Critical loss radius in a Penning trap subject to multipole fields

Fajans, J.; Madsen, N.; Robicheaux, F.

doi:10.1063/1.2899306

Cited by 21 publications

(23 citation statements)

References 25 publications

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“…The antiprotons oscillate between the two ends of the electrostatic well, following field lines that typically extend between a radial minimum at one end of the well and a radial maximum at the other end of the well. These radial maxima occur in magnetic cusps [33,34], four to each side, caused by the octupole's radial fields. Guiding center drifts cause the antiprotons to slowly rotate around the trap axis, so that the trajectories slowly alternate between cusps at each end.…”

Section: Appendix B Mirror-trapped Antiproton Trajectoriesmentioning

confidence: 96%

Discriminating between antihydrogen and mirror-trapped antiprotons in a minimum-B trap

et al. 2012

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Recently, antihydrogen atoms were trapped at CERN in a magnetic minimum (minimum-B) trap formed by superconducting octupole and mirror magnet coils. The trapped antiatoms were detected by rapidly turning off these magnets, thereby eliminating the magnetic minimum and releasing any antiatoms contained in the trap. Once released, these antiatoms quickly hit the trap wall, whereupon the positrons and antiprotons in the antiatoms annihilate. The antiproton annihilations produce easily detected signals; we used these signals to prove that we trapped antihydrogen. However, our technique could be confounded by mirror-trapped antiprotons, which would produce seemingly identical annihilation signals upon hitting the trap wall. In this paper, we discuss possible sources of mirror-trapped antiprotons and show that antihydrogen and antiprotons can be readily distinguished, often with the aid of applied electric fields, by analyzing the annihilation locations and times. We further discuss the general properties of antiproton and antihydrogen trajectories in this magnetic geometry, and reconstruct the antihydrogen energy distribution from the measured annihilation time history.

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Section: Appendix B Mirror-trapped Antiproton Trajectoriesmentioning

confidence: 96%

Discriminating between antihydrogen and mirror-trapped antiprotons in a minimum-B trap

et al. 2012

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“…In the most extreme case, this manifests as a 'critical radius' [4], outside which particles can be lost from the trap simply because the magnetic field lines along which the particles move intersect the electrode walls. Even if particles are not lost, the transverse field results in a higher rate of plasma diffusion [5].…”

Section: Atom Trapmentioning

confidence: 98%

Towards antihydrogen trapping and spectroscopy at ALPHA

et al. 2011

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Spectroscopy of antihydrogen has the potential to yield high-precision tests of the CPT theorem and shed light on the matter-antimatter imbalance in the Universe. The ALPHA antihydrogen trap at CERN's Antiproton Decelerator aims to E. Butler et al. prepare a sample of antihydrogen atoms confined in an octupole-based Ioffe trap and to measure the frequency of several atomic transitions. We describe our techniques to directly measure the antiproton temperature and a new technique to cool them to below 10 K. We also show how our unique position-sensitive annihilation detector provides us with a highly sensitive method of identifying antiproton annihilations and effectively rejecting the cosmic-ray background.

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“…In this case it is necessary that the radial extent of the particle ensembles is smaller than the so-called critical radius, a dynamic aperture introduced by the superposition of an octupole on a Penning-Malmberg trap [15]. Particles beyond this critical radius will be lost.…”

Section: Antihydrogen Formationmentioning

confidence: 99%

Search for trapped antihydrogen in ALPHAThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at École de Physique, les Houches, France, 30 May – 4 June, 2010.

et al. 2011

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Antihydrogen spectroscopy promises precise tests of the symmetry of matter and antimatter, and can possibly offer new insights into the baryon asymmetry of the universe. Antihydrogen is, however, difficult to synthesize and is produced only in small quantities. The ALPHA collaboration is therefore pursuing a path towards trapping cold antihydrogen to permit the use of precision atomic physics tools to carry out comparisons of antihydrogen and hydrogen. ALPHA has addressed these challenges. Control of the plasma sizes has helped to lower the influence of the multipole field used in the neutral atom trap, and thus lowered the temperature of the created atoms. Finally, the first systematic attempt to identify trapped antihydrogen in our system is discussed. This discussion includes special techniques for fast release of the trapped antiatoms, as well as a silicon vertex detector to identify antiproton annihilations. The silicon detector reduces the background of annihilations, including background from antiprotons that can be mirror trapped in the fields of the neutral atom trap. A description of how to differentiate between these events and those resulting from trapped antihydrogen atoms is also included.Résumé : La spectroscopie de l'anti-hydrogène promet des tests précieux de la symétrie entre matière et antimatière dans l'univers. Cependant, l'anti-hydrogène est difficile à synthétiser et il n'est produit qu'en petite quantité. Le groupe de collaborateurs ALPHA poursuit donc des travaux pour capturer de l'anti-hydrogène froid afin de permettre l'utilisation d'outils précis de mesure en physique atomique pour comparer l'anti-hydrogène avec l'hydrogène. Nous montrons comment ALPHA s'est attaqué à cette tâche et comment le contrôle du volume de plasma a aidé à diminuer l'influence des champs multipolaires utilisés dans le piège pour atomes neutres et ainsi abaisser la température des atomes produits. Finalement, nous discutons le premier essai systématique pour identifier l'anti-hydrogène piégé dans notre système. Ceci inclut des techniques spéciales pour relâcher rapidement les anti-atomes piégés, ainsi qu'un détecteur au silicium pour identifier l'annihilation de l'anti-proton. Nous avons utilisé le détecteur au silicium pour réduire le fond d'annihilation, incluant celui produit par les anti-protons qui peuvent être dans le piège miroir des champs du piège à atomes neutres. Nous décrivons aussi comment nous pouvons différentier entre ces événements et ceux qui résultent des atomes d'anti-hydrogène piégés.[Traduit par la Rédaction]

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Critical loss radius in a Penning trap subject to multipole fields

Cited by 21 publications

References 25 publications

Discriminating between antihydrogen and mirror-trapped antiprotons in a minimum-B trap

Discriminating between antihydrogen and mirror-trapped antiprotons in a minimum-B trap

Towards antihydrogen trapping and spectroscopy at ALPHA

Search for trapped antihydrogen in ALPHAThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at École de Physique, les Houches, France, 30 May – 4 June, 2010.

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