| 1. |
- Hirai, T., et al.
(författare)
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Characterization and heat flux testing of beryllium coatings on Inconel for JET ITER-like wall project
- 2007
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T128, s. 166-170
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Tidskriftsartikel (refereegranskat)abstract
- In order to perform a fully integrated material test, JET has launched the ITER-like wall project with the aim of installing a full metal wall during the next major shutdown. The material foreseen for the main chamber wall is bulk Be at the limiters and Be coatings on inconel tiles elsewhere. R&D process comprises global characterization ( structure, purity etc) of the evaporated films and testing of their performance under heat loads. The major results are (i) the layers have survived energy loads of 20 MJ m(-2) which is significantly above the required level of 5 - 10 MJ m(-2), (ii) melting limit of beryllium coating would be at the energy level of 30 MJ m(-2), (iii) cyclic thermal load of 10 MJ m(-2) for up to 50 cycles have not induced any noticeable damage such as flaking or detachment.
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| 2. |
- Ivanova, Darya, et al.
(författare)
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Survey of dust formed in the TEXTOR tokamak : structure and fuel retention
- 2009
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Ingår i: Physica scripta. T. - : Institute of Physics Publishing (IOPP). - 0281-1847. ; T138, s. 014025-
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Tidskriftsartikel (refereegranskat)abstract
- A detailed survey of erosion and deposition on plasma-facing components was performed in the TEXTOR tokamak. Co-deposits and dust particles were collected from graphite limiters and from several locations on the Inconel liner. The total amount of dust (loose material), originating mainly from carbon-rich co-deposits detached from the limiters and the liner, was around 2 g, with sizes from 0.1 mu m to 1 mm. The morphology and fuel retention was determined using microscopy methods, ion beam analysis and thermal desorption spectrometry. The study revealed differences in structure and fuel content between deposits from the toroidal and main poloidal limiters. There were also splashes, up to 1 mm in diameter, of molten metal (mainly nickel) on the toroidal limiters. Issues of the dust conversion factor (erosion-to-dust) are addressed and a comparison with results of previous dust surveys at TEXTOR is also briefly presented.
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| 3. |
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| 4. |
- Kreter, A., et al.
(författare)
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Deuterium retention in different carbon materials exposed in TEXTOR :
- 2008
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Ingår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY. - Bristol : IOP PUBLISHING LTD. ; , s. 062024-
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Konferensbidrag (refereegranskat)abstract
- CFC NB31, CFC DMS780 and fine-grain graphite EK98 were simultaneously exposed in the SOL of TEXTOR in order to measure the retention of deuterium in the material bulk. After exposure, the samples were analysed by thermal desorption spectrometry and nuclear reaction analysis with a conventional beam as well as with a microbeam. The deuterium retention amounts (2-4).10(21) D/m(2) for the incident fluence of similar to 2.10(25) D/m(2). The retention values are similar for both CFC materials and lower by similar to 20-40% for EK98. The retention in all three materials scales roughly with a square root of incident fluence without saturation for the range of fluences obtained. The majority of deuterium is stored in a surface layer of <8 mu m. However, in NB31 deuterium is detectable as deep as 80 mu m. The in-bulk retention estimated for a TEXTOR experimental campaign of approximate to 7500 s of plasma has a contribution of approximate to 10% to the total retention, which is dominated by deuterium-carbon co-deposition.
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| 5. |
- Krieger, K., et al.
(författare)
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Be wall sources and migration in L-mode discharges after Be evaporation in the JET tokamak
- 2009
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 390-91, s. 110-114
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Tidskriftsartikel (refereegranskat)abstract
- First wall material erosion and migration after fresh Be evaporation in the JET tokamak were studied in a series of consecutive identical L-mode discharges. The evolution of Be and C wall and divertor sources towards steady state conditions after deposition of a finite amount of Be at the carbon first wall of JET by the beryllium evaporation procedure provides a data set for benchmarking impurity transport simulations. Furthermore the experiment serves as a reference case for comparison of Be erosion to that of the planned ITER-like wall experiment with mainly Be plasma facing components (PFCs) in the main chamber. The experimental results confirm the migration pattern obtained by campaign integrated accounting of impurity sources and sinks, which is characterised by the main chamber wall and outer divertor as erosion dominated zones and migration of eroded material predominantly to the inner divertor where the material is finally deposited at the target plates.
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| 6. |
- Psoda, M., et al.
(författare)
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Material mixing on plasma-facing components : Compound formation
- 2009
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Ingår i: Journal of Nuclear Materials. - : Elsevier. - 0022-3115 .- 1873-4820. ; 386-388, s. 740-743
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Tidskriftsartikel (refereegranskat)abstract
- Two different tungsten limiters (castellated bulk metal block and W-coated graphite), subjected to high power loads in the TEXTOR tokamak, were examined in order to determine chemical composition of deposits inside the castellated grooves and on side surfaces of the coated limiter. Comprehensive analyses carried out by X-ray diffraction, ion beam analysis and other methods revealed: (i) the formation of tungsten oxide (WO2) inside the castellated grooves: (ii) the formation of tungsten carbides (WC main phase and traces of W2C) on side surfaces of the coated limiter. Elemental tungsten was found in deposits on side surfaces only in trace quantities thus indicating that tungsten eroded from the limiter top and transported to the scrape-off layer reacted with carbon. Based on thermodynamic data, the pathways leading to the formation of compounds are discussed.
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| 7. |
- Rubel, Marek, et al.
(författare)
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Comprehensive First Mirror Test for ITER at JET with Carbon Walls
- 2010
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Ingår i: Proceedings of the23rd IAEA Fusion Energy Conference.
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Konferensbidrag (refereegranskat)abstract
- Metallic mirrors will be essential components of all optical spectroscopy and imaging systems forplasma diagnosis that will be used on the next-step magnetic fusion experiment, ITER. Any change of the mirrorperformance, in particular reflectivity, will influence the quality and reliability of detected signals. On therequest of the ITER Design Team, a First Mirror Test (FMT) has been carried out at JET during campaigns in2005-2007 and 2008-2009. To date, it has been the most comprehensive test performed with a large number oftest mirrors exposed in an environment containing both carbon and beryllium; the total plasma time (in 2005-2007 period) over 35 h including 27 h of X-point operation. 32 stainless steel and polycrystalline molybdenumflat-front and 45oangled mirrors were installed in separate channels of cassettes on the outer wall and in the MkII HD divertor: inner leg, outer leg and base plate under the load bearing tile. Post exposure studies comprisedreflectivity measurements and surface analyses with microscopy, secondary ion mass spectrometry, ion beamanalysis and energy dispersive X-ray spectroscopy.. The essential results are: (i) on the outer wall highreflectivity (~90%) is maintained for mirrors close to the channel entrance but it is degraded by 30-40 % deeperin the channel (ii) reflectivity loss by 70-90% is measured for mirrors placed in the divertor: outer, inner andbase; (iii) deuterium and carbon are the main elements detected on all mirror surfaces and the presence ofberyllium is also found; (iv) thick deposits show rough columnar structure and thickness is 1-20 μm; (v) bubblelike structures are detected in deposits; (vi) the deposition in channels in the divertor cassettes is pronounced atthe very entrance; (vii) photonic cleaning with laser removes deposits but the surface is damaged by laser pulses.In summary, reflectivity of all tested mirrors is degraded either by erosion with CX neutrals or by the formationof thick deposits. The implications of results obtained for first mirrors in next-step device are discussed andcritical assessment of various methods for in-situ cleaning of mirrors is presented. The conclusion is thatengineering solutions should be developed in order to install shutters or to implement a cassette with mirrors toreplace periodically the degraded ones
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| 8. |
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| 9. |
- Rubel, Marek J., et al.
(författare)
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An overview of a comprehensive First Mirror Test for ITER at JET
- 2009
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Ingår i: Journal of Nuclear Materials. - Amsterdam : ELSEVIER SCIENCE BV. - 0022-3115 .- 1873-4820. ; 390-91, s. 1066-1069
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Tidskriftsartikel (refereegranskat)abstract
- The test was performed with 32 stainless steel and molybdenum mirrors placed in pan-pipe shaped cassettes and exposed in JET in the divertor and on the main chamber wall for 127000 s including 97000 s of X-point operation. Surface composition and total reflectivity were determined afterwards All mirrors. from the divertor were coated with deuterated carbon deposits causing the reflectivity loss by a factor of 6-10 in the visible range. Flaking and exfoliation of deposits were observed in some cases On the main. chamber wall the deposition occurred mainly on mirrors located deep in cassette channels whereas mirrors close to the channels entrances were free from deposits and retained fair reflectivity (similar to 90% of initial value) especially in the infra-red range. No significant differences in behaviour of steel and molybdenum were noted. The need for development of methods for mirror cleaning and/or protection in a reactor-class device is addressed.
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| 10. |
- Rubel, Marek J., et al.
(författare)
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Beryllium plasma-facing components for the ITER-Like Wall Project at JET
- 2008
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Ingår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY. - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- ITER-Like Wall Project has been launched at the JET tokamak in order to study a tokamak operation with beryllium components on the main chamber wall and tungsten in the divertor. To perform this first comprehensive test of both materials in a thermonuclear fusion environment, a broad program has been undertaken to develop plasma-facing components and assess their performance under high power loads. The paper provides a concise report on scientific and technical issues in the development of a beryllium first wall at JET.
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