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Advanced Electro-chemical Deposition of State-of-the-art Nb3Sn Films

Cutting-edge electro-chemical deposition technique for producing superconducting Nb3Sn films, detailed characterization at FNAL, with comparisons and future steps outlined.

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Advanced Electro-chemical Deposition of State-of-the-art Nb3Sn Films

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  1. State-of-the-art Nb3Sn Films by Electro-chemical DepositionEmanuela Barzi, Fermilab

  2. Premise • 2014-2016. Half a dozen of superconducting Nb3Sn films produced by electro-chemical deposition at Politecnico di Milano were characterized at FNAL, where the appropriate heat treatment was developed. This originally was for the purpose of testing flux pinning models. [E. Barzi et al., ”Synthesis of superconducting Nb3Sn coatings on Nb substrates,” Supercond. Sci. Technol. 29 015009 (2016)] • Since 2016, work in this area continued under Task 3, SRF cavity thin-film coating technologies for transformational performance, of the U.S.-Japan Science and Technology Cooperation Program in High Energy Physics - LAB 17-1699 Advanced Accelerator Technology [FNAL - Emanuela Barzi, Daniele Turrioni, graduate students Stefano Falletta and Carlo Ciaccia; NIMS - Akihiro Kikuchi; JLAB - GrigoryEremeev, Anne Marie Valente-Feliciano, RongliGeng, JLab, Bob Rimmer; KEK - Hitoshi Hayano, Takayuki Saeki, PhD student Hayato Ito] • At FNAL, several dozens of superconducting Nb3Sn films – flat and cylinders - were obtained on Nb substrates by studying and optimizing most parameters of the electro-plating process. Advantages of electroplating are simplicity, accurate control, and low costs. State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  3. Outline • Conceptual description of the technique. • Comparison of some results between original and latest samples. • Detailed description of the technique. • Show examples of Electron Probe Microanalysis (EPMA) for elemental quantitative analysis with Wavelength-Dispersive Spectroscopy (WDS), DC and inductive tests of critical temperature Tc0, and lower critical field Hc1(4.2 K) by SQUID. • Next steps and conclusions. State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  4. Nb3Sn Films on Nb - Concepts • A Nb-Sn composite is obtained by electrodeposition of Sn layers and Cu intermediate layers onto Nb substrates. This is done at near room temperature (40 and 50°C) and atmospheric pressure. • Nb3Sn is formed through solid diffusion by heat treating the multi-layered samples in inert atmosphere (argon) using a temperature profile with a maximum temperature of 700C. Four magnetic cryostats with up to 15T/17 T background field, and with cold apertures between 64 mm and147 mm are connected to new vent and vacuum systems. Five ovens up to 1500◦C for heat treatment in Argon and in Oxygen. SEM State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  5. Comparison of DC Test Results of Tc0 IMPROVEMENT AND REPRODUCIBILITY State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  6. Critical Current as function of Magnetic Field Ic||(4.2K, B) compared with previous [pub] samples 14/16 T magnetic cryostat for critical current measurements at field The upper critical field 0Hc20 as a free parameter in the Ic (B) data fitting was 23.2 T for both previous and current samples. State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  7. Chemical Electrodeposition For ADHESION, THICKNESS CONTROL and UNIFORMITY, optimize: • Bath composition and anode materials for each of the three deposition steps; • Current densities, deposition times, stirring rates, and cathode and anode relative orientation in DC mode; • Current densities, deposition times, stirring rates, cathode and anode relative orientation, pulse frequen-cies, and duty cycles in pulsed mode. The pulsed mode was eventually chosen for all three deposition steps. State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  8. Experimental Setup for Deposition State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  9. Bath Composition for the Three Steps STEP 3 STEP 2 STEP 1 State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  10. Pictures of Samples at Each Step STEP 1 STEP 2 STEP 3 Samples for SC characterization Two-inch discs for surface inductance measurements at JLAB State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  11. Nb Subtrate Roughness Requirements Data from Confocal Microscope State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  12. Example – Sample No. 21 Electron Probe Microanalysis (EPMA) for elemental quantitative analysis with Wavelength-Dispersive Spectroscopy (WDS) State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  13. Characterization – Sample No. 21 DC Tc0=17.6K (FNAL) SQUID Tc0=17.7K (NIMS) M-H curve obtained with SQUID magnetometer (NIMS). Hc1(4.2 K) = 550 Oe. State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  14. Example – Sample No. 23 Electron Probe Microanalysis (EPMA) for elemental quantitative analysis with Wavelength-Dispersive Spectroscopy (WDS) State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  15. Characterization – Sample No. 23 SQUID Tc0=17.6K (NIMS) DC Tc0=17.5K (FNAL) M-H curve obtained with SQUID magnetometer (NIMS). Hc1(4.2 K) = 600 Oe. State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  16. Cylinders Coating – In progress State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  17. Prospects for SRF State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

  18. NEWS NEWS: NEw WindowS on the universe and technological advancements from trilateral EU-US-Japan collaboration H2020-MSCA-RISE-2016 ⎯ Grant Agreement N°734303 • H2020 EU Research and Innovation program • → Excellent Science • → Marie Sklodowska Curie Actions • → RISE (Research and Innovation Staff Exchange) 2016

  19. NEWS Work Packages and Scientific Board 2017-2021 S. Donati – NEWS MB & SB kick-off meeting 19

  20. Conclusions • Advantages of electroplating are its simplicity, accurate control, and low costs. • JLab and to KEK are developing the appropriate etching and/or electropolishing techniques to remove the few micrometres of Cu and bronze phases at the samples’ outer surface. • Electrochemical techniques could eliminate the problem of a low tin concentration at the niobium interface, which is a fundamental limit of the current vapor deposition techniques. • Electrochemical deposition should also provide a more uniform Nb3Sn coating. Improving the quality of the Nb3Sn could reduce the large gap between the theoretical and measured Hsh. • Lastly, electrodeposition can be performed on any 3D surface such as the inner surface of SRF cavities. State-of-the-art Nb3Sn Films by Electro-chemical Deposition, Oct. 9 2018

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