The beamline optical design is conceptually simple and includes an ionization chamber, a delay line (delay range ±30 ps), an ellipsoidal focusing mirror with 1.4 m focal lenght. Solid state filters (thin films) can be inserted just after the delay line to eventually filter out the 1st and/or the 3rd harmonic from one of (or both) the two FEL beams emerging from the delay stage, in this way two colors pump-probe FEL measurements could be carried out. Additional filters, detection systems (invasive or not), fluorescence and semi-trasparent screens can be inserted in different places along the beamline for allignement and beam monitoring purposes.

The experimental chamber and the sample environment have been kept quite flexible and can accommodate various possible configurations for single-shot experiments, including simple EUV and soft x-ray absorption/reflection and pump-probe experiments where the probe can be either an external laser or a FEL pulse (and its harmonics). When a FEL pulse is used as probe, it is possible to exploit the wavelenght tunability of the source for performing pump-probe EUV absorption experiments; for instance a 1st harmonic FEL pulse could excite the sample while a time-delayed 3rd harmonic FEL beam is varied across a specific absorption edge. In the case of the external laser probe beam, the pump-probe signal would be tracked either in reflection and/or scattering geometry (a theta/2theta setup is available). The optical laser can be used as a pump too. The time jitter in FEL/laser pump-probe experiments has been found to be about 6 fs. 

The main piece of equipment of the EIS-TIMEX end-station is the 5-axis motorized sample manipulator stage working in the main EIS-TIMEX chamber. The manipulator can operate for single-shot measurements and allows accurate sample alignment in the interaction region with pump and probe pulses. Diagnostics include a long-distance microscope (telemicroscope) for fine alignment and rough beam profile measurements; further space is left for additional instrumentations. The main chamber is also equipped with a set of detectors, mainly Si photodiodes for transmission and reflectivity measurements; a high-energy bolometer can be also used for direct beam measurements. The sample chamber can be interfaced through a translation stage with a sample preparation chamber equipped for surface characterizations of fresh specimens before one-shot experiments.

The main EIS-TIMEX chamber is reported in the picture on the left, the sample manipulator is on the top flange. The focusing elliptical mirror is about 1.4 m before the chamber. The box on the right contains the fs laser setup for pump-probe measurements.


Sketch of the EIS-TIMEX experimental chamber and setup (since July 2013)

Graduated scale used to calibrate the telemicroscope (top)
and FEL spot at the sample monitored on a YAG screen by the telemicroscope

The setup is equipped with a circular rotating rail 

This upgrade serves as:
1) theta/2theta reflectivity geometry 
2) absolute measurements of reflectivity
3) alternate several detectors during measurements avoiding venting

On the left: sketch (top view) of the current endstation setup (2017)

Ongoing upgrades includes:
1) Silicon drift detector for TFY spectroscopy
2) EUV spectrometer (WEST) collinear with the FEL primary beam
3) Supercontinuum compressed probe 
4) Low noise pump-probe absorption spectroscopy setup
5) MCP-based photon detection 

Last Updated on Monday, 20 July 2020 12:59