84 research outputs found

    Results of the Excitation Test of the LHD Helical Coils Cooled by Subcooled Helium

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    Large helical device, the largest superconducting stellarator, has been operated for the research of fusion plasma since 1998. The toroidal field of almost 3 T is produced by a pair of pool-cooled helical coils, in the innermost layers of which a normal-zone had been induced several times at the bottom of the coil at higher currents than 11.0 kA. Since the field is not the highest there, the local cooling conditions are probably deteriorated by bubbles gathered by buoyancy. In order to improve the cryogenic stability by subcooling, an additional cooler with two-stage cold compressors was installed at the inlet of the coil in 2006. The inlet and outlet temperatures of the coils were successfully lowered to 3.2 K and 3.8 K, respectively, with a mass flow of 50 g/s. In spite of a half charging rate to reduce AC losses, a normal-zone was induced near the top of the coil at 11.45 kA. It propagated to one side and stopped near the inner equator, where the field is the highest. In comparison with the stability tests with a model coil, the local temperatures of the innermost layers near the top is considered to have been raised up to almost the saturated temperature of 4.4 K by charging. The excitation method was revised to waiting cool-down at 11.0 kA, and the excitations up to 11.5 kA have been attained

    Backward-angle photoproduction of π0\pi^0 mesons on the proton at EγE_\gamma = 1.5--2.4 GeV

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    Differential cross sections and photon beam asymmetries for π0\pi^0 photoproduction have been measured at EγE_\gamma = 1.5--2.4 GeV and at the π0\pi^0 scattering angles, --1 << cosΘc.m.<\Theta_{c.m.} < --0.6. The energy-dependent slope of differential cross sections for uu-channel π0\pi^0 production has been determined. An enhancement at backward angles is found above EγE_\gamma = 2.0 GeV. This is inferred to be due to the uu-channel contribution and/or resonances. Photon beam asymmetries have been obtained for the first time at backward angles. A strong angular dependence has been found at Eγ>E_\gamma > 2.0 GeV, which may be due to the unknown high-mass resonances.Comment: 12 pages, 4 figures, submitted to PL

    Near-threshold Lambda(1520) production by the gamma p -> K+Lambda(1520) reaction at forward K+ angles

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    Differential cross sections and photon-beam asymmetries for the gamma p -> K+ Lambda(1520) reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at 0.6<cos(theta)<1. A new bump structure was found at W=2.11 GeV in the cross sections. The bump is not well reproduced by theoretical calculations introducing a nucleon resonance with J<=3/2. This result suggests that the bump might be produced by a nucleon resonance possibly with J>=5/2 or by a new reaction process, for example an interference effect with the phi photoproduction having a similar bump structure in the cross sections.Comment: 5 pages, 4 figures, published in Phys. Rev. Let

    Measurement of the γ⃗p→K+Λ\vec{\gamma} p \to K^+ \Lambda Reaction at Backward Angles

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    Cross sections for the γp→K+Λ\gamma p \to K^+ \Lambda have been measured at backward angles using linearly polarized photons in the range 1.50 to 2.37 GeV. In addition, the beam asymmetry for this reaction has been measured for the first time at backward angles. The Λ\Lambda was detected at forward angles in the LEPS spectrometer via its decay to pπ−p\pi^- and the K^+ was inferred using the technique of missing mass. These measurements, corresponding to kaons at far backward angles in the center-of-mass frame, complement similar CLAS data at other angles. Comparison with theoretical models shows that the reactions in these kinematics provide further opportunities to investigate the reaction mechanisms of hadron dynamics.Comment: 6 figures, submitted to PRC rapid communication

    Forward coherent Ï•\phi-meson photoproduction from deuterons near threshold

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    Differential cross sections and decay asymmetries for coherent ϕ\phi-meson photoproduction from deuterons were measured for the first time at forward angles using linearly polarized photons at EγE_{\gamma}= 1.5-2.4 GeV. This reaction offers a unique way to directly access natural-parity Pomeron dynamics and gluon exchange at low energies. The cross sections at zero degrees increase with increasing photon energy. The decay asymmetries demonstrate a complete dominance of natural-parity exchange processes, showing that isovector unnatural-parity π\pi-meson exchange is small. Nevertheless the deduced cross sections of ϕ\phi-mesons from nucleons contributed by isoscalar t-channel exchange processes are not well described by the conventional Pomeron model.Comment: 14 pages, 6 figures. Final published versio

    Prescription sequence symmetry analysis: assessing risk, temporality, and consistency for adverse drug reactions across datasets in five countries

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    Abstract not availableNicole Pratt, Esther W. Chan, Nam-Kyong Choi, Michio Kimura, Tomomi Kimura, Kiyoshi Kubota, Edward Chia-Cheng Lai, Kenneth K.C. Man, Nobuhiro Ooba, Byung-Joo Park, Tsugumichi Sato, Ju-Young Shin, Ian C.K. Wong, Yea-Huei Kao Yang, and Elizabeth E. Roughea
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