Burkart, F. Aßmann, R.W. Dinter, H. Jaster-Merz, S. Kuropka, W. Mayet, F. Vinatier, T. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-215-8 10.18429/JACoW-LINAC2022-THPOJO01 English 691-694 experiment electron linac acceleration diagnostics Contribution to a conference proceedings 2022 2022-09 https://doi.org/10.18429/JACoW-LINAC2022-THPOJO01 https://jacow.org/linac2022/papers/thpojo01.pdf The generation and acceleration of ultra-short, high quality electron beams has attracted more and more interest in accelerator science. Electron bunches with these properties are necessary to operate and test novel diagnostics and advanced high gradient accelerating schemes. Furthermore, several medical and industrial applications require high-brightness electron beams. The dedicated R&D linac ARES at DESY (Deutsches Elektronen-Synchrotron) is now fully operational and able to produce these electron beams at the nominal energy of 155 MeV and deliver it to users. This paper gives an overview of the ARES linac and summarizes the beam parameter measurements. The possibilities for user operation will be described in detail.