F. W. H. Böhm³, M. Braß⁸, L. Calza³, K. Chrysalidis⁹, M. Door^7,†, H. Dorrer⁵, Ch. E. Düllmann^5,10,11, K. Eberhardt^5,10, S. Eliseev⁷, C. Enss^3,4, P. Filianin⁷, A. Fleischmann³, R. Gartmann⁴, L. Gastaldo^3,‡, M. Griedel^3,§, A. Göggelmann¹², R. Hammann^3,∥, R. Hasse⁶, M. W. Haverkort⁸, S. Heinze⁸, D. Hengstler³, R. Jeske³, J. Jochum¹², K. Johnston⁹, N. Karcher⁴, S. Kempf^2,4, T. Kieck^11,10, U. Köster¹³, N. Kovac^3,¶, N. Kneip⁶, K. Kromer⁷, F. Mantegazzini^3,*, B. A. Marsh^9,†, M. Merstorf⁸, T. Muscheid⁴, M. Neidig², Y. N. Novikov⁷, R. Pandey³, A. Reifenberger³, D. Richter³, A. Rischka⁷, S. Rothe⁹, O. Sander⁴, R. X. Schüssler⁷, S. Scholl¹², Ch. Schweiger⁷, C. Velte³, M. Weber¹⁴, M. Wegner^4,2, K. Wendt⁶, and T. Wickenhäuser³ (ECHo Collaboration)

• ¹Institute for Astroparticle Physics, Karlsruhe Institute of Technology, Karlsruhe, Germany
• ²Institute for Micro- and Nanoelectronic Systems, Karlsruhe Institute of Technology, Karlsruhe, Germany
• ³Kirchhoff Institute for Physics, Heidelberg University, Heidelberg, Germany
• ⁴Institute for Data Processing and Electronics, Karlsruhe Institute of Technology, Karlsruhe, Germany
• ⁵Department of Chemistry—TRIGA Site, Johannes Gutenberg University Mainz, Mainz, Germany
• ⁶Institute of Physics, Johannes Gutenberg University Mainz, Mainz, Germany
• ⁷Max Planck Institute for Nuclear Physics, Heidelberg, Germany
• ⁸Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany
• ⁹ISOLDE, CERN, Geneve, Switzerland/France
• ¹⁰Helmholtz Institute Mainz, Mainz, Germany
• ¹¹GSI Helmholtz Centre for Heavy Ion Research GmbH, Darmstadt, Germany
• ¹²Physics Institute, University of Tübingen, Tübingen, Germany
• ¹³Institut Laue-Langevin, Grenoble, France
• ¹⁴Division V, Karlsruhe Institute of Technology, Karlsruhe, Germany

• ^*Present address: Fondazione Bruno Kessler (FBK), I-38123 Trento, Italy and INFN- TIFPA, I-38123 Trento, Italy.
• ^†Present address: Laboratoire Kastler Brossel, Sorbonne University, CNRS, ENS-PSL University, Collège de France, Paris, France.
• ^‡Contact author: Gastaldo@kip.uni-heidelberg.de
• ^§Present address: Institute for Quantum Material and Technologies, Karlsruhe Institute of Technology, Germany.
• ^∥Present address: Max Planck Institute for Nuclear Physics, Heidelberg, Germany.
• ^¶Present address: Institute for Astroparticle Physics, Karlsruhe Institute of Technology, Germany.