A powerful and robust control system is a crucial, often neglected, pillar of any modern, complex physics experiment that requires the management of a multitude of different devices and their precise time synchronisation. The AEḡIS collaboration presents CIRCUS, a novel, autonomous control system optimised for time-critical experiments such as those at CERN’s Antiproton Decelerator and, more broadly, in atomic and quantum physics research. Its setup is based on Sinara/ARTIQ and TALOS, integrating the ALPACA analysis pipeline, the last two developed entirely in AEḡIS. It is suitable for strict synchronicity requirements and repeatable, automated operation of experiments, culminating in autonomous parameter optimisation via feedback from real-time data analysis. CIRCUS has been successfully deployed and tested in AEḡIS; being experiment-agnostic and released open-source, other experiments can leverage its capabilities.

We report on laser cooling of a large fraction of positronium (Ps) in free flight by strongly saturating the 1^{3}S-2^{3}P transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived 2^{3}P states. The second effect is one-dimensional Doppler cooling of Ps, reducing the cloud's temperature from 380(20) to 170(20) K. We demonstrate a 58(9)% increase in the fraction of Ps atoms with v_{1D}<3.7×10^{4}  ms^{-1}.

We report on laser cooling of a large fraction of positronium (Ps) in free flight by strongly saturating the 13S−23P transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived 23P states. The second effect is one-dimensional Doppler cooling of Ps, reducing the cloud’s temperature from 380(20) to 170(20) K. We demonstrate a 58(9)% increase in the fraction of Ps atoms with v1D<3.7×104 ms−1. Published by the American Physical Society 2024

Modern physics experiments are frequently very complex, relying on multiple simultaneous events to happen in order to obtain the desired result. The experiment control system plays a central role in orchestrating the measurement setup: However, its development is often treated as secondary with respect to the hardware, its importance becoming evident only during the operational phase. Therefore, the AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) collaboration has created a framework for easily coding control systems, specifically targeting atomic, quantum, and antimatter experiments. This framework, called Total Automation of LabVIEW Operations for Science (TALOS), unifies all the machines of the experiment in a single entity, thus enabling complex high-level decisions to be taken, and it is constituted by separate modules, called MicroServices, that run concurrently and asynchronously. This enhances the stability and reproducibility of the system while allowing for continuous integration and testing while the control system is running. The system demonstrated high stability and reproducibility, running completely unsupervised during the night and weekends of the data-taking campaigns. The results demonstrate the suitability of TALOS to manage an entire physics experiment in full autonomy: being open-source, experiments other than the AEgIS experiment can benefit from it.

The primary goal of the AEgIS experiment is to precisely measure the free fall of antihydrogen within Earth's gravitational field. To this end, a cold  50K antihydrogen beam has to pass through two grids forming a moiré deflectometer before annihilating onto a position-sensitive detector, which shall determine the vertical position of the annihilation vertex relative to the grids with micrometric accuracy. Here we introduce a vertexing detector based on a modified mobile camera sensor and experimentally demonstrate that it can measure the position of antiproton annihilations with an accuracy of 0.62^+0.40_-0.22μ m, which represents a 35-fold improvement over the previous state-of-the-art for real-time antiproton vertexing. Importantly, these antiproton detection methods are directly applicable to antihydrogen. Moreover, the sensitivity to light of the sensor enables the in-situ calibration of the moiré deflectometer, significantly reducing systematic errors. This sensor emerges as a breakthrough technology for achieving the scientific goals and has been selected as the basis for the development of a large-area detector for conducting antihydrogen gravity measurements.

Low-temperature antihydrogen atoms are an effective tool to probe the validity of the fundamental laws of Physics, for example the Weak Equivalence Principle (WEP) for antimatter, and -generally speaking- it is obvious that colder atoms will increase the level of precision. After the first production of cold antihydrogen in 2002 [1], experimental efforts have substantially progressed, with really competitive results already reached by adapting to cold antiatoms some well-known techniques pre- viously developed for ordinary atoms. Unfortunately, the number of antihydrogen atoms that can be produced in dedicated experiments is many orders of magnitude smaller than of hydrogen atoms, so the development of novel techniques to enhance the production of antihydrogen with well defined (and possibly controlled) conditions is essential to improve the sensitivity. We present here some experimental results achieved by the AEgIS Collaboration, based at the CERN AD (Antiproton Decelerator) on the production of antihydrogen in a pulsed mode where the production time of 90% of atoms is known with an uncertainty of ~ 250 ns [2]. The pulsed antihydrogen source is generated by the charge-exchange reaction between Rydberg positronium (Ps*) and an antiproton (p¯): p¯ + Ps* → H¯* + e−, where Ps* is produced via the implantation of a pulsed positron beam into a mesoporous silica target, and excited by two consecutive laser pulses, and antiprotons are trapped, cooled and manipulated in Penning-Malmberg traps. The pulsed production (which is a major milestone for AEgIS) makes it possible to select the antihydrogen axial temperature and opens the door for the tuning of the antihydrogen Rydberg states, their de-excitation by pulsed lasers and the manipulation through electric field gradients. In this paper, we present the results achieved by AEgIS in 2018, just before the Long Shutdown 2 (LS2), as well as some of the ongoing improvements to the system, aimed at exploiting the lower energy antiproton beam from ELENA [3].

We present a hybrid imaging/timing detector for force sensitive inertial measurements designed for measurements on positronium, the metastable bound state of an electron and a positron, but also suitable for applications involving other low intensity, low energy beams of neutral (antimatter)-atoms, such as antihydrogen. The performance of the prototype detector was evaluated with a tunable low energy positron beam, resulting in a spatial resolution of approximate to <i 12 mm, a detection efficiency of up to 40% and a time-resolution in the order of tens of ns.

The primary goal of the AEgIS collaboration at CERN is to measure the gravitational acceleration on neutral antimatter. Positronium (Ps), the bound state of an electron and a positron, is a suitable candidate for a force-sensitive inertial measurement by means of deflectometry/interferometry. In order to conduct such an experiment, the impact position and time of arrival of Ps atoms at the detector must be detected simultaneously. The detection of a low-velocity Ps beam with a spatial resolution of (88 ± 5) μm was previously demonstrated [1]. Based on the methodology employed in [1] and [2], a hybrid imaging/timing detector with increased spatial resolution of about 10 μm was developed. The performance of a prototype was tested with a positron beam. The concept of the detector and first results are presented.

G. Kornakov, M. Auzins, B. Bergmann, P. Burian, G. Bonomi, R. S. Brusa, f ,g A. Camper, R. Caravita, f ,g F. Castelli, j P. Cheinet, R. Ciuryło, D. Comparat, G. Consolati, M. Doser, H. Gjersdal, L. T. Glöggler, Ł. Graczykowski, F. Guatieri, f ,g S. Haider, S. Huck, M. Janik, G. Kasprowicz, G. Khatri, Ł. Kłosowski, L. Lappo, C. Malbrunot, S. Mariazzi, f G. Nebbia, L. Nowak, D. Nowicka, E. Oswald, D. Pagano, L. Penasa, f ,g V. Petracek, M. Piwiński, S. Pospisil, L. Povolo, f F. Prelz, S. Rangwala, B. Rienäcker, A. Rotondi, O. M. Røhne, H. Sandaker, I. Stekl, D. Tefelski, I. C. Tietje, M. Volponi, f ,g,n T. Wolz, M. Zawada, C. Zimmer and N. Zurlo

Nanochanneled silicon targets with high positron/positronium (Ps) conversion rate and efficient Ps cooling were produced. Morphological parameters of the nanochannels, such as their diameter and length, were adjusted to get a large fraction of thermalized Ps at room temperature being emitted into vacuum. Ps cooling measurements were conducted combining single-shot positron annihilation lifetime spectroscopy and Doppler spectroscopy of the 13S → 23P transition. 2γ–3γ annihilation ratio measurements were also performed to estimate the positron/Ps conversion efficiency. In a converter with nanochannel diameter of 7–10 nm and depth of 3.89 μm, ∼28% of implanted positrons with an energy of 3.3 keV was found to be emitted as Ps with a transverse kinetic energy of 11 ± 2 meV. The reduction of the nanochannels depth to 1.13 μm, without changing the nanochannel diameter, was found to result in a less efficient cooling, highlighting the presence of Ps reflection from the bottom end of nanochannels.

In this contribution, the system of the external plastic scintillator slabs of the AEgIS experiment is presented. These slabs, surrounding the superconducting magnet and operating at room temperature, are read out by photomultiplier tubes (PMTS) that are calibrated and equalised to be exploited as a whole detector with useful segmentation and redundancy to effectively detect single antiparticle annihilations. In particular, thanks to periodically recurring calibrations with cosmic rays and to a detailed study of the system in different operational conditions, including extensive Monte Carlo (MC) simulations, these scintillators can be used to identify antiproton annihilations over the constant background represented by cosmic rays and over the strongly time-dependent background due to positrons/positronium annihilations. By means of the sampling and digitization of the analog signal produced by each phototube and the consequent analysis of the amplitude of the recorded events, the energy released by the particle in the scintillator slab can be estimated consistently and with good accuracy. As a consequence, we are able to identify an amplitude range where positrons/positronium annihilations can be univocally excluded. This prerequisite allows us to exploit the array of external plastic scintillators for antihydrogen annihilations tagging.

From the experimental point of view, very little is known about the gravitational interaction between matter and antimatter. In particular, the Weak Equivalence Principle, which is of paramount importance for the General Relativity, has not yet been directly probed with antimatter. The main goal of the AEgIS experiment at CERN is to perform a direct measurement of the gravitational force on antimatter. The idea is to measure the vertical displacement of a beam of cold antihydrogen atoms, traveling in the gravitational field of the Earth, by the means of a moiré deflectometer. An overview of the physics goals of the experiment, of its apparatus and of the first results is presented.

We characterized the pulsed Rydberg-positronium production inside the AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) apparatus in view of antihydrogen formation by means of a charge exchange reaction between cold antiprotons and slow Rydberg-positronium atoms. Velocity measurements on positronium along two axes in a cryogenic environment (10K) and in 1T magnetic field were performed. The velocimetry was done by MCP-imaging of photoionized positronium previously excited to the n=3 state. One direction of velocity was measured via Doppler-scan of this n=3-line, another direction perpendicular to the former by delaying the exciting laser pulses in a time-of-flight measurement. Self-ionization in the magnetic field due to motional Stark effect was also quantified by using the same MCP-imaging technique for Rydberg positronium with an effective principal quantum number n_eff ranging between 14 and 22. We conclude with a discussion about the optimization of our experimental parameters for creating Rydberg-positronium in preparation for an efficient pulsed production of antihydrogen.

A main scientific goal of theAEg over bar ISgon antihydrogen. The Weak Equivalence Principle is a foundation of General Relativity. It has been extensively tested with ordinary matter but very little is known about the gravitational interaction between matter and antimatter. Antihydrogen is produced inAEg over bar IS<ivia resonant charge-exchange reaction between cold Rydberg-excited positronium and cooled down antiprotons. The achievements for the development of a pulsed cold antihydrogen source are presented. Large number of antiprotons, necessary for a significant production rate of antihydrogen, are captured, accumulated, compressed and cooled over an extended period of time. Positronium (Ps) is formed through e(+)-Ps conversion in a silica porous target at 10 K temperature in a reflection geometry inside the main apparatus. The so-formed Ps cloud is then laser-excited to Rydberg levels, for the first time in a 1 T magnetic field. Consequently, a detailed characterization of the Ps source for antihydrogen production in magnetic field needed to be performed. Several detection techniques are extensively used to monitor antiproton and positron manipulations in the formation process of antihydrogen inside the main apparatus. Positronium detection techniques underwent extensive improvements in sensitivity during the last antiproton run. At the same time, major efforts to improve integrate and commission the detectors sensitive to antihydrogen production took place.

We present the commissioning of the Fast Annihilation Cryogenic Tracker detector (FACT), installed around the antihydrogen production trap inside the 1T superconducting magnet of the AEgIS experiment. FACT is designed to detect pions originating from the annihilation of antiprotons. Its 794 scintillating fibers operate at 4 K and are read out by silicon photomultipliers (MPPCs) at near room temperature. FACT provides the antiproton/antihydrogen annihilation position information with a few ns timing resolution. We present the hardware and software developments which led to the successful operation of the detector for antihydrogen detection and the results of an antiproton-loss based efficiency assessment. The main background to the antihydrogen signal is that of the positrons impinging onto the positronium conversion target and creating a large amount of gamma rays which produce a sizeable signal in the MPPCs shortly before the antihydrogen signal is expected. We detail the characterization of this background signal and its impact on the antihydrogen detection efficiency.

Data taken by the DELPHI experiment at centre-of-mass energies of 183 GeV and 189 GeV with a total integrated luminosity of 212 pb^{-1} have been used to search for the supersymmetric partners of the electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model (MSSM). The decay topologies searched for were the direct decay ({\tilde \ell} -> \ell {\tilde \chi_1^0}), producing acoplanar lepton pairs plus missing energy, and the cascade decay ({\tilde \ell} -> \ell {\tilde \chi_2^0} > \ell \gamma {\tilde \chi_1^0}), producing acoplanar lepton and photon pairs plus missing energy. The observed number of events is in agreement with Standard Model predictions. The 95% CL excluded mass limits for selectrons, smuons and staus are m_{\tilde {e}} \leq 87 GeV/c^2, m_{\tilde {\mu}} \leq 80 GeV/c^2 and m_{\tilde {\tau}} \leq 75 GeV/c^2, respectively, for values of \mu=-200 GeV/c^2 and tan(beta)=1.5.

In this work we present a hybrid detection method providing simultaneous imaging and timing information suitable for fully monitoring positronium (Ps) formation, its laser excitation, and its spatial propagation for the first trials of pulsed antihydrogen ((H) over bar) production through a charge-exchange reaction with trapped antiprotons ((p) over bar). This combined method, based on the synchronous acquisition of an EJ-200 scintillation detector and a microchannel plate (MCP) detector with a dual readout (phosphor screen image and electrical pick-up signal), allows all relevant events in the experiment to be accurately determined in time while allowing high resolution images of e(+) from Ps laser photodissociations to be acquired. The timing calibration process of the two detectors discussed in details as well as the future perspectives opened by this method.

In this work, we show recent measurements of 2(3)S long-lived positronium production via spontaneous decay from the 3(3)P level. The possibility to tune the velocity of the 2(3)S positronium, excited following this scheme, is presented. In the light of these results, we discuss the use of the 3(3)P -> 2(3)S transition to realize a monochromatic pulsed 2(3)S positronium beam with low angular divergence. Preliminary tests of 2(3)S beam production are presented. The possibility to overcome the natural 3(3)P -> 2(3)S branching ratio via stimulated emission, and thus increasing the intensity of the 2(3)S source, is also shown. A position-sensitive detector for a pulsed beam of positronium, with spatial resolution of approximate to 90 mu m, is finally described in view of its possible application for the spatial characterization of the 2(3)S beam.

AE g ¯ IS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is a CERN based experiment aiming to probe the Weak Equivalence Principle of General Relativity with antimatter by studying free fall of antihydrogen in the Earth’s gravitational field. A pulsed cold beam of antihydrogen produced by charge exchange between Rydberg positronium and cold antiprotons will be horizontally accelerated by an electric field gradient. The free fall of antihydrogen will then be measured by a classical moire deflectometer. An overview of the experimental setup, present status of the experiment along with current achievements and results is presented.

Forming a pulsed beam of cold antihydrogen using charge-exchange with Rydberg positronium (Ps) is the goal of the AEgIS collaboration, which aims to a first gravity measurement on neutral antimatter. Recently achieved results in Ps formation and laser spectroscopy in the main AEgIS apparatus are summarized. First, Ps has been produced using nanochanneled silicon targets in a cryogenic environment (similar to 15 K) with 1 T magnetic field and observed by means of Single-Shot Positron Annihilation Lifetime Spectroscopy. The first demonstration of Ps n=3 excitation has been obtained as well using the same technique, validating the proof-of-concept of AEgIS. Subsequently, a new fast and high sensitivity detection method for laser-excited Ps in high magnetic field has been developed, using the combination of laser/field ionization and an high sensitivity MCP detector coupled to a low noise CMOS camera. This technique will form the basis of future experiments involving Rydberg Ps spectroscopy in AEgIS.