| Summary: | We describe 280 GHz bolometric detector arrays that instrument the balloon-borne polarimeter spider. A primary science goal of spider is to measure the large-scale B-mode polarization of the cosmic microwave background (cmb) in search of the cosmic-inflation, gravitational-wave signature. 280 GHz channels aid this science goal by constraining the level of B-mode contamination from galactic dust emission. We present the focal plane unit design, which consists of a 16x16 array of conical, corrugated feedhorns coupled to a monolithic detector array fabricated on a 150 mm diameter silicon wafer. Detector arrays are capable of polarimetric sensing via waveguide probe-coupling to a multiplexed array of transition-edge-sensor (TES) bolometers. The spider receiver has three focal plane units at 280 GHz, which in total contains 765 spatial pixels and 1,530 polarization sensitive bolometers. By fabrication and measurement of single feedhorns, we demonstrate 14.7° FHWM Gaussian-shaped beams with <1% ellipticity in a 30% fractional bandwidth centered at 280 GHz. We present electromagnetic simulations of the detection circuit, which show 94% band-averaged, single-polarization coupling efficiency, 3% reflection and 3% radiative loss. Lastly, we demonstrate a low thermal conductance bolometer, which is well-described by a simple TES model and exhibits an electrical noise equivalent power (NEP) = 2.6 x 10^(-17) W/√Hz, consistent with the phonon noise prediction. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE). Contribution of NIST not subject to copyright. The spider project is supported by NASA under APRA grant NNX12AE95G, issued through the Science Mission Directorate, by the NSF through the award PLR-1043515, and by the David and Lucile Packard Foundation. Logistical support for the Antarctic deployment and operations was provided by the NSF through the U.S. Antarctic Program. We performed our 3D electromagnetic simulations on the Baker-Jarvis Cluster and supporting infrastructure in the ...
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