Multi-scale turbulence simulation suggesting improvement of electron heated plasma confinement

Maeyama, Shinya*; Watanabe, Tomohiko*; Nakata, Motoki*; Nunami, Masanori*; Asahi, Yuichi; Ishizawa, Akihiro*

Nature Communications (Internet), 13, p.3166_1 - 3166_8, 2022/06

https://doi.org/10.1038/s41467-022-30852-0

Turbulent transport is a key physics process for confining magnetic fusion plasma. Recent theoretical and experimental studies of existing fusion experimental devices revealed the existence of cross-scale interactions between small (electron)-scale and large (ion)-scale turbulence. Since conventional turbulent transport modelling lacks cross-scale interactions, it should be clarified whether cross-scale interactions are needed to be considered in future experiments on burning plasma, whose high electron temperature is sustained with fusion-born alpha particle heating. Here, we present supercomputer simulations showing that electron scale turbulence in high electron temperature plasma can affect the turbulent transport of not only electrons but also fuels and ash. Electron-scale turbulence disturbs the trajectories of resonant electrons responsible for ion-scale micro-instability and suppresses large-scale turbulent fluctuations. Simultaneously, ion-scale turbulent eddies also suppress electron-scale turbulence. These results indicate a mutually exclusive nature of turbulence with disparate scales. We demonstrate the possibility of reduced heat flux via cross-scale interactions.

Progress report of Japanese simulation research projects using the high-performance computer system Helios in the International Fusion Energy Research Centre

Ishizawa, Akihiro*; Idomura, Yasuhiro; Imadera, Kenji*; Kasuya, Naohiro*; Kanno, Ryutaro*; Satake, Shinsuke*; Tatsuno, Tomoya*; Nakata, Motoki*; Nunami, Masanori*; Maeyama, Shinya*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 92(3), p.157 - 210, 2016/03

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2016_03/jspf2016_03-157.pdf

The high-performance computer system Helios which is located at The Computational Simulation Centre (CSC) in The International Fusion Energy Research Centre (IFERC) started its operation in January 2012 under the Broader Approach (BA) agreement between Japan and the EU. The Helios system has been used for magnetised fusion related simulation studies in the EU and Japan and has kept high average usage rate. As a result, the Helios system has contributed to many research products in a wide range of research areas from core plasma physics to reactor material and reactor engineering. This project review gives a short catalogue of domestic simulation research projects. First, we outline the IFERC-CSC project. After that, shown are objectives of the research projects, numerical schemes used in simulation codes, obtained results and necessary computations in future.

Cross-scale interactions between electron and ion scale turbulence in a tokamak plasma

Maeyama, Shinya*; Idomura, Yasuhiro; Watanabe, Tomohiko*; Nakata, Motoki*; Yagi, Masatoshi; Miyato, Naoaki; Ishizawa, Akihiro*; Nunami, Masanori*

Physical Review Letters, 114(25), p.255002_1 - 255002_5, 2015/06

https://doi.org/10.1103/PhysRevLett.114.255002

Multiscale gyrokinetic turbulence simulations with the real ion-to-electron mass ratio and value are realized for the first time, where the value is given by the ratio of plasma pressure to magnetic pressure and characterizes electromagnetic effects on microinstabilities. Numerical analysis at both the electron scale and the ion scale is used to reveal the mechanism of their cross-scale interactions. Even with the real- mass scale separation, ion-scale turbulence eliminates electron-scale streamers and dominates heat transport, not only of ions but also of electrons. When the ion-scale modes are stabilized by finite- effects, the contribution of the electron-scale dynamics to the turbulent transport becomes non-negligible and turns out to enhance ion-scale turbulent transport.

Exploring phase space turbulence in magnetic fusion plasmas

Watanabe, Tomohiko*; Idomura, Yasuhiro; Maeyama, Shinya; Nakata, Motoki; Sugama, Hideo*; Nunami, Masanori*; Ishizawa, Akihiro*

Journal of Physics; Conference Series, 510, p.012045_1 - 012045_11, 2014/05

https://doi.org/10.1088/1742-6596/510/1/012045

Plasma turbulence accompanied with fluctuations of the distribution function and the electromagnetic fields develops on the phase space composed of the configuration space and the velocity space. Detailed structures of the distribution function in magnetic fusion plasmas are investigated by means of gyrokinetic simulations performed on massively parallel supercomputers. The gyrokinetic simulations of drift wave turbulence have demonstrated entropy transfer in the phase space, zonal flow enhancement by helical fields and the resultant transport reduction. The state-of-the-art high performance computing is utilized for a multi- scale turbulence simulation covering ion- and electron-scales and for a global-scale simulation of turbulent transport in a sub-ITER sized plasma.

Electromagnetic gyrokinetic turbulence in finite-beta helical plasmas

Ishizawa, Akihiro*; Watanabe, Tomohiko*; Sugama, Hideo*; Maeyama, Shinya; Nakajima, Noriyoshi*

Physics of Plasmas, 21(5), p.055905_1 - 055905_10, 2014/05

https://doi.org/10.1063/1.4876960

Numerical techniques for parallel dynamics in electromagnetic gyrokinetic Vlasov simulations

Maeyama, Shinya; Ishizawa, Akihiro*; Watanabe, Tomohiko*; Nakajima, Noriyoshi*; Iio, Shunji*; Tsutsui, Hiroaki*

Computer Physics Communications, 184(11), p.2462 - 2473, 2013/11

https://doi.org/10.1016/j.cpc.2013.06.014

Gyrokinetic turbulence simulations of high-beta tokamak and helical plasmas with full-kinetic and hybrid models

Ishizawa, Akihiro*; Maeyama, Shinya; Watanabe, Tomohiko*; Sugama, Hideo*; Nakajima, Noriyoshi*

Nuclear Fusion, 53(5), p.053007_1 - 053007_13, 2013/05

https://doi.org/10.1088/0029-5515/53/5/053007

Turbulence spectra, transport, and flows in helical plasmas

Watanabe, Tomohiko*; Nunami, Masanori*; Sugama, Hideo*; Satake, Shinsuke*; Matsuoka, Seikichi*; Ishizawa, Akihiro*; Maeyama, Shinya; Tanaka, Kenji*

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2012/10

http://www-naweb.iaea.org/napc/physics/FEC/FEC2012/papers/460_TH81.pdf

Large coherent structure formation by magnetic stretching term in two-dimensional MHD turbulence

*; *

Journal of the Physical Society of Japan, 67(12), p.4302 - 4303, 1998/12

https://doi.org/10.1143/JPSJ.67.4302

no abstracts in English

Wavelet analysis of two-dimensional MHD turbulence

*; *

Journal of the Physical Society of Japan, 67(2), p.441 - 450, 1998/02

https://doi.org/10.1143/JPSJ.67.441

no abstracts in English