Development and Characterisation of a Laser-Based Hard X-Ray Source

Abstract: A laser-produced plasma was generated by focusing 100 fs laser pulses, with an energy of 150 mJ, onto metal targets. The laser intensity was expected to reach 10E17 W/cm2. Radiation was emitted from the created plasma, with photon energies extending up to the MeV regime. The laser-based X-ray source was optimised, with the purpose of making it a realistic source of hard X-rays (>10 keV). Dedicated equipment was developed for efficient generation and utilisation of the hard X-rays. The X-ray source was characterised with respect to its spatial extent and the X-ray yield. Measurements were made of the spectral distribution, by the use of single-photon-counting detectors in different geometries, crystal spectro-meters and dose measurements in combination with absorption filters. Ablation of the target material in the laser-produced plasma was investigated. Imaging applications have been demonstrated, including ultrafast (picosecond) X-ray imaging, magnification imaging of up to x80, differential imaging in the spectral domain, and imaging of various biological and technical objects. The biological response of ultra-intense X-ray pulses was assessed in cell-culture exposures. The results indicate that the biological response from ultra-intense X-ray exposures is similar to the response from exposures with conventional X-ray tubes.