Ion mobility spectrometry (IMS) is mostly used for detection of chemical compounds, all over the world. The ion source in IMS, especially for explosives, is a challenge. The radioactive 63 Ni is the most common ionization source used for IMS. Despite its small size, low weight, and non-reliance on external power supplies, 63 Ni faces limitations in application because of safety regulations. This limitation motivates the use of a substitute nonradioactive ionization source in IMS. VUV source has limited lifetime and low sensitivity. Corona discharge in air produces NO x that interferes with explosives. In this thesis, we introduced a new simple, low-cost and long-lived effective ion source based on thermal ionization for the detection of chemical compounds in air. It consists of a heating filament powered by an isolating power supply. The ionization was assisted by doping chlorinated compounds either in solid phase, coated on a heating filament or in gas phase using chlorinated hydrocarbons in contact with the heating element to yield Cl - reactant ion. The solid phase was nano-?-alumina (Al 2 O 3 ) in which MX (M = K, Na, Li, Cs, and X = Cl, I, F) was doped to make MX @Al 2 O 3 . Alkali and halide ion peaks were observed by IMS in the positive and negative modes, respectively. The lifetime of the ion source for different alkali halides was measured in the range of several weeks. For the case of gas phase, several chlorinated hydrocarbons were evaluated as the reagent chemical for providing Cl - reactant ions. The new negative ion source is inexpensive while it has a virtually unlimited lifetime compared to the VUV ion source. The ion source was evaluated by recording ion mobility spectra of common explosives including; TNT, RDX and PETN in air.
