Measurement and Analysis of Uranium Using Laser-Induced Breakdown Spectroscopy

To promote the application of LIBS technology in the detection of trace heavy metals and nuclear pollution detection, and improve the sensitivity and accuracy of detection, laser double-pulse LIBS technology and photoelectric double-pulse LIBS technology were used to analyze the uranium elements in soil and silica respectively. Firstly, optimizing the laser pulse energy, voltage and acquisition delay parameters to improve the intensity and signal-to-noise ratio of the characteristic spectrum of uranium; Then, under the conditions of optimized experimental parameters, the soil samples and silica samples containing different concentrations of uranium were analyzed. Two characteristic spectral lines of uranium element UII 367. 01 nm and UII 454. 36 nm were selected as the analysis line, and the calibration curve was established through the linear relationship between the uranium element concentration and the characteristic spectral line intensity. Under the condition of laser double pulse excitation, laser 1 was used as the pre-pulse, the main parameters were 1 064 nm, 90 mJ, 9. 2 ns, and laser 2 was used as the reheating pulse, the main parameters are 355 nm, 50 mJ, 8 ns. The time interval between the two pulses is 800 ns, and the spectral acquisition is delayed by 1 mu s, the lower detection limits of the concentration of uranium in the soil and silica samples were 572 and 110 mg center dot kg (1), respectively, and the goodness of fit value R-2 were respectively 0. 958 and 0. 999. Under the condition of photoelectric double pulse excitation, the laser pulse was used as the pre-pulse, the main parameters were 355 nm, 50 mJ, 8 ns, the high-voltage electric pulse was used as the reheating pulse, the main parameters were 3 900 V, square wave, pulse width 50 mu s, the time interval of the two pulses 1 mu s. The lower detection limits of the concentration of uranium in soil and silica samples were 108 and 64 mg center dot kg (1), and the goodness-of-fit values R-2 were 0. 991 and 0. 997, respectively. The research results show that under the same excitation conditions, the characteristic spectrum of uranium has an obvious matrix effect, which has higher spectral intensity, lower detection limit and higher goodness of fit value in silica samples. Compared with double laser pulse, the photoelectric double pulse can significantly enhance the intensity, stability and signal-to-noise ratio of the characteristic spectrum of uranium element, and the optical path of the photoelectric double pulse system is simpler has an important reference for the development and application of LIBS technology significance. The research method and results can provide technical support for detecting heavy metal pollution in soil and the emergency monitoring of soil and aerosol in the event of nuclear leakage.