Institutskolloquium des IPP 2018

Due to the presence of multiple physical scales and complex nonlinear interactions, the numerical simulation of fusion plasmas often leads to computational problems of huge complexity. A long-standing challenge is then to design numerical methods that are computationally efficient, high order accurate and stable on very long time scales. Fortunately, steady progresses in the theory of structure-preserving discretizations have provided a solid mathematical ground for the development of stable high order numerical schemes. In this lecture I will give a brief review of the compatible Finite Element methods that have been developed in this direction, and I will explain how these tools are now being extended to design stable numerical models for the Vlasov-Maxwell equations. Recent ideas that allow to further improve the computational efficiency of such methods will be presented, along with a novel approach to low-noise particle approximations. [mehr]

Comparing North Korea's achievements in the field of missiles with the programs of other countries, one gets the impression that North Korea is a nation of rocket scientists. The recent glorious successes appear like a deja vu of the early days of North Korea's missile program in the 1980s and 1990s, when the country managed to present a full missile program out of the blue. But a close look from an engineer's perspective reveals some discrepancies in the common narrative, thus allowing for some surprising insights into the current situation of North Korea's missile threat. [mehr]

The European Spallation Source (ESS), which is currently under construction in Lund, Sweden, is designed to push the limits of research with neutrons to new horizons. ESS will open up new scientific opportunities which are complementary to those at X-ray sources. These will include unprecedented in-situ and in-operando experiments which are only possible with neutrons due to their special properties. After a short summary of the design and the specifications of the European Spallation Source an overview of the current status and schedule of the ESS construction project will be given with a strong focus on the instruments and the surrounding scientific infrastructure. The overall goal of ESS is to begin user operation in 2023 and ramp up to 15 instruments by 2026. Selected examples of new scientific opportunities in the field of materials and life science will be discussed. [mehr]

Large-scale plasma instabilities with the potential of damaging wall structures or reducing their lifetime are a significant concern for magnetic confinement fusion. Among the most critical are disruptions and edge localized modes. Predicting the behavior of such instabilities and their control for ITER and beyond is a challenging task for which input from experiments, theory, and simulations is needed. This presentation describes non-linear MHD simulations of edge localized modes, disruptions and control strategies. The talk will explain why simulations or large-scale instabilities are needed and show that our simulations have already revealed a lot of aspects about the physics of large-scale instabilities. It will also give some insights into the actual work involved “behind the scenes” and challenges we are facing for the future. [mehr]