engLebrun, PSuperconductivity and Cryogenics for the Large Hadron ColliderAccelerators and Storage RingsLHC-Project-Report-441CERN-LHC-Project-Report-441Key technologies to the Large Hadron Collider (LHC), the 26.7 km circumference high-energy, high-luminosity particle collider under construction at CERN, are high-field superconducting magnets and superfluid helium cryogenics. After recalling the main challenges of the project, we present the rationale for applying these technologies on an unprecedented scale and briefly indicate the status of their implementation.2000-10-27http://cds.cern.ch/record/473537http://cds.cern.ch/record/473537oai:cds.cern.ch:473537 engAnushat, VDahlerup-Petersen, KErokhin, AKussul, AMedvedko, A SModeling and Computer Simulation of the Pulsed Powering of Mechanical D.C. Circuit Breakers for the CERN/LHC Superconducting Magnet Energy Extraction SystemAccelerators and Storage RingsLHC-Project-Report-442CERN-LHC-Project-Report-442This article presents the results of modeling and computer simulation of non-linear devices such as the Electromagnetic Driver of a D.C. Circuit Breaker. The mechanical and electromagnetic parts of the Driver are represented as equivalent electrical circuits and all basic processes of the Driver's magnetic circuit are calculated.2000-11-16http://cds.cern.ch/record/477523http://cds.cern.ch/record/477523oai:cds.cern.ch:477523 engVöllinger, ChristineAleksa, MartinRussenschuck, StephanModified Bean Model and FEM Method Combined for Persistent Current Calculation in Superconducting CoilsAccelerators and Storage RingsLHC-Project-Report-445CERN-LHC-Project-Report-445Field variations in the LHC superconducting magnets, e. g. during the ramping of the magnets, induce magnetization currents in the superconducting material, the so-called persistent currents that do not decay but persist due to the lack of resistivity. This paper describes a semi-analytical hysteresis model for hard superconductors, which has been developed for the computation of the total field errors arising from persistent currents. Since the superconducting coil is surrounded by a ferromagnetic yoke structure, the persistent current model is combined with the finite element method (FEM), as the non-linear yoke can only be calculated numerically. The used finite element method is based on a reduced vector potential formulation that avoids the meshing of the coil while calculating the part of the field arising from the source currents by means of the Biot-Savart Law. The combination allows to determine persistent current induced field errors as function of the excitation and for arbitrarily shaped iron yokes. The model has been implemented into the ROXIE program and is tested using the LHC dipole magnet as an example.2000-12-15http://cds.cern.ch/record/480809http://cds.cern.ch/record/480809oai:cds.cern.ch:480809 engRussenschuck, StephanAleksa, MartinBazan, MLucas, JRamberger, SVöllinger, ChristineIntegrated Design of Superconducting Magnets with the CERN Field Computation Program ROXIEAccelerators and Storage RingsLHC-Project-Report-446CERN-LHC-Project-Report-446The program package ROXIE has been developed at CERN for the field computation of superconducting accelerator magnets and is used as an approach towards the integrated design of such magnets. It is also an example of fruitful international collaborations in software development.The integrated design of magnets includes feature based geometry generation, conceptual design using genetic optimization algorithms, optimization of the iron yoke (both in 2d and 3d) using deterministic methods, end-spacer design and inverse field calculation.The paper describes the version 8.0 of ROXIE which comprises an automatic mesh generator, an hysteresis model for the magnetization in superconducting filaments, the BEM-FEM coupling method for the 3d field calculation, a routine for the calculation of the peak temperature during a quench and neural network approximations of the objective function for the speed-up of optimization algorithms, amongst others.New results of the magnet design work for the LHC are given as examples.2000-12-15http://cds.cern.ch/record/480810http://cds.cern.ch/record/480810oai:cds.cern.ch:480810 doi:10.1103/PhysRevSTAB.3.122402engVöllinger, ChristineAleksa, MartinRussenschuck, StephanCalculation of Persistent Currents in Superconducting MagnetsAccelerators and Storage RingsLHC-Project-Report-447CERN-LHC-Project-Report-447The paper describes a semi-analytical hysteresis model for hard superconductors. The model is based on the critical state model considering the dependency of the critical current density on the varying local field in the superconducting filaments. By combining this hysteresis model with numerical field computation methods, it is possible to calculate the persistent current multipole errors in the magnet taking local saturation effects in the magnetic iron parts into consideration. As an application of the method, the use of soft magnetic iron sheets (coil protection sheets mounted between the coils and the collars) for the part compensation of the multipole errors during the ramping of the magnets is investigated.2000-12-15http://cds.cern.ch/record/48081110.1103/PhysRevSTAB.3.122402http://cds.cern.ch/record/480811oai:cds.cern.ch:480811 engAleksa, MartinRussenschuck, StephanVöllinger, ChristineParametric Quadrilateral Meshes for the Design and Optimization of Superconducting MagnetsAccelerators and Storage RingsLHC-Project-Report-448CERN-LHC-Project-Report-448The program package ROXIE [1] has been developed at CERN for the design and optimization of the superconducting magnets for the LHC.The necessity of extremely uniform (coil dominated) fields in accelerator magnets requires very accurate methods of .eld computation. For this purpose a coupled boundary-element/ finite-element technique (BEM-FEM) is used [2]. Quadrilateral higher order finite-elements are used for the discretization of the iron domain.This is necessary for the accurate modeling of the iron contours and is favorable for 3D meshes. A new quadrilateral mesh generator using geometrically optimized domain decomposition which was developed at the University of Stuttgart, Germany [3] has been implemented into the ROXIE program providing fully automatic and user friendly mesh generation.The frequent application of mathematical optimization techniques requires parametric models which are set-up using a feature-based approach.The structure of the magnet cross-section can be modeled using parametric objects such as holes of different forms, elliptic, parabolic or hyperbolic arcs, notches, slots,etc. Investigations of the speed-up of the computations due to geometrically optimized meshes will be presented. For sensitivity analysis, point based morphing algorithms are applied to the generated mesh.2000-12-15http://cds.cern.ch/record/480812http://cds.cern.ch/record/480812oai:cds.cern.ch:480812 doi:10.1016/S0011-2275(01)00019-4engBottura, LBreschi, MRosso, CA General Model for Thermal, Hydraulic and Electric Analysis of Superconducting CablesAccelerators and Storage RingsLHC-Project-Report-456CERN-LHC-Project-Report-456In this paper we describe a generic, multi-component and multi-channel model for the analysis of superconducting cables. The aim of the model is to treat in a general and consistent manner simultaneous thermal, electric and hydraulic transients in cables. The model is devised for most general situations, but reduces in limiting cases to most common approximations without loss of efficiency. We discuss here the governing equations, and we write them in a matrix form that is well adapted to numerical treatment. We finally demonstrate the model capability by comparison with published experimental data on current distribution in a two-strand cable.2000-12-22http://cds.cern.ch/record/48349410.1016/S0011-2275(01)00019-4http://cds.cern.ch/record/483494oai:cds.cern.ch:483494 engBenda, VBozzini, DRiddone, GVandoni, GiovannaMeasurement on Different MLI Systems Between 77 K and 4 K and their Application in Cryogenic EngineeringAccelerators and Storage RingsLHC-Project-Report-457CERN-LHC-Project-Report-457Precise thermal measurements were done on different types of large surface MLI samples under various boundary conditions. The measurements were focused on the use of MLI for large industrial plants considering quick and simple installation. The results of the measurements aim at optimising MLI parameters, which control the thermal behaviour. Practical recommendations of MLI materials and their installation are given.2000-12-11http://cds.cern.ch/record/483800http://cds.cern.ch/record/483800oai:cds.cern.ch:483800 engBremer, JDelikaris, DDelruelle, NHaug, FPassardi, GiorgioPerinic, GCryogenics for the Large Hadron Collider ExperimentsAccelerators and Storage RingsLHC-Project-Report-458CERN-LHC-Project-Report-458High Energy Physics experiments have frequently adopted cryogenic versions of their apparatus to achieve the desired performance. Among the four new experiments for the CERN Large Hadron Collider (LHC) the two largest, ATLAS and CMS, include spectrometers using 4.5 K superconducting magnets and detectors filled with liquid argon at 87 K, respectively for particle momentum and energy measurements. These detectors are of unprecedented size and complexity and the definition of the associated cryogenic systems is the result of a collaboration between CERN and several external institutes all around the world. A review of the various systems is presented with particular emphasis to the basic cooling principles, the special cryogenic features and the operation scenarios.2000-12-11http://cds.cern.ch/record/483801http://cds.cern.ch/record/483801oai:cds.cern.ch:483801 doi:10.1016/S0011-2275(01)00015-7engSanfilippo, SSiemko, AMethods for the Evaluation of Quench Temperature Profiles and their Application for LHC Superconducting Short Dipole MagnetsAccelerators and Storage RingsLHC-Project-Report-459CERN-LHC-Project-Report-459This paper presents a study of the thermal effects on quench performance for several Large Hadron Collider single aperture short dipole models. The analysis is based on the temperature profile in a superconducting magnet evaluated after a quench. Peak temperatures and temperature gradients in the magnet coil are estimated for different thicknesses of insulation layer between the quench heaters and the coil and different powering and protection parameters. The results show clear correlation between the thermo-mechanical response of the magnet and quench performance. They also display that the optimisation of the position of quench heaters can reduce the decrease of training performance caused by the coexistence of a mechanical weak region and of a local temperature rise.2001-01-19http://cds.cern.ch/record/48393910.1016/S0011-2275(01)00015-7http://cds.cern.ch/record/483939oai:cds.cern.ch:483939 doi:10.1103/PhysRevSTAB.3.122403engFerracin, PScandale, WalterTodesco, EzioWolf, RModeling of random geometric errors in superconducting magnets with applications to the CERN Large Hadron ColliderAccelerators and Storage RingsLHC-Project-Report-460CERN-LHC-Project-Report-460Estimates of random field-shape errors induced by cable mispositioning in superconducting magnets are presented and specific applications to the Large Hadron Collider (LHC) main dipoles and quadrupoles are extensively discussed. Numerical simulations obtained with Monte Carlo methods are compared to analytic estimates and are used to interpret the experimental data for the LHC dipole and quadrupole prototypes. The proposed approach can predict the effect of magnet tolerances on geometric components of random field-shape errors, and it is a useful tool to monitor the obtained tolerances during magnet production.2001-01-19http://cds.cern.ch/record/48394010.1103/PhysRevSTAB.3.122403http://cds.cern.ch/record/483940oai:cds.cern.ch:483940 engChorowski, MGrzegory, PParente, CRiddone, GOptimisation of Multilayer Insulation: an Engineering ApproachAccelerators and Storage RingsLHC-Project-Report-464CERN-LHC-Project-Report-464A mathematical model has been developed to describe the heat flux through multilayer insulation (MLI). The total heat flux between the layers is the result of three distinct heat transfer modes: radiation, residual gas conduction and solid spacer conduction. The model describes the MLI behaviour considering a layer-to-layer approach and is based on an electrical analogy, in which the three heat transfer modes are treated as parallel thermal impedances. The values of each of the transfer mode vary from layer to layer, although the total heat flux remains constant across the whole MLI blanket. The model enables the optimisation of the insulation with regard to different MLI parameters, such as residual gas pressure, number of layers and boundary temperatures. The model has been tested with experimental measurements carried out at CERN and the results revealed to be in a good agreement, especially for insulation vacuum between 10-5 Pa and 10-3 Pa.2001-02-12http://cds.cern.ch/record/486721http://cds.cern.ch/record/486721oai:cds.cern.ch:486721 doi:10.1016/S0011-2275(01)00016-9engChorowski, MGrzegory, PSerio, LVan Weelderen, RModelling of Helium-mediated Quench Propagation in the LHC Prototype Test String-1Accelerators and Storage RingsLHC-Project-Report-468CERN-LHC-Project-Report-468The Large Hadron Collider (LHC) prototype test string-1, hereafter referred to as the string, is composed of three ten-meter long prototype dipole magnets and one six-meter long prototype quadrupole magnet. The magnets are immersed in a pressurized static bath of superfluid helium that is maintained at a pressure of about 1 bar and at a temperature of about 1.9 K. This helium bath constitutes one single hydraulic unit, extending along the 42.5 m of the string length. We have measured the triggering of quenches of the string magnets due to the quenching of a single dipole magnet located at the string's extremity; i.e. "quench propagation". Previously reported measurements enabled to establish that in this configuration the quench propagation is mediated by the helium and not by the inter-magnet busbar connections [1], [2]. We present a model of helium mediated quench propagation based on the qualitative conclusions of these two previous papers, and on additional information gained from a dedicated series of quench propagation measurements that were not previously reported. We will discuss the specific mechanisms and their main parameters involved at different time scales of the propagation process, and apply the model to make quantitative predictions.2001-03-23http://cds.cern.ch/record/49332410.1016/S0011-2275(01)00016-9http://cds.cern.ch/record/493324oai:cds.cern.ch:493324