Speaker
Nikola Jaksic
(Max Planck Institute for Plasma Physics)
Description
“This project has received funding from the Euratom research and training programme 2014-2018”
In plasma fusion research the neutral gas density is usually measured using hot cathode ionisation gauges which are modified for the application in high magnetic fields and for a measurement range between 10-3-3 Pa and 20 Pa. For obtaining sufficient electron emission, high temperatures in the order of 1800 K are required and thus high usually direct currents for heating. To compensate for the induced Lorentz-forces, the filament must be relatively thick to provide sufficient mechanical stability which implicates increases of heating currents.
The heating current could be reduced by using a thinner filament in combination with alternating current with suitably chosen frequency to reduce mechanical stresses. To estimate the suitability of such a solution a feasibility study by means of numerical methods has been carried out. The main subject of the investigation was the hot-filament for which alternating current has been used as power source. The geometry of the pressure gauge filament used in the analysis is based on the ASDEX pressure gauge which operates with direct current.
This paper provides first of all the main guidelines and features important in developing a pressure gauge filament heated by alternating current from the mechanical point of view. Exemplary, two different filament designs have been evaluated. Concerted multiphysics numerical analyses needed for this development are presented. The analyses, beginning with thermomechanical followed by electrodynamic and finally structural dynamic analysis are described. For these analyses the commercial numerical analysis package ANSYS including the MAXWEL extension have been used. Finally, the important issues for developing such a filament conceptual design like fatigue, creep, evaporation and aging of the filament are discussed as well.
Co-authors
Andrea Scarabosio
(Max Planck Institute for Plasma Physics, Garching, Germany)
Hans Meister
(Max Planck Institute for Plasma Physics, Garching, Germany)
Nikola Jaksic
(Max Planck Institute for Plasma Physics, Garching, Germany)
