Fabrication of Feedhorn-Coupled Transition Edge Sensor Arrays for Measurement of the Cosmic Microwave Background Polarization

TL;DR

This paper details the development of 90 GHz feedhorn-coupled TES detector modules, featuring a modular design and hybridization process, for precise measurement of CMB polarization in space-based and ground-based telescopes.

Contribution

It introduces a scalable, modular fabrication process for 90 GHz TES detector modules with increased wiring density and wafer-level hybridization, suitable for large CMB focal planes.

Findings

Successful fabrication of 90 GHz detector modules

Modules are tile-able for large focal plane assembly

Detectors will be deployed in the CLASS telescope

Abstract

Characterization of the minute cosmic microwave background polarization signature requires multi-frequency, high-throughput precision instrument systems. We have previously described the detector fabrication of a 40 GHz focal plane and now describe the fabrication of detector modules for measurement of the CMB at 90 GHz. The 90 GHz detectors are a scaled version of the 40 GHz architecture where, due to smaller size detectors, we have implemented a modular (wafer level) rather than the chip-level architecture. The new fabrication process utilizes the same design rules with the added challenge of increased wiring density to the 74 TES's as well as a new wafer level hybridization procedure. The hexagonally shaped modules are tile-able, and as such, can be used to form the large focal planes required for a space-based CMB polarimeter. The detectors described here will be deployed in two focal planes with 7 modules each in the Johns Hopkins University led ground-based Cosmology Large Angular Scale Surveyor (CLASS) telescope.