The purpose of this work is to determine a date for the next reloading operation of the panoramic gamma irradiator of the Moroccan National Institute of Agronomic Research (NIAR) by studying the variation with time of the dosimetric mapping at the inside the irradiation casemate between 2021 and 2030. Monte Carlo simulation via the Geant4 code was used as a tool to establish the distribution of isodose in the irradiation room due to its important role in meeting the dosimetric requirements for this type of facilities. The results show that from 01/01/2024, serious measures must be taken to arrange a date for the NIAR irradiator reloading operation not later than 2027.
Show AbstractFor the purpose for exploring the thermal phenomenon under the electron irradiation process in the scanning electron microscope (SEM) imaging, a Monte Carlo (MC) simulation method was used to mainly calculate the spatial distributions of local temperature rise in two commonly-used nanostructures: a capsule-shaped gold nanorod (Au NR) and a silicon (Si) pitch. The influences of the primary electron (PE) beam energy and the PE beam size on the heat generation were systematically investigated. This work verified that 1) the heat in the main body of an Au NR is larger than that in two ends; 2) the heat in the periphery of an Au NR is less than that inside. As the PE energy increases, the distribution region of temperature rise gradually expands from the upper surface deep into interior and its amount rises proportionately. This study next presents that the distribution of temperature rise in a Si pitch becomes uniform with the increase of PE energy, but showing a weakening local intensity. The PE beam size affects the heat generation in both two structures significantly. Specifically, the distribution of temperature rise shows a gradually reduced intensity towards the larger PE beam size. Furthermore, this work revealed that the total electron (TE) line-scan profile inversely relates the temperature contour map. On the basis of the analysis of the electron trajectory and the electron-solid interaction, the underlying mechanism of these results was explained in detail. Compared with earlier reports that just focused on bulks, this work is of great benefit to study the relations between the local thermal issue and the structure of samples under a PE beam irradiation. It is believed that this research will greatly promote the development of the semiconductor industry.
Show AbstractUsing a method that combines double high-speed photography and a pump-probe method, it was found that a femtosecond laser pulse is able to change the domain wall velocity in a ferrite film. The combination of these methods was used for the first time. The change in the velocity of the domain wall depends on both the energy of the pump pulse and the domain wall velocity itself, and does not depend on the pump pulse polarization. This result is not associated with local magnetization reversal and cannot be explained by local heating of the material, since a temperature increase leads to an increase of the domain wall mobility. To explain the results, we propose a model in which the domain wall velocity is controlled by the photo-induced generation of vertical Bloch lines.
Show AbstractThe microstructure of the membrane alloy Pd-9.1 at. % Y is studied by X-ray diffraction using synchrotron radiation and transmission electron microscopy with electron diffraction. It is shown that the matrix phase in the alloy has a face-centered cubic lattice. The presence of Guinier-Preston zones and the formation of the alloy atoms ordering are determined. The presence of defects enriched with atoms of the same type are revealed. The deformation fields created by them are shown.
Show AbstractThe paper investigates the conditions on the initial function in a parabolic problem for a onedimensional reaction-diffusion equation with a front-like solution, so that over time the front is stabilized to the solution of the corresponding stationary problem. The study of the work extends the class of the indicated initial functions previously obtained by V.F.Butuzov. and I.V. Nedelko from twice continuously differentiable to continuous piecewise smooth with a finite number of points where the function is not smooth. In this paper, the domain of attraction of a stable stationary solution is determined using the upper and lower front-form solutions of parabolic problem. This approach makes it possible to take into account the estimates for the front velocity and, due to this, to refine the time it takes for the solution of the parabolic problem to be in a small neighborhood of the stationary solution. This result is practically important for the application of numerical methods of stationing when solving elliptical problems.
Show AbstractThe basic aspects of ghost polarimetry (GP), a new promising direction in ghost optics, which we have been developing recently, are discussed. In modern terminology GP is an intelligent optical imaging system that belongs to the class of artificial intelligence systems. The principles of constructing the theory of GP in both classical and quantum light are considered. Techniques and schemes for the experimental implementation of GP are described. The descriptions of the instrument base, created by us, allowing to realize GP in quantum light are given: counters of single photons; time-to-digital converter; SPDC-sources of correlated photons and a quantum tomograph.
Show AbstractThe process of Rydberg blockade--which is considered now as one of the most promising approaches to the quantum computing--can loose its efficiency substantially due to the interatomic interactions, shifting the excitation frequency of the originally blocked particles to the resonant band with the external laser irradiation. Here, we develop the analytical theory of this effect based on the self-consistent model of two Rydberg atoms affecting each other by their dipole electric fields and experiencing the corresponding Stark splitting of their energy levels. As follows from our calculations, the characteristic interatomic distance were the effect of unblocking due to the "parasitic" resonances begins to develop approximately coincides with the previous qualitative estimates. However, the number of such resonances can be much greater than in the recent numerical simulations of some particular systems. Therefore, the possibility of breaking the Rydberg blockade at small interatomic distances should be taken into account very carefully in any applications for the quantum computing.
Show AbstractVerification of radiation therapy plans on the Tomotherapy device is generally performed by comparing the measured dose distribution in the phantom with the calculated dose from the Tomotherapy planning system. However, the number of points at which measurement is possible is limited, and the time of the verification procedure exceeds the time of the patient's treatment. At the same time, the exit detectors of the machine have the ability to measure the output radiation fluence throughout the entire irradiation time, they have a high spatial resolution, and do not require additional installation efforts. The article develops a method for processing data from the exit detectors of Tomotherapy and for comparing them with data from the planning system. An application has been created in the MATLAB that processes 2 types of data: a radiation therapy plan in DICOM format from the planning system and raw data from the exit detectors. A method for resulting the data to a single view is developed by taking into account correction factors, such as background radiation, the shape of the detector, the influence of neighboring leafs, and the leaf-channel relationship. It is possible to compare two sets of data using a two-dimensional gamma index. The created method will make the verification of radiation therapy plans more informative, accurate and easier, and in the future, it can help evaluate the accuracy of dose delivery and the accuracy of patient positioning during treatment.
Show AbstractStatistical estimates of the relationship between the characteristic sizes and lifetime of polar lows (PL) were obtained using STARS data (Sea Surface Temperature and Altimeter Synergy for Improved Forecasting Polar Lows) for the period 2002-2010. The features of their nonlinear relationship are noted. A model explanation is proposed for the power-law, in the simplest case, linear, relationship for the large-scale and long-lived PL. Keywords: STARS data, relationship between size and lifetime of polar lows, model estimates
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