Development of soft x-ray lasers at PALS

Abstract

Program of development of deeply saturated Ne-like zinc soft X-ray laser at the PALS (Prague Asterix Laser System) Centre, employing as a pump device a kilojoule high-power iodine laser, is reviewed. The active medium giving rise to laser action at 21.2 nm is generated using a sequence of multiple-100-ns IR pump pulses, consisting of a weak prepulse (<10J), followed after 10 or 50 ns by the main pump pulse (~500 J). The population inversion in the resulting long scale-length density plasma allows to generate an extremely bright and narrowly collimated X-ray laser beam, providing up to ~10 mJ pulses and ~100 MW of peak power, which is the most powerful soft X-ray laser yet implemented. This device was recently used as radiation source in pilot radiobiology study of DNA damage in the soft X-ray region, and in material ablation. A novel interferometric device, based on double Lloyd's mirror, is being developed for surface nanometric probing with teh soft X-ray laser as a source. A test experiment was performed to assess focusing properties of the X-ray laser beam down to a narrow spot, with the ultimate goal of achieving 1013 Wcm-2 for novel applications relevant to e.g. laboratory astrophysics.