ANL, Argonne, Illinois
An important tool to study the fundamental processes of chemistry and solid-state physics is the femtosecond-resolving visible/IR pump, X-ray probe technique. It requires ultrashort pulses of light and X-rays in few-femtosecond synchronism with each other. Here, a scheme is proposed to derive both types of radiation from the same electrons in an emittance-sliced XFEL [1]. For this, the same emittance contrast that is imposed onto the bunches in an XFEL to modulate the SASE process is also used to generate a coherence enhancement of transition undulator radiation [2] (TUR). This results in an intense single-cycle pulse of near-infrared, coherent TUR (CTUR) light that is perfectly synchronized to the SASE X-rays, and has about 100 μJ of energy (based upon LCLS parameters). The idea will be presented and conceptual issues will be discussed, such as near-field effects in the CTUR. Furthermore, practical issues arising from the integration into an XFEL facility will be adressed, such as impact on beam-position monitoring, direct use of the CTUR for pumping vs. cross-correlation with a short-pulse laser, and scanning delays.
[1] P. Emma et al., Phys. Rev. Lett. 92, 074801 (2004)
[2] K.-J. Kim, Phys. Rev. Lett. 76, 1244 (1996)
[3] B. W. Adams, Rev. Sci. Instrum. 76, 063304 (2005)
