Showing papers by "Yoshio Arai published in 2007"

ILC Reference Design Report Volume 3 - Accelerator

Abstract: The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2 s^-1. The complex includes a polarized electron source, an undulator-based positron source, two 6.7 km circumference damping rings, two-stage bunch compressors, two 11 km long main linacs and a 4.5 km long beam delivery system. This report is Volume III (Accelerator) of the four volume Reference Design Report, which describes the design and cost of the ILC.

Extensive multiband study of the X-ray rich GRB 050408: A likely off-axis event with an intense energy injection

Abstract: Aims. Understand the shape and implications of the multiband ligth curve of GRB 050408, an X-ray rich (XRR) burst. Methods. We present a multiband optical light curve, covering the time from the onset of the γ-ray event to several months after, when we only detect the host galaxy. Together with X-ray, millimetre and radio observations we compile what, to our knowledge, is the most complete multiband coverage of an XRR burst afterglow to date. Results. The optical and X-ray light curve is characterised by an early flattening and an intense bump peaking around 6 days after the burst onset. We explain the former by an off-axis viewed jet, in agreement with the predictions made for XRR by some models, and the latter with an energy injection equivalent in intensity to the initial shock. The analysis of the spectral flux distribution reveals an extinction compatible with a low chemical enrichment surrounding the burst. Together with the detection of an underlying starburst host galaxy we can strengthen the link between XRR and classical long-duration bursts.

Simultaneous measurement of nanoprobe indentation force and photoluminescence of InGaAs/GaAs quantum dots and its simulation

Abstract: Simultaneous measurement of the nanoprobe indentation force and the photoluminescence (PL) of In 0.5 Ga 0.5 As/GaAs quantum dots (QDs) is successfully achieved by introducing a specially designed loadcell into the nanoprobe indentation system. By using this improved system, the emission properties of self-assembled In 0.5 Ga 0.5 As/GaAs QDs under nanoprobe indentation are investigated under low temperature and high vacuum conditions. Energy shifts as large as 90 meV induced by nanoprobe indentation are observed in the QDs. Further, the increase in the emission energy of the QDs varies from peak to peak under the same indentation force. In order to clarify this mechanism, simulations are carried out based on a three-dimensional finite element and six-band strain-dependent k · p Hamiltonian. The simulation results are in good agreement with the experimental ones. The results of the nanoprobe indentation experiments show that the change in the position of the QD relative to the nanoprobe results in a variation in its energy shift rate. This dependence of the energy shift rate of a QD on its position is also validated by repeated indentation with horizontal scan experiment.

The new front-end electronics for the Super-Kamiokande experiment

Abstract: Super-Kamiokande is a ring imaging water Cherenkov detector for astro-particle physics that consists of 50 kton pure water and about 13000 photomultiplier tubes (PMTs). We are planning to upgrade all the front-end electronics in next year. By high speed signal processing electronics, we will record all the hits of all the PMTs without any hardware filtering, aiming observations of much fainter signals of the supernova relic neutrinos, lower energy (~ 3 MeV) solar neutrinos, neutrino burst from nearby galactic supernova, and so on. The energy resolutions of multi-GeV atmospheric neutrino events will also be improved by the electronics. The new front-end electronics is based on charge to time converters (QTCs) and multi-hit TDCs. TCP/IP based readout channel is implemented to handle large amounts of data. We have developed a custom ASIC QTC and evaluated the characteristics of the chip and the prototypical board; high-speed (1 MHz cycle), high sensitivity for single photo- electron signal, good charge (0.1 pC RMS) and timing (0.3 ns RMS) responses, and wide charge dynamic range (2500 pC). In this paper, the design and the performance of the front-end board are described.

Development of New Front-End Electronics for Super-Kamiokande

Abstract: Super-Kamiokande is a ring imaging water Cherenkov detector for astro-particle physics that consists of 50 kton pure water and about 13000 photomultiplier tubes (PMTs). We are planning to upgrade all the front-end electronics in next year. By high speed signal processing electronics, we will record all the hits of all the PMTs without any hardware filtering, aiming observations of much fainter signals of the supernova relic neutrinos, lower energy (~3 MeV) solar neutrinos, neutrino burst from nearby galactic supernova, and so on. The energy resolutions of multi-GeV atmospheric neutrino events will also be improved by the electronics. The new front-end electronics is based on a charge to time converter (QTC) and a multi-hit TDC. TCP/IP based readout channel is implemented to handle large amounts of data. We have developed a custom ASIC QTC and evaluated the characteristics of the chip and the prototypical board; high-speed (1 MHz cycle), high sensitivity for single photo-electron signal, good charge (0.1 pC RMS) and timing (0.3 ns RMS) responses, and wide charge dynamic range (2500 pC). In this paper, the design and the performance of the front-end board are discribed.

Location of quantum dots identified by microscopic photoluminescence changes during nanoprobe indentation with a horizontal scan

Abstract: The location of quantum dots (QDs) embedded in a GaAs matrix is successfully identified by microscopic photoluminescence (PL) measurement during nanoprobe indentation with a horizontal scan at low temperature $(10\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. By introducing a high-sensitive load cell and a focused ion beam-fabricated flat-apex nanoprobe, the indentation force and PL of QDs are measured simultaneously at each point in the direction of the nanoprobe horizontal scanning with a constant indentation force. The experimental results show that the emission energy from QDs has a strong dependence on the location of QDs relative to the nanoprobe-indented location. Consequently, the emission energy shifts with the nanoprobe scan, generating an emission trace with a constant indentation force. Based on the energy shift of the ground state of the QD simulated by the combination of three-dimensional finite element strain calculation and strain-dependent $\mathbf{k}\mathbf{∙}\mathbf{p}$ Hamiltonian, an estimation method is developed, which enables us to identify the location of the QD from its emission trace in the nanoprobe indentation experiment. Results indicate that all the emission traces clearly observed are emitted from the QDs around the edge of the nanoprobe-indented area. Further discussion reveals that the evolution of shear strain generates hole accumulation around the contact edge of the indented nanoprobe. Consequently, the high density of holes enhances the PL of the QDs in that region.

Provision of information by local governments using the Internet: case studies in Japan

Abstract: The Internet is an effective medium that has great potential for the low-cost provision of information from local government. This paper discusses the relationship between geographic conditions and local government policy for the use of Information and Communications Technologies (ICTs), via case studies of official websites operated by local governments in Japan. This paper explores three main issues. First, the process of the diffusion of local government websites in Japan is analyzed. Second, the diversity of website content presented by local governments is assessed. Finally, the effects of national policy on Internet utilization by local governments is discussed. The following results are based on data collected by a questionnaire survey and an analysis of websites for local governments in selected areas of Japan. The diffusion of official websites for local governments began in the mid-1990s and was largely complete by 2000. In the early stages of this diffusion process, many websites aimed to transmit information to audiences outside of the municipality. In the later stages, however, larger cities established official websites and a greater proportion of websites were internally oriented. The content of these sites targeted the multiple needs of the local residents in terms of public services. Although the Japanese Government established a positive policy with the aim of improving ICT utilization by both local and national government, the national policy had only a minor effect on official local government websites.

WITHDRAWN: R&D of a monolithic pixel sensor based on 0.15 μm fully depleted SOI technology

Abstract: The Publisher regrets that this article is an accidental duplication of an article that will be published in Nucl. Instr. and Meth. A , doi: 10.1016/j.nima.2007.07.111 . The duplicate article has therefore been withdrawn.

Strength Evaluation of Aluminium Cast Alloy Locally Reinforced by SiC Particles and Al2O3 Whiskers and Its Fractography

Abstract: In this paper, fracture mechanisms under monotonic and cyclic load and its stress distribution of an aluminum cast alloy locally reinforced by SiC particles and Al2O3 whiskers are investigated experimentally and numerically. The material is monotonically and cyclically deformed to failure at room temperature. The fracture origin and the fracture path are investigated on the fracture surfaces. The fracture occurs in the reinforced part under both monotonic and cyclic loads. SEM analysis of the fracture surface shows that the fatigue fracture is controlled by the fracture of coarse Al2O3 whiskers. On the other hand the static fracture (monotonic loading) shows that the fracture mechanism is the combination of reinforcing particle fracture and interfacial debonding between reinforcing ceramics and matrix metal. The stress distributions around the boundary between the reinforced part and unreinforced part are calculated based on an inclusion array model considering the microscopic inhomogeneous effects. Both the experimental results and the finite element simulation results show that the critical location for fracture is changed by the external stress level which controls the local stress distribution through plastic constraint between reinforcing particle and matrix alloy.