Investigation of a Compact S-band Coaxial Multi-beam Relativistic Klystron Amplifier with Modular Periodic Permanent Magnet

A compact modular periodic permanent magnet system (MPPM) with a combination of inner and outer magnetic blocks and soft magnets is proposed in this paper. Its weight and maximum guided magnetic field strength is 50 kg and 0.3 T respectively. Compared with the uniform permanent magnet system, its weight is only about 1/10. Besides, we have simulated a coaxial multi-beam relativistic klystron amplifier (CMB-RKA) with the MPPM. The output microwave power of CMB-RKA with MPPM and the uniform ideal magnetic field is 0.78 GW and 0.84 GW respectively when the beam voltage and current are 525 kV and 4.62 kA. This demonstrated that a CMBRKA using MPPM is achievable. These results provide a new technical route for lightweight and small relativistic klystron amplifiers.