Interpretative analysis of experimental data to assess overall power balance in ST40 plasma facing components

In pulsed high-power-density fusion devices, it is necessary to model thermal sinks, as well as sources, as part of multiphysics analysis workflows to accurately predict bulk plasma facing component (PFC) temperatures especially. The Heat flux and Engineering Analysis Toolkit (HEAT) [1] has been developed to simulate realistic deposited heat flux on the PFCs. It’s recently been coupled with a power fraction model to account for the power sharing between all four divertor targets in near-double null magnetic geometries and lack of diagnostic coverage in the lower divertor in ST40 [2]. HEAT makes use of OpenFOAM [3], an open-source computational fluid dynamics software, to evaluate the thermal response from the simulated heat fluxes. We have updated the OpenFOAM module in HEAT by adding multi-material conduction capability which better models the effects of inertial cooling and provides a more accurate prediction of the bulk PFC temperature. This enables us to include a more realistic representation of the PFC architecture in ST40, which is composed of Mo plasma-facing armor with CuCrZr backing plates and Cu heat sink. This new multiphysics workflow is used to provide an interpretative analysis of ST40 infrared camera data (including both plasma heating and subsequent cooling after a shot) to have a better understanding of the PFC power balance in ST40.

[1] T. Looby et al., Fusion Sci. Technol. 78 (2022) 10-27.

[2] E. J. C. Tinacba et al., IEEE TPS in review

[3] H. G. Weller et al., Comput. Phys. 12 (6) (1998) 620–631.