Towards time-dependent 1D models for detachment access and control*

Fusion power plants require sustained divertor detachment to prevent excessive heat loads, thermal stress-induced cracking and erosion of the divertor targets. For current devices, detachment onset conditions and reattachment timescales can be predicted using simple 0D and 1D models [Kallenbach 2016, Henderson 2023, Henderson 2024]. In this study, we present a comparison of these models to time-dependent Hermes 1D Braginskii simulations [Dudson 2024]. First, we show that neglecting cross-field transport in the divertor results in a Lengyel-like detachment onset scaling in Hermes 1D [Body 2024], which has a weaker density dependence than what is found in [Kallenbach 2016, Henderson 2024]. This discrepancy indicates that additional physics is needed to match experimental results. To address this, we implemented several additional effects in Hermes 1D, including an effective model for heat-flux spreading due to cross-field transport and a ‘neutral reservoir’ model, following the method of [Derks 2024]. We are currently investigating how these effects modify the detachment onset scaling predicted by Hermes 1D, with the goal of developing time-dependent detachment models suitable for future fusion devices.

[Kallenbach2016] doi.org/10.1088/0741-3335/58/4/045013

[Henderson2023] doi.org/10.1088/1741-4326/ace2d6

[Henderson2024] doi.org/10.1088/1741-4326/ad3970

[Dudson2024] doi.org/10.1016/j.cpc.2023.108991

[Body2024] doi.org/10.48550/arXiv.2406.16375

[Derks2024] doi.org/10.1088/1361-6587/ad2e37