Faculty of Physics
M.V. Lomonosov Moscow State University

# Issue 2, 2023

Physics of nuclei and elementary particles

## Measurement of the tensor analyzing power $T_{20}$ for the reaction $\gamma d \to p n \pi^0$ in the region of low proton energies

### B. I. Vasilishin$^1$, V. V. Gauzshtein$^2$, E. M. Darwish$^4$, A. I. Fix$^1$, M. I. Levchuk$^3$, M. Y. Kuzin$^1$, A. Yu. Loginov$^5$, D. M. Nikolenko$^6$, I. A. Rachek$^6$, Yu. V. Shestakov$^6$, D. K. Toporkov$^6$, A. V. Yurchenko$^6$, S. A. Zevakov$^6$

Moscow University Physics Bulletin 2023. N 2.

In this paper, we present new experimental results for the tensor analyzing power $T_{20}$ of the reaction $\gamma d \to p n \pi^{0}$ in the region of low proton energies. The results are presented in the photon energy range of $300\,\text{MeV} < E_{\gamma}< 600\,\text{MeV}$ and the proton energy range of $10\,\text{MeV} < E_{p} < 40\,\text{MeV}$. The paper uses the experimental statistics accumulated at the VEPP-3 accelerator complex in 2013. To identify the events of the reaction $\gamma d \to p n \pi^{0}$, we used the registration of the proton and two $\gamma$-quanta from the decay $\pi^{0} \to 2 \gamma$ in coincidence. The experimental results were compared with the results of statistical simulation. To perform the statistical simulation, we used the unitary isobar model MAID 2007 for the elementary pion-nucleon photoproduction amplitude and took into account $\pi N$ and $N N$ rescattering in the final state of the reaction $\gamma d \to p n \pi^{0}$.

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## EVALUATION OF SECONDARY NEUTRON PRODUCED IN PROTON THERAPY USING PHITS

### M. B. Mohamed$^1$, Z. Sadoune$^1$, H. El Bekkouri$^2$, A. Didi$^3$, C. El Mahjoub$^2$

Moscow University Physics Bulletin 2023. N 2.

Proton therapy uses high-energy proton beams to kill cancer cells while spare surrounding healthy tissues, due to their Bragg peak characteristics, which has become the choice treatment for many types of tumors. However, the production of secondary neutrons by the interactions of primary protons with the body and the environment might provide undesirable extra radiation outside the treatment volume, which could reduce the benefit of this over the traditional radiation therapy. The purpose of this research is to evaluate the secondary neutrons produced from a spot scanning beam in the soft tissue phantom and their contribution in terms of dose mainly to the distal of the Bragg peak, the flux, and energy spectra as well as evaluated using the Monte Carlo code PHITS. According to this study, the contribution to the overall dose that occurred after the peak maximum was at least a thousand times lower. We concluded that this dose has no natural effect on a potentially application therapeutic.

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Theoretical and mathematical physics

## JT Gravity, Random Matrix Theory and Third-Order Phase Transition

### J. J. Zhou$^1$

Moscow University Physics Bulletin 2023. N 2.

The partition functions of Jackiw-Teitelboim (JT) gravity corresponds to random matrix integral. And we can define three different versions of bosonic JT gravity which are dual to matrix integrals of GUE, GOE and GSE, respectively. In fact, the largest eigenvalue λmax of the Gaussian unitary random matrix GUE is described by the Tracy-Widom distribution. Then we show that there is a third-order order phase transition in the JT gravity as λmax crosses its mean value from left weakly coupled tail to right strongly coupled tail.

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## Phase transition temperature in some lattice models

### A. O. Shishanin

Moscow University Physics Bulletin 2023. N 2.

A method for calculating the phase transition temperature using only one cell is considered. This method has been tested for various lattice models: Ising model on triangular, hexagonal and tetrahedral lattices, three-position Potts model on a square lattice. In particular, exact replies are reproduced in the Ising model for square and triangular lattices. Also, this method was used to analyze some multi-spin models.

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## Evaluation of the efficiency of the simplified simulator of the optical coating deposition process

### A. N. Sharov$^1$, D. V. Lukyanenko$^1$, A. V. Tikhonravov$^2$, A. G. Yagola$^1$

Moscow University Physics Bulletin 2023. N 2.

The paper presents a comparison of the results of simulating the processes of deposition of optical coatings using a simplified simulator and a full simulator that takes into account the main error-producing factors of deposition processes and control of coating layer thicknesses. For the simulators under consideration, the distributions of error vector norms in the layer thicknesses of coating, layer error correlation coefficients, and error self-compensation coefficients are calculated. It is shown that the simplified simulator allows one to obtain adequate results for evaluating the deposition process of real multilayer optical coatings and, thus, can be used for faster modeling of a large number of coatings with further analysis of their stability against manufacturing errors.

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Engineering physics

## Neutron and Gamma Flux Distributions of an Americium-Beryllium Facility: Modelling and Simulation

### A. Didi$^{1,2}$, H. Amsil$^1$, H. Bounouira$^1$, K. Laraki$^1$, H. Marah$^1$, H. Dekhissi$^2$, A. Dadouch$^3$, I. Aarab$^1$

Moscow University Physics Bulletin 2023. N 2.

This study aims to enhance and advance the Technique of Analysis by Neutron Activation, which is widely utilized in various industries. The use of alternative neutron sources, rather than nuclear reactors, is a crucial approach to prevent incidents. The primary objectiThis study aims to enhance and advance the Technique of Analysis by Neutron Activation, which is widely utilized in various industries. The use of alternative neutron sources, rather than nuclear reactors, is a crucial approach to prevent incidents. The primary objective of this research was to assess the neutron flux profile, lateral gamma flux, and axial gamma flux to determine the optimal location of a sample for efficient neutron irradiation. Furthermore, the feasibility of using an \textsuperscript{241}Am-Be neutron source facility as an alternative to a nuclear reactor for irradiation was evaluated through simulations conducted with the MCNP6 code.ve of this research was to assess the neutron flux profile, lateral gamma flux, and axial gamma flux to determine the optimal location of a sample for efficient neutron irradiation. Furthermore, the feasibility of using an Am-Be neutron source facility as an alternative to a nuclear reactor for irradiation was evaluated through simulations conducted with the MCNP6 code.

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## Sputtering of CuPt alloy

### V. S. Chernysh, D. K. Minnebaev, D. S. Kireev

Moscow University Physics Bulletin 2023. N 2.

The paper reports the results of an experimental study of sputtering of a polycrystalline CuPt alloy irradiated with Ar+ ions with energies of 20 keV and 80 keV. The sputtering yield of the alloy was measured using Rutherford backscattering of He+ ions with an energy of 2 MeV. It is found that the sputtering yield of the alloy is less than the corresponding value for Cu, but higher than the value for Pt. The results are discussed in the framework of modern concepts about the preferential sputtering of multicomponent materials.

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## Scattering and ion emission from insulator films

### E. Yu. Zykova, A. E. Ieshkin, K. F. Minnebaev, K. E. Ozerova, N. G. Orlikovskaya, E. I. Rau, A. A. Tatarintsev

Moscow University Physics Bulletin 2023. N 2.

To determine the effect of the surface potential of dielectric samples on the yield of positive ions during ion irradiation, we studied the dependence of the current of secondary particles on the thickness of dielectric films. It is shown that the yield of positive secondary particles increases significantly with increasing thickness if the film charging potential does not exceed the breakdown value determined by the electrical strength of the film. An indirect confirmation of the film charging in these experiments is the time dependence of the current from the sample holder. An experimental evaluation of the apparatus effect caused by the emission of secondary electrons from a hemispherical collector has been carried out. Possible mechanisms of the observed phenomena are discussed.

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Optics and spectroscopy. Laser physics

## Finite voxel size compensation for microprinting of parabolic X-ray lenses by two-photon lithography

### M. I. Sharipova, T. G. Baluyan, A. S. Sverchkov, D. A. Shilkin, V. O. Bessonov, A. A. Fedyanin

Moscow University Physics Bulletin 2023. N 2.

3D-microprinting by two-photon lithography can be applied to fabricate X-ray lenses. However, when the lens' curvature radius approaches voxel size, the lens' refractive surface essentially differs from the defined model. This shape distortion leads to defocusing of X-ray irradiation and astigmatism. In current work we suggest the compensation of the parabolic lens model taking into account finite voxel size.

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## Radiation and transition losses in curved waveguides for Bloch surface waves

### D. A. Shilkin, K. R. Safronov, A. D. Rozanov, V. O. Bessonov, A. A. Fedyanin

Moscow University Physics Bulletin 2023. N 2.

One-dimensional photonic crystals that support the propagation of Bloch surface electromagnetic waves attract the interest of researchers as an alternative platform for integrated optics with potential applications in nanophotonics, sensing, and optical manipulation of micro- and nanoparticles. In this paper, we numerically study the properties of surface wave modes in curved waveguides on top of a one-dimensional photonic crystal. It is shown that, when the waveguide is bent, an additional channel of radiation losses appears, which is associated with light leakage from the surface wave mode into bulk modes of the photonic crystal, and the waveguide mode profile becomes asymmetric with respect to the middle of the waveguide. We also determine the conditions for minimizing transition losses, which occur at the junctions of waveguides with different curvatures, by transverse displacement of the waveguide facets relative to each other.

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Condensed matter physics

## Nanostructured coatings based on titanium for electrodes of electrochemical devices with solid polymer electrolyte

### M. V. Sinyakov$^{1,2}$, A. A. Zasypkina$^1$, V. V. Tishkin$^1$, N. A. Ivanova$^1$, E. A. Vorobyeva$^{1,3}$, O. K. Alekseeva$^1$

Moscow University Physics Bulletin 2023. N 2.

During the operation of electrochemical devices with a proton-exchange membrane under the action of oxygen, the electrode is gradually destroyed and degraded from the anode side. It is possible to increase the performance and service life of electrodes of electrochemical devices by applying Ti-based protective coatings to the surface of current collectors. In this work, nanostructured films of the compositions Ti, TiOx, TiNy, TiOxNy were obtained by magnetron sputtering of a titanium target under various conditions. The structure and composition of the samples were studied by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction phase analysis. The effect of various modes and conditions of magnetron sputtering on the composition and structure of titanium coatings has been established. The service life of an electrode coated with the TiNy composition in the electrolyzer mode is 2 times higher than the service life of an anode without a coating under similar conditions with comparable efficiency.

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## Platonic and Archimedean bodies as the basis of the structure of self-accommodating complexes of martensite crystals in alloys with shape memory effects.

### A. G. Khundjua, E. A. Brovkina

Moscow University Physics Bulletin 2023. N 2.

The aim of the work is to analyze the relationship of the architecture of self-accommodation complexes (SC) with the lattice syngony of martensite crystals. Self-accommodating complexes consist of a set of pairwise twinned domains – crystals of martensite belonging to crystallographically equivalent variants of the orientation relationship between the lattices of austenite and martensite. The simplest SC are calculated for tetragonal, orthorhombic, rhombohedral and monoclinic distortion of the cubic lattice of austenite. It is shown that complete self-accommodation is possible only in complexes containing simultaneously all variants of the orientation relation. The issue of external faceting of complexes is discussed. The reason for the formation of SC is the minimization of elastic energy, i.e. the appearance regulated by the energy of the interphase boundary. On the other hand, if the outer surface of the SC is a polyhedron, then its symmetry should "fit" into the anisotropy of the elastic properties of austenite. For reasons of symmetry, it is clear that the polyhedron must be correct and have the same symmetry elements as the cubic lattice of austenite, while the axes of symmetry of the cubic lattice of austenite must coincide with the axes of symmetry of the polyhedron. Similar polyhedra are some of the bodies of Platon and Archimedes, which have axes of symmetry of the 2nd, 3rd and 4th order. A number of examples calculated in the work confirms the possibility of the existence of complexes in the form of these polyhedra.

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## effect stability

### T. T. Muratov

Moscow University Physics Bulletin 2023. N 2.

in article is considered

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Chemical physics, physical kinetics, and plasma physics

## Experimental study of the motion of a shock wave in the plasma of a pulsed volume discharge in air

### A. A. Ivanova, I. V. Mursenkova

Moscow University Physics Bulletin 2023. N 2.

The motion of quasi-plane shock waves with Mach numbers М = 2.20–3.50 in the plasma of a nanosecond combined volume discharge in air at an initial pressure of 10–100 Torr has been experimentally studied on the basis of high-speed shadow registration of the flow field. The dynamics of shock-wave configurations after the discharge at various stages of an unsteady supersonic flow, which is formed after the diffraction of a plane shock wave by a rectangular obstacle, is studied. An increase in the velocity of the shock wave front over a time interval of up to 15 µs in a plasma region of 9–40 mm long and its dependence on the plasma parameters is found. An analysis of relaxation processes in plasma showed that the acceleration of the shock wave front can be caused by air heating due to the quenching of electronically excited nitrogen molecules, in which the internal energy is converted into thermal energy at times up to 30 μs.

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Biophysics and medical physics

## Nanoscale biosensor with integrated thermoregulation controller for DNA diagnostics

### I. I. Tsiniaikin$^1$, G. V. Presnova$^2$, I. V. Bozhev$^1$, A. A. Skorik$^1$, M. Yu. Rubtsova$^2$, A. S. Trifonov$^1$, O. V. Snigirev$^1$, V. A. Krupenin$^1$, D. A. Presnov$^{1,3}$

Moscow University Physics Bulletin 2023. N 2.

We present a CMOS compatible technique for fabrication a sensor system based on field-effect transistors with a nanowire channel with an integrated thermoregulation elements. The proposed system provides the necessary temperature regimes for many bioanalytical studies. Field-effect transistors with a nanowire channel were fabricated using of reactive-ion etching of the upper layer of a silicon on insulator through a mask formed by electron beam lithography. Titanium thermoresistive strips for temperature control were located on the surface of the chip nearby to the nanowire transistors. Their fabrication is carried out simultaneously with the formation of contact pads to the transistor electrodes, which made it possible to avoid additional technological steps. A demonstration of a system with a built-in temperature controller for the determination of nucleic acids was carried out on model oligonucleotides. Increasing the operating temperature of the device to the ranges at which DNA hybridization occurs most efficiently allows increasing specificity and avoiding false positive results, as well as reducing analysis time. The possibility of heating up to 85-90°C allows you to reuse such devices.

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Astronomy, astrophysics, and cosmology

## Сolor transformation between photometric systems of 2MASS catalog and ASTRONIRCAM of SAI MSU 2.5-m telescope

### A. M. Tatarnikov$^{1,2}$, A. A. Tatarnikov$^{1,2}$

Moscow University Physics Bulletin 2023. N 2.

In this paper, we consider a method for determining the coefficients of the transformation equations between different photometric systems based on the photometry of all field stars recorded during observations of the primary standards of one of the photometric systems. Using this method, the coefficients of color transformation equations between the photometric system of ASTRONIRCAM of the 2.5-m telescope KGO SAI MSU and the 2MASS all-sky survey catalog photometric system are obtained.

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## Refinement of the motion model of the Linus satellite of the asteroid (22) Kalliope

### P. A. Budnikova$^1$, N. V. Emelyanov$^2$, B. S. Safonov$^2$

Moscow University Physics Bulletin 2023. N 2.

The aim of this article is to analyze the dynamics of the Linus satellite of the asteroid (22) Kalliope. New results have been obtained, and now they are being published. New observations of the satellite were made at the Caucasus Mountain Observatory of the SAI from October 2021 to March 2022. The obtained astrometric results are presented in the article. Based on the updated set of observations, the parameters of the satellite's orbit were re-determined. An increase in the accuracy of ephemeris with the addition of new observations is shown. A new attempt was made to determine the precession of the satellite's orbit caused by the compression of a rapidly rotating asteroid. The goal was to determine the dynamic compression of the central body. The entire observation interval is divided into groups. From the observations of each group the position of the axis of the satellite's orbit was found. Changing the position of the axis gives the desired precession. Studies on several examples show that the position of the axis from such groups of observations is determined very unreliably. The reason lies in the strong correlation between the determined parameters with limited observational accuracy. Ways of studying precession are outlined by joint determination of dynamic parameters on the basis of all available observations.

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