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Exceptionally slow antiprotons


ELENA ring - start of first beam
The commissioning of ELENA continued in 2018, culminating in the production of the first very-low-energy antiproton beams (Image: CERN)


ELENA (Extra Low ENergy Antiproton), the new antimatter deceleration ring, will soon form the link between the Antiproton Decelerator (AD) and the antimatter experiments. At present, ELENA is able to supply only the GBAR experiment, which received its first beams of antiprotons last year, but during Long Shutdown 2 (LS2), extraction lines will be installed between ELENA and the other experiments (ALPHA, ASACUSA, ATRAP and BASE).

“During the 2017/2018 extended year-end technical stop (EYETS), we were able to install the electron cooling system,” explains Gérard Tranquille, who is responsible for this essential equipment. “Even though we had to resolve a vacuum leak problem, we were able to install the ELENA ring in its nominal configuration and continue with the commissioning.” The electron cooling system makes it possible to concentrate the particle beams by reducing the beam emittance, or in other words, the transverse dimensions of the beam and its energy spread. In this way, the experiments can be supplied with denser beams, increasing their chances of trapping antiprotons.

The members of the team had to deal with several technical problems during commissioning, but they are pleased with the machine’s performance: “The last tests carried out in November were very encouraging,” explains Christian Carli, ELENA project leader. “We were able to produce antiproton beams with characteristics that were sufficiently close to the nominal values,” adds Tommy Eriksson, who is responsible for organising the machine’s commissioning. “Thanks to ELENA, the antimatter experiments will see a notable improvement in their operating conditions, as they will have the opportunity to work with beams with an energy of 0.1 MeV.”

Following the tests with beam in November, the transport team and the people in charge of the equipment, with the support of the technical coordination team, started dismantling the magnetic lines connecting the AD to the experiments in the old experiment area. “These lines are gradually being replaced by the electrostatic lines that will connect ELENA to the experiments,” explains François Butin, the project’s technical coordinator. “There’s no turning back now... but we have every faith in ELENA; we’re sure that the machine will be ready to supply very-low-energy antiproton beams after LS2,” concludes Wolfgang Bartmann, who is in charge of coordinating the design and construction of these lines.


For more information on ELENA, see our previous articles: