Guiding center atoms: Three-body recombination in a strongly magnetized plasma

Glinsky, Michael E.; O’Neil, T. M.

doi:10.1063/1.859820

Cited by 164 publications

(166 citation statements)

References 11 publications

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“…H production, for example, would be inhibited if e À substitute for e þ in what would otherwise be the replacement collisions [15] that form more deeply bound H atoms. The inverted situation for embedded e À cooling, with N p ) N e and each e À surrounded by many p, cools p much more slowly but no less effectively.…”

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confidence: 99%

Adiabatic Cooling of Antiprotons

et al. 2011

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Adiabatic Cooling of Antiprotons

et al. 2011

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“…Even if the distribution is not isotropic, the high rate supports the feasibility of spectroscopic investigations to follow. Rydberg states formed at a high rate likely start with a three-body recombination collision [8] between a p and two e , with deexcitation continuing via other processes [13,14].…”

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Background-Free Observation of Cold Antihydrogen with Field-Ionization Analysis of Its States

et al. 2002

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A background-free observation of cold antihydrogen atoms is made using field ionization followed by antiproton storage, a detection method that provides the first experimental information about antihydrogen atomic states. More antihydrogen atoms can be field ionized in an hour than all the antimatter atoms that have been previously reported, and the production rate per incident high energy antiproton is higher than ever observed. The high rate and the high Rydberg states suggest that the antihydrogen is formed via three-body recombination.

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“…Antihydrogen atoms produced by the three-body process (involving two positrons and an antiproton) [ 45,46 ] are created in excited states. De-excitation to the ground state takes place via cascades involving radiative and collisional (i.e., between the atom and a positron) processes.…”

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Confinement of antihydrogen for 1,000 seconds

et al. 2011

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Reported trapping times of magnetically confined (matter) atoms range from <1 s in the first, room temperature, traps [ 18 ] to 10 to 30 minutes in cryogenic devices [ 19,20,21,22 ]. However, antimatter atoms can annihilate on background gases. Also, the loading of our trap (i.e., anti-atom production via merging of cold plasmas) is different from that of ordinary atom traps, and the loading dynamics could adversely affect the trapping and orbit dynamics. Mechanisms exist for temporary magnetic trapping of particles (e.g., in quasi-stable trapping orbits [ 23 ], or in excited internal states [ 24 ]); such particles could be short-lived with a trapping time of a few 100 ms. Thus, it is not a priori obvious what trapping time should be expected for antihydrogen. 5In this article, we report the first systematic investigations of the characteristics of trapped antihydrogen. These studies were made possible by significant advances in our trapping techniques subsequent to Ref. [ 17 ]. These developments, including incorporation of evaporative antiproton cooling[ 25 ] into our trapping operation, and optimisation of autoresonant mixing [ 26 ], resulted in up to a factor of five increase in the number of trapped atoms per attempt. A total sample of 309 trapped antihydrogen annihilation events was studied, a large increase from the previously published 38 events.Here we report trapping of antihydrogen for 1000 s, extending earlier results [ 17 ] by nearly four orders of magnitude. Further, we have exploited the temporal and spatial resolution of our detector system to perform a detailed analysis of the antihydrogen release process, from which we infer information on the trapped antihydrogen kinetic energy distribution.The ALPHA antihydrogen trap [ 27,28 ] is comprised of the superposition of a Penning trap for antihydrogen production and a magnetic field configuration that has a three-dimensional minimum in magnitude (Fig. 1). For ground-state antihydrogen, our trap well-depth is 0.54 K (in temperature units).The large discrepancy in the energy scales between the magnetic trap depth (~50 eV), and the characteristic energy scale of the trapped plasmas (a few eV) presents a formidable challenge to trapping neutral anti-atoms. antiprotons at ~100K, with radius 0.4 mm and density 7x10 7 cm -3 is prepared for mixing with positrons.Independently, the positron plasma, accumulated in a Surko-type buffer gas accumulator [ 33 ,34 ], is transferred to the mixing region, and is also radially compressed. The magnetic trap is then energized, 6 and the positron plasma is cooled further via evaporation, resulting in a plasma with a radius of 0.8 mm and containing 1x10 6 positrons at a density of 5x10 7 cm -3 and a temperature of ~40 K. The silicon vertex detector, surrounding the mixing trap in three layers (Fig. 1 a) ]. Knowledge of annihilation positions also provides sensitivity to the antihydrogen energy distribution, as we will show.In Table 1 and Fig. 2, we present the results for a series of measurements, wherein the confinemen...

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Guiding center atoms: Three-body recombination in a strongly magnetized plasma

Cited by 164 publications

References 11 publications

Adiabatic Cooling of Antiprotons

Adiabatic Cooling of Antiprotons

Background-Free Observation of Cold Antihydrogen with Field-Ionization Analysis of Its States

Confinement of antihydrogen for 1,000 seconds

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