arXiv subjects

S. S. Baturin

Publications and source records attributed to S. S. Baturin.

At least 19 recordsLinked to original sources

arXiv2026

Orbital Angular Momentum Transfer and Beam-Quality Limits in Fork-Grating Electron Diffraction

We analyze fork-grating generation of electron vortex beams beyond the ideal single-mode approximation. The incident beam is described as a paraxial Gaussian ensemble with finite transverse momentum spread and a first electromagnetic Hartree phase accumulated before the grating. Within Fresnel propagation we derive an analytical expression for each diffraction order and determine the corresponding orbital-angular-momentum statistics. The mean OAM of a selected order remains fixed by the topological rule, $\langle L_z\rangle_m=mp\hbar$, while its variance is set by the residual transverse momentum spread of the beam prepared at the grating. For the Gaussian mixture, the transverse purity is $\mathcal P_{\perp,m}=[1+2(ΔL_{z,m}/\hbar)^2]^{-1}$. The observed annular profile is governed by a separate propagation-dependent blurring scale, so a beam can retain well-defined mean OAM while having low transverse purity or a partially filled vortex minimum. Within the radial phase-screen approximation, the Hartree self-field modifies the propagated profile while preserving the full-plane OAM moments and transverse purity.

physics.optics↗

arXiv2026

State-resolved quantum transport of vortex electrons in accelerators

Vortex electrons carry a quantized orbital angular momentum (OAM) degree of freedom, but whether this internal structure can survive repeated transport through an accelerator lattice remains unclear. Here we formulate a density-matrix theory for periodic round lattices and show that the symmetry-protected quantity is a Lewis-Floquet OAM invariant, rather than the instantaneous kinetic OAM. The classical transfer map lifts to unitary state evolution, while stochastic field errors generate a Lindblad channel. This framework exposes a sharp separation between visibility and state survival. Dipole jitter displaces the wavepacket, rapidly smearing a vortex signature measured about a fixed origin without altering its recentered internal OAM distribution. Quadrupole fluctuations instead drive genuine $Δ\ell=\pm2$ leakage. For a matched $n=0$, $|\ell|=1$ mode, white-noise estimates based on representative IOTA and PETRA III parameters give fixed-frame smearing scales of $4.9\times10^2$ and $3.3$ turns, but intrinsic-leakage scales of $2.1\times10^5$ and $2.2\times10^6$ turns, respectively. Thus loss of an unrecentered vortex image need not signal destruction of the vortex state: its internal OAM structure can persist hundreds to hundreds of thousands of times longer. Centroid tracking and quadrupole stability are therefore distinct experimental requirements for observability and state survival, respectively.

physics.acc-ph↗

arXiv2026

Angular momentum flux of twisted light in paraxial and nonparaxial regimes

We present a theoretical framework for the derivation of the $z$-directed total angular momentum density of a Bessel wave and of the corresponding intercepted angular momentum flux in an ideal perfectly absorbing disk model. Exact expressions for these quantities are obtained in both paraxial and nonparaxial regimes. We then analyze several experimentally relevant setups in the large-argument asymptotic of the Bessel functions. By varying the beam wavelength, polarization, and cone angle, we identify several distinct regimes of the intercepted angular momentum flux. Within the ideal absorber model, this intercepted flux may be identified with the corresponding mechanical torque. The results suggest potential applications for size-sensitive probing and controlled flux manipulation within the idealized macroscopic model.

physics.optics↗

arXiv2026

Geometry-Enabled Radiation from Structured Paraxial Electrons

We present a microscopic calculation of spontaneous photon emission by twisted (paraxial) electrons propagating through inhomogeneous, axisymmetric magnetic fields. We construct exact electron states that incorporate transverse mode structure and wavefront curvature by combining the Foldy-Wouthuysen transformation with a geometric framework based on Lewis-Ermakov invariants and metaplectic transformations. We show that the evolution of such structured states corresponds to an open path in the space of quadratic forms, giving rise to a geometric contribution to the emission amplitude that cannot be eliminated by gauge choice or adiabatic arguments. The inverse radius of curvature of the electron wavefront controls a finite-window boundary contribution to the emission amplitude in regions where the external magnetic field vanishes locally, this contribution vanishes when the observation window is extended to infinity. Presented mechanism generalizes Landau-level radiation to nonasymptotic, structured electron states and establishes a direct connection between noncyclic geometric evolution and photon emission.

quant-ph↗

arXiv2026

Generalized Theory of Blowout-Regime Plasma Wakefields via a Lagrangian Formulation

The blowout regime of plasma wakefield acceleration is a strongly nonlinear plasma response in which an intense relativistic beam or laser pulse expels plasma electrons forming a nearly uniform ion column. Existing self-consistent theories describe this structure primarily in the axisymmetric limit, reducing the bubble dynamics to a single radial degree of freedom. This restriction is inadequate for flat beams with highly asymmetric transverse emittances, as required in future linear colliders to control luminosity and beamstrahlung. Using a reduced Lagrangian formulation, we generalize the existing theory beyond axisymmetry and derive a coupled system of equations governing the wake potential driven by an asymmetric beam. This theory self-consistently predicts the focusing fields and their variation along the co-moving coordinate, as well as the accelerating field and its transverse nonuniformity. The resulting theoretical predictions are benchmarked against particle-in-cell simulations, demonstrating the theory's ability to describe and interpret wakefields driven by nonaxisymmetric sources.

physics.acc-ph↗

arXiv2026

Fringe field induced spin-OAM mixing of twisted electrons

We study spin effects in twisted-electron propagation through the entrance or exit region of an axially symmetric magnetic coil. Starting from the Foldy-Wouthuysen reduction of the Dirac equation, we derive a paraxial spinor equation in which the longitudinally varying solenoidal field produces, in addition to the usual diagonal Zeeman term, a transverse Pauli coupling proportional to the fringe-field gradient. The scalar transverse dynamics is treated exactly by the Ermakov mapping, which absorbs the longitudinally dependent focusing into a metaplectic scaling transformation and reduces the orbital evolution to that of a stationary two-dimensional oscillator. On this background, the transverse Pauli term is treated perturbatively and yields an explicit first-order correction for arbitrary realistic solenoidal profiles. Axial symmetry implies conservation of the total projection of angular momentum, so each spin flip is accompanied by a compensating one-quantum change of orbital angular momentum. In addition, the linear coordinate structure of the perturbation restricts the first-order dynamics to at most two neighboring radial sidebands for each incoming oscillator component. We derive the corresponding transition amplitudes and show how their phases are governed jointly by the Ermakov accumulation and the diagonal spin-orbital rotation. The resulting framework provides a direct way to quantify spin-orbit mixing of twisted electrons in realistic magnetic lenses and solenoidal beam-line elements, and it identifies a route toward controlled spin-OAM conversion in engineered sequences of magnetic-field edges.

quant-ph↗

arXiv2026

Comment on "Angular momentum dynamics of vortex particles in accelerators''

We comment on Ref.[D. Karlovets, D. Grosman, and I. Pavlov, Phys. Rev. Lett. 136, 085002 (2026)], which proposes a BMT-like equation for the mean kinetic orbital angular momentum (OAM) of vortex particles in accelerator fields and draws spin-like conclusions about depolarization, resonances, and control. We show that the proposed closure is not generally valid even at the mean-value level. In the authors' own homogeneous-field model, Eq.(8) already makes $\langle L_z\rangle$ depend on the packet second moment $\langle ρ^2\rangle(τ)$; for an exact family of breathing Landau/LG packets this yields an explicit oscillation incompatible with Eq.(9) except in the nongeneric matched case. Moreover, the Appendix A assumption that mixed correlators are negligible suppresses the transverse kinetic-OAM components themselves, since those correlators are precisely the building blocks of $L_x$ and $L_y$. We also stress that, even if a closed equation for $\langle \hat{\mathbf L}\rangle$ were available, it would still not constitute a transport equation for a vortex quantum state. Mean-OAM transport does not determine OAM spectra, inter-mode coherences, or fidelity. State-level claims therefore require a mode-resolved density-matrix treatment rather than an Ehrenfest equation for a low-order moment.

physics.acc-ph↗

arXiv2026

Tennis-racket instability of twisted electrons

We demonstrate that a weak nonlinear magnetic entrance edge induces a tennis-racket (Dzhanibekov) instability in the shell-resolved orbital pseudospin dynamics of twisted electrons propagating in a nominally uniform solenoidal field. Starting from a Maxwell-consistent thin-edge extension of the entrance field, we derive an effective fixed-shell Hamiltonian in which linear Schwinger pseudospin precession acquires an anisotropic quadratic correction. In the symmetric aligned limit, an exact linear eigenstate (a Laguerre-Gaussian vortex state) becomes a hyperbolic fixed point of the large-shell dynamics, producing recurrent reversals of the mean pseudospin projection. These reversals appear in real space as repeated conversions of the transverse profile between Laguerre-Gaussian vortex and Hermite-Gaussian multi-lobed states. The unavoidable Lewis-Ermakov breathing of realistic wave packets does not generate a separate mechanism; it naturally modulates the nonlinear strength and sets the growth time scale. Microscope-scale estimates show that the required regime is accessible with standard octupole correctors in a transmission electron microscope.

quant-ph↗

arXiv2026

Effective Caldirola-Kanai Model for Accelerating Twisted Dirac States in Nonuniform Axial Fields

We study relativistic twisted (orbital-angular-momentum) states of a massive charged particle propagating through an axially symmetric, longitudinally inhomogeneous solenoid field and a co-directed accelerating or decelerating electric field. Starting from the Dirac equation and using controlled spinless and paraxial approximations, we show that the transverse envelope obeys an effective nonstationary Schrödinger equation governed by a Caldirola--Kanai Hamiltonian. The longitudinal energy gain or loss encoded in $f(z)=[E_0-V(z)]^2-m^2$ generates an effective gain or damping rate $\widetildeγ(z)=\partial_z f(z)/[2f(z)]$ and a $z$-dependent oscillator frequency $\widetildeω(z)=p_0Ω(z)/\sqrt{f(z)}$. Exploiting the Ermakov mapping (unitary equivalence of Caldirola--Kanai systems), we obtain a closed-form propagated twisted wave function by transforming the stationary Landau basis. The transverse evolution is controlled by a single scaling function $b(z)$ that satisfies a generalized Ermakov--Pinney equation with coefficients determined by $E_z(z)$ and $B_z(z)$. In the limiting cases of uniform acceleration with $B_z=0$ and of solenoid focusing with negligible acceleration, our solution reduces to previously known analytic results, providing a direct bridge to established models.

quant-ph↗

arXiv2026

Universal Analytic Solution for the Quantum Transport of Structured Matter-Waves in Magnetic Optics

We present a closed-form analytic solution for the propagation of an arbitrary charged scalar state in a non-uniform magnetic field. The dynamics are governed by classical beam optics parameters (Courant-Snyder parameters), the Twiss functions, and phase advance, revealing a direct map between quantum evolution and its classical counterpart. The solution decomposes into three components, exhibiting a complex rotation dependent on the sign of the orbital angular momentum (OAM) projection, alongside an intrinsic distortion from interference governed by a generalized Gouy phase. For a relevant Glaser-type magnetic field and a half-blocked twisted electron, we demonstrate that asymmetry reveals interference-driven dynamics beyond rigid rotation. Our fully relativistic framework provides a practical tool for predicting beam behavior in particle accelerators and electron microscopes.

quant-ph↗

arXiv2025

Analytical theory of the skewed wake effect

Recently, the experimental discovery of a new type of wakefield effect, the "skewed wake effect", has been reported. We provide an explanation of the nature of the skewed wake effect based on a simple three-particle model that we have developed. Taking a step forward, we analyze this effect for the case of a highly elliptical beam, provide a simple estimate of the skew angle, and analyze the wake amplitude effects associated with this effect.

physics.acc-ph↗

arXiv2024

Vacuum polarization and Wichmann-Kroll correction in the finite basis set approximation

The finite basis set method is commonly used to calculate atomic spectra, including QED contributions such as bound-electron self-energy. Still, it remains problematic and underexplored for vacuum-polarization calculations. We fill this gap by trying this approach in its application to the calculation of the vacuum-polarization charge density and the Wichmann-Kroll correction to the electron binding energy in a hydrogen-like ion. We study the convergence of the method with different types and sizes of basis sets. We cross-check our results for the Wichmann-Kroll correction by direct integration of the Green's function. As a relevant example, we consider several heavy hydrogen-like ions and evaluate the vacuum polarization correction for $S$ and $P$ electron orbitals.

physics.atom-ph↗

arXiv2024

Twisted charged particles in the uniform magnetic field with broken symmetry

We present a theoretical description of charged particles with nonzero projection of the orbital angular momentum (OAM) in a uniform magnetic field with broken axial symmetry. The wave functions we find naturally account for the asymmetry of the magnetic field at the entrance of the solenoid through the continuous parameter and are a generalization of the Laguerre-Gauss states commonly used to describe twisted charged particles. We analyze the asymmetric Hamiltonian from an algebraic point of view and show how the OAM projection of the twisted state is modified by symmetry breaking. We provide analytical frameworks for properties of the asymmetric states, such as energy, RMS size, and Cazimir invariant, and discuss advantages of the proposed description.

quant-ph↗

arXiv2024

Conversion of twistedness from light to atoms

We develop a simple model and propose a scheme that allows the production of twisted atoms in free space using the absorption of twisted photons by a bound electron. We show that in the inelastic collision of a photon and an atom, the twisted state of the photon is transferred to the center-of-mass state, so that the projection of the orbital momentum of the atom becomes $m_γ-Δm_e$. We also show that, depending on the experimental conditions, the twistedness of the photon is either transferred to the atomic center-of-mass quantum state or modifies the selection rule for the bound electron transition. Proposed scheme is general and enables complex shaping of the atomic wavefront.

quant-ph↗

arXiv2024

Theoretical consideration of a twisted atom

We investigate the twisted state of an atom and the possible effect of such a state on the properties of the photons emitted as a result of an electron transition in that atom. We first propose a framework for describing the twisted atomic state, and then explore possible differences in the nuclear recoil effects in the twisted atom compared to those in the plane-wave atom. We conclude that if the initial atomic state is twisted, then the photon distribution is altered. We point out that in a certain observation scheme, one can detect a feature of this twist in the distribution of the emitted photons, even in zero order in $m/M$.

quant-ph↗

arXiv2023

Bounds on geometric wakefields in collimators and step transitions of arbitrary cross sections

We present the wakefield conformal mapping technique that can be readily applied to the analysis of the radiation generated by an ultra-relativistic particle in the step transition and a collimator. We derive simple analytical expressions for the lower and upper bounds of both longitudinal and transverse wake potentials. We test the derived expressions against well-known formulas in several representative examples. The proposed method can greatly simplify the optimization of collimating sections, as well as become a useful tool in the shape optimization problems.

physics.acc-ph↗

arXiv2023

Unitary equivalence of twisted quantum states

We present the time dynamics of twisted quantum states. We find an explicit connection between the well-known stationary Landau state and an evolving twisted state, even when the Hamiltonian accounts for linear energy dissipation. Utilizing this unitary connection, we analyze nonstationary Landau states and unveil some of their properties. The proposed transformation enables simple evaluation of different operator mean values for the evolving twisted state based on the solution to the classical Ermakov equation and matrix elements calculated on the stationary Landau states. The suggested formalism may significantly simplify analysis and become a convenient tool for further theoretical development on the dissipative evolution of the twisted quantum wave packet.

quant-ph↗

arXiv2023

Single-shot Transverse Wakefield Mapping with a Hollow Electron Beam

Beam-driven wakefield accelerators are foreseen to enable compact accelerator-based light sources and play a critical role in future linear-collider concepts. This class of wakefield acceleration has been extensively studied over the last four decades with a focus on demonstrating its ability to support high-accelerating gradient and, most recently, enhanced transformer ratios. Yet, the associated detrimental transverse wakefields have not been examined in as many details due to the limited diagnostics available. In this paper, we introduce a beam-based single-shot transverse-wakefield measurement technique. The approach employs a witness ''hollow" electron beam to probe the wakefields generated by a drive bunch. We show how the transverse distortions of the hollow probe provide a direct measurement of the wakefield distribution within the area circumscribed by the probe. The ability to directly measure a full structure of the transverse wakefield could help to develop mitigation schemes and ultimately suppress the adverse beam-break-up instabilities. We discuss a practical implementation of the method and demonstrate its performance with the help of start-to-end simulations.

physics.acc-ph↗