Speaker: Dr. Thomas Klinger, Max-Planck-Institut für Plasmaphysik and Greifswald University
Title: Steady state and high performance plasmas on the superconducting stellarator device Wendelstein 7-X
Abstract: Stellarators have two well-known advantages: They have no current disruptions and they can operate the plasma in steady state. Another advantage is stable plasma operation at much higher densities, compared to tokamaks, which scales favourably in both confinement and triple product. The optimized superconducting stellarator device Wendelstein 7-X (major radius 5.5 m, minor radius 0.5 m, 30 m3 plasma volume, 2.5 T magnetic induction on axis) has a fully water-cooled first wall made of a metal/graphite material mixture, more specifically graphite heat shields and baffles and 10 island divertor modules equipped with carbon-fibre reinforced carbon targets. With presently about 8 MW microwave heating power and 5 MW neutral beam heating, high performance plasmas are generated that allow one to further extend the scientific basis for the extrapolation to a next step device. The new steady state extruder pellet injector allows for efficient plasma fueling and active density profile control. Controlled density peaking leads to reduced ion temperature gradient driven turbulence and thereby improved energy confinement, which resulted in new records in stellarator plasma performance. Plasma operation at reduced magnetic field strength (1.7 T magnetic induction) allows one to study finite- effects, e.g. electromagnetic instabilities and turbulence. Wendelstein 7-X is designed for steady-state high-power operation, more specifically for 1800 s at 10 MW input power with 18 GJ energy turnaround. The next milestone is 2 GJ, using more than 5 MW microwave heating power. Here the limiting factor is heat and particle exhaust via the island divertor.
This talk aims to give an overview of the present physics understanding and technology developments, required to establish a path towards steady state high performance plasma operation on optimized stellarators.
Bio: Thomas Klinger, born in 1965 in Eutin/Germany, studied physics at the Christian-Albrechts University of Kiel. After a research period in France he obtained his PhD in 1994 with a thesis on non-linear plasma dynamics. As a research assistant at the University of Kiel, Klinger was concerned with drift wave turbulence and nonlinear plasma structures. As visiting scientist he conducted research at the Alfvén Laboratory in Stockholm, the Centre de Physique Théorique and the Université Aix-Provence in Marseille and Max-Planck-Institute of Plasma Physics in Garching. He obtained his habilitation in 1998 with a thesis on the control of plasma instabilities. Shortly thereafter he was appointed Professor of Experimental Physics at the University of Greifswald, where he has headed the Institute of Physics as chair from 2000 till 2001. He is head of the "Stellarator Dynamics and Transport" Division and since 2005 scientific director of the project Wendelstein 7-X.
Event details: In-person seminars are only available to CU ID holders. At this time, Non-Columbia affiliates and the general public are only invited to participate remotely. Contact [email protected] if you would like the Zoom link for this seminar.