J. Likonen

Material migration patterns and overview of first surface analysis of the JET ITER-like wall

Following the first JET ITER-like wall operations a detailed in situ photographic survey of the main chamber and divertor was completed. In addition, a selection of tiles and passive diagnostics were removed from the vessel and made available for post mortem analysis. From the photographic survey and results from initial analysis, the first conclusions regarding erosion, deposition, fuel retention and material transport during divertor and limiter phases have been drawn. The rate of deposition on inner and outer base divertor tiles and remote divertor corners was more than an order of magnitude less than during the preceding carbon wall operations, as was the concomitant deuterium retention. There was however beryllium deposition at the top of the inner divertor. The net beryllium erosion rate from the mid-plane inner limiters was found to be higher than for the previous carbon wall campaign although further analysis is required to determine the overall material balance due to erosion and re-deposition.

Beryllium Migration in JET ITER-like Wall Plasmas

JET is used as a test bed for ITER, to investigate beryllium migration which connects the lifetime of first-wall components under erosion with tokamak safety, in relation to long-term fuel retention. The (i) limiter and the (ii) divertor configurations have been studied in JET-ILW (JET with a Be first wall and W divertor), and compared with those for the former JET-C (JET with carbon-based plasma-facing components (PFCs)). (i) For the limiter configuration, the Be gross erosion at the contact point was determined in situ by spectroscopy as between 4% (Ein = 35 eV) and more than 100%, caused by Be self-sputtering (Ein = 200 eV). Chemically assisted physical sputtering via BeD release has been identified to contribute to the effective Be sputtering yield, i.e. at Ein = 75 eV, erosion was enhanced by about 1/3 with respect to the bare physical sputtering case. An effective gross yield of 10% is on average representative for limiter plasma conditions, whereas a factor of 2 difference between the gross erosion and net erosion, determined by post-mortem analysis, was found. The primary impurity source in the limiter configuration in JET-ILW is only 25% higher (in weight) than that for the JET-C case. The main fraction of eroded Be stays within the main chamber. (ii) For the divertor configuration, neutral Be and BeD from physically and chemically assisted physical sputtering by charge exchange neutrals and residual ion flux at the recessed wall enter the plasma, ionize and are transported by scrape-off layer flows towards the inner divertor where significant net deposition takes place. The amount of Be eroded at the first wall (21 g) and the Be amount deposited in the inner divertor (28 g) are in fair agreement, though the balancing is as yet incomplete due to the limited analysis of PFCs. The primary impurity source in the JET-ILW is a factor of 5.3 less in comparison with that for JET-C, resulting in lower divertor material deposition, by more than one order of magnitude. Within the divertor, Be performs far fewer re-erosion and transport steps than C due to an energetic threshold for Be sputtering, and inhibits as a result of this the transport to the divertor floor and the pump duct entrance. The target plates in the JET-ILW inner divertor represent at the strike line a permanent net erosion zone, in contrast to the net deposition zone in JET-C with thick carbon deposits on the CFC (carbon-fibre composite) plates. The Be migration identified is consistent with the observed low long-term fuel retention and dust production with the JET-ILW.

Erosion and deposition in the JET divertor during the first ILW campaign

Erosion and deposition were studied in the JET divertor during the first JET ITER-like wall campaign 2011 to 2012 using marker tiles. An almost complete poloidal section consisting of tiles 0, 1, 3 ...

Surface analysis of tiles and samples exposed to the first JET campaigns with the ITER-like wall

This paper reports on the first post-mortem analyses of tiles removed from JET after the first campaigns with the ITER-like wall (ILW) during 2011?12?[1]. Tiles from the divertor have been analysed by ion beam analysis techniques and by secondary ion mass spectrometry to determine the amount of beryllium deposition and deuterium retention in the tiles exposed to the scrape-off layer. Films 10?20??m thick were present at the top of tile 1, but only very thin films (<?1??m) were found in the shadowed areas and on other divertor tiles. The total amount of Be found in the divertor following the ILW campaign was a factor of ???9 less than the material deposited in the 2007?09 carbon campaign, after allowing for the longer operations in 2007?09.

Long-term fuel retention in JET ITER-like wall

Post-mortem studies with ion beam analysis, thermal desorption, and secondary ion mass spectrometry have been applied for investigating the long-term fuel retention in the JET ITERlike wall components. The retention takes place via implantation and co-deposition, and the highest retention values were found to correlate with the thickness of the deposited impurity layers. From the total amount of retained D fuel over half was detected in the divertor region. The majority of the retained D is on the top surface of the inner divertor, whereas the least retention was measured in the main chamber on the mid-plane of the inner wall limiter. The recessed areas of the inner wall showed significant contribution to the main chamber total retention. Thermal desorption spectroscopy analysis revealed the energetic T from DD reactions being implanted in the divertor. The total T inventory was assessed to be >0.3 mg.

Experience of handling beryllium, tritium and activated components from JET ITER like wall

JET components are removed periodically for surface analysis to assess material migration and fuel retention. This paper describes issues related to handling JET components and procedures for preparing samples for analysis; in particular a newly developed procedure for cutting beryllium tiles is presented. Consideration is also given to the hazards likely due to increased tritium inventory and material activation from 14 MeV neutrons following the planned TT and DT operations (DTE2) in 2017. Conclusions are drawn as to the feasibility of handling components from JET post DTE2.

Investigation on the erosion/deposition processes in the ITER-like wall divertor at JET using glow discharge optical emission spectrometry technique

As a complementary method to Rutherford back scattering (RBS), glow discharge optical emission spectrometry (GDOES) was used to investigate the depth profiles of W, Mo, Be, O and C concentrations into marker coatings (CFC/Mo/W/Mo/W) and the substrate of divertor tiles up to a depth of about 100 μm. A number of 10 samples cored from particular areas of the divertor tiles were analyzed. The results presented in this paper are valid only for those areas and they cannot be extrapolated to the entire tile. Significant deposition of Be was measured on Tile 3 (near to the top), Tile 6 (at about 40 mm from the innermost edge) and especially on Tile 0 (HFGC). Preliminary experiments seem to indicate a penetration of Be through the pores and imperfections of CFC material up to a depth of 100 μm in some cases. No erosion and a thin layer of Be (<1 μm) was detected on Tiles 4, 7 and 8. On Tile 1 no erosion was found at about 1/3 from bottom.

First results from the 10Be marker experiment in JET with ITER-like wall

When the ITER-like wall was installed in JET, one of the 218 Be inner wall guard limiter tiles had been enriched with Be-10 as a bulk isotopic marker. During the shutdown in 2012-2013, a set of til ...

EFD-C(13)03/21 Re-Deposition Dynamics of Trace 13C in H-mode Divertor Conditions

M.I. Airila1, T. Makkonen2, A. Järvinen2, M. Groth2, S. Brezinsek3, J.P. Coad1, S. Jachmich4, A. Kirschner3, J. Likonen1, A. Meigs5, M. Rubel6, A. Widdowson5 and JET-EFDA Contributors∗ JET-EFDA, Culham Science Centre, Abingdon, UK 1 VTT Technical Research Centre of Finland, Association EURATOM-Tekes, Finland 2 Aalto University, Association EURATOM-Tekes, Finland 3 Forschungszentrum Jülich, Association EURATOM-FZJ, Germany 4 Association “EURATOM Belgian State” Laboratory for Plasma Physics, Belgium 5 Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, UK 6 Association EURATOM-VR, Fusion Plasma Physics, EES, KTH, Sweden

Analysis of Boron in LDL-Matrix

New boronated molecules that accumulate in tumor cells through various mechanisms have been introduced in recent years. The Finnish BNCT research group is studying boronated LDL as a potential 10B carrier1,2. Boron concentrations have been determined by charged particle bombardment and by different forms of inductively-coupled plasma analysis3,4,5. Also, the use of thermal neutrons in prompt-γ analysis of 10B has been described recently6,7. In this study four boron analysis methods have been tested: proton induced gamma emission analysis, inductively coupled atomic emission spectrometry and mass spectrometry, and secondary ion mass spectrometry.