The key objective of the High Field Magnet work package of the European Project EuCARD is to design and fabricate the Nb3Sn dipole magnet FRESCA2. It has an aperture of 100 mm and a target bore field of 13 T. The design features four 1.5 m long double-layer coils wound with a 21 mm wide cable. The project has now entered its experimental phase in view of the magnet fabrication. We present the experimental test campaign conducted on cable samples in order to understand and to control better the cable behavior and geometry. One full scale double-layer coil using copper cable with the final dimensions and insulation scheme has been wound and heat treated in order to check the fabrication process. This has given useful feedback on the fabrication procedure and on the expected magnet dimensions, as well as on the tooling itself.

This paper reports on the assembly process and cool-down to cryogenic temperature of the support structure of FRESCA2, which is a dipole magnet for upgrading the actual CERN cable test facility FRESCA. The structure of the FRESCA2 magnet is designed to provide the adequate pre-stress, through the use of keys, bladders, and an Al alloy shrinking cylinder. To qualify the assembly and loading procedures, the structure was assembled with Al blocks (dummy coils) that replaced the brittle Nb3Sn coils, and then cooled-down to 77 K with liquid nitrogen. The evolution of the mechanical behavior was monitored via strain gauges located on different components of the structure (shell, rods, yokes and dummy coils). We focus on the expected stresses within the structure after assembly, loading and cool-down. The expected stresses were determined from the 3-D finite element model of the structure. A comparison of the 3-D model stress predictions with the strain gauge data measurements is made. The coherence between the predicted stresses with the experimental gauge measurements will validate the FEM model of the structure.

— Longitudinal and transverse quench propagation tests were performed at LNCMI high field test facility on instrumented double pancake coils fabricated by CEA-Saclay using co-wound HTS tapes. Energy deposited on an embedded heater initiated a quench and its subsequent propagations. Following the resulting thermo-mechanical analysis, a conductor design with stacked HTS tapes co-wound with stabilizers was conceived. A 10-turn demonstrator racetrack coil has been fabricated from the stacked HTS conductor with an aim to investigate the operation margin of an HTS coil in a background magnetic field misaligned from the coil axis as expected for the operating condition of an accelerator magnet insert. A test set up with a high current capacity up to 3 kA and angular variability that utilizes a room temperature ø 376 mm bore 10 T resistive magnet at LNCMI in Grenoble has been built. The performances and operation margin of the racetrack coil were investigated. 

Longitudinal and transverse quench propagation tests were performed at the Laboratoire National des Champs Magnetiques Intenses (LNCMI) high-field test facility on instrumented double pancake coils fabricated by CEA-Saclay using co-wound high-temperature superconductor (HTS) tapes. Energy deposited on an embedded heater initiated a quench and its subsequent propagations. Following the resulting thermomechanical analysis, a conductor design with stacked HTS tapes co-wound with stabilizers was conceived. A ten-turn demonstrator racetrack coil has been fabricated from the stacked HTS conductor with an aim to investigate the operation margin of an HTS coil in a background magnetic field misaligned from the coil axis as expected for the operating condition of an accelerator magnet insert. A test setup with a high current capacity up to 3 kA and angular variability that utilizes a room-temperature 376-mm-bore 10-T resistive magnet at LNCMI in Grenoble has been built. The performances and operation margin of the racetrack coil were investigated.

The large scale particle accelerators of the future in the 20 T regime are enabled by high temperature superconducting magnets. The dipole magnets needed in new high-field accelerators can be constructed with an YBCO insert and a Nb 3 Sn outsert. Such a configuration makes the quench analysis and magnet protection challenging because the quench behavior in both of these coils is different and there is very strong inductive coupling between the coils. The Nb 3 Sn coil is characterized by high energy and current and relatively fast quench propagation velocity. However, quench propagates slowly in YBCO coils because of typically wide spread large temperature margin. Currently, in the EuCARD project, a European collaboration is targeting to construct a small-scale high field YBCO-Nb 3 Sn hybrid magnet. In this paper, we scrutinize quench in the YBCO insert. We utilized an approach based on a solution of the heat diffusion equation with the finite element method. Additionally, we present a protection scheme for the coil.

In the EuCARD project, we aim to construct a dipole magnet in YBCO producing 6 T in the background field of a 13 T Nb3Sn dipole FRESCA II. This paper reviews the quench analysis and protection of the YBCO coil. In addition, a recommendation for the protection system of the YBCO coil is presented.

The EuCARD project aims on construction of a 19 T hybrid dipole; it will be made of a 6 T HTS dipole associated to a 13 T outsert Nb3Sn dipole [1]. This paper reviews the quench analysis and protection of the 13 T Nb3Sn dipole.

The key objective of the superconducting high field magnet work package of the European Project EuCARD, and specifically of the high field model task, is to design and fabricate the Nb3Sn dipole magnet FRESCA2. With an aperture of 100 mm and a target bore field of 13 T, the magnet is aimed at upgrading the FRESCA cable test facility at CERN. The design features four 1.5-m-long double-layer coils wound with a 21-mm-wide cable. The windings are contained in a support structure based on a 65-mm-thick aluminum shell pretensioned with bladders. In order to qualify the assembly and loading procedure and to validate the finite element stress computations, the structure will be assembled around aluminum blocks, which replace the superconducting coils, and instrumented with strain gauges. In this paper, we report on the status of the assembly and we update on the progress on design and fabrication of tooling and coils.

Future accelerator magnets will need to reach field in the 20-T range. Reaching such a magnetic field is a challenge only attainable 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. The HFM EUCARD program is aimed to design and manufacture 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 A/mm2 under 19 T are required to reach the performances. This paper summarizes the results of magnetic and mechanical finite element analysis of the HTS dipole insert magnet. The nonlinearity of the ferromagnetic material is also taken into account. The mechanical analysis of the magnet is carried out under Lorentz forces.

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.

High-temperature superconductors are promising materials for future applications such as high field magnets thanks to their ability to carry high current densities. Nevertheless, their protection still remains a key issue mainly due to the slow velocity of quench propagation. To understand the quench behavior of a YBCO coil, a simulation code has been developed using the CASTEM-CEA finite element software. Simulations can be performed considering constant current and magnetic field. Results of those simulations will be displayed and a way for improving the protection by adding a stabilizer will be discussed. Two well instrumented YBCO coils were fabricated in order to obtain experimental data on quench propagation in pancake configuration. Their design and some measurements are reported in this paper along with another experiment on a double pancake made by and tested at CNRS Grenoble. Finally, we compare the numerical and experimental results and discuss the accuracy of our simulations.

This paper reports on the design of FRESCA2, a dipole magnet model wound with Nb3Sn Rutherford cable. This magnet is one of the deliverables of the High Field Magnets work package of the European FP7-EuCARD project. The nominal magnetic flux density of 13 Tesla in a 100 mm bore will make it suitable for upgrading the FRESCA cable test facility at CERN. The magnetic layout is based on a block coil, with four layers per pole. The mechanical structure is designed to provide adequate pre-stress, through the use of bladders, keys and an aluminum alloy shrinking cylinder.

The key objective of the Superconducting High Field Magnet work package of the European Project EuCARD, and specifically of the High Field Model task, is to design and fabricate the Nb3Sn dipole magnet FRESCA2. With an aperture of 100 mm and a target bore field of 13 T, the magnet is aimed at upgrading the FRESCA cable test facility at CERN. The design features four 1.5 m long double-layer coils wound with a 21 mm wide cable. The windings are contained in a support structure based on a 65 mm thick aluminum shell pre-tensioned with bladders. In order to qualify the assembly and loading procedure and to validate the finite element stress computations, the structure will be assembled around aluminum blocks, which replace the superconducting coils, and instrumented with strain gauges. In this paper, we report on the status of the assembly and we update on the progress on design and fabrication of tooling and coils.

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.

High critical temperature superconductors (HTS) bring a lot of opportunities for SMES (Superconducting Magnetic Energy Storage). The large current densities under very high fields and the mechanical strength of IBAD route ReBaCuO coated conductors are very favorable characteristics. Electricity storage still is an issue in general and SMES bring a very interesting solution for pulse current supplies especially if its energy density increases. The record for SC magnet is 13.4 kJ/kg today. We study how to enhance this value. One of the main limitations for the SMES energy density is the mechanical stress as shown i.a. by the viriel theorem, which links simply stress and energy. The current density is another limitation not only the critical characteristic. Indeed protection also plays an important part and often is the real limitation for LTS magnets. We optimized solenoids with mechanical stress and current density constraints. 20 kJ/kg requires current densities of the order of 400 and stresses of about 400 MPa. These values are compatible with YBCO data but pose protection difficulties, which should be perhaps rethought. The design and these protection issues are discussed.