共查询到20条相似文献,搜索用时 687 毫秒
1.
Gabrielse G Bowden NS Oxley P Speck A Storry CH Tan JN Wessels M Grzonka D Oelert W Schepers G Sefzick T Walz J Pittner H Hänsch TW Hessels EA;ATRAP Collaboration 《Physical review letters》2002,89(23):233401
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. 相似文献
2.
Amoretti M Amsler C Bonomi G Bowe PD Canali C Carraro C Cesar CL Charlton M Ejsing AM Fontana A Fujiwara MC Funakoshi R Genova P Hangst JS Hayano RS Jørgensen LV Kellerbauer A Lagomarsino V Lodi Rizzini E Macrì M Madsen N Manuzio G Mitchard D Montagna P Posada LG Pruys H Regenfus C Rotondi A Telle HH Testera G Van der Werf DP Variola A Venturelli L Yamazaki Y Zurlo N;ATHENA Collaboration 《Physical review letters》2006,97(21):213401
Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n = 11 quantum state by the introduction of light from a CO2 continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration. 相似文献
3.
T. E. Cowan B. R. Beck J. H. Hartley R. H. Howell R. R. Rohatgi J. Fajans R. Gopalan 《Hyperfine Interactions》1993,76(1):135-142
The development of a high density cryogenic pure positron plasma trap at the LLNL positron beam facility opens new possibilities
for antihydrogen research. We discuss a planned measurement of the three-body collisional recombination rate in magnetized
plasmas, a possible antihydrogen atomic beam experiment, and other applications of pure positron plasmas. 相似文献
4.
Andreas Wolf 《Hyperfine Interactions》1993,76(1):189-201
Laser-stimulated radiative transitions from states close to the ionization threshold to low-lying atomic levels are considered
for protons (antiprotons) in a cold electron (positron) plasma and estimates for the resulting formation rate of hydrogen
(antihydrogen) atoms in the ground state are given. The estimates apply to both laser-stimulated recombination and induced
radiative stabilization of high Rydberg levels. First experiments concerning laser-stimulated recombination in merged beams
of electrons and protons are discussed, which have confirmed the rate predictions for this process. In view of antihydrogen
formation in a cold trapped positron plasma, the use of two successive stimulated transitions is considered for obtaining
a high formation rate of ground-state atoms at relatively low radiation intensity. 相似文献
5.
Peter Blatt 《Hyperfine Interactions》1989,44(1-4):295-304
The production of antihydrogen via positron-antiproton radiative capture can be enhanced considerably by the process of stimulated
photon emission. The gained yield of antihydrogen due to this process is evaluated for experimental conditions, where a positron
beam is merged with antiprotons circulating in a storage ring, and the overlap area of both beams is illuminated with intense
laser light. The scaling characteristics of the laser-induced gain are pointed out, considering the influence of particle
and laser beam properties, as well as competing processes like reionization and free-free transitions. A gain factor of at
least an order of magnitude seems achievable by stimulating positron capture, either into high-lying bound states using CO2 laser light or into then=2 state by means of a pulsed dye laser. 相似文献
6.
Gabrielse G Bowden NS Oxley P Speck A Storry CH Tan JN Wessels M Grzonka D Oelert W Schepers G Sefzick T Walz J Pittner H Hänsch TW Hessels EA 《Physical review letters》2002,89(21):213401
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. 相似文献
7.
N. Kuroda Y. Enomoto K. Michishio C. H. Kim H. Higaki Y. Nagata Y. Kanai H. A. Torii M. Corradini M. Leali E. Lodi-Rizzini L. Venturelli N. Zurlo K. Fujii M. Ohtsuka K. Tanaka H. Imao Y. Nagashima Y. Matsuda B. Juhász E. Widmann A. Mohri Y. Yamazaki 《Hyperfine Interactions》2012,212(1-3):31-40
The ASACUSA collaboration has been making a path to realize high precision microwave spectroscopy of ground-state hyperfine transitions of antihydrogen atom in flight for stringent test of the CPT symmetry. For this purpose, an efficient extraction of a spin polarized antihydrogen beam is essential. In 2010, we have succeeded in synthesizing our first cold antihydrogen atoms employing a CUSP trap. The CUSP trap confines antiprotons and positrons simultaneously with its axially symmetric magnetic field to form antihydrogen atoms. It is expected that antihydrogen atoms in the low-field-seeking states are preferentially focused along the cusp magnetic field axis whereas those in the high-field-seeking states are defocused, resulting in the formation of a spin-polarized antihydrogen beam. 相似文献
8.
The performance of proposed antihydrogen spectroscopy or gravity experiments will crucially depend on the temperature of the initial antihydrogen sample. Measurements by ATRAP and ATHENA have shown that antihydrogen produced with the nested-trap technique is much hotter than the temperature of the surrounding trap. Therefore, novel schemes for antihydrogen recombination as well as for the pre-cooling of antiprotons are being considered. We are investigating a possible antiproton cooling technique based on the laser cooling of negative osmium ions. If demonstrated to be successful, it will allow the sympathetic cooling of antiprotons—or any negatively charged particles—to microkelvin temperatures. As a first milestone toward the laser cooling of negative ions, we have performed collinear laser spectroscopy on negative osmium and determined the transition frequency and the cross-section of the relevant bound–bound electric-dipole transition. 相似文献
9.
Small transverse magnetic quadrupole fields sharply degrade the confinement of non-neutral plasmas held in Malmberg-Penning traps. For example, a quadrupole magnetic field of only 0.02 G/cm doubles the diffusion rate in a trap with a 100 G axial magnetic field. Larger quadrupole fields noticeably change the shape of the plasma. The transport is greatest at an orbital resonance. These results cast doubt on plans to use magnetic quadrupole neutral atom traps to confine antihydrogen atoms created in double-well positron/antiproton Malmberg-Penning traps. 相似文献
10.
Fujiwara MC Amoretti M Amsler C Bonomi G Bouchta A Bowe PD Canali C Carraro C Cesar CL Charlton M Doser M Fontana A Funakoshi R Genova P Hangst JS Hayano RS Jørgensen LV Kellerbauer A Lagomarsino V Landua R Lodi-Rizzini E Macri M Madsen N Manuzio G Mitchard D Montagna P Pruys H Regenfus C Rotondi A Testera G Variola A Venturelli L van der Werf DP Yamazaki Y Zurlo N;ATHENA Collaboration 《Physical review letters》2008,101(5):053401
We demonstrate temporally controlled modulation of cold antihydrogen production by periodic RF heating of a positron plasma during antiproton-positron mixing in a Penning trap. Our observations have established a pulsed source of atomic antimatter, with a rise time of about 1 s, and a pulse length ranging from 3 to 100 s. Time-sensitive antihydrogen detection and positron plasma diagnostics, both capabilities of the ATHENA apparatus, allowed detailed studies of the pulsing behavior, which in turn gave information on the dependence of the antihydrogen production process on the positron temperature T. Our data are consistent with power law scaling T (-1.1+/-0.5) for the production rate in the high temperature regime from approximately 100 meV up to 1.5 eV. This is not in accord with the behavior accepted for conventional three-body recombination. 相似文献
11.
A pulsed source of positrons has been developed which may be useful for antihydrogen (
) formation because it is portable when compared to accelerator-based sources. This positron accumulator uses a Penning-style
trap to collect moderated positrons from a radioactive source. The positron pulses may be emitted with repetition rates in
the range of 50–1000 Hz, which is appropriate for
production schemes involving laser-induced recombination. Bunching techniques may be used to vary the width of the positron
pulses over the range 30–120 ns (FWHM) to match the width of the antiproton and/or laser pulses. The efficiency of the accumulator
increases from ∼ 10% at 100 Hz to ∼ 50% at 1000 Hz. 250 Hz the efficiency is ∼ 25% and the accumulator has delivered up to
8 e+/pulse per mCi of positron activity. This translates into ∼ 1.2 × 105 e+/pulse for a 100 Ci58Co source. 相似文献
12.
Inward transport of a magnetized pure positron plasma confined in a Penning-Malmberg trap is produced by applying a rotating electric field to the plasma. Compression is observed over a broad range of frequencies. Compression factors up to 20 in central density were obtained. Positron collisions with a neutral buffer gas are used to counteract the heating due to the rotating electric field. The results have implications for a variety of applications including the production of brightness enhanced positron beams, the study of electron-positron plasmas, and antihydrogen production. 相似文献
13.
We report on the trapping of long-lived strongly magnetized Rydberg atoms. 85Rb atoms are laser cooled and collected in a superconducting magnetic trap with a strong bias field (2.9 T) and laser excited to Rydberg states. Collisions scatter a small fraction of the Rydberg atoms into long-lived high-angular momentum "guiding-center" Rydberg states, which are magnetically trapped. The Rydberg atomic cloud is examined using a time-delayed, position-sensitive probe. We observe magnetic trapping of these Rydberg atoms for times up to 200 ms. Oscillations of the Rydberg-atom cloud in the trap reveal an average magnetic moment of the trapped Rydberg atoms of approximately -8microB. These results provide guidance for other Rydberg-atom trapping schemes and illuminate a possible route for trapping antihydrogen. 相似文献
14.
Andresen G Bertsche W Boston A Bowe PD Cesar CL Chapman S Charlton M Chartier M Deutsch A Fajans J Fujiwara MC Funakoshi R Gill DR Gomberoff K Hangst JS Hayano RS Hydomako R Jenkins MJ Jørgensen LV Kurchaninov L Madsen N Nolan P Olchanski K Olin A Povilus A Robicheaux F Sarid E Silveira DM Storey JW Telle HH Thompson RI van der Werf DP Wurtele JS Yamazaki Y;ALPHA Collaboration 《Physical review letters》2007,98(2):023402
We have demonstrated storage of plasmas of the charged constituents of the antihydrogen atom, antiprotons and positrons, in a Penning trap surrounded by a minimum-B magnetic trap designed for holding neutral antiatoms. The neutral trap comprises a superconducting octupole and two superconducting, solenoidal mirror coils. We have measured the storage lifetimes of antiproton and positron plasmas in the combined Penning-neutral trap, and compared these to lifetimes without the neutral trap fields. The magnetic well depth was 0.6 T, deep enough to trap ground state antihydrogen atoms of up to about 0.4 K in temperature. We have demonstrated that both particle species can be stored for times long enough to permit antihydrogen production and trapping studies. 相似文献
15.
We study the ionization of atomic hydrogen by a fast positron in the presence of an external linearly polarized laser field. We concentrate on the limit of a small momentum transfer and describe the fast positron's continuum states by Volkov wave functions. The ejected electron is described by a Coulomb-Volkov wave function. We are limited to small laser intensities such that the dressed state of the target is treatable within the time-dependent perturbation theory, even though the laser intensity is still quite high by laboratory standards. Numerical results for the triply differential cross sections and their dependencies on laser-field parameters are discussed and compared with the results of laser-assisted ionization by electron impact. 相似文献
16.
Madsen N Amoretti M Amsler C Bonomi G Bowe PD Carraro C Cesar CL Charlton M Doser M Fontana A Fujiwara MC Funakoshi R Genova P Hangst JS Hayano RS Jørgensen LV Kellerbauer A Lagomarsino V Landua R Lodi-Rizzini E Macri M Mitchard D Montagna P Pruys H Regenfus C Rotondi A Testera G Variola A Venturelli L van der Werf DP Yamazaki Y Zurlo N;ATHENA Collaboration 《Physical review letters》2005,94(3):033403
Antihydrogen is formed when antiprotons are mixed with cold positrons in a nested Penning trap. We present experimental evidence, obtained using our antihydrogen annihilation detector, that the spatial distribution of the emerging antihydrogen atoms is independent of the positron temperature and axially enhanced. This indicates that antihydrogen is formed before the antiprotons are in thermal equilibrium with the positron plasma. This result has important implications for the trapping and spectroscopy of antihydrogen. 相似文献
17.
The unique capability to confine particles with opposite charge and very different mass simultaneously in the same spatial
region makes the combined trap a promising device for future synthesis of antihydrogen. For recombination experiments it is
desirable to detect particles in the combined trap non-destructively. A detection scheme is proposed for that purpose which
is based upon the interaction between stored electrons (or positrons) and the field in the microwave trap resonator.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
C. Canali C. Carraro D. Krasnicky V. Lagomarsino L. Di Noto G. Testera S. Zavatarelli 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(3):499-504
Antihydrogen experiments are currently based on non neutral electron, positron or
antiproton plasma manipulation techniques in cylindrical Malmberg-Penning traps. An
experimental study of a plasma manipulation technique based on off-axis diocotron
displacement is presented. The use of the autoresonant excitation of (1, 0) diocotron mode
of pure electron plasma allows a precise positioning of the plasma by moving it across the
magnetic field and allows dumping such plasma in a desired angular position. The
experimental procedure described here will pave the way to positron loading into an
off-axial Penning trap terminated with a positronium converter target as it is proposed
for the AEgIS experimental apparatus. The technique was studied over a range of confining
magnetic field values and reproduces experimental conditions similar to most of the
currently running antihydrogen experiments.
The efficiency of the autoresonant excitation – in terms of plasma expansion rate and
particle loss – is analyzed, studying the behaviour of electron plasma subjected to large
off-axial displacements, showing that this method fulfills the requirements imposed by the
AEgIS experiment. 相似文献
19.
N. Beverini V. Lagomarsino G. Manuzio F. Scuri G. Torelli 《Hyperfine Interactions》1989,44(1-4):207-215
The performances of proposed decelerators are compared using as figure of merit their efficiency to produce low energy antihydrogen,
by means of catching the antiproton-bunch in a trap for successive cooling and recombination with positrons. 相似文献
20.
Vrinceanu D Granger BE Parrott R Sadeghpour HR Cederbaum L Mody A Tan J Gabrielse G 《Physical review letters》2004,92(13):133402
Internal orbits of experimentally analyzed antihydrogen (H) atoms depend as much on an external magnetic field as on the Coulomb force. A circular "guiding center atom" model is used to understand their field ionization. This useful model, assumed in the theory of three-body H recombination so far, ignores the important coupling between internal and center-of-mass motion. A conserved pseudomomentum, effective potential, saddle point analysis, and numerical simulation show where the simple model is valid and classify the features of the general case, including "giant dipole states." 相似文献