# Cryogenic $^9$Be$^+$ Penning trap for precision measurements with (anti-)protons

## TL;DR

This paper presents a novel cryogenic Penning trap setup that sympathetically cools protons and antiprotons via Coulomb interaction with laser-cooled $^9$Be$^+$ ions, enhancing precision in fundamental symmetry tests.

## Contribution

It introduces a new experimental apparatus demonstrating ion coupling in a Penning trap, enabling advanced cooling and measurement techniques for protons and antiprotons.

## Key findings

- Successful loading and Doppler cooling of ions.
- First demonstration of coupling between identical ions in a Penning trap.
- Potential for improved motional control in high-precision experiments.

## Abstract

Cooling and detection schemes using laser cooling and methods of quantum logic can contribute to high precision CPT symmetry tests in the baryonic sector. This work introduces an experiment to sympathetically cool protons and antiprotons using the Coulomb interaction with a $^9$Be$^+$ ion trapped in a nearby but separate potential well. We have designed and set up an apparatus to show such coupling between two identical ions for the first time in a Penning trap. In this paper, we present evidence for successful loading and Doppler cooling of clouds and single ions. Our coupling scheme has applications in a range of high-precision measurements in Penning traps and has the potential to substantially improve motional control in these experiments.