High-power MMW sheet beam amplifiers

NRL has developed and demonstrated a unique sheet-beam electron gun, which produces a 3.5-4-A, 0.3 × 4 mm electron beam at ~20 kV. This electron beam has been successfully used to power multi-kW amplifiers at both Ka and W bands. The devices developed thus far employ a permanent magnet solenoidal field of 6 - 8 kG to transport the electron beam through the interaction circuit. While a periodic permanent magnet (PPM) structure would be much more compact, some compromises in performance are required to utilize PPM focusing. We will discuss some of the design considerations and requirements for high-power sheet beam amplifiers and review some key features of the amplifiers demonstrated thus far.