Search Results - (Author, Cooperation:M. Wada)

2018-07-20

American Physical Society (APS)

0556-2813

1089-490X

Physics

Nuclear Structure

2018-06-09

American Physical Society (APS)

0556-2813

1089-490X

Physics

Nuclear Structure

2011-09-03

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Adsorption ; Biomass ; Cellobiose/metabolism ; Cellulose/chemistry/*metabolism ; Cellulose 1,4-beta-Cellobiosidase/*metabolism ; Crystallization ; Hydrolysis ; Kinetics ; Microscopy, Atomic Force ; Trichoderma/enzymology

2014-10-04

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Academies and Institutes/economics ; Budgets ; *Guidelines as Topic ; Japan ; Research Personnel/ethics/*legislation & jurisprudence ; Research Support as Topic/economics ; Retraction of Publication as Topic ; Scientific Misconduct/*legislation & jurisprudence ; Stem Cells

0020-708X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Energy, Environment Protection, Nuclear Power Engineering

Physics

Electronic Resource

2018-07-03

Genetics Society of America (GSA)

2160-1836

Biology

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

Negative sodium ions and negative dimer ions of sodium are extracted from a sodium plasma. The extraction characteristics of Na− and Na2− from a low power discharge (about 1 W) through a single aperture (φ1.5 mm) are described. Both extracted currents of Na− and Na2− increase with the temperature of the heat shield inside the discharge chamber. The current ratio of Na− to Na2− is almost constant independent of discharge voltage. By increasing the discharge power, the value of the bias voltage of the plasma electrode that gives the optimum extraction currents of Na− and Na2− increases. The extracted current of Na2− is lower than that of Na− by two orders of magnitude.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

A single stage 6.4 GHz ECR ion source for an isotope separator on-line based radioactive nuclear beam facility at KEK-Tanashi, is under an on-line test for the effective production of 19Ne2+ ions by using alpha beams from a cyclotron. Synchronized with the pulsed operation of heavy ion linacs, the millisecond beam bunching is now being performed to reduce the loss of radioactive ions in acceleration by using a pulsed-gating potential method. The highest beam intensity at 100 Hz and 20% duty factor reaches 60% of that obtained in a continuous-wave mode. © 1998 American Institute of Physics.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

Spatial distributions of the current density of the ion beams extracted from an electron-stimulated-desorption-type powdery sample ion source have been measured. The vertical profile showed an asymmetry which can be attributable to the localized ion emission at the powder surface. The deflection of the beam in the horizontal direction caused by the magnetic field for guiding the electron's motion to hit the powder surface was also confirmed. Despite the presence of this inhomogeneity which may degrade the beam quality, the positive and negative oxygen ion beams produced from BaO powder with the beam energy as low as 2 kV were focused to about 2 mm diameter. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Magnetic aftereffect and irreversible flux loss at elevated temperatures were studied for fully dense isotropic and anisotropic Nd-Fe-Co−B magnets consolidated from rapidly quenched powder by direct joule heating. The consolidation process and the subsequent alignment of c axis do not affect the aftereffect constant Sv and the prepared magnets have roughly the same Sv as a bonded magnet, independent of coercivity at room temperature (650–1200 kA/m), exposure temperature (60–120 °C), and anisotropy of the magnets. Thus the magnitude of the aftereffect is determined mainly by the magnitude of the irreversible susceptibility χirr. It was also clarified empirically that the irreversible flux loss FL is proportional in magnitude to χirr. However, the slopes of the FL vs χirr line for isotropic magnets are much larger than those for the anisotropic ones. Thus FL can be reduced by decreasing χirr and/or making magnets anisotropic.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

The energy distributions of C− and C2− beams extracted from a plasma-sputter-type negative ion source with the concave graphite target were measured by a retarding field energy analyzer having 1.5% resolving power. The reduction in energy spread of the energy distribution functions was observed by adding Cs into the discharge. The observed energy spreads of C− beam for 650 V target bias were 15 eV without Cs and 13 eV with Cs, respectively. The shift toward the lower energy due to Cs supply was also observed. The observed negative energy shift was constant at about 3.7 eV for the C beam, the value corresponded to the work function reduction from a pure graphite to Cs covered graphite surface. © 2000 American Institute of Physics.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

For an isotope separator on-line based radioactive nuclear beam facility at KEK-Tanashi, two different types of ion sources are currently employed: a single stage 6.4 GHz electron cyclotron resonance ion source for 18Ne2+ and 19Ne2+ ions and a surface ionization-type ion source for 8Li1+ ions. The production target for Ne radioisotopes is LiF powder. Enclosed in a water-cooled Cu target cell, the target can sustain proton beam power of 120 W for a long term. The methods to suppress unwanted isotopes, like 19F in 19Ne and 18O in 18Ne, are discussed. For the production of 8Li1+ with the surface ionization-type ion source, a recoil-catcher method is adopted. The feasibility is discussed, comparing to a thick target method. © 2000 American Institute of Physics.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

The velocity distribution function of the gas effusing from a 5.5-cm-diam, 5-cm-long small ion source was measured by the mass separated time-of-flight method. The measured distribution function could be fitted to a Maxwellian distribution before the commencement of a discharge, when the deuterium pressure in the ion source was below 0.6 Pa. The effect of discharge upon the distribution function of neutral deuterium below this operating pressure was investigated by changing the arc power. The deuterium gas temperature determined by fitting the measured distribution function to a Maxwellian showed a maximum gas temperature of 800 K at discharge power density of 6 W/cm3. Effects of discharge upon argon and helium gas temperature were also measured, which showed a monotonic increase against the discharge power. © 2002 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Systematic study on the effects of the waveguide thickness Wg has been carried out for 200-μm-wide stripe separate-confinement-heterostructure lasers in the range of Wg=0.22–1.2 μm while the width of single quantum well is kept constant at 10 nm. The internal loss αi is reduced from 1.7 to 1 cm−1 when Wg is increased from 0.22 to 1.2 μm. It is shown that αi is not determined by the free-carrier absorption of clad layers, but primarily by Γ, the optical confinement factor, most probably due to scattering at the quantum well/waveguide interfaces. The external differential quantum efficiency ηd monotonically increases with Wg for pulsed operation. By contrast, ηd is maximum at Wg=0.8 μm for continuous-wave (cw) operation. Both the threshold carrier density and the threshold temperature sensitivity increases with Wg for Wg≥0.8 μm, which decreases ηd in cw operation. When 200-μm-wide devices (20%/97% coated) were life tested at 2 W and 30 °C, the median degradation rate shows a minimal value of 3×10−6 h−1 at Wg=0.8 μm, which is 7 times smaller than that at Wg=0.22 μm. The facet temperature measured by the modulation reflectance is also minimized at Wg=0.8 μm. In broad-waveguide lasers with increasing Wg, the increase in carrier overflow competes with the reduction of optical power density, and thus self-absorption in the quantum well, which determines the optimal Wg. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The crystallographic texture of heat-treated Cu thin films and its effects on stress-migration resistance were studied as a function of film thickness within a range of 50–900 nm. All as-deposited films had (111) texture. After heat treatment at 723 K, texture transition from (111) to (100) was observed in films of thickness greater than 300 nm. The (111) texture films after heat treatment showed severe stress migration; in contrast, the (100) texture films showed no noticeable stress migration. The observed stress-migration resistance in the (100) texture films can be attributed to the absence of twins and to lower thermal stress as compared with the (111) texture films. © 2002 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The temperature dependence of the band gap in InAsyP1−y (y=0–0.67) has been determined by photoluminescence, x-ray diffraction, and absorption spectra measurements. We found that the measured data within the temperature range of 77–300 K can be expressed by the equation proposed by O'Donnell and Chen. The band gap at 77 K is given by Eg=1.407−1.073y+0.089y2, while the compositional dependence of the band gap observed at 300 K, agrees with the values previously reported. We confirmed that changes in temperature caused a slight change in the bowing parameters, and hence found that the band gap temperature dependence of InAsyP1−y (y=0–1) varies very little with changes in composition (2.5–3.5×10−4 eV/K). © 2000 American Institute of Physics.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

A plasma sputter negative ion source was evaluated for its applicability for measuring the plasma potentials in fusion devices. Both the beam current density and the beam energy spread are key issues for this application. The energy spectra of self-extracted Au− beams from the source were measured under the condition of a constant work function of the production surface. The FWHM increases from 3 to 9 eV monotonically as the target voltage increases from 50 to 300 V, independently from the target surface work function of 2.2–3 eV.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

A beam of negative lithium ions (Li−) with a current density as high as 3×10−5 A/cm2 was extracted from a 5 cm diam, 7 cm long multicusp ion source. The extracted Li− current was correlated to the plasma temperature and density measured with Langmuir probes heated to avoid Li condensation. The neutral lithium flux from the ion source was measured with a Langmuir–Taylor detector, and it showed a linear correlation with the extracted Li− current. Further increase in efficiency to produce Li− current is expected by improving the plasma confinement of the ion source.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

An apparatus capable of measuring the angle-resolved energy distribution function of ions produced by backscattering at metal surfaces is designed and tested. To exclude noise due to other impurity ions and electrons from the signal of target ions, a water-cooled magnetic deflection-type momentum analyzer is installed on a rotating table in a vacuum chamber. In addition to the beam forming and beam diagnostics components, work function monitoring equipment and an ion source for surface cleaning are installed. Preliminary tests of the apparatus was conducted to measure He+ emission from neutral He beam injection onto a Mo surface. With an improvement of the signal-to-noise ratio, the apparatus can be used to measure the angle-resolved energy distribution function of He− produced at a metal surface by He beam injection. © 2002 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The photoelectric work function of a cesiated molybdenum converter surface in a cesiated hydrogen discharge and the negative-hydrogen-ion (H−) current produced at the surface were simultaneously measured. With the negative bias potential of the converter constant, the H− yield increased exponentially as the work function was decreased by introducing Cs into the discharge. The yield of H− current was always higher for a higher bias potential on the surface, provided the measured surface work function was nearly the same. When the concentration of Cs in a discharge was nearly constant, the bias potential of the surface at which the H− production became maximum was observed. At this bias potential, the surface work function was close to the work-function minimum.

Electronic Resource