Table of contents

The Painlevé analysis is conducted on the 2 + 1 dimensional equations of the type of derivative NLS and of Three-Wave Interactions. We find in the first case that certain pseudo appearance of logarithmic terms may be alleviated in the Painlevé test, while in the second case we show that the multiorder resonances at index zero for vector equations may co-exist with the Painlevé property. Both cases are thus shown to pass the WTC Painlevé test.

Mass resolution and collection efficiency properties of time-of-flight (TOF) mass spectrometers have been studied by means of numerical calculations. Some comparisons with first experimental test measurements are also made. A useful measure of mass-resolving power has been introduced. The calculations show that good mass resolution is achieved with short length of source region and long drift tube. The main reason for calculated peak broadening is the initial kinetic energy of the ions. The broadening can be minimized with high extraction fields. High collection efficiency can be achieved by using high extracting fields and short drift tubes with large diameter detectors.

We present some physics interests for the study of beauty baryons produced in pp interactions at a center-of-mass energy corresponding to the Large Hadron Collider (LHC) project, √s ≃ 14 TeV. The comparison of beauty-baryon (N_b) production with their charge conjugate particles (_b) is discussed as well as the measurement of their polarization. The search for CP violation in the N_b, _b decays is considered. A possibility for estimating the |V_cb| CKM matrix element is also presented. In order to evaluate the N_b production rates and their detection efficiencies, we utilize the pp luminosity of = 10³³ cm^-2 s^-1 and the example of the Compact Muon Solenoid (CMS) detector.

The derivation of explicit expressions for main global characteristics of the characteristic emission spectrum and the emissive and receptive zones of the configurations involved in transitions is described. All types of transitions for which emissive or receptive zone coincides with the corresponding configuration are found. The mean deviation from the average energy and skewness are investigated by comparing the theoretical values with the results obtained from the existing experimental data for the transitions 3d^N 4p → 3d^{N + 1} in the three times ionized atoms, 4d⁹ 4f^N → 4d¹⁰ 4f^{N - 1} in the neutral lanthanides and 3d⁸4p + 3p⁵3d¹⁰ → 3d⁹ in the Co I isoelectronic sequence. The global characteristics of spectra are employed to investigate the shift and the narrowing of the emission spectrum, as well as to calculate the multiplet broadening of K_α1,2 lines in the iron group elements and the satellite shifts of these lines that are due to the additional ionization of atoms.

143 line emission cross-sections of Ca I and 15 line emission cross-sections of Ca II have been measured at an electron energy of 30eV. The optical excitation functions (OEF) are recorded in a range of electron energy from 0 to 200eV: 59 OEF for Ca I and 5 OEF for Ca II. The investigated lines are located in a spectrum region 227-745 nm. For the cross-sections of 5 singlet series and 10 triplet ones of Ca I, consideration has been given to series relationships that are characterized by the power relationship between the cross-section value and the principal quantum number of the upper level. Deviations from the power relationship take place in the perturbed Ca I series. The perturbations manifest themselves also by changing the OEF shape.

The wavelengths and transitions probabilities of the radiative transitions 1s2s²2p –1s²2s², 1s2s2p²–1s²2s2p, 1s2p³–1s²2p² and autoionization rates of the states 1s2s²2p, 1s2s2p², 1s2p³ for Be-like multicharged ions with Z = 6–54 were calculated. These data were used for the calculation of relative intensities of dielectronic satellite spectra for highly charged He-like ions. Synthetic spectra will be built from these data for different plasma sources. A perturbation theory method is described for the calculation of atomic properties of autoionization state. Correlation, relativistic and radiative effects were taken into account. The application both of LS- and jj-coupling schemes was considered depending on the value of Z. All results were calculated in the intermediate coupling scheme. Mixing of the configurations is considered in details for different Z to understand the transpositions of levels. Z-dependencies of radiative transition probabilities and autoionization rates are discussed.

Corrections to L Ward, A Wännström, A Arnesen, R Hallin and O Vogel Physica Scripta31 149 (1985)

Transport simulations of TFTR temperature and density profiles have been carried out with the Nordman-Weiland transport model for η_i and trapped electron modes (including impurities and finite Larmor radius effects) combined together with resistive ballooning mode and neoclassical transport models. The Nordman-Weiland model is combined together with models for transport driven by pressure gradients to compute the coefficients for the transport of ion heat, hydrogen ions, and electron heat. The predictions of this model are compared with the experimentally observed profiles for TFTR L-mode and supershot plasmas.

Edge plasma fluctuations are studied with inserted triple Langmuir probes and magnetic coils in the TPE-1RM20 reversed-field pinch. Two-point measurements show that density and potential fluctuations have relatively low mode numbers (m < 3, n < 40). High coherence (γ = 0.5) with magnetic field fluctuations and similar mode spectra suggest that density and potential fluctuations are mainly caused by electromagnetic turbulence. Broadband magnetic fluctuations are dominated by m = 0, low-n modes and internally resonant m = 1 and m = 2 modes. A coherent (f = 20-30 kHz) m = 0, low-n mode is also observed. Particle flux driven by electrostatic electric field fluctuations is 50-100% of total flux obtained from D_α line intensity measurement. Low-frequency fluctuations (f < 100 kHz) give the main contribution to the total flux. Electrostatic fluctuation driven electron energy flux is only of the order of 10% of total non-radiative power loss.

In order to make confinement predictions for ITER it is necessary to develop confinement scaling laws and local transport models and validate them against tokamak experiments. This paper reviews comparisons of existing scaling laws and models with results and data from JET and COMPASS and also the novel tight aspect ratio device START which provides an extreme test of their validity. Results from COMPASS-D on transitions from L-mode to H-mode are also discussed.

Electrostatic fluctuations have been measured in the scrape-off layer of ASDEX and W7-AS by Langmuir probes and by observation of H_α light and light emitted from a fast Li atom beam with high spatial and temporal resolution. It was demonstrated that these fluctuations contribute a significant, if not dominant, fraction of the anomalous radial particle transport. The basic properties of the fluctuations are the same in both experiments. A model for an instability mechanism specific to the SOL is presented including density, temperature and electric potential fluctuations. From this model mixing length estimates for the radial transport and resulting density and pressure gradients in the SOL are derived and compared to measurements in the mid-plane and in the divertor of ASDEX. In spite of several simplifications in the model a quantitative agreement up to factors of 1-3 and a qualitative agreement for variations of discharge parameters is achieved between the model predictions and the measurements. Data from poloidal multi-pin probe arrays are decomposed into a sum of spatial-temporal "events" by means of a fitting procedure. Centres of selected events serve as reference points for the analysis of the dynamics in their surroundings. Averaging shows that positive and negative potential events appear mostly in pairs with the E x B drift in between directed radially outward.

Several discharges have been analysed in Tore Supra in order to improve the understanding of anomalous transport. In ohmic discharges, it has been shown that both particle and heat diffusion coefficients improve with increasing density, then saturate. The level of edge density fluctuations behave in the same way. In the presence of additional heating, the bulk and the edge turbulences behave differently. The level of edge density fluctuations remains constant in most discharges with additional heating (up to 8 MW). In practice, it only depends on edge conditions. On the contrary, the level of core magnetic fluctuations increases systematically with any additional power. Finally, a lowering of the level of the edge density fluctuations has been observed when using the Tore Supra ergodic divertor. This improvement is accompanied by the onset of a temperature pedestal between the plasma bulk and the ergodic layer. This explains why the global confinement remains unchanged in presence of the ergodic divertor in spite of the reduced radius of the last closed magnetic surface.

Recent progress in the characterization of the nonlinear nature of the broadband fluctuations in magnetically confined devices has provided a missing link between experimental measurements and theoretical turbulence models. At the same time, the study of influence of atomic physics drives (ionization and radiation) on plasma turbulence has stimulated new experimental developments. A view of the latest experimental results in these areas is presented.

Transport studies in the RTP tokamak are presented. A Z_eff scan shows a weak dependence of χ_e on collisionality. Studies of the progagation of heat pulses, induced by both modulated ECRH and sawteeth, show that χ^inc is independent of input power. Moreover, these perturbative studies indicate a transport barrier related to the q = 1 surface. Independent evidence for the existence of such a transport barrier comes from high-resolution multiposition Thomson Scattering measurements.

Low frequency electrostatic fluctuations are studied experimentally in a low-β plasma, with particular attention to their importance for the anomalous plasma transport across magnetic field lines. The presence of large coherent structures in a turbulent background is demonstrated by a conditional analysis. The importance of these structures for the turbulent transport is demonstrated.

Drift waves are destabilized by the ionization of neutrals at the plasma edge and stabilized by electron Landau damping. The transport equations, the "Ansatz" Q_e* ∝ Γ_e*T_e (where Q_e*, respectively Γ_e*, is the electron heat, respectively the particle flux) and the mode's marginal stability condition form a self-contained set for the determination of the edge temperature and density profiles. The electron temperature at the separatrix and the particle confinement time are also obtained and compared to experimental values; the particle confinement time, in particular, is very close to the heuristic energy confinement time of Kaye-Goldston. If it is further assumed that energy and particle exhausts are along the open field lines of a magnetic island belt associated with the instability and intersecting the last closed equilibrium magnetic surface, then the theory provides an estimate of the level of the magnetic component of the mode, which is also compared to some experimental data, and a scenario for equilibrium bifurcation. Independently from the details of the transport mechanism, the bifurcation can, quite generally, be associated with the positive (∝ T_e^3/2) dependence of electron Landau damping on temperature.

The H-mode operating boundaries and confinement regimes in ASDEX Upgrade are described. The L to H mode threshold power is shown to linearly increase with the product of line-averaged electron density times magnetic field. The analyses of the boundaries between different ELM types show that mainly the steady-state ELMing H-mode discharges with type-I ELMs are achieved above the power threshold. The global confinement time of such discharges is analysed. Discharges of the same type with high edge radiation power (80% of the input power radiated) obtained by neon puffing remain in the H-mode and have a good confinement. The importance of strong deuterium puffing in addition to neon is demonstrated. These promising results for power load reduction of the divertor in ITER are discussed.

Recent scattering experiments on fusion and space plasmas suggest important effects of macroscopic fluid-like plasma motion on fluctuations of various plasma quantities and on electromagnetic wave scattering from such macroscopically agitated magnetized plasma. Fluid-like flows perturb the motion of a test particle and the cloud of polarization charge around it. These effects of modified test-particle transition probability and shielding can determine fluctuation spectra and respectively scattering spectra for the kinetically stable but macrosopically agitated plasma. Possibilities to infer information about macroscopic or turbulent plasma motion from fluctuation and scattering spectra are discussed, and it is shown that one has to distinguish between particle and fluid properties of plasma motion while interpreting experimental observations.

Parameter scans in density, heating power and isotope mass have been carried out in W7-AS. ECRH at a frequency of 140 GHz has allowed to study the density scaling of the energy confinement time of ECRH plasmas up to densities of 10²⁰ m⁻³. In power scans it has been tried to relate the power degradation of the energy confinement to a local plasma parameter. Transport analyses using power balance an heat wave techniques indicate that the transport coefficient does not depend on the electron temperature or related parameters. This observation can be reconciled with power degradation if the transport coefficient is formally allowed to vary with changes in the heating power on a faster than the diffusive time scale. Such a transport process describes also the observations in the dynamic phases following large changes in the heating power.

Experimental data on the states of strong impurity radiation from the plasma edge to tokamak TEXTOR - "detached" plasma, radiative periphery with neon puffing - are presented. The basic assumptions and equations underlying the transport code RITM (Radiation from Impurity in a Transport Model) developed for the description of such states are given. The results of the modelling of "detached" plasmas in the TEXTOR ohmic discharges and of conditions and dynamics of their formation are presented. The impact of neon radiation on plasma transport properties in discharges with auxiliary heating is discussed. It is shown that the experimentally found improvement of energy confinement with increase of radiation can be explained by the decrease of particle recycling and of the plasma heat conductivity. Plasma thermal stability at a high level of impurity edge radiation is considered.