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Journal Articles

Modeling of butt joint composed of Nb$$_{3}$$Sn cable-in-conduit conductors

Obana, Tetsuhiro*; Takahata, Kazuya*; Hamaguchi, Shinji*; Natsume, Kyohei*; Imagawa, Shinsaku*; Mito, Toshiyuki*; Kizu, Kaname; Murakami, Haruyuki; Yoshida, Kiyoshi

Plasma and Fusion Research (Internet), 9(Sp.2), p.3405122_1 - 3405122_4, 2014/07

To evaluate the fabrication technology of the butt joint composed of Nb$$_{3}$$Sn CIC conductors, joint resistance and quench current were measured using a sample developed for the JT-60SA CS coil. The measurements indicate that the butt joint fulfilled the design requirements. To simulate the characteristics of the butt joint, one dimensional numerical model simplifying the butt joint configuration was developed. Using the model, joint resistance and quench current of the butt joint were calculated. The calculations were in good agreement with the measurements. As a result, the model will be valid for the simulation of the butt joint.

Journal Articles

Charge transfer cross sections of slow multiply charged neon ions in collisions with noble gas atoms

Kusakabe, Toshio*; Shirai, Toshizo*

Plasma and Fusion Research (Internet), 9(Sp.2), p.3401119_1 - 3401119_4, 2014/07

We have measured the single- and multiple-charge transfer cross sections of Ne$$^{q+}$$ ions (q = 2 $$sim$$ 6) in collisions with Ne, Ar, Kr and Xe atoms at 2 kV in acceleration voltage. The multiply charged neon ions were extracted from a compact electron beam ion source called micro-EBIS using a strong ring permanent magnet. The cross sections of charge transfer were determined based on an initial growth rate method. In the Ne$$^{5+}$$ + Ar, Kr and Xe, and Ne$$^{6+}$$ + Ne, Ar and Xe collisions, five fold-charge transfer cross sections were derived. In the Ne atoms, the double-charge transfer of Ne$$^{2+}$$ ions, triple-charge transfer ofNe$$^{3+}$$ ions, and four fold-charge transfer of Ne$$^{4+}$$ ions are the so-called symmetric resonant charge transfer processes. The present data in these collisions are found to be in good accordance with the previous data of Kaneko et al.

Journal Articles

Statistics of clusters of ionized regions in the simulation of discharge using the percolation model

Sasaki, Akira; Kato, Susumu*

Plasma and Fusion Research (Internet), 9(Sp.2), p.3401120_1 - 3401120_4, 2014/07

We calculate sudden formation of complex path of discharges with branching and detouring using the percolation model. The simulation is based on a cell model, the discharge is considered to occur when a connection between the positive and negative electrode by the patches of the ionized regions is established. The model is applied to the calculation of the temporal evolution of discharge in the SF$$_6$$, to reproduce experimental behaviors of the discharge. Before the breakdown occurs, the ionized regions, which are initially produced randomly, grows in space, connects each other, forming clusters of the ionized region. It is shown that the statistics of the clusters, such as the distribution of the size and number of clusters have significant effect to the electric property of the discharge.

Journal Articles

Role of the electron temperature in the current decay during disruption in JT-60U

Shibata, Yoshihide; Isayama, Akihiko; Matsunaga, Go; Kawano, Yasunori; Miyamoto, Seiji*; Lukash, V.*; Khayrutdinov, R.*; JT-60 Team

Plasma and Fusion Research (Internet), 9(Sp.2), p.3402084_1 - 3402084_5, 2014/06

We performed the disruption simulation using DINA code to investigate the effect of the electron temperature $$T_{rm e}$$ on the plasma current decay after the initial phase of current quench (CQ). In this calculation, we used the measured $$T_{rm e}$$ profile during the initial phase of CQ. After the initial phase of CQ, we assumed that the $$T_{rm e}$$ profile does not change in time and used the value at the end of the initial phase of current quench because $$T_{rm e}$$ profile could not be measured after the initial phase of CQ. From the simulation results, it was found that the time evolution of plasma current calculated by DINA was similar to experimental one in this calculation. However, the time evolution of $$T_{rm e}$$profile in this calculation was different from the measured $$T_{rm e}$$ profile because Te after first mini-collapse rapidly decreased until the value below a measurement limit (less than 0.1 keV). Moreover, the time evolution of poloidal cross-section S calculated by DINA code was rapidly decreased although the experimental one was gradually decreased. The plasma current decay during the disruption is determined by various parameters, $$dL_{rm p}/dt$$, $$T_{rm e}$$ and S. It is necessary to evaluate the effect of $$T_{rm e}$$ profile on the plasma current decay after the initial phase of CQ by using various assumed $$T_{rm e}$$ model and DINA code.

Journal Articles

Divertor study on DEMO reactor

Hoshino, Kazuo; Asakura, Nobuyuki; Shimizu, Katsuhiro; Tokunaga, Shinsuke; Takizuka, Tomonori*; Someya, Yoji; Nakamura, Makoto; Uto, Hiroyasu; Sakamoto, Yoshiteru; Tobita, Kenji

Plasma and Fusion Research (Internet), 9(Sp.2), p.3403070_1 - 3403070_8, 2014/06

no abstracts in English

Journal Articles

Study of plasma equilibrium control for JT-60SA using MECS

Miyata, Yoshiaki; Suzuki, Takahiro; Ide, Shunsuke; Urano, Hajime

Plasma and Fusion Research (Internet), 9(Sp.2), p.3403045_1 - 3403045_5, 2014/05

The precise control of the plasma position is essential in safe and stable plasma operation. An MHD equilibrium control simulator has been developed in order to study the techniques of plasma equilibrium control for JT-60SA. In this study, the modules of plasma shape reconstruction, power supply, PF and FPPC coils are incorporated in order to simulate the real plasma equilibrium control. The plasma equilibrium control is simulated during Ip ramp-up within the power supply capability using MECS.

Journal Articles

Progress of preparation for ITER divertor thermocouple in JADA

Kitazawa, Sin-iti; Yamamoto, Tsuyoshi; Kawano, Yasunori; Itami, Kiyoshi

Plasma and Fusion Research (Internet), 9(Sp.2), p.3405049_1 - 3405049_4, 2014/05

The Japan Domestic Agency (JADA) is scheduled to procure a divertor thermocouple (DTC) system for the divertor outer vertical targets in the ITER project. The DTC is a diagnostic device that will directly measure the surface temperature of the divertor, a plasma-facing component, and will be installed on the surface of the divertors which are in the scope of JADA procurement sharing. A thermocouple itself is a conventional device used for measuring temperature, however, for the DTC to be able to take highly reliable operation under the ultrahigh vacuum and high radiation field of the ITER environment. Therefore various advanced research and development is necessary. Development of the DTC control system, which is based on ITER standards, should also be performed since it is included within the scope of JADA procurement. In this presentation, we will show the current status of research & development on the DTC.

Journal Articles

Progress of full-f gyrokinetic simulation toward reactor relevant numerical experiments

Idomura, Yasuhiro; Nakata, Motoki; Jolliet, S.*

Plasma and Fusion Research (Internet), 9(Sp.2), p.3503028_1 - 3503028_7, 2014/04

Full-f gyrokinetic simulations compute both turbulent transport and profile formations under fixed power, momentum, and particle input as in experiments. This approach has the capability of dictating plasma profiles, provided that time scale of the simulation is long enough to establish power, momentum, and particle balance conditions. Recent Peta-scale supercomputers made such long time scale simulations feasible, and full-f gyrokinetic simulations are applied to reactor relevant numerical experiments. In this paper, physical models, numerical approaches, and accuracy issues of the gyrokinetic full-f Eulerian code GT5D are summarized, and then, its recent applications to the scaling studies of turbulent transport with respect to plasma size and heating power are reviewed.

Journal Articles

Simulation study on nonlocal transport for peripheral density source

Yagi, Masatoshi; Miyato, Naoaki; Matsuyama, Akinobu; Takizuka, Tomonori*

Plasma and Fusion Research (Internet), 9, p.3403030_1 - 3403030_4, 2014/04

Journal Articles

On kinetic resistive wall mode theory with sheared rotation

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go

Plasma and Fusion Research (Internet), 9, p.3403027_1 - 3403027_4, 2014/04

To investigate the rotation shear effect on the RWM (Resistive Wall Mode) stability, we generalize the formalism of kinetic RWM theory to include a general equilibrium rotation. Starting from the guiding-center Lagrangian with the non-uniform rotation, we generalize the energy functional associated with the drift-kinetic resonance. By the generalized kinetic energy functional, we derive a new dispersion relation in the large aspect ratio limit. Numerical analysis of the new dispersion relation indicates that the rotation shear stabilizes the RWMs as observed in experiments

Oral presentation

Response of turbulence associated with the change of density profiles in LHD heliotron and JT-60U tokamak

Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Yoshida, Maiko; Michael, C.*; Vyacheslavov, L. N.*; Mikkelsen, D. R.*; Yokoyama, Masayuki*; Oyama, Naoyuki; Urano, Hajime; et al.

no journal, , 

Density profile and turbulence was compared in JT-60U tokamak and LHD heliotron. Density peaking increases with decrease of collisionality in JT-60U. Density gradient predicted from zero flux condition agrees within factor 2 for Te/Ti=1, but large discrepancies are found for Te/Ti $$<$$ =0.5. In LHD, peaked profile and increase of density peaking with decrease of collisionality are found in strong magnetic hill configuration (Rax = 3.5 m). Hollowed-peaked density profile and increase of density peaking with increase of collisionality are found in weak magnetic hill configuration (Rax = 3.6 m). Fluctuation is localized in core gradient region and edge gradient region. Density gradient predicted from zero flux condition are compared. Then both cases agrees the sign and absolute values within factor 2.

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