We present quantifiable images of the angular distributions (AD's) of parametric x radiation (PXR), and vacuum-ultraviolet transition radiation (vuv TR) from 230 MeV electrons interacting with a silicon crystal. Both AD's are highly polarized. The vuv TR and optical TR data provide measurements of the beam energy and effective divergence angle. Using these quantities and separately known values of the electronic susceptibility igoi, we show that the measured PXR AD is in good agreement with the predictions of single crystal theory. Our analysis suggests a method to measure iyoi using PXR AD's.

Recent experiments exploring the use of transition radiation as an intense source of tunable, coherent x rays included a measurement of the energy spectra and angular distribution of transition radiation in the soft-x-ray energy range. The radiation was produced when 25-MeV electrons penetrated a stack of eighteen l-)u,m-thick beryllium foils. The most striking result is the demonstration of coherence of the photons emitted at the two surfaces of a single foil.