Power exhaust in the ARC fusion power plant

To demonstrate fusion as an attractive electricity source, ARC will need to operate near-continuously, reliably producing energy over long pulses with minimal down-time. To produce ~1GW of thermal fusion power, ARC will need to operate with detached divertors, in a scenario which avoids type-I ELMs. In this talk, we discuss the divertor design and possible operational scenarios for ARC. ARC has been designed with up-down-symmetric divertors, with long, tightly-baffled divertor legs with a secondary X-point in each divertor leg [1]. This maximizes the parallel connection length and the total flux expansion along the divertor leg — increasing the range of upstream conditions compatible with divertor detachment and decreasing the sensitivity of the detachment front [2]. We then discuss type-I-ELM-free candidates for ARC, focusing on scenarios which are able to integrate high performance with divertor detachment. For this talk, we focus our analysis on the quasi-continuous exhaust (QCE) scenario. Based on shaping and edge collisionality requirements [3], we show that ARC should be able to operate in the QCE regime. Using a model developed to match the Kallenbach detachment onset [4,5] scaling, we calculate that ARC should reach detachment with a ~1% argon concentration in the divertor. To test the performance and access to detachment of type-I-ELM-free scenarios, SPARC experiments will be used to demonstrate that ARC has a viable solution for power exhaust.

[1] B. LaBombard et al 2015 Nucl. Fusion 55 053020

[2] K. Verhaegh et al 2025 Commun. Phys. 8 215

[3] M. Faitsch et al 2025 Nuclear Materials and Energy 42 101904

[4] A. Kallenbach et al PPCF 58 045013

[5] T. Body, A. Kallenbach & T. Eich Nucl. Fusion 65 086002