Talk: Unexpected accuracy of calculation of power deposition on tokamak first wall

• Wayne Arter (Plasma Simulation)

The assemblage of SMARDDA software modules which makes up the SMARDDA-PFC code, has been used to calculate the deposition of power (escaping from the central tokamak plasma) onto a wide range of designs of the first wall of the enclosing vacuum vessel, ranging from reactor-size conventional devices to the MAST-U spherical tokamak. Calculations typically involve tracking a time-steady, spatially exponentially decaying power source at device midplane along magnetic field-lines onto the first wall. Sampling is governed by the triangulation of the plasma-facing components, and the unexpected result is that accurate conservation of total power is commonly achieved using triangle sizes that are comparable to the e-folding length of the source distribution. Explanation is provided by the arguments of ref. [1] and the sensitivity of the effect to meshing and other discretisation effects, important for confidence in predictive results, is described in ref. [2]. Refs.[1,2] and further material describing the SMARDDA modules, form the basis for the first conference presentation of the bulk of the cited material. [1] W. Arter. Error Estimation for Plasma Power Deposition in Tokamak First Wall Designs. IEEE Transactions on Plasma Science, 52(5):1909–1918, 2024. https://dx.doi.org/10.1109/TPS.2024.3399929. [2] W. Arter. Sensitivity Studies of Power Deposition Computed on Tokamak First Wall. IEEE Transactions on Plasma Science, 53(3):463-475, 2025. https://dx.doi.org/10.1109/TPS.2024.3485530

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