In this work we describe a high-resolution position-sensitive detector for positronium. The detection scheme is based on the photoionization of positronium in a magnetic field and the imaging of the freed positrons with a Microchannel Plate assembly. A spatial resolution of ± (88 5) μm on the position of the ionized positronium -in the plane perpendicular to a 1.0 T magnetic field-is obtained. The possibility to apply the detection scheme for monitoring the emission into vacuum of positronium from positron/positronium converters, imaging posihttps://doi.

Positronium in the 2 3 S metastable state exhibits a low electrical polarizability and a long lifetime (1140 ns) making it a promising candidate for interferometry experiments with a neutral matterantimatter system. In the present work, 2 3 S positronium is produced -in absence of electric field -via spontaneous radiative decay from the 3 3 P level populated with a 205 nm UV laser pulse. Thanks to the short temporal length of the pulse, 1.5 ns full-width at half maximum, different velocity populations of a positronium cloud emitted from a nanochannelled positron/positronium converter were selected by delaying the excitation pulse with respect to the production instant. 2 3 S positronium atoms with velocity tuned between 7 · 10 4 m s −1 and 10 · 10 4 m s −1 were thus produced. Depending on the selected velocity, a 2 3 S production efficiency ranging from ∼ 0.8% to ∼ 1.7%, with respect to the total amount of emitted positronium, was obtained. The observed results give a branching ratio for the 3 3 P-2 3 S spontaneous decay of (9.7 ± 2.7)%. The present velocity selection technique could allow to produce an almost monochromatic beam of ∼ 1 · 10 3 2 3 S atoms with a velocity spread < 10 4 m s −1 and an angular divergence of ∼ 50 mrad.

We describe a multi-step "rotating wall" compression of a mixed cold antiproton-electron non-neutral plasma in a 4.46 T Penning-Malmberg trap developed in the context of the AEḡIS experiment at CERN. Such traps are routinely used for the preparation of cold antiprotons suitable for antihydrogen production. A tenfold antiproton radius compression has been achieved, with a minimum antiproton radius

Antihydrogen atoms with K or sub-K temperature are a powerful tool to precisely probe the validity of fundamental physics laws and the design of highly sensitive experiments needs antihydrogen with controllable and well defined conditions. We present here experimental results on the production of antihydrogen in a pulsed mode in which the time when 90% of the atoms are produced is known with an uncertainty of ~250 ns. The pulsed source is generated by the charge-exchange reaction between Rydberg positronium atoms—produced via the injection of a pulsed positron beam into a nanochanneled Si target, and excited by laser pulses—and antiprotons, trapped, cooled and manipulated in electromagnetic traps. The pulsed production enables the control of the antihydrogen temperature, the tunability of the Rydberg states, their de-excitation by pulsed lasers and the manipulation through electric field gradients. The production of pulsed antihydrogen is a major landmark in the AE$$\bar{g}$$ ḡ IS experiment to perform direct measurements of the validity of the Weak Equivalence Principle for antimatter.

No abstract