Cutting-edge research in Berlin: BESSY II light source to be equipped with new features and capabilities

With the transformation of the BESSY II light source into a variable-pulse-length storage ring, Berlin will become even more attractive as a location for science to researchers from the world over

The Senate of the Helmholtz Association resolved on June 1st, 2017 to support the transformation of BESSY II into a variable-pulse-length storage ring (BESSY-VSR). The Helmholtz Association will provide funding of 11.9 million euros for the upgrade project, with 10.1 million euros provided by internal resources of its operator, the Helmholtz-Zentrum Berlin (HZB). Following the upgrade, BESSY-VSR will be the first synchrotron light source in the world to deliver brilliant X-ray pulses with user-selectable durations: short and long light pulses will be simultaneously produced in the same ring. This will open up new opportunities for researchers, including new studies on energy materials that contribute to sustainable energy supplies and storage.

BESSY II is a light source providing VUV and soft X-rays operated by the Helmholtz-Zentrum Berlin. As a third-generation synchrotron light source, it has been providing an outstanding and reliable research environment since 1998 not only for researchers at HZB who primarily use the light for research on energy materials, but also for the approximately 2000 guest researchers who travel each year to Berlin from the world over in order to study their samples at BESSY II.

During its current regular operations, BESSY II provides brilliant X-ray pulses having a duration of 17 picoseconds (1 picosecond = 10^-12 s). It is already feasible for a few days each year to change the operating mode over so that samples can also be studied using shorter pulses of about three picoseconds. Short pulses are necessary in order to image fast atomic processes over time, for example. Up to now, though, this allocation sharply reduced the intensity of the photon flux to only a fraction of its regular level.

BESSY-VSR will offer both short and longer light pulses

The upgrade will usher in some important innovations. BESSY-VSR will offer short light pulses with durations of two picoseconds as well as longer pulses with durations of 15 picoseconds, while the high level of photon flux remains constant – even during the shorter pulses. Users will be able to select the pulse length necessary for their experiment and even combine differing pulse lengths for experiments requiring this.

That will bring advancements in energy materials research at HZB. Scientists will be able to trace how the electronic structure of reactants changes during a chemical reaction, for example.

“I am very pleased that we were able to persuade the Senate of the Helmholtz Association of the project’s quality”, says Prof. Bernd Rech, acting Scientific Director of the HZB. “The upgrade ensures that we will continue to operate a synchrotron light source in Berlin that meets world-wide demand.”

Superconducting high-power cavity resonators are one of the things needed to realise BESSY-VSR. The State of Berlin has made available 7.4 million euros from the European Regional Development Fund (ERDF) for the set up of the SupraLab@HZB application lab that will carry out the advanced development of these cavity resonators. Researchers together with collaborating industrial organisations will develop the technology to the point where it is ready for incorporation in BESSY-VSR and other synchrotron light sources.