Wendelstein 7-AS

Wendelstein 7-AS
Name	Wendelstein 7-AS
Country	West Germany
Institution	Max Planck Institute for Plasma Physics
Location	Garching bei München
Type	Stellarator
Operation	1988–2002
Major components	Precision magnetic coils, vacuum vessel, cryogenics

Wendelstein 7-AS

Wendelstein 7-AS was an experimental stellarator device operated by the Max Planck Institute for Plasma Physics at a site near Garching bei München, designed to investigate advanced magnetic confinement concepts and plasma transport. The project involved collaborations with institutions such as KfK and engineering groups from Siemens and informed later machines through studies linked to Wendelstein 7-X, ASDEX Upgrade, and the international ITER program. It addressed key questions raised by earlier devices like Wendelstein 7-A, Heliotron-E, LHD, and TJ-II while interacting with theoretical work from groups at Princeton Plasma Physics Laboratory, Culham Centre for Fusion Energy, and MIT Plasma Science and Fusion Center.

Introduction

Wendelstein 7-AS operated as a medium-sized experimental fusion reactor in the tradition of European and Japanese stellarator efforts such as Heliotron-J and CHS. Funded and managed primarily by the Max Planck Society, the project drew on design heritage from Wendelstein 7-A and technical partnerships with firms like Siemens and institutions including Stuttgart University and Technical University of Munich. Its mission aligned with broader initiatives exemplified by Euratom cooperation, agenda items at EUROfusion meetings, and comparative studies with tokamak programs exemplified by JET and TFTR.

Design and Construction

The device featured complex, non-planar magnetic coils engineered using numerical tools developed by groups at IPP Garching and software contributions inspired by algorithms from Lawrence Livermore National Laboratory and CEA. Manufacturing involved precision machining contractors with backgrounds from Krupp and measurement approaches from metrology groups connected to PTB. The vacuum vessel, cryogenic support, and power systems reflected engineering practices seen at ASDEX, DIII-D, and TFTR, while diagnostics benches were patterned after systems at Alcator C-Mod and NSTX. Funding and project governance intersected with administrative structures similar to those at Max Planck Institute for Plasma Physics, Deutsches Elektronen-Synchrotron, and regional stakeholders in Bavaria.

Stellarator Configuration and Magnetic Geometry

The magnetic geometry implemented a modular, quasi-optimized stellarator topology drawing on theoretical concepts developed by proponents of three-dimensional confinement such as LHD designers and theorists influenced by Boozer coordinates and work from Hastie and Helander. The coil set produced helical and toroidal field components comparable in conception to specifications studied at NIFS and Kyoto University, and modeling used codes from European Transport Solver efforts and numerical methods related to those at Princeton University and Culham. The device probed neoclassical transport regimes and ripple effects investigated alongside experiments at DIII-D and ASDEX Upgrade, and it served as a platform for validating analytic approaches advanced by researchers at IPP Garching and Max Planck Institute for Plasma Physics.

Operational History and Experimental Results

Commissioned in the late 1980s, the device ran campaigns through the 1990s producing results on confinement, bootstrap currents, and impurity behavior that informed projects at Wendelstein 7-X and theoretical programs at CEA and Politecnico di Milano. Experimental partnerships included diagnostics development with groups at Culham Centre for Fusion Energy and comparative analyses with tokamak datasets from JET and TFTR. Publications arising from campaigns interacted with the literature produced by teams at Princeton Plasma Physics Laboratory, Los Alamos National Laboratory, and Oak Ridge National Laboratory. Results on island formation, edge transport, and plasma rotation contributed to international discussions at conferences such as the European Physical Society Conference on Plasma Physics and meetings organized by the IAEA.

Diagnostics and Instrumentation

Diagnostics suites combined microwave interferometry and scattering techniques similar to instruments used at Alcator C-Mod and TFTR, along with spectroscopy methods developed in collaboration with institutes like University of Oxford and Imperial College London. Magnetic probe arrays, vacuum gauges, and bolometry systems paralleled approaches at DIII-D and ASDEX Upgrade, while control and data acquisition used architectures influenced by CERN and computing groups at Max Planck Society. Teams from Forschungszentrum Jülich and University of Stuttgart contributed to diagnostic calibration, and work with laser scattering drew on expertise from MIT and UCLA.

Contributions to Fusion Research and Legacy

The machine's legacy includes informing the coil optimization and physics rationale for Wendelstein 7-X and contributing empirical data relevant to design choices debated within EUROfusion and at ITER planning workshops. It fostered careers of researchers who moved to institutes such as IPP Garching, Culham Centre for Fusion Energy, and Princeton Plasma Physics Laboratory, and influenced numerical toolchains used by groups at CEA, LLNL, and Oak Ridge National Laboratory. Technical lessons on three-dimensional coil manufacturing, metrology, and vacuum systems fed engineering practices at Siemens and industrial partners, while experimental findings on transport and stability informed comparative studies with LHD, TJ-II, and tokamak devices like JET. The project remains cited in reviews and textbooks alongside work from Spitzer, Boozer, and Helander for its role in advancing stellarator physics and fusion research.

Category:Stellarators Category:Max Planck Institute for Plasma Physics