The superconducting magnet system for the ATLAS Detector for the Large Hadron Collider at CERN is under construction since 1997. The magnet system is a hybrid of 4 superconducting magnets, a 2.5 m bore, 5.3 m long 2 T central solenoid servicing the inner detector and three 4 T toroids with global dimensions of 20 m diameter, 25 m long providing the magnetic field of about 1 T for the muon detectors. The operating currents of the solenoid and toroids are 8 and 20 kA respectively with a total stored energy of 1.6 GJ. The realization of the system is challenging due to its unusual size and complexity. Last year the construction of the coils and cryostats commenced in industry. The manufacture of the solenoid cold mass is already finished and the delivery of the individual toroid coils will commence in 2001. An on-surface test of all magnets will occur. After installation in a new cavern 100 m underground this will start in 2003 leading to commissioning of the entire magnet system in early 2005. In the paper various magnets are introduced as well as the common infrastructure and services required. The status of the project is reviewed.

The superconducting magnet system for the ATLAS Detector at CERN

The ATLAS magnet system consists of a barrel toroid (BT), two end-cap toroids (ECT) and a central solenoid (CS). The BT with overall dimensions of 20 m diameter by 26 m length is made of 8 coils placed in their individual cryostats and symmetrically assembled around the central axis. The ATLAS magnet test facility is being completed at CERN and will host in the next years to come pairs of BT coils at the same time as well as the ECT and the CS systems already fully assembled. Two model coils will be tested in the years 2000-2001, the B00 model coil and the B0 model coil, a 9 m short version of the BT coil built to verify the functionality and the construction concepts of the BT.

The ATLAS magnets test facility at CERN

Evaluation of superfluid helium cooling schemes and application for HL-LHC recombination dipole D2

The ATLAS superconducting magnet system consists of a Barrel Toroid, two End-Cap Toroids and a Central Solenoid. The Barrel Toroid, with overall dimensions of 20-m diameter by 26-m length, is made of eight individual coils symmetrically assembled around the central axis with a warm structure. The system is presently under construction in industry. In order to verify the construction concepts a model coil B0, a 9-m short version of a single Barrel Toroid coil, was built. Since April 2001, an extensive test program is underway at CERN to characterize the mechanical, thermal, electrical and magnetic properties of the coil. The magnet successfully achieved the 20-kA nominal operating current in July 2001. The test program and the main results are reported.

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ATLAS B0 toroid model coil test at CERN

Liquid helium centrifugal pump characteristics from 80 g/s to 1200 g/s

The superconducting magnet system of the ATLAS detector will consist of a central solenoid, two end-cap toroidal magnets (ECT) and the barrel toroid magnet (BT) made of eight coils symmetrically placed around the central axis of the detector. The magnets will be tested individually in a 5000 m/sup 2/ experimental area prior to their final installation at an underground cavern of the LHC Collider. For the BT magnets, a dedicated cryogenic test facility has been designed which is currently under the construction and commissioning phase. A liquid nitrogen pre-cooling unit and a 1200 W@4.5K refrigerator will allow flexible operating conditions via a rather complex distribution and transfer line system. Flow of two-phase helium for cooling the coils is provided by centrifugal pumps immersed in a saturated liquid helium bath. The integration of the pumps in an existing cryostat required the adoption of novel mechanical solutions. Tests conducted permitted the validation of the technical design of the cryostat and its instrumentation. The characteristics of one pump were measured and pressure rise of 300 mbar at nominal flow of 80 g/s confirmed the specifications.

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The CERN cryogenic test facility for the ATLAS barrel toroid magnets

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 1200 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.

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J.-P. Orlic

Papers

The CERN cryogenic test facility for the ATLAS barrel toroid magnets

First cryogenic testing of the ATLAS superconducting prototype magnets