Microwave-enhanced laser-induced breakdown spectroscopy of Zirconium metal

A microwave-enhanced laser-induced breakdown spectrometer (MWE-LIBS) was developed to produce high emission intensities and a high signal-to-noise ratio for spectrochemical and analytical applications inside the Fukushima Daiichi Nuclear Power Station. MWE-LIBS potentially solves the problem of signal attenuation in fiber-coupled laser-induced breakdown spectroscopy (LIBS), which may be experienced in an intense radiation environment. Zirconium (Zr) metal was used as the target material in this study. The variations of the emission intensity enhancement factor and SNR with increasing the microwave power were investigated. The results revealed that the SNR for the atomic Zr I and ionic Zr II emissions was increased to several hundred times higher than that under standard LIBS. The interaction of the microwave and plasma enhanced the excitation and recombination cycles of Zr I and released stronger emissions for analysis. Consequently, ionization and the molecular formation of ZrO were enhanced and sustained for extended periods. The lifetime of the emissions lasted longer than the microwave duration of 1000 µs. The microwaves also enlarged the plasma by twenty times the initial volume.