Readout system with on-board demodulation for CMB polarization experiments using coherent polarimeter arrays

TL;DR

This paper presents a readout system with on-board demodulation for CMB polarization experiments using a large coherent polarimeter array, enabling direct extraction of polarization signals free from noise and non-polarized components.

Contribution

The authors developed and validated a novel on-board demodulation readout system with a master clock strategy for large polarimeter arrays in CMB experiments.

Findings

System components meet experimental requirements.

The readout system effectively extracts polarization signals.

Performance tests confirm suitability for B-mode measurements.

Abstract

B-modes are special patterns in cosmic microwave background (CMB) polarization. The detection of them is a smoking-gun signature of primordial gravitational waves. The generic strategy of the CMB polarization experiments is to employ a large number of polarimeters for improving the statistics. The Q/U Imaging ExperimenT-II (QUIET-II) has been proposed to detect the B-modes using the world's largest coherent polarimeter array (2,000 channels). An unique detection technique using QUIET's polarimeters, which is a modula- tion/demodulation scheme, enables us directly extracting the polarization signal. The extracted signal is free from non- polarized components and intrinsic 1/f noise. We developed a data readout system with on-board demodulation functions for the QUIET-II experiment. We employed a "master" clock strategy. This strategy guarantees phase matching between the modulation by the polarimeters and the demodulation by ADC modules. The single master generates all carrier clocks and distributes them to each module. The developed electronics, clock modules, and the ADC modules fulfill requirements. Tests with a setup similar to that of the real experiment proved that the system works properly. The performance of all system components are validated to be suitable for B-mode measurements.