Commissioning of a two-target DC cylindrical magnetron sputter coater for depositing Nb₃Sn film on Nb superconducting radiofrequency cavities

Journal Article · Tue Aug 29 00:00:00 EDT 2023 · Vacuum

DOI:https://doi.org/10.1016/j.vacuum.2023.112563· OSTI ID:1993404

Shakel, Md Sharifuzzaman ^[1]; Sayeed, Md Nizam ^[1]; Eremeev, Grigory V. ^[2]; Valente-Feliciano, Anne-Marie ^[3]; Pudasaini, Uttar ^[3]; Hani E. Elsayed-Ali, Hani Elsayed-Ali ^[1]

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1. Old Dominion U. (main); Jefferson Lab
2. Fermilab
3. Jefferson Lab

A DC cylindrical magnetron sputter coater was commissioned and used to coat Nb 2.6 GHz superconducting radiofrequency (SRF) cavity with Nb3Sn. The sputter coater has two identical cylindrical magnetrons that can move, with a controlled speed, along the axis of the SRF cavity to coat the inside surface of the cavity. The design of the sputter coater is discussed, along with its performance. Initially, a sample holder that allows coating on flat substrates at positions similar to the equator and beam tubes of a 2.6 GHz SRF cavity was used to test conditions for fabricating Nb3Sn layers. Multilayers of Nb and Sn were sequentially sputtered on flat Nb and sapphire substrates mounted on the equivalent positions of the cavity's beam tubes and the equator using the two identical cylindrical magnetrons. Then, the Nb/Sn multilayers were annealed at 950 °C for 3 h. The ∼1.2 μm thick Nb3Sn film did not show any other Nb–Sn compounds and had a superconducting transition temperature of 17.61–17.76 K. The 2.6 GHz SRF cavity was coated using similar conditions as flat samples. Cryogenic RF testing of the Nb3Sn-coated cavity demonstrated a quality factor of 3.2 × 10⁸ at an accelerating gradient of 5 MV/m at 4.4 K. •Two-magnetron cylindrical sputter coater was commissioned.•Multilayers of Nb and Sn were sequentially sputtered.•Annealed Nb/Sn multilayers form Nb3Sn film with Tc = 17.61–17.76 K.•Nb3Sn-coated cavity at 4.4 K has a quality factor = 3.2 × 10⁸ at 5 MV/m gradient.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Old Dominion U. (main)
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: AC02-07CH11359; 89243024CSC000002
• OSTI ID: 1993404
• Report Number(s): FERMILAB-PUB-23-246-TD; JLAB-ACC-23-3854; oai:inspirehep.net:2678090
• Journal Information: Vacuum, Journal Name: Vacuum Vol. 217
• Country of Publication: United States
• Language: English

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