In order to measure the plasma temperature and density in the spherical tokamak ETE, a one-channel Thomson scattering system was implemented. During the upgrade of capacitor banks and optimization since the beginning of operation, the plasma pulse duration has increased from 1.5 ms up to 12 ms with plasma currents varying from 10 kA to 60 kA. During this phase, the electron temperature was increased from 20 eV to 160 eV with densities as high as 3.5×10(19) m-3. Presently, the Thomson scattering diagnostic is being upgraded based on the time-delay technique, that consists in usingfi bers of different lengths to transmit the scattered light signals to the same polychromator. This system will allow measurements of electron temperature and density profi les with ten spatial points per laser shot and per polychromator. This work describes in details the Thomson scattering system, presents a selection of results obtained by this system since the initial phase of operation, and shows details of the proposed upgrade of the Thomson scattering system.

This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the steps in the development of the ETE (Experimento Tokamak Esférico) project, its research program, technical characteristics and operating conditions as of December, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil.