Особенности повреждаемости ниобия импульсным лазерным излучением в сравнении с пучково-плазменным воздействием

Abstract

The features of damageability of niobium by pulsed fluxes of laser radiation (LR) in the free-running modes (power density qFR = 105 – 106 W/cm2 with pulse duration τFR = 700 μs) and Q-switch mode (q = 108 – 109 W/cm2, τMD = 80 ns) in comparison with the pulsed effects of helium ion (HI) and helium plasma (HP) fluxes in the Plasma Focus (PF) setup at a flux power density qi ~ 108 W/cm2 and qp ~ 107 W/cm2, respectively and pulse durations τi ≈ 30 – 50 ns and τp ≈ 100 ns. LR fluxes were exposed to Nb in air; the working gas in the PF chamber was helium. It is shown that, in contrast to the effect of IG and HP fluxes on niobium in the PF installation, which contribute to the erosion of the material, the irradiation of niobium by pulsed LR in air fluxes under the conditions implemented does not cause noticeable surface erosion. When Nb is exposed to pulsed LR in the FR mode, the melt interacts with the air and forms on the irradiated surface of a thin film of elements of the liquid and gas phases. A similar nature of damage to Nb under the conditions of laser and beam-plasma treatment was found: a wavy relief of the irradiated surface with the presence of drop-like fragments on it, extended wave crests and microcracks. Irradiation of Nb by pulsed LR fluxes in the FR mode leads to the formation in the surface layer (SL) of sections with block and cellular structures, which are also formed after experiments in the PF chamber. It was found that after laser treatment in the FR and Q-switch modes, bubbles (blisters) are not formed in the SL of niobium, which are always present on the irradiated surface when exposed to pulsed fluxes of HI and HP in the PF chamber due to the implantation of helium ions in Nb. It is noted that in laser experiments there is no possibility of implanting working gas ions into the material, which is characteristic of beam-plasma impacts in PF devices, which affects the parameters of damageability and modification of the structure of the irradiated SL.