Plasma and Fusion Research
Online ISSN : 1880-6821
ISSN-L : 1880-6821
Volume 7
Showing 151-159 articles out of 159 articles from the selected issue
Regular Articles
  • Yuichi TAMURA, Yuki TAKABATAKE, Naoya KASHIMA, Tomohiro UMETANI
    2012 Volume 7 Pages 2406036
    Published: May 10, 2012
    Released: January 10, 2014
    JOURNALS FREE ACCESS
    This paper proposes a localization system using the Microsoft Kinect sensor. It is difficult to accurately measure self-position and self-posture by a red-green-blue (RGB) image sensor, since the accuracy in the depth direction of an image sensor tends to be worse than that in other directions using only an RGB image sensor. The Kinect sensor has both an RGB image sensor and a depth sensor. This sensor can directly calculate the depth value; therefore, the accuracy in the depth direction is better. In the proposed system, natural feature points are detected from an image by a Harris interest operator, and the depth data of these feature points are obtained from the depth sensor. After that, these points are tracked by the template matching method. The camera's position and posture are calculated from the position of these tracked points. Finally, we provide examples of 3D scene reconstruction and estimation results.
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  • Soichiro IKUNO, Yoshihisa FUJITA, Taku ITOH, Susumu NAKATA, Hiroaki NA ...
    2012 Volume 7 Pages 2406044
    Published: May 10, 2012
    Released: January 10, 2014
    JOURNALS FREE ACCESS
    The electromagnetic wave propagation in various shaped wave guide is simulated by using meshless time domain method (MTDM). Generally, Finite Differential Time Domain (FDTD) method is applied for electromagnetic wave propagation simulation. However, the numerical domain should be divided into rectangle meshes if FDTD method is applied for the simulation. On the other hand, the node disposition of MTDM can easily describe the structure of arbitrary shaped wave guide. This is the large advantage of the meshless time domain method. The results of computations show that the damping rate is stably calculated in case with R < 0.03, where R denotes a support radius of the weight function for the shape function. And the results indicate that the support radius R of the weight functions should be selected small, and monomials must be used for calculating the shape functions.
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  • Taku ITOH, Ayumu SAITOH, Atsushi KAMITANI, Hiroaki NAKAMURA
    2012 Volume 7 Pages 2406068
    Published: September 13, 2012
    Released: January 10, 2014
    JOURNALS FREE ACCESS
    To generate a smooth implicit function that behaves naturally over an entire domain, a method to smoothly combine an implicit function f(x) with a global support function g(x) has been proposed. The proposed method can be applied to large scattered point data, since the implicit function f(x) is generated by a partition-of-unity-based method. The global support function g(x) is generated by a radial basis function-based method or by the least-squares method. To ensure a smooth combination of f(x) and g(x), an appropriate weight function is employed. In numerical experiments, the proposed method is applied to large point data. The results illustrate that the proposed method can generate a smooth implicit function F(x) with natural behavior over the entire domain. In addition, on the given points, the accuracy of F(x) is exactly the same as that of f(x). Furthermore, the computational cost for generation of F(x) is almost the same as that of f(x).
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  • Ayumu SAITOH, Taku ITOH, Nobuyuki MATSUI, Atsushi KAMITANI, Hiroaki NA ...
    2012 Volume 7 Pages 2406096
    Published: July 26, 2012
    Released: January 10, 2014
    JOURNALS FREE ACCESS
    The numerical method for solving the nonlinear eigenvalue problem has been developed by using the collocation Element-Free Galerkin Method (EFGM) and its performance has been numerically investigated. The results of computations show that the approximate solution of the nonlinear eigenvalue problem can be obtained stably by using the developed method. Therefore, it can be concluded that the developed method is useful for solving the nonlinear eigenvalue problem.
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  • Tomohiro YAMADA, Masayuki YOSHIKAWA, Junko KOHAGURA, Yoriko SHIMA, Yus ...
    2012 Volume 7 Pages 2406122
    Published: September 13, 2012
    Released: January 10, 2014
    JOURNALS FREE ACCESS
    A phase-imaging interferometer is used to measure the electron density distribution in the plug region in GAMMA 10. The electron density is derived by the Abel transform technique. We attempt to determine the plasma density distribution for an asymmetric Abel transform by using finite-difference time-domain simulations. Moreover, we try to construct the asymmetric Abel transform for an asymmetric plasma distribution.
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Overview Articles
  • Teresa ESTRADA, Kazunobu NAGASAKI, Emilio BLANCO, Germán PEREZ, Victor ...
    2012 Volume 7 Pages 2502055
    Published: September 13, 2012
    Released: January 10, 2014
    JOURNALS FREE ACCESS
    Microwave reflectometry technique has experienced significant advances in the last two decades becoming a very attractive diagnostic presently used in almost all fusion devices. This technique allows measuring electron density profiles, plasma instabilities, turbulence and radial electric fields with excellent spatial and temporal resolution. Although it is not straightforward, the extension of reflectometry to future devices is possible partially due to the limited access needed to accommodate the antennas inside the vacuum vessel keeping the sensitive elements as microwave sources and detectors outside the radiation area. However, in order to achieve a good diagnostic performance, limitations related to relativistic effects, intense neutron- and γ-radiation and long pulse operation have to be considered in the reflectometer design phase.
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  • Gia Tuong HOANG, Léna DELPECH, Annika EKEDAHL, Young-soon BAE, Joelle ...
    2012 Volume 7 Pages 2502140
    Published: October 15, 2012
    Released: January 10, 2014
    JOURNALS FREE ACCESS
    The paper gives a picture of the present status and understanding of technology and physics of Lower Hybrid Current Drive for long pulse operation in tokamaks, including the development of continuous wave (CW) high power klystrons, and its evolutions towards ITER. 3.7 GH / 700 kW CW klystrons produced in series by Thales Electron Devices are now in operation on Tore Supra. First series of eight klystrons delivered more than 4 MW to sustain non-inductive plasmas during 50 s. Moreover, a prototype of 500 kW CW klystron operating at 5 GHz developed for KSTAR by Toshiba Electron Tubes and Devices, and foreseen for ITER, is able to produce RF output powers of 300 kW / 800 s and 450 kW / 20 s on matched load. The situation on wave coupling and antennas is reported, with the latest Tore Supra results of the new CW Passive-Active Multi-junction (PAM) launcher: the antenna concept foreseen for ITER. First experiments with the PAM antenna in Tore Supra have provided extremely encouraging results in terms of power handling and coupling. Relevant ITER power density of ∼25 MW/m2 (2.7 MW of power injected into the plasma) has been maintained over ∼80 s. In addition, LH power of 2.7 MW has been coupled at a plasma-antenna distance of 10 cm.
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  • Antoine POCHELON, Paolo ANGELINO, Roland BEHN, Stephan BRUNNER, Stefan ...
    2012 Volume 7 Pages 2502148
    Published: November 22, 2012
    Released: January 10, 2014
    JOURNALS FREE ACCESS
    The TCV tokamak facility is used to study the effect of innovative plasma shapes on core and edge confinement properties. In low collisionality L-mode plasmas with electron cyclotron heating (ECH) confinement increases with increasing negative triangularity δ. The confinement improvement correlates with a decrease of the inner core electron heat transport, even though triangularity vanishes to the core, pointing to the effect of non-local transport properties. TCV has recently started the study of the effects of negative triangularity in H-mode plasmas. H-mode confinement is known to improve towards positive triangularity, due to the increase of pedestal height, though plagued by increasingly large edge localised modes (ELMs). An optimum triangularity could thus be sought between steep edge barriers (δ > 0) with large ELMs, and improved core confinement (δ < 0) with small ELMs. This opens the possibility for a reactor of having H-mode-level confinement within an L-mode edge, or at least with mitigated ELMs. In TCV, ELMy H-modes with upper triangularity δtop < 0 are explored, showing a reduction of ELM peak energy losses compared to δtop > 0. Alternative shapes are proposed on the basis of ideal MHD stability calculations. Shaping has the potential to bring at the same time key solutions to confinement, stability and wall loading issues and, from the comparison of experimental and simulation results, to give deeper insight in transport and stability.
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  • Izuru YONEKAWA, Antonio Vergara FERNANDEZ, Jean-Marc FOURNERON, Jean-Y ...
    2012 Volume 7 Pages 2505047
    Published: September 13, 2012
    Released: January 10, 2014
    JOURNALS FREE ACCESS
    ITER is a long-pulse tokamak with elongated plasma. The nominal inductive operation produces a D-T fusion power of 500 MW for a burn length of 300-500 s, with the injection of 50 MW of auxiliary power. With non-inductive current drive from the H&CD systems, the burn duration is envisaged to be extended to 3000 s. The term ITER Instrumentation & Control (I&C) includes every thing required to operate the ITER facility. It comprises three vertical tiers; conventional control, interlock system and safety system, and two horizontal layers; central I&C systems and plant system I&C. CODAC (Control, Data Access and Communication) system forms the upper level of the hierarchy, and is the conventional central control system of ITER architecture. CODAC system is responsible for integrating all plant system I&C and enable operation of ITER as a single integrated plant. CODAC system provides overall plant systems coordination, supervision, plant status monitoring, alarm handling, data archiving, plant visualization (HMI) and remote experiment functions. CIS (Central Interlock System) and CSS (Central Safety System) also form the upper level of the hierarchy to supervising and integrating all plant system interlock and safety functions. Plant system I&C forms the lower level of the hierarchy, and provide dedicated plant data acquisition, plant status monitoring, plant control and plant protection functions to perform individual plant system operation under the supervision of central I&C systems.
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