Plasma surface interactions
The PSI department studies the interaction at the interface between plasma and materials. Focus of the research lies on providing both theoretical and experimental support to the design and validation of plasma facing materials for the fusion experiment ITER and future devices.
ITER (www.iter.org) is a large scale (10 billion euro) international scientific experiment designed to prove the viability of fusion as a source of efficient, clean and sustainable energy. The ITER machine is based on the tokamak concept. In such a device magnetically confined plasma is heated to temperatures where fusion of light atoms occurs.The exhaust of the machine, the divertor, is subject to steady state heat fluxes of up to 10 MW m-2 and continues bombardment by neutrons. Additionally extreme transient heat fluxes can occur due to instabilities in the plasma. One of the key issues in ITER and future devices is the development of plasma facing components that provide long lifetime, low pollution of the core plasma and comply with safety regulations.
The maximum tolerable concentration of impurities in the core plasma (figure 2, right) depends on the atomic number of the element. For low atomic number (Be, C), a higher concentration is allowed. For higher atomic number (Mo, W) per atom, more energy is lost due to radiation and therefore the tolerable concentration is lower. The blue and red lines in the figure are the boundary conditions determined by the operational goal set for ITER, an energy gain of a factor 10.
Theoretical and experimental and research into the behavior of materials under these extreme conditions is essential to develop materials suitable for the divertor and other plasma facing components.
The scientific program of the PSI department is aimed towards understanding the physics of these processes; mixing of materials at the surface, changes of surface morphology (dust formation, blistering), erosion, (re-)deposition and retention of hydrogen (important for safety aspects). For experimental work the department operates the linear plasma device Pilot-PSI and Magnum-PSI that can simulate plasma conditions on the divertor.
The PSI department is divided into four groups:
Computational plasma physics low temperature
Development and application of advanced numerical and theoretical models to describe the physics of low temperature plasma and plasma surface interaction.
Plasma surface interactions – Experimental
Perform basic plasma-surface interaction research needed for the design of the plasma facing components of future fusion devices.
Low temperature plasma physics and heating
Experimental low temperature plasma physics for understanding of fusion reactor grade divertor plasma (high density, low temperature). Physics and development of plasma source and radio-frequency heating system for dense magnetized plasmas.
Plasma surface interactions – Operations
Operation of the linear plasma devices Magnum-PSI and Pilot-PSI. Investigation of plasma facing components.
The PSI research at DIFFER is performed in close collaboration with its partners in the Trilateral Euregio Cluster (TEC). These partners are the FZ-Jülich and KMS/ERM-Brussels. Additionally there are several smaller national and international collaborations.
Internships
This section is about internships in the PSI department; for general information, see the (Dutch language) page on intern positions.
The PSI department offers students the opportunity of doing an internship within an academic research environment. Students from Dutch technical schools or universities are welcome to participate in our research, with their stay lasting anywhere between a few weeks and a full year. Potential subjects for internships can be parts of most current activities of the group such as spectroscopy, numerical modeling, plasma source development etc. Interested students are encouraged to contact the group leader for further information on possibilities for internship projects.
Interns are supervised by one of the department's researchers and can choose between experimental, modelling or theoretical work. The exact topic and details of the research assignment are often determined in mutual consideration, to get a good match between the student and research.
Results from previous internships are:
MSc internships
Biesheuvel J.(Jurriaan) - "Laser Induced Fluorescence and absorption in the magnetized plasma jet of Pilot-PSI" (2009) In this project, the student investigated the feasibility of using Laser Induced Fluorescence (LIF) for measuring temperature, velocity and density of hydrogen ions in a Pilot plasma. Reliable data on ion parameters is essential for plasma surface interaction experiments. The results obtained have been compared to results from other diagnostics such as Thomson Scattering (TS) and Optical Emission Spectroscopy (OES).
Cuenen, R.M. (Raymond) - "The expanding magnetized plasma jet" (2006) In this project, a numerical model for the steady state expansion of a plasma jet in a magnetic field was created. The model is a tool vital for cascaded arc source development on Pilot and for the design of future large diameter plasma (up to 10 cm) sources required for Magnum. The code was developed employing numerical techniques such as Particle-In-Cell (PIC) and Monte-Carlo (MC) modeling.
BSc internship
Rottier, O. (Otto) - "Continuum and Line Emission Measurements on Pilot-PSI" (2010) Here the student investigated plasma composition using optical techniques such as Thomson Scattering (TS) and Optical Emission Spectroscopy (OES). These results combined with a collisional radiative model, developed in collaboration with IPP Garching were used to make estimates of the densities of various plasma species and to determine important hydrogen excitation pathways.