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17 november 2017

The exhaust of heat and particles is recognized as one of the largest outstanding challenges 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 allowing, a cold dense plasma state to be maintained in the exhaust region. This is known as detachment. In present devices and in ITER, detachment is predominately achieved through inducing radiation in the plasma periphery. For future reactors, a significantly larger of fraction of the total power needs to be radiated, including from the plasma core. This can be achieved by injection of heavy impurities such as Ar and Kr into the plasma. Many open questions surround such high-radiation-fraction scenarios. What is the impact of the injected impurities on global confinement? How are the impurities transported from the wall to the core in different regimes? This PhD position investigates these questions within the framework of core-edge coupled integrated modelling. Obtaining validated transport models and confidence in impurity transport predictions in high-radiation-fraction scenarios is necessary for extrapolation to future devices. This PhD position is within the framework of a DIFFER Strategic Programme aiming to enhance our understanding of the physics of power exhaust, and to develop advanced control strategies for high-performance, low wall load operation. Significant interaction with other PhD and postdoc positions within this Programme is envisioned.

Job description
This project focuses initially on JET modelling using the JINTRAC suite of codes. JINTRAC combines core transport with semi-empirical or first-principle-based turbulence models, neoclassical transport, and edge coupled fluid and Monte-Carlo neutral modelling for the SOL and divertor (EDGE2D-Eirene). The core and edge are coupled through boundary conditions at the separatrix. Experiments are analysed, where light (e.g. N) and heavy (e.g. Kr) impurities are puffed into tokamaks to tailor the edge and core radiation profile profiles necessary for heat exhaust control vital in future machines, while avoiding H-L back-transitions. Extensive visits to the JINTRAC team at JET is envisaged for training and analysis tasks.

Responsibilities and tasks:

  • Gain expertise on the JINTRAC suite of tokamak integrated modelling codes for coupled core and edge simulations. Understand fundamentals of diagnostic systems used to validate the simulations;
  • Fully coupled JINTRAC simulations with core, pedestal and edge transport. Validated core-edge coupled simulations for JET discharges. Reproduce differences in core temperature and density profiles and radiation between impurity-seeded and non-seeded cases. Highlight key physical processes and predict avenues for scenario optimization;
  • Repeat analysis on another tokamak (e.g. TCV, AUG);
  • Sensitivity analysis. Study impact of edge conditions and ELM frequency on impurity penetration to the core.

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.

Job requirements
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 degree (or an equivalent diploma giving access to doctoral studies) in theoretical or experimental physics. Experience with tokamak plasma simulation is highly beneficial. Good verbal and written communication skills (in English) are mandatory.

Conditions of employment
When fulfilling a PhD position at NWO-I, the Institutes Organisation of NWO, 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.

Further information on the vacancy is available through the group leader of the integrated modelling and transport group, Dr. Jonathan Citrin,
31 40 333 48 37.
General information on working at NWO-I can also be found at the NWO-I website.

You can apply by electronically submitting a Curriculum Vitae (CV), letter of motivation and grade transcripts to vacancies@differ.nl. Please refer to vacancy 17-003.