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  • 1
    Language: English
    In: Review of scientific instruments, 2019-05, Vol.90 (5), p.053302-053302
    Description: A zero-field cooled superconducting shield was previously proposed to realize a high-field (at least 3 T) septum magnet for the Future Circular Collider proton-proton ring. In this paper, we present the conceptual design of a complete septum magnet prototype including a shield with an optimized shape and a simple and cost-effective superconducting magnet using the canted cosine theta concept. 2D optimization of the coil geometry and a realistic 2D simulation of the fieldmap and field homogeneity are presented taking into account the nonlinear penetration of the magnetic field into the shield.
    ISSN: 0034-6748
    E-ISSN: 1089-7623
    Source: American Institute of Physics (AIP) Publications
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 2
    Language: English
    In: IEEE transactions on applied superconductivity, 2019-08, Vol.29 (5), p.1-4
    Description: The short-sample critical current is only an indicative property for the maximum current a magnet can be continuously operated with. This was especially visible in the experiments of one of the world's first Roebel-cable-based high temperature superconductors dipole magnet prototype built and tested at CERN in 2017 where the thermal runaway developed very slowly in many cases. Consequently, the maximum stable operation current could be overstepped and stable operation could be recovered by lowering the current below the maximum of the stable range again. It is non-trivial to quantitatively predict this behavior from the critical current measurements which are observed under specific cooling conditions and based on an arbitrarily selected electric field criterion for the critical current. To make more rigorous predictions on the maximum stable operation current, one needs to consider in detail the interplay of cooling over the magnet surface and heat generation in the winding. This paper presents a methodology to determine the maximum stable operation current for a given magnet, as well as studies its mathematical background. Insight to this problem comes from the Roebel-cable-based dipole magnet studied at CERN during 2017.
    Subject(s): Heating systems ; High-temperature superconductors ; Cooling ; modeling ; Computational modeling ; finite element methods ; optimization ; Magnetic domains ; Superconducting magnets ; HTS magnets ; Thermal stability
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 3
    Language: English
    In: IEEE transactions on applied superconductivity, 2019-08, Vol.29 (5), p.1-8
    Description: Very high electromagnetic forces are generated in the superconducting coils of high field accelerator magnets. The cables, which are used to wind the coils, can withstand limited pressure levels and strains generated during the powering without degradation. To protect the cables from mechanical damage, reliable prediction of strain and stress inside the coil is paramount for designing suitable support structure of the magnet. This is naturally done before a magnet is built and tested, which emphasizes the need for reliable modeling. Conventionally, the mechanics in superconducting coils are modeled assuming homogenized material properties inside a homogenized coil volume. Using this so-called coil block approach, predicting the actual cable strain or stress inside the homogenized volume is unreliable. In order to predict reliably the stress in the cable, more detailed representation of the modeling domain is needed. This paper presents a workflow to perform a detailed mechanical analysis using finite-element analysis following the envisioned and more detailed approach. As an example, a high field 20 T+ magnet with clover leaf ends is studied, and results are discussed. The results reveal considerable difference between the behavior of modeled homogenized coil blocks and coils where turns are individually considered.
    Subject(s): Coils ; Solid modeling ; quadrupoles ; modeling ; Magnetomechanical effects ; correctors ; simulation ; Superconducting magnets ; Stress ; Strain ; superconducting magnet mechanical factors ; finite element methods ; magnet supports ; Magnetic domains ; computer aided engineering ; magnet structure ; Accelerator magnets: dipoles ; HTS magnets
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 4
    Language: English
    In: IEEE transactions on applied superconductivity, 2019-01, Vol.29 (1), p.1-8
    Description: For reaching very high magnetic fields in fully superconducting magnets, beyond 16 T for particle accelerators dipoles and beyond 23 T for solenoids, the use of high-temperature superconductors (HTS) is unavoidable. Due to the high minimum quench energy in HTS these coils are much more difficult to protect against quenches using conventional methods, such as quench heaters or coupling loss induced quench (CLIQ). Although it is possible to use a dump resistor on a short HTS magnet, extracting the energy externally, this does not provide a solution for longer magnets or magnets operated in a string, because the extraction voltage becomes unacceptably high. Here, a method named E 3 SPreSSO (External Energy Extraction Symbiotic Protection System for Series Operation) is proposed that allows for fast energy extraction in HTS magnets. The E 3 SPreSSO comprises of units with a near-zero self-inductance superconducting circuit, connected in series with the main magnet. When the protection is triggered, these devices are turned resistive, using quench heaters, overcurrent or CLIQ, causing them to absorb the energy of the system. The units can be located outside the main magnet and do not generate magnetic field. Therefore, it is possible to use relatively cost-efficient and robust Nb-Ti or possibly MgB 2 (at higher temperatures). This paper introduces the concept and provides an analytical method weighing the different options for designing the E 3 SPreSSO units themselves.
    Subject(s): Coils ; Resistance ; Heating systems ; Resistors ; High-temperature superconductors ; quench protection ; Superconducting magnets ; High-temperature-superconductors (HTS) ; Magnetic circuits ; switch
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 5
    Language: English
    In: IEEE transactions on applied superconductivity, 2015-12, Vol.25 (6), p.1-5
    Description: Due to the wide spectrum of current sharing temperatures in a high-temperature superconducting (HTS) magnet, estimating the energy required to quench the magnet is a complicated task. On the other hand, quenching a low-temperature superconducting (LTS) magnet for quench characterization purposes with a heater is straightforward due to the small temperature margin and correspondingly low minimum quench energy (MQE). To estimate the required energy for the LTS magnet, the analytical concept of MQE can be utilized. In this paper, we propose that only numerical simulations can give adequate estimates to the MQE of an HTS magnet, for measurement purposes. Furthermore, due to the high enthalpy margin, the utilization of spot heaters with short energy pulses becomes questionable. We present in detail the effect of heater's pulselength to the MQE, when a strip heater is utilized for quenching. In addition, the effect of the heater area on MQE is studied. We consider the model of a REBCO coil to be constructed and tested in the Enhanced European Coordination for Accelerator Research and Development (EuCARD-2) Project. According to the results: 1) MQE increases almost linearly for pulselengths between 100 and 500 ms; 2) when the heater area is enlarged, the required energy per area saturates to a certain value related to the coil's enthalpy margin; 3) MQE obtained with a traditional analytic approach based on a minimum propagating zone considerably underestimates the numerically obtained MQE.
    Subject(s): High-temperature superconductors ; high temperature superconductors ; quench simulation ; super conducting magnets ; Superconducting magnets ; Stability analysis ; minimum quench energy ; High temperature superconductivity ; Research ; Metals ; Methods ; Quenching
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 6
    Language: English
    In: IEEE transactions on applied superconductivity, 2019-08, Vol.29 (5), p.1-5
    Description: In the frame of the high-luminosity upgrade project for the large hadron collider, new twin aperture beam orbit corrector magnets will be installed near the recombination dipole (D2). These magnets are 2.2 m long canted cosine theta NbTi dipoles, with two independently powered apertures oriented such that their field vectors are perpendicular to each other and to the direction of the beams. A 0.5 m model magnet in single and double aperture configuration and a full-length double aperture prototype were built and tested at CERN. In this paper, the performance of these magnets at 1.9 K in terms of training behavior, quench detection and protection, and other tests is discussed. In addition, the thermal response of the magnet to a hypothetical beam discharge is simulated and analyzed.
    Subject(s): Temperature measurement ; Resistors ; quench ; Current measurement ; CCT ; Prototypes ; Superconducting magnets ; Apertures ; NbTi ; Magnetic tunneling
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 7
    Language: English
    In: Superconductor science & technology, 2021-03-18
    ISSN: 0953-2048
    E-ISSN: 1361-6668
    Source: IOPscience extra
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  • 8
    Conference Proceeding
    Conference Proceeding
    2019
    ISSN: 1757-8981  ISSN: 1757-899X 
    Language: English
    In: IOP conference series. Materials Science and Engineering, 2019-04-01, Vol.502 (1), p.12002
    Description: Looking into the future of CERN's higher energy Accelerators, as in the Future Circular Collider (FCC) and beyond, 16T magnetic fields and above are needed. High Temperature Superconductors (HTS) are now delivering ultra-high fields, with 30 Tesla and higher being achieved by many groups around the world. CERN has the first results of using a high current (10 kA) HTS, with REBCO cables, in an Accelerator type magnet development. This paper presents the multiple technologies and new concepts that were used in the design, build, and testing of a set of high current dipole models. We present the technology advancements in the areas of: advanced modelling, materials used in the magnet construction, quench detection and protection, and field quality. Finally, we take a glimpse at CERN's exciting 20+ Tesla accelerator conceptual magnet designs.
    ISSN: 1757-8981
    ISSN: 1757-899X
    E-ISSN: 1757-899X
    Source: IOPscience extra
    Source: Alma/SFX Local Collection
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  • 9
    Language: English
    In: IEEE transactions on applied superconductivity, 2018-06, Vol.28 (4), p.1-9
    Description: ReBCO high temperature superconducting (HTS) coated conductor tapes are a promising candidate for pushing the magnetic fields in accelerator magnets well beyond 20 T. They are capable of very high current densities in intense applied magnetic field, have a very high thermal stability, can withstand high transverse pressures and allow operation in 20-30 K helium gas flow, potentially reducing operating cost significantly. During the EuCARD2 program, significant developments have been made in terms of coil design, manufacturing, and testing. Now that EuCARD2 has come to an end, CERN and collaborators are initiating a new program to continue the development of HTS accelerator magnets. This paper presents our initial thoughts on the conceptual design of a 20 T+ accelerator magnet, using the results and technologies from EuCARD2 combined with some new ideas. The paper discusses the options available for the cross-sectional layout, the use of a hybrid configurations, including Aligned Block, the design of the coil-ends and dual aperture configurations. Also, discussed is the quench protection of the magnets. Due to the high thermal stability of the conductor and high energy densities, it will be required to explore an entirely a new approach.
    Subject(s): High-temperature superconductors ; quench protection ; Accelerator dipoles ; magnet stability ; magnet structure ; Superconducting magnets ; Conductors ; Accelerator magnets ; Perpendicular magnetic anisotropy ; Current density ; HTS magnets
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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  • 10
    Language: English
    In: IEEE transactions on applied superconductivity, 2020-06, Vol.30 (4), p.1-6
    Description: This paper discusses the simulated and experimentally observed quench behavior of the first HL-LHC Twin Aperture Orbit Corrector Prototype, also known as the MCBRDp1 magnet. This superconducting magnet features two independently powered apertures. Each aperture comprises two concentric canted-cosine-theta-type Nb-Ti/Cu coils that together generate a dipolar magnetic field over the bore. These coils are held in place by conductive aluminum-alloy formers. The circuit is protected by a combination of energy extraction and quench-back in the coils. When the coils are discharged over an energy extractor, eddy currents are generated in the formers, and the resulting heat quickly and efficiently brings the Nb-Ti/Cu strands above their current sharing temperature, provided that the resistive voltage over the energy extractor is sufficiently large. This paper compares simulations and experimental observations. It is shown that with the BBQ tool, the initial voltage development after a training quench is correctly reproduced. The ProteCCT simulation tool is shown to be consistent with experimentally observed discharges of the MCBRDp1 prototype for different bath temperatures, energy extractor types, and initial operating currents. The baseline energy extractor resistor value of 1.5 Ω and the non-linear varistor option both give worst-case hotspot temperatures below the 200 K hotspot temperature limit. At ultimate current, the resulting hotspot temperatures are 143 and 167 K, and the peak voltages-to-ground are 590 and 440 V, respectively.
    Subject(s): Coils ; Insulation ; MCBRD ; Canted-cosine-theta ; quench simulation ; Tools ; Superconducting magnets ; ProteCCT ; Discharges (electric) ; BBQ ; Simulation ; Apertures ; HL-LHC
    ISSN: 1051-8223
    E-ISSN: 1558-2515
    Source: IEEE Electronic Library (IEL)
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