Effect of partially ionized high-Z atoms on fast electron dynamics in tokamak plasmas

Y. Peysson (1, 2) , D. Mazon (2) , A. Jardin (3) , K Król (3) , J Bielecki (3) , D Dworak (3) , M Scholz (3) , O Embréus (4) , L Hesslow (4) , T Fülop (4) , M Hoppe (4) , J Decker (5)

1 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
2 IRFM - Institut de Recherche sur la Fusion par confinement Magnétique
3 H. Niewodniczanski Institute of Nuclear Physics
4 Chalmers University of Technology [Göteborg]
5 EPFL - Ecole Polytechnique Fédérale de Lausanne

The dynamics of fast electrons driven inductively or by resonant interactions with radio-frequency waves is known to be highly sensitive to the presence of impurities in hot magnetized hydrogen plasmas. The possibility to use tungsten for the ITER divertor, thanks to its low tritium retention and high melting temperature, has raised the question of the impact of partially ionized high-Z atoms on current drive efficiency by enhancing pitch-angle scattering but also collisional slowing-down and inelastic scattering. Pioneering work on the impact of the screening effect of partially ionized atoms in kinetic calculations was carried out primarily for the problem of runaway electron mitigation in very cold post-disruptive plasmas [1]. In the present paper, this approach is adapted and extended to regular plasma regimes, allowing to take into account any type of high-Z metallic impurity in the plasma core on the fast electron dynamics and the non-thermal bremsstrahlung. This work has been implemented in LUKE Fokker-Planck solver [2] and the quantum relativistic radiation code R5-X2 [3] and the impact of partially ionized high-Z impurities on Lower Hybrid driven current in the WEST tokamak has been investigated.

Domains: Physics [physics]; Physics [physics]; Plasma Physics [physics.plasm-ph]

Y. Peysson, D. Mazon, A. Jardin, K Król, J Bielecki, et al.. Effect of partially ionized high-Z atoms on fast electron dynamics in tokamak plasmas. IAEA FEC 2020 - The 28th IAEA Fusion Energy Conference, May 2021, Nice (E-Conference), France. ⟨cea-03249410⟩