First results from the JET time of flight neutral particle analyser

A Time of Flight (TOF) Neutral Particle Analyser (NPA) has been recently installed at JET. The system consists of a single NPA based on the measurement of the time of flight of the analysed particles, so that a random background can be discriminated by a standard coincidence technique. The analyser energy range is 0.5-200 keV and it has been absolutely calibrated for hydrogen, deuterium and helium neutrals. The analyser is located at the bottom of the machine and its line of sight follows a vertical chord passing at a major radius R = 3.1 m on the equatorial plane of the torus. The neutrals coming from the plasma are ionised in a gas stripping cell and energy analysed with a cylindrical electrostatic plate system. The inner cylindrical plate is terminated at both ends by two flat electrodes and is set to a positive potential. This configuration provides the focalization of the ion beam from the stripping cell in both planes parallel and perpendicular to the cylinder axis. (author) 1 ref., 8 figs