为研究样品温度变化对激光诱导击穿铝(Al)等离子体特征参数的影响,采用双脉冲激光器诱导激发在中频炉中加热的Al样品形成等离子体,对比分析了样品温度变化时不同特征谱线强度的变化;分析了CCD相机采集的不同样品温度下等离子体羽的形态变化;在局部热力学平衡条件下,用Boltzmann斜线法和Stark展宽法分析了等离子体电子温度和电子密度随样品温度的演化规律;使用Lorentz线型拟合分析了随样品温度变化的不同谱线的半峰全宽(FWHMs)。研究结果表明,等离子体羽的形态大小变化可以作为其电子温度和电子密度等特征参数随样品温度变化的直观反映;随着样品温度升高,等离子羽形态、谱线强度、FWHM、电子温度和电子密度都增大至饱和状态,并且样品温度对离子线和原子线的谱线强度和FWHM有不同的增强效果。

In order to study the effect of sample temperature on the characteristic parameters of laser induced breakdown aluminum (Al) plasma, we use a double-pulse laser to induce the Al sample heated in intermediate frequency furnace to form plasma. And then we analyze the intensity changes of different characteristic spectral lines and the morphology changes of plasma plume collected by CCD camera when the Al sample temperature changes. Under the assumption of local thermodynamic equilibrium, we use Boltzmann oblique line method and Stark broadening method to analyze the evolution law of plasma electron temperature and electron density with the sample temperature. The full widths at half maximum (FWHMs) of different spectral lines varing with different sample temperatures are analyzed by Lorentz linetype fitting. The experimental results show that the morphology and size change of plasma plume is a direct reflection of the change of the characteristic parameters of plasma such as electron temperature and electron density. As the sample temperature increases, morphology of plasma plume, spectral line intensity, FWHM, electron temperature, and electron density will become saturated. For ionic and atomic lines, the sample temperature has different enhancement effects on the spectrum intensity and FWHM.