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The design and performance of a novel ion detector is described. The detector produces a two-dimensional image which displays the time-of-flight distribution of a pulsed packet of ions. Pulse sequencing within the detector allows for simultaneous mass and velocity resolution of the detected ions. The image capturing hardware combines long-term signal integration with single-ion detection in order to provide a wide dynamic range in ion sensitivity.

The paper presents new information on the accuracy of the heuristic approximations in two important theories of multiple scattering in random media of discrete scatterers: Twersky's “freespace” and “two‐space scatterer” formalisms. Two complementary approaches, based primarily on a one‐dimensional model and the one‐dimensional forms of the theories, are used. For scatterer distributions of low average density, the “heuristic” asymptotic forms for the coherent field and the incoherent intensity are compared with asymptotic forms derived from a systematic analysis of the multiple scattering processes. For distributions of higher density, both in the average number of scatterers per wavelength and in the degree of packing of finite‐size scatterers, the analysis is carried out “experimentally” by means of a Monte Carlo computer simulation. Approximate series expressions based on the systematic approach are numerically evaluated along with the heuristic expressions. The comparison (for both forward‐ and back‐scattered field moments) is made for the worst‐case conditions of strong multiple scattering for which the theories have not previously been evaluated. Several significant conclusions are drawn which have certain practical implications: (a) in application of the theories to describe some of the scattering phenomena which occur in the troposphere, and (b) in the further evaluation of the theories using experiments on physical models.

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