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Published in Phillip A. Laplante, Dictionary of Computer Science, Engineering, and Technology, 2017
beam tracing a method of rendering similar to ray tracing but using an arbitrarily shaped projection, commonly a polygonal cone, rather than a single ray. It is an improvement on ray tracing since it reduces the CPU overhead and reduces aliasing artifacts by taking advantage of known spatial coherence in the beam.
Recent EUROfusion Achievements in Support of Computationally Demanding Multiscale Fusion Physics Simulations and Integrated Modeling
Published in Fusion Science and Technology, 2018
I. Voitsekhovitch, R. Hatzky, D. Coster, F. Imbeaux, D. C. McDonald, T. B. Fehér, K. S. Kang, H. Leggate, M. Martone, S. Mochalskyy, X. Sáez, T. Ribeiro, T.-M. Tran, A. Gutierrez-Milla, T. Aniel, D. Figat, L. Fleury, O. Hoenen, J. Hollocombe, D. Kaljun, G. Manduchi, M. Owsiak, V. Pais, B. Palak, M. Plociennik, J. Signoret, C. Vouland, D. Yadykin, F. Robin, F. Iannone, G. Bracco, J. David, A. Maslennikov, J. Noé, E. Rossi, R. Kamendje, S. Heuraux, M. Hölzl, S. D. Pinches, F. Da Silva, D. Tskhakaya
Asymptotic methods for solving the wave equation in the short-wavelength limit (e.g., ray and beam tracing) are generally computationally fast and give sufficiently accurate calculations of the heating power needed, for example, for transport studies. However, problems like mode conversion, wave dispersion due to density fluctuations, prediction of high spatial resolution (few millimetres) diagnostics or neoclassical tearing mode stabilization by driving a well-localized radio frequency (RF) current require a computationally demanding full-wave modeling. HLST efforts have been devoted to three full-wave codes including REFMULX (Refs. 24 and 25), FWTOR (Refs. 26 and 27), and COCHLEA (Refs. 27 and 28), which have different physics applications (Table I). These codes solve the Maxwell’s equations using a finite-difference time-domain numerical technique, which requires a fine spatial grid discretization to minimize the error and a high-resolution time discretization to comply with the conditions for convergence. Also, as the size requirements increase in an effort to simulate large devices, memory demands become important.