A Transmissive Optics Approach for Time-Slicing the LCLS X-Ray Pulse

This paper investigates the use of off-axis zone plate optical systems to deliver time-sliced LCLS FEL pulses to users under the 3 energy chirp scenarios elucidated by P. Emma. We present formulas for designing off-axis zone plate optical systems that achieve a given time-slice duration and intensity. The results show that it is feasible to fabricate zone-plate systems capable of providing intense spots of time-sliced 8.275 KeV photons under the scenario of a 2.0% chirp, but that it is beyond current and envisioned fabrication capabilities to create zone-plate systems of similar performance under the scenarios offering energy chirps of < 0.25%. Finally we present results of numerical calculations of the electric fields delivered to the user by an off-axis zone plate optical system producing time-slices of (le) 50 · fs with photon densities of 200 photons/(angstrom)2 under the 2% energy chirp scenario