München 2019 – wissenschaftliches Programm
P 18.51: Poster
Donnerstag, 21. März 2019, 16:30–18:30, Foyer Audimax
An optimized geometry for high speed pellet guiding tube on ASDEX Upgrade — •Bernhard Ploeckl, Albrecht Herrmann, Holger Köhnlein, and Peter T. Lang — Max Planck Institute for Plasma Physics, 85748 Garching, Germany
Cryogenic pellet injection from the magnetic high field side will be the prime candidate to fuel future fusion power plants. The launching system on ASDEX Upgrade injects cryogenic hydrogen pellets with a speed up to 1000 m/s from the magnetic high field side of the tokamak using guiding tubes. Pellets passing the guiding tube are sliding on a gas cushion, generated by the Leidenfrost effect. The amount of the ablated gas depends on centrifugal forces, hence from curvature and speed. The actual trajectory has a rectangular cross section and is composed of a series of ellipses in order to generate the required 270° turn; the length is 17m. The last part of this track is marked by strong geometrical constraints from vacuum vessel port. The design presently in operation is composed by a sequence of three sections of ellipses, tangentially constant but discontinuous with regard to the curvature. These steps in curvature are supposed to limit the system performance. A new geometry has been designed using clothoids, a well-known method from civil engineering (e.g. railroad track design). Clothoids provide a smooth transition between the geometrical elements, keeping the curvatures continuously differentiable. The presented measure will help to improve pellet system performance on ASDEX Upgrade and provide knowledge for the design of pellet guiding tubes in future fusion devices.