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1.
2.
Michael Charlton 《Hyperfine Interactions》1996,100(1):55-64
We survey the progress made towards the production of antihydrogen by antiproton-positronium collisions as of June 1995. The tasks remaining before such an experiment can be attempted are outlined. Some comments are made concerning the effects of the intended closure of the Low Energy Antiproton Ring (LEAR) at the end of 1996. We conclude with a personal account of the development of, in particular, the Aarhus—UCL collaboration and some memories of Bernie Deutch. 相似文献
3.
We discuss the behavior of magnetically trapped antihydrogen (
) at temperatures relevant for gravity and spectroscopy experiments (well below 1 K) and the possibilities of attaining these
temperatures. Two possible options are considered. In the discussion of the first one, i.e.
as admixture in cold H gas, we develop the quantum-mechanical theory of
-H (and also
-H) elastic and rearrangement collisions at ultra-low (sub-Kelvin) energies, when s-wave scattering in the incoming channel
dominates. The rate constant of rearrangement leading to
decay turns out to be large, which makes the possibilities for
collisional cooling in H gas and
-H coexistence rather limited. As we show, the most promising is the other option, i.e.
atoms in the collisionless regime. For this regime the possibility of one-dimensional adiabatic cooling of
is demonstrated by using the example of the Ioffe trap. This phenomenon, interesting from the fundamental point of view,
offers the opportunity to cool
below 1 mK. 相似文献
4.
5.
R. J. Hughes 《Hyperfine Interactions》1993,76(1):1-16
The prospects for testing CPT invariance and the weak equivalence principle (WEP) for antimatter with spectroscopic measurements
on antihydrogen are discussed. The potential precisions of these tests are compared with those from other measurements.
“If there is negative electricity, why not negative gold, as yellow...as our own, with the same boiling point and identical
spectrallines...”
A. Schuster [1], 1898 相似文献
6.
The antihydrogen formation via two-body recombination in a cylindrical trap is studied and a very crude estimation of the formation rate is presented. The possibility of using the thermal wave model to describe the particle distribution function in a trap has been checked in some simple cases. 相似文献
7.
8.
B. I. Deutch 《Hyperfine Interactions》1992,73(1-2):175-191
The main suggested routes for atomic antihydrogen (
) formation will be reviewed in a pedestrian fashion. These are the following reactions:
, and (iii)
. The present status of the projects related to these reactions, as well as the projects' experimental scope, will also be
discussed or referred to. Some speculations will be made regarding the physics that can be yielded by an antihydrogen probe. 相似文献
9.
In this paper we study the properties of a Paul trap with a superimposed magnetic field (combined trap) and discuss the possibility
of using this trap to simultaneously store positrons and antiprotons to form antihydrogen. 相似文献
10.
In view of current interest in the trapping of antihydrogen (
) atoms at low temperatures [1–3], we have carried out a full four-body variational calculation to determine s-wave elastic phase shifts for hydrogen antihydrogen scattering, using the Kohn Variational Principle. Terms outside the Born–Oppenheimer
approximation have been taken into account using the formalism of Kołos and Wolniewicz [4]. As far as we are aware, this is
the first time that these terms have been included in an H
scattering calculation. This is a continuation of earlier work on H–
interactions [5–7]. Preliminary results differ substantially from those calculated using the Born–Oppenheimer approximation
[8–10]. A method is outlined for reducing this discrepancy and taking the rearrangement channel into account.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
In this paper we show how the ATHENA data samples on the antihydrogen ( ${\bar{\rm H}}$ ) formation in very different conditions provide useful information on the two different possible mechanisms: the 3-body reaction ( $\bar{p}+{e^+}+{e^+}\rightarrow {\bar{\rm H}}+ e^+$ ) and the 2-body reaction ( $\bar{p}+{\rm e^+}\rightarrow {\bar{\rm H}}+{h\nu}$ ). 相似文献
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H. Poth 《Applied Physics A: Materials Science & Processing》1987,43(4):287-293
In this paper the production of a beam of antihydrogen atoms through the capture of positrons by antiprotons in an arrangement of merged parallel beams is considered. The achievable luminosity is estimated on the basis of available antiproton and positron intensities. The scaling of the luminosity with various parameters is investigated. It is argued that an intense beam of antihydrogen can be obtained if antiprotons and positrons are stored, recirculated and cooled. While the number of stored antiprotons which can be achieved at present is already high, schemes for the accumulation of slow and cooled positrons have to be developed. Possible ways are pointed out. The fact that a high number of both species of charged particles can be accumulated, stored, and recirculated, compensates largely for the low capture cross-section.Invited talk given at the International Symposium on the Production of Low-Energy Positrons with Accelerators and Applications, Giessen, Fed. Rep. Germany (25–27 September 1986)Visitor at CERN, Geneva, Switzerland 相似文献
14.
Gabrielse G Larochelle P Le Sage D Levitt B Kolthammer WS McConnell R Richerme P Wrubel J Speck A George MC Grzonka D Oelert W Sefzick T Zhang Z Carew A Comeau D Hessels EA Storry CH Weel M Walz J;ATRAP Collaboration 《Physical review letters》2008,100(11):113001
Slow antihydrogen (H) is produced within a Penning trap that is located within a quadrupole Ioffe trap, the latter intended to ultimately confine extremely cold, ground-state H[over ] atoms. Observed H[over ] atoms in this configuration resolve a debate about whether positrons and antiprotons can be brought together to form atoms within the divergent magnetic fields of a quadrupole Ioffe trap. The number of detected H atoms actually increases when a 400 mK Ioffe trap is turned on. 相似文献
15.
I.N. Meshkov 《Hyperfine Interactions》1997,109(1-4):225-232
16.
Marco G. Giammarchi 《Few-Body Systems》2013,54(5-6):779-782
The main goal of the AEGIS experiment at the CERN Antiproton Decelerator is testing fundamental laws such as the weak equivalence principle (WEP) and the CPT symmetry. In the first phase of AEGIS, a beam of antihydrogen will be formed whose fall in the gravitational field is measured in a Moirè deflectometer; this will constitute the first test of the WEP with antimatter. 相似文献
17.
H. Poth B. Seligmann W. Schwab M. Wörtge A. Wolf R. Conti W. Frieze D. Gidley A. Rich M. Skalsey J. Van House P. Zitzewitz J. Berger P. Blatt R. Neumann G. Zu Putlitz 《Hyperfine Interactions》1989,44(1-4):257-270
The production of antihydrogen by merging beams of antiprotons and positrons is described. Both beams, kept in storage devices,
are continuously recirculated. Antihydrogen is formed by radiative recombination of positrons and antiprotons. Production
rates of a few thousand per second are expected. The semi-relativistic atomic beam of antihydrogen would have a divergence
of less than 1 mrad and a beam diameter of a few millimeter. The possibilities to increase these rates by induced recomtination
are discussed. The scheme of antihydrogen production in overlapping beams is compared to other approaches. 相似文献
18.
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 S. Eriksson J. Fajans T. Friesen M. C. Fujiwara D. R. Gill A. Gutierrez J. S. Hangst W. N. Hardy R. S. Hayano M. E. Hayden A. J. Humphries J. L. Hurt R. Hydomako S. Jonsell L. Kurchaninov N. Madsen S. Menary P. Nolan K. Olchanski A. Olin 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 Y. Yamazaki 《Hyperfine Interactions》2012,212(1-3):61-67
In efforts to trap antihydrogen, a key problem is the vast disparity between the neutral trap energy scale ( $\sim\!50\,\upmu\mathrm{eV}$ ), 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. 相似文献
19.
In view of current interest in the trapping of antihydrogen atoms at low temperatures [1–3], we have investigated the reasons for considering that does not have a bound state. We go on to carry out a four-body variational calculation for s-wave hydrogen-antihydrogen scattering, using the Kohn variational method. This is a continuation of earlier work on interactions [5–7].
Received October 30, 2001; accepted for publication November 21, 2001 相似文献
20.
《Hyperfine Interactions》1997,109(1-4):1-32
The study of CPT invariance with the highest achievable precision in all particle sectors is of fundamental importance for
physics. Equally important is the question of the gravitational acceleration of antimatter.
In recent years, impressive progress has been achieved at the Low Energy Antiproton Ring (LEAR) at CERN in capturing antiprotons
in specially designed Penning traps, in cooling them to energies of a few milli-electron volts, and in storing them for hours
in a small volume of space. Positrons have been accumulated in large numbers in similar traps, and low energy positron or
positronium beams have been generated. Finally, steady progress has been made in trapping and cooling neutral atoms.
Thus the ingredients to form antihydrogen at rest are at hand. We propose to investigate the different methods to form antihydrogen
at low energy, and to utilize the best of these methods to capture a number of antihydrogen atoms sufficient for spectroscopic
studies in a magnetostatic trap.
Once antihydrogen atoms have been captured at low energy, spectroscopic methods can be applied to interrogate their atomic
structure with extremely high precision and compare it to its normal matter counterpart, the hydrogen atom. Especially the
1S-2S transition, with a lifetime of the excited state of 122 ms and thereby a natural linewidth of 5 parts in 1016, offers in principle the possibility to directly compare matter and antimatter properties at a level of 1 part in 1018.
Additionally, comparison of the gravitational masses of hydrogen and antihydrogen, using either ballistic or spectroscopic
methods, can provide direct experimental tests of the Weak Equivalence Principle for antimatter at a high precision.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献