Features of Niobium Damage by Pulsed Laser Radiation in Comparison with Beam-Plasma Impact

Inorganic Materials: Applied Research. 2022. Vol. 13. No. 5. P. 1238–1246.

Pimenov V. N., Borovitskaya I. V., Demin A. S., Epifanov N. A., Kazilin E. E., Latyshev S. V., Maslyaev S. A., Morozov E. V., Sasinovskaya I. P., Bondarenko G.G., Gaydar A. I.

Translator: K. Gumerov

The features of damageability of niobium by pulsed fluxes of laser radiation (LR) in free-running
(power density qFR = 105–106 W/cm2 with pulse duration τFR = 700 μs) and Q-switched (q = 108–109 W/cm2,
τQS = 80 ns) modes in comparison with 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 were studied. 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 helium ion and helium plasma
fluxes on niobium in the PF installation, which contribute to the erosion of the material, irradiation of niobium
with pulsed LR in air fluxes under the implemented conditions does not cause noticeable surface erosion.
When Nb is exposed to pulsed LR in the FR mode, the melt interacts with air and forms a thin film of
elements of liquid and gas phases on the irradiated surface. A similar nature of Nb damageability under conditions
of laser and beam-plasma treatment was found: a wavy relief of the irradiated surface with the presence
of droplike fragments on it, extended wave crests, and microcracks. Irradiation of Nb with pulsed LR fluxes
in the FR mode leads to formation of sections with block and cellular structures in the surface layer (SL),
which are also formed after experiments in the PF chamber. It was found that, after laser treatment in the FR
and Q-switched 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 owing to implantation
of helium ions into Nb. It is noted that, in laser experiments, there is no possibility of implanting working gas
ions into the material, which is typical of beam-plasma impacts in PF devices, which affects damageability
parameters and modification of the structure of the irradiated SL.

Keywords: niobium, ниобий, импульсное лазерное излучение, Pulsed Laser Radiation, beam-plasma impact, пучково-плазменное воздействие