Efficient water-window X-ray pulse generation from femtosecond-laser-produced plasma by using a carbon nanotube target

We adopt a multiwalled carbon nanotube target to increase the efficiency of water-window and _]K X-ray pulse conversion from femtosecond-laser-produced plasma. The diameter of the carbon nanotubes is around 30 nm and the length is about 12-m. The X-ray fluence enhancement in the water-window region is sevenfold compared with a conventional carbon plate target. Further enhancement can be expected by optimizing the size of the carbon nanotubes. Soft X-ray pulse duration is 26 ps. It is also found that the _]K X-ray line emission from the Si substrate of the carbon nanotube target was enhanced. This result indicates that by covering various solid materials with carbon nanotubes, enhanced short _]K X-ray pulses with the corresponding wavelength can be obtained. These 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 and time-resolved X-ray diffraction. PACS 52.50.Jm; 52.38.-r; 52.38.Ph; 68.37.Yz; 78.67.-n