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.
- Battery research: visualisation of aging processes operandoLithium button cells with electrodes made of nickel-manganese-cobalt oxides (NMC) are very powerful. Unfortunately, their capacity decreases over time. Now, for the first time, a team has used a non-destructive method to observe how the elemental composition of the individual layers in a button cell changes during charging cycles. The study, now published in the journal Small, involved teams from the Physikalisch-Technische Bundesanstalt (PTB), the University of Münster, researchers from the SyncLab research group at HZB and the BLiX laboratory at the Technical University of Berlin. Measurements were carried out in the BLiX laboratory and at the BESSY II synchrotron radiation source.
- New instrument at BESSY II: The OÆSE endstation in EMILA new instrument is now available at BESSY II for investigating catalyst materials, battery electrodes and other energy devices under operating conditions: the Operando Absorption and Emission Spectroscopy on EMIL (OÆSE) endstation in the Energy Materials In-situ Laboratory Berlin (EMIL). A team led by Raul Garcia-Diez and Marcus Bär showcases the instrument’s capabilities via a proof-of-concept study on electrodeposited copper.
- Green hydrogen: A cage structured material transforms into a performant catalystClathrates are characterised by a complex cage structure that provides space for guest ions too. Now, for the first time, a team has investigated the suitability of clathrates as catalysts for electrolytic hydrogen production with impressive results: the clathrate sample was even more efficient and robust than currently used nickel-based catalysts. They also found a reason for this enhanced performance. Measurements at BESSY II showed that the clathrates undergo structural changes during the catalytic reaction: the three-dimensional cage structure decays into ultra-thin nanosheets that allow maximum contact with active catalytic centres. The study has been published in the journal ‘Angewandte Chemie’.