Muneaki Wakamatsu

Detection of Cesium from Pollucite Using Laser-Induced Breakdown Spectroscopy

The purpose of this research is to detect the atomic spectrum of cesium using laser-induced breakdown spectroscopy (LIBS). In this study, pollucite ((Cs,Na)(AlSi2)O6.nH2O) was used as a test sample for the LIBS measurement. LIBS is a useful tool for the determination of the elemental composition of various materials and it does not require any preprocessing step. The Nd:YAG laser was operated at 1064 nm to generate a 50-mJ Q-switched pulse with a width of 8 ns (full width at half maximum, FWHM). The breakdown emissions were dispersed by a grating with a groove density of 1200 lines/mm and the resulting electrical signal was recorded using a streak camera. The plasma intensity was optimized with respect to the background. Spectral measurements were carried out after an appropriate delay time to allow for the decay of the continuum radiation. In the experiments, 100 laser shots were used to record data for each spectrum in ambient air. The results of the experiments showed that the atomic signals corresponding to pollucite were obtained easily by LIBS measurements. Thus, spectrum peaks due to cesium, sodium, aluminum, and silicon are observed. In particular, the characteristics of the cesium spectrum play an important role in establishing the LIBS system for environmental monitoring, which may be used to detect radioactive elements emitted from nuclear plants.

Multi-spectral Analytical Systems Using LIBS and LII Techniques

In this paper, we propose an advanced approach to particle analysis, involving laser-induced breakdown spectroscopy (LIBS) and laser-induced incandescence (LII) temporal analytical techniques. Various technical properties of fine particles are analyzed via LIBS and LII. LIBS is a useful tool for determining the elemental composition and relative concentration of various materials, whereas LII facilitates the measurement of particle size. Both techniques do not require any pre-processing. The combined use of the LIBS and LII techniques enables highly synergistic fine particle measurement. In the LIBS section, we propose spectrometric analysis via a novel ink-jet technique, and we discuss the effectiveness of Ar as a surrounding gas. In the LII section, we compare the calculated particle size prediction with the experimental results.

Development of cesium detection system using laser-induced breakdown spectroscopy

This report presents a new cesium sensing method that uses laser-induced breakdown spectroscopy (LIBS). Conventionally, beta rays and germanium semiconductor detectors have been used for Cs-137 analysis. These methods typically require laboratory-scale analytical facilities. On the other hand, LIBS allows for direct elemental composition measurement of samples regardless of their physical state without preprocessing or laboratory facilities. Even if it is nearly impossible to separate isotopic data from the spectrum of an LIBS measurement, measurement of cesium levels is important for investigating the causes of abnormal radiation levels because the abundance of cesium is low under normal conditions. We report on cesium spectra results as measured by LIBS; the measurements were of sufficient resolution to obtain quantitative information for calculating the expected quantity of radioactive cesium from the isotope ratios.

Sensing system for quantitative analysis of metal particles using laser-induced breakdown spectroscopy

This report describes a real-time sensing system for the detection and analysis of fine metal particles using laser-induced breakdown spectroscopy (LIBS). In conventional particle measurement methods, the scanning mobility particle sizer (SMPS) is widely used to obtain particle size distributions. However, when more details on particles are required, another chemical analysis must be performed separately from the one involving the SMPS. Hence, it is difficult to obtain the size and composition of fine particles in real time by conventional methods. By the proposed LIBS method, it is possible to obtain information on the density of fine particles as well as the chemical components of even ultrafine particles. Metal particles are focused on because the use of metal nanoparticles is expanding with emerging micro- and nanotechnologies. This work describes the use of the LIBS system as a fine metal particle monitoring system in a fabrication process using nanometal materials.

Development of sensing system for carbonaceous particles using LIBS combined with LII temporal analytical technique

This report describes a new sensing system for carbonaceous particles detection using combination with two techniques of laser-induced breakdown spectroscopy (LIBS) and laser-induced incandescence (LII). Our research group has improved LIBS system applied for quantitative analysis. Although the basic principal of the LIBS quantitative measurements were well understood, several uncertainties still remained for complete description especially for the particle size measurement. Elemental composition and density of the particle were determined by using LIBS. Particle size measurement was accomplished with the help of LII. On the presented system, only controlling the power density of the light source allowed to switch from LIBS to LII.

Control of a Micro-Droplet for Laser-induced Breakdown Spectroscopy Solution Measurement

In this paper, laser-induced breakdown spectroscopy (LIBS) using micro-droplet NaCl solution and set-up for control of micro-droplets are described. Micro-droplets controlling technique is important for solution quantitative analysis. In this study, micro-droplet ejection system for sampling is designed and presented. This micro-droplet ejection system enable a constant volume of the sample liquid to be obtained and it takes advantage of the liquid physical state; the density of the solution can be controlled accurately. The method presented here generates small droplets (diameter 30 μm) by confining the entire volume of the sample material in the laser beam spot area (minimum beam spot diameter: 53.2 μm) and separating it from its surroundings. Using this liquid micronizing method, improved sensitivities are obtained. The Advantage of LIBS is a useful method for determining the elemental composition of various materials regardless of their physical state (solid, liquid, or gas) and without any preprocessing; it is a type of atomic emission spectroscopy (AES). Despite the advantage of qualitative analysis, quantitative analysis is difficult because of sample and plasma fluctuations. Generating constant volume of micro-size sample and proper sample control technique contribute to LIBS quantitative analysis.

Laser-Induced Breakdown Spectroscopy Measurements for Dielectric Materials and Metals

This chapter describes an optical sensing system for elemental analysis using laser-induced electro-avalanche fluorescence on wide bandgap materials, and laser-induced plasma on metal objects. This method of measurement and analysis is called “laser-induced breakdown spectroscopy” (LIBS). In LIBS, the vaporizing and exciting plasma is produced by high-powered focused laser pulses. Pulses from a laser are focused on the sample using a lens, and plasma emission light is collected and collimated using a second lens. The light is transported to a wavelength selective device on the spectrograph, and recorded time-resolved, or gate setting, devices to improve the signal-to-noise and signal-to-background ratio. This provides discrimination against interference from an emission continuum, called “bremsstrahlung.” Plasma light is initially dominated by a white light continuum, that has little intensity variation as a function of wavelength because of bremsstrahlung and radiation from the plasma as free electrons and ions recombine in the plasma cooling process. If the emission is recorded over the entire time, this light continuum seriously interferes with the detection of weaker emissions from atomic species. For this reason, temporal resolving measurement is carried out using LIBS. This chapter introduces a LIBS system applied to wide-bandgap materials like sodium, and metal objects containing small metal particles.

Ultratrace measurement using micro-droplet with gas-flow assistance in laser-induced breakdown spectroscopy

A new setup for laser-induced breakdown spectroscopy (LIBS) is introduced. This setup was designed for high sensitive quantitative analysis using the ink-jet technology and gas-flow assistance. The setup presented here allowed precise detection of a micro-droplet for guiding it into a laser beam spot area. The micro-droplet ejection system created constant volume of sample liquid and taking advantage of liquid physical state; density of the solution can be controlled accurately. That means the constant amount of media was maintained in a micro-droplet. This sampling system allowed generating small droplet (diameter 30 mum) confining the whole fixed volume of the sample material in the laser beam spot area (minimum beam spot diameter 53.2 mum), under the effects of any ambient gas. In this paper, the stability with practical use and improvement of detection limit for LIBS measurement is reported.

Evaluation of Laser-Induced Breakdown Spectroscopy Quantitative Sensing Performance Using a Micro-Droplet Ejection System

A new and reliable evaluating method for a laser induced breakdown spectroscopy (LIBS) quantitative measurement using a micro-droplet sample ejection system is introduced. LIBS has been investigated extensively to establish proper chemical analysis of specimens. There is an indefinable boundary which is ablated or not when laser focusing on the sample. Generating micro-droplets from concentration tuned solution, and leading to the correct beam spot area are important for determining the total amount of media in a droplet. The LIBS measures the sodium chloride concentration of a micro-droplet as a quantitative measurement by recording intensity from the sample plasma. As a result, LIBS with the micro-drop ejection system produced greater intensities than the old technique of bulk-liquid measurement based on data from 100 laser pulse shots.

Study of laser-induced breakdown spectroscopy from micro-droplet of NaCl Solution

The laser-induced breakdown spectroscopy (LIBS) using micro-droplet sodium chloride solution is presented. Micronizing the sample made possible that whole volume of a sample was confined in the laser beam spot area and was separated from its surrounding condition. If the samples physical state was liquid, the density of solution could be controlled as needed. Originally designed ink-jet system for sampling procedure was presented. According to the new method, improved calibration curves for the LIBS quantitative measurement were obtained.