Search

The scattering and absorption of a high-power picosecond laser pulse by a solid target were investigated experimentally making use of the 'Progress-P' Nd:glass laser facility (λ = 1053 nm, τ = 1.4 ps) at radiation intensities I = 10¹⁶ — 10¹⁹ W cm^-2 on the target surface. It was found that, for I ≤ 10¹⁷ W cm^-2, more than 30% of the intensity of the scattered light was contained in the specularly reflected component. The absorption coefficient of the laser radiation with intensities ranging from 10¹⁸ to 10¹⁹ W cm^-2 was higher for targets made of materials with higher atomic numbers.

A Nd:YLF/Nd:glass laser facility with chirped-pulse amplification capable of generating pulses with a duration of 1.5 ps and a power up to 30 TW at the wavelength of 1053 nm was investigated. The facility consists of a initial laser system, producing a chirped pulse with an energy up to ~1 J, a main three-stage rod amplifying channel with a 85-mm aperture of the output stage, a pulse compressor based on 210 mm × 420 mm diffraction gratings, and a focusing axial parabolic mirror (with an aperture ratio of 1:11). Optimisation of the parameters of the laser facility allowed us to generate an output laser beam with an angular divergence close to the diffraction limit and an intensity up to ~10¹⁹ W cm^-2 . Laser radiation with such parameters can be employed in experiments on the interaction of superstrong laser fields with matter.

AbstractThe linear elastic analysis of International Thermonuclear Experimental Reactor (ITER) Divertor Cassette was performed by means of finite element method. The finite element model of the cassette included model of the cassette body with inner structure and multi-layeral models of High Heat Flux Components. Analyzed load cases included neutron heating, Central Plasma Disruption, and Vertical Displacement Event. A special computer code was developed to extrapolate electromagnetic loads computed using a simplified finite element model to the full-scale finite element model used for elastic analysis of the dWertor cassette.

Abstract3D thermo-elasto-plastic finite element (FE) analysis of high heat flux elements (HHFEs) stress state and estimation of damage levels have been performed. The models with two types of armour under several thermal load regimes have been investigated. Carried out analysis of 3D HHFEs thermo-elasto-plastic problems:• shows the necessity to take into account correct dependence of thermo-mechanical properties on temperature in order to obtain reliable results;•allows to estimate 3D stress state of HHFEs, dimensions of plastic zones and their evolution at cyclic thermal loading;•points to actuality of using special high-accurate numeric methods for solution of nonlinear problems;•allows to estimate possibilily of using 2D model;•allows to estimate damage of HHFEs based on continual concept taking into account load history.

An investigation was made of a laser (Nd : YLF/Nd glass) laser system generating pulses of 1.5 ps duration and up to 0.4 TW power at the 1053 nm wavelength. Chirped pulse amplification in a multipass amplifier was used. The amplifier had a misaligned conjugate cavity and a net gain of ≈ 4 × 10⁶ , as well as two additional amplifiers with an output aperture 20 mm in diameter. After optimisation of the parameters of this multipass amplifier the angular divergence of the output radiation was close to the diffraction limit and the average intensity was up to ≈ 10¹⁷ W cm^-2 in a focused beam. This laser system was developed as the frontend component of a multiterawatt laser facility under construction for research on the interaction of ultrastrong fields with matter.

Experimental and theoretical investigations were made of the characteristics of the interaction between solid targets and picosecond laser pulses with a complex profile. A prepulse preceding the main picosecond pulse increased the absorption of the s-polarised radiation and reduced the absorption of p-polarised radiation. Moreover, the prepulse made it possible to control the intensity of various components of the x-ray radiation emitted by the laser plasma. A satisfactory agreement between the experimental results and numerical calculations was obtained and a theoretical optimisation of the efficiency of x-ray generation was made.

We have investigated the effect of the laser spot shape on the spatial distribution of accelerated ions on the front and back sides of a thin target irradiated by a picosecond laser pulse having the intensity of . Experimental data are compared with numerical calculations. It is shown that the spatial structure of the ion bunch on the front side of the target resembles the laser spot structure rotated by .