Laser-induced ablation of a steel sample in different ambient gases by use of collinear multiple laser pulses

The sensitivity of laser-induced breakdown spectroscopy of solid samples depends on the number of ablated and excited analytes. Laser ablation of solid samples can be enhanced by using collinear multiple laser pulses, for example double or triple pulses, rather than single laser pulses with the same total laser pulse energy. The ablation rates and the plasma conditions are affected by the ambient gas. In this study laser ablation was examined by varying the interpulse separation of the multiple pulses, within double and triple-pulse bursts, and the gas mass density at constant gas pressure. Different ambient gases and gas mixtures consisting of argon, oxygen, and nitrogen were used to study their effect on ablation rates. In a pure argon atmosphere (99.999% v/v Ar) the ablation burst number required to penetrate a steel plate of thickness 100 µm is reduced by a factor of approximately six by use of triple-pulse bursts with a symmetric interpulse separation of 15 µs rather than single pulses with the same total burst energy of 105 mJ. For double and single pulses the factors are 1.6 for Ar and 2.8 for synthetic air. Analyte lines are 4 to 8 times more intense if an argon atmosphere, rather than air, is used

Laser induced breakdown spectroscopy : from research to industry, new frontiers for process control

This paper presents R&D activities to explore new laser parameter ranges in pulse energy, time and space for laser-induced breakdown spectroscopy. The collinear double pulse effect, which is well studied for pulses of typically several 100 mJ energy can also be observed for laser pulses having a pulse energy two orders of magnitude lower. In this case, maximum line emission intensity occurs at interpulse separations of a few 100 ns. Temporal pulse tailoring to improve the performance of LIBS is only a first step. A comprehensive approach includes spatial pulse shaping to generate craters with predefined shape or to improve spatial averaging for the analysis of inhomogeneous samples. High performance components for LIBS systems such as spectrometers, electronics and sample stands are required to enable industrial applications. Latest developments offer wide-band single spectra acquisition with a high spectral resolution at a measuring frequency of up to 500 Hz. The next generation of multi-channel integrator electronics for Paschen-Runge spectrometers equipped with PMT detectors will further push the measuring speed to up to 5 kHz, thus opening a new area of high-speed LIBS microanalysis. Novel LIBS devices for various industrial applications presented include analysis of metallic process control samples with scale layers, on-site analysis of stag samples in secondary metallurgy, high-speed identification of Al scrap, mix-up detection of pipe fittings as well as recent work towards in-process identification of hot coils in a rolling mill

On-line multi-elemental analysis using laser-induced breakdown spectrometry (LIBS) : research fields, industrial applications and future perspectives

Extended knowledge of the interaction mechanisms between pulsed laser radiation and matter as well as methodological and technological progress achieved over the last years have opened new R&D fields and industrial applications for laser-induced breakdown spectrometry (LIBS). This paper gives an overview of current LIBS R&D activities focused on industrial applications ranging from quality assurance and process control tasks in steel industry, via speciation analysis by combination of chromatographic separation techniques with LIBS to the fast identification of scrap pieces for material specific recycling in high-throughput sorting lines. The dual use of laser radiation as a contactless processing tool and an analyzing tool to determine the chemical composition of samples without the need of any mechanical or chemical preparation is a promising perspective for LIBS to simplify and to shorten existing process chains