Shielding for space microelectronics needs to provide an acceptable dose rate with minimum shield mass. The analysis presented here shows that the best approach is, in general, to use a graded-Z shield, with a high-Z layer sandwiched between two low-Z materials. A graded-Z shield is shown to reduce the electron dose rate by more than sixty percent over a single-material shield of the same areal density. For protons, the optimal shield would consist of a single, low-Z material owever, it is shown that a graded-Z shield is nearly as effective as a single-material shield, as long as a low-Z layer is located adjacent to the microelectronics. A specific shield design depends upon the details of the radiation environment, system model, design margins/levels, compatibility of shield materials, etc. Therefore, we present here general principles for designing effective shields and describe how the computer codes are used for this application.
A bstract Algorithms are developed that permit the use of periodic and albedo boundary conditions in the ITS system of coupled electrodphoton Monte Carlo transport codes when simulating transport in repetitive structures in satellite systems. Mutual verification is provided through the application of both algorithms to a simplified periodic geometry based on an array of microelectronics cards. The albedo algorithm is then employed to benchmark the predictions of energy deposition in silicon by a mass sectoring code for this same application and to predict the shielding effectiveness of a hexagonal honeycomb structure. Use of these algorithms results in a major reduction in the required problem input and significant variance reduction that could otherwise be achieved only via postprocessing that is much more problem dependent.
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