Progress on HL-LHC Nb<sub>3</sub>Sn Magnets

Todesco, E.; Annarella, M.; Ambrosio, G.; Apollinari, G.; Ballarino, A.; Bajas, Hugues; Bajko, M.; Bordini, B.; Bossert, R.; Bottura, L.; Cavanna, Eugenio; Cheng, D.; Chlachidze, G.; Rijk, G. de; DiMarco, J.; Ferracin, P.; Fleiter, J.; Guinchard, Michael; Hafalia, A.R.; Holik, Eddie Frank; Bermúdez, Susana Izquierdo; Lackner, F.; Marchevsky, M.; Loeffler, C.; Pérez, Juan Carlos; Prestemon, S.; Ravaioli, Emmanuele; Rossi, L.; Sabbi, G.; Salmi, Tiina; Savary, F.; Stoynev, S.; Strauss, T.; Tartaglia, M.; Vallone, Giorgio; Velev, G.; Wanderer, P.; Wang, X.; Willering, Gerard; Yu, Min

doi:10.1109/tasc.2018.2830703

Cited by 24 publications

(14 citation statements)

References 29 publications

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“…The Future Circular collider (FCC) or upgrades to the Large Hadron Collider (LHC) require Nb3Sn dipole magnets to operate up to 16 T [1][2][3], an operating range about twice the Nb-Ti capability of the present LHC magnets [4], and about 5 T higher than the Nb3Sn magnets planned for the High Luminosity LHC upgrade [5,6]. To achieve such not yet achieved dipole fields requires magnet conductors with the not yet achieved high current density (Jc) of 1500 A/mm 2 at 16 T (4.2 K), while simultaneously maintaining high Cu stabilizer residual resistivity ratio (RRR) ≥ 100 and a large strand diameter of order 1 mm [7].…”

Section: Introductionmentioning

confidence: 99%

Beneficial influence of Hf and Zr additions to Nb4at%Ta on the vortex pinning of Nb₃Sn with and without an O source

Balachandran

Tarantini

Lee

et al. 2019

Supercond. Sci. Technol.

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Here we show that addition of Hf to Nb4Ta can significantly improve the high field performance of Nb3Sn, making it suitable for dipole magnets for a machine like the 100 TeV future circular collider (FCC). A big challenge of the FCC is that the desired non-Cu critical current density (Jc) target of 1500 A/mm 2 (16 T, 4.2 K) is substantially above the best present Nb3Sn conductors doped with Ti or Ta (~1300 A/mm 2 in the very best sample of the very best commercial wire). Recent success with internal oxidation of Nb-Zr precursor has shown significant improvement in the layer Jc of Nb3Sn wires, albeit with the complication of providing an internal oxygen diffusion pathway and avoiding degradation of the irreversibility field HIrr. We here extend the Nb1Zr oxidation approach by comparing Zr and Hf additions to the standard Nb4Ta alloy of maximum Hc2 and Hirr. Nb4Ta rods with 1Zr or 1Hf were made into monofilament wires with and without SnO2 and their properties measured over the entire superconducting range at fields up to 31 T. We found that group IV alloying of Nb4Ta does raise HIrr, though adding O2 still degrades this slightly. As noted in earlier Nb1Zr work with an O source, the pinning force density Fp is strongly enhanced and its peak value shifted to higher field by internal oxidation. A surprising result of this work is that we found better properties in Nb4Ta1Hf without SnO2, FpMax achieving 2.35 Times that of the standard Nb4Ta alloy, while the oxidized Nb4Ta1Zr alloy achieved 1.54 times that of the Nb4Ta alloy. The highest layer Jc(16 T, 4.2 K) of 3700 A/mm 2 was found in the SnO2free wire made with Nb4Ta1Hf alloy. Using a standard A15 cross-section fraction of 60% for modern PIT and RRP wires, we estimated that a non-Cu Jc of 2200 A/mm 2 is obtainable in modern conductors, well above the 1500 A/mm 2 FCC specification. Moreover, since the best properties were obtained without SnO2, the Nb4Ta1Hf alloy appears to open a straightforward route to enhanced properties in Nb3Sn wires manufactured by virtually all the presently used commercial routes employed today.

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Section: Introductionmentioning

confidence: 99%

Beneficial influence of Hf and Zr additions to Nb4at%Ta on the vortex pinning of Nb₃Sn with and without an O source

Balachandran

Tarantini

Lee

et al. 2019

Supercond. Sci. Technol.

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“…Nb3Sn provides the most technologically ready conductors for the realization of high field accelerator magnets beyond the limits of Nb-Ti. In fact, Nb3Sn has been selected for the magnets employed in the Hi-Luminosity upgrade of the Large Hadron Collider (LHC) 1,2,3 and it is the first choice for the realization of the Future Circular Collider (FCC). 4 Because of the very demanding requirements of this project and broad interest in improving the performance for other applications like NMR spectroscopy, compact cyclotrons and magnetically confined fusion reactors, a better understanding of the limits of present commercially available conductor could provide insights for further improvements or development of new conductor designs.…”

Section: Introductionmentioning

confidence: 99%

Ta, Ti and Hf effects on Nb₃Sn high-field performance: temperature-dependent dopant occupancy and failure of Kramer extrapolation

Tarantini¹,

Balachandran²,

Heald³

et al. 2019

Supercond. Sci. Technol.

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The increasing demand for improving the high-field (16-22 T) performance of Nb3Sn conductors requires a better understanding of the properties of modern wires much closer to irreversibility field, HIrr. In this study we investigated the impact of Ta, Ti and Hf doping on the high-field pinning properties, the upper critical field, Hc2, and HIrr. We found that the pinning force curves of commercial Ti and Ta doped wires at different temperatures do not scale and that the Kramer extrapolation, typically used by magnet designers to estimate highfield critical current density and magnet operational margins from lower field data, is not reliable and significantly overestimates the actual HIrr. In contrast, new laboratory scale conductors made with Nb-Ta-Hf alloy have improved high-field Jc performance and, despite contributions by both grain boundary and point defect pinning mechanisms, have more predictable high-field behavior. Using Extended X-ray Absorption Fine Structure spectroscopy, EXAFS, we found that for the commercial Ta and Ti doped conductors, the Ta site occupancy in the A15 structure gradually changes with the heat treatment temperature whereas Ti is always located on the Nb site with clear consequences for Hc2. This work reveals the still limited understanding of what determines Hc2, HIrr and the high-field Jc performance of Nb3Sn and the complexity of optimizing these conductors so that they can reach their full potential for high-field applications.

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“…The requirement for larger-aperture quadrupole magnets, and shorter dipole magnets to allow space for additional collimators, necessitates a significant increase in magnetic field from a peak field of up to 8.6 T on the conductor in the LHC, to 11.6 T for HL-LHCwhich cannot be achieved with Nb-Ti, as used for the LHC. Suitable Nb3Sn conductors have been developed using both the Rod Restack Process (RRP ® ) and powder-in-tube technologies, and series production of these wires is advancing towards completion [1].…”

Section: Introductionmentioning

confidence: 99%

The CERN FCC Conductor Development Program: A Worldwide Effort for the Future Generation of High-Field Magnets

Ballarino

Hopkins

Bordini

et al. 2019

IEEE Trans. Appl. Supercond.

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The study of next generation high energy accelerators based on 16 T dipoles has emphasized the need for higher performance, cost-effective Nb3Sn superconducting wires. A Conductor Development Program aiming to reach a non-copper critical current density (Jc) of 1500 A/mm 2 at 16 T and 4.2 K has been launched by CERN, with the involvement of industry and laboratories worldwide. In this article, the targets and strategy of the program are presented, with an overview of the wire layouts and development activities being pursued by each partner, and the latest characterization results are reported. Three of the four participating manufacturers have successfully reached the first stage Jc milestone, but a significant advance is still needed to achieve the final target. The next steps are briefly discussed, as the program focuses increasingly on novel alloys and methods to maximize Jc.

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Progress on HL-LHC Nb₃Sn Magnets

Cited by 24 publications

References 29 publications

Beneficial influence of Hf and Zr additions to Nb4at%Ta on the vortex pinning of Nb₃Sn with and without an O source

Beneficial influence of Hf and Zr additions to Nb4at%Ta on the vortex pinning of Nb₃Sn with and without an O source

Ta, Ti and Hf effects on Nb₃Sn high-field performance: temperature-dependent dopant occupancy and failure of Kramer extrapolation

The CERN FCC Conductor Development Program: A Worldwide Effort for the Future Generation of High-Field Magnets

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Progress on HL-LHC Nb3Sn Magnets

Cited by 24 publications

References 29 publications

Beneficial influence of Hf and Zr additions to Nb4at%Ta on the vortex pinning of Nb3Sn with and without an O source

Beneficial influence of Hf and Zr additions to Nb4at%Ta on the vortex pinning of Nb3Sn with and without an O source

Ta, Ti and Hf effects on Nb3Sn high-field performance: temperature-dependent dopant occupancy and failure of Kramer extrapolation

The CERN FCC Conductor Development Program: A Worldwide Effort for the Future Generation of High-Field Magnets

Contact Info

Product

Resources

About

Progress on HL-LHC Nb₃Sn Magnets

Beneficial influence of Hf and Zr additions to Nb4at%Ta on the vortex pinning of Nb₃Sn with and without an O source

Beneficial influence of Hf and Zr additions to Nb4at%Ta on the vortex pinning of Nb₃Sn with and without an O source

Ta, Ti and Hf effects on Nb₃Sn high-field performance: temperature-dependent dopant occupancy and failure of Kramer extrapolation