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Enhanced Water-Window X-Ray Pulse Generation from Femtosecond-Laser-Produced Plasma with a Carbon Nanotube Target

We adopt a carbon nanotube target to increase the efficiency of water-window X-ray pulse conversion from femtosecond-laser-produced plasma. The target is an array of vertically aligned multiwalled carbon nanotubes, each 30 nm in diameter and about 12-µm long. Center-to-center nanotube distance is around 150 nm. The X-ray fluence enhancement in the water-window region is seven-fold compared with a conventional carbon plate target. Further enhancement can be expected by optimizing the size of the carbon nanotubes. X-ray pulse duration is 26 ps. The results show that carbon nanotubes are very attractive as a target for femtosecond laser-produced-plasma X-ray sources in single-shot X-ray microscopy.