Laser holographic interferometry of short ultraviolet radiation with high power density interaction with condensed metters

Abstract

The dynamics and macrostructure of near-surface vapor-plasma fluxes arising from condensed substances evaporation in the field of broadband radiation of the UV-VUV spectrum range are studied using double-exposure laser holographic interferometry and schlieren photography (the Toepler scheme in the light field mode). The experimental setup was created on the basis of the unique scientific facility "Beam-M". Broadband UV and VUV radiation was generated by a plasma-dynamic emitting discharge of an end geometry coaxial erosion-type magnetoplasma compressor with an ablating fluoroplastic plasma-forming insulating sleeve in a gas. To control the emission spectrum of the discharge, gas filters were used (Ar, Ne, air, Ne mixture with 5% air). The emitter operated in the following mode: U = 20 kV, the stored energy W = 3.6 kJ, the energy input to the discharge was up to 3.2 kJ, with 30% in the first half-cycle of current, the maximum current is 160 kA, the half-cycle of discharge is 6 μs; the total radiation energy from the discharge was 1.0-1.2 kJ; the fraction of radiation in the VUV range of the spectrum was about 50% in Ne (hν ≤ 20 eV) and about 45% in Ar (hν ≤ 16 eV). It was shown that the implemented scheme of electromagnetic compatibility and protection ensures reliable synchronization of the electric discharge circuit and optical diagnostics components in the whole range of discharge characteristics. Optical diagnostics of near-surface gas-plasma flows was implemented on the basis of a second harmonic (532 nm) of a solid-state Nd:YAG laser (Solar LQ-115), its versatility was shown for studying various pulsed plasma processes with characteristic changes in gas concentrations of about 10 17-10 18 cm-3 and gradients of 10 19-10 20 cm-3. On the schlieren-pictures and interferograms, the zones characteristic of the studied type of radiation effects on materials were recorded: the gas-dynamic evaporation mode was realized (plasma piston mode), there was a shock wave in the gas, the contact boundary between the shock-compressed gas and the vapor plasma. The analysis of interferograms indicates that the regime of developed evaporation was preceded by a regime of diffusion evaporation. The use of extended samples allowed us to observe successive stages in the development of gas-dynamic perturbations during evaporation (due to the different distances between the target areas and the discharge). On the interferograms above the target, at different distances from the source of irradiation, 3 types of gas-dynamic perturbations were observed: acoustic wave, simple wave (Riemann wave), and shock wave. The effect of the energy characteristics of the discharge and the spectral composition of the radiation on the evaporation pattern was experimentally shown.

Experimental Study of Irradiation of Thin Oxide and Mo/Si Multilayers by High Brightness Broadband VUV/UV Radiation and Their Degradation

“…The moment of laser triggering was detected by a photodiode. A detailed description of the optical diagnostics has been presented earlier [27,38].…”

“…Another important feature of the MPC is the generation of the plasma flows with a complex inner structure that includes strong shock waves, turbulent vortexes, zones of chemical and photochemical reactions, etc. [27]. In this case, it is possible to carry out a complex impact on materials, including mechanical loads and radiation exposure.…”

About graphite evaporation dynamics caused by radiation in near zone of magnetoplasma compressor discharge

“…The study of the interaction of high-power fluxes of short-wave radiation of the UV and VUV spectral range with graphite samples was carried out on an experimental setup described in [9]. This setup was created on the basis of a plasmodynamic discharge -the discharge of an erosion type magnetoplasma compressor 1, 2, 3 (Figure 1) [7,9,10], which was installed in a vacuum chamber 4. The source of radiation in such a discharge is a plasma focus, which is formed on the axis of symmetry near the central electrode [11].…”

“…The experimental methods were similar to our previous works [9,13]. The vacuum chamber was pumped out to a pressure of p ≤ 1 Pa, then filled with background gas (in this series of experiments we used Ne).…”

Recording of Long Low-Amplitude Bulk Elastic Waves in Transparent Solid Waveguides by Digital and Classical Holography

“…The development of high-speed digital cameras equipped with fast, global shutters allowed eliminating the need to probe rapid dynamic processes using pulsed lasers [26]. At the same time, despite much more frequent use of digital holography, especially in the field of microscopy and biology [27][28][29][30][31], holographic interferometry with traditional recording on holographic plates and films is still in demand in a number of applications [32][33][34][35][36]. Among these applications is the recording of elastic waves of different types in solids, in particular, shock and strain solitary waves (solitons) in solid waveguides.…”