SSD - Helander Seminar

Prof. Dr. Per Helander - Fusion Energy, Stellarators, and the Wendelstein 7-X Project

Department of Stellarator Theory, Max Planck Institute for Plasma Physics Greifswald, Germany

Abstract

Do we need new energy sources? Despite all the rhetoric from politicians, the vast majority of all energy still comes from fossil fuels and will continue to do so for the foreseeable future – the main reason being the enormous technical difficulties facing any alternative solution. There are, in fact, only very few carbon-free options that could even remotely satisfy Mankind’s present hunger for energy.

Fusion energy is one of these options. Fusion reactions occur in the Sun and other stars, but another reaction, that between deuterium and tritium producing helium, has a much higher cross section and would be easier to realise on Earth. The fuel must however be heated to at least 100 million degrees and be thermally insulated from the surroundings. The most promising way to accomplish this task is to confine the resulting plasma in a toroidal magnetic field.

Two main confinement concepts have emerged along these lines, the tokamak and the stellarator. They have been explored over decades of research and taken great strides in recent years. A very large tokamak, ITER, is now being built in Cadarache in the south of France, with the aim of demonstrating a positive energy balance from a fusion plasma for the first time. A much more modest stellarator – but still the world’s largest experiment of this type – has recently started operation in Greifswald. This device, Wendelstein 7-X, aims to show the feasibility of fusion in stellarators, which offers potential benefits in comparison with tokamaks.

In my talk, I will elaborate on the need for fusion research and on the physical principles of magnetic plasma confinement, and describe the Wendelstein 7-X project. I will also show the latest results from this device, which recently managed to achieve the best plasma confinement ever in a stellarator.