G. Volpini

The EuCARD-2 Future Magnets European Collaboration for Accelerator-Quality HTS Magnets

EuCARD-2 is a project supported by FP7-European Commission that includes, inter alia, a work-package (WP10) called “Future Magnets.” This project is part of the long term development that CERN is launching to explore magnet technology at 16 T to 20 T dipole operating field, within the scope of a study on Future Circular Colliders. The EuCARD2 collaboration is closely liaising with similar programs for high field accelerator magnets in the USA and Japan. The main focus of EuCARD2 WP10 is the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, The cable will be used to wind a stand-alone magnet 500 mm long and with an aperture of 40 mm. This magnet should yield 5 T, when stand-alone, and will enable to reach a 15 to 18 T dipole field by placing it in a large bore background dipole of 12-15 T. REBCO based Roebel cables is the baseline. Various magnet configurations with HTS tapes are under investigation and also use of Bi-2212 round wire based cables is considered. The paper presents the structure of the collaboration and describes the main choices made in the first year of the program, which has a breadth of five to six years of which four are covered by the FP7 frame.

Development of a Curved Fast Ramped Dipole for FAIR SIS300

At present, one of the main options for beam bending dipoles of the SIS 300 synchrotron, under design for the FAIR facility at GSI, is a single layer magnet 7.8 m long, 100 mm in bore diameter, generating 4.5 T. This coil has two main features: it is curved, with a curvature radius of 66.67 m (the corresponding sagitta is 114 mm), and shall be ramped at 1 T/s. Both these characteristics demand challenging R&D, aimed at the development of the required conductor and winding technology. The paper discusses both these aspects, in the frame of a general ongoing R&D program at INFN, under the name DISCORAP. Its goal is the construction of a short prototype (3.8 m) dipole, fully integrated into its horizontal cryostat, within three years. The R&D program includes: 1) the activities required to develop low loss superconducting wires and cable; 2) the technological developments (at the industrial level) for defining and optimizing the dipole constructing methods; 3) the construction of curved dipole coil winding models; 4) the construction of the complete curved dipole; 5) the test of the curved dipole in a vertical cryostat; 6) the integration of the curved dipole into a horizontal cryostat, for the final test at GSI.

Field Quality and Losses for the 4.5 T Superconducting Pulsed Dipole of SIS300

This paper presents the 2D design of the SIS300 synchrotron dipole of the FAIR facility at GSI. The dipole has a length of 7.8 m, a field of 4.5 T, in a 100 mm bore, and is ramped at 1 T/s. The studies are performed by INFN (Frascati, Genova and Milano-LASA) in a R&D collaboration with GSI. The program started in 2006 (DISCORAP) and has as a final goal the construction and test of a prototype. Particular emphasis is given to the study of the field quality and of the losses during the ramping of the magnet. Some calculation methods and different codes for magnet design are evaluated and compared.

Low-Loss NbTi Rutherford Cable for Application to the SIS-300 Dipole Magnet Prototype

INFN (Istituto Nazionale di Fisica Nucleare, Italy) has started in 2006 the DISCORAP project, which foresees the design, manufacture and test of a dipole prototype for the SIS-300 synchrotron of the FAIR facility at GSI. In order to minimize the losses produced by the fast ramp rate (1 T/s) at which the magnet is operated, we are developing with European industries, a Rutherford cable which incorporates several technologies to reduce the losses, and namely a NbTi filament diameter on the order of 2.5-3.5 mum, Cu 0.5 wt%Mn interfilamentary matrix and stainless steel core. In this paper we present the design principles and the first experimental results; we also analyze the impact of the CuMn paramagnetism on the field distortion at the different operating magnetic fields.

The 16 T Dipole Development Program for FCC

A key challenge for a future circular collider (FCC) with centre-of-mass energy of 100 TeV and a circumference in the range of 100 km is the development of high-field superconducting accelerator magnets, capable of providing a 16 T dipolar field of accelerator quality in a 50 mm aperture. This paper summarizes the strategy and actions being undertaken in the framework of the FCC 16 T Magnet Technology Program and the Work Package 5 of the EuroCirCol.

HTS Insert Magnet Design Study

Future accelerator magnets will need to reach higher field in the range of 20 T. This field level is very difficult to reach using only Low Temperature Superconductor materials whereas High Temperature Superconductors (HTS) provide interesting opportunities. High current densities and stress levels are needed to design such magnets. YBCO superconductor indeed carries large current densities under high magnetic field and provides good mechanical properties especially when produced using the IBAD approach. The HFM EUCARD program studies the design and the realization of an HTS insert of 6 T inside a dipole of 13 T at 4.2 K. In the HTS insert, engineering current densities higher than 250 under 19 T are required to fulfill the specifications. The stress level is also very severe. YBCO IBAD tapes theoretically meet these challenges from presented measurements. The insert protection is also a critical because HTS materials show low quench propagation velocities and the coupling with the magnet makes the problem even more challenging. The magnetic and mechanical designs of the HTS insert as well as some protection investigation ways will be presented.

Synthesis of technological developments for the B0 model coil and the ATLAS Barrel Toroid Coils

The Barrel Toroid Magnet is part of the Magnet System of the ATLAS Detector for the LHC. It provides the magnetic field required by the muon spectrometer. It consists of eight flat superconducting coils and will extend over a length of 26 meters with an inner bore of 9 meters and an outer diameter of 20 meters. The general design (pancakes, coil casing, tie rods, circular cryostats and warm voussoirs) has been presented in MT15. The present paper concentrates on the technological developments for the B0 model coil and for the BT coils: industrial production of conductor, welding technique for the coil casing, prestress of the coil with bladders, cold to warm supports, construction and assembly of the cryostat.

HTS Dipole Insert Developments

Future accelerator magnets will need to reach a magnetic field in the 20 T range. Reaching such a magnetic field is a challenge only reachable using high temperature superconductor (HTS) material. The high current densities and stress levels needed to satisfy the design criterion of such magnets make YBaCuO superconductor the most appropriate candidate especially when produced using the IBAD route. The HFM EUCARD program is aimed at designing and manufacturing a dipole insert made of HTS material generating 6 T inside a Nb3Sn dipole of 13 T at 4.2 K. In the HTS insert, engineering current densities higher than 250 MA/m2 under 19 T are required to reach the performances. The stress level is consequently very high. The insert protection is also a critical issue as HTS shows low quench propagation velocity. The coupling with the Nb3Sn dipole makes the problem even more difficult. The magnetic and mechanical designs of the HTS insert will be presented as well as the technological developments underway to realize this compact dipole insert.

On-Surface Test of the ATLAS Barrel Toroid Coils: Overview

The Barrel Toroid (BT) provides the magnetic field for the muon detectors in the ATLAS experiment at CERN. The Toroid is built up from eight superconducting coils. Each coil consists of two 25 m times 5 m racetrack shape double pancakes impregnated and pre-stressed inside an aluminum coil casing. The 42-tons cold mass is cooled by forced-flow liquid helium circulating in aluminum pipes glued to its surface. The coils are tested on surface prior to their underground installation. The test program has started in September 2004 and finished in June 2005. This paper describes the test set up and various commissioning tests performed at the ATLAS Magnet Test Facility. It includes the aspects of test preparation, vacuum pumping, leak testing, cooling down, powering and warming up. The 8 coils have passed the tests successfully and have been assembled into the Toroid in the ATLAS cavern. The testing completes the production of the so far largest racetrack coils in the world

Manufacturing and integration progress of the ATLAS barrel toroid magnet at CERN

ATLAS is one of the two experiments dedicated the search of the Higgs boson, which will be installed on the LHC ring at CERN in 2006. The ATLAS barrel toroid air-core magnet (BT) is 20 m in diameter and consists of 8 superconducting coils, each one 25 m long and 5 m wide. After several years of technological development, the major concepts have been proved in 1999/2000 during the construction of the B0 prototype; a technological model for BT. The delivery by several European industrial companies of all the major components for BT is nearly finished. The eight BT coils are now being integrated at CERN. The paper presents a general overview of the component manufacturing and integration progress. A special emphasis is put on the major component delivery (conductor, double pancake windings, aluminum coil casing and cryostat) together with a description of the two phases of the integration process: integration of the windings into their coil casings and integration of the cold mass into the vacuum vessel. The integration of the windings in their coil casings will be completed in October 2003. The closure of the first cryostat is planned for the end of the year. The start of the first cold test and the assembly in the cavern is foreseen for the beginning of 2004.