Speaker: Dr. Tim Happel, Max Planck IPP
Title: "Overview of Recent Physics Investigations from the ASDEX Upgrade Tokamak"
Abstract: ASDEX Upgrade is a tokamak (R = 1.65 m, a = 0.5 m) operated since 1991 in Garching, Germany. It is being operated by three experimental physics divisions. This talk gives a general overview of ASDEX Upgrade, with a focus on the contributions by the Plasma Dynamics division.
ASDEX Upgrade has recently been equipped with additional in-vessel coils, enabling alternative divertor configurations. The coils were bent in-vessel during a 2-year shutdown, and they can now be used to create and modify standard, snowflake and compact radiative divertor configurations. Since tiles are not inclined toroidally, discharges can be run in both helicities. First results scanning the divertor coil currents are shown, showing power spreading in the SOL. The upper divertor is well equipped with diagnostics, and a new two-color thermal helium beam diagnostic for background and fluctuation measurements is presented.
Furthermore, an overview of recent studies regarding turbulence and negative triangularity is given. Here, a detailed validation study is presented in detail, in which experimental density and electron temperature turbulence measurements were compared with gyrokinetic simulations, yielding almost perfect agreement. Furthermore, a completely detached ELM-free discharge going from stationary L-mode into stationary H-mode is presented. The talk finishes by presenting the latest results on negative triangularity investigation, where the L-H transition could be avoided, in agreement with ideal-MHD stability calculations.
Bio: Tim Happel studied physics in Kiel in Germany from 2000 to 2006. During his diploma thesis, he gained his first insight into fusion research at the stellarator TJ-K. He worked on the characterization of micro-instabilities at the transition from closed to open field lines.
For his PhD, Tim Happel went to the Spanish fusion research laboratory at CIEMAT in Madrid, where the second largest stellarator in the world, TJ-II, is operated. There, he developed a Doppler backscattering system, enabling him to successfully observe plasma flows and their interaction with turbulent structures. For this work, Tim Happel received the Itoh Prize for Plasma Turbulence.
After completing his PhD, Tim Happel moved to the Max Planck Institute for Plasma Physics in Garching near Munich in 2011, where he continued his research into plasma flows at the ASDEX Upgrade tokamak. In this context, he has led the Turbulence research group since 2023. At IPP, he expanded his studies to include tokamak operation modes with enhanced energy confinement. He is particularly interested in the Improved Energy Confinement Mode (I-Mode) and plasmas with negative triangularity.
Since 2024, Tim Happel is scientific member of the Max Planck Society and head of the Plasma Dynamics Division at the Max Planck Institute for Plasma Physics in Garching near Munich. Since April 2026, he holds the Chair of Plasma Dynamics at the Technical University of Munich.
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