Predictive simulations of NBI ion power load to the ICRH antenna in Wendelstein 7-X

Funding Information: The calculations were performed on Marconi-Fusion, the High Performance Computer at the CINECA headquarters in Bologna (Italy). The computational resources provided by Aalto Science-IT project are also acknowledged. This work was partially funded by the Academy of Finland Project No. 298126. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2022 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. | openaire: EC/H2020/633053/EU//EUROfusionIn Wendelstein 7-X (W7-X), a new ion cyclotron resonance heating (ICRH) antenna will be commissioned during the operational campaign OP2.1. The antenna will have to sustain power loads not only from thermal plasma and radiation but also fast ions. Predictive simulations of fast-ion power loads to the antenna components are therefore important to establish safe operational limits. In this work, the fast-ion power loads from the W7-X neutral beam injection (NBI) system to the ICRH antenna was simulated using the ASCOT suite of codes. Five reference magnetic configurations and five antenna positions were considered to provide an overview of power load behavior under various operating conditions. The NBI power load was found to have an exponential dependence on the antenna insertion depth. Differences between magnetic configurations were significant, with the antenna limiter power load varying between 380 W and 100 kW depending on the configuration. Qualitative differences in power load patterns between configurations were also observed, with the low mirror and low iota configurations exhibiting higher loads to the sensitive antenna straps. The local fast-ion power flux to the antenna limiter was also considered and found to exceed the 2.0 MW m−2 steady-state safety limit only in specific cases. The NBI system might thus pose a safety concern to the ICRH antenna during concurrent NBI-ICRH operation, but additional heat propagation simulations of antenna components are needed to establish more realistic operational time limits.Peer reviewe