Results 1 - 10 of 360
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[en] Using a technique of rearrangement, very sharp estimates for a non-linear problem arising from plasma physics are obtained
[fr]Pour un probleme issu de la physique des plasmas, on presente quelques estimations a priori obtenues par une methode de rearrangement. On montre que ces estimations sont les meilleures possibles
[en] A low flow, δf gyrokinetic formulation to obtain the intrinsic rotation profiles is presented. The momentum conservation equation in the low-flow ordering contains new terms, neglected in previous first-principles formulations, that may explain the intrinsic rotation observed in tokamaks in the absence of external sources of momentum. The intrinsic rotation profile depends on the density and temperature profiles and on the up-down asymmetry.
[en] In this paper we describe two laboratory test facilities constructed and operated at Saclay for general studies on thermal properties of He II at variable temperatures and pressures related to the cooling of superconducting magnets. Two other He II facilities also in operation at Saclay and built in a joint collaboration of three CEA Laboratories (Fontenay-aux-Roses, Grenoble and Saclay) for the qualification tests of a new tokomak 'Tore Supra', under construction in France, have already been reported in detail
[en] In this paper, we measured plasma horizontal displacement using two experimental methods in the IR-T1 tokamak. First, two poloidal flux loops were designed and installed on the outer surface of the IR-T1 tokamak and were used to measure the Shafranov shift. Also, modified Rogowski and saddle sine coils based on the multipole moment method were designed, constructed and used. The results from these two methods are compared and are found to be in good agreement.
[en] Radial fluxes of parallel momentum due to and magnetic drifts are shown to be correlated in tokamak plasmas. This correlation comes from the onset of poloidal convective cells generated by turbulence. The entire process requires a symmetry breaking mechanism, e.g. a mean shear flow. An analytical calculation shows that anti-correlation between the poloidal and parallel components of the turbulent Reynolds stress results in anti-correlation of the fluxes of parallel momentum generated by and curvature drifts. (paper)
[en] Tokamak experiments have reached a stage where large scale application of superconductors can be envisaged for machines becoming operational within the next decade. Existing designs for future devices already indicate some of the tasks and problems associated with large superconducting magnet systems. Using this information the coming magnet system requirements are summarized, some design considerations given and in conclusion a brief survey describes already existing Tokamak magnet development programs
[en] Simulations of tokamak plasmas require a number of inputs whose values are uncertain. The effects of these input uncertainties on the reliability of model predictions is of great importance when validating predictions by comparison to experimental observations, and when using the predictions for design and operation of devices. However, high fidelity simulation of tokamak plasmas, particular those aimed at characterization of the edge plasma physics, are computationally expensive, so lower cost surrogates are required to enable practical uncertainty estimates. Two surrogate modeling techniques have been explored in the context of tokamak plasma simulations using the XGC family of plasma simulation codes. The first is a response surface surrogate, and the second is an augmented surrogate relying on scenario extrapolation. In addition, to reduce the costs of the XGC simulations, a particle resampling algorithm was developed, which allows marker particle distributions to be adjusted to maintain optimal importance sampling. This means that the total number of particles in and therefore the cost of a simulation can be reduced while maintaining the same accuracy.