Chord length distributions for rectangular parallelepipeds of various relative dimensions were studied in relation to radiation hardness testing. For each geometry, a differential chord length distribution was generated using a Monte Carlo method to simulate exposure to an isotropic radiation source. The frequency and dose distributions of chord length crossings for each geometry, as well as the means of these distributions, are presented. In every case, the dose mean chord length was greater than the frequency mean chord length with a 34.5% increase found for the least extreme case of a cube. This large increase of the dose mean chord length relative to the frequency mean chord length demonstrates the need to consider rare, long-chord-length crossings in radiation hardness testing of electronic components. 1. Introduction Microdosimetry is the study of the patterns of energy deposition from ionizing radiation interacting with microscopic volumes much smaller than the range of secondary particles generated by the incident particle. Since its inception less than 50 years ago, it has been very important in the field of radiobiology [1]. Because of this, metrics evolved around a standard geometry of a 1？ m sphere [2] and published results from experimental measurements are related to radiation interaction with a spherical or cylindrical detector. Over the past decade or so, increasingly small components have been developed to meet the demands of the electronics industry and, as a result, the amount of charge necessary for inducing a single event effect (SEE) becomes correspondingly smaller [3]. In deep space SEE production results mainly from the traversal by heavy ions that make up the galactic cosmic ray (GCR) spectrum. In low-Earth orbits SEE production is dominated by proton-induced spallation reactions [3]. As many of the components manufactured today can easily have dimensions on the order of several micrometers, the principles of microdosimetry have application in stability testing of these microchips intended for use in radiation fields. However, the differences in geometry between the sphere and the parallelepiped need to be considered. A significant amount of work has been performed at accelerator facilities to test the radiation hardness of electronic components. Attention is often given to the influence of geometric factors on SEE rates. While several recent studies have considered the incident angle of the beam in radiation hardness testing [4–7], many apparently do not [8, 9] and this is a crucial factor when analyzing upsets as a function of
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