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Projects / Programmes source: ARIS

Study of the plasma parameters for conditioning of the inner surfaces of a fusion reactor

Research activity

Code Science Field Subfield
2.03.02  Engineering sciences and technologies  Energy engineering  Fuels and energy conversion technology 

Code Science Field
T160  Technological sciences  Nuclear engineering and technology 
Keywords
energy, fusion, ITER, tokamak, plasma, etching, cleaning, sheath, probes
Evaluation (rules)
source: COBISS
Researchers (11)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  18271  PhD Miha Čekada  Materials science and technology  Researcher  2008 - 2011  441 
2.  01116  PhD Milan Čerček  Physics  Researcher  2008 - 2011  318 
3.  26476  PhD Aleksander Drenik  Electronic components and technologies  Junior researcher  2008 - 2009  694 
4.  10401  PhD Tomaž Gyergyek  Physics  Head  2008 - 2011  414 
5.  15602  Damjan Matelič    Technical associate  2008 - 2011 
6.  10429  PhD Miran Mozetič  Electronic components and technologies  Researcher  2008 - 2011  1,353 
7.  09090  PhD Peter Panjan  Materials science and technology  Researcher  2008 - 2011  792 
8.  06527  Branko Petrič  Electric devices  Researcher  2008 - 2011  23 
9.  01718  PhD Iztok Šorli  Electronic components and technologies  Researcher  2008 - 2011  63 
10.  20048  PhD Alenka Vesel  Electronic components and technologies  Researcher  2008 - 2011  689 
11.  29275  PhD Tjaša Vrlinič  Engineering sciences and technologies  Researcher  2008 - 2011  16 
Organisations (4)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  90,724 
2.  0341  MIKROIKS, microelectronics engineering, consulting and service  Ljubljana  5286646  70 
3.  1538  University of Ljubljana, Faculty of Electrical Engineering  Ljubljana  1626965  27,771 
4.  2341  INDUKTIO L.t.d.  Ljubljana  1840711  23 
Abstract
Chemical etching of the CFC parts of fusion devices represents the major problem in current fusion reactors as well as the future reactor ITER which is due to start operating in the next future. The etched material is deposited in remote parts of fusion reactors and, as nowadays, it is believed to cause major problem in fuel retention. The deposits should be removed occasionally in order to assure proper operation of fusion reactors. The removal of these deposits will be addresed within this project. A novel technique for removal of deposits will de developed. The technique is based on interaction of neutral oxygen or nitrogen atoms with deposited carbon and hydrogenated carbon films. First, a source of O atoms, and N atoms will be constructed and thouroughly characterized. Second, a system for delivering atoms into remote parts of fusion reactors will be developed, and third, ecxtensive experiments on application for deposits removal will be performed. In the final stage, a portable device for removal deposits at TEXTOR fusion plasma reactor will be constructed and applied for routine removal of the deposits. The device will be later optimized for the removal of the deposits in ITER, when ready. Since almost all the activity in the proposed project is related to the plasma-surface interaction, the study of the potential formation in front of electrodes immersed in multicomponent magnetized and nonmagnetized plasmas will also be a part of this project. Sheath and probe related investigations will contain experimental and theoretical studies supproted by computer simulation. An important activity forseen within this project is promotion of fusion as an ecologically benign source of energy. It is foreseen to gradually publish contributions for newspapers and magazines to explain that nuclear fusion is neither a nuclear threat nor a scientific illusion but rather a real alternative to fossile fuels.
Significance for science
The results of extensive research performed in the field of modelling and simulation of plasma potential formation in front of a negative electrode revealed that the modified shooting method developed within this project is applicable as the key criterium for the determination of the discharge regime. The potential fall in front of the cathode in such plasma depends on the ratio between the density and electron energy distribution function of hot and cool electrons. Our results therefore greatly contribute to the understanding of pheomena in complex plasma, specially to understanding of edge fusion plasma. The research on behavior of the matching unit between the high frequency generator and plasma revealed some phenomena that, to the best of our knowledge, have not been mentioned in relevant literature. We found spontaneous transitions between inductive and capacitive modes of plasma. Such transitions are characterized by a sudden drop in the density of neutral oxygen atoms. The systematic work performed within this project showed that such transitions depend on the matching between the oscillation circuits. It can be controlled rather well by modifications in the quality of the secondarry oscillation circuit. Results of extensive experimental work represent a solid database which will be used in next future by scientists working on modeling of interaction between plasma and surfaces in fusion centers worldwide. The scientists will be able to predict the processes on walls of present and future fusion devices. The database includes the state of the art of previously published data as well as our original results obtained within the work program of this project. The recombination and interaction coefficients are given as a function of discharge parameters, the type of material as well as its temperature. To the best of our knowledge it is the first database of this kind worldwide. Results of our measurements revealed an important observation on the influence of the coefficient for heterogeneous surface recombination of oxygen and hydrogen atoms on the morphology of samples. These results open a wide field for future research. To the best of our knowledge, no results of systematic measurements of the recombination of atoms on materials with the same structure but with different morphology have ever been reported in literature. The results are particularly interesting for scientists working in plasma nanoscience – a new, rapidly expanding field of plasma science. An important discovery is reduction of tungsten oxide thin films by hydrogen plasma. Scientists worldwide have believed that the reduction is not possible in hydrogen atmosphere at relatively low temperature. We performed systematic measurements at our partner in Font Romeau, France. The results clearly showed that reduction is possible providing extremely nonequilibrium plasma with almost 100% dissociation fraction is supplied. We also able to explain the paradox: The measured value for the reaction probability was found to be of the order of 0.0001 only. Other authors do not have plasma with extremely high hydrogen atom density and that is why they were not able to reduce the oxide by their own plasmas.
Significance for the country
A major task of this project is a development of a large plasma reactor as a source of neutral reactive atoms. The project is heavily co-funded by European Community (Euratom) and our industrial partner Induktio Ltd. The major purpose of this new plasma reactor is fulfilling demands of this project, but the knowledge and experiences gained within this project will contribute to further improval of our R&D activities in the way of development novel ecological benign dry plasma technologies for modification of the surface properties of meterials and components for our industrial partners. Such plasma technologies will gradually replace the ecological unsuitable wet chemical methods. The results represent an important contribution to recognition and reputation of Slovenian science in international fusion community as well as in EFDA (European Fusion Development Agreement). They show that even small associations, such as Slovenian in contribute important results towards strategic goals of a huge organization such as EFDA. By these means the Slovenian association fruitfully contributes to the final goal of EFDA – development of reactors for environmentally benign production of energy. Another contribution of the achieved results is towards development of high-tech society. The results obtained within this project contribute to understanding the complex mechanisms of interaction between gaseous plasma and materials. Our research group is traditionally involved in development of new high value added and ecologically friendly technologies for treatment of various materials at our (mainly Slovenian) industrial partners. The results therefore directly contribute to increasing level of knowledge and thus to development of new technological processes needed to increase the competitiveness of the Slovenian industry in the world. Last but not least, the research contributes indirectly to a low carbon society since the energy obtained from fusion does not produce any carbon dioxide.
Most important scientific results Annual report 2008, 2009, final report, complete report on dLib.si
Most important socioeconomically and culturally relevant results Annual report 2008, 2009, final report, complete report on dLib.si
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