Author: Li, C.

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1 articles found

Laser-induced breakdown spectroscopy for Wendelstein 7-X stellarator limiter tile analysis

Author: Li, C. ; et. al.

Journal: Physica Scripta (2017)

Applications

DOI: 10.1088/0031-8949/2017/T170/014004

Authors

Keywords

laser-induced breakdown spectroscopy; plasma wall interaction; fuel retention; deposition; erosion;

Abstract

Laser-induced breakdown spectroscopy is a well-established elemental composition analysis method as well as one of the most promising candidates for in situ first wall diagnosis of fusion devices. In this work, limiter graphite tiles, which were exposed in the initial operational phase of the Wendelstein 7-X stellarator to He and H plasma, are analyzed ex situ by LIBS employing a picosecond pulsed laser for the first time and compared with post mortem analysis techniques. Depth profiles of each element and 2D profile of the ratio of H and C atoms on the surface are investigated. Both H content and retention depth on the deposition dominated zone are higher than on the erosion dominated zone due to the formation of C-H co-deposition layer. The results from LIBSare in agreement with those from the cross-sectional scanning electron microscopic image and electron dispersive x-ray spectroscopy.

Area:

Nuclear industry

Material:

Tokamak wall

Elements:

Lines [nm]:

H I 656.27 nm

Lines [nm]:

C II 657.81 nm

Lines [nm]:

Na I 589.00 nm

Lines [nm]:

Fe I 396.91 nm

Emmision lines:
Fe I 396.91 nm
Na I 589.00 nm
H I 656.27 nm
C II 657.81 nm

Co-author: Li, C.

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4 articles found

Temporal and spatial dynamics of optical emission from laser ablation of the first wall materials of fusion device

Author: Zhao, D. ; et. al.

Journal: Plasma Science and Technology (2018)

Applications

DOI: 10.1088/2058-6272/aa96a0

Authors
Ding, H. B. ; Gao, L. ; Hu, Z. H. ; Li, C. ; Luo, G. N. ; Wang, Y. ; Wang, Z. W. ; Wu, J.

Keywords

laser induced breakdown spectroscopy; EAST tokamak; temporal and spatial dynamics;INDUCED BREAKDOWN SPECTROSCOPY; TUNGSTEN PLASMA; MAGNETIC-FIELD; DIAGNOSTICS; DEPOSITION

Abstract

Laser-induced breakdown spectroscopy (LIBS) has been developed to in situ diagnose the chemical compositions of the first wall in the EAST tokamak. However, the dynamics of optical emission of the key plasma-facing materials, such as tungsten, molybdenum and graphite have not been investigated in a laser produced plasma (LPP) under vacuum. In this work, the temporal and spatial dynamics of optical emission were investigated using the spectrometer with ICCD. Plasma was produced by an Nd:YAG laser (1064 nm) with pulse duration of 6 ns. The results showed that the typical lifetime of LPP is less than 1.4 mu s, and the lifetime of ions is shorter than atoms at similar to 10(-6) mbar. Temporal features of optical emission showed that the optimized delay times for collecting spectra are from 100 to 400 ns which depended on the corresponding species. For spatial distribution, the maximum LIBS spectral intensity in plasma plume is obtained in the region from 1.5 to 3.0 mm above the sample surface. Moreover, the plasma expansion velocity involving the different species in a multicomponent system was measured for obtaining the proper timing (gate delay time and gate width) of the maximum emission intensity and for understanding the plasma expansion mechanism. The order of expansion velocities for various species is V-C+ > V-H > V-Si+ > V-Li > V-Mo > V-W. These results could be attributed to the plasma sheath acceleration and mass effect. In addition, an optimum signal-to-background ratio was investigated by varying both delay time and detecting position.

Area:

Nuclear industry

Material:

Fusion device ; Wall

Elements:

Lines [nm]:

Mo I 550.65 nm Mo I 553.30 nm Mo I 557.04 nm

Lines [nm]:

W I 400.88 nm W I 407.44 nm

Lines [nm]:

H I 656.28 nm

Lines [nm]:

Li I 670.78 nm

Lines [nm]:

C II 657.81 nm

...

Emmision lines:
W I 400.88 nm
W I 407.44 nm
Mo I 550.65 nm
Mo I 553.30 nm
Mo I 557.04 nm
Dy I 655.80 nm
H I 656.28 nm
C II 657.81 nm
Li I 670.78 nm

Development of laser-based technology for the routine first wall diagnostic on the tokamak EAST: LIBS and LIAS

Author: Hu, Z. ; et. al.

Journal: Physica Scripta (2017)

Applications

DOI: 10.1088/1402-4896/aa8650

Authors
Li, C.

Keywords

plasma-material interactions; plasma diagnostic techniques; laser induced breakdown spectroscopy; laser induced ablation spectroscopy;FUSION DEVICES; COMPONENTS

Abstract

A laser based method combined with spectroscopy, such as laser-induced breakdown spectroscopy and laser-induced ablation spectroscopy , is a promising technology for plasma-wall interaction studies. In this work, we report the development of in situ laser-based diagnostics for the assessment of static and dynamic fuel retention on the first wall without removing the tiles between and during plasma discharges in the Experimental Advanced Superconducting Tokamak . The fuel retention on the first wall was measured after different wall conditioning methods and daily plasma discharges by in situ LIBS. The result indicates that the LIBS can be a useful tool to predict the wall condition in EAST. With the successful commissioning of a refined timing system for LIAS, an in situ approach to investigate fuel retention is proposed.

Area:

Nuclear industry

Material:

Tokamak wall

Elements:

Lines [nm]:

Li II 548.57 nm Li I 670.79 nm Li II 548.36 nm

Lines [nm]:

Mo I 550.65 nm Mo I 553.30 nm Mo I 557.04 nm

Emmision lines:
Li II 548.36 nm
Li II 548.57 nm
Mo I 550.65 nm
Mo I 553.30 nm
Mo I 557.04 nm
Li I 670.79 nm

Laser-induced breakdown spectroscopy to monitor ion cyclotron range of frequency wall cleaning Li/D co-deposition in EAST tokamak

Author: Liu, P. ; et. al.

Journal: Fusion Engineering and Design (2017)

Applications

DOI: 10.1016/j.fusengdes.2017.03.021

Authors
Ding, H. ; Hai, R. ; Hu, J. S. ; Hu, Z. H. ; Chen, J. L. ; Li, C. ; Luo, G. N. ; Sun, L. Y. ; Wang, L. ; Wu, D. ; Zhao, D. Y.

Keywords

Ambient gas; Magnetic field; LIBS; EAST; ICRF wall cleaning;TRANSVERSE MAGNETIC-FIELD; INDUCED PLASMA SPECTROSCOPY; OPTICAL-EMISSION; PLUME; PERFORMANCE

Abstract

In this paper, laser-induced breakdown spectroscopy (LIBS) under magnetic field condition has been studied in laboratory and EAST tokamak. The experimental results reveal that in helium ambient gas, the magnetic field significantly enhances the LIBS signal intensity (similar to 3 times). The effect of time delay and laser fluence on the intensity of LIBS has been investigated for optimizing the signal to background ratio (S/B). The developed LIBS approach has been applied to monitor the cleaning performance of the first wall in the fusion device of EAST using the ion cyclotron range of frequency (ICRF). The experimental results demonstrate that the cleaning performance for Li/D co-deposition layer is effective under helium ambient gas. The removing rate of Li on the surface of W tile is faster than that on Mo tile in He-ICRF cleaning and the D/(D + H) ratio on Mo tile is higher by similar to 1.2 times than that on W tile. This work would indicate the feasibility of using LIBS to monitor the wall cleaning processes in EAST tokamak. (C) 2017 Elsevier B.V. All rights reserved.

Area:

Nuclear industry

Material:

Cleaning ; Tokamak wall

Elements:

Lines [nm]:

Li I 610.35 nm

Emmision lines:
Li I 610.35 nm

Preliminary results of in situ laser-induced breakdown spectroscopy for the first wall diagnostics on EAST

Author: Hu, Z. ; et. al.

Journal: Plasma Science and Technology (2017)

Applications

DOI: 10.1088/2058-6272/19/2/025502

Authors
Ding, F. ; Ding, H. B. ; Li, C. ; Liu, P. ; Luo, G. N. ; Mao, H. M. ; Wu, J. ; Xiao, Q. M. ; Zhao, D. Y.

Keywords

tokamak; laser-induced breakdown spectroscopy; impurity deposition; fuel retention; plasma wall interaction;ADVANCED SUPERCONDUCTING TOKAMAK; PLASMA-FACING COMPONENTS; CO-DEPOSITED LAYERS; FUSION-REACTORS; RETENTION; REMOVAL

Abstract

Post-mortem methods cannot fulfill the requirement of monitoring the lifetime of the plasma facing components (PFC) and measuring the tritium inventory for the safety evaluation. Laser-induced breakdown spectroscopy (LIBS) is proposed as a promising method for the in situ study of fuel retention and impurity deposition in a tokamak. In this study, an in situ LIBS system was successfully established on EAST to investigate fuel retention and impurity deposition on the first wall without the need of removal tiles between plasma discharges. Spectral lines of D, H and impurities (Mo, Li, Si, ...) in laser-induced plasma were observed and identified within the wavelength range of 500-700 nm. Qualitative measurements such as thickness of the deposition layers, element depth profile and fuel retention on the wall are obtained by means of in situ LIBS. The results demonstrated the potential applications of LIBS for in situ characterization of fuel retention and co-deposition on the first wall of EAST.

Area:

Nuclear industry

Material:

Plasma facing component

Elements:

Lines [nm]:

Li I 610.37 nm Li I 670.79 nm Li II 548.45 nm

Lines [nm]:

Mo I 550.65 nm Mo I 553.30 nm Mo I 557.04 nm

Lines [nm]:

Ca II 393.37 nm Ca II 396.85 nm

Lines [nm]:

H I 656.28 nm

Lines [nm]:

Dy I 655.80 nm

Emmision lines:
Ca II 393.37 nm
Ca II 396.85 nm
Li II 548.45 nm
Mo I 550.65 nm
Mo I 553.30 nm
Mo I 557.04 nm
Li I 610.37 nm
Dy I 655.80 nm
H I 656.28 nm
Li I 670.79 nm

Author: Li, C.

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Co-author: Li, C.

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