton and ion beams are injected into LHC at 450 GeV by two kicker magnet systems, producing magnetic field pulses of up to 7.8 ms flat top duration with rise and fall times of not more than 900 ns and 3 ms, respectively. Both systems are composed of four travelling wave kicker magnets, powered by pulse forming networks. One of the stringent design requirements of these systems is a field flat top and postpulse ripple of less than ±0.5 %. A carefully matched high bandwidth system is required to obtain the required pulse response. Screen conductors are placed in the aperture of the kicker magnet to provide a path for the image current of the, high intensity, LHC beam and screen the ferrite against wake fields. However, these conductors affect the field pulse response. Recent injection tests provided the opportunity to directly measure the shape of the kick field pulse, with high accuracy, using a pilot beam. This paper details the measurements and compares the results with predictions and laboratory measurements.2010-06-01http://cds.cern.ch/record/1277702http://cds.cern.ch/record/1277702oai:cds.cern.ch:1277702 engSermeus, LBarnes, M JFowler, TThe Kicker Systems for the PS Multi-turn ExtractionAccelerators and Storage RingsCERN-ATS-2010-140A five-turn continuous extraction has up to now been used to transfer the proton beam from the CERN PS to the SPS. This extraction uses an electrostatic septum to cut the filament beam into five slices, causing losses of about 15 %. These losses would be an even greater drawback when the beam intensity is increased for the CERN Neutrinos to Gran Sasso (CNGS) facility. To overcome this Multi-Turn Extraction (MTE) has been implemented, in which the beam is separated, prior to extraction, into a central beam core and four islands. Each beamlet is extracted using a set of kickers and a magnetic septum. For the kickers two new pulse generators have been built, each containing a lumped element Pulse Forming Network (PFN) of 12.5 W, 80 kV and 10.5 ms. For cost reasons existing 15 W transmission line kicker magnets are reused. The PFN characteristic impedance deliberately mismatches that of the magnets to allow a higher maximum kick. The PFN design has been optimised such that undesirable side-effects of the impedance mismatch on kick rise-time and flat-top remain within acceptable limits. The kicker systems put in place for the current first phase of MTE are presented.2010-06-01http://cds.cern.ch/record/1277699http://cds.cern.ch/record/1277699oai:cds.cern.ch:1277699 engHessler, CGoddard, BMeddahi, MThe Final Beam Line Design for the HiRadMat Test FacilityAccelerators and Storage RingsCERN-ATS-2010-138The High Radiation to Materials facility - hereafter HiRadMat - is designed to allow testing of accelerator components, in particular those of the LHC and its injectors, with the impact of high-intensity pulsed beams. The facility is currently under construction, as an approved CERN project. The installation of the dedicated primary beam line and experimental area is planned during the 2010-2011 technical stop. It will be ready for users after commissioning and some test running in October 2011. A detailed proton beam line design has been performed in order to fulfil the beam parameter specification, in particular the demanding optics flexibility at the test stand location. The studies presented include trajectory correction and aperture studies as well as specifications of magnetic systems, power converters, beam instrumentation and vacuum systems2010-06-01http://cds.cern.ch/record/1277693http://cds.cern.ch/record/1277693oai:cds.cern.ch:1277693 engMeddahi, MFartoukh, SFuchsberger, KGoddard, BHerr, WKain, VKaltchev, DMertens, VWenninger, JResults of 2009 Optics Studies of the SPS to LHC Transfer LinesAccelerators and Storage RingsCERN-ATS-2010-137In 2008, the SPS-to-LHC transfer line operation allowed for the first time to perform beam measurements in the last part of the lines and into the LHC. Beam parameters were measured and compared with expectation. Discrepancies were observed in the dispersion matching into the LHC, and also in the vertical phase advance along the line. In 2009, extensive theoretical and simulation work was performed in order to understand the possible sources of these discrepancies. This allowed establishing an updated model of the beam line, taking into account the importance of the full magnetic model, the limited dipole corrector strengths and the precise alignment of beam elements. During 2009, beam time was allocated in order to perform further measurements, checking and refining the optical model of the transfer line and LHC injection region and validating the different assumptions. Results of the 2009 optics measurements and comparison with the beam specification and model are presented..2010-06-01http://cds.cern.ch/record/1277691http://cds.cern.ch/record/1277691oai:cds.cern.ch:1277691 engSchoerling, DBaumbach, TBernhard,Burkart, FEhlers, SGerstl, SGrau, APeiffer, PRossmanith, RWollmann, DInductive Shimming of Superconductive Undulators - Preparations for a realistic testAccelerators and Storage RingsCERN-ATS-2010-136The monochromaticity and intensity of synchrotron light emitted by undulators strongly depend on the undulator field quality. For the particular case of superconductive undulators it was shown recently that their field quality can be significantly improved by an array of coupled high temperature superconductor loops attached to the surface of the superconductive undulator. Local field errors induce currents in the coupled closed superconducting loops and, as a result, the hereby generated magnetic field minimizes the field errors. In previous papers the concept was described theoretically and a proof-of-principle experiment was reported. This paper reports on a prepatation experiment for the first quantitative measurement of the phase error reduction in a 13-period short model undulator equipped with a full-scale induction shimming system.2010-06-01http://cds.cern.ch/record/1277687http://cds.cern.ch/record/1277687oai:cds.cern.ch:1277687 engUythoven, JCarlier, EDucimetière, LGoddard, BKain, VMagnin, NBeam Commissioning and Performance Characterisation of the LHC Beam Dump Kicker SystemsAccelerators and Storage RingsCERN-ATS-2010-135The LHC beam dump system was commissioned with beam in 2009. This paper describes the operational experience with the kicker systems and the tests and measurements to qualify them for operation. The kicker performance was characterized with beam by measurements of the deflection angles, using bunches extracted at different times along the kicker sweep. The kicker performance was also continuously monitored for each dump with measurement and analysis of all kick pulses, allowing diagnostic of errors and of long-term drifts. The results are described and compared to the expectations.2010-06-01http://cds.cern.ch/record/1277686http://cds.cern.ch/record/1277686oai:cds.cern.ch:1277686 engSenaj, VDucimetière, LVossenberg, EUpgrade of the Super Proton Synchrotron Vertical Beam Dump SystemAccelerators and Storage RingsCERN-ATS-2010-134The vertical beam dump system of the CERN Super Proton Synchrotron (SPS) uses two matched magnets with an impedance of 2 W and a combined kick strength of 1.152 Tm at 60 kV supply voltage. For historical reasons the two magnets are powered from three 3 W pulse forming networks (PFN) through three thyratronignitron switches. Recently flashovers were observed at the entry of one of the magnets, which lead, because of the electrical coupling between the kickers, to a simultaneous breakdown of the pulse in both magnets. To improve the reliability an upgrade of the system was started. In a first step the radii of surfaces at the entry of the weak magnet were increased, and the PFN voltage was reduced by 4%; the kick strength could be preserved by reducing the magnet termination resistance by 10 %. The PFNs were protected against negative voltage reflections and their last cell was optimised. In a second step the two magnets will be electrically separated and powered individually by new 2 W PFNs with semiconductor switches..2010-06-01http://cds.cern.ch/record/1277676http://cds.cern.ch/record/1277676oai:cds.cern.ch:1277676SPS beam dump engBartmann, WAssmann, RBracco, CDehning, BGoddard, BHolzer, E BKain, VMeddahi, MNordt, ARedaelli, SRossi, ASapinski, MWollmann, DBeam Commissioning of the Injection Protection System of the LHCAccelerators and Storage RingsCERN-ATS-2010-133The movable LHC injection protection devices in the SPS-to-LHC transfer lines and downstream of the injection kicker in the LHC were commissioned with low-intensity beam. The different beam-based alignment measurements used to determine the beam centre and size are described, together with the results of measurements of the transverse beam distribution at large amplitude. The system was set up with beam to its nominal settings and the protection level against various failures was determined by measuring the transmission and transverse distribution into the LHC. Beam loss levels for regular operation were also extrapolated. The results are compared with the expected device settings and protection level, and the implications for LHC operation discussed.2010-06-01http://cds.cern.ch/record/1277672http://cds.cern.ch/record/1277672oai:cds.cern.ch:1277672 engBorburgh, JBalhan, BBarnes, M JFowler, THinterschuster, FHourican, MKramer, TPalm, MProst, ASermeus, LStadlbauer, TDesign and Development of Kickers and Septa for MedaustronAccelerators and Storage RingsCERN-ATS-2010-132The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and ions for both cancer therapy and research. Different types of bumpers, septa and kickers will be used in the low energy beam transfer line, the synchrotron and the high energy extraction lines.They are presently being designed in collaboration with CERN. Both 2D and 3D finite element simulations have been carried out to verify and optimize the field strength and homogeneity for each type of magnet and, where applicable, the transient field response. The detailed designs for the injection and dump bumpers, the magnetic septa and the fast chopper dipoles are presented. A novel design for the electrostatic septa is outlined.2010-06-01http://cds.cern.ch/record/1277664http://cds.cern.ch/record/1277664oai:cds.cern.ch:1277664 engKramer, TBartmann, WBracco, CGoddard, BMeddahi, MPerformance Studies for Protection Against Asynchronous Dumps in the LHCAccelerators and Storage RingsCERN-ATS-2010-131The LHC beam dump system has to safely dispose all beams in a wide energy range of 450 GeV to 7 TeV. A 3 ms abort gap in the beam structure for the switch-on of the extraction kicker field ideally allows a loss-free extraction under normal operating conditions. However, a low number of asynchronous beam aborts is to be expected from reliability calculations and from the first year's operational experience with the beam dump kickers. For such cases, MAD-X simulations including all optics and alignment errors have been performed to determine loss patterns around the LHC as a function of the position of the main protection elements in interaction region six. Special attention was paid to the beam load on the tungsten collimators which protect the triplets in the LHC experimental insertions, and the tracking results compared with semi-analytical numerical estimates. The simulations are also compared to the results of beam commissioning of these protection devices.2010-06-01http://cds.cern.ch/record/1277650http://cds.cern.ch/record/1277650oai:cds.cern.ch:1277650 engCastañeda Serra, AKwiatkowski, MTodd, BDependable Design Using Programmable Logic DevicesAccelerators and Storage RingsCERN-ATS-2010-130Mission critical systems at the European Organisation for Nuclear Research (CERN) make extensive use of Programmable Logic Devices (PLDs) such as Field Programmable Gate Arrays (FPGAs) to implement their safety critical functions. The dependability of these safety critical functions is difficult to determine using traditional techniques. A robust approach is needed if PLD technology is to be accepted in mission critical systems. This paper discusses techniques which are being developed and employed by CERN to give confidence in the use of PLDs in mission critical systems, the Safe Machine Parameter system development is used as an example2010-06-01http://cds.cern.ch/record/1277646http://cds.cern.ch/record/1277646oai:cds.cern.ch:1277646 engFormenti, FCharifoulline, ZCoelingh, G JDahlerup-Petersen, KDenz, RHonma, ARavaioli, ESchmidt, RSiemko, ASteckert, JFeher, SFlora, R HPfeffer, HUpgrade of the Quench Protection Systems for the Superconducting Circuits of the LHC Machine at CERN: From Concept and Design to the First Operational ExperienceAccelerators and Storage RingsCERN-ATS-2010-129Two events, occurring in 2008 during commissioning of the LHC circuits, lead to fundamental changes to the scope of circuit protection. The discovery of aperturesymmetric quenches and the accidental rupture at 9 kA of an interconnecting busbar resulted in an emergency program for development and implementation of new protection facilities. The new scheme comprises a distributed busbar supervision system with early warning capabilities based on high-precision splice resistance measurements and system interlocks for rapid deexcitation of the circuit in case of sudden splice resistance increase. The developed symmetric quench detectors are digital systems with radiation-resistant FPGA logic controllers, having magnet heater firing capabilities. This program successfully allowed a safe re-powering of the collider. The concept of the new electronics boards and the powering modules will be described. More than 14600 extra cables and 6000 new detector and control cards were added to the existing Quench Protection System (QPS). A first evaluation of the system performance as well as a number of interesting discoveries made during the commissioning will be presented.2010-06-01http://cds.cern.ch/record/1277645http://cds.cern.ch/record/1277645oai:cds.cern.ch:1277645 engPuccio, BCastañeda Serra, AKwiatkowski, MRomera Ramirez, ITodd, BThe CERN Beam Interlock System: Principle and Operational ExperienceAccelerators and Storage RingsCERN-ATS-2010-128A complex Machine Protection System has been designed to protect the LHC machine from an accidental release of the beam energy, with about 20 subsystems providing status information to the Beam Interlock System that is the backbone of machine protection. Only if the subsystems are in the correct state for beam operation, the Beam Interlock System receives a status flag and beam can be injected into LHC (Large Hadron Collider). The Beam Interlock System also relays commands from the connected subsystems in case of failure for triggering the LHC Beam Dumping System. To maintain the required level of safety of the Beam Interlock System, the performance of the key components is verified before every fill of the machine and validated after every emergency beam dump before beam operation is allowed to continue. This includes all critical paths, starting from the inputs from connected systems triggering a beam dump request, followed by the correct interruption and propagation sequence of the two redundant beam permit loops until the final extraction of the beam via the LHC beam dumping system. In this paper we report about the experience with the Beam Interlock System that has been deployed for some years in the Super Proton Synchrotron (SPS), in its transfer lines and recently in LHC.2010-06-01http://cds.cern.ch/record/1277643http://cds.cern.ch/record/1277643oai:cds.cern.ch:1277643 engGoddard, BKain, VMeddahi, MComparison of Emittance Growth for 450 GeV Rigidity PB82+ ions and P+ in Thin ScatterersAccelerators and Storage RingsCERN-ATS-2010-127The beam profile screens in the long SPS-to-LHC transfer lines were used to measure with high precision the emittance growth arising from scattering. The effective thickness of the scatterer could be varied by adding thick Al2O3 fluorescent screens, with the emittance measurement made using very thin Ti OTR screens. The technique allows the intrinsic variation in the emittance from the injector chain to be factored out of the measurement, and was applied to Pb82+ and protons, both with 450 GeV rigidity. The results are presented and the possible applications to the accurate benchmarking of nuclear interaction codes discussed.2010-06-01http://cds.cern.ch/record/1277642http://cds.cern.ch/record/1277642oai:cds.cern.ch:1277642 engGoddard, BAiba, MBracco, CCarli, CMeddahi, MWeterings, W J MStripping Foil Issues for H- Injection into the CERN PSB at 160 MeVAccelerators and Storage RingsCERN-ATS-2010-126Beam physics considerations for the stripping foil of the 160 MeV PSB H- injection systems are described, including the arguments for the foil type, thickness, geometry and positioning. The foil performance considerations are described, including expected stripping efficiency, emittance growth, energy straggling, temperature and lifetime. The different beam loss mechanisms are quantified in the context of the aperture limits, operational considerations and collimation requirements.2010-06-01http://cds.cern.ch/record/1277640http://cds.cern.ch/record/1277640oai:cds.cern.ch:1277640 engGoddard, BBartmann, WBracco, CKain, VMeddahi, MMertens, VUythoven, JAperture Measurements of the LHC Injection Regions and Beam Dump SystemsAccelerators and Storage RingsCERN-ATS-2010-125The commissioning of the beam transfer systems for LHC included detailed aperture measurements in the injection regions and for the beam dump systems. The measurements, mainly single pass, were made using systematic scans of different oscillation phases and amplitudes, and the results compared with the expectations from the physical aperture model of the LHC. In this paper the measurements and results are presented and compared with the specified apertures in these critical areas.2010-06-01http://cds.cern.ch/record/1277634http://cds.cern.ch/record/1277634oai:cds.cern.ch:1277634 engMeddahi, MBart Pedersen, SBoccardi, AButterworth, AFisher, A SGianfelice-Wendt, EGoddard, BHemelsoet, G HHöfle, WJacquet, DJaussi, MKain, VLefevre, TShaposhnikova, EUythoven, JValuch, DLHC Abort Gap Monitoring and CleaningAccelerators and Storage RingsCERN-ATS-2010-124Unbunched beam is a potentially serious issue in the LHC as it may quench the superconducting magnets during a beam abort. Unbunched particles, either not captured by the RF system at injection or leaking out of the RF bucket, will be removed by using the existing damper kickers to excite resonantly the particles in the abort gap. Following beam simulations, a strategy for cleaning the abort gap at different energies was proposed. The plans for the commissioning of the beam abort gap cleaning are described and first results from the beam commissioning are presented.2010-06-01http://cds.cern.ch/record/1277630http://cds.cern.ch/record/1277630oai:cds.cern.ch:1277630 engKoratzinos, MBertinelli, FCharifoulline, ZDahlerup-Petersen, KDenz, RFlora, R HPfeffer, HScheuerlein, CSchmidt, RSiemko, AStrait, JVerweij, AHigh-Current Bus Splice Resistances and Implications for the Operating Energy of the LHCAccelerators and Storage RingsCERN-ATS-2010-175At each interconnection between LHC main magnets a low-resistance solder joint must be made between superconducting cables in order to provide a continuous current path through the superconductor and also to the surrounding copper stabilizer in case the cable quenches [1]. About 10,000 such joints exist in the LHC. An extensive campaign has been undertaken to characterize and map the resistances of these joints. All of the superconducting cable splices were measured at 1.9 K and no splices were found with a resistance larger than 3 nW. Non-invasive measurements of the stabilizer joints were made at 300 K in 5 of the 8 sectors, and at 80 K in 3 sectors. More precise local measurements were made on suspect interconnects that were opened up, and poor joints were repaired. However, it is likely that additional imperfect stabilizer joints still exist in the LHC. A statistical analysis is used to place bounds on the remaining worst-case resistances. This sets limits on the maximum operating energy of the LHC, prior to a more extensive intervention [2].2010-06-01http://cds.cern.ch/record/1283478http://cds.cern.ch/record/1283478oai:cds.cern.ch:1283478 engThiesen, HCerqueira Bastos, MHudson, GKing, QMontabonnet, VNisbet, DPage, SHigh Precision Current Control for the LHC Main Power ConvertersAccelerators and Storage RingsCERN-ATS-2010-176Since restarting at the end of 2009, the LHC has reached a new energy record in March 2010 with the two 3.5 TeV beams. To achieve the performance required for the good functioning of the accelerator, the currents in the main circuits (Main Bends and Main Quadrupoles) must be controlled with a higher precision than ever previously requested for a particle accelerator at CERN: a few parts per million (ppm) of nominal current. This paper describes the different challenges that were overcome to achieve the required precision for the current control of the main circuits. Precision tests performed during the hardware commissioning of the LHC illustrate this paper.2010-06-01http://cds.cern.ch/record/1283530http://cds.cern.ch/record/1283530oai:cds.cern.ch:1283530