Research On Three Military Explosives’ Terahertz Spectrums

As a novel spectral technology, terahertz time-domain spectral technology (THz-TDS)has an important practical value and broad application prospect in the nondestructivemeasuring and security fields, due to the strong penetrability and low-energy characteristics.The reason is the vibration and rotation energy levels of many explosives lie in the THzwave band, the THz-TDS can be applied to detecting and identifying the category andconstruction of the explosives and this is an essential part of researching on theTHz-Security Detectors. Based on the THz-TDS, using the portable MIN-ZTHz-spectrometer, three novel military explosives including DNAN, HNS and DNMT aredetected into the THz reflection and transmitted spectrums. Through data processing andanalysis, three explosive’s characteristic absorption spectra has been extracted and reported.The other part of this paper is to work around the data processing. The analyzing results onthe different three platforms are reported and the comparison among the three analyticalapproaches is worked, this provides a initial verification for the prototype developing. Thefollowing is a brief summary of the works conducted in this thesis and the results achieved:(1) The former THz-TDS testing system and the current MINI-Z system are compared.Base on the MINI-Z system, the terahertz spectrum detecting system is built. By analyzingthree samples’physical properties, chemical properties and detection methods, the detectingstates of the samples are determined as the powder.(2) Using the detection system built, three explosives’reflection and transmittedspectrums are tested and the characteristic absorption peaks are extracted successful by thecomparison with the spectrum of air. The results are reported and expand the database of theexplosive terahertz spectrums successfully. As an addition research, the FIRT spectrums ofthe explosives are tested and the detecting frequency is determined accurately. The db10wavelet function is determined which is suit for the explosives spectral data. The error from the environment is eliminated and the possibility of the wrong extracting absorption peak isavoided effectively.(3) On three different platforms the spectrums are analyzed including the Oringin,MATLAB and Labview. The characteristic absorbing peaks within 0.1-2.5THz are analyzedand extracted. As the samples properties, the locations and the number of these peaks areused in the recognition algorithm, which is a fuzzy clustering analysis algorithm based onthe Hamming distance. The algorithm can be used to recognize and classify the explosives’spectrums, and the distinguishing result between the air’s spectrum and the explosives’spectrum s and the classification of different explosive are determined. At last the work ofthe thesis and looks forward to the future of the THz spectra technology are included.