Three-Dimensional Annihilation Imaging of Trapped Antiprotons

Fujiwara, M.; Amoretti, M.; Bonomi, G.; Bouchta, A.; Bowe, P. D.; Carraro, C.; Cesar, C. L.; Charlton, M.; Doser, M.; Filippini, V.; Fontana, A.; Funakoshi, R.; Genova, P.; Hangst, J. S.; Hayano, R. S.; Jørgensen, L. V.; Lagomarsino, V.; Landua, R.; Lodi-Rizzini, E.; Marchesotti, M.; Macrı́, M.; Madsen, N.; Manuzio, G.; Montagna, P.; Riedler, P.; Rotondi, A.; Rouleau, G.; Testera, G.; Variola, A.; Werf, D. P. van der; Yamazaki, Y.

doi:10.1103/physrevlett.92.065005

Cited by 45 publications

(27 citation statements)

References 30 publications

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“…We can compress the p density by a factor of ten and decrease the radii to 0.29 mm. These clouds are 10-20 times smaller in radius than the clouds reported by ATHENA [27] and ATRAP [28]. Control of the radial profile of the p's is critical to their survival in a Minimum-B trap.…”

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confidence: 62%

Compression of Antiproton Clouds for Antihydrogen Trapping

Andresen¹,

Bertsche²,

Bowe³

et al. 2008

Phys. Rev. Lett.

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Control of the radial profile of trapped antiproton clouds is critical to trapping antihydrogen. We report the first detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial profile and its relation to that of the electron plasma.

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confidence: 62%

Compression of Antiproton Clouds for Antihydrogen Trapping

Andresen¹,

Bertsche²,

Bowe³

et al. 2008

Phys. Rev. Lett.

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“…Antihydrogen, when released from the magnetic trap, annihilates on the Penning trap electrodes. The antiproton annihilation events are registered using a silicon vertex detector [ 36,37 ]. For most of the data presented here, an axial, static, electric bias field of 500 Vm -1 was applied during the confinement and shutdown stages to deflect bare antiprotons which may have been trapped via the magnetic mirror effect [ 17 ].…”

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confidence: 99%

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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“…This technique complements direct imaging of the inner radial profile [9], and provides more precise and reliable information than earlier techniques [11,12]. We have tested the diagnostic by varying the electrostatic well length and shape, and by varying the ramp time, and we have used the diagnostic to study several procedures and manipulations pertinent to the synthesis of antihydrogen atoms.…”

Section: Discussionmentioning

confidence: 99%

“…5) that p's hit the wall at the ends of the electrostatic well. We expect to observe this type of loss pattern as it is at the ends of the trap that the accessible field lines extend furthest outward; we note, however, that annihilations tend to occur at the ends of the electrostatic well even in the absence of an octupole field [11].…”

Section: Diagnostic Descriptionmentioning

confidence: 99%

“…Until recently, only two techniques that measure the p radial profile have been reported in detail. The first, based on p annihilation on the background gas [11], yields a crude [∼ 4 mm (1σ)] three-dimensional image of the p cloud. To observe a sufficient number of annihilations, the background gas pressure must be much higher than is normally used when synthesizing antihydrogen atoms.…”

Section: Introductionmentioning

confidence: 99%

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A novel antiproton radial diagnostic based on octupole induced ballistic loss

et al. 2008

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We report results from a novel diagnostic that probes the outer radial profile of trapped antiproton clouds. The diagnostic allows us to determine the profile by monitoring the time-history of antiproton losses that occur as an octupole field in the antiproton confinement region is increased. We show several examples of how this diagnostic helps us to understand the radial dynamics of antiprotons in normal and nested Penning-Malmberg traps. Better understanding of these dynamics may aid current attempts to trap antihydrogen atoms.

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Three-Dimensional Annihilation Imaging of Trapped Antiprotons

Cited by 45 publications

References 30 publications

Compression of Antiproton Clouds for Antihydrogen Trapping

Compression of Antiproton Clouds for Antihydrogen Trapping

Confinement of antihydrogen for 1,000 seconds

A novel antiproton radial diagnostic based on octupole induced ballistic loss

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