Field Ionization of Strongly Magnetized Rydberg Positronium: A New Physical Mechanism for Positron Accumulation

Estrada, J.; Roach, Timothy; Tan, Joseph N.; Yesley, P.; Gabrielse, Gerald

doi:10.1103/physrevlett.84.859

Cited by 72 publications

(76 citation statements)

References 17 publications

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“…During accumulation, 9 Be + ions were stored in the trap but were at low density because the laser-cooling and rotating wall were turned off. Similar to [17], we were able to accumulate positrons with a reverse bias of a few volts on the moderator crystal which would prevent low-energy positrons from entering the trap. Figure 7 shows the accumulation of [17] we observe an increase in the number of accumulated positrons as the maximum electric field strength within the trap is increased.…”

Section: Positron Accumulation and Lifetimementioning

confidence: 90%

“…Similar to [17], we were able to accumulate positrons with a reverse bias of a few volts on the moderator crystal which would prevent low-energy positrons from entering the trap. Figure 7 shows the accumulation of [17] we observe an increase in the number of accumulated positrons as the maximum electric field strength within the trap is increased. However, our maximum accumulation rate (trap voltage ∼200 V) occurs at an electric field strength that is 5 to 10 times greater than observed in [17].…”

Section: Positron Accumulation and Lifetimementioning

confidence: 90%

“…[17] of field ionizing high-Rydberg positronium. We summarize here the accumulation rate obtained with this method.…”

Section: Positron Accumulation and Lifetimementioning

confidence: 99%

“…Positrons have been trapped using resistive cooling of the positrons [12], by ramping the trap electrostatic potential [13], and in a magneticmirror configuration by electron cyclotron resonance heating [14]. Recent experiments by Gabrielse and co-workers [15,16,17] have successfully trapped more than 10 6 positrons in 17 hours through a method where apparently positronium in a high Rydberg state created on the surface of the moderator is field-ionized in the trap. They used a 3 mCi positron source and a tungsten positron moderator in the experiment.…”

Section: Introductionmentioning

confidence: 99%

“…We load positrons by following the prescription of Gabrielse and coworkers [15,16,17] for fieldionizing high Rydberg positronium. We observe centrifugal separation of the positrons and 9 Be + ions, which enables us to determine the positron density and place a rough upper bound on the positron temperature.…”

Section: Introductionmentioning

confidence: 99%

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A Laser-cooled Positron Plasma

Jelenković

Bollinger

Newbury

et al.

New Directions in Antimatter Chemistry and Physics

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We present results on trapping and cooling of positrons in a Penning trap. Positrons from a 2 mCi 22 Na source travel along the axis of a 6 T magnet and through the trap after which they strike a Cu reflection moderator crystal. Up to a few thousand positrons are trapped and lose energy through Coulomb collisions (sympathetic cooling) with laser-cooled 9 Be + . By imaging the 9 Be + laser-induced fluorescence, we observe centrifugal separation of the 9 Be + ions and positrons, with the positrons coalescing into a column along the trap axis. This indicates the positrons have the same rotation frequency and comparable density ( 4 × 10 9 cm −3 ) as the 9 Be + ions, and places an upper limit of approximately 5 K on the positron temperature of motion parallel to the magnetic field. We estimate the number of trapped positrons from the volume of this column and from the annihilation radiation when the positrons are ejected from the trap. The measured positron lifetime is > 8 days in our room temperature vacuum of 10 −8 Pa.

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Section: Positron Accumulation and Lifetimementioning

confidence: 90%

Section: Positron Accumulation and Lifetimementioning

confidence: 90%

“…[17] of field ionizing high-Rydberg positronium. We summarize here the accumulation rate obtained with this method.…”

Section: Positron Accumulation and Lifetimementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Laser-cooled Positron Plasma

Jelenković

Bollinger

Newbury

et al.

New Directions in Antimatter Chemistry and Physics

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ATRAP antihydrogen experiments

Storry

Aggarwal

Akbari

et al. 2007

Phys. Status Solidi (c)

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Antihydrogen (Hbar) was first produced at CERN in 1996. Over the past decade our ATRAP collaboration has made massive progress toward our goal of producing large numbers of cold Hbar atoms that will be captured in a magnetic gradient trap for precise comparison between the atomic spectra of matter and antimatter. The AD at CERN provides bunches of 3x10 7 low energy Pbars every 100 seconds. We capture and cool to 4 K, 0.1% of these in a cryogenic Penning trap. By stacking many bunches we are able to do experiments with 3x10 5 Pbars. ~100 e + /sec from a 22 Na radioactive source are captured and cooled in the trap, with 5x106 available experiments.We have developed 2 ways to make Hbar from these cold ingredients, namely 3-body collisions, and 2-stage Rydberg charge exchange. In the first case, Pbars are injected into a nested trap containing e + . Hbar is formed when 2 e + and 1 Pbar collide. In 2-stage Rydberg charge exchange, laser-excited caesium (Cs) enters the trap through a small hole. Rydberg positronium is formed when a e + captures an e-from a Cs. These atoms exit the trap, some passing through a nearby cloud of cold Pbars. A 2nd charge-exchange results when a Pbar captures the e + , forming Hbar. We have also developed techniques to measure the excited-state distribution of the Hbar and measure their velocity. I will present results from these experiments and discuss the next generation of apparatus to be commissioned this year. This new apparatus includes a e+ accumulator built at York University providing many more e + . The new Pbar annihilation detector provides spatial information of annihilations. Windows allow lasers to enter the trap for spectroscopic measurements and for laser cooling of the Hbar. Possibly the most exciting inclusion in this new apparatus is the inclusion of a neutral particle trap which may, for the first time, capture the Hbar and lead to the first atomic spectrum from antimatter.

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Perspectives on Physics with Low Energy Positrons: Fundamentals, Beams and Scattering

Charlton

New Directions in Antimatter Chemistry and Physics

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Field Ionization of Strongly Magnetized Rydberg Positronium: A New Physical Mechanism for Positron Accumulation

Cited by 72 publications

References 17 publications

A Laser-cooled Positron Plasma

A Laser-cooled Positron Plasma

ATRAP antihydrogen experiments

Perspectives on Physics with Low Energy Positrons: Fundamentals, Beams and Scattering

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