Remote <i>in situ</i> laser-induced breakdown spectroscopic approach for diagnosis of the plasma facing components on experimental advanced superconducting tokamak

De-you, Zhao; Liu, Cong; Hu, Zhenhua; Feng, Chao; Xiao, Qingbo; Hai, Ran; Liu, Ping; Sun, Liying; Wu, Ding; Fu, Cailong; Liu, Shiyuan; Farid, Nagy A.; Ding, Fang; Luo, Guang–Nan; Wang, Liang

doi:10.1063/1.5024848

Cited by 56 publications

(14 citation statements)

References 36 publications

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“…Moreover, LIBS also has great potential for depth analysis of multilayer samples based on laser ablation and atomic emission spectroscopy [10]. With these special benefits, LIBS had been installed in several tokamak devices and proposed for future application in W7-X for PWI research including fuel retention and erosion/deposition studies [11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Quantification of erosion pattern using picosecond-LIBS on a vertical divertor target element exposed in W7-X

De-you¹,

Yi²,

Eksaeva³

et al. 2020

Nucl. Fusion

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A set of dedicated marker samples consisting of fine-grain graphite as substrate, an interlayer of 0.2–0.4 μm molybdenum (Mo) employed as marker, and a 5–10 μm thick carbon (C) marker layer on top were installed in Wendelstein 7-X (W7-X) to investigate locally the C erosion and deposition. In this study, a set of five individual marker tiles, installed in a vertical divertor element of the test divertor unit in half-module 50, and exposed to about 40 min of plasma predominant in the standard magnetic divertor configuration in the first year of divertor operation in W7-X (OP1.2A), were retrieved from the vessel for post-mortem analysis. Picosecond laser induced breakdown spectroscopy (ps-LIBS) was applied on these marker tiles in order to determine the local erosion/deposition pattern caused by plasma impact. The general erosion/deposition pattern on the vertical target element was studied with the aid of depth-profiling by Mo line emission due to ps-LIBS with the number of applied laser pulses (355 nm, 2.3 J cm−2, 35 ps) at one probing location. Several potential asymmetry factors which avoid a perfect layer-by-layer ablation process in the laser ablations are proposed and discussed when a rough layered structure sample with a rough surface is analysed by the ps-LIBS technique. Thereby, a simulation model was developed to correct the measurement error of the ps-LIBS method caused by the non-perfect rectangle profile of the applied laser beam. The depth resolution of the applied ps-LIBS system was determined by quantification of the laser ablation rates of the different layers and the C substrate which were measured utilising profilometry and cross comparison with the thicknesses of the C and Mo marker layers determined by a combined focused ion beam and scanning electron microscopy technique. For the first time, the erosion/deposition pattern on the vertical target was mapped and quantified by ps-LIBS technique. A relatively wide net erosion zone with a poloidal extend of about 200 mm was identified which can be correlated to the main particle interaction zone at the magnetic strike-line of the dominantly applied standard magnetic divertor configuration. At the position of peak erosion, not only 7.6 × 1019 C atoms/cm2 but also 2 × 1018 Mo atoms/cm2 which results can be extrapolated to total 15 × 1019 C atoms/cm2, were eroded due to plasma fuel particle (H, He) and impurity (O, C) ion impact.

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Section: Introductionmentioning

confidence: 99%

Quantification of erosion pattern using picosecond-LIBS on a vertical divertor target element exposed in W7-X

De-you¹,

Yi²,

Eksaeva³

et al. 2020

Nucl. Fusion

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“…It should be noted that this work describes T retention measurement systems that should operate during the maintenance phase of a fusion reactor and perform measurements over a wide area inside the reactor vessel. For in-situ measurement of T during the operational phases of the reactor some LIBS systems are already designed or tested [50][51][52], these systems are mainly applied for a limited number of locations in the first wall of the reactor. Secondly, it is noted that the scope of this work concerns the conceptual design of a LIBS system that will be applied during maintenance periods of a fusion reactor, issues concerning neutron radiation from the activated vessel components are beyond the scope of this work.…”

Section: Discussionmentioning

confidence: 99%

Monitoring of tritium and impurities in the first wall of fusion devices using a LIBS based diagnostic

Meiden¹,

Almaviva²,

Butikova³

et al. 2021

Nucl. Fusion

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Laser-induced breakdown spectroscopy (LIBS) is one of the most promising methods for quantitative in-situ determination of fuel retention in plasma-facing components (PFCs) of magnetically confined fusion devices like ITER and JET. In this article, the current state of understanding in LIBS development for fusion applications will be presented, based on a complete review of existing results and complemented with newly obtained data. The work has been performed as part of a research programme, set up in the EUROfusion Consortium, to address the main requirements for ITER: (a) quantification of fuel from relevant surfaces with high sensitivity, (b) the technical demonstration to perform LIBS with a remote handling system and (c) accurate detection of fuel at ambient pressures relevant for ITER. For the first goal, the elemental composition of ITER-like deposits and proxies to them, including deuterium (D) or helium (He) containing W–Be, W, W–Al and Be–O–C coatings, was successfully determined with a typical depth resolution ranging from 50 up to 250 nm per laser pulse. Deuterium was used as a substitute for tritium (T) and in the LIBS experiments deuterium surface densities below 1016 D/cm2 could be measured with an accuracy of ∼30%, confirming the required high sensitivity for fuel-retention investigations. The performance of different LIBS configurations was explored, comprising LIBS systems based on single pulse (pulse durations: ps–ns) and double pulse lasers with different pulse durations. For the second goal, a remote handling application was demonstrated inside the Frascati-Tokamak-Upgrade (FTU), where a compact, remotely controlled LIBS system was mounted on a multipurpose deployer providing an in-vessel retention monitor system. During a shutdown phase, LIBS was performed at atmospheric pressure, for measuring the composition and fuel content of different area of the stainless-steel FTU first wall, and the titanium zirconium molybdenum alloy tiles of the toroidal limiter. These achievements underline the capability of a LIBS-based retention monitor, which complies with the requirements for JET and ITER operating in DT with a beryllium wall and a tungsten divertor. Concerning the capabilities of LIBS at pressure conditions relevant for ITER, quantitative determination of the composition of PFC materials at ambient pressures up to 100 mbar of N2, the D content could be determined with an accuracy of 25%, while for atmospheric pressure conditions, an accuracy of about 50% was found when using single-pulse lasers. To improve the LIBS performance in atmospheric pressure conditions, a novel approach is proposed for quantitative determination of the retained T and the D/T ratio. This scenario is based on measuring the LIBS plume emission at two different time delays after each laser pulse. On virtue of application of a double pulse LIBS system, for LIBS application at N2 atmospheric pressure the distinguishability of the spectra from H isotopes could be significantly improved, but further systematic research is required.

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“…When affected by a disturbed electric field caused by the motion of charged particles, the energy levels of atoms and ions will be broadened, which leads to spectral broadening. Stark broadening is caused by the interaction of a radiation system with charged particles of LIP and is the main reason for spectral broadening of LIBS [19].…”

Section: Electron Densitymentioning

confidence: 99%

Radial characteristics of laser-induced plasma under the influence of air pressure

Yuan

Liu

et al. 2023

J. Phys. D: Appl. Phys.

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Air pressure is one of the key factors affecting laser induced breakdown spectroscopy (LIBS), and the mechanism of its influence on the spatial-temporal evolution of laser induced plasma (LIP) is still not fully understood due to the complex physical processes. In this study, the spatially and temporally resolved LIP’s spectra at different pressures were collected from the direction of laser incidence, and the radial distribution characteristics of LIP along the target surface under the influence of air pressure was studied. Furthermore, the spatial-temporal evolution of radial distribution of electron density ne and electron temperature Te were studied by the Stark broadening and Boltzmann plot. Finally, the radial distribution of LIP satisfying the McWhirter’s criterion, and the influence of air pressure on its spatial-temporal evolution were studied. It was found that air pressure has a significant effect on radial distribution of LIP. Spectral intensity, electron density ne, electron temperature Te of LIP decrease faster against distance r from LIP core and slower with delay time Td in a higher air pressure environment. What’s more, the LIP will gradually fail to satisfy the McWhirter’s criterion with the increase of radius r and delay time Td; and the lifetime of LIP which satisfies the McWhirter’s criterion is longer at higher-pressure. This study is helpful to clarify the influence of air pressure on the spatial-temporal evolution of LIP, optimize the experimental parameters of LIBS, and provide a reference for application of LIBS.

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Remote in situ laser-induced breakdown spectroscopic approach for diagnosis of the plasma facing components on experimental advanced superconducting tokamak

Cited by 56 publications

References 36 publications

Quantification of erosion pattern using picosecond-LIBS on a vertical divertor target element exposed in W7-X

Quantification of erosion pattern using picosecond-LIBS on a vertical divertor target element exposed in W7-X

Monitoring of tritium and impurities in the first wall of fusion devices using a LIBS based diagnostic

Radial characteristics of laser-induced plasma under the influence of air pressure

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