engBottura, LPauletta, SRemondino, VittorioSanfilippo, SScandale, WalterTodesco, EzioStatus Report on Field Quality in the Main LHC DipolesAccelerators and Storage RingsLHC-Project-Report-579CERN-LHC-Project-Report-579We give the present status of the field quality in the main LHC dipoles. Special emphasis is given to the collared coil data: a few tens of coils have been built, allowing a first analysis of the variability between producers, and estimates of the random part. Effects of the corrective actions implemented to fine tune the systematics components of low-order multipoles are presented. Correlations of collared coil data to the magnetic field measurements in operational conditions are discussed. Comparison to specifications imposed by beam dynamics allows to pin out the most critical requirements that will have to be met during the LHC dipole production.2002-07-02http://cds.cern.ch/record/570942http://cds.cern.ch/record/570942oai:cds.cern.ch:570942 engBaglin, VCollins, I RGröbner, OswaldGrünhagel, CJenninger, BCryosorber Studies for the LHC Long Straight Section Beam Screens with COLDEXAccelerators and Storage RingsLHC-Project-Report-580CERN-LHC-Project-Report-580The cold bore experiment (COLDEX), that can be cooled below 3 K, has been fitted with a ~ 2 m long actively cooled beam screen equipped with cryosorber to simulate the LHC Long Straight Section (LSS) beam screens. Effects of both synchrotron radiation at grazing incidence with 194 eV critical energy and gas injections have been studied. Results as a function of temperature, gas species and gas coverage are presented. Possible implications to LHC LSS design and operation are discussed.2002-07-02http://cds.cern.ch/record/569477http://cds.cern.ch/record/569477oai:cds.cern.ch:569477 engBottura, LRedaelli, SRemondino, VittorioSanfilippo, SSavary, FScandale, WalterTodesco, EzioOptimization of the Even Normal Multipole Components in the Main Dipole of the Large Hadron ColliderAccelerators and Storage RingsLHC-Project-Report-578CERN-LHC-Project-Report-578In this paper we discuss even multipolar components of the Large Hadron Collider dipole in relation to the manufacturing features and target values required by beam dynamics. Due to the two-in-one collar geometry, systematic components are induced by the mutual influence of the two apertures and are strongly affected by the shape of the magnetic iron yoke. In order to optimize the normal quadrupole and octupole harmonics, a new design was chosen for the ferromagnetic insert between the iron yoke and the collars. Three different insert shapes were selected and installed in a full scale prototype. The measured dependence of the even multipoles on the insert shape shows a good agreement with simulations based on a magnetostatic code. A final design of the insert has been worked out and implemented in pre-series magnets. Data relative to even multipoles in pre-series magnets are presented, both at room temperature and at the operational temperature of 1.9 K. Comparison with target values required by beam dynamics is discussed.2002-07-02http://cds.cern.ch/record/569476http://cds.cern.ch/record/569476oai:cds.cern.ch:569476 engMuratori, BStudy of Offset Collisions and Beam Adjustment in the LHC Using a Strong-Strong Simulation ModelAccelerators and Storage RingsLHC-Project-Report-593CERN-LHC-Project-Report-593The bunches of the two opposing beams in the LHC do not always collide head-on. The beam-beam effects cause a small, unavoidable separation under nominal operational conditions. During the beam adjustment and when the beams are brought into collision the beams are separated by a significant fraction of the beam size. A result of small beam separation can be the excitation of coherent dipole oscillations or an emittance increase. These two effects are studied using a strong-strong multi particle simulation model. The aim is to identify possible limitations and to find procedures which minimise possible detrimental effects.2002-07-08http://cds.cern.ch/record/569471http://cds.cern.ch/record/569471oai:cds.cern.ch:569471 engAssmann, R WSchmidt, FZimmermann, FrankZorzano-Mier, M PEquilibrium Beam Distribution and Halo in the LHCAccelerators and Storage RingsLHC-Project-Report-592CERN-LHC-Project-Report-597CERN-LHC-Project-Report-592LHC-Project-Report-597The equilibrium LHC beam distribution at large amplitudes is a crucial input to the collimation and machine protection design, as well as to background studies. Its estimation requires a knowledge of the diffusion rates at which beam particles are transported to large transverse or longitudinal amplitudes. Important known mechanisms of particle diffusion include Touschek scattering, synchrotron radiation, intrabeam scattering (IBS) the nonlinear motion due to the long-range (LR) beam-beam (BB) collisions at top energy, persistent-current field errors during injection and at the start of acceleration, and Coulomb scattering off the residual gas. We summarize the expected contributions from different sources, introduce a diffusion model, and illustrate the evolution of the beam distribution at 7 TeV.2002-07-08http://cds.cern.ch/record/569470http://cds.cern.ch/record/569470oai:cds.cern.ch:569470Same report as LHC-Project-Report-597 engHayes, MSimulating Dynamic Effects in Superconducting Magnets at the LHCAccelerators and Storage RingsLHC-Project-Report-591CERN-LHC-Project-Report-591Changes in multipole errors (during injection or ramping) of the superconducting magnets in the LHC affect important beam parameters such as the closed orbit, tune and chromaticity. In the following it is described how the currently used simulation tool (SixTrack) has been modified to simulate this time dependence in order to reproduce these effects. Preliminary results are shown.2002-07-08http://cds.cern.ch/record/569469http://cds.cern.ch/record/569469oai:cds.cern.ch:569469 engHayes, MTolerances of the Spool Piece Correction System for the LHCAccelerators and Storage RingsLHC-Project-Report-590CERN-LHC-Project-Report-590The LHC main superconducting dipoles are provided with a spool piece correction system which is to be used to correct locally the non-linear multipole errors b3, b4 and b5. The tolerances of this correction system to failures are discussed. Also discussed are simple methods of ensuring they are set correctly during commissioning.2002-07-08http://cds.cern.ch/record/569468http://cds.cern.ch/record/569468oai:cds.cern.ch:569468 engAssmann, R WFartoukh, Stéphane DavidHayes, MWenninger, JThe Influence of Time-Dependent Magnetic Field Errors on the Specifications of Feedback and Collimation SystemsAccelerators and Storage RingsLHC-Project-Report-589CERN-LHC-Project-Report-589During injection and ramping at the LHC the time dependence of the errors in the main dipoles will have an effect on the beam dynamics. These time dependencies are simulated using the latest tracking codes. The effects on beam dynamics and beam stability are examined. Collimation and control feedback issues are also studied.2002-07-08http://cds.cern.ch/record/569466http://cds.cern.ch/record/569466oai:cds.cern.ch:569466 engZimmermann, FrankTwo-Stream Effects in Present and Future AcceleratorsAccelerators and Storage RingsLHC-Project-Report-588CERN-LHC-Project-Report-588Electron beams are perturbed by ions in a similar way as proton and positron beams are by electrons, generated via gas ionization, photoemission, or multipacting. Fast beam-ion or electron-cloud "two-stream" instabilities become more severe for higher beam current or closer bunch spacing, and they may limit the ultimate performance of an accelerator. For the Large Hadron Collider (LHC), the heat load deposited by electrons on the beam screen inside the superconducting magnets is a concern. I compare theories and simulations of these two-stream effects with observations at various storage rings, e.g., ALS, PLS, SPS, and KEKB, and comment on future machines, such as the LHC, the damping rings of a future linear collider, and a possible LHC upgrade operating with long "superbunches".2002-07-08http://cds.cern.ch/record/569465http://cds.cern.ch/record/569465oai:cds.cern.ch:569465 engAngal-Kalinin, DeepaBrandt, DVos, LIntermediate Review of Single Bunch Collective Effects in the LHCAccelerators and Storage RingsLHC-Project-Report-587CERN-LHC-Project-Report-587This paper presents an intermediate review of the single bunch collective effects in the LHC. It first reviews the LHC impedance budget including all elements for which a design is presently available. Then, based on this updated budget, the corresponding rise times and thresholds for single bunch instabilities are evaluated and discussed.2002-07-08http://cds.cern.ch/record/569464http://cds.cern.ch/record/569464oai:cds.cern.ch:569464 engAssmann, R WFartoukh, Stéphane DavidZimmermann, FrankMeasuring Beta Functions and Dispersion in the Early LHCAccelerators and Storage RingsLHC-Project-Report-586CERN-LHC-Project-Report-586Achieving nominal beam conditions in the LHC requires a small beta beating and a small dispersion mismatch. We compare the linear optics errors expected from linear and nonlinear magnetic field imperfections and magnet mis-alignments with the required values. The measurement procedures are simulated in a machine with collimators, realistic aperture restrictions, and different bunch intensities, in order to infer the expected measurement accuracies for beta beating and dispersion. Consequences for possibly required beam-based correction tools are discussed.2002-07-08http://cds.cern.ch/record/569463http://cds.cern.ch/record/569463oai:cds.cern.ch:569463 engAngal-Kalinin, DeepaVos, LCoupled Bunch Instabilities in the LHCAccelerators and Storage RingsLHC-Project-Report-585CERN-LHC-Project-Report-585In the LHC, the coupled bunch instabilities will be mainly driven by the RF cavities and the resistive wall effect. The growth times of these instabilities have been estimated taking into consideration the undamped and damped higher order modes of these cavities. These estimates show that the rise times of the longitudinal coupled bunch instabilities are under control. The proposed transverse feed-back system allows the same conclusion to be drawn for the transverse resistive wall instability.2002-07-08http://cds.cern.ch/record/569462http://cds.cern.ch/record/569462oai:cds.cern.ch:569462 engMelikidze, ADobrovitski, V VDe Raedt, H AKatsnelson, M IHarmon, B NParity Effects in Spin DecoherenceGeneral Theoretical Physicsquant-ph/0212097We demonstrate that decoherence of many-spin systems can drastically differ from decoherence of single-spin systems. The difference originates at the most basic level, being determined by parity of the central system, i.e. by whether the system comprises even or odd number of spin-1/2 entities. Therefore, it is very likely that similar distinction between the central spin systems of even and odd parity is important in many other situations. Our consideration clarifies the physical origin of the unusual two-step decoherence found previously in the two-spin systems.2002-12-16http://cds.cern.ch/record/597544http://cds.cern.ch/record/597544oai:cds.cern.ch:597544 eng Airapetian, A Measurement of single-spin azimuthal asymmetries in semi-inclusive electroproduction of pions and kaons on a longitudinally polarised deuterium target Particle Physics - Experiment hep-ex/0212039 DESY-02-226 DESY-2002-226 Single-spin asymmetries have been measured for semi-inclusive electroproduction of $\pi^+$, $\pi^-$, $\pi^0$ and $K^+$ mesons in deep-inelastic scattering off a longitudinally polarised deuterium target. The asymmetries appear in the distribution of the hadrons in the azimuthal angle $\phi$ around the virtual photon direction, relative to the lepton scattering plane. The corresponding analysing powers in the $\sin \phi$ moment of the cross section are $0.012 \pm 0.002 {(stat.)} \pm 0.002 {(syst.)}$ for $\pi^+$, $0.006 \pm 0.003 {(stat.)} \pm 0.002 {(syst.)}$ for $\pi^-$, $0.021 \pm 0.005 {(stat.)} \pm 0.003 {(syst.)}$ for $\pi^0$ and $0.013 \pm 0.006 {(stat.)} \pm 0.003 {(syst.)}$ for $K^+$. The $\sin 2\phi$ moments are compatible with zero for all particles. 2002-12-16 http://cds.cern.ch/record/597266 http://cds.cern.ch/record/597266 eng CERN. Geneva Queen Mary University of London (QMUL) Legal Service: Memorandum of Understanding between CERN (European Organization for Nuclear Research) and QMUL (Queen Mary University of London (SMD)) Concerns the TMS project : thermo-mechanical and thermo-electrical devices (TMS), cellular thermal management structures (CTMS), and encased thermal management systems (ETMS) 2002-12-18T23:00:00Z http://cds.cern.ch/record/97476 http://cds.cern.ch/record/97476 engBaglin, VCollins, I RGröbner, OswaldGrünhagel, CJenninger, BSynchrotron radiation studies of the LHC dipole beam screen with COLDEXAccelerators and Storage RingsLHC-Project-Report-584CERN-LHC-Project-Report-584The cold bore experiment (COLDEX) installed in a beam line of the electron-positron accumulator (EPA) at CERN, has been used to study the effect of synchrotron radiation onto the LHC dipole beam screen. The ~ 2 m long cryostat, that can be cooled below 3 K, is fitted with an actively cooled beam screen. A 'sawtooth' copper co-laminated type beam screen has been submitted to grazing synchrotron radiation with 194 eV critical energy. Experiments studying the effect of photon dose, gas condensation onto beam screen or cold bore and temperature oscillations is presented. Implications to LHC operation is discussed.2002-07-02http://cds.cern.ch/record/566864http://cds.cern.ch/record/566864oai:cds.cern.ch:566864 2002-12-16T23:00:00Z http://cds.cern.ch/record/9535 http://cds.cern.ch/record/9535 2002-12-17T23:00:00Z http://cds.cern.ch/record/11496 http://cds.cern.ch/record/11496 2002-12-16T23:00:00Z http://cds.cern.ch/record/11495 http://cds.cern.ch/record/11495 engHenrist, BernardHilleret, NoëlScheuerlein, CTaborelli, MVorlaufer, GThe variation of the secondary electron yield and of the desorption yield of copper under electron bombardment: Origin and impact on the conditioning of the LHCAccelerators and Storage RingsLHC-Project-Report-583CERN-LHC-Project-Report-583The operation of most radio-frequency components in accelerators rely on the conditioning obtained usually by gradually increasing the power fed into these devices. This effect is related to the reduction of the desorption yields and of the secondary electron yields of surfaces exposed to electron bombardment. In LHC, similar decreases will also limit the detrimental consequences of the electron cloud phenomenon on the beam stability, the power deposited in the cryogenic system and the gas density. The parallel evolution of the desorption yield and of the secondary electron yield will be discussed and compared to the changes to the surface composition as observed by surface analytical techniques. The possible origin of the secondary electron yield decrease will also be discussed at the light of these new results.2002-07-02http://cds.cern.ch/record/566863http://cds.cern.ch/record/566863oai:cds.cern.ch:566863 2002-12-16T23:00:00Z http://cds.cern.ch/record/11493 http://cds.cern.ch/record/11493 2002-12-16T23:00:00Z http://cds.cern.ch/record/11492 http://cds.cern.ch/record/11492 engRathjen, CMechanical behaviour of vacuum chambers and beam screens under quench conditions in dipole and quadrupole fieldsAccelerators and Storage RingsLHC-Project-Report-582CERN-LHC-Project-Report-582A method based on analytical formulas is described to calculate bending moments, stresses, and deformations of vacuum chambers and beam screens in dipole and in quadrupole fields during a magnet quench. Solutions are given for circular and racetrack shaped structures. Without the need of time consuming calculations the solutions enable a quick design and verification of vacuum chambers and beam screens.2002-07-02http://cds.cern.ch/record/566862http://cds.cern.ch/record/566862oai:cds.cern.ch:566862 2002-12-15T23:00:00Z http://cds.cern.ch/record/10981 http://cds.cern.ch/record/10981 doi:10.5170/CERN-2002-001.123engRossi, ARumolo, GiovanniZimmermann, FrankA simulation study of the electron cloud in the experimental regions of the LHCAccelerators and Storage RingsLHC-Project-Report-581CERN-LHC-Project-Report-581The LHC experimental regions (ATLAS, ALICE, CMS and LHCb) are characterised by having a variable geometry, non-uniform magnetic field, and the presence of two beams that will collide at the Interaction Point (IP). A detailed study of electron multipacting in the experimental chambers is needed to establish the pressure increase due to electron stimulated desorption, especially critical in the experimental regions. Furthermore, knowledge of the predicted electron cloud density all along the experimental regions will allow for an estimation of its possible effects on the beam stability.CERN2002-07-02http://cds.cern.ch/record/56686110.5170/CERN-2002-001.123http://cds.cern.ch/record/566861oai:cds.cern.ch:566861 engDenz, RRodríguez-Mateos, FVergara-Fernández, AReliability analysis for the quench detection in the LHC machineAccelerators and Storage RingsLHC-Project-Report-596CERN-LHC-Project-Report-596The Large Hadron Collider (LHC) will incorporate a large amount of superconducting elements that require protection in case of a quench. Key elements in the quench protection system are the electronic quench detectors. Their reliability will have an important impact on the down time as well as on the operational cost of the collider. The expected rates of both false and missed quenches have been computed for several redundant detection schemes. The developed model takes account of the maintainability of the system to optimise the frequency of foreseen checks, and evaluate their influence on the performance of different detection topologies. Seen the uncertainty of the failure rate of the components combined with the LHC tunnel environment, the study has been completed with a sensitivity analysis of the results. The chosen detection scheme and the maintainability strategy for each detector family are given.2002-07-22http://cds.cern.ch/record/571872http://cds.cern.ch/record/571872oai:cds.cern.ch:571872 engAssmann, R WJeanneret, J BKaltchev, D IEfficiency for the imperfect LHC collimation systemAccelerators and Storage RingsLHC-Project-Report-598CERN-LHC-Project-Report-598The LHC collimation system requires a high cleaning efficiency in order to prevent magnet quenches due to regular beam diffusion. The cleaning efficiency is significantly reduced due to imperfections of the collimator jaws and the machine optics. Tracking tools have been set up to predict the cleaning efficiency in presence of multiple imperfections. The deterioration of cleaning efficiency is quantified for different errors, including collimator surface non-flatness, collimator alignment errors, beta beating, orbit errors, non-linear field errors, and chromatic effects.2002-07-24http://cds.cern.ch/record/572774http://cds.cern.ch/record/572774oai:cds.cern.ch:572774 engFaus-Golfe, AVerdier, AOptics Studies for Diffractive Physics at the LHCAccelerators and Storage RingsLHC-Project-Report-601CERN-LHC-Project-Report-601Forward protons with momenta close to the beam-momentum arise either from elastic scattering or from single or double diffraction. These protons are very close to the beamline and can only be measured downstream using "beam close detectors". In this paper we present a complete study of the optics (low, medium and high beta), possible locations of the detectors and running scenarios for these measurements at insertions IR1 and IR5 of the LHC. These optics are compatible with the latest layout of the LHC insertions and the commissioning beam parameters.2002-01-08http://cds.cern.ch/record/574080http://cds.cern.ch/record/574080oai:cds.cern.ch:574080revised version number 1 submitted on 2002-08-01 10:49:35 engAssmann, R WBaishev, I SBrugger, MBruno, LBurkhardt, HBurtin, GDehning, BerndFischer, CGoddard, BGschwendtner, EHayes, MJeanneret, J BJung, RKain, VKaltchev, D ILamont, MSchmidt, RVossenberg, Eugène BWeisse, EWenninger, JRequirements for the LHC collimation systemAccelerators and Storage RingsLHC-Project-Report-599CERN-LHC-Project-Report-599The LHC requires efficient collimation during all phases of the beam cycle. Collimation plays important roles in prevention of magnet quenches from regular beam diffusion, detection of abnormal beam loss and subsequent beam abort, radiation protection, and passive protection of the superconducting magnets in case of failures. The different roles of collimation and the high beam power in the LHC impose many challenges for the design of the collimation system. In particular, the collimators must be able to withstand the expected particle losses. The requirements for the LHC collimation system are presented.2002-07-24http://cds.cern.ch/record/572775http://cds.cern.ch/record/572775oai:cds.cern.ch:572775 engLebrun, PHelium cryogenic systems for the LEP2 and LHC projects at CERNAccelerators and Storage RingsCERN-LHC-96-005-ACRCERN is presently operating a large distributed 4.5 K helium cryogenic system (48 kW@4.5 K equivalent) for cooling the superconducting acceleration cavities of the 26.7 km circumference LEP2 lepton collider. This also constitutes the first part of the 1.8 K cryogenic system (about 150 kW@4.5 K equivalent) for the future Large Hadron Collider (LHC), the high-field superconducting magnets of which will operate in superfluid helium. We briefly describe the main features of each system, and review the progress of their development, construction and operation.1996-05-25http://cds.cern.ch/record/305166http://cds.cern.ch/record/305166oai:cds.cern.ch:305166 doi:10.5170/CERN-1996-003.321engLebrun, POperating at 1.8 K: the technology of superfluid heliumAccelerators and Storage RingsCERN-LHC-96-002-ARCThe technical properties of helium II ("superfluid" helium) are presented from the user point of view. Its applications to the cooling of superconducting devices, particularly in accelerators and colliders are discussed in terms of heat transfer capability and limitations in conductive and convective modes. Large-capacity refrigeration techniques below 2 K are reviewed, as concerns thermodynamic cycles as well as process machinery. Examples drawn from existing or planned projects illustrate the presentation.CERN1996-02-20http://cds.cern.ch/record/30071810.5170/CERN-1996-003.321http://cds.cern.ch/record/300718oai:cds.cern.ch:300718