The impact of non-local fluid models on 1D impurity driven detachment in ITER

Understanding parallel thermal transport in the scrape-off layer (SOL) is crucial for designing future high-powered tokamak exhaust systems. Fluid models, whilst computationally efficient, cannot accurately predict heat flux in conditions with large temperature gradients or low upstream collisionality, where non-local effects are significant. The classical Spitzer-Härm (SH) closure fails to capture these effects, prompting the use of non-local heat flux models such as flux limitation (FL) and the more sophisticated multigroup diffusion model by Shurtz, Nicolaï , and Busquet (SNB). The impact of these non-local models on key detachment processes is often overlooked. The Hermes-3 multi-fluid SOL code is applied to a medium collisionality (L/λe ~ 50) ITER scenario in 1D, comparing FL and SNB to SH. A neon fixed-fraction impurity seeding model is applied at increasing percentage until detachment is observed. Competing behaviour between FL and impurity seeding on target temperatures is observed, whilst the SNB model agrees qualitatively with SH, showing earlier detachment onset compared to FL (at~2% lower neon fraction). Transient events can inject significant power fluxes into the SOL, exacerbating non-local effects and motivating further investigation of their impact on detachment processes.