Development of MKIDs for measurement of the Cosmic Microwave Background with the South Pole Telescope

TL;DR

This paper details the design, simulation, and initial testing of MKID-based detectors for the South Pole Telescope's new receiver, aiming to improve measurements of the cosmic microwave background's secondary anisotropies.

Contribution

It introduces optimized MKID designs for the SPT-3G+ receiver, including simulation-backed pixel configurations and fabrication strategies for high detector density.

Findings

Prototype MKIDs show promising initial dark characterization results.

Design choices enhance resonator quality and uniformity.

Simulation results support the effectiveness of the proposed detector configurations.

Abstract

We present details of the design, simulation, and initial test results of prototype detectors for the fourth-generation receiver of the South Pole Telescope (SPT). Optimized for the detection of key secondary anisotropies of the cosmic microwave background (CMB), SPT-3G+ will measure the temperature and polarization of the mm/sub-mm sky at 220, 285, and 345 GHz, beyond the peak of the CMB blackbody spectrum. The SPT-3G+ focal plane will be populated with microwave kinetic inductance detectors (MKIDs), allowing for significantly increased detector density with reduced cryogenic complexity. We present simulation-backed designs for single-color dual-polarization MKID pixels at each SPT-3G+ observation frequency. We further describe design choices made to promote resonator quality and uniformity, enabling us to maximize the available readout bandwidth. We also discuss aspects of the fabrication process that enable rapid production of these devices and present an initial dark characterization of a series of prototype devices.