ELENA: the extra low energy anti-proton facility at CERN

At the last LEAP conference in Vancouver 2011 the authors stated that a project ”ELENA”, as an abbreviation for Extra Low ENergy Antiproton ring and as first discussed in 1982 for LEAR by H. Herr et al., was freshly proposed with a substantial new design and revised layout and that it was under consideration to be built at CERN. ELENA is an upgrade of the Anti-proton Decelerator (AD) at CERN and is devoted to special experiments with physics using low energy anti-protons. The main topics are the anti-hydrogen production and consecutive studies of the features of this anti-matter atom as well as the anti-proton nucleon interaction by testing the QED to high precision. During the last years the project underwent several steps in presentations at different committees at CERN and was finally approved such that the construction has started. ELENA will increase the number of useful anti-protons by about two orders of magnitude and will allow to serve up to four experiments simultaneously. Very first and convincing results from the experiments at the AD have been published recently. For high precision physics, however, it appears to be cumbersome, time consuming and ineffective when collecting the needed large numbers and high densities of anti-proton clouds with the present AD. Both the effectiveness and the availability for additional experiments at this unique facility will drastically increase, when the anti-proton beam of presently 5 MeV kinetic energy is reduced by the additional decelerator ELENA to 100 keV.