First Cold Powering Test of REBCO Roebel Wound Coil for the EuCARD2 Future Magnet Development Project

Abstract

International audienceEuCARD-2 is a project partly supported by FP7-European Commission aiming at exploring accelerator magnet technology for 20 T dipole operating field. The EuCARD-2 collaboration is liaising with similar programs for high field magnets in the USA and Japan. EuCARD-2 focuses, through the work-package 10 “Future magnets,” on the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, for a 5 T stand-alone dipole of 40 mm bore and about 1 m length. After standalone testing, the magnet will possibly be inserted in a large bore background dipole, to be tested at a peak field up to 18 T. This paper starts by reporting on a few of the highlight simulations that demonstrate the progress made in predicting: dynamic current distribution and influence on field quality, complex quench propagation between tapes, and minimum quench energy in the multitape cable. The multiphysics output importantly helps predicting quench signals and guides the development of the novel early detection systems. Knowing current position within individual tapes of each cable we present stress distribution throughout the coils. We report on the development of the mechanical component and assembly processes selected for Feather-M2 the 5 T EuCARD2 magnet. We describe the CERN variable temperature flowing helium cold gas test system. We describe the parallel integration of the FPGA early quench detection system, using pickup coils and temperature sensors, alongside the standard CERN magnet quench detection system using voltage taps. Finally we report on the first cold tests of the REBCO 10 kA class Roebel subscale coil named Feather-M0

Performance and Quench Characteristics of a Pancake Coil Wound With the 2G YBCO Roebel Cable

“…T HE high current carrying capability and strong pinning in high magnetic field make the 2G HTS Roebel cable desirable for future high energy accelerators at CERN and tokamak devices [1]- [4]. Some research has already shown a more complex current sharing and normal zone propagation is expected for Roebel cables than those found in traditional superconducting composites due to the non-continuous touch contacts among the Roebel strands [1]- [3], [5]- [8].…”

“…Some research has already shown a more complex current sharing and normal zone propagation is expected for Roebel cables than those found in traditional superconducting composites due to the non-continuous touch contacts among the Roebel strands [1]- [3], [5]- [8]. Therefore, the standard method of experimental quench studies on adiabatic short conductors [9]- [11] becomes impractical for Roebel cables with long current sharing length [2].…”

Quench and stability of Roebel cables at 77 K and self-field: Minimum quench power, cold end cooling, and cable cooling efficiency

“…HTS is already being considered for insert coils within the Future Circular Collider's high field dipole magnets [1,2]. Numerous high-field magnets and insert magnets have been demonstrated using HTS conductors and a few high-field HTS-hybrid research magnets are nearly complete for user facilities [3][4][5][6]. Bi:2212 cables will likely require a high-pressure, atmospherically-controlled, wind-and-react, and epoxy impregnated magnet manufacturing process while Rare-Earth Barium Copper Oxide (ReBCO) will be react-and-wind, have simpler insulation options, and may not require epoxy impregnation depending on the stresses and cable type [7][8][9][10].…”

“…Previous stability studies have already been performed on ReBCO tapes, cables, and coils [6,[12][13][14][15][16][17][18][19]. The large temperature margins of HTS conductors will likely prevent epoxy cracking, friction from sudden mechanical motion, and flux jumps from initiating a quench [6]. Additionally, the large temperature margin will result in relatively long quench decision times on the order seconds even under adiabatic conditions [15].…”

Dipole Magnets above 20 Tesla: Research Needs for a Path via High-Temperature Superconducting REBCO Conductors

“…The collaboration successfully demonstrated a record bore field of 5.37 T in racetrack coils with a stack of two tapes at 4.2 K [75,76]. Focusing on the Roebel cables [22,77], the EuCARD2 program demonstrated the record dipole field of 3.1 T at 5.7 K with an aligned-block dipole magnet [78,79]. Designs of hybrid dipole magnets with HTS inserts [80] and stand-alone REBCO dipole magnets were also developed [67].…”