As director of the Max Planck Institute for Plasma Physics, Sibylle Günter oversaw the completion and operation of Wendelstein 7-X—the world's most advanced stellarator—while advancing the theoretical physics of magnetically confined plasmas.
The stellarator, once considered the eccentric cousin of the tokamak, has undergone a scientific rehabilitation in the twenty-first century. No one deserves more credit for that resurgence than Sibylle Günter, who served as Scientific Director of the Max Planck Institute for Plasma Physics (IPP) from 2011 to 2023, guiding the institute through the commissioning and early scientific exploitation of Wendelstein 7-X (W7-X)—the largest and most sophisticated stellarator ever built.
Günter's scientific credentials are rooted in theoretical plasma physics, with particular expertise in magnetohydrodynamics (MHD), magnetic reconnection, and transport phenomena in toroidal plasmas. Her research on neoclassical tearing modes and their stabilization in tokamaks contributed to understanding one of the key instabilities that can degrade confinement and trigger disruptions.1 This theoretical depth gave her a unique vantage point from which to assess the promise of the stellarator concept, which avoids many of the instability challenges inherent to tokamaks by generating the confining magnetic field entirely through external coils.
W7-X achieved first plasma in December 2015, and its subsequent experimental campaigns have progressively validated the physics principles underlying its design. The machine's magnetic field geometry was optimized computationally over decades to minimize neoclassical transport—the collisional losses that historically plagued stellarators and made them uncompetitive with tokamaks in energy confinement.2
Results published under Günter's leadership confirmed that W7-X achieved its design goals: the magnetic field configuration matched computational predictions with extraordinary precision, and the measured neoclassical transport was consistent with the optimized geometry.3 These results established that computational optimization of three-dimensional magnetic fields is not merely a theoretical exercise but a practical engineering tool—a finding with implications far beyond W7-X itself.
Günter's leadership extended well beyond W7-X. As IPP director, she oversaw a dual programme that included both the stellarator effort in Greifswald and the ASDEX Upgrade tokamak in Garching. Managing these complementary programmes required balancing competing demands for resources and attention while maintaining scientific coherence across the institute. She also championed the development of computational plasma physics capabilities at IPP, recognizing that the future of fusion research would depend increasingly on high-fidelity simulation.4
Under her guidance, IPP expanded its collaborations with international partners and contributed significantly to the ITER physics programme through ASDEX Upgrade experiments on ELM control, disruption mitigation, and advanced plasma scenarios.
Günter's tenure coincided with—and helped catalyze—a broader reassessment of the stellarator's role in fusion energy. The success of W7-X has inspired new stellarator concepts in the private sector and renewed interest in stellarator research at institutions worldwide. The demonstration that computational optimization works in practice has opened design possibilities that were unimaginable when W7-X was first conceived in the 1980s.5
As the fusion community debates the relative merits of tokamaks, stellarators, and alternative concepts, Günter's contribution has ensured that the stellarator path rests on solid experimental and theoretical foundations.