Some numerical aspects of the conservative PSM scheme in a 4D drift-kinetic code.

The purpose of this work is simulation of magnetised plasmas in the ITER project framework. In this context, kinetic Vlasov-Poisson like models are used to simulate core turbulence in the tokamak in a toroidal geometry. This leads to heavy simulations because a 6D dimensional problem has to be solved, even if reduced to a 5D in so called gyrokinetic models. Accurate schemes, parallel algorithms need to be designed to bear these simulations. This paper describes the numerical studies to improve robustness of the conservative PSM scheme in the context of its development in the GYSELA code. In this paper, we only consider the 4D drift-kinetic model which is the backbone of the 5D gyrokinetic models and relevant to build a robust and accurate numerical method

Quasi-neutrality equation in a polar mesh

In this work, we are concerned with the numerical resolution of the quasi-neutrality equation arising in plasma physics. A classic method is based on a Padé approximation. Two other methods are proposed in this paper: a Padé approximation of higher order and a direct method in the space configuration which consists in integrating on the gyrocircles using interpolation operator. Numerical comparisons are performed with analytical solutions and considering the 4D drift-kinetic model with one Larmor radius. This is a preliminary study; further study in GYSELA is envisioned

The semi-Lagrangian method on curvilinear grids

International audienceWe study the semi-Lagrangian method on curvilinear grids. The classical backward semi-Lagrangian method [1] preserves constant states but is not mass conservative. Natural reconstruction of the field permits nevertheless to have at least first order in time conservation of mass, even if the spatial error is large. Interpolation is performed with classical cubic splines and also cubic Hermite interpolation with arbitrary reconstruction order of the derivatives. High odd order reconstruction of the derivatives is shown to be a good ersatz of cubic splines which do not behave very well as time step tends to zero. A conservative semi-Lagrangian scheme along the lines of [2] is then described; here conservation of mass is automatically satisfied and constant states are shown to be preserved up to first order in time

Semiannual progress report no. 1, 16 November 1964 - 30 June 1965

Summary reports of research in bioelectronics, electron streams and interactions, plasmas, quantum and optical electronics, radiation and propagation, and solid-state electronic

Design Studies for the Pixelized Readout of a TPC for the ILD

A large Time Projection Chamber (TPC) is foreseen as central tracking device of the International Large Detector (ILD), as it provides a large number of measured track points simultaneously with a minimum of material budget. Many modern TPCs rely on micro-pattern gaseous detectors (MPGDs) as amplification stage and a readout based on pads or strips. The performance can be further improved with a pixelized readout structure, as the size of the amplification stage is matched by the granularity of the readout. A pixelized readout can be realized with pixel chips with an integrated Micromegas structure which is added to the chips by techniques of industrial post-processing. The holes of the grid are perfectly aligned to the pixels, i.e. there is only one hole above each pixel. Due to the alignment, the gas amplification takes place directly above a single pixel and the created charge is mostly collected by this pixel. This way, even single electrons of the primary ionization can be separated. To apply this kind of readout in large experiments, such as the TPC of the ILD, the technology has to be available in large quantities, as several square meters of readout area have to be covered. To this end, the original production process is transferred to the production on 8 00-wafers. Post-processed chips from this new production process are tested in terms of energy resolution, occupancy, detection efficiency and discharge stability. The results are compared with those obtained with devices of the original method of fabrication. For the application in a TPC for the ILD it has to be ensured that pixelized readouts are capable of dealing with backgrounds present in the detector. Hence, the two main backgrounds, γγ → hadrons and e+ e--pairs are simulated with the required precision and the performance of an integrated pixel readout is examined, especially with the respect to the momentum resolution required at the ILD