Accelerators 2013.

Looking back over the year 2013 reveals tremendous progress and success with our accelerator activities at DESY, in machine operation and construction projects as well as research and development. At the same time, we had to face a few challenges in some areas. The PETRA III synchrotron radiation source was switched from positron to electron operation during the 2012/13 Christmas shutdown. The restart in January went remarkably well and quickly, putting the machine back into regular user operation without delay. The beam dynamics issues due to electron cloud effects, which had manifested themselves during positron operation in an increase of the vertical emittance for certain bunch patterns, had disappeared, as expected. Electron beam operation now shows signs of beam–ion instability, but these occur only in a smaller range of operation modes and are generally less harmful than the previous electron cloud effects. The PETRA III user run, originally scheduled until September, was extended until Christmas 2013 because of a delay in the start of civil construction work for the PETRA III extension project. The operation of PETRA III was very satisfactory throughout most of the year, with availability slightly above the design goal of 95%. In the fourth quarter, however, a few failures caused the yearly averaged availability to drop slightly below 95%. Test beams at the DESY II synchrotron were delivered with more than 98% availability and were used heavily throughout the year. After a few challenges with the tendering for the PETRA III extension civil construction work, orders were placed and first preparatory work started in late autumn 2013. During a few-week summer break of user operation, the PETRA III team performed very interesting and successful machine studies at reduced beam energy, demonstrating a world record of 160 pm rad in horizontal emittance at 3 GeV, fully in accordance with theoretical expectations. These studies are important for future considerations of a possible upgrade of PETRA III to a diffraction-limited storage ring.