Plasma and ions interaction with tungsten surfaces: interests for nuclear fusion

Speaker

• Dr. Marco Minissale - Centre national de la recherche scientifique (CNRS), Physique des Interaction Ioniques et Moleculaire (PIIM) Laboratory

Abstract

Using nuclear fusion’s power is the goal of the ITER tokamak, an international fusion reactor under construction in Cadarache (France). In the tokamak, a magnetically confined plasma of hydrogen isotopes (deuterium and radioactive tritium) is heated to millions of kelvin, and power exhaust is realized on the divertor tiles made of tungsten (W). A detailed understanding of the interaction of W with fusion fuel (deuterium and tritium) is needed, especially because tritium is a scarce and radioactive element. The interaction of ions with W can induce modifications in the material, such as blisters and bubbles [1-3]. Such (near-) surface modifications can be responsible, for example, of an increased fuel inventory in the reactor walls [4] and affect the optical properties of tungsten due to both an increasing surface roughness and a change of electronic properties of implanted materials. A cursory knowledge of the evolution of the divertor's optical properties during plasma interaction represents a risk as it may lead to inaccurate thermography measurements of plasma-facing components during reactor operation [5,6]. The proper functioning of fusion reactor therefore seems to be linked to a better understanding of the fundamental mechanisms controlling the interaction of charged particles (HI and He ions) with tungsten.
In this contribution we present different experimental studies performed at the PIIM laboratory (Aix-Marseille University, CNRS, France) using an arsenal of plasma and surface science technics: ion mass and energy spectrometry analysis, temperature programmed desorption, LEED, Auger spectroscopy, X-ray and UV Photoelectron Spectroscopy, ellipsometry.
We will focus on two main studies:
1) The retention behavior of deuterium in single-crystal tungsten and on recrystallized polycrystalline W samples [7-9].
2) The evolution of ellipsometry signal in presence of trapped deuterium.
Eventually, we will discuss the potential interest of these experimental findings for fusion applications.

[1] Manhard, Balden, and Von Toussaint, Nucl. Fusion 57 (2017) 126012
[2] Gao et al, Nucl. Fusion 54 (2014) 122003
[3] Balden et al. J. Nucl. Matel. 452 (2014) 248–56
[4] Nishijima et al., Nucl. Fusion 45 (2005) 669–674
[5] Guilhem et al. IEEE Transactions on Plasma Science, 48 (2019) 2495-2501
[6] Minissale et al. J. Phys. D: Applied Phys. 50 (2017) 45560
[7] Hodille et al, Nucl. Fusion. 57 (2017) 076019
[8] Ghiorghiu et al., Nucl. Instr. Meth. B, 461 (2019) 159-165
[9] Dunand et al., Nucl. Fusion, 62 (2022) 054002

Further References

• A. Dunand, M. Minissale, T. Angot and R. Bisson, Flux dependence of helium retention in clean W(110): Experimental evidence for He self trapping,Nuclear Materials and Energy 34, 101324 (2023), https://doi.org/10.1016/j.nme.2022.101324
• M. Minissale, C. Louis De Canonville, C. Pardanaud , B. Butoi, R. Bisson and L. Gallais, The role of defects, deuterium, and surface morphology on the optical response of beryllium, Nuclear Fusion 62, 056012 (2022), https://doi.org/10.1088/1741-4326/ac4c71
• A. Dunand, M. Minissale, J.-B. Faure, L. Gallais, T. Angot and R. Bisson, Surface oxygen versus native oxide on tungsten: contrasting effects on deuterium retention and release, Nuclear Fusion, 62, 054002(2022) https://doi.org/10.1088/1741-4326/ac583a
•  F. Ghiourghiu, M. Minissale, E. Hodille et al., Comparison of dynamic deuterium retention in single-crystal and poly-crystals of tungsten: The role of natural defects, Nuclear Instruments and Methods B, 461, 159-165 (2019) https://doi.org/10.1016/j.nimb.2019.09.032
•  M. Minissale, C. Pardanaud, R. Bisson, L. Gallais, The temperature dependence of optical properties of tungsten in visible and near-infrared domain: an experimental and theoretical study, Journal of Physics D: Applied Physics, 50, 455601 (2017), https://doi.org/10.1088/1361-6463/aa81f3
•  E.A. Hodille, F. Ghiorghiu, Y. Addab, A. Zalovnik, M. Minissale, Z. Piazza, C. Martin, T. Angot, L. Gallais, M.-F. Barthe, C.S. Becquart, S. Markelj, J. Mougenot, C. Grisolia and R. Bisson, Retention and Release of Hydrogen Isotopes in Tungsten Plasma Facing Components: the Role of Grain Boundaries and the Native Oxide Layer from a Joint Experiment-Simulation Integrated Approach, Nuclear Fusion, 57, 076019 (2017),https://doi.org/10.1088/1741-4326/aa6d24