LiteBIRD is a JAXA-led strategic Large-Class satellite mission designed to measure the polarization of the cosmic microwave background and cosmic foregrounds from 34 to 448 GHz across the entire sky from L2 in the late 2020's. The primary focus of the mission is to measure primordially generated B-mode polarization at large angular scales. Beyond its primary scientific objective LiteBIRD will generate a data-set capable of probing a number of scientific inquiries including the sum of neutrino masses. The primary responsibility of United States will be to fabricate the three flight model focal plane units for the mission. The design and fabrication of these focal plane units is driven by heritage from ground based experiments and will include both lenslet-coupled sinuous antenna pixels and horn-coupled orthomode transducer pixels. The experiment will have three optical telescopes called the low frequency telescope, mid frequency telescope, and high frequency telescope each of which covers a portion of the mission's frequency range. JAXA is responsible for the construction of the low frequency telescope and the European Consortium is responsible for the mid- and high- frequency telescopes. The broad frequency coverage and low optical loading conditions, made possible by the space environment, require development and adaptation of detector technology recently deployed by other cosmic microwave background experiments. This design, fabrication, and characterization will take place at UC Berkeley, NIST, Stanford, and Colorado University, Boulder. We present the current status of the US deliverables to the LiteBIRD mission.
We report on the development of commercially fabricated multi-chroic antenna coupled Transition Edge Sensor (TES) bolometer arrays for Cosmic Microwave Background (CMB) polarimetry experiments. The orders of magnitude increase in detector count for next generation CMB experiments require a new approach in detector wafer production to increase fabrication throughput.
We describe collaborative efforts with a commercial superconductor electronics fabrication facility (SeeQC Inc.) to fabricate detector arrays for CMB application. We have successfully fabricated dual-polarization, dichroic sinuous antenna-coupled TES detector arrays on 150 mm diameter wafers. We report on our recent progress on process optimization to achieve target detector performance such as superconducting transition temperature of a sensor, impedance of sensors, band pass placement, and optical efficiency. We will also report on development of orthomode transducer coupled horn detector fabrication at SeeQC Inc.
The Simons Array is a set of three millimeter-wavelength telescopes in the Atacama Desert in northern Chile. It is designed to measure the polarization of the cosmic microwave background caused by density perturbations, gravitational lensing, and primordial gravitational waves. Polarbear-2b (PB-2b) is the receiver that will be mounted onto the Paul Simons Telescope, the second Simons Array telescope. Each pixel in the PB-2b focal plane has a broadband sinuous antenna coupled to transition-edge sensor (TES) bolometers. In all, there are more than 7,500 antenna-coupled TES bolometers which are biased and read out using a digital frequency-domain multiplexing framework. We implement a multiplexing factor of 40 with resonator frequencies ranging from 1.6 MHz to 4.6 MHz. These resonators are connected to superconducting quantum interference device arrays that provide a signal amplification stage. We present Polarbear-2b detector and readout characterization results from in-lab testing that enabled the deployment of PB-2b to Chile in March 2020.
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