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William Alan Bertsche,
G. B. Andresen,
M. D. Ashkezari,
M. Baquero-Ruiz,
P. D. Bowe,
P. T. Carpenter,
E. Butler,
C. L. Cesar,
S. F. Chapman,
M. Charlton, [......],
F. Robicheaux,
E. Sarid,
D. M. Silveira,
C. So,
J. W. Storey,
R. I. Thompson, D. P. van der Werf,
J. S. Wurtele,
Y. Yamazaki,
ALPHA Collaboration
[show abstract]
[hide abstract]
ABSTRACT: In efforts to trap antihydrogen, a key problem is the vast disparity between the neutral trap energy scale (
~ 50\upmueV\sim\!50\,\upmu\mathrm{eV}), and the energy scales associated with plasma confinement and space charge (~1 eV). In order to merge charged particle species
for direct recombination, the larger energy scale must be overcome in a manner that minimizes the initial antihydrogen kinetic
energy. This issue motivated the development of a novel injection technique utilizing the inherent nonlinear nature of particle
oscillations in our traps. We demonstrated controllable excitation of the center-of-mass longitudinal motion of a thermal
antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense and highly collective in nature,
we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast,
only a fraction of the antiprotons in a warm or tenuous plasma can be similarly excited. Antihydrogen was produced and trapped
by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination. The nature of
this injection overcomes some of the difficulties associated with matching the energies of the charged species used to produce
antihydrogen.
KeywordsAntihydrogen–Plasma–Nonlinear–Dynamics
Hyperfine Interactions 05/2012; · 0.21 Impact Factor
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E. Butler,
G. B. Andresen,
M. D. Ashkezari,
M. Baquero-Ruiz,
W. Bertsche,
P. D. Bowe,
C. L. Cesar,
S. Chapman,
M. Charlton,
A. Deller, [......],
E. Sarid,
S. Seif el Nasr,
D. M. Silveira,
C. So,
J. W. Storey,
R. I. Thompson, D. P. van der Werf,
J. S. Wurtele,
Y. Yamazaki,
ALPHA Collaboration
[show abstract]
[hide abstract]
ABSTRACT: Precision spectroscopic comparison of hydrogen and antihydrogen holds the promise of a sensitive test of the Charge-Parity-Time
theorem and matter-antimatter equivalence. The clearest path towards realising this goal is to hold a sample of antihydrogen
in an atomic trap for interrogation by electromagnetic radiation. Achieving this poses a huge experimental challenge, as state-of-the-art
magnetic-minimum atom traps have well depths of only ∼1T (∼0.5K for ground state antihydrogen atoms). The atoms annihilate
on contact with matter and must be ‘born’ inside the magnetic trap with low kinetic energies. At the ALPHA experiment, antihydrogen
atoms are produced from antiprotons and positrons stored in the form of non-neutral plasmas, where the typical electrostatic
potential energy per particle is on the order of electronvolts, more than 104 times the maximum trappable kinetic energy. In November 2010, ALPHA published the observation of 38 antiproton annihilations
due to antihydrogen atoms that had been trapped for at least 172ms and then released—the first instance of a purely antimatter
atomic system confined for any length of time (Andresen etal., Nature 468:673, 2010). We present a description of the main components of the ALPHA traps and detectors that were key to realising this result.
We discuss how the antihydrogen atoms were identified and how they were discriminated from the background processes. Since
the results published in Andresen etal. (Nature 468:673, 2010), refinements in the antihydrogen production technique have allowed many more antihydrogen atoms to be trapped, and held
for much longer times. We have identified antihydrogen atoms that have been trapped for at least 1,000s in the apparatus
(Andresen etal., Nature Physics 7:558, 2011). This is more than sufficient time to interrogate the atoms spectroscopically, as well as to ensure that they have relaxed
to their ground state.
KeywordsAntihydrogen–Antimatter–CPT–Atom trapping
Hyperfine Interactions 04/2012; · 0.21 Impact Factor
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E. Butler,
G. B. Andresen,
M. D. Ashkezari,
M. Baquero-Ruiz,
W. Bertsche,
P. D. Bowe,
C. C. Bray,
C. L. Cesar,
S. Chapman,
M. Charlton, [......],
E. Sarid,
D. M. Silveira,
C. So,
J. W. Storey,
R. I. Thompson, D. P. van der Werf,
D. Wilding,
J. S. Wurtele,
Y. Yamazaki,
ALPHA Collaboration
[show abstract]
[hide abstract]
ABSTRACT: Spectroscopy of antihydrogen has the potential to yield high-precision tests of the CPT theorem and shed light on the matter-antimatter
imbalance in the Universe. The ALPHA antihydrogen trap at CERN’s Antiproton Decelerator aims to prepare a sample of antihydrogen
atoms confined in an octupole-based Ioffe trap and to measure the frequency of several atomic transitions. We describe our
techniques to directly measure the antiproton temperature and a new technique to cool them to below 10K. We also show how
our unique position-sensitive annihilation detector provides us with a highly sensitive method of identifying antiproton annihilations
and effectively rejecting the cosmic-ray background.
KeywordsAntihydrogen–Antimatter–CPT–Penning trap–Atom trap
Hyperfine Interactions 04/2012; 199(1):39-48. · 0.21 Impact Factor
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C Amole,
M D Ashkezari,
M Baquero-Ruiz,
W Bertsche,
P D Bowe,
E Butler,
A Capra,
C L Cesar,
M Charlton,
A Deller, [......],
C Ø Rasmussen,
F Robicheaux,
E Sarid,
C R Shields,
D M Silveira,
S Stracka,
C So,
R I Thompson, D P van der Werf,
J S Wurtele
[show abstract]
[hide abstract]
ABSTRACT: The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom's stature lies in its simplicity and in the accuracy with which its spectrum can be measured and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and--by comparison with measurements on its antimatter counterpart, antihydrogen--the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves.
Nature 03/2012; 483(7390):439-43. · 36.28 Impact Factor
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C Amole,
G B Andresen,
M D Ashkezari,
M Baquero-Ruiz,
W Bertsche,
E Butler,
C L Cesar,
S Chapman,
M Charlton,
A Deller, [......],
A Povilus,
P Pusa,
F Robicheaux,
E Sarid,
D M Silveira,
C So,
J W Storey,
R I Thompson, D P van der Werf,
J S Wurtele
[show abstract]
[hide abstract]
ABSTRACT: Recently, antihydrogen atoms were trapped at CERN in a magnetic minimum (minimum-B) trap formed by superconducting octupole and mirror magnet coils. The trapped antiatoms were detected by rapidly turning off these magnets, thereby eliminating the magnetic minimum and releasing any antiatoms contained in the trap. Once released, these antiatoms quickly hit the trap wall, whereupon the positrons and antiprotons in the antiatoms annihilate. The antiproton annihilations produce easily detected signals; we used these signals to prove that we trapped antihydrogen. However, our technique could be confounded by mirror-trapped antiprotons, which would produce seemingly identical annihilation signals upon hitting the trap wall. In this paper, we discuss possible sources of mirror-trapped antiprotons and show that antihydrogen and antiprotons can be readily distinguished, often with the aid of applied electric fields, by analyzing the annihilation locations and times. We further discuss the general properties of antiproton and antihydrogen trajectories in this magnetic geometry, and reconstruct the antihydrogen energy distribution from the measured annihilation time history.
New Journal of Physics 01/2012; 14(1):015010. · 4.18 Impact Factor
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C. Amole,
G. B. Andresen,
M. D. Ashkezari,
M. Baquero-Ruiz,
W. Bertsche,
E. Butler,
C. L. Cesar,
S. Chapman,
M. Charlton,
A. Deller, [......],
A. Povilus,
P. Pusa,
F. Robicheaux,
E. Sarid,
D. M. Silveira,
C. So,
J. W. Storey,
R. I. Thompson, D. P. van der Werf,
J. S. Wurtele
[show abstract]
[hide abstract]
ABSTRACT: Recently, antihydrogen atoms were trapped at CERN in a magnetic minimum
(minimum-B) trap formed by superconducting octupole and mirror magnet coils.
The trapped antiatoms were detected by rapidly turning off these magnets,
thereby eliminating the magnetic minimum and releasing any antiatoms contained
in the trap. Once released, these antiatoms quickly hit the trap wall,
whereupon the positrons and antiprotons in the antiatoms annihilated. The
antiproton annihilations produce easily detected signals; we used these signals
to prove that we trapped antihydrogen. However, our technique could be
confounded by mirror-trapped antiprotons, which would produce
seemingly-identical annihilation signals upon hitting the trap wall. In this
paper, we discuss possible sources of mirror-trapped antiprotons and show that
antihydrogen and antiprotons can be readily distinguished, often with the aid
of applied electric fields, by analyzing the annihilation locations and times.
We further discuss the general properties of antiproton and antihydrogen
trajectories in this magnetic geometry, and reconstruct the antihydrogen energy
distribution from the measured annihilation time history.
01/2012;
-
E Lodi Rizzini,
L Venturelli,
N Zurlo,
M Charlton,
C Amsler,
G Bonomi,
C Canali,
C Carraro,
A Fontana,
P Genova, [......],
R Landua,
M Macrí,
G Manuzio,
P Montagna,
C Regenfus,
A Rotondi,
G Testera,
A Variola, D P Van Der Werf,
L V Jørgensen
[show abstract]
[hide abstract]
ABSTRACT: We describe an experiment performed in the ATHENA apparatus in which there is evidence that the antiproton-proton bound state, protonium, has been produced at very low energies in vacuum following the interaction of cold antiprotons with a trapped cloud of molecular hydrogen ions. The latter were confined in a centrifugally separated belt outside a positron plasma used for antihydrogen formation. Studies have been performed at low positron plasma temperatures in which the protonium annihilation signal has been identified along with that from antihydrogen, and we discuss how their contributions can be disentangled. With the positron plasma heated to around 10000 K the ions become distributed in the positrons, and the majority of the annihilation signal can be explained in terms of protonium formation, as antihydrogen creation is heavily suppressed. In this case we compare the observed protonium formation rate with expectations from theory and find reasonable accord, when experimental systematics are taken into account. The effect on the annihilation signals of the passage of an electron current through a pre-loaded positron plasma has been studied in detail, and the results are presented here for the first time.
The European Physical Journal Plus. 01/2012; 127(124).
-
[show abstract]
[hide abstract]
ABSTRACT: Positron lifetime experiments have been performed on CO2 and SF6 gases at temperatures in the range 297–400 K and at densities up to 10 amagat. The ensemble-averaged Zeff parameter has been extracted at each temperature from the observed density dependence of the annihilation rates. The latter was found to be consistent with annihilation via positron interactions both with single molecules and with pairs. The three-body (positron-plus-two molecules) annihilation coefficient, b, has also been obtained at each temperature. Both Zeff and b are found to be approximately independent of temperature in the range investigated. A simple three-body collision model for b is developed and discussed.
Journal of Physics B Atomic Molecular and Optical Physics 08/2011; 44(17):175204. · 1.88 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The application of an asymmetric dipolar electric field rotating at a frequency close to that of the axial bounce of a collection of trapped positrons has, in the presence of a low pressure molecular gas to provide cooling, been used to achieve compression of the cloud. A theory of this effect has been developed for a Penning trap potential, with the cooling modeled in the Stokes viscous drag approximation. Good agreement between the theory and measurements of the frequency dependence of the cloud compression rate has been found, establishing that the phenomenon is a new form of sideband cooling.
Physical Review Letters 07/2011; 107(3):033201. · 7.37 Impact Factor
-
ALPHA Collaboration,
G. B. Andresen,
M. D. Ashkezari,
M. Baquero-Ruiz,
W Bertsche,
E. Butler,
C L Cesar,
A. Deller,
S. Eriksson,
J. Fajans, [......],
C. Ø. Rasmussen,
F. Robicheaux,
E. Sarid,
D. M. Silveira,
C. So,
J. W. Storey,
R. I. Thompson, D P van der Werf,
J. S. Wurtele,
Y Yamazaki
[show abstract]
[hide abstract]
ABSTRACT: Atoms made of a particle and an antiparticle are unstable, usually surviving
less than a microsecond. Antihydrogen, made entirely of antiparticles, is
believed to be stable, and it is this longevity that holds the promise of
precision studies of matter-antimatter symmetry. We have recently demonstrated
trapping of antihydrogen atoms by releasing them after a confinement time of
172 ms. A critical question for future studies is: how long can anti-atoms be
trapped? Here we report the observation of anti-atom confinement for 1000 s,
extending our earlier results by nearly four orders of magnitude. Our
calculations indicate that most of the trapped anti-atoms reach the ground
state. Further, we report the first measurement of the energy distribution of
trapped antihydrogen which, coupled with detailed comparisons with simulations,
provides a key tool for the systematic investigation of trapping dynamics.
These advances open up a range of experimental possibilities, including
precision studies of CPT symmetry and cooling to temperatures where
gravitational effects could become apparent.
04/2011;
-
G B Andresen,
M D Ashkezari,
M Baquero-Ruiz,
W Bertsche,
P D Bowe,
E Butler,
C L Cesar,
S Chapman,
M Charlton,
A Deller, [......],
P Pusa,
F Robicheaux,
E Sarid,
D M Silveira,
C So,
J W Storey,
R I Thompson, D P van der Werf,
J S Wurtele,
Y Yamazaki
[show abstract]
[hide abstract]
ABSTRACT: Charges in cold, multiple-species, non-neutral plasmas separate radially by mass, forming centrifugally separated states. Here, we report the first detailed measurements of such states in an electron-antiproton plasma, and the first observations of the separation dynamics in any centrifugally separated system. While the observed equilibrium states are expected and in agreement with theory, the equilibration time is approximately constant over a wide range of parameters, a surprising and as yet unexplained result. Electron-antiproton plasmas play a crucial role in antihydrogen trapping experiments.
Physical Review Letters 04/2011; 106(14):145001. · 7.37 Impact Factor
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M Charlton,
G B Andresen,
M D Ashkezari,
M Baquero-Ruiz,
W Bertsche,
P D Bowe,
C C Bray,
E Butler,
C L Cesar,
S Chapman, [......],
E Sarid,
S Seif El Nasr,
D M Silveira,
C So,
J W Storey,
R I Thompson, D P Van Der Werf,
D Wilding,
J S Wurtele,
Y Yamazaki
[show abstract]
[hide abstract]
ABSTRACT: Sources of positrons and antiprotons that are currently used for the formation of antihydrogen with low kinetic energies are reviewed, mostly in the context of the ALPHA collaboration and its predecessor ATHENA. The experiments were undertaken at the Antiproton Decelerator facility, which is located at CERN. Operations performed on the clouds of antiparticles to facilitate their mixing to produce antihydrogen are described. These include accumulation, cooling and manipulation. The formation of antihydrogen and some of the characteristics of the anti-atoms that are created are discussed. Prospects for trapping antihydrogen in a magnetic minimum trap, as envisaged by the ALPHA collaboration, are reviewed.
Journal of Physics Conference Series 01/2011; 262(1):012001.
-
G B Andresen,
M D Ashkezari,
M Baquero-Ruiz,
W Bertsche,
P D Bowe,
E Butler,
P T Carpenter,
C L Cesar,
S Chapman,
M Charlton, [......],
P Pusa,
F Robicheaux,
E Sarid,
D M Silveira,
C So,
J W Storey,
R I Thompson, D P van der Werf,
J S Wurtele,
Y Yamazaki
[show abstract]
[hide abstract]
ABSTRACT: We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination.
Physical Review Letters 01/2011; 106(2):025002. · 7.37 Impact Factor
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N. Madsen,
G. B. Andresen,
M. D. Ashkezari,
M. Baquero-Ruiz,
W. Bertsche,
P. D. Bowe,
C. Bray,
E. Butler,
C. L. Cesar,
S. Chapman, [......],
F. Robicheaux,
E. Sarid,
S. S. El Nasr,
D. M. Silveira,
C. So,
J. W. Storey,
R. I. Thompson, D. P. van der Werf,
J. S. Wurtele,
Y. Yamazaki
[show abstract]
[hide abstract]
ABSTRACT: Antihydrogen spectroscopy promises precise tests of the symmetry of matter and antimatter, and can possibly offer new insights into the baryon asymmetry of the universe. Antihydrogen is, however, difficult to synthesize and is produced only in small quantities. The ALPHA collaboration is therefore pursuing a path towards trapping cold antihydrogen to permit the use of precision atomic physics tools to carry out comparisons of antihydrogen and hydrogen. ALPHA has addressed these challenges. Control of the plasma sizes has helped to lower the influence of the multipole field used in the neutral atom trap, and thus lowered the temperature of the created atoms. Finally, the first systematic attempt to identify trapped antihydrogen in our system is discussed. This discussion includes special techniques for fast release of the trapped anti-atoms, as well as a silicon vertex detector to identify antiproton annihilations. The silicon detector reduces the background of annihilations, including background from antiprotons that can be mirror trapped in the fields of the neutral atom trap. A description of how to differentiate between these events and those resulting from trapped antihydrogen atoms is also included.La spectroscopie de l'anti-hydrogène promet des tests précieux de la symétrie entre matière et antimatière dans l'univers. Cependant, l'anti-hydrogène est difficile à synthétiser et il n'est produit qu'en petite quantité. Le groupe de collaborateurs ALPHA poursuit donc des travaux pour capturer de l'anti-hydrogène froid afin de permettre l'utilisation d'outils précis de mesure en physique atomique pour comparer l'anti-hydrogène avec l'hydrogène. Nous montrons comment ALPHA s'est attaqué à cette tâche et comment le contrôle du volume de plasma a aidé à diminuer l'influence des champs multipolaires utilisés dans le piège pour atomes neutres et ainsi abaisser la température des atomes produits. Finalement, nous discutons le premier essai systématique pour identifier l'anti-hydrogène piégé dans notre système. Ceci inclut des techniques spéciales pour relâcher rapidement les anti-atomes piégés, ainsi qu'un détecteur au silicium pour identifier l'annihilation de l'anti-proton. Nous avons utilisé le détecteur au silicium pour réduire le fond d'annihilation, incluant celui produit par les anti-protons qui peuvent être dans le piège miroir des champs du piège à atomes neutres. Nous décrivons aussi comment nous pouvons différentier entre ces événements et ceux qui résultent des atomes d'anti-hydrogène piégés.
Canadian Journal of Physics 12/2010; 89(1):7-16. · 0.86 Impact Factor
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G B Andresen,
M D Ashkezari,
M Baquero-Ruiz,
W Bertsche,
P D Bowe,
E Butler,
C L Cesar,
S Chapman,
M Charlton,
A Deller, [......],
F Robicheaux,
E Sarid,
S Seif el Nasr,
D M Silveira,
C So,
J W Storey,
R I Thompson, D P van der Werf,
J S Wurtele,
Y Yamazaki
[show abstract]
[hide abstract]
ABSTRACT: Antimatter was first predicted in 1931, by Dirac. Work with high-energy antiparticles is now commonplace, and anti-electrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the bound state of an antiproton and a positron, has been produced at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature's fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 10(14) for the frequency of the 1s-to-2s transition), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen could also be used to study the gravitational behaviour of antimatter. However, so far experiments have produced antihydrogen that is not confined, precluding detailed study of its structure. Here we demonstrate trapping of antihydrogen atoms. From the interaction of about 10(7) antiprotons and 7 × 10(8) positrons, we observed 38 annihilation events consistent with the controlled release of trapped antihydrogen from our magnetic trap; the measured background is 1.4 ± 1.4 events. This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen.
Nature 11/2010; 468(7324):673-6. · 36.28 Impact Factor
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G B Andresen,
M D Ashkezari,
M Baquero-Ruiz,
W Bertsche,
P D Bowe,
E Butler,
C L Cesar,
S Chapman,
M Charlton,
J Fajans, [......],
F Robicheaux,
E Sarid,
D M Silveira,
C So,
J W Storey,
R I Thompson, D P van der Werf,
D Wilding,
J S Wurtele,
Y Yamazaki
[show abstract]
[hide abstract]
ABSTRACT: We report the application of evaporative cooling to clouds of trapped antiprotons, resulting in plasmas with measured temperature as low as 9 K. We have modeled the evaporation process for charged particles using appropriate rate equations. Good agreement between experiment and theory is observed, permitting prediction of cooling efficiency in future experiments. The technique opens up new possibilities for cooling of trapped ions and is of particular interest in antiproton physics, where a precise CPT test on trapped antihydrogen is a long-standing goal.
Physical Review Letters 07/2010; 105(1):013003. · 7.37 Impact Factor
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G. B. Andresen,
W Bertsche,
P D Bowe,
C. Bray,
E. Butler,
C L Cesar,
S. Chapman,
M Charlton,
J. Fajans,
M C Fujiwara, [......],
P. Pusa,
F. Robicheaux,
E. Sarid,
S. Seif El Nasr,
D. M. Silveira,
J. W. Storey,
R. I. Thompson, D P van der Werf,
J. S. Wurtele,
Y Yamazaki
[show abstract]
[hide abstract]
ABSTRACT: Antihydrogen production in a neutral atom trap formed by an octupole-based magnetic field minimum is demonstrated using field-ionization of weakly bound anti-atoms. Using our unique annihilation imaging detector, we correlate antihydrogen detection by imaging and by field-ionization for the first time. We further establish how field-ionization causes radial redistribution of the antiprotons during antihydrogen formation and use this effect for the first simultaneous measurements of strongly and weakly bound antihydrogen atoms. Distinguishing between these provides critical information needed in the process of optimizing for trappable antihydrogen. These observations are of crucial importance to the ultimate goal of performing CPT tests involving antihydrogen, which likely depends upon trapping the anti-atom.
02/2010;
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[show abstract]
[hide abstract]
ABSTRACT: Magnetised positronium is formed by impacting low energy positrons onto a gas covered target immersed in a magnetic field (B ≥ 1T). The resulting weakly bound positronium atoms subsequently travel some distance in an arrangement of Penning-type traps whereupon they can be field ionised. The remnant positrons are accumulated and then detected by forced annihilation on the target. The production efficiency of the magnetised atoms has been measured for different species of gases, gas layer thickness and the strength of the magnetic field. The positronium loss as a function of the distance travelled has been measured and is shown to be caused by the magnetron drift of the positronium atom.
Journal of Physics Conference Series 01/2010; 199(1):012005.
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[show abstract]
[hide abstract]
ABSTRACT: 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 n2e, 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 01/2010; 199(1):012008.
-
D P Van Der Werf,
G B Andresen,
M D Ashkezari,
M Baquero-Ruiz,
W Bertsche,
P D Bowe,
C C Bray,
E Butler,
C L Cesar,
S Chapman, [......],
A Povilus,
P Pusa,
F Robicheaux,
E Sarid,
D M Silveira,
C So,
J W Storey,
R I Thompson,
J S Wurtele,
Y Yamazaki
J. Phys.: Conf. Ser. 01/2010; 257126162.
