Journal of Plasma and Fusion Research
Print ISSN : 0918-7928
Volume 80 , Issue 6
Showing 1-20 articles out of 20 articles from the selected issue
Rapid Communications
Special Topic Article : Study of Equation of State Using Laser-Induced Shock-Wave Compression
Contributed Paper
  • Kouhei ICHIYANAGI, Yoshitaka IGARASHI, Akitaka MATSUDA, Ken-ichi KONDO ...
    2004 Volume 80 Issue 6 Pages 472-475
    Published: 2004
    Released: October 08, 2004
    JOURNALS FREE ACCESS
    A laser shock wave is generated by the irradiation of a 10-ns pulsed laser beam using a plasma confinement target assembly. Nanosecond time-resolved fluorescence spectroscopy is performed on rhodamine-6G dye in an ethanol solution. The fluorescence spectra show a red shift under shock compression. The observed data demonstrate that the fluorescence of rhodamine-6G dye is suitable for use as a pressure scale for laser shock compression at the examined pressure range.
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  • Takatoshi ONO, Kazuo A. TANAKA, Norimasa OZAKI, Takeshi SHIOTA, Keiji ...
    2004 Volume 80 Issue 6 Pages 476-481
    Published: 2004
    Released: October 08, 2004
    JOURNALS FREE ACCESS
    Experiments, to measure temperature, pressure and shock wave velocity of compressed polystyrene (PS) simultaneously, are first carried out using the GEKKO XII⁄ HIPER laser system of the Institute of Laser Engineering, Osaka University. An optical system is made of Schwarzschild microscope and a biprism, which allowed the image of rear surfaces of a double-step target to be split into two and focused onto a slit of a visible streak-camera. Each image through two different band-pass filters is then recorded by using the streak-camera for spatially and temporally resolved measurement. First, pressure and shock wave velocity are calculated by observing the emissions from shock break out at the each step. Secondly, we measure the emissivities of the ultra-violet (UV) and blue range of spectrum from the shock wave-front passing in PS and decide color temperature from the ratio.
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  • Tomokazu SANO, Hiroaki MORI, Etsuji OHMURA, Isamu MIYAMOTO
    2004 Volume 80 Issue 6 Pages 482-485
    Published: 2004
    Released: October 08, 2004
    JOURNALS FREE ACCESS
    The quenching of the ε phase of iron, which has not been observed under a conventional shock compression, was attained using a femtosecond laser. The crystalline structure in a recovered iron sample was determined using an electron backscatter diffraction pattern method and an electron diffraction pattern method. A small quantity of the γ phase of iron also existed. Thermodynamic state inside the shock front has to be known because the shock induced phase transition occurs inside the shock front. Therefore, the temperature inside the shock front was calculated using thermodynamic equations. It was found that the ε phase was induced by the shock itself but not the γ phase. The γ phase was suggested to be induced as an intermediate structure between the α-ε transition. The femtosecond laser driven shock may have the potential to quench high-pressure phases which has not been attained using conventional methods.
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Review Paper
  • Norimasa OZAKI, Kazuo A. TANAKA, Takatoshi ONO, Kikuo TAKAMATSU, Keiji ...
    2004 Volume 80 Issue 6 Pages 486-491
    Published: 2004
    Released: October 08, 2004
    JOURNALS FREE ACCESS
    The GEKKO⁄HIPER-laser driven shock experiments were characterized in detail for studies on equation-of-state (EOS) in ultra-high pressure regime. High-quality shock waves were produced with optically smoothed laser beams. Key issues on EOS measurement with shock waves, the spatial uniformity and the temporal steadiness of shock, and the preheating problem were investigated by measurements of the self-emission and reflectivity from target rear surface. Our experiments and analysis based on impedance matching method were validated by use of double-step targets consisting of two Hugoniot standard metals. Extreme shock waves previously only achieved in nuclear explosion experiments were generated using the laser direct-drive experimental scheme.
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Lecture Note : Multiscale Modeling of Fusion Materials Behavior under Irradiation
  • Eiichi KURAMOTO, Masato HIRATANI, Taira OKITA, Kazunori MORISHITA, Nao ...
    2004 Volume 80 Issue 6 Pages 492-499
    Published: 2004
    Released: October 08, 2004
    JOURNALS FREE ACCESS
    The multiscale simulation method for the damage evolution in irradiated materials is presented. It is shown that the bias effect plays an important role in the damage evolution, such as void swelling and others. The bias effects in general can be categorized into two, dislocation bias and production bias, and basic behaviors for these processes are investigated from the viewpoint of (i) the interaction between a dislocation and point defects and defect clusters, and (ii) one dimensional motion of interstitial clusters (bundled crowdions). Not only the atomistic features in a model lattice (in the region of smaller scale), but also the elastic features in the elastic body (in the region of larger scale) are presented. From these fundamental studies the prediction of the damage evolution in materials under irradiation will become available.
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Contributed Paper
  • Tomohide NAKANO, Hirotaka KUBO, Nobuyuki ASAKURA, Katsuhiro SHIMIZU, S ...
    2004 Volume 80 Issue 6 Pages 500-510
    Published: 2004
    Released: October 08, 2004
    JOURNALS FREE ACCESS
    The ratio of population densities of C3+ excited levels, C3+(3p2P3⁄2), C3+(n = 6), and C3+(n = 7), indicates that C3+(n = 7) is predominantly excited by electron collision with the ground state of C3+ in attached plasmas. Hence, Doppler broadening of the C IV (n = 6-7) spectral line provides C3+ temperature. Regression analysis of the spectrum results in two C3+ temperature components. The higher C3+ temperature ranges from 50 eV to 150 eV, the lower around 20 eV. From the results of the analyses with plasma and impurity transport codes and a collisional-radiative model, the higher and the lower C3+ temperature correspond to the C3+ temperature of the common flux (divertor) plasma and of the private plasma, respectively. In the inner divertor, C3+ temperature is close to D+ temperature, and the C IV spectral line is predominantly emitted around the inner divertor leg. Therefore, it is concluded that D+ temperature around the inner divertor leg can be measured from the C IV spectral line. On the contrary, it is found difficult to measure the D+ temperature in the outer divertor.
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  • Takahiro SUZUKI, Shunsuke IDE, Kiyotaka HAMAMATSU, C.C. PETTY, L.L. LA ...
    2004 Volume 80 Issue 6 Pages 511-515
    Published: 2004
    Released: October 08, 2004
    JOURNALS FREE ACCESS
    Recent progress in the development of electron cyclotron heating⁄current drive systems in regard to power and pulse duration have allowed the extension of two normalized parameters (toroidal electric field Eφ and wave power density p). In the extended regime, the conventional theory requires consideration of a distorted electron distribution function. The first validation of the ECCD theory in the extended regime having large Eφ and p is presented. Linear calculation has a tendency to overestimate the EC driven current, as normalized parameters for Eφ and p increase. While the EC driven current IEC obtained by a linearized Fokker-Planck calculation (1.1 MA) did not agree with the measured EC driven current (0.74 ± 0.06MA), non-linear calculation of the Fokker-Planck equation considering the effect of Eφ (0.76 MA) shows close agreement with the experimental result. Calculations show that the decreasing effect of Eφ on IEC was stronger than the increasing effect of p on IEC in the experiment.
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  • Shinsuke MAKI, Nobuyuki WATARAI, Kiyoyuki YAMBE, Junya SEKIKAWA, Hidek ...
    2004 Volume 80 Issue 6 Pages 516-522
    Published: 2004
    Released: October 08, 2004
    JOURNALS FREE ACCESS
    The energy distribution of neutral particles emitted from STP-3(M) reversed field pinch (RFP) plasma has been investigated by a neutral particle analyzer (NPA) using a two-channel energy detector with the time resolution of 0.5μs over the whole duration of the discharge. NPA data show a high energy tail as well as the bulk ion distribution. It is found that the ion temperatures of bulk and high energy tail component have reached to the maximum before reversed magnetic field configuration, and that the tail temperature increases in the quiet period (QP). Furthermore, we found that the high energy ion density increases in both the relaxation period and the QP. The ion energy confinement time evaluated from magnetic reconnection model and the obtained ion energy spectrum is found to be about 720μs much longer than the electron energy confinement time 60-100μs, when ion heating mechanisms are discussed.
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  • Hideo WATANABE, Takeo MUROGA, Naoaki YOSHIDA
    2004 Volume 80 Issue 6 Pages 523-528
    Published: 2004
    Released: October 08, 2004
    JOURNALS FREE ACCESS
    Recent progresses of varying temperature irradiation experiments on microstructure development in austenitic stainless steels using HFIR are summarized. Each irradiation cycle consisted of 0.05 dpa at lower temperature irradiation (225 and 360°C), followed by 0.45 dpa at higher temperature (340 and 520°C). The specimens were irradiated for a total of 8 irradiation cycles, which resulted in 4 dpa. After the irradiation the TEM samples were electro polished and examined by an electron microscope. The microstructure of the samples irradiated at varying temperature condition (225⁄340°C, 360⁄520°C) were compared with those of same alloys continuously irradiated at 340 and 520°C.
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