Science.gov

Sample records for compton diode detectors

  1. Diamond Detectors for Compton Polarimetry

    NASA Astrophysics Data System (ADS)

    Martin, J. W.; Dutta, D.; Narayan, A.; Wang, P.

    2009-12-01

    Parity-violating electron scattering experiments aim to test the standard model of particle physics through precise low-energy determinations of the weak mixing angle. These experiments require determination of the polarization of the incident electron beam to the 1% level or better. An example of this type of experiment is the Q-weak experiment, which will be conducted in Hall C at Jefferson Lab in 2010 and beyond. We are constructing a Compton polarimeter in Hall C to provide continuous monitoring of the polarization with the goal of 1% absolute polarization determination. In our Compton polarimeter, circularly polarized laser light will impinge upon the electron beam. Electrons scattered by the Compton process will be momentum-analyzed in a dipole magnet downstream of the interaction point. A diamond strip tracker will be placed further downstream of the dipole to sense the Compton-scattered electrons and determine their momenta. The design of the polarimeter, focusing on electron detection, and our progress in prototyping and constructing the diamond strip tracker, are discussed.

  2. Why compton-suppressed germanium detector arrays?

    SciTech Connect

    Diamond, R.M.

    1993-10-01

    Nuclear spectroscopic studies have provided a strong incentive to obtain {gamma}-ray detectors with increasingly better energy resolution, higher full-energy peak efficiencies, and greater sensitivity or resolving power. A major step was the introduction of Ge detectors in the early 60`s. But because of the low atomic number of Ge they have a poor response function; a majority of interacting gamma rays of moderate energy Compton scatter out of the detector leaving a large low-energy background. The remedy was to add a Compton-suppression shield made of NaI around the Ge crystal, and if interactions occurred simultaneously in the NaI scintillator and in the Ge detector to veto that event. Efficiencies also increased greatly when an English-Danish collaboration assembled five Ge detectors, each with a NaI suppressor, into the first array at the end of 1980. Obviously, a system of five such detectors gave much better statistics than the usual two bare detectors used for obtaining coincidence data (by a factor of 10). A few years later, another major improvement came with replacement of the NaI suppressors with shields made of the much denser bismuth germanate (BGO) as scintillator, as these could be thinner leading to arrays with of order 20 detectors. Use of such a large number of detectors led to the realization that for cascades of coincident gamma rays, as in going down a band, the improvement in the peak/background ratio observed and already appreciated in going from singles spectra to gated (double-) coincidence spectra continued when doubly-gated triple-coincidence data were compared for the first time to singly-gated double-coincidence ones. The higher-gated spectra were much cleaner and more selective, though with poorer statistics, and the advantages of higher folds and efficiencies led to the proposals for the larger 4{pi} arrays of today, Eurogam and GASP in Europe and Gammasphere in the U.S.

  3. Testing of the BGO Compton-suppression detectors for gammasphere

    SciTech Connect

    Carpenter, M.P.; Ahmad, I.; Annan, G.A.

    1995-08-01

    Gammasphere, the national {gamma}-ray facility, when completed will consist of 110 Compton-suppressed Ge detectors. The bismuth germanate (BGO) Compton-suppression detector system for each Ge detector consists of one tapered hexagonal BGO side shield and one slotted BGO back plug. Due to the geometry of the array, three types of annular shields are required. These types are referred to as B, C and D, and the array consists of 60, 30 and 20 of these units, respectively. Shield types B, C and D have a hexagonal geometry. They are divided into six optically separate sections, each with its own pair of photomultiplier tubes. Argonne assumed responsibility for the procurement and testing of the BGO Compton-suppression units. We received all detectors from the two vendors. In the past year, twenty-four of the B-type detectors were delivered to Stony Brook for evaluation tests. Since the number of crystals to test is quite large (six per detector), we involved undergraduate students working at ANL under the Department of Educational Programs (DEP) in this effort. The quality of students was excellent, and they played a major role in the performance testing of these detectors. Ninety-nine of the hexagonal side shields and 112 backplug detectors were shipped to LBL for use in Gammasphere. The remaining detectors did not meet the performance criteria when they were first delivered and tested and are either at the vendor being repaired or were returned to us for retesting. We anticipate that the remaining detectors will be ready for use in Gammasphere within the next few months.

  4. Compton-edge-based energy calibration of double-sided silicon strip detectors in Compton camera

    NASA Astrophysics Data System (ADS)

    Seo, Hee; Park, Jin Hyung; Kim, Chan Hyeong; Lee, Ju Hahn; Lee, Chun Sik; Sung Lee, Jae

    2011-05-01

    Accurate energy calibration of double-sided silicon strip detectors (DSSDs) is very important, but challenging for high-energy photons. In the present study, the calibration was improved by considering the Compton edge additionally to the existing low-energy calibration points. The result, indeed, was very encouraging. The energy-calibration errors were dramatically reduced, from, on average, 15.5% and 16.9% to 0.47% and 0.31% for the 356 (133Ba) and 662 keV (137Cs) peaks, respectively. The imaging resolution of a double-scattering-type Compton camera using DSSDs as the scatterer detectors, for a 22Na point-like source, also was improved, by ˜9%.

  5. Transition-radiation-Compton-scattering detector for very relativistic nuclei

    NASA Technical Reports Server (NTRS)

    Osborne, W. Z.; Mack, J. E.

    1975-01-01

    The paper presents the design and predicted performance of a large acceptance (2 sq m sr) transition-radiation-Compton-scattering detector system which can be used to measure energy spectra up to several thousand Gev/nucleon for nuclei with Z between 6 and 28, as well as up to 40,000 GeV/nucleon for He. The following circumstances made such a detector system practicable: (1) transition radiation output is proportional to the square of particle charge; (2) output varies at least as rapidly as the square of Lorentz factor over the range from several hundred to several thousand.

  6. Measurement of Compton scattering in phantoms by germanium detectors

    SciTech Connect

    Zasadny, K.R.; Koral, K.F. . Medical Center); Floyd, C.E. Jr.; Jaszczak, R.J. . Dept. of Radiology)

    1990-04-01

    Quantitative Anger-camera tomography requires correction for Compton scattering. The Anger camera spectral-fitting technique can measure scatter fractions at designated positions in an image allowing for correction. To permit verification of those measurements for {sup 131}I, the authors have determined scatter fractions with a high-purity germanium (HPGe) detector and various phantom configurations. The scatter fraction values for {sup 99m}Tc were also measured and are compared to results from Monte Carlo simulation. The phantom consisted of a 22.2 cm diameter {times} 18.6 cm high cylinder filled with water and a 6 cm diameter water-filled sphere placed at various locations inside the cylinder. Radioisotope is added to either the sphere or the cylinder. The source is collimated by an Anger camera collimator and the active area of the HPGe detector is defined by a 0.6 cm diameter hole in a lead shielding mask. Corrections include accounting for the HPGe detector efficiency as a function of gamma-ray energy, the finite energy resolution of detector and the HPGe detector energy resolution compared to that for a NaI(Tl) Anger camera.

  7. Compton rejection for HPGe detectors via real-time pulse shape analysis

    SciTech Connect

    Beckedahl, D; Blair, J J; Friensehner, A; Kammeraad, J E; Kreek, S A; Payne, B; Schmid, G J

    1998-07-31

    A Lawrence Livermore National Laboratory-developed pulse shape analysis (PSA) technique which performs real-time Compton suppression in High Purity Germanium (HPGe) detectors without the use of anti-coincidence detectors is described. Some preliminary measurements of a variety of sources with a standard HPGe detector system and our prototype PSA algorithm have been made and indicate that a reduction in Compton continuum can be achieved via PSA. These measurements represent an initial assessment of the effectiveness of the prototype PSA system for the improvement of spectral quality and future improvements are expected. Additional work is progressing to optimize the effectiveness of the algorithm for Compton rejection in standard HPGe detectors. Work is also progressing to extend the methodology to segmented HPGe detectors which could potentially yield significantly better Compton rejection and gamma-ray ima

  8. Spectral line-diode registry effects with photodiode array detectors

    SciTech Connect

    Winge, R.K.; Fassel, V.A.; Eckels, D.E.

    1986-05-01

    A limitation of photodiode array detectors for spectroscopic intensity measurements relates to the spacing of the diodes and the errors generated when a spectral line is not in exact registry with the diode or diodes from which its intensity is being measured. These misregistry intensity errors, which may be as high as 25 to 30%, are documented for a range of spectral bandwidths and for single diode (pixel) intensities and multiple diode summations of intensities.

  9. X-Rays Compton Detectors For Biomedical Application

    SciTech Connect

    Rossi, Paolo; Fontana, Cristiano Lino; Moschini, Giuliano; Baldazzi, Giuseppe; Navarria, Francesco; Battistella, Andrea; Bello, Michele; Bollini, Dante; Bonvicini, Valter; Rashevsky, Alexander; Zampa, Gianluigi; Zampa, Nicola; Vacchi, Andrea; Gennaro, Gisella; Uzunov, Nikolay

    2011-06-01

    Collimators are usually needed to image sources emitting X-rays that cannot be focused. Alternately, one may employ a Compton Camera (CC) and measure the direction of the incident X-ray by letting it interact with a thin solid, liquid or gaseous material (Tracker) and determine the scattering angle. With respect to collimated cameras, CCs allow higher gamma-ray efficiency in spite of lighter geometry, and may feature comparable spatial resolution. CCs are better when the X-ray energy is high and small setups are required. We review current applications of CCs to Gamma Ray Astronomy and Biomedical systems stressing advantages and drawbacks. As an example, we focus on a particular CC we are developing, which is designed to image small animals administered with marked pharmaceuticals, and assess the bio-distribution and targeting capability of these latter. This camera has to address some requirements: relatively high activity of the imaged objects; detection of gamma-rays of different energies that may range from 140 keV (Tc99m) to 511 keV; presence of gamma and beta radiation with energies up to 2 MeV in case of 188Re. The camera consists of a thin position-sensitive Silicon Drift Detector as Tracker, and a further downstream position-sensitive system employing scintillating crystals and a multi-anode photo-multiplier (Calorimeter). The choice of crystal, pixel size, and detector geometry has been driven by measurements and simulations with the tracking code GEANT4. Spatial resolution, efficiency and scope are discussed.

  10. Sensitivity booster for DOI-PET scanner by utilizing Compton scattering events between detector blocks

    NASA Astrophysics Data System (ADS)

    Yoshida, Eiji; Tashima, Hideaki; Yamaya, Taiga

    2014-11-01

    In a conventional PET scanner, coincidence events are measured with a limited energy window for detection of photoelectric events in order to reject Compton scatter events that occur in a patient, but Compton scatter events caused in detector crystals are also rejected. Scatter events within the patient causes scatter coincidences, but inter crystal scattering (ICS) events have useful information for determining an activity distribution. Some researchers have reported the feasibility of PET scanners based on a Compton camera for tracing ICS into the detector. However, these scanners require expensive semiconductor detectors for high-energy resolution. In the Anger-type block detector, single photons interacting with multiple detectors can be obtained for each interacting position and complete information can be gotten just as for photoelectric events in the single detector. ICS events in the single detector have been used to get coincidence, but single photons interacting with multiple detectors have not been used to get coincidence. In this work, we evaluated effect of sensitivity improvement using Compton kinetics in several types of DOI-PET scanners. The proposed method promises to improve the sensitivity using coincidence events of single photons interacting with multiple detectors, which are identified as the first interaction (FI). FI estimation accuracy can be improved to determine FI validity from the correlation between Compton scatter angles calculated on the coincidence line-of-response. We simulated an animal PET scanner consisting of 42 detectors. Each detector block consists of three types of scintillator crystals (LSO, GSO and GAGG). After the simulation, coincidence events are added as information for several depth-of-interaction (DOI) resolutions. From the simulation results, we concluded the proposed method promises to improve the sensitivity considerably when effective atomic number of a scintillator is low. Also, we showed that FI estimate

  11. The determination of the efficiency of a Compton suppressed HPGe detector using Monte Carlo simulations.

    PubMed

    McNamara, A L; Heijnis, H; Fierro, D; Reinhard, M I

    2012-04-01

    A Compton suppressed high-purity germanium (HPGe) detector is well suited to the analysis of low levels of radioactivity in environmental samples. The difference in geometry, density and composition of environmental calibration standards (e.g. soil) can contribute to excessive experimental uncertainty to the measured efficiency curve. Furthermore multiple detectors, like those used in a Compton suppressed system, can add complexities to the calibration process. Monte Carlo simulations can be a powerful complement in calibrating these types of detector systems, provided enough physical information on the system is known. A full detector model using the Geant4 simulation toolkit is presented and the system is modelled in both the suppressed and unsuppressed mode of operation. The full energy peak efficiencies of radionuclides from a standard source sample is calculated and compared to experimental measurements. The experimental results agree relatively well with the simulated values (within ∼5 - 20%). The simulations show that coincidence losses in the Compton suppression system can cause radionuclide specific effects on the detector efficiency, especially in the Compton suppressed mode of the detector. Additionally since low energy photons are more sensitive to small inaccuracies in the computational detector model than high energy photons, large discrepancies may occur at energies lower than ∼100 keV. PMID:22304994

  12. A measurement method of a detector response function for monochromatic electrons based on the Compton scattering

    NASA Astrophysics Data System (ADS)

    Bakhlanov, S. V.; Bazlov, N. V.; Derbin, A. V.; Drachnev, I. S.; Kayunov, A. S.; Muratova, V. N.; Semenov, D. A.; Unzhakov, E. V.

    2016-06-01

    In this paper we present a method of scintillation detector energy calibration using the gamma-rays. The technique is based on the Compton scattering of gamma-rays in a scintillation detector and subsequent photoelectric absorption of the scattered photon in the Ge-detector. The novelty of this method is that the source of gamma rays, the germanium and scintillation detectors are immediately arranged adjacent to each other. The method presents an effective solution for the detectors consisting of a low atomic number materials, when the ratio between Compton effect and photoelectric absorption is large and the mean path of gamma-rays is comparable to the size of the detector. The technique can be used for the precision measurements of the scintillator light yield dependence on the electron energy.

  13. A Compton-Vetoed Germanium Detector with Increased Sensitivity at Low Energies

    SciTech Connect

    Friedrich, S; Bates, C; Drury, O B; Burks, M; DiPrete, D

    2012-03-29

    The difficulty to directly detect plutonium in spent nuclear fuel due to the high Compton background of the fission products motivates the design of a Gamma detector with improved sensitivity at low energies. We have built such a detector by operating a thin high-purity Ge detector with a large scintillator Compton veto directly behind it. The Ge detector is thin to absorb just the low-energy Pu radiation of interest while minimizing Compton scattering of high energy radiation from the fission products. The subsequent scintillator is large so that forward scattered photons from the Ge detector interact in it at least once to provide an anti-coincidence veto for the Ge detector. For highest sensitivity, additional material in the line-of-sight is minimized, the radioactive sample is kept thin, and its radiation is collimated. We will discuss the instrument design, and demonstrate the feasibility of the approach with a prototype that employs two large CsI scintillator vetoes. Initial spectra of a thin Cs-137 calibration source show a background suppression of a factor of {approx}2.5 at {approx}100 keV, limited by an unexpectedly thick 4 mm dead layer in the Ge detector.

  14. The performance of a single-crystal BGO annulus as a Compton- suppression detector

    SciTech Connect

    Ussery, L.E. ); Matthews, S.K. )

    1991-01-01

    We have tested a single-crystal bismuth-germanate annulus in conjunction with a high-purity germanium detector as a Compton-suppression spectrometer, and have measured gamma-ray energies of up to 6.13 MeV. 1 ref., 9 figs., 2 tabs.

  15. Directional gamma sensing from covariance processing of inter-detector Compton crosstalk energy asymmetries

    NASA Astrophysics Data System (ADS)

    Trainham, R.; Tinsley, J.

    2014-06-01

    Energy asymmetry of inter-detector crosstalk from Compton scattering can be exploited to infer the direction to a gamma source. A covariance approach extracts the correlated crosstalk from data streams to estimate matched signals from Compton gammas split over two detectors. On a covariance map the signal appears as an asymmetric cross diagonal band with axes intercepts at the full photo-peak energy of the original gamma. The asymmetry of the crosstalk band can be processed to determine the direction to the radiation source. The technique does not require detector shadowing, masking, or coded apertures, thus sensitivity is not sacrificed to obtain the directional information. An angular precision of better than 1° of arc is possible, and processing of data streams can be done in real time with very modest computing hardware.

  16. Directional gamma sensing from covariance processing of inter-detector Compton crosstalk energy asymmetries.

    PubMed

    Trainham, R; Tinsley, J

    2014-06-01

    Energy asymmetry of inter-detector crosstalk from Compton scattering can be exploited to infer the direction to a gamma source. A covariance approach extracts the correlated crosstalk from data streams to estimate matched signals from Compton gammas split over two detectors. On a covariance map the signal appears as an asymmetric cross diagonal band with axes intercepts at the full photo-peak energy of the original gamma. The asymmetry of the crosstalk band can be processed to determine the direction to the radiation source. The technique does not require detector shadowing, masking, or coded apertures, thus sensitivity is not sacrificed to obtain the directional information. An angular precision of better than 1° of arc is possible, and processing of data streams can be done in real time with very modest computing hardware. PMID:24985816

  17. High-Resolution Compton-Suppressed CZT Detector for Fission Products Identification

    SciTech Connect

    R. Aryaeinejd; J. K. Hartwell; Wade W. Scates

    2004-10-01

    Room temperature semiconductor CdZnTe (CZT) detectors are currently limited to total detector volumes of 1-2 cm3, which is dictated by the poor charge transport characteristics. Because of this size limitation one of the problems in accurately determining isotope identification is the enormous background from the Compton scattering events. Eliminating this background will not only increase the sensitivity and accuracy of measurements but also help us to resolve peaks buried under the background and peaks in close vicinity of others. We are currently developing a fission products detection system based on the Compton-suppressed CZT detector. In this application, the detection system is required to operate in high radiation fields. Therefore, a small 10x10x5 mm3 CZT detector is placed inside the center of a well-shielded 3" in diameter by 3" long Nal detector. So far we have been able to successfully reduce the Compton background by a factor of 5.4 for a 137Cs spectrum. This reduction of background will definitely enhance the quality of the gamma-ray spectrum in the information-rich energy range below 1 MeV, which consequently increases the detection sensitivity. In this work, we will discuss the performance of this detection system as well as its applications.

  18. Design and First Results of the CoDeX Liquid-Xenon Compton-Imaging Detector

    NASA Astrophysics Data System (ADS)

    Tennyson, Brian; Cahn, Sidney; Bernard, Ethan; Boulton, Elizabeth; Destefano, Nicholas; Edwards, Blair; Hackenburg, Ariana; Horn, Markus; Larsen, Nicole; Nikkel, James; Wahl, Christopher; Gai, Moshe; McKinsey, Daniel

    2016-03-01

    CoDeX (Compton-imaging Detector in Xenon) is an R&D Compton gamma-ray imaging detector that uses 30 kg of xenon in a two-phase time projection chamber. Time projection relative to the initial scintillation signal provides the vertical interaction positions, and either PMT-sensed gas electroluminescence or a charge-sensitive amplifier quantifies the drifted ionization signal. Detector features to enable Compton imaging are a pair of instrumented wire grids added to sense the horizontal position of clouds of drifted electrons that traverse the detector. Each wire is individually amplified in the cold xenon environment. Design choices addressing the thermodynamic and xenon purity constraints of this system will be discussed. We will also discuss the mechanical designs, engineering challenges, and performance of this Compton-imaging detector.

  19. Evaluation of detector material and radiation source position on Compton camera's ability for multitracer imaging.

    PubMed

    Uche, C Z; Round, W H; Cree, M J

    2012-09-01

    We present a study on the effects of detector material, radionuclide source and source position on the Compton camera aimed at realistic characterization of the camera's performance in multitracer imaging as it relates to brain imaging. The GEANT4 Monte Carlo simulation software was used to model the physics of radiation transport and interactions with matter. Silicon (Si) and germanium (Ge) detectors were evaluated for the scatterer, and cadmium zinc telluride (CZT) and cerium-doped lanthanum bromide (LaBr(3):Ce) were considered for the absorber. Image quality analyses suggest that the use of Si as the scatterer and CZT as the absorber would be preferred. Nevertheless, two simulated Compton camera models (Si/CZT and Si/LaBr(3):Ce Compton cameras) that are considered in this study demonstrated good capabilities for multitracer imaging in that four radiotracers within the nuclear medicine energy range are clearly visualized by the cameras. It is found however that beyond a range difference of about 2 cm for (113m)In and (18)F radiotracers in a brain phantom, there may be a need to rotate the Compton camera for efficient brain imaging. PMID:22829298

  20. The millimeter wave super-Schottky diode detector

    NASA Technical Reports Server (NTRS)

    Silver, A. H.; Pedersen, R. J.; Mccoll, M.; Dickman, R. L.; Wilson, W. J.

    1981-01-01

    The 31 and 92 GHz measurements of the superconductor-Schottky diode extended to millimeter wavelengths by a redesign of the semiconductor interface are reported. Diodes were fabricated by pulse electroplating Pb on 2 x 10 to the 19th/cu cm p-Ga-As etched with HCl; a thin Au overplate is deposited to protect the Pb film from degradation and to improve its lifetime. The noise performance was almost ideal at 31 and 92 GHz; it was concluded that this diode is a quantum-limited-detector at 31 GHz, with excessive parasitic losses at 92 GHz.

  1. A Germanium Detector with Optimized Compton Veto for High Sensitivity at Low Energy

    SciTech Connect

    Friedrich, S

    2011-11-30

    We have built a prototype germanium detector with a Compton veto that is optimized for high sensitivity in the low-energy range around {approx}100 keV. It is specifically designed to address the problem to directly detect plutonium gamma emissions in spent nuclear fuel by non-destructive assay. This is not possible with current detectors due to the large low-energy background of Compton-scattered high-energy radiation from the fission products, whose gamma flux is at least 6 to 7 orders of magnitude higher than the Pu signal. Our instrument is designed to assess the feasibility to selectively suppress the background in the low-energy region around {approx}100 keV with the strongest Pu X-ray and gamma emissions lines. It employs a thin Ge detector with a large Compton veto directly behind it to suppress the background from forward-scattered radiation by anti-coincidence vetoing. This report summarizes the design considerations and the performance of the instrument.

  2. Evaluation of Si(Li) detectors for use in Compton telescopes

    SciTech Connect

    Tindall, C.; Hau, I.D.; Luke, P.N.

    2002-05-01

    Si(Li) detectors are currently being developed for use in large Compton telescopes. A major advantage of silicon when compared with germanium is its ability to operate at significantly higher temperature. To determine the feasibility of using Si(Li) detectors in a Compton telescope, their performance as a function of temperature has been studied. We present leakage current, noise data and gamma-ray spectral performance at various temperatures for single 6-mm thick planar devices. It has been determined that for detectors without a guard ring, the noise began to rise significantly around 210K. Adding a guard ring improved the leakage current by about an order of magnitude and reduced the total noise (detector plus electronics) by about 25 percent. The noise of the detectors with {approx}130 mm2 area and a guard ring did not exceed our performance goal of 2 keV FWHM until the temperature was approximately 240K. For 122 keV gamma rays, no evidence of ballistic deficit was seen at 8 ms peaking time and bias voltages corresponding to an internal electric field of {approx}1150 V/cm. Some evidence of ballistic deficit was seen for 662 keV gamma rays at temperatures above 220K.

  3. Applications of Gas Imaging Micro-Well Detectors to an Advanced Compton Telescope

    NASA Technical Reports Server (NTRS)

    Bloser, P. F.; Hunter, S. D.; Ryan, J. M.; McConnell, M. L.; Miller, R. S.; Jackson, T. N.; Bai, B.; Jung, S.

    2003-01-01

    We present a concept for an Advanced Compton Telescope (ACT) based on the use of pixelized gas micro-well detectors to form a three-dimensional electron track imager. A micro-well detector consists of an array of individual micro-patterned proportional counters opposite a planar drift electrode. When combined with thin film transistor array readouts, large gas volumes may be imaged with very good spatial and energy resolution at reasonable cost. The third dimension is determined by timing the drift of the ionization electrons. The primary advantage of this approach is the excellent tracking of the Compton recoil electron that is possible in a gas volume. Such good electron tracking allows us to reduce the point spread function of a single incident photon dramatically, greatly improving the imaging capability and sensitivity. The polarization sensitivity, which relies on events with large Compton scattering angles, is particularly enhanced. We describe a possible ACT implementation of this technique, in which the gas tracking volume is surrounded by a CsI calorimeter, and present our plans to build and test a small prototype over the next three years.

  4. Core-shell diodes for particle detectors

    NASA Astrophysics Data System (ADS)

    Jia, Guobin; Plentz, Jonathan; Höger, Ingmar; Dellith, Jan; Dellith, Andrea; Falk, Fritz

    2016-02-01

    High performance particle detectors are needed for fundamental research in high energy physics in the exploration of the Higgs boson, dark matter, anti-matter, gravitational waves and proof of the standard model, which will extend the understanding of our Universe. Future particle detectors should have ultrahigh radiation hardness, low power consumption, high spatial resolution and fast signal response. Unfortunately, some of these properties are counter-influencing for the conventional silicon drift detectors (SDDs), so that they cannot be optimized simultaneously. In this paper, the main issues of conventional SDDs have been analyzed, and a novel core-shell detector design based on micro- and nano-structures etched into Si-wafers is proposed. It is expected to simultaneously reach ultrahigh radiation hardness, low power consumption, fast signal response and high spatial resolution down to the sub-micrometer range, which will probably meet the requirements for the most powerful particle accelerators in the near future. A prototype core-shell detector was fabricated using modern silicon nanotechnology and the functionality was tested using electron-beam-induced current measurements. Such a high performance detector will open many new applications in extreme radiation environments such as high energy physics, astrophysics, high resolution (bio-) imaging and crystallography, which will push these fields beyond their current boundaries.

  5. Spectrometry and dosimetry of fast neutrons using pin diode detectors

    NASA Astrophysics Data System (ADS)

    Zaki Dizaji, H.; Kakavand, T.; Abbasi Davani, F.

    2014-03-01

    Elastic scattering of light nuclei, especially hydrogen, is widely used for detection of fast neutrons. Semiconductor devices based on silicon detectors are frequently used for different radiation detections. In this work, a neutron spectrometer consisting of a pin diode coupled with a polyethylene converter and aluminum degrader layers has been developed. Aluminum layers are used as discriminators of different neutron energies for detectors. The response of the converter-degrader-pin diode configuration, the optimum thickness of the converter and the degrader layers have been extracted using MCNP and SRIM simulation codes. The possibility of using this type of detector for fast neutron spectrometry and dosimetry has been investigated. A fairly good agreement was seen between neutron energy spectrum and dose obtained from our configurations and these specifications from an 241Am-Be neutron source.

  6. Application of AXUV diode detectors at ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Bernert, M.; Eich, T.; Burckhart, A.; Fuchs, J. C.; Giannone, L.; Kallenbach, A.; McDermott, R. M.; Sieglin, B.

    2014-03-01

    In the ASDEX Upgrade tokamak, a radiation measurement for a wide spectral range, based on semiconductor detectors, with 256 lines of sight and a time resolution of 5μs was recently installed. In combination with the foil based bolometry, it is now possible to estimate the absolutely calibrated radiated power of the plasma on fast timescales. This work introduces this diagnostic based on AXUV (Absolute eXtended UltraViolet) n-on-p diodes made by International Radiation Detectors, Inc. The measurement and the degradation of the diodes in a tokamak environment is shown. Even though the AXUV diodes are developed to have a constant sensitivity for all photon energies (1 eV-8 keV), degradation leads to a photon energy dependence of the sensitivity. The foil bolometry, which is restricted to a time resolution of less than 1 kHz, offers a basis for a time dependent calibration of the diodes. The measurements of the quasi-calibrated diodes are compared with the foil bolometry and found to be accurate on the kHz time scale. Therefore, it is assumed, that the corrected values are also valid for the highest time resolution (200 kHz). With this improved diagnostic setup, the radiation induced by edge localized modes is analyzed on fast timescales.

  7. Application of AXUV diode detectors at ASDEX Upgrade.

    PubMed

    Bernert, M; Eich, T; Burckhart, A; Fuchs, J C; Giannone, L; Kallenbach, A; McDermott, R M; Sieglin, B

    2014-03-01

    In the ASDEX Upgrade tokamak, a radiation measurement for a wide spectral range, based on semiconductor detectors, with 256 lines of sight and a time resolution of 5 μs was recently installed. In combination with the foil based bolometry, it is now possible to estimate the absolutely calibrated radiated power of the plasma on fast timescales. This work introduces this diagnostic based on AXUV (Absolute eXtended UltraViolet) n-on-p diodes made by International Radiation Detectors, Inc. The measurement and the degradation of the diodes in a tokamak environment is shown. Even though the AXUV diodes are developed to have a constant sensitivity for all photon energies (1 eV-8 keV), degradation leads to a photon energy dependence of the sensitivity. The foil bolometry, which is restricted to a time resolution of less than 1 kHz, offers a basis for a time dependent calibration of the diodes. The measurements of the quasi-calibrated diodes are compared with the foil bolometry and found to be accurate on the kHz time scale. Therefore, it is assumed, that the corrected values are also valid for the highest time resolution (200 kHz). With this improved diagnostic setup, the radiation induced by edge localized modes is analyzed on fast timescales. PMID:24689581

  8. Application of AXUV diode detectors at ASDEX Upgrade

    SciTech Connect

    Bernert, M. Eich, T.; Burckhart, A.; Fuchs, J. C.; Giannone, L.; Kallenbach, A.; McDermott, R. M.; Sieglin, B.

    2014-03-15

    In the ASDEX Upgrade tokamak, a radiation measurement for a wide spectral range, based on semiconductor detectors, with 256 lines of sight and a time resolution of 5μs was recently installed. In combination with the foil based bolometry, it is now possible to estimate the absolutely calibrated radiated power of the plasma on fast timescales. This work introduces this diagnostic based on AXUV (Absolute eXtended UltraViolet) n-on-p diodes made by International Radiation Detectors, Inc. The measurement and the degradation of the diodes in a tokamak environment is shown. Even though the AXUV diodes are developed to have a constant sensitivity for all photon energies (1 eV-8 keV), degradation leads to a photon energy dependence of the sensitivity. The foil bolometry, which is restricted to a time resolution of less than 1 kHz, offers a basis for a time dependent calibration of the diodes. The measurements of the quasi-calibrated diodes are compared with the foil bolometry and found to be accurate on the kHz time scale. Therefore, it is assumed, that the corrected values are also valid for the highest time resolution (200 kHz). With this improved diagnostic setup, the radiation induced by edge localized modes is analyzed on fast timescales.

  9. Dead layer measurements on diode detectors

    NASA Astrophysics Data System (ADS)

    Danagoulian, Areg; Barron-Palos, Libertad; Klein, Andreas; Wilburn, Scott

    2007-10-01

    The goal of the abBA experiment involves coincidence measurements of protons and electrons from the neutron beta decay. While electron detection is rather straightforward, the detection of the protons is complicated due to their low energies. In order to understand the detector reponse and to determine the lower cut off value for the energy a technique for determining the thickness of the dead layer has been developed. A discussion of the measurement and of the results will be presented.

  10. Dual diode detector for homodyne EPR microwave bridges

    NASA Astrophysics Data System (ADS)

    Koscielniak, Janusz; Berliner, Lawrence J.

    1994-07-01

    After low noise FET amplifiers found widespread use in both X-band and low-frequency systems, it became possible to use multidiode mixers for signal detection. Here, a novel dual diode mixer is described for use in homodyne microwave bridges for both cw and pulsed electron paramagnetic resonance spectrometers. The structure is composed of a 90° hybrid coupler and separate detectors in two arms. The device provides common mode rejection of noise-like regular balanced mixers but, by making diode dc currents accessible, offers big advantages for tuning of the bridge when low Q sample probes are used. Although the use of this detector does not affect sensitivity directly, tuning precision and increased long-term stability leads to unexpected improvements.

  11. DSSD detectors development PACT, a new space Compton telescope at the horizon 2025

    NASA Astrophysics Data System (ADS)

    Laurent, P.; Khalil, M.; Dolgorouki, Y.; Bertoli, W.; Oger, R.; Bréelle, E.

    2015-07-01

    PACT is a Pair and Compton telescope that aims to make a sensitive survey of the gamma-ray sky between 100 keV and 100 MeV . It will be devoted to the detection of radioactivity lines from present and past supernova explosions, the observation of thousands of new blazars, and the study of polarized radiations from gamma-ray bursts, pulsars and accreting black holes. It will reach a sensitivity of one to two orders of magnitude lower than COMPTEL/CGRO (e.g. about 50 times lower for the broad-band, survey sensitivity at 1 MeV after 5 years). The PACT telescope is based upon three main components: a silicon-based gamma-ray tracker, a crystal-based calorimeter (e.g. CeBr3), and an anticoincidence detector made of plastic scintillator panels. Prototypes of the Silicon detector planes have been optimized and are currently tested in the APC laboratory.

  12. Development of an anti-Compton veto for HPGe detectors operated in liquid argon using silicon photo-multipliers

    NASA Astrophysics Data System (ADS)

    Janicskó Csáthy, J.; Aghaei Khozani, H.; Caldwell, A.; Liu, X.; Majorovits, B.

    2011-10-01

    A proof of concept detector is presented for scintillation light detection in liquid argon using silicon photo-multipliers. The aim of the work is to build an anti-Compton veto for germanium detectors operated directly in liquid argon as in the GERDA experiment. Wavelength shifting fibers are used to collect the scintillation light and to guide it to Multi-Pixel Photon Counters (MPPC). Sufficient light yield was achieved to realize an effective anti-Compton veto. Properties of the MPPC were studied at cryogenic temperatures and are additionally reported.

  13. Monte-Carlo optimisation of a Compton suppression system for use with a broad-energy HPGe detector

    NASA Astrophysics Data System (ADS)

    Britton, R.; Burnett, J. L.; Davies, A. V.; Regan, P. H.

    2014-10-01

    Monte-Carlo simulations are used to evaluate and optimise multiple components of a Compton Suppression System based upon a Broad-energy HPGe primary detector. Several materials for the secondary crystal are evaluated, including NaI(Tl), BGO and LaBr3(Ce). BGO was found to be the most effective across the required energy range, with the sizes of the proposed veto detector then optimised to extract the maximum performance for a given volume of material. Suppression factors are calculated for a range of nuclides (both single and cascade emitters) with improvements of 2 for the Compton Suppression Factors, and 10 for the continuum reduction when compared to the Compton suppression system currently in use. This equates to a reduction in the continuum by up to a factor of ~240 for radionuclides such as 60Co, which is crucial for the detection of low-energy, low-activity γ emitters typically swamped by such a continuum.

  14. Iterative Monte Carlo simulation with the Compton kinematics-based GEB in a plastic scintillation detector

    NASA Astrophysics Data System (ADS)

    Kim, Chankyu; Kim, Yewon; Moon, Myungkook; Cho, Gyuseong

    2015-09-01

    Plastic scintillators have been used for gamma ray detection in the fields of dosimetry and homeland security because of their desired characteristics such as a fast decay time, a low production cost, availability in a large-scale, and a tissue-equivalence. Gaussian energy broadening (GEB) in MCNP simulation is an effective treatment for tallies to calculate the broadened response function of a detector similarly to measured spectra. The full width at half maximum (FWHM) of a photopeak has been generally used to compute input parameters required for the GEB treatment. However, it is hard to find the photopeak in measured gamma spectra with plastic scintillators so that computation of the input parameters for the GEB has to be taken with another way. In this study, an iterative method for the GEB treated MCNP simulation to calculate the response function of a plastic scintillator is suggested. Instead of the photopeak, Compton maximum and Compton edge were used to estimate energy broadening in the measured spectra and to determine the GEB parameters. In a demonstration with a CsI(Tl) scintillator, the proposed iterative simulation showed the similar gamma spectra to the existing method using photopeaks. The proposed method was then applied to a polystyrene scintillator, and the simulation result were in agreement with the measured spectra with only a little iteration.

  15. Compton polarimeter as a focal plane detector for hard X-ray telescope

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, T.; Vadawale, S. V.

    X-ray polarimetry is expected to provide unique opportunity to study the behavior of matter and radiation under extreme magnetic fields and extreme gravitational fields. However sensitivity of the X-ray polarimeters has always been an issue for the last three decades; there is almost no progress in this field whereas there is a significant advance in the fields of X-ray spectroscopy, imaging and timing. Recently significant improvement in the sensitivity is expected in polarimetric measurements using GEM-based photoelectron tracking polarimeters coupled to soft X-ray telescopes. However they are sensitive in the soft X-ray regime. On the other hand mostly for the X-ray sources higher degree of polarisation at hard X-rays is expected because of the dominance of nonthermal X-ray emission mechanisms over the thermal counterpart. So polarisation measurement in hard X-ray can yield significant insights into such processes. Of late with the advent of high energy focussing telescopes (e.g. Nu STAR, ASTRO-H), sensitivity of X-ray detectors in hard X-ray range is expected to improve significantly. In this context we explore feasibility of a focal plane hard X-ray polarimeter based on Compton scattering having a thin plastic scatterer surrounded by cylindrical array of scintillator detectors. We have carried out detailed Geant4 simulations to estimate the modulation factor for 100% polarized beam as well as polarimetric efficiency of this configuration. Polarimetric sensitivity of the instrument critically depends on low energy threshold in central plastic scatterer. We estimated the sensitivity for a range of plastic threshold energy. We also discuss the methodology to measure the threshold energy in plastic scatterer. Here we present the initial results of polarisation sensitivities of such focal plane Compton polarimeter coupled with the reflection efficiency of present era hard X-ray optics and the experimental results for threshold measurements in plastic.

  16. Evaluation of Compton gamma camera prototype based on pixelated CdTe detectors.

    PubMed

    Calderón, Y; Chmeissani, M; Kolstein, M; De Lorenzo, G

    2014-06-01

    A proposed Compton camera prototype based on pixelated CdTe is simulated and evaluated in order to establish its feasibility and expected performance in real laboratory tests. The system is based on module units containing a 2×4 array of square CdTe detectors of 10×10 mm(2) area and 2 mm thickness. The detectors are pixelated and stacked forming a 3D detector with voxel sizes of 2 × 1 × 2 mm(3). The camera performance is simulated with Geant4-based Architecture for Medicine-Oriented Simulations(GAMOS) and the Origin Ensemble(OE) algorithm is used for the image reconstruction. The simulation shows that the camera can operate with up to 10(4) Bq source activities with equal efficiency and is completely saturated at 10(9) Bq. The efficiency of the system is evaluated using a simulated (18) F point source phantom in the center of the Field-of-View (FOV) achieving an intrinsic efficiency of 0.4 counts per second per kilobecquerel. The spatial resolution measured from the point spread function (PSF) shows a FWHM of 1.5 mm along the direction perpendicular to the scatterer, making it possible to distinguish two points at 3 mm separation with a peak-to-valley ratio of 8. PMID:24932209

  17. New uncooled thermal IR detector using silicon-diode-micromachined isolated silicon diode for IR detection (MISIR)

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Kwan; Han, Chul-Hi

    2000-12-01

    A new thermal infrared detector using temperature characteristics of a diode has been developed. This micromachined isolated silicon diode for IR detection (MISIR) utilizes an electrochemical etching technique to achieve the thermal isolation of the diode. Experimental dependence of the diode current on the junction temperature enables a high responsivity of the MISIR and the electrochemical etch stop provides an effective isolation at simple and low-cost. The fabricated MISIR has demonstrated a detectivity of 1.2x1010(cm(DOT)HzHLF/W) at room temperature in air ambient.

  18. Photo-detectors integrated with resonant tunneling diodes.

    PubMed

    Romeira, Bruno; Pessoa, Luis M; Salgado, Henrique M; Ironside, Charles N; Figueiredo, José M L

    2013-01-01

    We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems. PMID:23881142

  19. Photo-Detectors Integrated with Resonant Tunneling Diodes

    PubMed Central

    Romeira, Bruno; Pessoa, Luis M.; Salgado, Henrique M.; Ironside, Charles N.; Figueiredo, José M. L.

    2013-01-01

    We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems. PMID:23881142

  20. The detector response matrices of the burst and transient source experiment (BATSE) on the Compton Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Pendleton, Geoffrey N.; Paciesas, William S.; Mallozzi, Robert S.; Koshut, Tom M.; Fishman, Gerald J.; Meegan, Charles A.; Wilson, Robert B.; Horack, John M.; Lestrade, John Patrick

    1995-01-01

    The detector response matrices for the Burst And Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory (CGRO) are described, including their creation and operation in data analysis. These response matrices are a detailed abstract representation of the gamma-ray detectors' operating characteristics that are needed for data analysis. They are constructed from an extensive set of calibration data coupled with a complex geometry electromagnetic cascade Monte Carlo simulation code. The calibration tests and simulation algorithm optimization are described. The characteristics of the BATSE detectors in the spacecraft environment are also described.

  1. Flat-response x-ray-diode-detector development

    SciTech Connect

    Tirsell, G.

    1982-10-01

    In this report we discuss the design of an improved sub-nanosecond flat response x-ray diode detector needed for ICF diagnostics. This device consists of a high Z cathode and a complex filter tailored to flatten the response so that the total x-ray energy below 1.5 keV can be measured using a single detector. Three major problems have become evident as a result of our work with the original LLNL design including deviation from flatness due to a peak in the response below 200 eV, saturation at relatively low x-ray fluences, and long term gold cathode instability. We are investigating grazing incidence reflection to reduce the response below 200 eV, new high Z cathode materials for long term stability, and a new complex filter for improved flatness. Better saturation performance will require a modified XRD detector under development with reduced anode to cathode spacing and increased anode bias voltage.

  2. Determination of electron beam polarization using electron detector in Compton polarimeter with less than 1% statistical and systematic uncertainty

    NASA Astrophysics Data System (ADS)

    Narayan, Amrendra

    The Q-weak experiment aims to measure the weak charge of proton with a precision of 4.2%. The proposed precision on weak charge required a 2.5% measurement of the parity violating asymmetry in elastic electron - proton scattering. Polarimetry was the largest experimental contribution to this uncertainty and a new Compton polarimeter was installed in Hall C at Jefferson Lab to make the goal achievable. In this polarimeter the electron beam collides with green laser light in a low gain Fabry-Perot Cavity; the scattered electrons are detected in 4 planes of a novel diamond micro strip detector while the back scattered photons are detected in lead tungstate crystals. This diamond micro-strip detector is the first such device to be used as a tracking detector in a nuclear and particle physics experiment. The diamond detectors are read out using custom built electronic modules that include a preamplifier, a pulse shaping amplifier and a discriminator for each detector micro-strip. We use field programmable gate array based general purpose logic modules for event selection and histogramming. Extensive Monte Carlo simulations and data acquisition simulations were performed to estimate the systematic uncertainties. Additionally, the Moller and Compton polarimeters were cross calibrated at low electron beam currents using a series of interleaved measurements. In this dissertation, we describe all the subsystems of the Compton polarimeter with emphasis on the electron detector. We focus on the FPGA based data acquisition system built by the author and the data analysis methods implemented by the author. The simulations of the data acquisition and the polarimeter that helped rigorously establish the systematic uncertainties of the polarimeter are also elaborated, resulting in the first sub 1% measurement of low energy (~1GeV) electron beam polarization with a Compton electron detector. We have demonstrated that diamond based micro-strip detectors can be used for tracking in a

  3. Determination of electron beam polarization using electron detector in Compton polarimeter with less than 1% statistical and systematic uncertainty

    SciTech Connect

    Narayan, Amrendra

    2015-05-01

    The Q-weak experiment aims to measure the weak charge of proton with a precision of 4.2%. The proposed precision on weak charge required a 2.5% measurement of the parity violating asymmetry in elastic electron - proton scattering. Polarimetry was the largest experimental contribution to this uncertainty and a new Compton polarimeter was installed in Hall C at Jefferson Lab to make the goal achievable. In this polarimeter the electron beam collides with green laser light in a low gain Fabry-Perot Cavity; the scattered electrons are detected in 4 planes of a novel diamond micro strip detector while the back scattered photons are detected in lead tungstate crystals. This diamond micro-strip detector is the first such device to be used as a tracking detector in a nuclear and particle physics experiment. The diamond detectors are read out using custom built electronic modules that include a preamplifier, a pulse shaping amplifier and a discriminator for each detector micro-strip. We use field programmable gate array based general purpose logic modules for event selection and histogramming. Extensive Monte Carlo simulations and data acquisition simulations were performed to estimate the systematic uncertainties. Additionally, the Moller and Compton polarimeters were cross calibrated at low electron beam currents using a series of interleaved measurements. In this dissertation, we describe all the subsystems of the Compton polarimeter with emphasis on the electron detector. We focus on the FPGA based data acquisition system built by the author and the data analysis methods implemented by the author. The simulations of the data acquisition and the polarimeter that helped rigorously establish the systematic uncertainties of the polarimeter are also elaborated, resulting in the first sub 1% measurement of low energy (?1 GeV) electron beam polarization with a Compton electron detector. We have demonstrated that diamond based micro-strip detectors can be used for tracking in a

  4. Microwave detectors based on the spin-torque diode effect

    NASA Astrophysics Data System (ADS)

    Prokopenko, O. V.; Slavin, A. N.

    2015-05-01

    The spin-transfer torque (STT) effect provides a new method of manipulation of magnetization in nanoscale objects. The STT effect manifests itself as a transfer of spin angular momentum between the parallel magnetic layers separated by a nonmagnetic spacer and traversed by a dc electric current. The transfer of the spin angular momentum from one layer to another could result in the excitation of the microwave-frequency magnetization dynamics in one of the magnetic layers. On the other hand, when a magnetization dynamics is excited in a magnetic layered structure by an external microwave signal both the structure electrical resistance and current through the structure will acquire microwave components resulting in the appearance of a rectified dc voltage on the magnetic structure. This "spin-torque diode effect" can be used for the development of ultra-sensitive spin-torque microwave detectors (STMD). Below we present a brief review of our recent work on the general properties of STMDs, analyze the performance of the "resonance-type" and "threshold-type STMD" and consider the possible applications for such microwave detectors.

  5. Spectral perturbations from silicon diode detector encapsulation and shielding in photon fields

    SciTech Connect

    Eklund, Karin; Ahnesjoe, Anders

    2010-11-15

    Purpose: Silicon diodes are widely used as detectors for relative dose measurements in radiotherapy. The common manufacturing practice is to encapsulate the diodes in plastic for protection and to facilitate mounting in scanning devices. Diodes intended for use in photon fields commonly also have a shield of a high atomic number material (usually tungsten) integrated into the encapsulation to selectively absorb low-energy photons to which silicon diodes would otherwise over-response. However, new response models based on cavity theories and spectra calculations have been proposed for direct correction of the readout from unshielded (e.g., ''electron'') diodes used in photon fields. This raises the question whether it is correct to assume that the spectrum in a water phantom at the location of the detector cavity is not perturbed by the detector encapsulation materials. The aim of this work is to investigate the spectral effects of typical encapsulations, including shielding, used for clinical diodes. Methods: The effects of detector encapsulation of an unshielded and a shielded commercial diode on the spectra at the detector cavity location are studied through Monte Carlo simulations with PENELOPE-2005. Variance reduction based on correlated sampling is applied to reduce the CPU time needed for the simulations. Results: The use of correlated sampling is found to be efficient and to not introduce any significant bias to the results. Compared to reference spectra calculated in water, the encapsulation for an unshielded diode is demonstrated to not perturb the spectrum, while a tungsten shielded diode caused not only the desired decrease in low-energy scattered photons but also a large increase of the primary electron fluence. Measurements with a shielded diode in a 6 MV photon beam proved that the shielding does not completely remove the field-size dependence of the detector response caused by the over-response from low-energy photons. Response factors of a properly

  6. Optimizing diode thickness for thin-film solid state thermal neutron detectors

    SciTech Connect

    Murphy, John W.; Mejia, Israel; Quevedo-Lopez, Manuel A.; Gnade, Bruce; Kunnen, George R.; Allee, David

    2012-10-01

    In this work, we investigate the optimal thickness of a semiconductor diode for thin-film solid state thermal neutron detectors. We evaluate several diode materials, Si, CdTe, GaAs, C (diamond), and ZnO, and two neutron converter materials, {sup 10}B and {sup 6}LiF. Investigating a coplanar diode/converter geometry, we determine the minimum semiconductor thickness needed to achieve maximum neutron detection efficiency. By keeping the semiconductor thickness to a minimum, gamma rejection is kept as high as possible. In this way, we optimize detector performance for different thin-film semiconductor materials.

  7. Development of Gamma-Ray Compton Imager Using Room-Temperature 3-D Position Sensitive Semiconductor Detectors

    SciTech Connect

    Zhong He; David Whe; Glenn Knoll

    2003-05-14

    During the three years of this project, two 3-dimensional position sensitive CdZnTe spectrometers were upgraded in collaboration with Johns Hopkins University Applied Physics Laboratory. A prototype Compton-scattering gamma-ray imager was assembled using the two upgraded CdZnTe detectors. The performance of both gamma-ray spectrometers were individually tested. The angular resolution and detection sensitivity of the imaging system were measured using both a point and a line-shaped 137 Cs radiation source. The measurement results are consistent with that obtained from Monte-Carlo simulations performed during the early phase of the project.

  8. EVALUATION OF SILICON DIODES AS IN-SITU CRYOGENIC FIELD EMISSION DETECTORS FOR SRF CAVITY DEVELOPMENT

    SciTech Connect

    Ari Palczewski, Rongli Geng

    2012-07-01

    We performed in-situ cryogenic testing of four silicon diodes as possible candidates for field emission (FE) monitors of superconducting radio frequency (SRF) cavities during qualification testing and in accelerator cryo-modules. We evaluated diodes from 2 companies - from Hamamatsu corporation model S1223-01; and from OSI Optoelectronics models OSD35-LR-A, XUV-50C, and FIL-UV20. The measurements were done by placing the diodes in superfluid liquid helium near the top of a field emitting 9-cell cavity during its vertical test. For each diode, we will discuss their viability as a 2K cryogenic detector for FE mapping of SRF cavities and the directionality of S1223-01 in such environments. We will also present calibration curves between the diodes and JLab's standard radiation detector placed above the Dewar's top plate.

  9. Measuring multimegavolt pulsed voltages using Compton-generated electrons

    NASA Astrophysics Data System (ADS)

    Swanekamp, S. B.; Weber, B. V.; Pereira, N. R.; Hinshelwood, D. D.; Stephanakis, S. J.; Young, F. C.

    2004-01-01

    The "Compton-Hall" voltmeter is a radiation-based voltage diagnostic that has been developed to measure voltages on high-power (TW) pulsed generators. The instrument collimates photons generated from bremsstrahlung produced in the diode onto an aluminum target to generate Compton-generated electrons. Permanent magnets bend the Compton electron orbits that escape the target toward a silicon pin diode detector. A GaAs photoconductive detector (PCD) detects photons that pass through the Compton target. The diode voltage is determined from the ratio of the electron dose in the pin detector to the x-ray dose in the PCD. The Integrated Tiger Series of electron-photon transport codes is used to determine the relationship between the measured dose ratio and the diode voltage. Variations in the electron beam's angle of incidence on the bremsstrahlung target produce changes in the shape of the photon spectrum that lead to large variations in the voltage inferred from the voltmeter. The voltage uncertainty is minimized when the voltmeter is fielded at an angle of 45° with respect to the bremsstrahlung target. In this position, the photon spectra for different angles of incidence all converge onto a single spectrum reducing the uncertainty in the voltage to less than 10% for voltages below 4 MV. Higher and lower voltages than the range considered in this article can be measured by adjusting the strength of the applied magnetic field or the position of the electron detector relative to the Compton target. The instrument was fielded on the Gamble II pulsed-power generator configured with a plasma opening switch. Measurements produced a time-dependent voltage with a peak (3.7 MV) that agrees with nuclear activation measurements and a pulse shape that is consistent with the measured radiation pulse shape.

  10. Low energy gamma ray observations with the MPI-Compton telescope. [balloon-borne detectors

    NASA Technical Reports Server (NTRS)

    Graml, F.; Penningsfeld, F. P.; Schoenfelder, V.

    1978-01-01

    Although the evaluation of data from the first balloon-flight of a large area Compton telescope is incomplete, two preliminary results are discussed. From the measured background spectrum at float altitude, the sensitivity of the telescope for the detection of cosmic gamma ray lines is estimated. The energy spectra is determined for an enhanced gamma ray flux observed from the direction of the Seyfert galaxy NGC 4151. A schematic drawing of the telescope is presented and discussed.

  11. Bandpass x-ray diode and x-ray multiplier detector

    DOEpatents

    Wang, C.L.

    1982-09-27

    An absorption-edge of an x-ray absorption filter and a quantum jump of a photocathode determine the bandpass characteristics of an x-ray diode detector. An anode, which collects the photoelectrons emitted by the photocathode, has enhanced amplification provided by photoelectron-multiplying means which include dynodes or a microchannel-plate electron-multiplier. Suppression of undesired high frequency response for a bandpass x-ray diode is provided by subtracting a signal representative of energies above the passband from a signal representative of the overall response of the bandpass diode.

  12. Performance evaluation of a lossy transmission lines based diode detector at cryogenic temperature

    NASA Astrophysics Data System (ADS)

    Villa, E.; Aja, B.; de la Fuente, L.; Artal, E.

    2016-01-01

    This work is focused on the design, fabrication, and performance analysis of a square-law Schottky diode detector based on lossy transmission lines working under cryogenic temperature (15 K). The design analysis of a microwave detector, based on a planar gallium-arsenide low effective Schottky barrier height diode, is reported, which is aimed for achieving large input return loss as well as flat sensitivity versus frequency. The designed circuit demonstrates good sensitivity, as well as a good return loss in a wide bandwidth at Ka-band, at both room (300 K) and cryogenic (15 K) temperatures. A good sensitivity of 1000 mV/mW and input return loss better than 12 dB have been achieved when it works as a zero-bias Schottky diode detector at room temperature, increasing the sensitivity up to a minimum of 2200 mV/mW, with the need of a DC bias current, at cryogenic temperature.

  13. Performance evaluation of a lossy transmission lines based diode detector at cryogenic temperature.

    PubMed

    Villa, E; Aja, B; de la Fuente, L; Artal, E

    2016-01-01

    This work is focused on the design, fabrication, and performance analysis of a square-law Schottky diode detector based on lossy transmission lines working under cryogenic temperature (15 K). The design analysis of a microwave detector, based on a planar gallium-arsenide low effective Schottky barrier height diode, is reported, which is aimed for achieving large input return loss as well as flat sensitivity versus frequency. The designed circuit demonstrates good sensitivity, as well as a good return loss in a wide bandwidth at Ka-band, at both room (300 K) and cryogenic (15 K) temperatures. A good sensitivity of 1000 mV/mW and input return loss better than 12 dB have been achieved when it works as a zero-bias Schottky diode detector at room temperature, increasing the sensitivity up to a minimum of 2200 mV/mW, with the need of a DC bias current, at cryogenic temperature. PMID:26827340

  14. Detection of nitrite by flow injection analysis using a novel paired emitter-detector diode (PEDD) as a photometric detector

    NASA Astrophysics Data System (ADS)

    O'Toole, Martina; Shepherd, Roderick; Lau, King-Tong; Diamond, Dermot

    2007-09-01

    An inexpensive flow injection analysis system for determining low concentration levels of nitrite employing the Griess reagent spectrophotometric method is reported. The novel photometric detector applied within this manifold is a highly sensitive, low cost, miniaturized light emitting diode (LED) based flow detector. This colorimetric detector employs two LEDs, operating one as a light source and the other as a light detector. The emitter LED is forward biased and the detector reverse biased. The emitter and detector LED had a λmax of 530 nm and 623 nm respectively. The emission spectrum of the emitter LED efficiently overlapped with the absorbance spectrum of 9 µM NO2 and Griess reagent complex. A simple timer circuit measures the time taken for the photocurrent generated by the emitter LED to discharge the detector LED from 5 V (logic 1) to 1.7 V (logic 0). The Griess reagent method employed for nitrite determination is based on the formation of an azo dye, the intensity of which is directly related to nitrite concentration. The linear range, reproducibility and limit of detection were investigated. Detection limits in the nanomolar range were achieved using the Paired Emitter-Detector Diode (PEDD) flow analysis device. For a comparative study the linear range and limit of detection were also investigated using a platewell reader. Higher sensitivity and improved precision were obtained from the PEDD compared to the commercially available plate well reader.

  15. The Light-Emitting Diode as a Light Detector

    ERIC Educational Resources Information Center

    Baird, William H.; Hack, W. Nathan; Tran, Kiet; Vira, Zeeshan; Pickett, Matthew

    2011-01-01

    A light-emitting diode (LED) and operational amplifier can be used as an affordable method to provide a digital output indicating detection of an intense light source such as a laser beam or high-output LED. When coupled with a microcontroller, the combination can be used as a multiple photogate and timer for under $50. A similar circuit is used…

  16. Submicron nickel-oxide-gold tunnel diode detectors for rectennas

    NASA Technical Reports Server (NTRS)

    Hoofring, A. B.; Kapoor, V. J.; Krawczonek, W.

    1989-01-01

    The characteristics of a metal-oxide-metal (MOM) tunnel diode made of nickel, nickel-oxide, and gold, designed and fabricated by standard integrated circuit technology for use in FIR rectennas, are presented. The MOM tunnel diode was formed by overlapping a 0.8-micron-wide layer of 1000-A of nickel, which was oxidized to form a thin layer of nickel oxide, with a 1500 A-thick layer of gold. The dc current-voltage characteristics of the MOM diode showed that the current dependence on voltage was linear about zero bias up to a bias of about 70 mV. The maximum detection of a low-level signal (10-mV ac) was determined to be at a dc voltage of 70 mV across the MOM diode. The rectified output signal due to a chopped 10.6-micron CO2 laser incident upon the rectenna device was found to increase with dc bias, with a maximum value of 1000 nV for a junction bias of 100 mV at room temperature.

  17. Compton polarimeter as a focal plane detector for hard X-ray telescope: sensitivity estimation with Geant4 simulations

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, T.; Vadawale, S. V.; Pendharkar, J.

    2013-04-01

    X-ray polarimetry can be an important tool for investigating various physical processes as well as their geometries at the celestial X-ray sources. However, X-ray polarimetry has not progressed much compared to the spectroscopy, timing and imaging mainly due to the extremely photon-hungry nature of X-ray polarimetry leading to severely limited sensitivity of X-ray polarimeters. The great improvement in sensitivity in spectroscopy and imaging was possible due to focusing X-ray optics which is effective only at the soft X-ray energy range. Similar improvement in sensitivity of polarisation measurement at soft X-ray range is expected in near future with the advent of GEM based photoelectric polarimeters. However, at energies >10 keV, even spectroscopic and imaging sensitivities of X-ray detector are limited due to lack of focusing optics. Thus hard X-ray polarimetry so far has been largely unexplored area. On the other hand, typically the polarisation degree is expected to increase at higher energies as the radiation from non-thermal processes is dominant fraction. So polarisation measurement in hard X-ray can yield significant insights into such processes. With the recent availability of hard X-ray optics (e.g. with upcoming NuSTAR, Astro-H missions) which can focus X-rays from 5 KeV to 80 KeV, sensitivity of X-ray detectors in hard X-ray range is expected to improve significantly. In this context we explore feasibility of a focal plane hard X-ray polarimeter based on Compton scattering having a thin plastic scatterer surrounded by cylindrical array scintillator detectors. We have carried out detailed Geant4 simulation to estimate the modulation factor for 100 % polarized beam as well as polarimetric efficiency of this configuration. We have also validated these results with a semi-analytical approach. Here we present the initial results of polarisation sensitivities of such focal plane Compton polarimeter coupled with the reflection efficiency of present era hard X

  18. A Multiyear Light Curve of Scorpius X-1 Based on Compton Gamma Ray Observatory BATSE Spectroscopy Detector Observations

    NASA Astrophysics Data System (ADS)

    McNamara, B. J.; Harrison, T. E.; Mason, P. A.; Templeton, M.; Heikkila, C. W.; Buckley, T.; Galvan, E.; Silva, A.; Harmon, B. A.

    1998-06-01

    A multiyear light curve of the low mass X-ray binary, Scorpius X-1, is constructed based on the Compton Gamma Ray Observatory Burst and Transient Source Experiment (BATSE) Spectroscopy Detector (SD) data in the nominal energy range of 10-20 keV. A detailed discussion is given of the reduction process of the BATSE/SD data. Corrections to the SD measurements are made for off-axis pointings, spectral and bandpass changes, and differences in the eight SD sensitivities. The resulting 4.4 yr Sco X-1 SD light curve is characterized in terms of the timescales over which various types of emission changes occur. This light curve is then compared with Sco X-1 light curves obtained by Ariel 5, the BATSE Large Area Detectors (LADs), and the RXTE all-sky monitor (ASM). Coincident temporal coverage by the BATSE/SD and RXTE/ASM allows a direct comparison of the behavior of Sco X-1 over a range of high energies to be made. These ASM light curves are then used to discuss model constraints on the Sco X-1 system.

  19. Extraction of depth-dependent perturbation factors for silicon diodes using a plastic scintillation detector

    SciTech Connect

    Lacroix, Frederic; Guillot, Mathieu; McEwen, Malcolm; Gingras, Luc; Beaulieu, Luc

    2011-10-15

    Purpose: This work presents the experimental extraction of the perturbation factor in megavoltage electron beams for three models of silicon diodes (IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded) using a plastic scintillation detector (PSD). Methods: The authors used a single scanning PSD mounted on a high-precision scanning tank to measure depth-dose curves in 6-, 12-, and 18-MeV clinical electron beams. They also measured depth-dose curves using the IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded diodes. The authors used the depth-dose curves measured with the PSD as a perturbation-free reference to extract the perturbation factors of the diodes. Results: The authors found that the perturbation factors for the diodes increased substantially with depth, especially for low-energy electron beams. The experimental results show the same trend as published Monte Carlo simulation results for the EFD diode; however, the perturbations measured experimentally were greater. They found that using an effective point of measurement (EPOM) placed slightly away from the source reduced the variation of perturbation factors with depth and that the optimal EPOM appears to be energy dependent. Conclusions: The manufacturer recommended EPOM appears to be incorrect at low electron energy (6 MeV). In addition, the perturbation factors for diodes may be greater than predicted by Monte Carlo simulations.

  20. X-ray detectors based on GaN Schottky diodes

    SciTech Connect

    Duboz, Jean-Yves; Frayssinet, Eric; Chenot, Sebastien; Reverchon, Jean-Luc; Idir, Mourad

    2010-10-18

    GaN Schottky diodes have been fabricated and tested as x-ray detectors in the range from 6 to 21 keV. The spectral response has been measured and is compared to its theoretical value. The study of the response and its temporal dynamics as a function of the bias allows to identify a photovoltaic behavior at low bias and a photoconductive one at larger reverse biases. The GaN diode turned out to be linear as a function of the incident power. The noise and detectivity are given and discussed.

  1. Design and Preliminary Monte Carlo Calculations of an Active Compton Suppressed LaBr3(Ce) Detector System for TRU Assay in Remote-Handled Wastes

    SciTech Connect

    J. Kulisek; J. K. Hartwell; M. E. McIlwain; R. P. Gardner

    2006-09-01

    Recent studies indicate LaBr3(Ce) scintillation detectors have desirable attributes, such as room temperature operability, which may make them viable alternatives as primary detectors (PD) in a Compton suppression spectrometer (CSS) used for remote-handled transuranic (RH-TRU) waste assay. A CSS with a LaBr3(Ce) PD has been designed and its expected performance evaluated using Monte Carlo analysis. The unique design of this unit minimizes the amount of "dead" material between the PD and the secondary guard detector. The analysis results indicate that this detector will have a relatively high Compton-suppression capability, with greater suppression ability for large angle-scattered photons in the PD. J. K. Hartwell1, M. E. McIlwain1, R. P. Gardner2, J. Kulisek3 1) Idaho National Laboratory, PO Box 1625, Idaho Falls, ID 83415-2114 USA 2) North Carolina State University, Dept of Nuclear Eng., PO Box 7909, Raleigh, NC 27695 USA 3) Ohio State University, Columbus, Ohio 43210 The US Department of Energy’s transuranic (TRU) waste inventory includes about 4,500 m3 of remote-handled TRU (RH-TRU) wastes. The RH-TRU waste stream is composed of a variety of containerized waste forms having a contact surface dose rate that exceeds 2 mSv/hr (200 mrem/hr) containing waste materials with a total TRU concentration greater than 3700 Bq/g (100 nCi/g). As part of a research project to investigate the use of active Compton-suppressed room-temperature gamma-ray detectors for direct non-destructive quantification of the TRU content of these RH-TRU wastes, we have designed and purchased a unique detector system using a LaBr3(Ce) primary detector and a NaI(Tl) suppression mantle. The expected detector performance has been modeled using MCNP-X [1] and CEARCPG [2], and incorporates certain design features modeled as important to active Compton suppression systems in previously-published work [3]. The unique detector system is sketched in Fig. 1. The ~25 mm diameter by 75 mm long LaBr3(Ce

  2. Characteristics of a CsI(Tl) Compton-suppressed clover detector

    NASA Astrophysics Data System (ADS)

    Zhang, N. T.; Lei, X. G.; Guo, Y. X.; Zhou, X. H.; Zhang, Y. H.; Ma, F.; Li, S. C.; Liu, M. L.; Zheng, Y.; Fang, Y. D.; Hua, W.; Guo, S.; Qiang, Y. H.; Wang, J. G.; Gao, B. S.; Xu, S. W.; Chen, S. Z.

    2013-03-01

    The performance of a four fold segmented clover detector coupled to a CsI-suppressed shield has been tested using several standard radioactive sources. The summing characteristics, hit patterns and absolute efficiency were measured in both crystal and clover modes. Peak-to-total ratios of 57.3% and 45.6% in suppressed clover mode have been determined for 137Cs and 60Co sources, respectively. A Geant4 simulation of the suppressed clover detector, including the segmentation of the germanium crystals, has been created, and the simulation results agreed very well with the experimental data.

  3. The effects of Doppler broadening and detector resolution on the performance of three-stage Compton cameras

    SciTech Connect

    Mackin, Dennis; Polf, Jerimy; Peterson, Steve; Beddar, Sam

    2013-01-15

    Purpose: The authors investigated how the characteristics of the detectors used in a three-stage Compton camera (CC) affect the CC's ability to accurately measure the emission distribution and energy spectrum of prompt gammas (PG) emitted by nuclear de-excitations during proton therapy. The detector characteristics they studied included the material (high-purity germanium [HPGe] and cadmium zinc telluride [CZT]), Doppler broadening (DB), and resolution (lateral, depth, and energy). Methods: The authors simulated three-stage HPGe and CZT CCs of various configurations, detecting gammas from point sources with energies ranging from 0.511 to 7.12 MeV. They also simulated a proton pencil beam irradiating a tissue target to study how the detector characteristics affect the PG data measured by CCs in a clinical proton therapy setting. They used three figures of merit: the distance of closest approach (DCA) and the point of closest approach (PCA) between the measured and actual position of the PG emission origin, and the calculated energy resolution. Results: For CCs with HPGe detectors, DB caused the DCA to be greater than 3 mm for 14% of the 6.13 MeV gammas and 20% of the 0.511 MeV gammas. For CCs with CZT detectors, DB caused the DCA to be greater than 3 mm for 18% of the 6.13 MeV gammas and 25% of the 0.511 MeV gammas. The full width at half maximum (FWHM) of the PCA in the z-caret direction for HPGe and CZT detectors ranged from 1.3 to 0.4 mm for gammas with incident energy ranging from 0.511 to 7.12 MeV. For CCs composed of HPGe detectors, the resolution of incident gamma energy calculated by the CC ranged from 6% to 1% for gammas with true incident energies from 0.511 to 7.12 MeV. For CCs composed of CZT detectors, the resolution of gamma energy calculated by the CC ranged from 10% to 1% for gammas with true incident energies from 0.511 to 7.12 MeV. For HPGe and CZT CCs in which all detector effect were included, the DCA was less than 3 mm for 75% and 68% of the

  4. The effects of Doppler broadening and detector resolution on the performance of three-stage Compton cameras

    PubMed Central

    Mackin, Dennis; Polf, Jerimy; Peterson, Steve; Beddar, Sam

    2013-01-01

    Purpose: The authors investigated how the characteristics of the detectors used in a three-stage Compton camera (CC) affect the CC's ability to accurately measure the emission distribution and energy spectrum of prompt gammas (PG) emitted by nuclear de-excitations during proton therapy. The detector characteristics they studied included the material (high-purity germanium [HPGe] and cadmium zinc telluride [CZT]), Doppler broadening (DB), and resolution (lateral, depth, and energy). Methods: The authors simulated three-stage HPGe and CZT CCs of various configurations, detecting gammas from point sources with energies ranging from 0.511 to 7.12 MeV. They also simulated a proton pencil beam irradiating a tissue target to study how the detector characteristics affect the PG data measured by CCs in a clinical proton therapy setting. They used three figures of merit: the distance of closest approach (DCA) and the point of closest approach (PCA) between the measured and actual position of the PG emission origin, and the calculated energy resolution. Results: For CCs with HPGe detectors, DB caused the DCA to be greater than 3 mm for 14% of the 6.13 MeV gammas and 20% of the 0.511 MeV gammas. For CCs with CZT detectors, DB caused the DCA to be greater than 3 mm for 18% of the 6.13 MeV gammas and 25% of the 0.511 MeV gammas. The full width at half maximum (FWHM) of the PCA in the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}\\hat z\\end{equation*} \\end{document}z^ direction for HPGe and CZT detectors ranged from 1.3 to 0.4 mm for gammas with incident energy ranging from 0.511 to 7.12 MeV. For CCs composed of HPGe detectors, the resolution of incident gamma energy calculated by the CC ranged from 6% to 1% for gammas with true incident energies from 0.511 to 7.12 Me

  5. Inverse Compton for Compton

    NASA Astrophysics Data System (ADS)

    Suortti, Pekka

    2016-04-01

    A novel concept for a high resolution Compton spectrometer is introduced. 88 keV radiation from an Inverse Compton Compact Source is focused using crossed cylindrically bent Laue-type Si perfect crystals, and dispersed on the sample with a constant energy gradient. Dispersion is compensated exactly at a Ge crystal analyzer, so that the same wavelength shift is observed for all wavelengths of the incident beam. The ThomX source is used as a concrete example. Detailed dimensions and flux estimates at successive locations of the spectrometer are given, and the performance is compared with the dispersion compensating spectrometer at ID15 of the ESRF. The momentum resolution is better than 0.1 atomic units in both cases. The intensity of scattering with the compact source is an order of magnitude smaller, but still adequate for high resolution Compton profile measurements.

  6. Performance of a Low Noise Front-end ASIC for Si/CdTe Detectors in Compton Gamma-ray Telescope

    SciTech Connect

    Tajima, H

    2004-03-29

    Compton telescopes based on semiconductor technologies are being developed to explore the gamma-ray universe in an energy band 0.1-20 MeV, which is not well covered by the present or near-future gamma-ray telescopes. The key feature of such Compton telescopes is the high energy resolution that is crucial for high angular resolution and high background rejection capability. The energy resolution around 1 keV is required to approach physical limit of the angular resolution due to Doppler broadening. We have developed a low noise front-end ASIC (Application-Specific Integrated Circuit), VA32TA, to realize this goal for the readout of Double-sided Silicon Strip Detector (DSSD) and Cadmium Telluride (CdTe) pixel detector which are essential elements of the semiconductor Compton telescope. We report on the design and test results of the VA32TA. We have reached an energy resolution of 1.3 keV (FWHM) for 60 keV and 122 keV at 0 C with a DSSD and 1.7 keV (FWHM) with a CdTe detector.

  7. Natural gas pipeline leak detector based on NIR diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Gao, Xiaoming; Fan, Hong; Huang, Teng; Wang, Xia; Bao, Jian; Li, Xiaoyun; Huang, Wei; Zhang, Weijun

    2006-09-01

    The paper reports on the development of an integrated natural gas pipeline leak detector based on diode laser absorption spectroscopy. The detector transmits a 1.653 μm DFB diode laser with 10 mW and detects a fraction of the backscatter reflected from the topographic targets. To eliminate the effect of topographic scatter targets, a ratio detection technique was used. Wavelength modulation and harmonic detection were used to improve the detection sensitivity. The experimental detection limit is 50 ppm m, remote detection for a distance up to 20 m away topographic scatter target is demonstrated. Using a known simulative leak pipe, minimum detectable pipe leak flux is less than 10 ml/min.

  8. Natural gas pipeline leak detector based on NIR diode laser absorption spectroscopy.

    PubMed

    Gao, Xiaoming; Fan, Hong; Huang, Teng; Wang, Xia; Bao, Jian; Li, Xiaoyun; Huang, Wei; Zhang, Weijun

    2006-09-01

    The paper reports on the development of an integrated natural gas pipeline leak detector based on diode laser absorption spectroscopy. The detector transmits a 1.653 microm DFB diode laser with 10 mW and detects a fraction of the backscatter reflected from the topographic targets. To eliminate the effect of topographic scatter targets, a ratio detection technique was used. Wavelength modulation and harmonic detection were used to improve the detection sensitivity. The experimental detection limit is 50 ppmm, remote detection for a distance up to 20 m away topographic scatter target is demonstrated. Using a known simulative leak pipe, minimum detectable pipe leak flux is less than 10 ml/min. PMID:16563854

  9. Large-area CdTe diode detector for space application

    NASA Astrophysics Data System (ADS)

    Nakazawa, K.; Takahashi, T.; Watanabe, S.; Sato, G.; Kouda, M.; Okada, Y.; Mitani, T.; Kobayashi, Y.; Kuroda, Y.; Onishi, M.; Ohno, R.; Kitajima, H.

    2003-10-01

    The current status of Schottky CdTe diode detectors, especially in view of their space application for hard X-ray and gamma-ray astronomy, are reported. For practical use in space science, a large-area CdTe diode with a size of 21.5×21.5mm2 and a thickness of 0.5mm was developed. A good energy resolution, 2.8keV (FWHM) at -20°C, and high homogeneity to within 0.2% over the detector were achieved for the spectral performance. This device has successfully passed a series of tests required for its use in space, in view of utilizing Japanese M-V rockets. The tests include the mechanical environment test, vacuum test, long run for weeks and proton-beam radiation. Initial results from a 2×2 segmented electrode large-area device with a guard-ring are also presented.

  10. Measurement and deconvolution of detector response time for short HPM pulses: Part 1, Microwave diodes

    SciTech Connect

    Bolton, P.R.

    1987-06-01

    A technique is described for measuring and deconvolving response times of microwave diode detection systems in order to generate corrected input signals typical of an infinite detection rate. The method has been applied to cases of 2.86 GHz ultra-short HPM pulse detection where pulse rise time is comparable to that of the detector; whereas, the duration of a few nanoseconds is significantly longer. Results are specified in terms of the enhancement of equivalent deconvolved input voltages for given observed voltages. The convolution integral imposes the constraint of linear detector response to input power levels. This is physically equivalent to the conservation of integrated pulse energy in the deconvolution process. The applicable dynamic range of a microwave diode is therefore limited to a smaller signal region as determined by its calibration.

  11. Tests of a multichannel photometer based on silicon diode detectors

    NASA Technical Reports Server (NTRS)

    Borucki, William J.; Allen, L. E.; Taylor, S. W.; Torbet, E. B.; Schaefer, A. R.; Fowler, J.

    1988-01-01

    A breadboard photometer was constructed that demonstrates a precision of 2 times 10 to the 4th power in the laboratory and scintillation-limited performance when used with an 0.5 m aperture telescope. Because the detectors and preamps are not cooled, only stars with m sub v approx. less than 4 are bright enough to allow the photometer to attain a precision of 1 times 10 to the 3rd power for three minute observations with an 0.5 m aperature telescope. Cooling the telescope should allow much fainter stars to be observed. Increasing the aperture of the telescope will allow higher precision and the observation of fainter stars.

  12. Characterization of zero-bias microwave diode power detectors at cryogenic temperature.

    PubMed

    Giordano, Vincent; Fluhr, Christophe; Dubois, Benoît; Rubiola, Enrico

    2016-08-01

    We present the characterization of commercial tunnel diode low-level microwave power detectors at room and cryogenic temperatures. The sensitivity as well as the output voltage noise of the tunnel diodes is measured as functions of the applied microwave power. We highlight strong variations of the diode characteristics when the applied microwave power is higher than a few microwatts. For a diode operating at 4 K, the differential gain increases from 1000 V/W to about 4500 V/W when the power passes from -30 dBm to -20 dBm. The diode white noise floor is equivalent to a Noise Equivalent Power of 0.8 pW/Hz and 8 pW/Hz at 4 K and 300 K, respectively. Its flicker noise is equivalent to a relative amplitude noise power spectral density Sα(1 Hz) = - 120 dB/Hz at 4 K. Flicker noise is 10 dB higher at room temperature. PMID:27587142

  13. A car-borne highly sensitive near-IR diode-laser methane detector

    SciTech Connect

    Berezin, A G; Ershov, Oleg V; Shapovalov, Yu P

    2003-08-31

    A highly sensitive automated car-borne detector for measuring methane concentration in real time is designed, developed and tested under laboratory and field conditions. Measurements were made with the help of an uncooled tunable near-IR 1.65-{mu}m laser diode. The detector consists of a multipass optical cell with a 45-m long optical path and a base length of 0.5 m. The car-borne detector is intended for monitoring the methane concentration in air from the moving car to reveal the leakage of domestic gas. The sensitivity limit (standard deviation) under field conditions is 1 ppm (20 ppb under laboratory conditions) for a measuring time of 0.4 s. The measuring technique based on the detection of a single methane line ensured a high selectivity of methane detector relative to other gases. The methane detector can be easily modified for measuring other simple-molecule gases (e.g., CO, CO{sub 2}, HF, NO{sub 2}, H{sub 2}O) by replacing the diode laser and varying the parameters of the control program. (special issue devoted to the memory of academician a m prokhorov)

  14. An ultra-thin Schottky diode as a transmission particle detector for biological microbeams

    PubMed Central

    Harken, Andrew; Randers-Pehrson, Gerhard; Attinger, Daniel; Brenner, David J.

    2013-01-01

    We fabricated ultrathin metal-semiconductor Schottky diodes for use as transmission particle detectors in the biological microbeam at Columbia University’s Radiological Research Accelerator Facility (RARAF). The RARAF microbeam can deliver a precise dose of ionizing radiation in cell nuclei with sub-micron precision. To ensure an accurate delivery of charged particles, the facility currently uses a commercial charged-particle detector placed after the sample. We present here a transmission detector that will be placed between the particle accelerator and the biological specimen, allowing the irradiation of samples that would otherwise block radiation from reaching a detector behind the sample. Four detectors were fabricated with co-planar gold and aluminum electrodes thermally evaporated onto etched n-type crystalline silicon substrates, with device thicknesses ranging from 8.5 μm – 13.5 μm. We show coincident detections and pulse-height distributions of charged particles in both the transmission detector and the commercial detector above it. Detections are demonstrated at a range of operating conditions, including incoming particle type, count rate, and beam location on the detectors. The 13.5 μm detector is shown to work best to detect 2.7 MeV protons (H+), and the 8.5 μm detector is shown to work best to detect 5.4 MeV alpha particles (4He++). The development of a transmission detector enables a range of new experiments to take place at RARAF on radiation-stopping samples such as thick tissues, targets that need immersion microscopy, and integrated microfluidic devices for handling larger quantities of cells and small organisms. PMID:24058378

  15. 640 x 480 pixel uncooled infrared FPA with SOI diode detectors

    NASA Astrophysics Data System (ADS)

    Ueno, Masashi; Kosasayama, Yasuhiro; Sugino, Takaki; Nakaki, Yoshiyuki; Fujii, Yoshio; Inoue, Hiromoto; Kama, Keisuke; Seto, Toshiki; Takeda, Munehisa; Kimata, Masafumi

    2005-05-01

    This paper describes the structure and performance of a 25-micron pitch 640 x 480 pixel uncooled infrared focal plane array (IR FPA) with silicon-on-insulator (SOI) diode detectors. The uncooled IR FPA is a thermal type FPA that has a temperature sensor of single crystal PN junction diodes formed in an SOI layer. In the conventional pixel structure, the temperature sensor and two support legs for thermal isolation are made in the lower level of the pixel, and an IR absorbing structure is made in the upper pixel level to cover almost the entire pixel area. The IR absorption utilizes IR reflections from the lower level. Since the reflection from the support leg portions is not perfect due to the slits in the metal reflector, the reflection becomes smaller as the support leg section increases in reduced pixel pitches. In order to achieve high thermal isolation and high IR absorption simultaneously, we have developed a new pixel structure that has an independent IR reflector between the lower and upper levels. The structure assures perfect IR reflection and thus improves IR absorption. The FPA shows a noise equivalent temperature difference (NETD) of 40 mK (f/1.0) and a responsivity non-uniformity of less than 0.9%. The good uniformity is due to the high uniformity of the electrical characteristics of SOI diodes made of single crystal silicon (Si). We have confirmed that the SOI diodes architecture is suitable for large format uncooled IR FPAs.

  16. Excitability and optical pulse generation in semiconductor lasers driven by resonant tunneling diode photo-detectors.

    PubMed

    Romeira, Bruno; Javaloyes, Julien; Ironside, Charles N; Figueiredo, José M L; Balle, Salvador; Piro, Oreste

    2013-09-01

    We demonstrate, experimentally and theoretically, excitable nanosecond optical pulses in optoelectronic integrated circuits operating at telecommunication wavelengths (1550 nm) comprising a nanoscale double barrier quantum well resonant tunneling diode (RTD) photo-detector driving a laser diode (LD). When perturbed either electrically or optically by an input signal above a certain threshold, the optoelectronic circuit generates short electrical and optical excitable pulses mimicking the spiking behavior of biological neurons. Interestingly, the asymmetric nonlinear characteristic of the RTD-LD allows for two different regimes where one obtain either single pulses or a burst of multiple pulses. The high-speed excitable response capabilities are promising for neurally inspired information applications in photonics. PMID:24103966

  17. Dosimetric Characteristics of a Two-Dimensional Diode Array Detector Irradiated with Passively Scattered Proton Beams

    PubMed Central

    Liengsawangwong, Praimakorn; Sahoo, Nanayan; Ding, Xiaoning; Lii, MingFwu; Gillin, Michale T.; Zhu, Xiaorong Ronald

    2015-01-01

    Purpose: To evaluate the dosimetric characteristics of a two-dimensional (2D) diode array detector irradiated with passively scattered proton beams. Materials and Methods: A diode array detector, MapCHECK (Model 1175, Sun Nuclear, Melbourne, FL, USA) was characterized in passive-scattered proton beams. The relative sensitivity of the diodes and absolute dose calibration were determined using a 250 MeV beam. The pristine Bragg curves (PBCs) measured by MapCHECK diodes were compared with those of an ion chamber using a range shift method. The water-equivalent thickness (WET) of the diode array detector’s intrinsic buildup also was determined. The inverse square dependence, linearity, and other proton dosimetric quantities measured by MapCHECK were also compared with those of the ion chambers. The change in the absolute dose response of the MapCHECK as a function of accumulated radiation dose was used as an indicator of radiation damage to the diodes. 2D dose distribution with and without the compensator were measured and compared with the treatment planning system (TPS) calculations. Results: The WET of the MapCHECK diode’s buildup was determined to be 1.7 cm. The MapCHECK-measured PBC were virtually identical to those measured by a parallel-plate ion chamber for 160, 180, and 250 MeV proton beams. The inverse square results of the MapCHECK were within ±0.4% of the ion chamber results. The linearity of MapCHECK results was within 1% of those from the ion chamber as measured in the range between 10 and 300 MU. All other dosimetric quantities were within 1.3% of the ion chamber results. The 2D dose distributions for non-clinical fields without compensator and the patient treatment fields with the compensator were consistent with the TPS results. The absolute dose response of the MapCHECK was changed by 7.4% after an accumulated dose increased by 170 Gy. Conclusions: The MapCHECK is a convenient and useful tool for 2D dose distribution measurements using passively

  18. SU-F-18C-05: Characterization of a Silicon Strip Photon-Counting Detector in the Presence of Compton Scatter: A Simulation Study

    SciTech Connect

    Ziemer, B; Ding, H; Cho, H

    2014-06-15

    Purpose: To investigate the effect of Compton scatter on detection efficiency and charge-sharing for a Si strip photon-counting detector as a function of pixel pitch, slice thickness and total pixel length. Methods: A CT imaging system employing a silicon photon-counting detector was implemented using the GATE Monte Carlo package. A focal spot size of 300 µm, magnification of 1.33, and pixel pitches of 0.1 and 0.5mm were initially investigated. A 60 kVp spectrum with 3 mm Al filter was used and energy spectral degradation based on a prototype detector was simulated. To study charge-sharing, a single pixel was illuminated, and the detector response in neighboring pixels was investigated. A longitudinally semiinfinite detector was simulated to optimize the quantum detection efficiency of the imaging system as a function of pixel pitch, slice thickness and depth of interaction. A 2.5 mm thick tungsten plate with a 0.01 mm by 1.5 mm slit was implemented to calculate the modulation transfer function (MTF) from projection-based images. A threshold of 15 keV was implemented in the detector simulation. The preliminary charge sharing investigation results considered only scattering effects and the detector electronics related factors were neglected. Results: Using a 15 keV threshold, 1% of the pixel charge migrated into neighboring pixels with a pixel size of 0.1×0.1 mm{sup 2}. The quantum detection efficiency was 77%, 84%, 87% and 89% for 15 mm, 22.5 mm, 30 mm, and 45 mm length silicon detector pixels, respectively. For a pixel pitch of 0.1 mm, the spatial frequency at 10% of the maximum MTF was found to be 5.2 lp/mm. This agreed with an experimental MTF measurement of 5.3 lp/mm with a similar detector configuration. Conclusion: Using optimized design parameters, Si strip photon-counting detectors can offer high detection efficiency and spatial resolution even in the presence of Compton scatter.

  19. A laser diode based system for calibration of fast time-of-flight detectors

    NASA Astrophysics Data System (ADS)

    Bertoni, R.; Bonesini, M.; de Bari, A.; Rossella, M.

    2016-05-01

    A system based on commercially available items, such as a laser diode, emitting in the visible range ~ 400 nm, and multimode fiber patches, fused fiber splitters and optical switches may be assembled, for time calibration of multi-channels time-of-flight (TOF) detectors with photomultipliers' (PMTs') readout. As available laser diode sources have unfortunately limited peak power, the main experimental problem is the tight light power budget of such a system. In addition, while the technology for fused fiber splitters is common in the Telecom wavelength range (λ ~ 850, 1300–1500 nm), it is not easily available in the visible one. Therefore, extensive laboratory tests had to be done on purpose, to qualify the used optical components, and a full scale timing calibration prototype was built. Obtained results show that with such a system, a calibration resolution (σ) in the range 20–30 ps may be within reach. Therefore, fast multi-channels TOF detectors, with timing resolutions in the range 50–100 ps, may be easily calibrated in time. Results on tested optical components may be of interest also for time calibration of different light detection systems based on PMTs, as the ones used for detection of the vacuum ultraviolet scintillation light emitted by ionizing particles in large LAr TPCs.

  20. Absorbance detector based on a deep UV light emitting diode for narrow-column HPLC.

    PubMed

    Bui, Duy Anh; Bomastyk, Benjamin; Hauser, Peter C

    2013-10-01

    A detector for miniaturized HPLC based on deep UV emitting diodes and UV photodiodes was constructed. The measurement is accomplished by the transverse passage of the radiation from the light-emitting diode (LED) through fused-silica tubing with an internal diameter of 250 μm. The optical cell allows flexible alignment of the LED, tubing, and photodiode for optimization of the light throughput and has an aperture to block stray light. A beam splitter was employed to direct part of the emitted light to a reference photodiode and the Lambert-Beer law was emulated with a log-ratio amplifier circuitry. The detector was tested with two LEDs with emission bands at 280 and 255 nm and showed noise levels as low as 0.25 and 0.22 mAU, respectively. The photometric device was employed successfully in separations using a column of 1 mm inner diameter in isocratic as well as gradient elution. Good linearities over three orders of magnitude in concentration were achieved, and the precision of the measurements was better than 1% in all cases. Detection down to the low micromolar range was possible. PMID:23893947

  1. InGaAs Schottky barrier diode array detector for a real-time compact terahertz line scanner.

    PubMed

    Han, Sang-Pil; Ko, Hyunsung; Park, Jeong-Woo; Kim, Namje; Yoon, Young-Jong; Shin, Jun-Hwan; Kim, Dae Yong; Lee, Dong Hun; Park, Kyung Hyun

    2013-11-01

    We present a terahertz (THz) broadband antenna-integrated 1 × 20 InGaAs Schottky barrier diode (SBD) array detector with an average responsivity of 98.5 V/W at a frequency of 250 GHz, which is measured without attaching external amplifiers and Si lenses, and an average noise equivalent power (NEP) of 106.6 pW/√Hz. The 3-dB bandwidth of the SBD detector is also investigated at approximately 180 GHz. For implementing an array-type SBD detector by a simple fabrication process to achieve a high yield, a structure comprising an SiN(x) layer instead of an air bridge between the anode and the cathode is designed. THz line beam imaging using a Gunn diode emitter with a center frequency of 250 GHz and a 1 × 20 SBD array detector is successfully demonstrated. PMID:24216813

  2. Ge-diode detector combined with crystal-diffraction spectrometer permits high-resolution gamma ray spectroscopy

    NASA Technical Reports Server (NTRS)

    Namenson, A. I.; Smither, R. K.

    1969-01-01

    Crystal-diffraction spectrometer, combined with a lithium-drifted Ge-diode detector, performs high-resolution gamma ray spectroscopy on the complicated neutron-capture gamma ray spectra. The system is most useful in the 1-3 MeV energy range and improves the signal to background ratio.

  3. A Simple, Small-Scale Lego Colorimeter with a Light-Emitting Diode (LED) Used as Detector

    ERIC Educational Resources Information Center

    Asheim, Jonas; Kvittingen, Eivind V.; Kvittingen, Lise; Verley, Richard

    2014-01-01

    This article describes how to construct a simple, inexpensive, and robust colorimeter from a few Lego bricks, in which one light-emitting diode (LED) is used as a light source and a second LED as a light detector. The colorimeter is suited to various grades and curricula.

  4. Beam related response of in vivo diode detectors for external radiotherapy

    NASA Astrophysics Data System (ADS)

    Baci, Syrja; Telhaj, Ervis; Malkaj, Partizan

    2016-03-01

    In Vivo Dosimetry (IVD) is a set of methods used in cancer treatment clinics to determine the real dose of radiation absorbed by target volume in a patient's body. IVD has been widely implemented in radiotherapy treatment centers and is now recommended part of Quality Assurance program by many International health and radiation organizations. Because of cost and lack of specialized personnel, IVD has not been practiced as yet, in Albanian radiotherapy clinics. At Hygeia Hospital Tirana, patients are irradiated with high energy photons generated by Elekta Synergy Accelerators. We have recently started experimenting with the purpose of establishing an IVD practice at this hospital. The first set of experiments was aimed at calibration of diodes that are going to be used for IVD. PMMA, phantoms by PTW were used to calibrate p - type Si, semiconductor diode dosimeters, made by PTW Freiburg for entrance dose. Response of the detectors is affected by energy of the beam, accumulated radiation dose, dose rate, temperature, angle against the beam axis, etc. Here we present the work done for calculating calibration factor and correction factors of source to surface distance, field size, and beam incidence for the entrance dose for both 6 MV photon beam and 18 MV photon beam. Dependence of dosimeter response was found to be more pronounced with source to surface distance as compared to other variables investigated.

  5. Spin-torque diode radio-frequency detector with voltage tuned resonance

    NASA Astrophysics Data System (ADS)

    Skowroński, Witold; Frankowski, Marek; Wrona, Jerzy; Stobiecki, Tomasz; Ogrodnik, Piotr; Barnaś, Józef

    2014-08-01

    We report on a voltage-tunable radio-frequency (RF) detector based on a magnetic tunnel junction (MTJ). The spin-torque diode effect is used to excite and/or detect RF oscillations in the magnetic free layer of the MTJ. In order to reduce the overall in-plane magnetic anisotropy of the free layer, we take advantage of the perpendicular magnetic anisotropy at the interface between ferromagnetic and insulating layers. The applied bias voltage is shown to have a significant influence on the magnetic anisotropy, and thus on the resonance frequency of the device. This influence also depends on the voltage polarity. The obtained results are accounted for in terms of the interplay of spin-transfer-torque and voltage-controlled magnetic anisotropy effects.

  6. Spin-torque diode radio-frequency detector with voltage tuned resonance

    SciTech Connect

    Skowroński, Witold Frankowski, Marek; Stobiecki, Tomasz; Wrona, Jerzy; Ogrodnik, Piotr; Barnaś, Józef

    2014-08-18

    We report on a voltage-tunable radio-frequency (RF) detector based on a magnetic tunnel junction (MTJ). The spin-torque diode effect is used to excite and/or detect RF oscillations in the magnetic free layer of the MTJ. In order to reduce the overall in-plane magnetic anisotropy of the free layer, we take advantage of the perpendicular magnetic anisotropy at the interface between ferromagnetic and insulating layers. The applied bias voltage is shown to have a significant influence on the magnetic anisotropy, and thus on the resonance frequency of the device. This influence also depends on the voltage polarity. The obtained results are accounted for in terms of the interplay of spin-transfer-torque and voltage-controlled magnetic anisotropy effects.

  7. Semiconductor diodes as neutron detectors for position-sensitive measurements and for application in personal neutron dosimetry

    NASA Astrophysics Data System (ADS)

    Balzhaeuser, Michael; Dehoff, A.; Engels, R.; Hoengesberg, F.; Lauter, J.; Luth, Hans; Reetz, M.; Reinartz, Richard; Richter, H.; Schelten, Jim; Schmitz, Th.; Steffen, A.; Vockenberg, Th.

    1997-02-01

    A new design for a position-sensitive detector system for thermal neutrons is introduced. The detection principle with a thin 6LiF converter on the surface of a semiconductor diode is described. In experiments with thermal neutrons, a spatial resolution of 1.25 mm was obtained. The detector is insensitive to (gamma) -rays with energies up to 1.5 MeV. The design of a detector with an improvement of the detection efficiency for thermal neutrons from 2.5 percent up to 35 percent is also proposed and the present state of the process development for its fabrication is described.

  8. Dead layer on silicon p-i-n diode charged-particle detectors

    SciTech Connect

    Wall, B. L.; Amsbaugh, John F.; Beglarian, A.; Bergmann, T.; Bichsel, H. C.; Bodine, L. I.; Boyd, N. M.; Burritt, Tom H.; Chaoui, Z.; Corona, T. J.; Doe, Peter J.; Enomoto, S.; Harms, F.; Harper, Gregory; Howe, M. A.; Martin, E. L.; Parno, D. S.; Peterson, David; Petzold, Linda; Renschler, R.; Robertson, R. G. H.; Schwarz, J.; Steidl, M.; Van Wechel, T. D.; VanDevender, Brent A.; Wustling, S.; Wierman, K. J.; Wilkerson, J. F.

    2014-04-21

    Abstract Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon p-i-n diode used in the KATRIN neutrinomass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the "dead" layer evidently escapes by discussion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored.

  9. Proximity detector circuits: an attractive alternative to tunnel diode oscillators for contactless measurements in pulsed magnetic fields

    SciTech Connect

    Altarawneh, Moaz M; Mielke, Charles H

    2009-01-01

    A new radio frequency oscillator circuit based on a proximity detector integrated circuit is described as an alternative for the traditional tunnel diode oscillator used for pulsed magnetic field measurements at low temperatures. The new circuit has been successfully applied to measure the superconducting upper critical field in Ba{sub 0.55}K{sub 0.45}Fe{sub 2}As{sub 2} single crystfl.ls up to 60 T. The new circuit design avoids many of the problems associated with tunnel diode circuits while keeping the advantages of contact less measurements in pulsed magnets.

  10. The studies of Schottky-diode based co-plane detector for surface plasmon resonance sensing

    NASA Astrophysics Data System (ADS)

    Liu, Chien-Sheng; Wen, Tsun-Yu; Wang, Da-Shin; Lin, Chii-Wann

    2010-08-01

    The Surface Plasmon Resonance (SPR) is a label-free, highly sensitive and real time sensing technique and has been extensively applied to biosensing and assay for decades. In a conventional SPR biosensor, a prism is used to create the total reflection in which the evanescent wave can excite the surface plasmon mode at the metal-dielectric interface at certain angle, at which condition the reflectivity of incident TM-polarized vanished as measured by a far-field photodetector. This is the optical detection of surface plasmon resonance. In this research, zinc oxide (ZnO) was used as the dielectric thin-film material above the gold surface on the glass substrate to form a co-plane Schottky diode; this structure is designed to be an alternative way to detect SPR. The strength of plasmonic field is possible to be monitored by measuring the photocurrent under the reverse bias. According to our experimental results, the measured photocurrents with TM-polarized illumination (representing the SPR case), TE-polarized illumination (non-SPR case) and no illumination conditions under DC -1.5V bias are -76.158mA (2.5μA), -76.085mA (3.6μA) and -76.089mA (3.4μA), respectively. Based on the results, we have demonstrated this Schottky diode based co-plane device has the potential to be used as the SPR detector and provides a possible solution for the need of a low-cost, miniaturized, electronically integrated, and portable SPR biosensor in the near future.

  11. Characterization of a novel two dimensional diode array the ''magic plate'' as a radiation detector for radiation therapy treatment

    SciTech Connect

    Wong, J. H. D.; Fuduli, I.; Carolan, M.; Petasecca, M.; Lerch, M. L. F.; Perevertaylo, V. L.; Metcalfe, P.; Rosenfeld, A. B.

    2012-05-15

    Purpose: Intensity modulated radiation therapy (IMRT) utilizes the technology of multileaf collimators to deliver highly modulated and complex radiation treatment. Dosimetric verification of the IMRT treatment requires the verification of the delivered dose distribution. Two dimensional ion chamber or diode arrays are gaining popularity as a dosimeter of choice due to their real time feedback compared to film dosimetry. This paper describes the characterization of a novel 2D diode array, which has been named the ''magic plate'' (MP). It was designed to function as a 2D transmission detector as well as a planar detector for dose distribution measurements in a solid water phantom for the dosimetric verification of IMRT treatment delivery. Methods: The prototype MP is an 11 x 11 detector array based on thin (50 {mu}m) epitaxial diode technology mounted on a 0.6 mm thick Kapton substrate using a proprietary ''drop-in'' technology developed by the Centre for Medical Radiation Physics, University of Wollongong. A full characterization of the detector was performed, including radiation damage study, dose per pulse effect, percent depth dose comparison with CC13 ion chamber and build up characteristics with a parallel plane ion chamber measurements, dose linearity, energy response and angular response. Results: Postirradiated magic plate diodes showed a reproducibility of 2.1%. The MP dose per pulse response decreased at higher dose rates while at lower dose rates the MP appears to be dose rate independent. The depth dose measurement of the MP agrees with ion chamber depth dose measurements to within 0.7% while dose linearity was excellent. MP showed angular response dependency due to the anisotropy of the silicon diode with the maximum variation in angular response of 10.8% at gantry angle 180 deg. Angular dependence was within 3.5% for the gantry angles {+-} 75 deg. The field size dependence of the MP at isocenter agrees with ion chamber measurement to within 1.1%. In

  12. Standoff gas leak detectors based on tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Frish, M. B.; Wainner, R. T.; Green, B. D.; Laderer, M. C.; Allen, M. G.

    2005-11-01

    Trace gas sensing and analysis by Tunable Diode Laser Absorption Spectroscopy (TDLAS) has become a robust and reliable technology accepted for industrial process monitoring and control, quality assurance, environmental sensing, plant safety, and infrastructure security. Sensors incorporating well-packaged wavelength-stabilized near-infrared (1.2 to 2.0 μm) laser sources sense over a dozen toxic or industrially-important gases. A large emerging application for TDLAS is standoff sensing of gas leaks, e.g. from natural gas pipelines. The Remote Methane Leak Detector (RMLD), a handheld standoff TDLAS leak survey tool that we developed, is replacing traditional leak detection tools that must be physically immersed within a leak to detect it. Employing a 10 mW 1.6 micron DFB laser, the RMLD illuminates a non-cooperative topographic surface, up to 30 m distant, and analyzes returned scattered light to deduce the presence of excess methane. The eye-safe, battery-powered, 6-pound handheld RMLD enhances walking pipeline survey rates by more than 30%. When combined with a spinning or rastering mirror, the RMLD serves as a platform for mobile leak mapping systems. Also, to enable high-altitude surveying and provide aerial disaster response, we are extending the standoff range to 3000 m by adding an EDFA to the laser transmitter.

  13. Background rejection capabilities of a Compton imaging telescope setup with a DSSD Ge planar detector and AGATA

    NASA Astrophysics Data System (ADS)

    Doncel, M.; Quintana, B.; Gadea, A.; Recchia, F.; Farnea, E.

    2011-08-01

    In this work, we show the first Monte Carlo results about the performance of the Ge array which we propose for the DESPEC experiment at FAIR, when the background algorithm developed for AGATA is applied. The main objective of our study is to characterize the capabilities of the γ-spectroscopy system, made up of AGATA detectors in a semi-spherical distribution covering a 1π solid angle and a set of planar Ge detectors in a daisy configuration, to discriminate between γ sources placed at different locations.

  14. The effect of detector size and energy resolution on image quality in multi-projection Compton scatter tomography.

    PubMed

    Chighvinadze, Tamar; Pistorius, Stephen

    2014-01-01

    The reconstructed electron density image quality is sensitive to the detector size and energy resolution, which contribute to the blurring and noise in the image. This work evaluates optimal values of the detector parameters for a realistic system through analytical simulations of the transverse slice of the dedicated breast CT system geometry. This study introduces a spectroscopic x-ray tomography technique which uses multiple projections to reconstruct electron density images by backprojecting scattered photons over isogonic curves. The reconstruction can be obtained using a single projection yet its quality degrades as the acquisition conditions i.e. detector size and energy resolution deviate from the ideal. The reconstruction quality becomes inconsistent throughout the image due to the data under sampling caused by the finite resolution of the detector. The extension to the multi-projection mode effectively fills-in the missing data space and improves the ability to reconstruct an object. This work demonstrates the possibility to obtain images in the presence of noise. PMID:24463390

  15. Design and testing of a unique active Compton-suppressed LaBr3(Ce) detector system for improved sensitivity assays of TRU in remote-handled TRU wastes

    SciTech Connect

    J. K. Hartwell; M. E. McIlwain; J. A. Kulisek

    2007-10-01

    The US Department of Energy’s transuranic (TRU) waste inventory includes about 4,500 m3 of remote-handled TRU (RH-TRU) wastes composed of a variety of containerized waste forms having a contact surface dose rate that exceeds 2 mSv/hr (200 mrem/hr) containing waste materials with a total TRU concentration greater than 3700 Bq/g (100 nCi/g). As part of a research project to investigate the use of active Compton-suppressed room-temperature gamma-ray detectors for direct non-destructive quantification of the TRU content of these RH-TRU wastes, we have designed and purchased a unique detector system using a LaBr3(Ce) primary detector and a NaI(Tl) suppression mantle. The LaBr3(Ce) primary detector is a cylindrical unit ~25 mm in diameter by 76 mm long viewed by a 38 mm diameter photomultiplier. The NaI(Tl) suppression mantle (secondary detector) is 175 mm by 175 mm with a center well that accommodates the primary detector. An important feature of this arrangement is the lack of any “can” between the primary and secondary detectors. These primary and secondary detectors are optically isolated by a thin layer (.003") of aluminized kapton, but the hermetic seal and thus the aluminum can surrounds the outer boundary of the detector system envelope. The hermetic seal at the primary detector PMT is at the PMT wall. This arrangement virtually eliminates the “dead” material between the primary and secondary detectors, a feature that preliminary modeling indicated would substantially improve the Compton suppression capability of this device. This paper presents both the expected performance of this unit determined from modeling with MCNPX, and the performance measured in our laboratory with radioactive sources.

  16. A Self-Synchronized Optoelectronic Oscillator based on an RTD Photo-Detector and a Laser Diode.

    PubMed

    Romeira, Bruno; Seunarine, Kris; Ironside, Charles N; Kelly, Anthony E; Figueiredo, José M L

    2011-08-15

    We propose and demonstrate a simple and stable low-phase noise optoelectronic oscillator (OEO) that uses a laser diode, an optical fiber delay line and a resonant tunneling diode (RTD) free-running oscillator that is monolithic integrated with a waveguide photo-detector. The RTD-OEO exhibits single-side band phase noise power below -100 dBc/Hz with more than 30 dB noise suppression at 10 kHz from the center free-running frequency for fiber loop lengths around 1.2 km. The oscillator power consumption is below 0.55 W, and can be controlled either by the injected optical power or the fiber delay line. The RTD-OEO stability is achieved without using other high-speed optical/optoelectronic components and amplification. PMID:23814452

  17. A Self-Synchronized Optoelectronic Oscillator based on an RTD Photo-Detector and a Laser Diode

    PubMed Central

    Romeira, Bruno; Seunarine, Kris; Ironside, Charles N.; Kelly, Anthony E.; Figueiredo, José M. L.

    2013-01-01

    We propose and demonstrate a simple and stable low-phase noise optoelectronic oscillator (OEO) that uses a laser diode, an optical fiber delay line and a resonant tunneling diode (RTD) free-running oscillator that is monolithic integrated with a waveguide photo-detector. The RTD-OEO exhibits single-side band phase noise power below −100 dBc/Hz with more than 30 dB noise suppression at 10 kHz from the center free-running frequency for fiber loop lengths around 1.2 km. The oscillator power consumption is below 0.55 W, and can be controlled either by the injected optical power or the fiber delay line. The RTD-OEO stability is achieved without using other high-speed optical/optoelectronic components and amplification. PMID:23814452

  18. Silicon PIN diode hybrid arrays for charged particle detection: Building blocks for vertex detectors at the SSC

    SciTech Connect

    Kramer, G.; Gaalema, S.; Shapiro, S.L.; Dunwoodie, W.M.; Arens, J.F.; Jernigan, J.G.

    1989-05-01

    Two-dimensional arrays of solid state detectors have long been used in visible and infrared systems. Hybrid arrays with separately optimized detector and readout substrates have been extensively developed for infrared sensors. The characteristics and use of these infrared readout chips with silicon PIN diode arrays produced by MICRON SEMICONDUCTOR for detecting high-energy particles are reported. Some of these arrays have been produced in formats as large as 512 /times/ 512 pixels; others have been radiation hardened to total dose levels beyond 1 Mrad. Data generation rates of 380 megasamples/second have been achieved. Analog and digital signal transmission and processing techniques have also been developed to accept and reduce these high data rates. 9 refs., 15 figs., 2 tabs.

  19. Polarization Measurements with Compton Telescopes

    NASA Astrophysics Data System (ADS)

    Akyuz, A.; O'Neill, T. J.; Bhattacharya, D.; Dixon, D. D.; Tumer, T. O.; White, R. S.; Zych, A. D.

    1994-12-01

    The response of the Tracking and Imaging Gamma-Ray Experiment (TIGRE) instrument to polarized celestial gamma rays above 300 keV is presented. TIGRE uses multilayers of silicon strip detectors both as a gamma-ray converter and to track Compton recoil electrons and positron-electron pairs up to 100 MeV. For Compton events, the direction and energy of the Compton scattered gamma ray are measured with arrays of small CsI(Tl)-photodiode detectors. A small balloon prototype instrument is being constructed that has a high absolute detection efficiency of 10% and a sensitivity of 100 milliCrabs for an exposure of 12 hours. The prototype's sensitivity to polarized gamma radiation has been calculated with the MCNP detector simulation code which was modified to include the polarization dependence of the Klein-Nishina formula. Polarized events and unpolarized source events with background are combined to simulate an observation of the Crab Nebula and pulsar. TIGRE's polarization modulation factor varies from 0.17 to 0.42 depending on the energy and Compton scatter angle cuts that are used. With 12 hours of observation on the Crab, polarized gamma radiation can be detected down to the level of about 10%. Potential celestial sources of polarized gamma-ray emission will be discussed.

  20. Development of the large-area silicon PIN diode with 2 millimeter-thick depletion layer for hard x-ray detector (HXD) on board ASTRO-E

    NASA Astrophysics Data System (ADS)

    Sugizaki, Mutsumi; Kubo, S.; Murakami, Toshio; Ota, Naomi; Ozawa, Hideki; Takahashi, Tadayuki; Kaneda, Hidehiro; Iyomoto, Naoko; Kamae, Tuneyoshi; Kokubun, Motohide; Kubota, Aya; Makishima, Kazuo; Tamura, Takayuki; Tashiro, Makoto

    1997-07-01

    ASTRO-E is the next Japanese x-ray satellite to be launched in the year 2000. It carries three high-energy astrophysical experiments, including the hard x-ray detector (HXD) which is unique in covering the wide energy band from 10 keV to 700 keV with an extremely low background. The HXD is a compound-eye detector, employing 16 GSO/BGO well-type phoswich scintillation counters together with 64 silicon PIN detectors. The scintillation counters cover an energy range of 40 - 700 keV, while the PIN diodes fill the intermediate energy range from 10 keV to 70 keV with an energy resolution about 3 keV. In this paper, we report on the developments of the large area, thick silicon PIN diodes. In order to achieve a high quantum efficiency up to 70 keV with a high energy resolution, we utilize a double stack of silicon PIN diodes, each 20 by 20 mm(superscript 2) in size and 2 mm thick. Signals from the two diodes are summed into a single output. Four of these stacks (or eight diodes) are placed inside the deep BGO active-shield well of a phoswich counter, to achieve an extremely low background environment. Thus, the HXD utilizes 64 stacked silicon PIN detectors, achieving a total geometrical collecting area of 256 cm(superscript 2). We have developed the 2 mm thick silicon PIN diodes which have low leakage current, a low capacitance, and a high breakdown voltage to meet the requirements of our goal. Through various trials in fabricating PIN diodes with different structures, we have found optimal design parameters, such as mask design of the surface p(superscript +) layer and the implantation process.

  1. RESPONSE LINEARIZATION OF A DIODE DETECTOR TYPE RADIO FREQUENCY ELECTRIC FIELD PROBE

    EPA Science Inventory

    An EPROM-based linearization circuit with a resolution of 0.1 percent of full scale has been designed to linearize the response of an orthogonal dipole electric field probe terminated with diodes. Design approach, performance, and probe characteristics are discussed. The nonlinea...

  2. A new modeling and simulation method for important statistical performance prediction of single photon avalanche diode detectors

    NASA Astrophysics Data System (ADS)

    Xu, Yue; Xiang, Ping; Xie, Xiaopeng; Huang, Yang

    2016-06-01

    This paper presents a new modeling and simulation method to predict the important statistical performance of single photon avalanche diode (SPAD) detectors, including photon detection efficiency (PDE), dark count rate (DCR) and afterpulsing probability (AP). Three local electric field models are derived for the PDE, DCR and AP calculations, which show analytical dependence of key parameters such as avalanche triggering probability, impact ionization rate and electric field distributions that can be directly obtained from Geiger mode Technology Computer Aided Design (TCAD) simulation. The model calculation results are proven to be in good agreement with the reported experimental data in the open literature, suggesting that the proposed modeling and simulation method is very suitable for the prediction of SPAD statistical performance.

  3. Fill-factor improvement of Si CMOS single-photon avalanche diode detector arrays by integration of diffractive microlens arrays.

    PubMed

    Intermite, Giuseppe; McCarthy, Aongus; Warburton, Ryan E; Ren, Ximing; Villa, Federica; Lussana, Rudi; Waddie, Andrew J; Taghizadeh, Mohammad R; Tosi, Alberto; Zappa, Franco; Buller, Gerald S

    2015-12-28

    Single-photon avalanche diode (SPAD) detector arrays generally suffer from having a low fill-factor, in which the photo-sensitive area of each pixel is small compared to the overall area of the pixel. This paper describes the integration of different configurations of high efficiency diffractive optical microlens arrays onto a 32 × 32 SPAD array, fabricated using a 0.35 µm CMOS technology process. The characterization of SPAD arrays with integrated microlens arrays is reported over the spectral range of 500-900 nm, and a range of f-numbers from f/2 to f/22. We report an average concentration factor of 15 measured for the entire SPAD array with integrated microlens array. The integrated SPAD and microlens array demonstrated a very high uniformity in overall efficiency. PMID:26832039

  4. Absorbance detector for capillary electrophoresis based on light-emitting diodes and photodiodes for the deep-ultraviolet range.

    PubMed

    Bui, Duy Anh; Hauser, Peter C

    2015-11-20

    A new absorbance detector for capillary electrophoresis featuring relatively high intensity light-emitting diodes as radiation sources and photodiodes for the deep-UV range was developed. The direct relationship of absorbance values and concentrations was obtained by emulating Lambert-Beer's law with the application of a beam splitter to obtain a reference signal and a log-ratio amplifier circuitry. The performance of the cell was investigated at 255 nm with the detection of sulfanilic, 4-nitrobenzoic, 4-hydroxybenzoic and 4-aminobenzoic acid and the indirect detection of acetate, propionate, butyrate and caproate using benzoate as the displacement dye molecule. Vanillic acid, L-tyrosine and DL-tryptophan as well as the sulfonamides sulfamerazine, sulfathiazole and sulfamethazine were determined at 280 nm. Good linearities over 3 orders of magnitude were obtained. The noise level recorded was as low as 50 μAU and the drift typically <200 μAU/5 min. PMID:26091783

  5. SPEIR: A Ge Compton Camera

    SciTech Connect

    Mihailescu, L; Vetter, K M; Burks, M T; Hull, E L; Craig, W W

    2004-02-11

    The SPEctroscopic Imager for {gamma}-Rays (SPEIR) is a new concept of a compact {gamma}-ray imaging system of high efficiency and spectroscopic resolution with a 4-{pi} field-of-view. The system behind this concept employs double-sided segmented planar Ge detectors accompanied by the use of list-mode photon reconstruction methods to create a sensitive, compact Compton scatter camera.

  6. SiC Schottky Diode Detectors for Measurement of Actinide Concentrations from Alpha Activities in Molten Salt Electrolyte

    SciTech Connect

    Windl, Wolfgang; Blue, Thomas

    2013-01-28

    In this project, we have designed a 4H-SiC Schottky diode detector device in order to monitor actinide concentrations in extreme environments, such as present in pyroprocessing of spent fuel. For the first time, we have demonstrated high temperature operation of such a device up to 500 °C in successfully detecting alpha particles. We have used Am-241 as an alpha source for our laboratory experiments. Along with the experiments, we have developed a multiscale model to study the phenomena controlling the device behavior and to be able to predict the device performance. Our multiscale model consists of ab initio modeling to understand defect energetics and their effect on electronic structure and carrier mobility in the material. Further, we have developed the basis for a damage evolution model incorporating the outputs from ab initio model in order to predict respective defect concentrations in the device material. Finally, a fully equipped TCAD-based device model has been developed to study the phenomena controlling the device behavior. Using this model, we have proven our concept that the detector is capable of performing alpha detection in a salt bath with the mixtures of actinides present in a pyroprocessing environment.

  7. Optimization and small-signal modeling of zero-bias InAs self-switching diode detectors

    NASA Astrophysics Data System (ADS)

    Westlund, A.; Sangaré, P.; Ducournau, G.; Iñiguez-de-la-Torre, I.; Nilsson, P.-Å.; Gaquière, C.; Desplanque, L.; Wallart, X.; Millithaler, J. F.; González, T.; Mateos, J.; Grahn, J.

    2015-02-01

    Design optimization of the InAs self-switching diode (SSD) intended for direct zero-bias THz detection is presented. The SSD, which consists of nanometer-sized channels in parallel, was described using an equivalent small-signal circuit. Expressions for voltage responsivity and noise equivalent power (NEP) were derived in terms of geometrical design parameters of the SSD, i.e. the channel length and the number of channels. Modeled design dependencies were confirmed by RF and DC measurements on InAs SSDs. In terms of NEP, an optimum number of channels were found with the detector driven by a 50 Ω source. With a matched source, the model predicted a responsivity of 1900 V/W and NEP of 7.7 pW/Hz½ for a single-channel InAs SSD with 35 nm channel width. Monte Carlo device simulations supported observed design dependencies. The proposed small-signal model can be used to optimize SSDs of any material system for low-noise and high-frequency operation as zero-bias detectors. In large signal measurements, the responsivity of the InAs SSDs exhibited a 1 dB deviation from linear responsivity at an input power of -3 dBm from a 50 Ω source.

  8. A facile light-emitting-diode induced fluorescence detector coupled to an integrated microfluidic device for microchip electrophoresis.

    PubMed

    Yang, Fan; Li, Xin-chun; Zhang, Wen; Pan, Jian-bin; Chen, Zuan-guang

    2011-05-30

    In this paper, a compact and inexpensive light emitting diode induced fluorescence (LED-IF) detector with simplified optical configuration was developed and assembled in an integrated microfluidic device for microscale electrophoresis. The facile detector mainly consisted of an LED, a focusing pinhole, an emission filter and a photodiode, and was encapsulated in the upper layer of an aluminum alloy device with two layers. At the bottom layer, integrated circuit (IC) was assembled to manipulate the voltage for sample injection and separation, LED emission and signal amplifying. A high-power LED with fan-shaped heat sink was used as excitation source. The excitation light was focused by a 1.1mm diameter pinhole fabricated in a thin piece of silver foil, and the obtained sensitivity was about 3 times as high as that using electrode plate. Other important parameters including LED driven current, fluorescence collection angle and detection distance have also been investigated. Under optimal conditions, considerable high-response of 0.09 fmol and 0.18 fmol mass detection limits at 0.37 nL injection volume for sodium fluorescein (SF) and FITC was achieved, respectively. This device has been successfully employed to separate penicillamine (PA) enantiomers. Due to such significant features as low-cost, integration, miniaturization, and ease of commercialization, the presented microfluidic device may hold great promise for clinical diagnostics and bioanalytical applications. PMID:21530784

  9. Compton coincidence volumetric imaging: a new x-ray volumetric imaging modality based on Compton scattering

    NASA Astrophysics Data System (ADS)

    Xu, Xiaochao

    2014-03-01

    Compton scattering is a dominant interaction during radiography and computed tomography x-ray imaging. However, the scattered photons are not used for extracting imaging information, but seriously degrade image quality. Here we introduce a new scheme that overcomes most of the problems associated with existing Compton scattering imaging schemes and allows Compton scattered photons to be effectively used for imaging. In our scheme, referred as Compton coincidence volumetric imaging (CCVI), a collimated monoenergetic x-ray beam is directed onto a thin semiconductor detector. A small portion of the photons is Compton scattered by the detector and their energy loss is detected. Some of the scattered photons intersect the imaging object, where they are Compton scattered a second time. The finally scattered photons are recorded by an areal energy resolving detector panel around the object. The two detectors work in coincidence mode. CCVI images the spatial electron density distribution in the imaging object. Similar to PET imaging, the event location can be located within a curve; therefore the imaging reconstruction algorithms are also similar to those of PET. Two statistical iterative imaging reconstruction algorithms are tested. Our study verifies the feasibility of CCVI in imaging acquisition and reconstruction. Various aspects of CCVI are discussed. If successfully implemented, it will offer a great potential for imaging dose reduction compared with x-ray CT. Furthermore, a CCVI modality will have no moving parts, which potentially offers cost reduction and faster imaging speed.

  10. Response corrections for solid-state detectors in megavoltage photon dosimetry

    NASA Astrophysics Data System (ADS)

    Yin, Z.; Hugtenburg, R. P.; Beddoe, A. H.

    2004-08-01

    Solid-state detectors offer high sensitivity, stability and resolution and are frequently the dosimeter of choice for on-line dosimetry and small field therapies such as stereotactic radiosurgery. The departure from tissue equivalence of many solid-state devices, including diodes and MOSFETs, has to be carefully considered at lower energies and for Compton scattered radiation where the strongly Z-dependent photoelectric effect is significant. A modification of Burlin cavity theory is proposed that treats primary and scatter photon spectra separately and this has been applied to determine the correction factors for diode detector measurements of 6 and 15 MV linear accelerator beams. Uncorrected, an unshielded diode overestimates the dose at depth by as much as 15% for the 6 MV beam. The model predicts the effect to within 1% for both energies offering a basis for the correction of diodes for use in routine dosimetry.

  11. Liquid Chromatography-diode Array Detector-electrospray Mass Spectrometry and Principal Components Analyses of Raw and Processed Moutan Cortex

    PubMed Central

    Deng, Xian-Mei; Yu, Jiang-Yong; Ding, Meng-Jin; Zhao, Ming; Xue, Xing-Yang; Che, Chun-Tao; Wang, Shu-Mei; Zhao, Bin; Meng, Jiang

    2016-01-01

    Background: Raw Moutan Cortex (RMC), derived from the root bark of Paeonia suffruticosa, and Processed Moutan Cortex (PMC) is obtained from RMC by undergoing a stir-frying process. Both of them are indicated for different pharmacodynamic action in traditional Chinese medicine, and they have been used in China and other Asian countries for thousands of years. Objective: To establish a method to study the RMC and PMC, revealing their different chemical composition by fingerprint, qualitative, and quantitative ways. Materials and Methods: High-performance liquid chromatography coupled with diode array detector and electrospray mass spectrometry (HPLC-DAD-ESIMS) were used for the analysis. Therefore, the analytes were separated on an Ultimate TM XB-C18 analytical column (250 mm × 4.6 mm, 5.0 μm) with a gradient elution program by a mobile phase consisting of acetonitrile and 0.1% (v/v) formic acid water solution. The flow rate, injection volume, detection wavelength, and column temperature were set at 1.0 mL/min, 10 μL, 254 nm, and 30°C, respectively. Besides, principal components analysis and the test of significance were applied in data analysis. Results: The results clearly showed a significant difference among RMC and PMC, indicating the significant changes in their chemical compositions before and after the stir-frying process. Conclusion: The HPLC-DAD-ESIMS coupled with chemometrics analysis could be used for comprehensive quality evaluation of raw and processed Moutan Cortex. SUMMARY The experiment study the RMC and PMC by HPLC-DAD-ESIMS couple with chemometrics analysis. The results of their fingerprints, qualitative, and quantitative all clearly showed significant changes in their chemical compositions before and after stir-frying processed. Abbreviation used: HPLC-DAD-ESIMS: High-performance Liquid Chromatography-Diode Array Detector-Electrospray Mass Spectrometry, RMC: Raw moutan cortex, PMC: Processed moutan cortex, TCM: Traditional Chinese medicine

  12. Concentration of uncompensated impurities as a key parameter of CdTe and CdZnTe crystals for Schottky diode x\\ssty{/}γ-ray detectors

    NASA Astrophysics Data System (ADS)

    Kosyachenko, L. A.; Lambropoulos, C. P.; Aoki, T.; Dieguez, E.; Fiederle, M.; Loukas, D.; Sklyarchuk, O. V.; Maslyanchuk, O. L.; Grushko, E. V.; Sklyarchuk, V. M.; Crocco, J.; Bensalah, H.

    2012-01-01

    In this paper we report on the strong impact of the concentration of uncompensated impurities on the detection efficiency of CdTe and Cd0.9Zn0.1Te Schottky diodes. The results of our study explain the observed poor detection properties of some Cd0.9Zn0.1Te detectors with resistivity and lifetime of carriers comparable to those of good CdTe detectors. We show that the concentration of uncompensated impurities in a highly efficient CdTe Schottky diode detector is several orders of magnitude higher than that of a CdZnTe, which does not register the gamma spectra of commonly used isotopes (59-662 keV) by using photoelectric measurements. The significant difference of the concentration of uncompensated impurities between CdTe and Cd0.9Zn0.1Te crystals is confirmed by our study of the temperature change of the resistivity and of the Fermi level energy. The degree of compensation of the donor complex, responsible for the electrical conductivity of the material, is much lower in the CdTe crystal compared to that in the Cd0.9Zn0.1Te crystal. The calculations of the detection efficiency of x/γ-radiation by a Schottky diode result in a dependence on the concentration of uncompensated impurities described by a curve with a pronounced maximum. The position of this maximum occurs at a concentration of uncompensated impurities which ranges from 3 × 1010 to 3 × 1012 cm-3 depending on the registered photon energy of x/γ-rays and on the lifetime of the charge carriers. Our measurements and calculations lead to the conclusion that the concentration of uncompensated impurities in this range is a necessary condition for the effective operation of x- and γ-ray Schottky diode detectors based on CdTe and Cd1-xZnxTe crystals.

  13. Quantification of lycopene in the processed tomato-based products by means of the light-emitting diode (LED) and compact photoacoustic (PA) detector

    NASA Astrophysics Data System (ADS)

    Bicanic, D.; Skenderović, H.; Marković, K.; Dóka, O.; Pichler, L.; Pichler, G.; Luterotti, S.

    2010-03-01

    The combined use of a high power light emitting diode (LED) and the compact photoacoustic (PA) detector offers the possibility for a rapid (no extraction needed), accurate (precision 1.5%) and inexpensive quantification of lycopene in different products derived from the thermally processed tomatoes. The concentration of lycopene in selected products ranges from a few mg to several tens mg per 100 g fresh weight. The HPLC was used as the well established reference method.

  14. Spectral light measurements in microbenthic phototrophic communities with a fiber-optic microprobe coupled to a sensitive diode array detector

    SciTech Connect

    Kuehl, M. ); Joergensen, B.B. )

    1992-12-01

    A diode array detector system for microscale light measurements with fiber-optic microprobes was developed; it measures intensities of 400-900-nm light over >6 orders of magnitude with a spectral resolution of 2-5 nm. Fiber-optic microprobes to measure field radiance or scalar irradiance were coupled to the detector system and used for spectral light measurements in hypersaline microbial mats and in laminated phototrophic communities of coastal sediments. The vertical distribution of major photopigments of microalgae, cyanobacteria, and anoxygenic phototrophic bacteria could be identified from extinction maxima in measured radiance spectra at 430-550 nm (Chl a and carotenoids), 620-625 nm (phycocyanin), 675 nm (Chl a), 745-750 nm (BChl c), 800-810 nm, and 860-880 nm (BChl a). Scalar irradiance spectra exhibited a different spectral composition and a higher light intensity at the sediment surface as compared to incident light. IR light thus reached 200% of incident at the sediment surface. Maximal light penetration was found for IR light, whereas visible light was strongly attenuated in the upper 0-2 mm of the sediment. Measurements of photon scalar irradiance (400-700 nm) were combined with microelectrode measurements of oxygenic photosynthesis in the coastal sediment. With an incident light intensity of 200 [mu]Einst m[sup [minus]2]s[sup [minus]1], photon scalar irradiance reached a maximum of 283 [mu]Einst m[sup [minus]2]s[sup [minus]1] at the sediment surface. The lower boundary of the euphotic zone was 2.2 mm below the surface at a light intensity of 12 [mu]Einst m[sup [minus]2]s[sup [minus]1]. 20 refs., 6 figs.

  15. Analysis of factors affecting the light collection efficiency in CT detector: CWO+PIN diode

    NASA Astrophysics Data System (ADS)

    Kwak, Sung W.; Kim, Kwang Hyun; Kim, Ho K.; Cho, Gyuseong; Ahn, Seong Kyu; Goh, Sung Min; Lee, Yoon; Park, Jung Byung

    2002-05-01

    The solid-state detector(SSD) for X-CT consists of photodiode coupled to CdWO4$(CWO. It is important to maximize the light collection in respect of a patient's dose, radiation effect and X-ray efficiency. The factors affecting the light collection efficiency are analyzed and optimized by using experimental data and appropriate simulation code. Quantum nomogram is used to investigate the signal propagation characteristics of optimally designed solid-state detector and to ensure at which stage quantum sink occurs. This paper shows that the part of SSD, the CWO of treatment with ground top/ground side yields higher quanta than that of ground top/polish side, which is different from the result of previous studies. We also shows that optimum thickness of SiN passivation and p-layer is 0.12mm and 0.1mm, respectively. From the quantum nomogram calculated for optimal design, it is predicted that the most serious signal degradation occurs at the photodiode.

  16. A Compton scatter attenuation gamma ray spectrometer

    NASA Technical Reports Server (NTRS)

    Austin, W. E.

    1972-01-01

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

  17. Simultaneous determination of four neuroprotective compounds of Tilia amurensis by high performance liquid chromatography coupled with diode array detector

    PubMed Central

    Lee, Bohyung; Weon, Jin Bae; Yun, Bo-Ra; Lee, Jiwoo; Eom, Min Rye; Ma, Choong Je

    2014-01-01

    Background: Tilia amurensis consists of various compounds, such as flavonoids and terpenoids. Objective: A simple and reliable high performance liquid chromatography (HPLC) coupled with the diode array detector (DAD) method has been established for simultaneous determination of epicatechin, nudiposide, lyoniside, and scopoletin isolated from Tilia amurensis. Materials and Methods: Optimum separations were obtained with a SHISEIDO C18 column by gradient eluton, with 0.1% Trifluoroacetic acid (TFA) water-methanol as the mobile phase. The gradient elution system was completed within 40 minutes. The flow rate and detection wavelength were 1 mL/minute, 205 nm, 250 nm, and 280 nm, respectively. Results: Validation of the analytical method was evaluated by linearity, precision, and the accuracy test. The calibration curve was linear over the established range with R2 > 0.997. The limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.01-15.20 μg/mL and 0.03-46.06 μg/mL. The method exhibited an intraday and interday precision range of 96.25-105.66% and 93.52-109.92%, respectively (RSD <2.80%). The recoveries and relative standard deviation (RSD) of the four compounds in Tilia amurensis were in the range of 90.42-104.84% and 0.2-2.58%. Conclusion: This developed method was accurate and reliable for the quality evaluation of the four compounds isolated from Tilia amurensis. PMID:25210303

  18. Study of Generalized Parton Distributions and Deeply Virtual Compton Scattering on the nucleon with the CLAS and CLAS12 detectors at the Jefferson Laboratory

    SciTech Connect

    Guegan, Baptiste

    2012-11-01

    The exclusive leptoproduction of a real photon is considered to be the "cleanest" way to access the Generalized Parton Distribution (GPD). This process is called Deeply Virtual Compton Scattering (DVCS) lN {yields} lN{gamma} , and is sensitive to all the four GPDs. Measuring the DVCS cross section is one of the main goals of this thesis. In this thesis, we present the work performed to extract on a wide phase-space the DVCS cross-section from the JLab data at a beam energy of 6 GeV.

  19. Compton scattering with low intensity radioactive sources

    NASA Astrophysics Data System (ADS)

    Quarles, Carroll

    2012-03-01

    Compton scattering experiments with gamma rays typically require a ``hot'' source (˜5mCi of Cs137) to observe the scattering as a function of angle. (See Ortec AN34 Experiment #10 Compton Scattering) Here a way is described to investigate Compton scattering with micro Curie level radioactive sources that are more commonly available in the undergraduate laboratory. A vertical-looking 2 inch coaxial hpGe detector, collimated with a 2 inch thick lead shield, was used. Cylindrical Al targets of various thicknesses were placed over the collimator and several available sources were placed around the target so that the average Compton scattering angle into the collimator was 90 deg. A peak could be observed at the expected energy for 90 deg. Compton scattering by doing 24 hour target-in minus target-out runs. The peak was broadened by the spread in the scattering angle due to the variation in the angle of the incoming gamma ray and the angular acceptance of the collimator. A rough analysis can be done by modeling the angular spread due to the geometry and correcting for the gamma ray absorption from the target center. Various target materials and sources can be used and some variation in average Compton scattering angle can be obtained by adjusting the geometry of the source and target.

  20. Compton tomography system

    DOEpatents

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

    2016-02-02

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

  1. Study of Compton vs. Photoelectric Interactions

    SciTech Connect

    Gronberg, J B; Johnson, S C; Lange, D J; Wright, D M; Beiersdorfer, P

    2004-07-09

    We have studied how often incoming photons interact via a Compton interaction and/or a photoelectric interaction as a function of energy and detector material Results are using a 1m{sup 3} detector, and discrete energy photons from 0.1 MeV up to 10 MeV. Essentially all of the lower energy photons interact at least once in a detector of this size. This is not the case at higher energies. Each detector, photon energy combination was simulated with 2000 photons.

  2. Competition between the barrier and injection mechanisms of nonlinearity of the current-voltage characteristic in Mott-barrier detector diodes

    NASA Astrophysics Data System (ADS)

    Shashkin, V. I.; Vostokov, N. V.

    2009-08-01

    We obtain an analytical solution to the problem of transverse injection current in an undoped semiconductor i layer of arbitrary thickness with account of self-consistent boundary conditions. Charge transfer in the semiconductor bulk is described in the drift-diffusion approximation. Current transfer through the boundaries of an undoped layer is described in terms of the thermoelectron emission theory. Thus, the generalized thermoemission-diffusion approach applies for semiconductors with both low and high mobilities of charge carriers. On the basis of the obtained solution, we analyze the characteristics of the current nonlinearity of the Mott-barrier diodes. The generalized approach is used for describing current transfer in low-barrier diodes based on Mott contacts with near-surface δ-doping. Characteristics of detection of low-barrier diodes are analyzed. Limiting values of the volt-watt and threshold sensitivities of the detectors based on these diodes in the subterahertz frequency range (up to 1 THz) are determined.

  3. Real-time continuous-wave terahertz line scanner based on a compact 1 × 240 InGaAs Schottky barrier diode array detector.

    PubMed

    Han, Sang-Pil; Ko, Hyunsung; Kim, Namje; Lee, Won-Hui; Moon, Kiwon; Lee, Il-Min; Lee, Eui Su; Lee, Dong Hun; Lee, Wangjoo; Han, Seong-Tae; Choi, Sung-Wook; Park, Kyung Hyun

    2014-11-17

    We demonstrate real-time continuous-wave terahertz (THz) line-scanned imaging based on a 1 × 240 InGaAs Schottky barrier diode (SBD) array detector with a scan velocity of 25 cm/s, a scan line length of 12 cm, and a pixel size of 0.5 × 0.5 mm². Foreign substances, such as a paper clip with a spatial resolution of approximately 1 mm that is hidden under a cracker, are clearly detected by this THz line-scanning system. The system consists of the SBD array detector, a 200-GHz gyrotron source, a conveyor system, and several optical components such as a high-density polyethylene cylindrical lens, metal cylindrical mirror, and THz wire-grid polarizer. Using the THz polarizer, the signal-to-noise ratio of the SBD array detector improves because the quality of the source beam is enhanced. PMID:25402136

  4. Quantification of maltol in Korean ginseng (Panax ginseng) products by high-performance liquid chromatography-diode array detector

    PubMed Central

    Jeong, Hyun Cheol; Hong, Hee-Do; Kim, Young-Chan; Rhee, Young Kyoung; Choi, Sang Yoon; Kim, Kyung-Tack; Kim, Sung Soo; Lee, Young-Chul; Cho, Chang-Won

    2015-01-01

    Background: Maltol, as a type of phenolic compounds, is produced by the browning reaction during the high-temperature treatment of ginseng. Thus, maltol can be used as a marker for the quality control of various ginseng products manufactured by high-temperature treatment including red ginseng. For the quantification of maltol in Korean ginseng products, an effective high-performance liquid chromatography-diode array detector (HPLC-DAD) method was developed. Materials and Methods: The HPLC-DAD method for maltol quantification coupled with a liquid-liquid extraction (LLE) method was developed and validated in terms of linearity, precision, and accuracy. An HPLC separation was performed on a C18 column. Results: The LLE methods and HPLC running conditions for maltol quantification were optimized. The calibration curve of the maltol exhibited good linearity (R2 = 1.00). The limit of detection value of maltol was 0.26 μg/mL, and the limit of quantification value was 0.79 μg/mL. The relative standard deviations (RSDs) of the data of the intra- and inter-day experiments were <1.27% and 0.61%, respectively. The results of the recovery test were 101.35–101.75% with an RSD value of 0.21–1.65%. The developed method was applied successfully to quantify the maltol in three ginseng products manufactured by different methods. Conclusion: The results of validation demonstrated that the proposed HPLC-DAD method was useful for the quantification of maltol in various ginseng products. PMID:26246746

  5. A novel liquid chromatography method using diode-array detector for the determination of oleuropein in dietary supplements.

    PubMed

    Bertolini, Tiziana; Vicentini, Lorenza; Boschetti, Silvia; Andreatta, Paolo; Gatti, Rita

    2016-09-10

    A simple and fast chromatographic method using ultraviolet diode-array detector (UV-DAD) was developed for the automatic high performance liquid chromatography (HPLC) determination of the title of oleuropein in a new dietary supplements in form of effervescent granules. The chromatographic separations were performed on a C18 core-shell column with detection at λ=232nm. The mobile phase consisted of deionized water with 0.1% TFA and acetonitrile under gradient conditions at a flow-rate of 0.8mL/min. Oleuropein and oleuroside present in the raw material were characterized by high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The validation of the analytical procedure has been performed determining the following parameters: specificity, linearity, repeatability, reproducibility, accuracy, limit of quantification (LOQ), stability of the standard and sample solutions. Linear response was observed in fortified placebo solutions (determination coefficient: 0.9998). Intra-day precision (relative standard deviation, RSD) was ≤5.0% for peak area and for retention times (tR) without significant differences between intra- and inter-day data. The limits of quantitation (LOQ) was about 5μg/mL and 9pmol/inject. Oleuropein recovery studies gave good results (99.9%) with a R.S.D. of 0.5%. The speed of analysis and the stability of the solutions with a fluctuation Δ (%) ≤2.0 at room temperature means an undoubted advantage of the method allowing the simultaneous preparation of many samples and consecutive chromatographic analyses by using an autosampler. The developed method is suitable for the quality control of oleuropein in raw material and industrial products. The method can be applied in any analytical laboratory not requiring a sophisticated instrumentation. PMID:27429369

  6. Design of a Compton scatter based radiation tracking system

    NASA Astrophysics Data System (ADS)

    Healy, Heather

    Gamma spectroscopy is one of the most common techniques used for the detection of radiologic materials. This technology is deployed in a variety of scenarios such as emergency response, monitoring, and the recovery of lost, stolen, or otherwise unaccounted radiologic material. In most practical scenarios, it is useful to know the location of a source in relation to a detector, in addition to the classic output from gamma spectrometers such as decay rate and energy peak information. In collaboration with the Remote Sensing Laboratory (RSL) at Andrews Air Force Base, a novel detector design by RSL, which utilizes a 360° detectable range in order to increase the probability of remote detection, was investigated for the possibility to recreate source location information from Compton scattering events within the detector. A recreation of this novel detector is simulated using Geant4 to determine the optimal dimensions of sodium iodide detectors that produce the most single Compton scattering events in order to facilitate source location through the back-projection of Compton scattering angles. The optimal detector dimensions are determined by maximizing the number of single Compton scatter events and minimizing the percentage of Compton events that undergo multiple successive scatters in detectors of varying thicknesses and lengths. The optimal detector thickness was chosen to be 1.88 in, and the optimal detector length was chosen to be 4 to 4.5 in. In future projects, these optimized detectors can be used to apply suggested back-projection algorithms in order to determine the feasibility and functionality of this detector design for the purpose of radiologic source location.

  7. Photo-detector diode based on thermally oxidized TiO2 nanostructures/p-Si heterojunction

    NASA Astrophysics Data System (ADS)

    Hosseini, Z. S.; Shasti, M.; Ramezani Sani, S.; Mortezaali, A.

    2016-01-01

    Titanium oxide (TiO2)-based photodetectors were fabricated using a thermal oxidation technique. The effect of two different annealing temperatures on morphology, structure, and I-V characteristics has been investigated. TiO2/Si heterostructure exhibited diode-like rectifying I-V behavior both in dark and under illumination. Dependence in photoresponse on annealing temperature was observed that was related to effective surface area of quasi-one-dimensional TiO2 nanostructures. Fabricated TiO2/Si diodes in 850 °C as the lower annealing temperature showed higher responsivity and sensitivity compared with grown ones in 950 °C (R850 °C/R950 °C ˜ 5 and S850 °C/S950 °C ˜ 1.6). Rather good photoresponse and simple fabrication process make the 850 °C-TiO2/Si diode a promising candidate for practical applications.

  8. Hard X-ray and gamma-ray detector for ASTRO-H based on Si and CdTe imaging sensors

    NASA Astrophysics Data System (ADS)

    Hxi/Sgd Team; Kokubun, M.; Watanabe, S.; Nakazawa, K.; Tajima, H.; Fukazawa, Y.; Takahashi, T.; Kataoka, J.; Kamae, T.; Katagiri, H.; Madejski, G. M.; Makishima, K.; Mizuno, T.; Ohno, M.; Sato, R.; Takahashi, H.; Tanaka, T.; Tashiro, M.; Terada, Y.; Yamaoka, K.; HXI/SGD Team

    2010-11-01

    We have been developing a hard X-ray imager and soft gamma-ray detector as on board instruments of the ASTRO-H mission. The Hard X-ray Imager (HXI) is one of the three focal plane detectors of ASTRO-H, which is aimed to realize the focusing imaging of hard X-ray photons in combination with hard X-ray telescopes. By use of the hybrid structure composed of double-sided silicon strip detectors and a cadmium telluride strip detector, it fully covers the energy range up to 80 keV with a high quantum efficiency. High spatial resolutions of 250μm pitch and energy resolutions of 1-2 keV (FWMH) are at the same time achieved with low noise front-end ASICs. The Soft Gamma-ray Detector (SGD) is a novel and unique detector which is characterized by semiconductor Compton cameras surrounded by narrow field-of-view active shields, and covers a higher energy range (30-600 keV) than that of HXI. It consists of four Compton Cameras constructed with many layers of Silicon and CdTe pad detectors. With its multi-layer structure and Compton reconstruction capability, in addition to the BGO active shields read by Avalanche photo-diodes, this detector will achieve an extremely high background rejection efficiency in the orbit. We report the current status of hardware development including the design requirement, expected performance, and technical readinesses of key technologies.

  9. Portable compton gamma-ray detection system

    DOEpatents

    Rowland, Mark S.; Oldaker, Mark E.

    2008-03-04

    A Compton scattered gamma-ray detector system. The system comprises a gamma-ray spectrometer and an annular array of individual scintillators. The scintillators are positioned so that they are arrayed around the gamma-ray spectrometer. The annular array of individual scintillators includes a first scintillator. A radiation shield is positioned around the first scintillator. A multi-channel analyzer is operatively connected to the gamma-ray spectrometer and the annular array of individual scintillators.

  10. Deeply Virtual Compton Scattering with CLAS

    SciTech Connect

    F.X. Girod

    2007-12-17

    The beam spin asymmetries of the reaction ep -> epg in the Bjorken regime were measured over a wide kinematical domain using the CLAS detector and a new lead-tungstate calorimeter. Through the interference of the Bethe-Heitler process with Deeply Virtual Compton Scattering, those asymmetries provide constraints for the nucleon Generalized Parton Distributions models. The observed shapes are in agreement with twist-2 dominance predictions.

  11. Detectors

    DOEpatents

    Orr, Christopher Henry; Luff, Craig Janson; Dockray, Thomas; Macarthur, Duncan Whittemore; Bounds, John Alan; Allander, Krag

    2002-01-01

    The apparatus and method provide techniques through which both alpha and beta emission determinations can be made simultaneously using a simple detector structure. The technique uses a beta detector covered in an electrically conducting material, the electrically conducting material discharging ions generated by alpha emissions, and as a consequence providing a measure of those alpha emissions. The technique also offers improved mountings for alpha detectors and other forms of detectors against vibration and the consequential effects vibration has on measurement accuracy.

  12. Silicon diode detectors used in radiological physics measurements. Part II: Measurement of dosimetry data for high-energy photons.

    PubMed

    Wright, A E; Gager, L D

    1977-01-01

    Initial calibration of a linear accelerator requires physics instruments to measure accurately central axis depth-dose and off-axis data, both in and out of the beam. These data for an 8- MeV unit were first measured using film, a Farmer 0.6-cm3 ion chamber, a 0.3-cm3 ion chamber, and a 0.1-cm3 silicon diode. Both small probes and film gave a high response compared to the Farmer probe, which has a uniform energy response. Measurements with the diode interfaced to an X-Y recorder required only a fraction of the time required with the chambers, minimizing error due to change in machine output, and permitted resolution of isodose lines in the penumbra. However, corrections required at points in depth due to nonuniform energy response of the unshielded diode were laborious. Construction of a partially shielded diode which duplicates the response of the Farmer probe eliminated the necessity for corrections, permitting rapid accumulation of a wide range of depth-dose and off-axis data. PMID:927387

  13. Diode Structure for Microwave and Infrared Applications

    NASA Technical Reports Server (NTRS)

    Alcorn, George; Leinteran, Charles; Chiang, Bing

    1987-01-01

    Microwave signals switched or modulated optically. Planar diode with transparent cathode made in BaAs, Si, and InSb versions. Depending on specific configuration and material, such diode used for optical modulation of microwave signal or as infrared detector. Transparent cathode fabricated on GaAs diode so diode illuminates to generate and control short-circuit current.

  14. Fluorometric flow-immunoassay for alkylphenol polyethoxylates on a microchip containing a fluorescence detector comprised of an organic light emitting diode and an organic photodiode.

    PubMed

    Liu, Rong; Ishimatsu, Ryoichi; Yahiro, Masayuki; Adachi, Chihaya; Nakano, Koji; Imato, Toshihiko

    2015-03-01

    A compact fluorescence detector was constructed on a microchip from an organic light emitting diode (OLED) as the light source and an organic photodiode (OPD) as the photo-detector and was used in an immunoassay for alkylphenol polyethoxylates (APE). The OLED based on a terbium complex emitted a sharp light at the main wavelength of 546 nm with a full width at half maximum of 9 nm. The incident photo-to-current conversion efficiency (IPCE) of the OPD fabricated with Fullerene 70 (C70) and tris[4-(5-phenylthiopen-2-yl)phenyl]-amine (TPTPA) was approximately 44% for light at a wavelength of 586 nm. The performance of the fluorescence detector was evaluated for the determination of resorufin (λ(em)=586 nm) and the photocurrent of the OPD due to the fluorescence of resorufin was proportional to the concentration of resorufin in the range from 0 to 18 µM with a detection limit (S/N=3) of 0.6 µM. The fluorescence detector was successfully utilized in a competitive enzyme-linked immunosorbent assay for APE, where an anti-APE antibody was immobilized on the surface of the channel of the Polydimethylsiloxane (PDMS) microchip or on the surface of magnetic microbeads. After an immunoreaction with a sample solution of APE containing a horse radish peroxidase (HRP)-labeled APE, the fluorescence of resorufin generated just after introduction of a mixed solution of Amplex Red and H2O2 was measured using the fluorescence detector. The calibration curve for the photocurrent signals of the OPD due to the fluorescence of resorufin against the logarithmic concentration of APE was sigmoidal in shape. The detection limits defined as IC80 were ca. 1 ppb and ca. 2 ppb, respectively, for the methods using the anti-APE antibody immobilized on the surface of the microchannel and in the case where the antibody was immobilized on the surface of magnetic microbeads. PMID:25618638

  15. The development of a Compton lung densitometer

    SciTech Connect

    Loo, B.W.; Goulding, F.S.; Madden, N.W.; Simon, D.S.

    1988-11-01

    A field instrument is being developed for the non-invasive determination of absolute lung density using unique Compton backscattering techniques. A system consisting of a monoenergetic gamma-ray beam and a shielded high resolution high-purity-germanium (HPGe) detector in a close-coupled geometry is designed to minimize errors due to multiple scattering and uncontrollable attenuation in the chestwall. Results of studies on system performance with phantoms, the optimization of detectors, and the fabrication of a practical gamma-ray source are presented. 3 refs., 6 figs., 2 tabs.

  16. Timelike Compton Scattering

    SciTech Connect

    T. Horn, Y. Illieva, F. J. Klein, P. Nadel‐Turonski, R. Paremuzyan, S. Stepanyan

    2011-10-01

    Generalized Parton Distributions (GPDs) have become a key concept in our studies of hadron structure in QCD. The measurement of suitable experimental observables and the extraction of GPDs from these data is one of the high priority 12 GeV programs at Jefferson Lab. Deeply Virtual Compton Scattering (DVCS) is generally thought of as the most promising channel for probing GPDs in the valence quark region. However, the inverse process, Timelike Compton Scattering (TCS) can provide an important complementary measurement, in particular of the real part of the Compton amplitude and power corrections at intermediate values of Q2. The first studies of TCS using real tagged and quasi-real untagged photons were performed in Hall B at Jefferson Lab.

  17. The Compton generator revisited

    NASA Astrophysics Data System (ADS)

    Siboni, S.

    2014-09-01

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

  18. Charge transport properties of p-CdTe/n-CdTe/n{sup +}-Si diode-type nuclear radiation detectors based on metalorganic vapor-phase epitaxy-grown epilayers

    SciTech Connect

    Niraula, M.; Yasuda, K.; Wajima, Y.; Yamashita, H.; Tsukamoto, Y.; Suzuki, Y.; Matsumoto, M.; Takai, N.; Tsukamoto, Y.; Agata, Y.

    2013-10-28

    Charge transport properties of p-CdTe/n-CdTe/n{sup +}-Si diode-type nuclear radiation detectors, fabricated by growing p-and n-type CdTe epilayers on (211) n{sup +}-Si substrates using metalorganic vapor-phase epitaxy (MOVPE), were studied by analyzing current-voltage characteristics measured at various temperatures. The diode fabricated shows good rectification properties, however, both forward and reverse biased currents deviate from their ideal behavior. The forward current exhibits typical feature of multi-step tunneling at lower biases; however, becomes space charge limited type when the bias is increased. On the other hand, the reverse current exhibits thermally activated tunneling-type current. It was found that trapping centers at the p-CdTe/n-CdTe junction, which were formed due to the growth induced defects, determine the currents of this diode, and hence limit the performance of the nuclear radiation detectors developed.

  19. SU-E-T-446: Evaluation of the Dosimetric Properties of a Diode Detector to Proton Radiosurgery

    SciTech Connect

    Teran, A; McAuley, G; Slater, J M; Slater, J D; Wroe, A

    2014-06-01

    Purpose: To test the PTW PR60020 proton dosimetry diode in radiation fields relevant to proton radiosurgery applications and evaluate its suitability as a high resolution, real time dosimetry device. Methods: Data was collected using our standard nominal radiosurgery energies of 126 MeV and 155 MeV through a single stage scattering system, corresponding to a range of 9.7 and 15 cm in water respectively. Various beam modulations were tested as part of this study. Depth dose and beam profile measurements were completed with the PTW PR60020 dosimetry diode with comparative measurements using a PTW Markus ionization chamber and EBT2 Gafchromic film. Monte Carlo simulations were also completed for comparison. Results: The single 1 mm{sup 2} by 20 μm thick sensitive volume allowed for high spatial resolution measurements while maintaining sufficient sensitive volume to ensure that measurements could be completed without excessive beam delivery. Depth dose profiles exhibited negligible LET dependence which typically impacts film and other solid state dosimetry devices, while beam ranges measured with the PTW diode were within 1 mm of ion chamber data. In an edge on arrangement beam profiles were also measured within 0.5 mm full-width at half-maximum at various depths as compared to film and simulation data. Conclusion: The PTW PR60020 proved to be a very useful radiation metrology apparatus for proton radiosurgery applications. Its waterproof and rugged construction allowed for easy deployment in phantoms or water tanks that are commonly used in proton radiosurgery QA. Dosimetrically, the diode exhibited negligible LET dependence as a function of depth, while in edge on arrangement to the incident proton beam it facilitated the measurement of beam profiles with a spatial resolution comparable to both Monte Carlo and film measurements. This project was sponsored in part by funding from the Department of Defense (DOD# W81XWH-BAA-10-1)

  20. Hard modeling methods for the curve resolution of data from liquid chromatography with a diode array detector and on-flow liquid chromatography with nuclear magnetic resonance spectroscopy.

    PubMed

    Wasim, Mohammad; Brereton, Richard G

    2006-01-01

    Hard modeling methods have been performed on data from high-performance liquid chromatography with a diode array detector (LC-DAD) and on-flow liquid chromatography with 1H nuclear magnetic spectroscopy (LC-NMR). Four methods have been used to optimize parameters to model concentration profiles, three of which belong to classical optimization methods (the simplex method of Nelder-Mead, sequential quadratic programming approach, and Levenberg-Marquardt method), and the fourth is the application of genetic algorithms using real-value encoding. Only classical methods worked well for LC-DAD data, while all of the methods produced good results when LC-NMR data were divided into small spectral windows of peak clusters and parameters were optimized over each window. PMID:16711734

  1. Imaging Performance of the Si/Ge Hybrid Compton Imager

    SciTech Connect

    Burks, M; Chivers, D; Cork, C; Cunningham, M; Fabris, L; Gunter, D; Hull, E; Lange, D; Manini, H; Mihailescu, L; Nelson, K; Niedermayr, T; Valentine, J; Vetter, K; Wright, D

    2005-11-10

    The point spread function (PSF) of a fully-instrumented silicon/germanium Compton telescope has been measured as a function of energy and angle. Overall, the resolution ranged from 3{sup o} to 4{sup o} FWHM over most of the energy range and field of view. The various contributions to the resolution have been quantified. These contributions include the energy uncertainty and position uncertainty of the detector; source energy; Doppler broadening; and the 1/r broadening characteristic of Compton back-projection. Furthermore, a distortion of the PSF is observed for sources imaged off-axis from the detector. These contributions are discussed and compared to theory and simulations.

  2. Deeply virtual Compton scattering

    NASA Astrophysics Data System (ADS)

    Marukyan, Hrachya

    2015-11-01

    This paper reviews the experimental measurements in the field of deeply virtual Compton scattering and related theoretical efforts aimed for the extraction of generalized parton distributions, objects, describing the three-dimensional structure of nucleons and nuclei. The future experiments and theoretical expectations are also considered.

  3. Nucleon Compton Scattering

    SciTech Connect

    Bogdan Wojtsekhowski

    2006-06-04

    Review of Nucleon Compton Scattering in wide angle regime is presented. JLab experimental data strongly support dominance of handbag mechanism in the RCS process. The approved ALLRCS experiment with polarized target and future plans with 12 GeV beam are discussed.

  4. Compton scattering overview

    SciTech Connect

    Hartemann, F V

    2008-12-01

    An overview of linear and nonlinear Compton scattering is presented, along with a comparison with Thomson scattering. Two distinct processes play important roles in the nonlinear regime: multi-photon interactions, leading to the generation of harmonics, and radiation pressure, yielding a downshift of the radiated spectral features. These mechanisms, their influence on the source brightness, and different modeling strategies are also briefly discussed.

  5. Virtual Compton Scattering

    SciTech Connect

    Helene Fonvieille

    2003-05-01

    Virtual Compton Scattering off the proton: {gamma}^+p --> {gamma}p is a new field of investigation of nucleon structure. Several dedicated experiments have been performed at low c.m. energy and various momentum transfers, yielding specific information on the proton. This talk reviews the concept of nucleon Generalized Polarizabilities and the present experimental status.

  6. Hybrid Compton camera/coded aperture imaging system

    DOEpatents

    Mihailescu, Lucian; Vetter, Kai M.

    2012-04-10

    A system in one embodiment includes an array of radiation detectors; and an array of imagers positioned behind the array of detectors relative to an expected trajectory of incoming radiation. A method in another embodiment includes detecting incoming radiation with an array of radiation detectors; detecting the incoming radiation with an array of imagers positioned behind the array of detectors relative to a trajectory of the incoming radiation; and performing at least one of Compton imaging using at least the imagers and coded aperture imaging using at least the imagers. A method in yet another embodiment includes detecting incoming radiation with an array of imagers positioned behind an array of detectors relative to a trajectory of the incoming radiation; and performing Compton imaging using at least the imagers.

  7. A sensitive and versatile detector for atmospheric NO2 and NOx based on blue diode laser cavity ring-down spectroscopy.

    PubMed

    Fuchs, Hendrik; Dubé, William P; Lerner, Brian M; Wagner, Nicholas L; Williams, Eric J; Brown, Steven S

    2009-10-15

    A sensitive, small detector was developed for atmospheric NO2 and NOx concentration measurements. NO2 is directly detected by laser diode based cavity ring-down spectroscopy (CRDS) at 404 nm. The sum of NO and NO2 (=NOx) is simultaneously measured in a second cavity by quantitative conversion of ambient NO to NO2 in excess ozone. Interferences due to absorption by other trace gases at 404 nm, such as ozone and water vapor, are either negligible or small and are easily quantified. The limit of detection is 22 pptv (2sigma precision) for NO2 at 1 s time resolution. The conversion efficiency of NO to NO2 is 99% in excess O3. The accuracy of the NO2 measurement is mainly limited by the NO2 absorption cross section to +/-3%. Because of the formation of undetectable higher nitrogen oxides in subsequent reactions of NO2 with ozone in the NOx channel, the (1sigma) accuracy of the NOx measurement is increased to approximately +/-5% depending on the level of NOx. The new instrument was designed to be easily deployed in the field with respect to size, weight and consumables. Measurements were validated against a photolysis/chemiluminescence detector during six days of sampling ambient air with colocated inlets. The data sets for NO2, NO and NOx exhibit high correlation and good agreement within the combined accuracies of both methods. Linear fits for all three species give similar slopes of 0.99 in ambient air. PMID:19921901

  8. Energy and coincidence time resolution measurements of CdTe detectors for PET

    PubMed Central

    Ariño, G.; Chmeissani, M.; De Lorenzo, G.; Puigdengoles, C.; Cabruja, E.; Calderón, Y.; Kolstein, M.; Macias-Montero, J.G.; Martinez, R.; Mikhaylova, E.; Uzun, D.

    2013-01-01

    We report on the characterization of 2 mm thick CdTe diode detector with Schottky contacts to be employed in a novel conceptual design of PET scanner. Results at −8°C with an applied bias voltage of −1000 V/mm show a 1.2% FWHM energy resolution at 511 keV. Coincidence time resolution has been measured by triggering on the preamplifier output signal to improve the timing resolution of the detector. Results at the same bias and temperature conditions show a FWHM of 6 ns with a minimum acceptance energy of 500 keV. These results show that pixelated CdTe Schottky diode is an excellent candidate for the development of next generation nuclear medical imaging devices such as PET, Compton gamma cameras, and especially PET-MRI hybrid systems when used in a magnetic field immune configuration. PMID:23750177

  9. Determination of analytes in medical herbs extracts by SPE coupled with two-dimensional planar chromatography in combination with diode array scanning densitometry and HPLC-diode array detector.

    PubMed

    Tuzimski, Tomasz

    2011-01-01

    The purpose of this study is to demonstrate an application of 2-D high-performance planar chromatography-diode array detector (DAD) and HPLC-DAD after solid-phase extraction (SPE) for identification and quantitative analysis of pesticides (isoproturon, aziprotryne, hexazinone, flufenoxuron, methabenzthiazuron, procymidone, and α-cypermethrin) in Melissa officinalis L. (Labiatae) samples. The procedure described for the determination of compounds is inexpensive and can be applied to routine analysis of analytes in medical herbs' samples after preliminary cleanup and concentration by SPE. Average recoveries on C18 SPE cartridges of pesticides eluted with 5 mL tetrahydrofuran by the proposed HPLC-DAD method, before and after 2-D-high-performance planar chromatography separation of analytes from M. officinalis L. samples spiked with pesticide at a concentration level of 10 μg/g in plant material are presented. Method validation parameters for the quantification of pesticides by the proposed HPLC-DAD after SPE method are also presented. PMID:21171173

  10. Geometrical optimization of an annulus Compton suppression system using Monte Carlo simulation.

    PubMed

    Han, Jubong; Lee, K B; Park, T S; Lee, J M; Lee, S H

    2013-11-01

    We are planning to construct a Compton-suppression system permitting accurate and precise determinations of radioactivity of low-level environmental samples. An annulus guard detector (NaI) and a plug-in detector (NaI) are being used as suppression detectors with an HPGe primary detector. The geometry of the Compton suppression spectrometer was optimized by simulation with PENELOPE for obtaining the highest suppression factor (SF) for a point source. The results of the simulations show that the ultimate value of the suppression factor is 7.87 ± 0.18, obtained when the source is located at 57% of an annuls guard detector. PMID:23583087

  11. A Planar, Chip-Based, Dual-Beam Refractometer Using an Integrated Organic Light Emitting Diode (OLED) Light Source and Organic Photovoltaic (OPV) Detectors

    PubMed Central

    Ratcliff, Erin L.; Veneman, P. Alex; Simmonds, Adam; Zacher, Brian; Huebner, Daniel

    2010-01-01

    We present a simple chip-based refractometer with a central organic light emitting diode (OLED) light source and two opposed organic photovoltaic (OPV) detectors on an internal reflection element (IRE) substrate, creating a true dual-beam sensor platform. For first-generation platforms, we demonstrate the use of a single heterojunction OLED based on electroluminescence emission from an Alq3/TPD heterojunction (tris-(8-hydroxyquinoline)aluminum/N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine) and light detection with planar heterojunction pentacene/C60 OPVs. The sensor utilizes the considerable fraction of emitted light from conventional thin film OLEDs that is coupled into guided modes in the IRE instead of into the forward (display) direction. A ray-optics description is used to describe light throughput and efficiency-limiting factors for light coupling from the OLED into the substrate modes, light traversing through the IRE substrate, and light coupling into the OPV detectors. The arrangement of the OLED at the center of the chip provides for two sensing regions, a “sample” and “reference” channel, with detection of light by independent OPV detectors. This configuration allows for normalization of the sensor response against fluctuations in OLED light output, stability, and local fluctuations (temperature) which might influence sensor response. The dual beam configuration permits significantly enhanced sensitivity to refractive index changes relative to single-beam protocols, and is easily integrated into a field-portable instrumentation package. Changes in refractive index (ΔR.I.) between 10−2 and 10−3 R.I. units could be detected for single channel operation, with sensitivity increased to ΔR.I. ≈ 10−4 units when the dual beam configuration is employed. PMID:20218580

  12. Fluorescence-suppressed time-resolved Raman spectroscopy of pharmaceuticals using complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector.

    PubMed

    Rojalin, Tatu; Kurki, Lauri; Laaksonen, Timo; Viitala, Tapani; Kostamovaara, Juha; Gordon, Keith C; Galvis, Leonardo; Wachsmann-Hogiu, Sebastian; Strachan, Clare J; Yliperttula, Marjo

    2016-01-01

    In this work, we utilize a short-wavelength, 532-nm picosecond pulsed laser coupled with a time-gated complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector to acquire Raman spectra of several drugs of interest. With this approach, we are able to reveal previously unseen Raman features and suppress the fluorescence background of these drugs. Compared to traditional Raman setups, the present time-resolved technique has two major improvements. First, it is possible to overcome the strong fluorescence background that usually interferes with the much weaker Raman spectra. Second, using the high photon energy excitation light source, we are able to generate a stronger Raman signal compared to traditional instruments. In addition, observations in the time domain can be performed, thus enabling new capabilities in the field of Raman and fluorescence spectroscopy. With this system, we demonstrate for the first time the possibility of recording fluorescence-suppressed Raman spectra of solid, amorphous and crystalline, and non-photoluminescent and photoluminescent drugs such as caffeine, ranitidine hydrochloride, and indomethacin (amorphous and crystalline forms). The raw data acquired by utilizing only the picosecond pulsed laser and a CMOS SPAD detector could be used for identifying the compounds directly without any data processing. Moreover, to validate the accuracy of this time-resolved technique, we present density functional theory (DFT) calculations for a widely used gastric acid inhibitor, ranitidine hydrochloride. The obtained time-resolved Raman peaks were identified based on the calculations and existing literature. Raman spectra using non-time-resolved setups with continuous-wave 785- and 532-nm excitation lasers were used as reference data. Overall, this demonstration of time-resolved Raman and fluorescence measurements with a CMOS SPAD detector shows promise in diverse areas, including fundamental chemical research, the

  13. Miniaturized time-resolved Raman spectrometer for planetary science based on a fast single photon avalanche diode detector array.

    PubMed

    Blacksberg, Jordana; Alerstam, Erik; Maruyama, Yuki; Cochrane, Corey J; Rossman, George R

    2016-02-01

    We present recent developments in time-resolved Raman spectroscopy instrumentation and measurement techniques for in situ planetary surface exploration, leading to improved performance and identification of minerals and organics. The time-resolved Raman spectrometer uses a 532 nm pulsed microchip laser source synchronized with a single photon avalanche diode array to achieve sub-nanosecond time resolution. This instrument can detect Raman spectral signatures from a wide variety of minerals and organics relevant to planetary science while eliminating pervasive background interference caused by fluorescence. We present an overview of the instrument design and operation and demonstrate high signal-to-noise ratio Raman spectra for several relevant samples of sulfates, clays, and polycyclic aromatic hydrocarbons. Finally, we present an instrument design suitable for operation on a rover or lander and discuss future directions that promise great advancement in capability. PMID:26836075

  14. A packaged Schottky diode as detector, harmonic mixer, and harmonic generator in the 25 500 GHz range

    NASA Astrophysics Data System (ADS)

    Goy, P.

    1982-03-01

    This paper describes experimental results obtained with a packaged GaAs Schottky barrier diode in contact with a coaxial connector and placed across waveguides for bands Ka, V, E, W or F. Among the microwave sources used for calibration were 9 carcinotrons in the frequency interval 51 490 GHz. As soon as the frequency F is above the waveguide cut-off frequency, the different characteristics do not depend critically on the waveguide size for V, E, W and F bands. The video detection sensitivity, of several 100 mV/mW at 50 GHz and below, decreases as F-4 in the range 51 500 GHz. Coupling an X-band centimeter frequency via the coaxial connector and a millimeter frequency via the waveguide permits harmonic mixing in the diode. Between 36 and 490 GHz, the harmonic mixing number varies from 3 up to the very large value 40 with conversion losses from 18 to 88 dB. The minimum detectable signal in the 100 kHz band can be as low as -90 dBm at 80 GHz. A noticeable millimeter power is available at the waveguide output from injected centimeter power by harmonic generation. Starting for instance with 100 mW around 11.5 GHz, we have measured 0.1 mW at 80 GHz and 0.1 μW at 230 GHz. To illustrate the possibility of creating usable millimeter and submillimeter wave without heavy equipment (such as carcinotrons or millimeter klystron) we report spectroscopic experiments in Rydberg atoms. Resonances have been observed up to 340 GHz by harmonic generation (28th harmonic) from an X-band klystron).

  15. The GSFC Advanced Compton Telescope (ACT)

    NASA Astrophysics Data System (ADS)

    Hartman, R.; Fichtel, C.; Kniffen, D.; Trombka, J.; Stacy, G.

    1983-08-01

    A new telescope is being developed at GSFC for the study of point sources of gamma rays in the energy range 1-30 MeV. Using the detection principle of a Compton scatter in a 2.5 cm thick NaI(Tl) detector followed by absorption in a 15 cm thick NaI(Tl) detector, the telescope uses a rocking collimator for field-of-view reduction and background subtraction. Background reduction techniques include lead-plastic scintillator shielding, pulse shape discrimination and Anger camera operation to both NaI detectors, as well as a time-of-flight measurement between them. The instrument configuration and status is described.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  17. Reverse Phase-ultra Flow Liquid Chromatography-diode Array Detector Quantification of Anticancerous and Antidiabetic Drug Mangiferin from 11 Species of Swertia from India

    PubMed Central

    Kshirsagar, Parthraj R.; Gaikwad, Nikhil B.; Panda, Subhasis; Hegde, Harsha V.; Pai, Sandeep R.

    2016-01-01

    Background: Genus Swertia is valued for its great medicinal potential, mainly Swertia chirayita (Roxb. ex Fleming) H. Karst. is used in traditional medicine for a wide range of diseases. Mangiferin one of xanthoids is referred with enormous pharmacological potentials. Objective: The aim of the study was to quantify and compare the anticancerous and antidiabetic drug mangiferin from 11 Swertia species from India. The study also evaluates hierarchical relationships between the species based on mangiferin content using multivariate analysis. Materials and Methods: The reverse phase-ultra flow liquid chromatography-diode array detector analyses was performed and chromatographic separation was achieved on a Lichrospher 100, C18e (5 μm) column (250–4.6 mm). Mobile phase consisting of 0.2% triethylamine (pH-4 with O-phosphoric acid) and acetonitrile (85:15) was used for separation with injection volume 20 μL and detection wave length at 257 nm. Results: Results indicated that concentration of mangiferin has been found to vary largely between Swertia species collected from different regions. Content of mangiferin was found to be highest in Swertia minor compared to other Swertia species studied herein from the Western Ghats and Himalayan region also. The same was also evident in the multivariate analysis, wherein S. chirayita, S. minor and Swertia paniculata made a separate clade. Conclusion: Conclusively, the work herein provides insights of mangiferin content from 11 Swertia species of India and also presents their hierarchical relationships. To best of the knowledge this is the first report of higher content of mangiferin from any Swertia species. SUMMARY The present study quantifies and compares mangiferin in 11 species of Swertia from India. The study also evaluates hierarchical relationships between the species based on mangiferin content using multivariate analysis. The mangiferin content was highest in S. minor compared to the studied Swertia species. To the

  18. Results of a Si/Cdte Compton Telescope

    SciTech Connect

    Oonuki, Kousuke; Tanaka, Takaaki; Watanabe, Shin; Takeda, Shin'ichiro; Nakazawa, Kazuhiro; Mitani, Takefumi; Takahashi, Tadayuki; Tajima, Hiroyasu; Fukazawa, Yasushi; Nomachi, Masaharu; /Sagamihara, Inst. Space Astron. Sci. /Tokyo U. /SLAC /Hiroshima U. /Osaka U.

    2005-09-23

    We have been developing a semiconductor Compton telescope to explore the universe in the energy band from several tens of keV to a few MeV. We use a Si strip and CdTe pixel detector for the Compton telescope to cover an energy range from 60 keV. For energies above several hundred keV, the higher efficiency of CdTe semiconductor in comparison with Si is expected to play an important role as an absorber and a scatterer. In order to demonstrate the spectral and imaging capability of a CdTe-based Compton Telescope, we have developed a Compton telescope consisting of a stack of CdTe pixel detectors as a small scale prototype. With this prototype, we succeeded in reconstructing images and spectra by solving the Compton equation from 122 keV to 662 keV. The energy resolution (FWHM) of reconstructed spectra is 7.3 keV at 511 keV and 3.1 keV at 122 keV, respectively. The angular resolution obtained at 511 keV is measured to be 12.2{sup o}(FWHM).

  19. Qualitative and quantitative analysis of an alkaloid fraction from Piper longum L. using ultra-high performance liquid chromatography-diode array detector-electrospray ionization mass spectrometry.

    PubMed

    Li, Kuiyong; Fan, Yunpeng; Wang, Hui; Fu, Qing; Jin, Yu; Liang, Xinmiao

    2015-05-10

    In a previous research, an alkaloid fraction and 18 alkaloid compounds were prepared from Piper longum L. by series of purification process. In this paper, a qualitative and quantitative analysis method using ultra-high performance liquid chromatography-diode array detector-mass spectrometry (UHPLC-DAD-MS) was developed to evaluate the alkaloid fraction. Qualitative analysis of the alkaloid fraction was firstly completed by UHPLC-DAD method and 18 amide alkaloid compounds were identified. A further qualitative analysis of the alkaloid fraction was accomplished by UHPLC-MS/MS method. Another 25 amide alkaloids were identified according to their characteristic ions and neutral losses. At last, a quantitative method for the alkaloid fraction was established using four marker compounds including piperine, pipernonatine, guineensine and N-isobutyl-2E,4E-octadecadienamide. After the validation of this method, the contents of above four marker compounds in the alkaloid fraction were 57.5mg/g, 65.6mg/g, 17.7mg/g and 23.9mg/g, respectively. Moreover, the relative response factors of other three compounds to piperine were calculated. A comparative study between external standard quantification and relative response factor quantification proved no remarkable difference. UHPLC-DAD-MS method was demonstrated to be a powerful tool for the characterization of the alkaloid fraction from P. longum L. and the result proved that the quality of alkaloid fraction was efficiently improved after appropriate purification. PMID:25746504

  20. Simultaneous determination three phytosterol compounds, campesterol, stigmasterol and daucosterol in Artemisia apiacea by high performance liquid chromatography-diode array ultraviolet/visible detector

    PubMed Central

    Lee, Jiwoo; Weon, Jin Bae; Yun, Bo-Ra; Eom, Min Rye; Ma, Choong Je

    2015-01-01

    Background: Artemisia apiacea is a traditional herbal medicine using treatment of eczema and jaundice in Eastern Asia, including China, Korea, and Japan. Objective: An accurate and sensitive analysis method using high performance liquid chromatography-diode array ultraviolet/visible detector and liquid chromatography–mass spectrometry for the simultaneous determination of three phytosterol compounds, campesterol, stigmasterol and daucosterol in A. apiacea was established. Materials and Methods: The analytes were separated on a Shiseido C18 column (5 μm, 4.6 mm I.D. ×250 mm) with gradient elution of 0.1% trifluoroacetic acid and acetonitrile. The flow rate was 1 mL/min and detection wavelengths were set at 205 and 254 nm. Results: Validation of the method was performed to demonstrate its linearity, precision and accuracy. The calibration curves showed good linearity (R2 > 0.9994). The limits of detection and limits of quantification were within the ranges 0.55–7.07 μg/mL and 1.67–21.44 μg/mL, respectively. And, the relative standard deviations of intra- and inter-day precision were <2.93%. The recoveries were found to be in the range of 90.03–104.91%. Conclusion: The developed method has been successfully applied to the analysis for quality control of campesterol, stigmasterol and daucosterol in A. apiacea. PMID:25829768

  1. Simultaneous Determination of 11 Components in Yinzhihuang Preparations and Their Constituent Herbs by High-Performance Liquid Chromatography with Diode Array Detector.

    PubMed

    Du, Yan; Han, Jie; Sun, Shi-An; Li, Zheng; Yang, Fang-Xiu; Dong, Lu-Lu; Yang, Dong-Zhi; Tang, Dao-Quan

    2016-04-01

    A simple and sensitive liquid chromatography method with diode array detector was established for simultaneous determination of 11 components (geniposidic acid, chlorogenic acid, caffeic acid, geniposide, luteoloside, isochlorogenic acid C, baicalin, luteolin, wogonoside, baicalein and wogonin) in various commercial Yinzhihuang preparations and their herbs by optimizing the extraction, separation and analytical conditions. Eleven components were identified on the basis of their retention times and mass spectra. Chromatographic separation was performed on a C18 analytical column with a gradient elution of acetonitrile and 0.1% formic acid water solution at a flow rate of 1.0 mL/min. The linearity, precision and accuracy of the data obtained were acceptable. The method was used to analyze four Yinzhihuang preparations (powder, capsule, oral liquid and injection) and related herbs (Radix Scutellariae, Flos Lonicerae, Herba Artemisiae Scopariae and Fructus gardeniae). Results suggested that the optimized method could be considered as a good approach to control the quality of Yinzhihuang preparations and their herbs. PMID:26809640

  2. The scanning Compton polarimeter for the SLD experiment

    SciTech Connect

    Woods, M.; SLD Collaboration

    1996-10-01

    For the 1994/95 run of the SLD experiment at SLAC, a Compton polarimeter measured the luminosity-weighted electron beam polarization to be (77.2 {+-} 0.5)%. This excellent accuracy is achieved by measuring the rate asymmetry of Compton-scattered electrons near the kinematic endpoint. The polarimeter takes data continuously while the electron and positron beams are in collision and achieves a statistical precision of better than 1% in a three minute run. To calibrate the polarimeter and demonstrate its accuracy, many scans are frequently done. These include scans of the laser polarization, the detector position with respect to the kinematic edge, and the laser power.

  3. Low-level gamma spectrometry using beta coincidence and Compton suppression.

    PubMed

    Grigorescu, E L; De Felice, P; Razdolescu, Anamaria-Cristina; Luca, A

    2004-01-01

    A low-level gamma-ray spectrometry system was developed using a Ge(Li) detector with 6% relative efficiency coupled to a 2pi beta plastic detector for coincidence selection and a massive NaI(Tl) detector for Compton suppression. The integral background count rate for (50-1500)keV was 0.5 s(-1)kg(-1) (Ge), using only beta coincidences. With Compton suppression, a value of 0.25 s(-1)kg(-1) (Ge) was obtained. Spectra with and without Compton suppression were studied for 60Co, 137Cs and 152Eu point sources. Considerations are made concerning the Compton suppression advantages in different situations. PMID:15177343

  4. Analytical reconstruction formula for one-dimensional Compton camera

    SciTech Connect

    Basko, R.; Zeng, G.L.; Gullberg, G.T.

    1996-12-31

    The Compton camera has been proposed as an alternative to the Anger camera in SPECT. The advantage of the Compton camera is its high geometric efficiency due to electronic collimation. The Compton camera collects projections that are integrals over cone surfaces. Although some progress has been made toward image reconstruction from cone projections, at present no filtered backprojection algorithm exists. This paper investigates a simpler 2D version of the imaging problem. An analytical formula is developed for 2D reconstruction from data acquired by a 1D Compton camera that consists of two linear detectors, one behind the other. Coincidence photon detection allows the localization of the 2D source distribution to two lines in the shape of a {open_quotes}V{close_quotes} with the vertex on the front detector. A set of {open_quotes}V{close_quotes} projection data can be divided into subsets whose elements can be viewed as line-integrals of the original image added with its mirrored shear transformation. If the detector has infinite extent, reconstruction of the original image is possible using data from only one such subset. Computer simulations were performed to verify the newly developed algorithm.

  5. Recent Results From a Si/CdTe Semiconductor Compton Telescope

    SciTech Connect

    Tanaka, T.; Watanabe, S.; Takeda, S.; Oonuki, K.; Mitani, T.; Nakazawa, K.; Takashima, T.; Takahashi, T.; Tajima, H.; Sawamoto, N.; Fukazawa, Y.; Nomachi, M.; /JAXA, Sagamihara /Tokyo U. /SLAC /Hiroshima U. /Osaka U.

    2007-01-23

    We are developing a Compton telescope based on high resolution Si and CdTe detectors for astrophysical observations in sub-MeV/MeV gamma-ray region. Recently, we constructed a prototype Compton telescope which consists of six layers of double-sided Si strip detectors and CdTe pixel detectors to demonstrate the basic performance of this new technology. By irradiating the detector with gamma-rays from radio isotope sources, we have succeeded in Compton reconstruction of images and spectra. The obtained angular resolution is 3.9{sup o} (FWHM) at 511 keV, and the energy resolution is 14 keV (FWHM) at the same energy. In addition to the conventional Compton reconstruction, i.e., drawing cones in the sky, we also demonstrated a full reconstruction by tracking Compton recoil electrons using the signals detected in successive Si layers. By irradiating {sup 137}Cs source, we successfully obtained an image and a spectrum of 662 keV line emission with this method. As a next step, development of larger double-sided Si strip detectors with a size of 4 cm x 4 cm is underway to improve the effective area of the Compton telescope. We are also developing a new low-noise analog ASIC to handle the increasing number of channels. Initial results from these two new technologies are presented in this paper as well.

  6. Simplified slow anti-coincidence circuit for Compton suppression systems.

    PubMed

    Al-Azmi, Darwish

    2008-08-01

    Slow coincidence circuits for the anti-coincidence measurements have been considered for use in Compton suppression technique. The simplified version of the slow circuit has been found to be fast enough, satisfactory and allows an easy system setup, particularly with the advantage of the automatic threshold setting of the low-level discrimination. A well-type NaI detector as the main detector surrounded by plastic guard detector has been arranged to investigate the performance of the Compton suppression spectrometer using the simplified slow circuit. The system has been tested to observe the improvement in the energy spectra for medium to high-energy gamma-ray photons from terrestrial and environmental samples. PMID:18222698

  7. Design and fabrication of endoscope-type Compton camera

    NASA Astrophysics Data System (ADS)

    Nakamura, Y.; Shimazoe, K.; Takahashi, H.

    2013-12-01

    We are constructing an endoscope coupled with a Compton camera to intra-operatively inspect early stage cancer and metastatic lymph node (5 mm-10 mm). The radiation imaging system is composed of pixelated semiconductor detectors, which are Si array and CdTe array, whose sizes are less than 10 mm×10 mm, and a digital signal-processing unit with ASIC and FPGA and reconstruction algorithm using spherical harmonics that can compute in real time. In this paper, we show some simulation results on the performance of the proposed prototype detector using EGS5, Monte Carlo simulation code. The FWHM of 1 mm spatial resolution for an object located 10 mm away from the detector surface and the intrinsic efficiency of 0.05% were observed. Imaging and data acquisition time to take fine images are just 1 min. It therefore can be considered that the endoscopic Compton camera is useful for intra-operative inspection.

  8. An energy-subtraction Compton scatter camera design for in vivo medical imaging of radiopharmaceuticals

    SciTech Connect

    Rohe, R.C.; Valentine, J.D.

    1996-12-01

    A Compton scatter camera (CSC) design is proposed for imaging radioisotopes used as biotracers. A clinical version may increase sensitivity by a factor of over 100, while maintaining or improving spatial resolution, as compared with existing Anger cameras that use lead collimators. This novel approach is based on using energy subtraction ({Delta}E = E{sub 0} {minus} E{sub SC}, where E{sub 0}, {Delta}E, and E{sub SC} are the energy of the emitted gamma ray, the energy deposited by the initial Compton scatter, and the energy of the Compton scattered photon) to determine the amount of energy deposited in the primary system. The energy subtraction approach allows the requirement of high energy resolution to be placed on a secondary detector system instead of the primary detector system. Requiring primary system high energy resolution has significantly limited previous CSC designs for medical imaging applications. Furthermore, this approach is dependent on optimizing the camera design for data acquisition of gamma rays that undergo only one Compton scatter in a low-Z primary detector system followed by a total absorption of the Compton scattered photon in a high-Z secondary detector system. The proposed approach allows for a more compact primary detector system, a more simplified pulse processing interface, and a much less complicated detector cooling scheme as compared with previous CSC designs. Analytical calculations and Monte Carlo simulation results for some specific detector materials and geometries are presented.

  9. Deeply Virtual Compton Scattering off 4He

    NASA Astrophysics Data System (ADS)

    Joosten, Sylvester; CLAS Collaboration

    2015-10-01

    The European Muon Collaboration (EMC) observed the first signs of a modification of the partonic structure of the nucleon when present in a nuclear medium. The precise nature of these effects, as well as their underlying cause, is yet to be determined. The generalized parton distribution (GPD) framework provides a powerful tool to study the partonic structure of nucleons inside a nucleus. Hard exclusive leptoproduction of a real photon off a nucleon, deeply virtual Compton scattering (DVCS), is presently considered the cleanest experimental access to the GPDs, through the Compton form factors (CFFs). This is especially the case for scattering off the spin-zero helium nucleus, where only a single CFF contributes to the process. The real and imaginary parts of this CFF can be constrained through the beam-spin asymmetry (BSA). We will present the first measurements of the DVCS process off 4He using the CEBAF 6 GeV polarized electron beam and the CLAS detector at JLab. The CLAS detector was supplemented with an inner electromagnetic calorimeter for photons produced at small angles, as well as a radial time projection chamber (RTPC) to detect low-energy recoil nuclei. This setup allowed for a clean measurement of the BSA in both the coherent and incoherent channels.

  10. A Compton camera application for the GAMOS GEANT4-based framework

    NASA Astrophysics Data System (ADS)

    Harkness, L. J.; Arce, P.; Judson, D. S.; Boston, A. J.; Boston, H. C.; Cresswell, J. R.; Dormand, J.; Jones, M.; Nolan, P. J.; Sampson, J. A.; Scraggs, D. P.; Sweeney, A.; Lazarus, I.; Simpson, J.

    2012-04-01

    Compton camera systems can be used to image sources of gamma radiation in a variety of applications such as nuclear medicine, homeland security and nuclear decommissioning. To locate gamma-ray sources, a Compton camera employs electronic collimation, utilising Compton kinematics to reconstruct the paths of gamma rays which interact within the detectors. The main benefit of this technique is the ability to accurately identify and locate sources of gamma radiation within a wide field of view, vastly improving the efficiency and specificity over existing devices. Potential advantages of this imaging technique, along with advances in detector technology, have brought about a rapidly expanding area of research into the optimisation of Compton camera systems, which relies on significant input from Monte-Carlo simulations. In this paper, the functionality of a Compton camera application that has been integrated into GAMOS, the GEANT4-based Architecture for Medicine-Oriented Simulations, is described. The application simplifies the use of GEANT4 for Monte-Carlo investigations by employing a script based language and plug-in technology. To demonstrate the use of the Compton camera application, simulated data have been generated using the GAMOS application and acquired through experiment for a preliminary validation, using a Compton camera configured with double sided high purity germanium strip detectors. Energy spectra and reconstructed images for the data sets are presented.

  11. Compton Scattering from Bulk and Surface of Water

    NASA Astrophysics Data System (ADS)

    Wang, Wenjie; Kuzmenko, Ivan; Vaknin, David

    2014-03-01

    Elastic and Compton scattering at grazing angle X-ray incidence from water show distinct behaviors below and above the critical angle for total reflections suggesting surface restructuring of the water surface. Using X-ray synchrotron radiation in reflectivity mode, we collect the Thomson and Compton scattering signals with energy dispersive detector at various angles near the normal to surface as a function of the angle of incidence. Analysis of the ratio between the Thomson and Compton intensity above the critical angle (which mainly probes bulk water) is a constant as expected from incoherent scattering from single water molecule, whereas the signal from the surface shows strong angular dependence on the incident angle. Although we do not fully understand the phenomena, we attribute the observation to more organized water at the interface. Ames Laboratory, DOE under contract No. DE-AC02-07CH11358 and Advanced Photon Source, DOE under contract No. DE-AC02-06CH11357.

  12. Compton suppressed LaBr3 detection system for use in nondestructive spent fuel assay

    NASA Astrophysics Data System (ADS)

    Bender, S.; Heidrich, B.; Ünlü, K.

    2015-06-01

    Current methods for safeguarding and accounting for spent nuclear fuel in reprocessing facilities are extremely resource and time intensive. The incorporation of autonomous passive gamma-ray detectors into the procedure could make the process significantly less burdensome. In measured gamma-ray spectra from spent nuclear fuel, the Compton continuum from dominant fission product photopeaks obscure the lower energy lines from other isotopes. The application of Compton suppression to gamma-ray measurements of spent fuel may reduce this effect and allow other less intense, lower energy peaks to be detected, potentially improving the accuracy of multivariate analysis algorithms. Compton suppressed spectroscopic measurements of spent nuclear fuel using HPGe, LaBr3, and NaI(Tl) primary detectors were performed. Irradiated fuel was measured in two configurations: as intact fuel elements viewed through a collimator and as feed solutions in a laboratory to simulate the measurement of a dissolved process stream. These two configurations allowed the direct assessment and quantification of the differences in measured gamma-ray spectra from the application of Compton suppression. In the first configuration, several irradiated fuel elements of varying cooling times from the Penn State Breazeale Reactor spent fuel inventory were measured using the three collimated Compton suppression systems. In the second geometry, Compton suppressed measurements of two samples of Approved Test Material commercial fuel elements were recorded inside the guard detector annulus to simulate the siphoning of small quantities from the main process stream for long dwell measurement periods. Compton suppression was found to improve measured gamma-ray spectra of spent fuel for multivariate analysis by notably lowering the Compton continuum from dominant photopeaks such as 137Cs and 140La, due to scattered interactions in the detector, which allowed more spectral features to be resolved. There was a

  13. Compton polarimetry revisited

    NASA Astrophysics Data System (ADS)

    Bernard, D.

    2015-11-01

    We compute the average polarisation asymmetry from the Klein-Nishina differential cross-section on free electrons at rest. As expected from the expression for the asymmetry, the average asymmetry is found to decrease like the inverse of the incident photon energy asymptotically at high energy. We then compute a simple estimator of the polarisation fraction that makes optimal use of all the kinematic information present in an event final state, by the use of "moments" method, and we compare its statistical power to that of a simple fit of the azimuthal distribution. In contrast to polarimetry with pair creation, for which we obtained an improvement by a factor of larger than two in a previous work, here for Compton scattering the improvement is only of 10-20%.

  14. A Compton profile representation for some second period elements

    NASA Astrophysics Data System (ADS)

    Harding, Geoffrey; Olesinski, Stephan

    2011-09-01

    Compton profiles for the elements C, N and O, which are important both in medical science and security screening, are represented here as weighted sums of three Gaussians. Simple scaling relationships describe the dependence on atomic number ( Z) of the amplitudes and standard deviations of the component Gaussians, which are identified with the Compton profiles of the 1s, 2s and 2p orbitals. This representation of the Compton profile agrees with tabulated values for C, N and O to a rms deviation of the order of 1% of the mean profile amplitude over the momentum range 0≤ q≤4, where q is expressed in units of the hydrogen ground state momentum. This representation allows a "mean atomic number" for mixtures and compounds dominated by second period elements to be assigned on the basis of experimental measurements of the Doppler broadening of back-scattered X-ray K characteristic lines. Processed spectra of water and ethanol from a Compton spectrometer equipped with a room-temperature semiconductor detector are compared with the Compton profiles synthesized as suggested here, and a satisfactory agreement between the measured and theoretical mean atomic numbers and the profile shapes is found.

  15. SU-E-T-223: Investigation of the Accuracy of Two-Dimensional Dose Distributions Measurement From High-Dose-Rate Brachytherapy Ir-192 Source Using Multiple-Diode-Array Detector (MapCheck2)

    SciTech Connect

    Taguenang, J; De La Fuente, T Herman; Ahmad, S; Ali, I

    2014-06-01

    Purpose: To investigate the dosimetric accuracy of multiple-diode-array detector (Mapcheck2) for high-dose-rate brachytherapy Ir-192 source. The two-dimensional (2D) dose distributions measured with MapCheck2 were validated with EBT2 Gafchromic film measurement and AAPM task-group- 43 (TG-43) modeling. Methods: 2D-dose distributions from Ir-192 source were measured with MapCheck2 and EBT2-films. MapCheck2 response was corrected for effects: directional dependence, diode and phantom heterogeneity. Optical density growth of the film was controlled by synchronized scanning of the film exposed to Ir-192 and calibration films exposed to 6 MV linac beams. Similarly, MapCheck2 response was calibrated to dose using 6 MV beams. An empirical model was developed for the dose distributions measured with Mapcheck2 that considered directional, diode and phantom heterogeneity corrections. The dose deposited in solid-state-detectors was modeled using a cavity theory model for the diode. This model was then validated with measurements using EBT2-films and calculations with TG-43. Results: The response of MapCheck2 has been corrected for different effects including: (a) directional dependence of 0–20% over angular range 0o–90o, (b) phantom heterogeneity (3%) and (c) diode heterogeneity (9%). The corrected dose distributions measured with MapCheck2 agreed well with the measured dose distributions from EBT2-film and with calculations using TG-43 within 5% over a wide range of dose levels and rates. The advantages of MapCheck2 include less noisy, linear and stable response compared with film. The response of MapCheck2 exposed to 192Ir-source showed no energy dependence similar to its response to MV energy beam. Detection spatial-resolution of individual diodes was 0.8×0.8 mm2, however, 2DMapCheck2 resolution is limited by distance between diodes (7.07 mm). Conclusion: The dose distribution measured with MapCheck2 agreed well within 5% with that measured using EBT2-films; and

  16. Magnetic ligand fishing combination with high-performance liquid chromatography-diode array detector-mass spectrometry to screen and characterize cyclooxygenase-2 inhibitors from green tea.

    PubMed

    Deng, Xu; Shi, Shuyun; Li, Simin; Yang, Tianlun

    2014-10-22

    Cyclooxygenase-2 (COX-2) inhibitors may be used to efficiently treat inflammation or cancer diseases. In the present study, we established a new screening assay based on magnetic Fe3O4@SiO2-COX-2 ligand fishing combination with high-performance liquid chromatography-diode array detector-mass spectrometry (HPLC-DAD-MS(n)) to screen and identify COX-2 inhibitors from green tea. Optimized conditions (pH at 7.4, temperature at 30°C, and incubation time for 30min) for fishing out COX-2 inhibitors were achieved by testing positive control, celecoxib, with active and inactive COX-2. Notably, immobilized COX-2 showed high stability (remained 94.7% after ten consecutive cycles), reproducibility (RSD<10% for batch-to-batch evaluation). Finally, eight catechins with COX-2 binding activity were screened in green tea, and their structures were characterized by ultraviolet (UV), accurate molecular weight, diagnostic fragment ions and nuclear magnetic resonance (NMR). Particularly, the COX-2 inhibitory activities of two rare catechins, [(-)-epigallocatechin-3-(3″-O-methyl)-gallate (3″-O-methyl-EGCG, IC50=0.17±0.03μM 0.16±0.01), (-)-epicatechin-3-(3″-O-methyl)-gallate (3″-O-methyl-ECG, IC50=0.16±0.02μM)], were reported for the first time. The results indicated that the proposed method was a simple, robust and reproducible approach for the discovery of COX-2 inhibitors from complex matrix. PMID:25464095

  17. Determination of low levels of polycyclic aromatic hydrocarbons in soil by high performance liquid chromatography with tandem fluorescence and diode-array detectors.

    PubMed

    Huang, Yujuan; Wei, Jing; Song, Jing; Chen, Mengfang; Luo, Yongming

    2013-08-01

    Risk assessment of polycyclic aromatic hydrocarbons (PAHs) contaminated soil and source apportionment require accurate analysis of the concentration of each PAH congener in the soil. However, determination of low level PAH congeners in soil is difficult because of similarity in the chemical properties of 16 PAHs and severe matrix interferences due to complex composition of soils. It is therefore imperative to develop a sensitive and accurate method for determination of low level PAHs in soil. In this work, high performance liquid chromatography equipped with fluorescence and diode-array detectors (HPLC-FLD-DAD) was used to determine the concentration of 16 PAHs in soil. The separation of the 16 PAHs was achieved by optimization of the mobile phase gradient elution program and FLD wavelength switching program. Qualitative analysis of the 16 PAHs was based on the retention time (RT) and each PAH specific spectrum obtained from DAD. In contrast, the quantitative analysis of individual PAH congeners was based on the peak areas at the specific wavelength with DAD and FLD. Under optimal conditions the detection limit was in the range 1.0-9.5 μg L(-1) for 16 PAHs with DAD and 0.01-0.1 μg L(-1) for 15 PAHs with FLD, and the RSD of PAHs was less than 5% with DAD and 3% with FLD. The spiked recoveries were in the range 61-96%, with the exception of NaP (<40%). The results show that HPLC-FLD-DAD can provide more accurate and reliable analysis of low level PAH congeners in soil samples. PMID:23659963

  18. Development of a rapid resolution liquid chromatography-diode array detector method for the determination of three compounds in Ziziphora clinopodioides Lam from different origins of Xinjiang

    PubMed Central

    Tian, Shuge; Yu, Qian; Wang, Dongdong; Upur, Halmuart

    2012-01-01

    Context: As a traditional Uygur medicinal plant, Z. clinopodioides Lam has various uses in Xinjiang. Aims: A reversed-phase rapid resolution liquid chromatography (RP-RRLC) method with diode array detector (DAD) was developed for simultaneous determination of diosmin, linarin, and pulegone from Ziziphora clinopodioides Lam, a widely used in traditional Uygur medicine for treating heart disease, high blood pressure, and other diseases. Settings and Design: Compounds were separated on a XDB-C18 reversed-phase analytical column (50 mm × 4.6 mm, 1.8 μm) with gradient elution using methanol and 1% aqueous acetic acid (v/v) at 0.9 mL/min. he detection wavelength was set at 270 nm. Materials and Methods: Ziziphora clinopodioides Lam. were collected from ten different origins in Xinjiang, including the Ban fang ditch, Tuoli, the Altay mountains, Terks, Xiata Road, Zhaosu Highway, Guozigou, Fukang, Jimsar, Wulabo. Statistical Analysis Used: The intra-day and inter-day precisions of all three compounds were less than 0.89% and the average recoveries ranged from 97.4 to 104.1%. There were highly significant linear correlations between component concentrations and specific chromatographic peak areas (R2 > 0.999). Results: The proposed method was successfully applied to determine the levels of three active components in Z. clinopodioides Lam. samples from different locations in Xinjiang. Conclusions: The proposed method is simple, consistent, accurate, and could be utilized as a quality control method for Z. clinopodioides Lam. PMID:24082631

  19. Development and validation of an high-performance liquid chromatography-diode array detector method for the simultaneous determination of six phenolic compounds in abnormal savda munziq decoction

    PubMed Central

    Tian, Shuge; Liu, Wenxian; Liu, Feng; Zhang, Xuejia; Upur, Halmuart

    2015-01-01

    Aims: Given the high-effectiveness and low-toxicity of abnormal savda munziq (ASMQ), its herbal formulation has long been used in traditional Uyghur medicine to treat complex diseases, such as cancer, diabetes, and cardiovascular diseases. Settings and Design: ASMQ decoction by reversed-phase high-performance liquid chromatography coupled with a diode array detector was successfully developed for the simultaneous quality assessment of gallic acid, protocatechuic acid, caffeic acid, rutin, rosmarinic acid, and luteolin. The six phenolic compounds were separated on an Agilent TC-C18 reversed-phase analytical column (4.6 × 250 mm, 5 μm) by gradient elution using 0.3% aqueous formic acid (v/v) and 0.3% methanol formic acid (v/v) at 1.0 mL/min. Materials and Methods: The plant material was separately ground and mixed at the following ratios (10): Cordia dichotoma (10.6), Anchusa italic (10.6), Euphorbia humifusa (4.9), Adiantum capillus-veneris (4.9), Ziziphus jujube (4.9), Glycyrrhiza uralensis (7.1), Foeniculum vulgare (4.9), Lavandula angustifolia (4.9), Dracocephalum moldavica L. (4.9), and Alhagi pseudoalhagi (42.3). Statistical Analysis Used: The precisions of all six compounds were <0.60%, and the average recoveries ranged from 99.39% to 104.85%. Highly significant linear correlations were found between component concentrations and specific chromatographic peak areas (R2 > 0.999). Results: The proposed method was successfully applied to determine the levels of six active components in ASMQ. Conclusions: Given the simplicity, precision, specificity, and sensitivity of the method, it can be utilized as a quality control approach to simultaneously determining the six phenolic compounds in AMSQ. PMID:25709227

  20. Weak Deeply Virtual Compton Scattering

    SciTech Connect

    Ales Psaker; Wolodymyr Melnitchouk; Anatoly Radyushkin

    2007-03-01

    We extend the analysis of the deeply virtual Compton scattering process to the weak interaction sector in the generalized Bjorken limit. The virtual Compton scattering amplitudes for the weak neutral and charged currents are calculated at the leading twist within the framework of the nonlocal light-cone expansion via coordinate space QCD string operators. Using a simple model, we estimate cross sections for neutrino scattering off the nucleon, relevant for future high intensity neutrino beam facilities.

  1. Image Artifacts Resulting from Gamma-Ray Tracking Algorithms Used with Compton Imagers

    SciTech Connect

    Seifert, Carolyn E.; He, Zhong

    2005-10-01

    For Compton imaging it is necessary to determine the sequence of gamma-ray interactions in a single detector or array of detectors. This can be done by time-of-flight measurements if the interactions are sufficiently far apart. However, in small detectors the time between interactions can be too small to measure, and other means of gamma-ray sequencing must be used. In this work, several popular sequencing algorithms are reviewed for sequences with two observed events and three or more observed events in the detector. These algorithms can result in poor imaging resolution and introduce artifacts in the backprojection images. The effects of gamma-ray tracking algorithms on Compton imaging are explored in the context of the 4π Compton imager built by the University of Michigan.

  2. A calibration system for Compton polarimetry at e+e- linear colliders

    NASA Astrophysics Data System (ADS)

    Vormwald, B.; List, J.; Vauth, A.

    2016-01-01

    Polarimetry with permille-level precision is essential for future electron-positron linear colliders. Compton polarimeters can reach negligible statistical uncertainties within seconds of measurement time. The dominating systematic uncertainties originate from the response and alignment of the detector which records the Compton scattered electrons. The robust baseline technology for the Compton polarimeters foreseen at future linear colliders is based on an array of gas Cherenkov detectors read out by photomultipliers. In this paper, we will present a calibration method which promises to monitor nonlinearities in the response of such a detector at the level of a few permille. This method has been implemented in an LED-based calibration system which matches the existing prototype detector. The performance of this calibration system is sufficient to control the corresponding contribution to the total uncertainty on the extracted polarisation to better than 0.1%.

  3. Prototype TIGRE Compton γ-ray balloon-borne telescope

    NASA Astrophysics Data System (ADS)

    Bhattacharya, D.; O'Neill, T. J.; Akyüz, A.; Samimi, J.; Zych, A. D.

    2004-02-01

    A prototype balloon-borne telescope is being constructed for γ-ray observations in the MeV energy range. The Tracking and Imaging Gamma-Ray Experiment (TIGRE) uses multi-layers of thin silicon detectors to track and measure the energy losses of Compton recoil electrons. When combined with the direction and energy of the Compton scattered γ-ray a unique incident direction for each photon event is determined. This facilitates background rejection, improved sensitivity and image reconstruction. The converter/tracker also serves as an electron-positron pair detector for γ-rays up to 100 MeV. The initial continental US flight will be used to determine the sub-orbital atmospheric backgrounds and search for polarized γ-emission for the Crab pulsar. Longer southern hemisphere flights with an enhanced instrument will map out the 26Al emissions from the galactic center region.

  4. Photon detector system

    DOEpatents

    Ekstrom, Philip A.

    1981-01-01

    A photon detector includes a semiconductor device, such as a Schottky barrier diode, which has an avalanche breakdown characteristic. The diode is cooled to cryogenic temperatures to eliminate thermally generated charge carriers from the device. The diode is then biased to a voltage level exceeding the avalanche breakdown threshold level such that, upon receipt of a photon, avalanche breakdown occurs. This breakdown is detected by appropriate circuitry which thereafter reduces the diode bias potential to a level below the avalanche breakdown threshold level to terminate the avalanche condition. Subsequently, the bias potential is reapplied to the diode in preparation for detection of a subsequently received photon.

  5. Method and apparatus for measuring lung density by Compton backscattering

    DOEpatents

    Loo, Billy W.; Goulding, Frederick S.

    1991-01-01

    The density of the lung of a patient suffering from pulmonary edema is monitored by irradiating the lung by a single collimated beam of monochromatic photons and measuring the energies of photons Compton backscattered from the lung by a single high-resolution, high-purity germanium detector. A compact system geometry and a unique data extraction scheme are utilized to monimize systematic errors due to the presence of the chestwall and multiple scattering.

  6. Method and apparatus for measuring lung density by Compton backscattering

    DOEpatents

    Loo, B.W.; Goulding, F.S.

    1988-03-11

    The density of the lung of a patient suffering from pulmonary edema is monitored by irradiating the lung by a single collimated beam of monochromatic photons and measuring the energies of photons compton back-scattered from the lung by a single high-resolution, high-purity germanium detector. A compact system geometry and a unique data extraction scheme are utilized to minimize systematic errors due to the presence of the chestwall and multiple scattering. 11 figs., 1 tab.

  7. The electromagnetic calorimeter in JLab Real Compton Scattering Experiment

    SciTech Connect

    Albert Shahinyan; Eugene Chudakov; A. Danagoulian; P. Degtyarenko; K. Egiyan; V. Gorbenko; J. Hines; E. Hovhannisyan; Ch. Hyde; C.W. de Jager; A. Ketikyan; V. Mamyan; R. Michaels; A.M. Nathan; V. Nelyubin; I. Rachek; M. Roedelbrom; A. Petrosyan; R. Pomatsalyuk; V. Popov; J. Segal; Yu. Shestakov; J. Templon; H. Voskanyan; B. Wojtsekhowski

    2007-04-16

    A hodoscope calorimeter comprising of 704 lead-glass blocks is described. The calorimeter was constructed for use in the JLab Real Compton Scattering experiment. The detector provides a measurement of the coordinates and the energy of scattered photons in the GeV energy range with resolutions of 5 mm and 6\\%/$\\sqrt{E_\\gamma \\, [GeV]}$, respectively. Design features and performance parameters during the experiment are presented.

  8. Measurement and simulation of a Compton suppression system for safeguards application

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  9. A Compton imaging device for radioactive material detection

    NASA Astrophysics Data System (ADS)

    Hoover, Andrew S.; Baird, William; Kippen, R. Marc; Rawool-Sullivan, Mohini W.; Sullivan, John P.

    2004-10-01

    The most serious terrorist threat we face today may come from radiological dispersion devices and unsecured nuclear weapons. It is imperative for national security that we develop and implement radiation detection technology capable of locating and tracking nuclear material moving across and within our borders. Many radionuclides emit gamma rays in the 0.2 -- 3 MeV range. Unfortunately, current gamma ray detection technology is inadequate for providing precise and efficient measurements of localized radioactive sources. Common detectors available today suffer from large background rates and have only minimal ability to localize the position of the source without the use of mechanical collimators, which reduces efficiency. Imaging detectors using the Compton scattering process have the potential to provide greatly improved sensitivity through their ability to reject off-source background. We are developing a prototype device to demonstrate the Compton imaging technology. The detector consists of several layers of pixelated silicon detectors followed by an array of CsI crystals coupled to photodiodes. Here we present the concept of our detector design and results from Monte Carlo simulations of our prototype detector.

  10. The performance determination of a Compton-suppression spectrometer and the measurement of the low level radioactive samples.

    PubMed

    Fan, Yuan-Qing; Wang, Shi-Lian; Li, Qi; Zhao, Yun-Gang; Zhang, Xin-Jun; Jia, Huai-Mao

    2013-11-01

    The performance of a new Compton-suppression spectrometer consisting of one HPGe detector and three NaI(Tl) detectors was studied. The peak-to-Compton ratio for a (137)Cs source is 1150 and the integral background count rate is 0.3 5s(-1) over the energy interval 20-3000 keV. The spectrometer was used to acquire both Compton-suppressed and non-suppressed spectra of aerosol samples collected in Beijing following the Fukushima nuclear accident. PMID:23587699

  11. A new cryogenic diode thermometer

    NASA Astrophysics Data System (ADS)

    Courts, S. S.; Swinehart, P. R.; Yeager, C. J.

    2002-05-01

    While the introduction of yet another cryogenic diode thermometer is not earth shattering, a new diode thermometer, the DT-600 series, recently introduced by Lake Shore Cryotronics, possesses three features that make it unique among commercial diode thermometers. First, these diodes have been probed at the chip level, allowing for the availability of a bare chip thermometer matching a standard curve-an important feature in situations where real estate is at a premium (IR detectors), or where in-situ calibration is difficult. Second, the thermometry industry has assumed that interchangeability should be best at low temperatures. Thus, good interchangeability at room temperatures implies a very good interchangeability at cryogenic temperature, resulting in a premium priced sensor. The DT-600 series diode thermometer is available in an interchangeability band comparable to platinum RTDs with the added advantage of interchangeability to 2 K. Third, and most important, the DT-600 series diode does not exhibit an instability in the I-V characteristic in the 8 K to 20 K temperature range that is observed in other commercial diode thermometer devices [1]. This paper presents performance characteristics for the DT-600 series diode thermometer along with a comparison of I-V curves for this device and other commercial diode thermometers exhibiting an I-V instability.

  12. The Compton Effect Red Shift

    NASA Astrophysics Data System (ADS)

    Kierein, John

    2004-05-01

    In 1923 (Phil Mag. 46, 897.) A. H. Compton noted that the Compton effect produces a red shift for all wavelengths when the scattered electron is free and not bound to an atom or molecule. He suggested that the red shift in the visible spectrum at the limb of the sun is larger than that at the center due to the Compton effect from the greater number of free electrons in the sun's atmosphere along the line of sight. Kierein and Sharp (1968, Solar Physics 3, 450) quantified this and showed a good correlation of red shift observations with the variation in the number of these electrons along the line of sight from center to limb and suggested that the quasar red shift and cosmological red shift could be similarly explained. Grote Reber mapped and measured the background hectometric radiation and found it to be unexpectedly bright. In 1968 (J. Franklin Inst. 285,1), while describing these measurements and maps he explained this brightness as being due to the Compton effect causing the cosmological red shift and accelerating intergalactic electrons. The resulting universe is static. The predicted red shift from the Compton effect deviates from Hubble's law only at large red shifts.

  13. Materials characterization in petroleum pipeline using Compton Scattering technique

    NASA Astrophysics Data System (ADS)

    Gouveia, M. A. G.; Lopes, R. T.; de Jesus, E. F. O.; Camerini, C. S.

    2003-06-01

    In this paper Compton Scattering technique is analyzed as a possible tool for the characterization of materials inside draining petroleum pipelines. The study was accomplished in laboratory scale, so the results should be analyzed to conclude if the system could be used in the field. The system used was composed of two detectors aligned by a Ce-137 source forming an angle of 90° with the detectors line (662 keV—direct beam, and 288 keV—scattered beam). The results obtained show the capability of the system for the characterization of materials like sand, paraffin and water inside pipelines.

  14. Compton scattering and generalized polarizabilities

    SciTech Connect

    Scherer, S.

    2005-05-06

    In recent years, real and virtual Compton scattering off the nucleon have attracted considerable interest from both the experimental and theoretical sides. Real Compton scattering gives access to the so-called electromagnetic polarizabilities containing the structure information beyond the global properties of the nucleon such as its charge, mass, and magnetic moment. These polarizabilities have an intuitive interpretation in terms of induced dipole moments and thus characterize the response of the constituents of the nucleon to a soft external stimulus. The virtual Compton scattering reaction e- p {yields} e- p{gamma} allows one to map out the local response to external fields and can be described in terms of generalized electromagnetic polarizabilities. A simple classical interpretation in terms of the induced electric and magnetic polarization densities is proposed. We will discuss experimental results for the polarizabilities of the proton and compare them with theoretical predictions.

  15. The Compton Observatory Science Workshop

    NASA Technical Reports Server (NTRS)

    Shrader, Chris R. (Editor); Gehrels, Neil (Editor); Dennis, Brian (Editor)

    1992-01-01

    The Compton Observatory Science Workshop was held in Annapolis, Maryland on September 23-25, 1991. The primary purpose of the workshop was to provide a forum for the exchange of ideas and information among scientists with interests in various areas of high energy astrophysics, with emphasis on the scientific capabilities of the Compton Observatory. Early scientific results, as well as reports on in-flight instrument performance and calibrations are presented. Guest investigator data products, analysis techniques, and associated software were discussed. Scientific topics covered included active galaxies, cosmic gamma ray bursts, solar physics, pulsars, novae, supernovae, galactic binary sources, and diffuse galactic and extragalactic emission.

  16. First-Generation Hybrid Compact Compton Imager

    SciTech Connect

    Cunningham, M; Burks, M; Chivers, D; Cork, C; Fabris, L; Gunter, D; Krings, T; Lange, D; Hull, E; Mihailescu, L; Nelson, K; Niedermayr, T; Protic, D; Valentine, J; Vetter, K; Wright, D

    2005-11-07

    At Lawrence Livermore National Laboratory, we are pursuing the development of a gamma-ray imaging system using the Compton effect. We have built our first generation hybrid Compton imaging system, and we have conducted initial calibration and image measurements using this system. In this paper, we present the details of the hybrid Compton imaging system and initial calibration and image measurements.

  17. Study of Compton suppression for use in spent nuclear fuel assay

    NASA Astrophysics Data System (ADS)

    Bender, Sarah

    The focus of this study has been to assess Compton suppressed gamma-ray detection systems for the multivariate analysis of spent nuclear fuel. This objective has been achieved using direct measurement of samples of irradiated fuel elements in two geometrical configurations with Compton suppression systems. In order to address the objective to quantify the number of additionally resolvable photopeaks, direct Compton suppressed spectroscopic measurements of spent nuclear fuel in two configurations were performed: as intact fuel elements and as dissolved feed solutions. These measurements directly assessed and quantified the differences in measured gamma-ray spectrum from the application of Compton suppression. Several irradiated fuel elements of varying cooling time from the Penn State Breazeale Reactor spent fuel inventory were measured using three Compton suppression systems that utilized different primary detectors: HPGe, LaBr3, and NaI(Tl). The application of Compton suppression using a LaBr3 primary detector to the measurement of the current core fuel element, which presented the highest count rate, allowed four additional spectral features to be resolved. In comparison, the HPGe-CSS was able to resolve eight additional photopeaks as compared to the standalone HPGe measurement. Measurements with the NaI(Tl) primary detector were unable to resolve any additional peaks, due to its relatively low resolution. Samples of Approved Test Material (ATM) commercial fuel elements were obtained from Pacific Northwest National Laboratory. The samples had been processed using the beginning stages of the PUREX method and represented the unseparated feed solution from a reprocessing facility. Compton suppressed measurements of the ATM fuel samples were recorded inside the guard detector annulus, to simulate the siphoning of small quantities from the main process stream for long dwell measurement periods. Photopeak losses were observed in the measurements of the dissolved ATM

  18. Performance of MACACO Compton telescope for ion-beam therapy monitoring: first test with proton beams.

    PubMed

    Solevi, Paola; Muñoz, Enrique; Solaz, Carles; Trovato, Marco; Dendooven, Peter; Gillam, John E; Lacasta, Carlos; Oliver, Josep F; Rafecas, Magdalena; Torres-Espallardo, Irene; Llosá, Gabriela

    2016-07-21

    In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verification techniques are necessary to detect deviations from the planned treatment. Efforts are currently oriented towards the development of devices for real-time range monitoring. Among the different detector concepts proposed, Compton cameras are employed to detect prompt gammas and represent a valid candidate for real-time range verification. We present the first on-beam test of MACACO, a Compton telescope (multi-layer Compton camera) based on lanthanum bromide crystals and silicon photo-multipliers. The Compton telescope was first characterized through measurements and Monte Carlo simulations. The detector linearity was measured employing (22)Na and Am-Be sources, obtaining about 10% deviation from linearity at 3.44 MeV. A spectral image reconstruction algorithm was tested on synthetic data. Point-like sources emitting gamma rays with energy between 2 and 7 MeV were reconstructed with 3-5 mm resolution. The two-layer Compton telescope was employed to measure radiation emitted from a beam of 150 MeV protons impinging on a cylindrical PMMA target. Bragg-peak shifts were achieved via adjustment of the PMMA target location and the resulting measurements used during image reconstruction. Reconstructed Bragg peak profiles proved sufficient to observe peak-location differences within 10 mm demonstrating the potential of the MACACO Compton Telescope as a monitoring device for ion-beam therapy. PMID:27352107

  19. Performance of MACACO Compton telescope for ion-beam therapy monitoring: first test with proton beams

    NASA Astrophysics Data System (ADS)

    Solevi, Paola; Muñoz, Enrique; Solaz, Carles; Trovato, Marco; Dendooven, Peter; Gillam, John E.; Lacasta, Carlos; Oliver, Josep F.; Rafecas, Magdalena; Torres-Espallardo, Irene; Llosá, Gabriela

    2016-07-01

    In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verification techniques are necessary to detect deviations from the planned treatment. Efforts are currently oriented towards the development of devices for real-time range monitoring. Among the different detector concepts proposed, Compton cameras are employed to detect prompt gammas and represent a valid candidate for real-time range verification. We present the first on-beam test of MACACO, a Compton telescope (multi-layer Compton camera) based on lanthanum bromide crystals and silicon photo-multipliers. The Compton telescope was first characterized through measurements and Monte Carlo simulations. The detector linearity was measured employing 22Na and Am-Be sources, obtaining about 10% deviation from linearity at 3.44 MeV. A spectral image reconstruction algorithm was tested on synthetic data. Point-like sources emitting gamma rays with energy between 2 and 7 MeV were reconstructed with 3–5 mm resolution. The two-layer Compton telescope was employed to measure radiation emitted from a beam of 150 MeV protons impinging on a cylindrical PMMA target. Bragg-peak shifts were achieved via adjustment of the PMMA target location and the resulting measurements used during image reconstruction. Reconstructed Bragg peak profiles proved sufficient to observe peak-location differences within 10 mm demonstrating the potential of the MACACO Compton Telescope as a monitoring device for ion-beam therapy.

  20. Adaptation of filtered back-projection to compton imaging with non-uniform azimuthal geometry

    NASA Astrophysics Data System (ADS)

    Lee, Hyounggun; Lee, Taewoong; Lee, Wonho

    2016-05-01

    For Compton image reconstruction, analytic reconstruction methods such as filtered backprojection have been used for real-time imaging. The conventional filtered back-projection method assumes a uniformly distributed azimuthal response in the detector system. In this study, we applied filtered back-projection to the experimental data from detector systems with limited azimuthal angle coverage ranges and estimated the limitations of the analytic reconstruction methods when applied to these systems. For the system with a uniform azimuthal response, the images reconstructed by using filtered back-projection showed better angular resolutions than the images obtained by using simple back-projection did. However, when filtered back-projection was applied to reconstruct Compton images based on measurements performed by using Compton cameras with limited response geometries, the reconstructed images exhibited artifacts caused by the geometrical limitations. Our proposed method employs the Compton camera's rotation to overcome the angular response limitations; when the rotation method was applied in this study, the artifacts in the reconstructed images caused by angular response limitations were minimized. With this method, filtered back-projection can be applied to reconstruct real-time Compton images even when the radiation measurements are performed by using Compton cameras with non-uniform azimuthal response geometries.

  1. SU-E-I-15: Quantitative Evaluation of Dose Distributions From Axial, Helical and Cone-Beam CT Imaging by Measurement Using a Two-Dimensional Diode-Array Detector

    SciTech Connect

    Chacko, M; Aldoohan, S; Sonnad, J; Ahmad, S; Ali, I

    2015-06-15

    Purpose: To evaluate quantitatively dose distributions from helical, axial and cone-beam CT clinical imaging techniques by measurement using a two-dimensional (2D) diode-array detector. Methods: 2D-dose distributions from selected clinical protocols used for axial, helical and cone-beam CT imaging were measured using a diode-array detector (MapCheck2). The MapCheck2 is composed from solid state diode detectors that are arranged in horizontal and vertical lines with a spacing of 10 mm. A GE-Light-Speed CT-simulator was used to acquire axial and helical CT images and a kV on-board-imager integrated with a Varian TrueBeam-STx machine was used to acquire cone-beam CT (CBCT) images. Results: The dose distributions from axial, helical and cone-beam CT were non-uniform over the region-of-interest with strong spatial and angular dependence. In axial CT, a large dose gradient was measured that decreased from lateral sides to the middle of the phantom due to large superficial dose at the side of the phantom in comparison with larger beam attenuation at the center. The dose decreased at the superior and inferior regions in comparison to the center of the phantom in axial CT. An asymmetry was found between the right-left or superior-inferior sides of the phantom which possibly to angular dependence in the dose distributions. The dose level and distribution varied from one imaging technique into another. For the pelvis technique, axial CT deposited a mean dose of 3.67 cGy, helical CT deposited a mean dose of 1.59 cGy, and CBCT deposited a mean dose of 1.62 cGy. Conclusions: MapCheck2 provides a robust tool to measure directly 2D-dose distributions for CT imaging with high spatial resolution detectors in comparison with ionization chamber that provides a single point measurement or an average dose to the phantom. The dose distributions measured with MapCheck2 consider medium heterogeneity and can represent specific patient dose.

  2. Compton imaging with the PorGamRays spectrometer

    NASA Astrophysics Data System (ADS)

    Judson, D. S.; Boston, A. J.; Coleman-Smith, P. J.; Cullen, D. M.; Hardie, A.; Harkness, L. J.; Jones, L. L.; Jones, M.; Lazarus, I.; Nolan, P. J.; Pucknell, V.; Rigby, S. V.; Seller, P.; Scraggs, D. P.; Simpson, J.; Slee, M.; Sweeney, A.; PorGamRays Collaboration

    2011-10-01

    The PorGamRays project aims to develop a portable gamma-ray detection system with both spectroscopic and imaging capabilities. The system is designed around a stack of thin Cadmium Zinc Telluride (CZT) detectors. The imaging capability utilises the Compton camera principle. Each detector is segmented into 100 pixels which are read out through custom designed Application Specific Integrated Circuits (ASICs). This device has potential applications in the security, decommissioning and medical fields. This work focuses on the near-field imaging performance of a lab-based demonstrator consisting of two pixelated CZT detectors, each of which is bonded to a NUCAM II ASIC. Measurements have been made with point 133Ba and 57Co sources located ˜35 mm from the surface of the scattering detector. Position resolution of ˜20 mm FWHM in the x and y planes is demonstrated.

  3. The Compton Gamma Ray Observatory

    NASA Astrophysics Data System (ADS)

    Gehrels, N.; Chipman, E.; Kniffen, D.

    1994-06-01

    The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments, and the observing program of the first 2 years of the mission. Examples of early discoveries by Compton are enumerated, including the discovery that gamma-ray bursts are isotropic but spatially inhomogeneous in their distribution; the discovery of a new class of high-energy extragalacatic gamma-ray sources, the gamma-ray AGNs; the discovery of emission from SN 1987A in the nuclear line of Co-57; and the mapping of emission from Al-26 in the interstellar medium (ISM) near the Galactic center. Future observations will include deep surveys of selected regions of the sky, long-tem studies of individual objects, correlative studies of objects at gamma-ray and other energies, a Galactic plane survey at intermediate gamma-ray energies, and improved statistics on gamma-ray bursts to search for small anisotropies. After completion of the all-sky survey, a Guest Investigator program is in progress with guest observers' time share increasing from 30% upward for the late mission phases.

  4. The Compton Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Gehrels, N.; Chipman, E.; Kniffen, D.

    1994-01-01

    The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments, and the observing program of the first 2 years of the mission. Examples of early discoveries by Compton are enumerated, including the discovery that gamma-ray bursts are isotropic but spatially inhomogeneous in their distribution; the discovery of a new class of high-energy extragalacatic gamma-ray sources, the gamma-ray AGNs; the discovery of emission from SN 1987A in the nuclear line of Co-57; and the mapping of emission from Al-26 in the interstellar medium (ISM) near the Galactic center. Future observations will include deep surveys of selected regions of the sky, long-tem studies of individual objects, correlative studies of objects at gamma-ray and other energies, a Galactic plane survey at intermediate gamma-ray energies, and improved statistics on gamma-ray bursts to search for small anisotropies. After completion of the all-sky survey, a Guest Investigator program is in progress with guest observers' time share increasing from 30% upward for the late mission phases.

  5. "Stereo Compton cameras" for the 3-D localization of radioisotopes

    NASA Astrophysics Data System (ADS)

    Takeuchi, K.; Kataoka, J.; Nishiyama, T.; Fujita, T.; Kishimoto, A.; Ohsuka, S.; Nakamura, S.; Adachi, S.; Hirayanagi, M.; Uchiyama, T.; Ishikawa, Y.; Kato, T.

    2014-11-01

    The Compton camera is a viable and convenient tool used to visualize the distribution of radioactive isotopes that emit gamma rays. After the nuclear disaster in Fukushima in 2011, there is a particularly urgent need to develop "gamma cameras", which can visualize the distribution of such radioisotopes. In response, we propose a portable Compton camera, which comprises 3-D position-sensitive GAGG scintillators coupled with thin monolithic MPPC arrays. The pulse-height ratio of two MPPC-arrays allocated at both ends of the scintillator block determines the depth of interaction (DOI), which dramatically improves the position resolution of the scintillation detectors. We report on the detailed optimization of the detector design, based on Geant4 simulation. The results indicate that detection efficiency reaches up to 0.54%, or more than 10 times that of other cameras being tested in Fukushima, along with a moderate angular resolution of 8.1° (FWHM). By applying the triangular surveying method, we also propose a new concept for the stereo measurement of gamma rays by using two Compton cameras, thus enabling the 3-D positional measurement of radioactive isotopes for the first time. From one point source simulation data, we ensured that the source position and the distance to the same could be determined typically to within 2 meters' accuracy and we also confirmed that more than two sources are clearly separated by the event selection from two point sources of simulation data.

  6. Demonstrating the Light-Emitting Diode.

    ERIC Educational Resources Information Center

    Johnson, David A.

    1995-01-01

    Describes a simple inexpensive circuit which can be used to quickly demonstrate the basic function and versatility of the solid state diode. Can be used to demonstrate the light-emitting diode (LED) as a light emitter, temperature sensor, light detector with both a linear and logarithmic response, and charge storage device. (JRH)

  7. Precise polarization measurements via detection of compton scattered electrons

    SciTech Connect

    Tvaskis, Vladas; Dutta, Dipangkar; Gaskell, David J.; Narayan, Amrendra

    2014-01-01

    The Qweak experiment at Jefferson Lab aims to make a 4% measurement of the parity-violating asymmetry in elastic scattering at very low Q{sup 2} of a longitudinally polarized electron beam off a proton target. One of the dominant experimental systematic uncertainties in Qweak will result from determining the beam polarization. A new Compton polarimeter was installed in the fall of 2010 to provide a non-invasive and continuous monitoring of the electron beam polarization in Hall C at Jefferson Lab. The Compton-scattered electrons are detected in four planes of diamond micro-strip detectors. We have achieved the design goals of <1% statistical uncertainty per hour and expect to achieve <1% systematic uncertainty.

  8. New Compton densitometer for measuring pulmonary edema

    SciTech Connect

    Loo, B.W.; Goulding, F.S.; Simon, D.S.

    1985-10-01

    Pulmonary edema is the pathological increase of extravascular lung water found most often in patients with congestive heart failure and other critically ill patients who suffer from intravenous fluid overload. A non-invasive lung density monitor that is accurate, easily portable, safe and inexpensive is needed for clinical evaluation of pulmonary edema. Other researchers who have employed Compton scattering techniques generally used systems of extended size and detectors with poor energy resolution. This has resulted in significant systematic biases from multiply-scattered photons and larger errors in counting statistics at a given radiation dose to the patient. We are proposing a patented approach in which only backscattered photons are measured with a high-resolution HPGe detector in a compact system geometry. By proper design and a unique data extraction scheme, effects of the variable chest wall on lung density measurements are minimized. Preliminary test results indicate that with a radioactive source of under 30 GBq, it should be possible to make an accurate lung density measurement in one minute, with a risk of radiation exposure to the patient a thousand times smaller than that from a typical chest x-ray. The ability to make safe, frequent lung density measurements could be very helpful for monitoring the course of P.E. at the hospital bedside or outpatient clinics, and for evaluating the efficacy of therapy in clinical research. 6 refs., 5 figs.

  9. A new telescope for wide-band gamma-ray astronomy: The Silicon Compton Recoil Telescope (SCRT)

    NASA Astrophysics Data System (ADS)

    Tuemer, O. Tuemay; Ait-Ouamer, Farid; Blair, Scott C.; Case, Gary L.; O'Neill, Brendan P.; O'Neill, Terrence J.; White, R. Stephen; Zych, Allen D.

    1994-06-01

    A new prototype gamma-ray telescope is described which is sensitive from 0.3 to 30 MeV as a Compton telescope and to 100 MeV as a pair detector. The Silicon Compton Recoil Telescope (SCRT) uses multilayers of silicon strip detectors as a Compton gamma-ray converter. Recoil electrons are tracked with the silicon strip detectors, and their energy losses and directions are measured. The direction and energy of the Compton-scattered gamma rays are measured with CsI(Tl)-photodiode detectors. Thus unique directions and energies are found for each incident gamma ray for the first time and without the background of overlapping rings. SCRT is the first Compton telescope to image the gamma-ray sky directly. It can also detect electron-positron pairs from gamma rays above 5 MeV, extending SCRT's sensitivity to above 100 MeV. Typical resolutions are 3% (FWHM) in energy at 2 MeV and 0.5 deg (1 sigma) in angle. The proposed prototype SCRT instrument has a sensitive area of 650 sq cm, a detection efficiency of 3%, a size reduction by about an order of magnitude, and a sensitivity of 15 millicrab for a typical Compton Observatory exposure. SCRT can also measure the polarization of the incident gamma rays, especially at low energies and large scattered angles. Simulation calculations and a discussion of results with a laboratory model are presented.

  10. Noise evaluation of Compton camera imaging for proton therapy.

    PubMed

    Ortega, P G; Torres-Espallardo, I; Cerutti, F; Ferrari, A; Gillam, J E; Lacasta, C; Llosá, G; Oliver, J F; Sala, P R; Solevi, P; Rafecas, M

    2015-03-01

    Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming γ energy is considered as a variable in the reconstruction inverse problem. Jointly with prompt gamma, secondary neutrons and scattered photons, not strongly correlated with the dose map, can also reach the imaging detector and produce false events. These events deteriorate the image quality. Also, high intensity beams can produce particle accumulation in the camera, which lead to an increase of random coincidences, meaning events which gather measurements from different incoming particles. The noise scenario is expected to be different if double or triple events are used, and consequently, the reconstructed images can be affected differently by spurious data. The aim of the present work is to study the effect of false events in the reconstructed image, evaluating their impact in the determination of the beam particle ranges. A simulation study that includes misidentified events (neutrons and random coincidences) in the final image of a Compton Telescope for PT monitoring is presented. The complete chain of

  11. Noise evaluation of Compton camera imaging for proton therapy

    NASA Astrophysics Data System (ADS)

    Ortega, P. G.; Torres-Espallardo, I.; Cerutti, F.; Ferrari, A.; Gillam, J. E.; Lacasta, C.; Llosá, G.; Oliver, J. F.; Sala, P. R.; Solevi, P.; Rafecas, M.

    2015-02-01

    Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming γ energy is considered as a variable in the reconstruction inverse problem. Jointly with prompt gamma, secondary neutrons and scattered photons, not strongly correlated with the dose map, can also reach the imaging detector and produce false events. These events deteriorate the image quality. Also, high intensity beams can produce particle accumulation in the camera, which lead to an increase of random coincidences, meaning events which gather measurements from different incoming particles. The noise scenario is expected to be different if double or triple events are used, and consequently, the reconstructed images can be affected differently by spurious data. The aim of the present work is to study the effect of false events in the reconstructed image, evaluating their impact in the determination of the beam particle ranges. A simulation study that includes misidentified events (neutrons and random coincidences) in the final image of a Compton Telescope for PT monitoring is presented. The complete chain of

  12. Compton polarimeter for 10–30 keV x rays

    SciTech Connect

    Weber, S.; Beilmann, C.; Shah, C.; Tashenov, S.

    2015-09-15

    We present a simple and versatile polarimeter for x rays in the energy range of 10–30 keV. It uses Compton scattering in low-Z materials such as beryllium or boron carbide. The azimuthal distribution of the scattered x rays is sampled by an array of 12 silicon PIN diodes operated at room temperature. We evaluated the polarimetry performance using Monte-Carlo simulations and show experimental results.

  13. Compton polarimeter for 10-30 keV x rays.

    PubMed

    Weber, S; Beilmann, C; Shah, C; Tashenov, S

    2015-09-01

    We present a simple and versatile polarimeter for x rays in the energy range of 10-30 keV. It uses Compton scattering in low-Z materials such as beryllium or boron carbide. The azimuthal distribution of the scattered x rays is sampled by an array of 12 silicon PIN diodes operated at room temperature. We evaluated the polarimetry performance using Monte-Carlo simulations and show experimental results. PMID:26429432

  14. A Compton-suppression detection system for use in manganese bath measurements

    NASA Astrophysics Data System (ADS)

    Ghal-Eh, N.; Doostizadeh, H.; Hazami, Z.; Doust-Mohammadi, V.

    2015-07-01

    The manganese sulfate bath technique is a standard tool for neutron source strength measurement (Park et al., 2005). However, the dominate Compton continuum of most sodium iodide scintillators used in manganese bath systems (MBSs) does not allow the precise identification of induced gamma rays required for such measurements. In this research, to resolve this problem, a Compton-suppression system has been proposed which consists of a 2 in. by 2 in. NaI(Tl) right cylindrical scintillator as the main and a set of eight rectangular NE102 plastic scintillators of 12×12×15 cm3 dimensions as suppression detectors. Both detectors operate in anti-coincidence circuit to suppress the Compton continuum. The proposed system has been simulated with the MCNPX code with two different approaches and the corresponding measurements with 137Cs gamma-ray source and neutron-activated MnSO4 solution have been undertaken that give rise to a promising agreement.

  15. Nano-scale NiSi and n-type silicon based Schottky barrier diode as a near infra-red detector for room temperature operation

    NASA Astrophysics Data System (ADS)

    Roy, S.; Midya, K.; Duttagupta, S. P.; Ramakrishnan, D.

    2014-09-01

    The fabrication of nano-scale NiSi/n-Si Schottky barrier diode by rapid thermal annealing process is reported. The characterization of the nano-scale NiSi film was performed using Micro-Raman Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The thickness of the film (27 nm) has been measured by cross-sectional Secondary Electron Microscopy and XPS based depth profile method. Current-voltage (I-V) characteristics show an excellent rectification ratio (ION/IOFF = 105) at a bias voltage of ±1 V. The diode ideality factor is 1.28. The barrier height was also determined independently based on I-V (0.62 eV) and high frequency capacitance-voltage technique (0.76 eV), and the correlation between them has explained. The diode photo-response was measured in the range of 1.35-2.5 μm under different reverse bias conditions (0.0-1.0 V). The response is observed to increase with increasing reverse bias. From the photo-responsivity study, the zero bias barrier height was determined to be 0.54 eV.

  16. Nano-scale NiSi and n-type silicon based Schottky barrier diode as a near infra-red detector for room temperature operation

    SciTech Connect

    Roy, S.; Midya, K.; Duttagupta, S. P.; Ramakrishnan, D.

    2014-09-28

    The fabrication of nano-scale NiSi/n-Si Schottky barrier diode by rapid thermal annealing process is reported. The characterization of the nano-scale NiSi film was performed using Micro-Raman Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The thickness of the film (27 nm) has been measured by cross-sectional Secondary Electron Microscopy and XPS based depth profile method. Current–voltage (I–V) characteristics show an excellent rectification ratio (I{sub ON}/I{sub OFF} = 10⁵) at a bias voltage of ±1 V. The diode ideality factor is 1.28. The barrier height was also determined independently based on I–V (0.62 eV) and high frequency capacitance–voltage technique (0.76 eV), and the correlation between them has explained. The diode photo-response was measured in the range of 1.35–2.5 μm under different reverse bias conditions (0.0–1.0 V). The response is observed to increase with increasing reverse bias. From the photo-responsivity study, the zero bias barrier height was determined to be 0.54 eV.

  17. The Compton polarimeter for SLC

    SciTech Connect

    Fero, M.J.; The SLD Collaboration

    1992-12-01

    We report on the use of a Compton scattering based polarimeter to measure beam polarization near the e{sup +}e{sub -} interaction point at the SLAC Linear Collider (SLC). Measurement of the beam polarization to a statistical precision of {delta}P/P={plus_minus}3% requires approximately three minutes under normal conditions. An average beam polarization of 22.4{plus_minus}0.7%(syst.) was measured over the course of the 1992 polarized beam run.

  18. The Compton polarimeter for SLC

    SciTech Connect

    Fero, M.J. )

    1992-12-01

    We report on the use of a Compton scattering based polarimeter to measure beam polarization near the e[sup +]e[sub -] interaction point at the SLAC Linear Collider (SLC). Measurement of the beam polarization to a statistical precision of [delta]P/P=[plus minus]3% requires approximately three minutes under normal conditions. An average beam polarization of 22.4[plus minus]0.7%(syst.) was measured over the course of the 1992 polarized beam run.

  19. Compton Sources of Electromagnetic Radiation

    SciTech Connect

    Geoffrey Krafft,Gerd Priebe

    2011-01-01

    When a relativistic electron beam interacts with a high-field laser beam, intense and highly collimated electromagnetic radiation will be generated through Compton scattering. Through relativistic upshifting and the relativistic Doppler effect, highly energetic polarized photons are radiated along the electron beam motion when the electrons interact with the laser light. For example, X-ray radiation can be obtained when optical lasers are scattered from electrons of tens-of-MeV beam energy. Because of the desirable properties of the radiation produced, many groups around the world have been designing, building, and utilizing Compton sources for a wide variety of purposes. In this review article, we discuss the generation and properties of the scattered radiation, the types of Compton source devices that have been constructed to date, and the prospects of radiation sources of this general type. Due to the possibilities of producing hard electromagnetic radiation in a device that is small compared to the alternative storage ring sources, it is foreseen that large numbers of such sources may be constructed in the future.

  20. Verification of Compton Collision and Klein-Nishina Formulas--An Undergraduate Laboratory Experiment

    ERIC Educational Resources Information Center

    Singhal, R. P.; Burns, A. J.

    1978-01-01

    Describes an experiment to verify the Compton collision formula and the angular dependance of the Klein-Nishina formula. Equipment used is a 1-mCi(137)Cs source, 2x2 in. NaI detector and a multichannel analyzer. Suitable for honor undergraduates. (Author/GA)

  1. Development of an optimized Compton suppression gamma-ray spectrometric system using Monte Carlo simulation.

    PubMed

    Choi, Y; Lee, K B; Kim, K J; Han, J; Yi, E S

    2016-03-01

    We have chosen to establish the Compton Suppression Spectrometer (CSS) for low activity environmental samples with a high purity germanium (HPGe) primary detector and a removable plug-in detector (NaI(Tl)) surrounded with a cylindrical annulus guard detector (NaI(Tl)). Monte Carlo simulation with PENELOPE (PENetration and Energy LOss of Positrons and Electrons) is used to determine the optimal geometry of the CSS. To verify a correlation between experiment and simulation, the energy distribution of (137)Cs and (60)Co point sources is measured and simulated for each condition. The CSS parameters are studied to determine optimal detector geometry and Compton Suppression Factor (CSF). The timing resolution of the CSS was found to be 44ns (FWHM), which is an outstanding result in the semiconductor-based gamma-ray spectrometry. All measured values of CSF agree within 5% with the values obtained from the simulation. The optimum geometry and CSF values are discussed. PMID:26778448

  2. DETECTION AND IMAGING OF THE CRAB NEBULA WITH THE NUCLEAR COMPTON TELESCOPE

    SciTech Connect

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

    2011-09-01

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

  3. The role of Compton scattering in scinti-mammography

    SciTech Connect

    Pani, R.; Scopinaro, F.; Pergola, A.

    1996-12-31

    Functional breast imaging using {sup 99m}Tc MIBI is showing that this technique is able to detect cancer with more than 90% specificity. Using a dedicated gamma camera, with the breast under compression, i.e. in similar conditions of mammography, the detection of sub-centimeter cancers can be improved. A number of factors affects the detection of small cancers as: thickness of the breast, distance between tumor and collimator, cardiac activity. Radioactivity emitted from the body can obscure the breast activity mainly due to the large difference on radioactivity concentration. In this work we analyze the intensity and the energy distribution of Compton scattering coming from the breast by a Germanium detector and by a dedicated imager with a small FOV placed in a geometrical condition similar to mammography. In vivo measurements were performed in patients with a breast cancer ranging between 8 mm and 15 mm. Intensity of Compton scattering from 4 to 10 times greater than full energy peak events resulted. Measurements were compared with ones obtained by a phantom simulating the breast without chest activity demonstrating how large is the Compton contribution from the chest.

  4. Experimental Study of a Si/CdTe Semiconductor Compton Camera for the Next Generation of Gamma-ray Astronomy

    NASA Astrophysics Data System (ADS)

    Takeda, Shinichiro

    A Compton camera is the most promising detector for gamma-ray astronomy in the energy band from a few tens of keV to MeV. Its detection method, based on Compton scattering kinematics, allows us to determine the direction of incident gamma-rays and significantly reduce background events caused by cosmic charged particle or detector activation in orbit. In this thesis, we describe a new Compton camera, named the Si/CdTe semiconductor Compton camera, which consists of many layers of position-sensitive Silicon and CdTe detectors. In order to verify the performance and to understand the detector response, we construct prototype Si/CdTe Compton cameras. The spectral response is studied by taking charge sharing, charge collection efficiency and thermal diffusion inside the Si and CdTe semiconductor devices used in the detectors. The imaging capability with various kinds of gamma-ray targets, such as a point source, arranged point sources and extended sources, is examined. Utilizing the maximum-likelihood iteration algorithm, the extended source and adjacent sources were successfully deconvolved with its internal structure. The ability of polarization measurements, which is one of key features of the Compton camera, are demonstrated through the experiment at synchrotron beam facility. The direction of the polarization vector is determined to within an accuracy of 1o. For the 92.5 % polarized 170 keV gamma-rays, the modulation factor of 0.82 is obtained. Based on the Monte Carlo simulator verified by the results from various experiments in this thesis, in-orbit performances for all-sky survey is studied. We confirmed that the Si/CdTe Compton camera can achieve one order of magnitude higher sensitivity in comparison with the COMPTEL onboard CGRO in the energy band from 500 keV to a few MeV

  5. Spectral properties of Compton inverse radiation: Application of Compton beams

    NASA Astrophysics Data System (ADS)

    Bulyak, Eugene; Urakawa, Junji

    2014-05-01

    Compton inverse radiation emitted due to backscattering of laser pulses off the relativistic electrons possesses high spectral density and high energy of photons - in hard x-ray up to gamma-ray energies - because of short wavelength of laser radiation as compared with the classical electromagnetic devices such as undulators. In this report, the possibility of such radiation to monochromatization by means of collimation is studied. Two approaches have been considered for the description of the spectral-angular density of Compton radiation based on the classical field theory and on the quantum electrodynamics. As is shown, both descriptions produce similar total spectra. On the contrary, angular distribution of the radiation is different: the classical approach predicted a more narrow radiation cone. Also proposed and estimated is a method of the 'electronic' monochromatization based on the electronic subtraction of the two images produced by the electron beams with slightly different energies. A 'proof-of-principle' experiment of this method is proposed for the LUXC facility of KEK (Japan).

  6. Data Diode

    SciTech Connect

    2014-11-07

    The Data Diode is a data security technology that can be deployed within an organization's defense-in-depth computer network strategy for information assurance. For internal security, the software creates an environment within the network where an organization's approved users can work freely inside an enclave of protected data, but file transfers out of the enclave is restricted. For external security, once a network intruder has penetrated the network, the intruder is able to "see" the protected data, but is unable to download the actual data. During the time it takes for the intruder to search for a way around the obstacle created by the Data Diode, the network's intrusion detection technologies can locate and thwart the malicious intent of the intruder. Development of the Data Diode technology was made possible by funding from the Intelligence Advanced Research Projects Activity (IARPA).

  7. Data Diode

    Energy Science and Technology Software Center (ESTSC)

    2014-11-07

    The Data Diode is a data security technology that can be deployed within an organization's defense-in-depth computer network strategy for information assurance. For internal security, the software creates an environment within the network where an organization's approved users can work freely inside an enclave of protected data, but file transfers out of the enclave is restricted. For external security, once a network intruder has penetrated the network, the intruder is able to "see" the protectedmore » data, but is unable to download the actual data. During the time it takes for the intruder to search for a way around the obstacle created by the Data Diode, the network's intrusion detection technologies can locate and thwart the malicious intent of the intruder. Development of the Data Diode technology was made possible by funding from the Intelligence Advanced Research Projects Activity (IARPA).« less

  8. The HERMES Recoil Detector

    SciTech Connect

    Kaiser, R.

    2006-07-11

    The HERMES Collaboration is installing a new Recoil Detector to upgrade the spectrometer for measurements of hard exclusive electron/positron scattering reactions, in particular deeply virtual Compton scattering. These measurements will provide access to generalised parton distributions and hence to the localisation of quarks inside hadrons and to their orbital angular momentum. The HERMES Recoil Detector consists of three active components: a silicon detector surrounding the target cell inside the beam vacuum, a scintillating fibre tracker and a photon detector consisting of three layers of tungsten/scintillator. All three detectors are located inside a solenoidal magnetic field of 1 Tesla. The Recoil Detector was extensively tested with cosmic muons over the summer of 2005 and is being installed in the winter of 2005/6 for data taking until summer 2007.

  9. Carbon-Nanotube Schottky Diodes

    NASA Technical Reports Server (NTRS)

    Manohara, Harish; Wong, Eric; Schlecht, Erich; Hunt, Brian; Siegel, Peter

    2006-01-01

    Schottky diodes based on semiconducting single-walled carbon nanotubes are being developed as essential components of the next generation of submillimeter-wave sensors and sources. Initial performance predictions have shown that the performance characteristics of these devices can exceed those of the state-of-the-art solid-state Schottky diodes that have been the components of choice for room-temperature submillimeter-wave sensors for more than 50 years. For state-of-the-art Schottky diodes used as detectors at frequencies above a few hundred gigahertz, the inherent parasitic capacitances associated with their semiconductor junction areas and the resistances associated with low electron mobilities limit achievable sensitivity. The performance of such a detector falls off approximately exponentially with frequency above 500 GHz. Moreover, when used as frequency multipliers for generating signals, state-of-the-art solid-state Schottky diodes exhibit extremely low efficiencies, generally putting out only micro-watts of power at frequencies up to 1.5 THz. The shortcomings of the state-of-the-art solid-state Schottky diodes can be overcome by exploiting the unique electronic properties of semiconducting carbon nanotubes. A single-walled carbon nanotube can be metallic or semiconducting, depending on its chirality, and exhibits high electron mobility (recently reported to be approx.= 2x10(exp 5)sq cm/V-s) and low parasitic capacitance. Because of the narrowness of nanotubes, Schottky diodes based on carbon nanotubes have ultra-small junction areas (of the order of a few square nanometers) and consequent junction capacitances of the order of 10(exp -18) F, which translates to cutoff frequency >5 THz. Because the turn-on power levels of these devices are very low (of the order of nano-watts), the input power levels needed for pumping local oscillators containing these devices should be lower than those needed for local oscillators containing state-of-the-art solid

  10. A Compton camera for spectroscopic imaging from 100 keV to 1 MeV

    SciTech Connect

    Earnhart, J.R.D.

    1998-12-31

    A review of spectroscopic imaging issues, applications, and technology is presented. Compton cameras based on solid state semiconductor detectors stands out as the best system for the nondestructive assay of special nuclear materials. A camera for this application has been designed based on an efficient specific purpose Monte Carlo code developed for this project. Preliminary experiments have been performed which demonstrate the validity of the Compton camera concept and the accuracy of the code. Based on these results, a portable prototype system is in development. Proposed future work is addressed.

  11. Compton Dry-Cask Imaging System

    ScienceCinema

    None

    2013-05-28

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

  12. Spin Degrees of Freedom in Compton Scattering

    NASA Astrophysics Data System (ADS)

    Miskimen, R.

    2016-02-01

    The next generation of Compton scattering experiments is underway at Mainz and other laboratories, where the goal is precision measurements of the scalar and vector polarizabilities of the nucleon using polarized photons and polarized targets. Results are presented for the first double polarized Compton scattering experiment utilizing a polarized proton target. Preliminary results are presented for the four spin polarizabilities of the proton.

  13. Compton Dry-Cask Imaging System

    SciTech Connect

    2011-01-01

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

  14. GRAPE: A Compton Polarimetry Experiment

    NASA Astrophysics Data System (ADS)

    Connor, Taylor; Bloser, Peter; Legere, Jason; McConnell, Mark; Ryan, James

    2009-10-01

    We review the design, calibration and data analysis of the Gamma Ray Polarimetry Experiment (GRAPE), a Compton polarimeter device for measuring the polarization of photons in the 50-500 keV energy range. In Compton scattering, X-ray and gamma-ray photons tend to scatter at right angles with respect to their polarization vector. We exploit this fact to measure the polarization of the incident radiation by looking at the azimuthal distribution of the scattered photons. This distribution gives us a measure of both the level of polarization and the orientation of the polarization vector. These measurements will allow us to probe the particle acceleration regions of astronomical sources. GRAPE will be flown in the fall of 2011 on as a high altitude balloon payload. The primary target of that flight will be the Crab Nebula, with the Sun (solar flares) and Cygnus X-1 as secondary targets. Our observations of the Crab will be compared to the findings of the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), which provided constraints on the location of the particle acceleration region within the Crab Nenbula. Following the initial flight in 2011, we hope to fly GRAPE on a long duration balloon flight from Antarctica to study gamma-ray bursts.

  15. Inspection of reinforced concrete samples by Compton backscattering technique

    NASA Astrophysics Data System (ADS)

    Boldo, E. M.; Appoloni, C. R.

    2014-02-01

    Reinforced concrete structures require frequent monitoring to ensure the concrete quality during its service life and for evaluation of in situ existing conditions. Compton backscattering of gamma rays is a nondestructive technique used for material characterization and detection of defects and inclusions in materials and can be employed on reinforced concrete. The methodology allows one-sided inspection of large structures, is relatively inexpensive and can be portable. The concept is based on detection of backscattered radiation produced from a collimated beam aimed at the sample. By measuring the spectrum of these scattered gamma rays it is possible to determine local density perturbations. In this work we used the Compton backscattering technique to locate and measure steel, defects and crushed stone inside concrete. The samples were irradiated with gamma rays from a Ø2 mm diameter collimated 241Am (100 mCi) source and the inelastically scattered photons were recorded at an angle of 135° by a high resolution CdTe semiconductor detector. Scanning was achieved by lateral movement of the sample blocks across the source and detector field of view in steps of 1 mm. A previous optimization of the experimental setup was performed with Monte Carlo simulation. The results showed that it was possible to locate inclusions and defects with Ø8 mm positioned at a depth of 20 mm below the surface of the sample. It was observed that aggregates such as crushed stone could mask defects at specific points due to high attenuation of the incident and scattered beam.

  16. A Monte Carlo evaluation of three Compton camera absorbers.

    PubMed

    Uche, C Z; Round, W H; Cree, M J

    2011-09-01

    We present a quantitative study on the performance of cadmium zinc telluride (CZT), thallium-doped sodium iodide (NaI(Tl)) and germanium (Ge) detectors as potential Compton camera absorbers. The GEANT4 toolkit was used to model the performance of these materials over the nuclear medicine energy range. CZT and Ge demonstrate the highest and lowest efficiencies respectively. Although the best spatial resolution was attained for Ge, its lowest ratio of single photoelectric to multiple interactions suggests that it is most prone to inter-pixel cross-talk. In contrast, CZT, which demonstrates the least positioning error due to multiple interactions, has a comparable spatial resolution with Ge. Therefore, we modelled a Compton camera system based on silicon (Si) and CZT as the scatterer and absorber respectively. The effects of the detector parameters of our proposed system on image resolution were evaluated and our results show good agreement with previous studies. Interestingly, spatial resolution which accounted for the least image degradation at 140.5 keV became the dominant degrading factor at 511 keV, indicating that the absorber parameters play some key roles at higher energies. The results of this study have validated the predictions by An et al. which state that the use of a higher energy gamma source together with reduction of the absorber segmentation to sub-millimetre could achieve the image resolution of 5 mm required in medical imaging. PMID:21710232

  17. A Compton camera prototype for prompt gamma medical imaging

    NASA Astrophysics Data System (ADS)

    Thirolf, P. G.; Aldawood, S.; Böhmer, M.; Bortfeldt, J.; Castelhano, I.; Dedes, G.; Fiedler, F.; Gernhäuser, R.; Golnik, C.; Helmbrecht, S.; Hueso-González, F.; Kolff, H. v. d.; Kormoll, T.; Lang, C.; Liprandi, S.; Lutter, R.; Marinšek, T.; Maier, L.; Pausch, G.; Petzoldt, J.; Römer, K.; Schaart, D.; Parodi, K.

    2016-05-01

    Compton camera prototype for a position-sensitive detection of prompt γ rays from proton-induced nuclear reactions is being developed in Garching. The detector system allows to track the Comptonscattered electrons. The camera consists of a monolithic LaBr3:Ce scintillation absorber crystal, read out by a multi-anode PMT, preceded by a stacked array of 6 double-sided silicon strip detectors acting as scatterers. The LaBr3:Ce crystal has been characterized with radioactive sources. Online commissioning measurements were performed with a pulsed deuteron beam at the Garching Tandem accelerator and with a clinical proton beam at the OncoRay facility in Dresden. The determination of the interaction point of the photons in the monolithic crystal was investigated.

  18. Compton scatter with polychromatic sources for lung densitometry.

    PubMed

    Hanson, J A; Moore, W E; Figley, M M; Duke, P R

    1984-01-01

    A mobile lung densitometer using conventional x-ray tubes, NaI detectors, and principles of two-source, two-detector Compton scattered densitometry, is described. The device is capable of one to two per second density measurements from a 45-cm3 volume with a precision of 5%. The expected in vivo accuracy (2%-3%) is determined by using an anthropomorphic phantom with replaceable lung inserts. The unintentional detection of multiple-scattered x rays results in a small density-dependent error. This error is predictable and relatively insensitive to differences in surrounding absorbers such as the chest wall. With this device, dynamic in vivo densitometry of the lung in the clinical laboratory and intensive care unit will be possible. PMID:6503878

  19. Installation and performance testing of an XtRa-NaI(Tl) Compton Suppression System at the NED-NTUA.

    PubMed

    Savva, M I; Karfopoulos, K L; Karangelos, D J; Anagnostakis, M J; Simopoulos, S E

    2014-05-01

    This paper presents the Compton Suppression System, recently installed at the Nuclear Engineering Department of NTUA. The system consists of an XtRa Ge detector coupled with a NaI(Tl) guard detector. The electronic set-up allows for the simultaneous collection of both the suppressed and the unsuppressed spectra. System performance is investigated using certified point and volume sources. Parameters such as Peak Suppression Factors, peak-to-Compton ratios and minimum detectable activity for specific radionuclides are determined. PMID:24315283

  20. Improving the effectiveness of a low-energy Compton suppression system

    NASA Astrophysics Data System (ADS)

    Britton, R.; Burnett, J. L.; Davies, A. V.; Regan, P. H.

    2013-11-01

    A novel method for collecting and processing coincidence data from a Compton Suppressed Low Energy Photon Spectrometer (LEPS) is presented, greatly simplifying the current setup and extending the suppression abilities of the system. Offline analysis is used, eliminating the need to discard coincidence data when vetoing coincident events with fast-timing electronics. Additional coincident events are identified that are usually missed, and which represent interactions in the active NaI(Tl) shield prior to an interaction in the LEPS detector. By suppressing these events, the Compton Suppression factor was improved by 144% for the 661.66 keV decay line in a 137Cs source. The geometry used for this particular Compton suppression system is highly sensitive to these effects, however similar event profiles are expected in all coincidence systems.

  1. Accurate, low-energy Compton polarimetry for Hall C at Jefferson Lab

    NASA Astrophysics Data System (ADS)

    Jones, Donald

    2012-03-01

    A new Compton polarimeter has recently been commissioned in Hall C at Jefferson Lab in Newport News, VA, to provide a non-invasive, continuous measurement of electron beam polarization. The new Compton polarimeter is currently measuring electron beam polarization for Qweak, an experiment with a strict error budget allowing a combined statistical and systematic error of only ±1% for beam polarization. Using well-established techniques we are able to determine electron beam polarization by measuring the scattering asymmetry of both the backscattered photons and the scattered electrons. Although the photon and electron detectors provide somewhat independent measurements they share the common systematic of the laser polarization. I discuss the optical setup for the photon target used in the Compton polarimeter and recent efforts in reducing systematic error in determination of laser polarization.

  2. A Compton scattering technique to determine wood density and locating defects in it

    SciTech Connect

    Tondon, Akash Sandhu, B. S.; Singh, Bhajan; Singh, Mohinder

    2015-08-28

    A Compton scattering technique is presented to determine density and void location in the given wooden samples. The technique uses a well collimated gamma ray beam from {sup 137}Cs along with the NaI(Tl) scintillation detector. First, a linear relationship is established between Compton scattered intensity and known density of chemical compounds, and then density of the wood is determined from this linear relation. In another experiment, the ability of penetration of gamma rays is explored to detect voids in wooden (low Z) sample. The sudden reduction in the Compton scattered intensities agrees well with the position and size of voids in the wooden sample. It is concluded that wood density and the voids of size ∼ 4 mm and more can be detected easily by this method.

  3. Quantitative Analysis and Comparison of Four Major Flavonol Glycosides in the Leaves of Toona sinensis (A. Juss.) Roemer (Chinese Toon) from Various Origins by High-Performance Liquid Chromatography-Diode Array Detector and Hierarchical Clustering Analysis

    PubMed Central

    Sun, Xiaoxiang; Zhang, Liting; Cao, Yaqi; Gu, Qinying; Yang, Huan; Tam, James P.

    2016-01-01

    Background: Toona sinensis (A. Juss.) Roemer is an endemic species of Toona genus native to Asian area. Its dried leaves are applied in the treatment of many diseases; however, few investigations have been reported for the quantitative analysis and comparison of major bioactive flavonol glycosides in the leaves harvested from various origins. Objective: To quantitatively analyze four major flavonol glycosides including rutinoside, quercetin-3-O-β-D-glucoside, quercetin-3-O-α-L-rhamnoside, and kaempferol-3-O-α-L-rhamnoside in the leaves from different production sites and classify them according to the content of these glycosides. Materials and Methods: A high-performance liquid chromatography-diode array detector (HPLC-DAD) method for their simultaneous determination was developed and validated for linearity, precision, accuracy, stability, and repeatability. Moreover, the method established was then employed to explore the difference in the content of these four glycosides in raw materials. Finally, a hierarchical clustering analysis was performed to classify 11 voucher specimens. Results: The separation was performed on a Waters XBridge Shield RP18 column (150 mm × 4.6 mm, 3.5 μm) kept at 35°C, and acetonitrile and H2O containing 0.30% trifluoroacetic acid as mobile phase was driven at 1.0 mL/min during the analysis. Ten microliters of solution were injected and 254 nm was selected to monitor the separation. A strong linear relationship between the peak area and concentration of four analytes was observed. And, the method was also validated to be repeatable, stable, precise, and accurate. Conclusion: An efficient and reliable HPLC-DAD method was established and applied in the assays for the samples from 11 origins successfully. Moreover, the content of those flavonol glycosides varied much among different batches, and the flavonoids could be considered as biomarkers to control the quality of Chinese Toon. SUMMARY Four major flavonol glycosides in the leaves

  4. Bulk Comptonization by turbulence in accretion discs

    NASA Astrophysics Data System (ADS)

    Kaufman, J.; Blaes, O. M.

    2016-06-01

    Radiation pressure dominated accretion discs around compact objects may have turbulent velocities that greatly exceed the electron thermal velocities within the disc. Bulk Comptonization by the turbulence may therefore dominate over thermal Comptonization in determining the emergent spectrum. Bulk Comptonization by divergenceless turbulence is due to radiation viscous dissipation only. It can be treated as thermal Comptonization by solving the Kompaneets equation with an equivalent `wave' temperature, which is a weighted sum over the power present at each scale in the turbulent cascade. Bulk Comptonization by turbulence with non-zero divergence is due to both pressure work and radiation viscous dissipation. Pressure work has negligible effect on photon spectra in the limit of optically thin turbulence, and in this limit radiation viscous dissipation alone can be treated as thermal Comptonization with a temperature equivalent to the full turbulent power. In the limit of extremely optically thick turbulence, radiation viscous dissipation is suppressed, and the evolution of local photon spectra can be understood in terms of compression and expansion of the strongly coupled photon and gas fluids. We discuss the consequences of these effects for self-consistently resolving and interpreting turbulent Comptonization in spectral calculations in radiation magnetohydrodynamic simulations of high luminosity accretion flows.

  5. Bayesian Event Reconstruction for Advanced Compton Telescopes

    NASA Astrophysics Data System (ADS)

    Zoglauer, A.; ACT

    2004-12-01

    Measuring gamma rays via Compton scattering in a space environment is a challenging task: weak source signals have to be extracted from dominating background, which mainly originates from cosmic rays (prompt interactions as well as delayed decays) and earth albedo photons. The approach of Advanced Compton Telescopes (ACT) to overcome this problem is to measure more parameters of the events (several Compton interactions, the recoil electron direction, etc.) with a higher accuracy than previous Compton telescopes like COMPTEL. Still, this leaves the event reconstruction with three main tasks: Find the correct sequence of interactions, identify background and suppress incompletely absorbed events. The most promising approach to accomplish those tasks is based on Bayesian statistics: The Compton interactions are parameterized in an eight-dimensional data space, which contains the interaction information of the Compton sequence. For each data space cell the probability that the corresponding interaction sequence is those of a correctly ordered, completely absorbed source photon can be determined by detailed simulations. The result is an absolute quality factor for each event, based on which source events can be distinguished from background and incompletely absorbed photons. We will report on the performance of the algorithm for a typical advanced Compton telescope design.

  6. The Compton Gamma Ray Observatory

    NASA Astrophysics Data System (ADS)

    Gehrels, N.; Chipman, E.; Kniffen, D. A.

    1993-01-01

    The Arthur Holly Compton Gamma Ray Observatory (Compton) was launched by the Space Shuttle Atlantis on 5 April 1991. The spacecraft and instruments are in good health and returning exciting results. The mission provides nearly six orders of magnitude in spectral coverage, from 30 keV to 30 GeV, with sensitivity over the entire range an order of magnitude better than that of previous observations. The 16,000 kilogram observatory contains four instruments on a stabilized platform. The mission began normal operations on 16 May 1991 and is now over half-way through a full-sky survey. The mission duration is expected to be from six to ten years. A Science Support Center has been established at Goddard Space Flight Center for the purpose of supporting a vigorous Guest Investigator Program. New scientific results to date include: (1) the establishment of the isotropy, combined with spatial inhomogeneity, of the distribution of gamma-ray bursts in the sky; (2) the discovery of intense high energy (100 MeV) gamma-ray emission from 3C 279 and other quasars and BL Lac objects, making these the most distant and luminous gamma-ray sources ever detected; (3) one of the first images of a gamma-ray burst; (4) the observation of intense nuclear and position-annihilation gamma-ray lines and neutrons from several large solar flares; and (5) the detection of a third gamma-ray pulsar, plus several other transient and pulsing hard X-ray sources.

  7. Second-order capillary electrophoresis diode array detector data modeled with the Tucker3 algorithm: A novel strategy for Argentinean white wine discrimination respect to grape variety.

    PubMed

    Azcarate, Silvana M; de Araújo Gomes, Adriano; Vera-Candioti, Luciana; Cesar Ugulino de Araújo, Mário; Camiña, José M; Goicoechea, Héctor C

    2016-07-01

    Data obtained by capillary electrophoresis with diode array detection (CE-DAD) were modeled with the purpose to discriminate Argentinean white wines samples produced from three grape varieties (Torrontés, Chardonnay, and Sauvignon blanc). Thirty-eight samples of commercial white wine from four wine-producing provinces of Argentina (Mendoza, San Juan, Salta, and Rio Negro) were analyzed. CE-DAD matrices with dimensions of 421 elution times (from 1.17 to 7.39 minutes) × 71 wavelengths (from 227 to 367 nm) were joined in a three way data array and decomposed by Tucker3 method under non-negativity constraint, employing 18, 18 and six factors in the modes 1, 2 and 3, respectively. Using the scores of Tucker model, it was possible to discriminate samples of Argentinean white wine by linear discriminant analysis and Kernel linear discriminant analysis. Core element analysis of the Tucker3 model allows identifying the loading profiles in spectral mode related to Argentinean white wine samples. PMID:27028847

  8. Characterization via liquid chromatography coupled to diode array detector and tandem mass spectrometry of supercritical fluid antioxidant extracts of Spirulina platensis microalga.

    PubMed

    Mendiola, Jose A; Marín, Francisco R; Hernández, S Francisco; Arredondo, Bertha O; Señoráns, F Javier; Ibañez, Elena; Reglero, Guillermo

    2005-06-01

    Spirulina platensis microalga has been extracted on a pilot scale plant using supercritical fluid extraction (SFE) under various extraction conditions. The extraction yield and the antioxidant activity of the extracts were evaluated in order to select those extracts with both the highest antioxidant capacity and a good extraction yield. These extracts were characterized using LC coupled to diode array detection (DAD) and LC coupled to mass spectrometry (MS) with two different interfaces, atmospheric pressure chemical ionization (APCI) and electrospray (ESI) which allowed us to perform tandem MS by using an ion trap analyzer. The best extraction conditions were as follows: CO2 with 10% of modifier (ethanol) as extraction solvent, 55 degrees C (extraction temperature) and 220 bar (extraction pressure). Fractionation was achieved by cascade depressurization providing two extracts with different activity and chemical composition. Several compounds have been identified in the extracts, corresponding to different carotenoids previously identified in Spirulina platensis microalga along with chlorophyll a and some degradation products. Also, the structure of some phenolic compounds could be tentatively identified. The antioxidant activity of the extracts could be attributed to some of the above mentioned compounds. PMID:16013830

  9. Performance measurements of hybrid PIN diode arrays

    SciTech Connect

    Shapiro, S.L. ); Arens, J.F.; Jernigan, J.G. . Space Sciences Lab.); Kramer, G. ); Collins, T.; Worley, S. ); Wilburn, C.D. ); Skubic, P. )

    1990-10-01

    We report the successful development of hybrid PIN diode arrays and a series of room-temperature measurements in a high-energy pion beam at FNAL. A PMOS VLSI 256 {times} 256 readout array having 30 {mu}m square pixels was indium-bump bonded to a mating PIN diode detector array. Preliminary measurements on the resulting hybrid show excellent signal-to-noise at room temperature. 3 refs., 5 figs.

  10. Real Compton scattering via color dipoles

    SciTech Connect

    Kopeliovich, B. Z.; Schmidt, Ivan; Siddikov, M.

    2009-09-01

    We study the photoabsorption reaction and real Compton scattering within the color dipole model. We rely on a photon wave function derived in the instanton-vacuum model and on the energy-dependent phenomenological elastic dipole amplitude. Data for the photoabsorption cross section at high energies agree with our parameter-free calculations. We also provide predictions for the differential real Compton scattering cross section. Although no data for small angle Compton scattering are available so far, this process can be measured in ultraperipheral hadronic and nuclear collisions at the LHC.