Study of damage structure formation on aluminum film targets by picosecond soft X-ray laser ablation around threshold region

We irradiated soft X-ray laser pulses onto aluminum film targets, which were evaporated on silicon and lithium fluoride substrates. After laser irradiation, we observed irradiated surfaces and confirmed damage with nanometer scale-modified structures. These damage structures were the same as those formed on the aluminum bulk surface. In this article, we discuss a possibility of the growth process of damage structures on the Al surface based on the experimental results.