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Reece, C.

Publications and source records attributed to Reece, C..

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Nb3Sn Coating of Twin Axis Cavity for SRF Applications

The twin axis cavity with two identical accelerating beams has been proposed for Energy recovery linac (ERL) applications. Nb3Sn is a superconducting material with a higher critical temperature and a higher critical field as compared to Nb, which promises a lower operating cost due to higher quality factors. Two niobium twin axis cavities fabricated at JLab and were proposed to be coated with Nb3Sn. Due to their more complex geometry, the typical coating process used for basic elliptical cavities needs to be improved to coat these cavities. This devel-opment advances the current coating system at JLab for coating complex cavities. Two twin axis cavities were coated recently for the first time. This contribution dis-cusses initial results from coating of twin axis cavities, RF testing and witness sample analysis with an overview of the current challenges towards high performance Nb3Sn coated twin axis cavities.

Tiskumara, J.↗
DOE OSTI2019

Replication Data for: Crossing the great divide between single-crystal reactivity and actual catalyst selectivity with pressure transients

The data underlying this published work have been made publicly available in this repository as part of the IMASC Data Management Plan. This work was supported as part of the Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012573.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Superconducting Nb thin films on Cu and Cu alloys for applications in SRF accelerators

This article presents the results of Nb thin films deposited on Cu and phosphor bronze via coaxial energetic deposition (CEDTM). CEDTM is a non-equilibrium cathodic arc process that drives medium energy (50 - 150 eV) ions into a few atomic layers beneath the surface to promote the growth of dense, ordered films via sub-plantation physics1. Nb films deposited on crystalline substrates by CEDTM have shown bulk-Nb like (>300-500) RRR values1. Here we describe Nb films of 1-10 ?m deposited on coupons and complex structures made of Cu and phosphor bronze at substrate temperatures of 100 have been achieved on fine grain Cu with little surface preparation. The vortex penetration magnetic field was measured by DC SQUID and these results are presented along with comparisons between bulk Nb and thin film Nb on crystalline substrates. The CEDTM approach has applications in superconducting bellows interconnects as well as to SRF cavities. 1 M. Krishnan, E. Valderrama, B. Bures, K. Wilson-Elliott, X. Zhao, L. Phillips, Anne-Marie Valente-Feliciano, Joshua Spradlin, C. Reece and K. Seo, Superconductor Science and Technology, vol. 24, no. 11, p. 115002, Nov. 2011.

James, C.↗
DOE OSTI2012

Nb3Sn thin films grown using energetic condensation for SRF applications

The traditional method used to coat thin films of Nb3Sn onto SRF cavities has been to start with a Nb cavity and dip it into molten Sn. At high temperatures (>1100 °C), the Sn diffuses into the Nb to create a stoichiometrically correct film1,2 that offers superconducting properties. Here we describe a lower-temperature process that uses two separate plasmas of Nb and Sn to fire 50-150eV ions of Nb and Sn at a substrate that is heated to <400 °C. The non-equilibrium energetic condensation of Nb and Sn ions via subplantation3 creates a high crystal quality film of Nb3Sn. The stoichiometry of this film is controlled by adjusting the currents to the two separate cathodes that in turn controls the ion fluxes to the substrate. EDX, Tc, RRR and other measurements show that this method enables growth of superconducting films even on relatively low temperature substrates. This approach might offer a path to creating higher temperature Cu SRF cavities of the future that might reduce materials and cryogenics costs. 1 G. Arnolds-Mayer, Proc. SRF2, Geneva, Switzerland, pp. 643-666, 1984 2 Sam Posen, Matthias Liepe, Yi Xie, N. Valles, Proceedings of Thin Films Workshop, Padua Italy, October 2010 3 M. Krishnan et al., Superconductor Science and Technology, vol. 24, no. 11, p. 115002, Nov. 2011

James, C.↗
DOE OSTI2012

Thin Films Development For Superconducting RF Applications

Significant progress has recently been made in the development of niobium (Nb) films for Superconducting RF (SRF) applications using energetic condensation of ions extracted from plasma generated by Electron Cyclotron Resonance. Nb films with RRR comparable to bulk values are readily produced on both metallic and insulating substrates. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. Particular attention is given to the nucleation conditions to create a favorable template for growing the final surface exposed to SRF fields. The influence of the deposition energy is investigated with the characterization of the film surface, structure, superconducting properties and RF performance. With a similar approach, High Power Impulse Magnetron Sputtering (HiPIMS) is investigated for the development of multilayer SIS (superconductor-insulator-superconductor) structures which have the theoretical prospect to reach RF performance beyond bulk Nb. This paper presents results on the correlation of the surface and material characteristics with the superconducting properties and RF surface impedance for Nb and multilayered NbTiN-based SIS films produced on a variety of substrates.

Zhao, X.↗