Vacuum-free femtosecond fiber laser microplasma X-ray source for radiography

Radiographic imaging using X-rays is a tool for basic research and applications in industry, materials science, and medical diagnostics. In this article, we present a novel approach for the generation of X-rays using a vacuum-free microplasma by femtosecond fiber laser. By tightly focusing a laser pulse onto a micrometer-sized solid density near-surface plasma from a rotating copper target, we demonstrate the generation of Cu K-photons (8-9 keV) with high yield ∼ 1.6 × 10⁹ phot/s/2π, and with a source size diameter of approximately 10 microns. Femtosecond fiber laser allows working with a high repetition rate (∼2 MHz) and moderate energy levels (10-40 µJ), ensuring the effective quasi-continuous generation of X-ray photons. Furthermore, we introduce a hybrid scheme that combines the tightly focusing laser-plasma X-ray generator with an online control unit for microplasma size source based on the back-reflected second harmonic generated in the laser-induced microplasma. The compactness and high performance of this vacuum-free femtosecond fiber laser microplasma X-ray source makes it a promising solution for advanced radiographic applications. Our preliminary results on the creation of a microfocus X-ray source provide insights into the feasibility and potential of this innovative approach.