Design Study of CANGAROO-III, Stereoscopic Imaging Atmospheric Cherenkov Telescopes for sub-TeV Gamma-ray

CANGAROO-III is an Imaging Atmospheric Cherenkov Telescope (IACT) array of four 10 m telescopes for very high energy (sub-TeV) gamma-ray astronomy. A design study of the CANGAROO-III telescope system was carried out using the Monte Carlo technique in order to optimize the pixel size and the telescope spacing. Studies were also made of observations at low elevation angles.Comment: 17pages, 13 figures, elsart, to appear in Astro. Part. Phy

Detection of Gamma-rays around 1TeV from RX J0852.0-4622 by CANGAROO-II

We have detected gamma-ray emission at the 6sigma level at energies greater than 500GeV from the supernova remnant RX J0852.0-4622 (G266.2-1.2) using the CANGAROO-II Imaging Atmospheric Cherenkov Telescope (IACT). The flux was 0.12 times of that of Crab at 1TeV. The signal centroid is consistent with the peak of the X-ray emission in the north-west rim of the remnant.Comment: 12pages, 4figures, to be published in ApJ

A Search for TeV Gamma-ray Emission from the PSR B1259-63/SS2883 Binary System with the CANGAROO-II 10-m Telescope

Observations of the PSR B1259-63/SS2883 binary system using the CANGAROO-II Cherenkov telescope are reported. This nearby binary consists of a 48msec radio pulsar in a highly eccentric orbit around a Be star, and offers a unique laboratory to investigate the interactions between the outflows of the pulsar and Be star at various distances. It has been pointed out that the relativistic pulsar wind and the dense mass outflow of the Be star may result in the emission of gamma rays up to TeV energies. We have observed the binary in 2000 and 2001, 47 and 157 days after the October 2000 periastron. Upper limits at the 0.13--0.54 Crab level are obtained. A new model calculation for high-energy gamma-ray emission from the Be star outflow is introduced and the estimated gamma-ray flux considering Bremsstrahlung, inverse Compton scattering, and the decay of neutral pions produced in proton-proton interactions, is found to be comparable to the upper limits of these observations. Comparing our results with these model calculations, the mass-outflow parameters of the Be star are constrained.Comment: 29 pages, 10 figures, accepted by Ap

Internal Stress and Dislocation Interaction of Plate-Shaped Misfitting Precipitates in Aluminum Alloys

The fine misfit precipitates in age-hardenable aluminum alloys have important roles due to their excellent age-hardening ability, by their interaction with dislocations. The present study focused on the internal stress field of plate-shaped misfitting precipitates to evaluate their roles in dislocation overcoming the precipitates by means of micromechanics based on Green’s function method. The stress field of misfit precipitates on {001} and {111} habit planes were reproduced by homogeneous misfit strain (eigenstrain) of the precipitate (Eshelby inclusion method), and the dislocation motion vector on the primary slip plane was predicted by the force acted on the dislocation by the Peach–Koehler formula. According to simulation results, the dislocation interaction strongly depends on the stress field and geometry of misfit precipitates; repulsive and attractive forces are operated on the dislocations lying on the primary slip plane when the dislocation approaches the misfit precipitates. The hardening ability of different orientations of precipitation variants was discussed in terms of interaction force acted on the dislocation

Similarity and dissimilarity of joint interface morphology in magnetic pulse welded Al/Cu and Al/Ni plates

A characteristic wavy morphology often appears at the joint interface of magnetic pulse welding (MPW), and an intermediate layer is formed in some metal combinations. It has been known that the wavy morphology changes mainly depend on the density difference between the metals. A sinusoidal wavy interface is formed for the combination of similar metals (Al/Al, Cu/Cu) and that of dissimilar metals having almost the same density (Cu/Ni). In contrast, a trigger-like wavy interface is formed for the combination having a large density difference (Al/Cu, Al/Fe). The difference in strength (hardness) of the solid metal is also assumed to affect the wavy interface morphology. In the present study, two metal combinations (Al/Cu and Al/Ni) were subjected to the MPW to elucidate the effect of hardness difference, since Cu and Ni have almost the same density, but different hardness. Both the MPWed Al/Cu and Al/Ni joints showed a trigger-like wave interface. The wave size (wave-height and wavelength) of Al/Ni was smaller than that of Al/Cu. In Al/Ni, the distribution of intermediate phase was more continuous tracing the outline of the wave. The numerical simulation of the wave formation process was performed using the Smoothed Particle Hydrodynamics (SPH) method. It was revealed that the extent of metal jet penetration into the metal in the process of joining behind the collision point was weaker in Ni than in Cu. This is considered to be due to the larger deformation resistivity of Ni, which is harder than that of Cu

Orientation Dependent Hardening by <001> Rod-Shaped Misfitting Precipitates in Aluminium Alloys

A coherent precipitate formed in a metallic alloy is of importance in its strengthening mechanism, owing to dislocation/precipitate interaction. Therefore, the present study investigated the effect of <001> rod-shaped precipitates on misfit hardening in aluminium alloys by means of parametric dislocation dynamics simulation based on Green’s function method. The simulation results revealed that the topological evolution of the dislocation microstructure is greatly influenced by local internal stress around the <001> rod precipitate. The strong orientation dependence of misfit hardening was observed for the gradients of the stress–strain curves and their maximum shear stresses, where the difference in the maximum stress values amounted to 30%. The strong and weak hardening behaviours associated with the internal stress of <001> rod precipitates were implemented in terms of the energy associated with the dislocation motion

Two ways to estimate precipitate elastic fields through Eshelby inclusion theory

The stress-free misfit strain obtained from simulation, neglecting the constraint from the matrix phase, serves as the inhomogeneity eigenstrain. On the other hand, the experimentally measured misfit strain under the constraint of the matrix phase serves as the constrained strain. This study demonstrates two ways to calculate the equivalent eigenstrain for precipitates through Eshelby inclusion theory: the inhomogeneity eigenstrain way (IEW) and the constrained strain way (CSW)

Compositional Dependent Amorphization in Zr Alloy Films by Means of Ni-Implantation

Ni-implantation has been conducted for sputter deposited Zr alloy films to investigate compositional dependent amorphization behavior in proportion to Ni in Zr alloys. As-deposited Zr and Zr–Cu with thickness of 200 nm shows columnar hcp-Zr and nano-crystalline hcp-Zr(Cu), respectively. Implantation of 150 keV Niþ with the amount of 1 1017 ions/cm2 induces amorphization of Zr and Zr(Cu) with 100 nm in thick. Critical amorphization concentration of penetrated Ni decreases for Ni-implanted Zr–Cu film to be 10 at%Ni as comparison with that of 20 at%Ni for Zr film. The displacement collision effect has been examined by penetration of 300 keV-Niþ. As increasing the beam energy, penetration depth increases to yield equi-axed crystalline surface and inside amorphization, which corresponding to compositional gradient of penetrated Ni. This compositional dependent amorphization via ion implantation implies that induced amorphization is attributed to chemical reaction between penetrated Ni with constituents