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Clifford M Surko - One of the best experts on this subject based on the ideXlab platform.
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emerging science and technology of antimatter plasmas and trap based beams
Physics of Plasmas, 2004Co-Authors: Clifford M Surko, R. G. GreavesAbstract:Progress in the ability to accumulate and cool Positrons and antiprotons is enabling new scientific and technological opportunities. The driver for this work is plasma physics research—developing new ways to create and manipulate antimatter plasmas. An overview is presented of recent results and near-term goals and challenges. In atomic physics, new experiments on the resonant capture of Positrons by molecules provide the first direct evidence that Positrons bind to “ordinary” matter (i.e., atoms and molecules). The formation of low-energy antihydrogen was observed recently by injecting low-energy antiprotons into a cold positron plasma. This opens up a range of new scientific opportunities, including precision tests of fundamental symmetries such as invariance under charge conjugation, parity, and time reversal, and study of the chemistry of matter and antimatter. The first laboratory study of electron-positron plasmas has been conducted by passing an electron beam through a positron plasma. The next maj...
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Positron Plasmas in the Laboratory
2002Co-Authors: Clifford M SurkoAbstract:Abstract : This grant supported work to develop efficient methods to accumulate low-energy Positrons in the laboratory and to use the resulting positron plasmas for a range of scientific and technological applications. Techniques for trapping and manipulating Positrons were refined and expanded. A new generation of positron accumulator was designed and built. It functions up to specifications, confining 3 x 10(exp 8) Positrons at densities >- 10(exp 7)/cu cm. A new technique to create ultra-cold positron beams with these plasmas was used for new studies of the instabilities created when a cold electron beam is passed through a positron plasma. This cold beam technique has now been used for a wide range of novel positron scattering and annihilation experiments to study the interaction of low-energy Positrons with atoms and molecules. A new high magnetic field, cryogenic positron storage trap was constructed and is being tested. Other accomplishments during the grant period include the development of a rotating electric field technique to radially compress positron plasmas. This, in turn, was enabled by the development of a method to cool the Positrons with a polyatomic buffer gas. This cooling technique also provides new capabilities for the generation of cold positron beams operating at high repetition rates.
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Practical limits on positron accumulation and the creation of electron-positron plasmas
AIP Conference Proceedings, 2002Co-Authors: R. G. Greaves, Clifford M SurkoAbstract:The tasks of accumulating large numbers of Positrons, creating high-density positron plasmas, and confining electron-positron plasmas present a number of technical challenges. Some practical considerations and limitations of common confinement schemes are discussed. A novel design for a multi-cell Penning-Malmberg trap is proposed for the accumulation of large numbers of Positrons (e.g., >1012 and T∼0.5 eV). A method is described to create a low density, electron-positron plasma (e.g., n∼107 cm−3) for basic plasma physics studies that uses a combination of radio-frequency and magnetic confinement. The possibilities for confinement of a hot (e.g., T>10 keV) electron-positron plasma in a magnetic mirror are also discussed.
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Antimatter plasmas and antihydrogen
Physics of Plasmas, 1997Co-Authors: R. G. Greaves, Clifford M SurkoAbstract:Recent successes in confining antimatter in the form of positron and antiproton plasmas have created new scientific and technological opportunities. Plasma techniques have been the cornerstone of experimental work in this area, and this is likely to be true for the foreseeable future. Work by a number of groups on trapping antimatter plasmas is summarized, and an overview of the promises and challenges in this field is presented. Topics relating to positron plasmas include the use of Positrons to study the unique properties of electron–positron plasmas, the interaction between Positrons and ordinary matter, and the laboratory modeling of positron-annihilation processes in interstellar media. The availability of cold, trapped antiprotons and Positrons makes possible the production of neutral antimatter in the form of antihydrogen. This is expected to enable precise comparisons of the properties of matter and antimatter, including tests of fundamental symmetries and the measurement of the interaction of ant...
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Positron-molecule interactions
1994Co-Authors: Clifford M SurkoAbstract:Abstract : The objective of this research was to study the interaction of Positrons with molecules at energies below the threshold for positronium atom formation. While there is evidence that Positrons bind, or form long-lived resonances with large atoms and molecules, this phenomenon is not understood. This phenomenon has a number of potentially important scientific and technological applications, including aspects of atomic and molecular physics, the formation of positive ions for mass spectrometry, and gamma ray astronomy. Many facets of the interaction of low-energy Positrons with molecules were illuminated, including the scaling of positron annihilation rate with molecular ionization potential the identification of other trends as a function of chemical structure. Spectra of the gamma ray radiation resulting when a positron annihilates on a molecule were also measured. The measurements indicate that the site of positron binding is on the C-H bond in hydrocarbon molecules and on the fluorine atoms in fluorine compounds. The measured annihilation rates on large aromatics indicate that these molecules are likely to be an important source of the annihilation radiation observed from the interstellar medium. Positrons, Atomic and molecular physics, Annihilation radiation.
Abdullah Al Mamun - One of the best experts on this subject based on the ideXlab platform.
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Electrostatic Nonplanar Positron-Acoustic Shock Waves in Superthermal Electron-Positron-Ion Plasmas
Communications in Theoretical Physics, 2015Co-Authors: M. J. Uddin, M. S. Alam, Abdullah Al MamunAbstract:The basic properties of the nonlinear propagation of the nonplanar (cylindrical and spherical) positron-acoustic (PA) shock waves (SHWs) in an unmagnetized electron-positron-ion (e-p-i) plasma containing immobile positive ions, mobile cold Positrons, and superthermal (kappa distributed) hot Positrons and electrons are investigated both analytically and numerically. The modified Burgers equation (mBE) is derived by using the reductive perturbation method. The basic features of PA SHWs are significantly modified by the cold positron kinematic viscosity (η), superthermal parameter of electrons (κe), superthermal parameter of hot Positrons (κp), the ratio of the electron temperature to hot positron temperature (σ), the ratio of the electron number density to cold positron number density and the ratio of the hot positron number density to cold positron number density (μph). This study could be useful to identify the basic properties of nonlinear electrostatic disturbances in dissipative space and laboratory plasmas.
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Positron-acoustic solitary waves in a magnetized electron-positron-ion plasma with nonthermal electrons and Positrons
Astrophysics and Space Science, 2015Co-Authors: M. M. Rahman, M. S. Alam, Abdullah Al MamunAbstract:Obliquely propagating positron-acoustic solitary waves (PASWs) in a magnetized electron-positron-ion plasma (containing nonthermal hot Positrons and electrons, inertial cold Positrons, and immobile positive ions) are precisely investigated by deriving the Zakharov-Kuznetsov equation. It is found that the characteristics of the PASWs are significantly modified by the effects of external magnetic field, obliqueness, nonthermality of hot Positrons and electrons, temperature ratio of hot Positrons and electrons, and respective number densities of hot Positrons and electrons. The findings of our results can be employed in understanding the localized electrostatic structures and the characteristics of PASWs in various space and laboratory plasmas.
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Positron-acoustic shock waves associated with cold viscous positron fluid in superthermal electron-positron-ion plasmas
Physics of Plasmas, 2015Co-Authors: M. J. Uddin, M. S. Alam, Abdullah Al MamunAbstract:A theoretical investigation is made on the positron-acoustic (PA) shock waves (SHWs) in an unmagnetized electron-positron-ion plasma containing immobile positive ions, cold mobile Positrons, and hot Positrons and electrons following the kappa (κ) distribution. The cold positron kinematic viscosity is taken into account, and the reductive perturbation method is used to derive the Burgers equation. It is found that the viscous force acting on cold mobile positron fluid is a source of dissipation and is responsible for the formation of the PA SHWs. It is also observed that the fundamental properties of the PA SHWs are significantly modified by the effects of different parameters associated with superthermal (κ distributed) hot Positrons and electrons.
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Nonplanar positron-acoustic Gardner solitary waves in electron-positron-ion plasmas with superthermal electrons and Positrons
Physics of Plasmas, 2015Co-Authors: M. J. Uddin, M. S. Alam, Abdullah Al MamunAbstract:Nonplanar (cylindrical and spherical) positron-acoustic (PA) Gardner solitary waves (SWs) in an unmagnetized plasma system consisting of immobile positive ions, mobile cold Positrons, and superthermal (kappa distributed) hot Positrons and electrons are investigated. The modified Gardner equation is derived by using the reductive perturbation technique. The effects of cylindrical and spherical geometries, superthermal parameter of hot Positrons and electrons, relative temperature ratios, and relative number density ratios on the PA Gardner SWs are studied by using the numerical simulations. The implications of our results in various space and laboratory plasma environments are briefly discussed.
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Positron acoustic shock waves in four-component plasmas with nonthermal electrons and Positrons
Journal of the Korean Physical Society, 2014Co-Authors: M. M. Rahman, Abdullah Al Mamun, M. S. AlamAbstract:Positron acoustic shock waves (PASWs) in an unmagnetized four-component plasma system consisting of a cold mobile viscous positron fluid, hot Positrons and electrons following the nonthermal distributions of Cairns et al. [Geophys. Res. Lett. 22, 2709 (1995)], and immobile positive ions are studied both analytically and numerically. The well-known reductive perturbation method is used to derive the Burgers equation. The basic features of the PASWs are significantly modified by the effects of the kinematic viscosity, the nonthermal electrons and hot Positrons, the ratio of the electron temperature to the hot positron temperature σ, and the ratio of the hot positron (electron) number density to the cold positron number density μ 1 (μ 2). The importance of our results to various astrophysical and laboratory plasmas are concisely discussed.
R. G. Greaves - One of the best experts on this subject based on the ideXlab platform.
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emerging science and technology of antimatter plasmas and trap based beams
Physics of Plasmas, 2004Co-Authors: Clifford M Surko, R. G. GreavesAbstract:Progress in the ability to accumulate and cool Positrons and antiprotons is enabling new scientific and technological opportunities. The driver for this work is plasma physics research—developing new ways to create and manipulate antimatter plasmas. An overview is presented of recent results and near-term goals and challenges. In atomic physics, new experiments on the resonant capture of Positrons by molecules provide the first direct evidence that Positrons bind to “ordinary” matter (i.e., atoms and molecules). The formation of low-energy antihydrogen was observed recently by injecting low-energy antiprotons into a cold positron plasma. This opens up a range of new scientific opportunities, including precision tests of fundamental symmetries such as invariance under charge conjugation, parity, and time reversal, and study of the chemistry of matter and antimatter. The first laboratory study of electron-positron plasmas has been conducted by passing an electron beam through a positron plasma. The next maj...
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Practical limits on positron accumulation and the creation of electron-positron plasmas
AIP Conference Proceedings, 2002Co-Authors: R. G. Greaves, Clifford M SurkoAbstract:The tasks of accumulating large numbers of Positrons, creating high-density positron plasmas, and confining electron-positron plasmas present a number of technical challenges. Some practical considerations and limitations of common confinement schemes are discussed. A novel design for a multi-cell Penning-Malmberg trap is proposed for the accumulation of large numbers of Positrons (e.g., >1012 and T∼0.5 eV). A method is described to create a low density, electron-positron plasma (e.g., n∼107 cm−3) for basic plasma physics studies that uses a combination of radio-frequency and magnetic confinement. The possibilities for confinement of a hot (e.g., T>10 keV) electron-positron plasma in a magnetic mirror are also discussed.
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Antimatter plasmas and antihydrogen
Physics of Plasmas, 1997Co-Authors: R. G. Greaves, Clifford M SurkoAbstract:Recent successes in confining antimatter in the form of positron and antiproton plasmas have created new scientific and technological opportunities. Plasma techniques have been the cornerstone of experimental work in this area, and this is likely to be true for the foreseeable future. Work by a number of groups on trapping antimatter plasmas is summarized, and an overview of the promises and challenges in this field is presented. Topics relating to positron plasmas include the use of Positrons to study the unique properties of electron–positron plasmas, the interaction between Positrons and ordinary matter, and the laboratory modeling of positron-annihilation processes in interstellar media. The availability of cold, trapped antiprotons and Positrons makes possible the production of neutral antimatter in the form of antihydrogen. This is expected to enable precise comparisons of the properties of matter and antimatter, including tests of fundamental symmetries and the measurement of the interaction of ant...
Ya. Shpotyuk - One of the best experts on this subject based on the ideXlab platform.
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Nanoscale mechanism of rare-earth doping in Ga-codoped glassy As-Sb selenides
Journal of the American Ceramic Society, 2017Co-Authors: Ya. ShpotyukAbstract:The method of annihilating Positrons in positron annihilation lifetime measuring mode is applied to study mechanism of rare-earth doping in Ga-codoped arsenic selenide As2Se3 glass modified with Sb. The atomic-deficient structure of parent As2Se3 glass is imagined as containing positron-trapping sites in the form of free-volume voids within cycle-type arrangement of corner-sharing trigonal AsSe3/2 pyramids, composed of atomic-accessible geometrical holes arrested by surrounding atomic-inaccessible Se-based bond-free solid angles. The Ga codoping in As2Se3 glass causes gradual decrease in trapping rate and fraction of trapped Positrons due to agglomeration of free-volume voids. Partial As-to-Sb replacement in Ga-codoped As-Se glasses leads to better stability against crystallization processes and possibility to further rare-earth doping without principal changes in the type of positron-trapping defects. Effect of 500wppm of Pr3+ in Ga-2(As0.28Sb0.12Se0.60)(98) glass is explained in terms of competitive contribution of changed occupancy sites in Ga-modified glassy network available for rare-earth ions and annihilating Positrons.
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Effect of rare-earth doping on the free-volume structure of Ga-modified Te20As30Se50 glass
RSC Advances, 2016Co-Authors: Ya. Shpotyuk, A. Ingram, O. Shpotyuk, Catherine Boussard-plédel, Virginie Nazabal, Bruno BureauAbstract:By exploring the positron-electron annihilation technique in positron lifetime measuring mode, it is shown that principal rare-earth (RE) induced structural reconfiguration in Ga-codoped TAS-235 glass (that is a glassy Te20As29Ga1Se50 alloy) is related to occupation of intrinsic free-volume voids by embedded RE ions tightly connected with Ga-based tetrahedrons via strong covalent RE-Se/Te-Ga links. A gradual decrease in the intensity of the second component of two-term decomposed lifetime spectra of annihilating Positrons accompanied with a detectable increase in the defect-related positron lifetime (thus inducing essentially a depressed rate in positron trapping) is evidenced by the example of Pr3+ ions added homogeneously to Te20As29Ga1Se50 glass in the amount of 500 ppmw. Observed changes in positron lifetime spectra are explained in terms of the competitive contribution of different occupancy positions in Ga-codoped glass available for RE ions and trapped Positrons.
Gerry Skinner - One of the best experts on this subject based on the ideXlab platform.
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an asymmetric distribution of Positrons in the galactic disk revealed by gamma rays
Nature, 2008Co-Authors: G Weidenspointner, P. Jean, Gerry Skinner, J Knodlseder, Peter Von Ballmoos, G F Bignami, R Diehl, A W StrongAbstract:Antimatter is not an exotic rarity found only in the depths of the Universe: there are large quantities in our own Galaxy. We know this because we see the 511-keV γ-ray emission line, a signature of electron–positron annihilation, coming from the general direction of the Galactic Centre. The origin of the Positrons has remained a mystery, but the distribution of the annihilation line radiation provides a clue. Astronomers now have the tools that can work out that distribution, and analysis of more than four years of spectroscopic data from the INTEGRAL satellite reveals an unexpected distribution of the 511-keV γ-ray emission from the inner Galactic disk, suggesting that the Positrons originate in binary stars containing black holes or neutron stars. Gamma-ray line radiation at 511 keV is the signature of electron–positron annihilation, which comes from the general direction of the Galactic centre, but the origin of the Positrons was a mystery. This paper reports a distinct asymmetry in the 511 keV line emission coming from the inner Galactic disk, which resembles an asymmetry in the distribution of low mass X-ray binaries with strong emission at photon energies >20 keV, indicating that they may be the dominant origin of the Positrons. Gamma-ray line radiation at 511 keV is the signature of electron–positron annihilation. Such radiation has been known for 30 years to come from the general direction of the Galactic Centre1, but the origin of the Positrons has remained a mystery. Stellar nucleosynthesis2,3,4, accreting compact objects5,6,7,8, and even the annihilation of exotic dark-matter particles9 have all been suggested. Here we report a distinct asymmetry in the 511-keV line emission coming from the inner Galactic disk (∼10–50° from the Galactic Centre). This asymmetry resembles an asymmetry in the distribution of low mass X-ray binaries with strong emission at photon energies >20 keV (‘hard’ LMXBs), indicating that they may be the dominant origin of the Positrons. Although it had long been suspected that electron–positron pair plasmas may exist in X-ray binaries, it was not evident that many of the Positrons could escape to lose energy and ultimately annihilate with electrons in the interstellar medium and thus lead to the emission of a narrow 511-keV line. For these models, our result implies that up to a few times 1041 Positrons escape per second from a typical hard LMXB. Positron production at this level from hard LMXBs in the Galactic bulge would reduce (and possibly eliminate) the need for more exotic explanations, such as those involving dark matter.
