Citation: Jolly, M.; Voikopoulos, S.; Lamour, E.; Méry, A.; Bräuning-Demian, A.; Chesnel, J.-Y.; Gumberidze, A.; Lestinsky, M.; Macé, S.; Prigent, C.; et al. Performance of a keV/u Ion Spectrometer for the FISIC Platform. Atoms 2022, 10, 146. https://doi.org/ 10.3390/atoms10040146 Academic Editors: Izumi Murakami, Daiji Kato, Hiroyuki A. Sakaue and Hajime Tanuma Received: 25 October 2022 Accepted: 30 November 2022 Published: 3 December 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). atoms Article Performance of a keV/u Ion Spectrometer for the FISIC Platform Mariette Jolly 1, *, Spyridon Voikopoulos 1 , Emily Lamour 1 , Alain Méry 2 , Angela Bräuning-Demian 3 , Jean-Yves Chesnel 2 , Alexandre Gumberidze 3 , Michael Lestinsky 3 , Stéphane Macé 1 , Christophe Prigent 1 , Jean-Marc Ramillon 2 , Jimmy Rangama 2 , Patrick Rousseau 2 , Daniel Schury 1 , Uwe Spillmann 3 , Sébastien Steydli 1 , Thomas Stöhlker 3,4,5 , Martino Trassinelli 1 and Dominique Vernhet 1 1 Institut des Nanosciences de Paris, Sorbonne Université, CNRS UMR 7588, 75005 Paris, France 2 CIMAP, CEA/CNRS/ENSICAEN/Université de Caen Normandie, 14050 Caen, France 3 GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany 4 Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany 5 Helmholtz-Institut Jena, Fröbelstieg 3, 07743 Jena, Germany * Correspondence: jolly@insp.upmc.fr Abstract: The design and performances of a newly built electrostatic charge state analyzer constructed to act as a spectrometer for keV/u ions are reported. It consists of two 90 ◦ curved electrodes enclosed by Matsuda electrodes. This setup was recently tested using Ar 9+ and Ar 12+ ion beams at an energy of 10 keV per charge unit. This spectrometer achieves a good separation of different charge states formed by electron capture processes during collisions between primary ions and the residual gas. Thanks to these first tests, we have identified up to three different background contributions on the detector that need to be reduced or suppressed. Keywords: ion spectrometer; ion-atom collisions; MCP detectors; electron capture 1. Introduction When studying ion-matter interaction, analyzing the ion charge state after the inter- action is often one of the key parameters. It gives information about electronic processes at play. For that purpose, specific instruments are developed. They must be able to both separate the charge states after the interaction, count the number of ions whose charge state changed and reach performances allowing coincidence detection. Here, we present a multipurpose home-made ion spectrometer mainly developed for the FISIC (Fast Ion- Slow Ion Collision) project [1], but that can be used in any setups involving ion charge exchanges. The FISIC program aims to perform ion-ion collisions in an energy regime where cross-sections are barely known. The first collision systems will be studied using slow (keV/u) ion beams coming from the FISIC platform and fast (MeV/u) ion beams delivered by CRYRING@ESR (Heavy Ion Storage Ring Facility) [2]. The spectrometer will be placed downstream the collision zone to analyze the charge state of the slow ion beam. To measure absolute cross-sections of elementary electronic processes, coincidence mea- surements between slow and fast ion charge states after the collision zone are mandatory. The ion spectrometer must be charge dispersive for multicharged ions with keV/u energies, and must be able to count several charge states at once. We have chosen a full electrostatic system for which we present here the first tests performed at the ARIBE (French acronym for Accelerator for Research with Low Energy Ions) facility [3] in Caen, France. In this paper, we first discuss the design of the spectrometer with its associated detection system. Second, we present selected experimental results and their comparison with simulations made using the SIMION software [4]. To conclude, we present the limitations of the set-up as well as future upgrades considered to reduce the different background contributions. Atoms 2022, 10, 146. https://doi.org/10.3390/atoms10040146 https://www.mdpi.com/journal/atoms