Experimental and Theoretical Studies of Fundamental Limits of Surface Resistance of Superconductors for Next Generation Particle Accelerators

下一代粒子加速器超导体表面电阻基本极限的实验和理论研究

• 批准号: 1416051
• 负责人: Jean Delayen
• 金额: $ 66.42万
• 依托单位: Old Dominion University Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1416051&HistoricalAwards=false
• 关键词: Experimental; Theoretical; Studies; Fundamental; Limits

Superconducting Radio Frequency (SRF) cavities have been used in a variety of particle accelerators for quite some time. The ulra-low electrical resistivity of a superconductor material allows a radio frequency resonator (needed for an accelerator) to obtain a high quality factor (Q) which allows energy storage with very low loss. Future accelerators, important in many areas of science and medicine, will benefit from advances such as the techniques in this award. This award is for advanced studies of superconductors used in SRF accelerators. Superconductors used in SRF are limited by the fundamental surface resistance. The next significant breakthrough in the SRF cavity technology is only possible if the physics of surface resistance is fully understood. The main goal of this research is to provide an understanding of the origin of the various contributions to the power dissipation in superconducting niobium and in particular the origin of the non-linear behavior as a function of the radio frequency field. This award includes integrated experimental and theoretical parts to address the unresolved issues of the surface resistance of superconductors at high radio frequency field, and in particular how the surface composition and structure can be modified and tuned in order to reduce surface resistance. The theoretical work will guide the experimental work which, in turn, will provide feedback to further develop the theory. This research will be performed by two graduate students and thus contribute to the education of accelerator scientists, who are in extremely short supply. The successful completion of this work will be very beneficial for the ongoing R&D of high performance SRF cavities. Addressing the outstanding problems of the residual surface resistance and the increase of the quality factor Q with the radio frequency field magnitude can help guide the ongoing R&D of SRF cavities and evaluate possibilities of promising new materials as possible SRF materials. This work will have a significant impact on the application of the SRF technology in general, and to accelerators operating in continuous wave mode in particular.In this award some of the unresolved issues in our understanding of the surface resistance of superconductors will be addressed, in particular: (1) the physics of the residual resistance, which can exceed 20% of the theoretical contribution; (2) mechanisms of the observed increase of Q with the field and the possibilities of using this effect to extend the increase of Q to higher fields to boost the cavity performance; (3) possibilities of increasing the Q factor by managing impurities; and (4) making SRF materials other than Niobium useful for low field accelerator applications at low temperature.

超导射频（SRF）腔已在各种粒子加速器中使用相当长一段时间了。超导材料的超低电阻率使射频谐振器（加速器所需）能够获得高品质因数 (Q)，从而以极低的损耗进行能量存储。未来的加速器在科学和医学的许多领域都很重要，将受益于该奖项中的技术等进步。该奖项旨在表彰 SRF 加速器中使用的超导体的高级研究。 SRF 中使用的超导体受到基本表面电阻的限制。只有充分理解表面电阻的物理原理，SRF 腔技术的下一个重大突破才有可能实现。这项研究的主要目标是了解超导铌中功率耗散的各种贡献的起源，特别是作为射频场函数的非线性行为的起源。该奖项包括综合实验和理论部分，旨在解决高射频场下超导体表面电阻的未解决问题，特别是如何修改和调整表面成分和结构以降低表面电阻。理论工作将指导实验工作，反过来，实验工作将为进一步发展理论提供反馈。这项研究将由两名研究生进行，从而有助于加速器科学家的教育，而加速器科学家的供应极其短缺。这项工作的成功完成对于高性能SRF腔体的持续研发将非常有益。解决残余表面电阻和品质因数Q随射频场强度增加的突出问题可以帮助指导SRF腔体的持续研发，并评估有前途的新材料作为可能的SRF材料的可能性。这项工作将对SRF技术的一般应用，特别是对连续波模式下运行的加速器产生重大影响。在这个奖项中，我们对超导体表面电阻的理解中一些未解决的问题将得到解决，特别是：（1）残余电阻的物理原理，它可以超过理论贡献的20％； (2) 观察到的 Q 随场增加的机制以及利用这种效应将 Q 的增加扩展到更高场以提高腔性能的可能性； (3)通过管理杂质来提高Q因子的可能性； (4)使铌以外的SRF材料可用于低温下的低场加速器应用。