Undulator radiation in a parallel plate waveguide: Inclusion of off-axis motion and higher-order energy corrections

The theory of undulator radiation in a parallel plate waveguide is reconsidered with the inclusion of energy corrections upto K3/γ3 and the relevant physical consequences. We also discuss the role of betatron oscillations and the modifications induced in the spectral brightness which arise when the electrons are injected off the undulator-axis.