Aerodynamic lenses can increase the local particle number density of the aerosol beam. The particle number density of aerosol has an important effect on the excitation probability and spectral intensity of laser-induced plasma. Therefore, aerodynamic lenses have the potential to improve the identification efficiency of Laser Induced Breakdown Spectroscopy (LIBS) in aerosol real-time monitoring. In this study, the effects of an aerodynamic lens on laser excited aerosol particles were developed by experiments and simulations. The process of aerosol beam passing through an aerodynamic lens was simulated by using the CFD software FLUENT. The simulation results show that the setup can increase the aerosol concentration by three orders of magnitude. The Aerosol Focusing-Laser Induced Breakdown Spectroscopy (Aerosol Focusing-LIBS) experimental setup is established. The experimental and simulation results are in good agreement. And the experimental results show that the laser excitation probability has increased by about 5 times, the average intensity of the excitation spectrum has increased by about three times.
Laser-induced breakdown spectroscopy (LIBS) is a promising technology for nuclear safeguard because of the advantages of rapid analysis, in situ and real-time detection. The potential application of LIBS is simulatively investigated for continuous uranium emission monitoring during the nuclear accident. The aerosol containing UOx is generated with laser ablation to simulate the uranium emission in laboratory. The laser induced plasma emission in the aerosol has been continuously analyzed with a spectroscopy. The characteristic spectral lines of uranium have been clearly identified. The intensity variation of uranium spectral lines agrees well with UOx particles emission and sedimentation process in aerosol. The potential of LIBS is demonstrated for emergency and continuous emission monitor in nuclear accidents.
Raman spectroscopy technology is a spectral analysis technology based on Raman effect. With this technology, the molecular structure information can be identified and analyzed quickly, nondestructively and effectively, and it has high spectral specificity. Raman spectroscopy technology can provide the mineral components information of lunar soil samples, which is of great significance for lunar surface exploration and future resource utilization. In this paper, a 785nm Raman spectroscopy detection system was set up, and used to detect and identify phosphate components with different doping concentrations in various types of earth soils, which provided data support for further analysis of lunar samples.
Nuclear aerosol simulant generated in laboratory plays a unique role for the development of in-situ monitoring technology of nuclear facility emission. To simulate the emission of the trace uranium aerosol, an aerosol generator based on laser ablation was set up and tested experimentally. It is shown that the concentration of aerosol particles has a linear relationship in the range of 36.28 μg/m3 to 277.13 μg/m3 while the laser intensity keeps above 7.6×106 W/cm2 . The aerosol particle size distribution is stable, while the most particles are inhalable particles based on the measurement of an aerosol spectrometer. The composition is verified with a laser induced plasma spectroscopy. Several spectral lines of uranium have been clearly identified. It is demonstrated that aerosols generated based on laser ablation can simulate nuclear facilities emission effectively. The method will be used in further work to develop direct radioactive aerosol monitoring technology.
With the deepening of globalization, security inspection has gradually become a necessary means in many occasions. Therefore, rapid and accurate identification of components in the opaque shielding material, without destroying the outer packaging, has become a necessary detection method. Spatially offset Raman spectroscopy (SORS) , as a new Raman spectroscopy technology, can meet such demands. In this paper, the SORS of NaNO3 aqueous solution contained in opaque PTFE vessel has been obtained, using a self-built SORS detection system. In addition, some important parameters such as offset distance and detection concentration has been also studied experimentally.
Laser induced plasma spectroscopy (LIPS, also LIBS) is a promising technique for the challenging issues associated with the real-time and in-situ monitoring the major elements of aerosol particulate matters. A prototype of Aero-LIPS had been set up with the techniques of aerosol beam focusing, enhanced plasma emission collector and conditional data filter to demonstrate the potential application of air pollution composition monitoring. The prototype can identify more than 40 elements from aerosols and continuously monitor 20 elements with the time resolution of 10 minutes. In the field test of an Asian dust event, the major elements, such as Ca, Mg, Al, Si, Cl, P, S, etc. have been real-time monitored, which took 77.9% part of the total particulate matter mass. The evolutions of temporal elemental concentrations went well along with the particle matter concentration. It is interesting that several persist lines of U and Th have been detected from Asian dust aerosol while their concentration in local air should range in the level of nano-grams per cubic-meter. It might indicate that the enhanced-LIPS has a potential to monitor the nuclear facility emission for Nuclear Security and Safeguards.
Defense and security applications often require definitive and non-destructive testing or identification of samples to enable testers to make effective decisions and preserve potential evidence. Raman spectroscopy has consistently demonstrated its effectiveness as an analytical technique in defense research and applications without interfering with sample integrity. Aiming at the fact that Raman spectroscopy is limited to detect sample composition within the near surface layer or transparent medium, Rutherford Appleton Laboratory proposed the spatial offset Raman spectroscopy. This technique can effectively suppress the powerful Raman and fluorescent signal interference from the surface substance, and realize the composition detection under the opaque diffuse scattering medium material of a few mm or cm. In this paper, we have detected and analyzed the spatially offset Raman spectroscopy of sodium nitrate, sodium sulphate and their mixture powder.
The fused silica is an important optical material in the large laser devices, which are often subject to laser induced damage in the laser systems. In this work we studied nanosecond laser induced damage in JGS1 fused silica at the three harmonic wavelengths of the 1064 nm, 355 nm and 248 nm. Under 1064nm/10ns, 355nm/10ns and 248nm/22.8ns laser irradiation, the bulk damage threshold is 150 J/cm2, 15 J/cm2 and 7 J/cm2, respectively. The results showed that the weakest point of bulk damage threshold among the three tested wavelengths is 248 nm. And the damage threshold decreases sharply with the decrease of wavelength.
As a new type of conventional Raman spectroscopy(CRS) technology, spatially offset Raman spectroscopy(SORS) can acquire subsurface information of the multi-layered materials and realize the detection of concealed materials in nonmetallic opaque and translucent containers. In this paper, the spectrum of NaNO3 powder in a red opaque plastic bottle and a brown translucent glass bottle were detected with a 785nm SORS detection system. According to comparison and analysis, the Raman signal and fluorescence of the surface opaque HDPE container and the surface translucent glass container were suppressed by SORS. The subsurface concealed NaNO3 Raman spectrum peak was detected successfully.
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