PhD position: The effect of magnetic flux expansion on the threshold and stability of plasma detachment in tokamak divertors

This position is part of a large, five year research programme with the aim of taking a large step forward in understanding, optimizing, and controlling power exhaust in fusion reactors.  The goal of this PhD ...

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Van Vollenhovenlaan, Utrecht, Utrecht
Tijdelijk contract / Tijdelijke opdracht
Uren per week:
40 uur
€ 2834 per maand


This position is part of a large, five year research programme with the aim of taking a large step forward in understanding, optimizing, and controlling power exhaust in fusion reactors. The goal of this PhD project is to investigate if detachment can be facilitated and stabilized by modifying the geometry of the magnetic field in the divertor. The experimental part of this project will be carried out at TCV in Lausanne, Switzerland, a tokamak with unique plasma shaping capabilities. A major part of the project will be to make a new diagnostic system for the edge plasma operational on TCV. This system, called MANTIS, will provide unique new data on the physics of the SOL and divertor, and will enable the development of new types of observers for control systems.
In the past few years, a range of alternative divertor geometries have started being investigated in several tokamaks worldwide. All geometries differentiate themselves by their magnetic flux expansion: a (poloidal or toroidal) spreading of magnetic field lines. The planned experiments will investigate how the 2D profiles of radiation, plasma temperature, and plasma density evolve as a function of the way the flux expansion is modified, and how these profiles respond to transient events. This should lead to improved insight into the fundamental processes underlying detachment. The results will be used to optimize the shape of the divertor plasma towards easier and more stable detachment. The measurements will rely on a new multi-spectral imaging system (MANTIS) that is currently under development at DIFFER. The interpretation of MANTIS data requires a sophisticated spectral model to translate the measured spectral emissivities into physics quantities. In addition to the mentioned main scientific questions, the PhD project will contribute to the ongoing development of this spectral model.

Responsibilities and tasks
Test, commission, operate, and maintain the MANTIS diagnostic on TCV (part-time)

  • Perform experiments on the effect of flux expansion and transients on detachment;

  • Analyse (multispectral imaging and other) experimental data with Matlab and/or Python;

  • Formulate interpretations of the experimental results;

  • Write high-quality scientific publications;

  • Present work at international scientific conferences, and to peer-groups;

  • Provide data and transfer knowledge to the other PhD projects of 'Taming the flame'.


We seek enthusiastic and highly talented candidates that are willing to work in an international and interdisciplinary team of physicists and engineers. The applicant should have a Master's degree (or an equivalent diploma giving access to doctoral studies) in physics or chemistry. Good verbal and written communication skills (in English) are mandatory. Experience with experimental plasma physics, Matlab or Python programming and/or plasma diagnostics are considered to be highly beneficial.


A key challenge in the development of fusion power plants is figuring out how to exhaust the gigawatts of liberated fusion power from the machine without damaging the walls surrounding the plasma. A significant fraction of this power (hundreds of megawatts) will be transported via a thin layer of unconfined plasma wrapping the hot fusion core (the scrape-off layer or SOL) towards a part of the wall called the divertor. The SOL plasma needs to be strongly cooled to reach the low temperatures (< 5 eV) necessary for keeping the divertor wall load below the material limit. At such low temperatures, the plasma can even (partially or fully) detach from the divertor wall. SOL cooling can be achieved by injecting various impurities into the plasma edge that radiate the exhaust power in all directions. However, it is a great challenge to do this in a way that does not degrade the energy confinement of the core. For example, divertor detachment can in some cases trigger a thermal instability that may in serious cases lead to a collapse of the core.


When fulfilling a PhD position at NWO, you will get the status of junior scientist. You will have an employee status and can participate in all the employee benefits NWO offers. You will get a contract for four years. Your salary will be up to a maximum of 2,834 euro gross per month. The salary is supplemented with a holiday allowance of 8 percent and an end-of-year bonus of 8.33 percent. You are expected to have a thesis completed by the end of your four year term with NWO. A training programme is part of the agreement. You and your supervisor will draw up a plan for the additional education and supervising that you specifically need. The conditions of employment are laid down in the Collective Labour Agreement for Research Centres. The doctoral degree will be awarded by the Eindhoven University of Technology. Part of the work will be carried out at the EPFL in Lausanne, Switzerland, likely by means of multiple extended visits.

Additional information

Further information on the vacancy is available through the project leader of MANTIS, Dr. Wouter Vijvers +31 040 333 49 29. General information on working at NWO can also be found at the NWO website. The 'NWO job interview code' applies to this position.


DIFFER (Dutch Institute for Fundamental Energy Research) is one of the NWO institutes and focuses on a multidisciplinary approach to energy research combining physics, chemistry, engineering and materials science. The institute is based on two main strands, solar fuels for the conversion and storage of renewable energy and fusion energy as clean and unlimited source of energy. DIFFER is developing and supporting a national network on fundamental energy research and is closely collaborating with academic institutions, research institutes and industry.


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