XV International Symposium on "Radiation from Relativistic Electrons in Periodic Structures "RREPS-25"

15 Sept 2025, 08:25 → 19 Sept 2025, 23:59 Asia/Shanghai

Ruxin Li (SIOM, CAS), Baifei Shen (Shanghai Normal University, Shanghai, China), Pavel Karataev (Royal Holloway, University of London), Alexander Potylitsyn (Tomsk polytechnic university), Tongpu Yu

Dear Colleagues,

The XV International Symposium "Radiation from Relativistic Electrons in Periodic Structures" (RREPS-25)  will be held in Shanghai,China, September 15-19, 2025, and is organized by Chinese Laser Press.
We warmly welcome you to come and join us to share your great progress and experience!

The Symposium will focus on the following topics:

• General radiation properties from relativistic particles
• Transition Radiation, Diffraction Radiation, Cherenkov radiation, and Smith Purcell Effect
• Parametric X-ray radiation (PXR)
• Compton Scattering and its Applications
• Coherent bremsstrahlung and channeling
• Crystal-assisted processes
• Laser-driven particle accelerators and radiation sources
• Applications of monochromatic X/r-ray and Terahertz beams produced at electron accelerators

 

Dear participants of the XV International Symposium RREPS-25!

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

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 15 September

1 Welcoming

Speaker: Ruxin Li (SIOM, CAS)

2 Leonid Sukhikh Opening Speech

Speaker: Leonid Sukhikh (Tomsk Polytechnic University)

3 Ye Li Opening Speech

Speaker: Ye Li (Shanghai Normal University)

4 Pavel Karataev Opening Speech

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

5 The Progress of SHINE Project

Speaker: Zhi Liu (ShanghaiTech University)

09:20 Coffee Break & Photo

Applications of monochromatic X, γ – ray and Terahertz beams produced by electron accelerators

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

6 Applied X-ray Studies of Metal Artefacts Uncovered at Archaeological Sites in Armenia

X-ray based experimental techniques are widely used in the analysis of cultural heritage objects, particularly archaeological artefacts. One of the most important tasks in such analysis is to identify the materials and manufacturing techniques used in their creation, as this information is essential for their proper study, conservation, and restoration.
This report presents the results of X-ray fluorescence and microtomography studies of metal jewellery uncovered at two archaeological sites in Armenia: the Nerkin Naver Burial Mound (Middle Bronze Age) and the Teishebaini Necropolis (Urartian period). The investigated objects include a gold bead from Nerkin Naver, dated to around 2000 BCE, and a set of bronze jewellery dated to the 7th century BCE.
The conducted studies revealed key technological processes involved in the production of these artefacts, as well as specific features of the elemental composition of the materials used.

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

Speaker: Dr Yury Cherepennikov

7 Terawatt attosecond X-ray free-electron laser based on self-chirping and cascaded amplification

Attosecond X-ray pulses are a critical tool for tracking ultrafast electron dynamics. AttoSHINE, proposed for the Shanghai High Repetition Rate XFEL and Extreme Light Facility (SHINE), employs a self chirping compression scheme that enables continuous wave (CW) XFELs to deliver high power attosecond X-ray pulses at megahertz repetition rates. Two operating points have been identified: one where a current spike forms at the head of the electron bunch and another where it forms at the tail. Compared with the head current spike case, the tail current spike case offers a richer platform for advanced XFEL operation modes. In this study, we take advantage of tail-current spike configuration by utilizing a magnetic chicane, which shifts the pulse emitted from the tail spike into a fresh slice of the bunch. The secondary amplification step yields even higher-power attosecond X-ray pulses, reaching peak powers at the terawatt scale, and we also examine the superradiant behavior emerging during this process. These enhanced capabilities highlight the potential of continuous-wave (CW) XFELs as powerful attosecond X-ray sources for real-time tracking of electron dynamics in complex systems.

Speaker: Chenzhi Xu (Institute of Applied Physics, Chinese Academy of Sciences, Shanghai)

8 Modulation of relativistic electron beam characteristics by 3D-printed periodic structures

By leveraging additive manufacturing, complex objects with varying internal structures can be produced, enabling systematic investigation of how different layering patterns, density gradients, and geometric parameters influence electron scattering, absorption, and transmission. This capability provides a versatile experimental platform for developing advanced beam-modulating materials, radiation shielding, and detector components.
In this study, we present a combined experimental and computational analysis of how 3D-printed plastic samples alter the depth dose distribution of relativistic electron beams. Samples were fabricated from pure polylactic acid (PLA) and PLA with metallic impurities, with controlled variations in internal geometry, density, and spatial configuration. The propagation of 6–15 MeV electron beams through these structures was evaluated using Monte Carlo simulations and validated against clinical linear accelerator measurements.
Key findings reveal that tailored 3D-printed structures induce significant modifications in electron beam depth dose profiles, with close agreement between experimental and simulated results. These results demonstrate the feasibility of engineering 3D-printed objects with specific internal configurations to achieve precise beam modulation effects in relativistic electron applications.

This research was supported by TPU development program Priority 2030.

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

9 An optical-fiber scanner for transverse-profile measurement of low-intensity charged-particle beams

Traditional methods for measuring the transverse dimensions of low-intensity beams of charged particles involve the use of wire scanners and luminescent screens. These methods possess undoubted advantages, such as simplicity and clarity of measurements, but their application is often limited due to the elevated X-ray background. Most luminescent screens exhibit sensitivity to X-rays, which can distort measurements of the transverse beam profile due to a high background of X-ray photons. The use of a wire scanner involves two methods of detecting the useful signal: measuring the current from the wire and detecting bremsstrahlung photons generated during the interaction of the charged particle beam with the wire material. Direct current measurement from the wire is a complex technical challenge associated with removing the electrical contact from the vacuum chamber. Additional difficulties may arise when recording weak signals during diagnostics of low-intensity beams. The elevated X-ray radiation background in the accelerator hall interferes with the registration of bremsstrahlung photons, affecting the signal-to-noise ratio.
To address these limitations, there is a growing trend towards developing novel methods that integrate the advantages of existing techniques. In this report, we propose a novel concept of a charged particle beam transverse-profile scanner based on an optical fiber. The initial testing and implementation of this method were successfully conducted at the microtron TPU with the following electron beam parameters: energy of 5.7 MeV, macro-pulse with duration of 0.5 μs containing 108 bunches, bunch population ~ 100 pC. In contrast with the aforementioned methods we measured light yield from a side surface of the 1.15 mm thickness fiber (PMMA Polymethyl methacrylate is Plexiglas (organic glass) which is an amorphous thermoplastic) at right angle. The optical scheme consisted of the objective (Tamron 70-300mm f/4.5-6.3 ) and CCD camera (QHY533C ). The performance and functionality of the proposed scanner were validated through comparative measurements with a traditional wire scanner and a luminescent screen.
This research was supported by TPU development program Priority 2030.

Speaker: Mikhail Shevelev (Tomsk Polytechnic University)

10 Measuring the Transverse Intensity Distribution of a High-Energy Electron Beam with a Multichannel Ionization Chamber System

Electron beams produced by various accelerators have a broad spectrum of applications across multiple fields, including industry, medicine, agriculture, and scientific research. Precise monitoring of the transverse distribution of the electron beams is essential for modern accelerator technologies.
Existing methods for measuring spatial beam properties utilize a variety of detectors, yet many of these techniques face limitations due to the rapid degradation of materials, which can compromise the accuracy and reliability of the measurements. Profilometers serve as effective tools for determining the position and spatial distribution of particle beams, as they are designed to measure the radiation incident on the detector in the transverse plane.
The research proposes a multiangle scanning technique aimed at capturing transverse intensity distributions, which involves rotating the profilometer at various angles around the beam's central axis. This study introduces a cylindrical ionization chamber designed as a detector. A multichannel profilometer equipped with several ionization chambers was designed and tested. The detection system integrates linear motion of the detector with rotational adjustments concerning the beam axis. The dataset generated reflects variations in the beam profile corresponding to different scanning angles. By employing reconstruction algorithms such as the inverse Radon transform, it becomes possible to reconstruct a two-dimensional intensity map of the beam.
The results obtained for the 7 MeV electron beam of the Microtron MT-25 facility (Dubna, Russian Federation) demonstrate the potential of ionization chambers as effective detectors for determining the transverse distribution of the high-energy electron beam intensity.

This research was supported by TPU development program Priority 2030.

Speaker: Angelina Bulavskaya (Tomsk Polytechnic University)

12:10 Lunch

Laser-driven particle accelerators and radiation sources

Convener: Wenjun Ma (Peking University)

11 Thomson Scattering X-ray Sources Based on Flying Focus Laser Pulse Interacting with Relativistic e-beam

Thomson scattering X-ray sources have the characteristics of high energy, short pulse, small focal spot, good collimation and monochromaticity. These features make Thomson scattering X-ray sources have broad application prospects in radiation imaging, NRF and nuclear excitation, plasma diagnosis and other aspects. All-optical Thomson scattering based on laser wakefield electron acceleration can further reduce the electron acceleration length and device scale. However, due to the small Thomson scattering cross-section of laser and the short interaction distance, the photon yield still needs to be further improved to meet the requirements of many applications. To further improve the brightness of laser Thomson scattering X-ray sources, the authors proposes a new method of enhancing Thomson scattering X-ray sources by the interaction of flying focus laser and relativistic electron beam, and this talk will present the numerical simulation results.

Speaker: Yuqiu Gu (Shanghai Institute of Laser Plasma, Laser Fusion Research Center, CAEP)

12 Numerical Investigation of Polarization Dynamics in Strong-Field QED

The primary QED processes involved in the physics driven by the new generation of PW (petawatt) lasers include the electron's incoherent photon emission process under an external field
(nonlinear Compton scattering, NCS) and the decay of high-energy photons into electron-positron pairs (nonlinear Breit-Wheeler process, NBW). Recent research has shown that the effect
of electron-spin and photon polarization on these processes can exceed 10\%, making them non-negligible. Additionally, polarized electrons, positrons, and photon beams generated through
QED polarization effects serve as irreplaceable probes in experimental high-energy physics, materials science, and other fields. For instance, high-energy polarized photons provide critical
insights into polarization-dependent phenomena, such as photon-photon scattering and pair production in strong electromagnetic fields, particularly within nonlinear QED regimes. Such beams
can also enable laboratory-scale investigations of astrophysical radiation mechanisms, including gamma-ray bursts and black hole jet emissions, by facilitating controlled studies of polarization
effects and high-energy interactions. Additionally, these highly polarized gamma-ray beams are indispensable for calibrating advanced detectors in high-energy astrophysics missions, thereby
improving the precision of cosmic gamma-ray polarization measurements. As such, the purification of photon polarization in $\gamma$-ray sources is a longstanding challenge critical for leveraging
the potential of polarized $\gamma$ rays in scientific research and practical applications.

In this tall, we present a three-step theoretical framework to calculate QED polarization dynamics in ultra-intense laser-electron beam interactions. Building on this methodology, we propose
novel schemes to produce ''spin-polarized relativistic electron sources,'' ''polarized high-brilliance gamma-ray sources,'' and ''spin-polarized positron sources'' via ultra-intense lasers.
Recently, we demonstrate that highly linearly polarized GeV $\gamma$-rays can be generated via nonlinear Compton scattering using unpolarized electrons (Fig. 1). Although the photon polarization is
initially negligible (~0\%) at the high-energy spectral edge, we show that it can exceed 90\% in a single interaction. This enhancement is mediated by vacuum dichroism, which induces asymmetric
photon decay (pair production) between polarization states.

Fig. 1. Scenario for generating highly polarized $\gamma$ rays via ultraintense-laser-electron interactions. (a): A linearly polarized laser pulse (polarization along the x-axis)
propagates along the +z direction and collides head-on with an unpolarized electron beam from a laser plasma accelerator, producing linearly polarized $\gamma$ rays (also polarized along the x-axis).
A magnet is used to isolate the desired $\gamma$ rays from electrons and positrons. (b): The polarization degree is significantly enhanced by vacuum dichroism, which arises from the asymmetric
pair production between opposite polarization states of photons as they propagate in the laser field.
References
[1] Xian-Zhang Wu, et al., Commun Phys 8, 156 (2025).
[2] Yan-Fei Li, et al., Phys. Rev. Letts. 125, 044802 (2022).
[3] Yan-Fei Li, et al., Phys. Rev. Lett. 124, 014801 (2020).
[4] Yan-Fei Li, et al., Phys. Rev. Lett. 122, 154801 (2019).

Speaker: Yan-Fei Li (Department of Nuclear Science and Technology, Xi'an Jiaotong University)

13 Novel Transport and Radiation of High-current Relativistic Electron Beam in Porous Materials

The advent of short intense lasers has revolutionized the generation of relativistic electron beams (REBs), enabling unprecedented currents up to mega-amperes -- surpassing any previously achievable in laboratory settings by several orders of magnitude. As these high-current REBs propagate through materials, the latter is immediately ionized into plasma, giving rise to various new phenomena. Transport of these high-current REBs in plasma is a fundamental issue relevant to high-energy-density space and laboratory plasmas, and has attracted much research interest. The problems involved include collisionless shocks, cosmic magnetic field generation, gamma-ray bursts, etc. It is also relevant to many applications, including inertial confinement fusion, compact particle and/or radiation sources. In this paper, I will introduce our recent research progress on the microscopic transport of REB in porous materials and its application in generating ultrabrilliant gamma-ray sources. Some interesting new results are obtained, including the branching, super-channeling, and anomalous stopping of REB in porous materials. Based on these new phenomena, we have further extended the applications of REB in generating high-brilliance incoherent gamma-rays. In particular, super-channeling of high-current electron beam in disordered microstructures is discovered and this phenomenon can lead to extremely high conversion efficiency gamma-rays. These results should be of much interest to researchers in many areas.

Speaker: Taiwu Huang

14 VIGAS(Very compact Inverse Compton scattering Gamma-ray source) and its applications at Tsinghua

Speaker: Jiaru Shi (Tsinghua University)

15:10 Coffee Break

Laser-driven particle accelerators and radiation sources

Convener: Yuqiu Gu (Shanghai Institute of Laser Plasma, Laser Fusion Research Center, CAEP)

15 Boosting the Yield of High-energy Photons with Nano-targets

Recent results indicate that targets composed of nanosized elements are highly promising for the generation of brilliant EUV, X-rays and gamma-rays. This presentation will give a review and perspective on the mechanism, advantages and potential of X-ray sources based on nanotargets.

Speaker: Wenjun Ma (Peking University)

16 Efficiently Laser Driven Terahertz Surface Plasmon Polaritons on Long Metal Wire

Terahertz (THz) radiation holds great promise for applications in materials science, biosensing, and next-generation communications, but generating and guiding intense THz radiation efficiently remains a challenge. In our study, we discover a compact and efficient way to produce powerful THz waves by focusing a femtosecond laser onto a metal wire about a meter long. This setup generates single-cycle THz surface waves-called surface plasmon polaritons-with peak powers reaching 10 megawatts.
We find that this THz radiation results from coherent transition radiation emitted by electrons driven by the laser. Surprisingly, it is not the fastest, highly relativistic electrons that contribute the most, but rather the slower, subrelativistic ones. These electrons turn out to be more efficient at converting laser energy into THz radiation. With this method, we achieve an energy conversion efficiency of up to 2.4 percent, one of the highest ever reported for laser-driven THz SPP sources.
Our approach uses widely available laser technology and does not require large-scale facilities, making it a practical solution for real-world applications. This compact method could be used in endoscopic THz imaging for medical diagnostics, waveguide-based particle accelerators, nonlinear THz spectroscopy, and integrated THz technologies.

Speaker: Guang-Yue Hu (University of Science and Technology of China)

17 Advanced Seeding Experiments at the Shanghai Soft X-ray FEL Facility

The Shanghai Soft X-ray Free-Electron Laser (SXFEL) facility, China's first X-ray FEL, has employed various external seeding modes to enhance its performance. We present the results of advanced seeding experiments at SXFEL, which were specifically designed to generate coherent radiation across the terahertz (THz) and extreme ultraviolet (XUV) ranges. These experiments push beyond the current limitations of conventional external seeding techniques, creating new opportunities for a wide range of advanced user experiments.

Speaker: Chao Feng (Shanghai Advanced Research Institute)

18 Generating 10 GW-class Zeptosecond X-ray Bursts through Bootstrapping Two Plasma-based Accelerator Stages

A method is proposed to generate coherent and intense zeptosecond x-ray pulses by using the electron beam produced by a laser wakefield accelerator (LWFA) stage as the driver
for a beam driven plasma wakefield accelerator (PWFA) stage. The LWFA injector stage requires a readily available 100 TW laser driver to produce a GeV class self-injected electron beam.
This beam is focused and used as the driver in a PWFA stage that utilizes a solid-density plasma with a modulated density downramp. The concept is shown to be capable of producing an
ultra-short electron beam with unprecedented density (1026 $cm^{-3}$) and brightness (1024 A/$m^2$/rad$^2$), that is also pre-bunched on 0.1 Angstrom scales. By colliding this pre-bunched
extreme beam with an optical undulator, an intense zeptosecond pulse can be emitted if the spatially focusing region is matched with the lasing region of the beam. Multi-dimensional particle-in-cell
simulations are performed of the entire concept to demonstrate that an isolated 10 GW-class zeptosecond pulse with a full-width-half-maximum duration of 700 zs can be generated in a tapered laser pulse.
Such an intense zeptosecond pulse generation scheme may provide an essential probe for nuclear physics and quantum electrodynamics processes.

Speaker: Xinlu Xu (State Key Laboratory of Nuclear Physics and Technology and Key Laboratory of HEDP of the Ministry of Education, CAPT, School of Physics, Peking University)

19 Transition radiation from electrons moving along spiral trajectory

Hollow electron beams have a ring-shaped transverse profile. They are actively studied in accelerator physics. For example, they are the basis of hollow electron lenses that focus proton beams [1], acceleration of positrons in donut wake fields [2] etc. However, they are most valuable in view of studying the generation and use of beams (of electrons or photons) with non-zero angular orbital momentum.

Computer simulations of hollow electron beam dynamics show that electrons follow spiral trajectories with different radii and different spiral steps inside the beam [3]. The question arises about how the helical trajectory affects the transition radiation characteristics.

In this report, we present the theory of x-ray transition radiation, generated when an electron moves along a spiral trajectory and crosses the boundary between two media. We obtained the general expression for the field of radiation, which includes both limiting cases: synchrotron radiation in the absence of a medium and transition radiation for a zero radius of the spiral trajectory. We find three particular cases for which the obtained expressions can be simplified. We compare the properties of the transition radiation emitted by an electron moving in a helical path with those emitted by a uniformly moving electron.

D.S. is thankful for financial support to the Foundation for the Advancement of Theoretical Physics and Mathematics BASIS, Project No. 23-1-3-2-1.

[1] S. Redaelli, R.B. Appleby, R. Bruce, et al., Hollow electron lenses for beam collimation at the High-Luminosity Large Hadron Collider (HL-LHC), Journ. of Instrum. 16, P03042 (2021).
[2] N. Jain, T. M. Jr. Antonsen, J. P. Palastro, Positron acceleration by plasma wakefields driven by a hollow electron beam, Phys. Rev. Lett. 115, 195001 (2015).
[3] A. Rossi, D. Nikiforov, M. Arsentyeva, A. Barnyakov, A. Levichev, Electron dynamics for high-intensity hollow electron beams, Journ. of Instrum. 16, P03043 (2021).

Speaker: Darya Sergeeva

20 High-order Harmonics Generation from Spatiotemporal Plasma Photonic Crystal Driven by Relativistic Laser Pulses

High-order harmonics emitted from interaction between relativistic laser and solid target can be extreme ultraviolet source. Through numerical simulations and theoretical studies, we propose a scheme to efficiently generate harmonics with abundant components of different emission angles, where two P-polarized lasers are used to drive surface plasma oscillation, and one S-polarized laser is used to generated harmonics of S-polarization. We propose that this process can be understood in perspective of spatiotemporal photonic crystals, showing the generation, selection rules and efficiency enhancement of harmonics. We also understand this process from the perspective of laser-plasma interaction, which show a high degree of consistency.

Speaker: Haojie Zhang (Shanghai Jiao Tong University)

18:30 Dinner

Tuesday 16 September

X-ray Free Electron Laser Workshop

Convener: Nanshun Huang (Shanghai Advanced Research Institute, Chinese Academy of Sciences)

21 The Basics of Free Electron Lasers

Speaker: Haixiao Deng (Shanghai Advanced Research Institute, Chinese Academy of Sciences)

22 Status & user operation at SXFEL

Speaker: Huaidong Jiang (ShanghaiTech University)

23 Overview and Status of SHINE Project

Speaker: Bo Liu (Shanghai Advanced Research Institute)

24 Advances in FEL ultrafast scattering methods and the design of the RSS endstation at S3FEL

Speaker: YINPENG ZHONG

10:15 Coffee-Break

X-ray Free Electron Laser Workshop

Convener: Haixiao Deng (Shanghai Advanced Research Institute, Chinese Academy of Sciences)

25 Cavity-based XFEL R&Ds at Shanghai

Speaker: Nanshun Huang (Shanghai Advanced Research Institute)

26 Nanoscale EUV and X-ray Thin Film Optics for Free Electron Laser Applications

Speaker: Qiushi Huang (Tongji University)

27 Statua of Optical Electron Beam Diagnostics at the Novosibirsk FEL

We present an overview of recent and upcoming enhancements to the optical electron beam diagnostics stations at the Novosibirsk Free Electron Laser (FEL) facility. These diagnostic stations are designed to measure key beam parameters, including beam energy spread, length and emittance, at the third FEL of Novosibirsk FEL. Currently, the stations for measuring electron beam energy spread and undulator radiation spectrum are in the commissioning phase, with initial results already obtained. The new optical diagnostics are essential for the precise tuning of the magnet system used in electron outcoupling experiments. This paper provides a comprehensive overview of the new diagnostic systems, discusses the preliminary measurement results of beam parameters, and outlines the experiments planned for the near future.

Speaker: Vladislav Borin (Budker INP)

28 Generation of High-power Beyond Extreme Ultraviolet FEL Radiation with Flexible Polarization at SHINE

Speaker: Hanxiang Yang (Shanghai Advanced Research Institute, CAS)

12:20 Lunch

Transition Radiation, Diffraction Radiation, Cherenkov radiation, and Smith-Purcell Effect

Convener: Haixiao Deng (Shanghai Advanced Research Institute, Chinese Academy of Sciences)

29 Experimental Investigation of Coherent Cherenkov Diffraction Radiation: Polarization and Spatial Properties

Cherenkov Diffraction Radiation (ChDR), which occurs when a fast charged particle moves parallel to and near a dielectric interface, has become the focus of intense research. As a form of polarization radiation, ChDR arises due to the dynamic polarization of the medium. Its properties are highly sensitive to various beam parameters, including the beam size, position, direction, energy, and bunch length.
Coherent ChDR is produced when the radiation wavelength is longer than or comparable to the longitudinal size of the bunch. In this regime, all electrons radiate nearly in phase, mutually enhancing each other's emission. As a result, the radiation intensity becomes proportional to the square of the bunch charge, leading to a significant increase in photon yield.
When coherent ChDR is generated by a periodic train of bunches, the radiation fields from each bunch interfere constructively. This leads to further amplification at discrete frequencies determined by the accelerating RF frequency. This regime is known as super-radiant emission [1], and it enables the production of ultra-monochromatic radiation lines [2], with intensity governed by the single-bunch length.
In this report, we present the fundamental properties of super-radiant ChDR in the millimeter-wavelength range, as experimentally observed at the MT-25 microtron in Dubna. We will discuss the spatial distribution of the radiation in the pre-wave zone, and present an investigation into the polarization characteristics of super-radiant spectral lines at various frequencies.

We thank FLAP Collaboration for in-kind contribution and discussing the results. This research was supported by TPU development program Priority 2030. This work was partially carried out within the framework of the state assignment of the National Research University “BelSU,” number FZWG-2025-0010.

References
[1] A. Gover, et al., Rev. Mod. Phys. 90, 035002 (2018).
[2] P. Karataev, et al., Scientific Reports (2020) 10:20961

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

30 Investigation of Spectral Parameters of Coherent Cherenkov Radiation Emitted by Pair Electron Bunches at the AREAL Accelerator

This study presents experimental findings on the spectral characteristics of coherent Cherenkov radiation generated by two electron bunches at the AREAL Accelerator. A cylindrical Teflon resonator employed as the radiation target. The study investigates the dependence of coherent radiation on the delay between the electron bunches (from 2 to 11 picoseconds). Detection was carried out using a QOD (Quasi-Optical Detector equipped with a Schottky Barrier Diode), capable of measuring frequencies in the 30–1000 GHz range and two narrowband Schottky barrier diode detectors equipped with waveguide pyramidal horn antennae designed for frequncy regions of 33–50 GHz and 90–140 GHz. A measurement scheme based on the Martin–Puplett interferometer was employed to analyze the spectral characteristics of the detected radiation. The results were analysed in comparison with earlier experimental data and theoretical predictions.

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

Speaker: Dr Vahan Kocharyan (Institute of Applied Problems of Physics of NAS RA)

31 Radiated energy and power of transition radiation generated by a twisted fermion incident on a metallic mirror

Transition radiation occurs when a particle crosses the boundary between two media with different dielectric permittivities. To eliminate the effects of wave packet scattering on the atoms of the medium the particle enters, it is necessary to create an aperture in the medium that is much larger than the characteristic size of the incoming wave packet. Due to the motion of a charged particle along a surface, for example, a metal, atomic electrons inside the material are excited, polarization currents arise, and a secondary electromagnetic field is generated, which is observed as radiation.
In a number of recent studies [1–4], it has been shown that quantum effects in radiation are not limited to quantum recoil and spin-induced radiation. The spatial structure of a charged particle can play a significant role, which generates interest in the search for new quantum effects in transition radiation associated with this structure. In particular, the spectral-angular distribution of the radiation depends on the value of the orbital angular momentum [1–4].
In this work, formula (42) for the inclusive probability of transition radiation from a Dirac particle, obtained in [4], was used. The inclusive radiation probability refers to the probability of photon detection, averaged over all possible final states. Using this formula, explicit dependencies of the emitted energy and power of transition radiation on the wave packet width and the value of the orbital angular momentum were obtained. As the wave packet width increases, the emitted energy corresponding to polarization in the reaction plane decreases, while the energy emitted outside the reaction plane increases. At small wave packet widths, a parabolic growth of the total emitted energy is observed.
This research was supported by TPU development program Priority 2030.
1. K.Y. Bliokh and other, Theory and applications of free-electron vortex states, Phys. Report 690, 1–70 (2017).
2. I. P. Ivanov and D. V. Karlovets, Polarization radiation of vortex electrons with large orbital angular momentum, Phys. Rev. A 88, 043840 (2013).
3. A. S. Konkov, A. P. Potylitsyn, and M. S. Polonskaya, Transition radiation of electrons with a nonzero orbital angular momentum, JETP Lett. 100, 421 (2014).
4. P.O. Kazinski and G.Yu. Lazarenko, Transition radiation from a Dirac-particle wave packet traversing a mirror, Phys. Rev. A. Vol. 103, 012216 (2021).

Speaker: Malygina Nataliya (Tomsk Polytechnic University)

32 Transition radiation produced by a chain of N-Gaussians

A uniformly moving electron passing through a dielectric slab generates electromagnetic emission is known as transition radiation [1]. The radiation produced by a single particle has been thoroughly investigated within both classical electrodynamics and quantum mechanics. Current active research focuses on accounting for charged particle beam structure and targets with complex geometries.
Recent studies [2,3] demonstrate that quantum effects involve not only radiation recoil and spin-flip transitions but also depend significantly on the wave packet structure. The wave packet represents a superposition of waves with closely spaced frequencies that is localized in both space and time. A single particle can be described as a superposition of N-Gaussian wave functions with different central frequencies and wave numbers.
This work examines transition radiation from a chain of N-Gaussian wave packets. We demonstrate that coherent enhancement of radiation can be achieved, analogous to the emission from multiple particles [4]. The coherence arises from the periodic structure of the wave packet rather than from synchronized particle motion as in conventional multi-particle systems.
When considering only the contribution from the maxima of each Gaussian component in the inclusive radiation probability formula (see Eq. (26) in [2]), the emission probability takes the form of the probabilities sum corresponding to each of these maxima. Thus, its structure resembles the formula for incoherent radiation from a particle with multiple momentum states. As part of this work, we have derived the explicit expression for the radiation probability.
This research was supported by TPU development program Priority 2030.

1. A. P. Potylitsyn, M. I. Ryazanov, M. N. Strikhanov, and A. A. Tishchenko, Diffraction Radiation from Relativistic Particles, Springer Tracts in Modern Physics (Springer, Berlin, 2010), Vol. 239.
2. P.O. Kazinski and G.Yu. Lazarenko, Transition radiation from a Dirac-particle wave packet traversing a mirror, Phys. Rev. A. Vol. 103, 012216 (2021).
3. Kazinski P.O., Solovyev T.V. Coherent radiation of photons by particle wave packets, EPJC. V. 82, No. 9 (2022)
4. D. Marcuse, Emission of radiation from a modulated electron beam, J. Appl. Phys. V. 42, 2255 (1971).

Speaker: George Lazarenko

33 Quantum corrections to Cherenkov X-ray radiation

Cherenkov radiation is generated by a charged particle moving through a medium when its velocity exceeds the phase velocity of light in that medium. Contrary to popular belief, Cherenkov radiation can also be emitted in the X-ray frequency range [1]. This becomes possible near the photoabsorption edges of certain materials, where the real part of the dielectric susceptibility exhibits a sharp jump and becomes positive. X-ray Cherenkov radiation has been observed experimentally [2, 3].

The first quantum-mechanical theories describing Cherenkov radiation appeared soon after its discovery [4, 5]. In recent years, macroscopic quantum electrodynamics (QED) has seen significant development [6, 7], and Cherenkov radiation can also be described within this framework. Recent works have addressed quantum corrections to Cherenkov radiation and the influence of the wave nature of elementary particles on this effect [8-10]. However, to the best of our knowledge, quantum corrections associated with medium dispersion have not been previously considered. Clearly, such corrections are expected to be significant in the X-ray wavelength range.

In this work, we derive expressions for the spectral-angular and spectral intensity distributions of X-ray Cherenkov radiation, taking into account dispersion in the medium. We discuss quantum corrections arising from the dispersion of the refractive index and show that these corrections can lead to a substantial change in the radiation intensity. Finally, the applicability of macroscopic QED is discussed.

The study was partially supported by the Ministry of Science and Higher Education of the Russian Federation, Project No. FSWU-2023-0075.

References

1. V. A. Bazylev, V. I. Glebov, E. I. Denisov, et al. Sov. Phys. JETP, 81, 1664 (1981).
2. V. A. Bazylev, V. I. Glebov, E. I. Denisov, et al. JETP Letters, 34, 103 (1981).
3. W. Knulst, O. J. Luiten, M. J. Van der Wiel, J. Verhoeven, Applied Physics Letters, 79, 2999 (2001)
4. V. L. Ginzburg, Sov. Phys. JETP, 10, 589 (1940).
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6. S. Scheel, S. Y. Buhmann, Acta Phys. Slovaca, 58, 675 (2008).
7. N. Rivera, I. Kaminer, Nature Reviews Physics, 2, 538 (2020).
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10. D. Karlovets, A. Chaikovskaia, D. Grosman, et al. Communications Physics, 8, 192 (2025).

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

15:05 Coffee Break

Transition Radiation, Diffraction Radiation, Cherenkov radiation, and Smith-Purcell Effect

Convener: Dr Vahan Kocharyan (Institute of Applied Problems of Physics of NAS RA)

34 The investigation of the potential for the generation of Cherenkov diffraction radiation using 3D-printed plastic targets

The generation of polarized radiation by electron beams in the vicinity of dielectric objects has attracted the attention of researchers, due to its potential applications in both measuring beam parameters and generating intense electromagnetic radiation at THz and sub-THz frequencies. One particularly interesting form of this radiation is the Cherenkov diffraction radiation (ChDR), which occurs when high-energy electrons pass along a dielectric boundary. The characteristics of this radiation depend on the properties of the charged particles involved.
By understanding and controlling the properties of electron beams, it is possible to create dielectric targets with various shapes, which can generate ChDR with specific characteristics. To produce such targets with the required level of precision, it is crucial to use techniques for manufacturing dielectric samples with intricate geometries. This can be achieved through 3D plastic printing – fused filament fabrication. However, before implementing this approach, a comprehensive study of the dielectric properties of samples produced via 3D printing is necessary.
In this study, a series of experimental samples from various polymers was produced using the fused filament fabrication technique. The refractive index, absorption, and reflection coefficients were measured. Based on the obtained data, the appropriate materials were selected for the targets manufacture with special geometry for ChDR generation.
A series of experiments were conducted at the MT-25 microtron (Dubna, Russia) to study the generation of ChDR in the 3D-printed target created when the 7 MeV electron beam passes parallel to their surface. After that, the super-radiant spectrum of the emitted radiation on several harmonic lines was analyzed using a spectrum analyzer. The obtained data were compared with those obtained from ChDR generated under similar conditions by a standard teflon target produced by milling cast material.

This research was supported by TPU development program Priority 2030.

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

35 Longitudinal Beam Diagnostics Based on Super-Radiant Coherent Cherenkov Diffraction Radiation

Longitudinal diagnostics are essential for accelerator installations that generate short particle bunches arranged in extended pulse trains. While several methods exist for diagnosing individual short bunches—each with their own advantages and limitations—effective diagnostics for long trains of ultra-short bunches remain scarce. On the other hand, parameters such as bunch uniformity, intra-bunch spacing, and total train length are especially important to know to optimise accelerator performance.
One promising solution is based on coherent radiation emitted by short electron bunches. Since the radiation intensity scales with the square of the bunch charge, it offers a strong signal even for very low intensity bunches. Additionally, when a long train of such bunches is involved, intra-train resonances occur, producing ultra-monochromatic spectral lines. The shape of these lines encode valuable information about the number of bunches, bunch separation, and overall train length.
A particularly suitable mechanism for generating this radiation is Cherenkov Diffraction Radiation (ChDR), which is produced when a charged particle moves near and parallel to a dielectric interface. ChDR offers several benefits for diagnostics: it is a non-invasive method, as the beam does not interact directly with the material, and its intensity scales linearly with the radiator length, providing an adjustable parameter for optimization.
In this report, we present experimental measurements of ChDR in the super-radiant regime, generated by an extremely long train of electron bunches. The experiment was performed at MT-25 microtron in Dubna. We demonstrate how the average single bunch length can be extracted from the envelope of the super-radiant spectrum, and how the individual spectral lines reveal the number of bunches and the total train length. These results are then validated against reference data provided by the accelerator operators.

We thank FLAP Collaboration for in-kind contribution and discussing the results. This research was supported by TPU development program Priority 2030. This work was partially carried out within the framework of the state assignment of the National Research University “BelSU,” number FZWG-2025-0010.

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

36 Coherent Cherenkov Diffraction Radiation from Short Electron Bunches in Electro-Optic Crystals

Electro-optic crystals (EOCs), such as lithium niobate, are widely used in accelerator physics for measuring the duration of sub-picosecond electron bunches. When an electron bunch passes near such a crystal, its Coulomb field modifies the dielectric tensor of the material, εᵢₖ, via the Pockels effect. This results in a change in the polarization state of a probe laser beam traversing the EOC [1].
It should be noted that in this geometry, the electron bunch also generates coherent Cherenkov diffraction radiation (CChDR) within the bulk of the EOC. The spectral characteristics and propagation angle of this radiation are determined by the parameters of the bunch [2]. The method of polarization currents enables the calculation of CChDR characteristics, taking into account both the spatial extent and frequency dispersion of the radiator material. In the case of EOCs, it is also necessary to consider the spatial dispersion of the dielectric tensor εᵢₖ, as well as its dependence on the strength of the Coulomb field of the bunch.
In this report, we consider the characteristics of CChDR in a lithium niobate crystal generated by an electron bunch with the following parameters: energy of 25 MeV, charge of 1 nC, and length of 100 micron. The bunch travels near the crystal at a distance of 300 microns. The dependence of the radiation field on the Pockels coefficients is considered in a first-order approximation.
In the specific geometry where a single electron propagates along the X-axis, generating an electric field directed along the Z-axis, CChDR at a frequency of 1 THz is emitted at the Cherenkov angle ϑCh = 82.1° relative to the X-axis. Under the influence of a bunch field with a peak strength of approximately 108 V/m, this angle shifts to 81.4°. After extracting the CChDR into vacuum – e.g., using a silicon prism – such a shift can be detected using a commercially available 2D THz detector array by TeraSense (Tera-4096) with a spatial resolution of 1.5 mm.
This research was supported by TPU development program Priority 2030.

[1] T. Srinivasan-Rao et al., Phys. Rev. ST Accel. Beams 5, 042801 (2002).
[2] T. Curcio et al., Phys. Rev. Accel. Beams 23, 022802 (2020).

Speaker: Alexander Potylitsyn

37 Smith-Purcell radiation in medium for microelectronics

The Smith-Purcell effect has various applications, from noninvasive diagnostics of relativistic electron beams and generation of powerful THz radiation to micro- and nano-electronics. In the latter field, the instruments and devices operate with small currents, down to single electrons. Being sensitive to electrons passing near periodic structures, Smith-Purcell radiation (SPR) can be used to create current sensors. In the 1990s, infrared Smith-Purcell radiation was used to measure the mean free path of hot electrons in GaAd/AIGaAs heterostructures [1]. Periodic gratings with different period lengths, of the order of hundreds of nanometers, were organized on the top layer of the heterostructure. A similar structure was used in [2] to measure the velocity distribution of two-dimensional electron gas in heterostructures. The success of both experiments confirms the prospects of using Smith-Purcell effect in electronics. Interestingly, research into interaction of two-dimensional electron flows with surface periodic arrays continues today, but in other applications such as flash-memory [3], and so on.
In microelectronics, electrons move essentially inside material, contrary to the traditional applications of SPR. The motion inside material affects SPR, since dielectric properties of the material screen the field of the beam and affect the interference of radiation, leading to a change in SPR dispersion relation. Earlier, the SPR in medium was considered in recent papers of Schepkovich et al. [4] and Potylitsyn et al. [5], but only for the electrons moving beyond medium.
In this report we present the results of our studies of the SPR generated by electrons moving in a medium. Based on previously developed methods [6-9], we have obtained expressions for the characteristics of the radiation, including the field, the spectral and angular energy distributions. We discuss the role of frequency dispersion of the medium properties: new, impossible out of medium, diffraction orders of SPR and special features of SPR in the regions of anomalous dispersion. We also review new prospects for the application of SPR in microelectronics.
The study was supported by a grant from the Russian Science Foundation No. 24-72-00150.

[1] C. Kiener, C. Wirner, W. Boxleitner, E. Gornik, G. Bohm, G. Weimann, Investigation of the mean free path of hot electrons in GaAs/AIGaAs heterostructures, Semiconductor Science and Technology 9, 193 (1994).
[2] E. Gornik, W. Boxleitner, V. Robkopf, M. Hauser, C. Wirner, G. Weimann, Smith-Purcell effect in GaAs/AIGaAs heterostructures, Superlattices and Microstructures 15, 399 (1994).
[3] Y. Xiang, C. Wang, C. Liu, T. Wang, Y. Jiang, Y. Wang, S. Wang, and P. Zhou, Subnanosecond flash memory enabled by 2D-enhanced hot-carrier injection, Nature 641, 90 (2025).
[4] D. Konakhovych, D. Sniezek, O. Warmusz, D. S. Black, Z. Zhao, R. J. England, A. Szczepkowicz,
Internal Smith-Purcell radiation and its interplay with Cherenkov diffraction radiation in silicon -- a combined time and frequency domain numerical study, arXiv: 2105.07682 (2021).
[5] A.P. Potylitsyn, Smith–Purcell Radiation in Dielectric and the Anomalous Doppler Effect, JETP Letters 121, 691 (2025).
[6] A.A. Tishchenko, D.Yu. Sergeeva, Near-field resonances in photon emission via interaction of electrons with coupled nanoparticles, Phys. Rev. B 100, 235421 (2019).
[7] D.Yu. Sergeeva, A.A. Tishchenko, Enhanced Smith-Purcell radiation based on quasibound states in the continuum in dimers aligned in a chain, Phys. Rev. B 108, 155435 (2023).
[8] D. I. Garaev, D. Yu. Sergeeva, A. A. Tishchenko, Theory of Smith-Purcell radiation from a 2D array of small noninteracting particles, Phys. Rev. B 103, 075403 (2021).
[9] D. Yu. Sergeeva, A. S. Aryshev, A. A. Tishchenko, K. E. Popov, N. Terunuma, J. Urakawa, THz Smith–Purcell and grating transition radiation from metasurface: experiment and theory, Optics Letters 46, 544 (2021).

Speaker: Alexey Tishchenko

Poster: Poster Session

18:30 Dinner

Wednesday 17 September

Compton Scattering and its Applications

Convener: Yan-Fei Li (Xi'an Jiaotong University)

38 KEK ATF status and upgrades

The KEK ATF (Accelerator Test Facility) serves as a dedicated testbed for developing beam instrumentation technologies in support of the International Linear Collider (ILC) project. As such, it incorporates a variety of diagnostic tools based on laser systems and photodetection technologies. At the ATF, nanometer-scale beam (nanobeam) technology development is underway using the Final Focus System Test Beamline, with the aim of replicating the beam conditions expected at the ILC. This involves achieving an ultra-compact beam size of 37 nm, corresponding to the 7 nm vertical beam size required for collisions at the ILC, and advancing beam position control at the nanometer scale. To date, a vertical beam size of 41 nm has been attained, alongside the successful implementation of a fast position feedback system capable of stabilizing the beam at nanometer precision. The ATF2 (1.28 GeV) stands out as a unique facility for this research, featuring a cavity-type beam position monitor (BPM) system with 20 nm resolution and a laser interference fringe beam size monitor (IPBSM) for nanobeam measurement. This report outlines the current status of the KEK ATF facility and highlights recent upgrades and experimental studies carried out within the ATF3 collaboration framework.

Speaker: Dr Alexander Aryshev (KEK)

39 Controlling the Polarization and Vortex Charge of γ Photons via Nonlinear Compton Scattering

Controlling the Polarization and Vortex Charge of γ Photons via Nonlinear Compton Scattering

High-energy vortex 𝛾 photons have significant applications in many fields. However, their generation and angular momentum manipulation are still great challenges. Here, we first investigated the generation of vortex 𝛾 photons with controllable spin and orbital angular momenta via nonlinear Compton scattering of two-color counter-rotating circularly polarized (𝐶⁢𝑃) laser fields. The radiation probabilities of vortex photons are calculated using the semiclassical approach that resolves angular momenta of emitted photons. We find that the angular momenta transferred to emitted photons are determined by the dominating photon absorption channel, leading to a structured spectrum with alternations in helicity and twist directions. By tuning the relative intensity ratio of the two-color 𝐶⁢𝑃 laser fields, the polarization and vortex charge of the emitted 𝛾 photons can be controlled, enabling the generation of 𝐶⁢𝑃 vortex 𝛾 photons with a user-defined polarization and topological charge, which may have multiple applications in nuclear physics, astrophysics, particle physics, etc.

Speaker: Prof. Yue-Yue Chen

40 Installation and commissioning of the photogun test facility for the Russian synchrotron light source SYLA

The 4th generation synchrotron light source SYLA is the flagship project of the new State light sources program of the Russian Federation. The SYLA will be constructed on the site of the NRC Kurchatov institute – IHEP in Protvino, Moscow Region. The SYLA will consist of both storage synchrotron and a free electron laser. The 6 GeV electron linac will be used for both injection into the synchrotron (top-up injection) and as a driver of short high-brightness electron bunches for the FEL. Two front ends will be developed and constructed for these purposes: the classical electron gun using a thermionic cathode for injection and the photogun to generate short ps bunches. The regular part of the e-linac will include more than 100 identical accelerating structures and will operate with both types of the electron beams.
Currently, the main components of the SYLA complex are being developed. The photogun test facility has been developed at MEPhI for the light source. It includes pi-mode accelerating structure with an energy of 7 MeV, photocathodes exchange chamber, laser system developed by IAP RAS and Avesta LLC, diagnostics chamber and all necessary engineering systems such as vacuum, focusing, adjustment, and thermostabilization, etc. All parts of the photogun test facility have been manufactured and installed and the test facility is now undergoing commissioning.
Main results of the photogun test facility development and commissioning will be presented in a report.

Speaker: Sergey Polozov

Installation and commissioning of the photogun ENG.pdf

41 Simulating electron beam evolution under inverse Compton scattering

Nowadays the intensity of existing inverse Compton scattering (ICS) sources is far from what is desired by users due to a number of unsolved problems, one of which is the recoil effect. This effect is considered primarily in terms of its influence on characteristics of the generated radiation [1], whereas its impact on characteristics of an electron beam after interaction with a laser beam is usually neglected. This is due to the fact that in most existing ring accelerators, the short beam lifetime prevents electrons from interacting with the laser pulse multiple times.
New storage ring based ICS sources, however, are now being designed with the electron beam lifetimes expected to be long enough to collide with laser pulses multiple times. This repeated interaction leads to a considerable evolution of the electron beams’ characteristics.
In this contribution, we show enhancements to our previously developed Geant4 ISC code [2]. Based on the theoretical model we developed in [3], we have implemented new features to simulate a storage ring based ICS source with arbitrary collision and beam tilting angles and possibility to track the electron beams’ evolution over multiple collisions. We demonstrate that this evolution must be taken into account, as it critically affects the properties of the resulting radiation. These new capabilities make our code a valuable tool for designing the next generation of ultra-bright ICS sources.

[1] C. Curatolo, I. Drebot, V. Petrillo, L. Serafini, Analytical description of photon beam phase spaces in inverse Compton scattering sources, Phys. Rev. AB 20, 080701 (2017).
[2] A.A. Savchenko, A.A. Tishchenko, and D.Yu. Sergeeva, Geant4 for inverse Compton radiation source simulations, in Proc. 27th Russian Particle Accelerator Conf. (RuPAC-2021), TUPSB29, 286 (2021).
[3] A.P. Potylitsyn, D.V. Gavrilenko, M.N. Strikhanov, and A.A. Tishchenko, Crab crossing in inverse Compton scattering, Phys. Rev. Accel. Beams 26, 040701 (2023).

Speaker: Dr Aleksandr Savchenko

10:05 Coffee-Break

Compton Scattering and its Applications

Convener: Alexey Tishchenko (National Research Nuclear University (MEPhI))

42 Strong Field QED Physics Based on Ultra-intense Laser and XFEL

Speaker: Liangliang Ji (Shanghai Institute of Optics and Fine Mechanics)

43 Attosecond gamma rays, and positrons and alpha particles production from intense laser-irradiated nano-micro array

With the development of Nano-Micro-array (NMA) fabrication, intense laser-irradiated NMAs have been proposed to produce brilliant gamma-rays and high-yield positrons with appealing conversion efficiency. In this presentation, we introduce how to emply a laser-irradiated NMA scheme to produce brilliant attosecond gamma-ray flashes and high-yield positron bunches with high conversion efficiency. We further introduce an enhanced generation of α particles in laser-irradiated NWAs composed of hydrogen-containing boron nitride. We conclude that the schemes using NMAs would provide effective avenues toward investigating attosecond nuclear science and HED physics with the available 10 PW laser facilities.

Speaker: Wen Luo (University of South China)

44 Near plans of the SYLA photogun test facility development

As mentioned in the report test facility installation and commissioning of the photogun, the prototype of a photogun for the Russian synchrotron light source SYLA was developed at MEPhI for the NRC Kurchatov institute. Today we have started the new project directed to further development of this facility. The project plans to upgrade the MW system to increase the photogun beam energy to 10 MeV, as well as to develop and to manufacture the 50 MeV booster section and precise bunch diagnostic devices. All these components are planned to be used for the full-scale 6 GeV injection e-linac for the SYLA. Additionally it is also planned that the Accelerator Test Facility (ATF) based on the photogun and booster accelerating sections prototypes and the especially designed experimental chamber will be installed in MEPhI. It is proposed that short ps high-brightness bunches can be used for the generation of different types of radiation as well as Cherenkov, Smith-Purcell and transient. The ATF can generate electron bunches having variable energy of 7-50 MeV with the bunch length of 1-2 ps, the bunch charge up to 300-400 pC and the repetition rates up to 100 Hz. The photon flux could be used both for study of new methods of the bunch parameters diagnostics and for the material sciences experiments.

Speaker: Taras Bondarenko (National Research Nuclear University MEPhI)

45 Stern-Gerlach Effect in Standing Wave X-ray Laser Beams

The quantum nature of light can be observed in diffraction experiments with a grating. In the Kapitza-Dirac effect [1-3] the roles of light and matter are interchanged in the diffraction process: Instead of light diffraction at a material grating an electron (matter) is diffracted an optical grating (light) which is created in form of a standing light wave of two counter-propagating laser beams. It is possible to setup a spin-dependent electron diffraction in Kapitza-Dirac scattering, in which electron diffraction only takes place for a specific electron spin-polarization [4]. Such dynamics correspond to the implementation of the first explicit observation of the spin of free electrons in the famous Stern-Gerlach experiment [5-7]. However, while the electrons in the Stern-Gerlach experiment necessarily (for reasons of the Heisenberg uncertainty) need to be bound in the shells of Silver atoms, the spin-dependent Kapitza-Dirac effect one of the rare methods for inferring the spin state of an electron which is freely moving in space. Since the spin-dependent dynamics is suppressed by the fraction of the photon energy over the electron rest mass, an implementation with standing light waves with high photon energies is essential. Therefore, the XFEL of the SHINE facility at ShanghaiTech University is one of the few places in the world, where the fundamental observation of the spin of a freely moving electron is possible [4]. In our contribution, we discuss this scenario and present a theoretical demonstration of such a spin effect in form of a fully relativistic quantum simulation [9] of the electron in a standing wave X-ray laser field.

References
[1] P. L. Kapitza, P. A. M. Dirac, Math. Proc. Cambridge Philos. Soc.29, 297 (1933).
[2] D. L. Freimund, K. Aflatooni, H. Batelaan, Nature (London) 413, 142 (2001).
[3] D. L. Freimund, H. Batelaan, Phys. Rev. Lett. 89, 283602 (2002).
[4] S. Ahrens, Z.F. Liang, T. \v Cade\v z, B.F. Shen, Phys. Rev. A 102, 033106 (2020).
[5] W. Gerlach, O. Stern, Z. Phys. 8, 110 (1922).
[6] W. Gerlach, O. Stern, Z. Phys. 9, 349 (1922).
[7] W. Gerlach, O. Stern, Z. Phys. 9, 353 (1922).
[9] P. Ge, S. Ahrens, B.F. Shen Phys. Rev. A 109, 022240 (2024).

Speaker: Sven Ahrens (Mathematics & Science College, Shanghai Normal University)

46 Ultrashort pulses using Compton backscattering on a multi-color laser

Ultrashort pulses using Compton backscattering on a multi-color laser

D.V. Gavrilenko*, A.A. Tishchenko
National Research Nuclear University “MEPhI”, Moscow 115409, Russian Federation

Inverse Compton Scattering (ICS) is a highly promising method for the generation of X-ray radiation. For various applications, particularly for probing ultrafast phenomena on an atomic scale, radiation pulses of attosecond duration are required. Conventional approaches to generate such pulses include Amplified Spontaneous Emission (ASE) [1], Self-Amplified Spontaneous Emission (SASE) [2], the use of ultrashort electron bunches to achieve a coherent regime [3], and the utilization of chirped laser and electron beams [4].
In this work, we propose a scheme where electron bunches are scattered not by a monochromatic laser, but by a multichromatic field composed of several distinct laser frequencies, and as a result, the radiation field has a broad spectrum. We demonstrate that this interaction of multi-color fields stochastically leads to a compression of the generated X-ray pulse duration. Significantly, we identify parameter regimes under which the generation of isolated attosecond pulses is feasible.

References
1. I. Inoue, R. Robles, A. Halavanau, Experimental demonstration of attosecond hard X-ray pulses, preprint arXiv:2506.07968 (2025).
2. J. P. Duris, J. P. MacArthur, J. M. Glownia et al. Controllable X-ray pulse trains from enhanced self-amplified spontaneous emission. Phys. Rev. Lett. 126, 104802 (2021).
3. J. Xiong, H. Xu, L. Ji, C. Feng, Zeptosecond Gamma-Ray Pulses Generation via FEL-Driven Microbunching and Laser-Compton Scattering, preprint arXiv:2503.00899v1 (2025).
4. B.H. Schaap, P.W. Smorenburg, O.J. Luiten, Isolated attosecond X-ray pulses from superradiant thomson scattering by a relativistic chirped electron mirror, Sci Rep 12, 19727 (2022).

Speaker: Dmitrii Gavrilenko

12:10 Lunch

13:30 visit to XFEL & SULF

18:30 Banquet

Thursday 18 September

Channeling and Crystal-assisted Processes

Convener: Alexander Potylitsyn

47 Modern Beams Channeling: Novel Accelerator Concepts

Channeling is the phenomenon well-known in the physics world mostly related to the motion of the beams of charged particles in aligned crystals. Since the beginning of 1970s channeling of high-energy leptons (electrons/positrons of several MeV up to hundreds of GeV energies) and hadrons (protons/ions of tens GeV up to several TeV energies) has been applied at various famous world research centers within different national/international projects related to the phenomenon utilization for shaping the beams as well as for producing high power X-ray and  radiation sources.

Modern studies on the channeling techniques proves high potentiality of historically well-known phenomenon, which has explained features of charged particle beams interaction in aligned crystals. The feasibility for application of channeling phenomenology to describe various mechanisms of interaction of both charged and neutral particles beams in the laser, plasma fields has been also demonstrated in several research.
In this review I intend to discuss new ideas being realized in the world within the studies dedicated to the construction of next generation of accelerator machines. Peculiarities of channeling interaction suggest novel compact solutions to handle the beams in an optimized way to get desired characteristics of the beams motion (collimation, undulation, acceleration).

1. S.B. Dabagov, Channeling of neutral partciles in micro- and nanocapillaries (Review of Topical Problems), Physics Uspekhi 46 (10) (2003) 1053.
2. S.B. Dabagov, Advanced Channeling Technologies in Plasma and Laser Fields (Invited Review), European Physical Journal Web Confs 167 (2018) 01002.
3. S.B. Dabagov, Yu.P. Gladkikh, Advanced Channeling Technologies for X-ray Applications (Invited Review), Radiation Physics and Chemistry 154 (2019) 3-16.
4. S.B. Dabagov, A.V. Dik, Surface Channeling of Charged and Neutral Beams in Capillary Guides (Invited Review), Quantum Beam Sci. 6(1) (2022) 8 doi: 10.3390/qubs6010008 (on volume cover)

E-mail: sultan.dabagov@lnf.infn.it

Speaker: Sultan Dabagov

48 Channeling experiments at the Mainz Microtron MAMI

The Institute for Nuclear Physics of the University of Mainz operates the accelerator complex MAMI which supplies an electron beam with a maximum energy of 1.6 GeV and a beam current of up to 100 µA. Outstanding qualities of MAMI is the continuous beam with an excellent beam quality of 4 pi nm rad emittance, a very low energy spread of less than 10$^{-4}$, as well as its extremely high reliability. All kind of channeling experiments require such a high quality beam with a low divergence.
The possibility to produce undulator-like radiation in the hundreds of keV up to the MeV region by means of channeling in periodically bent crystals is well known. A diamond superlattice with a period length of 3.54 μm was grown on a high quality straight (100) diamond plate with the method of Chemical Vapour Deposition (CVD). A sinusoidal varying boron doping profile resulted in a periodic variation of the lattice constant, and in turn four sinusoidally deformed (110) planes with a period length of 5.0 μm and an amplitude of 0.138 nm. A channeling experiment was performed with the 855 MeV electron beam. The impinging electrons perform sinusoidal oscillations resulting in the emission of quasi-monochromatic γ radiation. For the first time a clear peak was observed close to the expected photon energy of 1.33 MeV. Gross properties like photon energy, width and intensity of the peak can be reproduced fairly well by idealized Monte-Carlo simulation calculations.
Positrons, however, are more preferable because they have a significant longer de-channeling length. A new project was started to produce a high-quality positron beam using the MAMI accelerator. First channeling experiments with the new positron beamline at MAMI will be presented.

Speaker: Werner Lauth (University Mainz)

49 High-harmonic Optical Vortex Generation and Amplification in a Laser-driven ''Shaken Waveguide''

High-order harmonic generation by diffraction of a relativistically strong laser beam can facilitate spin-orbital interaction of light and leads to the generation of XUV optical vortex, where the spin angular momentum of a circularly polarized pulse is converted into the orbital angular momentum of the harmonic beams. These harmonic lights can be further amplified by employing a microplasma waveguide. We demonstrate a ''self-phase-matching'' effect is responsible for this amplification. A ''shaken waveguide'' model is developed to explain this effect, that shows due to nonlinear plasma response to the laser field, self-induced periodic structures are produced at the inner boundary of the waveguide, which modifies electromagnetic wave propagation, and keeps the phase velocities of all harmonic beams automatically matched to the drive laser pulse.

Speaker: Longqing Yi (Shanghai Jiao Tong University)

50 Observation of X-ray parametric radiation from a relativistic electron passing a stack of Si crystal plates

The radiation emitted by relativistic charged particles traversing natural or artificial periodic structures has been extensively studied in recent decades. Research has demonstrated that, within such periodic media, well-known phenomena, including Parametric X-ray Radiation (PXR), Cherenkov radiation, and transition radiation undergo interference effects that can significantly influence their properties. This report presents the investigation of PXR generated by electrons with energies between 0.7 and 4 GeV as they traverse a stack of Si crystal plates. Two crystal stacks, each consisting of 11 plates, were used in the study, one with a plate thickness of approximately 200 µm and the other with 400 µm. Previous studies have demonstrated that the use of a multi-plate crystal target enhances PXR intensity as a result of interference effects. However, in these studies, separate crystal plates were used as target, potentially resulting in minor misalignments that could not be fully eliminated. In our study, we used a stack of crystal plates mounted on a single base and cut from the same crystal, ensuring significantly better alignment. In the experiment, PXR from Si(220) reflecting planes was recorded using an AMPTEK X-123SDD X-ray spectrometer equipped with a Silicon Drift Detector. The detector was positioned at an angle of 27.3° relative to the primary electron beam direction and placed 25 cm from the crystal target. The observed PXR peak energy was 13.7 keV, with FWHM of approximately 1 keV. The spectrometer’s energy resolution at this energy is 135 eV. The results indicate that increasing the electron energy leads to a reduction in PXR intensity and a corresponding narrowing of the spectral peak.

Speakers: Dr Vahan Kocharyan (Institute of Applied Problems of Physics of NAS RA), Dr Yury Cherepennikov

10:05 Coffee-Break

Channeling and Crystal-assisted Processes

Convener: Werner Lauth (University Mainz)

51 Coherent combining of phase-locked high power microwave radiations

Relativistic klystron amplifier is a promising device to lock and steer the phases of high power microwave radiations, by which coherent combining of multiple radiations can be achieved to enhance the total equivalent radiation power. We report the investigations on coherent combining of phase-steerable high power microwaves (HPMs) generated by X-band relativistic triaxial klystron amplifiers which function like seeded free-electron masers that yields coherent emissions by the mechanism of transition radiation. It was found that electronically agile manipulation of the HPM phase is achieved with a mean discrepancy of 4° at the gain level of 110 dB. The coherent combining efficiency has reached remarkably as high as 98.4%, leading to combined radiations with equivalent peak power of 4.3 GW in X-band and average pulse duration of 112 ns. Owing to high spatial and temporal coherences, the presented gigawatt-class HPMs with electronic agility in phase may be applied to many other fields, for example, to drive high-gradient accelerators or to build coherent high power radars even with phase coding, and this study may also excite new interest in more comprehensive research in phase-steerable masers and their applications.

Speaker: Jinchuan JU (national university of defense technology)

52 Periodically Boron-doped diamond to achieve a crystal undulator

Undulators are the insertion devices mostly used to produce X-ray beams in modern synchrotron radiation facilities. It was pointed out [1] that by using the channeling process of ultra-relativistic electrons within the planes of periodically doped single crystals (Si-Ge, Boron doped diamond) it could be possible to achieve a compact crystal undulator in the MeV range and beyond. Indeed a periodically doped layer, with period lengths in the few 𝜇m range, deposited on a (001) surface, will display a periodical variation of lattice parameter along [001] and consequently a periodic curvature of the (011) planes. An undulator radiation can consequently be produced by the channeling of electron beams, with energies in the 108-109 eV range, along these (011) planes.
Diamond is a particularly interesting material for this application. The present work describes the protocol we established to produce periodically boron-doped layers on a diamond substrate. We are particularly concerned in the present work with a 4-period diamond superlattice with a thickness of 20 𝜇m produced with the method of Microwave Power Chemical Vapour Deposition (MP-CVD). The used substrate is a high-crystal-quality HPHT type IIa that only displays, on Bragg diffraction imaging images, a few dislocations (~102 cm-2) and some isolated defects introduced by surface processing, and where no stacking faults, growth sector boundary, or inclusion are observed. The growth process of the periodically varying boron doped layers on this diamond substrate included a tailored dilution stage, with precise control of the mass flow controllers, to ensure a sinusoidal boron doping pattern in the gas phase. Based on established calibration curves, the expected boron doping level in the diamond ranges from 1× 1020 cm−3 to 19 × 1020 cm−3. Different characterization techniques, such as Secondary-ion mass spectrometry (SIMS) and Synchrotron Rocking Curve Imaging (RCI), confirm the achievement of this sinusoidal Boron doping profile as well as good crystalline quality of the Boron-doped diamond layer (with the exception of a few hillocks that formed on surface defects of the substrate).
This allowed, on the large regions not affected by the hillocks, the successful observation of a clear radiation peak close to the expected photon energy of 1.2 MeV, during a planar (011) channeling experiment performed with the 855 MeV electron beam of the Mainz Microtron MAMI accelerator facility.
[1] A.Korol. A. Solov’yov, Novel Lights Sources Beyond Free Electron Lasers, Springer Nature Switzerland AG, Gewerbestr. 11,6330 Cham, Switzerland

Speaker: Dr Thu Nhi Tran Caliste (European Synchrotron Radiation Facility)

53 Electrons vs positrons in bent silicon crystals: deflection dynamics and coherent radiation at Sub-GeV energies

We present a comprehensive experimental and simulation study of beam steering and radiation emission by sub-GeV electrons and positrons traversing bent silicon crystals, performed at the Mainz Microtron (MAMI). Using electron beams at 855, 600, and 300 MeV and a 15 μm-thick silicon crystal bent along the (111) planes, we investigated both angular deflection profiles and gamma-ray emission. Our results demonstrate highly efficient steering via planar channeling and volume reflection, with channeling efficiencies exceeding 50% even at 300 MeV. Radiation spectra recorded under aligned crystal conditions exhibit enhancements of up to a factor of six compared to the amorphous orientation, even at the lowest energy. Complementary Geant4 simulations, with trajectory classification based on interaction states, reveal a clear correlation between microscopic beam dynamics and the observed radiation yield.

When compared to electrons, positrons at 530 MeV interacting with a 30 μm-thick bent silicon crystal exhibit even greater deflection efficiencies. Although radiation emission was not measured for positrons, the angular distributions display well-defined structures in the channeled and volume-reflected components, in excellent agreement with simulations. These results underscore the distinct interaction dynamics of positrons in bent crystals and enrich our understanding of charge-dependent steering phenomena.

Together, these findings confirm the effectiveness of bent silicon crystals for sub-GeV beam control and compact gamma-ray generation, with implications for slow extraction systems in circular accelerators and the development of advanced radiation sources based on channeling.

Acknowledgments:
This work was supported by the European Commission through the H2020-MSCA-RISE N-LIGHT (Grant Agreement No. 872196), EIC-PATHFINDER-OPEN TECHNO-CLS (Grant Agreement No. 101046458).

Speaker: Riccardo Negrello (Universita e INFN, Ferrara (IT))

54 Germanium crystal undulator realization through pulsed laser melting technique

Germanium crystal undulator realization through pulsed laser melting technique

D. Valzani¹², F. Sgarbossa¹², G. Maggioni¹², C. Carraro¹², F. Nicolasi¹², A. Sytov³, L. Bandiera³, D. De Salvador¹²

¹ Dipartimento di Fisica e Astronomia, Università di Padova, Via Marzolo 8, I-35131 Padova, Italy
² National Institute for Nuclear Physics INFN, Laboratori Nazionali di Legnaro, Viale dell’Università 2, 35020 Legnaro, Italy
³ Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Via Saragat 1, 44121 Ferrara, Italy

📧 Contact: davide.valzani@phd.unipd.it

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Crystal-based undulators are breakthrough devices for developing new gamma-ray light sources. Operating at photon energies ranging from 100 keV to several tens of MeV, they offer a promising approach to high-brilliance gamma-ray generation [1]. By exploiting the channeling phenomenon, a periodically bent crystal can be aligned with relativistic particle beams to produce high-energy photons. When particles are confined within atomic channels and follow a periodic trajectory due to the crystal’s curvature, directional light emission occurs.

Figure 1; see the attachment file with the abstract [2].
.
In this context, precise control over the manipulation of crystal planes to achieve a sinusoidal elastic deformation of the lattice is crucial for enabling this technology.

This work investigates the induction of strain in monocrystalline semiconductor materials using the pulsed laser melting (PLM) technique, with the goal of meeting the bending requirements of such devices. PLM is a non-equilibrium process in which a high-intensity pulsed UV laser beam melts the crystal surface to a depth of several hundred nanometers within a few nanoseconds. During the rapid cooling phase, the crystal resolidifies epitaxially in less than a hundred nanoseconds. If a controlled layer of heterogeneous atoms is deposited on the surface beforehand, these atoms diffuse into the molten phase and become incorporated into the crystal during regrowth. As a result, large quantities of dopants or alloying elements can be introduced, often exceeding the limits of equilibrium-based techniques. This approach is particularly advantageous for hyperdoping applications in nanoelectronics, photonics, and radiation detector fabrication.

By combining PLM with sputter deposition [3], strain can be induced in germanium monocrystals through the formation of a pseudomorphic alloy layer in the near-surface region. A range of laser parameters, such as pulse energy and pulse count, has been tested to optimize the induced strain. Moreover, different crystallographic orientations were explored, revealing a strong correlation between crystal direction and the lattice relaxation mechanisms that ultimately limit the maximum achievable strain.

Finally, applying this technology within a carefully designed photolithographic process enables the practical fabrication of crystals with sinusoidally bent planes. Further characterization of the fabricated structures confirms the feasibility of this approach for realizing this type of advanced device.

Figure 2; see the attachment file with the abstract.

The fabricated devices were characterized using diffraction techniques, and their structure was simulated and optimized through finite element mechanical calculations. Based on the deformation of the crystal planes, the undulator dynamics of a 35 GeV positron beam and the spectral probability of gamma photon emission from the device were calculated [4].

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Bibliography

[1] Romagnoni, M., Guidi, V., Bandiera, L., de Salvador, D., Mazzolari, A., Sgarbossa, F., Soldani, M., Sytov, A., & Tamisari, M. (2022). Bent Crystal Design and Characterization for High-Energy Physics Experiments. Crystals, 12(9). https://doi.org/10.3390/cryst12091263

[2] Korol, A., & Solov’yov, A. V. (2022). Crystalline Undulators. In A. Korol & A. V. Solov’yov (Eds.), Novel Light Sources Beyond Free Electron Lasers (pp. 137–180). Springer. https://doi.org/10.1007/978-3-031-04282-9_6

[3] Carraro, C., Milazzo, R., Sgarbossa, F., Fontana, D., Maggioni, G., Raniero, W., Scarpa, D., Baldassarre, L., Ortolani, M., Andrighetto, A., Napoli, D. R., de Salvador, D., & Napolitani, E. (2020). N-type heavy doping with ultralow resistivity in Ge by Sb deposition and pulsed laser melting. Applied Surface Science, 509. https://doi.org/10.1016/j.apsusc.2019.145229

[4] Sytov, A., Bandiera, L., Cho, K., Cirrone, G. A. P., Guatelli, S., Haurylavets, V., Hwang, S., Ivanchenko, V., Pandola, L., Rosenfeld, A., & Tikhomirov, V. (2023). Geant4 simulation model of electromagnetic processes in oriented crystals for accelerator physics. Journal of the Korean Physical Society, 83(2), 132–139. https://doi.org/10.1007/s40042-023-00834-6

Speaker: Davide Valzani (INFN - Laboratori Nazionali di Legnaro, Università degli Studi di Padova)

12:10 Lunch

Laser-driven particle accelerators and radiation sources

Convener: Tian Ye (State Key Laboratory of Ultra-intense Laser Science and Technology, Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS))

55 Generation Mechanism of High-energy Polarized and Vortex Particle Beams Driven by Strong Fields

Recently, with the rapid developments of ultra-strong ultra-short laser technologies, strong laser field driven high-energy polarized and vortex particle beams (e.g., electrons, positrons and Gamma-photons) with spin and orbital angular momenta, which have significant applications in many fields, have attracted broad interests. However, their generation and measurement are still great challenges. In this talk, we would like to introduce the related progresses of our group [1-6].

References
[1] J. Jiang, et al. Controlling the Polarization and Vortex Charge of $\gamma$ Photons via Nonlinear Compton Scattering. Phys. Rev. Lett. 134, 153802 (2025).
[2] Z. Li, et al. Ultrafast Spin Rotation of Relativistic Lepton Beams via Terahertz Wave in a Dielectric-Lined Waveguide. Phys. Rev. Lett. 134, 075001 (2025).
[3] Z. Lu, et al. Angular Momentum Resolved Inelastic Electron Scattering for Nuclear Giant Resonances. Phys. Rev. Lett. 134, 052501 (2025).
[4] T. Sun, et al. Generation of ultrabrilliant polarized attosecond electron bunch via dual-wake injection. Phys. Rev. Lett. 132, 054001 (2024).
[5] K. Xue, et al. Generation of high density high-polarization positrons via single-shot strong laser-foil interaction. Phys. Rev. Lett. 131, 175101 (2023). Editors' Suggestion.
[6] Z. Lu, et al. Manipulation of Giant Multipole Resonances via Vortex $\gamma$ Photons. Phys. Rev. Lett. 131, 202502 (2023)

Speaker: Jianxing Li (Xi'an Jiaotong University)

56 Compact Free-Electron Lasers: Progress and Prospects

Laser wakefield accelerators (LWFAs) possess extraordinary acceleration gradients exceeding 100 GV/m, offering remarkable potential for compact particle accelerators and table-top X-ray free-electron lasers (FELs). The realization of a table-top FEL driven by laser wakefield acceleration has been identified as one of the most significant challenges in this field for the decade. While several research teams have successfully demonstrated proof-of-principle table-top FEL configurations, challenges remain regarding electron beam quality and stability. Substantial obstacles must be overcome to enhance the performance of table-top FEL systems. This presentation will outline our team's roadmap for developing table-top FEL technology. We will elucidate the key physical mechanisms and optimization strategies for generating high-quality electron beams through laser wakefield acceleration, along with recent advancements in driving table-top FELs. Furthermore, we will provide perspectives on future development plans and prospects for table-top FEL systems.

Speaker: Ke Feng (Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences)

57 Attosecond Electron and γ-Ray Pulse Generation Using Intense Spatiotemporal Optical Vortex Lasers

Isolated attosecond γ-ray pulses are valuable for probing ultrafast phenomena, particularly in nuclear research. Traditional Gaussian lasers achieve this in the direct acceleration mechanisms but suffer from beam divergence and require dual laser systems, limiting compactness. Here, we demonstrate the generation of an isolated attosecond γ-ray pulse with transverse orbital angular momentum (TOAM) using a circularly polarized spatiotemporal optical vortex (STOV) laser in three-dimensional particle-in-cell simulations. An isolated attosecond electron slice accelerated by the STOV laser collides with its reflected front, producing an isolated attosecond collimated (~4°), ultra-brilliant γ-ray pulse. This STOV-driven mechanism enables single-laser attosecond γ-ray generation with TOAM, offering new opportunities in ultrafast imaging, nuclear excitation, and detection.

Speaker: Wenpeng Wang (Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences)

58 Dynamics and Radiation of Relativistic Electrons in Counter-propagating Laser Fields

Speaker: Qingzheng Lv (University of Chinese Academy of Sciences)

15:10 Coffee Break

Laser-driven particle accelerators and radiation sources

Convener: Jianxing Li (Xi'an Jiaotong University)

59 Research on Microscale Free-Electron Periodic Modulation of Terahertz and X-Ray Radiation

Free-electron radiation underpins modern light sources, from R\"ontgen's X-rays to today's fourth-generation X-ray free electron lasers (XFELs). When electrons interact with periodic electromagnetic environments, they emit radiation with a spectrum covering microwaves to X-rays. In recent years, the rapid progress of nanophotonics, advances in high-intensity lasers, and the cross-disciplinary integration of these fields have aroused great interest in controlling electron radiation. In particular, coherent emission has attracted significant attention. In particular, near-field photonics such as surface plasmon polaritons (SPPs), with their strong subwavelength confinement, offer a promising platform for compact radiation sources and integrated photonics.
Here, we demonstrate both the mechanism and experimental realization of free-electron--driven coherent amplification of terahertz SPPs. By coherently seeding SPPs with femtosecond laser pulses and synchronizing free-electron pulses, we achieve phase-locked interactions and observe energy gains exceeding three orders of magnitude within a 1.5-mm interaction length, a performance comparable to high-gain FELs.
Furthermore, we propose that quasi-periodic magnetic arrays arise in plasma through Weibel instability ($\sim 10^4$\;T), serves as an undulator or wiggler. In this configuration, the electrons undergo transverse oscillations, and by tuning the plasma parameters, the emitted radiation can be tuned continuously from the ultraviolet to the X-ray regime.
In addition, we also introduce the on-chip light source configuration, constructed with a dielectric nanopillar array. Laser excitation of such periodic structures couples into electromagnetic near fields, that provide periodic transverse acceleration to relativistic electrons. Through relativistic frequency up-conversion, this configuration produces tunable high-energy photons spanning ultraviolet to X-ray and $\gamma$-ray frequencies, while offering high operational stability and reduced damage risk.
By exploiting novel optical materials and constructing diversified periodic electromagnetic environments for free-electron interactions, we establish a versatile framework for radiation spanning from THz to X-ray frequencies. Our work not only demonstrates compact coherent free-electron sources but also expands the concept and implementation of micro-undulators, laying the foundation for multidimensional free-electron--periodic structure interactions and opening new avenues for miniaturized, tunable, and coherent electron-driven radiation.

Speaker: Ye Tian (Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences)

60 Demonstration of a High Power Superradiant THz FEL Covering\newline 1-20 THz Tuning Range with Bunch Trains

We'll report the first demonstration of an ultra-widely tunable (1-20THz) superradiant THz free-electron laser (FEL) driven by high-peak-current electron microbunch trains. The emission efficiency is substantially improved as the ultra-short electron microbunches emit in phase and engage in strong interactions with the generated THz waves within the undulator. We further demonstrate that the implementation of a tapered undulator configuration leads to a two-fold enhancement in emission intensity compared to the non-tapered case, elevating the pulse energy of the narrow-band THz radiation to the millijoule-level in a one-meter-long undulator. This experimental breakthrough represents a critical step toward realizing a compact, high-power, narrow-band THz source capable of fully bridging the 'THz gap' and will unlock numerous opportunities across a wide range of scientific disciplines.

Speaker: Lixin Yan (Tsinghua University)

61 Structured Extreme Field Driven Compton Scattering and QED Exploration

The theory of Quantum electrodynamics (QED) is considered to be the most precise theory for electromagnet field. With the development of high-power laser technology, the experimental verification of strong field QED is possible. All-optical Compton scattering with dual-beam high-power femtosecond laser is one of the best testbed to study SFQED.
A dual-beam platform for all-optical electron-photon scattering, or Thomson/Compton scattering, with adjustable collision-angle and parameter tuning ability has been developed. In principle, it can be used for the verification of strong-field quantum electrodynamics (SFQED) effects via nonlinear Compton scattering. Combining this platform with a PW Ti:Sapphire laser system, we demonstrated the generation of inverse Compton scattering X/gamma-rays with tunable energies from tens of keV to tens of MeV. The polarization of X/gamma radiation was shown to be controlled by manipulating the polarization of scattering beam. In the near future, by combining this experimental platform with multi-PW laser facilities, it is proposed to experimentally generate X/gamma radiation with orbital angular momentum for the nuclear isomer excitation, more importantly, to explore the regime transition from nonlinear Thomson scattering to nonlinear Compton scattering and eventually verification of theories at extremely strong field quantum electrodynamics effects. Also, preliminary plan of SFQED study in two high-power laser facilities, 0.5PW in SJTU and 2.5PW in TDLI will be presented, both of the lasers include two independently compressed two beam lines.

References
[1] A Platform for All-Optical Thomson/Compton Scattering with Versatile Parameters. HPLSE. 2025 (in Press).
[2] Experimental Evidence of Vortex $\gamma$ Photons in All-Optical Inverse Compton Scattering. arXiv:2503.18843
[3] Plasma-state metasurfaces for ultra-intensive field manipulation arXiv:2503.15567
[4] Gamma-ray Vortex Burst in Nonlinear Thomson Scattering with Refocusing Spiral Plasma Mirror. Ultrafast Science. 3: 0005. (2023)
[5] High-order multiphoton Thomson scattering, Nature Photonics 11, 514-520 (2017)

Speaker: Wenchao Yan (1) State Key Laboratory of Dark Matter Physics, Key Laboratory for Laser Plasmas (MoE), School of Physics and Astronomy, Shanghai Jiao Tong University; 2 )Collaborative Innovation Center of IFSA, Shanghai Jiao Tong University)

62 Finite Beaming Effect on QED Cascades

The quantum electrodynamic (QED) theory predicts the photon emission and pair creation involved in QED cascades occur mainly in a forward cone with finite angular spread $\Delta\theta\sim 1/\gamma_i$ along the momenta of incoming particles. This finite beaming effect has been assumed to be negligible because of the particles' ultra-relativistic Lorentz factor $\gamma_i\gg 1$ in laser-driven QED cascades. We develop an energy- and angularly resolved particle-tracking code, resolving both the energy spectra and the momentum profile of the outgoing particles in each QED event. We investigate QED cascades driven by two counter-propagating circularly polarized laser pulses, and show that the narrow beaming could be accumulated to effectively suppress the long-term growth of cascades, even though it can hardly affect the early formation of cascades. For QED cascades longer than 10 laser cycles, the finite beaming effect could decrease the final pair yield, especially at ultrahigh intensities $\xi>600$, by more than 10\%. We also show that for QED cascades induced by GeV electron beams colliding with linearly polarized laser pulses, this finite beaming could effectively increase the divergence of the particle beam in the direction perpendicular to the laser field, which may provide a robust signature for radiation reaction effect.

References
[1] Suo Tang, Finite beaming effect on QED cascades, Phys. Lett. B 859, 139136 (2024).

Speaker: Suo Tang (College of Physics and Optoelectronic Engineering, Ocean University of China)

63 Extremely Dense Gamma-rays and Polarized Leptons from Beam-plasma Interactions

Significant advances in the multi-petawatt laser technology have opened the door to the study of light-matter interactions in unexplored high-field regimes [1, 2]. Under such extreme conditions, strong-field quantum electrodynamics (QED) effects dominate and play a key role in collective plasma physics effects, resulting in a new class of QED plasmas [3, 4]. During the interaction, a large amount of electron energy can be converted into high-energy photons, which in turn decay further into electron-positron pairs. In this talk, we will present our recent work on efficient generation of extremely dense gamma-rays and polarized leptons from beam-plasma interactions [5-8].
For example, recently we discovered an efficient scheme for generating high-energy polarized positrons simply based upon electron-beam-solid interactions.
In this scheme, the electron beam needs to be focused to a density close to a solid target density by use of a properly designed hollow cone in order to trigger QED processes during the beam interaction with a solid target, since modern accelerators cannot yet produce beams with such a high density. When such a focused dense beam impinges on a solid target along its surface, asymmetric intense magnetic fields are induced near the target surface due to the large plasma electron backflows. The fields are high enough to trigger the multiphoton Breit-Wheeler process, leading to the generation of copious energetic positrons inside the target near the surface. Because the probability of spin-resolved pair production is intrinsically asymmetric and there are asymmetric field effects, most positrons are polarized via radiative spin flips. The polarized positrons can be created with an unprecedented high efficiency up to 10$^8$ positrons/J and the yield of about 0.3 e$^+$/e$^-$, which cannot be achieved by other methods in the prior art. Such polarized dense positron sources may open the door to many research frontiers.

References
[1] A. Di Piazza et al., Rev. Mod. Phys. 84, 1177 (2012).
[2] A. Gonoskov et al., Rev. Mod. Phys. 94, 045001 (2022).
[3] X.-L. Zhu et al., Nat. Commun. 7, 13686 (2016).
[4] X.-L. Zhu et al., Sci. Adv. 6, eaaz7240 (2020).
[5] X.-L. Zhu et al., Optica 10, 118 (2023).
[6] X.-L. Zhu et al., Phys. Rev. Lett. 132, 235001 (2024).
[7] X.-L. Zhu et al., Phys. Rev. Research 6, L042069 (2024).
[8] X. L. Zhu et al., arxiv: 2412.15706 (2024).

Speaker: Xing-Long Zhu (Institute for Fusion Theory and Simulation, Zhejiang University)

64 Surface photoelectric effect as a source of twisted electrons for future accelerators

Recently, there has been a considerable progress in investigating the effects induced by quantum states of electrons and photons with a definite projection of angular momentum on a specific axis, known as twisted states [1]. In high energy physics, such states are used to induce nondipole transitions in nuclei [2-4], or to retrieve information about the phase of scattering amplitudes that is directly inaccessible in experiments with plane-wave states of particles [1,5], or to produce radiation with peculiar properties [6,7]. Despite the fact that several techniques for producing twisted electrons have been developed [1], there remains a need for new, pure sources of twisted electrons that are experimentally simple to realize.
In the present study, we propose to employ the surface photoelectric effect as a simple tool for generation of twisted electrons [8]. We show that a pure source of twisted electrons can be realized by means of the surface photoelectric effect when a doped semiconductor with a small effective electron mass, such as n-InSb, or in Dirac or Weyl semimetals, is used at low temperatures. The temperature should be the helium one for n-InSb, whereas for Dirac or Weyl semimetals the liquid nitrogen temperature is enough. In this case the angular momentum of the twisted photon is almost entirely transferred to the photoelectron. We derive the restrictions on the parameters of the crystal, photoelectrons, and incident twisted photons necessary to achieve this. In particular, these estimates reveal that the photoelectric effect in ordinary metals cannot be used as a pure source of twisted electrons.
This report was supported by the Ministry of Education and Science of the Russian Federation, the contract FSWM-2020-0033.

[1] K.Y. Bliokh et al., Phys. Rep. 690, 1 (2017).
[2] P.O. Kazinski, A.A. Sokolov, Phys. Atom. Nuclei 87, 561 (2024).
[3] Z.-W. Lu et al., Phys. Rev. Lett. 131, 202502 (2023).
[4] Z.-W. Lu et al., Phys. Rev. Lett. 134, 052501 (2025).
[5] I.P. Ivanov, Phys. Rev. D 85, 76001 (2012).
[6] P.O. Kazinski, G.Yu. Lazarenko, Phys. Rev. A 103, 012216 (2021).
[7] A. Pupasov-Maksimov, D. Karlovets, Phys. Rev. A 105, 042206 (2022).
[8] P.O. Kazinski, M.V. Mokrinskiy, V.A Ryakin, Proc. R. Soc. A 481, 20240777 (2025).

Speaker: Prof. Peter Kazinski (Tomsk State University)

65 Self-consistent approach to simulate charge carrier transport in photocathodes to obtain initial electron beam distribution in RF photoguns

Advanced radiation sources demand high-brightness electron bunches. To date, such bunches are routinely provided by radiofrequency (RF) photoguns, where short laser pulses meet the photocathode surface and lead to photoelectron emission.

In RF photoguns, desired electron distributions within bunches are generated by inducing laser pulses of respective shapes. Some distributions, such as flat-top and Gaussian, successfully suppress parasitic Coulomb effects, which limit bunch brightness in RF photoguns. However, the electron bunch profile does not just follow the one for the laser pulse. As it takes a non-zero time for photoelectrons to reach the photocathode-vacuum surface, due attention has to be paid to the transport phenomena in the photocathode.

At the Department of Electrophysical Facilities of NRNU MEPhI, investigation of charge carrier transport in semiconductor photocathodes for RF photoguns has been conducted for some time. To describe the evolution of nonequilibrium electron and hole concentrations, partial-derivative equation formalism is employed. Taking into account the physics underneath photoemission in RF photoguns, charge carrier dynamics is considered to be driven by drift, diffusion, and recombination, while generation is responsible for the emergence of excessive electrons and holes.

In this research, we reveal the most recent results in constructing the self-consistent approach to simulate charge carrier transport in photocathodes for RF photoguns. The obtained characteristic initial electron beam distributions are utilized to simulate beam dynamics for the RF photoinjector for the SYLA project. The effect of electron beam parameters on photon flux to be discussed.

Speaker: Mr Mikhail Vladimirov (NRNU MEPhI)

18:45 Dinner

Friday 19 September

General radiation properties from relativistic particles

Convener: Sultan Dabagov (INFN)

66 Proposal of terawatt-attosecond X-ray pulses from an efficient freshslice multistage free-electron laser

We present the proposal of generating high-power and short FEL pulses using the fresh-slice multi-stage amplification scheme at FEL-II, the soft X-ray beamline of Shanghai Hard X-ray. We use a transversely tilted electron beam traveling through the unique FEL-II layout with magnetic chicanes between every two undulator modules. The tail of the bunch produces a short pulse in the first amplification stage. The rest of the
electron beam further amplifies the short FEL pulse in up to three additional stages. Our results show the production of FEL radiation with peak power of 2.5 terawatts and pulse durations of about 800 attosecond. This operation mode will allow us to advance the scientific opportunities of single pulse X-ray diffraction, X-ray scattering and X-ray spectroscopy methodologies.

Speaker: Mr zhiqiang Rao (Shanghai Institute ofApplied Physics, Chinese Academy of Sciences)

67 Radiation of a Twisted Electron Beam from a Magnetic Metasurface

Free electron radiation is currently being actively studied in the context of new photonic structures, including metamaterials [1,2], which electromagnetic properties can differ fundamentally from those of ordinary substances, especially due to their pronounced magnetic properties.
The opposite situation when it is not the substance but the free charge that has magnetic properties is also of great interest. This is possible even in the case of an electron, if it carries an angular momentum, which, generally speaking, can consist of a spin and an orbital angular momentum. In the presence of the latter, the electron is called twisted, since the front of its wave function forms a twisted spiral [3]. Unlike the spin, the magnitude of the orbital angular momentum is not limited (the maximum achieved to date is about a thousand), and therefore the effects associated with the magnetic moment can be quite significant (see, for example, [4-6]).
The third possible case – when both the beam and the substance have magnetic properties – has not yet been considered in the literature. This is the issue considered in the present paper. A theory of radiation of a twisted electron from a metasurface consisting of subwave elements with pronounced magnetic responses is constructed. The influence of these effects on the nature of the radiation is discussed.

[1] C. Roques-Carmes, et al., Free-electron–light interactions in nanophotonics, App. Phys. Rev. 10 (2023);
[2] M.V. Rybin and M.F. Limonov, Resonance effects in photonic crystals and metamaterials, Phys. Usp. 62 (2019);
[3] K. Y. Bliokh, et al., Theory and applications of free-electron vortex states, Phys. Rep. 690 (2017);
[4] I. P. Ivanov, V. G. Serbo, and V. A. Zaytsev, Quantum calculation of the Vavilov-Cherenkov radiation by twisted electrons, Phys. Rev. A 93 (2016);
[5] A. S. Konkov, A. P. Potylitsyn and M. S. Polonskaya, Transition radiation of electrons with a nonzero orbital angular momentum, JETP Lett. 100 (2014);
[6] I. P. Ivanov and D. V. Karlovets, Polarization radiation of vortex electrons with large orbital angular momentum, Phys. Rev. A 88 (2013).

Speaker: Damir Garaev

68 Radiation by an annular beam moves coaxially outside a dielectric ball

We investigate the electromagnetic radiation generated by an annular beam moves coaxially outside a dielectric ball. We derive analytical formulas for the spectral and spectral-angular distributions of the emitted energy and provide numerical evaluations of the radiation spectrum. A central aim of this study is to identify the specific geometrical and material conditions under which electromagnetic radiation—especially Cherenkov radiation—is significantly amplified or attenuated, owing to the structural configuration and frequency-dependent properties of the medium. Employing the Green function formalism in conjunction with methods of complex analysis, we rigorously derive the spectral-angular characteristics of the radiation and establish optimization criteria for maximizing the field intensity within the GHz–THz frequency domain.

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

69 Light propagation and radiation in helical metamaterials with strong spatial dispersion

It is known that transition and Cherenkov radiations in media with helical symmetry, such as cholesterics [1,2], can be used for generation of twisted photons [3, 4]. Usually, the spatial dispersion in such materials is negligible. In the present study, we investigate helical metamaterials – structured media of conducting spiral wires possessing strong spatial dispersion [5-7]. Using the effective field theory approach, we derive the general form of the permittivity tensor with spatial dispersion that respects the helical symmetry near a plasmon resonance and we apply it to a specific case of helical metamaterials.
Due to the presence of a plasmon field, the dispersion relation of the electromagnetic modes acquires an additional branch, and new polarization-dependent and total forbidden bands appear. The position and widths of these bands are tunable over a wide range of energies. We solve the corresponding Maxwell's equations in the paraxial and short-wavelength approximations. The scattering of electromagnetic waves by a plate made of a helical metamaterial is considered. As predicted by general theory [3], the radiation from charged particles traversing the helical metamaterial along the symmetry axis consists of twisted photons. The strong spatial dispersion effects enhance the intensity of radiation from charged particles in such media in comparison with cholesteric liquid crystals.
The study was supported by the Russian Science Foundation, grant No. 25-21-00283, https://rscf.ru/en/project/25-21-00283/
[1] Belyakov, V.A.; Sonin, A.S. (1982). Optics of Cholesteric Liquid Crystals [in Russian]. Nauka: Moscow, Russia.
[2] De Gennes, P.G., Prost, J. (1993). The physics of liquid crystals, Oxford university press.
[3] Bogdanov, O. V., Kazinski, P. O, Lazarenko, G. Yu. (2019). Phys. Rev. A 100, 043836.
[4] Bogdanov, O. V., Kazinski, P. O, Korolev, P.S, Lazarenko, G. Yu. (2021). J. Mol. Liq. 326, 115278.
[5] Silveirinha, M. G. (2008). IEEE Trans. Antenn. and Prop., 56(2), 390-401.
[6] Kaschke, J., Wegener, M. (2016). Nanophotonics, 5(4), 510-523.
[7] Kazinski, P. O., Korolev, P. S. (2025). J. Phys. A: Math. Theor. 58, 09570.

Speaker: Petr Korolev (Tomsk State University)

70 Susceptibility of a neutron wave packet

In quantum electrodynamics, there exists a class of coherent processes where, in scattering of wave packets of particles, the scattering amplitudes from each point of the wave packet add up constructively. Such coherent processes and resulting effects are significant for small-angle scattering, where the freely passed part of the particle wave packet interferes with the scattered part.
One of such processes – coherent elastic scattering of wave packets of electrons and hadrons – was thoroughly investigated in [1]. It was shown that, in the limit of small recoil, an interference pattern arises in scattering of electron by a single hadron wave packet. Even more interesting effects emerge when considering Compton scattering of wave packets. It turns out that coherent Compton scattering on a wave packet can effectively be treated as scattering on a macroscopic continuous medium with a certain dielectric susceptibility tensor. In other words, the wave packet of a single particle can be described by macroscopic characteristics inherent to many-particle systems. Thus, it was demonstrated in [2] that the wave packet of an individual photon can be regarded as a birefringent gyrotropic dispersive medium in a photon-photon scattering. It was proved in [3] that the wave packet of a single electron can be endowed with the susceptibility tensor and this tensor has the same form as for an electron plasma in the small recoil limit. The investigation of the polarization operator off the photon mass-shell [4] revealed that the wave packet of an electron can support quasiparticles—plasmons. Moreover, the solutions of the Maxwell equations in such a medium consisting of a single electron were obtained.
In the papers [3,4], the leading contribution to the electromagnetic vertex comes from the particle electric charge. In the present study, we investigate the form of the susceptibility tensor, both on and off the mass-shell, for a neutral particle where the main contribution to the interaction is given by the magnetic moment of the particle. In other words, we study the susceptibility tensor of a single neutron wave packet.
This research was supported by TPU development program Priority 2030.

1. Kazinski P.O., Rubtsova D.I., Sokolov A.A. Inclusive probability to record an electron in elastic electromagnetic scattering by a spin one-half hadron wave packet // Phys. Rev. D. 2023. V. 108, No. 9.
2. Kazinski P.O., Solovyev T.V., Susceptibility of a single photon wave packet // Phys. Rev. D. 2023. V. 108, No. 1.
3. Kazinski P.O., Solovyev T.V., Coherent radiation of photons by particle wave packets // EPJC. 2022. V. 82, No. 9.
4. Akimov I.M., Kazinski P.O., Sokolov A. A. Plasmon-polariton modes on a single electron wave packet // Phys. Rev. D. 2025. V. 111, No. 3.

Speaker: Alexei Sokolov (Tomsk Polytechnic University)

71 Low-frequency radiation of charged particle bunch on single and double grid screens

We consider the radiation of a thin charged particle bunch moving in the presence of a planar grid screens with square cells. The grid is composed of thin conductors that have galvanic contact in the cross points. It is assumed that the wavelengths under consideration are much greater than the cell size (so-called ‘’longwave’’ radiation), and the latter is much greater than the transverse size of the conductor. In this approximation, the grid screen can be described by the averaged boundary conditions (ABC) of M.I. Kontorovich [1]. Note that earlier the ABC method was successfully applied in a series of the ‘’longwave’’ problems (see, in particular, articles [2-4]).

In the first problem, we analyze the radiation of the bunch passing through the single grid screen. With the use of the ABC method we obtain the general analytical solution which is investigated asymptotically. It is shown that the radiation consists only of volume (spherical) waves. The Fourier-transforms of the electromagnetic field components are obtained, the dependences of the energy characteristics on the bunch properties and geometrical parameters of the structure are analyzed. In particular, it is demonstrated that, at certain grid parameters, one can generate the radiation which is practically indistinguishable from the one in the case of a perfectly conductive solid plane.

In the second problem, we analyze the radiation of the bunch passing through the double grid screen. It is assumed that the grids are parallel to each other, and the distance between them is much greater than the cell size. As before, the general analytical solution is obtained by the use of the ABC method. The asymptotic investigation of the solution is carried out to obtain the Fourier-transforms of the field components in the far-filed zone. It is shown that, in the area between the grids, the bunch generates a number of waveguide modes (cylindrical waves). As it demonstrated in the work, it is possible that only one propagating mode is generated. Outside this area, the propagating modes are excited as well, but each mode exists in the certain range of angles. The dependences of the energy characteristics of the cylindrical waves on the grid parameters are obtained and analyzed. We examine spherical waves as well. It is shown that, in the area between the grids, one can neglect these waves at the relatively great distance from the trajectory of the bunch motion, whereas outside this area the spherical waves can be dominant.

It should be emphasized that the obtained results can be useful for the development of methods for detection and diagnostics of particle bunches. It is important to note that the use of the grid screen composed of thin conductors does not require precise positioning of a bunch in the screen plane, and the methods of diagnostics can be noninvasive.

1. M.I. Kontorovich, M.I. Astrakhan, V.P. Akimov, G.A. Fersman. Elektrodinamika setchatyh struktur. Moskva, Radio i Sviaz, 1987 (in Russian).
2. E.G. Doil’nitsina, A.V. Tyukhtin. Selective screening of waveguide modes by a system of two grids with square cells. J. Commun. Technol. Electron., vol. 54, pp. 1171–1174 (2009).
3. A.V. Tyukhtin, V.V. Vorobev, S.N. Galyamin. Radiation excited by a charged-particle bunch on a planar periodic structure. Phys. Rev. ST-AB, vol. 17, 122802 (2014).
4. A.V. Tyukhtin, V.V. Vorobev, S.N. Galyamin. Radiation of charged-particle bunches passing perpendicularly by the edge of a semi-infinite planar wire structure. Phys. Rev. E, vol. 91, 063202 (2015).

Speaker: Evgenii Simakov (Saint-Petersburg state university)

72 Modified Electrodynamics with Gravitational Coupling: An f(R)-Approach to the Dynamics of Relativistic Particles and Radiation Analysis in Electromagnetic Fields

Within the framework of the theory of electrodynamics, a modification is proposed where the standard rapidity of a relativistic particle is replaced by a new rapidity-dependent function describing the particle’s dynamics in an electromagnetic field. This function enables the incorporation of gravitational effects in the presence of an electromagnetic field and exhibits an analogy with the f(R)-theory of gravity. The limits of applicability of the proposed theory are established. The influence of various gravitational potentials on the trajectory of a relativistic particle in an electromagnetic field is investigated. Additionally, the impact of electromagnetic wave polarization on the particle’s motion in a gravitational potential is examined. It is demonstrated how modulated electromagnetic waves can be utilized to analyze the emitted radiation from a particle in a gravitational potential. The study is aimed at exploring the general radiative properties of relativistic particles within the extended electrodynamic theory.

Speakers: Nikolai Akintsov (Nantong University), Prof. Stepan Andreev (Department of Radiophotonics, Research Center for Telecommunications, Moscow Institute of Physics and Technology (National Research University))

10:15 Coffee-Break

Closing remarks & Best Posters

12:10 Lunch