Speaker: Philip Drews, Heinrich-Heine-Universitä Düsseldorf
Abstract: The Langmuir probe diagnostic has been present since the discovery of the plasma state of matter.
They are still used in contemporary experiments like EAST, JET or W7-X, both fixed on plasma facing components and mounted on manipulators for profile measurements.
The diagnostic can observe the electron temperature and density, as well as flow velocities and information about the turbulence in the plasma.
The main advantages of the Langmuir probe are the simple setup, analysis, as well as high spatial and temporal resolution. While the utility of the diagnostic is obvious, limitations and pitfalls of Langmuir and other probe measurements should be highlighted.
The presentation will focus on results obtained from diagnostics probes utilized in conjunction with the Multipurpose Manipulator (MPM) system at W7-X.
Furthermore, the practical aspects of advanced diagnostic concepts like the retarding field analyzer for ion temperature measurements are discussed.
A new probe head for HSX was developed for the measurement of plasma edge parameters, like the electron density and temperature, the ion temperature and turbulence. The experiences from both W7-X and HSX were used to design a probe that should be minimally invasive during the measurement and provide good coverage of the aforementioned plasma parameters.
Finally, the integration of Probe measurements at W7-X into the wider picture of other diagnostic measurements and the use of modelling will be presented.