Takahiro Morishima

Application of matrix decomposition algorithms for singular matrices to the Pawley method in Z-Rietveld

Z-Rietveld is a program suite for Rietveld analysis and the Pawley method; it was developed for analyses of powder diffraction data in the Materials and Life Science Facility of the Japan Proton Accelerator Research Complex. Improvements have been made to the nonlinear least-squares algorithms of Z-Rietveld so that it can deal with singular matrices and intensity non-negativity constraints. Owing to these improvements, Z-Rietveld successfully executes the Pawley method without requiring any constraints on the integrated intensities, even in the case of severely or exactly overlapping peaks. In this paper, details of these improvements are presented and their advantages discussed. A new approach to estimate the number of independent reflections contained in a powder pattern is introduced, and the concept of good reflections proposed by Sivia [J. Appl. Cryst. (2000), 33, 1295–1301] is shown to be explained by the presence of intensity non-negativity constraints, not the intensity linear constraints.

Development of a neutron detector based on a position-sensitive photomultiplier

A neutron scintillation detector based on a position-sensitive photomultiplier has been developed for neutron spin echo and small angle neutron scattering measurements. This photomultiplier has good spatial resolution, less than 1 mm2. The detection efficiency of gamma ray background is very low for using a thin ZnS/6LiF scintillator. The effective area of this detector is around 60 cm2.

AKARI FAR-INFRARED ALL-SKY SURVEY MAPS

Far-infrared observations provide crucial data for the investigation and characterisation of the properties of dusty material in the Interstellar Medium (ISM), since most of its energy is emitted between~100 and 200 ㎛. We present the first all-sky image from a sensitive all-sky survey using the Japanese AKARI satellite, in the wavelength range 50 ? 180 ㎛. Covering > 99% of the sky in four photometric bands with four filters centred at 65 ㎛, 90 ㎛, 140 ㎛, and 160 ㎛ wavelengths, this achieved spatial resolutions from 1 to 2 arcmin and a detection limit of -1 , with absolute and relative photometric accuracies of < 20%. All-sky images of the Galactic dust continuum emission enable astronomers to map the large-scale distribution of the diffuse ISM cirrus, to study its thermal dust temperature, emissivity and column density, and to measure the interaction of the Galactic radiation field and embedded objects with the surrounding ISM. In addition to the point source population of stars, protostars, star-forming regions, and galaxies, the high Galactic latitude sky is shown to be covered with a diffuse filamentary-web of dusty emission that traces the potential sites of high latitude star formation. We show that the temperature of dust particles in thermal equilibrium with the ambient interstellar radiation field can be estimated by using 90 ㎛, 140 ㎛, and 160 ㎛ data. The FIR AKARI full-sky maps provide a rich new data set within which astronomers can investigate the distribution of interstellar matter throughout our Galaxy, and beyond.

Terahertz direct detector using superconducting tunnel junctions

High-sensitivity terahertz direct detectors using superconducting tunnel junctions were fabricated. They were designed for detecting terahertz radiation in the frequency range of 0.4 and 0.65 THz with the fractional bandwidth of above 10 percent. The results of their performance evaluation of five detector elements are presented. We show the results of the frequency response as well as that the absolute efficiency ranged from 10 to 30 percent and that the the sensitivity was 1.9 x 10-16 W Hz-0.5 in noise equivalent power.

Development of superconducting tunnel junctions as an energy-dispersive detector for UV and visible photons

Abstract We are developing an energy-dispersive detector for UV and visible photons that uses superconducting tunnel junctions (STJs) with Al trapping layers. As a first step to achieve this, we evaluated the performance of the detector for extreme ultraviolet (EUV) photons by using a synchrotron radiation facility. We achieved an energy resolution of FWHM=17.8±0.6 eV (including electrical noise of 17.6±0.2 eV) for 55 eV EUV photons with a 100×100 μm2 STJ. The electrical noise was the main component of the energy resolution. We achieved the electrical noise of FWHM=2.1±0.1 eV for a 20×20 μm2 STJ by replacing the cables connecting the STJ to a preamplifier operated at room temperature. A stronger signal resulting from a thinner tunnel barrier will lead to better energy resolution for detecting UV and visible photons.

The general relativistic effects on the magnetic moment in Earth’s gravity

The general relativistic effects to the anomalous magnetic moment of muons moving in the Earths gravitational field have been examined. The Dirac equation generalized to include the general relativity suggests the magnetic moment of fermions measured on the ground level is influenced by the Earths gravitational field as

Collapsing open isotropic universe generated by nonminimally coupled scalar field

\mu_{\rm m}^{\rm eff} \!\simeq\! (1\!+\!3\phi/c^2)\,\mu_{\rm m}

Advantages of the AKARI FIR all-sky maps

, where

Discrete Symmetry Tests In Neutron-induced Compound States

\mu_{\rm m}

The Filamentary Web of Star Formation

is the magnetic moment in the flat spacetime and