Higher order parametric x-rays

Abstract

Parametric x-radiation (PXR) may be described as the Bragg scattering of virtual photons to produce real x-rays when satisfy the Bragg condition dsin0=nl, where 0 is the angle between the electron beam direction and a crystal axis. Enhanced higher order parametric x-radiation from the (002) plane of a mosaic graphite crystal has been observed. Production of PXR of the order n=2 exceed that from the first order, and x-rays of order up to n=6 are readily seen. the production of higher order is obtained by using a thick crystal where the formation and attenuation lengths are exploited to enhance higher energy x-ray formation relative to the lower energy first order radiation, Photons of energy 5 to 30 MeV have been measured. The experiment was conducted with a 90 MeV electron beam from the Naval Postgraduate School electron linear accelerator. A three axis target position program, Easy-Mover, was developed to allow for precision orientation of the crystal axis with respect to the electron beam.