Monochromatic extreme-ultraviolet ultrafast beamline

CITIUS is a multi-partner and multi-disciplinary project lead by University of Nova Gorica (Slovenia) to develop a facility based on a high repetition rate and ultra-short tunable laser source that is used to produce ultrafast extreme-ultraviolet (XUV) pulses through high-order harmonic (HH) generation [1]. The XUV radiation is monochromatized and can be focused on different end-stations for materials and surface science and atomic and molecular physics and chemistry. We present here the characterization of the monochromatic XUV source. The HHs are generated in a gas cell using a Ti:Sa laser operated at 5-Khz repetition rate with an energy of 2 mJ/pulse. The XUV beam is monochromatized and focused in the experimental chamber. Since the beam is handled by a grating monochromator, a temporal broadening has to be accepted at the output due to the pulse front-tilt given by the diffraction [2]. In the case of the CITIUS beamline, an innovative single-grating configuration has been adopted, that combines in a single instrument two different grating geometries: the classical-diffraction mount (CDM) and the off-plane mount (OPM), as shown in Fig. 1. It has been demonstrated that the two geometries are complementary [3]: the CDM is used for relatively long instrumental response in the 100-200 fs range, and high spectral resolution, i.e. ?/?? > 200; the OPM is used for ultrashort responses in the 10-50 fs range and low spectral resolution, i.e. ?/?? < 200 [4]. © 2013 IEEE.