Recent developments for plasma edge diagnostics using atomic beams

Abstract

Li-atom beams with velocities of 1.5 × 10 5 cm/s and 1× 10 6 cm/s have been used to measure n e profiles in the density range 10 11–10 13 cm −3 from the Li line emission with a spatial resolution of about 1 mm. Injecting in addition a different type of atoms, the ionization rate of which shows a strong dependance on the electron temperature in the interesting range of 5–100 eV (e.g. carbon and helium), also radial T e profiles are obtained. A high intensity 30 keV Li beam is employed to measure radial profiles of impurity ion concentrations (e.g. He, C, 0) by charge exchange recombination spectroscopy. For the different purposes several types of injectors have been developed: thermal beams using ovens, suprathermal beams using laser ablation techniques, and a high energy beam using a plasma ion source in combination with a charge exchange cell. They are located at different poloidal and toroidal positions. The spatial line emission profiles of the beams are recorded either by Si diode array cameras or by a photomultiplier in combination with a scanning mirror so that a spatial resolution better than 2 mm is achieved. The combination of all these systems delivers information about the structure of the TEXTOR boundary layer in poloidal and toroidal direction.