Young scientists receive EUROfusion grants

Three young scientist of the E2M department successfully applied for EUROfusion Research/Engineering Grants.

Dr. Athina Kappatou and Dr. Liang Gao are among the 11 physicists from the whole of Europe who received a research grant in December 2016. Alexander von Müller receives one of the 20 Engineering Grants which intend to attract young engineers for fusion research.

Dr. Athina Kappatou started her PhD project at the FOM Institute DIFFER in the Netherlands in 2010. She was located at IPP from the beginning of 2012. In October 2014 she graduated from the Eindhoven University of Technology (TU/e). The title of her thesis is “Investigations of helium transport in ASDEX Upgrade plasmas with charge exchange recombination spectroscopy”.  

Dr. Liang Gao started at IPP in the end of 2011 with his PhD project entitled: “Interaction of Deuterium Plasma with pre-nitrided Tungsten Surfaces”. He graduated at the Ruhr University Bochum in October 2015.

After having studied at RWTH Aachen, Imperial College London and Friedrich-Schiller-Universität Jena, Alexander v. Müller holds a Diploma in mechanical engineering as well as a Master of Science in solid state physics. In 2014 he started his work at IPP with a focus on W-Cu composite materials for plasma-facing component applications.

from left: Dipl. Ing. Alexander von Müller, Dr. Athina Kappatou, Dr. Liang Gao Zoom Image
from left: Dipl. Ing. Alexander von Müller, Dr. Athina Kappatou, Dr. Liang Gao

We congratulate the successful candidates and wish them great success for realization of their project objectives. Short versions of the project proposals are:

Dr. Athina Kappatou: The behaviour of helium in fusion plasmas

The presence of helium in a fusion plasma is fundamentally connected to the performance of a fusion reactor. The helium produced by the deuterium-tritium fusion reactions is required to heat the plasma through collisions with the plasma particles. However, an increased thermalised helium content in the plasma has to be avoided as it would dilute the fusion fuel, leading to a reduction of the produced fusion power. In addition, helium may cause deterioration of the energy confinement of the plasma, even at low concentrations similar to the levels expected in ITER, an effect that is not yet understood.

It is, therefore, crucial to investigate and understand the behavior of helium in fusion plasmas and how it affects the plasma performance. This project aims to address these long-standing questions through detailed experimental and theoretical investigations. First, the goal is to improve our understanding of helium transport, so that the helium density profile in future machines can be predicted. Second, the degrading effect of helium on plasma performance will be addressed in order to shed light on the underlying physics mechanism.

Dr. Liang Gao: Influence of Impurities on Hydrogen Isotopes Transport and Retention in Tungsten

To bridge the gap when extrapolating the laboratory results with well-defined experimental conditions to fusion experiments with rather complex plasma-surface interaction processes, the work will focus on the influence of intrinsically generated helium (He) and extrinsically seeded nitrogen (N2) on D diffusion and retention in W. By using a model system of co-deposited W layers containing D or D together with impurity species (He or N) and corresponding modeling, the D diffusion coefficients in different W samples will be determined from nuclear reaction analysis and thermal desorption experiments supplemented by modeling. A newly-developed depth profiling method will allow deducing the concentration profiles of He/N and D with nanometer depth resolution. The analyses will provide a more-detailed insight into the hydrogen isotopes transport and retention characteristic of tungsten, especially for the near-surface region where impurities are expected to be implanted.  It is expected that the results of the study will allow reconciling some of the apparent contradictions in the current data base, and thus improving the reliability of the extrapolations that are necessary for estimating tritium retention and permeation losses in a future fusion reactor.

Dipl. Ing. Alexander von Müller: Advanced manufacturing methods for divertor plasma facing components

The exhaust of power and particles is regarded as one of the ultimate challenges in view of the design of a future magnetic confinement nuclear fusion demonstration power plant (DEMO). In such a future reactor, highly loaded plasma-facing components, like the divertor vertical targets, have to withstand severe particle and heat flux loads as well as considerable neutron irradiation and their behaviour under these loads represents a key issue. The tolerable peak power load on the divertor target plates represents a crucial constraint on the design of a DEMO reactor and is expected to determine its operating scenario.        
Against this background, the development of novel innovative materials and solutions for plasma-facing component design is mandatory while the key to such advanced solutions is the capability of realising, i.e. manufacturing them with high quality reliably.
The research project aims at devising advanced design schemes for divertor targets and realising the manufacture of corresponding mock-ups for high heat flux testing. Specifically, this includes the use of metallic composite materials that are currently regarded as promising candidate materials for plasma-facing component applications.       

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