Characterization of Low-noise Backshort-Under-Grid Kilopixel Transition Edge Sensor Arrays for PIPER

TL;DR

This paper details the laboratory characterization of low-noise, kilo-pixel TES arrays with backshort-under-grid design for PIPER, demonstrating their performance in terms of thermal and noise properties suitable for CMB polarization measurements.

Contribution

It introduces a novel backshort-under-grid TES array design for PIPER and provides comprehensive performance measurements including transition temperature, thermal conductance, and noise.

Findings

Detectors achieve saturation power below 1 pW

Phonon NEP on the order of a few aW/rtHz

Successful pre-flight testing in simulated balloon conditions

Abstract

We present laboratory characterization of kilo-pixel, filled backshort-under-grid (BUG) transition-edge sensor (TES) arrays developed for the Primordial Inflation Polarization ExploreR (PIPER) balloon-borne instrument. PIPER is designed to map the polarization of the CMB on the largest angular scales and characterize dust foregrounds by observing a large fraction of the sky in four frequency bands in the range 200 to 600 GHz. The BUG TES arrays are read out by planar SQUID-based time division multiplexer chips (2dMUX) of matching form factor and hybridized directly with the detector arrays through indium bump bonding. Here, we discuss the performance of the 2dMUX and present measurements of the TES transition temperature, thermal conductance, saturation power, and preliminary noise performance. The detectors achieve saturation power below 1 pW and phonon noise equivalent power (NEP) on the order of a few aW/rtHz. Detector performance is further verified through pre-flight tests in the integrated PIPER receiver, performed in an environment simulating balloon float conditions.