Review article on density and radiation limits in tokamaks published
08/04/2025
Operating a tokamak at high confinement, high heating power, and high density is likely to encounter the H-mode density limit (HDL), making it a central issue for magnetically confined fusion. Despite its importance, the HDL is far from being as thoroughly investigated and understood as its counterpart in the L-mode. There are several mechanisms that limit the achievable density, and theories have been developed that show excellent agreement with the experiments. However, when examining the observations in the various tokamaks, these are contradictory. But if these are viewed as competing mechanisms that limit the achievable density of the H-mode, the observations can be reconciled. The article was recently published in Nuclear Fusion.
Tabletop protoplanetary disk
07/03/2025
We have succeeded in setting up a laboratory experiment with which we can simulate Keplerian rotation, which is relevant for astrophysical accretion disks. It is based on a tornado in which the rotation is introduced by counter-rotating water jet streams. The resulting hyperbolic free surface acts as an effective gravitational potential. Using tracer particles, the Keplerian rotation profile could be demonstrated.
This work was recently published by Stefan Knauer in Monthly Notices of the Royal Astronomical Society.
07/21/2025
Development of profiles and fluctuations approaching the L-mode density limit in ASDEX Upgrade
07/15/2025
The density limit in discharges in the L-mode is disruptive and before that a MARFE occurs when the plasma is cooled down. But how does this happen, what happens before it? The chain of events before the MARFE has been studied in detail in ASDEX Upgrade by Gustavo Grenfell and the results have recently been published in Nuclear Fusion.
Peter Manz introduced the SepOS at the Festival de Théorie
07/04/2025
This year's theme of the Festival of Theory in Aix-en-Provence is “Turbulent Boundary Layers”. What could be more appropriate than the Separatix Operational Space (SepOS) concept, which describes the operational boundaries of the tokamak based on the conditions at the outer rim, the last closed flux surface. Peter Manz gave an overview presentation. Peter Manz and Stefan Knauer thank the organizers for the extraordinary scientifically stimulating environment.
Azmirah Ahmed joins the group
06/2025
Azmirah Ahmed from CPP-IPR Sonapur, Assam in India joined our working group at the beginning of June. She is part of the Max Planck Fellow group and will be working on Wendelstein 7-X as well as on the experiments at our University.