Baking of the vacuum vessel prototype of the Spanish Stellarator with a control system based on neural network

To bake uniformly, up to 150°C, the vacuum vessel of the Spanish Stellarator TJ-II represents a difficult task to be demonstrated. In order to study the temperature distribution in the vessel, a prototype of this vacuum vessel, mounted in a stainless steel structure, has been heated by means of electrical panels and eddy currents. The induction heating system is provided applying 498 A/11.7 V at 50 Hz to the toroidal field coil located in the middle of the vessel prototype. Practically, this system only heats adequately the rings and poorly the so called “groove” of the vacuum vessel. On the contrary, the electrical heaters, with a power density of 0.5 W/cm² , heat the external part of the sectors and ports. The high density of temperature sensors ensures the uniformity of the heating process during the long heating cycles, making advisable a fault-tolerant control system based on Artificial Neural Networks (ANNs) that implements the control loop to regulate and protect both heating systems. This paper deals with the results of this experiment