arXiv subjects

V. V. Kobets

Publications and source records attributed to V. V. Kobets.

6 recordsLinked to original sources

arXiv2026

Generation of high-OAM ultraviolet twisted light for RF-photoinjector applications

The generation of relativistic vortex electron beams via photoemission requires ultraviolet laser beams with well-controlled orbital angular momentum (OAM) and compatibility with radio-frequency (RF) photoinjector drive-laser systems. High-OAM vortex beams at a wavelength of 266 nm are generated using three fabricated diffractive optical elements integrated into an operational photoinjector beamline: a reflective fork grating, a high-topological-charge spiral phase plate, and binary axicons. The spiral phase plate produces a high-purity Laguerre-Gaussian mode with an OAM of l = 64 and a conversion efficiency of 80%, whereas binary axicons generate low-divergence quasi-Bessel beams forming a superposition of multiple OAM states with a finite OAM bandwidth imposed by their binary phase structure. Fork gratings provide flexible access to lower OAM values and enable robust modal diagnostics. The generated beams are characterized using cylindrical-lens mode conversion and radial intensity analysis, demonstrating practical control of both the OAM content and spectral bandwidth of ultraviolet structured light for accelerator-based applications.

quant-ph↗

arXiv2026

Classical and quantum beam dynamics simulation of the RF photoinjector test bench

We present beam-dynamics simulations for an S-band RF photoinjector test bench under development at the Joint Institute for Nuclear Research, aimed at producing high-quality electron beams and enabling future generation of relativistic vortex electrons with a quantized orbital angular momentum (OAM). Simulations of the 1.5-cell photogun are performed assuming an RF gradient of 45 MV/m, which, in accordance with our simulations with CST Studio, corresponds to the currently achieved input RF power of 3 MW. At low charge (Q = 0.63 pC), stable bunch formation is obtained, with weak space-charge effects and transverse emittance dominated by RF-induced correlations. Optimization of the injection phase and cathode solenoid results in a robust emittance-compensated regime with a final normalized emittance of 2.08 pi mm mrad. To assess prospects for accelerating vortex electron beams, we additionally model the quantum evolution of single-electron Laguerre-Gaussian wave packets. The results show that multi-MeV acceleration suppresses free-space spreading of the electron packet and preserves the packet's initial OAM structure, indicating that the test bench provides suitable conditions for forthcoming experimental studies of relativistic vortex electrons.

physics.acc-ph↗

arXiv2025

Experimental and theoretical research of photoneutron reactions in the 181Ta nucleus

Bremsstrahlung fluxes for irradiating tantalum samples were formed by irradiating a tungsten converter with an electron beam with energy up to 130 MeV. The relative yields and flux-averaged cross-sections of multinucleon photonuclear reactions with the emission of up to 9 neutrons in 181Ta nuclei were determined. Monte Carlo simulations to study the yields of photonuclear reactions were performed using Geant4 and TALYS-2.0 codes. The obtained experimental results were compared with the available literature data and calculated results. The comparison showed that the values of the relative reaction yield and the flux-averaged cross-section coincide with the literature data, taking into account the different geometry of the experiments. The calculated results coincide with the experimental ones only for reactions with the emission of up to 5 neutrons from the nucleus.

nucl-ex↗

arXiv2024

Photonuclear reactions on $^{59}$Co at bremsstrahlung end-point energies of 40-130 MeV

Relative yields have been measured in the 40-130 MeV bremsstrahlung induced reactions of 59Co. The experiments have been performed with the beam from the electron linear accelerator LINAC-200 using the activation and off-line γ-ray spectrometric technique. The bremsstrahlung photon flux has been calculated with the Geant4 program. The cross sections were calculated by using computer code TALYS-1.96 with different models and are found to be in good agreement with the experimental data.

nucl-ex↗

arXiv2024

Interaction of photons with silver and indium nuclei at energies up to 20 MeV

The yields of photonuclear reactions in the 107Ag, 113In, and 115In nuclei have been measured. Monte Carlo simulations have been performed using the Geant4 code, and the results have been compared with the experimental ones. The isomeric ratios of the yields in the reactions 107Ag(γ,n)106m,gAg and 113In(γ,n)112m,gIn have been determined. The cross sections for the reactions 107Ag(γ,n)106gAg and 107Ag(γ,2n)105Ag at an energy of 20 MeV have been calculated on the basis of the experimental data.

nucl-ex↗

arXiv2000

Linac Lue200. First Testing Results

"LUE200" - 200 MeV electron linac is being created at JINR as a driver of the pulsed neutron source "IREN" [1]. The special full-scale facilities for testing the main systems of LUE-200 (FSTF) are used at JINR, BINP, MEPhI and YerPhI [2]. The verification of the linac accelerating system is providing at the VEPP-5 preinjector constructed at BINP [3]. The accelerating system of LUE200 includes two S-band (2856 MHz) accelerating sections of 3 m long. The sections are connected with modulator based one 5045 klystron (SLAC production). There are SLED-systems for the multiplying the pulse RF power. The first results of the accelerating system test on the VEPP-5 preinjector are presented. The electron beam energy up to 92 MeV and consequently average rate of acceleration of the electron beam more than 30 MeV/m were achieved after acceleration in one section.

physics.acc-ph↗