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We propose a slanting collision scheme for Compton scattering of a laser light against a relativistic electron beam. This scheme is suitable to generate an energy-tunable X/gamma-ray source. In this paper, we present theoretical study and simulation of the spectral, spatial and temporal characteristics of such a source. We also describe two terms laser-Compton scattering (LCS) experiments at the 100 MeV Linac of Shanghai Institute of Applied Physics, where quasi-monochromatic LCS X-ray energy spectra with peak energies of similar to 30 keV are observed successfully. These preliminary investigations are carried out to understand the feasibility of developing an energy-tunable quasi-monochromatic X/-gamma-ray source, the future Shanghai Laser Electron Gamma Source.

Numerical simulations are conducted on the scheme of energetic proton-bunch driven plasma wakefield acceleration and the possibility of the selfinjection scenario in proton-bunch driven plasma wakefield acceleration by using a density transition of plasma with the help of 2D3V PIC code. The simulations show that enhanced selfinjection of electrons in the scenario is realized successfully. It is found that the number of trapped particles increases as the amplitude of density transition increases．

The transport of a relativistic electron beam in dense plasmas with a cold return electron current is examined by two-dimensional particle-in-cell simulation. The filamentation and coalescence of currents and related magnetic field patterns, caused by the electromagnetic-beam-plasma instability, are observed. In the later simulation time, the electrons of the relativistic electron beam are trapped into the potential wells of the wave excited by the instability, and transport resonantly with the wave.

In this paper we study the effects of transverse profile of incident laser on trapping of electrons in an electron bow-wave injection regime. By using the particle-in-cell code, we find that the super-gaussian profile laser pulse can drive more energetic electrons of the electron bow-wave into the bubble with higher longitudinal injection velocity. At last, the total number of trapped electrons increases almost 5 times. And the quality of electron beam is also improved obviously.

In this paper we suggest a simple structure consisting of a thin foil and a solid target with specified gap width to achieve the laser-field amplification, and study the trapping process of a single pulse. Both the theoretical and simulation results show that the EM fields are trapped as standing waves between two layers of enhanced electron density. The laser energy can be accumulated like the accumulation of charges in capacitor, a stably trap is reached after several oscillations. The compressing and the expanding of the electron layer, generated by the incident light pressure, the trapped light pressure and the charge electrostatic fields, are the direct reason for the energy oscillations.

The X-ray ionizations and atmospheric temporal evolutions of different altitude nuclear explosions at different distances are numerically simulated. The effects of energetic electron impact ionization on radiation ionization process are analyzed in this paper. It is concluded that the energetic electron impact ionization process is important for radiation ionization, and in the case of 1 kt equivalent explosion at 80 km, the electron density at 1.5 km distance from explosion center increases two orders because of the energetic electron impact ionization. In 5 μs the spectral energy distribution of energetic electrons varies with time, and the number density of energetic electrons decaying with electron energy will present an approximately negative exponential distribution. The peak time of electron density and the influence area of ionization increase with explosion altitude increasing. The ionization effect for 1 kt equivalent explosion at 80 km has an important influence on micro-wave communication in a 100 km range.

The X-ray ionizations and the atmospheric temporal evolutions with different altitude nuclear explosions are numerically simulated in this paper. It is concluded that the density of electrons generated by X-ray ionization has a peak value at 100 ns after the X-rays have arrived, and the peak density reduced with the increase of distance from the stripped nucleus area. The life time of electrons is long, and increases with the distance from the stripped nucleus area. O+, O2+, N2+ are generated by X-ray ionization. The distance of X-ray ionization in atmosphere is within a few tens of kilometers. The peak density of explosion at 80 km high is larger than at 120 km high in the area close to stripped nucleus area, but the scenario is opposite in the area far from stripped nucleus area.

The X-ray radiation ionization processes at different altitudes of atmosphere with high-altitude nuclear explosions are numerically simulated, and the temporal and spatial distribution curves of electrons are shown in this paper. The electron density has one maximal point with 1 kt equivalent explosion at 80 kilometers, which is near the explosion point. It is different from the explosion point above 80 kilometers, and the electron density has two maximal points in that case. One is near the explosion point, and the other is near 90 km altitude, where the ionization effect range of high-altitude nuclear explosion is widest. The X-ray of high-altitude nuclear explosion has no effect at below 70 km altitude. With the increase of radiation angle, the altitude of the second electron density maximal point increases, and the cut-off altitude of X-ray increases too.

This paper focuses on the influence upon the structure of the wake-field and the production of hot electrons due to a finite-width laser of high intensity and ultra-short duration propagation through an underdense plasma. Under the action of lognitudinal and transverse pondermotive forces, the plasma density forms a horseshoe cavity which acts as a moving convex to make the laser pulse self-focusing. The wake wave front curvature increases with time until a transverse wav e breaking occurs which depresses the wave breaking limit of the electrostatic f ield. The decrease of transverse wave breaking pushes more electrons into the ac celerating phase region to be trapped by wake wave and decreases the maximum ele ctronic kinetic energy.