We examine the electron acceleration induced by an ultra-relativistic intensity laser–plasma interaction in a two-dimensional plasma channel in the presence of a self-generated transverse magnetic field. We find that the electron dynamics is strongly affected by the laser pulse polarization angle, plasma density, and magnetic field strength. We investigate in detail, the dependencies of the electron acceleration in terms of different parameters and find excellent agreement with non-magnetized plasma in the absence of the magnetic field. The numerical results show that the self-generated magnetic field plays a constructive role in the electron acceleration process. It is shown that electron acceleration is more affected by self-generated magnetic field for the laser radiations with large polarization angles. The numerical results show the maximum enhancement for electron acceleration for a laser radiation with polarization angle θ = π/2.

The development of laser wakefield accelerators (LWFA) over the past several years has led to an interest in very compact sources of X-ray radiation – such as “table-top” free electron lasers. However, the use of conventional undulators using permanent magnets also implies system sizes which are large. In this work, we assess the possibilities for the use of novel mini-undulators in conjunction with a LWFA so that the dimensions of the undulator become comparable with the acceleration distances for LWFA experiments (i.e., centimeters). The use of a prototype undulator using laser machining of permanent magnets for this application is described and the emission characteristics and limitations of such a system are determined. Preliminary electron propagation and X-ray emission measurements are taken with a LWFA electron beam at the University of Michigan.

High-intensity femtosecond laser–plasma interaction experiments were performed to investigate laser–plasma wakefield acceleration in the “bubble” regime. Using a 15 TW laser pulse, the emission of side-scattered radiation was spectrally and spatially resolved and was consequently used to diagnose the evolution of the laser pulse during the acceleration process. Side-scattered emission was observed immediately before wavebreaking at a frequency of ωL + 1.7ωp (where ωL is the laser frequency and ωp is the background plasma frequency). This emission may result from scattering of laser light by large amplitude plasma oscillations generated in the shell of the wakefield “bubble” and which occurs immediately prior to the wavebreaking/injection process. The observed variation of the frequency of scattered light with electron density agrees with theoretical estimates.

The quantum behavior of the system composed of an electron in an electromagnetic field is described by the Dirac equation, whose solution is a wave function represented by a column matrix with four components. We prove, without using any approximation, that these components can be put in a form which reveals directly the values of the electron energy, laser beam intensity, or amplitude of the electric field intensity, for which the quantum electrodynamics effects are generated. Our results are in good agreement with the experimental data reported in the literature. We prove that the four components of the wave function verify the continuity equation of quantum electrodynamics. Our treatment is in good agreement with the Compton relation. We show that the interaction of electrons with laser beams could be modeled using classical approaches regardless of the laser beam intensity as long as the electrons are non-relativistic, in agreement with published experimental data.

The main purpose of this theory is to present a simple picture of magnetic field generation by a relativistic equilibrium counterstreaming electron–negative hydrogen ion (e–H−) plasmas propagating parallel to an ambient external magnetic field. The existence of such kind of plasma flows can be imagined during the negative hydrogen ion propagation through neutralizing plasma, in order to generate an energetic neutral hydrogen beam. The produced magnetic field deflects the electron and negative hydrogen ion flows and reduces the efficiency of hydrogen neutral beam generation. We focused our analysis on the influences of the negative hydrogen ion contribution, the particles thermal velocity and the external magnetic field on the growth rate of generated sheared magnetic field. The dispersion relation is obtained using a relativistic two-fluid model and Maxwell equations. The analytical and numerical solutions admit generation of a purely growing transverse electromagnetic field across the ambient external magnetic field. It is shown that H− current filaments are responsible for deep penetration of the sheared magnetic fields into plasma, however, applying a weak magnetic field ${\rm \omega} _{{\rm ce}}^2 {\rm \ll} {\rm \omega} _{{\rm pe}}^2 $ suppresses magnetic field generation for a counterstreaming e–H− plasma in the absence of H− ions dynamics. On the other hand, a magnetic field exists with a small growth rate for strongly magnetized (${\rm \omega} _{{\rm ce}}^2 \;{\rm \gg}\; {\rm \omega} _{{\rm pe}}^2 $) e–H− plasma when the influence of H− ions is included. Although the growth rate is small, we expect that magnetic field generation is further amplified and the penetration depth is increased owing to H− ions stream, on a time scale much longer than the plasma period $t\;{\rm \gg}\; {\rm \omega} _{{\rm pe}}^{ - 1} $.

We prove that the radiation damping force and the rate of change of the damping energy, in the Landau-Lifshitz forms, in interactions between very intense laser beams and relativistic electron beams, are periodic functions of only one variable, that is the phase of the electromagnetic field. The property is proved without using any approximation, in the most general case, when the degree of polarization of the electromagnetic field, the initial phase of the incident field and the initial energy of the electron have arbitrary values. This property leads to a strong simplification of the calculation of the radiation reaction parameters and of their dependence on the initial electron energy and angular frequency of the laser beam. Our analysis is performed in the proper inertial system of the electron. The radiation reaction is significant for laser beam intensities of the order 1022 W/cm2, and for electron energy greater than 1 GeV. The calculations reveal limitations of the method of generating hard radiations by interactions between laser beams and relativistic electron beams.

We have performed extensive one dimensional particle-in-cell (PIC) simulations to explore generation of electrostatic waves driven by two-stream instability (TSI) that arises due to the interaction between two symmetric counterstreaming electron beams. The electron beams are considered to be cold, collisionless and magnetic-field-free in the presence of neutralizing background of static ions. Here, electrons are described by the non-extensive q-distributions of the Tsallis statistics. Results shows that the electron holes structures are different for various q values such that: (i) for q > 1 cavitation of electron holes are more visible and the excited waves were more strong (ii) for q < 1 the degree of cavitation decreases and for q = 0.5 the holes are not distinguishable. Furthermore, time development of the velocity root-mean-square (VRMS) of electrons for different q-values demonstrate that the maximum energy conversion is increased upon increasing the non-extensivity parameter q up to the values q > 1. The normalized total energy history for a arbitrary entropic index q = 1.5, approves the energy conserving in our PIC simulation.

Accurate dose calculations are very important in radiotherapytreatment planning. The Monte Carlo method has proven to be an accurateand reliable method for simulation of the dose distributions fromelectron beams and can provide theoretically more accurate distributionsthan conventional planning system algorithms (e.g. theGeneralized Gaussian Pencil Beam algorithm) for more complex targetconfigurations. The aim of this work was to assess the parametersand spectrum of a given electron beam (Varian CLINAC 2100 C/D) from experimentaldepth dose distribution and then simulate dose distributions inan experimental arrangement with a 3D polymer gel dosimeter. Thecomparison of data from experimental measurements, Monte Carlo calculationsand the planning system enabled us to verify experimentally thesimulation model and technique as well as the planning system results. Bothsimple and more complex systems (e.g. dose distributions closeto different material interfaces) can be studied. The generationand influence of the “bremsstrahlung” photons in the electron beamswas also analyzed using the simulation technique. The computations,experimental methods used and results obtained are presented anddiscussed.

A two-layer target irradiated by an intense laser to generate strong interface magnetic field is proposed. The mechanism is analyzed through a simply physical model and investigated by two-dimensional particle-in-cell simulation. The effect of laser intensity on the resulting magnetic field strength is also studied. It is found that the magnetic field can reach up to several ten megagauss for laser intensity at 1019 Wcm−2.

Scattering of energetic electron and proton beams by cold matter is significantly different from the scattering of these particles by plasma, which may be either highly ionized or dense strongly coupled plasma. This is due to the difference in the shielding of the target nuclei between the two cases. Quantitatively, we treat the problem by means of the Bethe Moliere multiple scattering theory and the version of this theory for plasma as derived by Lampe. We propose to use this effect as a plasma diagnostic tool, utilizing monoenergetic, well-collimated electron or proton beams produced either by femtosecond laser plasma interactions or by accelerators. The effect is first illustrated for simplicity, by calculating the widths of the angular distribution of scattered particles interacting with the extreme cases of very hot fully ionized carbon, and iron plasmas, and comparing these results to the corresponding cold material. The more relevant case of electron scattering from partially ionized iron and carbon plasmas covering the entire range from a cold to a completely ionized target is also dealt with here. This paper brings up and highlights the difference between scattering by plasma and by cold material in light of the recent proposals to employ particle beams for various fusion applications.

It is known that relativistic laser plasma interactions can already today induce accelerating fields beyond some TV/m, which are indeed capable to efficiently accelerate plasma background electrons as well as protons. An introduction to the current state of the art will be given and possible applications of these optically induced charged particle sources will be discussed.

The electric field in the temporal and spectral domain of coherent diffraction-limited transition radiation is studied. An electron bunch, with arbitrary longitudinal momentum distribution, propagating at normal incidence to a sharp metal-vacuum boundary with finite transverse dimension is considered. A general expression for the spatiotemporal electric field of the transition radiation is derived, and closed-form solutions for several special cases are given. The influence of parameters such as radial boundary size, electron momentum distribution, and angle of observation on the waveform (e.g., radiation pulse length and amplitude) are discussed. For a Gaussian electron bunch, the coherent radiation waveform is shown to have a single-cycle profile. Application to a novel THz source based on a laser-driven accelerator is discussed.

We analyze the influence of a high-intensity laser field in the inverse mean free path of electrons moving through a degenerate electron gas. Our calculations are based on the random-phase-approximation formalism, in terms of the dielectric function of the medium, where the effects of the laser field are included in the dynamical response. The main effects on the slowing down of the electrons are studied as a function of the intensity and frequency of the laser field, as well as a function of the projectile velocity. A modification of the electron inverse mean free path for plasmon and electron-hole excitations is obtained due to multiphoton-exchange processes.