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G. Cartry - One of the best experts on this subject based on the ideXlab platform.
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Impact of positive ion energy on carbon-surface production of Negative Ions in deuterium plasmas
Journal of Physics D: Applied Physics, 2019Co-Authors: D. Kogut, R. Moussaoui, Ning Ning, J. Faure, J. Layet, T Farley, J. Achard, A. Gicquel, G. CartryAbstract:This work focuses on the production of Negative-Ions on graphite and diamond surfaces bombarded by positive Ions in a low pressure (2 Pa) low power (20 W) capacitively coupled deuterium plasma. A sample is placed opposite a mass spectrometer and Negatively biased so that surface produced Negative Ions can be self-extracted from the plasma and measured by the mass spectrometer. The ratio between Negative-ion counts at mass spectrometer and positive ion current at sample surface defines a relative Negative-ion yield. Changes in Negative-ion production yields versus positive ion energy in the range 10-60 eV are analysed. While the Negative-ion production yield is decreasing for diamond surfaces when increasing the positive ion impact energy, it is strongly increasing for graphite. This increase is attributed to the onset of the sputtering mechanisms between 20 and 40 eV which creates Negative Ions at rather low energy that are efficiently collected by the mass spectrometer. The same mechanism occurs for diamond but is mitigated by a strong decrease of the ionization probability due to defect creation and loss of diamond electronic properties.
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Reconstruction of energy and angle distribution function of surface-emitted Negative Ions in hydrogen plasmas using mass spectrometry
Plasma Sources Science and Technology, 2017Co-Authors: D. Kogut, R. Moussaoui, J. Layet, K. Achkasov, J. Dubois, J.b. Faure, A. Simonin, G. CartryAbstract:A new method involving mass spectrometry and modelling is described in this work, which may highlight the production mechanisms of Negative Ions on surface in low pressure plasmas. Positive hydrogen Ions from plasma impact a sample which is biased Negatively with respect to the plasma potential. Negative Ions (NI) are produced on the surface through the ionization of sputtered and backscattered particles and detected according to their energy and mass by a mass spectrometer placed in front of the sample. The shape of the measured Negative-ion energy distribution function (NIEDF) strongly differs from the NIEDF of the Ions emitted by the sample because of the limited acceptance angle of the mass spectrometer. The reconstruction method proposed here allows to compute the distribution function in energy and angle (NIEADF) of the Negative-Ions emitted by the sample based on the NIEDF measurements at different tilt angles of the sample. The reconstruction algorithm does not depend on the NI surface production mechanism, so it can be applied to any type of surface and/or NI. The NIEADFs for HOPG (Highly Oriented Pyrolitic Graphite) and Gadolinium (low work-function metal) are presented and compared with the SRIM modelling. HOPG and Gd show comparable integrated NI yields, however the key differences in mechanisms of NI production can be identified. While for Gd the major process is backscattering of Ions with the peak of NIEDF at 36 eV, in case of HOPG the sputtering contribution due to adsorbed H on the surface is also important and the NIEDF peak is found at 5 eV.
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reconstruction of energy and angle distribution function of surface emitted Negative Ions in hydrogen plasmas using mass spectrometry
Plasma Sources Science and Technology, 2017Co-Authors: D. Kogut, R. Moussaoui, K. Achkasov, J. Dubois, J.b. Faure, A. Simonin, Jean Marc Layet, G. CartryAbstract:A new method involving mass spectrometry and modeling is described in this work, which may highlight the production mechanisms of Negative Ions (NIs) on surface in low pressure plasmas. Positive hydrogen Ions from plasma impact a sample which is biased Negatively with respect to the plasma potential. NIs are produced on the surface through the ionization of sputtered and backscattered particles and detected according to their energy and mass by a mass spectrometer (MS) placed in front of the sample. The shape of the measured Negative-ion energy distribution function (NIEDF) strongly differs from the NIEDF of the Ions emitted by the sample because of the limited acceptance angle of the MS. The reconstruction method proposed here allows to compute the distribution function in energy and angle (NIEADF) of the NIs emitted by the sample based on the NIEDF measurements at different tilt angles of the sample. The reconstruction algorithm does not depend on the NI surface production mechanism, so it can be applied to any type of surface and/or NI. The NIEADFs for highly oriented pyrolitic graphite (HOPG) and gadolinium (low work-function metal) are presented and compared with the SRIM modeling. HOPG and Gd show comparable integrated NI yields, however the key differences in mechanisms of NI production can be identified. While for Gd the major process is backscattering of Ions with the peak of NIEDF at 36 eV, in case of HOPG the sputtering contribution due to adsorbed H on the surface is also important and the NIEDF peak is found at 5 eV.
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Negative-ion surface production in hydrogen plasmas: Determination of the Negative-ion energy and angle distribution function using mass spectrometry
Journal of Applied Physics, 2016Co-Authors: J. Dubois, D. Kogut, J. Layet, K. Achkasov, A. Simonin, A. Ahmad, G. CartryAbstract:This work focuses on the understanding of the production mechanism of Negative-Ions on surface in low pressure plasmas of H2/D2. The Negative Ions are produced on a HOPG sample (Highly Oriented Pyrolitic Graphite) Negatively biased with respect to plasma potential. The Negative Ions created under the positive ion bombardment are accelerated towards the plasma, self-extracted and detected according to their energy and mass by a mass spectrometer placed in front of the sample. The shape of the measured Negative-Ion Energy Distribution Function (NIEDF) strongly differs from the NIEDF of the Ions emitted by the sample because of the limited acceptance angle of the mass spectrometer. To get information on the production mechanisms, we propose a method to obtain the distribution functIons in energy and angle (NIEADFs) of the Negative-Ions emitted by the sample. It is based on an a priori determination of the NIEADF and on an a posteriori validation of the choice by comparison of the modelled and experimental NIEDFs.
P K Shukla - One of the best experts on this subject based on the ideXlab platform.
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arbitrary amplitude dust ion acoustic shock waves in a dusty plasma with positive and Negative Ions
Physics of Plasmas, 2009Co-Authors: Abdullah Al Mamun, P K Shukla, Bengt EliassonAbstract:Arbitrary amplitude dust ion-acoustic shock waves in a multi-ion dusty plasma (composed of electrons, light positive Ions, heavy Negative Ions, and stationary massive dust grains) has been studied. For this purpose, the coupled Poisson and dust-charging equatIons, which accounts for the fluctuation of charges on static dust, have been numerically solved. The large amplitude shocks are associated with a sudden decrease in the electrostatic potential and of the dust grain charge. It is found that in the lower speed limit small amplitude shocks are formed, while in the larger speed limit large amplitude shocks are formed. It is anticipated that the profiles and amplitudes of the DIA shocks predicted here will be observed in forthcoming laboratory and space experiments.
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fully nonlinear ion acoustic solitary waves in a plasma with positive Negative Ions and nonthermal electrons
Physics of Plasmas, 2009Co-Authors: R Sabry, W M Moslem, P K ShuklaAbstract:Properties of fully nonlinear ion-acoustic solitary waves in a plasma with positive-Negative Ions and nonthermal electrons are investigated. For this purpose, the hydrodynamic equatIons for the pos ...
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wake potential with mobile positive Negative Ions in multicomponent dusty plasmas
Physics Letters A, 2008Co-Authors: S Ali, W M Moslem, P K ShuklaAbstract:We employ the test charge approach to calculate the electrostatic potential for a test charge in a multicomponent dusty plasma, whose constituents are the Boltzmann distributed electrons, mobile positive and Negative Ions, and immobile positive/Negative charged dust particles. By using the modified dielectric constant of the dust-ion-acoustic (DIA) waves, the Debye screening and wake potentials are obtained. It is found that the presence of mobile Negative Ions significantly modify the DIA speed and the wake potential. The present results are relevant to polar mesosphere and microelectronic in the context of charged particle attraction and repulsion.
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dust ion acoustic solitary waves in a dusty plasma with positive and Negative Ions
Physics of Plasmas, 2008Co-Authors: Fatema Sayed, P K Shukla, M M Haider, Abdullah Al Mamun, Bengt Eliasson, N C AdhikaryAbstract:Properties of small but finite amplitude dust ion-acoustic (DIA) solitary waves in a dusty plasma composed of inertialess electrons, positive and Negative inertial Ions, and immobile Negative/positive charged dust grains are investigated. By using the multifluid dusty plasma model, the Kortweg–de Vries equation and energy integral for small and large amplitude solitary pulses, are derived. It is found that the presence of the Negative Ions modifies the properties of the solitary DIA waves, and provides the possibility of positive and Negative solitary potential structures to coexist. The present results may be useful for understanding the salient features of localized DIA excitatIons that may appear in data from forthcoming laboratory experiments and space observatIons.
D. Kogut - One of the best experts on this subject based on the ideXlab platform.
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Impact of positive ion energy on carbon-surface production of Negative Ions in deuterium plasmas
Journal of Physics D: Applied Physics, 2019Co-Authors: D. Kogut, R. Moussaoui, Ning Ning, J. Faure, J. Layet, T Farley, J. Achard, A. Gicquel, G. CartryAbstract:This work focuses on the production of Negative-Ions on graphite and diamond surfaces bombarded by positive Ions in a low pressure (2 Pa) low power (20 W) capacitively coupled deuterium plasma. A sample is placed opposite a mass spectrometer and Negatively biased so that surface produced Negative Ions can be self-extracted from the plasma and measured by the mass spectrometer. The ratio between Negative-ion counts at mass spectrometer and positive ion current at sample surface defines a relative Negative-ion yield. Changes in Negative-ion production yields versus positive ion energy in the range 10-60 eV are analysed. While the Negative-ion production yield is decreasing for diamond surfaces when increasing the positive ion impact energy, it is strongly increasing for graphite. This increase is attributed to the onset of the sputtering mechanisms between 20 and 40 eV which creates Negative Ions at rather low energy that are efficiently collected by the mass spectrometer. The same mechanism occurs for diamond but is mitigated by a strong decrease of the ionization probability due to defect creation and loss of diamond electronic properties.
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Reconstruction of energy and angle distribution function of surface-emitted Negative Ions in hydrogen plasmas using mass spectrometry
Plasma Sources Science and Technology, 2017Co-Authors: D. Kogut, R. Moussaoui, J. Layet, K. Achkasov, J. Dubois, J.b. Faure, A. Simonin, G. CartryAbstract:A new method involving mass spectrometry and modelling is described in this work, which may highlight the production mechanisms of Negative Ions on surface in low pressure plasmas. Positive hydrogen Ions from plasma impact a sample which is biased Negatively with respect to the plasma potential. Negative Ions (NI) are produced on the surface through the ionization of sputtered and backscattered particles and detected according to their energy and mass by a mass spectrometer placed in front of the sample. The shape of the measured Negative-ion energy distribution function (NIEDF) strongly differs from the NIEDF of the Ions emitted by the sample because of the limited acceptance angle of the mass spectrometer. The reconstruction method proposed here allows to compute the distribution function in energy and angle (NIEADF) of the Negative-Ions emitted by the sample based on the NIEDF measurements at different tilt angles of the sample. The reconstruction algorithm does not depend on the NI surface production mechanism, so it can be applied to any type of surface and/or NI. The NIEADFs for HOPG (Highly Oriented Pyrolitic Graphite) and Gadolinium (low work-function metal) are presented and compared with the SRIM modelling. HOPG and Gd show comparable integrated NI yields, however the key differences in mechanisms of NI production can be identified. While for Gd the major process is backscattering of Ions with the peak of NIEDF at 36 eV, in case of HOPG the sputtering contribution due to adsorbed H on the surface is also important and the NIEDF peak is found at 5 eV.
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reconstruction of energy and angle distribution function of surface emitted Negative Ions in hydrogen plasmas using mass spectrometry
Plasma Sources Science and Technology, 2017Co-Authors: D. Kogut, R. Moussaoui, K. Achkasov, J. Dubois, J.b. Faure, A. Simonin, Jean Marc Layet, G. CartryAbstract:A new method involving mass spectrometry and modeling is described in this work, which may highlight the production mechanisms of Negative Ions (NIs) on surface in low pressure plasmas. Positive hydrogen Ions from plasma impact a sample which is biased Negatively with respect to the plasma potential. NIs are produced on the surface through the ionization of sputtered and backscattered particles and detected according to their energy and mass by a mass spectrometer (MS) placed in front of the sample. The shape of the measured Negative-ion energy distribution function (NIEDF) strongly differs from the NIEDF of the Ions emitted by the sample because of the limited acceptance angle of the MS. The reconstruction method proposed here allows to compute the distribution function in energy and angle (NIEADF) of the NIs emitted by the sample based on the NIEDF measurements at different tilt angles of the sample. The reconstruction algorithm does not depend on the NI surface production mechanism, so it can be applied to any type of surface and/or NI. The NIEADFs for highly oriented pyrolitic graphite (HOPG) and gadolinium (low work-function metal) are presented and compared with the SRIM modeling. HOPG and Gd show comparable integrated NI yields, however the key differences in mechanisms of NI production can be identified. While for Gd the major process is backscattering of Ions with the peak of NIEDF at 36 eV, in case of HOPG the sputtering contribution due to adsorbed H on the surface is also important and the NIEDF peak is found at 5 eV.
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Negative-ion surface production in hydrogen plasmas: Determination of the Negative-ion energy and angle distribution function using mass spectrometry
Journal of Applied Physics, 2016Co-Authors: J. Dubois, D. Kogut, J. Layet, K. Achkasov, A. Simonin, A. Ahmad, G. CartryAbstract:This work focuses on the understanding of the production mechanism of Negative-Ions on surface in low pressure plasmas of H2/D2. The Negative Ions are produced on a HOPG sample (Highly Oriented Pyrolitic Graphite) Negatively biased with respect to plasma potential. The Negative Ions created under the positive ion bombardment are accelerated towards the plasma, self-extracted and detected according to their energy and mass by a mass spectrometer placed in front of the sample. The shape of the measured Negative-Ion Energy Distribution Function (NIEDF) strongly differs from the NIEDF of the Ions emitted by the sample because of the limited acceptance angle of the mass spectrometer. To get information on the production mechanisms, we propose a method to obtain the distribution functIons in energy and angle (NIEADFs) of the Negative-Ions emitted by the sample. It is based on an a priori determination of the NIEADF and on an a posteriori validation of the choice by comparison of the modelled and experimental NIEDFs.
Yasuyuki Nagashima - One of the best experts on this subject based on the ideXlab platform.
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experiments on positronium Negative Ions
Physics Reports, 2014Co-Authors: Yasuyuki NagashimaAbstract:Abstract This paper is a review of new developments in the experimental field of the efficient emission of the positronium Negative ion, a bound state of one positron and two electrons, from alkali-metal coated surfaces. Following the prediction of its existence by Wheeler in 1946, this ion has been one of the most attractive subjects for theorists to investigate in the field of positron physics, resulting in a large number of studies. Though the first observation of the Ions, formed using a carbon thin film, was made in 1981 by Mills, there have been few experimental works since, limited by the low-production efficiency achievable for nearly 30 years. In 2008, a dramatic effect on the ion emission from tungsten surfaces was discovered upon coating it with Cs. This has opened the door to a new era of experimental investigatIons of this ion. This paper reports the investigatIons performed so far. Advances discussed include efficient formation of the ion, its photodetachment and the production of an energy-tunable positronium beam based on the technique of the photodetachment.
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durable emission of positronium Negative Ions from na and k coated w 100 surfaces
New Journal of Physics, 2012Co-Authors: Hiroki Terabe, Takayuki Tachibana, Koji Michishio, Yasuyuki NagashimaAbstract:The emission of positronium Negative Ions from Na- and K-coated W(100) surfaces has been studied. The emission efficiencies (the fractIons of incident slow positrons yielding the Ions) for both samples were found to be as high as 1.5%. Although the efficiencies decreased with time after coating, the effects were more durable than that for Cs coating. In particular, the efficiency after Na coating was still higher than 0.5% after three days. The successful development of a durable Ps− source opens the door to a new era of experimental investigatIons on the Ps− ion.
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photodetachment of positronium Negative Ions
Physical Review Letters, 2011Co-Authors: Koji Michishio, Ken Wada, Toshio Hyodo, Takayuki Tachibana, A Yagishita, Hiroki Terabe, A Igarashi, Takahiro Kuga, Yasuyuki NagashimaAbstract:Photodetachment of the positronium Negative ion, a bound state of one positron and two electrons, has been observed. Development of a method to produce the Ions efficiently using a Na coated tungsten surface has enabled the first observation of the photodetachment. The obtained lower limit of the photodetachment cross section for the wavelength of 1064 nm is consistent with the theoretical calculatIons reported so far. The experimental field developed in the present work gives new opportunities to explore the quantum mechanical three-body problem and to develop energy-tunable positronium beams.
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efficient emission of positronium Negative Ions from cs deposited w 100 surfaces
New Journal of Physics, 2008Co-Authors: Yasuyuki Nagashima, Toshihide Hakodate, Ayaka Miyamoto, Koji MichishioAbstract:The emission of positronium Negative Ions from Cs deposited W(100) surfaces has been studied. A dramatic change in the emission efficiency was observed upon coating a W(100) surface with Cs. The conversion efficiency (the fraction of incident slow positrons yielding the Ions) of the W(100) target with a 2.2?1014?atoms?cm- 2 Cs coverage, measured over a time interval of 3?103?s immediately after deposition, was found to be 1.25%, which is two orders of magnitude higher than that obtained for the clean, uncoated W(100) surface and 45 times greater than the highest efficiency reported thus far.
J. Dubois - One of the best experts on this subject based on the ideXlab platform.
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Reconstruction of energy and angle distribution function of surface-emitted Negative Ions in hydrogen plasmas using mass spectrometry
Plasma Sources Science and Technology, 2017Co-Authors: D. Kogut, R. Moussaoui, J. Layet, K. Achkasov, J. Dubois, J.b. Faure, A. Simonin, G. CartryAbstract:A new method involving mass spectrometry and modelling is described in this work, which may highlight the production mechanisms of Negative Ions on surface in low pressure plasmas. Positive hydrogen Ions from plasma impact a sample which is biased Negatively with respect to the plasma potential. Negative Ions (NI) are produced on the surface through the ionization of sputtered and backscattered particles and detected according to their energy and mass by a mass spectrometer placed in front of the sample. The shape of the measured Negative-ion energy distribution function (NIEDF) strongly differs from the NIEDF of the Ions emitted by the sample because of the limited acceptance angle of the mass spectrometer. The reconstruction method proposed here allows to compute the distribution function in energy and angle (NIEADF) of the Negative-Ions emitted by the sample based on the NIEDF measurements at different tilt angles of the sample. The reconstruction algorithm does not depend on the NI surface production mechanism, so it can be applied to any type of surface and/or NI. The NIEADFs for HOPG (Highly Oriented Pyrolitic Graphite) and Gadolinium (low work-function metal) are presented and compared with the SRIM modelling. HOPG and Gd show comparable integrated NI yields, however the key differences in mechanisms of NI production can be identified. While for Gd the major process is backscattering of Ions with the peak of NIEDF at 36 eV, in case of HOPG the sputtering contribution due to adsorbed H on the surface is also important and the NIEDF peak is found at 5 eV.
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reconstruction of energy and angle distribution function of surface emitted Negative Ions in hydrogen plasmas using mass spectrometry
Plasma Sources Science and Technology, 2017Co-Authors: D. Kogut, R. Moussaoui, K. Achkasov, J. Dubois, J.b. Faure, A. Simonin, Jean Marc Layet, G. CartryAbstract:A new method involving mass spectrometry and modeling is described in this work, which may highlight the production mechanisms of Negative Ions (NIs) on surface in low pressure plasmas. Positive hydrogen Ions from plasma impact a sample which is biased Negatively with respect to the plasma potential. NIs are produced on the surface through the ionization of sputtered and backscattered particles and detected according to their energy and mass by a mass spectrometer (MS) placed in front of the sample. The shape of the measured Negative-ion energy distribution function (NIEDF) strongly differs from the NIEDF of the Ions emitted by the sample because of the limited acceptance angle of the MS. The reconstruction method proposed here allows to compute the distribution function in energy and angle (NIEADF) of the NIs emitted by the sample based on the NIEDF measurements at different tilt angles of the sample. The reconstruction algorithm does not depend on the NI surface production mechanism, so it can be applied to any type of surface and/or NI. The NIEADFs for highly oriented pyrolitic graphite (HOPG) and gadolinium (low work-function metal) are presented and compared with the SRIM modeling. HOPG and Gd show comparable integrated NI yields, however the key differences in mechanisms of NI production can be identified. While for Gd the major process is backscattering of Ions with the peak of NIEDF at 36 eV, in case of HOPG the sputtering contribution due to adsorbed H on the surface is also important and the NIEDF peak is found at 5 eV.
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Negative-ion surface production in hydrogen plasmas: Determination of the Negative-ion energy and angle distribution function using mass spectrometry
Journal of Applied Physics, 2016Co-Authors: J. Dubois, D. Kogut, J. Layet, K. Achkasov, A. Simonin, A. Ahmad, G. CartryAbstract:This work focuses on the understanding of the production mechanism of Negative-Ions on surface in low pressure plasmas of H2/D2. The Negative Ions are produced on a HOPG sample (Highly Oriented Pyrolitic Graphite) Negatively biased with respect to plasma potential. The Negative Ions created under the positive ion bombardment are accelerated towards the plasma, self-extracted and detected according to their energy and mass by a mass spectrometer placed in front of the sample. The shape of the measured Negative-Ion Energy Distribution Function (NIEDF) strongly differs from the NIEDF of the Ions emitted by the sample because of the limited acceptance angle of the mass spectrometer. To get information on the production mechanisms, we propose a method to obtain the distribution functIons in energy and angle (NIEADFs) of the Negative-Ions emitted by the sample. It is based on an a priori determination of the NIEADF and on an a posteriori validation of the choice by comparison of the modelled and experimental NIEDFs.
