L-Band Beam Modulator for X-Band Linear Accelerator

RadiaBeam Technologies will develop a wideband (20%) beam intensity modulator, based on the novel concept of twisted accelerating waveguide. The modulator design will be optimized to provide a 3-10 ?s-long train of amplitude or frequency modulated electron bunches that will then be accelerated in X-band accelerator. In the proposed modulation system, the beam is pre-accelerated to ~30 keV in a triode DC gun with focusing electrodes. Then the DC beam arrives at the waveguide section with a low-phase velocity, driven by the sub-harmonic microwave signal with modulation. This signal interacts with the DC beam, causing its velocity modulation. Then, due to the phase oscillations the beam intensity modulation, equivalent to that of the input microwave signal will develop. The beam is then injected directly into the main X-band linac, where it is accelerated to the final energy and converted to X-ray signal.