Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

AIP conference proceedings

Developments in the Trapping and Accumulation of Slow Positrons using the Buffer Gas Technique

J. Clarke

Published Jan 1, 2003• 3 citations
Publisher

Abstract

A compact, two‐stage positron accumulator has been designed, constructed and tested at Swansea, as part of a larger experiment to study Rydberg states of the positronium atom. It uses the well‐understood nitrogen buffer gas technique to trap and accumulate positrons obtained from a Na‐22 radioactive source, and slowed by a solid neon moderator. The main development this system embodies over previous accumulators is reduced physical dimension, made possible by the shorter storage times required.

DOI
10.1063/1.1635173

Related papers

Investigation of buffer gas trapping of positrons

C. J. Baker, Christopher Aled Isaac, D Edwards +4 more

Abstract A study of positron capture in a two-(pressure) stage buffer gas accumulation apparatus is presented for a variety of species, including some molecules which are known to be either efficient for positron trapping, or are frequently used to cool the particles when held in these devices. Absolute accumulation efficiencies are reported for all species. A detailed optimisation procedure, which has identified the main processes responsible for positron capture and loss in the trap, has been deployed to explore accumulation efficiency as the gas pressure and the electrostatic well depth in the trap are systematically varied. Accumulation exploiting energy loss via molecular vibrational transitions has been observed for the first time for a number of gases, though at much lower efficiency than achieved using electronic excitation processes.

Journal of Physics B Atomic Molecular and Optical Physics•Jun 29, 2020•9 citations

Experimental progress in positronium laser physics

D. B. Cassidy

The field of experimental positronium physics has advanced significantly in the last few decades, with new areas of research driven by the development of techniques for trapping and manipulating positrons using Surko-type buffer gas traps. Large numbers of positrons (typically ≥106) accumulated in such a device may be ejected all at once, so as to generate an intense pulse. Standard bunching techniques can produce pulses with ns (mm) temporal (spatial) beam profiles. These pulses can be converted into a dilute Ps gas in vacuum with densities on the order of 107 cm−3 which can be probed by standard ns pulsed laser systems. This allows for the efficient production of excited Ps states, including long-lived Rydberg states, which in turn facilitates numerous experimental programs, such as precision optical and microwave spectroscopy of Ps, the application of Stark deceleration methods to guide, decelerate and focus Rydberg Ps beams, and studies of the interactions of such beams with other atomic and molecular species. These methods are also applicable to antihydrogen production and spectroscopic studies of energy levels and resonances in positronium ions and molecules. A summary of recent progress in this area will be given, with the objective of providing an overview of the field as it currently exists, and a brief discussion of some future directions.

The European Physical Journal D•Mar 1, 2018•169 citations

The Buffer-Gas Positron Accumulator and Resonances in Positron-Molecule Interactions

Clifford M. Surko

This is a personal account of the development of our buffer-gas positron trap and the new generation of cold beams that these traps enabled. Dick Drachman provided much appreciated advice to us from the time we started the project. The physics underlying trap operation is related to resonances (or apparent resonances) in positron-molecule interactions. Amusingly, experiments enabled by the trap allowed us to understand these processes. The positron-resonance "box score" to date is one resounding "yes," namely vibrational Feshbach resonances in positron annihilation on hydrocarbons; a "probably" for positron-impact electronic excitation of CO and NZ;an d a "maybe" for vibrational excitation of selected molecules. Two of these processes enabled the efficient operation of the trap, and one almost killed it in infancy. We conclude with a brief overview of further applications of the trapping technology discussed here, such as "massive" positron storage and beams with meV energy resolution.

•Jan 1, 2007•0 citations

Laser excitation of positronium produced in various materials at a range of temperatures

B. S. Cooper

Methods and techniques in the production, manipulation, and accumulation of positrons in a `Surko-type' buffer-gas trap are presented. The pulsed output of the trap is optimised for laser excitation of positronium (Ps). The techniques of positron time compression and single-shot positron annihilation lifetime spectroscopy (SSPALS) are discussed in detail and used throughout the study. A small array or Ps converter materials have been characterised at various temperatures. Ps cooling as a function of positron implantation is presented and discussed. Direct laser irradiation of the samples, and the effect on the Ps yield has also been studied. In some cases, particularly at cryogenic temperatures, laser induced paramagnetic centres are formed and this has a detrimental effect on the Ps yield as they cause triplet Ps to convert to the shorter-lived singlet state. Whereas in single crystal semiconductors, the laser has an enhancing effect due to an exciton-like positron-electron surface state. Many of the Ps converter materials studied here are formed from porous structures. The long term confinement of Ps within isolated cavities has also been observed, where a lifetime measurement technique using an excitation laser is presented. General methods of Ps-laser spectroscopy are also presented and the applications of which are discussed including laser-enhanced time-of-flight spectroscopy (LEPTOF), and the production, and electrostatic guiding of highly excited Rydberg Ps. Using these techniques a crossed beam scattering experiment involving Rydberg Ps, electrons, and Argon ions was carried out. This work presents important considerations for experiments to create a laser-cooled Bose-Einstein condensate (BEC) of Ps in an engineered porous material at cryogenic temperatures.

•Mar 28, 2018•0 citations

Positron scattering from atoms and molecules using a magnetized beam

James Patrick Sullivan, S. J. Gilbert, Joan P. Marler +3 more

The development of buffer-gas trapping and magnetized beam formation has provided positron beams with significantly improved energy resolution $(\ensuremath{\Delta}E<~0.025\mathrm{eV})$ compared to those available previously. Analysis techniques have been developed to take advantage of the fact that the beam is in a magnetic field of $\ensuremath{\sim}0.1\mathrm{T}.$ This has enabled scattering experiments at lower energies and with significantly improved state selectivity for excitation experiments than had been possible previously. A detailed description of these techniques is presented. Data are presented for a variety of cross sections for scattering of positrons from atomic and molecular targets.

Physical Review A•Oct 15, 2002•99 citations

Cold trapped positrons and progress to cold antihydrogen

J. Estrada

A new physical mechanism for positron accumulation is explained and demonstrated. Strongly magnetized Rydberg positronium is formed and then ionized, allowing us to trap equal numbers of either positrons or electrons over a wide range of conditions. Antiprotons are trapped, cooled, and stacked from the new Antiproton Decelerator facility for the first time. Combining positrons and antiprotons, we have demonstrated the first positron cooling of antiprotons. The cooling takes place in a 4.2 K, nested Penning trap where conditions are ideal for the eventual goal of the formation of antihydrogen.

•Jan 1, 2002•2 citations
A compact, two‐stage positron accumulator has been designed, constructed and tested at Swansea, as part of a larger experiment to study Rydberg states of the positronium atom. It uses the well‐understood nitrogen buffer gas technique to trap and accumulate positrons obtained from a Na‐22 radioactive source, and slowed by a solid neon moderator. The main development this system embodies over previous accumulators is reduced physical dimension, made possible by the shorter storage times required.
Abstract A study of positron capture in a two-(pressure) stage buffer gas accumulation apparatus is presented for a variety of species, including some molecules which are known to be either efficient for positron trapping, or are frequently used to cool the particles when held in these devices. Absolute accumulation efficiencies are reported for all species. A detailed optimisation procedure, which has identified the main processes responsible for positron capture and loss in the trap, has been deployed to explore accumulation efficiency as the gas pressure and the electrostatic well depth in the trap are systematically varied. Accumulation exploiting energy loss via molecular vibrational transitions has been observed for the first time for a number of gases, though at much lower efficiency than achieved using electronic excitation processes.
The field of experimental positronium physics has advanced significantly in the last few decades, with new areas of research driven by the development of techniques for trapping and manipulating positrons using Surko-type buffer gas traps. Large numbers of positrons (typically ≥106) accumulated in such a device may be ejected all at once, so as to generate an intense pulse. Standard bunching techniques can produce pulses with ns (mm) temporal (spatial) beam profiles. These pulses can be converted into a dilute Ps gas in vacuum with densities on the order of 107 cm−3 which can be probed by standard ns pulsed laser systems. This allows for the efficient production of excited Ps states, including long-lived Rydberg states, which in turn facilitates numerous experimental programs, such as precision optical and microwave spectroscopy of Ps, the application of Stark deceleration methods to guide, decelerate and focus Rydberg Ps beams, and studies of the interactions of such beams with other atomic and molecular species. These methods are also applicable to antihydrogen production and spectroscopic studies of energy levels and resonances in positronium ions and molecules. A summary of recent progress in this area will be given, with the objective of providing an overview of the field as it currently exists, and a brief discussion of some future directions.
This is a personal account of the development of our buffer-gas positron trap and the new generation of cold beams that these traps enabled. Dick Drachman provided much appreciated advice to us from the time we started the project. The physics underlying trap operation is related to resonances (or apparent resonances) in positron-molecule interactions. Amusingly, experiments enabled by the trap allowed us to understand these processes. The positron-resonance "box score" to date is one resounding "yes," namely vibrational Feshbach resonances in positron annihilation on hydrocarbons; a "probably" for positron-impact electronic excitation of CO and NZ;an d a "maybe" for vibrational excitation of selected molecules. Two of these processes enabled the efficient operation of the trap, and one almost killed it in infancy. We conclude with a brief overview of further applications of the trapping technology discussed here, such as "massive" positron storage and beams with meV energy resolution.
Methods and techniques in the production, manipulation, and accumulation of positrons in a `Surko-type' buffer-gas trap are presented. The pulsed output of the trap is optimised for laser excitation of positronium (Ps). The techniques of positron time compression and single-shot positron annihilation lifetime spectroscopy (SSPALS) are discussed in detail and used throughout the study. A small array or Ps converter materials have been characterised at various temperatures. Ps cooling as a function of positron implantation is presented and discussed. Direct laser irradiation of the samples, and the effect on the Ps yield has also been studied. In some cases, particularly at cryogenic temperatures, laser induced paramagnetic centres are formed and this has a detrimental effect on the Ps yield as they cause triplet Ps to convert to the shorter-lived singlet state. Whereas in single crystal semiconductors, the laser has an enhancing effect due to an exciton-like positron-electron surface state. Many of the Ps converter materials studied here are formed from porous structures. The long term confinement of Ps within isolated cavities has also been observed, where a lifetime measurement technique using an excitation laser is presented. General methods of Ps-laser spectroscopy are also presented and the applications of which are discussed including laser-enhanced time-of-flight spectroscopy (LEPTOF), and the production, and electrostatic guiding of highly excited Rydberg Ps. Using these techniques a crossed beam scattering experiment involving Rydberg Ps, electrons, and Argon ions was carried out. This work presents important considerations for experiments to create a laser-cooled Bose-Einstein condensate (BEC) of Ps in an engineered porous material at cryogenic temperatures.
The development of buffer-gas trapping and magnetized beam formation has provided positron beams with significantly improved energy resolution $(\ensuremath{\Delta}E<~0.025\mathrm{eV})$ compared to those available previously. Analysis techniques have been developed to take advantage of the fact that the beam is in a magnetic field of $\ensuremath{\sim}0.1\mathrm{T}.$ This has enabled scattering experiments at lower energies and with significantly improved state selectivity for excitation experiments than had been possible previously. A detailed description of these techniques is presented. Data are presented for a variety of cross sections for scattering of positrons from atomic and molecular targets.
A new physical mechanism for positron accumulation is explained and demonstrated. Strongly magnetized Rydberg positronium is formed and then ionized, allowing us to trap equal numbers of either positrons or electrons over a wide range of conditions. Antiprotons are trapped, cooled, and stacked from the new Antiproton Decelerator facility for the first time. Combining positrons and antiprotons, we have demonstrated the first positron cooling of antiprotons. The cooling takes place in a 4.2 K, nested Penning trap where conditions are ideal for the eventual goal of the formation of antihydrogen.