Operation of an RF Modulated Thermionic Electron Source at TRIUMF

The electron source in the TRIUMF ARIEL project is a gridded dispenser cathode. The cathode is biased at -300kV, and the grid requires a RF control signal of up to 150V at 650 MHz. The required RF power is approximately 20 W and is provided by an RF amplifier located outside the gun vessel. This RF power is coupled into the gun circuit through a ceramic transmission line. The design of this ceramic transmission line, as well as the impedance transformation circuit which provides both the impedance matching and the dc powers to the gun assembly are described.