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Sample records for photon energy spectrum

  1. Electron energy spectrum and maximum disruption angle under multi-photon beamstrahlung

    SciTech Connect

    Yokoya, Kaoru; Chen, Pisin

    1989-03-01

    The final electron energy spectrum under multi-photon beamstrahlung process is derived analytically in the classical and the intermediate regimes. The maximum disruption angle from the low energy tail of the spectrum is also estimated. The results are then applied to the TLC and the CLIC parameters. 6 refs., 1 fig., 1 tab.

  2. Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources

    PubMed Central

    Ghorbani, Mahdi; Davenport, David

    2016-01-01

    Abstract Aim The aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters. Background Different photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources. Materials and methods MCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared. Results Dose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours. Conclusions Dosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems. PMID:27247558

  3. Variability in fluence and spectrum of high-energy photon bursts produced by lightning leaders

    NASA Astrophysics Data System (ADS)

    Celestin, Sebastien; Xu, Wei; Pasko, Victor P.

    2015-12-01

    In this paper, we model the production and acceleration of thermal runaway electrons during negative corona flash stages of stepping lightning leaders and the corresponding terrestrial gamma ray flashes (TGFs) or negative cloud-to-ground (-CG) lightning-produced X-ray bursts in a unified fashion. We show how the source photon spectrum and fluence depend on the potential drop formed in the lightning leader tip region during corona flash and how the X-ray burst spectrum progressively converges toward typical TGF spectrum as the potential drop increases. Additionally, we show that the number of streamers produced in a negative corona flash, the source electron energy distribution function, the corresponding number of photons, and the photon energy distribution and transport through the atmosphere up to low-orbit satellite altitudes exhibit a very strong dependence on this potential drop. This leads to a threshold effect causing X-rays produced by leaders with potentials lower than those producing typical TGFs extremely unlikely to be detected by low-orbit satellites. Moreover, from the number of photons in X-ray bursts produced by -CGs estimated from ground observations, we show that the proportionality between the number of thermal runaway electrons and the square of the potential drop in the leader tip region during negative corona flash proposed earlier leads to typical photon fluences on the order of 1 ph/cm2 at an altitude of 500 km and a radial distance of 200 km for intracloud lightning discharges producing 300 MV potential drops, which is consistent with observations of TGF fluences and spectra from satellites.

  4. Exclusive Measurements of the b to s gamma Transition Rate and Photon Energy Spectrum

    SciTech Connect

    Lees, J.P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Brown, David Nathan; Kerth, L.T.; Kolomensky, Yu.G.; Lynch, G.; Koch, H.; Schroeder, T.; Asgeirsson, D.J.; Hearty, C.; Mattison, T.S.; McKenna, J.A.; Khan, A.; Blinov, V.E.; Buzykaev, A.R.; /more authors..

    2012-08-30

    We use 429 fb{sup -1} of e{sup +}e{sup -} collision data collected at the {Upsilon}(4S) resonance with the BABAR detector to measure the radiative transition rate of b {yields} s{gamma} with a sum of 38 exclusive final states. The inclusive branching fraction with a minimum photon energy of 1.9 GeV is found to be {Beta}({bar B} {yields} Xs{gamma}) = (3.29 {+-} 0.19 {+-} 0.48) x 10{sup -4} where the first uncertainty is statistical and the second is systematic. We also measure the first and second moments of the photon energy spectrum and extract the best fit values for the heavy-quark parameters, m{sub b} and {mu}{sub {pi}}{sup 2}, in the kinetic and shape function models.

  5. Analysis of Energy Spectrum with Low Photon Counts via Bayesian Posterior Simulation

    NASA Astrophysics Data System (ADS)

    van Dyk, David A.; Protassov, Rostislav; Kashyap, Vinay L.; Siemiginowska, Aneta; Connors, Alanna

    1999-04-01

    Recently Bayesian methods have grown rapidly in popularity in many scientific disciplines as several computationally intensive statistical algorithms have become feasible with modern computer power. In this paper, we demonstrate how we have employed these state-of-the-art techniques (e.g., Gibbs sampler and Metropolis-Hastings) to fit today's high-quality, high resolution astrophysical spectral data. These algorithms are very flexible and can be used to fit models that account for the highly hierarchical structure in the collection of high-quality spectra and thus can keep pace with the accelerating progress of new telescope designs. We explicitly model photon arrivals as a Poisson process and, thus, have no difficulty with high resolution low count X-ray and gamma-ray data. These methods will be useful not only for the soon-to-be-launched Chandra X-ray observatory but also such new generation telescopes as XMM, Constellation X, and GLAST. We also explicitly incorporate the instrument response (e.g. via a response matrix and effective area vector), plus background contamination of the data. In particular, we appropriately model the background as the realization of a second Poisson process, thereby eliminating the need to directly subtract off the background counts and the rather embarrassing problem of negative photon counts. The source energy spectrum is modeled as a mixture of a Generalized Linear Model which accounts for the continuum plus absorption and several (Gaussian) line profiles. Generalized Linear Models are the standard method for incorporating covariate information (as in regression) into non-Gaussian models and are thus an obvious but innovative choice in this setting. Using several examples, we illustrate how Bayesian posterior sampling can be used to compute point (i.e., ``best'') estimates of the various model parameters as well as compute error bars on these estimates and construct statistical tests.

  6. Measurement of the B to Xs gammaBranching Fraction and Photon Energy Spectrum usingthe Recoil Method

    SciTech Connect

    Aubert, B.

    2007-12-04

    We present a measurement of the branching fraction and photon energy spectrum for the decay B {yields} X{sub s}{gamma} using data from the BABAR experiment. The data sample corresponds to an integrated luminosity of 210 fb{sup -1}, from which approximately 680,000 B{bar B} events are tagged by a fully reconstructed hadronic decay of one of the B mesons. In the decay of the second B meson, an isolated high-energy photon is identified. We measure {Beta}(B {yields} X{sub s}{gamma}) = (3.66 {+-} 0.85{sub stat} {+-} 0.60{sub syst}) x 10{sup -4} for photon energies E{sub {gamma}} above 1.9 GeV in the B rest frame. From the measured spectrum we calculate the first and second moments for different minimum photon energies, which are used to extract the heavy-quark parameters m{sub b} and {mu}{sub {pi}}{sup 2}. In addition, measurements of the direct CP asymmetry and isospin asymmetry are presented.

  7. Exposure dose reduction for the high energy spectrum in the photon counting mammography: simulation study based on Japanese breast glandularity and thickness

    NASA Astrophysics Data System (ADS)

    Niwa, Naoko; Yamazaki, Misaki; Kodera, Yoshie; Yamamuro, Mika; Yamada, Kanako; Asai, Yoshiyuki; Yamada, Koji

    2015-03-01

    Recently, digital mammography with a photon counting silicon detector has been developed. With the aim of reducing the exposure dose, we have proposed a new mammography system that uses a cadmium telluride series photon counting detector. In addition, we also propose to use a high energy X-ray spectrum with a tungsten anode. The purpose of this study was assessed that the effectiveness of the high X-ray energy spectrum in terms of image quality using a Monte Carlo simulation. The proposed photon counting system with the high energy X-ray is compared to a conventional flat panel detector system with a Mo/Rh spectrum. The contrast-to-noise ratio (CNR) is calculated from simulation images with the use of breast phantoms. The breast model phantoms differed by glandularity and thickness, which were determined from Japanese clinical mammograms. We found that the CNR values were higher in the proposed system than in the conventional system. The number of photons incident on the detector was larger in the proposed system, so that the noise values was lower in comparison with the conventional system. Therefore, the high energy spectrum yielded the same CNR as using the conventional spectrum while allowing a considerable dose reduction to the breast.

  8. Precision measurement of the B → Xs γ photon energy spectrum, branching fraction, and direct CP asymmetry A(CP)((B → X(s+d)γ).

    PubMed

    Lees, J P; Poireau, V; Tisserand, V; Garra Tico, J; Grauges, E; Palano, A; Eigen, G; Stugu, B; Brown, D N; Kerth, L T; Kolomensky, Yu G; Lynch, G; Koch, H; Schroeder, T; Asgeirsson, D J; Hearty, C; Mattison, T S; McKenna, J A; So, R Y; Khan, A; Blinov, V E; Buzykaev, A R; Druzhinin, V P; Golubev, V B; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Todyshev, K Yu; Yushkov, A N; Bondioli, M; Kirkby, D; Lankford, A J; Mandelkern, M; Atmacan, H; Gary, J W; Liu, F; Long, O; Vitug, G M; Campagnari, C; Hong, T M; Kovalskyi, D; Richman, J D; West, C A; Eisner, A M; Kroseberg, J; Lockman, W S; Martinez, A J; Schumm, B A; Seiden, A; Winstrom, L; Chao, D S; Cheng, C H; Echenard, B; Flood, K T; Hitlin, D G; Ongmongkolkul, P; Porter, F C; Rakitin, A Y; Andreassen, R; Huard, Z; Meadows, B T; Sokoloff, M D; Sun, L; Bloom, P C; Ford, W T; Gaz, A; Nauenberg, U; Smith, J G; Wagner, S R; Ayad, R; Toki, W H; Spaan, B; Schubert, K R; Schwierz, R; Bernard, D; Verderi, M; Clark, P J; Playfer, S; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Fioravanti, E; Garzia, I; Luppi, E; Munerato, M; Piemontese, L; Santoro, V; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Rama, M; Zallo, A; Contri, R; Guido, E; Lo Vetere, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Bhuyan, B; Prasad, V; Lee, C L; Morii, M; Edwards, A J; Adametz, A; Uwer, U; Lacker, H M; Lueck, T; Dauncey, P D; Mallik, U; Chen, C; Cochran, J; Meyer, W T; Prell, S; Rubin, A E; Gritsan, A V; Guo, Z J; Arnaud, N; Davier, M; Derkach, D; Grosdidier, G; Le Diberder, F; Lutz, A M; Malaescu, B; Roudeau, P; Schune, M H; Stocchi, A; Wormser, G; Lange, D J; Wright, D M; Chavez, C A; Coleman, J P; Fry, J R; Gabathuler, E; Hutchcroft, D E; Payne, D J; Touramanis, C; Bevan, A J; Di Lodovico, F; Sacco, R; Sigamani, M; Cowan, G; Brown, D N; Davis, C L; Denig, A G; Fritsch, M; Gradl, W; Griessinger, K; Hafner, A; Prencipe, E; Barlow, R J; Jackson, G; Lafferty, G D; Behn, E; Cenci, R; Hamilton, B; Jawahery, A; Roberts, D A; Dallapiccola, C; Cowan, R; Dujmic, D; Sciolla, G; Cheaib, R; Lindemann, D; Patel, P M; Robertson, S H; Biassoni, P; Neri, N; Palombo, F; Stracka, S; Cremaldi, L; Godang, R; Kroeger, R; Sonnek, P; Summers, D J; Nguyen, X; Simard, M; Taras, P; De Nardo, G; Monorchio, D; Onorato, G; Sciacca, C; Martinelli, M; Raven, G; Jessop, C P; Knoepfel, K; Losecco, J M; Wang, W F; Honscheid, K; Kass, R; Brau, J; Frey, R; Lu, M; Sinev, N B; Strom, D; Torrence, E; Feltresi, E; Gagliardi, N; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simi, G; Simonetto, F; Stroili, R; Akar, S; Ben-Haim, E; Bomben, M; Bonneaud, G R; Briand, H; Calderini, G; Chauveau, J; Hamon, O; Leruste, Ph; Marchiori, G; Ocariz, J; Sitt, S; Biasini, M; Manoni, E; Pacetti, S; Rossi, A; Angelini, C; Batignani, G; Bettarini, S; Carpinelli, M; Casarosa, G; Cervelli, A; Forti, F; Giorgi, M A; Lusiani, A; Oberhof, B; Paoloni, E; Perez, A; Rizzo, G; Walsh, J J; Lopes Pegna, D; Olsen, J; Smith, A J S; Telnov, A V; Anulli, F; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Li Gioi, L; Mazzoni, M A; Piredda, G; Bünger, C; Grünberg, O; Hartmann, T; Leddig, T; Schröder, H; Voss, C; Waldi, R; Adye, T; Olaiya, E O; Wilson, F F; Emery, S; Hamel de Monchenault, G; Vasseur, G; Yèche, Ch; Aston, D; Bard, D J; Bartoldus, R; Bechtle, P; Benitez, J F; Cartaro, C; Convery, M R; Dorfan, J; Dubois-Felsmann, G P; Dunwoodie, W; Ebert, M; Field, R C; Franco Sevilla, M; Fulsom, B G; Gabareen, A M; Graham, M T; Grenier, P; Hast, C; Innes, W R; Kelsey, M H; Kim, P; Kocian, M L; Leith, D W G S; Lewis, P; Lindquist, B; Luitz, S; Luth, V; Lynch, H L; Macfarlane, D B; Muller, D R; Neal, H; Nelson, S; Perl, M; Pulliam, T; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Snyder, A; Su, D; Sullivan, M K; Va'vra, J; Wagner, A P; Wisniewski, W J; Wittgen, M; Wright, D H; Wulsin, H W; Young, C C; Ziegler, V; Park, W; Purohit, M V; White, R M; Wilson, J R; Randle-Conde, A; Sekula, S J; Bellis, M; Burchat, P R; Miyashita, T S; Alam, M S; Ernst, J A; Gorodeisky, R; Guttman, N; Peimer, D R; Soffer, A; Lund, P; Spanier, S M; Ritchie, J L; Ruland, A M; Schwitters, R F; Wray, B C; Izen, J M; Lou, X C; Bianchi, F; Gamba, D; Zambito, S; Lanceri, L; Vitale, L; Martinez-Vidal, F; Oyanguren, A; Ahmed, H; Albert, J; Banerjee, Sw; Bernlochner, F U; Choi, H H F; King, G J; Kowalewski, R; Lewczuk, M J; Nugent, I M; Roney, J M; Sobie, R J; Tasneem, N; Gershon, T J; Harrison, P F; Latham, T E; Puccio, E M T; Band, H R; Dasu, S; Pan, Y; Prepost, R; Wu, S L

    2012-11-01

    The photon spectrum in the inclusive electromagnetic radiative decays of the B meson, B → X(s)γ plus B → X(d)γ, is studied using a data sample of (382.8 ± 4.2) × 10(6)Υ(4S) → BB decays collected by the BABAR experiment at SLAC. The spectrum is used to extract the branching fraction B(B → X(s)γ) = (3.21 ± 0.33) × 10(-4) for E(γ) >1.8 GeV and the direct CP asymmetry A(CP) (B → X(s+d)γ) = 0.057 ± 0.063. The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the B meson rest frame. PMID:23215373

  9. Precision measurement of the B → Xs γ photon energy spectrum, branching fraction, and direct CP asymmetry A(CP)((B → X(s+d)γ).

    PubMed

    Lees, J P; Poireau, V; Tisserand, V; Garra Tico, J; Grauges, E; Palano, A; Eigen, G; Stugu, B; Brown, D N; Kerth, L T; Kolomensky, Yu G; Lynch, G; Koch, H; Schroeder, T; Asgeirsson, D J; Hearty, C; Mattison, T S; McKenna, J A; So, R Y; Khan, A; Blinov, V E; Buzykaev, A R; Druzhinin, V P; Golubev, V B; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Todyshev, K Yu; Yushkov, A N; Bondioli, M; Kirkby, D; Lankford, A J; Mandelkern, M; Atmacan, H; Gary, J W; Liu, F; Long, O; Vitug, G M; Campagnari, C; Hong, T M; Kovalskyi, D; Richman, J D; West, C A; Eisner, A M; Kroseberg, J; Lockman, W S; Martinez, A J; Schumm, B A; Seiden, A; Winstrom, L; Chao, D S; Cheng, C H; Echenard, B; Flood, K T; Hitlin, D G; Ongmongkolkul, P; Porter, F C; Rakitin, A Y; Andreassen, R; Huard, Z; Meadows, B T; Sokoloff, M D; Sun, L; Bloom, P C; Ford, W T; Gaz, A; Nauenberg, U; Smith, J G; Wagner, S R; Ayad, R; Toki, W H; Spaan, B; Schubert, K R; Schwierz, R; Bernard, D; Verderi, M; Clark, P J; Playfer, S; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Fioravanti, E; Garzia, I; Luppi, E; Munerato, M; Piemontese, L; Santoro, V; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Rama, M; Zallo, A; Contri, R; Guido, E; Lo Vetere, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Bhuyan, B; Prasad, V; Lee, C L; Morii, M; Edwards, A J; Adametz, A; Uwer, U; Lacker, H M; Lueck, T; Dauncey, P D; Mallik, U; Chen, C; Cochran, J; Meyer, W T; Prell, S; Rubin, A E; Gritsan, A V; Guo, Z J; Arnaud, N; Davier, M; Derkach, D; Grosdidier, G; Le Diberder, F; Lutz, A M; Malaescu, B; Roudeau, P; Schune, M H; Stocchi, A; Wormser, G; Lange, D J; Wright, D M; Chavez, C A; Coleman, J P; Fry, J R; Gabathuler, E; Hutchcroft, D E; Payne, D J; Touramanis, C; Bevan, A J; Di Lodovico, F; Sacco, R; Sigamani, M; Cowan, G; Brown, D N; Davis, C L; Denig, A G; Fritsch, M; Gradl, W; Griessinger, K; Hafner, A; Prencipe, E; Barlow, R J; Jackson, G; Lafferty, G D; Behn, E; Cenci, R; Hamilton, B; Jawahery, A; Roberts, D A; Dallapiccola, C; Cowan, R; Dujmic, D; Sciolla, G; Cheaib, R; Lindemann, D; Patel, P M; Robertson, S H; Biassoni, P; Neri, N; Palombo, F; Stracka, S; Cremaldi, L; Godang, R; Kroeger, R; Sonnek, P; Summers, D J; Nguyen, X; Simard, M; Taras, P; De Nardo, G; Monorchio, D; Onorato, G; Sciacca, C; Martinelli, M; Raven, G; Jessop, C P; Knoepfel, K; Losecco, J M; Wang, W F; Honscheid, K; Kass, R; Brau, J; Frey, R; Lu, M; Sinev, N B; Strom, D; Torrence, E; Feltresi, E; Gagliardi, N; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simi, G; Simonetto, F; Stroili, R; Akar, S; Ben-Haim, E; Bomben, M; Bonneaud, G R; Briand, H; Calderini, G; Chauveau, J; Hamon, O; Leruste, Ph; Marchiori, G; Ocariz, J; Sitt, S; Biasini, M; Manoni, E; Pacetti, S; Rossi, A; Angelini, C; Batignani, G; Bettarini, S; Carpinelli, M; Casarosa, G; Cervelli, A; Forti, F; Giorgi, M A; Lusiani, A; Oberhof, B; Paoloni, E; Perez, A; Rizzo, G; Walsh, J J; Lopes Pegna, D; Olsen, J; Smith, A J S; Telnov, A V; Anulli, F; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Li Gioi, L; Mazzoni, M A; Piredda, G; Bünger, C; Grünberg, O; Hartmann, T; Leddig, T; Schröder, H; Voss, C; Waldi, R; Adye, T; Olaiya, E O; Wilson, F F; Emery, S; Hamel de Monchenault, G; Vasseur, G; Yèche, Ch; Aston, D; Bard, D J; Bartoldus, R; Bechtle, P; Benitez, J F; Cartaro, C; Convery, M R; Dorfan, J; Dubois-Felsmann, G P; Dunwoodie, W; Ebert, M; Field, R C; Franco Sevilla, M; Fulsom, B G; Gabareen, A M; Graham, M T; Grenier, P; Hast, C; Innes, W R; Kelsey, M H; Kim, P; Kocian, M L; Leith, D W G S; Lewis, P; Lindquist, B; Luitz, S; Luth, V; Lynch, H L; Macfarlane, D B; Muller, D R; Neal, H; Nelson, S; Perl, M; Pulliam, T; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Snyder, A; Su, D; Sullivan, M K; Va'vra, J; Wagner, A P; Wisniewski, W J; Wittgen, M; Wright, D H; Wulsin, H W; Young, C C; Ziegler, V; Park, W; Purohit, M V; White, R M; Wilson, J R; Randle-Conde, A; Sekula, S J; Bellis, M; Burchat, P R; Miyashita, T S; Alam, M S; Ernst, J A; Gorodeisky, R; Guttman, N; Peimer, D R; Soffer, A; Lund, P; Spanier, S M; Ritchie, J L; Ruland, A M; Schwitters, R F; Wray, B C; Izen, J M; Lou, X C; Bianchi, F; Gamba, D; Zambito, S; Lanceri, L; Vitale, L; Martinez-Vidal, F; Oyanguren, A; Ahmed, H; Albert, J; Banerjee, Sw; Bernlochner, F U; Choi, H H F; King, G J; Kowalewski, R; Lewczuk, M J; Nugent, I M; Roney, J M; Sobie, R J; Tasneem, N; Gershon, T J; Harrison, P F; Latham, T E; Puccio, E M T; Band, H R; Dasu, S; Pan, Y; Prepost, R; Wu, S L

    2012-11-01

    The photon spectrum in the inclusive electromagnetic radiative decays of the B meson, B → X(s)γ plus B → X(d)γ, is studied using a data sample of (382.8 ± 4.2) × 10(6)Υ(4S) → BB decays collected by the BABAR experiment at SLAC. The spectrum is used to extract the branching fraction B(B → X(s)γ) = (3.21 ± 0.33) × 10(-4) for E(γ) >1.8 GeV and the direct CP asymmetry A(CP) (B → X(s+d)γ) = 0.057 ± 0.063. The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the B meson rest frame.

  10. Effective dose of A-bomb radiation in Hiroshima and Nagasaki as assessed by chromosomal effectiveness of spectrum energy photons and neutrons.

    PubMed

    Sasaki, M S; Endo, S; Ejima, Y; Saito, I; Okamura, K; Oka, Y; Hoshi, M

    2006-07-01

    The effective dose of combined spectrum energy neutrons and high energy spectrum gamma-rays in A-bomb survivors in Hiroshima and Nagasaki has long been a matter of discussion. The reason is largely due to the paucity of biological data for high energy photons, particularly for those with an energy of tens of MeV. To circumvent this problem, a mathematical formalism was developed for the photon energy dependency of chromosomal effectiveness by reviewing a large number of data sets published in the literature on dicentric chromosome formation in human lymphocytes. The chromosomal effectiveness was expressed by a simple multiparametric function of photon energy, which made it possible to estimate the effective dose of spectrum energy photons and differential evaluation in the field of mixed neutron and gamma-ray exposure with an internal reference radiation. The effective dose of reactor-produced spectrum energy neutrons was insensitive to the fine structure of the energy distribution and was accessible by a generalized formula applicable to the A-bomb neutrons. Energy spectra of all sources of A-bomb gamma-rays at different tissue depths were simulated by a Monte Carlo calculation applied on an ICRU sphere. Using kerma-weighted chromosomal effectiveness of A-bomb spectrum energy photons, the effective dose of A-bomb neutrons was determined, where the relative biological effectiveness (RBE) of neutrons was expressed by a dose-dependent variable RBE, RBE(gamma, D (n)), against A-bomb gamma-rays as an internal reference radiation. When the newly estimated variable RBE(gamma, D (n)) was applied to the chromosome data of A-bomb survivors in Hiroshima and Nagasaki, the city difference was completely eliminated. The revised effective dose was about 35% larger in Hiroshima, 19% larger in Nagasaki and 26% larger for the combined cohort compared with that based on a constant RBE of 10. Since the differences are significantly large, the proposed effective dose might have an

  11. The effect of energy spectrum change on DNA damage in and out of field in 10-MV clinical photon beams.

    PubMed

    Ezzati, A O; Xiao, Y; Sohrabpour, M; Studenski, M T

    2015-01-01

    The aim of this study was to quantify the DNA damage induced in a clinical megavoltage photon beam at various depths in and out of the field. MCNPX was used to simulate 10 × 10 and 20 × 20 cm(2) 10-MV photon beams from a clinical linear accelerator. Photon and electron spectra were collected in a water phantom at depths of 2.5, 12.5 and 22.5 cm on the central axis and at off-axis points out to 10 cm. These spectra were used as an input to a validated microdosimetric Monte Carlo code, MCDS, to calculate the RBE of induced DSB in DNA at points in and out of the primary radiation field at three depths. There was an observable difference in the energy spectra for photons and electrons for points in the primary radiation field and those points out of field. In the out-of-field region, the mean energy for the photon and electron spectra decreased by a factor of about six and three from the in-field mean energy, respectively. Despite the differences in spectra and mean energy, the change in RBE was <1 % from the in-field region to the out-of-field region at any depth. There was no significant change in RBE regardless of the location in the phantom. Although there are differences in both the photon and electron spectra, these changes do not correlate with a change in RBE in a clinical MV photon beam as the electron spectra are dominated by electrons with energies >20 keV.

  12. The Pair Beam Production Spectrum from Photon-Photon Annihilation in Cosmic Voids

    NASA Astrophysics Data System (ADS)

    Schlickeiser, R.; Elyiv, A.; Ibscher, D.; Miniati, F.

    2012-10-01

    Highly beamed relativistic e ±-pair energy distributions result in double photon collisions of the beamed gamma rays from TeV blazars at cosmological distances with the isotropically distributed extragalactic background light (EBL) in the intergalactic medium. The typical energies k 0 ~= 10-7 in units of mec 2 of the EBL are more than 10 orders of magnitude smaller than the observed gamma-ray energies k 1 >= 107. Using the limit k 0 Lt k 1, we demonstrate that the angular distribution of the generated pairs in the lab frame is highly beamed in the direction of the initial gamma-ray photons. For the astrophysically important case of power-law distributions of the emitted gamma-ray beam up to the maximum energy M interacting with Wien-type N(k 0)vpropkq 0exp (- k 0/Θ) soft photon distributions with total number density N 0, we calculate analytical approximations for the electron production spectrum. For distant objects with luminosity distances dL Gt r 0 = (σ T N 0)-1 = 0.49N -1 0 Mpc (with Thomson cross section σ T ), the implied large values of the optical depth τ0 = dL /r 0 indicate that the electron production spectra differ at energies inside and outside the interval [(Θln τ0)-1, τ0/Θ], given the maximum gamma-ray energy M Gt Θ-1. In the case M Gt Θ-1, the production spectrum is strongly peaked near E ~= Θ-1, being exponentially reduced at small energies and decreasing with the steep power law vpropE -1 - p up to the maximum energy E = M - (1/2).

  13. THE PAIR BEAM PRODUCTION SPECTRUM FROM PHOTON-PHOTON ANNIHILATION IN COSMIC VOIDS

    SciTech Connect

    Schlickeiser, R.; Ibscher, D.; Elyiv, A.; Miniati, F. E-mail: ibscher@tp4.rub.de E-mail: fm@phys.ethz.ch

    2012-10-20

    Highly beamed relativistic e {sup {+-}}-pair energy distributions result in double photon collisions of the beamed gamma rays from TeV blazars at cosmological distances with the isotropically distributed extragalactic background light (EBL) in the intergalactic medium. The typical energies k {sub 0} {approx_equal} 10{sup -7} in units of m{sub e}c {sup 2} of the EBL are more than 10 orders of magnitude smaller than the observed gamma-ray energies k {sub 1} {>=} 10{sup 7}. Using the limit k {sub 0} << k {sub 1}, we demonstrate that the angular distribution of the generated pairs in the lab frame is highly beamed in the direction of the initial gamma-ray photons. For the astrophysically important case of power-law distributions of the emitted gamma-ray beam up to the maximum energy M interacting with Wien-type N(k {sub 0}){proportional_to}k{sup q} {sub 0}exp (- k {sub 0}/{Theta}) soft photon distributions with total number density N {sub 0}, we calculate analytical approximations for the electron production spectrum. For distant objects with luminosity distances d{sub L} >> r {sub 0} = ({sigma} {sub T} N {sub 0}){sup -1} = 0.49N {sup -1} {sub 0} Mpc (with Thomson cross section {sigma} {sub T}), the implied large values of the optical depth {tau}{sub 0} = d{sub L} /r {sub 0} indicate that the electron production spectra differ at energies inside and outside the interval [({Theta}ln {tau}{sub 0}){sup -1}, {tau}{sub 0}/{Theta}], given the maximum gamma-ray energy M >> {Theta}{sup -1}. In the case M >> {Theta}{sup -1}, the production spectrum is strongly peaked near E {approx_equal} {Theta}{sup -1}, being exponentially reduced at small energies and decreasing with the steep power law {proportional_to}E {sup -1-p} up to the maximum energy E = M - (1/2).

  14. Proliferative characteristics of intestinal stem cells. Response and protection to high-energy or fission spectrum neutrons or photons. Technical report, 1 December 1983-1 December 1985

    SciTech Connect

    Hanson, W.R.

    1986-04-30

    Cytosine Arabinoside (Ara/C) is an S-phase cytoxic agent. Since nearly half the proliferating cells in the murine crypt are in the S phase, Ara/c treatment, the clonogenic cells (the cells responsible for tissue regeneration) in the crypt are considerably less sensitive to photon radiation than colonogenic cells of control animals. Evidence suggests that the reason for this radioprotection by a toxic agent is the Ara/c-induced alteration in the cell age distribution of the clonogenic cells. Normally, the clonogenic cells are in a G/sub 1/ or G/sub 0/ stage of the cell cycle and are unaffected directly by Ara/c; however, following Ara/c treatment of an animal, the clonogenic cells enter the cell cycle. By 12 hours, the clonogenic cells proceed in a partially synchronized fashion to a mid toi late S phase of the cell cycle where they are less sensitive. WR-2721 appears to protect cells from radiation throughout the cell cycle and most likely acts through a mechanism different from Ara/c. Results of this contrast showed that the combination of Ara/c and WR-2721 protected the gut from photon injury to a greater extent than each agent alone. The protection from Fermilab neutrons by the combination was slightly better than each agent and there was no additional protection of Ara/c combined with WR-2721 for injury by JANUS fission spectrum neutrons. These treatments did not alter the animal response at doses in the bone marrow lethal range.

  15. Universal energy spectrum from point sources

    NASA Technical Reports Server (NTRS)

    Tomozawa, Yukio

    1992-01-01

    The suggestion is made that the energy spectrum from point sources such as galactic black hole candidates (GBHC) and active galactic nuclei (AGN) is universal on the average, irrespective of the species of the emitted particles, photons, nucleons, or others. The similarity between the observed energy spectra of cosmic rays, gamma-rays, and X-rays is discussed. In other words, the existing data for gamma-rays and X-rays seem to support the prediction. The expected data from the Gamma Ray Observatory are to provide a further test.

  16. Formation of ions by high-energy photons

    SciTech Connect

    Drukarev, E. G.; Mikhailov, A. I.; Mikhailov, I. A.; Rakhimov, Kh. Yu.; Scheid, W.

    2007-03-15

    We calculate the electron energy spectrum of ionization by a high-energy photon, accompanied by creation of an e{sup -}e{sup +} pair. The total cross section of the process is also obtained. The asymptotics of the cross section does not depend on the photon energy. At the photon energies exceeding a certain value {omega}{sub 0} this appears to be the dominant mechanism of formation of the ions. The dependence of {omega}{sub 0} on the value of nuclear charge is obtained. Our results are consistent with experimental data.

  17. Measurement of the moments of the photon energy spectrum in B{yields}X{sub s}{gamma} decays and determination of |V{sub cb}| and m{sub b} at Belle

    SciTech Connect

    Schwanda, C.; Mandl, F.; Mitaroff, W.; Urquijo, P.; Barberio, E.; Limosani, A.; Dalseno, J.; Moloney, G. R.; Sevior, M. E.; Taylor, G. N.; Wedd, R.; Adachi, I.; Haba, J.; Hazumi, M.; Itoh, R.; Iwasaki, Y.; Katayama, N.; Kichimi, H.; Krokovny, P.; Nakao, M.

    2008-08-01

    Using the previous Belle measurement of the inclusive photon energy in B{yields}X{sub s}{gamma} decays, we determine the first and second moments of this spectrum for minimum photon energies in the B meson rest frame ranging from 1.8 to 2.3 GeV. Combining these measurements with recent Belle data on the lepton energy and hadronic mass moments in B{yields}X{sub c}l{nu} decays, we perform fits to theoretical expressions derived in the 1S and kinetic mass schemes and extract the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element V{sub cb}, the b-quark mass, and other nonperturbative parameters. In the 1S scheme analysis we find |V{sub cb}|=(41.56{+-}0.68(fit){+-}0.08({tau}{sub B}))x10{sup -3} and m{sub b}{sup 1S}=(4.723{+-}0.055) GeV. In the kinetic scheme, we obtain |V{sub cb}|=(41.58{+-}0.69(fit){+-}0.08({tau}{sub B}){+-}0.58(th))x10{sup -3} and m{sub b}{sup kin}=(4.543{+-}0.075) GeV.

  18. Is there a low-energy enhancement in the photon strength function in molybdenum?

    NASA Astrophysics Data System (ADS)

    Sheets, S. A.

    2008-04-01

    Recent claims of a low-energy enhancement in the photon strength function of 96Mo are investigated. Using the DANCE detector the gamma-ray spectra following resonance neutron capture was measured. The spectrum fitting method was used to indirectly extract a photon strength function from the gamma-ray spectra. No strong low energy enhancement in the photon strength function was found.

  19. Is there a low energy enhancement in the photon strength function in molybdenum?

    SciTech Connect

    Sheets, S A

    2008-01-30

    Recent claims of a low energy enhancement in the photon strength function of {sup 96}Mo are investigated. Using the DANCE detector the gamma-ray spectra following resonance neutron capture was measured. The spectrum fitting method was used to indirectly extract a photon strength function from the gamma-ray spectra. No strong low energy enhancement in the photon strength function was found.

  20. Two-photon excitation of atoms by ultrashort electromagnetic pulses in a discrete spectrum

    NASA Astrophysics Data System (ADS)

    Astapenko, V. A.; Sakhno, S. V.

    2016-07-01

    The paper is devoted to the theoretical investigation of two-photon excitation of atom in a discrete energy spectrum by ultrashort electromagnetic pulses of femto- and subfemtosecond ranges of durations. An analytical expression for the total probability of the process is derived. Numerical simulations are made for hydrogen and sodium atoms. It is shown that the total probability of the process is nonlinear function of pulse duration and character of this function depends strongly on the frequency detuning of pulse carrier frequency from two-photon resonance.

  1. Simulation of energy absorption spectrum in NaI crystal detector for multiple gamma energy using Monte Carlo method

    SciTech Connect

    Wirawan, Rahadi; Waris, Abdul; Djamal, Mitra; Handayani, Gunawan

    2015-04-16

    The spectrum of gamma energy absorption in the NaI crystal (scintillation detector) is the interaction result of gamma photon with NaI crystal, and it’s associated with the photon gamma energy incoming to the detector. Through a simulation approach, we can perform an early observation of gamma energy absorption spectrum in a scintillator crystal detector (NaI) before the experiment conducted. In this paper, we present a simulation model result of gamma energy absorption spectrum for energy 100-700 keV (i.e. 297 keV, 400 keV and 662 keV). This simulation developed based on the concept of photon beam point source distribution and photon cross section interaction with the Monte Carlo method. Our computational code has been successfully predicting the multiple energy peaks absorption spectrum, which derived from multiple photon energy sources.

  2. The effects of photon spectrum and variable thermal conductivity on the distribution of temperature in an inclined plate crotch absorber

    SciTech Connect

    Choi, M.

    1989-11-01

    Absorption of photons in a metal is varied up to the photon energy spectrum. For example, larger wavelength photons generally can be more easily absorbed when they pass through an absorber while shorter ones tend to penetrate. This spectral variation of photon energy absorption takes place angularly due to the angular variation of the synchrotron radiation power. In this note, the effects of photon spectrum have been investigated for the thermal analysis of crotch absorbers. In addition, the effects of variable thermal conductivity have also been investigated. The heat generation due to the photon energy deposition diffuses throughout the metal with the thermal conductivity k which is dependent on the temperature field. This temperature dependence of the conductivity results in a non-linear heat conduction equation. This note presents both effects of the photon spectrum and the variable thermal conductivity on the temperature distribution for inclined crotch absorbers. A finite difference program was written and the calculation results were compared with the previous analytical solution which assumed constant conductivity and absorption coefficient.

  3. The grand unified photon spectrum: A coherent view of the diffuse extragalactic background radiation

    NASA Technical Reports Server (NTRS)

    Ressell, M. Ted; Turner, Michael S.

    1989-01-01

    The spectrum of diffuse extragalactic background radiation (DEBRA) at wavelengths from 10(exp 5) to 10(exp -24) cm is presented in a coherent fashion. Each wavelength region, from the radio to ultra-high energy photons and cosmic rays, is treated both separately and as part of the grand unified photon spectrum (GUPS). A discussion of, and references to, the relevant literature for each wavelength region is included. This review should provide a useful tool for those interested in diffuse backgrounds, the epoch of galaxy formation, astrophysical/cosmological constraints to particle properties, exotic early Universe processes, and many other astrophysical and cosmological enterprises. As a worked example, researchers derive the cosmological constraints to an unstable-neutrino spies (with arbitrary branching ratio to a radiative decay mode) that follow from the GUPS.

  4. Loophole to the universal photon spectrum in electromagnetic cascades and application to the cosmological lithium problem.

    PubMed

    Poulin, Vivian; Serpico, Pasquale Dario

    2015-03-01

    The standard theory of electromagnetic cascades onto a photon background predicts a quasiuniversal shape for the resulting nonthermal photon spectrum. This has been applied to very disparate fields, including nonthermal big bang nucleosynthesis (BBN). However, once the energy of the injected photons falls below the pair-production threshold the spectral shape is much harder, a fact that has been overlooked in past literature. This loophole may have important phenomenological consequences, since it generically alters the BBN bounds on nonthermal relics; for instance, it allows us to reopen the possibility of purely electromagnetic solutions to the so-called "cosmological lithium problem," which were thought to be excluded by other cosmological constraints. We show this with a proof-of-principle example and a simple particle physics model, compared with previous literature.

  5. Loophole to the universal photon spectrum in electromagnetic cascades and application to the cosmological lithium problem.

    PubMed

    Poulin, Vivian; Serpico, Pasquale Dario

    2015-03-01

    The standard theory of electromagnetic cascades onto a photon background predicts a quasiuniversal shape for the resulting nonthermal photon spectrum. This has been applied to very disparate fields, including nonthermal big bang nucleosynthesis (BBN). However, once the energy of the injected photons falls below the pair-production threshold the spectral shape is much harder, a fact that has been overlooked in past literature. This loophole may have important phenomenological consequences, since it generically alters the BBN bounds on nonthermal relics; for instance, it allows us to reopen the possibility of purely electromagnetic solutions to the so-called "cosmological lithium problem," which were thought to be excluded by other cosmological constraints. We show this with a proof-of-principle example and a simple particle physics model, compared with previous literature. PMID:25793793

  6. The low-energy photon tagger NEPTUN

    NASA Astrophysics Data System (ADS)

    Savran, D.; Lindenberg, K.; Glorius, J.; Löher, B.; Müller, S.; Pietralla, N.; Schnorrenberger, L.; Simon, V.; Sonnabend, K.; Wälzlein, C.; Elvers, M.; Endres, J.; Hasper, J.; Zilges, A.

    2010-02-01

    A new photon tagging spectrometer was built at the superconducting Darmstadt electron linear accelerator (S-DALINAC). The system is designed for tagging photons in an energy range from 6 to 20 MeV with the emphasis on best possible energy resolution and intensity. The absolute energy resolution of photons at 10 MeV is expected to be about 20 keV. With scintillating fibres as focal-plane detectors a maximum rate of tagged photons of 104 keV -1s -1 will be achieved. Detailed design studies including Monte Carlo simulations are presented, as well as results for the measured tagged photon energy profile of the system realized so far. This photon-tagging facility will allow to determine the photon absorption cross-sections as a function of excitation energy and to study the decay patterns of nuclear photo-excitations in great detail.

  7. GZK photons as ultra-high-energy cosmic rays

    SciTech Connect

    Gelmini, G. B.; Kalashev, O. E. Semikoz, D. V.

    2008-06-15

    We calculate the flux of 'GZK photons,' namely, the flux of ultra-high-energy cosmic rays (UHECRs) consisting of photons produced by extragalactic nucleons through the resonant photoproduction of pions, the so-called GZK effect. We show that for primary nucleons, the GZK-photon fraction of the total UHECR flux is between 10{sup -4} and 10{sup -2} above 10{sup 19} eV and up to the order of 0.1 above 10{sup 20} eV. The GZK-photon flux depends on the assumed UHECR spectrum, the slope of the nucleon flux at the source, and the distribution of sources and intervening backgrounds. Detection of this photon flux would open the way for UHECR gamma-ray astronomy. Detection of a larger photon flux would imply the emission of photons at the source or new physics. We compare the photon fractions expected for GZK photons and the minimal fractions predicted by top-down models. We find that the photon fraction above 10{sup 19} eV is a crucial test for top-down models.

  8. Photon Science for Renewable Energy

    SciTech Connect

    Hussain, Zahid; Tamura, Lori; Padmore, Howard; Schoenlein, Bob; Bailey, Sue

    2010-03-31

    Our current fossil-fuel-based system is causing potentially catastrophic changes to our planet. The quest for renewable, nonpolluting sources of energy requires us to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels. Light-source facilities - the synchrotrons of today and the next-generation light sources of tomorrow - are the scientific tools of choice for exploring the electronic and atomic structure of matter. As such, these photon-science facilities are uniquely positioned to jump-start a global revolution in renewable and carbonneutral energy technologies. In these pages, we outline and illustrate through examples from our nation's light sources possible scientific directions for addressing these profound yet urgent challenges.

  9. Photon energy conversion efficiency in gamma-ray spectrometry.

    PubMed

    Švec, Anton

    2016-01-01

    Photon energy conversion efficiency coefficient is presented as the ratio of total energy registered in the collected spectrum to the emitted photon energy. This parameter is calculated from the conventional gamma-ray histogram and in principle is not affected by coincidence phenomena. This feature makes it particularly useful for calibration and measurement of radionuclide samples at close geometries. It complements the number of efficiency parameters used in gamma-ray spectrometry and can partly change the view as to how the gamma-ray spectra are displayed and processed.

  10. Photon Detector For Inverse Photoemission Spectroscopy With Improved Energy Resolution

    SciTech Connect

    Maniraj, M.; D'Souza, S. W.; Barman, S. R.

    2011-07-15

    We present the results from newly designed and fabricated double window photon detector to improve the overall energy resolution for inverse photoemission spectroscopy (IPES). This simple design allows us to introduce an absorption gas (Krypton) to decrease the band-width of the energy selective photon detector and thus improve the resolution. Resonance absorption line of Kr of wavelength of 123.6 nm was used. By fitting the Fermi edge of the IPES spectrum of silver, we find an overall energy resolution improved by 73 meV. The design is modular and ensures ease and safety of handling.

  11. Energy spectrum of sputtered uranium

    NASA Technical Reports Server (NTRS)

    Weller, R. A.; Tombrello, T. A.

    1977-01-01

    The fission track technique for detecting uranium 235 was used in conjunction with a mechanical time-of-flight spectrometer to measure the energy spectrum in the region 1 eV to 1 keV of material sputtered from a 93% enriched U-235 foil by 80 keV Ar-40(+) ions. The spectrum was found to exhibit a peak in the region 2-4 eV and to decrease approximately as E to the -1.77 power for E is approximately greater than 100 eV. The design, construction and resolution of the mechanical spectrometer are discussed and comparisons are made between the data and the predictions of the ramdom collision cascade model of sputtering.

  12. Partial cross sections of helium satellites at medium photon energies

    SciTech Connect

    Wehlitz, R.; Sellin, I.A.; Hemmers, O.

    1997-04-01

    Still of current interest is the important role of single ionization with excitation compared to single ionization alone. The coupling between the electrons and the incoming photon is a single-particle operator. Thus, an excitation in addition to an ionization, leading to a so-called satellite line in a photoelectron spectrum, is entirely due to electron-electron interaction and probes the electron correlation in the ground and final state. Therefore the authors have undertaken the study of the intensity of helium satellites He{sup +}nl (n = 2 - 6) relative to the main photoline (n = 1) as a function of photon energy at photon energies well above threshold up to 900 eV. From these results they could calculate the partial cross-sections of the helium satellites. In order to test the consistency of their satellite-to-1s ratios with published double-to-single photoionization ratios, the authors calculated the double-to-single photoionization ratio from their measured ratios using the theoretical energy-distribution curves of Chang and Poe and Le Rouzo and Dal Cappello which proved to be valid for photon energies below 120 eV. These calculated double-to-single ionization ratios agree fairly well with recent ion measurements. In the lower photon energy range the authors ratios agree better with the ratios of Doerner et al. while for higher photon energies the agreement is better with the values of Levin et al.

  13. Continuous Energy MC Neutron/Photon

    1991-10-10

    VIM solves the three-dimensional steady-state multiplication eigenvalue or fixed source neutron or photon (VIM3.0) transport problem using continuous energy-dependent nuclear data. It was designed for the analysis of fast critical experiments. In VIM3.0, the photon interactions i.e., pair production, coherent and incoherent scattering, and photoelectric events, and photon heating are tallied by group, region, and isotope.

  14. Triplet-triplet annihilation photon-upconversion: towards solar energy applications.

    PubMed

    Gray, Victor; Dzebo, Damir; Abrahamsson, Maria; Albinsson, Bo; Moth-Poulsen, Kasper

    2014-06-14

    Solar power production and solar energy storage are important research areas for development of technologies that can facilitate a transition to a future society independent of fossil fuel based energy sources. Devices for direct conversion of solar photons suffer from poor efficiencies due to spectrum losses, which are caused by energy mismatch between the optical absorption of the devices and the broadband irradiation provided by the sun. In this context, photon-upconversion technologies are becoming increasingly interesting since they might offer an efficient way of converting low energy solar energy photons into higher energy photons, ideal for solar power production and solar energy storage. This perspective discusses recent progress in triplet-triplet annihilation (TTA) photon-upconversion systems and devices for solar energy applications. Furthermore, challenges with evaluation of the efficiency of TTA-photon-upconversion systems are discussed and a general approach for evaluation and comparison of existing systems is suggested.

  15. Is there a low-energy enhancement in the photon strength function in molybdenum?

    SciTech Connect

    Sheets, S. A.

    2008-04-17

    Recent claims of a low-energy enhancement in the photon strength function of {sup 96}Mo are investigated. Using the DANCE detector the gamma-ray spectra following resonance neutron capture was measured. The spectrum fitting method was used to indirectly extract a photon strength function from the gamma-ray spectra. No strong low energy enhancement in the photon strength function was found.

  16. Double pair production by ultra-high-energy cosmic ray photons

    SciTech Connect

    Demidov, S. V. Kalashev, O. E.

    2009-05-15

    Using the CompHEP package, we provide a detailed estimate of the influence of double e{sup +}e{sup -} pair production (DPP) by photons on the propagation of ultra-high-energy electromagnetic cascades. We show that in the models where the cosmic ray photon energy reaches a few 10{sup 3} EeV, a refined DPP analysis may lead to a substantial difference in the predicted photon spectrum compared to the previous rough estimates.

  17. Photonic crystal: energy-related applications

    SciTech Connect

    Ye, Zhuo; Park, Joong-Mok; Constant, Kristen; Kim, Tae-Geun; Ho, Kai-Ming

    2012-06-08

    We review recent work on photonic-crystal fabrication using soft-lithography techniques. We consider applications of the resulting structures in energy-related areas such as lighting and solar-energy harvesting. In general, our aim is to introduce the reader to the concepts of photonic crystals, describe their history, development, and fabrication techniques and discuss a selection of energy-related applications.

  18. Ultrahigh energy photons, electrons, and neutrinos, the microwave background, and the universal cosmic-ray hypothesis

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1972-01-01

    The production of ultrahigh energy photons, electrons and neutrinos as the decay products of pions produced in photomeson interactions between cosmic ray nucleons and the blackbody microwave background is discussed in terms of the resultant energy spectra of these particles. Simple asymptotic formulas are given for calculating the ultrahigh energy photon spectrum predicted for the universal cosmic ray hypothesis and the resulting spectra are compared with those obtained previously by numerical means using a different propagation equation for the photons. Approximate analytic solutions for the photon spectra are given in terms of simple power-law energy functions and slowly varying logarithmic functions.

  19. Cathodoluminescence Spectrum Imaging Software

    2011-04-07

    The software developed for spectrum imaging is applied to the analysis of the spectrum series generated by our cathodoluminescence instrumentation. This software provides advanced processing capabilities s such: reconstruction of photon intensity (resolved in energy) and photon energy maps, extraction of the spectrum from selected areas, quantitative imaging mode, pixel-to-pixel correlation spectrum line scans, ASCII, output, filling routines, drift correction, etc.

  20. Low-energy photons in high-energy photon fields--Monte Carlo generated spectra and a new descriptive parameter.

    PubMed

    Chofor, Ndimofor; Harder, Dietrich; Willborn, Kay; Rühmann, Antje; Poppe, Björn

    2011-09-01

    The varying low-energy contribution to the photon spectra at points within and around radiotherapy photon fields is associated with variations in the responses of non-water equivalent dosimeters and in the water-to-material dose conversion factors for tissues such as the red bone marrow. In addition, the presence of low-energy photons in the photon spectrum enhances the RBE in general and in particular for the induction of second malignancies. The present study discusses the general rules valid for the low-energy spectral component of radiotherapeutic photon beams at points within and in the periphery of the treatment field, taking as an example the Siemens Primus linear accelerator at 6 MV and 15 MV. The photon spectra at these points and their typical variations due to the target system, attenuation, single and multiple Compton scattering, are described by the Monte Carlo method, using the code BEAMnrc/EGSnrc. A survey of the role of low energy photons in the spectra within and around radiotherapy fields is presented. In addition to the spectra, some data compression has proven useful to support the overview of the behaviour of the low-energy component. A characteristic indicator of the presence of low-energy photons is the dose fraction attributable to photons with energies not exceeding 200 keV, termed P(D)(200 keV). Its values are calculated for different depths and lateral positions within a water phantom. For a pencil beam of 6 or 15 MV primary photons in water, the radial distribution of P(D)(200 keV) is bellshaped, with a wide-ranging exponential tail of half value 6 to 7 cm. The P(D)(200 keV) value obtained on the central axis of a photon field shows an approximately proportional increase with field size. Out-of-field P(D)(200 keV) values are up to an order of magnitude higher than on the central axis for the same irradiation depth. The 2D pattern of P(D)(200 keV) for a radiotherapy field visualizes the regions, e.g. at the field margin, where changes of

  1. Photon induced L3 vacancy alignment at tuned photon energies

    NASA Astrophysics Data System (ADS)

    Bansal, Himani; Kaur, Gurpreet; Tiwari, Manoj K.; Mittal, Raj

    2016-04-01

    Photon induced L3 X-ray measurements for Lα/Lℓ cross-section ratios in elements, 66 ⩽ Z ⩽ 83, at tuned photon energies on synchrotron Beamline-16 at Indus-2, India have been used to study the effect of Coster-Kronig (CK) transitions and photon energies on alignment of L3 vacancies. Certainty and reliability of the measurements were checked from comparison of measured Lα and Lℓ fluorescence cross-sections at E1 excitation with available theoretical/empirical/experimental values that required additional measurements for source, geometry and efficiency factor S0GɛLα/ℓ in the used set-up. Fall/rise trend of the ratios with energy for different Z's was found to resemble the off/on-set pattern of CK transitions as pointed out by Bambynek et al. and Campbell. Evaluated alignment parameter A2 values are very much within the limits, 0.05 energy for Dy, W, Pt, Hg and Bi resembles our previously reported theoretical patterns that lends mutual support for both current measurements and earlier theoretical results.

  2. High-Energy QCD Asymptotics of Photon--Photon Collisions

    SciTech Connect

    Brodsky, Stanley J.

    2002-07-26

    The high-energy behavior of the total cross section for highly virtual photons, as predicted by the BFKL equation at next-to-leading order (NLO) in QCD, is discussed. The NLO BFKL predictions, improved by the BLM optimal scale setting, are in good agreement with recent OPAL and L3 data at CERN LEP2. NLO BFKL predictions for future linear colliders are presented.

  3. Compressive spectrum sensing of radar pulses based on photonic techniques.

    PubMed

    Guo, Qiang; Liang, Yunhua; Chen, Minghua; Chen, Hongwei; Xie, Shizhong

    2015-02-23

    We present a photonic-assisted compressive sampling (CS) system which can acquire about 10(6) radar pulses per second spanning from 500 MHz to 5 GHz with a 520-MHz analog-to-digital converter (ADC). A rectangular pulse, a linear frequency modulated (LFM) pulse and a pulse stream is respectively reconstructed faithfully through this system with a sliding window-based recovery algorithm, demonstrating the feasibility of the proposed photonic-assisted CS system in spectral estimation for radar pulses.

  4. NREL Spectrum of Clean Energy Innovation (Brochure)

    SciTech Connect

    Not Available

    2011-09-01

    This brochure describes the NREL Spectrum of Clean Energy Innovation, which includes analysis and decision support, fundamental science, market relevant research, systems integration, testing and validation, commercialization and deployment. Through deep technical expertise and an unmatched breadth of capabilities, the National Renewable Energy Laboratory (NREL) leads an integrated approach across the spectrum of renewable energy innovation. From scientific discovery to accelerating market deployment, NREL works in partnership with private industry to drive the transformation of our nation's energy systems. NREL integrates the entire spectrum of innovation, including fundamental science, market relevant research, systems integration, testing and validation, commercialization, and deployment. Our world-class analysis and decision support informs every point on the spectrum. The innovation process at NREL is inter-dependent and iterative. Many scientific breakthroughs begin in our own laboratories, but new ideas and technologies may come to NREL at any point along the innovation spectrum to be validated and refined for commercial use.

  5. Meson production in two-photon interactions at LHC energies

    SciTech Connect

    Da Silva, D. T.; Goncalves, V. P.; Sauter, W. K.

    2013-03-25

    The LHC opens a new kinematical regime at high energy, where several questions related to the description of the high-energy regime of the Quantum Chromodynamics (QCD) remain without satisfactory answers. Some open questions are the search for non-q-bar q resonances, the determination of the spectrum of q-bar q states and the identification of states with anomalous {gamma}{gamma} couplings. A possible way to study these problems is the study of meson production in two-photon interactions. In this contribution we calculate the meson production in two-photon interactions at LHC energies considering proton - proton collisions and estimate the total cross section for the production of the mesons {pi}, a, f, {eta} and {chi}.

  6. Electrical conductivity of the quark-gluon plasma and soft photon spectrum in heavy-ion collisions

    DOE PAGESBeta

    Yin, Yi

    2014-10-06

    We extract the electrical conductivity σ0 of the quark gluon plasma (QGP) and study the effects of magnetic field and chiral anomaly on soft photon azimuthal anisotropy, v₂, based on the thermal photon spectrum at 0.4GeV < p⊥< 0.6GeV at the RHIC energy. As a basis for my analysis, we derive the behavior of retarded photon self-energy of a strongly interacting neutral plasma in hydrodynamic regime in the presence of magnetic field and chiral anomaly. By evolving the resulting soft thermal photon production rate over the realistic hydrodynamic background and comparing the results with the data from the PHENIX Collaboration,more » I found that the electrical conductivity at QGP temperature is in the range: 0.4 < σ₀/(e²T) < 1.1, which is comparable with recent studies on lattice. I also compare the contribution from the magnetic field and chiral anomaly to soft thermal photon v₂ with the data. I argue that at the CERN Large Hadron Collider, the chiral magnetic wave would give negative contribution to photon v₂.« less

  7. Electrical conductivity of the quark-gluon plasma and soft photon spectrum in heavy-ion collisions

    SciTech Connect

    Yin, Yi

    2014-10-06

    We extract the electrical conductivity σ0 of the quark gluon plasma (QGP) and study the effects of magnetic field and chiral anomaly on soft photon azimuthal anisotropy, v₂, based on the thermal photon spectrum at 0.4GeV < p⊥< 0.6GeV at the RHIC energy. As a basis for my analysis, we derive the behavior of retarded photon self-energy of a strongly interacting neutral plasma in hydrodynamic regime in the presence of magnetic field and chiral anomaly. By evolving the resulting soft thermal photon production rate over the realistic hydrodynamic background and comparing the results with the data from the PHENIX Collaboration, I found that the electrical conductivity at QGP temperature is in the range: 0.4 < σ₀/(e²T) < 1.1, which is comparable with recent studies on lattice. I also compare the contribution from the magnetic field and chiral anomaly to soft thermal photon v₂ with the data. I argue that at the CERN Large Hadron Collider, the chiral magnetic wave would give negative contribution to photon v₂.

  8. Modeling of High-Energy Photon Bursts From Lightning Leader

    NASA Astrophysics Data System (ADS)

    Celestin, S. J.; Xu, W.; Pasko, V. P.

    2015-12-01

    Terrestrial gamma-ray flashes (TGFs) are bursts of high-energy photons originating from the Earth's atmosphere in association with thunderstorm activity [e.g., Briggs et al., JGR, 118, 3805, 2013]. Additionally, X-ray bursts observed from the ground have been discovered to be produced by negative cloud-to-ground (-CG) lightning leaders in association with stepping processes [Dwyer et al., GRL, 32, L01803, 2005]. Using numerical modeling, it has been shown that the production of thermal runaway electrons by stepping lightning leaders and their further acceleration could explain the TGF spectrum for intracloud (IC) lightning potentials above ~100 MV [Xu et al., GRL, 39, L08801, 2012] and X-ray burst spectrum for -CG lightning potentials of ~5 MV [Xu et al., GRL, 41, 7406, 2014]. In this work, we address the physical processes leading to X-ray bursts from -CG discharges and TGFs produced by IC discharges in a unified fashion. We show how the leader-produced photon spectrum becomes harder with increasing lightning leader potential and how it progressively converges to typical photon spectrum associated with relativistic runaway electron avalanches (RREAs) in large-scale ambient electric fields for potentials greater than ~150 MV. We also demonstrate that the photon fluence in a burst is a very sharp function of the potential. This implies that only lightning leaders forming the strongest potentials can lead to the production of observable TGFs from space. We specifically study the effects of source altitudes on the results and the production of the required high potentials in lightning leaders in realistic thunderstorm charge configurations.

  9. Ultra high energy cosmic ray spectrum

    NASA Technical Reports Server (NTRS)

    Baltrusaitis, R. M.; Cady, R.; Cassiday, G. L.; Cooper, R.; Elbert, J. W.; Gerhardy, P. R.; Ko, P. R.; Loh, E. C.; Mizumoto, Y.; Salamon, M. H.

    1985-01-01

    Ultra-high energy cosmic rays have been observed by means of atmospheric fluorescence with the Fly's Eye since 1981. The differential energy spectrum above 0.1 EeV is well fitted by a power law with slope 2.94 + or - 0.02. Some evidence of flattening of the spectrum is observed or energies greater than 10 EeV, however only one event is observed with energy greater than 50 EeV and a spectral cutoff is indicated above 70 EeV.

  10. A freon-filled, holographic bubble chamber as a high energy photon burst spectrometer

    SciTech Connect

    Dendooven, P.G.; Lerche, R.A.

    1994-04-26

    A small holographic, freon-filled bubble chamber is being built to measure the energy spectrum of high-energy photons (energy above a few 100 keV) emitted in a short burst (less than about 1 ms duration). The photon energy is calculated from the scattered electron`s energy and direction in the case of Compton scattering or from the electron and positron energies in the case of pair production. Electron and positron energies are determined from the curvature of the tracks in a magnetic field. The use of freon results in a large photon interaction probability. Holography combines good spatial resolution with large depth of field. The main concern for the holographic system is the minimization of the bubble image size, so as to maximize the number of bubbles visible in one hologram. A high energy photon burst spectrometer has several potential applications in Inertial Confinement Fusion research.

  11. A freon-filled, holographic bubble chamber as a high-energy photon burst spectrometer

    SciTech Connect

    Dendooven, P.G.; Lerche, R.A. )

    1995-01-01

    A small holographic, freon-filled bubble chamber is being built to measure the energy spectrum of high-energy photons (energy above a few 100 keV) emitted in a short burst (less than about 1-[mu]s duration). The photon energy is calculated from the scattered electron's energy and direction in the case of Compton scattering or from the electron and positron energies in the case of pair production. Electron and positron energies are determined from the curvature of the tracks in a magnetic field. The use of freon results in a large photon interaction probability. Holography combines good spatial resolution with large depth of field. The main concern for the holographic system is the minimization of the bubble image size, so as to maximize the number of bubbles visible in one hologram. A high-energy photon burst spectrometer has several potential applications in inertial confinement fusion research.

  12. Multimode Brillouin spectrum in a long tapered birefringent photonic crystal fiber.

    PubMed

    Tchahame, Joël Cabrel; Beugnot, Jean-Charles; Kudlinski, Alexandre; Sylvestre, Thibaut

    2015-09-15

    We investigate the stimulated Brillouin scattering (SBS) in a long tapered birefringent solid-core photonic crystal fiber (PCF) and compare our results with a similar but untapered PCF. It is shown that the taper generates a broadband and multipeaked Brillouin spectrum, while significantly increasing the threshold power. Furthermore, we observe that the strong fiber birefringence gives rise to a frequency shift of the Brillouin spectrum which increases along the fiber. Numerical simulations are also presented to account for the taper effect and the birefringence. Our findings open a new means to control or inhibit the SBS by tapering photonic crystal fibers. PMID:26371916

  13. Photon-photon colliders

    SciTech Connect

    Sessler, A.M.

    1995-04-01

    Since the seminal work by Ginsburg, et at., the subject of giving the Next Linear Collider photon-photon capability, as well as electron-positron capability, has drawn much attention. A 1990 article by V.I. Teinov describes the situation at that time. In March 1994, the first workshop on this subject was held. This report briefly reviews the physics that can be achieved through the photon-photon channel and then focuses on the means of achieving such a collider. Also reviewed is the spectrum of backscattered Compton photons -- the best way of obtaining photons. We emphasize the spectrum actually obtained in a collider with both polarized electrons and photons (peaked at high energy and very different from a Compton spectrum). Luminosity is estimated for the presently considered colliders, and interaction and conversion-point geometries are described. Also specified are laser requirements (such as wavelength, peak power, and average power) and the lasers that might be employed. These include conventional and free-electron lasers. Finally, we describe the R&D necessary to make either of these approaches viable and explore the use of the SLC as a test bed for a photon-photon collider of very high energy.

  14. New calorimetric all-particle energy spectrum

    NASA Technical Reports Server (NTRS)

    Linsley, J.

    1985-01-01

    Both the maximum size N sub m and the sea level muon size N sub mu have been used separately to find the all-particle energy spectrum in the air shower domain. However the conversion required, whether from N sub m to E or from N sub mu to E, has customarily been carried out by means of calculations based on an assumed cascase model. It is shown here that by combining present data on N sub m and N sub mu spectra with data on: (1); the energy spectrum of air shower muons and (2) the average width of the electron profile, one can obtain empirical values of the N sub m to E and N sub mu to E conversion factors, and an empirical calorimetric all-particle spectrum, in the energy range 2 x 10 to the 6th power E 2 x 10 to the 9th power GeV.

  15. Quantum teleportation of the angular spectrum of a single-photon field

    SciTech Connect

    Walborn, S. P.; Ether, D. S.; Matos Filho, R. L. de; Zagury, N.

    2007-09-15

    We propose a quantum teleportation scheme for the angular spectrum of a single-photon field, which allows for the transmission of a large amount of information. Our proposal also provides a method to tune the frequencies of spatially entangled fields, which is useful for interactions with stationary qubits.

  16. Energy spectrum control for modulated proton beams

    SciTech Connect

    Hsi, Wen C.; Moyers, Michael F.; Nichiporov, Dmitri; Anferov, Vladimir; Wolanski, Mark; Allgower, Chris E.; Farr, Jonathan B.; Mascia, Anthony E.; Schreuder, Andries N.

    2009-06-15

    In proton therapy delivered with range modulated beams, the energy spectrum of protons entering the delivery nozzle can affect the dose uniformity within the target region and the dose gradient around its periphery. For a cyclotron with a fixed extraction energy, a rangeshifter is used to change the energy but this produces increasing energy spreads for decreasing energies. This study investigated the magnitude of the effects of different energy spreads on dose uniformity and distal edge dose gradient and determined the limits for controlling the incident spectrum. A multilayer Faraday cup (MLFC) was calibrated against depth dose curves measured in water for nonmodulated beams with various incident spectra. Depth dose curves were measured in a water phantom and in a multilayer ionization chamber detector for modulated beams using different incident energy spreads. Some nozzle entrance energy spectra can produce unacceptable dose nonuniformities of up to {+-}21% over the modulated region. For modulated beams and small beam ranges, the width of the distal penumbra can vary by a factor of 2.5. When the energy spread was controlled within the defined limits, the dose nonuniformity was less than {+-}3%. To facilitate understanding of the results, the data were compared to the measured and Monte Carlo calculated data from a variable extraction energy synchrotron which has a narrow spectrum for all energies. Dose uniformity is only maintained within prescription limits when the energy spread is controlled. At low energies, a large spread can be beneficial for extending the energy range at which a single range modulator device can be used. An MLFC can be used as part of a feedback to provide specified energy spreads for different energies.

  17. Wigner spectrum and coherent feedback control of continuous-mode single-photon Fock states

    NASA Astrophysics Data System (ADS)

    Dong, Zhiyuan; Cui, Lei; Zhang, Guofeng; Fu, Hongchen

    2016-10-01

    Single photons are very useful resources in quantum information science. In real applications it is often required that the photons have a well-defined spectral (or equivalently temporal) modal structure. For example, a rising exponential pulse is able to fully excite a two-level atom while a Gaussian pulse cannot. This motivates the study of continuous-mode single-photon Fock states. Such states are characterized by a spectral (or temporal) pulse shape. In this paper we investigate the statistical property of continuous-mode single-photon Fock states. Instead of the commonly used normal ordering (Wick order), the tool we proposed is the Wigner spectrum. The Wigner spectrum has two advantages: (1) it allows to study continuous-mode single-photon Fock states in the time domain and frequency domain simultaneously; (2) because it can deal with the Dirac delta function directly, it has the potential to provide more information than the normal ordering where the Dirac delta function is always discarded. We also show how various control methods in particular coherent feedback control can be used to manipulate the pulse shapes of continuous-mode single-photon Fock states.

  18. Modeling silicon diode energy response factors for use in therapeutic photon beams.

    PubMed

    Eklund, Karin; Ahnesjö, Anders

    2009-10-21

    Silicon diodes have good spatial resolution, which makes them advantageous over ionization chambers for dosimetry in fields with high dose gradients. However, silicon diodes overrespond to low-energy photons, that are more abundant in scatter which increase with large fields and larger depths. We present a cavity-theory-based model for a general response function for silicon detectors at arbitrary positions within photon fields. The model uses photon and electron spectra calculated from fluence pencil kernels. The incident photons are treated according to their energy through a bipartition of the primary beam photon spectrum into low- and high-energy components. Primary electrons from the high-energy component are treated according to Spencer-Attix cavity theory. Low-energy primary photons together with all scattered photons are treated according to large cavity theory supplemented with an energy-dependent factor K(E) to compensate for energy variations in the electron equilibrium. The depth variation of the response for an unshielded silicon detector has been calculated for 5 x 5 cm(2), 10 x 10 cm(2) and 20 x 20 cm(2) fields in 6 and 15 MV beams and compared with measurements showing that our model calculates response factors with deviations less than 0.6%. An alternative method is also proposed, where we show that one can use a correlation with the scatter factor to determine the detector response of silicon diodes with an error of less than 3% in 6 MV and 15 MV photon beams.

  19. Towards energy-efficient photonic interconnects

    NASA Astrophysics Data System (ADS)

    Demir, Yigit; Hardavellas, Nikos

    2015-03-01

    Silicon photonics have emerged as a promising solution to meet the growing demand for high-bandwidth, low-latency, and energy-efficient on-chip and off-chip communication in many-core processors. However, current silicon-photonic interconnect designs for many-core processors waste a significant amount of power because (a) lasers are always on, even during periods of interconnect inactivity, and (b) microring resonators employ heaters which consume a significant amount of power just to overcome thermal variations and maintain communication on the photonic links, especially in a 3D-stacked design. The problem of high laser power consumption is particularly important as lasers typically have very low energy efficiency, and photonic interconnects often remain underutilized both in scientific computing (compute-intensive execution phases underutilize the interconnect), and in server computing (servers in Google-scale datacenters have a typical utilization of less than 30%). We address the high laser power consumption by proposing EcoLaser+, which is a laser control scheme that saves energy by predicting the interconnect activity and opportunistically turning the on-chip laser off when possible, and also by scaling the width of the communication link based on a runtime prediction of the expected message length. Our laser control scheme can save up to 62 - 92% of the laser energy, and improve the energy efficiency of a manycore processor with negligible performance penalty. We address the high trimming (heating) power consumption of the microrings by proposing insulation methods that reduce the impact of localized heating induced by highly-active components on the 3D-stacked logic die.

  20. Photon-photon colliders

    SciTech Connect

    Sessler, Andrew M.

    1996-01-01

    Since the seminal work by Ginsburg, et al., the subject of giving the Next Linear Collider photon-photon capability, as well as electron-positron capability, has drawn much attention [1]. A 1990 article by V.I. Telnov describes the situation at that time [2]. In March 1994, the first workshop on this subject was held [3]. This report briefly reviews the physics that can be achieved through the photon-photon channel and then focuses on the means of achieving such a collider. Also reviewed is the spectrum of backscattered Compton photons—the best way of obtaining photons. We emphasize the spectrum actually obtained in a collider with both polarized electrons and photons (peaked at high energy and very different from a Compton spectrum). Luminosity is estimated for the presently considered colliders, and interaction and conversion-point geometries are described. Also specified are laser requirements (such as wavelength, peak power, and average power) and the lasers that might be employed. These include conventional and free-electron lasers. Finally, we describe the R&D necessary to make either of these approaches viable and explore the use of the SLC as a test bed for a photon-photon collider of very high energy.

  1. Experimental demonstration on structure-parameter dependence of photonic crystal optical spectrum.

    PubMed

    Wang, Chunxia; Kan, Qiang; Xu, Xingsheng; Du, Wei; Chen, Hongda

    2009-02-01

    We present fabrication and experimental measurement of a series of photonic crystal waveguides and coupled structure of PC waveguide and PC micro-cavity. The complete devices consist of an injector taper down from 3 microm into a triangular-lattice air-holes single-line-defect waveguide. We fabricated these devices on a silicon-on-insulator substrate and characterized them using tunable laser source. We've obtained high-efficiency light propagation and broad flat spectrum response of photonic-crystal waveguides. A sharp attenuation at photonic crystal waveguide mode edge was observed for most structures. The edge of guided band is shifted about 31 nm with the 10 nm increase of lattice constant. Mode resonance was observed in coupled structure. Our experimental results indicate that the optical spectra of photonic crystal are very sensitive to structure parameters. PMID:19441451

  2. On the high energy proton spectrum measurements

    NASA Technical Reports Server (NTRS)

    Ellsworth, R. W.; Ito, A.; Macfall, J.; Siohan, F.; Streitmatter, R. E.; Tonwar, S. C.; Vishwanath, P. R.; Yodh, G. B.; Balasubrahmanyan, V. K.

    1977-01-01

    The steepening of the proton spectrum beyond 1000 GeV and the rise in inelastic cross sections between 20 and 600 GeV observed by the PROTON-1-2-3 satellite experiments were explained by systematic effects of energy dependent albedo (backscatter) from the calorimeter.

  3. Adaptive, full-spectrum solar energy system

    DOEpatents

    Muhs, Jeffrey D.; Earl, Dennis D.

    2003-08-05

    An adaptive full spectrum solar energy system having at least one hybrid solar concentrator, at least one hybrid luminaire, at least one hybrid photobioreactor, and a light distribution system operably connected to each hybrid solar concentrator, each hybrid luminaire, and each hybrid photobioreactor. A lighting control system operates each component.

  4. A photon counting and a squeezing measurement method by the exact absorption and dispersion spectrum of Λ-type Atoms.

    PubMed

    Naeimi, Ghasem; Alipour, Samira; Khademi, Siamak

    2016-01-01

    Recently, the master equations for the interaction of two-mode photons with a three-level Λ-type atom are exactly solved for the coherence terms. In this paper the exact absorption spectrum is applied for the presentation of a non-demolition photon counting method, for a few number of coupling photons, and its benefits are discussed. The exact scheme is also applied where the coupling photons are squeezed and the photon counting method is also developed for the measurement of the squeezing parameter of the coupling photons. PMID:27610321

  5. The energy spectrum of ultra high energy cosmic rays

    NASA Astrophysics Data System (ADS)

    Abuzayyad, Tareq Ziad

    2000-11-01

    The Energy Spectrum of Ultra High Energy Cosmic Rays is measured by the first of two High Resolution Fly's Eye detectors in the monocular mode. The data set collected in the period of May 1997 to June 1999 was used for the measurement. A new reconstruction procedure (profile constrained geometry fit) was developed to analyze the data. This procedure gives reasonably good energy resolution, but poor xmax resolution. Resolution and systematics are discussed in the thesis. The spectrum measurement results are consistent with previous measurements in normalization and general shape. The spectrum appears to continue beyond the Greisen-Zatsepin-Kuz'min cutoff.

  6. Distortion-free spectrum sliced microwave photonic signal processor: analysis, design and implementation.

    PubMed

    Li, Liwei; Yi, Xiaoke; Huang, Thomas X H; Minasian, Robert A

    2012-05-01

    A new switchable microwave photonic filter based on a novel spectrum slicing technique is presented. The processor enables programmable multi-tap generation with general transfer function characteristics and offers tunability, reconfigurabiliy, and switchability. It is based on connecting a dispersion controlled spectrum slicing filter after the modulated bipolar broadband light source, which consequently generates multiple spectrum slices with bipolarity, and compensates dispersion induced RF degradation simultaneously within a single device. A detailed theoretical model for this microwave photonic filter design is presented. Experimental results are presented which verify the model, and demonstrate a 33 bipolar-tap microwave filter with significant reduction of passband attenuations at high frequencies. The RF response improvement of the new microwave photonic filter is investigated, for both an ideal linear group delay line and for the experimental fiber delay line that has second order group delay and the results show that this new structure is effective for RF filters with various free spectral range values and spectrum slice bandwidths. Finally, a switchable bipolar filter that has a square-top bandpass filter response with more than 30 dB stopband attenuation that can be switched on/off via software control is demonstrated.

  7. Measurement of the direct photon spectrum from the UPSILON(1/ital S/)

    SciTech Connect

    Schutte, J.

    1989-04-25

    Using the Crystal Ball detector at the /ital e//sup +//ital e/minus// storage ring DORIS II we have measured the direct photon spectrum from the UPSILON(1/ital S/). Interpreting these photons to come from the decay UPSILON/r arrow/..gamma../ital gg/ we determine the ratio /ital r/=/sup GAMMA(UPSILON/r arrow/..gamma../ital gg/)//sub GAMMA(UPSILON/r arrow//ital ggg/)/=(2.7+-0.2+-0.4)%.Thisratio /ital r/ is used to deduce the strong coupling constant in the /ital MS/ scheme at/ital Q//sup 2/=(1.5 GeV)/sup 2/ to be ..cap alpha../sub /ital s//=0.25+-0.02+-0.04. While the prediction ofthe shape of the spectrum by R. D. Field fits our data well, the prediction oflowest order QCD can clearly be ruled out.

  8. Octave-spanning spectrum generation in tapered silica photonic crystal fiber by Yb:fiber ring laser above 500 MHz.

    PubMed

    Jiang, Tongxiao; Wang, Guizhong; Zhang, Wei; Li, Chen; Wang, Aimin; Zhang, Zhigang

    2013-02-15

    We report octave-spanning spectrum generated in a tapered silica photonic crystal fiber by a mode-locked Yb:fiber ring laser at a repetition rate as high as 528 MHz. The output pulses from this laser were compressed to 62 fs. By controlling the hole expansion and core diameter, a silica PCF was tapered to 20 cm with an optimal d/Λ ratio of 0.6. Pulses with the energy of 280 pJ and the peak power of 4.5 kW were injected into the tapered fiber and the pulse spectrum was expanded from 500 to 1600 nm at the level of -30 dB.

  9. An accurate method for energy spectrum reconstruction of Linac beams based on EPID measurements of scatter radiation

    NASA Astrophysics Data System (ADS)

    Juste, B.; Miró, R.; Verdú, G.; Santos, A.

    2014-06-01

    This work presents a methodology to reconstruct a Linac high energy photon spectrum beam. The method is based on EPID scatter images generated when the incident photon beam impinges onto a plastic block. The distribution of scatter radiation produced by this scattering object placed on the external EPID surface and centered at the beam field size was measured. The scatter distribution was also simulated for a series of monoenergetic identical geometry photon beams. Monte Carlo simulations were used to predict the scattered photons for monoenergetic photon beams at 92 different locations, with 0.5 cm increments and at 8.5 cm from the centre of the scattering material. Measurements were performed with the same geometry using a 6 MeV photon beam produced by the linear accelerator. A system of linear equations was generated to combine the polyenergetic EPID measurements with the monoenergetic simulation results. Regularization techniques were applied to solve the system for the incident photon spectrum. A linear matrix system, A×S=E, was developed to describe the scattering interactions and their relationship to the primary spectrum (S). A is the monoenergetic scatter matrix determined from the Monte Carlo simulations, S is the incident photon spectrum, and E represents the scatter distribution characterized by EPID measurement. Direct matrix inversion methods produce results that are not physically consistent due to errors inherent in the system, therefore Tikhonov regularization methods were applied to address the effects of these errors and to solve the system for obtaining a consistent bremsstrahlung spectrum.

  10. Scaling-law for the energy dependence of anatomic power spectrum in dedicated breast CT

    SciTech Connect

    Vedantham, Srinivasan; Shi, Linxi; Glick, Stephen J.; Karellas, Andrew

    2013-01-15

    Purpose: To determine the x-ray photon energy dependence of the anatomic power spectrum of the breast when imaged with dedicated breast computed tomography (CT). Methods: A theoretical framework for scaling the empirically determined anatomic power spectrum at one x-ray photon energy to that at any given x-ray photon energy when imaged with dedicated breast CT was developed. Theory predicted that when the anatomic power spectrum is fitted with a power curve of the form k f{sup -{beta}}, where k and {beta} are fit coefficients and f is spatial frequency, the exponent {beta} would be independent of x-ray photon energy (E), and the amplitude k scales with the square of the difference in energy-dependent linear attenuation coefficients of fibroglandular and adipose tissues. Twenty mastectomy specimens based numerical phantoms that were previously imaged with a benchtop flat-panel cone-beam CT system were converted to 3D distribution of glandular weight fraction (f{sub g}) and were used to verify the theoretical findings. The 3D power spectrum was computed in terms of f{sub g} and after converting to linear attenuation coefficients at monoenergetic x-ray photon energies of 20-80 keV in 5 keV intervals. The 1D power spectra along the axes were extracted and fitted with a power curve of the form k f{sup -{beta}}. The energy dependence of k and {beta} were analyzed. Results: For the 20 mastectomy specimen based numerical phantoms used in the study, the exponent {beta} was found to be in the range of 2.34-2.42, depending on the axis of measurement. Numerical simulations agreed with the theoretical predictions that for a power-law anatomic spectrum of the form k f{sup -{beta}}, {beta} was independent of E and k(E) =k{sub 1}[{mu}{sub g}(E) -{mu}{sub a}(E)]{sup 2}, where k{sub 1} is a constant, and {mu}{sub g}(E) and {mu}{sub a}(E) represent the energy-dependent linear attenuation coefficients of fibroglandular and adipose tissues, respectively. Conclusions: Numerical

  11. Cerenkov light spectrum in an optical fiber exposed to a photon or electron radiation therapy beam

    SciTech Connect

    Lambert, Jamil; Yin Yongbai; McKenzie, David R.; Law, Sue; Suchowerska, Natalka

    2009-06-20

    A Cerenkov signal is generated when energetic charged particles enter the core of an optical fiber. The Cerenkov intensity can be large enough to interfere with signals transmitted through the fiber. We determine the spectrum of the Cerenkov background signal generated in a poly(methyl methacrylate) optical fiber exposed to photon and electron therapeutic beams from a linear accelerator. This spectral measurement is relevant to discrimination of the signal from the background, as in scintillation dosimetry using optical fiber readouts. We find that the spectrum is approximated by the theoretical curve after correction for the wavelength dependent attenuation of the fiber. The spectrum does not depend significantly on the angle between the radiation beam and the axis of the fiber optic but is dependent on the depth in water at which the fiber is exposed to the beam.

  12. Precision timing measurements for high energy photons

    SciTech Connect

    Anderson, Dustin; Apreysan, Artur; Bornheim, Adi; Duarte, Javier; Newman, Harvey; Pena, Cristian; Ronzhin, Anatoly; Spiropulu, Maria; Trevor, Jason; Xie, Si; Zhu, Ren-Yuan

    2014-11-21

    Particle colliders operating at high luminosities present challenging environments for high energy physics event reconstruction and analysis. We discuss how timing information, with a precision on the order of 10 ps, can aid in the reconstruction of physics events under such conditions. We present calorimeter based timing measurements from test beam experiments in which we explore the ultimate timing precision achievable for high energy photons or electrons of 10 GeV and above. Using a prototype calorimeter consisting of a 1.7×1.7×1.7 cm3 lutetium–yttrium oxyortho-silicate (LYSO) crystal cube, read out by micro-channel plate photomultipliers, we demonstrate a time resolution of 33.5±2.1 ps for an incoming beam energy of 32 GeV. In a second measurement, using a 2.5×2.5×20 cm3 LYSO crystal placed perpendicularly to the electron beam, we achieve a time resolution of 59±11 ps using a beam energy of 4 GeV. We also present timing measurements made using a shashlik-style calorimeter cell made of LYSO and tungsten plates, and demonstrate that the apparatus achieves a time resolution of 54±5 ps for an incoming beam energy of 32 GeV.

  13. The fractal energy measurement and the singularity energy spectrum analysis

    NASA Astrophysics Data System (ADS)

    Xiong, Gang; Zhang, Shuning; Yang, Xiaoniu

    2012-12-01

    The singularity exponent (SE) is the characteristic parameter of fractal and multifractal signals. Based on SE, the fractal dimension reflecting the global self-similar character, the instantaneous SE reflecting the local self-similar character, the multifractal spectrum (MFS) reflecting the distribution of SE, and the time-varying MFS reflecting pointwise multifractal spectrum were proposed. However, all the studies were based on the depiction of spatial or differentiability characters of fractal signals. Taking the SE as the independent dimension, this paper investigates the fractal energy measurement (FEM) and the singularity energy spectrum (SES) theory. Firstly, we study the energy measurement and the energy spectrum of a fractal signal in the singularity domain, propose the conception of FEM and SES of multifractal signals, and investigate the Hausdorff measure and the local direction angle of the fractal energy element. Then, we prove the compatibility between FEM and traditional energy, and point out that SES can be measured in the fractal space. Finally, we study the algorithm of SES under the condition of a continuous signal and a discrete signal, and give the approximation algorithm of the latter, and the estimations of FEM and SES of the Gaussian white noise, Fractal Brownian motion and the multifractal Brownian motion show the theoretical significance and application value of FEM and SES.

  14. First starlight spectrum captured using an integrated photonic micro-spectrograph

    NASA Astrophysics Data System (ADS)

    Cvetojevic, N.; Jovanovic, N.; Betters, C.; Lawrence, J. S.; Ellis, S. C.; Robertson, G.; Bland-Hawthorn, J.

    2012-08-01

    Photonic technologies have received growing consideration for incorporation into next-generation astronomical instrumentation, owing to their miniature footprint and inherent robustness. In this paper we present results from the first on-telescope demonstration of a miniature photonic spectrograph for astronomy, by obtaining spectra spanning the entire H-band from several stellar targets. The prototype was tested on the 3.9 m Anglo-Australian telescope. In particular, we present a spectrum of the variable star π 1 Gru, with observed CO molecular absorption bands, at a resolving power R = 2500 at 1600 nm. Furthermore, we successfully demonstrate the simultaneous acquisition of multiple spectra with a single spectrograph chip by using multiple fibre inputs.

  15. Observations and analysis of high energy photon bursts from lightning

    NASA Astrophysics Data System (ADS)

    Lundberg, James Lawrence

    Lightning is both one of the most familiar natural phenomena and one of the least understood. Despite centuries of research into the nature of lightning, questions persist about its initiation, propagation, and evolution. This thesis is about an attempt to probe the unknowns of lightning remotely through observations of high-energy (10 keV to multiple MeV) photon emissions. Lightning and thunderstorms have been observed to produce a variety of these high-energy emissions. In this thesis, an upper limit is placed on lightning produced radioactive chlorine. Lightning associated high-energy photons are most likely produced through the scattering of high-energy electron populations in the atmosphere and can thus provide us indirect clues as to the nature of the electron population at various stages of lightning development. Gaining more information about this high-energy electron population may be essential to understanding the process of electrical breakdown in air in the presence of electric fields that span large regions and near the intense fields created by lightning leader channels. Data from an observation campaign at Langmuir Lab in New Mexico will be presented. Short (10s of microseconds), intense bursts of x-rays were observed during lightning activity. A novel analysis method used to explore these unique signals will be presented as well as the results of an attempt to link this activity back to particular lightning structures using data from the Langmuir Lab lightning mapping array. Comparison of observed x-ray spectrum to model spectra suggests the initial electron population was consistent with an exponential distribution energy spectrum with 7.3 MeV e-folding and a total initial electron population of 6.7 x 1015 electrons. This result is consistent with the occurrence of a Relativistic Runaway Electron Avalanche for this lightning strike. Previous observations have suggested that RREA is not acting, therefore this result has important implications if

  16. ADAPTIVE FULL-SPECTRUM SOLOR ENERGY SYSTEMS

    SciTech Connect

    Byard D. Wood

    2004-04-01

    This RD&D project is a three year team effort to develop a hybrid solar lighting (HSL) system that transports solar light from a paraboloidal dish concentrator to a luminaire via a large core polymer fiber optic. The luminaire can be a device to distribute sunlight into a space for the production of algae or it can be a device that is a combination of solar lighting and electric lighting. A benchmark prototype system has been developed to evaluate the HSL system. Sunlight is collected using a one-meter paraboloidal concentrator dish with two-axis tracking. A secondary mirror consisting of eight planar-segmented mirrors directs the visible part of the spectrum to eight fibers (receiver) and subsequently to eight luminaires. This results in about 8,200 lumens incident at each fiber tip. Each fiber can illuminate about 16.7 m{sup 2} (180 ft{sup 2}) of office space. The IR spectrum is directed to a thermophotovoltaic (TPV) array to produce electricity. During this reporting period, the project team made advancements in the design of the second generation (Alpha) system. For the Alpha system, the eight individual 12 mm fibers have been replaced with a centralized bundle of 3 mm fibers. The TRNSYS Full-Spectrum Solar Energy System model has been updated and new components have been added. The TPV array and nonimaging device have been tested and progress has been made in the fiber transmission models. A test plan was developed for both the high-lumen tests and the study to determine the non-energy benefits of daylighting. The photobioreactor team also made major advancements in the testing of model scale and bench top lab-scale systems.

  17. Two-photon excitation energy transfer microscopy

    NASA Astrophysics Data System (ADS)

    Periasamy, Ammasi

    2000-04-01

    Fluorescence resonance energy transfer (FRET) imaging is a unique tool used to visualize the spaciotemporal dynamics of protein-protein interactions in living cells. We used FRET to study the dimerization of the pituitary-specific transcription factor of Pit-1 fused with blue flourescent protein and green fluorescent protein. Transcriptional activity of the GFP- and BFP-Pit-1 fusion proteins was demonstrated by their ability to activate the prolactin gene promoter. The energy transfer in the conventional fluorescence microscopy was less efficient due to photobleaching of the BFP-Pit-1 donor molecules. In our studies we developed two-photon excitation energy transfer microscopy, where the photobleaching of blue flourescent protein was considerably reduced. This 2p-FRET imaging system was used to acquire the donor and acceptor images for a living HeLa cell nucleus. We selected 732 nm from the tunable Verdi pumped ti:sapphire laser, in a way that only excites the BFP-Pit-1 and not the GFP-Pit-1 proteins. The efficiency of the 2p-FRET signal increased to 30 percent compared to the conventional FRET imaging, which clearly demonstrates that there is considerable reduction in photobleaching of donor molecules in the 2p-FRET microscopy.

  18. Revealing spectral features in two-photon absorption spectrum of Hoechst 33342: a combined experimental and quantum-chemical study.

    PubMed

    Olesiak-Banska, Joanna; Matczyszyn, Katarzyna; Zaleśny, Robert; Murugan, N Arul; Kongsted, Jacob; Ågren, Hans; Bartkowiak, Wojciech; Samoc, Marek

    2013-10-10

    We present the results of wide spectral range Z-scan measurements of the two-photon absorption (2PA) spectrum of the Hoechst 33342 dye. The strongest 2PA of the dye in aqueous solution is found at 575 nm, and the associated two-photon absorption cross section is 245 GM. A weak but clearly visible 2PA band at ∼850 nm is also observed, a feature that could not be anticipated from the one-photon absorption spectrum. On the basis of the results of hybrid quantum mechanics/molecular mechanics calculations, we put forward a notion that the long-wavelength feature observed in the two-photon absorption spectrum of Hoechst 33342 is due to the formation of dye aggregates. PMID:24016295

  19. Analysis of the 237Np-233Pa photon spectrum using the full response function method.

    PubMed

    Shchukin, G; Iakovlev, K; Morel, J

    2004-01-01

    A study has been made of X- and gamma-ray emission from 237Np in equilibrium with 233Pa using the full response function method. This analysis process is characterised by photon spectrometry in which the entire spectrum is modelled in a pseudo-empirical way by means of elementary functions describing the total absorption and escape peaks, the Compton diffusion internal and external to the detector and the peaks resulting from detection of internal conversion electrons. This method has been applied to determine the L X-, K X- and gamma-rays emission probabilities in 237Np and 233Pa decay studies.

  20. Analysis of the 237Np-233Pa photon spectrum using the full response function method.

    PubMed

    Shchukin, G; Iakovlev, K; Morel, J

    2004-01-01

    A study has been made of X- and gamma-ray emission from 237Np in equilibrium with 233Pa using the full response function method. This analysis process is characterised by photon spectrometry in which the entire spectrum is modelled in a pseudo-empirical way by means of elementary functions describing the total absorption and escape peaks, the Compton diffusion internal and external to the detector and the peaks resulting from detection of internal conversion electrons. This method has been applied to determine the L X-, K X- and gamma-rays emission probabilities in 237Np and 233Pa decay studies. PMID:14987650

  1. Particle and Photon Detection: Counting and Energy Measurement.

    PubMed

    Janesick, James; Tower, John

    2016-05-12

    Fundamental limits for photon counting and photon energy measurement are reviewed for CCD and CMOS imagers. The challenges to extend photon counting into the visible/nIR wavelengths and achieve energy measurement in the UV with specific read noise requirements are discussed. Pixel flicker and random telegraph noise sources are highlighted along with various methods used in reducing their contribution on the sensor's read noise floor. Practical requirements for quantum efficiency, charge collection efficiency, and charge transfer efficiency that interfere with photon counting performance are discussed. Lastly we will review current efforts in reducing flicker noise head-on, in hopes to drive read noise substantially below 1 carrier rms.

  2. Particle and Photon Detection: Counting and Energy Measurement.

    PubMed

    Janesick, James; Tower, John

    2016-01-01

    Fundamental limits for photon counting and photon energy measurement are reviewed for CCD and CMOS imagers. The challenges to extend photon counting into the visible/nIR wavelengths and achieve energy measurement in the UV with specific read noise requirements are discussed. Pixel flicker and random telegraph noise sources are highlighted along with various methods used in reducing their contribution on the sensor's read noise floor. Practical requirements for quantum efficiency, charge collection efficiency, and charge transfer efficiency that interfere with photon counting performance are discussed. Lastly we will review current efforts in reducing flicker noise head-on, in hopes to drive read noise substantially below 1 carrier rms. PMID:27187398

  3. Energy response improvement for photon dosimetry using pulse analysis

    NASA Astrophysics Data System (ADS)

    Zaki, Dizaji H.

    2016-02-01

    During the last few years, active personal dosimeters have been developed and have replaced passive personal dosimeters in some external monitoring systems, frequently using silicon diode detectors. Incident photons interact with the constituents of the diode detector and produce electrons. These photon-induced electrons deposit energy in the detector's sensitive region and contribute to the response of diode detectors. To achieve an appropriate photon dosimetry response, the detectors are usually covered by a metallic layer with an optimum thickness. The metallic cover acts as an energy compensating shield. In this paper, a software process is performed for energy compensation. Selective data sampling based on pulse height is used to determine the photon dose equivalent. This method is applied to improve the energy response in photon dosimetry. The detector design is optimized for the response function and determination of the photon dose equivalent. Photon personal dose equivalent is determined in the energy range of 0.3-6 MeV. The error values of the calculated data for this wide energy range and measured data for 133Ba, 137Cs, 60Co and 241Am-Be sources respectively are up to 20% and 15%. Fairly good agreement is seen between simulation and dose values obtained from our process and specifications from several photon sources.

  4. Thermophotovoltaic energy conversion using photonic bandgap selective emitters

    DOEpatents

    Gee, James M.; Lin, Shawn-Yu; Fleming, James G.; Moreno, James B.

    2003-06-24

    A method for thermophotovoltaic generation of electricity comprises heating a metallic photonic crystal to provide selective emission of radiation that is matched to the peak spectral response of a photovoltaic cell that converts the radiation to electricity. The use of a refractory metal, such as tungsten, for the photonic crystal enables high temperature operation for high radiant flux and high dielectric contrast for a full 3D photonic bandgap, preferable for efficient thermophotovoltaic energy conversion.

  5. No Photon Left Behind: Advanced Optics at ARPA-E for Buildings and Solar Energy

    NASA Astrophysics Data System (ADS)

    Branz, Howard M.

    2015-04-01

    Key technology challenges in building efficiency and solar energy utilization require transformational optics, plasmonics and photonics technologies. We describe advanced optical technologies funded by the Advanced Research Projects Agency - Energy. Buildings technologies include a passive daytime photonic cooler, infra-red computer vision mapping for energy audit, and dual-band electrochromic windows based on plasmonic absorption. Solar technologies include novel hybrid energy converters that combine high-efficiency photovoltaics with concentrating solar thermal collection and storage. Because the marginal cost of thermal energy storage is low, these systems enable generation of inexpensive and dispatchable solar energy that can be deployed when the sun doesn't shine. The solar technologies under development include nanoparticle plasmonic spectrum splitting, Rugate filter interference structures and photovoltaic cells that can operate efficiently at over 400° C.

  6. Silicon photonics: Energy-efficient communication

    NASA Astrophysics Data System (ADS)

    Asghari, Mehdi; Krishnamoorthy, Ashok V.

    2011-05-01

    Scaling IT infrastructure from microscale processors to macroscale data centres and telecommunications networks requires high-bandwidth technologies that are cheap, low-power and small. Silicon photonics that utilizes scalable CMOS technology may offer a highly integrated photonics transmission platform for such applications.

  7. Branches of the essential spectrum of the lattice spin-boson model with at most two photons

    NASA Astrophysics Data System (ADS)

    Rasulov, T. Kh.

    2016-02-01

    We consider a lattice analogue of the A m model of light radiation with a fixed atom and at most m photons ( m = 1, 2). We describe the essential spectrum of the operator A 2 in terms of the spectrum of the operator A 1, i.e., we find the "two-particle" and "three-particle" branches of the essential spectrum of A 2. We prove that the essential spectrum is a union of at most six intervals, and we study their positions. We derive an estimate for the lower bound of the "two-particle" and "three-particle" branches.

  8. Aperiodic TiO2 nanotube photonic crystal: full-visible-spectrum solar light harvesting in photovoltaic devices.

    PubMed

    Guo, Min; Xie, Keyu; Wang, Yu; Zhou, Limin; Huang, Haitao

    2014-09-23

    Bandgap engineering of a photonic crystal is highly desirable for photon management in photonic sensors and devices. Aperiodic photonic crystals (APCs) can provide unprecedented opportunities for much more versatile photon management, due to increased degrees of freedom in the design and the unique properties brought about by the aperiodic structures as compared to their periodic counterparts. However, many efforts still remain on conceptual approaches, practical achievements in APCs are rarely reported due to the difficulties in fabrication. Here, we report a simple but highly controllable current-pulse anodization process to design and fabricate TiO2 nanotube APCs. By coupling an APC into the photoanode of a dye-sensitized solar cell, we demonstrate the concept of using APC to achieve nearly full-visible-spectrum light harvesting, as evidenced by both experimental and simulated results. It is anticipated that this work will lead to more fruitful practical applications of APCs in high-efficiency photovoltaics, sensors and optoelectronic devices.

  9. Photon Strength Function at Low Energies in 95Mo

    NASA Astrophysics Data System (ADS)

    Wiedeking, M.; Bernstein, L. A.; Allmond, J. M.; Basunia, M. S.; Bleuel, D. L.; Burke, J. T.; Fallon, P.; Firestone, R. B.; Goldblum, B. L.; Hatarik, R.; Krtička, M.; Lake, P. T.; Larsen, A. C.; Lee, I.-Y.; Lesher, S. R.; Paschalis, S.; Petri, M.; Phair, L.; Scielzo, N. D.

    2014-05-01

    A new and model-independent experimental method has been developed to determine the energy dependence of the photon strength function. It is designed to study statistical feeding from the quasi continuum to individual low-lying discrete levels. This new technique is presented and results for 95Mo are compared to data from the University of Oslo. In particular, questions regarding the existence of the low-energy enhancement in the photon strength function are addressed.

  10. Measurement of high-energy direct photons in psi decays

    SciTech Connect

    Abrams, G.S.; Alam, M.S.; Blocker, C.A.; Boyarski, A.M.; Briedenbach, M.; Burke, D.L.; Carithers, W.C.; Chinowsky, W.; Coles, W.W.; Cooper, S.; Dieterle, W.E.; Dillon, J.B.; Dorenbosch, J.; Dorfan, J.M.; Eaton, M.W.; Feldman, G.J.; Franklin, M.E.B.; Gidal, G.; Goldhaber, G.; Hanson, G.; Hayes, K.G.; Himel, T.; Hitlin, D.G.; Hollebeek, R.J.; Innes, W.R.; Jaros, J.A.; Jenni, P.; Johnson, A.D.; Kadyk, J.A.; Lankford, A.J.; Larsen, R.R.; Lueth, V.; Millikan, R.E.; Nelson, M.E.; Pang, C.Y.; Patrick, J.F.; Perl, M.L.; Richter, B.; Roussarie, A.; Scharre, D.L.; Schindler, R.H.; Schwitters, R.F.; Siegrist, J.L.; Strait, J.; Taureg, H.; Tonutti, M.; Trilling, G.H.; Vella, E.N.; Vidal, R.A.; Videau, I.; Weiss, J.M.; Zaccone, H.

    1980-01-21

    The inclusive ..gamma.. and ..pi../sup 0/ momentum distributions at the psi have been measured. Using these data and estimates of eta production, it is found that (4.1 +- 0.8) % of psi decays contain a direct photon with energy greater than 60% of the beam energy. The expected momentum distribution for direct photons calculated to lowest order in quantum chromodynamics is qualitatively different from that observed in the data.

  11. Angular spectrum detection instrument for label-free photonic crystal sensors.

    PubMed

    Liu, Longju; Xu, Zhen; Dong, Liang; Lu, Meng

    2014-05-01

    An angular spectrum analysis system was demonstrated to monitor the optical resonant mode of a photonic crystal (PC) sensor comprised of a one-dimensional grating structure. Exposed to solutions with different refractive indices or adsorbed with biomaterials, the PC sensor exhibited changes of the optical resonant modes. The developed detection system utilized a focused laser beam to detect shifts of the resonant angle, and thereby allowed a kinetic analysis of chemical absorption. Such a detection apparatus offers an adjustable angular resolution and a tunable detection range for a wide variety of refractometric sensing applications. A limit of detection of 6.57×10(-5) refractive index unit has been observed. The instrument also offers an imaging capability of rapidly characterizing low-contrast samples deposited on the PC surface with a spatial resolution of 10 μm. PMID:24784094

  12. Intracavity Multi-Photon-Absorption and the Quantum Noise Spectrum of Light

    NASA Astrophysics Data System (ADS)

    Herzog, Ulrike

    The intensity noise spectrum is investigated quantum-mechanically for incident coherent light passing through a resonator which is filled with a k-photon-absorber. For k 2 the noise of the outgoing light is reduced below the shot noise level the reduction being maximal for frequencies that are small in comparison to the cavity bandwidth. It turns out that the highest possible value of this low-frequency noise reduction is obtained when the resonator losses due to transmission through the outcoupling mirror are 2k - 1 times as large as the k-photon absorption losses. In this case the noise at zero frequency is reduced with respect to the shot noise level by a factor of k/(2k - 1).Translated AbstractQuantenrauschen bei Mehrphotonenabsorption im ResonatorFür kohärent eingestrahltes Licht, das einen mit einem k-Photon-Absorber gefüllten Resonator durchläuft, wird das Intensitäts-Rauschspektrum quantenmechanisch unter-sucht. Für k 2 liegt das Rauschen des austretenden Lichtes unterhalb des Schrotrauschens, wobei die Rauschreduktion für Frequenzen, die klein im Vergleich zur Resonatorbandbreite sind, am größten ist. Es stellt sich heraus, daß diese niederfrequente Rauschunterdrückung ihren höchsten Wert erreicht, wenn die Resonatorverluste, die infolge der Transmission durch den Auskoppelspiegel entstehen, 2k - 1 mal so groß sind wie die k-Photonen-Absorptionsverluste. In diesem Fall reduziert sich das Rauschen bei der Frequenz Null im Vergleich zum Schrotrauschen um den Faktor k/2k - 1.

  13. Two-photon spectrum of 87Rb using optical frequency comb

    NASA Astrophysics Data System (ADS)

    Wang, Li-Rong; Zhang, Yi-Chi; Xiang, Shao-Shan; Cao, Shu-Kai; Xiao, Lian-Tuan; Jia, Suo-Tang

    2015-06-01

    The high precision two-photon excitation measurements for 5S1/2 (Fg = 2) to 5D5/2 (Fe = 4 to 1) of 87Rb are performed by using an optical frequency comb. The two counter-propagating femtosecond pulses (5S1/2 → 5P3/2 at 780 nm, and 5P3/2 → 5D5/2 at 776 nm) act on 87Rb vapor, and the Doppler broadened background signal is effectively eliminated. The temperature and power dependences of the two-photon spectrum are studied in this paper. Project supported by the National Basic Research Program of China (Grant No. 2012CB921603), the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT13076), the National Natural Science Foundation of China (Grant Nos. 61378049 and 10934004), the International Science and Technology Cooperation Program of China (Grant No. 2011DFA12490), and the Natural Science Foundation of Shanxi Province, China (Grant No. 2011011004).

  14. The Dosepix detector—an energy-resolving photon-counting pixel detector for spectrometric measurements

    NASA Astrophysics Data System (ADS)

    Zang, A.; Anton, G.; Ballabriga, R.; Bisello, F.; Campbell, M.; Celi, J. C.; Fauler, A.; Fiederle, M.; Jensch, M.; Kochanski, N.; Llopart, X.; Michel, N.; Mollenhauer, U.; Ritter, I.; Tennert, F.; Wölfel, S.; Wong, W.; Michel, T.

    2015-04-01

    The Dosepix detector is a hybrid photon-counting pixel detector based on ideas of the Medipix and Timepix detector family. 1 mm thick cadmium telluride and 300 μm thick silicon were used as sensor material. The pixel matrix of the Dosepix consists of 16 x 16 square pixels with 12 rows of (200 μm)2 and 4 rows of (55 μm)2 sensitive area for the silicon sensor layer and 16 rows of pixels with 220 μm pixel pitch for CdTe. Besides digital energy integration and photon-counting mode, a novel concept of energy binning is included in the pixel electronics, allowing energy-resolved measurements in 16 energy bins within one acquisition. The possibilities of this detector concept range from applications in personal dosimetry and energy-resolved imaging to quality assurance of medical X-ray sources by analysis of the emitted photon spectrum. In this contribution the Dosepix detector, its response to X-rays as well as spectrum measurements with Si and CdTe sensor layer are presented. Furthermore, a first evaluation was carried out to use the Dosepix detector as a kVp-meter, that means to determine the applied acceleration voltage from measured X-ray tubes spectra.

  15. Numerical study on laser and infrared compatible stealth by forming "hole-digging spectrum" of doped photonic crystal

    NASA Astrophysics Data System (ADS)

    Zhao, Xuanke; Zhao, Qingwu; Zhang, Qinghua; Wang, Lianfen

    2010-10-01

    Compatible stealth of laser and infrared is an urgent demand of modern battlefield, but the demand is ambivalent for conventional materials. As a new type of artificial structure function material, photonic crystals can realize broadband thermal infrared stealth based on its high-reflection photon forbidden band. By forming a "hole-digging" reflection spectrum of doped photonic crystals, high transmittance at military laser wavelength of 1.06μm and 10.6μm can be achieved, so compatible stealth of laser and infrared can be achieved too. In this paper, we selected middle and far infrared-transparent materials, PbTe and Na3AlF6 as high refractive index and low refractive index material respectively, and designed a one-dimensional two-defect-mode photonic crystal based on principles of distributed Bragg reflector microcavity. And then its photon forbidden band was broaden to 1~20μm by constructing two heterojunction photonic crystals. The reflection spectrum and transmission spectrum of the photonic crystals were calculated by characteristic matrix method of thin-film optical theory. The calculation results show that the designed multi-cycle dual-heterojunction photonic crystal has a high spectral reflectance in the near, middle and far infrared band, whose spectral reflectivity is greater than 99% in 1~5μm and 8~14μm infrared bands, and spectral transmittance at 1.06μm and 10.6μm is greater than 96%. This will satisfy the laser and infrared compatible stealth in the near, middle and far infrared bands.

  16. Ultra high energy photons and neutrinos with JEM-EUSO

    NASA Astrophysics Data System (ADS)

    Adams, J. H.; Ahmad, S.; Albert, J.-N.; Allard, D.; Anchordoqui, L.; Andreev, V.; Anzalone, A.; Arai, Y.; Asano, K.; Ave Pernas, M.; Baragatti, P.; Barrillon, P.; Batsch, T.; Bayer, J.; Bechini, R.; Belenguer, T.; Bellotti, R.; Belov, K.; Berlind, A. A.; Bertaina, M.; Biermann, P. L.; Biktemerova, S.; Blaksley, C.; Blanc, N.; Błȩcki, J.; Blin-Bondil, S.; Blümer, J.; Bobik, P.; Bogomilov, M.; Bonamente, M.; Briggs, M. S.; Briz, S.; Bruno, A.; Cafagna, F.; Campana, D.; Capdevielle, J.-N.; Caruso, R.; Casolino, M.; Cassardo, C.; Castellinic, G.; Catalano, C.; Catalano, G.; Cellino, A.; Chikawa, M.; Christl, M. J.; Cline, D.; Connaughton, V.; Conti, L.; Cordero, G.; Crawford, H. J.; Cremonini, R.; Csorna, S.; Dagoret-Campagne, S.; de Castro, A. J.; De Donato, C.; de la Taille, C.; De Santis, C.; del Peral, L.; Dell'Oro, A.; De Simone, N.; Di Martino, M.; Distratis, G.; Dulucq, F.; Dupieux, M.; Ebersoldt, A.; Ebisuzaki, T.; Engel, R.; Falk, S.; Fang, K.; Fenu, F.; Fernández-Gómez, I.; Ferrarese, S.; Finco, D.; Flamini, M.; Fornaro, C.; Franceschi, A.; Fujimoto, J.; Fukushima, M.; Galeotti, P.; Garipov, G.; Geary, J.; Gelmini, G.; Giraudo, G.; Gonchar, M.; González Alvarado, C.; Gorodetzky, P.; Guarino, F.; Guzmán, A.; Hachisu, Y.; Harlov, B.; Haungs, A.; Hernández Carretero, J.; Higashide, K.; Ikeda, D.; Ikeda, H.; Inoue, N.; Inoue, S.; Insolia, A.; Isgrò, F.; Itow, Y.; Joven, E.; Judd, E. G.; Jung, A.; Kajino, F.; Kajino, T.; Kaneko, I.; Karadzhov, Y.; Karczmarczyk, J.; Karus, M.; Katahira, K.; Kawai, K.; Kawasaki, Y.; Keilhauer, B.; Khrenov, B. A.; Kim, J.-S.; Kim, S.-W.; Kim, S.-W.; Kleifges, M.; Klimov, P. A.; Kolev, D.; Kreykenbohm, I.; Kudela, K.; Kurihara, Y.; Kusenko, A.; Kuznetsov, E.; Lacombe, M.; Lachaud, C.; Lee, J.; Licandro, J.; Lim, H.; López, F.; Maccarone, M. C.; Mannheim, K.; Maravilla, D.; Marcelli, L.; Marini, A.; Martinez, O.; Masciantonio, G.; Mase, K.; Matev, R.; Medina-Tanco, G.; Mernik, T.; Miyamoto, H.; Miyazaki, Y.; Mizumoto, Y.; Modestino, G.; Monaco, A.; Monnier-Ragaigne, D.; Morales de los Ríos, J. A.; Moretto, C.; Morozenko, V. S.; Mot, B.; Murakami, T.; Murakami, M. Nagano; Nagata, M.; Nagataki, S.; Nakamura, T.; Napolitano, T.; Naumov, D.; Nava, R.; Neronov, A.; Nomoto, K.; Nonaka, T.; Ogawa, T.; Ogio, S.; Ohmori, H.; Olinto, A. V.; Orleański, P.; Osteria, G.; Panasyuk, M. I.; Parizot, E.; Park, I. H.; Park, H. W.; Pastircak, B.; Patzak, T.; Paul, T.; Pennypacker, C.; Perez Cano, S.; Peter, T.; Picozza, P.; Pierog, T.; Piotrowski, L. W.; Piraino, S.; Plebaniak, Z.; Pollini, A.; Prat, P.; Prévôt, G.; Prieto, H.; Putis, M.; Reardon, P.; Reyes, M.; Ricci, M.; Rodríguez, I.; Rodríguez Frías, M. D.; Ronga, F.; Roth, M.; Rothkaehl, H.; Roudil, G.; Rusinov, I.; Rybczyński, M.; Sabau, M. D.; Sáez-Cano, G.; Sagawa, H.; Saito, A.; Sakaki, N.; Sakata, M.; Salazar, H.; Sánchez, S.; Santangelo, A.; Santiago Crúz, L.; Sanz Palomino, M.; Saprykin, O.; Sarazin, F.; Sato, H.; Sato, M.; Schanz, T.; Schieler, H.; Scotti, V.; Segreto, A.; Selmane, S.; Semikoz, D.; Serra, M.; Sharakin, S.; Shibata, T.; Shimizu, H. M.; Shinozaki, K.; Shirahama, T.; Siemieniec-Oziȩbło, G.; Silva López, H. H.; Sledd, J.; Słomińska, K.; Sobey, A.; Sugiyama, T.; Supanitsky, D.; Suzuki, M.; Szabelska, B.; Szabelski, J.; Tajima, F.; Tajima, N.; Tajima, T.; Takahashi, Y.; Takami, H.; Takeda, M.; Takizawa, Y.; Tenzer, C.; Tibolla, O.; Tkachev, L.; Tokuno, H.; Tomida, T.; Tone, N.; Toscano, S.; Trillaud, F.; Tsenov, R.; Tsunesada, Y.; Tsuno, K.; Tymieniecka, T.; Uchihori, Y.; Unger, M.; Vaduvescu, O.; Valdés-Galicia, J. F.; Vallania, P.; Valore, L.; Vankova, G.; Vigorito, C.; Villaseñor, L.; von Ballmoos, P.; Wada, S.; Watanabe, J.; Watanabe, S.; Watts, J.; Weber, M.; Weiler, T. J.; Wibig, T.; Wiencke, L.; Wille, M.; Wilms, J.; Włodarczyk, Z.; Yamamoto, T.; Yamamoto, Y.; Yang, J.; Yano, H.; Yashin, I. V.; Yonetoku, D.; Yoshida, K.; Yoshida, S.; Young, R.; Zotov, M. Yu.; Zuccaro Marchi, A.

    2015-11-01

    Ultra high energy photons and neutrinos are carriers of very important astrophysical information. They may be produced at the sites of cosmic ray acceleration or during the propagation of the cosmic rays in the intergalactic medium. In contrast to charged cosmic rays, photon and neutrino arrival directions point to the production site because they are not deflected by the magnetic fields of the Galaxy or the intergalactic medium. In this work we study the characteristics of the longitudinal development of showers initiated by photons and neutrinos at the highest energies. These studies are relevant for development of techniques for neutrino and photon identification by the JEM-EUSO telescope. In particular, we study the possibility of observing the multi-peak structure of very deep horizontal neutrino showers with JEM-EUSO. We also discuss the possibility to determine the flavor content of the incident neutrino flux by taking advantage of the different characteristics of the longitudinal profiles generated by different type of neutrinos. This is of grate importance for the study of the fundamental properties of neutrinos at the highest energies. Regarding photons, we discuss the detectability of the cosmogenic component by JEM-EUSO and also estimate the expected upper limits on the photon fraction which can be obtained from the future JEM-EUSO data for the case in which there are no photons in the samples.

  17. High-energy photon splitting on heavy atoms

    NASA Astrophysics Data System (ADS)

    Lee, R. N.; Milstein, A. I.; Strakhovenko, V. M.

    1998-04-01

    The helicity amplitudes of high-energy photon splitting in an external Coulomb field are obtained exactly in the parameter Zα. The consideration is based on the quasiclassical approach, valid for small angles between all photon momenta. A new representation of the quasiclassical electron Green function is exploited. General expressions obtained are analyzed in detail when the transverse momenta of both final photons are much larger than the electron mass. It is shown that, at Zα~1, Coulomb corrections essentially change the cross section as compared to the Born approximation. Screened and unscreened potentials are considered.

  18. Particle and Photon Detection: Counting and Energy Measurement

    PubMed Central

    Janesick, James; Tower, John

    2016-01-01

    Fundamental limits for photon counting and photon energy measurement are reviewed for CCD and CMOS imagers. The challenges to extend photon counting into the visible/nIR wavelengths and achieve energy measurement in the UV with specific read noise requirements are discussed. Pixel flicker and random telegraph noise sources are highlighted along with various methods used in reducing their contribution on the sensor’s read noise floor. Practical requirements for quantum efficiency, charge collection efficiency, and charge transfer efficiency that interfere with photon counting performance are discussed. Lastly we will review current efforts in reducing flicker noise head-on, in hopes to drive read noise substantially below 1 carrier rms. PMID:27187398

  19. Characterization of γ-ray detectors using the photon tagger NEPTUN for energies up to 20 MeV

    NASA Astrophysics Data System (ADS)

    Schnorrenberger, L.; Savran, D.; Glorius, J.; Lindenberg, K.; Löher, B.; Pietralla, N.; Sonnabend, K.

    2014-01-01

    A new setup for the characterization of γ-ray detectors has been installed at the NEPTUN photon tagger facility of TU Darmstadt. The tagging technique used at NEPTUN provides a quasi monoenergetic photon source up to about 20 MeV by selecting single γ-ray energies within a bremsstrahlung spectrum. The energy is freely selectable by changing the tagging condition. The detector response function (DRF) of γ-ray detectors for quasi monoenergetic incident photons can be measured. This allows to investigate DRFs of various photon detectors as a function of the incident γ-ray energy. Simulations of DRFs that are intensively used in the analysis of nuclear physics experiments can be tested and compared to experimental data. The experimental setup is presented and the measurement of the DRF of a large volume high-purity Germanium detector is described as an example.

  20. On muon energy spectrum in muon groups underground

    NASA Technical Reports Server (NTRS)

    Bakatanov, V. N.; Chudakov, A. E.; Novoseltsev, Y. F.; Novoseltseva, M. V.; Stenkin, Y. V.

    1985-01-01

    A method is described which was used to measure muon energy spectrum characteristics in muon groups underground using mu-e decays recording. The Baksan Telescope's experimental data on mu-e decays intensity in muon groups of various multiplicities are analyzed. The experimental data indicating very flat spectrum does not however represent the total spectrum in muon groups. Obviously the muon energy spectrum depends strongly on a distance from the group axis. The core attraction effect makes a significant distortion, making the spectrum flatter. After taking this into account and making corrections for this effect the integral total spectrum index in groups has a very small depencence on muon multiplicity and agrees well with expected one: beta=beta (sub expected) = 1.75.

  1. Photonic Crystal Emitters for Thermophotovoltaic Energy Conversion

    NASA Astrophysics Data System (ADS)

    Stelmakh, Veronika; Chan, Walker R.; Ghebrebrhan, Michael; Soljacic, Marin; Joannopoulos, John D.; Celanovic, Ivan

    2015-12-01

    This paper reports the design, fabrication, and characterization of 2D photonic crystal (PhC) thermal emitters for a millimeter-scale hydrocarbon TPV microgenerator as a possible replacement for batteries in portable microelectronics, robotics, etc. In our TPV system, combustion heats a PhC emitter to incandescence and the resulting radiation is converted by a low-bandgap TPV cell. The PhC tailors the photonic density of states to produce spectrally confined thermal emission that matches the bandgap of the TPV cell, enabling high heat-to-electricity conversion efficiency. The work builds on a previously developed fabrication process to produce a square array of cylindrical cavities in a metal substrate. We will present ongoing incremental improvements in the optical and thermo-mechanical properties, the fabrication process, and the system integration, as recently combined with fabrication using novel materials, such as sputtered coatings, to enable a monolithic system.

  2. Dual concentric crystal low energy photon detector

    DOEpatents

    Guilmette, R.A.

    A photon detector for biological samples includes a block of NaI(T1) having a hole containing a thin walled cylinder of CsI(T1). At least three photo multiplier tubes are evenly spaced around the parameter of the block. Biological samples are placed within the hole, and emissions which are sensed by at least two of the photo multipliers from only the NaI(T1) detector are counted.

  3. High-energy electron-positron photoproduction cross section close to the end of the spectrum

    SciTech Connect

    Di Piazza, A.; Milstein, A. I.

    2010-10-15

    We consider the cross section of electron-positron pair production by a high-energy photon in a strong Coulomb field close to the end of the electron or positron spectrum. We show that the cross section essentially differs from the result obtained in the Born approximation as well as from the result which takes into account the Coulomb corrections under the assumption that both electron and positron are ultrarelativistic. The cross section of bremsstrahlung in a strong Coulomb field by a high-energy electron is also obtained in the region where the final electron is not ultrarelativistic.

  4. Energy calibration of energy-resolved photon-counting pixel detectors using laboratory polychromatic x-ray beams

    NASA Astrophysics Data System (ADS)

    Youn, Hanbean; Han, Jong Chul; Kam, Soohwa; Yun, Seungman; Kim, Ho Kyung

    2014-10-01

    Recently, photon-counting detectors capable of resolving incident x-ray photon energies have been considered for use in spectral x-ray imaging applications. For reliable use of energy-resolved photon-counting detectors (ERPCDs), energy calibration is an essential procedure prior to their use because variations in responses from each pixel of the ERPCD for incident photons, even at the same energy, are inevitable. Energy calibration can be performed using a variety of methods. In all of these methods, the photon spectra with well-defined peak energies are recorded. Every pixel should be calibrated on its own. In this study, we suggest the use of a conventional polychromatic x-ray source (that is typically used in laboratories) for energy calibration. The energy calibration procedure mainly includes the determination of the peak energies in the spectra, flood-field irradiation, determination of peak channels, and determination of calibration curves (i.e., the slopes and intercepts of linear polynomials). We applied a calibration algorithm to a CdTe ERPCD comprised of 128×128 pixels with a pitch of 0.35 mm using highly attenuated polychromatic x-ray beams to reduce the pulse pile-up effect, and to obtain a narrow-shaped spectrum due to beam hardening. The averaged relative error in calibration curves obtained from 16,384 pixels was about 0.56% for 59.6 keV photons from an Americium radioisotope. This pixel-by-pixel energy calibration enhanced the signal- and contrast-to-noise ratios in images, respectively, by a factor of ~5 and 3 due to improvement in image homogeneity, compared to those obtained without energy calibration. One secondary finding of this study was that the x-ray photon spectra obtained using a common algorithm for computing x-ray spectra reasonably described the peaks in the measured spectra, which implies easier peak detection without the direct measurement of spectra using a separate spectrometer. The proposed method will be a useful alternative to

  5. High-energy photon interrogation for nonproliferation applications

    NASA Astrophysics Data System (ADS)

    Jones, J. L.; Blackburn, B. W.; Watson, S. M.; Norman, D. R.; Hunt, A. W.

    2007-08-01

    There is an immediate need for technologies that can successfully address homeland security challenges related to the inspection of commercial rail, air and maritime-cargo container inspections for nuclear and radiological devices. The pulsed photonuclear assessment (PPA) technology, developed through collaboration between Idaho National Laboratory (INL), Los Alamos National Laboratory (LANL) and the Idaho Accelerator Center (IAC) has demonstrated the ability to detect shielded/unshielded nuclear material primarily through the analysis of delayed neutrons and gamma-rays produced via photonuclear reactions. Because of current food irradiation limitations, however, most active photon (i.e. bremsstrahlung) interrogation studies have been performed with electron beam energies at or below 10 MeV. While this energy limit currently applies to cargo inspections, the World Health Organization has indicated that higher energy electron beam operations could be considered for future operations. Clinical applications using photon energies well in excess of 10 MeV are already well established. Notwithstanding the current limitation of 10 MeV, there is a definite advantage in using higher photon energies for cargo inspections. At higher energies, several phenomena contribute to increased sensitivity in regards to detecting shielded nuclear material. Two of the most important are: (1) increased ability for source photons to penetrate shielding; and (2) enhanced signature production via increased (γ,n) and (γ,f) cross-sections in materials such as 235U and 239Pu directly leading to faster inspection throughput. Experimental assessments have been conducted for various electron beam energies from 8 to 25 MeV. Increases of up to three orders of magnitude in delayed signatures have been measured over these energy ranges. Through the continued investigation into PPA-based inspection applications using photon energies greater than 10 MeV, higher detection sensitivities with potentially

  6. A new universal photon energy-luminosity relationship for GRBs

    SciTech Connect

    Willingale, Dick; O'Brien, Paul; Goad, Mike; Osborne, Julian; Page, Kim; Tanvir, Nial

    2008-05-22

    We define a new characteristic photon energy for the Band function, E{sub wz}, and describe a new way of estimating the peak luminosity of the prompt emission from GRBs, L{sub iso}, which is not dependent on the time binning. We show that E{sub wz} and L{sub iso} are correlated for all bursts, long and short. The new photon energy-luminosity relationship gives us a strong indication that the underlying process responsible for the prompt GRB emission is thermal.

  7. Energy Modulated Photon Radiotherapy: A Monte Carlo Feasibility Study

    PubMed Central

    Zhang, Ying; Feng, Yuanming; Ming, Xin

    2016-01-01

    A novel treatment modality termed energy modulated photon radiotherapy (EMXRT) was investigated. The first step of EMXRT was to determine beam energy for each gantry angle/anatomy configuration from a pool of photon energy beams (2 to 10 MV) with a newly developed energy selector. An inverse planning system using gradient search algorithm was then employed to optimize photon beam intensity of various beam energies based on presimulated Monte Carlo pencil beam dose distributions in patient anatomy. Finally, 3D dose distributions in six patients of different tumor sites were simulated with Monte Carlo method and compared between EMXRT plans and clinical IMRT plans. Compared to current IMRT technique, the proposed EMXRT method could offer a better paradigm for the radiotherapy of lung cancers and pediatric brain tumors in terms of normal tissue sparing and integral dose. For prostate, head and neck, spine, and thyroid lesions, the EMXRT plans were generally comparable to the IMRT plans. Our feasibility study indicated that lower energy (<6 MV) photon beams could be considered in modern radiotherapy treatment planning to achieve a more personalized care for individual patient with dosimetric gains. PMID:26977413

  8. The Cosmic Rays Energy Spectrum observed by the TALE detector

    NASA Astrophysics Data System (ADS)

    Abuzayyad, Tareq; Telescope Array Collaboration Collaboration

    2016-03-01

    We report on a cosmic ray energy spectrum measurement by the Telescope Array Low-Energy extension (TALE) fluorescence detector (FD). The TALE FD is an air fluorescence detector which is also sensitive to the Cerenkov light produced by shower particles. Low energy cosmic rays, in the PeV energy range, are detectable by TALE as ``Cerenkov Events''. Using these events, we measure the energy spectrum from a low energy of 4 PeV to an energy greater than 100 PeV. Starting at around 100 PeV, TALE also observes showers by their fluorescence light; and above this energy fluorescence becomes the dominant light production mechanism by which most showers are observed. The event processing and reconstruction procedures are identical for both low and high energy regions. This allows for treating the Cherenkov events and Fluorescence events as a single data set and thus calculating a single cosmic rays energy spectrum based on this data set, which extends from an energy of 4 PeV to above 1 EeV. In this talk, we will describe the detector, explain the technique, and present results from the measurement of the spectrum in this energy range by the Telescope Array experiment.

  9. Spectrum and energy transfer in steady Burgers turbulence

    NASA Technical Reports Server (NTRS)

    Girimaji, Sharath S.; Zhou, YE

    1995-01-01

    The spectrum, energy transfer, and spectral interactions in steady Burgers turbulence are studied using numerically generated data. The velocity field is initially random and the turbulence is maintained steady by forcing the amplitude of a band of low wavenumbers to be invariant in time, while permitting the phase to change as dictated by the equation. The spectrum, as expected, is very different from that of Navier-Stokes turbulence. It is demonstrated that the far range of the spectrum scales as predicted by Burgers. Despite the difference in their spectra, in matters of the spectral energy transfer and triadic interactions Burgers turbulence is similar to Navier-Stokes turbulence.

  10. Measurement of the excitation spectrum of a Bose condensate, and direct observation of the phonon energy

    NASA Astrophysics Data System (ADS)

    Ozeri, Roee; Steinhauer, Jeff; Katz, Nadav; Davidson, Nir

    2002-05-01

    The excitation spectrum gives the energy, hw(k), of each excitation in the Bose condensate (BEC) as a function of its wave vector k. We report the first measurement of the excitation spectrum [1]. The excitation spectrum is measured by Bragg spectroscopy [2]. The response of the condensate to the two-photon Bragg pulse is extracted from time of flight (TOF) images. The resonance frequency of the excitation for momentum hk is taken as w(k). The measured w(k) agrees with the Bogoliubov spectrum predictions. A linear phonon regime is seen for low k. The superfluid critical velocity is bounded by w(k)/k of this regime. In addition, the energy and momentum of the atoms are measured directly from the TOF image, computerized tomography is used to reconstruct the cylindrical density distribution, from a single absorption picture [3]. The excitation energies measured this way are in agreement with the value measured using Bragg spectroscopy. Our measurements also indicate that all of the excitation energy is carried by the atoms in the released-phonon cloud. [1] J. Steinhauer et. al. Phys. Rev. Lett. in press (Cond. Mat. 0111438). [2] J. Stenger, et. al. Phys. Rev. Lett. 82, 4569-4573 (1999). [3] R. Ozeri, et. al. Cond. Mat. 0112496.

  11. Derivation of photon energy spectra from transmission measurements using large fields

    NASA Astrophysics Data System (ADS)

    Nes, Elena

    Modern treatment planning systems based on Monte Carlo technique require, in order to calculate the dose, knowledge of the photon spectra produced by medical linear accelerators. The accuracy of the dose determination will increase when the spectra are better known. In the present work the 6 MV photon spectrum of a Varian 2100C linear accelerator was determined from attenuation measurements performed in large fields. The iterative algorithm written in MathematicaRTM used as input data Monte Carlo-predetermined pencil beam monoenergetic scatter kernels for various water phantom thicknesses, open beam fluences and beam fluences measured in air with phantoms of different thicknesses placed in the beam. The experimental data was measured using an ionization chamber and two types of film, GAFCHROMICRTMEBT film and KODAK EDR2 film. The iteration started with a flat spectrum used to calculate the polyenergetic kernels for each water thickness. The spectrum-dependent scatter for different thicknesses of water was calculated convolving the corresponding polyenergetic kernel with the signal obtained with the water phantom removed from the beam. For each thickness of water, transmissions on the central axis were given by the ratios of central axis primary fluences to the open beam fluence. The reconstructed energy spectrum was determined from the transmission values using the simulated annealing technique. Simulated annealing was preferred because it reaches the true global minimum better than other optimization techniques. The spectrum determined at the end of the simulated annealing loop was compared to the input spectrum of the general algorithm. If they matched within acceptable errors this was the final primary spectrum. If not, the spectrum was fed as input for a new iteration. Monte Carlo monoenergetic scatter kernels were derived for six water thicknesses. The amplitude of the monoenergetic scatter kernels increases with energy and water phantom thickness. For thin

  12. Self-energy shift of the energy levels of atomic hydrogen in photonic crystal medium

    NASA Astrophysics Data System (ADS)

    Gainutdinov, R. Kh; Khamadeev, M. A.; Steryakov, O. V.; Ziyatdinova, K. A.; Salakhov, M. Kh

    2016-05-01

    Corrections to the average kinetic energy of atomic electrons caused by the change in electron mass in the photonic crystal medium are investigated. Corresponding shift of energy levels of atoms placed in a photonic crystal is shown to be of order of the ordinary Lamb shift.

  13. The High Energy Spectrum of NGC 4151

    NASA Technical Reports Server (NTRS)

    Beckmann, V.; Gehrels, N.; Shrader, C.; Soldi, S.; Lubinski, P.; Zdziarski, A. A.; Petrucci, P.-O.; Malzac, J.

    2005-01-01

    We present first INTEGRAL observations of the type 1.5 Seyfert galaxy NGC 4151. Combining several INTEGRAL observations performed during 2003, totaling approximately 400 ksec of exposure time, allow us to study the spectrum in the 3 - 300 keV range. The measurements presented here reveal an overall spectrum from X-rays up to the soft gamma-rays that can be described by an absorbed (N(sub H) approximately equal to 5 x 10(exp 22) per square centimeter) and non-variable thermal component, plus a Fe Kalpha line, and an exponential cutoff occurs at 110 keV, consistent with earlier claims. The Galactic hydrogen column density in the line of sight is N(sub H), Gal approximately equal to 2.1 x 10 (exp 20) per square centimeter. The time resolved analysis shows little variation of the spectral parameters. The comparison with CGRO/OSSE data shows that the same spectral model can be applied over a time span of 15 years, while the flux varied by a factor of 2. Applying a Compton reflection component improves the model fit to the INTEGRAL data. Nonetheless the data available to date cannot significantly confirm or exclude the existence of reflection, nor is a high iron overabundance in the absorber, as had been previously suggested, clearly detectable.

  14. Photon spectrum behind biological shielding of the LVR-15 research reactor

    SciTech Connect

    Klupak, V.; Viererbl, L.; Lahodova, Z.; Marek, M.; Vins, M.

    2011-07-01

    The LVR-15 reactor is a light water research reactor situated at the Research Centre Rez, near Prague. It operates as a multipurpose facility with a maximum thermal power of 10 MW. The reactor core usually contains from 28 to 32 fuel assemblies with a total mass of {sup 235}U of about 5 kg. Emitted radiation from the fuel caused by fission is shielded by moderating water, a steel reactor vessel, and heavy concrete. This paper deals with measurement and analysis of the gamma spectrum near the outer surface of the concrete wall, behind biological shielding, mainly in the 3- to 10-MeV energy range. A portable HPGe detector with a portable multichannel analyzer was used to measure gamma spectra. The origin of energy lines in gamma detector spectra was identified. (authors)

  15. Light-spectrum modification of warm white-light-emitting diodes with 3D colloidal photonic crystals to approximate candlelight.

    PubMed

    Lai, Chun-Feng; Hsieh, Cheng-Liang; Wu, Chia-Jung

    2013-09-15

    This study presents the light-spectrum modification of warm white-light-emitting diodes (w-WLEDs) with 3D colloidal photonic crystals (3D CPhCs) to approximate candlelight. The study measures the angular-resolved transmission properties of the w-WLEDs with CPhCs, which exhibit photonic stop bands based on the CPhC photonic band structures. The w-WLEDs with 3D CPhCs produce a low correlated color temperature of 1963 K, a high color-rendering index of 85, and a luminous flux of 22.8 lm (four times that of a candle). This study presents the successful development of a novel low-cost technique to produce candlelight w-WLEDs for use as an indoor light source. PMID:24104827

  16. Photon and dilepton production in high energy heavy ion collisions

    DOE PAGESBeta

    Sakaguchi, Takao

    2015-05-07

    The recent results on direct photons and dileptons in high energy heavy ion collisions, obtained particularly at RHIC and LHC are reviewed. The results are new not only in terms of the probes, but also in terms of the precision. We shall discuss the physics learned from the results.

  17. Microheater-integrated silicon coupled photonic crystal microcavities for low-power thermo-optic switching over a wide spectrum

    NASA Astrophysics Data System (ADS)

    Zhang, Xingyu; Chakravarty, Swapnajit; Chung, Chi-Jui; Pan, Zeyu; Yan, Hai; Chen, Ray T.

    2016-03-01

    We design, fabricate and experimentally demonstrate a compact thermo-optic gate switch comprising a 3.78μm-long coupled L0-type photonic crystal microcavities on a silicon-on-insulator substrate. A nanohole is inserted in the center of each individual L0 photonic crystal microcavity. Coupling between identical microcavities gives rise to bonding and antibonding states of the coupled photonic molecules. The coupled photonic crystal microcavities are numerically simulated and experimentally verified with a 6nm-wide flat-bottom resonance in its transmission spectrum, which enables wider operational spectrum range than microring resonators. An integrated micro-heater is in direct contact with the silicon core to efficiently drive the device. The thermo-optic switch is measured with an optical extinction ratio of 20dB, an on-off switching power of 18.2mW, a therm-optic tuning efficiency of 0.63nm/mW, a rise time of 14.8μsec and a fall time of 18.5μsec. The measured on-chip loss on the transmission band is as low as 1dB.

  18. Ultra-compact and wide-spectrum-range thermo-optic switch based on silicon coupled photonic crystal microcavities

    NASA Astrophysics Data System (ADS)

    Zhang, Xingyu; Chakravarty, Swapnajit; Chung, Chi-Jui; Pan, Zeyu; Yan, Hai; Chen, Ray T.

    2015-11-01

    We design, fabricate, and experimentally demonstrate a compact thermo-optic gate switch comprising a 3.78 μm-long coupled L0-type photonic crystal microcavities on a silicon-on-insulator substrate. A nanohole is inserted in the center of each individual L0 photonic crystal microcavity. Coupling between identical microcavities gives rise to bonding and anti-bonding states of the coupled photonic molecules. The coupled photonic crystal microcavities are numerically simulated and experimentally verified with a 6 nm-wide flat-bottom resonance in its transmission spectrum, which enables wider operational spectrum range than microring resonators. An integrated micro-heater is in direct contact with the silicon core to efficiently drive the device. The thermo-optic switch is measured with an optical extinction ratio of 20 dB, an on-off switching power of 18.2 mW, a thermo-optic tuning efficiency of 0.63 nm/mW, a rise time of 14.8 μs, and a fall time of 18.5 μs. The measured on-chip loss on the transmission band is as low as 1 dB.

  19. Generation of "perfect" vortex of variable size and its effect in angular spectrum of the down-converted photons.

    PubMed

    Jabir, M V; Apurv Chaitanya, N; Aadhi, A; Samanta, G K

    2016-01-01

    The "perfect" vortex is a new class of optical vortex beam having ring radius independent of its topological charge (order). One of the simplest techniques to generate such beams is the Fourier transformation of the Bessel-Gauss beams. The variation in ring radius of such vortices require Fourier lenses of different focal lengths and or complicated imaging setup. Here we report a novel experimental scheme to generate perfect vortex of any ring radius using a convex lens and an axicon. As a proof of principle, using a lens of focal length f = 200 mm, we have varied the radius of the vortex beam across 0.3-1.18 mm simply by adjusting the separation between the lens and axicon. This is also a simple scheme to measure the apex angle of an axicon with ease. Using such vortices we have studied non-collinear interaction of photons having orbital angular momentum (OAM) in spontaneous parametric down-conversion (SPDC) process and observed that the angular spectrum of the SPDC photons are independent of OAM of the pump photons rather depends on spatial profile of the pump beam. In the presence of spatial walk-off effect in nonlinear crystals, the SPDC photons have asymmetric angular spectrum with reducing asymmetry at increasing vortex radius. PMID:26912184

  20. Ultra-compact and wide-spectrum-range thermo-optic switch based on silicon coupled photonic crystal microcavities

    SciTech Connect

    Zhang, Xingyu E-mail: swapnajit.chakravarty@omegaoptics.com Chung, Chi-Jui; Pan, Zeyu; Yan, Hai; Chakravarty, Swapnajit E-mail: swapnajit.chakravarty@omegaoptics.com; Chen, Ray T. E-mail: swapnajit.chakravarty@omegaoptics.com

    2015-11-30

    We design, fabricate, and experimentally demonstrate a compact thermo-optic gate switch comprising a 3.78 μm-long coupled L0-type photonic crystal microcavities on a silicon-on-insulator substrate. A nanohole is inserted in the center of each individual L0 photonic crystal microcavity. Coupling between identical microcavities gives rise to bonding and anti-bonding states of the coupled photonic molecules. The coupled photonic crystal microcavities are numerically simulated and experimentally verified with a 6 nm-wide flat-bottom resonance in its transmission spectrum, which enables wider operational spectrum range than microring resonators. An integrated micro-heater is in direct contact with the silicon core to efficiently drive the device. The thermo-optic switch is measured with an optical extinction ratio of 20 dB, an on-off switching power of 18.2 mW, a thermo-optic tuning efficiency of 0.63 nm/mW, a rise time of 14.8 μs, and a fall time of 18.5 μs. The measured on-chip loss on the transmission band is as low as 1 dB.

  1. On the Linearly-Balanced Kinetic Energy Spectrum

    NASA Technical Reports Server (NTRS)

    Lu, Huei,-Iin; Robertson, F. R.

    1999-01-01

    It is well known that the earth's atmospheric motion can generally be characterized by the two dimensional quasi-geostrophic approximation, in which the constraints on global integrals of kinetic energy, entrophy and potential vorticity play very important roles in redistributing the wave energy among different scales of motion. Assuming the hypothesis of Kolmogrov's local isotropy, derived a -3 power law of the equilibrium two-dimensional kinetic energy spectrum that entails constant vorticity and zero energy flows from the energy-containing wave number up to the viscous cutoff. In his three dimensional quasi-geostrophic theory, showed that the spectrum function of the vertical scale turbulence - expressible in terms of the available potential energy - possesses the same power law as the two dimensional kinetic energy spectrum. As the slope of kinetic energy spectrum in the inertial range is theoretically related to the predictability of the synoptic scales (Lorenz, 1969), many general circulation models includes a horizontal diffusion to provide reasonable kinetic energy spectra, although the actual power law exhibited in the atmospheric general circulation is controversial. Note that in either the atmospheric modeling or the observational analyses, the proper choice of wave number Index to represent the turbulence scale Is the degree of the Legendre polynomial.

  2. Impact of low-energy photons on the characteristics of prompt fission γ -ray spectra

    NASA Astrophysics Data System (ADS)

    Oberstedt, A.; Billnert, R.; Hambsch, F.-J.; Oberstedt, S.

    2015-07-01

    In this paper we report on a new study of prompt γ -rays from the spontaneous fission of 252Cf . Photons were measured in coincidence with fission fragments by employing four different lanthanide halide scintillation detectors. Together with results from a previous work of ours, we determined characteristic parameters with high precision, such as the average γ -ray multiplicity ν¯γ=(8.29 ±0.13 ), the average energy per photon ɛγ=(0.80 ±0.02 ) MeV, and the total γ -ray energy release per fission Eγ ,tot=(6.65 ±0.10 ) MeV. The excellent agreement between the individual results obtained in all six measurements proves the good repeatability of the applied experimental technique. The impact of low-energy photons, i.e., below 500 keV, on prompt fission γ -ray spectra characteristics has been investigated as well by comparing our results with those taken with the DANCE detector system, which appears to suffer from absorption effects in the low-energy region. Correction factors for this effect were estimated, giving results comparable to ours as well as to historical ones. From this we demonstrate that the different techniques of determining the average γ -ray multiplicity, either from a properly measured and normalized spectrum or a measured multiplicity distribution, give equivalent and consistent results.

  3. Scoping studies - photon and low energy neutron interrogation

    SciTech Connect

    Becker, G.; Harker, Y.; Jones, J.; Harmon, F.

    1997-11-01

    High energy photon interrogation of waste containers, with the aim of producing photo nuclear reactions, in specific materials, holds the potential of good penetration and rapid analysis. Compact high energy ({le} 10 MeV) photon sources in the form of electron linacs producing bremstrahlung radiation are readily available. Work with the Varitron variable energy accelerator at ISU will be described. Advantages and limitations of the technique will be discussed. Using positive ion induced neutron producing reactions, it is possible to generate neutrons in a specific energy range. By this means, variable penetration and specific reactions can be excited in the assayed material. Examples using the {sup 3}H(p,n) and {sup 7}Li(p,n) reactions as neutron sources will be discussed. 4 refs., 7 figs.

  4. Analysis of some lunar soil and rocks samples in terms of photon interaction and photon energy absorption

    NASA Astrophysics Data System (ADS)

    El-Khayatt, A. M.; Al-Rajhi, M. A.

    2015-04-01

    Understanding the space radiation environment is critical to future manned lunar missions, and this includes photons. In this paper, the attenuation properties of gamma rays in 20 lunar soil and rocks, found at landing site during the Apollo 17, are investigated. Effective atomic numbers Zeff for photon interaction and photon energy absorption for a wide range of photon energies are determined. The results indicate that within the wide compositional range of the Apollo 17 samples, three categories, each one have broadly similar attenuation properties. As well as the results showed that the Zeff has been successfully characterize and correlate the different soil samples with mixing of prevalent local rocks.

  5. Lorentz Invariance Violation and the Observed Spectrum of Ultrahigh Energy Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Scully, S. T.; Stecker, F. W.

    2009-01-01

    There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn of photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with photons of the cosmic background radiation and thereby eliminate the resulting sharp steepening in the spectrum of the highest energy CRs predicted by Greisen Zatsepin and Kuzmin (GZK). Recent measurements of the UHECR spectrum reported by the HiRes and Auger collaborations, however, indicate the presence of the GZK effect. We present the results of a detailed calculation of the modification of the UHECR spectrum caused by LIV using the formalism of Coleman and Glashow. We then compare these results with the experimental UHECR data from Auger and HiRes. Based on these data, we find a best fit amount of LIV of 4.5+1:5 ..4:5 x 10(exp -23),consistent with an upper limit of 6 x 10(exp -23). This possible amount of LIV can lead to a recovery of the cosmic ray spectrum at higher energies than presently observed. Such an LIV recovery effect can be tested observationally using future detectors.

  6. Teager Energy Spectrum for Fault Diagnosis of Rolling Element Bearings

    NASA Astrophysics Data System (ADS)

    Feng, Zhipeng; Wang, Tianjin; Zuo, Ming J.; Chu, Fulei; Yan, Shaoze

    2011-07-01

    Localized damage of rolling element bearings generates periodic impulses during running. The repeating frequency of impulses is a key indicator for diagnosing the localized damage of bearings. A new method, called Teager energy spectrum, is proposed to diagnose the faults of rolling element bearings. It exploits the unique advantages of Teager energy operator in detecting transient components in signals to extract periodic impulses of bearing faults, and uses the Fourier spectrum of Teager energy to identify the characteristic frequency of bearing faults. The effectiveness of the proposed method is validated by analyzing the experimental bearing vibration signals.

  7. Kolmogorov's hypotheses and global energy spectrum of turbulence

    NASA Astrophysics Data System (ADS)

    Liao, Zi-Ju; Su, Wei-Dong

    2015-04-01

    We relate the justification of Kolmogorov's hypotheses on the local isotropy and small-scale universality in real turbulent flows to an observed universality of basis independence for the global energy spectrum and energy flux of small-scale turbulence. To readily examine the small-scale universality, an approach is suggested that investigates the global energy spectrum in a general spectral space for which the nonlinear interscale interaction may not be Fourier-triadic. Specific verifications are performed based on direct numerical simulations of turbulence in a spherical geometry and reexaminations of several existing results for turbulent channel flows.

  8. NREL Spectrum of Clean Energy Innovation: Issue 3 (Book)

    SciTech Connect

    Not Available

    2012-11-01

    This quarterly magazine is dedicated to stepping beyond the technical journals to reveal NREL's vital work in a real-world context for our stakeholders. Continuum provides insights into the latest and most impactful clean energy innovations, while spotlighting those talented researchers and unique facilities that make it all happen. This edition focuses on the NREL Spectrum of Clean Energy Innovation.

  9. Hadron intensity and energy spectrum at 4380 m above level

    NASA Technical Reports Server (NTRS)

    Cananov, S. D.; Chadranyan, E. K.; Khizanishvili, L. A.; Ladaria, N. K.; Roinishvili, N. N.

    1985-01-01

    The flux value of hadrons with E (sup gamma) h or = 5 TeV, where E (sup gamma) h or = is the energy transferred into electromagnetic component is presented. It is shown that the energy spectrum slope beta of hadrons with E h or = 20 TeV is equal to 1.9.

  10. Aperiodic TiO2 Nanotube Photonic Crystal: Full-Visible-Spectrum Solar Light Harvesting in Photovoltaic Devices

    PubMed Central

    Guo, Min; Xie, Keyu; Wang, Yu; Zhou, Limin; Huang, Haitao

    2014-01-01

    Bandgap engineering of a photonic crystal is highly desirable for photon management in photonic sensors and devices. Aperiodic photonic crystals (APCs) can provide unprecedented opportunities for much more versatile photon management, due to increased degrees of freedom in the design and the unique properties brought about by the aperiodic structures as compared to their periodic counterparts. However, many efforts still remain on conceptual approaches, practical achievements in APCs are rarely reported due to the difficulties in fabrication. Here, we report a simple but highly controllable current-pulse anodization process to design and fabricate TiO2 nanotube APCs. By coupling an APC into the photoanode of a dye-sensitized solar cell, we demonstrate the concept of using APC to achieve nearly full-visible-spectrum light harvesting, as evidenced by both experimental and simulated results. It is anticipated that this work will lead to more fruitful practical applications of APCs in high-efficiency photovoltaics, sensors and optoelectronic devices. PMID:25245854

  11. Indirect dark matter signatures in the cosmic dark ages. II. Ionization, heating, and photon production from arbitrary energy injections

    NASA Astrophysics Data System (ADS)

    Slatyer, Tracy R.

    2016-01-01

    Any injection of electromagnetically interacting particles during the cosmic dark ages will lead to increased ionization, heating, production of Lyman-α photons and distortions to the energy spectrum of the cosmic microwave background, with potentially observable consequences. In this paper we describe numerical results for the low-energy electrons and photons produced by the cooling of particles injected at energies from keV to multi-TeV scales, at arbitrary injection redshifts (but focusing on the post-recombination epoch). We use these data, combined with existing calculations modeling the cooling of these low-energy particles, to estimate the resulting contributions to ionization, excitation and heating of the gas, and production of low-energy photons below the threshold for excitation and ionization. We compute corrected deposition-efficiency curves for annihilating dark matter, and demonstrate how to compute equivalent curves for arbitrary energy-injection histories. These calculations provide the necessary inputs for the limits on dark matter annihilation presented in the accompanying paper I, but also have potential applications in the context of dark matter decay or deexcitation, decay of other metastable species, or similar energy injections from new physics. We make our full results publicly available at http://nebel.rc.fas.harvard.edu/epsilon, to facilitate further independent studies. In particular, we provide the full low-energy electron and photon spectra, to allow matching onto more detailed codes that describe the cooling of such particles at low energies.

  12. Spectrum tailoring of the neutron energy spectrum in the context of delayed neutron detection

    SciTech Connect

    Koehler, William E; Tobin, Steve J; Sandoval, Nathan P; Fensin, Mike L

    2010-01-01

    For the purpose of measuring plutonium mass in spent fuel, a delayed neutron instrument is of particular interest since, if properly designed, the delayed neutron signal from {sup 235}U is significantly stronger than the signature from {sup 239}Pu or {sup 241}Pu. A key factor in properly designing a delayed neutron instrument is to minimize the fission of {sup 238}U. This minimization is achieved by keeping the interrogating neutron spectrum below {approx} 1 MeV. In the context of spent fuel measurements it is desirable to use a 14 MeV (deuterium and tritium) neutron generator for economic reasons. Spectrum tailoring is the term used to describe the inclusion of material between the 14 MeV neutrons and the interrogated object that lower the neutron energy through nuclear reactions and moderation. This report quantifies the utility of different material combination for spectrum tailoring.

  13. Parameterizations of Pion Energy Spectrum in Nucleon-Nucleon Collisions

    NASA Technical Reports Server (NTRS)

    Cucinotta, Franics A.; Wilson, John W.; Norbury, John W.

    1998-01-01

    The effects of pion (PI) production are expected to play an important role in radiation exposures in the upper atmosphere or on the Martian surface. Nuclear databases for describing pion production are developed for radiation transport codes to support these studies. We analyze the secondary energy spectrum of pions produced in nucleon-nucleon (NN) collisions in the relativistic one-pion exchange model. Parametric formulas of the isospin cross sections for one-pion production channels are discussed and are used to renormalize the model spectrum. Energy spectra for the deuteron related channels (NN yields dPi) are also described.

  14. Energy Spectrum in the Dissipation Range of Fluid Turbulence

    NASA Technical Reports Server (NTRS)

    Martinez, D. O.; Chen, S.; Doolen, G. D.; Kraichnan, R. H.; Wang, L.-P.; Zhou, Y.

    1996-01-01

    High resolution, direct numerical simulations of the three-dimensional incompressible Navier-Stokes equations are carried out to study the energy spectrum in the dissipation range. An energy spectrum of the form A(k/k( sub d))(sup alpha) exp[- betak/k(sub d) is confirmed. The possible values of the parameters alpha and beta, as well as their dependence on Revnolds numbers and length scales, are investigated, showing good agreement with recent theoretical predictions. A "bottleneck'-type effect is reported at k/k(sub d) approximately 4, exhibiting a possible transition from near-dissipation to far- dissipation.

  15. High energy photon emission from wakefields

    NASA Astrophysics Data System (ADS)

    Farinella, D. M.; Lau, C. K.; Zhang, X. M.; Koga, J. K.; Taimourzadeh, S.; Hwang, Y.; Abazajian, K.; Canac, N.; Ebisuzaki, T.; Taborek, P.; Tajima, T.

    2016-07-01

    Experimental evidence has accumulated to indicate that wakefield acceleration (WFA) accompanies intense and sometimes coherent emission of radiation such as from betatron radiation. The investigation of this issue has additional impetus nowadays because we are learning (1) there is an additional acceleration process of the ponderomotive acceleration; (2) WFA may become relevant in much higher density regimes; (3) WFA has been proposed as the mechanism for extreme high energy cosmic ray acceleration and gamma ray bursts for active galactic nuclei. These require us to closely examine the radiative mechanisms in WFA anew. We report studies of radiation from wakefield (self-injected betatron) and ponderomotive (laser field) mechanisms in scalings of the frequency and intensity of the driver, as well as the plasma density.

  16. High Energy Atmospheric Neutrino Fluxes From a Realistic Primary Spectrum

    NASA Astrophysics Data System (ADS)

    Campos Penha, Felipe; Dembinski, Hans; Gaisser, Thomas K.; Tilav, Serap

    2016-03-01

    Atmospheric neutrino fluxes depend on the energy spectrum of primary nucleons entering the top of the atmosphere. Before the advent of AMANDA and the IceCube Neutrino Observatory, measurements of the neutrino fluxes were generally below ~ 1TeV , a regime in which a simple energy power law sufficed to describe the primary spectrum. Now, IceCube's muon neutrino data extends beyond 1PeV , including a combination of neutrinos from astrophysical sources with background from atmospheric neutrinos. At such high energies, the steepening at the knee of the primary spectrum must be accounted for. Here, we describe a semi-analytical approach for calculating the atmospheric differential neutrino fluxes at high energies. The input is a realistic primary spectrum consisting of 4 populations with distinct energy cutoffs, each with up to 7 representative nuclei, where the parameters were extracted from a global fit. We show the effect of each component on the atmospheric neutrino spectra, above 10TeV . The resulting features follow directly from recent air shower measurements included in the fit. Felipe Campos Penha gratefully acknowledges financial support from CAPES (Processo BEX 5348/14-5), CNPq (Processo 142180/2012-2), and the Bartol Research Institute.

  17. Heavy Meson Production at a Low-Energy Photon Collider

    SciTech Connect

    Asztalos, S

    2004-04-15

    A low-energy {gamma}{gamma} collider has been discussed in the context of a testbed for a {gamma}{gamma} interaction region at the Next Linear Collider(NLC). We consider the production of heavy mesons at such a testbed using Compton-backscattered photons and demonstrate that their production rivals or exceeds those by BELLE, BABAR or LEP where they are produced indirectly via virtual {gamma}{gamma} luminosities.

  18. Extra Dimensions in Photon or Jet plus Missing Transverse Energy

    SciTech Connect

    Cardaci, Marco

    2010-02-10

    Recent studies of the CMS collaboration are presented on the sensitivity to searches for large (ADD) extra dimensions in channels with missing transverse energy (MET), i.e. the channels jets plus MET and photon plus MET. These studies are based on detailed detector simulation, including all Standard Model backgrounds. Particular emphasis is given to possible early discoveries, i.e. with 100 pb{sup -1} or less. Projected 95% CL exclusion limits as function of luminosity are presented as well.

  19. PRESTO, the on-line photon energy spectrometer at FERMI: design, features and commissioning results.

    PubMed

    Svetina, Cristian; Cocco, Daniele; Mahne, Nicola; Raimondi, Lorenzo; Ferrari, Eugenio; Zangrando, Marco

    2016-01-01

    Measurement of the emission wavelength and the spectral content of the photon radiation is essential information for both machine and experimental physicists at a free-electron laser (FEL) user facility. Knowledge of the photon beam spectral properties is needed during the machine optimization and for performing machine studies (i.e. monitoring the change of the FEL output as a function of the machine parameters). The experimentalists, on the other hand, need to know the photon beam spectral distribution of the source, shot to shot, to discriminate the acquired data. Consequently, the main requirement for the instrument, supposed to obtain this information, is the capability of working on-line and shot-to-shot, with minimal perturbation of the beam delivered to the experimental stations. Starting from the grating fundamental equations, the conceptual design of the FERMI Pulse-Resolved Energy Spectrometer: Transparent and On-line (PRESTO) is presented, explaining the optical design in detail. The performance of PRESTO, in terms of resolving power, efficiency and spectral response, is also discussed. Finally, some useful features beyond the usual measurement of the energy spectrum are reported, as they have been routinely used by both machine and experimental physicists. PMID:26698043

  20. TOPICAL REVIEW: RBE of low energy electrons and photons

    NASA Astrophysics Data System (ADS)

    Nikjoo, Hooshang; Lindborg, Lennart

    2010-05-01

    Relative biological effectiveness (RBE) compares the severity of damage induced by a radiation under test at a dose D relative to the reference radiation Dx for the same biological endpoint. RBE is an important parameter in estimation of risk from exposure to ionizing radiation (IR). The present work provides a review of the recently published data and the knowledge of the RBE of low energy electrons and photons. The review presents RBE values derived from experimental data and model calculations including cell inactivation, chromosome aberration, cell transformation, micronuclei formation and induction of double-strand breaks. Biophysical models, including physical features of radiation track, and microdosimetry parameters are presented, analysed and compared with experimental data. The biological effects of low energy electrons and photons are of particular interest in radiation biology as these are strongly absorbed in micrometer and sub-micrometer layers of tissue. RBE values not only depend on the electron and photon energies but also on the irradiation condition, cell type and experimental conditions.

  1. Energy spectrum of extragalactic gamma-ray sources

    NASA Technical Reports Server (NTRS)

    Protheroe, R. J.

    1985-01-01

    The result of Monte Carlo electron photon cascade calculations for propagation of gamma rays through regions of extragalactic space containing no magnetic field are given. These calculations then provide upper limits to the expected flux from extragalactic sources. Since gamma rays in the 10 to the 14th power eV to 10 to the 17th power eV energy range are of interest, interactions of electrons and photons with the 3 K microwave background radiation are considered. To obtain an upper limit to the expected gamma ray flux from sources, the intergalactic field is assumed to be so low that it can be ignored. Interactions with photons of the near-infrared background radiation are not considered here although these will have important implications for gamma rays below 10 to the 14th power eV if the near infrared background radiation is universal. Interaction lengths of electrons and photons in the microwave background radiation at a temperature of 2.96 K were calculated and are given.

  2. GENERATION OF HIGH-ENERGY PHOTONS AT ULTRA-RELATIVISTIC SHOCK BREAKOUT IN SUPERNOVAE

    SciTech Connect

    Ohtani, Yukari; Suzuki, Akihiro; Shigeyama, Toshikazu

    2013-11-10

    We present theoretical expectations for non-thermal emission due to the bulk Comptonization at the ultra-relativistic shock breakout. We calculate the transfer of photons emitted from the shocked matter with a Monte Carlo code fully taking into account special relativity. As a hydrodynamical model, we use the self-similar solution of Nakayama and Shigeyama. Our calculations reveal that the spectral shape exhibits a double peak or a single peak depending on the shock temperature at breakout; if it is significantly smaller than the rest energy of an electron, the spectrum has a double peak. We also include a few sample light curves, and estimate the total radiation energy. In comparison with observations of γ-ray bursts, a part of the higher energy component in the spectra and the total energy can be reproduced by some parameter sets. Meanwhile, the lower energy counterpart in the Band function is not reproduced by our results and the duration seems too short to represent an entire γ-ray burst. Therefore the subsequent phase will constitute the lower energy part of the spectrum.

  3. High energy primary electron spectrum observed by the emulsion chamber

    NASA Technical Reports Server (NTRS)

    Nishimura, J.; Fujii, M.; Aizu, H.; Hiraiwa, N.; Taira, T.; Kobayashi, T.; Niu, K.; Koss, T. A.; Lord, J. J.; Golden, R. L.

    1978-01-01

    A detector of the emulsion chamber type is used to measure the energy spectrum of cosmic-ray electrons. Two large emulsion chambers, each having an area of 40 by 50 sq cm, are exposed for about 25.5 hr at an average pressure altitude of 3.9 mbar. About 500 high-energy cascades (no less than about 600 GeV) are detected by searching for dark spots on the X-ray films. A power-law energy dependence formula is derived for the spectrum of primary cosmic-ray electrons in the energy region over 100 GeV. The results are in good agreement with the transition curves obtained previously by theoretical and Monte Carlo calculations.

  4. Improving the neutron-to-photon discrimination capability of detectors used for neutron dosimetry in high energy photon beam radiotherapy.

    PubMed

    Irazola, L; Terrón, J A; Bedogni, R; Pola, A; Lorenzoli, M; Sánchez-Nieto, B; Gómez, F; Sánchez-Doblado, F

    2016-09-01

    The increasing interest of the medical community to radioinduced second malignancies due to photoneutrons in patients undergoing high-energy radiotherapy, has stimulated in recent years the study of peripheral doses, including the development of some dedicated active detectors. Although these devices are designed to respond to neutrons only, their parasitic photon response is usually not identically zero and anisotropic. The impact of these facts on measurement accuracy can be important, especially in points close to the photon field-edge. A simple method to estimate the photon contribution to detector readings is to cover it with a thermal neutron absorber with reduced secondary photon emission, such as a borated rubber. This technique was applied to the TNRD (Thermal Neutron Rate Detector), recently validated for thermal neutron measurements in high-energy photon radiotherapy. The positive results, together with the accessibility of the method, encourage its application to other detectors and different clinical scenarios.

  5. Improving the neutron-to-photon discrimination capability of detectors used for neutron dosimetry in high energy photon beam radiotherapy.

    PubMed

    Irazola, L; Terrón, J A; Bedogni, R; Pola, A; Lorenzoli, M; Sánchez-Nieto, B; Gómez, F; Sánchez-Doblado, F

    2016-09-01

    The increasing interest of the medical community to radioinduced second malignancies due to photoneutrons in patients undergoing high-energy radiotherapy, has stimulated in recent years the study of peripheral doses, including the development of some dedicated active detectors. Although these devices are designed to respond to neutrons only, their parasitic photon response is usually not identically zero and anisotropic. The impact of these facts on measurement accuracy can be important, especially in points close to the photon field-edge. A simple method to estimate the photon contribution to detector readings is to cover it with a thermal neutron absorber with reduced secondary photon emission, such as a borated rubber. This technique was applied to the TNRD (Thermal Neutron Rate Detector), recently validated for thermal neutron measurements in high-energy photon radiotherapy. The positive results, together with the accessibility of the method, encourage its application to other detectors and different clinical scenarios. PMID:27337649

  6. The Spectrum of Ultrahigh Energy Cosmic Rays and Constraints on Lorentz Invariance Violation

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    2008-01-01

    There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn off photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with photons of the cosmic background radiation and thereby eliminate the resulting sharp steepening in the spectrum of the highest energy CRs predicted by Greisen Zatsepin and Kuzmin (GZK). Recent measurements of the UHECR spectrum reported by the HiRes and Auger collaborations, however, indicate the presence of the GZK effect. We present the results of a detailed calculation of the modification of the UHECR spectrum caused by LIV using the formalism of Coleman and Glashow. We then use a chi-squared analysis to compare our results with the experimental UHECR data and thereby place limits on the amount of LIV. We also discuss how a small amount of LIV that is consistent with the experimental data can still lead to a recovery of the cosmic ray flux at higher energies than presently observed.

  7. The effective penetration distance of ultrahigh-energy electrons and photons traversing a cosmic blackbody photon gas

    NASA Technical Reports Server (NTRS)

    Gould, R. J.; Rephaeli, Y.

    1978-01-01

    The effective average energy loss for an energetic (at least about 10 to the 15th power eV) particle traversing the microwave background radiation is evaluated. Electron-photon transformations by Compton scattering and pair production (in photon-photon collisions) are computed, with the energy loss considered to be carried away by the least energetic of the outgoing particles. Considering the most energetic of the outgoing particles as the high-energy particle, the relative probability and mean time for the particle to be a photon or electron (or positron) is evaluated. The effects of synchrotron losses for electrons and positrons are emphasized and compared with Compton losses to determine a critical energy (for given magnetic field) above which synchrotron losses dominate. Magnetic deflections are also treated for the case where the magnetic field is disordered, having a characteristic 'cell' size.

  8. Effective atomic numbers for photon energy absorption and photon attenuation of tissues from human organs.

    PubMed

    Shivaramu

    2002-01-01

    Effective atomic numbers for photon energy- absorption (Z(PEA)eff) and photon interaction (ZPI(eff)) of human organs and tissues such as cortical bone, ovary, eye lens, testis, breast tissue, adipose tissue, lung tissue, soft tissue, soft tissue, (4-component), blood (whole), brain (grey/white matter), and skeletal muscle have been calculated by a direct method in the energy region of 1 keV to 20 MeV. The ZPEAeff and ZPIeff values steadily increase, up to 8-50 keV, and steadily decrease up to 1.25-2.0 MeV for all of the substances studied. From 2.0 MeV, the values rise with the increase in energy, up to 20 MeV. Significant differences exist between the ZPIeff and ZPEAeff in the energy region of 20-400 keV and 3-20 MeV for cortical bone; 15-150 keV for soft tissue, ovary, testis, blood, brain, lung, and skeletal muscle; 15-100 keV for breast tissue, eye lens, and soft tissue (4-component); and 10-100 keV for adipose tissue. A maximum difference of 28.37% is observed at 100 keV for cortical bone, and 30.43% at 40 keV for adipose tissue. For ovary, eye lens, testis, breast tissue, lung tissue, soft tissue, soft tissue (4-component), blood (whole), brain (grey/white matter), and skeletal muscle, a maximum difference of 31.74%, 29.60%, 31.87%, 30.61%, 31.47%, 31.52%, 29.95%, 31.63%, 32.36%, and 31.42%, respectively, is seen at 50 keV. The energy positions at which the maximum of ZPEAeff and ZPIeff occurs differ. The single effective atomic number directly obtained using the program XMuDat (Z(XMUDATTeff)) are found to be higher compared to those of ZPEAeff and ZPIeff values. The effect of absorption edge on effective atomic numbers, and its variation with photon energy and the possibility of defining 2 set values of effective atomic numbers below the absorption edges of elements present in the organs and tissues, are discussed.

  9. High-energy diffraction microscopy at the advanced photon source

    SciTech Connect

    Lienert, U.; Li, S.; Hefferan, C.; Lind, J.; Suter, R.; Bernier, J.; Barton, N.; Brandes, M.; Mills, M.; Miller, M.; Jakobsen, B.; Pantleon, W.

    2012-02-28

    The status of the High Energy Diffraction Microscopy (HEDM) program at the 1-ID beam line of the Advanced Photon Source is reported. HEDM applies high energy synchrotron radiation for the grain and sub-grain scale structural and mechanical characterization of polycrystalline bulk materials in situ during thermomechanical loading. Case studies demonstrate the mapping of grain boundary topology, the evaluation of stress tensors of individual grains during tensile deformation and comparison to a finite element modeling simulation, and the characterization of evolving dislocation structure. Complementary information is obtained by post mortem electron microscopy on the same sample volume previously investigated by HEDM.

  10. LDRD project 151362 : low energy electron-photon transport.

    SciTech Connect

    Kensek, Ronald Patrick; Hjalmarson, Harold Paul; Magyar, Rudolph J.; Bondi, Robert James; Crawford, Martin James

    2013-09-01

    At sufficiently high energies, the wavelengths of electrons and photons are short enough to only interact with one atom at time, leading to the popular %E2%80%9Cindependent-atom approximation%E2%80%9D. We attempted to incorporate atomic structure in the generation of cross sections (which embody the modeled physics) to improve transport at lower energies. We document our successes and failures. This was a three-year LDRD project. The core team consisted of a radiation-transport expert, a solid-state physicist, and two DFT experts.

  11. ENERGY SPECTRUM AND CHEMICAL COMPOSITION OF ULTRAHIGH ENERGY COSMIC RAYS FROM SEMI-RELATIVISTIC HYPERNOVAE

    SciTech Connect

    Liu Ruoyu; Wang Xiangyu

    2012-02-10

    It has been suggested that hypernova remnants, with a substantial amount of energy in semi-relativistic ejecta, can accelerate intermediate mass or heavy nuclei to ultrahigh energies and provide a sufficient amount of energy in cosmic rays to account for the observed flux. We here calculate the expected energy spectrum and chemical composition of ultrahigh energy cosmic rays from such semi-relativistic hypernovae. With a chemical composition equal to that of the hypernova ejecta and a flat or hard spectrum for cosmic rays at the sources, the spectrum and composition of the propagated cosmic rays observed at the Earth can be compatible with the measurements by the Pierre Auger Observatory.

  12. Photon strength and the low-energy enhancement

    NASA Astrophysics Data System (ADS)

    Wiedeking, M.; Bernstein, L. A.; Krtička, M.; Bleuel, D. L.; Allmond, J. M.; Basunia, M. S.; Burke, J. T.; Fallon, P.; Firestone, R. B.; Goldblum, B. L.; Hatarik, R.; Lake, P. T.; Lee, I.-Y.; Lesher, S. R.; Paschalis, S.; Petri, M.; Phair, L.; Scielzo, N. D.

    2014-08-01

    Several measurements in medium mass nuclei have reported a low-energy enhancement in the photon strength function. Although, much effort has been invested in unraveling the mysteries of this effect, its physical origin is still not conclusively understood. Here, a completely model-independent experimental approach to investigate the existence of this enhancement is presented. The experiment was designed to study statistical feeding from the quasi-continuum (below the neutron separation energy) to individual low-lying discrete levels in 95Mo produced in the (d, p) reaction. A key aspect to successfully study gamma decay from the region of high-level density is the detection and extraction of correlated particle-gamma-gamma events which was accomplished using an array of Clover HPGe detectors and large area annular silicon detectors. The entrance channel excitation energy into the residual nucleus produced in the reaction was inferred from the detected proton energies in the silicon detectors. Gating on gamma-transitions originating from low-lying discrete levels specifies the state fed by statistical gamma-rays. Any particle-gamma-gamma event in combination with specific energy sum requirements ensures a clean and unambiguous determination of the initial and final state of the observed gamma rays. With these requirements the statistical feeding to individual discrete levels is extracted on an event-by-event basis. The results are presented and compared to 95Mo photon strength function data measured at the University of Oslo.

  13. Photon strength and the low-energy enhancement

    SciTech Connect

    Wiedeking, M.; Bernstein, L. A.; Bleuel, D. L.; Burke, J. T.; Hatarik, R.; Lesher, S. R.; Scielzo, N. D.; Krtička, M.; Allmond, J. M.; Basunia, M. S.; Fallon, P.; Firestone, R. B.; Lake, P. T.; Lee, I-Y.; Paschalis, S.; Petri, M.; Phair, L.; Goldblum, B. L.

    2014-08-14

    Several measurements in medium mass nuclei have reported a low-energy enhancement in the photon strength function. Although, much effort has been invested in unraveling the mysteries of this effect, its physical origin is still not conclusively understood. Here, a completely model-independent experimental approach to investigate the existence of this enhancement is presented. The experiment was designed to study statistical feeding from the quasi-continuum (below the neutron separation energy) to individual low-lying discrete levels in {sup 95}Mo produced in the (d, p) reaction. A key aspect to successfully study gamma decay from the region of high-level density is the detection and extraction of correlated particle-gamma-gamma events which was accomplished using an array of Clover HPGe detectors and large area annular silicon detectors. The entrance channel excitation energy into the residual nucleus produced in the reaction was inferred from the detected proton energies in the silicon detectors. Gating on gamma-transitions originating from low-lying discrete levels specifies the state fed by statistical gamma-rays. Any particle-gamma-gamma event in combination with specific energy sum requirements ensures a clean and unambiguous determination of the initial and final state of the observed gamma rays. With these requirements the statistical feeding to individual discrete levels is extracted on an event-by-event basis. The results are presented and compared to {sup 95}Mo photon strength function data measured at the University of Oslo.

  14. PHOTON-HADRON INTERACTIONS AT RHIC AND LHC ENERGIES.

    SciTech Connect

    WHITE,S.N.

    2002-03-01

    Heavy Ion Collisions at RHIC and LHC energies are potentially an interesting laboratory for the study of QED. In these collisions, a Heavy Ion in one beam sees a highly Lorentz contracted electric field due to an oncoming beam particle. The Electric field reaches a maximum value of E {approx_equal} {gamma}{sub eff} {center_dot} Z {center_dot} e/b{sup 2}, where the apparent Lorentz factor, {gamma}{sub eff} = 2 {center_dot} {gamma}{sub beam}{sup 2} - 1. The collision may be viewed in terms of a flux of photons colliding with a stationary ion target using the equivalent photon approximation, originally introduced by Fermi in 1924. We show that the cross section for Inelastic Electromagnetic Interactions of Heavy Ions are both calculable and have been measured in the first RHIC running period.

  15. Photonic sensing of organic solvents through geometric study of dynamic reflection spectrum

    PubMed Central

    Zhang, Yuqi; Fu, Qianqian; Ge, Jianping

    2015-01-01

    Traditional photonic sensing based on the change of balanced reflection of photonic structures can hardly distinguish chemical species with similar refractive indices. Here a sensing method based on the dynamic reflection spectra (DRS) of photonic crystal gel has been developed to distinguish even homologues, isomers and solvents with similar structures and physical properties. There are inherent relationships between solvent properties, diffusion behaviour and evolution of reflection signals, so that the geometric characteristics of DRS pattern including ascending/descending, colour changes, splitting/merging and curvature of reflection band can be utilized to recognize different organic solvents. With adequate solvents being tested, a database of DRS patterns can be established, which provide a standard to identify an unknown solvent. PMID:26082186

  16. Two-photon double ionization of helium in the region of photon energies 42-50eV

    NASA Astrophysics Data System (ADS)

    Ivanov, I. A.; Kheifets, A. S.

    2007-03-01

    We report the total integrated cross section (TICS) of two-photon double ionization of helium in the photon energy range from 42to50eV . Our computational procedure relies on a numerical solution of the time-dependent Schrödinger equation on a square-integrable basis and subsequent projection of this solution on a set of final field-free states describing correlation in the two-electron continuum. Our results suggest that the TICS grows monotonically as a function of photon energy in the region of 42-50eV , possibly reaching a maximum in the vicinity of 50eV . We also present fully resolved triple-differential cross sections for selected photon energies.

  17. Two-photon double ionization of helium in the region of photon energies 42-50 eV

    SciTech Connect

    Ivanov, I. A.; Kheifets, A. S.

    2007-03-15

    We report the total integrated cross section (TICS) of two-photon double ionization of helium in the photon energy range from 42 to 50 eV. Our computational procedure relies on a numerical solution of the time-dependent Schroedinger equation on a square-integrable basis and subsequent projection of this solution on a set of final field-free states describing correlation in the two-electron continuum. Our results suggest that the TICS grows monotonically as a function of photon energy in the region of 42-50 eV, possibly reaching a maximum in the vicinity of 50 eV. We also present fully resolved triple-differential cross sections for selected photon energies.

  18. Energy dispersive photon counting detectors for breast imaging

    NASA Astrophysics Data System (ADS)

    Barber, William C.; Wessel, Jan C.; Malakhov, Nail; Wawrzyniak, Gregor; Hartsough, Neal E.; Gandhi, Thulasidharan; Nygard, Einar; Iwanczyk, Jan S.

    2013-09-01

    We report on our efforts toward the development of silicon (Si) strip detectors for energy-resolved clinical breast imaging. Typically, x-ray integrating detectors based on scintillating cesium iodide CsI(Tl) or amorphous selenium (a- Se) are used in most commercial systems. Recently, mammography instrumentation has been introduced based on photon counting silicon Si strip detectors. Mammography requires high flux from the x-ray generator, therefore, in order to achieve energy resolved single photon counting, a high output count rate (OCR) for the detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel, provided that the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions. We present our methods and results from the optimization of prototype detectors based on Si strip structures. We describe the detector optimization and the development of ASIC readout electronics that provide the required spatial resolution, low noise, high count rate capabilities and minimal power consumption.

  19. The FiR 1 photon beam model adjustment according to in-air spectrum measurements with the Mg(Ar) ionization chamber.

    PubMed

    Koivunoro, H; Schmitz, T; Hippeläinen, E; Liu, Y-H; Serén, T; Kotiluoto, P; Auterinen, I; Savolainen, S

    2014-06-01

    The mixed neutron-photon beam of FiR 1 reactor is used for boron-neutron capture therapy (BNCT) in Finland. A beam model has been defined for patient treatment planning and dosimetric calculations. The neutron beam model has been validated with an activation foil measurements. The photon beam model has not been thoroughly validated against measurements, due to the fact that the beam photon dose rate is low, at most only 2% of the total weighted patient dose at FiR 1. However, improvement of the photon dose detection accuracy is worthwhile, since the beam photon dose is of concern in the beam dosimetry. In this study, we have performed ionization chamber measurements with multiple build-up caps of different thickness to adjust the calculated photon spectrum of a FiR 1 beam model.

  20. Photon Strength and the Low-Energy Enhancement

    SciTech Connect

    Wiedeking, M; Bernstein, L A; Krticka, M; Bleuel, D L; Allmond, J M; Basunia, M S; Burke, J T; Fallon, P; Firestone, R B; Goldblum, B L; Hatarik, R; Lake, P T; Lee, I Y; Lesher, S R; Paschalis, S; Petri, M; Phair, L; Scielzo, N D

    2012-02-22

    The ability of atomic nuclei to emit and absorb photons with energy E{sub {gamma}} is known as the photon strength function f(E{sub {gamma}}). It has direct relevance to astrophysical element formation via neutron capture processes due to its central role in nuclear reactions. Studies of f(E{sub {gamma}}) have benefited from a wealth of data collected in neutron capture and direct reactions but also from newly commissioned inelastic photon scattering facilities. The majority of these experimental methods, however, rely on the use of models because measured {gamma}-ray spectra are simultaneously sensitive to both the nuclear level density and f(E{sub {gamma}}). As excitation energy increases towards the particle separation energies, the level density increases rapidly, creating the quasi-continuum. Nuclear properties in this excitation energy region are best characterized using statistical quantities, such as f(E{sub {gamma}}). A point of contention in studies of the quasi-continuum has been an unexpected and unexplained increase in f(E{sub {gamma}}) at low {gamma}-ray energies (i.e. below E{sub {gamma}} {approx}3 MeV) in a subset of light-to-medium mass nuclei. Ideally, a new model-independent experimental technique is required to address questions regarding the existence and origin of this low-energy enhancement in f(E{sub {gamma}}). Here such a model-independent approach is presented for determining the shape of f(E{sub {gamma}}) over a wide range of energies. The method involves the use of coupled high-resolution particle and {gamma}-ray spectroscopy to determine the emission of {gamma} rays from the quasi-continuum in a nucleus with defined excitation energy to individual discrete levels of known spins and parities. This method shares characteristics of two neutron capture-based techniques: the Average Resonance Capture (ARC) and the Two-Step Cascade analysis (TSC). The power of the new technique lies in the additional ability to positively identify primary

  1. Energy Spectrum of Cosmic-Ray Electrons at TeV Energies

    SciTech Connect

    Aharonian, F.; Akhperjanian, A. G.; Sahakian, V.; Barres de Almeida, U.; Chadwick, P. M.; Cheesebrough, A.; Dickinson, H. J.; Hadjichristidis, C.; Keogh, D.; McComb, T. J. L.; Nolan, S. J.; Orford, K. J.; Osborne, J. L.; Rayner, S. M.; Rulten, C. B.; Spangler, D.; Ward, M.; Bazer-Bachi, A. R.; Borrel, V.; Olive, J-F.

    2008-12-31

    The very large collection area of ground-based {gamma}-ray telescopes gives them a substantial advantage over balloon or satellite based instruments in the detection of very-high-energy (>600 GeV) cosmic-ray electrons. Here we present the electron spectrum derived from data taken with the High Energy Stereoscopic System (H.E.S.S.) of imaging atmospheric Cherenkov telescopes. In this measurement, the first of this type, we are able to extend the measurement of the electron spectrum beyond the range accessible to direct measurements. We find evidence for a substantial steepening in the energy spectrum above 600 GeV compared to lower energies.

  2. Unfolding linac photon spectra and incident electron energies from experimental transmission data, with direct independent validation

    SciTech Connect

    Ali, E. S. M.; McEwen, M. R.; Rogers, D. W. O.

    2012-11-15

    Purpose: In a recent computational study, an improved physics-based approach was proposed for unfolding linac photon spectra and incident electron energies from transmission data. In this approach, energy differentiation is improved by simultaneously using transmission data for multiple attenuators and detectors, and the unfolding robustness is improved by using a four-parameter functional form to describe the photon spectrum. The purpose of the current study is to validate this approach experimentally, and to demonstrate its application on a typical clinical linac. Methods: The validation makes use of the recent transmission measurements performed on the Vickers research linac of National Research Council Canada. For this linac, the photon spectra were previously measured using a NaI detector, and the incident electron parameters are independently known. The transmission data are for eight beams in the range 10-30 MV using thick Be, Al and Pb bremsstrahlung targets. To demonstrate the approach on a typical clinical linac, new measurements are performed on an Elekta Precise linac for 6, 10 and 25 MV beams. The different experimental setups are modeled using EGSnrc, with the newly added photonuclear attenuation included. Results: For the validation on the research linac, the 95% confidence bounds of the unfolded spectra fall within the noise of the NaI data. The unfolded spectra agree with the EGSnrc spectra (calculated using independently known electron parameters) with RMS energy fluence deviations of 4.5%. The accuracy of unfolding the incident electron energy is shown to be {approx}3%. A transmission cutoff of only 10% is suitable for accurate unfolding, provided that the other components of the proposed approach are implemented. For the demonstration on a clinical linac, the unfolded incident electron energies and their 68% confidence bounds for the 6, 10 and 25 MV beams are 6.1 {+-} 0.1, 9.3 {+-} 0.1, and 19.3 {+-} 0.2 MeV, respectively. The unfolded spectra

  3. Photonic design for efficient solid state energy conversion

    NASA Astrophysics Data System (ADS)

    Agrawal, Mukul

    The efficiency of conversion between electrical and photonic energy in optoelectronic devices such as light-emitting diodes, photodetectors and solar cells is strongly affected by the photonic modes supported by the device structure. In this thesis, we show how tuning of the local photon density of states in subwavelength structures can be used to optimize device performance. The first part of the thesis is focused on organic light emitting diodes (OLEDs), a candidate technology for next-generation displays and solid-state lighting. An important unsolved problem in OLEDs is to ensure that a significant fraction of photons emitted by the organic emissive layer couple out of the device structure instead of remaining trapped in the device. It is shown using modeling and experiments that optimized non-periodic dielectric multilayer stacks can significantly increase the photon outcoupling while maintaining display quality brightness uniformity over the viewing cone. In the second part, we discuss the theoretical limits to broadband light harvesting in photovoltaic cells. First, it is shown that the extent to which one-dimensional optical cavities can be used to enhance light absorption over a broad spectral range is limited by the requirement that the cavity mirrors have a causal response. This result is used as a guide to design practical dielectric structures that enhance light harvesting in planar thin-film organic solar cells. Finally, we consider the enhancement of optical absorption in two- and three-dimensional structures in which incident light is scattered into quasi-trapped modes for more effective utilization of solar radiation. It is shown that there is an upper bound to the degree to which optical absorption can be enhanced that is identical to the limit found in the geometric optics regime. Rigorous optical simulations are used to show that an optical structure consisting of a two-dimensional array of inverted pyramids comes close to this limit. Before

  4. Controlling the spectrum of photons generated on a silicon nanophotonic chip

    PubMed Central

    Kumar, Ranjeet; Ong, Jun Rong; Savanier, Marc; Mookherjea, Shayan

    2014-01-01

    Directly modulated semiconductor lasers are widely used, compact light sources in optical communications. Semiconductors can also be used to generate nonclassical light; in fact, CMOS-compatible silicon chips can be used to generate pairs of single photons at room temperature. Unlike the classical laser, the photon-pair source requires control over a two-dimensional joint spectral intensity (JSI) and it is not possible to process the photons separately, as this could destroy the entanglement. Here we design a photon-pair source, consisting of planar lightwave components fabricated using CMOS-compatible lithography in silicon, which has the capability to vary the JSI. By controlling either the optical pump wavelength, or the temperature of the chip, we demonstrate the ability to select different JSIs, with a large variation in the Schmidt number. Such control can benefit high-dimensional communications where detector-timing constraints can be relaxed by realizing a large Schmidt number in a small frequency range. PMID:25410792

  5. The polaritonic spectrum of two-dimensional photonic crystals based on uniaxial polar materials

    NASA Astrophysics Data System (ADS)

    Gómez-Urrea, H. A.; Duque, C. A.; Mora-Ramos, M. E.

    2015-11-01

    We investigate the dispersion relations of two-dimensional photonic crystals made of cylindrical rods of uniaxial polar materials that exhibit transverse phonon-polariton excitations. The rods are considered to be embedded in a dielectric background. The photonic properties are obtained with the use of the finite-difference time domain (FDTD) method and the auxiliary differential equation (ADE) technique. The anisotropy of the dielectric function is explicitly considered using an empirical approach that assigns different weights to contributions of the parallel (z) and transversal (t) polaritonic relations. The effective dielectric function is then expressed as a weighted combination of the longitudinal and transversal components: ε (ω) =αzεz (ω) +αtεt (ω) . Different sets of values of the coefficients αz and αt have been considered. The frequencies of the allowed electromagnetic modes are determined as the local maxima of the spectral analysis using a fast Fourier transform (FFT). The particular case of a square photonic crystal superlattice geometry is analyzed, and input data corresponding to phonon frequencies of wurtzite nitride semiconductors is used. It is shown that larger values of the quantity |νz,T -νt,T | are desirable if the associated dielectric anisotropy is used as a tool for tuning photonic properties in the system.

  6. THE {gamma}-RAY SPECTRUM OF GEMINGA AND THE INVERSE COMPTON MODEL OF PULSAR HIGH-ENERGY EMISSION

    SciTech Connect

    Lyutikov, Maxim

    2012-09-20

    We reanalyze the Fermi spectra of the Geminga and Vela pulsars. We find that the spectrum of Geminga above the break is well approximated by a simple power law without the exponential cutoff, making Geminga's spectrum similar to that of Crab. Vela's broadband {gamma}-ray spectrum is equally well fit with both the exponential cutoff and the double power-law shapes. In the broadband double power-law fits, for a typical Fermi spectrum of a bright {gamma}-ray pulsar, most of the errors accumulate due to the arbitrary parameterization of the spectral roll-off. In addition, a power law with an exponential cutoff gives an acceptable fit for the underlying double power-law spectrum for a very broad range of parameters, making such fitting procedures insensitive to the underlying Fermi photon spectrum. Our results have important implications for the mechanism of pulsar high-energy emission. A number of observed properties of {gamma}-ray pulsars-i.e., the broken power-law spectra without exponential cutoffs and stretching in the case of Crab beyond the maximal curvature limit, spectral breaks close to or exceeding the maximal breaks due to curvature emission, patterns of the relative intensities of the leading and trailing pulses in the Crab repeated in the X-ray and {gamma}-ray regions, presence of profile peaks at lower energies aligned with {gamma}-ray peaks-all point to the inverse Compton origin of the high-energy emission from majority of pulsars.

  7. Energy-resolved CT imaging with a photon-counting silicon-strip detector

    NASA Astrophysics Data System (ADS)

    Persson, Mats; Huber, Ben; Karlsson, Staffan; Liu, Xuejin; Chen, Han; Xu, Cheng; Yveborg, Moa; Bornefalk, Hans; Danielsson, Mats

    2014-11-01

    Photon-counting detectors are promising candidates for use in the next generation of x-ray computed tomography (CT) scanners. Among the foreseen benefits are higher spatial resolution, better trade-off between noise and dose and energy discriminating capabilities. Silicon is an attractive detector material because of its low cost, mature manufacturing process and high hole mobility. However, it is sometimes overlooked for CT applications because of its low absorption efficiency and high fraction of Compton scatter. The purpose of this work is to demonstrate that silicon is a feasible material for CT detectors by showing energy-resolved CT images acquired with an 80 kVp x-ray tube spectrum using a photon-counting silicon-strip detector with eight energy thresholds developed in our group. We use a single detector module, consisting of a linear array of 50 0.5 × 0.4 mm detector elements, to image a phantom in a table-top lab setup. The phantom consists of a plastic cylinder with circular inserts containing water, fat and aqueous solutions of calcium, iodine and gadolinium, in different concentrations. By using basis material decomposition we obtain water, calcium, iodine and gadolinium basis images and demonstrate that these basis images can be used to separate the different materials in the inserts. We also show results showing that the detector has potential for quantitative measurements of substance concentrations.

  8. Variability in High-Energy Photon Bursts Produced by Lightning Discharges

    NASA Astrophysics Data System (ADS)

    Celestin, Sebastien; Xu, Wei; Pasko, Victor

    2015-04-01

    Terrestrial gamma-ray flashes (TGFs) are bursts of high-energy photons originating from the Earth's atmosphere in association with thunderstorm activity. They have been discovered by Fishman et al. [Science, 264, 1313, 1994] using BATSE detectors aboard the Compton Gamma-Ray Observatory originally launched to perform observations of celestial gamma-ray sources. These events have also been detected by the RHESSI [Smith et al., Science, 307, 1085, 2005], AGILE [Marisaldi et al., JGR, 115, A00E13, 2010], and the Fermi Gamma-ray Space Telescope [Briggs et al., JGR, 115, A07323, 2010]. Moreover, measurements have correlated TGFs with initial development stages of normal polarity intra-cloud lightning that transports negative charge upward (+IC) [e.g, Lu et al., JGR, 116, A03316, 2011]. Photon spectra corresponding to relativistic runaway electron avalanches (RREAs) in large-scale thunderstorm electric fields usually provide a very good agreement with satellite observations [Dwyer and Smith, GRL, 32, L22804, 2005]. However, it has been suggested that high-potential +IC lightning leaders could produce a sufficient number of energetic electrons to explain TGFs [Celestin and Pasko, JGR, 116, A03315, 2011], and Xu et al. [GRL, 39, L08801, 2012] have shown that this mechanism could explain the TGF spectrum for lightning potentials higher than 100 MV. In addition to TGFs, X-ray bursts are produced by negative cloud-to-ground (-CGs) lightning leaders in association with stepping processes and are observed from the ground [Dwyer et al., GRL, 32, L01803, 2005]. In this work, we will investigate the variation of photon spectra and photon fluences with respect to the electrical properties of the causative lightning discharge in a unified fashion for TGFs and CG-lightning-produced X-ray bursts. We will show how the lightning-produced X-ray spectrum converges toward the RREA spectrum for very high potential drops in the vicinity of the lightning leader tip, and demonstrate why only

  9. Synthesis and two-photon absorption spectrum of fluorenone-based molecules

    NASA Astrophysics Data System (ADS)

    Dipold, J.; Batista, R. J. M. B.; Fonseca, R. D.; Silva, D. L.; Moura, G. L. C.; dos Anjos, J. V.; Simas, A. M.; De Boni, L.; Mendonca, C. R.

    2016-09-01

    The two-photon absorption (2PA) of five symmetrical fluorenone-based molecules is studied by femtosecond wavelength-tunable Z-scan, as well as quantum-chemical calculations. The molecules are transparent for wavelengths greater than 500 nm and two main one-photon absorption bands are observed in the blue region; one weak, centered at 450 nm, and a stronger one at approximately 360 nm. We observed a strong 2PA band located around 720 nm with maxima 2PA cross-sections between 100 and 230 GM. Quantum chemical calculations employing the response function formalism were performed at the Density Function Theory level to support the interpretation of the experimental nonlinear spectra.

  10. Exact ultra cold neutrons' energy spectrum in gravitational quantum mechanics

    NASA Astrophysics Data System (ADS)

    Pedram, Pouria

    2013-10-01

    We find exact energy eigenvalues and eigenfunctions of the quantum bouncer in the presence of the minimal length uncertainty and the maximal momentum. This form of Generalized (Gravitational) Uncertainty Principle (GUP) agrees with various theories of quantum gravity and predicts a minimal length uncertainty proportional to and a maximal momentum proportional to , where β is the deformation parameter. We also find the semiclassical energy spectrum and discuss the effects of this GUP on the transition rate of the ultra cold neutrons in gravitational spectrometers. Then, based on Nesvizhevsky's famous experiment, we obtain an upper bound on the dimensionless GUP parameter.

  11. The energy spectrum and the optical absorption spectrum of C{sub 60} fullerene within the Hubbard model

    SciTech Connect

    Silant’ev, A. V.

    2015-10-15

    Anticommutator Green’s functions and the energy spectrum of C{sub 60} fullerene are calculated in the approximation of static fluctuations within the Hubbard model. On the basis of this spectrum, an interpretation is proposed for the experimentally observed optical absorption bands of C{sub 60} fullerene. The parameters of C{sub 60} fullerene that characterize it within the Hubbard model are calculated by the optical absorption spectrum.

  12. XTE Proposal #20102--"SS 433's High Energy Spectrum"

    NASA Technical Reports Server (NTRS)

    Band, David L.; Blanco, P.; Rothschild, R.; Kawai, N.; Kotani, T.; Oka, T.; Wagner, R. M.; Hjellming, R.; Rupen, M.; Brinkmann, W.

    1999-01-01

    We observed the jet-producing compact binary system SS 433 with RXTE during three multiwavelength campaigns, the first in conjunction with ASCA observations, the second simultaneous with a VLA-VLBA-MERLIN campaign, and the third associated with a Nobeyama millimeter-band campaign. All these campaigns included optical observations. Occurring at different jet precession and binary phases, the observations also monitored the system during a radio flare. The data provide SS 433's X-ray spectrum over more than an energy decade, and track the spectral variations as the X-ray source was partially eclipsed. The continuum can be modeled as a power law with an exponential cutoff, which can be detected to approximately 50 keV. Strong line emission is evident in the 5-10 keV range which can be modeled as a broad line whose energy is precession independent and a narrow line whose energy does vary with jet precession phase; this line model is clearly an over simplification since the PCA does not have sufficient energy resolution to detect the lines ASCA observed. The eclipses are deeper at high energy and at jet precession phases when the jets are more inclined towards and away from us. A large radio flare occurred between two sets of X-ray monitoring observations; an X-ray observation at the peak of the flare found a softer spectrum with a flux approximately 1/3 that of the quiescent level.

  13. Illuminating dark photons with high-energy colliders

    NASA Astrophysics Data System (ADS)

    Curtin, David; Essig, Rouven; Gori, Stefania; Shelton, Jessie

    2015-02-01

    High-energy colliders offer a unique sensitivity to dark photons, the mediators of a broken dark U(1) gauge theory that kinetically mixes with the Standard Model (SM) hypercharge. Dark photons can be detected in the exotic decay of the 125 GeV Higgs boson, h→ ZZ D →4 ℓ, and in Drell-Yan events, pp→ Z D → ℓℓ. If the dark U(1) is broken by a hidden-sector Higgs mechanism, then mixing between the dark and SM Higgs bosons also allows the exotic decay h → Z D Z D → 4 ℓ. We show that the 14 TeV LHC and a 100 TeV proton-proton collider provide powerful probes of both exotic Higgs decay channels. In the case of kinetic mixing alone, direct Drell-Yan production offers the best sensitivity to Z D , and can probe ɛ ≳ 9 × 10-4 (4 × 10-4) at the HL-LHC (100 TeV pp collider). The exotic Higgs decay h → ZZ D offers slightly weaker sensitivity, but both measurements are necessary to distinguish the kinetically mixed dark photon from other scenarios. If Higgs mixing is also present, then the decay h → Z D Z D can allow sensitivity to the Z D for ɛ ≳ 10-9 - 10-6 (10-10 - 10-7) for the mass range by searching for displaced dark photon decays. We also compare the Z D sensitivity at pp colliders to the indirect, but model-independent, sensitivity of global fits to electroweak precision observables. We perform a global electroweak fit of the dark photon model, substantially updating previous work in the literature. Electroweak precision measurements at LEP, Tevatron, and the LHC exclude ɛ as low as 3 × 10-2. Sensitivity can be improved by up to a factor of ˜ 2 with HL-LHC data, and an additional factor of ˜ 4 with ILC/GigaZ data.

  14. Search for ultra high energy primary photons at the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Colalillo, Roberta

    2016-07-01

    The Pierre Auger Observatory, located in Argentina, provides an unprecedented integrated aperture in the search for primary photons with energy above 1017 eV over a large portion of the southern sky. Such photons can be detected in principle via the air showers they initiate at such energies, using the complement of Auger Observatory detectors. We discuss the results obtained in diffuse and directional searches for primary photons in the EeV energy range.

  15. Photon Energy Becomes the Third Dimension in Crystallographic Texture Analysis.

    PubMed

    Grünewald, Tilman A; Rennhofer, Harald; Tack, Pieter; Garrevoet, Jan; Wermeille, Didier; Thompson, Paul; Bras, Wim; Vincze, Laszlo; Lichtenegger, Helga C

    2016-09-26

    Conventional analysis of the preferred orientation of crystallites (crystallographic texture) involves X-ray diffraction with area detectors and 2D data output. True 3D, spatially resolved information requires sample rotation in the beam, thus changing the probed volume, which introduces signal smearing and precludes the scanning of complex structures. This obstacle has been overcome by energy-dispersive Laue diffraction. A method has been devised to reach a large portion of reciprocal space and translate the X-ray photon energy into the missing third dimension of space. Carbon fibers and lobster exoskeleton as examples of biomineralized tissue have been analyzed. The major potential of this method lies in its "one-shot" nature and the direct 3D information requiring no previous knowledge of the sample. It allows the texture of large samples with complex substructures to be scanned and opens up the conceptual possibility of following texture changes in situ, for example, during crystallization.

  16. Photon Energy Becomes the Third Dimension in Crystallographic Texture Analysis.

    PubMed

    Grünewald, Tilman A; Rennhofer, Harald; Tack, Pieter; Garrevoet, Jan; Wermeille, Didier; Thompson, Paul; Bras, Wim; Vincze, Laszlo; Lichtenegger, Helga C

    2016-09-26

    Conventional analysis of the preferred orientation of crystallites (crystallographic texture) involves X-ray diffraction with area detectors and 2D data output. True 3D, spatially resolved information requires sample rotation in the beam, thus changing the probed volume, which introduces signal smearing and precludes the scanning of complex structures. This obstacle has been overcome by energy-dispersive Laue diffraction. A method has been devised to reach a large portion of reciprocal space and translate the X-ray photon energy into the missing third dimension of space. Carbon fibers and lobster exoskeleton as examples of biomineralized tissue have been analyzed. The major potential of this method lies in its "one-shot" nature and the direct 3D information requiring no previous knowledge of the sample. It allows the texture of large samples with complex substructures to be scanned and opens up the conceptual possibility of following texture changes in situ, for example, during crystallization. PMID:27483396

  17. Proton therapy monitoring by Compton imaging: influence of the large energy spectrum of the prompt-γ radiation

    NASA Astrophysics Data System (ADS)

    Hilaire, Estelle; Sarrut, David; Peyrin, Françoise; Maxim, Voichiţa

    2016-04-01

    In proton therapy, the prompt-γ (PG) radiation produced by the interactions between protons and matter is related to the range of the beam in the patient. Tomographic Compton imaging is currently studied to establish a PG image and verify the treatment. However the quality of the reconstructed images depends on a number of factors such as the volume attenuation, the spatial and energy resolutions of the detectors, incomplete absorptions of high energy photons and noise from other particles reaching the camera. The impact of all these factors was not assessed in details. In this paper we investigate the influence of the PG energy spectrum on the reconstructed images. To this aim, we describe the process from the Monte Carlo simulation of the proton irradiation, through the Compton imaging of the PG distribution, up to the image reconstruction with a statistical MLEM method. We identify specific PG energy windows that are more relevant to detect discrepancies with the treatment plan. We find that for the simulated Compton device, the incomplete absorption of the photons with energy above about 2 MeV prevents the observation of the PG distributions at specific energies. It also leads to blurred images and smooths the distal slope of the 1D PG profiles obtained as projections on the central beam axis. We show that a selection of the events produced by γ photons having deposited almost all their energy in the camera allows to largely improve the images, a result that emphasizes the importance of the choice of the detector. However, this initial-energy-based selection is not accessible in practice. We then propose a method to estimate the range of the PG profile both for specific deposited-energy windows and for the full spectrum emission. The method relies on two parameters. We use a learning approach for their estimation and we show that it allows to detect few millimeter shifts of the PG profiles.

  18. Energy spectra of electrons and positrons produced in semi-infinite and infinite water phantoms irradiated by photons with energies up to 1 GeV.

    PubMed

    Rustgi, M L; Pandey, L N; Kassaee, A; Long, S A

    1989-04-01

    Previous Monte Carlo calculations for the energy spectra of electrons produced in water irradiated by photons are extended to 1 GeV. All of the physical processes believed to be important in the transport of electrons and positrons above 100 keV and photons starting with the ejection of L photoelectrons are considered. The results are presented in tabular form and can be conveniently used to compute kerma in water. The contributions of several physical processes, such as Compton scattering and pair-production to electron spectra, are separately tabulated. The results are compared with those of Todo et al. (1982) for the single interactions of monoenergetic photons. It is found that the inclusion of processes such as multiple Compton scattering, bremsstrahlung production, positron annihilation in flight, Møhiller and Bhabha scattering from electrons and Molière multiple scattering from atomic nuclei make a considerable difference in the inferred electron spectrum in water.

  19. Energy spectrum of sputtered uranium - A new technique

    NASA Technical Reports Server (NTRS)

    Weller, R. A.; Tombrello, T. A.

    1978-01-01

    The fission track technique for detecting U-235 has been used in conjunction with a mechanical time-of-flight spectrometer in order to measure the energy spectrum in the region 1 eV to 1 keV of material sputtered from a 93% enriched U-235 foil by 80 keV Ar-40(+) ions. The spectrum was found to exhibit a peak in the region 2-4 eV and to decrease approximately as E exp -1.77 for E not less than 100 eV. The design, construction and resolution of the mechanical spectrometer are discussed and comparisons are made between the data and the predictions of the random collision cascade model of sputtering.

  20. Influence of Neutron Energy Spectrum on Primary Damage Formation

    SciTech Connect

    Stoller, R.E. , Greenwood, L.R.

    1997-12-31

    Displacement cascade formation in iron has been investigated by the method of molecular dynamics (MD) for cascade energies up to 40 keV. The results of these simulations have been used to obtain effective, energy-dependent cross sections for two measures of primary damage production: (1) the number of surviving point defects expressed as a fraction of the those predicted by the standard secondary displacement model by Norgett, Robinson, and Torrens (NRT),and (2) the fraction of the surviving interstitials contained in clusters that formed during the cascade event. The primary knockon atom spectra for iron obtained from the SPECTER code have been used to weight these MD-based damage production cross sections in order to obtain spectrally-averaged values for several locations in commercial fission reactors, materials test reactors, a DT fusion reactor first wall, and a pulsed spallation neutron source. An evaluation of these results indicates that neutron energy spectrum differences between the various environments do not lead to significant differences between the average primary damage formation parameters. This conclusion implies that the displacement damage component of radiation damage produced in a high energy spallation neutron source should be well simulated by irradiation in a fission reactor neutron spectrum, and that differences in nuclear transmutation production may be a greater source of uncertainty in the prediction of material performance in the planned National Spallation Neutron Source.

  1. High-energy x-ray backlighter spectrum measurements using calibrated image plates

    NASA Astrophysics Data System (ADS)

    Maddox, B. R.; Park, H. S.; Remington, B. A.; Izumi, N.; Chen, S.; Chen, C.; Kimminau, G.; Ali, Z.; Haugh, M. J.; Ma, Q.

    2011-02-01

    The x-ray spectrum between 18 and 88 keV generated by a petawatt laser driven x-ray backlighter target was measured using a 12-channel differential filter pair spectrometer. The spectrometer consists of a series of filter pairs on a Ta mask coupled with an x-ray sensitive image plate. A calibration of Fuji™ MS and SR image plates was conducted using a tungsten anode x-ray source and the resulting calibration applied to the design of the Ross pair spectrometer. Additionally, the fade rate and resolution of the image plate system were measured for quantitative radiographic applications. The conversion efficiency of laser energy into silver Kα x rays from a petawatt laser target was measured using the differential filter pair spectrometer and compared to measurements using a single photon counting charge coupled device.

  2. High-energy x-ray backlighter spectrum measurements using calibrated image plates

    SciTech Connect

    Maddox, B.R.; Park, H.S.; Remington, B.A.; Izumi, N.; Chen, S.; Chen, C.; Kimminau, G.; Ali, Z.; Haugh, M.J.; Ma, Q.

    2012-10-10

    The x-ray spectrum between 18 and 88 keV generated by a petawatt laser driven x-ray backlighter target was measured using a 12-channel differential filter pair spectrometer. The spectrometer consists of a series of filter pairs on a Ta mask coupled with an x-ray sensitive image plate. A calibration of Fuji{trademark} MS and SR image plates was conducted using a tungsten anode x-ray source and the resulting calibration applied to the design of the Ross pair spectrometer. Additionally, the fade rate and resolution of the image plate system were measured for quantitative radiographic applications. The conversion efficiency of laser energy into silver K{alpha} x rays from a petawatt laser target was measured using the differential filter pair spectrometer and compared to measurements using a single photon counting charge coupled device.

  3. Sharp knee phenomenon of primary cosmic ray energy spectrum

    NASA Astrophysics Data System (ADS)

    Ter-Antonyan, Samvel

    2014-06-01

    Primary energy spectral models are tested in the energy range of 1-200 PeV using standardized extensive air shower responses from BASJE-MAS, Tibet, GAMMA and KASCADE scintillation shower arrays. Results point toward the two-component origin of observed cosmic ray energy spectra in the knee region consisting of a pulsar component superimposed upon rigidity-dependent power law diffuse Galactic flux. The two-component energy spectral model accounts for both the sharp knee shower spectral phenomenon and observed irregularity of all-particle energy spectrum in the region of 50-100 PeV. Alternatively, tested multipopulation primary energy spectra predicted by nonlinear diffusive shock acceleration models describe observed shower spectra in the knee region provided that the cutoff magnetic rigidities of accelerating particles are 6±0.3 and 45±2 PV for the first two populations, respectively. Both tested spectral models confirm the predominant H-He primary nuclei origin of observed shower spectral knee. The parameters of tested energy spectra are evaluated using solutions of the inverse problem on the basis of the corresponding parameterizations of energy spectra for primary H, He, O-like and Fe-like nuclei, standardized shower size spectral responses in the 550-1085 g/cm2 atmospheric slant depth range and near vertical muon truncated size spectra detected by the GAMMA array.

  4. SU-E-I-77: A Noise Reduction Technique for Energy-Resolved Photon-Counting Detectors

    SciTech Connect

    Lam Ng, A; Ding, H; Cho, H; Molloi, S

    2014-06-01

    Purpose: Finding the optimal energy threshold setting for an energy-resolved photon-counting detector has an important impact on the maximization of contrast-to-noise-ratio (CNR). We introduce a noise reduction method to enhance CNR by reducing the noise in each energy bin without altering the average gray levels in the projection and image domains. Methods: We simulated a four bin energy-resolved photon-counting detector based on Si with a 10 mm depth of interaction. TASMIP algorithm was used to simulate a spectrum of 65 kVp with 2.7 mm Al filter. A 13 mm PMMA phantom with hydroxyapatite and iodine at different concentrations (100, 200 and 300 mg/ml for HA, and 2, 4, and 8 mg/ml for Iodine) was used. Projection-based and Image-based energy weighting methods were used to generate weighted images. A reference low noise image was used for noise reduction purposes. A Gaussian-like weighting function which computes the similarity between pixels of interest was calculated from the reference image and implemented on a pixel by pixel basis for the noisy images. Results: CNR improvement compared to different methods (Charge-Integrated, Photon-Counting and Energy-Weighting) and after noise reduction was highly task-dependent. The CNR improvement with respect to the Charge-Integrated CNR for hydroxyapatite and iodine were 1.8 and 1.5, respectively. In each of the energy bins, the noise was reduced by approximately factor of two without altering their respective average gray levels. Conclusion: The proposed noise reduction technique for energy-resolved photon-counting detectors can significantly reduce image noise. This technique can be used as a compliment to the current energy-weighting methods in CNR optimization.

  5. Understanding the two-photon absorption spectrum of PE2 platinum acetylide complex.

    PubMed

    Vivas, Marcelo G; De Boni, Leonardo; Cooper, Thomas M; Mendonca, Cleber R

    2014-07-31

    Herein, we report on the two-absorption cross-section spectrum of trans-Pt(PBu3)2 (C≡C-C6H4-C≡C-C6H5)2 (PE2) platinum acetylide complex employing the femtosecond wavelength-tunable Z-scan technique. The PE2 complex can be visualized as two branches containing two phenylacetylene units, each one linked by a platinum center, completely transparent in the visible region. Because of this structure, large delocalization of π-electrons allied to the strong intramolecular interaction between the branches is expected. The 2PA absorption spectrum was measured using the femtosecond wavelength-tunable Z-scan technique with low repetition rate (1 kHz), in order to obtain the 2PA spectrum without excited-state contributions. Our results reveal that PE2 in dichloromethane solution presents two 2PA allowed bands located at 570 and 710 nm, with cross section of about 320 and 45 GM, respectively. The first one is related to the strong intramolecular interaction between the molecule's branches due to the presence of platinum atom, while the second one is associated with the breaking of symmetry of the chromophore in solution due, most probably to a large twisting angle of the ligand's phenyl rings relative to the Pt core.

  6. Solar energy conversion with photon-enhanced thermionic emission

    NASA Astrophysics Data System (ADS)

    Kribus, Abraham; Segev, Gideon

    2016-07-01

    Photon-enhanced thermionic emission (PETE) converts sunlight to electricity with the combined photonic and thermal excitation of charge carriers in a semiconductor, leading to electron emission over a vacuum gap. Theoretical analyses predict conversion efficiency that can match, or even exceed, the efficiency of traditional solar thermal and photovoltaic converters. Several materials have been examined as candidates for radiation absorbers and electron emitters, with no conclusion yet on the best set of materials to achieve high efficiency. Analyses have shown the complexity of the energy conversion and transport processes, and the significance of several loss mechanisms, requiring careful control of material properties and optimization of the device structure. Here we survey current research on PETE modeling, materials, and device configurations, outline the advances made, and stress the open issues and future research needed. Based on the substantial progress already made in this young topic, and the potential of high conversion efficiency based on theoretical performance limits, continued research in this direction is very promising and may yield a competitive technology for solar electricity generation.

  7. The energy spectrum of X-rays from rocket-triggered lightning

    NASA Astrophysics Data System (ADS)

    Arabshahi, S.; Dwyer, J. R.; Cramer, E. S.; Grove, J. E.; Gwon, C.; Hill, J. D.; Jordan, D. M.; Lucia, R. J.; Vodopiyanov, I. B.; Uman, M. A.; Rassoul, H. K.

    2015-10-01

    Although the production of X-rays from natural and rocket-triggered lightning leaders have been studied in detail over the last 10 years, the energy spectrum of the X-rays has never been well measured because the X-rays are emitted in very short but intense bursts that result in pulse pileup in the detectors. The energy spectrum is important because it provides information about the source mechanism for producing the energetic runaway electrons and about the electric fields that they traverse. We have recently developed and operated the first spectrometer for the energetic radiation from lightning. The instrument is part of the Atmospheric Radiation Imagery and Spectroscopy (ARIS) project and will be referred to as ARIS-S (ARIS Spectrometer). It consists of seven 3'' NaI(Tl)/photomultiplier tube scintillation detectors with different thicknesses of attenuators, ranging from no attenuator to more than 1'' of lead placed over the detector (all the detectors are in a 1/8'' thick aluminum box). Using X-ray pulses preceding 48 return strokes in 8 rocket-triggered lightnings, we found that the spectrum of X-rays from leaders is too soft to be consistent with Relativistic Runaway Electron Avalanche. It has a power law dependence on the energies of the photons, and the power index, λ, is between 2.5 and 3.5. We present the details of the design of the instrument and the results of the analysis of the lightning data acquired during the summer of 2012.

  8. Investigation of energy weighting using an energy discriminating photon counting detector for breast CT

    SciTech Connect

    Kalluri, Kesava S.; Mahd, Mufeed; Glick, Stephen J.

    2013-08-15

    Purpose: Breast CT is an emerging imaging technique that can portray the breast in 3D and improve visualization of important diagnostic features. Early clinical studies have suggested that breast CT has sufficient spatial and contrast resolution for accurate detection of masses and microcalcifications in the breast, reducing structural overlap that is often a limiting factor in reading mammographic images. For a number of reasons, image quality in breast CT may be improved by use of an energy resolving photon counting detector. In this study, the authors investigate the improvements in image quality obtained when using energy weighting with an energy resolving photon counting detector as compared to that with a conventional energy integrating detector.Methods: Using computer simulation, realistic CT images of multiple breast phantoms were generated. The simulation modeled a prototype breast CT system using an amorphous silicon (a-Si), CsI based energy integrating detector with different x-ray spectra, and a hypothetical, ideal CZT based photon counting detector with capability of energy discrimination. Three biological signals of interest were modeled as spherical lesions and inserted into breast phantoms; hydroxyapatite (HA) to represent microcalcification, infiltrating ductal carcinoma (IDC), and iodine enhanced infiltrating ductal carcinoma (IIDC). Signal-to-noise ratio (SNR) of these three lesions was measured from the CT reconstructions. In addition, a psychophysical study was conducted to evaluate observer performance in detecting microcalcifications embedded into a realistic anthropomorphic breast phantom.Results: In the energy range tested, improvements in SNR with a photon counting detector using energy weighting was higher (than the energy integrating detector method) by 30%–63% and 4%–34%, for HA and IDC lesions and 12%–30% (with Al filtration) and 32%–38% (with Ce filtration) for the IIDC lesion, respectively. The average area under the receiver

  9. Investigation of energy weighting using an energy discriminating photon counting detector for breast CT

    PubMed Central

    Kalluri, Kesava S.; Mahd, Mufeed; Glick, Stephen J.

    2013-01-01

    Purpose: Breast CT is an emerging imaging technique that can portray the breast in 3D and improve visualization of important diagnostic features. Early clinical studies have suggested that breast CT has sufficient spatial and contrast resolution for accurate detection of masses and microcalcifications in the breast, reducing structural overlap that is often a limiting factor in reading mammographic images. For a number of reasons, image quality in breast CT may be improved by use of an energy resolving photon counting detector. In this study, the authors investigate the improvements in image quality obtained when using energy weighting with an energy resolving photon counting detector as compared to that with a conventional energy integrating detector. Methods: Using computer simulation, realistic CT images of multiple breast phantoms were generated. The simulation modeled a prototype breast CT system using an amorphous silicon (a-Si), CsI based energy integrating detector with different x-ray spectra, and a hypothetical, ideal CZT based photon counting detector with capability of energy discrimination. Three biological signals of interest were modeled as spherical lesions and inserted into breast phantoms; hydroxyapatite (HA) to represent microcalcification, infiltrating ductal carcinoma (IDC), and iodine enhanced infiltrating ductal carcinoma (IIDC). Signal-to-noise ratio (SNR) of these three lesions was measured from the CT reconstructions. In addition, a psychophysical study was conducted to evaluate observer performance in detecting microcalcifications embedded into a realistic anthropomorphic breast phantom. Results: In the energy range tested, improvements in SNR with a photon counting detector using energy weighting was higher (than the energy integrating detector method) by 30%–63% and 4%–34%, for HA and IDC lesions and 12%–30% (with Al filtration) and 32%–38% (with Ce filtration) for the IIDC lesion, respectively. The average area under the

  10. One-photon mass-analyzed threshold ionization (MATI) spectroscopy of pyridine: determination of accurate ionization energy and cationic structure.

    PubMed

    Lee, Yu Ran; Kang, Do Won; Kim, Hong Lae; Kwon, Chan Ho

    2014-11-01

    Ionization energies and cationic structures of pyridine were intensively investigated utilizing one-photon mass-analyzed threshold ionization (MATI) spectroscopy with vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The present one-photon high-resolution MATI spectrum of pyridine demonstrated a much finer and richer vibrational structure than that of the previously reported two-photon MATI spectrum. From the MATI spectrum and photoionization efficiency curve, the accurate ionization energy of the ionic ground state of pyridine was confidently determined to be 73,570 ± 6 cm(-1) (9.1215 ± 0.0007 eV). The observed spectrum was almost completely assigned by utilizing Franck-Condon factors and vibrational frequencies calculated through adjustments of the geometrical parameters of cationic pyridine at the B3LYP/cc-pVTZ level. A unique feature unveiled through rigorous analysis was the prominent progression of the 10 vibrational mode, which corresponds to in-plane ring bending, and the combination of other totally symmetric fundamentals with the ring bending overtones, which contribute to the geometrical change upon ionization. Notably, the remaining peaks originate from the upper electronic state ((2)A2), as predicted by high-resolution photoelectron spectroscopy studies and symmetry-adapted cluster configuration interaction calculations. Based on the quantitatively good agreement between the experimental and calculated results, it was concluded that upon ionization the pyridine cation in the ground electronic state should have a planar structure of C(2v) symmetry through the C-N axis.

  11. One-photon mass-analyzed threshold ionization (MATI) spectroscopy of pyridine: Determination of accurate ionization energy and cationic structure

    SciTech Connect

    Lee, Yu Ran; Kang, Do Won; Kim, Hong Lae E-mail: hlkim@kangwon.ac.kr; Kwon, Chan Ho E-mail: hlkim@kangwon.ac.kr

    2014-11-07

    Ionization energies and cationic structures of pyridine were intensively investigated utilizing one-photon mass-analyzed threshold ionization (MATI) spectroscopy with vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The present one-photon high-resolution MATI spectrum of pyridine demonstrated a much finer and richer vibrational structure than that of the previously reported two-photon MATI spectrum. From the MATI spectrum and photoionization efficiency curve, the accurate ionization energy of the ionic ground state of pyridine was confidently determined to be 73 570 ± 6 cm{sup −1} (9.1215 ± 0.0007 eV). The observed spectrum was almost completely assigned by utilizing Franck-Condon factors and vibrational frequencies calculated through adjustments of the geometrical parameters of cationic pyridine at the B3LYP/cc-pVTZ level. A unique feature unveiled through rigorous analysis was the prominent progression of the 10 vibrational mode, which corresponds to in-plane ring bending, and the combination of other totally symmetric fundamentals with the ring bending overtones, which contribute to the geometrical change upon ionization. Notably, the remaining peaks originate from the upper electronic state ({sup 2}A{sub 2}), as predicted by high-resolution photoelectron spectroscopy studies and symmetry-adapted cluster configuration interaction calculations. Based on the quantitatively good agreement between the experimental and calculated results, it was concluded that upon ionization the pyridine cation in the ground electronic state should have a planar structure of C{sub 2v} symmetry through the C-N axis.

  12. Search for the end of the cosmic ray energy spectrum

    SciTech Connect

    Linsley, John

    1998-06-15

    The title I was asked to speak about expresses an idea that occurred rather recently in the history of cosmic ray studies. I argue that the idea of a possible end of the cosmic ray energy spectrum came into being after a sequence of three rapid advances in knowledge which I describe, calling them 'breakthroughs'. I suggest that the present workshop be regarded as a step toward a fourth breakthrough. I argue that this may occur through application of the Space Airwatch concept--the earth atmosphere as target and signal generator--as embodied in the NASA OWL project.

  13. Photobiological interactions of blue light and photosynthetic photon flux: effects of monochromatic and broad-spectrum light sources.

    PubMed

    Cope, Kevin R; Snowden, M Chase; Bugbee, Bruce

    2014-01-01

    Photosynthesis (Pn) and photomorphogenesis (Pm) are affected by light quality, light intensity and photoperiod. Although blue light (BL) is necessary for normal development, it is less efficient in driving Pn than other wavelengths of photosynthetically active radiation. The effects of BL on Pm are highly species dependent. Here we report the interacting effects of BL and photosynthetic photon flux (PPF) on growth and development of lettuce, radish and pepper. We used light-emitting diode (LED) arrays to provide BL fractions from 11% to 28% under broad-spectrum white LEDs, and from 0.3% to 92% under monochromatic LEDs. All treatments were replicated three times at each of two PPFs (200 and 500 μmol m(-2) s(-1)). Other than light quality, environmental conditions were uniformly maintained across chambers. Regardless of PPF, BL was necessary to prevent shade-avoidance responses in radish and lettuce. For lettuce and radish, increasing BL reduced stem length, and for both species, there were significant interactions of BL with PPF for leaf expansion. Increasing BL reduced petiole length in radish and flower number in pepper. BL minimally affected pepper growth and other developmental parameters. Pepper seedlings were more photobiologically sensitive than older plants. Surprisingly, there were few interactions between monochromatic and broad-spectrum light sources.

  14. Photon Energy Deposition in Strong-Field Single Ionization of Multielectron Molecules

    NASA Astrophysics Data System (ADS)

    Zhang, Wenbin; Li, Zhichao; Lu, Peifen; Gong, Xiaochun; Song, Qiying; Ji, Qinying; Lin, Kang; Ma, Junyang; He, Feng; Zeng, Heping; Wu, Jian

    2016-09-01

    Molecules exposed to strong laser fields may coherently absorb multiple photons and deposit the energy into electrons and nuclei, triggering the succeeding dynamics as the primary stage of the light-molecule interaction. We experimentally explore the electron-nuclear sharing of the absorbed photon energy in above-threshold multiphoton single ionization of multielectron molecules. Using CO as a prototype, vibrational and orbital resolved electron-nuclear sharing of the photon energy is observed. Different from the simplest one- or two-electron systems, the participation of the multiple orbitals and the coupling of various electronic states in the strong-field ionization and dissociation processes alter the photon energy deposition dynamics of the multielectron molecule. The population of numerous vibrational states of the molecular cation as the energy reservoir in the ionization process plays an important role in photon energy sharing between the emitted electron and the nuclear fragments.

  15. Photon Energy Deposition in Strong-Field Single Ionization of Multielectron Molecules.

    PubMed

    Zhang, Wenbin; Li, Zhichao; Lu, Peifen; Gong, Xiaochun; Song, Qiying; Ji, Qinying; Lin, Kang; Ma, Junyang; He, Feng; Zeng, Heping; Wu, Jian

    2016-09-01

    Molecules exposed to strong laser fields may coherently absorb multiple photons and deposit the energy into electrons and nuclei, triggering the succeeding dynamics as the primary stage of the light-molecule interaction. We experimentally explore the electron-nuclear sharing of the absorbed photon energy in above-threshold multiphoton single ionization of multielectron molecules. Using CO as a prototype, vibrational and orbital resolved electron-nuclear sharing of the photon energy is observed. Different from the simplest one- or two-electron systems, the participation of the multiple orbitals and the coupling of various electronic states in the strong-field ionization and dissociation processes alter the photon energy deposition dynamics of the multielectron molecule. The population of numerous vibrational states of the molecular cation as the energy reservoir in the ionization process plays an important role in photon energy sharing between the emitted electron and the nuclear fragments. PMID:27636472

  16. Photon Energy Deposition in Strong-Field Single Ionization of Multielectron Molecules.

    PubMed

    Zhang, Wenbin; Li, Zhichao; Lu, Peifen; Gong, Xiaochun; Song, Qiying; Ji, Qinying; Lin, Kang; Ma, Junyang; He, Feng; Zeng, Heping; Wu, Jian

    2016-09-01

    Molecules exposed to strong laser fields may coherently absorb multiple photons and deposit the energy into electrons and nuclei, triggering the succeeding dynamics as the primary stage of the light-molecule interaction. We experimentally explore the electron-nuclear sharing of the absorbed photon energy in above-threshold multiphoton single ionization of multielectron molecules. Using CO as a prototype, vibrational and orbital resolved electron-nuclear sharing of the photon energy is observed. Different from the simplest one- or two-electron systems, the participation of the multiple orbitals and the coupling of various electronic states in the strong-field ionization and dissociation processes alter the photon energy deposition dynamics of the multielectron molecule. The population of numerous vibrational states of the molecular cation as the energy reservoir in the ionization process plays an important role in photon energy sharing between the emitted electron and the nuclear fragments.

  17. Observing the Non-Thermal Universe with the Highest Energy Photons

    NASA Astrophysics Data System (ADS)

    Dingus, Brenda L.; HAWC, VERITAS, CTA

    2016-01-01

    Astrophysical sources of relativistic particles radiate gamma rays to such high energies that they can be detected from the ground. The existence of high energy gamma rays implies that even higher energy particles are being accelerated placing strong constraints on these non-thermal accelerators. Within our galaxy, TeV gamma rays have been detected from supernova remnants, pulsar wind nebula, x-ray binaries and some yet to be identified sources in the Galactic plane. In addition, these gamma rays have sufficient energy to be attenuated by the interaction with infrared photons producing an electron-positron pair. Thus the spectrum of gamma rays can also constrain the infrared photon density, which for distant extragalactic sources is a direct probe of cosmology. The known extragalactic TeV sources are primarily the blazer class of active galactic nuclei. And TeV gamma rays might even be produced by annihilating dark matter.The US currently supports two ground-based gamma-ray observatories—HAWC and VERITAS—and NSF is developing a prototype for the international Cherenkov Telescope Array (CTA) observatory. The HAWC (High Altitude Water Cherenkov) observatory just began operation of the full detector in March 2015 and with its wide field of view scans ~2/3 of the sky each day for TeV sources. VERITAS (Very EneRgetic Imaging Telescope Array System) is an array of four imaging atmospheric Cherenkov telescopes that follows individual sources to produce lightcurves and spectra from 85 GeV to > 30 TeV. The combination of both a survey and pointed observatory is very complementary with a broad scientific reach that includes the study of extragalactic and Galactic objects as well as the search for astrophysical signatures of dark matter and the measurement of cosmic rays. I will present the current view of the TeV sky and the latest results from HAWC and VERITAS as well as plans for CTA.

  18. On the Evolution of and High-Energy Emission from GHz-Peaked-Spectrum Sources

    SciTech Connect

    Stawarz, L.; Ostorero, L.; Begelman, M.C.; Moderski, R.; Kataoka, J.; Wagner, S.

    2007-12-18

    Here we discuss evolution and broad-band emission of compact (< kpc) lobes in young radio sources. We propose a simple dynamical description for these objects, consisting of a relativistic jet propagating into a uniform gaseous medium in the central parts of an elliptical host. In the framework of the proposed model, we follow the evolution of ultrarelativistic electrons injected from a terminal hotspot of a jet to expanding lobes, taking into account their adiabatic energy losses as well as radiative cooling. This allows us to discuss the broad-band lobe emission of young radio sources. In particular, we argue that the observed spectral turnover in the radio synchrotron spectra of these objects cannot originate from the synchrotron self-absorption process but is most likely due to free-free absorption effects connected with neutral clouds of interstellar medium engulfed by the expanding lobes and photoionized by active centers. We also find a relatively strong and complex high-energy emission component produced by inverse-Compton up-scattering of various surrounding photon fields by the lobes electrons. We argue that such high energy radiation is strong enough to account for several observed properties of GHz-peaked-spectrum (GPS) radio galaxies at UV and X-ray frequencies. In addition, this emission is expected to extend up to GeV (or possibly even TeV) photon energies and can thus be probed by several modern {gamma}-ray instruments. In particular, we suggest that GPS radio galaxies should constitute a relatively numerous class of extragalactic sources detected by GLAST.

  19. Two-photon-excited fluorescence resonance energy transfer in an aqueous system of CdTe quantum dots and Rhodamine B

    SciTech Connect

    Li, Muye; Lu, Peixiang; Li, Fang He, Zhicong; Zhang, Junpei; Han, Junbo

    2014-12-21

    Two-photon excited fluorescence resonance energy transfer (FRET) between CdTe quantum dots with different emission peaks and Rhodamine B in aqueous solution are investigated both experimentally and theoretically. The photoluminescence and lifetime are measured using a time-resolved fluorescence test system. The two-photon excited FRET efficiency is found to increase as the degree of spectral overlap of the emission spectrum of CdTe and the absorption spectrum of Rhodamine B increases, which is due to the increase of Forster radius of the sample. Moreover, FRET efficiency increases when the ratio of acceptor/donor concentration increases. The two-photon excited FRET efficiency was found to reach 40%.

  20. Energy spectrum and flux of fast neutrons in the atmosphere

    NASA Technical Reports Server (NTRS)

    Saint Onge, R. N.

    1977-01-01

    The neutron energy spectrum and flux in the atmosphere at the Pfotzer maximum (about 100 g per cm squared) were measured at geomagnetic latitude 42 deg N, using a system capable of detecting a small flux of fast (5 to 20 MeV) neutrons in a much larger background flux of gamma rays and charged particles. The detector consisted of a cylindrical cell of organic liquid scintillator coupled to a high-resolution two-parameter multiparticle pulse shape discriminator with a two-parameter logarithmic pulse-height analyzer. The spectral parameter for the differential neutron energy spectrum was found to decrease from 4.4 plus or minus 0.8 between 3.5 and 6.0 MeV to 1.5 plus or minus 1.0 in the interval 11 to 20 MeV; a value of 0.36 plus or minus 0.10 neutrons per cm squared was calculated for neutron flux between 3.5 and 10 MeV. The importance of these results for evaluating the role of albedo neutron leakage as a source of the energetic proton flux in the radiation belts is also considered.

  1. Cosmic-ray positron energy spectrum measured by PAMELA.

    PubMed

    Adriani, O; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Bianco, A; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bruno, A; Cafagna, F; Campana, D; Carbone, R; Carlson, P; Casolino, M; Castellini, G; De Donato, C; De Santis, C; De Simone, N; Di Felice, V; Formato, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S A; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergé, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Papini, P; Pearce, M; Picozza, P; Pizzolotto, C; Ricci, M; Ricciarini, S B; Rossetto, L; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stochaj, S J; Stockton, J C; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N; Zverev, V G

    2013-08-23

    Precision measurements of the positron component in the cosmic radiation provide important information about the propagation of cosmic rays and the nature of particle sources in our Galaxy. The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray positron flux and fraction that extends previously published measurements up to 300 GeV in kinetic energy. The combined measurements of the cosmic-ray positron energy spectrum and fraction provide a unique tool to constrain interpretation models. During the recent solar minimum activity period from July 2006 to December 2009, approximately 24,500 positrons were observed. The results cannot be easily reconciled with purely secondary production, and additional sources of either astrophysical or exotic origin may be required.

  2. Measurements and Monte Carlo calculations of photon energy distributions in MAYAK PA workplaces.

    PubMed

    Smetanin, M; Vasilenko, E; Semenov, M; Xanthos, S; Takoudis, G; Clouvas, A; Silva, J; Potiriadis, C

    2008-01-01

    Photon energy distributions were measured in different workplaces of the Mayak Production Association (MPA), which was the first plutonium production plant in the former Soviet Union. In situ gamma spectrometry measurements were performed with a portable germanium detector. The spectral stripping method is used for the conversion of the in situ gamma-ray spectra to photon fluence rate energy distribution. This method requires the simulation of the portable germanium detector, which has been performed based on the MCNP code of Los Alamos. Measured photon fluence rate energy distributions were compared with calculated photon energy distributions (with the MCNP code) in two different workplaces: in the first workplace the geometry exposure was known. On the contrary, in the second workplace, as in most workplaces of MPA, the exposure geometry was unknown. The results obtained from the comparison between the experimental and calculated photon fluence rate energy distributions are presented and discussed. PMID:18682405

  3. Broadband Supercontinuum Spectrum Generated Highly Nonlinear Photonic Crystal Fiber Applicable to Medical and Optical Communication Systems

    NASA Astrophysics Data System (ADS)

    Begum, Feroza; Namihira, Yoshinori; Kaijage, Shubi F.; Kinjo, Tatsuya

    2011-09-01

    Optical-fiber-based supercontinuum (SC) light sources have attracted much research attention in recent years. High-quality nonlinear optical fibers allow us to readily implement stable and practical SC sources. In this work, we present a highly nonlinear photonic crystal fiber (HN-PCF) in optical coherence tomography (OCT) and telecommunication windows that can generate SC spectra. The finite difference method with an anisotropic perfectly matched layer boundary condition is used to calculate different properties of the proposed HN-PCF. From numerical simulation results, it is found that the HN-PCF nonlinear coefficients are more than 108.0, 74.0, and 53.0 (W·km)-1 at 1.06, 1.31, and 1.55 µm, respectively. The flattened chromatic dispersion is 0 to -4.0 ps/(nm·km) in the wavelength range of 1.06 to 1.7 µm (640 nm bandwidth), and the confinement loss is lower than 10-2 dB/km in the entire wavelength range. The generated supercontinuum bandwidths are 295.0, 408.0, and 590.0 nm at 1.06, 1.31, and 1.55 µm, respectively. The calculated longitudinal resolutions for biomedical imaging are 1.2, 1.2, and 1.1 µm at 1.06, 1.31, and 1.55 µm, respectively.

  4. A hybrid Monte Carlo model for the energy response functions of X-ray photon counting detectors

    NASA Astrophysics Data System (ADS)

    Wu, Dufan; Xu, Xiaofei; Zhang, Li; Wang, Sen

    2016-09-01

    In photon counting computed tomography (CT), it is vital to know the energy response functions of the detector for noise estimation and system optimization. Empirical methods lack flexibility and Monte Carlo simulations require too much knowledge of the detector. In this paper, we proposed a hybrid Monte Carlo model for the energy response functions of photon counting detectors in X-ray medical applications. GEANT4 was used to model the energy deposition of X-rays in the detector. Then numerical models were used to describe the process of charge sharing, anti-charge sharing and spectral broadening, which were too complicated to be included in the Monte Carlo model. Several free parameters were introduced in the numerical models, and they could be calibrated from experimental measurements such as X-ray fluorescence from metal elements. The method was used to model the energy response function of an XCounter Flite X1 photon counting detector. The parameters of the model were calibrated with fluorescence measurements. The model was further tested against measured spectrums of a VJ X-ray source to validate its feasibility and accuracy.

  5. Numerical analysis of the supercontinuum spectrum generation in a couple of photonic crystal fibers with different structure by using the RK4IP method

    NASA Astrophysics Data System (ADS)

    Lauterio-Cruz, J. P.; Hernández-García, J. C.; Estudillo-Ayala, J. M.; Pottiez, O.; Rojas-Laguna, R.; Filoteo-Razo, J. D.; Samano-Aguilar, L. F.; Jauregui-Vazquez, D.

    2016-03-01

    In this work, we performed a numerical analysis of the supercontinuum spectrum generation in a couple of photonic crystal fibers with different structure. The proposed configuration initially has an input pulse with hyperbolic secant profile to generate noise-like pulses as output signal, by the Runge-Kutta method (RK4IP). By using the same configuration, now these noise-like pulses are used as pump for supercontinuum generation obtaining a broad and good flatness spectrum. The numerical analysis presented here demonstrates the potential of noise-like pulses from a passively mode-locked fiber laser for broadband spectrum generation combining two different photonic crystal fibers. Besides this paper helps to understand the phenomena of supercontinuum generation which is mainly related to Raman self-frequency shift.

  6. 180/sup 0/-correlated equal-energy photons from 5. 9-MeV/nucleon U + Th collisions

    SciTech Connect

    Danzmann, K.; Meyerhof, W.E.; Montenegro, E.C.; Xu, X.; Dillard, E.; Huelskotter, H.P.; Stephens, F.S.; Diamond, R.M.; Deleplanque, M.A.; Macchiavelli, A.O.

    1987-10-26

    We have found a narrow line (intrinsic width less than or equal to2.5 keV) at 1062 +- 1 keV in the summed-energy 180/sup 0/-c.m.-correlated two-photon spectrum from 5.95-MeV/nucleon U+Th collisions. Including possible systematic uncertainties, the production cross section is found to be 50 +- 25 ..mu..b, averaged over the 1-mg/cm/sup 2/ Th target thickness. This line may belong to the decay of a neutral system which also produces correlated electron-positron pairs found by others in the same reaction.

  7. Water and tissue equivalency of some gel dosimeters for photon energy absorption.

    PubMed

    Un, Adem

    2013-12-01

    The mass energy absorption coefficients,, effective atomic numbers for photon energy absorption, ZPEAeff, and effective electron numbers for photon-energy absorption, NPEAeff, is calculated for 14 polymer gel dosimeter, five gel dosimeter, soft tissue and water, in the energy range from 1 keV to 20 MeV. The ZPEAeff(Gel)/ZPEAeff(Tissue) and NPEAeff(Gel)/NPEAeff (Tissue) are used to evaluate the tissue equivalency.

  8. Quantum cryptography using entangled photons in energy-time bell states

    PubMed

    Tittel; Brendel; Zbinden; Gisin

    2000-05-15

    We present a setup for quantum cryptography based on photon pairs in energy-time Bell states and show its feasibility in a laboratory experiment. Our scheme combines the advantages of using photon pairs instead of faint laser pulses and the possibility to preserve energy-time entanglement over long distances. Moreover, using four-dimensional energy-time states, no fast random change of bases is required in our setup: Nature itself decides whether to measure in the energy or in the time base, thus rendering eavesdropper attacks based on "photon number splitting" less efficient.

  9. A rare gas optics-free absolute photon flux and energy analyzer for solar and planetary observations

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    We have developed a prototype spectrometer for space applications requiring long term absolute EUV photon flux measurements. In this recently developed spectrometer, the energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  10. Upgrades of DARWIN, a dose and spectrum monitoring system applicable to various types of radiation over wide energy ranges

    NASA Astrophysics Data System (ADS)

    Sato, Tatsuhiko; Satoh, Daiki; Endo, Akira; Shigyo, Nobuhiro; Watanabe, Fusao; Sakurai, Hiroki; Arai, Yoichi

    2011-05-01

    A dose and spectrum monitoring system applicable to neutrons, photons and muons over wide ranges of energy, designated as DARWIN, has been developed for radiological protection in high-energy accelerator facilities. DARWIN consists of a phoswitch-type scintillation detector, a data-acquisition (DAQ) module for digital waveform analysis, and a personal computer equipped with a graphical-user-interface (GUI) program for controlling the system. The system was recently upgraded by introducing an original DAQ module based on a field programmable gate array, FPGA, and also by adding a function for estimating neutron and photon spectra based on an unfolding technique without requiring any specific scientific background of the user. The performance of the upgraded DARWIN was examined in various radiation fields, including an operational field in J-PARC. The experiments revealed that the dose rates and spectra measured by the upgraded DARWIN are quite reasonable, even in radiation fields with peak structures in terms of both spectrum and time variation. These results clearly demonstrate the usefulness of DARWIN for improving radiation safety in high-energy accelerator facilities.

  11. Characterization of one- and two-photon excitation fluorescence resonance energy transfer microscopy.

    PubMed

    Elangovan, Masilamani; Wallrabe, Horst; Chen, Ye; Day, Richard N; Barroso, Margarida; Periasamy, Ammasi

    2003-01-01

    Advances in molecular biology provide various methods to define the structure and function of the individual proteins that form the component parts of subcellular structures. The ability to see the dynamic behavior of a specific protein inside the living cell became possible through the application of advanced fluorescence resonance energy transfer (FRET) microscope techniques. The fluorophore molecule used for FRET imaging has a characteristic absorption and emission spectrum that should be considered for characterizing the FRET signal. In this article we describe the system development for the image acquisition for one- and two-photon excitation FRET microscopy. We also describe the precision FRET (PFRET) data analysis algorithm that we developed to remove spectral bleed-through and variation in the fluorophore expression level (or concentration) for the donor and acceptor molecules. The acquired images have been processed using a PFRET algorithm to calculate the energy transfer efficiency and the distance between donor and acceptor molecules. We implemented the software correction to study the organization of the apical endosome in epithelial polarized MDCK cells and dimerization of the CAATT/enhancer binding protein alpha (C/EBPalpha). For these proteins, the results revealed that the extent of correction affects the conventionally calculated energy transfer efficiency (E) and the distance (r) between donor and acceptor molecules by 38 and 9%, respectively. PMID:12543072

  12. Spectrum of Quantized Energy for a Lengthening Pendulum

    SciTech Connect

    Choi, Jeong Ryeol; Song, Ji Nny; Hong, Seong Ju

    2010-09-30

    We considered a quantum system of simple pendulum whose length of string is increasing at a steady rate. Since the string length is represented as a time function, this system is described by a time-dependent Hamiltonian. The invariant operator method is very useful in solving the quantum solutions of time-dependent Hamiltonian systems like this. The invariant operator of the system is represented in terms of the lowering operator a(t) and the raising operator a{sup {dagger}}(t). The Schroedinger solutions {psi}{sub n}({theta}, t) whose spectrum is discrete are obtained by means of the invariant operator. The expectation value of the Hamiltonian in the {psi}{sub n}({theta}, t) state is the same as the quantum energy. At first, we considered only {theta}{sup 2} term in the Hamiltonian in order to evaluate the quantized energy. The numerical study for quantum energy correction is also made by considering the angle variable not only up to {theta}{sup 4} term but also up to {theta}{sup 6} term in the Hamiltonian, using the perturbation theory.

  13. Photon-tagged heavy meson production in high energy nuclear collisions

    SciTech Connect

    Kang, Z.B.; Vitev, I.

    2011-07-26

    We study the photon-triggered light and heavy meson production in both p+p and A+A collisions. We find that a parton energy loss approach that successfully describes inclusive hadron attenuation in nucleus-nucleus reactions at RHIC can simultaneously describe well the experimentally determined photon-triggered light hadron fragmentation functions. Using the same framework, we generalize our formalism to study photon-triggered heavy meson production. We find that the nuclear modification of photon-tagged heavy meson fragmentation functions in A+A collision is very different from that of the photon-tagged light hadron case. While photon-triggered light hadron fragmentation functions in A+A collisions are suppressed relative to p+p, photon-triggered heavy meson fragmentation functions can be either enhanced or suppressed, depending on the specific kinematic region. The anticipated smaller energy loss for b-quarks manifests itself as a flatter photon-triggered B-meson fragmentation function compared to that for the D-meson case. We make detailed predictions for both RHIC and LHC energies. We conclude that a comprehensive comparative study of both photon-tagged light and heavy meson production can provide new insights in the details of the jet quenching mechanism.

  14. Projection-based energy weighting on photon-counting X-ray images in digital subtraction mammography: a feasibility study

    NASA Astrophysics Data System (ADS)

    Choi, Sung-Hoon; Lee, Seung-Wan; Choi, Yu-Na; Lee, Young-Jin; Kim, Hee-Joung

    2014-03-01

    In digital subtraction mammography where subtracts the one image (with contrast medium) from the other (anatomical background) for observing the tumor structure, tumors which include more blood vessels than normal tissue could be distinguished through the enhancement of contrast-to-noise ratio (CNR). In order to improve CNR, we adopted projection-based energy weighting for iodine solutions with four different concentrations embedded in a breast phantom (50% adipose and 50% glandular tissues). In this study, a Monte Carlo simulation was used to simulate a 40 mm thickness breast phantom, which has 15 and 30 mg/cm3 iodine solutions with two different thicknesses, and an energy resolving photon-counting system. The input energy spectrum was simulated in a range of 20 to 45 keV in order to reject electronic noise and include k-edge energy of iodine (33.2 keV). The results showed that the projection-based energy weighting improved the CNR by factors of 1.05-1.86 compared to the conventional integrating images. Consequently, the CNR of images from the digital subtraction mammography could be improved by the projection-based energy weighting with photon-counting detectors.

  15. Development of dose delivery verification by PET imaging of photonuclear reactions following high energy photon therapy

    NASA Astrophysics Data System (ADS)

    Janek, S.; Svensson, R.; Jonsson, C.; Brahme, A.

    2006-11-01

    A method for dose delivery monitoring after high energy photon therapy has been investigated based on positron emission tomography (PET). The technique is based on the activation of body tissues by high energy bremsstrahlung beams, preferably with energies well above 20 MeV, resulting primarily in 11C and 15O but also 13N, all positron-emitting radionuclides produced by photoneutron reactions in the nuclei of 12C, 16O and 14N. A PMMA phantom and animal tissue, a frozen hind leg of a pig, were irradiated to 10 Gy and the induced positron activity distributions were measured off-line in a PET camera a couple of minutes after irradiation. The accelerator used was a Racetrack Microtron at the Karolinska University Hospital using 50 MV scanned photon beams. From photonuclear cross-section data integrated over the 50 MV photon fluence spectrum the predicted PET signal was calculated and compared with experimental measurements. Since measured PET images change with time post irradiation, as a result of the different decay times of the radionuclides, the signals from activated 12C, 16O and 14N within the irradiated volume could be separated from each other. Most information is obtained from the carbon and oxygen radionuclides which are the most abundant elements in soft tissue. The predicted and measured overall positron activities are almost equal (-3%) while the predicted activity originating from nitrogen is overestimated by almost a factor of two, possibly due to experimental noise. Based on the results obtained in this first feasibility study the great value of a combined radiotherapy-PET-CT unit is indicated in order to fully exploit the high activity signal from oxygen immediately after treatment and to avoid patient repositioning. With an RT-PET-CT unit a high signal could be collected even at a dose level of 2 Gy and the acquisition time for the PET could be reduced considerably. Real patient dose delivery verification by means of PET imaging seems to be

  16. Determination of neutron energy spectrum at KAMINI shielding experiment location.

    PubMed

    Sen, Sujoy; Bagchi, Subhrojit; Prasad, R R; Venkatasubramanian, D; Mohanakrishnan, P; Keshavamurty, R S; Haridas, Adish; Arul, A John; Puthiyavinayagam, P

    2016-09-01

    The neutron spectrum at KAMINI reactor south beam tube end has been determined using multifoil activation method. This beam tube is being used for characterizing neutron attenuation of novel shield materials. Starting from a computed guess spectrum, the spectrum adjustment/unfolding procedure makes use of minimization of a modified constraint function representing (a) least squared deviations between the measured and calculated reaction rates, (b) a measure of sharp fluctuations in the adjusted spectrum and (c) the square of the deviation of adjusted spectrum from the guess spectrum. The adjusted/unfolded spectrum predicts the reaction rates accurately. The results of this new procedure are compared with those of widely used SAND-II code. PMID:27389881

  17. Determination of neutron energy spectrum at KAMINI shielding experiment location.

    PubMed

    Sen, Sujoy; Bagchi, Subhrojit; Prasad, R R; Venkatasubramanian, D; Mohanakrishnan, P; Keshavamurty, R S; Haridas, Adish; Arul, A John; Puthiyavinayagam, P

    2016-09-01

    The neutron spectrum at KAMINI reactor south beam tube end has been determined using multifoil activation method. This beam tube is being used for characterizing neutron attenuation of novel shield materials. Starting from a computed guess spectrum, the spectrum adjustment/unfolding procedure makes use of minimization of a modified constraint function representing (a) least squared deviations between the measured and calculated reaction rates, (b) a measure of sharp fluctuations in the adjusted spectrum and (c) the square of the deviation of adjusted spectrum from the guess spectrum. The adjusted/unfolded spectrum predicts the reaction rates accurately. The results of this new procedure are compared with those of widely used SAND-II code.

  18. Chandra High-Energy Transmission Grating Spectrum of AE Aquarii

    NASA Astrophysics Data System (ADS)

    Mauche, Christopher W.

    2009-11-01

    The nova-like cataclysmic binary AE Aqr, which is currently understood to be a former supersoft X-ray binary and current magnetic propeller, was observed for over two binary orbits (78 ks) in 2005 August with the High-Energy Transmission Grating (HETG) on board the Chandra X-ray Observatory. The long, uninterrupted Chandra observation provides a wealth of details concerning the X-ray emission of AE Aqr, many of which are new and unique to the HETG. First, the X-ray spectrum is that of an optically thin multi-temperature thermal plasma; the X-ray emission lines are broad, with widths that increase with the line energy from σ ≈ 1 eV (510 km s-1) for O VIII to σ ≈ 5.5 eV (820 km s-1) for Si XIV; the X-ray spectrum is reasonably well fit by a plasma model with a Gaussian emission measure distribution that peaks at log T(K) = 7.16, has a width σ = 0.48, an Fe abundance equal to 0.44 times solar, and other metal (primarily Ne, Mg, and Si) abundances equal to 0.76 times solar; and for a distance d = 100 pc, the total emission measure EM = 8.0 × 1053 cm-3 and the 0.5-10 keV luminosity L X = 1.1 × 1031 erg s-1. Second, based on the f/(i + r) flux ratios of the forbidden (f), intercombination (i), and recombination (r) lines of the Heα triplets of N VI, O VII, and Ne IX measured by Itoh et al. in the XMM-Newton Reflection Grating Spectrometer spectrum and those of O VII, Ne IX, Mg XI, and Si XIII in the Chandra HETG spectrum, either the electron density of the plasma increases with temperature by over three orders of magnitude, from n e ≈ 6 × 1010 cm-3 for N VI [log T(K) ≈ 6] to n e ≈ 1 × 1014 cm-3 for Si XIII [log T(K) ≈ 7], and/or the plasma is significantly affected by photoexcitation. Third, the radial velocity of the X-ray emission lines varies on the white dwarf spin phase, with two oscillations per spin cycle and an amplitude K ≈ 160 km s-1. These results appear to be inconsistent with the recent models of Itoh et al., Ikhsanov, and Venter

  19. CHANDRA HIGH-ENERGY TRANSMISSION GRATING SPECTRUM OF AE AQUARII

    SciTech Connect

    Mauche, Christopher W.

    2009-11-20

    The nova-like cataclysmic binary AE Aqr, which is currently understood to be a former supersoft X-ray binary and current magnetic propeller, was observed for over two binary orbits (78 ks) in 2005 August with the High-Energy Transmission Grating (HETG) on board the Chandra X-ray Observatory. The long, uninterrupted Chandra observation provides a wealth of details concerning the X-ray emission of AE Aqr, many of which are new and unique to the HETG. First, the X-ray spectrum is that of an optically thin multi-temperature thermal plasma; the X-ray emission lines are broad, with widths that increase with the line energy from sigma approx 1 eV (510 km s{sup -1}) for O VIII to sigma approx 5.5 eV (820 km s{sup -1}) for Si XIV; the X-ray spectrum is reasonably well fit by a plasma model with a Gaussian emission measure distribution that peaks at log T(K) = 7.16, has a width sigma = 0.48, an Fe abundance equal to 0.44 times solar, and other metal (primarily Ne, Mg, and Si) abundances equal to 0.76 times solar; and for a distance d = 100 pc, the total emission measure EM = 8.0 x 10{sup 53} cm{sup -3} and the 0.5-10 keV luminosity L{sub X} = 1.1 x 10{sup 31} erg s{sup -1}. Second, based on the f/(i + r) flux ratios of the forbidden (f), intercombination (i), and recombination (r) lines of the Healpha triplets of N VI, O VII, and Ne IX measured by Itoh et al. in the XMM-Newton Reflection Grating Spectrometer spectrum and those of O VII, Ne IX, Mg XI, and Si XIII in the Chandra HETG spectrum, either the electron density of the plasma increases with temperature by over three orders of magnitude, from n {sub e} approx 6 x 10{sup 10} cm{sup -3} for N VI [log T(K) approx 6] to n {sub e} approx 1 x 10{sup 14} cm{sup -3} for Si XIII [log T(K) approx 7], and/or the plasma is significantly affected by photoexcitation. Third, the radial velocity of the X-ray emission lines varies on the white dwarf spin phase, with two oscillations per spin cycle and an amplitude K approx 160 km s

  20. Two-photon solvatochromism II: experimental and theoretical study of solvent effects on the two-photon absorption spectrum of Reichardt's dye.

    PubMed

    Wielgus, Małgorzata; Zaleśny, Robert; Murugan, N Arul; Kongsted, Jacob; Ågren, Hans; Samoc, Marek; Bartkowiak, Wojciech

    2013-11-11

    In this study, we report on the influence of solvent on the two-photon absorption (2PA) spectra of Reichardt's dye (RD). The measurement of 2PA cross-sections is performed for three solvents (chloroform, dimethyl formamide, and dimethyl sulfoxide) using the Z-scan technique. The key finding of this study is the observation that the cross-section, corresponding to the 2PA of the intramolecular charge-transfer state, diminishes substantially upon increasing the solvent polarity. To unravel the solvent dependence of the 2PA cross-section, the electronic structure of RD is determined using a hybrid quantum mechanics/molecular mechanics (QM/MM) approach, in which polarization between the solute and solvent is taken into account by using a self-consistent scheme in the solvent polarization. The two-state approximation proves to be adequate for the studied system, and allowed the observed solvent-polarity-induced decrease of the 2PA cross-section to be related to the decrease of the transition moment and the increase in the excitation energy. PMID:24106066

  1. Four-photon-excited fluorescence resonance energy transfer in an aqueous system from ZnSe:Mn/ZnS quantum dots to hypocrellin A.

    PubMed

    Feng, Yueshu; Liu, Liwei; Hu, Siyi; Ren, Yu; Liu, Yingyi; Xiu, Jingrui; Zhang, Xihe

    2016-08-22

    In this work, we established a fluorescence resonance energy transfer (FRET) system between ZnSe:Mn/ZnS quantum dots and Hypocrellin A (HA, a photosensitizer used for photodynamic therapy of cancer) in aqueous solution, excited by four-photon. Here, the QDs are the donors and the HA are the acceptors. The four-photon-excited fluorescence resonance energy transfer spectrum was obtained under 1300nm femtosecond laser pluses. The experimental results indicated that the highest efficiency of FRET can reach up to 61.3%. Furthermore, the viability test in cancer cells was further demonstrated for biological applications of FRET system. When FRET occurs the cell killing rate of the cancer cells will reach to 84.8% with the 1mM concentration of HA. Our work demonstrates that while the four-photon excited FRET system is promising in both optics and biological applications, is also needs further investigation. PMID:27557241

  2. Why arguments based on photon energy may be highly misleading for power line frequency electromagnetic fields.

    PubMed

    Vistnes, A I; Gjötterud, K

    2001-04-01

    When evaluating possible mechanisms by which low frequency electromagnetic fields may have a biological effect, arguments based on photon energy have often been used in a misleading way. For visible light the concept of photons has proved to be very useful in explaining experimental findings. However, the concept of photons cannot be used without major modifications in describing phenomena related to near field problems at power frequency (50 or 60 Hz) electric and magnetic fields. For this regime, the photon description is very complex. A very high number of highly coherent photons must be used in a quantum electrodynamic description of low frequency electromagnetic field phenomena. Thus, one-photon interaction descriptions must be replaced by multiple-photon interaction formalism. However, at low frequencies, a classical electromagnetic field description is far more useful than quantum electrodynamics. There is in principle no difference in how much energy an electron can pick up from a low frequency electric field as compared to from a high frequency photon. Thus, the total gain in energy is not limited to the energy carried by a single photon, which is E = hv, where h is Planck's constant and (v) is the frequency of the radiation. However, the time scale of the primary event in a mechanism of action is very different for ionizing radiation compared to power line frequency fields. The advice is to consider the time scale given by the inverse of the frequency of the fields, rather than photon energy, when one use physics as a guidance in evaluating possible mechanisms for biological effects from low frequency electromagnetic fields.

  3. Photon-energy dependence of single-photon simultaneous core ionization and core excitation in CO2

    NASA Astrophysics Data System (ADS)

    Carniato, S.; Selles, P.; Lablanquie, P.; Palaudoux, J.; Andric, L.; Nakano, M.; Hikosaka, Y.; Ito, K.; Marchenko, T.; Travnikova, O.; Goldsztejn, G.; Journel, L.; Guillemin, R.; Céolin, D.; Simon, M.; Piancastelli, M. N.; Penent, F.

    2016-07-01

    We have studied the K-2V process corresponding to simultaneous K -shell ionization and K -shell excitation in the C O2 molecule. We define these K-2V states as super shake-up, at variance with the "conventional" K-1v-1V shake-up states. While the nature and evolution with photon energy of the conventional shake-up satellites has been the object of many studies, no such data on a large photon-energy range were previously reported on super shake-up. The C O2 molecule is a textbook example because it exhibits two well-isolated K-2V resonances (with V being 2 πu* and 5 σg* ) with different symmetries resulting from shake-up processes of different origin populated in comparable proportions. The variation of the excitation cross section of these two resonances with photon energy is reported, using two different experimental approaches, which sheds light on the excitation mechanisms. Furthermore, double-core-hole spectroscopy is shown to be able to integrate and even expand information provided by conventional single-core-hole X-ray Photoelectron Spectroscopy (XPS) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) techniques, revealing, for instance, g -g dipole forbidden transitions which are only excited in NEXAFS spectra through vibronic coupling.

  4. ENERGY-DEPENDENT GAMMA-RAY BURST PULSE WIDTH DUE TO THE CURVATURE EFFECT AND INTRINSIC BAND SPECTRUM

    SciTech Connect

    Peng, Z. Y.; Ma, L.; Zhao, X. H.; Yin, Y.; Bao, Y. Y.

    2012-06-20

    Previous studies have found that the width of the gamma-ray burst (GRB) pulse is energy dependent and that it decreases as a power-law function with increasing photon energy. In this work we have investigated the relation between the energy dependence of the pulse and the so-called Band spectrum by using a sample including 51 well-separated fast rise and exponential decay long-duration GRB pulses observed by BATSE (Burst and Transient Source Experiment on the Compton Gamma Ray Observatory). We first decompose these pulses into rise and decay phases and find that the rise widths and the decay widths also behave as a power-law function with photon energy. Then we investigate statistically the relations between the three power-law indices of the rise, decay, and total width of the pulse (denoted as {delta}{sub r}, {delta}{sub d}, and {delta}{sub w}, respectively) and the three Band spectral parameters, high-energy index ({alpha}), low-energy index ({beta}), and peak energy (E{sub p} ). It is found that (1) {alpha} is strongly correlated with {delta}{sub w} and {delta}{sub d} but seems uncorrelated with {delta}{sub r}; (2) {beta} is weakly correlated with the three power-law indices, and (3) E{sub p} does not show evident correlations with the three power-law indices. We further investigate the origin of {delta}{sub d}-{alpha} and {delta}{sub w}-{alpha}. We show that the curvature effect and the intrinsic Band spectrum could naturally lead to the energy dependence of the GRB pulse width and also the {delta}{sub d}-{alpha} and {delta}{sub w}-{alpha} correlations. Our results hold so long as the shell emitting gamma rays has a curved surface and the intrinsic spectrum is a Band spectrum or broken power law. The strong {delta}{sub d}-{alpha} correlation and inapparent correlations between {delta}{sub r} and the three Band spectral parameters also suggest that the rise and decay phases of the GRB pulses have different origins.

  5. Secondary bremsstrahlung and the energy-conservation aspects of kerma in photon-irradiated media.

    PubMed

    Kumar, Sudhir; Nahum, Alan E

    2016-02-01

    Kerma, collision kerma and absorbed dose in media irradiated by megavoltage photons are analysed with respect to energy conservation. The user-code DOSRZnrc was employed to compute absorbed dose D, kerma K and a special form of kerma, K ncpt, obtained by setting the charged-particle transport energy cut-off very high, thereby preventing the generation of 'secondary bremsstrahlung' along the charged-particle paths. The user-code FLURZnrc was employed to compute photon fluence, differential in energy, from which collision kerma, K col and K were derived. The ratios K/D, K ncpt/D and K col/D have thereby been determined over a very large volumes of water, aluminium and copper irradiated by broad, parallel beams of 0.1 to 25 MeV monoenergetic photons, and 6, 10 and 15 MV 'clinical' radiotherapy qualities. Concerning depth-dependence, the 'area under the kerma, K, curve' exceeded that under the dose curve, demonstrating that kerma does not conserve energy when computed over a large volume. This is due to the 'double counting' of the energy of the secondary bremsstrahlung photons, this energy being (implicitly) included in the kerma 'liberated' in the irradiated medium, at the same time as this secondary bremsstrahlung is included in the photon fluence which gives rise to kerma elsewhere in the medium. For 25 MeV photons this 'violation' amounts to 8.6%, 14.2% and 25.5% in large volumes of water, aluminium and copper respectively but only 0.6% for a 'clinical' 6 MV beam in water. By contrast, K col/D and K ncpt/D, also computed over very large phantoms of the same three media, for the same beam qualities, are equal to unity within (very low) statistical uncertainties, demonstrating that collision kerma and the special type of kerma, K ncpt, do conserve energy over a large volume. A comparison of photon fluence spectra for the 25 MeV beam at a depth of  ≈51 g cm−2 for both very high and very low charged-particle transport cut-offs reveals the considerable

  6. Secondary bremsstrahlung and the energy-conservation aspects of kerma in photon-irradiated media

    NASA Astrophysics Data System (ADS)

    Kumar, Sudhir; Nahum, Alan E.

    2016-02-01

    Kerma, collision kerma and absorbed dose in media irradiated by megavoltage photons are analysed with respect to energy conservation. The user-code DOSRZnrc was employed to compute absorbed dose D, kerma K and a special form of kerma, K ncpt, obtained by setting the charged-particle transport energy cut-off very high, thereby preventing the generation of ‘secondary bremsstrahlung’ along the charged-particle paths. The user-code FLURZnrc was employed to compute photon fluence, differential in energy, from which collision kerma, K col and K were derived. The ratios K/D, K ncpt/D and K col/D have thereby been determined over a very large volumes of water, aluminium and copper irradiated by broad, parallel beams of 0.1 to 25 MeV monoenergetic photons, and 6, 10 and 15 MV ‘clinical’ radiotherapy qualities. Concerning depth-dependence, the ‘area under the kerma, K, curve’ exceeded that under the dose curve, demonstrating that kerma does not conserve energy when computed over a large volume. This is due to the ‘double counting’ of the energy of the secondary bremsstrahlung photons, this energy being (implicitly) included in the kerma ‘liberated’ in the irradiated medium, at the same time as this secondary bremsstrahlung is included in the photon fluence which gives rise to kerma elsewhere in the medium. For 25 MeV photons this ‘violation’ amounts to 8.6%, 14.2% and 25.5% in large volumes of water, aluminium and copper respectively but only 0.6% for a ‘clinical’ 6 MV beam in water. By contrast, K col/D and K ncpt/D, also computed over very large phantoms of the same three media, for the same beam qualities, are equal to unity within (very low) statistical uncertainties, demonstrating that collision kerma and the special type of kerma, K ncpt, do conserve energy over a large volume. A comparison of photon fluence spectra for the 25 MeV beam at a depth of  ≈51 g cm-2 for both very high and very low charged-particle transport cut

  7. Generation of “perfect” vortex of variable size and its effect in angular spectrum of the down-converted photons

    PubMed Central

    Jabir, M. V.; Apurv Chaitanya, N.; Aadhi, A.; Samanta, G. K.

    2016-01-01

    The “perfect” vortex is a new class of optical vortex beam having ring radius independent of its topological charge (order). One of the simplest techniques to generate such beams is the Fourier transformation of the Bessel-Gauss beams. The variation in ring radius of such vortices require Fourier lenses of different focal lengths and or complicated imaging setup. Here we report a novel experimental scheme to generate perfect vortex of any ring radius using a convex lens and an axicon. As a proof of principle, using a lens of focal length f = 200 mm, we have varied the radius of the vortex beam across 0.3–1.18 mm simply by adjusting the separation between the lens and axicon. This is also a simple scheme to measure the apex angle of an axicon with ease. Using such vortices we have studied non-collinear interaction of photons having orbital angular momentum (OAM) in spontaneous parametric down-conversion (SPDC) process and observed that the angular spectrum of the SPDC photons are independent of OAM of the pump photons rather depends on spatial profile of the pump beam. In the presence of spatial walk-off effect in nonlinear crystals, the SPDC photons have asymmetric angular spectrum with reducing asymmetry at increasing vortex radius. PMID:26912184

  8. Generation of “perfect” vortex of variable size and its effect in angular spectrum of the down-converted photons

    NASA Astrophysics Data System (ADS)

    Jabir, M. V.; Apurv Chaitanya, N.; Aadhi, A.; Samanta, G. K.

    2016-02-01

    The “perfect” vortex is a new class of optical vortex beam having ring radius independent of its topological charge (order). One of the simplest techniques to generate such beams is the Fourier transformation of the Bessel-Gauss beams. The variation in ring radius of such vortices require Fourier lenses of different focal lengths and or complicated imaging setup. Here we report a novel experimental scheme to generate perfect vortex of any ring radius using a convex lens and an axicon. As a proof of principle, using a lens of focal length f = 200 mm, we have varied the radius of the vortex beam across 0.3-1.18 mm simply by adjusting the separation between the lens and axicon. This is also a simple scheme to measure the apex angle of an axicon with ease. Using such vortices we have studied non-collinear interaction of photons having orbital angular momentum (OAM) in spontaneous parametric down-conversion (SPDC) process and observed that the angular spectrum of the SPDC photons are independent of OAM of the pump photons rather depends on spatial profile of the pump beam. In the presence of spatial walk-off effect in nonlinear crystals, the SPDC photons have asymmetric angular spectrum with reducing asymmetry at increasing vortex radius.

  9. UV DRIVEN EVAPORATION OF CLOSE-IN PLANETS: ENERGY-LIMITED, RECOMBINATION-LIMITED, AND PHOTON-LIMITED FLOWS

    SciTech Connect

    Owen, James E.; Alvarez, Marcelo A.

    2016-01-01

    We have investigated the evaporation of close-in exoplanets irradiated by ionizing photons. We find that the properties of the flow are controlled by the ratio of the recombination time to the flow timescale. When the recombination timescale is short compared to the flow timescale, the flow is in approximate local ionization equilibrium with a thin ionization front where the photon mean free path is short compared to the flow scale. In this “recombination-limited” flow the mass-loss scales roughly with the square root of the incident flux. When the recombination time is long compared to the flow timescale the ionization front becomes thick and encompasses the entire flow with the mass-loss rate scaling linearly with flux. If the planet's potential is deep, then the flow is approximately “energy-limited”; however, if the planet's potential is shallow, then we identify a new limiting mass-loss regime, which we term “photon-limited.” In this scenario, the mass-loss rate is purely limited by the incoming flux of ionizing photons. We have developed a new numerical approach that takes into account the frequency dependence of the incoming ionizing spectrum and performed a large suite of 1D simulations to characterize UV driven mass-loss around low-mass planets. We find that the flow is “recombination-limited” at high fluxes but becomes “energy-limited” at low fluxes; however, the transition is broad occurring over several orders of magnitude in flux. Finally, we point out that the transitions between the different flow types do not occur at a single flux value but depend on the planet's properties, with higher-mass planets becoming “energy-limited” at lower fluxes.

  10. A review on photoneutrons characteristics in radiation therapy with high-energy photon beams

    PubMed Central

    Naseri, Alireza; Mesbahi, Asghar

    2010-01-01

    In radiation therapy with high-energy photon beams (E > 10 MeV) neutrons are generated mainly in linacs head thorough (γ,n) interactions of photons with nuclei of high atomic number materials that constitute the linac head and the beam collimation system. These neutrons affect the shielding requirements in radiation therapy rooms and also increase the out-of-field radiation dose of patients undergoing radiation therapy with high-energy photon beams. In the current review, the authors describe the factors influencing the neutron production for different medical linacs based on the performed measurements and Monte Carlo studies in the literature. PMID:24376940

  11. Time-resolved electron beam energy spectrum diagnostics for Vanderbilt FEL

    NASA Astrophysics Data System (ADS)

    Feng, Bibo; Kozub, John A.; Gabella, William E.

    2002-06-01

    A fast electron energy spectrometer has been built using a photodiode array measuring the backward optical transition radiation from a thin film of aluminum. The resolution of the electron energy spectrometer is about 0.2% with a time resolution of 50 ns. The maximum energy spread that can be measured is 6.4%. We present the measurements of the time-resolved electron beam energy spectrum on the Mark III linear accelerator at Vanderbilt University, while lasing at different wavelengths and while not lasing. We also discuss the effects of different parameters, such as cathode heating, alpha magnet strength and RF phase, on the electron energy spectrum and optical spectrum. The diagnostics of time-resolved electron energy spectrum and time-resolved laser spectrum provide the technology to understand the physical process of the FEL interaction. Based on these diagnostics, the FEL facility can realize some special modes of operation, such as macropulse chirping and macropulse two color lasing.

  12. Energy spectrum measured by the telescope array surface detector

    NASA Astrophysics Data System (ADS)

    Ivanov, Dmitri

    2012-05-01

    Two conflicting measurements of the ultra high energy cosmic ray (UHECR) flux have been reported by the Akeno Giant Air Shower Array (AGASA) and the High Resolution Fly's Eye (HiRes) experiments. HiRes observes a ˜5sigma suppression at E = 1019.75 eV, which is in agreement with the prediction of Greisen-Zatsepin-Kuz'min (GZK) theory. AGASA, in contrast, sees the flux extended well beyond E = 1020 eV with no visible break, suggesting that the flux is limited only by the rate at which the sources can produce the UHECR and not by interaction of energetic particles with the cosmic microwave background, thus challenging the relativistic invariance principle. In response to this discrepancy, a new experiment named the Telescope Array (TA) has been deployed, which combines the detection elements used separately by HiRes and AGASA. We describe the TA surface detector (SD) analysis using a technique new to the field, which consists of a detailed Monte-Carlo (MC) simulation of the SD response to the natural cosmic rays, validating the MC by comparing its distributions with the data, and calculation of the SD aperture from the MC. We will also describe our reconstruction procedure, based solely upon the data, and its application to both data and the MC. Finally, we will describe the energy spectrum resulting from this analysis, which is found to be in excellent agreement with the HiRes result, and as such, is the first confirmation of the GZK effect by a ground array of scintillation counters.

  13. Possible dark energy imprints in the gravitational wave spectrum of mixed neutron-dark-energy stars

    SciTech Connect

    Yazadjiev, Stoytcho S.; Doneva, Daniela D. E-mail: daniela.doneva@uni-tuebingen.de

    2012-03-01

    In the present paper we study the oscillation spectrum of neutron stars containing both ordinary matter and dark energy in different proportions. Within the model we consider, the equilibrium configurations are numerically constructed and the results show that the properties of the mixed neuron-dark-energy star can differ significantly when the amount of dark energy in the stars is varied. The oscillations of the mixed neuron-dark-energy stars are studied in the Cowling approximation. As a result we find that the frequencies of the fundamental mode and the higher overtones are strongly affected by the dark energy content. This can be used in the future to detect the presence of dark energy in the neutron stars and to constrain the dark-energy models.

  14. Electromagnetic cascade in high-energy electron, positron, and photon interactions with intense laser pulses

    NASA Astrophysics Data System (ADS)

    Bulanov, S. S.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

    2013-06-01

    The interaction of high-energy electrons, positrons, and photons with intense laser pulses is studied in head-on collision geometry. It is shown that electrons and/or positrons undergo a cascade-type process involving multiple emissions of photons. These photons can consequently convert into electron-positron pairs. As a result charged particles quickly lose their energy developing an exponentially decaying energy distribution, which suppresses the emission of high-energy photons, thus reducing the number of electron-positron pairs being generated. Therefore, this type of interaction suppresses the development of the electromagnetic avalanche-type discharge, i.e., the exponential growth of the number of electrons, positrons, and photons does not occur in the course of interaction. The suppression will occur when three-dimensional effects can be neglected in the transverse particle orbits, i.e., for sufficiently broad laser pulses with intensities that are not too extreme. The final distributions of electrons, positrons, and photons are calculated for the case of a high-energy e-beam interacting with a counterstreaming, short intense laser pulse. The energy loss of the e-beam, which requires a self-consistent quantum description, plays an important role in this process, as well as provides a clear experimental observable for the transition from the classical to quantum regime of interaction.

  15. Ultra high energy events in ECHOS series and primary energy spectrum

    NASA Technical Reports Server (NTRS)

    Capdevielle, J. N.; Iwai, J.; Ogata, T.

    1985-01-01

    The compilation of ultra high energy jets suggests at present the existence of a bump in primary energy spectrum (with the standard concept of high energy collisions). The pseudo-rapidity distribution exhibits some typical anomalies, more than the (P sub t) behavior, which are (may be) the fingerprints of quark gluon plasma transition. The next results of Emulsion Chamber on Supersonic (ECHOS) will be in both cases determinant to confirm those tendancies, as well as an important effort of the cosmic ray community to develop in that sense a flying emulsion chamber experiment.

  16. Single photon energy dispersive x-ray diffraction.

    PubMed

    Higginbotham, Andrew; Patel, Shamim; Hawreliak, James A; Ciricosta, Orlando; Collins, Gilbert W; Coppari, Federica; Eggert, Jon H; Suggit, Matthew J; Tang, Henry; Wark, Justin S

    2014-03-01

    With the pressure range accessible to laser driven compression experiments on solid material rising rapidly, new challenges in the diagnosis of samples in harsh laser environments are emerging. When driving to TPa pressures (conditions highly relevant to planetary interiors), traditional x-ray diffraction techniques are plagued by increased sources of background and noise, as well as a potential reduction in signal. In this paper we present a new diffraction diagnostic designed to record x-ray diffraction in low signal-to-noise environments. By utilising single photon counting techniques we demonstrate the ability to record diffraction patterns on nanosecond timescales, and subsequently separate, photon-by-photon, signal from background. In doing this, we mitigate many of the issues surrounding the use of high intensity lasers to drive samples to extremes of pressure, allowing for structural information to be obtained in a regime which is currently largely unexplored.

  17. Single photon energy dispersive x-ray diffraction

    SciTech Connect

    Higginbotham, Andrew; Patel, Shamim; Ciricosta, Orlando; Suggit, Matthew J.; Wark, Justin S.; Hawreliak, James A.; Collins, Gilbert W.; Coppari, Federica; Eggert, Jon H.; Tang, Henry

    2014-03-15

    With the pressure range accessible to laser driven compression experiments on solid material rising rapidly, new challenges in the diagnosis of samples in harsh laser environments are emerging. When driving to TPa pressures (conditions highly relevant to planetary interiors), traditional x-ray diffraction techniques are plagued by increased sources of background and noise, as well as a potential reduction in signal. In this paper we present a new diffraction diagnostic designed to record x-ray diffraction in low signal-to-noise environments. By utilising single photon counting techniques we demonstrate the ability to record diffraction patterns on nanosecond timescales, and subsequently separate, photon-by-photon, signal from background. In doing this, we mitigate many of the issues surrounding the use of high intensity lasers to drive samples to extremes of pressure, allowing for structural information to be obtained in a regime which is currently largely unexplored.

  18. THE EXTRAGALACTIC BACKGROUND LIGHT FROM THE MEASUREMENTS OF THE ATTENUATION OF HIGH-ENERGY GAMMA-RAY SPECTRUM

    SciTech Connect

    Gong Yan; Cooray, Asantha

    2013-07-20

    The attenuation of high-energy gamma-ray spectrum due to the electron-positron pair production against the extragalactic background light (EBL) provides an indirect method to measure the EBL of the universe. We use the measurements of the absorption features of the gamma-rays from blazars as seen by the Fermi Gamma-ray Space Telescope to explore the EBL flux density and constrain the EBL spectrum, star formation rate density (SFRD), and photon escape fraction from galaxies out to z = 6. Our results are basically consistent with the existing determinations of the quantities. We find a larger photon escape fraction at high redshifts, especially at z = 3, compared to the result from recent Ly{alpha} measurements. Our SFRD result is consistent with the data from both gamma-ray burst and ultraviolet (UV) observations in the 1{sigma} level. However, the average SFRD we obtain at z {approx}> 3 matches the gamma-ray data better than the UV data. Thus our SFRD result at z {approx}> 6 favors the fact that star formation alone is sufficiently high enough to reionize the universe.

  19. Measurement of the Energy Spectrum of Cosmic Rays with the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Verzi, Valerio

    The energy spectrum of high-energy cosmic rays measured with the Pierre Auger Observatory is presented. The measurement is based on data collected until 31 December 2012 and extends over three orders of magnitude in energy from 3 × 1017 eV up to the very end of the spectrum. The spectral features are presented together with a detailed description of the recent improvements in determination of the energy scale.

  20. Reconstruction of the energy spectrum of electrons accelerated in the April 15, 2002 solar flare based on IRIS X-ray spectrometer measurements

    NASA Astrophysics Data System (ADS)

    Motorina, G. G.; Kudryavtsev, I. V.; Lazutkov, V. P.; Savchenko, M. I.; Skorodumov, D. V.; Charikov, Yu. E.

    2016-04-01

    We reconstruct the energy distribution of electrons accelerated in the April 15, 2002 solar flare on the basis of the data from the IRIS X-ray spectrometer onboard the CORONAS-F satellite. We obtain the solution to the integral equations describing the transformation of the spectrum of X-ray photons during the recording and reconstruction of the spectrum of accelerated electrons in the bremsstrahlung source using the random search method and the Tikhonov regularization method. In this event, we detected a singularity in the electron spectrum associated with the existence of a local minimum in the energy range 40-60 keV, which cannot be detected by a direct method.

  1. Beam hardening artefacts in computed tomography with photon counting, charge integrating and energy weighting detectors: a simulation study.

    PubMed

    Shikhaliev, Polad M

    2005-12-21

    Photon counting x-ray imaging provides efficient rejection of the electronics noise, no pulse height (Swank) noise, less noise due to optimal photon energy weighting and the possibility of energy resolved image acquisition. These advantages apply also to CT when projection data are acquired using a photon counting detector. However, photon counting detectors assign a weighting factor of 1 to all detected photons whereas the weighting factor of a charge integrating detector is proportional to the energy of the detected photon. Therefore, data collected by photon counting and charge integrating detectors represent the 'hardening' of the photon beam passed through the object differently. This affects the beam hardening artefacts in the reconstructed CT images. This work represents the first comparative evaluation of the effect of photon counting, charge integrating and energy weighting photon detectors on beam hardening artefacts in CT. Beam hardening artefacts in CT images were evaluated for 20 cm and 14 cm diameter water cylinders with bone and low contrast inserts, at 120 kVp and 90 kVp x-ray tube voltages, respectively. It was shown that charge integrating results in 1.8% less beam hardening artefacts from bone inserts (i.e., CT numbers in the 'shadow' of the bone are less by 1.8% as compared to CT numbers over the periphery of the image), as compared to photon counting. However, optimal photon energy weighting, which provides highest SNR, results in 7.7% higher beam hardening artefacts from bone inserts as compared to photon counting. The magnitude of the 'cupping' artefacts was lower by 1% for charge integrating and higher by 6.1% for energy weighting acquisitions as compared to photon counting. Only the photon counting systems provide an accurate representation of the beam hardening effect due to its flat energy weighting. Because of their energy dependent weighting factors, the charge integrating and energy weighting systems do not provide accurate

  2. Beam hardening artefacts in computed tomography with photon counting, charge integrating and energy weighting detectors: a simulation study

    NASA Astrophysics Data System (ADS)

    Shikhaliev, Polad M.

    2005-12-01

    Photon counting x-ray imaging provides efficient rejection of the electronics noise, no pulse height (Swank) noise, less noise due to optimal photon energy weighting and the possibility of energy resolved image acquisition. These advantages apply also to CT when projection data are acquired using a photon counting detector. However, photon counting detectors assign a weighting factor of 1 to all detected photons whereas the weighting factor of a charge integrating detector is proportional to the energy of the detected photon. Therefore, data collected by photon counting and charge integrating detectors represent the 'hardening' of the photon beam passed through the object differently. This affects the beam hardening artefacts in the reconstructed CT images. This work represents the first comparative evaluation of the effect of photon counting, charge integrating and energy weighting photon detectors on beam hardening artefacts in CT. Beam hardening artefacts in CT images were evaluated for 20 cm and 14 cm diameter water cylinders with bone and low contrast inserts, at 120 kVp and 90 kVp x-ray tube voltages, respectively. It was shown that charge integrating results in 1.8% less beam hardening artefacts from bone inserts (i.e., CT numbers in the 'shadow' of the bone are less by 1.8% as compared to CT numbers over the periphery of the image), as compared to photon counting. However, optimal photon energy weighting, which provides highest SNR, results in 7.7% higher beam hardening artefacts from bone inserts as compared to photon counting. The magnitude of the 'cupping' artefacts was lower by 1% for charge integrating and higher by 6.1% for energy weighting acquisitions as compared to photon counting. Only the photon counting systems provide an accurate representation of the beam hardening effect due to its flat energy weighting. Because of their energy dependent weighting factors, the charge integrating and energy weighting systems do not provide accurate

  3. Low-Energy Enhancement in the Photon Strength of Mo95

    NASA Astrophysics Data System (ADS)

    Wiedeking, M.; Bernstein, L. A.; Krtička, M.; Bleuel, D. L.; Allmond, J. M.; Basunia, M. S.; Burke, J. T.; Fallon, P.; Firestone, R. B.; Goldblum, B. L.; Hatarik, R.; Lake, P. T.; Lee, I.-Y.; Lesher, S. R.; Paschalis, S.; Petri, M.; Phair, L.; Scielzo, N. D.

    2012-04-01

    A new experimental technique is presented using proton-γ-γ correlations from Mo94(d,p)Mo95 reactions which allows for the model-independent extraction of the photon strength function at various excitation energies using primary γ-ray decay from the quasicontinuum to individual low-lying levels. Detected particle energies provide the entrance excitation energies into the residual nucleus while γ-ray transitions from low-lying levels specify the discrete states being fed. Results strongly support the existence of the previously reported low-energy enhancement in the photon strength function.

  4. Measurements of high energy photons in Z-pinch experiments on primary test stand

    SciTech Connect

    Si, Fenni Zhang, Chuanfei; Xu, Rongkun; Yuan, Xi; Huang, Zhanchang; Xu, Zeping; Ye, Fan; Yang, Jianlun; Ning, Jiamin; Hu, Qingyuan; Zhu, Xuebin

    2015-08-15

    High energy photons are measured for the first time in wire-array Z-pinch experiments on the Primary Test Stand (PTS) which delivers a current up to 8 MA with a rise time of 70 ns. A special designed detecting system composed of three types of detectors is used to measure the average energy, intensity, and pulse waveform of high energy photons. Results from Pb-TLD (thermoluminescence dosimeter) detector indicate that the average energy is 480 keV (±15%). Pulse shape of high energy photons is measured by the photodiode detector consisted of scintillator coupled with a photodiode, and it is correlated with soft x-ray power by the same timing signal. Intensity is measured by both TLD and the photodiode detector, showing good accordance with each other, and it is 10{sup 10} cm{sup −2} (±20%) at 2 m in the horizontal direction. Measurement results show that high energy photons are mainly produced in pinch regions due to accelerated electrons. PTS itself also produces high energy photons due to power flow electrons, which is one order smaller in amplitude than those from pinch region.

  5. Neutron spectral measurements in an intense photon field associated with a high-energy x-ray radiotherapy machine.

    PubMed

    Holeman, G R; Price, K W; Friedman, L F; Nath, R

    1977-01-01

    High-energy x-ray radiotherapy machines in the supermegavoltage region generate complex neutron energy spectra which make an exact evaluation of neutron shielding difficult. Fast neutrons resulting from photonuclear reactions in the x-ray target and collimators undergo successive collisions in the surrounding materials and are moderated by varying amounts. In order to examine the neutron radiation exposures quantitatively, the neutron energy spectra have been measured inside and outside the treatment room of a Sagittaire medical linear accelerator (25-MV x rays) located at Yale-New Haven Hospital. The measurements were made using a Bonner spectrometer consisting of 2-, 3-, 5-, 8-, 10- and 12-in.-diameter polyethylene spheres with 6Li and 7Li thermoluminescent dosimeter (TLD) chips at the centers, in addition to bare and cadmium-covered chips. The individual TLD chips were calibrated for neutron and photon response. The spectrometer was calibrated using a known PuBe spectrum Spectrometer measurements were made at Yale Electron Accelerator Laboratory and results compared with a neutron time-of-flight spectrometer and an activation technique. The agreement between the results from these independent methods is found to be good, except for the measurements in the direct photon beam. Quality factors have been inferred for the neutron fields inside and outside the treatment room. Values of the inferred quality factors fall primarily between 4 and 8, depending on location.

  6. Energy spectrum and mass composition of high-energy cosmic rays

    NASA Astrophysics Data System (ADS)

    Haungs, Andreas; Rebel, Heinigerd; Roth, Markus

    2003-07-01

    Primary cosmic rays above energies of about 100 TeV are investigated by observations of extensive air showers (EAS) using large area ground based detector installations for registering various components of the EAS cascade development. By such indirect studies of the primary cosmic rays a steepening of the power-law spectrum at around 3-5 PeV, known as the knee, has been identified. At higher energies around 5 EeV there appears a further change of the spectral index towards a flattening of the spectrum, called the ankle. The energy region above ca 50 EeV, where a cut-off of the cosmic ray spectrum (Greisen-Zatsepin-Kuz'min (GZK) cut-off) is theoretically predicted, is of particular current interest and provides an astrophysical enigma, since obviously trans-GZK events have been observed. Any explanation of these features of the cosmic ray spectrum needs sufficiently detailed knowledge of the shape of the spectrum and of the variation of the mass composition of cosmic rays. In this paper different experimental approaches deducing mass and energy sensitive information from the EAS experiments and their results are discussed. The experiments involve measurements of secondary particle distributions at various observation levels and of muons by deep underground detectors, as well as measurements of air Cherenkov light and, in particular at higher energies, of air fluorescence light emitted during the EAS development. Recently, methods for analysing multi-dimensional EAS parameter distributions have been favoured. They take into account correlations of different EAS parameters and, in particular by non-parametric techniques, also the influence of the intrinsic fluctuation of the air shower development. This paper illustrates the application of such methods in a coherent view of recent results. The advanced analysing methods are corroborated by hybrid experimental set-ups registering a larger set of different EAS observables simultaneously in an event-by-event mode. In

  7. High-energy photon radiography system using laser-Compton scattering for inspection of bulk materials

    NASA Astrophysics Data System (ADS)

    Toyokawa, Hiroyuki; Ohgaki, Hideaki; Mikado, Tomohisa; Yamada, Kawakatsu

    2002-09-01

    Transmission radiography of bulk materials using continuously energy-tunable quasimonochromatic photon beams has been performed with the photons of a few tens MeV. The photon beam is generated with the laser-Compton scattering of the 300-800 MeV electrons in the electron storage ring "TERAS" with laser lights. The present radiography system is applicable to an inspection of bulk materials and to nondestructive testing of large industrial products. The effectiveness of the method has been examined using metals, ceramics, and concrete blocks. The spatial resolution of the radiography system was measured to be 650 mum using a 1 mm collimator system.

  8. Analysis of triplet production by a circularly polarized photon at high energies

    SciTech Connect

    Gakh, G. I.; Konchatnij, M. I.; Levandovsky, I. S.; Merenkov, N. P.

    2013-07-15

    The possibility in principle of determining the circular polarization of a high-energy photon by measuring the created electron polarization in the process of triplet photoproduction {gamma} + e{sup -} {yields} e{sup +}e{sup -} + e{sup -} is investigated. The respective event number, which depends on polarization states of the photon and the created electron, does not decrease as the photon energy increases, and this circumstance can ensure the high efficiency in such experiments. We study different double and single distributions of the created electron (or positron), which allow probing the photon circular polarization and measuring its magnitude (the Stokes parameter {xi}{sub 2}) using the technique of Sudakov variables. Some experimental setups with different rules for event selection are studied and the corresponding numerical estimations are presented.

  9. The role of x-ray Swank factor in energy-resolving photon-counting imaging

    SciTech Connect

    Tanguay, Jesse; Kim, Ho Kyung; Cunningham, Ian. A.

    2010-12-15

    Purpose: Energy-resolved x-ray imaging has the potential to improve contrast-to-noise ratio by measuring the energy of each interacting photon and applying optimal weighting factors. The success of energy-resolving photon-counting (EPC) detectors relies on the ability of an x-ray detector to accurately measure the energy of each interacting photon. However, the escape of characteristic emissions and Compton scatter degrades spectral information. This article makes the theoretical connection between accuracy and imprecision in energy measurements with the x-ray Swank factor for a-Se, Si, CdZnTe, and HgI{sub 2}-based detectors. Methods: For a detector that implements adaptive binning to sum all elements in which x-ray energy is deposited for a single interaction, energy imprecision is shown to depend on the Swank factor for a large element with x rays incident at the center. The response function for each converter material is determined using Monte Carlo methods and used to determine energy accuracy, Swank factor, and relative energy imprecision in photon-energy measurements. Results: For each material, at energies below the respective K edges, accuracy is close to unity and imprecision is only a few percent. Above the K-edge energies, characteristic emission results in a drop in accuracy and precision that depends on escape probability. In Si, and to some extent a-Se, Compton-scatter escape also degrades energy precision with increasing energy. The influence of converter thickness on energy accuracy and imprecision is modest for low-Z materials but becomes important when using high-Z materials at energies greater than the K-edge energies. Conclusions: Accuracy and precision in energy measurements by EPC detectors are determined largely by the energy-dependent x-ray Swank factor. Modest decreases in the Swank factor (5%-15%) result in large increases in relative imprecision (30%-40%).

  10. Spectrum and ionization rate of low-energy Galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Nath, Biman B.; Gupta, Nayantara; Biermann, Peter L.

    2012-09-01

    We consider the rate of ionization of diffuse and molecular clouds in the interstellar medium by Galactic cosmic rays (GCRs) in order to constrain its low-energy spectrum. We extrapolate the GCR spectrum obtained from PAMELA at high energies (≥200 GeV nucleon-1) and a recently derived GCR proton flux at 1-200 GeV from observations of gamma-rays from molecular clouds, and find that the observed average Galactic ionization rate can be reconciled with this GCR spectrum if there is a low-energy cut-off for protons at 10-100 MeV. We also identify the flattening below a few GeV as being due to (a) decrease of the diffusion coefficient and dominance of convective loss at low energy and (b) the expected break in energy spectrum for a constant spectral index in momentum. We show that the inferred CR proton spectrum of ? for Ekin≤ few GeV is consistent with a power-law spectrum in momentum p-2.45± 0.4, which we identify as the spectrum at source. Diffusion loss at higher energies then introduces a steepening by E-α with α˜ 1/3, making it consistent with high-energy measurements.

  11. Investigating possible improvements in image quality with energy-weighting photon-counting breast CT

    NASA Astrophysics Data System (ADS)

    Glick, Stephen J.; Kalluri, Kesava

    2011-03-01

    In an effort to improve the early stage detection and diagnosis of breast cancer, a number of research groups have been investigating the use of x-ray computerized tomography (CT) systems dedicated for use in imaging the breast. For a number of reasons, the performance of energy integrating detectors are sub-optimal for use in CT imaging of the breast. It is expected that the next generation of x-ray detectors for digital radiography and CT will have the capability of counting individually measured photons and recording their energy. In this paper, we used computer simulations to evaluate improvements in image quality that can be attained using energy weighting photon counting detectors for breast CT and a lower kVp settings. Results from this study suggest that improvements in SNR performance can be attained with photon counting detectors as compared to energy integrating detectors.

  12. Energy spectrum of cascades generated by muons in Baksan underground scintillation telescope

    NASA Technical Reports Server (NTRS)

    Bakatanov, V. N.; Chudakov, A. E.; Novoseltsev, Y. F.; Novoseltseva, M. V.; Achkasov, V. M.; Semenov, A. M.; Stenkin, Y. V.

    1985-01-01

    Spectrum of cascades generated by cosmic ray muons underground is presented. The mean zenith angle of the muon arrival is theta=35 deg the depth approx. 1000 hg/sq cm. In cascades energy range 700 GeV the measured spectrum is in agreement with the sea-level integral muon spectrum index gamma=3.0. Some decrease of this exponent has been found in the range 4000 Gev.

  13. Electron escape depth variation in thin SiO2 films measured with variable photon energy

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.; Grunthaner, F. J.; Pianetta, P.; Johansson, L. I.; Lindau, I.

    1984-01-01

    A double crystal monochromator at the Stanford Synchrotron Radiation Laboratory is used to study the Si/SiO2 interface, using photon energies of hv = 1950-3700 eV. This photon energy range allows interfaces to be observed through oxide layers 50 A thick or more. Variations in electron escape depth and/or oxide density as a function of distance from the interface are observed over the entire kinetic energy range (100-3600 eV). These differences are attributed to a strained oxide layer near the interface.

  14. Cherenkov detectors for spatial imaging applications using discrete-energy photons

    NASA Astrophysics Data System (ADS)

    Rose, Paul B.; Erickson, Anna S.

    2016-08-01

    Cherenkov detectors can offer a significant advantage in spatial imaging applications when excellent timing response, low noise and cross talk, large area coverage, and the ability to operate in magnetic fields are required. We show that an array of Cherenkov detectors with crude energy resolution coupled with monochromatic photons resulting from a low-energy nuclear reaction can be used to produce a sharp image of material while providing large and inexpensive detector coverage. The analysis of the detector response to relative transmission of photons with various energies allows for reconstruction of material's effective atomic number further aiding in high-Z material identification.

  15. Measurement of energy and direction distribution of neutron and photon fluences in workplace fields.

    PubMed

    Luszik-Bhadra, M; Reginatto, M; Lacoste, V

    2004-01-01

    Within the EU Project EVIDOS, a spectrometer with 24 silicon detectors mounted on the surface of a polyethylene sphere is used for the determination of the energy and direction distribution of neutrons and photons. It has been characterized with respect to neutron radiation with energies from thermal up to 15 MeV and to photon radiation with energies from 65 keV to 6 MeV. The first measurements described here were performed in the simulated workplace field, CANEL, at Cadarache, with the purpose of checking the instrument and the unfolding procedures.

  16. Cosmological effects of scalar-photon couplings: dark energy and varying-α Models

    SciTech Connect

    Avgoustidis, A.; Martins, C.J.A.P.; Monteiro, A.M.R.V.L.; Vielzeuf, P.E.; Luzzi, G. E-mail: Carlos.Martins@astro.up.pt E-mail: up110370652@alunos.fc.up.pt

    2014-06-01

    We study cosmological models involving scalar fields coupled to radiation and discuss their effect on the redshift evolution of the cosmic microwave background temperature, focusing on links with varying fundamental constants and dynamical dark energy. We quantify how allowing for the coupling of scalar fields to photons, and its important effect on luminosity distances, weakens current and future constraints on cosmological parameters. In particular, for evolving dark energy models, joint constraints on the dark energy equation of state combining BAO radial distance and SN luminosity distance determinations, will be strongly dominated by BAO. Thus, to fully exploit future SN data one must also independently constrain photon number non-conservation arising from the possible coupling of SN photons to the dark energy scalar field. We discuss how observational determinations of the background temperature at different redshifts can, in combination with distance measures data, set tight constraints on interactions between scalar fields and photons, thus breaking this degeneracy. We also discuss prospects for future improvements, particularly in the context of Euclid and the E-ELT and show that Euclid can, even on its own, provide useful dark energy constraints while allowing for photon number non-conservation.

  17. Photocurrent spectrum study of a quantum dot single-photon detector based on resonant tunneling effect with near-infrared response

    SciTech Connect

    Weng, Q. C.; An, Z. H. E-mail: luwei@mail.sitp.ac.cn; Xiong, D. Y.; Zhu, Z. Q.; Zhang, B.; Chen, P. P.; Li, T. X.; Lu, W. E-mail: luwei@mail.sitp.ac.cn

    2014-07-21

    We present the photocurrent spectrum study of a quantum dot (QD) single-photon detector using a reset technique which eliminates the QD's “memory effect.” By applying a proper reset frequency and keeping the detector in linear-response region, the detector's responses to different monochromatic light are resolved which reflects different detection efficiencies. We find the reset photocurrent tails up to 1.3 μm wavelength and near-infrared (∼1100 nm) single-photon sensitivity is demonstrated due to interband transition of electrons in QDs, indicating the device a promising candidate both in quantum information applications and highly sensitive imaging applications operating in relative high temperatures (>80 K).

  18. Low-energy break in the spectrum of Galactic cosmic rays.

    PubMed

    Neronov, A; Semikoz, D V; Taylor, A M

    2012-02-01

    Measurements of the low-energy spectrum of Galactic cosmic rays (GCRs) by detectors on or near Earth are affected by solar modulation. To overcome this difficulty, we consider nearby molecular clouds as GCR detectors outside the Solar System. Using γ-ray observations of the clouds by the Fermi telescope, we derive the spectrum of GCRs in the clouds from the observed γ-ray emission spectrum. We find that the GCR spectrum has a low-energy break with the spectral slope hardening by ΔΓ=1.1±0.3 at an energy of E=9±3  GeV. Detection of a low-energy break enables a measurement of GCR energy density in the interstellar space U=0.9±0.3  eV/cm{3}.

  19. Energy-based dosimetry of low-energy, photon-emitting brachytherapy sources

    NASA Astrophysics Data System (ADS)

    Malin, Martha J.

    Model-based dose calculation algorithms (MBDCAs) for low-energy, photon-emitting brachytherapy sources have advanced to the point where the algorithms may be used in clinical practice. Before these algorithms can be used, a methodology must be established to verify the accuracy of the source models used by the algorithms. Additionally, the source strength metric for these algorithms must be established. This work explored the feasibility of verifying the source models used by MBDCAs by measuring the differential photon fluence emitted from the encapsulation of the source. The measured fluence could be compared to that modeled by the algorithm to validate the source model. This work examined how the differential photon fluence varied with position and angle of emission from the source, and the resolution that these measurements would require for dose computations to be accurate to within 1.5%. Both the spatial and angular resolution requirements were determined. The techniques used to determine the resolution required for measurements of the differential photon fluence were applied to determine why dose-rate constants determined using a spectroscopic technique disagreed with those computed using Monte Carlo techniques. The discrepancy between the two techniques had been previously published, but the cause of the discrepancy was not known. This work determined the impact that some of the assumptions used by the spectroscopic technique had on the accuracy of the calculation. The assumption of isotropic emission was found to cause the largest discrepancy in the spectroscopic dose-rate constant. Finally, this work improved the instrumentation used to measure the rate at which energy leaves the encapsulation of a brachytherapy source. This quantity is called emitted power (EP), and is presented as a possible source strength metric for MBDCAs. A calorimeter that measured EP was designed and built. The theoretical framework that the calorimeter relied upon to measure EP

  20. The high energy X-ray spectrum of the Crab Nebula observed from OSO 8

    NASA Technical Reports Server (NTRS)

    Dolan, J. F.; Crannell, L. J.; Dennis, B. R.; Orwig, L. E.; Maurer, G. S.; Frost, K. J.

    1977-01-01

    The X-ray spectrum of the Crab Nebula was measured with the scintillation spectrometer on board the OSO-8 satellite. The total emission of the X-ray source shows no long term variability. The spectrum itself can be described by a single power law out to energies of at least 500 keV.

  1. Energy response calibration of photon-counting detectors using X-ray fluorescence: a feasibility study

    PubMed Central

    Cho, H-M; Ding, H; Ziemer, BP; Molloi, S

    2014-01-01

    Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using X-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for X-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm2 in detection area. The angular dependence of X-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded X-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of X-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of X-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic X-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the X-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory. PMID:25369288

  2. Energy response calibration of photon-counting detectors using x-ray fluorescence: a feasibility study.

    PubMed

    Cho, H-M; Ding, H; Ziemer, B P; Molloi, S

    2014-12-01

    Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using x-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for x-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm(2) in detection area. The angular dependence of x-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded x-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of x-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of x-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic x-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the x-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory.

  3. Inclusive photon production at forward rapidities in pp collisions at LHC energies with the ALICE experiment

    NASA Astrophysics Data System (ADS)

    Sudipan Dethe ALICE Collaboration

    2016-04-01

    Measurements of multiplicity and pseudorapidity distributions of particles produced in pp collisions are important for the study of particle production mechanisms and to obtain baseline distributions to be compared with those from heavy-ion collisions. The inclusive photon measurements (dominated by π0 decays) are complementary to the charged particle measurements. The present work focuses on the forward rapidity region with comparisons to different models such as PYTHIA and PHOJET. We report the measurements of multiplicity and pseudorapidity distributions of inclusive photons using the ALICE Photon Multiplicity Detector (PMD) at forward rapidities (2.3 < η < 3.9) in pp collisions at = 0.9, 2.76 and 7 TeV. It is observed that the photon multiplicity distributions are well described by negative binomial distributions (NBD). Multiplicity distributions are studied in terms of KNO variables for each energy. It is shown that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and power law dependence. The results are compared to different model predictions. These models reproduce experimental results at lower energy while they are not accurate at higher energies.

  4. Photonic simulation of topological superconductor edge state and zero-energy mode at a vortex.

    PubMed

    Tan, Wei; Chen, Liang; Ji, Xia; Lin, Hai-Qing

    2014-12-09

    Photonic simulations of quantum Hall edge states and topological insulators have inspired considerable interest in recent years. Interestingly, there are theoretical predictions for another type of topological states in topological superconductors, but debates over their experimental observations still remain. Here we investigate the photonic analogue of the p(x) + ip(y) model of topological superconductor. Two essential characteristics of topological superconductor, particle-hole symmetry and p(x) + ip(y) pairing potentials, are well emulated in photonic systems. Its topological features are presented by chiral edge state and zero-energy mode at a vortex. This work may fertilize the study of photonic topological states, and open up the possibility for emulating wave behaviors in superconductors.

  5. Photonic simulation of topological superconductor edge state and zero-energy mode at a vortex

    PubMed Central

    Tan, Wei; Chen, Liang; Ji, Xia; Lin, Hai-Qing

    2014-01-01

    Photonic simulations of quantum Hall edge states and topological insulators have inspired considerable interest in recent years. Interestingly, there are theoretical predictions for another type of topological states in topological superconductors, but debates over their experimental observations still remain. Here we investigate the photonic analogue of the px + ipy model of topological superconductor. Two essential characteristics of topological superconductor, particle-hole symmetry and px + ipy pairing potentials, are well emulated in photonic systems. Its topological features are presented by chiral edge state and zero-energy mode at a vortex. This work may fertilize the study of photonic topological states, and open up the possibility for emulating wave behaviors in superconductors. PMID:25488408

  6. Effective atomic numbers for low-energy total photon interactions in human tissues

    SciTech Connect

    Yang, N.C.; Leichner, P.K.; Hawkins, W.G.

    1987-09-01

    A new method is introduced in which the total photon interaction cross sections per electron of human tissues are used to define effective atomic numbers for blood, bone, brain, fat, heart, kidney, liver, lung, muscle, ovary, pancreas, spleen, and water. These effective atomic numbers are equal within 4% from 10 to 200 keV in each soft tissue, whereas for bones of different chemical compositions the variation ranges from 2.86% to 5.03%. This effective atomic number definition is less energy dependent than a previous definition based on the total photon interaction cross section per atom averaged over all elements in the tissue, from which the computed effective atomic numbers varied by as much as 50% (in bone) as a function of photon energy over the energy range from 10 to 200 keV.

  7. Effective atomic numbers for low-energy total photon interactions in human tissues.

    PubMed

    Yang, N C; Leichner, P K; Hawkins, W G

    1987-01-01

    A new method is introduced in which the total photon interaction cross sections per electron of human tissues are used to define effective atomic numbers for blood, bone, brain, fat, heart, kidney, liver, lung, muscle, ovary, pancreas, spleen, and water. These effective atomic numbers are equal within 4% from 10 to 200 keV in each soft tissue, whereas for bones of different chemical compositions the variation ranges from 2.86% to 5.03%. This effective atomic number definition is less energy dependent than a previous definition based on the total photon interaction cross section per atom averaged over all elements in the tissue, from which the computed effective atomic numbers varied by as much as 50% (in bone) as a function of photon energy over the energy range from 10 to 200 keV.

  8. Effective atomic numbers for low-energy total photon interactions in human tissues.

    PubMed

    Yang, N C; Leichner, P K; Hawkins, W G

    1987-01-01

    A new method is introduced in which the total photon interaction cross sections per electron of human tissues are used to define effective atomic numbers for blood, bone, brain, fat, heart, kidney, liver, lung, muscle, ovary, pancreas, spleen, and water. These effective atomic numbers are equal within 4% from 10 to 200 keV in each soft tissue, whereas for bones of different chemical compositions the variation ranges from 2.86% to 5.03%. This effective atomic number definition is less energy dependent than a previous definition based on the total photon interaction cross section per atom averaged over all elements in the tissue, from which the computed effective atomic numbers varied by as much as 50% (in bone) as a function of photon energy over the energy range from 10 to 200 keV. PMID:3683305

  9. Cross two photon absorption in a silicon photonic crystal waveguide fiber taper coupler with a physical junction

    SciTech Connect

    Sarkissian, Raymond O'Brien, John

    2015-01-21

    Cross two photon absorption in silicon is characterized using a tapered fiber photonic crystal silicon waveguide coupler. There is a physical junction between the tapered fiber and the waveguide constituting a stand-alone device. This device is used to obtain the spectrum for cross two photon absorption coefficient per unit volume of interaction between photons of nondegenerate energy. The corresponding Kerr coefficient per unit volume of interaction is also experimentally extracted. The thermal resistance of the device is also experimentally determined and the response time of the device is estimated for on-chip all-optical signal processing and data transfer between optical signals of different photon energies.

  10. Signature-based search for delayed photons in exclusive photon plus missing transverse energy events from pp¯ collisions with s=1.96TeV

    NASA Astrophysics Data System (ADS)

    Aaltonen, T.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J. A.; Arisawa, T.; Artikov, A.; Asaadi, J.; Ashmanskas, W.; Auerbach, B.; Aurisano, A.; Azfar, F.; Badgett, W.; Bae, T.; Barbaro-Galtieri, A.; Barnes, V. E.; Barnett, B. A.; Barria, P.; Bartos, P.; Bauce, M.; Bedeschi, F.; Behari, S.; Bellettini, G.; Bellinger, J.; Benjamin, D.; Beretvas, A.; Bhatti, A.; Bland, K. R.; Blumenfeld, B.; Bocci, A.; Bodek, A.; Bortoletto, D.; Boudreau, J.; Boveia, A.; Brigliadori, L.; Bromberg, C.; Brucken, E.; Budagov, J.; Budd, H. S.; Burkett, K.; Busetto, G.; Bussey, P.; Butti, P.; Buzatu, A.; Calamba, A.; Camarda, S.; Campanelli, M.; Canelli, F.; Carls, B.; Carlsmith, D.; Carosi, R.; Carrillo, S.; Casal, B.; Casarsa, M.; Castro, A.; Catastini, P.; Cauz, D.; Cavaliere, V.; Cavalli-Sforza, M.; Cerri, A.; Cerrito, L.; Chen, Y. C.; Chertok, M.; Chiarelli, G.; Chlachidze, G.; Cho, K.; Chokheli, D.; Ciocci, M. A.; Clark, A.; Clarke, C.; Convery, M. E.; Conway, J.; Corbo, M.; Cordelli, M.; Cox, C. A.; Cox, D. J.; Cremonesi, M.; Cruz, D.; Cuevas, J.; Culbertson, R.; d'Ascenzo, N.; Datta, M.; De Barbaro, P.; Demortier, L.; Deninno, M.; d'Errico, M.; Devoto, F.; Di Canto, A.; Di Ruzza, B.; Dittmann, J. R.; D'Onofrio, M.; Donati, S.; Dorigo, M.; Driutti, A.; Ebina, K.; Edgar, R.; Elagin, A.; Erbacher, R.; Errede, S.; Esham, B.; Eusebi, R.; Farrington, S.; Fernández Ramos, J. P.; Field, R.; Flanagan, G.; Forrest, R.; Franklin, M.; Freeman, J. C.; Frisch, H.; Funakoshi, Y.; Garfinkel, A. F.; Garosi, P.; Gerberich, H.; Gerchtein, E.; Giagu, S.; Giakoumopoulou, V.; Gibson, K.; Ginsburg, C. M.; Giokaris, N.; Giromini, P.; Giurgiu, G.; Glagolev, V.; Glenzinski, D.; Gold, M.; Goldin, D.; Golossanov, A.; Gomez, G.; Gomez-Ceballos, G.; Goncharov, M.; González López, O.; Gorelov, I.; Goshaw, A. T.; Goulianos, K.; Gramellini, E.; Grinstein, S.; Grosso-Pilcher, C.; Group, R. C.; Guimaraes da Costa, J.; Hahn, S. R.; Han, J. Y.; Happacher, F.; Hara, K.; Hare, M.; Harr, R. F.; Harrington-Taber, T.; Hatakeyama, K.; Hays, C.; Heinrich, J.; Herndon, M.; Hocker, A.; Hong, Z.; Hopkins, W.; Hou, S.; Hughes, R. E.; Husemann, U.; Hussein, M.; Huston, J.; Introzzi, G.; Iori, M.; Ivanov, A.; James, E.; Jang, D.; Jayatilaka, B.; Jeon, E. J.; Jindariani, S.; Jones, M.; Joo, K. K.; Jun, S. Y.; Junk, T. R.; Kambeitz, M.; Kamon, T.; Karchin, P. E.; Kasmi, A.; Kato, Y.; Ketchum, W.; Keung, J.; Kilminster, B.; Kim, D. H.; Kim, H. S.; Kim, J. E.; Kim, M. J.; Kim, S. B.; Kim, S. H.; Kim, Y. J.; Kim, Y. K.; Kimura, N.; Kirby, M.; Knoepfel, K.; Kondo, K.; Kong, D. J.; Konigsberg, J.; Kotwal, A. V.; Kreps, M.; Kroll, J.; Kruse, M.; Kuhr, T.; Kurata, M.; Laasanen, A. T.; Lammel, S.; Lancaster, M.; Lannon, K.; Latino, G.; Lee, H. S.; Lee, J. S.; Leo, S.; Leone, S.; Lewis, J. D.; Limosani, A.; Lipeles, E.; Lister, A.; Liu, H.; Liu, Q.; Liu, T.; Lockwitz, S.; Loginov, A.; Lucà, A.; Lucchesi, D.; Lueck, J.; Lujan, P.; Lukens, P.; Lungu, G.; Lys, J.; Lysak, R.; Madrak, R.; Maestro, P.; Malik, S.; Manca, G.; Manousakis-Katsikakis, A.; Margaroli, F.; Marino, P.; Martínez, M.; Matera, K.; Mattson, M. E.; Mazzacane, A.; Mazzanti, P.; McNulty, R.; Mehta, A.; Mehtala, P.; Mesropian, C.; Miao, T.; Mietlicki, D.; Mitra, A.; Miyake, H.; Moed, S.; Moggi, N.; Moon, C. S.; Moore, R.; Morello, M. J.; Mukherjee, A.; Muller, Th.; Murat, P.; Mussini, M.; Nachtman, J.; Nagai, Y.; Naganoma, J.; Nakano, I.; Napier, A.; Nett, J.; Neu, C.; Nigmanov, T.; Nodulman, L.; Noh, S. Y.; Norniella, O.; Oakes, L.; Oh, S. H.; Oh, Y. D.; Oksuzian, I.; Okusawa, T.; Orava, R.; Ortolan, L.; Pagliarone, C.; Palencia, E.; Palni, P.; Papadimitriou, V.; Parker, W.; Pauletta, G.; Paulini, M.; Paus, C.; Phillips, T. J.; Piacentino, G.; Pianori, E.; Pilot, J.; Pitts, K.; Plager, C.; Pondrom, L.; Poprocki, S.; Potamianos, K.; Pranko, A.; Prokoshin, F.; Ptohos, F.; Punzi, G.; Ranjan, N.; Redondo Fernández, I.; Renton, P.; Rescigno, M.; Rimondi, F.; Ristori, L.; Robson, A.; Rodriguez, T.; Rolli, S.; Ronzani, M.; Roser, R.; Rosner, J. L.; Ruffini, F.; Ruiz, A.; Russ, J.; Rusu, V.; Sakumoto, W. K.; Sakurai, Y.; Santi, L.; Sato, K.; Saveliev, V.; Savoy-Navarro, A.; Schlabach, P.; Schmidt, E. E.; Schwarz, T.; Scodellaro, L.; Scuri, F.; Seidel, S.; Seiya, Y.; Semenov, A.; Sforza, F.; Shalhout, S. Z.; Shears, T.; Shepard, P. F.; Shimojima, M.; Shochet, M.; Shreyber-Tecker, I.; Simonenko, A.; Sinervo, P.; Sliwa, K.; Smith, J. R.; Snider, F. D.; Song, H.; Sorin, V.; Stancari, M.; Denis, R. St.; Stelzer, B.; Stelzer-Chilton, O.; Stentz, D.; Strologas, J.; Sudo, Y.; Sukhanov, A.; Suslov, I.; Takemasa, K.; Takeuchi, Y.; Tang, J.; Tecchio, M.; Teng, P. K.; Thom, J.; Thomson, E.; Thukral, V.; Toback, D.; Tokar, S.; Tollefson, K.; Tomura, T.; Tonelli, D.; Torre, S.; Torretta, D.; Totaro, P.; Trovato, M.; Ukegawa, F.; Uozumi, S.; Vázquez, F.; Velev, G.; Vellidis, C.; Vernieri, C.; Vidal, M.; Vilar, R.; Vizán, J.; Vogel, M.; Volpi, G.; Wagner, P.; Wallny, R.; Wang, S. M.; Warburton, A.; Waters, D.; Wester, W. C., III; Whiteson, D.; Wicklund, A. B.; Wilbur, S.; Williams, H. H.; Wilson, J. S.; Wilson, P.; Winer, B. L.; Wittich, P.; Wolbers, S.; Wolfe, H.; Wright, T.; Wu, X.; Wu, Z.; Yamamoto, K.; Yamato, D.; Yang, T.; Yang, U. K.; Yang, Y. C.; Yao, W.-M.; Yeh, G. P.; Yi, K.; Yoh, J.; Yorita, K.; Yoshida, T.; Yu, G. B.; Yu, I.; Zanetti, A. M.; Zeng, Y.; Zhou, C.; Zucchelli, S.

    2013-08-01

    We present the first signature-based search for delayed photons using an exclusive photon plus missing transverse energy final state. Events are reconstructed in a data sample from the CDF II detector corresponding to 6.3fb-1 of integrated luminosity from s=1.96TeV proton-antiproton collisions. Candidate events are selected if they contain a photon with an arrival time in the detector larger than expected from a promptly produced photon. The mean number of events from standard model sources predicted by the data-driven background model based on the photon timing distribution is 286±24. A total of 322 events are observed. A p value of 12% is obtained, showing consistency of the data with standard model predictions.

  11. Simulating three-dimensional nonthermal high-energy photon emission in colliding-wind binaries

    SciTech Connect

    Reitberger, K.; Kissmann, R.; Reimer, A.; Reimer, O.

    2014-07-01

    Massive stars in binary systems have long been regarded as potential sources of high-energy γ rays. The emission is principally thought to arise in the region where the stellar winds collide and accelerate relativistic particles which subsequently emit γ rays. On the basis of a three-dimensional distribution function of high-energy particles in the wind collision region—as obtained by a numerical hydrodynamics and particle transport model—we present the computation of the three-dimensional nonthermal photon emission for a given line of sight. Anisotropic inverse Compton emission is modeled using the target radiation field of both stars. Photons from relativistic bremsstrahlung and neutral pion decay are computed on the basis of local wind plasma densities. We also consider photon-photon opacity effects due to the dense radiation fields of the stars. Results are shown for different stellar separations of a given binary system comprising of a B star and a Wolf-Rayet star. The influence of orbital orientation with respect to the line of sight is also studied by using different orbital viewing angles. For the chosen electron-proton injection ratio of 10{sup –2}, we present the ensuing photon emission in terms of two-dimensional projections maps, spectral energy distributions, and integrated photon flux values in various energy bands. Here, we find a transition from hadron-dominated to lepton-dominated high-energy emission with increasing stellar separations. In addition, we confirm findings from previous analytic modeling that the spectral energy distribution varies significantly with orbital orientation.

  12. Energy spectrum of the recurrent cosmic rays variation during the solar minimum 23/24

    NASA Astrophysics Data System (ADS)

    Gil, Agnieszka; Alania, Michael

    2016-07-01

    We study temporal changes of the power-law energy/ rigidity spectrum of the first three harmonics of the recurrent variation of the galactic cosmic rays (GCR) intensity during the unusual solar minimum 23/24 and compare with four previous minima. We show that the energy spectrum of the amplitudes of the recurrent variation is soft in the minimum 23/24. Moreover, while the energy spectrum of the amplitudes of the first harmonic of the recurrent variation of the GCR intensity practically behaves as during earlier four minima, the energy spectrum of the amplitudes of the second and the third harmonics demonstrate a valuable softening. We attribute this phenomenon to the decrease of an extension of heliosphere caused by the drop of the solar wind dynamic pressure during the solar minimum 23/24.

  13. Cryogenic detectors based on superconducting transition-edge sensors for time-energy-resolved single-photon counters and for dark matter searches

    NASA Astrophysics Data System (ADS)

    Cabrera, B.; Clarke, R.; Miller, A.; Nam, S. W.; Romani, R.; Saab, T.; Young, B.

    2000-05-01

    We present the recent progress using transition-edge sensors (TES) for cryogenic particle detectors. First, by directly absorbing photons in tungsten TES devices, an instrument has been made which time stamps (0.1μs) and energy resolves (0.15 eV FWHM) each photon at rates up to 10 kHz. Observations of the Crab pulsar are the first broad spectrum infrared through full optical and time resolved on any astronomical object. Second, in the CDMS (cryogenic dark matter search) experiment looking for WIMPs, large crystals of silicon and germanium are instrumented with QET (quasiparticle-trap-assisted electrothermal-feedback transition-edge sensors) phonon sensors which provide the recoil energy and location in /x,y and /z for each event. Together with an ionization readout, these detectors provide powerful discrimination capabilities against known backgrounds and they are now probing new regions for WIMP dark matter.

  14. Energy spectrum analysis of blast waves based on an improved Hilbert-Huang transform

    NASA Astrophysics Data System (ADS)

    Li, L.; Wang, F.; Shang, F.; Jia, Y.; Zhao, C.; Kong, D.

    2016-07-01

    Using the improved Hilbert-Huang transform (HHT), this paper investigates the problems of analysis and interpretation of the energy spectrum of a blast wave. It has been previously established that the energy spectrum is an effective feature by which to characterize a blast wave. In fact, the higher the energy spectra in a frequency band of a blast wave, the greater the damage to a target in the same frequency band. However, most current research focuses on analyzing wave signals in the time domain or frequency domain rather than considering the energy spectrum. We propose here an improved HHT method combined with a wavelet packet to extract the energy spectrum feature of a blast wave. When applying the HHT, the signal is first roughly decomposed into a series of intrinsic mode functions (IMFs) by empirical mode decomposition. The wavelet packet method is then performed on each IMF to eliminate noise on the energy spectrum. Second, a coefficient is introduced to remove unrelated IMFs. The energy of each instantaneous frequency can be derived through the Hilbert transform. The energy spectrum can then be obtained by adding up all the components after the wavelet packet filters and screens them through a coefficient to obtain the effective IMFs. The effectiveness of the proposed method is demonstrated by 12 groups of experimental data, and an energy attenuation model is established based on the experimental data. The improved HHT is a precise method for blast wave signal analysis. For other shock wave signals from blasting experiments, an energy frequency time distribution and energy spectrum can also be obtained through this method, allowing for more practical applications.

  15. MicroCT with energy-resolved photon-counting detectors

    PubMed Central

    Wang, X; Meier, D; Mikkelsen, S; Maehlum, G E; Wagenaar, D J; Tsui, BMW; Patt, B E; Frey, E C

    2011-01-01

    The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with Kabsorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences. PMID:21464527

  16. In vivo imaging of cerebral energy metabolism with two-photon fluorescence lifetime microscopy of NADH

    PubMed Central

    Yaseen, Mohammad A.; Sakadžić, Sava; Wu, Weicheng; Becker, Wolfgang; Kasischke, Karl A.; Boas, David A.

    2013-01-01

    Minimally invasive, specific measurement of cellular energy metabolism is crucial for understanding cerebral pathophysiology. Here, we present high-resolution, in vivo observations of autofluorescence lifetime as a biomarker of cerebral energy metabolism in exposed rat cortices. We describe a customized two-photon imaging system with time correlated single photon counting detection and specialized software for modeling multiple-component fits of fluorescence decay and monitoring their transient behaviors. In vivo cerebral NADH fluorescence suggests the presence of four distinct components, which respond differently to brief periods of anoxia and likely indicate different enzymatic formulations. Individual components show potential as indicators of specific molecular pathways involved in oxidative metabolism. PMID:23412419

  17. Double electron ionization in Compton scattering of high energy photons by helium atoms

    SciTech Connect

    Amusia, M.Y.; Mikhailov, A.I.

    1995-08-01

    The cross section for double-electron ionization of two-electron atoms and ions in Compton scattering of high energy photons is calculated. It is demonstrated that its dependence on the incoming photon frequency is the same as that for single-electron ionization. The ratio of {open_quotes}double-to-single{close_quotes} ionization in Compton scattering was found to be energy independent and almost identical with the corresponding value for photoionization. For the He atom it is 1.68%. This surprising result deserves experimental verification.

  18. Energy spectrum and transport in narrow HgTe quantum wells

    SciTech Connect

    Germanenko, A. V.; Minkov, G. M.; Rut, O. E.; Sherstobitov, A. A.; Dvoretsky, S. A.; Mikhailov, N. N.

    2015-01-15

    The results of an experimental study of the transport phenomena and the hole energy spectrum of two-dimensional systems in the quantum well of HgTe zero-gap semiconductor with normal arrangement of quantum-confinement subbands are presented. An analysis of the experimental data allows us to reconstruct the carrier energy spectrum near the hole subband extrema. The results are interpreted using the standard kP model.

  19. Collimator-free photon tomography

    DOEpatents

    Dilmanian, F. Avraham; Barbour, Randall L.

    1998-10-06

    A method of uncollimated single photon emission computed tomography includes administering a radioisotope to a patient for producing gamma ray photons from a source inside the patient. Emissivity of the photons is measured externally of the patient with an uncollimated gamma camera at a plurality of measurement positions surrounding the patient for obtaining corresponding energy spectrums thereat. Photon emissivity at the plurality of measurement positions is predicted using an initial prediction of an image of the source. The predicted and measured photon emissivities are compared to obtain differences therebetween. Prediction and comparison is iterated by updating the image prediction until the differences are below a threshold for obtaining a final prediction of the source image.

  20. Collimator-free photon tomography

    DOEpatents

    Dilmanian, F.A.; Barbour, R.L.

    1998-10-06

    A method of uncollimated single photon emission computed tomography includes administering a radioisotope to a patient for producing gamma ray photons from a source inside the patient. Emissivity of the photons is measured externally of the patient with an uncollimated gamma camera at a plurality of measurement positions surrounding the patient for obtaining corresponding energy spectrums thereat. Photon emissivity at the plurality of measurement positions is predicted using an initial prediction of an image of the source. The predicted and measured photon emissivities are compared to obtain differences therebetween. Prediction and comparison is iterated by updating the image prediction until the differences are below a threshold for obtaining a final prediction of the source image. 6 figs.

  1. Simultaneous suppression of time and energy uncertainties in a single-photon frequency-comb state

    NASA Astrophysics Data System (ADS)

    Ren, Changliang; Hofmann, Holger F.

    2014-05-01

    A single photon prepared in a time-energy state described by a frequency comb combines the extreme precision of energy defined by a single tooth of the comb with a high sensitivity to small shifts in time defined by the narrowness of a single pulse in the long sequence of pulses that describe the frequency-comb state in the time domain. We show how this simultaneous suppression of time and energy uncertainties can be described by a separation of scales, and we compare this with the suppression of uncertainties in the two-particle correlations of an entangled state. To illustrate the sensitivity of the frequency-comb states to small shifts in time and frequency, we consider the Hong-Ou-Mandel dips observed in two-photon interference when both time and frequency shifts between the input photons are varied. It is shown that the interference of two photons in equivalent frequency-comb states results in a two-dimensional Hong-Ou-Mandel dip that is narrow in both time and frequency, while the corresponding entangled photon pairs are only sensitive to temporal shifts. Frequency-comb states thus represent an alternative approach to quantum operations beyond the uncertainty limit.

  2. The cosmic ray energy spectrum between 10 14 and 10 16 eV

    NASA Astrophysics Data System (ADS)

    Glasmacher, M. A. K.; Catanese, M. A.; Chantell, M. C.; Covault, C. E.; Cronin, J. W.; Fick, B. E.; Fortson, L. F.; Fowler, J. W.; Green, K. D.; Kieda, D. B.; Matthews, J.; Newport, B. J.; Nitz, D. F.; Ong, R. A.; Oser, S.; Sinclair, D.; van der Velde, J. C.

    1999-05-01

    The energy spectrum of cosmic rays with primary energies between 10 14 eV and 10 16 eV has been studied with the CASA-MIA air shower array. The measured differential energy spectrum is a power law ( dj/dE ∝ E -y) with spectral indices γ of 2.66±0.02 below approximately 10 15 eV and 3.00±0.05 above. A new method is used for measuring primary energy derived from ground-based data in a compositionally insensitive way. In contrast with some previous reports, the "knee" of the energy spectrum does not appear sharp, but rather a smooth transition over energies from 10 15 eV to 3.0 × 10 15 eV.

  3. Electromagnetic energy and energy flows in photonic crystals made of arrays of parallel dielectric cylinders.

    PubMed

    Kuo, Chao-Hsien; Ye, Zhen

    2004-10-01

    We consider electromagnetic propagation in two-dimensional photonic crystals, formed by parallel dielectric cylinders embedded a uniform medium. The frequency band structure is computed using the standard plane-wave expansion method, and the corresponding eigenmodes are obtained subsequently. The optical flows of the eigenmodes are calculated by a direct computation approach, and several averaging schemes of the energy current are discussed. The results are compared to those obtained by the usual approach that employs a group velocity calculation. We consider both the case in which the frequency lies within passing band and the situation in which the frequency is in the range of a partial band gap. The agreements and discrepancies between various averaging schemes and the group velocity approach are discussed in detail. The results indicate that the group velocity can be obtained by an appropriate averaging method. Existing experimental methods are also discussed.

  4. PROBING THE INFLATON: SMALL-SCALE POWER SPECTRUM CONSTRAINTS FROM MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND ENERGY SPECTRUM

    SciTech Connect

    Chluba, Jens; Erickcek, Adrienne L.; Ben-Dayan, Ido

    2012-10-20

    In the early universe, energy stored in small-scale density perturbations is quickly dissipated by Silk damping, a process that inevitably generates {mu}- and y-type spectral distortions of the cosmic microwave background (CMB). These spectral distortions depend on the shape and amplitude of the primordial power spectrum at wavenumbers k {approx}< 10{sup 4} Mpc{sup -1}. Here, we study constraints on the primordial power spectrum derived from COBE/FIRAS and forecasted for PIXIE. We show that measurements of {mu} and y impose strong bounds on the integrated small-scale power, and we demonstrate how to compute these constraints using k-space window functions that account for the effects of thermalization and dissipation physics. We show that COBE/FIRAS places a robust upper limit on the amplitude of the small-scale power spectrum. This limit is about three orders of magnitude stronger than the one derived from primordial black holes in the same scale range. Furthermore, this limit could be improved by another three orders of magnitude with PIXIE, potentially opening up a new window to early universe physics. To illustrate the power of these constraints, we consider several generic models for the small-scale power spectrum predicted by different inflation scenarios, including running-mass inflation models and inflation scenarios with episodes of particle production. PIXIE could place very tight constraints on these scenarios, potentially even ruling out running-mass inflation models if no distortion is detected. We also show that inflation models with sub-Planckian field excursion that generate detectable tensor perturbations should simultaneously produce a large CMB spectral distortion, a link that could potentially be established with PIXIE.

  5. Breast Radiotherapy with Mixed Energy Photons; a Model for Optimal Beam Weighting.

    PubMed

    Birgani, Mohammadjavad Tahmasebi; Fatahiasl, Jafar; Hosseini, Seyed Mohammad; Bagheri, Ali; Behrooz, Mohammad Ali; Zabiehzadeh, Mansour; Meskani, Reza; Gomari, Maryam Talaei

    2015-01-01

    Utilization of high energy photons (>10 MV) with an optimal weight using a mixed energy technique is a practical way to generate a homogenous dose distribution while maintaining adequate target coverage in intact breast radiotherapy. This study represents a model for estimation of this optimal weight for day to day clinical usage. For this purpose, treatment planning computed tomography scans of thirty-three consecutive early stage breast cancer patients following breast conservation surgery were analyzed. After delineation of the breast clinical target volume (CTV) and placing opposed wedge paired isocenteric tangential portals, dosimeteric calculations were conducted and dose volume histograms (DVHs) were generated, first with pure 6 MV photons and then these calculations were repeated ten times with incorporating 18 MV photons (ten percent increase in weight per step) in each individual patient. For each calculation two indexes including maximum dose in the breast CTV (Dmax) and the volume of CTV which covered with 95% Isodose line (VCTV, 95%IDL) were measured according to the DVH data and then normalized values were plotted in a graph. The optimal weight of 18 MV photons was defined as the intersection point of Dmax and VCTV, 95%IDL graphs. For creating a model to predict this optimal weight multiple linear regression analysis was used based on some of the breast and tangential field parameters. The best fitting model for prediction of 18 MV photons optimal weight in breast radiotherapy using mixed energy technique, incorporated chest wall separation plus central lung distance (Adjusted R2=0.776). In conclusion, this study represents a model for the estimation of optimal beam weighting in breast radiotherapy using mixed photon energy technique for routine day to day clinical usage.

  6. Gravitaton Wave and Gravitational-Photon Interaction

    NASA Astrophysics Data System (ADS)

    Khasanov, Kholmurad

    2013-06-01

    Gravitation waves and gravitational-photon interaction with high energy photons emission is found experimentally. Super-compressibility phenomenon was studied. Spectral investigations of supersonic jets and incandescent nichrome thread and wolfram spiral were studied. The shifting of the emission spectrum was detected depending on vector of gravity. The increasing frequency of light emitted against gravity vector is measured. Uneven along the spectrum character of intensity increasing is found. Generation of short-wavelength component of the spectrum is observed in case of more power of heating. The measurements show that presented interactions have resonance nature. Our experiments demonstrate the existence resonance nature. Our experiments demonstrate the gravitation wave and generation and existence of gravitational-photon interactions. From left to right: Fig. 1-2. Visualization of the gravitation wave. Fig. 3-5. Gravitational-photon interaction in HF field.

  7. Quantum theory of the emission spectrum from quantum dots coupled to structured photonic reservoirs and acoustic phonons

    NASA Astrophysics Data System (ADS)

    Roy-Choudhury, Kaushik; Hughes, Stephen

    2015-11-01

    Electron-phonon coupling in semiconductor quantum dots plays a significant role in determining the optical properties of excited excitons, especially the spectral nature of emitted photons. This paper presents a comprehensive theory and analysis of emission spectra from artificial atoms or quantum dots coupled to structured photon reservoirs and acoustic phonons, when excited with incoherent pump fields. As specific examples of structured reservoirs, we chose a Lorentzian cavity and a slow-light coupled-cavity waveguide, which have both been explored experimentally. For the case of optical cavities, we directly compare and contrast the spectra from three well-known and distinct theoretical approaches to treat electron-phonon coupling, including a Markovian polaron master equation, a non-Markovian phonon correlation expansion technique, and a semiclassical linear susceptibility approach, and we point out the limitations of these models. For the cavity-QED polaron master equation, which treats the cavity-mode operator at the level of a system operator, we give closed form analytical solutions to the phonon-assisted scattering rates in the weak excitation approximation, fully accounting for temperature, cavity-exciton detuning, and cavity-dot coupling. We also show explicitly why the semiclassical linear susceptibility approach fails to correctly account for phonon-mediated cavity feeding. For weakly coupled cavities, we calculate the optical spectra using a more general photon reservoir polaron master-equation approach, and explain its differences from the above approaches in the low-Q limit of a Lorentzian cavity. We subsequently use this general reservoir approach to calculate the emission spectra from quantum dots coupled to slow-light photonic crystal waveguides, which demonstrate a number of striking photon-phonon coupling effects.

  8. ENERGY SPECTRUM OF ENERGETIC PARTICLES ACCELERATED BY SHOCK WAVES: FROM FOCUSED TRANSPORT TO DIFFUSIVE ACCELERATION

    SciTech Connect

    Zuo Pingbing; Zhang Ming; Gamayunov, Konstantin; Rassoul, Hamid; Luo Xi

    2011-09-10

    The focused transport equation (FTE) includes all the necessary physics for modeling the shock acceleration of energetic particles with a unified description of first-order Fermi acceleration, shock drift acceleration, and shock surfing acceleration. It can treat the acceleration and transport of particles with an anisotropic distribution. In this study, the energy spectrum of pickup ions accelerated at shocks of various obliquities is investigated based on the FTE. We solve the FTE by using a stochastic approach. The shock acceleration leads to a two-component energy spectrum. The low-energy component of the spectrum is made up of particles that interact with shock one to a few times. For these particles, the pitch angle distribution is highly anisotropic, and the energy spectrum is variable depending on the momentum and pitch angle of injected particles. At high energies, the spectrum approaches a power law consistent with the standard diffusive shock acceleration (DSA) theory. For a parallel shock, the high-energy component of the power-law spectrum, with the spectral index being the same as the prediction of DSA theory, starts just a few times the injection speed. For an oblique or quasi-perpendicular shock, the high-energy component of the spectrum exhibits a double power-law distribution: a harder power-law spectrum followed by another power-law spectrum with a slope the same as the spectral index of DSA. The shock acceleration will eventually go into the DSA regime at higher energies even if the anisotropy is not small. The intensity of the energy spectrum given by the FTE, in the high-energy range where particles get efficient acceleration in the DSA regime, is different from that given by the standard DSA theory for the same injection source. We define the injection efficiency {eta} as the ratio between them. For a parallel shock, the injection efficiency is less than 1, but for an oblique shock or a quasi-perpendicular shock it could be greater.

  9. Ultra High Energy Cosmic Ray, Neutrino, and Photon Propagation and the Multi-Messenger Approach

    SciTech Connect

    Taylor, Andrew; De Castro, Alexandra; Castillo-Ruiz, Edith

    2009-04-30

    The propagation of UHECR nuclei for A = 1(protons) to A = 56(iron) from cosmological sources through extragalactic space is discussed in the first lecture. This is followed in the second and third lectures by a consideration of the generation and propagation of secondary particles produced via the UHECR loss interactions. In the second lecture we focus on the generation of the diffuse cosmogenic UHE-neutrino flux. In the third lecture we investigate the arriving flux of UHE-photon flux at Earth. In the final lecture the results of the previous lectures are put together in order to provide new insights into UHECR sources. The first of these providing a means with which to investigate the local population of UHECR sources through the measurement of the UHECR spectrum and their photon fraction at Earth. The second of these providing contraints on the UHECR source radiation fields through the possible observation at Earth of UHECR nuclei.

  10. Energy spectrum transfer equations of solar wind turbulence

    NASA Technical Reports Server (NTRS)

    Tu, C.-Y.

    1995-01-01

    The recent studies of transfer equations for solar wind magnetohydrodynamic (MHD) turbulence are reviewed with emphasis on the comparison with the statistical observational results. Helios and Voyager missions provide an opportunity to study the the radial evolution of the power spectrum. the cross-helicity the Alfven ratio and the minimum variance direction. Spectrum transfer equations are considered as a tool to explore the nature of this radial evolution of the fluctuations. The transfer equations are derived from incompressible MHD equations. Generally one needs to make assumptions about the nature of the fluctuations and the nature of the turbulent non-linear interactions to obtain numerical results which can be compared with the observations. Some special model results for several simple cases SUCH as for structures or strong mixing. for Alfven waves with weak turbulent interactions. and for a superposition of structures and Alfven waves. are discussed. The difference between the various approaches to derive and handle the transfer equations are also addressed. Finally some theoretical description of the compressible fluctuations are also briefly reviewed.

  11. EFTEM spectrum imaging at high-energy resolution.

    PubMed

    Schaffer, Bernhard; Kothleitner, Gerald; Grogger, Werner

    2006-01-01

    This paper deals with the application of high-energy resolution EFTEM image series and the corrections needed for reliable data interpretation. The detail of spectral information gained from an image series is largely determined by the intrinsic energy resolution. In this work we show that energy resolution values of as low as 0.8 eV in spectra extracted from EFTEM image series can be obtained with a small energy-selecting slit. At this resolution level aberrations of the energy filter, in particular the non-isochromaticity, can no longer be neglected. We show that the four most prominent factors for EFTEM image series data correction--spatial drift, non-isochromaticity, energy drift and image distortion--must not be treated independently but have to be corrected in unison. We present an efficient algorithm for this correction, and demonstrate the applied correction for the case of a GaN/AlN multilayer sample. PMID:16872748

  12. Recent results of the energy spectrum and mass composition from Telescope Array Fluorescence Detector

    NASA Astrophysics Data System (ADS)

    Ikeda, Daisuke

    2013-02-01

    The Telescope Array experiment is the largest hybrid detector to observe Ultra-High Energy Cosmic Rays in the northern hemisphere. The observation started in November 2007 for Fluorescence Detector (FD) and in March 2008 for Surface Detectors (SD). Here, we present the preliminary results of the energy spectrum and mass composition of the UHECRs measured by the FD and hybrid technique from the Telescope Array three year observations. The energy spectrum measured by the Middle Drum FD station, which is the refurbished HiRes-I detector is consistent with the results from HiRes. The energy spectrum with the two newly constructed FDs and SD is also in good agreement with the result from HiRes, especially for the energy scale. The mass composition study with the slant depth of the maximum shower development (Xmax) is obtained by using the stereo and hybrid analysis. The result of the mass composition is consistent with the proton prediction.

  13. Influence of the Richtmyer-Meshkov instability on the kinetic energy spectrum.

    SciTech Connect

    Weber, Christopher R.

    2010-09-01

    The fluctuating kinetic energy spectrum in the region near the Richtmyer-Meshkov instability (RMI) is experimentally investigated using particle image velocimetry (PIV). The velocity field is measured at a high spatial resolution in the light gas to observe the effects of turbulence production and dissipation. It is found that the RMI acts as a source of turbulence production near the unstable interface, where energy is transferred from the scales of the perturbation to smaller scales until dissipation. The interface also has an effect on the kinetic energy spectrum farther away by means of the distorted reflected shock wave. The energy spectrum far from the interface initially has a higher energy content than that of similar experiments with a flat interface. These differences are quick to disappear as dissipation dominates the flow far from the interface.

  14. Electron, photons, and molecules: Storing energy from light

    SciTech Connect

    Miller, J.R.

    1996-09-01

    Molecular charge separation has important potential for photochemical energy storage. Its efficiency can be enhanced by principals which maximize the rates of the electron transfer steps which separate charge and minimize those which recombine high-energy charge pairs to lose stored energy. Dramatic scientific progress in understanding these principals has occurred since the founding of DOE and its predecessor agency ERDA. While additional knowledge in needed in broad areas of molecular electron transfer, some key areas of knowledge hold particular promise for the possibility of moving this area from science toward technology capable of contributing to the nation`s energy economy.

  15. Accelerator Technology and High Energy Physics Experiments, Photonics Applications and Web Engineering, Wilga, May 2012

    NASA Astrophysics Data System (ADS)

    Romaniuk, Ryszard S.

    2012-05-01

    The paper is the second part (out of five) of the research survey of WILGA Symposium work, May 2012 Edition, concerned with accelerator technology and high energy physics experiments. It presents a digest of chosen technical work results shown by young researchers from different technical universities from this country during the XXXth Jubilee SPIE-IEEE Wilga 2012, May Edition, symposium on Photonics and Web Engineering. Topical tracks of the symposium embraced, among others, nanomaterials and nanotechnologies for photonics, sensory and nonlinear optical fibers, object oriented design of hardware, photonic metrology, optoelectronics and photonics applications, photonicselectronics co-design, optoelectronic and electronic systems for astronomy and high energy physics experiments, JET and pi-of-the sky experiments development. The symposium is an annual summary in the development of numerable Ph.D. theses carried out in this country in the area of advanced electronic and photonic systems. It is also a great occasion for SPIE, IEEE, OSA and PSP students to meet together in a large group spanning the whole country with guests from this part of Europe. A digest of Wilga references is presented [1-275].

  16. Intergalactic Photon Spectra from the Far-IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High-Energy Gamma Rays

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Malkan, M. A.; Scully, S. T.

    2006-01-01

    We calculate the intergalactic photon density as a function of both energy and redshift for 0photon energies from.003 eV to the Lyman limit cutoff at 13.6 eV in a (Omega)CDM universe with (Omega)(Lambda)=0.7 and (Omega)m=0.3. The basic features of our backward-evolution model for galaxies were developed in earlier papers by Malkan & Stecker. With a few improvements, we find that this evolutionary model gives predictions of new deep number counts from Spitzer, as well as a calculation of the spectral energy distribution of the diffuse infrared background, which are in good agreement with the data. We then use our calculated intergalactic photon densities to extend previous work on the absorption of high-energy Gamma-rays in intergalactic space owing to interactions with low-energy photons and the 2.7 K cosmic microwave background radiation. We calculate the optical depth of the universe, Tau , for Gamma-rays having energies from 4 GeV to 100 TeV emitted by sources at redshifts from 0 to 5. We also give an analytic fit with numerical coefficients for approximating (E(Gamma), z). As an example of the application of our results, we calculate the absorbed spectrum of the blazar PKS 2155-304 at z=0.117 and compare it with the spectrum observed by the HESS air Cerenkov Gamma-ray telescope array.

  17. Comparing human observer performance in detecting microcalcifications with energy weighting and photon counting breast CT

    NASA Astrophysics Data System (ADS)

    Kalluri, Kesava; Mahd, Mufeed; Glick, Stephen J.

    2012-03-01

    Breast CT (BCT) using a photon counting detector (PCD) has a number of advantages that can potentially improve clinical performance. Previous computer simulation studies showed that the signal to noise ratio (SNR) for microcalcifications is higher with energy weighted photon counting BCT as compared to cesium iodide energy integrating detector (CsI-EID) based BCT. CsI-EID inherently weighs the incident x-ray photons in direct proportion to the energy (contradicting the information content) which is not an optimal approach. PCD do not inherently weigh the incident photons. By choosing optimal energy weights, higher SNR can be achieved for microcalcifications and hence better detectability. In this simulation study, forward projection data of a numerical breast phantom with microcalcifications inserted were acquired using CsI-EID and PCD. The PCD projections were optimally weighed, and reconstructed using filtered back-projection. We compared observer performance in identifying microcalcifications in the reconstructed images using ROC analysis. ROC based results show that the average area(s) under curve(s) (AUC) for AUCPCD based methods are higher than the average AUCCsI-EID method.

  18. Historical review of lung counting efficiencies for low energy photon emitters

    DOE PAGESBeta

    Jeffers, Karen L.; Hickman, David P.

    2014-03-01

    This publication reviews the measured efficiency and variability over time of a high purity planar germanium in vivo lung count system for multiple photon energies using increasingly thick overlays with the Lawrence Livermore Torso Phantom. Furthermore, the measured variations in efficiency are compared with the current requirement for in vivo bioassay performance as defined by the American National Standards Institute Standard.

  19. Light-induced systemic regulation of photosynthesis in primary and trifoliate leaves of Phaseolus vulgaris: effects of photosynthetic photon flux density (PPFD) versus spectrum.

    PubMed

    Murakami, K; Matsuda, R; Fujiwara, K

    2014-01-01

    The objectives of this work using Phaseolus vulgaris were to examine whether the light spectrum incident on mature primary leaves (PLs) is related to leaf-to-leaf systemic regulation of developing trifoliate leaves (TLs) in photosynthetic characteristics, and to investigate the relative importance of spectrum and photosynthetic photon flux density (PPFD) in light-induced systemic regulation. Systemic regulation was induced by altering PPFD and the spectrum of light incident on PLs using a shading treatment and lighting treatments including either white, blue, green or red light-emitting diodes (LEDs). Photosynthetic characteristics were evaluated by measuring the light-limited and light-saturated net photosynthetic rates and the amounts of nitrogen (N), chlorophyll (Chl) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39). Shading treatment on PLs decreased the amounts of N, Chl and Rubisco of TLs and tended to decrease the photosynthetic rates. However, we observed no systemic effects induced by the light spectrum on PLs in this study, except that a higher amount of Rubisco of TLs was observed when the PLs were irradiated with blue LEDs. Our results imply that photoreceptors in mature leaves have little influence on photosynthetic rates and amounts of N and Chl of developing leaves through systemic regulation, although the possibility of the action of blue light irradiation on the amount of Rubisco cannot be ruled out. Based on these results, we concluded that the light spectrum incident on mature leaves has little systemic effect on developing leaves in terms of photosynthetic characteristics and that the light-induced systemic regulation was largely accounted for by PPFD.

  20. Constraints on axionlike particles with H.E.S.S. from the irregularity of the PKS 2155-304 energy spectrum

    NASA Astrophysics Data System (ADS)

    Abramowski, A.; Acero, F.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O.'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Gast, H.; Giebels, B.; Glicenstein, J. F.; Göring, D.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hague, J. D.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Nedbal, D.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spieß, F.; Stawarz, L.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2013-11-01

    Axionlike particles (ALPs) are hypothetical light (sub-eV) bosons predicted in some extensions of the Standard Model of particle physics. In astrophysical environments comprising high-energy gamma rays and turbulent magnetic fields, the existence of ALPs can modify the energy spectrum of the gamma rays for a sufficiently large coupling between ALPs and photons. This modification would take the form of an irregular behavior of the energy spectrum in a limited energy range. Data from the H.E.S.S. observations of the distant BL Lac object PKS 2155-304 (z=0.116) are used to derive upper limits at the 95% C.L. on the strength of the ALP coupling to photons, gγa<2.1×10-11GeV-1 for an ALP mass between 15 and 60 neV. The results depend on assumptions on the magnetic field around the source, which are chosen conservatively. The derived constraints apply to both light pseudoscalar and scalar bosons that couple to the electromagnetic field.

  1. Material separation in x-ray CT with energy resolved photon-counting detectors

    PubMed Central

    Wang, Xiaolan; Meier, Dirk; Taguchi, Katsuyuki; Wagenaar, Douglas J.; Patt, Bradley E.; Frey, Eric C.

    2011-01-01

    Purpose: The objective of the study was to demonstrate that, in x-ray computed tomography (CT), more than two types of materials can be effectively separated with the use of an energy resolved photon-counting detector and classification methodology. Specifically, this applies to the case when contrast agents that contain K-absorption edges in the energy range of interest are present in the object. This separation is enabled via the use of recently developed energy resolved photon-counting detectors with multiple thresholds, which allow simultaneous measurements of the x-ray attenuation at multiple energies. Methods: To demonstrate this capability, we performed simulations and physical experiments using a six-threshold energy resolved photon-counting detector. We imaged mouse-sized cylindrical phantoms filled with several soft-tissue-like and bone-like materials and with iodine-based and gadolinium-based contrast agents. The linear attenuation coefficients were reconstructed for each material in each energy window and were visualized as scatter plots between pairs of energy windows. For comparison, a dual-kVp CT was also simulated using the same phantom materials. In this case, the linear attenuation coefficients at the lower kVp were plotted against those at the higher kVp. Results: In both the simulations and the physical experiments, the contrast agents were easily separable from other soft-tissue-like and bone-like materials, thanks to the availability of the attenuation coefficient measurements at more than two energies provided by the energy resolved photon-counting detector. In the simulations, the amount of separation was observed to be proportional to the concentration of the contrast agents; however, this was not observed in the physical experiments due to limitations of the real detector system. We used the angle between pairs of attenuation coefficient vectors in either the 5-D space (for non-contrast-agent materials using energy resolved photon

  2. Is the Smagorinsky coefficient sensitive to uncertainty in the form of the energy spectrum?

    NASA Astrophysics Data System (ADS)

    Meldi, M.; Lucor, D.; Sagaut, P.

    2011-12-01

    We investigate the influence of uncertainties in the shape of the energy spectrum over the Smagorinsky ["General circulation experiments with the primitive equations. I: The basic experiment," Mon. Weather Rev. 91(3), 99 (1963)] subgrid scale model constant CS: the analysis is carried out by a stochastic approach based on generalized polynomial chaos. The free parameters in the considered energy spectrum functional forms are modeled as random variables over bounded supports: two models of the energy spectrum are investigated, namely, the functional form proposed by Pope [Turbulent Flows (Cambridge University Press, Cambridge, 2000)] and by Meyers and Meneveau ["A functional form for the energy spectrum parametrizing bottleneck and intermittency effects," Phys. Fluids 20(6), 065109 (2008)]. The Smagorinsky model coefficient, computed from the algebraic relation presented in a recent work by Meyers and Sagaut ["On the model coefficients for the standard and the variational multi-scale Smagorinsky model," J. Fluid Mech. 569, 287 (2006)], is considered as a stochastic process and is described by numerical tools streaming from the probability theory. The uncertainties are introduced in the free parameters shaping the energy spectrum in correspondence to the large and the small scales, respectively. The predicted model constant is weakly sensitive to the shape of the energy spectrum when large scales uncertainty is considered: if the large-eddy simulation (LES) filter cut is performed in the inertial range, a significant probability to recover values lower in magnitude than the asymptotic Lilly-Smagorinsky model constant is recovered. Furthermore, the predicted model constant occurrences cluster in a compact range of values: the correspondent probability density function rapidly drops to zero approaching the extremes values of the range, which show a significant sensitivity to the LES filter width. The sensitivity of the model constant to uncertainties propagated in the

  3. Harvesting UV photons for solar energy conversion applications.

    PubMed

    Wielopolski, Mateusz; Linton, Katharine E; Marszałek, Magdalena; Gulcur, Murat; Bryce, Martin R; Moser, Jacques E

    2014-02-01

    We report the synthesis and characterization of five new donor–π–spacer–acceptor dye molecules with a diphenylamine donor, fluorene–1,2,5-oxadiazole spacers and a range of acceptor/anchor groups (carboxylic acid 1, cyanoacrylic acid 2 and 3, alcohol 4 and cyano 5) to facilitate electron injection from the excited dye into the TiO2 photoanode in dye-sensitized solar cells (DSSCs). Detailed photophysical studies have probed the dyes' excited state properties and revealed structure–property relationships within the series. Density functional theory (DFT) and time dependent DFT (TDDFT) calculations provide further insights into how the molecular geometry and electronic properties impact on the photovoltaic performance. A special feature of these dyes is that their absorption features are located predominantly in the UV region, which means the dye-sensitized TiO2 is essentially colorless. Nevertheless, DSSCs assembled from 1 and 2 exhibit photovoltaic power conversion efficiencies of η = 1.3 and 2.2%, respectively, which makes the dyes viable candidates for low-power solar cells that need to be transparent and colorless and for applications that require enhanced harvesting of UV photons.

  4. [Application of the racial algorithm in energy dispersive X-ray fluorescence overlapped spectrum analysis].

    PubMed

    Zeng, Guo-Qiang; Luo, Yao-Yao; Ge, Liang-Quan; Zhang, Qing-Xian; Gu, Yi; Cheng, Feng

    2014-02-01

    In the energy dispersive X-ray fluorescence spectrum analysis, scintillation detector such as NaI (Tl) detector usually has a low energy resolution at around 8%. The low energy resolution causes problems in spectral data analysis especially in the high background and low counts condition, it is very limited to strip the overlapped spectrum, and the more overlapping the peaks are, the more difficult to peel the peaks, and the qualitative and quantitative analysis can't be carried out because we can't recognize the peak address and peak area. Based on genetic algorithm and immune algorithm, we build a new racial algorithm which uses the Euclidean distance as the judgment of evolution, the maximum relative error as the iterative criterion to be put into overlapped spectrum analysis, then we use the Gaussian function to simulate different overlapping degrees of the spectrum, and the racial algorithm is used in overlapped peak separation and full spectrum simulation, the peak address deviation is in +/- 3 channels, the peak area deviation is no more than 5%, and it is proven that this method has a good effect in energy dispersive X-ray fluorescence overlapped spectrum analysis.

  5. Particle Energy Spectrum, Revisited from a Counting Statistics Perspective

    SciTech Connect

    2012-07-28

    In nuclear science, gamma and neutron spectra are counted energy by energy, and then particle by particle. Until recently, few studies have been performed on how exactly those energy spectra are counted, or how those counts are correlated. Because of lack of investigation, cross section covariance and correlation matrices are usually estimated using perturbation method. We will discuss a statistical counting scheme that shall mimic the gamma and neutron counting process used in nuclear science. From this counting scheme, the cross section covariance and correlation can be statistically derived.

  6. Measurement of pair-production by high energy photons in an aligned tungsten crystal

    NASA Astrophysics Data System (ADS)

    Moore, R.; Parker, M. A.; Baurichter, A.; Kirsebom, K.; Medenwaldt, R.; Mikkelsen, U.; Møller, S. P.; Uggerhøj, E.; Worm, T.; Doble, N.; Elsener, K.; Ballestrero, S.; Sona, P.; Strakhovenko, V. M.; Biino, C.; Vilakazi, Z. Z.

    1996-10-01

    A new measurement has been made of the rate of pair-production in a 3.2 mm thick tungsten crystal, exposed to photons with energies in the range 10 to 150 GeV, for angles of incidence up to 10 mrad from the crystal axis. A strong enhancement of the pair-production rate is observed when the beam is aligned along the <100> crystal axis, as compared to a random orientation. This effect can be exploited in the NA48 CP-violation experiment by using a thin crystal rather than an amorphous material to convert photons, thus minimising the scattering of kaons in the converter.

  7. Variation of photon interaction parameters with energy for some Cu-Pb alloys

    SciTech Connect

    Singh, Tejbir Kaur, Sarpreet; Kaur, Parminder; Kaur, Harvinder; Singh, Parjit S.

    2015-08-28

    Various photon interaction parameters (mass attenuation coefficients, effective atomic numbers and effective electron numbers) have been computed for different compositions of Cu-Pb alloys in the wide energy regime of 1 keV to 100 GeV. The mass attenuation coefficients have been computed using mixture rule with the help of WinXCom (mass attenuation coefficient database for elements). The variation of mass attenuation coefficients, effective atomic numbers and electron density has been analysed and discussed in terms of dominance of different photon interaction processes viz. Compton scattering, photoelectric effect and pair production.

  8. Nonlinear photonic diode behavior in energy-graded core-shell quantum well semiconductor rod.

    PubMed

    Ko, Suk-Min; Gong, Su-Hyun; Cho, Yong-Hoon

    2014-09-10

    Future technologies require faster data transfer and processing with lower loss. A photonic diode could be an attractive alternative to the present Si-based electronic diode for rapid optical signal processing and communication. Here, we report highly asymmetric photonic diode behavior with low scattering loss, from tapered core-shell quantum well semiconductor rods that were fabricated to have a large gradient in their bandgap energy along their growth direction. Local laser illumination of the core-shell quantum well rods yielded a huge contrast in light output intensities from opposite ends of the rod.

  9. Variation of photon interaction parameters with energy for some Cu-Pb alloys

    NASA Astrophysics Data System (ADS)

    Singh, Tejbir; Kaur, Sarpreet; Kaur, Parminder; Kaur, Harvinder; Singh, Parjit S.

    2015-08-01

    Various photon interaction parameters (mass attenuation coefficients, effective atomic numbers and effective electron numbers) have been computed for different compositions of Cu-Pb alloys in the wide energy regime of 1 keV to 100 GeV. The mass attenuation coefficients have been computed using mixture rule with the help of WinXCom (mass attenuation coefficient database for elements). The variation of mass attenuation coefficients, effective atomic numbers and electron density has been analysed and discussed in terms of dominance of different photon interaction processes viz. Compton scattering, photoelectric effect and pair production.

  10. Quantum Entanglement Molecular Absorption Spectrum Simulator

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet; Kojima, Jun

    2006-01-01

    Quantum Entanglement Molecular Absorption Spectrum Simulator (QE-MASS) is a computer program for simulating two photon molecular-absorption spectroscopy using quantum-entangled photons. More specifically, QE-MASS simulates the molecular absorption of two quantum-entangled photons generated by the spontaneous parametric down-conversion (SPDC) of a fixed-frequency photon from a laser. The two-photon absorption process is modeled via a combination of rovibrational and electronic single-photon transitions, using a wave-function formalism. A two-photon absorption cross section as a function of the entanglement delay time between the two photons is computed, then subjected to a fast Fourier transform to produce an energy spectrum. The program then detects peaks in the Fourier spectrum and displays the energy levels of very short-lived intermediate quantum states (or virtual states) of the molecule. Such virtual states were only previously accessible using ultra-fast (femtosecond) laser systems. However, with the use of a single-frequency continuous wave laser to produce SPDC photons, and QEMASS program, these short-lived molecular states can now be studied using much simpler laser systems. QE-MASS can also show the dependence of the Fourier spectrum on the tuning range of the entanglement time of any externally introduced optical-path delay time. QE-MASS can be extended to any molecule for which an appropriate spectroscopic database is available. It is a means of performing an a priori parametric analysis of entangled photon spectroscopy for development and implementation of emerging quantum-spectroscopic sensing techniques. QE-MASS is currently implemented using the Mathcad software package.

  11. Bio-Inspired Photon Absorption and Energy Transfer for Next Generation Photovoltaic Devices

    NASA Astrophysics Data System (ADS)

    Magsi, Komal

    Nature's solar energy harvesting system, photosynthesis, serves as a model for photon absorption, spectra broadening, and energy transfer. Photosynthesis harvests light far differently than photovoltaic cells. These differences offer both engineering opportunity and scientific challenges since not all of the natural photon absorption mechanisms have been understood. In return, solar cells can be a very sensitive probe for the absorption characteristics of molecules capable of transferring charge to a conductive interface. The objective of this scientific work is the advancement of next generation photovoltaics through the development and application of natural photo-energy transfer processes. Two scientific methods were used in the development and application of enhancing photon absorption and transfer. First, a detailed analysis of photovoltaic front surface fluorescent spectral modification and light scattering by hetero-structure was conducted. Phosphor based spectral down-conversion is a well-known laser technology. The theoretical calculations presented here indicate that parasitic losses and light scattering within the spectral range are large enough to offset any expected gains. The second approach for enhancing photon absorption is based on bio-inspired mechanisms. Key to the utilization of these natural processes is the development of a detailed scientific understanding and the application of these processes to cost effective systems and devices. In this work both aspects are investigated. Dye type solar cells were prepared and tested as a function of Chlorophyll (or Sodium-Copper Chlorophyllin) and accessory dyes. Forster has shown that the fluorescence ratio of Chlorophyll is modified and broadened by separate photon absorption (sensitized absorption) through interaction with nearby accessory pigments. This work used the dye type solar cell as a diagnostic tool by which to investigate photon absorption and photon energy transfer. These experiments shed

  12. Material grain size characterization method based on energy attenuation coefficient spectrum and support vector regression.

    PubMed

    Li, Min; Zhou, Tong; Song, Yanan

    2016-07-01

    A grain size characterization method based on energy attenuation coefficient spectrum and support vector regression (SVR) is proposed. First, the spectra of the first and second back-wall echoes are cut into several frequency bands to calculate the energy attenuation coefficient spectrum. Second, the frequency band that is sensitive to grain size variation is determined. Finally, a statistical model between the energy attenuation coefficient in the sensitive frequency band and average grain size is established through SVR. Experimental verification is conducted on austenitic stainless steel. The average relative error of the predicted grain size is 5.65%, which is better than that of conventional methods.

  13. Anisotropy of low energy direct photons in relativistic heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Koide, T.; Kodama, T.

    2016-09-01

    Using the Wigner function approach for electromagnetic radiation fields, we investigate the behavior of low energy photons radiated by the deceleration processes of two colliding nuclei in relativistic heavy ion collisions. The angular distribution reveals information of the initial geometric configurations, which is reflected in the anisotropic parameter v 2, with an increasing v 2 as energy decreases. This behavior is qualitatively different to the v 2 from the hadrons produced in the collisions.

  14. SU-E-T-221: Investigation of Lower Energy (< 6 MV) Photon Beams for Cancer Radiotherapy

    SciTech Connect

    Zhang, Y; Ming, X; Feng, Y; Zhou, L; Ahmad, M; Deng, J; Nguyen, K; Griffin, M

    2014-06-01

    Purpose: To study the potential applications of the lower energy (< 6MV) photon beams in the radiotherapeutic management of pediatric cancer and lung cancer patients. Methods: Photon beams of 2, 3, 4, 5 and 6MV were first simulated with EGS4/BEAM and then used for Monte-Carlo dose calculations. For four pediatric patients with abdominal and brain lesions, six 3D-conformal radiotherapy (3DCRT) plans were generated using single photon energy (2 to 6MV) or mixed energies (3 and 6MV). Furthermore, a virtual machine of 3 and 6MV was commissioned in a treatment planning system (TPS) based on Monte-Carlo simulated data. Three IMRT plans of a lung cancer patient were generated on this virtual machine. All plans were normalized to D95% of target dose for 6MV plan and then compared in terms of integral dose and OAR sparing. Results: For the four pediatric patients, the integral dose for the 2, 3, 4 and 5MV plans increased by 9%, 5%, 3.5%, 1.7%, respectively as compared to 6MV. Almost all OARs in the 2MV plan received more than 10% more doses than 6MV. Mixed energy 3DCRT plans were of the same quality as 6MV plans. For the lung IMRT plans, both the 3MV plan and the mixed beam plan showed better OAR sparing in comparison to 6MV plan. Specifically, the maximum and mean doses to the spinal cord in the mixed energy plan were lower by 21% and 16%, respectively. Conclusion: Single lower energy photon beam was found to be inferior to 6MV in the radiotherapy of pediatric patients and lung cancer patients when the integral doses and the doses to the OARs were considered. However, mixed energy plans combining low with high energy beams showed significant OAR sparing while maintaining the same PTV coverage. Investigation with more patient data is ongoing for further confirmation.

  15. Evaluation of the efficiency curve of a Cadmiun Telluride detector for low-energy photon spectrometry.

    PubMed

    Correia, Amanda Ribeiro; Iwahara, Akira; da Cruz, Paulo Alberto Lima; da Silva, Carlos José; Tauhata, Luiz; Poledna, Roberto; da Silva, Ronaldo Lins; de Queiroz Filho, Pedro Pacheco; Lopes, Ricardo Tadeu

    2016-10-01

    The performance of a Cadmiun Telluride (CdTe) detector for low energy photon spectrometry was evaluated. Collected data were analyzed using the basic software package available with the CdTe detector system and the COLEGRAM code developed for photopeak deconvolution at LNHB/France. Several calibrated point sources were used to determine the energy versus efficiency curve. The efficiency curve was used in the determination of main X-ray intensities of (153)Sm and (177)Lu.

  16. Evaluation of the efficiency curve of a Cadmiun Telluride detector for low-energy photon spectrometry.

    PubMed

    Correia, Amanda Ribeiro; Iwahara, Akira; da Cruz, Paulo Alberto Lima; da Silva, Carlos José; Tauhata, Luiz; Poledna, Roberto; da Silva, Ronaldo Lins; de Queiroz Filho, Pedro Pacheco; Lopes, Ricardo Tadeu

    2016-10-01

    The performance of a Cadmiun Telluride (CdTe) detector for low energy photon spectrometry was evaluated. Collected data were analyzed using the basic software package available with the CdTe detector system and the COLEGRAM code developed for photopeak deconvolution at LNHB/France. Several calibrated point sources were used to determine the energy versus efficiency curve. The efficiency curve was used in the determination of main X-ray intensities of (153)Sm and (177)Lu. PMID:27544313

  17. Primary electron spectrometer, 18:63 UE: Electrostatic analyzer description and energy spectrum determination

    NASA Technical Reports Server (NTRS)

    Pongratz, M. B.

    1973-01-01

    The primary electron spectrometer used to detect auroral electrons on sounding rocket 18:63 UE is described. The spectrometer used exponentially decaying positive and negative voltages applied to spherical deflection plates for energy analysis. A method for determining the analyzer response which does not require the assumptions that the ratio of plate separation to mean radius, the entrance or the exit apertures are small is described. By comparison with experiment it is shown that the effect of neither entrance nor exit collimation can be ignored. The experimental and calculated values of the limiting orbits agree well. A non-iterative technique of unfolding the electron differential energy spectrum is described. This method does not require the usual assumption of a flat or histogram-type energy spectrum. The unfolded spectra using both this technique and one which assumes a flat spectrum are compared to actual input spectra. This technique is especially useful in analyzing peaked auroral electron energy spectra.

  18. High-energy properties of the high-redshift flat spectrum radio quasar PKS 2149-306

    NASA Astrophysics Data System (ADS)

    D'Ammando, F.; Orienti, M.

    2016-01-01

    We investigate the γ-ray and X-ray properties of the flat spectrum radio quasar PKS 2149-306 at redshift z = 2.345. A strong γ-ray flare from this source was detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope satellite in 2013 January, reaching on January 20 a daily peak flux of (301 ± 36) × 10-8 ph cm-2 s-1 in the 0.1-100 GeV energy range. This flux corresponds to an apparent isotropic luminosity of (1.5 ± 0.2) × 1050 erg s-1, comparable to the highest values observed by a blazar so far. During the flare the increase of flux was accompanied by a significant change of the spectral properties. Moreover significant flux variations on a 6-h time-scale were observed, compatible with the light crossing time of the event horizon of the central black hole. The broad-band X-ray spectra of PKS 2149-306 observed by Swift-XRT and NuSTAR are well described by a broken power-law model, with a very hard spectrum (Γ1 ˜ 1) below the break energy, at E break = 2.5-3.0 keV, and Γ2 ˜ 1.4-1.5 above the break energy. The steepening of the spectrum below ˜3 keV may indicate that the soft X-ray emission is produced by the low-energy relativistic electrons. This is in agreement with the small variability amplitude and the lack of spectral changes in that part of the X-ray spectrum observed between the two NuSTAR and Swift joint observations. As for the other high-redshift FSRQ detected by both Fermi-LAT and Swift-BAT, the photon index of PKS 2149-306 in hard X-ray is 1.6 or lower and the average γ-ray luminosity higher than 2 × 1048 erg s-1.

  19. Excitation energy dependent Raman spectrum of MoSe2

    PubMed Central

    Nam, Dahyun; Lee, Jae-Ung; Cheong, Hyeonsik

    2015-01-01

    Raman investigation of MoSe2 was carried out with eight different excitation energies. Seven peaks, including E1g, A1g, E2g1, and A2u2 peaks are observed in the range of 100–400 cm−1. The phonon modes are assigned by comparing the peak positions with theoretical calculations. The intensities of the peaks are enhanced at different excitation energies through resonance with different optical transitions. The A1g mode is enhanced at 1.58 and 3.82 eV, which are near the A exciton energy and the band-to-band transition between higher energy bands, respectively. The E2g1 mode is strongly enhanced with respect to the A1g mode for the 2.71- and 2.81-eV excitations, which are close to the C exciton energy. The different enhancements of the A1g and E2g1 modes are explained in terms of the symmetries of the exciton states and the exciton-phonon coupling. Other smaller peaks including E1g and A2u2 are forbidden but appear due to the resonance effect near optical transition energies. PMID:26601614

  20. The High Energy X-ray Spectrum of 4U1700-37 Observed from OSO-8

    NASA Technical Reports Server (NTRS)

    Dolan, J. F.; Coe, M. J.; Crannell, C. J.; Dennis, B. R.; Frost, K. J.; Maurer, G. S.; Orwig, L. E.

    1979-01-01

    The most intense hard X-ray source in the confused region in Scorpius is identified as 4U1700-37. The 3.4-day modulation is seen above 20 keV with the intensity during eclipse being consistent with zero flux. The photon-number spectrum from 20 to 150 keV is well represented by a single power law with a photo-number spectral index of -2.77 + or - 0.35 or by a thermal bremsstrahlung spectrum with kT = 27 96.8-min X-ray modulation previously reported at lower energies. Despite the difficulties in reconciling both the lack of periodic modulation in the emitted X-radiation and the orbital dynamics of the system with theories of the evolution and physical properties of neutron stars, the observed properties of 4U1700-37 are all consistent with the source being a spherically accreting neutron star rather than a black hole.

  1. Characterizing invisible electroweak particles through single-photon processes at high energy e+e- colliders

    NASA Astrophysics Data System (ADS)

    Choi, Seong Youl; Han, Tao; Kalinowski, Jan; Rolbiecki, Krzysztof; Wang, Xing

    2015-11-01

    We explore the scenarios where the only accessible new states at the electroweak scale consist of a pair of color-singlet electroweak particles, the masses of which are degenerate at the tree level and split only by electroweak symmetry breaking at the loop level. For the sake of illustration, we consider a supersymmetric model and study the following three representative cases with the lower-lying states as (a) two spin-1 /2 Higgsino SU(2 ) L doublets, (b) a spin-1 /2 wino SU(2 ) L triplet and (c) a spin-0 left-handed slepton SU(2 ) L doublet. Due to the mass degeneracy, those lower-lying electroweak states are difficult to observe at the LHC and rather challenging to detect at the e+e- collider as well. We exploit the pair production in association with a hard photon radiation in high energy e+e- collisions. If kinematically accessible, such single-photon processes at e+e- colliders with polarized beams enable us to characterize each scenario by measuring the energy of the associated hard photon and to determine the spin of the nearly invisible particles unambiguously through the threshold behavior in the photon energy distribution.

  2. Energy spectrum of the low-lying gluon excitations in the Coulomb gauge

    SciTech Connect

    Szczepaniak, Adam P.; Krupinski, Pawel

    2006-06-01

    We compute the energy spectrum of low-lying gluonic excitations in the presence of static quark-antiquark sources using Coulomb gauge and the quasiparticle representation. Within the valence sector of the Fock space we reproduce both, the overall normalization and the ordering of the spin-parity multiplets. We discus how the interactions induced by the nonabelian Coulomb kernel are central in to fine structure of the spectrum.

  3. Photon energy upconversion through thermal radiation with the power efficiency reaching 16%

    NASA Astrophysics Data System (ADS)

    Wang, Junxin; Ming, Tian; Jin, Zhao; Wang, Jianfang; Sun, Ling-Dong; Yan, Chun-Hua

    2014-11-01

    The efficiency of many solar energy conversion technologies is limited by their poor response to low-energy solar photons. One way for overcoming this limitation is to develop materials and methods that can efficiently convert low-energy photons into high-energy ones. Here we show that thermal radiation is an attractive route for photon energy upconversion, with efficiencies higher than those of state-of-the-art energy transfer upconversion under continuous wave laser excitation. A maximal power upconversion efficiency of 16% is achieved on Yb3+-doped ZrO2. By examining various oxide samples doped with lanthanide or transition metal ions, we draw guidelines that materials with high melting points, low thermal conductivities and strong absorption to infrared light deliver high upconversion efficiencies. The feasibility of our upconversion approach is further demonstrated under concentrated sunlight excitation and continuous wave 976-nm laser excitation, where the upconverted white light is absorbed by Si solar cells to generate electricity and drive optical and electrical devices.

  4. Photon energy upconversion through thermal radiation with the power efficiency reaching 16%.

    PubMed

    Wang, Junxin; Ming, Tian; Jin, Zhao; Wang, Jianfang; Sun, Ling-Dong; Yan, Chun-Hua

    2014-11-28

    The efficiency of many solar energy conversion technologies is limited by their poor response to low-energy solar photons. One way for overcoming this limitation is to develop materials and methods that can efficiently convert low-energy photons into high-energy ones. Here we show that thermal radiation is an attractive route for photon energy upconversion, with efficiencies higher than those of state-of-the-art energy transfer upconversion under continuous wave laser excitation. A maximal power upconversion efficiency of 16% is achieved on Yb(3+)-doped ZrO2. By examining various oxide samples doped with lanthanide or transition metal ions, we draw guidelines that materials with high melting points, low thermal conductivities and strong absorption to infrared light deliver high upconversion efficiencies. The feasibility of our upconversion approach is further demonstrated under concentrated sunlight excitation and continuous wave 976-nm laser excitation, where the upconverted white light is absorbed by Si solar cells to generate electricity and drive optical and electrical devices.

  5. Photon energy upconversion through thermal radiation with the power efficiency reaching 16%.

    PubMed

    Wang, Junxin; Ming, Tian; Jin, Zhao; Wang, Jianfang; Sun, Ling-Dong; Yan, Chun-Hua

    2014-01-01

    The efficiency of many solar energy conversion technologies is limited by their poor response to low-energy solar photons. One way for overcoming this limitation is to develop materials and methods that can efficiently convert low-energy photons into high-energy ones. Here we show that thermal radiation is an attractive route for photon energy upconversion, with efficiencies higher than those of state-of-the-art energy transfer upconversion under continuous wave laser excitation. A maximal power upconversion efficiency of 16% is achieved on Yb(3+)-doped ZrO2. By examining various oxide samples doped with lanthanide or transition metal ions, we draw guidelines that materials with high melting points, low thermal conductivities and strong absorption to infrared light deliver high upconversion efficiencies. The feasibility of our upconversion approach is further demonstrated under concentrated sunlight excitation and continuous wave 976-nm laser excitation, where the upconverted white light is absorbed by Si solar cells to generate electricity and drive optical and electrical devices. PMID:25430519

  6. Measurement of inclusive isolated prompt photon production at center of mass energy = 7 TeV with the ATLAS

    NASA Astrophysics Data System (ADS)

    Hance, Michael

    Prompt photons at hadron colliders are useful probes of perturbative quantum chromodynamics (pQCD), and are also found in signatures of new physics. A precise measurement of prompt photon production is both a useful test of theoretical models as well as an important step towards understanding final states that contain energetic photons. This thesis presents a measurement of the inclusive isolated prompt photon production cross section in proton-proton collisions at a center-of-mass energy of s = 7 TeV. The data are collected with the ATLAS detector at the Large Hadron Collider, and correspond to 35 pb-1 of integrated luminosity. The measurement is made in four photon pseudorapidity (etagamma) regions: 0 ≤ |etagamma| < 0.6; 0.6 ≤ |etagamma| < 1.37; 1.52 ≤ |eta gamma| < 1.81; and 1.81 ≤ |etagamma| < 2.37; and covers photon transverse energies ( EgT ) in the range 15 GeV ≤ EgT < 400 GeV. Photon candidates are reconstructed and identified through the use of the ATLAS calorimeter and tracking systems. The residual background, primarily from neutral meson decays, is estimated using in-situ techniques based on observed distributions of the total transverse energy in a narrow cone around the photon candidate. The measurements are compared to predictions from next-to-leading order pQCD calculations, with good agreement for photon transverse energies greater than 25 GeV.

  7. Physical origin of the high energy optical response of three dimensional photonic crystals.

    PubMed

    Dorado, Luis A; Depine, Ricardo A; Lozano, Gabriel; Míguez, Hernán

    2007-12-24

    The physical origin of the optical response observed in three-dimensional photonic crystals when the photon wavelength is equal or lower than the lattice parameter still remains unsatisfactorily explained and is the subject of an intense and interesting debate. Herein we demonstrate for the first time that all optical spectra features in this high energy region of photonic crystals arise from electromagnetic resonances within the ordered array, modified by the interplay between these resonances with the opening of diffraction channels, the presence of imperfections and finite size effects. All these four phenomena are taken into account in our theoretical approach to the problem, which allows us to provide a full description of the observed optical response based on fundamental phenomena as well as to attain fair fittings of experimental results.

  8. Can neutrino-induced photon production explain the low energy excess in MiniBooNE?

    NASA Astrophysics Data System (ADS)

    Zhang, Xilin; Serot, Brian D.

    2013-02-01

    This report summarizes our study of Neutral Current (NC)-induced photon production in MiniBooNE, as motivated by the low energy excess in this experiment [A.A. Aquilar-Arevalo et al., MiniBooNE Collaboration, Phys. Rev. Lett. 98 (2007) 231801; A.A. Aquilar-Arevalo et al., MiniBooNE Collaboration, Phys. Rev. Lett. 103 (2009) 111801]. It was proposed that NC photon production with two anomalous photon-Z boson-vector meson couplings might explain the excess. However, our computed event numbers in both neutrino and antineutrino runs are consistent with the previous MiniBooNE estimate that is based on their pion production measurement. Various nuclear effects discussed in our previous works, including nucleon Fermi motion, Pauli blocking, and the Δ resonance broadening in the nucleus, are taken into account. Uncertainty due to the two anomalous terms and nuclear effects are studied in a conservative way.

  9. Effects of target charging and ion emission on the energy spectrum of emitted electrons

    SciTech Connect

    Link, A.; Freeman, R. R.; Schumacher, D. W.; Van Woerkom, L. D.

    2011-05-15

    We present numerical simulations of the energy spectrum of electrons escaping from a target struck by an ultra-intense laser pulse using 2D implicit hybrid particle in cell code LSP (large scale plasma) [D. R. Welch et al., Phys. Plasmas 13, 063105 (2006)] and simple 1D capacitor model. The simulated energy spectrum as recorded by an electron spectrometer is found to differ significantly from the spectrum computed within the target. Analysis of the LSP simulations suggests two major mechanisms are responsible for this phenomenon: (1) The emitted electron energy spectrum is heavily influenced by the self-consistent electric fields generated along the target surface as the electrons escape and (2) these fields are themselves substantially modified by the simultaneous departure of accelerated surface ions. For electrons with internal energy greater than 4 MeV, both models predict a good correlation between the slope temperature of the input electron spectrum and that measured in a vacuum. We discuss the application of the inversion problem of obtaining internal electron energy distributions from experimental data.

  10. Energy spectrum, dissipation, and spatial structures in reduced Hall magnetohydrodynamic

    SciTech Connect

    Martin, L. N.; Dmitruk, P.; Gomez, D. O.

    2012-05-15

    We analyze the effect of the Hall term in the magnetohydrodynamic turbulence under a strong externally supported magnetic field, seeing how this changes the energy cascade, the characteristic scales of the flow, and the dynamics of global magnitudes, with particular interest in the dissipation. Numerical simulations of freely evolving three-dimensional reduced magnetohydrodynamics are performed, for different values of the Hall parameter (the ratio of the ion skin depth to the macroscopic scale of the turbulence) controlling the impact of the Hall term. The Hall effect modifies the transfer of energy across scales, slowing down the transfer of energy from the large scales up to the Hall scale (ion skin depth) and carrying faster the energy from the Hall scale to smaller scales. The final outcome is an effective shift of the dissipation scale to larger scales but also a development of smaller scales. Current sheets (fundamental structures for energy dissipation) are affected in two ways by increasing the Hall effect, with a widening but at the same time generating an internal structure within them. In the case where the Hall term is sufficiently intense, the current sheet is fully delocalized. The effect appears to reduce impulsive effects in the flow, making it less intermittent.

  11. Dose to tissue medium or water cavities as surrogate for the dose to cell nuclei at brachytherapy photon energies.

    PubMed

    Enger, Shirin A; Ahnesjö, Anders; Verhaegen, Frank; Beaulieu, Luc

    2012-07-21

    for most energies in brachytherapy, while LCT-D(w,m) should only be considered for source spectra well below 50 keV, since contributions to the absorbed dose inside the nucleus to a large degree stem from electrons released in the surrounding medium. MC-D(m,m) is not an appropriate substitute for MC-D(n,m) for the lowest photon energies for adipose and breast tissues. The ratio of MC-D(m,m) to MC-D(n,m) for adipose and breast tissue deviates from unity by 34% and 15% respectively for the lowest photon energy (20 keV), whereas the ratio is close to unity for higher energies. For prostate and muscle tissue MC-D(m,m) is a good substitute for MC-D(n,m). However, for all photon energies and tissue types the nucleus composition with the highest hydrogen content behaves differently than other compositions. Elemental compositions of the tissue and nuclei affect considerably the absorbed dose to the cell nuclei for brachytherapy sources, in particular those at the low-energy end of the spectrum. Thus, there is a need for more accurate data for the elemental compositions of tumours and healthy cells. For the nucleus compositions and tissue types investigated, MC-D(w,m) is a good substitute to MC-D(n,m) for all simulated photon energies. Whether other studied surrogates are good approximations to MC-D(n,m) depends on the target size, target composition, composition of the surrounding tissue and photon energy.

  12. The energy dependence and dose response of a commercial optically stimulated luminescent detector for kilovoltage photon, megavoltage photon, and electron, proton, and carbon beams

    SciTech Connect

    Reft, Chester S.

    2009-05-15

    Optically stimulated luminescent detectors, which are widely used in radiation protection, offer a number of potential advantages for application in radiation therapy dosimetry. Their introduction into this field has been somewhat hampered by the lack of information on their radiation response in megavoltage beams. Here the response of a commercially available optically stimulated luminescent detector (OSLD) is determined as a function of energy, absorbed dose to water, and linear energy transfer (LET). The detector response was measured as a function of energy for absorbed doses from 0.5 to 4.0 Gy over the following ranges: 125 kVp to18 MV for photons, 6-20 MeV for electrons, 50-250 MeV for protons, and 290 MeV/u for the carbon ions. For the low LET beams, the response of the detector was linear up to 2 Gy with supralinearity occurring at higher absorbed doses. For the kilovoltage photons, the detector response relative to 6 MV increased with decreasing energy due to the higher atomic number of aluminum oxide (11.2) relative to water (7.4). For the megavoltage photons and electrons, the response was independent of energy. The response for protons was also independent of energy, but it was about 6% higher than its response to 6 MV photons. For the carbon ions, the dose response was linear for a given LET from 0.5 to 4.0 Gy, and no supralinearity was observed. However, it did exhibit LET dependence on the response relative to 6 MV photons decreasing from 1.02 at 1.3 keV/{mu}m to 0.41 at 78 keV/{mu}m. These results provide additional information on the dosimetric properties for this particular OSL detector and also demonstrate the potential for their use in photon, electron, and proton radiotherapy dosimetry with a more limited use in high LET radiotherapy dosimetry.

  13. Monte Carlo simulation of MOSFET detectors for high-energy photon beams using the PENELOPE code

    NASA Astrophysics Data System (ADS)

    Panettieri, Vanessa; Amor Duch, Maria; Jornet, Núria; Ginjaume, Mercè; Carrasco, Pablo; Badal, Andreu; Ortega, Xavier; Ribas, Montserrat

    2007-01-01

    The aim of this work was the Monte Carlo (MC) simulation of the response of commercially available dosimeters based on metal oxide semiconductor field effect transistors (MOSFETs) for radiotherapeutic photon beams using the PENELOPE code. The studied Thomson&Nielsen TN-502-RD MOSFETs have a very small sensitive area of 0.04 mm2 and a thickness of 0.5 µm which is placed on a flat kapton base and covered by a rounded layer of black epoxy resin. The influence of different metallic and Plastic water™ build-up caps, together with the orientation of the detector have been investigated for the specific application of MOSFET detectors for entrance in vivo dosimetry. Additionally, the energy dependence of MOSFET detectors for different high-energy photon beams (with energy >1.25 MeV) has been calculated. Calculations were carried out for simulated 6 MV and 18 MV x-ray beams generated by a Varian Clinac 1800 linear accelerator, a Co-60 photon beam from a Theratron 780 unit, and monoenergetic photon beams ranging from 2 MeV to 10 MeV. The results of the validation of the simulated photon beams show that the average difference between MC results and reference data is negligible, within 0.3%. MC simulated results of the effect of the build-up caps on the MOSFET response are in good agreement with experimental measurements, within the uncertainties. In particular, for the 18 MV photon beam the response of the detectors under a tungsten cap is 48% higher than for a 2 cm Plastic water™ cap and approximately 26% higher when a brass cap is used. This effect is demonstrated to be caused by positron production in the build-up caps of higher atomic number. This work also shows that the MOSFET detectors produce a higher signal when their rounded side is facing the beam (up to 6%) and that there is a significant variation (up to 50%) in the response of the MOSFET for photon energies in the studied energy range. All the results have shown that the PENELOPE code system can

  14. A rare gas optics-free absolute photon flux and energy analyzer to provide absolute photoionization rates of inflowing interstellar neutrals

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    A prototype spectrometer has been developed for space applications requiring long term absolute EUV photon flux measurements. The energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  15. Energy spectrum and wavefunction of electrons in hybrid superconducting nanowires

    NASA Astrophysics Data System (ADS)

    Kruchinin, S. P.

    2016-03-01

    Recent experiments have fabricated structured arrays. We study hybrid nanowires, in which normal and superconducting regions are in close proximity, by using the Bogoliubov-de Gennes equations for superconductivity in a cylindrical nanowire. We succeed to obtain the quantum energy levels and wavefunctions of a superconducting nanowire. The obtained spectra of electrons remind Hofstadter’s butterfly.

  16. The duration-photon energy relation in gamma-ray bursts and its interpretations

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes; Titarchuk, Lev G.; Hua, Xin-Min

    1997-01-01

    A correlation between the spectral and temporal structure in gamma ray bursts was presented elsewhere, where it was discovered that the duration of the constituent subpulses of the time profile of a given gamma ray burst have a well-defined power law dependence, of approximately index 0.45, on the energy of the observed photons. Two models are presented which account for the observed correlation. These models involve: the impulsive injection of a population of relativistic electrons; their subsequent cooling by synchrotron radiation; the impulsive injection of mono-energetic high energy photons in a medium of a Thomson depth of approximately 5, and their subsequent downgrading in energy due to electron scattering. Arguments are presented for distinguishing between these two models from the existing data.

  17. Energy spectrum of ultra-high energy cosmic rays observed with the Telescope Array using a hybrid technique

    NASA Astrophysics Data System (ADS)

    Abu-Zayyad, T.; Aida, R.; Allen, M.; Anderson, R.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, E. J.; Cho, W. R.; Fujii, H.; Fujii, T.; Fukuda, T.; Fukushima, M.; Hanlon, W.; Hayashi, K.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Hiyama, K.; Honda, K.; Iguchi, T.; Ikeda, D.; Ikuta, K.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Iwamoto, S.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kanbe, T.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kido, E.; Kim, H. B.; Kim, H. K.; Kim, J. H.; Kim, J. H.; Kitamoto, K.; Kitamura, S.; Kitamura, Y.; Kobayashi, K.; Kobayashi, Y.; Kondo, Y.; Kuramoto, K.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lim, S. I.; Lundquist, J. P.; Machida, S.; Martens, K.; Matsuda, T.; Matsuura, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Miyata, K.; Murano, Y.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nam, S. W.; Nonaka, T.; Ogio, S.; Ohnishi, M.; Ohoka, H.; Oki, K.; Oku, D.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Roh, S. Y.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Sampson, A. L.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Shin, J. I.; Shirahama, T.; Smith, J. D.; Sokolsky, P.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T.; Suzuki, S.; Takahashi, Y.; Takeda, M.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Tsuyuguchi, Y.; Uchihori, Y.; Udo, S.; Ukai, H.; Urban, F.; Vasiloff, G.; Wada, Y.; Wong, T.; Yamakawa, Y.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zhou, X.; Zollinger, R.; Zundel, Z.

    2015-02-01

    We measure the spectrum of cosmic rays with energies greater than 1018.2 eV with the fluorescence detectors (FDs) and the surface detectors (SDs) of the Telescope Array Experiment using the data taken in our first 2.3-year observation from May 27, 2008 to September 7, 2010. A hybrid air shower reconstruction technique is employed to improve accuracies in determination of arrival directions and primary energies of cosmic rays using both FD and SD data. The energy spectrum presented here is in agreement with our previously published spectra and the HiRes results.

  18. Photon energy absorption coefficients for nuclear track detectors using Geant4 Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Singh, Vishwanath P.; Medhat, M. E.; Badiger, N. M.

    2015-01-01

    Geant4 Monte Carlo code simulations were used to solve experimental and theoretical complications for calculation of mass energy-absorption coefficients of elements, air, and compounds. The mass energy-absorption coefficients for nuclear track detectors were computed first time using Geant4 Monte Carlo code for energy 1 keV-20 MeV. Very good agreements for simulated results of mass energy-absorption coefficients for carbon, nitrogen, silicon, sodium iodide and nuclear track detectors were observed on comparison with the values reported in the literatures. Kerma relative to air for energy 1 keV-20 MeV and energy absorption buildup factors for energy 50 keV-10 MeV up to 10 mfp penetration depths of the selected nuclear track detectors were also calculated to evaluate the absorption of the gamma photons. Geant4 simulation can be utilized for estimation of mass energy-absorption coefficients in elements and composite materials.

  19. Energy spectrum of argon ions emitted from Filippov type Sahand plasma focus.

    PubMed

    Mohammadnejad, M; Pestehe, S J; Mohammadi, M A

    2013-07-01

    The energy and flux of the argon ions produced in Sahand plasma focus have been measured by employing a well-designed Faraday cup. The secondary electron emission effects on the ion signals are simulated and the dimensions of Faraday cup are optimized to minimize these effects. The measured ion energy spectrum is corrected for the ion energy loss and charge exchange in the background gas. The effects of the capacitor bank voltage and working gas pressure on the ion energy spectrum are also investigated. It has been shown that the emitted ion number per energy increases as the capacitor bank voltage increases. Decreasing the working gas pressure leads to the increase in the number of emitted ion per energy. PMID:23902061

  20. Energy spectrum of argon ions emitted from Filippov type Sahand plasma focus

    SciTech Connect

    Mohammadnejad, M.; Pestehe, S. J.; Mohammadi, M. A.

    2013-07-15

    The energy and flux of the argon ions produced in Sahand plasma focus have been measured by employing a well-designed Faraday cup. The secondary electron emission effects on the ion signals are simulated and the dimensions of Faraday cup are optimized to minimize these effects. The measured ion energy spectrum is corrected for the ion energy loss and charge exchange in the background gas. The effects of the capacitor bank voltage and working gas pressure on the ion energy spectrum are also investigated. It has been shown that the emitted ion number per energy increases as the capacitor bank voltage increases. Decreasing the working gas pressure leads to the increase in the number of emitted ion per energy.

  1. Energy spectrum of argon ions emitted from Filippov type Sahand plasma focus

    NASA Astrophysics Data System (ADS)

    Mohammadnejad, M.; Pestehe, S. J.; Mohammadi, M. A.

    2013-07-01

    The energy and flux of the argon ions produced in Sahand plasma focus have been measured by employing a well-designed Faraday cup. The secondary electron emission effects on the ion signals are simulated and the dimensions of Faraday cup are optimized to minimize these effects. The measured ion energy spectrum is corrected for the ion energy loss and charge exchange in the background gas. The effects of the capacitor bank voltage and working gas pressure on the ion energy spectrum are also investigated. It has been shown that the emitted ion number per energy increases as the capacitor bank voltage increases. Decreasing the working gas pressure leads to the increase in the number of emitted ion per energy.

  2. Influence of temperature and photon energy on quantum yield of photoemission from real iron surfaces

    NASA Astrophysics Data System (ADS)

    Momose, Yoshihiro; Suzuki, Daisuke; Sakurai, Takao; Nakayama, Keiji

    2014-07-01

    The influence of temperature and incident photon energy on the photoemission quantum yield, Y s, of real iron surfaces has been investigated by thermally assisted photoemission (TAPE). Measurements were carried out using a Geiger counter under a gaseous atmosphere of He containing 1 % isobutane vapor at normal atmospheric pressure in the temperature range 25-353 °C under UV irradiation with wavelengths of 200, 210, 220, and 230 nm. The Y s obtained under irradiation at a given wavelength was found to increase with temperature, particularly more rapidly with wavelengths of greater photon energy. From the Arrhenius plots, the Y s values were found to have activation energies of 0.112-0.040 eV, depending on the photon energy. The chemical composition of the surfaces after TAPE measurements at different temperatures was examined by X-ray photoelectron spectroscopy (XPS). The intensity of species thermally removed from the surface was also measured by temperature desorption spectroscopy (TDS). XPS and TDS results showed the removal of the surface water and weakly bound carbon material from the surface with temperature. It was concluded that the removal of these species with increasing temperature enabled the incident light to penetrate through the surface into the metal, causing the increase in the Y s. The dependence of the activation energies on the photon energy was explained by the change of UV light absorption spectra of the surface water, and the enhancement of the Y s with temperature was also attributed to the influence of iron cations (Fe3+) corresponding to positive holes produced in the surface oxide layer by UV light.

  3. ON THE VERY HIGH ENERGY SPECTRUM OF THE CRAB PULSAR

    SciTech Connect

    Chkheidze, N.; Machabeli, G.; Osmanov, Z.

    2011-04-01

    In the present paper, we construct a self-consistent theory interpreting the observations from the MAGIC Cherenkov Telescope of the very high energy (VHE) pulsed emission from the Crab pulsar. In particular, on the basis of Vlasov's kinetic equation, we study the process of quasi-linear diffusion (QLD) developed by means of the cyclotron instability. This mechanism provides simultaneous generation of low (radio) and VHE (0.01-25 GeV) emission on light cylinder scales in one location of the pulsar magnetosphere. A different approach to the synchrotron emission is considered, giving the spectral index of the VHE emission ({beta} = 2) and the exponential cutoff energy (23 GeV) in good agreement with the observational data.

  4. Energy transfer and energy absorption in photon interactions with matter revisited: A step-by-step illustrated approach

    NASA Astrophysics Data System (ADS)

    Abdel-Rahman, W.; Podgorsak, E. B.

    2010-05-01

    A clear understanding of energy transfer and energy absorption in photon interactions with matter is essential for the understanding of radiation dosimetry and development of new dosimetry techniques. The concepts behind the two quantities have been enunciated many years ago and described in many scientific papers, review articles, and textbooks. Data dealing with energy transfer and energy absorption as well as the associated mass energy transfer coefficient and the mass energy absorption coefficient are readily available in web-based tabular forms. However, tables, even when available in detailed and easy to access form, do not lend themselves to serve as visual aid to promote better understanding of the dosimetric quantities related to energy transfer and energy absorption as well as their relationship to the photon energy and absorber atomic number. This paper uses graphs and illustrations, in addition to well-known mathematical relationships, to guide the reader in a systematic manner through the various stages involved in the derivation of energy absorbed in medium and its associated quantity, the mass energy absorption coefficient, from the mass attenuation coefficient.

  5. A New Method of Prompt Fission Neutron Energy Spectrum Unfolding

    SciTech Connect

    Zeynalova, O. V.; Zeynalov, Sh.; Hambsch, F.-J.; Oberstedt, S.

    2010-11-25

    The prompt neutron emission in spontaneous fission of {sup 252}Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. The goal was to find out the reasons of a long time existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of fission fragments (FF). On the one hand the {sup 252}Cf(sf) reaction is one of the main references for nuclear data, on the other hand the understanding of PFN emission mechanism is very important for nuclear fission theory. Using a twin Frisch-grid ionization chamber for fission fragment (FF) detection and a NE213-equivalent neutron detector in total about 10{sup 7} fission fragment-neutron coincidences have been registered. Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12 bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. For the first time the dependence of the number of emitted neutrons as a function of total kinetic energy (TKE) of the fragments is in very good agreement with theoretical calculations in the range of TKE from 140-220 MeV.

  6. Perturbation correction for alanine dosimeters in different phantom materials in high-energy photon beams.

    PubMed

    von Voigts-Rhetz, P; Anton, M; Vorwerk, H; Zink, K

    2016-02-01

    In modern radiotherapy the verification of complex treatments plans is often performed in inhomogeneous or even anthropomorphic phantoms. For dose verification small detectors are necessary and therefore alanine detectors are most suitable. Though the response of alanine for a wide range of clinical photon energies in water is well know, the knowledge about the influence of the surrounding phantom material on the response of alanine is sparse. Therefore we investigated the influence of twenty different surrounding/phantom materials for alanine dosimeters in clinical photon fields via Monte Carlo simulations. The relative electron density of the used materials was in the range [Formula: see text] up to 1.69, covering almost all materials appearing in inhomogeneous or anthropomorphic phantoms used in radiotherapy. The investigations were performed for three different clinical photon spectra ranging from 6 to 25 MV-X and Co-60 and as a result a perturbation correction [Formula: see text] depending on the environmental material was established. The Monte Carlo simulation show, that there is only a small dependence of [Formula: see text] on the phantom material and the photon energy, which is below  ±0.6%. The results confirm the good suitability of alanine detectors for in-vivo dosimetry.

  7. Perturbation correction for alanine dosimeters in different phantom materials in high-energy photon beams

    NASA Astrophysics Data System (ADS)

    von Voigts-Rhetz, P.; Anton, M.; Vorwerk, H.; Zink, K.

    2016-02-01

    In modern radiotherapy the verification of complex treatments plans is often performed in inhomogeneous or even anthropomorphic phantoms. For dose verification small detectors are necessary and therefore alanine detectors are most suitable. Though the response of alanine for a wide range of clinical photon energies in water is well know, the knowledge about the influence of the surrounding phantom material on the response of alanine is sparse. Therefore we investigated the influence of twenty different surrounding/phantom materials for alanine dosimeters in clinical photon fields via Monte Carlo simulations. The relative electron density of the used materials was in the range {{n}e}/{{n}e,\\text{w}}=0.20 up to 1.69, covering almost all materials appearing in inhomogeneous or anthropomorphic phantoms used in radiotherapy. The investigations were performed for three different clinical photon spectra ranging from 6 to 25 MV-X and Co-60 and as a result a perturbation correction {{k}\\text{env}} depending on the environmental material was established. The Monte Carlo simulation show, that there is only a small dependence of {{k}\\text{env}} on the phantom material and the photon energy, which is below  ±0.6%. The results confirm the good suitability of alanine detectors for in-vivo dosimetry.

  8. The spectrum of darkonium in the Sun

    NASA Astrophysics Data System (ADS)

    Kouvaris, Chris; Langæble, Kasper; Grønlund Nielsen, Niklas

    2016-10-01

    Dark matter that gets captured in the Sun may form positronium-like bound states if it self-interacts via light dark photons. In this case, dark matter can either annihilate to dark photons or recombine in bound states which subsequently also decay to dark photons. The fraction of the dark photons that leave the Sun without decaying to Standard Model particles have a characteristic energy spectrum which is a mixture of the direct annihilation process, the decays of ortho- and para- bound states and the recombination process. The ultimate decay of these dark photons to positron-electron pairs (via kinetic mixing) outside the Sun creates a distinct signal that can either identify or set strict constraints on dark photon models.

  9. Photon-deficient Compton scattering by nonthermal electrons - Comparison with gamma-ray burst spectra

    NASA Technical Reports Server (NTRS)

    Zdziarski, Andrzej A.; Lamb, Don Q.

    1986-01-01

    The model of gamma-ray-burst spectra proposed by Zdziarski and Lamb (1986, 1987) is reviewed and compared with observed spectra. In the model, the spectrum arises from multiple Compton scatterings in a nonthermal source with a deficit of soft photons. The steady-state electron distribution in such a source is a nonthermal power law that joins at low energies onto a thermal distribution that may be either optically thick or thin. Both cases lead naturally to a two-component spectrum with a photon-energy index in the X-ray spectrum which is much less than one and a photon-energy index in the gamma-ray spectrum which is larger than the X-ray photon-energy index. Fits to the observed gamma-ray-burst spectra (where data exist for both X-ray and gamma-ray energies) show good agreement with the model.

  10. Directly measuring mean and variance of infinite-spectrum observables such as the photon orbital angular momentum

    PubMed Central

    Piccirillo, Bruno; Slussarenko, Sergei; Marrucci, Lorenzo; Santamato, Enrico

    2015-01-01

    The standard method for experimentally determining the probability distribution of an observable in quantum mechanics is the measurement of the observable spectrum. However, for infinite-dimensional degrees of freedom, this approach would require ideally infinite or, more realistically, a very large number of measurements. Here we consider an alternative method which can yield the mean and variance of an observable of an infinite-dimensional system by measuring only a two-dimensional pointer weakly coupled with the system. In our demonstrative implementation, we determine both the mean and the variance of the orbital angular momentum of a light beam without acquiring the entire spectrum, but measuring the Stokes parameters of the optical polarization (acting as pointer), after the beam has suffered a suitable spin–orbit weak interaction. This example can provide a paradigm for a new class of useful weak quantum measurements. PMID:26477715

  11. Changes in the energy spectrum of anomalous oxygen and helium during 1977-1985

    NASA Technical Reports Server (NTRS)

    Cummings, A. C.; Stone, E. C.; Webber, W. R.

    1985-01-01

    Data was used from the cosmic ray experiment on the Voyager spacecraft to measure the energy spectrum of anomalous O and He during the period 1977 to 1985. These spectra are found to change dramatically after the middle of 1980, with the peak of plateau region of the differential spectrum shifting to a higher energy. This change appears to be related to the reversal of the solar magnetic field and could imply that particle drifts are important to the acceleration of propagation of these particles.

  12. Energy spectrum of cosmic-ray iron nucleus observed with emulsion chamber

    NASA Technical Reports Server (NTRS)

    Sato, Y.; Shimada, E.; Ohta, I.; Tasaka, S.; Tanaka, S.; Sugimoto, H.; Taira, K.; Tateyama, N.

    1985-01-01

    Energy spectrum of cosmic-ray Fe-nucleus has been measured from 4 GeV per nucleon to beyond 100 GeV per nucleon. The data were obtained using emulsion chambers on a balloon from Sanriku, Japan. The energies were estimated by the opening angle method after calibrated using 1.88 GeV per nucleon Fe collisions. The spectrum of Fe is approximately E-2.5 in the range from 10 to 200 GeV per nucleon. This result is in good agreement with those of other experiments.

  13. Influence of high-energy photons from cobalt-57 flood sources on scintillation camera uniformity images.

    PubMed

    Sokole, E B; Heckenberg, A; Bergmann, H

    1996-04-01

    Cobalt-57 flood sources are often used for system flood-field uniformity checks of scintillation camera performance. Such sources are now available in large sizes and with high activities. Uniformity images using new 57Co sources have shown artefacts which are not present in uniformity images obtained from technetium-99m flood sources of the same activity. The high-energy photons emitted by 57Co and cobalt isotope impurities appear to influence the images obtained. This was investigated in three cameras using three 57Co sources of different age. The flood-field images obtained with the 57Co sources showed non-uniformity patterns that were dependent on the age of the cobalt source, the distance of the source to the collimator, and the specific camera type. Quantification of the uniformity images reflected these findings. Energy spectra of a new 57Co source, obtained with an external 1024-channel analyser connected to the camera, showed a broad tail of high-energy photons above the 122-keV photopeak, due to Compton scatter and collimator penetration. This tail diminished with older sources and with increased source to collimator distance, indicating that in both situations fewer high-energy photons were being measured by the camera system. This tail of high-energy photons contributes to the total count rate, but because this is not obvious from the counts observed in the photopeak window, the camera can unsuspectingly be operated at too high a total countrate where pile-up effects become significant. Caution is therefore advised when using 57Co sources. Problems may be minimized by purchasing low-activity sources (certainly no more than 370 MBq), by placing the source at a distance from the collimator, e.g. 50 cm, by allowing a new source to decay, and by manufacturers producing 57Co sources without detectable radioactive contaminants.

  14. Photon energy response of luminescence dosemeters and its impact on assessment of Hp(10) and Hp(0.07) in mixed fields of varying energies of photons and beta radiation.

    PubMed

    Pradhan, A S

    2002-01-01

    X and gamma rays continue to remain the main contributors to the dose to humans. As these photons of varying energies are encountered in various applications, the study of photon energy response of a dosemeter is an important aspect to ensure the accuracy in dose measurement. Responses of dosemeters have to be experimentally established because for luminescence dosemeters, they depend not only on the effective atomic number (ratio of mass energy absorption coefficients of dosemeter and tissue) of the detector, but also considerably on the luminescence efficiency and the material surrounding the dosemeters. Metal filters are generally used for the compensation of energy dependence below 200 keV and/or to provide photon energy discrimination. It is noted that the contribution to Hp(0.07) could be measured more accurately than Hp(10). For the dosemeters exhibiting high photon energy-dependent response, estimation of the beta component of Hp(0.07) becomes very difficult in the mixed field of beta radiation and photons of energy less than 100 keV. Recent studies have shown that the thickness and the atomic number of metal filters not only affect the response below 200 keV but also cause a significant over-response for high energy (>6 MeV) photons often encountered in the environments of pressurised heavy water reactors and accelerators. PMID:12382729

  15. Center of mass energy and system-size dependence of photon production at forward rapidity at RHIC

    SciTech Connect

    STAR Collaboration; Abelev, Betty

    2010-07-05

    We present the multiplicity and pseudorapidity distributions of photons produced in Au+Au and Cu+Cu collisions at {radical}s{sub NN} = 62.4 and 200 GeV. The photons are measured in the region -3.7 < {eta} < -2.3 using the photon multiplicity detector in the STAR experiment at RHIC. The number of photons produced per average number of participating nucleon pairs increases with the beam energy and is independent of the collision centrality. For collisions with similar average numbers of participating nucleons the photon multiplicities are observed to be similar for Au+Au and Cu+Cu collisions at a given beam energy. The ratios of the number of charged particles to photons in the measured pseudorapidity range are found to be 1.4 {+-} 0.1 and 1.2 {+-} 0.1 for {radical}s{sub NN} = 62.4 GeV and 200 GeV, respectively. The energy dependence of this ratio could reflect varying contributions from baryons to charged particles, while mesons are the dominant contributors to photon production in the given kinematic region. The photon pseudorapidity distributions normalized by average number of participating nucleon pairs, when plotted as a function of {eta} - ybeam, are found to follow a longitudinal scaling independent of centrality and colliding ion species at both beam energies.

  16. Quality assurance of electron and photon beam energy using the BQ-CHECK phantom.

    PubMed

    Speight, Richard J; Esmail, Ashraf; Weston, Steve J

    2011-02-01

    The BQ-CHECK phantom (PTW Freiburg, Germany) has been designed to be used with a 2D ion chamber array to facilitate the quality assurance (QA) of electron and photon beam qualities (BQ). The BQ-CHECK phantom has three wedges covering the diagonal axes of the beam: two opposed aluminum wedges used to measure electron energy and a single copper wedge used to measure photon energy. The purpose of this work was to assess the suitability of the BQ-CHECK phantom for use in a routine QA program. A range of percentage depth dose (PDD) curves for two photon beams and four electron beams were measured using a MP3 plotting tank (PTW Freiburg). These beams were used to irradiate a STARCHECK array (PTW Freiburg) with and without the BQ-CHECK phantom on top of the array. For photons, the ratio of the signals from two chambers underneath the copper wedge was used as an effective TPR measurement (TPR(eff)) and, for electrons, the full width at half maximum of the profile (E(FWHM)) underneath the aluminum wedges was used as an electron energy constancy measurement. PDD measurements were compared with TPR(eff) and E(FWHM) to assess the sensitivity of the BQ-CHECK phantom. The clinical tolerances of TPReff were determined for 6 MV (0.634-0.649), and 10MV (0.683-0.692). For electrons, the clinical tolerances of EFWHM were determined for 6 MeV (94.8-103.4 mm), 8 MeV (105.5-114.0 mm), 10 MeV (125.4-133.9 mm) and 12 MeV (138.8-147.3 mm).Electron and photon energy metrics are presented which demonstrate that the BQ-CHECK phantom could be used to form part of an efficient routine monthly QA program. Acceptable beam quality limits for various nominal beam energies were established and at these limits, modified profiles were acquired using the STARCHECK array. From the modified profiles, E(FWHM) and TPR(eff) were determined for the electron and photon beams, respectively. It was demonstrated that both E(FWHM) and the TPR(eff) have a linear relationship with conventional beam quality metrics.

  17. Photonic color filters integrated with organic solar cells for energy harvesting.

    PubMed

    Park, Hui Joon; Xu, Ting; Lee, Jae Yong; Ledbetter, Abram; Guo, L Jay

    2011-09-27

    Color filters are indispensable in most color display applications. In most cases, they are chemical pigment-based filters, which produce a particular color by absorbing its complementary color, and the absorbed energy is totally wasted. If the absorbed and wasted energy can be utilized, e.g., to generate electricity, innovative energy-efficient electronic media could be envisioned. Here we show photonic nanostructures incorporated with photovoltaics capable of producing desirable colors in the visible band and utilize the absorbed light to simultaneously generate electrical powers. In contrast to the traditional colorant-based filters, these devices offer great advantages for electro-optic applications.

  18. Measurement of electron-positron spectrum in high-energy cosmic rays in the PAMELA experiment

    NASA Astrophysics Data System (ADS)

    Karelin, A. V.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; De Donato, C.; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Koldashov, S. V.; Koldobskiy, S. A.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A. A.; Mayorov, A. G.; Malakhov, V. V.; Marcelli, L.; Martucci, M.; Menn, W.; Merge, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Rossetto, L.; Simon, M.; Sparvoli, R.; Spillantini, P.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.

    2015-08-01

    At present the existing data on the cosmic ray electron energy spectra in the high energy range are fragmented, and the situation is exacerbated by their small number. In the satellite PAMELA experiment measurements at high energies are carried out by the calorimeter. The experimental data accumulated for more than 8 years of measurements, with the information of the calorimeter, the neutron detector and the scintillation counters made it possible to obtain the total spectrum of high-energy electrons and positrons in energy range 0.3-3 TeV.

  19. Holographic lens spectrum splitting photovoltaic system for increased diffuse collection and annual energy yield

    NASA Astrophysics Data System (ADS)

    Vorndran, Shelby D.; Wu, Yuechen; Ayala, Silvana; Kostuk, Raymond K.

    2015-09-01

    Concentrating and spectrum splitting photovoltaic (PV) modules have a limited acceptance angle and thus suffer from optical loss under off-axis illumination. This loss manifests itself as a substantial reduction in energy yield in locations where a significant portion of insulation is diffuse. In this work, a spectrum splitting PV system is designed to efficiently collect and convert light in a range of illumination conditions. The system uses a holographic lens to concentrate shortwavelength light onto a smaller, more expensive indium gallium phosphide (InGaP) PV cell. The high efficiency PV cell near the axis is surrounded with silicon (Si), a less expensive material that collects a broader portion of the solar spectrum. Under direct illumination, the device achieves increased conversion efficiency from spectrum splitting. Under diffuse illumination, the device collects light with efficiency comparable to a flat-panel Si module. Design of the holographic lens is discussed. Optical efficiency and power output of the module under a range of illumination conditions from direct to diffuse are simulated with non-sequential raytracing software. Using direct and diffuse Typical Metrological Year (TMY3) irradiance measurements, annual energy yield of the module is calculated for several installation sites. Energy yield of the spectrum splitting module is compared to that of a full flat-panel Si reference module.

  20. All-Particle Cosmic Ray Energy Spectrum Measured with 26 Icetop Stations

    NASA Technical Reports Server (NTRS)

    Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Altmann, D.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Baum, V.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H; Bell, M.; Benabderrahmane, M. L.; BenZvi, S.; Stamatikos, M.

    2013-01-01

    We report on a measurement of the cosmic ray energy spectrum with the IceTop air shower array, thesurface component of the IceCube Neutrino Observatory at the South Pole. The data used in this analysiswere taken between June and October, 2007, with 26 surface stations operational at that time, corresponding to about one third of the final array. The fiducial area used in this analysis was 0.122 square kilometers.The analysis investigated the energy spectrum from 1 to 100 PeV measured for three different zenithangle ranges between 0 and 46. Because of the isotropy of cosmic rays in this energy range the spectrafrom all zenith angle intervals have to agree. The cosmic-ray energy spectrum was determined under differentassumptions on the primary mass composition. Good agreement of spectra in the three zenithangle ranges was found for the assumption of pure proton and a simple two-component model. Forzenith angles theta less than 30 deg., where the mass dependence is smallest, the knee in the cosmic ray energy spectrumwas observed at about 4 PeV, with a spectral index above the knee of about -3.1. Moreover, an indicationof a flattening of the spectrum above 22 PeV was observed.

  1. Optimal energy for cell radiosensitivity enhancement by gold nanoparticles using synchrotron-based monoenergetic photon beams.

    PubMed

    Rahman, Wan Nordiana; Corde, Stéphanie; Yagi, Naoto; Abdul Aziz, Siti Aishah; Annabell, Nathan; Geso, Moshi

    2014-01-01

    Gold nanoparticles have been shown to enhance radiation doses delivered to biological targets due to the high absorption coefficient of gold atoms, stemming from their high atomic number (Z) and physical density. These properties significantly increase the likelihood of photoelectric effects and Compton scattering interactions. Gold nanoparticles are a novel radiosensitizing agent that can potentially be used to increase the effectiveness of current radiation therapy techniques and improve the diagnosis and treatment of cancer. However, the optimum radiosensitization effect of gold nanoparticles is strongly dependent on photon energy, which theoretically is predicted to occur in the kilovoltage range of energy. In this research, synchrotron-generated monoenergetic X-rays in the 30-100 keV range were used to investigate the energy dependence of radiosensitization by gold nanoparticles and also to determine the photon energy that produces optimum effects. This investigation was conducted using cells in culture to measure dose enhancement. Bovine aortic endothelial cells with and without gold nanoparticles were irradiated with X-rays at energies of 30, 40, 50, 60, 70, 81, and 100 keV. Trypan blue exclusion assays were performed after irradiation to determine cell viability. Cell radiosensitivity enhancement was indicated by the dose enhancement factor which was found to be maximum at 40 keV with a value of 3.47. The dose enhancement factor obtained at other energy levels followed the same direction as the theoretical calculations based on the ratio of the mass energy absorption coefficients of gold and water. This experimental evidence shows that the radiosensitization effect of gold nanoparticles varies with photon energy as predicted from theoretical calculations. However, prediction based on theoretical assumptions is sometimes difficult due to the complexity of biological systems, so further study at the cellular level is required to fully characterize the effects

  2. {phi}-Meson Photoproduction with Linearly Polarized Photons at Threshold Energies

    SciTech Connect

    Salamanca, Julian; Cole, Philip L.

    2007-10-26

    The observables provided by linearly-polarized photons are of interest in delineating the contributions of the various hadronic processes giving rise to vector meson photoproduction. In particular, we describe how {phi}-meson production affords an incisive tool for exploring the nature of the parity exchange at threshold energies, the strangeness content of proton, as well as extracting signatures for the violation of Okubo-Zweig-Iizuka observation (OZI rule). Our goal is to study the {gamma}-vectorp{yields}{phi}p reaction, with {phi}{yields}K{sup +}K{sup -}, in the photon energy range of 1.7 to 2.1 GeV by using the Coherent Linear Bremsstrahlung Facility in Hall B of Jefferson Laboratory, Newport News, VA. The data were collected during the g8b run in the summer of 2005.

  3. Φ-Meson Photoproduction with Linearly Polarized Photons at Threshold Energies

    SciTech Connect

    Salamanca, Julian; Cole, Philip L

    2007-10-01

    The observables provided by linearly-polarized photons are of interest in delineating the contributions of the various hadronic processes giving rise to vector meson photoproduction. In particular, we describe how Φ-meson production affords an incisive tool for exploring the nature of the parity exchange at threshold energies, the strangeness content of proton, as well as extracting signatures for the violation of Okubo-Zweig-Iizuka observation (OZI rule). Our goal is to study the γp → Φp reaction, with Φ → K+K-, in the photon energy range of 1.7 to 2.1 GeV by using the Coherent Linear Bremsstrahlung Facility in Hall B of Jefferson Laboratory, Newport News, VA. The data were collected during the g8b run in the summer of 2005.

  4. Photon-photon collisions via relativisitic mirrors

    SciTech Connect

    Koga, James K.

    2012-07-11

    Photon-photon scattering at low energies has been predicted theoretically for many years. However, due to the extremely small cross section there has been no experimental confirmation of this. Due to the rapid increase in laser irradiances and projected peak irradiances in planned facilities regimes could be reached where photon-photon scattering could be experimentally observed. We will first review basic aspects of photon-photon collisions concentrating on the calculation of the photon-photon scattering cross section. Then we will discuss the possibilities for observing these phenomena in ultra-high irradiance laser-plasma interactions involving relativistic mirrors.

  5. Recoil-proton polarization in high-energy deuteron photodisintegration with circularly plarized photons.

    SciTech Connect

    Jiang, X.; Arrington, J.; Benmokhtar, F.; Camsonne, A.; Chen, J. P.; Holt, R. J.; Qattan, I. A.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K.; Physics; Rutgers Univ.; Univ. Blaise Pascal; Thomas Jefferson National Accelerator Facility

    2007-05-01

    We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

  6. Recoil-Proton Polarization in High-Energy Deuteron Photodisintegration with Circularly Polarized Photons

    SciTech Connect

    Jiang, X.; Benmokhtar, F.; Glashauser, C.; McCormick, K.; Ransome, R. D.; Arrington, J.; Holt, R. J.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K.; Camsonne, A.

    2007-05-04

    We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

  7. Recoil-Proton Polarization in High-Energy Deuteron Photodisintegration with Circularly Polarized Photons

    SciTech Connect

    X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J. P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D. W. Higinbotham; R. J. Holt; C. W. de Jager; M. K. Jones; L. J. Kaufman; E. R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z.-E. Meziani; R. Michaels; B. Moffit; P. Monaghan; S. Nanda; K. D. Paschke; C. F. Perdrisat; V. Punjabi; I. A. Qattan; R. D. Ransome; P. E. Reimer; B. Reitz; A. Saha; E. C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G. M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; and L. Zhu

    2007-05-01

    We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

  8. An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks.

    PubMed

    Salim, Shelly; Moh, Sangman

    2016-01-01

    A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead. PMID:27376290

  9. An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks

    PubMed Central

    Salim, Shelly; Moh, Sangman

    2016-01-01

    A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead. PMID:27376290

  10. An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks.

    PubMed

    Salim, Shelly; Moh, Sangman

    2016-06-30

    A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead.

  11. Long-term differential energy spectrum for solar-flare iron-group particles

    NASA Technical Reports Server (NTRS)

    Blanford, G. E.; Fruland, R. M.; Morrison, D. A.

    1975-01-01

    A long-term solar-flare differential energy spectrum for iron-group nuclei from approximately 0.1 to approximately 600 MeV/amu is derived from track density profile measurements in sample 64455 and sample 68815. Measurements from uneroded surfaces were obtained from quench crystals of plagioclase in 64455, and a Kr-81/Kr method indicates that the exposure age of this sample is 2,010,000 yrs. The power laws which best fit the normalized track density data are reported; the energy spectrum consists of two power law curves smoothly joined together which in turn are smoothly connected to a modulated galactic cosmic-ray spectrum. Standard track production versus depth profiles can be used to determine solar-flare track exposure ages and erosion rates for lunar samples.

  12. Oscillations in two-dimensional photon-echo signals of excitonic and vibronic systems: Stick-spectrum analysis and its computational verification

    SciTech Connect

    Egorova, Dassia

    2014-01-21

    Stick-spectrum expressions for electronic two-dimensional (2D) photon-echo (PE) signal of a generic multi-level system are presented and employed to interrelate oscillations in individual peaks of 2D PE signal and the underlying properties (eigenstates and coherent dynamics) of excitonic or vibronic systems. When focusing on the identification of the origin of oscillations in the rephasing part of 2D PE it is found, in particular, that multiple frequencies in the evolution of the individual peaks do not necessarily directly reflect the underlying system dynamics. They may originate from the excited-state absorption contribution to the signal, or arise due to multi-level vibrational structure of the electronic ground state, and represent a superposition of system frequencies, while the latter may evolve independently. The analytical stick-spectrum predictions are verified and illustrated by numerical calculations of 2D PE signals of an excitonic trimer and of a displaced harmonic oscillator with unequal vibrational frequencies in the two electronic states. The excitonic trimer is the smallest excitonic oligomer where excited-state absorption may represent a superposition of excited-state coherences and significantly influence the phase of the observed oscillations. The displaced oscillator is used to distinguish between the frequencies of the ground-state and of the excited-state manifolds, and to demonstrate how the location of a cross peak in 2D pattern of the PE signal “predetermines” its oscillatory behavior. Although the considered models are kept as simple as possible for clarity, the stick-spectrum analysis provides a solid general basis for interpretation of oscillatory signatures in electronic 2D PE signals of much more complex systems with multi-level character of the electronic states.

  13. Energy-Sensitive Single-Photon X-ray and Particle Imaging

    NASA Astrophysics Data System (ADS)

    Lotto, Christian

    Energy-sensitive detectors perform asynchronous arrival detection of single X-Ray photons and particles. Their ability of measuring the detected particles' energy improves the performance of the particle counting applications and enables spectroscopic applications. In such detectors, either a semiconductor layer for direct conversion or a combination of a scintillator and a semiconductor sensing device for visible photons is used for generation of an electrical charge pulse per absorbed particle. This charge amount, which represents the particle energy, is detected by an asynchronous charge pulse detecting circuit. The noise of such circuits defines the lowest discrimination threshold of counting systems and the energy resolution of spectroscopic applications. Therefore, low noise, low power consumption, and low area are requirements for charge pulse detecting circuits used in segmented energy sensitive particle detectors with a high number of pixels. Choice of a sensing device, definition of the charge pulse detecting circuit's topology, and analysis of interdependences amongst the above performance parameters are covered and a context with employed readout schemes, processing circuits, and target applications is established in this chapter. Energy-sensitive detectors perform asynchronous arrival detection of single X-Ray photons and particles. Their ability of measuring the detected particles' energy improves the performance of the particle counting applications and enables spectroscopic applications. In such detectors, either a semiconductor layer for direct conversion or a combination of a scintillator and a semiconductor sensing device for visible photons is used for generation of an electrical charge pulse per absorbed particle. This charge amount, which represents the particle energy, is detected by an asynchronous charge pulse detecting circuit. The noise of such circuits defines the lowest discrimination threshold of counting systems and the energy

  14. Characterization of energy response for photon-counting detectors using x-ray fluorescence

    PubMed Central

    Ding, Huanjun; Cho, Hyo-Min; Barber, William C.; Iwanczyk, Jan S.; Molloi, Sabee

    2014-01-01

    Purpose: To investigate the feasibility of characterizing a Si strip photon-counting detector using x-ray fluorescence. Methods: X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on an edge illuminated Si strip detector. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing silver (Ag), iodine (I), barium (Ba), and gadolinium (Gd), were placed in small plastic containers with a diameter of approximately 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known fluorescence energies. The energy resolutions and charge-sharing fractions were also obtained from analytical fittings of the recorded fluorescence spectra. An analytical model, which employed four parameters that can be determined from the fluorescence calibration, was used to estimate the detector response function. Results: Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The average gain and offset of all pixels for detector energy calibration were determined to be 6.95 mV/keV and −66.33 mV, respectively. The detector’s energy resolution remained at approximately 2.7 keV for low energies, and increased slightly at 45 keV. The average charge-sharing fraction was estimated to be 36% within the investigated energy range of 20–45 keV. The simulated detector output based on the proposed response function agreed well with the experimental measurement. Conclusions: The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the

  15. Characterization of energy response for photon-counting detectors using x-ray fluorescence

    SciTech Connect

    Ding, Huanjun; Cho, Hyo-Min; Molloi, Sabee; Barber, William C.; Iwanczyk, Jan S.

    2014-12-15

    Purpose: To investigate the feasibility of characterizing a Si strip photon-counting detector using x-ray fluorescence. Methods: X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on an edge illuminated Si strip detector. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing silver (Ag), iodine (I), barium (Ba), and gadolinium (Gd), were placed in small plastic containers with a diameter of approximately 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known fluorescence energies. The energy resolutions and charge-sharing fractions were also obtained from analytical fittings of the recorded fluorescence spectra. An analytical model, which employed four parameters that can be determined from the fluorescence calibration, was used to estimate the detector response function. Results: Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The average gain and offset of all pixels for detector energy calibration were determined to be 6.95 mV/keV and −66.33 mV, respectively. The detector’s energy resolution remained at approximately 2.7 keV for low energies, and increased slightly at 45 keV. The average charge-sharing fraction was estimated to be 36% within the investigated energy range of 20–45 keV. The simulated detector output based on the proposed response function agreed well with the experimental measurement. Conclusions: The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the

  16. Specific absorbed fractions of energy at various ages from internal photon sources: 6, Newborn

    SciTech Connect

    Cristy, M.; Eckerman, K.F.

    1987-04-01

    Specific absorbed fraction (PHI's) in various organs of the body (target organs) from sources of monoenergetic photons in various other organs (source organs) are tabulated. In this volume PHI-values are tabulated for a newborn or 3.4-kg person. These PHI-values can be used in calculating the photon component of the dose-equivalent rate in a given target from a given radionuclide that is present in a given source organ. The International Commission on Radiological Protection recognizes that the endosteal, or bone surface, cells are the tissue at risk for bone cancer. We have applied the dosimetry methods that Spiers and co-workers developed for beta-emitting radionuclides deposited in bone to follow the transport of secondary electrons that were freed by photon interactions through the microscopic structure of the skeleton. With these methods we can estimate PHI in the endosteal cells and can better estimate PHI in the active marrow; the latter is overestimated with other methods at photon energies below 200 keV. 12 refs., 2 tabs.

  17. Contribution of activation products to occupational exposure following treatment using high-energy photons in radiotherapy.

    PubMed

    Petrović, Nina; Krestić-Vesović, Jelena; Stojanović, Darko; Ciraj-Bjelac, Olivera; Lazarević, Dorde; Kovacević, Milojko

    2011-01-01

    When high-energy photon beams are used for irradiation in radiotherapy, neutrons that are the result of photonuclear reactions create activation products that affect the occupational dose of radiotherapy staff. For the assessment of activation products in situ gamma spectroscopy was performed parallel to dose-rate measurements following irradiation, by using a high-energy photon beam from a linear accelerator Elekta Precise (Elekta, Stockholm, Sweden) used in radiotherapy. The major identified activation products were the following radioisotopes: (28)Al, (24)Na, (56)Mn, (54)Mn, (187)W, (64)Cu and (62)Cu. Based on the typical workload and dose-rate measurement, the assessed additional annual occupational dose ranged from 1.7 to 0.25 mSv. As the measured dose rate arising from the activation products rapidly decreases as a function of time, the assessed additional dose is negligible after 10 min following irradiation. To keep the occupational dose as low as reasonably achievable, it is recommended to delay entrance to the therapy room at least 2-4 min, when high-energy photons are used. This would reduce the effective dose by 30%.

  18. Calculated shielding characteristics of eight materials for neutrons and secondary photons produced by monoenergetic source neutrons with energies less than 400 MeV

    SciTech Connect

    Nakanishi, Noriyoshi; Shikata, Takashi; Fujita, Shin; Kosako, Toshiso

    1995-10-01

    Shielding characteristics of iron, lead, ordinary concrete, heavy concrete, graphite, marble, water, and paraffin were calculated for monoenergetic source neutrons with energies < 400 MeV. The depth dependence of neutron and secondary photon transmitted dose equivalents at the exit surfaces of shields of varying thickness is exhibited for some monoenergetic source neutrons and for each material. Their shielding characteristics are compared and discussed in terms of the degradation process of neutron energy and the change of neutron spectrum in typical shielding materials. Calculations were carried out by using the one-dimensional discrete ordinates code ANISN-JR and the cross-section library DLC-87/HILO. Systematic knowledge concerning the shielding of neutrons with energies < 400 MeV was successfully obtained.

  19. Photon-photon collisions

    SciTech Connect

    Brodsky, S.J.

    1985-01-01

    The study of photon-photon collisions has progressed enormously, stimulated by new data and new calculational tools for QCD. In the future we can expect precise determinations of ..cap alpha../sub s/ and ..lambda../sup ms/ from the ..gamma..*..gamma.. ..-->.. ..pi../sup 0/ form factor and the photon structure function, as well as detailed checks of QCD, determination of the shape of the hadron distribution amplitudes from ..gamma gamma.. ..-->.. H anti H, reconstruction of sigma/sub ..gamma gamma../ from exclusive channels at low W/sub ..gamma gamma../, definitive studies of high p/sub T/ hadron and jet production, and studies of threshold production of charmed systems. Photon-photon collisions, along with radiative decays of the psi and UPSILON, are ideal for the study of multiquark and gluonic resonances. We have emphasized the potential for resonance formation near threshold in virtually every hadronic exclusive channel, including heavy quark states c anti c c anti c, c anti c u anti u, etc. At higher energies SLC, LEP, ...) parity-violating electroweak effects and Higgs production due to equivalent Z/sup 0/ and W/sup + -/ beams from e ..-->.. eZ/sup 0/ and e ..-->.. nu W will become important. 44 references.

  20. Spectrum measurement with the Telescope Array Low Energy Extension (TALE) fluorescence detector

    NASA Astrophysics Data System (ADS)

    Zundel, Zachary James

    The Telescope Array (TA) experiment is the largest Ultra High Energy cosmic ray observatory in the northern hemisphere and is designed to be sensitive to cosmic ray air showers above 1018eV. Despite the substantial measurements made by TA and AUGER (the largest cosmic ray observatory in the southern hemisphere), there remains uncertainty about whether the highest energy cosmic rays are galactic or extragalactic in origin. Locating features in the cosmic ray energy spectrum below 1018eV that indicate a transition from galactic to extragalactic sources would clarify the interpretation of measurements made at the highest energies. The Telescope Array Low Energy Extension (TALE) is designed to extend the energy threshold of the TA observatory down to 1016.5eV in order to make such measurements. This dissertation details the construction, calibration, and operation of the TALE flu- orescence detector. A measurement of the flux of cosmic rays in the energy range of 1016.5 -- 1018.5eV is made using the monocular data set taken between September 2013 and January 2014. The TALE fluorescence detector observes evidence for a softening of the cosmic spectrum at 1017.25+/-0.5eV. The evidence of a change in the spectrum motivates continued study of 1016.5 -- 1018.5eV cosmic rays.

  1. Measurement of changes in linear accelerator photon energy through flatness variation using an ion chamber array

    SciTech Connect

    Gao Song; Balter, Peter A.; Rose, Mark; Simon, William E.

    2013-04-15

    Purpose: To compare the use of flatness versus percent depth dose (PDD) for determining changes in photon beam energy for a megavoltage linear accelerator. Methods: Energy changes were accomplished by adjusting the bending magnet current by up to {+-}15% in 5% increments away from the value used clinically. Two metrics for flatness, relative flatness in the central 80% of the field (Flat) and average maximum dose along the diagonals normalized by central axis dose (F{sub DN}), were measured using a commercially available planner ionization chamber array. PDD was measured in water at depths of 5 and 10 cm in 3 Multiplication-Sign 3 cm{sup 2} and 10 Multiplication-Sign 10 cm{sup 2} fields using a cylindrical chamber. Results: PDD was more sensitive to changes in energy when the beam energy was increased than when it was decreased. For the 18-MV beam in particular, PDD was not sensitive to energy reductions below the nominal energy. The value of Flat was found to be more sensitive to decreases in energy than to increases, with little sensitivity to energy increases above the nominal energy for 18-MV beams. F{sub DN} was the only metric that was found to be sensitive to both increases and reductions of energy for both the 6- and 18-MV beams. Conclusions: Flatness based metrics were found to be more sensitive to energy changes than PDD, In particular, F{sub DN} was found to be the most sensitive metric to energy changes for photon beams of 6 and 18 MV. The ionization chamber array allows this metric to be conveniently measured as part of routine accelerator quality assurance.

  2. Design and Fabrication of Photonic Crystals for Thermal Energy Conservation

    SciTech Connect

    Professor John Joannopoulos; Professor Yoel Fink

    2009-09-17

    The vision of intelligent and large-area fabrics capable of signal processing, sensing and energy harvesting has made incorporating electronic devices into flexible fibers an active area of research. Fiber-integrated rectifying junctions in the form of photovoltaic cells and light-emitting diodes (LEDs) have been fabricated on optical fiber substrates. However, the length of these fiber devices has been limited by the processing methods and the lack of a sufficiently conductive and transparent electrode. Their cylindrical device geometry is ideal for single device architectures, like photovoltaics and LEDs, but not amenable to building multiple devices into a single fiber. In contrast, the composite preform-to-fiber approach pioneered in our group addresses the key challenges of device density and fiber length simultaneously. It allows one to construct structured fibers composed of metals, insulators and semiconductors and enables the incorporation of many devices into a single fiber capable of performing complex tasks such as of angle of incidence and color detection. However, until now, devices built by the preform-to-fiber approach have demonstrated only ohmic behavior due to the chalcogenide semiconductor's amorphous nature and defect density. From a processing standpoint, non-crystallinity is necessary to ensure that the preform viscosity during thermal drawing is large enough to extend the time-scale of breakup driven by surface tension effects in the fluids to times much longer than that of the actual drawing. The structured preform cross-section is maintained into the microscopic fiber only when this requirement is met. Unfortunately, the same disorder that is integral to the fabrication process is detrimental to the semiconductors' electronic properties, imparting large resistivities and effectively pinning the Fermi level near mid-gap. Indeed, the defect density within the mobility gap of many chalcogenides has been found to be 1018-1019 cm-3 eV-1

  3. EDITORIAL: Semiconductor nanotechnology: novel materials and devices for electronics, photonics and renewable energy applications Semiconductor nanotechnology: novel materials and devices for electronics, photonics and renewable energy applications

    NASA Astrophysics Data System (ADS)

    Goodnick, Stephen; Korkin, Anatoli; Krstic, Predrag; Mascher, Peter; Preston, John; Zaslavsky, Alex

    2010-04-01

    Electronic and photonic information technology and renewable energy alternatives, such as solar energy, fuel cells and batteries, have now reached an advanced stage in their development. Cost-effective improvements to current technological approaches have made great progress, but certain challenges remain. As feature sizes of the latest generations of electronic devices are approaching atomic dimensions, circuit speeds are now being limited by interconnect bottlenecks. This has prompted innovations such as the introduction of new materials into microelectronics manufacturing at an unprecedented rate and alternative technologies to silicon CMOS architectures. Despite the environmental impact of conventional fossil fuel consumption, the low cost of these energy sources has been a long-standing economic barrier to the development of alternative and more efficient renewable energy sources, fuel cells and batteries. In the face of mounting environmental concerns, interest in such alternative energy sources has grown. It is now widely accepted that nanotechnology offers potential solutions for securing future progress in information and energy technologies. The Canadian Semiconductor Technology Conference (CSTC) forum was established 25 years ago in Ottawa as an important symbol of the intrinsic strength of the Canadian semiconductor research and development community, and the Canadian semiconductor industry as a whole. In 2007, the 13th CSTC was held in Montreal, moving for the first time outside the national capital region. The first three meetings in the series of 'Nano and Giga Challenges in Electronics and Photonics'— NGCM2002 in Moscow, NGCM2004 in Krakow, and NGC2007 in Phoenix— were focused on interdisciplinary research from the fundamentals of materials science to the development of new system architectures. In 2009 NGC2009 and the 14th Canadian Semiconductor Technology Conference (CSTC2009) were held as a joint event, hosted by McMaster University (10

  4. Balloon measurements of the energy spectrum of cosmic electrons between 1 and 25 GeV.

    NASA Technical Reports Server (NTRS)

    Earl, J. A.; Neely, D. E.; Rygg, T. A.

    1972-01-01

    During three balloon flights made in 1966 and 1967, cosmic electrons were investigated with the aid of a hodoscope detector that provided extensive and detailed information on each cosmic-ray event triggering the apparatus. Similar information obtained during calibration exposures to protons and pions as well as to electrons was used to provide identification of cosmic electrons and to determine their energies. Differential primary electron intensities measured in the range from 1 to 25 GeV were substantially larger than some earlier measurements. In conjunction with existing measurements at energies above 100 GeV, this finding indicates that the energy spectrum of cosmic electrons is steeper than that of cosmic-ray nuclei and consequently suggests that Compton/synchrotron energy loss plays a significant role in shaping the electron spectrum.

  5. Semiclassical analysis of the Efimov energy spectrum in the unitary limit

    SciTech Connect

    Bhaduri, Rajat K.; Brack, Matthias; Murthy, M. V. N.

    2011-06-15

    We demonstrate that the (s-wave) geometric spectrum of the Efimov energy levels in the unitary limit is generated by the radial motion of a primitive periodic orbit (and its harmonics) of the corresponding classical system. The action of the primitive orbit depends logarithmically on the energy. It is shown to be consistent with an inverse-squared radial potential with a lower cutoff radius. The lowest-order WKB quantization, including the Langer correction, is shown to reproduce the geometric scaling of the energy spectrum. The (WKB) mean-squared radii of the Efimov states scale geometrically like the inverse of their energies. The WKB wave functions, regularized near the classical turning point by Langer's generalized connection formula, are practically indistinguishable from the exact wave functions even for the lowest (n=0) state, apart from a tiny shift of its zeros that remains constant for large n.

  6. Power Versus Spectrum 2-D Sensing in Energy Harvesting Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    Zhang, Yanyan; Han, Weijia; Li, Di; Zhang, Ping; Cui, Shuguang

    2015-12-01

    Energy harvester based cognitive radio is a promising solution to address the shortage of both spectrum and energy. Since the spectrum access and power consumption patterns are interdependent, and the power value harvested from certain environmental sources are spatially correlated, the new power dimension could provide additional information to enhance the spectrum sensing accuracy. In this paper, the Markovian behavior of the primary users is considered, based on which we adopt a hidden input Markov model to specify the primary vs. secondary dynamics in the system. Accordingly, we propose a 2-D spectrum and power (harvested) sensing scheme to improve the primary user detection performance, which is also capable of estimating the primary transmit power level. Theoretical and simulated results demonstrate the effectiveness of the proposed scheme, in term of the performance gain achieved by considering the new power dimension. To the best of our knowledge, this is the first work to jointly consider the spectrum and power dimensions for the cognitive primary user detection problem.

  7. The effect of stochastic re-acceleration on the energy spectrum of shock-accelerated protons

    SciTech Connect

    Afanasiev, Alexandr; Vainio, Rami; Kocharov, Leon

    2014-07-20

    The energy spectra of particles in gradual solar energetic particle (SEP) events do not always have a power-law form attributed to the diffusive shock acceleration mechanism. In particular, the observed spectra in major SEP events can take the form of a broken (double) power law. In this paper, we study the effect of a process that can modify the power-law spectral form produced by the diffusive shock acceleration: the stochastic re-acceleration of energetic protons by enhanced Alfvénic turbulence in the downstream region of a shock wave. There are arguments suggesting that this process can be important when the shock propagates in the corona. We consider a coronal magnetic loop traversed by a shock and perform Monte Carlo simulations of interactions of shock-accelerated protons with Alfvén waves in the loop. The wave-particle interactions are treated self-consistently, so the finiteness of the available turbulent energy is taken into account. The initial energy spectrum of particles is taken to be a power law. The simulations reveal that the stochastic re-acceleration leads either to the formation of a spectrum that is described in a wide energy range by a power law (although the resulting power-law index is different from the initial one) or to a broken power-law spectrum. The resulting spectral form is determined by the ratio of the energy density of shock-accelerated protons to the wave energy density in the shock's downstream region.

  8. A phenomenological study of photon production in low energy neutrino nucleon scattering

    SciTech Connect

    Jenkins, James P; Goldman, Terry J

    2009-01-01

    Low energy photon production is an important background to many current and future precision neutrino experiments. We present a phenomenological study of t-channel radiative corrections to neutral current neutrino nucleus scattering. After introducing the relevant processes and phenomenological coupling constants, we will explore the derived energy and angular distributions as well as total cross-section predictions along with their estimated uncertainties. This is supplemented throughout with comments on possible experimental signatures and implications. We conclude with a general discussion of the analysis in the context of complimentary methodologies. This is based on a talk presented at the DPF 2009 meeting in Detroit MI.

  9. Simulation of Photon energy Spectra Using MISC, SOURCES, MCNP and GADRAS

    SciTech Connect

    Tucker, Lucas P.; Shores, Erik F.; Myers, Steven C.; Felsher, Paul D.; Garner, Scott E.; Solomon, Clell J. Jr.

    2012-08-14

    The detector response functions included in the Gamma Detector Response and Analysis Software (GADRAS) are a valuable resource for simulating radioactive source emission spectra. Application of these response functions to the results of three-dimensional transport calculations is a useful modeling capability. Using a 26.2 kg shell of depleted uranium (DU) as a simple test problem, this work illustrates a method for manipulating current tally results from MCNP into the GAM file format necessary for a practical link to GADRAS detector response functions. MISC (MCNP Intrinsic Source Constructor) and SOURCES 4C were used to develop photon and neutron source terms for subsequent MCNP transport, and the resultant spectrum is shown to be in good agreement with that from GADRAS. A 1 kg DU sphere was also modeled with the method described here and showed similarly encouraging results.

  10. Additions to the spectrum and energy levels and critical compilation of doubly ionized boron, B III

    NASA Astrophysics Data System (ADS)

    Kramida, A. E.; Ryabtsev, A. N.; Ekberg, J. O.; Kink, I.; Mannervik, S.; Martinson, I.

    2008-08-01

    We have undertaken the study of the Li-like spectrum of doubly ionized boron, B III. The spectroscopic data have been obtained with beam-foil spectroscopy and high-resolution spark spectroscopy. The experimental work was combined with theoretical calculations using ab initio and semi-empirical techniques. About 50 new transitions have been observed, and most of the previously known lines have been measured with improved accuracy. We have also critically evaluated all previous and recent data for this spectrum. Complete data on wavelengths and energy levels based on this analysis are tabulated.

  11. Search for anomalous production of events with a high energy lepton and photon at the Tevatron

    SciTech Connect

    Loginov, Andrey Borisovich

    2006-01-01

    We present results of a search for the anomalous production of events containing a high-transverse momentum charged lepton (ℓ, either e or μ) and photon (γ), accompanied by missing transverse energy (ET), and/or additional leptons and photons, and jets (X). We use the same kinematic selection criteria as in a previous CDF search, but with a substantially larger data set, 305 pb-1, a p$\\bar{p}$ collision energy of 1.96 TeV, and the upgraded CDF II detector. We find 42 ℓγET events versus a standard model expectation of 37.3 ± 5.4 events. The level of excess observed in Run I, 16 events with an expectation of 7.6 ± 0.7 events (corresponding to a 2.7 σ effect), is not supported by the new data. In the signature of ℓℓγ + X we observe 31 events versus an expectation of 23.0 ± 2.7 events. In this sample we find no events with an extra photon or ET and so find no events like the one eeγγ ET event observed in Run I.

  12. Testing oscillating primordial spectrum and oscillating dark energy with astronomical observations

    SciTech Connect

    Liu, Jie; Li, Hong; Zhang, Xinmin; Xia, Jun-Qing E-mail: hongli@ihep.ac.cn E-mail: xmzhang@ihep.ac.cn

    2009-07-01

    In this paper we revisit the issue of determining the oscillating primordial scalar power spectrum and oscillating equation of state of dark energy from the astronomical observations. By performing a global analysis with the Markov Chain Monte Carlo method, we find that the current observations from five-year WMAP and SDSS-LRG matter power spectrum, as well as the ''union'' supernovae sample, constrain the oscillating index of primordial spectrum and oscillating equation of state of dark energy with the amplitude less than |n{sub amp}| < 0.116 and |w{sub amp}| < 0.232 at 95% confidence level, respectively. This result shows that the oscillatory structures on the primordial scalar spectrum and the equation of state of dark energy are still allowed by the current data. Furthermore, we point out that these kinds of modulation effects will be detectable (or gotten a stronger constraint) in the near future astronomical observations, such as the PLANCK satellite, LAMOST telescope and the currently ongoing supernovae projects SNLS.

  13. Photon collider at TESLA

    NASA Astrophysics Data System (ADS)

    Telnov, Valery

    2001-10-01

    High energy photon colliders ( γγ, γe) based on backward Compton scattering of laser light is a very natural addition to e +e - linear colliders. In this report, we consider this option for the TESLA project. Recent study has shown that the horizontal emittance in the TESLA damping ring can be further decreased by a factor of four. In this case, the γγ luminosity in the high energy part of spectrum can reach about (1/3) Le +e -. Typical cross-sections of interesting processes in γγ collisions are higher than those in e +e - collisions by about one order of magnitude, so the number of events in γγ collisions will be more than that in e +e - collisions. Photon colliders can, certainly, give additional information and they are the best for the study of many phenomena. The main question is now the technical feasibility. The key new element in photon colliders is a very powerful laser system. An external optical cavity is a promising approach for the TESLA project. A free electron laser is another option. However, a more straightforward solution is "an optical storage ring (optical trap)" with a diode pumped solid state laser injector which is today technically feasible. This paper briefly reviews the status of a photon collider based on the linear collider TESLA, its possible parameters and existing problems.

  14. ESRF-type lattice design and optimization for the High Energy Photon Source

    NASA Astrophysics Data System (ADS)

    Xu, Gang; Jiao, Yi; Peng, Yue-Mei

    2016-02-01

    A new generation of storage ring-based light sources, called diffraction-limited storage rings (DLSRs), with emittance approaching the diffraction limit for multi-keV photons by means of multi-bend achromat lattices, has attracted extensive studies worldwide. Among various DLSR proposals, the hybrid multi-bend achromat concept developed at the European Synchrotron Radiation Facility (ESRF) predicts an effective way of minimizing the emittance while keeping the required chromatic sextupole strengths to an achievable level. For the High Energy Photon Source planned to be built in Beijing, an ESRF-type lattice design consisting of 48 hybrid seven-bend achromats is proposed to reach emittance as low as 60 pm·rad with a circumference of about 1296 m. Sufficient dynamic aperture, allowing vertical on-axis injection, and moderate momentum acceptance are achieved simultaneously for a promising ring performance. Supported by NSFC (11475202, 11405187) and Youth Innovation Promotion Association CAS (2015009)

  15. DISENTANGLING HADRONIC AND LEPTONIC CASCADE SCENARIOS FROM THE VERY-HIGH-ENERGY GAMMA-RAY EMISSION OF DISTANT HARD-SPECTRUM BLAZARS

    SciTech Connect

    Takami, Hajime; Murase, Kohta; Dermer, Charles D. E-mail: murase@ias.edu

    2013-07-10

    Recent data from the Fermi Large Area Telescope have revealed about a dozen distant hard-spectrum blazars that have very-high-energy (VHE; {approx}> 100 GeV) photons associated with them, but most of them have not yet been detected by imaging atmospheric Cherenkov Telescopes. Most of these high-energy gamma-ray spectra, like those of other extreme high-frequency peaked BL Lac objects, can be well explained either by gamma rays emitted at the source or by cascades induced by ultra-high-energy cosmic rays, as we show specifically for KUV 00311-1938. We consider the prospects for detection of the VHE sources by the planned Cherenkov Telescope Array (CTA) and show how it can distinguish the two scenarios by measuring the integrated flux above {approx}500 GeV (depending on source redshift) for several luminous sources with z {approx}< 1 in the sample. Strong evidence for the origin of ultra-high-energy cosmic rays could be obtained from VHE observations with CTA. Depending on redshift, if the often quoted redshift of KUV 00311-1938 (z = 0.61) is believed, then preliminary H.E.S.S. data favor cascades induced by ultra-high-energy cosmic rays. Accurate redshift measurements of hard-spectrum blazars are essential for this study.

  16. Mars Energy Spectrum studies from Assimilated MCS data using the UK MGCM

    NASA Astrophysics Data System (ADS)

    Valeanu, Alexandru; Read, Peter; Wang, Yixiong; Lewis, Stephen; Montabone, Luca; Tabataba-Vakili, Fachreddin

    2015-04-01

    Introduction The energy spectrum (ES) analysis is a renowned tool for understanding the driving mechanisms behind atmospheric turbulence (Lindborg, 1998). We aim to investigate whether energy and enstrophy inertial ranges exist in the kinetic energy spectrum (KES), and to quantify the corresponding cascades (with their ranges), and relationship with the atmospheric forcing and energy dissipation scales. The calculation of the ES from observational data is known to be highly non-trivial due to the lack of global coverage in space and time. Gage and Nastrom (1984) were the first to overcome this problem for Earth but this has not so far been attempted for Mars. Our approach is to take the sparse observational data and assimilate it using a global numerical model. We present preliminary results using the Mars Climate Sounder (MCS) retrievals and the LMD-UK Mars GCM (MGCM). This was pioneered by Lewis and Read (1999). Methodology The equations we used to calculate the Eddy and Zonal Mean kinetic energies are derived from total KES formula presented in Lindborg and Augier (2013). Hence, adding the two spectra together, we obtain the full KES spectrum as presented in their paper. For the Available Potential Energy Spectrum (APES), we have used a preliminary simplified version of the approach presented in Lindborg and Augier (2013). The Energy Spectra To date we have assimilated the MCS data at the resolution of T31 (triangular truncation), hence the ES only spans up to total wavenumber 31. This encompasses a portion of the energy inertial range, which might be expected to manifest the -3 exponential law by analogy with the Earth (Gage & Nastrom, 1984). Features: - velocities and corresponding KEs are higher with increasing height compared to Earth, - "-3" slope is restricted to ~30 km altitude, suggesting an early departure from the enstrophy inertial range, - boundary layer velocities are similar to Earth References 1. Gage and Nastrom, A Climatology of Atmospheric

  17. Photon Collider Physics with Real Photon Beams

    SciTech Connect

    Gronberg, J; Asztalos, S

    2005-11-03

    Photon-photon interactions have been an important probe into fundamental particle physics. Until recently, the only way to produce photon-photon collisions was parasitically in the collision of charged particles. Recent advances in short-pulse laser technology have made it possible to consider producing high intensity, tightly focused beams of real photons through Compton scattering. A linear e{sup +}e{sup -} collider could thus be transformed into a photon-photon collider with the addition of high power lasers. In this paper they show that it is possible to make a competitive photon-photon collider experiment using the currently mothballed Stanford Linear Collider. This would produce photon-photon collisions in the GeV energy range which would allow the discovery and study of exotic heavy mesons with spin states of zero and two.

  18. Integration of Semiconducting Sulfides for Full-Spectrum Solar Energy Absorption and Efficient Charge Separation.

    PubMed

    Zhuang, Tao-Tao; Liu, Yan; Li, Yi; Zhao, Yuan; Wu, Liang; Jiang, Jun; Yu, Shu-Hong

    2016-05-23

    The full harvest of solar energy by semiconductors requires a material that simultaneously absorbs across the whole solar spectrum and collects photogenerated electrons and holes separately. The stepwise integration of three semiconducting sulfides, namely ZnS, CdS, and Cu2-x S, into a single nanocrystal, led to a unique ternary multi-node sheath ZnS-CdS-Cu2-x S heteronanorod for full-spectrum solar energy absorption. Localized surface plasmon resonance (LSPR) in the nonstoichiometric copper sulfide nanostructures enables effective NIR absorption. More significantly, the construction of pn heterojunctions between Cu2-x S and CdS leads to staggered gaps, as confirmed by first-principles simulations. This band alignment causes effective electron-hole separation in the ternary system and hence enables efficient solar energy conversion.

  19. Measurements of the spectrum and energy dependence of X-ray transition radiation

    NASA Technical Reports Server (NTRS)

    Cherry, M. L.

    1978-01-01

    The results of experiments designed to test the theory of X-ray transition radiation and to verify the predicted dependence of the characteristic features of the radiation on the radiator dimensions are presented. The X-ray frequency spectrum produced by 5- to 9-GeV electrons over the range 4 to 30 keV was measured with a calibrated single-crystal Bragg spectrometer, and at frequencies up to 100 keV with an NaI scintillator. The interference pattern in the spectrum and the hardening of the radiation with increasing foil thickness are clearly observed. The energy dependence of the total transition-radiation intensity was studied using a radiator with large dimensions designed to yield energy-dependent signals at very high particle energies, up to E/mc-squared approximately equal to 100,000. The results are in good agreement with the theoretical predictions.

  20. Spectrum and energy levels of five-times ionized zirconium (Zr VI)

    NASA Astrophysics Data System (ADS)

    Reader, Joseph; Lindsay, Mark D.

    2016-02-01

    We carried out a new analysis of the spectrum of five-times-ionized zirconium Zr VI. For this we used sliding-spark discharges together with normal- and grazing-incidence spectrographs to observe the spectrum from 160 to 2000 Å. These observations showed that the analysis of this spectrum by Khan et al (1985 Phys. Scr. 31 837) contained a significant number of incorrect energy levels. We have now classified ˜420 lines as transitions between 23 even-parity levels 73 odd-parity levels. The 4s24p5, 4s4p6, 4s24p44d, 5s, 5d, 6s configurations are now complete, although a few levels of 4s24p45d are tentative. We determined Ritz-type wavelengths for ˜135 lines from the optimized energy levels. The uncertainties range from 0.0003 to 0.0020 Å. Hartree-Fock calculations and least-squares fits of the energy parameters to the observed levels were used to interpret the observed configurations. Oscillator strengths for all classified lines were calculated with the fitted parameters. The results are compared with values for the level energies, percentage compositions, and transition probabilities from recent ab initio theoretical calculations. The ionization energy was revised to 777 380 ± 300 cm-1 (96.38 ± 0.04 eV).

  1. Wavelet Spatial Energy Spectrums Studies on Drag Reduction by Micro-bubble Injection

    SciTech Connect

    Ling Zhen; Yassin Hassan

    2006-07-01

    In this study, continuous wavelet transforms and spatial correlation techniques are employed to determine the space-localized wavenumber energy spectrum of the velocity signals in turbulent channel flow. The flow conditions correspond to single phase flow and micro-bubbles injected two phase flow. The wavelet energy spectrums demonstrate that the wavenumber (eddy size) content of the velocity signals is not only space-dependent but also micro-bubbles can impact the eddy size content. Visual observations of the wavelet energy spectrum spatial distribution was realized by using Particle Image Velocimetry (PIV) measurement technique. The two phase flow condition corresponds to a drag reduction of 38.4% with void fraction of 4.9%. The present results provide evidence that micro-bubbles in the boundary layer of a turbulent channel flow can help adjust the eddy size distributions near the wall. This can assist in explaining that micro-bubbles are performing as buffers to keep the energy of fluid particles going in stream-wise direction and reducing the energy of fluid particles going in normal direction. (authors)

  2. Specific absorbed fractions of energy from internal photon sources in brain tumor and cerebrospinal fluid

    SciTech Connect

    Evans, J.F. )); Stubbs, J.B. )

    1995-03-01

    Transferrin, radiolabeled with In-111, can be coinjected into glioblastoma multiforme lesions, and subsequent scintigraphic imaging can demonstrate the biokinetics of the cytotoxic transferrin. The administration of [sup 111]In transferrin into a brain tumor results in distribution of radioactivity in the brain, brain tumor, and the cerebrospinal fluid (CSF). Information about absorbed radiation doses to these regions, as well as other nearby tissues and organs, is important for evaluating radiation-related risks from this procedure. The radiation dose is usually estimated for a mathematical representation of the human body. We have included source/target regions for the eye, lens of the eye, spinal column, spinal CSF, cranial CSF, and a 100-g tumor within the brain of an adult male phantom developed by Cristy and Eckerman. The spinal column, spinal CSF, and the eyes have not been routinely included in photon transport simulations. Specific absorbed fractions (SAFs) as a function of photon energy were calculated using the ALGAMP computer code, which utilizes Monte Carlo techniques for simulating photon transport. The ALGAMP code was run three times, with the source activity distributed uniformly within the tumor, cranial CSF, and the spinal CSF volumes. These SAFs, which were generated for 12 discrete photon energies ranging from 0.01 to 4.0 MeV, were used with decay scheme data to calculate [ital S]-values needed for estimating absorbed doses. [ital S]-values for [sup 111]In are given for three source regions (brain tumor, cranial CSF, and spinal CSF) and all standard target regions/organs, the eye and lens, as well as to tissues within these source regions. [ital S]-values for the skeletal regions containing active marrow are estimated. These results are useful in evaluating the radiation doses from intracranial administration of [sup 111]In transferrin.

  3. Simulation of ultra-high energy photon propagation in the geomagnetic field

    NASA Astrophysics Data System (ADS)

    Homola, P.; Góra, D.; Heck, D.; Klages, H.; PeĶala, J.; Risse, M.; Wilczyńska, B.; Wilczyński, H.

    2005-12-01

    The identification of primary photons or specifying stringent limits on the photon flux is of major importance for understanding the origin of ultra-high energy (UHE) cosmic rays. UHE photons can initiate particle cascades in the geomagnetic field, which leads to significant changes in the subsequent atmospheric shower development. We present a Monte Carlo program allowing detailed studies of conversion and cascading of UHE photons in the geomagnetic field. The program named PRESHOWER can be used both as an independent tool or together with a shower simulation code. With the stand-alone version of the code it is possible to investigate various properties of the particle cascade induced by UHE photons interacting in the Earth's magnetic field before entering the Earth's atmosphere. Combining this program with an extensive air shower simulation code such as CORSIKA offers the possibility of investigating signatures of photon-initiated showers. In particular, features can be studied that help to discern such showers from the ones induced by hadrons. As an illustration, calculations for the conditions of the southern part of the Pierre Auger Observatory are presented. Catalogue identifier:ADWG Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWG Program obtainable: CPC Program Library, Quen's University of Belfast, N. Ireland Computer on which the program has been thoroughly tested:Intel-Pentium based PC Operating system:Linux, DEC-Unix Programming language used:C, FORTRAN 77 Memory required to execute with typical data:<100 kB No. of bits in a word:32 Has the code been vectorized?:no Number of lines in distributed program, including test data, etc.:2567 Number of bytes in distributed program, including test data, etc.:25 690 Distribution format:tar.gz Other procedures used in PRESHOWER:IGRF [N.A. Tsyganenko, National Space Science Data Center, NASA GSFC, Greenbelt, MD 20771, USA, http://nssdc.gsfc.nasa.gov/space/model/magnetos/data-based/geopack.html], bessik

  4. Corrections on energy spectrum and scatterings for fast neutron radiography at NECTAR facility

    NASA Astrophysics Data System (ADS)

    Liu, Shu-Quan; Bücherl, Thomas; Li, Hang; Zou, Yu-Bin; Lu, Yuan-Rong; Guo, Zhi-Yu

    2013-11-01

    Distortions caused by the neutron spectrum and scattered neutrons are major problems in fast neutron radiography and should be considered for improving the image quality. This paper puts emphasis on the removal of these image distortions and deviations for fast neutron radiography performed at the NECTAR facility of the research reactor FRM- II in Technische Universität München (TUM), Germany. The NECTAR energy spectrum is analyzed and established to modify the influence caused by the neutron spectrum, and the Point Scattered Function (PScF) simulated by the Monte-Carlo program MCNPX is used to evaluate scattering effects from the object and improve image quality. Good analysis results prove the sound effects of the above two corrections.

  5. The puzzle of the ankle in the Ultrahigh Energy Cosmic Ray Spectrum, and composition indicators

    NASA Astrophysics Data System (ADS)

    Farrar, Glennys

    2015-08-01

    The sharp change in slope of the ultra-high energy cosmic ray spectrum around 10^18.6 eV (the ankle), combined with evidence of a light but extragalactic component near and below the ankle and intermediate composition above, has proved exceedingly challenging to understand theoretically. In this talk I discuss two possible solutions to the puzzle and how they can be (in)validated.First, I present a new mechanism whereby photo-disintegration of ultra-high energy nuclei in the region surrounding a UHECR accelerator naturally accounts for the observed spectrum and inferred composition (using LHC-tuned models extrapolated to UHE) at Earth. We discuss the conditions required to reproduce the spectrum above 10^17.5 eV and the composition, which -- in our model -- consists below the ankle of extragalactic protons and the high energy tail of Galactic Cosmic Rays, and above the ankle of surviving nuclei from the extended source. Predictions for the spectrum and flavors of neutrinos resulting from this process will be presented, and also implications for candidate sources.The other possible explanation is that in actuality UHECRs are entirely or almost entirely protons, and the cross-section for p-Air scattering increases more rapidly above center-of-mass energy of 70 TeV (10 times the current LHC cm energy) than predicted in conventional models. This gives an equally good fit to the depth-of-shower maximum behavior obverved by Auger, while being an intriguing sign of new state in QCD at extremely high energy density.

  6. Spectrum of synchronous picosecond sonoluminescence

    NASA Astrophysics Data System (ADS)

    Hiller, Robert; Putterman, Seth J.; Barber, Bradley P.

    1992-08-01

    The clocklike emission of picosecond pulses of light with a peak power over 30 mW has been observed to originate from a bubble trapped at the velocity node of a resonant sound field in water. The spectrum of this bright sonoluminescence is broadband and our measurements show that if a spectral peak exists, it lies at photon energies above 6 eV.

  7. Energy spectrum and chemical composition of cosmic rays between 0.3 and 10 PeV determined from the cherenkov-light and charged-particle distributions in air showers

    NASA Astrophysics Data System (ADS)

    HEGRA-Collaboration; Arqueros, F.; Barrio, J. A.; Bernlöhr, K.; Bojahr, H.; Calle, I.; Contreras, J. L.; Cortina, J.; Deckers, T.; Denninghoff, S.; Fonseca, V.; Gebauer, J.; González, J. C.; Haustein, V.; Heinzelmann, G.; Hohl, H.; Horns, D.; Ibarra, A.; Kestel, M.; Kirstein, O.; Kornmayer, H.; Kranich, D.; Krawczynski, H.; Lindner, A.; Lorenz, E.; Magnussen, N.; Meyer, H.; Mirzoyan, R.; Moralejo, A.; Padilla, L.; Petry, D.; Plaga, R.; Prahl, J.; Rauterberg, G.; Rhode, W.; Röhring, A.; Samorski, M.; Schmele, D.; Schröder, F.; Stamm, W.; Wiebel-Sooth, B.; Willmer, M.; Wittek, W.

    2000-07-01

    Measurements of the lateral distribution of Cherenkov photons with the wide-angle atmospheric Cherenkov light detector array AIROBICC and of the charged particle lateral distribution with the scintillator matrix of the HEGRA air-shower detector complex in air showers are reported. They are used in conjunction to determine the energy spectrum and coarse chemical composition of charged cosmic rays in the energy interval from 0.3 PeV to 10 PeV. With the atmospheric shower-front sampling technique these detectors measure the electromagnetic component of an extensive air shower via the lateral density distribution of the shower particles and of the Cherenkov photons. The data are compared with events generated with the CORSIKA program package with the QGSJET hadronic-event generator. Consistency checks performed with primary energy-reconstruction methods based on different shower observables indicate satisfactory agreement between these extensive air shower simulations and the experimental data. This permits to derive results concerning the energy spectrum and composition of charged cosmic rays. The energy spectrum features a so called ``knee'' at an energy of E_knee=3.98+4.66-0.83 (stat) +/- 0.53 (syst) PeV. Power law fits to the differential energy spectrum yield indices of -2.72+0.02-0.03 (stat) +/- 0.07 (syst) below and -3.22+0.47-0.59 (stat) +/- 0.08 (syst) above the knee. The best-fit elongation rate for the whole energy range is determined to 78.3 +/- 1.0 (stat) +/- 6.2 (syst) g/cm2. At the highest energies it seems to decrease slightly. The best-fit fraction of light nuclei decreases from 37 +28-21% (combined statistical and systematic) to 8 +32-8% (combined statistical and systematic) \\ in the energy range discussed here. A detailed study of the systematic errors reveals that a non-changing composition cannot be excluded.

  8. Relation between lineal energy distribution and relative biological effectiveness for photon beams according to the microdosimetric kinetic model.

    PubMed

    Okamoto, Hiroyuki; Kanai, Tatsuaki; Kase, Yuki; Matsumoto, Yoshitaka; Furusawa, Yoshiya; Fujita, Yukio; Saitoh, Hidetoshi; Itami, Jun; Kohno, Toshiyuki

    2011-01-01

    Our cell survival data showed the obvious dependence of RBE on photon energy: The RBE value for 200 kV X-rays was approximately 10% greater than those for mega-voltage photon beams. In radiation therapy using mega-voltage photon beams, the photon energy distribution outside the field is different with that in the radiation field because of a large number of low energy scattering photons. Hence, the RBE values outside the field become greater. To evaluate the increase in RBE, the method of deriving the RBE using the Microdosimetric Kinetic model (MK model) was proposed in this study. The MK model has two kinds of the parameters, tissue-specific parameters and the dose-mean lineal energy derived from the lineal energy distributions measured with a Tissue-Equivalent Proportional Counter (TEPC). The lineal energy distributions with the same geometries of the cell irradiations for 200 kV X-rays, (60)Co γ-rays, and 6 MV X-rays were obtained with the TEPC and Monte Carlo code GEANT4. The measured lineal energy distribution for 200 kV X-rays was quite different from those for mega-voltage photon beams. The dose-mean lineal energy of 200 kV X-rays showed the greatest value, 4.51 keV/µm, comparing with 2.34 and 2.36 keV/µm for (60)Co γ-rays and 6 MV X-rays, respectively. By using the results of the TEPC and cell irradiations, the tissue-specific parameters in the MK model were determined. As a result, the RBE of the photon beams (y(D): 2~5 keV/µm) in arbitrary conditions can be derived by the measurements only or the calculations only of the dose-mean lineal energy.

  9. High-energy two-electron capture with emission of a single photon

    SciTech Connect

    Drukarev, E. G.; Mikhailov, A. I.; Mikhailov, I. A.; Scheid, W.

    2007-12-15

    We investigate the two-electron capture with emission of a single photon to the ground state in the Coulomb field of a heavy nucleus in its collision with a light atom. Describing electron-electron interactions in the bound state perturbatively, we obtained an analytical formula for the high-energy limit of the cross section. In combination with previous results obtained in the same approach we calculated the cross section in a broad interval of energies of the collision. We show that the amplitude of the process at high energy depends on the behavior of the bound state wave function near the triple coalescence point. We analyze the properties of the approximate wave functions which are necessary for the description of the high-energy limit.

  10. X-ray grating interferometry at photon energies over 180 keV

    NASA Astrophysics Data System (ADS)

    Ruiz-Yaniz, M.; Koch, F.; Zanette, I.; Rack, A.; Meyer, P.; Kunka, D.; Hipp, A.; Mohr, J.; Pfeiffer, F.

    2015-04-01

    We report on the implementation and characterization of grating interferometry operating at an x-ray energy of 183 keV. With the possibility to use this technique at high x-ray energies, bigger specimens could be studied in a quantitative way. Also, imaging strongly absorbing specimens will benefit from the advantages of the phase and dark-field signals provided by grating interferometry. However, especially at these high photon energies the performance of the absorption grating becomes a key point on the quality of the system, because the grating lines need to keep their small width of a couple of micrometers and exhibit a greater height of hundreds of micrometers. The performance of high aspect ratio absorption gratings fabricated with different techniques is discussed. Further, a dark-field image of an alkaline multicell battery highlights the potential of high energy x-ray grating based imaging.

  11. X-ray grating interferometry at photon energies over 180 keV

    SciTech Connect

    Ruiz-Yaniz, M.; Koch, F.; Meyer, P.; Kunka, D.; Mohr, J.; Zanette, I.; Rack, A.; Hipp, A.; Pfeiffer, F.

    2015-04-13

    We report on the implementation and characterization of grating interferometry operating at an x-ray energy of 183 keV. With the possibility to use this technique at high x-ray energies, bigger specimens could be studied in a quantitative way. Also, imaging strongly absorbing specimens will benefit from the advantages of the phase and dark-field signals provided by grating interferometry. However, especially at these high photon energies the performance of the absorption grating becomes a key point on the quality of the system, because the grating lines need to keep their small width of a couple of micrometers and exhibit a greater height of hundreds of micrometers. The performance of high aspect ratio absorption gratings fabricated with different techniques is discussed. Further, a dark-field image of an alkaline multicell battery highlights the potential of high energy x-ray grating based imaging.

  12. The joint NASA/Goddard-University of Maryland research program in charged particle and high energy photon detector technology

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Progress made in the following areas is discussed: low energy ion and electron experiments; instrument design for current experiments; magnetospheric measurement of particles; ion measurement in the earth plasma sheet; abundance measurement; X-ray data acquisition; high energy physics; extragalactic astronomy; compact object astrophysics; planetology; and high energy photon detector technology.

  13. Influence of electrodes on the photon energy deposition in CVD-diamond dosimeters studied with the Monte Carlo code PENELOPE.

    PubMed

    Górka, B; Nilsson, B; Fernández-Varea, J M; Svensson, R; Brahme, A

    2006-08-01

    A new dosimeter, based on chemical vapour deposited (CVD) diamond as the active detector material, is being developed for dosimetry in radiotherapeutic beams. CVD-diamond is a very interesting material, since its atomic composition is close to that of human tissue and in principle it can be designed to introduce negligible perturbations to the radiation field and the dose distribution in the phantom due to its small size. However, non-tissue-equivalent structural components, such as electrodes, wires and encapsulation, need to be carefully selected as they may induce severe fluence perturbation and angular dependence, resulting in erroneous dose readings. By introducing metallic electrodes on the diamond crystals, interface phenomena between high- and low-atomic-number materials are created. Depending on the direction of the radiation field, an increased or decreased detector signal may be obtained. The small dimensions of the CVD-diamond layer and electrodes (around 100 microm and smaller) imply a higher sensitivity to the lack of charged-particle equilibrium and may cause severe interface phenomena. In the present study, we investigate the variation of energy deposition in the diamond detector for different photon-beam qualities, electrode materials and geometric configurations using the Monte Carlo code PENELOPE. The prototype detector was produced from a 50 microm thick CVD-diamond layer with 0.2 microm thick silver electrodes on both sides. The mean absorbed dose to the detector's active volume was modified in the presence of the electrodes by 1.7%, 2.1%, 1.5%, 0.6% and 0.9% for 1.25 MeV monoenergetic photons, a complete (i.e. shielded) (60)Co photon source spectrum and 6, 18 and 50 MV bremsstrahlung spectra, respectively. The shift in mean absorbed dose increases with increasing atomic number and thickness of the electrodes, and diminishes with increasing thickness of the diamond layer. From a dosimetric point of view, graphite would be an almost perfect

  14. Influence of electrodes on the photon energy deposition in CVD-diamond dosimeters studied with the Monte Carlo code PENELOPE

    NASA Astrophysics Data System (ADS)

    Górka, B.; Nilsson, B.; Fernández-Varea, J. M.; Svensson, R.; Brahme, A.

    2006-08-01

    A new dosimeter, based on chemical vapour deposited (CVD) diamond as the active detector material, is being developed for dosimetry in radiotherapeutic beams. CVD-diamond is a very interesting material, since its atomic composition is close to that of human tissue and in principle it can be designed to introduce negligible perturbations to the radiation field and the dose distribution in the phantom due to its small size. However, non-tissue-equivalent structural components, such as electrodes, wires and encapsulation, need to be carefully selected as they may induce severe fluence perturbation and angular dependence, resulting in erroneous dose readings. By introducing metallic electrodes on the diamond crystals, interface phenomena between high- and low-atomic-number materials are created. Depending on the direction of the radiation field, an increased or decreased detector signal may be obtained. The small dimensions of the CVD-diamond layer and electrodes (around 100 µm and smaller) imply a higher sensitivity to the lack of charged-particle equilibrium and may cause severe interface phenomena. In the present study, we investigate the variation of energy deposition in the diamond detector for different photon-beam qualities, electrode materials and geometric configurations using the Monte Carlo code PENELOPE. The prototype detector was produced from a 50 µm thick CVD-diamond layer with 0.2 µm thick silver electrodes on both sides. The mean absorbed dose to the detector's active volume was modified in the presence of the electrodes by 1.7%, 2.1%, 1.5%, 0.6% and 0.9% for 1.25 MeV monoenergetic photons, a complete (i.e. shielded) 60Co photon source spectrum and 6, 18 and 50 MV bremsstrahlung spectra, respectively. The shift in mean absorbed dose increases with increasing atomic number and thickness of the electrodes, and diminishes with increasing thickness of the diamond layer. From a dosimetric point of view, graphite would be an almost perfect electrode

  15. Quantum Spread Spectrum Communication

    SciTech Connect

    Humble, Travis S

    2011-01-01

    We show that communication of single-photon quantum states in a multi-user environment is improved by using spread spectrum communication techniques. We describe a framework for spreading, transmitting, despreading, and detecting single-photon spectral states that mimics conventional spread spectrum techniques. We show in the cases of inadvertent detection, unintentional interference, and multi-user management, that quantum spread spectrum communications may minimize receiver errors by managing quantum channel access.

  16. The X-ray spectrum and spectral energy distribution of FIRST J155633.8+351758: a LoBAL quasar with a probable polar outflow

    NASA Astrophysics Data System (ADS)

    Berrington, Robert C.; Brotherton, Michael S.; Gallagher, Sarah C.; Ganguly, Rajib; Shang, Zhaohui; DiPompeo, Michael; Chatterjee, Ritaban; Lacy, Mark; Gregg, Michael D.; Hall, Patrick B.; Laurent-Muehleisen, S. A.

    2013-12-01

    We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD Imaging Spectrometer S-array (ACIS-S) observation of the reddened, radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We investigated a number of models of varied sophistication to fit the 531-photon spectrum. These models ranged from simple power laws to power laws absorbed by hydrogen gas in differing ionization states and degrees of partial covering. Preferred fits indicate that the intrinsic X-ray flux is consistent with that expected for quasars of similarly high luminosity, i.e. an intrinsic, dereddened and unabsorbed optical to X-ray spectral index of -1.7. We cannot tightly constrain the intrinsic X-ray power-law slope, but find indications that it is flat (photon index Γ = 1.7 or flatter at a >99 per cent confidence for a neutral hydrogen absorber model). Absorption is present, with a column density a few times 1023 cm-2, with both partially ionized models and partially covering neutral hydrogen models providing good fits. We present several lines of argument that suggest the fraction of X-ray emissions associated with the radio jet is not large. We combine our Chandra data with observations from the literature to construct the spectral energy distribution of FIRST J1556+3517 from radio to X-ray energies. We make corrections for Doppler beaming for the pole-on radio jet, optical dust reddening and X-ray absorption, in order to recover a probable intrinsic spectrum. The quasar FIRST J1556+3517 seems to be an intrinsically normal radio-quiet quasar with a reddened optical/UV spectrum, a Doppler-boosted but intrinsically weak radio jet and an X-ray absorber not dissimilar from that of other broad absorption line quasars.

  17. The Cosmic Ray Energy Spectrum and Related Measurements with the Pierre Auger Observatory

    SciTech Connect

    Abraham, : J.; Abreu, P.; Aglietta, M.; Aguirre, C.; Ahn, E.J.; Allard, D.; Allekotte, I.; Allen, J.; Alvarez-Muniz, J.; Ambrosio, M.; Anchordoqui, L.

    2009-06-01

    These are presentations to be presented at the 31st International Cosmic Ray Conference, in Lodz, Poland during July 2009. It consists of the following presentations: (1) Measurement of the cosmic ray energy spectrum above 10{sup 18} eV with the Pierre Auger Observatory; (2) The cosmic ray flux observed at zenith angles larger than 60 degrees with the Pierre Auger Observatory; (3) Energy calibration of data recorded with the surface detectors of the Pierre Auger Observatory; (4) Exposure of the Hybrid Detector of The Pierre Auger Observatory; and (5) Energy scale derived from Fluorescence Telescopes using Cherenkov Light and Shower Universality.

  18. The knee in the cosmic ray energy spectrum from the simultaneous EAS charged particles and muon density spectra

    NASA Astrophysics Data System (ADS)

    Bijay, Biplab; Banik, Prabir; Bhadra, Arunava

    2016-09-01

    In this work we examine with the help of Monte Carlo simulation whether a consistent primary energy spectrum of cosmic rays emerges from both the experimentally observed total charged particles and muon size spectra of cosmic ray extensive air showers considering primary composition may or may not change beyond the knee of the energy spectrum. It is found that EAS-TOP observations consistently infer a knee in the primary energy spectrum provided the primary is pure unchanging iron whereas no consistent primary spectrum emerges from simultaneous use of the KASCADE observed total charged particle and muon spectra. However, it is also found that when primary composition changes across the knee the estimation of spectral index of total charged particle spectrum is quite tricky, depends on the choice of selection of points near the knee in the size spectrum.

  19. ART-XC: A Medium-energy X-ray Telescope System for the Spectrum-R-Gamma Mission

    NASA Technical Reports Server (NTRS)

    Arefiev, V.; Pavlinsky, M.; Lapshov, I.; Thachenko, A.; Sazonov, S.; Revnivtsev, M.; Semena, N.; Buntov,M.; Vikhlinin, A.; Gubarev, M.; ODell, S.; Ramsey, B.; Romaine, S.; Swartz. D/; Weisskopf, M.; Hasinger, G.; Predehl, P.; Grigorovich, S.; Litvin, D.; Meidinger, N.; Strueder, L. W.

    2008-01-01

    The ART-XC instrument is an X-ray grazing-incidence telescope system in an ABRIXAS-type optical configuration optimized for the survey observational mode of the Spectrum-RG astrophysical mission which is scheduled to be launched in 2011. ART-XC has two units, each equipped with four identical X-ray multi-shell mirror modules. The optical axes of the individual mirror modules are not parallel but are separated by several degrees to permit the four modules to share a single CCD focal plane detector, 1/4 of the area each. The 450-micron-thick pnCCD (similar to the adjacent eROSITA telescope detector) will allow detection of X-ray photons up to 15 keV. The field of view of the individual mirror module is about 18 x 18 arcminutes(exp 2) and the sensitivity of the ART-XC system for 4 years of survey will be better than 10(exp -12) erg s(exp -1) cm(exp -2) over the 4-12 keV energy band. This will allow the ART-XC instrument to discover several thousand new AGNs.

  20. Attenuation of photons at 3 to 14 keV energies in helium

    SciTech Connect

    Azuma, Y.; Berry, H.G.; Gemmell, D.S.

    1995-08-01

    Using X-ray photons at the X24A, X23B and X23A2 beam lines at NSLS, we measured the total photo-attenuation cross section of helium for photons in the energy range of 3 to 14 keV. In this range the photoionization cross section decreases rapidly with energy, so that Compton scattering is significant at 4 keV and dominates at the highest energies. The apparatus consisted of a 1.4-m long helium-absorption tube, 5 cm in diameter, with 75-{mu} thick, 7-mm diameter, kapton end windows. The tube could be filled with helium up to a pressure of 10{sup 6} Pa. We attained a precision of 1-2% in the attenuation cross section. The measurements verify the dominance of Compton scattering in this energy range and its importance in recent measurements of the ratio of double-to-single photoionization of helium. The measured cross sections are close to the combined calculated cross sections for Compton scattering and photoionization, and we are able to distinguish the contributions of the two effects.

  1. Two-photon excited quantum dots as energy donors for photosensitizer chlorin e6.

    PubMed

    Skripka, Artiom; Valanciunaite, Jurga; Dauderis, Gediminas; Poderys, Vilius; Kubiliute, Reda; Rotomskis, Ricardas

    2013-07-01

    The excitation-related problems in photodynamic therapy of cancer might be solved by combining two-photon (TP) irradiation and quantum dots (QDs) as effective energy donors for conventional photosensitizers (PS). Here, it is demonstrated for the first time that QD-chlorin e6 (Ce6) complex formed due to the hydrophobic interaction between Ce6 molecules and lipid coating of QDs can be effectively excited via TP irradiation at 1030 nm, which spectrally coincides with the biological tissue optical window. TP absorption cross-section for free QDs and Ce6 at 1030 nm was 3325 and 13 Goeppert-Mayer, respectively. Upon TP excitation of QD-Ce6 solution, the fluorescence band of bound Ce6 molecules was observed via energy transfer from excited QDs. Increasing concentration of Ce6 resulted in quenching of the photoluminescence of QDs and an increase in the fluorescence intensity of bound Ce6 molecules. These intensity changes coincided well with those observed upon single-photon excitation of QD-Ce6 solution when QDs alone are excited. The efficiency of energy transfer in QD-Ce6 complex upon TP excitation was about 80% (QD∶Ce61∶5). These results indicate that the effective excitation of PS with a low TP absorption cross-section is possible in such type noncovalent complexes via energy transfer from TP excited QDs.

  2. Two-photon excited quantum dots as energy donors for photosensitizer chlorin e6.

    PubMed

    Skripka, Artiom; Valanciunaite, Jurga; Dauderis, Gediminas; Poderys, Vilius; Kubiliute, Reda; Rotomskis, Ricardas

    2013-07-01

    The excitation-related problems in photodynamic therapy of cancer might be solved by combining two-photon (TP) irradiation and quantum dots (QDs) as effective energy donors for conventional photosensitizers (PS). Here, it is demonstrated for the first time that QD-chlorin e6 (Ce6) complex formed due to the hydrophobic interaction between Ce6 molecules and lipid coating of QDs can be effectively excited via TP irradiation at 1030 nm, which spectrally coincides with the biological tissue optical window. TP absorption cross-section for free QDs and Ce6 at 1030 nm was 3325 and 13 Goeppert-Mayer, respectively. Upon TP excitation of QD-Ce6 solution, the fluorescence band of bound Ce6 molecules was observed via energy transfer from excited QDs. Increasing concentration of Ce6 resulted in quenching of the photoluminescence of QDs and an increase in the fluorescence intensity of bound Ce6 molecules. These intensity changes coincided well with those observed upon single-photon excitation of QD-Ce6 solution when QDs alone are excited. The efficiency of energy transfer in QD-Ce6 complex upon TP excitation was about 80% (QD∶Ce61∶5). These results indicate that the effective excitation of PS with a low TP absorption cross-section is possible in such type noncovalent complexes via energy transfer from TP excited QDs. PMID:23864017

  3. Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

    DOE PAGESBeta

    Fukuda, Makoto; Kiran Kumar, N. A. P.; Koyanagi, Takaaki; Garrison, Lauren M.; Snead, Lance L.; Katoh, Yutai; Hasegawa, Akira

    2016-07-02

    We performed a neutron irradiation to single crystal pure tungsten in the mixed spectrum High Flux Isotope Reactor (HFIR). In order to investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ~90–~800 °C and fast neutron fluences were 0.02–9.00 × 1025 n/m2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. Moreover, the hardness and microstructure changes exhibitedmore » a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 1025 n/m2 (E > 0.1 MeV). Finally, irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 1025 n/m2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.« less

  4. Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

    NASA Astrophysics Data System (ADS)

    Fukuda, Makoto; Kiran Kumar, N. A. P.; Koyanagi, Takaaki; Garrison, Lauren M.; Snead, Lance L.; Katoh, Yutai; Hasegawa, Akira

    2016-10-01

    Neutron irradiation to single crystal pure tungsten was performed in the mixed spectrum High Flux Isotope Reactor (HFIR). To investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ∼90-∼800 °C and fast neutron fluences were 0.02-9.00 × 1025 n/m2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. The hardness and microstructure changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 1025 n/m2 (E > 0.1 MeV). Irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 1025 n/m2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.

  5. Quantitative material decomposition using spectral computed tomography with an energy-resolved photon-counting detector.

    PubMed

    Lee, Seungwan; Choi, Yu-Na; Kim, Hee-Joung

    2014-09-21

    Dual-energy computed tomography (CT) techniques have been used to decompose materials and characterize tissues according to their physical and chemical compositions. However, these techniques are hampered by the limitations of conventional x-ray detectors operated in charge integrating mode. Energy-resolved photon-counting detectors provide spectral information from polychromatic x-rays using multiple energy thresholds. These detectors allow simultaneous acquisition of data in different energy ranges without spectral overlap, resulting in more efficient material decomposition and quantification for dual-energy CT. In this study, a pre-reconstruction dual-energy CT technique based on volume conservation was proposed for three-material decomposition. The technique was combined with iterative reconstruction algorithms by using a ray-driven projector in order to improve the quality of decomposition images and reduce radiation dose. A spectral CT system equipped with a CZT-based photon-counting detector was used to implement the proposed dual-energy CT technique. We obtained dual-energy images of calibration and three-material phantoms consisting of low atomic number materials from the optimal energy bins determined by Monte Carlo simulations. The material decomposition process was accomplished by both the proposed and post-reconstruction dual-energy CT techniques. Linear regression and normalized root-mean-square error (NRMSE) analyses were performed to evaluate the quantitative accuracy of decomposition images. The calibration accuracy of the proposed dual-energy CT technique was higher than that of the post-reconstruction dual-energy CT technique, with fitted slopes of 0.97-1.01 and NRMSEs of 0.20-4.50% for all basis materials. In the three-material phantom study, the proposed dual-energy CT technique decreased the NRMSEs of measured volume fractions by factors of 0.17-0.28 compared to the post-reconstruction dual-energy CT technique. It was concluded that the

  6. Contribution from individual nearby sources to the spectrum of high-energy cosmic-ray electrons

    NASA Astrophysics Data System (ADS)

    Sedrati, R.; Attallah, R.

    2014-04-01

    In the last few years, very important data on high-energy cosmic-ray electrons and positrons from high-precision space-born and ground-based experiments have attracted a great deal of interest. These particles represent a unique probe for studying local comic-ray accelerators because they lose energy very rapidly. These energy losses reduce the lifetime so drastically that high-energy cosmic-ray electrons can attain the Earth only from rather local astrophysical sources. This work aims at calculating, by means of Monte Carlo simulation, the contribution from some known nearby astrophysical sources to the cosmic-ray electron/positron spectra at high energy (≥ 10 GeV). The background to the electron energy spectrum from distant sources is determined with the help of the GALPROP code. The obtained numerical results are compared with a set of experimental data.

  7. Diffuse gamma radiation. [intensity, energy spectrum and spatial distribution from SAS 2 observations

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Simpson, G. A.; Thompson, D. J.

    1978-01-01

    Results are reported for an investigation of the intensity, energy spectrum, and spatial distribution of the diffuse gamma radiation detected by SAS 2 away from the galactic plane in the energy range above 35 MeV. The gamma-ray data are compared with relevant data obtained at other wavelengths, including 21-cm emission, radio continuum radiation, and the limited UV and radio information on local molecular hydrogen. It is found that there are two quite distinct components to the diffuse radiation, one of which shows a good correlation with the galactic matter distribution and continuum radiation, while the other has a much steeper energy spectrum and appears to be isotropic at least on a coarse scale. The galactic component is interpreted in terms of its implications for both local and more distant regions of the Galaxy. The apparently isotropic radiation is discussed partly with regard to the constraints placed on possible models by the steep energy spectrum, the observed intensity, and an upper limit on the anisotropy.

  8. Energy Spectrum and Composition of Ultra High Energy Cosmic Ray Showers Using Hybrid Analysis from Telescope Array

    NASA Astrophysics Data System (ADS)

    Jui, Charles; Allen, Monica; Abu-Zayyad, Tareq; Stokes, Benjamin; Ivanov, Dmitri

    2013-04-01

    The Telescope Array (TA) consists of 38 fluorescence telescopes spread over three detector sites. The three sites at located the periphery of a surface array of 507 scintillation counters, covering 700 square km, with a spacing of 1.2 km. TA is designed to study the energy spectrum, composition, and arrival direction anisotropy of ultrahigh energy cosmic rays (UHECR). A unique feature of TA is that one of three fluorescence detector (FD) sites, Middle Drum (MD), is instrumented with 14 refurbished telescopes from the High Resolution Fly's Eye (HiRes) experiment. This commonality provides TA with a direct link back to the HiRes experiment and data. Using the scintillator detector data in conjunction with the MD data improves the geometrical reconstruction and hence provides a more accurate reconstruction of the energy of the primary particle and shower profile. The Middle Drum hybrid spectrum composition results will be presented.

  9. The photon

    NASA Astrophysics Data System (ADS)

    Collins, Russell L.

    2009-10-01

    There are no TEM waves, only photons. Lets build a photon, using a radio antenna. A short antenna (2L<< λ) simplifies the calculation, letting B fall off everywhere as 1/r^2. The Biot-Savart law finds B = (μ0/4π)(LI0/r^2)θφt. The magnetic flux thru a semi-circle of radius λ/2 is set equal to the flux quantum h/e, determining the needed source strength, LI0. From this, one can integrate the magnetic energy density over a sphere of radius λ/2 and finds it to be 1.0121 hc/λ. Pretty close. A B field collapses when the current ceases, but the photon evades this by creating a ɛ0E / t displacement current at center that fully supports the toroidal B assembly as it moves at c. This E=vxB arises because the photon moves at c. Stopped, a photon decays. At every point along the photon's path, an observer will note a transient oscillation of an E field. This sources the EM ``guiding wave'', carrying little or no energy and expanding at c. At the head of the photon, all these spherical guiding waves gather ``in-phase'' as a planar wavefront. This model speaks to all the many things we know about light. The photon is tiny, but its guiding wave is huge.

  10. Electronic structure of ReO3Me by variable photon energy photoelectron spectroscopy, absorption spectroscopy and density functional calculations.

    PubMed

    de Simone, Monica; Coreno, Marcello; Green, Jennifer C; McGrady, Sean; Pritchard, Helen

    2003-03-24

    Valence photoelectron (PE) spectra have been measured for ReO(3)Me using a synchrotron source for photon energies ranging between 20 and 110 eV. Derived branching ratios (BR) and relative partial photoionization cross sections (RPPICS) are interpreted in the context of a bonding model calculated using density functional theory (DFT). Agreement between calculated and observed ionization energies (IE) is excellent. The 5d character of the orbitals correlates with the 5p --> 5d resonances of the associated RPPICS; these resonances commence around 47 eV. Bands with 5d character also show a RPPICS maximum at 35 eV. The RPPICS associated with the totally symmetric 4a(1) orbital, which has s-like character, shows an additional shape resonance with an onset of 43 eV. The PE spectrum of the inner valence and core region measured with photon energies of 108 and 210 eV shows ionization associated with C 2s, O 2s, and Re 4f and 5p electrons. Absorption spectra measured in the region of the O1s edge showed structure assignable to excitation to the low lying empty "d" orbitals of this d(0) molecule. The separation of the absorption bands corresponded with the calculated orbital splitting and their intensity with the calculated O 2p character. Broad bands associated with Re 4d absorption were assigned to (2)D(5/2) and (2)D(3/2) hole states. Structure was observed associated with the C1s edge but instrumental factors prevented firm assignment. At the Re 5p edge, structure was observed on the (2)P(3/2) absorption band resulting from excitation to the empty "d" levels. The intensity ratios differed from that of the O 1s edge structure but were in good agreement with the calculated 5d character of these orbitals. An absorption was observed at 45 eV, which, in the light of the resonance in the 4a(1) RPPICS, is assigned to a 4a(1) --> ne, na(2) transition. The electronic structure established for ReO(3)Me differs substantially from that of TiCl(3)Me and accounts for the difference in

  11. Photonic effects on the Förster resonance energy transfer efficiency

    NASA Astrophysics Data System (ADS)

    Rabouw, Freddy T.; den Hartog, Stephan A.; Senden, Tim; Meijerink, Andries

    2014-04-01

    Förster resonance energy transfer (ET) between luminescent species is applied in bio-imaging, lighting and photovoltaics, and has an important role in photosynthesis. However, the fundamental question of whether ET rates and efficiencies can be tuned by the photonic environment remains under debate. Here we show that ET rates are independent of the photonic environment, using the model system of LaPO4 nanocrystals co-doped with Ce3+ donors and Tb3+ acceptors. Although the radiative emission rate of the Ce3+ excited state increases with the refractive index of the solvent in which the nanocrystals are dispersed, the Ce3+-to-Tb3+ ET rate does not. We demonstrate that, as a result, lower refractive index solvents enable higher ET efficiencies leading to higher Tb3+ emission intensities. Furthermore, an analytical model for ET in (nano)crystalline host materials is presented, able to predict the dependence of ET efficiencies on the photonic environment and the concentration of acceptor ions.

  12. Microsystem for remote sensing of high energy radiation with associated extremely low photon flux densities

    NASA Astrophysics Data System (ADS)

    Otten, A.; Jain, V. K.

    2015-08-01

    This paper presents a microsystem for remote sensing of high energy radiation in extremely low flux density conditions. With wide deployment in mind, potential applications range from nuclear non-proliferation, to hospital radiation-safety. The daunting challenge is the low level of photon flux densities - emerging from a Scintillation Crystal (SC) on to a ~1 mm-square detector, which are a factor of 10000 or so lower than those acceptable to recently reported photonic chips (including `single-photon detection' chips), due to a combination of low Lux, small detector size, and short duration SC output pulses - on the order of 1 μs. These challenges are attempted to be overcome by the design of an innovative `System on a Chip' type microchip, with high detector sensitivity, and effective coupling from the SC to the photodetector. The microchip houses a tiny n+ diff p-epi photodiode (PD) as well as the associated analog amplification and other related circuitry, all fabricated in 0.5micron, 3-metal 2-poly CMOS technology. The amplification, together with pulse-shaping of the photocurrent-induced voltage signal, is achieved through a tandem of two capacitively coupled, double-cascode amplifiers. Included in the paper are theoretical estimates and experimental results.

  13. Two-photon above-threshold ionization of hydrogen over the photon energy range from 15 eV to 50 keV

    SciTech Connect

    Florescu, Viorica; Budriga, Olimpia; Bachau, Henri

    2011-09-15

    We investigate the absorption of two identical photons from the ground state of hydrogen-like atoms over an energy range that extends beyond that explored up to now. Our approach is based on a hybrid formula, valid in second-order perturbation theory, in which the A{sup 2} contribution from the nonrelativistic Hamiltonian is treated exactly, while the A{center_dot}P contribution is calculated in dipole approximation. We find that, at least up to 50 keV, the nonrelativistic dipole approximation, based only on the A{center_dot}P contribution, determines the values of the total cross section. Our numerical results, covering photon energies from 90 nm (13.7 eV) to 0.0248 nm (50 keV) are in very good agreement with most previous theoretical works. Differences with recent results are discussed.

  14. Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

    SciTech Connect

    Bromberger, H. Liu, H.; Chávez-Cervantes, M.; Gierz, I.; Ermolov, A.; Belli, F.; Abdolvand, A.; Russell, P. St. J.; Travers, J. C.; Calegari, F.; Li, M. T.; Lin, C. T.; Cavalleri, A.

    2015-08-31

    A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few μJ energy generate vacuum ultraviolet radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi{sub 2}Se{sub 3} with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials.

  15. Constructing Interfacial Energy Transfer for Photon Up- and Down-Conversion from Lanthanides in a Core-Shell Nanostructure.

    PubMed

    Zhou, Bo; Tao, Lili; Chai, Yang; Lau, Shu Ping; Zhang, Qinyuan; Tsang, Yuen Hong

    2016-09-26

    We report a new mechanistic strategy for controlling and modifying the photon emission of lanthanides in a core-shell nanostructure by using interfacial energy transfer. By taking advantage of this mechanism with Gd(3+) as the energy donor, we have realized efficient up- and down-converted emissions from a series of lanthanide emitters (Eu(3+) , Tb(3+) , Dy(3+) , and Sm(3+) ) in these core-shell nanoparticles, which do not need a migratory host sublattice. Moreover, we have demonstrated that the Gd(3+) -mediated interfacial energy transfer, in contrast to energy migration, is the leading process contributing to the photon emission of lanthanide dopants for the NaGdF4 @NaGdF4 core-shell system. Our finding suggests a new direction for research into better control of energy transfer at the nanometer length scale, which would help to stimulate new concepts for designing and improving photon emission of the lanthanide-based luminescent materials.

  16. Cosmic ray energy spectrum around the knee obtained by the Tibet Experiment and future prospects

    NASA Astrophysics Data System (ADS)

    Katayose, Yusaku

    The measurement of the energy spectrum and the chemical composition of cosmic rays at the 'Knee' energy region have been made in the Tibet-AS experiment since 1990. The 1st phase of the Tibet hybrid experiment(1996-1999) consisted of Tibet II air-shower array(AS), Emulsion Chamber(EC) and burst detector(BD). The EC was used to detect high energy-gamma-families of the energy greater than 20 TeV at the core of ASs of which more than 80% are induced by light nuclei like protons or helium. Due to the high spatial resolution of the EC, proton and helium events were separated from others and we obtained the energy spectrum of each of them using 177 family events. We also obtained all-particle energy spectrum of primary cosmic rays in a wide range from 1014 eV to 1017 eV by the Tibet-III air-shower array. The size spectrum exhibits a sharp knee at a corresponding primary energy around 4 PeV. These results strongly indicated that the fraction of the light component to the all particle spectrum is decreasing around the knee.The observation of the AS core has been continued with upgraded Tibet III array and burst detectors without using X-ray films, which still works as the selector for the air showers induced by light component (pHe). This second phase experiment shows that the dominance of the heavy elements at the knee reported by the first phase experiment is confirmed with higher statistics by one order.Our results suggest that the main component at the knee is heavy elements (heavier than helium) because of the low intensities of observed proton and helium fluxes, whose summed flux are less than 30% of all particles. A new air-shower-core detector(YAC) will be added to the Tibet AS array to explicitly measure the heavy elements around the knee and beyond. In this paper, the results of composition study with the Tibet experiment are summarized and the prospects for the next phase experiment are described.

  17. In-phantom neutron dose distribution for bladder cancer cases treated with high-energy photons

    NASA Astrophysics Data System (ADS)

    Khaled, N. E.; Attalla, E. M.; Ammar, H.; Khalil, W.

    2011-06-01

    This work presents an estimation of the neutron dose distribution for common bladder cancer cases treated with high-energy photons of 15 MV therapy accelerators. Neutron doses were measured in an Alderson phantom, using TLD 700 and 600 thermoluminescence dosimeters, resembling bladder cancer cases treated with high-energy photons from 15 MV LINAC and having a treatment plan using the four-field pelvic box technique. Thermal neutron dose distribution in the target area and the surrounding tissue was estimated. The sensitivity of all detectors for both gamma and neutrons was estimated and used for correction of the TL reading. TLD detectors were irradiated with a Co60 gamma standard source and thermal neutrons at the irradiation facility of the National Institute for Standards (NIS). The TL to dose conversion factor was estimated in terms of both Co60 neutron equivalent dose and thermal neutron dose. The dose distribution of photo-neutrons throughout each target was estimated and presented in three-dimensional charts and isodose curves. The distribution was found to be non-isotropic through the target. It varied from a minimum of 0.23 mSv/h to a maximum of 2.07 mSv/h at 6 cm off-axis. The mean neutron dose equivalent was found to be 0.63 mSv/h, which agrees with other published literature. The estimated average neutron equivalent to the bladder per administered therapeutic dose was found to be 0.39 mSv Gy-1, which is also in good agreement with published literature. As a consequence of a complete therapeutic treatment of 50 Gy high-energy photons at 15 MV, the total thermal neutron equivalent dose to the abdomen was found to be about 0.012 Sv.

  18. Luminescence imaging of water during irradiation of X-ray photons lower energy than Cerenkov- light threshold

    NASA Astrophysics Data System (ADS)

    Yamamoto, Seiichi; Koyama, Shuji; Komori, Masataka; Toshito, Toshiyuki

    2016-10-01

    Luminescence imaging of water using X-ray photon irradiation at energy lower than maximum energy of ~200 keV is thought to be impossible because the secondary electrons produced in this energy range do not emit Cerenkov- light. Contrary to this consensus assumption, we show that the luminescence imaging of water can be achieved by X-ray irradiation at energy lower than 120 keV. We placed water phantoms on a table with a conventional X-ray imaging system, and luminescence images of these phantoms were measured with a high-sensitivity, cooled charge coupled device (CCD) camera during X-ray photon irradiation at energy below 120 keV. We also carried out such imaging of an acrylic block and plastic scintillator. The luminescence images of water phantoms taken during X-ray photon irradiation clearly showed X-ray photon distribution. The intensity of the X-ray photon images of the phantom increased almost proportionally to the number of X-ray irradiations. Lower-energy X-ray photon irradiation showed lower-intensity luminescence at the deeper parts of the phantom due to the higher X-ray absorption in the water phantom. Furthermore, lower-intensity luminescence also appeared at the deeper parts of the acrylic phantom due to its higher density than water. The intensity of the luminescence for water was 0.005% of that for plastic scintillator. Luminescence imaging of water during X-ray photon irradiation at energy lower than 120 keV was possible. This luminescence imaging method is promising for dose estimation in X-ray imaging systems.

  19. Towards hybrid pixel detectors for energy-dispersive or soft X-ray photon science.

    PubMed

    Jungmann-Smith, J H; Bergamaschi, A; Brückner, M; Cartier, S; Dinapoli, R; Greiffenberg, D; Huthwelker, T; Maliakal, D; Mayilyan, D; Medjoubi, K; Mezza, D; Mozzanica, A; Ramilli, M; Ruder, Ch; Schädler, L; Schmitt, B; Shi, X; Tinti, G

    2016-03-01

    JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications at free-electron lasers and synchrotron light sources. The JUNGFRAU 0.4 prototype presented here is specifically geared towards low-noise performance and hence soft X-ray detection. The design, geometry and readout architecture of JUNGFRAU 0.4 correspond to those of other JUNGFRAU pixel detectors, which are charge-integrating detectors with 75 µm × 75 µm pixels. Main characteristics of JUNGFRAU 0.4 are its fixed gain and r.m.s. noise of as low as 27 e(-) electronic noise charge (<100 eV) with no active cooling. The 48 × 48 pixels JUNGFRAU 0.4 prototype can be combined with a charge-sharing suppression mask directly placed on the sensor, which keeps photons from hitting the charge-sharing regions of the pixels. The mask consists of a 150 µm tungsten sheet, in which 28 µm-diameter holes are laser-drilled. The mask is aligned with the pixels. The noise and gain characterization, and single-photon detection as low as 1.2 keV are shown. The performance of JUNGFRAU 0.4 without the mask and also in the charge-sharing suppression configuration (with the mask, with a `software mask' or a `cluster finding' algorithm) is tested, compared and evaluated, in particular with respect to the removal of the charge-sharing contribution in the spectra, the detection efficiency and the photon rate capability. Energy-dispersive and imaging experiments with fluorescence X-ray irradiation from an X-ray tube and a synchrotron light source are successfully demonstrated with an r.m.s. energy resolution of 20% (no mask) and 14% (with the mask) at 1.2 keV and of 5% at 13.3 keV. The performance evaluation of the JUNGFRAU 0.4 prototype suggests that this detection system could be the starting point for a future detector development effort for either applications in the soft X-ray energy regime or for an energy

  20. Potential and challenges of upgrading the Advanced Photon Source to an Energy Recovery Linac.

    SciTech Connect

    Borland, M.; Decker, G.; Nassiri, A.; Sun, Y.-e; White, M.; Accelerator Systems Division

    2007-01-01

    The Advanced Photon Source (APS) is a third generation synchrotron radiation source operating at 7 GeV that has been in operation for over 10 years. In that time, the emittance has been improved from 8 nm to the present value of 3.1 nm, which is close to the practical minimum. Recently, APS undertook an intensive exploration of potential upgrades, including options for a replacement storage ring or Energy Recovery Linac (ERL) injector. Our conclusion was that only the ERL would provide a dramatically new capability. This paper discusses the potential performance available from an ERL upgrade to the APS and reviews the challenges of delivering this performance.

  1. Towards hybrid pixel detectors for energy-dispersive or soft X-ray photon science.

    PubMed

    Jungmann-Smith, J H; Bergamaschi, A; Brückner, M; Cartier, S; Dinapoli, R; Greiffenberg, D; Huthwelker, T; Maliakal, D; Mayilyan, D; Medjoubi, K; Mezza, D; Mozzanica, A; Ramilli, M; Ruder, Ch; Schädler, L; Schmitt, B; Shi, X; Tinti, G

    2016-03-01

    JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications at free-electron lasers and synchrotron light sources. The JUNGFRAU 0.4 prototype presented here is specifically geared towards low-noise performance and hence soft X-ray detection. The design, geometry and readout architecture of JUNGFRAU 0.4 correspond to those of other JUNGFRAU pixel detectors, which are charge-integrating detectors with 75 µm × 75 µm pixels. Main characteristics of JUNGFRAU 0.4 are its fixed gain and r.m.s. noise of as low as 27 e(-) electronic noise charge (<100 eV) with no active cooling. The 48 × 48 pixels JUNGFRAU 0.4 prototype can be combined with a charge-sharing suppression mask directly placed on the sensor, which keeps photons from hitting the charge-sharing regions of the pixels. The mask consists of a 150 µm tungsten sheet, in which 28 µm-diameter holes are laser-drilled. The mask is aligned with the pixels. The noise and gain characterization, and single-photon detection as low as 1.2 keV are shown. The performance of JUNGFRAU 0.4 without the mask and also in the charge-sharing suppression configuration (with the mask, with a `software mask' or a `cluster finding' algorithm) is tested, compared and evaluated, in particular with respect to the removal of the charge-sharing contribution in the spectra, the detection efficiency and the photon rate capability. Energy-dispersive and imaging experiments with fluorescence X-ray irradiation from an X-ray tube and a synchrotron light source are successfully demonstrated with an r.m.s. energy resolution of 20% (no mask) and 14% (with the mask) at 1.2 keV and of 5% at 13.3 keV. The performance evaluation of the JUNGFRAU 0.4 prototype suggests that this detection system could be the starting point for a future detector development effort for either applications in the soft X-ray energy regime or for an energy

  2. Setting the jet energy scale in the CMS calorimeter using events with direct photons

    NASA Astrophysics Data System (ADS)

    Golutvin, I. A.; Zarubin, A. V.; Kodolova, O. L.; Konoplyanikov, V. F.; Ul'Yanov, A. L.; Shmatov, S. V.

    2008-09-01

    The procedure of setting the jet energy using events with direct photons proposed as one of the methods of jet calibration in the CMS is studied. Based on complete simulation of events in the CMS including the effects of pile-up of additional events for the initial beam luminosity of the accelerator ( L = 2 × 1033 cm-2s-1), the rules for event selection during calibration are proposed. Errors of the proposed method due to the background and the radiation in the ISRare estimated.

  3. Physics of reflective optics for the soft gamma-ray photon energy range

    DOE PAGESBeta

    Fernandez-Perea, Monica; Descalle, Marie -Anne; Soufli, Regina; Ziock, Klaus P.; Alameda, Jennifer; Baker, Sherry L.; McCarville, Tom J.; Honkimaki, Veijo; Ziegler, Eric; Jakobsen, Anders C.; et al

    2013-07-12

    Traditional multilayer reflective optics that have been used in the past for imaging at x-ray photon energies as high as 200 keV are governed by classical wave phenomena. However, their behavior at higher energies is unknown, because of the increasing effect of incoherent scattering and the disagreement between experimental and theoretical optical properties of materials in the hard x-ray and gamma-ray regimes. Here, we demonstrate that multilayer reflective optics can operate efficiently and according to classical wave physics up to photon energies of at least 384 keV. We also use particle transport simulations to quantitatively determine that incoherent scattering takesmore » place in the mirrors but it does not affect the performance at the Bragg angles of operation. Furthermore, our results open up new possibilities of reflective optical designs in a spectral range where only diffractive optics (crystals and lenses) and crystal monochromators have been available until now.« less

  4. Development of Phase-Stable Photon Upconverters for Efficient Solar Energy Utilization

    NASA Astrophysics Data System (ADS)

    Murakami, Yoichi

    Photon upconversion based on triplet-triplet annihilation (TTA) of excited triplet molecules is drawing attention due to its applicability for weak incident light, possessing a potential for improving efficiencies of solar energy conversion devices. Since energy transfer between triplet levels of different molecules and TTA are based on the Dexter mechanism, inter-molecular collision is necessary and hence the majority of previous studies have been done with organic solvents, which are volatile and flammable. This paper presents the development and characterization of phase-stable photon upconverters fabricated with ionic liquids, which are room temperature molten salts with negligible vapor pressure and high thermal stability. The employed aromatic molecules, which are carrier of photo-created energies and are non-polar (or weakly polar) molecules, are found to be stable in the polar environment of ionic liquids, contrary to expectation. The mechanism of the stable solvation is proposed. The upconversion quantum yields are found to rapidly saturate as the excitation light power increases. An analytical model was developed and compared with the experimental data. It is shown that ionic liquids are not viscous media for the purpose of TTA-based upconversion.

  5. Energy spectrum of the Dirac equation for the Scharzschild and Kerr fields

    SciTech Connect

    Ternov, I.M.; Gaina, A.B.

    1988-08-01

    We consider the effect of relativistic corrections and rotation of the central body on the structure of the energy spectrum of a particle with spin in the Schwarzchild and Kerr fields. A splitting of levels is obtained, which corresponds to the classical shift of the perihelion of the orbit and precession of the plane of the gravitational spin-orbit interaction and several nonlinear spin effects are calculated.

  6. Maximum pixel spectrum: a new tool for detecting and recovering rare, unanticipated features from spectrum image data cubes.

    PubMed

    Bright, D S; Newbury, D E

    2004-11-01

    A new software tool, the maximum pixel spectrum, detects rare events within a spectrum image data cube, such as that generated with electron-excited energy-dispersive X-ray spectrometry in a scanning electron microscope. The maximum pixel spectrum is a member of a class of 'derived spectra' that are constructed from the spectrum image data cube. Similar to a conventional spectrum, a derived spectrum is a linear array of intensity vs. channel index that corresponds to photon energy. A derived spectrum has the principal characteristics of a real spectrum so that X-ray peaks can be recognized. A common example of a derived spectrum is the summation spectrum, which is a linear array in which the summation of all pixels within each energy plane gives the intensity value for that channel. The summation spectrum is sensitive to the dominant features of the data cube. The maximum pixel spectrum is constructed by selecting the maximum pixel value within each X-ray energy plane, ignoring the remaining pixels. Peaks corresponding to highly localized trace constituents or foreign contaminants, even those that are confined to one pixel of the image, can be seen at a glance when the maximum pixel spectrum is compared with the summation spectrum. PMID:15516230

  7. Magnetic diffusion effects on the ultra-high energy cosmic ray spectrum and composition

    SciTech Connect

    Mollerach, Silvia; Roulet, Esteban E-mail: roulet@cab.cnea.gov.ar

    2013-10-01

    We discuss the effects of diffusion of high energy cosmic rays in turbulent extra-galactic magnetic fields. We find an approximate expression for the low energy suppression of the spectrum of the different mass components (with charge Z) in the case in which this suppression happens at energies below ∼ Z EeV, so that energy losses are dominated by the adiabatic ones. The low energy suppression appears when cosmic rays from the closest sources take a time comparable to the age of the Universe to reach the Earth. This occurs for energies E < Z EeV (B/nG)√(l{sub c}/Mpc)(d{sub s}/70Mpc) in terms of the magnetic field RMS strength B, its coherence length l{sub c} and the typical separation between sources d{sub s}. We apply this to scenarios in which the sources produce a mixed composition and have a relatively low maximum rigidity (E{sub max} ∼ (2–10)Z EeV), finding that diffusion has a significant effect on the resulting spectrum, the average mass and on its spread, in particular reducing this last one. For reasonable values of B and l{sub c} these effects can help to reproduce the composition trends observed by the Auger Collaboration for source spectra compatible with Fermi acceleration.

  8. The hybrid energy spectrum of Telescope Array's Middle Drum Detector and surface array

    NASA Astrophysics Data System (ADS)

    Abbasi, R. U.; Abe, M.; Abu-Zayyad, T.; Allen, M. G.; Anderson, R.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Chae, M. J.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, W. R.; Fujii, T.; Fukushima, M.; Goto, T.; Hanlon, W.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Honda, K.; Ikeda, D.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kawata, K.; Kido, E.; Kim, H. B.; Kim, J. H.; Kim, J. H.; Kitamura, S.; Kitamura, Y.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lim, S. I.; Lundquist, J. P.; Machida, K.; Martens, K.; Matsuda, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Mukai, K.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nonaka, T.; Nozato, A.; Ogio, S.; Ogura, J.; Ohnishi, M.; Ohoka, H.; Oki, K.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Sampson, A. L.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Shin, H. S.; Smith, J. D.; Sokolsky, P.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T. A.; Suzawa, T.; Takamura, M.; Takeda, M.; Takeishi, R.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Uchihori, Y.; Udo, S.; Urban, F.; Vasiloff, G.; Wong, T.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yashiro, K.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zollinger, R.; Zundel, Z.

    2015-08-01

    The Telescope Array experiment studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated when a primary cosmic ray particle interacts with the atmosphere. Meanwhile, scintillator detectors measure the lateral distribution of secondary shower particles that hit the ground. The Middle Drum (MD) fluorescence telescope station consists of 14 telescopes from the High Resolution Fly's Eye (HiRes) experiment, providing a direct link back to the HiRes measurements. Using the scintillator detector data in conjunction with the telescope data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. The Middle Drum hybrid spectrum is presented and compared to that measured by the Middle Drum station in monocular mode. Further, the hybrid data establishes a link between the Middle Drum data and the surface array. A comparison between the Middle Drum hybrid energy spectrum and scintillator Surface Detector (SD) spectrum is also shown.

  9. Peculiarities of the electron energy spectrum in the Coulomb field of a superheavy nucleus

    NASA Astrophysics Data System (ADS)

    Voronov, B. L.; Gitman, D. M.; Levin, A. D.; Ferreira, R.

    2016-05-01

    We consider the peculiarities of the electron energy spectrum in the Coulomb field of a superheavy nucleus and discuss the long history of an incorrect interpretation of this problem in the case of a pointlike nucleus and its current correct solution. We consider the spectral problem in the case of a regularized Coulomb potential. For some special regularizations, we derive an exact equation for the point spectrum in the energy interval (-m,m) and find some of its solutions numerically. We also derive an exact equation for charges yielding bound states with the energy E = -m; some call them supercritical charges. We show the existence of an infinite number of such charges. Their existence does not mean that the oneparticle relativistic quantum mechanics based on the Dirac Hamiltonian with the Coulomb field of such charges is mathematically inconsistent, although it is physically unacceptable because the spectrum of the Hamiltonian is unbounded from below. The question of constructing a consistent nonperturbative second-quantized theory remains open, and the consequences of the existence of supercritical charges from the standpoint of the possibility of constructing such a theory also remain unclear.

  10. Energy spectrum of superfluid turbulence with no normal-fluid component.

    PubMed

    Araki, Tsunehiko; Tsubota, Makoto; Nemirovskii, Sergey K

    2002-09-30

    The energy of superfluid turbulence without the normal fluid is studied numerically under the vortex filament model. Time evolution of the Taylor-Green vortex is calculated under the full nonlocal Biot-Savart law. It is shown that for k<2pi/l the energy spectrum is very similar to the Kolmogorov's -5/3 law which is the most important statistical property of the conventional turbulence, where k is the wave number of the Fourier component of the velocity field and l is the average intervortex spacing. The vortex length distribution converges to a scaling property reflecting the self-similarity of the tangle. PMID:12366052

  11. ATOMIC AND MOLECULAR PHYSICS: Energy spectrum and superfluidity of spin-2 ultracold bosons in optical lattices

    NASA Astrophysics Data System (ADS)

    Wang, Yong-Jun; Liu, Xian-Feng; Han, Jiu-Rong

    2009-12-01

    This paper studies the superfluidity of ultracold spin-2 Bose atoms with weak interactions in optical lattices by calculating the excitation energy spectrum using the Bogoliubov approach. The energy spectra exhibit the characteristics of the superfluid-phase explicitly and it finds the nonvanishing critical speeds of superfluid. The obtained results display that the critical speeds of superfluid are different for five spin components and can be controlled by adjusting the lattice parameters in experiments. Finally it discusses the feasibilities of implementing and measuring superfluid.

  12. VERIFICATION OF THE INL/COMBINE7 NEUTRON ENERGY SPECTRUM CODE

    SciTech Connect

    Barry D. Ganapol; Woo Y. Yoon; David W. Nigg

    2008-09-01

    We construct semi-analytic benchmarks for the neutron slowing down equations in the thermal, resonance and fast energy regimes through mathematical embedding. The method features a fictitious time-dependent slowing down equations solved via Taylor series expansion over discrete “time” intervals. Two classes of benchmarks are considered- the first treats methods of solution and the second the multigroup approximation itself. We present several meaningful benchmark methods comparisons with the COMBINE7 energy spectrum code and a simple demonstration of convergence of the multigroup approximation.

  13. Usefulness of an energy-binned photon-counting x-ray detector for dental panoramic radiographs

    NASA Astrophysics Data System (ADS)

    Fukui, Tatsumasa; Katsumata, Akitoshi; Ogawa, Koichi; Fujiwara, Shuu

    2015-03-01

    A newly developed dental panoramic radiography system is equipped with a photon-counting semiconductor detector. This photon-counting detector acquires transparent X-ray beams by dividing them into several energy bands. We developed a method to identify dental materials in the patient's teeth by means of the X-ray energy analysis of panoramic radiographs. We tested various dental materials including gold alloy, dental amalgam, dental cement, and titanium. The results of this study suggest that X-ray energy scattergram analysis could be used to identify a range of dental materials in a patient's panoramic radiograph.

  14. Measurements of the energy spectrum of electrons emanating from solid materials irradiated by a picosecond laser

    SciTech Connect

    Di Stefano, C. A. Kuranz, C. C.; Thomas, A. G. R.; Drake, R. P.; Keiter, P. A.; Rasmus, A. M.; Wan, W. C.; Joglekar, A. S.; McKelvey, A.; Zhao, Z.; Klein, S. R.; Seely, J. F.; Williams, G. J.; Park, J.; Chen, H.; Kemp, G. E.; MacDonald, M. J.; Pereira, N. R.; Jarrott, L. C.; Peebles, J.; and others

    2015-04-15

    In this work, we present the results of experiments observing the properties of the electron stream generated laterally when a laser irradiates a metal. We find that the directionality of the electrons is dependent upon their energies, with the higher-energy tail of the spectrum (∼1 MeV and higher) being more narrowly focused. This behavior is likely due to the coupling of the electrons to the electric field of the laser. The experiments are performed by using the Titan laser to irradiate a metal wire, creating the electron stream of interest. These electrons propagate to nearby spectator wires of differing metals, causing them to fluoresce at their characteristic K-shell energies. This fluorescence is recorded by a crystal spectrometer. By varying the distances between the wires, we are able to probe the divergence of the electron stream, while by varying the medium through which the electrons propagate (and hence the energy-dependence of electron attenuation), we are able to probe the energy spectrum of the stream.

  15. A Monte Carlo study of reflection electron energy loss spectroscopy spectrum of a carbon contaminated surface

    SciTech Connect

    Da, B.; Li, Z. Y.; Chang, H. C.; Ding, Z. J.; Mao, S. F.

    2014-09-28

    It has been experimentally found that the carbon surface contamination influences strongly the spectrum signals in reflection electron energy loss spectroscopy (REELS) especially at low primary electron energy. However, there is still little theoretical work dealing with the carbon contamination effect in REELS. Such a work is required to predict REELS spectrum for layered structural sample, providing an understanding of the experimental phenomena observed. In this study, we present a numerical calculation result on the spatially varying differential inelastic mean free path for a sample made of a carbon contamination layer of varied thickness on a SrTiO{sub 3} substrate. A Monte Carlo simulation model for electron interaction with a layered structural sample is built by combining this inelastic scattering cross-section with the Mott's cross-section for electron elastic scattering. The simulation results have clearly shown that the contribution of the electron energy loss from carbon surface contamination increases with decreasing primary energy due to increased individual scattering processes along trajectory parts carbon contamination layer. Comparison of the simulated spectra for different thicknesses of the carbon contamination layer and for different primary electron energies with experimental spectra clearly identifies that the carbon contamination in the measured sample was in the form of discontinuous islands other than the uniform film.

  16. Evaluation of bremsstrahlung contribution to photon transport in coupled photon-electron problems

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    The most accurate description of the radiation field in x-ray spectrometry requires the modeling of coupled photon-electron transport. Compton scattering and the photoelectric effect actually produce electrons as secondary particles which contribute to the photon field through conversion mechanisms like bremsstrahlung (which produces a continuous photon energy spectrum) and inner-shell impact ionization (ISII) (which gives characteristic lines). The solution of the coupled problem is time consuming because the electrons interact continuously and therefore, the number of electron collisions to be considered is always very high. This complex problem is frequently simplified by neglecting the contributions of the secondary electrons. Recent works (Fernández et al., 2013; Fernández et al., 2014) have shown the possibility to include a separately computed coupled photon-electron contribution like ISII in a photon calculation for improving such a crude approximation while preserving the speed of the pure photon transport model. By means of a similar approach and the Monte Carlo code PENELOPE (coupled photon-electron Monte Carlo), the bremsstrahlung contribution is characterized in this work. The angular distribution of the photons due to bremsstrahlung can be safely considered as isotropic, with the point of emission located at the same place of the photon collision. A new photon kernel describing the bremsstrahlung contribution is introduced: it can be included in photon transport codes (deterministic or Monte Carlo) with a minimal effort. A data library to describe the energy dependence of the bremsstrahlung emission has been generated for all elements Z=1-92 in the energy range 1-150 keV. The bremsstrahlung energy distribution for an arbitrary energy is obtained by interpolating in the database. A comparison between a PENELOPE direct simulation and the interpolated distribution using the data base shows an almost perfect agreement. The use of the data base increases

  17. Validation of a dose deposited by low-energy photons using GATE/GEANT4.

    PubMed

    Thiam, C O; Breton, V; Donnarieix, D; Habib, B; Maigne, L

    2008-06-01

    The GATE Monte Carlo simulation platform based on the Geant4 toolkit has now become a diffused tool for simulating PET and SPECT imaging devices. In this paper, we explore its relevance for dosimetry of low-energy 125I photon brachytherapy sources used to treat prostate cancers. To that end, three 125-iodine sources widely used in prostate cancer brachytherapy treatment have been modelled. GATE simulations reproducing dosimetric reference observables such as radial dose function g(r), anisotropy function F(r, theta) and dose-rate constant (Lambda) were performed in liquid water. The calculations were splitted on the EGEE grid infrastructure to reduce the computing time of the simulations. The results were compared to other relevant Monte Carlo results and to measurements published and fixed as recommended values by the AAPM Task Group 43. GATE results agree with consensus values published by AAPM Task Group 43 with an accuracy better than 2%, demonstrating that GATE is a relevant tool for the study of the dose induced by low-energy photons.

  18. Indoor light on thermoluminescence of CVD diamond film used as a high-energy photon dosimeter.

    PubMed

    Liu, Chi-Chang; Chu, Tieh-Chi; Lin, Sung-Yen; Lin, Jao-Perng

    2003-01-01

    The effect of light on polycrystalline diamond film that was produced by chemical vapor deposition and is used as a thermoluminescent dosimeter should be considered, although some researchers have indicated that such an effect was theoretically unlikely to happen. A 15 min exposure to a normal desk light bulb induces significant thermoluminescence (TL) comparable to a 0.5 Gy exposure to high-energy photons. This light-induced TL will be saturated within 2 h. The saturated TL intensity depends on the frequency of the light and the blue light dominates. The TL peak area at a temperature of 605 K is insensitive to light but is sensitive to high-energy photons. Another peak at about 410 K is caused by light only, because the TL from the ionization radiation at the same location is bleached. The effect of light could be easily distinguished by a numerical or an experimental method. Lamps with a green lampshade or pure red lights are suggested for use as indoor light sources. To reduce the effect of light, pre-heating treatment before readout is also suggested.

  19. Measurement of the UHECR Energy Spectrum by the Telescope Array Fluorescence Detectors

    NASA Astrophysics Data System (ADS)

    Stroman, Thomas; Bergman, Douglas

    2013-04-01

    Ultra-high-energy cosmic rays (UHECRs), subatomic charged particles of extraterrestrial origin and with kinetic energies near or exceeding 10^18 eV, are very rare. The Telescope Array (TA) experiment in western Utah is the northern hemisphere's largest UHECR detector, and consists of three atmospheric fluorescence detectors (FDs) and a ground array of 507 scintillator detectors. In stand-alone ``monocular'' operation, the FDs can observe the widest range in primary UHECR energies. One FD employs refurbished hardware from the High-Resolution Fly's Eye experiment; the remaining two FDs were designed for TA and employ new hardware and analysis. We will present the UHECR energy spectrum measured by the FDs in monocular mode using data collected during the first four years of operation.

  20. LDEF (Flight), M0002-01 : Trapped-Proton Energy Spectrum Determination, Tray G12

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The flight photograph was taken from the Orbiter aft flight deck during the LDEF retrieval prior to berthing the LDEF in the Orbiter cargo bay. The Trapped Proton Energy Spectrum Determination Experiment is one of four experiments located in a three (3) inch deep LDEF end center tray. Additional Trapped Proton Energy Experi ments are located in peripheral LDEF integrated experiment tray in the D03 and D09 tray loca tions. The Trapped Proton Energy experiment, located in the upper left quadrant of the integrated tray, appears to be intact with with no visible damage. A brown discoloration is visible on the Trapped Proton Energy experiment detector housings and along the upper surfaces of the experiment sup port structure. The discoloration around the outer edges of the experiment mounting plate appears to be a much lighter tan color. The sub-experiments are intact and secure with no visible dam age.

  1. Microdosimetric and Biological Effects of Photon Irradiation at Different Energies in Bone Marrow.

    PubMed

    Belley, Matthew D; Ashcraft, Kathleen A; Lee, Chen-Ting; Cornwall-Brady, Milton R; Chen, Jane-Jane; Gunasingha, Rathnayaka; Burkhart, Markus; Dewhirst, Mark; Yoshizumi, Terry T; Down, Julian D

    2015-10-01

    To ensure reliability and reproducibility of radiobiological data, it is necessary to standardize dosimetry practices across all research institutions. The photoelectric effect predominates over other interactions at low energy and in high atomic number materials such as bone, which can lead to increased dose deposition in soft tissue adjacent to mineral bone due to secondary radiation particles. This may produce radiation effects that deviate from higher energy photon irradiation that best model exposure from clinical radiotherapy or nuclear incidences. Past theoretical considerations have indicated that this process should affect radiation exposure of neighboring bone marrow (BM) and account for reported differences in relative biological effectiveness (RBE) for hematopoietic failure in rodents. The studies described herein definitively estimate spatial dose distribution and biological effectiveness within the BM compartment for (137)Cs gamma rays and 320 kVp X rays at two levels of filtration: 1 and 4 mm Cu half-value layer (HVL). In these studies, we performed: 1. Monte Carlo simulations on a 5 μm resolution model of mouse vertebrae and femur derived from micro-CT images; 2. In vitro biological experiments irradiating BM cells plated directly on the surface of a bone-equivalent material (BEM); and 3. An in vivo study on BM cell survival in irradiated live mice. Simulation results showed that the relative dose increased in proximity to bone at the lower radiation energies and produced averaged values of relative dose over the entire BM volume within imaged trabecular bone of 1.17, 1.08 and 1.01 for beam qualities of 1 mm Cu HVL, 4 mm Cu HVL and (137)Cs, respectively. In accordance with Monte Carlo simulations, in vitro irradiation of BM cells located on BEM and in vivo whole-body irradiation at a prescribed dose to soft tissue of 6 Gy produced relative cell killing of hematopoietic progenitors (CFU-C) that significantly increased for the 1 mm Cu HVL X rays

  2. A multiple-time-scale turbulence model based on variable partitioning of turbulent kinetic energy spectrum

    NASA Technical Reports Server (NTRS)

    Kim, S.-W.; Chen, C.-P.

    1987-01-01

    A multiple-time-scale turbulence model of a single point closure and a simplified split-spectrum method is presented. In the model, the effect of the ratio of the production rate to the dissipation rate on eddy viscosity is modeled by use of the multiple-time-scales and a variable partitioning of the turbulent kinetic energy spectrum. The concept of a variable partitioning of the turbulent kinetic energy spectrum and the rest of the model details are based on the previously reported algebraic stress turbulence model. Example problems considered include: a fully developed channel flow, a plane jet exhausting into a moving stream, a wall jet flow, and a weakly coupled wake-boundary layer interaction flow. The computational results compared favorably with those obtained by using the algebraic stress turbulence model as well as experimental data. The present turbulence model, as well as the algebraic stress turbulence model, yielded significantly improved computational results for the complex turbulent boundary layer flows, such as the wall jet flow and the wake boundary layer interaction flow, compared with available computational results obtained by using the standard kappa-epsilon turbulence model.

  3. Advantages of Real-Time Spectrum Analyzers in High-Energy Physics Applications

    SciTech Connect

    Parker, Louis

    2004-11-10

    Typically, particles are injected into the ring at low energy levels and then 'ramped up' to higher levels. During ramping, it is important that the horizontal and vertical tune frequencies do not shift, lest they hit upon a resonant combination that causes beam instability or sudden total loss of ring beam current (beam blow up). Beam instabilities can be caused by a number of factors. Non-linearities and/or different response times of independent controls such as beam position monitor (BPM) cables and circuits, magnets for guidance and focusing of the beam, Klystrons or Tetrodes (which provide power to RF cavities that transmit energy to the beam), and vacuum pumps and monitors can all cause beam instabilities. Vibrations and lack of proper shielding are other factors. The challenge for operators and researchers is to correctly identify the factors causing beam instabilities and blow up so that costly accelerator time is not interrupted and experimental results are not compromised. The instrument often used to identify problems in particle accelerator applications is the spectrum analyzer. This paper will discuss the advantages of real time spectrum analyzers (RSA) versus swept frequency spectrum analyzers in HEP applications. The main focus will be on monitoring beam position and stability, especially during ramp-up. Also covered will be use of RSA for chromaticity measurements, Phase Locked Loop (PLL) diagnostics, and vibration analysis.

  4. Advantages of Real-Time Spectrum Analyzers in High-Energy Physics Applications

    NASA Astrophysics Data System (ADS)

    Parker, Louis

    2004-11-01

    Typically, particles are injected into the ring at low energy levels and then "ramped up" to higher levels. During ramping, it is important that the horizontal and vertical tune frequencies do not shift, lest they hit upon a resonant combination that causes beam instability or sudden total loss of ring beam current (beam blow up). Beam instabilities can be caused by a number of factors. Non-linearities and/or different response times of independent controls such as beam position monitor (BPM) cables and circuits, magnets for guidance and focusing of the beam, Klystrons or Tetrodes (which provide power to RF cavities that transmit energy to the beam), and vacuum pumps and monitors can all cause beam instabilities. Vibrations and lack of proper shielding are other factors. The challenge for operators and researchers is to correctly identify the factors causing beam instabilities and blow up so that costly accelerator time is not interrupted and experimental results are not compromised. The instrument often used to identify problems in particle accelerator applications is the spectrum analyzer. This paper will discuss the advantages of real time spectrum analyzers (RSA) versus swept frequency spectrum analyzers in HEP applications. The main focus will be on monitoring beam position and stability, especially during ramp-up. Also covered will be use of RSA for chromaticity measurements, Phase Locked Loop (PLL) diagnostics, and vibration analysis.

  5. Validating plastic scintillation detectors for photon dosimetry in the radiologic energy range

    SciTech Connect

    Lessard, Francois; Archambault, Louis; Plamondon, Mathieu; and others

    2012-09-15

    Purpose: Photon dosimetry in the kilovolt (kV) energy range represents a major challenge for diagnostic and interventional radiology and superficial therapy. Plastic scintillation detectors (PSDs) are potentially good candidates for this task. This study proposes a simple way to obtain accurate correction factors to compensate for the response of PSDs to photon energies between 80 and 150 kVp. The performance of PSDs is also investigated to determine their potential usefulness in the diagnostic energy range. Methods: A 1-mm-diameter, 10-mm-long PSD was irradiated by a Therapax SXT 150 unit using five different beam qualities made of tube potentials ranging from 80 to 150 kVp and filtration thickness ranging from 0.8 to 0.2 mmAl + 1.0 mmCu. The light emitted by the detector was collected using an 8-m-long optical fiber and a polychromatic photodiode, which converted the scintillation photons to an electrical current. The PSD response was compared with the reference free air dose rate measured with a calibrated Farmer NE2571 ionization chamber. PSD measurements were corrected using spectra-weighted corrections, accounting for mass energy-absorption coefficient differences between the sensitive volumes of the ionization chamber and the PSD, as suggested by large cavity theory (LCT). Beam spectra were obtained from x-ray simulation software and validated experimentally using a CdTe spectrometer. Correction factors were also obtained using Monte Carlo (MC) simulations. Percent depth dose (PDD) measurements were compensated for beam hardening using the LCT correction method. These PDD measurements were compared with uncorrected PSD data, PDD measurements obtained using Gafchromic films, Monte Carlo simulations, and previous data. Results: For each beam quality used, the authors observed an increase of the energy response with effective energy when no correction was applied to the PSD response. Using the LCT correction, the PSD response was almost energy independent, with

  6. Efficient photoinduced energy transfer in a newly developed hybrid SBA-15 photonic antenna.

    PubMed

    Cucinotta, Fabio; Carniato, Fabio; Devaux, André; De Cola, Luisa; Marchese, Leonardo

    2012-11-26

    A new hybrid photostable donor-acceptor mesoporous SBA-15 silica system was designed and prepared. It consists of an encapsulated donor, the Super Yellow (SY) polymer, which transfers the photoexcitation energy directly to an acceptor dye that is linked outside the framework. The obtained composite material was characterized by X-ray diffraction, nitrogen-physisorption porosimetry, diffuse-reflectance (DR)-UV/Vis spectroscopy and photoluminescence, space- and time-resolved confocal microscopy. The physico-chemical analyses showed that the system behaves as an efficient Förster resonance energy transfer (FRET) pair, and high photoluminescence was observed from the acceptor. The presented photonic antenna is the first example of dye sensitization by polymer-loaded mesoporous silica and represents a step forward in the search for new efficient and stable materials with opto-electronic applications. PMID:23055456

  7. Heavy quark production in photon-Pomeron interactions at high energies

    SciTech Connect

    Machado, M. M.; Goncalves, V. P.

    2013-03-25

    The diffractive heavy quark cross sections are estimated considering photon-Pomeron interactions in hadron - hadron at RHIC, Tevatron, and CERN LHC energies. We assume the validity of the hard diffractive factorization and calculate the charm and bottom total cross sections and rapidity distributions using the diffractive parton distribution functions of the Pomeron obtained by the H1 Collaboration at DESY-HERA. Such processes are sensitive to the gluon content of the Pomeron at high energies and are a good place to constrain the behavior of this distribution. We also compare our predictions with those obtained using the dipole model, and verify that these processes are a good test of the different mechanisms for heavy quarks diffractive production at hadron colliders.

  8. Monte Carlo study of the energy and angular dependence of the response of plastic scintillation detectors in photon beams

    SciTech Connect

    Wang, Lilie L. W.; Klein, David; Beddar, A. Sam

    2010-10-15

    Purpose: By using Monte Carlo simulations, the authors investigated the energy and angular dependence of the response of plastic scintillation detectors (PSDs) in photon beams. Methods: Three PSDs were modeled in this study: A plastic scintillator (BC-400) and a scintillating fiber (BCF-12), both attached by a plastic-core optical fiber stem, and a plastic scintillator (BC-400) attached by an air-core optical fiber stem with a silica tube coated with silver. The authors then calculated, with low statistical uncertainty, the energy and angular dependences of the PSDs' responses in a water phantom. For energy dependence, the response of the detectors is calculated as the detector dose per unit water dose. The perturbation caused by the optical fiber stem connected to the PSD to guide the optical light to a photodetector was studied in simulations using different optical fiber materials. Results: For the energy dependence of the PSDs in photon beams, the PSDs with plastic-core fiber have excellent energy independence within about 0.5% at photon energies ranging from 300 keV (monoenergetic) to 18 MV (linac beam). The PSD with an air-core optical fiber with a silica tube also has good energy independence within 1% in the same photon energy range. For the angular dependence, the relative response of all the three modeled PSDs is within 2% for all the angles in a 6 MV photon beam. This is also true in a 300 keV monoenergetic photon beam for PSDs with plastic-core fiber. For the PSD with an air-core fiber with a silica tube in the 300 keV beam, the relative response varies within 1% for most of the angles, except in the case when the fiber stem is pointing right to the radiation source in which case the PSD may over-response by more than 10%. Conclusions: At {+-}1% level, no beam energy correction is necessary for the response of all three PSDs modeled in this study in the photon energy ranges from 200 keV (monoenergetic) to 18 MV (linac beam). The PSD would be even closer

  9. Monte Carlo study of the energy and angular dependence of the response of plastic scintillation detectors in photon beams

    PubMed Central

    Wang, Lilie L. W.; Klein, David; Beddar, A. Sam

    2010-01-01

    Purpose: By using Monte Carlo simulations, the authors investigated the energy and angular dependence of the response of plastic scintillation detectors (PSDs) in photon beams. Methods: Three PSDs were modeled in this study: A plastic scintillator (BC-400) and a scintillating fiber (BCF-12), both attached by a plastic-core optical fiber stem, and a plastic scintillator (BC-400) attached by an air-core optical fiber stem with a silica tube coated with silver. The authors then calculated, with low statistical uncertainty, the energy and angular dependences of the PSDs’ responses in a water phantom. For energy dependence, the response of the detectors is calculated as the detector dose per unit water dose. The perturbation caused by the optical fiber stem connected to the PSD to guide the optical light to a photodetector was studied in simulations using different optical fiber materials. Results: For the energy dependence of the PSDs in photon beams, the PSDs with plastic-core fiber have excellent energy independence within about 0.5% at photon energies ranging from 300 keV (monoenergetic) to 18 MV (linac beam). The PSD with an air-core optical fiber with a silica tube also has good energy independence within 1% in the same photon energy range. For the angular dependence, the relative response of all the three modeled PSDs is within 2% for all the angles in a 6 MV photon beam. This is also true in a 300 keV monoenergetic photon beam for PSDs with plastic-core fiber. For the PSD with an air-core fiber with a silica tube in the 300 keV beam, the relative response varies within 1% for most of the angles, except in the case when the fiber stem is pointing right to the radiation source in which case the PSD may over-response by more than 10%. Conclusions: At ±1% level, no beam energy correction is necessary for the response of all three PSDs modeled in this study in the photon energy ranges from 200 keV (monoenergetic) to 18 MV (linac beam). The PSD would be even closer

  10. Influence of trace elements in human tissue in low-energy photon brachytherapy dosimetry

    NASA Astrophysics Data System (ADS)

    White, Shane A.; Landry, Guillaume; van Gils, Francis; Verhaegen, Frank; Reniers, Brigitte

    2012-06-01

    The aim of this paper is to determine the dosimetric impact of trace elements in human tissues for low-energy photon sources used in brachytherapy. Monte Carlo dose calculations were used to investigate the dosimetric effect of trace elements present in normal or cancerous human tissues. The effect of individual traces (atomic number Z = 11-30) was studied in soft tissue irradiated by low-energy brachytherapy sources. Three other tissue types (prostate, adipose and mammary gland) were also simulated with varying trace concentrations to quantify the contribution of each trace to the dose distribution. The dose differences between cancerous and healthy prostate tissues were calculated in single- and multi-source geometries. The presence of traces in a tissue produces a difference in the dose distribution that is dependent on Z and the concentration of the trace. Low-Z traces (Na) have a negligible effect (<0.3%) in all tissues, while higher Z (K) had a larger effect (>3%). There is a potentially significant difference in the dose distribution between cancerous and healthy prostate tissues (4%) and even larger if compared to the trace-free composition (15%) in both single- and multi-sourced geometries. Trace elements have a non-negligible (up to 8% in prostate D90) effect on the dose in tissues irradiated with low-energy photon sources. This study underlines the need for further investigation into accurate determination of the trace composition of tissues associated with low-energy brachytherapy. Alternatively, trace elements could be incorporated as a source of uncertainty in dose calculations. This work was part of an invited presentation at the ‘International Workshop on Recent Advances in Monte Carlo Techniques for Radiation Therapy’, held in Montreal, June 8-10, 2011.

  11. Photon generator

    DOEpatents

    Srinivasan-Rao, Triveni

    2002-01-01

    A photon generator includes an electron gun for emitting an electron beam, a laser for emitting a laser beam, and an interaction ring wherein the laser beam repetitively collides with the electron beam for emitting a high energy photon beam therefrom in the exemplary form of x-rays. The interaction ring is a closed loop, sized and configured for circulating the electron beam with a period substantially equal to the period of the laser beam pulses for effecting repetitive collisions.

  12. Coleman-Glashow Massive Photon and Ultra-HighEnergy Cosmic Rays beyond the GZK Cutoff

    NASA Astrophysics Data System (ADS)

    Takahashi, Yoshiyuki

    2000-04-01

    Very high-energy gamma rays and neutrinos could be probes of quantum gravity (QG) nature of vacuum [Amelio-Camella, et al, 1998]. Extreme Energy (EE) photons lose energy by pair production in a vacuum due to the ubiquitous microwave photons. Their path length at EE energies is limited to less than 10 Mpc in ordinary space and they are believed to be unable to reach earth from Gamma Ray BurstUs (GRB) of cosmological distances. However, EE gamma rays in the QG vacuum can pass through a large distance exceeding many Gpc, because electron-pair production with 2.7K (E') microwave background may be kinematically prohibited above 10 TeV under the QG structure of vacuum. The energy-momentum conservation for the pair process does not hold for E >> 10 TeV for E' = 10-3 (Kifune, 1999), because 4 mc^4 = E^2 - (pc)^2 = E^2 (E'/E - k E/E0) < 0, where k = 1. The reported observation of EECRUs above 4 4 10^eV with unaccounted pair or triple coincidence in spatial and temporal ( ~ 2 years) coordinates is also a mystery. They also seem to be correlated with high luminosity GRBUs within 1 year [Milgrom and Usov, 1995; Takahashi, 1998]. If this correlation is true, then the ballpark correlation of one-year is hard to understand with any theory, while a possible explanation is available if Quantum Gravity (QG) is considered with Planck mass (10^28eV/c^2) grain of spacetime (10-33 cm). The QG scheme [Amelio-Camella, et al, 1998] leads to a delay time of gamma rays of the order of 1 year at 5 x 10^19 eV from cosmological distance (L) of GRB's (typically, L ~ 1 Gpc). The reduced speed of EHE gamma rays in QG is v = (1 - k 4 E/E0)c, where E0 is the Planck mass (10^20 eV/c^2) or gravitino mass (E0/k, k as a parameter O(1)). The fundamental question is whether such high energy particle acceleration occurs in GRBUs. Studies of photonic acceleration in extreme photon outburst sites, GRBUs, might lead to an even more profound cosmological test of the vacuum of Universe; in particular

  13. Photonuclear dose calculations for high-energy photon beams from Siemens and Varian linacs.

    PubMed

    Chibani, Omar; Ma, Chang-Ming Charlie

    2003-08-01

    The dose from photon-induced nuclear particles (neutrons, protons, and alpha particles) generated by high-energy photon beams from medical linacs is investigated. Monte Carlo calculations using the MCNPX code are performed for three different photon beams from two different machines: Siemens 18 MV, Varian 15 MV, and Varian 18 MV. The linac head components are simulated in detail. The dose distributions from photons, neutrons, protons, and alpha particles are calculated in a tissue-equivalent phantom. Neutrons are generated in both the linac head and the phantom. This study includes (a) field size effects, (b) off-axis dose profiles, (c) neutron contribution from the linac head, (d) dose contribution from capture gamma rays, (e) phantom heterogeneity effects, and (f) effects of primary electron energy shift. Results are presented in terms of absolute dose distributions and also in terms of DER (dose equivalent ratio). The DER is the maximum dose from the particle (neutron, proton, or alpha) divided by the maximum photon dose, multiplied by the particle quality factor and the modulation scaling factor. The total DER including neutrons, protons, and alphas is about 0.66 cSv/Gy for the Siemens 18 MV beam (10 cm x 10 cm). The neutron DER decreases with decreasing field size while the proton (or alpha) DER does not vary significantly except for the 1 cm x 1 cm field. Both Varian beams (15 and 18 MV) produce more neutrons, protons, and alphas particles than the Siemens 18 MV beam. This is mainly due to their higher primary electron energies: 15 and 18.3 MeV, respectively, vs 14 MeV for the Siemens 18 MV beam. For all beams, neutrons contribute more than 75% of the total DER, except for the 1 cm x 1 cm field (approximately 50%). The total DER is 1.52 and 2.86 cSv/Gy for the 15 and 18 MV Varian beams (10 cm x 10 cm), respectively. Media with relatively high-Z elements like bone may increase the dose from heavy charged particles by a factor 4. The total DER is sensitive to

  14. Nonlinear processes in cosmic-ray precursor of strong supernova shock: Maximum energy and average energy spectrum of accelerated particles

    NASA Astrophysics Data System (ADS)

    Ptuskin, V. S.; Zirakashvili, V. N.

    The instability in the cosmic-ray precursor of a supernova shock is studied. The level of turbulence in this region determines the maximum energy of accelerated particles. The consideration is not limited by the case of weak turbulence. It is assumed that the Kolmogorov type nonlinear wave interactions together with the ion-neutral collisions restrict the amplitude of random magnetic field. As a result, the maximum energy of accelerated particles strongly depends on the age of a SNR. The average spectrum of cosmic rays injected in the interstellar medium in the course of adiabatic SNR evolution takes the approximate form E-2 at energies larger than 10 30 GeV/nucleon with the maximum energy that is close to the position of the knee in cosmic-ray spectrum at 4 × 1015 eV. At an earlier stage of SNR evolution the ejecta-dominated stage, the particles are accelerated to higher energies and have a rather steep power-law distribution. These results suggest that the knee may mark the transition from the ejecta-dominated to the adiabatic evolution of SNR shocks which accelerate cosmic rays.

  15. Dual energy CT with photon counting and dual source systems: comparative evaluation

    NASA Astrophysics Data System (ADS)

    Atak, Haluk; Shikhaliev, Polad M.

    2015-12-01

    Recently, new dual energy (DE) computed tomography (CT) systems—dual source CT (DSCT) and photon counting CT (PCCT) have been introduced. Although these systems have the same clinical targets, they have major differences as they use dual and single kVp acquisitions and different x-ray detection and energy resolution concepts. The purpose of this study was theoretical and experimental comparisons of DSCT and PCCT. The DSCT Siemens Somatom Flash was modeled for simulation study. The PCCT had the same configuration as DSCT except it used a photon counting detector. The soft tissue phantoms with 20, 30, and 38 cm diameters included iodine, CaCO3, adipose, and water samples. The dose (air kerma) was 14 mGy for all studies. The low and high energy CT data were simulated at 80 kVp and 140 kVp for DSCT, and in 20-58 keV and 59-120 keV energy ranges for PCCT, respectively. The experiments used Somatom Flash DSCT system and PCCT system based on photon counting CdZnTe detector with 2  ×  256 pixel configuration and 1  ×  1 mm2 pixels size. In simulated general CT images, PCCT provided higher contrast-to-noise ratio (CNR) than DSCT with 0.4/0.8 mm Sn filters. The PCCT with K-edge filter provided higher CNR than the PCCT with a Cu filter, and DSCT with 0.4 mm Sn filter provided higher CNR than the DSCT with a 0.8 mm Sn filter. In simulated DE subtracted images, CNR of the DSCT was comparable to the PCCT with a Cu filter. However, DE PCCT with Ho a K-edge filter provided 30-40% higher CNR than the DE DSCT with 0.4/0.8 mm Sn filters. The experimental PCCT provided higher CNR in general imaging compared to the DSCT. In experimental DE subtracted images, the DSCT provided higher CNR than the PCCT with a Cu filter. However, experimental CNR with DE PCCT with K-edge filter was 15% higher than in DE DSCT, which is less than 30-40% increase predicted by the simulation study. It is concluded that ideal PCCT can provide substantial advantages over ideal

  16. Dual energy CT with photon counting and dual source systems: comparative evaluation.

    PubMed

    Atak, Haluk; Shikhaliev, Polad M

    2015-12-01

    Recently, new dual energy (DE) computed tomography (CT) systems-dual source CT (DSCT) and photon counting CT (PCCT) have been introduced. Although these systems have the same clinical targets, they have major differences as they use dual and single kVp acquisitions and different x-ray detection and energy resolution concepts. The purpose of this study was theoretical and experimental comparisons of DSCT and PCCT. The DSCT Siemens Somatom Flash was modeled for simulation study. The PCCT had the same configuration as DSCT except it used a photon counting detector. The soft tissue phantoms with 20, 30, and 38 cm diameters included iodine, CaCO3, adipose, and water samples. The dose (air kerma) was 14 mGy for all studies. The low and high energy CT data were simulated at 80 kVp and 140 kVp for DSCT, and in 20-58 keV and 59-120 keV energy ranges for PCCT, respectively. The experiments used Somatom Flash DSCT system and PCCT system based on photon counting CdZnTe detector with 2  ×  256 pixel configuration and 1  ×  1 mm(2) pixels size. In simulated general CT images, PCCT provided higher contrast-to-noise ratio (CNR) than DSCT with 0.4/0.8 mm Sn filters. The PCCT with K-edge filter provided higher CNR than the PCCT with a Cu filter, and DSCT with 0.4 mm Sn filter provided higher CNR than the DSCT with a 0.8 mm Sn filter. In simulated DE subtracted images, CNR of the DSCT was comparable to the PCCT with a Cu filter. However, DE PCCT with Ho a K-edge filter provided 30-40% higher CNR than the DE DSCT with 0.4/0.8 mm Sn filters. The experimental PCCT provided higher CNR in general imaging compared to the DSCT. In experimental DE subtracted images, the DSCT provided higher CNR than the PCCT with a Cu filter. However, experimental CNR with DE PCCT with K-edge filter was 15% higher than in DE DSCT, which is less than 30-40% increase predicted by the simulation study. It is concluded that ideal PCCT can provide substantial advantages over ideal

  17. Dual energy CT with photon counting and dual source systems: comparative evaluation.

    PubMed

    Atak, Haluk; Shikhaliev, Polad M

    2015-12-01

    Recently, new dual energy (DE) computed tomography (CT) systems-dual source CT (DSCT) and photon counting CT (PCCT) have been introduced. Although these systems have the same clinical targets, they have major differences as they use dual and single kVp acquisitions and different x-ray detection and energy resolution concepts. The purpose of this study was theoretical and experimental comparisons of DSCT and PCCT. The DSCT Siemens Somatom Flash was modeled for simulation study. The PCCT had the same configuration as DSCT except it used a photon counting detector. The soft tissue phantoms with 20, 30, and 38 cm diameters included iodine, CaCO3, adipose, and water samples. The dose (air kerma) was 14 mGy for all studies. The low and high energy CT data were simulated at 80 kVp and 140 kVp for DSCT, and in 20-58 keV and 59-120 keV energy ranges for PCCT, respectively. The experiments used Somatom Flash DSCT system and PCCT system based on photon counting CdZnTe detector with 2  ×  256 pixel configuration and 1  ×  1 mm(2) pixels size. In simulated general CT images, PCCT provided higher contrast-to-noise ratio (CNR) than DSCT with 0.4/0.8 mm Sn filters. The PCCT with K-edge filter provided higher CNR than the PCCT with a Cu filter, and DSCT with 0.4 mm Sn filter provided higher CNR than the DSCT with a 0.8 mm Sn filter. In simulated DE subtracted images, CNR of the DSCT was comparable to the PCCT with a Cu filter. However, DE PCCT with Ho a K-edge filter provided 30-40% higher CNR than the DE DSCT with 0.4/0.8 mm Sn filters. The experimental PCCT provided higher CNR in general imaging compared to the DSCT. In experimental DE subtracted images, the DSCT provided higher CNR than the PCCT with a Cu filter. However, experimental CNR with DE PCCT with K-edge filter was 15% higher than in DE DSCT, which is less than 30-40% increase predicted by the simulation study. It is concluded that ideal PCCT can provide substantial advantages over ideal

  18. Bremsstrahlung in Mo and Pt targets produced by {sup 90}Sr beta particles in the photon energy region of 1-100 keV

    SciTech Connect

    Singh, Amrit; Dhaliwal, A. S.

    2015-08-28

    Bremsstrahlung spectra in thick targets of Mo and Pt, produced by beta emitter {sup 90}Sr (end point energy = 546 keV) have been studied in the photon energy range of 1-100 keV. The experimentally measured bremsstrahlung spectra measured with Si(Li) detector were compared with the theoretical spectral distributions calculated from Elwert corrected (non relativistic) Bethe-Heitler [EBH] theory, modified Elwert factor (relativistic) Bethe-Heitler (F{sub mod}BH) theory for ordinary bremsstrahlung (OB) and the modified Elwert factor (relativistic) Bethe-Heitler (F{sub mod}BH+PB) theory, which includes the polarization bremsstrahlung (PB) into total bremsstrahlung (BS). The present results indicate the correctness of F{sub mod}BH+PB theory in the low energy region, where the contributions of PB into BS are dominant, which is described in terms of stripped atom (SA) approximation. But at the middle and higher energy region of the bremsstrahlung spectrum, where the contribution of PB is negligible, the F{sub mod}BH theory is more close to the experimental results. Hence, it is clear that the production of PB in the low energy region, due to the dynamic response of the target atom suppresses the production of bremsstrahlung at higher energy ends.

  19. Studies on effective atomic numbers for photon energy absorption and electron density of some narcotic drugs in the energy range 1 keV-20 MeV

    NASA Astrophysics Data System (ADS)

    Gounhalli, Shivraj G.; Shantappa, Anil; Hanagodimath, S. M.

    2013-04-01

    Effective atomic numbers for photon energy absorption ZPEA,eff, photon interaction ZPI,eff and for electron density Nel, have been calculated by a direct method in the photon-energy region from 1 keV to 20 MeV for narcotic drugs, such as Heroin (H), Cocaine (CO), Caffeine (CA), Tetrahydrocannabinol (THC), Cannabinol (CBD), Tetrahydrocannabivarin (THCV). The ZPEA,eff, ZPI,eff and Nel values have been found to change with energy and composition of the narcotic drugs. The energy dependence ZPEA,eff, ZPI,eff and Nel is shown graphically. The maximum difference between the values of ZPEA,eff, and ZPI,eff occurs at 30 keV and the significant difference of 2 to 33% for the energy region 5-100 keV for all drugs. The reason for these differences is discussed.

  20. Neutron field produced by 25 MeV deuteron on thick beryllium for radiobiological study; energy spectrum.

    PubMed

    Takada, Masashi; Mihara, Erika; Sasaki, Michiya; Nakamura, Takashi; Honma, Toshihiko; Kono, Koji; Fujitaka, Kazunobu

    2004-01-01

    Biological data is necessary for estimation of protection from neutrons, but there is a lack of data on biological effects of neutrons for radiation protection. Radiological study on fast neutrons has been done at the National Institute of Radiological Sciences. An intense neutron source has been produced by 25 MeV deuterons on a thick beryllium target. The neutron energy spectrum, which is essential for neutron energy deposition calculation, was measured from thermal to maximum energy range by using an organic liquid scintillator and multi-sphere moderated 3He proportional counters. The spectrum of the gamma rays accompanying the neutron beam was measured simultaneously with the neutron spectrum using the organic liquid scintillator. The transmission by the shield of the spurious neutrons originating from the target was measured to be less than 1% by using the organic liquid scintillator placed behind the collimator. The measured neutron energy spectrum is useful in dose calculations for radiobiology studies.

  1. Evaluation of beam hardening and photon scatter by brass compensator for IMRT.

    PubMed

    Hashimoto, Shimpei; Karasawa, Katsuyuki; Fujita, Yukio; Miyashita, Hisayuki; Chang, Weishan; Kawachi, Toru; Katayose, Tetsurou; Kobayashi, Nao; Kunieda, Etsuo; Saitoh, Hidetoshi

    2012-11-01

    When a brass compensator is set in a treatment beam, beam hardening may take place. This variation of the energy spectrum may affect the accuracy of dose calculation by a treatment planning system and the results of dose measurement of brass compensator intensity modulated radiation therapy (IMRT). In addition, when X-rays pass the compensator, scattered photons are generated within the compensator. Scattered photons may affect the monitor unit (MU) calculation. In this study, to evaluate the variation of dose distribution by the compensator, dose distribution was measured and energy spectrum was simulated using the Monte Carlo method. To investigate the influence of beam hardening for dose measurement using an ionization chamber, the beam quality correction factor was determined. Moreover, to clarify the effect of scattered photons generated within the compensator for the MU calculation, the head scatter factor was measured and energy spectrum analyses were performed. As a result, when X-rays passed the brass compensator, beam hardening occurred and dose distribution was varied. The variation of dose distribution and energy spectrum was larger with decreasing field size. This means that energy spectrum should be reproduced correctly to obtain high accuracy of dose calculation for the compensator IMRT. On the other hand, the influence of beam hardening on k(Q) was insignificant. Furthermore, scattered photons were generated within the compensator, and scattered photons affect the head scatter factor. These results show that scattered photons must be taken into account for MU calculation for brass compensator IMRT.

  2. Next-Generation Photon Sources for Grand Challenges in Science and Energy

    SciTech Connect

    2009-05-01

    The next generation of sustainable energy technologies will revolve around transformational new materials and chemical processes that convert energy efficiently among photons, electrons, and chemical bonds. New materials that tap sunlight, store electricity, or make fuel from splitting water or recycling carbon dioxide will need to be much smarter and more functional than today's commodity-based energy materials. To control and catalyze chemical reactions or to convert a solar photon to an electron requires coordination of multiple steps, each carried out by customized materials and interfaces with designed nanoscale structures. Such advanced materials are not found in nature the way we find fossil fuels; they must be designed and fabricated to exacting standards, using principles revealed by basic science. Success in this endeavor requires probing, and ultimately controlling, the interactions among photons, electrons, and chemical bonds on their natural length and time scales. Control science - the application of knowledge at the frontier of science to control phenomena and create new functionality - realized through the next generation of ultraviolet and X-ray photon sources, has the potential to be transformational for the life sciences and information technology, as well as for sustainable energy. Current synchrotron-based light sources have revolutionized macromolecular crystallography. The insights thus obtained are largely in the domain of static structure. The opportunity is for next generation light sources to extend these insights to the control of dynamic phenomena through ultrafast pump-probe experiments, time-resolved coherent imaging, and high-resolution spectroscopic imaging. Similarly, control of spin and charge degrees of freedom in complex functional materials has the potential not only to reveal the fundamental mechanisms of high-temperature superconductivity, but also to lay the foundation for future generations of information science. This

  3. Energy spectrum of iron nuclei measured inside the MIR space craft using CR-39 track detectors.

    PubMed

    Gunther, W; Leugner, D; Becker, E; Flesch, F; Heinrich, W; Huntrup, G; Reitz, G; Rocher, H; Streibel, T

    1999-06-01

    We have exposed stacks of CR-39 plastic nuclear track detectors inside the MIR space craft during the EUROMIR95 space mission for almost 6 months. Over this long period a large number of tracks of high LET events was accumulated in the detector foils. The etching and measuring conditions for this experiment were optimized to detect tracks of stopping iron nuclei. We found 185 stopping iron nuclei inside the stack and identified their trajectories through the material of the experiment. Based on the energy-range relation the energy at the surface of the stack was determined. These particles allow the determination of the low energy part of the spectrum of iron nuclei behind shielding material inside the MIR station.

  4. LDEF (Postflight), M0002-01 : Trapped-Proton Energy Spectrum Determination, Tray G12

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The postflight photograph was taken in SAEF II at KSC after the experiment tray was removed from the LDEF. The Trapped Proton Energy Spectrum Determination Experiment is one of four experiments located in a three (3) inch deep LDEF end center tray. Additional Trapped Proton Energy Experiments are located in periph eral LDEF integrated experiment trays in the D03 and D09 tray locations. The Trapped Proton Energy experiment, located in the upper left quadrant of the integrated tray, appears to be intact with no apparent physical damage. The brown discoloration appears to be much lighter in this photograph than in the flight photograph, however, the postflight photograph of the individual experiment verifies the darker discoloration in the flight photograph. The light ing angle and intensity appear to have washed out the colors in the upper half of the integrated tray. The sub experiments appear to be intact and secure.

  5. Simulation of ultra-high energy photon propagation with PRESHOWER 2.0

    NASA Astrophysics Data System (ADS)

    Homola, P.; Engel, R.; Pysz, A.; Wilczyński, H.

    2013-05-01

    In this paper we describe a new release of the PRESHOWER program, a tool for Monte Carlo simulation of propagation of ultra-high energy photons in the magnetic field of the Earth. The PRESHOWER program is designed to calculate magnetic pair production and bremsstrahlung and should be used together with other programs to simulate extensive air showers induced by photons. The main new features of the PRESHOWER code include a much faster algorithm applied in the procedures of simulating the processes of gamma conversion and bremsstrahlung, update of the geomagnetic field model, and a minor correction. The new simulation procedure increases the flexibility of the code so that it can also be applied to other magnetic field configurations such as, for example, encountered in the vicinity of the sun or neutron stars. Program summaryProgram title: PRESHOWER 2.0 Catalog identifier: ADWG_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWG_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3968 No. of bytes in distributed program, including test data, etc.: 37198 Distribution format: tar.gz Programming language: C, FORTRAN 77. Computer: Intel-Pentium based PC. Operating system: Linux or Unix. RAM:< 100 kB Classification: 1.1. Does the new version supercede the previous version?: Yes Catalog identifier of previous version: ADWG_v1_0 Journal reference of previous version: Comput. Phys. Comm. 173 (2005) 71 Nature of problem: Simulation of a cascade of particles initiated by UHE photon in magnetic field. Solution method: The primary photon is tracked until its conversion into an e+ e- pair. If conversion occurs each individual particle in the resultant preshower is checked for either bremsstrahlung radiation (electrons) or secondary gamma conversion (photons). Reasons for

  6. Irradiation of Pyrimidine in Pure H2O Ice with High-Energy Ultraviolet Photons

    PubMed Central

    Chen, Yu-Jung; Hu, Wei-Jie; Qiu, Jun-Ming; Wu, Shang-Ruei; Fung, Hok-Sum; Chu, Ching-Chi; Yih, Tai-Sone; Ip, Wing-Huen; Wu, C.-Y. Robert

    2014-01-01

    Abstract The detection of nucleobases, the informational subunits of DNA and RNA, in several meteorites suggests that these compounds of biological interest were formed via astrophysical, abiotic processes. This hypothesis is in agreement with recent laboratory studies of irradiation of pyrimidine in H2O-rich ices with vacuum UV photons emitted by an H2-discharge lamp in the 6.9–11.3 eV (110–180 nm) range at low temperature, shown to lead to the abiotic formation of several compounds including the nucleobases uracil, cytosine, and thymine. In this work, we irradiated H2O:pyrimidine ice mixtures under astrophysically relevant conditions (14 K, ≤10−9 torr) with high-energy UV photons provided by a synchrotron source in three different ranges: the 0th order light (4.1–49.6 eV, 25–300 nm), the He i line (21.2 eV, 58.4 nm), and the He ii line (40.8 eV, 30.4 nm). The photodestruction of pyrimidine was monitored with IR spectroscopy, and the samples recovered at room temperature were analyzed with liquid and gas chromatographies. Uracil and its precursor 4(3H)-pyrimidone were found in all samples, with absolute and relative abundances varying significantly from one sample to another. These results support a scenario in which compounds of biological interest can be formed and survive in environments subjected to high-energy UV radiation fields. Key Words: Pyrimidine—Nucleobases—Interstellar ices—Cometary ices—High-energy photons—Molecular processes—Prebiotic chemistry. Astrobiology 14, 119–131. PMID:24512484

  7. Mesoscale Science with High Energy X-ray Diffraction Microscopy at the Advanced Photon Source

    NASA Astrophysics Data System (ADS)

    Suter, Robert

    2014-03-01

    Spatially resolved diffraction of monochromatic high energy (> 50 keV) x-rays is used to map microstructural quantities inside of bulk polycrystalline materials. The non-destructive nature of High Energy Diffraction Microscopy (HEDM) measurements allows tracking of responses as samples undergo thermo-mechanical or other treatments. Volumes of the order of a cubic millimeter are probed with micron scale spatial resolution. Data sets allow direct comparisons to computational models of responses that frequently involve long-ranged, multi-grain interactions; such direct comparisons have only become possible with the development of HEDM and other high energy x-ray methods. Near-field measurements map the crystallographic orientation field within and between grains using a computational reconstruction method that simulates the experimental geometry and matches orientations in micron sized volume elements to experimental data containing projected grain images in large numbers of Bragg peaks. Far-field measurements yield elastic strain tensors through indexing schemes that sort observed diffraction peaks into sets associated with individual crystals and detect small radial motions in large numbers of such peaks. Combined measurements, facilitated by a new end station hutch at Advanced Photon Source beamline 1-ID, are mutually beneficial and result in accelerated data reduction. Further, absorption tomography yields density contrast that locates secondary phases, void clusters, and cracks, and tracks sample shape during deformation. A collaboration led by the Air Force Research Laboratory and including the Advanced Photon Source, Lawrence Livermore National Laboratory, Carnegie Mellon University, Petra-III, and Cornell University and CHESS is developing software and hardware for combined measurements. Examples of these capabilities include tracking of grain boundary migrations during thermal annealing, tensile deformation of zirconium, and combined measurements of nickel

  8. Metallic photonic crystals for thermophotovoltaic applications

    NASA Astrophysics Data System (ADS)

    Walsh, Timothy A.

    Since the idea of a photonic bandgap was proposed over two decades ago, photonic crystals have been the subject of significant interest due to their novel optical properties which enable new and varied applications. In this research, the photonic bandgap effect is exploited to tailor the thermal radiation spectrum to a narrow range of wavelengths determined by the lattice symmetry and dimensions of the photonic crystal structure. This sharp emission peak can be matched to the electronic bandgap energy of a p-n junction photovoltaic cell for high efficiency thermophotovoltaic energy conversion. This thesis explores aspects of photonic crystal design, materials considerations, and manufacture for thermophotovoltaic applications. Photonic crystal structures come in many forms, exhibiting various types of 1D, 2D, and 3D lattice symmetry. In this work, the "woodpile" 3D photonic crystal is studied. One advantage of the woodpile lattice is that it can be readily fabricated on a large scale using common integrated circuit manufacturing techniques. Additionally this structure lends itself to efficient and accurate modeling with the use of a plane-wave expansion based transfer matrix method to calculate the scattering properties and band structure of the photonic crystal. This method is used to explore the geometric design parameters of the woodpile structure. Optimal geometric proportions for the structure are found which yield the highest narrowband absorption peak possible. By Kirchoffs law of thermal emission, this strong and sharp absorptance will yield high power and narrowband thermal radiation. The photonic crystal thermal emission spectrum is then evaluated in a TPV system model to evaluate the electrical power density and system efficiency achievable. The results produced by the photonic crystal emitter are compared with the results assuming a blackbody thermal radiation spectrum. The blackbody represents a universal standard against which any selective emitter

  9. Monte Carlo-based energy response studies of diode dosimeters in radiotherapy photon beams.

    PubMed

    Arun, C; Palani Selvam, T; Dinkar, Verma; Munshi, Prabhat; Kalra, Manjit Singh

    2013-01-01

    This study presents Monte Carlo-calculated absolute and normalized (relative to a (60)Co beam) sensitivity values of silicon diode dosimeters for a variety of commercially available silicon diode dosimeters for radiotherapy photon beams in the energy range of (60)Co-24 MV. These values were obtained at 5 cm depth along the central axis of a water-equivalent phantom of 10 cm × 10 cm field size. The Monte Carlo calculations were based on the EGSnrc code system. The diode dosimeters considered in the calculations have different buildup materials such as aluminum, brass, copper, and stainless steel + epoxy. The calculated normalized sensitivity values of the diode dosimeters were then compared to previously published measured values for photon beams at (60)Co-20 MV. The comparison showed reasonable agreement for some diode dosimeters and deviations of 5-17 % (17 % for the 3.4 mm brass buildup case for a 10 MV beam) for some diode dosimeters. Larger deviations of the measurements reflect that these models of the diode dosimeter were too simple. The effect of wall materials on the absorbed dose to the diode was studied and the results are presented. Spencer-Attix and Bragg-Gray stopping power ratios (SPRs) of water-to-diode were calculated at 5 cm depth in water. The Bragg-Gray SPRs of water-to-diode compare well with Spencer-Attix SPRs for ∆ = 100 keV and above at all beam qualities.

  10. A systematic characterization of the low-energy photon response of plastic scintillation detectors.

    PubMed

    Boivin, Jonathan; Beddar, Sam; Bonde, Chris; Schmidt, Daniel; Culberson, Wesley; Guillemette, Maxime; Beaulieu, Luc

    2016-08-01

    To characterize the low energy behavior of scintillating materials used in plastic scintillation detectors (PSDs), 3 PSDs were developed using polystyrene-based scintillating materials emitting in different wavelengths. These detectors were exposed to National Institute of Standards and Technology (NIST)-matched low-energy beams ranging from 20 kVp to 250 kVp, and to (137)Cs and (60)Co beams. The dose in polystyrene was compared to the dose in air measured by NIST-calibrated ionization chambers at the same location. Analysis of every beam quality spectrum was used to extract the beam parameters and the effective mass energy-absorption coefficient. Monte Carlo simulations were also performed to calculate the energy absorbed in the scintillators' volume. The scintillators' expected response was then compared to the experimental measurements and an energy-dependent correction factor was identified to account for low-energy quenching in the scintillators. The empirical Birks model was then compared to these values to verify its validity for low-energy electrons. The clear optical fiber response was below 0.2% of the scintillator's light for x-ray beams, indicating that a negligible amount of fluorescence contamination was produced. However, for higher-energy beams ((137)Cs and (60)Co), the scintillators' response was corrected for the Cerenkov stem effect. The scintillators' response increased by a factor of approximately 4 from a 20 kVp to a (60)Co beam. The decrease in sensitivity from ionization quenching reached a local minimum of about [Formula: see text] between 40 keV and 60 keV x-ray beam mean energy, but dropped by 20% for very low-energy (13 keV) beams. The Birks model may be used to fit the experimental data, but it must take into account the energy dependence of the kB quenching parameter. A detailed comprehension of intrinsic scintillator response is essential for proper calibration of PSD dosimeters for radiology.

  11. Modulated photon radiotherapy (XMRT): an algorithm for the simultaneous optimization of photon beamlet energy and intensity in external beam radiotherapy (EBRT) planning.

    PubMed

    McGeachy, Philip; Villarreal-Barajas, Jose Eduardo; Zinchenko, Yuriy; Khan, Rao

    2016-02-21

    This is a proof of principle study on an algorithm for optimizing external beam radiotherapy in terms of both photon beamlet energy and fluence. This simultaneous beamlet energy and fluence optimization is denoted modulated photon radiotherapy (XMRT). XMRT is compared with single-energy intensity modulated radiotherapy (IMRT) for five clinically relevant test geometries to determine whether treating beamlet energy as a decision variable improves the dose distributions. All test geometries were modelled in a cylindrical water phantom. XMRT optimized the fluence for 6 and 18 MV beamlets while IMRT optimized with only 6 MV and only 18 MV. CERR (computational environment for radiotherapy research) was used to calculate the dose deposition matrices and the resulting dose for XMRT and IMRT solutions. Solutions were compared via their dose volume histograms and dose metrics, such as the mean, maximum, and minimum doses for each structure. The homogeneity index (HI) and conformity number (CN) were calculated to assess the quality of the target dose coverage. Complexity of the resulting fluence maps was minimized using the sum of positive gradients technique. The results showed XMRT's ability to improve healthy-organ dose reduction while yielding comparable coverage of the target relative to IMRT for all geometries. All three energy-optimization approaches yielded similar HI and CNs for all geometries, as well as a similar degree of fluence map complexity. The dose reduction provided by XMRT was demonstrated by the relative decrease in the dose metrics for the majority of the organs at risk (OARs) in all geometries. Largest reductions ranged between 5% to 10% in the mean dose to OARs for two of the geometries when compared with both single-energy IMRT schemes. XMRT has shown potential dosimetric benefits through improved OAR sparing by allowing beam energy to act as a degree of freedom in the EBRT optimization process.

  12. Reconstruction of a energy wave spectrum using a non-intrusive technique

    NASA Astrophysics Data System (ADS)

    Vargas, Diana; Lugo, Adolfo; Mendoza, Edgar; Silva, Rodolfo

    2014-11-01

    For studies taken in a wave flume, it is frequent to use wave gauges to measure directly the free surface fluctuations. Sometimes these gauges can interfere the measures because this probes act as obstacles to water. Therefore we designed a non intrusive technique using a bubble curtain. In this work we pretend to reconstruct the energy wave spectrum of regular and irregular waves, generated in a wave flume, assuming linear and non linear wave theory by analyzing the time series of the bubbles velocity field given with the aid of PIV.

  13. Quantum control of isomerization by robust navigation in the energy spectrum

    SciTech Connect

    Murgida, G. E.; Arranz, F. J.; Borondo, F.

    2015-12-07

    In this paper, we present a detailed study on the application of the quantum control technique of navigation in the energy spectrum to chemical isomerization processes, namely, CN–Li⇆ Li–CN. This technique is based on the controlled time variation of a Hamiltonian parameter, an external uniform electric field in our case. The main result of our work establishes that the navigation involved in the method is robust, in the sense that quite sizable deviations from a pre-established control parameter time profile can be introduced and still get good final results. This is specially relevant thinking of a experimental implementation of the method.

  14. Calculation of quasiparticle energy spectrum of silicon using the correlated Hartree-Fock method

    NASA Astrophysics Data System (ADS)

    Ishihara, Takamitsu; Yamagami, Hiroshi; Matsuzawa, Kazuya; Yasuhara, Hiroshi

    1999-06-01

    We present quasiparticle energy spectrum calculations of silicon using the correlated Hartree-Fock method proposed by Yasuhara and Takada [Phys. Rev. B 43, 7200 (1991)], in which the information on the effective mass of an electron liquid is included in the form of a nonlocal spin-parallel potential in addition to a local potential. The calculated band gaps of silicon are much improved, compared with the local density approximation values. The minimum indirect band gap is evaluated to be 1.37 eV.

  15. Comparative characteristics of electron energy spectrum in PIG and arc type discharge plasmas

    NASA Technical Reports Server (NTRS)

    Romanyuk, L. I.; Suavilnyy, N. Y.

    1978-01-01

    The electron distribution functions relative to the velocity component directed along the magnetic field are compared for PIG and arc type discharges. The identity of these functions for the plasma region pierced by the primary electron beam and their difference in the peripheral part of the discharge are shown. It is concluded that the electron distribution function in the PIG type discharge is formed during one transit of the primary electron through the discharge gap. The mechanisms of electron energy spectrum formation in both the axis region and the peripheral region of the discharge are discussed.

  16. Fractal energy spectrum of a polariton gas in a Fibonacci quasiperiodic potential.

    PubMed

    Tanese, D; Gurevich, E; Baboux, F; Jacqmin, T; Lemaître, A; Galopin, E; Sagnes, I; Amo, A; Bloch, J; Akkermans, E

    2014-04-11

    We report on the study of a polariton gas confined in a quasiperiodic one-dimensional cavity, described by a Fibonacci sequence. Imaging the polariton modes both in real and reciprocal space, we observe features characteristic of their fractal energy spectrum such as the opening of minigaps obeying the gap labeling theorem and log-periodic oscillations of the integrated density of states. These observations are accurately reproduced solving an effective 1D Schrödinger equation, illustrating the potential of cavity polaritons as a quantum simulator in complex topological geometries. PMID:24765996

  17. COMPREHENSIVE OBSERVATIONS OF THE ULTRAVIOLET SPECTRUM AND IMPROVED ENERGY LEVELS FOR SINGLY IONIZED CHROMIUM (Cr II)

    SciTech Connect

    Sansonetti, Craig J.; Nave, Gillian; Reader, Joseph; Kerber, Florian

    2012-10-15

    We report new observations of the spectrum of singly ionized chromium (Cr II) in the region 1142-3954 A. The spectra were recorded with the National Institute of Standards and Technology 10.7 m normal-incidence vacuum spectrograph and FT700 vacuum ultraviolet Fourier transform spectrometer. More than 3600 lines are classified as transitions among 283 even and 368 odd levels. The new spectral data are used to re-optimize the energy levels, reducing their uncertainties by a typical factor of 20.

  18. Quantum Spread Spectrum Communication

    SciTech Connect

    Humble, Travis S

    2010-01-01

    We demonstrate that spectral teleportation can coherently dilate the spectral probability amplitude of a single photon. In preserving the encoded quantum information, this variant of teleportation subsequently enables a form of quantum spread spectrum communication.

  19. Verification of Compton scattering spectrum of a 662keV photon beam scattered on a cylindrical steel target using MCNP5 code.

    PubMed

    Thanh, Tran Thien; Nguyen, Vo Hoang; Chuong, Huynh Dinh; Tran, Le Bao; Tam, Hoang Duc; Binh, Nguyen Thi; Tao, Chau Van

    2015-11-01

    This article focuses on the possible application of a (137)Cs low-radioactive source (5mCi) and a NaI(Tl) detector for measuring the saturation thickness of solid cylindrical steel targets. In order to increase the reliability of the obtained experimental results and to verify the detector response function of Compton scattering spectrum, simulation using Monte Carlo N-particle (MCNP5) code is performed. The obtained results are in good agreement with the response functions of the simulation scattering and experimental scattering spectra. On the basis of such spectra, the saturation depth of a steel cylinder is determined by experiment and simulation at about 27mm using gamma energy of 662keV ((137)Cs) at a scattering angle of 120°. This study aims at measuring the diameter of solid cylindrical objects by gamma-scattering technique. PMID:26363240

  20. The energy spectrum of ultra-high-energy cosmic rays measured by the Telescope Array FADC fluorescence detectors in monocular mode

    NASA Astrophysics Data System (ADS)

    Abu-Zayyad, T.; Aida, R.; Allen, M.; Anderson, R.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, E. J.; Cho, W. R.; Fujii, H.; Fujii, T.; Fukuda, T.; Fukushima, M.; Hanlon, W.; Hayashi, K.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Hiyama, K.; Honda, K.; Iguchi, T.; Ikeda, D.; Ikuta, K.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Iwamoto, S.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kanbe, T.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kido, E.; Kim, H. B.; Kim, H. K.; Kim, J. H.; Kim, J. H.; Kitamoto, K.; Kitamura, S.; Kitamura, Y.; Kobayashi, K.; Kobayashi, Y.; Kondo, Y.; Kuramoto, K.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lim, S. I.; Lundquist, J. P.; Machida, S.; Martens, K.; Matsuda, T.; Matsuura, T.; Matsuyama, T.; Matthews, J. N.; Myers, I.; Minamino, M.; Miyata, K.; Murano, Y.; Nagataki, S.; Nakamura, T.; Nam, S. W.; Nonaka, T.; Ogio, S.; Ogura, J.; Ohnishi, M.; Ohoka, H.; Oki, K.; Oku, D.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Roh, S. Y.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Sampson, A. L.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Shin, J. I.; Shirahama, T.; Smith, J. D.; Sokolsky, P.; Sonley, T. J.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T. A.; Suzuki, S.; Takahashi, Y.; Takeda, M.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Tsuyuguchi, Y.; Uchihori, Y.; Udo, S.; Ukai, H.; Vasiloff, G.; Wada, Y.; Wong, T.; Yamakawa, Y.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zollinger, R.; Zundel, Z.

    2013-08-01

    We present a measurement of the energy spectrum of ultra-high-energy cosmic rays performed by the Telescope Array experiment using monocular observations from its two new FADC-based fluorescence detectors. After a short description of the experiment, we describe the data analysis and event reconstruction procedures. Since the aperture of the experiment must be calculated by Monte Carlo simulation, we describe this calculation and the comparisons of simulated and real data used to verify the validity of the aperture calculation. Finally, we present the energy spectrum calculated from the merged monocular data sets of the two FADC-based detectors, and also the combination of this merged spectrum with an independent, previously published monocular spectrum measurement performed by Telescope Array's third fluorescence detector [T. Abu-Zayyad et al., The energy spectrum of Telescope Array's middle drum detector and the direct comparison to the high resolution fly's eye experiment, Astroparticle Physics 39 (2012) 109-119, http://dx.doi.org/10.1016/j.astropartphys.2012.05.012, Available from: ]. This combined spectrum corroborates the recently published Telescope Array surface detector spectrum [T. Abu-Zayyad, et al., The cosmic-ray energy spectrum observed with the surface detector of the Telescope Array experiment, ApJ 768 (2013) L1, http://dx.doi.org/10.1088/2041-8205/768/1/L1, Available from: ] with independent systematic uncertainties.