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We present the design and measured performance of a new carbon fiber strut design that is used in a cryogenically cooled truss for the Simons Observatory small aperture telescope. The truss consists of two aluminum 6061 rings separated by 24 struts. Each strut consists of a central carbon fiber tube fitted with two aluminum end caps. We tested the performance of the strut and truss by (i) cryogenically cycling and destructively pull-testing strut samples, (ii) non-destructively pull-testing the final truss, and (iii) measuring the thermal conductivity of the carbon fiber tubes. We found that the strut strength is limited by the mounting fasteners and the strut end caps, not the epoxy adhesive or the carbon fiber tube. This result is consistent with our numerical predictions. Our thermal measurements suggest that the conductive heat load through the struts (from 4 to 1 K) will be less than 1 mW. This strut design may be a promising candidate for use in other cryogenic support structures.

The Simons Observatory (SO) is a cosmic microwave background (CMB) experiment from the Atacama Desert in Chile comprising three small-aperture telescopes (SATs) and one large-aperture telescope (LAT). In total, SO will field over 60,000 transition-edge sensor (TES) bolometers in six spectral bands centered between 27 and 280 GHz in order to achieve the sensitivity necessary to measure or constrain numerous cosmological quantities. In this work, we focus on the SATs which are optimized to search for primordial gravitational waves that are detected as parity-odd polarization patterns called a B-modes on degree scales in the CMB. Each SAT employs a single optics tube with TES arrays operating at 100 mK. The high throughput optics system has a 42 cm aperture and a 35-degree field of view coupled to a 36 cm diameter focal plane. The optics consist of three metamaterial anti-re ection coated silicon lenses. Cryogenic ring baffles with engineered blackbody absorbers are installed in the optics tube to minimize the stray light. The entire optics tube is cooled to 1 K. A cryogenic continuously rotating half-wave plate near the sky side of the aperture stop helps to minimize the effect of atmospheric uctuations. The telescope warm baffling consists of a forebaffle, an elevation stage mounted co-moving shield, and a fixed ground shield that together control the far side-lobes and mitigates ground-synchronous systematics. We present the status of the SAT development., Comment: 8 pages, 6 figures

Advances in cosmic microwave background (CMB) science depend on increasing the number of sensitive detectors observing the sky. New instruments deploy large arrays of superconducting transition-edge sensor (TES) bolometers tiled densely into ever larger focal planes. High multiplexing factors reduce the thermal loading on the cryogenic receivers and simplify their design. We present the design of focal-plane modules with an order of magnitude higher multiplexing factor than has previously been achieved with TES bolometers. We focus on the novel cold readout component, which employs microwave SQUID multiplexing ($��$mux). Simons Observatory will use 49 modules containing 60,000 bolometers to make exquisitely sensitive measurements of the CMB. We validate the focal-plane module design, presenting measurements of the readout component with and without a prototype detector array of 1728 polarization-sensitive bolometers coupled to feedhorns. The readout component achieves a $95\%$ yield and a 910 multiplexing factor. The median white noise of each readout channel is 65 $\mathrm{pA/\sqrt{Hz}}$. This impacts the projected SO mapping speed by $< 8\%$, which is less than is assumed in the sensitivity projections. The results validate the full functionality of the module. We discuss the measured performance in the context of SO science requirements, which are exceeded., Accepted to The Astrophysical Journal

The Simons Observatory (SO) is an upcoming cosmic microwave background (CMB) experiment located on Cerro Toco, Chile, that will map the microwave sky in temperature and polarization in six frequency bands spanning 27 to 285 GHz. SO will consist of one 6-m large aperture telescope fielding $$\sim$$ 30,000 detectors and an array of three 0.42-m small aperture telescopes (SATs) fielding an additional 30,000 detectors. This synergy will allow for the extremely sensitive characterization of the CMB over angular scales ranging from an arcmin to tens of degrees, enabling a wide range of scientific output. Here we focus on the SATs targeting degree angular scales with successive dichroic instruments observing at mid-frequency (MF: 93/145 GHz), ultra-high-frequency (UHF: 225/285 GHz), and low-frequency (LF: 27/39 GHz). The three SATs will be able to map $$\sim$$ 10% of the sky to a noise level of $$\sim$$ $$2\,\upmu {\hbox {K}}$$ -arcmin when combining 93 and 145 GHz. The multiple frequency bands will allow the CMB to be separated from galactic foregrounds (primarily synchrotron and dust), with the primary science goal of characterizing the primordial tensor-to-scalar ratio, r, at a target level of $$\sigma (r) \approx 0.003$$ .

We report a measurement of the E-mode polarization power spectrum of the cosmic microwave background (CMB) using 150 GHz data taken from July 2014 to December 2016 with the POLARBEAR experiment. We reach an effective polarization map noise level of $32\,\mu\mathrm{K}$-$\mathrm{arcmin}$ across an observation area of 670 square degrees. We measure the EE power spectrum over the angular multipole range $500 \leq \ell, Comment: 15 pages, 5 figures, submitted to ApJ

We present the design and characterization of a ground-based absolute polarization angle calibrator accurate to better than 0.1° for use with polarization sensitive cosmic microwave background (CMB) experiments. The calibrator's accuracy requirement is driven by the need to reduce upper limits on cosmic polarization rotation, which is expected to be zero in a large class of cosmological models. Cosmic polarization effects such as cosmic birefringence and primordial magnetic fields can generate spurious B-modes that result in non-zero CMB TB and EB correlations that are degenerate with a misalignment of detector orientation. Common polarized astrophysical sources used for absolute polarization angle calibration have not been characterized to better than 0.5°. Higher accuracy can be achieved through self-calibration methods, however these are subject to astrophysical foreground contamination and inherently assume the absence of effects like cosmic polarization rotation. The deficiencies in these two calibration methods highlight the need for a well characterized polarized source. The calibrator we present utilizes a 76 GHz Gunn oscillator coupled to a frequency doubler, pyramidal horn antenna, and co-rotating wire-grid polarizer. A blackened optics tube was built around the source in order to mitigate stray reflections, attached to a motor-driven rotation stage, then mounted in a blackened aluminum enclosure for further reflection mitigation and robust weatherproofing. We use an accurate bubble level in combination with four precision-grade aluminum planes located within the enclosure to calibrate the source's linear polarization plane with respect to the local gravity vector to better than the 0.1° goal. In 2017 the calibrator was deployed for an engineering test run on the POLARBEAR CMB experiment located in Chile's Atacama Desert and is being upgraded for calibration of the POLARBEAR-2b receiver in 2018. In the following work we present a detailed overview of the calibrator design, systematic control, characterization, deployment, and plans for future CMB experiment absolute polarization calibration.

Vacuum birefringence from Lorentz and CPT violation in the Standard-Model Extension can be constrained using ground-based optical polarimetry of extragalactic sources. We describe results from a pilot program with an automated system that can perform simultaneous optical polarimetry in multiple passbands on different telescopes with an effective 0.45 m aperture. Despite the limited collecting area, our polarization measurements of AGN using a wider effective optical passband than previous studies yielded individual line-of-sight constraints for Standard-Model Extension mass dimension $d = 5$ operators within a factor of about one to ten of comparable broadband polarimetric bounds obtained using data from a 3.6 m telescope with roughly 64 times the collecting area. Constraining more general anisotropic Standard-Model Extension coefficients at higher $d$ would require more AGN along different lines of sight. This motivates a future dedicated ground-based, multi-band, optical polarimetry AGN survey with $\gtrsim 1$ m-class telescopes, to obtain state-of-the-art anisotropic Standard-Model Extension $d = 4, 5, 6$ constraints, while also using complementary archival polarimetry. This could happen more quickly and cost-effectively than via spectropolarimetry and long before more competitive constraints from space- or balloon-based x-ray/$\gamma$-ray polarization measurements., Comment: Presented at the Eighth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, May 12-16, 2019; typo in one author name changed from v1

Various quantum gravity approaches that extend beyond the Standard Model predict Lorentz invariance and charge-parity-time violation at energies approaching the Planck scale. These models frequently predict a wavelength-dependent speed of light, which would result in time delays between promptly emitted photons at different energies, as well as a wavelength-dependent rotation of the plane of linear polarization for photons resulting from vacuum birefringence. Here, we describe a pilot program with an automated system of small telescopes that can simultaneously conduct high cadence optical photometry and polarimetry of active galactic nuclei (AGN) in multiple passbands. We use these observations as a proof of principle to demonstrate how such data can be used to test various Lorentz violation models, including special cases of the Standard Model extension (SME). In our initial campaign with this system, the Array Photo Polarimeter, we observed two AGN sources, including BL Lacertae at redshift $z=0.069$, and S5 $\mathrm{B}0716+714$ at $z=0.31$. We demonstrate that optical polarimetry with a broadband Luminance filter combined with simultaneous ${I}_{c}$-band observations yields SME parameter constraints that are up to $\ensuremath{\sim}10$ and $\ensuremath{\sim}30$ times more sensitive than with a standard ${I}_{c}$-band filter, for SME models with mass dimension $d=5$ and $d=6$, respectively. Using only a small system of telescopes with an effective 0.45-m aperture, we further demonstrate $d=5$ constraints for individual lines of sight that are within a factor of $\ensuremath{\sim}1--10$ in sensitivity to comparable constraints from optical polarimetry with a 3.6-m telescope. Such an approach could significantly improve existing SME constraints via a polarimetric all-sky survey of AGN with multiple 1-meter class telescopes.

We quantify the calibration requirements for systematic uncertainties for next-generation ground-based observatories targeting the large-angle $B$-mode polarization of the Cosmic Microwave Background, with a focus on the Simons Observatory (SO). We explore uncertainties on gain calibration, bandpass center frequencies, and polarization angles, including the frequency variation of the latter across the bandpass. We find that gain calibration and bandpass center frequencies must be known to percent levels or less to avoid biases on the tensor-to-scalar ratio $r$ on the order of $\Delta r\sim10^{-3}$, in line with previous findings. Polarization angles must be calibrated to the level of a few tenths of a degree, while their frequency variation between the edges of the band must be known to ${\cal O}(10)$ degrees. Given the tightness of these calibration requirements, we explore the level to which residual uncertainties on these systematics would affect the final constraints on $r$ if included in the data model and marginalized over. We find that the additional parameter freedom does not degrade the final constraints on $r$ significantly, broadening the error bar by ${\cal O}(10\%)$ at most. We validate these results by reanalyzing the latest publicly available data from the BICEP2/Keck collaboration within an extended parameter space covering both cosmological, foreground and systematic parameters. Finally, our results are discussed in light of the instrument design and calibration studies carried out within SO., Comment: 41 pages, 18 figures

The Simons Observatory (SO) is a Cosmic Microwave Background (CMB) experiment to observe the microwave sky in six frequency bands from 30GHz to 290GHz. The Observatory -- at $\sim$5200m altitude -- comprises three Small Aperture Telescopes (SATs) and one Large Aperture Telescope (LAT) at the Atacama Desert, Chile. This research note describes the design and current status of the LAT along with its future timeline., 4 pages, 1 figure

The Simons Observatory (SO) is a set of cosmic microwave background instruments that will be deployed in the Atacama Desert in Chile. The key science goals include setting new constraints on cosmic inflation, measuring large scale structure with gravitational lensing, and constraining neutrino masses. Meeting these science goals with SO requires high sensitivity and improved calibration techniques. In this paper, we highlight a few of the most important instrument calibrations, including spectral response, gain stability, and polarization angle calibrations. We present their requirements for SO and experimental techniques that can be employed to reach those requirements., 13 pages, 4 figures, SPIE Astronomical Telescopes and Instrumentation 2018

We present the design and characterization of a ground-based absolute polarization angle calibrator accurate to better than 0.1 degrees for use with polarization sensitive cosmic microwave background (CMB) experiments. The calibrator's accuracy requirement is driven by the need to reduce upper limits on cosmic polarization rotation, which is expected to be zero in a large class of cosmological models. Cosmic polarization effects such as cosmic birefringence and primordial magnetic fields can generate spurious B-modes that result in non-zero CMB TB and EB correlations that are degenerate with a misalignment of detector orientation. Common polarized astrophysical sources used for absolute polarization angle calibration have not been characterized to better than 0.5 degrees. Higher accuracy can be achieved through self-calibration methods, however these are subject to astrophysical foreground contamination and inherently assume the absence of effects like cosmic polarization rotation. The deficiencies in these two calibration methods highlight the need for a well characterized polarized source. The calibrator we present utilizes a 76 GHz Gunn oscillator coupled to a frequency doubler, pyramidal horn antenna, and co-rotating wire-grid polarizer. We use an accurate bubble level in combination with four precision-grade aluminum planes located within the enclosure to calibrate the source's linear polarization plane with respect to the local gravity vector to better than the 0.1 degree goal. In 2017 the calibrator was deployed for an engineering test run on the POLARBEAR CMB experiment located in Chile's Atacama Desert and is being upgraded for calibration of the POLARBEAR-2b receiver in 2018. In the following work we present a detailed overview of the calibrator design, systematic control, characterization, deployment, and plans for future CMB experiment absolute polarization calibration., Comment: 15 pages, 7 figures, 2 tables, SPIE conference Austin 2018

著者人数: 93名（所属. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS): 羽澄, 昌史), Accepted: 2018-08-27, 資料番号: SA1180208000

In this sixth decade of the nuclear age, the US and many other nations face daunting technical challenges to the disposal of nuclear waste. There are many contributing factors, not the least of which are the sheer volumes of waste and the great number of chemical and physical forms in which it exists at defense and civilian sites both here and abroad. (See figure 1, for example, and see also John Ahearne's article on page 24.)

Secondary age standards are valuable in intra- and interlaboratory calibration. At present very few such standards are available for fission track dating that is older than Tertiary. Several altered volcanic ash beds occur in the Middle Jurassic Carmel Formation in southwestern Utah. The formation was deposited in a shallow marine/sabhka environment. Near Gunlock, Utah, eight ash beds have been identified. Sanidines from one of the ash beds (GUN-F) give a single-crystal laser-probe 40 Ar/ 39 Ar age of 166.3±0.8 Ma (2 σ ). Apatite and zircon fission track ages range from 152–185 Ma with typically 15–20 Ma errors (2σ). Track densities in zircons are high and most grains are not countable. Apatites are fairly common in most of the ash beds and have reasonable track densities ranging between 1.2–1.5 × 10 6 tracks/cm 2 . Track length distributions in apatites are unimodal, have standard deviations μ m, and mean track lengths of about 14–14.5 μm. High Cl apatites (F:Cl:OH ratio of 39:33:28) are particularly abundant and large in ash GUN-F, and are fairly easy to concentrate, but the concentrates contain some siderite, most of which can be removed by sieving. GUN-F shows evidence of some reworking and detriaal contamination based on older single grain 40 Ar/ 39 Ar analyses and some rounding of grains, but the apatite population appears to be largely uncontaminated. At present BJK has approximately 12 of apatite separate from GUN-F.

Two apatites, one zircon and one glass were made available to the fission track research community for analysis prior to the 1988 Fission Track Workshop held in Besancon, France, from 3 to 9 September. Thirty aliquots of apatite and zircon and 10 aliquots of glass were distributed. To date, analyses by 26 different scientists have been reported. Significant scatter is found in the sample data sets. Consequently, as recommended in 1985, it remains important for individual analysts to calibrate their experimental techniques and counting procedures against age standards and to publish the results of these calibrations whenever reporting fission track analytical data.

The program LENMODEL is a forward model for annealing of fission tracks in apatite. It provides estimates of the track-length distribution, fission-track age, and areal track density for any user-supplied thermal history. The program approximates the thermal history, in which temperature is represented as a continuous function of time, by a series of isothermal steps of various durations. Equations describing the production of tracks as a function of time and annealing of tracks as a function of time and temperature are solved for each step. The step calculations are summed to obtain estimates for the entire thermal history. Computational efficiency is maximized by performing the step calculations backwards in model time. The program incorporates an intuitive and easy-to-use graphical interface. Thermal history is input to the program using a mouse. Model options are specified by selecting context-sensitive commands from a bar menu. The program allows for considerable selection of equations and parameters used in the calculations. The program was written for PC-compatible computers running DOS TM 3.0 and above (and Windows TM 3.0 or above) with VGA or SVGA graphics and a Microsoft TM -compatible mouse. Single copies of a runtime version of the program are available from the author by written request as explained in the last section of this paper.

Apatite fission-track analysis of Early Miocene to Quaternary distal Bengal Fan sediments from ODP Leg 116 provides a unique perspective on denudation processes associated with the Tertiary Himalayan orogeny. These sediments yield pooled apatite fission-track ages that are 0- to 10-m.y. older than depositional ages. Mean track lengths range from 13.2 to 14.8 [mu]m. These young ages and long track lengths indicate that rocks in the upper crust of Bengal Fan source areas cooled rapidly ([ge]15[degrees]C/m.y.), implying denudation rates of several hundreds of meters per million years. These observations support the hypothesis that nearly continuous unroofing of a large source area, similar to the dimensions of the present Himalayan and southern Tibetan Plateau deformation front, and an efficient transport system, similar to the present Himalaya-Ganges-Brahmaputra system, supplied sediment to the Bengal Fan since the Early Miocene.

Kinetic models for apatite fission-track annealing and vitrinite maturation were used to examine hypotheses for the burial and thermal history of the Michigan basin. Fission-track ages between 160 and 200 Ma were measured for Carboniferous outcrop samples (>300 Ma) near Saginaw Bay. Published vitrinite reflectance and conodont alteration data from the Michigan basin are higher than predicted from current depths and temperatures for the samples. Both sets of data are broadly consistent with elevated temperatures due to additional burial at present geothermal gradients. The depth of additional burial varies systematically from less than 1 km in the basin center to more than 2 km near the adjacent arches. The additional burial could explain the occurrence of diagenetic banding in portions of the St. Peter Sandstone that are currently at depths shallower than the critical window for this phenomenon.

Apatite fission track ages and confined-length distributions were collected from 38 basement outcrop and 5 basement drillcore samples in order to reconstruct the Phanerozoic thermal history of the Michigan Basin and southern Canadian Shield. The apatite data indicate two periods of thermal activity in the region: Triassic heating/cooling that affected the basin and adjacent shield and Cretaceous or post-Cretaceous heating/cooling that primarily affected the basin. The magnitude, timing, and cause of Cretaceous thermal activity cannot be identified with the present data. Model calculations suggest that some of the shield samples and probably all of the basin samples were heated to temperatures of at least 90C just prior to relatively rapid cooling in the Triassic. Available stratigraphic and geochemical constraints suggest that these elevated temperatures were the result of burial by an additional 2-5 km of late Paleozoic (probably Pennsylvanian and Permian) sediments. It is likely that the basin was buried during the Alleghenian Orogeny as observed for the adjacent Appalachian Basin.

The semi-analytical solution of an equation describing the production and shortening of fission tracks in apatite suggests that certain thermal histories have unique length-distribution “signatures”. Isothermal-heating histories should be characterized by flattened, length-shortened distributions; step-heating histories should be characterized by bimodal track length distributions; and linear-cooling histories should be characterized by negatively skewed, length-shortened distributions. The model formulated here to investigate track length distributions can be used to constrain the thermal histories of natural samples for which unbiased track length data are available-provided that the geologic history of the system of interest can be used to partially constrain one of the unknowns in the model equations, time or temperature.

Apatite fission-track ages of basement from the Superior craton in eastern Manitoba, western Ontario and eastern North Dakota record two periods of Late Proterozoic epeirogeny and erosion. The latter period, which involves basement beneath and adjacent to the eastern flank of the Williston Basin, precedes basin subsidence and roughly coincides in time with breakup of the Proterozoic supercontinent. We speculate that these events are genetically related.

Apparent apatite fission-track ages from drill core penetrating basement on the flank of the Transcontinental Arch in northwestern Iowa range from 934 ± 86 to 641 ± 90 Ma. These ages, the oldest reported in North America, record at least two thermal events. The 934 Ma age, which is synchronous with K-Ar ages in the Grenville Province and many K-Ar whole-rock and Rb-Sr isochron ages from the Lake Superior region, may document basement cooling caused by regional uplift and erosion of the crust. The remaining fission-track ages are products of a more recent thermal event, relative to the age of the samples, which raised temperatures into the zone of partial annealing. Heating may have occurred between the Middle Ordovician and Middle Cretaceous by burial of the basement with additional sediment. It is estimated that burial raised temperatures in the part of the basement sampled by the core to between 50 and 75°C. These temperature estimates imply paleogeothermal gradients of about 20°C/km, approximately two and one-half times present-day values, and burial of the basement by an additional 2–3 km of sediment.

This paper reports a series of irradiation experiments performed to illustrate the effects of neutron energy on fission-track age determinations. These experiments reveal that errors of several percent can be introduced into an age determination when fluence monitors which contain U in non-natural isotopic ratios and (or) contain Th are used in the irradiations, or when age standards and samples of unknown age are irradiated at different conditions (i.e. with neutrons having different energy spectra). To avoid errors in age determinations it is recommended that all irradiations be performed at identical conditions, preferably with a highly thermalized neutron flux, or that fluence monitors which do not contain Th and which contain U in natural abundances be used in the age-determination process.

The preservation of depositional events in sedimentary sequences is investigated using a Monte-Carlo model in which sedimentation rates are constant and the magnitudes of the events follow a lognormal frequency distribution. The model indicates that sedimentation processes act as a stationary, low-pass filter that preserves an amplitude-distorted record of the depositional events imposed on the modern environment. This low-pass filter gives rise to two concepts of completeness of sedimentary sequences: (1) Preservation of time lines in sedimentary sequences, or temporal completeness; and (2) Preservation of depositional events in sedimentary sequences, or spatial completeness. The model suggests that as sedimentation rate decreases, (1) the number of time lines preserved decreases exponentially and the completeness of the record of depositional events decreases linearly; and (2) low-magnitude events are progressively eliminated from the record. The latter characteristic of the model, which arises because of the assumption of stationarity of the time series, may be in conflict with observations from real sedimentary sequences. A nonstationary component can be added to the model by taking into account other depositional variations that have been observed in modern environments.

Three time series of varves from the Eocene Green River Formation in Colorado, consisting of 1469, 1869, and 4158 annual thickness measurements, were analyzed by a variety of statistical techniques to characterize climate variations. The analyses reveal that the time series are lognormal after adjustment for a trend. Moreover, the analyses suggest that the time series are generally nonstationary and are noiselike in structure. Fourier spectra and maximum entropy spectra of the time series are “reddish,” indicating the importance of nonoscillatory changes in varve thickness at time scales ranging from tens to hundreds of years. There are no statistically significant peaks in Fourier spectra for the entire time series; however, one segment of one of the three time series displays statistically significant peaks corresponding to periods of 10.8 and 5.4 years. Overall, the time series are suggestive of a nonperiodic and weakly predictive climate during the time periods corresponding to deposition of the varves.

We have tested the hypothesis that the lithosphere beneath the Williston Basin was heated, uplifted, and eroded prior to basin subsidence; this was accomplished by fission-track dating of apatite from samples of basement rock beneath and adjacent to the basin. Apatite fission-track ages of basement rocks beneath the basin range from about 4 Ma near the center to 554 Ma near the eastern edge. Combined with stratigraphic evidence, the ages suggest that at least 3 km of basement were eroded prior to subsidence of the Williston Basin. Rates of apparent uplift and erosion were on the order of 0.10 to 0.15 km/m.y. Apatite fission-track ages of basement outcrop samples on the eastern flank of the basin range from about 572 Ma to 441 Ma. These ages suggest that erosion of the flank occurred from the Early Cambrian to the Late Ordovician. We conclude that timing of uplift of the basement prior to subsidence of the Williston Basin is consistent with the thermal-origin hypothesis of basin formation.