Non-Destructive Positron Plasma Diagnostics for Antihydrogen Production

Abstract

Production of antihydrogen atoms by mixing antiprotons with a cold, confined, positron plasma depends on parameters such as the plasma density and temperature. We discuss a nondestructive diagnostic, based on an analysis of excited, low-order plasma modes, that provides comprehensive characterization of the positron plasma in the ATHENA antihydrogen apparatus. The dipole and quadrupole modes of a spheroidal positron plasma are interpreted in the framework of a cold fluid theory. In particular, the excitation and detection of the dipole mode are analytically modeled considering the response of the center-of-mass to a resonant driving perturbation. The model is compared to, and validated by, numerical simulations with a particle-in-cell code. Measurements of the positron plasma properties are discussed.

Detecting Antihydrogen: The Challenges and the Applications

“…We will likely encounter unexpected new effects. Given the situation, the importance of real time imaging, together with other plasma diagnosis techniques we developed for ATHENA [5,6], cannot be overstated.…”

“…A basic trigger scheme is illustrated in Figs. 6. A good feature of the IDEAS VA-TA readout chips used in ATHENA was their selftriggering capability.…”

Temperature dependence of anti-hydrogen production in the ATHENA experiment

“…A radio frequency signal (RF heating) was applied to induce a positron plasma temperature increase (DT ). The shape, size, particle density and temperature increase of the positron plasma have been deduced using a non-destructive diagnostics method, based on the excitation and detection of the lowest (dipole, quadrupole) plasma modes [8]. We collected statistics for four different plasma temperatures:…”