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Latest News
Max Planck’s ELISE reaches record values for ITER plasma heating
The Max Planck Institute for Plasma Physics (IPP) announced that it recently has achieved a new record for ion current density for neutral particle heating at its ELISE (Extraction from a Large Ion Source Experiment) experimental testing facility in Garching, Germany. ELISE is being used to test neutral beam injection (NBI) systems that will be used to heat the plasma of the ITER fusion experiment in France.
Yoshiki Oshima, Tomohiro Endo, Akio Yamamoto
Nuclear Science and Engineering | Volume 196 | Number 4 | April 2022 | Pages 379-394
Technical Paper | doi.org/10.1080/00295639.2021.1982549
Articles are hosted by Taylor and Francis Online.
The convergence performance of nonlinear acceleration methods for the method of characteristics (MOC) with flat source (FS) approximation (FS MOC) or linear source (LS) approximation (LS MOC) is numerically investigated by focusing on the spatial and angular approximations in the acceleration calculations. The convergence of nonlinear acceleration depends on the consistency of the calculation models between the higher-order and lower-order (acceleration) methods. The convergence of four acceleration methods is evaluated to clarify the relationship between model consistency and convergence performance. These methods consist of FS or LS for the spatial source distribution and P1 or discrete angle for the angular distribution, i.e., (1) FS analytic coarse mesh finite difference (ACMFD) acceleration (FS ACMFD), (2) LS ACMFD, (3) FS angular-dependent discontinuity factor MOC (ADMOC) acceleration (FS ADMOC), and (4) LS ADMOC. The ACMFD and ADMOC accelerations are based on P1 and discrete angle approximations, respectively. The FS MOC and LS MOC are considered higher-order methods. The FS MOC and LS MOC with five acceleration methods, i.e., the aforementioned four acceleration methods and the conventional coarse mesh finite difference acceleration method, are used to perform fixed-source calculations in one-group one-dimensional homogeneous slab geometry, and the spectral radii are numerically evaluated. The numerical results indicate that (1) the nonlinear acceleration methods that are unconditionally stable for FS MOC also show similar convergence properties for LS MOC in one-dimensional slab geometry; (2) better convergence is observed when the consistency of higher- and lower-order models is high; and (3) when a coarse mesh is optically thick, the spatial homogenization degrades the convergence performance, even if spatial and angular approximations are consistent between the higher- and lower-order models.