Table of contents

A new method of calculation of power spectra emitted by relativistic electrons has been developed. It has been shown, that one can avoid difficulties, connected with the rapidly oscillating integrands in the radiation problem. The method permits one to discover the general features of the radiation spectra at high electron energies such as: nonsynchrotron nature of the radiation process, the saw like shape of the spectrum etc. A few different particular cases are considered.

The relation between chaotic behaviour and complexity for the cubic map f_r(x) = rx³ + (1 − r)x is discussed as a function of the bifurcation parameter r. The one-dimensional map is mapped into a ternary string via symbolic dynamics in order to evaluate the complexity. We apply the complexity measure of Lempel and Ziv to this tenary string. To characterize the chaotic behaviour we calculate the Ljapunov exponent. We find that the complexity measure recognizes exactly the periodic windows of the non-linear map when the bifurcation parameter of the map is changed. Other one-dimensional maps show the same behaviour.

We study a dimer system of a generalized discrete nonlinear Schrödinger equation that interpolates between the integrable Ablowitz-Ladic equation and the nonintegrable discrete nonlinear Schrödinger equation (DNLS). We find analytically and verify numerically the occurrence of selftrapping in the parameter space of the two nonlinearity coefficients. We also study the stationary solutions and discuss their stability properties.

The notion of f-oscillators generalizing q-oscillators is introduced. For classical and quantum cases, an interpretation of the f-oscillator is provided as corresponding to a special nonlinearity of vibration for which the frequency of oscillation depends on the energy. The f-coherent states (nonlinear coherent states) generalizing q-coherent states are constructed. Applied to quantum optics, photon distribution function, photon number means, and dispersions are calculated for the f-coherent states as well as the Wigner function and Q-function. As an example, it is shown how this nonlinearity may affect the Planck distribution formula.

We consider the time-dependent Schrödinger equation for a quadratic potential with an exponentially decaying force constant. General analytical solutions are presented and we highlight, in particular, the signatures of classical mechanics in the wave packet dynamics.

In-sample scattering contribution of fluorescent radiation to the x-ray fluorescence line intensity were studied in thick, pure samples. The Compton peak/photopeak area ratios for pure elements Cu, Zr, Ag, Sn, Ba, Gd, Dy and Yb were determined as a function of characteristic x-ray energy and sample thickness for annular-shaped Am-241 isotope excitation. The results show that the contribution of scattering is within 2-15% of the primary fluorescence. The results were compared with theoretical results.

Effects due to the temperature dependence of the nuclear binding energy upon the equation of state (EOS) for hot nuclear matter are studied. Nuclear contributions to the free energy are represented by temperature dependent liquid drop model terms.

Phase coexistence is assumed for temperatures of the order of 1MeV ⩽ T ⩽ 6 MeV, baryon number densities ρ of the order of 10⁻⁴ fm⁻³ ⩽ ρ ⩽ 10⁻¹ fm⁻³ and lepton fractions of the order of 0.2 ⩽ y₁ ⩽ 0.4. It is found that the total pressure of the system is not affected by the temperature dependence of the nuclear free energy, in spite of changes observed in the nuclear pressure due to the different parametrizations used to represent the nuclear binding energy.

The 3d⁶(⁵D)6h subconfiguration of Fe II is established by means of 74 newly identified 5g–6h transitions. These lines are observed in a Fourier-transform spectrum of iron emitted from a hollow-cathode discharge in the region 5350–5410 cm^-1. The application of the "quadrupolic" approximation shows that the JK coupling is well represented in the 3d⁶6h configuration. The identification of the lines in the spectra was facilitated by the comparison of the observed intensities with oscillator strengths calculated in the framework of the relativistic Hartree–Fock (HFR) approximation and also by consideration of the full width at half maximum (FWHM) of the profiles.

Collisional radiative models (CRM) are needed to simulate experimental line brightnesses and emissivities from fusion devices. CRM are built for H-like and He-like carbon and oxygen ions, following a detailed review of the published literature on the required atomic data (including both collision rate coefficients and atomic transition probabilities). The impurity ion radial distribution is obtained using a transport code with two radius dependent transport parameters: a diffusion coefficient D and an inward convection velocity V. Reliable atomic data are a prerequisite to these simulations, since they are supposed to be well known; adjustement of the simulations to the experimental line and/or continuum brightnesses and emissivities is done by varying only D and V. Examples are given of the quantitative interpretation of experimental spectroscopic data from two fusion devices: the Tore Supra Tokamak and the Reversed Field Pinch RFX. As a consequence of the order of magnitude difference in the central electron temperatures in the two devices, the sensitivity of the H-like and He-like ion emissions to the transport parameters is different. These differences are highlighted in the examples given.

The configuration 4f¹⁰5d6s6p of Ho I is studied theoretically. Slater and spin-orbit parameters are determined from 60 energy levels and hyperfine one-electron parameters are derived from magnetic dipole A and electric quadrupole B constants formerly determined in the analysis of Fourier transform emission spectra. A similar study of 4f¹⁰5d²6s is performed. New energy levels are found in analyzing the visible spectrum of holmium, including an excited level of the ground configuration 4f¹¹6s²⁴F_9/2 at 13094 cm⁻¹, and some of the lowest levels of 4f¹¹6s6d and 4f¹¹6s6d and 4f¹⁰5d²6p.

High resolution spectra of neutral vanadium excited in a hollow cathode discharge with helium, neon and argon as carrier gases have been recorded in the infrared region (1800-9000 cm⁻¹) by Fourier transform spectroscopy. A detailed analysis of the spectra has allowed to determine some missing terms in the doublet, quartet and sextet systems of the configurations 3d⁵, 3d³4s5p, 3d⁴4s, 3d⁴4s, and 3d⁴5d of V I. Investigation of the hyperfine structure patterns has confirmed the identification of the transitions and has given rise to the determination of 67 new magnetic dipole constants.

The Magnetic Electron Drift Vortex (MEDV) modes in a homogeneous magnetized plasma are investigated using the Braginskii's fluid model for electrons. It is found that the modes become unstable when the propagation is in both parallel and perpendicular directions with respect to density and temperature gradients. The instability characteristics of the mode are presented by analyzing it analytically as well as numerically. The relevance to wave phenomena in space and laboratory plasmas is pointed out.

Stability analyses of internal resistive MHD modes resonating at surfaces with q = 1,2 or higher values in Tokamak are examined. The resistive scalings for modes with different poloidal mode numbers are studied. Special attention is paid to the transitions induced either by reducing the resistivity, or by the β value, or by shaping the current density profile. For the m/n = 2/1 modes a kink-tearing transition appears while for the higher-m modes mutual transitions take place between the kink modes and the interchange modes. Global and local shaping of the current and the pressure profiles can dramatically suppress the low-n modes in agreement with experimental results. For typical experimental values of resistivity, violation of the Suydam criterion does not have a noticeable effect on the growth rate. However, the ideal modes will dominate for high β.

The excitation of waves and wave power release are considered in a helicon plasma source driven by an axially-symmetric m = 0 antenna. The volume power input via helicon waves is shown to be enhanced and more peaked near the plasma axis as compared with the case of a source driven by an axially anti-symmetric antenna. The resistance of the antenna loaded by the wave excitation is found to minimize near antiresonance states which provides the condition for a helicon discharge stability.

A numerical simulation is performed to study the effect of a viscous dissipation term on the generation of shear flow at a plasma edge in the guiding center approximation. The guiding center model includes the effects of finite Larmor radius corrections and polarization drift. The numerical code applies the method of fractional steps to the fluid guiding center equations. We attempt to discriminate between the smoothing of the microstructure by a small viscous dissipation term to control numerical instabilities, and the modification of the macroscopic physical results introduced by this small viscous dissipation term. The finite Larmor radius effect allows for a charge separation to exist, which can be further accentuated by the polarization drift. A difference in the viscous term between electrons and ions can add to the charge separation effect at the plasma edge, which can modify the physical results. The numerical calculation is effected using a slab model, periodic in one direction and finite in the other direction, with an inhomogeneous density of guiding centers to simulate a plasma edge. The evolution of the system shows the potential evolving to a shape characterized by the longest wavelength associated with the transverse dimension of the system, an evolution characteristic of an inverse cascade. We present an analysis of the effect of different values of the viscous term on the time evolution of this guiding center system, and on the formation and existence of a charge separation and an electric field at the edge of a plasma and the associated shear in the E × B flow.

Some methods used for analysing thermal desorption spectra are presented. The methods can be applied to the first-order rate equation, but they are also applicable when analysing second-order spectra. The classical Arrhenius method is discussed critically. Some new formulae for the analysis are introduced. The methods utilize the peak area, peak shape or the half-width of the peak.

Thermal conductivity and thermal diffusivity of three rare earth oxide powders (Gadolinium oxide, Samarium oxide and Yttrium oxide) are measured experimentally using Transient Plane Source (TPS) technique at ambient temperature. An attempt has been made to accommodate the effect of porosity of the powders on thermal conductivity. Calculation of effective thermal conductivity on the basis of a theoretical model has been carried out and it has been found that the theoretical results are in good agreement with the experimental values. Further it has been shown that the TPS technique is an effective method for the measurement of thermal conductivity of powders.

EPR and optical spectra of vanadyl doped Cadmium Ammonium Phosphate Hexa Hydrate (CAPH) are investigated both at room and liquid nitrogen temperatures. The results and analysis reveal that the site symmetry of the VO²⁺ ion is tetragonal (C_4v). The following crystal field and spin Hamiltonian parameters are evaluated.

Dq = 1600 cm⁻¹, Ds = −3275 cm⁻¹ and Dt = 488 cm⁻¹, g_|| = 1.931, g_⊥ = 1.993, A_|| = 183 × 10⁻⁴ cm⁻¹, A_⊥ = 72 × 10⁻⁴ cm⁻¹