[en] The Third International Copenhagen Symposium on Detection of Breast Cancer afforded a further opportunity for scientists from all over the world to come together and present important papers concerning breast cancer and early diagnosis procedures. The symposium was an opportunity to learn from extensive screening procedures carried out at outstanding centers in the United States, Sweden, the Netherlands, and England. Furthermore, the symposium dealt with new modalities such as ultra-sonography, magnification techniques, and magnetic resonance; and significant contributions concerning self-examination, fine needle aspiration biopsy, and radiation risks were presented. A whole section was also dedicated to the highly important cooperation between radiologist, surgeon, and pathologist

[en] Simulations of electron transport are carried out by solving the Fokker-Planck equation in the diffusive approximation. The system of a single laser hot spot, with open boundary conditions, is systematically studied by performing a scan over a wide range of the two relevant parameters: (1) Ratio of the stopping length over the width of the hot spot. (2) Relative importance of the heating through inverse Bremsstrahlung compared to the thermalization through self-collisions. As for uniform illumination [J.P. Matte et al., Plasma Phys. Controlled Fusion 30 (1988) 1665], the bulk of the velocity distribution functions (VDFs) present a super-Gaussian dependence. However, as a result of spatial transport, the tails are observed to be well represented by a Maxwellian. A similar dependence of the distributions is also found for multiple hot spot systems. For its relevance with respect to stimulated Raman scattering, the linear Landau damping of the electron plasma wave is estimated for such VD Fs. Finally, the nonlinear Fokker-Planck simulations of the single laser hot spot system are also compared to the results obtained with the linear non-local hydrodynamic approach [A.V. Brantov et al., Phys. Plasmas 5 (1998) 2742], thus providing a quantitative limit to the latter method: The hydrodynamic approach presents more than 10% inaccuracy in the presence of temperature variations of the order delta T/T greater than or equal to 1%, and similar levels of deformation of the Gaussian shape of the Maxwellian background

[en] Nonlinear, kinetic simulations of Stimulated Raman Scattering (SRS) for laser-fusion-relevant conditions present a bursting behavior. Different explanations for this regime has been given in previous studies: Saturation of SRS by increased nonlinear Landau damping [K. Estabrook et al., Phys. Fluids B 1 (1989) 1282] and detuning due to the nonlinear frequency shift of the plasma wave [H.X. Vu et al., Phys. Rev. Lett. 86 (2001) 4306]. Another mechanism, also assigning a key role to the trapped electrons, is proposed here: The break-up of the plasma wave through the trapped-particle instability

[en] The dispersion properties of ion acoustic waves and their nonlinear coupling to light waves through ponderomotive and thermal forces are sensitive to the strength of electron-ion collisions. Here, we consider the growth rate of stimulated Brillouin scattering (SBS) when the driven acoustic wave frequency and wavelength span the range of small to large compared to electron-ion collision frequency and mean free path respectively. We find in all cases the thermal contributions to the SBS growth rate are insignificant if the ion acoustic wave frequency is greater than the electron-ion collision frequency and the wavelength is much shorter than the electron-ion mean free path. On the other hand, the purely growing filamentation instability remains thermally driven for shorter wavelengths than SBS even when the growth rate is larger than the acoustic frequency

[en] The delta-f approach is extended for simulating the transport time-scale evolution of near-Maxwellian distributions in collisional plasmas. This involves simultaneously advancing weighted marker particles for representing the intrinsically kinetic component delta-f, and fluid equations for the parameters of the shifted Maxwellian background f(subSM). The issue of increasing numerical noise in a collisional delta-f algorithm, due to marker particle weight spreading, is addressed in detail, and a solution to this problem is proposed. To obtain higher resolution in critical regions of phase space, a practical procedure for implementing sources and sinks of marker particles is developed. As a proof of principal, this set of methods are applied for computing electrical Spitzer conductivity as well as collisional absorption in a homogeneous plasma

[en] Nonlocal electron heat transport calculations are carried out by making use of some of the techniques developed previously for extending the delta f method to transport time scale simulations. By considering the relaxation of small amplitude temperature perturbations of a homogeneous Maxwellian background, only the linearized Fokker-Planck equation has to be solved, and direct comparisons can be made with the equivalent, nonlocal hydrodynamic approach. A quasineutrality-conserving algorithm is derived for computing the self-consistent electric fields driving the return currents. In the low-collisionality regime, results illustrate the importance of taking account of nonlocality in both space and time

[en] There are a large number of codes treating wave propagation in plasmas. All of these use very different approaches depending on what there are dedicated to study. The LEMan code [1], which was developed in CRPP, is designed to treat electromagnetic waves in the low-frequency range (i.e. Alfven and ion cyclotron domain) in a 3D geometry. With this constraint, the most obvious method was to use a full wave code. The reason for that is the variation of the plasma parameters during a period of the wave because the low frequency domain involves long wavelengths. Other methods like WKB are not fully adapted for this purpose. As a first step, developments were formulated with a cold model. The code solves the following relation derived from the Maxwell's equations. (Author)

[en] Tokamak-like plasmas are modeled by a periodic cylindrical system with magnetic shear and realistic density and temperature profiles. Linear electrostatic microinstabilities in such plasmas are studied by solving the eigenvalue problem starting from gyrokinetic theory. The actual eigenvalue equation is then of integral type. With this approach, finite Larmor radius (FLR) effects to all orders are taken into account. FLR effects provide for the only radial coupling in a cylinder and to lowest order correspond to polarization drift. This effectively one-dimensional problem helped us to gain useful knowledge for solving gyrokinetic equations in a curved system. When searching for the eigenfrequencies of the global modes, two different methods have been tested and compared. Either the true eigenvalue problem is solved by finding the zeros of the characteristic equation, or one considers a system driven by an antenna and looks for resonances in the power response of the plasma. In addition, mode structures were computed as well in direct as in Fourier space. The advantages and disadvantages of these various approaches are discussed. Ion temperature gradient (ITG) instabilities are studied over a wide range of parameters and for wavelengths perpendicular to the magnetic field down to the scale of ion Larmor radii. Flute instabilities driven by magnetic curvature drifts are also considered. Some of these results are compared with a time evolution PIC code. Such comparisons are valuable as the convergence of PIC results is often questioned. Work considering true toroidal geometry is in progress

[en] The study of wave propagation is an important topic in plasma physics as it can play a considerable role in heating or instability processes. The LEMan code is designed to treat low-frequency waves e.g. in the Alfven and ion-cyclotron domain. In this range of frequencies, the main points of interest are heating in the ion-cyclotron domain (ICRH) and the global Alfven modes that can be driven unstable by the fast ions resulting either from fusion reactions or from neutral beam injection (NBI). A warm model has been implemented in the LEMan code. To determine the corresponding dielectric tensor, the linearized Vlasov equation is solved by the same method used in, but retaining only the lowest order terms in the finite Larmor radius expansion. In order to compute the parallel gradient of the perturbed distribution function, the latter is decomposed in term of Fourier harmonics. A linear system is thus obtained and leads to a dielectric tensor whose form corresponds to a convolution connecting together the components of the Fourier series of the electric current density and field. Such a method permits to take into account the poloidal up shift of the parallel wave vector and to avoid using approximations that are quite delicate in stellarator geometries. In the Alfven range, the main kinetic effects that can be modelled with this formulation are the Kinetic Alfven Wave (KAW) and the electron Landau damping. Lack of symmetry in stellarator systems gives rise to a larger variety of global modes (TAE, HEA, MAE, etc...). These modes already exist in the cold model but can also be influenced by kinetic effects. Investigation will be done to see how the different methods act on the results. The computation of a straight helix has been done and points out the presence of a helicity-induced Alfven Eigenmode (HAE). Adding other effects like toroidicity to the previous geometry will influence the spectrum and may modify the characteristics of the HAE. (Author)

[en] We have measured the cyclotron frequencies of He⁺, H⁺₂ and D⁺₂ ions in a room temperature Penning trap. The resonances were detected destructively by a time-of-flight technique. The statistical uncertainty of the resonance frequencies was generally below 1 ppb. A detailed account of measures to minimize systematic frequency shift is presented. Using the accepted values for the proton and deuteron mass we obtain a value for the ⁴He mass: M(⁴He)=4.0026032489(22) (0.5 ppb). It is in agreement with the accepted value. (orig.)