The role of Helium plasma in improving the sensitivity of Hydrogen detection in laser induced plasma spectroscopy

Abstract

The experimental studies have been performed on the characteristics of laser induced He plasma that give influence to the sensitivity enhancement and the long lifetime of hydrogen emission line. Under He ambient gas, the emission intensity of spectra of hydrogen and oxygen increase with low background emission. In order to confirm the intensity enhancement, spatial intensity distribution of hydrogen and helium was measured along the plasma expansion direction. The result revealed that the maxima come at the far end of the plasma where the available shock wave generated thermal excitation energy should have been significantly reduced. It implies the time-mismatch effect on the shock wave excitation process and the presence of possible contribution of helium metastable excited state in He plasma.