Green light for upgrading BESSY II into a variable-pulse-length storage ring (BESSY-VSR)

With the upgrade BESSY VSR, Helmholtz-Zentrum Berlin will continue in future to offer a highly demanded synchrotron source for energy materials research with international appeal. Photo: ©: / Robert Grahn

The General Assembly of the Helmholtz Association has unanimously endorsed the realisation of a unique accelerator project at the BESSY II synchrotron radiation source

The General Assembly of the Helmholtz Association unanimously supports the Helmholtz-Zentrum Berlin’s proposed concept for upgrading BESSY II into a variable-pulse-length storage ring (BESSY- VSR). The body of chairpersons from the 18 Helmholtz Centres has unanimously suggested to the Senate of the Helmholtz Association the financial subsidising of BESSY-VSR to the sum of 11.8  million euros. Converting BESSY II into a variable-pulse-length storage ring is a unique project in accelerator research and has attracted great interest and support from the expert community.

After the upgrade, BESSY VSR will deliver its brilliant X-ray pulses of different durations. This gives researchers entirely new opportunities for development of energy materials that will contribute towards the sustainable supply and storage of energy. A total of 29 million euros are being invested in the upgrade of BESSY II. BESSY-VSR is an essential component of the HZB Strategy 2020+, for which HZB has received the explicit agreement of the Supervisory Board and of the Helmholtz Association.

Scientific director of HZB, Prof. Anke Kaysser-Pyzalla, emphasised the strategic importance of BESSY- VSR to Helmholtz-Zentrum Berlin. “I am pleased that we were able to convince the General Assembly of the quality of the project, and thank the researchers involved for the outstanding preparation of the BESSY-VSR concept, which shows in great detail the technical feasibility of the highly ambitious project. From detailed discussions among the experts, we know that there is enormous interest in upgrading BESSY II into a variable-pulse-length storage ring. The upgrade will ensure that Helmholtz-Zentrum Berlin will continue to offer a synchrotron source for energy materials research that has international appeal and will be in great demand.”

BESSY-VSR offers short and long pulses at the same time

HZB operates the BESSY II light source in the soft X-ray and VUV X-ray range, which is especially suitable for researchingnew energy materials. In its normal operating mode, BESSY II currently delivers high-brilliancy X-ray pulses having a duration of 17 picoseconds (1 picosecond = 10-12 s). Additionally, it is already possible to convert BESSY II to a different operating mode for a few days per year in order to study samples using extremely short pulses (about 3 picoseconds). To do so, however, the photon flux has to be greatly reduced. This will fundamentally change with BESSY-VSR. "With the BESSY-VSR variable-pulse-length storage ring, the high proton  flux remains constant and our users will be able to select the necessary pulse length at any time and for any experiment", explains Prof. Dr. Andreas Jankowiak, head of the Institute for Accelerator Physics. BESSY-VSR will offer short pulses of 1.5 picosecond length and longer pulses of 15 picoseconds. BESSY-VSR thus fills a gap between storage rings such as PETRA III and the free-electron lasers.

Many research fields will benefit from the selectable pulse lengths. Scientists could, for example, gain new insights into ultrafast changes in electronic structure during chemical reactions, investigate quantum-physical effects on a picosecond timescale, or observe fast switching processes in novel materials for future information technologies. Prof. Dr. Alexander Föhlisch, head of the HZB Institute of Methods and Instrumentation for Synchrotron Radiation Research, developed the scientific case for the BSSY-VSR project. 

Developing new accelerator components for realising BESSY-VSR

Realising BESSY-VSR will require, among other things, high-current superconducting cavity resonators. These are key components in the operation of BESSY-VSR. The State of Berlin is providing HZB with generous financial support of 7.4 million euros from the European Regional Development Fund (ERDF) for developing these resonators and setting up the “SupraLab@HZB” application laboratory. “We therefore have the opportunity to advance this technology substantially, until it can be applied in light sources. This will also benefit the realisation of BESSY-VSR,” says Prof. Dr. Jens Knobloch, head of the HZB Institute of SRF – Science and Technology.

Broad approval of BESSY-VSR in the expert community

HZB is conducting detailed discusssions to ensure the needs of users are given central importance in the advanced development of BESSY II. The Komitee Forschung mit Synchrotronstrahlung (KFS), which represents German synchrotron users, approved of the upgrade of BESSY-VSR and stressed its relevance: “The BESSY-VSR project will add unique capabilities to the facilities available for synchrotron users in Germany, Europe, and the world.” An independent body of experts, the Machine Advisory Committee (MAC), confirmed: “The BESSY-VSR approach is a perfect match for BESSY II and its user community.”

 Clips about BESSY VSR

- about the project

- about the principle and the problem of BESSY VSR