Pulsed electric system for production and confinement of plasma in ETE (Spherical tokamak experiment)

Summary form only given. In this paper we present project and results of the Pulsed Electric System of the ETE tokamak. Tokamaks are experimental devices based on a vacuum chamber with toroidal geometry, inside of which plasmas of high temperature are generated and magnetically confined. For that, tokamaks possess a system of coils that generate the necessary magnetic and electric fields to firstly produce breakdown in the low pressure neutral gas and then to drive and sustain a current in the toroidal direction, this way creating a fully ionized plasma and heating it up to temperatures above 106 K. The magnitude of the electric power required to generate such magnetic fields is such that tokamaks are usually built to work in pulsed regime. The ETE project consists of the construction and operation of a spherical tokamak of small dimensions, even so with important parameters to explore the attractiveness of low aspect ratio configurations for the construction of future compact fusion reactors. As in any tokamak, in the operation of ETE the performance of the pulsed electric system ia of fundamental importance. We will describe ETE´s Pulsed Electric System configuration, composed of several pulsed power circuits based on energy storage capacitor banks, its Computerized Control System and a Pneumatic Safety System. The three fundamental pulsed power circuits of ETE are the Toroidal Field Circuit (50kAx1.25kV/spl times/380kJ), the Vertical Field Circuit (6kA/spl times/10kV/spl times/100kJ) and the Ohmic Heating Circuit (20kA/spl times/8kV/spl times/740kJ), where the parameters are given for the full configuration of ETE´s first phase, when plasma currents of 220kA/spl times/15ms should be obtained. A second phase with currents reaching above 400kA is planned. So far, a system with about 10% of total available energy, enough to produce discharges with plasma currents around 50kA, has been built and tested, producing ETE´s first tokamak plasmas.