[en] The Tokamak à configuration variable (TCV) features the highest electron cyclotron wave power density available to resonantly heat (ECRH) the electrons and to drive noninductive currents in a fusion grade plasma (ECCD). In more than 15 years of exploitation, much effort has been expended on real and velocity space engineering of the plasma electron energy distribution function and thus making electron physics a major research contribution of TCV. When a plasma was first subjected to ECCD, a surprising energisation of the ions, perpendicular to the confining magnetic field, was observed on the charge exchange spectrum measured with the vertical neutral particle analyser (VNPA). It was soon concluded that the ion acceleration was not due to power equipartition between electrons and ions, which, due to the absence of direct ion heating on TCV, has thus far been considered as the only mechanism heating the ions. However, although observed for more than ten years, little attention was paid to this phenomenon, whose cause has remained unexplained to date. The key subject of this thesis is the experimental study of this anomalous ion acceleration, the characterisation in terms of relevant parameters and the presentation of a model simulation of the potential process responsible for the appearance of fast ions. The installation of a new compact neutral particle analyser (CNPA) with an extended high energy range (≥ 50 keV) greatly improved the fast ion properties diagnosis. The CNPA was commissioned and the information derived from its measurement (ion temperature and density, isotopic plasma composition) was validated against other ion diagnostics, namely the active carbon charge exchange recombination spectroscopy system (CXRS) and a neutron counter. In ohmic plasmas, where the ion heating agrees with classical theory, the radial ion temperature profile was successfully reconstructed by vertically displacing the plasma across the horizontal CNPA line of sight. Active charge exchange measurements, by doping the plasma with ion neutralisation targets injected with the diagnostic neutral beam (DNBI), were used to absolutely calibrate the NPA. Advanced modelling of the measured hydrogenic charge exchange spectra with the neutralisation and neutral transport codes KN1D and DOUBLE-TCV permitted a calculation of the absolute neutral density profiles of the plasma species.The energisation and the properties of fast ions were studied in dedicated, low density, cold ion, hot electron plasmas, resonantly heated at the second harmonic of the electron cyclotron frequency. The ion acceleration occurs on a characteristic timescale in the sub-millisecond range and comprises up to 20 % of the plasma ions. The number of fast ions n_i^s and their effective temperature T_i^s are found to depend strongly on the bulk and suprathermal electron parameters, in particular T_i^s ≥ T_e^b (electron bulk) and n_i^s ∼ v_de (toroidal electron drift speed). The suprathermal electrons, abundantly generated in plasmas subjected to ECCD, are diagnosed with perpendicular and oblique viewing electron cyclotron emission (ECE) antennas and the measured frequency spectra are reconstructed with the relativistic ECE radiation balance code NOTEC-TCV. With steady-state ECRH and ECCD, the fast ion population reaches an equilibrium state. The spatial fast ion temperature profile is broad, of similar shape compared to the bulk ion temperature profile. The hottest suprathermal temperature observed is T_i^s ≥ 6 keV. Various potential ion acceleration mechanisms were examined for relevance in the TCV parameter range. The simultaneous wave-electron and wave-ion resonances of ion acoustic turbulence (IAT) show the best correlation with the available experimental knowledge. Ion acoustic waves are emitted by the weakly relativistic circulating electrons and are mainly Landau damped onto the ions. Destabilisation of IAT is markedly facilitated by the important degree of nonisothermicity T_e/T_i ≥ 40 of X2 EC heated TCV plasmas. Efforts were undertaken to consistently model the experimental observations using a numerical experiment. The relevant physics describing IAT was implemented in a finite difference code solving the quasilinear diffusion equation describing the time evolution of the electron and ion distribution functions. The simulations, fed as far as possible with experimentally available information, confirm the growth and saturation of IAT. Electrons and ions are initially preferentially heated in the toroidal direction. As the ions gain energy, the ion waves are damped more efficiently and only modes propagating at oblique angles can still grow, thus accelerating ions into the radial perpendicular direction. The simulation shows that turbulence reaches a steady-state when the ions are sufficiently hot to permanently stabilise IAT. The parameters describing the tail of the modelled equilibrium ion distribution agree quantitatively well with the CNPA measurement. Preliminary studies investigated on the interaction of fast ions with the sawtooth instability. It is found that the fast ion population in sawtoothing plasmas is transiently enforced with each sawtooth collapse. It is presently thought that the toroidal electric reconnection field lowers the IAT stability threshold thus producing more suprathermal ions. (author)

[en] The flux of charge exchange (CX) neutrals measured by neutral particle analysers (NPAs) is the line integral along the view line of the NPA and contains information about the ion energy distribution of the observed plasma. On the Tokamak a Configuration Variable (TCV) a single chord NPA is used to scan the plasma cross section by vertically displacing a reproducible discharge across its fixed line of sight. The ion temperature inferred from the passive CX flux as a function of the distance of the NPA chord to the magnetic axis is used to obtain an ion temperature profile T_i(ρ). To model the neutral source, simulations of neutral particle penetration from the edge and the neutralization processes are reported. In plasmas with thermalized ion populations, the NPA hydrogen or deuterium temperature profiles agree with the carbon ion temperature profile measured by charge exchange recombination spectroscopy. Matching the simulation with synchronous NPA measurements of two plasma species provides absolute profiles of neutral particles densities and the isotopic composition of the plasma, which are required for the transport analysis. With further modelling, the ion temperature profile may be iteratively reconstructed from the CX spectrum without displacing the plasma

[en] This paper focuses on interpreting variations in the NPA measured energy distribution of neutral fluxes from the TCV high density H-mode plasma discharges with strong third harmonic electron cyclotron heating (P_X3>P_Ω). Two quasi-stationary regimes: ELMy H-mode and ELM-free H-mode, routinely and reproducibly obtained in TCV, with a plasma density 5-10x10¹⁹ m^-3, electron temperature 2-3 keV and ion temperature of 0.7-1.0 keV. The ELMy X3-heated H-mode plasma on TCV is significantly perturbed by ELMs, sawteeth activity and modes. In X3-heated plasmas ELMs are characterised by increased amplitudes and lower frequencies than are typical in ohmic H-modes with strong sawteeth synchronised with ELM cycle. The energy losses per ELM can exceed the 15% of the total stored energy and the plasma density and electron temperature profiles were resolved during the ELM cycle. NPA measurements in the presence of ELMs and sawteeth cannot be explained with the classical theory of two-body Coulomb electron-ion collisions alone. Additional effects (such as a modification of the ion temperature radial profile and/or ion redistribution in the coordinate and velocity space due to plasma perturbations) must be considered

[en] The natural occurrence of compounds of uranium (U), a radioactive heavy metal, in food and drinking water is summarized. The results of U determinations of community well waters and table mineral waters in Switzerland, frequently contributing to a considerable increase of the daily U intake, are presented. The toxicological data are reviewed and a no observable effect level (NOEL) of 1 mgU/kg bodyweight/day based on a dog feeding study concerning nephrotoxic effects is proposed. The comparison between the NOEL and the actual daily U intake reveals a substantial margin of safety with respect to chemical toxicity. Concerning radiotoxicity an U intake of 40 μg (1 Bq)/person/day, maximum estimated dietary intake in Switzerland, results in a fatal cancer lifetime risk in the order of 10^-4. Criteria for the evaluation of cancer risks and their applicability in the regulation of naturally occurring radionuclides in food and water are discussed and compared with those criteria commonly used in food toxicology for the evaluation of chemical carcinogens. (author)

[en] The behaviour of particle and impurity density profiles in electron heated Ohmic, ECH and ECCD L-modes and H-modes as well as eITB's is investigated in view of developing physics understanding for a predictive capability for a-heated, ignited reactor conditions. Experimental observations in stationary L - modes show that density peaking depends mainly on the edge safety factor. Additional electron heating generally leads to a broadening of the density profiles and appearance of dependence on the power and it's deposition location. The dominant edge safety factor dependence observed is supportive of turbulent equipartition (TEP) theory, which predicts inward convection in the presence of turbulence. On the other hand, the correlation of the density peaking with temperature gradients in eITB regimes points out to the dominance of the turbulence of thermodiffusive type. Carbon profiles in L-mode discharges is found to be peaked with anomalous transport coefficients. (author)