超导国家重点实验室学术报告

题目：“Go beyond the performance of Nb cavity: potential of alternative materials in SRF”

报告人：Doctor Takayuki Kubo
           High Energy Accelerator Research Organization,Japan  (KEK)

报告时间：2018年12月14日（星期五）上午10:00-11:00
报告地点：M238会议室
联系人：  金魁 82649729

报告摘要：
Superconducting radio-frequency (SRF) resonant cavities for particle accelerators regularly achieve a very high qualityfactor, Q0~1010, and high accelerating electric field Eacc~30-40MV/m. Improving these two parameters even more has been the main challenge for SRF researchers. Cavities must be operated in Meissner state to keep Q0 very high, so naively, the maximum field inside the cavity is limited by Hc1 of the cavity material. Thus, the modern SRF cavities are made from pure Nb with Hc1~170mT at 2K, which is the largest Hc1 among materials available.This corresponds to 40MV/mof the present standard cavity shape for electron accelerators. To achieve much higher Eacc, a simple bulk Nb is not enough, but Nblooks the best because of its Hc1. Then, how to go beyond Nb cavity?In this talk, the superconductor–insulator–superconductor (S’IS) multilayer structure forapplication in SRF cavities for higher Eaccis reviewed. S’IS multilayer consists of a thin superconducting layer with a higher thermodynamic critical field formed on a bulk superconductor with a higher Hc1 (i.e., Nb).The theoretical field limit,optimum layer thicknesses and material combination are discussed for theS’IS structure and are also reviewed for the superconductor–superconductor (S’S) bilayer structure.

报告人简介：
Takayuki Kubo is an Assistant Professor of High Energy Accelerator Research Organization (KEK). Kubo obtained his Bachelor of chemical engineering from Kyoto University and his PhD in physics from the Graduate University for Advanced Studies. Kubo was a postdoctoral researcher at KEK where he started to study superconducting radio-frequency (SRF) resonant cavity for particle accelerators, in particular for the proposed International Linear Collider. His study on multilayer coating of SRF cavity, which was proposed in 2006 and had been regarded as the next generation SRF structure for long years but not yet realized, revealed how to optimize thicknesses and combinations of multilayer. He won the Young Scientist Best Poster Award at SRF2013, Paris. His review paper “Multilayer coating for higher accelerating fields in superconducting radio-frequency cavities: a review of theoretical aspects [Superconductor Science and Technology 30, 023001 (2017)]”was chosen as Highlights in 2017 bySuperconductor Science and Technology.