Inflation is the leading theory of the first instant of the universe. Inflation, which postulates that the universe underwent a period of rapid expansion an instant after its birth, provides convincing explanation for cosmological observations. Recent advancements in detector technology have opened opportunities to explore primordial gravitational waves generated by the inflation through "B-mode" (divergent-free) polarization pattern embedded in the Cosmic Microwave Background anisotropies. If detected, these signals would provide strong evidence for inflation, point to the correct model for inflation, and open a window to physics at ultra-high energies.LiteBIRD is a satellite mission with a goal of detecting degree-and-larger-angular-scale B-mode polarization. Lite-BIRD will observe at the second Lagrange point with a 400 mm diameter telescope and 2,622 detectors. It will survey the entire sky with 15 frequency bands from 40 to 400 GHz to measure and subtract foregrounds.The U.S. LiteBIRD team is proposing to deliver sub-Kelvin instruments that include detectors and readout electronics. A lenslet-coupled sinuous antenna array will cover low-frequency bands (40 GHz to 235 GHz) with four frequency arrangements of trichroic pixels. An orthomode-transducer-coupled corrugated horn array will cover high-frequency bands (280 GHz to 402 GHz) with three types of single frequency detectors. The detectors will be made with Transition Edge Sensor (TES) bolometers cooled to a 100 milli-Kelvin base temperature by an adiabatic demagnetization refrigerator. The TES bolometers will be read out using digital frequency multiplexing with Superconducting QUantum Interference Device (SQUID) amplifiers. Up to 78 bolometers will be multiplexed with a single SQUID amplier.We report on the sub-Kelvin instrument design and ongoing developments for the LiteBIRD mission.
Millimeter-wave hybrid un-cooled narrow-gap hot-carrier and Schottky diodes direct detectors Appl. Phys. Lett. 101, 082108 (2012) Tuning the dynamic properties of electrons between a quantum well and quantum dots J. Appl. Phys. 112, 043702 (2012) Fully integrated InGaAs/InP single-photon detector module with gigahertz sine wave gating Rev. Sci. Instrum. 83, 083111 (2012) "N" structure for type-II superlattice photodetectors Appl. Phys. Lett. 101, 073505 (2012) Additional information on Rev. Sci. Instrum. A technological milestone for experiments employing transition edge sensor bolometers operating at sub-Kelvin temperature is the deployment of detector arrays with 100s-1000s of bolometers. One key technology for such arrays is readout multiplexing: the ability to read out many sensors simultaneously on the same set of wires. This paper describes a frequency-domain multiplexed readout system which has been developed for and deployed on the APEX-SZ and South Pole Telescope millimeter wavelength receivers. In this system, the detector array is divided into modules of seven detectors, and each bolometer within the module is biased with a unique ∼MHz sinusoidal carrier such that the individual bolometer signals are well separated in frequency space. The currents from all bolometers in a module are summed together and pre-amplified with superconducting quantum interference devices operating at 4 K. Room temperature electronics demodulate the carriers to recover the bolometer signals, which are digitized separately and stored to disk. This readout system contributes little noise relative to the detectors themselves, is remarkably insensitive to unwanted microphonic excitations, and provides a technology pathway to multiplexing larger numbers of sensors.
satellite: JAXA's new strategic L-class mission for all-sky surveys of cosmic microwave background polarization,"
The Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic microwave background (CMB) over angular scales between 1 arcminute and tens of degrees using over 60,000 detectors and sampling frequencies between 27 and 270 GHz. SO will consist of a six-meteraperture telescope coupled to over 30,000 detectors and an array of half-meter aperture refractive cameras, coupled to an additional 30,000+ detectors. The unique combination of large and small apertures in a single CMB observatory will allow us to sample a wide range of angular scales over a common survey area while providing an important stepping stone towards the realization of CMB-Stage IV. CMB-Stage IV is a proposed project that will combine and expand on existing facilities in Chile and Antarctica to reach the 500,000 detectors required for CMB-Stage IV's science objectives. SO and CMB-Stage IV will measure fundamental cosmological parameters of our universe, constrain primordial fluctuations, find high redshift clusters via the Sunyaev-Zeldovich effect, constrain properties of neutrinos, and trace the density and velocity of the matter in the universe over cosmic time. The complex set of technical and science requirements for SO has led to innovative instrumentation solutions which we will discuss. For instance, the SO large aperture telescope will couple to a cryogenic receiver that is 2.4 m in diameter and 2.4 m long. We will give an overview of the drivers for and designs of the SO telescopes and cameras as well as the current status of the project. We will also discuss the current status of CMB-Stage IV and important next steps in the project's development.
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