Study of 14 GHz VLEPP klystrons with 11 and 15 mm aperture

Results of experimental study of two variants of relativistic klystron for VLEPP are presented. Investigations have been performed using the driving beam of the JINR LIA‐3000 induction accelerator (E=1 MeV, I=300 A, τ=250 ns). The main emphasis is put on the study of the self‐excitation parasitic modes and their temporal evolution. A concept of relativistic klystron with RF absorbing drift tubes is proposed to solve the problem of the parasitic oscillations suppression. The results of preliminary experiments with such a klystron are presented, too.