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Yamamoto, Y

Publications and source records attributed to Yamamoto, Y.

A Comparison of Creep-Rupture Tested Cast Alloys HR282, IN740 and 263 for Possible Application in Advanced Ultrasupercritical Steam Turbine and Boiler

Cast forms of traditionally wrought Ni-base precipitation-strengthened superalloys are being considered for service in the ultra-supercritical conditions (760°C, 35MPa) of next-generation steam boilers and turbines. After casting and homogenization, these alloys were given heat-treatments typical for each in the wrought condition to develop the gamma-prime phase. Specimens machined from castings were creep-rupture tested in air at 800°C. In their wrought forms, alloy 282 is expected to precipitate M<SUB>23</SUB>C<SUB>6</SUB> within grain boundaries, alloy 740 is expected to precipitate several grain boundary phases including M<SUB>23</SUB>C<SUB>6</SUB>, G Phase, and η phase, and alloy 263 has M<SUB>23</SUB>C6 and MC within its grain boundaries. This presentation will correlate the observed creep-life of these cast alloys with the microstructures developed during creep-rupture tests, with an emphasis on the phase identification and chemistry of precipitated grain boundary phases. The suitability of these cast forms of traditionally wrought alloys for turbine and boiler components will also be discussed.

36 MATERIALS SCIENCE↗

Evaluation of surface damage on organic materials irradiated with Ar cluster ion beam

The sputtering yields of organic materials under large cluster ion bombardment are much higher than those under conventional monomer ion bombardment. The sputtering rate of arginine remains constant with fluence for an Ar cluster ion beam, but decreases with fluence for Ar monomer. Additionally, because Ar cluster etching induces little damage, Ar cluster ion can be used to achieve molecular depth profiling of organic materials. In this study, we evaluated the damage to poly methyl methacrylate (PMMA) and arginine samples irradiated with Ar atomic and Ar cluster ion beams. Arginine samples were analyzed by secondary ion mass spectrometry (SIMS) and PMMA samples were analyzed by X-ray photoelectron spectroscopy (XPS). The chemical structure of organic materials remained unchanged after Ar cluster irradiation, but was seriously damaged. These results indicated that bombardment with Ar cluster ions induced less surface damage than bombardment with Ar atomic ion. The damage layer thickness with 5 keV Ar cluster ion bombardment was less than 1 nm.

36 MATERIALS SCIENCE↗

Development of high productivity medium current ion implanter 'EXCEED 3000AH Evo2'

High productivity medium current ion implanter 'EXCEED 3000AH Evo2' is developed. In semiconductor manufacturing field, improvement of the productivity is continuously required. Especially mass production lines recently tend to use low energy beam and 2 pass implant for higher throughput. The 'Evo2' has been developed in an effort to fulfill these requirements. The 'Evo2' increases low energy beam current by 150 to 250% by applying electrostatic einzel lens called 'V-lens' installed at the exit of the Collimator magnet. This lens is also able to control the beam incident angle by adjusting the upper and lower electrode's voltages independently. Besides, mechanical scanning speed is enhanced to minimize process time of 2 pass implant, while also frequency of the fast beam scanning is enhanced to keep dose uniformity. In addition, a vacuum pumping capability at the target chamber is enhanced to reduce a vacuum waiting time during processing photo-resist wafers. This improvement achieved to reduce process time by 40% for a specific recipe. Furthermore, a modified Indirectly Heated Cathode with electron active Reflection 2 (IHC-R2) ion source which has a long life time filament has been installed. These new elements and/or functions have realized typically 25% improvement of productivity compared to standard EXCEED, and also improve a precise implantation capability.

43 PARTICLE ACCELERATORS↗

Repulsive nature of optical potentials for high-energy heavy-ion scattering

The recent works by the present authors predicted that the real part of heavy-ion optical potentials changes its character from attraction to repulsion around the incident energy per nucleon E/A=200-300 MeV on the basis of the complex G-matrix interaction and the double-folding model (DFM) and revealed that the three-body force plays an important role there. In the present paper, we have precisely analyzed the energy dependence of the calculated DFM potentials and its relation to the elastic-scattering angular distributions in detail in the case of the {sup 12}C+{sup 12}C system in the energy range of E/A=100-400 MeV. The tensor force contributes substantially to the energy dependence of the real part of the DFM potentials and plays an important role to lower the attractive-to-repulsive transition energy. The nearside and farside (N/F) decompositions of the elastic-scattering amplitudes clarify the close relation between the attractive-to-repulsive transition of the potentials and the characteristic evolution of the calculated angular distributions with the increase of the incident energy. Based on the present analysis, we propose experimental measurements for the predicted strong diffraction phenomena of the elastic-scattering angular distribution caused by the N/F interference around the attractive-to-repulsive transition energy together with the reduced diffractions below and above the transition energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Five-Body Cluster Structure of the Double-{Lambda} Hypernucleus {sub {Lambda}{Lambda}}{sup 11}Be

Energy levels of the double {Lambda} hypernucleus, {sub {Lambda}{Lambda}}{sup 11}Be are calculated within the framework of a {alpha}{alpha}n{Lambda}{Lambda} five-body model. Interactions between constituent particles are determined so as to reproduce reasonably the observed low-energy properties of the {alpha}{alpha}, {alpha}{alpha}n nuclei and the existing data for {Lambda}-binding energies of the {alpha}{Lambda}, {alpha}{alpha}{Lambda}, {alpha}n{Lambda}, and {alpha}{alpha}n{Lambda} systems. An effective {Lambda}{Lambda} interaction is constructed so as to reproduce, within the {alpha}{Lambda}{Lambda} three-body model, the B{sub {Lambda}{Lambda}}of {sub {Lambda}{Lambda}}{sup 6}He, which was extracted from the emulsion experiment, the NAGARA event. With no adjustable parameters for the {alpha}{alpha}n{Lambda}{Lambda} system, B{sub {Lambda}{Lambda}}of the ground and bound excited states of {sub {Lambda}{Lambda}}{sup 11}Be are calculated with the Gaussian expansion method. The Hida event, recently observed at KEK-E373 experiment, is interpreted as an observation of the ground state of the {sub {Lambda}{Lambda}}{sup 11}Be.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗