DEVELOPMENT OF UNIPOLAR ION GENERATOR - SEPARATION OF IONS IN AXIAL DIRECTION OF FLOW

Although ions in the atmosphere play important roles in nucleation and gas-phase chemical reactions, their dynamic behavior is not well unde rstood. To study ion behavior, reliable techniques for ion generation and measurement are needed. In this work, we describe a stable unipola r ion generator using an Am-241 source, and an improved version of the ion counter and Faraday cage electrometer by reducing deposition of i ons in these instruments. The new ion generator produced unipolar ions at concentrations as high as 1 x 10(13) m(-3). The improved ion count er measured the ion concentration as low as 2.5 x 10(8) m(-3) at a how rate of 1.5 L/min. (C) 1997 American Association for Aerosol Research .