共查询到20条相似文献,搜索用时 15 毫秒
1.
The storage of extremely cold (4 K) antiprotons in a Penning trap is an important step toward the creation and study of cold
antihydrogen. The other required ingredient, the largest possible number of comparably cold positrons, is still lacking. These
would be recombined in a high vacuum with the trapped antiprotons, already stored at a pressure below 5×10−17 Torr, thereby avoiding annihilation of the antihydrogen atoms before they can be used in high accuracy measurements or in
controlled collision experiments. In an exploratory experiment, positrons from a 18 mCi22Na source follow fringing field lines of a 6 T superconducting solenoid through tiny apertures in the electrodes of a Penning
trap to strike a tungsten (reflection) moderator. The positron beam is chopped mechanically and a lock-in directly detects
a positron current of 2.5×106e+/s on the moderator. The use of a moderator, unlike an earlier experiment in which < 100 positrons were confined in vacuum,
should greatly increase the number of positrons trapped in high vacuum. 相似文献
2.
A method of trapping large numbers of positrons at liquid helium temperatures in a 6 Tesla magnetic field is described. Positrons
from a sodium-22 source are moderated to low energies with a tungsten reflection moderator. A Penning trap with hyperbolic
electrodes holds the positrons in a magnetron (EXB) orbit. The positrons are then cooled via coupling to a tuned circuit that
is in resonance with the axial oscillation of the positrons. At this point, many slow positrons are permanently trapped in
the Penning trap. The positrons are centered in the trap by applying a radio-frequency field at a frequency near the sum of
the axial and magnetron frequencies. This method promises to produce 106 trapped positrons at a density of 107 to 108 per cm3. Such densities of positrons would be useful in producing antihydrogen in combination with existing antiproton plasmas. 相似文献
3.
Positrons from a 12 mCi22Na source are slowed by a W(110) reflection moderator and then captured in a Penning trap, by damping their motion with a tuned circuit. Because of the stability of the Penning trap and the cryogenic ultra-high vacuum environment, we anticipate that positrons can be accumulated and stored indefinitely. A continuous loading rate of 0.14 e+/s is observed for 32 h in this initial demonstration. More than 1.6×104 positrons have thus been trapped and stored at 4 K, with improvements expected. The extremely high vacuum is required for compatibility with an existing antiproton trap, which has already held more than 105 antiprotons at 4 K, for producing antihydrogen at low temperatures. The extremely cold positrons in high vacuum may also prove to be useful for cooling highly stripped ions. 相似文献
4.
H. Meier Z. Halabuka K. Hencken D. Trautmann G. Baur 《The European Physical Journal C - Particles and Fields》1998,5(2):287-291
Antihydrogen has recently been produced in collisions of antiprotons with ions. While passing through the Coulomb field of
a nucleus an antiproton will create an electron-positron pair. In rare cases the positron is bound by the antiproton and an
antihydrogen atom produced. We calculate the production of relativistic antihydrogen atoms by bound-free pair production.
The cross section is calculated in the semiclassical approximation (SCA), or equivalently in the plane wave Born approximation
(PWBA) using exact Dirac-Coulomb wave functions. We compare our calculations to the equivalent photon approximation (EPA).
Received: 19 December 1997 / Published online: 10 March 1998 相似文献
5.
G. Gabrielse W. Jhe D. Phillips W. Quint C. Tseng L. Haarsma K. Abdullah J. Gröbner H. Kalinowsky 《Hyperfine Interactions》1993,76(1):81-93
The possibility to produce, trap and study antihydrogen atoms rests upon the recent availability of extremely cold antiprotons
in a Penning trap. Over the last five years, our TRAP Collaboration has slowed, cooled and stored antiprotons at energies
1010 lower than was previously possible. The storage time exceeds 3.4 months despite the extremely low energy, which corresponds
to 4.2 K in temperature units. The first example of measurements which become possible with extremely cold antiprotons is
a comparison of the antiproton inertial masses which shows they are the same to a fractional accuracy of 4×10−8. (This is 1000 times more accurate than previous comparisons and large additional increases in accuracy are anticipated.)
To increase the number of trapped antiprotons available for antihydrogen production, we have demonstrated that we can accumulate
or “stack” antiprotons cooled from successive pulsed injections into our trap. 相似文献
6.
R. Conti A. Rich D. Gidley M. Skalsey J. Van House P. W. Zitzewitz H. Poth W. Schwab B. Seligmann M. Wörtge A. Wolf 《Hyperfine Interactions》1989,44(1-4):201-206
We propose a scheme to stack and accumulate positrons, emitted randomly from a radioactive source. The positrons are moderated
and accumulated at low energy. 相似文献
7.
《Physics letters. [Part B]》2004,578(1-2):23-32
We show that antihydrogen production is the dominant process when mixing antiprotons and positrons in the ATHENA apparatus, and that the initial production rate exceeds 300 Hz, decaying to 30 Hz within 10 s. A fraction of 65% of all observed annihilations is due to antihydrogen. 相似文献
8.
9.
Since antiprotons have been captured in an ion trap, we consider the possibility of producing antihydrogen by merging cold
trapped plasmas of antiprotons and positrons. The calculated, instantaneous rate for antihydrogen production by the 3-body
recombination
is much higher than for other proposed techniques, opening up intriguing experimental possibilities. 相似文献
10.
The possible formation of antihydrogen atoms via the collision of metastable antiprotonic helium atoms with positrons and
positroniums is discussed based on the known behavior of positrons in helium media. 相似文献
11.
G. Gabrielse W. Jhe D. Phillips W. Quint L. Haarsma K. Abdullah H. Kalinowsky J. Gröbner 《Hyperfine Interactions》1993,81(1-4):5-14
During the last several years, our TRAP collaboration has pioneered techniques for slowing, trapping, cooling and indefinitely storing antiprotons to energies more than 1010 times lower than previously possible. The radio signal from a single trapped antiproton is now being used for precision measurements. Many cold antiprotons are stacked as another important step toward the eventual production of antihydrogen, and positrons have been trapped in vacuum. 相似文献
12.
Amoretti M Amsler C Bonomi G Bouchta A Bowe PD Carraro C Cesar CL Charlton M Doser M Filippini V Fontana A Fujiwara MC Funakoshi R Genova P Hangst JS Hayano RS Jørgensen LV Lagomarsino V Landua R Lindelöf D Rizzini EL Macrí M Madsen N Manuzio G Montagna P Pruys H Regenfus C Rotondi A Testera G Variola A van der Werf DP;ATHENA Collaboration 《Physical review letters》2003,91(5):055001
Production of antihydrogen atoms by mixing antiprotons with a cold, confined, positron plasma depends critically on parameters such as the plasma density and temperature. We discuss nondestructive measurements, based on a novel, real-time analysis of excited, low-order plasma modes, that provide comprehensive characterization of the positron plasma in the ATHENA antihydrogen apparatus. The plasma length, radius, density, and total particle number are obtained. Measurement and control of plasma temperature variations, and the application to antihydrogen production experiments are discussed. 相似文献
13.
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
14.
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
15.
G. Baur G. Boero S. Brauksiepe A. Buzzo W. Eyrich R. Geyer D. Grzonka J. Hauffe K. Kilian M. LoVetere M. Macri M. Moosburger R. Nellen W. Oelert S. Passaggio A. Pozzo K. Röhrich K. Sachs G. Schepers T. Sefzick R.S. Simon R. Stratmann F. Stinzing M. Wolke 《Hyperfine Interactions》1997,109(1-4):191-203
The observation of the production of antihydrogen atoms \overlineH 0\equiv\barpe+, the simplest atomic bound state of antimatter, is presented.
A method has been used by the PS210 collaboration at LEAR which assumes that the production of \overlineH0 is predominantly mediated by the e+e--pair creation via the two-photon mechanism in the antiproton--nucleus interaction. Neutral \overlineH0 atoms are indentified by a unique sequence of characteristics. In principle \overlineH0 is well suited for investigations of fundamental CPT violation studies under different forces, however, in our investigations
we concentrate on the production of this antimatter object, since so far it had not been observed.
The production of eleven antihydrogen atoms is reported including possibly 2± 1 background signals, the observed yield agrees
with theoretical predictions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
M. G. Giammarchi 《Hyperfine Interactions》2009,193(1-3):321-327
Antihydrogen production by charge exchange reaction between positronium (Ps) and antiprotons requires an efficient excitation of Ps atoms up to high-n levels (Rydberg levels). We propose a two-step laser light excitation, the first from ground to n?=?3 and the second from this level to a Rydberg level n?>?15. In this study it is assumed that a Ps cloud is produced by positrons hitting a target converter located in a Penning-Malmberg trap within a uniform ~ 1 T magnetic field. We model the optical transition structure by taking into account Doppler and motional Stark effects. The predicted efficiency for population deposition in high n states is of ~30%. 相似文献
17.
A summary is given of the techniques of positron and positronium production which may be of relevance to the production of
antihydrogen atoms at low kinetic energies. Topics covered include positron beams from radioactive isotopes and via pair production
at electron accelerators, methods for trapping and accumulating positrons and prospects for the use of slow positrons to create
antihydrogen at CERN. 相似文献
18.
Driscoll CF 《Physical review letters》2004,92(14):149303; author reply 149304
19.
Heinrich Hora 《Optical and Quantum Electronics》1973,5(6):491-501
Starting from the non-linear relativistic equations of motion for charged particles in the very high intensity fields of laser radiation, the maximum kinetic energy kin of the resulting oscillation is derived exactly. In non-relativistic conditions kin agrees with the well-known valuee
2
E
v
2/(2m02|n|), showing a dependence on the rest massm
0 of the particle. In the relativistic case, the mass dependence vanishes. The multipole radiation is calculated on the basis of Sommerfeld's formula for relativistic conditions. It is shown that this radiation is not important for oscillation energies up to
=70m
0
c
2 for electrons in neodymium glass laser radiation and up to higher values for CO2 lasers and for protons. With the limitationm
0
c
2 < kin <
, the formula for kin is used to calculate the pair production (a) for singly oscillating particles in vacuum without collisions and (b) for plasmas with collisions. Taking into account the local increase of the effective electric laser field near the cut-off density due to the decrease of ¦n¦ (n is the complex refractive index), there is the possibility of efficient proton pair production at intensities of 1019 W cm–2 for neodymium glass lasers and of 1017 W cm–2 for CO2 lasers, besides electron pair production. 相似文献
20.
M. C. Fujiwara G. Andresen W. Bertsche A. Boston P. D. Bowe C. L. Cesar S. Chapman M. Charlton M. Chartier A. Deutsch J. Fajans R. Funakoshi D. R. Gill K. Gomberoff J. S. Hangst W. N. Hardy R. S. Hayano R. Hydomako M. J. Jenkins L. V. Jørgensen L. Kurchaninov N. Madsen P. Nolan K. Olchanski A. Olin R. D. Page A. Povilus F. Robicheaux E. Sarid D. M. Silveira J. W. Storey R. I. Thompson D. P. van der Werf J. S. Wurtele Y. Yamazaki 《Hyperfine Interactions》2006,172(1-3):81-89
ALPHA is an international project that has recently begun experimentation at CERN’s Antiproton Decelerator (AD) facility.
The primary goal of ALPHA is stable trapping of cold antihydrogen atoms with the ultimate goal of precise spectroscopic comparisons
with hydrogen. We discuss the status of the ALPHA project and the prospects for antihydrogen trapping. 相似文献