The next generation of high-field magnets that will operate at magnetic fields substantially above 20 T, or at temperatures substantially above 4.2 K, requires high-temperature superconductors (HTS). ...Conductor on round core (CORC) cables, in which RE-Ba sub(2)Cu sub(3)O sub(7- delta ) (RE = rare earth) (REBCO) coated conductors are wound in a helical fashion on a flexible core, are a practical and versatile HTS cable option for low-inductance, high-field magnets. We performed the first tests of CORC magnet cables in liquid helium in magnetic fields of up to 20 T. A record critical current I sub(c) of 5021 A was measured at 4.2 K and 19 T. In a cable with an outer diameter of 7.5 mm, this value corresponds to an engineering current density J sub(c) of 114 A mm super(-2), the highest J sub(c) ever reported for a superconducting cable at such high magnetic fields. Additionally, the first magnet wound from an HTS cable was constructed from a 6 m-long CORC cable. The 12-turn, double-layer magnet had an inner diameter of 9 cm and was tested in a magnetic field of 20 T, at which it had an I sub(c) of 1966 A. The cables were quenched repetitively without degradation during the measurements, demonstrating the feasibility of HTS CORC cables for use in high-field magnet applications.
Measuring the complex impedance of a superconducting magnet as a function of frequency provides valuable insight into its electrodynamics. In particular, the characteristic features of some ...non-conform behaviour, such as an insulation fault, may be easier to assess when performing impedance measurements rather than observing time-domain signals. A physics-driven equivalent circuit model of a superconducting magnet has been recently developed, whose parameters are derived using solely measured geometric and material properties. This contribution describes its validation against impedance measurements of a spare LHC superconducting main dipole, performed at the CERN magnet test facility. The proposed model includes lumped-elements capturing individual physical phenomena, such as superconducting filament magnetization, inter-filament and inter-strand coupling currents, eddy currents in the strand copper matrix and various magnet components, and stray capacitances. It is possible to predict the impact of different physical effects in different frequency ranges and compare simulations to experimental results. It is shown that the validated model can accurately reproduce the magnet's impedance in a frequency range up to 5 kHz in the different conditions considered.
The Main Bending Recombination Dipole (MBRD), or D2, is one of the magnets foreseen by the High-Luminosity upgrade of the Large Hadron Collider (LHC). D2 features a double aperture, Nb-Ti, cos ...<inline-formula><tex-math notation="LaTeX">\theta</tex-math></inline-formula> dipole, with a central field of 4.5 T for a length of 7.78 m, hence with an integrated magnetic field of 35 T<inline-formula><tex-math notation="LaTeX">\cdot</tex-math></inline-formula> m, in a 105 mm bore. The project includes the fabrication of a 1.6 m long model, a full-length prototype and six series magnets, two of which are spare. Till now, the short model and the prototype have been successfully constructed and tested in 2020 and 2023, while the series magnets are presently under manufacturing and the warm magnetic measurements of the first built magnet were performed at the end of July 2023. This contribution will report the final field quality analysis of the prototype and the preliminary one of the series magnets, including results of the first measurements at room temperature (RT), a comparison with the ROXIE simulations and the expected field quality at operating conditions.
Future application of high-temperature superconductors in large volume, high field magnets and in magnet current distribution systems requires cabling of RE-Ba2Cu3O7 − δ coated conductor tapes. The ...substantial aspect ratio of RE-Ba2Cu3O7 − δ coated conductors and the highly resistive buffer layers in these tapes make the development of compact and homogeneous cable terminals complex. The contact resistance between individual tapes and the cable terminations of two types of high-temperature superconducting cables was determined at 77 K at relatively low current ramp rates using a non-destructive method. The current distribution between tapes in the cables caused by a variation in contact resistance was calculated with a simple model, which was validated using different experimental methods. The results show that the current distribution at low current ramp rates in cables made from RE-Ba2Cu3O7 − δ coated conductors is mainly dictated by the variations in contact resistances between tapes in the cable and the cable terminals. Development of practical cable terminals that minimize the variations in contact resistances is therefore instrumental for the successful application of high-temperature superconducting cables in magnets.
A conceptual design is presented of a novel energy-recovering linac (ERL) facility for the development and application of the energy recovery technique to linear electron accelerators in the ...multi-turn, large current and large energy regime. The main characteristics of the powerful energy recovery linac experiment facility (PERLE) are derived from the design of the Large Hadron electron Collider, an electron beam upgrade under study for the LHC, for which it would be the key demonstrator. PERLE is thus projected as a facility to investigate efficient, high current (HC) (>10 mA) ERL operation with three re-circulation passages through newly designed SCRF cavities, at 801.58 MHz frequency, and following deceleration over another three re-circulations. In its fully equipped configuration, PERLE provides an electron beam of approximately 1 GeV energy. A physics programme possibly associated with PERLE is sketched, consisting of high precision elastic electron-proton scattering experiments, as well as photo-nuclear reactions of unprecedented intensities with up to 30 MeV photon beam energy as may be obtained using Fabry-Perot cavities. The facility has further applications as a general technology test bed that can investigate and validate novel superconducting magnets (beam induced quench tests) and superconducting RF structures (structure tests with HC beams, beam loading and transients). Besides a chapter on operation aspects, the report contains detailed considerations on the choices for the SCRF structure, optics and lattice design, solutions for arc magnets, source and injector and on further essential components. A suitable configuration derived from the here presented design concept may next be moved forward to a technical design and possibly be built by an international collaboration which is being established.
The High-Luminosity project (HL-LHC) of the CERN Large Hadron Collider (LHC), requires low <inline-formula><tex-math notation="LaTeX">\beta</tex-math></inline-formula>* quadrupole magnets in Nb ...<inline-formula><tex-math notation="LaTeX">_\text{3}</tex-math></inline-formula>Sn technology that will be installed on each side of the ATLAS and CMS experiments. After a successful short-model magnet manufacture and test campaign, the project has advanced with the production, assembly, and test of full-size 7.15-m-long magnets. In the last two years, two CERN-built prototypes (MQXFBP1 and MQXFBP2) have been tested and magnetically measured at the CERN SM18 test facility. These are the longest accelerator magnets based on Nb <inline-formula><tex-math notation="LaTeX">_\text{3}</tex-math></inline-formula>Sn technology built and tested to date. In this paper, we present the test and analysis results of these two magnets, with emphasis on quenches and training, voltage-current measurements and the quench localization with voltage taps and a new quench antenna.
MCBXF magnets are orbit nested correctors for the HL-LHC project, an upgrade of the Large Hadron Collider (LHC). The magnet design consists of two nested dipoles, with an aperture of 150 mm. The ...magnets have been designed in two physical lengths, namely of 2.5 m (MCBXFA) and 1.5 m (MCBXFB), with the same cross section according to the necessities. Two prototypes and the first series magnet of the short version were manufactured at CIEMAT and assembled at CERN. The series production of the rest of the series magnets, 6 long (MCBXFA) and 11 short (MCBXFB) magnets, is being carried out at the premises of the company Elytt Energy. In this paper the powering test results of the first batch of MCBXFB magnets produced in the industry are presented, including both the results of training and magnetic measurements. An endurance test was made to check the reliability of the magnets after a large number of powering cycles and torque inversions.
This paper describes the standalone magnet cold testing of the high temperature superconducting (HTS) magnet Feather-M2.1-2. This magnet was constructed within the European funded FP7-EUCARD2 ...collaboration to test a Roebel type HTS cable, and is one of the first high temperature superconducting dipole magnets in the world. The magnet was operated in forced flow helium gas with temperatures ranging between 5 and 85 K. During the tests a magnetic dipole field of 3.1 T was reached inside the aperture at a current of 6.5 kA and a temperature of 5.7 K. These values are in agreement with the self-field critical current of the used SuperOx cable assembled with Sunam tapes (low-performance batch), thereby confirming that no degradation occurred during winding, impregnation, assembly and cool-down of the magnet. The magnet was quenched many tens of times by ramping over the critical current and no degradation nor training was evident. During the tests the voltage over the coil was monitored in the microvolt range. An inductive cancellation wire was used to remove the inductive component, thereby significantly reducing noise levels. Close to the quench current, drift was detected both in temperature and voltage over the coil. This drifting happens in a time scale of minutes and is a clear indication that the magnet has reached its limit. All quenches happened approximately at the same average electric field and thus none of the quenches occurred unexpectedly.
Racetrack model coils (RMC) have been built at CERN during the past decade, as an R&D tool to qualify conductors and technologies developed for high field superconducting accelerator magnets (Perez ...et al. , 2016). RMC, assembled in a dipole magnet configuration, proved to be an efficient instrument reducing cost and feed-back time while developing new magnets. In a similar way, as for the High-Luminosity Large Hadron Collider (HL-LHC) project, CERN has designed the enhanced RMC (eRMC) made of two flat coils using 40 (1 mm diameter) Nb 3 Sn strand cable produced with Rod Restack Process (RRP) technology. This conductor geometry, originally designed and produced to build the block coil dipole magnet FRESCA2 (Rochepault et al. , 2019), was chosen to reduce the production time and shorten the road towards the feasibility demonstration to reach 16-18 T magnetic fields in a dipolar configuration. Like previous model coils built at CERN (Short model coils (SMC) & RMC), eRMC1a has been built using the "bladders and keys" type mechanical structure. This paper describes the main construction steps and the powering test results. At 1.9 K the magnet produced 16.5 T peak field in the conductor, the highest ever for a dipole magnet of this configuration.
MCBXF magnets are nested orbit combined correctors for the upgrade of the LHC. Two prototypes and the first series magnet were manufactured at CIEMAT and assembled at CERN, in the framework of the ...HL-LHC project. A fine tuning of the inner dipole design was introduced in the first series magnet to improve the mechanical support at the inner dipole coil ends, with a significant performance improvement. The contract to supply the rest of the series magnets, 6 long (MCBXFA) and 11 short (MCBXFB) magnets, has been awarded to the company Elytt Energy. This paper depicts the manufacturing and powering test results of the first MCBXFB magnet produced in Elytt Energy. In order to mitigate risks prior to the assembly of this magnet, a new reassembly of the second prototype magnet with shorter inner coils, according to the above-mentioned fine tuning, has been tested. The results of this powering test are also detailed.
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