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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

280 GHz Focal Plane Unit Design and Characterization for the Spider-2 Suborbital Polarimeter

We describe the construction and characterization of the 280 GHz bolometric focal plane units (FPUs) to be deployed on the second flight of the balloon-borne Spider instrument. These FPUs are vital to Spider’s primary science goal of detecting or placing an upper limit on the amplitude of the primordial gravitational wave signature in the cosmic microwave background (CMB) by constraining the B-mode contamination in the CMB from Galactic dust emission. Each 280 GHz focal plane contains a $16 \times 16$ grid of corrugated silicon feedhorns coupled to an array of aluminum–manganese transition-edge sensor (TES) bolometers fabricated on 150 mm diameter substrates. In total, the three 280 GHz FPUs contain 1530 polarization-sensitive bolometers (765 spatial pixels) optimized for the low loading environment in flight and read out by time-division SQUID multiplexing. In this paper, we describe the mechanical, thermal, and magnetic shielding architecture of the focal planes and present cryogenic measurements which characterize yield and the uniformity of several bolometer parameters. The assembled FPUs have high yields, with one array as high as 95% including defects from wiring and readout. We demonstrate high uniformity in device parameters, finding the median saturation power for each TES array to be $\sim $ 3 pW at 300 mK with a less than 6% variation across each array at $1\sigma $ . These focal planes will be deployed alongside the 95 and 150 GHz telescopes in the Spider-2 instrument, slated to fly from McMurdo Station in Antarctica in December 2018.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

The POLARBEAR-2 and Simons Array Focal Plane Fabrication Status

We present on the status of POLARBEAR-2 A (PB2-A) focal plane fabrication. The PB2-A is the first of three telescopes in the Simons Array, which is an array of three cosmic microwave background polarization-sensitive telescopes located at the POLARBEAR site in Northern Chile. As the successor to the PB experiment, each telescope and receiver combination is named as PB2-A, PB2-B, and PB2-C. PB2-A and -B will have nearly identical receivers operating at 90 and 150 GHz while PB2-C will house a receiver operating at 220 and 270 GHz. Each receiver contains a focal plane consisting of seven close-hex packed lenslet-coupled sinuous antenna transition edge sensor bolometer arrays. Each array contains 271 dichroic optical pixels, each of which has four TES bolometers for a total of 7588 detectors per receiver. We have produced a set of two types of candidate arrays for PB2-A. The first we call Version 11 (V11) uses a silicon oxide (SiOx) for the transmission lines and crossover process for orthogonal polarizations. The second we call Version 13 (V13) uses silicon nitride (SiNx) for the transmission lines and cross-under process for orthogonal polarizations. We have produced enough of each type of array to fully populate the focal plane of the PB2-A receiver. The average wirebond yield for V11 and V13 arrays is 93.2% and 95.6%, respectively. The V11 arrays had a superconducting transition temperature (T-c) of 452 +/- 15 mK, a normal resistance (R-n) of 1.25 +/- 0.20 Omega, and saturation powers of 5.2 +/- 1.0 pW and 13 +/- 1.2 pW for the 90 and 150 GHz bands, respectively. The V13 arrays had a superconducting transition temperature (T-c) of 456 +/- 6 mK, a normal resistance (R-n) of 1.1 +/- 0.2 Omega, and saturation powers of 10.8 +/- 1.8 pW and 22.9 +/- 2.6 pW for the 90 and 150 GHz bands, respectively. Production and characterization of arrays for PB2-B are ongoing and are expected to be completed by the summer of 2018. We have fabricated the first three candidate arrays for PB2-C but do not have any characterization results to present at this time.

CMB↗
DOE OSTI2018

Design and Bolometer Characterization of the SPT-3G First-Year Focal Plane

During the austral summer of 2016-2017, the third-generation camera, SPT-3G, was installed on the South Pole Telescope, increasing the detector count in the focal plane by an order of magnitude relative to the previous generation. Designed to map the polarization of the cosmic microwave background, SPT-3G contains ten 6 ''-hexagonal modules of detectors, each with 269 trichroic and dual-polarization pixels, read out using 68x frequency-domain multiplexing. Here we discuss design, assembly, and layout of the modules, as well as early performance characterization of the first-year array, including yield and detector properties.

bolometer↗
DOE OSTI2023

Single-shot, phase-diversity phase retrieval for high-energy beam focal-spot diagnostics

A single-shot, phase-diversity phase-retrieval method is demonstrated for directly characterizing the on-target focal spot at kilojoule energy in the OMEGA 60-beam laser. A 2D holographic grating that introduces diversity focal spots is installed in an existing on-target focal-spot diagnostic to obtain a single-shot diversity focal-spot image. A nonlinear optimization phase-retrieval algorithm with four diversity focal spots is employed to determine modal coefficients for the incident wavefront. The agreement between the measured and calculated focal spots is excellent. Furthermore, this approach can be easily adapted for other high-energy focal-spot diagnostics.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Diagnostic accuracy of F-18 FDG PET/CT for characterization of colorectal focal FDG uptake: a systematic review and meta-analysis

Introduction: We aimed to explore the role of the diagnostic accuracy of F-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) for characterization of incidental colorectal focal FDG uptake through a systematic review and meta-analysis. Methods: The MEDLINE, EMBASE, and Cochrane Library database, from the earliest available date of indexing through April 30, 2018, were searched for studies evaluating the diagnostic performance of F-18 FDG PET/CT for characterization of incidental colorectal focal FDG uptake. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR+ and LR−), and constructed summary receiver operating characteristic curves. Results: Across 8 studies (1451 patients), the pooled sensitivity for F-18 FDG PET/CT was 0.87 (95% CI 0.82–0.90) without heterogeneity (χ{sup 2} = 10.84, p = 0.37) and a pooled specificity of 0.83 (95% CI 0.76–0.89) with heterogeneity (χ{sup 2} = 130.1, p = 0.00). Likelihood ratio (LR) syntheses gave an overall positive likelihood ratio (LR+) of 5.2 (95% CI 3.6–7.4) and negative likelihood ratio (LR−) of 0.16 (95% CI 0.12–0.22). The pooled DOR was 32 (95% CI 20–51). Conclusion: F-18 FDG PET/CT demonstrated good sensitivity and specificity for characterization of incidental colorectal focal FDG uptake. At present, the literature regarding the use of F-18 FDG PET/CT for characterization of incidental colorectal focal FDG uptake remains still limited; thus, further large multicenter studies would be necessary to substantiate the diagnostic accuracy of F-18 FDG PET/CT for characterization of incidental colorectal focal FDG uptake.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Focal mass-like cardiac uptake on oncologic FDG PET/CT: Real lesion or atypical pattern of physiologic uptake?

Background: Cardiac uptake on oncologic FDG PET/CT can be unpredictable. Focal or mass-like cardiac uptake not confined to normal pattern is a real challenge for interpretation due to great variability in physiologic uptake and rarity of either primary or metastatic cardiac neoplasms. Methods and Results: Eight patients with suspicious mass-like cardiac uptake on oncologic FDG PET/CT were retrospectively analyzed with correlation to cardiac workups including contrast CT, echocardiography, and repeat PET/CT. Four patients had real cardiac lesions or metastases. Focal uptake was benign and might represent papillary muscle in the other four. SUV{sub max} ratio between the cardiac focus and surrounding background cardiac uptake was statistically higher in the true-positive group than that in the false-positive group. In addition, the patients with true-positive cardiac uptake had more diffuse distant metastases compared to those with false-positive cardiac uptake. Conclusions: Focal suspicious cardiac uptake on oncology FDG PET/CT warranted further evaluation. SUV{sub max} ratio between the cardiac focus and surrounding background cardiac uptake and status of distant metastases might help to differentiate malignant from benign nature of the focal cardiac uptake on FDG PET/CT. Focal uptake of the right ventricle on oncologic FDG PET/CT is more likely suggestive of a neoplasm.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2023

Approximating large-basis coupled-cluster theory vibrational frequencies using focal-point approximations

The focal-point approximation can be used to estimate a high-accuracy, slow quantum chemistry computation by combining several lower-accuracy, faster computations. We examine the performance of focal-point methods by combining second-order Møller–Plesset perturbation theory (MP2) with coupled-cluster singles, doubles, and perturbative triples [CCSD(T)] for the calculation of harmonic frequencies and that of fundamental frequencies using second-order vibrational perturbation theory (VPT2). In contrast to standard CCSD(T), the focal-point CCSD(T) method approaches the complete basis set (CBS) limit with only triple-ζ basis sets for the coupled-cluster portion of the computation. The predicted harmonic and fundamental frequencies were compared with the experimental values for a set of 20 molecules containing up to six atoms. Here, the focal-point method combining CCSD(T)/aug-cc-pV(T + d)Z with CBS-extrapolated MP2 has mean absolute errors vs experiment of only 7.3 cm −1 for the fundamental frequencies, which are essentially the same as the mean absolute error for CCSD(T) extrapolated to the CBS limit using the aug-cc-pV(Q + d)Z and aug-cc-pV(5 + d)Z basis sets. However, for H 2 O, the focal-point procedure requires only 3% of the computation time as the extrapolated CCSD(T) result, and the cost savings will grow for larger molecules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

High-speed Focal Plane Wave Front Sensing with an Optical Chopper

Focal plane wave front sensing and control is a critical approach to reducing noncommon path errors between a conventional astronomical adaptive optics (AO) wave front sensor (WFS) detector and a science camera. However, in addition to mitigating noncommon path errors, recent focal plane wave front sensing techniques have been developed to operate at speeds fast enough to enable "multi-WFS" AO, where residual atmospheric errors are further corrected by a focal plane WFS. Although a number of such techniques have been recently developed for coronagraphic imaging, here we present one designed for noncoronagraphic imaging. Utilizing conventional AO system components, this concept additionally requires (1) a detector imaging the focal plane of the WFS light source and (2) a pupil plane optical chopper device that is the noncommon path to the first WFS and is synchronized to the focal plane imager readout. These minimal hardware requirements enable the temporal amplitude modulation to resolve the sine ambiguity of even wave-front modes for low, mid, and high wave front spatial frequencies. Similar capabilities have been demonstrated with classical phase diversity by defocusing the detector, but such techniques are incompatible with simultaneous science observations. This optical chopping technique, however, enables science imaging at up to 50% duty cycle. In conclusion, we present both simulations and laboratory validation of this concept on SEAL, the Santa Cruz Extreme AO Laboratory testbed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Microseismic Focal Mechanisms and Implications for Changes in Stress during the 2014 Newberry EGS Stimulation

We adapt the relative polarity method from Shelly et al. (2016) to compute focal mechanisms for microearthquakes associated with the 2014 hydroshearing stimulation at the Newberry volcano geothermal site. We focus the analysis on events relocated by Aguiar and Myers (2018), who report that six event clusters predominantly comprise the 2014 sequence. Data quality allows focal mechanism analysis for four of the six event clusters. We use Hardebeck and Shearer (2002, 2003; hereafter HASH) to compute focal mechanisms based on first–motion polarities and S/P amplitude ratios. We manually determine P– and S–wave polarities for a well–recorded reference event in each cluster, then use waveform cross correlation to determine whether recordings of other events in the cluster are the same or reversed polarity at each network station. Here, most waveform polarities are consistent with the affiliated reference event, indicating similar focal mechanisms within each cluster. The deeper clusters are east–west–striking normal faults, whereas the shallower clusters, close to the top of the open–hole section of the borehole, are strike slip with east–west motion. Regional studies and prestimulation borehole breakouts find the maximum stress direction is vertical and maximum horizontal stress is approximately north–south. Fault geometry and focal mechanisms of microseismicity during the stimulation suggest that increased pressure from fluid injection predominantly caused changes in horizontal stress, consistent with predictions from numerical studies of stress change caused by fluid injection. At shallow depths, where previous studies suggest the difference between vertical and horizontal stress is lowest, injection appears to have rotated the direction of maximum stress from vertical to horizontal, resulting in strike–slip motion. At greater depth, vertical stress continued to be the dominant direction during the stimulation, but fault orientation indicates either reactivation of pre–existing fractures or rotation of the direction of maximum horizontal stress from approximately north–south to east–west.

15 GEOTHERMAL ENERGY↗
DOE OSTI2024

Inferring the Focal Depths of Small Earthquakes in Southern California Using Physics-Based Waveform Features

Determining the depths of small crustal earthquakes is challenging in many regions of the world, because most seismic networks are too sparse to resolve trade-offs between depth and origin time with conventional arrival-time methods. Precise and accurate depth estimation is important, because it can help seismologists discriminate between earthquakes and explosions, which is relevant to monitoring nuclear test ban treaties and producing earthquake catalogs that are uncontaminated by mining blasts. Here, we examine the depth sensitivity of several physics-based waveform features for ~8000 earthquakes in southern California that have well-resolved depths from arrival-time inversion. We focus on small earthquakes (2 < M L < 4) recorded at local distances (<150 km), for which depth estimation is especially challenging. We find that differential magnitudes (M w /M L –M c ) are positively correlated with focal depth, implying that coda wave excitation decreases with focal depth. We analyze a simple proxy for relative frequency content, Φ≡log 10 (M 0 )+3log 10 (f c ), and find that source spectra are preferentially enriched in high frequencies, or “blue-shifted,” as focal depth increases. Here, we also find that two spectral amplitude ratios Rg 0.5–2 Hz/Sg 0.5–8 Hz and Pg/Sg at 3–8 Hz decrease as focal depth increases. Using multilinear regression with these features as predictor variables, we develop models that can explain 11%–59% of the variance in depths within 10 subregions and 25% of the depth variance across southern California as a whole. We suggest that incorporating these features into a machine learning workflow could help resolve focal depths in regions that are poorly instrumented and lack large databases of well-located events. Some of the waveform features we evaluate in this study have previously been used as source discriminants, and our results imply that their effectiveness in discrimination is partially because explosions generally occur at shallower depths than earthquakes.

58 GEOSCIENCES↗
DOE OSTI2019

Temporal changes in MRI appearance of the prostate after focal ablation

Purpose: The purpose of our study was to retrospectively evaluate and categorize temporal changes in MRI appearances of the prostate in patients who underwent focal therapy with MRI follow-up. Methods: The Institutional Review Board approved this retrospective study and waived the requirement for informed consent. Thirty-seven patients (median age 61; 48–70 years) with low-to-intermediate-risk, clinically organ-confined prostate cancer underwent focal ablation therapy from 2009 to 2014. Two radiologists reviewed post-treatment MRIs (n = 76) and categorized imaging features blinded to the time interval between the focal therapy and the follow-up MRI. Inter-reader agreement was assessed (kappa) and generalized linear regression was used to examine associations between an imaging feature being present/absent and days between ablation and MRI. Results: Inter-reader agreement on MRI features ranged from fair to substantial. Edema was found present at earlier times after ablation (median 16–25 days compared to MRIs without edema, median 252–514 days), as was rim enhancement of the ablation zone (18–22.5 days vs. 409–593 days), a hypointense rim around the ablation zone on T2-weighted images (53-57.5 days vs. 279–409 days) and the presence of an appreciable ablation cavity (48.5–60 days vs. 613–798 days, all p < 0.05). Enhancement of the ablation zone/scar (553–731 days vs. 61.5–162 days) and the formation of a T2-hypointense scar were found to be present on later MRI scans (514–553 days vs. 29–32 days, one reader). Conclusions: The MRI appearance of the prostate after focal ablation changes substantially over time. Identification of temporal patterns in the appearance of imaging features should help reduce image interpretation variability and errors when assessing post-therapeutic scans.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Characterization and performance of the second-year SPT-3G focal plane

The third-generation instrument for the 10-meter South Pole Telescope, SPT-3G, was first installed in January 2017. In addition to completely new cryostats, secondary telescope optics, and readout electronics, the number of detectors in the focal plane has increased by an order of magnitude from previous instruments to ~16,000. The SPT-3G focal plane consists of ten detector modules, each with an array of 269 trichroic, polarization-sensitive pixels on a six-inch silicon wafer. Within each pixel is a broadband, dual-polarization sinuous antenna; the signal from each orthogonal linear polarization is divided into three frequency bands centered at 95, 150, and 220 GHz by in-line lumped element filters and transmitted via superconducting microstrip to Ti/Au transition-edge sensor (TES) bolometers. Properties of the TES film, microstrip filters, and bolometer island must be tightly controlled to achieve optimal performance. For the second year of SPT-3G operation, we have replaced all ten wafers in the focal plane with new detector arrays tuned to increase mapping speed and improve overall performance. Here we discuss the TES superconducting transition temperature and normal resistance, detector saturation power, bandpasses, optical efficiency, and full array yield for the 2018 focal plane.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

A positive feedback loop involving the Spa2 SHD domain contributes to focal polarization

Focal polarization is necessary for finely arranged cell-cell interactions. The yeast mating projection, with its punctate polarisome, is a good model system for this process. We explored the critical role of the polarisome scaffold protein Spa2 during yeast mating with a hypothesis motivated by mathematical modeling and tested by in vivo experiments. Our simulations predicted that two positive feedback loops generate focal polarization, including a novel feedback pathway involving the N-terminal domain of Spa2. We characterized the latter using loss-of-function and gain-of-function mutants. The N-terminal region contains a Spa2 Homology Domain (SHD) which is conserved from yeast to humans, and when mutated largely reproduced the spa2Δ phenotype. Our work together with published data show that the SHD domain recruits Msb3/4 that stimulates Sec4-mediated transport of Bud6 to the polarisome. There, Bud6 activates Bni1-catalyzed actin cable formation, recruiting more Spa2 and completing the positive feedback loop. We demonstrate that disrupting this loop at any point results in morphological defects. Gain-of-function perturbations partially restored focal polarization in a spa2 loss-of-function mutant without restoring localization of upstream components, thus supporting the pathway order. Thus, we have collected data consistent with a novel positive feedback loop that contributes to focal polarization during pheromone-induced polarization in yeast.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

FOCAL Campaign IV: Integrated System Control: Turbine + Hull

Campaign IV of the Floating Offshore-wind Controls Advanced Laboratory Experimental Program (FOCAL) aimed to generate a dataset enabling the validation of a floating offshore wind turbine with turbine and hull controls. The turbine considered in this campaign is the scaled IEA 15MW Reference Wind Turbine similar to the setup considered in FOCAL Campaign I. This turbine is mounted on the VolturnUS platform with integrated hull controls similar to the hull considered in FOCAL Campaign II/III. This system is deployed for a fully-coupled wind and wave testing campaign at the University of Maine's Harold Alfond Wind and Wave (W2) facility. System dynamics and turbine characteristics are measured to determine global performance and assess the effect of the control strategies employed. NREL's reference open-source controller (ROSCO) is used for active blade pitch control and hull structural control is examined through the use of tuned mass dampers (TMD's) tuned to the systems pitch and tower-bending natural frequency. The naming convention of the load cases considered are described in the data details section. Detailed properties on the modeled system are found in the following reference: Lenfest E., Floating Offshore-wind Controls Advanced Laboratory (FOCAL) Experimental Program - Campaign IV: 1:70 Model-scale Testing of the IEA-Wind 15MW Reference Turbine and the VolturnUS-S Platform. UMaine ASCC Report Number 23-57-1183.

17 WIND ENERGY↗
DOE OSTI2018

DESI Focal Plane Assembly: Time-Lapse Video

This 56-second time-lapse video shows three different camera views of assembly work for the Dark Energy Spectroscopic Instrument’s Focal Plane. First, it shows the process of joining separate lengths of fiber-optic cables, known as fusion splicing. More than 5,000 fiber-optic cables, each measuring over 50 meters, will extend from near the top of the Mayall Telescope down to devices known as spectrographs that will be used to measure the properties of light from millions of distant galaxies. The Mayall Telescope is at Kitt Peak National Observatory near Tucson, Arizona. The middle portion of the video shows another view of the focal plane assembly area, and the final camera view shows the installation of robotic positioners into a wedge-shaped “petal.” The focal plan will be composed of 10 of these petals, each carrying 500 robotic positioners. (Credit: Berkeley Lab)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗