SMuK 2021 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 5: Poster I
P 5.34: Poster
Dienstag, 31. August 2021, 14:00–16:00, P
Performance of neutral pressure gauges using LaB6-emitters in deuterium plasmas — •Victoria Haak1, Uwe Wenzel1, and Gen Motojima2 — 1Max Planck Institute for Plasma Physics, Greifswald, Germany — 2National Institute for Fusion Science, Toki, Japan
Neutral pressure gauges using a LaB6-crystal as an emitter, an advanced type of neutral pressure gauge optimized for the use in high magnetic fields are used to measure the neutral gas pressure in fusion experiments. They were successfully operated in hydrogen plasmas in Wendelstein 7-X (W7-X) during OP1.2b [1]. Due to the low heating current of 2-2.5 A, LaB6 neutral pressure gauges present a promising concept for measurements of the neutral gas pressure in future fusion devices. Two LaB6-neutral pressure gauges were installed and tested in the Large Helical Device for the last two campaigns in order to study the effect of neutrons on the electron emission properties of LaB6.
Both crystals showed stable electron emission during operation in hydrogen and helium atmosphere and were operated at a low heating current of 1.7 A. One of the emitters experienced an increase of the heating current from 1.7 to 4 A during deuterium operation. Apart from damage to the crystal, the neutral pressure gauge cannot be reliably used for measurements once the heating current reaches a given limit. As stability of the emission properties is essential for the use of LaB6 in neutral pressure gauges, degradation of the emission properties is studied in this contribution, in particular the role of neutron damage.
[1] U. Wenzel et al, Rev. Sci. Instrum., 90, 123507 (2019).