Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Design and Performance of the SPT-SLIM Receiver Cryostat

M. R. Young, M. Adamic, A. J. Anderson, P. S. Barry, B. A. Benson, C. S. Benson, E. Brooks, J. E. Carlstrom, T. Cecil, C. L. Chang, K. R. Dibert, M. Dobbs, K. Fichman, M. Hollister, K. S. Karkare, G. K. Keating, A. M. Lapuente, M. Lisovenko, D. P. Marrone, D. Mitchell, J. Montgomery, T. Natoli, Z. Pan, A. Rahlin, G. Robson, M. Rouble, G. Smecher, V. Yefremenko, C. Yu, J. A. Zebrowski, C. Zhang

TL;DR

SPT-SLIM demonstrates a pathfinder for on-chip mm-wave spectrometers aimed at line intensity mapping, deployed on the South Pole Telescope to validate cryogenic design and automated operation. The paper details a compact cryostat powered by a two-stage adiabatic demagnetization refrigerator to achieve a 150 mK focal plane, with extensive thermal management and shielding to minimize gradients. Measurements show good agreement with thermal models, achieving up to 81% observing efficiency and sub-millikelvin stability during operation, aided by targeted design improvements and a robust Observatory Control System for automated remote cycling and telescope scheduling. The work establishes a practical framework for deploying multi-pixel LEKID-based spectrometers in constrained environments and highlights the integration of cryogenic control with observatory software for efficient LIM observations.

Abstract

The South Pole Telescope Shirokoff Line Intensity Mapper (SPT-SLIM) is a millimeter-wavelength line-intensity mapping experiment, which was deployed on the South Pole Telescope (SPT) during the 2024-2025 Austral summer season. This pathfinder experiment serves to demonstrate the on-sky operation of multi-pixel on-chip spectrometer technology. We report on the cryogenic performance of the SPT-SLIM receiver for the first year of commissioning observations. The SPT-SLIM receiver utilizes an Adiabatic Demagnetization Refrigerator (ADR) for cooling the focal plane of superconducting filterbank spectrometers to a temperature of 150 mK. We demonstrate stable thermal performance of the focal plane module during observations consistent with thermal modeling, enabling a cryogenic operating efficiency above 80%. We also report on the receiver control system design utilizing the Observatory Control System (OCS) platform for automated cryogenic operation on the SPT.

Design and Performance of the SPT-SLIM Receiver Cryostat

TL;DR

SPT-SLIM demonstrates a pathfinder for on-chip mm-wave spectrometers aimed at line intensity mapping, deployed on the South Pole Telescope to validate cryogenic design and automated operation. The paper details a compact cryostat powered by a two-stage adiabatic demagnetization refrigerator to achieve a 150 mK focal plane, with extensive thermal management and shielding to minimize gradients. Measurements show good agreement with thermal models, achieving up to 81% observing efficiency and sub-millikelvin stability during operation, aided by targeted design improvements and a robust Observatory Control System for automated remote cycling and telescope scheduling. The work establishes a practical framework for deploying multi-pixel LEKID-based spectrometers in constrained environments and highlights the integration of cryogenic control with observatory software for efficient LIM observations.

Abstract

The South Pole Telescope Shirokoff Line Intensity Mapper (SPT-SLIM) is a millimeter-wavelength line-intensity mapping experiment, which was deployed on the South Pole Telescope (SPT) during the 2024-2025 Austral summer season. This pathfinder experiment serves to demonstrate the on-sky operation of multi-pixel on-chip spectrometer technology. We report on the cryogenic performance of the SPT-SLIM receiver for the first year of commissioning observations. The SPT-SLIM receiver utilizes an Adiabatic Demagnetization Refrigerator (ADR) for cooling the focal plane of superconducting filterbank spectrometers to a temperature of 150 mK. We demonstrate stable thermal performance of the focal plane module during observations consistent with thermal modeling, enabling a cryogenic operating efficiency above 80%. We also report on the receiver control system design utilizing the Observatory Control System (OCS) platform for automated cryogenic operation on the SPT.
Paper Structure (5 sections, 6 figures, 1 table)

This paper contains 5 sections, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. Receiver Design
  3. Cryogenic Performance
  4. Receiver Control System
  5. Conclusion

Figures (6)

  • Figure 1: Cross-section of the SPT-SLIM receiver cryostat design, electronics package insert, and focal plane unit. Cooling the focal plane to 150 mK is achieved using an ADR, backed by a PT407 cryocooler. The electronics package can be assembled independently before installing within the cryostat.
  • Figure 2: Partial cross-section of the SPT receiver cabin, showing the SPT-SLIM cryostat mounting location and auxiliary mirrors for diverting the main SPT beam into the receiver.
  • Figure 3: Left: The SPT-SLIM cryostat during installation on the SPT. The PTC angle is offset by 40° to account for typical telescope elevation tilt during observations. Right: The electronics package insert, containing the ADR, LNAs, focal plane package, and associated readout lines.
  • Figure 4: Left: Topside of the focal plane package, featuring a gold-plated copper shield above the aluminum detector module box. The shield is mounted via copper tabs to the underside. Right: Underside of the focal plane package, showing the gold-plated copper spiderweb mount for the detector module box. These features were highly effective in reducing loading and thermal gradients across the detector module while also minimizing additional thermal mass.
  • Figure 5: Deployment cooldown curve of the SPT-SLIM cryostat, taking 46 hours to reach base temperature for ADR operation. The sharp feature at 26 hrs is a result of exercising the heat switch, briefly decoupling the sub-Kelvin stages from the PTC.
  • ...and 1 more figures