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Negative hydrogen ions are produced and extracted using an aluminum plasma grid, without cesium through irradiation with hydrogen plasma. The negative ion amount increases sharply, up to ∼115 μA·cm−2, at a discharge power of 1 kW with an electric field downstream of the grid. These negative ions are extracted with high purity. In addition, it is suggested that negative ions are produced by positive hydrogen ions and hydrogen atoms. As high-density plasmas enhance the negative ion production, the current density of negative ions is expected to increase with plasma discharge power. [ABSTRACT FROM AUTHOR]

In this study, hydrogen electron plasma is irradiated on an aluminum plate, and negative hydrogen ions are produced on the plate surface. Hydrogen ionic plasma is maintained near the surface, where a deflection magnetic field is applied using a pair of magnets in the vicinity of the surface. When no magnetic field is applied, ionic plasma is not formed. The interface position between the ionic and the electron plasma depends on the quantity of negative ions produced and the deflection magnetic flux density. The deflection magnetic field that controls the electron flux toward the surface, while maintaining quasi-neutrality, is indispensable for the formation of ionic plasma. [ABSTRACT FROM AUTHOR]

To realize stable negative ion beams for 100 s required in the neutral beam injector of JT-60SA, a physical model to control cesium (Cs) distribution inside the negative ion source has been developed in order to maintain the stable negative ion production at the plasma grid (PG) surface with Cs. In this work, to quantitatively evaluate Cs coverage on the PG, a three-dimensional Cs transportation code was introduced to consider the spatial Cs distribution in the source. The spatial temperature distribution of the chamber wall was also introduced in this model. As a result, the reasonable variation of the Cs coverage for 100 s was obtained, compared to that in the initial model. Based on the modified model, the operational temperature of the chamber wall was proposed to be less than 60 °C to suppress the desorption of Cs in the chamber wall and to sustain the stable negative ion production. In addition, it was also suggested that a slightly higher wall temperature before the operation leads to a decrease in the amount of Cs stored at the chamber wall, resulting in suppression of Cs consumption in the ion source. [ABSTRACT FROM AUTHOR]

In this study, a hydrogen ionic plasma with relatively low residual fractional electron concentration (ne/n+ ∼ 10−2) is generated using an aluminum plasma grid for the production of negative hydrogen ions and a control grid for negative ion extraction and electron removal. The ionic plasma is composed of negative and positive ions, containing molecular ions. Negative ions are in part produced using positive ions with several electron volts. A positive ion beam with 50 eV or more contributes to increase the density of the ionic plasma. The positive ion beam energy and the control grid bias voltage are tuned in such a way that a high-density ionic plasma is maintained. [ABSTRACT FROM AUTHOR]

Metal grids made of nickel, copper, titanium, and iron are used for production of negative hydrogen ions through the irradiation of positive ions. It is easy to determine the existing negative ions in the diffused plasma through the Langmuir probe measurement; however, the negative current, indicating the diminution of the extraction current from the grid, is found to not clearly depend on the work function and electronegativity. [ABSTRACT FROM AUTHOR]

Negative hydrogen ions are produced in the apertures of a plasma grid made of aluminum under the irradiation of positive ions, generating an ionic plasma consisting of positive and negative ions. The saturation current ratio obtained using a Langmuir probe reflects the existence ratio of electrons and is found to increase in connection with the diffusion of the ionic plasma. The local increment of the current ratio suggests the collapse of negative ions and the replacement of detached electrons. [ABSTRACT FROM AUTHOR]

Negative hydrogen ions are produced on a nickel grid with positive-ion irradiation. In order to investigate the production mechanism, a copper grid without the chemisorption of hydrogen atoms and positive helium ions without negative ionization are used for comparison. Positive hydrogen ions reflected on the metal surface obtain two electrons from the surface and become negatively ionized. It is found that the production yield of negative ions by desorption ionization of chemisorbed hydrogen atoms seems to be small, and the production is a minor mechanism. [ABSTRACT FROM AUTHOR]

Negative hydrogen ions are produced by plasma-assisted catalytic ionization using a nickel grid. When positive ions passing through the grid are decelerated by an electric field, the extraction current density of passing positive ions is sharply reduced by neutralization and negative ionization of the ions. This phenomenon is found to depend on the specific surface area of the grid and the current density. [ABSTRACT FROM AUTHOR]

Positive and negative hydrogen ions are produced by plasma-assisted catalytic ionization using a nickel grid, where the irradiation current density of positive ions onto the grid can be controlled by the discharge power. The irradiation energy can be controlled by both the grid potential and the discharge plasma potential. Extraction properties and energy distributions of positive and negative ions produced in the cases of using the grid and a porous nickel plate are compared. Two production mechanisms of negative ions are found in the process of plasma-assisted catalytic ionization. [ABSTRACT FROM AUTHOR]

Positive and negative hydrogen ions are produced by plasma-assisted catalytic ionization using a porous nickel plate, where the irradiation current density and energy of positive ions produced by discharge to the porous plate are controlled. The ion energy distributions are analyzed from the properties of current densities of positive and negative ions extracted from the porous surface. Positive ions passing through fine pores of the porous plate and positive and negative ions produced on the porous surface are observed. It is clarified that the produced fluxes of positive and negative ions and the flux balance between them are controlled by the irradiation current density and energy, respectively. [ABSTRACT FROM AUTHOR]

Hydrogen atomic pair ions, i.e., H+ and H- ions, are produced by plasma-assisted catalytic ionization using a porous nickel plate. Positive ions in a hydrogen plasma generated by dc arc discharge are irradiated to the porous plate, and pair ions are produced from the back of the irradiation plane. It becomes clear that the production quantity of pair ions mainly depends on the irradiation current of positive ions and the irradiation energy affects the production efficiency of H- ions. [ABSTRACT FROM AUTHOR]

Our basic-plasma experiments relating to fusion-oriented and space plasmas have yielded deep and unique insight into wave and instability physics in ordinary electron-ion and unusual pair-particle plasmas. Here recent results on flow shears, polarization reversal and pair-ions are presented in the way that light is shed on the underlying physics. [ABSTRACT FROM AUTHOR]

To generate a hydrogen pair-ion plasma consisting of only hydrogen atomic pair ions, i.e., H+ and H- ions, the efficient production of pair ions is required. When discharged hydrogen plasma is irradiated to a Ni catalyst, pair ions are produced on the catalyst surface. It is clarified that hydrogen chemisorption on the catalyst affects pair-ion production. [ABSTRACT FROM AUTHOR]

A fullerene pair-ion plasma without electrons is generated and electrostatic modes propagating along magnetic-field lines are externally excited in the range of low frequencies. It is found that four kinds of wave modes, including theoretically unexpected ones, exist in the plasma, and the phase lag between the density fluctuations of positive and negative ions strongly depends on the frequency. In order to illuminate further collective motion of pair-ion plasmas in the range of high frequencies, a concept of a hydrogen pair-ion plasma consisting of only H+ and H- is proposed and an experimental configuration is presented. On the basis of the production of a hydrogen plasma by Penning ionization gauge discharge, the principles of ion cyclotron resonance and E×B drift motion are shown to be effective for ion-species analysis/selection and separated electron detection from negative ions in the generation of pure hydrogen pair-ion plasmas. [ABSTRACT FROM AUTHOR]

Abstract: Two fullerene plasmas are generated for mass production of fullerene dimers. The fullerene positive and negative ions are produced by electron impact ionization and attachment. The negative ions are accelerated and injected into the target plasma, and collide with the positive ions and/or neutral fullerenes, yielding the collisional product as a dimer C121. This direct production of dimers leads to the volume production and the fusion-type structure formation with strong linkage without catalysts or nonallotropic fullerene derivatives. [Copyright &y& Elsevier]

Abstract: Positive and negative fullerene ions are produced coincidentally with impact ionization and attachment of electrons, and the generation of single pair-ion plasma is achieved. Because negative ions are accelerated by the electric field formed between a cathode and a grounded grid, they collide with positive ions, yielding the collision products as dimers. When the cathode setup is modified, double pair-ion plasmas are generated on each side and are miscible with each other. Both the ions are accelerated in the opposite direction by the electric field formed between two cathodes which can be diversely biased, and collide with each other, yielding effectively the collision products. This novel method without catalysts or nonallotropic fullerene derivatives has prospects of mass production of fullerene-fusion materials. [Copyright &y& Elsevier]

An alkali-halogen plasma is generated by a dc magnetron discharge using thermal cathodes under a uniform magnetic field. Alkali-salt vapor is dissociated and ionized by E×B-drift electron impact, and alkali positive ions and halogen negative ions are produced. A magnetic-filter region is situated at an exit of the discharge region and electrons are removed from the plasma. The electron emission and E/B fields are optimized, resulting in the alkali-halogen plasma with the ion density of 3×108 cm-3 at B=0.2 T. [ABSTRACT FROM AUTHOR]

Radio-frequency discharges are performed in low magnetic fields (0-0 mT) using three types of helicon-wave exciting antennas with the azimuthal mode number of ¦m¦ =1. The most pronounced peak of plasma density is generated in the case of a phased helical antenna at only a few mT, where the helicon wave with in m = + 1 is purely excited and propagates. An analysis based on the dispersion relation well explains the density-peak phenomenon in terms of the correspondence between the antenna one-wavelength and the helicon wavelength, bringing forth the optimization principle of plasma source design in very low magnetic fields. [ABSTRACT FROM AUTHOR]