Preview

Vestnik natsional'nogo issledovatel'skogo yadernogo universiteta "MIFI"

Advanced search
Vol 12, No 6 (2023)
View or download the full issue PDF (Russian)

TECHNICAL PHYSICS

313-320 131
Abstract

In modern practice, collimators are employed in electron beam therapy to shape the radiation field into standard configurations. However, tumors often exhibit complex shapes, necessitating collimators with individually created collimation windows, typically made of metal alloys. The production of such devices is time-consuming, limiting their widespread use. A promising approach to collimator manufacturing lies in three-dimensional printing, using a fused filament fabrication that makes it possible to produce three-dimensional objects quick and accurate. Presently, the polymer materials used allow for 3D printing products with a density of up to 1.3 g/cm³, which leads the necessity to manufacture a collimator of relatively large thickness. This study proposes the utilization of plastics infused with metal impurities for 3D printing collimators created for the electron beam therapy. Numerical simulations were conducted using the Monte Carlo method to calculate the requisite collimator thickness for effective absorption of electron beams therapeutic energies range. Consequently, a modular collimator was designed and 3D printed, offering the flexibility to vary the diameter of the collimation window from 0.5 to 6 cm. Based on the experimental data obtained for the medical electron beam with an energy of 6 MeV, it was defined that the 3D printed device can effectively shaped a radiation field corresponding to the choosing diameter of the collimation window. It is important to consider the features of electron beam field shaping using a plastic collimator during the electron beam treatment planning.

MATHEMATICAL MODELS AND NUMERICAL METHODS

321-325 104
Abstract

A special class of nonlinear differential equations with solutions in the form of solitary waves is considered. The main feature of these differential equations is that they have a solution in the complex plane with an arbitrary pole order. It is shown that using a modification of the method of simple equations allows one to find exact solutions in the form of solitary waves. The presented method is used to obtain stationary solitary waves to describe processes in a liquid with gas bubbles. Also, this method is used to find stationary solitary waves of bacterial concentration when taking phototaxis into account.

326-331 108
Abstract

The generalized Chavy–Waddy–Kolokolnikov equation is considered, which describes nonlinear physical and biological processes, in particular, the movement of bacteria under the influence of stimuli. Numerical study of the model is carried out using the pseudospectral method. To test the program, exact solutions of the generalized Chavy–Waddy–Kolokolnikov equation are used. For numerical modeling, initial conditions are used in the form of periodic and solitary waves, as well as in the form of white noise. Graphs of the results of numerical simulation are presented. It is shown that at different values of the model parameters, periodic structures are formed.

332-338 81
Abstract

A model of nonlinear optics described by the generalized fourth-order Schrödinger equation with nonlinearities of the third, fifth, seventh and ninth degrees is considered. An analysis of the stability in the first approximation of the exact solution of this model in the form of a monochromatic wave is carried out. Analysis of stability in the first approximation allows us to obtain the condition for the instability of the exact solution. The split-step Fourier method is used to numerically solve the model. An analysis of the stability in the first approximation of the solution of the numerical model in the form of a monochromatic wave corresponding to the exact solution of the analytical model is carried out. The instability condition in the first approximation of the solution of the numerical model in the form of a monochromatic wave is derived. It is demonstrated that from the fulfillment of the instability condition in the first approximation, obtained for the exact solution in the form of a monochromatic wave, the fulfillment of the instability condition for the numerical solution follows, while the converse is not true. A condition is given for the time step of the numerical model, under which the instability conditions in the first approximation for the numerical and analytical solutions coincide.

COMPUTER SIMULATION OF PHYSICAL AND TECHNOLOGICAL PROCESSES

339-351 129
Abstract

Nowadays, the learning process occurs in different forms, with traditional methods of learning being supplemented and replaced with new online and blended learning formats. The capabilities of modern information technologies make it possible to widely use online courses and specializations produced at numerous universities and leading companies that develop new technologies. E-Learning has become an international trend. Various Massive Open Online Course (MOOC) platforms have become very important, including the National Open Education Platform developed in the Russian Federation. Many modern nuclear physics and engineering courses are developed in collaboration with leading scientific centers and the State Atomic Energy Corporation Rosatom (ROSATOM). This article provides information about the successful cooperation of the large international, intergovernmental scientific center, the Joint Institute for Nuclear Research (JINR), and the National Research Nuclear University «MEPhI» (NRNU MEPhI) with the participation of universities of Bulgaria, Mongolia, Vietnam, Egypt, Serbia and the Republic of South Africa. Such cooperation is aimed to provide an open information and educational environment of fundamental and applied research support, online courses for national and international platforms, and virtual laboratory workshops in nuclear physics and nuclear electronics. In addition to information about e-learning, this article talks about research practices and master class organization for high school students and schoolchildren from different countries, including Egypt, Mexico, India, Vietnam, and the Republic of South Africa. Despite the fact that educational courses about nuclear physics and related technologies are used by a relatively small circle of students and young professionals, our analysis shows that they have a wide audience around the world, including countries that collaborate with JINR, NRNU MEPhI, and ROSATOM. Virtual laboratory workshops dedicated to the basics of experimental nuclear physics are already used at universities in many countries worldwide.

352-356 120
Abstract

The radiation therapy is one of the methods used for treating malignant tumors. Ionizing radiation during the interaction with tumor cells cause their destruction. However, during the radiation treatment of malignant tumors, there is inevitably a side effect on healthy cells as well. Therefore, an important task of beam therapy is to ensure optimal dose distribution, in order to minimize the impact of radiation on healthy tissues and deliver the maximum dose to the tumor. One device that allows for the formation of depth dose distribution in the patient's body is a bolus. Previously, boluses for electron beam therapy have been manufactured using three-dimensional printing methods. The aim of this study was to develop a numerical model to determine the electron beam depth dose distribution in plastics modified with metallic additives. The use of these materials enables the creation of smaller boluses, which can accelerate the manufacturing time and simplify the device fixation procedure on the patient's body. Numerical models of electron beam source and plastic boluses were developed using the GEANT4 toolkit. Numerical experiments were conducted using the Monte Carlo method. As a result of the simulation the depth dose distributions of electron beams with nominal energies of 6, 12, and 15 MeV were obtained in modified plastics with copper additives. In the future, the obtained data will allow for the selection of the thickness of the forming device created using three-dimensional printing from the studied plastics, according to the clinical task.

AUTOMATION AND ELECTRONICS

357-367 184
Abstract

For qualitative work of  X-ray diagnostic equipment and simple detection of the fact of malfunction should be carried out routine checks and focused on the X-ray operator. The purpose of the article was to develop a simplified approach to periodical technical control of X-ray equipment and to verify the equipment functioning stability without the use of a specialized test object. The article presents the results of theoretical and experimental study of the method of operative checking the operability of X-ray diagnostic machines with digital receptor in the conditions of continuous functioning of the department. The presented method is oriented on the estimation of digital X-ray diagnostic apparatus operability based on the determination of the parameters of the registered image obtained in the absence of the test-object in the input plane of the receptor and the further estimation of the output signal-to-noise ratio and the receptor transmission coefficient. An algorithm for operational control of the digital X-ray diagnostic apparatus efficiency was developed. The expert method was used to determine the valid ranges of key image parameters changes. The study shows the operability of the method and its simplicity.



Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.


ISSN 2304-487X (Print)