First Switching Network Unit for the JT-60SA superconducting Central Solenoid

•The manufacturing of the first SNU for JT-60SA was completed.•The SNU can interrupt a direct current up to 20kA in less than 100μs producing a voltage of 5kV.•An exhaustive set of tests were performed on single devices and on the complete SNU.•The full current and voltage tests were performed in FTU reproducing the operating conditions.•The tests demonstrated the capabilities of the SNU to comply with the JT-60SA requirements. This paper presents the main characteristics and test results of the first Switching Network Unit (SNU) of the Central Solenoid for plasma initiation in the international experiment JT-60SA. The SNU can interrupt a direct current up to 20kA producing at its terminals a voltage up to 5kV with a rise time shorter than 100μs. This is obtained by synchronizing the operation of a light electromechanical contactor with a static switch in order to combine the benefits of both devices. Even though the design was based on the JT-60SA specifications, the adopted solutions can be extended to many fusion and industrial applications. Due to the novelty of the developed solutions, an exhaustive set of tests were performed both on relevant single devices and on the complete SNU, even at full current, full voltage and full energy. The most relevant tests were performed using the Frascati Tokamak Upgrade (FTU) facilities reproducing the JT-60SA operating conditions. As the presented tests demonstrated the capabilities of the SNU to comply with the requirements, the manufacturing of the remaining three Central Solenoid SNUs can proceed and is expected to be completed by 2015.