Papers - Hoshino, Kazuo

IMPGYRO: The full-orbit impurity transport code for SOL/divertor and its successful application to tungsten impurities

Yamoto S., Homma Y., Hoshino K., Toma M., Hatayama A.

Computer Physics Communications 248   106979 2020.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00104655

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© 2019 Elsevier B.V. In future fusion reactors, tungsten (W) is currently regarded as one of the most feasible candidates for the plasma-facing components (PFCs). Once the W impurities sputtered from the PFCs penetrate into the core plasma, the large radiation cooling and fuel dilution, which leads to the deterioration of the core plasma performance, take place. To understand and to control W impurity transport are indispensable for future fusion reactors. In order to understand W transport, we are continuing to develop the kinetic impurity transport code IMPGYRO for SOL/divertor in fusion reactors. The IMPGYRO has obtained following unique features compared to other existing kinetic impurity transport codes through the 15-years development activity; (i) the exact Larmor motion of impurity ions are computed so that the effects of drifts are automatically taken into account, (ii) the Coulomb collision between impurities and background plasma ions are modelled by the Binary Collision Method which kinetically calculates more precise friction and thermal forces, and (iii) the background plasma transport and impurity transport are computed self-consistently by the coupled calculation with SOL/divertor plasma transport code such as SOLPS-ITER. Although the IMPGYRO transport model has significantly improved from the initial development phase, the modelling improvement of the IMPGYRO has never been described in detail. In this paper, (a) the current W generation/transport model, and (b) the coupling strategy between the SOLPS-ITER and the IMPGYRO are summarized. The new results (c) the check of the prompt re-deposition model of the IMPGYRO, and (d) the further extension of the Coulomb collision modelling of the IMPGYRO towards the neoclassical (NC) transport handling capability has been performed. The effects of the NC transport processes on a simple circular tokamak geometry are compared with the anomalous diffusion by means of the extended IMPGYRO to obtain better understanding of cross-field transport process of W. The results show that the NC transport process may become non-negligible compared to the anomalous diffusion at least in this configuration. Based on these recent improvements, the present version of the IMPGYRO is very useful tool for understanding and prediction of W transport in SOL/divertor regions of fusion devices.

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Simulation study of mixed-impurity seeding with extension of integrated divertor code SONIC

S. Yamoto, K. Hoshino, Y. Homma, T. Nakano, N. Hayashi

Plasma Physics and Controlled Fusion 62 ( 4 ) 045006 2020.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  07413335

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© 2020 IOP Publishing Ltd. Aimed at obtaining key physics that determine the controllability of impurity transport in the scrape-off layer (SOL)/divertor regions, the integrated divertor code SONIC has been further extended to handle three or more impurity species kinetically. The extended SONIC code has been applied to the steady-state high-beta scenario-like plasma of JT-60SA as a testbed. We first performed a Ne transport simulation on the fixed Ar-seeded background plasma. Different radiation power distribution along the magnetic field line was obtained between Ar and Ne. The Ar radiation is strong around the top region of the SOL, which is mainly due to the line radiation of highly charged Ar ions trapped by the thermal force. In contrast, the Ne radiation is strong around the high-field side near the X point, mainly due to the line radiation of Ne7+ trapped by the balance between the thermal force and the frictional force with D+ parallel flow. We performed a parametric survey of Ne seeding rate as a second step. The effects of Ne transport on the plasma are self-consistently computed. The Ne impurities are injected into the plasma with a fixed puff rate of Ar. Even a small Ne seeding rate of 0.02 Pa m3 s-1 results in lower Ar radiation power in the SOL and core edge than in the Ar-only case. This is mainly due to the high D+ parallel flow velocity towards the inner divertor in the Ar + Ne seeding case. The resultant frictional force transports the Ar impurities towards the inner divertor region. When the line radiation of Ne7+ is switched off in the simulation, such high D+ parallel flow cannot be seen. These results suggest that the line radiation of Ne7+ has a key role for the high D+ parallel flow. The results show the possibility of impurity transport control in the SOL by mixed-impurity seeding.

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Development of a three dimensional plasma fluid code using a Lagrange-Monte-Carlo scheme

R. Tatsumi, A. Rnunov, R. Schneider, K. Hoshno, A. Hatayama

Plasma and Fusion Research (社団法人 プラズマ・核融合学会)  15 ( 0 ) 1403003 - 1403003 2020.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1880-6821

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<p>We are developing a Lagrange (LG)-Monte-Carlo (MC) scheme for three-dimensional (3D) SOL/Divertor plasma fluid modeling. By using test particles, the scheme is suitable for handling 3D complex geometries. The semi-implicit treatment of the pressure gradient term enables us to improve the robustness of the coupling of the continuity and the momentum equations. Detailed numerical checks of the integrated scheme of LG-MC have been done for a simple 1D geometry. Benchmark tests between the new LG-MC and a conventional Finite-Volume scheme were carried out and good agreement was obtained. A first test calculation for a 3D cylindrical geometry has been also successfully done.</p>

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Global modelling of tungsten impurity transport based on drift-kinetic equation

R. Kanno, G. Kawamura, M. Nunami, Y. Homma, A. Hatayama, K. Hoshino

Nuclear Fusion 60 ( 1 ) 016033 2019.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00295515

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© 2019 IAEA, Vienna. A global kinetic simulation model of collisional impurity transport is developed for evaluating the radial particle flux of tungsten impurity in the edge region of a tokamak plasma. Here, the plasma including the impurity and the background ion is presupposed to be quasi-steady. The simulation model is based on the drift-kinetic equation of the impurity affected by the friction force and the thermal force, which were formulated in the previous study (Homma et al 2016 Nucl. Fusion 56 036009). The model is implemented in a drift-kinetic δf simulation code. We find that the magnetic drift term in the drift-kinetic equation causes the 'global effect' on the impurity transport. Here, the global effect means that the solution δfz of the drift-kinetic equation (and also the radial particle flux) on a magnetic flux surface is influenced by the values of the solution δfz all over the edge region.

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Numerical Simulatino for the Enhancement of H^- Production in the DC Arc-discharge H^- Ion Source for Medical Use

S. Yamada, H. Kitami, S. Nomura, Y. Aoki, K. Hoshino, A. Hatayama

Plasma Fusion Research (社団法人 プラズマ・核融合学会)  14 ( 0 ) 3401160 - 3401160 2019.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1880-6821

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<p>A multi-cusp DC arc-discharge hydrogen negative ion (H⁻) source has been developed for proton cyclotron, which is used for Boron Neutron Capture Therapy (BNCT). The purpose of this study is to understand the dependence of H⁻production on the operation parameters and optimize H⁻production in the source. In this paper, we focus on the effect of magnetic filter field on H⁻volume production. The H⁻density in the extraction region has been numerically estimated in the three patterns of magnetic filter field by using 3D electron transport code and 0D rate equations. The result suggests that the magnetic filter field which is localized in the vicinity of the extraction region is suitable for the efficient H⁻volume production.</p>

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Study of end-cell plasma parameters of GAMMA 10/PDX by the LINDA code

M.S. Islam, Y. Nakashima, A. Hatayama, S. Ishiguro, K. Hoshino, N. Ezumi, M. Sakamoto

Plasma Physics and Controlled Fusion 61 ( 2019 ) 125005 2019.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  07413335

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© 2019 IOP Publishing Ltd. This research numerically investigates the plasma behavior during neutral gases puffing into the west end-cell of the linear plasma confinement device GAMMA 10/PDX. A multi-fluid code named 'LINDA' is developed and applied at the west end-cell of the device to explore the processes of plasma detachment and energy loss mechanism during plasma-neutral interactions. The ion heat flux limiter is newly introduced in the LINDA code. In the paper, we investigate the influence of the ion heat flux limiter in our divertor plasma models to understand how the ion heat flux limiter affects the computed plasma parameters. The upstream plasma parameters are ni = 1 × 1019 m-3,Te = 30 eV and Ti = 100 eV. The effect of ion heat flux limiting reduces the ion temperature and heat flux in the direction of the target plate. The ion temperature profile is shown to be similar when the heat flux limiting factor (α i) is varied from 0.2 to 2.0. The effect of Hydrogen (H) and Argon (Ar) gas puffing has been investigated under the condition of ion heat flux limiting factors α i = 1.0. The ion temperature is shown to be similar between Ar and without Ar puffing. On the other hand, T e reduces remarkably for Ar puffing by enhancing the radiation cooling of Ar. The ion and electron loss are greatly enhanced for combined puffing of Ar and H. The ionization loss is found to be slightly higher and the charge-exchange loss is found to be slightly lower during the ion heat flux limiting case. These outcomes may contribute to understanding the plasma detachment processes in fusion devices.

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Advances in the physics studies for the JT-60SA tokamak exploitation and research plan

G. Giruzzi, M. Yoshida, N. Aiba, J.F. Artaud, J. Ayllon-Guerola, O. Beeke, A. Bierwage, T. Bolzonella, M. Bonotto, C. Boulbe, M. Chernyshova, S. Coda, R. Coelho, D. Corona, N. Cruz, S. Davis, C. Day, G. De Tommasi, M. Dibon, D. Douai, D. Farina, A. Fassina, B. Faugeras, L. Figini, M. Fukumoto, S. Futatani, K. Galazka, J. Garcia, M. Garcia-Muñoz, L. Garzotti, L. Giudicotti, N. Hayashi, M. Honda, K. Hoshino, A. Iantchenko, S. Ide, S. Inoue, A. Isayama, E. Joffrin, Y. Kamada, K. Kamiya, M. Kashiwagi, H. Kawashima, T. Kobayashi, A. Kojima, T. Kurki-Suonio, P. Lang, Ph. Lauber, E. de la Luna, G. Marchiori, G. Matsunaga, A. Matsuyama, M. Mattei, S. Mazzi, A. Mele, Y. Miyata, S. Moriyama, J. Morales, A. Moro, T. Nakano, R. Neu, S. Nowak, F.P. Orsitto, V. Ostuni, N. Oyama, S. Paméla, R. Pasqualotto, B. Pégourié, E. Perelli, L. Pigatto, C. Piron, A. Pironti, P. Platania, B. Ploeckl, D. Ricci, M. Romanelli, G. Rubino, S. Sakurai, K. Särkimäki, M. Scannapiego, K. Shinohara, J. Shiraishi, S. Soare, C. Sozzi, T. Suzuki, Y. Suzuki, T. Szepesi, M. Takechi, K. Tanaka, H. Tojo, M. Turnyanskiy, H. Urano, M. Valisa, M. Vallar, J. Varje, J. Vega, F. Villone, T. Wakatsuki, T. Wauters, M. Wischmeier, S. Yamoto, R. Zagórski

Plasma Physics and Controlled Fusion (Plasma Physics and Controlled Fusion)  62 ( 2020 ) 014009 2019.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  07413335

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© Gerardo Giruzzi. JT-60SA, the largest tokamak that will operate before ITER, has been designed and built jointly by Japan and Europe, and is due to start operation in 2020. Its main missions are to support ITER exploitation and to contribute to the demonstration fusion reactor machine and scenario design. Peculiar properties of JT-60SA are its capability to produce long-pulse, high-β, and highly shaped plasmas. The preparation of the JT-60SA Research Plan, plasma scenarios, and exploitation are producing physics results that are not only relevant to future JT-60SA experiments, but often constitute original contributions to plasma physics and fusion research. Results of this kind are presented in this paper, in particular in the areas of fast ion physics, high-beta plasma properties and control, and non-linear edge localised mode stability studies.

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Effects of the Extraction Voltage on the Beam Divergence for a H− Ion Source

M. Lindqvist, S. Nishioka, K. Miyamoto, K. Hoshino, J. Lettry, A. Hatayama

Journal of Applied Physics 126 ( 2019 ) 123303 2019.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00218979

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© 2019 Author(s). Negative hydrogen (H-) ion sources have a wide range of applications. The general requirement for these H-ion sources is to produce intense H-ion beams with good beam optics. The purpose of this paper is to clarify the effects of the beam extraction voltage on the beam divergence angle by three-dimensional Particle-in-Cell (PIC) modeling. Perveance matching has been studied for a wide range of the extraction voltage with the model geometry of a Linac4 H-ion source. The extracted H-beam divergence angle is evaluated for extraction voltages ranging from 7 to 14 kV by using the Keio-BFX PIC code. The results show divergence minima in the range of 9.2-11.5 kV for the case without surface H-production, which correspond to experimental results. The dependence of divergence on the extraction voltage is explained by the change of the shape of the meniscus. In particular, a flat meniscus corresponds to low beam divergence, and particles extracted through the center of the meniscus have a lower divergence than particles extracted near the Plasma Electrode.

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Effects of the Plasma Blob Nonlinear Formation/Transport on Impurity Transport in the SOL Regions

MAEDA Tomoyuki, HASEGAWA Hiroki, ISHIGURO Seiji, HOSHINO Kazuo, HATAYAMA Akiyoshi

Plasma and Fusion Research (The Japan Society of Plasma Science and Nuclear Fusion Research)  14 ( 0 ) 3403133 - 3403133 2019.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1880-6821

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<p>The purpose of this study is to make clear the effects of the plasma blob on the impurity transport in the Scrape-Off Layer (SOL) regions. By using the two-dimensional (2D) interchange turbulence model with plasma transport along magnetic field line, we have simulated the plasma blob formation and transport in the SOL regions. We have studied the effects of the plasma blob on the impurity transport by using impurity equations of motion in the trace impurity limit. The results show that the plasma blob transport direction is not only the radial direction but also poloidal direction due to the plasma transport along the magnetic field line. Also, the impurity ions are transported radially outward with the plasma blob transport and the velocity of the impurity ions transport is the same order to the plasma blob velocity radially outward. These results implied that the impurity transport with the plasma blob may possibly be not only diffusion but also convection. Moreover, this motion of the impurity ions seems like eddy motion. As a next step, we study relation between this eddy motion of impurity ions and the plasma blob motion. That is our future work.</p>

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Analysis of Molecular Activated Recombination in Detached Divertor Plasmas

TSUBOTANI Yuka, TATSUMI Ryoko, HOSHINO Kazuo, HATAYAMA Akiyoshi

Plasma and Fusion Research (The Japan Society of Plasma Science and Nuclear Fusion Research)  14 ( 0 ) 2403108 - 2403108 2019.07

Research paper (scientific journal), Joint Work, Accepted

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<p>Molecular activated recombination (MAR) has been received attention as one of the most important processes to realize the detached state, specifically in the linear plasma device, GAMMA10/PDX. The impact of ELMs on the MAR reaction and the resultant detached state, however, have not fully been understood. We have developed a zero-dimensional model of atomic-molecular processes which takes into account MAR by separate treatment of vibrational excited states of H₂molecules, and the high energy tail of the electron energy distribution function (EEDF) during the ELM heat pulse. The results show that the rate of MAR increases during ELMs due to an increase in excited molecules.</p>

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Investigation of Dependence of Power Transfer on Frequency in the Linac4 Negative Hydrogen Ion Source

KOBAYASHI Wakaba, NISHIDA Kenjiro, NOLL Daniel, LETTRY Jacques, HOSHINO Kazuo, HATAYAMA Akiyoshi

Plasma and Fusion Research (The Japan Society of Plasma Science and Nuclear Fusion Research)  14 ( 0 ) 3401094 - 3401094 2019.06

Research paper (scientific journal), Joint Work, Accepted

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<p>Linac4 is radio frequency (RF) driven type negative hydrogen H⁻ion source. In the RF system, it is required to match the impedance between the RF-system and plasma loading. In order to match the impedance, it is essential to analyze the plasma impedance. In this study, we analyze the dependence of power transfer on the input parameters (frequency, input power and H₂gas pressure) by using the plasma impedance prediction model. The results indicate that in the case of frequency = 2 MHz, which is often used in the experiment, efficient power supply is seen in the wide range of input power and H₂gas pressure. Also, if the optimum value of input power and H₂gas pressure is input, it may be possible to reduce the influence of the frequency value on the power reflection efficiency.</p>

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Analysis of Ar impurity transport in the large tandem mirror device GAMMA 10/PDX plasmas

Takechi S., Tatsumi R., Islam M., Hoshino K., Hatayama A., Nakashima Y.

Plasma and Fusion Research (The Japan Society of Plasma Science and Nuclear Fusion Research)  14 ( 0 ) 2403045 - 2403045 2019.03

Research paper (scientific journal), Joint Work, Accepted

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<p>The purpose of this study is to understand the Ar impurity transport process in the GAMMA 10/PDX. In the present study, the initial simulation using LINDA code and IMPGYRO code has been done to establish the basis of further understanding of the Ar impurity transport. The validity of the simulation model has been discussed by comparisons with those by the theoretical estimations of the friction force and the thermal force. The simulation results show that the Ar impurities with <i>Z </i>= 1 are transported towards the core region, since the thermal force dominates over the friction force under the present calculation conditions. The tendency does not contradict the experimental results and is reasonably explained by the theoretical prediction, i.e., the force balance between the thermal force and the friction force. The robust basis for further model validation and understanding of the Ar transport in the GAMMA 10/PDX has been established.</p>

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Analysis of plasma impedance in the Linac4 negative hydrogen ion source

W. Kobayashi, K. Nishida, S. Mattei, J. Lettry, K. Hoshino, A. Hatyama

AIP Conference Proceedings 2052   050009 2018.12

Research paper (international conference proceedings), Joint Work, Accepted

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© 2018 Author(s). Linac4 is radio frequency (RF) driven type negative hydrogen H- ion source. In the RF system, it is required to match the impedance between the RF-system and plasma loading. In order to match the impedance, it is essential to analyze the plasma impedance. In this study, we analyze the plasma impedance by using the Electro-Magnetic Particle in Cell model. As a result, plasma impedance calculated by the Electro-Magnetic Particle in Cell model agrees qualitatively with one calculated by fluid model model in the steady state. On the other hand, plasma impedance calculated by the numerical simulation code is significantly different from one calculated by the zero dimensional equivalent circuit model during plasma ignition. The results show that the kinetic effects are necessary especially during plasma ignition. It is useful to propose more efficiency power transfer.

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Numerical Simulation for the Development of DC Arc-discharge Hydrogen Negative Ion for Medical Use

S. Yamada, Y. Aoki, N. Takahashi, H. Kitami, M. Yaguchi, K. Hoshino, A. Hatayama

AIP Conference Proceedings 2052   060004 2018.12

Research paper (international conference proceedings), Joint Work, Accepted

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© 2018 Author(s). Multi cusp DC arc-discharge hydrogen negative ion (H-) source has been developed for the proton cyclotron applications. The purpose of this study is to understand the dependence of the H- production on the operation parameters and optimize the H- production in the source. In this paper, we focus on the effect of magnetic filter field on the H- volume production. The H- volume production in the source has been numerically calculated in the two case of magnetic filter field by using 3D electron transport code and 0D rate equations. The result has suggest that the effect of magnetic filter field on H- beam current could be explained by the enhanced electron density in the extraction region.

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Plasma exhaust and divertor studies in Japan and Europe broader approach, DEMO design activity

Asakura Nobuyuki, Hoshino Kazuo, Utoh Hiroyasu, Someya Youji, Suzuki Satoshi, Bachmann Christian, Reimerdes Holger, Wenninger Ronald, Kudo Hironobu, Tokunaga Shinsuke, Homma Yuki, Sakamoto Yoshiteru, Hiwatari Ryoji, Tobita Kenji, You Jeong Ha, Federici Gianfranco, Ezato Koichiro, Seki Yohji, Ueda Yoshio, Ohno Noriyasu

Fusion Engineering and Design 136   1214 - 1220 2018.11

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  0920-3796

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<p>Power exhaust scenario and divertor design for a steady-state Japan (JA) DEMO and a pulse Europe (EU) DEMO1 have been investigated as one of the most important common issues in Broader Approach DEMO Design Activity. Radiative cooling is a common approach for the power exhaust scenario. For the JA DEMO, development of the divertor design appropriate for high P_sep/R_p ∼30 MW m⁻¹ is required, while the radiation fraction in the main plasma (f_rad ^main = P_rad ^main/P_heat) is ITER-level (0.40–0.45) and the exhaust power above the L- to H-mode power threshold (f_LH = P_sep/P_th ^LH) is large margin (∼2). For the EU DEMO1, larger f_rad ^main (=0.67) and smaller f_LH (=1.2) plasma is required, using higher-Z impurity seeding, in order to apply ITER-level divertor (P_sep/R_p = 17 MW m⁻¹). ITER technology, i.e. water cooling with W-monoblock and Cu-alloy (CuCrZr) heat sink, is a baseline for JA and EU to handle the peak heat load of 10 MW m⁻²-level, and neutron flux and irradiation dose are comparable. For the JA DEMO, two different water-cooling pipes, i.e. CuCrZr and F82H steel, are proposed. For the EU DEMO1, the heat sink consists of all Cu-alloy pipe, and the divertor size is reduced with replacing the baffles by the breeding blankets. Choices of the heat sink components have been developed appropriate to the high irradiation dose condition. These JA and EU approaches of the power exhaust scenario will provide important case studies for the future decision of the DEMO divertor design.</p>

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Overview of the DEMO conceptual design activity in Japan

Tobita Kenji, Hiwatari Ryoji, Utoh Hiroyasu, Miyoshi Yuya, Asakura Nobuyuki, Sakamoto Yoshiteru, Someya Youji, Homma Yuki, Nakamura Makoto, Hoshino Kazuo, Tanigawa Hiroyasu, Nakamichi Masaru, Tokunaga Shinsuke, Kudo Hironobu, Nishimura Arata

Fusion Engineering and Design 136   1024 - 1031 2018.11

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  0920-3796

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<p>The requirements for Japanese DEMO are to demonstrate (1) steady and stable electrical power generation, (2) plant availability on a level relevant for commercialization, and (3) self-sufficiency of fuels. The DEMO design activity has been mainly focused on challenging DEMO design issues such as divertor heat removal, superconducting magnets, breeding blankets, remote maintenance and the water cooling system, in order to reach the systemic consistency toward a promising DEMO concept. The current status of the DEMO conceptual design activity is presented.</p>

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Predictive modelling of JT-60SA high-beta steady-state plasma with impurity accumulation

N. Hayashi, K. Hoshino, M. Honda, S. Ide

Nuclear Fusion 58 ( 6 ) 066001 2018.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0029-5515

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© 2018 IAEA, Vienna. The integrated modelling code TOPICS has been extended to include core impurity transport, and applied to predictive modelling of JT-60SA high-beta steady-state plasma with the accumulation of impurity seeded to reduce the divertor heat load. In the modelling, models and conditions are selected for a conservative prediction, which considers a lower bound of plasma performance with the maximum accumulation of impurity. The conservative prediction shows the compatibility of impurity seeding with core plasma with high-beta (β N > 3.5) and full current drive conditions, i.e. when Ar seeding reduces the divertor heat load below 10 MW m-2, its accumulation in the core is so moderate that the core plasma performance can be recovered by additional heating within the machine capability to compensate for Ar radiation. Due to the strong dependence of accumulation on the pedestal density gradient, high separatrix density is important for the low accumulation as well as the low divertor heat load. The conservative prediction also shows that JT-60SA has enough capability to explore the divertor heat load control by impurity seeding in high-beta steady-state plasmas.

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Study of mirror effect on scrape‐off layer‐divertor plasma based on a generalized fluid model incorporating ion temperature anisotropy

S. Togo, T. Takizuka, D. Reiser, K. Hoshino, K. Ibano, Y. Li, Y. Ogawa, M. Sakamoto, N. Ezumi, Y. Nakashima

Contributions to Plasma Physics 58 ( 6-8 ) 556 - 562 2018.05

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  08631042

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© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The mirror effect on scrape-off layer (SOL)-divertor plasma profiles was studied by relaxing the assumption of homogeneous magnetic fields used in a one-dimensional (1D) plasma fluid model, which incorporates the anisotropic ion temperature. For collisionless plasmas, the perpendicular ion temperature proportional to the magnetic field strength is observed, which reflects the conservation of the magnetic moment. In diverging field cases, the plasma flow becomes supersonic, while it is kept subsonic in contracting field cases. Parallel momentum gains/losses and energy transfers between parallel and perpendicular components caused by the mirror effect are also observed. In addition, it is indicated that the viscous flux approximation is invalid in inhomogeneous magnetic fields regardless of the plasma collisionality.

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An extended kinetic model for the thermal force on impurity particles in weakly collisional plasmas

Y. Homma, K. Hoshino, S. Tokunaga, S. Yamoto, A. Hatayama, N. Asakura, Y. Sakamoto, K. Tobita, Joint Special Design Team for Fusion DEMO

Contributions to Plasma Physics 58 ( 6-8 ) 629 - 637 2018.04

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  08631042

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© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim We have developed an extended kinetic model for the thermal force (Formula presented.) on test impurity particles in plasmas. This model makes use of a combination of the plasma ion heat flux q GM derived from the generalized moment equations (E. Zawaideh et al., Phys. Fluids 1988, 31) and the numerical algorithm presented earlier (Y. Homma, A. Hatayama, J. Comput. Phys. 2013, 250). The applicable condition extends from collisional to weakly collisional plasmas, and (Formula presented.) weakens when the plasma collisionality decreases. A test simulation is performed assuming a tentative weakly collisional plasma. The results show that it can have a non-negligible influence on transient impurity transport in a DEMO-scale tokamak to take into account the effect of plasma collisionality in thermal force modelling.

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Multi-impurity divertor simulation using a Monte-Carlo kinetic impurity transport model

K. Hoshino, Y. Homma, S. Tokunaga, K. Shimizu

Contributions to Plasma Physics 58 ( 6-8 ) 638 - 642 2018.04

Research paper (international conference proceedings), Joint Work, Lead author, Accepted,  ISSN  08631042

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© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The effects of multi-impurity transport are important for the divertor plasma performance. To simulate the radiative divertor plasma precisely, we have extended the integrated divertor code, SONIC, to the simulation with multi-impurity species. For SONIC extension, a new integrated modelling framework using the multiple-program multiple-data approach and message passing interface data exchange has been developed. In the framework, two impurities and more can be treated simultaneously with several Monte Carlo kinetic impurity codes. The extended SONIC code has been applied to analyse the JT-60SA radiative divertor plasma. The SONIC simulation including multi-impurity transport demonstrates that the radiative divertor plasma scenario compatible with the steady-state high-β plasma can be achieved.

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