25-km Low-Temperature Multiple-Reflection Cell

Abstract

A low-temperature multiple-pass White cell is described which can be operated at any temperature between 120 K and room temperature. The path length can be varied from 60 m up to 2540 m in 80-m steps. The four-row multiple reflection system, a modified White arrangement, is enclosed in an aluminum dewar and can be focused externally while cold. An approximate expression for the astigmatic image distortion in a cell of the described type is derived.