Detection system for forward emitted photons at the Experimental Storage Ring at GSI

TL;DR

The paper presents a new photon detection system at GSI's ESR that significantly improves collection efficiency, enabling advanced laser-spectroscopy measurements of highly charged ions without disrupting the stored beam.

Contribution

Development of a movable parabolic mirror-based photon detection system that enhances collection efficiency over previous methods at ESR.

Findings

Collection efficiency increased by over 5 times.

No significant impact on ion beam stability.

First detection of hyperfine M1 transition in lithium-like bismuth.

Abstract

A single photon counting system has been developed for efficient detection of forward emitted fluorescence photons at the Experimental Storage Ring (ESR) at GSI. The system employs a movable parabolic mirror with a central slit that can be positioned around the ion beam and a selected low noise photomultiplier for detection of the collected photons. Compared to the previously used system of mirror segments installed inside the ESR the collection efficiency for forward-emitted photons is improved by more than a factor of 5. No adverse effects on the stored ion beam have been observed during operation besides a small drop in the ion current of about 5% during movement of the mirror into the beam position. The new detection system has been used in the LIBELLE experiment at ESR and enabled for the first time the detection of the ground-state hyperfine M1 transition in lithium-like bismuth (209Bi80+) in a laser-spectroscopy measurement.