Transition radiation from a beam of hot electrons generated in ultraintense laser plasma interaction is theoretically studied. The total radiation is separated into two parts: one is incoherent transition radiation (ITR), the other is coherent transition radiation (CTR). The spectrum of ITR just depends on the particle velocity distribution in the beam. The angular distribution of ITR varies from sin2 u, and approaches the angular distribution of the beam when the hot electron temperature increases from the nonrelativistic limit (T《mc2) to the ultrarelativistic limit (T》mc2). The spectrum of CTR is dependent on the particle configuration as well as their velocities. Any microbunching in the beam can greatly enhance the CTR intensity at the microbunching frequency, from which the dominant heating process can be inferred. The effects of target thickness and hot electron temperature on CTR intensity are also calculated. The simplified model shows that the CTR intensity decreases with the increase of the target thickness, and increases with the hot electron temperature. The divergence of the beam can broaden the CTR spectrum.

Hot electrons and optical emission are measured from the rear surface of a metallic foil. The spectra of the optical emission in the near infrared region have a sharp spike around the wavelength of the incident laser pulse. The optical emission is ascribed to coherent transition radiation due to microbunching in the hot electron beam. It is found that the optical emission closely correlates with the hot electrons accelerated in resonance absorption.

The intermittent chaos in the multicomponent plasmas with negative ions has been investigated experimentally. The phenomena are modeled as a variant of classical type-I intermittency, which is studied numerically in detail. The experimental results confirmed the numerical prediction of 1/f noise, the probability distribution of laminar length, and the scaling law of Lyapunov exponents. A qualitative explanation on the intermittent chaos in the multicomponent plasmas with negative ions is also given.

Abstract. A numerical solution to the linearized ion Fokker-Planck (FP) equation is presented. By reducing the FP equation to an eigenvalue problem via moment expansion of a perturbed ion distribution function, the frequencies and damping rates of ion-acoustic waves and the specific heat ratio are calculated. Numerical calculation shows that this technique is very efficient, as ion Landau damping is negligible in comparison with collisional damping.

The dynamic form factor for Thomson scattering with a non-Maxwellian (super-Gaussian) electron velocity distribution is analytically and numerically studied for the first time. Both the ion and electron features of the spectra for a. 1 are found to be affected strongly. For the ion feature, the use of the usual theoretical spectra with the assumption of a Maxwellian distribution for fitting the measured Thomson scattering spectra may have resulted in some errors in calculating the plasma parameters in high-Z plasmas irradiated with high intensity light. However, it is impossible to use the ion feature of the measured spectra alone to deduce the form of the electron distribution. For the electron feature, the spectral shape (in particular the peak amplitude) changes sensitively with the distribution index. It would be possible to detect the super-Gaussian distribution by simultaneously measuring the ion and electron features of the spectra.