15.4: Design of terahertz Extended Interaction Klystrons

The development of terahertz power amplifiers presents significant new challenges as it brings into focus design, fabrication, and measurement issues that are not important factors at lower frequencies. In this paper, we describe our design approach to meet these challenges with particular emphasis on a 0.67 THz Extended-Interaction Klystron (EIK). This device is being designed to generate a peak power of ~0.5 W with gain of ~23 dB over an instantaneous bandwidth of 15 GHz. The circuit will be driven by a 100 mA, 25 kV electron beam confined in a 0.005"diameter beam tunnel with ~1 Tesla magnetic field. This choice of beam size ensures that the same electron gun can be employed for all program development phases culminating in a 1.03 THz amplifier. A highly efficient depressed collector has also been designed to meet the efficiency requirement.