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    Coherent emission and gain from a bunched electron beam
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    Abstract:
    The radiation from a modulated electron beam, such as that produced in a radio-frequency accelerator, passing through a magnetic undulator is analyzed. The authors show that in a waveguide free electron laser (FEL), this may lead to an emission of a significant amount of coherent radiation in the far infrared to millimeter wave range. A simple and powerful method of calculating the spectral distribution of the radiated power is presented along with an analysis of the gain and the saturated power. The experimental results of spontaneous emission measurements on an RF driven FEL, are presented and compared to theoretical predictions.< >
    Keywords:
    Undulator
    Free-electron laser
    Extremely high frequency
    The performance of a free-electron laser (FEL) depends significantly on the various parameters of the driving electron beam. In particular, a large energy spread in the beam results in a substantial reduction of the FEL gain, an effect which is especially relevant when one considers FELs driven by plasma accelerators or ultimate storage rings. For such cases, one possible solution is to use a transverse gradient undulator (TGU). In this concept, the energy spread problem is mitigated by properly dispersing the electron beam and introducing a linear, transverse field dependence in the undulator. This paper presents a self-consistent theoretical analysis of a TGU-based, high-gain FEL which takes into account three-dimensional (3D) effects, including beam size variations along the undulator. The results of our theory compare favorably with simulation and are used in fast optimization studies of various x-ray FEL configurations.
    Undulator
    Free-electron laser
    Free electron model
    Abstract : This communication illustrates the technique used for the dipole moment measurement of a set of SmCo permanent magnets. These magnets have been used for the realization of a laser undulator for the ENEA-Frascati free electron laser device. The main results of the measurements are summarized. Some criteria for the assembling of the undulator are analyzed in order to minimize the effects of the differences between the magnets. The evaluation of experimental error measurement is included. Finally it is described the computer code that suggested the best configuration according to the above criteria.
    Undulator
    Free-electron laser
    Dipole magnet
    Realization (probability)
    Citations (0)
    High-gain free-electron lasers (FELs) are being developed as extremely bright sources for a next-generation x-ray facility. In this paper, we review the basic theory of the start-up, the exponential growth, and the saturation of the high-gain process, emphasizing the self-amplified spontaneous emission. The radiation characteristics of an x-ray FEL, including its transverse coherence, temporal characteristics, and harmonic content, are discussed. FEL performance in the presence of machine errors and undulator wakefields is examined. Various enhancement schemes through seeding and beam manipulations are summarized.
    Undulator
    Free-electron laser
    Free electron model
    High-gain antenna
    An unaveraged 3D model of the free electron laser (FEL) is presented which is capable of modelling electron interactions with broad bandwidth radiation that includes electron beam shot-noise and coherent spontaneous emission effects. Non-localised electron transport throughout the beam is modelled self-consistently allowing better modelling of systems where a larger electron energy range is required. The FEL interaction can be modelled with undulator fields of variable polarisation. A modular undulator system allows insertion of other magnetic structures, such as chicanes. A set of working equations that describe the model are derived, the parallel numerical method that solves them described, and some example FEL interactions presented.
    Undulator
    Free-electron laser
    Citations (0)
    A wide range-infrared free electron laser (IR-FEL) is being constructed for science and industrial applications in the Accelerator Technologies Institute, Ankara University. In the facility, in order to obtain electron beam with energy 40 MeV, 4.5 cell RF cavities are considered. IR-FEL system covers 2.5-250 µm wavelength range that based on 15-40 MeV e-linac and two undulators to generate up to 250 μm coherent infrared radiations. In this study, IR-FEL Resonator System parameters, mirror parameters, undulator parameters besides mirror diffraction losses are calculated and optimized with analytically and by using Optical Propagation Code and GENESIS 1.3. These Codes are also used to simulate beam behavior inside the resonator and along the undulator while GLAD Code is used for mirror diffraction losses.
    Undulator
    Free-electron laser
    Free electron model
    Citations (2)