Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Watanabe, Tomohiko*; Idomura, Yasuhiro; Todo, Yasushi*; Honda, Mitsuru*
Nihon Genshiryoku Gakkai-Shi ATOMO
, 64(3), p.152 - 156, 2022/03
Understanding of physical processes of particle, momentum, and thermal transports is essential for predicting the confinement performance of burning plasmas in ITER, which is targeting the scientific demonstration of magnetic confinement fusion. First principles based simulations on Fugaku disclosed physical mechanisms such as complex transport processes of multi-scale turbulence in deuterium-tritium plasmas and kinetic effects in energetic particle transport due to electromagnetic fluctuations. We promote further research and development of first principles based simulations towards the performance prediction of burning plasmas.
Idomura, Yasuhiro; Ina, Takuya*; Ali, Y.*; Imamura, Toshiyuki*
Dai-34-Kai Suchi Ryutai Rikigaku Shimpojiumu Koen Rombunshu (Internet), 6 Pages, 2020/12
A new communication avoiding (CA) Krylov solver with a FP16 (half precision) preconditioner is developed for a semi-implicit finite difference solver in the Gyrokinetic Toroidal 5D full-f Eulerian code GT5D. In the solver, the bottleneck of global collective communication is resolved using a CA-Krylov subspace method, and halo data communication is reduced by the FP16 preconditioner, which improves the convergence property. The FP16 preconditioner is designed based on the physics properties of the operator and is implemented using the new support for FP16 SIMD operations on A64FX. The solver is ported also on GPUs, and the performance of ITER size simulations with 
trillion grids is measured on Fugaku (A64FX) and Summit (V100). The new solver accelerates GT5D by 
from the conventional non-CA solver, and excellent strong scaling is obtained up to 5,760 CPUs/GPUs both on Fugaku and Summit.
Idomura, Yasuhiro; Watanabe, Tomohiko*; Todo, Yasushi*
Shimyureshon, 38(2), p.79 - 86, 2019/06
We promote the research and development of exascale fusion plasma simulations on Post-K towards estimation and prediction of core plasma performance, and exploration of improved operation scenarios on the next generation fusion experimental reactor ITER. In this paper, we review developed exascale simulation technologies and outcomes from validation studies on existing experimental devices, and discuss perspectives on exascale fusion plasma simulations on Post-K.
Idomura, Yasuhiro
Journal of Computational Physics, 313, p.511 - 531, 2016/05
Times Cited Count：36 Percentile：91.82(Computer Science, Interdisciplinary Applications)A new hybrid kinetic electron model is developed for electrostatic full-f gyrokinetic simulations of the ion temperature gradient driven trapped electron mode (ITG-TEM) turbulence at the ion scale. In the model, a full kinetic electron model is applied to the full-f gyrokinetic equation, the multi-species linear Fokker-Planck collision operator, and an axisymmetric part of the gyrokinetic Poisson equation, while in a non-axisymmetric part of the gyrokinetic Poisson equation, turbulent fluctuations are determined only by kinetic trapped electrons responses. By using this approach, the so-called 
mode is avoided with keeping important physics such as the ITG-TEM, the neoclassical transport, the ambipolar condition, and particle trapping and detrapping processes. The model enables full- f gyrokinetic simulations of ITG-TEM turbulence with a reasonable computational cost.
Idomura, Yasuhiro
NIFS-PROC-58, p.46 - 50, 2004/07
no abstracts in English
Kishimoto, Yasuaki
Shimyureshon, 22(2), p.89 - 97, 2003/06
This is a collection of review article related to the "Multiple Time and Spatial Scale Plasma Simulation" of various fields including fundamental research area of self-organization, magnetic and laser fusion field, space and astrophysics field where a plasma plays an essential roles.
Idomura, Yasuhiro; Adachi, Masaaki*; Gorai, Kazuo; Suzuki, Yoshio; Wang, X.*
Purazuma, Kaku Yugo Gakkai-Shi, 79(2), p.172 - 187, 2003/02
Under the Numerical EXperiment of Tokamak (NEXT) research project, various fluid, particle, and hybrid codes have been developed. These codes require a computational environment which consists of high performance processors, high speed storage system, and high speed parallelized visualization system. In this paper, the performance of the JAERI Origin3800 system is examined from a point of view of these requests. In the performance tests, it is shown that the representative particle and fluid codes operate with 
% of processing efficiency up to 512 processors. A storage area network (SAN) provides high speed parallel data transfer. A parallel visualization system enables order of magnitude faster visualization of a large scale simulation data compared with the previous graphic workstations. Accordingly, an extremely advanced simulation environment is realized on the JAERI Origin3800 system. Recently, development of a storage grid is underway in order to improve a computational environment of remote users. The storage grid is constructed by a combination of SAN and a wavelength division multiplexer (WDM). The preliminary tests show that compared with the existing data transfer methods, it enables dramatically high speed data transfer 
Gbps over a wide area network.
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
New Journal of Physics (Internet), 4(1), p.101.1 - 101.13, 2002/12
The ion temperature gradient driven (ITG) mode in reversed shear tokamaks is analyzed using a gyrokinetic toroidal particle code. It is found that the ITG mode in the reversed shear configuration shows a coupled mode structure between the slab and toroidal ITG modes. Especially in the 
region, a slab like feature due to the reversed shear slab ITG mode becomes strong. This coupled eigenmode structure is changed from a slab mode to a toroidal mode depending on 
and 
. Results show that in reversed shear tokamaks, the ITG mode is determined from a competition between the slab and toroidal ITG modes.
Idomura, Yasuhiro; Adachi, Masaaki*; Suzuki, Yoshio; Wang, X.*
Saientifikku, Shisutemu Kenkyukai Heisei-14-Nendo Kagaku Gijutsu Keisan Bunkakai Dai-1-Kai Kaigo Shiryo, p.43 - 59, 2002/08
no abstracts in English
Matsumoto, Taro; Tokuda, Shinji; Kishimoto, Yasuaki; Naito, Hiroshi*
Earth Planets and Space, 53(6), p.565 - 570, 2001/06
Times Cited Count：0 Percentile：0.01(Geosciences, Multidisciplinary)no abstracts in English
Naito, Hiroshi*; Matsumoto, Taro
Purazuma, Kaku Yugo Gakkai-Shi, 77(6), p.549 - 552, 2001/06
no abstracts in English
Idomura, Yasuhiro
Purazuma, Kaku Yugo Gakkai-Shi, 77(6), p.528 - 531, 2001/06
no abstracts in English
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki; Wakatani, Masahiro*
Nuclear Fusion, 41(4), p.437 - 445, 2001/04
Times Cited Count：13 Percentile：40.83(Physics, Fluids & Plasmas)no abstracts in English
Idomura, Yasuhiro
JAERI 1341, 91 Pages, 2001/01
no abstracts in English
Matsumoto, Taro; Tokuda, Shinji; Kishimoto, Yasuaki; Naito, Hiroshi*
Earth Planets and Space, 53(6), p.565 - 570, 2001/00
no abstracts in English
Matsumoto, Taro; Tokuda, Shinji; Kishimoto, Yasuaki; Naito, Hiroshi*
IAEA-CN-77 (CD-ROM), 8 Pages, 2001/00
no abstracts in English
B zonal flow in electron temperature gradient driven turbulenceIdomura, Yasuhiro; Wakatani, Masahiro*; Tokuda, Shinji
Physics of Plasmas, 7(9), p.3551 - 3566, 2000/09
Times Cited Count：56 Percentile：82.67(Physics, Fluids & Plasmas)no abstracts in English
; Tokuda, Shinji; Wakatani, Masahiro*
Purazuma, Kaku Yugo Gakkai-Shi, 75(2), p.131 - 142, 1999/02
no abstracts in English
Tokuda, Shinji; Takizuka, Tomonori; Kishimoto, Yasuaki; Yamagiwa, Mitsuru; Shimizu, Katsuhiro; Ishii, Yasutomo; Azumi, Masafumi;
ANU-PRL-TP-96/01, 0, p.70 - 72, 1996/00
no abstracts in English
Matsuoka, Seikichi; Idomura, Yasuhiro
no journal, ,
Recently, full-f gyrokinetic simulations, in which the total plasma distribution is evolved based on the first principle, attracted much attention in the plasma transport study. Rich physics has been revealed by the simulations in axisymmetric tokamak plasmas such as JT-60 and ITER. However, no full-f gyrokinetic simulations in non-axisymmetric, or three-dimensional magnetic field equilibria such as stellarators and/or helical devices have been reported so far due to their complicated magnetic field geometries which requires more computational resources. In this work, we extend a full-f gyrokinetic simulation code, GT5D, to treat three-dimensional magnetic equilibria by modifying its coordinates, and develop a new interface between GT5D and VMEC, where VMEC is a numerical tool to construct a three-dimensional magnetic equilibria. In the presentation, we present benchmark results as a numerical verification of GT5D+VMEC by comparing the collisional (neoclassical) transport.
