Study and analysis of self-absorption-free laser-induced breakdown spectroscopy with high-repetition rate acousto-optic gating
To eliminate the self-absorption effect in laser-induced breakdown spectroscopy(LIBS)and im-prove the accuracy of elemental quantitative analysis,the device of self-absorption free laser-induced break-down spectroscopy(SAF-LIBS)technology needs to be miniaturized to meet the requirement of convenient elemental analysis in industry.This paper presents a novel quantitative analysis technique,the high repetition rate acousto-optic gated SAF-LIBS method.To enhance integral spectral intensity,a high repetition rate laser is used to produce quasi-continuous plasmas.In addition,an AOM(acousto-optic modulator)serves as an op-tical gating switch,enabling the use of a compact charge-coupled device(CCD)spectrometer and AOM in-stead of the intensified charge coupled device(ICCD)and medium step grating spectrometer in conventional large-scale SAF-LIBS devices.The results in a self-absorption-free system that is less bulky and less expens-ive.After optimizing the system parameters,the quantitative analysis and prediction of the Al element in the sample was achieved.Experimental results show that plasma characteristics are impacted by the laser repeti-tion rate,which affects the intensity of spectral signal.The doublet intensity of Al I 394.4 nm and Al I 396.15 nm is enhanced and then diminished at a laser repetition rate ranging from 1 kHz to 50 kHz,with the optimal re-petition rate identified as being 10 kHz.The doublet line intensity ratios of Al decrease with delay time un-der different fiber collection angles.The highest signal-to-noise ratio is achieved at an angle of 45°,while the optimal optically thin time tot is 426 ns at a certain integration time.Al is quantitatively analyzed and pre-dicted at a laser repetition rate of 10 kHz,fiber collection angle of 45°,and delay time of 400 ns.The experi-mental results show that the calibration curve linearity of R2 is 0.982 and an average absolute prediction error of aluminum is reduced from 0.8%of single LIBS to 0.18%,which is equivalent to that of traditional SAF-LIBS.Additionally,the high repetition rate acousto-optic gating SAF-LIBS not only effectively eliminates continuous background radiation and broadens spectral lines in optically thick plasma,but also offers the ad-vantages of miniaturization,low cost,convenience,and reliability.Therefore,this study plays a significant role in advancing SAF-LIBS technology from laboratory testing to industrial applications.
laser-induced breakdown and spectroscopyself-absorption freeoptically thinhigh repetition rate laseracousto-optic gating
国家科技期刊平台
NSTL
万方数据
