Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall
Introduction
Plasma-wall interactions, material migration and the resulting surface modification of plasma facing components are identified as key elements in the preparation for future fusion devices [1]. To facilitate material migration studies in the Joint European Torus (JET) with ITER-like wall [2,3], a significant number of probes have been installed; both in the divertor and in the main chamber [4]. Such probes are retrieved for ex-situ analysis during major shutdowns. The aim of this paper is to provide an analysis of deposited layers on components retrieved from remote corners in the JET divertor between 2012 and 2017, after three ITER-like wall campaigns (ILW-1 to ILW-3). Layer thickness, composition and depth profiles of atomic concentrations are investigated. Conclusions about material deposition are drawn while keeping in mind uncertainties and error sources related to the chosen analysis methods. Sample surface morphology and the presence of dust particles are also described. The analysed components are cubic blocks of Inconel-600 with side length 15 mm, referred to as spatial blocks (SB) and 76 mm long stainless steel covers for quartz microbalance (QMB) deposition monitors.
Section snippets
Sample descriptions and plasma exposure conditions
Five SB were included in the present study; SB 4, 5, 6, 8 and 9, all of which, while present in JET, were attached to the carbon ribs of the divertor carrier in Module 14 inner wide (IW) beneath and behind Tile 3. SB4-6 were in the machine between 2011 and 2012, during ILW-1 while SB8-9 were present from 2015 to 2016, during ILW-3. Two sets of four QMB covers each, numbered 1, 2, 3 and 5 were studied. The first such set was present in JET between 2012 and 2014, during ILW-2, except the cover
Spatial blocks 4–6 from ILW-1
ToF-ERDA measurements were performed on three sides of SB4-6: the side facing towards the plasma, the opposite one facing away from the plasma (referred to below as the backside) and one of the sides 90° from the plasma facing direction, opposite to the side fastened on the divertor carrier rib. The geometry of the ToF-ERDA setup was modified for the measurement on the side facing 90° from the plasma; entry angle was 30° and exit angle 15°. Deposited layers whose thickness decreased with the
Discussion
As stated in Section 3.1, out of all ToF-ERDA results presented here, only those from the 90° side of SB4-6 were compensated for ion-induced gas release. The results for D in Table 1 show that when such compensation is applied along with detection efficiency compensation, quantitative agreement between NRA and ToF-ERDA is achieved. Ideally, all ToF-ERDA results for species that can leave the sample as diatomic gases (here H, D 14N, 16O and 18O) should be compensated. This task is, however,
Summary and concluding remarks
Deposits on SB and QMB covers retrieved from remote corners in the JET-ILW divertor have been studied with IBA, SEM and EDS. Layer thicknesses on the order of 1 μm or more were found on the plasma facing side of SB6 from ILW-1, while all other layers on SB were limited to less than 1 μm. Typical layer thicknesses 90° from the plasma facing direction on the SB were a few hundred nm, with slightly thicker layers on SB8-9 from ILW-3 than on SB4-6 from ILW-1, due to the longer divertor plasma time
Data availability
The raw and processed data required to reproduce these findings are available to download from Mendeley Data via the links supplied with the online version of this paper.
Acknowledgments
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under grant agreement number 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Work was performed under work package WPJET2. The Tandem Laboratory has been supported by grants from the Swedish Foundation for Strategic Research, grant number RIF14-0053, and the Swedish
References (29)
- et al.
Overview of the JET ITER-like wall project
Fusion Eng. Des.
(2010) - et al.
Overview of erosion-deposition diagnostic tools for the ITER-Like Wall in the JET tokamak
J. Nucl. Mater.
(2013) - et al.
Quartz micro-balance results of pulse-resolved erosion/deposition in the JET-ILW divertor
Nucl. Mater. Energy
(2017) - et al.
Diagnostics for studying deposition and erosion processes in JET
Fusion Eng. Des.
(2005) - et al.
Potku – new analysis software for heavy ion elastic recoil detection analysis
Nucl. Instrum. Methods
(2014) - et al.
Differential cross-section of the D(3He,p)4He nuclear reaction and depth profiling of deuterium up to large depths
Nucl. Instrum. Methods Phys. Res.
(2005) - et al.
Trapping, detrapping and replacement of keV hydrogen implanted into graphite
J. Nucl. Mater.
(1980) - et al.
Ion-induced release of deuterium from co-deposits by high energy helium bombardment
J. Nucl. Mater.
(1997) - et al.
JET EFDA contributors, Microstructure and inhomogeneous fuel trapping at divertor surfaces in the JET tokamak
Nucl. Instrum. Methods Phys. Res.
(2014) - et al.
Allegria: a new interface to the ERD program
Nucl. Instrum. Methods Phys. Res.
(2004)
Surface oxide and roughness on test samples for the ultra high vacuum section of the laser heater for the European XFEL
Vacuum
SRIM – the stopping and range of ions in matter
Nucl. Instrum. Methods Phys. Res.
Fuel removal from plasma-facing components by oxidation-based techniques. An overview of surface conditions after oxidation
J. Nucl. Mater.
Oxidation and hydrogen isotope exchange in amorphous, deuterated carbon films
J. Nucl. Mater.
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See the author list of X. Litaudon et al., Nucl. Fusion 57 (2017) 102001.