SILICON PLASMA HEATING IN AIR AT THE COMBINED BICHROMATIC LASER RADIATION AT WAVELENGTHS OF 355 and 532 nm

The formation and heating of laser plasma under the irradiation of silicon in ambient air by pulsed laser radiation with wavelengths of 355 and 532 nm at radiation power density up to 5 GW/cm2 has been experimentally investigated. An increased efficiency of the formation and heating of ablation plasma under bichromatic irradiation of silicon with advanced action of nanosecond pulses with a wavelength of 355 nm has been established.

Measurement and Evaluation of Radiation Power Density Emitted from Mobile Cellular Base Stations in Abuja and its Environ, Nigeria

This paper presents measurement and evaluation of radiation power density emitted from mobile cellular base stations in Abuja and it’s environ. Forty (40) mobile base stations with ten (10) each from AIRTEL, ETISALAT, GLO and MTN located in areas with high population were randomly examined across Abuja. Broadband analysis method was employed in the measurement of the radiation power density. The results obtained shows that most of the base stations recorded lower radiation power density below the safety standard value of 4.5watt/m2 , 22.5 watt/m2 for 900MHz frequency though few base stations recorded above standard value: GLO-BS02, GLO-BS03 and MTN-BS02 recorded 59.02 mW/m2, 39.76 mW/m2 and 46.70 mW/m2 respectively. The result also revealed that as distance increases, the mean power density reduces. This is to said that human exposure to radio frequency radiation have less or no health hazard at distance far away from the mobile cellular base station.

Simulation of Tandem Thin-Film Solar Cell on the Basis of CuInSe2

CuInSe2 thin-film solar cells are promising materials for photovoltaic devices. One of the main tasks of researchers is to find ways to increase the solar cells efficiency. In this paper we propose an original structure of a thin-film solar cell based on a tandem connection of a photoelectric converter and a thermoelectric layer based on CuInSe2. The photoelectric converter consists of CuInSe2 and CdS layers. A 3D model of the proposed thin-film solar cell was implemented in the COMSOL Multiphysics environment with using the Heat Transfer module. The simulation was carried out taking into account the diurnal and seasonal variations of both the ambient temperature and the power density of the AM1.5 solar spectrum for the geographical coordinates of Minsk. The solar radiation power density of about 500 kW/m2 can be achieved by using concentrators. The temperature pattern and temperature gradients are calculated in each layer of the solar cell without and with the temperature stabilization of the substrate back side as well as without and with the thermal insulation of the substrate ends. Graphs of the temperature gradients of the thermoelectric layer and the temperature variations of the photoelectric converter of the solar cell are given. As a result of the simulation, it is shown how the uneven heating of both the surface of a thin-film solar cell and its layers occur under conditions of diurnal and seasonal variations of both the ambient temperature and the solar radiation power density. Under concentrated solar radiation exposure, the photoelectric converter surface can be heated up to 700 °C without temperature stabilization of the solar cell substrate. The operating temperature of the photoelectric converter was maintained at no more than 2.35 °C in January and at no more than 14.23 °C in July due to the temperature stabilization of the substrate back side of the proposed device. This made it possible to achieve an increase in the output power of the solar cell both by summing the photoand thermoelectric output voltages and by the concentration of solar radiation.

Finite-element study of a toothed-crystal monochromator

A toothed-crystal monochromator, proposed in previous papers, is a modification of an inclined monochromator, which reduces the impinging radiation power density on the surface of a crystal for broad synchrotron radiation beams. The surface of the monochromator has a triangular toothed structure oriented in such a way that it represents an inclined monochromator. Finite-element analysis of thermally induced deformation was performed for a particular shape of toothed crystal and for a flat crystal of the same average thickness. It was estimated that the toothed-crystal monochromator may provide 70% higher radiation power than the flat-crystal monochromator.

Rotated-inclined double-crystal monochromator for synchrotron radiation: aberration and its compensation

A rotated-inclined double-crystal X-ray monochromator was designed for high-power undulator beamlines for SPring-8 to reduce the impinging radiation power density. Recently, it has been shown that an inclined double-crystal monochromator suffers from a certain type of geometrical aberration that may be relatively easily compensated. In this paper, it is shown that a similar aberration exists also in the case of rotated-inclined monochromators and that as in the inclined case the aberration may also be compensated.