Pop-up Langmuir probe diagnostic in the water cooled divertor of Wendelstein 7-X

Pandey, A.; Bohm, S.; Carls, A.; Cordes, C.; Endler, M.; Fellinger, J.; Freundt, S.; Gallowski, K.; Hammond, K.; Hathiramani, D.; Isberner, G.; Kallmeyer, J. P.; Krause, M.; Kügler, J.; Otte, M.; Pedersen, T. S.; Rondeshagen, D.; Ruhnau, J.; Schröder, T.; Sieber, T.; Wendorf, J.

doi:10.1063/5.0188738

Title: Pop-up Langmuir probe diagnostic in the water cooled divertor of Wendelstein 7-X

Journal Article · 02 April 2024 · Review of Scientific Instruments

DOI: https://doi.org/10.1063/5.0188738 · OSTI ID:2341804

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Max Planck Institute for Plasma Physics, Greifswald (Germany)
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Type One Energy, Madison, WI (United States)

The design, development, and successful implementation of pop-up Langmuir probes installed in the water-cooled divertor of W7-X are described. The probes are controlled by drive coils (actuators) installed behind the divertor plates. These drive coils make use of the magnetic field in W7-X to move the probe tips into and out of the plasma. The drive coils were installed in the vacuum vessel after extensively testing the durability of the coils and analyzing the criteria for safe operation. The probe design is carefully tailored for each of the 36 probe tips in order to be suitable for the different magnetic field configurations used in W7-X and ensure that the probes do not present leading edges to the magnetic flux tubes. An electronic bridge circuit is used for measurement to compensate for the effects of signal propagation time on the long cable lengths used. The diagnostic is integrated with the segment control of W7-X for automated operation and control of the diagnostic. The evaluation of the results from the plasma operation is presented after accounting for appropriate sheath expansion for negative bias voltage on the probes.

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Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Contributing Organization:: W7-X Team

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 2341804

Journal Information:: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 4 Vol. 95; ISSN 0034-6748

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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