For Ion Migration Rate Spectroscopy Of Transient Drift Electric Field Study

In the past decade, ion mobility spectrometer (IMS) has undergone significantadvancements. It's widely used for detecting chemical warfare, drugs, explosives,environmental pollution and so on. Compared with other analytical tools, it has advantagesof small volume, high sensitivity, broad applicability, high speed, working underatmospheric pressure. Because of the wide applications of IMS, now many internationalresearch departments and companies are engaged in studying IMS.In the conventional IMS, the design of the peripheral hardware circuit is dominated byhigh voltage. However, it's dangerous to use the high voltage. And the high voltage powersupply must be changed in order to switch between positive mode and negative mode. Inaddition, the high voltage source is difficult to be realized by integrated circuit.A new method of transient drifting electric field for IMS is proposed, analyzed anddemonstrated in this dissertation.In order to validate the method of transient drifting electric field, the experimentalequipment is built. The main part of the equipment is the control circuit system whichincludes sequential-logic control circuit and high speed switching circuit. Thesequential-logic control circuit generates control signals for the high speed switching circuitwhich places an output of positive or negative voltages or ground on selected drift ringelectrodes. As the sample ions of interest move and approach the edge of the electric field,the power supply is electronically disconnected from the drift ring electrodes and thenshifted to three other drift ring electrodes in 2μs so that the sample ions of interest continueto move in the desired direction.By applying low voltage at selected drift ring electrodes, the desired transient drifting electric field is generated with low voltage in the region where the ions are. The strengthand cycle of the transient drifting electric field can be adjusted according to the ion mobility.The experimental equipment has advantages of low voltage and easily switching betweenpositive mode and negative mode.The experiment of transient drifting electric field IMS was carried out and comparedwith conventional IMS. The results have validated the feasibility of the transient driftingfield IMS preliminarily.