دکتر حمیده دانشور

Radiation damages have destructive effects on the electronic components of satellites. Due to financial reasons and the presence of different restrictions, the utilize of commercial components ended up common in short-term and low-altitude missions. The most effective method of protection against radiation is the use of shields. The results of calculations obtained from PSTAR and ESTAR software show that in case heavier metals are utilized, the energy range of particles to stop increases. The result of SHIELDOSE, MULASSIS, PSTAR, and ESTAR software calculations is that the amount of thickness of different materials for the radiation tolerance of commercial parts does not differ much in terms of condensation thickness. Also, there is no need for complex protection and it can be used the usual protections. The maximum thickness required for the radiation tolerance of commercial parts is 0.5 mm from the combination of Aluminum and Tantalum. In order to achieve the best result considering the mass budget, it is better to use polyethylene material. From the results of the calculations to change the permutations of the aluminum and polyethylene shields, it can be concluded that it is better to have the first layer of polyethylene and the next layer of Aluminum.

Space radiation can affect the performance and reliability of components in space systems. This paper focuses on the investigation of three types of radiation damage including ionizing dose, displacement damage, and single event damage using OMERE software. Considering the outputs of this software, how to use and use a variety of electronic components with different commercial, military and space grades in LEO and GEO satellites is discussed. These components have the least risk of displacement damage. Mass budget constraints should also be considered when using commercial components in the GEO circuit. The maximum thickness for the safety of components in LEO and GEO circuits is 2.6 mm and 9.5 mm respectively. Given the inability of SEE damage to increase in thickness, the best solution to this damage is to use radiation-resistant solutions, especially software issues.

In this research work, hydroxyapatite was synthesized via solid-state method and effect of heat treatment on its thermoluminescence response was investigated for gamma-radiation dosimetry purposes. At the first, hydroxyapatite samples were synthesized in pure form. Then, the hydroxyapatite samples via the same synthesize method were doped with single impurities of Ce and La with concentrations of 1%, 2%, and 5% and were examined afterward.
In order to identify and evaluate the changes that occurred in the material structure and then on dosimetric response, x-ray diffraction apparatuses were used. The results were examined from different dosimetry aspects such as, glow curve change, dose response curve, reproducibility, and fading. The obtained results showed that synthesis in the higher temperature using the solid-state method, is more suitable for dosimetry purposes.

In this paper, multi layer radiation shield is designed for electrons and protons space environments to protect in all satellite orbits. The designed shield layer material and thickness is analyzed and optimized by MCNPX linked with Matlab. In Matlab, genetic algorithm is employed for optimization where the cost function is obtained from MCNPX. The designed shield achieves more than 53% TID reduction for proton environment and more 72% TID reduction for electron environment compared with aluminum by similar thickness. This good specifications prove the capability and ability of the deigned multilayer shields to protect the electronic parts in the satellite applications.

So far, various methods have been proposed for the synthesis of hydroxyapatite nanoparticles as the main ingredient in bone and enamel. In each of these methods, by varying initial conditions of synthesis, samples of size and shape, and the ratio of length to diameter can be achieved. In this study, pure hydroxypropyl nanoparticles were prepared using calcium nitrate precursors (Ca (NO3) 2-4H2O) and diammonium hydrogen phosphate ((NH4) 2HPO4) by hydrothermal method. The purpose of this study was to investigate the effects of changes in reaction conditions and the synthesis of this material on the size and shape of the particles. X-ray diffraction (XRD) and scanning electron microscopy (SEM) nanoparticles were investigated. The results of the experiment indicate that the concentration of the raw materials, the method and temperature of calcining, the speed of the addition of materials, the use or non-use of surfactants can have different effects on the size and shape of the hydroxyapatite particles.