Search

This work reports 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 anti-hydrogen 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 anti-hydrogen 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 anti-hydrogen production; however the increase of the plasma temperature due to the expansion could prevent to get trappable antihydrogen. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The ATHENA experiment at CERN produced for the first time in 2002 cold antihydrogen atoms by mixing of antiprotons and a positron plasma. The more relevant results obtained in the last three years are presented and discussed in the light of the antihydrogen formation processes. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

A ballistic method is presented for transferring positron plasmas emanating from a region with a low magnetic field and relatively high pressure into a 15 K Penning-Malmberg trap immersed in a 3 T magnetic field with a base pressure of the order of 10-13 mbar. Subsequent stacking resulted in a plasma containing 4.2 × 108 positrons. Using a rotating wall electric field a plasma containing 90 million positrons was compressed to a density of 3.6 × 109 cm-3. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

The merging of an intense localized vortex with an extended vortex is investigated by means of an experimental analysis performed on a Malmberg-Penning trap with photocathode, and numerical simulations with a two-dimensional (2D) particle in cell (PIC) code. The study is restricted to highly nonlinear conditions, where the perturbative approach does not hold. A very good agreement between experimental results and simulations is obtained. It is found that the localized vortex is firstly wrapped around by the extended vortex, then moves towards the center of the system, eventually approaching an almost stationary state of rotation characterized by the formation of vorticity holes. During the whole evolution the extended vortex gains energy from the field surrounding the vortices, while the energy of the localized vortex remains constant. [ABSTRACT FROM AUTHOR]

The first phase of the ATHENA (AnTiHydrogEN Apparatus) experiment is devoted to the study of cold antihydrogen production. The apparatus includes an antiproton capture trap designed to trap and to cool antiprotons coming from the CERN Antiproton Decelerator (AD). The antiproton cooling is achieved by means of the collisional interaction with a cold cloud of trapped electrons. The electron plasma is loaded in the trap before the antiproton capture by means of a small-size heated filament and cooled to sub-eV temperatures by cyclotron radiation. We report some measurements devoted to the characterization of the electron plasma. The ATHENA apparatus design does not allow the use of complex diagnostic; therefore the plasma properties are obtained using electrostatic wall probes, radio-frequency diagnostic, and dumping the electrons onto a charge collector. A simple experimental method to obtain an estimate of the electron plasma radius is discussed. [ABSTRACT FROM AUTHOR]

The Malmberg-Penning trap Eltrap recently installed at the University of Milano, features a magnetic field with a high degree of uniformity in a relatively large plasma volume, and an enhanced light collection by the CCD camera. A modular electrode design allows several variations of the experimental configuration, suitable both for electron confinement and beam studies. The major electronic components of the apparatus are a waveform generator, which controls the inject-hold-dump cycle, and two personal computers, which control the data acquisition, the setting, and the timing of the experiments. Different electron sources have been proposed for the project, and studies for advanced source production are in progress. [ABSTRACT FROM AUTHOR]