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
- What vibrating molecules might reveal about cell biologyInfrared vibrational spectroscopy at BESSY II can be used to create high-resolution maps of molecules inside live cells and cell organelles in native aqueous environment, according to a new study by a team from HZB and Humboldt University in Berlin. Nano-IR spectroscopy with s-SNOM at the IRIS beamline is now suitable for examining tiny biological samples in liquid medium in the nanometre range and generating infrared images of molecular vibrations with nanometre resolution. It is even possible to obtain 3D information. To test the method, the team grew fibroblasts on a highly transparent SiC membrane and examined them in vivo. This method will provide new insights into cell biology.
- Perovskite solar cells from Germany are competing with China's PV technology - HZB 2025 Technology Transfer AwardPhotovoltaics is the leading technology in the transition to clean energy. However, traditional silicon-based solar technology has reached its efficiency limit. Therefore, a HZB-team has developed a perovskite-based multi-junction cell architecture. For this, Kevin J. Prince and Siddhartha Garud received the Helmholtz-Zentrum Berlin's (HZB) Technology Transfer Prize of 5,000 euros.
- 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.