ELENA prepares a bright future for antimatter research
At its recent session in June, the CERN Council approved the construction of the Extra Low ENergy Antiproton ring (ELENA) – an upgrade of the existing Antiproton Decelerator. ELENA will allow the further deceleration of antiprotons, resulting in an increased number of particles trapped downstream in the experimental set-ups. This will give an important boost to antimatter research in the years to come.
Layout of the AD experimental hall: the Antiproton Decelerator ring (purple); the ALPHA, ASACUSA, and ATRAP experiments (green); the ACE experiment (not pictured); and the new ELENA ring (blue).
The Antiproton Decelerator (AD) is CERN’s widely recognized facility for the study of antimatter properties. The recent successes of the AD experiments are just the latest in a long list of important scientific results that started with LEAR (Low Energy Antiproton Ring). The scientific demand for low-energy antiprotons at the AD continues to grow. There are now four experiments running there (ATRAP, ALPHA, ASACUSA and ACE); a fifth, AEGIS, has been approved and will take beam for the first time at the end of the year. Further proposals are under consideration. Thus, CERN’s unique Antiproton Decelerator can no longer provide the number of antiprotons needed. As antihydrogen studies evolve into antihydrogen spectroscopy and gravitational measurements, the shortage will become even more acute.
The solution is a small magnet ring that will fit inside the present AD hall – ELENA, the recently approved upgrade of CERN’s antimatter factory. ELENA – a 30 m circumference decelerator – will slow the 5.3 MeV antiprotons from the AD to an energy of just 100 keV. Receiving slower antiprotons will help the experiments improve their efficiency in creating antimatter atoms in order to study their properties. In today’s set-up, about 99.9% of the antiprotons produced by the AD are lost due to the experiments' use of degrader foils needed to further decelerate them from the AD ejection energy down to around 5 keV, the energy needed for trapping. ELENA will bring a 10 to 100-fold increase in the experiments’ efficiency, as well as the possibility to accommodate an extra experimental area.
The new ring is located such that its assembly and commissioning will have a minimal impact on the current AD operation. In fact, the commissioning of the ELENA ring will essentially take place in parallel with the present physics programme, with short periods dedicated to commissioning during the physics run. The AD experimental area layout will not be significantly modified, but the much lower beam energies require the design and construction of completely new electrostatic transfer lines.
The construction of ELENA should begin in 2013, and the first physics injection should follow about 3 years later. The initial phase of the work will include the installation and commissioning of the ELENA ring while using the existing AD beam lines. The old ejection lines in all the experimental areas will then be replaced by the new electrostatic beam lines that will deliver antiprotons at the design energy of 100 keV. In its final configuration, ELENA will be able to deliver beams almost simultaneously to four experiments, resulting in a vital gain in total beam time for each experiment.
