Nakano, Tomohide; Shumack, A.*; Maggi, C. F.*
Journal of Physics B; Atomic, Molecular and Optical Physics, 2 Pages, 2016/01
Collaboration of researchers from Japan Atomic Energy Agency and EUROfusion Consortium (Dutch Institute For Fundamental Energy Research, Max-Planck-Institut fr Plasmaphysik and so on) successfully led to determination of tungsten ion density in high temperature plasmas in Joint European Torus (JET) with an upgraded X-ray spectrometer. The researchers used the FAC code and successfully identified , and spectral lines. The line identification was confirmed experimentally by Mo injection to the plasma. From the measured absolute intensity of these spectral lines, tungsten and molybdenum ion densities in the plasma core were determined.
Luo, G.; Shu, Wataru; Nishi, Masataka
Fusion Engineering and Design, 81(8-14), p.957 - 962, 2006/02
The influence of blistering on deuterium retention in W was investigated using the newly established plasma generator with controllable incident energies ranging from 100 eV down to around 10 eV and incident flux of 110 D/m/s. The retention in the irradiated samples was measured using a thermal desorption spectrometer (TDS) at a ramping rate of 5 C/s. The results indicate that only one peak appears in each spectrum, with the peak temperatures ranging from 500 until 850 C, much higher than those from the trapping sites like vacancies, grain boundaries, dislocation loops, or impurities, implying probably a direct origin from the molecules existing inside blisters, voids/bubbles. Significant decrease in the retention at a certain incident fluence after blister appearance was observed and attributed to rupturing of the blisters, consistent with the limited size and increasing number of the blisters with increasing the incident fluence, as observed by means of SEM.
Yoshida, Hajime; Yokoyama, Kenji; Taniguchi, Masaki; Ezato, Koichiro; Suzuki, Satoshi; Akiba, Masato
Fusion Engineering and Design, 81(1-7), p.361 - 366, 2006/02
A 100 V level, high-flux, large area and steady-state ion beam acceleration has been developed for the investigation of the interactions between fusion edge plasmas and plasma facing materials. We have developed the new electrodes and installed them in the Super Low Energy Ion Source (SLEIS). Obtained hydrogen ion flux is comparable to those of conventional high-flux ion source (1020 H/ms), though the accelerated voltage is extremely low (60-200 eV). This 100 V level ion beam acceleration will be useful to investigate the plasma wall interaction in divertor.
Suzuki, Satoshi; Ezato, Koichiro; Hirose, Takanori; Sato, Kazuyoshi; Yoshida, Hajime; Enoeda, Mikio; Akiba, Masato
Fusion Engineering and Design, 81(1-7), p.93 - 103, 2006/02
This paper presents an R&D activity on the plasma facing components (PFCs), such as first wall and divertor, for the fusion power plant. The PFCs of the power plant will be subjected to heavy neutron irradiation and high heat/particle flux from plasma during the continuous operation. In the present design of the PFCs, the candidate structural material is a reduced activation ferritic-martensitic steel, F82H, from the viewpoints of low activation and high robustness against neutron irradiation, and the candidate armor material is tungsten from the low sputtering yield and low tritium retention points of view. To realize the PFCs using such materials, JAERI has bee extensively conducting R&Ds on; (1) high performance cooling tube, (2) tungsten armor materials, (3) selection of a bonding technique for F82H and tungsten materials and (4) evaluation of structural integrity. Recent achievements on these R&Ds are presented.
Kasai, Satoshi*; Kamiya, Kensaku; Shinohara, Koji; Kawashima, Hisato; Ogawa, Hiroaki; Uehara, Kazuya; Miura, Yukitoshi; Okano, Fuminori; Suzuki, Sadaaki; Hoshino, Katsumichi; et al.
Fusion Science and Technology, 49(2), p.225 - 240, 2006/02
The diagnostic system of JFT-2M has consisted of about 30 individual diagnostic instruments,which were used to study the plasma production, control, equilibrium, stability, confinement, plasma heating by NBI and/or RF (LH, ICRF, ECH) and current drive by RF. In these instruments, the motional Stark effect (MSE) polarimeter, charge exchanged recombination spectroscopy (CXRS), heavy-ion beam probe (HIBP), time of flight (TOF) neutral particle analyzer, etc. have contributed to make clear the improved mechanism of confinement such as H-mode and High Recycling Steady (HRS) H-mode, and to search the operational region of these modes.The infrared TV camera system and lost ion probe have played a very important role to investigate the heat load onto the walls due to ripple loss particles and escaping ions from core plasma, respectively.
Kusakabe, Toshio*; Shiota, Kenji*; Kubo, Hirotaka; Shirai, Toshizo*
Journal of Plasma and Fusion Research SERIES, Vol.7, p.237 - 239, 2006/00
no abstracts in English
Matsumoto, Taro; Naito, Hiroshi*; Tokuda, Shinji; Kishimoto, Yasuaki*
Nuclear Fusion, 45(11), p.1264 - 1270, 2005/11
A gyrokinetic particle simulation is executed to clarify the effect of the electron inertia on the MHD phenomena in the reversed shear configuration (RSC) of a cylindrical tokamak plasma. It is found that the collisionless (kinetic) double tearing modes grow up at the Alfvn time scale, and nonlinearly induce the internal collapse when the helical flux at the magnetic axis is less than that at the outer resonant surface. After the internal collapse, the secondary reconnection is induced by the current concentration due to the convective flow. It is also clarified that a nonlinear dynamics accompanied with the elementary processes caused by the flow can generate a new RSC with resonant surfaces. In the presence of the density gradient, after the full reconnection induced by the mode, the radial electric field is found to be generated due to the difference of the motion between ions and electrons. However, the intensity of the radial field is not so large as that induced by the collisionless kink mode.
Matsumoto, Taro; Naito, Hiroshi*; Tokuda, Shinji; Kishimoto, Yasuaki
Physics of Plasmas, 12(9), p.092505_1 - 092505_7, 2005/09
The behavior of the collisionless magnetohydrodynamics modes is investigated by the gyro-kinetic particle simulation in a cylindrical tokamak plasma in the parameter region where the effects of electron inertia and electron parallel compressibility are competitive for magnetic reconnection. Although the linear growth of the internal kink-tearing mode is dominated by the electron inertia, it is found that the growth rate can be nonlinearly accelerated due to the electron parallel compressibility proportional to the ion sound Larmor radius . It is also found that, as decreasing the electron skin depth , the maximum growth rate before the internal collapse saturates independently of the microscopic scales such as and . The acceleration of growth rate is also observed in the nonlinear phase of the double tearing mode.
Amemiya, Hiroshi*; Wada, Motoi*; Toyoda, Hirotaka*; Nakamura, Keiji*; Ando, Akira*; Uehara, Kazuya; Oyama, Koichiro*; Sakai, Osamu*; Tachibana, Kunihide*
Purazuma, Kaku Yugo Gakkai-Shi, 81(7), p.482 - 525, 2005/07
This article is asked to write by the Japan Society of Plasma Science and Nuclear Fusion Research. The probe diagnostics in fusion plasma is explaind for many readers of the Journal of Plasma and Fusion Research, who have much concerned on various aspects.In section one, the method to estimate the electron temperature and the density as well as the electron energy distribution function with the single probe is given. In section two, the method to estimate the ion temperature and the flow velocity with the double probe is given. The practical measurements are explained introducing the data obtained at JFT-2, JFT-2a and JFT-2M in JAERI tokamak.
Shimada, Michiya; Costley, A. E.*; Federici, G.*; Ioki, Kimihiro*; Kukushkin, A. S.*; Mukhovatov, V.*; Polevoi, A. R.*; Sugihara, Masayoshi
Journal of Nuclear Materials, 337-339, p.808 - 815, 2005/03
ITER is an experimental fusion reactor for investigation and demonstration of burning plasmas, characterised of its heating dominated by alpha-particle heating. ITER is a major step from present devices and an indispensable step for fusion reactor development. ITER's success largely depends on the control of plasma-wall interactions(PWI), with power and particle fluxes and time scales one or two orders of magnitude larger than in present devices. The strategy for control of PWI includes the semi-closed divertor, strong fuelling and pumping, disruption and ELM control, replaceable plasma-facing materials and stepwise operation.
Hirai, Takeshi*; Ezato, Koichiro; Majerus, P.*
Materials Transactions, 46(3), p.412 - 424, 2005/03
no abstracts in English
Ikeda, Yoshitaka; Kubo, Shin*
Purazuma, Kaku Yugo Gakkai-Shi, 81(3), p.160 - 166, 2005/03
The local profile controls of electron temperature and current in fusion-oriented devices using the electron cyclotron (EC) wave is reviewed. Recent progress of the EC heating system that enabled those controls is briefly described. The specific feature of EC wave heating is local and high power density heating properties. Current drive and electron temperature profile control experiments using EC wave performed in order to improve and investigate plasma confinement properties are discussed.
Inoue, Takashi; Sakamoto, Keishi
Nihon Genshiryoku Gakkai-Shi, 47(2), p.120 - 127, 2005/02
no abstracts in English
Ueda, Yoshio*; Inoue, Takashi; Kurihara, Kenichi
Nihon Genshiryoku Gakkai-Shi, 46(12), p.845 - 852, 2004/12
no abstracts in English
Luo, G.; Shu, Wataru; Nakamura, Hirofumi; Ohira, Shigeru; Nishi, Masataka
Review of Scientific Instruments, 75(11), p.4374 - 4378, 2004/11
The ion species ratios in low energy high flux deuterium plasma beams formed in a linear plasma generator were measured by a quadrupole mass spectrometer. And the species control in the plasma generator was evaluated by changing the operational parameters like neutral pressure, arc current, and axial magnetic confinement to the plasma column. The measurements reveal that the lower pressures prefer to form more D ions, and the medium magnetic confinement at the higher pressures results in production of more D, while the stronger confinement and /or larger arc current are helpful to D conversion into D. Therefore, the ion species can be controlled by adjusting the operational parameters of the plasma generator. With suitable adjustment, we can easily achieve plasma beams highly enriched with a single species of D, D, or D, to a ratio over 80%. It has been found that the axial magnetic configuration played a significant role in the formation of D within the experimental pressure range.
Konovalov, S. V.; Mikhailovskii, A. B.*; Kovalishen, E. A.*; Kamenets, F. F.*; Ozeki, Takahisa; Shirokov, M. S.*; Takizuka, Tomonori; Tsypin, V. S.*
Doklady Physics, 49(7), p.405 - 408, 2004/07
Effect of feedback system, placed outside the vacuum vessel, on neoclassical tearing modes (NTMs) in tokamaks is analytically studied. External matching parameters for magnetic island chain are derived for the simplest case of step profile of equilibrium parallel current. The structure of dynamical equations for the island width and island rotation frequency in terms of matching parameters is explained. It is shown that such a feedback system can lead to essential shift of the island rotation, in particular, for stabilization of NTMs by the polarization current effect.
Hanada, Masaya; Kashiwagi, Mieko; Inoue, Takashi; Watanabe, Kazuhiro; Imai, Tsuyoshi
Review of Scientific Instruments, 75(5), p.1813 - 1815, 2004/05
A proof-of-principle test on plasma neutralizer, that is capable of enhancing a system efficiency of neutral beam injector for future fusion reactors, has been carried out. A 2 m long and 0.6 m diamater neutralizer with multicusp magnet line was used, improving the confinement of primary electrons flowed from both ends of the neutralizer by a pair of magnets. This improvement produced relatively high density Ar plasma of 10 - 10cm at low operating pressure of 0.002 Pa - 0.03 Pa. In the neutralization experiment, 200 keV H ion beams were neturalized with the plasms and gas. Compared with the gas neutralization, the maximaum neutralization efficiency by the plasma was 6% higher than that by the gas. Further, an optimum Ar gas line density for maximizing the neutralization efficiency was 30% lower than that by the gas. These results are in good agreements with results analyzed from the cross-section data for neturalization. Thus, it was experimentally verified that the neutralization effiency can be enhanced at relatively low line density by using the plasma.
Luo, G.; Shu, Wataru; Nakamura, Hirofumi; Ohira, Shigeru; Hayashi, Takumi; Nishi, Masataka
JAERI-Tech 2004-031, 27 Pages, 2004/03
A plasma source has been constructed for investigating plasma-surface interactions in a tokamak. It is a compact device with a total length less than 1 m, compared to other existing facilities in the world. However, it can provide with stable plasma beams of low energy (100 eV) and high flux (10 /m/s), close to the predicted edge plasma conditions near the ITER divertor. This report presents mainly its configuration and its characteristics, including influence of filament, arc discharge, magnetic field, bias voltage parameters, and so on, on plasma beam being delivered towards the sample. Also shown are the results of preliminary experiments of blister formation on tungsten samples irradiated by a deuterium plasma beam generated with the source.
Arai, Takashi; Nishiyama, Tomokazu; Yagyu, Junichi; Kasai, Satoshi; Sone, Isamu*; Abe, Mitsushi*; Miya, Naoyuki
Fusion Science and Technology, 45(1), p.65 - 68, 2004/01
In a nuclear fusion experiment device, a plasma discharge is to be sustained for a long time in steady state operation. In such a device an electromagnetic sensor that has a signal integrator to measure direct currents will cause a technical problem of zero point drift on signals. So, the detection device using new technology for direct current measurement, optical current transformer (optical CT), was developed. The device has an optical fiber specified for 1550nm (wavelength) was manufactured, and was applied to JT-60U experiments. A gamma ray irradiation examination was also done to the optical CT
Kawano, Yasunori; Chiba, Shinichi; Inoue, Akira*
Review of Scientific Instruments, 75(1), p.279 - 280, 2004/01
It has been successful to apply CVD diamond plate as the vacuum window for infrared CO laser interferometry and polarimetry for electron density measurement in the JT-60U tokamak. In comparison with to use the conventional zinc-selenide windows, the Faraday rotation component at diamond windows was small as negligible. This resulted in the improvement of the Faraday rotation measurement for a tokamak plasma by polarimetry.