A. Serbeto

Quantum wave kinetics of high-gain free-electron lasers

A wave kinetic equation equivalent to the Schrodinger-like equation for the electrons is derived from relativistic theory in the eikonal approximation. This equation is used to study the interaction of the relativistic electron beam in a wiggler field in the quantum regime, i.e., when the normalized quantum free-electron laser parameter ρ¯⩽1. A general quantum dispersion relation and an expression for free-electron laser instabilities are derived. Conditions for kinetic instability, which takes into account the Landau damping effect, are established.

Quantum plasma fluid model for high-gain free-electron lasers

Starting from the eikonal approximation (geometrical optics), a set of nonlinear quantum plasma fluid equations to describe the quantum free-electron laser (FEL) is presented. Subsequently, by using these fluid equations for a relativistic electron beam, interacting with stimulated radiation and an optical wiggler field, a general dispersion relation for quantum FEL instability is derived taking into account the beam space-charge mode modulated by the ponderomotive potential well. It is shown that the saturation time for the quantum FEL instability can be estimated from the solutions of three-wave coupled equations which describe the FEL dynamics in the fluid model.

Quantum fluid model of coherent stimulated radiation by a dense relativistic cold electron beam

Using a quantum fluid model, the linear dispersion relation for FEL pumped by a short wavelength laser wiggler is deduced. Subsequently, a new quantum corrected resonance condition is obtained. It is shown that, in the limit of low energy electron beam and low frequency pump, the quantum recoil effect can be neglected, recovering the classical FEL resonance condition, ks=4kwγ2. On the other hand, for short wavelength and high energy electron beam, the quantum recoil effect becomes strong and the resonance condition turns into ks=2kw/ƛcγ3/2, with ƛc being the reduced Compton wavelength. As a result, a set of nonlinear coupled equations, which describes the quantum FEL dynamics as a three-wave interaction, is obtained. Neglecting wave propagation effects, this set of equations is solved numerically and results are presented.

Fluid description of collective neutrino–plasma interaction

Abstract Classical two-fluid description of a neutrino beam interacting with a collisionless unmagnetized plasma is presented. The streaming neutrino dynamics is described by the beam density wavelike equation which is coupled to the excited plasma wave equation in a form analogous to beam–plasma interaction. The dispersion relation obtained is analyzed for elastic and inelastic neutrino plasma interactions. It is shown that the elastic interaction is the dominant scattering process with instability growth rate strong enough to generate plasma wave.

Neutrino (antineutrino) effective charge in a magnetized electron–positron plasma

Using dynamical techniques of the plasma physics, the neutrino (antineutrino) effective charge in a magnetized dense electron–positron plasma is determined here. It shown that its value, which is determined by the plasma collective processes, depends mainly on the propagation direction of plasma waves and neutrinos against the external magnetic field direction. The direction dependence of the effective charge occurs due to the fact that the magnetic field breaks the plasma isotropy. The present theory gives a unified picture of the problem which is valid for an external magnetic field below the Landau–Schwinger critical value. Comparison with some of the results from the quantum field theory has been made.

Neutrino effective charge in a plasma

Abstract By using dynamical techniques of the plasma physics, the neutrino effective charge in a plasma is determined here. Its value is determined by the plasma collective processes. The present theory gives a unified picture of the problem, and it also shows that the contribution of the proton motion can be very important, even if the direct weak interaction between neutrinos and protons is negligible. This results from the electron–proton correlations which are dominant in the low-frequency limit of the equivalent charge spectrum. Comparison with some of the results from the quantum field theory has been established.

Tokamak equilibria with non field-aligned axisymmetric divergence-free rotational flows

Rotational ideal divergence-free magnetohydrodynamic (MHD) equations are expressed in terms of transformed variables w→*=(μρ)1/2v→ and μp* = (μp + w*2/2), where v→, p, and ρ are plasma velocity, pressure, and mass density, respectively. With divergence-free flows, ∇·v→=0, the plasma density ρ does not appear in the MHD equations written in terms of w→* and μp*. The non field-aligned rotational Grad-Shafranov equation is represented in spherical coordinates. Tokamak-like axisymmetric equilibria with v→ ⊥∇ρ are obtained analytically by solving for torus solutions under only three source functions.

Neutrino-driven wakefield plasma accelerator

A classical fluid description is used to investigate the nonlinear interaction between neutrino bursts and a relativistic collisionless cold unmagnetized plasma. It is shown that during the interaction large amplitude electron plasma waves are excited in such a way that charged particles trapped in this high gradient potential can be accelerated to extremely high energies.

Gamma ray sources using imperfect relativistic mirrors

The collective backscattering of intense laser radiation by energetic electron beams is considered. Exact solutions for the radiation field are obtained, for arbitrary electron pulse shapes and laser intensities. The electron beams act as imperfect nonlinear mirrors on the incident laser radiation. This collective backscattering process can lead to the development of new sources of ultrashort pulse radiation in the gamma-ray domain. Numerical examples show that, for plausible experimental conditions, intense pulses of gamma rays, due to the double Doppler shift of the harmonics of the incident laser radiation, can be produced using the available technology, with durations less than one attosecond.

Neutrino-driven instabilities in very dense plasmas

Nonlinear interactions between intense neutrino bursts and electrostatic plasma oscillations in a very dense Fermi plasma are considered. By using the fluid description for intense neutrino bursts and the quantum hydrodynamic model for a dense Fermi plasma, we derive a system of equations that exhibit nonlinear couplings between neutrinos and electrostatic electron plasma waves/ion-acoustic oscillations. The latter incorporate the appropriate electron pressure law and the quantum force involving the strong electron density correlation in a dense Fermi plasma. The governing equations are Fourier transformed and combined to deduce the dispersion relations, which admit instabilities. It is found that for dense Fermi plasmas under extreme conditions, such as those in the interior of massive white dwarfs, the neutrino driven electrostatic instabilities develop rapidly, and they can be responsible for the neutrino energy absorption in dense astrophysical Fermi plasmas.