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Journal Articles

Iterative methods with mixed-precision preconditioning for ill-conditioned linear systems in multiphase CFD simulations

Ina, Takuya*; Idomura, Yasuhiro; Imamura, Toshiyuki*; Yamashita, Susumu; Onodera, Naoyuki

Proceedings of 12th Workshop on Latest Advances in Scalable Algorithms for Large-Scale Systems ScalA21) (Internet), 8 Pages, 2021/11

https://doi.org/10.1109/ScalA54577.2021.00006

Times Cited Count：1 Percentile：50.67(Computer Science, Software Engineering)

A new mixed-precision preconditioner based on the iterative refinement (IR) method is developed for preconditioned conjugate gradient (P-CG) and multigrid preconditioned conjugate gradient (MGCG) solvers in a multi-phase thermal-hydraulic CFD code JUPITER. In the IR preconditioner, all data is stored in FP16 to reduce memory access, while all computation is performed in FP32. The hybrid FP16/32 implementation keeps the similar convergence property as FP32, while the computational performance is close to FP16. The developed solvers are optimized on Fugaku (A64FX), and applied to ill-conditioned matrices in JUPITER. The P-CG and MGCG solvers with the new IR preconditioner show excellent strong scaling up to 8,000 nodes, and at 8,000 nodes, they are respectively accelerated up to 4.86 and 2.39 from the conventional ones on Oakforest-PACS (KNL).

Journal Articles

High-precision measurement of the wavelength of a nickel-like silver X-ray laser

Hasegawa, Noboru; Kawachi, Tetsuya; Utsumi, Takayuki*; Sasaki, Akira; Tanaka, Momoko; Kado, Masataka; Sukegawa, Kota*; Lu, P.; Kishimoto, Maki; Tai, R.; et al.

Japanese Journal of Applied Physics, Part 1, 43(5A), p.2519 - 2522, 2004/05

https://doi.org/10.1143/JJAP.43.2519

Times Cited Count：12 Percentile：45.06(Physics, Applied)

We conducted high-precision measurements of the wavelength of the nickel-like silver X-ray laser in order to compare it with a theoretical wavelength. The reasons for using this laser are as follows: First, this laser line is in the wavelength region of Mo/Si multi-layer mirrors; therefore, this laser line is important for applications. Second, the strongamplification of this laser line has been obtained in our previous work, and the higher order line in the spectra obtained by our spectrometer can be used. Third, since silver is arelatively low-z material (z = 47), this wavelength is a ideal benchmark of atomic structural codes such as the Multiconfiguration Dirac-Fock (MCDF) code. The wavelength of the nickel-like silver X-ray laser was determined to be 13.887 nm. The comparison with MCDF codes shows that the present experimental result can work as a good benchmark of the accuracy of the codes.

Journal Articles

Development of the large-scale fine and non-thermal manufacturing technology using femtosecond, highly- efficient, and high power free-electron laser

Minehara, Eisuke

Proceedings of 28th Linear Accelerator Meeting in Japan, p.402 - 403, 2003/08

The JAERI superconducting RF linac-based free-electron laser has successfully generated 6% highly-efficient, a few hundreds of femtosecond, and several kW class high power FEL light several years ago. In the presentation, it will be reprted that the JAERI plans to develop the higher power free-electron lasers and their application to large-scale non-thermal precision manufacturing technology.

Journal Articles

Dosimetry for 3-45 MeV/u ion beams using thin film dosimeters

Kojima, Takuji; Sunaga, Hiromi; Takizawa, Haruki; Hanaya, Hiroaki; Tachibana, Hiroyuki*

JAERI-Review 2002-035, TIARA Annual Report 2001, p.123 - 124, 2002/11

Thin film dosimeters of about 10-200 mm in thickness, which were well -characterized for $^{60}$ Co -rays or 2-MeV electrons, have been applied to dosimetry for ion beams. For development of dosimetry covering the dose range of 0.005 to 200 kGy with high precision within 5%, the linear energy transfer (LET) characteristics of thin films were studied involving development of precise fluence measurement. Dose mapping technique was also developed achieving high spatial resolution values of about 1m and 10m for lateral and depth directions respectively. The outline of the recent development is summarized in this paper.