Prebaking of T-15MD vacuum vessel.

• The purpose of prebaking of the vessel is to check the quality of the numerous welds. • The maximal baking power was 65 kW. • The maximal temperature of vacuum shell was 187 °C. • The difference between maximal and minimal temperatures of vessel shell was 60 °C. • After the end of baking, no leaks were found in shell welds. Presently, the Tokamak T-15MD is being built in the NRC "Kurchatov Institute". The vacuum vessel was manufactured and passed the preliminary vacuum tests at the plant in St. Petersburg (Efremov Institute) in 2016. Vacuum vessel consists of toroidal shell made from 321stainless steel of 5 mm and 8 mm thickness, horizontal and vertical ports (152 in total), in-vessel elements. The vessel volume is 47 m3 and the surface square faced to plasma is ˜200 m2. The purpose of prebaking of the vacuum vessel is to check the quality of the numerous welds. To bake the vacuum vessel up to 220 °C at the plant in Bryansk, the Ohmic heaters have been laid on vessel shell surface both outside and inside. The thermal insulation (basalt wool) was applied on the outer surface of the vessel. The vessel's surface temperature was controlled by thermocouples. The currents in heaters was regulated by four thyristor regulators. The temperature data were processed and stored using the data acquisition system. [ABSTRACT FROM AUTHOR]