Stationary two-unit detector of explosives with a light detector module based on traditional ion mobility spectrometry

The paper presents research and development of a laser ion mobility spectrometer for detection and identification of vapors of explosives consisting of a stationary industrial laser and a light portable analytical head - detector module. Laser radiation is delivered to the ion source of the analytical head by an optical fiber. Much attention in the work is paid to the analysis of propagation of ultraviolet radiation in the standard UV quartz fiber, with an intensity sufficient for the effective ionization of molecules of explosives. It is shown, that the threshold intensity of ultraviolet radiation with lambda =266 nm, at which there is still no degradation of the optical fiber, is q=7 center dot 10(7) W/cm(2). The process of laser desorption of molecules of explosives under ultraviolet laser irradiation from the output end of an optical fiber is considered. It is found that the output end of the fiber works as a concentrator of molecules, the desorption and ionization of which by laser radiation with lambda = 266 nm leads to an additional increase in the ion current of target analyte. The main characteristics of the developed spectrometer are studied. The resolving power of the spectrometer is equal to 53. The limit of detection for TNT and RDX were estimated at the level 1-2 ppt. Fluctuation of maximum of all ion peaks positions does not exceed +/- 45 mu s. Basically, the developed device is intended for stationary checkpoints, and, of course, it can be transported to crime scene investigation.