مجله فیزیک کاربردی
سال نهم شماره 3 (پیاپی 18، پاییز 1398)

The displacement of the atoms from their lattice sites is one of the results of neutron irradiation on materials. The primary knocked-on atoms spectrum and their angular distribution should be calculated for consideration of neutron radiation damage calculation. The AMTRACK program has been developed to calculate this information. This program extracts and analyzes information about the primary knocked-on atoms by using Ptrac output of the MCNPX code. In this study, Stainless Steel 316, one of the most important alloys in the reactor pressure vessel, is investigated. The material is irradiated by single energy neutrons of 1keV to 10MeV, the fraction of produced PKAs, their average energy, their maximum energy, and radiation damage value are calculated. The calculations are performed by using the neutron spectrum of the Bushehr reactor. Using this method, the amount of damage in the Bushehr reactor pressure vessel (for Stainless Steel 316) is equal to 7.2×10-22 (dpa/ fluence).

In this article, the thermal conductivity in one-dimensional devices, including semiconducting nanowires of silicon and gallium arsenide is calculated and plotted. The method used is solving the Boltzmann equation for phonon scattering. In case of purely specular interface scattering, the thermal conductivity is found to be high in silicon and gallium arsenide nanowires. The thermal conductivity increases with increasing nanowire diameter. In this work two different models for thermal conducting have been investigated. The first model solves the Boltzmann equation and finds solutions with the relaxation time approximation, and the other is a self-consistent solution of the Boltzmann equation. The answers in these two solutions are combined. The results show that the thermal conductivity in Si and GaAs semiconductor nanowires is reduced nearly 0.21 and 0.19 than that of bulk devices respectively in agreement to the reported data. It is found that the thermal conductivity of gallium arsenide nanowire is lower than that of silicon nanowire and comparing to recent published data for the corresponding Si nanowires with smaller diameter is overestimated and for larger nanowires diameter is underestimated which could be due to not taking into account the optical phonons decay to acoustic phonons and the effect of surface roughness on the thermal conductivity.

A four-level inverse Y-type atomic system with a microwave-driven field contained in a unidirectional ring cavity is proposed for controlling the optical bistability behavior with application on all-optical switching. Two circularly polarized components from a weak linearly-polarized probe beam are interacted separately by two transitions of this medium. A coherent coupling field derived another atomic transition. Under the steady state condition, we can control the occurrence of the optical bistability by modulating different parameters, such as the probe detuning ( ), the electronic cooperation parameter (C), the magnitude of electromagnetic field (B), and left- or right- handed circular polarized beams. Also, it is found that the stable output field of the optical cavity can be controlled by adjusting the intensity of the input field. It is demonstrated that the transmission coefficient of two orthogonally polarized beams at different frequencies can be achieved by adjusting the magnitude of the external magnetic field. It is found that the threshold of the optical bistability can be controlled by the magnitude of the external magnetic field. Also, it is shown that the optical bistability can be converted to optical multistability by switching the two orthogonally polarized beams. In this paper, in the case of the steady-state and transient response, we investigated the effect of external magnetic field on optical bistability of a four-level atomic system in the presence of strong coherent laser beam. Here, a laser probe signal consists of two left- and right- handed circular polarized beams which are interacted by two different transitions. The optical system provides a new experimental method to test optical bistability theory.

The influence of impurity parameters as well as the type of incident light polarization at the disk-like quantum dot with including the Rashba spin-orbit coupling on the second harmonic generation are studied. The impurity potential is assumed to be Gaussian and its effective parameters are: potential strength, decay length, impurity type and its location at the quantum dot. The calculations are performed in the framework of the effective mass approximation. The results showed that the presence of impurity leads to changes in the second harmonic generation, and the value of the second harmonic generation can be controlled by changing the impurity parameters. For example, in both types of the impurities, by increasing the impurity distance from dot center, the maximum value of this coefficient shifts to higher energies. The role of light polarization in this coefficient is also investigated and it was shown that the type of light polarization has no effect on the peak position of the second harmonic generation and only affects its peak value.

The aim of this project is to investigate the effects of 2-Pyrrole carboxylic acid molecule adsorption on the surface of pristine and Pd functionalized boron nitride nanocage (B12N12). All selected structures are optimized within the framework of DFT using B3LYP/Lanl2DZ. From optimized structures, the geometrical parameters (bond length, bond angle), HOMO and LUMO orbitals, infrared spectrum (IR), chemical shielding isotropic parameters (CSI), natural bonding orbital (NBO), quantum parameters, atom in molecule parameters (AIM) and molecular electrostatic potential (MEP) maps are calculated. The results indicate that in the functionalized B12N12 nanocage, the gap energy and global hardness of system decrease significantly from original state and so the conductivity and reactivity of BN nanocage increase.  The adsorption energy and enthalpy values of all adsorption models are negative and are exothermic and favorable in thermodynamic approach. The NBO, MEP and CSI parameters reveal that the electron charge transfer occurs from adsorbent toward nanocage, and this property is notable for electrophilic and nucleophilic attack in biological systems. The computational results demonstrate that the pristine and Pd functionalized BN nanocage can be used as a suitable candidate for fabricating detector and absorber for 2-Pyrrole carboxylic acid.

The study of ionic impurities present in tokamak plasma is an essential tool for studying plasma behavior and determining its various parameters such as temperature, electron density and plasma flow rate. For this purpose, high resolution optical spectroscopy system was installed on the Tokamak IR-T1 to measure the carbon-ion impurity temperature in the plasma. By processing the emission spectral lines recorded by the spectrometer, the location of the spectral line corresponding to the carbon impurity is estimated, and the effective width of the carbon spectral line is determined by matching a Gaussian function to the experimental data. Given the effective width of the carbon spectrum line, its doppler broadening and consequently the carbon ionic impurity temperature are calculated. Carbon CIII ion temperature is obtained about . The experimental impurity temperature is comparable to the results of ISTTOK and COMPASS tokamaks.