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Abstract In this work, we discuss the possibility of inertial sensing with positronium in the 23S metastable state for the measurement of optical dipole, relativistic and gravitational forces on a purely leptonic matter-antimatter system. Starting from the characteristics of an available 23S beam, we estimate the time necessary to measure accelerations ranging from ~105 m/s2 to 9.1 m/s2 with two different inertial sensitive devices: a classical moiré deflectometer and a Mach–Zehnder interferometer. The sensitivity of the Mach–Zehnder interferometer has been estimated to be several tens of times better than that of the moiré deflectometer, for the same measurement time. Different strategies to strengthen the 23S beam flux and to improve the sensitivity of the devices are proposed and analyzed. Among them, the most promising are reducing the divergence of the positronium beam through 2D laser Doppler cooling and coherent positronium Raman excitation from the ground state to the 23S level. If implemented, these improvements promise to result in the time required to measure an acceleration of 9.1 m/s2 of few weeks and 100 m/s2 of a few hours. Different detection schemes for resolving the fringe pattern shift generated on 23S positronium crossing the deflectometer/interferometer are also discussed. Graphical abstract

Abstract The process of implantation and diffusion of positron in nanochanneled silicon crystals has been simulated in detail through the Monte Carlo technique. Our implantation simulations evidenced the fraction of empty volume inside the sample to be the decisive factor in the determination of the shape of the implantation profile, with the specific shape of the nanoscopic structure playing a marginal role for implantation processes with an energy above 3 keV. Moreover we observed that, due to the high density of surfaces inside of the silicon sample, the subsequent diffusion process is highly suppressed and that thermalized positrons reach the surface of a nanoscopic channel close to their implantation depth. Due to this suppression of the diffusion process, 60–80% of the positrons implanted at an energy comprised between 4 and 13 keV will reach, at thermal energy, the surface of a channel without escaping the sample or undergoing annihilation. Graphical abstract

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 ḡ IS experiment to perform direct measurements of the validity of the Weak Equivalence Principle for antimatter. Antihydrogen atoms are a unique type of antimatter that can be used to probe small violations of fundamental laws of physics. The authors present experimental results obtained with the AEgIS project at CERN for the production of antihydrogen atoms (Hbar) via charge exchange with laser excited positronium that allow for precise timing of Hbar production.

Abstract 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 of only 0.17 mm. We describe the experimental conditions necessary to perform such a compression: minimizing the tails of the electron density distribution is paramount to ensure that the antiproton density distribution follows that of the electrons. Such electron density tails are remnants of rotating wall compression and in many cases can remain unnoticed. We observe that the compression dynamics for a pure electron plasma behaves the same way as that of a mixed antiproton and electron plasma. Thanks to this optimized compression method and the high single shot antiproton catching efficiency, we observe for the first time cold and dense non-neutral antiproton plasmas with particle densities n ≥ 1013 m−3, which pave the way for an efficient pulsed antihydrogen production in AEḡIS. Graphical abstract

The AEg̅IS collaboration at CERN’s AD produces antihydrogen atoms in the form of a pulsed, isotropic source with a precisely defined formation time. AEg̅IS has recently undergone major upgrades to fully benefit from the increased number of colder antiprotons provided by the new ELENA decelerator and to move toward forming a horizontal beam to directly investigate the influence of gravity on the H̅ atoms, thereby probing the Weak Equivalence Principle for antimatter. This contribution gives an overview of these upgrades as well as subsequent results from the first beam times with ELENA.

The AEgIS experiment aims at producing antihydrogen (and eventually measuring the effects of the Earth gravitational field on it) with a method based on the charge exchange reaction between antiproton and Rydberg positronium. To be precise, antiprotons are delivered by the CERN Antiproton Decelerator (AD) and are trapped in a multi-ring Penning trap, while positronium is produced by a nanoporous silica target and is excited to Rydberg states by means of a two steps laser excitation. New Monte Carlo simulations are presented in this paper in order to investigate the current status of the AEgIS experiment [1] and to interpret the recently collected data [2].

Positronium is the simplest bound state, built of an electron and a positron. Studies of positronium in vacuum and its decays in medium tell us about Quantum Electrodynamics, QED, and about the structure of matter and biological processes of living organisms at the nanoscale, respectively. Spectroscopic measurements constrain our understanding of QED bound state theory. Searches for rare decays and measurements of the effect of gravitation on positronium are used to look for new physics phenomena. In biological materials positronium decays are sensitive to the inter- and intra-molecular structure and to the metabolism of living organisms ranging from single cells to human beings. This leads to new ideas of positronium imaging in medicine using the fact that during positron emission tomography (PET) as much as 40% of positron annihilation occurs through the production of positronium atoms inside the patient's body. A new generation of the high sensitivity and multi-photon total-body PET systems opens perspectives for clinical applications of positronium as a biomarker of tissue pathology and the degree of tissue oxidation.

We report on recent developments in positronium work in the frame of antihydrogen production through charge exchange in the AEgIS collaboration [1]. In particular, we present a new technique based on spatially imaging a cloud of positronium by collecting the positrons emitted by photoionization. This background free diagnostic proves to be highly efficient and opens up new opportunities for spectroscopy on antimatter, control and laser manipulation of positronium clouds as well as Doppler velocimetry.

We describe a novel method to use a scintillating fiber detector similar to the Fast Annihilation Cryogenic Tracking (FACT) used at the antimatter experiment AEgIS to monitor the presence of ortho-positronium. A single scintillating fiber was coupled to a photomultiplier tube and irradiated by flashes of about \\(610^6\\) \\(511\\,keV\\) \\(\\)-rays produced by \\(10\\,ns\\) long positron pulses. The results were used to demonstrate the ability to track the creation and annihilation of ortho-positronium atoms over time in cryogenic and highly magnetic environments by using the FACT detector as a \"digital calorimeter\".