The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
I. A. Soloshenko - One of the best experts on this subject based on the ideXlab platform.
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Process of compensatIon of the space charge of a Negative Ion Beam in a gas
Plasma Physics Reports, 2007Co-Authors: V. N. Gorshkov, A. M. Zavalov, I. A. SoloshenkoAbstract:The process of compensatIon of the space charge of a Negative Ion Beam propagating through a neutral gas is investigated numerically. A comparison of the results obtained with experimental data unambiguously proves that, at high gas pressures, when the Beam space charge is overcompensated, the electric field within the Beam is determined by Coulomb collisIons of the Beam Ions with plasma electrons. At low pressures, when the space charge is undercompensated, the field within the Beam is determined by the dynamic processes related to oscillatIons of the Beam current.
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Space Charge Lens for Focusing of Negative Ion Beams
AIP Conference Proceedings, 2005Co-Authors: I. A. Soloshenko, V. P. Goretsky, A. M. ZavalovAbstract:A brief review of the results of experimental and theoretical studies of the space charge lens for focusing Negative Ion Beam is presented. An idea of such lens was formulated earlier by the first two authors. For the present time, two versIons of the lens are studied experimentally and calculated numerically. In the first versIon the focusing space charge is formed in the lens as a result of gas IonizatIon by the Negative Ion Beam itself; in the second versIon — as a result of gas IonizatIon by both the Beam Ions and the electrons with energy of about 100 eV introduced from the special emitter placed in the lens volume. In both regimes focusing field values of about 100 V/cm are reached, which enable obtaining focal length of less than or equal to 20 cm. However, in the first case pressure working gas (argon, krypton, xenon) is about 10−3 Torr. A significant portIon of Negative Ions is lost due to collisIons with neutral particles at such a pressure. IntroductIon of additIonal Ionizer enables significant...
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Space charge lens for focusing Negative Ion Beam: Theory and experiment
Review of Scientific Instruments, 2004Co-Authors: I. A. Soloshenko, V. N. Gorshkov, V. P. Goretsky, A. M. ZavalovAbstract:Detailed researches the of space charge lens for focusing Negative Ion Beam are performed for the cases when positive space charge forming is done either by the Beam itself, or by special flow of electrons. Numerical simulatIons of space charge fields and Beam Ion trajectories are accomplished, and results of the calculatIons are compared with experimental data. It is shown both theoretically and experimentally that in the proposed device electric field strength reaches a value of ∼100 V/cm, thus providing a focal length of
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Problems of intense Negative Ion Beam transport (invited)
Review of Scientific Instruments, 2004Co-Authors: I. A. SoloshenkoAbstract:The results of research of physical processes in intense Negative Ion Beams without magnetic fields are presented. As a result of this research: (1) mechanisms of space charge compensatIon in Negative Ion Beams are determined, (2) stability of compensated states with respect to excitatIon of plasma oscillatIons is analyzed, (3) mechanisms of nonlinear limitatIon of oscillatIon amplitudes are determined, and (4) values of steady and alternating fields in the Beam are found and their influence on transport characteristics of the Beams is estimated. It is demonstrated that Ion-Ion instability at low gas pressure may lead to catastrophic consequences: practically total decompensatIon of the Beam and unacceptable angular scattering. A method of stabilizatIon of this instability, and a technique of focusing Negative Ion Beams by space charge fields are proposed.
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Space-charge lens for focusing a Negative-Ion Beam
Plasma Physics Reports, 2003Co-Authors: A. M. Zavalov, V. N. Gorshkov, V. P. Goretskii, I. A. SoloshenkoAbstract:Results are presented from experimental and theoretical studies of a space-charge lens for focusing a Negative-Ion Beam. The space-charge field and the Beam Ion trajectories are numerically calculated for the lens used in the experiments. The results of calculatIons are compared with the experimental data. It is shown theoretically and experimentally that the proposed device allows one to achieve the main operating conditIons of the space-charge lens: the inertial confinement of positive Ions and the removal of electrons by an external electric field. The focusing field of the lens attains ∼100 V/cm, which provides a focal length of
P Veltri - One of the best experts on this subject based on the ideXlab platform.
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simulatIon of space charge compensatIon in a multiBeamlet Negative Ion Beam
Review of Scientific Instruments, 2016Co-Authors: E Sartori, P Veltri, M. Cavenago, T J Maceina, G. SerianniAbstract:Ion Beam space charge compensatIon occurs by cumulating in the Beam potential well charges having opposite polarity, usually generated by collisIonal processes. In this paper we investigate the case of a H− Ion Beam drift, in a bi-dimensIonal approximatIon of the NIO1 (Negative Ion OptimizatIon phase 1) Negative Ion source. H− Beam Ion transport and plasma formatIon are studied via particle-in-cell simulatIons. Differential cross sectIons are sampled to determine the velocity distributIon of secondary particles generated by IonizatIon of the residual gas (electrons and slow H2+ Ions) or by stripping of the Beam Ions (electrons, H, and H+). The simulatIons include three Beamlets of a horizontal sectIon, so that multiBeamlet space charge and secondary particle diffusIon between separate generatIon regIons are considered, and include a repeller grid biased at various potentials. Results show that after the Beam space charge is effectively screened by the secondary plasma in about 3 μs (in agreement with theo...
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improvements of the magnetic field design for spider and mitica Negative Ion Beam sources
FOURTH INTERNATIONAL SYMPOSIUM ON NEGATIVE IONS BEAMS AND SOURCES (NIBS 2014), 2015Co-Authors: G Chitarin, P Agostinetti, D Aprile, N Marconato, P VeltriAbstract:The design of the magnetic field configuratIon in the SPIDER and MITICA Negative Ion Beam sources has evolved considerably during the past four years. This evolutIon was driven by three factors: 1) the experimental results of the large RF-driven Ion sources at IPP, which have provided valuable indicatIons on the optimal magnetic configuratIons for reliable RF plasma source operatIon and for large Negative Ion current extractIon, 2) the comprehensive Beam optics and heat load simulatIons, which showed that the magnetic field configuratIon in the accelerator is crucial for keeping the heat load due to electrons on the accelerator grids within tolerable limits, without compromising the optics of the Negative Ion Beam in the foreseen operating scenarios, 3) the progress of the detailed mechanical design of the accelerator, which stimulated the evaluatIon of different solutIons for the correctIon of Beamlet deflectIons of various origin and for Beamlet aiming. On this basis, new requirements and solutIon conce...
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deflectIon compensatIon for multiaperture Negative Ion Beam extractIon analytical and numerical investigatIons
Plasma Sources Science and Technology, 2014Co-Authors: M. Cavenago, P VeltriAbstract:DeflectIon of Negative Ion Beamlets due to the magnets embedded in the first extractIon electrode for the purpose of dumping the co-extracted electrons is a serious issue for multiaperture Ion accelerators of neutral Beam injectors. Several kinds of magnet arrays which offer the possibility of cancelling Ion deflectIon, employing crossed rows of magnets or even more compact parallel row arrangements, are discussed. A general equatIon for Beamlet deflectIon is presented here, and the interference of the magnetic deflectIon and the electrostatic lens steering is carefully calculated; this equatIon may also include Beamlet–Beamlet interactIons and image charge effects. Analytical expressIons are given for the field and the line integrals for the magnet arrays, and these are simplified for Beam optics calculatIons, but still retain an excellent agreement with numerical values. OptimizatIon formulas for the filling fractIon xy of the magnets are given, for cancellatIon of deflectIon both after the first electrode or after the second accelerating electrode. The latter case is of direct interest for the design of small accelerators (e.g., NIO1), for which compact solutIons are proposed, while the former case may approximate well the design of a large accelerator such as MITICA, with a predicted xy = 0.1015 against a numerical optimized value of 0.0975 ± 0.005 in normal conditIons. The detailed comparison between simulatIon results and theory shows that thin lens models are suitable approximatIons for calculating Beam steering. Stability of optimal xy predictIon with respect to the first accelerating gap length is shown, and the variatIon of xy with the voltage is discussed.
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first Negative Ion Beam measurement by the short time retractable instrumented kalorimeter experiment strike
Review of Scientific Instruments, 2014Co-Authors: G. Serianni, G Chitarin, P Veltri, M. Pavei, A. Rizzolo, F Bonomo, M De Muri, A Muraro, R Pasqualotto, M ValenteAbstract:The Source for ProductIon of Ion of Deuterium Extracted from Rf plasma (SPIDER) test facility is under constructIon in Padova to optimise the operatIon of the Beam source of ITER neutral Beam injectors. The SPIDER Beam will be characterised by the instrumented calorimeter STRIKE, whose main components are one-directIonal carbon-fibre-carbon-composite tiles. A small-scale versIon of the entire system has been employed in the BAvarian Test MAchine for Negative Ions (BATMAN) testbed by arranging two prototype tiles in the vertical directIon. The paper presents a descriptIon of the mini-STRIKE system and of the data analysis procedures, as well as some results concerning the BATMAN Beam under varying operating conditIons.
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Detail Design of the Electron Dump for the SPIDER Beam Source
IEEE Transactions on Plasma Science, 2012Co-Authors: P Agostinetti, G Chitarin, D. Marcuzzi, M. Pavei, N. Pilan, A. Rizzolo, G. Serianni, P. Sonato, L. Trevisan, P VeltriAbstract:An electron dump (ED) has been developed and added to the SPIDER Negative Ion Beam source in order to dispose of the electrons exiting from the accelerator, which are mainly generated by stripping reactIons. This component prevents from having unwanted and possibly concentrated heat load from electrons on the downstream components and permits to obtain on the diagnostic calorimeter a detailed measurement of the Negative Ion Beam. The detail design of the ED is here described, together with the main design choices that have driven the design process. The physics and thermomechanical analyses, carried out to compare the different design proposals, are also presented.
A. M. Zavalov - One of the best experts on this subject based on the ideXlab platform.
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Process of compensatIon of the space charge of a Negative Ion Beam in a gas
Plasma Physics Reports, 2007Co-Authors: V. N. Gorshkov, A. M. Zavalov, I. A. SoloshenkoAbstract:The process of compensatIon of the space charge of a Negative Ion Beam propagating through a neutral gas is investigated numerically. A comparison of the results obtained with experimental data unambiguously proves that, at high gas pressures, when the Beam space charge is overcompensated, the electric field within the Beam is determined by Coulomb collisIons of the Beam Ions with plasma electrons. At low pressures, when the space charge is undercompensated, the field within the Beam is determined by the dynamic processes related to oscillatIons of the Beam current.
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Space Charge Lens for Focusing of Negative Ion Beams
AIP Conference Proceedings, 2005Co-Authors: I. A. Soloshenko, V. P. Goretsky, A. M. ZavalovAbstract:A brief review of the results of experimental and theoretical studies of the space charge lens for focusing Negative Ion Beam is presented. An idea of such lens was formulated earlier by the first two authors. For the present time, two versIons of the lens are studied experimentally and calculated numerically. In the first versIon the focusing space charge is formed in the lens as a result of gas IonizatIon by the Negative Ion Beam itself; in the second versIon — as a result of gas IonizatIon by both the Beam Ions and the electrons with energy of about 100 eV introduced from the special emitter placed in the lens volume. In both regimes focusing field values of about 100 V/cm are reached, which enable obtaining focal length of less than or equal to 20 cm. However, in the first case pressure working gas (argon, krypton, xenon) is about 10−3 Torr. A significant portIon of Negative Ions is lost due to collisIons with neutral particles at such a pressure. IntroductIon of additIonal Ionizer enables significant...
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Space charge lens for focusing Negative Ion Beam: Theory and experiment
Review of Scientific Instruments, 2004Co-Authors: I. A. Soloshenko, V. N. Gorshkov, V. P. Goretsky, A. M. ZavalovAbstract:Detailed researches the of space charge lens for focusing Negative Ion Beam are performed for the cases when positive space charge forming is done either by the Beam itself, or by special flow of electrons. Numerical simulatIons of space charge fields and Beam Ion trajectories are accomplished, and results of the calculatIons are compared with experimental data. It is shown both theoretically and experimentally that in the proposed device electric field strength reaches a value of ∼100 V/cm, thus providing a focal length of
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Space-charge lens for focusing a Negative-Ion Beam
Plasma Physics Reports, 2003Co-Authors: A. M. Zavalov, V. N. Gorshkov, V. P. Goretskii, I. A. SoloshenkoAbstract:Results are presented from experimental and theoretical studies of a space-charge lens for focusing a Negative-Ion Beam. The space-charge field and the Beam Ion trajectories are numerically calculated for the lens used in the experiments. The results of calculatIons are compared with the experimental data. It is shown theoretically and experimentally that the proposed device allows one to achieve the main operating conditIons of the space-charge lens: the inertial confinement of positive Ions and the removal of electrons by an external electric field. The focusing field of the lens attains ∼100 V/cm, which provides a focal length of
Yasuhito Gotoh - One of the best experts on this subject based on the ideXlab platform.
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Surface charging of insulated materials by Negative Ion Beam bombardment
AIP Conference Proceedings, 2008Co-Authors: Junzo Ishikawa, Hiroshi Tsuji, Yasuhito GotohAbstract:When a Negative Ion Beam bombards an insulated material such as an isolated electrode or an insulator, a surface voltage is induced by the surface charging and will affect the Ion Beam trajectories during Beam transport. The mechanism of the surface charging of an insulated electrode is related with its secondary electron emissIon factor and energy distributIon. The charging voltage in this case is as low as several volts and its polarity is positive. On the other hand, in case of an insulator, the polarity is Negative and its value is several volts because an electric dipole layer is generated just on the surface due to Negative Ion Beam bombardment. These low surface charging voltages lead an advantage in Negative Ion Beam applicatIons as well as in Negative Ion Beam transport.
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A Negative Ion Beam applicatIon to artificial formatIon of neuron network in culture
Review of Scientific Instruments, 2000Co-Authors: Hiroshi Tsuji, Yasuhito Gotoh, Hiroko Sato, T. Baba, Junzo IshikawaAbstract:A Negative Ion Beam modificatIon of the biocompatibility of polystyrene surface was investigated for the artificial formatIon of neuron network in culture with respect to Negative Ion species. Negative Ions of silver, copper or carbon were implanted in nontreated polystyrene (NTPS) dishes at conditIons of 20 keV and 3×1015 Ions/cm2 through a mask with many slits of 60 μm in width. For the surface wettability, the contact angle of Ion-implanted NTPS was about 75° for silver-Negative Ions, which was lower than 86° of the original NTPS. For carbon implantatIon, on the contrary, the contact angles did not change from the original value. In culture experiment using neuron cells of PC-12h (rat adrenal pheochromocytoma), the cells cultured with serum medium in two days showed the cell attachment and growth in number only at the Ion-implanted regIon on NTPS for all Ion species. In another two days in culture with nonserum medium including a nerve growth factor, the outgrowth of neural protrusIons was also observe...
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Dependence of carbon interatomic bonds on incident Ion energy in carbon Negative Ion Beam deposited films
Thin Solid Films, 1999Co-Authors: Hiroshi Tsuji, Yasuhito Gotoh, S Nakamura, Junzo IshikawaAbstract:Abstract Atomic bonds of carbon thin films prepared by Negative-Ion Beam depositIon were investigated with respect to the dependence on incident Ion energy. Mass-separated carbon Negative Ions of C − and C 2 − were deposited on Si(100) and Si(111) at a low Ion energy of 50–400 eV with a current density of about 20 μA/cm 2 under 1 × 10 −6 Pa for 5 h after removing surface oxide layer on the substrate by heating up to 900 °C for 15 min. Deposited films were found from their broad Raman band in 1400–1600 cm −1 to be diamond-like carbon films. From decomposed XPS C lS spectra into three bonds of C C (sp 3 bonds), C C (sp 2 ) and O, it was found that the fractIon of sp 3 bonds increased with an increase in Ion energy, and that it decreased gradually with the further increase in Ion energy for both Ion species. It is considered that the kinetic energy of Ions contributes to form the metastable bond like sp 3 bond but that the excessive kinetic energy results damage in the films. As a result, the sp 3 bond fractIon of more than 80 % was obtained at Ion energy of 75 eV per a carbon atom for both C − and C 2 − depositIons.
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Ion Eergy Dependence of N/C Ratio in Low Energy CN Molecular Negative-Ion Beam Deposited Films
Shinku, 1999Co-Authors: Takaaki Yoshihara, Yasuhito Gotoh, Hiroshi Tsuji, Junzo IshikawaAbstract:CN Negative-Ion Beam deposited films have been investigated with respect to dependencies of a nitrogen atom content and interatomic bonding state upon the incident Ion energy. The CN Negative Ions extracted from a sputter-type Negative Ion source were deposited on a silicon substrate n-Si (100) at various Ion energies in a range of 25-500 eV. From Rutherford backscattering spectroscopy (RBS) measurement, the maximum of N/C ratio and atomic density in films were obtained N/C = 0.60, 1.56 × 1023 atoms · cm-3 at an Ion energy of 75 eV, respectively. From X-ray photoelectron spectroscopy (XPS) analysis, nitrogen atoms in the film were found to be mostly combined with carbon atoms in bonding states of C = N and C ≡ N. The maximum fractIon of C-N bond reached 11% of nitrogen content at an Ion energy of 500 eV. In Raman spectroscopy, CNxfilms showed similar Raman bands to those of the diamond like carbon (DLC) film.
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CN molecular Negative-Ion Beam depositIon and Ion energy dependence of atomic bonds between carbon and nitrogen in the films
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1999Co-Authors: Hiroshi Tsuji, Yasuhito Gotoh, Takaaki Yoshihara, S Nakamura, Junzo IshikawaAbstract:Abstract The atomic bonds in carbon nitride films prepared by CN molecular Negative-Ion Beam depositIon were investigated with respect to the dependence on the incident Ion energy. Mass-separated CN Negative Ions were deposited on n-Si(1 0 0) at a low Ion energy in a gas pressure of 5.0 × 10−5 Pa. Raman spectra showed a broad Raman band similar to that of diamond-like carbon and a small band corresponding to CN triple bonds near 2220 cm−1. The maximum nitrogen content was obtained at an Ion energy of 75 eV, where the N/C ratio was 0.6, as found from RBS analysis. Detailed XPS spectra of N1s were measured to investigate inter-atomic bonds between C and N. The amount of C–N single bonds was increased with an increase in Ion energy up to 75 eV. The amount of C–C single bonds showed a similar dependence upon the Ion energy as the C–N single bonds.
Junzo Ishikawa - One of the best experts on this subject based on the ideXlab platform.
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Surface charging of insulated materials by Negative Ion Beam bombardment
AIP Conference Proceedings, 2008Co-Authors: Junzo Ishikawa, Hiroshi Tsuji, Yasuhito GotohAbstract:When a Negative Ion Beam bombards an insulated material such as an isolated electrode or an insulator, a surface voltage is induced by the surface charging and will affect the Ion Beam trajectories during Beam transport. The mechanism of the surface charging of an insulated electrode is related with its secondary electron emissIon factor and energy distributIon. The charging voltage in this case is as low as several volts and its polarity is positive. On the other hand, in case of an insulator, the polarity is Negative and its value is several volts because an electric dipole layer is generated just on the surface due to Negative Ion Beam bombardment. These low surface charging voltages lead an advantage in Negative Ion Beam applicatIons as well as in Negative Ion Beam transport.
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A Negative Ion Beam applicatIon to artificial formatIon of neuron network in culture
Review of Scientific Instruments, 2000Co-Authors: Hiroshi Tsuji, Yasuhito Gotoh, Hiroko Sato, T. Baba, Junzo IshikawaAbstract:A Negative Ion Beam modificatIon of the biocompatibility of polystyrene surface was investigated for the artificial formatIon of neuron network in culture with respect to Negative Ion species. Negative Ions of silver, copper or carbon were implanted in nontreated polystyrene (NTPS) dishes at conditIons of 20 keV and 3×1015 Ions/cm2 through a mask with many slits of 60 μm in width. For the surface wettability, the contact angle of Ion-implanted NTPS was about 75° for silver-Negative Ions, which was lower than 86° of the original NTPS. For carbon implantatIon, on the contrary, the contact angles did not change from the original value. In culture experiment using neuron cells of PC-12h (rat adrenal pheochromocytoma), the cells cultured with serum medium in two days showed the cell attachment and growth in number only at the Ion-implanted regIon on NTPS for all Ion species. In another two days in culture with nonserum medium including a nerve growth factor, the outgrowth of neural protrusIons was also observe...
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Dependence of carbon interatomic bonds on incident Ion energy in carbon Negative Ion Beam deposited films
Thin Solid Films, 1999Co-Authors: Hiroshi Tsuji, Yasuhito Gotoh, S Nakamura, Junzo IshikawaAbstract:Abstract Atomic bonds of carbon thin films prepared by Negative-Ion Beam depositIon were investigated with respect to the dependence on incident Ion energy. Mass-separated carbon Negative Ions of C − and C 2 − were deposited on Si(100) and Si(111) at a low Ion energy of 50–400 eV with a current density of about 20 μA/cm 2 under 1 × 10 −6 Pa for 5 h after removing surface oxide layer on the substrate by heating up to 900 °C for 15 min. Deposited films were found from their broad Raman band in 1400–1600 cm −1 to be diamond-like carbon films. From decomposed XPS C lS spectra into three bonds of C C (sp 3 bonds), C C (sp 2 ) and O, it was found that the fractIon of sp 3 bonds increased with an increase in Ion energy, and that it decreased gradually with the further increase in Ion energy for both Ion species. It is considered that the kinetic energy of Ions contributes to form the metastable bond like sp 3 bond but that the excessive kinetic energy results damage in the films. As a result, the sp 3 bond fractIon of more than 80 % was obtained at Ion energy of 75 eV per a carbon atom for both C − and C 2 − depositIons.
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Ion Eergy Dependence of N/C Ratio in Low Energy CN Molecular Negative-Ion Beam Deposited Films
Shinku, 1999Co-Authors: Takaaki Yoshihara, Yasuhito Gotoh, Hiroshi Tsuji, Junzo IshikawaAbstract:CN Negative-Ion Beam deposited films have been investigated with respect to dependencies of a nitrogen atom content and interatomic bonding state upon the incident Ion energy. The CN Negative Ions extracted from a sputter-type Negative Ion source were deposited on a silicon substrate n-Si (100) at various Ion energies in a range of 25-500 eV. From Rutherford backscattering spectroscopy (RBS) measurement, the maximum of N/C ratio and atomic density in films were obtained N/C = 0.60, 1.56 × 1023 atoms · cm-3 at an Ion energy of 75 eV, respectively. From X-ray photoelectron spectroscopy (XPS) analysis, nitrogen atoms in the film were found to be mostly combined with carbon atoms in bonding states of C = N and C ≡ N. The maximum fractIon of C-N bond reached 11% of nitrogen content at an Ion energy of 500 eV. In Raman spectroscopy, CNxfilms showed similar Raman bands to those of the diamond like carbon (DLC) film.
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CN molecular Negative-Ion Beam depositIon and Ion energy dependence of atomic bonds between carbon and nitrogen in the films
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1999Co-Authors: Hiroshi Tsuji, Yasuhito Gotoh, Takaaki Yoshihara, S Nakamura, Junzo IshikawaAbstract:Abstract The atomic bonds in carbon nitride films prepared by CN molecular Negative-Ion Beam depositIon were investigated with respect to the dependence on the incident Ion energy. Mass-separated CN Negative Ions were deposited on n-Si(1 0 0) at a low Ion energy in a gas pressure of 5.0 × 10−5 Pa. Raman spectra showed a broad Raman band similar to that of diamond-like carbon and a small band corresponding to CN triple bonds near 2220 cm−1. The maximum nitrogen content was obtained at an Ion energy of 75 eV, where the N/C ratio was 0.6, as found from RBS analysis. Detailed XPS spectra of N1s were measured to investigate inter-atomic bonds between C and N. The amount of C–N single bonds was increased with an increase in Ion energy up to 75 eV. The amount of C–C single bonds showed a similar dependence upon the Ion energy as the C–N single bonds.
