Upgrades and maintenance of the CRYRING@ESR electron cooler for improved internal electron target operation

TL;DR

This paper discusses upgrades to the CRYRING@ESR electron cooler, focusing on vacuum improvements and voltage modulation techniques to enhance its performance as an electron target and beam cooler.

Contribution

The study introduces new methods for vacuum management and voltage modulation that improve the cooler’s operation in electron target mode.

Findings

Successful replacement of the malfunctioning electron gun cathode.

Significant improvements in drift-electrode modulation of the acceleration voltage.

Enhanced stability and performance of the electron cooler.

Abstract

The electron cooler of the CRYRING@ESR storage ring at the GSI-FAIR accelerator complex is a unique instrument, which not only provides beam cooling of the stored ions, but also serves as a low-energy electron target for Dielectronic Recombination experiments. The minimisation of vacuum contamination and the response to rapid energy changes are key requirements of the cooler in electron target mode. Therefore, a test bench was prepared to study the outgassing behaviour of the electron gun components and a setup was constructed to evaluate the drift-electrode-modulation of the acceleration voltage of the cooler. The vacuum studies showed that the electron gun cathode was severely malfunctioning and resulted in its replacement. The drift-electrode-modulation of the acceleration voltage showed significant improvements compared to direct modulation of the terminal voltage of the cooler.