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Antihydrogen experiments are currently based on non neutral electron, positron or antiproton plasma manipulation techniques in cylindrical Malmberg-Penning traps. An experimental study of a plasma manipulation technique based on off-axis diocotron displacement is presented. The use of the autoresonant excitation of (1, 0) diocotron mode of pure electron plasma allows a precise positioning of the plasma by moving it across the magnetic field and allows dumping such plasma in a desired angular position. The experimental procedure described here will pave the way to positron loading into an off-axial Penning trap terminated with a positronium converter target as it is proposed for the AEgIS experimental apparatus. The technique was studied over a range of confining magnetic field values and reproduces experimental conditions similar to most of the currently running antihydrogen experiments. The efficiency of the autoresonant excitation - in terms of plasma expansion rate and particle loss - is analyzed, studying the behaviour of electron plasma subjected to large off-axial displacements, showing that this method fulfills the requirements imposed by the AEgIS experiment. [ABSTRACT FROM AUTHOR]

Abstract: Considerable efforts have been made and are still being made to verify the validity of the principle of the equivalence of gravitational and inertial mass, one of the cornerstones of the classical theory of general relativity. Specific attempts at quantummechanical formulations of gravity allow for non-Newtonian contributions, which might lead to a difference in the gravitational force on matter and antimatter. While it is widely expected that the gravitational interaction is independent of the composition of bodies, this has only been tested for matter systems, but never yet for antimatter systems. By combining techniques from different fields, and relying on recent developments in the production of Positronium and ongoing work to laser-excite Positronium to Rydberg states, such a test with neutral antimatter has become feasible. The primary goal of the AEGIS experiment being built at the Antiproton Decelerator at CERN is to carry out the first direct measurement of the Earth‘s gravitational acceleration on antihydrogen by means of a classical Moiré deflectometer. [Copyright &y& Elsevier]

In the ATHENA experiment, which has recently produced and detected cold antihydrogen, the antiatoms formation is performed by mixing two cold (meV) charged clouds of positrons and antiprotons. The antihydrogen production is strictly dependent on positron plasma parameters. For this purpose we developed a new system to investigate such properties in a non-destructive way. The method is based upon the measurement of the plasma response under a frequency sweep RF excitation and its subsequent analysis. Plasmas trapped in Penning trap exhibit typical resonant collective modes characterized by frequencies, amplitudes and widths dependent on the particle number, density, spatial extent and temperature. With this system it is so possible to have a real-time monitor of the plasma during antihydrogen production. [Copyright &y& Elsevier]

Abstract: This work reports for the first time experimental data obtained with electrons stored in a Penning–Malmberg trap surrounded by a sextupole radial magnetic field. This trap geometry is one of the candidates for trapping antihydrogen atoms in the place where they are produced starting from cold antiprotons and positrons or positronium. The measurements show that electron plasmas with parameters matching the range used for positrons and electrons in the antihydrogen experiments (number of particles ranging from few 106 up to several 107 and densities of the order of 108–109 cm−3, radius of the order of 1–2 mm) can be transported with 100% efficiency in a trap region that simultaneously confines completely the charged particles and the neutral antihydrogen in the radial plane. Inside this trap plasma storage times of the order of several tens of seconds up to some hundreds of seconds are measured. The plasma storage times are consistent with those needed for antihydrogen production; however the increase of the plasma temperature due to the expansion is not negligible; the consequences of this effect on the antihydrogen trapping are outlined. [Copyright &y& Elsevier]

Abstract: The ATHENA experiment at CERN, after producing cold antihydrogen atoms for the first time in 2002, has synthesised protonium atoms in vacuum at very low energies. Protonium, i.e. the antiproton–proton bound system, is of interest for testing fundamental physical theories. In the nested penning trap of the ATHENA apparatus protonium has been produced as result of a chemical reaction between an antiproton and the simplest matter molecule, . The formed protonium atoms have kinetic energies in the range 40–700meV and are metastable with mean lifetimes of the order of 1μs. Our result shows that it will be possible to start measurements on protonium at low energy antiproton facilities, such as the AD at CERN or FLAIR at GSI. [Copyright &y& Elsevier]

Abstract: The creation of cold antihydrogen by the ATHENA and ATRAP collaborations, working at CERN’s unique Antiproton Decelerator (AD) facility, has ushered in a new era in atomic physics. This contribution will briefly review recent results from the ATHENA experiment. These include discussions of antiproton slowing down in a cold positron gas during antihydrogen formation, information derived on the dependence of the antihydrogen formation rate upon the temperature of the stored positron plasma and, finally, upon the spatial distribution of the emitted anti-atoms. We will discuss the implications of these studies for the major outstanding goal of trapping samples of antihydrogen for precise spectroscopic comparisons with hydrogen. The physics motivations for undertaking these challenging experiments will be briefly recalled. [Copyright &y& Elsevier]

Antihydrogen, the atomic bound state of an antiproton and a positron, was produced at low energy for the first time by the ATHENA experiment, marking an important first step for precision studies of atomic antimatter. This paper describes the first production and some subsequent developments. [Copyright &y& Elsevier]

The ATHENA apparatus that recently produced and detected the first cold antihydrogen atoms is described. Its main features, which are described herein, are: an external positron accumulator, making it possible to accumulate large numbers of positrons; a separate antiproton catching trap, optimizing the catching, cooling and handling of antiprotons; a unique high resolution antihydrogen annihilation detector, allowing an clear determination that antihydrogen has been produced; an open, modular design making variations in the experimental approach possible and a “nested” Penning trap situated in a cryogenic, 3T magnetic field environment used for the mixing of the antiprotons and positrons. [Copyright &y& Elsevier]

The production and observation of cold antihydrogen atoms have been recently reported by the ATHENA experiment at the CERN Antiproton Decelerator. The antiatoms were produced by mixing low-energy antiprotons and positrons in an electromagnetic trap. The antihydrogen detection is based on the observation of a characteristic signature in the annihilation of the neutral antiatoms on the trap walls by means of an imaging particle detector. An overview of the apparatus is given and the results obtained are discussed. [Copyright &y& Elsevier]

The ATHENA experiment recently produced the first atoms of cold antihydrogen. This paper gives a brief review of how this was achieved. [Copyright &y& Elsevier]