High voltage electrical system of 8.56 GHz CW klystron for electron cyclotron heating on QUEST spherical tokamak.

• New high voltage power supply (PS) for a klystron has been developed. • This PS is used for the electron cyclotron heating (ECH). • 8.56 GHz-RF with the PS will be a promising ECH system in QUEST spherical tokamak. • An IGBT and a reactor can shut down the PS quickly to protect the klystron. • AC switching has been set up for the overload and overheat of the PS. A high voltage DC power supply for the cathode of the 8.56 GHz CW klystron has been set up for electron cyclotron heating (ECH) in steady state tokamak operation on QUEST spherical tokamak. The power supply is equipped with an IGBT array and a reactor for fast shutoff of the voltage in 10 μs, where the influx of electric energy at the short circuit is limited to 5 J. AC switches also have been installed in the three-phase power lines. High voltage relays are useful to save electric energy consumption. Fast three-phase AC switching by IGBT-stack is applicable to reduce the electric load of the components of the klystron power supply. [ABSTRACT FROM AUTHOR]