Image slicers - design for manufacturability

摘要

This paper describes our approach to the design of reflective, image-slicing Integral-Field Units. The first IFU built at the UK ATC (Ramsay-Howat et al 2004) has been successfully commissioned and is in routine use on the UKIRT. This IFU uses all diamond-turned optics and close attention was paid in the design to the manufacturability of the individual components, their alignment into groups and the overall alignment and integration of the IFU into the spectrometer. Building on this experience we are designing and making four IFUs for the MIRI on JWST where constraints on mass and launch survivability have led us to use monolithic arrays of slicing and re-imaging mirrors. This paper describes the ways in which the optical design and the manufacturing methods have each been adapted to: a) achieve image quality, pupil alignment and mass requirements b) ensure components can be reliably manufactured to the tolerances needed so that the IFUs can be aligned without adjustment and c) ensure that performance is maintained after launch and cooling to 7 K. We also show that, although designed specifically for a space instrument, such a compact and reproducible IFU is well suited to instruments where multiple IFUs are required.