Temporal pulse shaping aspects of refractive X-ray lenses

Refractive X-ray lenses are frequently used components at modern X-ray free-electron laser facilities. This work investigates the temporal effects of refractiveoptics on ultra-short X-ray pulses, particularly focusing on pulse elongation. Wepresent a model using full Fresnel theory to study the beam profile at the focusin space and time. Refractive X-ray lenses not only change the temporalstructure of the pulse, the focus size is also dependent on the incoming pulseduration. Further, we present a simplified ray-tracing model to estimate thepulse stretching effect of compound refractive lenses (CRLs), which we find tobe dependent only on the dispersion and the absorption of the CRL materia