Optics Study for ALMA Receivers

摘要: The design of the receiver optics plays a crucial part in ultimate sensitivity ALMA array. We present some general concepts to guide development optical layout final receivers. Relevant properties materials used path are examined, and various types elements discussed. General principles high efficiency train designs presented. In general, simple systems advocated, with minimal truncation losses. areas which have greatest uncertainty windows infrared filters where trade-offs between RF losses, blocking, pressure resistance gas permeability be carefully considered. A sample for Band 3 is given. I. INTRODUCTION achieved define system that can easily maintained over its lifetime. As benchmark we note achieve 1 % enhancement by increasing collecting area array would cost an estimated $US 2-3M. Al- though this document does not deal directly cost, reli- ability, or maintenance issues it gives sufficient details performance evaluation exam- ined once those other addressed. Since may compromised, memo discusses low-loss detail. concerns are: dissipative scat- tering losses; spillover telescope aberra- tions; window sizes; materials; filters; feed elements; frequency dependence; geometrical constraints. start discussion effects losses on performance. This followed survey available millimeter sub-millimeter components. Pertinent characteristics their influence perform- ance covered. Finally, look at princi- ples illustrated example. uses paraxial beams includ- ing higher order required describe non-Gaussian nature real feeds. All parameters affecting fraction percent more discussed quantita- tively.