Kα X-ray Emission from Nanowire Cu Targets Driven by Femtosecond Laser Pulses for X-ray Conversion and Backlight Imaging

A high quality X-ray source was proposed by modifying the target material structure characteristics driven by ultrahigh laser energy. The experiments were performed on the Ti:sapphire femtosecond laser beam device (4.3-6 J, 30 fs), one of the three XG-III lasers in Laser Fusion Research Center of China Academy of Engineering Physics. The femtosecond laser beam drove the nanowire copper material with an average length of 18-50 mu m and a diameter of about 260 nm. A single-photon counting charge-coupled device was employed to measure the copper K alpha X-ray emission of the nanowire and foil targets. A clear maximum photon yield of the nanowire target was calculated to be 3.6 X 10(8) photons sr(-1) s(-1), the conversion efficiency was up to 0.0087%, and the average yield was 2.5 times that of the copper foil targets. In addition, by using a pinhole imaging method of phi 10 mu m, the minimum full width at half maximum spot size of the X-ray source was calculated in the range of 85-240 mu m, which was similar to that of the copper foil material with a long radius of 170 mu m and a short radius of 63 mu m. The experimental data illustrate that the nanowire has the potential to enhance the energy absorption of femtosecond laser for X-ray conversion and backlight imaging.