New cavities successfully installed
The new cavities during their installation. © C. Jung /HZB
A glimps at the water circuits. © C. Jung / HZB
At the heart of BESSY II are four cavities, hollow resonators, providing the energy that electrons in the storage ring re-absorb after they have released it as light packets. The old cavities were still from the 1970s and were employed at DESY in Hamburg, then at BESSY I, and finally at BESSY II beginning in 1998. “However, the limit of their operating life has been reached”, says Dr. Wolfgang Anders from the HZB Institute of SRF – Science and Technology. Anders, an expert in the field, was responsible for replacing two of the four old cavities with new units during the summer shutdown.
The new cavities have been developed as an EU Project under the supervision of HZB. They are constructed of copper, as before, but have a somewhat more complex shape that is optimised to effectively avoid exciting undesirable oscillations, known as “higher-order modes”. These higher modes are excited by high beam energies and can lead to instabilities.
“The new cavities are significantly more robust and can store up to 80 kilowatts – twice as much as the old cavities. As a result, the requirements for cooling have increased as well”, explains Anders, pointing out the multitude of coolant pipes around the new cavities.
The beam energy at BESSY II is presently still restricted because the vacuum in the new cavities is still improving slowly. “We will be normalising the vacuum conditions over Christmas so that we can operate BESSY II at full beam energy afterwards”, says Anders.
Both of the other old cavities will be replaced during the 2015 summer shutdown so that all the advantages of the new cavities can come into play.
- 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.
- 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.
- Metallic nanocatalysts: what really happens during catalysisUsing a combination of spectromicroscopy at BESSY II and microscopic analyses at DESY's NanoLab, a team has gained new insights into the chemical behaviour of nanocatalysts during catalysis. The nanoparticles consisted of a platinum core with a rhodium shell. This configuration allows a better understanding of structural changes in, for example, rhodium-platinum catalysts for emission control. The results show that under typical catalytic conditions, some of the rhodium in the shell can diffuse into the interior of the nanoparticles. However, most of it remains on the surface and oxidises. This process is strongly dependent on the surface orientation of the nanoparticle facets.