Ceramic DMS—type detector

Abstract

IntroductionDMS Technology is based on ion segregation phenomenonwhen flowing through the volume of the detector. DMSdetector is made up with two parallel ceramic plates withelectrodes layered on each plate. High voltage and highfrequency of electric field generated in detector’s volumecauses ion segregation on collection electrode (see Fig. 1).Observed ion segregation in flowing gas is caused bydifferent mobilities of the analyzed chemicals in fieldscharacterized by lower and higher intensity. Ion mobilityvalue is dependent on ion mass, charge and velocity offlowing gas [1–4].Figure 2 depicts example flow gas through detector’svolume. Variable electric field put on electrodes causescapturing of these ions, which mobility does not enablestable (parallel to detector’s plates) flow through detector’svolume. Thus, phenomenon of ion mobility of ions flowingthrough the detector variableon compensated electricalfield, makes detector as special ion filter.For DMS detector, ion mobility is defined by followingequation:KEN¼ Kð0Þ 1þ aENð1ÞIn low intensity electrical fields, α equals 0.In cases, where intensity augments, thus effective tem-perature of ion raises, and in that case it’s temperature ishigher than ambient temperature [1].Important property determining low field condition is notjust the field but the field normalized to the drift gas molec-ular density, E/N, the unit being the Townsend (one Td1*10