Visible camera cryostat design and performance for the SuMIRe Prime Focus Spectrograph (PFS)

TL;DR

This paper details the design and performance evaluation of the large, multi-channel visible camera cryostats used in the SuMIRe Prime Focus Spectrograph, a complex multi-fiber astronomical instrument.

Contribution

It introduces the design and performance analysis of the cryostats for the SuMIRe PFS visible cameras, a novel implementation for large, multi-channel spectrograph modules.

Findings

Cryostat design successfully supports large aperture cameras.

Cryostat performance meets the operational requirements.

Design considerations for multi-channel spectrograph cryostats.

Abstract

We describe the design and performance of the SuMIRe Prime Focus Spectrograph (PFS) visible camera cryostats. SuMIRe PFS is a massively multi-plexed ground-based spectrograph consisting of four identical spectrograph modules, each receiving roughly 600 fibers from a 2394 fiber robotic positioner at the prime focus. Each spectrograph module has three channels covering wavelength ranges 380~nm -- 640~nm, 640~nm -- 955~nm, and 955~nm -- 1.26~um, with the dispersed light being imaged in each channel by a f/1.07 vacuum Schmidt camera. The cameras are very large, having a clear aperture of 300~mm at the entrance window, and a mass of $\sim$280~kg. In this paper we describe the design of the visible camera cryostats and discuss various aspects of cryostat performance.