مجله فیزیک کاربردی
سال دهم شماره 4 (پیاپی 23، زمستان 1399)

In this study, a fluorescence X-ray spectroscopy system was designed by the Solidworks computer code to detect and measure trace metals. Then, the designed device was simulated and developed by the Monte Carlo method in MCNPX software. The most excellent performance of the trace element detection system was respectively found at 3 cm and 30 cm for source-to-sample distance (SSD) and source-to-detector distance (SDD), respectively. According to the results of different runs of the simulation code, the largest intensity of absorbed X-ray by the detector was obtained for the collimator’s diameter of 3 mm. In addition, the absence of lead shielding around the surrounding metal walls of the detector, even with the use of a lead collimator at the entrance of the detector window, increases the entrance of background beams to the detector and so, it will cause the reduction of spectroscopic accuracy in detecting trace elements. The least amounts of concentration for detecting arsenic, lead, mercury, zinc, copper, and iron were calculated as 0.17 mg/kg, 0.40, 18.40, 20.00, 146.00, and 266.67 mg/kg, respectively. Due to the concentration and level of pollution of these elements, the rare metal detection device designed for research and educational samples, especially in environmental and agricultural samples, will be extremely practical and useful.

Highly excited Rydberg atoms are providing strong and controllable atomic interactions ideal for quantum technology with neutral atoms and photons. In this review article, the significant properties of Rydberg atoms and their scaling with principal numbers are discussed in detail. In addition, the application of laser-excited Rydberg atoms in neutral atom quantum computation is reviewed. This review article discusses, also, the application of Rydberg polaritons in quantum optics devices including single-photon sources, photonic gates, and transistors.

In this research, the electric, magnetic and structural behaviors of the Ag/Hf3NiOy nanostructures fabricated using the co-precipitation technique were studied. Since, the fabrication of ordered metallic structure arrays is habitually complex, the mass production of these structures is being prevented. In recent years, researchers have begun to explore materials with inherent DNG property. Metamaterials allow both field components of light to couple to meta-atoms and thus they enable entirely new optical properties and exciting applications.  Ag/Hf3NiOy disordered percolative composites contain conductive nanoparticles. When the concentration of metal nanoparticles in semi-continuous composites is less than the percolation threshold, the real part of the dielectric constant is positive. Also, the permeability constants can be controlled by silver content, meaning that this parameter is adjustable. Interestingly, decreased permeability was observed in samples with higher silver content. When the silver content exceeded the percolation threshold, silver networks were formed due to the interconnection of silver nanoparticles. The effective magnetic properties were due to the magnetic resonance and eddy current of the samples with an external magnetic field. The plasma oscillations of conduction electrons in the samples at a metallic state led to the negative permittivity.

Investigation of plasma heating is of crucial importance because of its extensive applications including plasma preheating in inertial confinement fusion and magnetic confinement fusion. By propagation of a high-power ultra-short laser pulse through the underdense plasma, the plasma wave is excited in the longitudinal direction behind the laser pulse due to the laser pondermotive force. The laser energy is transferred to the plasma environment via the laser plasma interaction with the particles, so leading to plasma heating. By increasing the laser intensity or plasma density, the wave-breaking phenomenon occurs. The maximum plasma heating occurs in the wave-breaking amplitude. In this paper, the effects of applying a homogenous magnetic field on the plasma wave excited by the propagation of high-power ultra-short laser pulse in the plasma in the amplitudes below the wave-breaking amplitude is investigated, using the 2D PIC simulation method. The results show that the application of this field causes the excited wave to distort and break due to the phase-mixing phenomenon. Moreover, the simulation results show that by applying an inhomogeneous magnetic field, the wave-breaking effects appear sooner than the homogenous one. Therefore, in the moderate laser intensities and low plasma densities, it is possible to gain the maximum heating of plasma by applying the homogenous and inhomogeneous magnetic fields.

In recent years, solar cells with perovskite absorber have attracted considerable attention due to rapid increase in their efficiency. In this research, MAPbI3 layers were coated by a two-step method. Spin-spin and spin-dip methods were studied and physical properties of prepared layers were compared. Their optical and structural properties were investigated by UV-VIS, XRD and FE-SEM techniques. The results of structural analysis showed the formation of cubic phase for MAPbI3 perovskite. In addition, the surface morphology of the layers was determined by FE-SEM images, which confirmed the formation of a uniform and cohesive layer, without any cracks or discontinuities on the surface of layer. Results showed that the optical band gap of the samples are in the range of 1.54-1.59 eV. Furthermore, the effect of precursor concentration on the physical properties of MAPbI3 layers prepared by both methods (spin-spin and spin-dip) was also investigated. The results showed that in both methods, with increasing PbI2 concentration, thicker layers with higher adsorption can be prepared.

Generation of entanglement in separable two qubits states using the one-axis counter twisting Hamiltonian in the presence/absence of a magnetic field is studied by introducing the geometric measure of entanglement. The exact expression for the geometric measure is obtained without calculating the time evolution of the system state using the method of the expectation values of spin. The graphs of this measure as a function of time are plotted. The results show that in order to obtain the maximum entanglement under the influence of one-axis counter twisting Hamiltonian around  axis in absence of magnetic field, the system initially must be in a tensor product of  or  eigenstates. Also, the system initially in the  eigenstates under the influence of one-axis counter twisting Hamiltonian around  axis in absence of a magnetic field is not entangled, but, under the influence of one-axis counter twisting Hamiltonian around  axis in presence of a magnetic field in  direction the entanglement for this state becomes maximum. For all states, the frequency of entanglement is an increasing function of the magnetic field.