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Sample records for par scintillation evolution

  1. The evolution of scintillating medical detectors

    NASA Astrophysics Data System (ADS)

    Hell, E.; Knüpfer, W.; Mattern, D.

    2000-11-01

    The principle of scintillation detectors has been among the first realizations of radiation detectors. Despite ongoing attempts to switch to direct converting detectors, scintillators have shown great persistence in the field of medical imaging. In radiography, computer tomography and nuclear medicine, a variety of scintillating devices are the 'workhorses' of the clinician today. For radiography, flat X-ray detectors (FDs) with evaporated scintillation layers are at the level of product introduction. However, X-ray image intensifier tubes (XIIs) are competitive and still have features that will be hard to beat in the near future. Although XIIs have disadvantages, they have experienced a significant evolution in robust image quality and cost reduction over the decades. The so-called 'offline' detectors from film to storage phosphors seemed to have reached a plateau since the late 1970s. However, the distinction between on- and offline may soften in the future, because of new readout concepts. Detectors in computer tomography (CT) have evolved from scintillators to gaseous direct converters back to scintillators. Extreme timing requirements and detector modularity have ruled out designs that would rank as `high performance' in other fields. Modern ultra-fast ceramic scintillation detectors are a prerequisite of subsecond CT and leave breathing room for future scan times even below 0.5 s. The field of nuclear medicine is a good example of how difficult it is, to replace a cheap and reliable technology. Since many years, direct converters like CdTe and the likes are discussed to overthrow the regime of NaI:Tl in combination with photomultipliers (PMTs). Both components are well known since the 1950s and have shown remarkable staying power. Still the scintillator with the highest light output, NaI:Tl in combination with the basically noiseless PMT is almost unbeatable in low cost. In combination with modern digital electronics, drawbacks of analog circuitry like

  2. Scintillator material

    DOEpatents

    Anderson, David F.; Kross, Brian J.

    1994-01-01

    An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography.

  3. Scintillator material

    DOEpatents

    Anderson, David F.; Kross, Brian J.

    1992-01-01

    An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography.

  4. Scintillator material

    DOEpatents

    Anderson, D.F.; Kross, B.J.

    1994-06-07

    An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography. 4 figs.

  5. Scintillator material

    DOEpatents

    Anderson, D.F.; Kross, B.J.

    1992-07-28

    An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography. 4 figs.

  6. Scintillation Counters

    NASA Astrophysics Data System (ADS)

    Bell, Zane W.

    Scintillators find wide use in radiation detection as the detecting medium for gamma/X-rays, and charged and neutral particles. Since the first notice in 1895 by Roentgen of the production of light by X-rays on a barium platinocyanide screen, and Thomas Edison's work over the following 2 years resulting in the discovery of calcium tungstate as a superior fluoroscopy screen, much research and experimentation have been undertaken to discover and elucidate the properties of new scintillators. Scintillators with high density and high atomic number are prized for the detection of gamma rays above 1 MeV; lower atomic number, lower-density materials find use for detecting beta particles and heavy charged particles; hydrogenous scintillators find use in fast-neutron detection; and boron-, lithium-, and gadolinium-containing scintillators are used for slow-neutron detection. This chapter provides the practitioner with an overview of the general characteristics of scintillators, including the variation of probability of interaction with density and atomic number, the characteristics of the light pulse, a list and characteristics of commonly available scintillators and their approximate cost, and recommendations regarding the choice of material for a few specific applications. This chapter does not pretend to present an exhaustive list of scintillators and applications.

  7. Identification of proopiomelanocortin-related peptides in the rostral pars distalis of the pituitary in coelacanth: evolutional implications.

    PubMed

    Takahashi, Akiyoshi; Yasuda, Akikazu; Sullivan, Craig V; Kawauchi, Hiroshi

    2003-02-15

    The coelacanth fish, genus Latimeria, flourished during the Devonian Period and is considered among the closest living relatives of tetrapods. It may therefore provide important information on the evolution of fishes into tetrapods. However, little is known about the components of the endocrine system in this fish. Here we describe the structural characterization of pituitary hormones derived from proopiomelanocortin (POMC) in Latimeria chalumnae. We identified alpha-melanocyte-stimulating hormone (MSH), N-Des-acetyl-alpha-MSH, beta-MSH, N-terminal peptide containing gamma-MSH, corticotropin-like intermediate lobe peptide (CLIP), and N-acetyl-beta-endorpin (END) in an extract from the rostral pars distalis of the pituitary by reversed-phase high-performance liquid chromatography, amino acid sequence analysis, and mass spectrometry. The occurrence of three different MSHs and one beta-END indicates that the structural organization of coelacanth POMC is the same as that of lungfish, tetrapods, and primitive ray-finned fish. The coelacanth alpha-MSH is identical to its mammalian counterpart. The coelacanth beta-MSH shows the highest sequence identity with the amphibian counterpart, and gamma-MSH and CLIP show the highest sequence identity with their amphibian and bird counterparts, whereas coelacanth beta-END is most similar to the sturgeon peptide. The coexistence of tetrapod-type and fish-type characteristics in the putative coelacanth POMC molecule reflects the phylogenetic position of this fish. When each hormonal segment was compared between coelacanth, lungfish, and tetrapod, MSH and CLIP of coelacanth were closer to their tetrapod counterparts than those of lungfish, whereas beta-MSH and beta-END of coelacanth are less closely related to their tetrapod counterparts than those of lungfish. gamma-MSH and CLIP may have evolved at a different rate from beta-MSH and beta-END in both the coelacanth and lungfish.

  8. SCINTILLATION SPECTROMETER

    DOEpatents

    Bell, P.R.; Francis, J.E.

    1960-06-21

    A portable scintillation spectrometer is described which is especially useful in radio-biological studies for determining the uptake and distribution of gamma -emitting substances in tissue. The spectrometer includes a collimator having a plurality of apertures that are hexagonal in cross section. Two crystals are provided: one is activated to respond to incident rays from the collimator; the other is not activated and shields the first from external radiation.

  9. Plastic scintillation dosimetry: Optimal selection of scintillating fibers and scintillators

    SciTech Connect

    Archambault, Louis; Arsenault, Jean; Gingras, Luc; Sam Beddar, A.; Roy, Rene; Beaulieu, Luc

    2005-07-15

    Scintillation dosimetry is a promising avenue for evaluating dose patterns delivered by intensity-modulated radiation therapy plans or for the small fields involved in stereotactic radiosurgery. However, the increase in signal has been the goal for many authors. In this paper, a comparison is made between plastic scintillating fibers and plastic scintillator. The collection of scintillation light was measured experimentally for four commercial models of scintillating fibers (BCF-12, BCF-60, SCSF-78, SCSF-3HF) and two models of plastic scintillators (BC-400, BC-408). The emission spectra of all six scintillators were obtained by using an optical spectrum analyzer and they were compared with theoretical behavior. For scintillation in the blue region, the signal intensity of a singly clad scintillating fiber (BCF-12) was 120% of that of the plastic scintillator (BC-400). For the multiclad fiber (SCSF-78), the signal reached 144% of that of the plastic scintillator. The intensity of the green scintillating fibers was lower than that of the plastic scintillator: 47% for the singly clad fiber (BCF-60) and 77% for the multiclad fiber (SCSF-3HF). The collected light was studied as a function of the scintillator length and radius for a cylindrical probe. We found that symmetric detectors with nearly the same spatial resolution in each direction (2 mm in diameter by 3 mm in length) could be made with a signal equivalent to those of the more commonly used asymmetric scintillators. With augmentation of the signal-to-noise ratio in consideration, this paper presents a series of comparisons that should provide insight into selection of a scintillator type and volume for development of a medical dosimeter.

  10. Plastic scintillation dosimetry: optimal selection of scintillating fibers and scintillators.

    PubMed

    Archambault, Louis; Arsenault, Jean; Gingras, Luc; Beddar, A Sam; Roy, René; Beaulieu, Luc

    2005-07-01

    Scintillation dosimetry is a promising avenue for evaluating dose patterns delivered by intensity-modulated radiation therapy plans or for the small fields involved in stereotactic radiosurgery. However, the increase in signal has been the goal for many authors. In this paper, a comparison is made between plastic scintillating fibers and plastic scintillator. The collection of scintillation light was measured experimentally for four commercial models of scintillating fibers (BCF-12, BCF-60, SCSF-78, SCSF-3HF) and two models of plastic scintillators (BC-400, BC-408). The emission spectra of all six scintillators were obtained by using an optical spectrum analyzer and they were compared with theoretical behavior. For scintillation in the blue region, the signal intensity of a singly clad scintillating fiber (BCF-12) was 120% of that of the plastic scintillator (BC-400). For the multiclad fiber (SCSF-78), the signal reached 144% of that of the plastic scintillator. The intensity of the green scintillating fibers was lower than that of the plastic scintillator: 47% for the singly clad fiber (BCF-60) and 77% for the multiclad fiber (SCSF-3HF). The collected light was studied as a function of the scintillator length and radius for a cylindrical probe. We found that symmetric detectors with nearly the same spatial resolution in each direction (2 mm in diameter by 3 mm in length) could be made with a signal equivalent to those of the more commonly used asymmetric scintillators. With augmentation of the signal-to-noise ratio in consideration, this paper presents a series of comparisons that should provide insight into selection of a scintillator type and volume for development of a medical dosimeter.

  11. Scintillators and applications thereof

    DOEpatents

    Williams, Richard T.

    2015-09-01

    Scintillators of various constructions and methods of making and using the same are provided. In some embodiments, a scintillator comprises at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region.

  12. Scintillators and applications thereof

    DOEpatents

    Williams, Richard T.

    2014-07-15

    Scintillators of various constructions and methods of making and using the same are provided. In some embodiments, a scintillator comprises at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region.

  13. Lead carbonate scintillator materials

    DOEpatents

    Derenzo, Stephen E.; Moses, William W.

    1991-01-01

    Improved radiation detectors containing lead carbonate or basic lead carbonate as the scintillator element are disclosed. Both of these scintillators have been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to other known scintillator materials. The radiation detectors disclosed are favorably suited for use in general purpose detection and in medical uses.

  14. Scintillator reflective layer coextrusion

    DOEpatents

    Yun, Jae-Chul; Para, Adam

    2001-01-01

    A polymeric scintillator has a reflective layer adhered to the exterior surface thereof. The reflective layer comprises a reflective pigment and an adhesive binder. The adhesive binder includes polymeric material from which the scintillator is formed. A method of forming the polymeric scintillator having a reflective layer adhered to the exterior surface thereof is also provided. The method includes the steps of (a) extruding an inner core member from a first amount of polymeric scintillator material, and (b) coextruding an outer reflective layer on the exterior surface of the inner core member. The outer reflective layer comprises a reflective pigment and a second amount of the polymeric scintillator material.

  15. LHCb Upgrade: Scintillating Fibre Tracker

    NASA Astrophysics Data System (ADS)

    Tobin, Mark

    2016-07-01

    The LHCb detector will be upgraded during the Long Shutdown 2 (LS2) of the LHC in order to cope with higher instantaneous luminosities and to read out the data at 40 MHz using a trigger-less read-out system. All front-end electronics will be replaced and several sub-detectors must be redesigned to cope with higher occupancy. The current tracking detectors downstream of the LHCb dipole magnet will be replaced by the Scintillating Fibre (SciFi) Tracker. The SciFi Tracker will use scintillating fibres read out by Silicon Photomultipliers (SiPMs). State-of-the-art multi-channel SiPM arrays are being developed to read out the fibres and a custom ASIC will be used to digitise the signals from the SiPMs. The evolution of the design since the Technical Design Report in 2014 and the latest R & D results are presented.

  16. Observation and Modeling of Ionospheric Scintillation Associated with Irregularities in the Polar Ionosphere

    NASA Astrophysics Data System (ADS)

    Priyadarshi, S.; Zhang, Q. H.; Ma, Y. Z.; Wang, Y.; Zanyang, X.

    2015-12-01

    It is well understood that Ionospheric scintillation is a consequence of random electron density fluctuations present in the ionosphere. They appear at all local time of the polar regions therefore, it is essential to understand their evolution and dynamics. Using Madrigal database and South Pole Scintillation Receiver data an empirical model of ionospheric scintillation has been proposed for South Pole. Model has been validated and compared with the observations. We have investigated some interesting scintillation patterns associated with polar patches and structured flux of precipitated electrons. Our results illustrate well the irregularity structures causing ionospheric scintillation at the polar ionosphere. Limitations of our modeling approach is discussed. Keywords: Ionospheric irregularities, polar patches, scintillation.

  17. Shifting scintillator neutron detector

    SciTech Connect

    Clonts, Lloyd G; Cooper, Ronald G; Crow, Jr., Morris Lowell; Hannah, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A

    2014-03-04

    Provided are sensors and methods for detecting thermal neutrons. Provided is an apparatus having a scintillator for absorbing a neutron, the scintillator having a back side for discharging a scintillation light of a first wavelength in response to the absorbed neutron, an array of wavelength-shifting fibers proximate to the back side of the scintillator for shifting the scintillation light of the first wavelength to light of a second wavelength, the wavelength-shifting fibers being disposed in a two-dimensional pattern and defining a plurality of scattering plane pixels where the wavelength-shifting fibers overlap, a plurality of photomultiplier tubes, in coded optical communication with the wavelength-shifting fibers, for converting the light of the second wavelength to an electronic signal, and a processor for processing the electronic signal to identify one of the plurality of scattering plane pixels as indicative of a position within the scintillator where the neutron was absorbed.

  18. Directed and persistent movement arises from mechanochemistry of the ParA/ParB system

    NASA Astrophysics Data System (ADS)

    Hu, Longhua; Vecchiarelli, Anthony G.; Mizuuchi, Kiyoshi; Neuman, Keir C.; Liu, Jian

    The segregation of DNA prior to cell division is essential for faithful genetic inheritance. In many bacteria, segregation of the low-copy-number plasmids involves an active partition system composed of ParA ATPase and its stimulator protein ParB. Recent experiments suggest that ParA/ParB system motility is driven by a diffusion-ratchet mechanism in which ParB-coated plasmid both creates and follows a ParA gradient on the nucleoid surface. However, the detailed mechanism of ParA/ParB-mediated directed and persistent movement remains unknown. We develop a theoretical model describing ParA/ParB-mediated motility. We show that the ParA/ParB system can work as a Brownian ratchet, which effectively couples the ATPase-dependent cycling of ParA-nucleoid affinity to the motion of the ParB bound cargo. Paradoxically, the resulting processive motion relies on quenching diffusive plasmid motion through a large number of transient ParA/ParB-mediated tethers to the nucleoid surface. Our work sheds light on a new emergent phenomenon in which non-motor proteins work collectively via mechanochemical coupling to propel cargos -- an ingenious solution shaped by evolution to cope with the lack of processive motor proteins in bacteria.

  19. Study of equatorial scintillations

    NASA Technical Reports Server (NTRS)

    Pomalaza, J.; Woodman, R.; Tisnado, G.; Nakasone, E.

    1972-01-01

    Observations of the amplitude scintillations produced by the F-region in equatorial areas are presented. The equipment used for conducting the observations is described. The use of transmissions from the ATS-1, ATS-3, and ATS-5 for obtaining data is described. The two principal subjects discussed are: (1) correlation between satellite and incoherent radar observations of scintillations and (2) simultaneous observations of scintillations at 136 MHz and 1550 MHz.

  20. Lead carbonate scintillator materials

    DOEpatents

    Derenzo, S.E.; Moses, W.W.

    1991-05-14

    Improved radiation detectors containing lead carbonate or basic lead carbonate as the scintillator element are disclosed. Both of these scintillators have been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to other known scintillator materials. The radiation detectors disclosed are favorably suited for use in general purpose detection and in medical uses. 3 figures.

  1. THE MEASURES PAR PROJECT

    NASA Astrophysics Data System (ADS)

    Frouin, R. J.; Franz, B.

    2009-12-01

    The solar energy available for photosynthesis, known as PAR, controls the growth of phytoplankton and, therefore, regulates the composition and evolution of marine ecosystems. Knowing the spatial and temporal distribution of PAR over the oceans is critical to understanding biogeochemical cycles of carbon, nutrients, and oxygen, and to address important climate and global change issues such as the fate of anthropogenic atmospheric carbon dioxide. In view of this, a 12-year time series of PAR at the ocean surface, starting in September 1997, is being produced by the NASA Ocean Biology Processing Group from SeaWiFS, MODIS-Terra, and MODIS-Aqua data. The product covers the global oceans, with a spatial resolution of about 9.3x9.3 km (equal area grid) and a temporal resolution of one day. PAR is computed as the difference between the 400-700 nm solar flux incident on the top of the atmosphere (known) and reflected back to space by the atmosphere and surface (derived from satellite radiance), taking into account atmospheric absorption (modeled). Knowledge of pixel composition is not required, eliminating the need for cloud screening and arbitrary assumptions about sub-pixel cloudiness. Combining data from satellite sensors with different equatorial crossing times accounts for the diurnal variability of clouds and, therefore, increases accuracy on a daily time scale. The processing system, including routine check of accuracy and control of quality, is designed to operate during the entire lifetime of SeaWiFS and MODIS, and to accommodate future sensors with ocean-color capabilities. Maps of daily, weekly, and monthly PAR obtained from individual sensors are presented, as well as merged products. Accuracy is quantified in comparisons with other satellite estimates, the National Centers for Environmental Prediction reanalysis product, and in-situ measurements from fixed buoys and platforms. The good statistical performance makes the satellite PAR product suitable for large

  2. Optical Design Considerations for Efficient Light Collection from Liquid Scintillation Counters

    SciTech Connect

    Bernacki, Bruce E.; Douglas, Matthew; Erchinger, Jennifer L.; Fuller, Erin S.; Keillor, Martin E.; Morley, Shannon M.; Mullen, Crystal A.; Orrell, John L.; Panisko, Mark E.; Warren, Glen A.; Wright, Michael E.

    2015-01-01

    Liquid scintillation counters measure charged particle-emitting radioactive isotopes and are used for environmental studies, nuclear chemistry, and life science. Alpha and beta emissions arising from the material under study interact with the scintillation cocktail to produce light. The prototypical liquid scintillation counter employs low-level photon-counting detectors to measure the arrival of the scintillation light produced as a result of the dissolved material under study interacting with the scintillation cocktail. For reliable operation the counting instrument must convey the scintillation light to the detectors efficiently and predictably. Current best practices employ the use of two or more detectors for coincidence processing to discriminate true scintillation events from background events due to instrumental effects such as photomultiplier tube dark rates, tube flashing, or other light emission not generated in the scintillation cocktail vial. In low background liquid scintillation counters additional attention is paid to shielding the scintillation cocktail from naturally occurring radioactive material (NORM) present in the laboratory and within the instruments construction materials. Low background design is generally at odds with optimal light collection. This study presents the evolution of a light collection design for liquid scintillation counting in a low background shield. The basic approach to achieve both good light collection and a low background measurement is described. The baseline signals arising from the scintillation vial are modeled and methods to efficiently collect scintillation light are presented as part of the development of a customized low-background, high sensitivity liquid scintillation counting system.

  3. Directed and persistent movement arises from mechanochemistry of the ParA/ParB system.

    PubMed

    Hu, Longhua; Vecchiarelli, Anthony G; Mizuuchi, Kiyoshi; Neuman, Keir C; Liu, Jian

    2015-12-22

    The segregation of DNA before cell division is essential for faithful genetic inheritance. In many bacteria, segregation of low-copy number plasmids involves an active partition system composed of a nonspecific DNA-binding ATPase, ParA, and its stimulator protein ParB. The ParA/ParB system drives directed and persistent movement of DNA cargo both in vivo and in vitro. Filament-based models akin to actin/microtubule-driven motility were proposed for plasmid segregation mediated by ParA. Recent experiments challenge this view and suggest that ParA/ParB system motility is driven by a diffusion ratchet mechanism in which ParB-coated plasmid both creates and follows a ParA gradient on the nucleoid surface. However, the detailed mechanism of ParA/ParB-mediated directed and persistent movement remains unknown. Here, we develop a theoretical model describing ParA/ParB-mediated motility. We show that the ParA/ParB system can work as a Brownian ratchet, which effectively couples the ATPase-dependent cycling of ParA-nucleoid affinity to the motion of the ParB-bound cargo. Paradoxically, this resulting processive motion relies on quenching diffusive plasmid motion through a large number of transient ParA/ParB-mediated tethers to the nucleoid surface. Our work thus sheds light on an emergent phenomenon in which nonmotor proteins work collectively via mechanochemical coupling to propel cargos-an ingenious solution shaped by evolution to cope with the lack of processive motor proteins in bacteria.

  4. Directed and persistent movement arises from mechanochemistry of the ParA/ParB system

    PubMed Central

    Hu, Longhua; Vecchiarelli, Anthony G.; Mizuuchi, Kiyoshi; Neuman, Keir C.; Liu, Jian

    2015-01-01

    The segregation of DNA before cell division is essential for faithful genetic inheritance. In many bacteria, segregation of low-copy number plasmids involves an active partition system composed of a nonspecific DNA-binding ATPase, ParA, and its stimulator protein ParB. The ParA/ParB system drives directed and persistent movement of DNA cargo both in vivo and in vitro. Filament-based models akin to actin/microtubule-driven motility were proposed for plasmid segregation mediated by ParA. Recent experiments challenge this view and suggest that ParA/ParB system motility is driven by a diffusion ratchet mechanism in which ParB-coated plasmid both creates and follows a ParA gradient on the nucleoid surface. However, the detailed mechanism of ParA/ParB-mediated directed and persistent movement remains unknown. Here, we develop a theoretical model describing ParA/ParB-mediated motility. We show that the ParA/ParB system can work as a Brownian ratchet, which effectively couples the ATPase-dependent cycling of ParA–nucleoid affinity to the motion of the ParB-bound cargo. Paradoxically, this resulting processive motion relies on quenching diffusive plasmid motion through a large number of transient ParA/ParB-mediated tethers to the nucleoid surface. Our work thus sheds light on an emergent phenomenon in which nonmotor proteins work collectively via mechanochemical coupling to propel cargos—an ingenious solution shaped by evolution to cope with the lack of processive motor proteins in bacteria. PMID:26647183

  5. Ionospheric Scintillation Explorer (ISX)

    NASA Astrophysics Data System (ADS)

    Iuliano, J.; Bahcivan, H.

    2015-12-01

    NSF has recently selected Ionospheric Scintillation Explorer (ISX), a 3U Cubesat mission to explore the three-dimensional structure of scintillation-scale ionospheric irregularities associated with Equatorial Spread F (ESF). ISX is a collaborative effort between SRI International and Cal Poly. This project addresses the science question: To what distance along a flux tube does an irregularity of certain transverse-scale extend? It has been difficult to measure the magnetic field-alignment of scintillation-scale turbulent structures because of the difficulty of sampling a flux tube at multiple locations within a short time. This measurement is now possible due to the worldwide transition to DTV, which presents unique signals of opportunity for remote sensing of ionospheric irregularities from numerous vantage points. DTV spectra, in various formats, contain phase-stable, narrowband pilot carrier components that are transmitted simultaneously. A 4-channel radar receiver will simultaneously record up to 4 spatially separated transmissions from the ground. Correlations of amplitude and phase scintillation patterns corresponding to multiple points on the same flux tube will be a measure of the spatial extent of the structures along the magnetic field. A subset of geometries where two or more transmitters are aligned with the orbital path will be used to infer the temporal development of the structures. ISX has the following broad impact. Scintillation of space-based radio signals is a space weather problem that is intensively studied. ISX is a step toward a CubeSat constellation to monitor worldwide TEC variations and radio wave distortions on thousands of ionospheric paths. Furthermore, the rapid sampling along spacecraft orbits provides a unique dataset to deterministically reconstruct ionospheric irregularities at scintillation-scale resolution using diffraction radio tomography, a technique that enables prediction of scintillations at other radio frequencies, and

  6. Optical design considerations for efficient light collection from liquid scintillation counters.

    PubMed

    Bernacki, Bruce E; Douglas, Matthew; Erchinger, Jennifer L; Fuller, Erin S; Keillor, Martin E; Morley, Shannon M; Mullen, Crystal A; Orrell, John L; Panisko, Mark E; Warren, Glen A; Wright, Michael E

    2015-03-20

    Liquid scintillation counters measure charged particle-emitting radioactive isotopes and are used for environmental studies, nuclear chemistry, and life science. Alpha and beta emissions arising from the material under study interact with the scintillation cocktail to produce light. The prototypical liquid scintillation counter employs low-level photon-counting detectors to measure the arrival of the scintillation. For reliable operation, the counting instrument must convey the scintillation light to the detectors efficiently and predictably. Current best practices employ the use of two or more detectors for coincidence processing to discriminate true scintillation events from background events due to instrumental effects such as photomultiplier tube dark rates, tube flashing, or other light emission not generated in the scintillation cocktail vial. In low-background liquid scintillation counters, additional attention is paid to shielding the scintillation cocktail from naturally occurring radioactive material present in the laboratory and within the instrument's construction materials. Low-background design is generally at odds with optimal light collection. This study presents the evolution of a light collection design for liquid scintillation counting (LSC) in a low-background shield. The basic approach to achieve both good light collection and a low-background measurement is described. The baseline signals arising from the scintillation vial are modeled and methods to efficiently collect scintillation light are presented as part of the development of a customized low-background, high-sensitivity LSC system. PMID:25968530

  7. Scintillator Measurements for SNO+

    NASA Astrophysics Data System (ADS)

    Kaptanoglu, Tanner; SNO+ Collaboration

    2016-03-01

    SNO+ is a neutrino detector located 2km underground in the SNOLAB facility with the primary goal of searching for neutrinoless double beta decay. The detector will be filled with a liquid scintillator target primarily composed of linear alkyl benzene (LAB). As charged particles travel through the detector the LAB produces scintillation light which is detected by almost ten thousand PMTs. The LAB is loaded with Te130, an isotope known to undergo double beta decay. Additionally, the LAB is mixed with an additional fluor and wavelength shifter to improve the light output and shift the light to a wavelength regime in which the PMTs are maximally efficient. The precise scintillator optics drastically affect the ultimate sensitivity of SNO+. I will present work being done to measure the optical properties of the SNO+ scintillator cocktail. The measured properties are used as input to a scintillation model that allows us to extrapolate to the SNO+ scale and ultimately predict the sensitivity of the experiment. Additionally, I will present measurements done to characterize the R5912 PMT, a candidate PMT for the second phase of SNO+ that provides better light collection, improved charge resolution, and a narrower spread in timing.

  8. Liquid Scintillator Purification

    SciTech Connect

    Kishimoto, Y.

    2005-09-08

    The KamLAND collaboration has studied background requirements and purification methods needed to observe the 7Be neutrino from the sun. First we will discuss the present background situation in KamLAND where it is found that the main background components are 210Pb and 85Kr. It is then described how to purify the liquid scintillator. The present status and results on how to remove 210Pb from the liquid scintillator are discussed. Specifically, the detailed analysis of the effects of distillation and adsorption techniques are presented.

  9. Testing Scintillators for Homeland Security

    NASA Astrophysics Data System (ADS)

    Bourbeau, James; Brandt, Andrew; Kenarangui, Rasool; Weiss, Alex; Chen, Wei

    2011-10-01

    Scintillating nanoparticles have a bright future in radiation detection, especially in the area of detecting nuclear devices. As part of a UTA nanoparticle scintillator development team funded by the Department of Homeland Security, I have been developing a scintillator test stand using various radioactive sources and a Hamamatsu S3590 photodiode. I will present initial test results.

  10. SCINTILLATION EXPOSURE RATE DETECTOR

    DOEpatents

    Spears, W.G.

    1960-11-01

    A radiation detector for gamma and x rays is described. The detector comprises a scintillation crystal disposed between a tantalum shield and the input of a photomultiplier tube, the crystal and the shield cooperating so that their combined response to a given quantity of radiation at various energy levels is substantially constant.

  11. Polysiloxane scintillator composition

    DOEpatents

    Walker, J.K.

    1992-05-05

    A plastic scintillator useful for detecting ionizing radiation comprising a matrix which comprises an optically transparent polysiloxane having incorporated therein at least one ionizing radiation-hard fluor capable of converting electromagnetic energy produced in the polysiloxane upon absorption of ionizing radiation to detectable light.

  12. Boron loaded scintillator

    DOEpatents

    Bell, Zane William [Oak Ridge, TN; Brown, Gilbert Morris [Knoxville, TN; Maya, Leon [Knoxville, TN; Sloop, Jr., Frederick Victor; Sloop, Jr., Frederick Victor [Oak Ridge, TN

    2009-10-20

    A scintillating composition for detecting neutrons and other radiation comprises a phenyl containing silicone rubber with carborane units and at least one phosphor molecule. The carbonate units can either be a carborane molecule dispersed in the rubber with the aid of a compatibilization agent or can be covalently bound to the silicone.

  13. Polysiloxane scintillator composition

    DOEpatents

    Walker, James K.

    1992-01-01

    A plastic scintillator useful for detecting ionizing radiation comprising a matrix which comprises an optically transparent polysiloxane having incorporated therein at least one ionizing radiation-hard fluor capable of converting electromagnetic energy produced in the polysiloxane upon absorption of ionizing radiation to detectable light.

  14. Scintillator requirements for medical imaging

    SciTech Connect

    Moses, William W.

    1999-09-01

    Scintillating materials are used in a variety of medical imaging devices. This paper presents a description of four medical imaging modalities that make extensive use of scintillators: planar x-ray imaging, x-ray computed tomography (x-ray CT), SPECT (single photon emission computed tomography) and PET (positron emission tomography). The discussion concentrates on a description of the underlying physical principles by which the four modalities operate. The scintillator requirements for these systems are enumerated and the compromises that are made in order to maximize imaging performance utilizing existing scintillating materials are discussed, as is the potential for improving imaging performance by improving scintillator properties.

  15. Scintillator Waveguide For Sensing Radiation

    DOEpatents

    Bliss, Mary; Craig, Richard A.; Reeder; Paul L.

    2003-04-22

    The present invention is an apparatus for detecting ionizing radiation, having: a waveguide having a first end and a second end, the waveguide formed of a scintillator material wherein the therapeutic ionizing radiation isotropically generates scintillation light signals within the waveguide. This apparatus provides a measure of radiation dose. The apparatus may be modified to permit making a measure of location of radiation dose. Specifically, the scintillation material is segmented into a plurality of segments; and a connecting cable for each of the plurality of segments is used for conducting scintillation signals to a scintillation detector.

  16. De Par en Par (Wide Open), 1993.

    ERIC Educational Resources Information Center

    De Par en Par, 1993

    1993-01-01

    This document consists of the four issues of the serial "De Par en Par" published during 1993. This serial provides lessons in Spanish for elementary school children. It is written by bilingual education teachers for use in the bilingual classroom. The magazine bases itself on the K-6 curriculum and offers a variety of activities for classroom…

  17. Cerium compounds as scintillators

    SciTech Connect

    Wojtowicz, A.J.; Berman, E.; Koepke, C.; Lempicki, A.

    1991-01-01

    Stoichiometric Ce-materials with negligible Ce-Ce interactions should have superior scintillator properties. We present two materials: CeF{sub 3} and Ce{sub x}La{sub 1-x}P{sub 5}O{sub 14}. While cerium trifluoride is a known scintillator, pentaphosphate is of a limited usefulness, except as a remarkable model material. We show that quenching in fluoride is responsible for loss of 50% of the light output and is the cause of the, so-called, ultra fast component (2 ns). Light output of fluoride (about 50% of BGO) could be significantly improved. Deeper understanding of Ce-systems is needed to fully exploit their potentials. 10 figs., 6 refs.

  18. Cerium compounds as scintillators

    SciTech Connect

    Wojtowicz, A.J.; Berman, E.; Koepke, C.; Lempicki, A.

    1991-12-31

    Stoichiometric Ce-materials with negligible Ce-Ce interactions should have superior scintillator properties. We present two materials: CeF{sub 3} and Ce{sub x}La{sub 1-x}P{sub 5}O{sub 14}. While cerium trifluoride is a known scintillator, pentaphosphate is of a limited usefulness, except as a remarkable model material. We show that quenching in fluoride is responsible for loss of 50% of the light output and is the cause of the, so-called, ultra fast component (2 ns). Light output of fluoride (about 50% of BGO) could be significantly improved. Deeper understanding of Ce-systems is needed to fully exploit their potentials. 10 figs., 6 refs.

  19. Composite scintillator screen

    DOEpatents

    Zeman, Herbert D.

    1994-01-01

    A scintillator screen for an X-ray system includes a substrate of low-Z material and bodies of a high-Z material embedded within the substrate. By preselecting the size of the bodies embedded within the substrate, the spacial separation of the bodies and the thickness of the screen, the sensitivity of the screen to X-rays within a predetermined energy range can be predicted.

  20. Lunar components in Lunping scintillations

    SciTech Connect

    Koster, J.R.; Lue, H.Y.; Wu, Hsi-Shu; Huang, Yinn-Nien

    1993-08-01

    The authors report on an anlysis of a 14 year data set of ionospheric scintillation data for 136 MHz signals transmitted from a Japanese satellite. They use a lunar age superposition method to analyze this data, breaking the data into blocks by seasons of the year. They observe a number of different scintillation types in the record, as well as impacts of lunar tides on the time record. They attempt to provide an origin for the different scintillation types.

  1. Statistical analysis of scintillation data

    SciTech Connect

    Chua, S.; Noonan, J.P.; Basu, S.

    1981-09-01

    The Nakagami-m distribution has traditionally been used successfully to model the probability characteristics of ionospheric scintillations at UHF. This report investigates the distribution properties of scintillation data in the L-band range. Specifically, the appropriateness of the Nakagami-m and lognormal distributions is tested. Briefly the results confirm that the Nakagami-m is appropriate for UHF but not for L-band scintillations. The lognormal provides a better fit to the distribution of L-band scintillations and is an adequate model allowing for an error of + or - 0.1 or smaller in predicted probability with a sample size of 256.

  2. Neutron crosstalk between liquid scintillators

    NASA Astrophysics Data System (ADS)

    Verbeke, J. M.; Prasad, M. K.; Snyderman, N. J.

    2015-09-01

    A method is proposed to quantify the fractions of neutrons scattering between liquid scintillators. Using a spontaneous fission source, this method can be utilized to quickly characterize an array of liquid scintillators in terms of crosstalk. The point model theory due to Feynman is corrected to account for these multiple scatterings. Using spectral information measured by the liquid scintillators, fractions of multiple scattering can be estimated, and mass reconstruction of fissile materials under investigation can be improved. Monte Carlo simulations of mono-energetic neutron sources were performed to estimate neutron crosstalk. A californium source in an array of liquid scintillators was modeled to illustrate the improvement of the mass reconstruction.

  3. Neutron crosstalk between liquid scintillators

    SciTech Connect

    Verbeke, J. M.; Prasad, M. K.; Snyderman, N. J.

    2015-05-01

    We propose a method to quantify the fractions of neutrons scattering between liquid scintillators. Using a spontaneous fission source, this method can be utilized to quickly characterize an array of liquid scintillators in terms of crosstalk. The point model theory due to Feynman is corrected to account for these multiple scatterings. Using spectral information measured by the liquid scintillators, fractions of multiple scattering can be estimated, and mass reconstruction of fissile materials under investigation can be improved. Monte Carlo simulations of mono-energetic neutron sources were performed to estimate neutron crosstalk. A californium source in an array of liquid scintillators was modeled to illustrate the improvement of the mass reconstruction.

  4. Research to Operations of Ionospheric Scintillation Detection and Forecasting

    NASA Astrophysics Data System (ADS)

    Jones, J.; Scro, K.; Payne, D.; Ruhge, R.; Erickson, B.; Andorka, S.; Ludwig, C.; Karmann, J.; Ebelhar, D.

    Ionospheric Scintillation refers to random fluctuations in phase and amplitude of electromagnetic waves caused by a rapidly varying refractive index due to turbulent features in the ionosphere. Scintillation of transionospheric UHF and L-Band radio frequency signals is particularly troublesome since this phenomenon can lead to degradation of signal strength and integrity that can negatively impact satellite communications and navigation, radar, or radio signals from other systems that traverse or interact with the ionosphere. Although ionospheric scintillation occurs in both the equatorial and polar regions of the Earth, the focus of this modeling effort is on equatorial scintillation. The ionospheric scintillation model is data-driven in a sense that scintillation observations are used to perform detection and characterization of scintillation structures. These structures are then propagated to future times using drift and decay models to represent the natural evolution of ionospheric scintillation. The impact on radio signals is also determined by the model and represented in graphical format to the user. A frequency scaling algorithm allows for impact analysis on frequencies other than the observation frequencies. The project began with lab-grade software and through a tailored Agile development process, deployed operational-grade code to a DoD operational center. The Agile development process promotes adaptive promote adaptive planning, evolutionary development, early delivery, continuous improvement, regular collaboration with the customer, and encourage rapid and flexible response to customer-driven changes. The Agile philosophy values individuals and interactions over processes and tools, working software over comprehensive documentation, customer collaboration over contract negotiation, and responding to change over following a rigid plan. The end result was an operational capability that met customer expectations. Details of the model and the process of

  5. Evolution.

    ERIC Educational Resources Information Center

    Mayr, Ernst

    1978-01-01

    Traces the history of evolution theory from Lamarck and Darwin to the present. Discusses natural selection in detail. Suggests that, besides biological evolution, there is also a cultural evolution which is more rapid than the former. (MA)

  6. Lithium-loaded liquid scintillators

    DOEpatents

    Dai, Sheng; Kesanli, Banu; Neal, John S.

    2012-05-15

    The invention is directed to a liquid scintillating composition containing (i) one or more non-polar organic solvents; (ii) (lithium-6)-containing nanoparticles having a size of up to 10 nm and surface-capped by hydrophobic molecules; and (iii) one or more fluorophores. The invention is also directed to a liquid scintillator containing the above composition.

  7. Hybrid scintillators for neutron discrimination

    DOEpatents

    Feng, Patrick L; Cordaro, Joseph G; Anstey, Mitchell R; Morales, Alfredo M

    2015-05-12

    A composition capable of producing a unique scintillation response to neutrons and gamma rays, comprising (i) at least one surfactant; (ii) a polar hydrogen-bonding solvent; and (iii) at least one luminophore. A method including combining at least one surfactant, a polar hydrogen-bonding solvent and at least one luminophore in a scintillation cell under vacuum or an inert atmosphere.

  8. Free liquid scintillation counting bibliography

    SciTech Connect

    1996-12-31

    Packard Instrument Company announces the availability of its newly updated Bibliography of Packard Tri-Carb Liquid Scintillation Analyzers. This unique new booklet lists 628 references in which Packard Tri-Carb{reg_sign} liquid scintillation analyzers have been used in life science, environmental, nuclear power and archaeological measurements. All listings are cross-referenced by radionuclide, specific field of study and author.

  9. Extruding plastic scintillator at Fermilab

    SciTech Connect

    Anna Pla-Dalmau; Alan D. Bross; Victor V. Rykalin

    2003-10-31

    An understanding of the costs involved in the production of plastic scintillators and the development of a less expensive material have become necessary with the prospects of building very large plastic scintillation detectors. Several factors contribute to the high cost of plastic scintillating sheets, but the principal reason is the labor-intensive nature of the manufacturing process. In order to significantly lower the costs, the current casting procedures had to be abandoned. Since polystyrene is widely used in the consumer industry, the logical path was to investigate the extrusion of commercial-grade polystyrene pellets with dopants to yield high quality plastic scintillator. This concept was tested and high quality extruded plastic scintillator was produced. The D0 and MINOS experiments are already using extruded scintillator strips in their detectors. An extrusion line has recently been installed at Fermilab in collaboration with NICADD (Northern Illinois Center for Accelerator and Detector Development). This new facility will serve to further develop and improve extruded plastic scintillator. This paper will discuss the characteristics of extruded plastic scintillator and its raw materials, the different manufacturing techniques and the current R&D program at Fermilab.

  10. Scintillation detector for carbon-14

    NASA Technical Reports Server (NTRS)

    Knoll, G. F.; Rogers, W. L.

    1971-01-01

    Detector consists of plastic, cylindrical double-wall scintillation cell, which is filled with gas to be analyzed. Thin, inner cell wall is isolated optically from outer (guard) scintillator wall by evaporated-aluminum coating. Bonding technique provides mechanical support to cell wall when device is exposed to high temperatures.

  11. Development of intrinsic IPT scintillator

    SciTech Connect

    Bross, A.D.

    1989-07-31

    We report on the development of a new polystyrene based plastic scintillator. Optical absorption, fluorescence and light output measurements are presented. Preliminary results of radiation damage effects are also given and compared to the effects on a commercial plastic scintillator, NE 110. 6 refs., 12 figs.

  12. Scintillator based beta batteries

    NASA Astrophysics Data System (ADS)

    Rensing, Noa M.; Tiernan, Timothy C.; Shirwadkar, Urmila; O'Dougherty, Patrick; Freed, Sara; Hawrami, Rastgo; Squillante, Michael R.

    2013-05-01

    Some long-term, remote applications do not have access to conventional harvestable energy in the form of solar radiation (or other ambient light), wind, environmental vibration, or wave motion. Radiation Monitoring Devices, Inc. (RMD) is carrying out research to address the most challenging applications that need power for many months or years and which have undependable or no access to environmental energy. Radioisotopes are an attractive candidate for this energy source, as they can offer a very high energy density combined with a long lifetime. Both large scale nuclear power plants and radiothermal generators are based on converting nuclear energy to heat, but do not scale well to small sizes. Furthermore, thermo-mechanical power plants depend on moving parts, and RTG's suffer from low efficiency. To address the need for compact nuclear power devices, RMD is developing a novel beta battery, in which the beta emissions from a radioisotope are converted to visible light in a scintillator and then the visible light is converted to electrical power in a photodiode. By incorporating 90Sr into the scintillator SrI2 and coupling the material to a wavelength-matched solar cell, we will create a scalable, compact power source capable of supplying milliwatts to several watts of power over a period of up to 30 years. We will present the latest results of radiation damage studies and materials processing development efforts, and discuss how these factors interact to set the operating life and energy density of the device.

  13. Pars Injuries in Athletes.

    PubMed

    Oren, Jonathan H; Gallina, Jason M

    2016-03-01

    Pars injuries are common causes of low back pain in adolescent athletes. Workup traditionally has included lumbar radiographs with oblique views and single-photon emission computed tomography (SPECT). However, recent literature has demonstrated the accuracy of MRI as a diagnostic modality. Acute injuries may be amenable to bracing with the goal of a healed lesion. Most cases of spondylolysis will result in asymptomatic non-union, though pars repair is an option for symptomatic pars defects without spondylolisthesis. PMID:26977552

  14. Proton recoil scintillator neutron rem meter

    DOEpatents

    Olsher, Richard H.; Seagraves, David T.

    2003-01-01

    A neutron rem meter utilizing proton recoil and thermal neutron scintillators to provide neutron detection and dose measurement. In using both fast scintillators and a thermal neutron scintillator the meter provides a wide range of sensitivity, uniform directional response, and uniform dose response. The scintillators output light to a photomultiplier tube that produces an electrical signal to an external neutron counter.

  15. Ionospheric scintillation studies

    NASA Technical Reports Server (NTRS)

    Rino, C. L.; Freemouw, E. J.

    1973-01-01

    The diffracted field of a monochromatic plane wave was characterized by two complex correlation functions. For a Gaussian complex field, these quantities suffice to completely define the statistics of the field. Thus, one can in principle calculate the statistics of any measurable quantity in terms of the model parameters. The best data fits were achieved for intensity statistics derived under the Gaussian statistics hypothesis. The signal structure that achieved the best fit was nearly invariant with scintillation level and irregularity source (ionosphere or solar wind). It was characterized by the fact that more than 80% of the scattered signal power is in phase quadrature with the undeviated or coherent signal component. Thus, the Gaussian-statistics hypothesis is both convenient and accurate for channel modeling work.

  16. Scintillator materials containing lanthanum fluorides

    DOEpatents

    Moses, William W.

    1991-01-01

    An improved radiation detector containing a crystalline mixture of LaF.sub.3 and CeF.sub.3 as the scintillator element is disclosed. Scintillators made with from 25% to 99.5% LaF.sub.3 and the remainder CeF.sub.3 have been found to provide a balance of good stopping power, high light yield and short decay constant that is equal to or superior to other known scintillator materials, and which may be processed from natural starting materials containing both rare earth elements. The radiation detectors disclosed are favorably suited for use in general purpose detection and in positron emission tomography.

  17. Scintillator materials containing lanthanum fluorides

    DOEpatents

    Moses, W.W.

    1991-05-14

    An improved radiation detector containing a crystalline mixture of LaF[sub 3] and CeF[sub 3] as the scintillator element is disclosed. Scintillators made with from 25% to 99.5% LaF[sub 3] and the remainder CeF[sub 3] have been found to provide a balance of good stopping power, high light yield and short decay constant that is equal to or superior to other known scintillator materials, and which may be processed from natural starting materials containing both rare earth elements. The radiation detectors disclosed are favorably suited for use in general purpose detection and in positron emission tomography. 2 figures.

  18. Nonconsecutive Pars Interarticularis Defects.

    PubMed

    Elgafy, Hossein; Hart, Ryan C; Tanios, Mina

    2015-12-01

    Lumbar spondylolysis is a well-recognized condition occurring in adolescents because of repetitive overuse in sports. Nonconsecutive spondylolysis involving the lumbar spine is rare. In contrast to single-level pars defects that respond well to conservative treatment, there is no consensus about the management of multiple-level pars fractures; a few reports indicated that conservative management is successful, and the majority acknowledged that surgery is often required. The current study presents a rare case of pars fracture involving nonconsecutive segments and discusses the management options. In this case report, we review the patient's history, clinical examination, radiologic findings, and management, as well as the relevant literature. An 18-year-old man presented to the clinic with worsening lower back pain related to nonconsecutive pars fractures at L2 and L5. After 6 months of conservative management, diagnostic computed tomography-guided pars block was used to localize the symptomatic level at L2, which was treated surgically; the L5 asymptomatic pars fracture did not require surgery. At the last follow-up 2 years after surgery, the patient was playing baseball and basketball, and denied any back pain. This article reports a case of rare nonconsecutive pars fractures. Conservative management for at least 6 months is recommended. Successful management depends on the choice of appropriate treatment for each level. Single-photon emission computed tomography scan, and computed tomography-guided pars block are valuable preoperative tools to identify the symptomatic level in such a case. PMID:26665257

  19. Nonconsecutive Pars Interarticularis Defects.

    PubMed

    Elgafy, Hossein; Hart, Ryan C; Tanios, Mina

    2015-12-01

    Lumbar spondylolysis is a well-recognized condition occurring in adolescents because of repetitive overuse in sports. Nonconsecutive spondylolysis involving the lumbar spine is rare. In contrast to single-level pars defects that respond well to conservative treatment, there is no consensus about the management of multiple-level pars fractures; a few reports indicated that conservative management is successful, and the majority acknowledged that surgery is often required. The current study presents a rare case of pars fracture involving nonconsecutive segments and discusses the management options. In this case report, we review the patient's history, clinical examination, radiologic findings, and management, as well as the relevant literature. An 18-year-old man presented to the clinic with worsening lower back pain related to nonconsecutive pars fractures at L2 and L5. After 6 months of conservative management, diagnostic computed tomography-guided pars block was used to localize the symptomatic level at L2, which was treated surgically; the L5 asymptomatic pars fracture did not require surgery. At the last follow-up 2 years after surgery, the patient was playing baseball and basketball, and denied any back pain. This article reports a case of rare nonconsecutive pars fractures. Conservative management for at least 6 months is recommended. Successful management depends on the choice of appropriate treatment for each level. Single-photon emission computed tomography scan, and computed tomography-guided pars block are valuable preoperative tools to identify the symptomatic level in such a case.

  20. Scintillator fiber optic long counter

    DOEpatents

    McCollum, Tom; Spector, Garry B.

    1994-01-01

    A flat response position sensitive neutron detector capable of providing neutron spectroscopic data utilizing scintillator fiber optic filaments embedded in a neutron moderating housing having an open end through which neutrons enter to be detected.

  1. Scintillator fiber optic long counter

    DOEpatents

    McCollum, T.; Spector, G.B.

    1994-03-29

    A flat response position sensitive neutron detector capable of providing neutron spectroscopic data utilizing scintillator fiber optic filaments embedded in a neutron moderating housing having an open end through which neutrons enter to be detected is described. 11 figures.

  2. Neutron crosstalk between liquid scintillators

    DOE PAGESBeta

    Verbeke, J. M.; Prasad, M. K.; Snyderman, N. J.

    2015-05-01

    We propose a method to quantify the fractions of neutrons scattering between liquid scintillators. Using a spontaneous fission source, this method can be utilized to quickly characterize an array of liquid scintillators in terms of crosstalk. The point model theory due to Feynman is corrected to account for these multiple scatterings. Using spectral information measured by the liquid scintillators, fractions of multiple scattering can be estimated, and mass reconstruction of fissile materials under investigation can be improved. Monte Carlo simulations of mono-energetic neutron sources were performed to estimate neutron crosstalk. A californium source in an array of liquid scintillators wasmore » modeled to illustrate the improvement of the mass reconstruction.« less

  3. About NICADD extruded scintillating strips

    SciTech Connect

    Dyshkant, A.; Beznosko, D.; Blazey, G.; Chakraborty, D.; Francis, K.; Kubik, D.; Lima, J.G.; Rykalin, V.; Zutshi, v.; Baldina, E.; Bross, A.; Deering, P.; Nebel, T.; Pla-Dalmau, A.; Schellpfeffer, J.; Serritella, C.; Zimmerman, J.; /Fermilab

    2005-04-01

    The results of control measurements of extruded scintillating strip responses to a radioactive source Sr-90 are provided, and details of strip choice, preparation, and method of measurement are included. About four hundred one meter long extruded scintillating strips were measured at four different points. These results were essential for prototyping a tail catcher and muon tracker for a future international electron positron linear collider detector.

  4. Ionospheric Scintillation Effects on GPS

    NASA Astrophysics Data System (ADS)

    Steenburgh, R. A.; Smithtro, C.; Groves, K.

    2007-12-01

    . Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within 20 degrees of the geomagnetic equator. As GPS applications and users increases, so does the potential for detrimental impacts from scintillation. We examined amplitude scintillation data spanning seven years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/Americas longitudinal sector at as well as data from Parepare, Indonesia; Marak Parak, Malaysia; Pontianak, Indonesia; Guam; and Diego Garcia, U.K.; in the Pacific longitudinal sector. From these data, we calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. Additionally, we determine Dilution of Precision at one minute resolution. We examine diurnal, seasonal and solar cycle characteristics and make spatial comparisons. In general, activity was greatest during the equinoxes and solar maximum, although scintillation at Antofagasta, Chile was higher during 1998 rather than at solar maximum.

  5. Par Pond water balance

    SciTech Connect

    Hiergesell, R.A.; Dixon, K.L.

    1996-06-01

    A water budget for the Par Pond hydrologic system was established in order to estimate the rate of groundwater influx to Par Pond. This estimate will be used in modeling exercises to predict Par Pond reservoir elevation and spillway discharge in the scenario where Savannah River water is no longer pumped and discharged into Par Pond. The principal of conservation of mass was used to develop the water budget, where water inflow was set equal to water outflow. Components of the water budget were identified, and the flux associated with each was determined. The water budget was considered balanced when inflow and outflow summed to zero. The results of this study suggest that Par Pond gains water from the groundwater system in the upper reaches of the reservoir, but looses water to the groundwater system near the dam. The rate of flux of groundwater from the water table aquifer into Par Pond was determined to be 13 cfs. The rate of flux from Par Pond to the water table aquifer near the dam was determined to be 7 cfs.

  6. Extruded plastic scintillator including inorganic powders

    DOEpatents

    Bross, Alan D.; Mellott, Kerry L.; Pla-Dalmau, Anna

    2006-06-27

    A method for producing a plastic scintillator is disclosed. A plurality of nano-sized particles and one or more dopants can be combined with a plastic material for the formation of a plastic scintillator thereof. The nano-sized particles, the dopant and the plastic material can be combined within the dry inert atmosphere of an extruder to produce a reaction that results in the formation of a plastic scintillator thereof and the deposition of energy within the plastic scintillator, such that the plastic scintillator produces light signifying the detection of a radiative element. The nano-sized particles can be treated with an inert gas prior to processing the nano-sized particles, the dopant and the plastic material utilizing the extruder. The plastic scintillator can be a neutron-sensitive scintillator, x-ray sensitive scintillator and/or a scintillator for the detection of minimum ionizing particles.

  7. Tropospheric scintillation prediction models for a high elevation angle based on measured data from a tropical region

    NASA Astrophysics Data System (ADS)

    Abdul Rahim, Nadirah Binti; Islam, Md. Rafiqul; J. S., Mandeep; Dao, Hassan; Bashir, Saad Osman

    2013-12-01

    The recent rapid evolution of new satellite services, including VSAT for internet access, LAN interconnection and multimedia applications, has triggered an increasing demand for bandwidth usage by satellite communications. However, these systems are susceptible to propagation effects that become significant as the frequency increases. Scintillation is the rapid signal fluctuation of the amplitude and phase of a radio wave, which is significant in tropical climates. This paper presents the analysis of the tropospheric scintillation data for satellite to Earth links at the Ku-band. Twelve months of data (January-December 2011) were collected and analyzed to evaluate the effect of tropospheric scintillation. Statistics were then further analyzed to inspect the seasonal, worst-month, diurnal and rain-induced scintillation effects. By employing the measured scintillation data, a modification of the Karasawa model for scintillation fades and enhancements is proposed based on data measured in Malaysia.

  8. FNAL-NICADD extruded scintillator

    SciTech Connect

    Beznosko, D.; Bross, A.; Dyshkant, A.; Pla-Dalmau, A.; Rykalin, V.; /Northern Illinois U.

    2005-09-01

    The possibility to produce a scintillator that satisfies the demands of physicists from different science areas has emerged with the installation of an extrusion line at Fermi National Accelerator Laboratory (FNAL). The extruder is the product of the fruitful collaboration between FNAL and Northern Illinois Center for Accelerator and Detector Development (NICADD) at Northern Illinois University (NIU). The results from the light output, light attenuation length and mechanical tolerance indicate that FNAL-NICADD scintillator is of high quality. Improvements in the extrusion die will yield better scintillator profiles and decrease the time needed for initial tuning. This paper will present the characteristics of the FNAL-NICADD scintillator based on the measurements performed. They include the response to MIPs from cosmic rays for individual extruded strips and irradiation studies where extruded samples were irradiated up to 1 Mrad. We will also discuss the results achieved with a new die design. The attractive perspective of using the extruded scintillator with MRS (Metal Resistive Semiconductor) photodetector readout will also be shown.

  9. Radiopure metal-loaded liquid scintillator

    SciTech Connect

    Rosero, Richard; Yeh, Minfang

    2015-08-17

    Metal-loaded liquid scintillator plays a key role in particle and nuclear physics experiments. The applications of metal ions in various neutrino experiments and the purification methods for different scintillator components are discussed in this paper.

  10. Radiopure Metal-Loaded Liquid Scintillator

    SciTech Connect

    Rosero, Richard; Yeh, Minfang

    2015-03-18

    Metal-loaded liquid scintillator plays a key role in particle and nuclear physics experiments. The applications of metal ions in various neutrino experiments and the purification methods for different scintillator components are discussed in this paper.

  11. Unitary scintillation detector and system

    DOEpatents

    McElhaney, S.A.; Chiles, M.M.

    1994-05-31

    The invention is a unitary alpha, beta, and gamma scintillation detector and system for sensing the presence of alpha, beta, and gamma radiations selectively or simultaneously. The scintillators are mounted in a light-tight housing provided with an entrance window for admitting alpha, beta, and gamma radiation and excluding ambient light from the housing. Light pulses from each scintillator have different decay constants that are converted by a photosensitive device into corresponding differently shaped electrical pulses. A pulse discrimination system identifies the electrical pulses by their respective pulse shapes which are determined by decay time. The identified electrical pulses are counted in separate channel analyzers to indicate the respective levels of sensed alpha, beta, and gamma radiations. 10 figs.

  12. Unitary scintillation detector and system

    DOEpatents

    McElhaney, Stephanie A.; Chiles, Marion M.

    1994-01-01

    The invention is a unitary alpha, beta, and gamma scintillation detector and system for sensing the presence of alpha, beta, and gamma radiations selectively or simultaneously. The scintillators are mounted in a light-tight housing provided with an entrance window for admitting alpha, beta, and gamma radiation and excluding ambient light from the housing. Light pulses from each scintillator have different decay constants that are converted by a photosensitive device into corresponding differently shaped electrical pulses. A pulse discrimination system identifies the electrical pulses by their respective pulse shapes which are determined by decay time. The identified electrical pulses are counted in separate channel analyzers to indicate the respective levels of sensed alpha, beta, and gamma radiations.

  13. Scintillation at two optical frequencies.

    PubMed

    Hubbard, W B; Reitsema, H J

    1981-09-15

    Stellar scintillation data were obtained on a single night at a variety of zenith distances and azimuths, using a photon-counting photometer recording at 100 Hz simultaneously at wavelengths of 0.475 microm and 0.870 microm. Orientable apertures of 42-cm diam separated by 1 m were used to establish the average upper atmosphere wind direction and velocity. Dispersion in the earth's atmosphere separate the average optical paths at the two wavelengths, permitting a reconstruction of the spatial cross-correlation function for scintillations, independent of assumptions about differential fluid motions. Although there is clear evidence of a complicated velocity field, scintillation power was predominantly produced by levels at pressures of 130 +/- 30 mbar. The data are not grossly inconsistent with layers of isotropic Kolmogorov turbulence, but there is some evidence for deviation from the Kolmogorov spectral index and/or anisotropy.

  14. Fracture-resistant lanthanide scintillators

    DOEpatents

    Doty, F. Patrick

    2011-01-04

    Lanthanide halide alloys have recently enabled scintillating gamma ray spectrometers comparable to room temperature semiconductors (<3% FWHM energy resolutions at 662 keV). However brittle fracture of these materials upon cooling hinders the growth of large volume crystals. Efforts to improve the strength through non-lanthanide alloy substitution, while preserving scintillation, have been demonstrated. Isovalent alloys having nominal compositions of comprising Al, Ga, Sc, Y, and In dopants as well as aliovalent alloys comprising Ca, Sr, Zr, Hf, Zn, and Pb dopants were prepared. All of these alloys exhibit bright fluorescence under UV excitation, with varying shifts in the spectral peaks and intensities relative to pure CeBr.sub.3. Further, these alloys scintillate when coupled to a photomultiplier tube (PMT) and exposed to .sup.137Cs gamma rays.

  15. Scintillation-Hardened GPS Receiver

    NASA Technical Reports Server (NTRS)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  16. Development of radiation hard scintillators

    SciTech Connect

    Markley, F.; Woods, D.; Pla-Dalmau, A.; Foster, G. ); Blackburn, R. )

    1992-05-01

    Substantial improvements have been made in the radiation hardness of plastic scintillators. Cylinders of scintillating materials 2.2 cm in diameter and 1 cm thick have been exposed to 10 Mrads of gamma rays at a dose rate of 1 Mrad/h in a nitrogen atmosphere. One of the formulations tested showed an immediate decrease in pulse height of only 4% and has remained stable for 12 days while annealing in air. By comparison a commercial PVT scintillator showed an immediate decrease of 58% and after 43 days of annealing in air it improved to a 14% loss. The formulated sample consisted of 70 parts by weight of Dow polystyrene, 30 pbw of pentaphenyltrimethyltrisiloxane (Dow Corning DC 705 oil), 2 pbw of p-terphenyl, 0.2 pbw of tetraphenylbutadiene, and 0.5 pbw of UVASIL299LM from Ferro.

  17. Measurement of Stratospheric Chromatic Scintillation with the AMON-RA Balloonborne Spectrometer.

    PubMed

    Renard, J B; Dalaudier, F; Hauchecorne, A; Robert, C; Lemaire, T; Pirre, M; Bertaux, J L

    2001-08-20

    The balloonborne instrument AMON (which is a French acronym for Absorption par les Minoritaires Ozone et NO(x)) has been modified to record chromatic scintillation during stellar occultation by the Earth's atmosphere. A 14-channel spectrophotometer with a sampling rate of 10 Hz was added, and the modified instrument, AMON-RA, performed successful measurements of the setting star Alnilam during the third European Stratospheric Experiment on Ozone (THESEO) project. Unambiguous records of the chromatic scintillation were obtained, to our knowledge for the first time from above the atmosphere, and some of its basic properties are reported. The properties of atmospheric structures that are responsible for this chromatic scintillation were found to be consistent with those of previous monochromatic measurements performed from space. A maximum chromatic delay of 2.5 s was observed for widely different wavelengths.

  18. Retrieving parameters of the anisotropic refractive index fluctuations spectrum in the stratosphere from balloon-borne observations of stellar scintillation.

    PubMed

    Robert, Clélia; Conan, Jean-Marc; Michau, Vincent; Renard, Jean-Baptiste; Robert, Claude; Dalaudier, Francis

    2008-02-01

    Scintillation effects are not negligible in the stratosphere. We present a model based on a 3D model of anisotropic and isotropic refractive index fluctuations spectra that predicts scintillation rates within the so-called small perturbation approximation. Atmospheric observations of stellar scintillation made from the AMON-RA (AMON, Absorption par les Minoritaires Ozone et NO(x); RA, rapid) balloon-borne spectrometer allows us to remotely probe wave-turbulence characteristics in the stratosphere. Data reduction from these observations brings out values of the inner scale of the anisotropic spectrum. We find metric values of the inner scale that are compatible with space-based measurements. We find a major contribution of the anisotropic spectrum relative to the isotropic contribution. When the sight line plunges into the atmosphere, strong scintillation occurs as well as coupled chromatic refraction effects.

  19. Three-dimensional printing of scintillating materials.

    PubMed

    Mishnayot, Y; Layani, M; Cooperstein, I; Magdassi, S; Ron, G

    2014-08-01

    We demonstrate, for the first time, the applicability of three-dimensional printing techniques to the manufacture of scintillation detectors. We report on the development of a formulation, usable in stereolithographic printing, that exhibits scintillation efficiency on the order of 30% of that of commercial polystyrene based scintillators. We discuss the applicability of these techniques and propose future enhancements that will allow tailoring the printed scintillation detectors to various applications.

  20. Nanophosphor composite scintillator with a liquid matrix

    DOEpatents

    McKigney, Edward Allen; Burrell, Anthony Keiran; Bennett, Bryan L.; Cooke, David Wayne; Ott, Kevin Curtis; Bacrania, Minesh Kantilal; Del Sesto, Rico Emilio; Gilbertson, Robert David; Muenchausen, Ross Edward; McCleskey, Thomas Mark

    2010-03-16

    An improved nanophosphor scintillator liquid comprises nanophosphor particles in a liquid matrix. The nanophosphor particles are optionally surface modified with an organic ligand. The surface modified nanophosphor particle is essentially surface charge neutral, thereby preventing agglomeration of the nanophosphor particles during dispersion in a liquid scintillator matrix. The improved nanophosphor scintillator liquid may be used in any conventional liquid scintillator application, including in a radiation detector.

  1. Hygroscopicity Evaluation of Halide Scintillators

    SciTech Connect

    Zhuravleva, M; Stand, L; Wei, H; Hobbs, C. L.; Boatner, Lynn A; Ramey, Joanne Oxendine; Burger, Arnold; Rowe, E; Bhattacharya, P.; Tupitsyn, E; Melcher, Charles L

    2014-01-01

    A collaborative study of relative hygroscopicity of anhydrous halide scintillators grown at various laboratories is presented. We have developed a technique to evaluate moisture sensitivity of both raw materials and grown crystals, in which the moisture absorption rate is measured using a gravimetric analysis. Degradation of the scintillation performance was investigated by recording gamma-ray spectra and monitoring the photopeak position, count rate and energy resolution. The accompanying physical degradation of the samples exposed to ambient atmosphere was photographically recorded as well. The results were compared with ben

  2. Composite scintillators for detection of ionizing radiation

    DOEpatents

    Dai, Sheng [Knoxville, TN; Stephan, Andrew Curtis [Knoxville, TN; Brown, Suree S [Knoxville, TN; Wallace, Steven A [Knoxville, TN; Rondinone, Adam J [Knoxville, TN

    2010-12-28

    Applicant's present invention is a composite scintillator having enhanced transparency for detecting ionizing radiation comprising a material having optical transparency wherein said material comprises nano-sized objects having a size in at least one dimension that is less than the wavelength of light emitted by the composite scintillator wherein the composite scintillator is designed to have selected properties suitable for a particular application.

  3. Photonic crystal scintillators and methods of manufacture

    SciTech Connect

    Torres, Ricardo D.; Sexton, Lindsay T.; Fuentes, Roderick E.; Cortes-Concepcion, Jose

    2015-08-11

    Photonic crystal scintillators and their methods of manufacture are provided. Exemplary methods of manufacture include using a highly-ordered porous anodic alumina membrane as a pattern transfer mask for either the etching of underlying material or for the deposition of additional material onto the surface of a scintillator. Exemplary detectors utilizing such photonic crystal scintillators are also provided.

  4. SNO+ Scintillator Purification and Assay

    NASA Astrophysics Data System (ADS)

    Ford, R.; Chen, M.; Chkvorets, O.; Hallman, D.; Vázquez-Jáuregui, E.

    2011-04-01

    We describe the R&D on the scintillator purification and assay methods and technology for the SNO+ neutrino and double-beta decay experiment. The SNO+ experiment is a replacement of the SNO heavy water with liquid scintillator comprised of 2 g/L PPO in linear alkylbenzene (LAB). During filling the LAB will be transported underground by rail car and purified by multi-stage distillation and steam stripping at a flow rate of 19 LPM. While the detector is operational the scintillator can be recirculated at 150 LPM (full detector volume in 4 days) to provide repurification as necessary by either water extraction (for Ra, K, Bi) or by functional metal scavenger columns (for Pb, Ra, Bi, Ac, Th) followed by steam stripping to remove noble gases and oxygen (Rn, O2, Kr, Ar). The metal scavenger columns also provide a method for scintillator assay for ex-situ measurement of the U and Th chain radioactivity. We have developed "natural" radioactive spikes of Pb and Ra in LAB and use these for purification testing. Lastly, we present the planned operating modes and purification strategies and the plant specifications and design.

  5. SNO+ Scintillator Purification and Assay

    SciTech Connect

    Ford, R.; Vazquez-Jauregui, E.; Chen, M.; Chkvorets, O.; Hallman, D.

    2011-04-27

    We describe the R and D on the scintillator purification and assay methods and technology for the SNO+ neutrino and double-beta decay experiment. The SNO+ experiment is a replacement of the SNO heavy water with liquid scintillator comprised of 2 g/L PPO in linear alkylbenzene (LAB). During filling the LAB will be transported underground by rail car and purified by multi-stage distillation and steam stripping at a flow rate of 19 LPM. While the detector is operational the scintillator can be recirculated at 150 LPM (full detector volume in 4 days) to provide repurification as necessary by either water extraction (for Ra, K, Bi) or by functional metal scavenger columns (for Pb, Ra, Bi, Ac, Th) followed by steam stripping to remove noble gases and oxygen (Rn, O{sub 2}, Kr, Ar). The metal scavenger columns also provide a method for scintillator assay for ex-situ measurement of the U and Th chain radioactivity. We have developed ''natural'' radioactive spikes of Pb and Ra in LAB and use these for purification testing. Lastly, we present the planned operating modes and purification strategies and the plant specifications and design.

  6. Scintillation materials for medical applications

    SciTech Connect

    Lempicki, A.; Wojtowicz, A.J.

    1992-01-01

    Scintillators are beginning to attract renewed attention because modern High Energy Physics accelerators are placing unprecedented demands of quantity and quality of detector materials and Positron Emission Tomography (PET), used by the medical field. Both applications required materials for scintillator detectors with properties beyond those delivered by traditional scintillators. Thallium doped halides are very efficient, but slow and chemically unstable. Two modern developments, namely the very fast BaF[sub 2], which owed its success to the newly discovered crossover transitions, and CeF[sub 3], which carried a promise of fast components, more practical wavelengths and attractive efficiency. Since traditional scintillators (Tl doped halides) are very efficient, and could be even more efficient at larger concentrations of Tl, if it were not for concentration quenching. However Tl transitions are spin forbidden and slow. Both ills could be remedied by replacing Tl with Ce, whose transitions are allowed and which is known to form fully concentrated compounds of high photoluminescent efficiency and no quenching. These materials, plus new Ce-doped materials, exhibiting highly promising properties for medical applications, became the target of our studies.

  7. Method of making a scintillator waveguide

    DOEpatents

    Bliss, Mary; Craig, Richard A.; Reeder, Paul L.

    2000-01-01

    The present invention is an apparatus for detecting ionizing radiation, having: a waveguide having a first end and a second end, the waveguide formed of a scintillator material wherein the therapeutic ionizing radiation isotropically generates scintillation light signals within the waveguide. This apparatus provides a measure of radiation dose. The apparatus may be modified to permit making a measure of location of radiation dose. Specifically, the scintillation material is segmented into a plurality of segments; and a connecting cable for each of the plurality of segments is used for conducting scintillation signals to a scintillation detector.

  8. Extruded plastic scintillator for MINERvA

    SciTech Connect

    Pla-Dalmau, Anna; Bross, Alan D.; Rykalin, Victor V.; Wood, Brian M.; /NICADD, DeKalb

    2005-11-01

    An extrusion line has recently been installed at Fermilab in collaboration with NICADD (Northern Illinois Center for Accelerator and Detector Development). This new facility will serve to further develop and improve extruded plastic scintillator. Since polystyrene is widely used in the consumer industry, the logical path was to investigate the extrusion of commercial-grade polystyrene pellets with dopants to yield high quality plastic scintillator. The D0 and MINOS experiments are already using extruded scintillator strips in their detectors. A new experiment at Fermilab is pursuing the use of extruded plastic scintillator. A new plastic scintillator strip is being tested and its properties characterized. The initial results are presented here.

  9. Energy resolution of scintillation detectors

    NASA Astrophysics Data System (ADS)

    Moszyński, M.; Syntfeld-Każuch, A.; Swiderski, L.; Grodzicka, M.; Iwanowska, J.; Sibczyński, P.; Szczęśniak, T.

    2016-01-01

    According to current knowledge, the non-proportionality of the light yield of scintillators appears to be a fundamental limitation of energy resolution. A good energy resolution is of great importance for most applications of scintillation detectors. Thus, its limitations are discussed below; which arise from the non-proportional response of scintillators to gamma rays and electrons, being of crucial importance to the intrinsic energy resolution of crystals. The important influence of Landau fluctuations and the scattering of secondary electrons (δ-rays) on intrinsic resolution is pointed out here. The study on undoped NaI and CsI at liquid nitrogen temperature with a light readout by avalanche photodiodes strongly suggests that the non-proportionality of many crystals is not their intrinsic property and may be improved by selective co-doping. Finally, several observations that have been collected in the last 15 years on the influence of the slow components of light pulses on energy resolution suggest that more complex processes are taking place in the scintillators. This was observed with CsI(Tl), CsI(Na), ZnSe(Te), and undoped NaI at liquid nitrogen temperature and, finally, for NaI(Tl) at temperatures reduced below 0 °C. A common conclusion of these observations is that the highest energy resolution, and particularly intrinsic resolution measured with the scintillators, characterized by two or more components of the light pulse decay, is obtainable when the spectrometry equipment integrates the whole light of the components. In contrast, the slow components observed in many other crystals degrade the intrinsic resolution. In the limiting case, afterglow could also be considered as a very slow component that spoils the energy resolution. The aim of this work is to summarize all of the above observations by looking for their origin.

  10. Scintillators for positron emission tomography

    SciTech Connect

    Moses, W.W.; Derenzo, S.E.

    1995-09-01

    Like most applications that utilize scintillators for gamma detection, Positron Emission Tomography (PET) desires materials with high light output, short decay time, and excellent stopping power that are also inexpensive, mechanically rugged, and chemically inert. Realizing that this ``ultimate`` scintillator may not exist, this paper evaluates the relative importance of these qualities and describes their impact on the imaging performance of PET. The most important PET scintillator quality is the ability to absorb 511 keV photons in a small volume, which affects the spatial resolution of the camera. The dominant factor is a short attenuation length ({le} 1.5 cm is required), although a high photoelectric fraction is also important (> 30% is desired). The next most important quality is a short decay time, which affects both the dead time and the coincidence timing resolution. Detection rates for single 511 keV photons can be extremely high, so decay times {le} 500 ns are essential to avoid dead time losses. In addition, positron annihilations are identified by time coincidence so {le}5 ns fwhm coincidence pair timing resolution is required to identify events with narrow coincidence windows, reducing contamination due to accidental coincidences. Current trends in PET cameras are toward septaless, ``fully-3D`` cameras, which have significantly higher count rates than conventional 2-D cameras and so place higher demands on scintillator decay time. Light output affects energy resolution, and thus the ability of the camera to identify and reject events where the initial 511 keV photon has undergone Compton scatter in the patient. The scatter to true event fraction is much higher in fully-3D cameras than in 2-D cameras, so future PET cameras would benefit from scintillators with a 511 keV energy resolution < 10--12% fwhm.

  11. A synoptic study of Doppler scintillation transients in the solar wind

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    1988-01-01

    This paper conducts the first synoptic study of Doppler scintillation transients caused by interplanetary disturbances. The Doppler scintillation data used are part of the 2.3-GHz navigation data collected by the NASA Deep Space Network when tracking planetary spacecraft during 1979-1983, a period that includes solar maximum. A total of 148 separate transients covering a heliocentric distance range of 5-179 solar radii were detected, including 26 transients detected by more than one spacecraft. The frequency of occurrence was highest near the sun and decreased with radial distance, a reflection of the radial evolution of the transients and the sensitivity of the Doppler scintillation measurements to transients. Since transients can be disruptive, as was demonstrated during the encounter of Saturn by Pioneer 11 in 1979, information on Doppler scintillation transients is essential.

  12. La pelade par plaques

    PubMed Central

    Spano, Frank; Donovan, Jeff C.

    2015-01-01

    Résumé Objectif Présenter aux médecins de famille des renseignements de base pour faire comprendre l’épidémiologie, la pathogenèse, l’histologie et l’approche clinique au diagnostic de la pelade par plaques. Sources des données Une recension a été effectuée dans PubMed pour trouver des articles pertinents concernant la pathogenèse, le diagnostic et le pronostic de la pelade par plaques. Message principal La pelade par plaques est une forme de perte pileuse auto-immune dont la prévalence durant une vie est d’environ 2 %. Des antécédents personnels ou familiaux de troubles auto-immuns concomitants, comme le vitiligo ou une maladie de la thyroïde, peuvent être observés dans un petit sous-groupe de patients. Le diagnostic peut souvent être posé de manière clinique en se fondant sur la perte de cheveux non cicatricielle et circulaire caractéristique, accompagnée de cheveux en « point d’exclamation » en périphérie chez ceux dont le problème en est aux premiers stades. Le diagnostic des cas plus complexes ou des présentations inhabituelles peut être facilité par une biopsie et un examen histologique. Le pronostic varie largement et de mauvais résultats sont associés à une apparition à un âge précoce, une perte importante, la variante ophiasis, des changements aux ongles, des antécédents familiaux ou des troubles auto-immuns concomitants. Conclusion La pelade par plaques est une forme auto-immune de perte de cheveux périodiquement observée en soins primaires. Les médecins de famille sont bien placés pour identifier la pelade par plaques, déterminer la gravité de la maladie et poser le diagnostic différentiel approprié. De plus, ils sont en mesure de renseigner leurs patients à propos de l’évolution clinique de la maladie ainsi que du pronostic général selon le sous-type de patients.

  13. Silicon photomultipliers for scintillating trackers

    NASA Astrophysics Data System (ADS)

    Rabaioli, S.; Berra, A.; Bolognini, D.; Bonvicini, V.; Bosisio, L.; Ciano, S.; Iugovaz, D.; Lietti, D.; Penzo, A.; Prest, M.; Rashevskaya, I.; Reia, S.; Stoppani, L.; Vallazza, E.

    2012-12-01

    In recent years, silicon photomultipliers (SiPMs) have been proposed as a new kind of readout device for scintillating detectors in many experiments. A SiPM consists of a matrix of parallel-connected pixels, which are independent photon counters working in Geiger mode with very high gain (∼106). This contribution presents the use of an array of eight SiPMs (manufactured by FBK-irst) for the readout of a scintillating bar tracker (a small size prototype of the Electron Muon Ranger detector for the MICE experiment). The performances of the SiPMs in terms of signal to noise ratio, efficiency and time resolution will be compared to the ones of a multi-anode photomultiplier tube (MAPMT) connected to the same bars. Both the SiPMs and the MAPMT are interfaced to a VME system through a 64 channel MAROC ASIC.

  14. Scintillation Monitoring Using Asymmetry Index

    NASA Astrophysics Data System (ADS)

    Shaikh, Muhammad Mubasshir; Mahrous, Ayman; Abdallah, Amr; Notarpietro, Riccardo

    Variation in electron density can have significant effect on GNSS signals in terms of propagation delay. Ionospheric scintillation can be caused by rapid change of such delay, specifically, when they last for a longer period of time. Ionospheric irregularities that account for scintillation may vary significantly in spatial range and drift with the background plasma at speeds of 45 to 130 m/sec. These patchy irregularities may occur several times during night, e.g. in equatorial region, with the patches move through the ray paths of the GNSS satellite signals. These irregularities are often characterized as either ‘large scale’ (which can be as large as several hundred km in East-West direction and many times that in the North-South direction) or ‘small scale’ (which can be as small as 1m). These small scale irregularities are regarded as the main cause of scintillation [1,2]. In normal solar activity conditions, the mid-latitude ionosphere is not much disturbed. However, during severe magnetic storms, the aurora oval extends towards the equator and the equator anomaly region may stretched towards poles extending the scintillation phenomena more typically associated with those regions into mid-latitudes. In such stormy conditions, the predicted TEC may deviate largely from the true value of the TEC both at low and mid-latitudes due to which GNSS applications may be strongly degraded. This work is an attempt to analyze ionospheric scintillation (S4 index) using ionospheric asymmetry index [3]. The asymmetry index is based on trans-ionospheric propagation between GPS and LEO satellites in a radio occultation (RO) scenario, using background ionospheric data provided by MIDAS [4]. We attempted to simulate one of the recent geomagnetic storms (NOAA scale G4) occurred over low/mid-latitudes. The storm started on 26 September 2011 at UT 18:00 and lasted until early hours of 27 September 2011. The scintillation data for the storm was taken from an ionospheric

  15. Detecting scintillations in liquid helium

    NASA Astrophysics Data System (ADS)

    Huffman, P. R.; McKinsey, D. N.

    2013-09-01

    We review our work in developing a tetraphenyl butadiene (TPB)-based detection system for a measurement of the neutron lifetime using magnetically confined ultracold neutrons (UCN). As part of the development of the detection system for this experiment, we studied the scintillation properties of liquid helium itself, characterized the fluorescent efficiencies of different fluors, and built and tested three detector geometries. We provide an overview of the results from these studies as well as references for additional information.

  16. Multi-PSPMT scintillation camera

    SciTech Connect

    Pani, R.; Pellegrini, R.; Trotta, G.; Scopinaro, F.; Soluri, A.; Vincentis, G. de; Scafe, R.; Pergola, A.

    1999-06-01

    Gamma ray imaging is usually accomplished by the use of a relatively large scintillating crystal coupled to either a number of photomultipliers (PMTs) (Anger Camera) or to a single large Position Sensitive PMT (PSPMT). Recently the development of new diagnostic techniques, such as scintimammography and radio-guided surgery, have highlighted a number of significant limitations of the Anger camera in such imaging procedures. In this paper a dedicated gamma camera is proposed for clinical applications with the aim of improving image quality by utilizing detectors with an appropriate size and shape for the part of the body under examination. This novel scintillation camera is based upon an array of PSPMTs (Hamamatsu R5900-C8). The basic concept of this camera is identical to the Anger Camera with the exception of the substitution of PSPMTs for the PMTs. In this configuration it is possible to use the high resolution of the PSPMTs and still correctly position events lying between PSPMTs. In this work the test configuration is a 2 by 2 array of PSPMTs. Some advantages of this camera are: spatial resolution less than 2 mm FWHM, good linearity, thickness less than 3 cm, light weight, lower cost than equivalent area PSPMT, large detection area when coupled to scintillating arrays, small dead boundary zone (< 3 mm) and flexibility in the shape of the camera.

  17. Morphology of auroral zone radio wave scintillation

    SciTech Connect

    Rino, C.L.; Matthews, S.J.

    1980-08-01

    This paper describes the morphology of midnight sector and morning sector auroral zone scintillation observations made over a two-year period using the Wideband satelite, which is in a sun-synchronous, low-altitude orbit. No definitive seasonal variation was found. The nighttime data showed the highest scintillation ocurrence levels, but significant amounts of morning scintillation were observed. For the most part the scintillation activity followed the general pattern of local magnetic activity. The most prominent feature in the nightime data is a localized amplitude and phase scintillation enhancement at the point where the propagation vector lies within an L shell. A geometrical effect due to a dynamic slab of sheetlike structures in the F region is hypothesized as the source of his enhancement. The data have been sorted by magnetic activity, proximity to local midnight, and season. The general features of the data are in agreement with the accepted morphology of auroral zone scintillation.

  18. La pelade par plaques

    PubMed Central

    Spano, Frank; Donovan, Jeff C.

    2015-01-01

    Résumé Objectif Présenter aux médecins de famille des renseignements de base pour faire comprendre les schémas thérapeutiques et les résultats des traitements pour la pelade par plaques, de même que les aider à identifier les patients pour qui une demande de consultation en dermatologie pourrait s’imposer. Sources des données Une recension a été effectuée dans PubMed pour trouver des articles pertinents concernant le traitement de la pelade par plaques. Message principal La pelade par plaques est une forme auto-immune de perte pileuse qui touche à la fois les enfants et les adultes. Même s’il n’y a pas de mortalité associée à la maladie, la morbidité découlant des effets psychologiques de la perte des cheveux peut être dévastatrice. Lorsque la pelade par plaques et le sous-type de la maladie sont identifiés, un schéma thérapeutique approprié peut être amorcé pour aider à arrêter la chute des cheveux et possiblement faire commencer la repousse. Les traitements de première intention sont la triamcinolone intralésionnelle avec des corticostéroïdes topiques ou du minoxidil ou les 2. Les médecins de famille peuvent prescrire ces traitements en toute sécurité et amorcer ces thérapies. Les cas plus avancés ou réfractaires pourraient avoir besoin de diphénylcyclopropénone topique ou d’anthraline topique. On peut traiter la perte de cils avec des analogues de la prostaglandine. Les personnes ayant subi une perte de cheveux abondante peuvent recourir à des options de camouflage ou à des prothèses capillaires. Il est important de surveiller les troubles psychiatriques en raison des effets psychologiques profonds de la perte de cheveux. Conclusion Les médecins de famille verront de nombreux patients qui perdent leurs cheveux. La reconnaissance de la pelade par plaques et la compréhension du processus pathologique sous-jacent permettent d’amorcer un schéma thérapeutique approprié. Les cas plus graves ou r

  19. Spacecraft Radio Scintillation and Solar System Exploration

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    1993-01-01

    When a wave propagates through a turbulent medium, scattering by the random refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study. The observed scattering effects include amplitude or intensity scintillation, phase scintillation, angular broadening, and spectral broadening, among others. In this paper, I will refer to these scattering effects collectively as scintillation. Although the most familiar example is probably the twinkling of stars (light wave intensity scintillation by turbulence in the Earth's atmosphere), scintillation has been encountered and investigated in such diverse fields as ionospheric physics, oceanography, radio astronomy, and radio and optical communications. Ever since planetary spacecraft began exploring the solar system, scintillation has appeared during the propagation of spacecraft radio signals through planetary atmospheres, planetary ionospheres, and the solar wind. Early studies of these phenomena were motivated by the potential adverse effects on communications and navigation, and on experiments that use the radio link to conduct scientific investigations. Examples of the latter are radio occultation measurements (described below) of planetary atmospheres to deduce temperature profiles, and the search for gravitational waves. However,these concerns soon gave way to the emergence of spacecraft radio scintillation as a new scientific tool for exploring small-scale dynamics in planetary atmospheres and structure in the solar wind, complementing in situ and other remote sensing spacecraft measurements, as well as scintillation measurements using natural (celestial) radio sources. The purpose of this paper is to briefly describe and review the solar system spacecraft radio scintillation observations, to summarize the salient features of wave propagation analyses employed in interpreting them, to underscore the unique remote sensing capabilities and scientific relevance of

  20. Neutron position-sensitive scintillation detector

    DOEpatents

    Strauss, Michael G.; Brenner, Raul

    1984-01-01

    A device is provided for mapping one- and two-dimensional distributions of neutron-positions in a scintillation detector. The device consists of a lithium glass scintillator coupled by an air gap and a light coupler to an array of photomultipliers. The air gap concentrates light flashes from the scintillator, whereas the light coupler disperses this concentrated light to a predetermined fraction of the photomultiplier tube array.

  1. ParABS Systems of the Four Replicons of Burkholderia cenocepacia: New Chromosome Centromeres Confer Partition Specificity†

    PubMed Central

    Dubarry, Nelly; Pasta, Franck; Lane, David

    2006-01-01

    Most bacterial chromosomes carry an analogue of the parABS systems that govern plasmid partition, but their role in chromosome partition is ambiguous. parABS systems might be particularly important for orderly segregation of multipartite genomes, where their role may thus be easier to evaluate. We have characterized parABS systems in Burkholderia cenocepacia, whose genome comprises three chromosomes and one low-copy-number plasmid. A single parAB locus and a set of ParB-binding (parS) centromere sites are located near the origin of each replicon. ParA and ParB of the longest chromosome are phylogenetically similar to analogues in other multichromosome and monochromosome bacteria but are distinct from those of smaller chromosomes. The latter form subgroups that correspond to the taxa of their hosts, indicating evolution from plasmids. The parS sites on the smaller chromosomes and the plasmid are similar to the “universal” parS of the main chromosome but with a sequence specific to their replicon. In an Escherichia coli plasmid stabilization test, each parAB exhibits partition activity only with the parS of its own replicon. Hence, parABS function is based on the independent partition of individual chromosomes rather than on a single communal system or network of interacting systems. Stabilization by the smaller chromosome and plasmid systems was enhanced by mutation of parS sites and a promoter internal to their parAB operons, suggesting autoregulatory mechanisms. The small chromosome ParBs were found to silence transcription, a property relevant to autoregulation. PMID:16452432

  2. Radio wave scintillations at equatorial regions

    NASA Technical Reports Server (NTRS)

    Poularikas, A. D.

    1972-01-01

    Radio waves, passing through the atmosphere, experience amplitude and phase fluctuations know as scintillations. A characterization of equatorial scintillation, which has resulted from studies of data recorded primarily in South America and equatorial Africa, is presented. Equatorial scintillation phenomena are complex because they appear to vary with time of day (pre-and postmidnight), season (equinoxes), and magnetic activity. A wider and more systematic geographical coverage is needed for both scientific and engineering purposes; therefore, it is recommended that more observations should be made at earth stations (at low-geomagnetic latitudes) to record equatorial scintillation phenomena.

  3. Divalent fluoride doped cerium fluoride scintillator

    DOEpatents

    Anderson, David F.; Sparrow, Robert W.

    1991-01-01

    The use of divalent fluoride dopants in scintillator materials comprising cerium fluoride is disclosed. The preferred divalent fluoride dopants are calcium fluoride, strontium fluoride, and barium fluoride. The preferred amount of divalent fluoride dopant is less than about two percent by weight of the total scintillator. Cerium fluoride scintillator crystals grown with the addition of a divalent fluoride have exhibited better transmissions and higher light outputs than crystals grown without the addition of such dopants. These scintillators are useful in radiation detection and monitoring applications, and are particularly well suited for high-rate applications such as positron emission tomography (PET).

  4. Waveshifters and Scintillators for Ionizing Radiation Detection

    SciTech Connect

    B.Baumgaugh; J.Bishop; D.Karmgard; J.Marchant; M.McKenna; R.Ruchti; M.Vigneault; L.Hernandez; C.Hurlbut

    2007-12-11

    Scintillation and waveshifter materials have been developed for the detection of ionizing radiation in an STTR program between Ludlum Measurements, Inc. and the University of Notre Dame. Several new waveshifter materials have been developed which are comparable in efficiency and faster in fluorescence decay than the standard material Y11 (K27) used in particle physics for several decades. Additionally, new scintillation materials useful for fiber tracking have been developed which have been compared to 3HF. Lastly, work was done on developing liquid scintillators and paint-on scintillators and waveshifters for high radiation environments.

  5. Solar flux dependence of coherence scales in scintillation patterns produced by ESF irregularities

    NASA Astrophysics Data System (ADS)

    Engavale, B.; Jeeva, K.; Nair, K. U.; Bhattacharyya, A.

    2005-11-01

    The coherence scale length, defined as the 50% decorrelation scale length along the magnetic east-west direction, in the ground scintillation pattern obtained at a dip equatorial location, due to scattering of VHF radio waves by equatorial spread F (ESF) irregularities, is calculated, using amplitude scintillation data recorded by two spaced receivers. The average east-west drift of the ground scintillation pattern, during the pre- and post-midnight periods, also calculated from the same observations, shows an almost linear increase with 10.7-cm solar flux. In the present paper the variability of the drift is automatically taken into account in the calculation of the coherence scale length of the ground scintillation pattern. For weak scintillations, the coherence scale depends on the Fresnel scale, which varies with the height of the irregularity layer, and also on the spectral index of the irregularity power spectrum. It is found that for weak scintillations, the coherence scales are much better organized according to the 10.7-cm solar flux, during the pre-midnight period, than during the post-midnight period, with a general trend of coherence scale length increasing with 10.7-cm solar flux except for cases with F 10.7-cm solar flux <100. This indicates that, during the initial phase of ESF irregularity development, the irregularity spectrum does not have much variability while further evolution of the spatial structure in ESF irregularities is controlled by factors other than the solar flux.

  6. Scintillation properties of lead sulfate

    SciTech Connect

    Moses, W.W.; Derenzo, S.E. ); Shlichta, P.J. )

    1991-11-01

    We report on the scintillation properties of lead sulfate (PbSO{sub 4}), a scintillator that show promise as a high energy photon detector. It physical properties are well suited for gamma detection, as its has a density of 6.4 gm/cm{sup 3}, a 1/e attenuation length for 511 keV photons of 1.2 cm, is not affected by air or moisture, and is cut and polished easily. In 99.998% pure PbSO{sub 4} crystals at room temperature excited by 511 keV annihilation photons, the fluorescence decay lifetime contains significant fast components having 1.8 ns (5%) and 19 ns (36%) decay times, but with longer components having 95 ns (36%) and 425 ns (23%) decays times. The peak emission wavelength is 335 nm, which is transmitted by borosilicate glass windowed photomultiplier tubes. The total scintillation light output increases with decreasing temperature fro 3,200 photons/MeV at +45{degrees}C to 4, 900 photons/MeV at room temperature (+25{degrees}C) and 68,500 photons/MeV at {minus}145{degrees}C. In an imperfect, 3 mm cube of a naturally occurring mineral form of PbSO{sub 4} (anglesite) at room temperature, a 511 keV photopeak is seen with a total light output of 60% that BGO. There are significant sample to sample variations of the light output among anglesite samples, so the light output of lead sulfate may improve when large synthetic crystals become available. 10 refs.

  7. Photodetectors for Scintillator Proportionality Measurement

    SciTech Connect

    Moses, William W.; Choong, Woon-Seng; Hull, Giulia; Payne, Steve; Cherepy, Nerine; Valentine, J.D.

    2010-10-18

    We evaluate photodetectors for use in a Compton Coincidence apparatus designed for measuring scintillator proportionality. There are many requirements placed on the photodetector in these systems, including active area, linearity, and the ability to accurately measure low light levels (which implies high quantum efficiency and high signal-to-noise ratio). Through a combination of measurement and Monte Carlo simulation, we evaluate a number of potential photodetectors, especially photomultiplier tubes and hybrid photodetectors. Of these, we find that the most promising devices available are photomultiplier tubes with high ({approx}50%) quantum efficiency, although hybrid photodetectors with high quantum efficiency would be preferable.

  8. Scintillator handbook with emphasis on cesium iodide

    NASA Technical Reports Server (NTRS)

    Tidd, J. L.; Dabbs, J. R.; Levine, N.

    1973-01-01

    This report provides a background of reasonable depth and reference material on scintillators in general. Particular attention is paid to the cesium iodide scintillators as used in the High Energy Astronomy Observatory (HEAO) experiments. It is intended especially for use by persons such as laboratory test personnel who need to obtain a working knowledge of these materials and their characteristics in a short time.

  9. Epoxy resins produce improved plastic scintillators

    NASA Technical Reports Server (NTRS)

    Markley, F. W.

    1967-01-01

    Plastic scintillator produced by the substitution of epoxy resins for the commonly used polystyrene is easy to cast, stable at room temperature, and has the desirable properties of a thermoset or cross-linked system. Such scintillators can be immersed directly in strong solvents, an advantage in many chemical and biological experiments.

  10. Binderless composite scintillator for neutron detection

    DOEpatents

    Hodges, Jason P [Knoxville, TN; Crow, Jr; Lowell, M [Oak Ridge, TN; Cooper, Ronald G [Oak Ridge, TN

    2009-03-10

    Composite scintillator material consisting of a binderless sintered mixture of a Lithium (Li) compound containing .sup.6Li as the neutron converter and Y.sub.2SiO.sub.5:Ce as the scintillation phosphor, and the use of this material as a method for neutron detection. Other embodiments of the invention include various other Li compounds.

  11. Extruded scintillator for the Calorimetry applications

    SciTech Connect

    Dyshkant, A.; Rykalin, V.; Pla-Dalmau, A.; Beznosko, D.

    2006-10-27

    An extrusion line has been installed and successfully operated at FNAL (Fermi National Accelerator Laboratory) in collaboration with NICADD (Northern Illinois Center for Accelerator and Detector Development). This new Facility will serve to further develop and improve extruded plastic scintillator. Recently progress has been made in producing co-extruded plastic scintillator, thus increasing the potential HEP applications of this Facility. The current R and D work with extruded and co-extruded plastic scintillator for a potential ALICE upgrade, the ILC calorimetry program and the MINERvA experiment show the attractiveness of the chosen strategy for future experiments and calorimetry. We extensively discuss extruded and co-extruded plastic scintillator in calorimetry in synergy with new Solid State Photomultipliers. The characteristics of extruded and co-extruded plastic scintillator will be presented here as well as results with non-traditional photo read-out.

  12. Extruded scintillator for the calorimetry applications

    SciTech Connect

    Dyshkant, A.; Rykalin, V.; Pla-Dalmau, A.; Beznosko, D.; /SUNY, Stony Brook

    2006-08-01

    An extrusion line has been installed and successfully operated at FNAL (Fermi National Accelerator Laboratory) in collaboration with NICADD (Northern Illinois Center for Accelerator and Detector Development). This new Facility will serve to further develop and improve extruded plastic scintillator. Recently progress has been made in producing co-extruded plastic scintillator, thus increasing the potential HEP applications of this Facility. The current R&D work with extruded and co-extruded plastic scintillator for a potential ALICE upgrade, the ILC calorimetry program and the MINERvA experiment show the attractiveness of the chosen strategy for future experiments and calorimetry. We extensively discuss extruded and co-extruded plastic scintillator in calorimetry in synergy with new Solid State Photomultipliers. The characteristics of extruded and co-extruded plastic scintillator will be presented here as well as results with non-traditional photo read-out.

  13. Scintillation proximity assay using polymeric membranes

    SciTech Connect

    Mansfield, R.K.

    1992-01-01

    Liquid scintillation counting (LSC) is typically used to quantify electron emitting isotopes. In LSC, radioactive samples are dissolved in an organic fluor solution (scintillation cocktail) to ensure that the label is close enough to the fluor molecules to be detected. Although efficient, scintillation cocktail is neither specific or selective for samples labeled with the same radioisotope. Scintillation cocktail is flammable posing significant health risks to the user and is expensive to purchase and discard. Scintillation Proximity Assay (SPA) is a radioanalytical technique where only those radiochemical entities (RCE's) bound to fluor containing matrices are detected. Only bound RCE's are in close enough proximity the entrapped fluor molecules to induce scintillations. Unbound radioligands are too far removed from the fluor molecules to be detected. The research in this dissertation focused on the development and evaluation of fluor-containing membranes (scintillation proximity membranes, SP membranes) to be used for specific radioanalytical techniques without using scintillation cocktail. Polysulfone and PVC SP membranes prepared in our laboratory were investigated for radioimmunossay (RIA) where only bound radioligand is detected, thereby eliminating the separation step impeding the automation of RIA. These SP membranes performed RIA where the results were nearly identical to commercial SP microbeads. SP membranes functionalized with quaternary ammonium hydroxide moieties were able to trap and quantify [sup 14]CO[sub 2] without using liquid scintillation cocktail. RCE's bound in the pore structure of SP membranes are intimate with the entrapped fluor providing the geometry needed for high detection efficiencies. Absorbent SP membranes were used in radiation surveys and were shown to be as effective as conventional survey techniques using filter paper and scintillation cocktail.

  14. Scintillation Effects on Space Shuttle GPS Data

    NASA Technical Reports Server (NTRS)

    Goodman, John L.; Kramer, Leonard

    2001-01-01

    Irregularities in ionospheric electron density result in variation in amplitude and phase of Global Positioning System (GPS) signals, or scintillation. GPS receivers tracking scintillated signals may lose carrier phase or frequency lock in the case of phase sc intillation. Amplitude scintillation can cause "enhancement" or "fading" of GPS signals and result in loss of lock. Scintillation can occur over the equatorial and polar regions and is a function of location, time of day, season, and solar and geomagnetic activity. Mid latitude regions are affected only very rarely, resulting from highly disturbed auroral events. In the spring of 1998, due to increasing concern about scintillation of GPS signals during the upcoming solar maximum, the Space Shuttle Program began to assess the impact of scintillation on Collins Miniaturized Airborne GPS Receiver (MAGR) units that are to replace Tactical Air Control and Navigation (TACAN) units on the Space Shuttle orbiters. The Shuttle Program must determine if scintillation effects pose a threat to safety of flight and mission success or require procedural and flight rule changes. Flight controllers in Mission Control must understand scintillation effects on GPS to properly diagnose "off nominal" GPS receiver performance. GPS data from recent Space Shuttle missions indicate that the signals tracked by the Shuttle MAGR manifest scintillation. Scintillation is observed as anomalous noise in velocity measurements lasting for up to 20 minutes on Shuttle orbit passes and are not accounted for in the error budget of the MAGR accuracy parameters. These events are typically coincident with latitude and local time occurrence of previously identified equatorial spread F within about 20 degrees of the magnetic equator. The geographic and seasonal history of these events from ground-based observations and a simple theoretical model, which have potential for predicting events for operational purposes, are reviewed.

  15. The improved scintillation crystal lead tungstate scintillation for PET

    NASA Astrophysics Data System (ADS)

    Wan, Youbao; WU, Rurong; Xiao, Linrong; Zhang, Jianxin; Yang, Peizhi; Yan, Hui

    2009-07-01

    As a valuable material for the detecting of γ-ray, PbWO4 and BaF2:PbWO4 crystals were grown by a novel multi-crucible temperature gradient system developed by ourselves. Utilizing a topical partial heating method, this system can form a topical partial high temperature in its hearth. Thus this system could melt raw materials in step by step as requirement. The advantage of this method is that there would be solid obstruct left on the melt in the procedure of the crystal growing up. The left obstruct could prevent the volatilization of the component in the melt. Hence it is helpful for the composition homogenization in the crystal. The system also offers a sustaining device for multi-crucibles and thus it can grow many crystals simultaneity. The optical properties and scintillation properties of the crystals were studied. The results reveal that the ions doping improves the scintillation properties of the crystal. The transmittance spectra show that the transmittance of BaF2:PbWO4 crystals are better than that of PbWO4 crystals. For the PbWO4 crystals, their absorption edge is at 325nm, and their maximum transmittance is 68%. For the BaF2:PbWO4 crystals, their absorption edge is at 325nm and their maximum transmittance is upto76%. The X-ray excited luminescence spectra shows that the luminescence peak is at 420nm for the samples of PbWO4 crystal while the peak is at 430nm for the samples of BaF2:PbWO4 crystal respectively. The luminescence intensity of the samples of BaF2:PbWO4 crystal is about two times than that of PbWO4 crystal. And their peak shape is different for the two kind of crystal. The light yield of BaF2:PbWO4 crystals is about 2.9 times than that of PbWO4 crystal Analyzing these scintillation properties, we find that the VPb 3+ and VO- defects do harm for the optical properties of the crystal. Ions doping method could reduce the defect concentration and improving its illumination performance of the crystal. Specially, the doped F- ions in O2- site can

  16. Measurement of radiation damage of water-based liquid scintillator and liquid scintillator

    DOE PAGESBeta

    Bignell, L. J.; Diwan, M. V.; Hans, S.; Jaffe, D. E.; Rosero, R.; Vigdor, S.; Viren, B.; Worcester, E.; Yeh, M.; Zhang, C.

    2015-10-19

    Liquid scintillating phantoms have been proposed as a means to perform real-time 3D dosimetry for proton therapy treatment plan verification. We have studied what effect radiation damage to the scintillator will have upon this application. We have performed measurements of the degradation of the light yield and optical attenuation length of liquid scintillator and water-based liquid scintillator after irradiation by 201 MeV proton beams that deposited doses of approximately 52 Gy, 300 Gy, and 800 Gy in the scintillator. Liquid scintillator and water-based liquid scintillator (composed of 5% scintillating phase) exhibit light yield reductions of 1.74 ± 0.55 % andmore » 1.31 ± 0.59 % after ≈ 800 Gy of proton dose, respectively. Some increased optical attenuation was observed in the irradiated samples, the measured reduction to the light yield is also due to damage to the scintillation light production. Based on our results and conservative estimates of the expected dose in a clinical context, a scintillating phantom used for proton therapy treatment plan verification would exhibit a systematic light yield reduction of approximately 0.1% after a year of operation.« less

  17. Measurement of radiation damage of water-based liquid scintillator and liquid scintillator

    SciTech Connect

    Bignell, L. J.; Diwan, M. V.; Hans, S.; Jaffe, D. E.; Rosero, R.; Vigdor, S.; Viren, B.; Worcester, E.; Yeh, M.; Zhang, C.

    2015-10-19

    Liquid scintillating phantoms have been proposed as a means to perform real-time 3D dosimetry for proton therapy treatment plan verification. We have studied what effect radiation damage to the scintillator will have upon this application. We have performed measurements of the degradation of the light yield and optical attenuation length of liquid scintillator and water-based liquid scintillator after irradiation by 201 MeV proton beams that deposited doses of approximately 52 Gy, 300 Gy, and 800 Gy in the scintillator. Liquid scintillator and water-based liquid scintillator (composed of 5% scintillating phase) exhibit light yield reductions of 1.74 ± 0.55 % and 1.31 ± 0.59 % after ≈ 800 Gy of proton dose, respectively. Some increased optical attenuation was observed in the irradiated samples, the measured reduction to the light yield is also due to damage to the scintillation light production. Based on our results and conservative estimates of the expected dose in a clinical context, a scintillating phantom used for proton therapy treatment plan verification would exhibit a systematic light yield reduction of approximately 0.1% after a year of operation.

  18. Equatorial scintillations: advances since ISEA-6

    SciTech Connect

    Not Available

    1985-01-01

    Our understanding of the morphology of equatorial scintillations has advanced due to more intensive observations at the equatorial anomaly locations in the different longitude zones. The unmistakable effect of the sunspot cycle in controlling irregularity belt width and electron concentration responsible for strong scintillation in the controlling the magnitude of scintillations has been recognized by interpreting scintillation observations inthe light of realistic models of total electron content at various longitudes. A hypothesis based on the alignment of the solar terminator with the geomagnetic flux tubes as an indicator of enhanced scintillation occurrence and another based on the influence of a transequatorial thermospheric neutral wind have been postulated to describe the observed longitudinal variation. A distinct class of equatorial irregularities known as the bottomside sinusoidal (BSS) type was identified. These irregularities occur in very large patches, sometimes in excess of several thousand kilometers in the E-W direction and are associated with frequency spread on ionograms. Scintillations caused by such irregularities exist only in the VHF band, exhibit Fresnel oscillations in intensity spectra and are found to give rise to extremely long durations (approx. several hours) of uninterrrupted scintillations.

  19. Scintillation Breakdowns in Chip Tantalum Capacitors

    NASA Technical Reports Server (NTRS)

    Teverovsky, Alexander

    2008-01-01

    Scintillations in solid tantalum capacitors are momentarily local breakdowns terminated by a self-healing or conversion to a high-resistive state of the manganese oxide cathode. This conversion effectively caps the defective area of the tantalum pentoxide dielectric and prevents short-circuit failures. Typically, this type of breakdown has no immediate catastrophic consequences and is often considered as nuisance rather than a failure. Scintillation breakdowns likely do not affect failures of parts under surge current conditions, and so-called "proofing" of tantalum chip capacitors, which is a controllable exposure of the part after soldering to voltages slightly higher than the operating voltage to verify that possible scintillations are self-healed, has been shown to improve the quality of the parts. However, no in-depth studies of the effect of scintillations on reliability of tantalum capacitors have been performed so far. KEMET is using scintillation breakdown testing as a tool for assessing process improvements and to compare quality of different manufacturing lots. Nevertheless, the relationship between failures and scintillation breakdowns is not clear, and this test is not considered as suitable for lot acceptance testing. In this work, scintillation breakdowns in different military-graded and commercial tantalum capacitors were characterized and related to the rated voltages and to life test failures. A model for assessment of times to failure, based on distributions of breakdown voltages, and accelerating factors of life testing are discussed.

  20. Scintillation observations near the sun

    NASA Technical Reports Server (NTRS)

    Coles, W. A.; Rickett, B. J.; Scott, S. L.

    1978-01-01

    Results on the electron density spectrum, the random velocity and the mean velocity of the solar wind in the region from 5 to 100 solar radii are presented. Results are based on intensity scintillations of incoherent radio sources at different locations and different radio frequencies. The shape of the electron density irregularity spectrum is shown to be well modeled by a power law in wavenumber with a slope that abruptly steepens at higher wavenumbers. This two slope power law model is shown to have a break (defined as the wavenumber of the change of slope) that increases with decreasing distance from the Sun. The fractional random velocity is shown to be insignificant at distances of greater than 40 solar radii, but shows a steady increase with decreasing solar distance inside of 40 solar radii.

  1. Temporal and spatial distributions of TEC depletions with scintillations and ROTI over south China

    NASA Astrophysics Data System (ADS)

    Deng, Baichang; Huang, Jiang; Kong, Debao; Xu, Jie; Wan, Dehuan; Lin, Guoguo

    2015-01-01

    This study investigated the temporal and spatial distributions of TEC depletions with scintillations and ROTI over south China. Data were collected from two GPS receiver stations in south China from 2011 to 2012. Our results revealed that maxima of distribution of TEC depletions were observed in vernal and autumnal equinox months. During pre-midnight hours and in the region of northern crest of equatorial anomaly, deep TEC depletions (approximately 20 TECU) well coincided with the occurrences of intense scintillations (S4 > 0.5) and large ROTI (approximately 2). But around midnight hours or at the outer edge of northern anomaly crest, only shallow TEC depletions (<10 TECU) were recorded with small ROTI (<1) and no scintillation. Our results suggest that the temporal and spatial variability of TEC depletions during equinox months over south China could be considered as a representative of the evolution phase of the plasma bubbles during post-sunset hours.

  2. New Organic Scintillators for Neutron Detection

    SciTech Connect

    Iwanowska, Joanna; Szczeniak, Tomasz

    2010-01-05

    This paper present the current work on neutron detection in Soltan Institute for Nuclear Studies. Lately, we have focused our research on the development of new organic scintillators including liquid scintillators for neutron detection and associated measurements. We measured liquid scintillators (also {sup 10}B-doped for thermal neutron detection){sup 3}He tubes, composites, etc. Response of the following detectors on thermal neutrons, fast neutrons and gamma radiation - the pulse shape discrimination (PSD)- has been mainly performed by means of a zero-crossing (ZC) method.

  3. Photodiode scintillation detector for radiac instrumentation

    NASA Astrophysics Data System (ADS)

    Nirschl, Joseph C.

    1984-10-01

    Scintillation detectors have traditionally employed photomultiplier tubes (PMTs), with the attendant drawback of relatively high cost and need for a high voltage supply. This article reviews evaluation of a photodiode type scintillation detector, which exhibits promising features (small size and low power) for radiation survey meter application. Gamma radiation response characteristics, both for pulse and dc-mode of detector operation are presented, along with an example of a simple, high-range digital radiacmeter (breadboard design), utilizing this photodiode scintillation detector in conjunction with a single-chip A/D converter/LCD display driver and featuring low power demand (15 mW).

  4. Large volume flow-through scintillating detector

    DOEpatents

    Gritzo, Russ E.; Fowler, Malcolm M.

    1995-01-01

    A large volume flow through radiation detector for use in large air flow situations such as incinerator stacks or building air systems comprises a plurality of flat plates made of a scintillating material arranged parallel to the air flow. Each scintillating plate has a light guide attached which transfers light generated inside the scintillating plate to an associated photomultiplier tube. The output of the photomultiplier tubes are connected to electronics which can record any radiation and provide an alarm if appropriate for the application.

  5. Measurement of light emission in scintillation vials

    SciTech Connect

    Duran Ramiro, M. Teresa; Garcia-Torano, Eduardo

    2005-09-15

    The efficiency and energy resolution of liquid scintillation counting (LSC) systems are strongly dependent on the optical characteristics of scintillators, vials, and reflectors. This article presents the results of measurements of the light-emission profile of scintillation vials. Two measurement techniques, autoradiographs and direct measurements with a photomultiplier tube, have been used to obtain light-emission distribution for standard vials of glass, etched glass and polyethylene. Results obtained with both techniques are in good agreement. For the first time, the effect of the meniscus in terms of light contribution has been numerically estimated. These results can help design LSC systems that are more efficient in terms of light collection.

  6. Exploring the Multi-Scale Statistical Analysis of Ionospheric Scintillation via Wavelets and Empirical Mode Decomposition

    NASA Astrophysics Data System (ADS)

    Piersanti, Mirko; Materassi, Massimo; Spogli, Luca; Cicone, Antonio; Alberti, Tommaso

    2016-04-01

    Highly irregular fluctuations of the power of trans-ionospheric GNSS signals, namely radio power scintillation, are, at least to a large extent, the effect of ionospheric plasma turbulence, a by-product of the non-linear and non-stationary evolution of the plasma fields defining the Earth's upper atmosphere. One could expect the ionospheric turbulence characteristics of inter-scale coupling, local randomness and high time variability to be inherited by the scintillation on radio signals crossing the medium. On this basis, the remote sensing of local features of the turbulent plasma could be expected as feasible by studying radio scintillation. The dependence of the statistical properties of the medium fluctuations on the space- and time-scale is the distinctive character of intermittent turbulent media. In this paper, a multi-scale statistical analysis of some samples of GPS radio scintillation is presented: the idea is that assessing how the statistics of signal fluctuations vary with time scale under different Helio-Geophysical conditions will be of help in understanding the corresponding multi-scale statistics of the turbulent medium causing that scintillation. In particular, two techniques are tested as multi-scale decomposition schemes of the signals: the discrete wavelet analysis and the Empirical Mode Decomposition. The discussion of the results of the one analysis versus the other will be presented, trying to highlight benefits and limits of each scheme, also under suitably different helio-geophysical conditions.

  7. New observations of scintillation climatology from the Scintillation Network Decision Aid (SCINDA)

    NASA Astrophysics Data System (ADS)

    Su, Y.; Caton, R. G.; Wiens, K.; Groves, K. M.

    2012-12-01

    The Scintillation Network Decision Aid (SCINDA) was established with three ground sites in the mid-1990's by the Air Force Research Laboratory and has continued to grow into a global scintillation observation network. This system consists of an array of VHF and GPS receivers which continually measure scintillation in the equatorial region. In the past few years, the extended network of ground stations has expanded into the African sector. Initial results from yearly scintillation data obtained from two VHF receivers in Narobi, Kenya and Bahir Dar, Ethiopia in 2011 indicate the presence of scintillation activity throughout the June-July -August (northern summer) season which is inconsistent with current state-of-the-art ionospheric climatology models. It is well known that seasonal equatorial scintillation patterns vary with longitude based on geographical location. For example, the scintillation activity at VHF frequencies are absent in the Pacific sector during the months of November to February while observations from South America show nearly continuous scintillation during this same time period. With little to no ground-based observations, the scintillation climatology over the African region has not been well understood. In the paper, we will present S4 measurements various longitudinal sectors, including the first look at solar maximum type conditions over the African sector, and provide comparisons with output from a global climatology model.

  8. Scintillations of partially coherent Laguerre Gaussian beams

    NASA Astrophysics Data System (ADS)

    Yüceer, M.; Eyyuboğlu, H. T.; Lukin, I. P.

    2010-12-01

    Scintillations of Laguerre-Gaussian (LG) beams for weak atmospheric turbulence conditions are derived for on-axis receiver positions by using Huygens-Fresnel (HF) method in semi-analytic fashion. Numerical evaluations indicate that at the fully coherent limit, higher values of radial mode numbers will give rise to more scintillations, at medium and low partial coherence levels, particularly at longer propagation distances, scintillations will fall against rises in radial mode numbers. At small source sizes, the scintillations of LG beams having full coherence will initially rise, reaching saturation at large source sizes. For LG beams with low partial coherence levels, a steady fall toward the larger source sizes is observed. Partially coherent beams of medium levels generally exhibit a rising trend toward the large source sizes, also changing the respective positions of the related curves. Beams of low coherence levels will be less affected by the variations in the refractive index structure constant.

  9. Ternary liquid scintillator for optical fiber applications

    DOEpatents

    Franks, Larry A.; Lutz, Stephen S.

    1982-01-01

    A multicomponent liquid scintillator solution for use as a radiation-to-light converter in conjunction with a fiber optic transmission system. The scintillator includes a quantity of 5-amino-9-diethylaminobenz (a) phenoxazonium nitrate (Nile Blue Nitrate) as a solute in a fluor solvent such as benzyl alcohol. The use of PPD as an additional solute is also disclosed. The system is controllable by addition of a suitable quenching agent, such as phenol.

  10. Current status on plastic scintillators modifications.

    PubMed

    Bertrand, Guillaume H V; Hamel, Matthieu; Sguerra, Fabien

    2014-11-24

    Recent developments of plastic scintillators are reviewed, from 2000 to March 2014, distributed in two different chapters. First chapter deals with the chemical modifications of the polymer backbone, whereas modifications of the fluorescent probe are presented in the second chapter. All examples are provided with the scope of detection of various radiation particles. The main characteristics of these newly created scintillators and their detection properties are given. PMID:25335882

  11. Liquid scintillators for optical fiber applications

    DOEpatents

    Franks, Larry A.; Lutz, Stephen S.

    1982-01-01

    A multicomponent liquid scintillator solution for use as a radiation-to-light converter in conjunction with a fiber optic transmission system. The scintillator includes a quantity of 1, 2, 4, 5, 3H, 6H, 1 OH, tetrahydro-8-trifluoromethyl (1) benzopyrano (9, 9a, 1-gh) quinolizin-10-one (Coumarin) as a solute in a fluor solvent such as benzyl alcohol or pseudo-cumene. The use of BIBUQ as an additional or primary solute is also disclosed.

  12. Multi-GNSS for Ionospheric Scintillation Studies

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2015-12-01

    GNSS have been widely used for ionospheric monitoring. We anticipate over 160 GNSS satellites broadcasting 400 signals by 2023, nearly double the number today. With their well-defined signal structures, high spatial density and spectral diversity, GNSS offers low cost and distributed passive sensing of ionosphere effects. There are, however, many challenges to utilize GNSS resources to characterize and forecast ionospheric scintillation. Originally intended for navigation purposes, GNSS receivers are designed to filter out nuisance effects due to ionosphere effects. GNSS measurements are plagued with errors from multipath, oscillator jitters, processing artifacts, and neutral atmosphere effects. Strong scintillation events are often characterized by turbulent structures in ionosphere, causing simultaneous deep amplitude fading and abrupt carrier phase changes. The combined weak signal and high carrier dynamics imposes conflicting requirements for GNSS receiver design. Therefore, GNSS receivers often experience cycle slips and loss of lock of signals during strong scintillation events. High quality, raw GNSS signals bearing space weather signatures and robust receiver algorithms designed to capture these signatures are needed in order for GNSS to be a reliable and useful agent for scintillation monitoring and forecasting. Our event-driven, reconfigurable data collection system is designed to achieve this purpose. To date, our global network has collected ~150TB of raw GNSS data during space weather events. A suite of novel receiver processing algorithms has been developed by exploitating GNSS spatial, frequency, temporal, and constellation diversity to process signals experiencing challenging scintillation impact. The algorithms and data have advanced our understanding of scintillation impact on GNSS, lead to more robust receiver technologies, and enabled high spatial and temporal resolution depiction of ionosphere responses to solar and geomagnetic conditions. This

  13. GNSS station characterisation for ionospheric scintillation applications

    NASA Astrophysics Data System (ADS)

    Romano, Vincenzo; Spogli, Luca; Aquino, Marcio; Dodson, Alan; Hancock, Craig; Forte, Biagio

    2013-10-01

    Ionospheric scintillations are fluctuations in the phase and amplitude of the signals from GNSS (Global Navigation Satellite Systems) occurring when they cross regions of electron density irregularities in the ionosphere. Such disturbances can cause serious degradation of several aspects of GNSS system performance, including integrity, accuracy and availability. The two indices adopted worldwide to characterise ionospheric scintillations are: the amplitude scintillation index, S4, which is the standard deviation of the received power normalised by its mean value, and the phase scintillation index, σΦ, which is the standard deviation of the de-trended carrier phase. Collaborative work between NGI and INGV supports a permanent network of GISTM (GPS Ionospheric Scintillation and TEC Monitor) receivers that covers a wide range of latitudes in the northern European sector. Data from this network has contributed significantly to several papers during the past few years (see e.g. De Franceschi et al., 2008; Aquino et al., 2009; Spogli et al., 2009, 2010; Alfonsi et al., 2011). In these investigations multipath effects and noise that contaminate the scintillation measurements are largely filtered by applying an elevation angle threshold. A deeper analysis of the data quality and the development of a more complex filtering technique can improve the results obtained so far. The structures in the environment of each receiver in the network which contaminate scintillation measurements should be identified in order to improve the quality of the scintillation and TEC data by removing error sources due to the local environment. The analysis in this paper considers a data set characterised by quiet ionospheric conditions of the mid-latitude station located in Nottingham (UK), followed by a case study of the severe geomagnetic storm, which occurred in late 2003, known generally as the "Halloween Storm".

  14. Crystal growth and scintillation properties of strontium iodide scintillators

    SciTech Connect

    van Loef, Edgar; Wilson, Cody; Cherepy, Nerine; Payne, Steven; Choong, Woon-Seng; Moses, William W.; Shah, Kanai

    2009-06-01

    Single crystals of SrI{sub 2}:Eu and SrI{sub 2}:Ce/Na were grown from anhydrous iodides by the vertical Bridgman technique in evacuated silica ampoules. Growth rates were of the order of 5-30 mm/day. Radioluminescence spectra of SrI{sub 2}:Eu and SrI{sub 2}:Ce/Na exhibit a broad band due to Eu{sup 2+} and Ce{sup 3+} emission, respectively. The maximum in the luminescence spectrum of SrI{sub 2}:Eu is found at 435 nm. The spectrum of SrI{sub 2}:Ce/Na exhibits a doublet peaking at 404 and 435 nm attributed to Ce{sup 3+} emission, while additional impurity - or defected - related emission is present at approximately 525 nm. The strontium iodide scintillators show very high light yields of up to 120,000 photons/MeV, have energy resolutions down to 3% at 662 keV (Full Width Half Maximum) and exhibit excellent light yield proportionality with a standard deviation of less than 5% between 6 and 460 keV.

  15. Scintillation Hole Observed by FORMOSAT-3/COSMIC

    NASA Astrophysics Data System (ADS)

    Chen, Shih Ping; Yenq Liu, Jann; Krishnanunni Rajesh, Panthalingal

    2013-04-01

    Ionospheric scintillations can significantly disturb satellite positioning, navigation, and communication. FORMOSAT-3/COSMIC provides the first 3-D global observation by solo instrument (radio occultation experiment, GOX). The GPS L-band amplitude fluctuation from 50Hz signal is received and recorded by F3/C GOX to calculate S4-index from 50-800km altitude. The global F3/C S4 index are subdivided and examined in various latitudes, longitudes, altitudes, and seasons during 2007-2012. The F-region scintillations in the equatorial and low-latitude ionosphere start around post-sunset period and often persist till post-midnight hours (0300 MLT, magnetic local time) during the March and September equinox as well as December Solstice seasons. The E-region scintillations reveal a clear solar zenith effect and yield pronounced intensities in mid-latitudes during the Summer Solstice seasons, which are well correlated with occurrences of the sporadic E-layer. It is interesting to find there is no scintillation, which is termed "scintillation hole", in the E region ranging from 80 to 130km altitude over the South Africa region, and become the most pronounced in November-January (December Solstice seasons or summer months). Other space-borne and ground based observations are use to confirm the existence of the scintillation hole.

  16. Ionospheric scintillation effects on single frequency GPS

    NASA Astrophysics Data System (ADS)

    Steenburgh, R. A.; Smithtro, C. G.; Groves, K. M.

    2008-04-01

    Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active within, although not limited to, a belt encircling the Earth within 20 degrees of the geomagnetic equator. As GPS applications and users increase, so does the potential for degraded precision and availability from scintillation. We examined amplitude scintillation data spanning 7 years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/American longitudinal sector as well as data from Parepare, Indonesia; Marak Parak, Malaysia; Pontianak, Indonesia; Guam; and Diego Garcia, U.K. in the Pacific longitudinal sector. From these data, we calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. Additionally, we determine Dilution of Precision at 1 min resolution. We examine diurnal, seasonal, and solar cycle characteristics and make spatial comparisons. In general, activity was greatest during the equinoxes and solar maximum, although scintillation at Antofagasta, Chile was higher during 1998 rather than at solar maximum.

  17. Design considerations for a scintillating plate calorimeter

    NASA Astrophysics Data System (ADS)

    Job, P. K.; Price, L. E.; Proudfoot, J.; Handler, T.; Gabriel, T. A.

    1992-06-01

    Results of the simulation studies for the design of a scintillating plate calorimeter for an SSC detector are presented. These simulation studies have been carried out with the CALOR89 code. The results show that both lead and uranium can yield good compensation in practical sampling geometries. However, the significant delayed energy release in the uranium systems can lead to a serious pile up problem at high rates. In the energy range under consideration, an iron-scintillator system is not compensating at any absorber to scintillator ratio. An inhomogeneous calorimeter with 4γ of lead-scintillator in a compensating configuration followed by 4γ of iron-scintillator with moderate sampling is found to perform as well as a homogeneous lead-scintillator compensating calorimeter. In such inhomogeneous systems the hadronic signal from different segments are weighted by a scheme based on minimum ionizing d E/d X. We show that, in a properly optimised three segment, compensation and good hadronic resolution can be achieved by appropriately weighting the signal from the segments.

  18. Par Pond vegetation status 1996

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1996-12-01

    The water level of Par Pond was lowered approximately 20 feet in mid-1991 in order to protect downstream residents from possible dam failure suggested by subsidence on the downstream slope of the dam and to repair the dam. This lowering exposed both emergent and nonemergent macrophyte beds to drying conditions resulting in extensive losses. A survey of the newly emergent, shoreline aquatic plant communities of Par Pond began in June 1995, three months after the refilling of Par Pond to approximately 200 feet above mean sea level. These surveys continued in July, September, and late October, 1995, and into the early spring and late summer of 1996. Communities similar to the pre-drawdown, Par Pond aquatic plant communities continue to become re-established. Emergent beds of maidencane, lotus, waterlily, watershield, and Pontederia are extensive and well developed. Measures of percent cover, width of beds, and estimates of area of coverage with satellite data indicate regrowth within two years of from 40 to 60% of levels prior to the draw down. Cattail occurrence continued to increase during the summer of 1996, especially in the former warm arm of Par Pond, but large beds common to Par Pond prior to the draw down still have not formed. Lotus has invaded and occupies many of the areas formerly dominated by cattail beds. To track the continued development of macrophytes in Par Pond, future surveys through the summer and early fall of 1997, along with the evaluation of satellite data to map the extent of the macrophyte beds of Par Pond, are planned.

  19. Ionosphere scintillations associated with features of equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Chandra, H.; Vats, H. O.; Sethia, G.; Deshpande, M. R.; Rastogi, R. G.; Sastri, J. H.; Murthy, B. S.

    1979-01-01

    Amplitude scintillations of radio beacons aboard the ATS-6 satellite on 40 MHz, 140 MHz and 360 MHz recorded during the ATS-6 phase II at an equatorial station Ootacamund (dip 4 deg N) and the ionograms at a nearby station Kodaikanal (dip 3.5 deg N) are examined for scintillation activity. Only sporadic E events, other than Es-q, Es-c or normal E are found to be associated with intense daytime scintillations. Scintillations are also observed during night Es conditions. The amplitude spread is associated with strong scintillations on all frequencies while frequency spread causes weaker scintillations and that mainly at 40 MHz.

  20. Radar detection during scintillation. Technical report

    SciTech Connect

    Knepp, D.L.; Reinking, J.T.

    1990-04-01

    Electromagnetic signals that propagate through a disturbed region of the ionosphere can experience scattering which can cause fluctuations in the received amplitude, phase, and angle-of-arrival. This report considers the performance of a radar that must operate through a disturbed propagation environment such as might occur during strong equatorial scintillation, during a barium release experiment or after a high altitude nuclear detonation. The severity of the channel disturbance is taken to range from weak scattering where the signal quadrature components are uncorrelated Gaussian variates. The detection performance of noncoherent combining is compared to that of double threshold (M out of N) combining under various levels of scintillation disturbance. Results are given for detection sensitivity as a function of the scintillation index and the ratio of the radar hopping bandwidth to the channel bandwidth. It is shown that both types of combining can provide mitigation of fading, and that noncoherent combining generally enjoys an advantage in detection sensitivity of about 2 dB. This work serves as a quantitative guideline to the advantages and disadvantages of certain types of detection strategies during scintillation and is, therefore, useful in the radar design process. However, a detailed simulation of the radar detection algorithms is necessary to evaluate a radar design strategy to predict performance under scintillation conditions.

  1. Thallium bromide photodetectors for scintillation detection

    NASA Astrophysics Data System (ADS)

    Hitomi, K.; Muroi, O.; Shoji, T.; Hiratate, Y.; Ishibashi, H.; Ishii, M.

    2000-07-01

    A wide bandgap compound semiconductor, TlBr, has been investigated as a blue sensitive photodetector material for scintillation detection. The TlBr photodetectors have been fabricated from the TlBr crystals grown by the TMZ method using materials purified by many pass zone refining. The performance of the photodetectors has been evaluated by measuring their leakage current, quantum efficiency, spatial uniformity, direct X-ray detection and scintillation detection characteristics. The photodetectors have shown high quantum efficiency for the blue wavelength region and high spatial uniformity for their optical response. In addition, good direct X-ray detection characteristics with an energy resolution of 4.5 keV FWHM for 22 keV X-rays from a 109Cd radioactive source have been obtained. Detection of blue scintillation from GSO and LSO scintillators irradiated with a 22Na radioactive source has been done successfully by using the photodetectors at room temperature. A clear full-energy peak for 511 keV γ-rays has been obtained with the TlBr photodetector coupled to the LSO scintillator with an energy resolution of 40% FWHM.

  2. Operational Principles for the Dynamics of the In Vitro ParA-ParB System

    PubMed Central

    Jindal, Lavisha; Emberly, Eldon

    2015-01-01

    In many bacteria the ParA-ParB protein system is responsible for actively segregating DNA during replication. ParB proteins move by interacting with DNA bound ParA-ATP, stimulating their unbinding by catalyzing hydrolysis, that leads to rectified motion due to the creation of a wake of depleted ParA. Recent in vitro experiments have shown that a ParB covered magnetic bead can move with constant speed over a DNA covered substrate that is bound by ParA. It has been suggested that the formation of a gradient in ParA leads to diffusion-ratchet like motion of the ParB bead but how it forms and generates a force is still a matter of exploration. Here we develop a deterministic model for the in vitro ParA-ParB system and show that a ParA gradient can spontaneously form due to any amount of initial spatial noise in bound ParA. The speed of the bead is independent of this noise but depends on the ratio of the range of ParA-ParB force on the bead to that of removal of surface bound ParA by ParB. We find that at a particular ratio the speed attains a maximal value. We also consider ParA rebinding (including cooperativity) and ParA surface diffusion independently as mechanisms for ParA recovery on the surface. Depending on whether the DNA covered surface is undersaturated or saturated with ParA, we find that the bead can accelerate persistently or potentially stall. Our model highlights key requirements of the ParA-ParB driving force that are necessary for directed motion in the in vitro system that may provide insight into the in vivo dynamics of the ParA-ParB system. PMID:26670738

  3. Characterization of ionospheric scintillation at a geomagnetic equatorial region station

    NASA Astrophysics Data System (ADS)

    Seba, Ephrem Beshir; Gogie, Tsegaye Kassa

    2015-11-01

    In this study, we analyzed ionospheric scintillation at Bahir Dar station, Ethiopia (11.6°N, 37.38°E) using GPS-SCINDA data between August 2010 and July 2011. We found that small scale variation in TEC caused high ionospheric scintillation, rather than large scale variation. We studied the daily and monthly variations in the scintillation index S4 during this year, which showed that scintillation was a post-sunset phenomenon on equinoctial days, with high activity during the March equinox. The scintillation activity observed on solstice days was relatively low and almost constant throughout the day with low post-sunset activity levels. Our analysis of the seasonal and annual scintillation characteristics showed that intense activity occurred in March and April. We also studied the dependence of the scintillation index on the satellite elevation angle and found that scintillation was high for low angles but low for high elevation angles.

  4. Isotopic response with small scintillator based gamma-ray spectrometers

    DOEpatents

    Madden, Norman W.; Goulding, Frederick S.; Asztalos, Stephen J.

    2012-01-24

    The intrinsic background of a gamma ray spectrometer is significantly reduced by surrounding the scintillator with a second scintillator. This second (external) scintillator surrounds the first scintillator and has an opening of approximately the same diameter as the smaller central scintillator in the forward direction. The second scintillator is selected to have a higher atomic number, and thus has a larger probability for a Compton scattering interaction than within the inner region. Scattering events that are essentially simultaneous in coincidence to the first and second scintillators, from an electronics perspective, are precluded electronically from the data stream. Thus, only gamma-rays that are wholly contained in the smaller central scintillator are used for analytic purposes.

  5. Testing Gravity Using Pulsar Scintillation Measurements

    NASA Astrophysics Data System (ADS)

    Yang, Huan; Nishizawa, Atsushi; Pen, Ue-Li

    2016-03-01

    We propose to use pulsar scintillation measurements to test predictions of alternative theories of gravity. Comparing to single-path pulsar timing measurements, the scintillation measurements can achieve a factor of 104 ~105 improvement in timing accuracy, due to the effect of multi-path interference. The self-noise from pulsar also does not affect the interference pattern, where the data acquisition timescale is 103 seconds instead of years. Therefore it has unique advantages in measuring gravitational effect or other mechanisms (at mHz and above frequencies) on light propagation. We illustrate its application in constraining scalar gravitational-wave background and measuring gravitational-wave speed, in which cases the sensitivities are greatly improved with respect to previous limits. We expect much broader applications in testing gravity with existing and future pulsar scintillation observations.

  6. Scintillating-glass-fiber neutron sensors

    NASA Astrophysics Data System (ADS)

    Abel, K. H.; Arthur, R. J.; Bliss, M.; Brite, D. W.; Brodzinski, R. L.; Craig, R. A.; Geelhood, B. D.; Goldman, D. S.; Griffin, J. W.; Perkins, R. W.; Reeder, P. L.; Richey, W. R.; Stahl, K. A.; Sunberg, D. S.; Warner, R. A.; Wogman, N. A.; Weber, M. J.

    1994-12-01

    Cerium-doped lithium-silicate glass fibers have been developed at Pacific Northwest Laboratory (PNL) for use as thermal neutron detectors. By using highly-enriched 6Li, these fibers efficiently capture thermal neutrons and produce scintillation light that can be detected at the ends of the fibers. Advantages of scintillating fibers over 3He or BF 3 proportional tubes include flexibility in geometric configuration, ruggedness in high-vibration environments, and less detector weight for the same neutron sensitivity. This paper describes the performance of these scintillating fibers with regard to count rates, pulse height spectra, absolute efficiencies, and neutron/gamma discrimination. Fibers with light transmission lengths ( {1}/{e}) of greater than 2 m have been produced at PNL. Neutron sensors in fiber form allow development of a variety of neutron detectors packaged in previously unavailable configurations. Brief descriptions of some of the devices already produced are included to illustrate these possibilities.

  7. New Efficient Organic Scintillators Derived from Pyrazoline.

    PubMed

    Bliznyuk, Valery N; Seliman, Ayman F; Ishchenko, Alexander A; Derevyanko, Nadezhda A; DeVol, Timothy A

    2016-05-25

    We report on the synthesis, spectroscopic and scintillation properties of three new pyrazoline core based fluorophores. Fluorescence properties of the fluorophores have been studied both in a solution state and in a solid polyvinyltoluene (PVT) resin matrix of different porosity. The synthesized fluorophores were found to be promising candidates for application in plastic scintillators for detection of ionizing radiation (alpha, beta particles, γ rays and neutrons) and demonstrated superior efficiency in comparison to the existing commercially used fluorophores (2-(1-naphthyl)-5-phenyloxazole (αNPO), 9,10-diphenylanthracene, etc.). Moreover, the suggested synthetic route allows functionalization of the fluorophores with a vinyl group for further covalent bound to the PVT or other vinyl polymer matrices, which dramatically improves chemical stability of the system simultaneously improving the photoluminescence quantum yield. Possible mechanisms of the enhanced scintillation properties are discussed based on preliminary quantum mechanical calculations and spectroscopic characteristics of the fluorophores under study. PMID:27163887

  8. Refractive scintillation in the interstellar medium

    NASA Astrophysics Data System (ADS)

    Coles, W. A.; Rickett, B. J.; Codona, J. L.; Frehlich, R. G.

    1987-04-01

    The slow variation in the apparent intensity of pulsars on time scales of days to months was recently shown to be due to a large-scale component of interstellar scintillation (Rickett, Coles, and Bourgois). These variations are greater than one would expect if the turbulence spectrum were a simple Kolmogorov power law. It is shown that this large-scale component can be greatly enhanced when the turbulence spectrum has a limiting "inner scale" of the order of 109m. The authors present a solution for the covariance of refractive scintillation of an extended source in an extended medium. The results show that refractive scintillations are also responsible for slow variations in "low-frequency variables".

  9. On the scintillation efficiency of carborane-loaded liquid scintillators for thermal neutron detection

    NASA Astrophysics Data System (ADS)

    Chang, Zheng; Okoye, Nkemakonam C.; Urffer, Matthew J.; Green, Alexander D.; Childs, Kyle E.; Miller, Laurence F.

    2015-01-01

    The scintillation efficiency in response to thermal neutrons was studied by loading different concentrations of carborane (0-8.5 wt%) and naphthalene (0 and 100 g/L) in five liquid organic scintillators. The sample was characterized in Pb and Cd shields under the irradiation of the thermal neutrons from a 252Cf source. A method was developed to extract the net neutron response from the pulse-height spectra. It was found that the order of scintillation efficiencies for both γ-rays and thermal neutrons is as follows: diisopropylnaphthalene>toluene (concentrated solutes)>toluene~pseudocumene~m-xylene. The quench constants, obtained by fitting the Stern-Volmer model to the plots of light output versus carborane concentration, are in the range of 0.35-1.4 M-1 for all the scintillators. The Birks factors, estimated using the specific energy loss profiles of the incident particles, are in the range of 9.3-14 mg cm-2 MeV-1 for all the samples. The light outputs are in the range of 63-86 keV electron equivalents (keVee) in response to thermal neutrons. Loading naphthalene generally promotes the scintillation efficiency of the scintillator with a benzene derivative solvent. Among all the scintillators tested, the diisopropylnaphthalene-based scintillator shows the highest scintillation efficiency, lowest Birks factor, and smallest quench constants. These properties are primarily attributed to the double fused benzene-ring structure of the solvent, which is more efficient to populate to the excited singlet state under ionizing radiation and to transfer the excitation energy to the fluorescent solutes.

  10. A step toward CNO solar neutrino detection in liquid scintillators

    NASA Astrophysics Data System (ADS)

    Villante, F. L.; Ianni, A.; Lombardi, F.; Pagliaroli, G.; Vissani, F.

    2011-07-01

    The detection of CNO solar neutrinos in ultrapure liquid scintillator detectors is limited by the background produced by bismuth-210 nuclei that undergo β-decay to polonium-210 with a lifetime of ˜7 days. Polonium-210 nuclei are unstable and decay with a lifetime equal to ˜200 days emitting α particles that can be also detected. In this Letter, we show that the Bi-210 background can be determined by looking at the time evolution of α-decay rate of Po-210, provided that α particle detection efficiency is stable over the data acquisition period and external sources of Po-210 are negligible. A sufficient accuracy can be obtained in a relatively short time. As an example, if the initial Po-210 event rate is ˜2000 cpd/100 ton or lower, a Borexino-like detector could start discerning CNO neutrino signal from Bi-210 background in Δt˜1 yr.

  11. The design of the TASD (totally active scintillator detector) prototype

    SciTech Connect

    Mefodiev, A. V. Kudenko, Yu. G.

    2015-12-15

    Totally active and magnetic segmented scintillation neutrino detectors are developed for the nextgeneration accelerator neutrino experiments. Such detectors will incorporate scintillation modules with scintillation counters that form X and Y planes. A single counter is a 7 × 10 × 90 mm{sup 3} scintillation bar with gluedin wavelength-shifting fibers and micropixel avalanche photodiodes. The results of measurements of the parameters of these detectors are presented.

  12. Scintillation index in strong oceanic turbulence

    NASA Astrophysics Data System (ADS)

    Baykal, Yahya

    2016-09-01

    Scintillation index of spherical wave in strongly turbulent oceanic medium is evaluated. In the evaluation, modified Rytov solution and our recent formulation that expresses the oceanic turbulence parameters by the atmospheric turbulence structure constant, are employed. Variations of the scintillation index in strong oceanic turbulence are examined versus the oceanic turbulence parameters such as the rate of dissipation of kinetic energy per unit mass of fluid, the rate of dissipation of mean-squared temperature, viscosity, wavelength, the link length, and the ratio of temperature to salinity contributions to the refractive index spectrum.

  13. The homestake surface-underground scintillations: Description

    NASA Technical Reports Server (NTRS)

    Cherry, M. L.; Corbato, S.; Daily, T.; Fenyves, E. J.; Kieda, D.; Lande, K.; Lee, C. K.

    1985-01-01

    Two new detectors are currently under construction at the Homestake Gold Mine a 140-ton Large Area Scintillation Detector (LASD) with an upper surface area of 130 square meters, a geometry factor (for an isotropic flux) of 1200 square meters, sr, and a depth of 4200 m.w.e.; and a surface air shower array consisting of 100 scintillator elements, each 3 square meters, spanning an area of approximately square kilometers. Underground, half of the LASD is currently running and collecting muon data; on the surface, the first section of the air shower array will begin operation in the spring of 1985. The detectors and their capabilities are described.

  14. New Structured Scintillators for Neutron Radiography

    NASA Astrophysics Data System (ADS)

    Nagarkar, V. V.; Ovechkina, E. E.; Bhandari, H. B.; Soundara-Pandian, L.; More, M. J.; Riedel, R. A.; Miller, S. R.

    We report on the development of novel neutron scintillators fabricated in microcolumnar formats using the physical vapour deposition (PVD) method. Such structures mitigate the conventional trade-off between spatial resolution and detection efficiency by channelling the scintillation light towards the detector while minimizing lateral spread in the film. Consequently, high resolution and high contrast neutron images can be acquired in a time efficient manner. In this paper, we discuss methods and characterization for scintillator films made from three distinct compositions, Thallium (Tl) or Europium (Eu) doped Lithium CesiumIodide (Li3Cs2I5:Tl,Eu, referred to as LCI), Tl or Eudoped Lithium Sodium Iodide (LixNa1-xI:Tl,Eu, referred to as LNI), and Cerium (Ce)-doped Gadolinium Iodide (GdI3:Ce, referred to as GDI). LCI and LNI scintillators are derived from the well-known CsI and NaI scintillators by the incorporation of 6Li into their lattice. Based on our measurements reported here, LCI/LNI scintillators have shown to exhibit bright emissions, fast, sub-microsecond decay, and an ability to effectively discriminate between neutron and gamma interactions using pulse shape (PSD) and/or pulse height (PHD) discrimination. LCI has a density of 4.5 g/cm3, a measured peak emission wavelength of 460 nm (doped with Eu), and a light yield of ∼50,000 photons/thermal neutron. LNI has a density of 3.6 g/cm3, an emission peak measured at 420 nm, and a light yield of ∼100,000 photons/thermal neutron. The recently discovered GDI exhibits excellent scintillation properties including a bright emission of up to 5,000 photons/thermal neutron interaction, 550 nm green emission, a rise time of ∼0.5 ns and a primary decay time of ∼38 ns (Glodo et al., 2006). Its high thermal neutron cross-section of ∼255 kb makes it an attractive candidate for neutron detection and imaging. Although it has high density of 5.2 gm/cm3 and effective atomic number of 57, its gamma sensitivity can be

  15. New liquid scintillators for fiber-optic applications

    SciTech Connect

    Lutz, S.S.; Franks, L.A.; Flournoy, J.M.; Lyons, P.B.

    1981-01-01

    New long-wavelength-emitting, high-speed, liquid scintillators have been developed and tailored specifically for plasma diagnostic experiments employing fiber optics. These scintillators offer significant advantages over commercially available plastic scintillators in terms of sensitivity and bandwidth. FWHM response times as fast as 350 ps have been measured. Emission spectra, time response data, and relative sensitivity information are presented.

  16. Upconverting nanoparticles for optimizing scintillator based detection systems

    DOEpatents

    Kross, Brian; McKisson, John E; McKisson, John; Weisenberger, Andrew; Xi, Wenze; Zom, Carl

    2013-09-17

    An upconverting device for a scintillation detection system is provided. The detection system comprises a scintillator material, a sensor, a light transmission path between the scintillator material and the sensor, and a plurality of upconverting nanoparticles particles positioned in the light transmission path.

  17. Spatial correlations in intense ionospheric scintillations - comparison between numerical computation and observation

    SciTech Connect

    Kumagai, H.

    1987-06-01

    The spatial correlations in intense ionospheric scintillations were analyzed by comparing numerical results with observational ones. The observational results were obtained by spaced-receiver scintillation measurements of VHF satellite radiowave. The numerical computation was made by using the fourth-order moment equation with fairly realistic ionospheric irregularity models, in which power-law irregularities with spectral index 4, both thin and thick slabs, and both isotropic and anisotropic irregularities, were considered. Evolution of the S(4) index and the transverse correlation function was computed. The numerical result that the transverse correlation distance decreases with the increase in S(4) was consistent with that obtained in the observation, suggesting that multiple scattering plays an important role in the intense scintillations observed. The anisotropy of irregularities proved to act as if the density fluctuation increased. This effect, as well as the effect of slab thickness, was evaluated by the total phase fluctuations that the radiowave experienced in the slab. On the basis of the comparison, the irregularity height and electron-density fluctuation which is necessary to produce a particular strength of scintillation were estimated. 30 references.

  18. The SNO+ Scintillator Purification Plant and Projected Sensitivity to Solar Neutrinos in the Pure Scintillator Phase

    NASA Astrophysics Data System (ADS)

    Pershing, Teal; SNO+ Collaboration

    2016-03-01

    The SNO+ detector is a neutrino and neutrinoless double-beta decay experiment utilizing the renovated SNO detector. In the second phase of operation, the SNO+ detector will contain 780 tons of organic liquid scintillator composed of 2 g/L 2,5-diphenyloxazole (PPO) in linear alkylbenzene (LAB). In this phase, SNO+ will strive to detect solar neutrinos in the sub-MeV range, including CNO production neutrinos and pp production neutrinos. To achieve the necessary detector sensitivity, a four-part scintillator purification plant has been constructed in SNOLAB for the removal of ionic and radioactive impurities. We present an overview of the SNO+ scintillator purification plant stages, including distillation, water extraction, gas stripping, and metal scavenger columns. We also give the projected SNO+ sensitivities to various solar-produced neutrinos based on the scintillator plant's projected purification efficiency.

  19. Development of scintillator plates with high energy resolution for alpha particles made of GPS scintillator grains

    NASA Astrophysics Data System (ADS)

    Shimaoka, Takehiro; Kaneko, Junichi H.; Izaki, Kenji; Tsubota, Youichi; Higuchi, Mikio; Nishiyama, Shusuke

    2014-01-01

    A scintillator plate with high energy resolution was developed to produce an alpha particle monitor used in nuclear fuel reprocessing plants and mixed plutonium-uranium oxide (MOX) fuel plants. Grains of a Gd2Si2O7 (GPS) scintillator of several 10 to 550 μm were fixed on a glass substrate and were then mechanically polished. By increasing the size of scintillator grains and removing fine powders, the collected light yield and energy resolution for alpha particles were drastically improved. Energy resolution of 9.3% was achieved using average grain size of 91 μm. Furthermore, the ratios between counts in a peak and total counts were improved by more than 60% by the further increase of grain size and adoption of mechanically polished surfaces on both sides. Beta and gamma ray influences were suppressed sufficiently by the thin 100 μm scintillator plates.

  20. Progress in studying scintillator proportionality: Phenomenological model

    SciTech Connect

    Bizarri, Gregory; Cherepy, Nerine; Choong, Woon-Seng; Hull, Giulia; Moses, William; Payne, Sephen; Singh, Jai; Valentine, John; Vasilev, Andrey; Williams, Richard

    2009-04-30

    We present a model to describe the origin of non-proportional dependence of scintillator light yield on the energy of an ionizing particle. The non-proportionality is discussed in terms of energy relaxation channels and their linear and non-linear dependences on the deposited energy. In this approach, the scintillation response is described as a function of the deposited energy deposition and the kinetic rates of each relaxation channel. This mathematical framework allows both a qualitative interpretation and a quantitative fitting representation of scintillation non-proportionality response as function of kinetic rates. This method was successfully applied to thallium doped sodium iodide measured with SLYNCI, a new facility using the Compton coincidence technique. Finally, attention is given to the physical meaning of the dominant relaxation channels, and to the potential causes responsible for the scintillation non-proportionality. We find that thallium doped sodium iodide behaves as if non-proportionality is due to competition between radiative recombinations and non-radiative Auger processes.

  1. High resolution scintillation detector with semiconductor readout

    DOEpatents

    Levin, Craig S.; Hoffman, Edward J.

    2000-01-01

    A novel high resolution scintillation detector array for use in radiation imaging such as high resolution Positron Emission Tomography (PET) which comprises one or more parallelepiped crystals with at least one long surface of each crystal being in intimate contact with a semiconductor photodetector such that photons generated within each crystal by gamma radiation passing therethrough is detected by the photodetector paired therewith.

  2. Temperature dependence of BCF plastic scintillation detectors

    PubMed Central

    Wootton, Landon; Beddar, Sam

    2013-01-01

    We examined temperature dependence in plastic scintillation detectors (PSDs) made of BCF-60 or BCF-12 scintillating fiber coupled to optical fiber with cyanoacrylate. PSDs were subjected to a range of temperatures using a temperature-controlled water bath and irradiated at each temperature while either the dose was measured using a CCD camera or the spectral output was measured using a spectrometer. The spectrometer was used to examine the intensity and spectral distribution of scintillation light emitted by the PSDs, Cerenkov light generated within the PSD, and light transmitted through an isolated optical coupling. BCF-60 PSDs exhibited a 0.50% decrease and BCF-12 PSDs a 0.09% decrease in measured dose per °C increase, relative to dose measured at 22°C. Spectrometry revealed that the total intensity of the light generated by BCF-60 and BCF-12 PSDs decreased by 0.32% and 0.13%, respectively, per °C increase. The spectral distribution of the light changed slightly with temperature for both PSDs, accounting for the disparity between the change in measured dose and total light output. The generation of Cerenkov light was temperature independent. However, light transmitted through optical coupling between the scintillator and the optical fiber also exhibited temperature dependence. PMID:23574889

  3. Ionospheric scintillations associated with equatorial E-region

    NASA Technical Reports Server (NTRS)

    Chandra, H.; Vats, H. O.; Sethia, G.; Deshpande, M. R.; Rastogi, R. G.; Sastri, J. H.

    1978-01-01

    Amplitude scintillations at 40, 140, and 360 MHz recorded at an equatorial station Ootacamund (dip 4 deg N) during the ATS-6 phase II and the ionograms at a nearby station Kodaikanal (dip 3.5 deg N) are examined for the scintillation activity. Various sporadic E events, but not the Es-q, are associated with intense daytime scintillations. There are no scintillations at times of normal E-layer or cusp type of Es. Scintillations are also present at times of night Es.

  4. Liquid Scintillator Production for the NOvA Experiment

    SciTech Connect

    Mufson, S.; Baugh, B.; Bower, C.; Coan, T.; Cooper, J.; Corwin, L.; Karty, J.; Mason, P.; Messier, M. D.; Pla-Dalmau, A.; Proudfoot, M.

    2015-04-15

    The NOvA collaboration blended and delivered 8.8 kt (2.72M gal) of liquid scintillator as the active detector medium to its near and far detectors. The composition of this scintillator was specifically developed to satisfy NOvA's performance requirements. A rigorous set of quality control procedures was put in place to verify that the incoming components and the blended scintillator met these requirements. The scintillator was blended commercially in Hammond, IN. The scintillator was shipped to the NOvA detectors using dedicated stainless steel tanker trailers cleaned to food grade.

  5. Outward atmospheric scintillation effects and inward atmospheric scintillation effects comparisons for direct detection ladar applications

    NASA Astrophysics Data System (ADS)

    Youmans, Douglas G.

    2014-06-01

    Atmospheric turbulence produces intensity modulation or "scintillation" effects on both on the outward laser-mode path and on the return backscattered radiation path. These both degrade laser radar (ladar) target acquisition, ranging, imaging, and feature estimation. However, the finite sized objects create scintillation averaging on the outgoing path and the finite sized telescope apertures produce scintillation averaging on the return path. We expand on previous papers going to moderate to strong turbulence cases by starting from a 20kft altitude platform and propagating at 0° elevation (with respect to the local vertical) for 100km range to a 1 m diameter diffuse sphere. The outward scintillation and inward scintillation effects, as measured at the focal plane detector array of the receiving aperture, will be compared. To eliminate hard-body surface speckle effects in order to study scintillation, Goodman's M-parameter is set to 106 in the analytical equations and the non-coherent imaging algorithm is employed in Monte Carlo realizations. The analytical equations of the signal-to-noise ratio (SNRp), or mean squared signal over a variance, for a given focal plane array pixel window of interest will be summarized and compared to Monte Carlo realizations of a 1m diffuse sphere.

  6. Cross beam scintillations in non-Kolmogorov medium.

    PubMed

    Baykal, Yahya

    2014-10-01

    For the collimated and focused cross beams, the on-axis scintillation index is evaluated when these beams propagate in weak non-Kolmogorov turbulence. In the limiting cases, our solution correctly reduces to the known Gaussian beam scintillations in Kolmogorov turbulence. For both the collimated and the focused cross beams, large power law exponent of the non-Kolmogorov turbulence is found to result in larger scintillations. Evaluating at a fixed power law exponent, the scintillation index of the collimated (focused) cross beam is higher (lower) than the collimated (focused) Gaussian beam scintillation index. When the asymmetry of the collimated (focused) cross beam increases, the scintillations increase (decrease). At a given cross beam configuration, change in the turbulence parameters varies the scintillations in the same manner for all power law exponent values.

  7. Non-Carbon Dyes For Platic Scintillators- Report

    SciTech Connect

    Teprovich, J.; Colon-Mercado, H.; Gaillard, J.; Sexton, L.; Washington, A.; Ward, P.; Velten, J.

    2015-10-19

    Scintillation based detectors are desirable for many radiation detection applications (portal and border monitoring, safeguards verification, contamination detection and monitoring). The development of next generation scintillators will require improved detection sensitivity for weak gamma ray sources, and fast and thermal neutron quantification. Radiation detection of gamma and neutron sources can be accomplished with organic scintillators, however, the single crystals are difficult to grow for large area detectors and subject to cracking. Alternatives to single crystal organic scintillators are plastic scintillators (PS) which offer the ability to be shaped and scaled up to produce large sized detectors. PS is also more robust than the typical organic scintillator and are ideally suited for deployment in harsh real-world environments. PS contain a mixture of dyes to down-convert incident radiation into visible light that can be detected by a PMT. This project will evaluate the potential use of nano-carbon dyes in plastic scintillators.

  8. Par Pond Fish, Water, and Sediment Chemistry

    SciTech Connect

    Paller, M.H.; Wike, L.D.

    1996-06-01

    The objectives of this report are to describe the Par Pond fish community and the impact of the drawdown and refill on the community, describe contaminant levels in Par Pond fish, sediments, and water and indicate how contaminant concentrations and distributions were affected by the drawdown and refill, and predict possible effects of future water level fluctuations in Par Pond.

  9. Parallel Climate Analysis Toolkit (ParCAT)

    SciTech Connect

    Smith, Brian Edward

    2013-06-30

    The parallel analysis toolkit (ParCAT) provides parallel statistical processing of large climate model simulation datasets. ParCAT provides parallel point-wise average calculations, frequency distributions, sum/differences of two datasets, and difference-of-average and average-of-difference for two datasets for arbitrary subsets of simulation time. ParCAT is a command-line utility that can be easily integrated in scripts or embedded in other application. ParCAT supports CMIP5 post-processed datasets as well as non-CMIP5 post-processed datasets. ParCAT reads and writes standard netCDF files.

  10. Real-time Scintillation Monitoring in Alaska from a Longitudinal Chain of ASTRA's SM-211 GPS TEC and Scintillation Receivers

    NASA Astrophysics Data System (ADS)

    Crowley, G.; Azeem, S. I.; Reynolds, A.; Santana, J.; Hampton, D. L.

    2013-12-01

    Amplitude and phase scintillation can cause serious difficulties for GPS receivers. Intense scintillation can cause loss of lock. High latitude studies generally show that phase scintillation can be severe, but the amplitude scintillation tends to be small. The reason for this is not yet understood. Furthermore, the actual causes of the ionospheric irregularities that produce high latitude scintillation are not well understood. While the gradient drift instability is thought to be important in the F-region, there may be other structures present in either the E- or F-regions. The role of particle precipitation is also not well understood. Four of ASTRA's CASES GPS receivers were deployed in Alaska to demonstrate our ability to map scintillation in realtime, to provide space weather services to GPS users, and to initiate a detailed investigation of these effects. These dual-frequency GPS receivers measure total electron content (TEC) and scintillation. The scintillation monitors were deployed in a longitudinal chain at sites in Kaktovic, Fort Yukon, Poker Flat, and Gakona. Scintillation statistics show phase scintillations to be largest at Kaktovic and smallest at Gakona. We present GPS phase scintillation and auroral emission results from the Alaska chain to characterize the correspondence between scintillation and auroral features, and to investigate the role of high latitude auroral features in driving the phase scintillations. We will also present data showing how phase scintillation can cause other GPS receivers to lose lock. The data and results are particularly valuable because they illustrate some of the challenges of using GPS systems for positioning and navigation in an auroral region like Alaska. These challenges for snowplough drivers were recently highlighted, along with the CASES SM-211 space weather monitor, in a special video in which ASTRA and three other small businesses were presented with an entrepreneurial award from William Shatner (http://youtu.be/bIVKEQH_YPk).

  11. Neutron spectroscopy with scintillation detectors using wavelets

    NASA Astrophysics Data System (ADS)

    Hartman, Jessica

    The purpose of this research was to study neutron spectroscopy using the EJ-299-33A plastic scintillator. This scintillator material provided a novel means of detection for fast neutrons, without the disadvantages of traditional liquid scintillation materials. EJ-299-33A provided a more durable option to these materials, making it less likely to be damaged during handling. Unlike liquid scintillators, this plastic scintillator was manufactured from a non-toxic material, making it safer to use, as well as easier to design detectors. The material was also manufactured with inherent pulse shape discrimination abilities, making it suitable for use in neutron detection. The neutron spectral unfolding technique was developed in two stages. Initial detector response function modeling was carried out through the use of the MCNPX Monte Carlo code. The response functions were developed for a monoenergetic neutron flux. Wavelets were then applied to smooth the response function. The spectral unfolding technique was applied through polynomial fitting and optimization techniques in MATLAB. Verification of the unfolding technique was carried out through the use of experimentally determined response functions. These were measured on the neutron source based on the Van de Graff accelerator at the University of Kentucky. This machine provided a range of monoenergetic neutron beams between 0.1 MeV and 24 MeV, making it possible to measure the set of response functions of the EJ-299-33A plastic scintillator detector to neutrons of specific energies. The response of a plutonium-beryllium (PuBe) source was measured using the source available at the University of Nevada, Las Vegas. The neutron spectrum reconstruction was carried out using the experimentally measured response functions. Experimental data was collected in the list mode of the waveform digitizer. Post processing of this data focused on the pulse shape discrimination analysis of the recorded response functions to remove the

  12. Nonproportionality of Scintillator Detectors: Theory and Experiment

    SciTech Connect

    Payne, Stephen; Cherepy, Nerine; Hull, Giulia; Valentine, John; Moses, William; Choong, Woon-Seng

    2009-08-17

    On the basis of nonproportionality data obtained for several scintillators, we have developed a theory to describe the carrier dynamics to fit the light yield versus electron energy. The theory of Onsager was adapted to explain how the carriers form excitons or sequentially arrive at the activators to promote the ion to an excited state, and the theory of Birks was employed to allow for exciton-exciton annihilation. We then developed a second theory to deduce the degradation in resolution that results from nonproportionality by evoking Landau fluctuations, which are essentially variations in the deposited energy density that occur as the high energy electron travels along its trajectory. In general there is good agreement with the data, in terms of fitting the nonproportionality curves and reproducing the literature values of nonproportionality's contribution to the scintillator resolution. With the resurgence of interest in developing scintillator detectors that have good energy resolution, an improved understanding of nonproportionality has become a crucial matter since it presents the fundamental limit to the achievable resolution. In order to hasten an improved understanding of scintillator nonproportionality, we have constructed an instrument referred to as SLYNCI (Scintillator Light Yield Nonproportionality Compton Instrument). This is a second-generation instrument to the original device developed by Valentine and coworkers, wherein several new principles of operation have served to increase the data rate by an order of magnitude as discussed in detail in References. In the present article, the focus is on a theory to describe the measured electron response, which is the light yield as a function of the electron energy. To do this, we account for transport of carriers and excitons, in terms of how they transfer their energy to the activators with competition from nonradiative decay pathways. This work builds on the original work of Murray and coworkers, and

  13. Studies of Plasma Bubbles & Comparision of TEC Fluctuations and Scintillations at Varanasi Using GPS Data

    NASA Astrophysics Data System (ADS)

    Priyadarshi, Shishir; Kumar, Sanjay; Singh, Abhay Kumar

    Ionospheric total electron content (TEC) and scintillations have been recorded continuously since January 2009 using a dual frequency GPS receiver at Varanasi, India (geographic lat. 25.30 N, long. 82.990 E). The trajectory of a GPS satellite plays an important role in observing the bubble characteristics. The GPS data with a sampling interval of 60 s were analyzed to determine TEC, the rate of change of TEC (ROT) and as well as ROTI, defined as the standard deviation of ROT. In this work we compare the S4 index of GPS scintillations with the ROTI values and there by investigated the evolution of large and small scale irregularities at scale length of few kilometers and 400 m respectively observed at low latitude station Varanasi. The effects of geomagnetic activity and geomagnetic storm on the generation of bubbles are studied using Kp index and Dst index respectively. Kew words: GPS, Plasma bubble, ROT, ROTI

  14. suPAR: The Molecular Crystal Ball

    PubMed Central

    Thunø, Maria; Macho, Betina; Eugen-Olsen, Jesper

    2009-01-01

    soluble urokinase Plasminogen Activator Receptor (suPAR) levels reflect inflammation and elevated suPAR levels are found in several infectious diseases and cancer. suPAR exists in three forms; suPARI-III, suPARII-III and suPARI which show different properties due to structural differences. Studies suggest that full-length suPAR is a regulator of uPAR/uPA by acting as uPA-scavenger, whereas the cleaved suPARII-III act as a chemotactic agent promoting the immune response via the SRSRY sequence in the linker-region. This review focus on the various suPAR fragments and their involvement in inflammation and pathogenic processes. We focus on the molecular mechanisms of the suPAR fragments and the link to the inflammatory process, as this could lead to medical applications in infectious and pathological conditions. PMID:19893210

  15. Divalent europium doped and un-doped calcium iodide scintillators: Scintillator characterization and single crystal growth

    DOE PAGESBeta

    Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.; Neal, John S.

    2015-02-21

    Initially, the alkaline-earth scintillator, CaI2:Eu2+, was discovered around 1964 by Hofstadter, Odell, and Schmidt. Serious practical problems quickly arose, however, that were associated with the growth of large monolithic single crystals of this material due to its lamellar, mica-like structure. As a result of its theoretically higher light yield, CaI2:Eu2+ has the potential to exceed the excellent scintillation performance of SrI2:Eu2+. In fact, theoretical predictions for the light yield of CaI2:Eu2+ scintillators suggested that an energy resolution approaching 2% at 662 keV could be achievable. Like the early SrI2:Eu2+ scintillator, the performance of CaI2:Eu2+ scintillators has traditionally suffered due, atmore » least in part, to outdated materials synthesis, component stoichiometry/purity, and single-crystal-growth techniques. Based on our recent work on SrI2:Eu2+ scintillators in single-crystal form, we have developed new techniques that are applied here to CaI2:Eu2+ and pure CaI2 with the goal of growing large un-cracked crystals and, potentially, realizing the theoretically predicted performance of the CaI2:Eu2+ form of this material. Calcium iodide does not adhere to modern glassy carbon Bridgman crucibles - so there should be no differential thermal-contraction-induced crystal/crucible stresses on cooling that would result in crystal cracking of the lamellar structure of CaI2. Here we apply glassy carbon crucible Bridgman growth, high-purity growth-charge compounds, our molten salt processing/filtration technique, and extended vacuum-melt-pumping methods to the growth of both CaI2:Eu2+ and un-doped CaI2. Moreover, large scintillating single crystals were obtained, and detailed characterization studies of the scintillation properties of CaI2:Eu2+ and pure CaI2 single crystals are presented that include studies of the effects of plastic deformation of the crystals on the scintillator performance.« less

  16. Divalent europium doped and un-doped calcium iodide scintillators: Scintillator characterization and single crystal growth

    SciTech Connect

    Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.; Neal, John S.

    2015-02-21

    Initially, the alkaline-earth scintillator, CaI2:Eu2+, was discovered around 1964 by Hofstadter, Odell, and Schmidt. Serious practical problems quickly arose, however, that were associated with the growth of large monolithic single crystals of this material due to its lamellar, mica-like structure. As a result of its theoretically higher light yield, CaI2:Eu2+ has the potential to exceed the excellent scintillation performance of SrI2:Eu2+. In fact, theoretical predictions for the light yield of CaI2:Eu2+ scintillators suggested that an energy resolution approaching 2% at 662 keV could be achievable. Like the early SrI2:Eu2+ scintillator, the performance of CaI2:Eu2+ scintillators has traditionally suffered due, at least in part, to outdated materials synthesis, component stoichiometry/purity, and single-crystal-growth techniques. Based on our recent work on SrI2:Eu2+ scintillators in single-crystal form, we have developed new techniques that are applied here to CaI2:Eu2+ and pure CaI2 with the goal of growing large un-cracked crystals and, potentially, realizing the theoretically predicted performance of the CaI2:Eu2+ form of this material. Calcium iodide does not adhere to modern glassy carbon Bridgman crucibles - so there should be no differential thermal-contraction-induced crystal/crucible stresses on cooling that would result in crystal cracking of the lamellar structure of CaI2. Here we apply glassy carbon crucible Bridgman growth, high-purity growth-charge compounds, our molten salt processing/filtration technique, and extended vacuum-melt-pumping methods to the growth of both CaI2:Eu2+ and un-doped CaI2. Moreover, large scintillating single crystals were obtained, and detailed characterization studies of the

  17. Divalent europium doped and un-doped calcium iodide scintillators: Scintillator characterization and single crystal growth

    NASA Astrophysics Data System (ADS)

    Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.; Neal, John S.

    2015-06-01

    The alkaline-earth scintillator, CaI2:Eu2+, was initially discovered around 1964 by Hofstadter, Odell, and Schmidt. Serious practical problems quickly arose, however, that were associated with the growth of large monolithic single crystals of this material due to its lamellar, mica-like structure. As a result of its theoretically higher light yield, CaI2:Eu2+ has the potential to exceed the excellent scintillation performance of SrI2:Eu2+. In fact, theoretical predictions for the light yield of CaI2:Eu2+ scintillators suggested that an energy resolution approaching 2% at 662 keV could be achievable. As in the case of the early SrI2:Eu2+ scintillator, the performance of CaI2:Eu2+ scintillators has traditionally suffered due, at least in part, to outdated materials synthesis, component stoichiometry/purity, and single-crystal-growth techniques. Based on our recent work on SrI2:Eu2+ scintillators in single-crystal form, we have developed new techniques that are applied here to CaI2:Eu2+ and pure CaI2 with the goal of growing large un-cracked crystals and, potentially, realizing the theoretically predicted performance of the CaI2:Eu2+ form of this material. Calcium iodide does not adhere to modern glassy carbon Bridgman crucibles-so there should be no differential thermal-contraction-induced crystal/crucible stresses on cooling that would result in crystal cracking of the lamellar structure of CaI2. Here we apply glassy carbon crucible Bridgman growth, high-purity growth-charge compounds, our molten salt processing/filtration technique, and extended vacuum-melt-pumping methods to the growth of both CaI2:Eu2+ and un-doped CaI2. Large scintillating single crystals were obtained, and detailed characterization studies of the scintillation properties of CaI2:Eu2+ and pure CaI2 single crystals are presented that include studies of the effects of plastic deformation of the crystals on the scintillator performance.

  18. Plastic fiber scintillator response to fast neutrons

    SciTech Connect

    Danly, C. R.; Sjue, S.; Wilde, C. H.; Merrill, F. E.; Haight, R. C.

    2014-11-15

    The Neutron Imaging System at NIF uses an array of plastic scintillator fibers in conjunction with a time-gated imaging system to form an image of the neutron emission from the imploded capsule. By gating on neutrons that have scattered from the 14.1 MeV DT energy to lower energy ranges, an image of the dense, cold fuel around the hotspot is also obtained. An unmoderated spallation neutron beamline at the Weapons Neutron Research facility at Los Alamos was used in conjunction with a time-gated imaging system to measure the yield of a scintillating fiber array over several energy bands ranging from 1 to 15 MeV. The results and comparison to simulation are presented.

  19. Scintillating 99Tc Selective Ion Exchange Resins

    SciTech Connect

    Mitchell Greenhalgh; Richard D. Tillotson

    2012-07-01

    Scintillating technetium (99Tc) selective ion exchange resins have been developed and evaluated for equilibrium capacities and detection efficiencies. These resins can be utilized for the in-situ concentration and detection of low levels of pertechnetate anions (99TcO4-) in natural waters. Three different polystyrene type resin support materials were impregnated with varying amounts of tricaprylmethylammonium chloride (Aliquat 336) extractant, several different scintillating fluors and wavelength shifters. The prepared resins were contacted batch-wise to equilibrium over a wide range of 99TcO4- concentrations in natural water. The measured capacities were used to develop Langmuir adsorption isotherms for each resin. 99Tc detection efficiencies were determined and up to 71.4 ± 2.6% was achieved with some resins. The results demonstrate that a low level detection limit for 99TcO4- in natural waters can be realized.

  20. Neutron detection with single crystal organic scintillators

    SciTech Connect

    Zaitseva, N; Newby, J; Hamel, S; Carman, L; Faust, M; Lordi, V; Cherepy, N; Stoeffl, W; Payne, S

    2009-07-15

    Detection of high-energy neutrons in the presence of gamma radiation background utilizes pulse-shape discrimination (PSD) phenomena in organics studied previously only with limited number of materials, mostly liquid scintillators and single crystal stilbene. The current paper presents the results obtained with broader varieties of luminescent organic single crystals. The studies involve experimental tools of crystal growth and material characterization in combination with the advanced computer modeling, with the final goal of better understanding the relevance between the nature of the organic materials and their PSD properties. Special consideration is given to the factors that may diminish or even completely obscure the PSD properties in scintillating crystals. Among such factors are molecular and crystallographic structures that determine exchange coupling and exciton mobility in organic materials and the impurity effect discussed on the examples of trans-stilbene, bibenzyl, 9,10-diphenylanthracene and diphenylacetylene.

  1. Fast scintillation counter system and performance

    NASA Technical Reports Server (NTRS)

    Sasaki, H.; Nishioka, A.; Ohmori, N.; Kusumose, M.; Nakatsuka, T.; Horiki, T.; Hatano, Y.

    1985-01-01

    An experimental study of the fast scintillation counter (FS) system to observe a shower disk structure at Mt. Norikura is described, especially the system performance and a pulse wave-form by a single charge particles. The photomultiplier tube (PT) pulse appears at the leading edge of the main pulse. To remove this PT-pulse from the main pulse, the frame of the scintillator vessel was changed. The fast triggering system was made to decrease the dead time which came from the use of the function of the self triggering of the storage oscilloscope (OSC). To provide a new field on the multi-parameter study of the cosmic ray showers, the system response of the FS system also improved as a result of many considerations.

  2. Internet access to data for scintillation compounds

    SciTech Connect

    Moses, W.W.; West, A.C.; Derenzo, S.E.

    1995-09-01

    The LBL Pulsed X-Ray Facility has scintillation data on a large variety of inorganic scintillators. We offer this information on all compounds that we have tested. The only restrictions/favors that we ask users of this data are: (1) The data is intended for research use and may not be sold; (2) If any portion of the data is used in a publication, that the following text appear somewhere in the publication: {open_quotes}This work was supported in part by the Director, Office of Energy Research, Office of Health and Environmental Research, Medical Applications and Biophysical Research Division of the U.S. Department of Energy under contract No. DE-AC03-76SF00098, and in part by Public Health Service Grant No. R01 CA48002 awarded by the National Cancer Institutes, Department of Health and Human Services.{close_quotes}.

  3. Codoped direct-gap semiconductor scintillators

    DOEpatents

    Derenzo, Stephen Edward; Bourret-Courchesne, Edith; Weber, Marvin J.; Klintenberg, Mattias K.

    2008-07-29

    Fast, bright inorganic scintillators at room temperature are based on radiative electron-hole recombination in direct-gap semiconductors, e.g. CdS and ZnO. The direct-gap semiconductor is codoped with two different impurity atoms to convert the semiconductor to a fast, high luminosity scintillator. The codopant scheme is based on dopant band to dopant trap recombination. One dopant provides a significant concentration of carriers of one type (electrons or holes) and the other dopant traps carriers of the other type. Examples include CdS:In,Te; CdS:In,Ag; CdS:In,Na; ZnO:Ga,P; ZnO:Ga,N; ZnO:Ga,S; and GaN:Ge,Mg.

  4. Codoped direct-gap semiconductor scintillators

    DOEpatents

    Derenzo, Stephen E.; Bourret-Courchesne, Edith; Weber, Marvin J.; Klintenberg, Mattias K.

    2006-05-23

    Fast, bright inorganic scintillators at room temperature are based on radiative electron-hole recombination in direct-gap semiconductors, e.g. CdS and ZnO. The direct-gap semiconductor is codoped with two different impurity atoms to convert the semiconductor to a fast, high luminosity scintillator. The codopant scheme is based on dopant band to dopant trap recombination. One dopant provides a significant concentration of carriers of one type (electrons or holes) and the other dopant traps carriers of the other type. Examples include CdS:In,Te; CdS:In,Ag; CdS:In,Na; ZnO:Ga,P; ZnO:Ga,N; ZnO:Ga,S; and GaN:Ge,Mg.

  5. Transparent Ceramic Scintillator Fabrication, Properties and Applications

    SciTech Connect

    Cherepy, N J; Kuntz, J D; Roberts, J J; Hurst, T A; Drury, O B; Sanner, R D; Tillotson, T M; Payne, S A

    2008-08-24

    Transparent ceramics offer an alternative to single crystals for scintillator applications such as gamma ray spectroscopy and radiography. We have developed a versatile, scaleable fabrication method, using Flame Spray Pyrolysis (FSP) to produce feedstock which is readily converted into phase-pure transparent ceramics. We measure integral light yields in excess of 80,000 Ph/MeV with Cerium-doped Garnets, and excellent optical quality. Avalanche photodiode readout of Garnets provides resolution near 6%. For radiography applications, Lutetium Oxide offers a high performance metric and is formable by ceramics processing. Scatter in transparent ceramics due to secondary phases is the principal limitation to optical quality, and afterglow issues that affect the scintillation performance are presently being addressed.

  6. Nanophosphor composite scintillators comprising a polymer matrix

    DOEpatents

    Muenchausen, Ross Edward; Mckigney, Edward Allen; Gilbertson, Robert David

    2010-11-16

    An improved nanophosphor composite comprises surface modified nanophosphor particles in a solid matrix. The nanophosphor particle surface is modified with an organic ligand, or by covalently bonding a polymeric or polymeric precursor material. The surface modified nanophosphor particle is essentially charge neutral, thereby preventing agglomeration of the nanophosphor particles during formation of the composite material. The improved nanophosphor composite may be used in any conventional scintillator application, including in a radiation detector.

  7. Simulating Silicon Photomultiplier Response to Scintillation Light

    PubMed Central

    Jha, Abhinav K.; van Dam, Herman T.; Kupinski, Matthew A.; Clarkson, Eric

    2015-01-01

    The response of a Silicon Photomultiplier (SiPM) to optical signals is affected by many factors including photon-detection efficiency, recovery time, gain, optical crosstalk, afterpulsing, dark count, and detector dead time. Many of these parameters vary with overvoltage and temperature. When used to detect scintillation light, there is a complicated non-linear relationship between the incident light and the response of the SiPM. In this paper, we propose a combined discrete-time discrete-event Monte Carlo (MC) model to simulate SiPM response to scintillation light pulses. Our MC model accounts for all relevant aspects of the SiPM response, some of which were not accounted for in the previous models. We also derive and validate analytic expressions for the single-photoelectron response of the SiPM and the voltage drop across the quenching resistance in the SiPM microcell. These analytic expressions consider the effect of all the circuit elements in the SiPM and accurately simulate the time-variation in overvoltage across the microcells of the SiPM. Consequently, our MC model is able to incorporate the variation of the different SiPM parameters with varying overvoltage. The MC model is compared with measurements on SiPM-based scintillation detectors and with some cases for which the response is known a priori. The model is also used to study the variation in SiPM behavior with SiPM-circuit parameter variations and to predict the response of a SiPM-based detector to various scintillators. PMID:26236040

  8. Studies of NICADD Extruded Scintillator Strips

    SciTech Connect

    Dychkant, Alexandre; et al.

    2005-03-01

    About four hundred one meter long, 10 cm wide and 5 mm thick extruded scintillating strips were measured at four different points. The results of measurements strip responses to a radioactive source {sup 90}Sr are provided, and details of strip choice, preparation, and method of measurement are included. This work was essential for prototyping a tail catcher and muon tracker for a future international electron positron linear collider detector.

  9. Sorohalide scintillators, phosphors, and uses thereof

    DOEpatents

    Yang, Pin; Deng, Haoran; Doty, F. Patrick; Zhou, Xiaowang

    2016-05-10

    The present invention relates to sorohalide compounds having formula A.sub.3B.sub.2X.sub.9, where A is an alkali metal, B is a rare earth metal, and X is a halogen. Optionally, the sorohalide includes a dopant D. Such undoped and doped sorohalides are useful as scintillation materials or phosphors for any number of uses, including for radiation detectors, solid-state light sources, gamma-ray spectroscopy, medical imaging, and drilling applications.

  10. Characteristics of Yerevan High Transparency Scintillators

    SciTech Connect

    Zorn, Carl; Asryan, Gegham; Egiyan, Kim; Tarverdyan, M.; Amaryan, Moscov; Amaryan, Moskov; Demirchyan, Raphael; Stepanyan, Stepan; Burkert, Volker; Sharabian, Youri

    1992-08-01

    Optical transmission, light output and time characteristics are given for long scintillator strips fabricated at the Yerevan Physics Institute using the extrusion method. It is shown that at 45% relative (to anthracene) light output, good transmission (2.5/2.9 m attenuation length with photomultiplier direct readout and 3/3.5 m attenuation length fiber readout) and time characteristics (average decay time 2.8 nsec) were obtained.

  11. Improved Neutron Scintillators Based on Nanomaterials

    SciTech Connect

    Dennis Friesel, PhD

    2008-06-30

    The development work conducted in this SBIR has so far not supported the premise that using nano-particles in LiFZnS:Ag foils improves their transparency to 420 (or other frequency) light. This conclusion is based solely on the light absorption properties of LiFZnS foils fabricated from nano- and from micro-particles. Furthermore, even for the case of the Gd{sub 2}O{sub 3} foils, the transmission of 420 nm light gained by using nano-particles all but disappears as the foil thickness is increased beyond about 0.2 mm, a practical scintillator thickness. This was not immediately apparent from the preliminary study since no foils thicker than about 0.04 mm were produced. Initially it was believed that the failure to see an improvement by using nano-particles for the LiFZnS foils was caused by the clumping of the particles in Toluene due to the polarity of the ZnS particles. However, we found, much to our surprise, that nano-particle ZnS alone in polystyrene, and in Epoxy, had worse light transmission properties than the micro-particle foils for equivalent thickness and density foils. The neutron detection measurements, while disappointing, are attributable to our inability to procure or fabricate Bulk Doped ZnS nanoparticles. The cause for the failure of nano-particles to improve the scintillation light, and hence improved neutron detection efficiency, is a fundamental one of light scattering within the scintillator. A consequence of PartTec's documentation of this is that several concepts for the fabrication of improved {sup 6}LiFZnS scintillators were formulated that will be the subject of a future SBIR submission.

  12. Boron-Loaded Silicone Rubber Scintillators

    SciTech Connect

    Bell, Z.W.; Maya, L.; Brown, G.M.; Sloop, F.V.Jr

    2003-05-12

    Silicone rubber received attention as an alternative to polyvinyltoluene in applications in which the scintillator is exposed to high doses because of the increased resistance of the rubber to the formation of blue-absorbing color centers. Work by Bowen, et al., and Harmon, et al., demonstrated their properties under gamma/x-ray irradiation, and Bell, et al. have shown their response to thermal neutrons. This last work, however, provided an example of a silicone in which both the boron and the scintillator were contained in the rubber as solutes, a formulation which led to the precipitation of solids and sublimation of the boron component. In the present work we describe a scintillator in which the boron is chemically bonded to the siloxane and so avoids the problem of precipitation and loss of boron to sublimation. Material containing up to 18% boron, by weight, was prepared, mounted on photomultipliers, and exposed to both neutron and gamma fluxes. Pulse height spectra showing the neutron and photon response were obtained, and although the light output was found to be much poorer than from samples in which boron was dissolved, the higher boron concentrations enabled essentially 100% neutron absorption in only a few millimeters' thickness of rubber.

  13. GPS scintillations over Vietnam on April 2006

    NASA Astrophysics Data System (ADS)

    Alfonsi, Lucilla; Spogli, Luca; Tong, Jenna R.; de Franceschi, Giorgiana; Romano, Vincenzo; Bourdillon, Alain; Le Huy, Minh; Mitchell, Cathryn N.

    2010-05-01

    In Vietnam, at Hue (16.4°N, 107.6°E) and Hoc Mon (10.9°N, 106.6°E), are located two GPS receivers specially modified for recording, at a sampling rate of 50 Hz, the phase and the amplitude of the L1 signal and the Total Electron Content (TEC) from L1 and L2. In April 2006 both the receivers have observed post-sunset scintillation inhibition when moderate magnetic storms occurred. These measurements together with a 3D plus time imaging of the ionosphere produced by the Multi-Instrument Data Analysis System (MIDAS) have revealed interesting features that will be described in the present paper. In particular, the results confirm the role of the ring current on the generation of the equatorial F layer irregularities of scale size from less than a hundred meters to a few kilometers, highlighting also its important role in inhibiting scintillation during the storm. The characterization of the different conditions of the Interplanetary Magnetic Field (IMF) will be illustrated, as well, to attempt a description of the scintillation effects over a region scarcely investigated in the open literature.

  14. Scintillators with potential to supersede lanthanum bromide

    SciTech Connect

    Cherepy, Nerine; Payne, Steven; Aszatlos, Steve; Hull, Giulia; Kuntz, J.; Niedermayr, Tom; Pimputkar, S.; Roberts, J.; Sanner, R.; Tillotson, T.; van Loef, Edger; Wilson, Cody; Shah, Kanai; Roy, U.; Hawrami, R.; Burger, Arnold; Boatner, Lynn; Choong, Woon-Seng; Moses, William

    2009-06-01

    New scintillators for high-resolution gamma ray spectroscopy have been identified, grown and characterized. Our development efforts have focused on two classes of high light yield materials: Europium-doped alkaline earth halides and Cerium-doped garnets. Of the halide single crystals we have grown by the Bridgman method - SrI{sub 2}, CaI{sub 2}, SrBr{sub 2}, BaI{sub 2} and BaBr{sub 2} - SrI{sub 2} is the most promising. SrI{sub 2}(Eu) emits into the Eu{sup 2+} band, centered at 435 nm, with a decay time of 1.2 {micro}s and a light yield of up to 115,000 photons/MeV. It offers energy resolution better than 3% FWHM at 662 keV, and exhibits excellent light yield proportionality. Transparent ceramics fabrication allows production of Gadolinium- and Terbium-based garnets which are not growable by melt techniques due to phase instabilities. While scintillation light yields of Cerium-doped ceramic garnets are high, light yield non-proportionality and slow decay components appear to limit their prospects for high energy resolution. We are developing an understanding of the mechanisms underlying energy dependent scintillation light yield non-proportionality and how it affects energy resolution. We have also identified aspects of optical design that can be optimized to enhance energy resolution.

  15. Detecting dark matter with scintillating bubble chambers

    NASA Astrophysics Data System (ADS)

    Zhang, Jianjie; Dahl, C. Eric; Jin, Miaotianzi; Baxter, Daniel

    2016-03-01

    Threshold based direct WIMP dark matter detectors such as the superheated bubble chambers developed by the PICO experiment have demonstrated excellent electron-recoil and alpha discrimination, excellent scalability, ease of change of target fluid, and low cost. However, the nuclear-recoil like backgrounds have been a limiting factor in their dark matter sensitivity. We present a new type of detector, the scintillating bubble chamber, which reads out the scintillation pulse of the scattering events as well as the pressure, temperature, acoustic traces, and bubble images as a conventional bubble chamber does. The event energy provides additional handle to discriminate against the nuclear-recoil like backgrounds. Liquid xenon is chosen as the target fluid in our prototyping detector for its high scintillation yield and suitable vapor pressure which simplifies detector complexity. The detector can be used as an R&D tool to study the backgrounds present in the current PICO bubble chambers or as a prototype for standalone dark matter detectors in the future. Supported by DOE Grant DE-SC0012161.

  16. Chloride, bromide and iodide scintillators with europium

    DOEpatents

    Zhuravleva, Mariya; Yang, Kan

    2016-09-27

    A halide scintillator material is disclosed where the halide may comprise chloride, bromide or iodide. The material is single-crystalline and has a composition of the general formula ABX.sub.3 where A is an alkali, B is an alkali earth and X is a halide which general composition was investigated. In particular, crystals of the formula ACa.sub.1-yEu.sub.yI.sub.3 where A=K, Rb and Cs were formed as well as crystals of the formula CsA.sub.1-yEu.sub.yX.sub.3 (where A=Ca, Sr, Ba, or a combination thereof and X=Cl, Br or I or a combination thereof) with divalent Europium doping where 0.ltoreq.y.ltoreq.1, and more particularly Eu doping has been studied at one to ten mol %. The disclosed scintillator materials are suitable for making scintillation detectors used in applications such as medical imaging and homeland security.

  17. Sillicon Photomultiplier and Scintillator Bar Systems

    NASA Astrophysics Data System (ADS)

    Shelor, Mark; Elizondo, Leonardo; Ritt, Stefan

    2016-03-01

    To analyze extraterrestrial cosmic rays via precise measurements of airshower axes directions of penetrating particles such as muons, we constructed a model detector consisting of two 1-meter long scintillator bars. Each bar is fitted with green wavelength shifting fibers to modulate input for two silicon photomultiplier (SiPM) light detectors to record light produced by cosmic rays via scintillation. The purpose of the experiment is to determine the performance of these devices. Two makes of SiPMs were evaluated - from AdvanSiD and Hamamatsu. In order to filter out noise, timing measurements of the apparatus were performed under several trigger conditions such as coincidence trigger with 2 photomultiplier detectors, as well as SiPM detector arrays in self-triggered mode. The DRS4 Digitizer 4-channel fast waveform sampler digitized SiPM detector waveforms. Signals were analyzed with the CERN PAW package. The speed of light in the scintillator using the SiPM modules was found to be approximately 66% of the speed of light in a vacuum which is in accordance with the index of refraction for the fibers given by the manufacturer's specifications. The results of our timing measurements would be presented. Dept. of Ed. Title V Grant PO31S090007.

  18. Interstellar Scintillation of Extragalactic Radio Sources

    NASA Astrophysics Data System (ADS)

    Rickett, Barney

    1998-05-01

    Interstellar scintillation (ISS) causes a Galactic seeing problem for radio astronomy. Thus the flux density from a very compact radio source appears to scintillate on a time scale that ranges from days to minutes depending on the wavelength and Galactic path length. I will review the observed variations from various sources, which are among the most compact cores of active galactic nuclei (AGN). An ISS interpretation of the observed variations yields estimates of the source sizes in the range 0.01 to 10 milliarcsec, often much smaller than the resolution from earth-based VLBI. The recognition of such variations as apparent reduces the implied brightness temperature by a factor as large as one million, compared to the extreme values deduced by interpreting the variations as intrinsic. Some such intraday variable sources also exhibit partially correlated variations in their polarized flux and angle. The changes in interstellar Faradya rotation are too slow to cause such variations by many orders of magnitude. I will report on attempts to model the polarized flux variations as due to independent ISS from polarized components with intrinsic polarization structure in the source at a level of tens of microarcseconds. I will also discuss how Frail et al. (Nature, 389, 261, 1997) used interstellar scintillation to estimate the size of the expanding fireball in the radio afterglow of gamma-ray burst 970508.

  19. Characterization of Ionospheric Scintillation Using Simultaneous Formosat-3/COSMIC Radio Occultation Observations and AFRL SCINDA Ground Scintillation Measurements

    NASA Astrophysics Data System (ADS)

    Starks, M. J.; Lin, C. S.; Groves, K. M.; Pedersen, T. R.; Basu, S.; Syndergaard, S.; Rocken, C.

    2007-05-01

    Ionospheric scintillation at low latitudes has been studied using ionospheric radio occultation (RO) measurements by the FORMOSAT-3/COSMIC micro-satellites in conjunction with ground-based data from the Scintillation Network Decision Aid (SCINDA) station at Kwajalein Atoll. The Air Force Research Laboratory has developed the SCINDA network for monitoring low-latitude ionospheric total electron content (TEC) and scintillation associated with equatorial spread F. The network currently consists of sixteen stations distributed around the globe and the data have been used to conduct numerous studies on the characteristics and climatology of equatorial scintillation. The present study focuses on COSMIC RO and SCINDA data during the three COSMIC campaigns in 2006. Radio occultation events are selected by requiring that ionospheric scintillation was detected by the SCINDA VHF scintillation monitor at Kwajalein, and that the occultation ray path intersected the Kwajalein longitude below the satellite altitude, which varied from 500 to 800 km for the six FORMOSAT-3 satellites. In order to exclude tropospheric effects, only GPS signal amplitudes from FORMOSAT-3 with ray path tangent altitudes above 100 km are considered. Locations of ionospheric scintillation are estimated by triangulation using the satellites and the SCINDA ground station. Airglow images at Kwajalein are also used to confirm occurrence of equatorial ionospheric scintillations. For the selected events, large amplitude L1 and L2 scintillations tend to occur at altitudes below 200 km at frequencies around 0.5 Hz. The results are discussed as a potential path toward better specifying the occurrence of equatorial scintillations.

  20. Disturbed time observations of the temporal dependence and dynamics of TEC, scintillation, and ionospheric irregularity zonal drifts

    NASA Astrophysics Data System (ADS)

    Muella, Marcio; de Paula, Eurico; Kintner, Paul; Kantor, Ivan; Cerruti, Alessandro; Mitchell, Cathryn; Crowley, Geoff; Smorigo, Paulo; Batista, Inez

    GPS amplitude scintillations at the L1 frequency (1.575 GHz) and integral data of total electron content (TEC) obtained from measurements of the Brazilian ground-based GPS network are used to study specific relationships between TEC, scintillations and ionospheric electron density imaged at near the southern crest of the Equatorial Ionization Anomaly (EIA). Using a time-dependent tomographic model, 3-dimensional images are created to couple the geophysical quantities measured by the GPS receivers during the storm time period of November 18-23. It allows studying large variations in the temporal and spatial evolution of the electron density affecting the behavior and dynamics of the scintillations. Estimations of the ionospheric irregularity zonal drift velocities at 350 km obtained from two-spaced GPS receivers observations, and the coupling of the neutral atmosphere and the ionosphere obtained from the ASPEN- TIMEGCM model results are also used in the investigation. The model is used to analyze the north-south symmetry/asymmetry conditions in the ionization distribution of the equatorial anomaly produced by a meridional/transequatorial wind, and its effect to the development and evolution of the scintillations associated to the ionospheric irregularities. In this work we present some relevant aspects of the ionospheric dynamics and the thermosphere-ionosphere coupling system, which are some of the most important topics of study during the occurrence of geomagnetic storms.

  1. Phase and coherence analysis of VHF scintillation over Christmas Island

    NASA Astrophysics Data System (ADS)

    Shume, E. B.; Mannucci, A. J.; Caton, R.

    2014-03-01

    This short paper presents phase and coherence data from the cross-wavelet transform applied on longitudinally separated very high frequency (VHF) equatorial ionospheric scintillation observations over Christmas Island. The phase and coherence analyses were employed on a pair of scintillation observations, namely, the east-looking and west-looking VHF scintillation monitors at Christmas Island. Our analysis includes 3 years of peak season scintillation data from 2008, 2009 (low solar activity), and 2011 (moderate solar activity). In statistically significant and high spectral coherence regions of the cross-wavelet transform, scintillation observations from the east-looking monitor lead those from the west-looking monitor by about 20 to 60 (40 ± 20) min (most frequent lead times). Using several years (seasons and solar cycle) of lead (or lag) and coherence information of the cross-wavelet transform, we envisage construction of a probability model for forecasting scintillation in the nighttime equatorial ionosphere.

  2. Metal-loaded organic scintillators for neutrino physics

    NASA Astrophysics Data System (ADS)

    Buck, Christian; Yeh, Minfang

    2016-09-01

    Organic liquid scintillators are used in many neutrino physics experiments of the past and present. In particular for low energy neutrinos when realtime and energy information are required, liquid scintillators have several advantages compared to other technologies. In many cases the organic liquid needs to be loaded with metal to enhance the neutrino signal over background events. Several metal loaded scintillators of the past suffered from chemical and optical instabilities, limiting the performance of these neutrino detectors. Different ways of metal loading are described in the article with a focus on recent techniques providing metal loaded scintillators that can be used under stable conditions for many years even in ton scale experiments. Applications of metal loaded scintillators in neutrino experiments are reviewed and the performance as well as the prospects of different scintillator types are compared.

  3. Separation of scintillation and Cherenkov lights in linear alkyl benzene

    NASA Astrophysics Data System (ADS)

    Li, Mohan; Guo, Ziyi; Yeh, Minfang; Wang, Zhe; Chen, Shaomin

    2016-09-01

    To separate scintillation and Cherenkov lights in water-based liquid scintillator detectors is a desired feature for future neutrino and proton decay experiments. Linear alkyl benzene (LAB) is one important ingredient of a water-based liquid scintillator currently under development. In this paper we report on the separation of scintillation and Cherenkov lights observed in an LAB sample. The rise and decay times of the scintillation light are measured to be (7.7 ± 3.0) ns and (36.6 ± 2.4) ns , respectively, while the full width [-3σ, 3σ] of the Cherenkov light is 12 ns and is dominated by the time resolution of the photomultiplier tubes. The scintillation light yield was measured to be (1.01 ± 0.12) ×103 photons / MeV .

  4. Methods for the continuous production of plastic scintillator materials

    DOEpatents

    Bross, Alan; Pla-Dalmau, Anna; Mellott, Kerry

    1999-10-19

    Methods for producing plastic scintillating material employing either two major steps (tumble-mix) or a single major step (inline-coloring or inline-doping). Using the two step method, the polymer pellets are mixed with silicone oil, and the mixture is then tumble mixed with the dopants necessary to yield the proper response from the scintillator material. The mixture is then placed in a compounder and compounded in an inert gas atmosphere. The resultant scintillator material is then extruded and pelletized or formed. When only a single step is employed, the polymer pellets and dopants are metered into an inline-coloring extruding system. The mixture is then processed under a inert gas atmosphere, usually argon or nitrogen, to form plastic scintillator material in the form of either scintillator pellets, for subsequent processing, or as material in the direct formation of the final scintillator shape or form.

  5. Protease-activated receptor-1 (PAR1) and PAR2 but not PAR4 mediate relaxations in lower esophageal sphincter.

    PubMed

    Huang, Shih-Che

    2007-07-01

    Protease-activated receptor-1 (PAR1), PAR2 and PAR4 activation can alter the gastrointestinal motility. To investigate effects mediated by PARs in the lower esophageal sphincter, we measured contraction or relaxation of transverse strips from the guinea-pig lower esophageal sphincter caused by PAR1 (TFLLR-NH2 and SFLLRN-NH2), PAR2 (SLIGKV-NH2 and SLIGRL-NH2) and PAR4 peptide agonists (GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2) as well as PAR protease activators (thrombin and trypsin). In resting lower esophageal sphincter strips, TFLLR-NH2 and SFLLRN-NH2 caused moderate concentration-dependent relaxation whereas thrombin did not cause any relaxation or contraction. Furthermore, in carbachol-contracted strips, TFLLR-NH2 and SFLLRN-NH2 caused marked whereas thrombin caused mild concentration-dependent relaxation. These indicate the existence of PAR1 mediating relaxation. Similarly, in resting lower esophageal sphincter strips, trypsin caused moderate concentration-dependent relaxation whereas SLIGRL-NH2 and SLIGKV-NH2 did not cause any relaxation or contraction. In addition, in carbachol-contracted strips, trypsin caused marked whereas SLIGRL-NH2 and SLIGKV-NH2 caused mild concentration-dependent relaxation. These indicate the existence of PAR2 mediating relaxation. The relaxant response of thrombin, TFLLR-NH2, trypsin and SLIGKV-NH2 was insensitive to atropine or tetrodotoxin, suggesting a direct effect. The relaxant response of trypsin was not affected by apamin, charybdotoxin, indomethacin and capsaicin but was attenuated by NG-nitro-L-arginine methyl ester, indicating involvement of NO. FSLLR-NH2, a PAR1 control peptide, and VKGILS-NH2, a PAR2 control peptide, as well as all three PAR4 peptide agonists, GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2, did not cause any relaxation or contraction. Taken together, these results demonstrate that PAR1 and PAR2 but not PAR4 mediate relaxations in the guinea-pig lower esophageal sphincter. PMID:17335921

  6. Lanthanide doped strontium-barium cesium halide scintillators

    SciTech Connect

    Bizarri, Gregory; Bourret-Courchesne, Edith; Derenzo, Stephen E.; Borade, Ramesh B.; Gundiah, Gautam; Yan, Zewu; Hanrahan, Stephen M.; Chaudhry, Anurag; Canning, Andrew

    2015-06-09

    The present invention provides for a composition comprising an inorganic scintillator comprising an optionally lanthanide-doped strontium-barium, optionally cesium, halide, useful for detecting nuclear material.

  7. Scintillation near the F-layer trough over Northern Europe

    SciTech Connect

    Kersley, L.; Pryse, S.E.; Russell, C.D.

    1990-05-03

    Results are presented of scintillation observations made during a two and a half year period at Lerwick in the Shetland Islands using more than 19000 passes of NNSS satellites. Examples of scintillation morphology, in the region near the scintillation boundary and the F-layer trough, for both amplitude and phase are discussed using exceedence levels for the S sub 4 and sigma sub psi indices respectively. The equatorwards advancement of the scintillation boundary in response to enhanced solar activity during the increasing phase of the solar cycle is shown to be a dominant feature in the observations.

  8. Chaotic behavior of ionospheric turbulence from scintillation measurements

    SciTech Connect

    Bhattacharyya, A. )

    1990-05-01

    Ionospheric amplitude and phase scintillation data have been analyzed to estimate the information dimension associated with the attractor of the system. For weak scintillations, both amplitude and phase data yield identical results which demonstrate that spatial fluctuations of electron density in the ionosphere may be characterized by a few degrees of freedom. Stronger scintillations are attributed to steepened density irregularities which cause focusing of the incident radio wave. This results in the amplitude scintillations exhibiting higher dimensional chaos but spatial fluctuations in ionospheric density still involve low dimensional chaos.

  9. Plasmonic light yield enhancement of a liquid scintillator

    SciTech Connect

    Bignell, Lindsey J.; Jackson, Timothy W.; Mume, Eskender; Lee, George P.

    2013-05-27

    We demonstrate modifications to the light yield properties of an organic liquid scintillator due to the localization of the tertiary fluorophore component to the surface of Ag-core silica-shell nanoparticles. We attribute this enhancement to the near-field interaction of Ag nanoparticle plasmons with these fluor molecules. The scintillation light yield enhancement is shown to be equal to the fluorescence enhancement within measurement uncertainties. With a suitable choice of plasmon energy and scintillation fluor, this effect may be used to engineer scintillators with enhanced light yields for radiation detection applications.

  10. Phase and coherence of longitudinally separated equatorial ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Shume, E. B.; Mannucci, A. J.

    2013-12-01

    This paper presents the first calculation of phase and coherence of cross-wavelet transform applied on longitudinally separated VHF and L-band equatorial ionospheric scintillation. The cross-wavelet analysis has utilized scintillation observations made over equatorial South America and Christmas Island. Part of the results of this study has been reported recently in the Geophysical Research Letters by Shume and Mannucci (2013). The phase and coherence analysis were employed on pairs of scintillation observations separated by longitudes thereby to develop VHF and L-band scintillation (and equatorial spread F) forecast tools west of observation sites.

  11. Energy Transfer Based Nanocomposite Scintillator for Radiation Detection

    NASA Astrophysics Data System (ADS)

    Aslam, Soha; Sahi, Sunil; Chen, Wei; Ma, Lun; Kenarangui, Rasool

    2014-09-01

    Scintillators are the materials that emit light upon irradiation with high energy radiation like X-ray or gamma-ray. Inorganic single crystal and organic (plastic and liquid) are the two most used scintillator types. Both of these scintillator kinds have advantages and disadvantages. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, single crystal scintillator such as NaI and CsI are very hygroscopic. On the other hand, organic scintillators have low density which limits their applications in gamma spectroscopy. Due to high quantum yield and size dependent emission, nanoparticles have attracted interested in various field of research. Here, we have studies the nanoparticles for radiation detection. We have synthesized nanoparticles of Cerium fluoride (CeF3), Zinc Oxide (ZnO), Cadmium Telluride (CdTe), Copper complex and Zinc sulfide (ZnS). We have used Fluorescence Resonance Energy Transfer (FRET) principle to enhance the luminescence properties of nanocomposite scintillator. Nanocomposites scintillators are structurally characterized with X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Optical properties are studied using Photoluminescence, UV-Visible and X-ray. Enhancements in the luminescence are observed under UV and X-ray excitation. Preliminary studies shows nanocomposite scintillators are promising for radiation detection. Scintillators are the materials that emit light upon irradiation with high energy radiation like X-ray or gamma-ray. Inorganic single crystal and organic (plastic and liquid) are the two most used scintillator types. Both of these scintillator kinds have advantages and disadvantages. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, single crystal scintillator such as NaI and CsI are very hygroscopic. On the other hand, organic scintillators have low density which limits their applications in gamma spectroscopy. Due to high quantum

  12. Composite solid-state scintillators for neutron detection

    DOEpatents

    Dai, Sheng; Im, Hee-Jung; Pawel, Michelle D.

    2006-09-12

    Applicant's present invention is a composite scintillator for neutron detection comprising a matrix material fabricated from an inorganic sol-gel precursor solution homogeneously doped with a liquid scintillating material and a neutron absorbing material. The neutron absorbing material yields at least one of an electron, a proton, a triton, an alpha particle or a fission fragment when the neutron absorbing material absorbs a neutron. The composite scintillator further comprises a liquid scintillating material in a self-assembled micelle formation homogeneously doped in the matrix material through the formation of surfactant-silica composites. The scintillating material is provided to scintillate when traversed by at least one of an electron, a proton, a triton, an alpha particle or a fission fragment. The scintillating material is configured such that the matrix material surrounds the micelle formation of the scintillating material. The composite scintillator is fabricated and applied as a thin film on substrate surfaces, a coating on optical fibers or as a glass material.

  13. Ionospheric scintillation observations over Kenyan region - Preliminary results

    NASA Astrophysics Data System (ADS)

    Olwendo, O. J.; Xiao, Yu; Ming, Ou

    2016-11-01

    Ionospheric scintillation refers to the rapid fluctuations in the amplitude and phase of a satellite signal as it passes through small-scale plasma density irregularities in the ionosphere. By analyzing ionospheric scintillation observation datasets from satellite signals such as GPS signals we can study the morphology of ionospheric bubbles. At low latitudes, the diurnal behavior of scintillation is driven by the formation of large-scale equatorial density depletions which form one to two hours after sunset via the Rayleigh-Taylor instability mechanism near the magnetic equator. In this work we present ionospheric scintillation activity over Kenya using data derived from a newly installed scintillation monitor developed by CRIRP at Pwani University (39.78°E, 3.24°S) during the period August to December, 2014. The results reveal the scintillation activity mainly occurs from post-sunset to post-midnight hours, and ceases around 04:00 LT. We also found that the ionospheric scintillation tends to appear at the southwest and northwest of the station. These locations coincide with the southern part of the Equatorial Ionization Anomaly crest over Kenya region. The occurrence of post-midnight L-band scintillation events which are not linked to pre-midnight scintillation observations raises fundamental question on the mechanism and source of electric fields driving the plasma depletion under conditions of very low background electron density.

  14. Development of polystyrene-based scintillation materials and its mechanisms

    NASA Astrophysics Data System (ADS)

    Nakamura, Hidehito; Kitamura, Hisashi; Shinji, Osamu; Saito, Katashi; Shirakawa, Yoshiyuki; Takahashi, Sentaro

    2012-12-01

    Scintillation materials based on polystyrene (PS) have been investigated. Para-terphenyl was employed as a fluorescent molecule (fluor) that functions as a wavelength shifter. A clear increase in photon yield of the scintillation materials relative to the pure PS was observed, which cannot be explained by the conventional theory of scintillation mechanism. Furthermore, the photon yield increased with flour concentration in accordance with a power-law. Here we reveal the emergence of a luminescence of PS-based scintillation materials and demonstrate that their photon yields can be controlled by the fluor concentration.

  15. Plasmonic light yield enhancement of a liquid scintillator

    NASA Astrophysics Data System (ADS)

    Bignell, Lindsey J.; Mume, Eskender; Jackson, Timothy W.; Lee, George P.

    2013-05-01

    We demonstrate modifications to the light yield properties of an organic liquid scintillator due to the localization of the tertiary fluorophore component to the surface of Ag-core silica-shell nanoparticles. We attribute this enhancement to the near-field interaction of Ag nanoparticle plasmons with these fluor molecules. The scintillation light yield enhancement is shown to be equal to the fluorescence enhancement within measurement uncertainties. With a suitable choice of plasmon energy and scintillation fluor, this effect may be used to engineer scintillators with enhanced light yields for radiation detection applications.

  16. Scintillation-producing Fresnel-scale irregularities associated with the regions of steepest TEC gradients adjacent to the equatorial ionization anomaly

    NASA Astrophysics Data System (ADS)

    Muella, M. T. A. H.; Kherani, E. A.; de Paula, E. R.; Cerruti, A. P.; Kintner, P. M.; Kantor, I. J.; Mitchell, C. N.; Batista, I. S.; Abdu, M. A.

    2010-03-01

    Using ground-based GPS and digital ionosonde instruments, we have built up at latitudes of the equatorial ionization anomaly (EIA), in the Brazilian sector, a time-evolving picture of total electron content (TEC), L-band amplitude scintillations, and F region heights, and we have investigated likely reasons for the occurrence or suppression of equatorial scintillations during the disturbed period of 18-23 November 2003. During the prestorm quiet nights, scintillations are occurring postsunset, as expected; however, during the storm time period, their spatial-temporal characteristics and intensity modify significantly owing to the dramatic changes in the ionospheric plasma density distribution and in the temporal evolution of TEC. The two-dimensional maps showing both TEC and amplitude scintillations revealed strong evidence of turbulences at the Fresnel length (causing scintillations) concurrent with those regions of steepest TEC gradients adjacent to the crests of the EIA. The largest density gradients have been found to occur in an environment of increased background electron density, and their spatial distribution and location during the disturbed period may differ significantly from the magnetic quiet night pattern. However, in terms of magnitude the gradients at equatorial and low latitudes appear to not change during both magnetic quiet and disturbed conditions. The scenarios for the formation or suppression of scintillation-producing Fresnel-scale irregularities during the prestorm quiet nights and disturbed nights are discussed in view of different competing effects computed from numerical simulation techniques.

  17. The Scintillation Prediction Observations Research Task (SPORT) Mission

    NASA Astrophysics Data System (ADS)

    Spann, James; Swenson, Charles; Durão, Otavio; Loures, Luis; Heelis, Rod; Bishop, Rebecca; Le, Guan; Abdu, Mangalathayil; Krause, Linda; Nardin, Clezio; Fonseca, Eloi

    2016-04-01

    Structure in the charged particle number density in the equatorial ionosphere can have a profound impact on the fidelity of HF, VHF and UHF radio signals that are used for ground-to-ground and space-to-ground communication and navigation. The degree to which such systems can be compromised depends in large part on the spatial distribution of the structured regions in the ionosphere and the background plasma density in which they are embedded. In order to address these challenges it is necessary to accurately distinguish the background ionospheric conditions that favor the generation of irregularities from those that do not. Additionally we must relate the evolution of those conditions to the subsequent evolution of the irregular plasma regions themselves. The background ionospheric conditions are conveniently described by latitudinal profiles of the plasma density at nearly constant altitude, which describe the effects of ExB drifts and neutral winds, while the appearance and growth of plasma structure requires committed observations from the ground from at least one fixed longitude. This talk will present an international collaborative CubeSat mission called SPORT that stands for the Scintillation Prediction Observations Research Task. This mission will advance our understanding of the nature and evolution of ionospheric structures around sunset to improve predictions of disturbances that affect radio propagation and telecommunication signals. The science goals will be accomplished by a unique combination of satellite observations from a nearly circular middle inclination orbit and the extensive operation of ground based observations from South America near the magnetic equator. This approach promises Explorer class science at a CubeSat price.

  18. The Scintillation Prediction Observations Research Task (SPORT) Mission

    NASA Astrophysics Data System (ADS)

    Spann, J. F.; Swenson, C.; Durão, O.; Loures, L.; Heelis, R. A.; Bishop, R. L.; Le, G.; Abdu, M. A.; Habash Krause, L.; De Nardin, C. M.; Fonseca, E.

    2015-12-01

    Structure in the charged particle number density in the equatorial ionosphere can have a profound impact on the fidelity of HF, VHF and UHF radio signals that are used for ground-to-ground and space-to-ground communication and navigation. The degree to which such systems can be compromised depends in large part on the spatial distribution of the structured regions in the ionosphere and the background plasma density in which they are embedded. In order to address these challenges it is necessary to accurately distinguish the background ionospheric conditions that favor the generation of irregularities from those that do not. Additionally we must relate the evolution of those conditions to the subsequent evolution of the irregular plasma regions themselves. The background ionospheric conditions are conveniently described by latitudinal profiles of the plasma density at nearly constant altitude, which describe the effects of ExB drifts and neutral winds, while the appearance and growth of plasma structure requires committed observations from the ground from at least one fixed longitude. This talk will present an international collaborative CubeSat mission called SPORT that stands for Scintillation Prediction Observations Research Task. This mission that will advance our understanding of the nature and evolution of ionospheric structures around sunset to improve predictions of disturbances that affect radio propagation and telecommunication signals. The science goals will be accomplished by a unique combination of satellite observations from a nearly circular middle inclination orbit and the extensive operation of ground based observations from South America near the magnetic equator. This approach promises Explorer class science at a CubeSat price.

  19. The Scintillation Prediction Observations Research Task (SPORT) Mission

    NASA Astrophysics Data System (ADS)

    Spann, James; Le, Guan; Swenson, Charles; Denardini, Clezio Marcos; Bishop, Rebecca L.; Abdu, Mangalathayil A.; Cupertino Durao, Otavio S.; Heelis, Roderick; Loures, Luis; Krause, Linda; Fonseca, Eloi

    2016-07-01

    Structure in the charged particle number density in the equatorial ionosphere can have a profound impact on the fidelity of HF, VHF and UHF radio signals that are used for ground-to-ground and space-to-ground communication and navigation. The degree to which such systems can be compromised depends in large part on the spatial distribution of the structured regions in the ionosphere and the background plasma density in which they are embedded. In order to address these challenges it is necessary to accurately distinguish the background ionospheric conditions that favor the generation of irregularities from those that do not. Additionally we must relate the evolution of those conditions to the subsequent evolution of the irregular plasma regions themselves. The background ionospheric conditions are conveniently described by latitudinal profiles of the plasma density at nearly constant altitude, which describe the effects of ExB drifts and neutral winds, while the appearance and growth of plasma structure requires committed observations from the ground from at least one fixed longitude. This talk will present an international collaborative CubeSat mission called SPORT that stands for the Scintillation Prediction Observations Research Task. This mission will advance our understanding of the nature and evolution of ionospheric structures around sunset to improve predictions of disturbances that affect radio propagation and telecommunication signals. The science goals will be accomplished by a unique combination of satellite observations from a nearly circular middle inclination orbit and the extensive operation of ground based observations from South America near the magnetic equator. This approach promises Explorer class science at a CubeSat price.

  20. Comparing the response of PSD-capable plastic scintillator to standard liquid scintillator

    NASA Astrophysics Data System (ADS)

    Woolf, Richard S.; Hutcheson, Anthony L.; Gwon, Chul; Phlips, Bernard F.; Wulf, Eric A.

    2015-06-01

    This work discusses a test campaign to characterize the response of the recently developed plastic scintillator with pulse shape discrimination (PSD) capabilities (EJ-299-33). PSD is a property exhibited by certain types of scintillating material in which incident stimuli (fast neutrons or γ rays) can be separated by exploiting differences in the scintillation light pulse tail. Detector geometries used were: a 10 cm×10 cm×10 cm cube and a 10-cm diameter×10-cm long cylinder. EJ-301 and EJ-309 liquid scintillators with well-known responses were also tested. The work was conducted at the University of Massachusetts Lowell Van De Graaff accelerator. The facility accelerated protons on a thin Li target to yield quasi-monoenergetic neutrons from the 7Li(p,n)7Be reaction (Q-value: -1.644 MeV). Collimated fast neutrons were obtained by placing detectors behind a neutron spectrometer. Rotating the spectrometer, and thus changing the neutron energy, allowed us to achieve 0.5-3.2 MeV neutrons in 200-300 keV steps. Data were acquired through a flash analog-to-digital converter (ADC) capable of performing digital PSD measurements. By using the PSD technique to separate the neutron events from unwanted γ background, we constructed a pulse height spectrum at each energy. Obtaining a relationship of the relative light output versus energy allowed us to construct the response function for the EJ-299-33 and liquid scintillator. The EJ-299-33 response in terms of electron equivalent energy (Ee.e.) vs. proton equivalent energy (Ep.e.), how it compared with the standard xylene-based EJ-301 (or, NE-213/BC-501 A equivalent) and EJ-309 liquid scintillator response, and how the EJ-301 and EJ-309 compared, are presented. We find that the EJ-299-33 demonstrated a lower light output by up to 40% for <1.0 MeV neutrons; and ranging between a 5-35% reduction for 2.5-3.0 MeV neutrons compared to the EJ-301/309, depending on the scintillator and geometry. Monte Carlo modeling techniques were

  1. PAR for the Course: A Congruent Pedagogical Approach for a PAR Methods Class

    ERIC Educational Resources Information Center

    Hammond, Joyce D.; Hicks, Maria; Kalman, Rowenn; Miller, Jason

    2005-01-01

    In the past two years, three graduate students and a senior faculty member have co-taught a participatory action research (PAR) course to undergraduate and graduate students. In this article the co-teachers advocate a set of pedagogical principles and practices in a PAR-oriented classroom that establishes congruency with community PAR projects in…

  2. Fundamental Limits of Scintillation Detector Timing Precision

    PubMed Central

    Derenzo, Stephen E.; Choong, Woon-Seng; Moses, William W.

    2014-01-01

    In this paper we review the primary factors that affect the timing precision of a scintillation detector. Monte Carlo calculations were performed to explore the dependence of the timing precision on the number of photoelectrons, the scintillator decay and rise times, the depth of interaction uncertainty, the time dispersion of the optical photons (modeled as an exponential decay), the photodetector rise time and transit time jitter, the leading-edge trigger level, and electronic noise. The Monte Carlo code was used to estimate the practical limits on the timing precision for an energy deposition of 511 keV in 3 mm × 3 mm × 30 mm Lu2SiO5:Ce and LaBr3:Ce crystals. The calculated timing precisions are consistent with the best experimental literature values. We then calculated the timing precision for 820 cases that sampled scintillator rise times from 0 to 1.0 ns, photon dispersion times from 0 to 0.2 ns, photodetector time jitters from 0 to 0.5 ns fwhm, and A from 10 to 10,000 photoelectrons per ns decay time. Since the timing precision R was found to depend on A−1/2 more than any other factor, we tabulated the parameter B, where R = BA−1/2. An empirical analytical formula was found that fit the tabulated values of B with an rms deviation of 2.2% of the value of B. The theoretical lower bound of the timing precision was calculated for the example of 0.5 ns rise time, 0.1 ns photon dispersion, and 0.2 ns fwhm photodetector time jitter. The lower bound was at most 15% lower than leading-edge timing discrimination for A from 10 to 10,000 photoelectrons/ns. A timing precision of 8 ps fwhm should be possible for an energy deposition of 511 keV using currently available photodetectors if a theoretically possible scintillator were developed that could produce 10,000 photoelectrons/ns. PMID:24874216

  3. Radiation damage by neutrons to plastic scintillators

    SciTech Connect

    Buss, G.; Dannemann, A.; Holm, U.; Wick, K.

    1995-08-01

    Polystyrene based scintillator SCSN38, wavelength shifter Y7 with polymethylmethacrylate matrix and pure PM-MA light guide GS218 have been irradiated in the mixed radiation field of a pool reactor. About 77% of the dose released in SCSN38 was caused by the {gamma}-field, 23% by fast neutrons. The total dose ranged from 2 to 105 kGy. The dose measurements were made using alanine dosimeters. Transmission and fluorescence of the samples have been measured before and several times after irradiation. The radiation damage results shown o differences to irradiations in pure {gamma}-fields with corresponding released doses.

  4. Fundamental limits of scintillation detector timing precision.

    PubMed

    Derenzo, Stephen E; Choong, Woon-Seng; Moses, William W

    2014-07-01

    In this paper we review the primary factors that affect the timing precision of a scintillation detector. Monte Carlo calculations were performed to explore the dependence of the timing precision on the number of photoelectrons, the scintillator decay and rise times, the depth of interaction uncertainty, the time dispersion of the optical photons (modeled as an exponential decay), the photodetector rise time and transit time jitter, the leading-edge trigger level, and electronic noise. The Monte Carlo code was used to estimate the practical limits on the timing precision for an energy deposition of 511 keV in 3 mm × 3 mm × 30 mm Lu2SiO5:Ce and LaBr3:Ce crystals. The calculated timing precisions are consistent with the best experimental literature values. We then calculated the timing precision for 820 cases that sampled scintillator rise times from 0 to 1.0 ns, photon dispersion times from 0 to 0.2 ns, photodetector time jitters from 0 to 0.5 ns fwhm, and A from 10 to 10,000 photoelectrons per ns decay time. Since the timing precision R was found to depend on A(-1/2) more than any other factor, we tabulated the parameter B, where R = BA(-1/2). An empirical analytical formula was found that fit the tabulated values of B with an rms deviation of 2.2% of the value of B. The theoretical lower bound of the timing precision was calculated for the example of 0.5 ns rise time, 0.1 ns photon dispersion, and 0.2 ns fwhm photodetector time jitter. The lower bound was at most 15% lower than leading-edge timing discrimination for A from 10 to 10,000 photoelectrons ns(-1). A timing precision of 8 ps fwhm should be possible for an energy deposition of 511 keV using currently available photodetectors if a theoretically possible scintillator were developed that could produce 10,000 photoelectrons ns(-1).

  5. Cherenkov and Scintillation Properties of Cubic Zirconium

    NASA Technical Reports Server (NTRS)

    Christl, M.J.; Adams, J.H.; Parnell, T.A.; Kuznetsov, E.N.

    2008-01-01

    Cubic zirconium (CZ) is a high index of refraction (n =2.17) material that we have investigated for Cherenkov counter applications. Laboratory and proton accelerator tests of an 18cc sample of CZ show that the expected fast Cherenkov response is accompanied by a longer scintillation component that can be separated by pulse shaping. This presents the possibility of novel particle spectrometers which exploits both properties of CZ. Other high index materials being examined for Cherenkov applications will be discussed. Results from laboratory tests and an accelerator exposure will be presented and a potential application in solar energetic particle instruments will be discussed

  6. Measurement of Scintillation and Ionization Yield and Scintillation Pulse Shape from Nuclear Recoils in Liquid Argon

    DOE PAGESBeta

    Cao, H.

    2015-05-26

    We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We also report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0more » to 970 V/cm. For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486 V/cm. Furthermore, we report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from 83mKr internal conversion electrons is comparable to that from 207Bi conversion electrons, we obtained the numbers of excitons (Nex) and ion pairs (Ni) and their ratio (Nex/Ni) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.« less

  7. Measurement of scintillation and ionization yield and scintillation pulse shape from nuclear recoils in liquid argon

    NASA Astrophysics Data System (ADS)

    Cao, H.; Alexander, T.; Aprahamian, A.; Avetisyan, R.; Back, H. O.; Cocco, A. G.; Dejongh, F.; Fiorillo, G.; Galbiati, C.; Grandi, L.; Guardincerri, Y.; Kendziora, C.; Lippincott, W. H.; Love, C.; Lyons, S.; Manenti, L.; Martoff, C. J.; Meng, Y.; Montanari, D.; Mosteiro, P.; Olvitt, D.; Pordes, S.; Qian, H.; Rossi, B.; Saldanha, R.; Sangiorgio, S.; Siegl, K.; Strauss, S. Y.; Tan, W.; Tatarowicz, J.; Walker, S.; Wang, H.; Watson, A. W.; Westerdale, S.; Yoo, J.; Scene Collaboration

    2015-05-01

    We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0 to 970 V /cm . For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486 V /cm . We also report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from Krm83 internal conversion electrons is comparable to that from 207Bi conversion electrons, we obtained the numbers of excitons (Nex) and ion pairs (Ni) and their ratio (Nex/Ni ) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.

  8. Measurement of Scintillation and Ionization Yield and Scintillation Pulse Shape from Nuclear Recoils in Liquid Argon

    SciTech Connect

    Cao, H.

    2015-05-26

    We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We also report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0 to 970 V/cm. For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486 V/cm. Furthermore, we report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from 83mKr internal conversion electrons is comparable to that from 207Bi conversion electrons, we obtained the numbers of excitons (Nex) and ion pairs (Ni) and their ratio (Nex/Ni) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.

  9. Statistical characteristics of low-latitude ionospheric scintillation over China

    NASA Astrophysics Data System (ADS)

    Liu, Kangkang; Li, Guozhu; Ning, Baiqi; Hu, Lianhuan; Li, Hongke

    2015-03-01

    The Global Positioning System (GPS) L-band ionospheric scintillation produced by electron density irregularities in the ionospheric E- and F-regions, is mainly a low- and high-latitude phenomenon. In this study, the statistical behavior of GPS ionospheric scintillation over a Chinese low-latitude station Sanya (18.3°N, 109.6°E; dip lat: 12.8°N) has been investigated. A detailed study on the seasonal and solar activity dependence of scintillation occurrence during July 2004-December 2012 show that the amplitude scintillation pattern, with a maximum occurrence during equinox of solar maximum, agrees with plasma bubble observations by in situ satellites in this longitude. A few daytime periodic scintillation events are found during June solstice months of solar minimum. Interestingly, a significant equinoctial asymmetry of scintillation onset time is found in 2011-2012. The initiation of scintillation during September-October is on average earlier than that of March-April about 25 min. Meanwhile, the zonal drifts of irregularities estimated using two spatially separated GPS receivers over Sanya show a similar behavior during the two equinoxes, slowly decreasing from 150 m/s at post-sunset to 50 m/s near midnight. The possible mechanisms responsible for the occurrence characteristics of GPS scintillation over Sanya, and relevant aspects of the zonal drifts of the irregularities are discussed.

  10. Microprocessor-based single particle calibration of scintillation counter

    NASA Technical Reports Server (NTRS)

    Mazumdar, G. K. D.; Pathak, K. M.

    1985-01-01

    A microprocessor-base set-up is fabricated and tested for the single particle calibration of the plastic scintillator. The single particle response of the scintillator is digitized by an A/D converter, and a 8085 A based microprocessor stores the pulse heights. The digitized information is printed. Facilities for CRT display and cassette storing and recalling are also made available.

  11. Characterizing Properties and Performance of 3D Printed Plastic Scintillators

    NASA Astrophysics Data System (ADS)

    McCormick, Jacob

    2015-10-01

    We are determining various characteristics of the performance of 3D printed scintillators. A scintillator luminesces when an energetic particle raises electrons to an excited state by depositing some of its energy in the atom. When these excited electrons fall back down to their stable states, they emit the excess energy as light. We have characterized the transmission spectrum, emission spectrum, and relative intensity of light produced by 3D printed scintillators. We are also determining mechanical properties such as tensile strength and compressibility, and the refractive index. The emission and transmission spectra were measured using a monochromator. By observing the transmission spectrum, we can see which optical wavelengths are absorbed by the scintillator. This is then used to correct the emission spectrum, since this absorption is present in the emission spectrum. Using photomultiplier tubes in conjunction with integration hardware (QDC) to measure the intensity of light emitted by 3D printed scintillators, we compare with commercial plastic scintillators. We are using the characterizations to determine if 3D printed scintillators are a viable alternative to commercial scintillators for use at Jefferson Lab in nuclear and accelerated physics detectors. I would like to thank Wouter Deconinck, as well as the Parity group at the College of William and Mary for all advice and assistance with my research.

  12. Statistics of ionospheric scintillation occurrence over European high latitudes

    NASA Astrophysics Data System (ADS)

    Sreeja, V.; Aquino, M.

    2014-12-01

    Rapid fluctuation in the amplitude and phase of transionospheric radio signals caused by small scale ionospheric plasma density irregularities is known as scintillation. Over the high latitudes, irregularities causing scintillation are associated with large scale plasma structures and scintillation occurrence is mainly enhanced during geomagnetic storms. This paper presents a statistical analysis of scintillation occurrence on GPS L1C/A signal at a high latitude station located in Bronnoysund (geographic latitude 65.5°N, geographic longitude 12.2°E; corrected geomagnetic (CGM) latitude 62.77°N), Norway, during the periods around the peaks of solar cycles 23 (2002-2003) and 24 (2011-2013). The analysis revealed that the scintillation occurrence at Bronnoysund during both the solar maximum periods maximises close to the midnight magnetic local time (MLT) sector. A higher occurrence of scintillation is observed on geomagnetically active days during both the solar maximum periods. The seasonal pattern of scintillation occurrence indicated peaks during the summer and equinoctial months. A comparison with the interplanetary magnetic field (IMF) components By and Bz showed an association of scintillation occurrence with the southward IMF Bz conditions.

  13. Performance comparison of scintillators for alpha particle detectors

    NASA Astrophysics Data System (ADS)

    Morishita, Yuki; Yamamoto, Seiichi; Izaki, Kenji; Kaneko, Junichi H.; Toui, Kohei; Tsubota, Youichi; Higuchi, Mikio

    2014-11-01

    Scintillation detectors for alpha particles are often used in nuclear fuel facilities. Alpha particle detectors have also become important in the research field of radionuclide therapy using alpha emitters. ZnS(Ag) is the most often used scintillator for alpha particle detectors because its light output is high. However, the energy resolution of ZnS(Ag)-based scintillation detectors is poor because they are not transparent. A new ceramic sample, namely the cerium doped Gd2Si2O7 (GPS) scintillator, has been tested as alpha particle detector and its performances have been compared to that one of three different scintillating materials: ZnS(Ag), GAGG and a standard plastic scintillator. The different scintillating materials have been coupled to two different photodetectors, namely a photomultiplier tube (PMT) and a Silicon Photo-multiplier (Si-PM): the performances of each detection system have been compared. Promising results as far as the energy resolution performances (10% with PMT and 14% with Si-PM) have been obtained in the case of GPS and GAGG samples. Considering the quantum efficiencies of the photodetectors under test and their relation to the emission wavelength of the different scintillators, the best results were achieved coupling the GPS with the PMT and the GAGG with the Si-PM

  14. Purification of KamLAND-Zen liquid scintillator

    SciTech Connect

    Ikeda, Haruo

    2013-08-08

    KamLAND-Zen is neutrino-less double-beta decay search experiment using enriched 300 kg of {sup 136}Xe dissolved in pure liquid scintillator. This report is purification work of liquid scintillator for KamLAND-Zen experiment before installation in the inner-balloon and background rejection processes after installation.

  15. Par Pond vegetation status Summer 1995 -- Summary

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1996-01-01

    The water level of Par Pond was lowered approximately 20 feet in mid-1991 in order to protect downstream residents from possible dam failure suggested by subsidence on the downstream slope of the dam and to repair the dam. This lowering exposed both emergent and nonemergent macrophyte beds to drying conditions resulting in extensive losses. A survey of the newly emergent, shoreline aquatic plant communities of Par Pond began in June 1995, three months after the refilling of Par Pond to approximately 200 feet above mean sea level. These surveys continued in July, September, and late October, 1995. Communities similar to the pre-drawdown, Par Pond aquatic plant communities are becoming re-established. Emergent beds of maidencane, lotus, waterlily, and watershield are extensive and well developed. Cattail occurrence continued to increase during the summer, but large beds common to Par Pond prior to the drawdown have not formed. Estimates from SPOT HRV, remote sensing satellite data indicated that as much as 120 hectares of emergent wetlands vegetation may have been present along the Par Pond shoreline by early October, 1995. To track the continued development of macrophytes in Par Pond, future surveys throughout 1996 and 1997, along with the continued evaluation of satellite data to map the areal extent of the macrophyte beds of Par Pond, are planned.

  16. Measurement of ortho-positronium properties in liquid scintillators

    SciTech Connect

    Perasso, S.; Franco, D.; Tonazzo, A.; Consolati, G.; Hans, S.; Yeh, M.; Jollet, C.; Meregaglia, A.

    2013-08-08

    Pulse shape discrimination in liquid scintillator detectors is a well-established technique for the discrimination of heavy particles from light particles. Nonetheless, it is not efficient in the separation of electrons and positrons, as they give rise to indistinguishable scintillator responses. This inefficiency can be overtaken through the exploitation of the formation of ortho-Positronium (o-Ps), which alters the time profile of light pulses induced by positrons. We characterized the o-Ps properties in the most commonly used liquid scintillators, i.e. PC, PXE, LAB, OIL and PC + PPO. In addition, we studied the effects of scintillator doping on the o-Ps properties for dopants currently used in neutrino experiments, Gd and Nd. Further measurements for Li-loaded and Tl-loaded liquid scintillators are foreseen. We found that the o-Ps properties are suitable for enhancing the electron-positron discrimination.

  17. Comparison of tropospheric scintillation prediction models of the Indonesian climate

    NASA Astrophysics Data System (ADS)

    Chen, Cheng Yee; Singh, Mandeep Jit

    2014-12-01

    Tropospheric scintillation is a phenomenon that will cause signal degradation in satellite communication with low fade margin. Few studies of scintillation have been conducted in tropical regions. To analyze tropospheric scintillation, we obtain data from a satellite link installed at Bandung, Indonesia, at an elevation angle of 64.7° and a frequency of 12.247 GHz from 1999 to 2000. The data are processed and compared with the predictions of several well-known scintillation prediction models. From the analysis, we found that the ITU-R model gives the lowest error rate when predicting the scintillation intensity for fade at 4.68%. However, the model should be further tested using data from higher-frequency bands, such as the K and Ka bands, to verify the accuracy of the model.

  18. Kinetic Monte Carlo simulations of scintillation processes in NaI(Tl)

    SciTech Connect

    Kerisit, Sebastien N.; Wang, Zhiguo; Williams, Richard; Grim, Joel; Gao, Fei

    2014-04-26

    Developing a comprehensive understanding of the processes that govern the scintillation behavior of inorganic scintillators provides a pathway to optimize current scintillators and allows for the science-driven search for new scintillator materials. Recent experimental data on the excitation density dependence of the light yield of inorganic scintillators presents an opportunity to incorporate parameterized interactions between excitations in scintillation models and thus enable more realistic simulations of the nonproportionality of inorganic scintillators. Therefore, a kinetic Monte Carlo (KMC) model of elementary scintillation processes in NaI(Tl) is developed in this work to simulate the kinetics of scintillation for a range of temperatures and Tl concentrations as well as the scintillation efficiency as a function of excitation density. The ability of the KMC model to reproduce available experimental data allows for elucidating the elementary processes that give rise to the kinetics and efficiency of scintillation observed experimentally for a range of conditions.

  19. The scintillating optical fiber calorimeter (SOFCAL) instrument

    NASA Astrophysics Data System (ADS)

    Christl, Mark J.; Fountain, W. F.; Parnell, Thomas A.; Roberts, F. E.; Benson, C.; Berry, Fred A.; Gregory, J. C.; Takahashi, Yoshiyuki

    1996-10-01

    A hybrid detector system is being developed for measuring the cosmic ray elemental composition and energy spectra above approximately GeV/nucleon. This system employs both a conventional 'passive' emulsion chamber and an 'active' ionization calorimeter incorporating scintillating fibers. Emulsion chambers have a proton energy threshold approximately greater than 5 TeV for detectable dark spots in the x-ray films which are used as a visual 'trigger.' The central element of this hybrid system is a calorimeter which has 10 x-y hodoscopic layers of 0.5 mm scintillating fibers interspersed with 4 mm lead plates. The fibers sample the hadronic and electromagnetic showers (cascades) initiated by interactions in the overlying emulsion chamber. The cascades are recorded by two image-intensified charge-coupled device (CCD) cameras which view the ends of the fibers to present orthogonal views. These showers are located and traced with microscopes in the emulsion chamber to provide an energy calibration through standard emulsion chamber methods, and an independent confirmation of the primary particle's charge (which is also measured with a Cerenkov counter above the emulsion chamber). The hybrid system will be used this fall for a balloon-borne measurement of the cosmic ray proton and helium spectra from approximately 400 GeV/n to approximately 10 TeV/n. An 8-hour test flight was performed in September 1995. Details of the detector system and sample results from the test flight are presented.

  20. Liquid Scintillation Detectors for High Energy Neutrinos

    SciTech Connect

    Smith, Stefanie N.; Learned, John G.

    2010-03-30

    Large open volume (not segmented) liquid scintillation detectors have been generally dedicated to low energy neutrino measurements, in the MeV energy region. We describe the potential employment of large detectors (>1 kiloton) for studies of higher energy neutrino interactions, such as cosmic rays and long-baseline experiments. When considering the physics potential of new large instruments the possibility of doing useful measurements with higher energy neutrino interactions has been overlooked. Here we take into account Fermat's principle, which states that the first light to reach each PMT will follow the shortest path between that PMT and the point of origin. We describe the geometry of this process, and the resulting wavefront, which we are calling the 'Fermat surface', and discuss methods of using this surface to extract directional track information and particle identification. This capability may be demonstrated in the new long-baseline neutrino beam from Jaeri accelerator to the KamLAND detector in Japan. Other exciting applications include the use of Hanohano as a movable long-baseline detector in this same beam, and LENA in Europe for future long-baseline neutrino beams from CERN. Also, this methodology opens up the question as to whether a large liquid scintillator detector should be given consideration for use in a future long-baseline experiment from Fermilab to the DUSEL underground laboratory at Homestake.

  1. Characterization of cerium fluoride nanocomposite scintillators

    SciTech Connect

    Stange, Sy; Esch, Ernst I; Brown, Leif O; Couture, Aaron J; Mckigney, Edward A; Muenchausen, Ross E; Del Sesto, Rico E; Gilbertson, Robert D; Mccleskey, T Mark; Reifarth, Rene

    2009-01-01

    Measurement of the neutron capture cross-sections of a number of short-lived isotopes would advance both pure and applied scientific research. These cross-sections are needed for calculation of criticality and waste production estimates for the Advanced Fuel Cycle Initiative, for analysis of data from nuclear weapons tests, and to improve understanding of nucleosynthesis. However, measurement of these cross-sections would require a detector with a faster signal decay time than those used in existing neutron capture experiments. Crystals of faster detector materials are not available in sufficient sizes and quantities to supply these large-scale experiments. Instead, we propose to use nanocomposite detectors, consisting of nanoscale particles of a scintillating material dispersed in a matrix material. We have successfully fabricated cerium fluoride (CeF{sub 3}) nanoparticles and dispersed them in a liquid matrix. We have characterized this scintillator and have measured its response to neutron capture. Results of the optical, structural, and radiation characterization will be presented.

  2. SDC conceptual design: Scintillating fiber outer tracker

    SciTech Connect

    Adams, D.; Baumbaugh, A.; Bird, F.; SDC Collaboration

    1992-01-22

    The authors propose an all-scintillating fiber detector for the purpose of outer tracking for the SDC. The objectives of this tracking system are to: (1) provide a first level trigger for {vert_bar}{eta}{vert_bar} < 2.3 with sharp p{sub T} threshold with the ability to resolve individual beam crossings; (2) provide pattern recognition capability and momentum resolution which complements and extends the capabilities of the inner silicon tracking system; (3) provide three dimensional linkage with outer detection systems including the shower maximum detector, muon detectors, and calorimetry; (4) provide robust tracking and track-triggering at the highest luminosities expected at the SSC. The many attractive features of a fiber tracker include good position resolution, low occupancy, low mass in the active volume, and excellent resistance to radiation damage. An additional important feature, especially at the SSC, is the intrinsically prompt response time of a scintillating fiber. This property is exploited in the construction of a level 1 trigger sensitive to individual beam crossings.

  3. Scintillation Proximity Assay of Arginine Methylation

    PubMed Central

    Wu, Jiang; Xie, Nan; Feng, You; Zheng, Y. George

    2011-01-01

    Methylation of arginine residues, catalyzed by protein arginine methyltransferases (PRMTs), is one important protein post-translational modification involved in epigenetic regulation of gene expression. A fast and effective assay for PRMT can provide valuable information for dissecting the biological functions of PRMTs, as well as for screening small-molecule inhibitors of arginine methylation. Currently, among the methods used for PRMT activity measurement, many contain laborious separation procedures, which restrict the applications of these assays for high-throughput screening (HTS) in drug discovery. The authors report here a mix-and-measure method to measure PRMT activity based on the principle of scintillation proximity assay (SPA). In this assay, 3H-AdoMet was used as methyl donor, and biotin-modified histone H4 peptide served as a methylation substrate. Following the methylation reaction catalyzed by PRMTs, streptavidin-coated SPA beads were added to the reaction solution, and SPA signals were detected by a MicroBeta scintillation counter. No separation step is needed, which simplifies the assay procedure and greatly enhances the assay speed. Particularly, the miniaturization and robustness suggest that this method is suited for HTS of PRMT inhibitors. PMID:21821785

  4. A scintillating fiber dosimeter for radiotherapy

    NASA Astrophysics Data System (ADS)

    Bartesaghi, G.; Conti, V.; Bolognini, D.; Grigioni, S.; Mascagna, V.; Prest, M.; Scazzi, S.; Mozzanica, A.; Cappelletti, P.; Frigerio, M.; Gelosa, S.; Monti, A.; Ostinelli, A.; Giannini, G.; Vallazza, E.

    2007-10-01

    Radiotherapy, together with chemotherapy and surgery, is one of the main methods applied in the fight against cancer; in order to increase the chances of a successful radiotherapy treatment the dose delivery to the tumor and the surrounding normal tissues has to be computed with high accuracy. Traditional dosimeters are accurate but single channel (ionization chambers and diodes) or non real-time (radiographic films) devices. At present there is no device water equivalent that can perform real-time and bidimensional measurements of a dose distribution. This article describes the development of a real-time dosimeter based on scintillating fibers for photon and electron beams; the fibers are made of polystyrene, that is water equivalent and thus tissue equivalent, allowing a direct dose calculation. Three prototypes (single and multichannel) have been assembled, consisting in small scintillators coupled to white fibers that carry the light to photomultiplier tubes. In this article the prototypes and the readout electronics are described, together with the results of the measurements with electron and photon beams with energy up to 20 MeV (produced by linear accelerators Varian Clinac 1800 and 2100CD).

  5. Scintillating bolometers for the LUCIFER project

    NASA Astrophysics Data System (ADS)

    Pattavina, L.; LUCIFER Collaboration

    2016-05-01

    Neutrinoless double beta decay (0vββ) is one of the most sensitive probes for physics beyond the Standard Model, providing unique information on the nature and masses of neutrinos. In order to explore the so-called inverted neutrino mass hierarchy region a further improvement on the upcoming 0vββ experiment is needed. In this respect, scintillating bolometers are the suitable technology for achieving such goal: they ensure excellent energy resolution and highly efficient particle discrimination. The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of 0vββ of 82Se. The matrix which embeds the source is an array of Zn 82Se crystals, where enriched 82Se is used as decay isotope. Taking advantage of the large Q-value (2997 keV) and of the particle discrimination, the expected background rate in the region of interest is as low as 10-3 c/keV/kg/y. The foreseen sensitivity after 2 years of live time will be 1.8×1025 years. We will report on the potential of such technology and on the present status of the project.

  6. Measuring scintillation light using Visible Light

    NASA Astrophysics Data System (ADS)

    Chavarria, Alvaro

    2006-11-01

    A new search for the neutron electric dipole moment (EDM) using ultra cold neutrons proposes an improvement on the neutron EDM by two orders of magnitude over the current limit (to 10-28 e*cm). Detection of scintillation light in superfluid ^4He is at the heart of this experiment. One possible scheme to detect this light is to use wavelength-shifting fibers in the superfluid ^4He to collect the scintillation light and transport it out of the measuring cell. The fiber terminates in a visible light photon counter (VLPC). VLPCs are doped, silicon based, solid state photomultipliers with high quantum efficiency (up to 80%) and high gain ( 40000 electrons per converted photon). Moreover, they are insensitive to magnetic fields and operate at temperatures of 6.5K. A test setup has been assembled at Duke University using acrylic cells wrapped in wavelength-shifting fibers that terminate on VLPCs. This setup is being used to evaluate the feasibility of this light detection scheme. The results obtained in multiple experiments done over the past summer (2006) and the current status of the project will be presented at the conference.Reference:A New Search for the Neutron Electric Dipole Moment, funding pre-proposal by the EDM collaboration; R. Golub and S. Lamoreaux, Phys. Rep. 237, 1 (1994).

  7. Relative light yield and temporal response of a stilbene-doped bibenzyl organic scintillator for neutron detection

    SciTech Connect

    Brown, J. A.; Goldblum, B. L. Brickner, N. M.; Daub, B. H.; Kaufman, G. S.; Bibber, K. van; Vujic, J.; Bernstein, L. A.; Bleuel, D. L.; Caggiano, J. A.; Hatarik, R.; Phillips, T. W.; Zaitseva, N. P.; Wender, S. A.

    2014-05-21

    The neutron time-of-flight (nTOF) diagnostics used to characterize implosions at the National Ignition Facility (NIF) has necessitated the development of novel scintillators that exhibit a rapid temporal response and high light yield. One such material, a bibenzyl-stilbene mixed single-crystal organic scintillator grown in a 99.5:0.5 ratio in solution, has become the standard scintillator used for nTOF diagnostics at NIF. The prompt fluorescence lifetime and relative light yield as a function of proton energy were determined to calibrate this material as a neutron detector. The temporal evolution of the intensity of the prompt fluorescent response was modeled using first-order reaction kinetics and the prompt fluorescence decay constant was determined to be 2.46 ± 0.01 (fit) ± 0.13 (systematic) ns. The relative response of the bibenzyl-stilbene mixed crystal generated by recoiling protons was measured, and results were analyzed using Birks' relation to quantify the non-radiative quenching of excitation energy in the scintillator.

  8. ParAB Partition Dynamics in Firmicutes: Nucleoid Bound ParA Captures and Tethers ParB-Plasmid Complexes

    PubMed Central

    Lioy, Virginia S.; Volante, Andrea; Soberón, Nora E.; Lurz, Rudi; Ayora, Silvia; Alonso, Juan C.

    2015-01-01

    In Firmicutes, small homodimeric ParA-like (δ2) and ParB-like (ω2) proteins, in concert with cis-acting plasmid-borne parS and the host chromosome, secure stable plasmid inheritance in a growing bacterial population. This study shows that (ω:YFP)2 binding to parS facilitates plasmid clustering in the cytosol. (δ:GFP)2 requires ATP binding but not hydrolysis to localize onto the cell’s nucleoid as a fluorescent cloud. The interaction of (δ:CFP)2 or δ2 bound to the nucleoid with (ω:YFP)2 foci facilitates plasmid capture, from a very broad distribution, towards the nucleoid and plasmid pairing. parS-bound ω2 promotes redistribution of (δ:GFP)2, leading to the dynamic release of (δ:GFP)2 from the nucleoid, in a process favored by ATP hydrolysis and protein-protein interaction. (δD60A:GFP)2, which binds but cannot hydrolyze ATP, also forms unstable complexes on the nucleoid. In the presence of ω2, (δD60A:GFP)2 accumulates foci or patched structures on the nucleoid. We propose that (δ:GFP)2 binding to different nucleoid regions and to ω2-parS might generate (δ:GFP)2 gradients that could direct plasmid movement. The iterative pairing and unpairing cycles may tether plasmids equidistantly on the nucleoid to ensure faithful plasmid segregation by a mechanism compatible with the diffusion-ratchet mechanism as proposed from in vitro reconstituted systems. PMID:26161642

  9. A Generic Receiver Tracking Model for GPS Ionospheric Amplitude Scintillation

    NASA Astrophysics Data System (ADS)

    Paula, E. R.; Moraes, A. D.; Perrella, W. J.; Galera Monico, J. F.

    2012-12-01

    Ionospheric scintillations result in rapid variations in phase and amplitude of the radio signal, which propagates through the ionosphere. Depending on the temporal and spatial situation, the scintillation can represent a problem in the availability and precision of the Global Navigation Satellite Systems (GNSS). Scintillations affect the receiver performance, specially the tracking loop level. Depending on the scintillation level, the receiver might increase the measurement errors or even can lead to a loss of lock of the carrier and code loops. In extreme cases, the scintillation can result in full disrupting of the receiver. In this work we introduce a generic model to evaluate the effects of ionospheric amplitude scintillation on GPS receiver tracking loops. This model is based on α-μ distribution, which can be seen as a generalized fading model, that includes a variety of distributions such as Gamma, Nakagami-m, Exponential, Weibull, one-sided Gaussian and Rayleigh. Differently from the model based only on Nakagami-m, this one is not limited to S4< 0,71 which allows using it to predict amplitude scintillation effects for stronger scenarios. The estimation of α-μ coefficients, the empirical parameterization based on field measurements and the typical values estimated based on observations made during the last solar maximum are presented and discussed.

  10. Cathodoluminescence studies of commercial and nano-structured scintillators

    NASA Astrophysics Data System (ADS)

    McDoanld, Warren; McKinney, George; Tzolov, Marian

    2014-03-01

    Scintillators have applications in fundamental research and in consumer products, e.g. detectors, scanners, and televisions. This research focused on analyzing the cathodoluminescence of different single-crystal scintillators with an originally developed method for evaluation of their performance, which allows for a direct comparison of different scintillators. We have studied yttrium aluminum garnet (YAG), yttrium aluminum perovskite (YAP) scintillators, zinc oxide single crystal, zinc tungstate single crystal, zinc oxide nanowires, and zinc tungstate film. The commercial scintillators are covered with conductive film which prevents low energy electrons from effectively interacting with the scintillator. We have varied the voltage accelerating the electrons with the intention of finding the threshold below which this effect will impact the performance of the scintillators. The same procedure was followed for the nanowires and zinc tungstate film which have enough conductivity and don't require a top conducting film. The threshold was established to be around 3 kV for the YAG and there is no threshold for the films, which perform much better at these low voltages. This property of the films has the potential for application in desktop scanning electron microscopes, where the accelerating voltage is low. The voltage dependence of the cathodoluminescence intensity follows an exponential trend and we present a model explaining it.

  11. Electronic Structure Engineering of Elpasolites for Brighter and Faster Scintillators

    NASA Astrophysics Data System (ADS)

    Du, Mao-Hua; Biswas, Koushik

    2013-03-01

    Utilization of scintillator materials is one of the primary methods for radiation detection. Elpasolites are a large family of quaternary halides that have attracted considerable interest for their potential applications as γ-ray and neutron scintillators. However, many elpasolite scintillator materials currently under development suffer from low light yield and long scintillation decay time. The low light yield is partially due to a large band gap while the long scintillation decay time is a result of slow carrier transport to Ce dopants, where electrons and holes recombine to emit photons. We suggest that these problems may be mitigated by optimizing the band gap and carrier mobility by selecting constituent elements of proper electronegativity. For example, cations with lower electronegativity may lower the conduction band and increase the conduction band dispersion simultaneously, resulting in higher light yield and faster scintillation. First-principles calculations of electronic structure, small polarons, and Ce dopants in Cs2LiYCl6 and Cs2AgYCl6 compounds show that the strategy of manipulating electronegativity can lead to brighter and faster elpasolite-based scintillators. This work was supported by the U.S. DOE Office of Nonproliferation Research and Development NA22.

  12. Development of scintillation materials for medical imaging and other applications

    SciTech Connect

    Melcher, C. L.

    2013-02-05

    Scintillation materials that produce pulses of visible light in response to the absorption of energetic photons, neutrons, and charged particles, are widely used in various applications that require the detection of radiation. The discovery and development of new scintillators has accelerated in recent years, due in large part to their importance in medical imaging as well as in security and high energy physics applications. Better understanding of fundamental scintillation mechanisms as well as the roles played by defects and impurities have aided the development of new high performance scintillators for both gamma-ray and neutron detection. Although single crystals continue to dominate gamma-ray based imaging techniques, composite materials and transparent optical ceramics potentially offer advantages in terms of both synthesis processes and scintillation performance. A number of promising scintillator candidates have been identified during the last few years, and several are currently being actively developed for commercial production. Purification and control of raw materials and cost effective crystal growth processes can present significant challenges to the development of practical new scintillation materials.

  13. Optimizing ZnS/6LiF scintillators for wavelength-shifting-fiber neutron detectors

    SciTech Connect

    Crow, Lowell; Funk, Loren L; Hannan, Bruce W; Hodges, Jason P; Riedel, Richard A; Wang, Cai-Lin

    2016-01-01

    In this paper we compare the performance of grooved and flat ZnS/6LiF scintillators in a wavelength shifting-fiber (WLSF) detector. Flat ZnS/6LiF scintillators with the thickness L=0.2-0.8 mm were characterized using photon counting and pulse-height analysis and compared to a grooved scintillator of approximately 0.8 mm thick. While a grooved scintillator considerably increases the apparent thickness of the scintillator to neutrons for a given coating thickness, we find that the flat scintillators perform better than the grooved scintillators in terms of both light yield and neutron detection efficiency. The flat 0.8-mm-thick scintillator has the highest light output, and it is 52% higher compared with a grooved scintillator of same thickness. The lower light output of the grooved scintillator as compared to the flat scintillator is consistent with the greater scintillator-WLSF separation and the much larger average emission angle of the grooved scintillator. We also find that the average light cone width, or photon travel-length as measured using time-of-flight powder diffraction of diamond and vanadium, decreases with increasing L in the range of L=0.6-0.8 mm. This result contrasts with the traditional Swank diffusion model for micro-composite scintillators, and could be explained by a decrease in photon diffusion-coefficient or an increase in micro-particle content in the flat scintillator matrix for the thicker scintillators.

  14. Scintillation properties of N2 and CF4 and performances of a scintillating ionization chamber

    NASA Astrophysics Data System (ADS)

    Lehaut, G.; Salvador, S.; Fontbonne, J.-M.; Lecolley, F.-R.; Perronnel, J.; Vandamme, Ch.

    2015-10-01

    In this work, we studied the emission yields, decay times and coincidence resolving times (CRT) of two gases, nitrogen (N2) and tetrafluoromethane (CF4), used for particle detection in the context of fission products measurement. The set-up was made of an ionization chamber and two photomultiplier tubes (PMTs) placed front-to-front on each side of the active zone of the chamber. Using the photomultiplier tubes, the number of photoelectrons (phe) converted at the photocathodes from the scintillation processes in each gas was quantified and the scintillation time spectra were recorded. A scintillation emission yield of 24 phe MeV-1 with a decay time of τd = 2.5 ns in N2, and 225 phe MeV-1 with τd = 6.2 ns for CF4, has been measured. With our set-up, the coincidence resolving time (σ values) between the two PMTs have been measured using alpha particles at 1.4 ns and 0.34 ns for N2 and CF4, respectively.

  15. Equatorial anomaly effects on GPS scintillations in brazil

    NASA Astrophysics Data System (ADS)

    de Paula, E. R.; Rodrigues, F. S.; Iyer, K. N.; Kantor, I. J.; Abdu, M. A.; Kintner, P. M.; Ledvina, B. M.; Kil, H.

    In a collaborative study, INPE and Cornell University have installed several Global Positioning System (GPS) based scintillation monitors over the Brazilian territory in order to study L Band scintillation. These scintillation monitors were developed by Cornell University to measure the amplitude scintillation observed at L1 (1.575 GHz) GPS signal and are sensitive to ionospheric irregularities of about 400 meters scale size. This paper describes some characteristics of the intensity of scintillations observed at three observation sites in Brazil: (1) São Luís (2.33 ° S, 44 ° W, dip latitude 1.3 ° S), located at magnetic equator, (2) São José dos Campos (23.21 ° S, 45.86 ° W, dip latitude 17.8 ° S), located under the equatorial anomaly peak and (3) Cuiabá (15.33 ° S, 56.46 ° W, dip latitude 6.1 ° S), an intermediate observation site located in between the magnetic equator and the equatorial anomaly peak. Analysis of data from January to March of 2000 showed that the occurrence percentage as well as the magnitude of the L Band scintillation increase with latitude from the magnetic equator to the equatorial anomaly crest as previously reported by Basu et al. (1988). Strong scintillation with S 4 index exceeding 0.5 only has been observed under equatorial anomaly peak while at magnetic equator scintillation intensity (S 4 index) did not exceed 0.3. Such studies from the network of stations set up by INPE and Cornell University in Brazil, where the effect of large declination controls the ESF statistics, will be very useful for developing a regional scintillation model for use in IRI.

  16. Surface preparation and coupling in plastic scintillator dosimetry.

    PubMed

    Ayotte, Guylaine; Archambault, Louis; Gingras, Luc; Lacroix, Frédéric; Beddar, A Sam; Beaulieu, Luc

    2006-09-01

    One way to improve the performance of scintillation dosimeters is to increase the light-collection efficiency at the coupling interfaces of the detector system. We performed a detailed study of surface preparation of scintillating fibers and their coupling with clear optical fibers to minimize light loss and increase the amount of light collected. We analyzed fiber-surface polishing with aluminum oxide sheets, coating fibers with magnesium oxide, and the use of eight different coupling agents (air, three optical gels, an optical curing agent, ultraviolet light, cyanoacrylate glue, and acetone). We prepared 10 scintillating fiber and clear optical fiber light guide samples to test different coupling methods. To test the coupling, we first cut both the scintillating fiber and the clear optical fiber. Then, we cleaned and polished both ends of both fibers. Finally, we coupled the scintillating fiber with the clear optical fiber in either a polyethylene jacket or a V-grooved support depending on the coupling agent used. To produce more light, we used an ultraviolet lamp to stimulate scintillation. A typical series of similar couplings showed a standard deviation in light-collection efficiency of 10%. This can be explained by differences in the surface preparation quality and alignment of the scintillating fiber with the clear optical fiber. Absence of surface polishing reduced the light collection by approximately 40%, and application of magnesium oxide on the proximal end of the scintillating fiber increased the amount of light collected from the optical fiber by approximately 39%. Of the coupling agents, we obtained the best results using one of the optical gels. Because a large amount of the light produced inside a scintillator is usually lost, better light-collection efficiency will result in improved sensitivity. PMID:17022248

  17. Surface preparation and coupling in plastic scintillator dosimetry

    SciTech Connect

    Ayotte, Guylaine; Archambault, Louis; Gingras, Luc; Lacroix, Frederic; Beddar, A. Sam; Beaulieu, Luc

    2006-09-15

    One way to improve the performance of scintillation dosimeters is to increase the light-collection efficiency at the coupling interfaces of the detector system. We performed a detailed study of surface preparation of scintillating fibers and their coupling with clear optical fibers to minimize light loss and increase the amount of light collected. We analyzed fiber-surface polishing with aluminum oxide sheets, coating fibers with magnesium oxide, and the use of eight different coupling agents (air, three optical gels, an optical curing agent, ultraviolet light, cyanoacrylate glue, and acetone). We prepared 10 scintillating fiber and clear optical fiber light guide samples to test different coupling methods. To test the coupling, we first cut both the scintillating fiber and the clear optical fiber. Then, we cleaned and polished both ends of both fibers. Finally, we coupled the scintillating fiber with the clear optical fiber in either a polyethylene jacket or a V-grooved support depending on the coupling agent used. To produce more light, we used an ultraviolet lamp to stimulate scintillation. A typical series of similar couplings showed a standard deviation in light-collection efficiency of 10%. This can be explained by differences in the surface preparation quality and alignment of the scintillating fiber with the clear optical fiber. Absence of surface polishing reduced the light collection by approximately 40%, and application of magnesium oxide on the proximal end of the scintillating fiber increased the amount of light collected from the optical fiber by approximately 39%. Of the coupling agents, we obtained the best results using one of the optical gels. Because a large amount of the light produced inside a scintillator is usually lost, better light-collection efficiency will result in improved sensitivity.

  18. Scintillating glass fiber-optic neutron sensors

    NASA Astrophysics Data System (ADS)

    Abel, K. H.; Arthur, R. J.; Bliss, M.

    1994-04-01

    Pacific Northwest Laboratory (PNL) has fabricated cerium-activated lithium silicate scintillating fibers via a hot-downdraw process. These fibers, which, as produced, typically have a transmission length (e(sup -1) length) of greater than 2 meters, are found to undergo aging when subjected to room air. The aging, which is complete in a few weeks, reduces the transmission length to the order of 0.5 meter. Because of the high alkali content of the glass (on the order of 20-30 mole percent lithia), we have attributed this aging to aqueous corrosion at the polymer cladding/glass interface. Changes in transmission with chemical treatment of the surface support the corrosion model. Fiber transmission performance has been preserved by modifying the hot-downdraw to a double crucible to produce glass-on-glass waveguides.

  19. The Oriented Scintillation Spectrometer Experiment - Instrument description

    NASA Astrophysics Data System (ADS)

    Johnson, W. N.; Kinzer, R. L.; Kurfess, J. D.; Strickman, M. S.; Purcell, W. R.; Grabelsky, D. A.; Ulmer, M. P.; Hillis, D. A.; Jung, G. V.; Cameron, R. A.

    1993-06-01

    The Oriented Scintillation Spectrometer Experiment on the Arthur Holly Compton Gamma Ray Observatory satellite uses four actively shielded NaI (Tl)-CsI(Na) phoswich detectors to provide gamma-ray line and continuum detection capability in the 0.05-10 MeV energy range. The instrument includes secondary capabilities for gamma-ray and neutron detection between 10 and 250 MeV. The detectors have 3.8 deg x 11.04 deg (FWHM) fields of view defined by tungsten collimators. Each detector has an independent, single-axis orientation system which permits offset pointing from the spacecraft Z-axis for background measurements and multitarget observations. The instrument, and its calibration and performance, are described.

  20. Bulk semiconducting scintillator device for radiation detection

    DOEpatents

    Stowe, Ashley C.; Burger, Arnold; Groza, Michael

    2016-08-30

    A bulk semiconducting scintillator device, including: a Li-containing semiconductor compound of general composition Li-III-VI.sub.2, wherein III is a Group III element and VI is a Group VI element; wherein the Li-containing semiconductor compound is used in one or more of a first mode and a second mode, wherein: in the first mode, the Li-containing semiconductor compound is coupled to an electrical circuit under bias operable for measuring electron-hole pairs in the Li-containing semiconductor compound in the presence of neutrons and the Li-containing semiconductor compound is also coupled to current detection electronics operable for detecting a corresponding current in the Li-containing semiconductor compound; and, in the second mode, the Li-containing semiconductor compound is coupled to a photodetector operable for detecting photons generated in the Li-containing semiconductor compound in the presence of the neutrons.

  1. SSPM Scintillator Readout for Gamma Radiation Detection

    SciTech Connect

    Baker, S A; Wendelberger, B; Young, J A; Green, J A; Guise, R E; Franks, L; Staples, C

    2011-09-01

    Silicon-based photodetectors offer several benefits relative to photomultiplier tube–based scintillator systems. Solid-state photomultipliers (SSPM) can realize the gain of a photomultiplier tube (PMT) with the quantum efficiency of silicon. The advantages of the solid-state approach must be balanced with adverse trade-offs, for example from increased dark current, to optimize radiation detection sensitivity. We are designing a custom SSPM that will be optimized for green emission of thallium-doped cesium iodide (CsI(Tl)). A typical field gamma radiation detector incorporates thallium doped sodium iodide (NaI(Tl)) and a radiation converter with a PMT. A PMT’s sensitivity peaks in the blue wavelengths and is well matched to NaI(Tl). This paper presents results of photomultiplier sensitivity relative to conventional SSPMs and discusses model design improvements. Prototype fabrications are in progress.

  2. Fiber optic thermal/fast neutron and gamma ray scintillation detector

    DOEpatents

    Neal, John S.; Mihalczo, John T

    2007-10-30

    A system for detecting fissile and fissionable material originating external to the system includes: a .sup.6Li loaded glass fiber scintillator for detecting thermal neutrons, x-rays and gamma rays; a fast scintillator for detecting fast neutrons, x-rays and gamma rays, the fast scintillator conjoined with the glass fiber scintillator such that the fast scintillator moderates fast neutrons prior to their detection as thermal neutrons by the glass fiber scintillator; and a coincidence detection system for processing the time distributions of arriving signals from the scintillators.

  3. Spectroscopic neutron detection using composite scintillators

    NASA Astrophysics Data System (ADS)

    Jovanovic, I.; Foster, A.; Kukharev, V.; Mayer, M.; Meddeb, A.; Nattress, J.; Ounaies, Z.; Trivelpiece, C.

    2016-09-01

    Shielded special nuclear material (SNM), especially highly enriched uranium, is exceptionally difficult to detect without the use of active interrogation (AI). We are investigating the potential use of low-dose active interrogation to realize simultaneous high-contrast imaging and photofission of SNM using energetic gamma-rays produced by low-energy nuclear reactions, such as 11B(d,nγ)12C and 12C(p,p‧)12C. Neutrons produced via fission are one reliable signature of the presence of SNM and are usually identified by their unique timing characteristics, such as the delayed neutron die-away. Fast neutron spectroscopy may provide additional useful discriminating characteristics for SNM detection. Spectroscopic measurements can be conducted by recoil-based or thermalization and capture-gated detectors; the latter may offer unique advantages since they facilitate low-statistics and event-by-event neutron energy measurements without spectrum unfolding. We describe the results of the development and characterization of a new type of capture-gated spectroscopic neutron detector based on a composite of scintillating polyvinyltoluene and lithium-doped scintillating glass in the form of millimeter-thick rods. The detector achieves >108 neutron-gamma discrimination resulting from its geometric properties and material selection. The design facilitates simultaneous pulse shape and pulse height discrimination, despite the fact that no materials intrinsically capable of pulse shape discrimination have been used to construct the detector. Accurate single-event measurements of neutron energy may be possible even when the energy is relatively low, such as with delayed fission neutrons. Simulation and preliminary measurements using the new composite detector are described, including those conducted using radioisotope sources and the low-dose active interrogation system based on low-energy nuclear reactions.

  4. Method for measuring multiple scattering corrections between liquid scintillators

    DOE PAGESBeta

    Verbeke, J. M.; Glenn, A. M.; Keefer, G. J.; Wurtz, R. E.

    2016-04-11

    In this study, a time-of-flight method is proposed to experimentally quantify the fractions of neutrons scattering between scintillators. An array of scintillators is characterized in terms of crosstalk with this method by measuring a californium source, for different neutron energy thresholds. The spectral information recorded by the scintillators can be used to estimate the fractions of neutrons multiple scattering. With the help of a correction to Feynman's point model theory to account for multiple scattering, these fractions can in turn improve the mass reconstruction of fissile materials under investigation.

  5. Neutron detector using lithiated glass-scintillating particle composite

    DOEpatents

    Wallace, Steven; Stephan, Andrew C.; Dai, Sheng; Im, Hee-Jung

    2009-09-01

    A neutron detector composed of a matrix of scintillating particles imbedded in a lithiated glass is disclosed. The neutron detector detects the neutrons by absorbing the neutron in the lithium-6 isotope which has been enriched from the natural isotopic ratio to a commercial ninety five percent. The utility of the detector is optimized by suitably selecting scintillating particle sizes in the range of the alpha and the triton. Nominal particle sizes are in the range of five to twenty five microns depending upon the specific scintillating particle selected.

  6. Method for measuring multiple scattering corrections between liquid scintillators

    NASA Astrophysics Data System (ADS)

    Verbeke, J. M.; Glenn, A. M.; Keefer, G. J.; Wurtz, R. E.

    2016-07-01

    A time-of-flight method is proposed to experimentally quantify the fractions of neutrons scattering between scintillators. An array of scintillators is characterized in terms of crosstalk with this method by measuring a californium source, for different neutron energy thresholds. The spectral information recorded by the scintillators can be used to estimate the fractions of neutrons multiple scattering. With the help of a correction to Feynman's point model theory to account for multiple scattering, these fractions can in turn improve the mass reconstruction of fissile materials under investigation.

  7. Alpha counting and spectrometry using liquid scintillation methods

    SciTech Connect

    McDowell, W J

    1986-01-01

    The material in this report is intended to be a practical introduction and guide to the use of liquid scintillation for alpha counting and spectrometry. Other works devoted to the development of the theory of liquid scintillation exist and a minimum of such material is repeated here. Much remains to be learned and many improvements remain to be made in the use of liquid scintillation for alpha counting and spectrometry. It is hoped that this modest work will encourage others to continue development in the field.

  8. Rayleigh scattering of linear alkylbenzene in large liquid scintillator detectors

    SciTech Connect

    Zhou, Xiang Zhang, Zhenyu; Liu, Qian; Zheng, Yangheng; Wurm, Michael; Zhang, Qingmin; Ding, Yayun; Zhou, Li; Cao, Jun; Wang, Yifang

    2015-07-15

    Rayleigh scattering poses an intrinsic limit for the transparency of organic liquid scintillators. This work focuses on the Rayleigh scattering length of linear alkylbenzene (LAB), which will be used as the solvent of the liquid scintillator in the central detector of the Jiangmen Underground Neutrino Observatory. We investigate the anisotropy of the Rayleigh scattering in LAB, showing that the resulting Rayleigh scattering length will be significantly shorter than reported before. Given the same overall light attenuation, this will result in a more efficient transmission of photons through the scintillator, increasing the amount of light collected by the photosensors and thereby the energy resolution of the detector.

  9. Angle scintillations in the laser return from a retroreflector.

    PubMed

    Hansen, J P; Madhu, S

    1972-02-01

    Angle scintillations of the laser return from a retroreflector were observed to exceed the value expected because of atmospheric turbulence. The observations and a theoretical analysis of a possible mechanism are presented. The experimental work was performed with a pulsed, 1.06-micro laser illuminating a corner cube. Angular scintillations of the laser return were measured to be eight times greater than that of a reference beacon. The theoretical analysis assumes phase fluctuations in the illuminating laser beam. An expression is derived for the scintillation angle as a function of a phase fluctuation parameter.

  10. Calibration of Small Plastic Scintillators for Imaging Applications

    SciTech Connect

    Pozzi, S.

    2005-01-19

    This report presents the results of measurements and simulations performed with 12 small plastic scintillation detectors manufactured by Scionix for imaging applications. The scintillator is equivalent to a Bicron BC-420 plastic scintillator. A gamma calibration is presented to determine the voltage to be applied on each detector to ensure uniform detector operation. Time of flight measurements performed with a Cf-252 source are also presented. Comparisons between experimental data and data from the Monte Carlo simulations show good agreement for time lags of 0 to 70 ns.

  11. Comparative cactus architecture and par interception

    SciTech Connect

    Geller, G.N.; Nobel, P.S. )

    1987-07-01

    Because CO{sup 2} uptake by cacti can be limited by low levels of photosynthetically active radiation (PAR) and because plant form affects PAR interception, various cactus forms were studied using a computer model, field measurements, and laboratory phototropic studies. Model predictions indicated that CO{sub 2} uptake by individual stems at an equinox was greatest when the stem were vertical, but at the summer and the winter solstice CO{sub 2} uptake was greatest for stems titled 30{degree} away from the equator. Stem tilting depended on form and taxonomic group. Not only can the shape of cacti be affected by PAR, but also shape influences PAR interception and hence CO{sub 2} uptake.

  12. Impact of the perturbation zonal velocity variation on the spatio/temporal occurrence pattern of L-band scintillation - a case study

    NASA Astrophysics Data System (ADS)

    Bagiya, Mala; Pant, Tarun; Choudhary, Raj Kumar; Sunda, Surendra; Sridharan, R.

    2016-07-01

    The earlier evolved method for the forecast of the spatio-temporal variation of L-band scintillation based on the expected variation of the perturbations [Bagiya et al., 2014; Sridharan et al., 2014], under favorable ionospheric/thermospheric conditions, has been refined by duly accounting for the local time variation of the zonal velocity of the perturbations. The unique combination of the two geostationary satellites (GSAT-8 and GSAT-10) over the Indian zone has been used to estimate the typical LT dependence of the perturbation velocities by closely following identifiable features in the scintillation pattern. The measured velocities, that registered a steady decrease with the progression of night, had been shown to significantly alter the forecast pattern of the scintillations with respect to longitude and local time. The significant improvement in the forecast pattern has been demonstrated through a case study putting the forecast method on a firmer footing. References: Bagiya, M. S., R. Sridharan, S. Sunda, L. Jose, T. K. Pant and R. Chaudhary, Critical assessment of the forecasting capability of L-band scintillations over the magnetic equatorial region - Campaign results, J. Atmos. and Sol. Terr. Phys., 110-111, 15-20 2014 Sridharan, R., Mala S. Bagiya, Surendra Sunda, Rajkumar Choudhary, Tarun K. Pant, Lijo Jose, First results on forecasting the spatial occurrence pattern of L-band scintillation and its temporal evolution, J. Atmos. and Sol. Terr. Phys., 119, 53-62 2014

  13. Evolution of the protease-activated receptor family in vertebrates

    PubMed Central

    JIN, MIN; YANG, HAI-WEI; TAO, AI-LIN; WEI, JI-FU

    2016-01-01

    Belonging to the G protein-coupled receptor (GPcr) family, the protease-activated receptors (Pars) consist of 4 members, PAR1-4. PARs mediate the activation of cells via thrombin, serine and other proteases. Such protease-triggered signaling events are thought to be critical for hemostasis, thrombosis and other normal pathological processes. In the present study, we examined the evolution of PARs by analyzing phylogenetic trees, chromosome location, selective pressure and functional divergence based on the 169 functional gene alignment sequences from 57 vertebrate gene sequences. We found that the 4 PARs originated from 4 invertebrate ancestors by phylogenetic trees analysis. The selective pressure results revealed that only PAR1 appeared by positive selection during its evolution, while the other PAR members did not. In addition, we noticed that although these PARs evolved separately, the results of functional divergence indicated that their evolutional rates were similar and their functions did not significantly diverge. The findings of our study provide valuable insight into the evolutionary history of the vertebrate PAR family. PMID:26820116

  14. Encapsulated scintillators monitor /sup 3/H-solute concentrations

    SciTech Connect

    Kirk, G.; Gruner, S.

    1982-02-01

    The short range of the /sup 3/H beta allows shielding of microbeds of scintillator by a several um thick coating of a water based gel. Gels may be used which are permeable to a wide variety of tritiated molecules. Thus, the light output of a mixture of the coated beads and a solution of the tritiated compound is proportional to the solution concentration of the tritiated substance. The mixture may also contain particles to which the gel is impermeable, such as cells, vesicles, large proteins, etc., but which can alter the concentration of the tritiated compound by uptake or release. In this case, the light output monitors the fractional uptake of the tritiated material. The design criteria for encapsulating the scintillators and dynamically monitoring the scintillation output are discussed. A simple method for encapsulating plastic scintillator microbeads, suitable for monitoring slow concentration changes, is described and tested.

  15. Final LDRD report : advanced plastic scintillators for neutron detection.

    SciTech Connect

    Vance, Andrew L.; Mascarenhas, Nicholas; O'Bryan, Greg; Mrowka, Stanley

    2010-09-01

    This report summarizes the results of a one-year, feasibility-scale LDRD project that was conducted with the goal of developing new plastic scintillators capable of pulse shape discrimination (PSD) for neutron detection. Copolymers composed of matrix materials such as poly(methyl methacrylate) (PMMA) and blocks containing trans-stilbene (tSB) as the scintillator component were prepared and tested for gamma/neutron response. Block copolymer synthesis utilizing tSBMA proved unsuccessful so random copolymers containing up to 30% tSB were prepared. These copolymers were found to function as scintillators upon exposure to gamma radiation; however, they did not exhibit PSD when exposed to a neutron source. This project, while falling short of its ultimate goal, demonstrated the possible utility of single-component, undoped plastics as scintillators for applications that do not require PSD.

  16. Radiowave Phase Scintillation and Precision Doppler Tracking of Spacecraft

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.

    1997-01-01

    Phase scintillation cause by propagation through irregularities in the solar wind, ionosphere, and tropospher, introduces noise in spacecraft radio science experiments. The observations reported here are uses to refine the propagation noise model for Doppler tracking of deep space probes.

  17. A scintillator purification plant and fluid handling system for SNO+

    NASA Astrophysics Data System (ADS)

    Ford, Richard J.

    2015-08-01

    A large capacity purification plant and fluid handling system has been constructed for the SNO+ neutrino and double-beta decay experiment, located 6800 feet underground at SNOLAB, Canada. SNO+ is a refurbishment of the SNO detector to fill the acrylic vessel with liquid scintillator based on Linear Alkylbenzene (LAB) and 2 g/L PPO, and also has a phase to load natural tellurium into the scintillator for a double-beta decay experiment with 130Te. The plant includes processes multi-stage dual-stream distillation, column water extraction, steam stripping, and functionalized silica gel adsorption columns. The plant also includes systems for preparing the scintillator with PPO and metal-loading the scintillator for double-beta decay exposure. We review the basis of design, the purification principles, specifications for the plant, and the construction and installations. The construction and commissioning status is updated.

  18. Scintillation effects on radio wave propagation through solar corona

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Sue, M. K.; Bedrossian, A.; Sniffin, R. W.

    2002-01-01

    When RF waves pass through the solar corona and solar wind regions close to the Sun, strong scintillation effects appear at their amplitude, frequency and phase, especially in the regions very close to the Sun (less than 4 solar radius).

  19. A scintillator purification plant and fluid handling system for SNO+

    SciTech Connect

    Ford, Richard J.

    2015-08-17

    A large capacity purification plant and fluid handling system has been constructed for the SNO+ neutrino and double-beta decay experiment, located 6800 feet underground at SNOLAB, Canada. SNO+ is a refurbishment of the SNO detector to fill the acrylic vessel with liquid scintillator based on Linear Alkylbenzene (LAB) and 2 g/L PPO, and also has a phase to load natural tellurium into the scintillator for a double-beta decay experiment with {sup 130}Te. The plant includes processes multi-stage dual-stream distillation, column water extraction, steam stripping, and functionalized silica gel adsorption columns. The plant also includes systems for preparing the scintillator with PPO and metal-loading the scintillator for double-beta decay exposure. We review the basis of design, the purification principles, specifications for the plant, and the construction and installations. The construction and commissioning status is updated.

  20. 21 CFR 892.1100 - Scintillation (gamma) camera.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...) Identification. A scintillation (gamma) camera is a device intended to image the distribution of radionuclides in the body by means of a photon radiation detector. This generic type of device may include...

  1. 21 CFR 892.1100 - Scintillation (gamma) camera.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...) Identification. A scintillation (gamma) camera is a device intended to image the distribution of radionuclides in the body by means of a photon radiation detector. This generic type of device may include...

  2. A fundamental limit on timing performance with scintillation detectors

    SciTech Connect

    Clinthorne, N.H.; Petrick, N.A.; Rogers, W.L. . Div. of Nuclear Medicine); Hero, A.O. . Dept. of Electrical Engineering and Computer Science)

    1990-04-01

    A new lower bound on the mean-squared error of post-detection {gamma}-ray time-of-flight estimators have been derived. Previously, the Cramer-Rao bound has been applied, but for nearly exponentially decaying scintillation pulses it gives an extremely optimistic picture of the achievable performance, depending critically on the dark current and photomultiplier characteristics. The new bound has been derived under the assumption that excited states in the scintillator leading to the emission of scintillation photons have an exponential lifetime density. The bound is a function of the mean state lifetime, the spectrum of energy deposited, and the energy conversion efficiency of the scintillator, and is exact for the observation of a mono-exponentially decaying photoelectron rate at the first dynode of the PMT given the {gamma}-ray arrival time.

  3. 21 CFR 892.1100 - Scintillation (gamma) camera.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) Identification. A scintillation (gamma) camera is a device intended to image the distribution of radionuclides in the body by means of a photon radiation detector. This generic type of device may include...

  4. A fine grained electromagnetic lead-liquid scintillator calorimeter

    NASA Astrophysics Data System (ADS)

    Bachman, L.; Bonesini, M.; Cavalli, D.; Costa, G.; Fischer, J.; Fluri, L.; Kienzle-Focacci, M. N.; Mandelli, L.; Martin, M.; Mazzanti, M.; Mermod, R.; Pensotti-Rancoita, S.; Perrin, D.; Rosselet, L.; Rutschmann, J.; Tamborini, M.; Vuilleumier, J. M.; Werlen, M.

    1983-02-01

    A new technique using liquid scintillator contained in teflon tubes to build a low cost high spatial resolution electromagnetic sampling calorimeter is described. Test results and comparison with a Monte Carlo simulation are presented.

  5. Cosmic-ray scintillation at the lunar surface

    SciTech Connect

    Benson, R.; Duller, N.M.; Green, P.J.

    1981-02-01

    The theory of cosmic-ray scintillations has developed rapidly over the past few years. Cosmic-ray scintillations arise from various irregularities in the magnetic fields through which cosmic-ray particles must travel before being observed. These scintillations are characterized by broad-band fluctuations in intensity over time. We have undertaken a study of the cosmic-ray background as observed with the Rice University Suprathermal Ion Detector Experimental (SIDE) that was deployed on the lunar surface during the Apollo 14 mission. The energy threshold for cosmic-ray protons was approximately 25 MeV in one sensor and 50 MeV in another. We find that the interplanetary cosmic-ray scintillations are observed with the SIDE and these observations are consistent with current theoretical models and with other experimental results.

  6. The response of scintillators to heavy ions: 1, Plastics

    SciTech Connect

    McMahan, M.A.

    1987-10-01

    The response of various scintillator detectors to ions of A = 1-84 and energies E/A = 5 to 30 MeV have been measured, and are found to be linear above an energy of 100 MeV. Results are presented for a typical organic plastic scintillator including parametrizations of the data as a function of Z, A, and energy. These results can be used by anyone using scintillators as heavy ion detectors, with one calibration point giving a normalization that allows use of the whole set of curves. The response functions are compared to previous parametrizations at lower energies and discussed in terms of the theory of delta-ray formation in the scintillator.

  7. Proteinase-activated receptor-1 (PAR(1)) and PAR(2) but not PAR(4) mediate contraction in human and guinea-pig gallbladders.

    PubMed

    Lee, M-C; Huang, S-C

    2008-04-01

    Proteinase-activated receptor-1 (PAR(1)) and PAR(2) mediate contraction in the guinea-pig gallbladder. To investigate and compare the effects mediated by PARs in the human gallbladder with those in the guinea-pig gallbladder, we measured contractions of isolated human and guinea-pig gallbladder strips caused by PAR agonists. Results in human were similar to those in guinea-pig gallbladder. The PAR(1) agonists, thrombin, TFLLR-NH2 and SFLLRN-NH2, as well as the PAR(2) agonists, trypsin, SLIGKV-NH2 and SLIGRL-NH2, caused contraction in both human and guinea-pig gallbladders. These indicate the existence of PAR(1) and PAR(2) mediating gallbladder contraction. Furthermore, the existence of PAR(1) and PAR(2) in the human gallbladder was confirmed by reverse transcription-polymerase chain reaction. In contrast, FSLLR-NH2, a PAR(1) control peptide, and VKGILS-NH2, a PAR(2) control peptide, as well as three PAR(4) agonists, GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2, did not cause any contraction or relaxation. The contractile responses to TFLLR-NH2, SFLLRN-NH2 and trypsin in both human and guinea-pig gallbladders were insensitive to atropine and tetrodotoxin, suggesting direct effects. These results demonstrate that, similar to the guinea-pig gallbladder, both PAR(1) and PAR(2) but not PAR(4) mediate muscle contraction in the human gallbladder. PAR(1) and PAR(2) may play important roles in the control of both human and guinea-pig gallbladder motility. PMID:18179608

  8. Proteinase-activated receptor-1 (PAR1) and PAR2 mediate relaxation of guinea pig internal anal sphincter.

    PubMed

    Huang, Shih-Che

    2014-02-10

    Activation of proteinase-activated receptor-1 (PAR1) and PAR2 stimulates contraction of the rat but relaxation of the guinea pig colon. The aim of the present study was to investigate PAR effects on internal anal sphincter (IAS) motility. We measured relaxation of isolated muscle strips from the guinea pig IAS caused by PAR agonists using isometric transducers. Reverse transcription polymerase chain reaction (RT-PCR) was performed to determine the existence of PAR. In the IAS, thrombin and PAR1 peptide agonists TFLLR-NH2 and SFLLRN-NH2 evoked moderate to marked relaxation in a concentration-dependent manner. In addition, trypsin and PAR2 peptide agonists 2-furoyl-LIGRLO-NH2, SLIGRL-NH2 and SLIGKV-NH2 produced relaxation. In contrast, both PAR1 and PAR2 inactive control peptides did not elicit relaxation. Furthermore, the selective PAR1 antagonist vorapaxar and PAR2 antagonist GB 83 specifically inhibited thrombin and trypsin-induced relaxations, respectively. RT-PCR revealed the presence of PAR1 and PAR2 in the IAS. This indicates that PAR1 and PAR2 mediate the IAS relaxation. The relaxant responses of TFLLR-NH2 and trypsin were attenuated by N(omega)-Nitro-L-arginine (L-NNA), indicating involvement of NO. These responses were not affected by tetrodotoxin, implying that the PAR effects are not neurally mediated. On the other hand, PAR4 agonists GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2 did not cause relaxation or contraction, suggesting that PAR4 is not involved in the sphincter motility. Taken together, these results demonstrate that both PAR1 and PAR2 mediate relaxation of the guinea pig IAS through the NO pathway. PAR1 and PAR2 may regulate IAS tone and might be potential therapeutic targets for anal motility disorders. PMID:24631471

  9. High effective atomic number polymer scintillators for gamma ray spectroscopy

    DOEpatents

    Cherepy, Nerine Jane; Sanner, Robert Dean; Payne, Stephen Anthony; Rupert, Benjamin Lee; Sturm, Benjamin Walter

    2014-04-15

    A scintillator material according to one embodiment includes a bismuth-loaded aromatic polymer having an energy resolution at 662 keV of less than about 10%. A scintillator material according to another embodiment includes a bismuth-loaded aromatic polymer having a fluor incorporated therewith and an energy resolution at 662 keV of less than about 10%. Additional systems and methods are also presented.

  10. The Use of Scintillation for Astronomical Site Testing

    NASA Astrophysics Data System (ADS)

    Sarazin, M. S.; Tokovinin, A.

    2009-09-01

    When site testing for future astronomical facilities (Extremely Large Telescopes, ELT), teams around the world use scintillation to locate the optically turbulent layers within the atmosphere. Several dedicated instruments are described which have been developed to retrieve the whole vertical Cn2 profile from close to the ground up to about 20km. MASS (Multi Aperture Scintillation Sensor) high altitude profilers in particular, when used in a network, can provide a 3D tracking of clear air turbulence during nighttime over large areas.

  11. Scintillation Observations and Response of The Ionosphere to Electrodynamics (SORTIE)

    NASA Astrophysics Data System (ADS)

    Crowley, G.

    2015-12-01

    The Scintillation Observations and Response of The Ionosphere to Electrodynamics, or SORTIE, mission is a 6U NASA Heliophysics CubeSat designed to study the ionosphere at altitudes below 400km. The SORTIE mission is being developed by a team including ASTRA (lead institution), AFRL, University of Texas at Dallas (UTD), COSMIAC (Satellite Integrator), and Boston College. SORTIE will address cutting-edge science in the area of ionospheric dynamics. The SORTIE mission will address the following science questions: Q1) Discover the sources of wave-like plasma perturbations in the F-region ionosphere. Q2) Determine the relative role of dynamo action and more direct mechanical forcing in the formation of wave-like plasma perturbations. To address these questions we plan to fly a CubeSat with novel sensors that measure key plasma parameters in a circular, low to middle inclination orbit near 350-400 km altitude. The sensors include an ion velocity meter (built by UTD) and a Planar Langmuir Probe (built by AFRL). The SORTIE mission plan is to describe the distribution of wave-like structures in the plasma density of the ionospheric F-region. In doing so, the SORTIE team will determine the possible role of these perturbations in aiding the growth of plasma instabilities. SORTIE will provide (1) the initial spectrum of wave perturbations which are the starting point for the RT calculation; (2) measured electric fields which determine the magnitude of the instability growth rate near the region where plasma bubbles are generated; (3) initial observations of irregularities in plasma density which result from RT growth. SORTIE results will be used as input to PBMOD, an assimilative first-principles physical model of the ionosphere, in order to predict evolution of EPBs. In this presentation, we will review the science objectives, provide an overview of the spacecraft and instrument design, and present a concept of operations plan.

  12. The space weather of the global ionosphere S4 scintillation

    NASA Astrophysics Data System (ADS)

    Liu, Jann-Yenq; Chen, Shih-Ping; Yeh, Wen-Hao

    2016-04-01

    In this paper, a method is introduced which converts S4 index observations by radio occultation of FORMOSAT-3/COSMIC (F3/C) to the scintillation on the ground. To carry out the conversion, three dimensional (3D) structures of S4max, the maximum value on each profile probed by F3/C, are constructed, which allows us to understand GPS scintillation variations at various local times, seasons, and solar activity conditions, as well as the geographical distribution from the space-based point of view. By applying the method to data of the 3D structure, maps of the worst case scenario on the ground as functions of geomagnetic local time and geographic coordinates are constructed and reported here. The converted S4max for the first time estimates the global distribution of ionospheric scintillations in the GPS L1 band C/A code signal on the ground. The results show that the worst-case scintillations appear within the low latitude region of ±30°N, peaking around ±20°N magnetic latitude; they begin at 1900 MLT, reach their maximum at 2100 MLT, and vanish by about 0200-0300 MLT. The most pronounced low-latitude scintillation occurs over the South American and African sectors. Finally, based on the above the above data, an empirical model is constructed. For a given time, location, and solar activity, the model forecasts the ionospheric S4 scintillation in the L1 band signal on the ground.

  13. Broadband meter-wavelength observations of ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Fallows, R. A.; Coles, W. A.; McKay-Bukowski, D.; Vierinen, J.; Virtanen, I. I.; Postila, M.; Ulich, Th.; Enell, C.-F.; Kero, A.; Iinatti, T.; Lehtinen, M.; Orispää, M.; Raita, T.; Roininen, L.; Turunen, E.; Brentjens, M.; Ebbendorf, N.; Gerbers, M.; Grit, T.; Gruppen, P.; Meulman, H.; Norden, M. J.; de Reijer, J.-P.; Schoenmakers, A.; Stuurwold, K.

    2014-12-01

    Intensity scintillations of cosmic radio sources are used to study astrophysical plasmas like the ionosphere, the solar wind, and the interstellar medium. Normally, these observations are relatively narrow band. With Low-Frequency Array (LOFAR) technology at the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) station in northern Finland we have observed scintillations over a three-octave bandwidth. "Parabolic arcs," which were discovered in interstellar scintillations of pulsars, can provide precise estimates of the distance and velocity of the scattering plasma. Here we report the first observations of such arcs in the ionosphere and the first broadband observations of arcs anywhere, raising hopes that study of the phenomenon may similarly improve the analysis of ionospheric scintillations. These observations were made of the strong natural radio source Cygnus-A and covered the entire 30-250 MHz band of KAIRA. Well-defined parabolic arcs were seen early in the observations, before transit, and disappeared after transit although scintillations continued to be obvious during the entire observation. We show that this can be attributed to the structure of Cygnus-A. Initial results from modeling these scintillation arcs are consistent with simultaneous ionospheric soundings taken with other instruments and indicate that scattering is most likely to be associated more with the topside ionosphere than the F region peak altitude. Further modeling and possible extension to interferometric observations, using international LOFAR stations, are discussed.

  14. Does the finite size of the proto-neutron star preclude supernova neutrino flavor scintillation due to turbulence?

    SciTech Connect

    Kneller, James P.; Mauney, Alex W.

    2013-08-23

    Here, the transition probabilities describing the evolution of a neutrino with a given energy along some ray through a turbulent supernova profile are random variates unique to each ray. If the proto-neutron-star source of the neutrinos were a point, then one might expect the evolution of the turbulence would cause the flavor composition of the neutrinos to vary in time i.e. the flavor would scintillate. But in reality the proto-neutron star is not a point source—it has a size of order ˜10km, so the neutrinos emitted from different points at the source will each have seen different turbulence. The finite source size will reduce the correlation of the flavor transition probabilities along different trajectories and reduce the magnitude of the flavor scintillation. To determine whether the finite size of the proto-neutron star will preclude flavor scintillation, we calculate the correlation of the neutrino flavor transition probabilities through turbulent supernova profiles as a function of the separation δx between the emission points. The correlation will depend upon the power spectrum used for the turbulence, and we consider two cases: when the power spectrum is isotropic, and the more realistic case of a power spectrum which is anisotropic on large scales and isotropic on small. Although it is dependent on a number of uncalibrated parameters, we show the supernova neutrino source is not of sufficient size to significantly blur flavor scintillation in all mixing channels when using an isotropic spectrum, and this same result holds when using an anisotropic spectrum, except when we greatly reduce the similarity of the turbulence along parallel trajectories separated by ˜10km or less.

  15. Does the finite size of the proto-neutron star preclude supernova neutrino flavor scintillation due to turbulence?

    DOE PAGESBeta

    Kneller, James P.; Mauney, Alex W.

    2013-08-23

    Here, the transition probabilities describing the evolution of a neutrino with a given energy along some ray through a turbulent supernova profile are random variates unique to each ray. If the proto-neutron-star source of the neutrinos were a point, then one might expect the evolution of the turbulence would cause the flavor composition of the neutrinos to vary in time i.e. the flavor would scintillate. But in reality the proto-neutron star is not a point source—it has a size of order ˜10km, so the neutrinos emitted from different points at the source will each have seen different turbulence. The finitemore » source size will reduce the correlation of the flavor transition probabilities along different trajectories and reduce the magnitude of the flavor scintillation. To determine whether the finite size of the proto-neutron star will preclude flavor scintillation, we calculate the correlation of the neutrino flavor transition probabilities through turbulent supernova profiles as a function of the separation δx between the emission points. The correlation will depend upon the power spectrum used for the turbulence, and we consider two cases: when the power spectrum is isotropic, and the more realistic case of a power spectrum which is anisotropic on large scales and isotropic on small. Although it is dependent on a number of uncalibrated parameters, we show the supernova neutrino source is not of sufficient size to significantly blur flavor scintillation in all mixing channels when using an isotropic spectrum, and this same result holds when using an anisotropic spectrum, except when we greatly reduce the similarity of the turbulence along parallel trajectories separated by ˜10km or less.« less

  16. Study of cosmic ray scintillations from 5-minute data of the scintillations telescope Izmran and world-wide network stations

    NASA Technical Reports Server (NTRS)

    Gulinsky, O. V.; Dorman, L. I.; Libin, I. Y.; Prilutsky, R. E.; Yudakhin, K. F.

    1985-01-01

    During cosmic ray propagation in interplanetary space there appear characteristic cosmic-ray intensity scintillations which are due to charged particle scattering on random inhomogeneities of the interplanetary magnetic field. The power spectra of cosmic ray scintillations on the Earth during some intervals from 1977 to 1982 (for quiet periods, for solar flares and Forbush decreases due to power shock waves) have been calculated from five-minute, one and two-hour values of the cosmic-ray intensity measured by the scintillator supertelescope IZMIRAN. The spectra were estimated by the methods of spectral analysis and by autoregressive methods which mutually control each other and make it possible not only to analyze scintillation powers at distinguished frequencies, but also to determine the behavior of spectrum slopes in some frequency ranges.

  17. Techniques for measuring intercepted and absorbed PAR in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.

    1984-01-01

    The quantity of radiation potentially available for photosynthesis that is captured by the crop is best described as absorbed photosynthetically active radiation (PAR). Absorbed PAR (APAR) is the difference between descending and ascending fluxes. The four components of APAR were measured above and within two planting densities of corn (Zea mays L.) and several methods of measuring and estimating APAR were examined. A line quantum sensor that spatially averages the photosynthetic photon flux density provided a rapid and portable method of measuring APAR. PAR reflectance from the soil (Typic Argiaquoll) surface decreased from 10% to less than 1% of the incoming PAR as the canopy cover increased. PAR reflectance from the canopy decreased to less than 3% at maximum vegetative cover. Intercepted PAR (1 - transmitted PAR) generally overestimated absorbed PAR by less than 4% throughout most of the growing season. Thus intercepted PAR appears to be a reasonable estimate of absorbed PAR.

  18. Approaching Long Genomic Regions and Large Recombination Rates with msParSm as an Alternative to MaCS

    PubMed Central

    Montemuiño, Carlos; Espinosa, Antonio; Moure, Juan C.; Vera, Gonzalo; Hernández, Porfidio; Ramos-Onsins, Sebastián

    2016-01-01

    The msParSm application is an evolution of msPar, the parallel version of the coalescent simulation program ms, which removes the limitation for simulating long stretches of DNA sequences with large recombination rates, without compromising the accuracy of the standard coalescence. This work introduces msParSm, describes its significant performance improvements over msPar and its shared memory parallelization details, and shows how it can get better, if not similar, execution times than MaCS. Two case studies with different mutation rates were analyzed, one approximating the human average and the other approximating the Drosophila melanogaster average. Source code is available at https://github.com/cmontemuino/msparsm. PMID:27721650

  19. Progress with the MICE scintillating fiber trackers

    NASA Astrophysics Data System (ADS)

    Overton, Edward

    2013-12-01

    The International Muon Ionization Cooling Experiment (MICE) is a proof of principle demonstration of ionization cooling, for application in a future neutrino factory or muon collider. MICE is under construction at the Rutherford Appleton Laboratory (UK), where a dedicated beam line has been commissioned to transport particles produced inside the ISIS accelerator facility. The beam emittance will be measured using two scintillating fiber trackers on each side of the cooling channel, which will be mounted inside a 4 T solenoid. As particles pass through the tracker, their position will be measured at 5 stations, each of which provides a position resolution of less than 0.5 mm. The fiber trackers have been validated using cosmic ray tests, which have allowed the light yield to be found. In addition, a spare tracking station was exposed to the MICE beam, which has enabled the tracker readout to be integrated with the MICE DAQ for the first time. This test required the integration gate on the D0 AFE-IIt readout boards to be synchronized with particle arrival by using diagnostic signals from the ISIS accelerator.

  20. Excitonic effects in oxyhalide scintillating host compounds

    SciTech Connect

    Shwetha, G.; Kanchana, V.; Valsakumar, M. C.

    2014-10-07

    Ab-initio calculations based on density functional theory have been performed to study the electronic, optical, mechanical, and vibrational properties of scintillator host compounds YOX (X = F, Cl, Br, and I). Semiempirical dispersion correction schemes are used to find the effect of van der Waals forces on these layered compounds and we found this effect to be negligible except for YOBr. Calculations of phonons and elastic constants showed that all the compounds studied here are both dynamically and mechanically stable. YOF and YOI are found to be indirect band gap insulators while YOCl and YOBr are direct band gap insulators. The band gap is found to decrease as we move from fluorine to iodine, while the calculated refractive index shows the opposite trend. As the band gap decreases on going down the periodic table from YOF to YOI, the luminescence increases. The excitonic binding energy calculated, within the effective mass approximation, is found to be more for YOF than the remaining compounds, suggesting that the excitonic effect to be more in YOF than the other compounds. The optical properties are calculated within the Time-Dependent Density Functional Theory (TDDFT) and compared with results obtained within the random phase approximation. The TDDFT calculations, using the newly developed bootstrap exchange-correlation kernel, showed significant excitonic effects in all the compounds studied here.

  1. sPHENIX Hadronic Calorimeter Scintillator Studies

    NASA Astrophysics Data System (ADS)

    Byrd, Reuben; Sphenix Collaboration

    2015-10-01

    A new form of matter called the Quark-Gluon Plasma (QGP) was discovered with the Relativistic Heavy Ion Collider (RHIC). PHENIX is an experiment at RHIC that helped with this discovery, but plans are being made to replace it with a new spectrometer with different capabilities. The sPHENIX detector will consist of a superconducting solenoid magnet, hadronic and electromagnetic calorimetry and charged particle tracking. sPHENIX will enable a rich jet physics program that will address fundamental questions about of the nature of the QGP. The new detector will provide full azimuthal coverage and +/- 1.1 in pseudorapidity. The Hadronic Calorimeter is a major subsystem in this detector. It is made of alternating layers of scintillating tiles and steel plates. In the current prototype the tiles are covered with a reflective coating and contain wavelength shifting fibers. As the second round of prototypes are developed for an upcoming beam test, special care is being taken to provide uniform light collection efficiency across the detector. Studies are being conducted to ensure this by careful alignment of the silicon photomultipliers to the fibers and varying coatings on the tiles. The effects of the coating will be presented along with the current status and ongoing plans.

  2. Lutetium oxide-based transparent ceramic scintillators

    DOEpatents

    Seeley, Zachary; Cherepy, Nerine; Kuntz, Joshua; Payne, Stephen A.

    2016-01-19

    In one embodiment, a transparent ceramic of sintered nanoparticles includes gadolinium lutetium oxide doped with europium having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YEu.sub.YO.sub.3, where X is any value within a range from about 0.05 to about 0.45 and Y is any value within a range from about 0.01 to about 0.2, and where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm. In another embodiment, a transparent ceramic scintillator of sintered nanoparticles, includes a body of sintered nanoparticles including gadolinium lutetium oxide doped with a rare earth activator (RE) having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YRE.sub.YO.sub.3, where RE is selected from the group consisting of: Sm, Eu, Tb, and Dy, where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm.

  3. PAR polarity: from complexity to design principles.

    PubMed

    Goehring, Nathan W

    2014-11-01

    The par-titioning-defective or PAR proteins comprise the core of an essential cell polarity network that underlies polarization in a wide variety of cell types and developmental contexts. The output of this network in nearly every case is the establishment of opposing and complementary membrane domains that define a cell׳s polarity axis. Yet, behind this simple pattern is a complex system of interactions, regulation and dynamic behaviors. How these various parts combine to generate polarized patterns of protein localization in cells is only beginning to become clear. This review, part of the Special Issue on Cell Polarity, aims to highlight several emerging themes and design principles that underlie the process of cell polarization by components of the PAR network. PMID:25128809

  4. Humanizing the Protease-Activated Receptor (PAR) Expression Profile in Mouse Platelets by Knocking PAR1 into the Par3 Locus Reveals PAR1 Expression Is Not Tolerated in Mouse Platelets

    PubMed Central

    French, Shauna L.; Paramitha, Antonia C.; Moon, Mitchell J.; Dickins, Ross A.; Hamilton, Justin R.

    2016-01-01

    Anti-platelet drugs are the mainstay of pharmacotherapy for heart attack and stroke prevention, yet improvements are continually sought. Thrombin is the most potent activator of platelets and targeting platelet thrombin receptors (protease-activated receptors; PARs) is an emerging anti-thrombotic approach. Humans express two PARs on their platelets–PAR1 and PAR4. The first PAR1 antagonist was recently approved for clinical use and PAR4 antagonists are in early clinical development. However, pre-clinical studies examining platelet PAR function are challenging because the platelets of non-primates do not accurately reflect the PAR expression profile of human platelets. Mice, for example, express Par3 and Par4. To address this limitation, we aimed to develop a genetically modified mouse that would express the same repertoire of platelet PARs as humans. Here, human PAR1 preceded by a lox-stop-lox was knocked into the mouse Par3 locus, and then expressed in a platelet-specific manner (hPAR1-KI mice). Despite correct targeting and the predicted loss of Par3 expression and function in platelets from hPAR1-KI mice, no PAR1 expression or function was detected. Specifically, PAR1 was not detected on the platelet surface nor internally by flow cytometry nor in whole cell lysates by Western blot, while a PAR1-activating peptide failed to induce platelet activation assessed by either aggregation or surface P-selectin expression. Platelets from hPAR1-KI mice did display significantly diminished responsiveness to thrombin stimulation in both assays, consistent with a Par3-/- phenotype. In contrast to the observations in hPAR1-KI mouse platelets, the PAR1 construct used here was successfully expressed in HEK293T cells. Together, these data suggest ectopic PAR1 expression is not tolerated in mouse platelets and indicate a different approach is required to develop a small animal model for the purpose of any future preclinical testing of PAR antagonists as anti-platelet drugs. PMID

  5. Scintillation and irregularities from the nightside part of a Sun-aligned polar cap arc

    NASA Astrophysics Data System (ADS)

    Meeren, Christer; Oksavik, Kjellmar; Lorentzen, Dag A.; Paxton, Larry J.; Clausen, Lasse B. N.

    2016-06-01

    In this paper we study the presence of irregularities and scintillation in relation to the nightside part of a long-lived, Sun-aligned transpolar arc on 15 January 2015. The arc was observed in DMSP UV and particle data and lasted at least 3 h between 1700 and 2000 UT. The arc was more intense than the main oval during this time. From all-sky imagers on Svalbard we were able to study the evolution of the arc, which drifted slowly westward toward the dusk cell. The intensity of the arc as observed from ground was 10-17 kR in 557.7 nm and 2-3.5 kR in 630.0 nm, i.e., significant emissions in both green and red emission lines. We have used high-resolution raw data from global navigation satellite systems (GNSS) receivers and backscatter from Super Dual Auroral Radar Network (SuperDARN) radars to study irregularities and scintillation in relation to the polar cap arc. Even though the literature has suggested that polar cap arcs are potential sources for irregularities, our results indicate only very weak irregularities. This may be due to the background density in the northward IMF polar cap being too low for significant irregularities to be created.

  6. A scintillating fission detector for neutron flux measurements

    SciTech Connect

    Stange, Sy; Esch, Ernst I; Burgett, Eric A; May, Iain; Muenchausen, Ross E; Taw, Felicia; Tovesson, Fredrik K

    2010-01-01

    Neutron flux monitors are commonly used for a variety of nuclear physics applications. A scintillating neutron detector, consisting of a liquid scintillator loaded with fissionable material, has been developed, characterized, and tested in the beam line at the Los Alamos Neutron Science Center, and shows a significant improvement in neutron sensitivity compared with a conventional fission chamber. Recent research on nanocomposite-based scintillators for gamma-ray detection indicates that this approach can be extended to load nanoparticles of fissionable material into a scintillating matrix, with up to three orders of magnitude higher loading than typical fission chambers. This will result in a rugged, cost-efficient detector with high efficiency, a short signal rise time, and the ability to be used in low neutron-flux environments. Initial efforts to utilize the luminescence of uranyl oxide to eliminate the need for wavelength-shifting dyes were unsuccessful. Excitation of uranyl compounds has been reported at wavelengths ranging from 266 nm to 532 nm. However, neither the 300 nm emission of toluene, nor the 350 nm emission of PPO, nor the 410 nm emission of POPOP resulted in significant excitation of and emission by uranyl oxide. As indicated by UV/visible spectroscopy, light emitted at these wavelengths was absorbed by the colored solution. {sup 235}U remains the most attractive candidate for a fissionable scintillator, due to its high fission cross-section and lack of a threshold fission energy, but all solutions containing molecular uranium compounds will be colored, most more highly than the U{sup 6+} compounds used here. Research is therefore continuing toward the fabrication of uranium nanoparticles, in which, due to Rayleigh scattering, the coloration should be less pronounced. The characterization of the thorium-loaded liquid scintillator and the fabrication of the 100 mL detectors for use at LANSCE demonstrated the feasibility of loading fissionable

  7. Radar measurement of ionospheric scintillation in the polar region

    NASA Astrophysics Data System (ADS)

    Knepp, Dennis L.

    2015-10-01

    This paper considers several estimators that use radar data to measure the S4 scintillation index that characterizes the severity of amplitude scintillation that may occur during RF propagation through ionospheric irregularities. S4 is defined to be the standard deviation of the fluctuations in received power normalized by division by the mean power. Estimates of S4 are based on radar returns obtained during track of targets which may themselves have intrinsic radar cross-section fluctuations. Key to this work is the consideration of thresholding, which is used in many radars to remove (from further processing) signals whose SNR is considered too low. We consider several estimators here. The "direct" estimator attempts to estimate S4 through the direct calculation of the mean and standard deviation of the SNR from a number of radar returns. The maximum likelihood (ML) estimator uses multiple hypothesis testing and the assumption of Nakagami-m statistics to estimate the scintillation index that best fits the radar returns from some number of pulses. The ML estimator has perfect knowledge of the number of radar returns that are below the threshold. The direct estimator is accurate for the case where there is no threshold and there are many returns or samples from which to estimate S4. However, the direct estimator is flawed (especially for strong scintillation) if deep fades that fall below the radar threshold are ignored. The modified ML estimator here is based on the ML technique but is useful if the count of missed returns is unavailable. We apply the modified ML estimator to several years of radar tracks of large calibration satellites to obtain the statistics of UHF scintillation as viewed from the early warning radar at Thule, Greenland. One-way S4 was measured from 5000 low Earth orbit tracks during the 3 year period after solar maximum in May 2000. The data are analyzed to quantify the exceedance or the level of scintillation experienced at various

  8. Indium-111-Photofrin-II scintillation scan

    SciTech Connect

    Origitano, T.C.; Karesh, S.M.; Reichman, O.H.; Henkin, R.E.; Caron, M.J.

    1989-04-01

    Photodynamic therapy is under intense investigation as an adjuvant treatment for malignant glial tumors of the central nervous system. Photofrin-II (HpD-II) is currently the most actively investigated photosensitizing agent. A crucial issue regarding the safe and efficacious usage of HpD-II-based photodynamic therapy is the individual in vivo kinetics of tumor uptake and retention, compared with normal brain clearance. The optimal time for photoactivation of sensitized tumor must be known to ensure a high target-to-nontarget ratio, resulting in the maximal tumor destruction while preserving normal brain. Our laboratory developed a radionuclide scan based on 111indium (111In)-labeled HpD-II to evaluate HpD-II localization and clearance noninvasively within a canine model of intracerebral gliosarcoma. Synthesis of the 111In-HpD-II complex in greater than 90% yield is achieved by a simple, rapid labeling method. Radiochemical purity and stability were verified by high-performance liquid chromatography. Using the canine model of intracerebral gliosarcoma, we followed the uptake of 111In-HpD-II in tumors with serial scintillation scanning. Localization of the tumor by 111In-HpD-II has been verified by contrast-enhanced computed tomographic scan followed by gross and histological examination of the enhancing brain region. Total body biodistribution of 111In-HpD-II at various times after injection has been evaluated. The ratio of uptake in tumor compared with surrounding brain peaked at 72 hours after injection. The knowledge of regional distribution and concentration of a photosensitizing agent within a tumor mass and surrounding brain allows for the most efficacious timing and localization of a photoactivating source.

  9. Angular correlation of the stellar scintillation for large telescopes

    NASA Astrophysics Data System (ADS)

    Kornilov, V.

    2012-09-01

    Stellar scintillation is one of the fundamental limitations to the precision of ground-based photometry. This paper examines the problem of the correlation of the scintillation of two close stars at the focus of a large telescope. The derived correlation functions were applied to data from the long-term study of the optical turbulence (OT) in the Northern Caucasus with the MASS (Multi-Aperture Scintillation Sensor) instrument in order to predict the angular correlation of the scintillation at the Sternberg institute 2.5-m telescope currently in construction. A median angular radius of the correlation as large as 20 arcsec was found for the case of Kolmogorov OT. On the basis of the obtained relations we also analyse the impact of correlation in ensemble photometry and conjugate plane photometry. It is shown that a reduction of the scintillation noise by up to 8 times can be achieved when using a crowded ensemble of comparison stars. The calculation of the angular correlation can be applied for any large telescope at a site where the OT vertical profiles are known.

  10. The uniformity and imaging properties of some new ceramic scintillators

    NASA Astrophysics Data System (ADS)

    Chac, George T. L.; Miller, Brian W.; Shah, Kanai; Baldoni, Gary; Domanik, Kenneth J.; Bora, Vaibhav; Cherepy, Nerine J.; Seeley, Zachary; Barber, H. Bradford

    2012-10-01

    Results are presented of investigations into the composition, uniformity and gamma-ray imaging performance of new ceramic scintillators with synthetic garnet structure. The ceramic scintillators were produced by a process that uses flame pyrolysis to make nanoparticles which are sintered into a ceramic and then compacted by hot isostatic compression into a transparent material. There is concern that the resulting ceramic scintillator might not have the uniformity of composition necessary for use in gamma-ray spectroscopy and gamma-ray imaging. The compositional uniformity of four samples of three ceramic scintillator types (GYGAG:Ce, GLuGAG:Ce and LuAG:Pr) was tested using an electron microprobe. It was found that all samples were uniform in elemental composition to the limit of sensitivity of the microprobe (few tenths of a percent atomic) over distance scales from ~ 1 cm to ~ 1 um. The light yield and energy resolution of all ceramic scintillator samples were mapped with a highly collimated 57Co source (122 keV) and performance was uniform at mapping scale of 0.25 mm. Good imaging performance with single gamma-ray photon detection was demonstrated for all samples using a BazookaSPECT system, and the imaging spatial resolution, measured as the FWHM of a LSF was 150 um.

  11. Counterintuitive MCNPX Results for Scintillator Surface Roughness Effect

    SciTech Connect

    Yuan, Ding; Guss, Paul

    2012-10-01

    We performed a number of comparative MCNPX simulations of gamma energy depositions of scintillation crystals with smooth and rough surfaces. In the study, nine surface patterns (8 micro-roughness + 1 smooth) were coupled with eight common scintillation crystals for a total of 72 possible combinations. Although this was a preliminary study, the outcome was counterintuitive; results generally favored surfaces with micro-roughness over a conventional smooth surface as measured in terms of average energy depositions. The advantage gained through surface roughness is less significant for CdSe and LaCl3, but is most significant for the common NaI and the glass-like SiO2 scintillators. Based on the results of the 64 rough-surface coupled MCNPX simulations, 57 of the 64 (~89%) simulations showed some improvement in energy deposition. The mean improvement in energy deposition was 2.52%. The maximum improvement was about 8.75%, which was achieved when roughening the surface of a SiO2 scintillator using a micro cutting pattern. Further, for a conventional NaI scintillator, MCNPX results suggest that any roughness pattern would improve the energy deposition, with an average improvement of 3.83%. Although the likely causes remain unclear, we intend to focus on presenting simulation results instead of offering a sound explanation of the underlying physics.

  12. Ionosphere Scintillation at Low and High Latitudes (Modelling vs Measurement)

    NASA Astrophysics Data System (ADS)

    Béniguel, Yannick

    2016-04-01

    This paper will address the problem of scintillations characteristics, focusing on the parameters of interest for a navigation system. Those parameters are the probabilities of occurrence of simultaneous fading, the bubbles surface at IPP level, the cycle slips and the fades duration statistics. The scintillation characteristics obtained at low and high latitudes will be compared. These results correspond to the data analysis performed after the ESA Monitor ionosphere measurement campaign [1], [2]. A second aspect of the presentation will be the modelling aspect. It has been observed that the phase scintillation dominates at high latitudes while the intensity scintillation dominates at low latitudes. The way it can be reproduced and implemented in a propagation model (e.g. GISM model [3]) will be presented. Comparisons of measurements with results obtained by modelling will be presented on some typical scenarios. References [1] R. Prieto Cerdeira, Y. Beniguel, "The MONITOR project: architecture, data and products", Ionospheric Effects Symposium, Alexandria (Va), May 2011 [2] Y. Béniguel, R Orus-Perez , R. Prieto-Cerdeira , S. Schlueter , S. Scortan, A. Grosu "MONITOR 2: ionospheric monitoring network in support to SBAS and other GNSS and scientific purposes", IES Conference, Alexandria (Va), May 2015-05-22 [3] Y. Béniguel, P. Hamel, "A Global Ionosphere Scintillation Propagation Model for Equatorial Regions", Journal of Space Weather Space Climate, 1, (2011), doi: 10.1051/swsc/2011004

  13. ParA and ParB coordinate chromosome segregation with cell elongation and division during Streptomyces sporulation

    PubMed Central

    Donczew, Magdalena; Mackiewicz, Paweł; Wróbel, Agnieszka; Flärdh, Klas; Zakrzewska-Czerwińska, Jolanta

    2016-01-01

    In unicellular bacteria, the ParA and ParB proteins segregate chromosomes and coordinate this process with cell division and chromosome replication. During sporulation of mycelial Streptomyces, ParA and ParB uniformly distribute multiple chromosomes along the filamentous sporogenic hyphal compartment, which then differentiates into a chain of unigenomic spores. However, chromosome segregation must be coordinated with cell elongation and multiple divisions. Here, we addressed the question of whether ParA and ParB are involved in the synchronization of cell-cycle processes during sporulation in Streptomyces. To answer this question, we used time-lapse microscopy, which allows the monitoring of growth and division of single sporogenic hyphae. We showed that sporogenic hyphae stop extending at the time of ParA accumulation and Z-ring formation. We demonstrated that both ParA and ParB affect the rate of hyphal extension. Additionally, we showed that ParA promotes the formation of massive nucleoprotein complexes by ParB. We also showed that FtsZ ring assembly is affected by the ParB protein and/or unsegregated DNA. Our results indicate the existence of a checkpoint between the extension and septation of sporogenic hyphae that involves the ParA and ParB proteins. PMID:27248800

  14. Use of internal scintillator radioactivity to calibrate DOI function of a PET detector with a dual-ended-scintillator readout

    SciTech Connect

    Bircher, Chad; Shao Yiping

    2012-02-15

    Purpose: Positron emission tomography (PET) detectors that use a dual-ended-scintillator readout to measure depth-of-interaction (DOI) must have an accurate DOI function to provide the relationship between DOI and signal ratios to be used for detector calibration and recalibration. In a previous study, the authors used a novel and simple method to accurately and quickly measure DOI function by irradiating the detector with an external uniform flood source; however, as a practical concern, implementing external uniform flood sources in an assembled PET system is technically challenging and expensive. In the current study, therefore, the authors investigated whether the same method could be used to acquire DOI function from scintillator-generated (i.e., internal) radiation. The authors also developed a method for calibrating the energy scale necessary to select the events within the desired energy window. Methods: The authors measured the DOI function of a PET detector with lutetium yttrium orthosilicate (LYSO) scintillators. Radiation events originating from the scintillators' internal Lu-176 beta decay were used to measure DOI functions which were then compared with those measured from both an external uniform flood source and an electronically collimated external point source. The authors conducted these studies with several scintillators of differing geometries (1.5 x 1.5 and 2.0 x 2.0 mm{sup 2} cross-section area and 20, 30, and 40 mm length) and various surface finishes (mirror-finishing, saw-cut rough, and other finishes in between), and in a prototype array. Results: All measured results using internal and external radiation sources showed excellent agreement in DOI function measurement. The mean difference among DOI values for all scintillators measured from internal and external radiation sources was less than 1.0 mm for different scintillator geometries and various surface finishes. Conclusions: The internal radioactivity of LYSO scintillators can be used

  15. Preparation and characterization of a novel UV-curable plastic scintillator

    NASA Astrophysics Data System (ADS)

    Zhu, Jun; Ding, Yunyu; Zhu, Jiayi; Qi, Di; Su, Ming; Xu, Yewei; Bi, Yutie; Lin, Runxiong; Zhang, Lin

    2016-05-01

    A novel UV-curable plastic scintillator was first prepared by using the technology of photosensitivity rapid prototyping. It used the copolymer of 621A-80, TPGDA and styrene as the matrix doped with PPO and POPOP. Its fluorescence spectra displayed a maximum emission wavelength at 428 nm. The light yield of the plastic scintillator was approximately 7.1% of anthracene on the basis of a comparison with the commercially available scintillator (ST-401). The as-prepared plastic scintillator also displayed a fast scintillation decay. Its decay time is 2.6 ns approximately. Importantly, through the technology of photosensitivity rapid prototyping, the plastic scintillator could be prepared in a short period of time at low temperature. What's more, this preparation method provides the possibility of combining the plastic scintillator with 3D printing technology, and then the applications of the plastic scintillator may be expanded greatly.

  16. suPAR and Team Nephrology

    PubMed Central

    2014-01-01

    Primary focal segmental glomerulosclerosis (FSGS) accounts for nearly 10 % of patients who require renal replacement therapy. Elevated circulating levels of soluble urokinase receptor (suPAR) have been identified as a biomarker to discriminate primary FSGS from other glomerulopathies. Subsequent reports have questioned the diagnostic utility of this test. In a study in BMC Medicine, Huang et al. demonstrate that urinary soluble urokinase receptor (suPAR) excretion assists in distinguishing primary FSGS from other glomerular diseases, and that high plasma suPAR concentrations are not directly linked to a decline in glomerular filtration rate (GFR). This observation suggests that further investigation of suPAR is warranted in patients with FSGS. It should be interpreted in light of a recent report that B7-1 is expressed in the podocytes of a subset of patients with FSGS, and that blocking this molecule may represent the first successful targeted intervention for this disease. These advances highlight the rapid pace of scientific progress in the field of nephrology. Nephrologists should work together, share resources, and expedite the design of protocols to evaluate these novel biomarkers in a comprehensive and scientifically valid manner. Please see related article http://www.biomedcentral.com/1741-7015/12/81. PMID:24885021

  17. Evaluate Scintillation Response Over a Continuous Energy Region

    SciTech Connect

    Zhang, Yanwen; Elfman, Mikael; Milbrath, Brian D.; Weber, William J.

    2008-06-26

    A recently developed fast analysis technique utilizing a time of flight (TOF) telescope is demonstrated to obtain relevant quantitative data on material scintillation response to energetic He particles. With superior energy resolution and fast response of the TOF telescope, energy of individual particle before impinging on a scintillating crystal can be determined with a high counting rate, which allows quantitative study of material performance over a continuous energy range in a relatively short time. Scintillation performances in terms of light output, nonlinearity and energy resolution in bismuth germinate (BGO) and europium-doped calcium fluoride (CaF2:Eu) Crystals are demonstrated, and the corresponding energy resolution is compared with gamma-ray tests on the same crystals.

  18. Scintillator-based fast ion loss measurements in the EAST

    NASA Astrophysics Data System (ADS)

    Chang, J. F.; Isobe, M.; Ogawa, K.; Huang, J.; Wu, C. R.; Xu, Z.; Jin, Z.; Lin, S. Y.; Hu, L. Q.

    2016-11-01

    A new scintillator-based fast ion loss detector (FILD) has been installed on Experimental Advanced Superconducting Tokamak (EAST) to investigate the fast ion loss behavior in high performance plasma with neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH). A two dimensional 40 mm × 40 mm scintillator-coated (ZnS:Ag) stainless plate is mounted in the front of the detector, capturing the escaping fast ions. Photons from the scintillator plate are imaged with a Phantom V2010 CCD camera. The lost fast ions can be measured with the pitch angle from 60° to 120° and the gyroradius from 10 mm to 180 mm. This paper will describe the details of FILD diagnostic on EAST and describe preliminary measurements during NBI and ICRH heating.

  19. Gasolines as primary solvents in liquid scintillation counting

    SciTech Connect

    Fernandez, A.; Ma Pinto, R.; Sillero, A.

    1986-11-01

    Gasolines from several commercial sources have been used as primary solvents in liquid scintillation counting of dry and aqueous samples of either /sup 3/H- or /sup 14/C-labeled compounds. Dry samples can be counted only by the addition of fluors to the gasolines, and compared to a standard liquid scintillator, efficiencies of around 75% were attained. For the counting of aqueous samples, gasolines must also be supplemented with secondary solvents (i.e., 10% naphthalene, 5% Triton X-100, or 10% methanol). Simply with Triton X-100, efficiencies similar to those obtained with a dioxane-based liquid scintillator were observed in the case of some gasolines. Drawbacks to gasoline are the higher toxicity and the variation of efficiency, probably depending on the presence of color markers. On the positive side is the low price of the gasolines, compared with either toluene or dioxane, and the facility of purchasing.

  20. High-latitude irregularity spectra deduced from scintillation measurements

    SciTech Connect

    Wernik, A.W.; Gola, M.; Liu, C.H.; Franke, S.J. Illinois Univ., Urbana )

    1990-10-01

    High-latitude scintillation data show that the strength and spectral index of intensity scintillation are dependent on the propagation geometry. It is shown here that anisotropic irregularity spectra, with different indices along and across the magnetic field, lead to geometrical effects similar to those observed. In general, the spectrum along the magnetic field is steeper than that across the field, and the difference is more pronounced for nighttime conditions. Spectral anisotropy can be interpreted as a size-dependent irregularity anisotropy. It is found that large-scale irregularities in the daytime and nighttime ionosphere are almost isotropic, while small-scale irregularities are anisotropic and considerably more so at night than during the day. It is shown that anisotropic irregularity spectra could account for the observed scintillation and in situ temporal spectra with frequency-dependent slope. 26 refs.

  1. High Latitude Scintillations during the ICI-4 Rocket Campaign.

    NASA Astrophysics Data System (ADS)

    Patra, S.; Moen, J.

    2015-12-01

    We present the first results from the Norwegian ICI-4 sounding rocket campaign in February 2015. The ICI-4 was launched into F-region auroral blobs from the Andøya Space Center. The multi needle langmuir probe (m-NLP) on board the rocket sampled the ionospheric density structures at a sub-meter spatial resolution. A multi-phase screen model has been developed to estimate the scintillations from the density measurements acquired on-board spacecrafts. The phase screen model is validated and the comparison of the estimated values with scintillations measured by ground receivers during the campaign will be presented. A combination of scintillation receivers in Svalbard and surrounding areas as well as all sky imagers at Ny Ålesund, Longyerbyen, and Skibotn are used to improve the performance of the model.

  2. Scintillation Properties of Eu2+-Activated Barium Fluoroiodide

    SciTech Connect

    Gundiah, Gautam; Bourret-Courchesne, Edith; Bizarri, Gregory; Hanrahan, Stephen M.; Chaudhry, Anurag; Canning, Andrew; Moses, William W.; Derenzo, Stephen E.

    2009-11-18

    The scintillation properties of powders and single-crystals of BaFI doped with Eu2+ are presented. Single crystals were grown by the vertical Bridgman technique. Under optical and X-ray excitation, the samples exhibit a narrow E2+ 5d-4f transition emission centered at 405 nm. The scintillation light output is estimated to be 55,000+-5,000 photons/MeV at 662 keV with 85percent of the light decaying within 600 ns. An energyresolution of 8.5percent full width at half maximum (FWHM) has been achieved using this scintillator for 662 keV excitation (137Cs source) at room temperature.

  3. Radiation characteristics of scintillator coupled CMOS APS for radiography conditions

    NASA Astrophysics Data System (ADS)

    Kim, Kwang Hyun; Kim, Soongpyung; Kang, Dong-Won; Kim, Dong-Kie

    2006-11-01

    Under industrial radiography conditions, we analyzed short-term radiation characteristics of scintillator coupled CMOS APS (hereinafter SC CMOS APS). By means of experimentation, the contribution of the transmitted X-ray through the scintillator to the properties of the CMOS APS and the afterimage, generated in the acquired image even at low dose condition, were investigated. To see the transmitted X-ray effects on the CMOS APS, Fein focus™ X-ray machine, two scintillators of Lanex™ Fine and Regular, and two CMOS APS array of RadEye™ were used under the conditions of 50 kV p/1 mAs and 100 kV p/1 mAs. By measuring the transmitted X-ray on signal and Noise Power Spectrum, we analytically examined the generation mechanism of the afterimage, based on dark signal or dark current increase in the sensor, and explained the afterimage in the SC CMOS APS.

  4. A potential base substrate for deformable scintillation materials

    NASA Astrophysics Data System (ADS)

    Nakamura, Hidehito; Sato, Nobuhiro; Kitamura, Hisashi; Shirakawa, Yoshiyuki; Takahashi, Sentaro

    2016-05-01

    Deformable scintillation materials for radiation detection are an original concept that will impact many applications. Here we reveal the optical characteristics of readily available, transparent grease that consists of adhesive aromatic ring polymers. The aromatic ring polymer is methyl phenyl polysiloxane, commonly used in cosmetics, lubrication, heat conduction, and mechanical damping. It has a 285-nm excitation maximum and emits short wavelength light that peaks at 315 nm. The stopping power for 1 MeV electrons is 1.78 MeV cm2/g. The light-yield distribution has distinct peaks at 976 keV from internal conversion electrons and at 5486 keV from alpha particles. In addition, this particular methyl phenyl polysiloxane is safe for use and disposal, which is an excellent advantage. These aromatic ring polymers are potential base substrates for deformable scintillation materials and make an important addition to the categories of scintillation materials.

  5. Neutron imaging using the anisotropic response of crystalline organic scintillators.

    SciTech Connect

    Brubaker, Erik; Steele, John T.

    2010-11-01

    An anisotropy in a scintillator's response to neutron elastic scattering interactions can in principle be used to gather directional information about a neutron source using interactions in a single detector. In crystalline organic scintillators, such as anthracene, both the amplitude and the time structure of the scintillation light pulse vary with the direction of the proton recoil with respect to the crystalline axes. Therefore, we have investigated the exploitation of this effect to enable compact, high-efficiency fast neutron detectors that have directional sensitivity via a precise measurement of the pulse shape. We report measurements of the pulse height and shape dependence on proton recoil angle in anthracene, stilbene, p-terphenyl, diphenyl anthracene (DPA), and tetraphenyl butadiene (TPB). Image reconstruction for simulated neutron sources is demonstrated using maximum likelihood methods for optimal directional sensitivity.

  6. Scintillator-fiber charged particle track-imaging detector

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Israel, M. H.; Klarmann, J.

    1983-01-01

    A scintillator-fiber charged-particle track-imaging detector was developed using a bundle of square cross section plastic scintillator fiber optics, proximity focused onto an image intensified charge injection device (CID) camera. The tracks of charged particle penetrating into the scintillator fiber bundle are projected onto the CID camera and the imaging information is read out in video format. The detector was exposed to beams of 15 MeV protons and relativistic Neon, Manganese, and Gold nuclei and images of their tracks were obtained. Details of the detector technique, properties of the tracks obtained, and preliminary range measurements of 15 MeV protons stopping in the fiber bundle are presented.

  7. A Novel Particle Detector: Quantum Dot Doped Liquid Scintillator

    NASA Astrophysics Data System (ADS)

    Winslow, Lindley; Conrad, Janet; Jerry, Ruel

    2010-02-01

    Quantum dots are semiconducting nanocrystals. When excited by light shorter then their characteristic wavelength, they re-emit in a narrow band around this wavelength. The size of the quantum is proportional to the characteristic wavelength so they can be tuned for many applications. CdS quantum dots are made in wavelengths from 360nm to 460nm, a perfect range for the sensitivity of photo-multiplier tubes. The synthesis of quantum dots automatically leaves them in toluene, a good organic scintillator and Cd is a particularly interesting material as it has one of the highest thermal neutron cross sections and has several neutrinoless double beta decay and double electron capture isotopes. The performance of quantum dot loaded scintillator compared to standard scintillators is measured and some unique properties presented. )

  8. Scintillation counters in modern high-energy physics experiments (Review)

    NASA Astrophysics Data System (ADS)

    Kharzheev, Yu. N.

    2015-07-01

    Scintillation counters (SCs) based on organic plastic scintillators (OPSs) are widely used in modern high-energy physics (HEP) experiments. A comprehensive review is given to technologies for production of OPS strips and tiles (extrusion, injection molding, etc.), optical and physical characteristics of OPSs, and methods of light collection based on the use of wavelength-shifting (WLS) fibers coupled to multipixel vacuum and silicon PMs. Examples are given of the use of SCs in modern experiments involved in the search for quarks and new particles, including the Higgs boson (D0, CDF, ATLAS, CMS), new states of matter (ALICE), CP violation (LHCb, KLOE), neutrino oscillations (MINOS, OPERA), and cosmic particles in a wide mass and energy interval (AMS-02). Scintillation counters hold great promise for future HEP experiments (at the ILC, NICA, FAIR) due to properties of a high segmentation, WLS fiber light collection, and multipixel silicon PMT readout.

  9. Tilt Estimation in Moderate-to-Strong Scintillation.

    PubMed

    Burl, J B; Roggemann, M C; Welsh, B

    2001-06-20

    Adaptive optics systems are being applied in ever more challenging environments, for example, the projection of lasers over long horizontal paths through the atmosphere. These long atmospheric paths corrupt the signal received from the beacon and typically yield highly scintillated received wave fronts. Tilt estimation for controlling the fast steering mirror in these systems is complicated by the presence of branch points in the scintillated received wave fronts. In particular, correlation between the tilt and the projected beam's centroid error at the target has been observed in horizontal laser beam projection experiments. The presence of this correlation indicates that better tracking performance should be achievable. We compare the performance of four estimation schemes applied to tilt estimation in a horizontal laser projection system. It is demonstrated that all four schemes underestimate the tilt required to return the laser beam to a target in highly scintillated environments. A method of correcting this tilt is presented, and the expected performance improvement is quantified.

  10. Characterizing and validating the PROSPECT segmented scintillator detector design

    NASA Astrophysics Data System (ADS)

    Norcini, Danielle; Prospect Collaboration

    2016-03-01

    The PROSPECT experiment will use two segmented liquid scintillator detectors positioned 7-20m from the High Flux Isotope Reactor (HFIR) core to perform a search for eV-scale sterile neutrinos and measure the antineutrino spectrum of uranium-235. A multi-year R&D program focused on background studies at the HFIR reactor, lithium-loaded liquid scintillator development, and characterization of multiple prototype detectors has culminated in the design of a segmented, 3-ton liquid scintillator detector for PROSPECT Phase I. This detector design is being validated with a 50 liter, 2-segment prototype detector, PROSPECT-50. We will report results of on-going performance and calibration studies and discuss implications for the PROSPECT physics program.

  11. Quenching correction for volumetric scintillation dosimetry of proton beams

    NASA Astrophysics Data System (ADS)

    Robertson, Daniel; Mirkovic, Dragan; Sahoo, Narayan; Beddar, Sam

    2013-01-01

    Volumetric scintillation dosimetry has the potential to provide fast, high-resolution, three-dimensional radiation dosimetry. However, scintillators exhibit a nonlinear response at the high linear energy transfer (LET) values characteristic of proton Bragg peaks. The purpose of this study was to develop a quenching correction method for volumetric scintillation dosimetry of proton beams. Scintillation light from a miniature liquid scintillator detector was measured along the central axis of a 161.6 MeV proton pencil beam. Three-dimensional dose and LET distributions were calculated for 85.6, 100.9, 144.9 and 161.6 MeV beams using a validated Monte Carlo model. LET values were also calculated using an analytical formula. A least-squares fit to the data established the empirical parameters of a quenching correction model. The light distribution in a tank of liquid scintillator was measured with a CCD camera at all four beam energies. The quenching model and LET data were used to correct the measured light distribution. The calculated and measured Bragg peak heights agreed within ±3% for all energies except 85.6 MeV, where the agreement was within ±10%. The quality of the quenching correction was poorer for sharp low-energy Bragg peaks because of blurring and detector size effects. The corrections performed using analytical LET values resulted in doses within 1% of those obtained using Monte Carlo LET values. The proposed method can correct for quenching with sufficient accuracy for dosimetric purposes. The required LET values may be computed effectively using Monte Carlo or analytical methods. Future detectors should improve blurring correction methods and optimize the pixel size to improve accuracy for low-energy Bragg peaks.

  12. Correlation analysis between ionospheric scintillation levels and receiver tracking performance

    NASA Astrophysics Data System (ADS)

    Sreeja, V.; Aquino, M.; Elmas, Z. G.; Forte, B.

    2012-06-01

    Rapid fluctuations in the amplitude and phase of a transionospheric radio signal caused by small scale plasma density irregularities in the ionosphere are known as scintillation. Scintillation can seriously impair a GNSS (Global Navigation Satellite Systems) receiver tracking performance, thus affecting the required levels of availability, accuracy and integrity, and consequently the reliability of modern day GNSS based applications. This paper presents an analysis of correlation between scintillation levels and tracking performance of a GNSS receiver for GPS L1C/A, L2C and GLONASS L1, L2 signals. The analyses make use of data recorded over Presidente Prudente (22.1°S, 51.4°W, dip latitude ˜12.3°S) in Brazil, a location close to the Equatorial Ionisation Anomaly (EIA) crest in Latin America. The study presents for the first time this type of correlation analysis for GPS L2C and GLONASS L1, L2 signals. The scintillation levels are defined by the amplitude scintillation index, S4 and the receiver tracking performance is evaluated by the phase tracking jitter. Both S4 and the phase tracking jitter are estimated from the post correlation In-Phase (I) and Quadra-Phase (Q) components logged by the receiver at a high rate. Results reveal that the dependence of the phase tracking jitter on the scintillation levels can be represented by a quadratic fit for the signals. The results presented in this paper are of importance to GNSS users, especially in view of the forthcoming high phase of solar cycle 24 (predicted for 2013).

  13. Smaller, Lower-Power Fast-Neutron Scintillation Detectors

    NASA Technical Reports Server (NTRS)

    Patel, Jagdish; Blaes, Brent

    2008-01-01

    Scintillation-based fast-neutron detectors that are smaller and less power-hungry than mainstream scintillation-based fast-neutron detectors are undergoing development. There are numerous applications for such detectors in monitoring fast-neutron fluxes from nuclear reactors, nuclear materials, and natural sources, both on Earth and in outer space. A particularly important terrestrial application for small, low-power, portable fast-neutron detectors lies in the requirement to scan for nuclear materials in cargo and baggage arriving at international transportation facilities. The present development of miniature, low-power scintillation-based fast-neutron detectors exploits recent advances in the fabrication of avalanche photodiodes (APDs). Basically, such a detector includes a plastic scintillator, typically between 300 and 400 m thick with very thin silver mirror coating on all its faces except the one bonded to an APD. All photons generated from scintillation are thus internally reflected and eventually directed to the APD. This design affords not only compactness but also tight optical coupling for utilization of a relatively large proportion of the scintillation light. The combination of this tight coupling and the avalanche-multiplication gain (typically between 750 and 1,000) of the APD is expected to have enough sensitivity to enable monitoring of a fast-neutron flux as small as 1,000 cm(exp -2)s(exp -1). Moreover, pulse-height analysis can be expected to provide information on the kinetic energies of incident neutrons. It has been estimated that a complete, fully developed fast-neutron detector of this type, would be characterized by linear dimensions of the order of 10 cm or less, a mass of no more than about 0.5 kg, and a power demand of no more than a few watts.

  14. Final Report on Actinide Glass Scintillators for Fast Neutron Detection

    SciTech Connect

    Bliss, Mary; Stave, Jean A.

    2012-10-01

    This is the final report of an experimental investigation of actinide glass scintillators for fast-neutron detection. It covers work performed during FY2012. This supplements a previous report, PNNL-20854 “Initial Characterization of Thorium-loaded Glasses for Fast Neutron Detection” (October 2011). The work in FY2012 was done with funding remaining from FY2011. As noted in PNNL-20854, the glasses tested prior to July 2011 were erroneously identified as scintillators. The decision was then made to start from “scratch” with a literature survey and some test melts with a non-radioactive glass composition that could later be fabricated with select actinides, most likely thorium. The normal stand-in for thorium in radioactive waste glasses is cerium in the same oxidation state. Since cerium in the 3+ state is used as the light emitter in many scintillating glasses, the next most common substitute was used: hafnium. Three hafnium glasses were melted. Two melts were colored amber and a third was clear. It barely scintillated when exposed to alpha particles. The uses and applications for a scintillating fast neutron detector are important enough that the search for such a material should not be totally abandoned. This current effort focused on actinides that have very high neutron capture energy releases but low neutron capture cross sections. This results in very long counting times and poor signal to noise when working with sealed sources. These materials are best for high flux applications and access to neutron generators or reactors would enable better test scenarios. The total energy of the neutron capture reaction is not the only factor to focus on in isotope selection. Many neutron capture reactions result in energetic gamma rays that require large volumes or high densities to detect. If the scintillator is to separate neutrons from gamma rays, the capture reactions should produce heavy particles and few gamma rays. This would improve the detection of a

  15. Scintillation reduction for combined Gaussian-vortex beam propagating through turbulent atmosphere

    SciTech Connect

    Berman, Gennady P; Gorshkov, V. N.; Torous, S. V.

    2010-12-14

    We numerically examine the spatial evolution of the structure of coherent and partially coherent laser beams (PCBs), including the optical vortices, propagating in turbulent atmospheres, The influence of beam fragmentation and wandering relative to the axis of propagation (z-axis) on the value of the scintillation index (SI) of the signal at the detector is analyzed. A method for significantly reducing the SI, by averaging the signal at the detector over a set of PCBs, is described, This novel method is to generate the PCBs by combining two laser beams - Gaussian and vortex beams, with different frequencies (the difference between these two frequencies being significantly smaller than the frequencies themselves). In this case, the SI is effectively suppressed without any high-frequency modulators.

  16. Applications for Large Solid Scintillator Detectors in Neutrino and Particle Astrophysics

    NASA Astrophysics Data System (ADS)

    Bross, Alan D.

    2012-08-01

    Applications for solid scintillator have expanded tremendously over the last decade due, in part, to the development of extruded plastic scintillator. In addition, the rapid development of new solid-state photo detectors over the last few years has further expanded the possibilities for this type of detector. This talk will review the state-of-the-art in solid scintillator detectors focusing on applications in neutrino physics, and will present some new possibilities for inorganic scintillator use in particle astrophysics experiments.

  17. Modelling plastic scintillator response to gamma rays using light transport incorporated FLUKA code.

    PubMed

    Ranjbar Kohan, M; Etaati, G R; Ghal-Eh, N; Safari, M J; Afarideh, H; Asadi, E

    2012-05-01

    The response function of NE102 plastic scintillator to gamma rays has been simulated using a joint FLUKA+PHOTRACK Monte Carlo code. The multi-purpose particle transport code, FLUKA, has been responsible for gamma transport whilst the light transport code, PHOTRACK, has simulated the transport of scintillation photons through scintillator and lightguide. The simulation results of plastic scintillator with/without light guides of different surface coverings have been successfully verified with experiments.

  18. Proton induced radiation damage in fast crystal scintillators

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Zhang, Liyuan; Zhu, Ren-Yuan; Kapustinsky, Jon; Nelson, Ron; Wang, Zhehui

    2016-07-01

    This paper reports proton induced radiation damage in fast crystal scintillators. A 20 cm long LYSO crystal, a 15 cm long CeF3 crystal and four liquid scintillator based sealed quartz capillaries were irradiated by 800 MeV protons at Los Alamos up to 3.3 ×1014 p /cm2. Four 1.5 mm thick LYSO plates were irradiated by 24 GeV protons at CERN up to 6.9 ×1015 p /cm2. The results show an excellent radiation hardness of LYSO crystals against charged hadrons.

  19. Coherence properties of wideband satellite signals caused by ionospheric scintillation

    NASA Technical Reports Server (NTRS)

    Rufenach, C. L.

    1975-01-01

    Radio scintillation on satellite signals caused by small-scale irregularities in F-region ionospheric electron density can be an important limitation on earth-satellite communication and navigation systems. Scintillation imposes distortion in both amplitude and phase on wideband signals. In the present work, the shallow-modulated phase screen theory is developed in terms of coherence bandwidth including a model based on a turbulent-like power-law description of the irregularities. The model results usually show a greater coherence bandwidth in the signal phase than in the signal amplitude. Therefore, systems that require phase coherence over a large bandwidth should be less affected than those requiring amplitude coherence.

  20. Computer model of high-latitude scintillation. [WBMOD program

    SciTech Connect

    Fremouw, E.J.

    1982-01-01

    The DNA Wideband satellite experiment provided extensive data on scintillation produced in high-altitude structured plasmas. A computer program, WBMOD, is being developed to summarize those data in an applications-oriented way. The program contains the phase-screen scattering theory of Rino and a morphological description of ionospheric irregularities (thus far only at auroral latitudes) based on Wideband observations. It permits a user to compute scintillation indices for both phase and intensity as a function of system operating parameters and solar-ionospheric disturbance level. Correction is made for multiple scatter, and the user may choose either one-way (communication) or two-way (radar) propagation.

  1. Effects of multiple scattering on scintillation of transionospheric radio signals

    NASA Technical Reports Server (NTRS)

    Liu, C. H.; Yeh, K. C.; Youakim, M. Y.; Wernik, A. W.

    1974-01-01

    Recent development in the optical scintillation theory has been adapted to the ionospheric geometry in order to study the ionospheric scintillation phenomenon in the presence of multiple scattering. Under approximations well satisfied in typical ionospheres for a frequency above about 20 MHz, the first through fourth moment equations have been derived and some analytic solutions given. The fourth moment equation has also been solved numerically. The numerical results show clearly the occurrence of focusing and saturation phenomena. The new multiple-scatter effects are emphasized.

  2. Evaluating Small Scintillating Cells for Digital Hadron Calorimeters

    SciTech Connect

    Francis, Kurt

    2004-01-01

    This thesis discusses the use of scintillator cells with digital electronics as a basis for a digital hadron calorimeter. The detection of a minimum ionizing particle (MIP), analysis of crosstalk, and determination of light yield for the array of scintillating cells are described. The cells were found to have a light yield (in terms of single photoelectrons per MIP) of 7 to 13. Crosstalk due to transfer of light between adjacent cells or photomultiplier tube channels can reach 45%. Rejection versus efficiency studies show that single-channel thresholds can be set that reject noise while accepting MIP signals.

  3. Scintillator-fiber charged-particle track-imaging detector

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Israel, M. H.; Klarmann, J.

    1983-01-01

    A scintillator-fiber charged-particle track-imaging detector has been developed using a bundle of square cross-section plastic scintillator fiber optics, proximity focused onto an image intensified Charge Injection Device (CID) camera. Detector to beams of 15 MeV protons and relativistic Neon, Manganese, and Gold nuclei have been exposed and images of their tracks are obtained. This paper presents details of the detector technique, properties of the tracks obtained, and range measurements of 15 MeV protons stopping in the fiber bundle.

  4. Scintillating optical fibers for fine-grained hodoscopes

    SciTech Connect

    Borenstein, S.R.; Strand, R.C.

    1981-01-01

    Fast detectors with fine spatial resolution will be needed to exploit high event rates at ISABELLE. Scintillating optical fibers for fine grained hodoscopes have been developed by the authors. A commercial manufacturer of optical fibers has drawn and clad PVT scintillator. Detection efficiencies greater than 99% have been achieved for a 1 mm fiber with a PMT over lengths up to 60 cm. Small diameter PMT's and avalanche photodiodes have been tested with the fibers. Further improvements are sought for the fiber and for the APD's sensitivity and coupling efficiency with the fiber.

  5. Data Analysis for the Scintillating Optical Fiber Calorimeter (SOFCAL)

    NASA Technical Reports Server (NTRS)

    Christl, Mark J.

    1997-01-01

    The scintillating optical fiber calorimeter is a hybrid instrument with both active and passive components for measuring the proton and helium cosmic ray spectra from 0.2 to IO TeV kinetic energy. A thin emulsion/x-ray film chamber is situated between a cerenkov counter and an imaging calorimeter. Scintillating optical fibers sample the electromagnetic showers that develop in the calorimeter and identify the trajectory of cosmic rays that interact in SOFCAL. The emulsion/x-ray film data provide an in flight calibration for SOFCAL. The data reduction techniques used will be discussed and interim results of the analysis from a 20 hour balloon flight will be presented.

  6. The Scintillating Optical Fiber Calorimeter Instrument Performance (SOFCAL)

    NASA Technical Reports Server (NTRS)

    Christl, M. J.; Benson, C. M.; Berry, F. A.; Fountain, W. F.; Gregory, J. C.; Johnson, J. S.; Munroe, R. B.; Parnell, T. A.; Takahashi, Y.; Watts, J. W.

    1999-01-01

    SOFCAL is a balloon-borne instrument designed to measure the P-He cosmic ray spectra from about 200 GeV/amu - 20 TeV/amu. SOFCAL uses a thin lead and scintillating-fiber ionization calorimeter to measure the cascades produced by cosmic rays interacting in the hybrid detector system. Above the fiber calorimeter is an emulsion chamber that provides the interaction target, primary particle identification and in-flight energy calibration for the scintillating fiber data. The energy measurement technique and its calibration are described, and the present results from the analysis of a 1 day balloon flight will be presented.

  7. Higher order mode laser beam scintillations in oceanic medium

    NASA Astrophysics Data System (ADS)

    Baykal, Yahya

    2016-01-01

    In a horizontal oceanic optical wireless communication link, the scintillation index (the measure for the intensity fluctuations) of the received intensity caused by the oceanic turbulence is formulated and evaluated when the source is a higher order mode laser. Variations in the scintillation index vs. the underwater turbulence parameters, size of the higher order mode laser source, link length, and the wavelength are examined. Underwater turbulence parameters are the ratio that determines the relative strength of temperature and salinity in driving the index fluctuations, the rate of dissipation of the mean squared temperature, the rate of dissipation of the turbulent kinetic energy, and the Kolmogorov microscale length.

  8. Scintillation characterization of thallium-doped lithium iodide crystals

    NASA Astrophysics Data System (ADS)

    Khan, Sajid; Kim, H. J.; Kim, Y. D.

    2015-09-01

    The paper discusses scintillation and luminescence properties of thallium-doped LiI crystals, grown by the Bridgman technique. X-ray induced emission spectrum is obtained between 380 nm and 600 nm, and is attributed to the Tl+ ion. The photoluminescence measurement with the excitation wavelength of 305 nm revealed a similar emission spectrum. Light yield, energy resolution and scintillation decay time profiles were studied under 662 keV (137Cs) γ-ray excitation. A maximum light yield of 14,000±1400 ph/MeV and two exponential decay time components were obtained.

  9. Design, fabrication, and test of a fast scintillation detector preamplifier

    NASA Astrophysics Data System (ADS)

    Bezboruah, T.; Boruah, K.; Boruah, P. K.

    2002-07-01

    A fast scintillation detector preamplifier is designed, which uses an operational video amplifier (type: LM733). Despite its simplicity, the preamplifier exhibits good noise and speed parameters. The amplifier is specially designed for an extensive air shower experiment [T. Bezboruh, K. Boruah, and P. K. Boruah, Nucl. Instrum. Methods Phys. Res. A 410, 206 (1998); Astropart. Phys. 11, 395 (1999)], Gauhati University, Assam, India. Plastic scintillators and fast photomultiplier tubes are used in the experiment to detect ultra high energy cosmic ray events. Here we report the characteristics of the amplifier including the hardware and its performances in the experiment.

  10. Alkali metal and alkali earth metal gadolinium halide scintillators

    DOEpatents

    Bourret-Courchesne, Edith; Derenzo, Stephen E.; Parms, Shameka; Porter-Chapman, Yetta D.; Wiggins, Latoria K.

    2016-08-02

    The present invention provides for a composition comprising an inorganic scintillator comprising a gadolinium halide, optionally cerium-doped, having the formula A.sub.nGdX.sub.m:Ce; wherein A is nothing, an alkali metal, such as Li or Na, or an alkali earth metal, such as Ba; X is F, Br, Cl, or I; n is an integer from 1 to 2; m is an integer from 4 to 7; and the molar percent of cerium is 0% to 100%. The gadolinium halides or alkali earth metal gadolinium halides are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

  11. Silica scintillating materials prepared by sol-gel methods

    SciTech Connect

    Werst, D.W.; Sauer, M.C. Jr.; Cromack, K.R.; Lin, Y.; Tartakovsky, E.A.; Trifunac, A.D.

    1993-12-31

    Silica was investigated as a rad-hard alternative to organic polymer hosts for organic scintillators. Silica sol-gels were prepared by hydrolysis of tetramethoxysilane in alcohol solutions. organic dyes were incorporated into the gels by dissolving in methanol at the sol stage of gel formation. The silica sol-gel matrix is very rad-hard. The radiation stability of silica scintillators prepared by this method is dye-limited. Transient radioluminescence was measured following excitation with 30 ps pulses of 20 MeV electrons.

  12. A decametric wavelength radio telescope for interplanetary scintillation observations

    NASA Technical Reports Server (NTRS)

    Cronyn, W. M.; Shawhan, S. D.

    1975-01-01

    A phased array, electrically steerable radio telescope (with a total collecting area of 18 acres), constructed for the purpose of remotely sensing electron density irregularity structure in the solar wind, is presented. The radio telescope is able to locate, map, and track large scale features of the solar wind, such as streams and blast waves, by monitoring a large grid of natural radio sources subject to rapid intensity fluctuation (interplanetary scintillation) caused by the irregularity structure. Observations verify the performance of the array, the receiver, and the scintillation signal processing circuitry of the telescope.

  13. Development of lithium-loaded liquid scintillator for PROSPECT

    NASA Astrophysics Data System (ADS)

    Norcini, Danielle; Prospect Collaboration

    2015-04-01

    The PROSPECT experiment will use a segmented detector positioned 7-20m from the High Flux Isotope Reactor core to measure the antineutrino spectrum of uranium-235 and perform a sterile neutrino search. Such measurements require the use of liquid scintillator with the capability to distinguish prompt and delayed signals from inverse beta decay events. The characterization of light yield, pulse shape discrimination performance, and neutron capture properties of the lithium-loaded scintillator have been studied with a test detector at Yale. These results will be discussed in the context of their application to antineutrino detection with the PROSPECT experiment. on behalf of the PROSPECT collaboration.

  14. The Plastic Scintillator Detector of the DAMPE space experiment

    NASA Astrophysics Data System (ADS)

    Sun, Zhiyu

    2016-07-01

    The DArk Matter Explorer (DAMPE) is a satellite based experiment aiming for dark matter search and many other topics astronomy interested. The Plastic Scintillator Detector (PSD) gives DAMPE the ability to measure charge of the crossing particles and separate gamma from electrons, which are necessary for achieving the goals of the experiment. The PSD is composed by 82 scintillator counters and read at both ends by a total of 162 photomultiplier tubes. In this paper, we describe the final design of DAMPE-PSD, the expected performances, and shows some results of the beam test carried on at CERN.

  15. Methods of alleviation of ionospheric scintillation effects on digital communications

    NASA Technical Reports Server (NTRS)

    Massey, J. L.

    1974-01-01

    The degradation of the performance of digital communication systems because of ionospheric scintillation effects can be reduced either by diversity techniques or by coding. The effectiveness of traditional space-diversity, frequency-diversity and time-diversity techniques is reviewed and design considerations isolated. Time-diversity signaling is then treated as an extremely simple form of coding. More advanced coding methods, such as diffuse threshold decoding and burst-trapping decoding, which appear attractive in combatting scintillation effects are discussed and design considerations noted. Finally, adaptive coding techniques appropriate when the general state of the channel is known are discussed.

  16. View from east to west of PAR site storage building; ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View from east to west of PAR site storage building; formerly PAR dispensary - Stanley R. Mickelsen Safeguard Complex, Storage Building, Across street from Family Housing Units 110 & 111, Nekoma, Cavalier County, ND

  17. View from west to east of PAR site resident engineer's ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View from west to east of PAR site resident engineer's office building (REOB) - Stanley R. Mickelsen Safeguard Complex, Resident Engineers Office Building, Southeast of intersection of PAR Access Road & Fourth Avenue, Nekoma, Cavalier County, ND

  18. GPS scintillation and TEC depletion near the northern crest of equatorial anomaly over South China

    NASA Astrophysics Data System (ADS)

    Deng, Baichang; Huang, Jiang; Liu, Weifeng; Xu, Jie; Huang, Lingfeng

    2013-02-01

    This study presents a statistical analysis of GPS L-band scintillation with data observed from July 2008 to March 2012 at the northern crest of equatorial anomaly stations in Guangzhou and Shenzhen of South China. The variations of the scintillation with local time, season, solar activity and duration of scintillation patches were investigated. The relationship between the scintillation and TEC depletion was also reported. Our results revealed that GPS scintillation occurred from 19:30 LT (pre-midnight) to 03:00 LT (post-midnight). During quiet solar activity years, the scintillation was only observed in pre-midnight hours of equinox months and patches durations were mostly less than 60 min. During high solar activity years, more scintillation occurred in the pre-midnight hours of equinox and winter months; and GPS scintillation started to occur in the post-midnight hours of summer and winter. The duration of scintillation patches extended to 180 min in high solar activity years. Solar activity had a larger effect to strong scintillations (S4 > 0.6) than to weak scintillations (0.6 ⩾ S4 > 0.2). Strong scintillations were accompanied by TEC depletion especially in equinox months. We also discussed the relationship between TEC depletion and plasma bubble.

  19. Simulation results of liquid and plastic scintillator detectors for reactor antineutrino detection - A comparison

    NASA Astrophysics Data System (ADS)

    Kashyap, V. K. S.; Pant, L. M.; Mohanty, A. K.; Datar, V. M.

    2016-03-01

    A simulation study of two kinds of scintillation detectors has been done using GEANT4. We compare plastic scintillator and liquid scintillator based designs for detecting electron antineutrinos emitted from the core of reactors. The motivation for this study is to set up an experiment at the research reactor facility at BARC for very short baseline neutrino oscillation study and remote reactor monitoring.

  20. Lithium-containing scintillators for thermal neutron, fast neutron, and gamma detection

    DOEpatents

    Zaitseva, Natalia P.; Carman, M. Leslie; Faust, Michelle A.

    2016-03-01

    In one embodiment, a scintillator includes a scintillator material; a primary fluor, and a Li-containing compound, where the Li-containing compound is soluble in the primary fluor, and where the scintillator exhibits an optical response signature for thermal neutrons that is different than an optical response signature for fast neutrons and gamma rays.

  1. A Combined Global and Local Approach to Elucidate Spatial Organization of the Mycobacterial ParB-parS Partition Assembly

    SciTech Connect

    B Chaudhuri; S Gupta; V Urban; M Chance; R DMello; L Smith; K Lyons; J Gee

    2011-12-31

    Combining diverse sets of data at global (size, shape) and local (residue) scales is an emerging trend for elucidating the organization and function of the cellular assemblies. We used such a strategy, combining data from X-ray and neutron scattering with H/D-contrast variation and X-ray footprinting with mass spectrometry, to elucidate the spatial organization of the ParB-parS assembly from Mycobacterium tuberculosis. The ParB-parS participates in plasmid and chromosome segregation and condensation in predivisional bacterial cells. ParB polymerizes around the parS centromere(s) to form a higher-order assembly that serves to recruit cyto-skeletal ParA ATPases and SMC proteins for chromosome segregation. A hybrid model of the ParB-parS was built by combining and correlating computational models with experiment-derived information about size, shape, position of the symmetry axis within the shape, internal topology, DNA-protein interface, exposed surface patches, and prior knowledge. This first view of the ParB-parS leads us to propose how ParB spread on the chromosome to form a larger assembly.

  2. A combined global and local approach to elucidate spatial organization of the Mycobacterial ParB-parS partition assembly.

    PubMed

    Chaudhuri, Barnali N; Gupta, Sayan; Urban, Volker S; Chance, Mark R; D'Mello, Rhijuta; Smith, Lauren; Lyons, Kelly; Gee, Jessica

    2011-03-22

    Combining diverse sets of data at global (size, shape) and local (residue) scales is an emerging trend for elucidating the organization and function of the cellular assemblies. We used such a strategy, combining data from X-ray and neutron scattering with H/D-contrast variation and X-ray footprinting with mass spectrometry, to elucidate the spatial organization of the ParB-parS assembly from Mycobacterium tuberculosis. The ParB-parS participates in plasmid and chromosome segregation and condensation in predivisional bacterial cells. ParB polymerizes around the parS centromere(s) to form a higher-order assembly that serves to recruit cyto-skeletal ParA ATPases and SMC proteins for chromosome segregation. A hybrid model of the ParB-parS was built by combining and correlating computational models with experiment-derived information about size, shape, position of the symmetry axis within the shape, internal topology, DNA-protein interface, exposed surface patches, and prior knowledge. This first view of the ParB-parS leads us to propose how ParB spread on the chromosome to form a larger assembly.

  3. A Combined Global and Local Approach to Elucidate Spatial Organization of the Mycobacterial ParB-parS Partition

    SciTech Connect

    Chaudhuri, Barnali; Gupta, Sayan; Urban, Volker S; Chance, Mark; D'Mello, Rhijuta; Smith, Lauren; Lyons, Kelly; Gee, Jessica

    2010-01-01

    Combining diverse sets of data at global (size, shape) and local (residue) scales is an emerging trend for elucidating the organization and function of the cellular assemblies. We used such a strategy, combining data from X-ray and neutron scattering with H/D-contrast variation and X-ray footprinting with mass spectrometry, to elucidate the spatial organization of the ParB-parS assembly from Mycobacterium tuberculosis. The ParB-parS participates in plasmid and chromosome segregation and condensation in predivisional bacterial cells. ParB polymerizes around the parS centromere(s) to form a higher-order assembly that serves to recruit cyto-skeletal ParA ATPases and SMC proteins for chromosome segregation. A hybrid model of the ParB-parS was built by combining and correlating computational models with experiment-derived information about size, shape, position of the symmetry axis within the shape, internal topology, DNA-protein interface, exposed surface patches, and prior knowledge. This first view of the ParB-parS leads us to propose how ParB spread on the chromosome to form a larger assembly.

  4. Host response biomarker in sepsis: suPAR detection.

    PubMed

    Giamarellos-Bourboulis, Evangelos J; Georgitsi, Marianna

    2015-01-01

    Recent studies of our group have shown that suPAR may complement APACHE II score for risk assessment in sepsis. suPAR may be measured in serum of patients by an enzyme immunosorbent assay developed by Virogates (suPARnostic™). Production of suPAR from circulating neutrophils and monocytes may be assessed after isolation of neutrophils and monocytes and ex vivo culture. This is followed by measurement of suPAR in culture supernatants.

  5. Methods of Fabricating Scintillators with Radioisotopes for Beta Battery Applications

    NASA Technical Reports Server (NTRS)

    Rensing, Noa M.; Squillante, Michael R.; Tieman, Timothy C.; Higgins, William; Shiriwadkar, Urmila

    2013-01-01

    Technology has been developed for a class of self-contained, long-duration power sources called beta batteries, which harvest the energy contained in the radioactive emissions from beta decay isotopes. The new battery is a significant improvement over the conventional phosphor/solar cell concept for converting this energy in three ways. First, the thin phosphor is replaced with a thick scintillator that is transparent to its own emissions. By using a scintillator sufficiently thick to completely stop all the beta particles, efficiency is greatly improved. Second, since the energy of the beta particles is absorbed in the scintillator, the semiconductor photodetector is shielded from radiation damage that presently limits the performance and lifetime of traditional phosphor converters. Finally, instead of a thin film of beta-emitting material, the isotopes are incorporated into the entire volume of the thick scintillator crystal allowing more activity to be included in the converter without self-absorption. There is no chemical difference between radioactive and stable strontium beta emitters such as Sr-90, so the beta emitter can be uniformly distributed throughout a strontium based scintillator crystal. When beta emitter material is applied as a foil or thin film to the surface of a solar cell or even to the surface of a scintillator, much of the radiation escapes due to the geometry, and some is absorbed within the layer itself, leading to inefficient harvesting of the energy. In contrast, if the emitting atoms are incorporated within the scintillator, the geometry allows for the capture and efficient conversion of the energy of particles emitted in any direction. Any gamma rays associated with secondary decays or Bremsstrahlung photons may also be absorbed within the scintillator, and converted to lower energy photons, which will in turn be captured by the photocell or photodiode. Some energy will be lost in this two-stage conversion process (high-energy particle

  6. Characterization of scintillator materials for fast-ion loss detectors in nuclear fusion reactors

    NASA Astrophysics Data System (ADS)

    Jiménez-Ramos, M. C.; García López, J.; García-Muñoz, M.; Rodríguez-Ramos, M.; Carmona Gázquez, M.; Zurro, B.

    2014-08-01

    In fusion plasma reactors, fast ion generated by heating systems and fusion born particles must be well confined. The presence of magnetohydrodynamic (MHD) instabilities can lead to a significant loss of these ions, which may reduce drastically the heating efficiency and may cause damage to plasma facing components in the vacuum vessel. In order to understand the physics underlying the fast ion loss mechanism, scintillator based detectors have been installed in several fusion devices. In this work we present the absolute photon yield and its degradation with ion fluence in terms of the number of photons emitted per incident ion of several scintillators thin coatings: SrGa2S4:Eu2+ (TG-Green), Y3Al5O12:Ce3+ (P46) and Y2O3:Eu3+ (P56) when irradiated with light ions of different masses (deuterium ions, protons and α-particles) at energies between approximately 575 keV and 3 MeV. The photon yield will be discussed in terms of the energy deposited by the particles into the scintillator. For that, the actual composition and thickness of the thin layers were determined by Rutherford Backscattering Spectrometry (RBS). A collimator with 1 mm of diameter, which defines the beam size for the experiments, placed at the entrance of the chamber. An electrically isolated sample holder biased to +300 V to collect the secondary electrons, connected to a digital current integrator (model 439 by Ortec) to measure the incident beam current. A home made device has been used to store the real-time evolution of the beam current in a computer file allowing the correction of the IL yields due to the current fluctuations. The target holder is a rectangle of 150 × 112 mm2 and can be tilted. The X and Y movements are controlled through stepping motors, which permits a fine control of the beam spot positioning as well as the study of several samples without venting the chamber. A silica optical fiber of 1 mm diameter fixed to the vacuum chamber, which collects the light from the scintillators

  7. On The Collocation of the Cusp Aurora and the GPS Phase Scintillation: A Statistical Study

    NASA Astrophysics Data System (ADS)

    Jin, Y.; Moen, J.; Miloch, W.

    2015-12-01

    The climatology map of the GPS phase scintillation identifies two regions of high scintillation occurrences at high latitudes: around magnetic noon and around magnetic midnight. The scintillation occurrence rate is higher around magnetic noon, while the scintillation level is stronger around magnetic midnight. This study focuses on the dayside scintillation region. In order to resolve the role of the cusp auroral processes in the production of irregularities, we put the GPS phase scintillation in the context of the observed auroral morphology. Results show that the occurrence rate of the GPS phase scintillation is highest inside the auroral cusp, regardless of the scintillation strength and the interplanetary magnetic field (IMF). On average the scintillation occurrence rate in the cusp region is about 5 times as high as in the region immediately poleward of it. The scintillation occurrence rate is higher when the IMF BZ is negative. When partitioning the scintillation data by the IMF BY, the distribution of the scintillation occurrence rate around magnetic noon is similar to that of the poleward moving auroral form (PMAF) statistics: there is a higher occurrence rate at earlier (later) magnetic local time when the IMF BY is positive (negative). This indicates that the irregularities which give rise to scintillations follow the IMF BY controlled East-West motion of the aurora and plasma. Furthermore, the scintillation occurrence rate is higher when IMF BY is positive when the cusp is shifted towards the post-noon sector where it may get easier access to the higher density plasma. This suggests that the combined auroral activities (e.g., PMAF) and the density of the intake solar EUV ionized plasma are crucial for the production of scintillations.

  8. Optical artefact characterization and correction in volumetric scintillation dosimetry

    NASA Astrophysics Data System (ADS)

    Robertson, Daniel; Hui, Cheukkai; Archambault, Louis; Mohan, Radhe; Beddar, Sam

    2014-01-01

    The goals of this study were (1) to characterize the optical artefacts affecting measurement accuracy in a volumetric liquid scintillator detector, and (2) to develop methods to correct for these artefacts. The optical artefacts addressed were photon scattering, refraction, camera perspective, vignetting, lens distortion, the lens point spread function, stray radiation, and noise in the camera. These artefacts were evaluated by theoretical and experimental means, and specific correction strategies were developed for each artefact. The effectiveness of the correction methods was evaluated by comparing raw and corrected images of the scintillation light from proton pencil beams against validated Monte Carlo calculations. Blurring due to the lens and refraction at the scintillator tank-air interface were found to have the largest effect on the measured light distribution, and lens aberrations and vignetting were important primarily at the image edges. Photon scatter in the scintillator was not found to be a significant source of artefacts. The correction methods effectively mitigated the artefacts, increasing the average gamma analysis pass rate from 66% to 98% for gamma criteria of 2% dose difference and 2 mm distance to agreement. We conclude that optical artefacts cause clinically meaningful errors in the measured light distribution, and we have demonstrated effective strategies for correcting these optical artefacts.

  9. Direct determination of lead-210 by liquid-scintillation counting

    NASA Technical Reports Server (NTRS)

    Fairman, W. D.; Sedlet, J.

    1969-01-01

    Soft betas, the internal conversion electrons, and unconverted gamma rays from lead-210 are efficiently detected in a liquid scintillation counting system with efficiency of 97 percent. The counter is interfaced with a multichannel pulse height analyzer. The spectra obtained is stored on paper tape and plotted on an x-y plotter.

  10. Ionospheric and tropospheric scintillation as a form of noise

    NASA Technical Reports Server (NTRS)

    Fremouw, E. J.; Rino, C. L.

    1975-01-01

    Recent tests of signals observed through the ionosphere, the solar wind, and a laboratory plasma have revealed a surprising consistency in parameters describing the first order statistics of a signal caused to scintillate by a randomly structured plasma. This paper describes a means for exploiting these new findings in a transionospheric communication channel model.

  11. Optical artefact characterization and correction in volumetric scintillation dosimetry

    PubMed Central

    Robertson, Daniel; Hui, Cheukkai; Archambault, Louis; Mohan, Radhe; Beddar, Sam

    2014-01-01

    The goals of this study were (1) to characterize the optical artefacts affecting measurement accuracy in a volumetric liquid scintillation detector, and (2) to develop methods to correct for these artefacts. The optical artefacts addressed were photon scattering, refraction, camera perspective, vignetting, lens distortion, the lens point spread function, stray radiation, and noise in the camera. These artefacts were evaluated by theoretical and experimental means, and specific correction strategies were developed for each artefact. The effectiveness of the correction methods was evaluated by comparing raw and corrected images of the scintillation light from proton pencil beams against validated Monte Carlo calculations. Blurring due to the lens and refraction at the scintillator tank-air interface were found to have the largest effect on the measured light distribution, and lens aberrations and vignetting were important primarily at the image edges. Photon scatter in the scintillator was not found to be a significant source of artefacts. The correction methods effectively mitigated the artefacts, increasing the average gamma analysis pass rate from 66% to 98% for gamma criteria of 2% dose difference and 2 mm distance to agreement. We conclude that optical artefacts cause clinically meaningful errors in the measured light distribution, and we have demonstrated effective strategies for correcting these optical artefacts. PMID:24321820

  12. Novel scintillators and silicon photomultipliers for nuclear physics and applications

    NASA Astrophysics Data System (ADS)

    Jenkins, David

    2015-06-01

    Until comparatively recently, scintillator detectors were seen as an old-fashioned tool of nuclear physics with more attention being given to areas such as gamma-ray tracking using high-purity germanium detectors. Next-generation scintillator detectors, such as lanthanum bromide, which were developed for the demands of space science and gamma- ray telescopes, are found to have strong applicability to low energy nuclear physics. Their excellent timing resolution makes them very suitable for fast timing measurements and their much improved energy resolution compared to conventional scintillators promises to open up new avenues in nuclear physics research which were presently hard to access. Such "medium-resolution" spectroscopy has broad interest across several areas of contemporary interest such as the study of nuclear giant resonances. In addition to the connections to space science, it is striking that the demands of contemporary medical imaging have strong overlap with those of experimental nuclear physics. An example is the interest in PET-MRI combined imaging which requires putting scintillator detectors in a high magnetic field environment. This has led to strong advances in the area of silicon photomultipliers, a solid-state replacement for photomultiplier tubes, which are insensitive to magnetic fields. Broad application to nuclear physics of this technology may be foreseen.

  13. Optical and scintillation properties of Nd-doped complex garnet

    NASA Astrophysics Data System (ADS)

    Yanagida, Takayuki; Sato, Hiroki

    2014-12-01

    Nd 1% doped complex garnet scintillators were prepared by Furukawa and their optical and scintillation properties were investigated on a comparison with previously reported Nd-doped YAG. Chemical compositions of newly developed complex garnets were Lu2Y1Al5O12, Lu2Y1Ga3Al2O12, Lu2Gd1Al5O12, Lu2Gd1Ga3Al2O12, Gd1Y2Al5O12, Gd1Y2Ga3Al2O12, and Gd3Ga3Al2O12. They all showed 50-80% transmittance from ultraviolet to near infrared wavelengths with several absorption bands due to Gd3+ or Nd3+ 4f-4f transition. In X-ray induced radioluminescence spectra, all samples exhibited intense lines at 310 nm due to Gd3+ or 400 nm due to Nd3+ depending on their chemical composition. Among them, the highest scintillation light yield was achieved by Lu2Y1Al5O12. Typical scintillation decay times of them resulted 1.5-3 μs. Thermally stimulated glow curve after 1 Gy exposure and X-ray induced afterglow were also investigated.

  14. Event Localization in Bulk Scintillator Crystals Using Coded Apertures

    SciTech Connect

    Ziock, Klaus-Peter; Braverman, Joshua B.; Fabris, Lorenzo; Harrison, Mark J.; Hornback, Donald Eric; Newby, Jason

    2015-06-01

    The localization of radiation interactions in bulk scintillators is generally limited by the size of the light distribution at the readout surface of the crystal/light-pipe system. By finding the centroid of the light spot, which is typically of order centimeters across, practical single-event localization is limited to ~2 mm/cm of crystal thickness. Similar resolution can also be achieved for the depth of interaction by measuring the size of the light spot. Through the use of near-field coded-aperture techniques applied to the scintillation light, light transport simulations show that for 3-cm-thick crystals, more than a five-fold improvement (millimeter spatial resolution) can be achieved both laterally and in event depth. At the core of the technique is the requirement to resolve the shadow from an optical mask placed in the scintillation light path between the crystal and the readout. In this paper, experimental results are presented that demonstrate the overall concept using a 1D shadow mask, a thin-scintillator crystal and a light pipe of varying thickness to emulate a 2.2-cm-thick crystal. Spatial resolutions of ~ 1 mm in both depth and transverse to the readout face are obtained over most of the crystal depth.

  15. Gas scintillation drift chambers with wave shifter fiber readout

    NASA Technical Reports Server (NTRS)

    Sadoulet, Bernard; Weiss, Steven; Parsons, Ann; Lin, Robert P.; Smith, Garth

    1988-01-01

    Results for a prototype xenon gas scintillation drift chamber are presented. Its operation is discussed using two types of light detection schemes: one based on an Anger camera geometry and one based on an array of wave-shifting light fibers. The results are judged to demonstrate the instrument's potential.

  16. Laser beam scintillation beyond the turbulent atmosphere A numerical computation

    NASA Technical Reports Server (NTRS)

    Bufton, J. L.; Taylor, L. S.

    1976-01-01

    The extended Huygens-Fresnel formulation for propagation through turbulence is used to examine scintillation of a finite laser beam. The method is demonstrated analytically for propagation beyond a weak Gaussian phase screen. A numerical integration technique is used to extend the results to a more realistic turbulence model. Results are compared with existing Gaussian beam propagation theory.

  17. Organic scintillator detector response simulations with DRiFT

    NASA Astrophysics Data System (ADS)

    Andrews, M. T.; Bates, C. R.; McKigney, E. A.; Solomon, C. J.; Sood, A.

    2016-09-01

    This work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNP® output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed-field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNP® 6 , which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discrimination plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.

  18. Positronium signature in organic liquid scintillators for neutrino experiments

    SciTech Connect

    Franco, D.; Consolati, G.; Trezzi, D.

    2011-01-15

    Electron antineutrinos are commonly detected in liquid scintillator experiments via inverse {beta} decay by looking at the coincidence between the reaction products: neutrons and positrons. Prior to positron annihilation, an electron-positron pair may form an orthopositronium (o-Ps) state, with a mean lifetime of a few nanoseconds. Even if the o-Ps decay is speeded up by spin-flip or pick-off effects, it may introduce distortions in the photon emission time distribution, crucial for position reconstruction and pulse shape discrimination algorithms in antineutrino experiments. Reversing the problem, the o-Ps-induced time distortion represents a new signature for tagging antineutrinos in liquid scintillator. In this article, we report the results of measurements of the o-Ps formation probability and lifetime for the most used solvents for organic liquid scintillators in neutrino physics (pseudocumene, linear alkyl benzene, phenylxylylethane, and dodecane). We characterize also a mixture of pseudocumene +1.5 g/l of 2,5-diphenyloxazole, a fluor acting as wavelength shifter. In the second part of the article, we demonstrate that the o-Ps-induced distortion of the scintillation photon emission time distributions represent an optimal signature for tagging positrons on an event by event basis, potentially enhancing the antineutrino detection.

  19. Complex Electronic Structure of Rare Earth Activators in Scintillators

    SciTech Connect

    Aberg, D.; Yu, S. W.; Zhou, F.

    2015-10-27

    To aid and further the understanding of the microscopic mechanisms behind the scintillator nonproportionality that leads to degradation of the attainable energy resolution, we have developed theoretical and experimental algorithms and procedures to determine the position of the 4f energy levels of rare earth dopants relative to the host band edge states.

  20. [Automatic collection system of waste scintillator solution using micro robots].

    PubMed

    Maeda, M; Yamada, R

    1985-12-01

    Industrial micro-robots are now being applied to hazardous jobs or tedious jobs. These in-house micro-robots (MELFA, RM-501, Mitsubishi Electric Inc.) were used to make a collection system of waste scintillator solution on the experimental basis. Newly developed were hands, vial holders and a system soft ware, and satisfactory results have been obtained.

  1. Bulk crystal growth of scintillator materials for gamma ray detectors

    NASA Astrophysics Data System (ADS)

    Aggarwal, Mohan

    2008-10-01

    Within the past few years, it has been demonstrated that several new rare earth halide scintillation detector crystals such as cerium doped lanthanum bromide (LaBr3:Ce) have high output and improved energy deposit to light linearity and thus they can substantially enhance the performance of the next generation of gamma ray detectors. These detectors have a variety of applications in NASA hard x-ray and gamma ray missions, high energy physics, home land security and medical imaging applications. This cerium doped lanthanum bromide crystal has ˜1100% the light output of BGO, resulting in better energy resolution than conventional scintillators. This is equivalent to 60000 photons per MeV of deposited energy. This new series of scintillator materials promise to usher a breakthrough in the field, if sufficiently large and clear crystals of this material can be grown. These halides however are highly hygroscopic and hence pose some difficulty in growing crystals. Efforts are being made to grow this and other materials in this family of crystals and successful results have been achieved. An overview of the challenges encountered during the synthesis and melt crystal growth of these rare earth halide scintillators shall be presented.

  2. Ca2+-Doped CeBr3 Scintillating Materials

    SciTech Connect

    Guss, Paul; Foster, Michael E.; Wong, Bryan M.; Doty, F. Patrick; Shah, Kanai; Squillante, Michael R.; Shirwadkar, Urmila; Hawrami, Rastgo; Tower, Josh; Yuan, Ding

    2014-01-01

    Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide, their commercial availability and application are limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. This investigation employed aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was used as a dopant to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca2+ dopant were grown. Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca2+-doped CeBr3 exhibited little or no change in the peak fluorescence emission for 371 nm optical excitation for CeBr3. The structural, electronic, and optical properties of CeBr3 crystals were studied using the density functional theory within the generalized gradient approximation. The calculated lattice parameters are in good agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr3, including the dielectric function, were calculated.

  3. Advanced Large Area Plastic Scintillator Project (ALPS): Final Report

    SciTech Connect

    Jordan, David V.; Reeder, Paul L.; Todd, Lindsay C.; Warren, Glen A.; McCormick, Kathleen R.; Stephens, Daniel L.; Geelhood, Bruce D.; Alzheimer, James M.; Crowell, Shannon L.; Sliger, William A.

    2008-02-05

    The advanced Large-Area Plastic Scintillator (ALPS) Project at Pacific Northwest National Laboratory investigated possible technological avenues for substantially advancing the state-of-the-art in gamma-ray detection via large-area plastic scintillators. The three predominant themes of these investigations comprised the following: * Maximizing light collection efficiency from a single large-area sheet of plastic scintillator, and optimizing hardware event trigger definition to retain detection efficiency while exploiting the power of coincidence to suppress single-PMT "dark current" background; * Utilizing anti-Compton vetoing and supplementary spectral information from a co-located secondary, or "Back" detector, to both (1) minimize Compton background in the low-energy portion of the "Front" scintillator's pulse-height spectrum, and (2) sharpen the statistical accuracy of the front detector's low-energy response prediction as impelmented in suitable energy-windowing algorithms; and * Investigating alternative materials to enhance the intrinsic gamma-ray detection efficiency of plastic-based sensors.

  4. A new tritiated water measurement method with plastic scintillator pellets.

    PubMed

    Furuta, Etsuko; Iwasaki, Noriko; Kato, Yuka; Tomozoe, Yusuke

    2016-01-01

    A new tritiated water measurement method with plastic scintillator pellets (PS-pellets) by using a conventional liquid scintillation counter was developed. The PS-pellets used were 3 mm in both diameter and length. A low potassium glass vial was filled full with the pellets, and tritiated water was applied to the vial from 5 to 100 μl. Then, the sample solution was scattered in the interstices of the pellets in a vial. This method needs no liquid scintillator, so no liquid organic waste fluid is generated. The counting efficiency with the pellets was approximately 48 % when a 5 μl solution was used, which was higher than that of conventional measurement using liquid scintillator. The relationship between count rate and activity showed good linearity. The pellets were able to be used repeatedly, so few solid wastes are generated with this method. The PS-pellets are useful for tritiated water measurement; however, it is necessary to develop a new device which can be applied to a larger volume and measure low level concentration like an environmental application. PMID:26856930

  5. 21 CFR 892.1100 - Scintillation (gamma) camera.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Scintillation (gamma) camera. 892.1100 Section 892.1100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... the body by means of a photon radiation detector. This generic type of device may include...

  6. 21 CFR 892.1100 - Scintillation (gamma) camera.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Scintillation (gamma) camera. 892.1100 Section 892.1100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... the body by means of a photon radiation detector. This generic type of device may include...

  7. Counterintuitive MCNPX Results for Scintillator Surface Roughness Effect

    SciTech Connect

    2012-08-12

    We have reported on our recent MCNPX simulation results of energy deposition for a group of 8 scintillation detectors, coupled with various rough surface patterns. The MCNPX results generally favored the detectors with various rough surface patterns. The observed MCNPX results are not fully explained by this work.

  8. Proteinase-activated receptors (PARs) as targets for antiplatelet therapy.

    PubMed

    Cunningham, Margaret; McIntosh, Kathryn; Bushell, Trevor; Sloan, Graeme; Plevin, Robin

    2016-04-15

    Since the identification of the proteinase-activated receptor (PAR) family as mediators of serine protease activity in the 1990s, there has been tremendous progress in the elucidation of their pathophysiological roles. The development of drugs that target PARs has been the focus of many laboratories for the potential treatment of thrombosis, cancer and other inflammatory diseases. Understanding the mechanisms of PAR activation and G protein signalling pathways evoked in response to the growing list of endogenous proteases has yielded great insight into receptor regulation at the molecular level. This has led to the development of new selective modulators of PAR activity, particularly PAR1. The mixed success of targeting PARs has been best exemplified in the context of inhibiting PAR1 as a new antiplatelet therapy. The development of the competitive PAR1 antagonist, vorapaxar (Zontivity), has clearly shown the value in targeting PAR1 in acute coronary syndrome (ACS); however the severity of associated bleeding with this drug has limited its use in the clinic. Due to the efficacy of thrombin acting via PAR1, strategies to selectively inhibit specific PAR1-mediated G protein signalling pathways or to target the second thrombin platelet receptor, PAR4, are being devised. The rationale behind these alternative approaches is to bias downstream thrombin activity via PARs to allow for inhibition of pro-thrombotic pathways but maintain other pathways that may preserve haemostatic balance and improve bleeding profiles for widespread clinical use. This review summarizes the structural determinants that regulate PARs and the modulators of PAR activity developed to date.

  9. Use of a large time-compensated scintillation detector in neutron time-of-flight measurements

    DOEpatents

    Goodman, Charles D.

    1979-01-01

    A scintillator for neutron time-of-flight measurements is positioned at a desired angle with respect to the neutron beam, and as a function of the energy thereof, such that the sum of the transit times of the neutrons and photons in the scintillator are substantially independent of the points of scintillations within the scintillator. Extrapolated zero timing is employed rather than the usual constant fraction timing. As a result, a substantially larger scintillator can be employed that substantially increases the data rate and shortens the experiment time.

  10. A study of liquid scintillator and fiber materials for use in a fiber calorimeter

    SciTech Connect

    Altice, P.P. Jr.

    1990-04-01

    This reports an investigation into the performance of selected scintillation oils and fiber materials to test their applicability in high energy, liquid scintillator calorimetry. Two scintillating oils, Bicron BC-517 and an oil mixed for the MACRO experiment, and two fiber materials, Teflon and GlassClad PS-252, were tested for the following properties: light yield, attenuation length and internal reflection angle. The results of these tests indicated that the scintillation oils and the fiber materials had an overall good performance with lower energies and would meet the requirements of liquid scintillator detection at SSC energies. 6 refs.

  11. Comparison of Ground Scintillation Spectra with Density Irregularities Observed in Space

    NASA Astrophysics Data System (ADS)

    Chen, K. Y.; Su, S. Y.; Liu, C. H.

    The embedded Quasi-Periodic diffraction patterns are extracted from the scintillation data taken at Ascension Island and analyzed with a newly developed time-frequency analysis method of Hilbert-Huang Transform (HHT). The scintillation spectra are studied for cases of strong and weak scintillations and compared with the spectra of plasma density irregularities observed by ROCSA-1/IPEI at 600 km altitude. Interesting results are obtained for the relationships between the locations of the irregularity density structure and the scintillation echoes during weak and strong scintillations.

  12. Review of plastic and liquid scintillation dosimetry for photon, electron, and proton therapy

    NASA Astrophysics Data System (ADS)

    Beaulieu, Luc; Beddar, Sam

    2016-10-01

    While scintillation dosimetry has been around for decades, the need for a dosimeter tailored to the reality of modern radiation therapy—in particular a real-time, water-equivalent, energy-independent dosimeter with high spatial resolution—has generated renewed interest in scintillators over the last 10 years. With the advent of at least one commercial plastic scintillation dosimeter and the ever-growing scientific literature on this subject, this topical review is intended to provide the medical physics community with a wide overview of scintillation physics, related optical concepts, and applications of plastic scintillation dosimetry.

  13. Fiber optic thermal/fast neutron and gamma ray scintillation detector

    DOEpatents

    Neal, John S.; Mihalczo, John T.

    2006-11-28

    A detector system that combines a .sup.6Li loaded glass fiber scintillation thermal neutron detector with a fast scintillation detector in a single layered structure. Detection of thermal and fast neutrons and ionizing electromagnetic radiation is achieved in the unified detector structure. The fast scintillator replaces the polyethelene moderator layer adjacent the .sup.6Li loaded glass fiber panel of the neutron detector and acts as the moderator for the glass fibers. Fast neutrons, x-rays and gamma rays are detected in the fast scintillator. Thermal neutrons, x-rays and gamma rays are detected in the glass fiber scintillator.

  14. High latitude scintillation effects on very high frequency /vhf/ and S-band satellite transmissions.

    NASA Technical Reports Server (NTRS)

    Pope, J. H.; Fritz, R. B.

    1971-01-01

    A scintillation study was conducted with the purpose to define the extent of scintillation activity in the S-band region, and to determine if such activities at higher frequencies are caused by ionospheric irregularities similar to those causing scintillations at vhf and lower frequencies. Simultaneous transmissions at 137 and 1695 MHz from polar orbiting satellites were used in this study. Scintillations were found to be present at S-band frequencies in the polar regions; it is concluded that they are caused by ionospheric characteristics similar to those causing scintillations at lower frequencies.

  15. Les Brulures Chimiques Par Le Laurier Rose

    PubMed Central

    Bakkali, H.; Ababou, M.; Nassim Sabah, T.; Moussaoui, A.; Ennouhi, A.; Fouadi, F.Z.; Siah, S.; Ihrai, H.

    2010-01-01

    Summary Le laurier rose ou Nerium oleander est un arbuste qui pousse naturellement dans les régions méditerranéennes. Au Maroc on le trouve dans les lieux humides. Il est réputé par ses risques de toxicité systémique en cas d'empoisonnement à cause de la présence de deux alcaloïdes, surtout l'oléandrine. La littérature illustre des cas d'utilisation locale des feuilles de cette plante contre la gale, les hémorroïdes et les furoncles. Nous rapportons deux cas de brûlures chimiques par le laurier rose de gravité différente. Cela doit aboutir à une information élargie de la population, ainsi qu'une réglementation stricte de sa commercialisation. PMID:21991211

  16. Discovery of Octahydroindenes as PAR1 Antagonists

    PubMed Central

    2013-01-01

    Octahydroindene was identified as a novel scaffold for protease activated receptor 1 (PAR1) antagonists. Herein, the 2-position (C2) was explored for structure–activity relationship (SAR) studies. Compounds 14, 19, and 23b showed IC50 values of 1.3, 8.6, and 2.7 nM in a PAR1 radioligand binding assay, respectively, and their inhibitory activities on platelet activation were comparable to that of vorapaxar in a platelet rich plasma (PRP) aggregation assay. This series of compounds showed high potency and no significant cytotoxicity; however, the compounds were metabolically unstable in both human and rat liver microsomes. Current research efforts are focused on optimizing the compounds to improve metabolic stability and physicochemical properties as well as potency. PMID:24900604

  17. A comparison of TEC fluctuations and scintillations at Ascension Island

    NASA Astrophysics Data System (ADS)

    Basu, S.; Groves, K. M.; Quinn, J. M.; Doherty, P.

    1999-11-01

    With increasing reliance on space-based platforms for global navigation and communication, concerns about the impact of ionospheric scintillation on these systems have become a high priority. Recently, the Air Force Research Laboratory (AFRL) performed amplitude scintillation measurements of L1 (1.575 MHz) signals from GPS satellites at Ascension Island (14.45° W, 7.95° S; magnetic latitude 16° S) during February-April, 1998, to compare amplitude scintillations with fluctuations of the total electron content (TEC). Ascension Island is located in the South Atlantic under the southern crest of the equatorial anomaly of F2 ionization where scintillations will be much enhanced during the upcoming solar maximum period. Ascension Island is included in the global network of the International GPS Service (IGS) and the GPS receivers in this network report the carrier to noise (C/N) ratio, the dual frequency carrier phase and pseudorange data at 30-s intervals. Such data with a sampling interval of 30 s were analyzed to determine TEC, the rate of change of TEC (ROT) and also ROTI, defined as the standard deviation of ROT. The spatial scale of ROTI, sampled at 30 s interval, will correspond to 6 km when the vector sum of the ionospheric projection of the satellite velocity and the irregularity drift orthogonal to the propagation path is of the order of 100 m/s. On the other hand, the scale-length of the amplitude scintillation index corresponds to the Fresnel dimension which is about 400 m for the GPS L1 frequency and an ionospheric height of 400 km. It is shown that, in view of the co-existence of large and small scale irregularities in equatorial irregularity structures, during the early evening hours, and small magnitude of irregularity drifts, ROTI measurements can be used to predict the presence of scintillation causing irregularities. The quantitative relationship between ROTI and S4, however, varies considerably due to variations of the ionospheric projection of the

  18. Combined DSEK and Transconjunctival Pars Plana Vitrectomy

    PubMed Central

    Sane, Mona; Shaikh, Naazli

    2016-01-01

    We report here three patients who underwent combined Descemet's stripping with endothelial keratoplasty and transconjunctival pars plana vitrectomy for bullous keratopathy and posterior segment pathology. A surgical technique and case histories are described. Anatomic and visual outcomes of combined Descemet's stripping with endothelial keratoplasty and vitrectomy were excellent. Our experience provides technical guidelines and limitations. The combined minimally invasive techniques allow for rapid anatomical recovery and return of function and visual acuity in a single sitting. PMID:27413563

  19. Par Pond refill water quality sampling

    SciTech Connect

    Koch, J.W. II; Martin, F.D.; Westbury, H.M.

    1996-08-01

    This study was designed to document anoxia and its cause in the event that the anoxia caused a fish kill. However, no fish kill was observed during this study, and dissolved oxygen and nutrient concentrations generally remained within the range expected for southeastern reservoirs. Par Pond water quality monitoring will continue during the second summer after refill as the aquatic macrophytes become reestablished and nutrients in the sediments are released to the water column.

  20. Maximum likelihood positioning and energy correction for scintillation detectors

    NASA Astrophysics Data System (ADS)

    Lerche, Christoph W.; Salomon, André; Goldschmidt, Benjamin; Lodomez, Sarah; Weissler, Björn; Solf, Torsten

    2016-02-01

    An algorithm for determining the crystal pixel and the gamma ray energy with scintillation detectors for PET is presented. The algorithm uses Likelihood Maximisation (ML) and therefore is inherently robust to missing data caused by defect or paralysed photo detector pixels. We tested the algorithm on a highly integrated MRI compatible small animal PET insert. The scintillation detector blocks of the PET gantry were built with the newly developed digital Silicon Photomultiplier (SiPM) technology from Philips Digital Photon Counting and LYSO pixel arrays with a pitch of 1 mm and length of 12 mm. Light sharing was used to readout the scintillation light from the 30× 30 scintillator pixel array with an 8× 8 SiPM array. For the performance evaluation of the proposed algorithm, we measured the scanner’s spatial resolution, energy resolution, singles and prompt count rate performance, and image noise. These values were compared to corresponding values obtained with Center of Gravity (CoG) based positioning methods for different scintillation light trigger thresholds and also for different energy windows. While all positioning algorithms showed similar spatial resolution, a clear advantage for the ML method was observed when comparing the PET scanner’s overall single and prompt detection efficiency, image noise, and energy resolution to the CoG based methods. Further, ML positioning reduces the dependence of image quality on scanner configuration parameters and was the only method that allowed achieving highest energy resolution, count rate performance and spatial resolution at the same time.

  1. Maximum likelihood positioning and energy correction for scintillation detectors.

    PubMed

    Lerche, Christoph W; Salomon, André; Goldschmidt, Benjamin; Lodomez, Sarah; Weissler, Björn; Solf, Torsten

    2016-02-21

    An algorithm for determining the crystal pixel and the gamma ray energy with scintillation detectors for PET is presented. The algorithm uses Likelihood Maximisation (ML) and therefore is inherently robust to missing data caused by defect or paralysed photo detector pixels. We tested the algorithm on a highly integrated MRI compatible small animal PET insert. The scintillation detector blocks of the PET gantry were built with the newly developed digital Silicon Photomultiplier (SiPM) technology from Philips Digital Photon Counting and LYSO pixel arrays with a pitch of 1 mm and length of 12 mm. Light sharing was used to readout the scintillation light from the 30 × 30 scintillator pixel array with an 8 × 8 SiPM array. For the performance evaluation of the proposed algorithm, we measured the scanner's spatial resolution, energy resolution, singles and prompt count rate performance, and image noise. These values were compared to corresponding values obtained with Center of Gravity (CoG) based positioning methods for different scintillation light trigger thresholds and also for different energy windows. While all positioning algorithms showed similar spatial resolution, a clear advantage for the ML method was observed when comparing the PET scanner's overall single and prompt detection efficiency, image noise, and energy resolution to the CoG based methods. Further, ML positioning reduces the dependence of image quality on scanner configuration parameters and was the only method that allowed achieving highest energy resolution, count rate performance and spatial resolution at the same time. PMID:26836394

  2. NEXT GENERATION NEUTRON SCINTILLATORS BASED ON SEMICONDUCTOR NANOSTRUCTURES

    SciTech Connect

    Cai-Lin Wang

    2008-06-30

    The results reported here successfully demonstrate the technical feasibility of ZnS QDs/{sup 6}LiF/polymer composites as thermal neutron scintillators. PartTec has obtained stable ZnS QDs with a quantum yield of 17% induced by UV light, and light pulse decay lifetimes of 10-30 ns induced by both UV and neutrons. These lifetime values are much shorter than those of commercial ZnS microparticle and {sup 6}Li-glass scintillators. Clear pulse height peaks induced by neutron irradiation were seen for PartTec's ZnS nanocomposites. By adjusting the concentrations, particle size and degree of dispersion of ZnS QD/{sup 6}LiF in a PVA matrix, the light absorption and light yield of films at 420-440 nm can be optimized. PartTec's novel scintillators will replace traditional {sup 6}Li-glass and ZnS/{sup 6}LiF:Ag scintillators if the PL quantum yield can be improved above 30%, and/or increase the transparency of present nanoscintillators. Time and resources inhibited PartTec's total success in Phase I. For example, bulk doping preparations of ZnS QDs with Ag{sup +}, Eu{sup 3+} or Ce{sup 3+} QDs was impractical given those constraints, nor did they permit PartTec to measure systematically the change of PL decay lifetimes in different samples. PartTec will pursue these studies in the current proposal, as well as develop a better capping and dopant along with developing brighter and faster ZnS QD scintillators.

  3. Lithium indium diselenide: A new scintillator for neutron imaging

    NASA Astrophysics Data System (ADS)

    Lukosi, Eric; Herrera, Elan; Hamm, Daniel; Lee, Kyung-Min; Wiggins, Brenden; Trtik, Pavel; Penumadu, Dayakar; Young, Stephen; Santodonato, Louis; Bilheux, Hassina; Burger, Arnold; Matei, Liviu; Stowe, Ashley C.

    2016-09-01

    Lithium indium diselenide, 6LiInSe2 or LISe, is a newly developed neutron detection material that shows both semiconducting and scintillating properties. This paper reports on the performance of scintillating LISe crystals for its potential use as a converter screen for cold neutron imaging. The spatial resolution of LISe, determined using a 10% threshold of the Modulation Transfer Function (MTF), was found to not scale linearly with thickness. Crystals having a thickness of 450 μm or larger resulted in an average spatial resolution of 67 μm, and the thinner crystals exhibited an increase in spatial resolution down to the Nyquist frequency of the CCD. The highest measured spatial resolution of 198 μm thick LISe (27 μm) outperforms a commercial 50 μm thick ZnS(Cu):6LiF scintillation screen by more than a factor of three. For the LISe dimensions considered in this study, it was found that the light yield of LISe did not scale with its thickness. However, absorption measurements indicate that the 6Li concentration is uniform and the neutron absorption efficiency of LISe as a function of thickness follows general nuclear theory. This suggests that the differences in apparent brightness observed for the LISe samples investigated may be due to a combination of secondary charged particle escape, scintillation light transport in the bulk and across the LISe-air interface, and variations in the activation of the scintillation mechanism. Finally, it was found that the presence of 115In and its long-lived 116In activation product did not result in ghosting (memory of past neutron exposure), demonstrating potential of LISe for imaging transient systems.

  4. Comparison of the scintillation noise above different observatories measured with MASS instruments

    NASA Astrophysics Data System (ADS)

    Kornilov, V.; Sarazin, M.; Tokovinin, A.; Travouillon, T.; Voziakova, O.

    2012-10-01

    Aims: Scintillation noise is a major limitation of ground-based photometric precision. Methods: An extensive dataset of stellar scintillation collected at 11 astronomical sites world-wide with MASS instruments was used to estimate the scintillation noise of large telescopes in the fast photometry and traditional long-exposure regime. Results: Statistical distributions of the corresponding parameters are given. The scintillation noise is mostly determined by turbulence and wind in the upper atmosphere and is comparable at all sites, with slightly lower values at Mauna Kea and the highest noise at Tolonchar in Chile. We show that the classical Young's formula underestimates the scintillation noise. The temporal variations of the scintillation noise are also similar at all sites, showing short-term variability at time scales of 1 - 2 h and slower variations, including marked seasonal trends (stronger scintillation and less clear sky during local winter). Some correlation was found between nearby observatories.

  5. N-(2-Ethylhexyl)carbazole: A New Fluorophore Highly Suitable as a Monomolecular Liquid Scintillator.

    PubMed

    Montbarbon, Eva; Sguerra, Fabien; Bertrand, Guillaume H V; Magnier, Élodie; Coulon, Romain; Pansu, Robert B; Hamel, Matthieu

    2016-08-16

    The synthesis, photophysical properties, and applications in scintillation counting of N-(2-ethylhexyl)carbazole (EHCz) are reported. This molecule displays all of the required characteristics for an efficient liquid scintillator (emission wavelength, scintillation yield), and can be used without any extra fluorophores. Thus, its scintillation properties are discussed, as well as its fast neutron/gamma discrimination. For the latter application, the material is compared with the traditional liquid scintillator BC-501 A, and other liquid fluorescent molecules classically used as scintillation solvents, such as xylene, pseudocumene (PC), linear alkylbenzenes (LAB), diisopropylnaphthalene (DIN), 1-methylnaphthalene (1-MeNapht), and 4-isopropylbiphenyl (iPrBiph). For the first time, an excimeric form of a molecule has been advantageously used in scintillation counting. A moderate discrimination between fast neutrons and gamma rays was observed in bulk EHCz, with an apparent neutron/gamma discrimination potential half of that of BC-501 A. PMID:27406840

  6. Numerical evaluation of the light transport properties of alternative He-3 neutron detectors using ceramic scintillators

    NASA Astrophysics Data System (ADS)

    Ohzu, A.; Takase, M.; Haruyama, M.; Kurata, N.; Kobayashi, N.; Kureta, M.; Nakamura, T.; Toh, K.; Sakasai, K.; Suzuki, H.; Soyama, K.; Seya, M.

    2015-10-01

    The light transport properties of scintillator light inside alternative He-3 neutron detectors using scintillator sheets have been investigated by a ray-tracing simulation code. The detector consists of a light-reflecting tube, a thin rectangular ceramic scintillator sheet laminated on a glass plate, and two photo-multiplier tubes (PMTs) mounted at both ends of the detector tube. The flashes of light induced on the surface of the scintillator sheet via nuclear interaction between the scintillator and neutrons are detected by the two PMTs. The light output at both ends of various detectors in which the scintillator sheets are installed with several different arrangements were examined and evaluated in comparison with experimental results. The results derived from the simulation reveal that the light transport property is strongly dependent on the arrangement of the scintillator sheet inside the tube and the shape of the tube.

  7. GAGG:ce single crystalline films: New perspective scintillators for electron detection in SEM.

    PubMed

    Bok, Jan; Lalinský, Ondřej; Hanuš, Martin; Onderišinová, Zuzana; Kelar, Jakub; Kučera, Miroslav

    2016-04-01

    Single crystal scintillators are frequently used for electron detection in scanning electron microscopy (SEM). We report gadolinium aluminum gallium garnet (GAGG:Ce) single crystalline films as a new perspective scintillators for the SEM. For the first time, the epitaxial garnet films were used in a practical application: the GAGG:Ce scintillator was incorporated into a SEM scintillation electron detector and it showed improved image quality. In order to prove the GAGG:Ce quality accurately, the scintillation properties were examined using electron beam excitation and compared with frequently used scintillators in the SEM. The results demonstrate excellent emission efficiency of the GAGG:Ce single crystalline films together with their very fast scintillation decay useful for demanding SEM applications.

  8. Characteristics of High-latitude and Equatorial Ionospheric Scintillation of GNSS Signals

    NASA Astrophysics Data System (ADS)

    Morton, Y.; Jiao, Y.

    2014-12-01

    In this paper, several years of multi-constellation global navigation satellite scintillation data collected at Alaska, Peru, and Ascension Island are analyzed to characterize scintillation features observed at high latitude and equatorial locations during the current solar maximum. Recognizing that strong scintillation data are often lost due to the lack of robustness in conventional GPS receivers used for ionosphere scintillation monitoring (ISM), an autonomous event driven scintillation data collection system using software-defined raw RF sampling devices have been developed deployed at a number of strategically selected high latitude and equatorial locations since 2009. This unique scintillation data recording system is triggered by indicators computed from a continuously operating ISM receiver and the raw RF data is post processed using advanced receiver signal processing algorithms designed to minimize carrier phase cycle slips and loss of lock of signals during strong scintillations. Based on scintillation events extracted from the raw data, several statistical distributions are established to characterize the intensity, duration and occurrence frequency of scintillation. Results confirm that scintillation at low latitudes is generally more intense and longer lasting, while high-latitude scintillation is milder and usually dominated by phase fluctuations. Results also reveal the impacts of solar activity, geomagnetic activity and seasons on scintillation in different areas. Combining measurements from a co-located geo-magnetometer and corresponding global geomagnetic activities, qualitative and quantitative correlations between scintillation and both local and global geomagnetic activities have been obtained. Results show that in Alaska, the occurrence frequency and intensity of scintillation, especially phase fluctuations, have strong correlations with geomagnetic field intensity disturbances, while in equatorial stations, the correlation is not obvious.

  9. Modelisation par elements finis du muscle strie

    NASA Astrophysics Data System (ADS)

    Leonard, Mathieu

    Ce present projet de recherche a permis. de creer un modele par elements finis du muscle strie humain dans le but d'etudier les mecanismes engendrant les lesions musculaires traumatiques. Ce modele constitue une plate-forme numerique capable de discerner l'influence des proprietes mecaniques des fascias et de la cellule musculaire sur le comportement dynamique du muscle lors d'une contraction excentrique, notamment le module de Young et le module de cisaillement de la couche de tissu conjonctif, l'orientation des fibres de collagene de cette membrane et le coefficient de poisson du muscle. La caracterisation experimentale in vitro de ces parametres pour des vitesses de deformation elevees a partir de muscles stries humains actifs est essentielle pour l'etude de lesions musculaires traumatiques. Le modele numerique developpe est capable de modeliser la contraction musculaire comme une transition de phase de la cellule musculaire par un changement de raideur et de volume a l'aide des lois de comportement de materiau predefinies dans le logiciel LS-DYNA (v971, Livermore Software Technology Corporation, Livermore, CA, USA). Le present projet de recherche introduit donc un phenomene physiologique qui pourrait expliquer des blessures musculaires courantes (crampes, courbatures, claquages, etc.), mais aussi des maladies ou desordres touchant le tissu conjonctif comme les collagenoses et la dystrophie musculaire. La predominance de blessures musculaires lors de contractions excentriques est egalement exposee. Le modele developpe dans ce projet de recherche met ainsi a l'avant-scene le concept de transition de phase ouvrant la porte au developpement de nouvelles technologies pour l'activation musculaire chez les personnes atteintes de paraplegie ou de muscles artificiels compacts pour l'elaboration de protheses ou d'exosquelettes. Mots-cles Muscle strie, lesion musculaire, fascia, contraction excentrique, modele par elements finis, transition de phase

  10. A modular scintillation camera for use in nuclear medicine

    SciTech Connect

    Milster, T.D.; Arendt, J.; Barrett, H.H.; Easton, R.L.; Rossi, G.R.; Selberg, L.A.; Simpson, R.G.

    1984-02-01

    A ''modular'' scintillation camera is discussed as an alternative to using Anger cameras for gamma-ray imaging in nuclear medicine. Each module is an independent gamma camera and consists of a scintillation crystal, light pipe and mask plane, PMT's, and processing electronics. Groups of modules efficiently image radionuclide distributions by effectively utilizing crystal area. Performance of each module is maximized by using Monte-Carlo computer simulations to determine the optical design of the camera, optimizing the signal processing of the PMT signals using maximum-likelihood (ML) estimators, and incorporating digital lookup tables. Each event is completely processed in 2 ..mu..sec, and FWHM of the PSF over the crystal area is expected to be 3 mm. Both one-dimensional and two-dimensional prototypes are tested for spatial and energy resolution

  11. Characterization and testing of EJ-309 and Stilbene scintillation detectors

    NASA Astrophysics Data System (ADS)

    Baramsai, B.; Jandel, M.; Bredeweg, T. A.; Couture, A.; Mosby, S.; Rusev, G.; Ullmann, J. L.; Walker, C. L.

    2015-09-01

    A new neutron detector array (NEUANCE) is under development at the Los Alamos Neutron Science Center (LANSCE). After completion, NEUANCE will be installed in the central cavity of the 3.6π Υ-ray detector array DANCE located at the Lujan Center of LANSCE. The detector system, with simultaneous neutron and -ray detection capability, will be used to study neutron-induced capture and session reactions. The response of a EJ-309 scintillation detector to Υ-ray and neutron radiation was measured using the standard Υ-ray and 252Cf sources. The light from the detector was collected using a Hamamatsu photomultiplier tube or a Silicon photomultiplier GEANT4 was used to understand the light output and the optical photon transport in the scintillation. The detector geometry and optimum parameters for the data acquisition system were determined based on the test results and the simulations.

  12. Atmospheric Scintillations: A Clue for Bird Orientation and Navigation

    NASA Astrophysics Data System (ADS)

    Petty, Charles; Bowden, Andrew; Benard, Andre

    2014-11-01

    The index-of-refraction of the troposphere is anisotropic at all scales even if the local turbulent velocity field is statistically homogeneous. This anisotropy is partly due to the coupling between the fluctuating velocity field with the Coriolis field and the Lorentz field. Thus, the redistribution of turbulent kinetic energy and the concomitant anisotropy in the index-of-refraction may provide a practical means for birds (and other animals and insects) to orient and navigate. Consequently, if birds migrate between two points on the Earth by following a great circle path, then local anisotropic scintillation phenomena may provide a means to determine the latitude, the longitude, and the bearing along an orthodromic migration path. Thus, scintillation phenomena may be an important fundamental component in the underlying mechanics that support bird orientation and navigation.

  13. Single-shot positron annihilation lifetime spectroscopy with LYSO scintillators

    NASA Astrophysics Data System (ADS)

    Alonso, A. M.; Cooper, B. S.; Deller, A.; Cassidy, D. B.

    2016-08-01

    We have evaluated the application of a lutetium yttrium oxyorthosilicate (LYSO) based detector to single-shot positron annihilation lifetime spectroscopy. We compare this detector directly with a similarly configured PbWO4 scintillator, which is the usual choice for such measurements. We find that the signal to noise ratio obtained using LYSO is around three times higher than that obtained using PbWO4 for measurements of Ps excited to longer-lived (Rydberg) levels, or when they are ionized soon after production. This is due to the much higher light output for LYSO (75% and 1% of NaI for LYSO and PbWO4 respectively). We conclude that LYSO is an ideal scintillator for single-shot measurements of positronium production and excitation performed using a low-intensity pulsed positron beam.

  14. Hydrothermal vent flow and turbulence measurements with acoustic scintillation instrumentation

    NASA Astrophysics Data System (ADS)

    di Iorio, D.; Xu, G.

    2009-12-01

    Acoustically derived measurements of hydrothermal vent flow and turbulence were obtained from the active black smoker Dante in the Main Endeavour vent field, using scintillation analysis from one-way transmissions. The scintillation transmitter and receiver array formed a 93 m acoustic path through the buoyant plume 20 m above the structure. The acoustic path was parallel to the valley sidewall where the M2 tidal currents are approximately aligned along ridge due to topographic steering by the valley walls and hence most of the plume displacement is expected to occur along the acoustic path. On one deployment, data were collected for 6.5 weeks and vertical velocities range from 0.1 to 0.2 m/s showing a strong dependence on the spring/neap tidal cycle. The refractive index fluctuations which can be paramaterized in terms of the root-mean-square temperature fluctuations also shows a strong tidal modulation during spring tide.

  15. Study of C band equatorial scintillation in the Asian sector

    SciTech Connect

    Mollen, T.A.; Liu, C.H.; Fang, D.J.

    1988-06-01

    Ionosphere scintillation data at 4 GHz obtained during the last solar maximum from two ionospheric locations are used to investigate the statistics of scintillating signals. The cumulative distribution functions of the signal are determined and compared with theoretical distributions. An empirical relation is found between S4 and the decibel levels of maximum peak, 5-percent peak, 95-percent fade, and maximum fade. This relation is then compared with results derived using a third peak method for SI-index determination. The variations of the decorrelation interval of the signal and the roll-off slope of the power spectrum are statistically studied. Diurnal and seasonal variations are considered, and a geophysical interpretation of the data is presented. 10 references.

  16. Scintillation estimates for a Jupiter entry probe: Phase 1

    NASA Technical Reports Server (NTRS)

    Woo, R.; Yang, F. C.

    1975-01-01

    A model of the electron density irregularities in the Jovian ionosphere is constructed based on a preliminary interpretation of the Pioneer 10 Jovian ionospheric scintillations. The ionospheric irregularities exist over an altitude range of 3000 km. The structure constant c sub n of refractive index fluctuations is constant throughout this altitude range. The spatial wavenumber spectrum of the electron density irregularities follows the Kolmogorov spectrum and the outer scale size is greater than 6 km. Estimates of scintillation for a Jovian entry probe based on this model indicate that it is small at S-band but could be substantial at 4000 MHz. The temporal frequency spectrum of the log-amplitude fluctuation is less than 1 Hz and is consequently rather narrow.

  17. Statistical characterizations of equatorial scintillation in the Asian region

    SciTech Connect

    Fang, D.J.; Liu, C.H.

    1984-01-01

    Attention is given to the statistical aspect of equatorial scintillations in the Asian region, using the power spectra of prominent scientillation events collected over a 16-month period during the solar maximum years of sunspot cycle 21. A series of comparisons between values is undertaken in order to assess such ionospheric parameters as the height and thickness of the irregularity layers, rms fluctuations of total electron content, and the axial ratio of the irregularities. The results obtained suggest that equatorial ionospheric irregularities in the F region, with sub-km sizes in the evening hours after local sunset, are the main cause of the GHz scintillations observed. The spectra of the irregularities appear to be of the power law type, with spectral indices whose values are generally greater than 4.

  18. Modeling solar wind with boundary conditions from interplanetary scintillations

    SciTech Connect

    Manoharan, P.; Kim, T.; Pogorelov, N. V.; Arge, C. N.

    2015-09-30

    Interplanetary scintillations make it possible to create three-dimensional, time- dependent distributions of the solar wind velocity. Combined with the magnetic field observations in the solar photosphere, they help perform solar wind simulations in a genuinely time-dependent way. Interplanetary scintillation measurements from the Ooty Radio Astronomical Observatory in India provide directions to multiple stars and may assure better resolution of transient processes in the solar wind. In this paper, we present velocity distributions derived from Ooty observations and compare them with those obtained with the Wang-Sheeley-Arge (WSA) model. We also present our simulations of the solar wind flow from 0.1 AU to 1 AU with the boundary conditions based on both Ooty and WSA data.

  19. Synthesis of transparent nanocomposite monoliths for gamma scintillation

    NASA Astrophysics Data System (ADS)

    Liu, Chao; Hajagos, Tibor J.; Kishpaugh, David; Jin, Yunxia; Hu, Wei; Chen, Qi; Pei, Qibing

    2015-08-01

    During the past decade, inorganic nanoparticles/polymer nanocomposites have been intensively studied to provide a low cost, high performance alternative for gamma scintillation. However, the aggregation of nanoparticles often occurs even at low nanoparticle concentrations and thus deteriorates the transparency and performance of these nanocomposite scintillators. Here we report an efficient fabrication protocol of transparent nanocomposite monoliths based on surface modified hafnium oxide nanoparticles. Using hafnium oxide nanoparticles with surface-grafted methacrylate groups, highly transparent bulk-size nanocomposite monoliths (2 mm thick, transmittance at 550 nm >75%) are fabricated with nanoparticle loadings up to 40 wt% (net hafnium wt% up to 28.5%). These nanocomposite monoliths of 1 cm diameter and 2 mm thickness are capable of producing a full energy photopeak for 662 keV gamma rays, with the best deconvoluted photopeak energy resolution reaching 8%.

  20. FLARES: A flexible scintillation light apparatus for rare event searches

    NASA Astrophysics Data System (ADS)

    Sisti, M.; Baldazzi, G.; Bonvicini, V.; Campana, R.; Capelli, S.; Evangelista, Y.; Feroci, M.; Fuschino, F.; Gironi, L.; Labanti, C.; Marisaldi, M.; Previtali, E.; Rignanese, L.; Rachevsky, A.; Vacchi, A.; Zampa, G.; Zampa, N.; Zuffa, M.

    2016-07-01

    FLARES is a project for an innovative detector technology to be applied to rare event searches, and in particular to neutrinoless double beta decay experiments. Its novelty is the enhancement and optimization of the collection of the scintillation light emitted by ultra-pure crystals through the use of arrays of high performance silicon photodetectors cooled to 120 K. This would provide scintillation detectors with 1% level energy resolution, with the advantages of a technology offering relatively simple low cost mass scalability and powerful background reduction handles, as requested by future neutrinoless double beta decay experimental programs. The performances of a first production of matrices of Silicon Drift Detectors are presented and discussed in this paper.

  1. Improved Scintillator Materials for Compact Electron Antineutrino Detectors

    SciTech Connect

    Dijkstra, Peter; Wortche, Heinrich J.; Browne, Wesley R.

    2011-04-27

    Developments in the fields of chemistry and materials science provide new components that hold the potential to improve the performance of liquid scintillation electron antineutrino detectors used for the monitoring of nuclear reactors. New compounds can provide for more efficient, stable, and safer operation of these detectors. Current detectors and their detector materials raise issues regarding size, quantum efficiency, stability, and spatial resolution for the vertex detection. For compact detectors (1 m{sup 3} active volume) improvement of these issues with existing liquid scintillation cocktails can be obtained by means of developing stable and efficient neutron capture agents. These agents comprise of boron or lithium containing coordination compounds, in addition advances in fluorescence detection technologies and optimization of solvent characteristics can improve the overall efficiency. Focus points of the new detector material design are to enable a compact, robust, and direction sensitive electron antineutrino detector.

  2. An apparatus for studying scintillator properties at high isostatic pressures

    SciTech Connect

    Gaume, R. M.; Lam, S.; Gascon, M.; Feigelson, R. S.; Setyawan, W.; Curtarolo, S.

    2013-01-15

    We describe the design and operation of a unique hydraulic press for the study of scintillator materials under isostatic pressure. This press, capable of developing a pressure of a gigapascal, consists of a large sample chamber pressurized by a two-stage hydraulic amplifier. The optical detection of the scintillation light emitted by the sample is performed, through a large aperture optical port, by a photodetector located outside the pressure vessel. In addition to providing essential pressure-dependent studies on the emission characteristics of radioluminescent materials, this apparatus is being developed to elucidate the mechanisms behind the recently observed dependency of light-yield nonproportionality on electronic band structure. The variation of the light output of a Tl:CsI crystal under 511-keV gamma excitation and hydrostatic pressure is given as an example.

  3. Novel Scintillation Detectors for Prompt Fission γ-Ray Measurements

    NASA Astrophysics Data System (ADS)

    Billnert, R.; Andreotti, E.; Hambsch, F.-J.; Hult, M.; Karlsson, J.; Marissens, G.; Oberstedt, A.; Oberstedt, S.

    In this work we present first results from measurements of prompt fission γ-rays from the spontaneous fission in 252Cf. New and accurate data on corresponding γ-rays from the reactions 235U(nth,f) and 239Pu(nth,f) are highly demanded for the modeling of new Generation-IV nuclear reactor systems. For these experiments we employed scintillation detectors made out of new materials (LaBr3, LaCl3 and CeBr3), whose properties were necessary to know in order to obtain reliable results. Hence, we have characterized these detectors. In all the important properties these detectors outshine sodium-iodine detectors that where used in the 1970s, when the existing data had been acquired. Our finding is that the new generation of scintillation detectors is indeed promising, as far as an improved precision of the demanded data is concerned.

  4. The wavelet transform function to analyze interplanetary scintillation observations

    NASA Astrophysics Data System (ADS)

    Aguilar-Rodriguez, E.; Rodriguez-Martinez, M.; Romero-Hernandez, E.; Mejia-Ambriz, J. C.; Gonzalez-Esparza, J. A.; Tokumaru, M.

    2014-05-01

    Interplanetary scintillation (IPS) observations are useful to remotely sense the inner heliosphere. We present a new technique to analyze IPS observations using a wavelet transform (WT) function. This technique allows us to derive, in a straightforward way, a simple method to obtain the scintillation index (m). We tested this WT technique to analyze IPS observations obtained by the Solar-Terrestrial Environment Laboratory (STEL) radio telescope. The analysis of the m index of the radio source 3C48 detected by STEL over the year 2012 shows the expected decrease with solar elongation reported in previous studies. The WT technique has a great potential for future solar wind studies using IPS observations from contemporary radio telescopes.

  5. Strong scintillations of pulsed Laguerrian beams in a turbulent atmosphere.

    PubMed

    Banakh, Viktor A; Gerasimova, Liliya O

    2016-08-22

    Turbulent fluctuations of the energy density of broadband pulsed Laguerre-Gaussian beams are studied based on numerical solution of the parabolic wave equation for the complex spectral amplitude of the wave field by the split-step method. It is shown that in the regime of strong scintillations, the relative variance of energy density of the pulsed beams can take values smaller than unity, in contrast to the strong scintillation index of the continuous-wave beams, which tends to unity with increasing the turbulence strength. The level of residual spatial correlation of the energy density of pulsed beams exceeds that for the continuous-wave beams. It increases with shortening of the pulse duration and increasing of the refractive turbulence strength. PMID:27557206

  6. Scintillation Proximity Radioimmunoassay Utilizing 125I-Labeled Ligands

    NASA Astrophysics Data System (ADS)

    Udenfriend, Sidney; Diekmann Gerber, Louise; Brink, Larry; Spector, Sydney

    1985-12-01

    A unique type of radioimmunoassay is described that does not require centrifugation or separation. Microbeads containing a fluorophor are covalently linked to antibody. When an 125I-labeled antigen is added it binds to the beads and, by its proximity, the emitted short-range electrons of the 125I excite the fluorophor in the beads. The light emitted can be measured in a standard scintillation counter. Addition of unlabeled antigen from tissue extracts displaces the labeled ligand and diminishes the fluorescent signal. Application of scintillation proximity immunoassay to tissue enkephalins, serum thyroxin, and urinary morphine is described. Applications of the principle to study the kinetics of interaction between receptors and ligands are discussed.

  7. Scintillation proximity radioimmunoassay utilizing 125I-labeled ligands

    SciTech Connect

    Udenfriend, S.; Gerber, L.D.; Brink, L.; Spector, S.

    1985-12-01

    A unique type of radioimmunoassay is described that does not require centrifugation or separation. Microbeads containing a fluorophor are covalently linked to antibody. When an /sup 125/I-labeled antigen is added it binds to the beads and, by its proximity, the emitted short-range electrons of the /sup 125/I excite the fluorophor in the beads. The light emitted can be measured in a standard scintillation counter. Addition of unlabeled antigen from tissue extracts displaces the labeled ligand and diminishes the fluorescent signal. Application of scintillation proximity immunoassay to tissue enkephalins, serum thyroxin, and urinary morphine is described. Applications of the principle to study the kinetics of interaction between receptors and ligands are discussed.

  8. Modeling solar wind with boundary conditions from interplanetary scintillations

    DOE PAGESBeta

    Manoharan, P.; Kim, T.; Pogorelov, N. V.; Arge, C. N.; Manoharan, P. K.

    2015-09-30

    Interplanetary scintillations make it possible to create three-dimensional, time- dependent distributions of the solar wind velocity. Combined with the magnetic field observations in the solar photosphere, they help perform solar wind simulations in a genuinely time-dependent way. Interplanetary scintillation measurements from the Ooty Radio Astronomical Observatory in India provide directions to multiple stars and may assure better resolution of transient processes in the solar wind. In this paper, we present velocity distributions derived from Ooty observations and compare them with those obtained with the Wang-Sheeley-Arge (WSA) model. We also present our simulations of the solar wind flow from 0.1 AUmore » to 1 AU with the boundary conditions based on both Ooty and WSA data.« less

  9. Transparent plastic scintillators for neutron detection based on lithium salicylate

    NASA Astrophysics Data System (ADS)

    Mabe, Andrew N.; Glenn, Andrew M.; Carman, M. Leslie; Zaitseva, Natalia P.; Payne, Stephen A.

    2016-01-01

    Transparent plastic scintillators with pulse shape discrimination containing 6Li salicylate have been synthesized by bulk polymerization with a maximum 6Li loading of 0.40 wt%. Photoluminescence and scintillation responses to gamma-rays and neutrons are reported herein. Plastics containing 6Li salicylate exhibit higher light yields and permit a higher loading of 6Li as compared to previously reported plastics based on lithium 3-phenylsalicylate. However, pulse shape discrimination performance is reduced in lithium salicylate plastics due to the requirement of adding more nonaromatic monomers to the polymer matrix as compared to those based on lithium 3-phenylsalicylate. Reduction in light yield and pulse shape discrimination performance in lithium-loaded plastics as compared to pulse shape discrimination plastics without lithium is interpreted in terms of energy transfer interference by the aromatic lithium salts.

  10. Synthesis of plastic scintillation microspheres: alpha/beta discrimination.

    PubMed

    Santiago, L M; Bagán, H; Tarancón, A; Garcia, J F

    2014-11-01

    Plastic scintillation microspheres (PSm) have been developed as an alternative for liquid scintillation cocktails due to their ability to avoid the mixed waste, besides other strengths in which the possibility for alpha/beta discrimination is included. The aim of this work was to evaluate the capability of PSm containing two combinations of fluorescence solutes (PPO/POPOP and pT/Bis-MSB) and variable amounts of a second organic solvent (naphthalene) to enhance the alpha/beta discrimination. Two commercial detectors with different Pulse Shape Discrimination performances (Quantulus and Triathler) were used to evaluate the alpha/beta discrimination. An optimal discrimination of alpha/beta particles was reached, with very low misclassification values (2% for beta particles and 0.5% for alpha particles), when PSm containing PPO/POPOP and between 0.6 and 2.0 g of naphthalene were evaluated using Triathler and the appropriate programme for data processing.

  11. Scintillation fiber array detector for measurement of neutron beam profile

    NASA Astrophysics Data System (ADS)

    Kim, Chong; Hong, Byungsik; Jo, Mihee; Lee, Kyong Sei; Sim, Kwang-Souk

    2009-10-01

    We built and tested a detector to measure the profile of fast-neutron beams delivered by the MC50 cyclotron at the Korea Institute of Radiological and Medical Science (KIRAMS). The core component of the detector is a 2×46 array of scintillation fibers. The light output of the scintillation fibers is transformed into a current signal by a 46-channel silicon photodiode and digitized by a current-mode signal processor. This scanning device was designed to cover a neutron beam area of 30×32 cm2. The detector was tested in a neutron beam delivered by the MC50 cyclotron at KIRAMS. We demonstrate that the detector can successfully measure the neutron beam profile at various beam currents from 10 to 20 μA. The proposed neutron beam profile detector will be useful, for example, in radiotherapy applications with neutron intensities above 107 Hz/cm2.

  12. Auger recombination in sodium-iodide scintillators from first principles

    SciTech Connect

    McAllister, Andrew; Åberg, Daniel; Schleife, André; Kioupakis, Emmanouil

    2015-04-06

    Scintillator radiation detectors suffer from low energy resolution that has been attributed to non-linear light yield response to the energy of the incident gamma rays. Auger recombination is a key non-radiative recombination channel that scales with the third power of the excitation density and may play a role in the non-proportionality problem of scintillators. In this work, we study direct and phonon-assisted Auger recombination in NaI using first-principles calculations. Our results show that phonon-assisted Auger recombination, mediated primarily by short-range phonon scattering, dominates at room temperature. We discuss our findings in light of the much larger values obtained by numerical fits to z-scan experiments.

  13. Mercuric Iodide Photocell Technology for Room Temperature Readout of Scintillators

    SciTech Connect

    Warnick Kernan et al.

    2007-08-31

    Mercuric iodide (HgI2) is a well known material for the direct detection of gamma rays; however, the largest volume achievable is limited by thickness of the detector, which needs to be a small fraction of the average trapping length for electrons. We are reporting here preliminary results in using HgI2 crystals to fabricate photocells used in the readout of various scintillators. The optical spectral response and efficiency of these photocells were measured and will be reported. Preliminary nuclear response from a HgI2 photocell that was optically matched to a Ce3+ :LaBr3 scintillator will also be presented and discussed. Further improvements will be sought by optimizing the transparent contact technology.

  14. Optical properties of quantum-dot-doped liquid scintillators

    PubMed Central

    Aberle, C.; Li, J.J.; Weiss, S.; Winslow, L.

    2014-01-01

    Semiconductor nanoparticles (quantum dots) were studied in the context of liquid scintillator development for upcoming neutrino experiments. The unique optical and chemical properties of quantum dots are particularly promising for the use in neutrinoless double-beta decay experiments. Liquid scintillators for large scale neutrino detectors have to meet specific requirements which are reviewed, highlighting the peculiarities of quantum-dot-doping. In this paper, we report results on laboratory-scale measurements of the attenuation length and the fluorescence properties of three commercial quantum dot samples. The results include absorbance and emission stability measurements, improvement in transparency due to filtering of the quantum dot samples, precipitation tests to isolate the quantum dots from solution and energy transfer studies with quantum dots and the fluorophore PPO. PMID:25392711

  15. Radon measurement of natural gas using alpha scintillation cells.

    PubMed

    Kitto, Michael E; Torres, Miguel A; Haines, Douglas K; Semkow, Thomas M

    2014-12-01

    Due to their sensitivity and ease of use, alpha-scintillation cells are being increasingly utilized for measurements of radon ((222)Rn) in natural gas. Laboratory studies showed an average increase of 7.3% in the measurement efficiency of alpha-scintillation cells when filled with less-dense natural gas rather than regular air. A theoretical calculation comparing the atomic weight and density of air to that of natural gas suggests a 6-7% increase in the detection efficiency when measuring radon in the cells. A correction is also applicable when the sampling location and measurement laboratory are at different elevations. These corrections to the measurement efficiency need to be considered in order to derive accurate concentrations of radon in natural gas.

  16. SCINTILLATOR COMPOSITION FOR COUNTERS AND METHOD OF MAKING

    DOEpatents

    Buck, W.L.; Swank, R.K.

    1958-02-25

    This patent deals with a new composition for plastic scintillators and the method of making them. This is accomplished by mixing a solvent, selected from the group consisting of styrene, methylstyrene where the methyl group is attached to the ring, and p-vinylbiphenyl with p-terphenyl as a primary fluor. Marked improvement in the fluorescent properties of this scintillator composition is obtained by incorporating as a second fluor, a small amount of a highly conjugated hydrocarbon having four phenyl groups such as quaterphenyl or 1,1,4,4- tetraphenyl-1,3-butadiene. It is advisable to use very pure monomers in this composition, and to carry out its preparation in the absence of air.

  17. A Conserved Mode of Protein Recognition and Binding in a ParD−ParE Toxin−Antitoxin Complex

    SciTech Connect

    Dalton, Kevin M.; Crosson, Sean

    2010-05-06

    Toxin-antitoxin (TA) systems form a ubiquitous class of prokaryotic proteins with functional roles in plasmid inheritance, environmental stress response, and cell development. ParDE family TA systems are broadly conserved on plasmids and bacterial chromosomes and have been well characterized as genetic elements that promote stable plasmid inheritance. We present a crystal structure of a chromosomally encoded ParD-ParE complex from Caulobacter crescentus at 2.6 {angstrom} resolution. This TA system forms an {alpha}{sub 2}{beta}{sub 2} heterotetramer in the crystal and in solution. The toxin-antitoxin binding interface reveals extensive polar and hydrophobic contacts of ParD antitoxin helices with a conserved recognition and binding groove on the ParE toxin. A cross-species comparison of this complex structure with related toxin structures identified an antitoxin recognition and binding subdomain that is conserved between distantly related members of the RelE/ParE toxin superfamily despite a low level of overall primary sequence identity. We further demonstrate that ParD antitoxin is dimeric, stably folded, and largely helical when not bound to ParE toxin. Thus, the paradigmatic model in which antitoxin undergoes a disorder-to-order transition upon toxin binding does not apply to this chromosomal ParD-ParE TA system.

  18. Transparent garnet ceramic scintillators for gamma-ray detection

    NASA Astrophysics Data System (ADS)

    Wang, Yimin; Baldoni, Gary; Rhodes, William H.; Brecher, Charles; Shah, Ananya; Shirwadkar, Urmila; Glodo, Jarek; Cherepy, Nerine; Payne, Stephen

    2012-10-01

    Lanthanide gallium/aluminum-based garnets have a great potential as host structures for scintillation materials for medical imaging. Particularly attractive features are their high density, chemical radiation stability and more importantly, their cubic structure and isotropic optical properties, which allow them to be fabricated into fully transparent, highperformance polycrystalline optical ceramics. Lutetium/gadolinium aluminum/gallium garnets (described by formulas ((Gd,Lu)3(Al,Ga)5O12:Ce, Gd3(Al,Ga)5O12:Ce and Lu3Al5O12:Pr)) feature high effective atomic number and good scintillation properties, which make them particularly attractive for Positron Emission Tomography (PET) and other γ- ray detection applications. The ceramic processing route offers an attractive alternative to single crystal growth for obtaining scintillator materials at relatively low temperatures and at a reasonable cost, with flexibility in dimension control as well as activator concentration adjustment. In this study, optically transparent polycrystalline ceramics mentioned above were prepared by the sintering-HIP approach, employing nano-sized starting powders. The properties and microstructures of the ceramics were controlled by varying the processing parameters during consolidation. Single-phase, high-density, transparent specimens were obtained after sintering followed by a pressure-assisted densification process, i.e. hot-isostatic-pressing. The transparent ceramics displayed high contact and distance transparency as well as high light yield as high as 60,000-65,000 ph/MeV under gamma-ray excitation, which is about 2 times that of a LSO:Ce single crystal. The excellent scintillation and optical properties make these materials promising candidates for medical imaging and γ-ray detection applications.

  19. Length measurements of mid-latitude scintillation irregularities

    SciTech Connect

    Macdougall, J.W. )

    1992-04-01

    The lengths of irregularities which produce 150-MHz amplitude scintillations have been measured at 43 deg N, 81 deg W (geographic) using arrays of receivers with large spacings. The average length (major axis radius) of the irregularities was 6.1 km. This is much shorter than expected and implies that the measurements are of 'young' irregularities, less than 1 minute old. These irregularities appear to be a large, 25-50-percent perturbation of the background density. 8 refs.

  20. Performance of photomultiplier tubes and sodium iodide scintillation detector systems

    NASA Technical Reports Server (NTRS)

    Meegan, C. A.

    1981-01-01

    The performance of photomultiplier tubes (PMT's) and scintillation detector systems incorporating 50.8 by 1.27 cm NaI (T l) crystals was investigated to determine the characteristics of the photomultiplier tubes and optimize the detector geometry for the Burst and Transient Source Experiment on the Gamma Ray Observatory. Background information on performance characteristics of PMT's and NaI (T l) detectors is provided, procedures for measurement of relevant parameters are specified, and results of these measurements are presented.

  1. A variety of neutron sensors based on scintillating glass waveguides

    SciTech Connect

    Bliss, M.; Craig, R.A.

    1995-05-01

    Pacific Northwest Laboratory (PNL) has fabricated cerium-activated, lithium-silicate glass scintillating fiber neutron sensors via a hot-downdraw process. These fibers typically have a transmission length (e{sup {minus}1} length) of greater than 2 meters. The underlying physics of, the properties of, and selected devices incorporating these fibers are described. These fibers constitute an enabling technology for a wide variety of neutron sensors.

  2. Variety of neutron sensors based on scintillating glass waveguides

    NASA Astrophysics Data System (ADS)

    Bliss, Mary; Craig, Richard A.

    1995-04-01

    Pacific Northwest Laboratory (PNL) has fabricated cerium-activated lithium silicate glass scintillating fiber waveguide neutron sensors via a hot-downdraw process. These fibers typically have a transmission length (e-1 length) of greater than 2 meters. The underlying physics of, the properties of, and selected devices incorporating these fibers are described. These fibers constitute an enabling technology for a wide variety of neutron sensors.

  3. Alpha detection in pipes using an inverting membrane scintillator

    SciTech Connect

    Kendrick, D.T.; Cremer, C.D.; Lowry, W.; Cramer, E.

    1995-12-31

    Characterization of surface alpha emitting contamination inside enclosed spaces such as piping systems presents an interesting radiological measurement challenge. Detection of these alpha particles from the exterior of the pipe is impossible since the alpha particles are completely absorbed by the pipe wall. Traditional survey techniques, using hand-held instruments, simply can not be used effectively inside pipes. Science and Engineering Associates, Inc. is currently developing an enhancement to its Pipe Explorer{trademark} system that will address this challenge. The Pipe Explorer{trademark} uses a unique sensor deployment method where an inverted tubular membrane is propagated through complex pipe runs via air pressure. The inversion process causes the membrane to fold out against the pipe wall, such that no part of the membrane drags along the pipe wall. This deployment methodology has been successfully demonstrated at several DOE sites to transport specially designed beta and gamma scintillation detectors into pipes ranging in length up to 250 ft. The measurement methodology under development overcomes the limitations associated with conventional hand-held survey instruments by remotely emplacing an alpha scintillator in direct contact with the interior pipe surface over the entire length to be characterized. This is accomplished by incorporating a suitable scintillator into the otherwise clear membrane material. Alpha particles emitted from the interior pipe surface will intersect the membrane, resulting in the emission of light pulses from the scintillator. A photodetector, towed by the inverting membrane, is used to count these light pulses as a function of distance into the pipe, thereby producing a log of the surface alpha contamination levels. It is anticipated that the resulting system will be able to perform measurements in pipes as small as two inches in diameter, and several hundred feet in length.

  4. Protease-activated receptor 1 (PAR1) signalling desensitization is counteracted via PAR4 signalling in human platelets.

    PubMed

    Fälker, Knut; Haglund, Linda; Gunnarsson, Peter; Nylander, Martina; Lindahl, Tomas L; Grenegård, Magnus

    2011-06-01

    PARs (protease-activated receptors) 1 and 4 belong to the family of G-protein-coupled receptors which induce both G(α12/13) and G(αq) signalling. By applying the specific PAR1- and PAR4-activating hexapeptides, SFLLRN and AYPGKF respectively, we found that aggregation of isolated human platelets mediated via PAR1, but not via PAR4, is abolished upon homologous receptor activation in a concentration- and time-dependent fashion. This effect was not due to receptor internalization, but to a decrease in Ca²⁺ mobilization, PKC (protein kinase C) signalling and α-granule secretion, as well as to a complete lack of dense granule secretion. Interestingly, subthreshold PAR4 activation rapidly abrogated PAR1 signalling desensitization by differentially reconstituting these affected signalling events and functional responses, which was sufficient to re-establish aggregation. The lack of ADP release and P2Y₁₂ receptor-induced G(αi) signalling accounted for the loss of the aggregation response, as mimicking G(αi/z) signalling with 2-MeS-ADP (2-methylthioadenosine-5'-O-diphosphate) or epinephrine (adrenaline) could substitute for intermediate PAR4 activation. Finally, we found that the re-sensitization of PAR1 signalling-induced aggregation via PAR4 relied on PKC-mediated release of both ADP from dense granules and fibrinogen from α-granules. The present study elucidates further differences in human platelet PAR signalling regulation and provides evidence for a cross-talk in which PAR4 signalling counteracts mechanisms involved in PAR1 signalling down-regulation. PMID:21391917

  5. Apoptosis and Tumor Resistance Conferred by Par-4

    PubMed Central

    Zhao, Yanming; Rangnekar, Vivek M.

    2009-01-01

    Par-4 is a tumor suppressor protein with a pro-apoptotic function. Epigenetic silencing of Par-4 is seen in diverse tumors, and Par-4 knockout mice develop spontaneous tumors in various tissues. Endogenous Par-4 is essential for sensitization of cells to diverse apoptotic stimuli, whereas ectopic expression of Par-4 can selectively induce apoptosis in cancer cells. The cancer-specific pro-apoptotic action of Par-4 resides in its centrally located SAC domain. This chapter reviews a novel mouse model with ubiquitous expression of the SAC domain. These SAC transgenic mice display normal development and life span, and, most importantly, are resistant to spontaneous, as well as oncogene-induced, autochthonous tumors. The tumor resistant phenotype and undetectable toxicity of SAC in vivo suggests the SAC domain possesses tremendous therapeutic potential. PMID:18836307

  6. Study of nonproportionality in the light yield of inorganic scintillators

    SciTech Connect

    Singh, Jai

    2011-07-15

    Using a phenomenological approach, the light yield is derived for inorganic scintillators as a function of the rates of linear, bimolecular, and Auger processes occurring in the electron track initiated by an x ray or a {gamma}-ray photon. A relation between the track length and incident energy is also derived. It is found that the nonproportionality in the light yield can be eliminated if either nonlinear processes of interaction among the excited electrons, holes, and excitons can be eliminated from occurring or the high density situation can be relieved by diffusion of carriers from the track at a faster rate than the rate of activation of nonlinear processes. The influence of the track length and radius on the yield nonproportionality is discussed in view of the known experimental results. Inventing new inorganic scintillating materials with high carrier mobility can lead to a class of proportional inorganic scintillators. Results agree qualitatively with experimental results for the dependence of light yield on the incident energy.

  7. The readout electronics for Plastic Scintillator Detector of DAMPE

    NASA Astrophysics Data System (ADS)

    Kong, Jie; Yang, Haibo; Zhao, Hongyun; Su, Hong; Sun, Zhiyu; Yu, Yuhong; JingZhe, Zhang; Wang, XiaoHui; Liu, Jie; Xiao, Guoqing; Ma, Xinwen

    2016-07-01

    The Dark Matter Particle Explorer (DAMPE) satellite, which launched in December 2015, is designed to find the evidence of the existence of dark matter particles in the universe via the detection of the high-energy electrons and gamma-ray particles produced possibly by the annihilation of dark matter particles. Plastic Scintillator Detector (PSD) is one of major part of the satellite payload, which is comprised of a crossed pair of layers with 41 plastic scintillator-strips, each read out from both ends by the same Hamamatsu R4443MOD2 photo-multiplier tubes (PMTs). In order to extend linear dynamic range of detector, PMTs read out each plastic scintillator-strip separately with two dynode pickoffs. Therefore, the readout electronics system comprises of four Front-end boards to receive the pulses from 328 PMTs and implement charge measurement, which is based on the Application Specific Integrated Circuit (ASIC) chip VA160, 16 bits ADC and FPGA. The electronics of the detector has been designed following stringent requirements on mechanical and thermal stability, power consumption, radiation hardness and double redundancy. Various experiments are designed and implemented to check the performance of the electronics, some excellent results has been achieved.According to experimental results analysis, it is proved that the readout electronics works well.

  8. EUV Scintillator for Localization and Detection of Laser Beam

    NASA Astrophysics Data System (ADS)

    Monserud, Nils; Urabanski, Lukasz; Malm, Eric; Brown, Christopher; Marconi, Mario

    2011-10-01

    We set out to find a means of detecting and locating an EUV laser beam at the wavelength of 46.9 nm in real time. This will facilitate the alignment of our experiments in nano-patterning, nano-fabrication, and holography, consequently allowing multiple experiments to be aligned simultaneously. Methods of detection are either CCD cameras or prints made with Poly(methyl methacrylate) (PMMA) on a coated wafer, neither of which are efficient to operate. We describe the implementation of an alternative imaging method which combines a phosphor scintillator and a web-cam. Using a phosphor scintillator screen provided by Applied Scintillations Technologies Limited the detection and localization of the EUV laser beam at 46.9 nm was seen consistently through reflection providing a distinct image of the beam in the initial tests. We were able to capture an image of the beam using the webcam through the use of a user interface developed in labview which allowed a snap shot to be taken at the exact moment the beam past through the screen.

  9. Structure of ionospheric irregularities from amplitude and phase scintillation observations

    SciTech Connect

    Bhattacharyya, A.; Rastogi, R.G. )

    1991-04-01

    The mutual coherence function Gamma 2, or the second moment of the complex amplitude of a radio wave which traverses through equatorial F region irregularities, is computed from amplitude and phase scintillation data. Theoretically, the equation satisfied by the coherence function has an analytic solution over the whole range of scintillation strength. This solution is directly related to the structure function for the phase fluctuations produced by the irregularities. Hence, the shape of the correlation function for variations in the total electron content along the signal path can be derived from the computed values of Gamma 2. With a suitable power-law model for the irregularities, an 'intermediate break scale', this scale, as well as the rms density fluctuation are deduced from a comparison of computed values for short-time lags with those expected from theory. During a postsunset scintillation event, this scale is found to increase with local time. In the context of the generalized Rayleigh-Taylor instability, which is the likely source of the irregularities, this increase may be attributed to a decline in the effective electric field prevailing in the region of the irregularities. 26 refs.

  10. Time-based position estimation in monolithic scintillator detectors

    NASA Astrophysics Data System (ADS)

    Tabacchini, Valerio; Borghi, Giacomo; Schaart, Dennis R.

    2015-07-01

    Gamma-ray detectors based on bright monolithic scintillation crystals coupled to pixelated photodetectors are currently being considered for several applications in the medical imaging field. In a typical monolithic detector, both the light intensity and the time of arrival of the earliest scintillation photons can be recorded by each of the photosensor pixels every time a gamma interaction occurs. Generally, the time stamps are used to determine the gamma interaction time while the light intensities are used to estimate the 3D position of the interaction point. In this work we show that the spatio-temporal distribution of the time stamps also carries information on the location of the gamma interaction point and thus the time stamps can be used as explanatory variables for position estimation. We present a model for the spatial resolution obtainable when the interaction position is estimated using exclusively the time stamp of the first photon detected on each of the photosensor pixels. The model is shown to be in agreement with experimental measurements on a 16 mm  ×  16 mm  ×  10 mm LSO : Ce,0.2%Ca crystal coupled to a digital photon counter (DPC) array where a spatial resolution of 3 mm (root mean squared error) is obtained. Finally we discuss the effects of the main parameters such as scintillator rise and decay time, light output and photosensor single photon time resolution and pixel size.

  11. New scintillator materials for future and present facilities

    SciTech Connect

    Camera, Franco; Giaz, Agnese

    2015-02-24

    In the recent years LaBr3:Ce crystals started a new generation of high performing scintillator detectors. In fact, a large number of different, new and promising scintillators are now becoming commercially available, as for example CeBr{sub 3}, CLYC, SrI{sub 2}. Some others, like GYGAG:Ce, CLLB, CLLC, will be available in the near future. The CLYC crystal enriched with {sup 6}Li provides extremely high efficiency for thermal neutron identification and detection with performances comparable to {sup 3}He tubes. The CLYC enriched with {sup 7}Li can provide the direct measurement of the neutron kinetic energy from the energy pulse signal. The most recent R and D activity shows that ‘co-doping’ technique has the effect to improve the crystal proportionality and the mechanical properties thus significantly increasing the reliability and energy resolution of LaBr{sub 3};Ce and CeBr{sub 3} scintillators. Such a new generation of detectors can be the backbone for the detectors array of the future accelerator facilities as for example ELI-NP which will provide very intense high-energy γ-ray beam with very low bandwidth.

  12. Auger recombination in scintillator materials from first principles

    NASA Astrophysics Data System (ADS)

    McAllister, Andrew; Kioupakis, Emmanouil; Åberg, Daniel; Schleife, André

    2015-03-01

    Scintillators convert high energy radiation into lower energy photons which are easier to detect and analyze. One of the uses of these devices is identifying radioactive materials being transported across national borders. However, scintillating materials have a non-proportional light yield in response to incident radiation, which makes this task difficult. One possible cause of the non-proportional light yield is non-radiative Auger recombination. Auger recombination can occur in two ways - direct and phonon-assisted. We have studied both types of Auger recombination from first principles in the common scintillating material sodium iodide. Our results indicate that the phonon-assisted process, assisted primarily by short-range optical phonons, dominates the direct process. The corresponding Auger coefficients are 5 . 6 +/- 0 . 3 ×10-32cm6s-1 for the phonon-assisted process versus 1 . 17 +/- 0 . 01 ×10-33cm6s-1 for the direct process. At higher electronic temperatures the direct Auger recombination rate increases but remains lower than the phonon-assisted rate. This research was supported by the National Science Foundation CAREER award through Grant No. DMR-1254314 and NA-22. Computational Resources provide by LLNL and DOE NERSC Facility.

  13. Detecting pulsars with interstellar scintillation in variance images

    NASA Astrophysics Data System (ADS)

    Dai, S.; Johnston, S.; Bell, M. E.; Coles, W. A.; Hobbs, G.; Ekers, R. D.; Lenc, E.

    2016-11-01

    Pulsars are the only cosmic radio sources known to be sufficiently compact to show diffractive interstellar scintillations. Images of the variance of radio signals in both time and frequency can be used to detect pulsars in large-scale continuum surveys using the next generation of synthesis radio telescopes. This technique allows a search over the full field of view while avoiding the need for expensive pixel-by-pixel high time resolution searches. We investigate the sensitivity of detecting pulsars in variance images. We show that variance images are most sensitive to pulsars whose scintillation time-scales and bandwidths are close to the subintegration time and channel bandwidth. Therefore, in order to maximize the detection of pulsars for a given radio continuum survey, it is essential to retain a high time and frequency resolution, allowing us to make variance images sensitive to pulsars with different scintillation properties. We demonstrate the technique with Murchision Widefield Array data and show that variance images can indeed lead to the detection of pulsars by distinguishing them from other radio sources.

  14. Gamma scintillator system using boron carbide for neutron detection

    NASA Astrophysics Data System (ADS)

    Ben-Galim, Y.; Wengrowicz, U.; Raveh, A.; Orion, I.

    2014-08-01

    A new approach for neutron detection enhancement to scintillator gamma-ray detectors is suggested. By using a scintillator coupled with a boron carbide (B4C) disc, the 478 keV gamma-photon emitted from the excited Li in 94% of the 10B(n,α)7Li interactions was detected. This suggests that the performance of existing gamma detection systems in Homeland security applications can be improved. In this study, a B4C disc (2 in. diameter, 0.125 in. thick) with ~19.8% 10B was used and coupled with a scintillator gamma-ray detector. In addition, the neutron thermalization moderator was studied in order to be able to increase the neutron sensitivity. An improvement in the detector which is easy to assemble, affordable and efficient was demonstrated. Furthermore, a tailored Monte-Carlo code written in MATLAB was developed for validation of the proposed application through efficiency estimation for thermal neutrons. Validation of the code was accomplished by showing that the MATLAB code results were well correlated to a Monte-Carlo MCNP code results. The measured efficiency of the assembled experimental model was observed to be in agreement with both models calculations.

  15. Scintillation of spacecraft radio signals on the interplanetary plasma

    NASA Astrophysics Data System (ADS)

    Molera Calves, Guifre; Pogrebenko, Sergei; Cimo, Giuseppe; Duev, Dmitry; Bocanegra, Tatiana

    2015-04-01

    Observations of planetary spacecraft radio signals within the solar system give a unique opportunity to study the temporal and spatial behaviour of the signal's phase fluctuations caused by its propagation through the interplanetary plasma and the Earth's ionosphere. The phase scintillation of the telemetry signal of the European Space Agency's (ESA) Venus Express (VEX) and Mars Express (MEX) spacecraft was observed at X-band with a number of radio telescopes of the European VLBI Network (EVN) in the period 2008-15, within the scope of Planetary Radio Interferometry and Doppler Experiment (PRIDE) project. It was found that the phase scintillation spectra follow a Kolmogorov distribution with nearly constant spectral index of -2.42 for a full range of Venus orbital phases, from superior to inferior conjunctions and back. The solar wind plasma dominates the scintillation index and Doppler noise along the orbit from superior conjunction to the greatest elongation. Here, I will present the latest results of these observations, while approaching the inferior conjunction, where the Earth ionosphere starts to dominate, and also at the superior conjunction. Empirical coefficients for both contributions were estimated and compared for VEX and MEX.

  16. Timing Measurements of Scintillator Bars with Silicon Phtotomultiplier Light Detectors

    NASA Astrophysics Data System (ADS)

    Shelor, Mark; Elizondo, Leonardo; Ritt, Stefan

    2016-03-01

    To track and analyze cosmic rays via precise measurements of muon and similarly penetrating particle's airshower axes directions, we constructed a prototype consisting of two 1-meter long scintillator bars. Each bar is embedded with green wavelength shifting fibers to increase detection rate of two silicon photomultiplier, SiPM, light detectors to record light produced by cosmic rays via scintillation. The focus of the experiment was to determine the performance of these devices. Evaluation was performed for two makes of SiPM models - from AdvanSiD and Hamamatsu. Timing measurements of the apparatus were performed under several trigger conditions to filter out noise such as coincidence trigger with 2 photomultiplier detectors, as well as SiPM detectors in self-triggered mode. The SiPM detector waveforms were digitized using a 4-channel fast waveform sampler, the DRS4 digitizer. Signals were analyzed with the CERN PAW package. From our results, we deduced the speed of light in the scintillator using the SiPM modules to be about 66% of the speed of light in a vacuum which is in accordance with the specifications of the index of refraction for the fibers given by the manufacturer's specifications. The results of our timing measurements would be presented. Dept. of Ed. Title V Grant PO31S090007.

  17. Separating Nightside Interplanetary and Ionospheric Scintillation with LOFAR

    NASA Astrophysics Data System (ADS)

    Fallows, R. A.; Bisi, M. M.; Forte, B.; Ulich, Th.; Konovalenko, A. A.; Mann, G.; Vocks, C.

    2016-09-01

    Observation of interplanetary scintillation (IPS) beyond Earth-orbit can be challenging due to the necessity to use low radio frequencies at which scintillation due to the ionosphere could confuse the interplanetary contribution. A recent paper by Kaplan et al. presenting observations using the Murchison Widefield Array (MWA) reports evidence of nightside IPS on two radio sources within their field of view. However, the low time cadence of 2 s used might be expected to average out the IPS signal, resulting in the reasonable assumption that the scintillation is more likely to be ionospheric in origin. To check this assumption, this Letter uses observations of IPS taken at a high time cadence using the Low Frequency Array (LOFAR). Averaging these to the same as the MWA observations, we demonstrate that the MWA result is consistent with IPS, although some contribution from the ionosphere cannot be ruled out. These LOFAR observations represent the first of nightside IPS using LOFAR, with solar wind speeds consistent with a slow solar wind stream in one observation and a coronal mass ejection expected to be observed in another.

  18. Scintillation proximity assay (SPA) technology to study biomolecular interactions.

    PubMed

    Cook, Neil; Harris, Alison; Hopkins, Alison; Hughes, Kelvin

    2002-05-01

    Scintillation proximity assay (SPA) is a versatile homogeneous technique for radioactive assays which eliminates the need for separation steps. In SPA, scintillant is incorporated into small fluomicrospheres. These microspheres or "beads" are constructed in such a way as to bind specific molecules. If a radioactive molecule is bound to the bead, it is brought into close enough proximity that it can stimulate the scintillant contained within to emit light. Otherwise, the unbound radioactivity is too distant, the energy released is dissipated before reaching the bead, and these disintegrations are not detected. In this unit, the application of SPA technology to measuring protein-protein interactions, Src Homology 2 (SH2) and 3 (SH3) domain binding to specific peptide sequences, and receptor-ligand interactions are described. Three other protocols discuss the application of SPA technology to cell-adhesion-molecule interactions, protein-DNA interactions, and radioimmunoassays. In addition, protocols are given for preparation of SK-N-MC cells and cell membranes. PMID:18429228

  19. Measuring the 14C content in liquid scintillators

    NASA Astrophysics Data System (ADS)

    Enqvist, T.; Barabanov, I. R.; Bezrukov, L. B.; Gangapshev, A. M.; Gavrilyuk, Y. M.; Grishina, V. Yu; Gurentsov, V. I.; Hissa, J.; Joutsenvaara, J.; Kazalov, V. V.; Krokhaleva, S.; Kutuniva, J.; Kuusiniemi, P.; Kuzminov, V. V.; Kurlovich, A. S.; Loo, K.; Lubsandorzhiev, B. K.; Lubsandorzhiev, S.; Morgalyuk, V. P.; Novikova, G. Y.; Pshukov, A. M.; Sinev, V. V.; Słupecki, M.; Trzaska, W. H.; Umerov, Sh I.; Veresnikova, A. V.; Virkajärvi, A.; Yanovich, Y. A.; Zavarzina, V. P.

    2016-05-01

    We are going to perform a series of measurements where the 14C/12 C ratio will be measured from several liquid scintillator samples with a dedicated setup. The setup is designed with the aim of measuring ratios smaller than 10-18. Measurements take place in two underground laboratories: in the Baksan Neutrino Observatory, Russia and in the Pyhäsalmi mine, Finland. In Baksan the measurements started in 2015 and in Pyhäsalmi they start in the beginning of 2015. In order to fully understand the operation of the setup and its background contributions a development of simulation packages has also been started. Low-energy neutrino detection with a liquid scintillator requires that the intrinsic 14C content in the liquid is extremely low. In the Borexino CTF detector at Gran Sasso, Italy the 14C/12C ratio of 2 × 10-18 has been achieved being the lowest 14C concentration ever measured. In principle, the older the oil or gas source that the liquid scintillator is derived of and the deeper it situates, the smaller the 14C/12C ratio is supposed to be. This, however, is not generally the case, and the ratio is probably determined by the U and Th content of the local environment.

  20. Chloride, bromide and iodide scintillators with europium doping

    DOEpatents

    Zhuravleva, Mariya; Yang, Kan

    2014-08-26

    A halide scintillator material is disclosed where the halide may comprise chloride, bromide or iodide. The material is single-crystalline and has a composition of the general formula ABX.sub.3 where A is an alkali, B is an alkali earth and X is a halide which general composition was investigated. In particular, crystals of the formula ACa.sub.1-yEu.sub.yI.sub.3 where A=K, Rb and Cs were formed as well as crystals of the formula CsA.sub.1-yEu.sub.yX.sub.3 (where A=Ca, Sr, Ba, or a combination thereof and X=Cl, Br or I or a combination thereof) with divalent Europium doping where 0.ltoreq.y.ltoreq.1, and more particularly Eu doping has been studied at one to ten mol %. The disclosed scintillator materials are suitable for making scintillation detectors used in applications such as medical imaging and homeland security.

  1. A new model for estimating boreal forest fPAR

    NASA Astrophysics Data System (ADS)

    Majasalmi, Titta; Rautiainen, Miina; Stenberg, Pauline

    2014-05-01

    Life on Earth is continuously sustained by the extraterrestrial flux of photosynthetically active radiation (PAR, 400-700 nm) from the sun. This flux is converted to biomass by chloroplasts in green vegetation. Thus, the fraction of absorbed PAR (fPAR) is a key parameter used in carbon balance studies, and is listed as one of the Essential Climate Variables (ECV). Temporal courses of fPAR for boreal forests are difficult to measure, because of the complex 3D structures. Thus, they are most often estimated based on models which quantify the dependency of absorbed radiation on canopy structure. In this study, we adapted a physically-based canopy radiation model into a fPAR model, and compared modeled and measured fPAR in structurally different boreal forest stands. The model is based on the spectral invariants theory, and uses leaf area index (LAI), canopy gap fractions and spectra of foliage and understory as input data. The model differs from previously developed more detailed fPAR models in that the complex 3D structure of coniferous forests is described using an aggregated canopy parameter - photon recollision probability p. The strength of the model is that all model inputs are measurable or available through other simple models. First, the model was validated with measurements of instantaneous fPAR obtained with the TRAC instrument in nine Scots pine, Norway spruce and Silver birch stands in a boreal forest in southern Finland. Good agreement was found between modeled and measured fPAR. Next, we applied the model to predict temporal courses of fPAR using data on incoming radiation from a nearby flux tower and sky irradiance models. Application of the model to simulate diurnal and seasonal values of fPAR indicated that the ratio of direct-to-total incident radiation and leaf area index are the key factors behind the magnitude and variation of stand-level fPAR values.

  2. Development and spectral characteristics of new scintillation materials based on oxide crystals

    NASA Astrophysics Data System (ADS)

    Bilyi, Mykola U.; Nedel'ko, S. G.; Hizhnyi, Yu. A.

    1998-08-01

    Scintillation crystals as components of scintillation detectors are widely used in modern science and technique, especially, in medicine and high energy physics. High density of scintillation material is one of the basic requirements for creating of effective detecting devices. This advantage is incident to oxide crystals, that possess low radiation length and high atomic weight. Therefore such substances as bismuth germanate, yttrium silicate, bivalent metals tungstates, and others became an object of intensive investigations, especially seeing the elaboration of large calorimetric devices for elementary particles accelerators. The analysis of scintillation properties of various scintillator types showed that oxide materials, being at disadvantage in relation to traditional alkali-halide crystal systems in some scintillation parameters, excel them in rapidity, radiation hardness, chemical and thermal stability and operate successfully under conditions of strong irradiation, high temperatures, chemically active environment, mechanical stress, etc.

  3. A theoretical study of CsI:Tl columnar scintillator image quality parameters by analytical modeling

    NASA Astrophysics Data System (ADS)

    Kalyvas, N.; Valais, I.; Michail, C.; Fountos, G.; Kandarakis, I.; Cavouras, D.

    2015-04-01

    Medical X-ray digital imaging systems such as mammography, radiography and computed tomography (CT), are composed from efficient radiation detectors, which can transform the X-rays to electron signal. Scintillators are materials that emit light when excited by X-rays and incorporated in X-ray medical imaging detectors. Columnar scintillator, like CsI:T1 is very often used for X-ray detection due to its higher performance. The columnar form limits the lateral spread of the optical photons to the scintillator output, thus it demonstrates superior spatial resolution compared to granular scintillators. The aim of this work is to provide an analytical model for calculating the MTF, the DQE and the emission efficiency of a columnar scintillator. The model parameters were validated against published Monte Carlo data. The model was able to predict the overall performance of CsI:Tl scintillators and suggested an optimum thickness of 300 μm for radiography applications.

  4. A comparison between large-scale irregularities and scintillations in the polar ionosphere

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Zhang, Q.-H.; Jayachandran, P. T.; Lockwood, M.; Zhang, S.-R.; Moen, J.; Xing, Z.-Y.; Ma, Y.-Z.; Lester, M.

    2016-05-01

    A comparison tool has been developed by mapping the global GPS total electron content (TEC) and large coverage of ionospheric scintillations together on the geomagnetic latitude/magnetic local time coordinates. Using this tool, a comparison between large-scale ionospheric irregularities and scintillations is pursued during a geomagnetic storm. Irregularities, such as storm enhanced density, middle-latitude trough, and polar cap patches, are clearly identified from the TEC maps. At the edges of these irregularities, clear scintillations appeared but their behaviors were different. Phase scintillations (σφ) were almost always larger than amplitude scintillations (S4) at the edges of these irregularities, associated with bursty flows or flow reversals with large density gradients. An unexpected scintillation feature appeared inside the modeled auroral oval where S4 were much larger than σφ, most likely caused by particle precipitations around the exiting polar cap patches.

  5. 2. HI PAR (ACQUISITION RADAR) TOWER AND ENLISTED MEN (EM) ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. HI PAR (ACQUISITION RADAR) TOWER AND ENLISTED MEN (EM) BARRACKS WITH RADAR ATTACHED. - Nike Hercules Missile Battery Summit Site, Battery Control Administration & Barracks Building, Anchorage, Anchorage, AK

  6. Characterization of scintillator materials for fast-ion loss detectors in nuclear fusion reactors

    NASA Astrophysics Data System (ADS)

    Jiménez-Ramos, M. C.; García López, J.; García-Muñoz, M.; Rodríguez-Ramos, M.; Carmona Gázquez, M.; Zurro, B.

    2014-08-01

    In fusion plasma reactors, fast ion generated by heating systems and fusion born particles must be well confined. The presence of magnetohydrodynamic (MHD) instabilities can lead to a significant loss of these ions, which may reduce drastically the heating efficiency and may cause damage to plasma facing components in the vacuum vessel. In order to understand the physics underlying the fast ion loss mechanism, scintillator based detectors have been installed in several fusion devices. In this work we present the absolute photon yield and its degradation with ion fluence in terms of the number of photons emitted per incident ion of several scintillators thin coatings: SrGa2S4:Eu2+ (TG-Green), Y3Al5O12:Ce3+ (P46) and Y2O3:Eu3+ (P56) when irradiated with light ions of different masses (deuterium ions, protons and α-particles) at energies between approximately 575 keV and 3 MeV. The photon yield will be discussed in terms of the energy deposited by the particles into the scintillator. For that, the actual composition and thickness of the thin layers were determined by Rutherford Backscattering Spectrometry (RBS). A collimator with 1 mm of diameter, which defines the beam size for the experiments, placed at the entrance of the chamber. An electrically isolated sample holder biased to +300 V to collect the secondary electrons, connected to a digital current integrator (model 439 by Ortec) to measure the incident beam current. A home made device has been used to store the real-time evolution of the beam current in a computer file allowing the correction of the IL yields due to the current fluctuations. The target holder is a rectangle of 150 × 112 mm2 and can be tilted. The X and Y movements are controlled through stepping motors, which permits a fine control of the beam spot positioning as well as the study of several samples without venting the chamber. A silica optical fiber of 1 mm diameter fixed to the vacuum chamber, which collects the light from the scintillators

  7. Systematic evaluation of photodetector performance for plastic scintillation dosimetry

    SciTech Connect

    Boivin, Jonathan Beaulieu, Luc; Beddar, Sam; Guillemette, Maxime

    2015-11-15

    Purpose: The authors’ objective was to systematically assess the performance of seven photodetectors used in plastic scintillation dosimetry. The authors also propose some guidelines for selecting an appropriate detector for a specific application. Methods: The plastic scintillation detector (PSD) consisted of a 1-mm diameter, 10-mm long plastic scintillation fiber (BCF-60), which was optically coupled to a clear 10-m long optical fiber of the same diameter. A light-tight plastic sheath covered both fibers and the scintillator end was sealed. The clear fiber end was connected to one of the following photodetectors: two polychromatic cameras (one with an optical lens and one with a fiber optic taper replacing the lens), a monochromatic camera with an optical lens, a PIN photodiode, an avalanche photodiode (APD), or a photomultiplier tube (PMT). A commercially available W1 PSD was also included in the study, but it relied on its own fiber and scintillator. Each PSD was exposed to both low-energy beams (120, 180, and 220 kVp) from an orthovoltage unit and high-energy beams (6 and 23 MV) from a linear accelerator. Various dose rates were tested to identify the operating range and accuracy of each photodetector. Results: For all photodetectors, the relative uncertainty was less than 5% for dose rates higher than 3 mGy/s. The cameras allowed multiple probes to be used simultaneously, but they are less sensitive to low-light signals. The PIN, APD, and PMT had higher sensitivity, making them more suitable for low dose rate and out-of-field dose monitoring. The relative uncertainty of the PMT was less than 1% at the lowest dose rate achieved (0.10 mGy/s), suggesting that it was optimal for use in live dosimetry. Conclusions: For dose rates higher than 3 mGy/s, the PIN diode is the most effective photodetector in terms of performance/cost ratio. For lower dose rates, such as those seen in interventional radiology or high-gradient radiotherapy, PMTs are the optimal choice.

  8. GPS Observations of Plasma Bubbles and Scintillations over Equatorial Africa

    NASA Astrophysics Data System (ADS)

    Carrano, C. S.; Valladares, C. E.; Semala, G. K.; Bridgwood, C. T.; Adeniyi, J.; Amaeshi, L. L.; Damtie, B.; D'Ujanga Mutonyi, F.; Ndeda, J. D.; Baki, P.; Obrou, O. K.; Okere, B.; Tsidu, G. M.

    2010-12-01

    Sponsored in part by the International Heliophysical Year (IHY) program, Boston College, Air Force Research Laboratory (AFRL), and several universities in Africa have collaborated to deploy a network of GPS receivers throughout equatorial Africa, a region which has been largely devoid of ground-based ionospheric monitoring instruments. High date-rate GPS receivers capable of measuring Total Electron Content (TEC) and GPS scintillations were installed at Abidjan, Ivory Coast (5.3°N, 4.0°W, dip 3.5°S); Addis Ababa (9.0°N, 38.8°E, dip 0.1°N ); Bahir Dar, Ethiopia (26.1°N, 50.6°E, dip 20.1°N); Cape Verde (16.6°S, 22.9°W, dip 4.9°N); Ilorin, Nigeria (8.4°S, 4.7°E, dip 1.9°S); Kampala, Uganda (0.3°S, 32.6°E, dip 9.2°S); Lagos, Nigeria (6.5°N, 3.4°E, dip 3.1°S); Nairobi, Kenya (1.3°S, 36.8°W, dip 10.7°S); Nsukka, Nigeria (6.8°S, 7.4°W, dip 3.0°S); and Zanzibar, Tanzania (6.2°S, 39.2°E, dip 15.9°S). In this paper we report on the longitudinal, local time and seasonal occurrence of plasma bubbles and L band scintillations over equatorial Africa in 2009 and 2010, as a first step toward establishing the climatology of ionospheric irregularities over Africa. The scintillation intensity is obtained by measuring the standard deviation of normalized GPS signal power. The plasma bubbles are detected using an automated technique, whereby the GPS TEC is detrended to remove the diurnal variation and excursions exceeding a particular threshold are extracted for further analysis. A harmonic analysis (FFT) of these extracted events is performed to exclude wavelike features indicative of gravity waves or traveling ionospheric disturbances, and the remaining events are identified as plasma bubbles. Our findings suggest that the occurrence of plasma bubbles and L band scintillations over Africa are well correlated, but that some discrepancies in their morphologies are evident. While plasma bubbles and scintillations are generally observed during equinoctial

  9. The next-generation liquid-scintillator neutrino observatory LENA

    NASA Astrophysics Data System (ADS)

    Wurm, Michael; Beacom, John F.; Bezrukov, Leonid B.; Bick, Daniel; Blümer, Johannes; Choubey, Sandhya; Ciemniak, Christian; D'Angelo, Davide; Dasgupta, Basudeb; Derbin, Alexander; Dighe, Amol; Domogatsky, Grigorij; Dye, Steve; Eliseev, Sergey; Enqvist, Timo; Erykalov, Alexey; von Feilitzsch, Franz; Fiorentini, Gianni; Fischer, Tobias; Göger-Neff, Marianne; Grabmayr, Peter; Hagner, Caren; Hellgartner, Dominikus; Hissa, Johannes; Horiuchi, Shunsaku; Janka, Hans-Thomas; Jaupart, Claude; Jochum, Josef; Kalliokoski, Tuomo; Kayunov, Alexei; Kuusiniemi, Pasi; Lachenmaier, Tobias; Lazanu, Ionel; Learned, John G.; Lewke, Timo; Lombardi, Paolo; Lorenz, Sebastian; Lubsandorzhiev, Bayarto; Ludhova, Livia; Loo, Kai; Maalampi, Jukka; Mantovani, Fabio; Marafini, Michela; Maricic, Jelena; Marrodán Undagoitia, Teresa; McDonough, William F.; Miramonti, Lino; Mirizzi, Alessandro; Meindl, Quirin; Mena, Olga; Möllenberg, Randolph; Muratova, Valentina; Nahnhauer, Rolf; Nesterenko, Dmitry; Novikov, Yuri N.; Nuijten, Guido; Oberauer, Lothar; Pakvasa, Sandip; Palomares-Ruiz, Sergio; Pallavicini, Marco; Pascoli, Silvia; Patzak, Thomas; Peltoniemi, Juha; Potzel, Walter; Räihä, Tomi; Raffelt, Georg G.; Ranucci, Gioacchino; Razzaque, Soebur; Rummukainen, Kari; Sarkamo, Juho; Sinev, Valerij; Spiering, Christian; Stahl, Achim; Thorne, Felicitas; Tippmann, Marc; Tonazzo, Alessandra; Trzaska, Wladyslaw H.; Vergados, John D.; Wiebusch, Christopher; Winter, Jürgen

    2012-06-01

    As part of the European LAGUNA design study on a next-generation neutrino detector, we propose the liquid-scintillator detector LENA (Low Energy Neutrino Astronomy) as a multipurpose neutrino observatory. The outstanding successes of the Borexino and KamLAND experiments demonstrate the large potential of liquid-scintillator detectors in low-energy neutrino physics. Low energy threshold, good energy resolution and efficient background discrimination are inherent to the liquid-scintillator technique. A target mass of 50 kt will offer a substantial increase in detection sensitivity. At low energies, the variety of detection channels available in liquid scintillator will allow for an energy - and flavor-resolved analysis of the neutrino burst emitted by a galactic Supernova. Due to target mass and background conditions, LENA will also be sensitive to the faint signal of the Diffuse Supernova Neutrino Background. Solar metallicity, time-variation in the solar neutrino flux and deviations from MSW-LMA survival probabilities can be investigated based on unprecedented statistics. Low background conditions allow to search for dark matter by observing rare annihilation neutrinos. The large number of events expected for geoneutrinos will give valuable information on the abundances of Uranium and Thorium and their relative ratio in the Earth's crust and mantle. Reactor neutrinos enable a high-precision measurement of solar mixing parameters. A strong radioactive or pion decay-at-rest neutrino source can be placed close to the detector to investigate neutrino oscillations for short distances and sub-MeV to MeV energies. At high energies, LENA will provide a new lifetime limit for the SUSY-favored proton decay mode into kaon and antineutrino, surpassing current experimental limits by about one order of magnitude. Recent studies have demonstrated that a reconstruction of momentum and energy of GeV particles is well feasible in liquid scintillator. Monte Carlo studies on the

  10. Interplanetary plasma scintillation parameters measurements retrieved from the spacecraft observations.

    NASA Astrophysics Data System (ADS)

    Molera Calvés, Guifré; Pogrebenko, S. V.; Wagner, J.; Maccaferri, G.; Colucci, G.; Kronschnabl, G.; Scilliro, F.; Bianco, G.; Pérez Ayúcar, M.; Cosmovici, C. B.

    2010-05-01

    Measurement of the Interplanetary Scintillations (IPS) of radio signals propagating through the plasma in the Solar System by the radio astronomical instruments is a powerful tool to characterise and study the spatial and temporal variation of the electron density in the Solar wind. Several techniques based on the observation of natural and artificial radio sources have been developed during the last 50 years. Here we report our results of the IPS parameters measurement based on the multi-station observations of the planetary mission spacecraft. The ESA Venus Express spacecraft was observed at X-band (8.4 GHz) by several European VLBI stations - Metsähovi Radio Observatory (Aalto University , FI), Medicina (INAF-RA, IT), Matera (ASI, IT), Wettzell (BKG, DE), Noto (INAF-IRA, IT) and Yebes (OAN-IGN, ES) during a 2008-2010 campaign in a framework of the PRIDE (Planetary Radio Interferometry and Doppler Experiments) project as a preparatory stage for the European Radio Astronomy VLBI facilities participation in the planned ESA planetary missions (EJSM, TESM, EVE and others). Observational data were processed at Metsähovi Radio Observatory with the on-purpose developed high performance, ultra-high spectral resolution and spacecraft tracking capable software spectrometer-correlator and analysed at the Joint Institute for VLBI in Europe (JIVE, NL). High quality of acquired and analysed data enables us to study and define several parameters of the S/C signal and accompanying "ranging" tones with milli-Hz accuracy, among which the phase fluctuations of the spacecraft signal carrier line can be used to characterise the interplanetary plasma density fluctuations along the signal propagation line at different spatial and temporal scales at different Solar elongations and which exhibits a near-Kolmogorov spectrum. Such essential parameters as the phase scintillation index and bandwidth of scintillations and their dependence on the solar elongation, distance to the target

  11. GNSS-based Observations and Simulations of Spectral Scintillation Indices in the Arctic Ionosphere

    NASA Astrophysics Data System (ADS)

    Durgonics, T.; Hoeg, P.; von Benzon, H. H.; Komjathy, A.

    2015-12-01

    During disturbed times, ionospheric scintillations can be severe and adversely impact satellite-based positioning and radio transmissions. The scintillation occurs in the amplitude, phase, polarization, and angle of arrival of the signal. Precise observation, classification, modeling, forecasting, and development of data-driven methodologies to accurately localize ionospheric irregularities and simulate GNSS scintillation signals are highly desired. Ionospheric scintillations have traditionally been quantified by amplitude (S4) and phase scintillations (σφ). Our study focuses on the Arctic, where scintillations, especially phase scintillations, are prominent. We will present observations acquired from a network of Greenlandic GNSS stations, including 2D amplitude and phase scintillation index maps for representative calm and storm periods. In addition to the traditional indices described above, we are exploring a set of indices derived from the power spectra of the signals. The observed corner frequency of the power spectrum is a function of the Fresnel radius and the drift speed of the irregularities, while the slope of the power spectrum is related to the Fresnel oscillations. We will demonstrate how spectral characteristics of the scintillations act under large total electron content (TEC) gradients and how physical parameters can be extracted from the power spectra, and will present how these parameters of the corner frequencies and power spectra slopes vary during ionospheric storms. The observations will then be compared to properties of simulated GNSS signals computed by the Fast Scintillation Mode (FSM). The FSM was developed to simulate ionospheric scintillations under different geophysical conditions, and is used to simulate GNSS signals with known scintillation characteristics. This comparison could lead to a better understanding of the observed ionospheric state.

  12. Scintillation statistics caused by atmospheric turbulence and speckle in satellite laser ranging

    NASA Technical Reports Server (NTRS)

    Bufton, J. L.; Iyer, R. S.; Taylor, L. S.

    1977-01-01

    We study the statistics of scintillation at the ground-based receiver for the earth-space-earth retroreflector configuration of satellite laser ranging. These statistics are governed by the joint effects of atmospheric turbulence and speckle produced by the retroreflector array. An expression for the probability density function of scintillation is obtained and evaluated numerically. Comparison of the normalized variance of scintillation calculated by using this function shows good agreement with results obtained by other methods.

  13. Lithium glass scintillator neutron detector as an improved alternative to the standard 3 he proportional counter

    SciTech Connect

    Vladimir Popov, Pavel Degtiarenko

    2011-06-01

    Lithium glass scintillator made from 6Li-enriched substrate is a well known for its neutron detection capability. In spite of neutron interaction, cross section of 6Li happens to be lower than that of 3He. However, the neutron detection efficiency could be higher due to higher volume content of 6Li nuclear in the solid scintillator vs. gas filled proportional counter. At the same time, as lithium glass is sensitive to gamma and charge particle radiation, non-neutron radiation discrimination is required. Our detector is composed of two equal-size cylindrical Li(Ce) glass scintillators. The first one is high-sensitive to thermal neutrons GS-20 (6Li doped), the second one is GS-30 (7Li doped) type Scint-Gobain made lithium glass scintillator. Each of scintillators is coupled with R7400U Hamamatsu subminiature photomultiplier tube, and all assembly is fitted into NP100H 3He tube size. 6Li absorbs thermal neutrons releasing alpha particles and triton with 4.8 MeV total energy deposit inside the scintillator (equivalent to about ~1.3 MeV gamma energy depositions). Because 7Li isotope does not absorb thermal neutrons, and the physical properties of the two scintillators are virtually identical, the difference between these two scintillators could be used to provide neutron dose rate information. Results of study of neutron detector assembled of two Li(Ce) scintillators and NP100H moderator are presented

  14. A 222Rn source for low-background liquid scintillation detectors

    NASA Astrophysics Data System (ADS)

    Johnson, Michael; Benziger, Jay; Stoia, Catherine; Calaprice, Frank; Chen, Mark; Darnton, Nicholas; Loeser, Fred; Bruce Vogelaar, R.

    A technique for producing a radioactive source suitable for use in a low-background liquid scintillation detector is described. 222Rn was concentrated from air to prepare liquid scintillator sources spiked with 10 6 Bq/m 3 of the radioisotope. Air was stripped of CO 2 and water vapor, and passed over cooled charcoal which trapped the radon. The accumulated radon was desorbed and transferred into a pseudocumene-based scintillator. These sources have been used for position calibration in the Counting Test Facility (a 5 m 3 spherical liquid scintillation detector) at the Laboratori Nazionali del Gran Sasso.

  15. High-efficiency scintillation detector for combined of thermal and fast neutrons and gamma radiation

    DOEpatents

    Chiles, Marion M.; Mihalczo, John T.; Blakeman, Edward D.

    1989-02-07

    A scintillation based radiation detector for the combined detection of thermal neutrons, high-energy neutrons and gamma rays in a single detecting unit. The detector consists of a pair of scintillators sandwiched together and optically coupled to the light sensitive face of a photomultiplier tube. A light tight radiation pervious housing is disposed about the scintillators and a portion of the photomultiplier tube to hold the arrangement in assembly and provides a radiation window adjacent the outer scintillator through which the radiation to be detected enters the detector. The outer scintillator is formed of a material in which scintillations are produced by thermal-neutrons and the inner scintillator is formed of a material in which scintillations are produced by high-energy neutrons and gamma rays. The light pulses produced by events detected in both scintillators are coupled to the photomultiplier tube which produces a current pulse in response to each detected event. These current pulses may be processed in a conventional manner to produce a count rate output indicative of the total detected radiation even count rate. Pulse discrimination techniques may be used to distinguish the different radiations and their energy distribution.

  16. High-efficiency scintillation detector for combined detection of thermal and fast neutrons and gamma radiation

    DOEpatents

    Chiles, M.M.; Mihalczo, J.T.; Blakeman, E.D.

    1987-02-27

    A scintillation based radiation detector for the combined detection of thermal neutrons, high-energy neutrons and gamma rays in a single detecting unit. The detector consists of a pair of scintillators sandwiched together and optically coupled to the light sensitive face of a photomultiplier tube. A light tight radiation pervious housing is disposed about the scintillators and a portion of the photomultiplier tube to hold the arrangement in assembly and provides a radiation window adjacent the outer scintillator through which the radiation to be detected enters the detector. The outer scintillator is formed of a material in which scintillations are produced by thermal-neutrons and the inner scintillator is formed of a material in which scintillations are produced by high-energy neutrons and gamma rays. The light pulses produced by events detected in both scintillators are coupled to the photomultiplier tube which produces a current pulse in response to each detected event. These current pulses may be processed in a conventional manner to produce a count rate output indicative of the total detected radiation event count rate. Pulse discrimination techniques may be used to distinguish the different radiations and their energy distribution.

  17. High-efficiency scintillation detector for combined of thermal and fast neutrons and gamma radiation

    DOEpatents

    Chiles, Marion M.; Mihalczo, John T.; Blakeman, Edward D.

    1989-01-01

    A scintillation based radiation detector for the combined detection of thermal neutrons, high-energy neutrons and gamma rays in a single detecting unit. The detector consists of a pair of scintillators sandwiched together and optically coupled to the light sensitive face of a photomultiplier tube. A light tight radiation pervious housing is disposed about the scintillators and a portion of the photomultiplier tube to hold the arrangement in assembly and provides a radiation window adjacent the outer scintillator through which the radiation to be detected enters the detector. The outer scintillator is formed of a material in which scintillations are produced by thermal-neutrons and the inner scintillator is formed of a material in which scintillations are produced by high-energy neutrons and gamma rays. The light pulses produced by events detected in both scintillators are coupled to the photomultiplier tube which produces a current pulse in response to each detected event. These current pulses may be processed in a conventional manner to produce a count rate output indicative of the total detected radiation even count rate. Pulse discrimination techniques may be used to distinguish the different radiations and their energy distribution.

  18. Echo scintillation Index affected by cat-eye target's caliber with Cassegrain lens

    NASA Astrophysics Data System (ADS)

    Shan, Cong-miao; Sun, Hua-yan; Zhao, Yan-zhong; Zheng, Yong-hui

    2015-10-01

    The optical aperture of cat-eye target has the aperture averaging effect to the active detecting laser of active laser detection system, which can be used to identify optical targets. The echo scintillation characteristics of the transmission-type lens target have been studied in previous work. Discussing the differences of the echo scintillation characteristics between the transmission-type lens target and Cassegrain lens target can be helpful to targets classified. In this paper, the echo scintillation characteristics of Cat-eye target's caliber with Cassegrain lens has been discussed . By using the flashing theory of spherical wave in the weak atmospheric turbulence, the annular aperture filter function and the Kolmogorov power spectrum, the analytic expression of the scintillation index of the cat-eye target echo of the horizontal path two-way transmission was given when the light is normal incidence. Then the impact of turbulence inner and outer scale to the echo scintillation index and the analytic expression of the echo scintillation index at the receiving aperture were presented using the modified Hill spectrum and the modified Von Karman spectrum. Echo scintillation index shows the tendency of decreasing with the target aperture increases and different ratios of the inner and outer aperture diameter show the different echo scintillation index curves. This conclusion has a certain significance for target recognition in the active laser detection system that can largely determine the target type by largely determining the scope of the cat-eye target which depending on echo scintillation index.

  19. Optimum design calculations for detectors based on ZnSe(Те,О) scintillators

    NASA Astrophysics Data System (ADS)

    Katrunov, K.; Ryzhikov, V.; Gavrilyuk, V.; Naydenov, S.; Lysetska, O.; Litichevskyi, V.

    2013-06-01

    Light collection in scintillators ZnSe(X), where X is an isovalent dopant, was studied using Monte Carlo calculations. Optimum design was determined for detectors of "scintillator—Si-photodiode" type, which can involve either one scintillation element or scintillation layers of large area made of small-crystalline grains. The calculations were carried out both for determination of the optimum scintillator shape and for design optimization of light guides, on the surface of which the layer of small-crystalline grains is formed.

  20. Study and understanding of n/γ discrimination processes in organic plastic scintillators

    NASA Astrophysics Data System (ADS)

    Hamel, Matthieu; Blanc, Pauline; Rocha, Licinio; Normand, Stéphane; Pansu, Robert

    2013-05-01

    For 50 years, it was assumed that unlike liquid scintillators or organic crystals, plastic scintillators were not able to discriminate fast neutrons from gamma. In this work, we will demonstrate that triplet-triplet annihilations (which are responsible of n/γ discrimination) can occur even in plastic scintillators, following certain conditions. Thus, the presentation will deal with the chemical preparation, the characterization and the comparison of n/γ pulse shape discrimination of various plastic scintillators. To this aim, scale-up of the process allowed us to prepare a Ø 100 mm × ≈ 110 mm thick.

  1. Organic liquid scintillation detector shape and volume impact on radiation portal monitors

    NASA Astrophysics Data System (ADS)

    Paff, Marc G.; Clarke, Shaun D.; Pozzi, Sara A.

    2016-07-01

    We have developed and tested a radiation portal monitor using organic liquid scintillation detectors. In order to optimize our system designs, neutron measurements were carried out with three organic liquid scintillation detectors of different shapes and sizes, along with a 3He radiation portal monitor (RPM) as a reference. The three liquids tested were a 7.62 cm diameter by 7.62 cm length cylindrical active volume organic liquid scintillation detector, a 12.7 cm diameter by 12.7 cm length cylindrical active volume organic liquid scintillation detector, and a 25 cm by 25 cm by 10 cm "paddle" shaped organic liquid scintillation detector. Background and Cf-252 neutron measurements were recorded to allow for a comparison of neutron intrinsic efficiencies as well as receiver operating characteristics (ROC) curves between detectors. The 12.7 cm diameter cylindrical active volume organic liquid scintillation detector exhibited the highest intrinsic neutron efficiency (54%) of all three liquid scintillators. An ROC curve analysis for a heavily moderated Cf-252 measurement showed that using the 12.7 cm diameter by 12.7 cm length cylindrical active volume Eljen EJ309 organic liquid scintillation detector would result in the fewest needed detector units in order to achieve a near 100% positive neutron alarm rate while maintaining a better than 1 in 10,000 false alarm rate on natural neutron background. A small number of organic liquid scintillation detectors could therefore be a valid alternative to 3He in some RPM applications.

  2. Apparatus and method for temperature correction and expanded count rate of inorganic scintillation detectors

    DOEpatents

    Ianakiev, Kiril D.; Hsue, Sin Tao; Browne, Michael C.; Audia, Jeffrey M.

    2006-07-25

    The present invention includes an apparatus and corresponding method for temperature correction and count rate expansion of inorganic scintillation detectors. A temperature sensor is attached to an inorganic scintillation detector. The inorganic scintillation detector, due to interaction with incident radiation, creates light pulse signals. A photoreceiver processes the light pulse signals to current signals. Temperature correction circuitry that uses a fast light component signal, a slow light component signal, and the temperature signal from the temperature sensor to corrected an inorganic scintillation detector signal output and expanded the count rate.

  3. Very fast doped LaBr.sub.3 scintillators and time-of-flight PET

    DOEpatents

    Shah, Kanai S.

    2006-10-31

    The present invention concerns very fast scintillator materials capable of resolving the position of an annihilation event within a portion of a human body cross-section. In one embodiment, the scintillator material comprises LaBr.sub.3 doped with cerium. Particular attention is drawn to LaBr.sub.3 doped with a quantity of Ce that is chosen for improving the timing properties, in particular the rise time and resultant timing resolution of the scintillator, and locational capabilities of the scintillator.

  4. Fiber scintillator/streak camera detector for burn history measurement in inertial confinement fusion experiment

    SciTech Connect

    Miyanaga, N.; Ohba, N.; Fujimoto, K.

    1997-01-01

    To measure the burn history in an inertial confinement fusion experiment, we have developed a new neutron detector based on plastic scintillation fibers. Twenty-five fiber scintillators were arranged in a geometry compensation configuration by which the time-of-flight difference of the neutrons is compensated by the transit time difference of light passing through the fibers. Each fiber scintillator is spliced individually to an ultraviolet optical fiber that is coupled to a streak camera. We have demonstrated a significant improvement of sensitivity compared with the usual bulk scintillator coupled to a bundle of the same ultraviolet fibers. {copyright} {ital 1997 American Institute of Physics.}

  5. Light yield and energy transfer in a new Gd-loaded liquid scintillator

    NASA Astrophysics Data System (ADS)

    Aberle, C.; Buck, C.; Hartmann, F. X.; Schönert, S.

    2011-11-01

    We investigate a new gadolinium-loaded organic liquid scintillator which is designed to detect electron antineutrinos. A model has been developed to account for the various energy transfer paths possible in a liquid scintillator with multiple solvents, one fluor and a quenching component. Experimental light yield measurements were carried out to determine the relative rates for the energy transfers included in the model. Model predictions were used to tune the luminescent properties of the Gd-loaded target scintillator and the unloaded Gamma Catcher scintillator for the reactor neutrino experiment Double Chooz.

  6. The features of electronics structure of the multichannel scintillation module for the EMMA experiment

    NASA Astrophysics Data System (ADS)

    Volchenko, V.; Volchenko, G.; Akhrameev, E.; Bezrukov, L.; Dzaparova, I.; Enqvist, T.; Inzhechik, L.; Izmaylov, A.; Joutsenvaara, J.; Khabibullin, M.; Khotjantsev, A.; Kuusiniemi, P.; Lubsandorzhiev, B.; Mineev, O.; Petkov, V.; Poleshuk, R.; Shaibonov, B.; Sarkamo, J.; Shaykhiev, A.; Trzaska, W.; Yanin, A.; Yershov, N.

    2011-05-01

    A brief description of the developed structural electric diagrams of 16-channel scintillation module for the underground EMMA experiment, the basic characteristics and parameters of the electrical diagrams of this module are presented. Multi-pixel photodiodes operating in a limited Geiger mode are used for photoreadout of the scintillator detectors in 16-channel scintillation module. The method of the automatic tuning of the photosensors gain based on the stabilization of an average counting rate of the scintillation detectors from gamma rays of a natural radioactive background is described.

  7. Transcriptome profiling reveals links between ParS/ParR, MexEF-OprN, and quorum sensing in the regulation of adaptation and virulence in Pseudomonas aeruginosa

    PubMed Central

    2013-01-01

    Background The ParS/ParR two component regulatory system plays critical roles for multidrug resistance in Pseudomonas aeruginosa. It was demonstrated that in the presence of antimicrobials, ParR enhances bacterial survival by distinct mechanisms including activation of the mexXY efflux genes, enhancement of lipopolysaccharide modification through the arn operon, and reduction of the expression of oprD porin. Results In this study, we report on transcriptomic analyses of P. aeruginosa PAO1 wild type and parS and parR mutants growing in a defined minimal medium. Our transcriptomic analysis provides the first estimates of transcript abundance for the 5570 coding genes in P. aeruginosa PAO1. Comparative transcriptomics of P. aeruginosa PAO1 and par mutants identified a total of 464 genes regulated by ParS and ParR. Results also showed that mutations in the parS/parR system abolished expression of the mexEF-oprN operon by down-regulating the regulatory gene mexS. In addition to the known effects on drug resistance genes, transcript abundances of the quorum sensing genes (rhlIR and pqsABCDE-phnAB) were higher in both parS and parR mutants. In accordance with these results, a significant portion of the ParS/ParR regulated genes belonged to the MexEF-OprN and quorum sensing regulons. Deletion of the par genes also led to increased phenazine production and swarming motility, consistent with the up-regulation of the phenazine and rhamnolipid biosynthetic genes, respectively. Conclusion Our results link the ParS/ParR two component signal transduction system to MexEF-OprN and quorum sensing systems in P. aeruginosa. These results expand our understanding of the roles of the ParS/ParR system in the regulation of gene expression in P. aeruginosa, especially in the absence of antimicrobials. PMID:24034668

  8. Mechanism of DNA Segregation in Prokaryotes: Replicon Pairing by parC of Plasmid R1

    NASA Astrophysics Data System (ADS)

    Jensen, Rasmus Bugge; Lurz, Rudi; Gerdes, Kenn

    1998-07-01

    Prokaryotic chromosomes and plasmids encode partitioning systems that are required for DNA segregation at cell division. The systems are thought to be functionally analogous to eukaryotic centromeres and to play a general role in DNA segregation. The parA system of plasmid R1 encodes two proteins ParM and ParR, and a cis-acting centromere-like site denoted parC. The ParR protein binds to parC in vivo and in vitro. The ParM protein is an ATPase that interacts with ParR specifically bound to parC. Using electron microscopy, we show here that parC mediates efficient pairing of plasmid molecules. The pairing requires binding of ParR to parC and is stimulated by the ParM ATPase. The ParM mediated stimulation of plasmid pairing is dependent on ATP hydrolysis by ParM. Using a ligation kinetics assay, we find that ParR stimulates ligation of parC-containing DNA fragments. The rate-of-ligation was increased by wild type ParM protein but not by mutant ParM protein deficient in the ATPase activity. Thus, two independent assays show that parC mediates pairing of plasmid molecules in vitro. These results are consistent with the proposal that replicon pairing is part of the mechanism of DNA segregation in prokaryotes.

  9. Developpement d'algorithmes de reconstruction statistique appliques en tomographie rayons-X assistee par ordinateur

    NASA Astrophysics Data System (ADS)

    Thibaudeau, Christian

    La tomodensitometrie (TDM) permet d'obtenir, et ce de facon non invasive, une image tridimensionnelle de l'anatomie interne d'un sujet. Elle constitue l'evolution logique de la radiographie et permet l'observation d'un volume sous differents plans (sagittal, coronal, axial ou n'importe quel autre plan). La TDM peut avantageusement completer la tomographie d'emission par positrons (TEP), un outil de predilection utilise en recherche biomedicale et pour le diagnostic du cancer. La TEP fournit une information fonctionnelle, physiologique et metabolique, permettant la localisation et la quantification de radiotraceurs a l'interieur du corps humain. Cette derniere possede une sensibilite inegalee, mais peut neanmoins souffrir d'une faible resolution spatiale et d'un manque de repere anatomique selon le radiotraceur utilise. La combinaison, ou fusion, des images TEP et TDM permet d'obtenir cette localisation anatomique de la distribution du radiotraceur. L'image TDM represente une carte de l'attenuation subie par les rayons-X lors de leur passage a travers les tissus. Elle permet donc aussi d'ameliorer la quantification de l'image TEP en offrant la possibilite de corriger pour l'attenuation. L'image TDM s'obtient par la transformation de profils d'attenuation en une image cartesienne pouvant etre interpretee par l'humain. Si la qualite de cette image est fortement influencee par les performances de l'appareil, elle depend aussi grandement de la capacite de l'algorithme de reconstruction a obtenir une representation fidele du milieu image. Les techniques de reconstruction standards, basees sur la retroprojection filtree (FBP, filtered back-projection), reposent sur un modele mathematiquement parfait de la geometrie d'acquisition. Une alternative a cette methode etalon est appelee reconstruction statistique, ou iterative. Elle permet d'obtenir de meilleurs resultats en presence de bruit ou d'une quantite limitee d'information et peut virtuellement s'adapter a toutes formes

  10. Proteases in agricultural dust induce lung inflammation through PAR-1 and PAR-2 activation.

    PubMed

    Romberger, Debra J; Heires, Art J; Nordgren, Tara M; Souder, Chelsea P; West, William; Liu, Xiang-de; Poole, Jill A; Toews, Myron L; Wyatt, Todd A

    2015-08-15

    Workers exposed to aerosolized dust present in concentrated animal feeding operations (CAFOs) are susceptible to inflammatory lung diseases, such as chronic obstructive pulmonary disease. Extracts of dust collected from hog CAFOs [hog dust extract (HDE)] are potent stimulators of lung inflammatory responses in several model systems. The observation that HDE contains active proteases prompted the present study, which evaluated the role of CAFO dust proteases in lung inflammatory processes and tested whether protease-activated receptors (PARs) are involved in the signaling pathway for these events. We hypothesized that the damaging proinflammatory effect of HDE is due, in part, to the proteolytic activation of PARs, and inhibiting the proteases in HDE or disrupting PAR activation would attenuate HDE-mediated inflammatory indexes in bronchial epithelial cells (BECs), in mouse lung slices in vitro, and in a murine in vivo exposure model. Human BECs and mouse lung slice cultures stimulated with 5% HDE released significantly more of each of the cytokines measured (IL-6, IL-8, TNF-α, keratinocyte-derived chemokine/CXC chemokine ligand 1, and macrophage inflammatory protein-2/CXC chemokine ligand 2) than controls, and these effects were markedly diminished by protease inhibition. Inhibition of PARs also blunted the HDE-induced cytokine release from BECs. In addition, protease depletion inhibited HDE-induced BEC intracellular PKCα and PKCε activation. C57BL/6J mice administered 12.5% HDE intranasally, either once or daily for 3 wk, exhibited increased total cellular and neutrophil influx, bronchial alveolar fluid inflammatory cytokines, lung histopathology, and inflammatory scores compared with mice receiving protease-depleted HDE. These data suggest that proteases in dust from CAFOs are important mediators of lung inflammation, and these proteases and their receptors may provide novel targets for therapeutic intervention in CAFO dust-induced airways disease.

  11. Proteases in agricultural dust induce lung inflammation through PAR-1 and PAR-2 activation.

    PubMed

    Romberger, Debra J; Heires, Art J; Nordgren, Tara M; Souder, Chelsea P; West, William; Liu, Xiang-de; Poole, Jill A; Toews, Myron L; Wyatt, Todd A

    2015-08-15

    Workers exposed to aerosolized dust present in concentrated animal feeding operations (CAFOs) are susceptible to inflammatory lung diseases, such as chronic obstructive pulmonary disease. Extracts of dust collected from hog CAFOs [hog dust extract (HDE)] are potent stimulators of lung inflammatory responses in several model systems. The observation that HDE contains active proteases prompted the present study, which evaluated the role of CAFO dust proteases in lung inflammatory processes and tested whether protease-activated receptors (PARs) are involved in the signaling pathway for these events. We hypothesized that the damaging proinflammatory effect of HDE is due, in part, to the proteolytic activation of PARs, and inhibiting the proteases in HDE or disrupting PAR activation would attenuate HDE-mediated inflammatory indexes in bronchial epithelial cells (BECs), in mouse lung slices in vitro, and in a murine in vivo exposure model. Human BECs and mouse lung slice cultures stimulated with 5% HDE released significantly more of each of the cytokines measured (IL-6, IL-8, TNF-α, keratinocyte-derived chemokine/CXC chemokine ligand 1, and macrophage inflammatory protein-2/CXC chemokine ligand 2) than controls, and these effects were markedly diminished by protease inhibition. Inhibition of PARs also blunted the HDE-induced cytokine release from BECs. In addition, protease depletion inhibited HDE-induced BEC intracellular PKCα and PKCε activation. C57BL/6J mice administered 12.5% HDE intranasally, either once or daily for 3 wk, exhibited increased total cellular and neutrophil influx, bronchial alveolar fluid inflammatory cytokines, lung histopathology, and inflammatory scores compared with mice receiving protease-depleted HDE. These data suggest that proteases in dust from CAFOs are important mediators of lung inflammation, and these proteases and their receptors may provide novel targets for therapeutic intervention in CAFO dust-induced airways disease. PMID

  12. Proteases in agricultural dust induce lung inflammation through PAR-1 and PAR-2 activation

    PubMed Central

    Heires, Art J.; Nordgren, Tara M.; Souder, Chelsea P.; West, William; Liu, Xiang-de; Poole, Jill A.; Toews, Myron L.; Wyatt, Todd A.

    2015-01-01

    Workers exposed to aerosolized dust present in concentrated animal feeding operations (CAFOs) are susceptible to inflammatory lung diseases, such as chronic obstructive pulmonary disease. Extracts of dust collected from hog CAFOs [hog dust extract (HDE)] are potent stimulators of lung inflammatory responses in several model systems. The observation that HDE contains active proteases prompted the present study, which evaluated the role of CAFO dust proteases in lung inflammatory processes and tested whether protease-activated receptors (PARs) are involved in the signaling pathway for these events. We hypothesized that the damaging proinflammatory effect of HDE is due, in part, to the proteolytic activation of PARs, and inhibiting the proteases in HDE or disrupting PAR activation would attenuate HDE-mediated inflammatory indexes in bronchial epithelial cells (BECs), in mouse lung slices in vitro, and in a murine in vivo exposure model. Human BECs and mouse lung slice cultures stimulated with 5% HDE released significantly more of each of the cytokines measured (IL-6, IL-8, TNF-α, keratinocyte-derived chemokine/CXC chemokine ligand 1, and macrophage inflammatory protein-2/CXC chemokine ligand 2) than controls, and these effects were markedly diminished by protease inhibition. Inhibition of PARs also blunted the HDE-induced cytokine release from BECs. In addition, protease depletion inhibited HDE-induced BEC intracellular PKCα and PKCε activation. C57BL/6J mice administered 12.5% HDE intranasally, either once or daily for 3 wk, exhibited increased total cellular and neutrophil influx, bronchial alveolar fluid inflammatory cytokines, lung histopathology, and inflammatory scores compared with mice receiving protease-depleted HDE. These data suggest that proteases in dust from CAFOs are important mediators of lung inflammation, and these proteases and their receptors may provide novel targets for therapeutic intervention in CAFO dust-induced airways disease. PMID

  13. Statistical study of the GPS phase scintillation associated with plasma blobs

    NASA Astrophysics Data System (ADS)

    Jin, Yaqi; Miloch, Wojciech; Moen, Joran

    2016-04-01

    We present a study of the space weather effect of GNSS scintillation in the auroral/polar cap ionosphere with multi-instrument observations, including GNSS scintillation receiver, all-sky imager, and EISCAT radar. We focus on the period when polar cap patches (islands of high density F region plasma with density enhanced more than twice above the surrounding) exit the polar cap. When the patch exits into the nightside auroral region (and then it is termed blob), the GNSS phase scintillation can be enhanced; indicating that the blob is important for the scintillation study [Jin et al., 2014]. In the present study, we expand the data set to see how representative it is. From November of 2010 to February of 2014, 41.4 hours of data from all-sky imager were collected in 16 days when the airglow patches were observed to hit the nightside aurora and when the aurora covered a quarter of the all-sky imager field of view at Ny-Ålesund. The collocated GNSS scintillation receiver is used to study the scintillation impact. This study clearly shows that the scintillation level of a blob is higher than the scintillation level of the corresponding patch. However, no clear relation between the blob scintillation and the pre-conditioning of polar cap patches is found. Furthermore, the aurora alone did not produce strong scintillation. This implies that the aurora plays a role in structuring of the blob and increases its scintillation level. We also look into possible instability mechanisms which produce the plasma density irregularities.

  14. Novel method of producing nanoparticles for gadolinium-scintillator-based digital radiography.

    PubMed

    Lee, Young Kyu; Park, Sung Kwang; Shin, Jung Wook; Oh, Kyung Min; Heo, Seung Uk; Cho, Gyu Seok; Kim, Jin Young; Nam, Sang Hee

    2013-10-01

    Radiation image sensor properties affect the dose of radiation that patients are exposed to in a clinical setting. Numerous radiation imaging systems use scintillators as materials that absorb radiation. Rare-earth scintillators produced from elements such as gadolinium, yttrium, lutetium, and lanthanum have been investigated to improve the properties of radiation imaging systems. Although such rare-earth scintillators are manufactured with a bulk structure, they exhibit low resolution and low efficiency when they are used as conversion devices. Nanoscintillators have been proposed and researched as a possible solution to these problems. According to the research, the optical properties and size of fine scintillators are affected by the sintering temperature used to produce nanoscintillators instead of the existing bulk-structured scintillators. Therefore, the main purpose of this research is to develop radiation-imaging sensors based on nanoscintillators in order to evaluate the quantitative properties of various scintillators produced under various conditions such as sintering temperature. This is accomplished by measuring acquired phantom images, and modulation transfer functions (MTFs) for complementary-symmetry metal-oxide-semiconductor (CMOS) image sensors under the same X-ray conditions. Low-temperature solution combustion was used to produce fine scintillators consisting of 5 wt% of europium as an activator dopant in a Gd2O3 scintillator host. Variations in the characteristics of the fine scintillators were investigated. The characteristics of fine scintillators produced at various sintering temperatures (i.e., 600, 800, or 1000 degrees C) and with a europium concentration of 0.5 wt% were also analyzed to determine the optimal conditions for synthesizing the fine scintillators.

  15. Probabilistic Forecasting of Ionospheric Scintillation and GNSS Receiver Signal Tracking Performance at High Latitudes

    NASA Astrophysics Data System (ADS)

    Prikryl, P.; Sreeja, V.; Aquino, M.; Jayachandran, P. T.

    2012-12-01

    At high latitudes, phase scintillation occurs predominantly on the dayside in the ionospheric footprint of magnetospheric cusp and in the nightside auroral oval. A new technique of probabilistic forecast of phase scintillation occurrence relative to arrival time of high-speed solar wind (HSSW) from coronal holes and interplanetary coronal mass ejections (ICMEs) has recently been proposed [Prikryl et al., 2012]. Cumulative probability distribution functions for the phase scintillation occurrence that are obtained can be specified for low and high (below- and above-median) values of various solar wind plasma parameters. Recent advances in solar wind modeling of HSSW and ICMEs combined with the probabilistic forecasting of scintillation will lead to improved operational space weather forecasting applications. Scintillation forecasting and mitigation techniques need to be developed to avoid potential costly failures of Global Navigation Satellite Systems (GNSS)-based technology in the near future, in particular during the upcoming solar maximum. GNSS receiver tracking performance during severe scintillation conditions can be assessed by the analysis of receiver phase lock loop (PLL) jitter variance. Tracking jitter variance maps [Sreeja et al, 2011] offer a potentially useful tool to provide users with expected tracking conditions, if based on scintillation prediction as proposed above. Scintillation indices are obtained from L1 GPS data collected with the Canadian High Arctic Ionospheric Network (CHAIN). Combined with high rate amplitude and phase data they can be used as input to receiver tracking models to develop scintillation mitigation techniques. References Prikryl, P., P. T. Jayachandran, S. C. Mushini, and I. G. Richardson (2012), Towards the Probabilistic Forecasting of High-Latitude GPS Phase Scintillation, Space Weather, doi:10.1029/2012SW000800, in press. Sreeja, V., M. Aquino, and Z. G. Elmas (2011), Impact of ionospheric scintillation on GNSS receiver

  16. Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera.

    PubMed

    Alhassen, Fares; Kudrolli, Haris; Singh, Bipin; Kim, Sangtaek; Seo, Youngho; Gould, Robert G; Nagarkar, Vivek V

    2011-06-01

    Preclinical SPECT offers a powerful means to understand the molecular pathways of drug interactions in animal models by discovering and testing new pharmaceuticals and therapies for potential clinical applications. A combination of high spatial resolution and sensitivity are required in order to map radiotracer uptake within small animals. Pinhole collimators have been investigated, as they offer high resolution by means of image magnification. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the detection scintillator at steep angles, introducing parallax errors due to variable depth-of-interaction in scintillator material, especially towards the edges of the detector field of view. These parallax errors ultimately limit the resolution of pinhole preclinical SPECT systems, especially for higher energy isotopes that can easily penetrate through millimeters of scintillator material. A pixellated, focused-cut (FC) scintillator, with its pixels laser-cut so that they are collinear with incoming rays, can potentially compensate for these parallax errors and thus improve the system resolution. We performed the first experimental evaluation of a newly developed focused-cut scintillator. We scanned a Tc-99m source across the field of view of pinhole gamma camera with a continuous scintillator, a conventional "straight-cut" (SC) pixellated scintillator, and a focused-cut scintillator, each coupled to an electron-multiplying charge coupled device (EMCCD) detector by a fiber-optic taper, and compared the measured full-width half-maximum (FWHM) values. We show that the FWHMs of the focused-cut scintillator projections are comparable to the FWHMs of the thinner SC scintillator, indicating the effectiveness of the focused-cut scintillator in compensating parallax errors.

  17. Radiation response of inorganic scintillators: Insights from Monte Carlo simulations

    SciTech Connect

    Prange, Micah P.; Wu, Dangxin; Xie, YuLong; Campbell, Luke W.; Gao, Fei; Kerisit, Sebastien N.

    2014-07-24

    The spatial and temporal scales of hot particle thermalization in inorganic scintillators are critical factors determining the extent of second- and third-order nonlinear quenching in regions with high densities of electron-hole pairs, which, in turn, leads to the light yield nonproportionality observed, to some degree, for all inorganic scintillators. Therefore, kinetic Monte Carlo simulations were performed to calculate the distances traveled by hot electrons and holes as well as the time required for the particles to reach thermal energy following γ-ray irradiation. CsI, a common scintillator from the alkali halide class of materials, was used as a model system. Two models of quasi-particle dispersion were evaluated, namely, the effective mass approximation model and a model that relied on the group velocities of electrons and holes determined from band structure calculations. Both models predicted rapid electron-hole pair recombination over short distances (a few nanometers) as well as a significant extent of charge separation between electrons and holes that did not recombine and reached thermal energy. However, the effective mass approximation model predicted much longer electron thermalization distances and times than the group velocity model. Comparison with limited experimental data suggested that the group velocity model provided more accurate predictions. Nonetheless, both models indicated that hole thermalization is faster than electron thermalization and thus is likely to be an important factor determining the extent of third-order nonlinear quenching in high-density regions. The merits of different models of quasi-particle dispersion are also discussed.

  18. Scintillation light from cosmic-ray muons in liquid argon

    NASA Astrophysics Data System (ADS)

    Whittington, D.; Mufson, S.; Howard, B.

    2016-05-01

    This paper reports the results of an experiment to directly measure the time-resolved scintillation signal from the passage of cosmic-ray muons through liquid argon. Scintillation light from these muons is of value to studies of weakly-interacting particles in neutrino experiments and dark matter searches. The experiment was carried out at the TallBo dewar facility at Fermilab using prototype light guide detectors and electronics developed for the Deep Underground Neutrino Experiment. Two models are presented for the time structure of the scintillation light, a phenomenological model and a composite model. Both models find τT = 1.52 μs for the decay time constant of the Ar2* triplet state. These models also show that the identification of the ``early'' light fraction in the phenomenological model, FE ≈ 25% of the signal, with the total light from singlet decays is an underestimate. The total fraction of singlet light is FS ≈ 36%, where the increase over FE is from singlet light emitted by the wavelength shifter through processes with long decay constants. The models were further used to compute the experimental particle identification parameter Fprompt, the fraction of light coming in a short time window after the trigger compared with the light in the total recorded waveform. The models reproduce quite well the typical experimental value ~0.3 found by dark matter and double β-decay experiments, which suggests this parameter provides a robust metric for discriminating electrons and muons from more heavily ionizing particles.

  19. A flexible scintillation light apparatus for rare event searches

    NASA Astrophysics Data System (ADS)

    Bonvicini, V.; Capelli, S.; Cremonesi, O.; Cucciati, G.; Gironi, L.; Pavan, M.; Previtali, E.; Sisti, M.

    2014-11-01

    Compelling experimental evidences of neutrino oscillations and their implication that neutrinos are massive particles have given neutrinoless double beta decay () a central role in astroparticle physics. In fact, the discovery of this elusive decay would be a major breakthrough, unveiling that neutrino and antineutrino are the same particle and that the lepton number is not conserved. It would also impact our efforts to establish the absolute neutrino mass scale and, ultimately, understand elementary particle interaction unification. All current experimental programs to search for are facing with the technical and financial challenge of increasing the experimental mass while maintaining incredibly low levels of spurious background. The new concept described in this paper could be the answer which combines all the features of an ideal experiment: energy resolution, low cost mass scalability, isotope choice flexibility and many powerful handles to make the background negligible. The proposed technology is based on the use of arrays of silicon detectors cooled to 120 K to optimize the collection of the scintillation light emitted by ultra-pure crystals. It is shown that with a 54 kg array of natural CaMoO scintillation detectors of this type it is possible to yield a competitive sensitivity on the half-life of the of Mo as high as years in only 1 year of data taking. The same array made of CaMoO scintillation detectors (to get rid of the continuous background coming from the two neutrino double beta decay of Ca) will instead be capable of achieving the remarkable sensitivity of years on the half-life of Mo in only 1 year of measurement.

  20. A new compact neutron/gamma ray scintillation detector

    NASA Astrophysics Data System (ADS)

    Buffler, A.; Comrie, A. C.; Smit, F. D.; Wörtche, H. J.

    2016-09-01

    Progress towards the realization of a new compact neutron spectrometer is described. The detector is based on EJ299-33 plastic scintillator coupled to silicon photomultipliers, and a digital implementation of pulse shape discrimination is used to separate events associated with neutrons from those associated with gamma rays. The spectrometer will be suitable over the neutron energy range 1-100 MeV, illustrated in this work with measurements made using an AmBe radioisotopic source and quasi-monoenergetic neutron beams produced using a cyclotron.