Saban, R I Bordry, Frederick Bozzini, D Dahlerup-Petersen, K Denz, R Puccio, B Rijllart, A Rodríguez-Mateos, F Schmidt, R Serio, L Thiesen, H IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018389 232-235 12 1 2002 2002 String 2 is a full-size model of a regular cell in an LHC arc. In the first phase, three dipole magnets and two quadrupole magnets have been assembled in String 2 and commissioning started in April 2001. By the beginning of 2002 three pre-series dipole magnets will be added to complete the cell. As for its predecessor String 1, the facility was built to individually validate the LHC systems and to investigate their collective behaviour for normal operation with the magnets at a temperature of 1.9 K, during transients as well as during exceptional conditions. String 2 is a precious milestone before installation and commissioning of the first LHC sector (1/8 of the machine) in 2004, with respect to infrastructure, installation, tooling and assembly procedures, testing and commissioning of individual systems, as well as the global commissioning of the technical systems. This paper describes the commissioning, and retraces the first powering history. Bottura, L Venturini-Delsolaro, W Haverkamp, M Kuijper, A IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018403 291-294 12 1 2002 2002 The time decay of field harmonics during current plateaus is a known drawback of superconducting accelerator magnets. The present understanding of this phenomenon refers to a combination of flux creep and of the interaction between the redistribution of currents in Rutherford cables and the filament magnetization. Current cycles of decreasing amplitude, called here degaussing, were found to reduce significantly the decay observed in accelerator magnets. This paper reports on the measured reduction of decay obtained in short dipole models for the LHC and on one experiment with a single LHC strand. Venturini-Delsolaro, W Ang, Z Bottura, L Sanfilippo, S Siemko, A Tommasini, D Walckiers, L IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018404 295-300 12 1 2002 2002 A full characterization of the magnetic field in warm and cold conditions was performed as a part of the standard test on the LHC 1-m long superconducting dipole models. Furthermore, dedicated measurement campaigns addressed the effect of current cycles and quenches on field quality. Powering and quenches were found to generate characteristic instabilities in the geometric harmonics. Detailed results are presented on this phenomenon, as well as correlations between warm and cold measurements and field reconstructions. Smirnov, N Bottura, L Chiusano, F Dunkel, O Legrand, P Schloss, S Schnizer, P Sievers, P IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018732 1688-1692 12 1 2002 2002 More than 400 twin aperture lattice quadrupoles are needed for the Large Hadron Collider (LHC) which is under construction at CERN. The main quadrupole is assembled with correction magnets in a common cryostat called the Short Straight Section (SSS). We plan to measure all SSS's in cold conditions with an unprecedented accuracy: integrated gradient of the field within 150 ppm, harmonics in a range of 1 to 5 ppm, magnetic axis of all elements within 0.1 mm and their field direction within 0.2 mrad. In this paper we describe the automatic measurement system that we have designed, built and calibrated. Based on the results obtained on the two first prototypes of the SSS's (SSS3 and SSS4) we show that this system meets all above requirements. Arn, A Arshad, S A Giloux, C Patru, F Reymond, H Senis, R Walckiers, L IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018731 1684-1687 12 1 2002 2002 The LHC accelerator will be equipped with more than 3500 superconducting spool corrector magnets. CERN has awarded the contract for the series production and testing of these corrector magnets to industry. Magnetic field measurements are done at the factory. Dedicated magnetic measurement benches have been built to test these corrector magnets in the resistive state at room temperature. The benches allow to measure the strength of the main field, normal and skew harmonics, the magnetic axis position and orientation of the main field with respect to the mechanical reference points of the magnet. This paper presents the objectives, a description and the performances obtained with the benches during first measurements at industry. Pugnat, P Schreiner, T Siemko, A IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018395 258-261 12 1 2002 2002 The windings of high-field accelerator magnets are usually made of Rutherford-type superconducting cables. The magnetic field distribution along the axis of such magnets exhibits a periodic modulation with a wavelength equal to the twist pitch length of the cable used in the winding. This effect, resulting from quasi-persistent currents, was investigated with a Hall probes array inserted inside the aperture of the LHC superconducting dipoles, both in short models and full-scale prototypes. The amplitude and the time dependence of this periodic field oscillation have been studied as a function of the magnet current history. The origin and the impact on the LHC dipoles stability of the non-uniform current redistribution producing such a field modulation are discussed. Bottura, L Buzio, M Schnizer, P Smirnov, N IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018730 1680-1683 12 1 2002 2002 When investigating the quality of a magnetic measurement system, one observes difficulties to identify the "trouble maker" of such a system as different effects can yield similar influences on the measurement results.We describe a tool in this paper that allows to investigate numerically the effects produced by different imperfections of components of such a system, including, but not limited to vibration and movements of the rotating coil, influence of electrical noise on the system, angular encoder imperfections. This system can simulate the deterministic and stochastic parts of those imperfections. We outline the physical models used that are generally based on experience or first principles. Comparisons to analytical results are shown. The modular structure of the general design of this tool permits to include new modules for new devices and effects. Aleksa, Martin Amet, S Ang, Z Bottura, L Buzio, M Ferracin, P Pagano, O Remondino, Vittorio Russenschuck, Stephan Sanfilippo, S Scandale, Walter Todesco, Ezio IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018392 247-250 12 1 2002 2002 We report the main results of the magnetic field measurements performed on the full-size LHC superconducting dipoles tested at CERN since summer 1998. Main field strength and field errors are summarised. We discuss in detail the contributions related to the geometry of the collared coil, the assembled cold mass, cool-down effects, magnetisation of the superconducting cable and saturation effects at high field. Dynamic effects on field harmonics, such as the field decay during injection and field errors during current ramps, are assessed statistically. Sanfilippo, S Siemko, A Tommasini, D Venturini-Delsolaro, W IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018393 251-253 12 1 2002 2002 The short model program, started in October 1995 to study and validate design variants and assembly of the main LHC dipoles, has achieved its last phase. The last models were focused on the validation of specific design choices to be implemented in the series production, and to the study of the training performance of the coil heads. This paper reports on the manufacturing features of the recent twin-aperture short models, reviews the results of the cold tests and presents a summary of the training quench performance and quench location. Bottura, L D'Angelo, G Gateau, M Legrand, P Modena, M Naoui, K Perini, D Pugnat, P Sanfilippo, S Savary, F Scandale, Walter Siemko, A Sievers, P Spigo, G Vlogaert, J Wyss, C IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018385 211-214 12 1 2002 2002 Within the LHC cryo-dipole program, six full-scale superconducting prototypes of final design were built in collaboration between Industry and CERN, followed by launching the manufacture of pre-series magnets. Five prototypes and the first of the pre-series magnets were tested at CERN. This paper reviews the main features and the performance of the cryo-dipoles tested at 4.2 K and 1.8 K. The results of the quench training, conductor performance, magnet protection, sensitivity to ramp rate and field characteristics are presented and discussed in terms of the design parameters. Benedico, E Bottura, L Haverkamp, M ten Haken, B ten Kate, H H J Sanfilippo, S IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018357 86-89 12 1 2002 2002 In superconducting particle accelerators significant changes occur in tune and chromaticity during the injection of particles and their subsequent acceleration. This behavior is caused by the decay of magnetic field components in the superconducting accelerator magnets during injection and their so-called "snapback" to the original hysteresis curve during the first few seconds after the start of the energy ramp. The two effects are closely related to a spatially periodic modulation of all field components along the magnet axis. In order to avoid a loss of particles the sextupole component in the dipoles has to be compensated with a very high accuracy. Standard magnetic measurements using rotating coils do not have the time resolution required to completely resolve the snapback. For this reason we have developed a fast system for sextupole measurements consisting of three Hall plates mounted on a ring. A new calibration procedure for the first time allows quantitative results. The detector is used to measure decay and snapback as a function of several parameters in the operation cycle. The results obtained help to better understand the interaction between current distribution and magnetization in the coil. Amet, S Bottura, L Deniau, L Walckiers, L IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018668 1417-1421 12 1 2002 2002 The measurements performed at CERN on prototypes and first pre-series main dipole magnets confirm the need of an active control of the Large Hadron Collider to compensate the dynamic field changes during the proton beam injection and acceleration. This control requires in turn an accurate forecast of the magnetic field in the accelerator. We plan to predict the field on the basis of two elements: theoretical field models tailored through the accumulated knowledge of the main magnets during series tests, and an on-line measurement system running on few reference magnets tracking the LHC current cycle. Data coming from this "Multipoles Factory" will result from the fusion of the two sources. Based on this system we foresee to deliver calibration information for pre-defined accelerator cycles as well as real time information for the active control. In this paper we report the conceptual design of the system, and we discuss the features and performance of the models that we have developed for the field forecast. Bottura, L Buzio, M Deferne, G Schnizer, P Sievers, P Smirnov, N IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018725 1659-1662 12 1 2002 2002 We discuss the method developed for the verification of alignment of magnetic elements contained in the LHC cryodipole cold mass during series tests at CERN. First, we outline motivations and requirements and then we focus on test strategy, equipment and procedures. Our goal is to express the magnetic field of the dipole and of its associated correctors w.r.t. the reference beam line, not accessible during cryogenic tests. To do so, we use traveling harmonic coil probes ("moles") that allow simultaneous measurement of the field and of the coil position. A laser tracker is used to relate these measurements to fiducials. In the dipole, the axis of the Quadrupole Configured Dipole (QCD) is used as an intermediate reference for the transfer. We provide details on the devices used for measurements in warm and cold conditions, some results from prototypes and pre-series dipoles and an assessment of the precision expected for the series tests. Akhmedov, A I IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018709 1595-1598 12 1 2002 2002 An equation has been derived which describes the current distribution in a flat cable subjected to a time-dependent magnetic field directed perpendicular to the cable wide face. Solutions of this equation obtained in the case when all parameters are uniform along the cable allow us to obtain the time constant spectrum, magnetic moment of the cable and A.C. loss. For a stack of cables with height much larger than the cable width, the contribution of the self-screening is calculated analytically. Numerical examples are provided based on geometrical characteristics and interstrand contact resistance of a typical LHC cable and the inductance of the LHC dipole. Akhmedov, A A Amet, S Balaazi, I Bottura, L Gateau, M Pugnat, P Walckiers, L IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018345 31-34 12 1 2002 2002 Knowledge of AC loss and dynamic magnetic field distortion in the main LHC dipoles is both important for the assessment of the accelerator performance and providing insight into the properties of assembled magnets. We measured the loss due to the current cycling in a few 1-meter long model dipoles, 15-meter long dipole prototypes and pre-series magnets. As expected the loss depends linearly on the rate of the current change. From the slope of this dependence, the contact resistance between the strands of the opposite layers of the cable, Rc, was evaluated for the inner winding of the dipole. We discuss the method to estimate the Rc value in the outer winding. The Rc value has been also derived independently from measurements of the magnetic field. For this, the ramp rate dependent component of the main field as well as of the harmonics has been measured. The main magnetic field measurements were performed using both stationary coils and Hall probes. Rotating coils were used to perform the harmonic measurements. Bozzini, D IEEE Trans. Appl. Supercond. 1269-1271 12 1 2002 2002 For the LHC, 1232 dipole magnets and about 400 quadrupole magnets operating at 1.9 K are installed in arcs and dispersion suppressors. Each cryo-magnet assembly comprises the main magnet and several small corrector magnets. Each assembly is equipped with voltage taps, quench heaters and cryogenic instrumentation. The number of instrumentation wires serving each magnet assembly and passing from cold to ambient is between 36 and 40. An Instrumentation Feedthrough System (IFS) will electrically and mechanically connect the instrument wires to the outside of the vacuum vessel. The IFS has to satisfy several requirements: simplicity of integration, optimal access during tests and commissioning, voltage withstand and reliability during the lifetime of the machine. The heat load to superfluid helium must be minimized, and the long-term stability of the insulation vacuum should be preserved. The solution foresees an open stainless steel tube housing the wires connected between the magnet and the outside of the vacuum vessel and terminated by a leak tight connector. The IFS is assembled from different standard components designed to fulfil the electrical, mechanical and thermal requirements and will be integrated by the industries that build the magnets. The standardization of the IFS for all types of cryo-magnet assemblies permits the same hardware interfaces and procedures to be used from the integration to commissioning and operation of the machine. This paper describes the main parameters, the technical choices, the performance and the integration techniques of the IFS system. Adam, J D Boutboul, T Cavallari, Giorgio Charifoulline, Z Denarié, C H Le Naour, S Leroy, D F Oberli, L R Richter, D Verweij, A P Wolf, R IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018583 1056-1062 12 1 2002 2002 Six contracts have been placed with industrial companies for the production of 1200 tons of the superconducting (SC) cables needed for the main dipoles and quadrupoles of the Large Hadron Collider (LHC). In addition, two contracts have been placed for the supply of 470 tons of NbTi and 26 tons of Nb sheets. The main characteristic of the specification is that it is functional. This means that the physical, mechanical and electrical properties of strands and cables are specified without defining the manufacturing processes. Facilities for the high precision measurements of the wire and cable properties have been implemented at CERN, such as strand and cable critical current, copper to superconductor ratio, interstrand resistance, magnetisation, RRR at 4.2 K and 1.9 K. The production has started showing that the highly demanding specifications can be fulfilled. This paper reviews the organisation of the contracts, the test facilities installed at CERN, the various types of measurements and the results of the main physical properties obtained on the first batches. The status of the deliveries is presented. Babic, S Beckers, F Brixhe, F Comel, S Peiro, G Verbeeck, T IEEE Trans. Appl. Supercond. 1219-1222 12 1 2002 2002 A total of 50'000 tonnes of low-carbon steel sheet has been ordered for the LHC main magnets. After three years of production, about 10'000 tonnes of steel sheet have been produced by Cockerill-Sambre Groupe Usinor. This paper gives a summary of the manufacturing process and improvements implemented as well as an overview of the difficulties encountered during this production. Preliminary statistics obtained for the mechanical and magnetic steel properties are presented. Fessia, P Lanza, C Perini, D Verbeeck, T IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018630 1256-1260 12 1 2002 2002 This paper reports on the manufacturing features and difficulties experienced for the preliminary mass production of the main mechanical components of the dipole cold mass. The production of about 600 km of superconducting coil copper wedges, 5'000 coil layer jump spacers and boxes, 12'500'000 austenitic steel collars and 5'800'000 low-carbon yoke laminations is spread over 4 European countries and involves 6 manufactory firms. The general technical requirements for the manufacturing process as well as the imposed production checks and quality controls are reviewed. An overview of the preliminary results is presented with an outlook towards the analysis and statistical which are in a process to be implemented for the follow-up of the mass production. Ferracin, P Rastogi, P K Scandale, Walter Todesco, Ezio Tropea, P IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018737 1709-12 12 1 2002 2002 Magnetic field quality in superconducting magnets mostly depends on conductor position in operational conditions (under pressure, at 1.9 K). For the case of the LHC main magnets, the conductor layout must agree with the nominal design within less than 0.05 mm to met the field quality specifications. Finite element models are a numerical tool to forecast loads and deformations of mechanical structures, and can be used to evaluate conductor displacements. To verify the FEM response at room temperature, we made displacement measurements using speckle interferometer on a short sample of the dipole coils. Experimental results are compared with the numerical calculations, allowing a stringent test of the most critical features of the FEM (interfaces between different materials and coil properties). Burgmer, R Bussjäger, R Krischel, D Peyrot, M Rifflet, J M Schmidt, P Simon, F Tortschanoff, Theodor IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018402 287-290 12 1 2002 2002 A collaboration agreement between CERN and CEA-Saclay resulted in the successful development and construction of prototypes of the LHC main superconducting quadrupole magnets and their assembly into cold masses. A call for tender was issued in October 1999 and led to the adjudication of a contract to ACCEL Instruments. A number of components will be provided by CERN to be used either directly by ACCEL for integration into the cold mass units or by sub-suppliers before delivery to ACCEL. During the series fabrication CEA's engineers and technicians, already experienced from their prototype work, will ensure the technology transfer and the technical follow up in the factory. ACCEL had to adapt two large fabrication halls to the needs of the magnet fabrication and the cold mass assembly. Procedures for a tight quality assurance and the logistics for the timely supply of components and a high production rate are being established in close collaboration by the three parties concerned. Ferracin, P Pagano, O Remondino, Vittorio Scandale, Walter Todesco, Ezio Tommasini, D IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018741 1727-1730 12 1 2002 2002 In superconducting accelerator magnets the coils are usually pre-stressed in order to avoid conductor movements induced by electro-magnetic forces. In this paper we use a finite element mechanical model of the main LHC dipole to evaluate the coil deformations determined by the pre-stress and their impact on magnetic field quality. The model explains the origin of the offsets between the nominal multipole values and those measured at room temperature in prototype and pre-series dipole magnets. We also present an experiment carried out to analyse the impact on field quality and coil stresses of coil azimuthal spacers (pole shims). A 1 m long dipole collared coil has been re-assembled several times with pole shims of different thickness and the field components have been measured each time. Experimental data are compared to numerical computations based on the mechanical model.One finds that variations of shim thickness induce not only a change of the azimuthal coil length, but also a different pattern in coil deformations. A good agreement is found between measurements and simulations. Derégel, J Devred, Arnaud Gourdin, C Hervieu, M Ogitsu, T Peyrot, M Rifflet, J M Schild, T Simon, F Tortschanoff, Theodor Tsuchiya, K IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018397 266-269 12 1 2002 2002 The construction of the third second-generation main quadrupole magnet prototype for LHC has been completed at CEA/Saclay in November 2000. The magnet was tested at 1.9 K. Similarly to the two first ones, this prototype has exceeded the operating current in one training step and exhibited excellent training memory after a thermal cycle. This paper describes the quench performance and quench start localization determined by means of voltage-taps and a quench antenna system developed in collaboration with KEK. As this magnet was equipped with capacitive gauges, the stresses during cool-down and powering have been recorded and are in agreement with FE computations. The newly designed quench heaters have improved efficiency and reproducibility compared to those of the first generation. Magnetic measurements have been performed at various stages. The cold measurements show minor differences with those at room temperature and are similar to those of the two first magnets of this design. These results prove that the magnets are mechanically stable and confirm the design retained for the series production of the 400 LHC main quadrupoles. Aznar, S Billan, J García-Pérez, J La China, M Ferracin, P Redaelli, S Scandale, Walter Todesco, Ezio IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018743 1736-1740 12 1 2002 2002 The LHC cryodipoles are composed of an evacuated cryostat and a cold mass, which is cooled by superfluid helium at 1.9 K. To obey constraints imposed by beam dynamics the particle beams must be centered within the mechanical axis of the dipole with a sub-millimeter accuracy. This requires in turn that the relative displacements between the cryostat and the cold mass must be monitored with accuracy at all times. Because of the extreme environmental conditions (the displacement must be measured in vacuum and between two points at a temperature difference of about 300 degrees), no adequate existing monitoring system was found for this application. We describe here a novel optical sensor developed for our scope and we present results of measurements made during the cold test of the dipoles. Belova, L M Genet, M Perinet-Marquet, J L Ivanov, P Urpin, C IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018642 1305-9 12 1 2002 2002 The main magnets of the LHC are series-connected electrically in different powering circuits by means of superconducting bus-bars, carrying a maximum current of 13 kA. These superconducting bus-bars consist of a superconducting cable thermally and electrically coupled to a copper profile all along the length. The function of the copper profile is essentially to provide an alternative path for the current in case the superconducting cable loses its superconducting state and returns to normal state because of a transient disturbance or of a normal zone propagation coming from the neighbouring magnets. When a superconducting bus-bar quenches to normal state its temperature must always stay below a safe values of about 100°C while the copper is conducting. When a resistive transition is detected, the protection systems triggers the ramping down of the current from 13000 A to 0. The ramp rate must not exceed a maximum value to avoid the transition of magnets series-connected in the circuit. This paper concerns the design and the manufacture of the high current superconducting bus-bars needed to interconnect the magnetic elements of the main dipoles, the main quadrupoles of the arcs and of the dispersion suppressors of the LHC. Bajko, M Chamizo, R Pardons, A IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018738 1713-1717 12 1 2002 2002 In order to predict the mechanical behavior of the LHC dipole cold mass in situations such as handling, transport and cool down, a number of important structural parameters are required. The dipole's flexural rigidity determines entirely the mechanical elastic behavior of the cold mass. Therefore, models of a bent cold mass were created to calculate its rigidity. This paper presents a simplified parametric finite element model, created to study the deflection of the cold mass in different situations and supporting conditions. The sensitivity of the models to the supporting conditions is computed. To provide the finite element and the analytical models with input, the deflection of the cold mass under discrete loads in normal condition and then 90-degrees rotated were measured with a laser tracker. By comparing models with measurements, the vertical and transversal rigidity of the cold mass assembly are determined. Additionally, the paper reports on the plastic behavior of the cold mass assembly in the range of the deformations that are needed to correct cold masses that result, after final welding of the outer skin, with unacceptable sagitta. Bajkó, M Pardons, A Savary, F IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018739 1718-1722 12 1 2002 2002 In order to provide the largest possible mechanical aperture for the LHC beam, the dipole cold masses have to match the circular trajectory of the particle beam. The requirements on the dipole cold mass geometry are dictated by the beam optics of the LHC machine and by the mechanical deformation limits of the interconnection zone. The geometry of the approximately 15 m long, 0.57 m diameter and 30 t weight dipole cold mass is verified by the measurement of the axes of the cold bore tubes. The tight tolerances imposed, necessitate the use of a high accuracy 3D measuring system based on optical methods. During the last 2 years, 6 prototypes and 4 pre-series magnets have been assembled at CERN. The summary of the results obtained on these cold masses is presented, as well as the evolution of the tooling and the measuring method. Lanza, C Perini, D IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018629 1252-1255 12 1 2002 2002 The LHC dipole structure is assembled using austenitic steel collars and austenitic steel end-laminations. The collars will be fine-blanked starting from 11'000 tonnes of steel; the end-laminations require 1'700 tonnes of steel. The procurement of the austenitic steels was divided in two phases: first we qualified different grades from different producers then we made the call for tender, adjudicated the contract and started the series production. The first part of this paper summarises the results of the first qualification phase when extensive checks and measurements were carried out on five different grades. The second part describes the approach used to control the series production and the results obtained. At the time of writing about 19% of the steel for collars and end-laminations has been manufactured and delivered. Aznar, S Billan, J Fischer, F Galbraith, Peter García-Pérez, J Goy, S Mermillod, N Peiro, G Patti, G Rathjen, C IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018742 1731-1735 12 1 2002 2002 In the context of the LHC superconducting magnet production, especially for dipoles and quadrupoles due to their complexity, it is foreseen to perform acceptance tests, at an early production stage, to detect possible significant deviations from the design values. The knowledge of the magnetic field geometry is very important, especially for the main magnets. In order to get this information a new device has been conceived that measures the magnets at room temperature during different stages of construction. This device incorporates a sensitive measuring probe and an efficient data acquisition system because the coils are only powered at about 10-5 of the nominal D.C. current. It is dedicated to Quadrupole and Dipole (by using Quadrupole-Configured Dipole (QCD) transformation) magnets, but is also easily adaptable to higher order magnets (n = 3, 4 and 5) by specific orientation of the search coils. It is equipped with magnetic sensors (4 fixed tangential coils and AC excitation current for the magnet) and position sensors (3D-laser tracker and light reflector) that allow the simultaneous detection of the magnetic field axis and the cold bore axis. It is equipped as well with a set of 4 LEDs and associated with a CCD camera that allows both the measurement of the cold bore diameter and its position with respect to the mole. This paper describes the system and reports the first results measured on the pre-series magnets recently assembled. Farina, E Fessia, P Perini, D Schiappapietra, A Seneé, L IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018686 1496-1500 12 1 2002 2002 The coil end spacers play an important role in the performance of superconducting coils, as their shape and location determine the mechanical stability of the conductors in the coil ends (and hence the overall coil training performance) and the local field quality. The dipole end spacers are often of a size and a geometry difficult to be industrially series manufactured and measured. Efficiency of the production and related costs are a key issue to achieve the required production rate of the LHC main dipoles at an affordable price. For the latter reasons, a design approach integrating state-of-the-art CAD/CAM optimization techniques allowing to considerably decrease design and machining time was implemented. This paper gives examples and describes the design criteria, the computation methods, the machining and measuring procedures adopted to carry out the pre-series production. Ferracin, P Scandale, Walter Todesco, Ezio Tommasini, D IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018736 1705-1708 12 1 2002 2002 We describe a finite element mechanical model of the main LHC dipole, based on the geometry and on the properties of its components; coil characteristics are derived from measurements on stacks of conductors. We show how to define equivalent properties of cable blocks that take into account the collaring procedure when it is not explicitly modelled. Numerical results are then compared to experimental measurements of loads and deformations in dipole prototypes. At cryogenic temperature, equivalent properties are used to implement in the model a pressure- dependent thermal contraction factor observed in stack measurements. This allows to forecast the large pre-stress loss during the cool-down observed in the LHC dipole prototypes. Fessia, P Perini, D IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018383 202-206 12 1 2002 2002 The dipoles for several different machines (LHC, SSC, HERA) were designed using non-magnetic metallic collars to contain the superconducting coils. The coils are of two types, main and floating. This paper describes a structure with combined steel and plastic collars. Since the floating collars do not give an important contribution to the global rigidity of the dipole we propose to suppress them. The plastic collars are just fillers to limit the helium contained in the cold mass. Some data about thermoplastic materials to be possibly used for the collars are given and some estimations of mass and cost of this configuration are made. Finally the results of the tests of a 1-m-long twin aperture dipole with mixed steel-plastic collars are shortly described. The replacement of expensive alloys by high performance plastic in non-structural components can be a cost-effective solution in view of future projects where superconducting magnets are involved and contained costs are a key issue. Ostojic, R IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018382 196-201 12 1 2002 2002 The Large Hadron Collider comprises eight insertions, four of which are dedicated to the LHC experiments while the others are used for the major collider systems. The various functions of the insertions are fulfilled by a variety of magnet systems, most of them based on the technology of NbTi superconductors cooled by superfluid helium at 1.9 K. A number of stand-alone magnets in the matching sections are operated at 4.5 K, while in the high radiation areas specialised resistive magnets are used. In this paper, we review the concepts underlying the design of the LHC insertions, and report on the design, procurement and testing of the various specialised magnet systems. Allitt, M Arshad, S A Hobl, A Ijspeert, Albert Karppinen, M Krischel, D Mazet, J Salminen, J Schillo, M Senis, R Walckiers, L IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018346 35-8 12 1 2002 2002 The main quadrupoles of the Large Hadron Collider (LHC) are connected in families of focusing and defocusing magnets. In order to make tuning corrections in the machine a number of quadrupole corrector magnets (designated MQT) are necessary. These 56 mm diameter aperture magnets have to be compact, with a maximum length of 395 mm and a coil radial thickness of 5 to 7.5 mm, while generating a minimum field gradient of 110 T/m. Two design options have been explored, both using the "counter-winding" system developed at CERN for the fabrication of low cost corrector coils. The first design, with the poles composed of two double-pancake coils, each counter-wound using a single wire, superposed to create 4-layer coils, was developed and built by ACCEL Instruments GmbH. A second design where single coils were counter-wound using a 3-wire ribbon to obtain 6-layer coils was developed at CERN. This paper describes the two designs and reports on the performance of the prototypes during testing. Völlinger, Christine Aleksa, Martin Russenschuck, Stephan IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018685 1492-1495 12 1 2002 2002 Magnetization effects in the coils of superconducting accelerator magnet deteriorate the field quality at injection field level. The CERN field computation program ROXIE has recently been extended to calculate the persistent current using a semi-analytical hysteresis model for hard superconductors. The model is combined with the coupling method of finite- and boundary-elements for the calculation of the non-linear iron yoke.Thi numerical method avoids the meshing of air domains and of the superconducting coil. Disjoint ferromagnetic iron domains can be meshed independently. This allows the easy modeling of very thin layers of arbitrary shape. In this paper, the reduction of persistent current induced field errors by mean of a ferromagnetic sheet in the aperture, a ferromagnetic (coil protection) shield and thin shim inside the superconducting cable are discussed. Karppinen, M Pérez, J C Senis, R IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018361 102-106 12 1 2002 2002 The eight Inner Triplets of the LHC will each house a combined corrector magnet assembly, MQSXA, which comprises a skew quadrupole (MQSX) in line with nested skew octupole (MCOSX), octupole (MCOX), and skew sextupole (MCSSX) windings. These superconducting single-aperture magnet assemblies have a bore of 70 mm diameter, and the complete MQSXA assemblies are 530 mm long, have an outer diameter of 180 mm and an approximate mass of 90 kg. In the Inner Triplets the MQSXA assemblies are flanged to the end plate of the high gradient quadrupoles (MQX). This paper presents the main design features of the MQSXA and the experience gained with the prototype of the nested part of this magnet assembly, which has been built at CERN. The results of the training tests at 4.3 K and 1.9 K together with the cold magnetic measurements are given. Allitt, M Hilaire, A Ijspeert, Albert Karppinen, M Mazet, J Pérez, J Salminen, J Karmarkar, M Puntambekar, A IEEE Trans. Appl. Supercond. 90-93 12 1 2002 2002 The Large Hadron Collider (LHC) needs more than 6000 superconducting corrector magnets. These must be sufficiently powerful, have enough margin, be compact and of low cost. The development of the 11 types of magnets was spread over several years and included the magnetic and mechanical design as well as prototype building and testing. It gradually led to the systematic application of a number of interesting construction principles that allow to realize the above mentioned goals. The paper describes the techniques developed and presently used in practically all the LHC corrector magnets ranging from dipoles to dodecapoles. Hilaire, A Ijspeert, Albert Pérez, J C IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018699 1553-6 12 1 2002 2002 In the LHC, the superconducting corrector magnets will be powered in series of up to 154 magnets. For protection in case of a quench, each magnet has been equipped with a parallel resistor as a bypass for the current. To validate and optimize the parallel resistor value, a test arrangement has been set up which allows quenching a single magnet as if it were connected in a large series of magnets. This simulation is obtained by maintaining the current for a certain time interval after the quench occurred. Calculations have shown that, depending on the magnet type, a current duration (after quench) of 0.2 s to 1 s simulates correctly the effect of the series of magnets. The paper gives calculation results comparing the real situation with the simulated one and reports on the test set-up that will be used to optimize the parallel resistors. Ballarino, A IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018635 1275-1280 12 1 2002 2002 The LHC current lead project is now entering into the stage of procurement of the components for integration into the machine. About 3300 current leads with ratings ranging from 60 A to 13000 A will be required for powering the numerous electrical circuits. The main design choices have been taken on the basis of the outcome of an intensive R&D program covering the characterization of suitable High Temperature Superconducting (HTS) materials for current leads, the validation of lead design options and the measurement of the thermo-electrical performance of prototypes tested under various operating conditions. Helium gas cooled leads integrating HTS material at the colder end will be used for high current leads (currents ³  600 A), while the corrector dipole magnets (60 A - 120 A) will be powered via specifically designed conduction-cooled resistive leads. An outline of the retained designs will be presented, together with required schedule for lead manufacture. Delruelle, N Dudarev, A Haug, F Mayri, C Orlic, J P Passardi, Giorgio Pirotte, O ten Kate, H H J IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018649 1336-1338 12 1 2002 2002 The superconducting magnet system of the ATLAS detector will consist of a central solenoid, two end-cap toroids and the barrel toroid made of eight coils (BT) symmetrically placed around the central axis of the detector. All these magnets will be individually tested in an experimental area prior to their final installation in the underground cavern of the LHC collider. A dedicated cryogenic test facility has been designed and built for this purpose. It mainly consists of a 1'200 W at 4.5 K refrigerator, a 10 kW liquid nitrogen pre-cooling unit, a cryostat housing liquid helium centrifugal pumps, a distribution valve box and transfer lines. Prior to the start of the series tests of the BT magnets, two model coils are used at this facility. The first one, the so-called B00 of comparatively small size, contains the three different types of superconductors used for the ATLAS magnets which are wound on a cylindrical mandrel. The second magnet, the B0, is a reduced model of basically identical design concept as the final BT magnets. Full commissioning of all sub-systems including cryogenics, electrical powering, magnet protection and control is done ahead of the arrival of the BT series magnets. This cryogenic test facility reproduces the final thermo-hydraulic conditions in the cooling circuits of the magnets in order to validate the design concept. Bottura, L Bruzzone, P L Marinucci, C IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018692 1524-1527 12 1 2002 2002 We present here the results of the analysis of the stability experiment SeCRETS, performed on two Nb$_{3}$Sn cable-in-conduit conductors with the same amount of total copper stabilizer, but different degree of segregation. The model used for the analysis, including superconducting strands, conductor jacket and helium, is solved with the code GandalfTM. We obtain a qualitative agreement of simulation results and experimental values. The simulation results confirm that in the operation regime explored in the experiment the segregated copper is not effective for stability. The details of the current sharing and the approximation taken for the transient heat transfer are shown to be critical for the interpretation. Bottura, L Bruzzone, P L Marinucci, C IEEE Trans. Appl. Supercond. 10.1109/TASC.2002.1018693 1528-1532 12 1 2002 2002 The CONDOPT (CONDuctor OPTimization) experiment has been recently completed in SULTAN. The current sharing behaviour of Nb$_{3}$Sn samples was assessed as a function of the number of cyclic loads experienced during current sweeps in a 10 T background field. We present here results of a computer analysis performed with the code THEATM (for consistent Thermal, Hydraulic and Electric Analysis) in support of the interpretation of the experimental results. We focus in particular on the critical current and current sharing temperature runs, providing details on the features and effects of current distribution among cable sub-stages.