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APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts

Observations of Cold Antihydrogen

G. Gabrielse

Published May 1, 2003• 0 citations
OpenAlex

Abstract

ATRAP’s e + cooling of p in a nested Penning trap has led to reports of cold Hproduced during such cooling by the ATHENA and ATRAP collaborations. ATHENA uses coincident annihilation detection and ATRAP uses field ionization followed by p storage. Advantages of the later method include the complete absence of a substantial background of false events intrinsic to the former, and the first way to measure which H states are produced. ATRAP enhances the H production rate by driving many cycles of e + cooling in the nested trap, with more H counted in an hour than the sum of all the other antimatter atoms ever reported. The number of Hcounted per incident high energy p is also higher than ever observed. The first measured distribution of H states is made using a pre-ionizing electric field between separated production and detection regions. The high rate and the high Rydberg states suggest that the H is formed via three-body recombination, as expected. 1

Related papers

Antiprotons and Cold Antihydrogen

G. Gabrielse

The author's ATRAP team has managed to simultaneously accumulate cold antiprotons and cold positrons. Cold antihydrogen is produced when antiprotons are repeatedly driven into collisions with cold positrons within a nested Penning trap. Efficient antihydrogen production takes place during many cycles of positron cooling of antiprotons. A first measurement of a distribution of antihydrogen states is made using a preionizing electric field between separated production and detection regions. Surviving antihydrogen is stripped in an ionization well that captures and stores the free antiproton for background-free detection. A background-free observation of cold antihydrogen atoms was made using field ionization followed by antiproton storage, a detection method that provided the first experimental information about antihydrogen atomic states. More antihydrogen atoms can be field ionized in an hour than all the anti-matter 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. This report presents bibliographic citations for 10 publications and 36 lectures that were produced during 2004 under this contract. The author also was the recipient of the George Ledlie Prize at Harvard University in 2004.

•Jan 1, 2001•0 citations

Production of Cold Antihydrogen in a Nested Trap

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The ATHENA experiment at CERN produced and detected the first cold antihydrogen atoms. Antiprotons and positrons are mixed in a double Penning trap, known as a nested trap. The production of antihydrogen atoms was identified by detecting their annihilations signatures at trap wall. With the ATHENA results subsequently confirmed by another CERN experiment, ATRAP, cold antihydrogen research is entering an exciting era.

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Driven Production of Cold Antihydrogen and the First Measured Distribution of Antihydrogen States

G. Gabrielse, N. S. Bowden, Paul Oxley +12 more

Cold antihydrogen is produced when antiprotons are repeatedly driven into collisions with cold positrons within a nested Penning trap. Efficient antihydrogen production takes place during many cycles of positron cooling of antiprotons. A first measurement of a distribution of antihydrogen states is made using a preionizing electric field between separated production and detection regions. Surviving antihydrogen is stripped in an ionization well that captures and stores the freed antiproton for background-free detection.

Physical Review Letters•Nov 19, 2002•220 citations

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

G. Gabrielse, N. S. Bowden, Paul Oxley +12 more

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.

Physical Review Letters•Oct 31, 2002•562 citations

The mechanisms of antihydrogen formationThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at University of Windsor, Windsor, Ontario, Canada on 21–26 July 2008.

Evandro Lodi Rizzini, L. Venturelli, Nicola Zurlo

Some years have passed since the report of the first production of cold antihydrogen by the Athena Collaboration and the Atrap Collaboration at CERN, but no clear answer has been given about the roles of the two mechanisms responsible for antihydrogen formation. A new preliminary analysis of the data acquired by the Athena Collaboration in different experimental conditions seems to suggest that three-body recombination mechanism is dominant in the first tens of seconds of the overlapping of the injected antiproton cloud with the positron plasma in the nested Penning trap, while radiative capture starts to become dominant afterwards.

Canadian Journal of Physics•Jul 1, 2009•0 citations

ATRAP antihydrogen experiments

C. H. Storry, M. M. Aggarwal, A. Akbari +37 more

Abstract 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 3 × 107 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 3 × 105 Pbars. ∼100 e+/sec from a 22Na radioactive source are captured and cooled in the trap, with 5 × 106 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. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Physica status solidi. C, Conferences and critical reviews/Physica status solidi. C, Current topics in solid state physics•Jul 11, 2007•3 citations
ATRAP’s e + cooling of p in a nested Penning trap has led to reports of cold Hproduced during such cooling by the ATHENA and ATRAP collaborations. ATHENA uses coincident annihilation detection and ATRAP uses field ionization followed by p storage. Advantages of the later method include the complete absence of a substantial background of false events intrinsic to the former, and the first way to measure which H states are produced. ATRAP enhances the H production rate by driving many cycles of e + cooling in the nested trap, with more H counted in an hour than the sum of all the other antimatter atoms ever reported. The number of Hcounted per incident high energy p is also higher than ever observed. The first measured distribution of H states is made using a pre-ionizing electric field between separated production and detection regions. The high rate and the high Rydberg states suggest that the H is formed via three-body recombination, as expected. 1
The author's ATRAP team has managed to simultaneously accumulate cold antiprotons and cold positrons. Cold antihydrogen is produced when antiprotons are repeatedly driven into collisions with cold positrons within a nested Penning trap. Efficient antihydrogen production takes place during many cycles of positron cooling of antiprotons. A first measurement of a distribution of antihydrogen states is made using a preionizing electric field between separated production and detection regions. Surviving antihydrogen is stripped in an ionization well that captures and stores the free antiproton for background-free detection. A background-free observation of cold antihydrogen atoms was made using field ionization followed by antiproton storage, a detection method that provided the first experimental information about antihydrogen atomic states. More antihydrogen atoms can be field ionized in an hour than all the anti-matter 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. This report presents bibliographic citations for 10 publications and 36 lectures that were produced during 2004 under this contract. The author also was the recipient of the George Ledlie Prize at Harvard University in 2004.
Cold antihydrogen is produced when antiprotons are repeatedly driven into collisions with cold positrons within a nested Penning trap. Efficient antihydrogen production takes place during many cycles of positron cooling of antiprotons. A first measurement of a distribution of antihydrogen states is made using a preionizing electric field between separated production and detection regions. Surviving antihydrogen is stripped in an ionization well that captures and stores the freed antiproton for background-free detection.
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.
Some years have passed since the report of the first production of cold antihydrogen by the Athena Collaboration and the Atrap Collaboration at CERN, but no clear answer has been given about the roles of the two mechanisms responsible for antihydrogen formation. A new preliminary analysis of the data acquired by the Athena Collaboration in different experimental conditions seems to suggest that three-body recombination mechanism is dominant in the first tens of seconds of the overlapping of the injected antiproton cloud with the positron plasma in the nested Penning trap, while radiative capture starts to become dominant afterwards.
Abstract 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 3 × 107 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 3 × 105 Pbars. ∼100 e+/sec from a 22Na radioactive source are captured and cooled in the trap, with 5 × 106 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. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)