Broadband High-Power 18-Beam S-Band Klystron Amplifier Design

Fundamental-mode multiple-beam klystrons (MBKs) offer the potential of high power and broad bandwidth with low noise at low beam voltages in a compact amplifier form factor. This paper presents the design approach and methodology for an S-band MBK. This amplifier will be driven by a newly developed 41.6-A 42-kV 18-beam electron gun. The high total beam perveance permits the circuit design to achieve a peak power of 670 kW in S-band and a corresponding 1-dB bandwidth of 13% (16% at 3-dB). The high beam perveance, however, requires special considerations in the common collector design, particularly with respect to the spent modulated electron beams. To fully account for the impact of the time-varying beam current, the time-dependent 3-D gun/collector code MICHELLE was employed for this collector design.