Speaker
Description
Understanding the mechanisms that govern heat and particle transport in the divertor region is critical for the design and operation of future fusion reactors. Turbulent cross-field transport plays a key role in determining the heat flux distribution at divertor targets, affecting both the peak heat load and the overall power exhaust scenario. A key metric for characterizing heat flux spreading is the S parameter in the Eich’s fit. While previous studies have investigated S under various conditions [1, 2, 3, 4], its behavior remains poorly constrained. A new generation of 3D plasma turbulence codes has been developed to tackle edge/SOL turbulence in diverted geometry (e.g. [5,6]), even revealing unexpected results under reactor-relevant conditions [7], highlighting the challenges of extrapolating current tokamak experiments to reactor scenarios in the edge and SOL regions.
In this contribution we present an exprimental test for such codes, based on the theoretical ideas proposed in [8]. The key idea is that the relative orientation of the magnetic curvature vector κ and the pressure gradient ∇p determines the turbulence transport into the private flux region of the two divertor legs, depending on their geometry. This alignment can either destabilize or stabilize drift-interchange and drift-wave turbulence. Controlling the turbulence drive and its impact on transport through diverted plasma geometry represents a promising approach in the design of alternative divertor configurations. Leveraging the shaping flexibility of the TCV tokamak, a scan of the outer divertor leg orientation has been performed while maintaining matched upstream plasma parameters and target flux expansion. Initial results from Langmuir probes and infrared analysis do not show any significant difference in the divertor spreading parameter S, while fast camera analysis is still ongoing. However, according to [8], the inner divertor leg is expected to be more affected, as the κ and ∇p drifts are parallel when the leg is vertically oriented. A database analysis is currently underway, based on discharges in negative triangularity, to further investigate this effect. Finally, taking advantage of the new upper divertor shaping capabilities at ASDEX Upgrade, similar but less extensive scans are planned for the ASDEX Upgrade tokamak as well.
[1] M. A. Makowski et al, Phys. Plasmas 19, 056122 (2012)
[2] B. Sieglin et al 2013 Plasma Phys. Control. Fusion 55 124039
[3] M. Roberto, Phd Thesis, EPFL (2020)
[4] D. Brida et al 2025 Nucl. Fusion 65 026065
[5] A. Stegmeir et al 2018 Plasma Phys. Control. Fusion 60 035005
[6] S Ku et al 2006 J. Phys.: Conf. Ser. 46 87
[7] C.S. Chang et al 2017 Nucl. Fusion 57 116023
[8] N. Walkden, et al. Commun Phys 5, 139 (2022)
| Speaker's title | Mr |
|---|---|
| Speaker's Affiliation | Department of Physics, University of Milano-Bicocca, Italy |
| Member State or IGO | Italy |
