Abstract: Ionized cluster beam (ICB) deposition has received considerable attention since its introduction in 1972 by Takagi et al, at Kyoto University because of its potential for low temperature film growth. While further investigation of many aspects of ICB deposition is warranted, it is first necessary to determine with some certainty whether large clusters are being produced. A complete analysis of the Eaton ICB source involving computer calculation of the potential fields and computer simulation of the electrons and ions as they react to and influence these fields provides an in-depth understanding of the dynamics that influence the final ion beam characteristics. A high resolution time-of-flight mass spectrometer was developed to experimentally investigate the cluster size distribution. No evidence of large clusters was found down to a level more than two orders of magnitude below what the Kyoto University group has reported.