[asac] [almanews] ALMA Memo 395 Released

[Stacy Oliver]

ALMA Memo #395

Alignment Tolerances for ALMA Optics

B.Lazareff (IRAM)

25-Oct-2001

Keywords: Receiver, Optics, Alignment, Tolerance

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.


View a pdf version of ALMA Memo 395.
	http://www.alma.nrao.edu/memos/html-memos/alma395/memo395.pdf

Download a ps version of ALMA Memo 395.
	http://www.alma.nrao.edu/memos/html-memos/alma395/memo395.ps

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