arXiv subjects

David Larbalestier

Publications and source records attributed to David Larbalestier.

7 recordsLinked to original sources

arXiv2025

The 2025 Roadmaps for the US Magnet Development Program

The US Physics community completed the Snowmass planning process in 2022, culminating in the HEPAP Particle Physics Project Prioritization Panel (P5) publishing its summary report at the end of 2023. Building on this, the US Magnet Development Program, a national accelerator magnet R&D program established by DOE-OHEP in 2016, has updated its strategic plan to align with the 2023 P5 report, resulting in this roadmap document.

physics.acc-ph↗

arXiv2023

Business models to assure availability of advanced superconductors for the accelerator sector and promote stewardship of superconducting magnet technology for the US economy

Stakeholders representing concerns of national and global leadership, industries that use superconducting magnets in products, manufacturers of superconducting wires and tapes that supply to industries, and innovation generators from small businesses and universities came together to address stewardship of superconducting magnet technology and assurance of supply of advanced superconductors to the accelerator sector. This report outlines potential public-private partnerships that develop and enhance domestic capabilities to meet the needs of science facilities in the accelerator systems sector and in the broader commercial ecosystem.

physics.acc-ph↗

arXiv2022

Challenges and opportunities to assure future manufacturing of magnet conductors for the accelerator sector

We take a comprehensive look at conductors used in superconducting magnets for the accelerator sector and explore the ramifications of the present marketplace for supply of conductor to future accelerator facilities. While there are thousands of superconductors, many of which have promising properties for applications, we outline the journey a promising material must take to become a magnet conductor that is manufactured at the scale needed for an accelerator facility. Among the few materials that actually reach this scale, Nb$_{3}$Sn is arguably the workhorse conductor for the next generation of accelerators. Yet, a marketplace pull equivalent to the medical imaging magnet industry, which consumes close to 1000 tons of commodity-scale Nb-Ti conductor per year, has not emerged. This aspect greatly complicates the steps that must be taken to assure readiness of manufacturing for the next accelerator facility. Meanwhile, high-temperature superconductors (HTS), which are capable of extremely high fields at low temperature, are advancing rapidly as magnet conductors, and the long horizons of large physics projects could provide time for them to emerge and displace Nb-based materials. We close by examining in more detail the ecosystem that connects accelerator magnet conductors with broader industry applications, in particular areas that are presently in rapid development such as fusion and wind turbines and which would potentially require hundreds of tons of conductor.

physics.acc-ph↗

arXiv2020

The 2020 Updated Roadmaps for the US Magnet Development Program

The US Magnet Development Program brings together teams from the leading US accelerator magnet research programs to develop the next generation of magnet technology for future collider applications. Sponsored by the DOE Office of High Energy Physics, the program strives to maintain and strengthen US Leadership in the field, while nurturing cross-cutting activities from other programs to further strengthen the research and its impact to the DOE Office of Science. The US MDP was initiated in 2016, and there has been significant progress on the original program roadmaps and major advancements in magnet science. These advances, together with the addition of Brookhaven National Laboratory to the MDP in 2019 and the onset of the next Snowmass community planning effort for High Energy Physics in early 2020, motivate a review and renewal of the program roadmaps. The updated roadmaps presented here are the result of significant discussion and planning with the MDP research staff, along with guidance from our Technical Advisory Committee, outreach to colleagues from the International Community, and feedback from DOE-OHEP.

physics.acc-ph↗

arXiv2019

Stable, predictable and training-free operation of superconducting Bi-2212 Rutherford cable racetrack coils at the very high wire current density of more than 1000 A/mm2

High-temperature superconductors (HTS) could enable high-field magnets much stronger than is possible with Nb-Ti and Nb3Sn, but two key limiting factors have so far been the difficulty of achieving high critical current density in long-length conductors, especially in high-current cables, and the danger of quenches out of the superconducting into the normal state. Here we demonstrate stable, reliable and training-quench-free performance of Bi-2212 racetrack coils wound with a 17-strand Rutherford cable fabricated from wires made with nanospray Bi-2212 powder. These multifilament wires are now being delivered in single lengths of more than 1 km with a new record whole-wire critical current density up to 950 A/mm2 at 30 T at 4.2 K. These coils carried up to 8.6 kA while generating a peak field of 3.5 T at 4.2 K, at a wire current density of 1020 A/mm2. Quite different from the unpredictable training performance of Nb-Ti and Nb3Sn magnets, these Bi-2212 magnets showed no training quenches and entered the flux flow state in a stable manner before thermal runaway and quench occurred. Also quite different from Nb-Ti, Nb3Sn, and REBCO magnets for which localized thermal runaways occur at unpredictable locations, the quenches of Bi-2212 magnets consistently occurred in the high field regions over a conductor length greater than one meter. These characteristics make quench detection rather simple, enabling safe protection, and suggest a new paradigm of constructing quench-predictable superconducting magnets from Bi-2212, which is, like Nb-Ti and Nb3Sn, isotropic, round, multifilament, uniform over km lengths and suitable for Rutherford cable use but, unlike them, much more tolerant of the energy disturbances that often lead Nb-based superconducting magnets to premature quench and long training cycles.

cond-mat.supr-con↗

arXiv2015

Study of grain boundary transparency in (Yb1-xCax)Ba2Cu3O bi-crystal thin films over a wide temperature, field and field orientation range

The residual low angle grain boundary (GB) network is still the most important current-limiting mechanism operating in bi-axially textured rare earth barium copper oxide (REBCO) coated conductors. While Ca-doping is well established to improve super-current flow across low angle GBs in weak fields at high temperatures, Ca-doping also depresses Tc, making it so far impractical for high temperature applications of REBCO coated conductors. On the other hand, high field magnet applications of REBCO require low temperatures. Here we systematically evaluate the effectiveness of Ca-doping in improving the GB transparency, r$^{GB}$= Jc$^{GB}$/Jc$^{grain}$ , of low angle Yb1-xCaxBaCuO [001] tilt bi-crystal films down to 10K and with magnetic fields perpendicular and parallel to the film surfaces, while varying the Ca and oxygen doping level. Using Low Temperature Scanning Laser Microscopy (LTSLM) and Magneto-Optical Imaging (MOI), we found rGB to strongly depend on the angle between magnetic field and the GB plane and clearly identified regimes in which Jc$^{GB}$ can exceed Jc$^{grain}$ (r$^{GB}$>1) where the GB pinning is optimized by the field being parallel to the GB dislocations. However, even in this favorable situation, we found that r$^{GB}$ became much smaller at lower temperatures. Calculations of the GB Ca segregation profile predict that the high Jc channels between the GB dislocation cores are almost Ca-free. It may be therefore that the positive effects of Ca doping seen by many authors near Tc are partly a consequence of the higher Tc of these Ca-free channels.

cond-mat.supr-con↗

arXiv2005

Electromagnetic, atomic-structure and chemistry changes induced by Ca-doping of low-angle $YBa_2Cu_3O_{7-δ}$ grain boundaries

Practical high temperature superconductors must be textured to minimize the reduction of the critical current density $J_{gb}$ at misoriented grain boundaries. Partial substitution of Ca for Y in $YBa_2Cu_3O_{7-δ}$ has shown significant improvement in $J_{gb}$ but the mechanisms are still not well understood. Here we report atomic-scale, structural and analytical electron microscopy combined with transport measurements on $7^{\circ}$ $[001]$-tilt $Y_{0.7}Ca_{0.3}Ba_2Cu_3O_{7-δ}$ and $YBa_2Cu_3O_{7-δ}$ grain boundaries, where the dislocation cores are well separated. We show that the enhanced carrier density, higher $J_{gb}$ and weaker superconductivity depression at the Ca-doped boundary result from a strong, non-monotonic Ca segregation and structural rearrangements on a scale of ~1 nm near the dislocation cores. We propose a model of the formation of $Ca^{2+}$ solute atmospheres in the strain and electric fields of the grain boundary and show that Ca doping expands the dislocation cores yet enhances $J_{gb}$ by improving the screening and local hole concentration.

cond-mat.mtrl-sci↗