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Abstract: Heat generation density of electric elements increases close to the limit of forced air-cooling. New cooling technology is required and a self-vibration heat pipe is proposed for the electric elements cooling. The self-vibration heat pipe, which has a meandering capillary channel, can operate for vertical and horizontal heat removal without gravity effects. However, the behaviors of the working fluid in the pipe have not been well studied. The purpose of this study is to clarify the working fluid phenomena in the heat pipe. The working fluid in the pipe was visualized by neutron radiography system at JRR-3 in Japan Atomic Energy Agency. The liquid columns in the meandering channel of the heat pipe were recorded by a high-speed camera. The obtained images were segmented and the meandering capillary channel was uncoiled by image processing methods to show the temporal vibration of the liquid columns in the stretched channel. Periods of the column oscillation were about 0.5–1.5s. The oscillation of the columns was analyzed by a mass-spring model. The periods of the oscillation were obtained and compared with the experiment results. It was shown that the analytical values agreed fairly with the experimental ones. [Copyright &y& Elsevier]

Abstract: In order to clarify the effects of water on performances of a Polymer Electrolyte Fuel Cell (PEFC), measurements of water distribution in a Japan Automobile Research Institute (JARI) standard PEFC were carried out by means of neutron radiography. Furthermore, the cell voltage and the pressure drop between inlet and outlet of the air were simultaneously measured. The effects of channel geometry, i.e. single-serpentine and three-serpentine, and relative humidity of air were investigated. The experimental conditions were current density of 200mA/cm2, hydrogen utilization of 9.5% and oxygen utilization of 40%. The membrane electrode assembly (MEA) area was 5×5cm2. The pictures were taken every 15s with an exposure time of 12s. The spatial resolution was 108μm. From the measurements, the relation between cell voltage, pressure drop and movement of the water plug in the channel was confirmed. The PEFC performances were recovered as the water plug evacuated. Condensed water in the channel decreased with the relative humidity of air. However, it may affect the MEA permanence. Therefore, the most appropriate operating conditions should be decided for taking into account both the cell performances and the permanencies. [Copyright &y& Elsevier]

A 230 MeV superconducting azimuthally varying field (AVF) cyclotron SC230 was developed by Sumitomo Heavy Industries Ltd., Japan. With a yoke diameter, height and weight of 2.8 m, 1.7 m and 65 t, respectively, it is currently the most compact isochronous cyclotron for proton therapy. Size reduction was achieved by a high magnetic field using cryogen-free superconducting coils. It adopts not only a superconducting magnet, but also sectors with a narrow pole gap and large spiral angle, two dees with low power consumption, and beam extraction using the precessional extraction method. It has a maximum beam current of 1 μ A. The total power consumption of its system is lower than 200 kW. After each component, including the magnet, was fabricated, the cyclotron was moved to a new test site, and a vacuum test and conditioning of some components were conducted. The beam commissioning started, and the first extracted beam was successfully observed. In this paper, the processes and results of the beam commissioning and the basic performance of the first beam are reported. [ABSTRACT FROM AUTHOR]

Abstract: The formation of an ion beam with a uniform transverse intensity distribution based on a nonlinear focusing method has been studied at the azimuthally varying field cyclotron facility of Japan Atomic Energy Agency. The method enables us to perform uniform irradiation at a constant particle fluence rate over the whole area of a large sample. To obtain a large-area highly uniform beam on the target, we first smooth the intensity distribution of the beam from the cyclotron by multiple scattering and then focus the smoothed beam using octupole magnets. An efficient technique to enhance the scattering effect with a small energy loss is discussed. By collimating the tail of the smoothed beam before octupole focusing, a beam with a nearly uniform profile can be attained on the target. Moreover, we also show that a misaligned beam can be transformed into a uniform beam by adding sextupole focusing. The possibility of ultra-short-time and ultra-low-fluence irradiation has been demonstrated toward advanced applications in materials and biological science. The characteristics of the uniform beam produced by the nonlinear focusing method are discussed from the viewpoint of a uniform irradiation method as compared to other conventional methods. [Copyright &y& Elsevier]

We are developing a Ti/Au TES microcalorimeter array for future Japanese X-ray astronomy missions. The goal is an energy resolution of 2–5 eV at 6 keV, and an array of 100–1000 pixels to achieve a geometrical area of >1 cm2 and a moderate spatial resolution simultaneously. The energy resolution was improved to ∼6 eV at 6 keV with a very fast time constant (<100 μs). To achieve a high coverage fraction, it is necessary to fabricate mushroom-shaped X-ray microabsorbers. We are developing an electrodeposition fabrication technique that is suitable for our process. Sn was used as absorber material, but the energy resolution was not good due to the existence of long-lived quasiparticles. Bi is also used, and the process is under optimization now. The readout strategy is to multiplex signals in the frequency domain, using a bridge circuit. So far, we succeeded in multiplexing two pixels modulated with 50 and 20 kHz at 440 mK. The energy resolution obtained at 110 mK was 33 eV (25 kHz). [Copyright &y& Elsevier]

We are developing transition edge sensor (TES) microcalorimeter arrays for future Japanese astronomy missions. Although 6.6 eV energy resolution for 5.9 keV and 74 μs decay time are achieved, our energy resolution was limited by the excess noise of unknown origin. The dominant noise showed 1/R dependence and it only appeared when the current through the TES, I, is larger than 10 μA. This is explained if we assume a constant voltage noise source with a level of ∼2(4kTCRn)1/2. We also investigated the influence of I on the TES performance and found the TES sensitivity α is reduced when the ratio of current to the critical current I/IC is large. It can explain the reduction of α observed when operated without a magnetic shield. We also found a strong correlation between IC and α or the baseline width. Thus, we conclude that IC is an essential parameter for the TES performance. [Copyright &y& Elsevier]

Abstract: At the Kansai Photon Science Institute of the Japan Atomic Energy Agency, we have developed a Compton backscattered X-ray source in the energy region of a few hundred keV. The X-ray source consists of a 150-MeV electron beam, with a pulse duration of 10ps (rms), accelerated by a Microtron accelerator and an Nd:YAG laser, with a pulse duration of 10ns (FWHM). In the first trial experiment, the X-ray flux is estimated to be (2.2±1.0)×102 photons/pulse. For the actual application of an X-ray source, it is important to increase the generated X-ray flux as much as possible. Thus, for the purpose of increasing the X-ray flux, we have developed the pulse compression system for the Nd:YAG laser via stimulated Brillouin scattering (SBS). The SBS pulse compression has the great advantages of a high conversion efficiency and a simple structure. In this article, we review the present status of the Compton backscattered X-ray source and describe the SBS pulse compression system. [Copyright &y& Elsevier]