Quantitative Analysis of Venus Radar Backscatter Data in ArcGIS

NASA Technical Reports Server (NTRS)

Long, S. M.; Grosfils, E. B.

2005-01-01

Ongoing mapping of the Ganiki Planitia (V14) quadrangle of Venus and definition of material units has involved an integrated but qualitative analysis of Magellan radar backscatter images and topography using standard geomorphological mapping techniques. However, such analyses do not take full advantage of the quantitative information contained within the images. Analysis of the backscatter coefficient allows a much more rigorous statistical comparison between mapped units, permitting first order selfsimilarity tests of geographically separated materials assigned identical geomorphological labels. Such analyses cannot be performed directly on pixel (DN) values from Magellan backscatter images, because the pixels are scaled to the Muhleman law for radar echoes on Venus and are not corrected for latitudinal variations in incidence angle. Therefore, DN values must be converted based on pixel latitude back to their backscatter coefficient values before accurate statistical analysis can occur. Here we present a method for performing the conversions and analysis of Magellan backscatter data using commonly available ArcGIS software and illustrate the advantages of the process for geological mapping.

HIGH ENERGY, HIGH BRIGHTNESS X-RAYS PRODUCED BY COMPTON BACKSCATTERING AT THE LIVERMORE PLEIADES FACILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tremaine, A M; Anderson, S G; Betts, S

2005-05-19

PLEIADES (Picosecond Laser Electron Interaction for the Dynamic Evaluation of Structures) produces tunable 30-140 keV x-rays with 0.3-5 ps pulse lengths and up to 10{sup 7} photons/pulse by colliding a high brightness electron beam with a high power laser. The electron beam is created by an rf photo-injector system, accelerated by a 120 MeV linac, and focused to 20 {micro}m with novel permanent magnet quadrupoles. To produce Compton back scattered x-rays, the electron bunch is overlapped with a Ti:Sapphire laser that delivers 500 mJ, 100 fs, pulses to the interaction point. K-edge radiography at 115 keV on Uranium has verifiedmore » the angle correlated energy spectrum inherent in Compton scattering and high-energy tunability of the Livermore source. Current upgrades to the facility will allow laser pumping of targets synchronized to the x-ray source enabling dynamic diffraction and time-resolved studies of high Z materials. Near future plans include extending the radiation energies to >400 keV, allowing for nuclear fluorescence studies of materials.« less

Gamma-ray momentum reconstruction from Compton electron trajectories by filtered back-projection

DOE PAGES

Haefner, A.; Gunter, D.; Plimley, B.; ...

2014-11-03

Gamma-ray imaging utilizing Compton scattering has traditionally relied on measuring coincident gamma-ray interactions to map directional information of the source distribution. This coincidence requirement makes it an inherently inefficient process. We present an approach to gamma-ray reconstruction from Compton scattering that requires only a single electron tracking detector, thus removing the coincidence requirement. From the Compton scattered electron momentum distribution, our algorithm analytically computes the incident photon's correlated direction and energy distributions. Because this method maps the source energy and location, it is useful in applications, where prior information about the source distribution is unknown. We demonstrate this method withmore » electron tracks measured in a scientific Si charge coupled device. While this method was demonstrated with electron tracks in a Si-based detector, it is applicable to any detector that can measure electron direction and energy, or equivalently the electron momentum. For example, it can increase the sensitivity to obtain energy and direction in gas-based systems that suffer from limited efficiency.« less

Development of a High-Average-Power Compton Gamma Source for Lepton Colliders

NASA Astrophysics Data System (ADS)

Pogorelsky, Igor; Polyanskiy, Mikhail N.; Yakimenko, Vitaliy; Platonenko, Viktor T.

2009-01-01

Gamma- (γ-) ray beams of high average power and peak brightness are of demand for a number of applications in high-energy physics, material processing, medicine, etc. One of such examples is gamma conversion into polarized positrons and muons that is under consideration for projected lepton colliders. A γ-source based on the Compton backscattering from the relativistic electron beam is a promising candidate for this application. Our approach to the high-repetition γ-source assumes placing the Compton interaction point inside a CO2 laser cavity. A laser pulse interacts with periodical electron bunches on each round-trip inside the laser cavity producing the corresponding train of γ-pulses. The round-trip optical losses can be compensated by amplification in the active laser medium. The major challenge for this approach is in maintaining stable amplification rate for a picosecond CO2-laser pulse during multiple resonator round-trips without significant deterioration of its temporal and transverse profiles. Addressing this task, we elaborated on a computer code that allows identifying the directions and priorities in the development of such a multi-pass picosecond CO2 laser. Proof-of-principle experiments help to verify the model and show the viability of the concept. In these tests we demonstrated extended trains of picosecond CO2 laser pulses circulating inside the cavity that incorporates the Compton interaction point.

Bathymetry and acoustic backscatter-outer mainland shelf, eastern Santa Barbara Channel, California

USGS Publications Warehouse

Dartnell, Peter; Finlayson, David P.; Ritchie, Andrew C.; Cochrane, Guy R.; Erdey, Mercedes D.

2012-01-01

In 2010 and 2011, scientists from the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), acquired bathymetry and acoustic-backscatter data from the outer shelf region of the eastern Santa Barbara Channel, California. These surveys were conducted in cooperation with the Bureau of Ocean Energy Management (BOEM). BOEM is interested in maps of hard-bottom substrates, particularly natural outcrops that support reef communities in areas near oil and gas extraction activity. The surveys were conducted using the USGS R/V Parke Snavely, outfitted with an interferometric sidescan sonar for swath mapping and real-time kinematic navigation equipment. This report provides the bathymetry and backscatter data acquired during these surveys in several formats, a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

Recommendations for improved and coherent acquisition and processing of backscatter data from seafloor-mapping sonars

NASA Astrophysics Data System (ADS)

Lamarche, Geoffroy; Lurton, Xavier

2018-06-01

Multibeam echosounders are becoming widespread for the purposes of seafloor bathymetry mapping, but the acquisition and the use of seafloor backscatter measurements, acquired simultaneously with the bathymetric data, are still insufficiently understood, controlled and standardized. This presents an obstacle to well-accepted, standardized analysis and application by end users. The Marine Geological and Biological Habitat Mapping group (Geohab.org) has long recognized the need for better coherence and common agreement on acquisition, processing and interpretation of seafloor backscatter data, and established the Backscatter Working Group (BSWG) in May 2013. This paper presents an overview of this initiative, the mandate, structure and program of the working group, and a synopsis of the BSWG Guidelines and Recommendations to date. The paper includes (1) an overview of the current status in sensors and techniques available in seafloor backscatter data from multibeam sonars; (2) the presentation of the BSWG structure and results; (3) recommendations to operators, end-users, sonar manufacturers, and software developers using sonar backscatter for seafloor-mapping applications, for best practice methods and approaches for data acquisition and processing; and (4) a discussion on the development needs for future systems and data processing. We propose for the first time a nomenclature of backscatter processing levels that affords a means to accurately and efficiently describe the data processing status, and to facilitate comparisons of final products from various origins.

Integrating Multibeam Backscatter Angular Response, Mosaic and Bathymetry Data for Benthic Habitat Mapping

PubMed Central

Che Hasan, Rozaimi; Ierodiaconou, Daniel; Laurenson, Laurie; Schimel, Alexandre

2014-01-01

Multibeam echosounders (MBES) are increasingly becoming the tool of choice for marine habitat mapping applications. In turn, the rapid expansion of habitat mapping studies has resulted in a need for automated classification techniques to efficiently map benthic habitats, assess confidence in model outputs, and evaluate the importance of variables driving the patterns observed. The benthic habitat characterisation process often involves the analysis of MBES bathymetry, backscatter mosaic or angular response with observation data providing ground truth. However, studies that make use of the full range of MBES outputs within a single classification process are limited. We present an approach that integrates backscatter angular response with MBES bathymetry, backscatter mosaic and their derivatives in a classification process using a Random Forests (RF) machine-learning algorithm to predict the distribution of benthic biological habitats. This approach includes a method of deriving statistical features from backscatter angular response curves created from MBES data collated within homogeneous regions of a backscatter mosaic. Using the RF algorithm we assess the relative importance of each variable in order to optimise the classification process and simplify models applied. The results showed that the inclusion of the angular response features in the classification process improved the accuracy of the final habitat maps from 88.5% to 93.6%. The RF algorithm identified bathymetry and the angular response mean as the two most important predictors. However, the highest classification rates were only obtained after incorporating additional features derived from bathymetry and the backscatter mosaic. The angular response features were found to be more important to the classification process compared to the backscatter mosaic features. This analysis indicates that integrating angular response information with bathymetry and the backscatter mosaic, along with their derivatives, constitutes an important improvement for studying the distribution of benthic habitats, which is necessary for effective marine spatial planning and resource management. PMID:24824155

Multisource multibeam backscatter data: developing a strategy for the production of benthic habitat maps using semi-automated seafloor classification methods

NASA Astrophysics Data System (ADS)

Lacharité, Myriam; Brown, Craig J.; Gazzola, Vicki

2018-06-01

The establishment of multibeam echosounders (MBES) as a mainstream tool in ocean mapping has facilitated integrative approaches towards nautical charting, benthic habitat mapping, and seafloor geotechnical surveys. The bathymetric and backscatter information generated by MBES enables marine scientists to present highly accurate bathymetric data with a spatial resolution closely matching that of terrestrial mapping, and can generate customized thematic seafloor maps to meet multiple ocean management needs. However, when a variety of MBES systems are used, the creation of objective habitat maps can be hindered by the lack of backscatter calibration, due for example, to system-specific settings, yielding relative rather than absolute values. Here, we describe an approach using object-based image analysis to combine 4 non-overlapping and uncalibrated (backscatter) MBES coverages to form a seamless habitat map on St. Anns Bank (Atlantic Canada), a marine protected area hosting a diversity of benthic habitats. The benthoscape map was produced by analysing each coverage independently with supervised classification (k-nearest neighbor) of image-objects based on a common suite of 7 benthoscapes (determined with 4214 ground-truthing photographs at 61 stations, and characterized with backscatter, bathymetry, and bathymetric position index). Manual re-classification based on uncertainty in membership values to individual classes—especially at the boundaries between coverages—was used to build the final benthoscape map. Given the costs and scarcity of MBES surveys in offshore marine ecosystems—particularly in large ecosystems in need of adequate conservation strategies, such as in Canadian waters—developing approaches to synthesize multiple datasets to meet management needs is warranted.

Foreign body detection in food materials using compton scattered x-rays

NASA Astrophysics Data System (ADS)

McFarlane, Nigel James Bruce

This thesis investigated the application of X-ray Compton scattering to the problem of foreign body detection in food. The methods used were analytical modelling, simulation and experiment. A criterion was defined for detectability, and a model was developed for predicting the minimum time required for detection. The model was used to predict the smallest detectable cubes of air, glass, plastic and steel. Simulations and experiments were performed on voids and glass in polystyrene phantoms, water, coffee and muesli. Backscatter was used to detect bones in chicken meat. The effects of geometry and multiple scatter on contrast, signal-to-noise, and detection time were simulated. Compton scatter was compared with transmission, and the effect of inhomogeneity was modelled. Spectral shape was investigated as a means of foreign body detection. A signal-to-noise ratio of 7.4 was required for foreign body detection in food. A 0.46 cm cube of glass or a 1.19 cm cube of polystyrene were detectable in a 10 cm cube of water in one second. The minimum time to scan a whole sample varied as the 7th power of the foreign body size, and the 5th power of the sample size. Compton scatter inspection produced higher contrasts than transmission, but required longer measurement times because of the low number of photon counts. Compton scatter inspection of whole samples was very slow compared to production line speeds in the food industry. There was potential for Compton scatter in applications which did not require whole-sample scanning, such as surface inspection. There was also potential in the inspection of inhomogeneous samples. The multiple scatter fraction varied from 25% to 55% for 2 to 10 cm cubes of water, but did not have a large effect on the detection time. The spectral shape gave good contrasts and signal-to-noise ratios in the detection of chicken bones.

A method to correct coordinate distortion in EBSD maps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y.B., E-mail: yubz@dtu.dk; Elbrønd, A.; Lin, F.X.

2014-10-15

Drift during electron backscatter diffraction mapping leads to coordinate distortions in resulting orientation maps, which affects, in some cases significantly, the accuracy of analysis. A method, thin plate spline, is introduced and tested to correct such coordinate distortions in the maps after the electron backscatter diffraction measurements. The accuracy of the correction as well as theoretical and practical aspects of using the thin plate spline method is discussed in detail. By comparing with other correction methods, it is shown that the thin plate spline method is most efficient to correct different local distortions in the electron backscatter diffraction maps. -more » Highlights: • A new method is suggested to correct nonlinear spatial distortion in EBSD maps. • The method corrects EBSD maps more precisely than presently available methods. • Errors less than 1–2 pixels are typically obtained. • Direct quantitative analysis of dynamic data are available after this correction.« less

Bathymetry and acoustic backscatter: Estero Bay, California

USGS Publications Warehouse

Hartwell, Stephen R.; Finlayson, David P.; Dartnell, Peter; Johnson, Samuel Y.

2013-01-01

Between July 30 and August 9, 2012, scientists from the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), acquired bathymetry and acoustic-backscatter data from Estero Bay, San Luis Obispo, California, under PCMSC Field Activity ID S-05-12-SC. The survey was done using the R/V Parke Snavely outfitted with a multibeam sonar for swath mapping and highly accurate position and orientation equipment for georeferencing. This report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

Concept of a small satellite for sub-MeV and MeV all sky survey: the CAST mission

NASA Astrophysics Data System (ADS)

Nakazawa, Kazuhiro; Takahashi, Tadayuki; Ichinohe, Yuto; Takeda, Shin'ichiro; Tajima, Hiroyasu; Kamae, Tuneyoshi; Kokubun, Motohide; Takashima, Takeshi; Tashiro, Makoto; Tamagawa, Toru; Terada, Yukikatsu; Nomachi, Masaharu; Fukazawa, Yasushi; Makishima, Kazuo; Mizuno, Tsunefumi; Mitani, Takefumi; Yoshimitsu, Tetsuo; Watanabe, Shin

2012-09-01

MeV and sub-MeV energy band from ~200 keV to ~2 MeV contains rich information of high-energy phenomena in the universe. The CAST (Compton Telescope for Astro and Solar Terrestrial) mission is planned to be launched at the end of 2010s, and aims at providing all-sky map in this energy-band for the first time. It is made of a semiconductor Compton telescope utilizing Si as a scatterer and CdTe as an absorber. CAST provides allsky sub-MeV polarization map for the first time, as well. The Compton telescope technology is based on the design used in the Soft Gamma-ray Detector (SGD) onboard ASTRO-H, characterized by its tightly stacked semiconductor layers to obtain high Compton reconstruction efficiency. The CAST mission is currently planned as a candidate for the small scientific satellite series in ISAS/JAXA, weighting about 500 kg in total. Scalable detector design enables us to consider other options as well. Scientific outcome of CAST is wide. It will provide new information from high-energy sources, such as AGN and/or its jets, supernova remnants, magnetors, blackhole and neutron-star binaries and others. Polarization map will tell us about activities of jets and reflections in these sources, as well. In addition, CAST will simultaneously observe the Sun, and depending on its attitude, the Earth.

Bathymetry and acoustic backscatter: Elwha River Delta, Washington

USGS Publications Warehouse

Finlayson, David P.; Miller, Ian M.; Warrick, Jonathan A.

2011-01-01

The surveys were conducted using the R/V Parke Snavely outfitted with an interferometric sidescan sonar for swath mapping and real-time kinematic navigation equipment for accurate shallow water operations. This report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

A Laser Cavity for a Future Photon Collider at ILC

NASA Astrophysics Data System (ADS)

Klemz, G.; Moenig, K.

2006-04-01

Within a future photon-collider based on the infrastructure of ILC the energy of near-infrared laser photons will be boosted by Compton backscattering on a high energy electron beam to well above 100 GeV. By reason of luminosity, an extremely powerful lasersystem is required that will exceed today's state-of-the-art capabilities. An auxiliary cavity for resonantly enhancing the optical peak-power can relax demands on the power output of the laser. In this paper a possible design and the static aspects of a passive cavity are discussed.

Bathymetry and Acoustic Backscatter: Northern Santa Barbara Channel, Southern California

USGS Publications Warehouse

Dartnell, Pete; Finlayson, David; Conrad, Jamie; Cochrane, Guy; Johnson, Samuel

2010-01-01

In the summer of 2008, as part of the California Seafloor Mapping Program (CSMP) the U.S. Geological Survey, Coastal and Marine Geology mapped a nearshore region of the northern Santa Barbara Channel in Southern California (fig 1). The CSMP is a cooperative partnership between Federal and State agencies, Universities, and Industry to create a comprehensive coastal/marine geologic and habitat basemap series to support the Marine Life Protection Act (MLPA) inititive. The program is supported by the California Ocean Protection Council and the California Coastal Conservancy. The 2008 mapping collected high resolution bathymetry and acoustic backscatter data using a bathymetric side scan system within State waters from about the 10-m isobath out over 3-nautical miles. This Open-File Report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and FGDC metadata.

Bathymetry, acoustic backscatter, and seafloor character of Farallon Escarpment and Rittenburg Bank, northern California

USGS Publications Warehouse

Dartnell, Peter; Cochrane, Guy R.; Finlayson, David P.

2014-01-01

In 2011, scientists from the U.S. Geological Survey’s Coastal and Marine Geology Program acquired bathymetry and acoustic-backscatter data along the upper slope of the Farallon Escarpment and Rittenburg Bank within the Gulf of the Farallones National Marine Sanctuary offshore of the San Francisco Bay area. The surveys were funded by the National Oceanic and Atmospheric Administration’s Deep Sea Coral Research and Technology Program to identify potential deep sea coral habitat prior to planned sampling efforts. Bathymetry and acoustic-backscatter data can be used to map seafloor geology (rock, sand, mud), and slope of the sea floor, both of which are useful for the prediction of deep sea coral habitat. The data also can be used for the prediction of sediment and contaminant budgets and transport, and for the assessment of earthquake and tsunami hazards. The surveys were conducted aboard National Oceanic and Atmospheric Administration’s National Marine Sanctuary Program’s 67-foot-long research vessel Fulmar outfitted with a U.S. Geological Survey 100-kHz Reson 7111 multibeam-echosounder system. This report provides the bathymetry and backscatter data acquired during these surveys, interpretive seafloor character maps in several formats, a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee metadata.

Multibeam Sonar Backscatter Data Acquisition and Processing: Guidelines and Recommendations from the GEOHAB Backscatter Working Group

NASA Astrophysics Data System (ADS)

Heffron, E.; Lurton, X.; Lamarche, G.; Brown, C.; Lucieer, V.; Rice, G.; Schimel, A.; Weber, T.

2015-12-01

Backscatter data acquired with multibeam sonars are now commonly used for the remote geological interpretation of the seabed. The systems hardware, software, and processing methods and tools have grown in numbers and improved over the years, yet many issues linger: there are no standard procedures for acquisition, poor or absent calibration, limited understanding and documentation of processing methods, etc. A workshop organized at the GeoHab (a community of geoscientists and biologists around the topic of marine habitat mapping) annual meeting in 2013 was dedicated to seafloor backscatter data from multibeam sonars and concluded that there was an overwhelming need for better coherence and agreement on the topics of acquisition, processing and interpretation of data. The GeoHab Backscatter Working Group (BSWG) was subsequently created with the purpose of documenting and synthetizing the state-of-the-art in sensors and techniques available today and proposing methods for best practice in the acquisition and processing of backscatter data. Two years later, the resulting document "Backscatter measurements by seafloor-mapping sonars: Guidelines and Recommendations" was completed1. The document provides: An introduction to backscatter measurements by seafloor-mapping sonars; A background on the physical principles of sonar backscatter; A discussion on users' needs from a wide spectrum of community end-users; A review on backscatter measurement; An analysis of best practices in data acquisition; A review of data processing principles with details on present software implementation; and finally A synthesis and key recommendations. This presentation reviews the BSWG mandate, structure, and development of this document. It details the various chapter contents, its recommendations to sonar manufacturers, operators, data processing software developers and end-users and its implication for the marine geology community. 1: Downloadable at https://www.niwa.co.nz/coasts-and-oceans/research-projects/backscatter-measurement-guidelines

Detection and Localization of Money Bills Concealed Behind Wooden Walls Using Compton Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wart, Jason A. van; Hussein, Esam M.A.; Waller, Edward J

2005-05-15

This work presents a portable device for detecting visually obscured contraband money bills that may be hidden within conventional household walls for the purpose of avoiding confiscation. The device utilizes the Compton backscattering of photons emitted from a collimated {sup 241}Am source. The scattered photons are detected with a thin NaI(Tl) detector, either over a wide field of view for surface scanning of the wall or within a confined view field for depth scanning. The design of the device was optimized for best density contrast and highest count rate for a given source activity. It was shown that the minimummore » detectable amount of contraband, with >95% confidence level, is 86 paper bills. The contraband was detectable when hidden in household walls made of gyprock or wooden paneling, even when masked by higher density materials such as metallic piping. The device's capability exceeded those of commercially available density-based portable contraband detectors.« less

Mapping biomass for a northern forest ecosystem using multi-frequency SAR data

NASA Technical Reports Server (NTRS)

Ranson, K. J.; Sun, Guoqing

1992-01-01

Image processing methods for mapping standing biomass for a forest in Maine, using NASA/JPL airborne synthetic aperture radar (AIRSAR) polarimeter data, are presented. By examining the dependence of backscattering on standing biomass, it is determined that the ratio of HV backscattering from a longer wavelength (P- or L-band) to a shorter wavelength (C) is a good combination for mapping total biomass. This ratio enhances the correlation of the image signature to the standing biomass and compensates for a major part of the variations in backscattering attributed to radar incidence angle. The image processing methods used include image calibration, ratioing, filtering, and segmentation. The image segmentation algorithm uses both means and variances of the image, and it is combined with the image filtering process. Preliminary assessment of the resultant biomass maps suggests that this is a promising method.

Mapping 180° polar domains using electron backscatter diffraction and dynamical scattering simulations

DOE PAGES

Burch, Matthew J.; Fancher, Chris M.; Patala, Srikanth; ...

2016-11-18

A novel technique, which directly and nondestructively maps polar domains using electron backscatter diffraction (EBSD) is described and demonstrated. Through dynamical diffraction simulations and quantitative comparison to experimental EBSD patterns, the absolute orientation of a non-centrosymmetric crystal can be determined. With this information, the polar domains of a material can be mapped. The technique is demonstrated by mapping the non-ferroelastic, or 180°, ferroelectric domains in periodically poled LiNbO 3 single crystals. Furthermore, the authors demonstrate the possibility of mapping polarity using this technique in other polar materials system.

Simulation of emittance dilution in electron storage ring from Compton backscattering

NASA Astrophysics Data System (ADS)

Blumberg, L. N.; Blum, E.

A Monte-Carlo simulation of Compton backscattered kappa(sub L) = 3.2-micron photons from an IR-FEL on 75-MeV electrons in a storage ring yields an RMS electron energy spread of delta(sub E) = 11.9-keV for a sample of 10(exp 7) single scattering events. Electrons are sampled from a beam of natural energy spread sigma(sub E) = 5.6-keV and damped transverse angle spreads sigma(sub x)(prime) = .041-mrad and sigma(sub y)(prime) = .052-mrad (100%) coupling, scaled from the 200-MeV BNL XLS compact storage ring. The Compton-scattered x-rays are generated from an integral of the CM Klein-Nishina cross-section transformed to the lab. A tracking calculation has also been performed in 6-dimensional phase space. Initial electron coordinates are selected randomly from a Gaussian distribution of RMS spreads sigma(sub xo) = .102-mm, sigma(sub x(prime)o) = .041-mrad, sigma(sub yo) = .018-mm, sigma(sub y(prime)o) = .052-mrad, sigma(sub (phi)o) = 22-mrad and sigma(sub Eo) = 6-keV. A sample of 10000 electrons were each following for 40000 turns around the ring through an RF cavity of f(sub RF) = 211.54-MHz and peak voltage V(sub m)=300-keV. Preliminary results indicate that the resulting energy distribution is quite broad with an RMS width of delta(sub E) = 124-keV. The transverse widths are only slightly increased from their original values, i.e. delta(sub x) = .106-mm and delta(sub x)(prime) = .043 mrad. The scaled energy spread of delta(sub E) approximately = 360-keV for approximately 350,000 turns desired in a 10-msec x-ray angiography exposure is well within the RF bucket used here; even V(sub m) less than 50-kV is adequate. Further, the electron energy spread adds a negligible RMS x-ray energy spread of delta(sub Ex) = .32-keV. The electron energy damping time of tau(sub E) = 379-msec at 75-MeV in an XLS-type ring allows for damping this induced spread and top-off of the ring between heart cycles.

The corona of the broad-line radio galaxy 3C 390.3

DOE PAGES

Lohfink, A. M.; Ogle, P.; Tombesi, F.; ...

2015-11-13

We present the results from a joint Suzaku/NuSTAR broadband spectral analysis of 3C 390.3. The high quality data enables us to clearly separate the primary continuum from the reprocessed components allowing us to detect a high energy spectral cut-off (more » $${E}_{\\mathrm{cut}}={117}_{-14}^{+18}$$ keV), and to place constraints on the Comptonization parameters of the primary continuum for the first time. The hard over soft compactness is $${69}_{-24}^{+124}$$ and the optical depth is $${4.1}_{-3.6}^{+0.5},$$ this leads to an electron temperature of $${30}_{-8}^{+32}$$ keV. Expanding our study of the Comptonization spectrum to the optical/UV by studying the simultaneous Swift-UVOT data, we find indications that the compactness of the corona allows only a small fraction of the total UV/optical flux to be Comptonized. Our analysis of the reprocessed emission show that 3C 390.3 only has a small amount of reflection (R ~ 0.3), and of that the vast majority is from distant neutral matter. Furthermore, we also discover a soft-X-ray excess in the source, which can be described by a weak ionized reflection component from the inner parts of the accretion disk. In addition to the backscattered emission, we also detect the highly ionized iron emission lines Fe xxv and Fe xxvi.« less

Compact tunable Compton x-ray source from laser-plasma accelerator and plasma mirror

NASA Astrophysics Data System (ADS)

Tsai, Hai-En; Wang, Xiaoming; Shaw, Joseph M.; Li, Zhengyan; Arefiev, Alexey V.; Zhang, Xi; Zgadzaj, Rafal; Henderson, Watson; Khudik, V.; Shvets, G.; Downer, M. C.

2015-02-01

We present an in-depth experimental-computational study of the parameters necessary to optimize a tunable, quasi-monoenergetic, efficient, low-background Compton backscattering (CBS) x-ray source that is based on the self-aligned combination of a laser-plasma accelerator (LPA) and a plasma mirror (PM). The main findings are (1) an LPA driven in the blowout regime by 30 TW, 30 fs laser pulses produce not only a high-quality, tunable, quasi-monoenergetic electron beam, but also a high-quality, relativistically intense (a0 ˜ 1) spent drive pulse that remains stable in profile and intensity over the LPA tuning range. (2) A thin plastic film near the gas jet exit retro-reflects the spent drive pulse efficiently into oncoming electrons to produce CBS x-rays without detectable bremsstrahlung background. Meanwhile, anomalous far-field divergence of the retro-reflected light demonstrates relativistic "denting" of the PM. Exploiting these optimized LPA and PM conditions, we demonstrate quasi-monoenergetic (50% FWHM energy spread), tunable (75-200 KeV) CBS x-rays, characteristics previously achieved only on more powerful laser systems by CBS of a split-off, counter-propagating pulse. Moreover, laser-to-x-ray photon conversion efficiency (˜6 × 10-12) exceeds that of any previous LPA-based quasi-monoenergetic Compton source. Particle-in-cell simulations agree well with the measurements.

Dipole strength distributions from HIGS Experiments

NASA Astrophysics Data System (ADS)

Werner, V.; Cooper, N.; Goddard, P. M.; Humby, P.; Ilieva, R. S.; Rusev, G.; Beller, J.; Bernards, C.; Crider, B. P.; Isaak, J.; Kelley, J. H.; Kwan, E.; Löher, B.; Peters, E. E.; Pietralla, N.; Romig, C.; Savran, D.; Scheck, M.; Tonchev, A. P.; Tornow, W.; Yates, S. W.; Zweidinger, M.

2015-05-01

A series of photon scattering experiments has been performed on the double-beta decay partners 76Ge and 76Se, in order to investigate their dipole response up to the neutron separation threshold. Gamma-ray beams from bremsstrahlung at the S-DALINAC and from Compton-backscattering at HIGS have been used to measure absolute cross sections and parities of dipole excited states, respectively. The HIGS data allows for indirect measurement of averaged branching ratios, which leads to significant corrections in the observed excitation cross sections. Results are compared to statistical calculations, to test photon strength functions and the Axel-Brink hypothesis

Development of ultrashort x-ray/gamma-ray sources using ultrahigh power lasers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kim, Hyung Taek; Nakajima, Kazuhisa; Hojbota, Calin; Jeon, Jong Ho; Rhee, Yong-Joo; Lee, Kyung Hwan; Lee, Seong Ku; Sung, Jae Hee; Lee, Hwang Woon; Pathak, Vishwa B.; Pae, Ki Hong; Sebban, Stéphane; Tissandier, Fabien; Gautier, Julien; Ta Phuoc, Kim; Malka, Victor; Nam, Chang Hee

2017-05-01

Short-pulse x-ray/gamma-ray sources have become indispensable light sources for investigating material science, bio technology, and photo-nuclear physics. In past decades, rapid advancement of high intensity laser technology led extensive progresses in the field of radiation sources based on laser-plasma interactions - x-ray lasers, betatron radiation and Compton gamma-rays. Ever since the installation of a 100-TW laser in 2006, we have pursued the development of ultrashort x-ray/gamma-ray radiations, such as x-ray lasers, relativistic high-order harmonics, betatron radiation and all-optical Compton gamma-rays. With the construction of two PW Ti:Sapphire laser beamlines having peak powers of 1.0 PW and 1.5 PW in 2010 and 2012, respectively [1], we have investigated the generation of multi-GeV electron beams [2] and MeV betatron radiations. We plan to carry out the Compton backscattering to generate MeV gamma-rays from the interaction of a GeV electron beam and a PW laser beam. Here, we present the recent progress in the development of ultrashort x-ray/gamma-ray radiation sources based on laser plasma interactions and the plan for developing Compton gamma-ray sources driven by the PW lasers. In addition, we will present the applications of laser-plasma x-ray lasers to x-ray holography and coherent diffraction imaging. [references] 1. J. H. Sung, S. K. Lee, T. J. Yu, T. M. Jeong, and J. Lee, Opt. Lett. 35, 3021 (2010). 2. H. T. Kim, K. H. Pae, H. J. Cha, I J. Kim, T. J. Yu, J. H. Sung, S. K. Lee, T. M. Jeong, J. Lee, Phys. Rev. Lett. 111, 165002 (2013).

Bathymetry and acoustic backscatter: outer mainland shelf and slope, Gulf of Santa Catalina, southern California

USGS Publications Warehouse

Dartnell, Peter; Conrad, James E.; Ryan, Holly F.; Finlayson, David P.

2014-01-01

In 2010 and 2011, scientists from the U.S. Geological Survey (USGS), Coastal and Marine Geology Program, acquired bathymetry and acoustic-backscatter data from the outer shelf and slope region offshore of southern California. The surveys were conducted as part of the USGS Marine Geohazards Program. Assessment of the hazards posed by offshore faults, submarine landslides, and tsunamis are facilitated by accurate and detailed bathymetric data. The surveys were conducted using the USGS R/V Parke Snavely outfitted with a 100-kHz Reson 7111 multibeam-echosounder system. This report provides the bathymetry and backscatter data acquired during these surveys in several formats, a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

A novel biometric X-ray backscatter inspection of dangerous materials based on a lobster-eye objective

NASA Astrophysics Data System (ADS)

Xu, Jie; Wang, Xin; Mu, Baozhong; Zhan, Qi; Xie, Qing; Li, Yaran; Chen, Yifan; He, Yanan

2016-10-01

In order to counter drug-related crimes effectively, and to safeguard homeland security as well as public safety, it is important to inspect drugs, explosives and other contraband quickly and accurately from the express mail system, luggage, vehicles and other objects. In this paper, we discuss X-ray backscatter inspection system based on a novel lobster-eye X-ray objective, which is an effective inspection technology for drugs, explosives and other contraband inspection. Low atomic number materials, such as drugs and explosives, leads to strong Compton scattering after irradiated by X-ray, which is much stronger than high atomic number material, such as common metals, etc. By detecting the intensity of scattering signals, it is possible to distinguish between organics and inorganics. The lobster-eye X-ray optical system imitates the reflective eyes of lobsters, which field of view can be made as large as desired and it is practical to achieve spatial resolution of several millimeters for finite distance detection. A novel lobster-eye X-ray objective is designed based on modifying Schmidt geometry by using multi-lens structure, so as to reduce the difference of resolution between the horizontal and vertical directions. The demonstration experiments of X-ray backscattering imaging were carried out. A suitcase, a wooden box and a tire with several typical samples hidden in them were imaged by the X-ray backscattering inspection system based on a lobster-eye X-ray objective. The results show that this X-ray backscattering inspection system can get a resolution of less than five millimeters under the FOV of more than two hundred millimeters with 0.5 meter object distance, which can still be improved.

Colored shaded-relief bathymetry, acoustic backscatter, and selected perspective views of the Inner Continental Borderland, southern California

USGS Publications Warehouse

Dartnell, Peter; Driscoll, Neal W.; Brothers, Daniel S.; Conrad, James E.; Kluesner, Jared; Kent, Graham; Andrews, Brian D.

2015-01-01

In late 2013, Scripps Institution of Oceanography collected multibeam bathymetry and acoustic-backscatter data of the Inner Continental Borderland Region, Southern California. The U.S. Geological Survey Pacific Coastal and Marine Science Center processed these data, and this report provides the data in a number of different formats in addition to a set of map sheets. The data catalog provides the new bathymetry and acoustic-backscatter data, collected mainly in the Gulf of Santa Catalina and San Diego Trough, as well as this new bathymetry data merged with other publically available bathymetry data from the region. Sheet 1 displays a colored shaded-relief bathymetry map of the Inner Continental Borderland generated from the merged bathymetry data. Sheet 2 displays the new acoustic-backscatter data along with other available backscatter data in the region. Sheet 3 displays selected perspective views of the bathymetry data highlighting submarine canyon and channel systems, knolls, and tectonic features.

Improved detection and mapping of deepwater hydrocarbon seeps: optimizing multibeam echosounder seafloor backscatter acquisition and processing techniques

NASA Astrophysics Data System (ADS)

Mitchell, Garrett A.; Orange, Daniel L.; Gharib, Jamshid J.; Kennedy, Paul

2018-06-01

Marine seep hunting surveys are a current focus of hydrocarbon exploration surveys due to recent advances in offshore geophysical surveying, geochemical sampling, and analytical technologies. Hydrocarbon seeps are ephemeral, small, discrete, and therefore difficult to sample on the deep seafloor. Multibeam echosounders are an efficient seafloor exploration tool to remotely locate and map seep features. Geophysical signatures from hydrocarbon seeps are acoustically-evident in bathymetric, seafloor backscatter, midwater backscatter datasets. Interpretation of these signatures in backscatter datasets is a fundamental component of commercial seep hunting campaigns. Degradation of backscatter datasets resulting from environmental, geometric, and system noise can interfere with the detection and delineation of seeps. We present a relative backscatter intensity normalization method and an oversampling acquisition technique that can improve the geological resolvability of hydrocarbon seeps. We use Green Canyon (GC) Block 600 in the Northern Gulf of Mexico as a seep calibration site for a Kongsberg EM302 30 kHz MBES prior to the start of the Gigante seep hunting program to analyze these techniques. At GC600, we evaluate the results of a backscatter intensity normalization, assess the effectiveness of 2X seafloor coverage in resolving seep-related features in backscatter data, and determine the off-nadir detection limits of bubble plumes using the EM302. Incorporating these techniques into seep hunting surveys can improve the detectability and sampling of seafloor seeps.

Development and Evaluation of Real-Time Volumetric Compton Gamma-Ray Imaging

NASA Astrophysics Data System (ADS)

Barnowski, Ross Wegner

An approach to gamma-ray imaging has been developed that enables near real-time volumetric (3D) imaging of unknown environments thus improving the utility of gamma-ray imaging for source-search and radiation mapping applications. The approach, herein dubbed scene data fusion (SDF), is based on integrating mobile radiation imagers with real time tracking and scene reconstruction algorithms to enable a mobile mode of operation and 3D localization of gamma-ray sources. The real-time tracking allows the imager to be moved throughout the environment or around a particular object of interest, obtaining the multiple perspectives necessary for standoff 3D imaging. A 3D model of the scene, provided in real-time by a simultaneous localization and mapping (SLAM) algorithm, can be incorporated into the image reconstruction reducing the reconstruction time and improving imaging performance. The SDF concept is demonstrated in this work with a Microsoft Kinect RGB-D sensor, a real-time SLAM solver, and two different mobile gamma-ray imaging platforms. The first is a cart-based imaging platform known as the Volumetric Compton Imager (VCI), comprising two 3D position-sensitive high purity germanium (HPGe) detectors, exhibiting excellent gamma-ray imaging characteristics, but with limited mobility due to the size and weight of the cart. The second system is the High Efficiency Multimodal Imager (HEMI) a hand-portable gamma-ray imager comprising 96 individual cm3 CdZnTe crystals arranged in a two-plane, active-mask configuration. The HEMI instrument has poorer energy and angular resolution than the VCI, but is truly hand-portable, allowing the SDF concept to be tested in multiple environments and for more challenging imaging scenarios. An iterative algorithm based on Compton kinematics is used to reconstruct the gamma-ray source distribution in all three spatial dimensions. Each of the two mobile imaging systems are used to demonstrate SDF for a variety of scenarios, including general search and mapping scenarios with several point gamma-ray sources over the range of energies relevant for Compton imaging. More specific imaging scenarios are also addressed, including directed search and object interrogation scenarios. Finally, the volumetric image quality is quantitatively investigated with respect to the number of Compton events acquired during a measurement, the list-mode uncertainty of the Compton cone data, and the uncertainty in the pose estimate from the real-time tracking algorithm. SDF advances the real-world applicability of gamma-ray imaging for many search, mapping, and verification scenarios by improving the tractability of the gamma-ray image reconstruction and providing context for the 3D localization of gamma-ray sources within the environment in real-time.

Filtered back-projection algorithm for Compton telescopes

DOEpatents

Gunter, Donald L [Lisle, IL

2008-03-18

A method for the conversion of Compton camera data into a 2D image of the incident-radiation flux on the celestial sphere includes detecting coincident gamma radiation flux arriving from various directions of a 2-sphere. These events are mapped by back-projection onto the 2-sphere to produce a convolution integral that is subsequently stereographically projected onto a 2-plane to produce a second convolution integral which is deconvolved by the Fourier method to produce an image that is then projected onto the 2-sphere.

Compact tunable Compton x-ray source from laser-plasma accelerator and plasma mirror

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Hai-En; Wang, Xiaoming; Shaw, Joseph M.

2015-02-15

We present an in-depth experimental-computational study of the parameters necessary to optimize a tunable, quasi-monoenergetic, efficient, low-background Compton backscattering (CBS) x-ray source that is based on the self-aligned combination of a laser-plasma accelerator (LPA) and a plasma mirror (PM). The main findings are (1) an LPA driven in the blowout regime by 30 TW, 30 fs laser pulses produce not only a high-quality, tunable, quasi-monoenergetic electron beam, but also a high-quality, relativistically intense (a{sub 0} ∼ 1) spent drive pulse that remains stable in profile and intensity over the LPA tuning range. (2) A thin plastic film near the gas jetmore » exit retro-reflects the spent drive pulse efficiently into oncoming electrons to produce CBS x-rays without detectable bremsstrahlung background. Meanwhile, anomalous far-field divergence of the retro-reflected light demonstrates relativistic “denting” of the PM. Exploiting these optimized LPA and PM conditions, we demonstrate quasi-monoenergetic (50% FWHM energy spread), tunable (75–200 KeV) CBS x-rays, characteristics previously achieved only on more powerful laser systems by CBS of a split-off, counter-propagating pulse. Moreover, laser-to-x-ray photon conversion efficiency (∼6 × 10{sup −12}) exceeds that of any previous LPA-based quasi-monoenergetic Compton source. Particle-in-cell simulations agree well with the measurements.« less

Skin dose mapping for non-uniform x-ray fields using a backscatter point spread function

NASA Astrophysics Data System (ADS)

Vijayan, Sarath; Xiong, Zhenyu; Shankar, Alok; Rudin, Stephen; Bednarek, Daniel R.

2017-03-01

Beam shaping devices like ROI attenuators and compensation filters modulate the intensity distribution of the xray beam incident on the patient. This results in a spatial variation of skin dose due to the variation of primary radiation and also a variation in backscattered radiation from the patient. To determine the backscatter component, backscatter point spread functions (PSF) are generated using EGS Monte-Carlo software. For this study, PSF's were determined by simulating a 1 mm beam incident on the lateral surface of an anthropomorphic head phantom and a 20 cm thick PMMA block phantom. The backscatter PSF's for the head phantom and PMMA phantom are curve fit with a Lorentzian function after being normalized to the primary dose intensity (PSFn). PSFn is convolved with the primary dose distribution to generate the scatter dose distribution, which is added to the primary to obtain the total dose distribution. The backscatter convolution technique is incorporated in the dose tracking system (DTS), which tracks skin dose during fluoroscopic procedures and provides a color map of the dose distribution on a 3D patient graphic model. A convolution technique is developed for the backscatter dose determination for the nonuniformly spaced graphic-model surface vertices. A Gafchromic film validation was performed for shaped x-ray beams generated with an ROI attenuator and with two compensation filters inserted into the field. The total dose distribution calculated by the backscatter convolution technique closely agreed with that measured with the film.

Variance-reduction normalization technique for a compton camera system

NASA Astrophysics Data System (ADS)

Kim, S. M.; Lee, J. S.; Kim, J. H.; Seo, H.; Kim, C. H.; Lee, C. S.; Lee, S. J.; Lee, M. C.; Lee, D. S.

2011-01-01

For an artifact-free dataset, pre-processing (known as normalization) is needed to correct inherent non-uniformity of detection property in the Compton camera which consists of scattering and absorbing detectors. The detection efficiency depends on the non-uniform detection efficiency of the scattering and absorbing detectors, different incidence angles onto the detector surfaces, and the geometry of the two detectors. The correction factor for each detected position pair which is referred to as the normalization coefficient, is expressed as a product of factors representing the various variations. The variance-reduction technique (VRT) for a Compton camera (a normalization method) was studied. For the VRT, the Compton list-mode data of a planar uniform source of 140 keV was generated from a GATE simulation tool. The projection data of a cylindrical software phantom were normalized with normalization coefficients determined from the non-uniformity map, and then reconstructed by an ordered subset expectation maximization algorithm. The coefficient of variations and percent errors of the 3-D reconstructed images showed that the VRT applied to the Compton camera provides an enhanced image quality and the increased recovery rate of uniformity in the reconstructed image.

Using SAR satellite data time series for regional glacier mapping

NASA Astrophysics Data System (ADS)

Winsvold, Solveig H.; Kääb, Andreas; Nuth, Christopher; Andreassen, Liss M.; van Pelt, Ward J. J.; Schellenberger, Thomas

2018-03-01

With dense SAR satellite data time series it is possible to map surface and subsurface glacier properties that vary in time. On Sentinel-1A and RADARSAT-2 backscatter time series images over mainland Norway and Svalbard, we outline how to map glaciers using descriptive methods. We present five application scenarios. The first shows potential for tracking transient snow lines with SAR backscatter time series and correlates with both optical satellite images (Sentinel-2A and Landsat 8) and equilibrium line altitudes derived from in situ surface mass balance data. In the second application scenario, time series representation of glacier facies corresponding to SAR glacier zones shows potential for a more accurate delineation of the zones and how they change in time. The third application scenario investigates the firn evolution using dense SAR backscatter time series together with a coupled energy balance and multilayer firn model. We find strong correlation between backscatter signals with both the modeled firn air content and modeled wetness in the firn. In the fourth application scenario, we highlight how winter rain events can be detected in SAR time series, revealing important information about the area extent of internal accumulation. In the last application scenario, averaged summer SAR images were found to have potential in assisting the process of mapping glaciers outlines, especially in the presence of seasonal snow. Altogether we present examples of how to map glaciers and to further understand glaciological processes using the existing and future massive amount of multi-sensor time series data.

Simulation of emittance dilution in electron storage ring from Compton backscattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blumberg, L.N.; Blum, E.

1993-07-01

A Monte-Carlo simulation of Compton backscattered {kappa}{sub L}=3.2-{mu}m photons from an IR-FEL on 75-MeV electrons in a storage ring yields an RMS electron energy spread of {Delta}{sub E}=11.9-keV for a sample of 10{sup 7} single scattering events. Electrons are sampled from a beam of natural energy spread {sigma}{sub E} = 5.6-keV and damped transverse angle spreads {sigma}{sub x}{prime}, = .041-mrad and {sigma}{sub y}{prime} = .052-mrad (100%) coupling, scaled from the 200-MeV BNL XLS compact storage ring. The Compton-scattered X-Rays are generated from an integral of the CM Klein-Nishina cross-section transformed to the lab. A tracking calculation has also been performedmore » in 6-dimensional phase space. Initial electron coordinates are selected randomly from a Gaussian distribution of RMS spreads {sigma}{sub xo}=.102-mm, {sigma}{sub x{prime}o}=.041-mrad, {sigma}{sub yo}=.018-mm, {sigma}{sub y{prime}o}=.052-mrad, {sigma}{sub {phi}o}=22-mrad and {sigma}{sub Eo}=6-keV. A sample of 10000 electrons were each following for 40000 turns around the ring through an RF cavity of f{sub rf}=211.54-MHz and peak voltage V{sub m}=300-keV. Preliminary results indicate that the resulting energy distribution is quite broad with an RMS width of {Delta}{sub E} = 124-keV. The transverse widths are only slightly increased from their original values, i.e. {Delta}{sub x} = .106-mm and {Delta}{sub x}{prime}=.043 mrad. The scaled energy spread of {Delta}{sub E} {approximately} 360-keV for {approximately} 350,000 turns desired in a 10-msec X-Ray angiography exposure is well within the RF bucket used here; even V{sub m} < 50-kV is adequate. Further, the electron energy spread adds a negligible RMS X-Ray energy spread of {Delta}{sub Ex}=.32-keV. The electron energy damping time of {tau}{sub E}=379-msec at 75-MeV in an XLS-type ring allows for damping this induced spread and top-off of the ring between heart cycles.« less

Polarization Reversal Over Flooded Regions and Applications to Large-Scale Flood Mapping with Spaceborne Scatterometers

NASA Technical Reports Server (NTRS)

Nghiem, Son V.; Liu, W. Timothy; Xie, Xiao-Su

1999-01-01

We present the polarization reversal in backscatter over flooded land regions, and demonstrate for the first time the utility of spaceborne Ku-band scatterometer for large-scale flood mapping. Scatterometer data were collected over the globe by the NASA Scatterometer (NSCAT) operated at 14 GHz on the Japanese ADEOS spacecraft from September 1996 to June 1997. During this time span, several severe floods occurred. Over most land surface, vertical polarization backscatter (Sigma(sub upsilon(upsilon)) is larger than horizontal polarization backscatter (sigma(sub hh)). Such polarization characteristics is reversed and sigma(sub upsilon(upsilon)) is smaller than sigma(sub hh) over flooded regions, except under a dense forest canopy. The total backscatter from the flooded landscape consists of direct backscatter and boundary-interaction backscatter. The direct term is contributed by direct backscattering from objects protruding above the water surface, and by backscattering from waves on the water surface. The boundary-interaction term is contributed by the forward scattering from the protruding objects and then reflected from the water surface, and also by the forward scattering from these objects after the water-surface reflection. Over flooded regions, the boundary-interaction term is dominant at large incidence angles and the strong water-surface reflection is much larger for horizontal polarization than the vertical one due to the Brewster effect in transverse-magnetic waves. These scattering mechanisms cause the polarization reversal over flooded regions. An example obtained with the Analytic Wave Theory is used to illustrate the scattering mechanisms leading to the polarization reversal. We then demonstrate the utility of spaceborne Ku-band scatterometer for large-scale flood mapping. We process NSCAT data to obtain the polarization ratio sigma(sub hh)/sigma(sub upsilon(upsilon)) with colocated data at incidence angles larger than 40 deg. The results over Asian summer monsoon regions in September-October 1996 indicate flooded areas in many countries such as Bangladesh, India, Lao, Vietnam, Cambodia, and China. Reports documented by the United Nation Department of Humanitarian Affairs (now called UN Office for the Coordination of Humanitarian Affairs) show loss of many lives and severe flood related damages which affected many million people in the corresponding flooded areas. We also map the NSCAT polarization ratio over the same regions in the "dry season" in January 1997 as a reference to confirm our results. Furthermore, we obtain concurrent ocean wind fields also derived from NSCAT data, and Asia topographic data (USGS GTOPO30) to investigate the flooded area. The results show that winds during summer monsoon season blowing inland, which perplex flood problems. Overlaying the topographic map over NSCAT results reveals an excellent correspondence between the confinement of flooded area within the relevant topographic features, which very well illustrates the value of topographic wetness index. Finally, we discuss the applications of future spaceborne scatterometers, including QuikSCAT and Seawinds, for flood mapping over the globe.

High Resolution Seafloor Environmental Characterization of Methane Seeps in the Mississippi Canyon Near Atwater Valley 13/14, Gulf of Mexico.

NASA Astrophysics Data System (ADS)

Gardner, J. M.; Hagen, R.; Hart, P.; Czarnecki, M.; Nishimura, C.; Hutchinson, D. R.

2005-12-01

The purpose of this project was to conduct detailed surface mapping of one of the areas drilled by the Joint Industry Project with ChevronTexaco to understand gas hydrates in the Gulf of Mexico. The gently sloping, mostly flat floor of the Mississippi Canyon is interrupted by mounds and depressions that presumably reflect the complex geology and geohydrology related to turbidite deposition and pervasive salt tectonism. The seafloor mounds we mapped in this study occur in approximately 1300 water depth along the floor of the Mississippi Canyon in lease block areas Atwater Valley 13 and 14. High resolution sidescan sonar (100 kHz and 500 kHz) backscatter imagery, and chirp sub-bottom profiler data were collected using the DT1 deep-towed oceanographic mapping instrument, concentrating on the region directly adjacent to and surrounding two mounds identified as, mounds D and F, and in the region directly adjacent to and surrounding the mounds. The backscatter data have been mosaiced and normalized to provide information on the shape and extent of the mounds, the possible lateral extent of fauna, such as mussel and clam fields on the mounds, possible seep related flows and the occurrence of carbonate material. The extent of a mudflow can be mapped on the southeastern side of mound F. Previously collected bottom camera images have been used to ground-truth the backscatter information. Coincident with the collection of backscatter information was the collection of very high-resolution bathymetric data. Together, the backscatter and bathymetric data show extremely high-resolution detail about the shape, relief, and morphology of the mounds. This information, coupled with porewater chemistry and heatflow data form a coherent picture of possible mechanics for fluid venting and flora/fauna of the seeps in this region.

Seabed maps showing topography, ruggedness, backscatter intensity, sediment mobility, and the distribution of geologic substrates in Quadrangle 6 of the Stellwagen Bank National Marine Sanctuary Region offshore of Boston, Massachusetts

USGS Publications Warehouse

Valentine, Page C.; Gallea, Leslie B.

2015-11-10

The U.S. Geological Survey (USGS), in cooperation with the National Oceanic and Atmospheric Administration's National Marine Sanctuary Program, has conducted seabed mapping and related research in the Stellwagen Bank National Marine Sanctuary (SBNMS) region since 1993. The area is approximately 3,700 square kilometers (km2) and is subdivided into 18 quadrangles. Seven maps, at a scale of 1:25,000, of quadrangle 6 (211 km2) depict seabed topography, backscatter, ruggedness, geology, substrate mobility, mud content, and areas dominated by fine-grained or coarse-grained sand. Interpretations of bathymetric and seabed backscatter imagery, photographs, video, and grain-size analyses were used to create the geology-based maps. In all, data from 420 stations were analyzed, including sediment samples from 325 locations. The seabed geology map shows the distribution of 10 substrate types ranging from boulder ridges to immobile, muddy sand to mobile, rippled sand. Mapped substrate types are defined on the basis of sediment grain-size composition, surface morphology, sediment layering, the mobility or immobility of substrate surfaces, and water depth range. This map series is intended to portray the major geological elements (substrates, topographic features, processes) of environments within quadrangle 6. Additionally, these maps will be the basis for the study of the ecological requirements of invertebrate and vertebrate species that utilize these substrates and guide seabed management in the region.

Processing ultrasound backscatter to monitor high-intensity focused ultrasound (HIFU) therapy

NASA Astrophysics Data System (ADS)

Kaczkowski, Peter J.; Anand, Ajay; Bailey, Michael R.

2005-09-01

The development of new noninvasive surgical methods such as HIFU for the treatment of cancer and internal bleeding requires simultaneous development of new sensing approaches to guide, monitor, and assess the therapy. Ultrasound imaging using echo amplitude has long been used to map tissue morphology for diagnostic interpretation by the clinician. New quantitative ultrasonic methods that rely on amplitude and phase processing for tissue characterization are being developed for monitoring of ablative therapy. We have been developing the use of full wave ultrasound backscattering for real-time temperature estimation, and to image changes in tissue backscatter spectrum as therapy progresses. Both approaches rely on differential processing of the backscatter signal in time, and precise measurement of phase differences. Noise and artifacts from motion and nonstationary speckle statistics are addressed by constraining inversions for tissue parameters with physical models. We present results of HIFU experiments with static point and scanned HIFU exposures in which temperature rise can be accurately mapped using a new heat transfer equation (HTE) model-constrained inverse approach. We also present results of a recently developed spectral imaging method that elucidates microbubble-mediated nonlinearity not visible as a change in backscatter amplitude. [Work supported by Army MRMC.

Implementation status of the extreme light infrastructure - nuclear physics (ELI-NP) project

NASA Astrophysics Data System (ADS)

Gales, S.; Zamfir, N. V.

2015-02-01

The Project Extreme Light Infrastructure (ELI) is part of the European Strategic Forum for Research Infrastructures (ESFRI) Roadmap. ELI will be built as a network of three complementary pillars at the frontier of laser technologies. The ELI-NP pillar (NP for Nuclear Physics) is under construction near Bucharest (Romania) and will develop a scientific program using two 10 PW lasers and a Compton back-scattering high-brilliance and intense gamma beam, a marriage of laser and accelerator technology at the frontier of knowledge. In the present paper, the technical description of the facility, the present status of the project as well as the science, applications and future perspectives will be discussed.

User expectations for multibeam echo sounders backscatter strength data-looking back into the future

NASA Astrophysics Data System (ADS)

Lucieer, Vanessa; Roche, Marc; Degrendele, Koen; Malik, Mashkoor; Dolan, Margaret; Lamarche, Geoffroy

2018-06-01

With the ability of multibeam echo sounders (MBES) to measure backscatter strength (BS) as a function of true angle of insonification across the seafloor, came a new recognition of the potential of backscatter measurements to remotely characterize the properties of the seafloor. Advances in transducer design, digital electronics, signal processing capabilities, navigation, and graphic display devices, have improved the resolution and particularly the dynamic range available to sonar and processing software manufacturers. Alongside these improvements the expectations of what the data can deliver has also grown. In this paper, we identify these user-expectations and explore how MBES backscatter is utilized by different communities involved in marine seabed research at present, and the aspirations that these communities have for the data in the future. The results presented here are based on a user survey conducted by the GeoHab (Marine Geological and Biological Habitat Mapping) association. This paper summarises the different processing procedures employed to extract useful information from MBES backscatter data and the various intentions for which the user community collect the data. We show how a range of backscatter output products are generated from the different processing procedures, and how these results are taken up by different scientific disciplines, and also identify common constraints in handling MBES BS data. Finally, we outline our expectations for the future of this unique and important data source for seafloor mapping and characterisation.

A framework to quantify uncertainties of seafloor backscatter from swath mapping echosounders

NASA Astrophysics Data System (ADS)

Malik, Mashkoor; Lurton, Xavier; Mayer, Larry

2018-06-01

Multibeam echosounders (MBES) have become a widely used acoustic remote sensing tool to map and study the seafloor, providing co-located bathymetry and seafloor backscatter. Although the uncertainty associated with MBES-derived bathymetric data has been studied extensively, the question of backscatter uncertainty has been addressed only minimally and hinders the quantitative use of MBES seafloor backscatter. This paper explores approaches to identifying uncertainty sources associated with MBES-derived backscatter measurements. The major sources of uncertainty are catalogued and the magnitudes of their relative contributions to the backscatter uncertainty budget are evaluated. These major uncertainty sources include seafloor insonified area (1-3 dB), absorption coefficient (up to > 6 dB), random fluctuations in echo level (5.5 dB for a Rayleigh distribution), and sonar calibration (device dependent). The magnitudes of these uncertainty sources vary based on how these effects are compensated for during data acquisition and processing. Various cases (no compensation, partial compensation and full compensation) for seafloor insonified area, transmission losses and random fluctuations were modeled to estimate their uncertainties in different scenarios. Uncertainty related to the seafloor insonified area can be reduced significantly by accounting for seafloor slope during backscatter processing while transmission losses can be constrained by collecting full water column absorption coefficient profiles (temperature and salinity profiles). To reduce random fluctuations to below 1 dB, at least 20 samples are recommended to be used while computing mean values. The estimation of uncertainty in backscatter measurements is constrained by the fact that not all instrumental components are characterized and documented sufficiently for commercially available MBES. Further involvement from manufacturers in providing this essential information is critically required.

2000 Multibeam Sonar Survey of Crater Lake, Oregon - Data, GIS, Images, and Movies

USGS Publications Warehouse

Gardner, James V.; Dartnell, Peter

2001-01-01

In the summer of 2000, the U.S. Geological Survey, Pacific Seafloor Mapping Project in cooperation with the National Park Service, and the Center for Coastal and Ocean Mapping, University of New Hampshire used a state-of-the-art multibeam sonar system to collect high-resolution bathymetry and calibrated, co-registered acoustic backscatter to support both biological and geological research in the Crater Lake area. This interactive CD-ROM contains the multibeam bathymetry and acoustic backscatter data, along with an ESRI ArcExplorer project (and software), images, and movies.

Mapping the plasmon response of Ag nanoislands on graphite at 100 nm resolution with scanning probe energy loss spectroscopy

NASA Astrophysics Data System (ADS)

Murphy, Shane; Bauer, Karl; Sloan, Peter A.; Lawton, James J.; Tang, Lin; Palmer, Richard E.

2015-12-01

We demonstrate plasmon mapping of Ag nanostructures on graphite using scanning probe energy loss spectroscopy (SPELS) with a spatial resolution of 100 nm. In SPELS, an STM tip is used as a localized source of field-emitted electrons to probe the sample surface. The energy loss spectrum of the backscattered electrons is measured to provide a chemical signature of the surface under the tip. We acquire three images simultaneously with SPELS: i) constant-current field-emission images, which provide topographical information; ii) backscattered electron images, which display material contrast; and iii) SPELS images, where material-dependent features such as plasmons are mapped.

X-ray inverse Compton emission from the radio halo of M87. M.S. Thesis

NASA Technical Reports Server (NTRS)

Wood, P. A. D.

1985-01-01

M87 has been observed in the 0.2-4 KeV X-ray band using the High Resolution Imager on the Einstein Observatory, and at 1.452 GHz using the Very Large Array. The radio map showed that the halo contained prominent asymmetries to the east and southwest. The X-ray map indicated similar asymmetries, but they were imbedded in the diffuse hot gas that surrounds the core out to a radius of several arcminutes. The hot X-ray emitting gas was assumed to be spherically symmetric and could, therefore, be subtracted from the image. The resultant image was asymmetric with major lobes to the east and southwest that coincide approximately with the asymmetries in the radio halo. The data indicates that inverse Compton emission is a plausible model for the X-rays coming from the asymmetric component.

Profiling of back-scattered electrons in opposed magnetic field of a Twin Electron Beam Gun

NASA Astrophysics Data System (ADS)

Sethi, S.; Gupta, Anchal; Dileep Kumar, V.; Mukherjee, Jaya; Gantayet, L. M.

2012-11-01

Electron gun is extensively used in material processing, physical vapour deposition and atomic vapour based laser processes. In these processes where the electron beam is incident on the substrate, a significant fraction of electron beam gets back-scattered from the target surface. The trajectory of this back scattered electron beam depends on the magnetic field in the vicinity. The fraction of back-scattered depends on the atomic number of the target metal and can be as high as ~40% of the incident beam current. These back-scattered electrons can cause undesired hot spots and also affect the overall process. Hence, the study of the trajectory of these back-scattered electrons is important. This paper provides the details of experimentally mapped back-scattered electrons of a 2×20kW Twin Electron Beam Gun (TEBG) in opposed magnetic field i.e. with these guns placed at 180° to each other.

Multi-temporal RADARSAT-1 and ERS backscattering signatures of coastal wetlands in southeastern Louisiana

USGS Publications Warehouse

Kwoun, Oh-Ig; Lu, Z.

2009-01-01

Using multi-temporal European Remote-sensing Satellites (ERS-1/-2) and Canadian Radar Satellite (RADARSAT-1) synthetic aperture radar (SAR) data over the Louisiana coastal zone, we characterize seasonal variations of radar backscat-tering according to vegetation type. Our main findings are as follows. First, ERS-1/-2 and RADARSAT-1 require careful radiometric calibration to perform multi-temporal backscattering analysis for wetland mapping. We use SAR backscattering signals from cities for the relative calibration. Second, using seasonally averaged backscattering coefficients from ERS-1/-2 and RADARSAT-1, we can differentiate most forests (bottomland and swamp forests) and marshes (freshwater, intermediate, brackish, and saline marshes) in coastal wetlands. The student t-test results support the usefulness of season-averaged backscatter data for classification. Third, combining SAR backscattering coefficients and an optical-sensor-based normalized difference vegetation index can provide further insight into vegetation type and enhance the separation between forests and marshes. Our study demonstrates that SAR can provide necessary information to characterize coastal wetlands and monitor their changes.

Geomorphology of unique reefs on the western Canadian shelf: sponge reefs mapped by multibeam bathymetry

NASA Astrophysics Data System (ADS)

Conway, Kim W.; Barrie, J. Vaughn; Krautter, Manfred

2005-09-01

Multibeam imagery of siliceous sponge reefs (Hexactinellida, Hexactinosida) reveals the setting, form, and organization of five reef complexes on the western Canadian continental shelf. The reefs are built by framework skeleton sponges which trap clay-rich sediments resulting in a distinctive pattern of low intensity backscatter from the reefs that colonize more reflective glacial sediments of higher backscatter intensity. Bathymetry and backscatter maps show the distribution and form of reefs in two large complexes in the Queen Charlotte Basin (QCB) covering hundreds of km2, and three smaller reef complexes in the Georgia Basin (GB). Ridges up to 7 km long and 21 m in height, together with diversely shaped, coalescing bioherms and biostromes form the principal reef shape in the QCB whereas chains of wave-form, streamlined mounds up to 14 m in height have developed in the GB. Reef initiation is dependent on the distribution of high backscatter-intensity relict glacial surfaces, and the variation in reef complex morphology is probably the result of tidally driven, near seabed currents.

Hydroacoustic estimation of zooplankton biomass at two shoal complexes in the Apostle Islands Region of Lake Superior

USGS Publications Warehouse

Holbrook, B.V.; Hrabik, T.R.; Branstrator, D.K.; Yule, D.L.; Stockwell, J.D.

2006-01-01

Hydroacoustics can be used to assess zooplankton populations, however, backscatter must be scaled to be biologically meaningful. In this study, we used a general model to correlate site-specific hydroacoustic backscatter with zooplankton dry weight biomass estimated from net tows. The relationship between zooplankton dry weight and backscatter was significant (p < 0.001) and explained 76% of the variability in the dry weight data. We applied this regression to hydroacoustic data collected monthly in 2003 and 2004 at two shoals in the Apostle Island Region of Lake Superior. After applying the regression model to convert hydroacoustic backscatter to zooplankton dry weight biomass, we used geostatistics to analyze the mean and variance, and ordinary kriging to create spatial zooplankton distribution maps. The mean zooplankton dry weight biomass estimates from plankton net tows and hydroacoustics were not significantly different (p = 0.19) but the hydroacoustic data had a significantly lower coefficient of variation (p < 0.001). The maps of zooplankton distribution illustrated spatial trends in zooplankton dry weight biomass that were not discernable from the overall means.

Improved spatial resolution in PET scanners using sampling techniques

PubMed Central

Surti, Suleman; Scheuermann, Ryan; Werner, Matthew E.; Karp, Joel S.

2009-01-01

Increased focus towards improved detector spatial resolution in PET has led to the use of smaller crystals in some form of light sharing detector design. In this work we evaluate two sampling techniques that can be applied during calibrations for pixelated detector designs in order to improve the reconstructed spatial resolution. The inter-crystal positioning technique utilizes sub-sampling in the crystal flood map to better sample the Compton scatter events in the detector. The Compton scatter rejection technique, on the other hand, rejects those events that are located further from individual crystal centers in the flood map. We performed Monte Carlo simulations followed by measurements on two whole-body scanners for point source data. The simulations and measurements were performed for scanners using scintillators with Zeff ranging from 46.9 to 63 for LaBr3 and LYSO, respectively. Our results show that near the center of the scanner, inter-crystal positioning technique leads to a gain of about 0.5-mm in reconstructed spatial resolution (FWHM) for both scanner designs. In a small animal LYSO scanner the resolution improves from 1.9-mm to 1.6-mm with the inter-crystal technique. The Compton scatter rejection technique shows higher gains in spatial resolution but at the cost of reduction in scanner sensitivity. The inter-crystal positioning technique represents a modest acquisition software modification for an improvement in spatial resolution, but at a cost of potentially longer data correction and reconstruction times. The Compton scatter rejection technique, while also requiring a modest acquisition software change with no increased data correction and reconstruction times, will be useful in applications where the scanner sensitivity is very high and larger improvements in spatial resolution are desirable. PMID:19779586

Improved Detection and Mapping of Deepwater Hydrocarbon Seeps: Optimizing Acquisition and Processing Parameters for Marine Seep Hunting

NASA Astrophysics Data System (ADS)

Mitchell, G. A.; Orange, D.; Gharib, J. J.; Saade, E. J.; Joye, S. B.

2016-12-01

Marine seep hunting surveys are a current focus of hydrocarbon exploration due to recent advances in offshore geophysical and geochemical technologies. Hydrocarbon seeps are ephemeral, small, discrete, and often difficult to sample on the deep seafloor. Low to mid-frequency multibeam echosounders (MBES) are an ideal exploration tool to remotely locate and map seafloor features associated with seepage. Geophysical signatures from hydrocarbon seeps are evident in bathymetric datasets (fluid expulsion features), seafloor backscatter datasets (carbonate outcrops, gassy sediments, methane hydrate deposits), and midwater backscatter datasets (gas bubble and oil droplet plumes). Interpretation of these geophysical seep signatures in backscatter datasets is a fundamental component in seep hunting. Degradation of backscatter datasets resulting from environmental, geometric, and system noise can interfere with the detection and delineation of seeps. We present a backscatter intensity normalization method and a 2X acquisition technique that can enhance the geologic resolvability within backscatter datasets and assist in interpretation and characterization of seeps. We use GC600 in the Northern Gulf of Mexico as a seep calibration site for a Kongsberg EM302 30 kHz MBES prior to the start of the Gigante seep hunting survey. We analyze the results of a backscatter intensity normalization, assess the effectiveness of 2X seafloor coverage in resolving geologic features in backscatter data, and determine off-nadir detection limits of bubble plumes. GC600's location and robust venting make it a natural laboratory in which to study natural hydrocarbon seepage. The site has been the focus of several near-seafloor surveys as well as in-situ studies using advanced deepwater technologies analyzing fluid flux and composition. These datasets allow for ground-truthing of our remote backscatter measurements prior to commencing exploration within the frontier regions of the Southern Gulf of Mexico and Caribbean Sea. Our study shows that a comprehensive multibeam calibration involving bathymetric difference grids, a seafloor backscatter intensity normalization, a 2X acquisition survey technique, and processing with multiple processing packages can improve resolvability of seep features and interpretation.

Implementation status of the extreme light infrastructure - nuclear physics (ELI-NP) project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gales, S., E-mail: sydney.gales@eli-np.ro; Zamfir, N. V., E-mail: sydney.gales@eli-np.ro

2015-02-24

The Project Extreme Light Infrastructure (ELI) is part of the European Strategic Forum for Research Infrastructures (ESFRI) Roadmap. ELI will be built as a network of three complementary pillars at the frontier of laser technologies. The ELI-NP pillar (NP for Nuclear Physics) is under construction near Bucharest (Romania) and will develop a scientific program using two 10 PW lasers and a Compton back-scattering high-brilliance and intense gamma beam, a marriage of laser and accelerator technology at the frontier of knowledge. In the present paper, the technical description of the facility, the present status of the project as well as themore » science, applications and future perspectives will be discussed.« less

Surface Parameters of Titan Feature Classes From Cassini RADAR Backscatter Measurements

NASA Astrophysics Data System (ADS)

Wye, L. C.; Zebker, H. A.; Lopes, R. M.; Peckyno, R.; Le Gall, A.; Janssen, M. A.

2008-12-01

Multimode microwave measurements collected by the Cassini RADAR instrument during the spacecraft's first four years of operation form a fairly comprehensive set of radar backscatter data over a variety of Titan surface features. We use the real-aperture scatterometry processor to analyze the entire collection of active data, creating a uniformly-calibrated dataset that covers 93% of Titan's surface at a variety of viewing angles. Here, we examine how the measured backscatter response (radar reflectivity as a function of incidence angle) varies with surface feature type, such as dunes, cryovolcanic areas, and anomalous albedo terrain. We identify the feature classes using a combination of maps produced by the RADAR, ISS, and VIMS instruments. We then derive surface descriptors including roughness, dielectric constant, and degree of volume scatter. Radar backscatter on Titan is well-modeled as a superposition of large-scale surface scattering (quasispecular scattering) together with a combination of small-scale surface scattering and subsurface volume scattering (diffuse scattering). The viewing geometry determines which scattering mechanism is strongest. At low incidence angles, quasispecular scatter dominates the radar backscatter return. At higher incidence angles (angles greater than ~30°), diffuse scatter dominates the return. We use a composite model to separate the two scattering regimes; we model the quasispecular term with a combination of two traditional backscatter laws (we consider the Hagfors, Gaussian, and exponential models), following a technique developed by Sultan-Salem and Tyler [1], and we model the diffuse term, which encompasses both diffuse mechanisms, with a simple cosine power law. Using this total composite model, we analyze the backscatter curves of all features classes on Titan for which we have adequate angular coverage. In most cases, we find that the superposition of the Hagfors law with the exponential law best models the quasispecular response. A generalized geometric optics approach permits us to combine the best-fit parameters from each component of the composite model to yield a single value for the surface dielectric constant and RMS slope [1]. In this way, we map the relative variation of composition and wavelength-scale structure across the surface. We also map the variation of radar albedo across the analyzed features, as well as the relative prevalence of the different scattering mechanisms through the measured ratio of diffuse power to quasispecular power. These map products help to constrain how different geological processes might be interacting on a global scale. [1] A. K. Sultan-Salem, G. L. Tyler, JGR 112, 2007.

Stress in recrystallized quartz by electron backscatter diffraction mapping

NASA Astrophysics Data System (ADS)

Llana-Fúnez, S.

2017-07-01

The long-term state of stress at middle and lower crustal depths can be estimated through the study of the microstructure of exhumed rocks from active and/or ancient shear zones. Constitutive equations for deformation mechanisms in experimentally deformed rocks relate differential stress to the size of recrystallized grains. Cross et al. (2017) take advantage of electron backscatter diffraction mapping to systematically separate new recrystallized grains from host grains on the basis of the measurable lattice distorsion within the grains. They produce the first calibrated piezometer for quartz with this technique, reproducing within error a previous calibration based on optical microscopy.

Microbialite Morphologies and Distributions-Geoacoustic Survey with an AUV of Pavilion Lake, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Gutsche, J. R.; Trembanis, A. C.

2010-12-01

With advances in lake bottom mapping it has been observed that modern microbialites, much like the ancient stromatolites, thrive in freshwater lake environments. Previously collected data shows that a diverse community of living stromatolites are present within Pavilion Lake (Laval et al., 2000, Lim et al., 2009). An additional comprehensive data set was collected in June-July 2010. By building on the previous dataset it is possible to compare two high-resolution geoacoustic datasets. Using Autonomous Underwater Vehicles (AUVs) as exploration platforms to conduct surveys of the lake bottom, very high-resolution sonar data has been collected. The data collected in June-July 2010 is composed of 125 km of AUV trackline. This length of trackline allowed for survey coverage of nearly the entire lake bottom. The Gavia AUV used for this survey collected bathymetry data collocated with backscatter information. The data has been processed and gridded to 1m, with specific high value areas gridded to a finer 0.5m. The bathymetric data was compiled to create a base map of the floor of Pavilion Lake. Backscatter data was also collected and processed using the same 1m grid resolution. After the backscatter data was processed, it was draped over the bathymetry map of Pavilion Lake. The tools offered within the Fledermaus software package allow for the bathymetry data to be analyzed with respect to slope and rugosity. By analyzing this dense phase measuring bathymetric sonar of the lake bottom, with respect to slope and rugosity, it is possible to map the morphological trends of the stromatolites. Additionally, the ability to compare two datasets allows for erosional changes in the lake bottom to be identified. The bathymetry data allows for the quantitative analysis of bed forms within Pavilion Lake, allowing for a better understanding of microbialite morphologies. The backscatter data is increasingly important to the Pavilion Lake project because of the location and general surroundings of the lake. The lake itself is located in a limestone canyon, which frequently sustains erosional episodes. The backscatter data allows for the differentiation between erosional deposits and microbial mounds. The combination of backscatter and bathymetry allows for a further understanding of bedforms and microbialite growth patterns.

Calibrating nadir striped artifacts in a multibeam backscatter image using the equal mean-variance fitting model

NASA Astrophysics Data System (ADS)

Yang, Fanlin; Zhao, Chunxia; Zhang, Kai; Feng, Chengkai; Ma, Yue

2017-07-01

Acoustic seafloor classification with multibeam backscatter measurements is an attractive approach for mapping seafloor properties over a large area. However, artifacts in the multibeam backscatter measurements prevent accurate characterization of the seafloor. In particular, the backscatter level is extremely strong and highly variable in the near-nadir region due to the specular echo phenomenon. Consequently, striped artifacts emerge in the backscatter image, which can degrade the classification accuracy. This study focuses on the striped artifacts in multibeam backscatter images. To this end, a calibration algorithm based on equal mean-variance fitting is developed. By fitting the local shape of the angular response curve, the striped artifacts are compressed and moved according to the relations between the mean and variance in the near-nadir and off-nadir region. The algorithm utilized the measured data of near-nadir region and retained the basic shape of the response curve. The experimental results verify the high performance of the proposed method.

Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars

NASA Astrophysics Data System (ADS)

Wadiasingh, Zorawar; Baring, Matthew G.; Gonthier, Peter L.; Harding, Alice K.

2018-02-01

Hard, nonthermal, persistent pulsed X-ray emission extending between 10 and ∼150 keV has been observed in nearly 10 magnetars. For inner-magnetospheric models of such emission, resonant inverse Compton scattering of soft thermal photons by ultrarelativistic charges is the most efficient production mechanism. We present angle-dependent upscattering spectra and pulsed intensity maps for uncooled, relativistic electrons injected in inner regions of magnetar magnetospheres, calculated using collisional integrals over field loops. Our computations employ a new formulation of the QED Compton scattering cross section in strong magnetic fields that is physically correct for treating important spin-dependent effects in the cyclotron resonance, thereby producing correct photon spectra. The spectral cutoff energies are sensitive to the choices of observer viewing geometry, electron Lorentz factor, and scattering kinematics. We find that electrons with energies ≲15 MeV will emit most of their radiation below 250 keV, consistent with inferred turnovers for magnetar hard X-ray tails. More energetic electrons still emit mostly below 1 MeV, except for viewing perspectives sampling field-line tangents. Pulse profiles may be singly or doubly peaked dependent on viewing geometry, emission locale, and observed energy band. Magnetic pair production and photon splitting will attenuate spectra to hard X-ray energies, suppressing signals in the Fermi-LAT band. The resonant Compton spectra are strongly polarized, suggesting that hard X-ray polarimetry instruments such as X-Calibur, or a future Compton telescope, can prove central to constraining model geometry and physics.

Airborne detection of oceanic turbidity cell structure using depth-resolved laser-induced water Raman backscatter

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1983-01-01

Airborne laser-induced, depth-resolved water Raman backscatter is useful in the detection and mapping of water optical transmission variations. This test, together with other field experiments, has identified the need for additional field experiments to resolve the degree of the contribution to the depth-resolved, Raman-backscattered signal waveform that is due to (1) sea surface height or elevation probability density; (2) off-nadir laser beam angle relative to the mean sea surface; and (3) the Gelbstoff fluorescence background, and the analytical techniques required to remove it. When converted to along-track profiles, the waveforms obtained reveal cells of a decreased Raman backscatter superimposed on an overall trend of monotonically decreasing water column optical transmission.

Multibeam Sonar Mapping and Modeling of a Submerged Bryophyte Mat in Crater Lake, Oregon

USGS Publications Warehouse

Dartnell, Peter; Collier, Robert; Buktenica, Mark; Jessup, Steven; Girdner, Scott; Triezenberg, Peter

2008-01-01

Traditionally, multibeam data have been used to map sea floor or lake floor morphology as well as the distribution of surficial facies in order to characterize the geologic component of benthic habitats. In addition to using multibeam data for geologic studies, we want to determine if these data can also be used directly to map the distribution of biota. Multibeam bathymetry and acoustic backscatter data collected in Crater Lake, Oregon, in 2000 are used to map the distribution of a deep-water bryophyte mat, which will be extremely useful for understanding the overall ecology of the lake. To map the bryophyte's distribution, depth range, acoustic backscatter intensity, and derived bathymetric index grids are used as inputs into a hierarchical decision-tree classification model. Observations of the bryophyte mat from over 23 line kilometers of lake-floor video collected in the summer of 2006 are used as controls for the model. The resulting map matches well with ground-truth information and shows that the bryophyte mat covers most of the platform surrounding Wizard Island as well as on outcrops around the caldera wall.

Shaded seafloor relief, backscatter strength, and surficial geology; German Bank, Scotian Shelf, offshore Nova Scotia

USGS Publications Warehouse

Todd, B.J.; Valentine, Page C.

2010-01-01

This map is part of a three-map series of German Bank, located on the Scotian Shelf off southern Nova Scotia.  This map is the product of a number of surveys (1997-2003) that used a multibeam sonar system to map 5321 km2 of the seafloor.  Other surveys collected geological data for scientific interpretation.  This map sheet shows the seafloor topography of German Bank in shaded-relief view and seafloor depth (coded by colour) at a scale of 1:1000,000.  Topographic contours generated from the multibeam data are shown (in white) on the colour-coded multibeam topography at a depth interval of 20 m.  Bathymetic contours (in blue) outside the multibeam survey area, presented at a depth interval of 10 m, are from the Natural Resource Map series (Canadian Hydrographic Service, 1967, 1971a, 1971b, 1972). Sheet 2 shows coloured backscatter strength in shaded-relief view.  Sheet 3 shows seafloor topography in shaded-relief view with colour-coded surficial geological units.

Monitoring monthly surface water dynamics of Dongting Lake using Sentinel-1 data at 10 m.

PubMed

Xing, Liwei; Tang, Xinming; Wang, Huabin; Fan, Wenfeng; Wang, Guanghui

2018-01-01

High temporal resolution water distribution maps are essential for surface water monitoring because surface water exhibits significant inner-annual variation. Therefore, high-frequency remote sensing data are needed for surface water mapping. Dongting Lake, the second-largest freshwater lake in China, is famous for the seasonal fluctuations of its inundation extents in the middle reaches of the Yangtze River. It is also greatly affected by the Three Gorges Project. In this study, we used Sentinel-1 data to generate surface water maps of Dongting Lake at 10 m resolution. First, we generated the Sentinel-1 time series backscattering coefficient for VH and VV polarizations at 10 m resolution by using a monthly composition method. Second, we generated the thresholds for mapping surface water at 10 m resolution with monthly frequencies using Sentinel-1 data. Then, we derived the monthly surface water distribution product of Dongting Lake in 2016, and finally, we analyzed the inner-annual surface water dynamics. The results showed that: (1) The thresholds were -21.56 and -15.82 dB for the backscattering coefficients for VH and VV, respectively, and the overall accuracy and Kappa coefficients were above 95.50% and 0.90, respectively, for the VH backscattering coefficient, and above 94.50% and 0.88, respectively, for the VV backscattering coefficient. The VV backscattering coefficient achieved lower accuracy due to the effect of the wind causing roughness on the surface of the water. (2) The maximum and minimum areas of surface water were 2040.33 km 2 in July, and 738.89 km 2 in December. The surface water area of Dongting Lake varied most significantly in April and August. The permanent water acreage in 2016 was 556.35 km 2 , accounting for 19.65% of the total area of Dongting Lake, and the acreage of seasonal water was 1525.21 km 2 . This study proposed a method to automatically generate monthly surface water at 10 m resolution, which may contribute to monitoring surface water in a timely manner.

MAPPING BATHYMETRY AND BOTTOM TYPE IN A SHALLOW ESTUARY

EPA Science Inventory

Bathymetry and bottom type are important in characterizing estuaries and their ecology but hard to map, especially in shallow estuaries. Acoustic backscattering was used to remotely sense these properties in the shallow Slocums River Estuary of Massachusetts. Acoustic pulses were...

Design study of an optical cavity for a future photon collider at ILC

NASA Astrophysics Data System (ADS)

Klemz, G.; Mönig, K.; Will, I.

2006-08-01

Hard photons well above 100 GeV have to be generated in a future photon collider which essentially will be based on the infrastructure of the planned International Linear Collider (ILC). The energy of near-infrared laser photons will be boosted by Compton backscattering against a high-energy relativistic electron beam. For high effectiveness, a very powerful laser system is required that exceeds today's state-of-the-art capabilities. In this paper a design of an auxiliary passive cavity is discussed that resonantly enhances the peak-power of the laser. The properties and prospects of such a cavity are addressed on the basis of the specifications for the European TeV Energy Superconducting Linear Accelerator (TESLA) proposal. Those of the ILC are expected to be similar.

Application of Satellite SAR Imagery in Mapping the Active Layer of Arctic Permafrost

NASA Technical Reports Server (NTRS)

Li, Shu-Sun; Romanovsky, V.; Lovick, Joe; Wang, Z.; Peterson, Rorik

2003-01-01

A method of mapping the active layer of Arctic permafrost using a combination of conventional synthetic aperture radar (SAR) backscatter and more sophisticated interferometric SAR (INSAR) techniques is proposed. The proposed research is based on the sensitivity of radar backscatter to the freeze and thaw status of the surface soil, and the sensitivity of INSAR techniques to centimeter- to sub-centimeter-level surface differential deformation. The former capability of SAR is investigated for deriving the timing and duration of the thaw period for surface soil of the active layer over permafrost. The latter is investigated for the feasibility of quantitative measurement of frost heaving and thaw settlement of the active layer during the freezing and thawing processes. The resulting knowledge contributes to remote sensing mapping of the active layer dynamics and Arctic land surface hydrology.

Los Angeles and San Diego Margin High-Resolution Multibeam Bathymetry and Backscatter Data

USGS Publications Warehouse

Dartnell, Peter; Gardner, James V.; Mayer, Larry A.; Hughes-Clarke, John E.

2004-01-01

Summary -- The U.S. Geological Survey in cooperation with the University of New Hampshire and the University of New Brunswick mapped the nearshore regions off Los Angeles and San Diego, California using multibeam echosounders. Multibeam bathymetry and co-registered, corrected acoustic backscatter were collected in water depths ranging from about 3 to 900 m offshore Los Angeles and in water depths ranging from about 17 to 1230 m offshore San Diego. Continuous, 16-m spatial resolution, GIS ready format data of the entire Los Angeles Margin and San Diego Margin are available online as separate USGS Open-File Reports. For ongoing research, the USGS has processed sub-regions within these datasets at finer resolutions. The resolution of each sub-region was determined by the density of soundings within the region. This Open-File Report contains the finer resolution multibeam bathymetry and acoustic backscatter data that the USGS, Western Region, Coastal and Marine Geology Team has processed into GIS ready formats as of April 2004. The data are available in ArcInfo GRID and XYZ formats. See the Los Angeles or San Diego maps for the sub-region locations. These datasets in their present form were not originally intended for publication. The bathymetry and backscatter have data-collection and processing artifacts. These data are being made public to fulfill a Freedom of Information Act request. Care must be taken not to confuse artifacts with real seafloor morphology and acoustic backscatter.

Combining pixel and object based image analysis of ultra-high resolution multibeam bathymetry and backscatter for habitat mapping in shallow marine waters

NASA Astrophysics Data System (ADS)

Ierodiaconou, Daniel; Schimel, Alexandre C. G.; Kennedy, David; Monk, Jacquomo; Gaylard, Grace; Young, Mary; Diesing, Markus; Rattray, Alex

2018-06-01

Habitat mapping data are increasingly being recognised for their importance in underpinning marine spatial planning. The ability to collect ultra-high resolution (cm) multibeam echosounder (MBES) data in shallow waters has facilitated understanding of the fine-scale distribution of benthic habitats in these areas that are often prone to human disturbance. Developing quantitative and objective approaches to integrate MBES data with ground observations for predictive modelling is essential for ensuring repeatability and providing confidence measures for habitat mapping products. Whilst supervised classification approaches are becoming more common, users are often faced with a decision whether to implement a pixel based (PB) or an object based (OB) image analysis approach, with often limited understanding of the potential influence of that decision on final map products and relative importance of data inputs to patterns observed. In this study, we apply an ensemble learning approach capable of integrating PB and OB Image Analysis from ultra-high resolution MBES bathymetry and backscatter data for mapping benthic habitats in Refuge Cove, a temperate coastal embayment in south-east Australia. We demonstrate the relative importance of PB and OB seafloor derivatives for the five broad benthic habitats that dominate the site. We found that OB and PB approaches performed well with differences in classification accuracy but not discernible statistically. However, a model incorporating elements of both approaches proved to be significantly more accurate than OB or PB methods alone and demonstrate the benefits of using MBES bathymetry and backscatter combined for class discrimination.

Sea floor maps showing topography, sun-illuminated topography, and backscatter intensity of the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts

USGS Publications Warehouse

Valentine, P.C.; Middleton, T.J.; Fuller, S.J.

2000-01-01

This data set contains the sea floor topographic contours, sun-illuminated topographic imagery, and backscatter intensity generated from a multibeam sonar survey of the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts, an area of approximately 1100 square nautical miles. The Stellwagen Bank NMS Mapping Project is designed to provide detailed maps of the Stellwagen Bank region's environments and habitats and the first complete multibeam topographic and sea floor characterization maps of a significant region of the shallow EEZ. Data were collected on four cruises over a two year period from the fall of 1994 to the fall of 1996. The surveys were conducted aboard the Candian Hydrographic Service vessel Frederick G. Creed, a SWATH (Small Waterplane Twin Hull) ship that surveys at speeds of 16 knots. The multibeam data were collected utilizing a Simrad Subsea EM 1000 Multibeam Echo Sounder (95 kHz) that is permanently installed in the hull of the Creed.

Nanometres-resolution Kikuchi patterns from materials science specimens with transmission electron forward scatter diffraction in the scanning electron microscope.

PubMed

Brodusch, N; Demers, H; Gauvin, R

2013-04-01

A charge-coupled device camera of an electron backscattered diffraction system in a scanning electron microscope was positioned below a thin specimen and transmission Kikuchi patterns were collected. Contrary to electron backscattered diffraction, transmission electron forward scatter diffraction provides phase identification and orientation mapping at the nanoscale. The minimum Pd particle size for which a Kikuchi diffraction pattern was detected and indexed reliably was 5.6 nm. An orientation mapping resolution of 5 nm was measured at 30 kV. The resolution obtained with transmission electron forward scatter diffraction was of the same order of magnitude than that reported in electron nanodiffraction in the transmission electron microscope. An energy dispersive spectrometer X-ray map and a transmission electron forward scatter diffraction orientation map were acquired simultaneously. The high-resolution chemical, phase and orientation maps provided at once information on the chemical form, orientation and coherency of precipitates in an aluminium-lithium 2099 alloy. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Quantitative use of multiincidence-angle SAR for geologic mapping

NASA Technical Reports Server (NTRS)

Farr, T. G.; Albee, A. L.; Evans, D. L.; Solomon, J. E.; Daily, M. I.; Labotka, T. C.; Smith, M. O.

1984-01-01

It is proposed that techniques be developed and used for quantitative interpretation of shuttle imaging radar-B (SIR-B) data for lithologic identification and mapping. The use of backscatter versus incidence angle signatures derived from SIR-B images is to be investigated. The use of SIR-B with other sensors for geologic mapping is also to be considered. Anticipated results are discussed in terms of geologic mapping.

Investigation of light scattering characteristics of individual leukocytes using three-dimensional refractive index maps

NASA Astrophysics Data System (ADS)

Sung, Kung-Bin; Lin, Yang-Hsien; Lin, Fong-jheng; Hsieh, Chao-Mao; Wu, Shang-Ju

2017-04-01

Three-dimensional (3D) refractive-index (RI) microscopy is an emerging technique suitable for live-cell imaging due to its label-free and fast 3D imaging capabilities. We have developed a common-path system to acquire 3D RI microscopic images of cells with excellent speed and stability. After obtaining 3D RI distributions of individual leukocytes, we used a 3D finite-difference time-domain tool to study light scattering properties. Backscattering spectra of lymphocytes, monocytes and neutrophils are different from each other. Backscattering spectra of lymphocytes matched well with those of homogeneous spheres as predicted by Mie theory while backscattering spectra of neutrophils are significantly more intense than those of the other two types. This suggests the possibility of classifying the three types of leukocytes based on backscattering.

Predicted seafloor facies of Central Santa Monica Bay, California

USGS Publications Warehouse

Dartnell, Peter; Gardner, James V.

2004-01-01

Summary -- Mapping surficial seafloor facies (sand, silt, muddy sand, rock, etc.) should be the first step in marine geological studies and is crucial when modeling sediment processes, pollution transport, deciphering tectonics, and defining benthic habitats. This report outlines an empirical technique that predicts the distribution of seafloor facies for a large area offshore Los Angeles, CA using high-resolution bathymetry and co-registered, calibrated backscatter from multibeam echosounders (MBES) correlated to ground-truth sediment samples. The technique uses a series of procedures that involve supervised classification and a hierarchical decision tree classification that are now available in advanced image-analysis software packages. Derivative variance images of both bathymetry and acoustic backscatter are calculated from the MBES data and then used in a hierarchical decision-tree framework to classify the MBES data into areas of rock, gravelly muddy sand, muddy sand, and mud. A quantitative accuracy assessment on the classification results is performed using ground-truth sediment samples. The predicted facies map is also ground-truthed using seafloor photographs and high-resolution sub-bottom seismic-reflection profiles. This Open-File Report contains the predicted seafloor facies map as a georeferenced TIFF image along with the multibeam bathymetry and acoustic backscatter data used in the study as well as an explanation of the empirical classification process.

A Three-Dimensional Analysis of the Galactic Gamma-Ray Emission Resulting from Cosmic-Ray Interactions with the Interstellar Gas and Radiation Fields

NASA Technical Reports Server (NTRS)

Sodroski, Thomas J.; Dwek, Eli

2000-01-01

The primary task objective is to construct a 3-D model for the distribution of high-energy (20 MeV - 30 GeV) gamma-ray emission in the Galactic disk. Under this task the contractor will utilize data from the EGRET instrument on the Compton Gamma-Ray Observatory, H I and CO surveys, radio-continuum surveys at 408 MHz, 1420 MHz, 5 GHz, and 19 GHz, the COBE Diffuse Infrared Background Experiment (DIRBE) all-sky maps from 1 to 240 microns, and ground-based B, V, J, H, and K photometry. The respective contributions to the gamma-ray emission from cosmic ray/matter interactions, inverse Compton scattering, and extragalactic emission will be determined.

Terrestrial Gamma-Ray Flashes (TGFs)

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

2010-01-01

This slide presentation reviews the observation of Terrestrial Gamma Ray Flashes (TGFs) by Gamma-Ray Telescopes. These were: (1) BATSE /Compton Observatory, (2) Solar Spectroscopic Imager, (3) AGILE Gamma-ray Telescope, and (4) Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope. It contains charts which display the counts over time, a map or the TGFs observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). and a map showing the latitude and longitude of 85 of the TGFs observed by the Fermi GBM.

Snow Cover Mapping and Ice Avalanche Monitoring from the Satellite Data of the Sentinels

NASA Astrophysics Data System (ADS)

Wang, S.; Yang, B.; Zhou, Y.; Wang, F.; Zhang, R.; Zhao, Q.

2018-04-01

In order to monitor ice avalanches efficiently under disaster emergency conditions, a snow cover mapping method based on the satellite data of the Sentinels is proposed, in which the coherence and backscattering coefficient image of Synthetic Aperture Radar (SAR) data (Sentinel-1) is combined with the atmospheric correction result of multispectral data (Sentinel-2). The coherence image of the Sentinel-1 data could be segmented by a certain threshold to map snow cover, with the water bodies extracted from the backscattering coefficient image and removed from the coherence segment result. A snow confidence map from Sentinel-2 was used to map the snow cover, in which the confidence values of the snow cover were relatively high. The method can make full use of the acquired SAR image and multispectral image under emergency conditions, and the application potential of Sentinel data in the field of snow cover mapping is exploited. The monitoring frequency can be ensured because the areas obscured by thick clouds are remedied in the monitoring results. The Kappa coefficient of the monitoring results is 0.946, and the data processing time is less than 2 h, which meet the requirements of disaster emergency monitoring.

Mapping Land Cover Types in Amazon Basin Using 1km JERS-1 Mosaic

NASA Technical Reports Server (NTRS)

Saatchi, Sassan S.; Nelson, Bruce; Podest, Erika; Holt, John

2000-01-01

In this paper, the 100 meter JERS-1 Amazon mosaic image was used in a new classifier to generate a I km resolution land cover map. The inputs to the classifier were 1 km resolution mean backscatter and seven first order texture measures derived from the 100 m data by using a 10 x 10 independent sampling window. The classification approach included two interdependent stages: 1) a supervised maximum a posteriori Bayesian approach to classify the mean backscatter image into 5 general land cover categories of forest, savannah, inundated, white sand, and anthropogenic vegetation classes, and 2) a texture measure decision rule approach to further discriminate subcategory classes based on taxonomic information and biomass levels. Fourteen classes were successfully separated at 1 km scale. The results were verified by examining the accuracy of the approach by comparison with the IBGE and the AVHRR 1 km resolution land cover maps.

Planck 2015 results: XXII. A map of the thermal Sunyaev-Zeldovich effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aghanim, N.; Arnaud, M.; Ashdown, M.

In this article, we have constructed all-sky Compton parameters maps, y-maps, of the thermal Sunyaev-Zeldovich (tSZ) effect by applying specifically tailored component separation algorithms to the 30 to 857 GHz frequency channel maps from the Planck satellite. These reconstructed y-maps are delivered as part of the Planck 2015 release. The y-maps are characterized in terms of noise properties and residual foreground contamination, mainly thermal dust emission at large angular scales, and cosmic infrared background and extragalactic point sources at small angular scales. Specific masks are defined to minimize foreground residuals and systematics. Using these masks, we compute the y-map angularmore » power spectrum and higher order statistics. From these we conclude that the y-map is dominated by tSZ signal in the multipole range, 20« less

Planck 2015 results: XXII. A map of the thermal Sunyaev-Zeldovich effect

DOE PAGES

Aghanim, N.; Arnaud, M.; Ashdown, M.; ...

2016-09-20

In this article, we have constructed all-sky Compton parameters maps, y-maps, of the thermal Sunyaev-Zeldovich (tSZ) effect by applying specifically tailored component separation algorithms to the 30 to 857 GHz frequency channel maps from the Planck satellite. These reconstructed y-maps are delivered as part of the Planck 2015 release. The y-maps are characterized in terms of noise properties and residual foreground contamination, mainly thermal dust emission at large angular scales, and cosmic infrared background and extragalactic point sources at small angular scales. Specific masks are defined to minimize foreground residuals and systematics. Using these masks, we compute the y-map angularmore » power spectrum and higher order statistics. From these we conclude that the y-map is dominated by tSZ signal in the multipole range, 20« less

Analysis of seafloor backscatter strength dependence on the survey azimuth using multibeam echosounder data

NASA Astrophysics Data System (ADS)

Lurton, Xavier; Eleftherakis, Dimitrios; Augustin, Jean-Marie

2018-06-01

The sediment backscatter strength measured by multibeam echosounders is a key feature for seafloor mapping either qualitative (image mosaics) or quantitative (extraction of classifying features). An important phenomenon, often underestimated, is the dependence of the backscatter level on the azimuth angle imposed by the survey line directions: strong level differences at varying azimuth can be observed in case of organized roughness of the seabed, usually caused by tide currents over sandy sediments. This paper presents a number of experimental results obtained from shallow-water cruises using a 300-kHz multibeam echosounder and specially dedicated to the study of this azimuthal effect, with a specific configuration of the survey strategy involving a systematic coverage of reference areas following "compass rose" patterns. The results show for some areas a very strong dependence of the backscatter level, up to about 10-dB differences at intermediate oblique angles, although the presence of these ripples cannot be observed directly—neither from the bathymetry data nor from the sonar image, due to the insufficient resolution capability of the sonar. An elementary modeling of backscattering from rippled interfaces explains and comforts these observations. The consequences of this backscatter dependence upon survey azimuth on the current strategies of backscatter data acquisition and exploitation are discussed.

Texture as a basis for acoustic classification of substrate in the nearshore region

NASA Astrophysics Data System (ADS)

Dennison, A.; Wattrus, N. J.

2016-12-01

Segmentation and classification of substrate type from two locations in Lake Superior, are predicted using multivariate statistical processing of textural measures derived from shallow-water, high-resolution multibeam bathymetric data. During a multibeam sonar survey, both bathymetric and backscatter data are collected. It is well documented that the statistical characteristic of a sonar backscatter mosaic is dependent on substrate type. While classifying the bottom-type on the basis on backscatter alone can accurately predict and map bottom-type, it lacks the ability to resolve and capture fine textural details, an important factor in many habitat mapping studies. Statistical processing can capture the pertinent details about the bottom-type that are rich in textural information. Further multivariate statistical processing can then isolate characteristic features, and provide the basis for an accurate classification scheme. Preliminary results from an analysis of bathymetric data and ground-truth samples collected from the Amnicon River, Superior, Wisconsin, and the Lester River, Duluth, Minnesota, demonstrate the ability to process and develop a novel classification scheme of the bottom type in two geomorphologically distinct areas.

Applications of Radarsat-1 synthetic aperture radar imagery to assess hurricane-related flooding of coastal Louisiana

USGS Publications Warehouse

Kiage, L.M.; Walker, N.D.; Balasubramanian, S.; Babin, A.; Barras, J.

2005-01-01

The Louisiana coast is subjected to hurricane impacts including flooding of human settlements, river channels and coastal marshes, and salt water intrusion. Information on the extent of flooding is often required quickly for emergency relief, repairs of infrastructure, and production of flood risk maps. This study investigates the feasibility of using Radarsat-1 SAR imagery to detect flooded areas in coastal Louisiana after Hurricane Lili, October 2002. Arithmetic differencing and multi-temporal enhancement techniques were employed to detect flooding and to investigate relationships between backscatter and water level changes. Strong positive correlations (R2=0.7-0.94) were observed between water level and SAR backscatter within marsh areas proximate to Atchafalaya Bay. Although variations in elevation and vegetation type did influence and complicate the radar signature at individual sites, multi-date differences in backscatter largely reflected the patterns of flooding within large marsh areas. Preliminary analyses show that SAR imagery was not useful in mapping urban flooding in New Orleans after Hurricane Katrina's landfall on 29 August 2005. ?? 2005 Taylor & Francis.

Recovery of singularities from a backscattering Born approximation for a biharmonic operator in 3D

NASA Astrophysics Data System (ADS)

Tyni, Teemu

2018-04-01

We consider a backscattering Born approximation for a perturbed biharmonic operator in three space dimensions. Previous results on this approach for biharmonic operator use the fact that the coefficients are real-valued to obtain the reconstruction of singularities in the coefficients. In this text we drop the assumption about real-valued coefficients and also establish the recovery of singularities for complex coefficients. The proof uses mapping properties of the Radon transform.

Acoustic backscatter of the 1995 flood deposit on the Eel shelf

USGS Publications Warehouse

Borgeld, J.C.; Hughes-Clarke, John E.; Goff, John A.; Mayer, Larry A.; Curtis, Jennifer A.

1999-01-01

Acoustic swath mapping and sediment box coring conducted on the continental shelf near the mouth of the Eel River revealed regional variations in acoustic backscatter that can be related to the shelf sedimentology. The acoustic-backscatter variations observed on the shelf were unusually narrow compared to the response of similar sediment types documented in other areas. However, the acoustic data revealed four principal bottom types on the shelf that can be related to sedimentologic differences observed in cores. The four areas are: (1) low acoustic backscatter associated with the nearshore-sand facies and the prodelta terraces of the Eel and Mad rivers, composed of fine sands and coarse silts with low porosity; (2) high acoustic backscatter associated with fine silts characterized by high porosity and deposited by the 1995 flood of the Eel River; (3) intermediate acoustic backscatter in the outer-shelf muds, where clayey silts are accumulating and the 1995 flood apparently had limited direct effect; and (4) intermediate acoustic backscatter near the fringes of the 1995 flood deposits and in areas where the flood sediments were more disrupted by post-depositional processes. The highest acoustic backscatter was identified in areas where the 1995 flood sediments remained relatively intact and near the shelf surface into the summer of 1995. Cores collected from these areas contained wavy or lenticular bedding. The rapid deposition of the high-porosity muddy layers results in better preservation of incorporated ripple forms than in areas less directly impacted by the flood deposit. The high-porosity muddy layers allow acoustic penetration into the sediments and result in greater acoustic backscatter from incorporated roughness elements.

Simulation Studies of Forest Structure using 3D Lidar and Radar Models

NASA Technical Reports Server (NTRS)

Sun, Guoqing; Ranson, K. Jon; Koetz, Benjamin; Liu, Dawei

2007-01-01

The use of lidars and radars to measure forest structure attributes such as height and biomass are being considered for future Earth Observation missions. Large footprint lidar makes a direct measurement of the heights of scatterers in the illuminated footprint and can yield information about the vertical profile of the canopy. Synthetic Aperture Radar (SAR) is known to sense the canopy volume, especially at longer wavelengths and is useful for estimating biomass. Interferometric SAR (InSAR) has been shown to yield forest canopy height information. For example, the height of scattering phase retrieved from InSAR data is considered to be correlated with the three height and the spatial structure of the forest stand. There is much interest in exploiting these technologies separately and together to get important information for carbon cycle and ecosystem science. More detailed information of the electromagnetic radiation interactions within forest canopies is needed. And backscattering models can be of much utility here. As part of a NASA funded project to explore data fusion, a three-dimensional (3D) coherent radar backscattering model and a 3D lidar backscatter models were used to investigate the use of large footprint lidar, SAR and InSAR for characterizing realistic forest scenes. For this paper, we use stem maps and other forest measurements to develop a realistic spatial structure of a spruce-hemlock forest canopy found in Maine, USA. The radar and lidar models used measurements of the 3D forest scene as input and simulated the coherent radar backscattering signature and 1064nm energy backscatter, respectively. The relationships of backscatter derived forest structure were compared with field measurements. In addition, we also had detailed airborne lidar (Laser Imaging Vegetation Sensor, LVIS) data available over the stem map sites that was used to study the accuracies of tree height derived from modeled SAR backscatter and the scattering phase center retrieved from the simulated InSAR data will be compared with the height indices, or other structure parameters derived from the lidar data. These results will address the possible synergies between lidar and radar in data in terms of forest structural information.

Two-dimensional strain-mapping by electron backscatter diffraction and confocal Raman spectroscopy

NASA Astrophysics Data System (ADS)

Gayle, Andrew J.; Friedman, Lawrence H.; Beams, Ryan; Bush, Brian G.; Gerbig, Yvonne B.; Michaels, Chris A.; Vaudin, Mark D.; Cook, Robert F.

2017-11-01

The strain field surrounding a spherical indentation in silicon is mapped in two dimensions (2-D) using electron backscatter diffraction (EBSD) cross-correlation and confocal Raman spectroscopy techniques. The 200 mN indentation created a 4 μm diameter residual contact impression in the silicon (001) surface. Maps about 50 μm × 50 μm area with 128 pixels × 128 pixels were generated in several hours, extending, by comparison, assessment of the accuracy of both techniques to mapping multiaxial strain states in 2-D. EBSD measurements showed a residual strain field dominated by in-surface normal and shear strains, with alternating tensile and compressive lobes extending about three to four indentation diameters from the contact and exhibiting two-fold symmetry. Raman measurements showed a residual Raman shift field, dominated by positive shifts, also extending about three to four indentation diameters from the contact but exhibiting four-fold symmetry. The 2-D EBSD results, in combination with a mechanical-spectroscopic analysis, were used to successfully predict the 2-D Raman shift map in scale, symmetry, and shift magnitude. Both techniques should be useful in enhancing the reliability of microelectromechanical systems (MEMS) through identification of the 2-D strain fields in MEMS devices.

Geomorphology, acoustic backscatter, and processes in Santa Monica Bay from multibeam mapping.

PubMed

Gardner, James V; Dartnell, Peter; Mayer, Larry A; Hughes Clarke, John E

2003-01-01

Santa Monica Bay was mapped in 1996 using a high-resolution multibeam system, providing the first substantial update of the submarine geomorphology since the initial compilation by Shepard and Emery [(1941) Geol. Soc. Amer. Spec. Paper 31]. The multibeam mapping generated not only high-resolution bathymetry, but also coregistered, calibrated acoustic backscatter at 95 kHz. The geomorphology has been subdivided into six provinces; shelf, marginal plateau, submarine canyon, basin slope, apron, and basin. The dimensions, gradients, and backscatter characteristics of each province is described and related to a combination of tectonics, climate, sea level, and sediment supply. Fluctuations of eustatic sea level have had a profound effect on the area; by periodically eroding the surface of Santa Monica plateau, extending the mouth of the Los Angeles River to various locations along the shelf break, and by connecting submarine canyons to rivers. A wetter glacial climate undoubtedly generated more sediment to the rivers that then transported the increased sediment load to the low-stand coastline and canyon heads. The trends of Santa Monica Canyon and several bathymetric highs suggest a complex tectonic stress field that has controlled the various segments. There is no geomorphic evidence to suggest Redondo Canyon is fault controlled. The San Pedro fault can be extended more than 30 km to the northwest by the alignment of a series of bathymetric highs and abrupt changes in direction of channel thalwegs.

Space Radar Image of Manaus, Brazil

NASA Image and Video Library

1999-01-27

These two images were created using data from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR). On the left is a false-color image of Manaus, Brazil acquired April 12, 1994, onboard space shuttle Endeavour. In the center of this image is the Solimoes River just west of Manaus before it combines with the Rio Negro to form the Amazon River. The scene is around 8 by 8 kilometers (5 by 5 miles) with north toward the top. The radar image was produced in L-band where red areas correspond to high backscatter at HH polarization, while green areas exhibit high backscatter at HV polarization. Blue areas show low backscatter at VV polarization. The image on the right is a classification map showing the extent of flooding beneath the forest canopy. The classification map was developed by SIR-C/X-SAR science team members at the University of California,Santa Barbara. The map uses the L-HH, L-HV, and L-VV images to classify the radar image into six categories: Red flooded forest Green unflooded tropical rain forest Blue open water, Amazon river Yellow unflooded fields, some floating grasses Gray flooded shrubs Black floating and flooded grasses Data like these help scientists evaluate flood damage on a global scale. Floods are highly episodic and much of the area inundated is often tree-covered. http://photojournal.jpl.nasa.gov/catalog/PIA01712

Atwater Valley Deep-Towed Sidescan Sonar Imagery and Bathymetric Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joan M. Gardner; Mike Czarnecki; Rick Hagen

2005-11-22

The purpose of this project was to conduct detailed surface mapping of one of the areas drilled by the Joint Industry Project with ChevronTexaco to understand gas hydrates in the Gulf of Mexico. The gently sloping, mostly flat floor of the Mississippi Canyon is interrupted by mounds and depressions that presumably reflect the complex geology and geohydrology related to turbidite deposition and pervasive salt tectonism. The seafloor mounds we mapped in this study occur in approximately 1300 water depth along the floor of the Mississippi Canyon in lease block areas Atwater Valley 13 and 14. High resolution sidescan sonar (100more » kHz and 500 kHz) backscatter imagery, and chirp sub-bottom profiler data were collected using the DT1 deep-towed oceanographic mapping instrument, concentrating on the region directly adjacent to and surrounding two mounds identified as, mounds D and F, and in the region directly adjacent to and surrounding the mounds. The backscatter data have been mosaiced and normalized to provide information on the shape and extent of the mounds, the possible lateral extent of fauna, such as mussel and clam fields on the mounds, possible seep related flows and the occurrence of carbonate material. The extent of a mudflow can be mapped on the southeastern side of mound F. The backscatter data show extremely high-resolution detail about the shape, relief, and morphology of the mounds. This information, coupled with porewater chemistry , DTAGS and heatflow data form a coherent picture of possible mechanics for fluid venting and flora/fauna of the seeps in this region.« less

Long-term variation of radar-auroral backscatter and the interplanetary sector structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yeoman, T.K.; Burrage, M.D.; Lester, M.

Recurrent variation of geomagnetic activity at the {approximately}27-day solar rotation period and higher harmonics is a well-documented phenomenon. Auroral radar backscatter data from the Sweden and Britain Radar-Auroral Experiment (SABRE) radar provide a continuous time series from 1981 to the present which is a highly sensitive monitor of geomagnetic activity. In this study, Maximum Entropy Method (MEM) dynamic power spectra of SABRE backscatter data from 1981 to 1989, concurrent interplanetary magnetic field (IMF) and solar wind parameters from 1981 to 1987, and the Kp index since 1932 are examined. Data since 1977 are compared with previously published heliospheric current sheetmore » measurements mapped out from the solar photosphere. Stong periodic behavior is observed in the radar backscatter during the declining phase of solar cycle 21, but this periodicity disappears at the start of solar cycle 22. Similar behavior is observed in earlier solar cycles in the Kp spectra. Details of the radar backscatter, IMF, and solar wind spectra indicate that the solar wind momentum density is the dominant parameter in determining the backscatter periodicity. The temporal evolution of two- and four-sector structures, as predicted by SABRE backscatter spectra, throughout solar cycle 21 generally still agree well with heliospheric current sheet measurements. For one interval, however, there is evidence that evolution of the current sheet has occurred between the photospheric source surface and the Earth.« less

Acoustic mapping of the regional seafloor geology in and around Hawaiian ocean dredged-material disposal sites

USGS Publications Warehouse

Torresan, Michael E.; Gardner, James V.

2000-01-01

During January and February 1998 the U.S. Geological Survey Coastal and Marine Geology Team (USGS) conducted regional high-resolution multibeam mapping surveys of the area surrounding EPA-designated ocean disposal sites located offshore of the Hawaiian Islands of Oahu, Kauai, Maui, and Hawaii. The sites are all located within 5 nautical miles of shore on insular shelves or slopes. Regional maps were required of areas much larger than the disposal sites themselves to assess both the regional seafloor geology and the immediate vicinity of the disposal sites. The purpose of the disposal site surveys was to delimit the extent of disposal material by producing detailed bathymetric and backscatter maps of the seafloor with a ± 1 m spatial accuracy and <1% depth error. The advantage of using multibeam over conventional towed, single-beam sidescan sonar is that the multibeam data are accurately georeferenced for precise location of all imaged features. The multibeam produces a coregistered acoustic-backscatter map that is often required to locate individual disposal deposits. These data were collected by the USGS as part of its regional seafloor mapping and in support of ocean disposal site monitoring studies conducted in cooperation with the US Environmental Protection Agency (EPA) and the US Army Corps of Engineers (COE).

Mapping dynamics of deforestation and forest degradation in tropical forests using radar satellite data

NASA Astrophysics Data System (ADS)

Joshi, Neha; Mitchard, Edward TA; Woo, Natalia; Torres, Jorge; Moll-Rocek, Julian; Ehammer, Andrea; Collins, Murray; Jepsen, Martin R.; Fensholt, Rasmus

2015-03-01

Mapping anthropogenic forest disturbances has largely been focused on distinct delineations of events of deforestation using optical satellite images. In the tropics, frequent cloud cover and the challenge of quantifying forest degradation remain problematic. In this study, we detect processes of deforestation, forest degradation and successional dynamics, using long-wavelength radar (L-band from ALOS PALSAR) backscatter. We present a detection algorithm that allows for repeated disturbances on the same land, and identifies areas with slow- and fast-recovering changes in backscatter in close spatial and temporal proximity. In the study area in Madre de Dios, Peru, 2.3% of land was found to be disturbed over three years, with a false positive rate of 0.3% of area. A low, but significant, detection rate of degradation from sparse and small-scale selective logging was achieved. Disturbances were most common along the tri-national Interoceanic Highway, as well as in mining areas and areas under no land use allocation. A continuous spatial gradient of disturbance was observed, highlighting artefacts arising from imposing discrete boundaries on deforestation events. The magnitude of initial radar backscatter, and backscatter decrease, suggested that large-scale deforestation was likely in areas with initially low biomass, either naturally or since already under anthropogenic use. Further, backscatter increases following disturbance suggested that radar can be used to characterize successional disturbance dynamics, such as biomass accumulation in lands post-abandonment. The presented radar-based detection algorithm is spatially and temporally scalable, and can support monitoring degradation and deforestation in tropical rainforests with the use of products from ALOS-2 and the future SAOCOM and BIOMASS missions.

Thick target bremsstrahlung spectra for 1.00-, 1.25-, and 1.40-Mev electrons

USGS Publications Warehouse

Miller, W.; Motz, J.W.; Cialella, C.

1954-01-01

The spectrum of radiation produced by 1.0-, 1.25-, and 1.40-Mev electrons incident on a thick tungsten target was measured at 0A????and 90A????with the incident beam by a method involving the magnetic analysis of Compton electrons. The effects of electron scattering and energy loss in the target preclude any simple interpretation of this data to yield a differential bremsstrahlung cross section. However, an estimate of the spectra to be expected at 0A????and 90A????was obtained by combining the Sauter expression for the bremsstrahlung cross section with the available information on electron scatter and energy loss in the target and backscatter from the target. The reliability of the estimate is limited because the Sauter formula was calculated by using the Born approximation, the electron scattering calculations are applicable to an infinite medium only, and the backscatter was estimated empirically from Bothe's experimental data which were obtained with lower energy electrons (370 kev). Furthermore electron energy straggling was neglected. Nevertheless, the predicted spectral shapes at 0A????and 90A????and the relative intensities at these two angles are in qualitative agreement with the measured values. The absolute magnitudes of the measured intensities at both angles are about a factor of two greater than the predicted values. ?? 1954 The American Physical Society.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shedlock, Daniel; Dugan, Edward T.; Jacobs, Alan M.

X-ray backscatter radiography by selective detection (RSD) is a field tested and innovative approach to non-destructive evaluation (NDE). RSD is an enhanced single-side x-ray Compton backscatter imaging (CBI) technique which selectively detects scatter components to improve image contrast and quality. Scatter component selection is accomplished through a set of specially designed detectors with fixed and movable collimators. Experimental results have shown that this NDE technique can be used to detect boric acid deposition on a metallic plate through steel foil reflective insulation commonly covering reactor pressure vessels. The current system is capable of detecting boric acid deposits with sub-millimeter resolution,more » through such insulating materials. Industrial systems have been built for Lockheed Martin Space Co. and NASA. Currently the x-ray backscatter RSD scanning systems developed by the University of Florida are being used to inspect the spray-on foam insulation (SOFI) used on the external tank of the space shuttle. RSD inspection techniques have found subsurface cracking in the SOFI thought to be responsible for the foam debris which separated from the external tank during the last shuttle launch. These industrial scanning systems can be customized for many applications, and a smaller, lighter, more compact unit design is being developed. The smaller design is approximately four inches wide, three inches high, and about 12 inches in length. This smaller RSD system can be used for NDE of areas that cannot be reached with larger equipment. X-ray backscatter RSD is a proven technology that has been tested on a wide variety of materials and applications. Currently the system has been used to inspect materials such as aluminum, plastics, honeycomb laminates, reinforced carbon composites, steel, and titanium. The focus of RSD is for one-sided detection for applications where conventional non-destructive examination methods either will not work or give poor results. Acquired images have clearly shown, for a variety of conditions, that proper selection of x-ray field scatter components leads to a significant improvement in image quality and contrast. Improvements are significant enough in some cases that objects not visible to conventional CBI or transmission radiography become readily discernable with RSD. (authors)« less

Radar response to vegetation. [soil moisture mapping via microwave backscattering

NASA Technical Reports Server (NTRS)

Ulaby, F. T.

1975-01-01

Active microwave measurements of vegetation backscatter were conducted to determine the utility of radar in mapping soil moisture through vegetation and mapping crop types. Using a truck-mounted boom, spectral response data were obtained for four crop types (corn, milo, soybeans, and alfalfa) over the 4-8 GHz frequency band, at incidence angles of 0 to 70 degrees in 10-degree steps, and for all four linear polarization combinations. Based on a total of 125 data sets covering a wide range of soil moisture, content, system design criteria are proposed for each of the aforementioned objectives. Quantitative soil moisture determination was best achieved at the lower frequency end of the 4-8 GHz band using HH polarized waves in the 5- to 15-degree incidence angle range. A combination of low and high frequency measurements are suggested for classifying crop types. For crop discrimination, a dual-frequency dual-polarization (VV and cross) system operating at incidence angles above 40 degrees is suggested.

Guiding the Design of Radiation Imagers with Experimentally Benchmarked Geant4 Simulations for Electron-Tracking Compton Imaging

NASA Astrophysics Data System (ADS)

Coffer, Amy Beth

Radiation imagers are import tools in the modern world for a wide range of applications. They span the use-cases of fundamental sciences, astrophysics, medical imaging, all the way to national security, nuclear safeguards, and non-proliferation verification. The type of radiation imagers studied in this thesis were gamma-ray imagers that detect emissions from radioactive materials. Gamma-ray imagers goal is to localize and map the distribution of radiation within their specific field-of-view despite the fact of complicating background radiation that can be terrestrial, astronomical, and temporal. Compton imaging systems are one type of gamma-ray imager that can map the radiation around the system without the use of collimation. Lack of collimation enables the imaging system to be able to detect radiation from all-directions, while at the same time, enables increased detection efficiency by not absorbing incident radiation in non-sensing materials. Each Compton-scatter events within an imaging system generated a possible cone-surface in space that the radiation could have originated from. Compton imaging is limited in its reconstructed image signal-to-background due to these source Compton-cones overlapping with background radiation Compton-cones. These overlapping cones limit Compton imaging's detection-sensitivity in image space. Electron-tracking Compton imaging (ETCI) can improve the detection-sensitivity by measuring the Compton-scattered electron's initial trajectory. With an estimate of the scattered electron's trajectory, one can reduce the Compton-back-projected cone to a cone-arc, thus enabling faster radiation source detection and localization. However, the ability to measure the Compton-scattered electron-trajectories adds another layer of complexity to an already complex methodology. For a real-world imaging applications, improvements are needed in electron-track detection efficiency and in electron-track reconstruction. One way of measuring Compton-scattered electron-trajectories is with high-resolution Charged-Coupled Devices (CCDs). The proof-of-principle CCD-based ETCI experiment demonstrated the CCDs' ability to measure the Compton-scattered electron-tracks as a 2-dimensional image. Electron-track-imaging algorithms using the electron-track-image are able to determine the 3-dimensional electron-track trajectory within +/- 20 degrees. The work presented here is the physics simulations developed along side the experimental proof-of-principle experiment. The development of accurate physics modeling for multiple-layer CCDs based ETCI systems allow for the accurate prediction of future ETCI system performance. The simulations also enable quick development insights for system design, and they guide the development of electron-track reconstruction methods. The physics simulation efforts for this project looked closely at the accuracy of the Geant4 Monte Carlo methods for medium energy electron transport. In older version of Geant4 there were some discrepancies between the electron-tracking experimental measurements and the simulation results. It was determined that when comparing the electron dynamics of electrons at very high resolutions, Geant4 simulations must be fine tuned with careful choices for physics production cuts and electron physics stepping sizes. One result of this work is a CCDs Monte Carlo model that has been benchmarked to experimental findings and fully characterized for both photon and electron transport. The CCDs physics model now match to within 1 percent error of experimental results for scattered-electron energies below 500 keV. Following the improvements of the CCDs simulations, the performance of a realistic two-layer CCD-stack system was characterized. The realistic CCD-stack system looked at the effect of thin passive-layers on the CCDs' front face and back-contact. The photon interaction efficiency was calculated for the two-layer CCD-stack, and we found that there is a 90 percent probability of scattered-electrons from a 662 keV source to stay within a single active layer. This demonstrates the improved detection efficiency, which is one of the strengths of the CCDs' implementation as a ETCI system. The CCD-stack simulations also established that electron-tracks scattering from one CCDs layer to another could be reconstructed. The passive-regions on the CCD-stack mean that these inter-layer scattered-electron-tracks will always loose both angular information and energy information. Looking at the angular changes of these electrons scattering between the CCDs layers showed us there is not a strong energy dependence on the angular changes due to the passive-regions of the CCDs. The angular changes of the electron track are, for the most part, a function of the thickness of the thin back-layer of the CCDs. Lastly, an approach using CCD-stack simulations was developed to reconstruct the energy transport across dead-layers and its feasibility was demonstrated. Adding back this lost energy will limit the loss of energy resolution of the scatter-interactions. Energy resolution losses would negatively impacted the achievable image resolution from image reconstruction algorithms. Returning some of the energy back to the reconstructed electron-track will help retain the expected performance of the electron-track trajectory determination algorithm.

Design of sub-Angstrom compact free-electron laser source

NASA Astrophysics Data System (ADS)

Bonifacio, Rodolfo; Fares, Hesham; Ferrario, Massimo; McNeil, Brian W. J.; Robb, Gordon R. M.

2017-01-01

In this paper, we propose for first time practical parameters to construct a compact sub-Angstrom Free Electron Laser (FEL) based on Compton backscattering. Our recipe is based on using picocoulomb electron bunch, enabling very low emittance and ultracold electron beam. We assume the FEL is operating in a quantum regime of Self Amplified Spontaneous Emission (SASE). The fundamental quantum feature is a significantly narrower spectrum of the emitted radiation relative to classical SASE. The quantum regime of the SASE FEL is reached when the momentum spread of the electron beam is smaller than the photon recoil momentum. Following the formulae describing SASE FEL operation, realistic designs for quantum FEL experiments are proposed. We discuss the practical constraints that influence the experimental parameters. Numerical simulations of power spectra and intensities are presented and attractive radiation characteristics such as high flux, narrow linewidth, and short pulse structure are demonstrated.

Some problems of the detection of the high energy gamma-radiation in space

NASA Astrophysics Data System (ADS)

Fradkin, M. I.; Ginzburg, V. L.; Kurnosova, L. V.; Labensky, A. G.; Razorenov, L. A.; Rusakovich, M. A.; Topchiev, N. P.; Kaplin, V. A.; Runtso, M. F.; Gorchakov, E. V.; Ignatiev, P. P.

1995-05-01

Diffuse gamma radiation in the Galaxy has been measured with instruments onboard the COS-B and Compton Gamma Ray Observatory (CGRO) satellites from the tens of keV up to about 30 GeV. There is no experimental data at higher energies, but this data is very important for the spectrum of primary cosmic rays and the existence of neutralinos (hypothetical supersymmetrical particles which are supposed to constitute dark matter in the Galaxy and create gamma-quanta in the process of annihilation). The GAMMA-400 collaboration is working on the design of a telescope for gamma-ray measurements in the 10-1000 GeV range. The electronics of the GAMMA-400 eliminate some hindering effects, in particular the influence of backscattered gammas emitted by the very massive calorimeter (calorimeter albedo). The GAMMA-400 project may be realized in the near future if economic conditions in Russia are favorable.

Geologic Map of the Sif Mons Quadrangle (V-31), Venus

USGS Publications Warehouse

Copp, Duncan L.; Guest, John E.

2007-01-01

The Magellan spacecraft orbited Venus from August 10, 1990, until it plunged into the Venusian atmosphere on October 12, 1994. Magellan Mission objectives included (1) improving the knowledge of the geological processes, surface properties, and geologic history of Venus by analysis of surface radar characteristics, topography, and morphology and (2) improving the knowledge of the geophysics of Venus by analysis of Venusian gravity. The Sif Mons quadrangle of Venus includes lat 0? to 25? N. and long 330? to 0? E.; it covers an area of about 8.10 x 106 km2 (fig. 1). The data used to construct the geologic map were from the National Aeronautics and Space Administration (NASA) Magellan Mission. The area is also covered by Arecibo images, which were also consulted (Campbell and Campbell, 1990; Campbell and others, 1989). Data from the Soviet Venera orbiters do not cover this area. All of the SAR products were employed for geologic mapping. C1-MIDRs were used for general recognition of units and structures; F-MIDRs and F-MAPs were used for more specific examination of surface characteristics and structures. Where the highest resolution was required or some image processing was necessary to solve a particular mapping problem, the images were examined using the digital data on CD-ROMs. In cycle 1, the SAR incidence angles for images obtained for the Sif Mons quadrangle ranged from 44? to 46?; in cycle 3, they were between 25? and 26?. We use the term 'high backscatter' of a material unit to imply a rough surface texture at the wavelength scale used by Magellan SAR. Conversely, 'low backscatter' implies a smooth surface. In addition, altimetric, radiometric, and rms slope data were superposed on SAR images. Figure 2 shows altimetry data; figure 3 shows images of ancillary data for the quadrangle; and figure 4 shows backscatter coefficient for selected units. The interpretation of these data was discussed by Ford and others (1989, 1993). For corrected backscatter and numerical ancillary data see tables 1 and 2; these data allow comparison with units at different latitudes on the planet, where the visual appearance may differ because of a different incidence angle. Synthetic stereo images, produced by overlaying SAR images and altimetric data, were of great value in interpreting structures and stratigraphic relations.

Experiences from using Autonomous Underwater Vehicles and Synthetic Aperture Sonar for Sediment and Habitat Mapping

NASA Astrophysics Data System (ADS)

Thorsnes, T.; Bjarnadóttir, L. R.

2017-12-01

Emerging platforms and tools like autonomous underwater vehicles and synthetic aperture sonars provide interesting opportunities for making seabed mapping more efficient and precise. Sediment grain-size maps are an important product in their own right and a key input for habitat and biotope maps. National and regional mapping programmes are tasked with mapping large areas, and survey efficiency, data quality, and resulting map confidence are important considerations when selecting the mapping strategy. Since 2005, c. 175,000 square kilometres of the Norwegian continental shelf and continental slope has been mapped with respect to sediments, habitats and biodiversity, and pollution under the MAREANO programme (www.mareano.no). At present the sediment mapping is based on a combination of ship-borne multibeam bathymetry and backscatter, visual documentation using a towed video platform, and grab sampling. We have now tested a new approach, using an Autonomous Underwater Vehicle (AUV) as the survey platform for the collection of acoustic data (Synthetic Aperture Sonar (SAS), EM2040 bathymetry and backscatter) and visual data (still images using a TFish colour photo system). This pilot project was conducted together the Norwegian Hydrographic Service, the Institute of Marine Research (biology observations) and the Norwegian Defence Research Establishment (operation of ship and AUV). The test site reported here is the Vesterdjupet area, offshore Lofoten, northern Norway. The water depth is between 170 and 300 metres, with sediments ranging from gravel, cobbles and boulders to sandy mud. A cold-water coral reef, associated with bioclastic sediments was also present in the study area. The presentation will give an overview of the main findings and experiences gained from this pilot project with a focus on geological mapping and will also discuss the relevance of AUV-based mapping to large-area mapping programmes like MAREANO.

Slow neutron mapping technique for level interface measurement

NASA Astrophysics Data System (ADS)

Zain, R. M.; Ithnin, H.; Razali, A. M.; Yusof, N. H. M.; Mustapha, I.; Yahya, R.; Othman, N.; Rahman, M. F. A.

2017-01-01

Modern industrial plant operations often require accurate level measurement of process liquids in production and storage vessels. A variety of advanced level indicators are commercially available to meet the demand, but these may not suit specific need of situations. The neutron backscatter technique is exceptionally useful for occasional and routine determination, particularly in situations such as pressure vessel with wall thickness up to 10 cm, toxic and corrosive chemical in sealed containers, liquid petroleum gas storage vessels. In level measurement, high energy neutrons from 241Am-Be radioactive source are beamed onto a vessel. Fast neutrons are slowed down mostly by collision with hydrogen atoms of material inside the vessel. Parts of thermal neutron are bounced back towards the source. By placing a thermal detector next to the source, these backscatter neutrons can be measured. The number of backscattered neutrons is directly proportional to the concentration of the hydrogen atoms in front of the neutron detector. As the source and detector moved by the matrix around the side of the vessel, interfaces can be determined as long as it involves a change in hydrogen atom concentration. This paper presents the slow neutron mapping technique to indicate level interface of a test vessel.

Faraday rotation in the M87 radio/X-ray halo

NASA Technical Reports Server (NTRS)

Dennison, B.

1980-01-01

Comparison of polarization maps at various wavelengths demonstrates the existence of a large Faraday rotation uniform over the radio core of M87. Much of this rotation must be external to the core, lest it appear completely depolarized when the rotation is about 90 degrees. The Faraday rotation is shown to occur primarily in the surrounding radio/X-ray halo. Using the electron density inferred from X-ray observations, the magnetic field in the halo is found to be 2.5 microgauss. The deduced magnetic field strength permits an evaluation of the importance of Compton scattering of 3 K background photons by relativistic electrons in the radio halo. The emergent Compton-scattered spectrum is calculated, and its contribution to the observed X-ray flux is small, probably about a percent or so, while the rest is due to thermal bremsstrahlung.

Comparison of spectral radiance responsivity calibration techniques used for backscatter ultraviolet satellite instruments

NASA Astrophysics Data System (ADS)

Kowalewski, M. G.; Janz, S. J.

2015-02-01

Methods of absolute radiometric calibration of backscatter ultraviolet (BUV) satellite instruments are compared as part of an effort to minimize pre-launch calibration uncertainties. An internally illuminated integrating sphere source has been used for the Shuttle Solar BUV, Total Ozone Mapping Spectrometer, Ozone Mapping Instrument, and Global Ozone Monitoring Experiment 2 using standardized procedures traceable to national standards. These sphere-based spectral responsivities agree to within the derived combined standard uncertainty of 1.87% relative to calibrations performed using an external diffuser illuminated by standard irradiance sources, the customary spectral radiance responsivity calibration method for BUV instruments. The combined standard uncertainty for these calibration techniques as implemented at the NASA Goddard Space Flight Center’s Radiometric Calibration and Development Laboratory is shown to less than 2% at 250 nm when using a single traceable calibration standard.

Method and apparatus for remote measurement of terrestrial biomass

NASA Technical Reports Server (NTRS)

Johnson, Patrick W. (Inventor)

1999-01-01

Method and apparatus for remote measurement of terrestrial biomass contained in vegetative elements, such as large tree boles or trunks present in an area of interest. The method includes providing an airborne radar system, overflying the area of interest while directing radar energy having a frequency of under 400 MHz, and preferably between 80 and 120 MHz, toward the area of interest, using the radar system to collect backscatter data from the radar energy as a function of incidence angle and frequency, and using an inversion algorithm to determine a magnitude of the biomass from the backscatter data for each radar resolution cell. A biomass map is generated showing the magnitude of the biomass of the vegetative elements as a function of location on the map by using each resolution cell as a unique location thereon.

Backscatter Analysis Using Multi-Temporal SENTINEL-1 SAR Data for Crop Growth of Maize in Konya Basin, Turkey

NASA Astrophysics Data System (ADS)

Abdikan, S.; Sekertekin, A.; Ustunern, M.; Balik Sanli, F.; Nasirzadehdizaji, R.

2018-04-01

Temporal monitoring of crop types is essential for the sustainable management of agricultural activities on both national and global levels. As a practical and efficient tool, remote sensing is widely used in such applications. In this study, Sentinel-1 Synthetic Aperture Radar (SAR) imagery was utilized to investigate the performance of the sensor backscatter image on crop monitoring. Multi-temporal C-band VV and VH polarized SAR images were acquired simultaneously by in-situ measurements which was conducted at Konya basin, central Anatolia Turkey. During the measurements, plant height of maize plant was collected and relationship between backscatter values and plant height was analysed. The maize growth development was described under Biologische Bundesanstalt, bundessortenamt und CHemische industrie (BBCH). Under BBCH stages, the test site was classified as leaf development, stem elongation, heading and flowering in general. The correlation coefficient values indicated high correlation for both polarimetry during the early stages of the plant, while late stages indicated lower values in both polarimetry. As a last step, multi-temporal coverage of crop fields was analysed to map seasonal land use. To this aim, object based image classification was applied following image segmentation. About 80 % accuracies of land use maps were created in this experiment. As preliminary results, it is concluded that Sentinel-1 data provides beneficial information about plant growth. Dual-polarized Sentinel-1 data has high potential for multi-temporal analyses for agriculture monitoring and reliable mapping.

An optical storage cavity-based, Compton-backscatter x-ray source using the MKV free electron laser

NASA Astrophysics Data System (ADS)

Hadmack, Michael R.

A compact, high-brightness x-ray source is presently under development at the University of Hawai`i Free Electron Laser Laboratory. This source utilizes Compton backscattering of an infrared laser from a relativistic electron beam to produce a narrow beam of monochromatic x-rays. The scattering efficiency is greatly increased by tightly focusing the two beams at an interaction point within a near-concentric optical storage cavity, designed with high finesse to coherently stack the incident laser pulses and greatly enhance the number of photons available for scattering with the electron beam. This dissertation describes the effort and progress to integrate and characterize the most important and challenging aspects of the design of this system. A low-power, near-concentric, visible-light storage cavity has been constructed as a tool for the exploration of the performance, alignment procedures, and diagnostics required for the operation of a high power infrared storage cavity. The use of off-axis reflective focussing elements is essential to the design of the optical storage cavity, but requires exquisite alignment to minimize astigmatism and other optical aberrations. Experiments using a stabilized HeNe laser have revealed important performance characteristics, and allowed the development of critical alignment and calibration procedures, which can be directly applied to the high power infrared storage cavity. Integration of the optical and electron beams is similarly challenging. A scanning-wire beam profiler has been constructed and tested, which allows for high resolution measurement of the size and position of the laser and electron beams at the interaction point. This apparatus has demonstrated that the electron and laser beams can be co-aligned with a precision of less than 10 microm, as required to maximize the x-ray production rate. Equally important is the stabilization of the phase of the GHz repetition rate electron pulses arriving at the interaction point and driving the FEL. A feed-forward amplitude and phase compensation system has been built and demonstrated to substantially improve the uniformity of the electron bunch phase, thus enhancing both the laser performance and the beam stability required for efficient x-ray production. Results of all of these efforts are presented, together with a summary of future work.

Maximum a posteriori classification of multifrequency, multilook, synthetic aperture radar intensity data

NASA Technical Reports Server (NTRS)

Rignot, E.; Chellappa, R.

1993-01-01

We present a maximum a posteriori (MAP) classifier for classifying multifrequency, multilook, single polarization SAR intensity data into regions or ensembles of pixels of homogeneous and similar radar backscatter characteristics. A model for the prior joint distribution of the multifrequency SAR intensity data is combined with a Markov random field for representing the interactions between region labels to obtain an expression for the posterior distribution of the region labels given the multifrequency SAR observations. The maximization of the posterior distribution yields Bayes's optimum region labeling or classification of the SAR data or its MAP estimate. The performance of the MAP classifier is evaluated by using computer-simulated multilook SAR intensity data as a function of the parameters in the classification process. Multilook SAR intensity data are shown to yield higher classification accuracies than one-look SAR complex amplitude data. The MAP classifier is extended to the case in which the radar backscatter from the remotely sensed surface varies within the SAR image because of incidence angle effects. The results obtained illustrate the practicality of the method for combining SAR intensity observations acquired at two different frequencies and for improving classification accuracy of SAR data.

Knowledge-based decision tree approach for mapping spatial distribution of rice crop using C-band synthetic aperture radar-derived information

NASA Astrophysics Data System (ADS)

Mishra, Varun Narayan; Prasad, Rajendra; Kumar, Pradeep; Srivastava, Prashant K.; Rai, Praveen Kumar

2017-10-01

Updated and accurate information of rice-growing areas is vital for food security and investigating the environmental impact of rice ecosystems. The intent of this work is to explore the feasibility of dual-polarimetric C-band Radar Imaging Satellite-1 (RISAT-1) data in delineating rice crop fields from other land cover features. A two polarization combination of RISAT-1 backscatter, namely ratio (HH/HV) and difference (HH-HV), significantly enhanced the backscatter difference between rice and nonrice categories. With these inputs, a QUEST decision tree (DT) classifier is successfully employed to extract the spatial distribution of rice crop areas. The results showed the optimal polarization combination to be HH along with HH/HV and HH-HV for rice crop mapping with an accuracy of 88.57%. Results were further compared with a Landsat-8 operational land imager (OLI) optical sensor-derived rice crop map. Spatial agreement of almost 90% was achieved between outputs produced from Landsat-8 OLI and RISAT-1 data. The simplicity of the approach used in this work may serve as an effective tool for rice crop mapping.

Applications of interferometrically derived terrain slopes: Normalization of SAR backscatter and the interferometric correlation coefficient

NASA Technical Reports Server (NTRS)

Werner, Charles L.; Wegmueller, Urs; Small, David L.; Rosen, Paul A.

1994-01-01

Terrain slopes, which can be measured with Synthetic Aperture Radar (SAR) interferometry either from a height map or from the interferometric phase gradient, were used to calculate the local incidence angle and the correct pixel area. Both are required for correct thematic interpretation of SAR data. The interferometric correlation depends on the pixel area projected on a plane perpendicular to the look vector and requires correction for slope effects. Methods for normalization of the backscatter and interferometric correlation for ERS-1 SAR are presented.

California State Waters Map Series-Offshore of Point Reyes, California

USGS Publications Warehouse

Watt, Janet T.; Dartnell, Peter; Golden, Nadine E.; Greene, H. Gary; Erdey, Mercedes D.; Cochrane, Guy R.; Johnson, Samuel Y.; Hartwell, Stephen R.; Kvitek, Rikk G.; Manson, Michael W.; Endris, Charles A.; Dieter, Bryan E.; Sliter, Ray W.; Krigsman, Lisa M.; Lowe, Erik; Chinn, John L.; Watt, Janet T.; Cochran, Susan A.

2015-01-01

This publication about the Offshore of Point Reyes map area includes ten map sheets that contain explanatory text, in addition to this descriptive pamphlet and a data catalog of geographic information system (GIS) files. Sheets 1, 2, and 3 combine data from four different sonar surveys to generate comprehensive high-resolution bathymetry and acoustic-backscatter coverage of the map area. These data reveal a range of physiographic features (highlighted in the perspective views on sheet 4) such as the flat, sediment-covered seafloor in Drakes Bay, as well as abundant “scour depressions” on the Bodega Head–Tomales Point shelf (see sheet 9) and local, tectonically controlled bedrock uplifts. To validate geological and biological interpretations of the sonar data shown in sheets 1, 2, and 3, the U.S. Geological Survey towed a camera sled over specific offshore locations, collecting both video and photographic imagery; these “ground-truth” surveying data are summarized on sheet 6. Sheet 5 is a “seafloor character” map, which classifies the seafloor on the basis of depth, slope, rugosity (ruggedness), and backscatter intensity and which is further informed by the ground-truth-survey imagery. Sheet 7 is a map of “potential habitats,” which are delineated on the basis of substrate type, geomorphology, seafloor process, or other attributes that may provide a habitat for a specific species or assemblage of organisms. Sheet 8 compiles representative seismic-reflection profiles from the map area, providing information on the subsurface stratigraphy and structure of the map area. Sheet 9 shows the distribution and thickness of young sediment (deposited over the last about 21,000 years, during the most recent sea-level rise) in both the map area and the larger Salt Point to Drakes Bay region, interpreted on the basis of the seismic-reflection data, and it identifies the Offshore of Point Reyes map area as lying within the Bodega Head–Tomales Point shelf, Point Reyes bar, and Bolinas shelf domains. Sheet 10 is a geologic map that merges onshore geologic mapping (compiled from existing maps by the California Geological Survey) and new offshore geologic mapping that is based on integration of high-resolution bathymetry and backscatter imagery (sheets 1, 2, 3), seafloor-sediment and rock samples (Reid and others, 2006), digital camera and video imagery (sheet 6), and high-resolution seismic-reflection profiles (sheet 8), as well as aerial-photographic interpretation of nearshore areas. The information provided by the map sheets, pamphlet, and data catalog have a broad range of applications. High-resolution bathymetry, acoustic backscatter, ground-truth-surveying imagery, and habitat mapping all contribute to habitat characterization and ecosystem-based management by providing essential data for delineation of marine protected areas and ecosystem restoration. Many of the maps provide high-resolution baselines that will be critical for monitoring environmental change associated with climate change, coastal development, or other forcings. High-resolution bathymetry is a critical component for modeling coastal flooding caused by storms and tsunamis, as well as inundation associated with longer term sea-level rise. Seismic-reflection and bathymetric data help characterize earthquake and tsunami sources, critical for natural-hazard assessments of coastal zones. Information on sediment distribution and thickness is essential to the understanding of local and regional sediment transport, as well as the development of regional sediment-management plans. In addition, siting of any new offshore infrastructure (for example, pipelines, cables, or renewable-energy facilities) will depend on high-resolution mapping. Finally, this mapping will both stimulate and enable new scientific research and also raise public awareness of, and education about, coastal environments and issues.

Evaluation of Sentinel-1A Data For Above Ground Biomass Estimation in Different Forests in India

NASA Technical Reports Server (NTRS)

Vadrevu, Krishna Prasad

2017-01-01

Use of remote sensing data for mapping and monitoring of forest biomass across large spatial scales can aid in addressing uncertainties in carbon cycle. Earlier, several researchers reported on the use of Synthetic Aperture Radar (SAR) data for characterizing forest structural parameters and the above ground biomass estimation. However, these studies cannot be generalized and the algorithms cannot be applied to all types of forests without additional information on the forest physiognomy, stand structure and biomass characteristics. The radar backscatter signal also saturates as forest parameters such as biomass and the tree height increase. It is also not clear how different polarizations (VV versus VH) impact the backscatter retrievals in different forested regions. Thus, it is important to evaluate the potential of SAR data in different landscapes for characterizing forest structural parameters. In this study, the SAR data from Sentinel-1A has been used to characterize forest structural parameters including the above ground biomass from tropical forests of India. Ground based data on tree density, basal area and above ground biomass data from thirty-eight different forested sites has been collected to relate to SAR data. After the pre-processing of Sentinel 1-A data for radiometric calibration, geo-correction, terrain correction and speckle filtering, the variability in the backscatter signal in relation tree density, basal area and above biomass density has been investigated. Results from the curve fitting approach suggested exponential model between the Sentinel-1A backscatter versus tree density and above ground biomass whereas the relationship was almost linear with the basal area in the VV polarization mode. Of the different parameters, tree density could explain most of the variations in backscatter. Both VV and VH backscatter signals could explain only thirty and thirty three percent of variation in above biomass in different forest sites of India. Results also suggested saturation of the Sentinel-1A backscatter signal around hundred tonnes per hectare for VV polarization and one hundred and forty five tonnes per hectare for VH polarization. The presentation will highlight the above results in addition to potentials and limitations of Sentinel-1A data for retrieving forest structural parameters. Also, background information on different forest types of India, biomass variations and forest type mapping efforts in the region will be presented.

Shallow geology, sea-floor texture, and physiographic zones of Buzzards Bay, Massachusetts

USGS Publications Warehouse

Foster, David S.; Baldwin, Wayne E.; Barnhardt, Walter A.; Schwab, William C.; Ackerman, Seth D.; Andrews, Brian D.; Pendleton, Elizabeth A.

2015-01-07

Geologic, sediment texture, and physiographic zone maps characterize the sea floor of Buzzards Bay, Massachusetts. These maps were derived from interpretations of seismic-reflection profiles, high-resolution bathymetry, acoustic-backscatter intensity, bottom photographs, and surficial sediment samples. The interpretation of the seismic stratigraphy and mapping of glacial and Holocene marine units provided a foundation on which the surficial maps were created. This mapping is a result of a collaborative effort between the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management to characterize the surface and subsurface geologic framework offshore of Massachusetts.

Planck 2015 results. XXII. A map of the thermal Sunyaev-Zeldovich effect

NASA Astrophysics Data System (ADS)

Planck Collaboration; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Bartolo, N.; Battaner, E.; Battye, R.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chiang, H. C.; Christensen, P. R.; Churazov, E.; Clements, D. L.; Colombo, L. P. L.; Combet, C.; Comis, B.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Génova-Santos, R. T.; Giard, M.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Holmes, W. A.; Hornstrup, A.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lacasa, F.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Macías-Pérez, J. F.; Maffei, B.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Melchiorri, A.; Melin, J.-B.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Noviello, F.; Novikov, D.; Novikov, I.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Sauvé, A.; Savelainen, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tramonte, D.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-09-01

We have constructed all-sky Compton parameters maps, y-maps, of the thermal Sunyaev-Zeldovich (tSZ) effect by applying specifically tailored component separation algorithms to the 30 to 857 GHz frequency channel maps from the Planck satellite. These reconstructed y-maps are delivered as part of the Planck 2015 release. The y-maps are characterized in terms of noise properties and residual foreground contamination, mainly thermal dust emission at large angular scales, and cosmic infrared background and extragalactic point sources at small angular scales. Specific masks are defined to minimize foreground residuals and systematics. Using these masks, we compute the y-map angular power spectrum and higher order statistics. From these we conclude that the y-map is dominated by tSZ signal in the multipole range, 20 <ℓ< 600. We compare the measured tSZ power spectrum and higher order statistics to various physically motivated models and discuss the implications of our results in terms of cluster physics and cosmology.

Forest above ground biomass estimation and forest/non-forest classification for Odisha, India, using L-band Synthetic Aperture Radar (SAR) data

NASA Astrophysics Data System (ADS)

Suresh, M.; Kiran Chand, T. R.; Fararoda, R.; Jha, C. S.; Dadhwal, V. K.

2014-11-01

Tropical forests contribute to approximately 40 % of the total carbon found in terrestrial biomass. In this context, forest/non-forest classification and estimation of forest above ground biomass over tropical regions are very important and relevant in understanding the contribution of tropical forests in global biogeochemical cycles, especially in terms of carbon pools and fluxes. Information on the spatio-temporal biomass distribution acts as a key input to Reducing Emissions from Deforestation and forest Degradation Plus (REDD+) action plans. This necessitates precise and reliable methods to estimate forest biomass and to reduce uncertainties in existing biomass quantification scenarios. The use of backscatter information from a host of allweather capable Synthetic Aperture Radar (SAR) systems during the recent past has demonstrated the potential of SAR data in forest above ground biomass estimation and forest / nonforest classification. In the present study, Advanced Land Observing Satellite (ALOS) / Phased Array L-band Synthetic Aperture Radar (PALSAR) data along with field inventory data have been used in forest above ground biomass estimation and forest / non-forest classification over Odisha state, India. The ALOSPALSAR 50 m spatial resolution orthorectified and radiometrically corrected HH/HV dual polarization data (digital numbers) for the year 2010 were converted to backscattering coefficient images (Schimada et al., 2009). The tree level measurements collected during field inventory (2009-'10) on Girth at Breast Height (GBH at 1.3 m above ground) and height of all individual trees at plot (plot size 0.1 ha) level were converted to biomass density using species specific allometric equations and wood densities. The field inventory based biomass estimations were empirically integrated with ALOS-PALSAR backscatter coefficients to derive spatial forest above ground biomass estimates for the study area. Further, The Support Vector Machines (SVM) based Radial Basis Function classification technique was employed to carry out binary (forest-non forest) classification using ALOSPALSAR HH and HV backscatter coefficient images and field inventory data. The textural Haralick's Grey Level Cooccurrence Matrix (GLCM) texture measures are determined on HV backscatter image for Odisha, for the year 2010. PALSAR HH, HV backscatter coefficient images, their difference (HHHV) and HV backscatter coefficient based eight textural parameters (Mean, Variance, Dissimilarity, Contrast, Angular second moment, Homogeneity, Correlation and Contrast) are used as input parameters for Support Vector Machines (SVM) tool. Ground based inputs for forest / non-forest were taken from field inventory data and high resolution Google maps. Results suggested significant relationship between HV backscatter coefficient and field based biomass (R2 = 0.508, p = 0.55) compared to HH with biomass values ranging from 5 to 365 t/ha. The spatial variability of biomass with reference to different forest types is in good agreement. The forest / nonforest classified map suggested a total forest cover of 50214 km2 with an overall accuracy of 92.54 %. The forest / non-forest information derived from the present study showed a good spatial agreement with the standard forest cover map of Forest Survey of India (FSI) and corresponding published area of 50575 km2. Results are discussed in the paper.

Monte Carlo investigation of backscatter point spread function for x-ray imaging examinations

NASA Astrophysics Data System (ADS)

Xiong, Zhenyu; Vijayan, Sarath; Rudin, Stephen; Bednarek, Daniel R.

2017-03-01

X-ray imaging examinations, especially complex interventions, may result in relatively high doses to the patient's skin inducing skin injuries. A method was developed to determine the skin-dose distribution for non-uniform x-ray beams by convolving the backscatter point-spread-function (PSF) with the primary-dose distribution to generate the backscatter distribution that, when added to the primary dose, gives the total-dose distribution. This technique was incorporated in the dose-tracking system (DTS), which provides a real-time color-coded 3D-mapping of skin dose during fluoroscopic procedures. The aim of this work is to investigate the variation of the backscatter PSF with different parameters. A backscatter PSF of a 1-mm x-ray beam was generated by EGSnrc Monte-Carlo code for different x-ray beam energies, different soft-tissue thickness above bone, different bone thickness and different entrance-beam angles, as well as for different locations on the SK-150 anthropomorphic head phantom. The results show a reduction of the peak scatter to primary dose ratio of 48% when X-ray beam voltage is increased from 40 keV to 120 keV. The backscatter dose was reduced when bone was beneath the soft tissue layer and this reduction increased with thinner soft tissue and thicker bone layers. The backscatter factor increased about 21% as the angle of incidence of the beam with the entrance surface decreased from 90° (perpendicular) to 30°. The backscatter PSF differed for different locations on the SK-150 phantom by up to 15%. The results of this study can be used to improve the accuracy of dose calculation when using PSF convolution in the DTS.

Characterizing the temporal variability of L-band backscatter using dense UAVSAR time-series in preparation for the NISAR mission

NASA Astrophysics Data System (ADS)

Lavalle, M.; Lee, A.; Shiroma, G. X. H.; Rosen, P. A.

2017-12-01

The NASA-ISRO SAR (NISAR) mission will deliver unprecedented global maps of L-band HH/HV backscatter every 12 days with resolution ranging from a few to tens of meters in support of ecosystem, solid Earth and cryosphere science and applications. Understanding and modeling the temporal variability of L-band backscatter over temporal scales of years, months and days is critical for developing retrieval algorithms that can robustly extract the biophysical variables of interest (e.g., forest biomass, soil moisture, etc.) from NISAR time series. In this talk, we will focus on the 5-year time series of 60 JPL/UAVSAR polarimetric images collected near the Sacramento Delta to characterize the inter-annual, seasonal and short-scale variability of the L-band polarimetric backscatter for a broad range of land cover types. Our preliminary analysis reveals that backscatter from man-made structures is very stable over time, whereas backscatter from bare soil and herbaceous vegetation fluctuates over time with standard deviation of 2.3 dB. Land-cover classes with larger biomass such as trees and tall vegetation show about 1.5 dB standard deviation in temporal backscatter variability. Closer examination of high-spatial resolution UAVSAR imagery reveal also that vegetation structure, speckle noise and horizontal forest heterogeneity in the Sacramento Delta area can significantly affect the point-wise backscatter value. In our talk, we will illustrate the long UAVSAR time series, describe our data analysis strategy, show the results of polarimetric variability for different land cover classes and number of looks, and discuss the implications for the development of NISAR L2/L3 retrieval algorithms of ecosystem science.

Regional Glacier Mapping by Combination of Dense Optical and SAR Satellite Image Time-Series

NASA Astrophysics Data System (ADS)

Winsvold, S. H.; Kääb, A.; Andreassen, L. M.; Nuth, C.; Schellenberger, T.; van Pelt, W.

2016-12-01

Near-future dense time series from both SAR (Sentinel-1A and B) and optical satellite sensors (Landsat 8, Sentinel-2A and B) will promote new multisensory time series applications for glacier mapping. We assess such combinations of optical and SAR data among others by 1) using SAR data to supplement optical time series that suffer from heavy cloud cover (chronological gap-filling), 2) merging the two data types based on stack statistics (Std.dev, Mean, Max. etc.), or 3) better explaining glacier facies patterns in SAR data using optical satellite images. As one example, summer SAR backscatter time series have been largely unexplored and even neglected in many glaciological studies due to the high content of liquid melt water on the ice surface and its intrusion in the upper part of the snow and firn. This water content causes strong specular scattering and absorption of the radar signal, and little energy is scattered back to the SAR sensor. We find in many scenes of a Sentinel-1 time series a significant temporal backscatter difference between the glacier ice surface and the seasonal snow as it melts up glacier. Even though both surfaces have typically wet conditions, we suggest that the backscatter difference is due to different roughness lengths of the two surfaces. Higher backscatter is found on the ice surface in the ablation area compared to the firn/seasonal snow surface. We find and present also other backscatter patterns in the Sentinel-1 time series related to glacier facies and weather events. For the Ny Ålesund area, Svalbard we use Radarsat-2 time series to explore the glacier backscatter conditions in a > 5 year period, discussing distinct temporal signals from among others refreezing of the firn in late autumn, or temporal lakes. All these examples are analyzed using the above 3 methods. By this multi-temporal and multi-sensor approach we also explore and describe the possible connection between combined SAR/optical time series and surface mass balance.

Test Operations Procedure (TOP) 1-2-612 Nuclear Environment Survivability

DTIC Science & Technology

2008-10-24

measurements. The area equal to the area of gamma dose sensitive electronics will be mapped using CaF2 (Mn) TLDs . The selection of each STT...October 2008 8 2.3.3 HEMP / SREMP Instrumentation / Dosimetry . Measurement Parameter Preferred Device Measurement Accuracy Current...Calcium Fluoride Manganese CaF2 (Mn) Thermoluminescent Dosimeter ( TLDs ) and Compton diodes, respectively. The measured gamma dose values will be

Beam Diagnostics of the Compton Scattering Chamber in Jefferson Lab's Hall C

NASA Astrophysics Data System (ADS)

Faulkner, Adam; I&C Group Collaboration

2013-10-01

Upcoming experimental runs in Hall C will utilize Compton scattering, involving the construction and installation of a rectangular beam enclosure. Conventional cylindrical stripline-style Beam Position Monitors (BPMs) are not appropriate due to their form factor; therefore to facilitate measurement of position, button-style BPMs are being considered due to the ease of placement within the new beam enclosure. Button BPM experience is limited at JLAB, so preliminary measurements are needed to characterize the field response, and guide the development of appropriate algorithms for the Analog to Digital receiver systems. -field mapping is performed using a Goubau Line (G-Line), which employs a surface wave to mimic the electron beam, helping to avoid problems associated with vacuum systems. Potential algorithms include simplistic 1/r modeling (-field mapping), look-up-tables, as well as a potential third order power series fit. In addition, the use of neural networks specifically the multi-layer Perceptron will be examined. The models, sensor field maps, and utility of the neural network will be presented. Next steps include: modification of the control algorithm, as well as to run an in-situ test of the four Button electrodes inside of a mock beam enclosure. The analysis of the field response using Matlab suggests the button BPMs are accurate to within 10 mm, and may be successful for beam diagnostics in Hall C. More testing is necessary to ascertain the limitations of the new electrodes. The National Science Foundation, Old Dominion University, The Department of Energy, and Jefferson Lab.

Forest Biomass Mapping from Prism Triplet, Palsar and Landsat Data

NASA Astrophysics Data System (ADS)

Ranson, J.; Sun, G.; Ni, W.

2014-12-01

The loss of sensitivity at higher biomass levels is a common problem in biomass mapping using optical multi-spectral data or radar backscattering data due to the lack of information on canopy vertical structure. Studies have shown that adding implicit information of forest vertical structure improves the performance of forest biomass mapping from optical reflectance and radar backscattering data. LiDAR, InSAR and stereo imager are the data sources for obtaining forest structural information. The potential of providing information on forest vertical structure by stereoscopic imagery data has drawn attention recently due to the availability of high-resolution digital stereo imaging from space and the advances of digital stereo image processing software. The Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observation Satellite (ALOS) has acquired multiple global coverage from June 2006 to April 2011 providing a good data source for regional/global forest studies. In this study, five PRISM triplets acquired on June 14, 2008, August 19 and September 5, 2009; PALSAR dual-pol images acquired on July 12, 2008 and August 30, 2009; and LANDSAT 5 TM images acquired on September 5, 2009 and the field plot data collected in 2009 and 2010 were used to map forest biomass at 50m pixel in an area of about 4000 km2in Maine, USA ( 45.2 deg N 68.6 deg W). PRISM triplets were used to generate point cloud data at 2m pixel first and then the average height of points above NED (National Elevation Dataset) within a 50m by 50m pixel was calculated. Five images were mosaicked and used as canopy height information in the biomass estimation along with the PALSAR HH, HV radar backscattering and optical reflectance vegetation indices from L-5 TM data. A small portion of this region was covered by the Land Vegetation and Ice Sensor (LVIS) in 2009. The biomass maps from the LVIS data was used to evaluate the results from combined use of PRISM, PALSAR and LANDSAT data. The results show that the canopy height index from PRISM stereo images significantly improves the biomass mapping accuracy and extends the saturation level of biomass, and results in a biomass map comparable with those generated from LVIS data.

Sea-Floor Images and Data from Multibeam Surveys in San Francisco Bay, Southern California, Hawaii, the Gulf of Mexico, and Lake Tahoe, California-Nevada

USGS Publications Warehouse

Dartnell, Peter; Gardiner, James V.

1999-01-01

Accurate base maps are a prerequisite for any geologic study, regardless of the objectives. Land-based studies commonly utilize aerial photographs, USGS 7.5-minute quadrangle maps, and satellite images as base maps. Until now, studies that involve the ocean floor have been at a disadvantage due to an almost complete lack of accurate marine base maps. Many base maps of the sea floor have been constructed over the past century but with a wide range in navigational and depth accuracies. Only in the past few years has marine surveying technology advanced far enough to produce navigational accuracy of 1 meter and depth resolutions of 50 centimeters. The Pacific Seafloor Mapping Project of the U.S. Geological Survey's, Western Coastal and Marine Geology Program, Menlo Park, California, U.S.A., in cooperation with the Ocean Mapping Group, University of New Brunswick, Fredericton, Canada, is using this new technology to systematically map the ocean floor and lakes. This type of marine surveying, called multibeam surveying, collects high-resolution bathymetric and backscatter data that can be used for various base maps, GIS coverages, and scientific visualization methods. This is an interactive CD-ROM that contains images, movies, and data of all the surveys the Pacific Seafloor Mapping Project has completed up to January 1999. The images and movies on this CD-ROM, such as shaded relief of the bathymetry, backscatter, oblique views, 3-D views, and QuickTime movies help the viewer to visualize the multibeam data. This CD-ROM also contains ARC/INFO export (.e00) files and full-resolution TIFF images of all the survey sites that can be downloaded and used in many GIS packages.

A spectral geometric model for Compton single scatter in PET based on the single scatter simulation approximation

NASA Astrophysics Data System (ADS)

Kazantsev, I. G.; Olsen, U. L.; Poulsen, H. F.; Hansen, P. C.

2018-02-01

We investigate the idealized mathematical model of single scatter in PET for a detector system possessing excellent energy resolution. The model has the form of integral transforms estimating the distribution of photons undergoing a single Compton scattering with a certain angle. The total single scatter is interpreted as the volume integral over scatter points that constitute a rotation body with a football shape, while single scattering with a certain angle is evaluated as the surface integral over the boundary of the rotation body. The equations for total and sample single scatter calculations are derived using a single scatter simulation approximation. We show that the three-dimensional slice-by-slice filtered backprojection algorithm is applicable for scatter data inversion provided that the attenuation map is assumed to be constant. The results of the numerical experiments are presented.

A 3-Dimensional Analysis of the Galactic Gamma-Ray Emission Resulting from Cosmic-Ray Interactions with the Interstellar Gas and Radiation Fields

NASA Technical Reports Server (NTRS)

Sodroski, Thomas J.; Dwek, Eli (Technical Monitor)

2001-01-01

The contractor will provide support for the analysis of data under ADP (NRA 96-ADP- 09; Proposal No . 167-96adp). The primary task objective is to construct a 3-D model for the distribution of high-energy (20 MeV - 30 GeV) gamma-ray emission in the Galactic disk. Under this task the contractor will utilize data from the EGRET instrument on the Compton Gamma-Ray Observatory, H I and CO surveys, radio-continuum surveys at 408 MHz, 1420 MHz, 5 GHz, and 19 GHz, the COBE Diffuse Infrared Background Experiment (DIME) all-sky maps from 1 to 240 p, and ground-based B, V, J, H, and K photometry. The respective contributions to the gamma-ray emission from cosmic ray/matter interactions, inverse Compton scattering, and extragalactic emission will be determined.

Surface properties and surficial deposits on Venus: New results from Magellan radar altimeter data analysis

NASA Astrophysics Data System (ADS)

Bondarenko, Nataliya V.; Kreslavsky, Mikhail A.

2018-07-01

Microwave remote sensing data acquired with Magellan Venus orbiter are the main source of information about the surface of the planet. We analyze variability of the backscattering function (dependence of radar cross-section on incidence angle) for steep incidence angles 0.25°-4.75° in the 75°N-55°S latitude zone with data from the Magellan radar altimeter at 12.6 cm wavelength. We show that all variability of the backscattering function can be described by three parameters, describing (1) surface reflectivity, (2) relative proportion of horizontal facets, and (3) general roughness. Analysis of maps of these parameters revealed that surficial deposits, for example, microdune fields, are abundant on Venus even in places, where they are not readily seen in the synthetic aperture radar images. Properties of surficial deposits rather than original volcanic flow roughness define the shape of the backscattering function on the majority of regional plains. A large radar-dark flow in Bereghinia Planitia has anomalously high proportion of horizontal facets, which is consistent with it being formed by a relatively recent plain-forming volcanic episode. Some crater-associated radar-dark diffuse features and splotches are also characterized by increased proportion of horizontal faces, which indicate the presence of mantles deposited from fluidized granular material. The backscattering functions of the anomalous radar-bright material of mountaintops are more consistent with the strong internal scattering hypothesis rather than the exotic surficial material hypothesis. Obtained maps can be useful for planning future lander missions to sites with access to surface material with known provenance.

Mapping local anisotropy axis for scattering media using backscattering Mueller matrix imaging

NASA Astrophysics Data System (ADS)

He, Honghui; Sun, Minghao; Zeng, Nan; Du, E.; Guo, Yihong; He, Yonghong; Ma, Hui

2014-03-01

Mueller matrix imaging techniques can be used to detect the micro-structure variations of superficial biological tissues, including the sizes and shapes of cells, the structures in cells, and the densities of the organelles. Many tissues contain anisotropic fibrous micro-structures, such as collagen fibers, elastin fibers, and muscle fibers. Changes of these fibrous structures are potentially good indicators for some pathological variations. In this paper, we propose a quantitative analysis technique based on Mueller matrix for mapping local anisotropy axis of scattering media. By conducting both experiments on silk sample and Monte Carlo simulation based on the sphere-cylinder scattering model (SCSM), we extract anisotropy axis parameters from different backscattering Mueller matrix elements. Moreover, we testify the possible applications of these parameters for biological tissues. The preliminary experimental results of human cancerous samples show that, these parameters are capable to map the local axis of fibers. Since many pathological changes including early stage cancers affect the well aligned structures for tissues, the experimental results indicate that these parameters can be used as potential tools in clinical applications for biomedical diagnosis purposes.

Automatic classification techniques for type of sediment map from multibeam sonar data

NASA Astrophysics Data System (ADS)

Zakariya, R.; Abdullah, M. A.; Che Hasan, R.; Khalil, I.

2018-02-01

Sediment map can be important information for various applications such as oil drilling, environmental and pollution study. A study on sediment mapping was conducted at a natural reef (rock) in Pulau Payar using Sound Navigation and Ranging (SONAR) technology which is Multibeam Echosounder R2-Sonic. This study aims to determine sediment type by obtaining backscatter and bathymetry data from multibeam echosounder. Ground truth data were used to verify the classification produced. The method used to analyze ground truth samples consists of particle size analysis (PSA) and dry sieving methods. Different analysis being carried out due to different sizes of sediment sample obtained. The smaller size was analyzed using PSA with the brand CILAS while bigger size sediment was analyzed using sieve. For multibeam, data acquisition includes backscatter strength and bathymetry data were processed using QINSy, Qimera, and ArcGIS. This study shows the capability of multibeam data to differentiate the four types of sediments which are i) very coarse sand, ii) coarse sand, iii) very coarse silt and coarse silt. The accuracy was reported as 92.31% overall accuracy and 0.88 kappa coefficient.

Investigating the use of the dual-polarized and large incident angle of SAR data for mapping the fluvial and aeolian deposits

NASA Astrophysics Data System (ADS)

Gaber, Ahmed; Amarah, Bassam A.; Abdelfattah, Mohamed; Ali, Sarah

2017-12-01

Mapping the spatial distributions of the fluvial deposits in terms of particles size as well as imaging the near-surface features along the non-vegetated aeolian sand-sheets, provides valuable geological information. Thus this work aims at investigating the contribution of the dual-polarization SAR data in classifying and mapping the surface sediments as well as investigating the effect of the radar incident-angle on improving the images of the hidden features under the desert sand cover. For mapping the fluvial deposits, the covariance matrix ([C2]) using four dual-polarized ALOS/PALSAR-1 scenes cover the Wadi El Matulla, East Qena, Egypt were generated. This [C2] matrix was used to generate a supervised classification map with three main classes (gravel, gravel/sand and sand). The polarimetric scattering response, spectral reflectance and temperatures brightness of these 3 classes were extracted. However for the aeolian deposits investigation, two Radarsat-1 and three full-polarimetric ALOS/PALSAR-1 images, which cover the northwestern sandy part of Sinai, Egypt were calibrated, filtered, geocoded and ingested in a GIS database to image the near-surface features. The fluvial mapping results show that the values of the radar backscattered coefficient (σ°) and the degree of randomness of the obtained three classes are increasing respectively by increasing their grain size. Moreover, the large incident angle (θi = 39.7) of the Radarsat-1 image has revealed a meandering buried stream under the sand sheet of the northwestern part of Sinai. Such buried stream does not appear in the other optical, SRTM and SAR dataset. The main reason is the enhanced contrast between the low backscattered return from the revealed meandering stream and the surroundings as a result of the increased backscattering intensity, which is related to the relatively large incident angle along the undulated surface of the study area. All archaeological observations support the existence of paleo-fresh water lagoon at the northwestern corner of the study area, which might have been the discharge lagoon of the revealed hidden stream.

Delineation of estuarine fronts in the German Bight using airborne laser-induced water Raman backscatter and fluorescence of water column constituents

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1982-01-01

The acquisition and application of airborne laser induced emission spectra from German Bight water during the 1979 MARSEN experiment is detailed for the synoptic location of estuarine fronts. The NASA Airborne Oceanographic Lidar (AOL) was operated in the fluorosensing mode. A nitrogen laser transmitter at 337.1 nm was used to stimulate the water column to obtain Gelbstoff or organic material fluorescence spectra together with water Raman backscatter. Maps showing the location and relative strength of estuarine fronts are presented. The distribution of the fronts indicates that mixing within the German Bight takes place across a relatively large area. Reasonable agreement between the patterns observed by the AOL and published results are obtained. The limitations and constraints of this technique are indicated and improvements to the AOL fluorosensor are discussed with respect to future ocean mapping applications.

User's guide for the Solar Backscattered Ultraviolet (SBUV) and the Total Ozone Mapping Spectrometer (TOMS) RUT-S and RUT-T data sets: October 31, 1978 to November 1, 1980

NASA Technical Reports Server (NTRS)

Fleig, A. J.; Heath, D. F.; Klenk, K. F.; Oslik, N.; Lee, K. D.; Park, H.; Bhartia, P. K.; Gordon, D.

1983-01-01

Raw data from the Solar Backscattered Ultrviolet/Total Ozone Mapping Spectrometer (SBUV/TOMS) Nimbus 7 operation are available on computer tape. These data are contained on two separate sets of RUTs (Raw Units Tapes) for SBUV and TOMS, labelled RUT-S and RUT-T respectively. The RUT-S and RUT-T tapes contain uncalibrated radiance and irradiance data, housekeeping data, wavelength and electronic calibration data, instrument field-of-view location and solar ephemeris information. These tapes also contain colocated cloud, terrain pressure and snow/ice thickness data, each derived from an independent source. The "RUT User's Guide" describes the SBUV and TOMS experiments, the instrument calibration and performance, operating schedules, and data coverage, and provides an assessment of RUT-S and -T data quality. It also provides detailed information on the data available on the computer tapes.

System, method, and apparatus for remote measurement of terrestrial biomass

DOEpatents

Johnson, Patrick W [Jefferson, MD

2011-04-12

A system, method, and/or apparatus for remote measurement of terrestrial biomass contained in vegetative elements, such as large tree boles or trunks present in an area of interest, are provided. The method includes providing an airborne VHF radar system in combination with a LiDAR system, overflying the area of interest while directing energy toward the area of interest, using the VHF radar system to collect backscatter data from the trees as a function of incidence angle and frequency, and determining a magnitude of the biomass from the backscatter data and data from the laser radar system for each radar resolution cell. A biomass map is generated showing the magnitude of the biomass of the vegetative elements as a function of location on the map by using each resolution cell as a unique location thereon. In certain preferred embodiments, a single frequency is used with a linear array antenna.

Use of capillary optics as a beam intensifier for a Compton x-ray source.

PubMed

Tompkins, P A; Abreu, C C; Carroll, F E; Xiao, Q F; MacDonald, C A

1994-11-01

The use of Kumakhov capillary optics will significantly enhance the performance of near-monochromatic, Compton backscattered x-ray programs. The Vanderbilt University Medical Free-Electron Laser Center is developing the capability to create these tunable x rays for medical imaging. The present transport has only reflection optics, and the beam is quite large in diameter at the laboratory. Low loss collimation of this beam would allow higher x-ray intensities after transport. This article describes experimental and computer simulation results which predict the expected performance for a multifiber Kumakhov collimator for use in the x-ray beam transport. Estimates from our research are that a multifiber optic formed of individual polycapillary fibers could be used to capture the full 7 mrad of the Vanderbilt x-ray beam and collimate it to a 1-2 mrad divergence with approximately 40%-50% transmission efficiency. This optic should increase the x-ray intensity at the laboratory level by a factor of > or = 5 by decreasing the beam divergence and subsequent spot size. Additionally, analysis of monolithic optics of fused multicapillary fibers predicts an increase in the intensity of the x rays at the laboratory by a factor of 55. These optics can have tapered channels that greatly decrease their exit divergence. This will greatly enhance the capabilities of this unique x-ray source. This article reports the initial results from a collaboration between Vanderbilt, The Center for X-Ray Optics at University at Albany, SUNY, and X-Ray Optical Systems in Albany, NY.

Rapid Mapping Of Floods Using SAR Data: Opportunities And Critical Aspects

NASA Astrophysics Data System (ADS)

Pulvirenti, Luca; Pierdicca, Nazzareno; Chini, Marco

2013-04-01

The potentiality of spaceborne Synthetic Aperture Radar (SAR) for flood mapping was demonstrated by several past investigations. The synoptic view, the capability to operate in almost all-weather conditions and during both day time and night time and the sensitivity of the microwave band to water are the key features that make SAR data useful for monitoring inundation events. In addition, their high spatial resolution, which can reach 1m with the new generation of X-band instruments such as TerraSAR-X and COSMO-SkyMed (CSK), allows emergency managers to use flood maps at very high spatial resolution. CSK gives also the possibility of performing frequent observations of regions hit by floods, thanks to the four-satellite constellation. Current research on flood mapping using SAR is focused on the development of automatic algorithms to be used in near real time applications. The approaches are generally based on the low radar return from smooth open water bodies that behave as specular reflectors and appear dark in SAR images. The major advantage of automatic algorithms is the computational efficiency that makes them suitable for rapid mapping purposes. The choice of the threshold value that, in this kind of algorithms, separates flooded from non-flooded areas is a critical aspect because it depends on the characteristics of the observed scenario and on system parameters. To deal with this aspect an algorithm for automatic detection of the regions of low backscatter has been developed. It basically accomplishes three steps: 1) division of the SAR image in a set of non-overlapping sub-images or splits; 2) selection of inhomogeneous sub-images that contain (at least) two populations of pixels, one of which is formed by dark pixels; 3) the application in sequence of an automatic thresholding algorithm and a region growing algorithm in order to produce a homogeneous map of flooded areas. Besides the aforementioned choice of the threshold, rapid mapping of floods may present other critical aspects. Searching for low SAR backscatter areas only may cause inaccuracies because flooded soils do not always act as smooth open water bodies. The presence of wind or of vegetation emerging above the water surface may give rise to an increase of the radar backscatter. In particular, mapping flooded vegetation using SAR data may represent a difficult task since backscattering phenomena in the volume between canopy, trunks and floodwater are quite complex in the presence of vegetation. A typical phenomenon is the double-bounce effect involving soil and stems or trunks, which is generally enhanced by the floodwater, so that flooded vegetation may appear very bright in a SAR image. Even in the absence of dense vegetation or wind, some regions may appear dark because of artefacts due to topography (shadowing), absorption caused by wet snow, and attenuation caused by heavy precipitating clouds (X-band SARs). Examples of the aforementioned effects that may limit the reliability of flood maps will be presented at the conference and some indications to deal with these effects (e.g. presence of vegetation and of artefacts) will be provided.

Mapping the Extent and Magnitude of Sever Flooding Induced by Hurricane IRMA with Multi-Temporal SENTINEL-1 SAR and Insar Observations

NASA Astrophysics Data System (ADS)

Zhang, B.; Wdowinski, S.; Oliver-Cabrera, T.; Koirala, R.; Jo, M. J.; Osmanoglu, B.

2018-04-01

During Hurricane Irma's passage over Florida in September 2017, many sections of the state experienced heavy rain and sequent flooding. In order to drain water out of potential flooding zones and assess property damage, it is important to map the extent and magnitude of the flooded areas at various stages of the storm. We use Synthetic Aperture Radar (SAR) and Interferometric SAR (InSAR) observations, acquired by Sentinel-1 before, during and after the hurricane passage, which enable us to evaluate surface condition during different stages of the hurricane. This study uses multi-temporal images acquired under dry condition before the hurricane to constrain the background backscattering signature. Flooded areas are detected when the backscattering during the hurricane is statistically significantly different from the average dry conditions. The detected changes can be either an increase or decrease of the backscattering, which depends on the scattering characteristics of the surface. In addition, water level change information in Palmdale, South Florida is extracted from an interferogram with the aid of a local water gauge as the reference. The results of our flooding analysis revealed that the majority of the study area in South Florida was flooded during Hurricane Irma.

LIDAR detection of forest fire smoke above Sofia

NASA Astrophysics Data System (ADS)

Grigorov, Ivan; Deleva, Atanaska; Stoyanov, Dimitar; Kolev, Nikolay; Kolarov, Georgi

2015-01-01

The distribution of aerosol load in the atmosphere due to two forest fires near Sofia (the capital city of Bulgaria) was studied using two aerosol lidars which operated at 510.6 nm and 1064 nm. Experimental data is presented as 2D-heatmaps of the evolution of attenuated backscatter coefficient profiles and mean profile of the aerosol backscatter coefficient, calculated for each lidar observation. Backscatter related Angstrom exponent was used as a criterion in particle size estimation of detected smoke layers. Calculated minimal values at altitudes where the aerosol layer was observed corresponded to predominant fraction of coarse aerosol. Dust-transport forecast maps and calculations of backward trajectories were employed to make conclusions about aerosol's origin. They confirmed the local transport of smoke aerosol over the city and lidar station. DREAM forecast maps predicted neither cloud cover, nor Saharan load in the air above Sofia on the days of measurements. The results of lidar observations are discussed in conjunction with meteorological situation, aiming to better explain the reason for the observed aerosol stratification. The data of regular radio sounding of the atmosphere showed a characteristic behavior with small differences of the values between the air temperature and dew-point temperature profiles at aerosol smoke layer altitude. So the resulting stratification revealed the existence of atmospheric layers with aerosol trapping properties.

On diel variability of marine sediment backscattering properties caused by microphytobenthos photosynthesis: Impact of environmental factors

NASA Astrophysics Data System (ADS)

Gorska, Natalia; Kowalska-Duda, Ewa; Pniewski, Filip; Latała, Adam

2018-06-01

The study has been motivated by the development of the hydroacoustic techniques for mapping and classifying the benthic habitats and for the research of the microbenthos photosynthesis in the semi-enclosed Baltic Sea, particularly sensitive to human activity. The investigation of the effect of the benthic microalgal photosynthesis on the echo signal from the Baltic sandy sediments is continuing. The study clarifies the impact of the abiotic and biotic factors on the diel variation of the backscattering caused by the benthic microalgal photosynthetic activity. Five multiday laboratory experiments, different in hydrophysical or biological conditions, were conducted. During each measurement series, the "day" (illumination) and "night" (darkness) conditions (L:D cycle) were simulated and the diel variations of the echo energy of the backscattered signal were analyzed. The hydroacoustic data were acquired along with measuring biological and biooptical parameters and oxygen concentration. The study demonstrated the impact of microphytobenthos photosynthesis on the backscattering properties of the marine sediment which is sensitive to the illumination level, benthic microalgal biomass and macrozoobenthos bioturbation.

Correlation analysis of 1 to 30 MeV celestial gamma rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, J.L.

1984-01-01

This paper outlines the development of a method of producing celestial sky maps from the data generated by the University of California, Riverside's double Compton scatter gamma ray telescope. The method makes use of a correlation between the telescope's data and theoretical calculated response functions. The results of applying this technique to northern hemisphere data obtained from a 1978 balloon flight from Palestine, Texas are included.

Probabilistic mapping of flood-induced backscatter changes in SAR time series

NASA Astrophysics Data System (ADS)

Schlaffer, Stefan; Chini, Marco; Giustarini, Laura; Matgen, Patrick

2017-04-01

The information content of flood extent maps can be increased considerably by including information on the uncertainty of the flood area delineation. This additional information can be of benefit in flood forecasting and monitoring. Furthermore, flood probability maps can be converted to binary maps showing flooded and non-flooded areas by applying a threshold probability value pF = 0.5. In this study, a probabilistic change detection approach for flood mapping based on synthetic aperture radar (SAR) time series is proposed. For this purpose, conditional probability density functions (PDFs) for land and open water surfaces were estimated from ENVISAT ASAR Wide Swath (WS) time series containing >600 images using a reference mask of permanent water bodies. A pixel-wise harmonic model was used to account for seasonality in backscatter from land areas caused by soil moisture and vegetation dynamics. The approach was evaluated for a large-scale flood event along the River Severn, United Kingdom. The retrieved flood probability maps were compared to a reference flood mask derived from high-resolution aerial imagery by means of reliability diagrams. The obtained performance measures indicate both high reliability and confidence although there was a slight under-estimation of the flood extent, which may in part be attributed to topographically induced radar shadows along the edges of the floodplain. Furthermore, the results highlight the importance of local incidence angle for the separability between flooded and non-flooded areas as specular reflection properties of open water surfaces increase with a more oblique viewing geometry.

On the origin of gamma rays in Fermi blazars: beyond the broad line region.

NASA Astrophysics Data System (ADS)

Costamante, L.; Cutini, S.; Tosti, G.; Antolini, E.; Tramacere, A.

2018-05-01

The gamma-ray emission in broad-line blazars is generally explained as inverse Compton (IC) radiation of relativistic electrons in the jet scattering optical-UV photons from the Broad Line Region (BLR), the so-called BLR External Compton scenario. We test this scenario on the Fermi gamma-ray spectra of 106 broad-line blazars detected with the highest significance or largest BLR, by looking for cut-off signatures at high energies compatible with γ-γ interactions with BLR photons. We do not find evidence for the expected BLR absorption. For 2/3 of the sources, we can exclude any significant absorption (τmax < 1), while for the remaining 1/3 the possible absorption is constrained to be 1.5-2 orders of magnitude lower than expected. This result holds also dividing the spectra in high and low-flux states, and for powerful blazars with large BLR. Only 1 object out of 10 seems compatible with substantial attenuation (τmax > 5). We conclude that for 9 out of 10 objects, the jet does not interact with BLR photons. Gamma-rays seem either produced outside the BLR most of the time, or the BLR is ˜100 × larger than given by reverberation mapping. This means that i) External Compton on BLR photons is disfavoured as the main gamma-ray mechanism, vs IC on IR photons from the torus or synchrotron self-Compton; ii) the Fermi gamma-ray spectrum is mostly intrinsic, determined by the interaction of the particle distribution with the seed-photons spectrum; iii) without suppression by the BLR, broad-line blazars can become copious emitters above 100 GeV, as demonstrated by 3C 454.3. We expect the CTA sky to be much richer of broad-line blazars than previously thought.

Evaluating the value of ENVISAT ASAR Data for the mapping and monitoring of peatland water table depths

NASA Astrophysics Data System (ADS)

Bechtold, Michel; Schlaffer, Stefan

2015-04-01

The Advanced Synthetic Aperture Radar (ASAR) onboard ENVISAT collected C-Band microwave backscatter data from 2005 to 2012. Backscatter in the C-Band depends to a large degree on the roughness and the moisture status of vegetation and soil surface with a penetration depth of ca. 3 cm. In wetlands with stable high water levels, the annual soil surface moisture dynamics are very distinct compared to the surrounding areas, which allows the monitoring of such environments with ASAR data (Reschke et al. 2012). Also in drained peatlands, moisture status of vegetation and soil surface strongly depends on water table depth due to high hydraulic conductivities of many peat soils in the low suction range (Dettmann et al. 2014). We hypothesize that this allows the characterization of water table depths with ASAR data. Here we analyze whether ASAR data can be used for the spatial and temporal estimation of water table depths in different peatlands (natural, near-natural, agriculturally-used and rewetted). Mapping and monitoring of water table depths is of crucial importance, e.g. for upscaling greenhouse gas emissions and evaluating the success of peatland rewetting projects. Here, ASAR data is analyzed with a new map of water table depths for the organic soils in Germany (Bechtold et al. 2014) as well as with a comprehensive data set of monitored peatland water levels from 1100 dip wells and 54 peatlands. ASAR time series from the years 2005-2012 with irregular temporal sampling intervals of 3-14 days were processed. Areas covered by snow were masked. Primary results about the accuracy of spatial estimates show significant correlations between long-term backscatter statistics and spatially-averaged water table depths extracted from the map at the resolution of the ASAR data. Backscatter also correlates with long-term averages of point-scale water table depth data of the monitoring wells. For the latter, correlation is highest between the dry reference backscatter values and summer mean water table depth. Using the boosted regression tree model of Bechtold et al., we evaluate whether the ASAR data can improve prediction accuracy and/or replace parts of ancillary data that is often not available in other countries. In the temporal domain primary results often show a better dependency between backscatter and water table depths compared to the spatial domain. For a variety of vegetation covers the temporal monitoring potential of ASAR data is evaluated at the level of annual water table depth statistics. Bechtold, M., Tiemeyer, B., Laggner, A., Leppelt, T., Frahm, E., and Belting, S., 2014. Large-scale regionalization of water table depth in peatlands optimized for greenhouse gas emission upscaling, Hydrol. Earth Syst. Sci., 18, 3319-3339. Dettmann, U., Bechtold, M., Frahm, E., Tiemeyer, B., 2014. On the applicability of unimodal and bimodal van Genuchten-Mualem based models to peat and other organic soils under evaporation conditions. Journal of Hydrology, 515, 103-115. Reschke, J., Bartsch, A., Schlaffer, S., Schepaschenko, D., 2012. Capability of C-Band SAR for Operational Wetland Monitoring at High Latitudes. Remote Sens. 4, 2923-2943.

Nondestructive Evaluation of Foam Insulation on the Space Shuttle External Tank

NASA Technical Reports Server (NTRS)

Richter, Joel; Walker, James L.

2006-01-01

Foam loss on the External Tank (ET) during launch can be caused by a number of factors. Voids are the best understood mechanism of foam loss, although it is known that delaminations, cracks and crushed foam can also lead to liberation of foam. Shortly after the Columbia accident, work began on non-destructive evaluation of foam targeted at finding voids and delaminations. After several months of searching for candidate methods capable of inspecting ET foam, the five most promising techniques were taken through a blind test and narrowed down to two methods to develop and use for inspection of the ET. These methods were backscatter radiography and terahertz imaging. The backscatter radiography system measures a test part by detecting Compton backscattered x-ray energy generated by a collimated beam of x-rays directed at the test subject. This collimated beam is scanned across the subject, recording scatter intensity data one pixel at a time until the area of interest is covered. The resulting data can be used to generate an image similar to a radiograph. Some depth information can be gathered utilizing apertures or collimation on the detectors. The detectors are located around the collimated source, making this a single sided inspection. The void detection limit with the currently utilized system is around 0.5 inches in diameter by 0.2 inches high. The terahertz imaging system inspects a test part by utilizing a transceiver to emit a pulse focused at the aluminum skin of the ET, which reflects it back to the transceiver where it is analyzed. The transceiver is scanned across the area of interest until a measurement has been taken at every location. Amplitude, time delay and frequency content are examined to note any discontinuities which may be the result of a void or other type of defect. The pulse currently utilized is in the millimeter wave regime. The void detection limit with this system is around 0.5 inches in diameter by 0.2 inches high. With increased interest in other causes of foam loss following the flight of Discovery in July 2005, laser shearography was added to the techniques used for inspecting ET foam. The shearography method records a sheared image of a laser speckle pattern projected on a test part before And after some sort of excitation. The resultant fringe pattern allows the slope of the out of plane displacement to be measured. For crushed and delaminated foam applications, a non-contact air coupled acoustic force is used to excite the surface of the foam. Regions without defects tend to respond differently to the sound energy than do regions with defects, generating a map of the foam integrity. Foam crushed to a depth of about 0.1 inches is detectable with shearography even after it has relaxed to its original shape.

Rice monitoring with multi-temporal and dual-polarimetric TerraSAR-X data

NASA Astrophysics Data System (ADS)

Koppe, Wolfgang; Gnyp, Martin L.; Hütt, Christoph; Yao, Yinkun; Miao, Yuxin; Chen, Xinping; Bareth, Georg

2013-04-01

This study assesses the use of TerraSAR-X data for monitoring rice cultivation in the Sanjiang Plain in Heilongjiang Province, Northeast China. The main objective is the understanding of the coherent co-polarized X-band backscattering signature of rice at different phenological stages in order to retrieve growth status. For this, multi-temporal dual polarimetric TerraSAR-X High Resolution SpotLight data (HH/VV) as well as single polarized StripMap (VV) data were acquired over the test site. In conjunction with the satellite data acquisition, a ground truth field campaign was carried out. The backscattering coefficients at HH and VV of the observed fields were extracted on the different dates and analysed as a function of rice phenology to provide a physical interpretation for the co-polarized backscatter response in a temporal and spatial manner. Then, a correlation analysis was carried out between TerraSAR-X backscattering signal and rice biomass of stem, leaf and head to evaluate the relationship with different vertical layers within the rice vegetation. HH and VV signatures show two phases of backscatter increase, one at the beginning up to 46 days after transplanting and a second one from 80 days after transplanting onwards. The first increase is related to increasing double bounce reflection from the surface-stem interaction. Then, a decreasing trend of both polarizations can be observed due to signal attenuation by increasing leaf density. A second slight increase is observed during senescence. Correlation analysis showed a significant relationship with different vertical layers at different phenological stages which prove the physical interpretation of X-band backscatter of rice. The seasonal backscatter coefficient showed that X-band is highly sensitive to changes in size, orientation and density of the dominant elements in the upper canopy.

Acoustic Seafloor Classification near the Duanqiao hydrothermal field at the Southwest Indian Ridge from Multibeam Backscatter Data

NASA Astrophysics Data System (ADS)

Wang, A.; Tao, C.; Xu, Y.; Zhang, G.; Liao, S.

2016-12-01

The inactive Duanqiao hydrothermal field is located on the 50.5°E SWIR axial high with a shallow depth of about 1700 meters. Seafloor morphology of the area surrounding the field is relatively flat, which exerts less influence on multibeam backscatter data than rugged terrains do. Therefore, it is an ideal experimental area to conduct seafloor classification utilizing multibeam sonar. This paper dealt with a backscatter analysis of Simrad EM120 multibeam sonar data, acquired during the Chinese DY115-34 cruise near the Duanqiao hydrothermal field, and comprehensively studied types and distribution characteristics of seafloor substrate by combining with visual interpretations and TV-Grab Samples. Firstly, a mosaic was built to analyze backscatter distribution after multibeam backscatter data were fully processed using Geocoder engine on CARIS HIPS&SIPS software. Prior information was gained by analyzing the link between the processed backscatter data and the visual interpretations of two deep-tow video survey lines. Among the two survey lines, one corresponds to sediment-dominated seafloor and the other corresponds to pillow basalt-dominated seafloor. Then, backscatter data of the mosaic were classified statistically to identify three types of seafloor: soft substrate, medium-hard substrate and hard substrate. Compared with visual interpretations and TV-Grab Samples, these three seafloor types were interpreted as sediment, breccia and pillow basalt, respectively. Finally, a seafloor classification map was generated. According to the results, we discovered two distinguished distribution characteristics of seafloor substrate: 1. there is a transition from pillow basalt-dominated seafloor to sediment-dominated seafloor away from the SWIR axis; 2. the Duanqiao hydrothermal field is mostly outcropped by pillow basalts and locally covered by breccias and sediments, the reason of which is probably that this field is a relatively recent volcanic area.

Use of SDWBA predictions for acoustic volume backscattering and the Self-Organizing Map to discern frequencies identifying Meganyctiphanes norvegica from mesopelagic fish species

NASA Astrophysics Data System (ADS)

Peña, M.; Calise, L.

2016-04-01

To acoustically assess the biomass of multiple species or taxa within a survey region, the volume backscatter data should be apportioned to the constituent sound scatterers. Typically, measured backscatter is attributed to certain species using predictions at different frequencies, mostly based on the difference in scattering at the frequencies of 38 and 120 kHz (dual frequency method). We used the full version of the stochastic distortedwave Born approximation (SDWBA) model to predict backscatter spectra for Meganyctiphanes norvegica and to explore the sensitivities of ΔMVBS to the model parameters, e.g. acoustic frequency and incidence angle, and animal density and sound speed contrast, length, and shape. The orientation is almost the unique parameter responsible for variation, with fatness affecting longer lengths. We present a summary of ΔMVBS that can serve as the basis for identification algorithms. Next, we simulate the scenario encountered in the Balearic Sea (western Mediterranean) where Northern krill are mixed with mesopelagic fish species (bristlemouths and lanternfishes), which are modeled with a prolate spheroid model. Simulated numerical data are employed to emulate the discrimination process with the most common identification techniques and typical survey frequencies. The importance of using density-independent techniques for acoustic classification is highlighted. Finally, an unsupervised neural network, the Self-Organizing Map (SOM), is used to cluster these theoretical data and identify the frequencies that provide, in this case, the most classification potential. The simulation results confirm that pairs of frequencies spanning the Rayleigh and geometric scattering regimes of the targets are the most useful for clustering; a minimum of four frequencies are necessary to separate the three species, while three frequencies are able to differentiate krill from mesopelagic fish species.

Exploratory study of fission product yield determination from photofission of 239Pu at 11 MeV with monoenergetic photons

NASA Astrophysics Data System (ADS)

Bhike, Megha; Tornow, W.; Krishichayan, Tonchev, A. P.

2017-02-01

Measurements of fission product yields play an important role for the understanding of fundamental aspects of the fission process. Recently, neutron-induced fission product-yield data of 239Pu at energies below 4 MeV revealed an unexpected energy dependence of certain fission fragments. In order to investigate whether this observation is prerogative to neutron-induced fission, a program has been initiated to measure fission product yields in photoinduced fission. Here we report on the first ever photofission product yield measurement with monoenergetic photons produced by Compton back-scattering of FEL photons. The experiment was performed at the High-Intensity Gamma-ray Source at Triangle Universities Nuclear Laboratory on 239Pu at Eγ=11 MeV. In this exploratory study the yield of eight fission products ranging from 91Sr to 143Ce has been obtained.

High-energy vacuum birefringence and dichroism in an ultrastrong laser field

NASA Astrophysics Data System (ADS)

Meuren, Sebastian; Bragin, Sergey; Keitel, Christoph H.; di Piazza, Antonino

2017-10-01

The interaction between real photons in vacuum is a long-standing prediction of quantum electrodynamics, which has never been observed experimentally. Upcoming 10 PW laser systems like the Extreme Light Infrastructure (ELI) will provide laser pulses with unprecedented intensities. If combined with highly energetic gamma photons - obtainable via Compton backscattering from laser-wakefield accelerated electron beams - the QED critical field becomes accessible. In we have derived how a generally polarized probe photon beam is influenced by both vacuum birefringence and dichroism in a strong linearly polarized plane-wave laser field. We put forward an experimental scheme to measure these effects in the nontrivial high-energy regime, where the QED critical field is reached and the Euler-Heisenberg approximation, valid for low-frequency electromagnetic fields, breaks down. Our results suggest the feasibility of verifying/rejecting the QED prediction for vacuum birefringence/dichroism at the 3 σ confidence level on the time scale of a few days at several upcoming laser facilities. Now at Princeton University, Princeton, NJ.

Exploratory study of fission product yield determination from photofission of Pu 239 at 11 MeV with monoenergetic photons

DOE PAGES

Bhike, Megha; Tornow, W.; Krishichayan, -; ...

2017-02-14

Here, measurements of fission product yields play an important role for the understanding of fundamental aspects of the fission process. Recently, neutron-induced fission product-yield data of  239Pu at energies below 4 MeV revealed an unexpected energy dependence of certain fission fragments. In order to investigate whether this observation is prerogative to neutron-induced fission, a program has been initiated to measure fission product yields in photoinduced fission. Here we report on the first ever photofission product yield measurement with monoenergetic photons produced by Compton back-scattering of FEL photons. The experiment was performed at the High-Intensity Gamma-ray Source at Triangle Universities Nuclear Laboratorymore » on  239Pu at E γ = 11 MeV. In this exploratory study the yield of eight fission products ranging from  91Sr to  143Ce has been obtained.« less

Exploratory study of fission product yield determination from photofission of Pu 239 at 11 MeV with monoenergetic photons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhike, Megha; Tornow, W.; Krishichayan, -

Here, measurements of fission product yields play an important role for the understanding of fundamental aspects of the fission process. Recently, neutron-induced fission product-yield data of  239Pu at energies below 4 MeV revealed an unexpected energy dependence of certain fission fragments. In order to investigate whether this observation is prerogative to neutron-induced fission, a program has been initiated to measure fission product yields in photoinduced fission. Here we report on the first ever photofission product yield measurement with monoenergetic photons produced by Compton back-scattering of FEL photons. The experiment was performed at the High-Intensity Gamma-ray Source at Triangle Universities Nuclear Laboratorymore » on  239Pu at E γ = 11 MeV. In this exploratory study the yield of eight fission products ranging from  91Sr to  143Ce has been obtained.« less

Mapping Parameterized Dataflow Graphs onto FPGA Platforms (Preprint)

DTIC Science & Technology

2014-02-01

Shen , Nimish Sane, William Plishker, Shuvra S. Bhattacharyya (University of Maryland) Hojin Kee (National Instruments) 5d. PROJECT NUMBER T2MC 5e...Rodyushkin, A. Ku - ranov, and V. Eruhimov. Computer vision workload analysis: Case study of video surveillance systems. Intel Technology Journal, 9, 2005...Prototyping, pages 1–7, Fairfax, Virginia, June 2010. [56] H. Wu, C. Shen , S. S. Bhattacharyya, K. Compton, M. Schulte, M. Wolf, and T. Zhang. Design and

Ice velocity and SAR backscatter record for the Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Scheuchl, B.; Mouginot, J.; Rignot, E. J.; Small, D.; Khazendar, A.; Seroussi, H. L.; Kellndorfer, J. M.

2017-12-01

The Antarctic Peninsula has undergone some dramatic changes in the last three decades. The latest high-profile change was the calving of iceberg A68 off the Larsen-C ice shelf, which resulted in the ice shelf to have the smallest extent since the beginning of satellite observations. A first indication of the beginning of the formation of the iceberg was reported based on 2008 ice velocity data by Khazendar et al. 2011 (GRL). With two long term funded missions as well as other available sensors, there is a wealth of data being collected not seen before. The European Sentinel-1 constellation provides InSAR coverage of the area every 6 days. In addition, lower resolution wide swath data are being collected over the Weddell sea and cover the shelf frequently. Landsat-8 thermal infrared imagery proved another valuable data source in monitoring the progression. USGS has committed Landsat-8 for frequent acquisitions in Antarctica during periods with available daylight. Here we take a longer term view of the Antarctic Peninsula and will provide a satellite data record of ice velocity data generated using SAR and optical data. In difference to our MEaSUREs Antarctica-wide 1 km annual product, this regional time series will be provided at 50 m posting to facilitate research that requires higher resolution velocity maps. We also use suitable InSAR data to determine the grounding line for the region. SAR backscatter can vary dramatically in the region, particularly in Austral summer. Low backscatter is an indication for surface melt, and in the case of Larsen-C, this can engulf the entire ice shelf at times. We will generate a calibrated backscatter time series using a precision DEM of the region. The maps will provide the temporal and spatial extent of surface melt and will be compared with results from the Regional Climate Model (RACMO) and, where available, with weather station data. We also use double difference interferograms, to chronicle the progression of the Larsen-C cracks that eventually formed A68 and likely subsequent icebergs. Using the velocity maps and a precision DEM, we look at the ice shelf rheology and its development over time.

A simple framework for modelling the dependence of bulk Comptonization by turbulence on accretion disc parameters

NASA Astrophysics Data System (ADS)

Kaufman, J.; Blaes, O. M.; Hirose, S.

2018-06-01

Warm Comptonization models for the soft X-ray excess in active galactic nuclei (AGN) do not self-consistently explain the relationship between the Comptonizing medium and the underlying accretion disc. Because of this, they cannot directly connect the fitted Comptonization temperatures and optical depths to accretion disc parameters. Since bulk velocities exceed thermal velocities in highly radiation pressure dominated discs, in these systems bulk Comptonization by turbulence may provide a physical basis in the disc itself for warm Comptonization models. We model the dependence of bulk Comptonization on fundamental accretion disc parameters, such as mass, luminosity, radius, spin, inner boundary condition, and α. In addition to constraining warm Comptonization models, our model can help distinguish contributions from bulk Comptonization to the soft X-ray excess from those due to other physical mechanisms, such as absorption and reflection. By linking the time variability of bulk Comptonization to fluctuations in the disc vertical structure due to magnetorotational instability (MRI) turbulence, our results show that observations of the soft X-ray excess can be used to study disc turbulence in the radiation pressure dominated regime. Because our model connects bulk Comptonization to 1D vertical structure temperature profiles in a physically intuitive way, it will be useful for understanding this effect in future simulations run in new regimes.

Shallow geology, sea-floor texture, and physiographic zones of Vineyard and western Nantucket Sounds, Massachusetts

USGS Publications Warehouse

Baldwin, Wayne E.; Foster, David S.; Pendleton, Elizabeth A.; Barnhardt, Walter A.; Schwab, William C.; Andrews, Brian D.; Ackerman, Seth D.

2016-09-02

Geologic, sediment texture, and physiographic zone maps characterize the sea floor of Vineyard and western Nantucket Sounds, Massachusetts. These maps were derived from interpretations of seismic-reflection profiles, high-resolution bathymetry, acoustic-backscatter intensity, bottom photographs/video, and surficial sediment samples collected within the 494-square-kilometer study area. Interpretations of seismic stratigraphy and mapping of glacial and Holocene marine units provided a foundation on which the surficial maps were created. This mapping is a result of a collaborative effort between the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management to characterize the surface and subsurface geologic framework offshore of Massachusetts.

Beyond Radar Backscatter: Estimating Forest Structure and Biomass with Radar Interferometry and Lidar Remote Sensing

NASA Astrophysics Data System (ADS)

Lavalle, M.; Ahmed, R.

2014-12-01

Mapping forest structure and aboveground biomass globally is a major challenge that the remote sensing community has been facing for decades. Radar backscatter is sensitive to biomass only up to a certain amount (about 150 tons/ha at L-band and 300 tons/ha at P-band), whereas lidar remote sensing is strongly limited by poor spatial coverage. In recent years radar interferometry, including its extension to polarimetric radar interferometry (PolInSAR), has emerged as a new technique to overcome the limitations of radar backscatter. The idea of PolInSAR is to use jointly interferometric and polarimetric radar techniques to separate different scattering mechanisms and retrieve the vertical structure of forests. The advantage is to map ecosystem structure continuously over large areas and independently of cloud coverage. Experiments have shown that forest height - an important proxy for biomass - can be estimated using PolInSAR with accuracy between 15% and 20% at plot level. At AGU we will review the state-of-art of repeat-pass PolInSAR for biomass mapping, including its potential and limitations, and discuss how merging lidar data with PolInSAR data can be beneficial not only for product cross-validation but also for achieving better estimation of ecosystem properties over large areas. In particular, lidar data are expected to aid the inversion of PolInSAR models by providing (1) better identification of ground under the canopy, (2) approximate information of canopy structure in limited areas, and (3) maximum tree height useful for mapping PolInSAR temporal decorrelation. We will show our tree height and biomass maps using PolInSAR L-band JPL/UAVSAR data collected in tropical and temperate forests, and P-band ONERA/TROPISAR data acquired in French Guiana. LVIS lidar data will be used, as well as SRTM data, field measurements and inventory data to support our study. The use of two different radar frequencies and repeat-pass JPL UAVSAR data will offer also the opportunity to compare our results with the new airborne P-band ECOSAR and L-band DBSAR instruments developed at the NASA Goddard Space Flight Center.

Monitoring high-intensity focused ultrasound (HIFU) therapy using radio frequency ultrasound backscatter to quantify heating

NASA Astrophysics Data System (ADS)

Kaczkowski, Peter J.; Anand, Ajay

2005-09-01

The spatial distribution and temporal history of tissue temperature is an essential indicator of thermal therapy progress, and treatment safety and efficacy. Magnetic resonance methods provide the gold standard noninvasive measurement of temperature but are costly and cumbersome compared to the therapy itself. We have been developing the use of ultrasound backscattering for real-time temperature estimation; ultrasonic methods have been limited to relatively low temperature rise, primarily due to lack of sensitivity at protein denaturation temperatures (50-70°C). Through validation experiments on gel phantoms and ex vivo tissue we show that temperature rise can be accurately mapped throughout the therapeutic temperature range using a new BioHeat Transfer Equation (BHTE) model-constrained inverse approach. Speckle-free temperature and thermal dose maps are generated using the ultrasound calibrated model over the imaged region throughout therapy delivery and post-treatment cooling periods. Results of turkey breast tissue experiments are presented for static HIFU exposures, in which the ultrasound calibrated BHTE temperature maps are shown to be very accurate (within a degree) using independent thermocouple measurements. This new temperature monitoring method may speed clinical adoption of ultrasound-guided HIFU therapy. [Work supported by Army MRMC.

Wetland Mapping with Quad-Pol Data Acquired during Tandem-X Science Phase

NASA Astrophysics Data System (ADS)

Mleczko, M.; Mroz, M.; Fitrzyk, M.

2016-06-01

The aim of this study was to exploit fully polarimetric SAR data acquired during TanDEM-X - Science Phase (2014/2015) over herbaceous wetlands of the Biebrza National Park (BbNP) in North-Eastern Poland for mapping seasonally flooded grasslands and permanent natural vegetation associations. The main goal of this work was to estimate the advantage of fully polarimetric radar images (QuadPol) versus alternative polarization (AltPol) modes. The methodology consisted in processing of several data subsets through polarimetric decompositions of complex quad-pol datasets, classification of multitemporal backscattering images, complementing backscattering images with Shannon Entropy, exploitation of interferometric coherence from tandem operations. In each case the multidimensional stack of images has been classified using ISODATA unsupervised clustering algorithm. With 6 QUAD-POL TSX/TDX acquisitions it was possible to distinguish correctly 5 thematic classes related to their water regime: permanent water bodies, temporarily flooded areas, wet grasslands, dry grasslands and common reed. This last category was possible to distinguish from deciduous forest only with Yamaguchi 4 component decomposition. The interferometric coherence calculated for tandem pairs turned out not so efficient as expected for this wetland mapping.

Backscattering analysis of high frequency ultrasonic imaging for ultrasound-guided breast biopsy

NASA Astrophysics Data System (ADS)

Cummins, Thomas; Akiyama, Takahiro; Lee, Changyang; Martin, Sue E.; Shung, K. Kirk

2017-03-01

A new ultrasound-guided breast biopsy technique is proposed. The technique utilizes conventional ultrasound guidance coupled with a high frequency embedded ultrasound array located within the biopsy needle to improve the accuracy in breast cancer diagnosis.1 The array within the needle is intended to be used to detect micro- calcifications indicative of early breast cancers such as ductal carcinoma in situ (DCIS). Backscattering analysis has the potential to characterize tissues to improve localization of lesions. This paper describes initial results of the application of backscattering analysis of breast biopsy tissue specimens and shows the usefulness of high frequency ultrasound for the new biopsy related technique. Ultrasound echoes of ex-vivo breast biopsy tissue specimens were acquired by using a single-element transducer with a bandwidth from 41 MHz to 88 MHz utilizing a UBM methodology, and the backscattering coefficients were calculated. These values as well as B-mode image data were mapped in 2D and matched with each pathology image for the identification of tissue type for the comparison to the pathology images corresponding to each plane. Microcalcifications were significantly distinguished from normal tissue. Adenocarcinoma was also successfully differentiated from adipose tissue. These results indicate that backscattering analysis is able to quantitatively distinguish tissues into normal and abnormal, which should help radiologists locate abnormal areas during the proposed ultrasound-guided breast biopsy with high frequency ultrasound.

Characterizing riverbed sediment using high-frequency acoustics 1: spectral properties of scattering

USGS Publications Warehouse

Buscombe, Daniel D.; Grams, Paul E.; Kaplinski, Matt A.

2014-01-01

Bed-sediment classification using high-frequency hydro-acoustic instruments is challenging when sediments are spatially heterogeneous, which is often the case in rivers. The use of acoustic backscatter to classify sediments is an attractive alternative to analysis of topography because it is potentially sensitive to grain-scale roughness. Here, a new method is presented which uses high-frequency acoustic backscatter from multibeam sonar to classify heterogeneous riverbed sediments by type (sand, gravel,rock) continuously in space and at small spatial resolution. In this, the first of a pair of papers that examine the scattering signatures from a heterogeneous riverbed, methods are presented to construct spatially explicit maps of spectral properties from geo-referenced point clouds of geometrically and radiometrically corrected echoes. Backscatter power spectra are computed to produce scale and amplitude metrics that collectively characterize the length scales of stochastic measures of riverbed scattering, termed ‘stochastic geometries’. Backscatter aggregated over small spatial scales have spectra that obey a power-law. This apparently self-affine behavior could instead arise from morphological- and grain-scale roughnesses over multiple overlapping scales, or riverbed scattering being transitional between Rayleigh and geometric regimes. Relationships exist between stochastic geometries of backscatter and areas of rough and smooth sediments. However, no one parameter can uniquely characterize a particular substrate, nor definitively separate the relative contributions of roughness and acoustic impedance (hardness). Combinations of spectral quantities do, however, have the potential to delineate riverbed sediment patchiness, in a data-driven approach comparing backscatter with bed-sediment observations (which is the subject of part two of this manuscript).

A high-brightness, electron-based source of polarized photons and neutrons

NASA Astrophysics Data System (ADS)

Spencer, J. E.

1999-06-01

A compact and comparatively inexpensive system that is practical for universities is described based on a low-energy, electron storage ring with at least one undulator based oscillator to store photons. If the oscillator cavity length is relativistically corrected to be an harmonic of the ring circumference (LC=βLRn/nB with nB the number of bunches), higher-energy, secondary photons from Compton backscattering may become significant. Then, besides synchrotron radiation from the ring dipoles and damping wigglers as well as undulator photons, there are frequency upshifted Compton photons and photoneutrons from low Q-value targets such as Beryllium (Qn=-1.66) or Deuterium (Qn=-2.22 MeV). For 100 MeV electron bunches, an adjustable-phase, planar, helical undulator can be made to produce circularly polarized UV photons having a fundamental ɛγ1=11.1 eV. If these photons are stored in a multimode, hole-coupled resonator they produce a Compton endpoint energy up to ɛγ2=1.7 MeV. When incident on a Be conversion target these secondary photons make unmoderated, epithermal neutrons having mean energy ɛn=24.8±6.8 keV from the two-body reaction Be9+γ→n+Be8(→2α)with negligible, residual radioactivity. The system is shown in Fig. 1. When the target is unpolarized, one expects neutron rates of 1011 epithermal n/s for 1015 Comptons/s and a circulating current of 1 A with polarizations PRHC(n⃗)=-0.5, PLHC(n⃗)=0.5, both with reduced flux, and PLin(n⃗)=0. With a 1 cm thick cylindrical tungsten sheath surrounding the Be to attenuate scattered photons exiting at 90° to the incident photons, there is a peak neutron flux of ≈109 epithermal n/s/cm2 cylindrically symmetric around the surface. No attempt was made to optimize this because there is still no accepted treatment protocol (dose rates or preferred neutron energy distribution). Although these factors depend on the individual case, several thousand BNCT treatments per year appear feasible. A potential clinical advantage of this system is that it also provides the photon beams required for analogs of NCT such as photon activation therapy PAT. Other medical applications, depending on electron energy, include real-time production of radioactive nuclides (both proton and neutron rich) e.g. tracers for PET scans useful for measuring boron uptake rate and distribution prior to treatment. While the primary electron energy depends on the application, higher energies are more versatile and technically simpler. Certain innovations that make such a system feasible are discussed.

Mapping local orientation of aligned fibrous scatterers for cancerous tissues using backscattering Mueller matrix imaging

NASA Astrophysics Data System (ADS)

He, Honghui; Sun, Minghao; Zeng, Nan; Du, E.; Liu, Shaoxiong; Guo, Yihong; Wu, Jian; He, Yonghong; Ma, Hui

2014-10-01

Polarization measurements are sensitive to the microstructure of tissues and can be used to detect pathological changes. Many tissues contain anisotropic fibrous structures. We obtain the local orientation of aligned fibrous scatterers using different groups of the backscattering Mueller matrix elements. Experiments on concentrically well-aligned silk fibers and unstained human papillary thyroid carcinoma tissues show that the m22, m33, m23, and m32 elements have better contrast but higher degeneracy for the extraction of orientation angles. The m12 and m13 elements show lower contrast, but allow us to determine the orientation angle for the fibrous scatterers along all directions. Moreover, Monte Carlo simulations based on the sphere-cylinder scattering model indicate that the oblique incidence of the illumination beam introduces some errors in the orientation angles obtained by both methods. Mapping the local orientation of anisotropic tissues may not only provide information on pathological changes, but can also give new leads to reduce the orientation dependence of polarization measurements.

Observations of MCG-5-23-16 with Suzaku, XMM-Newton and NuSTAR: Disk Tomography and Compton Hump Reverberation

NASA Technical Reports Server (NTRS)

Zoghbi, A.; Cackett, E. M.; Reynolds, C.; Kara, E.; Harrison, F. A.; Fabian, A. C.; Lohfink, A.; Matt, G.; Stern, D.; Zhang, W. W.

2014-01-01

MCG-5-23-16 is one of the first active galactic nuclei (AGNs) where relativistic reverberation in the iron K line originating in the vicinity of the supermassive black hole was found, based on a short XMM-Newton observation. In this work, we present the results from long X-ray observations using Suzaku, XMM-Newton, and NuSTAR designed to map the emission region using X-ray reverberation. A relativistic iron line is detected in the lag spectra on three different timescales, allowing the emission from different regions around the black hole to be separated. Using NuSTAR coverage of energies above 10 keV reveals a lag between these energies and the primary continuum, which is detected for the first time in an AGN. This lag is a result of the Compton reflection hump responding to changes in the primary source in a manner similar to the response of the relativistic iron K line.

Observations of MCG-5-23-16 with Suzaku, XMM-Newton and NuSTAR: Disk tomography and compton hump reverberation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zoghbi, A.; Reynolds, C.; Lohfink, A.

2014-07-01

MCG-5-23-16 is one of the first active galactic nuclei (AGNs) where relativistic reverberation in the iron K line originating in the vicinity of the supermassive black hole was found, based on a short XMM-Newton observation. In this work, we present the results from long X-ray observations using Suzaku, XMM-Newton, and NuSTAR designed to map the emission region using X-ray reverberation. A relativistic iron line is detected in the lag spectra on three different timescales, allowing the emission from different regions around the black hole to be separated. Using NuSTAR coverage of energies above 10 keV reveals a lag between thesemore » energies and the primary continuum, which is detected for the first time in an AGN. This lag is a result of the Compton reflection hump responding to changes in the primary source in a manner similar to the response of the relativistic iron K line.« less

Results from the energetic gamma-ray experiment telescope (EGRET) on the Compton Observatory

NASA Technical Reports Server (NTRS)

Fichtel, C. E.; Bertsch, D. L.; Dingus, B.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Kwok, P. W.; Lin, Y. C.; Mattox, J. R.

1993-01-01

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud (LMC) having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's

Estimating the age of arid-zone alluvial fan surfaces using roughness measurements from spaceborne radar backscatter

NASA Astrophysics Data System (ADS)

Hetz, G.; Mushkin, A.; Blumberg, D. G.; Baer, G.; Trabelsky, E.

2012-12-01

Alluvial fan surfaces respond to geologic and climate changes as they record the deposition and erosion processes that govern their evolution, which amongst others is manifested in the micro and meso scale topography of the surface. Remote sensing provides a regional view that is very useful for mapping. Some previous publications have demonstrated that relative dating can also be achieved by remote sensing using techniques common in planetary geology such as overlap relationships. This work focuses on the use of radar backscatter as suggested originally by Evans et al., (1992) to map ages but here we will try to provide an absolute geologic age. The objective of this paper is to demonstrate the use of radar backscatter to constrain surface roughness as a calibrated proxy for estimating age of alluvial surfaces. With the unique regional spatial perspective provided by spaceborne imaging, we aim at providing a new and complementary regional perspective for studying neotectonic and recent landscape evolution processes as well as paleoclimate. Moreover, the method (by radar backscattering measure) can be applied to the geomorphology of other planets. The current study is located in the southeastern part of the Negev desert, Israel on the late Pleistocene - Holocene Shehoret alluvial fan sequence. High resolution (0.5 cm) 3D roughness measurements were collected using a ground-based LIDAR (Leica HDS 3000) and these show a robust relationship between independently obtained OSL surface age and surface roughness; the fan surfaces become smoother with time over 103-105 yr timescales. Spaceborne backscatter radar data respond primarily to surface slope, roughness at a scale comparable to the radar wavelength, and other parameters such as dielectric properties of the surface. Therefore, radar can provide a good quantitative indication of surface roughness in arid zones, where vegetation cover is low. Preliminary results show a relationship between surface age and roughness and the radar cross section extracted from polarimetric spaceborne data. The best result is found in cross polarization (HV), L-band measured at an incidence angle of 38°.

Program Merges SAR Data on Terrain and Vegetation Heights

NASA Technical Reports Server (NTRS)

Siqueira, Paul; Hensley, Scott; Rodriguez, Ernesto; Simard, Marc

2007-01-01

X/P Merge is a computer program that estimates ground-surface elevations and vegetation heights from multiple sets of data acquired by the GeoSAR instrument [a terrain-mapping synthetic-aperture radar (SAR) system that operates in the X and bands]. X/P Merge software combines data from X- and P-band digital elevation models, SAR backscatter magnitudes, and interferometric correlation magnitudes into a simplified set of output topographical maps of ground-surface elevation and tree height.

Crystallographic orientation mapping with an electron backscattered diffraction technique in (Bi, Pb)2Sr2Ca2Cu3O10 superconductor tapes

NASA Astrophysics Data System (ADS)

Tan, T. T.; Li, S.; Oh, J. T.; Gao, W.; Liu, H. K.; Dou, S. X.

2001-02-01

It is believed that grain boundaries act as weak links in limiting the critical current density (Jc) of bulk high-Tc superconductors. The weak-link problem can be greatly reduced by elimination or minimization of large-angle grain boundaries. It has been reported that the distribution of the Jc in (Bi, Pb)2Sr2Ca2Cu3O10+x (Bi2223) superconductor tapes presents a parabolic relationship in the transverse cross section of the tapes, with the lowest currents occurring at the centre of the tapes. It was proposed that the Jc distribution is strongly dependent on the local crystallographic orientation distribution of the Bi2223 oxides. However, the local three-dimensional crystallographic orientation distribution of Bi2223 crystals in (Bi, Pb)2Sr2Ca2Cu3O10+x superconductor tapes has not yet been experimentally determined. In this work, the electron backscattered diffraction technique was employed to map the crystallographic orientation distribution, determine the misorientation of grain boundaries and also map the misorientation distribution in Bi2223 superconductor tapes. Through crystallographic orientation mapping, the relationship between the crystallographic orientation distribution, the boundary misorientation distribution and the fabrication parameters may be understood. This can be used to optimize the fabrication processes thus increasing the critical current density in Bi2223 superconductor tapes.

Maps showing bathymetry and modern sediment thickness on the inner continental shelf offshore of Fire Island, New York, pre-Hurricane Sandy

USGS Publications Warehouse

Schwab, William C.; Denny, Jane F.; Baldwin, Wayne E.

2014-01-01

The U.S. Geological Survey mapped approximately 336 square kilometers of the lower shoreface and inner continental shelf offshore of Fire Island, New York, in 2011 by using interferometric sonar and high-resolution chirp seismic-reflection systems. This report presents maps of bathymetry, acoustic backscatter, the coastal plain unconformity, the Holocene marine transgressive surface, and modern sediment thickness. These spatial data support research on the Quaternary evolution of the Fire Island coastal system and provide baseline information for research on coastal processes along southern Long Island.

Repeat AUV Mapping and ROV Observations of Active Mud Volcanos on the Canadian Beaufort Sea Continental Slope

NASA Astrophysics Data System (ADS)

Caress, D. W.; Paull, C. K.; Dallimore, S.; Lundsten, E. M.; Anderson, K.; Gwiazda, R.; Melling, H.; Lundsten, L.; Graves, D.; Thomas, H. J.; Cote, M.

2017-12-01

Two active submarine mud volcano sites located at 420 and 740 m depths on the margin of the Canadian Beaufort Sea were mapped in 2013 and again in 2016 using the same survey line pattern allowing detection of change over three years. The surveys were conducted using MBARI's mapping AUVs which fields a 200 kHz or 400 kHz multibeam sonar, a 1-6 kHz chirp sub-bottom profiler, and a 110 kHz chirp sidescan from a 50 m altitude. The resulting bathymetry has 1 m lateral resolution and 0.1 m vertical precision and sidescan mosaics have 1 m lateral resolution. Vertical changes of ≥0.2 m are observable by differencing repeat surveys. These features were also visited with MBARI's miniROV, which was outfitted for these dives with a manipulator mounted temperature probe. The 420 m mud volcano is nearly circular, 1100 m across, flat-topped, and superimposed on the pre-existing smooth slope. The central plateau has low relief <3 m consisting of concentric rings and ovoid mounds that appear to reflect distinct eruptions at shifting locations. The 740 m site contains 3 mud volcanoes, most prominently a 630 m wide, 30 m high flat-topped plateau with about 4 m of relief similar to the 420 m feature plus a 5 m high cone on the southern rim. North of this plateau is a smooth-textured conically shaped feature also standing about 30 m above the floor of the subsidence structure. Sidescan mosaics reveal significant changes in backscatter patterns at both mud volcano sites between surveys. Comparison of bathymetry also reveals new flows of up to 1.8 m thickness at both sites, as well as subtle spreading of the flat plateaus rims. An active mudflow was encountered during a miniROV dive on a high backscatter target at the 740 m site. This tongue of mud was observed to be slowly flowing downslope. The ROV temperature probe inserted 2 cm into the flow measured 23°C, compared to ambient water (-0.4°C), indicating the rapid ascent of the mud from considerable subsurface depths. Bubbles (presumably methane) were escaping from the active mudflow. Combining seafloor mapping with ROV observations indicates that new sediment flows with entrained methane bubbles exhibit very high backscatter which rapidly changes to very low backscatter following degassing of the smooth, bare mud. To our knowledge this is the first time an eruption on a submarine mud volcano has been observed.

Surficial geology and shaded seafloor relief of Georges Bank, Fundian Channel and Northeast Channel, Gulf of Maine

USGS Publications Warehouse

Todd, B.J.; Valentine, Page C.

2015-01-01

Georges Bank is a shallow submarine bank that lies south of Nova Scotia and east of Cape Cod and bounds the seaward side of the Gulf of Maine. The international boundary between Canada and the United States transects the bank, and the eastern part of the bank (~7500 square kilometres) lies in Canadian territory. This map shows the surficial geology of a part of Georges Bank at a scale of 1:50 000. This map has companion topographic and backscatter strength maps. These companion maps provide a basis for interpreting the origin of seafloor features and the nature of materials that form the seafloor. The maps are based on multibeam-sonar surveys conducted in 1999 and 2000 to map 11,965 square kilometres of the seafloor.

Enhanced Sidescan-Sonar Imagery Offshore of Southeastern Massachusetts

USGS Publications Warehouse

Poppe, Lawrence J.; McMullen, Kate Y.; Williams, S. Jeffress; Ackerman, Seth D.; Glomb, K.A.; Forfinski, N.A.

2008-01-01

The U.S. Geological Survey (USGS), National Oceanic and Atmospheric Administration (NOAA), and Massachusetts Office of Coastal Zone Management (CZM) have been working cooperatively to map and study the coastal sea floor. The sidescan-sonar imagery collected during NOAA hydrographic surveys has been included as part of these studies. However, the original sonar imagery contains tonal artifacts from environmental noise (for example, sea state), equipment settings (for example, power and gain changes), and processing (for example, inaccurate cross-track and line-to-line normalization), which impart a quilt-like patchwork appearance to the mosaics. These artifacts can obscure the normalized backscatter properties of the sea floor. To address this issue, sidescan-sonar imagery from surveys H11076 and H11079 offshore of southeastern Massachusetts was enhanced by matching backscatter tones of adjacent sidescan-sonar lines. These mosaics provide continuous grayscale perspectives of the backscatter, more accurately reveal the sea-floor geologic trends, and minimize the environment-, acquisition-, and processing-related noise.

Ocean currents and acoustic backscatter data from shipboard ADCP measurements at three North Atlantic seamounts between 2004 and 2015.

PubMed

Mohn, Christian; Denda, Anneke; Christiansen, Svenja; Kaufmann, Manfred; Peine, Florian; Springer, Barbara; Turnewitsch, Robert; Christiansen, Bernd

2018-04-01

Seamounts are amongst the most common physiographic structures of the deep-ocean landscape, but remoteness and geographic complexity have limited the systematic collection of integrated and multidisciplinary data in the past. Consequently, important aspects of seamount ecology and dynamics remain poorly studied. We present a data collection of ocean currents and raw acoustic backscatter from shipboard Acoustic Doppler Current Profiler (ADCP) measurements during six cruises between 2004 and 2015 in the tropical and subtropical Northeast Atlantic to narrow this gap. Measurements were conducted at seamount locations between the island of Madeira and the Portuguese mainland (Ampère, Seine Seamount), as well as east of the Cape Verde archipelago (Senghor Seamount). The dataset includes two-minute ensemble averaged continuous velocity and backscatter profiles, supplemented by spatially gridded maps for each velocity component, error velocity and local bathymetry. The dataset is freely available from the digital data library PANGAEA at https://doi.pangaea.de/10.1594/PANGAEA.883193.

Radarsat-1 and ERS InSAR analysis over southeastern coastal Louisiana: Implications for mapping water-level changes beneath swamp forests

USGS Publications Warehouse

Lu, Z.; Kwoun, Oh-Ig

2008-01-01

Detailed analysis of C-band European Remote Sensing 1 and 2 (ERS-1/ERS-2) and Radarsat-1 interferometric synthetic aperture radar (InSAR) imagery was conducted to study water-level changes of coastal wetlands of southeastern Louisiana. Radar backscattering and InSAR coherence suggest that the dominant radar backscattering mechanism for swamp forest and saline marsh is double-bounce backscattering, implying that InSAR images can be used to estimate water-level changes with unprecedented spatial details. On the one hand, InSAR images suggest that water-level changes over the study site can be dynamic and spatially heterogeneous and cannot be represented by readings from sparsely distributed gauge stations. On the other hand, InSAR phase measurements are disconnected by structures and other barriers and require absolute water-level measurements from gauge stations or other sources to convert InSAR phase values to absolute water-level changes. ?? 2006 IEEE.

Spacecraft instrument calibration and stability

NASA Technical Reports Server (NTRS)

Gille, J. C.; Feldman, P.; Hudson, R.; Lean, J.; Madden, R.; Mcmaster, L.; Mount, G.; Rottman, G.; Simon, P. C.

1989-01-01

The following topics are covered: instrument degradation; the Solar Backscatter Ultraviolet (SBUV) Experiment; the Total Ozone Mapping Spectrometer (TOMS); the Stratospheric Aerosol and Gas Experiment 1 (SAGE-1) and SAGE-2 instruments; the Solar Mesosphere Explorer (SME) UV ozone and near infrared airglow instruments; and the Limb Infrared Monitor of the Stratosphere (LIMS).

Modelling the distribution of hard seabed using calibrated multibeam acoustic backscatter data in a tropical, macrotidal embayment: Darwin Harbour, Australia

NASA Astrophysics Data System (ADS)

Siwabessy, P. Justy W.; Tran, Maggie; Picard, Kim; Brooke, Brendan P.; Huang, Zhi; Smit, Neil; Williams, David K.; Nicholas, William A.; Nichol, Scott L.; Atkinson, Ian

2018-06-01

Spatial information on the distribution of seabed substrate types in high use coastal areas is essential to support their effective management and environmental monitoring. For Darwin Harbour, a rapidly developing port in northern Australia, the distribution of hard substrate is poorly documented but known to influence the location and composition of important benthic biological communities (corals, sponges). In this study, we use angular backscatter response curves to model the distribution of hard seabed in the subtidal areas of Darwin Harbour. The angular backscatter response curve data were extracted from multibeam sonar data and analysed against backscatter intensity for sites observed from seabed video to be representative of "hard" seabed. Data from these sites were consolidated into an "average curve", which became a reference curve that was in turn compared to all other angular backscatter response curves using the Kolmogorov-Smirnov goodness-of-fit. The output was used to generate interpolated spatial predictions of the probability of hard seabed ( p-hard) and derived hard seabed parameters for the mapped area of Darwin Harbour. The results agree well with the ground truth data with an overall classification accuracy of 75% and an area under curve measure of 0.79, and with modelled bed shear stress for the Harbour. Limitations of this technique are discussed with attention to discrepancies between the video and acoustic results, such as in areas where sediment forms a veneer over hard substrate.

Single-Sided Noinvasive Inspection of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography

DTIC Science & Technology

2000-05-01

a vector , ρ "# represents the set of voxel densities sorted into a vector , and ( )A ρ $# "# represents a 8 mapping of the voxel densities to...density vector in equation (4) suggests that solving for ρ "# by direct inversion is not possible, calling for an iterative technique beginning with...the vector of measured spectra, and D is the diagonal matrix of the inverse of the variances. The diagonal matrix provides weighting terms, which

Ultra-powerful compact amplifiers for short laser pulses

NASA Astrophysics Data System (ADS)

Malkin, Vladimir

1999-11-01

Laser compressors-amplifiers more powerful and compact than ones based on the currently most advanced chirped pulse amplification technique must handle ultrahigh laser intensities. The medium capable of bearing those is plasma. An interesting kinetic regime of short laser pulse amplification by Compton backscattering of counterpropagating laser pump in plasma, akin to superradiant amplification in free-electron lasers, has been proposed recently (Shvets G., Fisch N. J., Pukhov A., and Meyer-ter-Vehn J., Phys. Rev. Lett., v.81, 4879 (1998)). However, the conversion efficiency of pump energy into a short pulse appears to be higher in a transient Raman backscattering regime (Malkin V. M., Shvets G. and Fisch N. J., Phys. Rev. Lett., v.82, 4448 (1999)), where the integrity of the three-wave interaction is maintained. In this regime the pump is completely depleted through the full nonlinear stage of the interaction, so that unwanted Raman and modulational instabilities limit just the amplification time, while the efficiency is kept about 100%. For instance, a 2*10^14 W/cm^2, 1 μm-wavelength laser pump can be compressed within 5 mm length, which is less than the length for filamentation instabilities to develop, to a 30--40 fsec pulse with fluence 6 kJ/cm^2. Such an output pulse is a thousand times shorter and a million time more intensive than outputs of conventional Raman amplifiers operating in a stationary regime. Yet larger amplification distances and output energies can be achieved by suppressing filamentation instabilities. It appears (Malkin V. M., Shvets G. and Fisch N. J., Submitted to Phys. Rev. Lett.) that appropriate detuning of the resonance (by plasma density gradient or/and chirping the pump laser) suppresses the Raman near-forward scattering instability of the pumped pulse, as well as the pump Raman backscattering instability to noise, while the high efficiency of the amplification still persists. The respective new class of transient amplification regimes, generalizing the classical pi-pulse regime of exactly resonant amplification, is described quantitatively. These regimes are of broad interest, being applicable also to other processes such as Brillouin scattering.

Compton scattering study of electron momentum distribution in lithium fluoride using 662 keV gamma radiations

NASA Astrophysics Data System (ADS)

Vijayakumar, R.; Shivaramu; Ramamurthy, N.; Ford, M. J.

2008-12-01

Here we report the first ever 137Cs Compton spectroscopy study of lithium fluoride. The spherical average Compton profiles of lithium fluoride are deduced from Compton scattering measurements on poly crystalline sample at gamma ray energy of 662 keV. To compare the experimental data, we have computed the spherical average Compton profiles using self-consistent Hartree-Fock wave functions employed on linear combination of atomic orbital (HF-LCAO) approximation. The directional Compton profiles and their anisotropic effects are also calculated using the same HF-LCAO approximation. The experimental spherical average profiles are found to be in good agreement with the corresponding HF-LCAO calculations and in qualitative agreement with Hartree-Fock free atom values. The present experimental isotropic and calculated directional profiles are also compared with the available experimental isotropic and directional Compton profiles using 59.54 and 159 keV γ-rays.

Improved Discrimination of Volcanic Complexes, Tectonic Features, and Regolith Properties in Mare Serenitatis from Earth-Based Radar Mapping

NASA Technical Reports Server (NTRS)

Campbell, Bruce A.; Hawke, B. Ray; Morgan, Gareth A.; Carter, Lynn M.; Campbell, Donald B.; Nolan, Michael

2014-01-01

Radar images at 70 cm wavelength show 4-5 dB variations in backscatter strength within regions of relatively uniform spectral reflectance properties in central and northern Mare Serenitatis, delineating features suggesting lava flow margins, channels, and superposition relationships. These backscatter differences are much less pronounced at 12.6 cm wavelength, consistent with a large component of the 70 cm echo arising from the rough or blocky transition zone between the mare regolith and the intact bedrock. Such deep probing is possible because the ilmenite content, which modulates microwave losses, of central Mare Serenitatis is generally low (2-3% by weight). Modeling of the radar returns from a buried interface shows that an average regolith thickness of 10m could lead to the observed shifts in 70 cm echo power with a change in TiO2 content from 2% to 3%. This thickness is consistent with estimates of regolith depth (10-15m) based on the smallest diameter for which fresh craters have obvious blocky ejecta. The 70 cm backscatter differences provide a view of mare flow-unit boundaries, channels, and lobes unseen by other remote sensing methods. A localized pyroclastic deposit associated with Rima Calippus is identified based on its low radar echo strength. Radar mapping also improves delineation of units for crater age dating and highlights a 250 km long, east-west trending feature in northern Mare Serenitatis that we suggest is a large graben flooded by late-stage mare flows.

Arthur H. Compton and Compton Scattering

Science.gov Websites

of X-rays, when he discovered the effect that is named after him in 1922. ... The Compton effect photon, when it interacts with matter. This effect demonstrates that light cannot be explained purely as overall momentum of the system is conserved. ... The explanation and measurement of the Compton effect

Evaluation of double photon coincidence Compton imaging method with GEANT4 simulation

NASA Astrophysics Data System (ADS)

Yoshihara, Yuri; Shimazoe, Kenji; Mizumachi, Yuki; Takahashi, Hiroyuki

2017-11-01

Compton imaging has been used for various applications including astronomical observations, radioactive waste management, and biomedical imaging. The positions of radioisotopes are determined in the intersections of multiple cone traces through a large number of events, which reduces signal to noise ratio (SNR) of the images. We have developed an advanced Compton imaging method to localize radioisotopes with high SNR by using information of the interactions of Compton scattering caused by two gamma rays at the same time, as the double photon coincidence Compton imaging method. The targeted radioisotopes of this imaging method are specific nuclides that emit several gamma rays at the same time such as 60Co, 134Cs, and 111In, etc. Since their locations are determined in the intersections of two Compton cones, the most of cone traces would disappear in the three-dimensional space, which enhances the SNR and angular resolution. In this paper, the comparison of the double photon coincidence Compton imaging method and the single photon Compton imaging method was conducted by using GEANT4 Monte Carlo simulation.

EGRET Diffuse Gamma Ray Maps Between 30 MeV and 10 GeV

NASA Technical Reports Server (NTRS)

Cillis, A, N.; Hartman, R. C.

2004-01-01

This paper presents all-sky maps of diffuse gamma radiation in various energy ranges between 30 MeV and 10 GeV, based on data collected by the EGRET instrument on the Compton Gamma Ray Observatory. Although the maps can be used for a variety of applications. the immediate goal is the generation of diffuse gamma-ray maps which can be used as a diffuse background/foreground for point source analysis of the data to be obtained from new high-energy gamma-ray missions like GLAST and AGILE. To generate the diffuse gamma maps from the raw EGRET maps, the point sources in the Third EGRET Catalog were subtracted out using the appropriate point spread function for each energy range. After that, smoothing was performed to minimize the effects of photon statistical noise. A smoothing length of 1 deg vas used for the Galactic plane maps. For the all-sky maps, a procedure was used which resulted in a smoothing length roughly equivalent to 4 deg. The result of this work is 16 maps of different energy intervals for absolute value of b < or equal to 20 deg, and 32 all-sky maps, 16 in equatorial coordinates (J2000) and 16 in Galactic coordinates.

EGRET Diffuse Gamma Ray Maps Between 30 MeV and 10 GeV

NASA Technical Reports Server (NTRS)

Cillis, A. N.; Hartman, R. C.

2004-01-01

This paper presents all-sky maps of diffuse gamma radiation in various energy ranges between 30 MeV and 10 GeV, based on data collected by the EGRET instrument on the Compton Gamma Ray Observatory. Although the maps can be used for a variety of applications, the immediate goal is the generation of diffuse gamma-ray maps which can be used as a diffuse background/foreground for point source analysis of the data to be obtained from new high-energy gamma-ray missions like GLAST and AGILE. To generate the diffuse gamma maps from the raw EGRET maps, the point sources in the Third EGRET Catalog were subtracted out using the appropriate point spread function for each energy range. After that, smoothing was performed to minimize the effects of photon statistical noise. A smoothing length of 1deg was used for the Galactic plane maps. For the all-sky maps, a procedure was used which resulted in a smoothing length roughly equivalent to 4deg. The result of this work is 16 maps of different energy intervals for [b]less than or equal to 20deg, and 32 all-sky maps, 16 in equatorial coordinates (J2000) and 16 in Galactic coordinates.

Seep Detection using E/V Nautilus Integrated Seafloor Mapping and Remotely Operated Vehicles on the United States West Coast

NASA Astrophysics Data System (ADS)

Gee, L. J.; Raineault, N.; Kane, R.; Saunders, M.; Heffron, E.; Embley, R. W.; Merle, S. G.

2017-12-01

Exploration Vessel (E/V) Nautilus has been mapping the seafloor off the west coast of the United States, from Washington to California, for the past three years with a Kongsberg EM302 multibeam sonar. This system simultaneously collects bathymetry, seafloor and water column backscatter data, allowing an integrated approach to mapping to more completely characterize a region, and has identified over 1,000 seafloor seeps. Hydrographic multibeam sonars like the EM302 were designed for mapping the bathymetry. It is only in the last decade that major mapping projects included an integrated approach that utilizes the seabed and water column backscatter information in addition to the bathymetry. Nautilus mapping in the Eastern Pacific over the past three years has included a number of seep-specific expeditions, and utilized and adapted the preliminary mapping guidelines that have emerged from research. The likelihood of seep detection is affected by many factors: the environment: seabed geomorphology, surficial sediment, seep location/depth, regional oceanography and biology, the nature of the seeps themselves: size variation, varying flux, depth, and transience, the detection system: design of hydrographic multibeam sonars limits use for water column detection, the platform: variations in the vessel and operations such as noise, speed, and swath overlap. Nautilus integrated seafloor mapping provided multiple indicators of seep locations, but it remains difficult to assess the probability of seep detection. Even when seeps were detected, they have not always been located during ROV dives. However, the presence of associated features (methane hydrate and bacterial mats) serve as evidence of potential seep activity and reinforce the transient nature of the seeps. Not detecting a seep in the water column data does not necessarily indicate that there is not a seep at a given location, but with multiple passes over an area and by the use of other contextual data, an area may be classified as likely or unlikely to host seeps.

Advanced Source Deconvolution Methods for Compton Telescopes

NASA Astrophysics Data System (ADS)

Zoglauer, Andreas

The next generation of space telescopes utilizing Compton scattering for astrophysical observations is destined to one day unravel the mysteries behind Galactic nucleosynthesis, to determine the origin of the positron annihilation excess near the Galactic center, and to uncover the hidden emission mechanisms behind gamma-ray bursts. Besides astrophysics, Compton telescopes are establishing themselves in heliophysics, planetary sciences, medical imaging, accelerator physics, and environmental monitoring. Since the COMPTEL days, great advances in the achievable energy and position resolution were possible, creating an extremely vast, but also extremely sparsely sampled data space. Unfortunately, the optimum way to analyze the data from the next generation of Compton telescopes has not yet been found, which can retrieve all source parameters (location, spectrum, polarization, flux) and achieves the best possible resolution and sensitivity at the same time. This is especially important for all sciences objectives looking at the inner Galaxy: the large amount of expected sources, the high background (internal and Galactic diffuse emission), and the limited angular resolution, make it the most taxing case for data analysis. In general, two key challenges exist: First, what are the best data space representations to answer the specific science questions? Second, what is the best way to deconvolve the data to fully retrieve the source parameters? For modern Compton telescopes, the existing data space representations can either correctly reconstruct the absolute flux (binned mode) or achieve the best possible resolution (list-mode), both together were not possible up to now. Here we propose to develop a two-stage hybrid reconstruction method which combines the best aspects of both. Using a proof-of-concept implementation we can for the first time show that it is possible to alternate during each deconvolution step between a binned-mode approach to get the flux right and a list-mode approach to get the best angular resolution, to get achieve both at the same time! The second open question concerns the best deconvolution algorithm. For example, several algorithms have been investigated for the famous COMPTEL 26Al map which resulted in significantly different images. There is no clear answer as to which approach provides the most accurate result, largely due to the fact that detailed simulations to test and verify the approaches and their limitations were not possible at that time. This has changed, and therefore we propose to evaluate several deconvolution algorithms (e.g. Richardson-Lucy, Maximum-Entropy, MREM, and stochastic origin ensembles) with simulations of typical observations to find the best algorithm for each application and for each stage of the hybrid reconstruction approach. We will adapt, implement, and fully evaluate the hybrid source reconstruction approach as well as the various deconvolution algorithms with simulations of synthetic benchmarks and simulations of key science objectives such as diffuse nuclear line science and continuum science of point sources, as well as with calibrations/observations of the COSI balloon telescope. This proposal for "development of new data analysis methods for future satellite missions" will significantly improve the source deconvolution techniques for modern Compton telescopes and will allow unlocking the full potential of envisioned satellite missions using Compton-scatter technology in astrophysics, heliophysics and planetary sciences, and ultimately help them to "discover how the universe works" and to better "understand the sun". Ultimately it will also benefit ground based applications such as nuclear medicine and environmental monitoring as all developed algorithms will be made publicly available within the open-source Compton telescope analysis framework MEGAlib.

Compton tomography system

DOEpatents

Grubsky, Victor; Romanoov, Volodymyr; Shoemaker, Keith; Patton, Edward Matthew; Jannson, Tomasz

2016-02-02

A Compton tomography system comprises an x-ray source configured to produce a planar x-ray beam. The beam irradiates a slice of an object to be imaged, producing Compton-scattered x-rays. The Compton-scattered x-rays are imaged by an x-ray camera. Translation of the object with respect to the source and camera or vice versa allows three-dimensional object imaging.

A comparison of supervised classification methods for the prediction of substrate type using multibeam acoustic and legacy grain-size data.

PubMed

Stephens, David; Diesing, Markus

2014-01-01

Detailed seabed substrate maps are increasingly in demand for effective planning and management of marine ecosystems and resources. It has become common to use remotely sensed multibeam echosounder data in the form of bathymetry and acoustic backscatter in conjunction with ground-truth sampling data to inform the mapping of seabed substrates. Whilst, until recently, such data sets have typically been classified by expert interpretation, it is now obvious that more objective, faster and repeatable methods of seabed classification are required. This study compares the performances of a range of supervised classification techniques for predicting substrate type from multibeam echosounder data. The study area is located in the North Sea, off the north-east coast of England. A total of 258 ground-truth samples were classified into four substrate classes. Multibeam bathymetry and backscatter data, and a range of secondary features derived from these datasets were used in this study. Six supervised classification techniques were tested: Classification Trees, Support Vector Machines, k-Nearest Neighbour, Neural Networks, Random Forest and Naive Bayes. Each classifier was trained multiple times using different input features, including i) the two primary features of bathymetry and backscatter, ii) a subset of the features chosen by a feature selection process and iii) all of the input features. The predictive performances of the models were validated using a separate test set of ground-truth samples. The statistical significance of model performances relative to a simple baseline model (Nearest Neighbour predictions on bathymetry and backscatter) were tested to assess the benefits of using more sophisticated approaches. The best performing models were tree based methods and Naive Bayes which achieved accuracies of around 0.8 and kappa coefficients of up to 0.5 on the test set. The models that used all input features didn't generally perform well, highlighting the need for some means of feature selection.

Oil spill detection from TerraSAR-X dual-polarized images using artificial neural network

NASA Astrophysics Data System (ADS)

Kim, D.; Jung, H.-S.

2017-10-01

Marine pollution from oil spills destroys ecosystems. In order to minimize the damage, it is important to fast cleanup it after predicting how the oil will spread. In order to predict the spread of oil spill, remote sensing technique, especially radar satellite image is widely used. In previous studies, only the back-scattering value is generally used for the detection of oil spill. However, in this study, oil spill was detected by applying ANN (Artificial Neural Network) as input data from the back-scattering value of the radar image as well as the phase information extracted from the dual polarization. In order to maximize the efficiency of oil spill detection using a back-scattering value, the speckle noise acting as an error factor should be removed first. NL-means filter was applied to multi-look image to remove it without smoothing of spatial resolution. In the coherence image, the sea has a high value and the oil spill area has a low value due to the scattering characteristics of the pulse. In order to using the characteristics of radar image, training sample was set up from NL-means filtered images(HH, VV) and coherence image, and ANN was applied to produce probability map of oil spill. In general, the value was 0.4 or less in the case of the sea, and the value was mainly in the range of 0.7 to 0.9 in the oil spill area. Using coherence images generated from different polarizations showed better detection results for relatively thin oil spill areas such as oil slick or oil sheen than using back-scattering information alone. It is expected that if the information about the look-alike of oil spill such as algae, internal wave and rainfall area is provided, the probability map can be produced with higher accuracy.

Mapping Near-Surface Salinization Using Long-wavelength AIRSAR

NASA Technical Reports Server (NTRS)

Paine, Jeffery G.

2003-01-01

In May 1999, NASA's Jet Propulsion Laboratory acquired airborne synthetic aperture radar (AIRSAR) data over the Hatchel and Montague Test Sites in Texas. We analyzed P- and L-band polarimetric radar data from these AIRSAR missions to assess whether AIRSAR could be used as a rapid and remote platform for screening large areas at risk for near-surface soil and water salinization. Ongoing geological, geophysical, and hydrological studies at the Hatchel Test Site in Runnels County and the Montague Test Site in Montague County have demonstrated the utility of high-resolution airborne electromagnetic (EM) induction in mapping electrical conductivity changes that accompany shallow natural and oil-field related salinization at these sites in the Colorado and Red River basins. We compared AIRSAR and airborne EM data quantitatively by (1) selecting representative flight lines from airborne EM surveys of the Hatchel and Montague sites, (2) extracting measurement locations and apparent conductivities at the highest available EM frequency, (3) identifying and extracting all P- and L-band backscatter intensities for all locations within 5 m of an airborne EM measurement, and (4) examining the spatial and magnitude relationships between apparent conductivity and all radar polarization and polarization-ratio combinations. For both test sites, backscatter intensity in all individual P- and L-band polarizations was slightly negatively correlated with apparent conductivity. In most modes this was manifested as a decrease in the range and magnitude of backscatter intensity as apparent conductivity increased. Select single-band and cross-band polarization ratios exhibited somewhat higher correlation with apparent conductivity by partly diminishing the dominance of the vegetation contribution to V backscatter intensity. The highest correlation with conductivity was obtained using the L-band vertical- to cross-polarization ratio, the P-band vertical- to L-band cross-polarization ratio, and the P-band vertical-to cross-polarization ratio. These correlations were higher for the more arid (and less electrically conductive) Hatchel Test Site than they were for the Montague Test Site.

Digital direct electron imaging of energy-filtered electron backscatter diffraction patterns

NASA Astrophysics Data System (ADS)

Vespucci, S.; Winkelmann, A.; Naresh-Kumar, G.; Mingard, K. P.; Maneuski, D.; Edwards, P. R.; Day, A. P.; O'Shea, V.; Trager-Cowan, C.

2015-11-01

Electron backscatter diffraction is a scanning electron microscopy technique used to obtain crystallographic information on materials. It allows the nondestructive mapping of crystal structure, texture, and strain with a lateral and depth resolution on the order of tens of nanometers. Electron backscatter diffraction patterns (EBSPs) are presently acquired using a detector comprising a scintillator coupled to a digital camera, and the crystallographic information obtainable is limited by the conversion of electrons to photons and then back to electrons again. In this article we will report the direct acquisition of energy-filtered EBSPs using a digital complementary metal-oxide-semiconductor hybrid pixel detector, Timepix. We show results from a range of samples with different mass and density, namely diamond, silicon, and GaN. Direct electron detection allows the acquisition of EBSPs at lower (≤5 keV) electron beam energies. This results in a reduction in the depth and lateral extension of the volume of the specimen contributing to the pattern and will lead to a significant improvement in lateral and depth resolution. Direct electron detection together with energy filtering (electrons having energy below a specific value are excluded) also leads to an improvement in spatial resolution but in addition provides an unprecedented increase in the detail in the acquired EBSPs. An increase in contrast and higher-order diffraction features are observed. In addition, excess-deficiency effects appear to be suppressed on energy filtering. This allows the fundamental physics of pattern formation to be interrogated and will enable a step change in the use of electron backscatter diffraction (EBSD) for crystal phase identification and the mapping of strain. The enhancement in the contrast in high-pass energy-filtered EBSD patterns is found to be stronger for lighter, less dense materials. The improved contrast for such materials will enable the application of the EBSD technique to be expanded to materials for which conventional EBSD analysis is not presently practicable.

Inundation Mapping for Heterogeneous Land Covers with Synthetic Aperture Radar and Auxiliary Data

NASA Astrophysics Data System (ADS)

Aristizabal, F.; Judge, J.

2017-12-01

Synthetic Aperture Radar (SAR) has been widely used to detect surface water inundation and provides an advantage over multi-spectral instruments due to cloud penetration and higher spatial resolutions. However, detecting inundation for densely vegetated and urban areas with SAR remains a challenge due to corner reflection and diffuse scattering. Additionally, flat urban surfaces such as roads exhibit similar backscatter coefficients as urban surface water. Differences between inundated and non-inundated backscatter over vegetated land covers of static spatial domains have been demonstrated in previous studies. However, these backscatter differences are sensitive to changes in water depth, soil moisture, SAR sensor parameters, terrain, and vegetation properties. These factors tend to make accurate inundation mapping of heterogeneous regions across varying spatial and temporal extents difficult with exclusive use of SAR. This study investigates the utility of auxiliary data specifically high-resolution (10m) terrain information in conjunction with SAR (10m) for detecting inundated areas. Digital elevation models provide an absolute elevation which could enhance inundation mapping given a limited study extent with similar topography. To counter this limitation, a hydrologically relevant terrain index is proposed known as the Height Above Nearest Drainage (HAND) which normalizes topography to the local relative elevation of the nearest point along the relevant drainage line. HAND has been used for assisting remote sensing inundation mapping in the pre-processing stage as a terrain correction tool and as a post-processing mask that eliminates areas of low inundation risk. While the latter technique is useful for reduction of commission errors, it does not employ HAND for reducing omission errors that can occur from dense vegetation, spectral noise, and urban features. Sentinel-1 dual-pol SAR as well as auxiliary HAND will be used as predictors by various supervised and unsupervised classification algorithms. The October 2016 record flood caused by Hurricane Matthew along the Neuse River in North Carolina will be used as a study area. For validation, locally inundated areas will be derived from observed river stages and high water marks furnished by the U.S. Geological Survey.

Development of a Compton camera for safeguards applications in a pyroprocessing facility

NASA Astrophysics Data System (ADS)

Park, Jin Hyung; Kim, Young Su; Kim, Chan Hyeong; Seo, Hee; Park, Se-Hwan; Kim, Ho-Dong

2014-11-01

The Compton camera has a potential to be used for localizing nuclear materials in a large pyroprocessing facility due to its unique Compton kinematics-based electronic collimation method. Our R&D group, KAERI, and Hanyang University have made an effort to develop a scintillation-detector-based large-area Compton camera for safeguards applications. In the present study, a series of Monte Carlo simulations was performed with Geant4 in order to examine the effect of the detector parameters and the feasibility of using a Compton camera to obtain an image of the nuclear material distribution. Based on the simulation study, experimental studies were performed to assess the possibility of Compton imaging in accordance with the type of the crystal. Two different types of Compton cameras were fabricated and tested with a pixelated type of LYSO (Ce) and a monolithic type of NaI(Tl). The conclusions of this study as a design rule for a large-area Compton camera can be summarized as follows: 1) The energy resolution, rather than position resolution, of the component detector was the limiting factor for the imaging resolution, 2) the Compton imaging system needs to be placed as close as possible to the source location, and 3) both pixelated and monolithic types of crystals can be utilized; however, the monolithic types, require a stochastic-method-based position-estimating algorithm for improving the position resolution.

Doppler Broadening and its Contribution to Compton Energy-Absorption Cross Sections: An Analysis of the Compton Component in Terms of Mass-Energy Absorption Coefficient

NASA Astrophysics Data System (ADS)

Rao, D. V.; Takeda, T.; Itai, Y.; Akatsuka, T.; Cesareo, R.; Brunetti, A.; Gigante, G. E.

2002-09-01

Compton energy absorption cross sections are calculated using the formulas based on a relativistic impulse approximation to assess the contribution of Doppler broadening and to examine the Compton profile literature and explore what, if any, effect our knowledge of this line broadening has on the Compton component in terms of mass-energy absorption coefficient. Compton energy-absorption cross sections are evaluated for all elements, Z=1-100, and for photon energies 1 keV-100 MeV. Using these cross sections, the Compton component of the mass-energy absorption coefficient is derived in the energy region from 1 keV to 1 MeV for all the elements Z=1-100. The electron momentum prior to the scattering event should cause a Doppler broadening of the Compton line. The momentum resolution function is evaluated in terms of incident and scattered photon energy and scattering angle. The overall momentum resolution of each contribution is estimated for x-ray and γ-ray energies of experimental interest in the angular region 1°-180°. Also estimated is the Compton broadening using nonrelativistic formula in the angular region 1°-180°, for 17.44, 22.1, 58.83, and 60 keV photons for a few elements (H, C, N, O, P, S, K, and Ca) of biological importance.

Using side-scan sonar to characterize and map physical habitat and anthropogenic underwater features in the St. Louis River.

EPA Science Inventory

Characterizing underwater habitat and other features is difficult and costly, especially in the large St. Louis River Estuary. We are using side-scan sonar (SSS), first developed in the 1960s to remotely sense underwater habitat features from reflected acoustic signals (backscatt...

Effect of Welding Heat Input on Microstructure and Texture of Inconel 625 Weld Overlay Studied Using the Electron Backscatter Diffraction Method

NASA Astrophysics Data System (ADS)

Kim, Joon-Suk; Lee, Hae-Woo

2016-12-01

The grain size and the texture of three specimens prepared at different heat inputs were determined using optical microscopy and the electron backscatter diffraction method of scanning electron microscopy. Each specimen was equally divided into fusion line zone (FLZ), columnar dendrite zone (CDZ), and surface zone (SZ), according to the location of the weld. Fine dendrites were observed in the FLZ, coarse dendrites in the CDZ, and dendrites grew perpendicular to the FLZ and CDZ. As the heat input increased, the melted zone in the vicinity of the FLZ widened due to the higher Fe content. A lower image quality value was observed for the FLZ compared to the other zones. The results of grain size measurement in each zone showed that the grain size of the SZ became larger as the heat input increased. From the inverse pole figure (IPF) map in the normal direction (ND) and the rolling direction (RD), as the heat input increased, a specific orientation was formed. However, a dominant [001] direction was observed in the RD IPF map.

Compton profiles of some composite materials normalized by a new method

NASA Astrophysics Data System (ADS)

Sankarshan, B. M.; Umesh, T. K.

2018-03-01

Recently, we have shown that as a novel approach, in the case of samples which can be treated as pure incoherent scatterers, the effective atomic number Zeff itself could be conveniently used to normalize their un-normalized Compton profiles. In the present investigation, we have attempted to examine the efficacy of this approach. For this purpose, we have first determined the single differential Compton scattering cross sections (SDCS) of the elements C and Al as well as of some H, C, N and O based polymer samples such as bakelite, epoxy, nylon and teflon which are pure incoherent scatterers. The measurements were made at 120° in a goniometer assembly that employs a high resolution high purity germanium detector. The SDCS values were used to obtain the Zeff and the un-normalized Compton profiles. These Compton profiles were separately normalized with their Zeff values (for Compton scattering) as well as with the normalization constant obtained by integrating their Hartree-Fock Biggs et al Compton profiles based on the mixture rule. These two sets of values agreed well within the range of experimental errors, implying that Zeff can be conveniently used to normalize the experimental Compton profiles of pure incoherent scatterers.

Building blocks of a multi-layer PET with time sequence photon interaction discrimination and double Compton camera

NASA Astrophysics Data System (ADS)

Ilisie, V.; Giménez-Alventosa, V.; Moliner, L.; Sánchez, F.; González, A. J.; Rodríguez-Álvarez, M. J.; Benlloch, J. M.

2018-07-01

Current PET detectors have a very low sensitivity, of the order of a few percent. One of the reasons is the fact that Compton interactions are rejected. If an event involves multiple Compton scattering and the total deposited energy lays within the photoelectric peak, then an energy-weighted centroid is the given output for the coordinates of the reconstructed interaction point. This introduces distortion in the final reconstructed image. The aim of our work is to prove that Compton events are a very rich source of additional information as one can improve the resolution of the detector and implicitly the final reconstructed image. This could be a real breakthrough for PET detector technology as one should be able to obtain better results with less patient radiation. Using a PET as a double Compton camera, by means of Compton cone matching i.e., Compton cones coming from the same event should be compatible, is applied to discard randoms, patient scattered events and also, to perform a correct matching among events with multiple coincidences. In order to fully benefit experimentally from Compton events using monolithic scintillators a multi-layer configuration is needed and a good time-of-flight resolution.

Laser driven nuclear science and applications: The need of high efficiency, high power and high repetition rate Laser beams

NASA Astrophysics Data System (ADS)

Gales, S.

2015-10-01

Extreme Light Infrastructure (ELI) is a pan European research initiative selected on the European Strategy Forum on Research Infrastructures Roadmap that aims to close the gap between the existing laboratory-based laser driven research and international facility-grade research centre. The ELI-NP facility, one of the three ELI pillars under construction, placed in Romania and to be operational in 2018, has as core elements a couple of new generation 10 PW laser systems and a narrow bandwidth Compton backscattering gamma source with photon energies up to 19 MeV. ELI-NP will address nuclear photonics, nuclear astrophysics and quantum electrodynamics involving extreme photon fields. Prospective applications of high power laser in nuclear astrophysics, accelerator physics, in particular towards future Accelerator Driven System, as well as in nuclear photonics, for detection and characterization of nuclear material, and for nuclear medicine, will be discussed. Key issues in these research areas will be at reach with significant increase of the repetition rates and of the efficiency at the plug of the high power laser systems as proposed by the ICAN collaboration.

kW picosecond thin-disk regenerative amplifier

NASA Astrophysics Data System (ADS)

Michel, Knut; Wandt, Christoph; Klingebiel, Sandro; Schultze, Marcel; Prinz, Stephan; Teisset, Catherine Y.; Stark, Sebastian; Grebing, Christian; Bessing, Robert; Herzig, Tobias; Häfner, Matthias; Budnicki, Aleksander; Sutter, Dirk; Metzger, Thomas

2018-02-01

TRUMPF Scientific Lasers provides ultrafast laser sources for the scientific community with high pulse energies and high average power. All systems are based on the industrialized TRUMPF thin-disk technology. Regenerative amplifiers systems with multi-millijoule pulses, kilohertz repetition rates and picosecond pulse durations are available. Record values of 220mJ at 1kHz could be demonstrated originally developed for pumping optical parametric amplifiers. The ultimate goal is to combine high energies, <100mJ per pulse, with average powers of several hundred watts to a kilowatt. Based on a regenerative amplifier containing two Ytterbium doped thin-disks operated at ambient temperature pulses with picosecond duration and more than 100mJ could be generated at a repetition rate of 10kHz reaching 1kW of average output power. This system is designed to operate at different repetition rates from 100kHz down to 5kHz so that even higher pulse energies can be reached. This type of ultrafast sources uncover new application fields in science. Laser based lightning rods, X-ray lasers and Compton backscatter sources are among them.

Generation of bright attosecond x-ray pulse trains via Thomson scattering from laser-plasma accelerators.

PubMed

Luo, W; Yu, T P; Chen, M; Song, Y M; Zhu, Z C; Ma, Y Y; Zhuo, H B

2014-12-29

Generation of attosecond x-ray pulse attracts more and more attention within the advanced light source user community due to its potentially wide applications. Here we propose an all-optical scheme to generate bright, attosecond hard x-ray pulse trains by Thomson backscattering of similarly structured electron beams produced in a vacuum channel by a tightly focused laser pulse. Design parameters for a proof-of-concept experiment are presented and demonstrated by using a particle-in-cell code and a four-dimensional laser-Compton scattering simulation code to model both the laser-based electron acceleration and Thomson scattering processes. Trains of 200 attosecond duration hard x-ray pulses holding stable longitudinal spacing with photon energies approaching 50 keV and maximum achievable peak brightness up to 10²⁰ photons/s/mm²/mrad²/0.1%BW for each micro-bunch are observed. The suggested physical scheme for attosecond x-ray pulse trains generation may directly access the fastest time scales relevant to electron dynamics in atoms, molecules and materials.

Nuclear Science and Applications with the Next Generation of High-Power Lasers and Brilliant Low-Energy Gamma Beams at ELI-NP

NASA Astrophysics Data System (ADS)

Gales, S.

The development of high power lasers and the combination of such novel devices with accelerator technology has enlarged the science reach of many research fields, in particular Particle and Nuclear Physics, Astrophysics as well as societal applications in Material Science, Nuclear Energy and Medicine. The European Strategic Forum for Research Infrastructures (ESFRI) has selected a proposal based on these new premises called "ELI" for Extreme Light Infrastructure. ELI will be built as a network of three complementary pillars at the frontier of laser technologies. The ELI-NP pillar (NP for Nuclear Physics) is under construction near Bucharest (Romania) and will develop a scientific program using two 10 PW lasers and a Compton back-scattering high-brilliance and intense low-energy gamma beam, a marriage of laser and accelerator technology at the frontier of knowledge. In the present paper, the technical description of the facility, the present status of the project as well as the science, applications and future perspectives will be discussed.

Nuclear Science and Applications with the Next Generation of High-Power Lasers and Brilliant Low-Energy Gamma Beams at ELI-NP

NASA Astrophysics Data System (ADS)

Gales, S.

2015-11-01

The development of high-power lasers and the combination of such novel devices with accelerator technology has enlarged the science reach of many research fields, in particular high-energy nuclear physics and astrophysics, as well as societal applications in material science, nuclear energy and medicine. The European Strategic Forum for Research Infrastructures (ESFRI) has selected a proposal based on these new premises called "ELI" for Extreme Light Infrastructure. ELI will be built as a network of three complementary pillars at the frontier of laser technologies. The ELI-NP pillar (NP for nuclear physics) is under construction near Bucharest (Romania) and will develop a scientific program using two 10-PW lasers and a Compton back-scattering high-brilliance and intense low-energy gamma beam, a marriage of laser and accelerator technology at the frontier of knowledge. In the present paper, the technical description of the facility, the present status of the project as well as the science, applications and future perspectives will be discussed.

The image enhancement and region of interest extraction of lobster-eye X-ray dangerous material inspection system

NASA Astrophysics Data System (ADS)

Zhan, Qi; Wang, Xin; Mu, Baozhong; Xu, Jie; Xie, Qing; Li, Yaran; Chen, Yifan; He, Yanan

2016-10-01

Dangerous materials inspection is an important technique to confirm dangerous materials crimes. It has significant impact on the prohibition of dangerous materials-related crimes and the spread of dangerous materials. Lobster-Eye Optical Imaging System is a kind of dangerous materials detection device which mainly takes advantage of backscatter X-ray. The strength of the system is its applicability to access only one side of an object, and to detect dangerous materials without disturbing the surroundings of the target material. The device uses Compton scattered x-rays to create computerized outlines of suspected objects during security detection process. Due to the grid structure of the bionic object glass, which imitate the eye of a lobster, grids contribute to the main image noise during the imaging process. At the same time, when used to inspect structured or dense materials, the image is plagued by superposition artifacts and limited by attenuation and noise. With the goal of achieving high quality images which could be used for dangerous materials detection and further analysis, we developed effective image process methods applied to the system. The first aspect of the image process is the denoising and enhancing edge contrast process, during the process, we apply deconvolution algorithm to remove the grids and other noises. After image processing, we achieve high signal-to-noise ratio image. The second part is to reconstruct image from low dose X-ray exposure condition. We developed a kind of interpolation method to achieve the goal. The last aspect is the region of interest (ROI) extraction process, which could be used to help identifying dangerous materials mixed with complex backgrounds. The methods demonstrated in the paper have the potential to improve the sensitivity and quality of x-ray backscatter system imaging.

Densitometry and temperature measurement of combustion gas by X-ray Compton scattering

PubMed Central

Sakurai, Hiroshi; Kawahara, Nobuyuki; Itou, Masayoshi; Tomita, Eiji; Suzuki, Kosuke; Sakurai, Yoshiharu

2016-01-01

Measurement of combustion gas by high-energy X-ray Compton scattering is reported. The intensity of Compton-scattered X-rays has shown a position dependence across the flame of the combustion gas, allowing us to estimate the temperature distribution of the combustion flame. The energy spectra of Compton-scattered X-rays have revealed a significant difference across the combustion reaction zone, which enables us to detect the combustion reaction. These results demonstrate that high-energy X-ray Compton scattering can be employed as an in situ technique to probe inside a combustion reaction. PMID:26917151

Densitometry and temperature measurement of combustion gas by X-ray Compton scattering.

PubMed

Sakurai, Hiroshi; Kawahara, Nobuyuki; Itou, Masayoshi; Tomita, Eiji; Suzuki, Kosuke; Sakurai, Yoshiharu

2016-03-01

Measurement of combustion gas by high-energy X-ray Compton scattering is reported. The intensity of Compton-scattered X-rays has shown a position dependence across the flame of the combustion gas, allowing us to estimate the temperature distribution of the combustion flame. The energy spectra of Compton-scattered X-rays have revealed a significant difference across the combustion reaction zone, which enables us to detect the combustion reaction. These results demonstrate that high-energy X-ray Compton scattering can be employed as an in situ technique to probe inside a combustion reaction.

Compton suppression in BEGe detectors by digital pulse shape analysis.

PubMed

Mi, Yu-Hao; Ma, Hao; Zeng, Zhi; Cheng, Jian-Ping; Li, Jun-Li; Zhang, Hui

2017-03-01

A new method of pulse shape discrimination (PSD) for BEGe detectors is developed to suppress Compton-continuum by digital pulse shape analysis (PSA), which helps reduce the Compton background level in gamma ray spectrometry. A decision parameter related to the rise time of a pulse shape was presented. The method was verified by experiments using 60 Co and 137 Cs sources. The result indicated that the 60 Co Peak to Compton ratio and the Cs-Peak to Co-Compton ratio could be improved by more than two and three times, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

The California Seafloor Mapping Program — Providing science and geospatial data for California's State Waters

NASA Astrophysics Data System (ADS)

Johnson, S. Y.; Cochrane, G. R.; Golden, N. E.; Dartnell, P.; Hartwell, S. R.; Cochran, S. A.; Watt, J. T.

2017-12-01

The California Seafloor Mapping Program (CSMP) is a collaborative effort to develop comprehensive bathymetric, geologic, and habitat maps and data for California's State Waters, which extend for 1,350 km from the shoreline to 5.6 km offshore. CSMP began in 2007 when the California Ocean Protection Council and NOAA allocated funding for high-resolution bathymetric mapping to support the California Marine Life Protection Act and update nautical charts. Collaboration and support from the USGS and other partners has led to development and dissemination of one of the world's largest seafloor-mapping datasets. CSMP data collection includes: (1) High-resolution bathymetric and backscatter mapping using swath sonar sensors; (2) "Ground-truth" imaging from a sled mounted with video and still cameras; (3) High-resolution seismic-reflection profiling at 1 km line spacing. Processed data are all publicly available. Additionally, 25 USGS map and datasets covering one third of California's coast have been published. Each publication contains 9 to 12 pdf map sheets (1:24,000 scale), an explanatory pamphlet, and a catalog of digital geospatial data layers (about 15 to 25 per map area) with web services. Map sheets display bathymetry, backscatter, perspective views, habitats, groundtruth imagery, seismic profiles, sediment distribution and thickness, and onshore-offshore geology. The CSMP goal is to serve a large constituency, ranging from senior GIS analysts in large agencies, to local governments with limited resources, to non-governmental organizations, the private sector, and concerned citizens. CSMP data and publications provide essential science and data for ocean and coastal management, stimulate and enable research, and raise public education and awareness of coastal and ocean issues. Specific applications include: Delineation and designation of marine protected areas Characterization and modeling of benthic habitats and ecosystems Updating nautical charts Earthquake hazard assessments Tsunami hazard assessments Planning and developing offshore infrastructure Providing baselines for monitoring change Input to models of sediment transport, coastal erosion, and coastal flooding Regional sediment management Understanding coastal aquifers Emergency (e.g., oil spill) response

High-Resolution Regional Biomass Map of Siberia from Glas, Palsar L-Band Radar and Landsat Vcf Data

NASA Astrophysics Data System (ADS)

Sun, G.; Ranson, K.; Montesano, P.; Zhang, Z.; Kharuk, V.

2015-12-01

The Arctic-Boreal zone is known be warming at an accelerated rate relative to other biomes. The taiga or boreal forest covers over 16 x106 km2 of Arctic North America, Scandinavia, and Eurasia. A large part of the northern Boreal forests are in Russia's Siberia, as area with recent accelerated climate warming. During the last two decades we have been working on characterization of boreal forests in north-central Siberia using field and satellite measurements. We have published results of circumpolar biomass using field plots, airborne (PALS, ACTM) and spaceborne (GLAS) lidar data with ASTER DEM, LANDSAT and MODIS land cover classification, MODIS burned area and WWF's ecoregion map. Researchers from ESA and Russia have also been working on biomass (or growing stock) mapping in Siberia. For example, they developed a pan-boreal growing stock volume map at 1-kilometer scale using hyper-temporal ENVISAT ASAR ScanSAR backscatter data. Using the annual PALSAR mosaics from 2007 to 2010 growing stock volume maps were retrieved based on a supervised random forest regression approach. This method is being used in the ESA/Russia ZAPAS project for Central Siberia Biomass mapping. Spatially specific biomass maps of this region at higher resolution are desired for carbon cycle and climate change studies. In this study, our work focused on improving resolution ( 50 m) of a biomass map based on PALSAR L-band data and Landsat Vegetation Canopy Fraction products. GLAS data were carefully processed and screened using land cover classification, local slope, and acquisition dates. The biomass at remaining footprints was estimated using a model developed from field measurements at GLAS footprints. The GLAS biomass samples were then aggregated into 1 Mg/ha bins of biomass and mean VCF and PALSAR backscatter and textures were calculated for each of these biomass bins. The resulted biomass/signature data was used to train a random forest model for biomass mapping of entire region from 50oN to 75oN, and 80oE to 145oE. The spatial patterns of the new biomass map is much better than the previous maps due to spatially specific mapping in high resolution. The uncertainties of field/GLAS and GLAS/imagery models were investigated using bootstrap procedure, and the final biomass map was compared with previous maps.

High resolution electron backscatter diffraction (EBSD) data from calcite biominerals in recent gastropod shells.

PubMed

Pérez-Huerta, Alberto; Dauphin, Yannicke; Cuif, Jean Pierre; Cusack, Maggie

2011-04-01

Electron backscatter diffraction (EBSD) is a microscopy technique that reveals in situ crystallographic information. Currently, it is widely used for the characterization of geological materials and in studies of biomineralization. Here, we analyze high resolution EBSD data from biogenic calcite in two mollusk taxa, Concholepas and Haliotis, previously used in the understanding of complex biomineralization and paleoenvironmental studies. Results indicate that Concholepas has less ordered prisms than in Haliotis, and that in Concholepas the level of order is not homogenous in different areas of the shell. Overall, the usefulness of data integration obtained from diffraction intensity and crystallographic orientation maps, and corresponding pole figures, is discussed as well as its application to similar studies. © 2010 Elsevier Ltd. All rights reserved.

Technical Note: Detection of gas bubble leakage via correlation of water column multibeam images

NASA Astrophysics Data System (ADS)

Schneider von Deimling, J.; Papenberg, C.

2011-07-01

Hydroacoustic detection of natural gas release from the seafloor has been conducted in the past by using singlebeam echosounders. In contrast modern multibeam swath mapping systems allow much wider coverage, higher resolution, and offer 3-D spatial correlation. However, up to the present, the extremely high data rate hampers water column backscatter investigations. More sophisticated visualization and processing techniques for water column backscatter analysis are still under development. We here present such water column backscattering data gathered with a 50 kHz prototype multibeam system. Water column backscattering data is presented in videoframes grabbed over 75 s and a "re-sorted" singlebeam presentation. Thus individual gas bubbles rising from the 24 m deep seafloor clearly emerge in the acoustic images and rise velocities can be determined. A sophisticated processing scheme is introduced to identify those rising gas bubbles in the hydroacoustic data. It applies a cross-correlation technique similar to that used in Particle Imaging Velocimetry (PIV) to the acoustic backscatter images. Tempo-spatial drift patterns of the bubbles are assessed and match very well measured and theoretical rise patterns. The application of this processing scheme to our field data gives impressive results with respect to unambiguous bubble detection and remote bubble rise velocimetry. The method can identify and exclude the main driver for misinterpretations, i.e. fish-mediated echoes. Even though image-based cross-correlation techniques are well known in the field of fluid mechanics for high resolution and non-inversive current flow field analysis, this technique was never applied in the proposed sense for an acoustic bubble detector.

Remote sensing for oceanography, hydrology and agriculture; Proceedings of Symposia A5, A3 and A9 of the COSPAR 29th Plenary Meeting, Washington, Aug. 28-Sept. 5, 1992

NASA Technical Reports Server (NTRS)

Gower, J. F. R. (Editor); Salomonson, V. V. (Editor); Engman, E. T. (Editor); Ormsby, J. P. (Editor); Gupta, R. K. (Editor)

1993-01-01

New results from satellite studies of the ocean and radar mapping of the earth are presented. Atttention is given to data from the ERS-1 satellite. Synthetic aperture radar mapping of land surface features and sea ice, radar backscatter measurements, and orbit altitude measurements are discussed. The use of remote sensing in hydrology, soil moisture determination, precipitation measurement, agricultural meteorology, and crop growth estimation is reviewed.

Wet Snow Mapping in Southern Ontario with Sentinel-1A Observations

NASA Astrophysics Data System (ADS)

Chen, H.; Kelly, R. E. J.

2017-12-01

Wet snow is defined as snow with liquid water present in an ice-water mix. It is can be an indicator for the onset of the snowmelt period. Knowledge about the extent of wet snow area can be of great importance for the monitoring of seasonal snowmelt runoff with climate-induced changes in snowmelt duration having implications for operational hydrological and ecological applications. Spaceborne microwave remote sensing has been used to observe seasonal snow under all-weather conditions. Active microwave observations of snow at C-band are sensitive to wet snow due to the high dielectric contrast with non-wet snow surfaces and synthetic aperture radar (SAR) is now openly available to identify and map the wet snow areas globally at relatively fine spatial resolutions ( 100m). In this study, a semi-automated workflow is developed from the change detection method of Nagler et al. (2016) using multi-temporal Sentinel-1A (S1A) dual-polarization observations of Southern Ontario. Weather station data and visible-infrared satellite observations are used to refine the wet snow area estimates. Wet snow information from National Operational Hydrologic Remote Sensing Center (NOHRSC) is used to compare with the S1A estimates. A time series of wet snow maps shows the variations in backscatter from wet snow on a pixel basis. Different land cover types in Southern Ontario are assessed with respect to their impacts on wet snow estimates. While forests and complex land surfaces can impact the ability to map wet snow, the approach taken is robust and illustrates the strong sensitivity of the approach to wet snow backscattering characteristics. The results indicate the feasibility of the change detection method on non-mountainous large areas and address the usefulness of Sentinel-1A data for wet snow mapping.

Characterization of the carbides and the martensite phase in powder-metallurgy high-speed steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Godec, Matjaz, E-mail: matjaz.godec@imt.si; Batic, Barbara Setina; Mandrino, Djordje

2010-04-15

A microstructural characterization of the powder-metallurgy high-speed-steel S390 Microclean was performed based on an elemental distribution of the carbide phase as well as crystallographic analyses. The results showed that there were two types of carbides present: vanadium-rich carbides, which were not chemically homogeneous and exhibited a tungsten-enriched or tungsten-depleted central area; and chemically homogeneous tungsten-rich M{sub 6}C-type carbides. Despite the possibility of chemical inhomogenities, the crystallographic orientation of each of the carbides was shown to be uniform. Using electron backscatter diffraction the vanadium-rich carbides were determined to be either cubic VC or hexagonal V{sub 6}C{sub 5}, while the tungsten-rich carbidesmore » were M{sub 6}C. The electron backscatter diffraction results were also verified using X-ray diffraction. Several electron backscatter diffraction pattern maps were acquired in order to define the fraction of each carbide phase as well as the amount of martensite phase. The fraction of martensite was estimated using band-contrast images, while the fraction of carbides was calculated using the crystallographic data.« less

A system to track skin dose for neuro-interventional cone-beam computed tomography (CBCT)

NASA Astrophysics Data System (ADS)

Vijayan, Sarath; Xiong, Zhenyu; Rudin, Stephen; Bednarek, Daniel R.

2016-03-01

The skin-dose tracking system (DTS) provides a color-coded illustration of the cumulative skin-dose distribution on a closely-matching 3D graphic of the patient during fluoroscopic interventions in real-time for immediate feedback to the interventionist. The skin-dose tracking utility of DTS has been extended to include cone-beam computed tomography (CBCT) of neurointerventions. While the DTS was developed to track the entrance skin dose including backscatter, a significant part of the dose in CBCT is contributed by exit primary radiation and scatter due to the many overlapping projections during the rotational scan. The variation of backscatter inside and outside the collimated beam was measured with radiochromic film and a curve was fit to obtain a scatter spread function that could be applied in the DTS. Likewise, the exit dose distribution was measured with radiochromic film for a single projection and a correction factor was determined as a function of path length through the head. Both of these sources of skin dose are added for every projection in the CBCT scan to obtain a total dose mapping over the patient graphic. Results show the backscatter to follow a sigmoidal falloff near the edge of the beam, extending outside the beam as far as 8 cm. The exit dose measured for a cylindrical CTDI phantom was nearly 10 % of the entrance peak skin dose for the central ray. The dose mapping performed by the DTS for a CBCT scan was compared to that measured with radiochromic film and a CTDI-head phantom with good agreement.

The National Ignition Facility (NIF) and High Energy Density Science Research at LLNL (Briefing Charts)

DTIC Science & Technology

2013-06-21

neutron activation detectors (FNADS) 2013-049951s2.ppt Detector locations • Average rR ~ 1 g/cm2 • ~ 50% variations Motivates new 2D backlit imaging...of the implosion Motivates Compton radiography for stagnated fuel shape g/cm2 DrR rR map from neutron Activation Detectors (90Zr(n,2n)  89Zr...high energy cosmic rays Oxford Univ./LLNL LLNL Novel phases of compressed diamond Synthesis of elements heavier than iron 1545 Neutron flux in

The effect of relativistic Compton scattering on thermonuclear burn of pure deuterium fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghasemizad, A.; Nazirzadeh, M.; Khanbabaei, B.

The relativistic effects of the Compton scattering on the thermonuclear burn-up of pure deuterium fuel in non-equilibrium plasma have been studied by four temperature (4T) theory. In the limit of low electron temperatures and photon energies, the nonrelativistic Compton scattering is valid and a convenient approximation, but in the high energy exchange rates between electrons and photons, is seen to break down. The deficiencies of the nonrelativistic approximation can be overcome by using the relativistic correction in the photons kinetic equation. In this research, we have utilized the four temperature (4T) theory to calculate the critical burn-up parameter for puremore » deuterium fuel, while the Compton scattering is considered as a relativistic phenomenon. It was shown that the measured critical burn-up parameter in ignition with relativistic Compton scattering is smaller than that of the parameter in the ignition with the nonrelativistic Compton scattering.« less

Observations of Sea Surface Mean Square Slope During the Southern Ocean Waves Experiment

NASA Technical Reports Server (NTRS)

Walsh, E. J.; Vandemark, D. C.; Hines, D. E.; Banner, M. L.; Chen, W.; Swift, R. N.; Scott, J. F.; Jensen, J.; Lee, S.; Fandry, C.

1999-01-01

For the Southern Ocean Waves Experiment (SOWEX), conducted in June 1992 out of Hobart, Tasmania, the 36 GHz (8.3 mm) NASA Scanning Radar Altimeter (SRA) was shipped to Australia and installed on a CSIRO Fokker F-27 research aircraft instrumented to make comprehensive surface layer measurements of air-sea interaction fluxes. The sea surface mean square slope (mss), which is predominantly caused by the short waves, was determined from the backscattered power falloff with incidence angle measured by the SRA in the plane normal to the aircraft heading. On each flight, data were acquired at 240 m altitude while the aircraft was in a 7 deg roll attitude, interrogating off-nadir incidence angles from -15 deg through nadir to +29 deg. The aircraft turned azimuthally through 810 deg in this attitude, mapping the azimuthal dependence of the backscattered power falloff with incidence angle. Two sets of turning data were acquired on each day, before and after the aircraft measured wind stress at low altitude (12 m to 65 m). Wave topography and backscattered power for mss were also acquired during those level flight segments whenever the aircraft altitude was above the SRA minimum range of 35 m. A unique feature of this experiment was the use of a nadir-directed low-gain horn antenna (35 deg beamwidth) to acquire azimuthally integrated backscattered power data versus incidence angle before and after the turn data.

Multi-angle backscatter classification and sub-bottom profiling for improved seafloor characterization

NASA Astrophysics Data System (ADS)

Alevizos, Evangelos; Snellen, Mirjam; Simons, Dick; Siemes, Kerstin; Greinert, Jens

2018-06-01

This study applies three classification methods exploiting the angular dependence of acoustic seafloor backscatter along with high resolution sub-bottom profiling for seafloor sediment characterization in the Eckernförde Bay, Baltic Sea Germany. This area is well suited for acoustic backscatter studies due to its shallowness, its smooth bathymetry and the presence of a wide range of sediment types. Backscatter data were acquired using a Seabeam1180 (180 kHz) multibeam echosounder and sub-bottom profiler data were recorded using a SES-2000 parametric sonar transmitting 6 and 12 kHz. The high density of seafloor soundings allowed extracting backscatter layers for five beam angles over a large part of the surveyed area. A Bayesian probability method was employed for sediment classification based on the backscatter variability at a single incidence angle, whereas Maximum Likelihood Classification (MLC) and Principal Components Analysis (PCA) were applied to the multi-angle layers. The Bayesian approach was used for identifying the optimum number of acoustic classes because cluster validation is carried out prior to class assignment and class outputs are ordinal categorical values. The method is based on the principle that backscatter values from a single incidence angle express a normal distribution for a particular sediment type. The resulting Bayesian classes were well correlated to median grain sizes and the percentage of coarse material. The MLC method uses angular response information from five layers of training areas extracted from the Bayesian classification map. The subsequent PCA analysis is based on the transformation of these five layers into two principal components that comprise most of the data variability. These principal components were clustered in five classes after running an external cluster validation test. In general both methods MLC and PCA, separated the various sediment types effectively, showing good agreement (kappa >0.7) with the Bayesian approach which also correlates well with ground truth data (r2 > 0.7). In addition, sub-bottom data were used in conjunction with the Bayesian classification results to characterize acoustic classes with respect to their geological and stratigraphic interpretation. The joined interpretation of seafloor and sub-seafloor data sets proved to be an efficient approach for a better understanding of seafloor backscatter patchiness and to discriminate acoustically similar classes in different geological/bathymetric settings.

Characterizing TPS Microstructure: A Review of Some techniques

NASA Technical Reports Server (NTRS)

Gasch, Matthew; Stackpole, Mairead; Agrawal, Parul; Chavez-Garcie, Jose

2011-01-01

I. When seeking to understand ablator microstructure and morphology there are several useful techniques A. SEM 1) Visual characteriza3on at various length scales. 2) Chemical mapping by backscatter or x-ray highlights areas of interest. 3) Combined with other techniques (density, weight change, chemical analysis) SEM is a powerful tool to aid in explaining thermo/structural data. B. ASAP. 1) Chemical characteriza3on at various length scales. 2) Chemical mapping of pore structure by gas adsorption. 3) Provides a map of pore size vs. pore volume. 4) Provided surface area of exposed TPS. II. Both methods help characterize and understand how ablators react with other chemical species and provides insight into how they oxidize.

Is Compton Cooling Sufficient to Explain Evolution of Observed Quasi-periodic Oscillations in Outburst Sources?

NASA Astrophysics Data System (ADS)

Mondal, Santanu; Chakrabarti, Sandip K.; Debnath, Dipak

2015-01-01

In outburst sources, quasi-periodic oscillation (QPO) frequency is known to evolve in a certain way: in the rising phase, it monotonically goes up until a soft intermediate state is achieved. In the propagating oscillatory shock model, oscillation of the Compton cloud is thought to cause QPOs. Thus, in order to increase QPO frequency, the Compton cloud must collapse steadily in the rising phase. In decline phases, the exact opposite should be true. We investigate cause of this evolution of the Compton cloud. The same viscosity parameter that increases the Keplerian disk rate also moves the inner edge of the Keplerian component, thereby reducing the size of the Compton cloud and reducing the cooling timescale. We show that cooling of the Compton cloud by inverse Comptonization is enough for it to collapse sufficiently so as to explain the QPO evolution. In the two-component advective flow configuration of Chakrabarti-Titarchuk, centrifugal force-induced shock represents the boundary of the Compton cloud. We take the rising phase of 2010 outburst of Galactic black hole candidate H 1743-322 and find an estimation of variation of the α parameter of the sub-Keplerian flow to be monotonically rising from 0.0001 to 0.02, well within the range suggested by magnetorotational instability. We also estimate the inward velocity of the Compton cloud to be a few meters per second, which is comparable to what is found in several earlier studies of our group by empirically fitting the shock locations with the time of observations.

Soft-photon emission effects and radiative corrections for electromagnetic processes at very high energies

NASA Technical Reports Server (NTRS)

Gould, R. J.

1979-01-01

Higher-order electromagnetic processes involving particles at ultrahigh energies are discussed, with particular attention given to Compton scattering with the emission of an additional photon (double Compton scattering). Double Compton scattering may have significance in the interaction of a high-energy electron with the cosmic blackbody photon gas. At high energies the cross section for double Compton scattering is large, though this effect is largely canceled by the effects of radiative corrections to ordinary Compton scattering. A similar cancellation takes place for radiative pair production and the associated radiative corrections to the radiationless process. This cancellation is related to the well-known cancellation of the infrared divergence in electrodynamics.

Utilizing Multibeam Bathymetry and Geographic Information Systems (GIS) to Expand Our Mapping Ability of Potential Rockfish Benthic Habitats in the San Juan Islands, Washington

NASA Astrophysics Data System (ADS)

Kelly-Slatten, K.

2013-12-01

In order to construct an accurate cartographic representation of the potential rockfish habitat zone in the San Juan Archipelago, Washington, bathymetric data is needed to form layers within Geographic Information Systems (GIS) that include, but are not limited to, slope, hillshade, and aspect. Backscatter data is also important in order to demonstrate the induration of the marine floor, which in turn may tell the researcher what type of sediment and substrate makes up that part of the benthic region. Once these layers are added to the GIS map, another layer (referred to as Potential Benthic Habitats) is created and inserted. This layer uses the same induration data but groups them into polygons, which are then color-coded and displayed on the map. With all the layers now pictured, it is clear that the intertidal zones are not complete. Aerial photographs are then added to fill in the gaps according to the GPS coordinates associated with the middle section of each picture. When all pictures and layers have been included, the GIS map is a somewhat three-dimensional, color-coordinated, aerial photograph enhanced depiction of Skipjack, Waldron, Orcas, and Sucia Islands. The bathymetric and backscatter data are plugged into Excel to graphically illustrate specific numbers that represent the various potential habitats. The given data support the idea that potential rockfish habitat (Sedimentary Bedrock and Fractured Bedrock) must be closely monitored and maintained in attempt to preserve and conserve the three either threatened or endangered rockfish species within the Puget Sound locale.

Gate simulation of Compton Ar-Xe gamma-camera for radionuclide imaging in nuclear medicine

NASA Astrophysics Data System (ADS)

Dubov, L. Yu; Belyaev, V. N.; Berdnikova, A. K.; Bolozdynia, A. I.; Akmalova, Yu A.; Shtotsky, Yu V.

2017-01-01

Computer simulations of cylindrical Compton Ar-Xe gamma camera are described in the current report. Detection efficiency of cylindrical Ar-Xe Compton camera with internal diameter of 40 cm is estimated as1-3%that is 10-100 times higher than collimated Anger’s camera. It is shown that cylindrical Compton camera can image Tc-99m radiotracer distribution with uniform spatial resolution of 20 mm through the whole field of view.

User's guide for the Solar Backscattered Ultraviolet (SBUV) instrument first year ozone-S data set

NASA Technical Reports Server (NTRS)

Fleig, A. J.; Klenk, K. F.; Bhartia, P. K.; Gordon, D.; Schneider, W. H.

1982-01-01

Total-ozone and ozone vertical profile results for Solar Backscattered Ultraviolet/Total Ozone Mapping Spectrometer (SBUV/TOMS) Nimbus 7 operation from November 1978 to November 1979 are available. The algorithm used have been thoroughly tested, the instrument performance has been examined in details, and the ozone results have been compared with Dobson, Umkehr, balloon, and rocket observations. The accuracy and precision of the satellite ozone data are good to at least within the ability of the ground truth to check and are self-consistent to within the specifications of the instrument. The 'SBUV User's Guide' describes the SBUV experiment and algorithms used. Detailed information on the data available on computer tape is provided including how to order tapes from the National Space Science Data Center.

Detection and Imaging of the Crab Nebula with the Nuclear Compton Telescope

NASA Astrophysics Data System (ADS)

Bandstra, M. S.; Bellm, E. C.; Boggs, S. E.; Perez-Becker, D.; Zoglauer, A.; Chang, H.-K.; Chiu, J.-L.; Liang, J.-S.; Chang, Y.-H.; Liu, Z.-K.; Hung, W.-C.; Huang, M.-H. A.; Chiang, S. J.; Run, R.-S.; Lin, C.-H.; Amman, M.; Luke, P. N.; Jean, P.; von Ballmoos, P.; Wunderer, C. B.

2011-09-01

The Nuclear Compton Telescope (NCT) is a balloon-borne Compton telescope designed for the study of astrophysical sources in the soft gamma-ray regime (200 keV-20 MeV). NCT's 10 high-purity germanium crossed-strip detectors measure the deposited energies and three-dimensional positions of gamma-ray interactions in the sensitive volume, and this information is used to restrict the initial photon to a circle on the sky using the Compton scatter technique. Thus NCT is able to perform spectroscopy, imaging, and polarization analysis on soft gamma-ray sources. NCT is one of the next generation of Compton telescopes—the so-called compact Compton telescopes (CCTs)—which can achieve effective areas comparable to the Imaging Compton Telescope's with an instrument that is a fraction of the size. The Crab Nebula was the primary target for the second flight of the NCT instrument, which occurred on 2009 May 17 and 18 in Fort Sumner, New Mexico. Analysis of 29.3 ks of data from the flight reveals an image of the Crab at a significance of 4σ. This is the first reported detection of an astrophysical source by a CCT.

Collective Evidence for Inverse Compton Emission from External Photons in High-Power Blazars

NASA Technical Reports Server (NTRS)

Meyer, Eileen T.; Fossati, Giovanni; Georganopoulos, Markos; Lister, Matthew L.

2012-01-01

We present the first collective evidence that Fermi-detected jets of high kinetic power (L(sub kin)) are dominated by inverse Compton emission from upscattered external photons. Using a sample with a broad range in orientation angle, including radio galaxies and blazars, we find that very high power sources (L(sub kin) > 10(exp 45.5) erg/s) show a significant increase in the ratio of inverse Compton to synchrotron power (Compton dominance) with decreasing orientation angle, as measured by the radio core dominance and confirmed by the distribution of superluminal speeds. This increase is consistent with beaming expectations for external Compton (EC) emission, but not for synchrotron self Compton (SSC) emission. For the lowest power jets (L(sub kin) < 10(exp 43.5) erg /s), no trend between Compton and radio core dominance is found, consistent with SSC. Importantly, the EC trend is not seen for moderately high power flat spectrum radio quasars with strong external photon fields. Coupled with the evidence that jet power is linked to the jet speed, this finding suggests that external photon fields become the dominant source of seed photons in the jet comoving frame only for the faster and therefore more powerful jets.

Doppler Broadening Calculations of Compton Scattering for Molecules, Plastics, Tissues, and Few Biological Materials in the X-Ray Region: An Analysis in Terms of Compton Broadening and Geometrical Energy Broadening

NASA Astrophysics Data System (ADS)

Rao, D. V.; Cesareo, R.; Brunetti, A.; Gigante, G. E.; Akatsuka, T.; Takeda, T.; Itai, Y.

2004-09-01

Relativistic and nonrelativistic Compton profile cross sections for H, C, N, O, P, and Ca and for a few important biological materials such as water, polyethylene, lucite, polystyrene, nylon, polycarbonate, bakelite, fat, bone and calcium hydroxyapatite are estimated for a number of Kα x-ray energies and for 59.54 keV (Am-241) γ photons. Energy broadening and geometrical broadening (ΔG) is estimated by assuming θmin and θmax are symmetrically situated around θ=90°. FWHM of J(PZ) and FWHM of Compton energy broadening are evaluated at various incident photon energies. These values are estimated around the centroid of the Compton profile with an energy interval of 0.1 and 1.0 keV for 59.54 keV photons. Total Compton, individual shell, and Compton energy-absorption scattering cross sections are evaluated in the energy region from 0.005 to 0.5 MeV. It is an attempt to know the effect of Doppler broadening for single atoms, many of which constitute the biological materials.

Evaluation of crop development stages with TerraSAR-X backscatter signatures (2010-12) by using Growing Degree Days

NASA Astrophysics Data System (ADS)

Ishaq, Atif; Pasternak, René; Wessollek, Christine

2017-10-01

TerraSAR-X images have been tested for agricultural fields of corn and wheat. The main purpose was to evaluate the impact of daily temperatures in crop development to optimize climate induced factors on the plant growth anomalies. The results are completed by utilizing Geographic Information Science, e.g. tools of ArcMap 10.3.1 and databases of ground truth and meteorological information. Synthetic Aperture Radar (SAR) images from German Aerospace Center (DLR) are acquired and the field survey datasets are sampled, each per month for three years (2010-2012) but only for the crop seasons (April-October). Correlation between SAR images and farmland anomalies is investigated in accordance with daily heat accumulations and a comparison of the three years' SAR backscatter signatures is explained for corn and wheat. Finding the influence of daily temperatures on crops and hence on the TerraSAR-X backscatter is developed by Growing Degree Days (GDD) which appears to be the most suitable parameter for this purpose. Observation of GDD permits that the coolest year was 2010, either rest of the years were warmer and GDD accumulated in 2011 was higher as compared to that of 2012 in the first half of the year, however 2012 had rather more heat accumulation in the second half of the year. SAR backscatter from farmland depicts the crop development stages which depend upon the time when satellite captures data during the crop season. It varies with different development stages of crop plants. Backscatter of each development stage changes as the roughness and the moisture content (dielectric property) of the plants changes and local temperature directly impacts crop growth and hence the development stages.

Constraints on the H˜ generalized parton distribution from deep virtual Compton scattering measured at HERMES

NASA Astrophysics Data System (ADS)

Guidal, M.

2010-09-01

We have analyzed the longitudinally polarized proton target asymmetry data of the Deep Virtual Compton process recently published by the HERMES Collaboration in terms of Generalized Parton Distributions. We have fitted these new data in a largely model-independent fashion and the procedure results in numerical constraints on the accent="true">H˜Im Compton Form Factor. We present its t- and ξ-dependencies. We also find improvement on the determination of two other Compton Form Factors, HRe and HIm.

High flux, narrow bandwidth compton light sources via extended laser-electron interactions

DOEpatents

Barty, V P

2015-01-13

New configurations of lasers and electron beams efficiently and robustly produce high flux beams of bright, tunable, polarized quasi-monoenergetic x-rays and gamma-rays via laser-Compton scattering. Specifically, the use of long-duration, pulsed lasers and closely-spaced, low-charge and low emittance bunches of electron beams increase the spectral flux of the Compton-scattered x-rays and gamma rays, increase efficiency of the laser-electron interaction and significantly reduce the overall complexity of Compton based light sources.

Characterization and Applications of a CdZnTe-Based Gamma-Ray Imager

NASA Astrophysics Data System (ADS)

Galloway, Michelle Lee

Detection of electromagnetic radiation in the form of gamma rays provides a means to discover the presence of nuclear sources and the occurrence of highly-energetic events that occur in our terrestrial and astrophysical environment. The highly penetrative nature of gamma rays allows for probing into objects and regions that are obscured at other wavelengths. The detection and imaging of gamma rays relies upon an understanding of the ways in which these high-energy photons interact with matter. The applications of gamma-ray detection and imaging are numerous. Astrophysical observation of gamma rays expands our understanding of the Universe in which we live. Terrestrial detection and imaging of gamma rays enable environmental monitoring of radioactivity. This allows for identification and localization of nuclear materials to prevent illicit trafficking and to ultimately protect against harmful acts. This dissertation focusses on the development and characterization of a gamma-ray detection and imaging instrument and explores its capabilities for the aforementioned applications. The High Efficiency Multimode Imager, HEMI, is a prototype instrument that is based on Cadmium Zinc Telluride (CdZnTe) semiconductor detectors. The detectors are arranged in a two-planar configuration to allow for both Compton and coded-aperture imaging. HEMI was initially developed as a prototype instrument to demonstrate its capabilities for nuclear threat detection, spectroscopy, and imaging. The 96-detector instrument was developed and fully characterized within the laboratory environment, yielding a system energy resolution of 2.4% FWHM at 662 keV, an angular resolution of 9.5 deg. FWHM at 662 keV in Compton mode, and a 10.6 deg. angular resolution in coded aperture mode. After event cuts, the effective area for Compton imaging of the 662 keV photopeak is 0.1 cm 22. Imaging of point sources in both Compton and coded aperture modes have been demonstrated. The minimum detectable activity of a 137Cs at a 20 m distance with 20 seconds of observation time is estimated to be ˜0.2 mCi in spectral mode and ˜20 mCi in Compton imaging mode. These performance parameters fulfilled the requirements of the nuclear security program. Following the Fukushima Dai-ichi Nuclear Power Plant accident of March, 2011, efficient methods to assess levels of radioactive contamination over large areas are needed to aid in clean-up efforts. Although a field study was not initially intended for the HEMI prototype, its portability, low mass, and low power requirements made it a good candidate to test Compton imaging from an aerial platform. The instrument was brought to Japan in August, 2013, allowing for the first test of a Compton imager from a helicopter. The instrument and detectors proved reliable and performed well under high temperature, high humidity, and vibrations. Single-detector hit energy resolutions ranged from 2.5 - 2.8% FWHM at 662 keV. The field testing of the HEMI instrument in Fukushima revealed areas of higher activity of cesium among a diffuse background through aerial-based countrate mapping and through ground measurements. Although the Compton reconstructed events were dominated by random coincidences, preliminary Compton imaging results are promising. A future mission in medium-energy gamma-ray astrophysics would allow for many scientific advancements, e.g., a possible explanation for the excess positron emission from the Galactic Center, a better understanding of nucleosynthesis and explosion mechanisms in Type Ia supernovae, and a look at the physical forces at play in compact objects such as black holes and neutron stars. A next-generation telescope requires good energy resolution, good angular resolution, and high sensitivity in order to achieve these objectives. Large-volume CdZnTe detectors are an attractive candidate for a future instrument because of their good absorption, simple design, and minimal or no cooling requirements. Using the benchmarked HEMI CdZnTe detectors, a Compton telescope with a passive coded mask was designed and simulated with the goal of creating a very sensitive instrument that is capable of high angular resolution. The simulated telescope showed achievable energy resolutions of 1.68% FWHM at 511 keV and 1.11% at 1809 keV, on-axis angular resolutions in Compton mode of 2.63 deg. FWHM at 511 keV and 1.30 deg. FWHM at 1809 keV, and is capable of resolving sources to at least 0.2 deg. at lower energies with the use of the coded mask. An initial assessment of the instrument yields an effective area of 183 cm 2 at 511 keV and an anticipated all-sky sensitivity of 3.6 x 10 -6 photons/cm2/s for a broadened 511 keV source over a 2 year observation time. Additionally, combining a coded mask with a Compton imager to improve point source localization for positron detection has been demonstrated. (Abstract shortened by UMI.)

The Atacama Cosmology Telescope (ACT): Beam Profiles and First SZ Cluster Maps

NASA Technical Reports Server (NTRS)

Hincks, A. D.; Acquaviva, V.; Ade, P. A.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Battistelli, E. S.; Bond, J. R.; Brown, B.;

Neutron Compton scattering from selectively deuterated acetanilide

NASA Astrophysics Data System (ADS)

Wanderlingh, U. N.; Fielding, A. L.; Middendorf, H. D.

With the aim of developing the application of neutron Compton scattering (NCS) to molecular systems of biophysical interest, we are using the Compton spectrometer EVS at ISIS to characterize the momentum distribution of protons in peptide groups. In this contribution we present NCS measurements of the recoil peak (Compton profile) due to the amide proton in otherwise fully deuterated acetanilide (ACN), a widely studied model system for H-bonding and energy transfer in biomolecules. We obtain values for the average width of the potential well of the amide proton and its mean kinetic energy. Deviations from the Gaussian form of the Compton profile, analyzed on the basis of an expansion due to Sears, provide data relating to the Laplacian of the proton potential.

SU-C-201-03: Coded Aperture Gamma-Ray Imaging Using Pixelated Semiconductor Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, S; Kaye, W; Jaworski, J

2015-06-15

Purpose: Improved localization of gamma-ray emissions from radiotracers is essential to the progress of nuclear medicine. Polaris is a portable, room-temperature operated gamma-ray imaging spectrometer composed of two 3×3 arrays of thick CdZnTe (CZT) detectors, which detect gammas between 30keV and 3MeV with energy resolution of <1% FWHM at 662keV. Compton imaging is used to map out source distributions in 4-pi space; however, is only effective above 300keV where Compton scatter is dominant. This work extends imaging to photoelectric energies (<300keV) using coded aperture imaging (CAI), which is essential for localization of Tc-99m (140keV). Methods: CAI, similar to the pinholemore » camera, relies on an attenuating mask, with open/closed elements, placed between the source and position-sensitive detectors. Partial attenuation of the source results in a “shadow” or count distribution that closely matches a portion of the mask pattern. Ideally, each source direction corresponds to a unique count distribution. Using backprojection reconstruction, the source direction is determined within the field of view. The knowledge of 3D position of interaction results in improved image quality. Results: Using a single array of detectors, a coded aperture mask, and multiple Co-57 (122keV) point sources, image reconstruction is performed in real-time, on an event-by-event basis, resulting in images with an angular resolution of ∼6 degrees. Although material nonuniformities contribute to image degradation, the superposition of images from individual detectors results in improved SNR. CAI was integrated with Compton imaging for a seamless transition between energy regimes. Conclusion: For the first time, CAI has been applied to thick, 3D position sensitive CZT detectors. Real-time, combined CAI and Compton imaging is performed using two 3×3 detector arrays, resulting in a source distribution in space. This system has been commercialized by H3D, Inc. and is being acquired for various applications worldwide, including proton therapy imaging R&D.« less

Analysis of X-ray spectral variability and black hole mass determination of the NLS1 galaxy Mrk 766

NASA Astrophysics Data System (ADS)

Giacchè, S.; Gilli, R.; Titarchuk, L.

2014-02-01

We present an XMM-Newton time-resolved spectral analysis of the narrow-line Seyfert 1 galaxy Mrk 766. We analysed eight available observations taken between May 2000 and June 2005 with the EPIC-pn camera in order to investigate the X-ray spectral variability produced by changes in the mass accretion rate. The 0.2 - 10 keV spectra are extracted in time bins longer than 3 ks to have at least 3 × 104 net counts in each bin and then accurately trace the variations of the best-fit parameters of our adopted Comptonization spectral model. We tested a bulk-motion Comptonization (BMC) model which is in general applicable to any physical system powered by accretion onto a compact object, and assumes that soft seed photons are efficiently up-scattered via inverse Compton scattering in a hot and dense electron corona. The Comptonized spectrum has a characteristic power law shape, whose slope was found to increase for large values of the normalization of the seed component, which is proportional to the mass accretion rate ṁ (in Eddington units). Our baseline spectral model also includes a warm absorber lying on the line of sight and radiation reprocessing from the accretion disc or from outflowing matter in proximity to the central compact object. Our study reveals that the normalization-slope correlation, observed in Galactic black hole sources (GBHs), also holds for Mrk 766: variations of the photon index in the range Γ ~ 1.9-2.4 are indeed likely to be related to the variations of ṁ, as observed in X-ray binary systems. We finally applied a scaling technique based on the observed correlation to estimate the BH mass in Mrk 766. This technique is commonly and successfully applied to measure masses of GBHs, and this is the first time it has been applied in detail to estimate the BH mass in an AGN. We obtained a value of MBH = 1.26-0.77+1.00×106 M⊙, which is in very good agreement with that estimated by the reverberation mapping. Appendix A is available in electronic form at http://www.aanda.org

Multibeam mapping of the Los Angeles, California Margin

USGS Publications Warehouse

Gardner, James V.; Dartnell, Peter

2002-01-01

The Los Angeles, California Margin was mapped using multibeam echosounders during three separate surveys (Figure 1). In 1996, the USGS surveyed the shelf and slope in Santa Monica Bay from Pt. Dume to south of the Palos Verdes Peninsula. The mapping was accomplished using a Kongsberg Simrad EM1000 multibeam sonar system that provided high-quality bathymetry and quantitative backscatter. In 1998, the USGS continued the mapping to the south and surveyed the outer shelf, slope, and proximal basin off Long Beach and Newport using a Kongsberg Simrad EM300 multibeam sonar system. In 1999, the Los Angeles Margin mapping was completed with the surveying of the inner Long Beach shelf from the Palos Verdes Peninsula, south to Newport. This survey used a dual Kongsberg Simrad EM3000D multibeam sonar system. These three surveys were conducted to support USGS projects studying marine pollution and geohazards along the Los Angeles Margin.

Ultralow-dose, feedback imaging with laser-Compton X-ray and laser-Compton gamma ray sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, Christopher P. J.

Ultralow-dose, x-ray or gamma-ray imaging is based on fast, electronic control of the output of a laser-Compton x-ray or gamma-ray source (LCXS or LCGS). X-ray or gamma-ray shadowgraphs are constructed one (or a few) pixel(s) at a time by monitoring the LCXS or LCGS beam energy required at each pixel of the object to achieve a threshold level of detectability at the detector. An example provides that once the threshold for detection is reached, an electronic or optical signal is sent to the LCXS/LCGS that enables a fast optical switch that diverts, either in space or time the laser pulsesmore » used to create Compton photons. In this way, one prevents the object from being exposed to any further Compton x-rays or gamma-rays until either the laser-Compton beam or the object are moved so that a new pixel location may be illumination.« less

Beta experiment

NASA Technical Reports Server (NTRS)

1982-01-01

A focused laser doppler velocimeter (LDV) system was developed for the measurement of atmospheric backscatter (beta) from aerosols at infrared wavelengths. A Doppler signal generator was used in mapping the coherent sensitive focal volume of a focused LDV system. System calibration data was analyzed during the flight test activity scheduled for the Beta system. These analyses were performed to determine the acceptability of the Beta measurement system's performance.

Data files from the Grays Harbor Sediment Transport Experiment Spring 2001

USGS Publications Warehouse

Landerman, Laura A.; Sherwood, Christopher R.; Gelfenbaum, Guy; Lacy, Jessica; Ruggiero, Peter; Wilson, Douglas; Chisholm, Tom; Kurrus, Keith

2005-01-01

This publication consists of two DVD-ROMs, both of which are presented here. This report describes data collected during the Spring 2001 Grays Harbor Sediment Transport Experiment, and provides additional information needed to interpret the data. Two DVDs accompany this report; both contain documentation in html format that assist the user in navigating through the data. DVD-ROM-1 contains a digital version of this report in .pdf format, raw Aquatec acoustic backscatter (ABS) data in .zip format, Sonar data files in .avi format, and coastal processes and morphology data in ASCII format. ASCII data files are provided in .zip format; bundled coastal processes ASCII files are separated by deployment and instrument; bundled morphology ASCII files are separated into monthly data collection efforts containing the beach profiles collected (or extracted from the surface map) at that time; weekly surface maps are also bundled together. DVD-ROM-2 contains a digital version of this report in .pdf format, the binary data files collected by the SonTek instrumentation, calibration files for the pressure sensors, and Matlab m-files for loading the ABS data into Matlab and cleaning-up the optical backscatter (OBS) burst time-series data.

Bulk Comptonization by Turbulence in Black Hole Accretion Discs

NASA Astrophysics Data System (ADS)

Kaufman, Jason

Radiation pressure dominated accretion discs may have turbulent velocities that exceed the electron thermal velocities. Bulk Comptonization by the turbulence may therefore dominate over thermal Comptonization in determining the emergent spectrum. We discuss how to self-consistently resolve and interpret this effect in calculations of spectra of radiation MHD simulations. In particular, we show that this effect is dominated by radiation viscous dissipation and can be treated as thermal Comptonization with an equivalent temperature. We investigate whether bulk Comptonization may provide a physical basis for warm Comptonization models of the soft X-ray excess in AGN. We characterize our results with temperatures and optical depths to make contact with other models of this component. We show that bulk Comptonization shifts the Wien tail to higher energy and lowers the gas temperature, broadening the spectrum. More generally, we model the dependence of this effect on a wide range of fundamental accretion disc parameters, such as mass, luminosity, radius, spin, inner boundary condition, and the alpha parameter. Because our model connects bulk Comptonization to one dimensional vertical structure temperature profiles in a physically intuitive way, it will be useful for understanding this effect in future simulations run in new regimes. We also develop a global Monte Carlo code to study this effect in global radiation MHD simulations. This code can be used more broadly to compare global simulations with observed systems, and in particular to investigate whether magnetically dominated discs can explain why observed high Eddington accretion discs appear to be thermally stable.

Mapping Seyfert and LINER Excitation Modes in the Inner kpc of NGC 3393

NASA Astrophysics Data System (ADS)

Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Paggi, Alessandro; Raymond, John; Wang, Junfeng; Storchi-Bergmann, Thaisa

2016-09-01

We mapped the extended narrowline region (ENLR) of NGC 3393 on scales of r≲ 4\\prime\\prime (˜ 1 kpc) from the nucleus using emission line images of Hα λ6563, [O III]λ 5007, and [S II]λ λ 6717,6731, taken with the Hubble Space Telescope as part of the CHandra survey of Extended Emission line Regions in nearby Seyfert galaxies (CHEERS). By mapping these lines onto a spatially resolved Baldwin-Phillips-Terlevich diagram, we investigate the impact of feedback from a Compton-thick active galactic nucleus on its circumnuclear ISM. We find that the expected Seyfert-like emission within the ionization bicone (≲ 3\\prime\\prime ; 770 pc). We also find a new, figure-8-shaped low ionization emission line region (LINER) cocoon enveloping the bicone and defining a sharp (≲ 100 pc) transition between higher and lower-ionization zones. These data illustrate the morphological dependence of ionization states of the ENLR relative to bicone and host gas geometries.

California State Waters Map Series Data Catalog

USGS Publications Warehouse

Golden, Nadine E.

2013-01-01

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California's State Waters. The CSMP approach is to create highly detailed seafloor maps and associated data layers through the collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. CSMP has divided coastal California into 110 map blocks (fig. 1), each to be published individually as USGS Scientific Investigations Maps (SIMs) at a scale of 1:24,000. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the seafloor geology and shallow (to about 100 m) subsurface geology. This CSMP data catalog contains much of the data used to prepare the SIMs in the California State Waters Map Series. Other data that were used to prepare the maps were compiled from previously published sources (for example, onshore geology) and, thus, are not included herein.

Machine-learning classifiers applied to habitat and geological substrate mapping offshore South Carolina

NASA Astrophysics Data System (ADS)

White, S. M.; Maschmeyer, C.; Anderson, E.; Knapp, C. C.; Brantley, D.

2017-12-01

Offshore of northern South Carolina holds considerable potential for wind energy development. This study describes a method for comprehensive and efficient evaluation of the geological framework and archaeological artifacts in potential Bureau of Ocean Energy Management lease blocks located 12 km offshore Myrtle Beach, South Carolina. Identification of cultural artifacts and potential critical habitats on the seafloor is critical to support for lease blocks designation, but must be done primarily using sonar data with limited visual data. We used bathymetry and backscatter to create 6 m seafloor grids of slope, and gray-level co-occurrence matrices: homogeneity, entropy, and second-moment. Supervised automated classification using an adaptive neuro-fuzzy inference system (ANFIS) in Matlab scripts provided comprehensive evaluation of the seafloor in the study area. Coastal Carolina University collected EM3002 multibeam sonar from the R/V Coastal Explorer on multiple cruises in 2015-2016 in a 32 km by 9 km area. We processed the multibeam using QPS Qimera and Fledermaus Geocoder to produce bathymetric and backscatter datasets gridded at 0.5 m with estimated 0.1 m vertical resolution. During Fall 2016, Coastal Carolina University collected ground-referenced tow-camera imagery of 68 km in 4 different sites within the multibeam survey zone. We created a ground-reference bottom-type dataset with over 75,000 reference points from the imagery. We extracted slope, backscatter intensity, and the first principal component of backscatter textures to each point. We trained an adaptive neuro-fuzzy inference system (ANFIS) on 2,500 points representing three classes: soft-bottom, hard-bottom, and cultural artifact, 101 km2 is soft-bottom, 1.5 km2 is rocky outcrop or hard-bottom, and there were 3 locations of cultural artifacts. Our classification is > 88% accurate. The extent of human artifacts, such as sunken ships and artificial reefs, are under-represented by 60% in our classification as the classifier confused flat parts with relatively flat sand data. 100% of testing data representing rocky portions of the seafloor were correctly classified. The use of machine-learning classifiers to determine seafloor-type provides a new solution to habitat mapping and offshore engineering problems.

Observations of Sea Surface Mean Square Slope During the Southern Ocean Waves Experiment

NASA Technical Reports Server (NTRS)

Walsh, E. J.; Vandemark, D. C.; Wright, C. W.; Banner, M. L.; Chen, W.; Swift, R. N.; Scott, J. F.; Hines, D. E.; Jensen, J.; Lee, S.;

Theoretical Compton profile anisotropies in molecules and solids. VI. Compton profile anisotropies and chemical binding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matcha, R.L.; Pettitt, B.M.

1979-03-15

An interesting empirical relationship between zero point Compton profile anisotropies ..delta..J (0) and nuclear charges is noted. It is shown that, for alkali halide molecules AB, to a good approximation ..delta..J (0) =N ln(Z/sub b//Z/sub a/).

Compton Dry-Cask Imaging System

ScienceCinema

None

2017-12-09

The Compton-Dry Cask Imaging Scanner is a system that verifies and documents the presence of spent nuclear fuel rods in dry-cask storage and determines their isotopic composition without moving or opening the cask. For more information about this project, visit http://www.inl.gov/rd100/2011/compton-dry-cask-imaging-system/

Relativistic thermal plasmas - Effects of magnetic fields

NASA Technical Reports Server (NTRS)

Araki, S.; Lightman, A. P.

1983-01-01

Processes and equilibria in finite, relativistic, thermal plasmas are investigated, taking into account electron-positron creation and annihilation, photon production by internal processes, and photon production by a magnetic field. Inclusion of the latter extends previous work on such plasmas. The basic relations for thermal, Comptonized synchrotron emission are analyzed, including emission and absorption without Comptonization, Comptonized thermal synchrotron emission, and the Comptonized synchrotron and bremsstrahlung luminosities. Pair equilibria are calculated, including approximations and dimensionless parameters, the pair balance equation, maximum temperatures and field strengths, and individual models and cooling curves.

On the line-shape analysis of Compton profiles and its application to neutron scattering

NASA Astrophysics Data System (ADS)

Romanelli, G.; Krzystyniak, M.

2016-05-01

Analytical properties of Compton profiles are used in order to simplify the analysis of neutron Compton scattering experiments. In particular, the possibility to fit the difference of Compton profiles is discussed as a way to greatly decrease the level of complexity of the data treatment, making the analysis easier, faster and more robust. In the context of the novel method proposed, two mathematical models describing the shapes of differenced Compton profiles are discussed: the simple Gaussian approximation for harmonic and isotropic local potential, and an analytical Gauss-Hermite expansion for an anharmonic or anisotropic potential. The method is applied to data collected by VESUVIO spectrometer at ISIS neutron and muon pulsed source (UK) on Copper and Aluminium samples at ambient and low temperatures.

Collection efficiency and acceptance maps of electron detectors for understanding signal detection on modern scanning electron microscopy.

PubMed

Agemura, Toshihide; Sekiguchi, Takashi

2018-02-01

Collection efficiency and acceptance maps of typical detectors in modern scanning electron microscopes (SEMs) were investigated. Secondary and backscattered electron trajectories from a specimen to through-the-lens and under-the-lens detectors placed on an electron optical axis and an Everhart-Thornley detector mounted on a specimen chamber were simulated three-dimensionally. The acceptance maps were drawn as the relationship between the energy and angle of collected electrons under different working distances. The collection efficiency considering the detector sensitivity was also estimated for the various working distances. These data indicated that the acceptance maps and collection efficiency are keys to understand the detection mechanism and image contrast for each detector in the modern SEMs. Furthermore, the working distance is the dominant parameter because electron trajectories are drastically changed with the working distance.

MeV gamma-ray observation with a well-defined point spread function based on electron tracking

NASA Astrophysics Data System (ADS)

Takada, A.; Tanimori, T.; Kubo, H.; Mizumoto, T.; Mizumura, Y.; Komura, S.; Kishimoto, T.; Takemura, T.; Yoshikawa, K.; Nakamasu, Y.; Matsuoka, Y.; Oda, M.; Miyamoto, S.; Sonoda, S.; Tomono, D.; Miuchi, K.; Kurosawa, S.; Sawano, T.

2016-07-01

The field of MeV gamma-ray astronomy has not opened up until recently owing to imaging difficulties. Compton telescopes and coded-aperture imaging cameras are used as conventional MeV gamma-ray telescopes; however their observations are obstructed by huge background, leading to uncertainty of the point spread function (PSF). Conventional MeV gamma-ray telescopes imaging utilize optimizing algorithms such as the ML-EM method, making it difficult to define the correct PSF, which is the uncertainty of a gamma-ray image on the celestial sphere. Recently, we have defined and evaluated the PSF of an electron-tracking Compton camera (ETCC) and a conventional Compton telescope, and thereby obtained an important result: The PSF strongly depends on the precision of the recoil direction of electron (scatter plane deviation, SPD) and is not equal to the angular resolution measure (ARM). Now, we are constructing a 30 cm-cubic ETCC for a second balloon experiment, Sub-MeV gamma ray Imaging Loaded-on-balloon Experiment: SMILE-II. The current ETCC has an effective area of 1 cm2 at 300 keV, a PSF of 10° at FWHM for 662 keV, and a large field of view of 3 sr. We will upgrade this ETCC to have an effective area of several cm2 and a PSF of 5° using a CF4-based gas. Using the upgraded ETCC, our observation plan for SMILE-II is to map of the electron-positron annihilation line and the 1.8 MeV line from 26Al. In this paper, we will report on the current performance of the ETCC and on our observation plan.

On the origin of gamma-rays in Fermi blazars: beyondthe broad-line region

NASA Astrophysics Data System (ADS)

Costamante, L.; Cutini, S.; Tosti, G.; Antolini, E.; Tramacere, A.

2018-07-01

The gamma-ray emission in broad-line blazars is generally explained as inverse Compton (IC) radiation of relativistic electrons in the jet scattering optical-UV photons from the broad-line region (BLR), the so-called BLR external Compton (EC) scenario. We test this scenario on the Fermi gamma-ray spectra of 106 broad-line blazars detected with the highest significance or largest BLR, by looking for cut-off signatures at high energies compatible with γ-γ interactions with BLR photons. We do not find evidence for the expected BLR absorption. For 2/3 of the sources, we can exclude any significant absorption (τmax < 1), while for the remaining 1/3 the possible absorption is constrained to be 1.5-2 orders of magnitude lower than expected. This result holds also dividing the spectra in high- and low-flux states, and for powerful blazars with large BLR. Only 1 object out of 10 seems compatible with substantial attenuation (τmax > 5). We conclude that for 9 out of 10 objects, the jet does not interact with BLR photons. Gamma-rays seem either produced outside the BLR most of the time, or the BLR is ˜100 × larger than given by reverberation mapping. This means that (i) EC on BLR photons is disfavoured as the main gamma-ray mechanism, versus IC on IR photons from the torus or synchrotron self-Compton; (ii) the Fermi gamma-ray spectrum is mostly intrinsic, determined by the interaction of the particle distribution with the seed-photon spectrum; and (iii) without suppression by the BLR, broad-line blazars can become copious emitters above 100 GeV, as demonstrated by 3C 454.3. We expect the CTA sky to be much richer of broad-line blazars than previously thought.

Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

NASA Technical Reports Server (NTRS)

Jezek, Kenneth C.

2002-01-01

An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the areally Integrated snow accumulation and the net ice discharge of the ice sheet. Uncertainties in this calculation Include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken from isolated spots across the ice sheet. The sparse data associated with ice cores juxtaposed against the high spatial and temporal resolution provided by remote sensing , has motivated scientists to investigate relationships between accumulation rate and microwave observations as an option for obtaining spatially contiguous estimates. The objective of this PARCA continuation proposal was to complete an estimate of surface accumulation rate on the Greenland Ice Sheet derived from C-band radar backscatter data compiled in the ERS-1 SAR mosaic of data acquired during, September-November, 1992. An empirical equation, based on elevation and latitude, is used to determine the mean annual temperature. We examine the influence of accumulation rate, and mean annual temperature on C-band radar backscatter using a forward model, which incorporates snow metamorphosis and radar backscatter components. Our model is run over a range of accumulation and temperature conditions. Based on the model results, we generate a look-up table, which uniquely maps the measured radar backscatter, and mean annual temperature to accumulation rate. Our results compare favorably with in situ accumulation rate measurements falling within our study area.

Characterizing riverbed sediment using high-frequency acoustics 2: scattering signatures of Colorado River bed sediment in Marble and Grand Canyons

USGS Publications Warehouse

Buscombe, Daniel D.; Grams, Paul E.; Kaplinski, Matt A.

2014-01-01

In this, the second of a pair of papers on the statistical signatures of riverbed sediment in high-frequency acoustic backscatter, spatially explicit maps of the stochastic geometries (length- and amplitude-scales) of backscatter are related to patches of riverbed surfaces composed of known sediment types, as determined by geo-referenced underwater video observations. Statistics of backscatter magnitudes alone are found to be poor discriminators between sediment types. However, the variance of the power spectrum, and the intercept and slope from a power-law spectral form (termed the spectral strength and exponent, respectively) successfully discriminate between sediment types. A decision-tree approach was able to classify spatially heterogeneous patches of homogeneous sands, gravels (and sand-gravel mixtures), and cobbles/boulders with 95, 88, and 91% accuracy, respectively. Application to sites outside the calibration, and surveys made at calibration sites at different times, were plausible based on observations from underwater video. Analysis of decision trees built with different training data sets suggested that the spectral exponent was consistently the most important variable in the classification. In the absence of theory concerning how spatially variable sediment surfaces scatter high-frequency sound, the primary advantage of this data-driven approach to classify bed sediment over alternatives is that spectral methods have well understood properties and make no assumptions about the distributional form of the fluctuating component of backscatter over small spatial scales.

Simulation Studies of the Effect of Forest Spatial Structure on InSAR Signature

NASA Technical Reports Server (NTRS)

Sun, Guoqing; Liu, Dawei; Ranson, K. Jon; Koetz, Benjamin

2007-01-01

The height of scattering phase retrieved from InSAR data is considered being correlated with the tree height and the spatial structure of the forest stand. Though some researchers have used simple backscattering models to estimate tree height from the height of scattering center, the effect of forest spatial structure on InSAR data is not well understood yet. A three-dimensional coherent radar backscattering model for forest canopies based on realistic three-dimensional scene was used to investigate the effect in this paper. The realistic spatial structure of forest canopies was established either by field measurements (stem map) or through use of forest growth model. Field measurements or a forest growth model parameterized using local environmental parameters provides information of forest species composition and tree sizes in certain growth phases. A fractal tree model (L-system) was used to simulate individual 3- D tree structure of different ages or heights. Trees were positioned in a stand in certain patterns resulting in a 3-D medium of discrete scatterers. The radar coherent backscatter model took the 3-D forest scene as input and simulates the coherent radar backscattering signature. Interferometric SAR images of 3D scenes were simulated and heights of scattering phase centers were estimated from the simulated InSAR data. The effects of tree height, crown cover, crown depth, and the spatial distribution patterns of trees on the scattering phase center were analyzed. The results will be presented in the paper.

Modeling of direct detection Doppler wind lidar. I. The edge technique.

PubMed

McKay, J A

1998-09-20

Analytic models, based on a convolution of a Fabry-Perot etalon transfer function with a Gaussian spectral source, are developed for the shot-noise-limited measurement precision of Doppler wind lidars based on the edge filter technique by use of either molecular or aerosol atmospheric backscatter. The Rayleigh backscatter formulation yields a map of theoretical sensitivity versus etalon parameters, permitting design optimization and showing that the optimal system will have a Doppler measurement uncertainty no better than approximately 2.4 times that of a perfect, lossless receiver. An extension of the models to include the effect of limited etalon aperture leads to a condition for the minimum aperture required to match light collection optics. It is shown that, depending on the choice of operating point, the etalon aperture finesse must be 4-15 to avoid degradation of measurement precision. A convenient, closed-form expression for the measurement precision is obtained for spectrally narrow backscatter and is shown to be useful for backscatter that is spectrally broad as well. The models are extended to include extrinsic noise, such as solar background or the Rayleigh background on an aerosol Doppler lidar. A comparison of the model predictions with experiment has not yet been possible, but a comparison with detailed instrument modeling by McGill and Spinhirne shows satisfactory agreement. The models derived here will be more conveniently implemented than McGill and Spinhirne's and more readily permit physical insights to the optimization and limitations of the double-edge technique.

Opposition effect of the Moon from LROC WAC data

NASA Astrophysics Data System (ADS)

Velikodsky, Yu. I.; Korokhin, V. V.; Shkuratov, Yu. G.; Kaydash, V. G.; Videen, Gorden

2016-09-01

LROC WAC images acquired in 5 bands of the visible spectral range were used to study the opposition effect for two mare and two highland regions near the lunar equator. Opposition phase curves were extracted from the images containing the opposition by separating the phase-curve effect from the albedo pattern by comparing WAC images at different phase angles (from 0° to 30°). Akimov's photometric function and the NASA Digital Terrain Model GLD100 were used in the processing. It was found that phase-curve slopes at small phase angles directly correlate with albedo, while at larger phase angles, they are anti-correlated. We suggest a parameter to characterize the coherent-backscattering component of the lunar opposition surge, which is defined as the maximum phase angle for which the opposition-surge slope increases with growing albedo. The width of the coherent-backscattering opposition effect varies from approximately 1.2° for highlands in red light to 3.9° for maria in blue light. The parameter depends on albedo, which is in agreement with the coherent-backscattering theory. The maximum amplitude of the coherent opposition effect is estimated to be near 8%. Maps of albedo and phase-curve slope at phase angles larger than those, at which the coherent-backscattering occurs, were built for the areas under study. Absolute calibration of WAC images was compared with Earth-based observations: the WAC-determined albedo is very close to the mean lunar albedo calculated using available Earth-based observations.

Monitoring evolution of HIFU-induced lesions with backscattered ultrasound

NASA Astrophysics Data System (ADS)

Anand, Ajay; Kaczkowski, Peter J.

2003-04-01

Backscattered radio frequency (rf) data from a modified commercial ultrasound scanner were collected in a series of in vitro experiments in which high intensity focused ultrasound (HIFU) was used to create lesions in freshly excised bovine liver tissue. Two signal processing approaches were used to visualize the temporal evolution of lesion formation. First, apparent tissue motion due to temperature rise was detected using cross-correlation techniques. Results indicate that differential processing of travel time can provide temperature change information throughout the therapy delivery phase and after HIFU has been turned off, over a relatively large spatial region. Second, changes in the frequency spectrum of rf echoes due to changes in the scattering properties of the heated region were observed well before the appearance of hyper-echogenic spots in the focal zone. Furthermore, the increase in attenuation in the lesion zone changes the measured backscatter spectrum from regions distal to it along the imaging beam. Both effects were visualized using spectral processing and display techniques that provide a color spatial map of these features for the clinician. Our results demonstrate potential for these ultrasound-based techniques in targeting and monitoring of HIFU therapy, and perhaps post-treatment visualization of HIFU-induced lesions.

BOREAS RSS-17 1994 ERS-1 Level-3 Freeze/Thaw Backscatter Change Images

NASA Technical Reports Server (NTRS)

Rignot, Eric; Nickeson, Jaime (Editor); Hall, Forrest G. (Editor); Way, JoBea; McDonald, Kyle C.; Smith, David E. (Technical Monitor)

2000-01-01

The Boreal Ecosystem-Atmosphere Study (BOREAS) Remote Sensing Science (RSS)-17 team acquired and analyzed imaging radar data from the European Space Agency's (ESA's) European Remote Sensing Satellite (ERS)-1 over a complete annual cycle at the BOREAS sites in Canada in 1994 to detect shifts in radar backscatter related to varying environmental conditions. Two independent transitions corresponding to soil thaw and possible canopy thaw were revealed by the data. The results demonstrated that radar provides an ability to observe thaw transitions at the beginning of the growing season, which in turn helps constrain the length of the growing season. The data set presented here includes change maps derived from radar backscatter images that were mosaicked together to cover the southern BOREAS sites. The image values used for calculating the changes are given relative to the reference mosaic image. The data are stored in binary image format files. The imaging radar data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Compton spectra of atoms at high x-ray intensity

NASA Astrophysics Data System (ADS)

Son, Sang-Kil; Geffert, Otfried; Santra, Robin

2017-03-01

Compton scattering is the nonresonant inelastic scattering of an x-ray photon by an electron and has been used to probe the electron momentum distribution in gas-phase and condensed-matter samples. In the low x-ray intensity regime, Compton scattering from atoms dominantly comes from bound electrons in neutral atoms, neglecting contributions from bound electrons in ions and free (ionized) electrons. In contrast, in the high x-ray intensity regime, the sample experiences severe ionization via x-ray multiphoton multiple ionization dynamics. Thus, it becomes necessary to take into account all the contributions to the Compton scattering signal when atoms are exposed to high-intensity x-ray pulses provided by x-ray free-electron lasers (XFELs). In this paper, we investigate the Compton spectra of atoms at high x-ray intensity, using an extension of the integrated x-ray atomic physics toolkit, xatom. As the x-ray fluence increases, there is a significant contribution from ionized electrons to the Compton spectra, which gives rise to strong deviations from the Compton spectra of neutral atoms. The present study provides not only understanding of the fundamental XFEL-matter interaction but also crucial information for single-particle imaging experiments, where Compton scattering is no longer negligible. , which features invited work from the best early-career researchers working within the scope of J. Phys. B. This project is part of the Journal of Physics series’ 50th anniversary celebrations in 2017. Sang-Kil Son was selected by the Editorial Board of J. Phys. B as an Emerging Leader.

Contribution of inner shell Compton ionization to the X-ray fluorescence line intensity

NASA Astrophysics Data System (ADS)

Fernández, Jorge E.; Scot, Viviana; Di Giulio, Eugenio

2016-10-01

The Compton effect is a potential ionization mechanism of atoms. It produces vacancies in inner shells that are filled with the same mechanism of atomic relaxation as the one following photo-absorption. This contribution to X-ray fluorescence emission is frequently neglected because the total Compton cross-section is apparently much lower than the photoelectric one at useful X-ray energies. However, a more careful analysis suggests that is necessary to consider single shell cross sections (instead of total cross sections) as a function of energy. In this article these Compton cross sections are computed for the shells K, L1-L3 and M1-M5 in the framework of the impulse approximation. By comparing the Compton and the photoelectric cross-section for each shell it is then possible to determine the extent of the Compton correction to the intensity of the corresponding characteristic lines. It is shown that for the K shell the correction becomes relevant for excitation energies which are too high to be influent in X-ray spectrometry. In contrast, for L and M shells the Compton contribution is relevant for medium-Z elements and medium energies. To illustrate the different grades of relevance of the correction, for each ionized shell, the energies for which the Compton contribution reaches the extent levels of 1, 5, 10, 20, 50 and 100% of the photoelectric one are determined for all the elements with Z = 11-92. For practical applications it is provided a simple formula and fitting coefficients to compute average correction levels for the shells considered.

Mapping lava morphology of the Galapagos Spreading Center at 92°W: fuzzy logic provides a classification of high-resolution bathymetry and backscatter

NASA Astrophysics Data System (ADS)

McClinton, J. T.; White, S. M.; Sinton, J. M.; Rubin, K. H.; Bowles, J. A.

2010-12-01

Differences in axial lava morphology along the Galapagos Spreading Center (GSC) can indicate variations in magma supply and emplacement dynamics due to the influence of the adjacent Galapagos hot spot. Unfortunately, the ability to discriminate fine-scale lava morphology has historically been limited to observations of the small coverage areas of towed camera surveys and submersible operations. This research presents a neuro-fuzzy approach to automated seafloor classification using spatially coincident, high-resolution bathymetry and backscatter data. The classification method implements a Sugeno-type fuzzy inference system trained by a multi-layered adaptive neural network and is capable of rapidly classifying seafloor morphology based on attributes of surface geometry and texture. The system has been applied to the 92°W segment of the western GSC in order to quantify coverage areas and distributions of pillow, lobate, and sheet lava morphology. An accuracy assessment has been performed on the classification results. The resulting classified maps provide a high-resolution view of GSC axial morphology and indicate the study area terrain is approximately 40% pillow flows, 40% lobate and sheet flows, and 10% fissured or faulted area, with about 10% of the study area unclassifiable. Fine-scale features such as eruptive fissures, tumuli, and individual pillowed lava flow fronts are also visible. Although this system has been applied to lava morphology, its design and implementation are applicable to other undersea mapping applications.

Geometric Corrections for Topographic Distortion from Side Scan Sonar Data Obtained by ANKOU System

NASA Astrophysics Data System (ADS)

Yamamoto, Fujio; Kato, Yukihiro; Ogasawara, Shohei

The ANKOU is a newly developed, full ocean depth, long-range vector side scan sonar system. The system provides real time vector side scan sonar data to produce backscattering images and bathymetric maps for seafloor swaths up to 10 km on either side of ship's centerline. Complete geometric corrections are made using towfish attitude and cross-track distortions known as foreshortening and layover caused by violation of the flat bottom assumption. Foreshortening and layover refers to pixels which have been placed at an incorrect cross-track distance. Our correction of this topographic distortion is accomplished by interpolating a bathymetric profile and ANKOU phase data. We applied these processing techniques to ANKOU backscattering data obtained from off Boso Peninsula, and confirmed their efficiency and utility for making geometric corrections of side scan sonar data.

Polarization reconstruction algorithm for a Compton polarimeter

NASA Astrophysics Data System (ADS)

Vockert, M.; Weber, G.; Spillmann, U.; Krings, T.; Stöhlker, Th

2018-05-01

We present the technique of Compton polarimetry using X-ray detectors based on double-sided segmented semiconductor crystals that were developed within the SPARC collaboration. In addition, we discuss the polarization reconstruction algorithm with particular emphasis on systematic deviations between the observed detector response and our model function for the Compton scattering distribution inside the detector.

Spatial resolution measurements of the advanced radiographic capability x-ray imaging system at energies relevant to Compton radiography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, G. N.; Izumi, N.; Landen, O. L.

2016-08-03

Compton radiography provides a means to measure the integrity, ρR and symmetry of the DT fuel in an inertial confinement fusion implosion near peak compression. Upcoming experiments at the National Ignition Facility will use the ARC (Advanced Radiography Capability) laser to drive backlighter sources for Compton radiography experiments, and will use the newly commissioned AXIS (ARC X-ray Imaging System) instrument as the detector. AXIS uses a dual-MCP (micro channel plate) to provide gating and high DQE at the 40–200keV x-ray range required for Compton radiography, but introduces many effects that contribute to the spatial resolution. Here, experiments were performed atmore » energies relevant to Compton radiography to begin characterization of the spatial resolution of the AXIS diagnostic.« less

The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD)

NASA Astrophysics Data System (ADS)

Watanabe, Shin; Tajima, Hiroyasu; Fukazawa, Yasushi; Ichinohe, Yuto; Takeda, Shin`ichiro; Enoto, Teruaki; Fukuyama, Taro; Furui, Shunya; Genba, Kei; Hagino, Kouichi; Harayama, Atsushi; Kuroda, Yoshikatsu; Matsuura, Daisuke; Nakamura, Ryo; Nakazawa, Kazuhiro; Noda, Hirofumi; Odaka, Hirokazu; Ohta, Masayuki; Onishi, Mitsunobu; Saito, Shinya; Sato, Goro; Sato, Tamotsu; Takahashi, Tadayuki; Tanaka, Takaaki; Togo, Atsushi; Tomizuka, Shinji

2014-11-01

The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60-600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton camera has been finalized and the final prototype, which has the same configuration as the flight model, has been fabricated for performance evaluation. The Compton camera has overall dimensions of 12 cm×12 cm×12 cm, consisting of 32 layers of Si pixel sensors and 8 layers of CdTe pixel sensors surrounded by 2 layers of CdTe pixel sensors. The detection efficiency of the Compton camera reaches about 15% and 3% for 100 keV and 511 keV gamma rays, respectively. The pixel pitch of the Si and CdTe sensors is 3.2 mm, and the signals from all 13,312 pixels are processed by 208 ASICs developed for the SGD. Good energy resolution is afforded by semiconductor sensors and low noise ASICs, and the obtained energy resolutions with the prototype Si and CdTe pixel sensors are 1.0-2.0 keV (FWHM) at 60 keV and 1.6-2.5 keV (FWHM) at 122 keV, respectively. This results in good background rejection capability due to better constraints on Compton kinematics. Compton camera energy resolutions achieved with the final prototype are 6.3 keV (FWHM) at 356 keV and 10.5 keV (FWHM) at 662 keV, which satisfy the instrument requirements for the SGD Compton camera (better than 2%). Moreover, a low intrinsic background has been confirmed by the background measurement with the final prototype.

Magnetic dipole excitations of 50Cr

NASA Astrophysics Data System (ADS)

Pai, H.; Beck, T.; Beller, J.; Beyer, R.; Bhike, M.; Derya, V.; Gayer, U.; Isaak, J.; Krishichayan, Kvasil, J.; Löher, B.; Nesterenko, V. O.; Pietralla, N.; Martínez-Pinedo, G.; Mertes, L.; Ponomarev, V. Yu.; Reinhard, P.-G.; Repko, A.; Ries, P. C.; Romig, C.; Savran, D.; Schwengner, R.; Tornow, W.; Werner, V.; Wilhelmy, J.; Zilges, A.; Zweidinger, M.

2016-01-01

The low-lying M 1 strength of the open-shell nucleus 50Cr has been studied with the method of nuclear resonance fluorescence up to 9.7 MeV using bremsstrahlung at the superconducting Darmstadt linear electron accelerator S-DALINAC and Compton backscattered photons at the High Intensity γ -ray Source (HI γ S ) facility between 6 and 9.7 MeV of the initial photon energy. Fifteen 1+ states have been observed between 3.6 and 9.7 MeV. Following our analysis the lowest 1+ state at 3.6 MeV can be considered as an isovector orbital mode with some spin admixture. The obtained results generally match the estimations and trends typical for the scissors-like mode. Detailed calculations within the Skyrme quasiparticle random-phase-approximation method and the large-scale shell model justify our conclusions. The calculated distributions of the orbital current for the lowest 1+-state suggest the schematic view of Lipparini and Stringari (isovector rotation-like oscillations inside the rigid surface) rather than the scissors-like picture of Lo Iudice and Palumbo. The spin M 1 resonance is shown to be mainly generated by spin-flip transitions between the orbitals of the f p shell.

NuSTAR REVEALS RELATIVISTIC REFLECTION BUT NO ULTRA-FAST OUTFLOW IN THE QUASAR PG 1211+143

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zoghbi, A.; Miller, J. M.; Walton, D. J.

We report on four epochs of observations of the quasar PG 1211+143 using NuSTAR. The net exposure time is 300 ks. Prior work on this source found suggestive evidence of an ultra-fast outflow (UFO) in the Fe K band with a velocity of approximately 0.1c. The putative flow would carry away a high-mass flux and kinetic power, with broad implications for feedback and black hole--galaxy co-evolution. NuSTAR detects PG 1211+143 out to 30 keV, meaning that the continuum is well-defined both through and above the Fe K band. A characteristic relativistic disk reflection spectrum is clearly revealed via a broadmore » Fe K emission line and Compton back-scattering curvature. The data offer only weak constraints on the spin of the black hole. A careful search for UFOs shows no significant absorption feature above 90% confidence. The limits are particularly tight when relativistic reflection is included. We discuss the statistics and the implications of these results in terms of connections between accretion onto quasars, Seyferts, and stellar-mass black holes, and feedback into their host environments.« less

NuSTAR Reveals Relativistic Reflection But No Ultra-Fast Outflow in the Quasar Pg∼1211+143

NASA Astrophysics Data System (ADS)

Zoghbi, A.; Miller, J. M.; Walton, D. J.; Harrison, F. A.; Fabian, A. C.; Reynolds, C. S.; Boggs, S. E.; Christensen, F. E.; Craig, W.; Hailey, C. J.; Stern, D.; Zhang, W. W.

2015-01-01

We report on four epochs of observations of the quasar PG 1211+143 using NuSTAR. The net exposure time is 300 ks. Prior work on this source found suggestive evidence of an ultra-fast outflow (UFO) in the Fe K band with a velocity of approximately 0.1c. The putative flow would carry away a high-mass flux and kinetic power, with broad implications for feedback and black hole--galaxy co-evolution. NuSTAR detects PG 1211+143 out to 30 keV, meaning that the continuum is well-defined both through and above the Fe K band. A characteristic relativistic disk reflection spectrum is clearly revealed via a broad Fe K emission line and Compton back-scattering curvature. The data offer only weak constraints on the spin of the black hole. A careful search for UFOs shows no significant absorption feature above 90% confidence. The limits are particularly tight when relativistic reflection is included. We discuss the statistics and the implications of these results in terms of connections between accretion onto quasars, Seyferts, and stellar-mass black holes, and feedback into their host environments.

The diffuse galactic gamma radiation: The Compton contribution and component separation by energy interval and galactic coordinates

NASA Technical Reports Server (NTRS)

Kniffen, D. A.; Fichtel, C.

1981-01-01

The radiation to be expected from cosmic ray interactions with matter and photons was examined. Particular emphasis is placed on the Compton emission. Both the photon density in and near the visible region and that in the region are deduced from the estimates of the emission functions throughout the Galaxy. The blackbody radiation is also included in the estimate of the total Compton emission. The result suggests that the gamma ray Compton radiation from cosmic ray ineractions with galactic visible and infrared photons is substantially larger than previously believed.

Virtual Compton scattering off a spinless target in AdS/QCD

NASA Astrophysics Data System (ADS)

Marquet, Cyrille; Roiesnel, Claude; Wallon, Samuel

2010-04-01

We study the doubly virtual Compton scattering off a spinless target γ* P → γ* P' within the Anti-de Sitter(AdS)/QCD formalism. We find that the general structure allowed by the Lorentz invariance and gauge invariance of the Compton amplitude is not easily reproduced with the standard recipes of the AdS/QCD correspondence. In the soft-photon regime, where the semi-classical approximation is supposed to apply best, we show that the measurements of the electric and magnetic polarizabilities of a target like the charged pion in real Compton scattering, can already serve as stringent tests.

Measurement and simulation of a Compton suppression system for safeguards application

NASA Astrophysics Data System (ADS)

Lee, Seung Kyu; Seo, Hee; Won, Byung-Hee; Lee, Chaehun; Shin, Hee-Sung; Na, Sang-Ho; Song, Dae-Yong; Kim, Ho-Dong; Park, Geun-Il; Park, Se-Hwan

2015-11-01

Plutonium (Pu) contents in spent nuclear fuels, recovered uranium (U) or uranium/transuranium (U/TRU) products must be measured in order to secure the safeguardability of a pyroprocessing facility. Self-induced X-Ray fluorescence (XRF) and gamma-ray spectroscopy are useful techniques for determining Pu-to-U ratios and Pu isotope ratios of spent fuel. Photon measurements of spent nuclear fuel by using high-resolution spectrometers such as high-purity germanium (HPGe) detectors show a large continuum background in the low-energy region, which is due in large part to Compton scattering of energetic gamma rays. This paper proposes a Compton suppression system for reducing of the Compton continuum background. In the present study, the system was configured by using an HPGe main detector and a BGO (bismuth germanate: Bi4Ge3O12) guard detector. The system performances for gamma-ray measurement and XRF were evaluated by means of Monte Carlo simulations and measurements of the radiation source. The Monte Carlo N-Particle eXtended (MCNPX) simulations were performed using the same geometry as for the experiments, and considered, for exact results, the production of secondary electrons and photons. As a performance test of the Compton suppression system, the peak-to-Compton ratio, which is a figure of merit to evaluate the gamma-ray detection, was enhanced by a factor of three or more when the Compton suppression system was used.

FULL SPECTRAL SURVEY OF ACTIVE GALACTIC NUCLEI IN THE ROSSI X-RAY TIMING EXPLORER ARCHIVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivers, Elizabeth; Markowitz, Alex; Rothschild, Richard, E-mail: erivers@ucsd.edu

2013-08-01

We have analyzed spectra for all active galactic nuclei (AGNs) in the Rossi X-ray Timing Explorer archive. We present long-term average values of absorption, Fe line equivalent width (EW), Compton reflection, and photon index, and calculate fluxes and luminosities in the 2-10 keV band for 100 AGN with sufficient brightness and overall observation time to yield high-quality spectral results. We compare these parameters across the different classifications of Seyferts and blazars. Our distributions of photon indices for Seyfert 1s and 2s are consistent with the idea that Seyferts share a common central engine; however, our distributions of Compton reflection humpmore » strengths do not support the classical picture of absorption by a torus and reflection off a Compton-thick disk with type depending only on inclination angle. We conclude that a more complex reflecting geometry such as a combined disk and torus or clumpy torus is likely a more accurate picture of the Compton-thick material. We find that Compton reflection is present in {approx}85% of Seyferts and by comparing Fe line EW's to Compton reflection hump strengths we have found that on average 40% of the Fe line arises in Compton thick material; however, this ratio was not consistent from object to object and did not seem to be dependent on optical classification.« less

Study of Compton suppression for use in spent nuclear fuel assay

NASA Astrophysics Data System (ADS)

Bender, Sarah

The focus of this study has been to assess Compton suppressed gamma-ray detection systems for the multivariate analysis of spent nuclear fuel. This objective has been achieved using direct measurement of samples of irradiated fuel elements in two geometrical configurations with Compton suppression systems. In order to address the objective to quantify the number of additionally resolvable photopeaks, direct Compton suppressed spectroscopic measurements of spent nuclear fuel in two configurations were performed: as intact fuel elements and as dissolved feed solutions. These measurements directly assessed and quantified the differences in measured gamma-ray spectrum from the application of Compton suppression. Several irradiated fuel elements of varying cooling time from the Penn State Breazeale Reactor spent fuel inventory were measured using three Compton suppression systems that utilized different primary detectors: HPGe, LaBr3, and NaI(Tl). The application of Compton suppression using a LaBr3 primary detector to the measurement of the current core fuel element, which presented the highest count rate, allowed four additional spectral features to be resolved. In comparison, the HPGe-CSS was able to resolve eight additional photopeaks as compared to the standalone HPGe measurement. Measurements with the NaI(Tl) primary detector were unable to resolve any additional peaks, due to its relatively low resolution. Samples of Approved Test Material (ATM) commercial fuel elements were obtained from Pacific Northwest National Laboratory. The samples had been processed using the beginning stages of the PUREX method and represented the unseparated feed solution from a reprocessing facility. Compton suppressed measurements of the ATM fuel samples were recorded inside the guard detector annulus, to simulate the siphoning of small quantities from the main process stream for long dwell measurement periods. Photopeak losses were observed in the measurements of the dissolved ATM fuel samples because the spectra was recorded from the source in very close proximity to the detector and surrounded by the guard annulus, so the detection probability is very high. Though this configuration is optimal for a Compton suppression system for the measurement of low count rate samples, measurement of high count rate samples in the enclosed arrangement leads to sum peaks in both the suppressed and unsuppressed spectra and losses to photopeak counts in the suppressed spectra. No additional photopeaks were detected using Compton suppression with this geometry. A detector model was constructed that can accurately simulate a Compton suppressed spectral measurement of radiation from spent nuclear fuel using HPGe or LaBr3 detectors. This is the first detector model capable of such an accomplishment. The model uses the Geant4 toolkit coupled with the RadSrc application and it accepts spent fuel composition data in list form. The model has been validated using dissolved ATM fuel samples in the standard, enclosed geometry of the PSU HPGe-CSS. The model showed generally good agreement with both the unsuppressed and suppressed measured fuel sample spectra, however the simulation is more appropriate for the generation of gamma-ray spectra in the beam source configuration. Photopeak losses due to cascade decay emissions in the Compton suppressed spectra were not appropriately managed by the simulation. Compton suppression would be a beneficial addition to NDA process monitoring systems if oriented such that the gamma-ray photons are collimated to impinge the primary detector face as a beam. The analysis has shown that peak losses through accidental coincidences are minimal and the reduction in the Compton continuum allows additional peaks to be resolved. (Abstract shortened by UMI.).

Spectra of clinical CT scanners using a portable Compton spectrometer.

PubMed

Duisterwinkel, H A; van Abbema, J K; van Goethem, M J; Kawachimaru, R; Paganini, L; van der Graaf, E R; Brandenburg, S

2015-04-01

Spectral information of the output of x-ray tubes in (dual source) computer tomography (CT) scanners can be used to improve the conversion of CT numbers to proton stopping power and can be used to advantage in CT scanner quality assurance. The purpose of this study is to design, validate, and apply a compact portable Compton spectrometer that was constructed to accurately measure x-ray spectra of CT scanners. In the design of the Compton spectrometer, the shielding materials were carefully chosen and positioned to reduce background by x-ray fluorescence from the materials used. The spectrum of Compton scattered x-rays alters from the original source spectrum due to various physical processes. Reconstruction of the original x-ray spectrum from the Compton scattered spectrum is based on Monte Carlo simulations of the processes involved. This reconstruction is validated by comparing directly and indirectly measured spectra of a mobile x-ray tube. The Compton spectrometer is assessed in a clinical setting by measuring x-ray spectra at various tube voltages of three different medical CT scanner x-ray tubes. The directly and indirectly measured spectra are in good agreement (their ratio being 0.99) thereby validating the reconstruction method. The measured spectra of the medical CT scanners are consistent with theoretical spectra and spectra obtained from the x-ray tube manufacturer. A Compton spectrometer has been successfully designed, constructed, validated, and applied in the measurement of x-ray spectra of CT scanners. These measurements show that our compact Compton spectrometer can be rapidly set-up using the alignment lasers of the CT scanner, thereby enabling its use in commissioning, troubleshooting, and, e.g., annual performance check-ups of CT scanners.

Hidden baryons: The physics of Compton composites

NASA Astrophysics Data System (ADS)

Mayer, Frederick J.

2016-06-01

A large fraction of the mass-energy of the Universe appears to be composed of Compton composites. How is it then that these composites are not frequently observed in experiments? This paper addresses this question, and others, by reviewing recent publications that: 1) introduced Compton composites, 2) showed how and where they are formed and 3) explained how they interact with other systems. Though ubiquitous in many physical situations, Compton composites are almost completely hidden in experiments due to their unique interaction characteristics. Still, their presence has been indirectly observed, though not interpreted as such until recently. Looking to the future, direct-detection experiments are proposed that could verify the composites' components. It is with deep sadness that I dedicate this paper to my mentor, collaborator, and friend, Dr. John R. Reitz, who passed away within days of the publication of our paper “Compton Composites Late in the Early Universe”.

NOAA Ship Okeanos Explorer 2012 Field Season in the Northern Gulf of Mexico and U.S. Atlantic Continental Margin

NASA Astrophysics Data System (ADS)

Skarke, A. D.; Lobecker, E.; Malik, M.; VerPlanck, N.

2012-12-01

The NOAA Ship Okeanos Explorer, jointly operated by the NOAA Office of Ocean Exploration and Research and the NOAA Office of Marine and Aviation Operations, is America's only federally managed ship dedicated solely to ocean exploration. The 2012 field season was spent exploring the northern Gulf of Mexico and the U.S. Atlantic continental shelf break and slope. In the Gulf of Mexico, mapping and remotely operated vehicle operations focused on the salt domes and canyons offshore Mississippi and Louisiana, and characterized several of the hundreds of seeps that were detected in the water column backscatter data collected with the ship's Kongsberg EM 302 multibeam sonar (30 kHz) during the 2011 field season. A team of NOAA and non-NOAA partners identified priority frontier areas along the continental shelf and slope between North Carolina and Cape Cod, mapping numerous canyons selected for focused mapping exploration in partnership with the North East Fisheries Science Center, the Mid-Atlantic Regional Council on the Ocean (a state level partnership between various states including NY, NJ, DE, MD, and VA), Woods Hole Oceanographic Institution (WHOI) and Virginia Sea Grant. The 2012 mapping efforts built on data collected during the 2011 field season. Okeanos Explorer data were leveraged by NOAA Ship Henry B. Bigelow to conduct towed camera operations to ground truth multibeam backscatter data for deepwater coral habitat assessment. The Blake Ridge and Cape Fear Diapirs offshore North Carolina were a third focus of exploration operations. Seven 900 meter high cold seeps were discovered in the diapir province. Exploration incorporated WHOI's Sentry autonomous underwater vehicle and its full suite of mapping and oceanographic sensors were used to characterize six seep sites. All data collected by Okeanos Explorer are available via the NOAA public archives with metadata records within 60 to 90 days of the end of each cruise.

Evaluation of single-band snow-patch mapping using high-resolution microwave remote sensing: an application in the maritime Antarctic

NASA Astrophysics Data System (ADS)

Mora, Carla; Jiménez, Juan Javier; Pina, Pedro; Catalão, João; Vieira, Gonçalo

2017-01-01

The mountainous and ice-free terrains of the maritime Antarctic generate complex mosaics of snow patches, ranging from tens to hundreds of metres. These can only be accurately mapped using high-resolution remote sensing. In this paper we evaluate the application of radar scenes from TerraSAR-X in High Resolution SpotLight mode for mapping snow patches at a test area on Fildes Peninsula (King George Island, South Shetlands). Snow-patch mapping and characterization of snow stratigraphy were conducted at the time of image acquisition on 12 and 13 January 2012. Snow was wet in all studied snow patches, with coarse-grain and rounded crystals showing advanced melting and with frequent ice layers in the snow pack. Two TerraSAR-X scenes in HH and VV polarization modes were analysed, with the former showing the best results when discriminating between wet snow, lake water and bare soil. However, significant overlap in the backscattering signal was found. Average wet-snow backscattering was -18.0 dB in HH mode, with water showing -21.1 dB and bare soil showing -11.9 dB. Single-band pixel-based and object-oriented image classification methods were used to assess the classification potential of TerraSAR-X SpotLight imagery. The best results were obtained with an object-oriented approach using a watershed segmentation with a support vector machine (SVM) classifier, with an overall accuracy of 92 % and Kappa of 0.88. The main limitation was the west to north-west facing snow patches, which showed significant error, an issue related to artefacts from the geometry of satellite imagery acquisition. The results show that TerraSAR-X in SpotLight mode provides high-quality imagery for mapping wet snow and snowmelt in the maritime Antarctic. The classification procedure that we propose is a simple method and a first step to an implementation in operational mode if a good digital elevation model is available.

Australian Multiexperimental Assessment of SIR-B (AMAS)

NASA Technical Reports Server (NTRS)

Richards, J. A.; Forster, B. C.; Milne, A. K.; Taylor, G. R.; Trinder, J. C.

1984-01-01

The utility of SIR-B data for analysis of surface properties and subsurface morphology in three arid regions of Australia is investigated. This study area is located in western New South Wales. It contains extensive aeolian and alluvially derived depositional plains and is the site of the University's Arid Zone Research Station; it is well-mapped and surveyed. Radar backscatter is mapped and evaluated against known terrain conditions. Relative components of surface and subsurface return are determined with a view to identifying structural properties of surface and subsurface morphology. The capability of microwave remote sensing in locating likely groundwater sources in the Bancannia Basin, near Fowler's Gap is assessed.

An acoustic backscatter thermometer for remotely mapping seafloor water temperature

NASA Astrophysics Data System (ADS)

Jackson, Darrell R.; Dworski, J. George

1992-01-01

A bottom-mounted, circularly scanning sonar operating at 40 kHz has been used to map changes in water sound speed over a circular region 150 m in diameter. If it is assumed that the salinity remains constant, the change in sound speed can be converted to a change in temperature. For the present system, the spatial resolution is 7.5 m and the temperature resolution is 0.05°C. The technique is based on comparison of successive sonar scans by means of a correlation algorithm. The algorithm is illustrated using data from the Sediment Transport Events on Slopes and Shelves (STRESS) experiment.

Unequal Pieces of a Shrinking Pie: The Struggle between African Americans and Latinos over Education, Employment, and Empowerment in Compton, California

ERIC Educational Resources Information Center

Straus, Emily E.

2009-01-01

This article discusses the role of education within communities and underscores the changing nature of minority groups in the United States. It specifically examines the struggle between African Americans and Latinos over education, employment, and empowerment in Compton, California. The story of Compton and its school district exposes…

Modulated method for efficient, narrow-bandwidth, laser Compton X-ray and gamma-ray sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, Christopher P. J.

A method of x-ray and gamma-ray generation via laser Compton scattering uses the interaction of a specially-formatted, highly modulated, long duration, laser pulse with a high-frequency train of high-brightness electron bunches to both create narrow bandwidth x-ray and gamma-ray sources and significantly increase the laser to Compton photon conversion efficiency.

Method for efficient, narrow-bandwidth, laser compton x-ray and gamma-ray sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, Christopher P. J.

A method of x-ray and gamma-ray generation via laser Compton scattering uses the interaction of a specially-formatted, highly modulated, long duration, laser pulse with a high-frequency train of high-brightness electron bunches to both create narrow bandwidth x-ray and gamma-ray sources and significantly increase the laser to Compton photon conversion efficiency.

Kinematics of the Elastic Scattering of $gamma$ in Hydrogen (Compton Effecte Between 300 and 1500 Mev; CINEMATICA DELLA DIFFUSIONE ELASTICA DI $gamma$ IN IDROGENO (EFFETTO COMPTON) TRA 300 E 1500 MEV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salvadori, P.

1962-10-31

The proton (p ) and gamma energy and angular distributions from the elastic (Compton) interaction p + gamma -- p + gamma are calculated. The results are tabulated for 25-Mev gamma increments, from 300 to 1500 Mev. (T.F.H.)

Determination of Rest Mass Energy of the Electron by a Compton Scattering Experiment

ERIC Educational Resources Information Center

Prasannakumar, S.; Krishnaveni, S.; Umesh, T. K.

2012-01-01

We report here a simple Compton scattering experiment which may be carried out in graduate and undergraduate laboratories to determine the rest mass energy of the electron. In the present experiment, we have measured the energies of the Compton scattered gamma rays with a NaI(Tl) gamma ray spectrometer coupled to a 1 K multichannel analyzer at…

G. E. M. Jauncey and the Compton Effect

NASA Astrophysics Data System (ADS)

Jenkin, John

In late 1922 Arthur Holly Compton (1892-1962) discovered that an X-ray quantum of radiation undergoes a discrete change in wavelength when it experiences a billiard-ball collision with a single atomic electron, a phenomenon that became known as the Compton effect and for which he shared the Nobel Prize in Physics for 1927. But for more than five years before he made his discovery, Compton had analyzed X-ray scattering in terms of classical electrodynamics. I suggest that his colleague at Washington University in St. Louis, G. E. M. Jauncey (1888-1947), helped materially to persuade him to embrace the quantum interpretation of his X-ray scattering experiments.

A Bulk Comptonization Model for the Prompt GRB Emission and its Relation to the Fermi GRB Spectra

NASA Technical Reports Server (NTRS)

Kazanas, Demosthenes

2010-01-01

We present a model in which the GRB prompt emission at E E(sub peak) is due to bulk Comptonization by the relativistic blast wave motion of either its own synchrotron photons of ambient photons of the stellar configuration that gave birth to the GRB. The bulk Comptonization process then induces the production of relativistic electrons of Lorentz factor equal to that of the blast wave through interactions with its ambient protons. The inverse compton emission of these electrons produces a power law component that extends to multi GeV energies in good agreement with the LAT GRB observations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furui, Shun’ya; Fukazawa, Yasushi; Ohno, Masanori

We construct an X-ray spectral model of reprocessing by a torus in an active galactic nucleus (AGN) with the Monte Carlo simulation framework MONACO. Two torus geometries of smooth and clumpy cases are considered and compared. In order to reproduce a Compton shoulder accurately, MONACO includes not only free electron scattering but also bound electron scattering. Raman and Rayleigh scattering are also treated, and scattering cross sections dependent on chemical states of hydrogen and helium are included. Doppler broadening by turbulence velocity can be implemented. Our model gives results consistent with other available models, such as MYTorus, except for differencesmore » due to different physical parameters and assumptions. We studied the dependence on torus parameters for a Compton shoulder, and found that a intensity ratio of a Compton shoulder to the line core mainly depends on column density, inclination angle, and metal abundance. For instance, an increase of metal abundance makes a Compton shoulder relatively weak. Also, the shape of a Compton shoulder depends on the column density. Furthermore, these dependences become different between smooth and clumpy cases. Then, we discuss the possibility of ASTRO-H/SXS spectroscopy of Compton shoulders in AGN reflection spectra.« less

Development of compact Compton camera for 3D image reconstruction of radioactive contamination

NASA Astrophysics Data System (ADS)

Sato, Y.; Terasaka, Y.; Ozawa, S.; Nakamura Miyamura, H.; Kaburagi, M.; Tanifuji, Y.; Kawabata, K.; Torii, T.

2017-11-01

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown after the large tsunami caused by the Great East Japan Earthquake of March 11, 2011. Very large amounts of radionuclides were released from the damaged plant. Radiation distribution measurements inside FDNPS buildings are indispensable to execute decommissioning tasks in the reactor buildings. We have developed a compact Compton camera to measure the distribution of radioactive contamination inside the FDNPS buildings three-dimensionally (3D). The total weight of the Compton camera is lower than 1.0 kg. The gamma-ray sensor of the Compton camera employs Ce-doped GAGG (Gd3Al2Ga3O12) scintillators coupled with a multi-pixel photon counter. Angular correction of the detection efficiency of the Compton camera was conducted. Moreover, we developed a 3D back-projection method using the multi-angle data measured with the Compton camera. We successfully observed 3D radiation images resulting from the two 137Cs radioactive sources, and the image of the 9.2 MBq source appeared stronger than that of the 2.7 MBq source.

Generalized Parton Distributions of the nucleon from exclusive lepto- and photo-production of lepton pairs

NASA Astrophysics Data System (ADS)

Boer, Marie

2017-09-01

Generalized Parton Distributions (GPDs) contain the correlation between the parton's longitudinal momentum and their transverse distribution. They are accessed through hard exclusive processes such as exclusive Compton processes, where two photons are exchanged with a quark of the nucleon, and at least one of them has a high virtuality. Exclusive Compton processes are considered ``golden'' channels, as the only non-perturbative part of the process corresponds to the GPDs. Deeply Virtual Compton Scattering (DVCS) corresponds to the lepto-production of a real photon and has been intensively studied in the past decade. We propose to access GPDs with the two other cases of exclusive Compton processes: Timelike Compton Scattering (TCS) corresponds to the photo-production of a lepton pair, and Double Deeply Virtual Compton Scattering (DDVCS) corresponds to the lepto-production of a lepton pair. The study of these two reactions is complementary to DVCS and will bring new constraints on our understanding of the nucleon structure, in particular for a tomographic interpretation of GPDs. We will discuss the interest of TCS and DDVCS in terms of GPD studies, and present the efforts held at Jefferson Lab for new experiments aiming at measuring TCS and DDVCS.

Measuring Multi-Megavolt Diode Voltages

NASA Astrophysics Data System (ADS)

Pereira, N. R.; Swanekamp, S. B.; Weber, B. V.; Commisso, R. J.; Hinshelwood, D. D.; Stephanakis, S. J.

2002-12-01

The voltage in high-power diodes can be determined by measuring the Compton electrons generated by the diode's bremsstrahlung radiation. This technique is implemented with a Compton-Hall (C-H) voltmeter that collimates the bremsstrahlung onto a Compton target and bends the emitted Compton electron orbits off to the side with an applied magnetic field off to Si pin diode detectors. Voltage is determined from the ratio of the Compton electron dose to the forward x-ray dose. The instrument's calibration and response are determined from coupled electron/photon transport calculations. The applicable voltage range is tuned by adjusting the position of the electron detector relative to the Compton target or by varying the magnetic field strength. The instrument was used to obtain time-dependent voltage measurements for a pinched-beam diode whose voltage is enhanced by an upstream opening switch. In this case, plasmas and vacuum electron flow from the opening switch make it difficult to determine the voltage accurately from electrical measurements. The C-H voltmeter gives voltages that are significantly higher than those obtained from electrical measurements but are consistent with measurements of peak voltage based on nuclear activation of boron-nitride targets.

Sky and Elemental Planetary Mapping Via Gamma Ray Emissions

NASA Technical Reports Server (NTRS)

Roland, John M.

2011-01-01

Low-energy gamma ray emissions ((is) approximately 30keV to (is) approximately 30MeV) are significant to astrophysics because many interesting objects emit their primary energy in this regime. As such, there has been increasing demand for a complete map of the gamma ray sky, but many experiments to do so have encountered obstacles. Using an innovative method of applying the Radon Transform to data from BATSE (the Burst And Transient Source Experiment) on NASA's CGRO (Compton Gamma-Ray Observatory) mission, we have circumvented many of these issues and successfully localized many known sources to 0.5 - 1 deg accuracy. Our method, which is based on a simple 2-dimensional planar back-projection approximation of the inverse Radon transform (familiar from medical CAT-scan technology), can thus be used to image the entire sky and locate new gamma ray sources, specifically in energy bands between 200keV and 2MeV which have not been well surveyed to date. Samples of these results will be presented. This same technique can also be applied to elemental planetary surface mapping via gamma ray spectroscopy. Due to our method's simplicity and power, it could potentially improve a current map's resolution by a significant factor.

Integration of ALOS/PALSAR backscatter with a LiDAR-derived canopy height map to quantify forest fragmentation

NASA Astrophysics Data System (ADS)

Pinto, N.; Dubayah, R.; Simard, M.; Fatoyinbo, T. E.

2011-12-01

Habitat loss is the main predictor of species extinctions and must be characterized in high-biodiversity ecosystems where land cover change is pervasive. Forests' ability to support viable animal populations is typically modeled as a function of the presence of linkages or corridors, and quantified with fragmentation metrics. In this scenario, small forest patches and linear (e.g. riparian) zones can act as keystone structures. Fine-resolution, all-weather Synthetic Aperture Radar (SAR) data from ALOS/PALSAR is well-suited to resolve forest fragments in tropical sites. This study summarizes a technique for integrating fragmentation metrics from ALOS/PALSAR with vertical structure data from ICESat/GLAS to produce fine-resolution (30 m) forest habitat metrics that capture both local quality (canopy height) as well as spatial context and multi-scale connectivity. We illustrate our approach with backscatter images acquired over the Brazilian Atlantic Forest, a biodiversity hotspot. ALOS/PALSAR 1.1 images acquired over the dry season were calibrated to calculate gamma naught and map forest cover via tresholding. We employ network algorithms to locate dispersal bottlenecks between conservation units. The location of keystone structures is compared against a model that uses coarse (500m) percent tree cover as an input.

Assessing Strain Mapping by Electron Backscatter Diffraction and Confocal Raman Microscopy Using Wedge-indented Si

PubMed Central

Friedman, Lawrence H.; Vaudin, Mark D.; Stranick, Stephan J.; Stan, Gheorghe; Gerbig, Yvonne B.; Osborn, William; Cook, Robert F.

2016-01-01

The accuracy of electron backscatter diffraction (EBSD) and confocal Raman microscopy (CRM) for small-scale strain mapping are assessed using the multi-axial strain field surrounding a wedge indentation in Si as a test vehicle. The strain field is modeled using finite element analysis (FEA) that is adapted to the near-indentation surface profile measured by atomic force microscopy (AFM). The assessment consists of (1) direct experimental comparisons of strain and deformation and (2) comparisons in which the modeled strain field is used as an intermediate step. Direct experimental methods (1) consist of comparisons of surface elevation and gradient measured by AFM and EBSD and of Raman shifts measured and predicted by CRM and EBSD, respectively. Comparisons that utilize the combined FEA-AFM model (2) consist of predictions of distortion, strain, and rotation for comparison with EBSD measurements and predictions of Raman shift for comparison with CRM measurements. For both EBSD and CRM, convolution of measurements in depth-varying strain fields is considered. The interconnected comparisons suggest that EBSD was able to provide an accurate assessment of the wedge indentation deformation field to within the precision of the measurements, approximately 2 × 10−4 in strain. CRM was similarly precise, but was limited in accuracy to several times this value. PMID:26939030

A GIS Library of Multibeam Data for Massachusetts Bay and the Stellwagen Bank National Marine Sanctuary, Offshore of Boston, Massachusetts

USGS Publications Warehouse

Butman, Bradford; Valentine, Page C.; Middleton, Tammie J.; Danforth, William W.

2007-01-01

Introduction The U.S. Geological Survey (USGS) has mapped the sea floor of the Stellwagen Bank National Marine Sanctuary and western Massachusetts Bay, offshore of Boston, Massachusetts (figure 1a, figure 1b). The mapping was carried out using a Simrad Subsea EM1000 Multibeam Echo Sounder (95 kHz) on the Frederick G. Creed on four cruises between 1994 and 1998. The mapping was conducted in cooperation with the National Oceanic and Atmospheric Administration (NOAA) and with support from the Canadian Hydrographic Service and the University of New Brunswick. This GIS Library contains images and grids of bathymetry, shaded relief bathymetry, and backscatter intensity data from these surveys in an Environmental Systems Research Institute (http://www.esri.com) (ESRI) ArcMap 9.1 Geographic Information System (GIS) project. The shapefiles, images, grids and associated metadata may also be downloaded individually. Descriptions and interpretations of the data are available in a series of published maps.

Airborne gamma-ray spectrometer and magnetometer survey, Durango A, B, C, and D, Colorado. Volume I. Detail area. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1983-01-01

An airborne combined radiometric and magnetic survey was performed for the Department of Energy (DOE) over the Durango A, Durango B, Durango C, and Durango D Detail Areas of southwestern Colorado. The Durango A Detail Area is within the coverage of the Needle Mountains and Silverton 15' map sheets, and the Pole Creek Mountain, Rio Grande Pyramid, Emerald Lake, Granite Peak, Vallecito Reservoir, and Lemon Reservoir 7.5' map sheets of the National Topographic Map Series (NTMS). The Durango B Detail Area is within the coverage of the Silverton 15' map sheet and the Wetterhorn Peak, Uncompahgre Peak, Lake City, Redcloudmore » Peak, Lake San Cristobal, Pole Creek Mountain, and Finger Mesa 7.5' map sheets of the NTMS. The Durango C Detail Area is within the coverage of the Platoro and Wolf Creek Pass 15' map sheets of the NTMS. The Durango D Detail Area is within the coverage of the Granite Lake, Cimarrona Peak, Bear Mountain, and Oakbrush Ridge 7.5' map sheets of the NTMS. Radiometric data were corrected for live time, aircraft and equipment background, cosmic background, atmospheric radon, Compton scatter, and altitude dependence. The corrected data were statistically evaluated, gridded, and contoured to produce maps of the radiometric variables, uranium, potassium, and thorium; their ratios; and the residual magnetic field. These maps have been analyzed in order to produce a multi-variant analysis contour map based on the radiometric response of the individual geological units. A geochemical analysis has been performed, using the radiometric and magnetic contour maps, the multi-variant analysis map, and factor analysis techniques, to produce a geochemical analysis map for the area.« less

Improved spatial mapping of rainfall events with spaceborne SAR imagery

NASA Technical Reports Server (NTRS)

Ulaby, F. T.; Brisco, B.; Dobson, C.

1983-01-01

The Seasat satellite acquired the first spaceborne synthetic-aperture radar (SAR) images of the earth's surface, in 1978, at a frequency of 1.275 GHz (L-band) in a like-polarization mode at incidence angles of 23 + or - 3 deg. Although this may not be the optimum system configuration for radar remote sensing of soil moisture, interpretation of two Seasat images of Iowa demonstrates the sensitivity of microwave backscatter to soil moisture content. In both scenes, increased image brightness, which represents more radar backscatter, can be related to previous rainfall activity in the two areas. Comparison of these images with ground-based rainfall observations illustrates the increased spatial coverage of the rainfall event that can be obtained from the satellite SAR data. These data can then be color-enhanced by a digital computer to produce aesthetically pleasing output products for the user community.

Absolute tracer dye concentration using airborne laser-induced water Raman backscatter

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1981-01-01

The use of simultaneous airborne-laser-induced dye fluorescence and water Raman backscatter to measure the absolute concentration of an ocean-dispersed tracer dye is discussed. Theoretical considerations of the calculation of dye concentration by the numerical comparison of airborne laser-induced fluorescence spectra with laboratory spectra for known dye concentrations using the 3400/cm OH-stretch water Raman scatter as a calibration signal are presented which show that minimum errors are obtained and no data concerning water mass transmission properties are required when the laser wavelength is chosen to yield a Raman signal near the dye emission band. Results of field experiments conducted with an airborne conical scan lidar over a site in New York Bight into which rhodamine dye had been injected in a study of oil spill dispersion are then indicated which resulted in a contour map of dye concentrations, with a minimum detectable dye concentration of approximately 2 ppb by weight.

Electron backscatter diffraction as a domain analysis technique in BiFeO(3)-PbTiO(3) single crystals.

PubMed

Burnett, T L; Comyn, T P; Merson, E; Bell, A J; Mingard, K; Hegarty, T; Cain, M

2008-05-01

xBiFeO(3)-(1-x)PbTiO(3) single crystals were grown via a flux method for a range of compositions. Presented here is a study of the domain configuration in the 0.5BiFeO(3)-0.5PbTiO(3) composition using electron backscatter diffraction to demonstrate the ability of the technique to map ferroelastic domain structures at the micron and submicron scale. The micron-scale domains exhibit an angle of approximately 85 degrees between each variant, indicative of a ferroelastic domain wall in a tetragonal system with a spontaneous strain, c/a - 1 of 0.10, in excellent agreement with the lattice parameters derived from x-ray diffraction. Contrast seen in forescatter images is attributed to variations in the direction of the electrical polarization vector, providing images of ferroelectric domain patterns.

Design data collection with Skylab microwave radiometer-scatterometer S-193, volume 2

NASA Technical Reports Server (NTRS)

Moore, R. K.; Ulaby, F. T. (Principal Investigator)

1975-01-01

The author has identified the following significant results. Skylab S-193 radiometer/scatterometer produced terrain responses with various polarizations and observation angles for cells of 100 to 400 sq km area. Classification of the observations into natural categories was achieved by K-means and spatial clustering algorithms. Microwave data acquired over the Great Salt Lake Desert area by sensors aboard Skylab and Nimbus 5 indicate that the microwave emission and backscatter were strongly influenced by contributions from subsurface layers of sediment saturated with brine. Correlations were noted between microwave backscatter response at approximately 33 deg from scatterometer (operating at 13.9 GHz) and the configuration of ground targets in Brazil as discerned from coarse scale maps. With limited, available ground truth, these correlations were sufficient to permit the production of image-like displays which bear a marked resemblance to known terrain features in several instances.

Measurement of sea ice backscatter characteristics at 36 GHz using the surface contour radar

NASA Technical Reports Server (NTRS)

Fedor, L. S.; Walsh, E. J.

1985-01-01

Scattering studies of sea ice off the coast of Greenland were performed in January 1984 using the 36-GHz Surface Contour Radar (SCR) aboard the NASA P-3 aircraft. An oscillating mirror scans an actual half-power width of 0.96 degrees laterally to measure the surface at 51 evenly spaced points. By banking the aircraft, real-time topographical mapping and relative backscattered power are obtained at incidence angles between 0 and 30 degrees off-nadar, achieving at 175 m altitude a 2.9 by 4.4 m spatial resolution at nadir. With an aircraft ground speed of 100 m/s, 5-m successive scan line spacing and 1.8-m cross-track direction spacing is provided. By circling the aircraft in the 15 degree bank, the azimuthal anisotropy of the scattering is investigated along with the incidence angle dependence.

Improving Geologic Mapping of Mid-ocean Ridges by Integrating sonar and Visual Observations through Seafloor Classification by Machine-learning Systems

NASA Astrophysics Data System (ADS)

White, S. M.; McClinton, J. T.

2011-12-01

Beyond the ability of modern near-bottom sonar systems to deliver air-photo-like images of the seafloor to help guide fieldwork, there is a tremendous amount of information hidden within sonar data that is rarely exploited for geologic mapping. Seafloor texture, backscatter amplitude, seafloor slope and roughness data can provide clues about seafloor geology but not straightforward to interpret. We present techniques for seafloor classification in volcanic terrains that integrate the capability of high-resolution, near-bottom sonar instruments to cover extensive areas of seafloor with the ability of visual mapping to discriminate differences in volcanic terrain. These techniques are adapted from the standard practices of terrestrial remote-sensing for use in the deep seafloor volcanic environment. A combination of sonar backscatter and bathymetry is used to supplement the direct seafloor visual observations by geologists to make quasi-geologic thematic maps that are consistent, objective, and most importantly spatially complete. We have taken two approaches to producing thematic maps of the seafloor for the accurate mapping of fine-scale lava morphology (e.g. pillow, lobate and sheet lava) and for the differentiation of distinct seafloor terrain types on a larger scale (e.g. hummocky or smooth). Mapping lava morphology is most accurate using fuzzy logic capable of making inferences between similar morphotypes (e.g. pillow and lobate) and where high-resolution side-scan and bathymetry data coexist. We present examples of lava morphology maps from the Galápagos Spreading Center that show the results from several analyses using different types of input data. Lava morphology is an important source of information on volcanic emplacement and eruptive dynamics. Terrain modeling can be accomplished at any resolution level, depending on the desired use of the model. For volcanic processes, input data needs to be at the appropriate scale to resolve individual volcanic features on the seafloor (e.g. small haystacks and lava channels). We present examples from the East Pacific Rise, which shows that the number of volcanic terrains differs from the tectonic provinces defined by following the spreading axis. Our terrain modeling suggests that differences in ocean crust construction and evolution can be meaningfully identified and explored without a priori assumptions about the geologic processes in a given region.

Highly dynamic biological seabed alterations revealed by side scan sonar tracking of Lanice conchilega beds offshore the island of Sylt (German Bight)

NASA Astrophysics Data System (ADS)

Heinrich, C.; Feldens, P.; Schwarzer, K.

2017-06-01

Hydroacoustic surveys are common tools for habitat investigation and monitoring that aid in the realisation of the aims of the EU Marine Directives. However, the creation of habitat maps is difficult, especially when benthic organisms densely populate the seafloor. This study assesses the sensitivity of entropy and homogeneity image texture parameters derived from backscatter strength data to benthic habitats dominated by the tubeworm Lanice conchilega. Side scan sonar backscatter surveys were carried out in 2010 and 2011 in the German Bight (southern North Sea) at two sites approx. 20 km offshore of the island of Sylt. Abiotic and biotic seabed facies, such as sorted bedforms, areas of fine to medium sand and L. conchilega beds with different tube densities, were identified and characterised based on manual expert analysis and image texture analysis. Ground truthing was performed by grab sampling and underwater video observations. Compared to the manual expert analysis, the k- means classification of image textures proves to be a semi-automated method to investigate small-scale differences in a biologically altered seabed from backscatter data. The texture parameters entropy and homogeneity appear linearly interrelated with tube density, the former positively and the latter negatively. Reinvestigation of one site after 1 year showed an extensive change in the distribution of the L. conchilega-altered seabed. Such marked annual fluctuations in L. conchilega tube cover demonstrate the need for dense time series and high spatial coverage to meaningfully monitor ecological patterns on the seafloor with acoustic backscatter methods in the study region and similar settings worldwide, particularly because the sand mason plays a pivotal role in promoting biodiversity. In this context, image texture analysis provides a cost-effective and reproducible method to track biologically altered seabeds from side scan sonar backscatter signatures.

A Compton scatter attenuation gamma ray spectrometer

NASA Technical Reports Server (NTRS)

Austin, W. E.

1972-01-01

A Compton scatter attenuation gamma ray spectrometer conceptual design is discussed for performing gamma spectral measurements in monodirectional gamma fields from 100 R per hour to 1,000,000 R per hour. Selectable Compton targets are used to scatter gamma photons onto an otherwise heavily shielded detector with changeable scattering efficiencies such that the count rate is maintained between 500 and 10,000 per second. Use of two sum-Compton coincident detectors, one for energies up to 1.5 MeV and the other for 600 keV to 10 MeV, will allow good peak to tail pulse height ratios to be obtained over the entire spectrum and reduces the neutron recoil background rate.

Evolution of regional to global paddy rice mapping methods

NASA Astrophysics Data System (ADS)

Dong, J.; Xiao, X.

2016-12-01

Paddy rice agriculture plays an important role in various environmental issues including food security, water use, climate change, and disease transmission. However, regional and global paddy rice maps are surprisingly scarce and sporadic despite numerous efforts in paddy rice mapping algorithms and applications. In this presentation we would like to review the existing paddy rice mapping methods from the literatures ranging from the 1980s to 2015. In particular, we illustrated the evolution of these paddy rice mapping efforts, looking specifically at the future trajectory of paddy rice mapping methodologies. The biophysical features and growth phases of paddy rice were analyzed first, and feature selections for paddy rice mapping were analyzed from spectral, polarimetric, temporal, spatial, and textural aspects. We sorted out paddy rice mapping algorithms into four categories: 1) Reflectance data and image statistic-based approaches, 2) vegetation index (VI) data and enhanced image statistic-based approaches, 3) VI or RADAR backscatter-based temporal analysis approaches, and 4) phenology-based approaches through remote sensing recognition of key growth phases. The phenology-based approaches using unique features of paddy rice (e.g., transplanting) for mapping have been increasingly used in paddy rice mapping. Based on the literature review, we discussed a series of issues for large scale operational paddy rice mapping.

High density of structurally controlled, shallow to deep water fluid seep indicators imaged offshore Costa Rica

NASA Astrophysics Data System (ADS)

Kluesner, Jared W.; Silver, Eli A.; Bangs, Nathan L.; McIntosh, Kirk D.; Gibson, James; Orange, Daniel; Ranero, Cesar R.; von Huene, Roland

2013-03-01

We used high-resolution mapping to document 161 sites of potential fluid seepage on the shelf and slope regions where no geophysical seep indicators had been reported. Identified potential seabed seepage sites show both high-backscatter anomalies and bathymetric expressions, such as pockmarks, mounds, and ridges. Almost all identified seabed features are associated with bright spots and flat spots beneath, as mapped within the 3-D seismic grid. We obtained EM122 multi-beam data using closely spaced receiver beams and 4-5 times overlapping multi-beam swaths, which greatly improved the sounding density and geologic resolvability of the data. At least one location shows an acoustic plume in the water column on a 3.5 kHz profile, and this plume is located along a fault trace and above surface and subsurface seepage indicators. Fluid indicators are largely associated with folds and faults within the sediment section, and many of the faults continue into and offset the reflective basement. A dense pattern of normal faults is seen on the outer shelf in the multi-beam bathymetry, backscatter, and 3-D seismic data, and the majority of fluid seepage indicators lie along mapped fault traces. Furthermore, linear mounds, ridges, and pockmark chains are found on the upper, middle, and lower slope regions. The arcuate shape of the shelf edge, projection of the Quepos Ridge, and high density of potential seep sites suggest that this area may be a zone of former seamount/ridge subduction. These results demonstrate a much greater potential seep density and distribution than previously reported across the Costa Rican margin.

Project PROBE Leg I - Report and archive of multibeam bathymetry and acoustic backscatter , CTD/XBT and GPS navigation data collected during USGS Cruise 02051 (NOAA Cruise RB0208) Puerto Rico Trench September 24, 2002 to September 30, 2002

USGS Publications Warehouse

ten Brink, Uri S.; Worley, Charles R.; Smith, Shep; Stepka, Thomas; Williams, Glynn F.

2006-01-01

On September 24-30, 2002, six days of scientific surveying to map a section of the Puerto Rico Trench (PRT) took place aboard the National Oceanic and Atmospheric Administration (NOAA) ship Ron Brown. The cruise was funded by NOAA's Office of Ocean Exploration. Multibeam bathymetry and acoustic-backscatter data were collected over an area of about 25,000 sq. km of the Puerto Rico trench and its vicinity at water depths of 4000-8400 m. Weather conditions during the entire survey were good; there were light to moderate winds and 1-2 foot swells experiencing minor chop. The roll and pitch of the ship's interaction with the ocean were not conspicuous. Cruise participants included personnel from USGS, NOAA, and University of New Hampshire Center for Coastal and Ocean Mapping/Joint Hydrographic Center. The cruise resulted in the discovery of a major active strike-slip fault system close to the trench, submarine slides on the descending North American tectonic plate, and an extinct mud volcano, which was cut by the strike-slip fault system. Another strike-slip fault system closer to Puerto Rico that was previously considered to accommodate much of the relative plate motion appears to be inactive. The seaward continuation of the Mona Rift, a zone of extension between Puerto Rico and the Dominican Republic that generated a devastating tsunami in 1918, was mapped for the first time.

Mapping Winter Wheat with Multi-Temporal SAR and Optical Images in an Urban Agricultural Region

PubMed Central

Zhou, Tao; Pan, Jianjun; Zhang, Peiyu; Wei, Shanbao; Han, Tao

2017-01-01

Winter wheat is the second largest food crop in China. It is important to obtain reliable winter wheat acreage to guarantee the food security for the most populous country in the world. This paper focuses on assessing the feasibility of in-season winter wheat mapping and investigating potential classification improvement by using SAR (Synthetic Aperture Radar) images, optical images, and the integration of both types of data in urban agricultural regions with complex planting structures in Southern China. Both SAR (Sentinel-1A) and optical (Landsat-8) data were acquired, and classification using different combinations of Sentinel-1A-derived information and optical images was performed using a support vector machine (SVM) and a random forest (RF) method. The interference coherence and texture images were obtained and used to assess the effect of adding them to the backscatter intensity images on the classification accuracy. The results showed that the use of four Sentinel-1A images acquired before the jointing period of winter wheat can provide satisfactory winter wheat classification accuracy, with an F1 measure of 87.89%. The combination of SAR and optical images for winter wheat mapping achieved the best F1 measure–up to 98.06%. The SVM was superior to RF in terms of the overall accuracy and the kappa coefficient, and was faster than RF, while the RF classifier was slightly better than SVM in terms of the F1 measure. In addition, the classification accuracy can be effectively improved by adding the texture and coherence images to the backscatter intensity data. PMID:28587066

Handheld real-time volumetric 3-D gamma-ray imaging

NASA Astrophysics Data System (ADS)

Haefner, Andrew; Barnowski, Ross; Luke, Paul; Amman, Mark; Vetter, Kai

2017-06-01

This paper presents the concept of real-time fusion of gamma-ray imaging and visual scene data for a hand-held mobile Compton imaging system in 3-D. The ability to obtain and integrate both gamma-ray and scene data from a mobile platform enables improved capabilities in the localization and mapping of radioactive materials. This not only enhances the ability to localize these materials, but it also provides important contextual information of the scene which once acquired can be reviewed and further analyzed subsequently. To demonstrate these concepts, the high-efficiency multimode imager (HEMI) is used in a hand-portable implementation in combination with a Microsoft Kinect sensor. This sensor, in conjunction with open-source software, provides the ability to create a 3-D model of the scene and to track the position and orientation of HEMI in real-time. By combining the gamma-ray data and visual data, accurate 3-D maps of gamma-ray sources are produced in real-time. This approach is extended to map the location of radioactive materials within objects with unknown geometry.

A soft X-ray map of the Perseus cluster of galaxies

NASA Technical Reports Server (NTRS)

Cash, W.; Malina, R. F.; Wolff, R. S.

1976-01-01

A 0.5-3-keV X-ray map of the Perseus cluster of galaxies is presented. The map shows a region of strong emission centered near NGC 1275 plus a highly elongated emission region which lies along the line of bright galaxies that dominates the core of the cluster. The data are compared with various models that include point and diffuse sources. One model which adequately represents the data is the superposition of a point source at NGC 1275 and an isothermal ellipsoid resulting from the bremsstrahlung emission of cluster gas. The ellipsoid has a major core radius of 20.5 arcmin and a minor core radius of 5.5 arcmin, consistent with the values obtained from galaxy counts. All acceptable models provide evidence for a compact source (less than 3 arcmin FWHM) at NGC 1275 containing about 25% of the total emission. Since the diffuse X-ray and radio components have radically different morphologies, it is unlikely that the emissions arise from a common source, as proposed in inverse-Compton models.

Three-beam aerosol backscatter correlation lidar for wind profiling

NASA Astrophysics Data System (ADS)

Prasad, Narasimha S.; Radhakrishnan Mylapore, Anand

2017-03-01

The development of a three-beam aerosol backscatter correlation (ABC) light detection and ranging (lidar) to measure wind characteristics for wake vortex and plume tracking applications is discussed. This is a direct detection elastic lidar that uses three laser transceivers, operating at 1030-nm wavelength with ˜10-kHz pulse repetition frequency and nanosec class pulse widths, to directly obtain three components of wind velocities. By tracking the motion of aerosol structures along and between three near-parallel laser beams, three-component wind speed profiles along the field-of-view of laser beams are obtained. With three 8-in. transceiver modules, placed in a near-parallel configuration on a two-axis pan-tilt scanner, the lidar measures wind speeds up to 2 km away. Optical flow algorithms have been adapted to obtain the movement of aerosol structures between the beams. Aerosol density fluctuations are cross-correlated between successive scans to obtain the displacements of the aerosol features along the three axes. Using the range resolved elastic backscatter data from each laser beam, which is scanned over the volume of interest, a three-dimensional map of aerosol density can be generated in a short time span. The performance of the ABC wind lidar prototype, validated using sonic anemometer measurements, is discussed.

Ground penetrating radar applied to rebar corrosion inspection

NASA Astrophysics Data System (ADS)

Eisenmann, David; Margetan, Frank; Chiou, Chien-Ping T.; Roberts, Ron; Wendt, Scott

2013-01-01

In this paper we investigate the use of ground penetrating radar (GPR) to detect corrosion-induced thinning of rebar in concrete bridge structures. We consider a simple pulse/echo amplitude-based inspection, positing that the backscattered response from a thinned rebar will be smaller than the similar response from a fully-intact rebar. Using a commercial 1600-MHz GPR system we demonstrate that, for laboratory specimens, backscattered amplitude measurements can detect a thinning loss of 50% in rebar diameter over a short length. GPR inspections on a highway bridge then identify several rebar with unexpectedly low amplitudes, possibly signaling thinning. To field a practical amplitude-based system for detecting thinned rebar, one must be able to quantify and assess the many factors that can potentially contribute to GPR signal amplitude variations. These include variability arising from the rebar itself (e.g., thinning) and from other factors (concrete properties, antenna orientation and liftoff, etc.). We report on early efforts to model the GPR instrument and the inspection process so as to assess such variability and to optimize inspections. This includes efforts to map the antenna radiation pattern, to predict how backscattered responses will vary with rebar size and location, and to assess detectability improvements via synthetic aperture focusing techniques (SAFT).

Compton scattering collision module for OSIRIS

NASA Astrophysics Data System (ADS)

Del Gaudio, Fabrizio; Grismayer, Thomas; Fonseca, Ricardo; Silva, Luís

2017-10-01

Compton scattering plays a fundamental role in a variety of different astrophysical environments, such as at the gaps of pulsars and the stagnation surface of black holes. In these scenarios, Compton scattering is coupled with self-consistent mechanisms such as pair cascades. We present the implementation of a novel module, embedded in the self-consistent framework of the PIC code OSIRIS 4.0, capable of simulating Compton scattering from first principles and that is fully integrated with the self-consistent plasma dynamics. The algorithm accounts for the stochastic nature of Compton scattering reproducing without approximations the exchange of energy between photons and unbound charged species. We present benchmarks of the code against the analytical results of Blumenthal et al. and the numerical solution of the linear Kompaneets equation and good agreement is found between the simulations and the theoretical models. This work is supported by the European Research Council Grant (ERC- 2015-AdG 695088) and the Fundao para a Céncia e Tecnologia (Bolsa de Investigao PD/BD/114323/2016).

The Absolute Spectrum Polarimeter (ASP)

NASA Technical Reports Server (NTRS)

Kogut, A. J.

2010-01-01

The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

X-Ray Quasi-periodic Oscillations in the Lense–Thirring Precession Model. I. Variability of Relativistic Continuum

NASA Astrophysics Data System (ADS)

You, Bei; Bursa, Michal; Życki, Piotr T.

2018-05-01

We develop a Monte Carlo code to compute the Compton-scattered X-ray flux arising from a hot inner flow that undergoes Lense–Thirring precession. The hot flow intercepts seed photons from an outer truncated thin disk. A fraction of the Comptonized photons will illuminate the disk, and the reflected/reprocessed photons will contribute to the observed spectrum. The total spectrum, including disk thermal emission, hot flow Comptonization, and disk reflection, is modeled within the framework of general relativity, taking light bending and gravitational redshift into account. The simulations are performed in the context of the Lense–Thirring precession model for the low-frequency quasi-periodic oscillations, so the inner flow is assumed to precess, leading to periodic modulation of the emitted radiation. In this work, we concentrate on the energy-dependent X-ray variability of the model and, in particular, on the evolution of the variability during the spectral transition from hard to soft state, which is implemented by the decrease of the truncation radius of the outer disk toward the innermost stable circular orbit. In the hard state, where the Comptonizing flow is geometrically thick, the Comptonization is weakly variable with a fractional variability amplitude of ≤10% in the soft state, where the Comptonizing flow is cooled down and thus becomes geometrically thin, the fractional variability of the Comptonization is highly variable, increasing with photon energy. The fractional variability of the reflection increases with energy, and the reflection emission for low spin is counterintuitively more variable than the one for high spin.

Double Compton and Cyclo-Synchrotron in Super-Eddington Discs, Magnetized Coronae, and Jets

NASA Astrophysics Data System (ADS)

McKinney, Jonathan C.; Chluba, Jens; Wielgus, Maciek; Narayan, Ramesh; Sadowski, Aleksander

2017-05-01

Black hole accretion discs accreting near the Eddington rate are dominated by bremsstrahlung cooling, but above the Eddington rate, the double Compton process can dominate in radiation-dominated regions, while the cyclo-synchrotron can dominate in strongly magnetized regions like a corona or a jet. We present an extension to the general relativistic radiation magnetohydrodynamic code harmrad to account for emission and absorption by thermal cyclo-synchrotron, double Compton, bremsstrahlung, low-temperature opal opacities, as well as Thomson and Compton scattering. The harmrad code and associated analysis and visualization codes have been made open-source and are publicly available at the github repository website. We approximate the radiation field as a Bose-Einstein distribution and evolve it using the radiation number-energy-momentum conservation equations in order to track photon hardening. We perform various simulations to study how these extensions affect the radiative properties of magnetically arrested discs accreting at Eddington to super-Eddington rates. We find that double Compton dominates bremsstrahlung in the disc within a radius of r ˜ 15rg (gravitational radii) at hundred times the Eddington accretion rate, and within smaller radii at lower accretion rates. Double Compton and cyclo-synchrotron regulate radiation and gas temperatures in the corona, while cyclo-synchrotron regulates temperatures in the jet. Interestingly, as the accretion rate drops to Eddington, an optically thin corona develops whose gas temperature of T ˜ 109K is ˜100 times higher than the disc's blackbody temperature. Our results show the importance of double Compton and synchrotron in super-Eddington discs, magnetized coronae and jets.

Compton camera study for high efficiency SPECT and benchmark with Anger system

NASA Astrophysics Data System (ADS)

Fontana, M.; Dauvergne, D.; Létang, J. M.; Ley, J.-L.; Testa, É.

2017-12-01

Single photon emission computed tomography (SPECT) is at present one of the major techniques for non-invasive diagnostics in nuclear medicine. The clinical routine is mostly based on collimated cameras, originally proposed by Hal Anger. Due to the presence of mechanical collimation, detection efficiency and energy acceptance are limited and fixed by the system’s geometrical features. In order to overcome these limitations, the application of Compton cameras for SPECT has been investigated for several years. In this study we compare a commercial SPECT-Anger device, the General Electric HealthCare Infinia system with a High Energy General Purpose (HEGP) collimator, and the Compton camera prototype under development by the French collaboration CLaRyS, through Monte Carlo simulations (GATE—GEANT4 Application for Tomographic Emission—version 7.1 and GEANT4 version 9.6, respectively). Given the possible introduction of new radio-emitters at higher energies intrinsically allowed by the Compton camera detection principle, the two detectors are exposed to point-like sources at increasing primary gamma energies, from actual isotopes already suggested for nuclear medicine applications. The Compton camera prototype is first characterized for SPECT application by studying the main parameters affecting its imaging performance: detector energy resolution and random coincidence rate. The two detector performances are then compared in terms of radial event distribution, detection efficiency and final image, obtained by gamma transmission analysis for the Anger system, and with an iterative List Mode-Maximum Likelihood Expectation Maximization (LM-MLEM) algorithm for the Compton reconstruction. The results show for the Compton camera a detection efficiency increased by a factor larger than an order of magnitude with respect to the Anger camera, associated with an enhanced spatial resolution for energies beyond 500 keV. We discuss the advantages of Compton camera application for SPECT if compared to present commercial Anger systems, with particular focus on dose delivered to the patient, examination time, and spatial uncertainties.

Design and Mechanical Stability Analysis of the Interaction Region for the Inverse Compton Scattering Gamma-Ray Source Using Finite Element Method

NASA Astrophysics Data System (ADS)

Khizhanok, Andrei

Development of a compact source of high-spectral brilliance and high impulse frequency gamma rays has been in scope of Fermi National Accelerator Laboratory for quite some time. Main goal of the project is to develop a setup to support gamma rays detection test and gamma ray spectroscopy. Potential applications include but not limited to nuclear astrophysics, nuclear medicine, oncology ('gamma knife'). Present work covers multiple interconnected stages of development of the interaction region to ensure high levels of structural strength and vibrational resistance. Inverse Compton scattering is a complex phenomenon, in which charged particle transfers a part of its energy to a photon. It requires extreme precision as the interaction point is estimated to be 20 microm. The slightest deflection of the mirrors will reduce effectiveness of conversion by orders of magnitude. For acceptable conversion efficiency laser cavity also must have >1000 finesse value, which requires a trade-off between size, mechanical stability, complexity, and price of the setup. This work focuses on advantages and weak points of different designs of interaction regions as well as in-depth description of analyses performed. This includes laser cavity amplification and finesse estimates, natural frequency mapping, harmonic analysis. Structural analysis is required as interaction must occur under high vacuum conditions.

First On-Site True Gamma-Ray Imaging-Spectroscopy of Contamination near Fukushima Plant

PubMed Central

Tomono, Dai; Mizumoto, Tetsuya; Takada, Atsushi; Komura, Shotaro; Matsuoka, Yoshihiro; Mizumura, Yoshitaka; Oda, Makoto; Tanimori, Toru

2017-01-01

We have developed an Electron Tracking Compton Camera (ETCC), which provides a well-defined Point Spread Function (PSF) by reconstructing a direction of each gamma as a point and realizes simultaneous measurement of brightness and spectrum of MeV gamma-rays for the first time. Here, we present the results of our on-site pilot gamma-imaging-spectroscopy with ETCC at three contaminated locations in the vicinity of the Fukushima Daiichi Nuclear Power Plants in Japan in 2014. The obtained distribution of brightness (or emissivity) with remote-sensing observations is unambiguously converted into the dose distribution. We confirm that the dose distribution is consistent with the one taken by conventional mapping measurements with a dosimeter physically placed at each grid point. Furthermore, its imaging spectroscopy, boosted by Compton-edge-free spectra, reveals complex radioactive features in a quantitative manner around each individual target point in the background-dominated environment. Notably, we successfully identify a “micro hot spot” of residual caesium contamination even in an already decontaminated area. These results show that the ETCC performs exactly as the geometrical optics predicts, demonstrates its versatility in the field radiation measurement, and reveals potentials for application in many fields, including the nuclear industry, medical field, and astronomy. PMID:28155883

Ice Types in the Beaufort Sea, Alaska

NASA Technical Reports Server (NTRS)

2003-01-01

Determining the amount and type of sea ice in the polar oceans is crucial to improving our knowledge and understanding of polar weather and long term climate fluctuations. These views from two satellite remote sensing instruments; the synthetic aperture radar (SAR) on board the RADARSAT satellite and the Multi-angle Imaging SpectroRadiometer (MISR), illustrate different methods that may be used to assess sea ice type. Sea ice in the Beaufort Sea off the north coast of Alaska was classified and mapped in these concurrent images acquired March 19, 2001 and mapped to the same geographic area.

To identify sea ice types, the National Oceanic and Atmospheric Administration (NOAA) National Ice Center constructs ice charts using several data sources including RADARSAT SAR images such as the one shown at left. SAR classifies sea ice types primarily by how the surface and subsurface roughness influence radar backscatter. In the SAR image, white lines delineate different sea ice zones as identified by the National Ice Center. Regions of mostly multi-year ice (A) are separated from regions with large amounts of first year and younger ice (B-D), and the dashed white line at bottom marks the coastline. In general, sea ice types that exhibit increased radar backscatter appear bright in SAR and are identified as rougher, older ice types. Younger, smoother ice types appear dark to SAR. Near the top of the SAR image, however, red arrows point to bright areas in which large, crystalline 'frost flowers' have formed on young, thin ice, causing this young ice type to exhibit an increased radar backscatter. Frost flowers are strongly backscattering at radar wavelengths (cm) due to both surface roughness and the high salinity of frost flowers, which causes them to be highly reflective to radar energy.

Surface roughness is also registered by MISR, although the roughness observed is at a different spatial scale. Older, rougher ice areas are predominantly backward scattering to the MISR cameras, whereas younger, smoother ice types are predominantly forward scattering. The MISR map at right was generated using a statistical classification routine (called ISODATA) and analyzed using ice charts from the National Ice Center. Five classes of sea ice were found based upon the classification of MISR angular data. These are described, based on interpretation of the SAR image, by the image key. Very smooth ice areas that are predominantly forward scattering are colored red. Frost flowers are largely smooth to the MISR visible band sensor and are mapped as forward scattering. Areas mapped as blue are predominantly backward scattering, and the other three classes have statistically distinct angular signatures and fall within the middle of the forward/backward scattering continuum. Some areas that may be first year or younger ice between the multi year ice floes are not discernible to SAR, illustrating how MISR potentially can make a unique contribution to sea ice mapping.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. This data product was generated from a portion of the imagery acquired during Terra orbit 6663. The MISR image has been cropped to include an area that is 200 kilometers wide, and utilizes data from blocks 30 to 33 within World Reference System-2 path 71.

MISR was built and is managed by NASA's Jet Propulsion Laboratory,Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

A Combined EOF/Variational Approach for Mapping Radar-Derived Sea Surface Currents

DTIC Science & Technology

2011-01-13

characterized by specific structure of the artificial gaps introduced into the simulated data set assess the benefits of the gap-filling technique. These...15 minutes and 1-2 km respectively. However, the back-scattered HFR signals suffer from to numerous distortions of artificial and natural origin. As a...data because information on the spatial structure of the velocity field within the gap is implicitly drawn from the idealized covariance function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, G. N., E-mail: hall98@llnl.gov; Izumi, N.; Landen, O. L.

Compton radiography provides a means to measure the integrity, ρR and symmetry of the DT fuel in an inertial confinement fusion implosion near peak compression. Upcoming experiments at the National Ignition Facility will use the ARC (Advanced Radiography Capability) laser to drive backlighter sources for Compton radiography experiments and will use the newly commissioned AXIS (ARC X-ray Imaging System) instrument as the detector. AXIS uses a dual-MCP (micro-channel plate) to provide gating and high DQE at the 40–200 keV x-ray range required for Compton radiography, but introduces many effects that contribute to the spatial resolution. Experiments were performed at energiesmore » relevant to Compton radiography to begin characterization of the spatial resolution of the AXIS diagnostic.« less

Electronic properties of Laves phase ZrFe{sub 2} using Compton spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatt, Samir, E-mail: sameerbhatto11@gmail.com; Kumar, Kishor; Ahuja, B. L.

First-ever experimental Compton profile of Laves phase ZrFe{sub 2}, using indigenous 20 Ci {sup 137}Cs Compton spectrometer, is presented. To analyze the experimental electron momentum density, we have deduced the theoretical Compton profiles using density functional theory (DFT) and hybridization of DFT and Hartree-Fock scheme within linear combination of atomic orbitals (LCAO) method. The energy bands and density of states are also calculated using LCAO prescription. The theoretical profile based on local density approximation gives a better agreement with the experimental profile than other reported schemes. The present investigations validate the inclusion of correlation potential of Perdew-Zunger in predicting themore » electronic properties of ZrFe{sub 2}.« less

The Compton generator revisited

NASA Astrophysics Data System (ADS)

Siboni, S.

2014-09-01

The Compton generator, introduced in 1913 by the US physicist A H Compton as a relatively simple device to detect the Earth's rotation with respect to the distant stars, is analyzed and discussed in a general perspective. The paper introduces a generalized definition of the generator, emphasizing the special features of the original apparatus, and provides a suggestive interpretation of the way the device works. To this end, an intriguing electromagnetic analogy is developed, which turns out to be particularly useful in simplifying the calculations. Besides the more extensive description of the Compton generator in itself, the combined use of concepts and methods coming from different fields of physics, such as particle dynamics in moving references frames, continuum mechanics and electromagnetism, may be of interest to both teachers and graduate students.

Application of Compton-suppressed self-induced XRF to spent nuclear fuel measurement

NASA Astrophysics Data System (ADS)

Park, Se-Hwan; Jo, Kwang Ho; Lee, Seung Kyu; Seo, Hee; Lee, Chaehun; Won, Byung-Hee; Ahn, Seong-Kyu; Ku, Jeong-Hoe

2017-11-01

Self-induced X-ray fluorescence (XRF) is a technique by which plutonium (Pu) content in spent nuclear fuel can be directly quantified. In the present work, this method successfully measured the plutonium/uranium (Pu/U) peak ratio of a pressurized water reactor (PWR)'s spent nuclear fuel at the Korea atomic energy research institute (KAERI)'s post irradiation examination facility (PIEF). In order to reduce the Compton background in the low-energy X-ray region, the Compton suppression system additionally was implemented. By use of this system, the spectrum's background level was reduced by a factor of approximately 2. This work shows that Compton-suppressed selfinduced XRF can be effectively applied to Pu accounting in spent nuclear fuel.

Maximum Likelihood Compton Polarimetry with the Compton Spectrometer and Imager

NASA Astrophysics Data System (ADS)

Lowell, A. W.; Boggs, S. E.; Chiu, C. L.; Kierans, C. A.; Sleator, C.; Tomsick, J. A.; Zoglauer, A. C.; Chang, H.-K.; Tseng, C.-H.; Yang, C.-Y.; Jean, P.; von Ballmoos, P.; Lin, C.-H.; Amman, M.

2017-10-01

Astrophysical polarization measurements in the soft gamma-ray band are becoming more feasible as detectors with high position and energy resolution are deployed. Previous work has shown that the minimum detectable polarization (MDP) of an ideal Compton polarimeter can be improved by ˜21% when an unbinned, maximum likelihood method (MLM) is used instead of the standard approach of fitting a sinusoid to a histogram of azimuthal scattering angles. Here we outline a procedure for implementing this maximum likelihood approach for real, nonideal polarimeters. As an example, we use the recent observation of GRB 160530A with the Compton Spectrometer and Imager. We find that the MDP for this observation is reduced by 20% when the MLM is used instead of the standard method.

Real-Time Tissue Change Monitoring on the Sonablate® 500 during High Intensity Focused Ultrasound (HIFU) Treatment of Prostate Cancer

NASA Astrophysics Data System (ADS)

Chen, Wo-Hsing; Sanghvi, Narendra T.; Carlson, Roy; Uchida, Toyoaki

2011-09-01

Sonablate® 500 (SB-500) HIFU devices have been successfully used to treat prostate cancer non-invasively. In addition, Visually Directed HIFU with the SB-500 has demonstrated higher efficacy. Visually Directed HIFU works by displaying hyperechoic changes on the B-mode ultrasound images. However, small changes in the grey-scale images are not detectable by Visually Directed HIFU. To detect all tissue changes reliably, the SB-500 was enhanced with quantitative, real-time Tissue Change Monitoring (TCM) software. TCM uses pulse-echo ultrasound backscattered RF signals in 2D to estimate changes in the tissue properties caused by HIFU. The RF signal energy difference is calculated in selected frequency bands (pre and post HIFU) for each treatment site. The results are overlaid on the real-time ultrasound image in green, yellow and orange to represent low, medium and high degree of change in backscattered energy levels. The color mapping scheme was derived on measured temperature and backscattered RF signals from in vitro chicken tissue experiments. The TCM software was installed and tested in a clinical device to obtain human RF data. Post HIFU contrast enhanced MRI scans verified necrotic regions of the prostate. The color mapping success rate at higher HIFU power levels was 94% in the initial clinical test. Based on these results, TCM software has been released for wider usage. The clinical studies with TCM in Japan and The Bahamas have provided the following PSA (ng/ml) results. Japan (n = 97), PSA pre-treatment/post-treatment; minimum 0.7/0.0, maximum 76.0/4.73, median 6.89/0.07, standard deviation 11.19/0.62. The Bahamas (n = 59), minimum 0.4/0.0, maximum 13.0/1.4, median 4.7/0.1, standard deviation 2.8/0.3.

On the possibility of using X-ray Compton scattering to study magnetoelectrical properties of crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, S. P., E-mail: steve.collins@diamond.ac.uk; Laundy, D.; Connolley, T.

2016-02-16

The possibility of using X-ray Compton scattering to reveal antisymmetric components of the electron momentum density, as a fingerprint of magnetoelectric sample properties, is investigated experimentally and theoretically by studying the polar ferromagnet GaFeO{sub 3}. This paper discusses the possibility of using Compton scattering – an inelastic X-ray scattering process that yields a projection of the electron momentum density – to probe magnetoelectrical properties. It is shown that an antisymmetric component of the momentum density is a unique fingerprint of such time- and parity-odd physics. It is argued that polar ferromagnets are ideal candidates to demonstrate this phenomenon and themore » first experimental results are shown, on a single-domain crystal of GaFeO{sub 3}. The measured antisymmetric Compton profile is very small (≃ 10{sup −5} of the symmetric part) and of the same order of magnitude as the statistical errors. Relativistic first-principles simulations of the antisymmetric Compton profile are presented and it is shown that, while the effect is indeed predicted by theory, and scales with the size of the valence spin–orbit interaction, its magnitude is significantly overestimated. The paper outlines some important constraints on the properties of the antisymmetric Compton profile arising from the underlying crystallographic symmetry of the sample.« less

Optimizing a three-stage Compton camera for measuring prompt gamma rays emitted during proton radiotherapy

PubMed Central

Peterson, S W; Robertson, D; Polf, J

2011-01-01

In this work, we investigate the use of a three-stage Compton camera to measure secondary prompt gamma rays emitted from patients treated with proton beam radiotherapy. The purpose of this study was (1) to develop an optimal three-stage Compton camera specifically designed to measure prompt gamma rays emitted from tissue and (2) to determine the feasibility of using this optimized Compton camera design to measure and image prompt gamma rays emitted during proton beam irradiation. The three-stage Compton camera was modeled in Geant4 as three high-purity germanium detector stages arranged in parallel-plane geometry. Initially, an isotropic gamma source ranging from 0 to 15 MeV was used to determine lateral width and thickness of the detector stages that provided the optimal detection efficiency. Then, the gamma source was replaced by a proton beam irradiating a tissue phantom to calculate the overall efficiency of the optimized camera for detecting emitted prompt gammas. The overall calculated efficiencies varied from ~10−6 to 10−3 prompt gammas detected per proton incident on the tissue phantom for several variations of the optimal camera design studied. Based on the overall efficiency results, we believe it feasible that a three-stage Compton camera could detect a sufficient number of prompt gammas to allow measurement and imaging of prompt gamma emission during proton radiotherapy. PMID:21048295

Modeling Surface Roughness to Estimate Surface Moisture Using Radarsat-2 Quad Polarimetric SAR Data

NASA Astrophysics Data System (ADS)

Nurtyawan, R.; Saepuloh, A.; Budiharto, A.; Wikantika, K.

2016-08-01

Microwave backscattering from the earth's surface depends on several parameters such as surface roughness and dielectric constant of surface materials. The two parameters related to water content and porosity are crucial for estimating soil moisture. The soil moisture is an important parameter for ecological study and also a factor to maintain energy balance of land surface and atmosphere. Direct roughness measurements to a large area require extra time and cost. Heterogeneity roughness scale for some applications such as hydrology, climate, and ecology is a problem which could lead to inaccuracies of modeling. In this study, we modeled surface roughness using Radasat-2 quad Polarimetric Synthetic Aperture Radar (PolSAR) data. The statistical approaches to field roughness measurements were used to generate an appropriate roughness model. This modeling uses a physical SAR approach to predicts radar backscattering coefficient in the parameter of radar configuration (wavelength, polarization, and incidence angle) and soil parameters (surface roughness and dielectric constant). Surface roughness value is calculated using a modified Campbell and Shepard model in 1996. The modification was applied by incorporating the backscattering coefficient (σ°) of quad polarization HH, HV and VV. To obtain empirical surface roughness model from SAR backscattering intensity, we used forty-five sample points from field roughness measurements. We selected paddy field in Indramayu district, West Java, Indonesia as the study area. This area was selected due to intensive decreasing of rice productivity in the Northern Coast region of West Java. Third degree polynomial is the most suitable data fitting with coefficient of determination R2 and RMSE are about 0.82 and 1.18 cm, respectively. Therefore, this model is used as basis to generate the map of surface roughness.

Compton-thick AGN at high and low redshift

NASA Astrophysics Data System (ADS)

Akylas, A.; Georgantopoulos, I.; Corral, A.; Ranalli, P.; Lanzuisi, G.

2017-10-01

The most obscured sources detected in X-ray surveys, the Compton-thick AGN present great interest both because they represent the hidden side of accretion but also because they may signal the AGN birth. We analyse the NUSTAR observations from the serendipitous observations in order to study the Compton-thick AGN at the deepest possible ultra-hard band (>10 keV). We compare our results with our SWIFT/BAT findings in the local Universe, as well as with our results in the CDFS and COSMOS fields. We discuss the comparison with X-ray background synthesis models finding that a low fraction of Compton-thick sources (about 15 per cent of the obscured population) is compatible with both the 2-10keV band results and those at harder energies.

Compton imaging tomography for nondestructive evaluation of spacecraft thermal protection systems

NASA Astrophysics Data System (ADS)

Romanov, Volodymyr; Burke, Eric; Grubsky, Victor

2017-02-01

Here we present new results of in situ nondestructive evaluation (NDE) of spacecraft thermal protection system materials obtained with POC-developed NDE tool based on a novel Compton Imaging Tomography (CIT) technique recently pioneered and patented by Physical Optics Corporation (POC). In general, CIT provides high-resolution three-dimensional Compton scattered X-ray imaging of the internal structure of evaluated objects, using a set of acquired two-dimensional Compton scattered X-ray images of consecutive cross sections of these objects. Unlike conventional computed tomography, CIT requires only one-sided access to objects, has no limitation on the dimensions and geometry of the objects, and can be applied to large multilayer non-uniform objects with complicated geometries. Also, CIT does not require any contact with the objects being imaged during its application.

A flow cell for measuring X-ray Compton scattering of liquid at temperatures up to 623 K and pressures up to 20 MPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ono, Takumi, E-mail: onot@scf.che.tohoku.ac.jp; Watanabe, Masaru; Sato, Yoshiyuki

2016-08-15

A flow-type cell was developed for measuring Compton scattering spectra of heat-sensitive aqueous solution. Compton scattering spectra of water and ethanol were measured in the region from ambient conditions to 623 K and 20 MPa. Compton profiles derived from measurement with the flow-type cell were comparable with those in the literature. Results obtained from the flow-type cell showed that delocalization of electronic charge density of water and ethanol at high temperatures occurred. Delocalization of the electronic charge density of ethanol was greater than that of water at high temperature, which is consistent with the prior works that use proton NMRmore » chemical shifts to describe hydrogen bonding.« less

Maximum Likelihood Compton Polarimetry with the Compton Spectrometer and Imager

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lowell, A. W.; Boggs, S. E; Chiu, C. L.

2017-10-20

Astrophysical polarization measurements in the soft gamma-ray band are becoming more feasible as detectors with high position and energy resolution are deployed. Previous work has shown that the minimum detectable polarization (MDP) of an ideal Compton polarimeter can be improved by ∼21% when an unbinned, maximum likelihood method (MLM) is used instead of the standard approach of fitting a sinusoid to a histogram of azimuthal scattering angles. Here we outline a procedure for implementing this maximum likelihood approach for real, nonideal polarimeters. As an example, we use the recent observation of GRB 160530A with the Compton Spectrometer and Imager. Wemore » find that the MDP for this observation is reduced by 20% when the MLM is used instead of the standard method.« less

EBSD as a tool to identify and quantify bainite and ferrite in low-alloyed Al-TRIP steels.

PubMed

Zaefferer, S; Romano, P; Friedel, F

2008-06-01

Bainite is thought to play an important role for the chemical and mechanical stabilization of metastable austenite in low-alloyed TRIP steels. Therefore, in order to understand and improve the material properties, it is important to locate and quantify the bainitic phase. To this aim, electron backscatter diffraction-based orientation microscopy has been employed. The main difficulty herewith is to distinguish bainitic ferrite from ferrite because both have bcc crystal structure. The most important difference between them is the occurrence of transformation induced geometrically necessary dislocations in the bainitic phase. To determine the areas with larger geometrically necessary dislocation density, the following orientation microscopy maps were explored: pattern quality maps, grain reference orientation deviation maps and kernel average misorientation maps. We show that only the latter allow a reliable separation of the bainitic and ferritic phase. The kernel average misorientation threshold value that separates both constituents is determined by an algorithm that searches for the smoothness of the boundaries between them.

Integrating geologic and satellite radar data for mapping dome-and-basin patterns in the In Ouzzal Terrane, Western Hoggar, Algeria

NASA Astrophysics Data System (ADS)

Deroin, Jean-Paul; Djemai, Safouane; Bendaoud, Abderrahmane; Brahmi, Boualem; Ouzegane, Khadidja; Kienast, Jean-Robert

2014-11-01

The In Ouzzal Terrane (IOT) located in the north-western part of the Tuareg Shield forms an elongated N-S trending block, more than 400 km long and 80 km wide. It involves an Archaean crust remobilized during a very high-temperature metamorphic event related to the Palaeoproterozoic orogeny. The IOT largely crops out in the rocky and sandy desert of Western Hoggar. It corresponds mainly to a flat area with some reliefs composed of Late Panafrican granites, dyke networks or Cambrian volcanic rocks. These flat areas are generally covered by thin sand veneers. They are favorable for discriminating bedrock geological units using imaging radar, backscattering measurements, and field checking, because the stony desert is particularly sensitive to the radar parameters such as wavelength or polarization. The main radar data used are those obtained with the ALOS-PALSAR sensor (L-band), in ScanSAR mode (large swath) and Fine Beam modes. The PALSAR sensor has been also compared to ENVISAT-ASAR and to optical imagery. Detailed mapping of some key areas indicates extensive Archaean dome-and-basin patterns. In certain parts, the supracrustal synforms and orthogneiss domes exhibit linear or circular features corresponding to shear zones or rolling structures, respectively. The geological mapping of these dome-and-basin structures, and more generally of the Archaean and Proterozoic lithological units, is more accurate with the SAR imagery, particularly when using the L-band, than with the optical imagery. A quantitative approach is carried out in order to estimate the backscatter properties of the main rock types. Due to the large variety of configurations, radar satellite imagery such as ALOS PALSAR represents a key tool for geological mapping in arid region at different scales from the largest (e.g., 1:500,000) to the smallest (e.g., 1:50,000).

Low-lying dipole strength of the open-shell nucleus 94Mo

NASA Astrophysics Data System (ADS)

Romig, C.; Beller, J.; Glorius, J.; Isaak, J.; Kelley, J. H.; Kwan, E.; Pietralla, N.; Ponomarev, V. Yu.; Sauerwein, A.; Savran, D.; Scheck, M.; Schnorrenberger, L.; Sonnabend, K.; Tonchev, A. P.; Tornow, W.; Weller, H. R.; Zilges, A.; Zweidinger, M.

2013-10-01

The low-lying dipole strength of the open-shell nucleus 94Mo was studied via the nuclear resonance fluorescence technique up to 8.7 MeV excitation energy at the bremsstrahlung facility at the Superconducting Darmstadt Electron Linear Accelerator (S-DALINAC), and with Compton backscattered photons at the High Intensity γ-ray Source (HIγS) facility. In total, 83 excited states were identified. Exploiting polarized quasi-monoenergetic photons at HIγS, parity quantum numbers were assigned to 41 states excited by dipole transitions. The electric dipole-strength distribution was determined up to 8.7 MeV and compared to microscopic calculations within the quasiparticle phonon model. Calculations and experimental data are in good agreement for the fragmentation, as well as for the integrated strength. The average decay pattern of the excited states was investigated exploiting the HIγS measurements at five energy settings. Mean branching ratios to the ground state and first excited 21+ state were extracted from the measurements with quasi-monoenergetic photons and compared to γ-cascade simulations within the statistical model. The experimentally deduced mean branching ratios exhibit a resonance-like maximum at 6.4 MeV which cannot be reproduced within the statistical model. This indicates a nonstatistical structure in the energy range between 5.5 and 7.5 MeV.

Development of a Hydrogen Møller Polarimeter for Precision Parity-Violating Electron Scattering

NASA Astrophysics Data System (ADS)

Gray, Valerie M.

2013-10-01

Parity-violating electron scattering experiments allow for testing the Standard Model at low energy accelerators. Future parity-violating electron scattering experiments, like the P2 experiment at the Johannes Gutenberg University, Mainz, Germany, and the MOLLER and SoLID experiments at Jefferson Lab will measure observables predicted by the Standard Model to high precision. In order to make these measurements, we will need to determine the polarization of the electron beam to sub-percent precision. The present way of measuring the polarization, with Møller scattering in iron foils or using Compton laser backscattering, will not easily be able to reach this precision. The novel Hydrogen Møller Polarimeter presents a non-invasive way to measure the electron polarization by scattering the electron beam off of atomic hydrogen gas polarized in a 7 Tesla solenoidal magnetic trap. This apparatus is expected to be operational by 2016 in Mainz. Currently, simulations of the polarimeter are used to develop the detection system at College of William & Mary, while the hydrogen trap and superconducting solenoid magnet are being developed at the Johannes Gutenberg University, Mainz. I will discuss the progress of the design and development of this novel polarimeter system. This material is based upon work supported by the National Science Foundation under Grant No. PHY-1206053.

Enhanced Compton Backscattering in a Periodic Mirror System for Polarized Positron Beam Generation

NASA Astrophysics Data System (ADS)

Miyahara, Yoshikazu

2002-05-01

By colliding a circularly polarized high power laser beam with a high-energy electron beam, intense circularly polarized γ-rays can be generated, which in turn can be used to produce a longitudinally polarized positron beam for a linear collider. In the present paper, an optical mirror system with periodic focal points is considered to generate intense polarized γ-rays. A CO2 laser beam propagates back and forth in a series of holed mirrors in a straight line. The diffraction loss through the holes is negligibly small, so that the laser beam can be used repeatedly for the collision. The beam size is reduced to 22 μm at a minimum and kept the same in 20 unit cells, ten of which are combined in series. A 5.8 GeV electron beam is focused to 30 μm at a minimum in a series of triplets of permanent quadrupole magnets to generate γ-rays of 60 MeV at a maximum. A γ-ray yield required for a positron beam in a linear collider can be obtained by 10 laser sources with a power of 3.1 kW each, which is considerably lower than the total power assumed in a previous proposal.

Electron Beam Instrumentation Techniques Using Coherent Radiation

NASA Astrophysics Data System (ADS)

Wang, D. X.

1997-05-01

In recent years, there has been increasing interest in short electron bunches for different applications such as short wavelength FELs, linear colliders, advanced accelerators such as laser or plasma wakefield accelerators, and Compton backscattering X-ray sources. A short bunch length is needed to meet various requirements such as high peak current, low momentum spread, high luminosity, small ratio of bunch length to plasma wavelength, or accurate timing. Meanwhile, much progress has been made on photoinjectors and different magnetic and RF bunching schemes to produce very short bunches. Measurement of those short bunches becomes essential to develop, characterize, and operate such demanding machines. Conventionally, bunch duration of short electron bunches is measured by transverse RF deflecting cavities or streak camera. With such devices it becomes very challenging to measure bunch length down to a few hundred femtoseconds. Many frequency domain techniques have been recently developed, based on a relation between bunch profile and coherent radiation spectrum. These techniques provide excellent performance for short bunches. In this paper, coherent radiation and its applications to bunch length measurement will be discussed. A strategy for bunch length control at Jefferson Lab will be presented, which includes a noninvasive coherent synchrotron radiation (CSR) monitor, a zero-phasing technique used to calibrate the CSR detector, and phase transfer measurement used to correct RF phase drifts.

Brilliant gamma beams for industrial applications: new opportunities, new challenges

NASA Astrophysics Data System (ADS)

Iancu, V.; Suliman, G.; Turturica, G. V.; Iovea, M.; Daito, I.; Ohgaki, H.; Matei, C.; Ur, C. A.; Balabanski, D. L.

2016-10-01

The Nuclear Physics oriented pillar of the pan-European Extreme Light Infrastructure (ELI-NP) will host an ultra-bright, energy tunable, and quasi-monochromatic gamma-ray beam system in the range of 0.2-19.5 MeV produced by laser-Compton backscattering technique. The applied research program envisioned at ELI-NP targets to use nuclear resonance fluorescence (NRF) and computed tomography to provide new opportunities for industry and society. High sensitivity NRF-based investigations can be successfully applied to safeguard applications and management of radioactive wastes as well as to uncharted fields like cultural heritage and medical imaging. Gamma-ray radioscopy and computed tomography performed at ELI-NP has the potential to achieve high resolution in industrial-sized objects provided the detection challenges introduced by the unique characteristics of the gamma beam are overcome. Here we discuss the foreseen industrial applications that will benefit from the high quality and unique characteristics of ELI-NP gamma beam and the challenges they present. We present the experimental setups proposed to be implemented for this goal, discuss their performance based on analytical calculations and numerical Monte-Carlo simulations, and comment about constrains imposed by the limitation of current scintillator detectors. Several gamma-beam monitoring devices based on scintillator detectors will also be discussed.

Studies on solar hard X-Rays and gamma-rays: Compton backscatter, anisotropy, polarization and evidence for two phases of acceleration. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Bai, T.

1977-01-01

Observations of solar X-rays and gamma-rays from large flares show that the hard X-ray spectrum extends into the gamma ray region, where a flattening in the spectrum of the continuum emission is observed above about 1 MeV. This emission is believed to be due to bremsstrahlung. In addition to electron-proton collisions, at energies greater than approximately 500 keV, bremsstrahlung due to electron-electron collisions becomes significant. Bremsstrahlung production was calculated for a variety of electron spectra extending from the nonrelativistic region to relativistic energies and electron-electron bremsstrahlung is taken into account. By comparing these calculations with data, it is shown that the flattening in the spectrum of the continuum emission can be best explained by an electron spectrum consisting of two distinctive components. This evidence, together with information on the X-ray and gamma ray time profiles, implied the existence of two phases of acceleration. The first phase accelerates electrons mainly up to about several hundred keV; the second phase accelerates a small fraction of the electrons accelerated in the first phase to relativistic energies and accelerates protons to tens and hundreds of MeV.

Gluing for Raman lidar systems using the lamp mapping technique.

PubMed

Walker, Monique; Venable, Demetrius; Whiteman, David N

2014-12-20

In the context of combined analog and photon counting (PC) data acquisition in a Lidar system, glue coefficients are defined as constants used for converting an analog signal into a virtual PC signal. The coefficients are typically calculated using Lidar profile data taken under clear, nighttime conditions since, in the presence of clouds or high solar background, it is difficult to obtain accurate glue coefficients from Lidar backscattered data. Here we introduce a new method in which we use the lamp mapping technique (LMT) to determine glue coefficients in a manner that does not require atmospheric profiles to be acquired and permits accurate glue coefficients to be calculated when adequate Lidar profile data are not available. The LMT involves scanning a halogen lamp over the aperture of a Lidar receiver telescope such that the optical efficiency of the entire detection system is characterized. The studies shown here involve two Raman lidar systems; the first from Howard University and the second from NASA/Goddard Space Flight Center. The glue coefficients determined using the LMT and the Lidar backscattered method agreed within 1.2% for the water vapor channel and within 2.5% for the nitrogen channel for both Lidar systems. We believe this to be the first instance of the use of laboratory techniques for determining the glue coefficients for Lidar data analysis.

Acoustic Seabed Characterization of the Porcupine Bank, Irish Margin

NASA Astrophysics Data System (ADS)

O'Toole, Ronan; Monteys, Xavier

2010-05-01

The Porcupine Bank represents a large section of continental shelf situated west of the Irish landmass, located in water depths ranging between 150 and 500m. Under the Irish National Seabed Survey (INSS 1999-2006) this area was comprehensively mapped, generating multiple acoustic datasets including high resolution multibeam echosounder data. The unique nature of the area's datasets in terms of data density, consistency and geographic extent has allowed the development of a large-scale integrated physical characterization of the Porcupine Bank for multidisciplinary applications. Integrated analysis of backscatter and bathymetry data has resulted in a baseline delineation of sediment distribution, seabed geology and geomorphological features on the bank, along with an inclusive set of related database information. The methodology used incorporates a variety of statistical techniques which are necessary in isolating sonar system artefacts and addressing sonar geometry related issues. A number of acoustic backscatter parameters at several angles of incidence have been analysed in order to complement the characterization for both surface and subsurface sediments. Acoustic sub bottom records have also been incorporated in order to investigate the physical characteristics of certain features on the Porcupine Bank. Where available, groundtruthing information in terms of sediment samples, video footage and cores has been applied to add physical descriptors and validation to the characterization. Extensive mapping of different rock outcrops, sediment drifts, seabed features and other geological classes has been achieved using this methodology.

Is the High-Energy Emission from Centaurus A Compton-Scattered Jet Radiation?

DTIC Science & Technology

1994-01-01

Is the High-Energy Emission from Centaurus A Compton-Scattered Jet Radiation? J. G. Skibo1, C. D. Dermer and R. L. Kinzer E. O. Hulburt Center for... Centaurus A is beamed radiation from the active nucleus which is Compton-scattered into our line- of-sight. We derive the spectrum and degree of...the scattering medium. We t the OSSE data from Centaurus A with this model and nd that if the scatterers are not moving relativistically, then the

Least-Squares Deconvolution of Compton Telescope Data with the Positivity Constraint

NASA Technical Reports Server (NTRS)

Wheaton, William A.; Dixon, David D.; Tumer, O. Tumay; Zych, Allen D.

1993-01-01

We describe a Direct Linear Algebraic Deconvolution (DLAD) approach to imaging of data from Compton gamma-ray telescopes. Imposition of the additional physical constraint, that all components of the model be non-negative, has been found to have a powerful effect in stabilizing the results, giving spatial resolution at or near the instrumental limit. A companion paper (Dixon et al. 1993) presents preliminary images of the Crab Nebula region using data from COMPTEL on the Compton Gamma-Ray Observatory.

Multi-Feature Classification of Multi-Sensor Satellite Imagery Based on Dual-Polarimetric Sentinel-1A, Landsat-8 OLI, and Hyperion Images for Urban Land-Cover Classification.

PubMed

Zhou, Tao; Li, Zhaofu; Pan, Jianjun

2018-01-27

This paper focuses on evaluating the ability and contribution of using backscatter intensity, texture, coherence, and color features extracted from Sentinel-1A data for urban land cover classification and comparing different multi-sensor land cover mapping methods to improve classification accuracy. Both Landsat-8 OLI and Hyperion images were also acquired, in combination with Sentinel-1A data, to explore the potential of different multi-sensor urban land cover mapping methods to improve classification accuracy. The classification was performed using a random forest (RF) method. The results showed that the optimal window size of the combination of all texture features was 9 × 9, and the optimal window size was different for each individual texture feature. For the four different feature types, the texture features contributed the most to the classification, followed by the coherence and backscatter intensity features; and the color features had the least impact on the urban land cover classification. Satisfactory classification results can be obtained using only the combination of texture and coherence features, with an overall accuracy up to 91.55% and a kappa coefficient up to 0.8935, respectively. Among all combinations of Sentinel-1A-derived features, the combination of the four features had the best classification result. Multi-sensor urban land cover mapping obtained higher classification accuracy. The combination of Sentinel-1A and Hyperion data achieved higher classification accuracy compared to the combination of Sentinel-1A and Landsat-8 OLI images, with an overall accuracy of up to 99.12% and a kappa coefficient up to 0.9889. When Sentinel-1A data was added to Hyperion images, the overall accuracy and kappa coefficient were increased by 4.01% and 0.0519, respectively.

Can X-ray spectrum imaging replace backscattered electrons for compositional contrast in the scanning electron microscope?

PubMed

Newbury, Dale E; Ritchie, Nicholas W M

2011-01-01

The high throughput of the silicon drift detector energy dispersive X-ray spectrometer (SDD-EDS) enables X-ray spectrum imaging (XSI) in the scanning electron microscope to be performed in frame times of 10-100 s, the typical time needed to record a high-quality backscattered electron (BSE) image. These short-duration XSIs can reveal all elements, except H, He, and Li, present as major constituents, defined as 0.1 mass fraction (10 wt%) or higher, as well as minor constituents in the range 0.01-0.1 mass fraction, depending on the particular composition and possible interferences. Although BSEs have a greater abundance by a factor of 100 compared with characteristic X-rays, the strong compositional contrast in element-specific X-ray maps enables XSI mapping to compete with BSE imaging to reveal compositional features. Differences in the fraction of the interaction volume sampled by the BSE and X-ray signals lead to more delocalization of the X-ray signal at abrupt compositional boundaries, resulting in poorer spatial resolution. Improved resolution in X-ray elemental maps occurs for the case of a small feature composed of intermediate to high atomic number elements embedded in a matrix of lower atomic number elements. XSI imaging strongly complements BSE imaging, and the SDD-EDS technology enables an efficient combined BSE-XSI measurement strategy that maximizes the compositional information. If 10 s or more are available for the measurement of an area of interest, the analyst should always record the combined BSE-XSI information to gain the advantages of both measures of compositional contrast. Copyright © 2011 Wiley Periodicals, Inc.

Application of Spaceborne Scatterometer for Mapping Freeze-Thaw State in Northern Landscapes as a Measure of Ecological and Hydrological Processes

NASA Technical Reports Server (NTRS)

McDonald, Kyle; Kimball, John; Zimmermann, Reiner; Way, JoBea; Frolking, Steve; Running, Steve

1999-01-01

Landscape freeze/thaw transitions coincide with marked shifts in albedo, surface energy and mass exchange, and associated snow dynamics. Monitoring landscape freeze/thaw dynamics would improve our ability to quantify the interannual variability of boreal hydrology and river runoff/flood dynamics. The annual duration of frost-free period also bounds the period of photosynthetic activity in boreal and arctic regions thus affecting the annual carbon budget and the interannual variability of regional carbon fluxes. In this study, we use the NASA scatterometer (NSCAT) to monitor the temporal change in the radar backscatter signature across selected ecoregions of the boreal zone. We have measured vegetation tissue temperatures, soil temperature profiles, and micrometeorological parameters in situ at selected sites along a north-south transect extending across Alaska from Prudhoe Bay to the Kenai Peninsula and in Siberia near the Yenisey River. Data from these stations have been used to quantify the scatterometer's sensitivity to freeze/thaw state under a variety of terrain and landcover conditions. Analysis of the NSCAT temporal response over the 1997 spring thaw cycle shows a 3 to 5 dB change in measured backscatter that is well correlated with the landscape springtime thaw process. Having verified the instrument's capability to monitor freeze/thaw transitions, regional scale mosaicked data are applied to derive temporal series of freeze/thaw transition maps for selected circumpolar high latitude regions. These maps are applied to derive areal extent of frozen and thawed landscape and demonstrate the utility of spaceborne radar for operational monitoring of seasonal freeze-thaw dynamics and associated biophysical processes for the circumpolar high latitudes.

Use of acoustic classification of sidescan sonar data for mapping benthic habitat in the Northern Channel Islands, California

USGS Publications Warehouse

Cochrane, Guy R.; Lafferty, Kevin D.

2002-01-01

Highly reflective seafloor features imaged by sidescan sonar in nearshore waters off the Northern Channel Islands (California, USA) have been observed in subsequent submersible dives to be areas of thin sand covering bedrock. Adjacent areas of rocky seafloor, suitable as habitat for endangered species of abalone and rockfish, and encrusting organisms, cannot be differentiated from the areas of thin sand on the basis of acoustic backscatter (i.e. grey level) alone. We found second-order textural analysis of sidescan sonar data useful to differentiate the bottom types where data is not degraded by near-range distortion (caused by slant-range and ground-range corrections), and where data is not degraded by far-range signal attenuation. Hand editing based on submersible observations is necessary to completely convert the sidescan sonar image to a bottom character classification map suitable for habitat mapping.

Sea ice type maps from Alaska synthetic aperture radar facility imagery: An assessment

NASA Technical Reports Server (NTRS)

Fetterer, Florence M.; Gineris, Denise; Kwok, Ronald

1994-01-01

Synthetic aperture radar (SAR) imagery received at the Alaskan SAR Facility is routinely and automatically classified on the Geophysical Processor System (GPS) to create ice type maps. We evaluated the wintertime performance of the GPS classification algorithm by comparing ice type percentages from supervised classification with percentages from the algorithm. The root mean square (RMS) difference for multiyear ice is about 6%, while the inconsistency in supervised classification is about 3%. The algorithm separates first-year from multiyear ice well, although it sometimes fails to correctly classify new ice and open water owing to the wide distribution of backscatter for these classes. Our results imply a high degree of accuracy and consistency in the growing archive of multiyear and first-year ice distribution maps. These results have implications for heat and mass balance studies which are furthered by the ability to accurately characterize ice type distributions over a large part of the Arctic.

Soil moisture retrival from Sentinel-1 and Modis synergy

NASA Astrophysics Data System (ADS)

Gao, Qi; Zribi, Mehrez; Escorihuela, Maria Jose; Baghdadi, Nicolas

2017-04-01

This study presents two methodologies retrieving soil moisture from SAR remote sensing data. The study is based on Sentinel-1 data in the VV polarization, over a site in Urgell, Catalunya (Spain). In the two methodologies using change detection techniques, preprocessed radar data are combined with normalized difference vegetation index (NDVI) auxiliary data to estimate the mean soil moisture with a resolution of 1km. By modeling the relationship between the backscatter difference and NDVI, the soil moisture at a specific NDVI value is retrieved. The first algorithm is already developed on West Africa(Zribi et al., 2014) from ERS scatterometer data to estimate soil water status. In this study, it is adapted to Sentinel-1 data and take into account the high repetitiveness of data in optimizing the inversion approach. Another new method is developed based on the backscatter difference between two adjacent days of Sentinel-1 data w.r.t. NDVI, with smaller vegetation change, the backscatter difference is more sensitive to soil moisture. The proposed methodologies have been validated with the ground measurement in two demonstrative fields with RMS error about 0.05 (in volumetric moisture), and the coherence between soil moisture variations and rainfall events is observed. Soil moisture maps at 1km resolution are generated for the study area. The results demonstrate the potential of Sentinel-1 data for the retrieval of soil moisture at 1km or even better resolution.

The growth and decay of equatorial backscatter plumes

NASA Astrophysics Data System (ADS)

Tsunoda, R. T.

1980-02-01

During the past three years, a series of rocket experiments from the Kwajalein Atoll, Marshall Islands, were conducted to investigate the character of intense, scintillation-producing irregularities that occur in the nighttime equatorial ionosphere. Because the source mechanism of equatorial irregularities, believed to be the Rayleigh-Taylor instability, is analogous to that which generates plasma-density striations in a nuclear-induced environment, there is considerable interest in the underlying physics that controls the characteristics of these irregularities. A primary objective of ALTAIR investigations of equatorial irregularities is to seek an understanding of the underlying physics by establishing the relationship between meter-scale irregularities (detected by ALTAIR), and the large-scale plasma-density depletions (or 'bubbles') that contain the kilometer-scale, scintillation-producing irregularities. We describe the time evolution of backscatter 'plumes' produced by one meter equatorial field-aligned irregularities. Using ALTAIR, a fully steerable backscatter radar, to repeatedly map selected plumes, we characterize the dynamic behavior of plumes in terms of growth and a decay phase. Most of the observed characteristics are found to be consistent with equatorial-irregularity generation predicted by current theories of Rayleigh-Taylor and gradient-drift instabilities. However, other characteristics have been found that suggest key roles played by the eastward neutral wind and by altitude-modulation of the bottomside F layer in establishing the initial conditions for plume growth.

A Compton scattering technique to determine wood density and locating defects in it

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tondon, Akash, E-mail: akashtondonnsl@gmail.com; Sandhu, B. S.; Singh, Bhajan

A Compton scattering technique is presented to determine density and void location in the given wooden samples. The technique uses a well collimated gamma ray beam from {sup 137}Cs along with the NaI(Tl) scintillation detector. First, a linear relationship is established between Compton scattered intensity and known density of chemical compounds, and then density of the wood is determined from this linear relation. In another experiment, the ability of penetration of gamma rays is explored to detect voids in wooden (low Z) sample. The sudden reduction in the Compton scattered intensities agrees well with the position and size of voidsmore » in the wooden sample. It is concluded that wood density and the voids of size ∼ 4 mm and more can be detected easily by this method.« less

Galaxy gas as obscurer - II. Separating the galaxy-scale and nuclear obscurers of active galactic nuclei

NASA Astrophysics Data System (ADS)

Buchner, Johannes; Bauer, Franz E.

2017-03-01

The 'torus' obscurer of active galactic nuclei (AGN) is poorly understood in terms of its density, sub-structure and physical mechanisms. Large X-ray surveys provide model boundary constraints, for both Compton-thin and Compton-thick levels of obscuration, as obscured fractions are mean covering factors fcov. However, a major remaining uncertainty is host-galaxy obscuration. In Paper I, we discovered a relation of {NH} ∝ M_{star }^{1/3} for the obscuration of galaxy-scale gas. Here, we apply this observational relation to the AGN population, and find that galaxy-scale gas is responsible for a luminosity-independent fraction of Compton-thin AGN, but does not produce Compton-thick columns. With the host-galaxy obscuration understood, we present a model of the remaining nuclear obscurer, which is consistent with a range of observations. Our radiation-lifted torus model consists of a Compton-thick component (fcov ∼ 35 per cent) and a Compton-thin component (fcov ∼ 40 per cent), which depends on both black hole mass and luminosity. This provides a useful summary of observational constraints for torus modellers who attempt to reproduce this behaviour. It can also be employed as a sub-grid recipe in cosmological simulations that do not resolve the torus. We also investigate host-galaxy X-ray obscuration inside cosmological, hydrodynamic simulations (Evolution and Assembly of Galaxies and their Environment; Illustris). The obscuration from ray-traced galaxy gas can agree with observations, but is highly sensitive to the chosen feedback assumptions.

Importance of Doppler broadening in Compton scatter imaging techniques

NASA Astrophysics Data System (ADS)

Rao, Donepudi V.; Takeda, Tohoru; Itai, Yuji; Seltzer, S. M.; Hubbell, John H.; Zeniya, Tsutomu; Akatsuka, Takao; Cesareo, Roberto; Brunetti, Antonio; Gigante, Giovanni E.

2001-12-01

Compton scattering is a potential tool for the determination of bone mineral content or tissue density for dose planning purposes, and requires knowledge of the energy distribution of the X-rays through biological materials of medical interest in the X-ray and (gamma) -ray region. The energy distribution is utilized in a number of ways in diagnostic radiology, for example, in determining primary photon spectra, electron densities in separate volumes, and in tomography and imaging. The choice of the X-ray energy is more related to X-ray absorption, where as that of the scattering angle is more related to geometry. The evaluation of all the contributions are mandatory in Compton profile measurements and is important in X-ray imaging systems in order to achieve good results. In view of this, Compton profile cross-sections for few biological materials are estimated at nineteen K(alpha) X-ray energies and 60 keV (Am-241) photons. Energy broadening, geometrical broadening from 1 to 180 degree(s), FWHM of J(Pz) and FWHM of Compton energy broadening has been evaluated at various incident photon energies. These values are estimated around the centroid of the Compton profile with an energy interval of 0.1 keV and 1.0 keV for 60 keV photons. The interaction cross sections for the above materials are estimated using fractions-by-weight of the constituent elements. Input data for these tables are purely theoretical.

Geology of the Lachesis Tessera Quadrangle (V-18), Venus

NASA Technical Reports Server (NTRS)

McGill, George E.

2008-01-01

The Lachesis Tessera Quadrangle (V-18) lies between 25deg and 50deg north, 300deg and 330deg east. Most of the quadrangle consists of "regional plains" (1) of Sedna and Guinevere Planitiae. A first draft of the geology has been completed, and the tentative number of mapped units by terrain type is: Tesserae - 2; plains - 4; ridge belts - 1; fracture belts - 1 (plus embayed fragments of possible additional belts); coronae - 3; central volcanoes - 1; shield flows - 2; paterae - 1; impact craters - 1; undifferentiated flows - 1; bright materials - 1. By far the areally most extensive materials are regional plains. These are mapped as two units, based on radar backscatter ("radar brightness"). The brighter unit appears to be younger than the darker unit. This inference is based on the common presence within the lighter unit of circular or nearly circular inliers of material with radar backscatter characteristic of the darker unit. The circular inliers are most likely low shield volcanoes, which are commonly present on the darker unit, that were only partially covered by the brighter unit. Clear cut examples of wrinkle ridges and fractures superposed on the darker unit but truncated by the brighter unit have not been found to date. These relationships indicate that the brighter unit is superposed on the darker unit, but that the difference in age between them is very small. Because they are so widespread, the regional plains are a convenient relative age time "marker." The number of impact craters superposed on these plains is too small to measure age differences (2), and thus we cannot estimate how much time elapsed between the emplacement of the darker and brighter regional plains units. More local plains units are defined by significantly lower radar backscatter or by a texture that is mottled at scores to hundreds of kilometers scale. A plains-like unit with a homogenous, bright diffuse backscatter is present as scattered exposures in the eastern part of the quadrangle. These exposures have been mapped as "bright material," but it is not clear at present if this is a valid unit or if it is part of the brighter regional plains unit. Tessera terrain is primarily found along the western border of the quadrangle, where Lachesis Tessera refers to the southern exposures, and Zirka Tessera refers to northern exposures. A second tessera unit has been mapped with the symbol "t?." This unit appears to be deformed by the requisite 2 sets of closely spaced structures, but it is so extensively flooded by regional plains materials that the structural fabric is partially obscured. Tessera terrain is present in the adjacent V-17 quadrangle, where both Lachesis Tessera and Zirka Tessera are areally more extensive than in V-18. Ridge and fracture belts are both present, but not as extensive as is the case in, for example, the Pandrosos Dorsa (3) and Lavinia Planitia (4) quadrangles. As is commonly the case, it is difficult to determine if the materials of these belts are older or younger than regional plains. A recent study using radar properties (5) demonstrated that at least most ridge belts appear to be older than regional plains. The materials of fracture belts probably are also older than regional plains, but the fractures themselves can be both older and younger than regional plains (e.g., 3).

Aerosol Profile Retrievals from Integrated Dual Wavelengths Space Lidar ESSP3-CENA and Spectral Radiance MODIS Data

NASA Technical Reports Server (NTRS)

Kaufman, Yoram; Mattoo, Shana; Tanre, Didier; Kleidman, Richard; Lau, William K. M. (Technical Monitor)

2001-01-01

The ESSP3-CENA space mission (formally PICASSO-CENA) will provide continues global observations with a two wavelength lidar. The attenuated backscattering coefficients measured by the lidar, have valuable information about the vertical distribution of aerosol particles and their sizes. However the information cannot be mapped into unique aerosol physical properties. Infinite number of physical solutions with different attenuations through the atmosphere can reconstruct the same two wavelength backscattered profile measured from space. Spectral radiance measured by MODIS simultaneously with the ESSP3 data can constrain the problem and resolve this ambiguity to a large extent. Sensitivity study shows that inversion of the integrated MODIS+ESSP3 data can derive the vertical profiles of the fine and coarse modes mixed in the same atmospheric column in the presence of moderate calibration uncertainties and electronic noise (approx. 10%). We shall present the sensitivity study and results from application of the technique to measurements in the SAFARI-2000 and SHADE experiments.

Acquisition of a High Resolution Field Emission Scanning Electron Microscope for the Analysis of Returned Samples

NASA Technical Reports Server (NTRS)

Nittler, Larry R.

2003-01-01

This grant furnished funds to purchase a state-of-the-art scanning electron microscope (SEM) to support our analytical facilities for extraterrestrial samples. After evaluating several instruments, we purchased a JEOL 6500F thermal field emission SEM with the following analytical accessories: EDAX energy-dispersive x-ray analysis system with fully automated control of instrument and sample stage; EDAX LEXS wavelength-dispersive x-ray spectrometer for high sensitivity light-element analysis; EDAX/TSL electron backscatter diffraction (EBSD) system with software for phase identification and crystal orientation mapping; Robinson backscatter electron detector; and an in situ micro-manipulator (Kleindiek). The total price was $550,000 (with $150,000 of the purchase supported by Carnegie institution matching funds). The microscope was delivered in October 2002, and most of the analytical accessories were installed by January 2003. With the exception of the wavelength spectrometer (which has been undergoing design changes) everything is working well and the SEM is in routine use in our laboratory.

Mid-Shelf Hardground Fish Habitats off the Georgia Coast

NASA Astrophysics Data System (ADS)

Platt, M.; Sautter, L.

2016-02-01

Multibeam sonar data were collected off the Georgia coast aboard the R/V Savannah by the College of Charleston BEAMS Program in May 2015. Kongsberg EM2040C data were post-processed in CARIS HIPS and SIPS 9.0 to create bathymetric maps overlain with backscatter intensity. The mid-shelf focus sites lie at depths between 25 and 40 m, and include the northern edge of Gray's Reef National Marine Sanctuary. The study sites are known areas of abundant fish congregations, identified by the South Carolina Department of Natural Resources' Marine Resources Monitoring, Assessment, & Prediction (MARMAP) program. The regional mid-shelf seafloor morphology consists of sand ridges, rock outcrops, and incised meandering channels 1 to 3 m deep. Backscatter analysis was used to identify hardground structures that might provide habitat for a high diversity of vertebrates and invertebrates. Multiple hardground structures were found and characterized at these locations and will be targeted for further research and possible inclusion in the Georgia and South Carolina continental shelf Marine Protected Areas.

On the Soil Roughness Parameterization Problem in Soil Moisture Retrieval of Bare Surfaces from Synthetic Aperture Radar

PubMed Central

Verhoest, Niko E.C; Lievens, Hans; Wagner, Wolfgang; Álvarez-Mozos, Jesús; Moran, M. Susan; Mattia, Francesco

2008-01-01

Synthetic Aperture Radar has shown its large potential for retrieving soil moisture maps at regional scales. However, since the backscattered signal is determined by several surface characteristics, the retrieval of soil moisture is an ill-posed problem when using single configuration imagery. Unless accurate surface roughness parameter values are available, retrieving soil moisture from radar backscatter usually provides inaccurate estimates. The characterization of soil roughness is not fully understood, and a large range of roughness parameter values can be obtained for the same surface when different measurement methodologies are used. In this paper, a literature review is made that summarizes the problems encountered when parameterizing soil roughness as well as the reported impact of the errors made on the retrieved soil moisture. A number of suggestions were made for resolving issues in roughness parameterization and studying the impact of these roughness problems on the soil moisture retrieval accuracy and scale. PMID:27879932

Orientation Dependence of the Deformation Microstructure of Ta-4%W after Cold-Rolling

NASA Astrophysics Data System (ADS)

Zhang, J.; Ma, G. Q.; Godfrey, A.; Shu, D. Y.; Chen, Q.; Wu, G. L.

2017-07-01

One of the common features of deformed face-centered cubic metals with medium to high stacking fault energy is the formation of geometrically necessary dislocation boundaries. The dislocation boundary arrangements in refractory metals with body-centered cubic crystal structure are, however, less well known. To address this issue a Ta-4%W alloy was cold rolled up to 70% in thickness in the present work. The resulting deformation microstructures were characterized by electron back-scattering diffraction and the dislocation boundary arrangements in each grain were revealed using sample-frame misorientation axis maps calculated using an in-house code. The maps were used to analyze the slip pattern of individual grains after rolling, revealing an orientation dependence of the slip pattern.

Photographs of the Sea Floor of Western Massachusetts Bay, Offshore of Boston, Massachusett, July 1999

USGS Publications Warehouse

Gutierrez, Benjamin T.; Butman, Bradford; Blackwood, Dann S.

2001-01-01

This CD-ROM contains photographs and sediment sample analyses of the sea floor obtained at 142 sites in western Massachusetts Bay (Figure 1) during a research cruise (USGS cruise ISBL99024) aboard the Fishing Vessel (FV) Isabel S. (Figure 2) conducted July 18-21, 1999. These photographs and samples provide critical ground truth information for the interpretation of shaded relief and backscatter intensity maps created using data collected with a multibeam echo sounder system (Butman and others, in press, a, b, c; Valentine and others, in press, a, b, c). Collection of these photographs and samples was undertaken in support of a large project whose overall objective is to map and describe the sea floor of Massachusetts Bay.

Comparison of TOMS and AVHRR volcanic ash retrievals from the August 1992 eruption of Mt. Spurr

USGS Publications Warehouse

Krotkov, N.A.; Torres, O.; Seftor, C.; Krueger, A.J.; Kostinski, A.; Rose, William I.; Bluth, G.J.S.; Schneider, D.; Schaefer, S.J.

1999-01-01

On August 19, 1992, the Advanced Very High Resolution Radiometer (AVHRR) onboard NOAA-12 and NASA's Total Ozone Mapping Spectrometer (TOMS) onboard the Nimbus-7 satellite simultaneously detected and mapped the ash cloud from the eruption of Mt. Spurr, Alaska. The spatial extent and geometry of the cloud derived from the two datasets are in good agreement and both AVHRR split window IR (11-12??m brightness temperature difference) and the TOMS UV Aerosol Index (0.34-0.38??m ultraviolet backscattering and absorption) methods give the same range of total cloud ash mass. Redundant methods for determination of ash masses in drifting volcanic clouds offer many advantages for potential application to the mitigation of aircraft hazards.

Establishment of Imaging Spectroscopy of Nuclear Gamma-Rays based on Geometrical Optics

PubMed Central

Tanimori, Toru; Mizumura, Yoshitaka; Takada, Atsushi; Miyamoto, Shohei; Takemura, Taito; Kishimoto, Tetsuro; Komura, Shotaro; Kubo, Hidetoshi; Kurosawa, Shunsuke; Matsuoka, Yoshihiro; Miuchi, Kentaro; Mizumoto, Tetsuya; Nakamasu, Yuma; Nakamura, Kiseki; Parker, Joseph D.; Sawano, Tatsuya; Sonoda, Shinya; Tomono, Dai; Yoshikawa, Kei

2017-01-01

Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that “Electron Tracking Compton Camera” (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics. PMID:28155870

Establishment of Imaging Spectroscopy of Nuclear Gamma-Rays based on Geometrical Optics.

PubMed

Tanimori, Toru; Mizumura, Yoshitaka; Takada, Atsushi; Miyamoto, Shohei; Takemura, Taito; Kishimoto, Tetsuro; Komura, Shotaro; Kubo, Hidetoshi; Kurosawa, Shunsuke; Matsuoka, Yoshihiro; Miuchi, Kentaro; Mizumoto, Tetsuya; Nakamasu, Yuma; Nakamura, Kiseki; Parker, Joseph D; Sawano, Tatsuya; Sonoda, Shinya; Tomono, Dai; Yoshikawa, Kei

2017-02-03

Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that "Electron Tracking Compton Camera" (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics.

Resonance condition and low-frequency quasi-periodic oscillations of the outbursting source H1743-322

NASA Astrophysics Data System (ADS)

Chakrabarti, Sandip K.; Mondal, Santanu; Debnath, Dipak

2015-10-01

It has long been proposed that low-frequency quasi-periodic oscillations (QPOs) in stellar-mass black holes or their equivalents in supermassive black holes are the result of resonances between infall and cooling timescales. We explicitly compute these two timescales in a generic situation to show that resonances are easily achieved. During an outburst of a transient black hole candidate, the accretion rate of the Keplerian disc as well as the geometry of the Comptonizing cloud change very rapidly. During some period, a resonance condition between the cooling timescale (predominantly by Comptonization) and the infall timescale of the Comptonizing cloud is roughly satisfied. This leads to low-frequency quasi-periodic oscillations (LFQPOs) of the Compton cloud and the consequent oscillation of hard X-rays. In this paper, we explicitly follow black hole candidate H1743-322 during its 2010 outburst. We compute the Compton cooling time and infall time over several days and show that QPOs take place when these two roughly agree within ˜50 per cent, i.e., the resonance condition is generally satisfied. We also confirm that for the sharper LFQPOs (i.e. higher Q-factors) the ratio of the two timescales is very close to 1.

A test of local Lorentz invariance with Compton scattering asymmetry

DOE PAGES

Mohanmurthy, Prajwal; Narayan, Amrendra; Dutta, Dipangkar

2016-12-14

Here, we report on a measurement of the constancy and anisotropy of the speed of light relative to the electrons in photon-electron scattering. We also used the Compton scattering asymmetry measured by the new Compton polarimeter in Hall~C at Jefferson Lab to test for deviations from unity of the vacuum refractive index (more » $n$). For photon energies in the range of 9 - 46 MeV, we obtain a new limit of $$1-n < 1.4 \\times 10^{-8}$$. In addition, the absence of sidereal variation over the six month period of the measurement constrains any anisotropies in the speed of light. These constitute the first study of Lorentz invariance using Compton asymmetry. Within the minimal standard model extension framework, our result yield limits on the photon and electron coefficients $$\\tilde{\\kappa}_{0^+}^{YZ}, c_{TX}, \\tilde{\\kappa}_{0^+}^{ZX}$$, and $$c_{TY}$$. Though, these limits are several orders of magnitude larger than the current best limits, they demonstrate the feasibility of using Compton asymmetry for tests of Lorentz invariance. For future parity violating electron scattering experiments at Jefferson Lab we will use higher energy electrons enabling better constraints.« less

Compton echoes from nearby gamma-ray bursts

NASA Astrophysics Data System (ADS)

Beniamini, Paz; Giannios, Dimitrios; Younes, George; van der Horst, Alexander J.; Kouveliotou, Chryssa

2018-06-01

The recent discovery of gravitational waves from GW170817, associated with a short gamma-ray burst (GRB) at a distance of 40 Mpc, has demonstrated that short GRBs can occur locally and at a reasonable rate. Furthermore, gravitational waves enable us to detect close-by GRBs, even when we are observing at latitudes far from the jet's axis. We consider here Compton echoes, the scattered light from the prompt and afterglow emission. Compton echoes, an as yet undetected counterpart of GRBs, peak in X-rays and maintain a roughly constant flux for hundreds to thousands of years after the burst. Though too faint to be detected in typical cosmological GRBs, a fraction of close-by bursts with a sufficiently large energy output in X-rays, and for which the surrounding medium is sufficiently dense, may indeed be observed in this way. The detection of a Compton echo could provide unique insight into the burst properties and the environment's density structure. In particular, it could potentially determine whether or not there was a successful jet that broke through the compact binary merger ejecta. We discuss here the properties and expectations from Compton echoes and suggest methods for detectability.

The impact of neutron star spin on X-ray spectra

NASA Astrophysics Data System (ADS)

Burke, M. J.; Gilfanov, M.; Sunyaev, R.

2018-02-01

We investigate whether the intrinsic spin of neutron stars (NSs) leaves an observable imprint on the spectral properties of X-ray binaries. To evaluate this, we consider a sample of nine NSs for which the spins have been measured that are not accreting pulsars (for which the accretion geometry will be different). For each source, we perform spectroscopy on a majority of RXTE hard-state observations. Our sample of sources and observations spans the range of the Eddington ratios LX/LEdd ˜ 0.005-0.100. We find a clear trend between the key Comptonization properties and the NS spin for a given accretion rate. Specifically, at a given L/LEdd, for more rapidly rotating NSs we find lower seed photon temperatures and a general increase in Comptonization strength, as parametrized by the Comptonization y parameter and amplification factor A. This is in good agreement with the theoretical scenario whereby less energy is liberated in a boundary layer for more rapidly spinning NSs, resulting in a lower seed photon luminosity and, consequently, less Compton cooling in the corona. This effect in extremis results in the hard states of the most rapidly spinning sources encroaching upon the regime of Comptonization properties occupied by black holes.

Characterizing post-drainage succession in Thermokarst Lake Basins on the Seward Peninsula, Alaska with TerraSAR-X Backscatter and Landsat-based NDVI data

USGS Publications Warehouse

Regmi, Prajna; Grosse, Guido; Jones, Miriam C.; Jones, Benjamin M.; Walter Anthony, Katey

2012-01-01

Drained thermokarst lake basins accumulate significant amounts of soil organic carbon in the form of peat, which is of interest to understanding carbon cycling and climate change feedbacks associated with thermokarst in the Arctic. Remote sensing is a tool useful for understanding temporal and spatial dynamics of drained basins. In this study, we tested the application of high-resolution X-band Synthetic Aperture Radar (SAR) data of the German TerraSAR-X satellite from the 2009 growing season (July–September) for characterizing drained thermokarst lake basins of various age in the ice-rich permafrost region of the northern Seward Peninsula, Alaska. To enhance interpretation of patterns identified in X-band SAR for these basins, we also analyzed the Normalized Difference Vegetation Index (NDVI) calculated from a Landsat-5 Thematic Mapper image acquired on July 2009 and compared both X-band SAR and NDVI data with observations of basin age. We found significant logarithmic relationships between (a) TerraSAR-X backscatter and basin age from 0 to 10,000 years, (b) Landat-5 TM NDVI and basin age from 0 to 10,000 years, and (c) TerraSAR-X backscatter and basin age from 50 to 10,000 years. NDVI was a better indicator of basin age over a period of 0–10,000 years. However, TerraSAR-X data performed much better for discriminating radiocarbon-dated basins (50–10,000 years old). No clear relationships were found for either backscatter or NDVI and basin age from 0 to 50 years. We attribute the decreasing trend of backscatter and NDVI with increasing basin age to post-drainage changes in the basin surface. Such changes include succession in vegetation, soils, hydrology, and renewed permafrost aggradation, ground ice accumulation and localized frost heave. Results of this study show the potential application of X-band SAR data in combination with NDVI data to map long-term succession dynamics of drained thermokarst lake basins.

Physical Conditions Associated with Widespread Seafloor Methane Discharge on the Northern US Atlantic Margin

NASA Astrophysics Data System (ADS)

Skarke, A. D.; Ruppel, C. D.; Brothers, D. S.

2014-12-01

Recent analysis of water column backscatter data and remotely operated vehicle (ROV) video imagery collected by NOAA Ship Okeanos Explorer between 2011 and 2013 revealed methane discharge from the seafloor at over 570 gas seep locations along the northern US Atlantic margin. To the best of our knowledge, such large-scale seepage has not previously been observed on a passive margin outside the Arctic or not spatially associated with a petroleum basin. This seepage has implications for the global carbon cycle, ocean chemistry (e.g., acidification), and in some cases, the climate system. Using data collected by Okeanos Explorer and NOAA's Deep Discoverer ROV, we combine water column backscatter data with video imagery and seafloor backscatter data to estimate gas flux and constrain the geoacoustic properties of the seabed at methane discharge sites. The total methane flux from the northern US Atlantic margin seeps is conservatively estimated at ~15-90 Mg y-1, based on observations of gas bubble volume, discharge rates, and discharge points per site. However, fewer than 1% of the identified seep sites have been inspected with a ROV, and this estimate is likely to be revised upward as the characteristics of the seeps are further constrained. Another important observation to emerge from our analysis is the lack of spatial correlation between seep sites and the ~5000 pockmarks mapped on the northern part of the US Atlantic margin. In this region, pockmarks, which are often easily identified by geophysical imaging of the seafloor, should not be considered potential target sites for finding undiscovered areas of seepage. Conversely, discrete patches of elevated relative seafloor acoustic backscatter amplitude do appear to be correlated with the spatial distribution of methane seeps, implying anomalous seafloor characteristic at seep loci. This finding is consistent with ROV video observations of authigenic carbonate outcrops and extensive chemosynthetic bivalve communities at seep sites, which create a seafloor substrate with higher acoustic impedance. This result suggests that seafloor acoustic reflectivity data, which are far more commonly collected and archived than water column backscatter data, might be used diagnostically to identify and constrain the distribution of seafloor locations of methane discharge.

Genetics Home Reference: erythrokeratodermia variabilis et progressiva

MedlinePlus

... P, Campanelli C, Compton JG, Bale SJ, DiGiovanna JJ, Uitto J. Genetic heterogeneity in erythrokeratodermia variabilis: novel ... Itin P, Hohl D, Epstein EH Jr, DiGiovanna JJ, Compton JG, Bale SJ. Mutations in the human ...

Generalized parton distributions from deep virtual compton scattering at CLAS

DOE PAGES

Guidal, M.

2010-04-24

Here, we have analyzed the beam spin asymmetry and the longitudinally polarized target spin asymmetry of the Deep Virtual Compton Scattering process, recently measured by the Jefferson Lab CLAS collaboration. Our aim is to extract information about the Generalized Parton Distributions of the proton. By fitting these data, in a largely model-independent procedure, we are able to extract numerical values for the two Compton Form Factorsmore » $$H_{Im}$$ and $$\\tilde{H}_{Im}$$ with uncertainties, in average, of the order of 30%.« less

A publicly available SSC+EC code.

NASA Astrophysics Data System (ADS)

Georganopoulos, M.; Perlman, E. S.; Kazanas, D.; Wingert, B.; Castro, R.

2004-08-01

We present a time-dependent one zone SSC+EC code that takes into account the KN-cross section, and calculates self-consistently all orders of Compton scattering. In particular, it produces separate results for the first order Compton component, and for the total Compton emission. The kinetic equation is solved using a stable implicit scheme, and the user can select from a range of physically motivated temporal electron injection profile. The code is written in C, is fully documented and will soon be publicly available through the Internet, along with a set of IDL visualization routines.

Reconstructed Image Spatial Resolution of Multiple Coincidences Compton Imager

NASA Astrophysics Data System (ADS)

Andreyev, Andriy; Sitek, Arkadiusz; Celler, Anna

2010-02-01

We study the multiple coincidences Compton imager (MCCI) which is based on a simultaneous acquisition of several photons emitted in cascade from a single nuclear decay. Theoretically, this technique should provide a major improvement in localization of a single radioactive source as compared to a standard Compton camera. In this work, we investigated the performance and limitations of MCCI using Monte Carlo computer simulations. Spatial resolutions of the reconstructed point source have been studied as a function of the MCCI parameters, including geometrical dimensions and detector characteristics such as materials, energy and spatial resolutions.

METALLIC AND CERAMIC MATERIALS RESEARCH Task Order 0003: Metallic Materials, Processing and Performance Development for Air Force Applications

DTIC Science & Technology

2015-10-01

journal articles and papers, and is referenced in the text. 15. SUBJECT TERMS high entropy alloys, titanium, inertia welding 16. SECURITY...Backscatter electron image and (b) inverse pole figure map of the IFW region showing transition from a flat (right) to wavy (left) weld interface...appearance. The weld interface is outlined by a white line in figure (b). The LSHR alloy is below the IFW interface and it is darker than the Mar-M247

Inversion of Ionospheric Backscatter Radar Data in Order to Map and Model the Ionosphere

DTIC Science & Technology

2006-08-17

M., Wild, J . A., Lester, M., Yeoman, T . K., Milan, S. E., Ye, H., Devlin, J . C., Frey, H. U., and Kikuchi, T ., Interhemispheric asymmetries in the...Devlin, J . and Salim, T ., Evaluation of Digital Generation and Phasing Techniques for Transmitter Signals of the TIGER N.Z. Radar. WARS02 (Workshop on...17. Conde, M. and Dyson, P. L., Thermospheric Vertical Winds Above Mawson , Antarctica, J . Atmos. Terr. Phys., Vol. 57, 589-596, 1995. 18. Conde, M

Site Survey of the Martha's Vineyard Coastal Observatory: Backscatter, Grain Size and Temporal Evolution of Rippled Scour Depressions

NASA Astrophysics Data System (ADS)

Goff, J. A.; Mayer, L.; Schwab, B.; Traykovski, P.; Wilkins, R.; Jenkins, C.; Kraft, B.; Evans, R.; Buynevich, I.

2002-12-01

The Office of Naval Research's Mine Burial Prediction program has chosen the Martha's Vineyard Coastal Observatory (MVCO) as a natural laboratory for experimental observations of object burial by nearshore processes (e.g., bedform migration, scour). In support of this program, the MVCO has been subject to an intensive site survey program, involving, since early 2001: (1) three swath backscatter and/or bathymetry surveys; (2) three high resolution seismic surveys; (3) ultra-high resolution sector-scanning sonar on pole mounts; (4) in situ geotechnical (velocity and resistivity) measurements, (5) grab sampling, and (6) vibracoring. These efforts are concentrated in water depths between ~8 and 18 m, centered on the site of the MVCO permanent node at ~12 m water depth Rippled scour depressions (RSDs) are pervasive within the MVCO. RSDs are ~shore-perpendicular bands of coarse sands separated by overlying fine sands. The term itself implies that the coarse sands are heavily rippled (~0.5-1 m wavelength, ~0.1 m amplitude) and slightly depressed relative to the fine sands which, in the MVCO, are generally just a few 10's of cm thick. The RSDs are clearly evident on sidescan data as bands of high backscatter. For the most part, grain size measurements confirm a strong positive correspondence between mean grain size and backscatter intensity. However, a critical exception is seen in deeper water where, well within the area of fine sands, backscatter increases noticeably as mean grain size decreases from ~150μ to ~130μ. Topographic expression related to the RSDs is confined primarily to evident scour depressions at the edges. The RSDs are highly asymmetric: backscatter is higher, the coarse/fine transition is more sharply defined, and the scour depression is deeper on one side than the other. This pattern changes within the survey: the higher backscatter edge is always to the west in the western part of the survey, and vice versa to the east. The strike of the RSDs also changes, from being slightly east of north in the western part of the survey to slightly west of north to the east. The MVCO site survey work establishes a baseline set of observations against which physical changes in the seafloor with time can be measured. Early evidence of significant change has been provided by comparison of the first two sidescan surveys, which indicates a shift in the RSD boundaries by as much as 50 m between February and September of 2001. Continued seafloor evolution is evidenced by the August 2002 grab sampling and sector scanning sonar. This dynamic setting will continue to be monitored by additional swath mapping and sampling in conjunction with the planned winter 2003/2004 mine burial experiment.

Virtual Compton Scattering and the Generalized Polarizabilities of the Proton

NASA Astrophysics Data System (ADS)

Hyde-Wright, Charles E.

2002-10-01

The Virtual Compton Scattering (VCS) process: e p arrow e p γ is sensitive to the Electromagnetic Polarizabilities of the proton. As a function of the wavelength of the virtual photon, it is possible to map out the spatial variation of the polarization response. The Low Energy Theorem (P. Guichon et al.,Nucl.Phys.A591:606-638,1995) and the Dispersion Relation formalism (B. Pasquini et al., Eur.Phys.J.A11:185-208,2001), permit the extraction of the electric and magnetic polarizabilities from VCS data up to the two pion production threshold. At Jefferson Lab, we have measured the electric and magnetic polarization response at Q^2 = 1 and 1.7 GeV^2. These complement earlier measurements at Q^2 = 0.33 (J. Roche, et al., Phys.Rev.Lett.85:708,2000) and 0.0 GeV^2 (V. Olmos de Leon, et al., Eur.Phys.J.A10:207-215,2001, B.E. MacGibbon, et al., Phys.Rev.C52:2097-2109,1995). The electric polarization and magnetic responses are very different as a function of distance scale. The electric polarizability falls with Q^2 in accord with the electric form factor of the proton: G_E(Q^2). However, for the magnetic polarizability the data illustrate the strong cancellation of para- and dia-magnetism at all distance scales within the proton.

The hydrogen anomaly problem in neutron Compton scattering

NASA Astrophysics Data System (ADS)

Karlsson, Erik B.

2018-03-01

Neutron Compton scattering (also called ‘deep inelastic scattering of neutrons’, DINS) is a method used to study momentum distributions of light atoms in solids and liquids. It has been employed extensively since the start-up of intense pulsed neutron sources about 25 years ago. The information lies primarily in the width and shape of the Compton profile and not in the absolute intensity of the Compton peaks. It was therefore not immediately recognized that the relative intensities of Compton peaks arising from scattering on different isotopes did not always agree with values expected from standard neutron cross-section tables. The discrepancies were particularly large for scattering on protons, a phenomenon that became known as ‘the hydrogen anomaly problem’. The present paper is a review of the discovery, experimental tests to prove or disprove the existence of the hydrogen anomaly and discussions concerning its origin. It covers a twenty-year-long history of experimentation, theoretical treatments and discussions. The problem is of fundamental interest, since it involves quantum phenomena on the subfemtosecond time scale, which are not visible in conventional thermal neutron scattering but are important in Compton scattering where neutrons have two orders of magnitude times higher energy. Different H-containing systems show different cross-section deficiencies and when the scattering processes are followed on the femtosecond time scale the cross-section losses disappear on different characteristic time scales for each H-environment. The last section of this review reproduces results from published papers based on quantum interference in scattering on identical particles (proton or deuteron pairs or clusters), which have given a quantitative theoretical explanation both regarding the H-cross-section reduction and its time dependence. Some new explanations are added and the concluding chapter summarizes the conditions for observing the specific quantum phenomena observed in neutron Compton scattering on protons and deuterons in condensed systems.

Optimization of Compton-suppression and summing schemes for the TIGRESS HPGe detector array

NASA Astrophysics Data System (ADS)

Schumaker, M. A.; Svensson, C. E.; Andreoiu, C.; Andreyev, A.; Austin, R. A. E.; Ball, G. C.; Bandyopadhyay, D.; Boston, A. J.; Chakrawarthy, R. S.; Churchman, R.; Drake, T. E.; Finlay, P.; Garrett, P. E.; Grinyer, G. F.; Hackman, G.; Hyland, B.; Jones, B.; Maharaj, R.; Morton, A. C.; Pearson, C. J.; Phillips, A. A.; Sarazin, F.; Scraggs, H. C.; Smith, M. B.; Valiente-Dobón, J. J.; Waddington, J. C.; Watters, L. M.

2007-04-01

Methods of optimizing the performance of an array of Compton-suppressed, segmented HPGe clover detectors have been developed which rely on the physical position sensitivity of both the HPGe crystals and the Compton-suppression shields. These relatively simple analysis procedures promise to improve the precision of experiments with the TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS). Suppression schemes will improve the efficiency and peak-to-total ratio of TIGRESS for high γ-ray multiplicity events by taking advantage of the 20-fold segmentation of the Compton-suppression shields, while the use of different summing schemes will improve results for a wide range of experimental conditions. The benefits of these methods are compared for many γ-ray energies and multiplicities using a GEANT4 simulation, and the optimal physical configuration of the TIGRESS array under each set of conditions is determined.

Consequences of hot gas in the broad line region of active galactic nuclei

NASA Technical Reports Server (NTRS)

Kallman, T.; Mushotzky, R.

1985-01-01

Models for hot gas in the broad line region of active galactic nuclei are discussed. The results of the two phase equilibrium models for confinement of broad line clouds by Compton heated gas are used to show that high luminosity quasars are expected to show Fe XXVI L alpha line absorption which will be observed with spectrometers such as those planned for the future X-ray spectroscopy experiments. Two phase equilibrium models also predict that the gas in the broad line clouds and the confining medium may be Compton thick. It is shown that the combined effects of Comptonization and photoabsorption can suppress both the broad emission lines and X-rays in the Einstein and HEAO-1 energy bands. The observed properties of such Compton thick active galaxies are expected to be similar to those of Seyfert 2 nuclei. The implications for polarization and variability are also discussed.

Compton cooling and the signature of Quasi Periodic Oscillations for the transient black hole candidate H 1743-322

NASA Astrophysics Data System (ADS)

Mondal, S.; Chakrabarti, S. K.; Debnath, D.; Jana, A.; Molla, A. A.

In black hole accretion cooling of the Compton cloud has an enormous effect on the dynamics of post-shock flow. We demonstrate that the Compton cooling is highly responsible for the origin of Quasi Periodic Oscillations (QPOs) during the outburst time of the galactic black hole candidates (BHCs). Our study shows that the disk oscillation will take place when infall time from the shock roughly agrees with cooling time in the post-shock region i.e., the resonance condition. We believe that this oscillation is responsible for the origin of QPOs and will occur only when a particular disk condition (disk rate, halo rate and shock strength) satisfies. We also confirm that shock moves with an average velocity of a few meters/sec for the transient BHC H1743-322 due to the presence of Compton cooling.

Extraction of Generalized Parton Distributions from combined Deeply Virtual Compton Scattering and Timelike Compton scattering fits

NASA Astrophysics Data System (ADS)

Boer, Marie

2017-09-01

Generalized Parton Distributions (GPDs) contain the correlation between the parton's longitudinal momentum and their transverse distribution. They are accessed through hard exclusive processes, such as Deeply Virtual Compton Scattering (DVCS). DVCS has already been measured in several experiments and several models allow for extracting GPDs from these measurements. Timelike Compton Scattering (TCS) is, at leading order, the time-reversal equivalent process to DVCS and accesses GPDs at the same kinematics. Comparing GPDs extracted from DVCS and TCS is a unique way for proving GPD universality. Combining fits from the two processes will also allow for better constraining the GPDs. We will present our method for extracting GPDs from DVCS and TCS pseudo-data. We will compare fit results from the two processes in similar conditions and present what can be expected in term of contraints on GPDs from combined fits.

Prototype Compton imager for special nuclear material

NASA Astrophysics Data System (ADS)

Wulf, Eric A.; Phlips, Bernard F.; Kurfess, James D.; Novikova, Elena I.; Fitzgerald, Carrie

2006-05-01

Compton imagers offer a method for passive detection of nuclear material over background radiation. A prototype Compton imager has been constructed using 8 layers of silicon detectors. Each layer consists of a 2×2 array of 2 mm thick cross-strip double-sided silicon detectors with active areas of 5.7 × 5.7 cm2 and 64 strips per side. The detectors are daisy-chained together in the array so that only 256 channels of electronics are needed to read-out each layer of the instrument. This imager is a prototype for a large, high-efficiency Compton imager that will meet operational requirements of Homeland Security for detection of shielded uranium. The instrument can differentiate between different radioisotopes using the reconstructed gamma-ray energy and can also show the location of the emissions with respect to the detector location. Results from the current instrument as well as simulations of the next generation instrument are presented.

In operando quantitation of Li concentration for a commercial Li-ion rechargeable battery using high-energy X-ray Compton scattering.

PubMed

Suzuki, Kosuke; Suzuki, Ayahito; Ishikawa, Taiki; Itou, Masayoshi; Yamashige, Hisao; Orikasa, Yuki; Uchimoto, Yoshiharu; Sakurai, Yoshiharu; Sakurai, Hiroshi

2017-09-01

Compton scattering is one of the most promising probes for quantitating Li under in operando conditions, since high-energy X-rays, which have high penetration power, are used as the incident beam and the Compton-scattered energy spectrum has specific line-shapes for each element. An in operando quantitation method to determine the Li composition in electrodes has been developed by using line-shape (S-parameter) analysis of the Compton-scattered energy spectrum. In this study, S-parameter analysis has been applied to a commercial coin cell Li-ion rechargeable battery and the variation of the S-parameters during the charge/discharge cycle at the positive and negative electrodes has been obtained. By using calibration curves for Li composition in the electrodes, the change in Li composition of the positive and negative electrodes has been determined using the S-parameters simultaneously.

Self-consistent Black Hole Accretion Spectral Models and the Forgotten Role of Coronal Comptonization of Reflection Emission

NASA Astrophysics Data System (ADS)

Steiner, James F.; García, Javier A.; Eikmann, Wiebke; McClintock, Jeffrey E.; Brenneman, Laura W.; Dauser, Thomas; Fabian, Andrew C.

2017-02-01

Continuum and reflection spectral models have each been widely employed in measuring the spins of accreting black holes. However, the two approaches have not been implemented together in a photon-conserving, self-consistent framework. We develop such a framework using the black hole X-ray binary GX 339-4 as a touchstone source, and we demonstrate three important ramifications. (1) Compton scattering of reflection emission in the corona is routinely ignored, but is an essential consideration given that reflection is linked to the regimes with strongest Comptonization. Properly accounting for this causes the inferred reflection fraction to increase substantially, especially for the hard state. Another important impact of the Comptonization of reflection emission by the corona is the downscattered tail. Downscattering has the potential to mimic the relativistically broadened red wing of the Fe line associated with a spinning black hole. (2) Recent evidence for a reflection component with a harder spectral index than the power-law continuum is naturally explained as Compton-scattered reflection emission. (3) Photon conservation provides an important constraint on the hard state’s accretion rate. For bright hard states, we show that disk truncation to large scales R\\gg {R}{ISCO} is unlikely as this would require accretion rates far in excess of the observed \\dot{M} of the brightest soft states. Our principal conclusion is that when modeling relativistically broadened reflection, spectral models should allow for coronal Compton scattering of the reflection features, and when possible, take advantage of the additional constraining power from linking to the thermal disk component.

NuSTAR SPECTROSCOPY OF MULTI-COMPONENT X-RAY REFLECTION FROM NGC 1068

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, Franz E.; Arévalo, Patricia; Walton, Dominic J.

2015-10-20

We report on high-energy X-ray observations of the Compton-thick Seyfert 2 galaxy NGC 1068 with NuSTAR, which provide the best constraints to date on its >10 keV spectral shape. The NuSTAR data are consistent with those from past and current instruments to within cross-calibration uncertainties, and we find no strong continuum or line variability over the past two decades, which is in line with its X-ray classification as a reflection-dominated Compton-thick active galactic nucleus. The combined NuSTAR, Chandra, XMM-Newton, and Swift BAT spectral data set offers new insights into the complex secondary emission seen instead of the completely obscured transmittedmore » nuclear continuum. The critical combination of the high signal-to-noise NuSTAR data and the decomposition of the nuclear and extranuclear emission with Chandra allow us to break several model degeneracies and greatly aid physical interpretation. When modeled as a monolithic (i.e., a single N{sub H}) reflector, none of the common Compton reflection models are able to match the neutral fluorescence lines and broad spectral shape of the Compton reflection hump without requiring unrealistic physical parameters (e.g., large Fe overabundances, inconsistent viewing angles, or poor fits to the spatially resolved spectra). A multi-component reflector with three distinct column densities (e.g., with best-fit values of N{sub H} of 1.4 × 10{sup 23}, 5.0 × 10{sup 24}, and 10{sup 25} cm{sup −2}) provides a more reasonable fit to the spectral lines and Compton hump, with near-solar Fe abundances. In this model, the higher N{sub H} component provides the bulk of the flux to the Compton hump, while the lower N{sub H} component produces much of the line emission, effectively decoupling two key features of Compton reflection. We find that ≈30% of the neutral Fe Kα line flux arises from >2″ (≈140 pc) and is clearly extended, implying that a significant fraction (and perhaps most) of the <10 keV reflected component arises from regions well outside a parsec-scale torus. These results likely have ramifications for the interpretation of Compton-thick spectra from observations with poorer signal-to-noise and/or more distant objects.« less

Nucleon spin-averaged forward virtual Compton tensor at large Q 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hill, Richard J.; Paz, Gil

The nucleon spin-averaged forward virtual Compton tensor determines important physical quantities such as electromagnetically-induced mass differences of nucleons, and two-photon exchange contributions in hydrogen spectroscopy. It depends on two kinematic variables:more » $$\

Demonstration of in-vivo Multi-Probe Tracker Based on a Si/CdTe Semiconductor Compton Camera

NASA Astrophysics Data System (ADS)

Takeda, Shin'ichiro; Odaka, Hirokazu; Ishikawa, Shin-nosuke; Watanabe, Shin; Aono, Hiroyuki; Takahashi, Tadayuki; Kanayama, Yousuke; Hiromura, Makoto; Enomoto, Shuichi

2012-02-01

By using a prototype Compton camera consisting of silicon (Si) and cadmium telluride (CdTe) semiconductor detectors, originally developed for the ASTRO-H satellite mission, an experiment involving imaging multiple radiopharmaceuticals injected into a living mouse was conducted to study its feasibility for medical imaging. The accumulation of both iodinated (131I) methylnorcholestenol and 85Sr into the mouse's organs was simultaneously imaged by the prototype. This result implies that the Compton camera is expected to become a multi-probe tracker available in nuclear medicine and small animal imaging.

The Compton Observatory Science Workshop

NASA Technical Reports Server (NTRS)

Shrader, Chris R. (Editor); Gehrels, Neil (Editor); Dennis, Brian (Editor)

1992-01-01

The Compton Observatory Science Workshop was held in Annapolis, Maryland on September 23-25, 1991. The primary purpose of the workshop was to provide a forum for the exchange of ideas and information among scientists with interests in various areas of high energy astrophysics, with emphasis on the scientific capabilities of the Compton Observatory. Early scientific results, as well as reports on in-flight instrument performance and calibrations are presented. Guest investigator data products, analysis techniques, and associated software were discussed. Scientific topics covered included active galaxies, cosmic gamma ray bursts, solar physics, pulsars, novae, supernovae, galactic binary sources, and diffuse galactic and extragalactic emission.

Suzaku  Observations of Heavily Obscured (Compton-thick) Active Galactic Nuclei Selected by the Swift/BAT Hard X-Ray Survey

NASA Astrophysics Data System (ADS)

Tanimoto, Atsushi; Ueda, Yoshihiro; Kawamuro, Taiki; Ricci, Claudio; Awaki, Hisamitsu; Terashima, Yuichi

2018-02-01

We present a uniform broadband X-ray (0.5–100.0 keV) spectral analysis of 12 Swift/Burst Alert Telescope selected Compton-thick ({log}{N}{{H}}/{{cm}}-2≥slant 24) active galactic nuclei (CTAGNs) observed with Suzaku. The Suzaku data of three objects are published here for the first time. We fit the Suzaku and Swift spectra with models utilizing an analytic reflection code and those utilizing the Monte-Carlo-based model from an AGN torus by Ikeda et al. The main results are as follows: (1) The estimated intrinsic luminosity of a CTAGN strongly depends on the model; applying Compton scattering to the transmitted component in an analytic model may largely overestimate the intrinsic luminosity at large column densities. (2) Unabsorbed reflection components are commonly observed, suggesting that the tori are clumpy. (3) Most of CTAGNs show small scattering fractions (<0.5%), implying a buried AGN nature. (4) Comparison with the results obtained for Compton-thin AGNs suggests that the properties of these CTAGNs can be understood as a smooth extension from Compton-thin AGNs with heavier obscuration; we find no evidence that the bulk of the population of hard-X-ray-selected CTAGNs are different from less obscured objects.

Comprehensive study of observables in Compton scattering on the nucleon

NASA Astrophysics Data System (ADS)

Grießhammer, Harald W.; McGovern, Judith A.; Phillips, Daniel R.

2018-03-01

We present an analysis of 13 observables in Compton scattering on the proton. Cross sections, asymmetries with polarised beam and/or targets, and polarisation-transfer observables are investigated for energies up to the Δ(1232) resonance to determine their sensitivity to the proton's dipole scalar and spin polarisabilities. The Chiral Effective Field Theory Compton amplitude we use is complete at N4LO, O(e2δ4), for photon energies ω˜ m_{π}, and so has an accuracy of a few per cent there. At photon energies in the resonance region, it is complete at NLO, O(e2δ0), and so its accuracy there is about 20%. We find that for energies from pion-production threshold to about 250 MeV, multiple asymmetries have significant sensitivity to presently ill-determined combinations of proton spin polarisabilities. We also argue that the broad outcomes of this analysis will be replicated in complementary theoretical approaches, e.g., dispersion relations. Finally, we show that below the pion-production threshold, 6 observables suffice to reconstruct the Compton amplitude, and above it 11 are required. Although not necessary for polarisability extractions, this opens the possibility to perform "complete" Compton-scattering experiments. An interactive Mathematica notebook, including results for the neutron, is available from judith.mcgovern@manchester.ac.uk.

Combining harmonic generation and laser chirping to achieve high spectral density in Compton sources

DOE PAGES

Terzić, Balša; Reeves, Cody; Krafft, Geoffrey A.

2016-04-25

Recently various laser-chirping schemes have been investigated with the goal of reducing or eliminating ponderomotive line broadening in Compton or Thomson scattering occurring at high laser intensities. Moreover, as a next level of detail in the spectrum calculations, we have calculated the line smoothing and broadening expected due to incident beam energy spread within a one-dimensional plane wave model for the incident laser pulse, both for compensated (chirped) and unchirped cases. The scattered compensated distributions are treatable analytically within three models for the envelope of the incident laser pulses: Gaussian, Lorentzian, or hyperbolic secant. We use the new results tomore » demonstrate that the laser chirping in Compton sources at high laser intensities: (i) enables the use of higher order harmonics, thereby reducing the required electron beam energies; and (ii) increases the photon yield in a small frequency band beyond that possible with the fundamental without chirping. We found that this combination of chirping and higher harmonics can lead to substantial savings in the design, construction and operational costs of the new Compton sources. This is of particular importance to the widely popular laser-plasma accelerator based Compton sources, as the improvement in their beam quality enters the regime where chirping is most effective.« less

Soft gamma-ray detector for the ASTRO-H Mission

NASA Astrophysics Data System (ADS)

Watanabe, Shin; Tajima, Hiroyasu; Fukazawa, Yasushi; Blandford, Roger; Enoto, Teruaki; Kataoka, Jun; Kawaharada, Madoka; Kokubun, Motohide; Laurent, Philippe; Lebrun, François; Limousin, Olivier; Madejski, Greg; Makishima, Kazuo; Mizuno, Tsunefumi; Nakamori, Takeshi; Nakazawa, Kazuhiro; Mori, Kunishiro; Odaka, Hirokazu; Ohno, Masanori; Ohta, Masayuki; Sato, Goro; Sato, Rie; Takeda, Shin'ichiro; Takahashi, Hiromitsu; Takahashi, Tadayuki; Tanaka, Takaaki; Tashiro, Makoto; Terada, Yukikatsu; Uchiyama, Hideki; Uchiyama, Yasunobu; Yamada, Shinya; Yatsu, Yoichi; Yonetoku, Daisuke; Yuasa, Takayuki

2012-09-01

ASTRO-H is the next generation JAXA X-ray satellite, intended to carry instruments with broad energy coverage and exquisite energy resolution. The Soft Gamma-ray Detector (SGD) is one of ASTRO-H instruments and will feature wide energy band (60-600 keV) at a background level 10 times better than the current instruments on orbit. The SGD is complimentary to ASTRO-H’s Hard X-ray Imager covering the energy range of 5-80 keV. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield where Compton kinematics is utilized to reject backgrounds. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and CdTe (cadmium telluride) sensors. Good energy resolution is afforded by semiconductor sensors, and it results in good background rejection capability due to better constraints on Compton kinematics. Utilization of Compton kinematics also makes the SGD sensitive to the gamma-ray polarization, opening up a new window to study properties of gamma-ray emission processes. In this paper, we will present the detailed design of the SGD and the results of the final prototype developments and evaluations. Moreover, we will also present expected performance based on the measurements with prototypes.

Marine Geophysical Characterization of the Chain Fracture Zone in the Equatorial Atlantic

NASA Astrophysics Data System (ADS)

Harmon, N.; Rychert, C.; Agius, M. R.; Tharimena, S.; Kendall, J. M.

2017-12-01

The Chain Fracture zone is part of a larger system of fracture zones along the Mid Atlantic Ridge that is thought to be one of the original zones of weakness during the break up of Pangea. It is over 300 km long and produces earthquakes as large as Mw 6.9 on segments of the active fault zone. Here we present the results of two marine geophysical mapping campaigns over the active part of the Chain Fracture zone as part of the PI-LAB (Passive Imaging of the Lithosphere-Asthenosphere Boundary) experiment. We collected swath bathymetry, backscatter imagery, gravity and total field magnetic anomaly. We mapped the fault scarps within the transform fault system using the 50 m resolution swath and backscatter imagery. In addition, a 30-40 mGal residual Mantle Bouguer Anomaly determined from gravity analysis suggests the crust is by up to 1.4-2.0 km beneath the Chain relative to the adjacent ridge segments. However, in the eastern 75 km of the active transform we find evidence for thicker crust. The active fault system cuts through the region of thicker crust and there is a cluster of MW > 6 earthquakes in this region. There is a cluster of similar sized earthquakes on the western end where thinner crust is inferred. This suggests that variations in melt production and crustal thickness at the mid ocean ridge systems may have only a minor effect on the seismicity and longevity of the transform fault system.

Mapping the seabed and habitats in National Marine Sanctuaries - Examples from the East, Gulf and West Coasts

USGS Publications Warehouse

Valentine, Page C.; Cochrane, Guy R.; Scanlon, Kathryn M.

2003-01-01

The National Marine Sanctuary System requires seabed and habitat maps to serve as a basis for managing sanctuary resources and for conducting research. NOAA, the agency that manages the sanctuaries, and the USGS have conducted mapping projects in three sanctuaries (Stellwagen Bank NMS, Flower Garden Banks NMS, and Channel Islands NMS) with an emphasis on collaboration of geologists and biologists from the two agencies and from academic institutions. Mapping of seabed habitats is a developing field that requires the integration of geologic and biologic studies and the use of swath imaging techniques such as multibeam and sidescan sonar. Major products of swath mapping are shaded-relief topographic imagery which shows seabed features in great detail, and backscatter imagery which provides an indication of the types of materials that constitute the seabed. Sea floor images provide an excellent basis for conducting the groundtruthing studies (using video, photo, and sampling techniques) that are required to collect the data necessary for making meaningful interpretative maps of the seabed. The compilation of interpretive maps showing seabed environments and habitats also requires the development of a sea floor classification system that will be a basis for comparing, managing, and researching characteristic areas of the seabed. Seabed maps of the sanctuaries are proving useful for management and research decisions that address commercial and recreational fishing, habitat disturbance, engineering projects, tourism, and cultural resources.

Investigating the Compton Effect with a Spreadsheet.

ERIC Educational Resources Information Center

Kinderman, Jesusa Valdez

1992-01-01

Describes a computer simulation of the Compton effect designed to lead students to discover (1) the relationship of the electron's final kinetic energy to its angle of scattering and (2) the relationship between the scattering angles of the outgoing electron and photon. (MDH)

An Overview of the Topography of Mars from the Mars Orbiter Laser Altimeter (MOLA)

NASA Technical Reports Server (NTRS)

Smith, David E.; Zuber, Maria T.

2000-01-01

The Mars Global Surveyor (MGS) spacecraft has now completed more than half of its one-Mars-year mission to globally map Mars. During the MGS elliptical and circular orbit mapping phases, the Mars Orbiter Laser Altimeter (MOLA), an instrument on the MGS payload, has collected over 300 million precise elevation measurements. MOLA measures the range from the MGS spacecraft to the Martian surface and to atmospheric reflections. Range is converted to topography through knowledge of the MGS spacecraft orbit. Ranges from MOLA have resulted in a precise global topographic map of Mars. The instrument has also provided measurements of the width of the backscattered optical pulse and of the 1064 nm reflectivity of the Martian surface and atmosphere. The range resolution of the MOLA instrument is 37.5 cm and the along-track resolution of MOLA ground shots is approx. 300 m; the across-track spacing depends on latitude and time in the mapping orbit. The best current topographic grid has a spatial resolution of approx. 1/16 deg and vertical accuracy of approx. one meter. Additional information is contained in the original extended abstract.

High-Resolution geophysical data from the inner continental shelf at Vineyard Sound, Massachusetts

USGS Publications Warehouse

Andrews, Brian D.; Ackerman, Seth D.; Baldwin, Wayne E.; Foster, David S.; Schwab, William C.

2013-01-01

The U.S. Geological Survey (USGS) and the Massachusetts Office of Coastal Zone Management (CZM) have mapped approximately 340 square kilometers of the inner continental shelf in Vineyard Sound, Massachusetts, under a cooperative mapping program. The geophysical data collected between 2009 and 2011 by the U.S. Geological Survey as part of this program are published in this report. The data include (1) swath bathymetry from interferometric sonar, (2) acoustic backscatter from sidescan sonar, and (3) seismic-reflection profiles from a chirp subbottom profiler. These data were collected to support research on the influence of sea-level change and sediment supply on coastal evolution and sediment transport processes and to provide baseline seabed characterization information required for management of coastal and offshore resources within the coastal zone of Massachusetts.

Millimeter and hard x ray/gamma ray observations of solar flares during the June 1991 GRO campaign

NASA Technical Reports Server (NTRS)

Kundu, M. R.; White, S. M.; Gopalswamy, N.; Lim, J.

1992-01-01

We have carried out high-spatial-resolution millimeter observations of solar flares using the Berkeley-Illinois-Maryland Array (BIMA). At the present time, BIMA consists of only three elements, which is not adequate for mapping highly variable solar phenomena, but is excellent for studies of the temporal structure of flares at millimeter wavelengths at several different spatial scales. We present BIMA observations made during the Gamma Ray Observatories (GRO)/Solar Max 1991 campaign in Jun. 1991 when solar activity was unusually high. Our observations covered the period 8-9 Jun. 1991; this period overlapped the period 4-15 Jun. when the Compton Telescope made the Sun a target of opportunity because of the high level of solar activity.

Hard X-ray Emission from Galaxy Clusters Observed with INTEGRAL and Prospects for Simbol-X

NASA Astrophysics Data System (ADS)

Eckert, D.; Paltani, S.; Courvoisier, T. J.-L.

2009-05-01

Some galaxy clusters are known to contain a large population of relativistic electrons, which produce radio emission through synchrotron radiation. Therefore, it is expected that inverse-Compton scattering of the relativistic electrons with the CMB produce non-thermal emission which should be observable in the hard X-ray domain. Here we focus on the recent results by INTEGRAL, which shed a new light on the non-thermal emission thanks to its angular resolution and sensitivity in the hard X-ray range. We also present the exciting prospects in this field for Simbol-X, which will allow us to detect the non-thermal emission in a number of clusters and map the magnetic field throughout the intra-cluster medium.

Advanced Compton scattering light source R&D at LLNL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albert, F; Anderson, S G; Anderson, G

2010-02-16

We report the design and current status of a monoenergetic laser-based Compton scattering 0.5-2.5 MeV {gamma}-ray source. Previous nuclear resonance fluorescence results and future linac and laser developments for the source are presented. At MeV photon energies relevant for nuclear processes, Compton scattering light sources are attractive because of their relative compactness and improved brightness above 100 keV, compared to typical 4th generation synchrotrons. Recent progress in accelerator physics and laser technology have enabled the development of a new class of tunable Mono-Energetic Gamma-Ray (MEGa-Ray) light sources based on Compton scattering between a high-brightness, relativistic electron beam and a highmore » intensity laser pulse produced via chirped-pulse amplification (CPA). A new precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linac designed in collaboration with SLAC will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range via Compton scattering. Based on the success of the previous Thomson-Radiated Extreme X-rays (T-REX) Compton scattering source at LLNL, the source will be used to excite nuclear resonance fluorescence lines in various isotopes; applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. After a brief presentation of successful nuclear resonance fluorescence (NRF) experiments done with T-REX, the new source design, key parameters, and current status are presented.« less

Optimization and verification of image reconstruction for a Compton camera towards application as an on-line monitor for particle therapy

NASA Astrophysics Data System (ADS)

Taya, T.; Kataoka, J.; Kishimoto, A.; Tagawa, L.; Mochizuki, S.; Toshito, T.; Kimura, M.; Nagao, Y.; Kurita, K.; Yamaguchi, M.; Kawachi, N.

2017-07-01

Particle therapy is an advanced cancer therapy that uses a feature known as the Bragg peak, in which particle beams suddenly lose their energy near the end of their range. The Bragg peak enables particle beams to damage tumors effectively. To achieve precise therapy, the demand for accurate and quantitative imaging of the beam irradiation region or dosage during therapy has increased. The most common method of particle range verification is imaging of annihilation gamma rays by positron emission tomography. Not only 511-keV gamma rays but also prompt gamma rays are generated during therapy; therefore, the Compton camera is expected to be used as an on-line monitor for particle therapy, as it can image these gamma rays in real time. Proton therapy, one of the most common particle therapies, uses a proton beam of approximately 200 MeV, which has a range of ~ 25 cm in water. As gamma rays are emitted along the path of the proton beam, quantitative evaluation of the reconstructed images of diffuse sources becomes crucial, but it is far from being fully developed for Compton camera imaging at present. In this study, we first quantitatively evaluated reconstructed Compton camera images of uniformly distributed diffuse sources, and then confirmed that our Compton camera obtained 3 %(1 σ) and 5 %(1 σ) uniformity for line and plane sources, respectively. Based on this quantitative study, we demonstrated on-line gamma imaging during proton irradiation. Through these studies, we show that the Compton camera is suitable for future use as an on-line monitor for particle therapy.

Space Radar Image of Manaus, Brazil

NASA Technical Reports Server (NTRS)

1999-01-01

These two images were created using data from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR). On the left is a false-color image of Manaus, Brazil acquired April 12, 1994, onboard space shuttle Endeavour. In the center of this image is the Solimoes River just west of Manaus before it combines with the Rio Negro to form the Amazon River. The scene is around 8 by 8 kilometers (5 by 5 miles) with north toward the top. The radar image was produced in L-band where red areas correspond to high backscatter at HH polarization, while green areas exhibit high backscatter at HV polarization. Blue areas show low backscatter at VV polarization. The image on the right is a classification map showing the extent of flooding beneath the forest canopy. The classification map was developed by SIR-C/X-SAR science team members at the University of California,Santa Barbara. The map uses the L-HH, L-HV, and L-VV images to classify the radar image into six categories: Red flooded forest Green unflooded tropical rain forest Blue open water, Amazon river Yellow unflooded fields, some floating grasses Gray flooded shrubs Black floating and flooded grasses Data like these help scientists evaluate flood damage on a global scale. Floods are highly episodic and much of the area inundated is often tree-covered. Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.v. (DLR), the major partner in science, operations and data processing of X-SAR.

Textural Analysis and Substrate Classification in the Nearshore Region of Lake Superior Using High-Resolution Multibeam Bathymetry

NASA Astrophysics Data System (ADS)

Dennison, Andrew G.

Classification of the seafloor substrate can be done with a variety of methods. These methods include Visual (dives, drop cameras); mechanical (cores, grab samples); acoustic (statistical analysis of echosounder returns). Acoustic methods offer a more powerful and efficient means of collecting useful information about the bottom type. Due to the nature of an acoustic survey, larger areas can be sampled, and by combining the collected data with visual and mechanical survey methods provide greater confidence in the classification of a mapped region. During a multibeam sonar survey, both bathymetric and backscatter data is collected. It is well documented that the statistical characteristic of a sonar backscatter mosaic is dependent on bottom type. While classifying the bottom-type on the basis on backscatter alone can accurately predict and map bottom-type, i.e a muddy area from a rocky area, it lacks the ability to resolve and capture fine textural details, an important factor in many habitat mapping studies. Statistical processing of high-resolution multibeam data can capture the pertinent details about the bottom-type that are rich in textural information. Further multivariate statistical processing can then isolate characteristic features, and provide the basis for an accurate classification scheme. The development of a new classification method is described here. It is based upon the analysis of textural features in conjunction with ground truth sampling. The processing and classification result of two geologically distinct areas in nearshore regions of Lake Superior; off the Lester River,MN and Amnicon River, WI are presented here, using the Minnesota Supercomputer Institute's Mesabi computing cluster for initial processing. Processed data is then calibrated using ground truth samples to conduct an accuracy assessment of the surveyed areas. From analysis of high-resolution bathymetry data collected at both survey sites is was possible to successfully calculate a series of measures that describe textural information about the lake floor. Further processing suggests that the features calculated capture a significant amount of statistical information about the lake floor terrain as well. Two sources of error, an anomalous heave and refraction error significantly deteriorated the quality of the processed data and resulting validate results. Ground truth samples used to validate the classification methods utilized for both survey sites, however, resulted in accuracy values ranging from 5 -30 percent at the Amnicon River, and between 60-70 percent for the Lester River. The final results suggest that this new processing methodology does adequately capture textural information about the lake floor and does provide an acceptable classification in the absence of significant data quality issues.

Electron Backscatter Diffraction (EBSD) Analysis and U-Pb Geochronology of the Oldest Lunar Zircon: Constraining Early Lunar Differentiation and Dating Impact-Related Deformation

NASA Technical Reports Server (NTRS)

Timms, Nick; Nemchin, Alexander; Grange, Marion; Reddy, Steve; Pidgeon, Bob; Geisler, Thorsten; Meyer, Chuck

2009-01-01

The evolution of the early moon was dominated by two processes (i) crystallization of the Lunar Magma Ocean (LMO) and differentiation of potassium-rare earth element-phosphorous-rich residual magma reservoir referred to as KREEP, and (ii) an intense meteorite bombardment referred to as lunar cataclysm . The exact timing of these processes is disputed, and resolution relies on collection and interpretation of precise age data. This study examines the microstructure and geochronology of zircon from lunar impact breccias collected during the Apollo 17 mission. A large zircon clast within lunar breccia 72215,195 shows sector zoning in optical microscopy, cathodoluminescence (CL) imaging and Raman mapping, and indicates that it was a relict fragment of a much larger magmatic grain. Sensitive high resolution ion microprobe (SHRIMP) U-Pb analysis of the zircon shows that U and Th concentration correlate with sector zoning, with darkest CL domains corresponding with high-U and Th (approx.150 and approx.100 ppm respectively), and the brightest-CL sectors containing approx.30-50 ppm U and approx.10-20 ppm Th. This indicates that variations in optical CL and Raman properties correspond to differential accumulation of alpha-radiation damage in each sector. Electron backscatter diffraction (EBSD) mapping shows that the quality of electron backscatter patterns (band contrast) varies with sector zoning, with the poorest quality patterns obtained from high-U and Th, dark-CL zones. EBSD mapping also reveals a deformation microstructure that is cryptic in optical, CL and Raman imaging. Two orthogonal sets of straight discrete and gradational low-angle boundaries accommodate approx.12 misorientation across the grain. The deformation bands are parallel to the crystallographic {a}-planes of the zircon, have misorientation axes parallel to the c-axis, and are geometrically consistent with formation by dislocation creep associated with <100>{010} slip. The deformation bands are unlike curved morphology of crystal-plastic microstructures in tectonically deformed terrestrial zircon, and geometrically similar to dislocation microstructures reported in experimentally shocked zircon. We interpret these crystal-plastic deformation microstructures to have resulted from a significant impact, either directly from impact shock, or during ductile flow directly following the impact. The deformation bands appear to continue undeflected through the non-indexed, radiation-damaged areas of the grain, which suggests that the orientation variation predates any significant mechanical weakening from radiation damage in the grain, and therefore occurred early in its history.

Assimilation of Global Radar Backscatter and Radiometer Brightness Temperature Observations to Improve Soil Moisture and Land Evaporation Estimates

NASA Technical Reports Server (NTRS)

Lievens, H.; Martens, B.; Verhoest, N. E. C.; Hahn, S.; Reichle, R. H.; Miralles, D. G.

2017-01-01

Active radar backscatter (s?) observations from the Advanced Scatterometer (ASCAT) and passive radiometer brightness temperature (TB) observations from the Soil Moisture Ocean Salinity (SMOS) mission are assimilated either individually or jointly into the Global Land Evaporation Amsterdam Model (GLEAM) to improve its simulations of soil moisture and land evaporation. To enable s? and TB assimilation, GLEAM is coupled to the Water Cloud Model and the L-band Microwave Emission from the Biosphere (L-MEB) model. The innovations, i.e. differences between observations and simulations, are mapped onto the model soil moisture states through an Ensemble Kalman Filter. The validation of surface (0-10 cm) soil moisture simulations over the period 2010-2014 against in situ measurements from the International Soil Moisture Network (ISMN) shows that assimilating s? or TB alone improves the average correlation of seasonal anomalies (Ran) from 0.514 to 0.547 and 0.548, respectively. The joint assimilation further improves Ran to 0.559. Associated enhancements in daily evaporative flux simulations by GLEAM are validated based on measurements from 22 FLUXNET stations. Again, the singular assimilation improves Ran from 0.502 to 0.536 and 0.533, respectively for s? and TB, whereas the best performance is observed for the joint assimilation (Ran = 0.546). These results demonstrate the complementary value of assimilating radar backscatter observations together with brightness temperatures for improving estimates of hydrological variables, as their joint assimilation outperforms the assimilation of each observation type separately.

A synopsis of X-band radar-derived results from New River Inlet, NC (May 2012): Wave transformation, bathymetry, and tidal currents

NASA Astrophysics Data System (ADS)

Honegger, D. A.; Haller, M. C.; Diaz Mendez, G. M.; Pittman, R.; Catalan, P. A.

2012-12-01

Land-based X-band marine radar observations were collected as part of the month-long DARLA-MURI / RIVET-DRI field experiment at New River Inlet, NC in May 2012. Here we present a synopsis of preliminary results utilizing microwave radar backscatter time series collected from an antenna located 400 m inside the inlet mouth and with a footprint spanning 1000 m beyond the ebb shoals. Two crucial factors in the forcing and constraining of nearshore numerical models are accurate bathymetry and offshore variability in the wave field. Image time series of radar backscatter from surface gravity waves can be utilized to infer these parameters over a large swath and during times of poor optical visibility. Presented are radar-derived wavenumber vector maps obtained from the Plant et al. (2008) algorithm and bathymetric estimates as calculated using Holman et al. (JGR, in review). We also evaluate the effects of tidal currents on the wave directions and depth inversion accuracy. In addition, shifts in the average wave breaking patterns at tidal frequencies shed light on depth- (and possibly current-) induced breaking as a function of tide level and tidal current velocity, while shifts over longer timescales imply bedform movement during the course of the experiment. Lastly, lowpass filtered radar image time series of backscatter intensity are shown to identify the structure and propagation of tidal plume fronts and multiscale ebb jets at the offshore shoal boundary.

Ionic liquid-based observation technique for nonconductive materials in the scanning electron microscope: Application to the characterization of a rare earth ore.

PubMed

Brodusch, Nicolas; Waters, Kristian; Demers, Hendrix; Gauvin, Raynald

2014-03-01

A new approach for preparing geological materials is proposed to reduce charging during their characterization in a scanning electron microscope. This technique was applied to a sample of the Nechalacho rare earth deposit, which contains a significant amount of the minerals fergusonite and zircon. Instead of covering the specimen surface with a conductive coating, the sample was immersed in a dilute solution of ionic liquid and then air dried prior to SEM analysis. Imaging at a wide range of accelerating voltages was then possible without evidence of charging when using the in-chamber secondary and backscattered electrons detectors, even at 1 kV. High resolution x-ray and electron backscatter diffraction mapping were successfully obtained at 20 and 5 kV with negligible image drifting and permitted the characterization of the microstructure of the zircon/fergusonite-Y aggregates encased in the matrix minerals. Because of the absence of a conductive layer at the surface of the specimen, the Kikuchi band contrast was improved and the backscatter electron signal increased at both 5 and 20 kV as confirmed by Monte Carlo modeling. These major developments led to an improvement of the spatial resolution and efficiency of the above characterization techniques applied to the rare earth ore and it is expected that they can be applied to other types of ores and minerals. Copyright © 2014 Wiley Periodicals, Inc.

A New Approach for Checking and Complementing CALIPSO Lidar Calibration

NASA Technical Reports Server (NTRS)

Josset, Damien B.; Vaughan, Mark A.; Hu, Yongxiang; Avery, Melody A.; Powell, Kathleen A.; Hunt, William H.; Winker, David M.; Pelon, Jacques; Trepte, Charles R.; Lucker, Patricia L.;

Occurrence and Magnitude of High Reflectance Materials on the Moon

NASA Astrophysics Data System (ADS)

Nuno, R. G.; Boyd, A. K.; Robinson, M. S.

2013-12-01

We utilize a Lunar Reconnaissance Orbiter (LRO) Wide Angle Camera (WAC) 643 nm photometrically normalized (30°, 0°, 30°; i, e, g) reflectance map to investigate the occurrence and origin of high reflectance materials on the Moon. Compositional differences (mainly iron and titanium content) and maturity state (e.g. Copernican crater rays and swirls) are the predominant factors affecting reflectance variations observed on the Moon. Therefore, comparing reflectance values of different regions yields insight into the composition and relative exposure age of lunar materials. But an accurate comparison requires precise reflectance values normalized across every region being investigated. The WAC [1] obtains monthly near-global ground coverage, each month's observations acquired with different lighting conditions. Boyd et al. [2] utilized a geologically homogeneous subset [0°N to 90°N, 146°E to 148°E] of the WAC observations to determine an equation that describes how viewing and lighting angles affect reflectance values. A normalized global reflectance map was generated by applying the local empirical solution globally, with photometric angles derived from the WAC Global Lunar Digital Terrain Model (DTM)(GLD100) [3]. The GLD100 enables accurate correction of reflectance differences caused by local topographic undulations at the scale of 300 meters. We compare reflectance values across the Moon within 80°S to 80°N latitude. The features with the highest reflectance are steep crater walls within Copernican aged craters, such as the walls of Giordano Bruno, which have normalized reflectance values up to 0.35. Near-impact ejecta of some craters have high reflectance values, such as Virtanen (0.22). There are also broad relatively flat features with high reflectance, such as the 900-km Thales-Compton region (0.24) and the 600-km extent of Anaxagoras (Copernican age) ejecta (0.20). Since the interior of Anaxagoras contains occurrences of pure anorthosite [4], the high reflectance of its ray system may be due to both composition and maturity. Some relatively small isolated features exhibit high reflectance, such as the Compton-Belkovich Volcanic Complex (0.24) and rilles in the floor of Compton crater (0.27). Features associated with pure anorthosite [4] are also found to have high reflectance values, such as occurrences in Mare Orientale (0.22). Since the photometric normalization accounted for topography up to the 300-m horizontal spatial scale, uncertainties remain for steep crater walls. We are currently reducing these uncertainties for selected craters with high resolution (15 meter baseline) stereo-based NAC DTMs. References: [1] Robinson et al. (2010), Space Sci. Rev. [2] Boyd et al. (2013) AGU, this conference. [3] Scholten et al. (2012) JGR. [4] Ohtake et al. (2009) Nature.

Multiwavelength Comparison of Modeled and Measured Remote Tropospheric Aerosol Backscatter Over Pacific Ocean

NASA Technical Reports Server (NTRS)

Cutten, D. R.; Pueschel, R. F.; Srivastava, V.; Clarke, A. D.; Rothermel, J.; Spinhirne, J. D.; Menzies, R. T.

1996-01-01

Aerosol concentrations and size distributions in the middle and upper troposphere over the remote Pacific Ocean were measured with a forward scattering spectrometer probe (FSSP) on the NASA DC-8 aircraft during NASA's Global Backscatter Experiment (GLOBE) in May-June 1990. The FSSP size channels were recalibrated based on refractive index estimates from flight-level aerosol volatility measurements with a collocated laser optical particle counter (LOPC). The recalibrated FSSP size distributions were averaged over 100-s intervals, fitted with lo-normal distributions and used to calculate aerosol backscatter coefficients at selected wavelengths. The FSSP-derived backscatter estimates were averaged over 300-s intervals to reduce large random fluctuations. The smoothed FSSP aerosol backscatter coefficients were then compared with LOPC-derived backscatter values and with backscatter measured at or near flight level from four lidar systems operating at 0.53, 1.06, 9.11, 9.25, and 10.59 micrometers. Agreement between FSSP-derived and lidar-measured backscatter was generally best at flight level in homogeneous aerosol fields and at high backscatter values. FSSP data often underestimated low backscatter values especially at the longer wavelengths due to poor counting statistics for larger particles (greater than 0.8 micrometers diameter) that usually dominate aerosol backscatter at these wavelengths. FSSP data also underestimated backscatter at shorter wavelengths when particles smaller than the FSSP lower cutoff diameter (0.35 micrometers) made significant contributions to the total backscatter.

Picosecond, tunable, high-brightness hard x-ray inverse Compton source at Duke storage ring

NASA Astrophysics Data System (ADS)

Litvinenko, Vladimir N.; Wu, Ying; Burnham, Bentley; Barnett, Genevieve A.; Madey, John M. J.

1995-09-01

We suggest a state-of-the art x-ray source using a compact electron storage ring with modest energy (less than 1 GeV) and a high power mm-wave as an undulator. A source of this type has x-ray energies and brightness comparable with third generation synchrotron light sources while it can be very compact and fit in a small university or industrial laboratory or hospital. We propose to operate an isochronous mm-wave FEL and a hard x-ray inverse Compton source at the Duke storage ring to test this concept. Resonant FEL conditions for the mm- wave will be provided by the off-axis interaction with an electromagnetic wave. A special optical resonator with holes for the e-beam is proposed for pumping a hard x-ray inverse Compton source with very high brightness. Simulation results of mm-wave FEL operation of the Duke storage ring are discussed. Expected performance of mm-wave FEL and hard x-ray inverse Compton source are presented.

A method for determination mass absorption coefficient of gamma rays by Compton scattering.

PubMed

El Abd, A

2014-12-01

A method was proposed for determination mass absorption coefficient of gamma rays for compounds, alloys and mixtures. It is based on simulating interaction processes of gamma rays with target elements having atomic numbers from Z=1 to Z=92 using the MCSHAPE software. Intensities of Compton scattered gamma rays at saturation thicknesses and at a scattering angle of 90° were calculated for incident gamma rays of different energies. The obtained results showed that the intensity of Compton scattered gamma rays at saturations and mass absorption coefficients can be described by mathematical formulas. These were used to determine mass absorption coefficients for compound, alloys and mixtures with the knowledge of their Compton scattered intensities. The method was tested by calculating mass absorption coefficients for some compounds, alloys and mixtures. There is a good agreement between obtained results and calculated ones using WinXom software. The advantages and limitations of the method were discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

BOW TIES IN THE SKY. I. THE ANGULAR STRUCTURE OF INVERSE COMPTON GAMMA-RAY HALOS IN THE FERMI SKY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Broderick, Avery E.; Shalaby, Mohamad; Tiede, Paul

2016-12-01

Extended inverse Compton halos are generally anticipated around extragalactic sources of gamma rays with energies above 100 GeV. These result from inverse Compton scattered cosmic microwave background photons by a population of high-energy electron/positron pairs produced by the annihilation of the high-energy gamma rays on the infrared background. Despite the observed attenuation of the high-energy gamma rays, the halo emission has yet to be directly detected. Here, we demonstrate that in most cases these halos are expected to be highly anisotropic, distributing the upscattered gamma rays along axes defined either by the radio jets of the sources or oriented perpendicularmore » to a global magnetic field. We present a pedagogical derivation of the angular structure in the inverse Compton halo and provide an analytic formalism that facilitates the generation of mock images. We discuss exploiting this fact for the purpose of detecting gamma-ray halos in a set of companion papers.« less

Joint refinement model for the spin resolved one-electron reduced density matrix of YTiO3 using magnetic structure factors and magnetic Compton profiles data.

PubMed

Gueddida, Saber; Yan, Zeyin; Kibalin, Iurii; Voufack, Ariste Bolivard; Claiser, Nicolas; Souhassou, Mohamed; Lecomte, Claude; Gillon, Béatrice; Gillet, Jean-Michel

2018-04-28

In this paper, we propose a simple cluster model with limited basis sets to reproduce the unpaired electron distributions in a YTiO 3 ferromagnetic crystal. The spin-resolved one-electron-reduced density matrix is reconstructed simultaneously from theoretical magnetic structure factors and directional magnetic Compton profiles using our joint refinement algorithm. This algorithm is guided by the rescaling of basis functions and the adjustment of the spin population matrix. The resulting spin electron density in both position and momentum spaces from the joint refinement model is in agreement with theoretical and experimental results. Benefits brought from magnetic Compton profiles to the entire spin density matrix are illustrated. We studied the magnetic properties of the YTiO 3 crystal along the Ti-O 1 -Ti bonding. We found that the basis functions are mostly rescaled by means of magnetic Compton profiles, while the molecular occupation numbers are mainly modified by the magnetic structure factors.

Rapid Compton-thick/Compton-thin Transitions in the Seyfert 2 Galaxy NGC 1365

NASA Technical Reports Server (NTRS)

Risaliti, G.; Elvis, M.; Fabbiano, G.; Baldi, A.; Zezas, A.

2006-01-01

We present multiple Chandra and XMM-Newton observations of the type 1.8 Seyfert galaxy NGC 1365, which shows the most dramatic X-ray spectral changes observed so far in an active galactic nucleus: the source switched from reflection-dominated to transmission-dominated and back in just 6 weeks. During this time the soft thermal component, arising from a approx. 1 kpc region around the center, remained constant. The reflection component is constant at all timescales, and its high flux relative to the primary component implies the presence of thick gas covering a large fraction of the solid angle. The presence of this gas, and the fast variability timescale, suggest that the Compton-thick to Compton-thin change is due to variation in the line-of-sight absorber rather than to extreme intrinsic emission variability. We discuss a structure of the circumuclear absorber/reflector that can explain the observed X-ray spectral and temporal properties.

Feasibility Study of Compton Cameras for X-ray Fluorescence Computed Tomography with Humans

PubMed Central

Vernekohl, Don; Ahmad, Moiz; Chinn, Garry; Xing, Lei

2017-01-01

X-ray fluorescence imaging is a promising imaging technique able to depict the spatial distributions of low amounts of molecular agents in vivo. Currently, the translation of the technique to preclinical and clinical applications is hindered by long scanning times as objects are scanned with flux-limited narrow pencil beams. The study presents a novel imaging approach combining x-ray fluorescence imaging with Compton imaging. Compton cameras leverage the imaging performance of XFCT and abolish the need of pencil beam excitation. The study examines the potential of this new imaging approach on the base of Monte-Carlo simulations. In the work, it is first presented that the particular option of slice/fan-beam x-ray excitation has advantages in image reconstruction in regard of processing time and image quality compared to traditional volumetric Compton imaging. In a second experiment, the feasibility of the approach for clinical applications with tracer agents made from gold nano-particles is examined in a simulated lung scan scenario. The high energy of characteristic x-ray photons from gold is advantageous for deep tissue penetration and has lower angular blurring in the Compton camera. It is found that Doppler broadening in the first detector stage of the Compton camera adds the largest contribution on the angular blurring; physically limiting the spatial resolution. Following the analysis of the results from the spatial resolution test, resolutions in the order of one centimeter are achievable with the approach in the center of the lung. The concept of Compton imaging allows to distinguish to some extend between scattered photons and x-ray fluorescent photons based on their difference in emission position. The results predict that molecular sensitivities down to 240 pM/l for 5 mm diameter lesions at 15 mGy for 50 nm diameter gold nano-particles are achievable. A 45-fold speed up time for data acquisition compared to traditional pencil beam XFCT could be achieved for lung imaging on cost of a small sensitivity decrease. PMID:27845933

Comparison of Modeled Backscatter using Measured Aerosol Microphysics with Focused CW Lidar Data over Pacific

NASA Technical Reports Server (NTRS)

Srivastava, Vandana; Clarke, Antony D.; Jarzembski, Maurice A.; Rothermel, Jeffry

1997-01-01

During NASA's GLObal Backscatter Experiment (GLOBE) II flight mission over the Pacific Ocean in May-June 1990, extensive aerosol backscatter data sets from two continuous wave, focused CO2 Doppler lidars and an aerosol microphysics data set from a laser optical particle counter (LOPC) were obtained. Changes in aerosol loading in various air masses with associated changes in chemical composition, from sulfuric acid and sulfates to dustlike crustal material, significantly affected aerosol backscatter, causing variation of about 3 to 4 orders of magnitude. Some of the significant backscatter features encountered in different air masses were the low backscatter in subtropical air with even lower values in the tropics near the Intertropical Convergence Zone (ITCZ), highly variable backscatter in the ITCZ, mid-tropospheric aerosol backscatter background mode, and high backscatter in an Asian dust plume off the Japanese coast. Differences in aerosol composition and backscatter for northern and southern hemisphere also were observed. Using the LOPC measurements of physical and chemical aerosol properties, we determined the complex refractive index from three different aerosol mixture models to calculate backscatter. These values provided a well-defined envelope of modeled backscatter for various atmospheric conditions, giving good agreement with the lidar data over a horizontal sampling of approximately 18000 km in the mid-troposphere.

High-Resolution Seafloor Mapping at A Deep-Sea Methane Seep Field with an Autonomous Underwater Vehicle

NASA Astrophysics Data System (ADS)

Skarke, A. D.

2017-12-01

A growing body of research indicates that points of seafloor gas emission, known as cold-seeps, are a common feature along many continental margins. Results from recent exploration efforts show that benthic environments at cold-seeps are characterized by extensive authigenic carbonate crusts and complex chemosynthetic communities. The seafloor morphology and geophysical properties of these locations are heterogeneous and relatively complex due to the three-dimensional structure created by carbonate buildups and dense bivalve beds. Seeps are often found clustered and the spatial extent of associated seafloor crusts and beds can reach multiple square kilometers. Here, the results of a 1.25 km2 autonomous underwater vehicle (AUV) survey of a deep-sea methane seep field with 13 vents, at a nominal depth of 1400 m, located near Veatch Canyon on the US Atlantic margin are presented. Multibeam sonar, sidescan sonar, and a sub bottom profiler on the AUV were used to make high-resolution observations of seafloor bathymetry (resolution 1m2) as well as water column, seafloor, and subsurface acoustic backscatter intensity. Additionally, a downward oriented camera was used to collect seafloor imagery coincident with acoustic observations at select locations. Acoustic results indicated the location of discrete gas plumes as well as a continuous area of elevated seafloor roughness and backscatter intensity consistent with the presence of large scale authigenic rock outcrops and extensive mussel beds, which were visually confirmed with camera imagery. Additionally, a linear area of particularly elevated seafloor roughness and acoustic backscatter intensity that lies sub-parallel to an adjacent ridge was interpreted to be controlled by underlying geologic processes such as soft sediment faulting. Automated analysis of camera imagery and coincident acoustic backscatter and bathymetry data as well as derivative metrics (e.g. slope and rugosity) was used to segment and classify bed type (carbonate rock, sediment, mussel bed), yielding insight into geologic and ecological processes within the seep field study area.

Inversion of the conical Radon transform with vertices on a surface of revolution arising in an application of a Compton camera

NASA Astrophysics Data System (ADS)

Moon, Sunghwan

2017-06-01

A Compton camera has been introduced for use in single photon emission computed tomography to improve the low efficiency of a conventional gamma camera. In general, a Compton camera brings about the conical Radon transform. Here we consider a conical Radon transform with the vertices on a rotation symmetric set with respect to a coordinate axis. We show that this conical Radon transform can be decomposed into two transforms: the spherical sectional transform and the weighted fan beam transform. After finding inversion formulas for these two transforms, we provide an inversion formula for the conical Radon transform.

Spin-dependent sum rules connecting real and virtual Compton scattering verified

NASA Astrophysics Data System (ADS)

Lensky, Vadim; Pascalutsa, Vladimir; Vanderhaeghen, Marc; Kao, Chung Wen

2017-04-01

We present a detailed derivation of the two sum rules relating the spin polarizabilities measured in real, virtual, and doubly virtual Compton scattering. For example, the polarizability δL T , accessed in inclusive electron scattering, is related to the spin polarizability γE 1 E 1 and the slope of generalized polarizabilities P(M 1 ,M 1 )1-P(L 1 ,L 1 )1 , measured in, respectively, the real and the virtual Compton scattering. We verify these sum rules in different variants of chiral perturbation theory, discuss their empirical verification for the proton, and prospect their use in studies of the nucleon spin structure.

A new length scale for quantum gravity: A resolution of the black hole information loss paradox

NASA Astrophysics Data System (ADS)

Singh, Tejinder P.

We show why and how Compton wavelength and Schwarzschild radius should be combined into one single new length scale, which we call the Compton-Schwarzschild length. Doing so offers a resolution of the black hole information loss paradox, and suggests Planck mass remnant black holes as candidates for dark matter. It also compels us to introduce torsion, and identify the Dirac field with a complex torsion field. Dirac equation and Einstein equations, are shown to be mutually dual limiting cases of an underlying gravitation theory which involves the Compton-Schwarzschild length scale, and includes a complex torsion field.

Intershell correlations in Compton photon scattering by an atom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopersky, Alexey N.; Nadolinsky, Alexey M.; Novikov, Sergey A.

The role of the intershell correlation effect is theoretically investigated using the example of the Ne atom in nonresonance Compton high-energy x-ray photon scattering by a free atom. The calculation results qualitatively reproduce the same results in the formalism of the generalized oscillator strength and the random phase approximation with exchange for the Compton photon and electron scattering by an atom; when the incident photon energy is 11 keV and the scattering angle is 90 deg., they correspond well with the results of the synchrotron experiment presented in the work by Jung et al. [Phys. Rev. Lett. 81, 1596 (1998)].

Gravitation and Special Relativity from Compton Wave Interactions at the Planck Scale: An Algorithmic Approach

NASA Technical Reports Server (NTRS)

Blackwell, William C., Jr.

2004-01-01

In this paper space is modeled as a lattice of Compton wave oscillators (CWOs) of near- Planck size. It is shown that gravitation and special relativity emerge from the interaction between particles Compton waves. To develop this CWO model an algorithmic approach was taken, incorporating simple rules of interaction at the Planck-scale developed using well known physical laws. This technique naturally leads to Newton s law of gravitation and a new form of doubly special relativity. The model is in apparent agreement with the holographic principle, and it predicts a cutoff energy for ultrahigh-energy cosmic rays that is consistent with observational data.

A New Comptonization Model for Weakly Magnetized Accreting NS LMXBs

NASA Astrophysics Data System (ADS)

Paizis, A.; Farinelli, R.; Titarchuk, L.; Frontera, F.; Cocchi, M.; Ferrigno, C.

2009-05-01

We have developed a new Comptonization model to propose, for the first time, a self consistent physical interpretation of the complex spectral evolution seen in NS LMXBs. The model and its application to LMXBs are presented and compared to the Simbol-X expected capabilities.

BOREAS RSS-15 SIR-C and Landsat TM Biomass and Landcover Maps of the NSA

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); Ranson, K. Jon

2000-01-01

As part of BOREAS, the RSS-15 team conducted an investigation using SIR-C, X-SAR, and Landsat TM data for estimating total above-ground dry biomass for the SSA and NSA modeling grids and component biomass for the SSA. Relationships of backscatter to total biomass and total biomass to foliage, branch, and bole biomass were used to estimate biomass density across the landscape. The procedure involved image classification with SAR and Landsat TM data and development of simple mapping techniques using combinations of SAR channels. For the SSA, the SIR-C data used were acquired on 06-Oct-1994, and the Landsat TM data used were acquired on 02-Sep-1995. The maps of the NSA were developed from SIR-C data acquired on 13-Apr-1994. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Land Cover Monitoring for Water Resources Management in Angola

NASA Astrophysics Data System (ADS)

Miguel, Irina; Navarro, Ana; Rolim, Joao; Catalao, Joao; Silva, Joel; Painho, Marco; Vekerdy, Zoltan

2016-08-01

The aim of this paper is to assess the impact of improved temporal resolution and multi-source satellite data (SAR and optical) on land cover mapping and monitoring for efficient water resources management. For that purpose, we developed an integrated approach based on image classification and on NDVI and SAR backscattering (VV and VH) time series for land cover mapping and crop's irrigation requirements computation. We analysed 28 SPOT-5 Take-5 images with high temporal revisiting time (5 days), 9 Sentinel-1 dual polarization GRD images and in-situ data acquired during the crop growing season. Results show that the combination of images from different sources provides the best information to map agricultural areas. The increase of the images temporal resolution allows the improvement of the estimation of the crop parameters, and then, to calculate of the crop's irrigation requirements. However, this aspect was not fully exploited due to the lack of EO data for the complete growing season.

Assessing backscatter change due to backscatter gradient over the Greenland ice sheet using Envisat and SARAL altimetry

NASA Astrophysics Data System (ADS)

Su, Xiaoli; Luo, Zhicai; Zhou, Zebing

2018-06-01

Knowledge of backscatter change is important to accurately retrieve elevation change time series from satellite radar altimetry over continental ice sheets. Previously, backscatter coefficients generated in two cases, namely with and without accounting for backscatter gradient (BG), are used. However, the difference between backscatter time series obtained separately in these two cases and its impact on retrieving elevation change are not well known. Here we first compare the mean profiles of the Ku and Ka band backscatter over the Greenland ice sheet (GrIS), with results illustrating that the Ku-band backscatter is 3 ∼ 5 dB larger than that of the Ka band. We then conduct statistic analysis about time series of backscatter formed separately in the above two cases for both Ku and Ka bands over two regions in the GrIS. It is found that the standard deviation of backscatter time series becomes slightly smaller after removing the BG effect, which suggests that the method for the BG correction is effective. Furthermore, the impact on elevation change from backscatter change due to the BG effect is separately assessed for both Ku and Ka bands over the GrIS. We conclude that Ka band altimetry would benefit from a BG induced backscatter analysis (∼10% over region 2). This study may provide a reference to form backscatter time series towards refining elevation change time series from satellite radar altimetry over ice sheets using repeat-track analysis.

Exploring the Dynamics of a Quantum-Mechanical Compton Generator

NASA Astrophysics Data System (ADS)

Kandes, Martin; Carretero, Ricardo

2017-01-01

In 1913, when American physicist Arthur Compton was an undergraduate, he invented a simple way to measure the rotation rate of the Earth with a tabletop-sized experiment. The experiment consisted of a large diameter circular ring of thin glass tubing filled with water and oil droplets. After placing the ring in a plane perpendicular to the surface of the Earth and allowing the fluid mixture of oil and water to come to rest, he then abruptly rotated the ring, flipping it 180 degrees about an axis passing through its own plane. The result of the experiment was that the water acquired a measurable drift velocity due to the Coriolis effect arising from the daily rotation of the Earth about its own axis. Compton measured this induced drift velocity by observing the motion of the oil droplets in the water with a microscope. This device, which is now named after him, is known as a Compton generator. The fundamental research objective of this project is to explore the dynamics of a quantum-mechanical analogue to the classical Compton generator experiment through the use of numerical simulations. We present our preliminary results on this system and the future direction of the project. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant Number ACI-1053575.

On the Compton scattering redistribution function in plasma

NASA Astrophysics Data System (ADS)

Madej, J.; Różańska, A.; Majczyna, A.; Należyty, M.

2017-08-01

Compton scattering is the dominant opacity source in hot neutron stars, accretion discs around black holes and hot coronae. We collected here a set of numerical expressions of the Compton scattering redistribution functions (RFs) for unpolarized radiation, which are more exact than the widely used Kompaneets equation. The principal aim of this paper is the presentation of the RF by Guilbert, which is corrected for the computational errors in the original paper. This corrected RF was used in the series of papers on model atmosphere computations of hot neutron stars. We have also organized four existing algorithms for the RF computations into a unified form ready to use in radiative transfer and model atmosphere codes. The exact method by Nagirner & Poutanen was numerically compared to all other algorithms in a very wide spectral range from hard X-rays to radio waves. Sample computations of the Compton scattering RFs in thermal plasma were done for temperatures corresponding to the atmospheres of bursting neutron stars and hot intergalactic medium. Our formulae are also useful to study the Compton scattering of unpolarized microwave background radiation in hot intracluster gas and the Sunyaev-Zeldovich effect. We conclude that the formulae by Guilbert and the exact quantum mechanical formulae yield practically the same RFs for gas temperatures relevant to the atmospheres of X-ray bursting neutron stars, T ≤ 108 K.

Spectral Monitoring of NGC 1365: Nucleus and Variable ULX

NASA Technical Reports Server (NTRS)

Mushotzky, Richard (Technical Monitor); Fabbiano, G.

2004-01-01

A letter has been submitted to ApJ, and is in the final stages of revision on the spectral variability of the nuclear source. We presented multiple Chandra and XMM-Newton observations of the Seyfert Galaxy NGC 1365, which shows the most dramatic X-ray spectral changes observed so far in an AGN: the source switched from reflection dominated to Compton- thin and back in just 6 weeks. During this time the soft thermal component, arising from a 1-kpc region around the center, remained constant. The reflection component is constant at all timescales, and its flux is a fraction of 5% or higher of the direct 2-10 keV emission, implying the presence of thick gas covering a big fraction of the solid angle. The presence of this gas, and the hst variability time scale, suggest that the Compton-thick to Compton thin change is due to variation in the line-of-sight absorber, rather than to extreme intrinsic emission variability. We discuss a structure of the circumnuclear absorbed reflector which can explain the observed X-ray spectral and temporal properties. But these important results come only from scratching the surface of the data, since we did not need any detailed spectral analysis to distinguish between the Compton thick and Compton thin states of the source, the difference in both spectral shape and flux being huge.

The first demonstration of the concept of "narrow-FOV Si/CdTe semiconductor Compton camera"

NASA Astrophysics Data System (ADS)

Ichinohe, Yuto; Uchida, Yuusuke; Watanabe, Shin; Edahiro, Ikumi; Hayashi, Katsuhiro; Kawano, Takafumi; Ohno, Masanori; Ohta, Masayuki; Takeda, Shin`ichiro; Fukazawa, Yasushi; Katsuragawa, Miho; Nakazawa, Kazuhiro; Odaka, Hirokazu; Tajima, Hiroyasu; Takahashi, Hiromitsu; Takahashi, Tadayuki; Yuasa, Takayuki

2016-01-01

The Soft Gamma-ray Detector (SGD), to be deployed on board the ASTRO-H satellite, has been developed to provide the highest sensitivity observations of celestial sources in the energy band of 60-600 keV by employing a detector concept which uses a Compton camera whose field-of-view is restricted by a BGO shield to a few degree (narrow-FOV Compton camera). In this concept, the background from outside the FOV can be heavily suppressed by constraining the incident direction of the gamma ray reconstructed by the Compton camera to be consistent with the narrow FOV. We, for the first time, demonstrate the validity of the concept using background data taken during the thermal vacuum test and the low-temperature environment test of the flight model of SGD on ground. We show that the measured background level is suppressed to less than 10% by combining the event rejection using the anti-coincidence trigger of the active BGO shield and by using Compton event reconstruction techniques. More than 75% of the signals from the field-of-view are retained against the background rejection, which clearly demonstrates the improvement of signal-to-noise ratio. The estimated effective area of 22.8 cm2 meets the mission requirement even though not all of the operational parameters of the instrument have been fully optimized yet.

RXTE Observation of Cygnus X-1: III. Implications for Compton Corona and ADAF Models. Report 3; Implications for Compton Corona and ADAF Models

NASA Technical Reports Server (NTRS)

Nowak, Michael A.; Wilms, Joern; Vaughan, Brian A.; Dove, James B.; Begelman, Mitchell C.

1999-01-01

We have recently shown that a 'sphere + disk' geometry Compton corona model provides a good description of Rossi X-ray Timing Explorer (RXTE) observations of the hard/low state of Cygnus X-1. Separately, we have analyzed the temporal data provided by RXTE. In this paper we consider the implications of this timing analysis for our best-fit 'sphere + disk' Comptonization models. We focus our attention on the observed Fourier frequency-dependent time delays between hard and soft photons. We consider whether the observed time delays are: created in the disk but are merely reprocessed by the corona; created by differences between the hard and soft photon diffusion times in coronae with extremely large radii; or are due to 'propagation' of disturbances through the corona. We find that the time delays are most likely created directly within the corona; however, it is currently uncertain which specific model is the most likely explanation. Models that posit a large coronal radius [or equivalently, a large Advection Dominated Accretion Flow (ADAF) region] do not fully address all the details of the observed spectrum. The Compton corona models that do address the full spectrum do not contain dynamical information. We show, however, that simple phenomenological propagation models for the observed time delays for these latter models imply extremely slow characteristic propagation speeds within the coronal region.

Prediction of Backscatter and Emissivity of Snow at Millimeter Wavelengths.

DTIC Science & Technology

1980-01-01

LIST OF FIGURES Figure Title Page C-I General Area Map 204 C-2 Location of Alpena National Weather 205 Service Station C-3 Photographs of Site E 206 C-4...February 5, 6, 7, 1979 were ob- tained from National Weather Service, Alpena Station and included in Tables C-9 through C-12. Figure C-2 shows the...relative position * 1 of the sites and the Alpena National Weather Service Station. 203 I 0 1 s LAKE HURON ROGERS CITY 20 0 5 10 MILES 0 C HEBOYGAN NORTH

Microstructural investigations of 0.2% carbon content steel

NASA Astrophysics Data System (ADS)

Tollabimazraehno, Sajjad; Hingerl, Kurt

2011-10-01

The effect of thermal annealing to get different phases on low carbon steel was investigated. Steel sheets (0.2 wt. % C) of 900 μm thickness were heat treated to produce different structures. All the samples have the same starting point, transformation to coarse austenite at 900 degree Celsius. The nano indentation results revealed that samples have different hadness. By making conventional SEM micrographs, focus ion beam maps, and Electron backscatter diffraction (EBSD) the microstructural development and grain boundary variation of transformed phases martensite, biainte, tempered martensite and different combination of these phases were studied.

Imaging, Mapping and Monitoring Environmental Radionuclide Transport Using Compton-Geometry Gamma Camera

NASA Astrophysics Data System (ADS)

Bridge, J. W.; Dormand, J.; Cooper, J.; Judson, D.; Boston, A. J.; Bankhead, M.; Onda, Y.

2014-12-01

The legacy to-date of the nuclear disaster at Fukushima Dai-ichi, Japan, has emphasised the fundamental importance of high quality radiation measurements in soils and plant systems. Current-generation radiometers based on coded-aperture collimation are limited in their ability to locate sources of radiation in three dimensions, and require a relatively long measurement time due to the poor efficiency of the collimation system. The quality of data they can provide to support biogeochemical process models in such systems is therefore often compromised. In this work we report proof-of-concept experiments demonstrating the potential of an alternative approach in the measurement of environmentally-important radionuclides (in particular 137Cs) in quartz sand and soils from the Fukushima exclusion zone. Compton-geometry imaging radiometers harness the scattering of incident radiation between two detectors to yield significant improvements in detection efficiency, energy resolution and spatial location of radioactive sources in a 180° field of view. To our knowledge we are reporting its first application to environmentally-relevant systems at low activity, dispersed sources, with significant background radiation and, crucially, movement over time. We are using a simple laboratory column setup to conduct one-dimensional transport experiments for 139Ce and 137Cs in quartz sand and in homogenized repacked Fukushima soils. Polypropylene columns 15 cm length with internal diameter 1.6 cm were filled with sand or soil and saturated slowly with tracer-free aqueous solutions. Radionuclides were introduced as 2mL pulses (step-up step-down) at the column inlet. Data were collected continuously throughout the transport experiment and then binned into sequential time intervals to resolve the total activity in the column and its progressive movement through the sand/soil. The objective of this proof-of-concept work is to establish detection limits, optimise image reconstruction algorithms, and develop a novel approach to time-lapse quantification of radionuclide dynamics in the soil-plant system. The aim is to underpin the development of a new generation of Compton radiometers equipped to provide high resolution, dynamic measurements of radionuclides in terrestrial biogeochemical environments.

Test of Compton camera components for prompt gamma imaging at the ELBE bremsstrahlung beam

NASA Astrophysics Data System (ADS)

Hueso-González, F.; Golnik, C.; Berthel, M.; Dreyer, A.; Enghardt, W.; Fiedler, F.; Heidel, K.; Kormoll, T.; Rohling, H.; Schöne, S.; Schwengner, R.; Wagner, A.; Pausch, G.

2014-05-01

In the context of ion beam therapy, particle range verification is a major challenge for the quality assurance of the treatment. One approach is the measurement of the prompt gamma rays resulting from the tissue irradiation. A Compton camera based on several position sensitive gamma ray detectors, together with an imaging algorithm, is expected to reconstruct the prompt gamma ray emission density map, which is correlated with the dose distribution. At OncoRay and Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a Compton camera setup is being developed consisting of two scatter planes: two CdZnTe (CZT) cross strip detectors, and an absorber consisting of one Lu2SiO5 (LSO) block detector. The data acquisition is based on VME electronics and handled by software developed on the ROOT framework. The setup has been tested at the linear electron accelerator ELBE at HZDR, which is used in this experiment to produce bunched bremsstrahlung photons with up to 12.5 MeV energy and a repetition rate of 13 MHz. Their spectrum has similarities with the shape expected from prompt gamma rays in the clinical environment, and the flux is also bunched with the accelerator frequency. The charge sharing effect of the CZT detector is studied qualitatively for different energy ranges. The LSO detector pixel discrimination resolution is analyzed and it shows a trend to improve for high energy depositions. The time correlation between the pulsed prompt photons and the measured detector signals, to be used for background suppression, exhibits a time resolution of 3 ns FWHM for the CZT detector and of 2 ns for the LSO detector. A time walk correction and pixel-wise calibration is applied for the LSO detector, whose resolution improves up to 630 ps. In conclusion, the detector setup is suitable for time-resolved background suppression in pulsed clinical particle accelerators. Ongoing tasks are the quantitative comparison with simulations and the test of imaging algorithms. Experiments at proton accelerators have also been performed and are currently under analysis.

Seabed deposits classification at the Precious Stone Mountain hydrothermal field using MultiBeam sonar data

NASA Astrophysics Data System (ADS)

Tao, C.; Zhang, G.; Li, H.; Zhou, J.; Liu, W.; Deng, X.; Chen, S.

2013-12-01

The seabed deposits type and distribution are very complex at the hydrothermal field. In this paper, we provided an approach to study the seabed deposits classification at the Precious Stone Mountain hydrothermal field (PSMHF) using MultiBeam sonar data (Figure 1). The PSMHF was found in the Galapogas microplate at the Leg 3 of the Chinese COMRA 21st Cruise. Using this approach, the seabed deposits at the PSMHF are mainly classified into three types, which are rock, breccia and sediment, respectively. We can find the distribution of the three types of seabed deposits according to the sonar back-scattering data. The rocks are mostly distributed around the hydrothermal vent. The breccia are located at the foot of the vent. Most sediments are distributed at the southwest to the vent due to bottom current. Combining with seabed video, TV-Grab sample and the backscatter data, we draw the map of the seabed deposits distribution at the PSMHF (Figure 2). Figure 1 The flow chart of the seabed deposits classification approach Figure 2 The seabed deposits distribution of the PSMHF

Probing amplitude, phase, and polarization of microwave field distributions in real time

NASA Astrophysics Data System (ADS)

King, R. J.; Yen, Y. H.

1981-11-01

A coherent (homodyne) detection system is used to map field distributions in real time. A key feature is the use of an electrically modulated (10-kHz) dipole scatterer which is also mechanically spun (150 Hz) to create an amplitude- and phase-modulated backscattered field. The system is monostatic. The backscattered field is coherently detected by mixing with the CW reference. A phase-insensitive detector is used, comprised of two balanced mixers which are fed in quadrature phase by one of the RF inputs followed by a phase quadrature combiner. The resulting amplitude and phase of the 10-kHz output are proportional to the square of the RF field component along the instantaneous axis of the spinning dipole. Both are measured simultaneously and independently in real time. From these, the polarization properties can also be found, so the field is uniquely described. The system's application to scanning the E-field transmitted through lossy, nonhomogeneous and anisotropic media (e.g., wood) is demonstrated. Other applications besides nondestructive testing are microwave vector holography, near-field antenna measurements, and inverse scattering.

Reconstruction of Laser-Induced Surface Topography from Electron Backscatter Diffraction Patterns.

PubMed

Callahan, Patrick G; Echlin, McLean P; Pollock, Tresa M; De Graef, Marc

2017-08-01

We demonstrate that the surface topography of a sample can be reconstructed from electron backscatter diffraction (EBSD) patterns collected with a commercial EBSD system. This technique combines the location of the maximum background intensity with a correction from Monte Carlo simulations to determine the local surface normals at each point in an EBSD scan. A surface height map is then reconstructed from the local surface normals. In this study, a Ni sample was machined with a femtosecond laser, which causes the formation of a laser-induced periodic surface structure (LIPSS). The topography of the LIPSS was analyzed using atomic force microscopy (AFM) and reconstructions from EBSD patterns collected at 5 and 20 kV. The LIPSS consisted of a combination of low frequency waviness due to curtaining and high frequency ridges. The morphology of the reconstructed low frequency waviness and high frequency ridges matched the AFM data. The reconstruction technique does not require any modification to existing EBSD systems and so can be particularly useful for measuring topography and its evolution during in situ experiments.

Time Resolved 3-D Mapping of Atmospheric Aerosols and Clouds During the Recent ARM Water Vapor IOP

NASA Technical Reports Server (NTRS)

Schwemmer, Geary; Miller, David; Wilkerson, Thomas; Andrus, Ionio; Starr, David OC. (Technical Monitor)

2001-01-01

The HARLIE lidar was deployed at the ARM SGP site in north central Oklahoma and recorded over 100 hours of data on 16 days between 17 September and 6 October 2000 during the recent Water Vapor Intensive Operating Period (IOP). Placed in a ground-based trailer for upward looking scanning measurements of clouds and aerosols, HARLIE provided a unique record of time-resolved atmospheric backscatter at 1 micron wavelength. The conical scanning lidar images atmospheric backscatter along the surface of an inverted 90 degree (full angle) cone up to an altitude of 20 km. 360 degree scans having spatial resolutions of 20 meters in the vertical and 1 degree in azimuth were obtained every 36 seconds. Various boundary layer and cloud parameters are derived from the lidar data, as well as atmospheric wind vectors where there is Sufficiently resolved structure that can be traced moving through the surface described by the scanning laser beam. Comparison of HARLIE measured winds with radiosonde measured winds validates the accuracy of this new technique for remotely measuring atmospheric winds without Doppler information.

Rocking curve imaging of high quality sapphire crystals in backscattering geometry

DOE PAGES

Jafari, A.; European Synchrotron Radiation Facility; Univ. of Liege,; ...

2017-01-23

Here, we report on the characterization of high quality sapphire single crystals suitable for high-resolution X-ray optics at high energy. Investigations using rocking curve imaging reveal the crystals to be of uniformly good quality at the level of ~10 -4 in lattice parameter variations, deltad/d. But, investigations using backscattering rocking curve imaging with lattice spacing resolution of deltad/d ~ 5.10 -8 shows very diverse quality maps for all crystals. Our results highlight nearly ideal areas with edge length of 0.2-0.5 mm in most crystals, but a comparison of the back re ection peak positions shows that even neighboring ideal areasmore » exhibit a relative difference in the lattice parameters on the order of deltad/d = 10-20.10 -8; this is several times larger than the rocking curve width. Furthermore, the stress-strain analysis suggests that an extremely stringent limit on the strain at a level of ~100 kPa in the growth process is required in order to produce crystals with large areas of the quality required for X-ray optics at high energy.« less

Coastal flood inundation monitoring with Satellite C-band and L-band Synthetic Aperture Radar data

USGS Publications Warehouse

Ramsey, Elijah W.; Rangoonwala, Amina; Bannister, Terri

2013-01-01

Satellite Synthetic Aperture Radar (SAR) was evaluated as a method to operationally monitor the occurrence and distribution of storm- and tidal-related flooding of spatially extensive coastal marshes within the north-central Gulf of Mexico. Maps representing the occurrence of marsh surface inundation were created from available Advanced Land Observation Satellite (ALOS) Phased Array type L-Band SAR (PALSAR) (L-band) (21 scenes with HH polarizations in Wide Beam [100 m]) data and Environmental Satellite (ENVISAT) Advanced SAR (ASAR) (C-band) data (24 scenes with VV and HH polarizations in Wide Swath [150 m]) during 2006-2009 covering 500 km of the Louisiana coastal zone. Mapping was primarily based on a decrease in backscatter between reference and target scenes, and as an extension of previous studies, the flood inundation mapping performance was assessed by the degree of correspondence between inundation mapping and inland water levels. Both PALSAR- and ASAR-based mapping at times were based on suboptimal reference scenes; however, ASAR performance seemed more sensitive to reference-scene quality and other types of scene variability. Related to water depth, PALSAR and ASAR mapping accuracies tended to be lower when water depths were shallow and increased as water levels decreased below or increased above the ground surface, but this pattern was more pronounced with ASAR. Overall, PALSAR-based inundation accuracies averaged 84% (n = 160), while ASAR-based mapping accuracies averaged 62% (n = 245).

Bilingual Program Application for Continuation Proposal: Compton Unified School District.

ERIC Educational Resources Information Center

Compton City Schools, CA.

This document contains the continuation proposal for the fourth grade Compton bilingual education program. A review of the third year is included with details on process evaluation, project personnel and duties, new vocabulary developed by the project for lexical references, and inservice training of teachers. Information concerning the proposed…

Detection of a long-duration solar gamma-ray flare on Jun. 11, 1991 with EGRET on Compton-GRO

NASA Technical Reports Server (NTRS)

Kanbach, G.; Bertsch, D. L.; Fitchel, C. E.; Hartman, R. C.; Hunter, S. D.; Kniffen, D. A.; Kwok, P. W.; Lin, Y. C.; Mattox, J. R.; Mayer-Hasslewander, H. A.

1992-01-01

On 11 Jun. 1991, the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (Comption-GRO) observed high energy gamma radiation above 30 MeV from the Sun following an intense flare around 2:00 Universal Time (UT). After the decay of most of the x ray flare, which caused nearly complete deadtime losses in EGRET, high energy emission was registered during the interval from about 3:30 UT to at least 10:30 UT. Gamma rays were detected up to energies above 1 GeV. The solar origin of the emission is assured by the time profile of the gamma ray count rate and by time resolved sky maps, which show a clear maximum at the position of the sun. The gamma ray lightcurve of the flare can be described with two components: a fast decaying emission with an e-folding time constant of about 25 minutes and a slow decay with about 255 minutes. There are indications for a spectral evolution with time, such that the emission below 100 MeV fades away earlier than the 100 to 300 MeV radiation, roughly in the time scale of the fast component. The spectrum of the flare can be fitted with a composite of a proton generated pion neutral spectrum and an electron bremsstrahlung component. The latter can be identified with the fast decaying component of the lightcurve.

A method for removing arm backscatter from EPID images

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, Brian W.; Greer, Peter B.; School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, New South Wales 2308

2013-07-15

Purpose: To develop a method for removing the support arm backscatter from images acquired using current Varian electronic portal imaging devices (EPIDs).Methods: The effect of arm backscatter on EPID images was modeled using a kernel convolution method. The parameters of the model were optimized by comparing on-arm images to off-arm images. The model was used to develop a method to remove the effect of backscatter from measured EPID images. The performance of the backscatter removal method was tested by comparing backscatter corrected on-arm images to measured off-arm images for 17 rectangular fields of different sizes and locations on the imager.more » The method was also tested using on- and off-arm images from 42 intensity modulated radiotherapy (IMRT) fields.Results: Images generated by the backscatter removal method gave consistently better agreement with off-arm images than images without backscatter correction. For the 17 rectangular fields studied, the root mean square difference of in-plane profiles compared to off-arm profiles was reduced from 1.19% (standard deviation 0.59%) on average without backscatter removal to 0.38% (standard deviation 0.18%) when using the backscatter removal method. When comparing to the off-arm images from the 42 IMRT fields, the mean {gamma} and percentage of pixels with {gamma} < 1 were improved by the backscatter removal method in all but one of the images studied. The mean {gamma} value (1%, 1 mm) for the IMRT fields studied was reduced from 0.80 to 0.57 by using the backscatter removal method, while the mean {gamma} pass rate was increased from 72.2% to 84.6%.Conclusions: A backscatter removal method has been developed to estimate the image acquired by the EPID without any arm backscatter from an image acquired in the presence of arm backscatter. The method has been shown to produce consistently reliable results for a wide range of field sizes and jaw configurations.« less

Evolution of regional to global paddy rice mapping methods: A review

NASA Astrophysics Data System (ADS)

Dong, Jinwei; Xiao, Xiangming

2016-09-01

Paddy rice agriculture plays an important role in various environmental issues including food security, water use, climate change, and disease transmission. However, regional and global paddy rice maps are surprisingly scarce and sporadic despite numerous efforts in paddy rice mapping algorithms and applications. With the increasing need for regional to global paddy rice maps, this paper reviewed the existing paddy rice mapping methods from the literatures ranging from the 1980s to 2015. In particular, we illustrated the evolution of these paddy rice mapping efforts, looking specifically at the future trajectory of paddy rice mapping methodologies. The biophysical features and growth phases of paddy rice were analyzed first, and feature selections for paddy rice mapping were analyzed from spectral, polarimetric, temporal, spatial, and textural aspects. We sorted out paddy rice mapping algorithms into four categories: (1) Reflectance data and image statistic-based approaches, (2) vegetation index (VI) data and enhanced image statistic-based approaches, (3) VI or RADAR backscatter-based temporal analysis approaches, and (4) phenology-based approaches through remote sensing recognition of key growth phases. The phenology-based approaches using unique features of paddy rice (e.g., transplanting) for mapping have been increasingly used in paddy rice mapping. Current applications of these phenology-based approaches generally use coarse resolution MODIS data, which involves mixed pixel issues in Asia where smallholders comprise the majority of paddy rice agriculture. The free release of Landsat archive data and the launch of Landsat 8 and Sentinel-2 are providing unprecedented opportunities to map paddy rice in fragmented landscapes with higher spatial resolution. Based on the literature review, we discussed a series of issues for large scale operational paddy rice mapping.

Mapping Water Level Dynamics over Central Congo River Using PALSAR Images, Envisat Altimetry, and Landsat NDVI Data

NASA Astrophysics Data System (ADS)

Kim, D.; Lee, H.; Jung, H. C.; Beighley, E.; Laraque, A.; Tshimanga, R.; Alsdorf, D. E.

2016-12-01

Rivers and wetlands are very important for ecological habitats, and it plays a key role in providing a source of greenhouse gases (CO2 and CH4). The floodplains ecosystems depend on the process between the vegetation and flood characteristics. The water level is a prerequisite to an understanding of terrestrial water storage and discharge. Despite the lack of in situ data over the Congo Basin, which is the world's third largest in size ( 3.7 million km2), and second only to the Amazon River in discharge ( 40,500 m3 s-1 annual average between 1902 and 2015 in the main Brazzaville-Kinshasa gauging station), the surface water level dynamics in the wetlands have been successfully estimated using satellite altimetry, backscattering coefficients (σ0) from Synthetic Aperture Radar (SAR) images and, interferometric SAR technique. However, the water level estimation of the Congo River remains poorly quantified due to the sparse orbital spacing of radar altimeters. Hence, we essentially have limited information only over the sparsely distributed the so-called "virtual stations". The backscattering coefficients from SAR images have been successfully used to distinguish different vegetation types, to monitor flood conditions, and to access soil moistures over the wetlands. However, σ0 has not been used to measure the water level changes over the open river because of very week return signal due to specular scattering. In this study, we have discovered that changes in σ0 over the Congo River occur mainly due to the water level changes in the river with the existence of the water plants (macrophytes, emergent plants, and submersed plant), depending on the rising and falling stage inside the depression of the "Cuvette Centrale". We expand the finding into generating the multi-temporal water level maps over the Congo River using PALSAR σ0, Envisat altimetry, and Landsat Normalized Difference Vegetation Index (NDVI) data. We also present preliminary estimates of the river discharge using the water level maps.

The Leading Edge of the Galapagos Hotspot: Geochemistry and Geochronology of Submarine Glasses Coupled to New Sidescan Sonar Imagery

NASA Astrophysics Data System (ADS)

Kurz, M. D.; Fornari, D. J.; Geist, D. J.; Johnson, P. D.; Curtice, J. M.; Lott, D. E.; Harpp, K.; Saal, A. E.; Peckman, U. G.

2001-12-01

Fernandina, the western-most volcano in the Galapagos archipelago, is at the leading edge of the hotspot with respect to plate motion. Recent mapping of the ocean floor west of Fernandina (on R/V Revelle, using the HMRG towed sidescan sonar MR1, and Simrad EM120 multibeam) provides a dramatic new view of the volcanic constructional processes that have created the islands. The western flank of the volcano is characterized by the prominent Northwest, West, and Southwest rift zones, which are constructed of hummocky pillow lavas. Older lava flow terrain is distinguished by weaker acoustic return, whereas extensive younger flows are characterized by strong backscatter patterns with distinctive flow-like margins. MR1 sidescan sonar mapping provides an important new geologic and stratigraphic context for understanding the submarine Galapagos platform, particularly from a geochemical perspective. Fernandina lavas have high 3He/4He ratios, up to 29 times atmospheric, and solar-like neon isotopic compositions, characteristics which suggest they are derived from the deep mantle. The high 3He/4He ratios, and rapid eruption rates at Fernandina also indicate that it lies directly above the center of the Galapagos hotspot. In order to place these geochemical data into a chronological framework, we have determined ages for Fernandina submarine glasses using the Th-U-He crushing/melting disequilibrium method. Preliminary Th-U-He ages (from the 2000 R/V Melville AHA-Nemo expedition), combined with the new MR1 sonar mapping, shows that the rift zones are characterized by extremely young ages (0 to 30 Ka) while older submarine lava flows with lower acoustic backscatter have significantly older ages ( ~ 100 Ka). The geochronological data, and the geological context from the side-scan sonar, provide new evidence for volcano growth rates in oceanic hotspot provinces, and will be used to determine the growth rate of the Galapagos platform.

Coastal bathymetry and backscatter data collected in 2012 from the Chandeleur Islands, Louisiana

USGS Publications Warehouse

DeWitt, Nancy T.; Bernier, Julie C.; Pfeiffer, William R.; Miselis, Jennifer L.; Reynolds, B.J.; Wiese, Dana S.; Kelso, Kyle W.

2014-01-01

As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys off the northern Chandeleur Islands, Louisiana, in July and August of 2012. The objective of the study is to better understand barrier island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1-5 years). Collecting geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the second in a series of three planned surveys in this area. High resolution geophysical data collected in each of 3 consecutive years along this rapidly changing barrier island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1-5 years). This Data Series report includes the geophysical data that were collected during two cruises (USGS Field Activity Numbers 12BIM03 and 12BIM04) aboard the RV Survey Cat and the RV Twin Vee along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana. Data were acquired with the following equipment: a Systems Engineering and Assessment, Ltd., SWATHplus interferometric sonar (468 kilohertz (kHz)), an EdgeTech 424 (4-24 kHz) chirp sub-bottom profiling system, and a Knudsen 320BP (210 kHz) echosounder. This report serves as an archive of processed interferometric swath and single-beam bathymetry data. Geographic information system data products include an interpolated digital elevation model, an acoustic backscatter mosaic, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata. NOTE: These data are scientific in nature and are not to be used for navigation.

Advances in detection of diffuse seafloor venting using structured light imaging.

NASA Astrophysics Data System (ADS)

Smart, C.; Roman, C.; Carey, S.

2016-12-01

Systematic, remote detection and high resolution mapping of low temperature diffuse hydrothermal venting is inefficient and not currently tractable using traditional remotely operated vehicle (ROV) mounted sensors. Preliminary results for hydrothermal vent detection using a structured light laser sensor were presented in 2011 and published in 2013 (Smart) with continual advancements occurring in the interim. As the structured light laser passes over active venting, the projected laser line effectively blurs due to the associated turbulence and density anomalies in the vent fluid. The degree laser disturbance is captured by a camera collecting images of the laser line at 20 Hz. Advancements in the detection of the laser and fluid interaction have included extensive normalization of the collected laser data and the implementation of a support vector machine algorithm to develop a classification routine. The image data collected over a hydrothermal vent field is then labeled as seafloor, bacteria or a location of venting. The results can then be correlated with stereo images, bathymetry and backscatter data. This sensor is a component of an ROV mounted imaging suite which also includes stereo cameras and a multibeam sonar system. Originally developed for bathymetric mapping, the structured light laser sensor, and other imaging suite components, are capable of creating visual and bathymetric maps with centimeter level resolution. Surveys are completed in a standard mowing the lawn pattern completing a 30m x 30m survey with centimeter level resolution in under an hour. Resulting co-registered data includes, multibeam and structured light laser bathymetry and backscatter, stereo images and vent detection. This system allows for efficient exploration of areas with diffuse and small point source hydrothermal venting increasing the effectiveness of scientific sampling and observation. Recent vent detection results collected during the 2013-2015 E/V Nautilus seasons will be presented. Smart, C. J. and Roman, C. and Carey, S. N. (2013) Detection of diffuse seafloor venting using structured light imaging, Geochemistry, Geophysics, Geosystems, 14, 4743-4757

Multi-Feature Classification of Multi-Sensor Satellite Imagery Based on Dual-Polarimetric Sentinel-1A, Landsat-8 OLI, and Hyperion Images for Urban Land-Cover Classification

PubMed Central

Pan, Jianjun

2018-01-01

This paper focuses on evaluating the ability and contribution of using backscatter intensity, texture, coherence, and color features extracted from Sentinel-1A data for urban land cover classification and comparing different multi-sensor land cover mapping methods to improve classification accuracy. Both Landsat-8 OLI and Hyperion images were also acquired, in combination with Sentinel-1A data, to explore the potential of different multi-sensor urban land cover mapping methods to improve classification accuracy. The classification was performed using a random forest (RF) method. The results showed that the optimal window size of the combination of all texture features was 9 × 9, and the optimal window size was different for each individual texture feature. For the four different feature types, the texture features contributed the most to the classification, followed by the coherence and backscatter intensity features; and the color features had the least impact on the urban land cover classification. Satisfactory classification results can be obtained using only the combination of texture and coherence features, with an overall accuracy up to 91.55% and a kappa coefficient up to 0.8935, respectively. Among all combinations of Sentinel-1A-derived features, the combination of the four features had the best classification result. Multi-sensor urban land cover mapping obtained higher classification accuracy. The combination of Sentinel-1A and Hyperion data achieved higher classification accuracy compared to the combination of Sentinel-1A and Landsat-8 OLI images, with an overall accuracy of up to 99.12% and a kappa coefficient up to 0.9889. When Sentinel-1A data was added to Hyperion images, the overall accuracy and kappa coefficient were increased by 4.01% and 0.0519, respectively. PMID:29382073

A New Method to Cross Calibrate and Validate TOMS, SBUV/2, and SCIAMACHY Measurements

NASA Technical Reports Server (NTRS)

Ahmad, Ziauddin; Hilsenrath, Ernest; Einaudi, Franco (Technical Monitor)

2001-01-01

A unique method to validate back scattered ultraviolet (buv) type satellite data that complements the measurements from existing ground networks is proposed. The method involves comparing the zenith sky radiance measurements from the ground to the nadir radiance measurements taken from space. Since the measurements are compared directly, the proposed method is superior to any other method that involves comparing derived products (for example, ozone), because comparison of derived products involve inversion algorithms which are susceptible to several type of errors. Forward radiative transfer (RT) calculations show that for an aerosol free atmosphere, the ground-based zenith sky radiance measurement and the satellite nadir radiance measurements can be predicted with an accuracy of better than 1 percent. The RT computations also show that for certain values of the solar zenith angles, the radiance comparisons could be better than half a percent. This accuracy is practically independent of ozone amount and aerosols in the atmosphere. Experiences with the Shuttle Solar Backscatter Ultraviolet (SSBUV) program show that the accuracy of the ground-based zenith sky radiance measuring instrument can be maintained at a level of a few tenth of a percent. This implies that the zenith sky radiance measurements can be used to validate Total Ozone Mapping Spectrometer (TOMS), Solar Backscatter Ultraviolet (SBUV/2), and The SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) radiance data. Also, this method will help improve the long term precision of the measurements for better trend detection and the accuracy of other BUV products such as tropospheric ozone and aerosols. Finally, in the long term, this method is a good candidate to inter-calibrate and validate long term observations of upcoming operational instruments such as Global Ozone Monitoring Experiment (GOME-2), Ozone Mapping Instrument (OMI), Ozone Dynamics Ultraviolet Spectrometer (ODUS), and Ozone Mapping and Profiler Suite (OMPS).

Summer snowmelt patterns in the South Shetlands using TerraSAR-X imagery

NASA Astrophysics Data System (ADS)

Mora, C.; Jimenez, J. J.; Catalao Fernades, J.; Ferreira, A.; David, A.; Ramos, M.; Vieira, G.

2014-12-01

Snow plays an important role in controlling ground thermal regime and thus influencing permafrost distribution in the lower areas of the South Shetlands archipelago, where late lying snowpatches protect the soil from summer warming. However, summer snow distribution is complex in the mountainous environments of the Maritime Antarctica and it is very difficult to obtain accurate mapping products of snow cover extent and also to monitor snowmelt. Field observations of snow cover in the region are currently based on: i) thickness data from a very scarce network of meteorological stations, ii) temperature poles allowing to estimate snow thickness, iii) and time-lapse cameras allowing for assessing snow distribution over relatively small areas. The high cloudiness of the Maritime Antarctic environment limits good mapping results from the analysis of optical remote sensing imagery such as Landsat, QuickBird or GeoEye. Therefore, microwave sensors provide the best imagery, since they are not influenced by cloudiness and are sensitive to wet-snow, typical of the melting season. We have acquired TerraSAR-X scenes for Deception and Livingston Islands for January-March 2014 in spotlight (HH, VV and HH/VV) and stripmap modes (HH) and analyse the radar backscattering for determining the differences between wet-snow, dry-snow and bare soil aiming at developing snow melt pattern maps. For ground truthing, snowpits were dug in order to characterize snow stratigraphy, grain size, grain type and snow density and to evaluate its effects on radar backscattering. Time-lapse cameras allow to identify snow patch boundaries in the field and ground surface temperatures obtained with minloggers, together with air temperatures, allow to identify the presence of snow cover in the ground. The current research is conducted in the framework of the project PERMANTAR-3 (Permafrost monitoring and modelling in Antarctic Peninsula - PTDC/AAG-GLO/3908/2012 of the FCT and PROPOLAR).

Intra- and intermolecular effects on the Compton profile of the ionic liquid 1,3-dimethylimidazolium chloride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koskelo, J., E-mail: jaakko.koskelo@helsinki.fi; Juurinen, I.; Ruotsalainen, K. O.

2014-12-28

We present a comprehensive simulation study on the solid-liquid phase transition of the ionic liquid 1,3-dimethylimidazolium chloride in terms of the changes in the atomic structure and their effect on the Compton profile. The structures were obtained by using ab initio molecular dynamics simulations. Chosen radial distribution functions of the liquid structure are presented and found generally to be in good agreement with previous ab initio molecular dynamics and neutron scattering studies. The main contributions to the predicted difference Compton profile are found to arise from intermolecular changes in the phase transition. This prediction can be used for interpreting futuremore » experiments.« less

Compton imaging tomography technique for NDE of large nonuniform structures

NASA Astrophysics Data System (ADS)

Grubsky, Victor; Romanov, Volodymyr; Patton, Ned; Jannson, Tomasz

2011-09-01

In this paper we describe a new nondestructive evaluation (NDE) technique called Compton Imaging Tomography (CIT) for reconstructing the complete three-dimensional internal structure of an object, based on the registration of multiple two-dimensional Compton-scattered x-ray images of the object. CIT provides high resolution and sensitivity with virtually any material, including lightweight structures and organics, which normally pose problems in conventional x-ray computed tomography because of low contrast. The CIT technique requires only one-sided access to the object, has no limitation on the object's size, and can be applied to high-resolution real-time in situ NDE of large aircraft/spacecraft structures and components. Theoretical and experimental results will be presented.

Analysis of C and Ku band ocean backscatter measurements under low-wind conditions

NASA Astrophysics Data System (ADS)

Carswell, James R.; Donnelly, William J.; McIntosh, Robert E.; Donelan, Mark A.; Vandemark, Douglas C.

1999-09-01

Airborne ocean backscatter measurements at C and Ku band wavelengths obtained in low to moderate-wind conditions are presented. The differences between the low-wind backscatter data and the CMOD4 and SASS-II models are reported. The measurements show that the upwind/crosswind backscatter ratio is greater than predicted. These large upwind/crosswind backscatter ratios are attributed to a rapid decrease in the crosswind backscatter at low winds. Qualitative agreement with the composite surface model proposed by Donelan and Pierson suggests the rapid decrease in the crosswind backscatter may be caused by viscous dampening of the Bragg-resonant capillary-gravity waves. We show that for larger antenna footprints typical of satellite-based scatterometers, the variability in the observed wind field smooths out the backscatter response such that the rapid decrease in the crosswind direction is not observed.

Detailed ocean current maps may lie over the horizon

NASA Astrophysics Data System (ADS)

Carlowicz, Michael

In another case of military swords being turned into scientific plowshares, two American researchers have used radar systems once designed to detect Soviet planes during the Cold War to map open-ocean currents instead.In the name of science, Thomas Georges and Jack Harlan of NOAA's Environmental Technology Laboratory borrowed some time last summer on the U.S. Navy's over-the-horizon (OTH) radar systems in both Virginia and Texas. Training the radars on the waters off of the southern coast of Florida, the researchers gathered enough data to deduce the surface motion of two 70,000 km2 swatches of the Caribbean Sea and Gulf of Mexico. By bouncing 5-28 MHz radio waves off the ionosphere down to the sea surface and back, the researchers were able to derive the characteristics of the ocean surface from Bragg backscatter resonance.

Sea-floor texture and physiographic zones of the inner continental shelf from Salisbury to Nahant, Massachusetts, including the Merrimack Embayment and Western Massachusetts Bay

USGS Publications Warehouse

Pendleton, Elizabeth E.; Barnhardt, Walter A.; Baldwin, Wayne E.; Foster, David S.; Schwab, William C.; Andrews, Brian D.; Ackerman, Seth D.

2015-10-26

A series of maps that describe the distribution and texture of sea-floor sediments and physiographic zones of Massachusetts State waters from Nahant to Salisbury, Massachusetts, including western Massachusetts Bay, have been produced by using high-resolution geophysical data (interferometric and multibeam swath bathymetry, lidar bathymetry, backscatter intensity, and seismic reflection profiles), sediment samples, and bottom photographs. These interpretations are intended to aid statewide efforts to inventory and manage coastal and marine resources, link with existing data interpretations, and provide information for research focused on coastal evolution and environmental change. Marine geologic mapping of the inner continental shelf of Massachusetts is a statewide cooperative effort of the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management.

High-resolution nuclear microprobe elemental mapping of teeth enamel-dentine interface exposed to acidic conditions

NASA Astrophysics Data System (ADS)

Pineda-Vargas, C. A.; Eisa, M. E.; Chikte, U. M. E.; Conradie, J. L.

2004-10-01

The process of demineralisation in tooth erosion due to exposure to acidic media was investigated in a group of test and control healthy human molar teeth. Analysis by micro-PIXE and proton-backscattering showed that the levels of trace elements were enriched and/or depleted according to experimental treatment. The atomic ratios of major constituents in the matrix were characteristic of test or controls with typical ratios: O 5P 1Ca 3F 1 for tests and O 6P 0.5Ca 3F 0.5 for controls. The correlation between maps of Ca and Zn in and around the interface between dentine and enamel in control samples showed two kinds of correlation strengths (for enamel and dentine). The strongest correlation was related to the enamel area.

Constitutive Behavior and Processing Map of T2 Pure Copper Deformed from 293 to 1073 K

NASA Astrophysics Data System (ADS)

Liu, Ying; Xiong, Wei; Yang, Qing; Zeng, Ji-Wei; Zhu, Wen; Sunkulp, Goel

2018-02-01

The deformation behavior of T2 pure copper compressed from 293 to 1073 K with strain rates from 0.01 to 10 s-1 was investigated. The constitutive equations were established by the Arrhenius constitutive model, which can be expressed as a piecewise function of temperature with two sections, in the ranges 293-723 K and 723-1073 K. The processing maps were established according to the dynamic material model for strains of 0.2, 0.4, 0.6, and 0.8, and the optimal processing parameters of T2 copper were determined accordingly. In order to obtain a better understanding of the deformation behavior, the microstructures of the compressed samples were studied by electron back-scattered diffraction. The grains tend to be more refined with decreases in temperature and increases in strain rate.

Method for tracking the location of mobile agents using stand-off detection technique

DOEpatents

Schmitt, Randal L [Tijeras, NM; Bender, Susan Fae Ann [Tijeras, NM; Rodacy, Philip J [Albuquerque, NM; Hargis, Jr., Philip J.; Johnson, Mark S [Albuquerque, NM

2006-12-26

A method for tracking the movement and position of mobile agents using light detection and ranging (LIDAR) as a stand-off optical detection technique. The positions of the agents are tracked by analyzing the time-history of a series of optical measurements made over the field of view of the optical system. This provides a (time+3-D) or (time+2-D) mapping of the location of the mobile agents. Repeated pulses of a laser beam impinge on a mobile agent, such as a bee, and are backscattered from the agent into a LIDAR detection system. Alternatively, the incident laser pulses excite fluorescence or phosphorescence from the agent, which is detected using a LIDAR system. Analysis of the spatial location of signals from the agents produced by repeated pulses generates a multidimensional map of agent location.

The Financial Resource Allocation Process at Compton Community College: A Redirection.

ERIC Educational Resources Information Center

Compton Community Coll. Federation of Teachers, CA.

This paper presents a historical portrait of the process of financial resource allocation at Compton Community College (CCC). Introductory material provides information on the college, its organization, and its budgeting and accounting procedures. Next, changes in finances occurring between 1974-75 and 1977-78 are outlined, including the growth of…

Early history of cosmic rays at Chicago

NASA Astrophysics Data System (ADS)

Yodh, Gaurang B.

2013-02-01

Cosmic ray studies at the University of Chicago were started by Arthur Compton during the late 1920s. The high points of cosmic ray studies at Chicago under Compton and Marcel Schein are the focus of this report, which summarizes the research done at Chicago up to the end of World War II.

Danger--School Ahead: Violence in the Public Schools.

ERIC Educational Resources Information Center

National Education Association, Washington, DC.

This report describes a study of violence in the schools of Compton, California, by a special team from the National Education Association. The study team examined the economic and social environment of the Compton community and how that environment contributes to an atmosphere of neglect and unrest in the area's schools. The study team also…

A Non-Relativistic Look at the Compton Effect

ERIC Educational Resources Information Center

Feller, Steve; Giri, Sandeep; Zakrasek, Nicholas; Affatigato, Mario

2014-01-01

In a usual modern physics class the Compton effect is used as the pedagogical model for introducing relativity into quantum effects. The shift in photon wavelengths is usually introduced and derived using special relativity. Indeed, this works well for explaining the effect. However, in the senior author's class one of the student coauthors…

VIG Seminar March 1, 2018 Alex Compton NCI-Frederick | Center for Cancer Research

Cancer.gov

Please join us for the Virology Interest Group Seminar on Thursday, March 1st, from 2:30 until 3:30 in Bethesda, Building 50, Room 2328. The seminar will also be broadcasted to Frederick, Building 549, Conference Room A. This seminar will be presented by Alex Compton, NCI-Frederick.

Evaluation of Origin Ensemble algorithm for image reconstruction for pixelated solid-state detectors with large number of channels

NASA Astrophysics Data System (ADS)

Kolstein, M.; De Lorenzo, G.; Mikhaylova, E.; Chmeissani, M.; Ariño, G.; Calderón, Y.; Ozsahin, I.; Uzun, D.

2013-04-01

The Voxel Imaging PET (VIP) Pathfinder project intends to show the advantages of using pixelated solid-state technology for nuclear medicine applications. It proposes designs for Positron Emission Tomography (PET), Positron Emission Mammography (PEM) and Compton gamma camera detectors with a large number of signal channels (of the order of 106). For PET scanners, conventional algorithms like Filtered Back-Projection (FBP) and Ordered Subset Expectation Maximization (OSEM) are straightforward to use and give good results. However, FBP presents difficulties for detectors with limited angular coverage like PEM and Compton gamma cameras, whereas OSEM has an impractically large time and memory consumption for a Compton gamma camera with a large number of channels. In this article, the Origin Ensemble (OE) algorithm is evaluated as an alternative algorithm for image reconstruction. Monte Carlo simulations of the PET design are used to compare the performance of OE, FBP and OSEM in terms of the bias, variance and average mean squared error (MSE) image quality metrics. For the PEM and Compton camera designs, results obtained with OE are presented.

Development and Testing of the AMEGO Silicon Tracker System

NASA Astrophysics Data System (ADS)

Griffin, Sean; Amego Team

2018-01-01

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe-class mission in consideration for the 2020 decadal review designed to operate at energies from ˜ 200 keV to > 10 GeV. Operating a detector in this energy regime is challenging due to the crossover in the interaction cross-section for Compton scattering and pair production. AMEGO is made of four major subsystems: a plastic anticoincidence detector for rejecting cosmic-ray events, a silicon tracker for measuring the energies of Compton scattered electrons and pair-production products, a CZT calorimeter for measuring the energy and location of Compton scattered photons, and a CsI calorimeter for measuring the energy of the pair-production products at high energies. The tracker comprises layers of dual-sided silicon strip detectors which provide energy and localization information for Compton scattering and pair-production events. A prototype tracker system is under development at GSFC; in this contribution we provide details on the verification, packaging, and testing of the prototype tracker, as well as present plans for the development of the front-end electronics, beam tests, and a balloon flight.

Applications of Gas Imaging Micro-Well Detectors to an Advanced Compton Telescope

NASA Technical Reports Server (NTRS)

Bloser, P. F.; Hunter, S. D.; Ryan, J. M.; McConnell, M. L.; Miller, R. S.; Jackson, T. N.; Bai, B.; Jung, S.

2003-01-01

We present a concept for an Advanced Compton Telescope (ACT) based on the use of pixelized gas micro-well detectors to form a three-dimensional electron track imager. A micro-well detector consists of an array of individual micro-patterned proportional counters opposite a planar drift electrode. When combined with thin film transistor array readouts, large gas volumes may be imaged with very good spatial and energy resolution at reasonable cost. The third dimension is determined by timing the drift of the ionization electrons. The primary advantage of this approach is the excellent tracking of the Compton recoil electron that is possible in a gas volume. Such good electron tracking allows us to reduce the point spread function of a single incident photon dramatically, greatly improving the imaging capability and sensitivity. The polarization sensitivity, which relies on events with large Compton scattering angles, is particularly enhanced. We describe a possible ACT implementation of this technique, in which the gas tracking volume is surrounded by a CsI calorimeter, and present our plans to build and test a small prototype over the next three years.

Sum rules across the unpolarized Compton processes involving generalized polarizabilities and moments of nucleon structure functions

NASA Astrophysics Data System (ADS)

Lensky, Vadim; Hagelstein, Franziska; Pascalutsa, Vladimir; Vanderhaeghen, Marc

2018-04-01

We derive two new sum rules for the unpolarized doubly virtual Compton scattering process on a nucleon, which establish novel low-Q2 relations involving the nucleon's generalized polarizabilities and moments of the nucleon's unpolarized structure functions F1(x ,Q2) and F2(x ,Q2). These relations facilitate the determination of some structure constants which can only be accessed in off-forward doubly virtual Compton scattering, not experimentally accessible at present. We perform an empirical determination for the proton and compare our results with a next-to-leading-order chiral perturbation theory prediction. We also show how these relations may be useful for a model-independent determination of the low-Q2 subtraction function in the Compton amplitude, which enters the two-photon-exchange contribution to the Lamb shift of (muonic) hydrogen. An explicit calculation of the Δ (1232 )-resonance contribution to the muonic-hydrogen 2 P -2 S Lamb shift yields -1 ±1 μ eV , confirming the previously conjectured smallness of this effect.

Fluorescent x-ray computed tomography to visualize specific material distribution

NASA Astrophysics Data System (ADS)

Takeda, Tohoru; Yuasa, Tetsuya; Hoshino, Atsunori; Akiba, Masahiro; Uchida, Akira; Kazama, Masahiro; Hyodo, Kazuyuki; Dilmanian, F. Avraham; Akatsuka, Takao; Itai, Yuji

1997-10-01

Fluorescent x-ray computed tomography (FXCT) is being developed to detect non-radioactive contrast materials in living specimens. The FXCT systems consists of a silicon channel cut monochromator, an x-ray slit and a collimator for detection, a scanning table for the target organ and an x-ray detector for fluorescent x-ray and transmission x-ray. To reduce Compton scattering overlapped on the K(alpha) line, incident monochromatic x-ray was set at 37 keV. At 37 keV Monte Carlo simulation showed almost complete separation between Compton scattering and the K(alpha) line. Actual experiments revealed small contamination of Compton scattering on the K(alpha) line. A clear FXCT image of a phantom was obtained. Using this system the minimal detectable dose of iodine was 30 ng in a volume of 1 mm3, and a linear relationship was demonstrated between photon counts of fluorescent x-rays and the concentration of iodine contrast material. The use of high incident x-ray energy allows an increase in the signal to noise ratio by reducing the Compton scattering on the K(alpha) line.

Contemporaneous broadband observations of three high-redshift BL Lac objects

DOE PAGES

Ackerman, M.

2016-03-20

We have collected broadband spectral energy distributions (SEDs) of three BL Lac objects, 3FGL J0022.1-1855 (z=0.689), 3FGL J0630.9-2406 (z > ~1.239), and 3FGL J0811.2-7529 (z=0.774), detected by Fermi with relatively flat GeV spectra. By observing simultaneously in the near-IR to hard X-ray band, we can well characterize the high end of the synchrotron component of the SED. Thus, fitting the SEDs to synchro-Compton models of the dominant emission from the relativistic jet, we can constrain the underlying particle properties and predict the shape of the GeV Compton component. Standard extragalactic background light (EBL) models explain the high-energy absorption well, withmore » poorer fits for high UV models. The fits show clear evidence for EBL absorption in the Fermi spectrum of our highest redshift source 3FGL J0630.9-2406. While synchrotron self-Compton models adequately describe the SEDs, the situation may be complicated by possible external Compton components.« less

Marsh dieback, loss, and recovery mapped with satellite optical, airborne polarimetric radar, and field data

USGS Publications Warehouse

Ramsey, Elijah W.; Rangoonwala, Amina; Chi, Zhaohui; Jones, Cathleen E.; Bannister, Terri

2014-01-01

Landsat Thematic Mapper and Satellite Pour l'Observation de la Terre (SPOT) satellite based optical sensors, NASA Uninhabited Aerial Vehicle synthetic aperture radar (UAVSAR) polarimetric SAR (PolSAR), and field data captured the occurrence and the recovery of an undetected dieback that occurred between the summers of 2010, 2011, and 2012 in the Spartina alterniflora marshes of coastal Louisiana. Field measurements recorded the dramatic biomass decrease from 2010 to 2011 and a biomass recovery in 2012 dominated by a decrease of live biomass, and the loss of marsh as part of the dieback event. Based on an established relationship, the near-infrared/red vegetation index (VI) and site-specific measurements delineated a contiguous expanse of marsh dieback encompassing 6649.9 ha of 18,292.3 ha of S. alterniflora marshes within the study region. PolSAR data were transformed to variables used in biophysical mapping, and of this variable suite, the cross-polarization HV (horizontal send and vertical receive) backscatter was the best single indicator of marsh dieback and recovery. HV backscatter exhibited substantial and significant changes over the dieback and recovery period, tracked measured biomass changes, and significantly correlated with the live/dead biomass ratio. Within the context of regional trends, both HV and VI indicators started higher in pre-dieback marshes and exhibited substantially and statistically higher variability from year to year than that exhibited in the non-dieback marshes. That distinct difference allowed the capturing of the S. alterniflora marsh dieback and recovery; however, these changes were incorporated in a regional trend exhibiting similar but more subtle biomass composition changes.

Skeletal growth phases of the cold-water coral Lophelia pertusa shown by scanning electron microscope and electron backscatter diffraction

NASA Astrophysics Data System (ADS)

Mouchi, Vincent; Vonlanthen, Pierre; Verrecchia, Eric P.; Crowley, Quentin G.

2016-04-01

Lophelia pertusa is a cold-water coral, which may form reefs by the association of multiple coralites within which a polyp lives. Each individual polyp builds an aragonite skeleton by an initial phase of early mineralization (traditionally referred to as centres of calcification) from which aragonite fibres grow in thickening deposits. The skeleton wall features successive optically opaque and translucent bands previously attributed to different regimes of growth as either uniform in crystal orientation (translucent bands) or with a chaotic organization (opaque bands). The processes involved in any organizational changes are still unknown. Microlayers in the coral wall, which represent separate periods of skeletal growth, have been recently identified and described. These growth patterns are readily visible under scanning electron microscope (SEM) after etching in dilute formic acid, but they do not necessarily form continuously visible structures. Here we present high quality SEM images and electron backscatter diffraction (EBSD) maps to study aragonite fibre orientation across the wall of L. pertusa. Both microlayers and opaque and translucent bands are compared to the crystallographic orientation of the aragonite fibres. EBSD maps and SEM images indicate that aragonite fibres do not exhibit a chaotic orientation, even in opaque bands. The absence of continuity of microlayers is partially explained by an association of multiple crystallographic preferred orientations of aragonite fibres. In the case of L. pertusa, careful textural characterisation is necessary prior to elemental or isotope analysis in order to select a skeletal transect representing a linear and continuous time period.

Damage Assessment of Heat Resistant Steels through Electron BackScatter Diffraction Strain Analysis under Creep and Creep-Fatigue Conditions

NASA Astrophysics Data System (ADS)

Fujiyama, Kazunari; Kimachi, Hirohisa; Tsuboi, Toshiki; Hagiwara, Hiroyuki; Ogino, Shotaro; Mizutani, Yoshiki

EBSD(Electron BackScatter Diffraction) analyses were conducted for studying the quantitative microstructural metrics of creep and creep-fatigue damage for austenitic SUS304HTB boiler tube steel and ferritic Mod.9Cr piping steel. KAM(Kernel Average Misorientation) maps and GOS(Grain Orientation Spread) maps were obtained for these samples and the area averaged values KAMave and GOSave were obtained. While the increasing trends of these misorientation metrics were observed for SUS304HTB steel, the decreasing trends were observed for damaged Mod.9Cr steel with extensive recovery of subgrain structure. To establish more universal parameter representing the accumulation of damage to compensate these opposite trends, the EBSD strain parameters were introduced for converting the misorientation changes into the quantities representing accumulated permanent strains during creep and creep-fatigue damage process. As KAM values were dependent on the pixel size (inversely proportional to the observation magnification) and the permanent strain could be expressed as the shear strain which was the product of dislocation density, Burgers vector and dislocation movement distance, two KAM strain parameters MεKAMnet and MεδKAMave were introduced as the sum of product of the noise subtracted KAMnet and the absolute change from initial value δKAMave with dislocation movement distance divided by pixel size. MεδKAMave parameter showed better relationship both with creep strain in creep tests and accumulated creep strain range in creep-fatigue tests. This parameter can be used as the strain-based damage evaluation and detector of final failure.

Development of a Compton camera for prompt-gamma medical imaging

NASA Astrophysics Data System (ADS)

Aldawood, S.; Thirolf, P. G.; Miani, A.; Böhmer, M.; Dedes, G.; Gernhäuser, R.; Lang, C.; Liprandi, S.; Maier, L.; Marinšek, T.; Mayerhofer, M.; Schaart, D. R.; Lozano, I. Valencia; Parodi, K.

2017-11-01

A Compton camera-based detector system for photon detection from nuclear reactions induced by proton (or heavier ion) beams is under development at LMU Munich, targeting the online range verification of the particle beam in hadron therapy via prompt-gamma imaging. The detector is designed to be capable to reconstruct the photon source origin not only from the Compton scattering kinematics of the primary photon, but also to allow for tracking of the secondary Compton-scattered electrons, thus enabling a γ-source reconstruction also from incompletely absorbed photon events. The Compton camera consists of a monolithic LaBr3:Ce scintillation crystal, read out by a multi-anode PMT acting as absorber, preceded by a stacked array of 6 double-sided silicon strip detectors as scatterers. The detector components have been characterized both under offline and online conditions. The LaBr3:Ce crystal exhibits an excellent time and energy resolution. Using intense collimated 137Cs and 60Co sources, the monolithic scintillator was scanned on a fine 2D grid to generate a reference library of light amplitude distributions that allows for reconstructing the photon interaction position using a k-Nearest Neighbour (k-NN) algorithm. Systematic studies were performed to investigate the performance of the reconstruction algorithm, revealing an improvement of the spatial resolution with increasing photon energy to an optimum value of 3.7(1)mm at 1.33 MeV, achieved with the Categorical Average Pattern (CAP) modification of the k-NN algorithm.

Signature of inverse Compton emission from blazars

NASA Astrophysics Data System (ADS)

Gaur, Haritma; Mohan, Prashanth; Wierzcholska, Alicja; Gu, Minfeng

2018-01-01

Blazars are classified into high-, intermediate- and low-energy-peaked sources based on the location of their synchrotron peak. This lies in infra-red/optical to ultra-violet bands for low- and intermediate-peaked blazars. The transition from synchrotron to inverse Compton emission falls in the X-ray bands for such sources. We present the spectral and timing analysis of 14 low- and intermediate-energy-peaked blazars observed with XMM-Newton spanning 31 epochs. Parametric fits to X-ray spectra help constrain the possible location of transition from the high-energy end of the synchrotron to the low-energy end of the inverse Compton emission. In seven sources in our sample, we infer such a transition and constrain the break energy in the range 0.6-10 keV. The Lomb-Scargle periodogram is used to estimate the power spectral density (PSD) shape. It is well described by a power law in a majority of light curves, the index being flatter compared to general expectation from active galactic nuclei, ranging here between 0.01 and 1.12, possibly due to short observation durations resulting in an absence of long-term trends. A toy model involving synchrotron self-Compton and external Compton (EC; disc, broad line region, torus) mechanisms are used to estimate magnetic field strength ≤0.03-0.88 G in sources displaying the energy break and infer a prominent EC contribution. The time-scale for variability being shorter than synchrotron cooling implies steeper PSD slopes which are inferred in these sources.

Development of Compton X-ray spectrometer for high energy resolution single-shot high-flux hard X-ray spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kojima, Sadaoki, E-mail: kojima-s@ile.osaka-u.ac.jp, E-mail: sfujioka@ile.osaka-u.ac.jp; Ikenouchi, Takahito; Arikawa, Yasunobu

Hard X-ray spectroscopy is an essential diagnostics used to understand physical processes that take place in high energy density plasmas produced by intense laser-plasma interactions. A bundle of hard X-ray detectors, of which the responses have different energy thresholds, is used as a conventional single-shot spectrometer for high-flux (>10{sup 13} photons/shot) hard X-rays. However, high energy resolution (Δhv/hv < 0.1) is not achievable with a differential energy threshold (DET) X-ray spectrometer because its energy resolution is limited by energy differences between the response thresholds. Experimental demonstration of a Compton X-ray spectrometer has already been performed for obtaining higher energy resolutionmore » than that of DET spectrometers. In this paper, we describe design details of the Compton X-ray spectrometer, especially dependence of energy resolution and absolute response on photon-electron converter design and its background reduction scheme, and also its application to the laser-plasma interaction experiment. The developed spectrometer was used for spectroscopy of bremsstrahlung X-rays generated by intense laser-plasma interactions using a 200 μm thickness SiO{sub 2} converter. The X-ray spectrum obtained with the Compton X-ray spectrometer is consistent with that obtained with a DET X-ray spectrometer, furthermore higher certainly of a spectral intensity is obtained with the Compton X-ray spectrometer than that with the DET X-ray spectrometer in the photon energy range above 5 MeV.« less

Development of a novel handheld intra-operative laparoscopic Compton camera for 18F-Fluoro-2-deoxy-2-D-glucose-guided surgery

NASA Astrophysics Data System (ADS)

Nakamura, Y.; Shimazoe, K.; Takahashi, H.; Yoshimura, S.; Seto, Y.; Kato, S.; Takahashi, M.; Momose, T.

2016-08-01

As well as pre-operative roadmapping by 18F-Fluoro-2-deoxy-2-D-glucose (FDG) positron emission tomography, intra-operative localization of the tracer is important to identify local margins for less-invasive surgery, especially FDG-guided surgery. The objective of this paper is to develop a laparoscopic Compton camera and system aimed at use for intra-operative FDG imaging for accurate and less-invasive dissections. The laparoscopic Compton camera consists of four layers of a 12-pixel cross-shaped array of GFAG crystals (2× 2× 3 mm3) and through silicon via multi-pixel photon counters and dedicated individual readout electronics based on a dynamic time-over-threshold method. Experimental results yielded a spatial resolution of 4 mm (FWHM) for a 10 mm working distance and an absolute detection efficiency of 0.11 cps kBq-1, corresponding to an intrinsic detection efficiency of  ˜0.18%. In an experiment using a NEMA-like well-shaped FDG phantom, a φ 5× 10 mm cylindrical hot spot was clearly obtained even in the presence of a background distribution surrounding the Compton camera and the hot spot. We successfully obtained reconstructed images of a resected lymph node and primary tumor ex vivo after FDG administration to a patient having esophageal cancer. These performance characteristics indicate a new possibility of FDG-directed surgery by using a Compton camera intra-operatively.

Mildly obscured active galaxies and the cosmic X-ray background

NASA Astrophysics Data System (ADS)

Esposito, V.; Walter, R.

2016-05-01

Context. The diffuse cosmic X-ray background (CXB) is the sum of the emission of discrete sources, mostly massive black-holes accreting matter in active galactic nuclei (AGN). The CXB spectrum differs from the integration of the spectra of individual sources, calling for a large population, undetected so far, of strongly obscured Compton-thick AGN. Such objects are predicted by unified models, which attribute most of the AGN diversity to their inclination on the line of sight, and play an important role for the understanding of the growth of black holes in the early Universe. Aims: The percentage of strongly obscured Compton-thick AGN at low redshift can be derived from the observed CXB spectrum, if we assume AGN spectral templates and luminosity functions. Methods: We show that high signal-to-noise stacked hard X-ray spectra, derived from more than a billion seconds of effective exposure time with the Swift/BAT instrument, imply that mildly obscured Compton-thin AGN feature a strong reflection and contribute massively to the CXB. Results: A population of Compton-thick AGN larger than that which is effectively detected is not required to reproduce the CXB spectrum, since no more than 6% of the CXB flux can be attributed to them. The stronger reflection observed in mildly obscured AGN suggests that the covering factor of the gas and dust surrounding their central engines is a key factor in shaping their appearance. These mildly obscured AGN are easier to study at high redshift than Compton-thick sources are.

X-rays from the radio halo of Virgo A = M87

NASA Technical Reports Server (NTRS)

1985-01-01

The purpose of this study is to investigate in more detail the associated X-ray and radio emission in the Virgo A halo discovered by SGF. Improved Einstein HRI data and new radio maps obtained with the Very Large Array are described and the relation between the X-ray and radio structures is carefully examined. Several possible explanations are presented for the X-ray emission. The inverse compton model is found to be viable only if the magnetic field is variable and substantially weaker than the equipartition value. The principal alternative is excess thermal X-rays due to compression of the intracluster medium by the radio lobe. In either case, the association of such prominent radio and X-ray structures is unique among known radio galaxies.