CERN Accelerating science

The performance of a caesium fountain frequency reference for use in precision measurements of trapped antihydrogen in the ALPHA experiment at CERN is evaluated. A description of the fountain is provided together with a characterisation of systematic effects. The impact of the magnetic environment in the Antimatter Factory, where the fountain is installed, on the performance of the fountain is considered and shown to be insignificant.

We develop a new algorithm to estimate the temperature of a nonneutral plasma in a Penning-Malmberg trap. The algorithm analyzes data obtained by slowly lowering a voltage that confines one end of the plasma and collecting escaping charges, and is a maximum likelihood estimator based on a physically-motivated model of the escape protocol presented in (Beck in Measurement of the magnetic and temperature dependence of the electron-electron anisotropic temperature relaxation rate.

A sequence of electron clouds is extracted from an electron plasma reservoir.

The ALPHA (Antihydrogen Laser PHysics Apparatus) collaboration at CERN is testing Charge-Parity-Time (CPT) symmetry through precise measurements with antihydrogen atoms and in the future will measure antihydrogen's free fall acceleration in Earth's gravitational field. The antihydrogen atoms are created by slowly merging cold plasmas of antiprotons and positrons. The production rate is highly sensitive to the parameters of these plasmas and typically only a few atoms have been available at a time for measurements.

Antihydrogen, composing an antiproton and positron, is the only bound state of two antiparticles yet to be synthesised, making for an enticing system to study the purported symmetry of matter and antimatter. As antihydrogen does not occur naturally in the observable universe, any study of this atom requires it to be synthesised in a lab, which the ALPHA experiment is routinely able to do. However, the absolute numbers are small and efficient detection is crucial for the experiment.