Accelerator physics: alternative material investigated for superconducting radio-frequency cavity resonators
The photomontage shows a sample of solid, pure niobium before coating (left), and coated with a thin layer of Nb3Sn (right). © HZB
In modern synchrotron sources and free-electron lasers, superconducting radio-frequency cavity resonators are able to supply electron bunches with extremely high energy. These resonators are currently constructed of pure niobium. Now an international collaboration has investigated the potential advantages a niobium-tin coating might offer in comparison to pure niobium.
At present, niobium is the material of choice for constructing superconducting radio-frequency cavity resonators. These will be used in projects at the HZB such as bERLinPro and BESSY-VSR, but also for free-electron lasers such as the XFEL and LCLS-II. However, a coating of niobium-tin (Nb3Sn) could lead to considerable improvements.
Coatings may save money and energy
Superconducting radio-frequency cavity resonators made of niobium must be operated at 2 Kelvin (-271 degrees Celsius), which requires expensive and complicated cryogenic engineering. In contrast, a coating of Nb3Sn might make it possible to operate resonators at 4 Kelvin instead of 2 Kelvin and possibly withstand higher electromagnetic fields without the superconductivity collapsing. In the future, this could save millions of euros in construction and electricity costs for large accelerators, as the cost of cooling would be substantially lower.
Experiments in the USA, Canada, Switzerland and HZB
A team led by Prof. Jens Knobloch, who heads the SRF Institute at HZB, has now carried out tests of superconducting samples coated with Nb3Sn by Cornell University, USA, in collaboration with colleagues from the USA, Canada, and Switzerland. The experiments took place at the Paul Scherrer Institute, Switzerland, at TRIUMF, Canada, and the HZB.
“We measured the critical magnetic field strengths of superconducting Nb3Sn samples in both static and radio-frequency fields”, says Sebastian Keckert, first author of the study, who is doing his doctorate as part of the Knobloch team. By combining different measurement methods, they were able to confirm the theoretical prediction that the critical magnetic field of Nb3Sn in radio-frequency fields is higher than that for static magnetic fields. However, the coated material should display a very much higher critical magnetic field level in a radio-frequency field. Thus, the tests have also shown that the coating process used currently for the production of Nb3Sn might be improved upon in order to more closely approach the theoretical values.
The publication has been mentioned on the Cover of „Superconductor Science and Technology“ , (2019): Critical fields of Nb3Sn prepared for superconducting cavities; S. Keckert, T. Junginger, T. Buck, D. Hall, P. Kolb, O. Kugeler, R. Laxdal, M. Liepe, S. Posen , T. Prokscha, Z. Salman, A. Suter and J. Knobloch.
doi:10.1088/1361-6668/ab119e
- Technology Transfer Prize Ceremony 2025This year’s Technology Transfer Prize Ceremony will take place on October 13 at 2 pm in the Lecture Hall, BESSY II Building, Adlershof.
- Novel technique shines light on next-gen nanomaterials: how MXenes truly workResearchers have for the first time measured the true properties of individual MXene flakes — an exciting new nanomaterial with potential for better batteries, flexible electronics, and clean energy devices. By using a novel light-based technique called spectroscopic micro-ellipsometry, they discovered how MXenes behave at the single-flake level, revealing changes in conductivity and optical response that were previously hidden when studying only stacked layers. This breakthrough provides the fundamental knowledge and tools needed to design smarter, more efficient technologies powered by MXenes.
- Porous Radical Organic framework improves lithium-sulphur batteriesA team led by Prof. Yan Lu, HZB, and Prof. Arne Thomas, Technical University of Berlin, has developed a material that enhances the capacity and stability of lithium-sulphur batteries. The material is based on polymers that form a framework with open pores (known as radical-cationic covalent organic frameworks or COFs). Catalytically accelerated reactions take place in these pores, firmly trapping polysulphides, which would shorten the battery life. Some of the experimental analyses were conducted at the BAMline at BESSY II.