[en] In this report one invited paper and six contributed papers presented by the CRPP Theory Group at the 7. European Fusion Theory Conference in Juelich are compiled. figs., tabs., refs

[en] The second stability regime for ion-temperature-gradient (ITG) modes is studied in details with a global linear gyrokinetic Particle-In-Cell code which takes the full toroidal MHD equilibrium data. The trapped-ion and the toroidal ITG regimes are explored. We perform simultaneous ideal MHD stability computations for both kink (n=1) and ballooning (n=∞) modes. We use the results to find partially optimized configurations that are stable to ideal MHD modes and where the ITG modes are stable or have very low growth rates. Such configurations are expected to have very low level of ITG-induced transport. (author) 3 figs., 13 refs

[en] The formulation of the guiding centre drift orbits is extended to relativistic particles in canonical coordinates with arbitrary time dependent electric and magnetic fields. The transformation to these coordinates from general flux coordinates is cumbersome for practical applications. This transformation is straightforward for Boozer magnetic coordinates which are canonical if the perturbed magnetic field is constrained to the form δB = ∇x(YB). (author) 5 refs

[en] Elongated plasmas up to κ=2.5 have been obtained in the Lausanne Tokamak TCV. for κ<2.3, the normalized current limit, I_N=I[MA]/a[m]B[T], increases with elongation and is limited by the standard ideal limit at q_a=2. However for κ>2.3, a disruption occurs at larger values of q_a(κ), such that the current limit stays about constant at I_N≅3. The modes observed at the disruption are typically m/n=2/1 and 3/2 modes. The observed disruption limit is consistent with the prediction of the n=1 ideal MHD limit for analytical plasma shapes. We have computed the ideal and resistive MHD limit for the actual experimental plasma shapes and profiles. We find that the shots which disrupted are indeed very close to the ideal n=1 external kink β-limit. We also see that, including resistivity, the 4/3, 3>/2 and 2/1 modes are unstable even well below this limit, which agrees with the experimental data. For 2.5<κ<3, we have varied the profiles over a wide range and our results confirm the prediction that only by keeping q_a just above 3 and decreasing the plasma inductance, l_i, one can find stable configurations. (author) 3 figs., 10 refs

[en] A simple configuration consisting in a set of toroidal, helical and vertical field coils is used to calculate free boundary equilibria with nonzero plasma current boundary. The amount of helical boundary deformation is controlled by the ratio of the current in the helical field coils to the current in the toroidal field coils. When this ratio is increased the (m,n)=(2,1) external kink is stabilized at β≅1% for inverse rotational transform profiles in the region q<2. (author) 4 figs., 5 refs

[en] We present the first simulations of Ion Temperature Gradient (ITG) modes in straight helical configurations. A linear particle-in-cell gyrokinetic global code initially developed for toroidal axisymmetric geometry has been modified to treat the case of helical symmetry. The model is based on gyrokinetic ions, adiabatic electrons and electrostatic quasineutral perturbations. The code simulates the full plasma cross-section. The potential is represented on a magnetic coordinate system and discretized with finite elements. Analytical extraction of the fast poloidal variation is done on a straight field line coordinate, allowing a speedup of one or two orders of magnitude. A l=1 vacuum field configuration is studied. The very low shear and small ∇B drifts imply that for a wide range of parameters the most unstable ITG modes are 'slab-like'. (author) 2 figs., 6 refs

[en] A gyrokinetic eigenvalue code has been developed for computing global ion temperature gradient (ITG)-related instabilities in tokamak configurations. Although trapped ion dynamics are not yet considered in this model, it contains full finite Larmor radius and finite orbit width effects of circulating ions. Non-adiabatic trapped electron dynamics are included through a bounce-averaged drift kinetic equation. Differences between the local ballooning approximation and the global approach are presented and discussed. The possible coupling between the trapped electron mode (TEM) and the toroidal-ITG mode is also investigated. Finally, the evolution of the spectrum of these different instabilities is studied for varying central negative magnetic shear configurations. (author) 4 figs., 19 refs

[en] The absorption of power is studied with fluid and gyrokinetic plasma models, when two Alfven or ion-ion hybrid resonances provide for a weak damping in a partially standing wave-field. Examples chosen in slab and toroidal geometry show that the fluid predictions based on resonance absorption are generally very different from the Landau damping of mode-converted (TAE) and the power deposition profiles obtained in the ion-cyclotron range of frequencies (ICRF) using fluid plasma models are very misleading. (author) 2 figs., 1 tab., 18 refs