Ahmed N. Kadachi

Effect of Optimum Parameters Setting on Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy is very attractive analytical method owing to many advantages, but it is complicated by the matrix effect due to complex nature of the laser–sample and plasma–particles interaction processes. For more precise and accurate analysis results, this effect must be reduced to a minimum. The approach used in this study to reduce the matrix effect was based on the selection of the optimum parameters of the system using pure element standards, followed by data processing and various normalization techniques. The copper alloys were selected for this study knowing that these materials are particularly difficult to be analyzed by laser-induced breakdown spectroscopy due to large differences in the physical properties of the metal constituents. But the accuracy improvements obtained by the proposed approach are encouraging to generalize it to other similar materials. Eighteen reference standards of copper alloys were measured to construct the calibration curves after optimum parameter settings. The coefficients of determination, R 2, obtained from the calibration curves of most elements present in copper alloys were close to 1 (0.99). The validation of this approach was verified by extra reference standards measurement, which gives relative measurement errors varying from about 1–8% according to the inverse level of the element concentration.

Processing and Thermal Properties of Multiwall Carbon Nanotube/Bismuth Antimony Telluride Composites for Nuclear Energy Applications

In this work the effects of ball milling and carbon nanotubes incorporation on the thermal conductivities of the bulk BiSbTe composites were evaluated. The coarse BiSbTe particles were obtained by crushing BiSbTe lumps and subsequently high energy ball milling was employed in an inert environment to form the fine BiSbTe powder. Multiwall carbon nanotubes in different (0.0, 0.5 and 1.5) vol. % were uniformly mixed in the BiSbTe powder through a combination of ultra-sonication and ball milling, and then processed by rapid high frequency induction heated sintering (HFIHS) to achieve fully dense nanocomposite. Thermal diffusivity of the composites was evaluated and heat capacity was approximated using Pyrocerarm as a reference material. The effect of carbon nanotubes inclusion and BiSbTe particle size reduction on the thermal conductivity was studied from 300 to 500 K. The results show a significant reduction in the thermal conductivity due to the enhanced thermal boundary interface resistance correlated with the fine microstructure/nanostructure in the composites as compared to pristine bulk bismuth antimony telluride.

Analysis of allyl diglycol carbonate by laser induced-breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been used to identify the impurities in the allyl diglycol carbonate, which is used as a charged particle track recording material in solid-state nuclear track detectors. Impurities of magnesium, calcium, sodium and silicon are detected. Plasma parameters such as temperature and electron density are also calculated at optimized conditions in air and argon atmosphere using the silicon lines. The temperature of the LIBS plasma produced in argon atmosphere was higher than the temperature of the LIBS plasma produced in air. Variation in the emission intensity of the carbon I line (247.8561 nm) with respect to acquisition delay and laser power is also studied. It is found that the intensities of Ca and Na lines from LIBS spectra were enhanced 30–40 times in an argon atmosphere as compared to air. Hence LIBS in an argon atmosphere can be used for better identification of impurities in plastics.

Energy Resolution of CsI (TL) Crystal Coupled with PIN Photodiode@@@قدرة تحليل الطاقة للبلورة CsI TL المقرونة بالشرائح الضوئية من نوع PIN

The emission spectrum of the CsI (Tl) scintillation crystal does not match well with the spectrum sensitivity of the standard pho- to-multiplier. This is the main handicap limiting the use of this crystal for radiation detection. However, the production of the new photodi- odes, with better characteristics, is likely to be a good candidate as a readout device for this crystal. One way to investigate this possibility is to study the energy resolution of the CsI (Tl) crystal coupled with a new large area PIN photodiode. The purpose of this paper is to deter- mine the different contributions affecting this resolution including that of the readout device.