The development of free electron laser (FEL) sources, which provide extreme ultraviolet (XUV) and soft x-ray radiation
of unprecedented coherence and almost transform-limited pulse structure, has opened up the realm of XUV/x-ray
non-linear optics. In particular, XUV four-wave-mixing (XFWM) experiments may allow, e.g., to probe correlations
among low-energy excitations and core states, and to access the “mesoscopic” wavevector range (0.1-1 nm-1), inaccessible
so far and fundamental to investigate nanostructures and disordered systems. In this manuscript we report on the latest
advances and future developments of the TIMER setup at FERMI (Elettra, Italy), specifically conceived for XFWM
experiments. In particular, we discuss the improvements on the XUV-probe and on the pump transport. Moreover, TIMER
and mini-TIMER (a test setup available at the DiProI end station) are also suitable for time-resolved second order nonlinear
experiments, which are intrinsically surface sensitive due to symmetry restrictions. We hereby discuss the foreseen
extension to the XUV of interface specific probing of electronic processes, for example charge and energy transfer, with
chemical specificity.
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