The design of the Ali CMB Polarization Telescope receiver

Abstract

Ali CMB Polarization Telescope (AliCPT-1) is the first CMB degree-scale polarimeter to be deployed on the Tibetan plateau at 5,250 m above sea level. AliCPT-1 is a 90/150 GHz 72 cm aperture, two-lens refracting telescope cooled down to 4 K. Alumina lenses, 800 mm in diameter, image the CMB in a 33.4 • field of view on a 636 mm wide focal plane. The modularized focal plane consists of dichroic polarization-sensitive Transition-Edge Sensors (TESes). Each module includes 1,704 optically active TESes fabricated on a 150 mm diameter silicon wafer. Each TES array is read out with a microwave multiplexing readout system capable of a multiplexing factor up to 2,048. Such a large multiplexing factor has allowed the practical deployment of tens of thousands of detectors, enabling the design of a receiver that can operate up to 19 TES arrays for a total of 32,376 TESes. AliCPT-1 leverages the technological advancements in the detector design from multiple generations of previously successful feedhorn-coupled polarimeters, and in the instrument design from BICEP-3, but applied on a larger scale. The cryostat receiver is currently under integration and testing. During the first deployment year, the focal plane will be populated with up to 4 TES arrays. Further TES arrays will be deployed in the following years, fully populating the focal plane with 19 arrays on the fourth deployment year. Here we present the AliCPT-1 receiver design, and how the design has been optimized to meet the experimental requirements.

Scalar quadratic maximum likelihood estimators for the CMB cross power spectrum

“…So we obtain a ∼ 78% sky coverage patch for the space-based CMB experiment showed in the upper panel of figure 1. Second, we consider the AliCPT-1 experiment (Li et al 2017;Salatino et al 2021), a CMB experiment in the northern hemisphere, to represent of…”

Fast scalar quadratic maximum likelihood estimators for the CMB B-mode power spectrum

“…We assume this is the observed sky patch with f sky ∼ 78.8%, which is representative of a 2 https://github.com/LSSTDESC/NaMaster space-based polarization experiment. In addition, we consider a f sky ∼ 15.1% sky patch in the northern hemisphere, based on the AliCPT-1 experiment (Li et al 2017;Salatino et al 2021), for the observed sky of the ground-based experiment simulations. We show the binary mask for these two sky patches in figure 1.…”

“…Great effort has been made to observe the CMB B-modes with ongoing ground-based experiments, such as BICEP-3 (Ahmed et al 2014), AdvACTPol (Henderson et al 2016) and SPT-3G (Benson et al 2014). Other upcoming experiments, like AliCPT-1 (Li et al 2017;Salatino et al 2021), Simons Observatory (Ade et al 2019), LSPE (The LSPE collaboration et al 2012), QUIJOTE (Pérez-de-Taoro et al 2014) and CMB-S4 (The CMB-S4 Collaboration et al 2020), will join the efforts to look for the primordial CMB B-mode from the ground, while the future LiteBIRD (Hazumi et al 2019) satellite aims to observe the CMB polarized signal from space.…”