Multiple-element analysis of coal using collinear double-pulse laser-induced breakdown spectroscopy.

Collinear double-pulse laser-induced breakdown spectroscopy has been developed to enhance the emission signal of coal plasma. The influence of the energy ratio and the inter-pulse delay time on the intensity enhancement factors of the emission lines of representative elements in coal (i.e. carbon, hydrogen, oxygen, together with some metal elements such as iron, calcium, sodium and potassium) was investigated. The results showed that the collinear double-pulse configuration could sufficiently enhance the emission signals with an optimized inter-pulse delay time and energy ratio, and significant intensity enhancement factors were achieved for most of the selected lines with an energy ratio of 20 : 100. Meanwhile, the correlation between the signal enhancement and the upper energy level was investigated using neutral and ionic calcium lines. Finally, the plasma temperature, lifetime and morphology were calculated and observed to better explain the enhancement mechanism with different energy ratios and inter-pulse delay times. [ABSTRACT FROM AUTHOR]