Superconducting magnet system for the ATLAS detector at CERN

The ATLAS Collaboration has started the construction of the superconducting magnet system of the ATLAS Experiment which will be installed in the ring of the new Large Hadron Collider at CERN, operational in year 2005. The ATLAS detectors require, for the particle separation, a specific distribution of magnetic field that will be generated by a system of superconducting coils. The system with overall dimensions of 20 meter diameter and 26 meter length consists of three toroidal magnets and a 2.5 m diameter central solenoid. The system is unique in size and complexity. In this paper, the various magnets are introduced as well as the common infrastructure and services required. The status of the project is also reviewed. (7 refs)

Conceptual Design of a New Large Superconducting Toroid for IAXO, the New International AXion Observatory

The International AXion Observatory (IAXO) will incorporate a new generation detector for axions, a hypothetical particle, which was postulated to solve one of the puzzles arising in the standard model of particle physics, namely the strong CP problem. The new IAXO experiment is aiming at achieving a sensitivity to the coupling between axions and photons of one order of magnitude beyond the limits of the current state-of-the-art detector, represented by the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field distributed over a very large volume to convert solar axions into x-ray photons. Utilizing the designs of the ATLAS barrel and end-cap toroids, a large superconducting toroidal magnet is currently being designed at CERN to provide the required magnetic field. The new toroid will be built up from eight, one meter wide and 20 m long, racetrack coils. The toroid is sized about 4 m in diameter and 22 m in length. It is designed to realize a peak magnetic field of 5.4 T with a stored energy of 500 MJ. The magnetic field optimization process to arrive at maximum detector yield is described. In addition, force and stress calculations are performed to select materials and determine their structure and sizing. Conductor dimensionality, quench protection and the cryogenic design are dealt with as well.Comment: 5 pages, 5 figures. To be published in IEEE Trans. Appl. Supercond. 23 (ASC 2012 conference special issue

New Superconducting Toroidal Magnet System for IAXO, the International AXion Observatory

Axions are hypothetical particles that were postulated to solve one of the puzzles arising in the standard model of particle physics, namely the strong CP (Charge conjugation and Parity) problem. The new International AXion Observatory (IAXO) will incorporate the most promising solar axions detector to date, which is designed to enhance the sensitivity to the axion-photon coupling by one order of magnitude beyond the limits of the current state-of-the-art detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field distributed over a very large volume to convert solar axions into X-ray photons. Inspired by the successful realization of the ATLAS barrel and end-cap toroids, a very large superconducting toroid is currently designed at CERN to provide the required magnetic field. This toroid will comprise eight, one meter wide and twenty one meter long, racetrack coils. The system is sized 5.2 m in diameter and 25 m in length. Its peak magnetic field is 5.4 T with a stored energy of 500 MJ. The magnetic field optimization process to arrive at maximum detector yield is described. In addition, materials selection and their structure and sizing has been determined by force and stress calculations. Thermal loads are estimated to size the necessary cryogenic power and the concept of a forced flow supercritical helium based cryogenic system is given. A quench simulation confirmed the quench protection scheme.Comment: Accepted for publication in Adv. Cryo. Eng. (CEC/ICMC 2013 special issue

The Superconducting Toroid for the New International AXion Observatory (IAXO)

IAXO, the new International AXion Observatory, will feature the most ambitious detector for solar axions to date. Axions are hypothetical particles which were postulated to solve one of the puzzles arising in the standard model of particle physics, namely the strong CP (Charge conjugation and Parity) problem. This detector aims at achieving a sensitivity to the coupling between axions and photons of one order of magnitude beyond the limits of the current detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field distributed over a very large volume to convert solar axions to detectable X-ray photons. Inspired by the ATLAS barrel and end-cap toroids, a large superconducting toroid is being designed. The toroid comprises eight, one meter wide and twenty one meters long racetrack coils. The assembled toroid is sized 5.2 m in diameter and 25 m in length and its mass is about 250 tons. The useful field in the bores is 2.5 T while the peak magnetic field in the windings is 5.4 T. At the operational current of 12 kA the stored energy is 500 MJ. The racetrack type of coils are wound with a reinforced Aluminum stabilized NbTi/Cu cable and are conduction cooled. The coils optimization is shortly described as well as new concepts for cryostat, cold mass, supporting structure and the sun tracking system. Materials selection and sizing, conductor, thermal loads, the cryogenics system and the electrical system are described. Lastly, quench simulations are reported to demonstrate the system's safe quench protection scheme.Comment: To appear in IEEE Trans. Appl. Supercond. MT 23 issue. arXiv admin note: substantial text overlap with arXiv:1308.2526, arXiv:1212.463

The Superconducting Magnet System for the ATLAS Detector at CERN

The ATLAS superconducting magnet system for the ATLAS detector in the LHC at CERN comprises a Barrel Toroid, two End Cap Toroids and a Central Solenoid, with overall dimensions of 20 m diameter by 26 m length. Though this magnet system is used for a particle detector, its size, geometrical arrangement and coil technology is comparable to what is usual for fusion machines. The manufacturing has started in the industry and integration of the magnets will start in the year 2001. Assembly in the cavern is planned in the year 2003, starting with BT installation. In this paper the Magnet System is presented as well as the common infrastructure and services

Modeling heat transfer from quench protection heaters to superconducting cables in Nb3Sn magnets

We use a recently developed quench protection heater modeling tool for an analysis of heater delays in superconducting high-field Nb3Sn accelerator magnets. The results suggest that the calculated delays are consistent with experimental data, and show how the heater delay depends on the main heater design parameters.Comment: 8 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet, Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva, Switzerlan

Current Redistribution around the Superconducting-to-normal Transition in Superconducting Nb-Ti Rutherford Cables

Sufficient thermal-electromagnetic stability against external heat sources is an essential design criterion for superconducting Rutherford cables, especially if operated close to the critical current. Due to the complex phenomena contributing to stability such as helium cooling, inter-strand current and heat transfer, its level is difficult to quantify. In order to improve our understanding, many stability tests were performed on different cable samples, each incorporating several point-like heaters. The current redistribution around the heat front is measured after inducing a local normal zone in one strand of the cable. By using voltage taps, expansion of the normal zone is monitored in the initially quenched strand as well as in adjacent strands. An array of Hall probes positioned at the cable edge is used to scan the selffield generated by the cable by which it becomes possible to estimate the inter-strand current transfer. In this paper it is demonstrated that two different stability regimes can be distinguished depending on the local conditions for local normal zone recovery through heat and current transfer to adjacent strands. It is shown that in the first regime every normal zone will lead to a quench, while in the second regime a normal zone in one strand can recover. Combining the predictions developed using a novel version of the numerical network model CUDI and new measurement results, it is possible to derive char acteristic quench decision times as well to calculate and predict the influence of a change in cable parameters