A seminar by Christian Theiler
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To limit divertor target heat loads, future magnetic-confinement fusion reactors will likely need to operate in a detached divertor regime. Achieving such a highly dissipative state without degrading plasma core performance remains a key challenge.
Optimising divertor magnetic topology and wall geometry through so-called Alternative Divertor Configurations (ADCs) offers significant potential to address this issue. These configurations range from relatively modest modifications, such as increased divertor leg length or enhanced flux expansion, to more complex geometries featuring additional or higher-order X-points.
The Tokamak à Configuration Variable (TCV) at EPFL, with its exceptional shaping flexibility and comprehensive diagnostic set, is uniquely suited for proof-of-principle studies of ADCs and for validating models used in reactor extrapolation. In this presentation, we will review recent progress in ADC studies on TCV. We will outline the motivation for the ongoing divertor upgrade, which aims to test the tightly-baffled, long-legged divertor concept that combines favourable geometrical features with engineering simplicity. Based on TCV experiments and modelling, we will also discuss in detail the expected benefits of a more complex configuration: the X-point target divertor foreseen for SPARC.
Christian Theiler obtained his Master's degree in physics from ETH Zurich in 2007 and his PhD from EPFL in 2011. He then joined MIT as a postdoctoral associate to work on the Alcator C-Mod tokamak. In 2014, he returned to EPFL as a EUROfusion fellow, to join the TCV tokamak team. Two years later, he was named Tenure Track Assistant Professor in Plasma Physics at EPFL. Christian's research focuses on tokamak boundary physics and related diagnostic techniques. He has contributed to the understanding of the formation, propagation, and control of turbulent plasma structures, called blobs, and gained new insights on the structure of transport barriers in the plasma periphery in different high-confinement regimes. His current research focuses on detachment physics and turbulence characteristics in conventional and alternative divertor magnetic geometries. In 2024, Christian was promoted to Associate Professor at EPFL.
