Letter
Open Access

Adiabatic expansion cooling of antihydrogen

M. Ahmadi¹, B. X. R. Alves², C. J. Baker³, W. Bertsche ^4,5,*, A. Capra ⁶, S. Cohen⁷, C. Torkzaban⁸, C. L. Cesar ⁹, M. Charlton ³ et al. (The ALPHA Collaboration)

M. Charlton ³, R. Collister⁶, S. Eriksson³, A. Evans^10,11, N. Evetts¹¹, J. Fajans ^8,†, T. Friesen^10,2, M. C. Fujiwara⁶, P. Granum ², J. S. Hangst², M. E. Hayden¹², D. Hodgkinson ^4,8,‡, C. A. Isaac³, M. A. Johnson ^4,5, S. A. Jones ^3,13, S. Jonsell ¹⁴, N. Kalem ⁸, N. Madsen ³, D. Maxwell³, J. T. K. McKenna ^6,2,4, S. Menary¹⁵, T. Momose ^11,6, J. Munich¹², K. Olchanski⁶, A. Olin ^6,16, P. Pusa¹, C. Ø. Rasmussen^2,17, F. Robicheaux ¹⁸, R. L. Sacramento⁹, M. Sameed ^4,17, E. Sarid^19,7, D. M. Silveira⁹, C. So^10,6, G. Stutter², T. D. Tharp²⁰, R. I. Thompson^10,6, D. P. van der Werf ³, and J. S. Wurtele⁸ (The ALPHA Collaboration)

¹Department of Physics, University of Liverpool, Liverpool L3 5TR, United Kingdom
²Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
³Department of Physics, Faculty of Science and Engineering, Swansea University, Swansea SA2 8PP, United Kingdom
⁴School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom
⁵Cockcroft Institute, Sci-Tech Daresbury, Warrington WA4 4AD, United Kingdom
⁶TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3
⁷Department of Physics, Ben Gurion University, Beer Sheva 8410501, Israel
⁸Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300, USA
⁹Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972, Brazil
¹⁰Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada T2N 1N4
¹¹Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
¹²Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
¹³Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, NL-9747 AG Groningen, The Netherlands
¹⁴Department of Physics, Stockholm University, SE-10691 Stockholm, Sweden
¹⁵Department of Physics and Astronomy, York University, Toronto, Ontario, Canada M3J 1P3
¹⁶Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada V8P 5C2
¹⁷CERN, Experimental Physics Department, CH-1211 Genève 23, Switzerland
¹⁸Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
¹⁹Soreq NRC, Yavne 81800, Israel
²⁰Physics Department, Marquette University, P.O. Box 1881, Milwaukee, Wisconsin 53201-1881, USA

^*Contact author: william.bertsche@manchester.ac.uk
^†Contact author: joelfajans@gmail.com
^‡Contact author: danielle.louise.hodgkinson@cern.ch

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Phys. Rev. Research 6, L032065 – Published 16 September, 2024

DOI: https://doi.org/10.1103/PhysRevResearch.6.L032065

Abstract

Magnetically trapped antihydrogen atoms can be cooled by expanding the volume of the trap in which they are confined. We report a proof-of-principle experiment in which antiatoms are deliberately released from expanded and static traps. Antiatoms escape at an average trap depth of $0.08 \pm 0.01 K$ (statistical errors only) from the expanded trap while they escape at average depths of $0.22 \pm 0.01$ and $0.17 \pm 0.01 K$ from two different static traps. (We employ temperature-equivalent energy units.) Detailed simulations qualitatively agree with the escape times measured in the experiment and show a decrease of $38 %$ (statistical $error < 0.2 %$ ) in the mean energy of the population after the trap expansion without significantly increasing antiatom loss compared to typical static confinement protocols. This change is bracketed by the predictions of one-dimensional and three-dimensional semianalytic adiabatic expansion models. These experimental, simulational, and model results are consistent with obtaining an adiabatically cooled population of antihydrogen atoms that partially exchanged energy between axial and transverse degrees of freedom during the trap expansion. This result is important for future antihydrogen gravitational experiments which rely on adiabatic cooling, and it will enable antihydrogen cooling beyond the fundamental limits of laser cooling.

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References (25)

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Phys. Rev. Research 6, L032065– Published 16 September, 2024

Vol. 6, Iss. 3 — September - November 2024

Received 10 May 2024
Accepted 18 July 2024

DOI: https://doi.org/10.1103/PhysRevResearch.6.L032065

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.

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Adiabatic expansion cooling of antihydrogen

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