# A hydrogen beam to characterize the ASACUSA antihydrogen hyperfine spectrometer

## TL;DR

This paper presents a hydrogen beam source and detection system designed to test and characterize the hyperfine spectroscopy apparatus used in antihydrogen experiments at CERN, enabling performance evaluation despite low antihydrogen production.

## Contribution

Development of a hydrogen source and detection system that simulates antihydrogen spectroscopy conditions for apparatus testing and calibration.

## Key findings

- Successfully produced a cooled, polarized hydrogen beam
- Demonstrated detection using quadrupole mass spectrometry and lock-in amplification
- Provided insights into the performance of the hyperfine spectroscopy apparatus

## Abstract

The antihydrogen programme of the ASACUSA collaboration at the antiproton decelerator of CERN focuses on Rabi-type measurements of the ground-state hyperfine splitting of antihydrogen for a test of the combined Charge-Parity-Time symmetry. The spectroscopy apparatus consists of a microwave cavity to drive hyperfine transitions and a superconducting sextupole magnet for quantum state analysis via Stern-Gerlach separation. However, the small production rates of antihydrogen forestall comprehensive performance studies on the spectroscopy apparatus. For this purpose a hydrogen source and detector have been developed which in conjunction with ASACUSA's hyperfine spectroscopy equipment form a complete Rabi experiment. We report on the formation of a cooled, polarized, and time modulated beam of atomic hydrogen and its detection using a quadrupole mass spectrometer and a lock-in amplification scheme. In addition key features of ASACUSA's hyperfine spectroscopy apparatus are discussed.t