The use of matrices to represent electron lenses is discussed. It is shown that it is more convenient and natural to represent a lens by a matrix and that the matrix elements show a more regular behavior than do the focal properties. Thus matrices are more convenient to use in computer programs. Matrix elements for the twohyphen;tube electrostatic lens are presented and their properties discussed. A simple analytical form for the matrix elements of lenses with nearhyphen;unity voltage ratios is given.
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