Simulation of a four-stage depressed collector for a W-band gyro-BWO

To improve the overall efficiency of the W-band gyrotron backward wave oscillator (gyro-BWO) currently being built in the University of Strathclyde, an energy recovery system using a four-stage depressed collector was simulated and designed. The spent beam information was exported from the simulation of the gyro-BWO using the 3D PIC code MAGIC. The geometry of the depressed collector was optimized using a genetic algorithm to achieve the optimum overall recovery efficiency for specific parameters of the spent beam. Secondary electron emissions were simulated to investigate the effects of the secondary electrons on the overall recovery efficiency and the backstreaming of the electrons from the collector region