Implementation of a tightly baffled long-legged divertor in TCV

Abstract The TCV tokamak contributes to the development of nuclear fusion energy with proof-of-principle experiments and by challenging models that are used to predict reactor performance. In the next upgrade of the TCV divertor it is planned to test a tightly baffled, long-legged divertor (TBLLD), a novel concept designed to enhance power exhaust handling with minimal modification to the magnetic configuration. The project is guided by simulations using the SOLPS-ITER code that indicate that a TBLLD can improve TCV’s power exhaust capability by up to an order of magnitude over its unbaffled configuration. Tight baffling sustains a high poloidal neutral density gradient along the divertor leg, thereby increasing the neutral density in front of the divertor target, which enhances volumetric power dissipation. The simulations informed the design of a proof-of-principle TBLLD for the outer TCV divertor, while ensuring compatibility with high-power plasma scenarios. The chosen straight, vertical design incorporates graphite baffle tiles, accommodates TCV’s reciprocating divertor probe array (RDPA) and maintains engineering simplicity. While the resulting divertor is more restrictive, it provides sufficient diagnostic access to assess the TBLLD concept. Poloidally distributed wall-mounted Langmuir probes, surface thermocouples and neutral pressure gauges, and horizontal spectrometric lines of sight at several heights will enable a comprehensive characterisation of the divertor state. A dedicated experimental campaign is planned for 2026.