Compression of Antiproton Clouds for Antihydrogen Trapping

Andresen, Gorm Bruun; Bertsche, W.; Bowe, P. D.; Bray, C. C.; Butler, E.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Fujiwara, M.; Funakoshi, R.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayano, R.; Hayden, M. E.; Hydomako, R.; Jenkins, Michael J.; Jørgensen, L. V.; Kurchaninov, L. L.; Lambo, R.; Madsen, N.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; Nasr, S. Seif El; Silveira, D. M.; Storey, J. W.; Thompson, R. I.; Werf, D. P. van der; Wurtele, J. S.; Yamazaki, Y.

doi:10.1103/physrevlett.100.203401

Cited by 60 publications

(52 citation statements)

References 28 publications

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“…Instead ALPHA has constructed an octupole (figures 4 and 5), which, for the same field strength at the edge of the trap, has a much lower field in the centre of the trap where the charged particles are held (Bertsche et al 2006). To further avoid influence of the neutral trap fields, ALPHA has implemented and developed techniques to radially compress the electrons, positrons and antiprotons (Andresen et al 2008). Our competitors in ATRAP initially used a quadrupole configuration, but are now constructing an octupole for the 2010 experimental season (G. Gabrielse 2009, personal communication).…”

Section: Trapping Antihydrogenmentioning

confidence: 99%

Cold antihydrogen: a new frontier in fundamental physics

Madsen

2010

Phil. Trans. R. Soc. A.

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The year 2002 heralded a breakthrough in antimatter research when the first low energy antihydrogen atoms were produced. Antimatter has inspired both science and fiction writers for many years, but detailed studies have until now eluded science. Antimatter is notoriously difficult to study as it does not readily occur in nature, even though our current understanding of the laws of physics have us expecting that it should make up half of the universe. The pursuit of cold antihydrogen is driven by a desire to solve this profound mystery. This paper will motivate the current effort to make cold antihydrogen, explain how antihydrogen is currently made, and how and why we are attempting to trap it. It will also discuss what kind of measurements are planned to gain new insights into the unexplained asymmetry between matter and antimatter in the universe.

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Section: Trapping Antihydrogenmentioning

confidence: 99%

Cold antihydrogen: a new frontier in fundamental physics

Madsen

2010

Phil. Trans. R. Soc. A.

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“…These keV antiprotons are cooled [ 30 ], typically with ~50% efficiency, by a preloaded cold electron plasma (2x10 7 electrons), and the resulting plasma is radially compressed [ 31,32 ]. After electron removal and evaporative cooling [ 25 ], a cloud of 1.5x10 4 antiprotons at ~100K, with radius 0.4 mm and density 7x10 7 cm -3 is prepared for mixing with positrons.…”

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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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“…The reconstruction makes assumptions about the applicability of the global thermal equilibrium state of these plasmas [13,14], and about the p temperature. We note that with our diagnostics (reported here and in [9]) we have seen many long-lived radial profiles that are not in global thermal equilibrium.…”

Section: Introductionmentioning

confidence: 86%

“…nostic is based on a MCP-phosphor screen system [9]. (A similar system has also been reported by the ASACUSA collaboration [15].)…”

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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Compression of Antiproton Clouds for Antihydrogen Trapping

Cited by 60 publications

References 28 publications

Cold antihydrogen: a new frontier in fundamental physics

Cold antihydrogen: a new frontier in fundamental physics

Confinement of antihydrogen for 1,000 seconds

A novel antiproton radial diagnostic based on octupole induced ballistic loss

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