# Antihydrogen level population evolution: impact of positron plasma length

## TL;DR

This paper investigates how the length of positron plasma affects the evolution of antihydrogen atom populations, especially focusing on the yield of ground-state antihydrogen, revealing different behaviors based on plasma length.

## Contribution

It introduces an analysis of the impact of positron plasma length on antihydrogen level populations, highlighting the dependence of ground-state yield on plasma dimensions.

## Key findings

- Ground-state antihydrogen yield varies with plasma length.
- Different power-law behaviors observed at short and long plasma lengths.
- Level population evolution is significantly influenced by plasma geometry.

## Abstract

Antihydrogen is produced by mixing an antiproton and a positron plasma in a cryogenic electromagnetic trap. The dominant antihydrogen formation mechanism is three-body recombination, while the subsequent level population evolution is governed by various processes, mainly collisional (de)excitation, ionisation and radiative decay. In this work the impact of various positron plasma lengths on the level population evolution is investigated. The main interest is the ground-state antihydrogen atom yield. It is found that the ground state level population shows different power-law behaviour at short or longer positron plasma lengths.