Analysis of Vase Shaped Pumping Cavity for Solar-Pumped Laser

Although sunlight is a promising renewable energy source, the light is incoherent and difficult to use directly. Therefore, a solar-pumped laser, which directly converts sunlight into coherent laser light of, is a promising technology. A solar-pumped laser collects sunlight into the laser medium to realize laser oscillation. In order to realize an efficient solar-pumped laser system, it is necessary to design a pumping cavity that absorbs maximal sunlight into the laser medium with minimal thermal shock. In this research, the pumping cavity shape was studied using a numerical ray tracing simulation. As a result, it was found that a cone shaped pumping cavity can be expected to improve the absorption rate by approximately 30% over a cylindrically shaped pumping cavity. Furthermore, the absorption power density distribution can be flattened by a vase shaped pumping cavity, while maintaining the same absorption efficiency. The vase shaped pumping cavity has almost half the dispersion of the absorbed power density in the laser medium when compared with the cone shaped pumping cavity.

Investigation of Radio-frequency Power Density Distribution around GSM Mast in Keffi Town, Nigeria

In this study, an investigation of radiofrequency power density distribution around GSM mast in Keffi town, Nigeria was determined. Radiofrequency meter (Electrosmog ED- 155A) was used to measure the EM radiation at 50, 70, 90,110, 130, 150, 170, and 190 m away from mobile base stations. A total of fifteen mobile base stations were randomly selected in Keffi town covering about four network providers (MTN, Globacom, Etisalat, and Airtel), according to their proximity to buildings, number of antennas mounted on their masts, how close they are to other base stations and the population density around them.The result reveal that MBS5 was found to have the highest value of average power density compared to that of the remainder, with a contribution of about 16% (2908.38 µW/m2). The least contribution was recorded in MBS3 with only about 1% (173.71 μW/m2). The other MBS with significant contribution are MBS6 (15%), MBS11 (15%), MBS10 (13%), MBS8 (13%) and MBS13 (11%) with average power densities of 2878.72μW/m2, 2767.28μW/m2, 2385.43 μW/m2, 2382.70 μW/m2, and 1996.36 μW/m2 respectively. The findings reveal that the measured values of power densities across all the sites are well below the RF radiation exposure safety limit set by International Commission on Non-ionizing Radiation Protection (ICNIRP) when compared with the findings in this study. Therefore, RF radiation exposure from mobile base stations in Keffi town may pose no health risk to the people living within the area.

Power Density Distribution for Laser Additive Manufacturing (SLM): Potential, Fundamentals and Advanced Applications

Problems with the laser additive manufacturing of metal parts related to its low efficiency are known to hamper its development and application. The method of selective laser melting of metallic powders can be improved by the installation of an additional laser beam modulator. This allows one to control the power density distribution optically in the laser beam, which can influence the character of heat and mass transfer in a molten pool during processing. The modulator contributes alternative modes of laser beam: Gaussian, flat top (top hat), and donut (bagel). The study of its influence includes a mathematical description and theoretical characterization of the modes, high-speed video monitoring and optical diagnostics, characterization of processing and the physical phenomena of selective laser melting, geometric characterization of single tracks, optical microscopy, and a discussion of the obtained dependences of the main selective laser melting (SLM) parameters and the field of its optimization. The single tracks were produced using the advanced technique of porosity lowering. The parameters of the obtained samples are presented in the form of 3D graphs. The further outlook and advanced applications are discussed.