Theoretical description and experimental detection of the interference between parametric X radiation and coherent bremsstrahlung

Parametric X radiation (PXR) produced by electrons with an energy of E-0 = 4 MeV interacting with the atoms in the (220) plane of a 20-mu m silicon an d a 55-mu m diamond crystal and observed at an angle of 44 degrees by a Si( Li) detector has been investigated with respect to the interference with co herent bremsstrahlung (CB) that originates in the same interaction process between the incoming relativistic electron and the crystal. Since the energ y of PXR and CB is identical, contributions of both types of radiation are indistinguishable. The newly derived analytical expressions describe the ra diation which consists of a coherent superposition of PXR and CB. For the c omparison of the experimental results with the theoretical predictions a Mo nte Carlo simulation taking into account all effects accompanying the radia tion process has been performed. The comparison shows very good agreement b etween experiment and theory.