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

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.

seashell analysis; LIBS; graphite enriched process; Sr/Ca; shell growth;RAMAN-SPECTROSCOPY; CLASSIFICATION; PROFILES; RATIOS; GROWTH; SHELLS

Seashell has been applied as an indicator for ocean research and element analysis of the seashell is used to track biological or environmental evolution. In this work, laser-induced breakdown spectroscopy (LIBS) was applied for elementary analysis of an ezo scallop-shell, and a graphite enrichment method was used as the assistance. It was found that LIBS signal intensity of Ca fluctuated less than 5%, in spite of the sampling positions, and Sr/Ca was related to the shell growth. A similar variation was also found when using a direct LIBS analysis on the shell surface, and it might be more practicable to track shell growth by investigating Sr/Ca ratio with Sr ionic line at 421.6 nm. The obtained results prove that calcium (Ca) is qualified as an internal reference for shell analysis, and LIBS is a potential analytical method for seashell study.

plasma parameter; laser induced plasma; plasma electron density; Saha-Boltzmann method; Stark broadening method;INDUCED BREAKDOWN SPECTROSCOPY; SPECTROCHEMICAL ANALYSIS; ALUMINUM-ALLOYS; SOLID SAMPLES; ABLATION; LINES; EMISSION; PARAMETERS; TEMPERATURE; LIBS

We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns-Nd: YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser energy and the effect of different laser wavelengths were compared. The experimentally observed line profiles of neutral aluminum have been used to extract the excitation temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadened as well as using the Saha-Boltzmann equation (SBE). Each approach was also carried out by using the Al emission line and Mg emission lines. It was observed that the SBE method generated a little higher electron number density value than the Stark broadening method, but within the experimental uncertainty range. Comparisons of N-e determined by the two methods show the presence of a linear relation which is independent of laser energy or laser wavelength. These results show the applicability of the SBE method for N-e determination, especially when the system does not have any pure emission lines whose electron impact factor is known. Also use of M-g lines gives superior results than Al lines.

LIBS; spatial confinement; cavity height; signal enhancement;INDUCED ALUMINUM PLASMA; TIME-RESOLVED EMISSION; OPTICAL-EMISSION; MAGNETIC-FIELD; PULSE; ENHANCEMENT; ABLATION; SILICON; LIBS; OPTIMIZATION

In this paper, we present a study on the spatial confinement effect of laser-induced plasma with a cylindrical cavity in laser-induced breakdown spectroscopy(LIBS). The emission intensity with the spatial confinement is dependent on the height of the confinement cavity. It is found that, by selecting the appropriate height of cylindrical cavity, the signal enhancement can be significantly increased. At the cylindrical cavity (diameter = 2mm) with a height of 6 mm, the enhancement ratio has the maximum value (approximately 8.3), and the value of the relative standard deviation (RSD) (7.6%) is at a minimum, the repeatability of LIBS signal is best. The results indicate that the height of confinement cavity is very important for LIBS technique to reduce the limit of detection and improve the precision.

LIBS; plasma plume; sample temperature; expansion dynamics;INDUCED BREAKDOWN SPECTROSCOPY; DOUBLE-PULSE CONFIGURATION; OPTICAL-EMISSION; MAGNETIC-FIELD; QUANTITATIVE-ANALYSIS; LIBS ANALYSIS; SPECTROMETRY; SINGLE; STEEL; ABLATION

In this paper, we investigated the influence of sample temperature on the expansion dynamics and the optical emission spectroscopy of laser-induced plasma, and Ge was selected as the test sample. The target was heated from room temperature (22 degrees C) to 300 degrees C, and excited in atmospheric environment by using a Q-Switched Nd:YAG pulse laser with the wavelength of 1064 nm. To study the plasma expansion dynamics, we observed the plasma plume at different laser energies (5.0, 7.4 and 9.4 mJ) and different sample temperatures by using time-resolved image. We found that the heated target temperature could accelerate the expansion of plasma plume. Moreover, we also measured the effect of target temperature on the optical emission spectroscopy and signal-to-noise ratio.