Transient Effects in an X-Band Magnicon Amplifier

The Naval Research Laboratory X-band magnicon is a frequency-doubling amplifier for accelerator applications at 11.4 GHz, with high power (10-20 MW), adjustable pulsewidth (200 ns-1 μs), stable gain (> 50 dB), and a modest tuning range (~0.1%) but a narrow bandwidth (a few megahertz). The magnicon is the heart of a facility to study dielectric-loaded accelerating structures, and to drive a compact linear accelerator. In these applications, frequency control is important. However, it was recently observed that in short pulse (~200 ns) operation, the output frequency does not match twice the drive frequency. This paper presents a brief description and analysis of this phenomenon as well as other transient effects that are observed in longer pulses.