Generation of hard X-rays using an ultrafast fiber laser system

We report the first hard X-ray source driven by a femtosecond fiber laser. The high energy fiber CPA system incorporated a 65mum LMA fiber amplifying stage which provided 300-fs recompressed pulses and diffraction limited beam quality with M(2) < 1.07. A deformable mirror was used to optimize the wavefront and the spot size was focused down to 2.3 mum with an f/1.2 paraboloidal mirror. 50muJ was deposited on the nickel target with 2x10(15)-W/cm(2) focal intensity and a distinctive Ni K(alpha)-line (7.48 keV) emission was measured with 5x10(-8) energy conversion efficiency.