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W7-X magnetic diagnostics: Rogowski coil performance for very long pulses
Andreas Werner1, Michael Endler, Joachim Geiger
1EURATOM Association, Max-Planck Institut fuer Plasmaphyisk, Wendelsteinstrasse 1, 17491 Greifswald, Germany.
The Review of Scientific Instruments
|December 3, 2008
Summary
Stellarators like Wendelstein 7-X minimize plasma currents for stable magnetic fields. Precise X-point control requires accurate current detection using new Rogowski coils.
Area of Science:
- Fusion energy research
- Plasma physics
- Magnetic confinement fusion
Background:
- Stellarators offer currentless operation for magnetic field generation.
- Wendelstein 7-X (W7-X) minimizes pressure-driven currents (bootstrap, Pfirsch-Schluter).
- HELIAS-type stellarators feature low magnetic shear for boundary islands.
Purpose of the Study:
- To investigate the influence of small net plasma currents on W7-X's diverting magnetic field structure.
- To enable precise X-point control for favorable edge plasma states.
- To ensure reliable stabilization of plasma currents within 1 kA accuracy for over 2000 seconds.
Main Methods:
- Minimizing pressure-driven currents in W7-X's optimized magnetic configuration.
- Utilizing adaptive controllers for precise X-point stabilization.
- Developing reliable current detection methods, including Rogowski coils.
Main Results:
- Small net plasma currents significantly influence the diverting magnetic field structure.
- W7-AS divertor data showed X-point location sensitivity to edge plasma conditions.
- Initial testing of W7-X Rogowski coils demonstrated integral performance and sensitivity.
Conclusions:
- Precise X-point control is crucial for optimizing plasma conditions in W7-X.
- Reliable current detection, via Rogowski coils, is essential for achieving stable plasma operation.
- The development and testing of Rogowski coils are a key step towards W7-X's operational goals.
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