Time-resolved high sensitivity signal detection of chromium in aluminum alloy by laser-induced breakdown spectroscopy

In order to eliminate the influence of strong Bremsstrahlung emission existed in laser-induced plasma on photomultiplier tube (PMT) and preamplifier and to improve signal detection sensitivity of laser-induced breakdown spectroscopy (LIBS), an end-on gated PMT was designed based on CR110 PMT and was used in weak signal detection of LIBS. The influence of strong Bremsstrahlung emission of the plasma could be successfully eliminated and the weak atomic emission signal could be further amplified after using this gated PMT combined with a preamplifier in signal detection, thus the spectral analysis sensitivity could be improved significantly. In analysis of chromium in aluminum alloy samples by LIBS, the limit of detection of chromium reached 5.55 ppm using this gated PMT as the signal detector, the detectability was improved nearly 6 folds in comparison with that using normal PMT. It was demonstrated that application of this gated photomultiplier tube in time-resolved signal detections could give good measurement results.