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

International Conference on Low Energy Antiproton Physics (LEAP)

Antihydrogen Formation and Level Population Evolution During Passage Through a Positron Plasma

B. Radics, Daniel J. Murtagh, Y. Yamazaki, F. Robicheaux

Published Nov 23, 2017• 0 citations
Publisher

Abstract

Antihydrogen is at the focus of antimatter research.One of the main aims is to perform a direct test of the fundamental CPT symmetry by comparing the spectroscopic properties of the ground-state antihydrogen atom with those of the hydrogen atom.In current experiments synthetized antihydrogen is formed mainly via the three-body recombination process after mixing positron and antiproton clouds together in a cryogenic trap.The major three-body formation process populates mainly highly excited Rydberg states, therefore before the antihydrogen atoms reach the ground-state additional processes may take place, such as collisional (de)excitation, ionization and spontaneous or stimulated radiative transitions.We have used a classical-trajectory Monte Carlo (CTMC) code along with regular atomic codes to generate a scattering database of rate coefficients in various experimentally achievable magnetic field strengths and in low temperature positron plasma conditions.We used these rates to calculate the evolution of level population of antihydrogen during formation, scattering and flight within our experimental conditions [1].The model and the results are presented.

DOI
10.7566/jpscp.18.011012

Related papers

Antihydrogen level population evolution: impact of positron plasma length

B. Radics, Y. Yamazaki

Abstract Antihydrogen is produced by mixing an antiproton and a positron plasma in a cryogenic electromagnetic trap. The dominant antihydrogen formation mechanism is three-body recombination, while the subsequent level population evolution is governed by various processes, mainly collisional (de)excitation, ionisation and radiative decay. In this work the impact of various positron plasma lengths on the level population evolution is investigated. The main interest is the ground-state antihydrogen atom yield. It is found that the ground state level population shows different power-law behaviors at short or longer positron plasma lengths.

arXiv:1905.03281•Journal of Physics B Atomic Molecular and Optical Physics•Mar 7, 2016•11 citations

Antimatter transport processes

Dirk Peter van der Werf, Gorm Bruun Andresen, M. D. Ashkezari +37 more

A comparison of the 1S-2S transitions of hydrogen and antihydrogen will yield a stringent test of CPT conservation. Necessarily, the antihydrogen atoms need to be trapped to perform high precision spectroscopy measurements. Therefore, an approximately 0.75 T deep neutral atom trap, equivalent to about 0.5 K for ground state (anti)hydrogen atoms, has been superimposed on a Penning-Malmberg trap in which the anti-atoms are formed. The antihydrogen atoms are produced following a number of steps. A bunch of antiprotons from the CERN Antiproton Decelerator is caught in a Penning-Malmberg trap and subsequently sympathetically cooled and then compressed using rotating wall electric fields. A positron plasma, formed in a separate accumulator, is transported to the main system and also compressed. Antihydrogen atoms are then formed by mixing the antiprotons and positrons. The velocity of the anti-atoms, and their binding energies, will strongly depend on the initial conditions of the constituent particles, for example their temperatures and densities, and on the details of the mixing process. In this paper the complete lifecycle of antihydrogen atoms will be presented, starting with the production of the constituent antiparticles and the description of the manipulations necessary to prepare them appropriately for antihydrogen formation. The latter will also be described, as will the possible fates of the anti-atoms.

Journal of Physics Conference Series•Nov 1, 2010•0 citations

Scaling behavior of the ground-state antihydrogen yield as a function of positron density and temperature from classical-trajectory Monte Carlo simulations

B. Radics, Daniel J. Murtagh, Y. Yamazaki +1 more

Antihydrogen production has reached such a level that precision spectroscopic measurements of its properties are within reach. In particular, the ground-state level population is of central interest for experiments aiming at antihydrogen spectroscopy. The positron density and temperature dependence of the ground-state yield is a result of the interplay between recombination, collisional, and radiative processes. Considering the fact that antihydrogen atoms with the principal quantum number $n=15$ or lower quickly cascade down to the ground state within 1 ms, the number of such states is adopted as a measure of useful antihydrogen atoms. It has been found that the scaling behavior of the useful antihydrogen yield is different depending on the positron density and positron temperature.

arXiv:1905.03242•Physical Review A•Sep 3, 2014•32 citations

Simulations of antihydrogen formation in a nested Penning trap

S. Jonsell, Dirk Peter van der Werf, M. Charlton

We have simulated the formation of antihydrogen through three-body recombination using classical trajectories of antiprotons and positrons. The simulations include several effects which are important in current antihydrogen experiments: the full motion of the antiproton repeatedly passing into and out of the positron plasma, the energy loss of antiprotons due to the interaction with the positron plasma, and the field-ionization of antihydrogen en route from the plasma to the detector. We find that whereas the overall simulated rate of formation of antihydrogen has a density dependence close to n 2 e , the rate of antihydrogen detection follows a power law less than 2. The difference is due to the effect of density dependent field ionization.

Journal of Physics Conference Series•Jan 1, 2010•0 citations

The Production and Investigation of Cold Antihydrogen Atoms

H. Pittner

This work reports on experiments in which antihydrogen atoms have been produced in cryogenic Penning traps from antiproton and positron plasmas by two different methods and on experiments that have been carried out subsequently in order to investigate the antihydrogen atoms. By the first method antihydrogen atoms have been formed during the process of positron cooling of antiprotons in so called nested Penning traps and detected via a field ionization method. A linear dependence of the number of detected antihydrogen atoms on the number of positrons has been found. A measurement of the state distribution has revealed that the antihydrogen atoms are formed in highly excited states. This suggests along with the high production rate that the antihydrogen atoms are formed by three-body recombination processes and subsequent collisional deexcitations. However current theory cannot yet account for the measured state distribution. Typical radii of the detected antihydrogen atoms lie in the range between 0.4 µm and 0.15 µm. The deepest bound antihydrogen atoms have radii below 0.1 µm. Antihydrogen atoms with that size have chaotic positron orbits so that for the first time antihydrogen atoms have been detected that cannot be described by the GCA-model. The kinetic energy of the weakest bound antihydrogen atoms has been measured to about 200 meV, which corresponds to an antihydrogen velocity of approximately 6200 m/s. A simple model suggests that these atoms are formed from only one deexcitation collision and methods that might lead to a decrease of the antihydrogen velocity are presented. By the second method antihydrogen atoms have been synthesized in charge-exchange processes. Lasers are used to produce a Rydberg cesium beam within the cryogenic Penning trap that collides with trapped positrons so that Rydberg positronium atoms are formed via charge-exchange reactions. Due to their charge neutrality the Rydberg positronium atoms are free to leave the positron trapping region. The Rydberg positronium atoms that collide with nearby stored antiprotons form antihydrogen atoms in charge-exchange reactions. So far, 14 +/- 4 antihydrogen atoms have been detected background-free via a field-ionization method. The antihydrogen atoms produced via the two-step charge-exchange mechanism are expected to have a temperature of 4.2 K, the temperature of the antiprotons from which they are formed. A method is proposed by which the antihydrogen temperature can be determined with an accuracy of better than 1 K from a measurement of the time delay between antihydrogen annihilation events and the laser pulse that initiates the antihydrogen production via the production of Rydberg cesium atoms. First experiments have been carried out during the last days of the 2004 beam time, but the number of detected antihydrogen annihilations has been too low for a determination of the antihydrogen temperature. Trapped antiprotons have been directly exposed to laser light delivered by a Titanium:Sapphire laser in order to investigate if the laser light causes any loss on the trapped antiprotons. Experiments have shown that no extra loss occurs for laser powers of less than 590 mW. This is an important result against the background of the future plan to confine antihydrogen atoms in a combined Penning-Ioffe trap and then to carry out laser spectroscopy on these atoms, since it reveals that laser light does not cause an increase of the pressure in the trapping region to the extend that annihilations with the background gas become noticeable. The ATRAP Collaboration plans to precisely investigate antihydrogen atoms. The ultimate goal is to test the CPT-theorem by a high precision measurement of the 1S-2S transition of antihydrogen and a comparison with the precisely known value of the corresponding transition in hydrogen. This thesis presents the achievement of the first step towards this challenging goal: the production of cold antihydrogen itself.

•Jan 1, 2005•0 citations

Antihydrogen formation, dynamics and trapping

Eoin Butler

Antihydrogen, the simplest pure-antimatter atomic system, holds the promise of direct tests of matter-antimatter equivalence and CPT invariance, two of the outstanding unanswered questions in modern physics. Antihydrogen is now routinely produced in charged-particle traps through the combination of plasmas of antiprotons and positrons, but the atoms escape and are destroyed in a minuscule fraction of a second. The focus of this work is the production of a sample of cold antihydrogen atoms in a magnetic atom trap. This poses an extreme challenge, because the state-of-the-art atom traps are only approximately 0.5 K deep for ground-state antihydrogen atoms, much shallower than the energies of particles stored in the plasmas. This thesis will outline the main parts of the ALPHA experiment, with an overview of the important physical processes at work. Antihydrogen production techniques will be described, and an analysis of the spatial annihilation distribution to give indications of the temperature and binding energy distribution of the atoms will be presented. Finally, we describe the techniques needed to demonstrate confinement of antihydrogen atoms, apply them to a data taking run and present the results, making a definitive identification of trapped antihydrogen atoms.

•Jan 1, 2011•7 citations
Antihydrogen is at the focus of antimatter research.One of the main aims is to perform a direct test of the fundamental CPT symmetry by comparing the spectroscopic properties of the ground-state antihydrogen atom with those of the hydrogen atom.In current experiments synthetized antihydrogen is formed mainly via the three-body recombination process after mixing positron and antiproton clouds together in a cryogenic trap.The major three-body formation process populates mainly highly excited Rydberg states, therefore before the antihydrogen atoms reach the ground-state additional processes may take place, such as collisional (de)excitation, ionization and spontaneous or stimulated radiative transitions.We have used a classical-trajectory Monte Carlo (CTMC) code along with regular atomic codes to generate a scattering database of rate coefficients in various experimentally achievable magnetic field strengths and in low temperature positron plasma conditions.We used these rates to calculate the evolution of level population of antihydrogen during formation, scattering and flight within our experimental conditions [1].The model and the results are presented.
Abstract Antihydrogen is produced by mixing an antiproton and a positron plasma in a cryogenic electromagnetic trap. The dominant antihydrogen formation mechanism is three-body recombination, while the subsequent level population evolution is governed by various processes, mainly collisional (de)excitation, ionisation and radiative decay. In this work the impact of various positron plasma lengths on the level population evolution is investigated. The main interest is the ground-state antihydrogen atom yield. It is found that the ground state level population shows different power-law behaviors at short or longer positron plasma lengths.
A comparison of the 1S-2S transitions of hydrogen and antihydrogen will yield a stringent test of CPT conservation. Necessarily, the antihydrogen atoms need to be trapped to perform high precision spectroscopy measurements. Therefore, an approximately 0.75 T deep neutral atom trap, equivalent to about 0.5 K for ground state (anti)hydrogen atoms, has been superimposed on a Penning-Malmberg trap in which the anti-atoms are formed. The antihydrogen atoms are produced following a number of steps. A bunch of antiprotons from the CERN Antiproton Decelerator is caught in a Penning-Malmberg trap and subsequently sympathetically cooled and then compressed using rotating wall electric fields. A positron plasma, formed in a separate accumulator, is transported to the main system and also compressed. Antihydrogen atoms are then formed by mixing the antiprotons and positrons. The velocity of the anti-atoms, and their binding energies, will strongly depend on the initial conditions of the constituent particles, for example their temperatures and densities, and on the details of the mixing process. In this paper the complete lifecycle of antihydrogen atoms will be presented, starting with the production of the constituent antiparticles and the description of the manipulations necessary to prepare them appropriately for antihydrogen formation. The latter will also be described, as will the possible fates of the anti-atoms.
Antihydrogen production has reached such a level that precision spectroscopic measurements of its properties are within reach. In particular, the ground-state level population is of central interest for experiments aiming at antihydrogen spectroscopy. The positron density and temperature dependence of the ground-state yield is a result of the interplay between recombination, collisional, and radiative processes. Considering the fact that antihydrogen atoms with the principal quantum number n=15n=15n=15 or lower quickly cascade down to the ground state within 1 ms, the number of such states is adopted as a measure of useful antihydrogen atoms. It has been found that the scaling behavior of the useful antihydrogen yield is different depending on the positron density and positron temperature.
We have simulated the formation of antihydrogen through three-body recombination using classical trajectories of antiprotons and positrons. The simulations include several effects which are important in current antihydrogen experiments: the full motion of the antiproton repeatedly passing into and out of the positron plasma, the energy loss of antiprotons due to the interaction with the positron plasma, and the field-ionization of antihydrogen en route from the plasma to the detector. We find that whereas the overall simulated rate of formation of antihydrogen has a density dependence close to n 2 e , the rate of antihydrogen detection follows a power law less than 2. The difference is due to the effect of density dependent field ionization.
This work reports on experiments in which antihydrogen atoms have been produced in cryogenic Penning traps from antiproton and positron plasmas by two different methods and on experiments that have been carried out subsequently in order to investigate the antihydrogen atoms. By the first method antihydrogen atoms have been formed during the process of positron cooling of antiprotons in so called nested Penning traps and detected via a field ionization method. A linear dependence of the number of detected antihydrogen atoms on the number of positrons has been found. A measurement of the state distribution has revealed that the antihydrogen atoms are formed in highly excited states. This suggests along with the high production rate that the antihydrogen atoms are formed by three-body recombination processes and subsequent collisional deexcitations. However current theory cannot yet account for the measured state distribution. Typical radii of the detected antihydrogen atoms lie in the range between 0.4 µm and 0.15 µm. The deepest bound antihydrogen atoms have radii below 0.1 µm. Antihydrogen atoms with that size have chaotic positron orbits so that for the first time antihydrogen atoms have been detected that cannot be described by the GCA-model. The kinetic energy of the weakest bound antihydrogen atoms has been measured to about 200 meV, which corresponds to an antihydrogen velocity of approximately 6200 m/s. A simple model suggests that these atoms are formed from only one deexcitation collision and methods that might lead to a decrease of the antihydrogen velocity are presented. By the second method antihydrogen atoms have been synthesized in charge-exchange processes. Lasers are used to produce a Rydberg cesium beam within the cryogenic Penning trap that collides with trapped positrons so that Rydberg positronium atoms are formed via charge-exchange reactions. Due to their charge neutrality the Rydberg positronium atoms are free to leave the positron trapping region. The Rydberg positronium atoms that collide with nearby stored antiprotons form antihydrogen atoms in charge-exchange reactions. So far, 14 +/- 4 antihydrogen atoms have been detected background-free via a field-ionization method. The antihydrogen atoms produced via the two-step charge-exchange mechanism are expected to have a temperature of 4.2 K, the temperature of the antiprotons from which they are formed. A method is proposed by which the antihydrogen temperature can be determined with an accuracy of better than 1 K from a measurement of the time delay between antihydrogen annihilation events and the laser pulse that initiates the antihydrogen production via the production of Rydberg cesium atoms. First experiments have been carried out during the last days of the 2004 beam time, but the number of detected antihydrogen annihilations has been too low for a determination of the antihydrogen temperature. Trapped antiprotons have been directly exposed to laser light delivered by a Titanium:Sapphire laser in order to investigate if the laser light causes any loss on the trapped antiprotons. Experiments have shown that no extra loss occurs for laser powers of less than 590 mW. This is an important result against the background of the future plan to confine antihydrogen atoms in a combined Penning-Ioffe trap and then to carry out laser spectroscopy on these atoms, since it reveals that laser light does not cause an increase of the pressure in the trapping region to the extend that annihilations with the background gas become noticeable. The ATRAP Collaboration plans to precisely investigate antihydrogen atoms. The ultimate goal is to test the CPT-theorem by a high precision measurement of the 1S-2S transition of antihydrogen and a comparison with the precisely known value of the corresponding transition in hydrogen. This thesis presents the achievement of the first step towards this challenging goal: the production of cold antihydrogen itself.
Antihydrogen, the simplest pure-antimatter atomic system, holds the promise of direct tests of matter-antimatter equivalence and CPT invariance, two of the outstanding unanswered questions in modern physics. Antihydrogen is now routinely produced in charged-particle traps through the combination of plasmas of antiprotons and positrons, but the atoms escape and are destroyed in a minuscule fraction of a second. The focus of this work is the production of a sample of cold antihydrogen atoms in a magnetic atom trap. This poses an extreme challenge, because the state-of-the-art atom traps are only approximately 0.5 K deep for ground-state antihydrogen atoms, much shallower than the energies of particles stored in the plasmas. This thesis will outline the main parts of the ALPHA experiment, with an overview of the important physical processes at work. Antihydrogen production techniques will be described, and an analysis of the spatial annihilation distribution to give indications of the temperature and binding energy distribution of the atoms will be presented. Finally, we describe the techniques needed to demonstrate confinement of antihydrogen atoms, apply them to a data taking run and present the results, making a definitive identification of trapped antihydrogen atoms.