Influence of laser-induced plasma parameters on the formation of laser-induced surface-periodic structures

The paper presents the results of processing a silicon surface with subpicosecond laser pulses under various exposure conditions. The variable conditions were: pressure in the working chamber, the speed of scanning the silicon surface with a laser beam and the laser pulse energy. Special attention was paid to the interaction of the laser-induced plasma plume with the surface of the processed material, with laser radiation and with the medium. The influence of the medium on the parameters of the laser-induced plasma is estimated. The result of this interaction is a change in the spatial characteristics of the laser-induced plasma channel, the period and type of the formed periodic surface structures, what is related to the change in the laser radiation passing through the medium at different pressures.

STUDYING MORPHOLOGY OF SUSPENSIONS BY THE METHOD OPTICAL SPECTROSCOPY

Методом оптической спектроскопии (УФ, видимая и ИК области спектра) исследованы две суспензии: вазелиновое масло (ВМ) наполненное слюдой и BaSO различной концентрации. Разработанный метод основан на анализе рассеивающей компоненты электромагнитного излучения, проходящего через образец, позволяющий определить средний размер и распределение рассеивающих частиц по размерам. Установлено, что с увеличением концентрации наполнителя частицы агрегируют, вследствие чего средний размер частиц увеличивается. Результаты, полученные спектроскопическим методом, хорошо согласуются с данными оптической микроскопии. Two suspensions were studied by optical spectroscopy (UV, visible, and IR): vaseline oil (VM) filled with mica and BaSO of different concentrations. The developed method is based on the analysis of the scattering component of electromagnetic radiation passing through the sample, which makes it possible to determine the average size and size distribution of scattering particles. It was found that with increasing filler concentration, the particles aggregate, resulting in an increase in the average particle size. The results obtained by the spectroscopic method are in good agreement with the optical microscopy data.

OPTICAL AND COLORIMETRICAL CHARACTERISTICS OF STRAINED LiF CRYSTALS UNDER X-RAY IRRADIATION

Here there were investigated the х-irradiation influence on the optical characteristics of LiF crystals and the colorimetric characteristics of optical radiation passing through crystals with different doses of irradiation. It was established that change of irradiation dose in the interval 0…1057 Р leads to reduce of absolute value of coordinates of the color and brightness of the radiation, passing through the crystal, but the color of the radiation thus remains constant.

RADIOMETRIC PROPERTIES OFAGRICULTURAL PERMEABLE COVERINGS

Nets are commonly used for agricultural applications. However, only little is known about the radiometric properties of net types and how to influence them. In order to investigate the influence of net construction parameters on their radiometric properties, a set of radiometric tests were performed on 45 types of agricultural nets. Laboratory tests on large size net samples was performed using a large and a small integrating sphere. Open field radiometric test were carried out by means of an experimental set up (120x120x50 cm) and a full scale shade house. Small differences (less than 5%) occurred between laboratory and open field tests. Results highlighted that the porosity and the mesh size, combined with the colour and secondarily, with the fabric and the kind of threads of the net influenced the shading performance of the net. The colour influenced the spectral distribution of the radiation passing through the net absorbing its complementary colours. Since nets are three-dimensional structures the transmissivity of direct light under different angles of incident of solar radiation changes when installed in the warp or weft direction. Transmissivity could be considered one of the main parameters involved in the agronomic performances of the netting system.