Preparing the future post-mortem analysis of beryllium-based JET and ITER samples by multi-wavelengths Raman spectroscopy on implanted Be, and co-deposited Be

Abstract

This study demonstrates that Raman microscopy is a suitable technique for future post mortem analyses of JET and ITER plasma facing components. We focus here on laboratory deposited and bombarded samples of beryllium and beryllium carbides and start to build a reference spectral databases for fusion relevant beryllium-based materials. We identified the beryllium phonon density of states, its second harmonic and E 2G and B 2G second harmonic and combination modes for defective beryllium in the spectral range 300-700 and 700-1300 cm -1 , lying close to Be-D modes of beryllium hydrides. We also identified beryllium carbide signature, Be 2 C, combining Raman microscopy and DFT calculation. We have shown that, depending on the optical constants of the material probed, in depth sensitivity at the nanometer scale can be performed using different wavelengths. This way, we demonstrate that multi-wavelength Raman microscopy is sensitive to in-depth stress caused by ion implantation (down to ≈30 nm under the surface for Be) and Be/C concentration (down to 400 nm or more under the surface for Be+C), which is a main contribution of this work. The depth resolution reached can then be adapted for studying the supersaturated surface layer found on tokamak deposits.2

Hydrogen in beryllium oxide investigated by DFT: on the relative stability of charged-state atomic versus molecular hydrogen

“…The work herein addresses the need of an atomic-scale investigation which models atomic and molecular hydrogen in its neutral and charged states (H 0 , H + , H -, H 2 , H 2 + , H investigate the many chemical bonds that beryllium establishes with oxygen and hydrogen [36,37] , vibrational frequencies at the gamma point are also computed to assist in the assignment of future Raman spectroscopy measurements.…”

Microstructural Transformation of Nanoscale Be Layers in the Mo/Be and Be/Mo Periodic Multilayer Mirrors Investigated by Raman Spectroscopy

“…In curve (a 1 ), a broad Raman band is located around 415.38 cm –1 TO (a-Be), which is red-shifted and became broader with an increase in film thickness (Figure a,c). This band is associated with bond-order and bond-length defects, and in this case, excitation of such phonon is contributed by PDOS. , This mode does not belong to the excitation of the fundamental E 2g mode of the ordered Be–Be bonding. However, the scattered energy of this band exists in the optical phonon region, and therefore we designate it as a transverse optical (TO) band of amorphous Be (a-Be) phase. , The intensity of this band consistently decreases with an increase in the thickness of the Be layer.…”

“…This band is associated with bondorder and bond-length defects, and in this case, excitation of such phonon is contributed by PDOS. 17,20 This mode does not belong to the excitation of the fundamental E 2g mode of the ordered Be−Be bonding. However, the scattered energy of this band exists in the optical phonon region, and therefore we designate it as a transverse optical (TO) band of amorphous Be (a-Be) phase.…”

“…The B 1g and E 2g belong to longitudinal and transverse optical modes, respectively, and only doubly degenerate E 2g mode is Raman-active. However, several other phonon bands may also be excited, which is originated by phonon density of state (PDOS) and defects. − The Be is a semimetal, which has shown a large electron–phonon coupling effect at the Be(0001) surface . This coupling may induce a possible effect on phonon excitation using Raman scattering.…”

Raman microscopy to characterize plasma-wall interaction materials: from carbon era to metallic walls

“…These bands are not allowed by quantum selection rules and crystal symmetry. They are identified as being due to the PDOS of beryllium and appear because of presence of defects [49]. Comparing the PDOS intensity to the Raman allowed band intensity allows obtaining qualitative information on the crystallinity of the material (figure 8 will refer to this point).…”