Hyperfine Interactions

, Volume 212, Issue 1–3, pp 15–29 | Cite as

Trapped antihydrogen

  • E. Butler
  • G. B. Andresen
  • M. D. Ashkezari
  • M. Baquero-Ruiz
  • W. Bertsche
  • P. D. Bowe
  • C. L. Cesar
  • S. Chapman
  • M. Charlton
  • A. Deller
  • S. Eriksson
  • J. Fajans
  • T. Friesen
  • M. C. Fujiwara
  • D. R. Gill
  • A. Gutierrez
  • J. S. Hangst
  • W. N. Hardy
  • M. E. Hayden
  • A. J. Humphries
  • R. Hydomako
  • M. J. Jenkins
  • S. Jonsell
  • L. V. Jørgensen
  • S. L. Kemp
  • L. Kurchaninov
  • N. Madsen
  • S. Menary
  • P. Nolan
  • K. Olchanski
  • A. Olin
  • A. Povilus
  • P. Pusa
  • C. Ø. Rasmussen
  • F. Robicheaux
  • E. Sarid
  • S. Seif el Nasr
  • D. M. Silveira
  • C. So
  • J. W. Storey
  • R. I. Thompson
  • D. P. van der Werf
  • J. S. Wurtele
  • Y. Yamazaki
  • ALPHA Collaboration
Article

Abstract

Precision spectroscopic comparison of hydrogen and antihydrogen holds the promise of a sensitive test of the Charge-Parity-Time theorem and matter-antimatter equivalence. The clearest path towards realising this goal is to hold a sample of antihydrogen in an atomic trap for interrogation by electromagnetic radiation. Achieving this poses a huge experimental challenge, as state-of-the-art magnetic-minimum atom traps have well depths of only ∼1 T (∼0.5 K for ground state antihydrogen atoms). The atoms annihilate on contact with matter and must be ‘born’ inside the magnetic trap with low kinetic energies. At the ALPHA experiment, antihydrogen atoms are produced from antiprotons and positrons stored in the form of non-neutral plasmas, where the typical electrostatic potential energy per particle is on the order of electronvolts, more than 104 times the maximum trappable kinetic energy. In November 2010, ALPHA published the observation of 38 antiproton annihilations due to antihydrogen atoms that had been trapped for at least 172 ms and then released—the first instance of a purely antimatter atomic system confined for any length of time (Andresen et al., Nature 468:673, 2010). We present a description of the main components of the ALPHA traps and detectors that were key to realising this result. We discuss how the antihydrogen atoms were identified and how they were discriminated from the background processes. Since the results published in Andresen et al. (Nature 468:673, 2010), refinements in the antihydrogen production technique have allowed many more antihydrogen atoms to be trapped, and held for much longer times. We have identified antihydrogen atoms that have been trapped for at least 1,000 s in the apparatus (Andresen et al., Nature Physics 7:558, 2011). This is more than sufficient time to interrogate the atoms spectroscopically, as well as to ensure that they have relaxed to their ground state.

Keywords

Antihydrogen Antimatter CPT Atom trapping 

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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • E. Butler
    • 1
    • 2
  • G. B. Andresen
    • 3
  • M. D. Ashkezari
    • 4
  • M. Baquero-Ruiz
    • 5
  • W. Bertsche
    • 2
  • P. D. Bowe
    • 3
  • C. L. Cesar
    • 6
  • S. Chapman
    • 5
  • M. Charlton
    • 2
  • A. Deller
    • 2
  • S. Eriksson
    • 2
  • J. Fajans
    • 5
    • 7
  • T. Friesen
    • 8
  • M. C. Fujiwara
    • 8
    • 9
  • D. R. Gill
    • 9
  • A. Gutierrez
    • 10
  • J. S. Hangst
    • 3
  • W. N. Hardy
    • 10
  • M. E. Hayden
    • 4
  • A. J. Humphries
    • 2
  • R. Hydomako
    • 8
  • M. J. Jenkins
    • 2
  • S. Jonsell
    • 11
  • L. V. Jørgensen
    • 2
  • S. L. Kemp
    • 1
  • L. Kurchaninov
    • 9
  • N. Madsen
    • 2
  • S. Menary
    • 12
  • P. Nolan
    • 13
  • K. Olchanski
    • 9
  • A. Olin
    • 9
  • A. Povilus
    • 5
  • P. Pusa
    • 13
  • C. Ø. Rasmussen
    • 3
  • F. Robicheaux
    • 14
  • E. Sarid
    • 15
  • S. Seif el Nasr
    • 10
  • D. M. Silveira
    • 16
    • 17
  • C. So
    • 5
  • J. W. Storey
    • 9
  • R. I. Thompson
    • 8
  • D. P. van der Werf
    • 2
  • J. S. Wurtele
    • 5
    • 7
  • Y. Yamazaki
    • 16
    • 17
  • ALPHA Collaboration
  1. 1.Physics DepartmentCERNGeneva 23Switzerland
  2. 2.Department of PhysicsSwansea UniversitySwanseaUK
  3. 3.Department of Physics and AstronomyAarhus UniversityAarhus CDenmark
  4. 4.Department of PhysicsSimon Fraser UniversityBurnabyCanada
  5. 5.Department of PhysicsUniversity of CaliforniaBerkeleyUSA
  6. 6.Instituto de FísicaUniversidade Federal do Rio de JaneiroRio de JaneiroBrazil
  7. 7.Lawrence Berkeley National LaboratoryBerkeleyUSA
  8. 8.Department of Physics and AstronomyUniversity of CalgaryCalgaryCanada
  9. 9.TRIUMFVancouverCanada
  10. 10.Department of Physics and AstronomyUniversity of British ColumbiaVancouverCanada
  11. 11.Department of PhysicsStockholm UniversityStockholmSweden
  12. 12.Department of Physics and AstronomyYork UniversityTorontoCanada
  13. 13.Department of PhysicsUniversity of LiverpoolLiverpoolUK
  14. 14.Department of PhysicsAuburn UniversityAuburnUSA
  15. 15.Department of PhysicsNRCN-Nuclear Research Center NegevBeer ShevaIsrael
  16. 16.Atomic Physics LaboratoryRIKEN Advanced Science InstituteSaitamaJapan
  17. 17.Graduate School of Arts and SciencesUniversity of TokyoTokyoJapan
  18. 18.Physics DepartmentCERNGeneva 23Switzerland
  19. 19.Department of PhysicsDurham UniversityDurhamUK
  20. 20.Physik-InstitutZurich UniversityZurichSwitzerland

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