Small-angle approximation in the description of radiative collective effects within an ultrarelativistic electron bunch

The problem of the evaluation of radiative collective effects accompanying accelerated motion of a short ultrarelativistic electron bunch in vacuum is considered within the framework of the small-angle approximation; second order expansion in the transverse velocity of electrons is performed in order to obtain an analytical expression for energy spread within the bunch. Comparison with earlier results by other authors shows good agreement

On self-induced transparency in laser-plasma interactions

We study fully relativistic nonlinear one-dimensional equations describing steady-state solutions for an electromagnetic wave interacting with a plasma in the self-induced transparency regime. In addition to the well-known solution that corresponds to the transmission of the electromagnetic wave into plasma, another steady-state solution is shown to exist in a certain range of amplitudes of the wave. The latter solution corresponds to total reflection of the incident wave. The coexistence of the two solutions indicates the possibility of hysteretic behavior in the self-induced transparency

Onset of nonlinear regime in beam-plasma interactions

We consider the process of excitation of a strong axisymmetrical plasma wave by a relativistic electron bunch. It is well known that in one-dimensional geometry the excited wave becomes essentially nonlinear when the beam density approaches half the plasma density, and wavebreaking occurs at beam densities higher than that. Such a simple relation, however, does not hold in three dimensions. We find that the total beam current, not only the current density, should exceed a certain threshold for nonlinearity to become visible. Just recently, new developments in accelerator technology have made it possible to produce relativistic electron beams powerful enough to enter this nonlinear regime. We show that a realistic electron bunch from an advanced accelerator can generate in its wake accelerating fields well above 10 GeV m-1

Generation of fast electrons by breaking of a laser-induced plasma wave

A one-dimensional model for fast electron generation by an intense, nonevolving laser pulse propagating through an underdense plasma has been developed. Plasma wave breaking is considered to be the dominant mechanism behind this process, and wave breaking both in front of and behind the laser pulse is discussed. Fast electrons emerge as a short bunch, and the electrostatic field of this bunch is shown to limit self-consistently the amount of generated fast electrons

Generation of fast electrons by breaking of a laser-induced plasma wave

A one-dimensional model for fast electron generation by an intense, nonevolving laser pulse propagating through an underdense plasma has been developed. Plasma wave breaking is considered to be the dominant mechanism behind this process, and wave breaking both in front of and behind the laser pulse is discussed. Fast electrons emerge as a short bunch, and the electrostatic field of this bunch is shown to limit self-consistently the amount of generated fast electrons

A Cherenkov radiator for FEL-synchronized VUV-pulses at a linac-based FEL

A possible way to carry out two-color IR + VUV pump-probe experiments at linac-based FELs is proposed. The idea is to supply an FEL facility with a gas cell filled with helium or hydrogen, so that the electron beam, upon passage through the undulator, could be used to generate ultraviolet Cherenkov radiation. Such a Cherenkov radiator is shown to provide a reasonably high spectral-angular density of photons in a wide range of wavelengths from visible (300–400 nm) down to the VUV (65–70 nm). When averaged over a macropulse, the intensity of such a source exceeds that of synchrotron radiation from a wiggler in a modern storage ring. The spatial quality of the source is inferior to that of synchrotron radiation, but the synchronization to the infrared FEL pulses, which is crucial for most applications, is obviously perfect

Modelling of laser-induced fast electron generation in a cold plasma

A 1-D model for fast electron generation by an intense, non-evolving laser pulse propagating through an underdense plasma has been developed. Plasma wave breaking is considered to be the dominant mechanism behind this process, and wave breaking both in front of and behind the laser pulse is discussed. Simulations have been performed to determine the wave breaking conditions for several different pulse shapes. Fast electrons emerge as a short bunch, and the electrostatic field of this bunch is shown to limit self-consistently the amount of generated fast electrons

Coherent synchrotron radiation transient effects in the energy-dependent region

Coherent synchrotron radiation (CSR) is a well known phenomenon that originates from coherent superposition of electromagnetic waves by ultrarelativistic electrons. CSR longitudinal effects during the passage of a Gaussian beam from a straight to a circular path have often been studied in a regime in which they are energy independent. Nevertheless, the approximations used in such a regime may fail in several practical situations, as in the case of low-energy injectors or for small-wavelength structures within the bunch distribution in CSR-related instability problems. These situations demand a deeper investigation of longitudinal transient effects in the region where the approximations above are no longer valid: a strong ¿ dependence is found, and described in this paper, in the rate of energy change induced by CSR during the transient of a Gaussian bunch between a straight and a circular path, which was studied with the help of the authors’ previous work. Results show that the overall CSR longitudinal effects, in this case, are reduced. One of the outcomes of previous work by Saldin et al. was extended to this situation and very good agreement between the two studies was found