Fusion

SFA - Slovenian fusion association

The work is performed in the frame of Slovenian fusion association

Our laboratory is actively involved in studies related to the current development of new generation of fusion reactors. This work is closely correlated with other activities within EU and coordinated by European Fusion Development Agreement (EFDA). We have two projects, P2 and P5, financially supported by Slovenian Fusion Association (SFA) (Association EURATOM - MHEST). Both projects are related to plasma - wall interaction and are included in the work program of EU Plasma-Wall Interaction Task Force. SFA hosted 5th annual meeting of TF PWI in Ljubljana from November 13-15, 2006. Very active collaboration with other fusion associations exists in particular with Forschungszentrum, Jülich and Max-Planck-Institut für Plasmaphysik, Garching.


Project P2:

Title:

Interaction of vibrationally excited hydrogen with fusion relevant materials

Collaborators: Iztok Čadež, Milan Čerček, Zvone Grabnar, Sabina Markelj, Primož Pelicon, Dušan Rudman, Zdravko Rupnik, Tomaž Gyergyek and Vida Žigman - Project performed in collaboration with Department for Rector Physics, JSI (M.Č. and D.R.), Faculty for Electrical Engineering, University of Ljubljana (T.G.) and University of Nova Gorica (V.Ž.)

The main goal of this project is to providing quantitative data for processes involving vibrationally excited hydrogen molecules that are needed for modelling of fusion edge plasma and plasma-wall interaction. We also search for specific phenomena with such molecules that might have high cross sections. Studies are performed with H2 and D2 in order to understand isotope effect and especially as deuterium is the main constituent of tokamak plasma. In particular we are interested in the following processes at surfaces of fusion relevant materials:

  • Vibrational distribution of molecules released from surfaces by thermal desorption and recombinative desorption for different surface temperatures and composition.
  • Ratio of atomic to molecular species released from a surface and its variation with surface parameters.
  • Interaction of vibrationally excited molecules with plasma-facing materials:
    • Change of vibrational distribution caused by interaction with the surfaces.
    • Transfer of vibrational energy to the wall and its effects on erosion yields.
    • Wall sticking probability for the excited molecules.
Due to importance of volume reactions in divertor plasma we are also interested in:
  • Binary collisions of vibrationally excited hydrogen molecules with other atomic particles.

For diagnostics of molecules participating in reactions we use vibrational spectrometer based on the properties of dissociative electron attachment in hydrogen and for characterising H and D concentration on/in the studied materials we use ERDA with 7Li2+ probing ion beam.

Contact person:

Dr. Iztok Čadež



Project P5:

Title:

Application of ion beam analytical methods to the studies of plasma wall interaction in tokamaks

Collaborators: Primož Pelicon, Iztok Čadež, Zvone Grabnar, Darko Hanžel, Matjaž Kavčič, Zdravko Rupnik, Jure Simčič

Research in the field of interaction between tokamak plasma and wall materials is performed in order to solve one of the most demanding technological problems in construction of thermonuclear reactor: construction and maintenance of its inner wall.

Experiments with deuterium in existing fusion reactors provide information, which is extrapolated to the operation of future thermonuclear reactor ITER. Iter will operate with a fuel mixture of tritium and deuterium. In the last two years the final appearance of ITER wall cleared out. To optimize wall against erosion and fuel retention, the wall will be constructed out of tungsten and beryllium, and carbon fiber composites will be used for plasma striking points of the diverter, where highest thermal load will take place. Fuel retention in the ITER wall presents serious thread to its operation, as the mobilisable tritium inventory limit is set to 350 g [1]. When the safety limit would be achieved, ITER will be shutdown and cleaned.

The one of most selective methods for detection of deuterium in materials is based on nuclear reaction D(3He,p)4He, which is exited by 3He ion beam with an energy above 500 keV. Application of focused 3He ion beam results in microdistribution of retained fuel with micrometer resolution [2]. Research results will improve the understanding of the retention process as well as of the appropriate cleaning techniques, which include exposure of the walls to cleaning plasma and light pulses. In the field of "post-mortem" analysis of the wall materials exposed in controlled experiments our group closely collaborates with Forshungszentrum Juelich and Royal Institute of technology, Stockholm [3], within EU-EFDA taskforce Plasma-Wall Interaction and Association EUROATOM-MHEST. In collaboration with laboratory CIEMAT from Madrid the retention in the wall segmentation gaps will be investigated.

  1. A. Kirschner, D. Borodin, S. Droste, V. Philipps, U. Samm, G. Federici, A. Kukushkin and A. Loarte, Journal of Nucl. Mat. 363-365 (2007) 91.
  2. H. Bergsaker, B. Emmoth, P. Petersson, G. Possnert, J.P. Coad, J. Likonen and T. Renvall, Journal of Nucl. Mat. 362, (2007), 215.
  3. A Kreter, S Brezinsek, M Rubel, B Emmoth, M Freisinger, P Pelicon, V Philipps, O Schmitz, P Sundelin, G Sergienko and TEXTOR team: Deuterium retention in different carbon materials exposed in TEXTOR, submitted to Journal of Physics- Conference Series.
Plasma-Wall Interaction in tokamak

Plasma-Wall Interaction in tokamak.

Plasma-Wall Interaction in tokamak

Fig. 2: Participation in post-mortem analysis: Model of tokamak limiter was exposed in tokamak TEXTOR, Forschungszentrum Juelich, Germany(A. Litnovsky et al, J. Nucl. Mater. 337-339, 917 (2005)). Transport processes, castellation gap deposition as well as fuel retention were investigated with IBA methods at JSI.

Plasma-Wall Interaction in tokamak

Exposure experiment performed at TEXTOR, FZJ. JSI collaborated in post-mortem analysis of deuterium in plasma-exposed Carbon-Fiber Composite materials.

Cleaved CFC
Map of the cleavage region
Cleaved CFC

Cleaved CFC NB31:
a) Map of the cleavage region with 3He focused beam employing D(3He,p)4He reaction.
b)Projection of the deuterium yield in the depth direction: D penetrates below surface (50 micrometers) in distinct points due to porosity in the CFC structure.
(A Kreter, S Brezinsek, M Rubel, B Emmoth, M Freisinger, P Pelicon, V Philipps, O Schmitz, P Sundelin, G Sergienko and TEXTOR team: Deuterium retention in different carbon materials exposed in TEXTOR, submitted to Journal of Physics- Conference Series)

Contact person:

Dr. Primož Pelicon



Last updated: 01/22/2014