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The Center for Bright Beams, A National Science Foundation Science and Technology Center

CBB applies for provisional patent on ZrNb Alloyed Surface as a Superconducting Material

Research Theme

Beam Acceleration
Published December 8, 2022

Inventors: Zeming Sun, Thomas Oseroff, Matthias Liepe

Invention Summary

The proposed invention represents novel methods for forming ordered, cubic β-ZrNb alloyed surfaces that yield high critical temperatures in the theoretical limit and improved superconducting properties desirable for superconducting radio-frequency (SRF) and quantum computing applications.

ZrNb Alloyed Surface as Superconducting Material illustration
Structural and superconducting properties of Nb-Zr samples. (a) X-ray diffraction pattern for evaporation-based samples annealed at 600°C for 10 h, with a subsequent HF etch. (b) BCS resistance before and after Nb-Zr alloying.

Technology Overview

The superconducting properties of SRF cavities used in the particle accelerators and future quantum computers depend on the surface material and the associated crystal structure and composition. The proposed method uses a novel ZrNb alloyed surface for SRF cavity, providing two distinct benefits, namely

1.     Achieving critical temperature, Tc, as high as 16 K, thus, minimizing energy dissipation and cryogenic costs, and

2.     Enhancing critical field, Bc, thus, allowing improved accelerating gradients.

These benefits make it possible to design energy efficient and compact particle accelerators and quantum computers. Formation of ZrNb surface can be achieved via either physical vapor deposition of Zr on Nb surface or an electrochemical reaction of ZrF4 with Nb surface, followed by thermal annealing under vacuum and subsequent HF etch. As shown in Figure 1, Tc values from ZrNb alloys made by both methods are essentially higher than Nb and sputtered ZrNb thin films or their random alloys in past studies. Figure 2 shows the 5.2 GHz low-field BCS surface resistance trends lower for Nb-Zr alloy than Nb, which is consistent with the expected benefit of the high Tc of the Nb-Zr material.

References:

Sun, Z., Oseroff, T., Liepe, M. U. (2022). First Demonstration of a ZrNb Alloyed Surface for Superconducting Radio-Frequency Cavities. Proceedings of North American Particle Accelerator Conference, Albuquerque, NM.

N. S. Sitaraman, Z. Sun, B. Francis, A. C. Hire, T. Oseroff, Z. Baraissov, T. A. Arias, R. Hennig, M. U. Liepe, D. A. Muller, and M. K. Transtrum, “Theory of Nb-Zr Alloy Superconductivity and First Experimental Demonstration for Superconducting Radio-Frequency Cavity Applications,” Aug. 2022, doi: 10.48550/arXiv.2208.10678. [Online]. Available: http://arxiv.org/abs/2208.10678