[asac] [almanews] ALMA Memo 394 Released

[Stacy Oliver]

ALMA Memo #394

ALMA Band 9 Optics Layout

A. Baryshev (SRON), W. Wild (SRON)

2001/09/10


In this report a mm wave optics prototype for an Atacama Large Millimeter
Array (ALMA) receiver cartridge is discussed. Mainly the ALMA frequency band
9 (602-720 GHz) is considered. However the same design approach is
applicable to the receiver optics of any other ALMA bands. The high
frequency cartridges (bands 7-10) have been decided to have no intermediate
optics between the telescope secondary mirror and the cartridge cold optics.
(See notes of Tucson optics meeting). Consequently, in the optical design of
band 9 cartridge full signal path with all focusing elements are considered
as free design parameters. In this report a concept of choosing and
optimizing these parameters is discussed. The design starts from an optimal
corrugated and diagonal horn field representation. A possibility of
distortion compensation by a pair of ellipsoidal mirrors is discussed. A
concept of frequency independent radiation coupling between the horn and the
Cassegrain telescope system is presented. An expression for parameters of
two elliptical mirrors giving rise to frequency independent matching of the
horn to the telescope is given. A practical corrugated horn for signal path
of mixer and a practical diagonal horn for local oscillator (LO) part of
mixer are proposed. Based on the horn and the ALMA prototype antenna design
a two-mirror layout for ALMA band 9 is proposed. The alignment accuracy of
optical components within the cartridge is considered. The alignment
accuracy between the cartridge and the secondary mirror is also considered.


View a pdf version of ALMA Memo 394.
		http://www.alma.nrao.edu/memos/html-memos/alma394/memo394.pdf

Download a ps version of ALMA Memo 394.
	http://www.alma.nrao.edu/memos/html-memos/alma394/memo394.ps

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