The variable pulse-length storage ring proposed by Helmholtz-Zentrum Berlin (BESSY-VSR)

BESSY-VSR is a novel approach to create in the Storage Ring BESSY II long and short photon pulses simultaneously for all beam lines through a pair of superconducting bunch compression cavities. Pulse-picking schemes will allow each individual user to freely switch between high average flux for X-ray spectroscopy, microscopy and scattering and picosecond pulses up to 500 MHz repetition rate for dynamic studies. Thus BESSY-VSR preserves the present average brilliance of BESSY II and adds the new capability of user accessible picosecond pulses at high repetition rate.

The investigations with X-rays from BESSY-VSR are highly complementary and compatible to dynamic studies conducted by users with optical lasers at their home universities and laboratories. BESSY-VSR represents also a missing link between the extreme average brilliance of ultimate storage rings like PETRA III and Free Electron Lasers. Technologically, the employed superconducting bunch compression cavities in BESSY-VSR are a direct synergy to the CW superconducting cavities developed for BERLinPro.