The yield of alpha particles in neutronless fusion reactions 11B +p in plasmas produced by picosecond laser pulses with the peak intensity of 2 x 10(18) W/cm2 has been observed. Experiments were carried out on the "Neodymium" laser facility at the pulse energy of 10-12 J and pulse duration of 1.5 ps. The composite targets 11B + (CH2)n were used. The yield of 10(3) alpha particles per pulse has been observed. The energy spectrum of alpha particles contains two maxima: at 3-4 MeV and at 6-10 MeV . The first of these peaks corresponds to the secondary alpha12 particles at the decay of the intermediate first excited state of 8Be, whereas the second peak demonstrates generation of alpha1 particles in the reaction 11B +p with the production of this excited state. Simultaneous measurements of neutrons result in zero yield, which proves the observation of neutronless fusion reactions in our experiments.

A very fast method to account for charged particle dynamics effects in calculations of spectral line shape emitted by plasmas is presented. This method is based on a formulation of the frequency fluctuation model (FFM), which provides an expression of the dynamic line shape as a functional of the static distribution of frequencies. Thus, the main numerical work rests on the calculation of the quasistatic Stark profile. This method for taking into account ion dynamics allows a very fast and accurate calculation of Stark broadening of atomic hydrogen high- n series emission lines. It is not limited to hydrogen spectra. Results on helium- beta and Lyman- alpha lines emitted by argon in microballoon implosion experiment conditions compared with experimental data and simulation results are also presented. The present approach reduces the computer time by more than 2 orders of magnitude as compared with the original FFM with an improvement of the calculation precision, and it opens broad possibilities for its application in spectral line-shape codes.

Recent experimental and theoretical investigations are reviewed concerning the generation of fast charged particles and superstrong magnetic fields in the interaction of ultrashort laser pulses with solid targets. The mechanisms of generating fast charged particles in superstrong light fields of laser radiation with intensities ranging from 10 17 to 10 21 W cm ±2 are considered. Electron acceleration due to vacuum heating, the ponderomotive potential, resonance absorption, the laserdriven wake field in the underdense part of plasma, cyclotron mechanism and some other mechanisms are thoroughly analyzed. Experimental data on the acceleration of protons and atomic ions by spatial charge fields on thin and thick solid targets are presented and theoretically interpreted. Particular attention is paid to the generation of superstrong quasistatic magnetic fields in laser plasmas and methods for measuring them under the action of various laser pulses of both femtoand picosecond durations. The possible formation of magnetic plasma configurations and magnetic plasma confinement are discussed.

A very fast method for calculating line shapes in the presence of an external magnetic field accounting for charge particle dynamics is proposed. It is based on a reformulation of the frequency fluctuation model, which provides an expression of the dynamic line shape as a functional of the static distribution function of frequencies. In the presence of an external magnetic field, the distribution of intensity and polarization of the emission depends on the angle between the observation line and the magnetic field's direction. Comparisons with numerical simulations and experimental results for various plasma conditions show very good agreement. Results on hydrogen lines in the context of magnetic fusion and the Lyman-α line, accounting for fine structure, emitted by argon in the context of inertial fusion, are also presented.

Time-resolved high-resolution soft x-ray spectra from gas-puff injected Ar impurity ions have been investigated for neutral beam heated and ohmically heated discharges in the TEXTOR tokamak. The experimental spectra show systematic deviations from corona model calculations for the line intensities of the forbidden He-like lines x, y, z and the Li-and Be-like dielectronic satellite spectra: theoretical corona model calculations predict intensities significantly too low. High-intensity Li-like inner-shell excited satellites correlate with the neutral beam injection. The discrepancies could also be observed in the stationary phase of an inductively heated discharge. In the heating phase the discrepancies are even larger. We propose charge-exchange processes between the neutral atoms and the impurity ions as an explanation of the experimental findings. Good agreement with the experimental observations can then be obtained without the need for invoking large (anomalous) diffusion coefficients. A self-consistent coupling of the population kinetics of the neutrals and the impurity ions, also taking into account charge-exchange processes from excited states of hydrogen/deuterium permit the determination of the neutral fraction and of the electron lifetime on the sole basis of impurity spectra analysis. Independent Monte Carlo simulations of neutral gas transport also provides the ionization degree in the centre and the electron lifetime. These calculations are also in good agreement with the spectroscopic results.

No abstract

No abstract

The alpha particles are coupled to the hydrogen/deuterium background plasma via charge exchange processes. Population kinetics calculations show that in the framework of standard models, the charge transfer from hydrogen/deuterium excited states to helium leads to a strong divergence of the atomic populations and to a critical dependence on the number of quantum states retained in the simulations. The divergence is related with the large crosssections for charge transfer from excited states of the background atoms. For typical parameter conditions (e.g., ITER) the charge-exchange-induced population flow may even reach the level of flow typically induced by turbulent diffusion. A self-consistent excited-states coupling approach of atomic kinetics is proposed, which avoids divergences and critical dependence on the number of states. This approach also removes free parameters from the system and provides therefore the ideal basis for a pure diffusion analysis in space which is requested to test global effects of turbulent transport theories.The confinement of the fusion plasma is one of the most important issues in the magnetic fusion research and intensive efforts have therefore been devoted to the understanding of the particle transport. However, the physical processes that underlie plasma transport in torodially confined plasmas are not so well understood. The plasma transport induced by Coulomb collisions (the so-called classical or neo-classical transport) is often much less than what is actually observed [1, 2] and thus the transport is called anomalous.Methods which determine the particle transport independent of theoretical plasma models are therefore of extraordinary and fundamental importance in the magnetic fusion research. Spectroscopic methods have turned out to be very effective. One of the most powerful spectroscopic methods is based on the space-and time-resolved observation of line emission from impurity ions [1][2][3]. This emission is simulated from an atomic physics model with given temperature and density profiles [1,4] and contrasted with the experimental data. Diffusion and convective velocity parameters, D and V , respectively are then determined by matching best the experimental observations [1-3].