GroundBIRD : A CMB polarization experiment with MKID arrays

TL;DR

GroundBIRD is a ground-based CMB polarization experiment utilizing MKID arrays, fast rotation scanning, and cold optics to achieve high sensitivity at large angular scales, aiming to constrain the tensor-to-scalar ratio.

Contribution

This paper introduces the design and development status of GroundBIRD, a novel CMB polarization experiment using MKID arrays and a unique scanning strategy for improved sensitivity.

Findings

Prototype MKID array under development

Telescope moved to Tenerife for testing

Expected to constrain tensor-to-scalar ratio

Abstract

GroundBIRD is a ground-based experiment for the precise observation of the polarization of the cosmic microwave background (CMB). To achieve high sensitivity at large angular scale, we adopt three features in this experiment: fast rotation scanning, microwave kinetic inductance detector (MKID) and cold optics. The rotation scanning strategy has the advantage to suppress $1/f$ noise. It also provides a large sky coverage of 40\%, which corresponds to the large angular scales of $l \sim 6$. This allows us to constrain the tensor-to-scalar ratio by using low $l$ B-mode spectrum. The focal plane consists of 7 MKID arrays for two target frequencies, 145 GHz and 220 GHz band. There are 161 pixels in total, of which 138 are for 144 GHz and 23 are for 220 GHz. This array is currently under development and the prototype will soon be evaluated in telescope. The GroundBIRD telescope will observe the CMB at the Teide observatory. The telescope was moved from Japan to Tenerife and is now under test. We present the status and plan of the GroundBIRD experiment.