Abstract
Abstract Tungsten sputtering rates and density profiles predicted using the edge plasma codes EDGE2D-EIRENE and DIVIMP are found to agree within a factor of 4 with measurements of neutral and singly-ionized W spectral line emission in the JET low-field side (LFS) divertor, and within a factor of 2 with SXR, VUV, and bolometric calculations of the W density in the main plasma. The edge plasma W predictions are extended to the core plasma using JINTRAC integrated core-edge modelling. Prompt redeposition of W is identified as the primary reason for the discrepancy between predicted and measured W emission in the divertor. The studied plasmas include attached divertor conditions in L-mode and type-I ELMy H-mode plasmas typical for JET. To more accurately reproduce the spectroscopically inferred W sputtering rates in EDGE2D-EIRENE, imposing the experimentally observed Be concentration of order 0.5% in the divertor is necessary. However, the W density in the main plasma is predicted to be insensitive to whether or not W is sputtered by Be at the divertor targets. Instead, the majority of the predicted core W originated in L-mode from sputtering due to fast D charge-exchange atoms at the W-coated tiles above the LFS divertor, and in H-mode due to D and W ions at the targets during ELMs.
Highlights
Tungsten (W) is the material of divertor plasma-facing components in ITER and the JET ITER-like wall [1], and a strong candidate for use in future fusion reactors
Tungsten sputtering rates and density profiles predicted using the edge plasma codes EDGE2D-EIRENE and DIVIMP are found to agree within a factor of 4 with measurements of neutral and singly-ionized W spectral line emission in the JET low-field side (LFS) divertor, and within a factor of 2 with SXR, VUV, and bolometric calculations of the W density in the main plasma
If EDGE2D-EIRENE is used to predict the Be flux to the LFS target by considering erosion and transport from Be components in the main chamber only, the resulting Be II line emission is lower than measured by a factor of 200 (Fig. 4(a), black line)
Summary
Tungsten (W) is the material of divertor plasma-facing components in ITER and the JET ITER-like wall [1], and a strong candidate for use in future fusion reactors. The erosion and transport of tungsten from the divertor plates into the core plasma is detrimental to the fusion performance due to the high radiation factor of W ions in the keV– MeV range [2]. The design of viable fusion reactors greatly benefits from the ability to predict the W erosion rate, the W screening by the scrape-off layer (SOL) and the main plasma W density as a function of time. This study uses recent calculations [3] based on JET W diagnostics to quantitatively assess the ability of the 2D edge plasma codes EDGE2D-EIRENE [4,5] and DIVIMP [6,7] to predict the spatially resolved W sputtering and the main plasma W density in JET. All information from the W diagnostics is reserved solely for validation and not used as input in the W transport simulations
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