Observation of multipath effects in the detection of RF-modulated x-rays
As part of the Air Force Research Laboratory’s ongoing research in particle accelerators and beams, we recently began investigating the interaction of RF-modulated x-ray beams with RF structures. Additionally, these bremsstrahlung x-rays, produced using an S-band RF electron linac and tungsten foil, were able to drive RF signals at the linac frequency and its integer harmonics in an S-band waveguide. This was interpreted as a result of secondary electron production inside the waveguide by the modulated x-ray beam and implied that the primary electron beam RF modulation was preserved, to at least some degree, through both the processes of x-ray and secondary electron production. The strength of these signals induced on the waveguide varied as the distance of the waveguide from the tungsten foil changed, with the nature of these changes suggesting the existence of an interference process resulting from multipath propagation of the modulated x-rays. Here, we report on our initial attempt to verify this multipath propagation by altering the configuration of shielding and reflective masses in the environment of the waveguide. Finally, these measurements support the existence of a multipath propagation effect and further indicate that the RF modulation of the x-rays is preserved as they undergo scattering events inside the accelerator vault.