The direct comparison of the properties of X-ray emission by hot plasma of solid target, driven by nano-, pico- and femtosecond laser radiation was performed for the first time. The transition from highly uniform angular distribution of X-rays to the relatively narrow spread along the target normal and laser reflection direction was revealed at the shortening of laser pulse from nanosecond to femtosecond range. The observed result is related to the fundamental differences in the electrons energy gain mechanisms and X-rays generation process typical for laser pulses with varied duration and peak intensity. The absolute yield of broadband X-rays in the range from ~0.5 keV to a few hundreds of keV was measured, providing an insight on the conversion of laser pulse energy into high energy quanta. The observed results are important for the efficient utilization of laser-plasma sources for radiography, backlighting of ultrafast phenomena etc.

Figure. Angular distribution of X-ray dose F emitted by plasma driven by nano-, pico- and femtosecond laser pulses. 90^o corresponds to target normal.

 Bolkhovitinov E.A. et al.,
JETP Letters 123, issue 9 (2026)