40 results on '"Charlton M"'
Search Results
2. Sympathetic cooling of positrons to cryogenic temperatures for antihydrogen production.
- Author
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Baker, C. J., Bertsche, W., Capra, A., Cesar, C. L., Charlton, M., Mathad, A. Cridland, Eriksson, S., Evans, A., Evetts, N., Fabbri, S., Fajans, J., Friesen, T., Fujiwara, M. C., Grandemange, P., Granum, P., Hangst, J. S., Hayden, M. E., Hodgkinson, D., Isaac, C. A., and Johnson, M. A.
- Subjects
ANTIHYDROGEN ,POSITRONS ,ANTIPARTICLES ,COOLING ,ANTIMATTER ,DENSE plasmas - Abstract
The positron, the antiparticle of the electron, predicted by Dirac in 1931 and discovered by Anderson in 1933, plays a key role in many scientific and everyday endeavours. Notably, the positron is a constituent of antihydrogen, the only long-lived neutral antimatter bound state that can currently be synthesized at low energy, presenting a prominent system for testing fundamental symmetries with high precision. Here, we report on the use of laser cooled Be
+ ions to sympathetically cool a large and dense plasma of positrons to directly measured temperatures below 7 K in a Penning trap for antihydrogen synthesis. This will likely herald a significant increase in the amount of antihydrogen available for experimentation, thus facilitating further improvements in studies of fundamental symmetries. Positrons are key to the production of cold antihydrogen. Here the authors report the sympathetic cooling of positrons by interacting them with laser-cooled Be+ ions resulting in a three-fold reduction of the temperature of positrons for antihydrogen synthesis. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
3. On the binding energies of antihydrogen formed by the interactions of antiprotons in cold positron plasmas.
- Author
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Jonsell, S and Charlton, M
- Subjects
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BINDING energy , *LOW temperature plasmas , *POSITRONS , *ANTIPROTONS , *ANTIHYDROGEN , *MAGNETIC flux density , *PLASMA density - Abstract
The binding energies of antihydrogen atoms formed when antiprotons are mixed with positron plasmas having densities ranging from 1013–1015 m−3, and at temperatures of 5–30 K, have been investigated using simulations. Major changes in the distribution of binding energies are observed, with more strongly bound states evident at the higher densities, and at lower temperatures. For deeper binding, the distribution of binding energies follows a power-law which is found to be strongly dependent upon plasma properties and the strength of the applied magnetic field. The underpinning role of collisions in determining the binding energies is explored. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
4. Investigation of buffer gas trapping of positrons.
- Author
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Baker, C J, Isaac, C A, Edwards, D, Evans, H T, Clayton, R, van der Werf, D P, and Charlton, M
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POSITRONS ,ELECTRONIC excitation ,ENERGY dissipation ,GASES ,POSITRONIUM - Abstract
A study of positron capture in a two-(pressure) stage buffer gas accumulation apparatus is presented for a variety of species, including some molecules which are known to be either efficient for positron trapping, or are frequently used to cool the particles when held in these devices. Absolute accumulation efficiencies are reported for all species. A detailed optimisation procedure, which has identified the main processes responsible for positron capture and loss in the trap, has been deployed to explore accumulation efficiency as the gas pressure and the electrostatic well depth in the trap are systematically varied. Accumulation exploiting energy loss via molecular vibrational transitions has been observed for the first time for a number of gases, though at much lower efficiency than achieved using electronic excitation processes. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
5. Accumulation of Positrons from a LINAC Based Source.
- Author
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NIANG, S., CHARLTON, M., CHOI, J. J., CHUNG, M., CLADÉ, P., COMINI, P., CRIVELLI, P., CRÉPIN, P.-P., DALKAROV, O., DEBU, P., DODD, L., DOUILLET, A., FROEHLICH, P., GAFRILLER, J., GUELLATI, S., HEINRICH, J., HERVIEUX, P.-A., HILICO, L., HUSSON, A., and INDELICATO, P.
- Subjects
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POSITRONS , *POSITRONIUM , *ANTIPROTONS , *IONS - Abstract
The GBAR experiment aims to measure the gravitational acceleration of antihydrogen H. It will use H+ ions formed by the interaction of antiprotons with a dense positronium cloud, which will require about 1010 positrons to produce one H+. We present the first results on the positron accumulation, reaching 3.8±0.4×108 e+ collected in 560 s. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
6. Antihydrogen accumulation for fundamental symmetry tests.
- Author
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Ahmadi, M., Alves, B. X. R., Baker, C. J., Bertsche, W., Butler, E., Capra, A., Carruth, C., Cesar, C. L., Charlton, M., Cohen, S., Collister, R., Eriksson, S., Evans, A., Evetts, N., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., and Hangst, J. S.
- Subjects
ANTIHYDROGEN ,ANTIPROTONS ,SOLENOIDS ,POSITRONS ,MAGNETIC flux density - Abstract
Antihydrogen, a positron bound to an antiproton, is the simplest anti-atom. Its structure and properties are expected to mirror those of the hydrogen atom. Prospects for precision comparisons of the two, as tests of fundamental symmetries, are driving a vibrant programme of research. In this regard, a limiting factor in most experiments is the availability of large numbers of cold ground state antihydrogen atoms. Here, we describe how an improved synthesis process results in a maximum rate of 10.5 ± 0.6 atoms trapped and detected per cycle, corresponding to more than an order of magnitude improvement over previous work. Additionally, we demonstrate how detailed control of electron, positron and antiproton plasmas enables repeated formation and trapping of antihydrogen atoms, with the simultaneous retention of atoms produced in previous cycles. We report a record of 54 detected annihilation events from a single release of the trapped anti-atoms accumulated from five consecutive cycles. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
7. Positron accumulation in the GBAR experiment.
- Author
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Blumer, P., Charlton, M., Chung, M., Cladé, P., Comini, P., Crivelli, P., Dalkarov, O., Debu, P., Dodd, L., Douillet, A., Guellati, S., Hervieux, P.-A., Hilico, L., Husson, A., Indelicato, P., Janka, G., Jonsell, S., Karr, J.-P., Kim, B.H., and Kim, E.S.
- Subjects
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POSITRONS , *POSITRONIUM , *ANTIHYDROGEN , *ULTRAHIGH vacuum , *GRAVITATIONAL fields , *ANTIPROTONS - Abstract
We present a description of the GBAR positron (e +) trapping apparatus, which consists of a three stage Buffer Gas Trap (BGT) followed by a High Field Penning Trap (HFT), and discuss its performance. The overall goal of the GBAR experiment is to measure the acceleration of the neutral antihydrogen (H ¯) atom in the terrestrial gravitational field by neutralising a positive antihydrogen ion ( H ¯ + ), which has been cooled to a low temperature, and observing the subsequent H ¯ annihilation following free fall. To produce one H ¯ + ion, about 1 0 10 positrons, efficiently converted into positronium (Ps), together with about 1 0 7 antiprotons (p ¯), are required. The positrons, produced from an electron linac-based system, are accumulated first in the BGT whereafter they are stacked in the ultra-high vacuum HFT, where we have been able to trap 1.4(2) × 109 positrons in 1100 s. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
8. Modelling the behavior of the positron plasma temperature in antihydrogen experimentation.
- Author
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Lodi-Rizzini, E., Mascagna, V., Venturelli, L., Zurlo, N., and Charlton, M.
- Subjects
POSITRONS ,PLASMA temperature ,ANTIHYDROGEN ,SYNCHROTRON radiation ,THREE-body problem ,QUANTUM mechanics - Abstract
Antihydrogen is now routinely produced at CERN by overlapping clouds of positrons and antiprotons. The mechanisms responsible for antihydrogen formation (radiative capture and the three-body reaction) are both dependent on the temperature of the positrons ( T), though with a different weight. Here we present a simple model of the behavior of the positron temperature based on the main processes involved during antihydrogen synthesis, namely: antiproton-positron collisions, positron heating due to plasma expansion and cooling via the emission of synchrotron radiation. The time evolution of T has been simulated by changing the relevant parameters of the mechanisms involved in order to highlight the importance of the different (competing) effects. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
9. Antiproton compression and radial measurements.
- Author
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Andresen, G. B., Bertsche, W., Bowe, P. D., Bray, C. C., Butler, E., Cesar, C. L., Chapman, S., Charlton, M., Fajans, J., Fujiwara, M. C., Funakoshi, R., Gill, D. R., Hangst, J. S., Hardy, W. N., Hayano, R. S., Hayden, M. E., Humphries, A. J., Hydomako, R., Jenkins, M. J., and Jo\rgensen, L. V.
- Subjects
ANTIPROTONS ,PROTONS ,ELECTRONS ,POSITRONS ,PARTICLES (Nuclear physics) ,NUCLEAR physics - Abstract
Control of the radial profile of trapped antiproton clouds is critical to trapping antihydrogen. We report detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, achieved by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial profile, and its relation to that of the electron plasma. We also measure the outer radial profile by ejecting antiprotons to the trap wall using an octupole magnet. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
10. Results from ATHENA.
- Author
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Rotondi, A., Amoretti, M., Amsler, C., Bonomi, G., Bowe, P. D., Canali, C., Carraro, C., Cesar, C. L., Charlton, M., Doser, M., Fontana, A., Fujiwara, M. C., Funakoshi, R., Genova, P., Hangst, J. S., Hayano, R. S., Jorgensen, L. V., Kellerbauer, A., Lagomarsino, V., and Landua, R.
- Subjects
ANTIPROTONS ,HYDROGEN ,POSITRONS ,PLASMA gases ,ATOMS ,PHYSICAL & theoretical chemistry - Abstract
The ATHENA experiment at CERN produced for the first time in 2002 cold antihydrogen atoms by mixing of antiprotons and a positron plasma. The more relevant results obtained in the last three years are presented and discussed in the light of the antihydrogen formation processes. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
11. Cold Antihydrogen at ATHENA: Experimental Observation and Beyond.
- Author
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Cesar, C. L., Amoretti, M., Bonomi, G., Bowe, P. D., Canali, C., Carraro, C., Charlton, M., Doser, M., Fontana, A., Fujiwara, M. C., Funakoshi, R., Genova, P., Hangst, J. S., Hayano, R. S., Johnson, I., Jørgensen, L. V., Kellerbauer, A., Lagomarsino, V., Landua, R., and Lodi Rizzini, E.
- Subjects
PHYSICAL & theoretical chemistry ,ATOMS ,PROTONS ,CONSTITUTION of matter ,POSITRONS ,HOLES (Electron deficiencies) - Abstract
Antihydrogen atoms may become the easiest and most precise way to probe deeply into tests of violation of the CPT (charge conjugation, parity, time reversal) symmetry and the Weak Equivalence Principle (WEP). We review the first production of cold antihydrogen atoms within the ATHENA/AD-1 experiment at CERN, its motivations and studies henceforth. The ATHENA success was followed almost immediately by the ATRAP group. From the initial claim of production of tens of thousand of these exotic species — by the mixing of cold and trapped positrons and antiprotons — we have evolved to better understand and control the system. The joint production for 2002 and 2003 has been re-evaluated to about one million antiatoms. We have performed cooling efficiency studies of antiprotons within the positron cloud; developed ways to excite and heat the positron cloud, and probe its number, density and temperature in situ; developed antiproton and antihydrogen imaging tomography. We have also been able to gather information on the velocity of the formed antiatoms. A large uncertainty and lack of control remains over the formation process — as revealed by its measured temperature dependence — and the quantum number distribution of the population. We discuss various aspects of our findings below as well as future prospects for physics tests with antihydrogen. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
12. Antihydrogen Formation using Cold Plasmas.
- Author
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Madsen, N., Amoretti, M., Amsler, C., Bonomi, G., Bouchta, A., Bowe, P. D., Carraro, C., Cesar, C. L., Charlton, M., Doser, M., Fontana, A., Fujiwara, M. C., Funakoshi, R., Genova, P., Hangst, J. S., Hayano, R. S., Johnson, I., Jørgensen, L. V., Kellerbauer, A., and Lagomarsino, V.
- Subjects
HYDROGEN ,ANTIPROTONS ,POSITRONS ,HOLES (Electron deficiencies) ,ANNIHILATION reactions ,NONMETALS - Abstract
Antihydrogen, the antimatter counterpart of the hydrogen atom, can be formed by mixing cold samples of antiprotons and positrons. In 2002 the ATHENA collaboration succeeded in the first production of cold antihydrogen. By observing and imaging the annihilation products of the neutral, non-confined, antihydrogen atoms annihilating on the walls of the trap we can observe the production in quasi-real-time and study the dynamics of the formation mechanism. The formation mechanism strongly influences the final state of the formed antihydrogen atoms, important for future spectroscopic comparison with hydrogen. This paper briefly summarizes the current understanding of the antihydrogen formation in ATHENA. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
13. Non-Destructive Positron Plasma Diagnostics for Antihydrogen Production.
- Author
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Amoretti, M., Amsler, C., Bonomi, G., Bouchta, A., Bowe, P.D., Carraro, C., Cesar, C.L., Charlton, M., Doser, M., Filippini, V., Fontana, A., Fujiwara, M.C., Funakoshi, R., Genova, P., Hangst, J.S., Hayaho, R.S., Jörgensen, L.V., Lagomarsino, V., and Landua, R.
- Subjects
PLASMA diagnostics ,POSITRONS ,ANTIPROTONS ,NONNEUTRAL plasma - Abstract
Production of antihydrogen atoms by mixing antiprotons with a cold, confined, positron plasma depends on parameters such as the plasma density and temperature. We discuss a non-destructive diagnostic, based on an analysis of excited, low-order plasma modes, that provides comprehensive characterization of the positron plasma in the ATHENA antihydrogen apparatus. The dipole and quadrupole modes of a spheroidal positron plasma are interpreted in the framework of a cold fluid theory. In particular, the excitation and detection of the dipole mode are analytically modeled considering the response of the center-of-mass to a resonant driving perturbation. The model is compared to, and validated by, numerical simulations with a particle-in-cell code. Measurements of the positron plasma properties are discussed. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2003
- Full Text
- View/download PDF
14. Transfer, stacking and compression of positron plasmas under UHV conditions.
- Author
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van der Werf, D.P., Amoretti, M., Bonomi, G., Bouchta, A., Bowe, P., Carraro, C., Cesar, C.L., Charlton, M., Doser, M., Filippini, V., Fontana, A., Fujiwara, M.C., Funakoshi, R., Genova, P., Hangst, J.S., Hayano, R.S., Jörgensen, L.V., Lagomarsino, V., and Landua, R.
- Subjects
PLASMA gases ,POSITRONS ,MAGNETIC traps - Abstract
A ballistic method is presented for transferring positron plasmas emanating from a region with a low magnetic field and relatively high pressure into a 15 K Penning-Malmberg trap immersed in a 3 T magnetic field with a base pressure of the order of 10-13 mbar. Subsequent stacking resulted in a plasma containing 4.2 × 108 positrons. Using a rotating wall electric field a plasma containing 90 million positrons was compressed to a density of 3.6 × 109 cm-3. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2003
- Full Text
- View/download PDF
15. Developments in the Trapping and Accumulation of Slow Positrons using the Buffer Gas Technique.
- Author
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Clarke, J., van der Werf, D.P., Charlton, M., Beddows, D., Griffiths, B., and Telle, H.H.
- Subjects
POSITRONS ,RYDBERG states ,POSITRONIUM - Abstract
A compact, two-stage positron accumulator has been designed, constructed and tested at Swansea, as part of a larger experiment to study Rydberg states of the positronium atom. It uses the well-understood nitrogen buffer gas technique to trap and accumulate positrons obtained from a Na-22 radioactive source, and slowed by a solid neon moderator. The main development this system embodies over previous accumulators is reduced physical dimension, made possible by the shorter storage times required. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2003
- Full Text
- View/download PDF
16. Recent progress on the ATHENA positron accumulator.
- Author
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Jørgensen, L. V., van der Werf, D. P., Watson, T. L., Charlton, M., and Collier, M. J. T.
- Subjects
POSITRONS ,PLASMA gases - Abstract
The Positron Accumulator for the ATHENA anti-hydrogen experiment at CERN, Geneva has recently been upgraded with a new 50 mCi [sup 22]Na β[sup +]-radioactive source. Following this, rapid progress has been made in optimizing and characterizing the properties of the positron plasma. The rotating wall technique has also been implemented in the accumulation region and has been shown to lead to compression of better than a factor of 10 in density and markedly increased lifetimes, even when using the N[sub 2] buffer gas as a cooling gas. Using these techniques we have routinely accumulated up to 2 x 10[sup 8] positrons in a few minutes. The positron plasma has a FWHM of only 3-4 mm when using the rotating wall which compares with a FWHM of 15 mm without the rotating wall. [ABSTRACT FROM AUTHOR]
- Published
- 2002
17. Antihydrogen formation by autoresonant excitation of antiproton plasmas.
- Author
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Bertsche, William, Andresen, G., Ashkezari, M., Baquero-Ruiz, M., Bowe, P., Carpenter, P., Butler, E., Cesar, C., Chapman, S., Charlton, M., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M., Gill, D., Gutierrez, A., Hangst, J., Hardy, W., Hayano, R., and Hayden, M.
- Subjects
ANTIHYDROGEN ,NUCLEAR excitation ,ANTIPROTONS ,POSITRONS ,ELECTRONS - Abstract
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. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
18. The behaviour of positron clouds in the single-particle regime under the influence of rotating wall electric fields.
- Author
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Van der Werf, D. P., Isaac, C. A., Baker, C. J., Mortensen, T., Kerrigan, S. J., and Charlton, M.
- Subjects
POSITRONS ,ELECTRIC fields ,ANNIHILATION reactions ,PHYSICS ,GASES - Abstract
Positron clouds are compressed following accumulation in a Surkotype two-stage buffer gas trap using an asymmetric rotating wall electric field. An analytic theory used to describe measurements of the rate of compression is discussed. Furthermore, we describe measurements taken without the rotating wall applied and with the rotating wall compression present during accumulation of the positron cloud. This has enabled total loss rates for the positrons via annihilation and collisional-induced radial transport to be isolated, with the latter mechanism found to be dominant. We have shown that the application of the rotating wall at a resonant frequency virtually eliminates radial transport, such that the positron loss is caused by annihilation in the gas. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
19. Discriminating between antihydrogen and mirror-trapped antiprotons in a minimum-B trap.
- Author
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Amole, C., Andresen, G. B., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Butler, E., Cesar, C. L., Chapman, S., Charlton, M., Deller, A., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayden, M. E., and Humphries, A. J.
- Subjects
ANTIHYDROGEN ,ANTIPROTONS ,POSITRONS ,MATHEMATICAL models ,NUMERICAL analysis - 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. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
20. Confinement of antihydrogen for 1,000 seconds.
- Author
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Andresen, G. B., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Bowe, P. D., Butler, E., Cesar, C. L., Charlton, M., Deller, A., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayano, R. S., Hayden, M. E., and Humphries, A. J.
- Subjects
ATOMS ,ATOMIC hydrogen ,LOW temperature engineering ,EXOTIC atoms ,PENNING trap mass spectrometry ,POSITRONS - 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 1,000?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 charge-parity-time reversal symmetry and cooling to temperatures where gravitational effects could become apparent. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
21. Trapped antihydrogen.
- Author
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Andresen, G. B., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Bowe, P. D., Butler, E., Cesar, C. L., Chapman, S., Charlton, M., Deller, A., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayden, M. E., and Humphries, A. J.
- Subjects
POSITRON emission tomography ,MAGNETIC traps ,SPECTROSCOPIC imaging ,NUCLEAR reactions ,ANTIPROTONS ,POSITRONS ,BIOCONJUGATES - 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 107 antiprotons and 7 × 108 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. [ABSTRACT FROM AUTHOR]- Published
- 2010
- Full Text
- View/download PDF
22. Antiproton, positron, and electron imaging with a microchannel plate/phosphor detector.
- Author
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Andresen, G. B., Bertsche, W., Bowe, P. D., Bray, C. C., Butler, E., Cesar, C. L., Chapman, S., Charlton, M., Fajans, J., Fujiwara, M. C., Gill, D. R., Hangst, J. S., Hardy, W. N., Hayano, R. S., Hayden, M. E., Humphries, A. J., Hydomako, R., Jørgensen, L. V., Kerrigan, S. J., and Kurchaninov, L.
- Subjects
MICROREACTORS ,FLUORESCENT screens ,ANTIPROTONS ,POSITRONS ,ELECTRONS ,SCIENTIFIC apparatus & instruments - Abstract
A microchannel plate (MCP)/phosphor screen assembly has been used to destructively measure the radial profile of cold, confined antiprotons, electrons, and positrons in the ALPHA experiment, with the goal of using these trapped particles for antihydrogen creation and confinement. The response of the MCP to low energy (10–200 eV, <1 eV spread) antiproton extractions is compared to that of electrons and positrons. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
23. Antihydrogen for precision tests in physics.
- Author
-
Charlton, M., Jonsell, S., Jørgensen, L. V., Madsen, N., and van der Werf, D. P.
- Subjects
- *
ATOMS , *ANTIMATTER , *PROPERTIES of matter , *MAGNETIC fields , *FIELD theory (Physics) , *PHYSICAL & theoretical chemistry - Abstract
The creation of atoms of antihydrogen under controlled conditions has opened up a new era in physics with antimatter. We describe the experimental realisation of low energy antihydrogen, via the mixing of carefully prepared clouds of positrons and antiprotons, and some of the progress that has been made in the last few years in characterising properties of the nascent anti-atoms. Ongoing efforts aimed at trapping the anti-atoms in magnetic field minima are discussed. Some of the motivations for undertaking experiments with antihydrogen are presented. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
24. Production and detection of cold antihydrogen atoms.
- Author
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Amoretti, M., Amsier, C., Bonomi, G., Bouchta, A., Bowell, P., Carraro, C., Cesar, C.L., Charlton, M., Collier, M.J.T., Doser, M., Filippini, V., Fine, K.S., Fontana, A., Fujiwara, M.C., Funakoshi, R., Genova, P., Hangst, J.S., Hayano, R.S., and Lindelof, D.
- Subjects
ANTIMATTER ,ATOMS ,ANTIPROTONS ,POSITRONS - Abstract
Discusses the production and detection of cold antihydrogen atoms. Mixing of trapped antiprotons and positrons in a cryogenic environment; Direct detection of neutral anti-atoms when they escape the trap and annihilate, producing a characteristic signature in an imaging particle detector.
- Published
- 2002
- Full Text
- View/download PDF
25. Metastable states in antihydrogen formation.
- Author
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Jonsell, S., Werf, D., and Charlton, M.
- Subjects
METASTABLE states ,ANTIHYDROGEN ,ANTIPROTONS ,POSITRONS ,PLASMA gases ,SIMULATION methods & models - Abstract
Formation of antihydrogen atoms from antiprotons immersed in a positron plasma is simulated. Special attention is devoted to the role of metastable states, arising from the near conservation of the energy stored in the cyclotron motion of the positrons. We find that the decay of such states changes the density scaling of the formation rate. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
26. Positron production using a 9 MeV electron linac for the GBAR experiment.
- Author
-
Charlton, M., Choi, J.J., Chung, M., Cladé, P., Comini, P., Crépin, P.-P., Crivelli, P., Dalkarov, O., Debu, P., Dodd, L., Douillet, A., Guellati-Khélifa, S., Hervieux, P.-A., Hilico, L., Husson, A., Indelicato, P., Janka, G., Jonsell, S., Karr, J.-P., and Kim, B.H.
- Subjects
- *
POSITRONS , *LINEAR accelerators , *ELECTRONS , *ELECTRON accelerators , *POSITRONIUM , *PAIR production , *KINETIC energy - Abstract
For the GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment at CERN's Antiproton Decelerator (AD) facility we have constructed a source of slow positrons, which uses a low-energy electron linear accelerator (linac). The driver linac produces electrons of 9 MeV kinetic energy that create positrons from bremsstrahlung-induced pair production. Staying below 10 MeV ensures no persistent radioactive activation in the target zone and that the radiation level outside the biological shield is safe for public access. An annealed tungsten-mesh assembly placed directly behind the target acts as a positron moderator. The system produces 5 × 1 0 7 slow positrons per second, a performance demonstrating that a low-energy electron linac is a superior choice over positron-emitting radioactive sources for high positron flux. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
27. Improvement of rare-gas solid moderators by using conical geometry.
- Author
-
Khatri, R., Charlton, M., Sferlazzo, P., Lynn, K. G., Mills, A. P., and Roellig, L. O.
- Subjects
- *
SOLID rare gases , *REACTOR moderators , *POSITRONS - Abstract
A slow positron beam with narrow energy spread can be obtained by moderating the β+ decay of a radioactive source. We report here the improvement in the efficiency of the rare-gas solid positron moderators by using a different geometry. The efficiency for slow positrons, ε, was measured for the cylindrical and the cone configurations of the moderator with the latter yielding ε of (4.6±0.2)×10-3 for solid neon deposited on an encapsulated radioactive 22Na source deposited on a 5 μm Cu98/Be2 window. No corrections were applied for the attenuation caused by the window. The ε for the conical configuration is (2.7 ± 0.2) times higher than that for the cylindrical configuration. Other rare-gas solids (e.g., Ar, Xe, Kr) yielded lower ε as compared to that for the solid neon in agreement with the earlier measured efficiencies of Mills and Gullikson [Appl. Phys. Lett. 49, 1121
(1986)]. [ABSTRACT FROM AUTHOR] - Published
- 1990
- Full Text
- View/download PDF
28. Radially selective inward transport of positrons in a Penning–Malmberg trap.
- Author
-
Deller, A, Mortensen, T, Isaac, C A, Werf, D P van der, and Charlton, M
- Subjects
POSITRONS ,PENNING trap mass spectrometry ,ELECTRIC fields ,ANHARMONIC motion ,ELECTRONS - Abstract
The anharmonic component of the electric field of a Penning–Malmberg trap is exploited to manipulate a subset of the radial (r) distribution of trapped positrons, using a dipole field made to rotate about the long-axis (z) of the trap. This ‘rotating wall’ technique (RW) induces inward transport at frequencies associated with the motion of trapped particles, although similarly it causes heating. The motional frequencies vary spatially within a non-ideal trap, thus resonant interaction with the rotating field may be restricted to a region selected to lie away from the trap centre, thereby forming a pseudo-potential barrier and reducing losses due to both heating and expansion. We demonstrate this effect for improved accumulation of positrons and further outline a technique to achieve strong compression with low RW amplitudes by chirping the drive frequency. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
29. Experimental and computational study of the injection of antiprotons into a positron plasma for antihydrogen production.
- Author
-
Amole, C., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Butler, E., Capra, A., Cesar, C. L., Charlton, M., Deller, A., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayden, M. E., Isaac, C. A., and Jonsell, S.
- Subjects
ANTIPROTONS ,PLASMA gas research ,POSITRONS ,ANTIHYDROGEN ,HYDROGEN production ,CP violation ,SYMMETRY (Physics) - Abstract
One of the goals of synthesizing and trapping antihydrogen is to study the validity of charge-parity-time symmetry through precision spectroscopy on the anti-atoms, but the trapping yield achieved in recent experiments must be significantly improved before this can be realized. Antihydrogen atoms are commonly produced by mixing antiprotons and positrons stored in a nested Penning-Malmberg trap, which was achieved in ALPHA by an autoresonant excitation of the antiprotons, injecting them into the positron plasma. In this work, a hybrid numerical model is developed to simulate antiproton and positron dynamics during the mixing process. The simulation is benchmarked against other numerical and analytic models, as well as experimental measurements. The autoresonant injection scheme and an alternative scheme are compared numerically over a range of plasma parameters which can be reached in current and upcoming antihydrogen experiments, and the latter scheme is seen to offer significant improvement in trapping yield as the number of available antiprotons increases. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
30. The ALPHA antihydrogen trapping apparatus.
- Author
-
Amole, C., Andresen, G.B., Ashkezari, M.D., Baquero-Ruiz, M., Bertsche, W., Bowe, P.D., Butler, E., Capra, A., Carpenter, P.T., Cesar, C.L., Chapman, S., Charlton, M., Deller, A., Eriksson, S., Escallier, J., Fajans, J., Friesen, T., Fujiwara, M.C., Gill, D.R., and Gutierrez, A.
- Subjects
- *
ANTIHYDROGEN , *NEUTRONS , *RADIATION trapping , *ATOM trapping , *NUCLEAR structure , *NUCLEAR physics experiments - Abstract
Abstract: The ALPHA collaboration, based at CERN, has recently succeeded in confining cold antihydrogen atoms in a magnetic minimum neutral atom trap and has performed the first study of a resonant transition of the anti-atoms. The ALPHA apparatus will be described herein, with emphasis on the structural aspects, diagnostic methods and techniques that have enabled antihydrogen trapping and experimentation to be achieved. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
31. Towards trapped antihydrogen
- Author
-
Jørgensen, L.V., Andresen, G., Bertsche, W., Boston, A., Bowe, P.D., Cesar, C.L., Chapman, S., Charlton, M., Fajans, J., Fujiwara, M.C., Funakoshi, R., Gill, D.R., Hangst, J.S., Hayano, R.S., Hydomako, R., Jenkins, M.J., Kurchaninov, L., Madsen, N., Nolan, P., and Olchanski, K.
- Subjects
- *
ATOMS , *ANTIPROTONS , *PHYSICS , *HYDROGEN - Abstract
Abstract: Substantial progress has been made in the last few years in the nascent field of antihydrogen physics. The next big step forward is expected to be the trapping of the formed antihydrogen atoms using a magnetic multipole trap. ALPHA is a new international project that started to take data in 2006 at CERN’s Antiproton Decelerator facility. The primary goal of ALPHA is stable trapping of cold antihydrogen atoms to facilitate measurements of its properties. We discuss the status of the ALPHA project and the prospects for antihydrogen trapping. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
32. A magnetic trap for antihydrogen confinement
- Author
-
Bertsche, W., Boston, A., Bowe, P.D., Cesar, C.L., Chapman, S., Charlton, M., Chartier, M., Deutsch, A., Fajans, J., Fujiwara, M.C., Funakoshi, R., Gomberoff, K., Hangst, J.S., Hayano, R.S., Jenkins, M.J., Jørgensen, L.V., Ko, P., Madsen, N., Nolan, P., and Page, R.D.
- Subjects
- *
MAGNETIC traps , *PLASMA confinement , *NONMETALS , *HYDROGEN - Abstract
Abstract: The goal of the ALPHA collaboration at CERN is to test CPT conservation by comparing the 1S–2S transitions of hydrogen and antihydrogen. To reach the ultimate accuracy of 1 part in , the (anti)atoms must be trapped. Using current technology, only magnetic minimum traps can confine (anti)hydrogen. In this paper, the design of the ALPHA antihydrogen trap and the results of measurements on a prototype system will be presented. The trap depth of the final system will be 1.16T, corresponding to a temperature of 0.78K for ground state antihydrogen. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
33. Progress with cold antihydrogen
- Author
-
Amoretti, M., Amsler, C., Bonomi, G., Bowe, P.D., Canali, C., Carraro, C., Cesar, C.L., Charlton, M., Doser, M., Fontana, A., Fujiwara, M.C., Funakoshi, R., Genova, P., Hangst, J.S., Hayano, R.S., Johnson, I., Jørgensen, L.V., Kellerbauer, A., Lagomarsino, V., and Landua, R.
- Subjects
- *
ANTIPROTONS , *POSITRONS , *HYDROGEN , *ATOMS - Abstract
Abstract: The creation of cold antihydrogen by the ATHENA and ATRAP collaborations, working at CERN’s unique Antiproton Decelerator (AD) facility, has ushered in a new era in atomic physics. This contribution will briefly review recent results from the ATHENA experiment. These include discussions of antiproton slowing down in a cold positron gas during antihydrogen formation, information derived on the dependence of the antihydrogen formation rate upon the temperature of the stored positron plasma and, finally, upon the spatial distribution of the emitted anti-atoms. We will discuss the implications of these studies for the major outstanding goal of trapping samples of antihydrogen for precise spectroscopic comparisons with hydrogen. The physics motivations for undertaking these challenging experiments will be briefly recalled. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
34. Antihydrogen production mechanisms in ATHENA
- Author
-
Bonomi, G., Amoretti, M., Bowe, P.D., Canali, C., Carraro, C., Cesar, C.L., Charlton, M., Doser, M., Fontana, A., Fujiwara, M.C., Funakoshi, R., Genova, P., Hangst, J.S., Hayano, R.S., Jørgensen, L.V., Kellerbauer, A., Lagomarsino, V., Landua, R., Lodi Rizzini, E., and Macrí, M.
- Subjects
- *
PROTONS , *ANTIPROTONS , *POSITRONS , *HOLES (Electron deficiencies) - Abstract
Production of cold antihydrogen in electromagnetic traps by mixing of antiprotons and positrons has been previously reported [M. Amoretti et al., Nature 419 (2002) 456; M. Amoretti et al., Phys. Lett. B 578 (2004) 23; G. Gabrielse et al., Phys. Rev. Lett. 89 (2002) 213401; G. Gabrielse et al., Phys. Rev. Lett. 89 (2002) 233401]. The study of the dependence of the antihydrogen production upon the positron plasma density and temperature is an important tool to distinguish between the possible processes for the formation of antiatoms. In this article results concerning the temperature dependence will be presented, along with a preliminary analysis of the density dependence. [Copyright &y& Elsevier]
- Published
- 2005
- Full Text
- View/download PDF
35. The ATHENA antihydrogen apparatus
- Author
-
Amoretti, M., Amsler, C., Bonomi, G., Bouchta, A., Bowe, P.D., Carraro, C., Charlton, M., Collier, M.J.T., Doser, M., Filippini, V., Fine, K.S., Fontana, A., Fujiwara, M.C., Funakoshi, R., Genova, P., Glauser, A., Grögler, D., Hangst, J., Hayano, R.S., and Higaki, H.
- Subjects
- *
POSITRONS , *ANTIPROTONS , *HYDROGEN , *ANNIHILATION reactions - Abstract
The ATHENA apparatus that recently produced and detected the first cold antihydrogen atoms is described. Its main features, which are described herein, are: an external positron accumulator, making it possible to accumulate large numbers of positrons; a separate antiproton catching trap, optimizing the catching, cooling and handling of antiprotons; a unique high resolution antihydrogen annihilation detector, allowing an clear determination that antihydrogen has been produced; an open, modular design making variations in the experimental approach possible and a “nested” Penning trap situated in a cryogenic, 3T magnetic field environment used for the mixing of the antiprotons and positrons. [Copyright &y& Elsevier]
- Published
- 2004
- Full Text
- View/download PDF
36. Production and detection of cold antihydrogen atoms
- Author
-
Amoretti, M., Amsler, C., Bonomi, G., Bouchta, A., Bowe, P.D., Carraro, C., Cesar, C.L., Charlton, M., Doser, M., Filippini, V., Fontana, A., Fujiwara, M.C., Funakoshi, R., Genova, P., Hangst, J.S., Hayano, R.S., Jørgensen, L.V., Lagomarsino, V., Landua, R., and Lindelöf, D.
- Subjects
- *
ANTIPROTONS , *ELECTROMAGNETISM , *POSITRONS , *IMAGE analysis - Abstract
The production and observation of cold antihydrogen atoms have been recently reported by the ATHENA experiment at the CERN Antiproton Decelerator. The antiatoms were produced by mixing low-energy antiprotons and positrons in an electromagnetic trap. The antihydrogen detection is based on the observation of a characteristic signature in the annihilation of the neutral antiatoms on the trap walls by means of an imaging particle detector. An overview of the apparatus is given and the results obtained are discussed. [Copyright &y& Elsevier]
- Published
- 2004
- Full Text
- View/download PDF
37. First production and detection of cold antihydrogen atoms
- Author
-
Fujiwara, M.C., Amoretti, M., Amsler, C., Bonomi, G., Bouchta, A., Bowe, P., Carraro, C., Cesar, C.L., Charlton, M., Doser, M., Filippini, V., Fontana, A., Funakoshi, R., Genova, P., Hangst, J.S., Hayano, R.S., Jørgensen, L.V., Lagomarsino, V., Landua, R., and Lindelöf, D.
- Subjects
- *
HYDROGEN , *PLASMA gases , *ATOMS - Abstract
The ATHENA experiment recently produced the first atoms of cold antihydrogen. This paper gives a brief review of how this was achieved. [Copyright &y& Elsevier]
- Published
- 2004
- Full Text
- View/download PDF
38. Temperature dependence of anti-hydrogen production in the ATHENA experiment
- Author
-
Bonomi, G., Amoretti, M., Amsler, C., Bouchta, A., Bowe, P., Carraro, C., Cesar, C.L., Charlton, M., Doser, M., Filippini, V., Fontana, A., Fujiwara, M.C., Funakoshi, R., Genova, P., Hangst, J.S., Hayano, R.S., Jørgensen, L.V., Lagomarsino, V., Landua, R., and Lindelöf, D.
- Subjects
- *
HYDROGEN , *TEMPERATURE control , *PROTONS , *POSITRONS - Abstract
The ATHENA experiment recently produced the first sample of cold anti-hydrogen atoms by mixing cold plasmas of anti-protons and positrons. The temperature of the positron plasma was increased by controlled RF heating and the anti-hydrogen production rate was measured. Preliminary results are presented. [Copyright &y& Elsevier]
- Published
- 2004
- Full Text
- View/download PDF
39. The ATHENA positron accumulator
- Author
-
van der Werf, D.P., Jørgensen, L.V., Watson, T.L., Charlton, M., Collier, M.J.T., Doser, M., and Funakoshi, R.
- Subjects
- *
POSITRONS , *MAGNETIC fields - Abstract
A positron accumulator has been constructed for use in the ATHENA anti-hydrogen experiment in CERN. Employing a solid neon moderator plated on to a 50 mCi
22Na source, a low energy beam of7×106 positrons/s is guided into a 0.14 T magnetic field where they are trapped and cooled down to room temperature using nitrogen as a buffer gas. Plasmas of up to2×108 positrons in 450 s, with an FWHM of 4 mm after compressing with the rotating electrical wall technique have been observed. In order to transfer the plasma to the main ATHENA (3 T) magnet, where the recombination trap is situated, a transfer section has been constructed consisting of a valve and a pulsed magnet with a pumping restriction inside. This magnet pulses to 1.2 T during the transfer. Preliminary tests have yielded transfer efficiencies in the order of 50%. [Copyright &y& Elsevier]- Published
- 2002
- Full Text
- View/download PDF
40. Real-time detector for plasma diagnostic in antimatter experiment
- Author
-
Carraro, C., Amoretti, M., Amsler, C., Bonomi, G., Bouchta, A., Bowe, P.D., Cesar, C.L., Charlton, M., Doser, M., Filippini, V., Fontana, A., Fujiwara, M.C., Funakoshi, R., Genova, P., Hangst, J.S., Hayano, R.S., Jørgensen, L.V., Lagomarsino, V., Landua, R., and Lindelöf, D.
- Subjects
- *
POSITRONS , *DETECTORS , *PLASMA gases , *NUCLEAR physics - Abstract
In the ATHENA experiment, which has recently produced and detected cold antihydrogen, the antiatoms formation is performed by mixing two cold (meV) charged clouds of positrons and antiprotons. The antihydrogen production is strictly dependent on positron plasma parameters. For this purpose we developed a new system to investigate such properties in a non-destructive way. The method is based upon the measurement of the plasma response under a frequency sweep RF excitation and its subsequent analysis. Plasmas trapped in Penning trap exhibit typical resonant collective modes characterized by frequencies, amplitudes and widths dependent on the particle number, density, spatial extent and temperature. With this system it is so possible to have a real-time monitor of the plasma during antihydrogen production. [Copyright &y& Elsevier]
- Published
- 2004
- Full Text
- View/download PDF
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