[en] The behavior of a FEL operating in the saturated pulsed regime, may be reproduced by the linear FEL integral equation, suitably modified to include saturation effects through a gain depression coefficient depending on the laser intensity. This simple method allows to evaluate several FEL parameters like gain, efficiency, band-width and optical pulse duration as functions of the optical cavity length, only with a numerical integration. The predictions have been compared with available experimental and numerical data, and the method has been applied to estimate the operating characteristics of some planned FEL experiments

[en] We analyze the problems associated with the generation of coherent undulator radiation by an e-beam having a longitudinally correlated phase space. The problem is treated by exploiting a suitable extension of the Courant-Snyder formalism to longitudinal dynamics. The role played by the bunching is clarified and a matching condition for the longitudinal phase space is found. (author)

[en] We analyse the behaviour of a master oscillator power amplifier FEL, where the amplifier operates on a harmonic of the oscillator. The premature saturation of the amplifier output power, due to the induced energy spread of the oscillator, is studied. The effects of saturation in the oscillator can be eliminated when the modulating section is provided with an optical-klystron configuration. We show that this configuration ensures a stable output power after the amplifier section

[en] In this note we analyze the structure of the code TREDI, devoted to the simulation of space-charge-dominated beam dynamics in three spatial dimensions. The integration method, based on the Lienard-Wiechert potential formalism, is quite general and allows the analysis of a wide class of physical problems ranging from Coulomb repulsion in low-energy beams to coherent synchrotron radiation effects in he high-energy regime. This versatility has been exploited in a simulation where the beam dynamics is followed starting from the cathode, through the acceleration/transport system, up to an undulator magnet

[en] We use the method of Padg approximants and Fourier transform techniques to treat analytically the problem of transverse and longitudinal mode evolution in FELs. We obtain simple relations providing a transparent understanding of the dynamic of pulse propagation effects and of transverse mode guiding. We discuss the interplay with inhomogeneous broadening effects and derive gain formulae including longitudinal and transverse mode couplings

[en] We discuss non-conventional undulator configurations for SASE FEL devices aimed at enhancing the emission on higher harmonics, reducing the saturation length and operating in less sensitive conditions for the electron beam qualities

[en] We develop a self-consistent general purpose code modelling the storage ring free electron laser devices. The code accounts for the beam longitudinal dynamics and the laser pulse propagation and is capable of reproducing the wealth of phenomenology associated with the laser-electron beam interplay and provides a deeper understanding of the mechanisms underlying the role of the laser in the suppression of instabilities of longitudinal type

[en] We discuss theγ-ray production by Compton backscattering of intracavity storage ring Free-Electron Laser radiation. We use a semi-analytical model which provides the build up of the signal combined with the storage ring damping mechanism and derive simple relations yielding the connection between backscattered. Photons brightness and the intercavity laser equilibrium intensity

[en] This paper is devoted to the study of some calculus techniques developed to analyse the spectral contents of the undulator wiggler radiation. Two different approaches are presented: 1) the Bessel function method; 2) a numerical procedure known as S-Luce. A detailed description of the two methods, together with a careful comparative analysis between their specific results, is presented (C.P.)

[en] Results are presented of a numerical code dedicated to the analysis of the spectral features of the undulator radiation. The developed numerical model includes the near-field effects, the inhomogeneous broadening due to the electron beam energy spread and emittances and the magnetic field random magnetization errors