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  • 1
    Electronic Resource
    Electronic Resource
    Estimate of cusp loss width in multicusp negative ion source : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 968-970 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Expression of cusp loss width derived by Bosch and Merlino is applied to JAERI's Kamaboko source. The width is related to the ambipolar diffusion coefficient across the cusp magnetic field. Electron–ion collision is found 1.2–7.4 times larger as compared with electron-neutral collision. Averaged cusp magnetic field in the diffusion coefficient is taken as a parameter in the simulation code for Kamaboko source. When the averaged magnetic field is 48 G, simulation results agree well with JAERI's experiment in a wide range of pressure and arc power variation. The value of 48 G is reasonable from the consideration of confining the equation of ion source plasma. The obtained width is about 10 times the value evaluated by two times ion Larmor radius on the surface of cusp magnet. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148603
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  • 2
    Electronic Resource
    Electronic Resource
    Numerical simulation of cesium cooling effects in H− ion source : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 880-882 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Cesium volume reactions are included in a two-point model numerical code for a high power hydrogen negative ion source. The energy balance equation for the electron temperature and rate equations of Cs and Cs+ are included in our code to investigate the electron cooling and volume effects by cesium seeding. Cesium density in the ion source is taken as a variable for the calculation. Cesium is ionized over 95% in the driver region of the ion source. The electron temperature begins to decrease at cesium density 1011 cm−3 and the electron density increases because of the ionization of cesium. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150320
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  • 3
    Electronic Resource
    Electronic Resource
    Monte Carlo simulation of negative ion production in the negative hydrogen ion source : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 883-886 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Two Monte Carlo simulation codes: (a) neutral transport code and (b) negative ion (H−) transport code, have been developed to understand transport phenomena in negative ion sources. In the neutral transport code, Boltzmann equations for hydrogen molecules (H2) and atoms (H) are solved. Three dimensional (3D) spatial distributions of H2, H, and H− production are obtained for a tandem negative ion source. The volume production of H− is limited to the area around the gas inlet in the first chamber and near the plasma grid in the second chamber. On the other hand, distribution of H− surface production is shown to be almost uniform over all the plasma grid surface. In the negative ion code, H− trajectories are calculated by numerically solving the 3D equation of motion for H− ions. The effects of the magnetic filter on the extraction probability of surface produced H− ions are mainly studied. The dependence of the extraction probability on the field strength is small. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150321
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  • 4
    Electronic Resource
    Electronic Resource
    Negative hydrogen ion source for TOKAMAK neutral beam injector (invited) : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 1219-1224 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Intense negative ion source producing multimegawatt hydrogen/deuterium negative ion beams has been developed for the neutral beam injector (NBI) in TOKAMAK thermonuclear fusion machines. Negative ions are produced in a cesium seeded multi-cusp plasma generator via volume and surface processes, and accelerated with a multistage electrostatic accelerator. The negative ion source for JT-60U has produced 18.5 A/360 keV (6.7 MW) H− and 14.3 A/380 keV (5.4 MW) D− ion beams at average current densities of 11 mA/cm2 (H−) and 8.5 mA/cm2 (D−). A high energy negative ion source has been developed for the next generation TOKAMAK such as the International Thermonuclear Experimental Reactor (ITER). The source has demonstrated to accelerate negative ions up to 1 MeV, the energy required for ITER. Higher negative ion current density of more than 20 mA/cm2 was obtained in the ITER concept sources. It was confirmed that the consumption rate of cesium is small enough to operate the source for a half year in ITER-NBI without maintenance. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150432
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  • 5
    Electronic Resource
    Electronic Resource
    Hydrogen negative ion beam acceleration in a multiaperture five-stage electrostatic accelerator : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 1231-1233 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: To develop a high power negative ion source/accelerator for 1 MeV class neutral beam injector, hydrogen negative ion beam acceleration has been studied using a five-stage, multiaperture electrostatic accelerator. After conditioning each accelerator stage, the negative ions are accelerated to 1 MeV successfully with a drain current of 25 mA for 1 s. Cs was introduced into the ion source to produce higher current density. The highenst acceleration current density of 15 mA/cm2 was successfully accelerated up to an energy of 700 keV for 1 s, keeping the optimum perveance. The total acceleration current of 200 mA was extracted from nine central apertures 14 mm diameter each. A preliminary measurement of the heat load in the accelerator showed that the direct interception of the beam for the first grid and the third grid was negligibly small. The highest heat load was 4.5% of the input power at the second grid. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150434
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  • 6
    Electronic Resource
    Electronic Resource
    Numerical simulation of the effect of Cs volume reaction in an H− ion source : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1132-1134 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Effects of cesium related reactions are investigated using a simulation code for H− ion sources. Effects begin to appear when cesium density is 1011 cm−3, but are still small and become large when the cesium density is greater than 1012 cm−3. The H− density decreases due to electron detachment. Decreasing the plasma potential by cesium seeding results in 12% smaller H− density. The minimum of the plasma potential shown experimentally by Bacal is found to correspond to a cesium coverage of 50% with the use of Langmuir adsorption isotherm. Surface production is effective only when the cesium density is around 1011 cm−3. For cesium density greater than 1012 cm−3, the effect of the cesium related volume reaction becomes larger. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148646
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  • 7
    Electronic Resource
    Electronic Resource
    Spatial resolved emission spectroscopic study on laser plume of Y1Ba2Cu3Ox at different oxygen pressures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3697-3702 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To investigate the characteristics of the plume generated by the laser ablation of Y1Ba2Cu3Ox, emission spectra of the ejected species were observed at different distances from the target in an oxygen atmosphere. It was found that velocities of ejected species increased with the distance from the target. At 35 mm from the target the emission intensities of Y, Ba, O atoms, and YO molecules drastically increased to an order of magnitude larger beyond several tens mTorr of oxygen pressure. This increase of emission intensity was due to the increment of the plasma density by a shock front formed at ∼35 mm. Above 0.5 Torr of oxygen pressure, molecular YO was produced by the oxidation of Y atoms. The plasma temperature was also elevated by shock heating. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361201
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  • 8
    Electronic Resource
    Electronic Resource
    Cross sections for 16O(He,He)16O resonant elastic scattering and application to elemental analysis of YBa2Cu4O8 and Nd1+xBa2−xCu3O7−δ films grown on SrTiO3 (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 14-20 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The differential cross sections for 16O(He,He)16O resonant elastic scattering at 3.034 and 3.078 MeV have been measured using stoichiometric thin (100 A(ring)) and thick (6000 A(ring)) SiO2 layers formed on Si(100) wafers by thermal oxidation at 900 °C under H2 and O2 flows. We have determined the resonance widths (Γ) and interaction radii (a), which are the parameters defining the cross sections in the partial wave analysis, by best fitting the angular and energy dependent scattering yields from oxygen. A computer simulation program for Rutherford backscattering including the 16O(He,He)16O resonant scattering has been synthesized and applied to the elemental analysis of thin YBa2Cu4O8 and Nd1+xBa2−xCu3O7−δ films grown on SrTiO3 substrates. The present elemental analysis is compared with the transition temperatures of superconductivity (Tc) in the context of the oxygen deficiency. The accuracy of oxygen content is estimated to be better than 0.1 (a few %). How to improve the accuracies of the elemental analysis, in particular the oxygen content, is discussed in detail. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360948
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  • 9
    Electronic Resource
    Electronic Resource
    Spatial uniformity of negative ion production in volume negative ion source : Papers from the Ninth International Conference on Ion Sources (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1064-1066 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A spatial uniformity of negative ion production has been studied experimentally in a tandem-type volume negative ion source, where the plasma is divided into two regions by a magnetic filter, i.e., a driver region and an extraction region near the plasma grid (PG). A plasma density profile and the negative ion beam profile were measured. By the Langmuir probe measurement, a strong nonuniformity of the plasma density was observed near the plasma grid when the plasma grid is biased electrically with respect to the anode. By changing the polarity of the bias voltage, the deviation of the plasma density profile changed to the direction of E×B. In the pure hydrogen operation, the extracted beam profile corresponded to the plasma density profile in the extraction region. In the Cs-seeded operation, on the other hand, the uniformity of the beam current density became uniform despite the nonuniformity of the plasma density profile in the extraction region. The uniformity of the negative ions corresponded to the plasma uniformity in the driver region. These results indicate that the negative ions are not produced by positive ions in the extraction region in the Cs-seeded operation. We conclude that the negative ions are produced mainly by neutral atoms produced in the driver region via the surface production on the PG. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1430527
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  • 10
    Electronic Resource
    Electronic Resource
    Direct high-resolution electron microscopy observation of nonunit-cell nucleation in the initial stage of high-Tc superconducting film growth (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1830-1832 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relationship between the starting and ending atomic layers of YBa2Cu3O7−x and Bi2Sr2CaCu2O8 thin films is studied by high-resolution electron microscopy. Experimental results show that the starting atomic layer of the thin film is determined by surface chemistry and the interaction between the thin film and the substrate, while the ending layer of the thin film is thermodynamically determined by the high-Tc cuprate itself. Therefore, nonunit cell nucleation is often observed in certain cases. The surface atomic layers of YBa2Cu3O7−x and Bi2Sr2CaCu2O8 were found to be the CuO layer and single BiO layer, respectively. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113336
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