Experimental Study of Multistage Energy Recovery in the SPbPU Gyrotron

Measurements have been carried out in a 4-mm wavelength gyrotron with a multi-stage depressed collector based on spatial separation of electrons in crossed axial electric and azimuthal magnetic fields. The results of the first experiments are discussed, in which the values of the total efficiency of ~ 70% for a four-stage and ~ 72% for a five-stage recuperation system were achieved. Suggestions for further increasing the gyrotron efficiency are proposed.