LiteBIRD is a JAXA-led spacecraft mission that has the objective of making a full-sky measurement of the CMB polarization B-modes to constrain the tensor-to-scalar ratio r with a sensitivity of σ(r) of 0.001. Its three telescopes will host a total of 4508 Transition-Edge Sensor (TES) bolometers at a temperature of 100 mK. The signal from the thousands of bolometers will be multiplexed using digital frequency-domain multiplexing (DfMux). In DfMux, each TES in a group of up to 68 is assigned to a frequency channel between 1.5 and 5.6 MHz by an inductor-capacitor (LC) chip, and the multiplexed signal is amplified by a Superconducting Quantum Interference Device (SQUID) Array Amplifier (SAA). Both SAA and LC chips will operate at sub-Kelvin temperatures and be mounted to the detector sub-assembly on the side opposite to the sky, in what is here defined as the cold readout sub-assembly. Components of the cold readout sub-assembly will need to withstand large mechanical stress during launch and achieve excellent electronic performance to meet the mission’s requirements. In this work we present the status of the design, prototyping and testing of cold readout sub-assembly components. This includes a measurement of the inductance of custom-made edge-coupled superconducting cables, which were found to be in the order of 0.5 nH/cm. Further, we demonstrate that a rigid-flex PCB could be used to thermally isolate SAAs while maintaining close to 5 nW of heat dissipation between the SAA and the LC temperature stages. Finally, we report on simulations of different magnetic shields that could be used to prevent pickup of environmental magnetic flux by the SAAs and the shields’ comparative effectiveness. The results presented here will be used to guide and predict the performance of the next iterations of the cold readout sub-assembly design for LiteBIRD.
LiteBIRD is a JAXA-led strategic large-class satellite mission designed to measure the polarization of the cosmic microwave background and Galactic foregrounds from 34 to 448 GHz across the entire sky from L2 in the late 2020s. The scientific payload includes three telescopes which are called the low-, mid-, and high-frequency telescopes each with their own receiver that covers a portion of the mission’s frequency range. The low frequency telescope will map synchrotron radiation from the Galactic foreground and the cosmic microwave background. We discuss the design, fabrication, and characterization of the low-frequency focal plane modules for low-frequency telescope, which has a total bandwidth ranging from 34 to 161 GHz. There will be a total of 4 different pixel types with 8 overlapping bands to cover the full frequency range. These modules are housed in a single low-frequency focal plane unit which provides thermal isolation, mechanical support, and radiative baffling for the detectors. The module design implements multi-chroic lenslet-coupled sinuous antenna arrays coupled to transition edge sensor bolometers read out with frequency-domain mulitplexing. While this technology has strong heritage in ground-based cosmic microwave background experiments, the broad frequency coverage, low optical loading conditions, and the high cosmic ray background of the space environment require further development of this technology to be suitable for LiteBIRD. In these proceedings, we discuss the optical and bolometeric characterization of a triplexing prototype pixel with bands centered on 78, 100, and 140 GHz.
The Simons Array is an experiment located in the Atacama Desert in Chile that will measure the polarization anisotropy of the Cosmic Microwave Background. It consists of three telescopes that house the receivers POLARBEAR-2A, POLARBEAR-2B and POLARBEAR-2C, which will observe the CMB at 90, 150, 220 and 270 GHz with over 22,000 Transition Edge Sensor (TES) bolometers. Each receiver contains a focal plane composed of seven hexagonal arrays of lenslet-coupled sinuous antenna bolometers, with each dichroic pixel containing four TESs. The readout system uses Superconducting Quantum Interference Devices for signal amplification and digital frequency-domain multiplexing with a multiplexing factor of 40. The sensitivity of the Simons Array instruments is governed by the detectors’ noise level and the telescope optical throughput, thus an on-site signal to noise characterization is essential to evaluate the instrument. We present the post-deployment measured readout noise and methods used to improve the noise performance of POLARBEAR-2A detectors, which measure radiation in the 90 and 150 GHz bands.
LiteBIRD is a satellite mission designed to map the polarization of the Cosmic Microwave Background (CMB) at degree and larger scales from 40 to 402 GHz. LiteBIRD will use 4,600 Transition-Edge Sensor (TES) bolometers biased and read out using Digital Frequency Domain Multiplexing (DfMux). The DfMux implementation for LiteBIRD uses sub-kelvin Superconducting Quantum Interference Device (SQUID) at the same 0.1 K thermal stage as the detectors, this allows for reduced parasitic impedances within the mK circuit and improved SQUID performance. Additionally it must work in the integrated system with the spacecraft’s wiring harnesses, which will be longer than is typical on similar ground based experiments, and therefore have more significant parasitic impedances which will impact readout performance. The properties of SQUID candidates at millikelvin temperatures and effects of the spacecraft-like meter scale wiring harness are investigated. Additionally, the possibility of inductively rather than resistively biasing our bolometers at the 0.1K stage, to reduce power dissipation in the bias element, is investigated. We will report progress on validating the cryogenic components of this readout system.
We present the conceptual design of the modular detector and readout system for the Cosmic Microwave Background – Stage four (CMB-S4) ground-based survey experiment. CMB-S4 will map the cosmic microwave background (CMB) and the millimeter-wave sky to unprecedented sensitivity, using 500,000 superconducting detectors observing from Chile and Antarctica to map over 60% of the sky. The fundamental building block of the detector and readout system is a detector module package operated at 100 mK, which is connected to a readout and amplification chain that carries signals out to room temperature. It uses arrays of feedhorn-coupled orthomode transducers (OMT) that collect optical power from the sky onto dc-voltage-biased transition-edge sensor (TES) bolometers. The resulting current signal in the TESs is then amplified by a two-stage cryogenic Superconducting Quantum Interference Device (SQUID) system with a time-division multiplexer to reduce wire count, and matching room-temperature electronics to condition and transmit signals to the data acquisition system. Sensitivity and systematics requirements are being developed for the detector and readout system over wide range of observing bands (20 to 300 GHz) and optical powers to accomplish CMB-S4’s science goals. While the design incorporates the successes of previous generations of CMB instruments, CMB-S4 requires an order of magnitude more detectors than any prior experiment. This requires fabrication of complex superconducting circuits on over 10 m2 of silicon, as well as significant amounts of precision wiring, assembly and cryogenic testing
Digital Frequency-Domain Multiplexing (DfMux) is a transition edge sensor multiplexing technique that has been used in mm-wave receivers with multiplexing factors as high as 68. It is the baseline readout technology for LiteBIRD and a potential upscope option for PICO. Recent efforts have been directed toward simplifying packaging, reducing parasitic impedance, and improving readout noise performance by integrating all cryogenic readout components onto a single cryogenic stage. Here we present recent progress including further improved performance and an increase in the scale of operation. This work marks an important step toward the development of DfMux for space-based mm-wave receivers.
The third-generation South Pole Telescope camera (SPT-3G) improves upon its predecessor (SPTpol) by an order of magnitude increase in detectors on the focal plane. The technology used to read out and control these detectors, digital frequency-domain multiplexing (DfMUX), is conceptually the same as used for SPTpol, but extended to accommodate more detectors. A nearly 5× expansion in the readout operating bandwidth has enabled the use of this large focal plane, and SPT-3G performance meets the forecasting targets relevant to its science objectives. However, the electrical dynamics of the higher-bandwidth readout differ from predictions based on models of the SPTpol system due to the higher frequencies used and parasitic impedances associated with new cryogenic electronic architecture. To address this, we present an updated derivation for electrical crosstalk in higher-bandwidth DfMUX systems and identify two previously uncharacterized contributions to readout noise, which become dominant at high bias frequency. The updated crosstalk and noise models successfully describe the measured crosstalk and readout noise performance of SPT-3G. These results also suggest specific changes to warm electronics component values, wire-harness properties, and SQUID parameters, to improve the readout system for future experiments using DfMUX, such as the LiteBIRD space telescope.
LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with its expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic microwave background (CMB) polarization over the full sky with unprecedented precision. Its main scientific objective is to carry out a definitive search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with an insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. To this end, LiteBIRD will perform full-sky surveys for three years at the Sun-Earth Lagrangian point L2 for 15 frequency bands between 34 and 448 GHz with three telescopes, to achieve a total sensitivity of 2.16 μK-arcmin with a typical angular resolution of 0.5° at 100 GHz. We provide an overview of the LiteBIRD project, including scientific objectives, mission requirements, top-level system requirements, operation concept, and expected scientific outcomes.
LiteBIRD has been selected as JAXA’s strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) B-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of -56 dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT : 34–161 GHz), one of LiteBIRD’s onboard telescopes. It has a wide field-of-view (18° x 9°) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90◦ are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at 5 K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented.
LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34 GHz to 448 GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Medium-and High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89{224 GHz) and the High-Frequency Telescope (166{448 GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5 K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100 mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD.
Digital Frequency Domain Multiplexing (DfMux) is a method of biasing and reading out many TES bolometers using superconducting MHz resonators and a SQUID amplifier. DfMux was recently deployed in two Cosmic Microwave Background receivers and is an alternative and baseline readout technology for CMB-S4 and LiteBIRD, respectively. The next generation of DfMux puts the SQUID,TES bias element, and resonators onto a common carrier at 100 mK in order to relax requirements on cryogenic wiring and allow for an increased multiplexing factor and improved TES performance. Characterization of a prototype system that is compatible with the POLARBEAR-2 receivers is presented.
The Simons Array upgrades the POLARBEAR experiment, which measures the cosmic microwave background from the Atacama Desert in Chile, with three newly developed receivers. Each receiver has 7,588 transition-edge sensor bolometers with a raw data rate of approximately 20 MB/s. This significantly increased data rate required us to develop a new data-acquisition (DAQ) and data-management system. As the network bandwidth from our observatory to our data-storage sites outside Chile is not high enough to send all the raw data, we compress the raw data on-site. The expected yearly compressed data rate is approximately 60 TB from each receiver. We have also developed a new housekeeping DAQ system. The new housekeeping DAQ system is a distributed system to handle the various newly added monitoring systems and to better understand our instruments and environments. Those data can also be fetched by another module for real-time monitoring of our instrument from all over the world with latencies on the order of minutes. We deployed the first receiver in late 2018 and started the commissioning of the DAQ system. The DAQ system has been working without significant problems and already accumulates a considerable amount of the new receiver data from the commissioning observations. In this presentation, we summarize and report the status of the new systems.
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.
The third generation South Pole Telescope camera (SPT-3G) improves over its predecessor (SPTpol) by an order of magnitude increase in detector number. The technology used to read out and control these detectors, digital frequency-domain multiplexing (DfMUX), is conceptually the same as used for SPTpol, but extended to accommodate more detectors. A nearly 5x expansion in the readout operating bandwidth has enabled the use of this large focal plane, and SPT-3G performance meets the forecasting targets relevant to its science objectives. However, the electrical dynamics of the higher-bandwidth system depart in significant ways from the characterization and models drawn from the previous generation of cameras. We present an updated derivation for electrical crosstalk in higher-bandwidth DfMUX systems, and identify two previously uncharacterized contributions to readout noise. The updated crosstalk and noise models successfully describe the measured crosstalk and readout noise performance of SPT-3G, and suggest improvements to the readout system for future experiments using DfMUX, such as the LiteBIRD satellite.
LiteBIRD is a candidate for JAXA’s strategic large mission to observe the cosmic microwave background (CMB) polarization over the full sky at large angular scales. It is planned to be launched in the 2020s with an H3 launch vehicle for three years of observations at a Sun-Earth Lagrangian point (L2). The concept design has been studied by researchers from Japan, U.S., Canada and Europe during the ISAS Phase-A1. Large scale measurements of the CMB B-mode polarization are known as the best probe to detect primordial gravitational waves. The goal of LiteBIRD is to measure the tensor-to-scalar ratio (r) with precision of r < 0:001. A 3-year full sky survey will be carried out with a low frequency (34 - 161 GHz) telescope (LFT) and a high frequency (89 - 448 GHz) telescope (HFT), which achieve a sensitivity of 2.5 μK-arcmin with an angular resolution 30 arcminutes around 100 GHz. The concept design of LiteBIRD system, payload module (PLM), cryo-structure, LFT and verification plan is described in this paper.
POLARBEAR-2 is a new receiver system, which will be deployed on the Simons Array telescope platform, for the measurement of Cosmic Microwave Background (CMB) polarization. The science goals with POLARBEAR-2 are to characterize the B-mode signal both at degree and sub-degree angular-scales. The degree-scale polarization data can be used for quantitative studies on inflation, such as the reconstruction of the energy scale of inflation. The sub-degree polarization data is an excellent tracer of large-scale structure in the universe, and will lead to precise constraints on the sum of the neutrino masses. In order to achieve these goals, POLARBEAR-2 employs 7588 polarization-sensitive antenna-coupled transition-edge sensor (TES) bolometers on the focal plane cooled to 0.27K with a three-stage Helium sorption refrigerator, which is ~6 times larger array over the current receiver system. The large TES bolometer array is read-out by an upgraded digital frequency-domain multiplexing system capable of multiplexing 40 bolometers through a single superconducting quantum interference device (SQUID).
The first POLARBEAR-2 receiver, POLARBEAR-2A is constructed and the end-to-end testing to evaluate the integrated performance of detector, readout, and optics system is being conducted in the laboratory with various types of test equipments. The POLARBEAR-2A is scheduled to be deployed in 2018 at the Atacama desert in Chile. To further increase measurement sensitivity, two more POLARBEAR-2 type receivers will be deployed soon after the deployment (Simons Array project). The Simons Array will cover four frequency bands at 95GHz, 150GHz, 220GH and 270GHz for better control of the foreground signal. The projected constraints on a tensor-to-scalar ratio (amplitude of inflationary B-mode signal) is σ(r=0.1) = $6.0 \times 10^{-3}$ after foreground removal ($4.0 \times 10^{-3}$ (stat.)), and the sensitivity to the sum of the neutrino masses when combined with DESI spectroscopic galaxy survey data is 40 meV at 1-sigma after foreground removal (19 meV(stat.)).
We will present an overview of the design, assembly and status of the laboratory testing of the POLARBEAR-2A receiver system as well as the Simons Array project overview.
POLARBEAR is a cosmic microwave background (CMB) polarization experiment located in the Atacama desert in Chile. The science goals of the POLARBEAR project are to do a deep search for CMB B-mode polarization created by inflationary gravitational waves, as well as characterize the CMB B-mode signal from gravitational lensing. POLARBEAR-1 started observations in 2012, and the POLARBEAR team has published a series of results from its first two seasons of observations, including the first measurement of a non-zero B-mode polarization angular power spectrum, measured at sub-degree scales where the dominant signal is gravitational lensing of the CMB. The Simons Array expands POLARBEAR to include an additional two telescopes with next-generation POLARBEAR-2 multi-chroic receivers, observing at 95, 150, 220, and 270 GHz.
The POLARBEAR-2A focal plane has 7,588 transition-edge sensor bolometers, read out with frequency-division multiplexing, with 40 frequency channels within the readout bandwidth of 1.5 to 4.5 MHz. The frequency channels are defined by a low-loss lithographed aluminum spiral inductor and interdigitated capacitor in series with each bolometer, creating a resonant frequency for each channel's unique voltage bias and current readout. Characterization of the readout includes measuring resonant peak locations and heights and fitting to a circuit model both above and below the bolometer superconducting transition temperature. This information is used determine the optimal detector bias frequencies and characterize stray impedances which may affect bolometer operation and stability. The detector electrical characterization includes measurements of the transition properties by sweeping in temperature and in voltage bias, measurements of the bolometer saturation power, as well as measuring and removing any biases introduced by the readout circuit. We present results from the characterization, tuning, and operation of the fully integrated focal plane and readout for the first POLARBEAR-2 receiver, POLARBEAR-2A, during its pre-deployment integration run.
Y. Inoue, P. Ade, Y. Akiba, C. Aleman, K. Arnold, C. Baccigalupi, B. Barch, D. Barron, A. Bender, D. Boettger, J. Borrill, S. Chapman, Y. Chinone, A. Cukierman, T. de Haan, M. Dobbs, A. Ducout, R. Dünner, T. Elleflot, J. Errard, G. Fabbian, S. Feeney, C. Feng, G. Fuller, A. Gilbert, N. Goeckner-Wald, J. Groh, G. Hall, N. Halverson, T. Hamada, M. Hasegawa, K. Hattori, M. Hazumi, C. Hill, W. Holzapfel, Y. Hori, L. Howe, F. Irie, G. Jaehnig, A. Jaffe, O. Jeong, N. Katayama, J. Kaufman, K. Kazemzadeh, B. Keating, Z. Kermish, R. Keskitalo, T. Kisner, A. Kusaka, M. Le Jeune, A. Lee, D. Leon, E. Linder, L. Lowry, F. Matsuda, T. Matsumura, N. Miller, K. Mizukami, J. Montgomery, M. Navaroli, H. Nishino, H. Paar, J. Peloton, D. Poletti, G. Puglisi, C. Raum, G. Rebeiz, C. Reichardt, P. Richards, C. Ross, K. Rotermund, Y. Segawa, B. Sherwin, I. Shirley, P. Siritanasak, N. Stebor, R. Stompor, J. Suzuki, A. Suzuki, O. Tajima, S. Takada, S. Takatori, G. Teply, A. Tikhomirov, T. Tomaru, N. Whitehorn, A. Zahn, O. Zahn
POLARBEAR-2 (PB-2) is a cosmic microwave background (CMB) polarization experiment that will be located in the Atacama highland in Chile at an altitude of 5200 m. Its science goals are to measure the CMB polarization signals originating from both primordial gravitational waves and weak lensing. PB-2 is designed to measure the tensor to scalar ratio, r, with precision σ(r) > 0:01, and the sum of neutrino masses, Σmz, with σ(Σmv) < 90 meV. To achieve these goals, PB-2 will employ 7588 transition-edge sensor bolometers at 95 GHz and 150 GHz, which will be operated at the base temperature of 250 mK. Science observations will begin in 2017.
LiteBIRD is a next generation satellite aiming for the detection of the Cosmic Microwave Background (CMB) B-mode polarization imprinted by the primordial gravitational waves generated in the era of the inflationary universe. The science goal of LiteBIRD is to measure the tensor-to-scaler ratio r with a precision of δr < 10-3♦, offering us a crucial test of the major large-single-field slow-roll inflation models. LiteBIRD is planned to conduct an all sky survey at the sun-earth second Lagrange point (L2) with an angular resolution of about 0.5 degrees to cover the multipole moment range of 2 ≤ ℓ ≤ 200. We use focal plane detector arrays consisting of 2276 superconducting detectors to measure the frequency range from 40 to 400 GHz with the sensitivity of
3.2 μK·arcmin. including the ongoing studies.
N. Stebor, P. Ade, Y. Akiba, C. Aleman, K. Arnold, C. Baccigalupi, B. Barch, D. Barron, S. Beckman, A. Bender, D. Boettger, J. Borrill, S. Chapman, Y. Chinone, A. Cukierman, T. de Haan, M. Dobbs, A. Ducout, R. Dunner, T. Elleflot, J. Errard, G. Fabbian, S. Feeney, C. Feng, T. Fujino, G. Fuller, A. Gilbert, N. Goeckner-Wald, J. Groh, G. Hall, N. Halverson, T. Hamada, M. Hasegawa, K. Hattori, M. Hazumi, C. Hill, W. Holzapfel, Y. Hori, L. Howe, Y. Inoue, F. Irie, G. Jaehnig, A. Jaffe, O. Jeong, N. Katayama, J. Kaufman, K. Kazemzadeh, B. Keating, Z. Kermish, R. Keskitalo, T. Kisner, A. Kusaka, M. Le Jeune, A. Lee, D. Leon, E. Linder, L. Lowry, F. Matsuda, T. Matsumura, N. Miller, J. Montgomery, M. Navaroli, H. Nishino, H. Paar, J. Peloton, D. Poletti, G. Puglisi, C. Raum, G. Rebeiz, C. Reichardt, P. Richards, C. Ross, K. Rotermund, Y. Segawa, B. Sherwin, I. Shirley, P. Siritanasak, L. Steinmetz, R. Stompor, A. Suzuki, O. Tajima, S. Takada, S. Takatori, G. Teply, A. Tikhomirov, T. Tomaru, B. Westbrook, N. Whitehorn, A. Zahn, O. Zahn
The Simons Array is a next generation cosmic microwave background (CMB) polarization experiment whose science target is a precision measurement of the B-mode polarization pattern produced both by inflation and by gravitational lensing. As a continuation and extension of the successful POLARBEAR experimental program, the Simons Array will consist of three cryogenic receivers each featuring multichroic bolometer arrays mounted onto separate 3.5m telescopes. The first of these, also called POLARBEAR-2A, will be the first to deploy in late 2016 and has a large diameter focal plane consisting of dual-polarization dichroic pixels sensitive at 95 GHz and 150 GHz. The POLARBEAR-2A focal plane will utilize 7,588 antenna-coupled superconducting transition edge sensor (TES) bolometers read out with SQUID amplifiers using frequency domain multiplexing techniques. The next two receivers that will make up the Simons Array will be nearly identical in overall design but will feature extended frequency capability. The combination of high sensitivity, multichroic frequency coverage and large sky area available from our mid-latitude Chilean observatory will allow Simons Array to produce high quality polarization sky maps over a wide range of angular scales and to separate out the CMB B-modes from other astrophysical sources with high fidelity. After accounting for galactic foreground separation, the Simons Array will detect the primordial gravitational wave B-mode signal to r > 0.01 with a significance of > 5σ and will constrain the sum of neutrino masses to 40 meV (1σ) when cross-correlated with galaxy surveys. We present the current status of this funded experiment, its future, and discuss its projected science return.
Y. Inoue, N. Stebor, P. A. Ade, Y. Akiba, K. Arnold, A. Anthony, M. Atlas, D. Barron, A. Bender, D. Boettger, J. Borrilll, S. Chapman, Y. Chinone, A. Cukierman, M. Dobbs, T. Elleflot, J. Errard, G. Fabbian, C. Feng, A. Gilbert, N. Halverson, M. Hasegawa, K. Hattori, M. Hazumi, W. Holzapfel, Y. Hori, G. Jaehnig, A. Jaffe, N. Katayama, B. Keating, Z. Kermish, Reijo Keskitalo, T. Kisner, M. Le Jeune, A. Lee, E. Leitch, E. Linder, F. Matsuda, T. Matsumura, X. Meng, H. Morii, M. Myers, M. Navaroli, H. Nishino, T. Okamura, H. Paar, J. Peloton, D. Poletti, G. Rebeiz, C. Reichardt, P. Richards, C. Ross, D. Schenck, B. Sherwin, P. Siritanasak, G. Smecher, M. Sholl, B. Steinbach, R. Stompor, A. Suzuki, J. Suzuki, S. Takada, S. Takakura, T. Tomaru, B. Wilson, A. Yadav, H. Yamaguchi, O. Zahn
POLARBEAR-2 (PB-2) is a cosmic microwave background (CMB) polarization experiment for B-mode detection. The PB-2 receiver has a large focal plane and aperture that consists of 7588 transition edge sensor (TES) bolometers at 250 mK. The receiver consists of the optical cryostat housing reimaging lenses and infrared filters, and the detector cryostat housing TES bolometers. The large focal plane places substantial requirements on the thermal design of the optical elements at the 4K, 50K, and 300K stages. Infrared filters and lenses inside the optical cryostat are made of alumina for this purpose. We measure basic properties of alumina, such as the index of refraction, loss tangent and thermal conductivity. All results meet our requirements. We also optically characterize filters and lenses made of alumina. Finally, we perform a cooling test of the entire optical cryostat. All measured temperature values satisfy our requirements. In particular, the temperature rise between the center and edge of the alumina infrared filter at 50 K is only 2:0 ± 1:4 K. Based on the measurements, we estimate the incident power to each thermal stage.
The Simons Array is an expansion of the POLARBEAR cosmic microwave background (CMB) polarization experiment currently observing from the Atacama Desert in Northern Chile. This expansion will create an array of three 3.5m telescopes each coupled to a multichroic bolometric receiver. The Simons Array will have the sensitivity to produce a ≥ 5σ detection of inationary gravitational waves with a tensor-to-scalar ratio r ≥ 0:01, detect the known minimum 58 meV sum of the neutrino masses with 3σ confidence when combined with a next-generation baryon acoustic oscillation measurement, and make a lensing map of large-scale structure over the 80% of the sky available from its Chilean site. These goals require high sensitivity and the ability to extract the CMB signal from contaminating astrophysical foregrounds; these requirements are met by coupling the three high-throughput telescopes to novel multichroic lenslet-coupled pixels each measuring CMB photons in both linear polarization states over multiple spectral bands. We present the status of this instrument already under construction, and an analysis of its capabilities.
POLARBEAR-2 is a next-generation receiver for precision measurements of polarization of the cosmic microwave background, scheduled to deploy in 2015. It will feature a large focal plane, cooled to 250 milliKelvin, with 7,588 polarization-sensitive antenna-coupled transition edge sensor bolometers, read-out with frequency domain multiplexing with 32 bolometers on a single SQUID amplifier. We will present results from testing and characterization of new readout components, integrating these components into a scaled-down readout system for validation of the design and technology.
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