Experimental researches using high power optical lasers combined with free electron lasers (FELs) open new frontiers in high energy density (HED) sciences. Probing and pumping capabilities are dramatically improved due to the brightness of the XFEL pulses with ultrafast duration. Besides, the peak intensities of Ti:sapphire laser Chirped Pulse Amplification (CPA) systems reach petawatt (PW)-class with operating in few tens of fs and commercially available at a few Hz of repetition rate. We have been developing an experimental platform for HED sciences using high power, high intensity optical lasers at the XFEL facility, SACLA.Currently, an experimental platform with a dual 0.5 PW Ti:Sapphire laser system is under beam commissioning for experiments combined with the SACLA’s x-ray beam for research objectives that require more peak power in the optical laser pulses with a few tens of fs. The optical laser system is designed to deliver two laser beams simultaneously with the maximum power of 0.5 PW in each into a target chamber located in an experimental hutch 6 (EH6) at BL2, which was recently commissioned as a SACLA’s 2nd hard x-ray beamline. A focusing capability using sets of compound refractive lenses will be applied to increase the x-ray fluence on the target sample. One of the most key issues for the integrated experimental platform is development of diagnostics that meets requirements both from the high power laser (e.g. resistance to harsh environments) and from the XFEL (e.g. adaptation to the available data acquisition system). The status and future perspective of the development including automatic laser alignment systems will be reported in the presentation. We will discuss the most promising and important new physics experiments that will be enabled by the combination of PW-class lasers and the world-class FEL’s x-ray beam.
Low energy electron beams with particle energies of typically 10 to 20 keV are used for pumping gas lasers. Extremely thin (300 nm) ceramic (SiNx) membranes are used as entrance foils for the electron beam. Laser gas pressure up to several atmospheres is possible using this technique if the dimension of one side of the foil is restricted to about 1 mm. Energy loss of the electrons in the foil is less than 10%. The short range of the low energy electrons in the laser medium leads to a high specific power deposition. In transverse geometry the beam pumped volume is cylindrical with typically 1 to 3 mm diameter. This is well matched with the diameter of optical modes in stable optical cavities. The new pumping method is demonstrated using the 1.73 micrometers 5d[3/2]1-6p[5/2]2 XeI laser line in Ar-Xe laser gas mixtures at pressures between 130 and 650 mbar. Laser effect was observed for Xe concentrations between 0.1 and 1%. A low threshold pumping power of 5.5 W and a maximum output power of 6 mW at 13 W pumping power were measured. Scaling to higher power and shorter wavelength laser systems is discussed.
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