The recently recommended experiment GBAR is foreseen to run at CERN at the AD/ELENA antiproton source. It aims at performing the first measurement of the Earth's gravitational acceleration on antimatter by observing the free-fall of antihydrogen atoms. This requires creating anti-atoms at an unprecedented low energy. The different steps of the experiment and their present status are reviewed.

The GBAR experiment: gravitational behaviour of antihydrogen at rest

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Proposal to measure the Gravitational Behaviour of Antihydrogen at Rest

The Einstein classical Weak Equivalence Principle states that the trajectory of a particle is independent of its composition and internal structure when it is only submitted to gravitational forces This fundamental principle has never been directly tested with antimatter However, theoretical models such as supergravity may contain components inducing repulsive gravity, thus violating this principle The GBAR project (Gravitational Behaviour of Antihydrogen at Rest) proposes to measure the free fall acceleration of ultracold neutral antihydrogen atoms in the terrestrial gravitational field The experiment consists in preparing antihydrogen ions (one antiproton and two positrons) and sympathetically cool them with Be+ ions to a few 10 μ K The ultracold ions will then be photoionized just above threshold, and the free-fall time over a known distance measured In this work, the GBAR project is described as well as possible improvements that use quantum reflection of antihydrogen on surfaces to use quantum methods of measurements

The Gbar project, or how does antimatter fall?

"Ion surfing" with radiofrequency carpets

High-precision Penning trap mass measurements of 9,10Be and the one-neutron halo nuclide 11Be

A segmented, radiofrequency quadrupole mass filter COLETTE (Cooler for Emittance Elimination) was designed for cooling continuous radioactive beams for injection into the transmission spectrometer MISTRAL at CERN–ISOLDE. A description of the design of COLETTE is given, along with details of performance including measured emittances of less than 8 π mm mrad with 20 keV beams from the test bench SIDONIE in Orsay. On-line results with stable and short-lived radionuclide beams from ISOLDE are also presented.

Sylvain Henry

Papers

COLETTE: A linear Paul-trap beam cooler for the on-line mass spectrometer MISTRAL