A tolerance analysis of the alignment of the ALMA FE optics is presented. The following performance criteria are taken into account: a) loss of on-axis efficiency from aperture plane misalignment; b) focal plane co-alignment of the two beams of each band; c) aberrations when off-axis mirrors operate between wavefronts not centered on the foci of the ellipsoid; d) non-uniform phase across the primary beam resulting from aperture plane misalignment. It is found, based on reasonable machining tolerances, and existing FEM simulations of pressure bending, that the adopted goals can be met, the driving goals being on-axis efficiency (a) and primary beam phase (d). The present study, especially in view of the fact that detailed designs of cartridge internal optics do not exist at the time of writing, can only be considered as a guideline.
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Last modified: 2001-10-26
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