An All Silicon Feedhorn-Coupled Focal Plane for Cosmic Microwave Background Polarimetry
Upcoming experiments aim to produce high fidelity polarization maps of the cosmic microwave background. To achieve the required sensitivity, the Truce collaboration is developing monolithic, feedhorn coupled TES polarimeter arrays. In this scheme, dual polarization sensitive TES detector arrays, which include on-chip band pass filters, couple to telescope optics by way of corrugated silicon feedhorn arrays. Current efforts focus on a 150~GHz band; however this technology scales between $\sim$~70-700~GHz. We describe this focal plane architecture and the current status of this technology, focusing on single-pixel polarimeters being deployed on the Atacama B-mode Search (ABS) and an 84-pixel demonstration feedhorn array backed by four 10-pixel polarimeter arrays. The feedhorn array exhibits highly symmetric beams, cross-polar response below -23~dB and excellent uniformity across the array. Monolithic polarimeter arrays, including arrays of silicon feedhorns, will be used in the Atacama Cosmology Telescope Polarimeter (ACTPol) and the South Pole Telescope Polarimeter (SPTpol) and have been proposed for upcoming balloon-borne instruments.
An All Silicon Feedhorn-Coupled Focal Plane for Cosmic Microwave Background Polarimetry, Journal of Low Temperature Physics, [online], https://doi.org/10.1007/s10909-011-0420-7
(Accessed December 4, 2023)