Speaker
Description
Accurate assessment of radiated power during Shattered Pellet Injection (SPI)–mitigated disruptions is essential for ensuring the protection of ITER plasma-facing components [1].
In this work, we extend the synthetic bolometry framework for ITER by incorporating a full 3D treatment of the diagnostic geometry, including inner apertures and sub-collimators, using the CHERAB framework.
This development enables more realistic modeling of the line-of-sight transmission and provides improved synthetic bolometer signals based on 3D JOREK simulations of SPI scenarios [2].
A series of dual Ne/H SPI simulations, obtained from the ITER Integrated Modelling & Analysis Suite (IMAS) disruption database, is used to evaluate the diagnostic performance. Geometrical response matrices are generated through ray-tracing on unstructured JOREK meshes, and the foil bolometer’s temporal response is modeled to assess its ability to follow the rapid variations during the thermal quench (TQ).
To enhance the accuracy of total radiated power estimation, we apply a weighted-sum method, which reduces systematic underestimation observed in simpler summation techniques [3].
We further investigate ITER’s capability to capture toroidal radiation asymmetries, which may arise during SPI due to localized shard ablation and MHD-driven redistribution.
By computing the Toroidal Peaking Factor (TPF) from the 3D emissivity and comparing it with the TPF inferred from synthetic bolometer signals, we assess how effectively the bolometer system can retrieve toroidally varying radiation patterns. The results indicate that, despite the limited number of toroidally separated cameras, the diagnostic retains the potential to resolve significant non-axisymmetric radiation structures, although local peaks may still be underestimated in regions of high TPF.
Finally, we evaluate the heat load on the bolometer foil itself during the intense, short-duration radiation bursts of the TQ phase.
When the measured time response is included, the resulting temperature rise remains within the diagnostic design requirements, demonstrating that the bolometer can tolerate even the strongest radiation spikes predicted by the SPI simulations.
These findings support the robustness of the ITER bolometer system and provide improved tools for analyzing 3D radiation behavior in SPI-mitigated disruptions, contributing to future disruption mitigation strategy optimization.
[1] M. Lehnen et al., J. Nucl. Mater. 463, 39 (2015)
[2] D. Hu et al., Nucl. Fusion 64, 86005 (2024)
[3] G. Partesotti et al., Nucl. Fusion 65, 16035 (2025)