The dc and 100 kHz low pressure discharges in acetylene-nitrogen mixture have been studied here. Optical emission spectroscopy was used for identification of active plasma components and to determine plasma temperature. Relative concentrations of H, CH and CN were investigated versus experimental conditions by optical actinometry techniques. Emission intensities of N2 and N$_2^+$ normalized to intensity of argon line were also monitored as a function of experimental parameters. The rotational temperatures from the N$_2^+$ B$^2\Sigma_{\rm u}^+$-X$^2\Sigma_{\rm g}^+$ (0-0) and CN B2Σ+-X2Σ+ (0-0) bands and vibrational temperatures from the CN (B2Σ+-X2Σ+) and N2 (C$^3\Pi_{\rm u}$-B$^3\Pi_{\rm g}$) spectra were determined. Plasma processes and plasma equilibrium state were discussed.

An iterative finite element technique is proposed as a numerical tool to solve Poisson's equation in coaxial system during the positive DC corona discharge. The physical - mathematical model developed by Hartmann which separates the interelectrode space in two distinct regions is adopted. The magnitude of the electric field at the ionisation-region/drift-region interface in air is now well known. It is equal to the value of the minimum ionisation field which is taken as a boundary condition or a convergence criterion of space charge at this border. The effectiveness of the proposed method has been tested through its application to the coaxial system where the electric field has been measured with the linear biased probe. The obtained results are in agreement with those obtained experimentally. The classical Kaptzov's assumption, largely used in the literature, is also discussed in this work in terms of the corona wire radius. The calculated electric field at the corona wire surface, with and without resorting to the Kaptzov's assumption, shows that, for large wire radius the assumption is valid. However, for very thin wires the disagreement with the measurements values is important.

Using a high-resolution Si(Li) X-ray detector, the Lα, Lβ and Lγ X-ray fluorescence cross sections and the relative intensities for elements with 57 ≤ Z ≤ 71 were measured at photon incident energy of 16.9 keV. We also theoretically calculated these cross sections, and discussed the experimental results in comparison with the theoretical values. As a result, we have found that our experimental results are in good agreement with the theoretical ones.

The non-local kinetics of the electrons in a cylindrical, axially symmetric hollow cathode discharge is theoretically investigated. A new multi-term method for solving the inhomogeneous Boltzmann equation in cylindrical coordinates has been developed to adequately describe the pronounced anisotropy of the electron velocity distribution function expected in the cathode fall region. This method is based on a tensorial representation of the expansion of the electron velocity distribution function in spherical harmonics. The resultant hierarchy of component equations has been specified to cylindrical geometry with rotational symmetry and axial uniformity. A subset of component equations could be separated which determines the relevant distribution parts needed to analyze the radial behaviour of important electron properties in the hollow cathode. Using measured profiles of the electric field, this subset has numerically been solved for a helium plasma at a discharge current of some mA and a pressure of few torr. Based on this approach in addition to the radial variation of the energy distribution, that of important transport properties and collision rates is studied and the non-local particle and power balance of the electrons are analysed. Some theoretical results are compared with available experimental ones.

Experiments were carried out to examine convection in a liquid fuel film subjected to flame spreading over the film. The flow in the liquid phase indicates the presence of vortices which are intimately associated to a pulsating regime of flame spread. Results bore out the close link between this regime and vortex structure generation in the liquid film. Thorough description of the core vortex structure shows how liquid motion controls the flame spread rate at a given temperature initially assigned to the liquid. Experiments were subsequently conducted over a wide range of initial liquid temperatures that directly controlled the characteristic size of liquid vortex structure. Such configurations contributed to both heat transfer evolution and a modification of the pulsating regime featuring an increase in the rate of spread.

This paper deals with the solution of inverse problems in magnetostatics. The cases the authors have broached are finding the current density or positions of air coils on the basis of magnetic field measurements. These problems are ill-posed, so regularization techniques are needed. The authors discuss the main iterative regularization principles, and the stability issues of these inverse problems. This method is applied to MRI magnets. Numerical results are presented.