Gold fineness measurement using single-shot spark assisted laser-induced breakdown spectroscopy.

Abstract

Here, a homemade gold fineness analyzer is fabricated based on calibration-free spark assisted laser-induced breakdown spectroscopy (CF SA-LIBS). The experimental arrangement consists of a Q-switched Nd:YAG laser combined with a spark generator and a single-channel CCD spectrometer. The well-arranged optical system, coupled with an electrical setup, allows us to successfully run SA-LIBS even at low energy single shots. The electric discharge contributes LIBS to reheat and promote more energetic plasma. Subsequently, plasma temperature elevates up to ∼20%, and its lifetime is elongated as much as 6 times. As a consequence, the relative signal intensity is enhanced up to 1 order of magnitude against that of LIBS at the same pulsed energy. Furthermore, the electron density is also measured based on the broadened spectral width of the intensified Hα line. The latter is used to obtain the ionic species concentrations more accurately according to the Saha-Eggert equation. As a result, we have assessed the gold karat with an analytical error less than 0.5% using CF SA-LIBS. In addition, the surface patterns recorded by the stylus profilometer reveal that the single-shot SA-LIBS benefits a smaller ablative mass against standard LIBS.