When you switch off a major accelerator after 15 years of data taking, you expect that someone will push a big red button. Instead, on 30 June at 11.23 p.m., Ferdinand Willeke – master of DESY's Hadron–Electron Ring Accelerator HERA – pushed two unremarkable grey buttons to dump the protons and positrons. That was the end of HERA, and the 80-strong crowd in the main control room applauded the team for years of successful collisions. Champagne flowed shortly after and the spectators toasted each other with pride, nostalgia and optimism.

Days before, DESY had celebrated its flagship machine in a two-day "HERA Fest" colloquium with international guests and HERA alumni and a party for staff and guests. More than 1800 people gathered in an enormous tent on the DESY site to listen to talks about scientific, technological and sociological achievements around the accelerator. "Exciting times are over – and more are ahead of us," said Rolf-Dieter Heuer, DESY Director for High Energy and Astroparticle Physics. "A new era starts now with the LHC and will hopefully continue with the ILC." "HERA will live on in physics textbooks and as a model for international collaboration," predicted Albrecht Wagner, chair of the DESY Directorate. And Brian Foster, former spokesperson of the ZEUS collaboration, admitted that there was "a certain amount of sadness. The detector worked like a dream and the collaboration formed a very good team".

In HERA, electrons and positrons collided with heavy protons and revealed details of proton structure. Physicists made detailed studies of the properties of the gluons inside the proton and proved the unification of two of nature's fundamental forces. Results from HERA have also helped in planning analyses for the LHC, and data analysis will continue well into the next decade. While the four experiments are being dismantled and in many cases shipped back to the institutes in charge, the accelerator remains in the tunnel, protected against wear, tear and corrosion. HERA is making way for one of DESY's next big projects, PETRA III, a high-brilliance synchrotron radiation source for X-rays. In the end, there was a big red button – on a whiteboard. Researchers had written farewells to their detector and the machine that drove it. Somebody had drawn a button with the caption "Push it".