PhD defence by Magnus Dam: Topological bifurcations of coherent structures and dimension reduction of plasma convection models

PhD defence by Magnus Dam, Monday 18 December 2017 at 14:00, DTU Kgs. Lyngby, Building 308, Auditorium 11.

Science summary:
The main goal for research in controlled nuclear fusion is the development of a green and sustainable energy source at competitive energy cost. Thermonuclear fusion can be achieved by heating a hydrogen gas to temperatures of hundreds of millions kelvin. At fusion temperatures some or all the electrons leave the atomic nucleus of the hydrogen atoms. This results in an overall neutral gaseous state of negatively charged free electrons and positively charged ions. This state of matter is called a plasma. To achieve and maintain fusion temperatures the plasma must avoid direct contact with any solid material. Since the plasma consists of charged particles it can be confined with a proper configuration of strong magnetic fields. Toroidal magnetic confinement devices such as the so-called tokamak are the most promising designs for energy production. A tokamak can operate in two distinct modes of operation. These are the low confinement mode (L-mode) and the high confinement mode (H-mode). The transition from the L-mode to the H-mode is called the L-H transition. The H-mode is the preferred operating mode for a fusion reactor. In the L-mode plasma is lost in bursts of high density blobs carrying volumes of plasma outside of the confinement region.
In this project we apply a dynamical systems approach to quantitatively describe the time evolution of simulated plasma blobs in a plasma convection model. Plasma simulations can be very computationally demanding. We apply various mathematical techniques to reduce a plasma convection model to models which are easier to simulate on a computer. The reduced models approximate the full model very well, with substantial savings of computational resources.

Read more about this thesis in DTU Orbit

Supervisor: Professor Morten Brøns
Co-supervisors: Professor Jens Juul Rasmusen, and Professor Volker Naulin

Professor Mads Peter Sørensen, DTU Compute
Professor Odd Erik Garcia, The Arctic University of Norway
Professor Mogens Høgh Jensen, University of Copenhagen

Chairman: Associate Professor Poul Hjorth, DTU Compute

Everyone is welcome.


man 18 dec 17


DTU Compute



DTU Kgs. Lyngby, Building 308, Auditorium 11