| 1. |
|
|
| 2. |
- Kirschner, Andreas, et al.
(författare)
-
Modelling of deposition and erosion of injected WF6 and MoF6 in TEXTOR
- 2016
-
Ingår i: Nuclear Materials and Energy. - : Elsevier. - 2352-1791.
-
Tidskriftsartikel (refereegranskat)abstract
- Tracer injection experiments in TEXTOR with MoF 6 and WF 6 lead to local deposition of about 6% for Mo and about 1% for W relative to the injected amount of Mo and W atoms. Modelling of these experiments has been done with ERO applying updated data for physical sputtering. The dissociation of the injected molecules has been treated in a simplified manner due to the lack of dissociation rate coefficients. How- ever, with this it was possible to reproduce the observed radial penetration of Mo and W atoms into the plasma. The modelled local deposition efficiencies are about 50% for Mo and 60% for W assuming typical plasma parameters for the experimental conditions used. To reproduce the measured deposition efficien- cies an enhancement factor for the erosion of deposited Mo and W has to be assumed ( ∼10 for Mo and ∼25 for W). Due to the rather low electron temperature T e of these plasma conditions (T e ∼15 eV at the location of injection), Mo and W are mostly sputtered by impurities whereas sputtering due to deuterium is negligible. A parameter study applying larger electron temperature leads to increased sputtering and thus to reduced local deposition efficiencies of about 30% for Mo and 5% for W. Though, even under these conditions enhanced erosion, albeit with reduced enhancement factors, is needed in the modelling to obtain the small measured deposition efficiencies.
|
|
| 3. |
- Litnovsky, Andrey, et al.
(författare)
-
Carbon transport, deposition and fuel accumulation in castellated structures exposed in TEXTOR
- 2007
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 367, s. 1481-1486
-
Tidskriftsartikel (refereegranskat)abstract
- In order to maintain the thermo-mechanical durability of ITER it is proposed to castellate the interior surface of the first wall and divertor by splitting them into small-size cells [W. Daener et a]., Fusion Eng. Des. 61&62 (2002) 61]. A concern is the accumulation of fuel in the gaps of the castellation. In TEXTOR, molybdenum limiters were exposed in the scrape-off layer (SOL) plasma to assess fuel accumulation. The first limiter was exposed under deposition-dominated conditions. Carbon deposits were formed both on top surfaces and in the gaps. About 0.12% of the impinging D-fluence was found in the gaps. Another castellated limiter was exposed under erosion-dominated conditions. Deposited layers were found only on the plasma shadowed areas of the gaps. A significant amount of molybdenum from the limiter was found intermixed in the deposit. The gaps contained similar to 0.03% of the impinging D-fluence. Modeling was performed to simulate carbon transport into the gaps.
|
|
| 4. |
- Weckmann, Armin, et al.
(författare)
-
Ageing of structural materials in tokamaks: TEXTOR liner study
- 2017
-
Ingår i: Physica scripta. T. - : Institute of Physics (IOP). - 0281-1847 .- 0031-8949 .- 1402-4896. ; T170
-
Tidskriftsartikel (refereegranskat)abstract
- After the final shut-down of the tokamak TEXTOR, all of its machine parts became accessible for comprehensive studies. This unique chance enabled the study of the Inconel 625 liner by a wide range of methods. The aim was to evaluate eventual alteration of surface and bulk characteristics from recessed wall elements that may influence the machine performance. The surface was covered with stratified layers consisting mainly of boron, carbon, oxygen, and in some cases also silicon. Wall conditioning and limiter materials hence predominantly define deposition on the liner. Deposited layers on recessed wall elements reach micrometre thickness within decades, peel off and may contribute to the dust inventory in tokamaks. Fuel retention was about 4 at% of the overall layers, with no evidence for diffusion into the Inconel substrate. Inconel 625 retained its mechanical strength despite 26 years of cyclic heating, stresses and particle bombardment.
|
|
| 5. |
- Weckmann, Armin, et al.
(författare)
-
Global material migration in tokamaks : patterns, material balance and transport mechanisms in TEXTOR
- 2017
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- As the last experiment before the final shutdown of the TEXTOR tokamak, equipped with all-graphite plasma-facing components (PFCs), MoF6 had been injected into the vacuum vessel. During decommissioning all PFCs became available for surface studies, enabling detailed mapping of previously injected Mo, W and intrinsic 625 Inconel metals. As a result, detailed deposition patterns for these metals were obtained, revealing a number of findings: a) High-Z metals are mainly globally deposited, with concentrations decaying exponentially with distance from the injection source; b) the decay length is of the order of 0.1 m on the main PFC and 1.0 m on the receded PFC; c) ion flow velocities co-decide the position of maximum deposition. Modelling with ERO shows exponential decay. Simulated decay lengths are between 0.15 – 1.30 m, depending on the anomalous cross field diffusion coefficient. Extensive measurements of Mo have been undertaken in order to quantify the amounts deposited on the graphite PFCs, showing that the ratio of local to global deposited high-Z metals is 0.3-0.4. However, only up to 20% of the injected Mo could be detected on all the PFCs. A large fraction of injected Mo may have been pumped out before being deposited. The bumper limiter is found to be the major repository for all probed elements. For W and F, this is solely due to the limiter size – the areal concentration is not enhanced. For Mo, Inconel metals, 15N and D the areal concentration on the bumper limiter is higher than on the toroidal belt limiter ALTII acting as main PFC.
|
|
