Successful operation of the ITER tokamak requires divertor operation in a detached plasma regime, in order to reduce the heat flux to the divertor plates to below the technological limits of actively-cooled plasma-facing components (PFCs), namely 10 MW/m2 at the plasma facing surfaces. The power that arrives at the divertor plates is transported through the sheath. The sheath acts to transfer energy from electrons to ions via electrostatic acceleration, in turn affecting the upstream plasma temperatures (i.e. so that Te<Ti in the SOL) and influencing sputtering yields. This energy transfer rate depends on electron reflection and secondary electron emission (SEE), which is a function of the plasma conditions and the surface properties, as well as the angle of the surface with respect to the magnetic field. It is characterized by the sheath heat transmission factor. The linear high-flux plasma generator Magnum-PSI enables to systematically study the effects of SEE, recycling and field line angle in a well diagnosed plasma. The main aim of this PhD project is the experimental validation of existing theories and their implementations in codes such as SOLPS-ITER. In addition a so-called tunnel probe will be used capable of measuring the ion current density, electron temperature and secondary electron emission at the target surface. The PhD will explore the sheath properties, by using the diagnostic park of Magnum-PSI. In This work focusses on full diagnosis of detached plasma, with tight interaction with modelling groups at DIFFER, FZJ and CEA.
Responsibilities and tasks
- Complete development/installation of electrostatic probe system in the Magnum-PSI target system;
- Study of sheath heat transmission factor evolution with density, pressure, magnetic field. Effect of gas species (He, Ne, N2). Influence of detachment regime on the sheath;
- Evolution of sheath physics with magnetic field incidence angle. Study of sheath properties at grazing angles. Comparison with tokamak studies.

We seek enthusiastic and highly talented candidates that are willing to work in an international and interdisciplinary team of physicists and chemists. The applicant should hold or be pursuing a Master degree (or an equivalent diploma giving access to doctoral studies) in experimental or technical physics. A background in at least plasma physics and optics is required. Good verbal and written communication skills in English are mandatory.

Fixed-term contract: four years.

When fulfilling a PhD position at NWO-I, you will get the status of junior scientist.  You will have an employee status and can participate in all the employee benefits NWO-I 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 supposed to have a thesis finished at the end of your four year term with NWO-I.  A training programme is part of the agreement. You and your supervisor will make up a plan for the additional education and supervising that you specifically need. This plan also defines which teaching activities you will be responsible (up to a maximum of ten percent of your time). The conditions of employment of NWO-I are laid down in the Collective Labour Agreement for Research Centres (Cao-Onderzoekinstellingen), more exclusive information is available at this website under Personeelsinformatie (in Dutch) or under Personnel (in English). General information about working at NWO-I can be found in the English part of this website under Personnel. The 'Job interview code'applies to this position.

The exhaust of heat and particles is recognized as the largest outstanding challenge in nuclear fusion research. This requires maintaining a high performance fusion plasma, while ensuring that the unprecedented power exhaust does not damage the reactor walls. This is achieved through inducing strong radiation of light from the plasma periphery and thereby maintaining a cold dense plasma state in the exhaust region known as detachment. This Strategic Programme aims to enhance our understanding of the physics of power exhaust, and to develop advanced control strategies for high-performance, low wall load operation.

DIFFER

DIFFER (Dutch Institute for Fundamental Energy Research), Eindhoven, is one of the institutes and focuses on a multidisciplinarily approach of the 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.