Hannover 2016 – scientific programme
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P: Fachverband Plasmaphysik
P 26: Poster Session-Plasma Diagnostics
P 26.20: Poster
Thursday, March 3, 2016, 16:30–19:00, Empore Lichthof
A phased array antenna for Doppler reflectometry in ASDEX Upgrade — •Stefan Wolf1, Carsten Lechte1, Walter Kasparek1, Pascale Hennequin2, Garrard Conway3, Tim Happel3, and ASDEX Upgrade Team3 — 1IGVP, Universität Stuttgart, D-70569 Stuttgart, Germany — 2Laboratoire de Physique des Plasmas, CNRS, Ecole Polytech., F-91128 Palaiseau, France — 3Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
In a toroidal plasma, Doppler reflectometry (DR) allows investigating electron density fluctuations with finite k⊥. The injected microwave beam’s frequency determines the radial position of the probed region, its tilt angle selects the wavenumber satisfying the Bragg condition for backscattering. The rotation velocity can be calculated from the Doppler shift of the backscattered signal’s frequency. By varying the injected frequency, radial profiles can be reconstructed. Varying the tilt angle resolves the k⊥-spectrum of the fluctuations. For DR, a pair of phased array antennas (PAAs) has been designed, built, and installed in the ASDEX Upgrade tokamak. Beam steering is done by slightly changing the injected frequency, thus, the PAAs do not need any movable parts or electronics inside the vacuum vessel. From 75 to 105 GHz, the PAAs feature 13 frequency bands, each with an angular scan range of −20 to +20∘. So, for each angle, there are 13 radial positions to be probed. The results from PAA characterisation, commissioning, and first DR measurements will be presented. This work was performed in the framework of the Helmholtz Virtual Institute on plasma dynamical processes and turbulence using advanced microwave diagnostics.