Laser plasma formed by a gamma-irradiated target

An investigation was made of the interaction of neodymium laser radiation (λ = 1.06 μm) with a sample of γ-irradiated n-type crystalline silicon. The irradiation was performed in a flux of γ photons from ⁶⁰Co with a power of 1.5 kR/s at doses of up to between 1 MR and 10 GR. The results of irradiation were studied using optical microscopy and laser time-of-flight mass spectroscopy. It was established experimentally that high-dose γ irradiation of silicon leads to an enlargement of the damage crater which appears under the action of q = 1–100-GW/cm² laser radiation and to a lowering of the threshold for the formation of a plasma with an ionic charge multiplicity of z≥2. A joint analysis of the charge and energy parameters of plasmas formed from silicon before and after γ irradiation and of their ability to absorb λ = 1.06-μm radiation demonstrated that γ irradiation of the investigated target promotes the formation of a denser plasma with more highly charged ions for the same input energy.