Optimization of a femtosecond laser generated x-ray source for pulsed radiography

X-ray radiography is an important tool in medicine as well as in life science and materials science. It is Kα radiation that is of primary interest in the fields of x-ray diffraction, whereas the whole x-ray flux receives most attention in the x-ray imaging application. We present a general Monte Carlo model of x-ray generation in femtosecond laser-irradiated solid material. Bremsstrahlung radiation is taken into account explicitly, permitting both whole x-ray and Kα emission to be calculated for arbitrary experimental conditions (i.e. target material, target thickness, target shape as well as laser intensity). The optimal thickness of both the whole x-ray and Kα emission from Titanium (Ti) foils irradiated with femtosecond laser pulse has been investigated. Comparing the results of whole x-ray with those of the Kα radiation, we find that the optimal thickness is increased by up to 118% for laser intensities I<5×1017 W/cm2, and this in turn leads to an increase in x-ray flux by 8%. The model may thus serve as a guide for experiments, particularly for hard x-ray radiography applications.