SIMULATION STUDIES OF RECONSTRUCTION ALGORITHMS FOR THE DETERMINATION OF OPTIMUM OPERATING PARAMETERS AND RESOLUTION OF GRADED SCREEN ARRAY SYSTEMS (NONCONVENTIONAL DIFFUSION BATTERIES)

Graded screen array (GSA) systems (nonconventional wire screen diffusion batteries) are increasingly finding application in the measurement of radioactive ultrafine cluster aerosols (0.5–5 nm in diameter), where conventional diffusion batteries are of limited utility. The GSA systems typically consist of varying mesh number, single/multiple wire screen stages operated either in series or in parallel, with the choice of a wide range of wire screen parameters and sampling flow rates. Numerical simulations studies of the expectation-maximization and Twomey size distribution reconstruction algorithms have yielded concepts that permit the optimization of GSA operating parameters, together with the determination of the potential size resolution of experimental GSA systems, the effects of random errors in the data, and algorithm stopping criteria. In general, a choice of wire screen operating parameters that result in the uniform fractioning of the sampled distribution among the various GSA stages and the inference of size intervals with successive midpoint diameters differing in diffusion coefficients by about one order of magnitude were found to be beneficial to the reconstruction process. © 1990 Elsevier Science Publishing Co., Inc.