Division of systems engineering

The EuCARD HTS insert is the first step towards using high-temperature superconductors for accelerator magnets. Its objective is to demonstrate whether it is possible to use ReBCO ceramic tape to generate a 5 T field at 4.2 K in the 13 T field of the FRESCA2 dipole. The magnet, designed, manufactured and tested in the laboratory, will be a dipole insert consisting of 3 double layer racetrack-type flat coils assembled around a central pole made from soft iron and clamped in place, and an external structure made from stainless steel. Initially the mechanical structure will consist of two parts with a rectangular section, fixed together around the jaws by a removable system; this will make it easier to modify when performing the first tests of the insert on its own. The removable mechanical structure will then be replaced by a Nitronic® 40 stainless steel cylindrical tube with an external diameter of 99 mm, which can be inserted in the central hole of the FRESCA2 dipole. Because the coils are flat, the insert will not have a central hole but a small cavity at the center for the diagnostic instrumentation (Hall effect sensors to measure the field at the center).

The insert conductor is a superconductor tape, provided by company SuperPower through CERN, and two insulated stabilizing tapes made from CuBe₂. The superconductor tape was received in 2013 and the stabilizing tape in December 2015 as a result of an insulation problem with the first lengths supplied. Coiling activities and a test assembly were carried out in 2015 to validate all the production procedures. The coils and assembly of the insert and its testing in a magnet-only configuration are planned for 2016.

The EuCARD-2 HTS dipole is a project to design and produce a 5 T dipole from a high-temperature superconductor with suitable characteristics for accelerators. For this reason the dipole could be considered as the second step towards using HTS tape for accelerator magnets. It will be tested in a magnet-only configuration, completed by a magnetic circuit, then in an insert configuration in the FRESCA2 background field. The project is part of European program EuCARD-2, a collaboration between eleven European institutes including CERN, the Grenoble Institute of Technology (INP), the University of Tampere and the Karlsruhe Institute of Technology. Meanwhile, different coil configurations have been studied at CERN, CEA and Grenoble INP.

The work carried out at CEA focuses on cosine-theta configurations. The cable to be used in this magnet is a Roebel cable, consisting of 13 to 15 ReBCO tapes cut into an S shape and assembled so as to give an entirely transposed cable. Two different designs have been proposed depending on the Roebel cable used. Detailed studies of the components and tools for making the coils began in 2015. The coils will be formed, then impregnated with resin under vacuum to give the Roebel mechanical strength and limit the degradation of the tapes inside the cable. A test coil was made in July 2015 and used to validate the design of the shims to be used to shape and hold the cable in the heads, and the output configuration of the cables at both ends of the coil. The shims used for the test were made by 3D printing at CEA (IRFU/SIS). Production of the superconductor coils is scheduled for 2016. It will be preceded by the production of coils and a test assembly.