High Voltage Pulse Generator And Its Application In Optical-electrical Dual Pulse LIBS

Elemental analysis based on neutral atom and ionic emission from plasma generated by focusing a powerful laser beam on a solid sample surface is known as laser induced breakdown spectroscopy (LIBS). More recently, this technology has been shown to have several analytical advantages: without complicate sample pretreatment, rapid, online and remote analysis. Therefore, it has been widely used in environment pollution monitoring, online industrial analysis, biotechnologies, historic preservation, nuclear industries, deep-space exploration and surface analysis, etc. Optical-electrical dual pulse LIBS(OEDP-LIBS) was a new technique in which a high voltage electrical pulse was used to enhance the intensity of atomic emission from laser plasma and extend the lifetime of the atomic emission. In comparison with traditional single-pulse LIBS, the analysis sensitivity of OEDP-LIBS can be enhanced significantly.The focus of this paper will be on high voltage pulse generator---the key equipment in OEDP-LIBS. We present the design scheme of high voltage pulse generator according to the system design. Based on the investigations, this paper proposes the periphery trigger circuit design. The high voltage pulse generator applied in OEDP-LIBS produces time-delay controllable high voltage pulses to excite the atoms in laser plasma for the second time to enhance their emission intensity, thus improving the system detection sensitivity and accuracy significantly. This system works well in the field of trace element analysis using LIBS.This paper puts forward a half bridge voltage source inverter as the main circuit for high voltage pulse generator; choosing SG3525 to be the main control unit to produce PWM signal; Choosing IR2110 to consist the driver circuit for IGBT; A single AC voltage regulator is introduced to regulate the voltage continuously and steadily. The trigger circuit includes the optical trigger circuit based on photodiode s1223 and the pulse generator based on AT89C51 MCU.Detection the Hg in water solution with OEDP-LIBS is introduced after the system was constructed. The detection sensitivity of mercury in OEDP-LIBS was enhanced two orders than that of single-pulse LIBS, and the measurement accuracy has also been improved, which shows that this experimental facility has good performance. Lots of valuable experiences have been got, which was helpful for building an OEDP-LIBS system for rapid and high sensitive detection of trace heavy metals in different samples.