Mechanical Stability of Filaments for ITER Diagnostic Pressure Gauges Relating to Creep and Fatigue

• Published in: IEEE transactions on plasma science Vol. 48; no. 6; pp. 1661 - 1665
• Main Authors: Arkhipov, Alexey, Mackel, Felix, Haas, Gunter, Koll, Jurgen, Meister, Hans, Seyvet, Fabien, Terron, Santiago, Andrew, Philip
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Creep; Cyclic loads; Diagnostic systems; Direct current; Electron emission; Fatigue; Fatigue failure; Fatigue tests; Filaments; Force; Gas pressure; Gauges; Heating systems; High temperature; Hot cathodes; International Thermonuclear Experimental Reactor (ITER); Magnetic fields; Magnetomechanical effects; Neutral gases; Plasma (physics); plasma diagnostic; Pressure gages; pressure gauge; Pressure gauges; Prototypes; Superconducting magnets; Thermal stress; tungsten filament
• ISSN: 0093-3813; 1939-9375
• DOI: 10.1109/TPS.2020.2968168

Diagnostic pressure gauges (DPGs) shall provide measurements of the neutral gas pressure in various locations of the International Thermonuclear Experimental Reactor (ITER) vacuum vessel. This parameter is essential for the basic control of ITER operation as well as for input to physics models of the plasma boundary. The hot cathode (filament) is the component of the DPG sensor that is exposed to most demanding loads. In order to reach the required electron emission from the filament, it has to be heated to high temperatures by a direct current. As a result, thermal stresses appear, and in the presence of a magnetic field, additional mechanical stresses caused by Lorentz forces arises. On the one hand, due to a large number of pulses foreseen in ITER, this load will be cyclic, which may result in filament failure caused by fatigue. On the other hand, the longest pulses in ITER are expected to be in the order of 30 min, and thus, filaments could fail due to creep. In order to verify that the filament of the DPG sensor can withstand fatigue and creep dedicated experiments have been conducted. Results of these tests are discussed in this article.