arXiv subjects

Anahit H. Shamamian

Publications and source records attributed to Anahit H. Shamamian.

3 recordsLinked to original sources

arXiv2025

FEL Gain Enhancement in an Optical Klystron

A system comprising two identical helical or planar undulators separated by a gap -- viz., an optical klystron (OK) -- is investigated. A formula for the frequency distribution of spontaneous radiation at zero angle is derived. It is shown that the spontaneous radiation line shape gradually narrows with increasing distance (up to an optimal value) between the undulators due to the constructive interference of the radiation fields formed in each of them, while the number of radiated photons decreases. The free-electron laser (FEL) gain coefficient also gradually increases, since it is proportional to the derivative of the spontaneous radiation line shape. Using the undulator parameters of the SASE XFEL and the bunch parameters of the LCLS, the total gain coefficient in the X-ray range is on the order of 2.5 and, for a different electron energy, reaches approximately 90 in the water window frequency range.

physics.acc-ph↗

arXiv2024

Line shape of soft photon radiation generated at zero angle in an undulator with a dispersive medium

The problem of undulator radiation from a bunch of charged particles, taking into account a medium polarization, is considered. In a dispersive medium, at a zero angle, in addition to hard photons, soft photons are also generated. If the wavelength of the soft photons is greater than or equal to the longitudinal size of the microbunches formed during the FEL process, the microbunches radiate coherently. Consequently, the radiation of the bunch will be partially coherent. As a result, intense, quasi-monochromatic, and directed X-ray photon beams are produced, which can have wide practical applications.

physics.acc-ph↗

arXiv2024

Dielectric permittivity of electron plasma with laser beat waves

Within the framework of the kinetic method, the process of interaction of a rarefied electron plasma with laser beat waves is investigated taking into account the initial spread in the velocities of plasma particles. Using the expression for the spectral distribution function of plasma particles in the presence of laser beat waves, an anisotropic tensor of the plasma dielectric permittivity is obtained. In this case, an expression for the nonequilibrium current density induced by the perturbed field and the constitutive equation connecting the conductivity tensor with the dielectric permittivity are determined. Assuming that in equilibrium the particle distribution function has the form of the Maxwellian distribution function, the dielectric tensor is diagonalized. Analytical expressions are obtained for the longitudinal and transverse components of the dielectric permittivity.

physics.plasm-ph↗