Abstract：Laser-induced breakdown spectroscopy (LIBS) is an elemental analysis technique widely used throughout science and engineering. A limitation of LIBS is the low analytical sensitivity for trace elements. Therefore, it is of great significance to enhance the signal intensity and reduce the detection limit of LIBS. To enhance LIBS signals, here we propose a method, multiple discharges-enhanced LIBS. The measurements were performed on a solid aluminum alloy. A nanosecond laser was focused on the alloy to generate plasma. The plasma was sputtered into the air between the two discharge electrodes, which triggered the discharge. Multiple discharges were generated by using a high-frequency discharge power source. The multiple discharges excite, heat the plasma and extend the plasma duration, thereby enhancing the signal intensity. Here, a direct current pulse power source with a frequency of 100 kHz was used, and five discharges occurred after each laser-induced breakdown. We show that compared with LIBS, the plasma duration is extended by approximately 50 μs. Multiple discharges-enhanced LIBS increases the signal intensity of Mg Ⅱ (at ~279 nm) by about 48 times; Al Ⅱ (at ~358 nm), 72 times; trace element Mn Ⅰ (at ~403 nm), 6.3 times; trace element Cu Ⅰ (at ~403 nm), 8.3 times. The detection limit of Mn Ⅰ (at ~403 nm) is reduced by a factor of 6; Cu, 8. Multiple discharges-enhanced LIBS dramatically enhances the signal intensity and improves the detection limit of LIBS, and it expands the applications of LIBS. This method has the potential to be applied to the identifications of valuables, rare materials and cultural relics.
Key words：LIBS; Discharge; Spectrum; Signal enhancement
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