Alignment and Timing Jitter in Flying-Focus Inverse Compton Scattering
Flying-focus laser pulses can extend the effective interaction length in inverse Compton sources by controlling the trajectory of the focal intensity. Their practical advantage, however, depends on tolerance to shot-to-shot electron--laser alignment and synchronization errors. We develop a semi-analytical model for the shot-averaged total photon yield in head-on inverse Compton scattering of an axisymmetric Gaussian electron bunch with a flying-focus laser pulse. The model includes finite electron-beam emittance, laser diffraction, transverse laser-centroid jitter, longitudinal focus-position jitter, and laser arrival-time jitter at the nominal interaction point. The ensemble averaging over these independent Gaussian errors and the integration over the longitudinal electron and laser coordinates are performed analytically, reducing the overlap problem to a single positive numerical quadrature. This formulation enables rapid evaluation of jitter-robust operating points and provides a compact tool for defining alignment and synchronization tolerances in flying-focus inverse Compton sources.