The Infrared Imaging Spectrograph (IRIS) for TMT: Prototyping of cryogenic compatible stage for the Imager

TL;DR

This paper presents the design, fabrication, and testing of a cryogenic-compatible, durable two-axis stage prototype for the IRIS Imager on TMT, capable of precise positioning under vacuum and cryogenic conditions.

Contribution

It introduces a novel cryogenic-compatible stage prototype with proven performance and durability for long-term astronomical instrument operation.

Findings

Achieved low wobbling and high positioning accuracy.

Demonstrated durability under simulated operational loads.

Validated mechanical design for cryogenic and vacuum environments.

Abstract

The IRIS Imager requires opt-mechanical stages which are operable under vacuum and cryogenic environment. Also the stage for the IRIS Imager is required to survive for 10 years without maintenance. To achieve these requirements, we decided prototyping of a two axis stage with 80 mm clear aperture. The prototype was designed as a double-deck stage, upper rotary stage and lower linear stage. Most of components are selected to take advantage of heritage from existing astronomical instruments. In contrast, mechanical components with lubricants such as bearings, linear motion guides and ball screws were modified to survive cryogenic environment. The performance proving test was carried out to evaluate errors such as wobbling, rotary and linear positioning error. We achieved 0.002 $\rm deg_{rms}$ wobbling, 0.08 $\rm deg_{0-p}$ rotational positioning error and 0.07 $\rm mm_{0-p}$ translational positioning error. Also durability test under anticipated load condition has been conducted. In this article, we report the detail of mechanical design, fabrication, performance and durability of the prototype.