门控光电倍增管在激光诱导击穿光谱信号检测中的应用

Application of Gated Photomultiplier Tube in Signal Detection of LIBS

激光诱导击穿光谱(LIBS)技术的分析灵敏度会明显受到等离子体中电子轫致辐射的影响。由于电子轫致辐射的弛豫时间一般比原子辐射的弛豫时间短,因而可以采用时间分辨的信号检测技术来提高信号与背景之比。采用带有一种简单的新门控电路的光电倍增管来检测LIBS中的信号并以更高的分析灵敏度分析了铝合金样品中的铜杂质。该门控光电倍增管对背景的抑制比可达15∶1。铝合金中铜的检出限达到了1.02×10-6,与不采用门控技术相比有明显改善。这种门控的光电倍增管可以用于降低LIBS技术中背景辐射的影响,同时改善LIBS的分析灵敏度和空间分辨本领。

The analytical sensitivity of laser-induced breakdown spectroscopy （LIBS） is significantly influenced by the electronic bremsstrahlung emission in plasma. Since the time duration of the background emission in LIBS is usually shorter than that of the atomic emission, it is possible to get high signal to background ratio by using timeresolved signal detection technique. A gated photomultiplier tube with a simple new gating circuit is applied in LIBS signal detection and the copper impurity in aluminum alloy is analyzed with improved analytical sensitivity. The rejection ratio of the background reaches 15： 1. The limit of detection of copper in aluminum alloy is determined to be 1.02× 10^-6 in single-pulse LIBS, which is much lower than that obtained without gating technique. The gated photomultiplier tube can be used to reduce influence of the background emission and will be helpful with improving both analytical sensitivity and spatial resolution of LIBS.