The storage ring BESSY II in Adlershof is at present the only third generation synchrotron radiation source in Germany. BESSY II emits extremely brilliant photon pulses ranging from the long wave terahertz region to hard X rays. Users can choose the energy range and the polarisation of the radiation. The forty six beam holes at the undulator, wiggler, and dipole sources offer users a many-faceted mix of beam holes and measuring sites with outstanding energy resolution. The combination of brilliance and photon pulses makes BESSY II the ideal microscope for space and time, allowing resolutions down to femtoseconds and picometres.
The profile of BESSY II is defined to a great degree by the users, now over 2500 in number. An important role is played by the scientists at the HZB, but also the institutional users like the Max Planck Society, the Federal Institute for Materials Research and Testing, and collaborating research groups. Consequently, as a result of the activities by the Physical Technical Institute PTB, BESSY II is the European radiation standard for the calibration of light sources and detectors.