Detectors and cryostat design for the SuMIRe Prime Focus Spectrograph (PFS)

TL;DR

This paper details the design of cryostats, detectors, and electronics for the SuMIRe Prime Focus Spectrograph, enabling multi-channel optical and infrared observations on the Subaru telescope.

Contribution

It introduces a unified cryostat design for multiple spectrograph channels with specific detector configurations and cooling solutions for the Subaru telescope's PFS.

Findings

Cryostat design accommodates optical and IR detectors with thermal management.

Use of advanced CCDs and HgCdTe sensors for broad wavelength coverage.

Thermal analysis informs effective cooling and background mitigation.

Abstract

We describe the conceptual design of the camera cryostats, detectors, and detector readout electronics for the SuMIRe Prime Focus Spectrograph (PFS) being developed for the Subaru telescope. The SuMIRe PFS will consist of four identical spectrographs, each receiving 600 fibers from a 2400 fiber robotic positioner at the prime focus. Each spectrograph will have three channels covering wavelength ranges 3800 {\AA} - 6700 {\AA}, 6500 {\AA} - 10000 {\AA}, and 9700 {\AA} - 13000 {\AA}, with the dispersed light being imaged in each channel by a f/1.10 vacuum Schmidt camera. In the blue and red channels a pair of Hamamatsu 2K x 4K edge-buttable CCDs with 15 um pixels are used to form a 4K x 4K array. For the IR channel, the new Teledyne 4K x 4K, 15 um pixel, mercury-cadmium-telluride sensor with substrate removed for short-wavelength response and a 1.7 um cutoff will be used. Identical detector geometry and a nearly identical optical design allow for a common cryostat design with the only notable difference being the need for a cold radiation shield in the IR camera to mitigate thermal background. This paper describes the details of the cryostat design and cooling scheme, relevant thermal considerations and analysis, and discusses the detectors and detector readout electronics.