arXiv subjects

A. Angelow

Publications and source records attributed to A. Angelow.

4 recordsLinked to original sources

arXiv2008

Method of Linear Invariants for description of beam dynamics of FEL undulator

We propose a new model for description of electrons beam dynamics in Free Electron Laser (FEL) undulator, based on the method of linear time-dependent invariants of quantum-mechanical charge particle. The magnetic field has periodic structure along the undulator. For this problem, described by time-dependent quadratic Hamiltonian, we obtain exact solution. The time-evolutions of the tree quantum fluctuations: covariance cov(q,p), var(q) and var(p) for the charge particle in this case are also determined. This research will help to optimize the FEL undulator: for example, using a 2.5 GeV linear electron accelerator it will be possible to emit radiation at 1.5 nm and shorter length. This method could be applicable also to any device with periodic structure of applied field (e.g. Tokamak, cyclic accelerators) for the case of charge non-relativistic quantum particles.

quant-ph↗

arXiv2000

Proximity Effect in Bulk LaBa_2Cu_3O_{7-y} Samples with Ag Additions

Bulk LaBa_2Cu_3O_(7-y) samples with different Ag additions were investigated. It was shown that Ag does not enter the crystallographic structure of the superconductor and segregates on the grain boundary region. Current path in these samples occurs through the proximity connected grains and this was confirmed from the temperature dependence of the critical current density and mutual inductance. By using the theory developed for the thin film structures we conclude that growing of the Ag content increased the effective cross section and the normal metal thickness. The first one prevails at low concentration increasing the current. The second dominates at higher concentration leading to saturation or even lowering of the critical current.

cond-mat.supr-con↗

arXiv1998

Frequency Switching of Quantum Harmonic Oscillator with Time-Dependent Frequency

An explicit solution of the equation for the classical harmonic oscillator with smooth switching of the frequency has been found . A detailed analysis of a quantum harmonic oscillator with such frequency has been done on the base of the method of linear invariants. It has been shown that such oscillator possesses cofluctuant states, different from widely studied Glauber's coherent and "ideal" squeezed states.

quant-ph↗

arXiv1998

Light Propagation in Nonlinear Waveguide and Classical Two-Dimensional Oscillator

The quantum optical problem of the propagation of electromagnetic waves in a nonlinear waveguide is related to the solutions of the classical nonstationary harmonic oscillator using the method of linear integrals of motion [ Malkin et.al., Phys Rev. 2D (1970) p.1371 ]. An explicit solution of the classical oscillator with a varying frequency, corresponding to the light propagation in an anisotropic waveguide is obtained using the expressions for the quantum field fluctuations. Substitutions have been found which allow to establish connections of the linear and quadratic invariants of Malkin et.al. to several types of invariants of quadratic systems, considered in later papers. These substitutions give the opportunity to relate the corresponding quantum problem to that of the classical two-dimensional nonstationary oscillator, which is physically more informative.

quant-ph↗