Radiation from Relativistic Electrons in Periodic Structures "RREPS-23" & Electron, Positron, Neutron and X-ray Scattering under External Influences "Meghri-23"

18 Sept 2023, 07:00 → 22 Sept 2023, 23:59 Asia/Yerevan

Dear Colleagues,

The XIV International Symposium "Radiation from Relativistic Electrons in Periodic Structures" merged with " Electron, Positron, Neutron and X-ray Scattering under External Influences" will be held in Tsaghkadzor, Republic of Armenia, September 17-22, 2023, and is organized by Organized by the Institute of Applied Problems of Physics NAS of Armenia and Yerevan State University, Republic of Armenia.

The Symposium will focus on the following topics:

• e^-/e⁺ beams interaction in solids
  • General Properties of Radiation from Relativistic Particles
  • Transition Radiation, Cherenkov Radiation
  • Parametric X–ray Radiation, Channeling Radiation
  • Diffraction Radiation, Smith–Purcell Effect
  • Coherent Bremsstrahlung and Electron–Positron Pair Creation in Crystals
• X–ray and neutron scattering in crystals
  • X–ray and Neutron Scattering under the External Influences
  • X–ray and Neutron Imaging
  • X–ray and Neutron Small Angle Scattering
  • X–ray Based Optics and Diffractometry
• e^–/e⁺, X–ray, THz, and neutron based applications
  • Interaction of Particles Beams with Artificial Structures
  • Control of Parameters of Plasma by Acoustic Superlattices
  • Radiation Processes and Material Science
  • Novel Positron Sources
  • THz generation and applications

 

Dear participants of the VIII International conference “Meghri-23” and XIV International Symposium RREPS-23 !

The Local Organizing Committee takes care of your transfer from Zvartnots International Airport to the conference venue hotel in Tsaghkadzor. Let us know the date and flight of your arrival in Yerevan.

Note that the proposed service is considered collective (group of persons), but guaranteed also in case of one passenger.

A poster board, A0 size (118.9 x 84.1 cm), in portrait orientation, will be available for each poster. We recommend to use a maximum size for the poster of 100cm x 70cm. Pins or thumbtacks are provided to mount your posters on the board. All presenters are required to mount their posters 30 mins before the session and remove them at the end of the session. Presenters are requested to stand by their posters during the session.

Monday, 18 September

07:00 → 08:30 Registration

09:00 → 10:00 Trip to Yerevan

10:00 → 10:20 Opening conference and greetings speech in the National Academy of Science of the Republic of Armenia

10:20 → 12:00 INVITED TALKS

Convener: Vahan Kocharyan (Institute of Applied Problems of Physics NAS RA, 25 Hr. Nersisyan, Yerevan, 0014, Armenia)

10:20 X-Ray Channeling for Tomographic Studies

Channeling is a well known phenomenon mostly related to specific motion of charged particles in aligned crystals. Since the middle of 60s of the last century when its phenomenology was developed, channeling of high-energy leptons (electrons/positrons of several MeV up to hundred GeV energies) and hadrons (protons/ions of tens GeV up to several TeV energies) has been applied to shape the charged beams as well as to produce high power X-ray and gamma radiation sources at various famous world research centers. Further studies have shown the feasibility of channeling phenomenology application for description of other various mechanisms of interaction of charged and neutral particles beams in solids, plasmas and electromagnetic fields covering the research fields from crystal/laser/plasma based undulators and collimators to capillary based X-ray and neutron optical elements.
Channeling studies are resulted in developing a new X-ray technique presently known as polycapillary optics, very compact solution to effective handle X-ray beams of wide frequency spectrum that provides an essential advantage in designing innovative scientific and industrial instruments in optics, spectrometry and imaging.
Within this review talk I will discuss actual X-ray channeling-based projects paying main attention to the basics of polycapillary optical systems as well as its use for advanced tomographic studies.

Speaker: Sultan Dabagov

10:40 All-optical dense GeV positron sources

Generation of energetic electron-positron pairs using multi-petawatt (PW) lasers has recently attracted increasing interest. However, some previous laser-driven positron beams have severe limitations in terms of energy spread, beam duration, density, and collimation. In this talk, we will show some novel schemes for the generation of dense ultra-short quasimonoenergetic positron bunches. By colliding a twisted laser pulse with a Gaussian laser pulse in near-critical-density (NCD) plasma, it is shown that, abundant γ-photons are first emitted via nonlinear Compton scattering of laser-driven electrons off the counter-propagating Gaussian lasers. Then copious number of positrons are subsequently generated during the headon collision of γ-photons with the Gaussian laser pulse. Due to the unique structure of the twisted laser pulse, the positrons generated are well confined by the radial electric fields of the drive pulse and experience phase-locked-acceleration by the longitudinal electric fields of the drive pulse. Three-dimensional particle-in-cell simulations demonstrate the generation of dense sub-femtosecond quasi-monoenergetic GeV positron bunches with tens of picocoulomb (pC) charge and extremely high brilliance above 10^14 /s/mm^2/mrad^2/eV. It is also shown that, the positron bunches generated can be also accelerated by terahertz waves. For example, abundant γ-photons and positrons can be generated during the collision of GeV electron beam and the scattering laser. Due to the strong longitudinal acceleration field and the transverse confining field of the emitted THz wave, the positrons can be efficiently accelerated to 800 MeV, with the peak beam brilliance of 2.26×10^12/s/mm^2mrad^2/eV. This can arouse potential research interests from PW-class laser facilities together with a GeV electron beamline.

Speaker: Tongpu Yu

11:00 FLAP Collaboration: Fundamental and applied Linear Accelerator Physics Collaboration

In 2020 a new international collaboration – FLAP has been established. In this report we present the scope of research of a new collaboration devoted to the study of the basics of electromagnetic interactions, particle generation, and new applications of controllable generation of electromagnetic radiation by relativistic electrons using functional materials. The collaboration was initially gathered around a new accelerator facility in Joint Institute for Nuclear Research in Dubna called Linac200. However, the scope goes beyond the use of a single facility but merges the efforts, experience, expertise, and infrastructures of institutional groups driven by common research interests.

Speaker: Pavel Karataev (University of London (GB))

11:20 Problems and Solutions of Digital Core Research

Speaker: Alexey Gogolev (T)

11:40 Monochromatic Cherenkov Radiation from Radiations with Frequency Dispersion

Speaker: Alexander Potylitsyn

14:00 → 15:00 Lunch

15:00 → 16:20 e–/e+ beams interaction in solids

Convener: Pavel Karataev (Royal Holloway, University of London)

15:00 Generation of Surface Polaritons on Cylindrical Interfaces

The radiation of surface polaritons by charged particles moving inside or outside a cylindrical dielectric waveguide is discussed. It is assumed that the waveguide is immersed in a homogeneous medium. As an active medium, supporting the propagation of surface polaritons, both the cases of interior and exterior media are considered. The radiation fields are explicitly separated in both those media and their behavior is investigated in asymptotic regions. For a charged particle moving parallel to the axis of the cylinder, the energy fluxes are evaluated through the plane perpendicular to the waveguide axis. It is shown that in the active medium (with negative real part of dielectric permittivity) the energy flux for surface polaritons is oppositely directed with respect to the particle motion, whereas in the medium with positive dielectric permittivity the energy flux is directed towards the particle motion.

Speaker: Aram Saharian

15:20 On-chip beam position monitor based on Smith-Purcell radiation

In this report, we propose an on-chip beam position monitor based on the spectral analysis of the Smith-Purcell (SPR) radiation that occurs when the beam passes near periodic chains of subwavelength particles [1]. Since the SPR is quasi-monochromatic and its spectral distribution harmonically depends on the chain period, it is easy to distinguish between radiation coming simultaneously from chains of different periods. Comparing these intensities from different chains, we can draw a conclusion about the position of the beam. We discuss the pros and cons of this new scheme of a beam trajectory diagnostics compared with standard beam position monitors [2].

[1] D.I. Garaev, D.Yu. Sergeeva, A.A. Tishchenko, Theory of Smith-Purcell radiation from 2D array of small non-interacting particles, Phys. Rev. B 103, 075403 (2021).
[2] P. Forck, Beam position monitors, CERN Accelerator School: Beam diagnostics (2008).

Speaker: Damir Garaev

15:40 Peculiarities of Spectral-Angular Distribution of Coherent Radiation by a Train of Electron Bunches Crossing a Conducting Ball

The spectral-angular distribution of the coherent radiation by a train of electron bunches crossing a conducting ball is teoreticaly studied. The work is based on the corresponding exact analytic solutions of Maxwell’s equations. The generalized Drude–Lorentz–Sommerfeld formula for the dielectric function of material of the ball is used in numerical calculations. It is shown that peaks in the radiation spectrum of the train may appear at some "resonance frequencies". Those peaks disappear in the geometry where the ball is replaced by a plane-parallel plate made of the same material and having a thickness equal to the diameter of the ball. A visual explanation of this phenomenon is given and its possible practical applications are discussed.

The work was partially supported by the Science Committee of RA, in the frames of the research project № 21AG-1C069.

Speaker: Anush Sargsyan (Institute of Applied Problems of Physics NAS RA)

16:00 Smith-Purcell radiation from surface plasmons

Smith-Purcell radiation (SPR) is a widely known effect considered as prospective for ultra-relativistic electron beam diagnostics. Yet, the applications of this effect are not limited to physics of high-energy accelerators: nowadays, it is investigated as the way for generation of radiation from plasmonic and meta-structures.
In this report i consider theoretically SPR from the periodical structures created on a plane surface by the field of plasmons running along the surface. The way of calculations for this problem can be similar to that which I used recently calculating SPR from a standing field of a laser along the surface and direction of motion of an electron beam. I calculate the SPR field and intensity and show how it is sensitive to the surface wave and the electron beam characteristics.

Speaker: Alexey Tishchenko (National Research Nuclear University MEPhI (RU))

16:20 → 16:40 Coffee break

16:40 → 18:00 Poster session I

17:10 Splitting effect of spectral lines for the coherent transition radiation from tilted grating

Currently, the search of new ways to generate monochromatic radiation is continued. One of the possible ways to generate such radiation is the use of transition radiation from the grating (so-called grating transition radiation) [1, 2]. However, up to date there is no theory which was developed to describe the spectral characteristics of this radiation [3].
This work presents the analytical theory of transition radiation from a tilted grating consisting of a finite set of flat ideally conducting strips with vacuum gaps between them and located in one plane. The theory limits are connected to the limitations of the surface current method and macroscopic electrodynamics as a general. The radiation spectrum dependencies were analyzed for various parameters, such as the angle of grating inclination, strip width, impact parameter, and the ratio of strip numbers lower and higher than the electron beam (it's the asymmetric passage of the beam through the grating).
The analysis has shown that radiation has different spectral characteristics depending on certain parameters. For example, one spectral line can be split into two lines for a certain diffraction order.
The study was partly supported by the Ministry of Science and Higher Education of the Russian Federation (program "Science" No. FSWW-2023-0003).

Speaker: Dmitry Shkitov (Tomsk Polytechnic University)

17:11 Polarization of the diffraction radiation on the metal sphere: possibilities for the beam diagnostics

The description of the diffraction radiation on the conductive sphere based on the method of images known from electrostatics has been proposed in [1, 2]. The developed approach was successfully used to calculate the polarization of the radiation [2, 3]. The method for determining the azimuth of a trajectory of the moving particle relatively the center of the sphere using a single polarization-sensitive detector for the radiation emitted in some pre-selected direction was offered there. Here we describe another approach to the same problem using three detectors without registration of the radiation polarization.

The second problem considered in the report is the coherent diffraction radiation on the sphere from the pancake-bunch. It is demonstrated that the polarization of the radiation in this case permits to estimate the position of the bunch edges in relation to the center of the sphere. This feature could be used for the non-destructive measurement of the characteristic dimensions of the bunch.

[1] Shul’ga N.F., Syshchenko V.V., Larikova E.A. // Nuclear Instrum. Methods B 402 (2017) 167.
[2] Shul'ga N.F., Syshchenko V.V. // Nuclear Instrum. Methods B 452 (2019) 55.
[3] Syshchenko V.V., Larikova E.A. // Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques 13 (2019) 990.

Speaker: Arthur Tarnovsky (Belgorod National Research University)

17:12 Diffraction radiation of a charged particle from a 1D fractal diffraction grating

When a charged particle moves parallel to a medium with a periodically changing refractive index, Smith-Purcell radiation occurs. In this report, we consider the radiation that occurs when a charged particle passes parallel to a 1D (one-dimensional) fractal diffraction grating. Such a grating can be considered as an array of sub-gratings similar to the original one. To describe it, we will implement a procedure of replacing a target with a similar sub-targets: this operation is repeated until the period of the subgrating violates the conditions of diffraction of radiation with a wavelength $\lambda\ll d$. One of the first theoretical models of Smith-Purcell and diffraction radiation was the scalar theory considering the diffraction of a charged particle field on a diffraction grating [1]. Using this approximation, we have obtained an analytical formula for the angular distribution of the radiation intensity. The radiation is described as a superposition of scattered fields from each sub-grating. We demonstrated that for some grating’s parameters, a constructive interference occurs, as a result of which the angular distribution of diffraction radiation has the form reflecting its fractal nature.

References
[1] B. M. Bolotovskii, E. A. Galst’yan, Diffraction and diffraction radiation, Phys. Usp. 43, 755 (2000).

Speaker: Pavel Shapovalov (National Research Nuclear University "MEPhI")

17:14 DESIGN AND SIMULATION OF A S-BAND RF PHOTOGUN FOR A LINAC – INJECTOR FOR THE USSR FEL

The Ultimate Source of Synchrotron Radiation (USSR) being developed at the NRC «Kurchatov Institute» will include 6 GeV storage ring with 7BA lattice which will allow to obtain a transverse emittance value of about 50 pm rad and a free electron laser. One linear accelerator for full energy is considered as the main top-up injector into the storage ring and as a driver of high-brightness bunches for FEL. A S-band RF-gun with photocathode based on 3.6-cells π-mode standing wave accelerating structure at operating frequency 2.8 GHz will be used for a high brightness bunch train generation. In this report the general concept of the RF-photogun is presented. An optimization of beam dynamics, electrodynamics properties, fields distribution in the resonator and coaxial RF-coupler were done. Thermal processes in structure waere studied and cooling system design was performed.

Speaker: Mr Ilia Ashanin (NRNU MEPHI)

17:16 Geant4 implementation of channeling radiation in classical description

Here we discuss the creation and implementation into Geant4 [1] of a new C++ module for channeling radiation (CR) simulation. The module we create is built into Geant4 as a discrete set of physical processes [2]. Such a form of integration makes it possible to combine new physical processes in single crystals with those already built into Geant4 (ordinary bremsstrahlung, different types of scattering of both photons and primary particles, etc.), which significantly increases the quality of simulation. The direct simulation of CR in Geant4 allows describing devices such as, e. g. positron sources, without using external programs for CR calculation.

[1] S. Agostinelli, J. Allison, K. Amako et al., Nucl. Instrum. Meth. A, 2003, 506, 250.
[2] A.A. Savchenko and W. Wagner, JINST 16 P12042 (2021).

Speaker: Aleksandr Savchenko (National Research Nuclear University MEPhI (RU); Belgorod State University (RU))

17:17 SOFT X-RAYS PRODUCED BY RELATIVISTIC ELECTRONS IN MULTILAYER STRUCTURES

Periodic structures as well as crystal structures can be used to generate tunable quasi-monochromatic X-rays. When a fast charged particle crosses a layered structure, various types of soft X-rays are produced, including parametric X-ray radiation (PXR) and diffracted transition radiation (DTR).
We present the results of an experimental study of the radiation generated in Co/C (period 5.10 nm) and Mo/B4C (period 2.24 nm) multilayer X-ray mirrors under the action of 7-MeV electrons. As a source of relativistic electrons, a microtron of the "Pakhra" accelerator complex of the Lebedev Physical Institute was used. X-ray spectra with energies from 240 to 480 eV were measured at observation angles of 90 and 120 degrees using an Amptek XR-100SDDfast silicon detector with an input window "C1". The experimental setup also made it possible to measure the orientation dependences of the x-ray yield. Our experimental data are in good agreement with the calculation results.
The work was supported by the grant from the President of the Russian Federation for young scientists-candidates of science MK-1320.2022.1.2.

Speaker: Ekaterina Kidanova (Belgorod State University, Belgorod, Russia)

17:18 Angular distribution of non-dipole axial channeling radiation

In our paper [1] we considered the non-dipolarity of axial channeling radiation (CR) generated in a tungsten single crystal at electron-beam energies of several GeV. It was shown that the non-dipole approximation results in a considerable variation of the CR spectrum. In this report, we explain this variation by means of the CR angular distribution calculation. Within the dipole approximation, CR is emitted in forward direction. Angular distribution of the non-dipole CR shows that also a sideward component occurs that is shown to be responsible for radiation spectrum variations.

[1] W. Wagner, A. A. Savchenko, B. Azadegan, and M. Shafiee, Nondipolarity of axial channeling radiation at GeV beam energies, Phys. Rev. Accel. Beams 22, 054502 (2019)

Speaker: Aleksandr Savchenko (National Research Nuclear University MEPhI (RU); Belgorod State University (RU))

17:19 Wave Functions of the Positrons Channeling along [111] Direction of the Silicon Crystal

The positively charged particles can perform the axial channeling in the small potential well formed between three neighboring [111] strings of the Silicon crystal. The transverse motion of the particle in the well is quantized in the quantum mechanical limit. The structure of the wave functions of the stationary states is of interest for the searching the quantum chaos manifestations in the individual quantum states [1] in addition to the ones in the statistics of the energy level sets [2]. Earlier it was made for the channeling electrons in [110] and [100] directions [3, 4]. In both cases the numerical simulation was performed on the square discrete spatial grid since the respective potential wells possess the symmetry $C_{2v}$ and $C_{4v}$ (the symmetry of the rectangular and the square), respectively. However, the potential well between the three [111] strings has the symmetry $C_{3v}$ (the symmetry of the equilateral triangle), so the use of the square grid leads to some artifacts of the numerical simulation.

Here we have developed the algorithm free of artifacts based on the hexagonal spatial grid. We found numerically the complete set of the transverse motion eigenfunctions for the 10 GeV positrons channeling in the [111] direction of the Silicon crystal. The results will be used in the further studies of the quantum chaos.

[1] Berezovoj V.P., Bolotin Yu.L., Cherkaskiy V.A. // Phys. Lett. A 323 (2004) 218.
[2] Stöckmann H.-J. Quantum Chaos. An Introduction, Cambridge University Press (2000).
[3] Shul’ga N.F., Syshchenko V.V., Tarnovsky A.I., Isupov A.Yu. // Journal of Physics: Conference Series 732 (2016) 012028.
[4] Shul’ga N.F., Syshchenko V.V., Tarnovsky A.I., Isupov A.Yu. // Nuclear Instrum. Methods B 370 (2016) 1.

Speaker: Arthur Tarnovsky (Belgorod National Research University)

17:21 Application of optical Cherenkov radiation for ion beam diagnostics

In this report, we present the theoretical background of the planned experimental investigation of optical Cherenkov radiation generated by moderately relativistic ion beam in target with frequency dispersion. The target material is a CVD-diamond. It is planned to conduct experiments on the basis of MARUSYA facility in the SPD test zone of the NICA accelerator complex. The available ion energy range is 1-4.5 GeV/n. The results obtained in the course of these studies will allow to evaluate the possibility and efficiency of using this effect as a tool for ion beam diagnostics. The analysis of the simulation results for experimental conditions was carried out. Test measurements have been carried out during the Nuclotron run in 2022-2023. The experimental setup has been prepared for experimental investigation of this effect during the nearest upcoming run of the LHEP accelerator complex.

Speaker: Veronika Bleko (Joint Institute for Nuclear Research)

17:23 Transition radiation of fast and slow particles on the metal right dihedral angle

The method of images [1] permits to describe the transition radiation not only on the infinite conducting plane [2], but also on the dihedral angle with the opening equal to the divisor of 180 degrees. Here we describe the transition radiation arising under the fast charged particle’s incidence on the target of two conducting half-planes that make rectangular dihedral angle (when the incidence takes the place from the inner side of the angle). The qualitative features of the radiation from the both fast and slow particles are considered, the pictorial interpretation of the results is given. The possibility of application of the interference effects in the radiation for the beam monitoring is discussed.

[1] Jackson J.D. Classical Electrodynamics, Wiley, New York (1999).
[2] Frank I., Ginzburg V. // J. Phys. USSR 9 (1945) 353.

Speaker: Arthur Tarnovsky (Belgorod National Research University)

17:24 Large-angular Emission of Quasi-Monochromatic Ultra-soft X-Ray from Multilayer Structure under Irradiation of 5.7 MeV Electrons

Previously, in [1-6], it was experimentally shown that the quasi-monochromatic radiation is generated when an electron beam interacts with a multilayer structure of an X-ray mirror in the direction of the Bragg diffraction. The spectrum of this radiation depends on the period of the structure and the tilt angle of the target relative to the electron beam. Here we present the results of the experimental and numerical studies of the angular distributions of this type of radiation in the ultra soft X-ray region (50÷150 eV) for a wide range of the target tilt angles, upon irradiation of a [Mo/Si]50 structure with a period of d=11.32 nm by electrons with an energy of 5.7 MeV. The comparison of the experimental data with the results of calculations following the theory [1, 2] has been done.

The work was supported by the Russian Science Foundation, grant No. 23-22-00187.

1. V.V. Kaplin, S.R. Uglov, V.N. Zabaev, M. A. Piestrup, C.K. Gary, N.N. Nasonov, M.K. Fuller, Appl. Phys. Lett. 76, 3647 (2000).
2. N. Nasonov, V. Kaplin, S. Uglov, M. Piestrup, C. Gary, Phys. Rev. E 68, 036504 (2003).
3. N. Nasonov, V. Kaplin, S. Uglov, V. Zabaev, M. Piestrup, C. Gary, Nucl. Instrum. and Meth. B 227, 41 (2005).
4. V.V. Kaplin, S.R. Uglov, V.V. Sohoreva, et al., Nucl. Instrum. and Meth. B 276, 777 (2009).
5. S.R. Uglov, V.V. Kaplin, A.P. Potylitsyn, L.G. Sukhikh, A.V. Vukolov and G. Kube, Jour. of Phys.: Conf. Ser. 517, 012009 (2014).
   [6] S.R. Uglov, V.V. Kaplin, L.G. Sukhikh, A.V. Vukolov. JETP Lett. 100, No. 8, 503 (2014).

Speaker: Mikhail Shevelev

17:25 Spectrum of Coherent VUV Radiation Generated by 5.7 MeV Electrons in the Periodic Structure of a Multilayer X-ray Mirror

Structures such as multilayer X-ray mirrors can be effective sources of vacuum ultraviolet and ultra-soft X-ray radiation with tunable radiation energy [1-3]. The emission band is determined by the period of the multilayer structure, the number of layers, and the tilt angle of the structure θ0 with respect to the direction of an electron beam. The main contribution to the radiation is made by the diffraction of transition radiation (DTR) and coherent radiation of the periodic structure of the target excited by an electron beam - an analog of parametric x-ray radiation in crystals (PXR). In this report, we show the calculation results of the angular and spectral properties of DTR and PXR generated by 5.7 MeV electrons in a structure consisting of 50 pairs of layers of molybdenum and silicon and consider approaches for extracting the contributions of DTR and PXR in the future experiment.
The work was supported by the Russian Science Foundation, grant No. 23-22-00187.

1. N. Nasonov, V. Kaplin, S. Uglov, V. Zabaev, M. Piestrup, C. Gary, Nucl. Instrum. and Meth. B 227, 41 (2005).
2. V.V. Kaplin, S.R. Uglov, V.V. Sohoreva, et al., Nucl. Instrum. and Meth. B 276, 777 (2009).
3. S.R. Uglov, V.V. Kaplin, L.G. Sukhikh, A.V. Vukolov, JETP Lett. 100, 503 (2014).

Speaker: Mikhail Shevelev

17:28 Beam parameters measurement at Novosibirsk FEL facility

Novosibirsk free electron laser (NovoFEL) facility operates with three FELs. The FELs are installed on one-, two- and four- track energy recovery linacs (ERLs) with a common accelerating system. The ERL type of accelerator allows to achieve high average electron current (ordinarily about 10 mA) and to get the high average FEL power generally more than 100 W). The new diagnostic system was developed to control and study the third FEL's radiation parameters. The new system acquires spontaneous undulator and laser radiation in the middle infrared area 8-14 mkm. The diagnostics is based on the simultaneous application of reflective double-slit interferometer and diffractive monochromator. Using this approach, we can measure spontaneous and laser radiation
parameters in time and spectral domain. Spectral data can be obtained directly using a monochromator and can be compared with the measured correlation function. The new station is also used for the laser radiation spatial characteristics measurements. The calculations and the first results obtained with the new diagnostics are presented. We also present the first results on measuring the beam length at the first FEL obtained using cherenkov radiator and streak-camera. The results and Further experiments are discussed.

Speaker: Vladislav Borin (Budker INP)

17:29 CALCULATION OF SPONTANEOUS EMISSION DURING CHANNELING OF RELATIVISTIC POSITRONS IN NON-CHIRAL NANOTUBES USING A QUADRATIC APPROXIMATION

The paper considers the features of positron channeling in non-chiral carbon nanotubes (CNTs) of types (8, 0), (10, 0), (12, 0), (8, 8), (10, 10) and (12, 12). The conditions under which the approximation U(\rho) = \alpha \rho^2 can be used for the interaction potentials of these positrons with the inner walls of CNTs are studied.
For such an approximation, the numerical values of the parameter α are found for all CNTs under consideration, and the minimum values of the Lorentz-factors are calculated for which the Schrödinger equation with a given function U(\rho) is solved. Using these data, the spectral distributions of spontaneous emission are calculated based on the methods of quantum mechanical and classical considerations for positron beams with different angular dispersions channeled along the CNT symmetry axes.

Speaker: Mr Mykola Maksyuta (Taras Shevchenko National University of Kyiv, Ukraine)

17:30 Cherenkov radiation from relativistic heavy ions with taking account of slowing-down in terms of the diffraction theory

The analogy of the Cherenkov radiation (ChR) theory with the theory of diffraction was first noted by I.M. Frank, who connected the ChR coherence condition with Fresnel zones, see a detailed presentation in the review by B.M. Bolotovsky [1]. This relationship has been traced for ChR with uniform and rectilinear motion of a charged particle in an optically transparent radiator. In the case of a multiply charged relativ-istic heavy ion (RHI), when moving in a radiator, the velocity decreases due to ionization energy losses. Therefore, the calculations of the characteristics of ChR (more precisely, the optical mixed Cherenkov-bremsstrahlung radiation) become more complicated [2-10].
In this work characteristics of the ChR from RHI, taking into account deceleration in a thin radiator, using an analogy with the Huygens-Fresnel diffraction theory were estimated and it was shown how the Cornu spiral, known in physical optics, arises in the theory of ChR from RHI and how it can be used for a qualitative and quantitative analysis of the shape and a quick assessment of the width of the angular distri-bution of the ChR from RHI.

References:
[1] B.M. Bolotovsky, Proceedings of FIAN, Vol. 140 (1982) P. 95.
[2] O.V. Bogdanov, E.I. Fiks, Yu.L. Pivovarov, J. Phys.: Conf. Ser. Vol. 357 (2012) 012002. P.1.
[3] O.V. Bogdanov, E.I. Fiks, Yu.L. Pivovarov, JETP. Vol. 115 No. 3 (2012) P. 392.
[4] E.I. Fiks, O.V. Bogdanov, Y.L. Pivovarov, H. Geissel, C. Scheidenberger, J. Ruzicka, Nucl. Instr. Meth. Phys. Res. B 314 (2013) P. 51
[5] E.I. Fiks, O.V. Bogdanov, Y.L. Pivovarov, H. Geissel, C. Scheidenberger, Nucl. Instr. Meth. Phys. Res. B Vol. 309 (2013) P. 146.
[6] E.I. Fiks, Y.L. Pivovarov, Russian Physics Journal Vol. 56 No. 4 (2013) P. 456.
[7] Y. Takabayashi, E.I. Fiks, Yu.L. Pivovarov. Phys. Lett. A Vol. 379 (2015) P. 1032.
[8] E.I. Fiks, Yu.L. Pivovarov, O.V. Bogdanov Nucl. Instr. Meth. Phys. Res. B Vol. 355 (2015) P. 86.
[9] E.I. Rozhkova, Yu.L. Pivovarov, Phys. Lett. A (2016) Vol. 380 P. 2386.
[10] E.I. Fiks, Yu.L. Pivovarov Nucl. Instr. Meth. Phys. Res. B Vol. 355 (2015) P. 184.

Speaker: Dr Oleg Bogdanov (Tomsk Polytechnic University)

Tuesday, 19 September

09:00 → 11:10 e–/e+ beams interaction in solids

Convener: Dr Alexander Shchagin (DESY)

09:00 Electron Beam Acceleration Driven by Self–Generated Cherenkov THz Pulse

Speaker: Weihao Liu (NUAA: Nanjing University of Aeronautics and Astronautics)

09:30 Cherenkov radiation and transition radiation from tilted corundum plate

Optical beam diagnostics is widely used to measure both transverse and longitudinal bunch sizes. In latter case a streak camera can provide time resolution of about 1 ps if the light intensity would be high enough. In photon counting devices a silica aerogel with refraction index of $n(\lambda)=1.05$ is used as a Cherenkov radiator. A complicated optical scheme should be used to transport and detect Cherenkov light in this case. Another disadvantage is a low photon yield due to small $n(\lambda)$.
There is an alternative way to generate intense light from a radiator with high optical density by a streak camera placed at a right angle relative to the electron beam. One can use a tilted transparent plate orientated such that the light (Cherenkov radiation, ChR, or optical transition radiation, OTR) is extracted towards the streak camera screen [1].
We investigated ChR and OTR generated by 70 MeV electrons in corundum plate with thickness of 0.5 mm using a CCD camera (Apogee Alta U30) [2], placed at 90 degrees relative to the beam trajectory. The target orientation for ChR measurements was $\psi = 24$ deg (“passage” geometry), but for OTR registration we used “mirror reflection” geometry ($\psi$ = - 45 deg). We have measured the photon yield in visible range for both cases and have obtained that OTR yield 5 times higher than the ChR one. This result strongly contradicted with the TR theory developed in [3] for a transparent plate. According to [3], in our case the ChR intensity should be at least 2 orders of magnitude higher than the OTR.
In this report, we propose to use transparent radiators such as corundum or CVD diamond for bunch length diagnostics.

This study was supported by the Russian Ministry of Science and Higher Education, project No FSWW-2023-0003.

1. A.P. Potylitsyn et al. Phys.Lett. A 417, 127680 (2021)
2. A.V. Vukolov et.al. PEPAN (in press)
3. V.E. Pafomov. Proc. P.N. Lebedev Phys.Inst., 44, 25 – 157 (1971)

Speaker: Alexander Potylitsyn

09:50 Quasi-Coherent Radiation from a Train of Electron Bunches Inside a Waveguide Partially Filled with Dielectric

We investigate the quasi-coherent radiation from a train of electron bunches moving along the axis of a cylindrical waveguide, assuming that a part of the waveguide is filled with a material. For the dielectric permittivity of the latter the general case of dispersion is considered. It is shown that under certain conditions on the dielectric function of the medium and the values of the problem parameters, the waveguide modes become equidistant. As a consequence, quasi-coherent Cherenkov radiation from the train of bunches may be generated on several waveguide modes simultaneously. A visual explanation of this phenomenon is provided.

The work was partially supported by the Science Committee of RA, in the frames of the research project № 21AG-1C069.

Speaker: Levon Grigoryan (Institute of Applied Problems of Physics NAS RA)

10:10 Quasidiscrete spectrum Cherenkov radiation from a charge moving inside a dielectric waveguide

We investigate the radiation from a charge moving inside a dielectric cylinder parallel to its axis. It is assumed that the cylinder is immersed in a homogeneous medium. Depending on dielectric permittivities of the cylinder and surrounding medium different types of radiations are emitted. They include the Cherenkov radiation propagating outside the cylinder, the Cherenkov radiation confined inside the cylinder and the radiation in the form of surface polaritons confined on the cylindrical interface. The latter radiation has been investigated recently and our main concern will be the Cherenkov radiation outside and inside the cylindrical waveguide. We show that under certain conditions on the dielectric permittivities strong narrow peaks appear in spectral distribution of the Cherenkov radiation propagating in the exterior medium. The location of those peaks are specified on the base of dispersion equation for the electromagnetic eigenmodes of the cylinder.

Speaker: Prof. Aram Saharian

10:30 Cherenkov X-ray radiation in a fractal medium

This report is devoted to the radiation arising from the motion of an ultra-relativistic particle in a fractal non-magnetic medium. The concept of a fractal medium is widely used in condensed matter physics [1]. Fractal materials are substances whose fractal dimension is different from the topological one: a topological dimension can be only 0, 1, 2, 3, while a fractal dimension can be a non-integral number. Experimental methods for determining the characteristics of a fractal medium (primarily fractal dimension) are of interest. We propose to use X-ray Cherenkov radiation for this purpose. Actually, one of the most popular examples of fractal materials is aerogel – highly porous substances with a record low density for solids (and hence the refractive index); on the other hand, aerogels are widely used as Cherenkov radiators [2].

Here, we calculate the analytical expressions describing the dependence of characteristics of X-ray Cherenkov radiation on the fractal dimension of the material in which the radiation is generated. A formula is given to determine the fractal dimension of the medium based on the radiation characteristics. The role of transition radiation on inhomogeneities inside the medium is discussed. It is shown that such radiation can also be attributed to the resulting Cherenkov radiation as long as the minimum coherence length is much larger than the pore size of the medium (which is true for real fractal materials).

References
[1] A. I. Olemskoi, A. Ya. Flat, Application of fractals in condensed-matter physics, Phys. Usp. 36, 1087 (1993).
[2] A. F. Danilyuk, S. A. Kononov, E. A. Kravchenko, A. P. Onuchin, Aerogel Cherenkov detectors in colliding beam experiments, Phys. Usp. 58, 503 (2015).

Speaker: Mr Pavel Shapovalov (National Research Nuclear University "MEPhI")

10:50 Cherenkov particle detector based on resonant elements

In modern particle physics, a variety of different detectors [1] is used for the particle identification, tracking [2, 3] and detecting their energy or other characteristics [4-6]. Each detector type can be characterized by the detection efficiency, temporal resolution, linearity of response, and energy and spatial resolutions. For example, for the time-of-flight positron emission tomography (PET), the most important parameters are the temporal and spatial resolutions, and the detection efficiency for 511 keV gamma photons [7, 8]. In this work, we show the simulation results obtained using Geant4 [9] for the time-of-flight PET detector based on Cherenkov radiation in a medium containing small resonant particles. The resonant behavior of the radiation in Geant4 is caused by introducing a special dispersion function of the dielectric permittivity, which we measure in the CST studio [10] for a material consisting of elements resonating in certain range. The resonance allows producing Cherenkov photons by secondary electrons with lower energy. We consider it as the way to increase the energy resolution as well as the efficiency of the detector. This detector should become the basis for a new technology of positron emission tomography.

[1] ECFA Detector R&D Roadmap Process Group, The 2021 ECFA detector research and development roadmap, Geneva, CERN-ESU-017 (2020).
[2] A. Andronic, J.P. Wessels, Nucl. Instr. Meth. A 666, 130 (2012).
[3] C. Lippmann, Nucl. Instr. Meth. A 666, 148 (2012).
[4] M. Beddo, E. Bielick, T. Fornek, et al., Nucl. Instr. Meth. A 499,725 (2003).
[5] N. Akchurin et al., Nucl. Instr. Meth. A 537, 537 (2005).
[6] L. Bandiera, V. Haurylavets, V. Tikhomirov, Nucl. Instr. Meth. A 936, 124 (2019).
[7] D. R. Schaart, Phys. Med. Biol. 66, 09TR01 (2021).
[8] A.A. Savchenko, A.A. Tishchenko, Rad. Det. Tech. Meth. (2023) https://doi.org/10.1007/s41605-023-00399-9
[9] J. Allison, K. Amako, J. Apostolakis et al., IEEE Trans. Nucl. Sci. 53, 270 (2006).
[10] CST Studio Suite, “CST Microwave Studio,” 2023. https://www.3ds.com/products-services/simulia/products/cst-studio-suite/

Speaker: Aleksandr Savchenko (National Research Nuclear University MEPhI (RU); Belgorod State University (RU))

11:10 → 11:30 Coffee break

11:30 → 13:30 e–/e+ beams interaction in solids

Convener: Aram Saharian

11:30 Generation of Superradiant Parametric X–rays (SPXR)

In the contribution we will describe generation mechanism of SPXR and will provide results of the theoretical research for characteristics of this new type of the coherent x-ray radiation.
In fact, we are considering the case of SPXR as result of interaction of mini-bunched electron beam modulated in density inside the undulator of a XFEL [1] and crystalline target, where the parametric x-rays are generated with the frequency ω dependent on a crystal structure and on the angle between the crystallographic planes and the electron velocity. As was recently considered, the highest intensity of PXR can be generated when the electrons propagate via the crystal target in the grazing geometry, i.e., within a thin layer inside the crystal parallel to the crystal-vacuum interface and the x-ray photons are emitted under the large angle to the electron velocity (PXR-EAD) [2]. This angle can be chosen in such a way that the resonant condition ω=ω0 is fulfilled (ω0=2π/d0 (h=c=1); d0 is the spatial modulation of the electron density which is directly defined by the period of an undulator).
As a result, in addition to the main XFEL pulse, generation of SPXR will originate the pulse with the intensity also proportional to the square of the number of electrons in the bunch. According to [3], the spectral density of PXR photons emitted by a single electron can be larger than the corresponding density of the undulator radiation. Consequently, the quantity of SPXR photons can exceed the corresponding number at the XFEL output. Besides, the SPXR pulses can be guided under the large angle to the electron velocity, that is can improve the applicability of a XFEL by the formation of additional channels for coherent x-rays.

1. A. Gover, R. Ianconescu, A. Friedman, C. Emma, N. Sudar, P. Musumeci, C. Pellegrini Superradiant and stimulated-superradiant emission of bunched electron beams // Rev. Mod. Phys., Vol. 91, No. 3, 2019, P. 035003.
2. O.D. Skoromnik, V.G. Baryshevsky, A.P. Ulyanenkov, I.D. Feranchuk, Radical increase of the parametric x-ray intensity under condition of extremely asymmetric diffraction // NIM B, Vol. 412, 2017, P. 86.
3. V.G. Baryshevsky, I.D. Feranchuk, and A.P. Ulyanenkov Parametric X-Ray Radiation in Crystals: Theory, Experiment and Applications / Springer Tracts in Modern Physics, Springer, 2006.

Speaker: A. Lobko

11:50 Use of Parametric X-ray Radiation of Electrons in Crystals to Determine the Parameters of Imaging plates

The good agreement between the results of calculation of the yield and angular distributions of parametric X-ray radiation (PXR) of electrons in crystals in the framework of the kinematic theory with experimental data [1, 2] makes it possible to use the results of PXR measurements to determine the parameters of experimental equipment, see, for example, [3].
The most interesting is the assessment of the dependence of the sensitivity of imaging plates (IP) on the photon energy. Recently, IPs have been produced by several companies and are widely used in medicine, X-ray flaw detection, and other fields of science and technology to measure the spatial distribution of ionizing radiation beams. It should be noted that there is no information on the exact composition of the plates and their density in the literature.
The results of processing the results of measurements of the PXR angular distributions of electrons with an energy of 255 MeV in a silicon crystal using several types of RP, performed on a Saga-LS linear accelerator, are presented. The spectral dependence of the IP sensitivity is determined for the photon energies of two reflection orders and for the (111) and (110) reflecting planes. An estimate of the density of the investigated plates is made.

References
1. K.-H. Brenzinger et al. // Phys. Rev. Lett. 1997 V.79 2462.
2. Yu.A. Goponov et al. // NIM B 2015 V. 355 P.150.
3. A.V. Shchagin et al. // NIM B 2001 V. 173 P.154.

Speaker: Igor Vnukov

12:10 Mixed (Regular and Chaotic) Dynamics under the Channeling of the High Energy Positrons in [100] Direction of the Silicon Crystal and Podolskiy-Narimanov Distribution

Speaker: Vladislav Syshchenko (Belgorod National Research University)

12:30 Dynamical Chaos and Level Splitting under the Channeling of the High Energy Positrons in [100] Direction of the Silicon Crystal

Speaker: Vladislav Syshchenko (Belgorod National Research University)

12:50 zoom

13:10 zoom

13:30 → 15:00 Lunch

15:00 → 16:40 e–/e+ beams interaction in solids

Convener: Weihao Liu (NUAA: Nanjing University of Aeronautics and Astronautics)

15:00 Coherent Transition Radiation from Finite-Size Screen in the Prewave Zone

In this report, we show experimental and theoretical investigation of coherent transition radiation from finite-size screen in the prewave zone. Experimental measurements were performed for sub-THz range at LINAC-200 facility (JINR). We compare the experimentally obtained results with numerical simulation and evaluate the longitudinal beam size.

Speaker: Mikhail Shevelev

15:20 Transition radiation from hollow beams

Hollow beams of charged particles are the beams having a transverse profile in the form of a ring. In recent years, they are actively studied. For example, the idea of using hollow electron beams for high-intensity beam collimation at the Large Hadron Collider at CERN was suggested in [1, 2]. Acceleration of charged particles is another promising area of using the hollow electron beams. It is possible to accelerate positrons to high energies in plasma wakefields, which are formed during the motion of hollow electron beams in plasma [3, 4]. While working with hollow electron lenses, the problem of diagnostics of the transverse sizes of both beams, the main and hollow electron beams, becomes acute. One of the ideas being actively developed now is to use gas fluorescence for the diagnostics [5]. The advantage of this method is that the properties of the beam remain practically undisturbed during measurements. Optical transition radiation is used in order to cross-check the method. For the correct processing of experimental data, it is necessary to have not only a reliable single-particle theory of radiation (i.e., radiation from a single charged particle), but also to know the analytical formula for the beam form-factor. Here we report on the theory of transition radiation from a hollow beam, taking into account the coherent effects. We calculate both the field of radiation and emitted energy per unit solid angle and per unit frequency. We also discuss the properties of such radiation from point of view of diagnostics of the beam parameters.

The research is supported by the Foundation for the Advancement of Theoretical Physics and Mathematics BASIS, Project No. 23-1-3-2-1.

[1] G. Stancari, A. Valishev, G. Annala, et al., Collimation with Hollow Electron Beams, Physical Review Letters 107, 084802 (2011).
[2] S. Redaelli, R.B. Appleby, R. Bruce, et al., Hollow electron lenses for beam collimation at the High-Luminosity Large Hadron Collider (HL-LHC), Journal of Instrumentation 16, P03042 (2021).
[3] N. Jain, Evolution of ultra-relativistic hollow electron beams during their propagation in plasmas, Physics of Plasmas 26, 023107 (2019).
[4] J. Vieira, J.T. Mendonca, Nonlinear Laser Driven Donut Wakefields for Positron and Electron Acceleration, Physical Review Letters 112, 215001 (2014).
[5] A. Salehilashkajani, H.D. Zhang, M. Ady, et al., A gas curtain beam profile monitor using beam induced fluorescence for high intensity charged particle beams, Applied Physics Letters 120, 174101 (2022)

Speaker: Dr Daria Sergeeva (National Research Nuclear University MEPhI (RU); Belgorod State University (RU))

15:40 Volume Reflection Undulator

Speaker: Dr Alexander Shchagin (DESY)

16:00 Electron beam profile determination by multi-angle scanning using scintillation optical fiber

Nowadays, the development of an approach for quick and accurate diagnostics of ionizing radiation beams is important. This study proposes a method of multi-angle scanning using scintillation optical fibers as detection elements for determining the energy electron beam profile. Beam characterization measurements by this method involve several steps, including mathematical processing based on inverse Radon transform.
To investigate the proposed method and detector material, an experiment was conducted at Tomsk Polytechnic University to determine the transverse profile of the 5.7 MeV electron beam. The beam shape was measured for an open field and for a deformed one by an additional target. After collecting and processing the data, a beam profile was reconstructed in the transverse plane. To assess the quality of the obtained profiles, similar experiments were performed using Gafchromic EBT3 dosimetry films.
As a result, a comparative analysis of the electron beam profiles was carried out, demonstrating the effectiveness of the multi-angle scanning method and the proposed setup based on the scintillation detection element. The proposed method and device offer a promising solution for quick and accurate diagnostics of high-energy electron beams.

This work is supported by the RSF project No. 19-79-10014-П.

Speaker: Dr Sergei Stuchebrov (National Research Tomsk Polytechnic University)

16:20 Quasi-continuous particle generation in a pyroelectric accelerator

Pyroelectric effect in the single crystals of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) gives unique possibility to generate and accelerate electrons to energies of the order of 100 keV. This phenomenon underlies conception of a pyroelectric accelerator. This device can be used as a portative X-ray tube, weak-intensity monoenergetic neutron source, a deflector of external particle beams, etc. The main challenge is to provide stable and reproducible operation mode with predictable electric potential difference and particle fluxes.
Here we report our progress concerning understanding of key processes allowing a pyroelectric accelerator be more applicable for industry enquires. The crucial factors (the way of change in temperature, relation of residual gas pressure and geometry, the target shape) are discussed. The non-standard avalanche discharge leading to electric potential stabilization is described. This process is quite attractive for control particle fluxes in the pyroelectric accelerator.

The work was financially supported a Program of the Ministry of Education and Science of the Russian Federation for higher education establishments, Project No. FZWG-2020-0032 (2019-1569). The work of PVK was supported by the Science and Technology Facilities Council via John Adams Institute for Accelerator Science at Royal Holloway, University of London (Grant Ref. No. ST/V001620/1).

Speaker: Andrei Oleinik (Belgorod State Unversity)

RREPS-2023-AO.pptx

16:40 → 17:00 Coffee break

17:00 → 18:00 Poster session II

17:00 Project of the source of relativistic electrons with angular momentum

Project of the source of relativistic electrons with angular momentum

Development of the source of relativistic "vortex" electrons (with orbital angular momentum) based on the LINAC-200 electron accelerator complex is started in JINR. First stage of this project is the testbench with the electron energy of 5 MeV for the RF-gun based option and of 400 keV for the DC-gun based one. Testbench technical description and current status is given.

Speaker: Mikhail Nozdrin (JINR)

17:02 Simulation and experimental results of electron beam interaction with 3D-printed samples made of modified plastics

One of the important parameters characterizing the interaction of electron beams with matter is the deep dose distribution. To develop a new approach for shaping electron beams using specially created materials suitable for the manufacture of complex 3D-printed devices, it is necessary to analyze the features of ionizing radiation propagation.
In this work, numerical simulations and experimental studies of the interaction between electron beams and plastic materials weighted with metallic impurities of different concentrations, suitable for fabricating samples using the rapid prototyping method, were carried out. Sets of plates made from the investigated plastics were created using the fused filament fabrication (FFF) technique.
Since the FFF sample fabrication process involves forming objects from a thermoplastic mass through layer-by-layer alignment, a distinctive feature of the printed samples is their lower actual density compared to the density of the material (filament) from which they are made. Taking this fact into account, the actual density of the polymer plates was calculated. Based on this data, numerical models of the plastic materials weighted with metallic impurities were developed, and virtual models of the experimental setup were created to calculate the electron beam deep dose distributions in the materials.
In the next step of the investigation, experimental studies were performed using electron beams with energies of 6 and 10 MeV. Pre-calibrated GafChromic EBT3 dosimetry films were used as detectors to obtain the experimental data on the electron beam deep dose distributions in the materials under consideration.
It was observed that with an increasing concentration of metal impurities in the plastic base, the deep dose distribution moves into smaller thicknesses. It was observed that the simulation and experimental results are in good agreement.

This work is supported by the RSF project No. 19-79-10014-П.

Speaker: Irina Miloichikova (National Research Tomsk Polytechnic University; Cancer Research Institute, Tomsk National Research Medical Center, Russian Academy of Sciences)

17:03 IMITATION MODEL OF SOURCE INFORMATION FORMATION IN HIGH ENERGY DIGITAL RADIOGRAPHY AND COMPUTER TOMOGRAPHY SYSTEMS

Nowadays, high-energy radiation sources are increasingly used in nondestructive X-ray inspection. The main reason for the growing popularity of gamma radiation sources with electron energies of more than 1 MeV is the possibility of their application in high-energy radiographic control with innovative digital systems. Such systems have the advantages of high penetration, high sensitivity of defect detection and can meet the needs for inspection of large complex structures.
The subject of our study is high-energy digital radiography and computed tomography systems. We have studied simulation models and programs that are used to create initial information in digital radiography and computed tomography systems. Our goal is to develop mathematical models, based on known physical laws of X-ray-matter interaction, for creating digital radiographic images and projections using a betatron radiation source with different parameters. We investigated the influence of betatron parameters, detector, collimator and object velocity on the obtained images. In the course of our study, we analyzed the existing scientific, technical and methodological literature related to mathematical and numerical modeling of high-energy digital radiography and computed tomography systems. We have developed mathematical models of these systems that take into account the features of scanning geometry and detector characteristics based on the American standard N42.46. Our models allow us to estimate the penetrating power, the limit of detection by wire diameter, horizontal and vertical spatial resolution, and contrast sensitivity.

This work was supported by the Russian Science Foundation, project no. 22-79-00249 (https://rscf.ru/project/22-79-00249/).

Speaker: Vladimir Smolyanskiy (Tomsk Polytechnic University)

17:04 Study of phase objects by dynamical diffraction of a spherical X-ray wave in a crystal using a temperature gradient

The use of a temperature gradient in the study of the dynamical diffraction of a spherical X-ray wave in the Laue geometry is due to the fact that the atomic reflecting planes in the crystal are fan-shaped, which makes it possible to control the focusing process. It was shown in [1] that in the case of a short period superlattice a smooth change in the gradient value can focus different satellites on the exit surface of the crystal, which makes it possible to determine their structure factors.
In the present work, we consider the possibility of studying the internal structure of phase objects by dynamical diffraction of a spherical X-ray wave in a crystal using a temperature gradient. If, prior to the incidence on the crystal, X-ray radiation from a point source passes through the phase object, then it acquires an additional phase. As a result of refraction at phase object inhomogeneities, the direction of radiation and the curvature of the wave front change locally. The use of a temperature gradient directed perpendicular to the crystal surface makes it possible to obtain a focal distribution of all point inhomogeneities in the phase object on the exit surface of the crystal.
The measurement process consists of moving the phase object along the direction of the diffraction vector and finding the corresponding gradient values that ensure focusing of the diffracted wave on the exit surface of the crystal. In this case, the displacement step must be smaller than the focus width in order to find the narrowest and highest intensity peak on the exit surface of the crystal.
Based on the data obtained, it is possible to find the additional phase of the wave acquired in the phase object and restore the internal structure of the corresponding section of the phase object.

Reference

1. L. Levonyan and H. Manukyan. ActaCryst. (2023), A79, 14-19.

Speaker: Dr Levon Levonyan (Yerevan State University)

17:05 NEW MICROFOCUS SOURCE BASED ON A BETATRON FOR HARD X-RAY IMAGING

Experimental results of a study of the properties of microfocus bremsstrahlung (Bs) generated in narrow inner silicon (Si) and tantalum (Ta) targets of a betatron with an electron energy of 18 MeV are presented. The targets were Si crystals 50 and 8 µm thick and Ta foil 13 µm thick oriented with a goniometer along the direction of the inner electron beam. The results showed a strong dependence of the shape of the angular radiation distribution on the target material and its orientation relative to the electron beam. Magnified radiographic images of the wire pairs of the radiographic image quality standard Duplex IQI showed that the resolution and contrast of their images depended on their position in the radiation cone, the target material, and its thickness. The results showed the role of absorption and refraction of radiation in the formation of magnified images of the edges of plastic and metal plates. Differences in contrast and sharpness of magnified images obtained using Si and Ta targets were determined by radiation of different regions of Bs spectrum. The sensitivity of detection of microobjects in the form of thin wires, narrow slits and thin inclusions inside of thick steel blocks was evaluated using radiation generated in the Ta target. The results were compared with the results obtained using X-rays of 450 kV X-ray tube with the focal size of 400 µm and the small-sized 7 MeV betatron with the focal size of 300 µm. The results obtained show the promise of using new microfocus sources based on compact betatrons with electron energy of several MeV for high-resolution radiography and tomography, as well as in laboratory experiments, for example, in materials science and X-ray optics.
This work was supported by the Russian Science Foundation, project no. 22-79-00249 (https://rscf.ru/project/22-79-00249/).

Speaker: Vladimir Smolyanskiy (Tomsk Polytechnic University)

17:06 Electron charge dynamics of the semiconductor photocathode during the laser-induced photoemission

Modern radiofrequency (RF) photoinjectors that are widely spread as $e^-$ sources for free-electron lasers, colliders and synchrotron radiation facilities, use semiconductor photocathodes quite often. Such photocathodes, as a rule, consist of a semiconductor layer (units-tens of $\text{nm}$) with a high QE and a metal substrate. The use of such structures is associated with a number of challenges, especially while generating high-charge electron bunches. One phenomenon is as follows;

Due to the laser pulse inducing photoemission process and the strong electric field $\textbf{E}$ existing in RF cavity semiconductor layer turns out to be depleted of electrons. The resulting positive charge of the semiconductor layer $q(t)$, in turn, affects the photoemission process and the photoinjector operation regime as a whole.

In this work, with some assumptions the diffusion problem for the conduction electrons in semiconductor layer of the photocathode is solved. The generation rate of the electrons inside the semiconductor is considered to be propotional to laser pulse profile. The resulted expression for electron distribution along the semiconductor layer $n(z,t)$ allows one to find the uncompensated charge $q(t)$.

Speaker: Mr Mikhail Vladimirov (NRNU MEPhI)

17:07 Investigation of the radiation resistance and optical properties of new composite thermal barrier coatings

Improved thermal barrier coatings (TBCs) will enable future gas turbines to operate at higher gas temperatures. Considerable effort is being invested, in identifying new materials with even better performance than the current industry standard, yttrium stabilized zirconia (YSZ). TBCs are also supposed to be applied in spacecrafts as protective layer against heat. The operation of spacecrafts in cosmic conditions in turn suggests continuous irradiation with cosmic rays, particularly with MeV energy protons, electrons and neutrons. Therefore, it is very important to investigate the behavior of such barrier coatings under irradiation conditions. In this work, we investigate the radiation resistance of TBCs based on silicate compounds obtained by a hydrothermal microwave method by using proton and neutron beam irradiation. For this purpose, zinc silicates and cerium-doped zinc silicates were irradiated with l8 MeV protons with doses 1013-1015 p/cm2 and neutrons with doses 1013, 1015 n/cm2. The diffuse reflectance measurements and X-ray diffraction analysis (XRD) of materials before and after irradiation indicated that the samples have high radiation resistance, and the samples maintain the crystalline structure.

Speaker: Anush Badalyan (A. I. Alikhanyan national science laboratory (Yerevan Physics Institute)" foundation)

17:08 The Molecular Mechanism of Smectisation and Regulation of Polymorphism in Nematic Liquid Crystal Systems

This study explores the application of catastrophe theory to describe the molecular mechanism of smectisation and the regulation of polymorphism in nematic liquid crystal (NLC) systems that are based on polar liquid crystals, whose molecules have a large dipole moment directed along the long axis of the mo¬¬le¬cule .We have identified a relationship between the control variables of cusp catastrophe and the smectic order parameter η of NLC systems.
Thus, we conducted thermodynamic potential ϕ minimization not only in terms of structural degrees of freedom, but also in terms of the molecular composition of NLC systems, in order to better understand the role of various types of intermolecular interactions in the process of polymorphism. Then for ϕ we finally get the expression: ϕ=1/(4 ) x^4+1/2 〖ax〗^2+bx which becomes the characteristic equation for the cusp catastrophe.
This equation makes the study of structural transitions in NLC system possible using the analysis of the critical points of ϕ(x;a,b) function. As the control (a,b) variables vary, a local minimum can disappear and the internal variable can suddenly jump to a different equilibrium state. Also the state (x;a,b) will be forced to jump to the other sheet when it crosses the fold curve. The bi¬furcation set is the critical image of the projection (x;a,b) from the equilibrium surface onto the control space (a,b).
On the other hand, the equilibrium state of Sm phase at given temperature and pressure ultimately determined by the equilibrium constants K_1, K_2 (control variables) of the DA and D_2 A type CTC. Thanks to the catastrophe theory it was possible to evaluate the area of K_1,K_2 change which allows system to remain in sustainable state. That is by controlling the value of K_1, K_2 it is possible to regulate the process of polymorphism in NLC systems. An important circumstance is the role of the control variables, a smooth change of which can lead to a jump-like change in the functionality of the system. The catastrophe theory at a sufficiently high level allows determining the scope of changing control variables and thereby ensure the operability of the device.

Speaker: Dr Liana Bezhanova (Institute of Applied Problems of Physics of the National Academy of Sciences of the Republic of Armenia)

17:09 Dynamics of interacting solitons

The purpose of this work is to obtain a dynamic picture of the interaction of two solitons by analyzing the solution of the KdV (Korteweg de Wriz) equation. By changing the variables in the exact solution of the KdV equation, a solution is obtained that can be used to visualize the internal mechanism of the interaction of two solitons. At the corresponding boundary transitions in the transformed KdV equation, the limiting values of the corresponding functions describing solitons are calculated taking into account the phases. A numerical experiment shows that at t- there is no interaction of solitons, and the equation describes two solitons. The coordinates of the centers of solitons with small amplitude and large amplitude after interaction are determined.
Colliding solitons exchange amplitudes, a large amplitude gradually decreases, and a small one increases. An analogy of this phenomenon is the elastic collision of particles, with the only difference that the particles exchange momenta, and the solitons exchange amplitudes. However, in both cases, the exchanged parameters are related to power. Thus, the numerical experiment showed that during the interaction the solitons change places. After the collision, two solitons reappear with the same energies and amplitudes as before the collision. Only their phases change. As a result of the collision, the fast soliton receives an additional forward shift by a certain amount, while the slow soliton, on the contrary, shifts back by the amount calculated by us. The values of the corresponding phases are calculated.
Thus, the numerical experiment has shown that the interaction of solitons is indeed described by an analytical solution of the Kortev de Vries equation. When solitons collide, no nonlinear effects are observed. In the process of interaction, a soliton with a large amplitude is gradually compressed, transferring its amplitude to a smaller one. Then after the interaction we have the same two solitons as before the interaction (with the same amplitudes and widths), except that the larger amplitude soliton leads in the slip direction.
Then, using a numerical experiment, it is shown that the KdV solution obtained by the method of the inverse scattering problem describes the propagation and interaction of N solitons and that the interaction of N solitons does not differ in nature from the collision of two solitons.
The absence of secondary waves during the propagation of solitons indicates that the energy of the soliton is not scattered in space, but is localized in the region of space where the soliton is located. This is a property of particles. Taking into account the analogy of the interaction of solitons with the interaction of particles, we can say that solitons have a corpuscular nature. It is on the basis of these properties that researchers in fiber optics have proposed the use of nonlinear effects to compensate for wave dispersion and obtain short soliton pulses in optical communication fibers. Calculations show that this makes it possible to increase the performance of information transmission over optical cables by several times.

Speaker: Mileta Arakelyan (Yerevan State Univercity)

17:10 Formation of Medical Radioisotopes 111In in Photonuclear Reactions

The possibility of the photonuclear production of radioisotope 111In is discussed. The 111In radionuclide is among those that are used most frequently in diagnostics since it is a short lived (T1/2 = 2.8 day) gamma emitter (Eγ = 171.3, 245.4 keV). Moreover, this radioisotope is used in Auger therapy.
Enriched tin targets 112Sn were irradiated at the linear electron accelerator of Alikhanian National Science Laboratory (Yerevan) at the energy of 55 MeV and the average current of 1 μA. The yields of products formed in the target were measured by the gamma-activation method. The activity induced in the targets was measured with the aid of a high-purity germanium (HPGe) detector.
The bremsstrahlung photon flux is formed when electrons pass through the target converter. The protons flux was monitored by natCu thin foil (thickness of 50 µm) via 65Cu(γ, n)64Cu and 63Cu(γ, 2n)61Cu reactions. Radioactive nuclei formed in the target during the irradiation were identified by their half-lives and the energies of characteristic gamma lines. The yield Y(Eγmax) of a photonuclear reaction (γ,x) characterized by a threshold Eth and a cross section σ(Eγ) is the convolution of the cross sections and the effective photon energy spectrum W(Eγ max,Eγ).
The yield of the reactions 112Sn(γ,x)111In, 112Sn(γ,n)111Sn, 112Sn(γ,2n)110Sn, 112Sn(γ,3n)109Sn, 112Sn(γ,pn)110mIn, 112Sn(γ,pn)110gIn, 112Sn(γ,p2n)109In have been measured. The experimental data in question were compared with their theoretical counterparts calculated on the basis of the TALYS 1.95 code.
The yield of 111In ensures the production of samples without a carrier that have a high activity and which do not contain admixtures of long-lived indium isotopes.

Speaker: Tiruhi Bakhshiyan (Institute of Applied Problems of Physics of the National Academy of Sciences of the Republic of Armenia IAPP NAS RA)

17:11 The electron beam propagation through 3D-printed plastic samples with different infill patterns

Three-dimensional printing has a wide range of applications in science and technology. Fused filament fabrication (FFF) is a commonly used 3D printing technology, which is now being increasingly employed in radiation physics. In FFF, the internal structure of an object is primarily determined by its fill pattern and selected print modes. Therefore, this study aims to examine the interaction between electron beams and 3D-printed plastic samples with various infill patterns.
The 3D-printed objects were produced using FFF with PLA plastic and different infill patterns, including Rectilinear, Grid, Triangles, Stars, Honeycomb, Concentric, Archimedean Chords, Gyroid, and Hilbert Curve. Infill densities of 80% and 90% were utilized. Tomographic methods were applied to analyze the resulting samples. The study provides tomograms of the internal structure for each infill pattern. It was observed that Rectilinear and Grid patterns produced the most homogeneous samples.
Additionally, GafChromic EBT3 film was used to measure the doses behind the plastic samples when exposed to 6 MeV electron beams. It was demonstrated that for 3D-printed plastic samples with different infill patterns for the same infill density, the irradiation dose varied within the error range of the detector.
The findings of this study contribute to understanding of the propagation of electron beams through 3D-printed plastic samples with complex internal structures.
This work is supported by the RSF project No. 23-79-01232.

Speaker: Angelina Bulavskaya (National Research Tomsk Polytechnic University)

17:12 Evaluation of the possibility of a multichannel detector application for electron beam profile measurement by the multi-angle scanning method

This research on the transverse profile of ionizing radiation beams and the development of a multi-angle beam scanning detection system is highly significant and applicable in various fields.
In technological and research applications, it is crucial to accurately determine the transverse profile of ionizing radiation beams for effective quality control purposes. However, most existing detectors do not meet all the necessary requirements. The proposed multi-angle beam scanning method addresses this issue by collecting data from multiple detectors at different angles. This method can provide high spatial and energy resolution, short processing time, and low beam distortion during measurements.
This study aims to find the optimal number of detectors for the development of a multichannel scanning system. For this purpose, experimental distributions of a 6 MeV electron beam were obtained using Gafchromic EBT3 dosimetry film. The obtained distributions were represented as matrices of image brightness values in each pixel. By summing up the values in each column, projections of the images at different angles were obtained. This allowed for the reconstruction of the electron beam test distributions at different numbers of detectors.
Based on the reconstructed images, it was demonstrated that a minimum of eight detectors is required to accurately determine the beam profile. This information is valuable for the design and implementation of multi-angle beam scanning detection systems. Overall, this research contributes to the development of improved detectors for determining the transverse profile of ionizing radiation beams.

This work is supported by the RSF project No. 19-79-10014-П.

Speaker: Dr Sergei Stuchebrov (National Research Tomsk Polytechnic University)

17:13 Characteristics of a neutron source based on an electron accelerator LINAC-200

As part of the commissioning work at the linear electron accelerator LINAC-200 (JINR), we conducted experiments to study the characteristics of a pulsed neutron source obtained by irradiating a converter target with a 140 MeV electron beam. We performed numerical simulations to estimate the parameters of the neutron source and the energy spectra of neutrons in lead and tungsten targets of different sizes. We also made estimations for measuring the target dimensions in the generated neutron fields. Additionally, we conducted experiments to measure the energy spectrum of neutron and gamma radiation using the high-resolution time-of-flight method. It has been found that the ratio of integral estimates for tungsten and lead targets between the calculated and average measured yields does not exceed ~ 30%. The fluence of resonant and thermal neutrons in the target is estimated at ~ 2.8∙1013 neutrons/s, which corresponds to the requirements for modern pulsed neutron sources.

Speaker: Vitold Bleko (JINR)

17:14 Observation of embrittlement of a stretched metallic wire by measuring the frequency of its natural oscillations

In the process of irradiation of materials by fluxes of heavy particles (protons, neutrons, alpha particles) damage of material structure is observed. As a result of accumulation of such damages, there is a subsequent change in the properties of materials, in particular, its embrittlement and hardening. In this work, to observe the effect of heavy irradiation particles on the mechanical properties of metals, we propose to use vibrating wire resonators, in which the natural frequency of oscillations of the wire clamped at the ends strongly depends on its tension. The change in the elastic characteristics of the wire is reflected in the value of the natural frequency of oscillations of the wire and is registered. Preliminary experiments to study the embrittlement effect of a stretched wire are performed by heating the wire with an electric current. In the case of short pulses, a significant increase in frequency is achieved, which is explained by the process of hardening of the material as a result of the thermal impact on the wire (rapid heating and cooling).

Speaker: Suren G. Arutunian (Alikhanyan National Science Laboratory, Yerevan, Armenia; CANDLE Institute for Synchrotron Research, Yerevan, Armenia)

17:15 On the Possibility of Using Corundum to Create Sensitive VUV Detectors

Abstract: Many properties of corundum, including the radiation and thermal resistance, large forbidden zone, high light output, and spectral and temporal characteristics, make it an attractive converter for UV and particle detectors.
We have at our disposal many corundum crystals of different thicknesses with various activators, which were studied in the UV range of the spectrum. The percentages of various mixtures in the newly synthesized crystals were determined in order to determine the composition of impurities that ensures the maximum conversion of UV radiation.
Studies of these crystals led to the conclusion that corundum can be used in as a photoconverter not only in the UV range but also for creating sensitive detectors in the VUV wavelength range.

Keywords: VUV and UV detectors, converter, corundum․

Speaker: Ms Julietta Vardanyan (Institute of Applied Problems of Physics NAS RA)

17:16 Proton Induced Reactions on 114Sn and 120Sn Targets

Cross sections of proton-induced reactions on tin up to energies of 18 MeV using the stacked-foil activation technique have been measured. Experimental values for 114Sn(p,α)111In, 114Sn(p,pn)113Sn, 114Sn(p,2n)113Sb, 120Sn(p,n)120m,gSb, 120Sn(p,α)117m,gIn reactions cross-sections are reported.
A stack of enriched 114Sn and 120Sn foils was irradiated using 18 MeV proton beam provided by compact medical cyclotron IBA Cyclone18/18 (Yerevan). The stack was composed of 6 blocks of natCu-114Sn-natCu-120Sn layers where tin foils were 20 to 40 μm thick and copper foils were 20 μm thick. The irradiation was 5 min long with a collimated 1 μA proton beam of the same diameter as the target (1.2 cm). After the irradiation the foils in the stack were detached, and the γ-spectra of each target were measured with a high-purity germanium detector GEM15P4-70. Residual nuclei were identified by their half-lives and the energies of characteristic gamma lines.
Measured cross sections have been compared to existing experimental values and numerical calculations based on Talys1.95.
Our data are in good agreement with all previous experiments, and also with Talys1.95 results except for 120Sn(p,α)117m,gIn reactions where the numerical calculations are shifted to higher energies.

Speaker: Gohar Hovhannisyan (Yerevan State University)

17:17 SINGLE-CHANNEL HIGH-PRECISION LASER RANGEFINDER

Abstract: The article deals with the construction of a single-channel light rangefinder. At the same time, one of the main difficulties is the presence of depolarization of light, which forms residual light at the output of the analyzer, which greatly affects the measurement accuracy. It is shown that in order to exclude residual light by compensating for depolarization, a KDP crystal plate with the possibility of rotation in a plane parallel to the optical axis is installed at the input of the demodulator.
The possibility of using an optical delay line on a single mirror with the possibility of moving along the axis of the radiation source is also considered. The normal to the mirror surface and the optical axes of the KDP crystals are located to the axis of the light source at an angle of 0.7-0.9°.

Speaker: Yeghisabet Hayrapetyan (National University of Architecture and Construction of Armenian, Yerevan, Republic of Armenia)

17:18 TUNING OF THE RESONANT FREQUENCY OF LIGHT MODEMS ON VOLUMETRIC RESONATORS

To operate a high-precision light rangefinder in a wide temperature range (-10 +40) ° C, as well as to resolve the ambiguity of the measurement, it is necessary to ensure a change in the resonant frequency within 10-15% of the fundamental frequency. At a fixed modulation frequency of 1200 MHz, a device for smoothly changing the modem frequency within 150-180 MHz should be install on the modem resonator.
The issues of changing the resonant frequency of coaxial and biaxial resonators when dielectrics are introduce into the free volume of the resonators are considered. The derived main dependences show that the distribution of the field lines E does not shift, the dependence of the resonator frequency change on the location of the dielectric is also derive, which allows determining the range of tuning of the resonant frequency, which also depends on the type and volume of the introduced dielectric.
Problems of change in the resonant frequency of the coaxial and biaxial resonators when the free volume cavities are introduced dielectrics. Derived basic relations show that it does not shift the distribution of the field lines E, also derived the dependence of the frequency of the resonator on the location of the dielectric, which allows determining the tuning range of the resonance frequency. The tuning range is also dependent on the type and volume of injected dielectric.

Speaker: Yeghisabet Hayrapetyan (Institut of Applied Problems of Physics NAS RA)

17:19 Compact REPM structures for synchrotron radiation source

Linear rare earth permanent magnet (REPM) structures of split-pole type with harmonic distribution of magnetization for generators of synchrotron radiation are considered. The main attention is paid to issues of high order harmonic amplitude decrease at longitudinal Fourier-expansion of the field along the electron beam axis. It’s presented by a comparison that relative oberton amplitudes decrease down to 0.1% is possible at moderate discreteness of approximation rule of magnetization distribution in longitudinal direction instead of continuous one. Also, some considered systems incorporate unified permanent magnet pieces, in contrast, the well-known split-pole designs requiring a lot of types on magnetization.

Speaker: Ms Irina Kilmetova (NRC Kurchatov Institute)

17:20 Microtron Experimental Facility at Tomsk Polytechnic University

Accelerators of charged particles are powerful experimental tools, which are used in many fundamental researches and applied tasks. Compact accelerators are currently widely used for pretesting and proof-of-principle experiments for MegaScience projects, as well as for applied purposes. In this work, we present the detailed technical report of Microtron Experimental Facility at Tomsk Polytechnic University after major upgrade and scope and current status of experimental studies.

Speaker: Dr Artem Vukolov (TPU)

17:21 Prospects of corundum crystals application as Cherenkov radiators

Cherenkov radiation is widely used effect, which finds a broad application in the charged particle beam diagnostics. Corundum crystals are prospective radiators for obtaining Cherenkov light. Corundum radiators may significantly change their optical properties during extensive exploitation with particle beams that would influence Cherenkov light intensity. In this report, we experimentally investigated the Cherenkov light from corundum crystals and studied the spectral transmittance of crystals before and after irradiation by electron beams.

This study was supported by the Science Committee of RA (Research project № 23PostDoc-1C002).

Speaker: Dr Yury Cherepennikov

17:22 DIFFRACTION OF LIGHT BY A SLIT IN ANISOTROPIC MEDIA WITH CLOSED AND OPEN WAVE VECTOR SURFACE .

The Fraunhofer diffraction of an electromagnetic wave by a slit on an opaque screen located between vacuum and an anisotropic material medium is considered. Two cases of anisotropic media are considered and compared: with a closed wave vector surface (CWVS) and with an open wave vector surface (OWVS).
Formulas that describe diffraction in these two types of anisotropic media are obtained. Differences in the features of the formation of diffraction minima and maxima are shown.

Speaker: Prof. Asatur Lalayan (Yerevan State University)

17:23 Li2∙3IO3∙H3O: Crystal Structure and IR Spectrum

In recent years studies have shown that doping a crystal with amino acids improves the non-linear optical properties of α-LiIO3crystal [1, 2]. The authors[3] have studied the interaction of lithium with iodic acid and have shown that, at compositions close to 0.2≤x≤O.34, 2LiIO3•HIO3crystals are formed in a mixture of Li1-xHxIO3.
The present work deals with the synthesis, IR spectrum, thermal, and crystal structure study of the new lithium iodate crystal Li2•3IO3•H3O.The crystal was obtained by doping the α-LiIO3 crystal with amino acids of more than 5mol․%.Crystal structure of 2(Li)+(H3O)+3(IO3)– was determined by single-crystal X-Ray diffraction analysis at 100(2) K. It crystallizes in the monoclinic system (P21/n) with the parameters: a=8.3266(12) Å, b = 10.9893(17) Å, c = 11.2472(17) Å, α= γ=90°, β= 111.360(4)°and Z(Z') = 4(1). The structure was refined to R = 0.0215 and ωR = 0.0580 for 2276 reflections. The structure contains a hydronium cation(H3O)+, three crystallographic independent trigonal pyramidal IO3 anions, two independent cations(Li+) coordinated each by four oxygen atoms (3IO3) at apices of strongly deformed tetrahedrons, see Fig. 1. The Li-O bond lengths are similar to the bond lengths in the Li2HPO3•H2O crystal [4]. The research results have revealed the mechanisms of crystal formation and the characteristic absorption bands of functional groups, which is of scientific importance.

Speaker: Dr Ruzan Sukiasyan (Institute of Applied Problems of Physics, NAS of Armenia)

17:24 Investigation of sputtering processes using acoustoplasmic magnetrons

The results of a study of deposition by a new type of magnetron developed by us - an acoustoplasmic low-frequency magnetron, are presented. The deposition of conductive and non-conductive materials is considered, and also polycrystalline and porous structures.

Speaker: Ruben Chilingaryan (Institute of Applied Problems of Physics (IAPP) NAS RA)

17:25 Design and modelling of a prototype U27 undulator for the SYLA project

Short-period, high-field undulators are widely used on modern SR sources to generate high-intensity coherent radiation. In order to achieve the stability of the properties and the quality of the radiation received in undulators magnetic field of ID has to meet very tough tolerances, which depend on the accuracy of the arrangement of magnets in the assembly. Such tolerances can be achieved by adjusting each magnetic element [1].
This paper presents the results of numerical simulation of an undulator U27 based on rare-earth permanent magnets (REPM) for the project of an accelerator-storage complex of a synchrotron radiation source with a free electron laser "SYLA". Geometry of magnet elements for different periods was optimized to produce the highest on-axis field. The magnetic field in such an undulator is calculated via a computer simulation using RADIA and analyzed, as well as the inhomogeneities of its components in the transverse plane. The report discusses the requirements for the accuracy of setting [2] and positioning of magnetic elements by angle and coordinate, as well as existing methods for implementing these requirements.
Further, design solutions are proposed to achieve the necessary accuracy of magnet arrangement, including an automatic adjustment system and an adjustment robot. Special attention is paid to the design of the system on flexible elements, its various configurations are offered, as well as the method of their semi-automatic selection.
The report examines the advantages and disadvantages of each configuration, and will also present the results of the assembly and the first tests of the undulator layout.

Speaker: Yakov Abakumov (National Research Centre "Kurchatov Institute")

17:26 Different methods for studying the magnetic properties of undulator systems for the synchrotron “SILA”

Synchrotron sources play an essential role in contemporary scientific investigations in physics, chemistry, biology, materials science, and other fields. They offer high intensity, a wide energy spectrum, and distinct synchrotron radiation characteristics, making them unmatched for a variety of experimental objectives. Recent years have witnessed substantial endeavors in advancing next-generation synchrotrons, particularly emphasizing 4th generation synchrotron undulator systems [1]. These fourth-generation undulators represent the latest phase in this evolution, delivering even greater intensity and radiation quality. To attain optimal brilliance and coherence from the undulator systems designed for the "SILA" synchrotron, methodologies for precise adjustment need development and refinement [2]. The magnetic field distribution quality within the undulator gap directly impacts the synchrotron radiation's quality, warranting a comprehensive approach to the tuning process.
Several traditional methods exist to validate the magnetic field distribution in undulator gaps, including the stretched wire technique and Hall sensor scanning [3]. Tailoring these measurement methods' design aspects has been undertaken to meet the technical prerequisites set for the permanent magnet undulators employed in the SILA synchrotron. A magneto-optical technique has also been proposed as an additional means to explore the magnetic field distribution in the undulator gap. This technique relies on measuring the rotation of the polarization plane in light passing through the undulator gap containing an optically transparent crystal. In this work we explore the fundamental feasibility of implementing this technique and its applicability to investigate various undulator radiation sources. The theoretical basis for solving this problem is the solution of the propagation of an electromagnetic wave in a magnetized medium problem using Maxwell's equations.
The comprehensive utilization of both existing and evolving tuning methodologies for 4th generation undulator systems stands as a pivotal stride towards achieving the specified attributes of the "SILA" synchrotron.
[1] Levichev E., Vinokurov N. Undulators and other insertion devices //Reviews of Accelerator Science and Technology. – 2010. – Т. 3. – №. 01. – С. 203-220.
[2] Kovalchuk M. V. et al. Fourth-Generation Synchrotron Radiation Source with X-ray Free-Electron Laser SILA: Concept of Accelerator–Storage Complex //Crystallography Reports. – 2022. – Т. 67. – №. 5. – С. 676-683.
[3] Elleaume P., Chavanne J., Faatz B. Design considerations for a 1 Å SASE undulator //Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. – 2000. – Т. 455. – №. 3. – С. 503-523.

Speaker: Aleksei Komlev (NIC Kurchatov institute)

17:27 Effect of Crystal Reflectivity on the Angular Distribution of Diffracted Transition Radiation from Relativistic Electrons

Recently, a number of works have appeared devoted to estimating the size, divergence, and emittance of beams of relativistic electrons (positrons) by recording the angular distributions of diffracted transition radiation (DTR) of particles in thin crystals [1, 2]. Diffracted transition radiation can be represented as a result of reflection of transition radiation (TR) with a characteristic photon emission angle ~ γ-1 on the crystal planes. Therefore, if the condition ω<<γωp is satisfied, where γ is the Lorentz factor and ωp is the medium plasmon energy, the angular distribution of the TR does not depend on the photon energy ω, but is determined only by the particle energy and the beam divergence.
The papers [1, 2] do not take into account the fact that the angular region of the total reflection of X-rays or the width of the so-called Darwin table Δθ depends on the photon energy and characteristics of the crystal used. Therefore, when the condition γ-1~Δθ is met, the angular distributions of TR and DTR begin to differ. The intensity at the minimum of the DTR angular distribution, in contrast to the TR one, is no longer equal to zero. The limits of applicability of the techniques [1, 2] and ways to extend them are discussed
References
1. S.V. Blazhevich et al.// Phys. Let. A 384 (2020) 127537.
2. Yu.A. Goponov et al. // NIM A 996 (2021) 165132.

Speaker: Igor Vnukov

17:28 Feasibility of using optical Cherenkov radiation for non-relativistic ion beam diagnostics

Optical transition radiation (OTR) is widely used for relativistic beam diagnostics. Recently such a technique was applied for transverse profile measurements at the GSI non-relativistic ion beam [1]. Authors of the paper [2] proposed a new method for measuring the ion energy based on the monochromatic optical Cherenkov radiation (ChR) from radiators with frequency dispersion.
This report considers whether these results could be applied to ion beams with finite transversal sizes, i.e., to more realistic Gaussian-like beam profiles. The consideration is done threefold – using different wave-nature-based ChR models [3,4] and using the standard corpuscular model via the Geant4 toolkit [5]. Besides ChR, the simultaneous registration of optical transition radiation is proposed as a tool for ion beam monitoring.
[1] R. Singh et al.Phys.Rev. AB 25,072801 (2022)
[2] A.P. Potylitsyn et al. JETP Letters,115,p.439 (2022)
[3] V.E. Pafomov. Proc. P.N. Lebedev Phys. Inst. 44 25 (1971)
[4] S. Gogolev, A.Potylitsyn. Phys.Lett.A, 383, p.9 (2019)
[5] S. Agostinelli et al Nucl. Instr. Meth. A 506 p.250 (2003)

Speaker: Blazo Djurnic

17:29 Computer Modeling of a Pyroelectric Accelerator

Speaker: Pavel Shapovalov (National Research Nuclear University "MEPhI")

Wednesday, 20 September

09:00 → 10:30 e–/e+, X–ray, THz, and neutron based applications

Convener: Alexander Potylitsyn

09:00 Twisted radiation from nonlinear Thomson scattering with arbitrary incident angle

Thomson/Compton scattering is well-known as a scattering process between electromagnetic radiation and charged particles, which is found in laboratories and nature. Here, we investigate the radiative properties of nonlinear Thomson scattering with arbitrary incident angle. Based on classical electrodynamics, the analytical universal expressions of the electric field and energy spectrum of the radiation emitted by a relativistic electron scattering of circularly polarized laser field are derived. It is shown that the spatial distributions of the radiation energy of high-order harmonics have annular shapes and the symmetry of the annular shapes is strongly affected by the incident angle, which may relate with the angular momentum of twisted high-order harmonics. These results would help the understanding of the properties of twisted $\gamma$/X-ray and high energy electron-laser scattering experiments in laboratory.

Speaker: Ke Liu (National University of Defense Technology)

09:20 Coherent Radiation at Electron Channeling in OL as a Mechanism to Increase the Laser Intensity

The processes of interaction of charged particles in crystals at channeling are well studied today. Based on the physics of channeling in crystals, new methods are being developed for controlling beams of both charged and neutral particles. However, in addition to the innovative tool of controlling particle beams through channeling, it is well known that the effect of channeling of charged particles in crystals can be used to generate electromagnetic radiation in the X-ray and gamma ranges. The field gradients of the crystallographic axes and planes are very large, far exceeding the values that can be obtained by all known physical instruments, which allows us to conclude that crystalline undulators can be the most powerful sources of electromagnetic radiation (channeling radiation). In fact, in order to create a powerful source of radiation based on the channeling effect, there is one essential problem associated with the fast dechanneling of a beam of charged particles due to inelastic scattering processes. In the case of negatively charged particles, in particular electrons, the problem is even more pronounced, since most of the time the beam is in close proximity to the crystal nuclei.
This problem is absent when electrons interact with the field of an optical lattice (OL) in the channeling mode. The interaction of a charged particle with the field of a laser wave is considered to be free from inelastic scattering.
We have been studying the channeling of electrons in OLs for a relatively long time, both in relation to the beam dynamics and in relation to the radiation during channeling in the OL field, which will be the subject of this report. Our latest results describe the coherent emission of an electron beam when channeled in an OL. In particular, it is shown that, under certain conditions, the radiation maximum during channeling of an electron beam in OL will coincide with the frequency of the field forming the OL. This effect can underlie a new method for increasing the intensity of laser radiation that forms the OL field.

Speaker: Sultan Dabagov

09:40 Electric field lines of the helical undulator

One of the devices for generating circularly polarized radiation of high frequency is a helical undulator in which a relativistic charged particle moves along a helical trajectory. In this paper, the spatial distribution of the electromagnetic field produced by such a particle is analyzed using electric field lines. The equations of electric field lines, which, due to the presence of curvature and torsion in the trajectory, do not contain a class of lines lying in the same plane, are precisely solved. A special algorithm for erasing invisible parts of the lines has been developed to represent the lines in space. Animation of field pictures for different viewing angles is applied. Several remarkable features of the field picture are revealed, in particular, that the hard component of the radiation is concentrated in the plane orthogonal to the undulator axis and passing through the position of the particle at the current moment of time.

Speaker: Suren G. Arutunian (Alikhanyan National Science Laboratory, Yerevan, Armenia; CANDLE Institute for Synchrotron Research, Yerevan, Armenia)

10:30 → 10:50 Coffee break

11:00 → 16:00 Excursion

Thursday, 21 September

09:00 → 10:40 X–ray and neutron scattering in crystals

Convener: Prof. Sultan Dabagov (INFN Laboratori di Frascati)

09:00 Absorption characteristics of diffracted X-ray radiation in a quartz crystal at an external temperature gradient

The characteristics of the redistribution of the intensities of passed and reflected X-rays by the Laue geometry of diffraction from the family of planes of a quartz crystal (101 ̅1) depending on the thickness of the single crystal and the magnitude of the temperature gradient were experimentally studied. In particular, the behavior of the interference absorption coefficient of X-rays depending on the thickness of the crystal and the magnitude of the thermal gradient was studied. Depending on the magnitude of the thermal gradient applied to the single crystal, measurements of both the transmitted and reflected beams, as well as their total intensities (registered at the same time) were carried out at different thicknesses.
As is known, in the presence of a temperature gradient, when the single crystal is under the condition of Bragg reflection for the Laue geometry, a significant increase in the intensity of the diffracted reflected beam is observed, and at a certain value of the action is observed a full pumping of the primary beam from the main direction to the direction of reflection. Under these conditions, a significant increase in the total intensity of the diffracted transmitted and reflected beams is observed compared to the intensity of the X-ray beam transmitted from the single crystal outside the Bragg condition, which is due to the change in the interference absorption coefficient of the radiation in the single crystal.
In this work, it is shown that the change in the total intensity (transmitted and reflected) depends both on the magnitude of the temperature gradient present in the crystal and on the thickness of the diffracting single crystal. The results of the study show that with an increase in the temperature gradient, the total intensity increases and reaches a maximum value at a certain value, and with a further increase, the total intensity begins to decrease, tending to the intensity of the beam that passed through the crystal outside the Bragg condition. As the thickness of the single crystal increases, the relative change in the total intensity increases. Let us also emphasize the following fact: for small values of the temperature gradient, a monotonic increase in both the reflected radiation intensity and the total intensity (the sum of the transmitted and reflected radiation) is observed.

Speaker: Vahan Kocharyan

09:20 Possibilities of laboratory and synchrotron diagnostics of crystalline materials under the external influences

Our scientific group based on the Laboratory of X-ray Methods of Analysis and Synchrotron Radiation of FSRC “Crystallography and Photonics” RAS specializes in the research of crystalline materials under external influences of various nature and their combinations: constant, alternating and pulsed electric and magnetic fields, laser illumination and heating, mechanical and ultrasonic loading.
The objects for research are a wide range of piezoelectric, ferroelectric, photovoltaic, ferromagnetic crystals and solid solutions, as well as functional elements and systems based on them. To obtain multidimensional information, a complex of X-ray and synchrotron techniques is used, supplemented by various auxiliary studies.
For the tasks described above, a comprehensive modernization of the laboratory triple-crystal X-ray spectrometer was pursued. The upgraded setup is a unique tool for time-resolved structural diagnostics. The diffractometer scheme includes specialized equipment for applying external influences, controlling and synchronizing the experiment. It became possible to implement a wide range of techniques for in-situ diagnostics under the electric field or laser radiation action on the sample: double- and triple-crystal diffractometry in static and time-resolved regimes, reciprocal space mapping, topography, rocking curve imaging and others.
The available possibilities make it possible to study induced effects, such as the processes of migration of charge carriers of ionic, vacancy, and polaron types in a crystal lattice, photoinduced processes, magnetoelastic interactions, deformation behavior, etc. Precision measurements of piezoelectric constants are conducted. The mechanisms of the formation of defects in the crystal lattice, in particular, as a result of thermal annealing under various conditions, are determined. Techniques for the rearrangement, organization and control of charged defects by means of external electric fields are developed. The action of external influences is studied to establish the relationship between the growth and synthesis technology, structural features and the defect structure with the physical properties of crystals.

Speaker: Dr Anton Kulikov (FSRC Crystallography and photonics RAS)

09:40 Adaptive X-ray Optical Elements Based on Bending Piezoactuators: Possibilities and Prospects of Practical Application

Crystalline materials are a key element of the modern microelectronics industry. Often, elements and devices manufactured on their basis operate under conditions of external influences that have a significant impact on their functional characteristics, up to complete failure. Therefore, one of the urgent problems of modern materials science is the study of the structure evolution of promising crystalline materials under various external influences in order to be able to predict their behavior under real operating conditions, evaluate performance, and search for new materials with unique properties.
The most effective tool for studying crystalline materials is X-ray radiation and methods based on it. The task of developing appropriate experimental techniques is being solved for a long time, and at the moment there are two principal approaches with greatest development: modern detecting equipment, which makes it possible to observe the processes of changing the structure of the sample in the "X-ray movie" mode, and, as well, the formation of a special structure of the X-ray radiation itself - in particular, pump-and-probe methods. Each of these approaches allows you to cover a certain range of time resolutions and processes under study.
However, none of the available approaches makes it possible to fully solve the problems of studying crystals, firstly, because of the limitations or impossibility of using the recommended experimental techniques on a wide range of devices, and, secondly, because of the limited efficiency when working with temporal resolutions range from seconds to microseconds, the most interesting for studying the evolution of the crystal structure.
One of the possible solutions to this problem is the adaptive elements of X-ray optics (AEXO) proposed by a team of scientists from the FSRC “Crystallography and photonics” RAS. These are unique devices that allow fast and precise tuning of the X-ray beam parameters directly during the experiment [1, 2]. Such elements include ultrasonic resonators of longitudinal vibrations [3], bending adaptive elements [1] and prospective combined two-frequency elements [4].

This paper provides principal information about each of the types of adaptive elements being developed, their unique features and opportunities for research. It is shown that on the basis of the proposed elements, it is possible to create simple and efficient devices and tools for equipping a wide range of research instruments - from laboratory X-ray diffractometers to synchrotron stations, including those based on fourth-generation sources being designed. Such devices can be used to conduct research with a time resolution down to microseconds of both ordered objects, for example, crystalline materials under external influences, and disordered objects, for example, dynamics of chemical transformations.
This work was supported by the Ministry of Science and Higher Education within the State Assignment of the Federal Research Center “Crystallography and Photonics” of the Russian Academy of Sciences and within the framework of grant No. 075-15-2021-1362.

1. E. Blagov, A. S. Bykov, I. V. Kubasov, M. D. Malinkovich, Yu. V. Pisarevskii, A. V. Targonskii, I. A. Eliovich, M. V. Kovalchuk. Instruments and Experimental Techniques. 2016. V. 59. P. 728–732.
2. A. Eliovich, V. I. Akkuratov, A. V. Targonskii, A. E. Blagov. Crystallography Reports. 2018. V. 63. No. 5. P. 724–728.
3. A.E. Blagov, P. A. Prosekov, A. V. Targonskii, Ya. A. Eliovich. Crystallography Reports. 2015. V. 60. P. 167–171.
4. Ya. A. Eliovich, A. E. Blagov, V. R. Kocharyan, A. S. Gogolev, A. V. Targonsky, A. E. Movsisyan, V. A. Korzhov, A. R. Mkrtchyan, M. V. Kovalchuk. JETP Letters. 2022. V. 115. P. 148–152.

Speaker: Yan Eliovich (FSRC "Crystallography and photonics" RAS)

10:00 Dynamic diffraction of X-rays and slow neutrons in crystals with continuous deformation field

Analytical solutions are constructed for the wave functions of diffracted X-ray and slow neutron waves in crystals with a lattice deformation field. An integral form is formulated for determining the quasi-amplitudes of diffracted waves in the framework of the initial spatially inhomogeneous beams, based on the constructed functions of the influence of a point source of X-ray and neutron waves for crystals with a deformation field.
A theoretical analysis of the phenomena of anomalous absorption, extinction, pendulum effect was carried out, with the identification of the features of these phenomena in a slightly deformed crystal. . It is shown that the deformation field of the crystal lattice plays a significant role both in the redistribution of amplitudes and phases wave fields in the lattice. As a result of this redistribution of the amplitude (intensity) of X-ray and thermal neutrons along the ray trajectories, they turn out to be largely dependent not only on incoherent energy losses (absorption), but also on the parameters of the lattice deformation field. The presence of a deformation field leads to energy transfer, on the one hand, between weakly and strongly absorbing field modes, and, on the other hand, between transmitted and reflected radiation fields in the crystal. As a result:
• there is a complete vanishing of the Bormann effect, i.e., equating the attenuation coefficients of weakly and strongly absorbed modes,
• .change in places of these modes, as a result of which the weakly absorbing mode turns into a strongly damped mode and vice versa,
• for certain values of the parameters of the deformation field and depending on their sign, an exponential increase in the amplitudes of these waves can be observed with a simultaneous exponential decrease in the other.

Speaker: Mr Karapet Trouni (Institute of Applied Problems Physics)

10:20 Synchrotron X-ray diffraction diagnostics of single-crystal materials under the external magnetic field

In this report the influence of the magnetic domain structure and the effects of surface magnetism on the perfection of crystalline materials and their diffraction characteristics will be discussed. The canted antiferromagnet FeBO3 was used as a model crystal due to its anomalously strong magnetoelastic interaction.
To carry out the experiments, a synchrotron technique for X-ray diagnostics under the influence of external magnetic fields has been developed. It was established that the magnetic domain structure and near-surface magnetism effects lead to the appearance of disordered areas in FeBO3 crystals and slight changes in the lattice parameters. This affects the broadening or splitting of the reciprocal lattice point and diffraction properties of the crystal become worse. An applied external magnetic field improves the diffraction characteristics of FeBO3 crystals.
The evolution of the magnetic domain structure of Fe1-xGaxBO3 single crystals in external magnetic fields was studied using X-ray topography. It is shown that the application of weak magnetic fields is sufficient to significantly reduce the X-ray diffraction contrast in the topograms and, accordingly, improve the degree of structural perfection of crystals. In addition, time-resolved synchrotron diffraction experiments were carried out on FeBO3 single crystals under the influence of alternating magnetic fields. It is was shown that it is possible the ability to control the parameters of the diffraction characteristics of iron borate crystal in accordance with the external magnetic field modulation law. allows to modulate the angular and spectral parameters of X-ray, reflected from the FeBO3 single crystal to be modulated. The developed technique and the results obtained are extremely important for practical applications of magnetically ordered crystals, such as iron borate FeBO3, in new high-tech fields of science and technology.
This work was performed with a financial support by the Ministry of Science and Higher Education under the State Assignment of the Federal Research Center “Crystallography and Photonics” of the Russian Academy of Sciences and within the framework of grant No. 075-15-2021-1362.

Speaker: Nikita Snegirev (Shubnikov Institute of Crystallography of FSRC “Crystallography and Photonics” Russian Academy of Sciences, 119333, Moscow, Russia Kurchatov Complex for Synchrotron and Neutron Investigations, NRC «Kurchatov institute», 123182, Moscow, Russia)

10:40 → 11:00 Coffee break

11:00 → 13:00 X–ray and neutron scattering in crystals

Convener: Prof. Artak Mkrchyan (Institute of Applied Problems of Physics (IAPP) NAS RA)

11:00 A complex X-ray diffraction technique for studying electrophysical properties and photovoltaic processes in crystals

Control of the ordered systems properties can be effectively implemented through deformations formed by various external influences, for example, electric fields, laser radiation or their combination. In a number of cases, crystals are sensitive to both types of influences, which, on the one hand, makes them promising materials within straintronics purposes, and, on the other hand, complicates their study due to the simultaneous activation of a complex of deformation processes. Highly informative X-ray diffraction methods can become the basis for a complex technique that would allow in-situ study physical properties of promising crystalline materials that are sensitive to both optical and electrical influences, as well as separate their contributions to the overall deformation pattern.
In this work, a complex technique for studying electrophysical properties and photovoltaic processes in functional crystals based on X-ray diffractometry methods is introduced. After initial estimation of the X-ray diffraction parameters of the sample, an algorithm of the techniques implies a series of measurements are sequentially carried out under conditions of separate and simultaneous exposure of an external electric field and laser radiation. X-ray diffraction measurements in double- and triple-crystal schemes allow one to separate deformation components of tension/compression and twisting. The time-resolved X-ray diffraction technique based on synchronization of the measuring equipment with the system of electrical and optical excitation of the sample using to record fast deformation dynamics. Finally, measurements with complementary methods are conducted, particularly, registration of electrophysical characteristics and sample temperature during an experiment, which make possible numerical estimation of the electrical and thermal components of deformation processes contribution respectively.
Approbation of the proposed technique in case of a photo- and electroactive Fe:LiNbO3 (Fe 0.02%) single crystal made it possible to separate the contributions of thermal expansion, pyroelectric and piezophotovoltaic effects to the overall deformation pattern, and also determine their amplitudes and formation times. Such results demonstrate high efficiency of the technique, which opens up prospects for creation of a new generation of sensors, energy-saving computing devices and information storage systems.
This work was supported by the Ministry of Science and Higher Education within the State Assignment of the Federal Research Center “Crystallography and Photonics” of the Russian Academy of Sciences and within the framework of grant No. 075-15-2021-1362.

Speaker: Fedor Pilyak (FSRC "Crystallography and Photonics" RAS)

11:20 NEW MATERIALS FOR RADIATIVE APPLICATIONS

New technologies invite researchers and developers to be creative, enabling them to consider theories and approaches which have thus far remained undeveloped. In our contribution we will introduce some considerations regarding involvement of new kind materials and possibility their dendrite structure to the research in field of physics of high-energy radiations.
First, we will consider several possible applications of currently commercially available single crystals of metals (e.g. [1]). We will share our preliminary research with aluminum (Al) single crystal and will discuss how we include experimental parameters of its texture to the realistic simulation of radiative processes using GEANT4 toolkit. Evaluation of Al single crystal use for the PXR generation will also be presented. Then, possible application of iridium (Ir) single crystal target for the effective generation of an intensive positron beam for future electron-positron colliders will be demonstrated.
At last, we will describe polycrystalline high-dendrite boron-enriched pyrolytic carbon (B-PyC) synthesized in our Institute in the in-house developed CVD facility [2]. The synthesis occurs on the inner surface of a cylindrical graphite assembly indirectly heated to the temperatures of 1450–1570 °C. Controlled low-density flows of nitrogen, boron trichloride, carbonaceous gases and low (0.01 to 2 % vol.) concentration oxygenic compound (e.g. water vapor or free air) react in the assembly and producing the B-PyC film characterized high concentration needle-shaped dendrites with highly extended surface. During the synthesis two-phase crystalline system is organized, that are hexagonal crystals of pyrolytic carbon and boron carbide B4С. Outstanding properties of the pyrolytic carbon are widely known, e.g. [3]. Properties and possible applications of the polycrystalline high-dendrite B-PyC will be presented in more detail.

1. https://mateck.com/en/content/7-metal-single-crystals;
2. Demidenko M.I., Adamchuk D.V., Rusanov A.P., Sirotkin S.V., Ivanko L.V., Maksimenko S.A. Boron-enriched pyrolitic carbon: material for biomedical and engineering applications // Doklady of the NAS of Belarus, Vol. 67, No. 3 (2023) pp. 250–256 (in Russian);
3. A.W. Moore, Pyrolytic Carbon and Graphite, Encyclopedia of Materials: Science and Technology, Elsevier, 2001, Pp. 7933-7937.

Speaker: A. Lobko

11:40 New concept of local and time-resolving structural diagnostic of nanostructures at high-brilliance synchrotron sources based on Kossel effect in multilayers

It is assumed to develop new class of XSW methods in the «normal incidence – grazing exit» geometry using optical reciprocity principle. The complex structure of the fluorescent signal, measured in grazing angles (an analogue of the Kossel effect), will be used for determination of the atoms distribution profiles in layered systems or atomic positions in the crystal lattice, receiving information equivalent to that one from XSW experiments.
The most progressive approach for research, including with time resolution, is the so-called "X-ray cinema". The main idea of this approach is "study in one frame" without rebuilding the parameters of the experimental scheme (angles, energies). An important methodological task is the development of new experimental methods that make it possible to obtain information about the structural properties of research objects without scanning.
The using of ultra-bright sources of synchrotron radiation with micro- and nano-focusing will make it possible to maximally localize the method for studying small (nanoscale) objects and performing three-dimensional diagnostics with the required resolution.
The important task of modern materials science is the addition of a time coordinate to the study of the structural characteristics of inorganic and bioorganic objects and the transition to experimental methods with time resolution using synchrotron radiation sources. The development and application of synchrotron time-resolving research methods will allow to look inside nonequilibrium processes, self-organization processes, nonequilibrium phase transitions and fluctuation processes, as well as the effects of nonlinear dynamics of the electron subsystem and crystalline sublattices under resonant excitation.
The developed algorithm, which implements a position-sensitive energy-dispersive analyzer, made it possible to carry out such experiments using two-dimensional X-ray cameras.
Testing of the experimental scheme was carried out on layered W-Ti-W systems. Shown are the results of spectral-selective studies in the non-scanning mode in the grazing fluorescence emission geometry, which are equivalent to the data of the XSW method in the standard grazing incidence geometry. Multispectral analysis of the wave fields of fluorescent lines with different distributions can be used to reconstruct the structural parameters.

Speaker: Anton Safonov (National Research Center "Kurchatov Institute")

12:00 A New Method for Revealing the Structure of the Defocusing Pattern Arising in X-ray L–L–L Interferometers

The paper presents a new method for revealing the fine structure of defocusing patterns that appear in three-block interferometers and the results of the corresponding studies. Three-unit defocused interferometers without a thick analyzer block, with a thick analyzer block and with a separate thick block (enlarger) are designed, manufactured and tested. It is shown that fine structures of interference patterns obtained from three-block defocused interferometers are observed in those cases when the analyzer block of the interferometer is thick or an enlarger is used (fourth thick block). Theoretical calculations show that in the presence of defocusing, as a result of superposition of beams, an interference pattern is formed on the input surface of the interferometer analyzer in the form of parallel fringes (lines) lying in the scattering plane. The coordinates of the maxima of the interference fringes (lines) and the period of the fringes are calculated in cases without a thick crystal and in its presence, as well as the linear magnification factor. It has been experimentally proved that a thick crystal (enlarger crystal) does not introduce new information into the interference pattern, but only increases its size in the scattering plane.

Speaker: Samvel Mkhitatyan (Institute of applied problems of physics NAS RA)

12:20 Identification of unknow material by X ray fluorescence analysis with a pyroelectric X ray generator

Development of advanced intense and reliable sources of charged particle beams is a direction within accelerator physics on its own right. By changing the temperature of Lithium Tantalate (LiTaO3) single crystal at moderate vacuum conditions leads to generation of strong electric field. The uncompensated polarization during the heating or cooling of the crystal causes the ejection of electrons from either the dielectric layer on the surface of the crystal or from a metal target depending on the polarity. The electrons are accelerated and gain energy of up to a 100 keV. The energy of these electrons can be determined by measuring the end-point energy of the X-ray spectrum that resulted from the electron interactions with the target. The conception of a pyroelectric accelerator enabled us to develop compact (portable) electron source, which does not require an external high-voltage and the use of hazardous materials.

By using the advantage in X-ray energy afforded by the lithium tantalate crystal, it was shown that the k-shell X-rays brass target was fluoresced. Using the same setup an unknown material was inserted to fluoresce using pyroelectric accelerator to analyze its element content. In this report we demonstrate how pyroelectric accelerators can be applied and complement the conventional sources such as X-ray tubes and radioisotopes or even large central facilities.

Speaker: Majid Ali

13:00 → 15:00 Lunch

15:00 → 16:20 e–/e+, X–ray, THz, and neutron based applications

Convener: Prof. Alexander Lobko (Byelorussian State University (BY))

15:00 Orbital angular momentum radiation of relativistic electrons in the laser wave field with linear polarization.

The problem of generation of twisted photons is well studied theoretically and is promising due to possible applications /1/. There are already prototypes of devices producing such photons in various energy ranges. The most developed area of research is optical and radio ranges.
Earlier we presented the results of research on generation of twisted photons by relativistic particles in strong laser fields with circular polarization. Calculations of the emission spectra of twisted photons were carried out taking into account the radiation reaction.
In this report we consider another way of generating hard twisted photons – the radiation caused by the motion of charged particles in the field of a strong laser wave with linear polarization. The results of numerical modeling of the orbital angular momentum per photon as a function of photon energy are presented. The effect of a blooming rose is demonstrated. A comparative analysis with the results of /2/ is given.
References
1. I.P. Ivanov, // Progress in Particle and Nuclear Physics, 2022, Volume 127, 103987
2. O.V. Bogdanov, P.O. Kazinski, G.Y. Lazarenko, // Physical Review D, 2019, 99, P.1-21

Speaker: Dr Oleg Bogdanov (Tomsk Polytechnic University)

15:20 Interaction of an electron with unipolar pulses of arbitrary shape

Interaction of an electron with unipolar pulses of arbitrary shape

D.V. Gavrilenko* a, A.P. Potylitsyn a,b, D. Yu. Sergeeva a, A.A. Tishchenko a
a National Research Nuclear University “MEPhI”, Moscow 115409, Russian Federation
b National Research Tomsk Polytechnic University, Tomsk 634050, Russian Federation

Unipolar pulses of electromagnetic radiation – the waves with practically constant electric field – were suggested by Bessonov in 1981 [1], and called “strange waves” even by the author. Now the term "unipolar" is used in a wider meaning and in the literature [2-3] they consider such pulses in which the electrical area $\int_{}^{}dt\cdot E(t)\neq 0$ is not equal to zero. Today the formation of unipolar pulses [4] and their possible applications for acceleration of free charged particles [5], as well as for interaction with electrons of atoms of the medium [2] are being intensively investigated.
Nevertheless, the question of the radiation generated by the interaction of relativistic electrons with unipolar pulses has still little been explored. In this report we calculate the trajectory of a charged particle in a unipolar pulse of arbitrary shape, which allows us to find the field of radiation generated in the process. We show that in the case of unipolar pulses in the Bessonov’s understanding the radiation has a characteristic spectrum determined by the pulse duration, which opens up possibilities for its tuning as well as for the generation of radiation of a wide spectrum. We also calculate the energy acquired by the charge during the interaction, which allows us to precise the approximations used in [5]. Separately, the particular cases of parallel/antiparallel wave vectors and electron momenta are analyzed. They are of especial interest, because the head-on collision is a case of maximum intense radiation, and anti-head-on collision is a way of acceleration of the electrons in the field of a unipolar pulse.

References
1. E.G. Bessonov, On a Class of Electromagnetic Waves, JETP 53, 433 (1981).
2. R. M. Arkhipov, M. V. Arkhipov, N. N. Rosanov, Unipolar light: existence, generation, propagation, and impact on microobjects, Quantum Electronics, 50, 801–815 (2020).
3. R. M. Arkhipov, M. V. Arkhipov, A.V. Pakhomov et al, Unipolar and Subcycle Extremely Short Pulses: Recent Results and Prospects (Brief Review), Jetp Lett. 117, 8–23 (2023).
4. A. Pakhomov, M. Arkhipov, Nikolay Rosanov, and Rostislav Arkhipov Phys. Rev. A 106, 053506 (2022).
5. N.N. Rosanov, N.V. Vysotina, JETP 130, 52 (2020)

*DVGavrilenko@mephi.ru

Speaker: Dmitrii Gavrilenko

15:40 Electrical, Dielectric and Nonlinear Optical Properties of SrB4O7

The noncentrosymmetric optical borates are promising materials for modern high-power laser systems because of high nonlinear optical (NLO) coefficients, wide transparency windows including visible and UV ranges, and high optical damage thresholds, etc. One of such borates is SrB4O7 (SBO). Large single crystals of SBO with high optical qualities were grown by the Kyropolus method [1]. SBO has been investigated as a potential NLO material with some excellent properties such as a transparency down to 120 nm, a high nonlinear coefficient, a high damage threshold, and no hygroscopicity [2]. Also, it was demonstrated that this crystal has the highest surface acoustic wave (SAW) velocity among piezoelectric crystals [3].
In this report, I will present the results of our investigation on the electrical and dielectric properties of SBO to describe its potential in terms of electronic application. For measurements, the SBO polycrystalline material was synthesized and analyzed by X-ray diffraction. After pellet preparation from the SBO powder, the measurements of current-voltage characteristic and temperature dependence of resistance were carried out. The study of dielectric parameters indicates that the SBO is a low dielectric constant and low dielectric loss material. These parameters are sufficiently stable at temperatures up to 200 oC. The NLO property of the synthesized material is investigated as well.

References
[1] F. Pan, G. Shen, R. Wang, X. Wang, D. Shen, J. Crystal Growth 241 (2002) 108
[2] Yu.S. Oseledchik, A.L. Prosvirnin, A.I. Pisarevskiy, V.V. Starshenko, V.V. Osadchuk, S.P. Belokrys, N.V. Svitanko, A.S. Korol, S.A. Krikunov, A.F. Selevich, Opt. Mater. 4 (1995) 669.
[3] R. Komatsu and K. Ikeda, Proceedingof 150th Committee on Acoustic Wave Device Technology 68th Technical meeting, Vol. 1, 25 July 2000, (in Japanese with English abstract).

*E-Mail: vgharutyunyan@gmail.com

Speaker: Dr V.G. Harutyunyan (Institute of Applied Problems of Physics, National Academy of Sciences of the Republic of Armenia, Yerevan 0014, Armenia)

16:00 Proton Irradiation Tolerance of Lead Halide Perovskites

During the last decade Lead Halide Perovskites (LHPs) have been widely researched in the photovoltaic and light emission fields due to their outstanding optoelectronic properties and exceptional performance. Owing to their low cost and easy fabrication, tremendous achievements were achieved in solar cell, photodetector, light‐emitting diode and laser research fields.
On the other hand, space application of perovskite solar cells (PSCs) is also anticipated, driving much research attention on the stability of PSCs in the space environment, as lightweight, large-area, high-efficiency solar cells are in high demand in the space industry. To be applied in space environment, radiation resistance of such materials is critical. Charged particles, such as protons and electrons can penetrate the into materials, and induce phase and structural deterioration limiting the operation lifetime of devices. In this sense radiation resistance of perovskites is an important issue to deal, prior to its application in space.
In this work CsPbBr3 perovskite thin films, obtained through double source physical vapor deposition method from CsBr and PbBr2, were subjected to proton-beam irradiation (proton energy from 1.4 MeV to 15.5 MeV, dose 1014 – 5×1015p/cm2) in order to assess the durability and radiation tolerance of PSCs against space radiation. We evaluate the effects of proton beams by focusing on the light absorption properties, crystal structure, and morphology by using UV-Vis spectroscopy, optical spectroscopy, X-ray diffraction, and scanning electron microscopy, correspondingly. The results show that proton irradiation with relatively high energy of 15.5 MeV and doses up to 1×1015p/cm2 does not significantly affect the crystal structure of the CsPbBr3 perovskite layer with 750 nm. In contrast, proton irradiation with higher doses up to 5×1015p/cm2 or low energy 1.4 MeV with 1015p/cm2 dose can cause damage to the crystal lattice due to longer exposure time of interaction with lattice ions.

Speaker: Anush Badalyan (A. I. Alikhanyan national science laboratory (Yerevan Physics Institute)" foundation)

18:00 → 22:00 Conference Dinner

Friday, 22 September

09:00 → 10:20 e–/e+, X–ray, THz, and neutron based applications

Convener: Prof. Vladislav Syshchenko (Belgorod National Research University)

09:00 APPLICATION OF PHOTONIC CRYSTALS FOR GENERATION OF BROADBAND RADIATION AT THE LINAC-200 LINEAR ACCELERATOR

The possibility of using ordered three-dimensional arrays of photonic crystals to generate gigahertz, optical, and neutron radiation during the interaction with them a beam of high-energy electrons is considered. Experiments were carried out to record two-dimensional images of objects in gamma and neutron fluxes obtained as a result of the interaction of an electron beam with various neutron-generating targets. The experimentally obtained characteristics of electromagnetic and neutron fields are presented. Comparative images of a biological object were obtained in gamma and neutron beams generated by a target irradiated by an electron beam.

Speaker: Maxim Karpov (Lebedev Physical Institute)

09:40 The far field diffraction of a plane wave on a system of randomly and in average periodically located point scatterers: the Debye-Waller factor.

In the framework of the report we discuss the description problem of a diffracted plane wave incident on system of randomly and in average periodically located scatterers. We suggest that the scatterers under the action of the prime field are appeared as sources of secondary sphere waves. The problem is considered in the Fraunhofer approximation.
Following the traditional approach, here we also assume that the random components of the problem are small quantities. At the same time, in contrast to the traditional approach, where the description of the diffraction pattern is given on the basis of field averaging (see C. Kittel, Introduction to solid state physics (Wiley & Sons, NY, 2005)), here the diffraction pattern is considered on the basis of intensity averaging. The above, in particular, refers to the influence of inhomogeneity on the values of intensity of the main maximums for an ideal structure, which, as it is known, in the traditional approach is determined by the factor Debye-Waller.

Speaker: Ashot Khachatrian (National Polytechnic University of Armenia, 105 Teryan Street, Yerevan 0009, Armenia)

10:00 Distributions of quasars as an indicator of the homogeneity or inhomogeneity in the Universe

Quasars are perhaps the brightest extragalactic sources, and due to their brightness, they are visible at greater distances. By studying the distribution of quasars in the Universe, it is possible to determine whether there are large-scale inhomogeneities in the Universe or not. If the distribution of quasars is inhomogeneous at large distances, then the same can be stated about the Universe. At small distances, quasars either do not exist, or their number is very small. Therefore, the distribution of quasars at small distances is highly conditional, and we cannot draw any conclusions about the homogeneity of the Universe there.
Therefore, the distribution of quasars allows us to determine the distribution of matter over large distances, which we use to detect large-scale inhomogeneities in the Universe.

Speaker: Martik Hovhannisyan (Institute of Applied Problems of Physics NAS RA)

10:20 → 11:00 Conference Closing

11:00 → 11:30 Coffee break

11:30 → 17:30 Departure