Japan Atomic Energy Research Institute

About: Japan Atomic Energy Research Institute is a based out in . It is known for research contribution in the topics: Neutron & Irradiation. The organization has 7707 authors who have published 14471 publications receiving 207688 citations.

Review of Discrete X-Ray Sources in the Small Magellanic Cloud: Summary of the ASCA Results and Implication on the Recent Star Forming Activity

Abstract: We made 22 observations on the Small Magellanic Cloud (SMC) and covered full regions by the end of the ASCA mission. We detected 106 discrete sources with a criterion of S/N > 5 and performed systematic analyses on all of the sources. We determined the source positions with an ~40'' error radius (90% confidence) for sources detected in the central 20' radius of the GIS. We detected coherent pulsations from 17 sources. Among them, eight were newly discovered during this study. We classified most of these pulsars as X-ray binary pulsars (XBPs) based on their properties, such as the flux variability and the existence of an optical counterpart. We detected X-ray emission from eight supernova remnants (SNRs). Among them, five SNRs showed emission lines in their spectra, hence we regarded the five as thermal SNRs. We found that XBPs and thermal SNRs in the SMC can be clearly separated by their spectral hardness ratio. Applying this empirical law to faint (thus unclassified) sources, we found 19 XBP candidates and four thermal SNR candidates. We also found several tens of candidates for active galactic nuclei, both from the hardness ratio and the logN--logS relation of extragalactic sources. Based on these ASCA results and further information from other sattelites, we compiled comprehensive catalogues of discrete X-ray sources in the Small Magellanic Cloud. Using the catalogues, we derived the spatial distributions of XBPs and SNRs. XBPs and SNRs were found to be concentrated in the main body and eastern wing, which resembles the distribution of young stars with ages of ~2e7yr. By comparing the source populations in the SMC and our Galaxy, we suggest that the star-forming rate (per unit mass) in the SMC was much higher than the Galaxy 1e7yr ago. We also discuss the recent change of the star-forming rate in the SMC.

A new trajectory analysis method for migratory planthoppers, Sogatella furcifera (Horváth) (Homoptera: Delphacidae) and Nilaparvata lugens (Stål), using an advanced weather forecast model

Abstract: 1 A new method of backward trajectory analysis for planthopper migration is presented. The method consists of two components: an advanced weather forecast model, MM5, for weather simulation, and a migration model for trajectory calculation. The weather forecast model simulates wind fields in which trajectories are calculated by the migration model. 2 It is assumed that planthoppers, Sogatella furcifera and Nilaparvata lugens, are transported at wind speeds and in wind directions. The method is evaluated using a migration event observed at Chikugo in Japan on 25 June 1969, which was recorded in hourly catch data. 3 The results indicate that the takeoff responsible for the migration occurred at 21 UTC (Coordinated Universal Time) on 23 June along the coastal region of Fujian province in China. This is the first time that the source region of this event has been accurately identified. Determinations of the migrating duration and height are also consistent with observations. 4 Although the landing process is not considered in the model, it is shown that the method is able to simulate the migration and accurately estimate various parameters. This study also shows the importance of high-quality weather simulation.

High power 170 GHz test of CVD diamond for ECH window

Abstract: In order to check the usability of large-size CVD (Chemical Vapor Deposition) diamond disks for high power millimeter wave vacuum barrier windows at room temperature (T = 293 K) a first series of experiments, using a 170 GHz, 0.4 MW, 0.2 s JAERI/Toshiba gyrotron1), have been performed. The dielectric loss tangent at a frequency of 170 GHz has been determined to be tan δ = 1.3·10−4. By comparing the experimental results to numerical simulations the thermal conductivity was estimated to be about k ≈ 1800 W/mK. This preliminary results indicate that a single-disk CVD diamond window assembly using a water-edge cooling could fulfill the requirements for a continuous wave (CW) transmission of millimeter wave power in the megawatt range. This is needed for the Electron Cyclotron Heating (ECH) on the International Thermonuclear Experimental Reactor (ITER).