High-Speed Elemental Characterization via Kilohertz LIBS Imaging

In fifteen words or less, explain the significance of this contribution (Novel Aspect).: New large format LIBS system for analyzing samples up to 500 cm² at 1000 Hz.

Abstract Text:

Laser-induced breakdown spectroscopy (LIBS) has become a very popular technique for spatially determining trace and major elements. LIBS offers the ability to measure C, H, O, N, and F, which are often difficult or unattainable by laser ablation–inductively coupled plasma mass spectrometry (LA-ICP-MS). In some examples, samples may exist with a somewhat ( >25 cm²) large two-dimensional foot print while requiring spatially resolved elemental analysis. In such instances, larger samples may not be readily suitable for standard laser ablation chambers, therefore requiring a different sampling interface. Although LA-ICP-MS can perform high-speed imaging at 1,000 Hz, it requires small spot sizes and fast single pulse responses (< 10 ms). For larger samples, greater spot sizes are required to keep the analysis within a reasonable time frame. In this case, LIBS is the ideal choice because the laser itself is the time limiting factor for measurements.

In this work, a new, large-format, high-speed LIBS system for analyzing samples that can be as large as 500 cm² will be presented. This system uses a multichannel complementary metal–oxide–semiconductor (CMOS) spectrometer to collect the spectral signal from 190 to 1,100 nm. The laser used in this work was a 193 nm ArF excimer laser operated at 1,000 Hz and with a 100 × 100 µm laser spot size. The samples analyzed in this work included granitic pegmatite, tourmaline in granite, turgite, quartz, lazulite, jasper, and lime. These samples were roughly 4–8 cm in width and 10–18 cm in length and were all analyzed in ≤35 min each. This method resulted in an output of approximately 1.75 million pixels per hour.