A variable delay line is being developed as part of a far-infrared or submillimeter- wavelength interferometer that would operate in a vacuum in the cryogenic temperature range. No such delay line for spatial interferometry has previously been built for operation under these conditions.

The delay line includes an aluminum carriage supported on four wheels that are constrained, by a set of preloaded steel straps, to move along straight lines. The only friction that occurs in the delay line is rolling friction between different materials; this aspect of the design minimizes the risk of vacuum adhesion between parts made of similar metals. Relative to a competing design based on flex pivots, the roller design of this device affords greater robustness, stiffness, range of motion, and compactness, all with fewer parts.

This work was done by James Moore, Mark Swain, and Peter Lawson of Caltech for NASA’s Jet Propulsion Laboratory.