Simulation design of a high power CW klystron

A new continuous-wave (CW) klystron for use in TOKAMAK is currently under development at IECAS. Numerical analysis has been carried out in order to meet all the requirements. Particular attention is paid to the electron gun and RF circuit of the tube to get excellent beam transport characteristics and high efficiency. The electron gun has a perveance of 1.0μP. The cathode load is lower than 0.7 A/cm² with a beam current of 16A. The beam focusing system is a solenoid magnet structure. Simulation indicates that the beam trajectories have a good laminar condition with a beam-to-tunnel radial fill factor less than 0.6. The beam ripple is 9 percent of the average beam radius. The RF circuit consists of five cavities. One-dimensional large signal simulation indicates that the circuit has an efficiency of more than 57% with a saturated gain of 50dB. With an operating voltage of 63kV and a beam current of 16A, the klystron is expected to produce 580kW RF power at 5GHz.