The German lab DESY is saying good-bye to one of its accelerator workhorses, the DORIS ring. On 2 January 2013 the final beam will go round its tunnel. It has already stopped being a light source: the last positron beam reached the HASYLAB experimental huts on 22 October. Between then and now, DORIS reverted to its original raison d’etre: an accelerator for particle physics.
DORIS, a child of the 70s, has had many lives. As one of the world’s first storage rings, it helped to investigate the properties of quarks, shed light on CP violation with the ARGUS experiment and was turned into an X-ray source in 1991. Bronze-age axes, van Gogh paintings, corals, magnetic nanostructures all sat in its X-ray beam, giving thousands of scientists from around the world insight into a wealth of worlds and even leading to a Nobel Prize for the investigation of the structure of the ribosome. Its last few months are devoted to particle physics again: the OLYMPUS experiment looks at the scattering of electrons and positrons by protons and the photon exchange that is happening during the scattering process.
A big shutdown celebration is planned in May 2013.