Experimental investigation of Fast ions transport in TORPEX

Full text: In fusion machines, fast ions may be introduced by ICRH, NBI and burning plasma sources. Fast ion transport in interchange-dominated plasmas is investigated in the basic toroidal plasma device TORPEX. The experimental setup consists of a miniaturized lithium 6+ ion source, which emits fast ions with energies up to 1 KeV, and a double gridded energy analyzer mounted on a 2D movable system. A toroidally movable system for the fast ions source, allowing the reconstruction of the 3D fast ions profile, is presently under development. The fast ions current profile is measured using synchronous detection by applying a modulated biasing voltage to the source. An analog lock-in amplifier has been developed, which allows removing capacitive noise due to the modulation. In the 2D configuration, we can characterize both vertical and radial transport of the fast ions, influenced by the magnetic field geometry and plasma perturbations from the ideal interchange instability. Preliminary results and future developments will be discussed. (author)