This title appears in the Scientific Report :
2021
Combined high fluence and high cycle number transient loading of ITER-like monoblocks in Magnum-PSI
Combined high fluence and high cycle number transient loading of ITER-like monoblocks in Magnum-PSI
Combined high fluence and high cycle number transient loading of ITER-like monoblocks in Magnum-PSI T.W. Morgan, Y. Lia,M. Baldenb, S. Brezinsekc, G. De TemmermandDIFFER -Dutch Institute for Fundamental Energy Research, De Zaale 20, 5612 AJ Eindhoven, the NetherlandsaEindhoven University of Technolo...
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Personal Name(s): | Morgan, T. W. |
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Li, Yun / Balden, M. / Brezinsek, S. (Corresponding author) / De Temmerman, G. | |
Contributing Institute: |
Troposphäre; IEK-8 Plasmaphysik; IEK-4 |
Imprint: |
2021
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Conference: | 24th International Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI 2020), virtuell (virtuell), 2021-01-25 - 2021-01-29 |
Document Type: |
Abstract |
Research Program: |
Plasma-Wand-Wechselwirkung |
Publikationsportal JuSER |
Combined high fluence and high cycle number transient loading of ITER-like monoblocks in Magnum-PSI T.W. Morgan, Y. Lia,M. Baldenb, S. Brezinsekc, G. De TemmermandDIFFER -Dutch Institute for Fundamental Energy Research, De Zaale 20, 5612 AJ Eindhoven, the NetherlandsaEindhoven University of Technology, Department of Mechanical Engineering, Groene Loper 3 5612 AE, Eindhoven, the NetherlandsbMax-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, GermanycForschungszentrum Jülich, Institut für Energie-und Klimaforschung, 52425 Jülich, GermanydITER Organization, Route de Vinon sur Verdon, CS90 046, 13067 St Paul Lez Durance Cedex, Francet.w.morgan@differ.nlPeak ELM energy fluence during the half-field half-current and full-field full-current phases of ITER is extrapolatedto be in the range ε||~ 2.5-7.5 MJ m-2and 10-30 MJ m-2,respectively [1]. Mitigation of ELM-loading to lower values (ε||<5 MJ m-2) is therefore essential to avoid full surface meltingof the tungsten plasma-facing material (PFM)[1]. However, e-beam measurements have found that cyclicalELM-like loading at much lower energies can lead to cracking via plastic deformation leading to fatigue-like behaviour [2]. It should be noted that plasma loading typically modifies most strongly only the very near surface region consisting of the top few microns of material. However, this is the same region which is most strongly affected by short transient loading as the heat penetration depth is typically in the 10’s of μm range. Thereforesynergy between plasma and ELM-like loading hasbeen previously observed(e.g. [3]). However, until now high plasma fluence and high cycle numbers have not been combinedduring ITER-monoblock loading, while a definition of the tolerable power level for ELM-loading under these conditions is of critical importance for predictions of safe ITER service conditions and PFM lifetime.A mockup consisting of five ITER-grade and dimensioned monoblocks mounted on a CuCrZr pipe was exposed in Magnum-PSI [4] to combined hydrogen plasma with superimposed transient loading using a high power welding laser. The blocks received a hydrogen fluence of between 1.1-2.9×1029m-2at a base temperature of 750-790 °C while 1 ms laser pulses with heat flux factor (HFF) of 2.3-11.2 MW m-2s0.5were superimposed during the plasma exposure. Up to 106pulses were applied. The surfaces were examined using SEMand CLSM. For the lowest applied HFF no surface modificationswereobserved, but for higher loading conditions a crack network extending across the laser spot region was created. The crack edges were smoothed by the plasma exposure, preventing small melt regions from forming, unlike for e-beam loading [2]. For the exposure at 5.5 MW m-2s0.5a large crack extending beyond the laser loaded region also appeared. Given that ITER may experience millions of ELMs, the results indicate that ELM energies need to be mitigated to at least below ε||~ 1.7MJ m-2in ITERto avoid comprehensive surface crack networks forming,similar to the limits determined for e-beam loading[2, 5].Whether this is an operational limit that wouldultimately lead to component failure is not yet clearhowever and requires future investigation.[1] T. Eich et al. Nucl. Mater. Energy 12 (2017) 84-90[2] Th. Loewenhoff et al. Phys. Scr. T145 (2011) 014057[3] G.G. van Eden et al. Nucl. Fusion 54 (2014) 123010[4] H.J.N. van Eck et al. Fusion Eng. Des. 142 (2019) 26-32[5] M. Wirtz et al. Nucl. Mater. Energy 12 (2017) 148-155. |