When neutrons interact with particular nuclei, the resulting energy of the interaction can be released in the form of gamma rays, which are characteristic of the nucleus involved in the reaction. The PELAN (Pulsed Elemental Analysis with Neutrons) system uses a pulsed neutron generator and an integral thermalizing shield that induce reactions that cover most of the entire gamma ray energy spectra. The neutron generator uses a D-T reaction, which releases fast 14MeV neutrons responsible for providing information on those nuclei that mostly respond to inelastic scattering. During the time period between pulses, the fast neutrons undergo multiple inelastic interactions that lower their energy making them easier to be captured by certain nuclei; this energy spectrum of gamma rays induced by these interactions are designated as the gamma ray thermal spectra. The PELAN system has been used for a number of applications where non-intrusive, non-destructive interrogation is needed. Although Pulsed Fast Thermal Neutron Analysis (PFTNA) has been around for approximately 30 years, the technology has never been successfully commercialized for practical applications. The following report illustrates examples of the performance of on a number of applications of interrogation of Unexploded Ordnance (UXO), mine confirmation, large vehicle bombs inspection and illicit drug smuggling detection.
Potential application of polymers containing ferrocene as their backbone compound in fiber optic gas sensors are discussed. The refractive indices of these polymers are comparable to silica glass and vary substantially upon exposure to certain gases. The variation in the refractive index of thin films of a ferrocene-based polymer known as methyl-phenyl-silane ferrocenylene polymer upon exposure to ammonia, nitrous oxide, nitric oxide, nitrogen, and oxygen is examined. The structure and operation of tapered optical fiber gas sensors fabricated with the aforementioned polymer are explained. Also covered are the sensitivity and reaction times of two different sensors to ammonia and nitrogen.