Characterization of X‐ray gas attenuator plasmas by optical emission and tunable laser absorption spectroscopies

X‐ray gas attenuators are used in high‐energy synchrotron beamlines as high‐pass filters to reduce the incident power on downstream optical elements. The absorption of the X‐ray beam ionizes and heats up the gas, creating plasma around the beam path and hence temperature and density gradients between the center and the walls of the attenuator vessel. The objective of this work is to demonstrate experimentally the generation of plasma by the X‐ray beam and to investigate its spatial distribution by measuring some of its parameters, simultaneously with the X‐ray power absorption. The gases used in this study were argon and krypton between 13 and 530 mbar. The distribution of the 2p excited states of both gases was measured using optical emission spectroscopy, and the density of argon metastable atoms in the 1s₅ state was deduced using tunable laser absorption spectroscopy. The amount of power absorbed was measured using calorimetry and X‐ray transmission. The results showed a plasma confined around the X‐ray beam path, its size determined mainly by the spatial dimensions of the X‐ray beam and not by the absorbed power or the gas pressure. In addition, the X‐ray absorption showed a hot central region at a temperature varying between 400 and 1100 K, depending on the incident beam power and on the gas used. The results show that the plasma generated by the X‐ray beam plays an essential role in the X‐ray absorption. Therefore, plasma processes must be taken into account in the design and modeling of gas attenuators.     

A simplified mathematical study of thermochemical preparation of particle oxide under counterflow configuration for use in biomedical applications

This study mathematically presents a counterflow non-premixed thermochemical technique for preparing a particle oxide used for cancer diagnosis and treatment. For this purpose, preheating, reaction, melting, and oxidation processes were simulated considering an asymptotic concept. Mass and energy conservation equations in dimensional and non-dimensional forms were solved using MATLAB^®. To preserve the continuity in the system and calculate the locations of melting and flame fronts, promising jump conditions were derived. In this research, variations in flame temperature, flame front location and mass fractions of the particle, particle oxide and oxidizer, with position, Lewis number and initial temperature of the particles were investigated. The simulation results were compared with those obtained from an earlier experimental study under the same conditions. Regarding the comparison, an appropriate compatibility was observed between the results. Based on the simulation results, flame temperature was found to be about 1310 K. Positions of flame and melting fronts were found to be ??1.8 mm and ??1.78 mm, respectively.

     

201Tl production through light charged-particle induced reactions on Tl and Hg isotopes: theoretical and simulation approaches

Investigation of the significant ²⁰¹Tl diagnostic radionuclide production via protons and deuterons induced reactions by using the ²⁰³Tl, ²⁰¹Hg and ²⁰²Hg isotope targets is the main goal of this study. The effect of three phenomenological and microscopic level density models utilizing the TALYS-1.8 code along with TENDL-2017 data were applied to excitation functions evaluations. Furthermore, simulation code was used for the above production processes. Subsequently the prediction of the production yield in each reaction was done. Finally, the comparison between EXFOR database experimental data and the theoretical and simulation-based calculations was implemented.

     

A smoothed particle hydrodynamics approach for numerical simulation of nano-fluid flows

Journal of Thermal Analysis and Calorimetry - Nano-fluidic flow and heat transfer around a horizontal cylinder at Reynolds numbers up to 250 are investigated by using weakly compressible smoothed...     

Modeling of Neurodegenerative Diseases Using Discrete Chaotic Systems

Parkinson's and Huntington's diseases are two of the most common neurodegenerative disorders.Tremor, muscle stiffness, and slowness of movement are symptoms of Parkinson's disease. The symptoms of Huntington's disease are severe reduction in muscle control, emotional disturbance, and pathological disorders in brain cells.These diseases are caused by destruction of the cells that secrete a substance called dopamine. In this paper,a new discrete chaotic system is introduced,which can mimic the brain's behavior for neurodegenerative diseases such as Parkinson,Huntington, and Hypokinesia. This system is described based on the similarity between the brain's behavior in normal and abnormal conditions and the chaotic systems. Bifurcation analysis is carried out with respect to different parameters, providing full spectrum of the behavior for different parameter values.Our results can be used to mathematically study the mechanisms behind these diseases.