Superconducting multilayer-structure for next-generation superconducting-accelerators

2020 Fiscal Year Final Research Report

• Project/Area Number: 17H04839
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: High Energy Accelerator Research Organization
• Principal Investigator: Kubo Takayuki 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: 加速器 / 超伝導 / 超伝導加速空洞 / 薄膜 / ニオブ / 窒化ニオブ / ニオブ３スズ

Outline of Final Research Achievements

The optimized superconducting multilayer structure is a candidate technology to improve the accelerating field of superconducting particle accelerators. In the present project, we have succeeded in proof-of-concept experiments and made progress in the theory of the multilayer structure. We fabricated samples of multilayer structures by coating bulk pure-Nb substrate with a thin NbN layer separated by an insulator layer. We measured the first vortex penetration field (Bv) for samples with different NbN thicknesses and confirmed the optimum thickness. The maximum Bv is 20% higher than bulk Nb alone. Also, we calculated the superheating field (Bsh) of the multilayer structure in the diffusive limit using the BCS theory and studied the thickness dependence of Bsh. Here, Bsh corresponds to the theoretical limit of Bv. The nonlinear surface resistances of multilayer structures were also calculated using the BCS theory.

Free Research Field

超伝導共振器

Academic Significance and Societal Importance of the Research Achievements

本研究は、超伝導積層薄膜構造の原理実証及び理論の精緻化を行ったものであり、積層薄膜構造の実機への応用に向けた最初の一歩と言える。今後、更に研究・開発が進み、積層薄膜構造による次世代超伝導空洞が実現すれば、最大加速電場は大きく向上する。このことは超伝導加速器の小型化または高エネルギー化を促進し、医療用・産業用加速器、X線自由電子レーザー、エネルギー回収型ライナック、高レベル廃棄物処分としての加速器駆動核変換技術、国際リニアコライダー等の加速器計画の建設費軽減につながる。また、医療用・産業用加速器の小型化が進めば、それらの大規模な普及も期待される。