次世代超伝導加速空洞のための超伝導積層薄膜構造の基礎的研究

2018 Fiscal Year Annual Research Report

• Project/Area Number: 17H04839
• Research Institution: High Energy Accelerator Research Organization
• Principal Investigator: 久保 毅幸 大学共同利用機関法人高エネルギー加速器研究機構, 加速器研究施設, 助教 (30712666)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 超伝導 / 加速器 / 加速空洞 / 薄膜

Outline of Annual Research Achievements

ニオブ製の超伝導加速空洞の加速電場は限界に達しつつあり、次世代超伝導加速空洞開発が急務である。そこで、超伝導積層薄膜構造の導入による加速電場の大幅な(２倍以上の)向上を目指すことが本研究の目的である。申請者は世界で初めて各層の最適な厚みの評価方法を明らかにする等、積層薄膜構造の理論研究で世界を牽引してきた。この優位性を利用して実験的研究を推進する。本研究では、限られた予算を最大限有効に使うため、安価な小型単セル空洞で試験を繰り返し、膜厚に関する広大なパラメータ空間を探索し、理論との比較を行うとともに、最適膜厚を有する空洞の実験において磁束侵入磁場の大幅な向上を確認することを目標としている。本研究は将来の加速器計画の建設費及び維持費の大幅な軽減につながる。
平成30年度は、研究協力者とともに窒化ニオブ-二酸化ケイ素-ニオブ基板からなる積層薄膜サンプルを用いた磁束侵入磁場の評価実験の解析を進めた。窒化ニオブ単体よりも、更にはニオブ基板単体よりも、磁束侵入磁場が向上している事を示す結果であり、理論と矛盾しないものであった。また、並行して研究協力者とともに、空洞部品の化学研磨と電子ビーム溶接を実施し、複数の小型ニオブ空洞及び銅空洞を完成させた。既に、ニオブ平板サンプル上への窒化ニオブ薄膜形成の技術は得られているため、これにより、次の段階である空洞内面への薄膜形成に向けての技術開発に入る準備が整った。

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

窒化ニオブ-二酸化ケイ素-ニオブ基板からなる積層薄膜サンプルを製作する技術は成熟している。既にサンプルを使った実験は磁束侵入磁場の向上を示している。更に、空洞の製作も完了しており、いよいよ空洞内面に薄膜を形成する段階に入った。

Strategy for Future Research Activity

研究協力者とともに、空洞内面への一様な薄膜形成の技術開発を進める。空洞内面の観察等を通じて膜質の改善を進める。そして製膜後の空洞を用いて性能測定を実施する。この際に得られる表面抵抗の値、及び、そのマイクロ波磁場強度依存を解析する事で、更なる改善を進める。

Research Products

• [Int'l Joint Research] Old Dominion University/Jefferson Lab(米国)
  • Country Name: U.S.A.
  • Counterpart Institution: Old Dominion University/Jefferson Lab
• [Int'l Joint Research] CEA irfu(フランス)
  • Country Name: FRANCE
  • Counterpart Institution: CEA irfu
• [Journal Article] 超伝導加速空洞の物理と課題、そして性能向上への理論的示唆 ー新規参入の誘いー (2019)
  • Author(s): 久保毅幸
  • Journal Title: 低温工学 Volume: 54 Pages: 印刷中
  • Peer Reviewed / Open Access
• [Journal Article] Evaluation of superconducting characteristics on the thin-film structure by NbN and Insulator coatings on pure Nb substrate (2018)
  • Author(s): R. Katayama, Y. Iwashita, H. Tongu, C.Z. Antoine, A. Four, H. Hayano, T. Kubo, T. Saeki, H. Ito, R. Ito, T. Nagata, H. Oikawa
  • Journal Title: Proceedings of 9th International Particle Accelerator Conference Volume: - Pages: 3653, 3655
  • DOI: doi: 10.18429/JACoW-IPAC2018-THPAL015
  • Open Access / Int'l Joint Research
• [Journal Article] Lower Critical Field Measurement System of Thin Film Superconductor (2018)
  • Author(s): H. Ito, C. Z. Antoine, A. Four, H. Hayano, T. Kubo, T. Saeki, R. Ito, T. Nagata, Y. Iwashita, R. Katayama, H. Tongu, H. Oikawa
  • Journal Title: Proceedings of 9th International Particle Accelerator Conference Volume: - Pages: 3882, 3884
  • DOI: doi: 10.18429/JACoW-IPAC2018-THPAL105
  • Open Access / Int'l Joint Research
• [Journal Article] Development of Coating Technique for Superconducting Multilayered Structure (2018)
  • Author(s): R. Ito, T. Nagata, H. Hayano, T. Kubo, T. Saeki, H. Ito, Y. Iwashita, R. Katayama, H. Oikawa
  • Journal Title: Proceedings of 9th International Particle Accelerator Conference Volume: - Pages: 4954, 4956
  • DOI: doi: 10.18429/JACoW-IPAC2018-THPML120
  • Open Access
• [Journal Article] Precise Evaluation of Characteristic of the Multi-layer Thin-film Superconductor Consisting of NbN and Insulator on Pure Nb Substrate (2018)
  • Author(s): R. Katayama, Y. Iwashita, H. Tongu, C. Z. Antoine, A. Four, H. Hayano, T. Kubo, T. Saeki, H. Ito, R. Ito, T. Nagata, H. Oikawa
  • Journal Title: Proceedings of 29th Linear Accelerator Conference Volume: - Pages: 391, 394
  • DOI: doi: 10.18429/JACoW-LINAC2018-TUPO030
  • Open Access / Int'l Joint Research
• [Journal Article] Lower Critical Field Measurement of Thin Film Superconductor (2018)
  • Author(s): H. Ito, C.Z. Antoine, A. Four, H. Hayano, T. Kubo, T. Saeki, R. Ito, T. Nagata, Y. Iwashita, R. Katayama, H. Tongu, H. Oikawa
  • Journal Title: Proceedings of 29th Linear Accelerator Conference Volume: - Pages: 484, 487
  • DOI: doi: 10.18429/JACoW-LINAC2018-TUPO066
  • Open Access / Int'l Joint Research
• [Journal Article] Construction of Thin-film Coating System Toward the Realization of Superconducting Multilayered Structure (2018)
  • Author(s): R. Ito, T. Nagata, H. Hayano, T. Kubo, T. Saeki, H. Ito, Y. Iwashita, R. Katayama, H. Oikawa
  • Journal Title: Proceedings of 29th Linear Accelerator Conference Volume: - Pages: 445, 447
  • DOI: doi: 10.18429/JACoW-LINAC2018-TUPO050
  • Open Access
• [Presentation] Field-dependent nonlinear surface resistance and its optimization by surface nano-structuring of the SRF cavities (2019)
  • Author(s): T. Kubo
  • Organizer: The 19th International Conference on RF Superconductivity, Dresden (Germany)
  • Int'l Joint Research / Invited
• [Presentation] Evaluation of superconducting characteristics on the thin-film structure by NbN and Insulator coatings on pure Nb substrate (2018)
  • Author(s): R. Katayama
  • Organizer: The 9th International Particle Accelerator Conference, Vancouver (Canada)
  • Int'l Joint Research
• [Presentation] Lower Critical Field Measurement System of Thin Film Superconductor (2018)
  • Author(s): H. Ito
  • Organizer: The 9th International Particle Accelerator Conference, Vancouver (Canada)
  • Int'l Joint Research
• [Presentation] Development of Coating Technique for Superconducting Multilayered Structure (2018)
  • Author(s): R. Ito
  • Organizer: The 9th International Particle Accelerator Conference, Vancouver (Canada)
  • Int'l Joint Research
• [Presentation] Precise Evaluation of Characteristic of the Multi-layer Thin-film Superconductor Consisting of NbN and Insulator on Pure Nb Substrate (2018)
  • Author(s): R. Katayama
  • Organizer: The 29th Linear Accelerator Conference, Beijing (China)
  • Int'l Joint Research
• [Presentation] Lower Critical Field Measurement of Thin Film Superconductor (2018)
  • Author(s): H. Ito
  • Organizer: The 29th Linear Accelerator Conference, Beijing (China)
  • Int'l Joint Research
• [Presentation] Construction of Thin-film Coating System Toward the Realization of Superconducting Multilayered Structure (2018)
  • Author(s): R. Ito
  • Organizer: The 29th Linear Accelerator Conference, Beijing (China)
  • Int'l Joint Research
• [Presentation] A theory of field-dependent surface resistance and possibilities of engineering optimal SN and SIS surface nano-structuring of the SRF cavities (2018)
  • Author(s): T. Kubo
  • Organizer: The 8th International Workshop on Thin Films and New Ideas for Pushing the Limits of RF Superconductivity, the Istituto Nazionale di Fisica Nucleare, Padova (Italy)
  • Int'l Joint Research / Invited
• [Remarks] researchmap
  • URL: https://researchmap.jp/kubotaka/