THE MULTIPLET CAVITY - A BUNCHER FOR BROAD-BANDWIDTH KLYSTRON AMPLIFIERS

The bandwidth of a klystron output cavity scales (approximately) as p( 0.8)P(0.2), where p is the beam perveance and P is the beam power [1], [2] For high-perveance (p > 10 mu pervs) high-power (P > 10 kW) elect ron beams, it is relatively straightforward to design a broad-band out put cavity, However, the design of the input cavity of the broad-band klystron is in some ways more difficult. The purpose of the input cavi ty is to produce a velocity-modulated electron beam with a frequency-d ependent modulation amplitude that will optimize the bandwidth of the entire klystron system, while providing a magnitude of velocity modula tion large enough to minimize the length of the klystron. This paper s hows how a multiplet (multiple cavity) buncher cavity can be designed to provide broad-band (>20%) operation while keeping short the drift s ection length of the klystron.