Mikio Kuzuya

Effect of Laser Energy and Atmosphere on the Emission Characteristics of Laser-Induced Plasmas

The effects of laser energy and atmosphere on the emission characteristics of laser-induced plasmas were studied with the use of a Q-switched Nd: YAG laser over a laser energy range of 20 to 95 mJ. Argon, helium, and air were used as surrounding atmospheres, and the pressures were changed from atmospheric pressure to 1 Torr. The experimental results showed that the maximum spectral intensity was obtained in argon at around 200 Torr at a high laser energy of 95 mJ, whereas the line-to-background ratio was maximized in helium at around 40 Torr at a low energy of 20 mJ. The results are discussed briefly on the basis of the temporal and spatial observations of the laser-induced plasmas.

Quantitative analysis of ceramics by laser-induced breakdown spectroscopy

Abstract A quantitative elemental analysis of ceramics was carried out with laser-induced breakdown spectroscopy. A Q-switched Nd:YAG laser was focused on ceramic targets in an argon atmosphere at reduced pressure, and the emission spectra from laser-induced plasma were measured using time-resolved spectroscopy. The experimental results showed that in argon at approximately 200 Torr, the spectral line intensity and the line-to-background ratio were maximized by observing the laser plasma with a time delay of 0.4 μs. Also, time-resolved measurement of a spectrum in the initial stage of plasma generation (∼1 μs) was effective for improving the slope of the calibration curve. Based on the results, standard ceramic samples were analyzed for magnesium, aluminum, calcium, iron and titanium, and linear calibration curves with a slope of unity were obtained by measuring spectra with a gate width of 0.4 μs at a delay time of 0.4 μs after the laser pulse in argon at 200 Torr.

Analysis of a high-concentration copper in metal alloys by emission spectroscopy of a laser-produced plasma in air at atmospheric pressure

In order to investigate the possibility of analysis of a high concentration (4.5–90%) of copper in metal alloy samples (Al alloys and brass) with a laser microprobe analyzer in air at atmospheric pressure, the emission characteristics of plasmas produced by a Q-switched Nd:YAG laser over a laser energy range of 30–90 mJ (irradiance: 9.5×109–2.9×1010 W cm−2) were studied using time-resolved spectroscopy. The experimental results showed that the effect of self-absorption can be reduced by increasing the laser pulse energy. The results of time-resolved spectroscopy of laser-induced plasmas indicated that self-absorption is predominant during short time-periods (t<0.4 μs) after the laser pulse, and a time delay is effective for the reduction of self-absorption. At a high laser energy of 90 mJ, a linear calibration curve with a slope near unity was obtained for the analysis of copper in the concentration range from 4.5 to 20% with a gate width of 0.4 μs at a delay time of 0.4 μs after the laser pulse.

Effect of Argon Atmosphere on Self-Absorption of a Spectral Line in Laser Microprobe Analysis

The effect of the reduced argon atmosphere on the self-absorption of a spectrum was studied with the use of a normal laser microprobe by changing the gas pressure and the observation height of spectral lines. At 150 Torr, a spectral line virtually free of self-absorption and a resultant high emission intensity were obtained about 1.5 mm above the sample surface. Using this condition, the linear calibration curve with unit slope was obtained for the analysis of copper (concentration:1–20%) in aluminium samples.

Effect of argon pressure on spectral emission of a plasma produced by a laser microprobe

The effect of an argon atmosphere on the self-absorption of emission spectra of a laser-induced plasma was studied with the use of a normal laser microprobe by changing the gas pressure. The degree of self-absorption was determined from the observed profiles of copper resonance lines using the curve-fitting method with the assumption of a Lorentzian profile. According to the results, self-absorption was reduced by decreasing the argon pressure and was eliminated at low pressures, the range of which depends on the analyte concentration. Studies of the spatially resolved spectrum show that the confining effect of the plasma by the argon atmosphere becomes effective at higher pressures, resulting in an increase in the emission intensity. As a result, there exists a moderate pressure at which self-absorption can be eliminated without losing too much intensity from reduction of confinement. At a pressure of around 150 Torr (1 Torr = 133.3 Pa) high emission intensity of the spectral line virtually free from self-absorption was obtained about 1.5 mm above the sample surface for the determination of copper (concentration 1–9.8%) in aluminium samples, and a linear calibration graph with a slope of unity was obtained.

Application of a quadrupole mass filter to laser ionization mass spectrometry: synchronization between the laser pulse and the mass scan

A quadrupole-based laser ionization mass spectrometry system was developed by combining a commercial quadrupole mass filter with a laser microprobe instrument, which employs a pulse generator that synchronizes the laser pulse with the quadrupole mass scan to detect the pulsed ion signals generated by laser induced ionization. Mass spectra were measured for several solid samples of pure metals (Al,Cu), metal alloys (Inconel 601, brass), and ceramics (BN). Reproducible spectra, with relative standard deviations of the ion signals less than 1%, were obtained with this system. Moreover, isotope abundance ratios were measured and compared with the natural abundance ratios.

Development of Smart Security System

We are developing an advanced safety life support system SSS (Smart Security System): The next generation security system which shares information of the individuals, the families, the friends and the neighbors by using IT. In this paper, we report the new sensing devices to obtain the various information that is one of the important factors in the operation of the security system. The contactless fingerprint and vein sensor, the intelligent detector of moving objects, the self-management security system on a Web and the 3D facial shape measurement system are introduced.

Quantitative Analysis of Trace Heavy Metals in Plastics by Laser-Induced Plasma Spectroscopy

A quantitative analysis of trace heavy metals (lead, cadmium, mercury, and chromium) in plastics was carried out with laser-induced plasma spectroscopy (LIPS). A Q-switched Nd: YAG laser beam (pulse energy, 90 mJ; pulse width, 10 ns; repetition rate, 10 Hz) was focused on plastic samples in an argon atmosphere at a pressure of 10 Torr, and the emission spectra of the laser-induced plasma were measured using time-resolved spectroscopy. The experimental results showed that time-resolved measurement of a spectrum with a delay time of 0.4 μs after the laser pulse was effective for reducing the effect of the spectral interference with matrix as well as the background. Under the above conditions, the standard plastic samples (polyethylene and polyvinyl chloride) were analyzed for trace elements of lead, cadmium, mercury, and chromium, and the linear calibration curves with a slope of unity were obtained. The detection limits are plastic material and element-dependent, but are on the order of 10 ppm.