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  • Open Access

Sympathetic cooling of charged particles in Penning traps using electron cyclotron radiation

Jost Herkenhoff*, Jonathan Notter, and Klaus Blaum

  • *Contact author: jost.herkenhoff@mpi-hd.mpg.de
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Phys. Rev. Research 8, 013071 – Published 23 January, 2026

DOI: https://doi.org/10.1103/zdsy-sxcl

Abstract

We present a technique for cooling arbitrary charged particles in a Penning trap by utilizing self-cooled electrons stored in a separate, macroscopically distant Penning trap as the cooling medium. The electrons decay predominantly to their motional ground state by emission of cyclotron radiation, which results in extremely low temperatures in the realm of single-digit quantum numbers in the motional degrees of freedom of the sympathetically cooled particle species. This opens up an exciting frontier of tests of fundamental physics in Penning traps. This article provides a conceptual overview as well as a quantum-mechanical description of the involved cooling dynamics. The first implementation of this technique is currently being realized at the dedicated ELCOTRAP experiment at the Max Planck Institute for Nuclear Physics, which introduces special features for a quick iterative technical development cycle. Its current status, first results from commissioning, and future prospects will be presented.

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References (58)

  1. K. Blaum, S. Eliseev, and S. Sturm, Perspectives on testing fundamental physics with highly charged ions in Penning traps, Quantum Sci. Technol. 6, 014002 (2020).
  2. K. Blaum, H. Kracke, S. Kreim, A. Mooser, C. Mrozik, W. Quint, C. C. Rodegheri, B. Schabinger, S. Sturm, S. Ulmer, A. Wagner, J. Walz, and G. Werth, G-factor experiments on simple systems in Penning traps, J. Phys. B: At. Mol. Opt. Phys. 42, 154021 (2009).
  3. G. Gabrielse, Antiproton mass measurements, Int. J. Mass. Spectrom 251, 273 (2006).
  4. C. Smorra, K. Blaum, L. Bojtar, M. Borchert, K. Franke, T. Higuchi, N. Leefer, H. Nagahama, Y. Matsuda, A. Mooser, M. Niemann, C. Ospelkaus, W. Quint, G. Schneider, S. Sellner, T. Tanaka, S. Van Gorp, J. Walz, Y. Yamazaki, and S. Ulmer, BASE—The baryon antibaryon symmetry experiment, Eur. Phys. J.: Spec. Top. 224, 3055 (2015).
  5. M. G. Kozlov, M. S. Safronova, J. R. Crespo López-Urrutia, and P. O. Schmidt, Highly charged ions: Optical clocks and applications in fundamental physics, Rev. Mod. Phys. 90, 045005 (2018).
  6. K. Kromer, C. Lyu, M. Door, P. Filianin, Z. Harman, J. Herkenhoff, P. Indelicato, C. H. Keitel, D. Lange, Y. N. Novikov, C. Schweiger, S. Eliseev, and K. Blaum, Observation of a low-lying metastable electronic state in highly charged lead by Penning-trap mass spectrometry, Phys. Rev. Lett. 131, 223002 (2023).
  7. J. C. Berengut, D. Budker, C. Delaunay, V. V. Flambaum, C. Frugiuele, E. Fuchs, C. Grojean, R. Harnik, R. Ozeri, G. Perez, and Y. Soreq, Probing new long-range interactions by isotope shift spectroscopy, Phys. Rev. Lett. 120, 091801 (2018).
  8. A. Wilzewski, et al., Nonlinear calcium king plot constrains new bosons and nuclear properties, Phys. Rev. Lett. 134, 233002 (2025).
  9. L. Gastaldo, et al., The electron capture in Ho163 experiment echo, Eur. Phys. J.: Spec. Top. 226, 1623 (2017).
  10. H.-J. Kluge and Y. Novikov, New promises for the determination of the neutrino mass? (A brainstorming meeting at GSI, Darmstadt), Nucl. Phys. News 17, 36 (2007).
  11. S. A. Eliseev, Y. N. Novikov, and K. Blaum, Search for resonant enhancement of neutrinoless double-electron capture by high-precision Penning-trap mass spectrometry, J. Phys. G: Nucl. Part. Phys. 39, 124003 (2012).
  12. M. Door, et al., Probing new bosons and nuclear structure with ytterbium isotope shifts, Phys. Rev. Lett. 134, 063002 (2025).
  13. J. Ketter, T. Eronen, M. Höcker, S. Streubel, and K. Blaum, First-order perturbative calculation of the frequency-shifts caused by static cylindrically-symmetric electric and magnetic imperfections of a Penning trap, Int. J. Mass. Spectrom 358, 1 (2014).
  14. J. Ketter, T. Eronen, M. Höcker, M. Schuh, S. Streubel, and K. Blaum, Classical calculation of relativistic frequency-shifts in an ideal Penning trap, Int. J. Mass. Spectrom 361, 34 (2014).
  15. F. Heiße, S. Rau, F. Köhler-Langes, W. Quint, G. Werth, S. Sturm, and K. Blaum, High-precision mass spectrometer for light ions, Phys. Rev. A 100, 022518 (2019).
  16. S. Sasidharan, O. Bezrodnova, S. Rau, W. Quint, S. Sturm, and K. Blaum, Penning-trap mass measurement of helium-4, Phys. Rev. Lett. 131, 093201 (2023).
  17. S. Ulmer, C. Smorra, A. Mooser, K. Franke, H. Nagahama, G. Schneider, T. Higuchi, S. Van Gorp, K. Blaum, Y. Matsuda, W. Quint, J. Walz, and Y. Yamazaki, High-precision comparison of the antiproton-to-proton charge-to-mass ratio, Nature (London) 524, 196 (2015).
  18. C. Smorra, S. Sellner, M. J. Borchert, J. A. Harrington, T. Higuchi, H. Nagahama, T. Tanaka, A. Mooser, G. Schneider, M. Bohman, K. Blaum, Y. Matsuda, C. Ospelkaus, W. Quint, J. Walz, Y. Yamazaki, and S. Ulmer, A parts-per-billion measurement of the antiproton magnetic moment, Nature (London) 550, 371 (2017).
  19. A. Schneider, A. Mooser, A. Rischka, K. Blaum, S. Ulmer, and J. Walz, A novel Penning-trap design for the high-precision measurement of the He32 + nuclear magnetic moment, Ann. Phys. 531, 1800485 (2019).
  20. M. Vogel, The anomalous magnetic moment of the electron, Contemp. Phys. 50, 437 (2009).
  21. S. Sturm, K. Blaum, I. Arapoglou, A. Egl, M. Höcker, S. Kraemer, T. Sailer, B. Tu, A. Weigel, R. Wolf, and J. C. López-Urrutia, The ALPHATRAP experiment, Eur. Phys. J.: Spec. Top. 227, 1425 (2019).
  22. R. S. Van Dyck, P. B. Schwinberg, and H. G. Dehmelt, Electron magnetic moment from geonium spectra, in Atomic Physics 7, edited by D. Kleppner and F. M. Pipkin (Springer US, Boston, MA, 1981), pp. 340–372.
  23. A. Egl, I. Arapoglou, M. Höcker, K. König, T. Ratajczyk, T. Sailer, B. Tu, A. Weigel, K. Blaum, W. Nörtershäuser, and S. Sturm, Application of the continuous Stern-Gerlach effect for laser spectroscopy of the ar 13 + 40 Fine structure in a Penning trap, Phys. Rev. Lett. 123, 123001 (2019).
  24. D. J. Heinzen and D. J. Wineland, Quantum-limited cooling and detection of radio-frequency oscillations by laser-cooled ions, Phys. Rev. A 42, 2977 (1990).
  25. M. Bohman, et al., Sympathetic cooling of a trapped proton mediated by an LC circuit, Nature (London) 596, 514 (2021).
  26. B. Tu, F. Hahne, I. Arapoglou, A. Egl, F. Heiße, M. Höcker, C. König, J. Morgner, T. Sailer, A. Weigel, R. Wolf, and S. Sturm, Tank-circuit assisted coupling method for sympathetic laser cooling, Adv. Quantum Technol. 4, 2100029 (2021).
  27. J. Morgner, B. Tu, C. M. König, T. Sailer, F. Heiße, H. Bekker, B. Sikora, C. Lyu, V. A. Yerokhin, Z. Harman, J. R. Crespo López-Urrutia, C. H. Keitel, S. Sturm, and K. Blaum, Stringent test of QED with hydrogen-like tin, Nature (London) 622, 53 (2023).
  28. J. Larmor, LXIII. On the theory of the magnetic influence on spectra; And on the radiation from moving ions, London, Edinburgh, Dublin Philos. Mag. J. Sci. 44, 503 (1897).
  29. E. A. Cornell, R. M. Weisskoff, K. R. Boyce, and D. E. Pritchard, Mode coupling in a Penning trap: Pi pulses and a classical avoided crossing, Phys. Rev. A 41, 312 (1990).
  30. M. O. Scully and M. S. Zubairy, Quantum Optics (Cambridge University Press, Cambridge, 1997).
  31. D. J. Griffiths, Introduction to Electrodynamics (Cambridge University Press, Cambridge, 2017).
  32. L. S. Brown and G. Gabrielse, Geonium theory: Physics of a single electron or ion in a Penning trap, Rev. Mod. Phys. 58, 233 (1986).
  33. M. Orszag, Quantum Optics: Including Noise Reduction, Trapped Ions, Quantum Trajectories, and Decoherence (Springer International Publishing, Cham, 2024).
  34. K. Kakazu and Y. S. Kim, Field quantization and spontaneous emission in circular cylindrical cavities, Prog. Theor. Phys. 96, 883 (1996).
  35. H.-P. Breuer and F. Petruccione, The Theory of Open Quantum Systems (Oxford University Press, Oxford, 2007).
  36. E. Fermi, Nuclear Physics: A Course given by Enrico Fermi at the University Of Chicago (University of Chicago Press, Chicago, 1950).
  37. B. Y.-K. Hu, Solving boundary-value electrostatics problems using Green’s reciprocity theorem, Am. J. Phys. 69, 1280 (2001).
  38. C. Will, et al., Sympathetic cooling schemes for separately trapped ions coupled via image currents, New J. Phys. 24, 033021 (2022).
  39. D. H. E. Dubin, Theory of electrostatic fluid modes in a cold spheroidal non-neutral plasma, Phys. Rev. Lett. 66, 2076 (1991).
  40. J. J. Bollinger, D. J. Wineland, and D. H. E. Dubin, Non-neutral ion plasmas and crystals, laser cooling, and atomic clocks, Phys. Plasmas 1, 1403 (1994).
  41. T. M. O’Neil and P. G. Hjorth, Collisional dynamics of a strongly magnetized pure electron plasma, Phys. Fluids 28, 3241 (1985).
  42. C. S. Weimer, J. J. Bollinger, F. L. Moore, and D. J. Wineland, Electrostatic modes as a diagnostic in Penning-trap experiments, Phys. Rev. A 49, 3842 (1994).
  43. D. H. Dubin and T. M. O’neil, Trapped nonneutral plasmas, liquids, and crystals (the thermal equilibrium states), Rev. Mod. Phys. 71, 87 (1999).
  44. J. H. Malmberg and C. F. Driscoll, Long-time containment of a pure electron plasma, Phys. Rev. Lett. 44, 654 (1980).
  45. J. R. Danielson and C. M. Surko, Torque-balanced high-density steady states of single-component plasmas, Phys. Rev. Lett. 94, 035001 (2005).
  46. X.-P. Huang, J. J. Bollinger, T. B. Mitchell, W. M. Itano, and D. H. E. Dubin, Precise control of the global rotation of strongly coupled ion plasmas in a Penning trap, Phys. Plasmas 5, 1656 (1998).
  47. M. B. Plenio and P. L. Knight, The quantum-jump approach to dissipative dynamics in quantum optics, Rev. Mod. Phys. 70, 101 (1998).
  48. J. R. Johansson, P. D. Nation, and F. Nori, QuTiP 2: A Python framework for the dynamics of open quantum systems, Comput. Phys. Commun. 184, 1234 (2013).
  49. J. Ekin, Experimental Techniques for Low-Temperature Measurements: Cryostat Design, Material Properties and Superconductor Critical-Current Testing (Oxford University Press, Oxford, 2006).
  50. J. Alonso, K. Blaum, S. Djekic, H.-J. Kluge, W. Quint, B. Schabinger, S. Stahl, J. Verdú, M. Vogel, and G. Werth, A miniature electron-beam ion source for in-trap creation of highly charged ions, Rev. Sci. Instrum. 77, 03A901 (2006).
  51. S. Sellner, M. Besirli, M. Bohman, M. J. Borchert, J. Harrington, T. Higuchi, A. Mooser, H. Nagahama, G. Schneider, C. Smorra, T. Tanaka, K. Blaum, Y. Matsuda, C. Ospelkaus, W. Quint, J. Walz, Y. Yamazaki, and S. Ulmer, Improved limit on the directly measured antiproton lifetime, New J. Phys. 19, 083023 (2017).
  52. D. J. Wineland and H. G. Dehmelt, Principles of the stored ion calorimeter, J. Appl. Phys. 46, 919 (1975).
  53. C. Böhm, et al., An ultra-stable voltage source for precision Penning-trap experiments, Nucl. Instrum. Methods Phys. Res., Sect. A 828, 125 (2016).
  54. Electrically conductive PEEK—TECAPEEK ELS nano black, Ensinger, 2026, https://www.ensingerplastics.com/en/shapes/peek-tecapeek-els-nano-black.
  55. G. Gabrielse and F. C. Mackintosh, Cylindrical Penning traps with orthogonalized anharmonicity compensation, Int. J. Mass Spectrom. Ion Processes 57, 1 (1984).
  56. P. Holzenkamp, Design of a microwave cavity Penning trap for the Lsym experiment, Ph.D. thesis, Ruprecht-Karls-Universität Heidelberg, 2025.
  57. F. Raab, Designing and characterization of a narrow microwave notch filter for the LSYM experiment in the 100 GHz regime, Ph.D. thesis, Ruprecht-Karls-Universität Heidelberg, 2024.
  58. J. Herkenhoff, K. Blaum, and J. Notter, Data from “Sympathetic cooling of charged particles in Penning traps using electron cyclotron radiation” [Data set], Zenodo (2025), https://doi.org/10.5281/zenodo.15723776.

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Phys. Rev. Research 8, 013071– Published 23 January, 2026
  • Received 23 June 2025
  • Accepted 24 December 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by Max Planck Society.

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