Understanding the fundamental mechanisms of new particle formation and growth (NPFG) is critical to the development of accurate quantitative models of atmospheric particulate matter. Challenges to elucidating the chemistry of these processes include accessing a variety of well-controlled experimental conditions approaching the point of new particle formation, and having an inexpensive system which can be reproducibly maintained with low levels of contaminants from previous runs and other sources. We describe here the design and characterization of a flow tube reactor for such studies, and its initial application to NPFG from the reaction of the gas phase precursors methanesulfonic acid and trimethylamine in the absence or presence of added water vapor. Insights into some of the fundamental processes involved in NPFG that could not be obtained in earlier studies using our large volume, slow flow system are described. (C) 2014 Elsevier Ltd. All rights reserved.