Optical and Electrical Diagnostics for the Investigation of Edge Turbulence in Fusion Plasmas

The new, 2D and fast diagnostic system has been developed for studying the dynamic structure of plasma turbulence; it will be used in the edge of the RFP (reversed-field pinch) toroidal devices. The system consists of a gas-puffing nozzle, 32 optical channels measuring H¥á emitted from the puffed gas (to study the optical emissivity of turbulent patterns and to analyse structures in two dimensions) and an array of Langmuir probes (to compare the turbulent pattern with the optical method and to measure the local plasma parameters). The diagnostic arrangement covers the observation region of about 8 cm along the toroidal direction and 4 cm in the radial one, by means of three optical fans directed at 38¢ª to each other. The central fan consists of 16 lines directed along the radial direction, while the lateral two have 8 lines each and reach the observation area through two mirrors mounted inside the access pipe. In the focal region the spacing between adjacent lines of sight is 5 mm and the beams have a diameter between 3 to 4 mm. The light is collected by the optics at the port window and sent through optical fibers to two detectors, each equipped with an interference filter for the H¥á line and a 16 channel photomultiplier array. The Hydrogen gas is filled in a reservoir at a pressure of 1 to 2 bars and the flux is regulated by a piezo electric valve.