A synchronized VUV light source based on high-order harmonic generation at FLASH

Abstract

Ultrafast measurements in the extreme ultraviolet (XUV) spectral region targeting femtosecond timescales rely until today on two complementary XUV laser sources: free electron lasers (FELs) and high-harmonic generation (HHG) based sources. The combination of these two source types was until recently not realized. The complementary properties of both sources including broad bandwidth, high pulse energy, narrowband tunability and femtosecond timing, open new opportunities for twocolor pump-probe studies. Here we show first results from the commissioning of a high-harmonic beamline that is fully synchronized with the free-electron laser FLASH, installed at beamline FL26 with permanent end-station including a reaction microscope (REMI). An optical parametric amplifier synchronized with the FEL burst mode drives the HHG process. First commissioning tests including electron momentum measurements using REMI, demonstrate long-term stability of the HHG source over more than 14 hours. This realization of the combination of these light sources will open new opportunities for time-resolved studies targeting different science cases including core-level ionization dynamics or the electron dynamics during the transformation of a molecule within a chemical reaction probed on femtosecond timescales in the ultraviolet to soft X-ray spectral region.

Synchronized beamline at FLASH2 based on high-order harmonic generation for two-color dynamics studies

“…Preliminary results on the performance of the VUV source are presented in detail by Appi et al 32 The generation of VUV radiation in the range 10-45 eV was achieved. The spectrum was resolved using a 1850 lines/mm grating with a grating-detector distance of 8 cm.…”

“…In the preliminary tests carried out at the VUV beamline, a harmonic pulse energy of 0.1 nJ in the 20-40 eV range was estimated (number of photons per pulse in the order of 10 7 and conversion efficiency in the order of 10 −7 ). 32 By inserting the hyperboloidal mirror in the beam path, the VUV radiation is sent toward the REMI endstation. For fine adjustments of the mirror alignment, the VUV beam position can be monitored on the interaction screen [see Fig.…”

“…V. A detailed presentation and discussion about the performance of the VUV source can be found in our previous publication. 32…”

Atomic, Molecular and Cluster Science with the Reaction Microscope Endstation at FLASH2

“…The setup of the HHG source is a result of a collaboration between MPIK, DESY and the university of Hanover [25]. The IR beam is transferred to a neighboring laser table where high harmonics in the XUV regime are generated in a noble-gas target [26].…”

“…First runs of the HHG source were successful and commissioning results can be found in Ref. [25]. The HHG-XUV light is coupled into the FEL beamline by a mirror under 8 • grazing incidence.…”