LiteBIRD, the next-generation cosmic microwave background (CMB) experiment, aims for a launch in Japan’s fiscal year 2032, marking a major advancement in the exploration of primordial cosmology and fundamental physics. Orbiting the Sun-Earth Lagrangian point L2, this JAXA-led strategic L-class mission will conduct a comprehensive mapping of the CMB polarization across the entire sky. During its 3-year mission, LiteBIRD will employ three telescopes within 15 unique frequency bands (ranging from 34 through 448 GHz), targeting a sensitivity of 2.2 μK-arcmin and a resolution of 0.5° at 100 GHz. Its primary goal is to measure the tensor-toscalar ratio r with an uncertainty δr = 0.001, including systematic errors and margin. If r ≥ 0.01, LiteBIRD expects to achieve a > 5σ detection in the ℓ = 2–10 and ℓ = 11–200 ranges separately, providing crucial insight into the early Universe. We describe LiteBIRD’s scientific objectives, the application of systems engineering to mission requirements, the anticipated scientific impact, and the operations and scanning strategies vital to minimizing systematic effects. We will also highlight LiteBIRD’s synergies with concurrent CMB projects.
The LiteBIRD experiment is an international spaceborne telescope, led by JAXA, to observe cosmic microwave background (CMB) radiation. The instrument will be deployed to measure and characterize the signature of the primordial gravitational waves from cosmic inflation in the B-mode polarization of the CMB radiation. These observations and measurements will take place over 15 separate bands in the range of 34 to 448 GHz. This paper will describe the process flow developed to fabricate the lowest bands of the detectors, namely in the range of 34 to 99 GHz. The detector wafer itself will be further divided into two process flows - one covering the cosmic ray mitigation structures and the other describing the trichroic polarization sensitive sinuous antenna, coupled to the transition-edge sensor (TES) detectors fabricated on the device side of the wafer. Building on the process flow previously developed for detector wafers in the adjacent higher low-frequency bands, these wafers will also incorporate Pd based cosmic ray mitigation structures, of different thicknesses, on both the skyside and device side.
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, a forthcoming JAXA mission, aims to accurately study the microwave sky within the 40-400 GHz frequency range divided into 15 distinct nominal bands. The primary objective is to constrain the CMB inflationary signal, specifically the primordial B-modes. LiteBIRD targets the CMB B-mode signal on large angular scales, where the primordial inflationary signal is expected to dominate, with the goal of reaching a tensor-to-scalar ratio sensitivity of σr ∼ 0.001. LiteBIRD frequency bands will be split among three telescopes, with some overlap between telescopes for better control of systematic effects. Here we report on the development status of the detector arrays for the Low Frequency Telescope (LFT), which spans the 34-161 GHz range, with 12 bands subdivided between four types of trichroic pixels consisting of lenslet-coupled sinuous antennas. The signal from the antenna is bandpass filtered and sensed by AlMn Transition-Edge Sensors (TES). We provide an update on the status of the design and development of LiteBIRD’s LFT LF1 (40-60-78 GHz), LF2 (50-68-89 GHz) pixels. We discuss design choices motivated by LiteBIRD scientific goals. In particular we focus on the details of the optimization of the design parameters of the sinuous antenna, on-chip bandpass filters, cross-under and impedance transformers and all the RF components that define the LF1 and LF2 pixel detection chain. We present this work in the context of the technical challenges and physical constraints imposed by the finite size of the instrument.
The Simons Observatory (SO) is a ground-based experiment aiming to enhance our understanding of the early universe, by making detailed measurements of the cosmic microwave background (CMB), across multiple spectral bands ranging from 30 to 280 GHz. The baseline project in the Atacama Desert in Chile, comprises four small-aperture telescopes (SATs) and one large-aperture telescope (LAT), housing a total of 60,000 detectors with angular resolutions ranging from 1-90 arc-minute. The low frequency detector arrays to be deployed in the LAT, feature anti-reflection (AR) coated lenslet-coupled sinuous antennas with a diplexing filter for the 30 and 40 GHz bands centers. Superconducting niobium (Nb) microstrip lines carry the signal for each polarization and band to titanium (Ti) load resistors which in turn heat up palladium (Pd) thermal ballasts and are sensed with transition edge sensors (TESs). The TESs are constructed from aluminum manganese (AlMn) and operate in their superconducting transitions (Tc) with a base temperature of 100mK. The sensors are read out by cryogenic microwave resonators using RF superconducting quantum interference devices (SQUIDs) in the microwave multiplexing (uMux) scheme. In these proceedings, we report on the current status of design, fabrication and characterization of the Simons Observatory low frequency detectors fabricated by UC Berekeley. The fabricated detector arrays have an average bolometer yield of 94% and desirable radio frequency (RF) characteristics.
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.
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 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.
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.
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.
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.
The Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic
microwave background (CMB) using a series of telescopes which will cover angular scales between 1 arcminute
and tens of degrees, contain over 40,000 detectors, and sample frequencies between 27 and 270 GHz. SO will
consist of a six-meter-aperture telescope coupled to over 20,000 detectors along with an array of half-meter
aperture refractive cameras, coupled to an additional 20,000+ detectors. The unique combination of large and
small apertures in a single CMB observatory, which will be located in the Atacama Desert at an altitude of
5190 m, will allow us to sample a wide range of angular scales over a common survey area. SO will measure
fundamental cosmological parameters of our universe, find high redshift clusters via the Sunyaev-Zeldovich effect,
constrain properties of neutrinos, and seek signatures of dark matter through gravitational lensing. The complex
set of technical and science requirements for this experiment has led to innovative instrumentation solutions
which we will discuss. The large aperture telescope will couple to a cryogenic receiver that is 2.4 m in diameter
and over 2 m long, creating a number of interesting technical challenges. Concurrently, we are designing an array
of half-meter-aperture cryogenic cameras which also have compelling design challenges. We will give an overview
of the drivers for and designs of the SO telescopes and the cryogenic cameras that will house the cold optical
components and detector arrays.
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.
The next generation inflationary satellite probe, LiteBIRD, aims to detect B-mode polarization at degree scales and larger. With 2,622 detectors, LiteBIRD will observe the sky using a reflector Low-Frequency Telescope (LFT) ranging from 40 – 235 GHz, and a refractor High-Frequency Telescope (HFT) ranging from 280 – 402 GHz. This allows for the characterization and subtraction of synchrotron foregrounds at low frequencies and thermal dust foregrounds at high frequencies. The U.S. LiteBIRD team proposes to deliver detector arrays, along with readout electronics, using lenslet-coupled sinuous antenna arrays in the LFT, and orthomode-transducer-coupled corrugated horn arrays in the HFT, both utilizing TES bolometer detectors cooled to 100 mK base temperatures. With insight from the Planck space mission, we know that an important consideration to make for the LiteBIRD experiment is the effect of cosmic ray impacts on low-ell systematics and data selection efficiency. The two primary mechanisms for these effects are events in on the 100 mK stage causing low-frequency variation in focal-plane temperature, and the propagation of ballistic phonons into nearby detectors causing “glitches”, or pulses in bolometer timestreams. LiteBIRD estimates a 5% data loss due to cosmic ray, utilizing straightforward mitigation techniques to increase thermal sinking and heat capacity of the detector wafers. We report on initial characterization and mitigation of ballistic phonon propagation in prototype detector wafers using 5.49 MeV alpha particles from an Americium-241 source. We look to present test results from mitigation techniques including removal of bulk silicon around the bolometer island, adding palladium and other conductors around the bolometer island, removal of the niobium ground plane around the bolometer island, and variations of the preceding methods.
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.
We describe the development of an ambient-temperature continuously-rotating half-wave plate (HWP) for study of the Cosmic Microwave Background (CMB) polarization by the POLARBEAR-2 (PB2) experiment. Rapid polarization modulation suppresses 1/f noise due to unpolarized atmospheric turbulence and improves sensitivity to degree-angular-scale CMB fluctuations where the inflationary gravitational wave signal is thought to exist. A HWP modulator rotates the input polarization signal and therefore allows a single polarimeter to measure both linear polarization states, eliminating systematic errors associated with differencing of orthogonal detectors. PB2 projects a 365-mm-diameter focal plane of 7,588 dichroic, 95/150 GHz transition-edge-sensor bolometers
onto a 4-degree field of view that scans the sky at ~ 1 degree per second. We find that a 500-mm-diameter
ambient-temperature sapphire achromatic HWP rotating at 2 Hz is a suitable polarization modulator for PB2.
We present the design considerations for the PB2 HWP, the construction of the HWP optical stack and rotation mechanism, and the performance of the fully-assembled HWP instrument. We conclude with a discussion of HWP polarization modulation for future Simons Array receivers.
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