Research On The Passive Q Switching Laser-induced Breakdown Spectroscopy

Laser-Induced Breakdown Spectroscopy?LIBS?is an atomic emission spectroscopy technique which uses highly energetic laser pulses to provoke optical sample excitation.The plasma of ionized matter produced after the interaction between the laser pulse and the sample.Plasma light em issions can provide special “spectral signatures” to identify chemical composition of many different kinds of materials.It is an analytical technique with which any type of matter regardless of its physical state can be analysed.This relatively simple measurement yields simultaneous sensitivity to many elements in the parts-per-million?ppm?range.LIBS is effectively non-invasive due to the very small sampling region?typically,pg to ng of material are transformed to plasma?,even no sample preparation required,and LIBS can be used in a standoff mode without perturbing the target.Firstly,a single pulse LIBS automatic collection system was set up in the laboratory,which based on the passive Q-switched laser.The laser and spectrometer were synchronized through the use of digital delay signal generator DG535.With the time-resolved spectrum data,the best SNR?signal to noise ratio?delay time for detection was found.Secondly,another single pulse LIBS system was set up based on the passive Q-switched laser,a small photoelectric conversion module and digital delay module were designed,the xenon lamp was used as a trigger signal spectrum acquisition synchronization in order to find the best working conditions.Finally,a pre-ablation double pulse LIBS system was set up with the same passive Q-switched laser.A stable double pulse laser was output with the interval about 35?s 40 ?s after the xenon lamp voltaged to 570,The diffuse reflection of the first pulse laser is used as the trigger signal,and th e spectrum collection is synchronized after the photoelectric conversion and the digital delay.The sample ablation experiment was compared with the se three LIBS systems.The pure copper sample was ablated,and all these systems were available in the pure copper sample spectrum.A higher SNR and stronger spectrum intensity obtained by the use of the double pulse LIBS system.An internal standard method was used to detect the copper ions in the solution.The 500 ppm MgCl₂ solution was used as the internal standard solution to detect different concentrations of copper ions.A carbon bar was used as the substrate and ablated after the evaporation of water.The double pulse LIBS system detection limit was 5.87 ppm.The elemental spectrum of seawater was detected,the two single pulse LIBS systems only detected elements with high levels of seawater,and more elements were detected with the double pulse LIBS system.The seawater around Xiao Shi Island and the domestic water to the sea of Ma Zigang in Wei Hai was analyzed.The result showed that the contents of Al,Fe and Cu were relatively high in Ma Zigang.It was also suggested that the above mentioned elements were relatively high in domestic sewage.