LIBS applicability for investigation of re-deposition and fuel retention in tungsten coatings exposed to pure and nitrogen-mixed deuterium plasmas of Magnum-PSI

Abstract

We have investigated the applicability of Laser Induced Breakdown Spectroscopy (LIBS) for analyzing the changes in the composition and fuel retention of W and W-Ta coatings following exposure to D2 or mixed D2-N2 plasma beams in the linear plasma device Magnum PSI. The exposed samples were characterized by in-situ ns-LIBS and complementary analysis methods Secondary Ion Mass Spectroscopy, Energy Dispersive X-Ray spectroscopy and Nuclear Reaction Analysis. In agreement with the used complementary analysis methods, LIBS revealed the formation of up to 200 nm thick co-deposited surface layer in the central region of the coatings which contained a higher concentration of the main plasma impurities, such as N, and metals, such as Ta and Mo, the latter originating mainly from the substrate and from the plasma source. The deuterium retention on the other hand was highest outside from the central region of the coatings.

Plasma rotation and axial flow velocities in Magnum-PSI from cross-correlation measurements

“…Magnum-PSI is a linear magnetized plasma generator designed to study the plasma-surface interaction (PSI) with relevance for the divertor region of the future ITER [13] and DEMO [14] fusion reactors: ion flux densities greater than 10 25 m −2 s −1 and energy flux densities greater than 50 MW m −2 [15]. Besides the knowledge of plasma parameters at the target, plasma flow is an important factor for understanding the physics of the PSI studies conducted in Magnum-PSI, such as: ITER divertor monoblock performance [16], plasma detachment [17], target surface modifications (erosion/redeposition) [18], impurity seeding effects [18,19], fuel retention [18,20] etc. Moreover, sheared plasma rotation in poloidal/azimuthal direction, which is mainly driven by E × B and diamagnetic drifts, is related to the achievement of the magnetic confinement in fusion reactors [21] and the transport of particles and heat in the divertor region [22].…”

Advances in Magnum-PSI probe diagnosis in support of plasma–surface interaction studies

“…However, the divergent configuration was a temporary solution until the superconducting magnet was commissioned. All studies of the plasma-surface interaction in Magnum-PSI, such as ITER divertor monoblock performance [22], target surface modifications (erosion/redeposition) [23], fuel retention [23,24], plasma detachment [7] etc, are now performed using the superconducting magnet confinement. A good understanding of the investigated phenomena requires accurate knowledge of the plasma parameters at the target surface.…”