Fakultät für Physik und Astronomie

Physikalisches Kolloquium

Freitag, 14. November 2025 17:00 Uhr News from Wendelstein 7-X: Towards Clean Energy from Fusion

Prof. Dr. Thomas Klinger , Max-Planck-Institut für Plasmaphysik, Garching High performance steady state fusion plasmas in the superconducting stellarator device Wendelstein 7-X T. Klinger, Greifswald/Germany Max-Planck Institute for Plasma Physics, Wendelsteinstrasse 1, 117489 Greifswald The stable generation of high-temperature and low-density hydrogen plasmas (ion and electron temperature in the range 10-20 keV resp. 100-200 million degree Kelvin) is the basis for the use of nuclear fusion to generate heat and electric power. The most promising path is to use strong, toroidally shaped, twisted magnetic fields to confine the electrically charged plasma particles in order to avoid heat losses to the cold, solid wall elements. Two magnetic confinement concepts have proven being most suitable: (a) the tokamak and (b) the stellarator. The stellarator creates the magnetic field by external coils only, the tokamak by combining the externally created field with the magnetic field generated by a strong current in the plasma. “Wendelstein 7-X” is the most advanced large superconducting stellarator that operates at the Max Planck Institute in Greifswald. With 30 m3 plasma volume, 3 T magnetic field on axis, and 10 MW micro wave plasma heating power, hydrogen plasmas are generated that allow one to establish a technical and scientific basis for the extrapolation to a future fusion power plant. It is a unique feature of Wendelstein 7-X to be able to operate high-power hydrogen plasmas under steady-state conditions, more specifically for 1800 s (note that the world standard is now in the 10 s ballpark). Furthermore, Wendelstein 7-X has recently proven to be at par with tokamak plasma performance for long discharges. This talk provides a brief review of the principles of nuclear fusion and discusses the key physics subjects of optimized stellarators. We summarize the most important findings of the previous performance operation campaigns and put them into the international context of fusion research. An outlook is given towards fusion power as a building block of future energy supply of the world. [1] National Geographic, November Issue 2025 https://www.nationalgeographic.com/science/article/stars-nuclear-fusion-energy [1] T. Klinger et al., Nuclear Fusion 2019, 59(11) 112004 [2] A. Dinklage et al., Nature Physics 2018, 14(8) 855

Teilchenkolloquium

CP asymmetry in D0?K0SK0S

Dr. Giulia Tuci, Physikalisches Institut, Uni Heidelberg

Astronomisches Kolloquium

Dienstag, 11. November 2025 16:30 Uhr Origin of supermassive black holes from dense star clusters: Implications for the Local Universe and for JWST

Dominik Schleicher, Sapienza University of Rome Recent discoveries by JWST have provided significant insight into the building-blocks of the high-redshift Universe. A cornerstone is the detection of Young Massive Star Clusters at high redshift, with masses between 10^5 and 10^7 solar. The masses of these clusters exceed the masses of young star clusters in nearby galaxies and even those of the most massive globular clusters. Some of them were found to be very compact with half-mass radii of less than a parsec. In this talk, we show that such clusters provide ideal initial conditions to form massive black holes of ~10^5 solar masses via collision-based channels. For this purpose, we present direct N-body simulations with stellar evolution demonstrating the formation of intermediate-mass black holes from such initial conditions. The models are verified through the comparison with data in the Local Universe, particularly with Nuclear Star Clusters. We subsequently discuss the relevance and implications of these models for Little Red Dots (LRDs), a new population of very compact red galaxies discovered by JWST. We show that such LRDs potentially have ideal conditions to efficiently form supermassive black holes through collision-based channels, and compare the predictions of this channel with upper limits from X-ray stacking based on the Chandra Deep Field South. To arrange a visit with the speaker during the visit, please contact their host: Marcelo Alberto Cortes Vergara

Zentrum für Quantendynamik Kolloquium

Mittwoch, 12. November 2025 16:30 Uhr Adventures on the Road to an Erbium-Potassium Mixture

Dr. Rob Smith, Department of Physics, University of Oxford Adventures on the Road to an Erbium-Potassium Mixture Dr. Rob Smith Department of Physics, University of Oxford My talk will consist of three parts. First, I will present our measurements of the modification of transition temperature for Bose Einstein Condensation (BEC) due to dipole-dipole interactions. Second, I will discuss the challenges and progress towards, the realization of a tuneable box-trapped mixture of erbium and potassium. Lastly, I will give a brief overview of our future plans, including explorations of binary supersolids, turbulence and polarons in a dipolar environment.

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