Design of 280 GHz feedhorn-coupled TES arrays for the balloon-borne polarimeter SPIDER

Published: July 07, 2016

Author(s)

Johannes Hubmayr, Jason E. Austermann, James A. Beall, Daniel T. Becker, Shannon M. Duff, Arpi L. Grigorian, Gene C. Hilton, Joel N. Ullom, Michael R. Vissers

Abstract

We describe 280 GHz bolometric detector arrays that instrument the balloon-borne polarimeter spider. A primary science goal of spider is to measure large-scale B-mode polarization of the cosmic microwave back-ground (cmb) in search of the cosmic-inflation gravity-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. Three such focal plane units instrument the spider receiver, which in total contains 765 spatial pixels and 1,530 polarization sensitive bolometers at 280 GHz. By fabrication and measurement of single feedhorns, we demonstrate 14.7 FHWM Gaussian-shaped beams with <1% ellipticity in a 30% fractional bandwidth centered on 280 GHz. We present electromagnetic simulations of the detection circuit, which show 94 % band-averaged, single-polarization coupling eciency, 3% reflection and 3% radiative loss. Lastly, we demonstrate low thermal conductance bolometers optimized for a space-like environment, which are well-described by a simple TES model and exhibit an electrical noise equivalent power (NEP) =2.6 x10^-17 w/√Hz, consistent with the phonon noise prediction.
Citation: Proceedings of SPIE
Volume: v2
Pub Type: Journals
Created July 07, 2016, Updated November 10, 2018