Limits for an inverse bremsstrahlung origin of the diffuse Galactic soft gamma-ray emission
DEFF Research Database (Denmark)
Pohl, M.
1998-01-01
origin of the soft Galactic gamma-ray continuum through inverse bremsstrahlung. A flux of low-energy cosmic rays strong enough to produce the observed spectrum of gamma-rays implies substantial gamma-ray emission at a few MeV through nuclear de-excitation. It is shown that the existing limits on excess 3......-7 MeV emission from the Galactic plane, in concert with the constraints from pi(0)-decay gamma-ray emission at higher energies, are in serious conflict with an inverse bremsstrahlung origin of the Galactic soft gamma-ray emission for any physically plausible low-energy cosmic ray spectrum. While...
Weibel instability due to inverse bremsstrahlung absorption
International Nuclear Information System (INIS)
Bendib, A.; Bendib, K.; Bendib, A.; Bendib, K.; Sid, A.; Bendib, K.
1997-01-01
A new Weibel source due to the inverse bremsstrahlung absorption is presented. It has been shown that in homogeneous plasmas, this mechanism may drive strong collisionless Weibel modes with growth rates of order of γ∼10 11 s -1 and negligible group velocities. In the laser-produced plasmas, for short laser wavelengths (λ L 10 14 W/cm 2 ), this Weibel source is most efficient as the ones due to the heat flux and the plasma expansion. The useful scaling law of the convective e-foldings, with respect to the laser and the plasma parameters, is also derived. copyright 1997 The American Physical Society
Stabilization effect of Weibel modes due to inverse bremsstrahlung ...
Indian Academy of Sciences (India)
2016-11-04
Nov 4, 2016 ... In this work, the Weibel instability due to inverse bremsstrahlung absorption in laser fusion plasma ... pling of self-generated magnetic field with the laser wave field. This is ... To describe fully ionized plasma where the interac-.
Relativistic electron acceleration by net inverse bremsstrahlung in a laser-irradiated plasma
International Nuclear Information System (INIS)
Kim, S.H.; Chen, K.W.
1985-01-01
Using the quantum-kinetic method, the net acceleration of relativistic electrons in a laser-irradiated plasma is studied as a function of the relevant parameters of the incident laser wave and the plasma wave. It is suggested that, in general, the net acceleration in laser-produced turbulent plasmas is primarily due to inverse bremsstrahlung proceses, and the acceleration gradient exceeds several hundreds gigavolt per meter when the electron energy is large (TeV) and the momentum spread of the beam is properly controlled
Inverse bremsstrahlung heating beyond the first Born approximation for dense plasmas in laser fields
International Nuclear Information System (INIS)
Moll, M; Schlanges, M; Bornath, Th; Krainov, V P
2012-01-01
Inverse bremsstrahlung (IB) heating, an important process in the laser-matter interaction, involves two different kinds of interaction—the interaction of the electrons with the external laser field and the electron-ion interaction. This makes analytical approaches very difficult. In a quantum perturbative approach to the IB heating rate in strong laser fields, usually the first Born approximation with respect to the electron-ion potential is considered, whereas the influence of the electric field is taken exactly in the Volkov wave functions. In this paper, a perturbative treatment is presented adopting a screened electron-ion interaction potential. As a new result, we derive the momentum-dependent, angle-averaged heating rate in the first Born approximation. Numerical results are discussed for a broad range of field strengths, and the conditions for the applicability of a linear approximation for the heating rate are analyzed in detail. Going a step further in the perturbation series, we consider the transition amplitude in the second Born approximation, which enables us to calculate the heating rate up to the third order of the interaction strength. (paper)
International Nuclear Information System (INIS)
Berger, Richard L.; Clark, Daniel S.; Solodov, Andrei; Valeo, Ernest J.; Fisch, Nathaniel J.
2003-01-01
Inverse bremsstrahlung absorption of the pump laser beam in a backward Raman amplifier over the round-trip light transit time through the sub-critical density plasma can more than double the electron temperature of the plasma and produce time-varying axial temperature gradients. The resulting increased Landau damping of the plasma wave and detuning of the resonance can act to stabilize the pump against unwanted amplification of Langmuir noise without disrupting nonlinear amplification of the femtosecond seed pulse. Because the heating rate increases with the charge state Z, only low-Z plasmas (hydrogen, helium, or helium-hydrogen mixtures) will maintain a low enough temperature for efficient operation
Thermodynamic inversion origin of living systems
Kompanichenko, Vladimir N
2017-01-01
This book discusses the theory, general principles, and energy source conditions allowing for the emergence of life in planetary systems. The author examines the material conditions found in natural hydrothermal sites, the appropriate analogs of prebiotic environments on early Earth. He provides an overview of current laboratory experiments in prebiotic materials chemistry and substantiation of a new direction for the experiments in the origin of life field. Describes thermodynamic inversion and how it relates to the living cell; Examines the current direction of experiments on prebiotic materials chemistry; Introduces and substantiates necessary conditions for the emergence of life.
Neutron-proton bremsstrahlung experiments
Energy Technology Data Exchange (ETDEWEB)
Koster, J.E. (Los Alamos National Lab., NM (United States)); Nelson, R.O. (Los Alamos National Lab., NM (United States)); Schillaci, M.E. (Los Alamos National Lab., NM (United States)); Wender, S.A. (Los Alamos National Lab., NM (United States)); Mayo, D. (Univ. of California at Davis, CA (United States)); Brady, F.P. (Univ. of California at Davis, CA (United States)); Romero, J. (Univ. of California at Davis, CA (United States)); Krofcheck, D. (Lawrence Livermore National Lab., CA (United States)); Blann, M. (Lawrence Livermore National Lab., CA (United States)); Anthony, P. (Lawrence Livermore National Lab., CA (United States)); Brown, V.R. (Lawrence Livermore National Lab., CA (United States)); Hansen, L. (Lawrence Livermore National Lab., CA (United States)); Pohl, B. (Lawrence Livermore National Lab., CA (United States)); Sangster, T.C. (Lawrence Livermore National Lab., CA (United States)); Nifenecker, H. (Inst. des Sciences Nucleaires, Grenoble (France)); Pinston,
1993-06-01
It is well known that charged particles emit bremsstrahlung radiation when they are accelerated. Classical electron bremsstrahlung occurs when a proton is emitted by an electron accelerated in the field of a nucleus. The bremsstrahlung process also occurs in the scattering of nucleons, for which it is the lowest energy inelastic process that can occur. Like electron bremsstrahlung, nucleon-nucleon bremsstrahlung also requires the exchange of a virtual particle to conserve energy and momentum. In electron bremsstrahlung a virtual photon is exchanged but with two nucleons a meson can be exchanged. Unlike electron bremsstrahlung, in nucleon-nucleon bremsstrahlung the photon can originate from the exchanged meson. This exchange contribution has been shown in calculations to be a significant fraction of bremsstrahlung events. Thus bremsstrahlung serves as a probe of exchange currents in the nucleon-nucleon interaction. Because of a lack of a free neutron target or an intense neutron beam, few measurements of neutron-proton bremsstrahlung exist, each having poor statistical accuracy and poor energy resolution. The white neutron source at the Weapons Neutron Research (WNR) target area at the Los Alamos Meson Physics Facility (LAMPF) produces neutrons with energies from below 50 to above 400 MeV. Using time-of-flight techniques and a liquid hydrogen target, we are measuring the outgoing photons of energies up to 250 MeV at gamma ray angles of around 90 relative to the incident beam. Protons scattered at very forward angles are also detected in coincidence with the gamma rays. (orig.)
Swanson, C.; Jandovitz, P.; Cohen, S. A.
2018-02-01
We measured Electron Energy Distribution Functions (EEDFs) from below 200 eV to over 8 keV and spanning five orders-of-magnitude in intensity, produced in a low-power, RF-heated, tandem mirror discharge in the PFRC-II apparatus. The EEDF was obtained from the x-ray energy distribution function (XEDF) using a novel Poisson-regularized spectrum inversion algorithm applied to pulse-height spectra that included both Bremsstrahlung and line emissions. The XEDF was measured using a specially calibrated Amptek Silicon Drift Detector (SDD) pulse-height system with 125 eV FWHM at 5.9 keV. The algorithm is found to out-perform current leading x-ray inversion algorithms when the error due to counting statistics is high.
Korol, Andrey V
2014-01-01
This book introduces and reviews both theory and applications of polarizational bremsstrahlung, i.e. the electromagnetic radiation emitted during collisions of charged particles with structured, thus polarizable targets, such as atoms, molecules and clusters. The subject, following the first experimental evidence a few decades ago, has gained importance through a number of modern applications. Thus, the study of several radiative mechanisms is expected to lead to the design of novel light sources, operating in various parts of the electromagnetic spectrum. Conversely, the analysis of the spectral and angular distribution of the photon emission constitutes a new tool for extracting information on the interaction of the colliding particles, and on their internal structure and dynamical properties. Last but not least, accurate quantitative descriptions of the photon emission processes determine the radiative energy losses of particles in various media, thereby providing essential information required f...
Polarizational radiation or 'atomic' bremsstrahlung
International Nuclear Information System (INIS)
Ya Amusia, M.
1992-01-01
It is demonstrated that a new kind of continuum spectrum radiation exists, where the mechanism of formation is quite different from that of ordinary bremsstrahlung. The latter originates due to slowing down of the charged projectile in the target field, while the former, called polarization radiation or 'atomic' bremsstrahlung, is a result of radiation either of the target or the projectile particles dipolarly polarized during the collision process. Not only general formulae, but also results of concrete calculations are presented. These demonstrate, that for electron-atom collisions the atomic contribution to the total bremsstrahlung spectrum becomes dominant for photon energies near and above the atomic ionization potential. As to atom-atom or ion-atom collisions, the bremsstrahlung spectrum is completely determined by the atomic contribution. The specific features of the case when the incoming particles are relativistic are discussed at length. A number of examples of colliding pairs are considered, for which the atomic bremsstrahlung process is quite essential: A bare nucleus and an atom, pair of atoms, at least one of which is excited, electron, or atom interacting with a molecule. The same mechanism is essential also in formation of radiation in nuclear and elementary particle collisions. (orig.)
International Nuclear Information System (INIS)
Fearing, H.W.
1990-01-01
We summarize some of the information about the nucleon-nucleon force which has been obtained by comparing recent calculations of proton-proton bremsstrahlung with cross section and analyzing power data from the new TRIUMF bremsstrahlung experiment. Some comments are made as to how these results can be extended to neutron-proton bremsstrahlung. (Author) 17 refs., 6 figs
International Nuclear Information System (INIS)
Liou, M.K.; Nutt, W.T.
1978-01-01
A method for applying the soft-photon theorem to bremsstrahlung is described and a detailed derivation of the formulae for π + -p bremsstrahlung is presented. The consistent treatment of the expansion of the bremsstrahlung cross-section around k=0 results in excellent fits to the experimental data. The data are consistent with small off-shell effects and no radiation from the Δ(1236) resonance
Beta Emission and Bremsstrahlung
Energy Technology Data Exchange (ETDEWEB)
Karpius, Peter Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-11-13
Bremsstrahlung is continuous radiation produced by beta particles decelerating in matter; different beta emitters have different endpoint energies; high-energy betas interacting with high-Z materials will more likely produce bremsstrahlung; depending on the data, sometimes all you can say is that a beta emitter is present.
NACP Regional: Original Observation Data and Biosphere and Inverse Model Outputs
National Aeronautics and Space Administration — This data set contains the originally-submitted observation measurement data, terrestrial biosphere model output data, and inverse model simulations that various...
NACP Regional: Original Observation Data and Biosphere and Inverse Model Outputs
National Aeronautics and Space Administration — ABSTRACT: This data set contains the originally-submitted observation measurement data, terrestrial biosphere model output data, and inverse model simulations that...
Bremsstrahlung and neutral currents
International Nuclear Information System (INIS)
Ellis, R.G.; McKellar, B.H.J.
1979-01-01
The utility of the bremsstrahlung process in detecting parity violations from V-A weak neutral current interference is analysed in two ways. Firstly, bremsstrahlung from polarized lepton-nucleus scattering has an asymmetry with respect to the polarization of the incident leptons, and secondly, bremsstrahlung from unpolarized lepton nucleus scattering has a small circular polarization. The magnitude of each effect is calculated. The ratio of the parity violating contribution and the parity conserving contribution to the cross section is shown to be a misleading measure of the utility of these experiments. A parameter, the figure of merit, is introduced and used to discuss the feasibility of possible experiments
Electron - atom bremsstrahlung
International Nuclear Information System (INIS)
Kim, L.
1986-01-01
Features of bremsstrahlung radiation from neutral atoms and atoms in hot dense plasmas are studied. Predictions for the distributions of electron-atom bremsstrahlung radiation for both the point-Coulomb potential and screened potentials are obtained using a classical numerical method. Results agree with exact quantum-mechanical partial-wave results for low incident electron energies in both the point-Coulomb and screened potentials. In the screened potential, the asymmetry parameter of a spectrum is reduced from the Coulomb values. The difference increases with decreasing energy and begins to oscillate at very low energies. The scaling properties of bremsstrahlung spectra and energy losses were also studied. It was found that the ratio of the radiative energy loss for positrons to that for electrons obeys a simple scaling law, being expressible fairly accurately as a function only of the quantity T 1 /Z 2 . This scaling is exact in the case of the point-Coulomb potential, both for classical bremsstrahlung and for the nonrelativistic dipole Sommerfeld formula. Bremsstrahlung from atoms in hot dense plasmas were also studied describing the atomic potentials by the temperature-and-density dependent Thomas-Fermi mode. Gaunt factors were obtained with the relativistic partial-wave method for atoms in plasmas of various densities and temperatures
The origin, global distribution, and functional impact of the human 8p23 inversion polymorphism.
Salm, Maximilian P A; Horswell, Stuart D; Hutchison, Claire E; Speedy, Helen E; Yang, Xia; Liang, Liming; Schadt, Eric E; Cookson, William O; Wierzbicki, Anthony S; Naoumova, Rossi P; Shoulders, Carol C
2012-06-01
Genomic inversions are an increasingly recognized source of genetic variation. However, a lack of reliable high-throughput genotyping assays for these structures has precluded a full understanding of an inversion's phylogenetic, phenotypic, and population genetic properties. We characterize these properties for one of the largest polymorphic inversions in man (the ∼4.5-Mb 8p23.1 inversion), a structure that encompasses numerous signals of natural selection and disease association. We developed and validated a flexible bioinformatics tool that utilizes SNP data to enable accurate, high-throughput genotyping of the 8p23.1 inversion. This tool was applied retrospectively to diverse genome-wide data sets, revealing significant population stratification that largely follows a clinal "serial founder effect" distribution model. Phylogenetic analyses establish the inversion's ancestral origin within the Homo lineage, indicating that 8p23.1 inversion has occurred independently in the Pan lineage. The human inversion breakpoint was localized to an inverted pair of human endogenous retrovirus elements within the large, flanking low-copy repeats; experimental validation of this breakpoint confirmed these elements as the likely intermediary substrates that sponsored inversion formation. In five data sets, mRNA levels of disease-associated genes were robustly associated with inversion genotype. Moreover, a haplotype associated with systemic lupus erythematosus was restricted to the derived inversion state. We conclude that the 8p23.1 inversion is an evolutionarily dynamic structure that can now be accommodated into the understanding of human genetic and phenotypic diversity.
International Nuclear Information System (INIS)
Strel'tsov, V.N.
1995-01-01
The vanishing of the 'retardation factor' leads to a significant growth of the intensity of the electromagnetic field 'velocity part' of the moving charge. The Cherenkov radiation is its physical consequence. The same reason also conditions the growth of another term: the 'acceleration part' of the field which gives rise to the 'Cherenkov Bremsstrahlung'. 4 refs
Polarization of Bremsstrahlung
International Nuclear Information System (INIS)
Miller, J.
1957-01-01
The numerical results for the polarization of Bremsstrahlung are presented. The multiple scattering of electrons in the target is taken into account. The angular-and photon energy dependences are seen on the curves for an incident 25 MeV electron energy. (Author) [fr
Multiphoton polarization Bremsstrahlung effect
International Nuclear Information System (INIS)
Golovinskij, P.A.
2001-01-01
A general approach to induced polarization effects was formulated on the basis of theory of many particles in a strong periodic field. Correlation with the perturbation theory is shown and the types of effective polarization potentials both for isolated atoms and ions, and for ions in plasma, are provided. State of art in the theory of forced polarization Bremsstrahlung effect is analyzed and some outlooks for further experimental and theoretical studies are outlined [ru
Gluon Bremsstrahlung in Weakly-Coupled Plasmas
International Nuclear Information System (INIS)
Arnold, Peter
2009-01-01
I report on some theoretical progress concerning the calculation of gluon bremsstrahlung for very high energy particles crossing a weakly-coupled quark-gluon plasma. (i) I advertise that two of the several formalisms used to study this problem, the BDMPS-Zakharov formalism and the AMY formalism (the latter used only for infinite, uniform media), can be made equivalent when appropriately formulated. (ii) A standard technique to simplify calculations is to expand in inverse powers of logarithms ln(E/T). I give an example where such expansions are found to work well for ω/T≥10 where ω is the bremsstrahlung gluon energy. (iii) Finally, I report on perturbative calculations of q.
Polarization bremsstrahlung in α decay
International Nuclear Information System (INIS)
Amusia, M. Ya.; Zon, B. A.; Kretinin, I. Yu.
2007-01-01
A mechanism of formation of electromagnetic radiation that accompanies α decay and is associated with the emission of photons by electrons of atomic shells due to the scattering of α particles by these atoms (polarization bremsstrahlung) is proposed. It is shown that, when the photon energy is no higher than the energy of K electrons of an atom, polarization bremsstrahlung makes a significant contribution to the bremsstrahlung in α decay
The elementary process of Bremsstrahlung
Haug, Eberhard
2004-01-01
This book deals with the theory and experiment of the elementary process of bremsstrahlung, where photons are detected in coincidence with decelerated outgoing electrons. Such experiments allow for a more stringent check of the theoretical work. The main emphasis is laid on electron-atom bremsstrahlung and electron-electron bremsstrahlung, but further bremsstrahlung processes are also dealt with. In the theoretical parts, triply differential cross sections are derived in various approximations, including electron spin and photon-polarization. In the experimental sections, electron-photon coinc
Brown, Malcolm
2009-01-01
Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…
Shigetoh, Keisuke; Horibuchi, Kayo; Nakamura, Daisuke
2017-11-01
Owing to the large differences in the chemical properties between Al and N polarities in aluminum nitride (AlN), the choice of the polar direction for crystal growth strongly affects not only the quality but also the shape (facet formation) of the grown crystal. In particular, N-polar (0 0 0 -1) has been considered to be a more preferable direction than Al-polar (0 0 0 1) for sublimation growth because compared to Al-polar (0 0 0 1), N-polar (0 0 0 -1) exhibits better stability at high growth rate (high supersaturation) conditions and enables easier lateral enlargement of the crystal. However, some critical growth conditions induce polarity inversion and hinder stable N-polar growth. Furthermore, the origin of the polarity inversion in AlN growth by the sublimation method is still unclear. To ensure stable N-polar growth without polarity inversion, the formation mechanism of the inversion domain during AlN sublimation growth must be elucidated. Therefore, herein, we demonstrate homoepitaxial growth on an N-polar seed and carefully investigate the obtained crystal that shows polarity inversion. Annular bright-field scanning transmission electron microscopy reveals that polarity is completely converted to the Al polarity via the formation of a 30 nm thick mixed polar layer (MPL) just above the seed. Moreover, three-dimensional atom probe tomography shows the segregation of the oxygen impurities in the MPL with a high concentration of about 3 atom%. Finally, by avoiding the incorporation of oxygen impurity into the crystal at the initial stage of the growth, we demonstrate an effective reduction (seven orders of magnitude) of the inversion domain boundary formation.
Origin of unipolar half-cycle pulses generation in inversion symmetric media
International Nuclear Information System (INIS)
Song, Xiaohong; Hao, Zhizhen; Yan, Ming; Wu, Miaoli; Yang, Weifeng
2015-01-01
We investigate the physical mechanism of unipolar half-cycle pulses generation in resonant two-level media with inversion symmetry. The unipolar half-cycle pulse contains substantial nonzero dc or zero-frequency component in its Fourier spectrum of the electric field. Here the origin of zero-frequency component generation in inversion symmetric media driven by symmetric electric field is identified. We show that in the regime of extreme nonlinear optics, i.e. the Rabi frequency is comparable to or even larger than the carrier frequency of the laser pulse, the time evolution of the polarization can display obvious up-down asymmetric structure under certain conditions, which manifests in the zero-frequency component generation, and is responsible for the formation of unipolar half-cycle pulses in the course of pulse propagation. (letter)
Factor VIII (F8) inversions in severe hemophilia A: Male germ cell origin and diagnosis with RT-PCR
Energy Technology Data Exchange (ETDEWEB)
Antonarakis, S.E. [Geneva Medical School (Switzerland)]|[Johns Hopkins School of Medicine, Baltimore, MD (United States); Rossiter, J.P. [Johns Hopkins School of Medicine, Baltimore, MD (United States); Young, M. [Geneva Medical School (Switzerland)] [and others
1994-09-01
The Factor VIII (F8) gene, which is defective in hemophilia A, is located in the most telomeric megabase of Xq. Inversions due to intrachromosomal homologous recombination between mispaired copies of gene A located within intron 22 of the gene and about 500 kb telomeric to it account for nearly half of the cases of severe hemophilia A. We hypothesized that pairing of Xq with its homolog inhibits the inversion process, and that therefore the event originates predominantly in male germ cells. In all 21 informative cases in which the inversion originated in a maternal grandparent, DNA polymorphism analysis using markers within or very closely linked to F8, determined that it occurred in the male germline. In addition, all but one of 56 mothers of sporadic cases due to inversions were carriers. The data indicate that the F8 gene inversions leading to severe hemophilia A occur almost exclusively in male germ cells. The mean age of maternal grandfathers at the birth of their carrier daughters was 29.9 years (13 cases), i.e. not different from the mean paternal age in the general population, supporting the hypothesis that the inversions occur in meiosis. The inversions can be diagnosed by Southern blot analysis. For more rapid diagnosis we have used RT-PCR of RNA ectopically expressed in blood. Oligonucleotides were used to PCR amplify, after the initial RT reaction of RNA samples using random hexamers, either the normal transcript (F8 exons 21 to 24;312 bp product) or the novel abnormal transcript that is generated after the inversion. Both type 1 and 2 inversions can be recognized in affecteds and carriers by the presence of the diagnostic PcR product of 248 bp. Correct diagnoses were made in samples from 6 patients and 2 carriers with type 1 inversions, 2 patients and 2 carriers with type 2 inversions and 5 normal controls.
Calculation of Bremsstrahlung yield for thin target
International Nuclear Information System (INIS)
Demir, N.; Akkurt, I.; Tekin, H. O.; Cakirli, R. B.; Akkus, B.; Kupa, I.
2010-01-01
The Bremsstrahlung photon is created by de-accelerating electron beam in an electric field which is usually a thin material so-called radiator. The obtained Bremsstrahlung yield depends on some parameter such as incoming electron beam energy, the thickness and also Z number of the radiator. The main aim of this work is to obtain optimum radiator to be used at Bremsstrahlung photon beam facility at TAC. For this purposes the Bremsstrahlung photon yield has been obtained using FLUKA code for different types materials.
Bremsstrahlung in atom-atom collisions
International Nuclear Information System (INIS)
Amus'ya, M.Y.; Kuchiev, M.Y.; Solov'ev, A.V.
1985-01-01
It is shown that in the collision of a fast atom with a target atom when the frequencies are on the order of the potentials or higher, there arises bremsstrahlung comparable in intensity with the bremsstrahlung emitted by an electron with the same velocity in the field of the target atom. The mechanism by which bremsstrahlung is produced in atom-atom collisions is elucidated. Results of specific calculations of the bremsstrahlung spectra are given for α particles and helium atoms colliding with xenon
Vicente-Salvador, David; Puig, Marta; Gayà-Vidal, Magdalena; Pacheco, Sarai; Giner-Delgado, Carla; Noguera, Isaac; Izquierdo, David; Martínez-Fundichely, Alexander; Ruiz-Herrera, Aurora; Estivill, Xavier; Aguado, Cristina; Lucas-Lledó, José Ignacio; Cáceres, Mario
2017-02-01
The growing catalogue of structural variants in humans often overlooks inversions as one of the most difficult types of variation to study, even though they affect phenotypic traits in diverse organisms. Here, we have analysed in detail 90 inversions predicted from the comparison of two independently assembled human genomes: the reference genome (NCBI36/HG18) and HuRef. Surprisingly, we found that two thirds of these predictions (62) represent errors either in assembly comparison or in one of the assemblies, including 27 misassembled regions in HG18. Next, we validated 22 of the remaining 28 potential polymorphic inversions using different PCR techniques and characterized their breakpoints and ancestral state. In addition, we determined experimentally the derived allele frequency in Europeans for 17 inversions (DAF = 0.01-0.80), as well as the distribution in 14 worldwide populations for 12 of them based on the 1000 Genomes Project data. Among the validated inversions, nine have inverted repeats (IRs) at their breakpoints, and two show nucleotide variation patterns consistent with a recurrent origin. Conversely, inversions without IRs have a unique origin and almost all of them show deletions or insertions at the breakpoints in the derived allele mediated by microhomology sequences, which highlights the importance of mechanisms like FoSTeS/MMBIR in the generation of complex rearrangements in the human genome. Finally, we found several inversions located within genes and at least one candidate to be positively selected in Africa. Thus, our study emphasizes the importance of careful analysis and validation of large-scale genomic predictions to extract reliable biological conclusions. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Foda, Hussein D; Brehm, Anthony; Goldsteen, Karen; Edelman, Norman H
2017-01-01
Prescriber disagreement is among the reasons for poor adherence to COPD treatment guidelines; it is yet not clear whether this leads to adverse outcomes. We tested whether undertreatment according to the original Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines led to increased exacerbations. Records of 878 patients with spirometrically confirmed COPD who were followed from 2005 to 2010 at one Veterans Administration (VA) Medical Center were analyzed. Analysis of variance was performed to assess differences in exacerbation rates between severity groups. Logistic regression analysis was performed to assess the relationship between noncompliance with guidelines and exacerbation rates. About 19% were appropriately treated by guidelines; 14% overtreated, 44% under-treated, and in 23% treatment did not follow any guideline. Logistic regression revealed a strong inverse relationship between undertreatment and exacerbation rate when severity of obstruction was held constant. Exacerbations per year by GOLD stage were significantly different from each other: mild 0.15, moderate 0.27, severe 0.38, very severe 0.72, and substantially fewer than previously reported. The guidelines were largely not followed. Undertreatment predominated but, contrary to expectations, was associated with fewer exacerbations. Thus, clinicians were likely advancing therapy primarily based upon exacerbation rates as was subsequently recommended in revised GOLD and other more recent guidelines. In retrospect, a substantial lack of prescriber adherence to treatment guidelines may have been a signal that they required re-evaluation. This is likely to be a general principle regarding therapeutic guidelines. The identification of fewer exacerbations in this cohort than has been generally reported probably reflects the comprehensive nature of the VA system, which is more likely to identify relatively asymptomatic (ie, nonexacerbating) COPD patients. Accordingly, these rates may
Polarizational bremsstrahlung in non-relativistic collisions
International Nuclear Information System (INIS)
Korol, A.V.; Solov'yov, A.V.
2006-01-01
We review the developments made during the last decade in the theory of polarization bremsstrahlung in the non-relativistic domain. A literature survey covering the latest history of the phenomenon is given. The main features which distinguish the polarization bremsstrahlung from other mechanisms of radiation are discussed and illustrated by the results of numerical calculations
Comparison of Classical and Quantum Bremsstrahlung
International Nuclear Information System (INIS)
Pratt, R.H.; Uskov, D.B.; Korol, A.V.; Obolensky, O.I.
2003-01-01
Classical features persist in bremsstrahlung at surprisingly high energies, while quantum features are present at low energies. For Coulomb bremsstrahlung this is related to the similar properties of Coulomb scattering. For bremsstrahlung in a screened potential, the low energy spectrum and angular distribution exhibit structures. In quantum mechanics these structures are associated with zeroes of particular angular-momentum transfer matrix elements at particular energies, a continuation of the Cooper minima in atomic photoeffect. They lead to transparency windows in free-free absorption. The trajectories of these zeroes in the plane of initial and final transition energies (bound and continuum) has been explored. Corresponding features have now been seen in classical bremsstrahlung, resulting from reduced contributions from particular impact parameters at particular energies. This has suggested the possibility of a more unified treatment of classical and quantum bremsstrahlung, based on the singularities of the scattering amplitude in angular momentum
Directory of Open Access Journals (Sweden)
Foda HD
2017-01-01
Full Text Available Hussein D Foda,1,2 Anthony Brehm,1,2 Karen Goldsteen,3 Norman H Edelman2,4 1Division of Pulmonary Critical Care and Sleep Medicine, Department of Medicine, Veterans Affairs Medical Center, Northport, 2Division of Pulmonary Critical Care and Sleep Medicine, Department of Medicine, Stony Brook University Medical Center, Stony Brook, NY, 3MPH Program, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, 4Department of Preventative Medicine and Program in Public Health, Stony Brook University Medical Center, Stony Brook, NY, USA Background: Prescriber disagreement is among the reasons for poor adherence to COPD treatment guidelines; it is yet not clear whether this leads to adverse outcomes. We tested whether undertreatment according to the original Global Initiative for Chronic Obstructive Lung Disease (GOLD guidelines led to increased exacerbations.Methods: Records of 878 patients with spirometrically confirmed COPD who were followed from 2005 to 2010 at one Veterans Administration (VA Medical Center were analyzed. Analysis of variance was performed to assess differences in exacerbation rates between severity groups. Logistic regression analysis was performed to assess the relationship between noncompliance with guidelines and exacerbation rates.Findings: About 19% were appropriately treated by guidelines; 14% overtreated, 44% undertreated, and in 23% treatment did not follow any guideline. Logistic regression revealed a strong inverse relationship between undertreatment and exacerbation rate when severity of obstruction was held constant. Exacerbations per year by GOLD stage were significantly different from each other: mild 0.15, moderate 0.27, severe 0.38, very severe 0.72, and substantially fewer than previously reported.Interpretation: The guidelines were largely not followed. Undertreatment predominated but, contrary to expectations, was associated with fewer exacerbations. Thus, clinicians were likely
Post-Newtonian gravitational bremsstrahlung
International Nuclear Information System (INIS)
Turner, M.; Will, C.M.
1978-01-01
We present formulae and numerical results for the gravitational radiation emitted during a low-deflection encounter between two massive bodies (''gravitational bremsstrahlung''). Our results are valid through post-Newtonian order within general relativity. We discuss in detail the gravitational waveform (transverse-traceless part of the metric perturbation tensor), the toal luminosity and total emitted energy, the angular distribution of emitted energy (antenna pattern), and the frequency spectrum. We also present a method of ''boosting'' the accuracy of these quantities to post-3/2-Newtonian order. A numerical comparison of our results with those of Peters and of Kovacs and Thorne shows that the post-Newtonian method is reliable to better than 0.1% at v=0.1c, to a few percent at v=0.35c, and to 10--20% at v=0.5c. We also compare our results with those of Smarr
Beta Bremsstrahlung dose in concrete shielding
Energy Technology Data Exchange (ETDEWEB)
Manjunatha, H.C., E-mail: manjunatha@rediffmail.com [Department of Physics, Government college for women, Kolar 563101, Karnataka (India); Chandrika, B.M. [Shravana, 592, Ist Cross, Behind St.Anne s School, PC Extension, Kolar 563101, Karnataka (India); Rudraswamy, B. [Department of Physics, Bangalore University, Bangalore 560056, Karnataka (India); Sankarshan, B.M. [Shravana, 592, Ist Cross, Behind St.Anne s School, PC Extension, Kolar 563101, Karnataka (India)
2012-05-11
In a nuclear reactor, beta nuclides are released during nuclear reactions. These betas interact with shielding concrete and produces external Bremsstrahlung (EB) radiation. To estimate Bremsstrahlung dose and shield efficiency in concrete, it is essential to know Bremsstrahlung distribution or spectra. The present work formulated a new method to evaluate the EB spectrum and hence Bremsstrahlung dose of beta nuclides ({sup 32}P, {sup 89}Sr, {sup 90}Sr-{sup 90}Y, {sup 90}Y, {sup 91}Y, {sup 208}Tl, {sup 210}Bi, {sup 234}Pa and {sup 40}K) in concrete. The Bremsstrahlung yield of these beta nuclides in concrete is also estimated. The Bremsstrahlung yield in concrete due to {sup 90}Sr-{sup 90}Y is higher than those of other given nuclides. This estimated spectrum is accurate because it is based on more accurate modified atomic number (Z{sub mod}) and Seltzer's data, where an electron-electron interaction is also included. Presented data in concrete provide a quick and convenient reference for radiation protection. The present methodology can be used to calculate the Bremsstrahlung dose in nuclear shielding materials. It can be quickly employed to give a first pass dose estimate prior to a more detailed experimental study. - Highlights: Black-Right-Pointing-Pointer Betas released in a nuclear reactor interact with shielding concrete and produces Bremsstrahlung. Black-Right-Pointing-Pointer The present work formulated a new method to evaluate the Bremsstrahlung spectrum and dose in concrete. Black-Right-Pointing-Pointer Presented data in concrete provide a quick and convenient reference for radiation protection.
Topological origin of edge states in two-dimensional inversion-symmetric insulators and semimetals
Miert, Guido van|info:eu-repo/dai/nl/413490378; Ortix, Carmine|info:eu-repo/dai/nl/413315304; de Morais Smith, C.|info:eu-repo/dai/nl/304836346
2017-01-01
Symmetries play an essential role in identifying and characterizing topological states of matter. Here, we classify topologically two-dimensional (2D) insulators and semimetals with vanishing spin-orbit coupling using time-reversal ($\\mathcal{T}$) and inversion ($\\mathcal{I}$) symmetry. This allows
NUMERICAL ANALYSIS OF AN INVERSE PROBLEM ORIGINATED IN PHENOMENON OF POLLUTION AIR URBAN
Directory of Open Access Journals (Sweden)
Aníbal Coronel
2016-12-01
Full Text Available This paper presents the calibration study of a two - dimensional mathematical model for the problem of urban air pollution. It is mainly assumed that air pollution is afected by wind convection, diffusion and chemical reactions of pollutants. Consequently, a convection-diffusion-reaction equation is obtained as a direct problem. In the inverse problem, the determination of the diffusion is analyzed, assuming that one has an observation of the pollutants in a nite time. To solve it numerically the nite volume method is used, the least squares function is considered as cost function and the gradient is calculated with the sensitivity method.
Engelhart, Steffen; Pleischl, Stefan; Lück, Christian; Marklein, Günter; Fischnaller, Edith; Martin, Sybille; Simon, Arne; Exner, Martin
2008-07-01
A case of hospital-acquired legionellosis occurred in a 75-year-old male patient who underwent surgery due to malignant melanoma. Legionellosis was proven by culture of Legionella pneumophila serogroup 1 from bronchoalveolar lavage (BAL) fluid. Being a chronic smoker the patient used to visit the sickroom balcony that was located about 90 m to the west of a hospital cooling tower. Routine cooling tower water samples drawn during the presumed incubation period revealed 1.0x10(4) CFU/100 ml (L. pneumophila serogroup 1). One of three isolates from the cooling tower water matched the patient's isolate by monoclonal antibody (mab)- and genotyping (sequence-based typing). Horizontal transport of cooling tower aerosols probably was favoured by meteorological conditions with thermal inversion. The case report stresses the importance of routine maintenance and microbiological control of hospital cooling towers.
Nonexistence of two forms of turbulent bremsstrahlung
International Nuclear Information System (INIS)
Kuijpers, J.; Melrose, D.B.
1985-01-01
It is shown that the forms of turbulent bremsstrahlung proposed by Tsytovich, Stenflo, and Wilhelmsson and by Nambu do not exist. The proposed mechanisms involve upconversion of ion sound turbulence into Langmuir turbulence, with the ion sound waves being emitted and absorbed resonantly and the Langmuir waves being emitted and absorbed nonresonantly. It is pointed out that a symmetry implicit in a standard QED treatment implies that there is another contribution to turbulent bremsstrahlung in addition to that calculated by Tsytovich, Stenflo, and Wilhelmsson and that the two contributions cancel exactly, leading to the null result. (Our arguments on this point have proved controversial.) Nambu made an approximation inconsistently, and when this approximation is not made, two terms in his analytic treatment cancel exactly. We argue that turbulent bremsstrahlung is related to a radiative correction in which the resonant emission of ion sound turbulence is modified by the nonresonant emission and absorption of Langmuir waves. Physically we interpret the nonexistence of turbulent bremsstrahlung as being due to each emission of a Langmuir quantum being associated with an absorption of an identical Langmuir quantum so that the Langmuir turbulence is unchanged. Proposed astrophysical applications of turbulent bremsstrahlung need to be reconsidered
Note on Inverse Bremsstrahlung in a Strong Electromagnetic Field
Bethe, H. A.
1972-09-01
The collisional energy loss of an electron undergoing forced oscillation in an electromagnetic field behaves quite differently in the low and high intensity limits. ... It is shown that in the case of an electromagnetic field v {sub o} >> v {sub t} the rate of transfer is much slower, and actually decreases with the strength of the field.
Electron and bremsstrahlung penetration and dose calculation
Watts, J. W., Jr.; Burrell, M. O.
1972-01-01
Various techniques for the calculation of electron and bremsstrahlung dose deposition are described. Energy deposition, transmission, and reflection coefficients for electrons incident on plane slabs are presented, and methods for their use in electron dose calculations were developed. A method using the straight-ahead approximation was also developed, and the various methods were compared and found to be in good agreement. Both accurate and approximate methods of calculating bremsstrahlung dose were derived and compared. Approximation is found to give a good estimate of dose where the electron spectrum falls off exponentially with energy.
The TAC Radiation Source for Bremsstrahlung Application
International Nuclear Information System (INIS)
Demir, N.
2008-01-01
The TAC is a project for the first Turkish radiation source and currently design study is produced with funding from the DPT (State Planning Unity). Two main part of the project will be IR-FEL and Bremsstrahlung facility. Each LINAC will provide max. electron energy of 20 MeV. The Bremsstrahlung facility at TAC will consist two of the LINAC module and will be obtained 35 MeV photon energy. This would provide a chance to investigate nuclear structure at this energy range and also some application of photonuclear physics. In this work the main parameter and plans for those of facility will be detailed
Bremsstrahlung from relativistic heavy ions in matter
DEFF Research Database (Denmark)
Sørensen, Allan Hvidkjær
2010-01-01
The emission of electromagnetic radiation by relativistic bare heavy ions penetrating ordinary matter is investigated. Our main aim is to determine the bremsstrahlung which we define as the radiation emitted when the projectile does not break up. It pertains to collisions without nuclear contact....... As a result of its relative softness, bremsstrahlung never dominates the energy-loss process for heavy ions. As to the emission of electromagnetic radiation in collisions with nuclear break-up, it appears modest when pertaining to incoherent action of the projectile nucleons in noncontact collisions...
DEFF Research Database (Denmark)
Jensen, Tue Vissing; Sørensen, Allan Hvidkjær
2013-01-01
A charged particle emits bremsstrahlung while traversing matter. We calculate the radiation cross section for bare heavy ions penetrating amorphous materials and single crystals at highly relativistic energies. The main component originates in scattering of the virtual photons of screened target...... in a pronounced directional dependence of the energy loss of bare heavy ions at extreme relativistic energies....
Probing few-body systems with bremsstrahlung
Kalantar-Nayestanaki, N; Kruppa, AT; Lovas, RG
2002-01-01
A series of bremsstrahlung measurements have been performed with the superconducting cyclotron, AGOR, at KVI. These measurements, on the proton-proton and proton-deuteron systems, aim to investigate the nucleon-nucleon interaction as the nucleons go off their mass shell. Cross sections and analyzing
Probing few-body systems with bremsstrahlung
Kalantar-Nayestanaki, N; Krivec, R; Golli, B; Rosina, M; Sirca, S
2003-01-01
A series of bremsstrahlung measurements have been performed with the superconducting cyclotron, AGOR, at KVI. These measurements, on the proton-proton and proton-deuteron systems, aim to investigate the nucleon-nucleon interaction far away from elastic channel. Cross sections and analyzing powers
Probing few-body systems with bremsstrahlung
Kalantar-Nayestanaki, N; Oryu, S; Kamimura, M; Ishikawa, S
2000-01-01
A series of bremsstrahlung measurements have been performed with the superconducting cyclotron, AGOR, at KVI. These measurements, on the proton-proton and proton-deuteron systems, aim to investigate the nucleon-nucleon interaction as the nucleons go off their mass shelf. Cross sections and analyzing
Bremsstrahlung in electron-positronium scattering
International Nuclear Information System (INIS)
Amusia, M.Ya.; Korol, A.V.; Solovyov, A.V.
1986-01-01
The spectrum of radiation formed in the fast nonrelativistic electron scattering on positronium is calculated. It is shown that all the radiation proceeds via virtual positronium deformations during the collision. An essential difference of bremsstrahlung spectra in electron on positronium and electron on hydrogen scattering is demonstrated. (orig.)
Bremsstrahlung: an experimentalists personal perspective on the post modern era
International Nuclear Information System (INIS)
Quarles, C.A.
2000-01-01
In this brief review I will discuss the recent experimental work on the doubly differential cross section, i.e. the photon energy and angular distribution, for electron Bremsstrahlung from thin solid film and gas targets. Since the beginning of the modern era in the study of Bremsstrahlung with the publication of the 1971 paper by Ts eng and Pratt, Professor Pratt has been the dominant influence in Bremsstrahlung research. Most, if not all, experimental research during the modern era has been motivated by the interest in comparing data with the theory of Pratt and his coworkers. As Bremsstrahlung research has moved into its post modern era, new experiments with increasing precision are concentrating on determining under what conditions ordinary Bremsstrahlung theory needs to be supplemented by a contribution from polarization Bremsstrahlung. Efforts to improve the comparison of thin-target experiment with theory have also led to new experimental and modeling work on Bremsstrahlung from thick solid targets. Thick-target Bremsstrahlung is interesting in its own right, but we also want to understand it better since it is the ever-present background in the thin-target experiments and the limiting factor in the effort to distinguish the polarization contribution to the total Bremsstrahlung spectrum. Professor Pratt ushered in the modern era in Bremsstrahlung research and has recently guided the transition into the post modern era. It can be expected that he will continue to have a formative influence on the developments of Bremsstrahlung research into the foreseeable future.
Diffractive corrections to the muon Bremsstrahlung
International Nuclear Information System (INIS)
Kel'ner, S.R.; Fedotov, A.M.
1999-01-01
The corrections to the muon Bremsstrahlung cross section due to diffraction of hard photons on nuclei are obtained. In this process the momentum is transmitted to a nucleus not by a charged particle but by the photon the interaction of which with the nucleus can be considered as diffraction on weakly absorbing ball. The amplitude of the process interferes with the usual Bremsstrahlung amplitude, therefore in the cross section together with the diffraction correction the interference term also appears, possessing different sings for μ + and μ - . The photon emission cross section also depends on the sing of muon charge and for muon energy about 10 TeV the difference between the cross section may reach 10%. The corrections to the radiation energy loss are also calculated [ru
Quantum-mechanical suppression of bremsstrahlung
Energy Technology Data Exchange (ETDEWEB)
Becker-Szendy, R.; Keller, L.; Niemi, G.; Perl, M.; Rochester, L. [Stanford Univ., CA (United States); Anthony, P. [Stanford Univ., CA (United States)]|[Lawrence Livermore National Lab., CA (United States); Bosted, P. [American Univ., Washington, DC (United States); Cavalli-Sforza, M.; Kelley, L.; Klein, S. [Univ. of California, Santa Cruz, CA (United States)] [and others
1994-12-01
The authors have studied quantum-mechanical suppression of bremsstrahlung of low-energy 1-500 MeV photons from high-energy 25 GeV electrons. They have measured the LPM effect, where multiple scattering of the radiating electron destroys coherence required for the emission of low-energy photons, and the dielectric effect, where the emitted photon traveling in the radiator medium interferes with itself. For the experiment, the collaboration developed a novel method of extracting a parasitic low-intensity high-energy electron beam into the fixed target area during normal SLC operation of the accelerator. The results agree quantitatively with Migdal`s calculation of the LPM effect. Surface effects, for which there is no satisfactory theoretical prediction, are visible at low photon energies. For very thin targets, the suppression disappears, as expected. Preliminary results on dielectric suppression of bremsstrahlung are in qualitative agreement with the expectation.
'Atomic Bremsstrahlung': Retrospectives, current status and perspectives
International Nuclear Information System (INIS)
Amusia, M.Ya.
2006-01-01
We describe here the 'Atomic bremsstrahlung' (AB)-emission of continuous spectrum electromagnetic radiation, which is generated in collisions of particles that have internal deformable structure that includes positively and negatively charged constituents. The deformation of one or both colliding partners induces multiple, mainly dipole, time-dependent electrical moments that become a source of radiation. The history of AB invention is presented and its unusual in comparison to ordinary bremsstrahlung (OB) properties, are discussed. As examples, fast electron atom, non-relativistic and relativistic collisions are considered. Attention is given to ion-atom and atom-atom collisions. Specifics of 'elastic' and 'inelastic' (i.e. radiation accompanied by destruction of collision partners) AB will be mentioned. Attention will be given to possible manifestation of AB in nature and in some exotic systems, for instance scattering of electrons upon muonic hydrogen. Some cooperative effects connected to AB will be considered. New classical schemes similar to AB will be presented
Using bremsstrahlung for electron density estimation and correction in EAST tokamak
Energy Technology Data Exchange (ETDEWEB)
Chen, Yingjie, E-mail: bestfaye@gmail.com; Wu, Zhenwei; Gao, Wei; Jie, Yinxian; Zhang, Jizong; Huang, Juan; Zhang, Ling; Zhao, Junyu
2013-11-15
Highlights: • The visible bremsstrahlung diagnostic provides a simple and effective tool for electron density estimation in steady state discharges. • This method can make up some disadvantages of present FIR and TS diagnostics in EAST tokamak. • Line averaged electron density has been deduced from central VB signal. The results can also be used for FIR n{sub e} correction. • Typical n{sub e} profiles have been obtained with T{sub e} and reconstructed bremsstrahlung profiles. -- Abstract: In EAST electron density (n{sub e}) is measured by the multi-channel far-infrared (FIR) hydrogen cyanide (HCN) interferometer and Thomson scattering (TS) diagnostics. However, it is difficult to obtain accurate n{sub e} profile for that there are many problems existing in current electron density diagnostics. Since the visible bremsstrahlung (VB) emission coefficient has a strong dependence on electron density, the visible bremsstrahlung measurement system developed to determine the ion effective charge (Z{sub eff}) may also be used for n{sub e} estimation via inverse operations. With assumption that Z{sub eff} has a flat profile and does not change significantly in steady state discharges, line averaged electron density (n{sup ¯}{sub e}) has been deduced from VB signals in L-mode and H-mode discharges in EAST. The results are in good coincidence with n{sup ¯}{sub e} from FIR, which proves that VB measurement is an effective tool for n{sub e} estimation. VB diagnostic is also applied to n{sup ¯}{sub e} correction when FIR n{sup ¯}{sub e} is wrong for the laser phase shift reversal together with noise causes errors when electron density changed rapidly in the H-mode discharges. Typical n{sub e} profiles in L-mode and H-mode phase are also deduced with reconstructed bremsstrahlung profiles.
Modeling the bremsstrahlung emission from converters
Mirea, M; Clapier, F; Hassaïne, M; Ibrahim, F; Müller, A C; Pauwels, N; Proust, J; Verney, D; Antoni, R; Bourgeois, L; Kandri-Rody, S
2001-01-01
The bremsstrahlung angular and energy theoretical distributions delivered from W and UCx thick converters are reported. This study is focussed on initial kinetic energies of the electron beam included in the range 30-60 MeV, suitable for the production of large radiative yields able to induce the $^{238}$U fission. These results offer the possibility to evaluate the required shielding for a neutron rich nuclei source.
Effects of a neutral current on the neutrino bremsstrahlung
International Nuclear Information System (INIS)
Ju, I.
1977-01-01
The energy-loss rate due to the neutrino bremsstrahlung from relativistic electrons in a dense matter such as a star is calculated in the framework of Weinberg's unified theory of weak and electromagnetic interactions by using the method of neutrino-energy expansion. The momentum-transfer integration, though complicated, can be carried out analytically, but the subsequent two electron integrals, called the distribution integrals, are helpless and do not allow any further analytic calculation. In order to avoid this difficulty, we set up a set of variables whose integration is simple enough to be expanded in series. It turns out that this series becomes a power series in the Fermi energy inverse after the distribution integrals. This enables us to keep only the leading terms, greatly simplifying the final result. Thus in principle we will be able to calculate arbitrary higher-order terms, even though most of them require prohibitively tedious labor. We carry out the next-higher-order calculations to find that the correction to the lowest-order contribution is within 5%. This confirms the earlier calculations of Festa and Ruderman, even though the two approaches are quite different: the neutrino-bremsstrahlung energy-loss rate is proportional to T 6 and independent of the density at extremely relativistic degenerate regions. We find that the asymptotic expression for the energy-loss rate is of the form A (β) + (rho/μ/sub e/) -1 / 3 kTB (β). The most striking effect of the neutral current is the muon-neutrino emission. The ratio of the energy-loss rate in Weinberg's theory to that in the conventional theory is 1/2 + 4 sin 4 theta/sub W/ at the extreme relativistic-degenerate and nondegenerate-nonrelativistic regions
Bremsstrahlung doses from natural uranium ingots
International Nuclear Information System (INIS)
Anderson, J. L.; Hertel, N. E.
2005-01-01
In the past, some privately owned commercial facilities in the United States were involved in producing or processing radioactive materials used in the production of atomic weapons. Seven different geometrical objects, representative of the configurations of natural uranium metal potentially encountered by workers at these facilities, are modelled to determine gamma ray and Bremsstrahlung dose rates. The dose rates are calculated using the MCNP5 code and also by using the MICROSHIELD point-kernel code. Both gamma ray and Bremsstrahlung dose rates are calculated and combined to obtain a total dose rate. The two methods were found to be in good agreement despite differences in modelling assumptions and method differences. Computed total dose rates on the surface of these objects ranged from ∼51-84 μSv h -1 and 17-95 μSv h -1 using the MCNP5 and the MICROSHIELD modeling, respectively. The partitioning of the computed dose rates between gamma rays and Bremsstrahlung were the same order of magnitude for each object. (authors)
Bremsstrahlung doses from natural uranium ingots.
Anderson, Jeri L; Hertel, Nolan E
2005-01-01
In the past, some privately owned commercial facilities in the United States were involved in producing or processing radioactive materials used in the production of atomic weapons. Seven different geometrical objects, representative of the configurations of natural uranium metal potentially encountered by workers at these facilities, are modelled to determine gamma ray and bremsstrahlung dose rates. The dose rates are calculated using the MCNP5 code and also by using the MICROSHIELD point-kernel code. Both gamma ray and bremsstrahlung dose rates are calculated and combined to obtain a total dose rate. The two methods were found to be in good agreement despite differences in modelling assumptions and method differences. Computed total dose rates on the surface of these objects ranged from approximately 51-84 microSv h(-1) and 17-95 microSv h(-1) using the MCNP5 and the MICROSHIELD modeling, respectively. The partitioning of the computed dose rates between gamma rays and bremsstrahlung were the same order of magnitude for each object.
Talbot, Austin; Devarajan, Deepa; Gustafson, Samantha J.; Fernandez, Israel; Bickelhaupt, F. Matthias; Ess, Daniel H.
2014-01-01
Heteroaromatic azadienes, especially 1,2,4,5-tetrazines, are extremely reactive partners with alkenes in inverse-electron-demand Diels–Alder reactions. Azadiene cycloaddition reactions are used to construct heterocycles in synthesis and are popular as bioorthogonal reactions. The origin of fast
International Nuclear Information System (INIS)
Scheithauer, M.; Schwedas, M.; Wiezorek, T.; Wendt, T.
2003-01-01
The present study focused on the reconstruction of the bremsstrahlung spectrum of a clinical linear accelerator from the measured transmission curve, with the aim of improving the accuracy of this method. The essence of the method was the analytic inverse Laplace transform of a parameter function fitted to the measured transmission curve. We tested known fitting functions, however they resulted in considerable fitting inaccuracy, leading to inaccuracies of the bremsstrahlung spectrum. In order to minimise the fitting errors, we employed a linear combination of n equations with 2n-1 parameters. The fitting errors are now considerably smaller. The measurement of the transmission function requires that the energy-dependent detector response is taken into account. We analysed the underlying physical context and developed a function that corrects for the energy-dependent detector response. The factors of this function were experimentally determined or calculated from tabulated values. (orig.) [de
Beta induced Bremsstrahlung dose rate in concrete shielding
International Nuclear Information System (INIS)
Manjunatha, H.C.
2013-01-01
Dosimetric study of beta-induced Bremsstrahlung in concrete is importance in the field of radiation protection. The efficiency, intensity and dose rate of beta induced Bremsstrahlung by 113 pure beta nuclides in concrete shielding is computed. The Bremsstrahlung dosimetric parameters such as the efficiency (yield), Intensity and dose rate of Bremsstrahlung are low for 199 Au and high for 104 Tc in concrete. The efficiency, Intensity and dose rate of Bremsstrahlung increases with maximum energy of beta nuclide (Emax) and modified atomic number (Zmod) of the target. The estimated Bremsstrahlung efficiency, Intensity and dose rate are useful in the calculations photon track-length distributions. These parameters are useful to determine the quality and quantity of the radiation (known as the source term). Precise estimation of this source term is very important in planning of radiation shielding. (author)
Resonance double magnetic bremsstrahlung in a strong magnetic field
International Nuclear Information System (INIS)
Fomin, P.I.; Kholodov, R.I.
2003-01-01
The possibility of resonance double magnetic bremsstrahlung in the approximation of weakly excited electron states in a strong external magnetic field is analyzed. The differential probability of this process in the Breit-Wigner form is obtained. The probability of double magnetic bremsstrahlung (second-order process of perturbation theory) is compared with the probability of magnetic bremsstrahlung (first-order process of perturbation theory)
Bremsstrahlung converter debris shields: test and analysis
International Nuclear Information System (INIS)
Reedy, E.D. Jr.; Perry, F.C.
1983-10-01
Electron beam accelerators are commonly used to create bremsstrahlung x-rays for effects testing. Typically, the incident electron beam strikes a sandwich of three materials: (1) a conversion foil, (2) an electron scavenger, and (3) a debris shield. Several laboratories, including Sandia National Laboratories, are developing bremsstrahlung x-ray sources with much larger test areas (approx. 200 to 500 cm 2 ) than ever used before. Accordingly, the debris shield will be much larger than before and subject to loads which could cause shield failure. To prepare for this eventuality, a series of tests were run on the Naval Surface Weapons Center's Casino electron beam accelerator (approx. 1 MeV electrons, 100 ns FWHM pulse, 45 kJ beam energy). The primary goal of these tests was to measure the stress pulse which loads a debris shield. These measurements were made with carbon gages mounted on the back of the converter sandwich. At an electron beam fluence of about 1 kJ/cm 2 , the measured peak compressive stress was typically in the 1 to 2 kbar range. Measured peak compressive stress scaled in a roughly linear manner with fluence level as the fluence level was increased to 10 kJ/cm 2 . The duration of the compressive pulse was on the order of microseconds. In addition to the stress wave measurements, a limited number of tests were made to investigate the type of damage generated in several potential shield materials
The bremsstrahlung induced by 0.3-2 keV electron scattering by Ar atoms
International Nuclear Information System (INIS)
Gnatchenko, E.V.; Tkachenko, A.A.; Verkhovtseva, E.T.
2002-01-01
The differential spectra of a bremsstrahlung resulting from a 0.3-2 keV electron scattering by Ar atoms are studied. Photon energies within the ultrasoft X-ray band from 124 to 190.8 eV, which is characterized by the low dynamic polarizability of the Ar atom, are considered. For the entire spectrum of photon energies (124-190.8 eV), the intensity of the bremsstrahlung differential spectra first grows with an increase in the electron energy from 0.3 to 0.7 keV and then decreases as the electron energy increases from 0.7 to 2 keV. The increase in intensity is directly proportional, and the decrease is inversely proportional to the square root of the energy of the scattered electrons. Within the context of a 'low-energy' approximation, the increase in the number of photons with the electron energy is due to the contribution of the atomic excitation and ionization channels being available during the bremsstrahlung process
Vector dark matter annihilation with internal bremsstrahlung
Energy Technology Data Exchange (ETDEWEB)
Bambhaniya, Gulab, E-mail: gulab@prl.res.in [Physical Research Laboratory, Ahmedabad 380009 (India); Kumar, Jason, E-mail: jkumar@hawaii.edu [Department of Physics & Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Marfatia, Danny, E-mail: dmarf8@hawaii.edu [Department of Physics & Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Nayak, Alekha C., E-mail: acnayak@iitk.ac.in [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Tomar, Gaurav, E-mail: tomar@prl.res.in [Physical Research Laboratory, Ahmedabad 380009 (India)
2017-03-10
We consider scenarios in which the annihilation of self-conjugate spin-1 dark matter to a Standard Model fermion–antifermion final state is chirality suppressed, but where this suppression can be lifted by the emission of an additional photon via internal bremsstrahlung. We find that this scenario can only arise if the initial dark matter state is polarized, which can occur in the context of self-interacting dark matter. In particular, this is possible if the dark matter pair forms a bound state that decays to its ground state before the constituents annihilate. We show that the shape of the resulting photon spectrum is the same as for self-conjugate spin-0 and spin-1/2 dark matter, but the normalization is less heavily suppressed in the limit of heavy mediators.
Coulomb correction calculations of pp Bremsstrahlung
International Nuclear Information System (INIS)
Katsogiannis, A.; Amos, K.; Jetter, M.; von Geramb, H.V.
1994-01-01
The effects of the Coulomb interaction upon the photon cross section and analyzing power from pp Bremsstrahlung have been studied in detail. Off-shell properties of the Coulomb T matrices have been considered but the associated, Coulomb modified, hadronic T matrices are important elements in any analyses of low energy, forward proton scattering data. At the lowest energy considered (5 MeV), the full calculations gave cross sections that were half the size of those found without Coulomb effects or with a simple model approximation to them. With increasing energy, the cross sections varied to those characteristic of magnetic interaction dominance and the specific differences due to Coulomb effects diminished. 47 refs., 7 figs
Gluon bremsstrahlung and elastic scattering of hadrons
International Nuclear Information System (INIS)
Povh, B.
2001-01-01
The differential and the total cross sections in high energy hadron-proton interactions give a beautiful insight in the low Q 2 structure of the nucleon. The cross section is composed of two parts: a large energy independent part corresponding to the interaction of the valence quark with the target without gluon radiation and an energy dependent part caused by gluon bremsstrahlung. The gluons are located at small transverse distances of about 0.3 fm from the valence quarks. The model with two scales, the size of the hadron (R 2 ∼ 1 fm 2 ) and the size of the gluonic cloud (r 0 2 ∼ 0.1 fm 2 ), correctly predicts the total and the differential cross sections and the behaviour of diffractive dissociation in hadronic and deep inelastic events. (orig.)
Zeff measurements in ATF using visible bremsstrahlung
International Nuclear Information System (INIS)
Morita, S.; Richards, R.K.; Horton, L.D.; Isler, R.C.; Crume, E.C. Jr.; Murakami, M.
1991-04-01
Measurements of the effective charge Z eff in plasmas with electron cyclotron heating (ECH) and neutral beam injection (NBI) in the Advanced Toroidal Facility (ATF) have been carried out using visible bremsstrahlung. The electron temperature needed for the analysis is calculated from the measured stored energy and electron density. The value of Z eff varies widely depending on experimental conditions. In ECH plasmas it is between 2 and 8. In NBI plasmas, which are subject to radiation collapse, Z eff is between 3 and 5 at the time the stored energy reaches a maximum. However, Z eff is less than 2.5 in quasi-steady medium-density plasmas and is close to 1.2 in the highest-density plasmas, where the average electron density bar n e is of the order of 10 14 cm -3 . 12 refs., 29 figs., 1 tab
High energy bremsstrahlung in an intense laser field
International Nuclear Information System (INIS)
Schlessinger, L.; Wright, J.A.
1980-02-01
The cross section for bremsstrahlung emission and absorption by electrons in an intense laser field has been calculated in the Born approximation for the electron-ion potential. Typical numerical results are presented as a function of the ratio of the electron guiver energy to its energy and the ratio of the bremsstrahlung energy to the electron energy. The intense field correction factor for the rate of bremsstrahlung emission and absorption for electrons with a Boltzmann distribution of energies has been calculated. Numerical results for the correction factor are presented for the Boltzmann case as a function of the ratio of the electron quiver energy to its thermal energy and the ratio of the bremsstrahlung energy to the thermal energy. For typical laser fusion parameters, this correction factor which is the ratio of the thermal bremsstrahlung emission rate in the intense laser field to the rate at zero field can be quite significant. For a laser of wavelength 1.06 μm at an intensity of 3 x 10 15 w/cm 2 and an electron temperature of 1 keV, the correction factor varies from 0.98 at a bremsstrahlung energy of 100 V to greater than 5 at a bremsstrahlung energy of 10 keV
Nonlinear effects on bremsstrahlung emission in dusty plasmas
International Nuclear Information System (INIS)
Kim, Young-Woo; Jung, Young-Dae
2004-01-01
Nonlinear effects on the bremsstrahlung process due to ion-dust grain collisions are investigated in dusty plasmas. The nonlinear screened interaction potential is applied to obtain the Fourier coefficients of the force acting on the dust grain. The classical trajectory analysis is applied to obtain the differential bremsstrahlung radiation cross section as a function of the scaled impact parameter, projectile energy, photon energy, and Debye length. The result shows that the nonlinear effects suppress the bremsstrahlung radiation cross section due to collisions of ions with positively charged dust grains. These nonlinear effects decrease with increasing Debye length and temperature, and increase with increasing radiation photon energy
A collimator optimization method for quantitative imaging: application to Y-90 bremsstrahlung SPECT.
Rong, Xing; Frey, Eric C
2013-08-01
Post-therapy quantitative 90Y bremsstrahlung single photon emission computed tomography (SPECT) has shown great potential to provide reliable activity estimates, which are essential for dose verification. Typically 90Y imaging is performed with high- or medium-energy collimators. However, the energy spectrum of 90Y bremsstrahlung photons is substantially different than typical for these collimators. In addition, dosimetry requires quantitative images, and collimators are not typically optimized for such tasks. Optimizing a collimator for 90Y imaging is both novel and potentially important. Conventional optimization methods are not appropriate for 90Y bremsstrahlung photons, which have a continuous and broad energy distribution. In this work, the authors developed a parallel-hole collimator optimization method for quantitative tasks that is particularly applicable to radionuclides with complex emission energy spectra. The authors applied the proposed method to develop an optimal collimator for quantitative 90Y bremsstrahlung SPECT in the context of microsphere radioembolization. To account for the effects of the collimator on both the bias and the variance of the activity estimates, the authors used the root mean squared error (RMSE) of the volume of interest activity estimates as the figure of merit (FOM). In the FOM, the bias due to the null space of the image formation process was taken in account. The RMSE was weighted by the inverse mass to reflect the application to dosimetry; for a different application, more relevant weighting could easily be adopted. The authors proposed a parameterization for the collimator that facilitates the incorporation of the important factors (geometric sensitivity, geometric resolution, and septal penetration fraction) determining collimator performance, while keeping the number of free parameters describing the collimator small (i.e., two parameters). To make the optimization results for quantitative 90Y bremsstrahlung SPECT more
Dynamic bremsstrahlung from relativistic particles scattered by atom
International Nuclear Information System (INIS)
Astapenko, V.A.; Bujmistrov, V.M.; Krotov, Yu.A.; Mikhajlov, L.K.; Trakhtenberg, L.I.
1985-01-01
The bremsstrahlung cross section for a relativistic particle scattered by an atom is calculated. In contrast to the screening approximation usually employed, the influence of the atomic electron on the bremsstrahlung is taken into account exactly, viz., the atomic electron is considered as a moving particle interacting with the electromagnetic field and not only as the source of a static external field. Consequently, along with the static term which leads to the Bethe-Heitw,ler formula, a ne dynamic, term appears in the transition amplitude. The corresponding cross section, the dynamic bremsstrahlung cross section, in certain frequensy ranges and certain ranges of the directions of photon emission exceeds considerably the static bremsstrahlung cross section
Measurement of the bremsstrahlung spectra generated from thick ...
Indian Academy of Sciences (India)
with those predicted by Monte-Carlo (MC) calculations using PENELOPE code. A close ... done on bremsstrahlung cross-section measurements and many theories have been given for ..... This probability is expected to be maximum for elastic.
International Nuclear Information System (INIS)
D'Enterria, D.G.
2000-05-01
The thermodynamical properties of nuclear matter at moderate temperatures and densities, in the vicinity of the predicted nuclear liquid-gas phase transition, are studied using as experimental probe the hard-photons (E γ > 30 MeV) emitted in nucleus-nucleus collisions. Photon and charged-particle production in four different heavy-ion reactions (Ar 36 + Au 197 , Ag 107 , Ni 58 , C 12 at 60 A*MeV) is measured exclusively and inclusively coupling the TAPS photon spectrometer with two charged-particle and intermediate-mass-fragment detectors covering nearly 4π. We confirm that Bremsstrahlung emission in first-chance (off-equilibrium) proton-neutron collisions (pnγ) is the dominant origin of hard photons. We also firmly establish the existence of a thermal radiation component emitted in second-chance proton-neutron collisions. This thermal Bremsstrahlung emission takes place in semi-central and central nucleus-nucleus reactions involving heavy targets. We exploit this observation i) to demonstrate that thermal equilibrium is reached during the reaction, ii) to establish a new thermometer of nuclear matter based on Bremsstrahlung photons, iii) to derive the thermodynamical properties of the excited nuclear sources and, in particular, to establish a 'caloric curve' (temperature versus excitation energy), and iv) to assess the time-scales of the nuclear break-up process. (author)
Directory of Open Access Journals (Sweden)
Artur de Vargas Giorgi
2011-02-01
Full Text Available This essay tightens the “origin” concept, its manifestation through puzzles and their relationship to techniques of reproduction. Contrary to the hegemonic critique of aesthetic and cultural objects – critique that, settled on the appearance and notions of identity, tradition, canon, etc., undervalues the reproductions of "originals" –, the aim is to deliver these objects from formal hierarchization dispositives, that is, release them of what is ideal and positively imposed, so that the reproducibility is potentiated as producer of singularities, of apparitions. The effort is to keep the undecided character of puzzles (bodies, texts, images in which the origin is manifest, so that the logic of the spectacle is reverted into sense opening, instance in which the aesthetic becomes a “performance” before contemporary complexity. With the reproducibility, an origin survives in passage: continually restored, but incomplete, present in trace, in absence.
Analytic approximate radiation effects due to Bremsstrahlung
Energy Technology Data Exchange (ETDEWEB)
Ben-Zvi I.
2012-02-01
The purpose of this note is to provide analytic approximate expressions that can provide quick estimates of the various effects of the Bremsstrahlung radiation produced relatively low energy electrons, such as the dumping of the beam into the beam stop at the ERL or field emission in superconducting cavities. The purpose of this work is not to replace a dependable calculation or, better yet, a measurement under real conditions, but to provide a quick but approximate estimate for guidance purposes only. These effects include dose to personnel, ozone generation in the air volume exposed to the radiation, hydrogen generation in the beam dump water cooling system and radiation damage to near-by magnets. These expressions can be used for other purposes, but one should note that the electron beam energy range is limited. In these calculations the good range is from about 0.5 MeV to 10 MeV. To help in the application of this note, calculations are presented as a worked out example for the beam dump of the R&D Energy Recovery Linac.
Bremsstrahlung X rays from Jovian auroral electrons
International Nuclear Information System (INIS)
Barbosa, D.D.
1990-01-01
The spectrum of X rays from the planet Jupiter is calculated according to an auroral electron beam model. The electrons are assumed to be accelerated by a field-aligned potential drop and penetrate into the atmosphere as a Maxwellian beam of primaries which are scattered, degraded in energy, and merged with a population of ionization secondaries having a power law energy distribution. The soft X rays observed by the Einstein Observatory satelltie are due to bremsstrahlung from the sedondary electrons in the H 2 atmosphere. A good match to the X ray data is obtained if the power law spectral index of the secondary electrons, γ e , is ≅ 2, yielding a power law slope for the photon flux γ X = γ e + 1 ≅ 3. The X ray intensity is best reconciled with a beam of primaries having a characteristic energy 30-100 keV and penetrating the homopause with an auroral energy flux typically of 10-20 ergs cm -2 s -1 but no greater than 50 ergs cm -2 s -1
Analytic approximate radiation effects due to Bremsstrahlung
International Nuclear Information System (INIS)
Ben-Zvi, I.
2012-01-01
The purpose of this note is to provide analytic approximate expressions that can provide quick estimates of the various effects of the Bremsstrahlung radiation produced relatively low energy electrons, such as the dumping of the beam into the beam stop at the ERL or field emission in superconducting cavities. The purpose of this work is not to replace a dependable calculation or, better yet, a measurement under real conditions, but to provide a quick but approximate estimate for guidance purposes only. These effects include dose to personnel, ozone generation in the air volume exposed to the radiation, hydrogen generation in the beam dump water cooling system and radiation damage to near-by magnets. These expressions can be used for other purposes, but one should note that the electron beam energy range is limited. In these calculations the good range is from about 0.5 MeV to 10 MeV. To help in the application of this note, calculations are presented as a worked out example for the beam dump of the R and D Energy Recovery Linac.
Bremsstrahlung convertors: materials design and development
International Nuclear Information System (INIS)
Allred, R.E.
1976-03-01
An improved bremsstrahlung convertor for use at high electron beam energies was developed. The convertor consists of three main components: (1) conversion foil; (2) electron scavenger; and (3) impulse shield. Structural failures of the impulse shield were experimentally determined to be caused by shock wave interactions. Convertor materials and design modifications were aimed at attenuation of the magnitude of the shock and maximization of energy absorption by the convertor materials. Techniques proven successful included the introduction of porosity into electron scavenger and impulse shield materials, the use of a standoff between the conversion foil and the electron scavenger, the insertion of a gap between the scavenger and impulse shield, and the use of advanced composite materials for the impulse shield. These modifications have increased the convertor operating range from 4 cal/gm Au to over 8 cal/gm Au. Kevlar 49 reinforced-resin composites have proven to have the best combination of strength, stiffness, toughness, and x-ray transport properties for use as bremmstrahlung convertor impulse shields
Gravitational bremsstrahlung in ultra-planckian collisions
Gal'tsov, Dmitry; Tomaras, Theodore N
2013-01-01
A classical computation of gravitational bremsstrahlung in ultra-planckian collisions of massive point particles is presented in an arbitrary number d of toroidal or non-compact extra dimensions. Our method generalizes the post-linear formalism of General Relativity to the multidimensional case. The total emitted energy, as well as its angular and frequency distribution are discussed in detail. In terms of the gravitational radius r_S of the collision energy, the impact parameter b and the Lorentz factor in the CM frame, the leading order radiation efficiency in the Lab frame is shown to be of order (r_S/b)^{3(d+1)} gamma_{cm} for d=0, 1 and of order (r_S/b)^{3(d+1)} gamma_{cm}^{2d-3} for d>1, up to a known d-dependent coefficient and a ln gamma_{cm} factor for d=2, while the characteristic frequency of the radiation is gamma/b. The contribution of the low frequency part of the radiation (soft gravitons) to the total radiated energy is shown to be negligible for all values of d. The domain of validity of the ...
International Nuclear Information System (INIS)
Desesquelles, P.
1997-01-01
Computer Monte Carlo simulations occupy an increasingly important place between theory and experiment. This paper introduces a global protocol for the comparison of model simulations with experimental results. The correlated distributions of the model parameters are determined using an original recursive inversion procedure. Multivariate analysis techniques are used in order to optimally synthesize the experimental information with a minimum number of variables. This protocol is relevant in all fields if physics dealing with event generators and multi-parametric experiments. (authors)
Energy Technology Data Exchange (ETDEWEB)
Rozhkova, E.I., E-mail: elenafiks@gmail.com; Pivovarov, Yu.L.
2016-07-15
The Cherenkov radiation (ChR) angular distribution is usually described by the Tamm–Frank (TF) theory, which assumes that relativistic charged particle moves uniformly and rectilinearly in the optically transparent radiator. According to the TF theory, the full width at half maximum (FWHM) of the ChR angular distribution inversely depends on the radiator thickness. In the case of relativistic heavy ions (RHI) a slowing-down in the radiator may sufficiently change the angular distribution of optical radiation in vicinity of the Cherenkov cone, since there appears a mixed ChR–Bremsstrahlung radiation. As a result, there occurs a drastic transformation of the FWHM of optical radiation angular distribution in dependence on the radiator thickness: from inversely proportional (TF theory) to the linearly proportional one. In our paper we present the first analysis of this transformation taking account of the gradual velocity decrease of RHI penetrating through a radiator. - Highlights: • Stopping of relativistic heavy ions leads to appearance of a Cherenkov–Bremsstrahlung radiation near the Cherenkov cone. • Mixed Cherenkov–Bremsstrahlung optical radiation FWHM differs from the standard one determined by the Tamm–Frank theory. • The Cherenkov–Bremsstrahlung radiation angular distribution FWHM linearly depends on the radiator thickness.
Differential bremsstrahlung and pair production cross sections at high energies
International Nuclear Information System (INIS)
Olsen, Haakon A.
2003-01-01
Detailed differential cross sections for high energy bremsstrahlung and pair production are derived with specific attention to the differences between the two processes, which are considerable. For the integrated cross sections, which are the only cross sections specifically known until now, the final state integration theorem guarantees that the exact cross section formulas can be exchanged between bremsstrahlung and pair production by the same substitution rules as for the Born-approximation Bethe-Heitler cross sections, for any amount of atomic screening. In fact the theorem states that the Coulomb corrections to the integrated bremsstrahlung and pair production cross sections are identical for any amount of screening. The analysis of the basic differential cross sections leads to fundamental physical differences between bremsstrahlung and pair production. Coulomb corrections occur for pair production in the strong electric field of the atom for 'large' momentum transfer of the order of mc. For bremsstrahlung, on the other hand, the Coulomb corrections take place at a 'large' distance from the atom of the order of ((ℎ/2π)/mc)ε, with a 'small' momentum transfer mc/ε, where ε is the initial electron energy in units of mc 2 . And the Coulomb corrections can be large, of the order of larger than (Z/137) 2 , which is considerably larger than the integrated cross section corrections
Study of bremsstrahlung photons in bulk target using MCNP code
Directory of Open Access Journals (Sweden)
S. Sangaroon
2017-11-01
Full Text Available The aim of this research was to study the feasibility of bremsstrahlung photon production in target bombarded by 1 GeV electrons. The calculations were performed by the Monte Carlo code MCNP. Six target materials with densities between 2 and 20 g/cm3 were studied. The bremsstrahlung photon flux is high for the target density above 8 g/cm3. Copper is the best target for 1 GeV electron beam due to high bremsstrahlung photon production, low scattering and low transmission electron flux. The copper target was altered to have different thicknesses between 0.01 and 2.5 cm. The results showed that the bremsstrahlung photon flux significantly increased when the target thickness increased from 0.01 to 1.5 cm. The angular distribution of the bremsstrahlung photons with angles between 0 and 120 degrees was determined for copper target. The maximum angle of the photon scattering was about 20 degree.
Shielding calculation for bremsstrahlung from β-emitters
International Nuclear Information System (INIS)
Ichimiya, Tsutomu
1990-01-01
Accompanying the revision of radiation injury prevention law, the shielding calculation method for photon corresponding to the dose equivalent was shown. However, regarding the electron from β decay nuclide and bremsstrahlung caused by shielding material, the shielding calculation method corresponding to the 1 cm dose equivalent has not been reported, hence, in this report, the spectrum of β-ray is calculated and the 1 cm dose equivalent transmission rate of the bremsstrahlung was calculated for three kinds of shielding materials (iron, lead, concrete). As the result of consideration, it is sufficient to think about the bremsstrahlung due to negative electron emission accompanying β-decay. In β-decay, electrons which constitute the continuous spectrum with maximum energy are emitted. The shape of the spectrum differs with nuclides. The maximum energy of β-ray of generally used nuclides is mostly below 3MeV and, besides, the electron ray itself is easily shielded, while the strength of bremsstrahlung depends on the atomic number of shielding materials and its generating mechanism is complicated. In this report, the actual shielding calculation method for bremsstrahlung is shown with regard to the most frequently used β-decay nuclides. (M.T.)
Hanson, Sara J; Byrne, Kevin P; Wolfe, Kenneth H
2014-11-11
Saccharomyces cerevisiae has a complex system for switching the mating type of haploid cells, requiring the genome to have three mating-type (MAT)-like loci and a mechanism for silencing two of them. How this system originated is unknown, because the three-locus system is present throughout the family Saccharomycetaceae, whereas species in the sister Candida clade have only one locus and do not switch. Here we show that yeasts in a third clade, the methylotrophs, have a simpler two-locus switching system based on reversible inversion of a section of chromosome with MATa genes at one end and MATalpha genes at the other end. In Hansenula polymorpha the 19-kb invertible region lies beside a centromere so that, depending on the orientation, either MATa or MATalpha is silenced by centromeric chromatin. In Pichia pastoris, the orientation of a 138-kb invertible region puts either MATa or MATalpha beside a telomere and represses transcription of MATa2 or MATalpha2. Both species are homothallic, and inversion of their MAT regions can be induced by crossing two strains of the same mating type. The three-locus system of S. cerevisiae, which uses a nonconservative mechanism to replace DNA at MAT, likely evolved from a conservative two-locus system that swapped genes between expression and nonexpression sites by inversion. The increasing complexity of the switching apparatus, with three loci, donor bias, and cell lineage tracking, can be explained by continuous selection to increase sporulation ability in young colonies. Our results provide an evolutionary context for the diversity of switching and silencing mechanisms.
DEFF Research Database (Denmark)
Blein, Sophie; Bardel, Claire; Danjean, Vincent
2015-01-01
of Investigators of Modifiers of BRCA1/2 for 129 mitochondrial polymorphisms using the iCOGS array. Haplogroup inference and association detection were performed using a phylogenetic approach. ALTree was applied to explore the reference mitochondrial evolutionary tree and detect subclades enriched in affected......, H and T clades), the T1a1 haplogroup has a HR of 0.62 (95% CI, 0.40 to 0.95; P = 0.03). We also identified three potential susceptibility loci, including G13708A/rs28359178, which has demonstrated an inverse association with familial breast cancer risk. CONCLUSIONS: This study illustrates how...... original approaches such as the phylogeny-based method we used can empower classical molecular epidemiological studies aimed at identifying association or risk modification effects....
Using a tungsten rollbar to characterize the source spot of a megavoltage bremsstrahlung linac
International Nuclear Information System (INIS)
Schach von Wittenau, A.E.; Logan, C.M.; Rikard, R.
2002-01-01
In photon teletherapy, the size and functional form of the photon source spot affect both the sharpness of the penumbra of treatment fields and the sharpness of portal images. Photon source spot parameters are also used in photon teletherapy dose calculation codes. A simple method for characterizing the source spot would complement the existing, more involved methods that have been described in the medical physics literature. Such a method, using a rollbar made of tungsten or other high-Z metal, is used in industrial radiography. We describe the use of a tungsten rollbar for characterizing the source spot edge spread function (and thereby the source spot size and shape) of a megavoltage bremsstrahlung photon source. We use Monte Carlo simulations to quantify anticipated experimental artifacts of the method, assuming typical spot sizes for circ-function, Gaussian, and Bennett line shapes. We illustrate the use of the rollbar method by characterizing the source spot of a typical 9 MV linac used for industrial radiography. The source spot is analyzed using two approaches: (a) fitting the rollbar image with analytic functions and (b) using Abel inversion to obtain the cylindrically symmetric spot profile consistent with the measured rollbar image. Monte Carlo simulations, based on a 6 MV photon teletherapy accelerator, suggest that aspects of the method are applicable to medical bremsstrahlung sources
Krause, L. Habsh; Gilchrist, B. E.; Nishikawa, Ken-Ichi
2013-01-01
Relativisitic electron precipitation (REP) events occur when beams or bunches of relativistic electrons of magnetospheric origin enter the Earth's atmosphere, typically at auroral latitudes. REP events are associated with a variety of space weather effects, including production of transitional and bremsstrahlung radiation, catalytic depletion of stratospheric ozone, and scintillation of transionospheric radio waves. This study examines the intensities of x-rays produced at airliner, manned balloon, and space reuseable launch vehicles (sRLVs). The monoenergetic beam is modeled in cylindrical symetry using the paraxial ray equation. Bremsstrahlung photon production is calculated using the traditional Sauter-Elwert cross-section, providing x-ray emission spectra differential in energy and angle. Attenuation is computed for a plane-stratified standard atmosphere, and the loss processes include photoionization, Rayleigh and Compton scattering, electron-positron pair production, and photonuclear interaction. Peak altitudes of electron energy deposition and bremsstrahlung x-ray production were calculated for beams of energies from 1 MeV through 100 MeV. The altitude peak of bremsstrahlung deposition was consistently and significantly lower that that of the electron deposition due to the longer mean free paths of x-rays compared to electrons within the atmosphere. For example, for a nadir-directed monoenergetic 5 MeV beam, the peak deposition altitude was calculated to be 42 km, but the resulting bremsstrahlung deposition peaked at 25 km. This has implications for crew and passenger safety, especially with the growth of the space tourism industry. A survey of results covering the 1-100 MeV spectrum for the three altitude ranges of interest will be presented.
Electron collision effects on the bremsstrahlung emission in Lorentzian plasmas
International Nuclear Information System (INIS)
Jung, Young-Dae; Kato, Daiji
2009-06-01
The electron-electron collision effects on the electron-ion bemsstranhlung process are investigated in warm Lorentzian plasmas. The effective electron-ion interaction potential is obtained by including the far-field terms caused by the electron-electron collisions with the effective Debye length in Lorentzian plasmas. The bremsstranhlung radiation cross section is obtained as a function of the electron energy, photon energy, collision frequency, spectral index, and Debye length using the Born approximation for the initial and final states of the projectile electron. It is shown that the non-Maxwellian character suppresses the bremsstrahlung radiation cross section. It is also shown that the electron-electron collision effect enhances the bremsstrahlung emission spectrum. In addition, the bremsstrahlung radiation cross section decreases with an increase of the plasma temperature. (author)
Bremsstrahlung emission probability in the α decay of 210Po
International Nuclear Information System (INIS)
Boie, Hans-Hermann
2009-01-01
A high-statistics measurement of bremsstrahlung emitted in the α decay of 210 Po has been performed. The measured differential emission probabilities, which could be followed up to γ-energies of ∝ 500 keV, allow for the first time for a serious test of various model calculations of the bremsstrahlung accompanied α decay. It is shown that corrections to the α-γ angular correlation due to the interference between the electric dipole and quadrupole amplitudes and due to the relativistic character of the process have to be taken into account. With the experimentally derived angular correlation the measured energydifferential bremsstrahlung emission probabilities show excellent agreement with the fully quantum mechanical calculation. (orig.)
Suppression of bremsstrahlung and pair production due to environmental factors
International Nuclear Information System (INIS)
Klein, Spencer
1999-01-01
The environment in which bremsstrahlung and pair creation occurs can strongly affect cross sections for these processes. Because ultrarelativistic electromagnetic interactions involve very small longitudinal momentum transfers, the reactions occur gradually, spread over long distances. During this time, even relatively weak factors can accumulate enough to disrupt the interaction. In the Landau-Pomeranchuk-Migdal effect, multiple scattering reduces the bremsstrahlung and pair production cross section. This review will discuss this and a variety of other factors that can suppress bremsstrahlung and pair production, as well as related effects involving beamstrahlung and QCD processes. After surveying different theoretical approaches, experimental measurements will be covered. Recent accurate measurements by the SLAC E-146 Collaboration will be highlighted, along with several recent theoretical works relating to the experiment. (c) 1999 The American Physical Society
Zeff from spectroscopic bremsstrahlung measurements at ASDEX Upgrade and JET
International Nuclear Information System (INIS)
Meister, H.; Fischer, R.; Horton, L.D.; Maggi, C.F.; Nishijima, D.; Giroud, C.; Zastrow, K.-D.; Zaniol, B.
2004-01-01
The effective ionic charge Z eff is a means to assess the impurity content of a fusion plasma. It can be derived from measurements of bremsstrahlung intensity. These have been extended at ASDEX Upgrade by the usage of the sight lines for the charge exchange recombination diagnostic. Together with a previously installed sight line array, it is now possible to routinely determine the bremsstrahlung intensity over the whole minor radius purely from spectroscopic measurements. In a tokamak where the plasma facing components are made up of various materials, this is necessary to check if measurements are contaminated by line radiation. The bremsstrahlung background of the respective spectra is determined using Bayesian probability theory, giving consistent and improved error statistics. Using the information for electron temperature and density profiles, the Z eff profile is determined by an integrated method. The same approach to assess the Z eff profile has been demonstrated to be successful also at the JET tokamak
Inverse photoemission of uranium oxides
International Nuclear Information System (INIS)
Roussel, P.; Morrall, P.; Tull, S.J.
2009-01-01
Understanding the itinerant-localised bonding role of the 5f electrons in the light actinides will afford an insight into their unusual physical and chemical properties. In recent years, the combination of core and valance band electron spectroscopies with theoretic modelling have already made significant progress in this area. However, information of the unoccupied density of states is still scarce. When compared to the forward photoemission techniques, measurements of the unoccupied states suffer from significantly less sensitivity and lower resolution. In this paper, we report on our experimental apparatus, which is designed to measure the inverse photoemission spectra of the light actinides. Inverse photoemission spectra of UO 2 and UO 2.2 along with the corresponding core and valance electron spectra are presented in this paper. UO 2 has been reported previously, although through its inclusion here it allows us to compare and contrast results from our experimental apparatus to the previous Bremsstrahlung Isochromat Spectroscopy and Inverse Photoemission Spectroscopy investigations
Partial decay energy of 51Cr from inner bremsstrahlung spectrum
International Nuclear Information System (INIS)
Sanjeeviah, H.; Sanjeevaiah, B.
1980-01-01
The inner bremsstrahlung spectrum accompanying orbital electron capture decay of 51 Cr to the first excited state in 51 V was measured in coincidence with 320 keV gamma rays. From the Jauch plot of the spectrum the partial decay energy was deduced to be 433 +- 18 keV in good agreement with the previously measured value and the accepted mass difference. The overall shape factor of the inner bremsstrahlung spectrum was found to be a constant X(1.1 +- 0.1). (author)
The Stonehenge technique. A method for aligning coherent bremsstrahlung radiators
International Nuclear Information System (INIS)
Livingston, Ken
2009-01-01
This paper describes a technique for the alignment of crystal radiators used to produce high energy, linearly polarized photons via coherent bremsstrahlung scattering at electron beam facilities. In these experiments the crystal is mounted on a goniometer which is used to adjust its orientation relative to the electron beam. The angles and equations which relate the crystal lattice, goniometer and electron beam direction are presented here, and the method of alignment is illustrated with data taken at MAMI (the Mainz microtron). A practical guide to setting up a coherent bremsstrahlung facility and installing new crystals using this technique is also included.
The Stonehenge technique. A method for aligning coherent bremsstrahlung radiators
Energy Technology Data Exchange (ETDEWEB)
Livingston, Ken [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)], E-mail: k.livingston@physics.gla.ac.uk
2009-05-21
This paper describes a technique for the alignment of crystal radiators used to produce high energy, linearly polarized photons via coherent bremsstrahlung scattering at electron beam facilities. In these experiments the crystal is mounted on a goniometer which is used to adjust its orientation relative to the electron beam. The angles and equations which relate the crystal lattice, goniometer and electron beam direction are presented here, and the method of alignment is illustrated with data taken at MAMI (the Mainz microtron). A practical guide to setting up a coherent bremsstrahlung facility and installing new crystals using this technique is also included.
The Stonehenge technique. A method for aligning coherent bremsstrahlung radiators
Livingston, Ken
2009-05-01
This paper describes a technique for the alignment of crystal radiators used to produce high energy, linearly polarized photons via coherent bremsstrahlung scattering at electron beam facilities. In these experiments the crystal is mounted on a goniometer which is used to adjust its orientation relative to the electron beam. The angles and equations which relate the crystal lattice, goniometer and electron beam direction are presented here, and the method of alignment is illustrated with data taken at MAMI (the Mainz microtron). A practical guide to setting up a coherent bremsstrahlung facility and installing new crystals using this technique is also included.
Impact of bremsstrahlung on the neutrinosphere for muon and tau neutrinos
Energy Technology Data Exchange (ETDEWEB)
Yasin, Hannah; Bartl, Alexander [Institut fuer Kernphysik, TU Darmstadt (Germany); Arcones, Almudena [Institut fuer Kernphysik, TU Darmstadt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany)
2015-07-01
Core-collapse supernovae present a challenging and exciting problem that strongly depends on all forces (strong, weak, electromagnetism, and gravity). Neutrinos, although weakly interacting, are key to transporting energy and momentum. Therefore, detailed treatment of neutrino reactions is critical to understand these high energy events. We have studied the impact of different neutrino reactions on the position of the neutrinosphere (i.e., region where neutrinos decouple from matter). Since the density in this region is high the effect of nuclear interactions has to be considered for bremsstrahlung: N+N→N+N+ν+ anti ν. We have employed new, improved approaches to calculate the inverse process and show the effect on the position of the neutrinosphere for muon and tau neutrinos.
Nuclear bremsstrahlung in proton induced reactions at 190 MeV (first experiments at AGOR)
Wilschut, HW
1998-01-01
An overview is given of the first experiments with the new KVI cyclotron AGOR. First experiments have focused on nuclear bremsstrahlung in few-and many-body reactions. A classical introduction to nuclear bremsstrahlung is given. First results on coherent bremsstrahlung are discussed.
Proton-proton bremsstrahlung in a relativistic covariant model
Martinus, Gerard Henk
1998-01-01
Proton-proton bremsstrahlung is one of the simplest processes involving the half off-shell NN interaction. Since protons are equally-charged particles with the same mass, electric-dipole radiation is suppressed and higher-order effects play an important role. Thus it is possible to get information
Evaluation of electon and nuclear bremsstrahlung in heavy ion collisions
International Nuclear Information System (INIS)
Gippner, P.
1975-01-01
The detection of quasimolecular X-ray continua provides the possibility of investigating the electron shells of quasimolecules transiently formed during adiabatic heavy ion-atomic collision. The contribution of the electron and nuclear bremsstrahlung to quasimolecular X-ray continua observed in bombarding various targets with 65 and 96 MeV Nb ions were estimated
Infrared phenomena in quantum electrodynamics : II. Bremsstrahlung and compton scattering
Haeringen, W. van
The infrared aspects of quantum electrodynamics are discussed by treating two examples of scattering processes, bremsstrahlung and Compton scattering. As in the previous paper one uses a non-covariant diagram technique which gives very clear insight in the cancelling of infrared divergences between
A detector for use in high energy bremsstrahlung shielding studies
International Nuclear Information System (INIS)
Wilson, O.J.; Thomson, J.E.M.
1983-01-01
The design, development and calibration of a detector based on the principle of the Moxon-Rae detector is discussed. It is ideally suited to the measurement of the energy fluence of photons transmitted through a thick shield which has been irradiated with high energy bremsstrahlung. The detection sensitivity is 10 4 to 10 5 times that of the P2 ion chamber
Proton-proton bremsstrahlung towards the elastic limit
Mahjour-Shafiei, M.; Amir-Ahmadi, H. R.; Bacelar, J. C. S.; Castelijns, R.; Ermisch, K.; van Garderen, E.; Gašparić, I.; Harakeh, M. N.; Kalantar-Nayestanaki, N.; Kiš, M.; Löhner, H.
2005-05-01
In oder to study proton-proton bremsstrahlung moving towards the elastic limit, a detection system, consisting of Plastic-ball and SALAD, was set up and an experiment at 190 MeV incident beam energy was performed. Here, the experimental setup and the data analysis procedure along with some results obtained in the measurement are discussed.
Proton-proton bremsstrahlung towards the elastic limit
International Nuclear Information System (INIS)
Mahjour-Shafiei, M.; Amir-Ahmadi, H.R.; Bacelar, J.C.S.; Castelijns, R.; Ermisch, K.; Garderen, E. van; Harakeh, M.N.; Kalantar-Nayestanaki, N.; Kis, M.; Loehner, H.; Gasparic, I.
2005-01-01
In oder to study proton-proton bremsstrahlung moving towards the elastic limit, a detection system, consisting of Plastic-ball and SALAD, was set up and an experiment at 190 MeV incident beam energy was performed. Here, the experimental setup and the data analysis procedure along with some results obtained in the measurement are discussed
Soft-photon analysis of pion-proton bremsstrahlung
International Nuclear Information System (INIS)
Liou, M.K.; Nutt, W.T.
1977-01-01
We define the soft-photon approximation consistent in its treatment of both the kinematical and dynamical aspects of bremsstrahlung. Using this consistent soft-photon approximation, we calculate π +- p cross sections and obtain excellent agreement with experiment. Our results suggest that the contributions from off-mass-shell effects and resonances are small
The resonance Bremsstrahlung of a fast charged particle in a medium
International Nuclear Information System (INIS)
Beshtoev, Kh.M.
1998-01-01
The Bremsstrahlung of the fast charged particle in the medium with dielectric permittivity ε at velocities υ ≥ c/n (n 2 =Reε) is considered. The Bremsstrahlung has singularity at β = 1/ncosθ (β = υ/c, θ is an angle of the Bremsstrahlung). This Bremsstrahlung is interpreted as resonance Bremsstrahlung with the width characterized by Imε=ε 2 , and the less ε 2 is, the higher the peak of this resonance rises. The angular distribution of the Bremsstrahlung is determined by cos θ=1/nβ and this angle coincides with the angle of the Cherenkov radiation. At β=1/n this resonance Bremsstrahlung goes in the forward direction and depends on frequency ω (ε=ε (ω))
Energy Technology Data Exchange (ETDEWEB)
D' Enterria, D.G
2000-05-15
The thermodynamical properties of nuclear matter at moderate temperatures and densities, in the vicinity of the predicted nuclear liquid-gas phase transition, are studied using as experimental probe the hard-photons (E{sub {gamma}} > 30 MeV) emitted in nucleus-nucleus collisions. Photon and charged-particle production in four different heavy-ion reactions (Ar{sup 36} + Au{sup 197}, Ag{sup 107}, Ni{sup 58}, C{sup 12} at 60 A*MeV) is measured exclusively and inclusively coupling the TAPS photon spectrometer with two charged-particle and intermediate-mass-fragment detectors covering nearly 4{pi}. We confirm that Bremsstrahlung emission in first-chance (off-equilibrium) proton-neutron collisions (pn{gamma}) is the dominant origin of hard photons. We also firmly establish the existence of a thermal radiation component emitted in second-chance proton-neutron collisions. This thermal Bremsstrahlung emission takes place in semi-central and central nucleus-nucleus reactions involving heavy targets. We exploit this observation i) to demonstrate that thermal equilibrium is reached during the reaction, ii) to establish a new thermometer of nuclear matter based on Bremsstrahlung photons, iii) to derive the thermodynamical properties of the excited nuclear sources and, in particular, to establish a 'caloric curve' (temperature versus excitation energy), and iv) to assess the time-scales of the nuclear break-up process. (author)
Directory of Open Access Journals (Sweden)
Cathleen eSpath
2013-04-01
Full Text Available Background: Recently, we demonstrated the beneficial effects of engineered heart tissues for the treatment of dilated cardiomyopathy in rats. For further development of this technique we started to produce engineered tissue (ET from mesenchymal stem cells. Interestingly, we observed a malignant tumour invading the heart with an inverse relationship between proliferation markers and connexin-expression.Methods: Commercial CD54+/CD90+/CD34-/CD45- bone marrow derived mesenchymal rat stem cells (cBM-MSC, characterized were used for production of mesenchymal stem-cell-ET (MSC-ET by suspending them in a collagen-I, matrigel-mixture and cultivating for 14 days with electrical stimulation. 3 MSC-ET were implanted around the beating heart of adult rats for days. Another 3 MSC-ET were produced from freshly isolated rat bone marrow derived stem cells (sBM-MSC.Results: 3 weeks after implantation of the MSC-ETs the hearts were surgically excised. While in 5/6 cases the ET was clearly distinguishable and was found as a ring containing mostly connective tissue around the heart, in 1/6 the heart was completely surrounded by a huge, undifferentiated, pleomorphic tumour originating from the cMSC-ET (cBM-MSC, classified as a high grade malignant sarcoma. Quantitatively we found a clear inverse relationship between cardiac connexin-expression (Cx43, Cx40 or Cx45 and increased Ki-67 expression (Cx43: p<0.0001, Cx45: p<0.03, Cx40: p<0.014. At the tumour-heart border there were significantly more Ki-67 positive cells (p=0.001, and only 2% Cx45 and Ki-67-expressing cells, while the other connexins were nearly completely absent (p<0.0001.Conclusions and hypothesis: These observations strongly suggest the hypothesis, that invasive tumour growth is accompanied by reduction in connexins. This implicates that gap junction communication between tumour and normal tissue is reduced or absent, which could mean that growth and differentiation signals can not be exchanged.
Bremsstrahlung Based Positron Annihilation Spectroscopy for Material Defect Analysis
International Nuclear Information System (INIS)
Selim, F.A.; Wells, D.P.; Harmon, F.; Kwofie, J.; Lancaster, G.; Jones, J.L.
2003-01-01
The Idaho Accelerator Center (IAC) has developed new techniques for Positron Annihilation Spectroscopy (PAS) using highly penetrating γ-rays to create positrons inside the material via pair production. γ-Ray induced positron annihilation spectroscopy can provide highly penetrating probes for material characterization and defect analysis. Bremsstrahlung beams from small, pulsed electron Linacs (6 MeV) have been used to bombard the materials to generate positrons, which annihilate with the material electrons emitting 511 keV radiation. We have also synchronized bremsstrahlung pulses with laser irradiation pulses to study dynamic structural changes in material. In addition, we have developed another method using (p,γ) reactions from a 2 MeV proton beam, which induce coincident γ-rays to perform positron life-time spectroscopy. We have showed the feasibility of extending PAS into thick samples and a wide variety of materials and industrial applications
The LPM effect in sequential bremsstrahlung: 4-gluon vertices
Energy Technology Data Exchange (ETDEWEB)
Arnold, Peter; Chang, Han-Chih [Department of Physics, University of Virginia,382 McCormick Road, Charlottesville, Virginia 22904-4714 (United States); Iqbal, Shahin [National Centre for Physics, Quaid-i-Azam University Campus, Islamabad, 45320 (Pakistan)
2016-10-24
The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. In this paper, we continue study of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-gluon approximations. In particular, this paper completes the calculation of the rate for real double gluon bremsstrahlung from an initial gluon with various simplifying assumptions (thick media; q̂ approximation; and large N{sub c}) by now including processes involving 4-gluon vertices.
Neutral bremsstrahlung radiation of Ne, Ar and O
International Nuclear Information System (INIS)
Kung, R.T.V.; Chang, C.H.
1976-01-01
The neutral Bremsstrahlung cross-sections of Ne, Ar and atomic oxygen around the 3 and 10μ wavelength regions were measured in a high temperature plasma generated in a shock tube. The results were generally a factor of three higher than the theoretical values calculated by Geltman (Geltman, S., JQSRT vol.13, 601 (1973)). Agreement with the experimental results of Taylor and Caledonia (Taylor, R.L. and Caledonia, G., JQSRT vol.9, 657; 681, 1969) around 3μ was good except for the case of Ne. The cross-sections around 10μ are the first measurements in this wavelength region. Enhanced radiation due to atomic line emission on top of the Bremsstrahlung continuum, as predicted by Hyman (Hyman, H.A. and Von Rosenberg, C.W. Jr., JQSRT, vol.15, 919, 1975) was observed around 7.44μ. (author)
Nuclear effects on bremsstrahlung neutrino rates of astrophysical interest
International Nuclear Information System (INIS)
Stoica, Sabin; Horvath, J.E.
2002-01-01
We calculate in this work the rates for the neutrino pair production by nucleon-nucleon bremsstrahlung taking into account the full contribution from a nuclear one-pion-exchange potential. It is shown that if the temperatures are low enough (T≤20 MeV), the integration over the nuclear part can be done for the general case, ranging from the completely degenerate (D) to the nondegenerate (ND) regime. We find that the inclusion of the full nuclear contribution enhances the neutrino pair production by nn and pp bremsstrahlung by a factor of about 2 in both the D and ND limits when compared with previous calculations. This result may be relevant for the physical conditions of interest in the semitransparent regions near the neutrinosphere in type II supernovae, cooling of neutron stars, and other astrophysical situations
Simulation of the Focal Spot of the Accelerator Bremsstrahlung Radiation
Sorokin, V.; Bespalov, V.
2016-06-01
Testing of thick-walled objects by bremsstrahlung radiation (BR) is primarily performed via high-energy quanta. The testing parameters are specified by the focal spot size of the high-energy bremsstrahlung radiation. In determining the focal spot size, the high- energy BR portion cannot be experimentally separated from the low-energy BR to use high- energy quanta only. The patterns of BR focal spot formation have been investigated via statistical modeling of the radiation transfer in the target material. The distributions of BR quanta emitted by the target for different energies and emission angles under normal distribution of the accelerated electrons bombarding the target have been obtained, and the ratio of the distribution parameters has been determined.
Bremsstrahlung radiation of a plasma expanding into vacuum
International Nuclear Information System (INIS)
Grigor'ev, V.G.; Silakov, V.P.; Fetisov, V.S.
1978-01-01
Bremsstrahlung of a flat layer of a dense hot homogeneous plasma expanding to vacuum is considered. The spread of plasma is assumed to be adiabatic, and the plasma density and temperature are considered as known functions of coordinates and time in the radiation transport equation. Formulae for radiation intensity have been obtained in cases when the plasma layer covered by the rarefaction wave are optically thin and optically thick. The dependences of radiation intensity on the parameter α characterizing the optical thickness of the plasma layer and the spectrum of radiation of the spreading layer are presented graphically. It is shown that spread has an essential effect on the heat transfer and the spectral composition of the bremsstrahlung of a dense high-temperature plasma
Density oscillations of nuclear matter probed via Bremsstrahlung photons
International Nuclear Information System (INIS)
Marques, F.M.; Ostendorf, R.W.
1996-01-01
From the extended experimental data on hard-photon production at intermediate energies the dominant source of hard-photons has been attributed to the Bremsstrahlung radiation emitted in first-chance proton-neutron (pn) collisions. Aside of the dominant source which produces direct hard-photons, at intermediate energies BUU calculations predict the existence of a second source of pn Bremsstrahlung photons occurring at a later stage of the heavy-ion collision when the system is almost fully thermalized, thermal hard-photons. The existence of this second photon source is searched for by analysing the energy spectra of inclusive and exclusive hard-photons and the photon-photon correlation function for three different systems. (K.A.)
Diffractive bremsstrahlung at high-β{sup *} LHC. Case study
Energy Technology Data Exchange (ETDEWEB)
Chwastowski, Janusz J.; Czekierda, Sabina; Staszewski, Rafal; Trzebinski, Maciej [The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krakow (Poland)
2017-04-15
Feasibility studies of the measurement of the exclusive diffractive bremsstrahlung cross-section in proton-proton scattering at the centre of mass energy of 13 TeV at the LHC are reported. Present studies were performed for the low luminosity LHC running with the betatron function value of 90 m using the ATLAS associated forward detectors ALFA and ZDC. A simplified approach to the event simulation and reconstruction is used. The background influence is also discussed. (orig.)
Possibility of some radionuclides production using high energy electron Bremsstrahlung
International Nuclear Information System (INIS)
Balzhinnyam, N.; Belov, A.G.; Gehrbish, Sh; Maslov, O.D.; Shvetsov, V.N.; Ganbold, G.
2008-01-01
The method of some radionuclides production using high energy Bremsstrahlung of electron accelerators and determination of photonuclear reaction yield and specific activities for some radionuclides is described. Photonuclear reaction yield and specific activities for some radionuclides are determined for 117m Sn, 111 In and 195m Pt. Based on the experimental data obtained at low energy (E e- e- = 75 MeV) of the IREN facility (FLNR, JINR) at irradiation of high purity platinum and tin metals
Excitation of spin-1 states in 166168170Er using bremsstrahlung
International Nuclear Information System (INIS)
Metzger, F.R.
1976-01-01
Some 40 states in 166 , 168 , 170 Er, most of them previously unknown, have been excited using bremsstrahlung with < or =4.2 MeV endpoint energy. For all but three of these levels, the angular distribution of the resonantly scattered radiation favors the assignment of spin 1. For some of the strongly excited levels, linear polarization measurements have been performed. They indicate that these levels have positive parity. The branching ratios further characterize them as K=1 excitations
Diffractive production off nuclei-shadow of hadronic bremsstrahlung
International Nuclear Information System (INIS)
Bialas, A.; Czyz, W.
1974-01-01
Diffractive production on nuclei is calculated using as an input a specific model for diffractive production on nucleons. In this model diffractive production is described as a shadow of non-diffractive multiple production of particles. The mechanism for non-diffractive production is taken to be hadronic bremsstrahlung of independently produced clusters. It is shown that such a model naturally explains the strikingly simple pattern of absorption observed in coherent production on nuclei. Possible generalizations of these results are indicated. (author)
Electron bremsstrahlung spectrum, 1--500 keV
International Nuclear Information System (INIS)
Lee, C.M.; Kissel, L.; Pratt, R.H.; Tseng, H.K.
1976-01-01
Numerical data are obtained for the electron bremsstrahlung energy spectrum resulting from incident electrons of kinetic energy 1--500 keV, under the assumption that the process is described as a single-electron transition in a relativistic self-consistent screened potential, using partial-wave expansions. Comparisons with simpler analytical approximations show that these are at best of qualitative validity in this energy range. Our data are used to construct more complete tables of the spectrum by interpolation
Assembler absolute forward thick-target bremsstrahlung spectra program
International Nuclear Information System (INIS)
Niculescu, V.I.R.; Baciu, G.; Ionescu-Bujor, M.
1981-12-01
The program is intended to compute the absolute forward thick-target bremsstrahlung spectrum for electrons in the energy range 1-24 MeV. The program takes into account the following phenomena: multiple scattering, energy loss and the attenuation of the emitted gamma rays. The computer program is written in Assembler having a higher degree of generality and is more performant than the FORTRAN version. (authors)
Bremsstrahlung of La and its dependence on electron energy
International Nuclear Information System (INIS)
Riehle, F.
1977-01-01
Measurements of La-bremsstrahlung isocromates with high resolution for quantum energies between 135 eV and 1867 eV are presented and discussed. In the whole energy range investigated, the isocromate structure, identified with the 4f band of La, is placed 5,45 +- 10,1 eV above the Fermi level. This is in contradiction with a calculation of Gloetzel, which predicts the 4f band maximum about 3eV above the Fermi level. This discrepancy is explained in the present work by the fact that the La electronic density of states depends on the occupation number of the states. The bremsstrahlung isocromate has to be considered as a direct copy of the La ion density of states, consisting of the La-atom and the additional primary electron. Resonance like intensity modulations of the x-ray radiation, resulting from transitions of the primary electron in f-like final states, are observed in an analysis of the La-bremsstrahlung isochromate energy dependence. For transitions of the primary electron in d-like final states, no resonances have been found. The energy dependence of the scattering probability in f-like final states can be explained by a model which assumes the final state as composed by a continuum state and a discrete state. (orig.) [de
Scintillating fiber array for tagging post-bremsstrahlung electrons
Cole, Philip; Alef, Stefan; Reitz, Björn-Eric; Schmieden, Hartmut; Hannappel, Jürgen; Jude, Thomas; Sandri, Paolo Levi; BGO-OD Collaboration
2016-03-01
We seek to extract the kinematic fingerprints of baryon resonances by making use of a high-quality beam of linearly polarized photons at the BGO-OD experiment at ELSA (Bonn, German). We constructed a unique device for precisely determining the degree of polarization in the coherent bremsstrahlung peak. Deflection of post-bremsstrahlung electrons in the magnetic field of the photon tagger provides precise information on the energy and polarization of the bremsstrahlung photons. And thereby will constrain the overall kinematics of the final-state particles in all decay channels of the photoproduced baryon resonances. We designed, prototyped, built, calibrated, and have been operating a three-layered, multi-stranded, scintillating-fiber detector for ensuring the quality of the linearly polarization of the photon beam. The overlapping 2.00-mm scintillating fibers form an array giving ARGUS over 500 channels. The very befitting name harkens to the mythological all-seeing creature Argus Panoptes, the multi-eyed giant. Our work was supported through a Fulbright Scholarship Award and by the Deutsche Forschungsgemeinschaft through the Collaborative Research Center (Sonderforschungsbereich SFB/TR-16) of the universities in Bonn, Giessen and Bochum, Germany. NSF-PHY-1307340.
Blein, Sophie; Bardel, Claire; Danjean, Vincent; McGuffog, Lesley; Healey, Sue; Barrowdale, Daniel; Lee, Andrew; Dennis, Joe; Kuchenbaecker, Karoline B; Soucy, Penny; Terry, Mary Beth; Chung, Wendy K; Goldgar, David E; Buys, Saundra S; Janavicius, Ramunas; Tihomirova, Laima; Tung, Nadine; Dorfling, Cecilia M; van Rensburg, Elizabeth J; Neuhausen, Susan L; Ding, Yuan Chun; Gerdes, Anne-Marie; Ejlertsen, Bent; Nielsen, Finn C; Hansen, Thomas Vo; Osorio, Ana; Benitez, Javier; Conejero, Raquel Andrés; Segota, Ena; Weitzel, Jeffrey N; Thelander, Margo; Peterlongo, Paolo; Radice, Paolo; Pensotti, Valeria; Dolcetti, Riccardo; Bonanni, Bernardo; Peissel, Bernard; Zaffaroni, Daniela; Scuvera, Giulietta; Manoukian, Siranoush; Varesco, Liliana; Capone, Gabriele L; Papi, Laura; Ottini, Laura; Yannoukakos, Drakoulis; Konstantopoulou, Irene; Garber, Judy; Hamann, Ute; Donaldson, Alan; Brady, Angela; Brewer, Carole; Foo, Claire; Evans, D Gareth; Frost, Debra; Eccles, Diana; Douglas, Fiona; Cook, Jackie; Adlard, Julian; Barwell, Julian; Walker, Lisa; Izatt, Louise; Side, Lucy E; Kennedy, M John; Tischkowitz, Marc; Rogers, Mark T; Porteous, Mary E; Morrison, Patrick J; Platte, Radka; Eeles, Ros; Davidson, Rosemarie; Hodgson, Shirley; Cole, Trevor; Godwin, Andrew K; Isaacs, Claudine; Claes, Kathleen; De Leeneer, Kim; Meindl, Alfons; Gehrig, Andrea; Wappenschmidt, Barbara; Sutter, Christian; Engel, Christoph; Niederacher, Dieter; Steinemann, Doris; Plendl, Hansjoerg; Kast, Karin; Rhiem, Kerstin; Ditsch, Nina; Arnold, Norbert; Varon-Mateeva, Raymonda; Schmutzler, Rita K; Preisler-Adams, Sabine; Markov, Nadja Bogdanova; Wang-Gohrke, Shan; de Pauw, Antoine; Lefol, Cédrick; Lasset, Christine; Leroux, Dominique; Rouleau, Etienne; Damiola, Francesca; Dreyfus, Hélène; Barjhoux, Laure; Golmard, Lisa; Uhrhammer, Nancy; Bonadona, Valérie; Sornin, Valérie; Bignon, Yves-Jean; Carter, Jonathan; Van Le, Linda; Piedmonte, Marion; DiSilvestro, Paul A; de la Hoya, Miguel; Caldes, Trinidad; Nevanlinna, Heli; Aittomäki, Kristiina; Jager, Agnes; van den Ouweland, Ans Mw; Kets, Carolien M; Aalfs, Cora M; van Leeuwen, Flora E; Hogervorst, Frans Bl; Meijers-Heijboer, Hanne Ej; Oosterwijk, Jan C; van Roozendaal, Kees Ep; Rookus, Matti A; Devilee, Peter; van der Luijt, Rob B; Olah, Edith; Diez, Orland; Teulé, Alex; Lazaro, Conxi; Blanco, Ignacio; Del Valle, Jesús; Jakubowska, Anna; Sukiennicki, Grzegorz; Gronwald, Jacek; Lubinski, Jan; Durda, Katarzyna; Jaworska-Bieniek, Katarzyna; Agnarsson, Bjarni A; Maugard, Christine; Amadori, Alberto; Montagna, Marco; Teixeira, Manuel R; Spurdle, Amanda B; Foulkes, William; Olswold, Curtis; Lindor, Noralane M; Pankratz, Vernon S; Szabo, Csilla I; Lincoln, Anne; Jacobs, Lauren; Corines, Marina; Robson, Mark; Vijai, Joseph; Berger, Andreas; Fink-Retter, Anneliese; Singer, Christian F; Rappaport, Christine; Kaulich, Daphne Geschwantler; Pfeiler, Georg; Tea, Muy-Kheng; Greene, Mark H; Mai, Phuong L; Rennert, Gad; Imyanitov, Evgeny N; Mulligan, Anna Marie; Glendon, Gord; Andrulis, Irene L; Tchatchou, Sandrine; Toland, Amanda Ewart; Pedersen, Inge Sokilde; Thomassen, Mads; Kruse, Torben A; Jensen, Uffe Birk; Caligo, Maria A; Friedman, Eitan; Zidan, Jamal; Laitman, Yael; Lindblom, Annika; Melin, Beatrice; Arver, Brita; Loman, Niklas; Rosenquist, Richard; Olopade, Olufunmilayo I; Nussbaum, Robert L; Ramus, Susan J; Nathanson, Katherine L; Domchek, Susan M; Rebbeck, Timothy R; Arun, Banu K; Mitchell, Gillian; Karlan, Beth Y; Lester, Jenny; Orsulic, Sandra; Stoppa-Lyonnet, Dominique; Thomas, Gilles; Simard, Jacques; Couch, Fergus J; Offit, Kenneth; Easton, Douglas F; Chenevix-Trench, Georgia; Antoniou, Antonis C; Mazoyer, Sylvie; Phelan, Catherine M; Sinilnikova, Olga M; Cox, David G
2015-04-25
Individuals carrying pathogenic mutations in the BRCA1 and BRCA2 genes have a high lifetime risk of breast cancer. BRCA1 and BRCA2 are involved in DNA double-strand break repair, DNA alterations that can be caused by exposure to reactive oxygen species, a main source of which are mitochondria. Mitochondrial genome variations affect electron transport chain efficiency and reactive oxygen species production. Individuals with different mitochondrial haplogroups differ in their metabolism and sensitivity to oxidative stress. Variability in mitochondrial genetic background can alter reactive oxygen species production, leading to cancer risk. In the present study, we tested the hypothesis that mitochondrial haplogroups modify breast cancer risk in BRCA1/2 mutation carriers. We genotyped 22,214 (11,421 affected, 10,793 unaffected) mutation carriers belonging to the Consortium of Investigators of Modifiers of BRCA1/2 for 129 mitochondrial polymorphisms using the iCOGS array. Haplogroup inference and association detection were performed using a phylogenetic approach. ALTree was applied to explore the reference mitochondrial evolutionary tree and detect subclades enriched in affected or unaffected individuals. We discovered that subclade T1a1 was depleted in affected BRCA2 mutation carriers compared with the rest of clade T (hazard ratio (HR) = 0.55; 95% confidence interval (CI), 0.34 to 0.88; P = 0.01). Compared with the most frequent haplogroup in the general population (that is, H and T clades), the T1a1 haplogroup has a HR of 0.62 (95% CI, 0.40 to 0.95; P = 0.03). We also identified three potential susceptibility loci, including G13708A/rs28359178, which has demonstrated an inverse association with familial breast cancer risk. This study illustrates how original approaches such as the phylogeny-based method we used can empower classical molecular epidemiological studies aimed at identifying association or risk modification effects.
Electron spectroscopy in the fundamental process of electron-nucleus bremsstrahlung
International Nuclear Information System (INIS)
Hillenbrand, Pierre-Michel
2013-07-01
Within the scope of this thesis the fundamental process of electron-nucleus bremsstrahlung was studied in inverse kinematics at the Experimental Storage Ring ESR at GSI. For the system U 88+ + N 2 at 90 MeV/u it was shown, that by using inverse kinematics coincidence measurements between the scattered electron and the emitted photon can be performed for the case, in which the incoming electron transfers almost all of its kinetic energy onto the emitted photon. The sensitivity to the fundamental process could be achieved by measuring triple differential cross sections as a function of the emission angle of the photon and the scattered electron as well as the energy of the scattered electron. The optics of the magnetic electron spectrometer used were thoroughly revised and optimized to the experimental requirements. Analyzing different coincidences in this collision system, it was possible to determine the contributions to the electron distribution arising from radiative electron capture to the projectile continuum, nonradiative electron capture to the projectile continuum, and electron loss to the projectile continuum. The experimental results of each of these processes were compared to theoretical calculations. The electron spectra for the radiative and the nonradiative electron capture to continuum clearly reproduce the opposite asymmetry predicted by theory. Furthermore electron spectra for collisions of U 28+ with different gases were measured.
Inner Bremsstrahlung accompanying the non-unique first forbidden β-decay of 141Ce
International Nuclear Information System (INIS)
Khalil, E.I.
1993-01-01
The inner Bremsstrahlung (I.B.) spectrum accompanying the β-decay of 141 Ce (non-unique first forbidden β-transition) was measured using a single channel scintillation spectrometer. The measured I.B. was analyzed by the variable width peeling-off method. This analyzed and corrected I.B. was compared with those calculated according to the original theories of Knipp and Uhlenbeck as well as of Bloch (KUB), the coulomb corrected theories of Lewis and Ford and of Nilsson, and according to detour-transition calculations of the Ford and Martin theory. Ths shape correction factor suggested by Konopinski and Uhlenbeck on the Fermi β-decay theory was applied to the calculated I.B. based on Nilsson's theory (modified KUB theory). The experimental results are in better agreement with the modified KUB theory than the other theories. (orig.)
Calculation of the inverse data space via sparse inversion
Saragiotis, Christos
2011-01-01
The inverse data space provides a natural separation of primaries and surface-related multiples, as the surface multiples map onto the area around the origin while the primaries map elsewhere. However, the calculation of the inverse data is far from trivial as theory requires infinite time and offset recording. Furthermore regularization issues arise during inversion. We perform the inversion by minimizing the least-squares norm of the misfit function by constraining the $ell_1$ norm of the solution, being the inverse data space. In this way a sparse inversion approach is obtained. We show results on field data with an application to surface multiple removal.
Planar gamma camera imaging and quantitation of Yttrium-90 bremsstrahlung
International Nuclear Information System (INIS)
Shen, S.; DeNardo, G.L.; Yuan, A.
1994-01-01
Yttrium-90 is a promising radionuclide for radioimmunotherapy of cancer because of its energetic beta emissions. Therapeutic management requires quantitative imaging to assess the pharmacokinetics and radiation dosimetry of the 90 Y-labeled antibody. Conventional gamma photon imaging methods cannot be easily applied to imaging of 90 Y-bremsstrahlung because of its continuous energy spectrum. The sensitivity, resolution and source-to-background signal ratio (S/B) of the detector system for 90 Y-bremsstrahlung were investigated for various collimators and energy windows in order to determine optimum conditions for quantitative imaging. After these conditions were determined, the accuracy of quantitation of 90 Y activity in an Alderson abdominal phantom was examined. When the energy-window width was increased, the benefit of increased sensitivity outweighed degradation in resolution and S/B ratio until the manufacturer's energy specifications for the collimator were exceeded. Using the same energy window, the authors improved resolution and S/B for the medium-energy (ME) collimator when compared to the low-energy, all-purpose (LEAP) collimator, and there was little additional improvement using the high-energy (HE) collimator. Camera sensitivity under tissue equivalent conditions was 4.2 times greater for the LEAP and 1.7 times greater for the ME collimators when compared to the HE collimator. Thus, the best, most practical selections were found to be the ME collimator and an energy window of 55-285 keV. When they used these optimal conditions for image acquisition, the estimation of 90 Y activity in organs and tumors was within 15% of the true activities. The results for this study suggest that reasonable accuracy can be achieved in clinical radioimmunotherapy using 90 Y-bremsstrahlung quantitation. 28 refs., 5 figs., 7 tabs
Internal bremsstrahlung signatures in light of direct dark matter searches
Energy Technology Data Exchange (ETDEWEB)
Garny, Mathias [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Ibarra, Alejandro; Pato, Miguel; Vogl, Stefan [Technische Univ. Muenchen, Garching (Germany). Physik Dept. T30d
2013-06-15
Although proposed long ago, the search for internal bremsstrahlung signatures has only recently been made possible by the excellent energy resolution of ground-based and satellite-borne gamma-ray instruments. Here, we investigate thoroughly the current status of internal bremsstrahlung searches in light of the results of direct dark matter searches and in the framework of minimal mass-degenerate scenarios. The constraints set by Fermi-LAT and H.E.S.S. extend uninterrupted from tens of GeV up to tens of TeV and are rather insensitive to the mass degeneracy in the particle physics model. In contrast, direct searches are best in the moderate to low mass splitting regime, where XENON100 limits overshadow Fermi-LAT and H.E.S.S. up to TeV masses if dark matter couples to (light) quarks. We examine carefully the prospects for GAMMA-400, CTA and XENON1T, all planned to come online in the near future, and find that: (a) CTA and XENON1T are fully complementary, with CTA most sensitive to multi-TeV masses and mass splittings around 10%, and XENON1T probing best small mass splittings up to TeV masses; and (b) current constraints from XENON100 already preclude the observation of any spectral feature with GAMMA-400 in spite of its impressive energy resolution, unless dark matter does not couple to light quarks. Finally, we point out that, unlike for direct searches, the possibility of detecting thermal relics in upcoming internal bremsstrahlung searches requires boost factors larger than {proportional_to}10.
Internal bremsstrahlung signatures in light of direct dark matter searches
International Nuclear Information System (INIS)
Garny, Mathias; Ibarra, Alejandro; Pato, Miguel; Vogl, Stefan
2013-07-01
Although proposed long ago, the search for internal bremsstrahlung signatures has only recently been made possible by the excellent energy resolution of ground-based and satellite-borne gamma-ray instruments. Here, we investigate thoroughly the current status of internal bremsstrahlung searches in light of the results of direct dark matter searches and in the framework of minimal mass-degenerate scenarios. The constraints set by Fermi-LAT and H.E.S.S. extend uninterrupted from tens of GeV up to tens of TeV and are rather insensitive to the mass degeneracy in the particle physics model. In contrast, direct searches are best in the moderate to low mass splitting regime, where XENON100 limits overshadow Fermi-LAT and H.E.S.S. up to TeV masses if dark matter couples to (light) quarks. We examine carefully the prospects for GAMMA-400, CTA and XENON1T, all planned to come online in the near future, and find that: (a) CTA and XENON1T are fully complementary, with CTA most sensitive to multi-TeV masses and mass splittings around 10%, and XENON1T probing best small mass splittings up to TeV masses; and (b) current constraints from XENON100 already preclude the observation of any spectral feature with GAMMA-400 in spite of its impressive energy resolution, unless dark matter does not couple to light quarks. Finally, we point out that, unlike for direct searches, the possibility of detecting thermal relics in upcoming internal bremsstrahlung searches requires boost factors larger than ∝10.
Polarization of Bremsstrahlung; Polarisation du rayonnement de freinage
Energy Technology Data Exchange (ETDEWEB)
Miller, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1957-07-01
The numerical results for the polarization of Bremsstrahlung are presented. The multiple scattering of electrons in the target is taken into account. The angular-and photon energy dependences are seen on the curves for an incident 25 MeV electron energy. (Author) [French] Le taux de polarisation d'un spectre de rayonnement de freinage est calcule pour une cible d'epaisseur finie en tenant compte de la diffusion multiple des electrons dans la cible. Les courbes sont tracees pour les electrons incidents d'energie 25 MeV, pour differentes energies de photons, et a differents angles. (auteur)
Secondary-electron-bremsstrahlung imaging for proton therapy
Energy Technology Data Exchange (ETDEWEB)
Yamaguchi, Mitsutaka; Nagao, Yuto [Takasaki Advanced Radiation Research Institute, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-Machi, Takasaki, Gunma (Japan); Ando, Koki; Yamamoto, Seiichi [Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, 1-1-20 Daiko-Minami, Higashi-Ku, Nagoya, Aichi (Japan); Toshito, Toshiyuki [Department of Proton Therapy Physics, Nagoya Proton Therapy Center, Nagoya City West Medical Center, 1-1-1 Hirate-cho, Kita-Ku, Nagoya, Aichi (Japan); Kataoka, Jun [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo (Japan); Kawachi, Naoki [Takasaki Advanced Radiation Research Institute, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-Machi, Takasaki, Gunma (Japan)
2016-10-11
A feasibility study on an imaging technique of a therapeutic proton-beam trajectory using a gamma camera by measuring secondary electron bremsstrahlung (SEB) was performed by means of Monte Carlo simulations and a beam-irradiation experiment. From the simulation and experimental results, it was found that a significant amount of SEB yield exists between the beam-injection surface and the range position along the beam axis and the beam trajectory is clearly imaged by the SEB yield. It is concluded that the SEB imaging is a promising technique for monitoring of therapeutic proton-beam trajectories.
Electron-electron Bremsstrahlung for bound target electrons
International Nuclear Information System (INIS)
Haug, E.
2008-01-01
For the process of electron-electron (e-e) Bremsstrahlung the momentum and energy distributions of the recoiling electrons are calculated in the laboratory frame. In order to get the differential cross section and the photon spectrum for target electrons which are bound to an atom, these formulae are multiplied by the incoherent scattering function and numerically integrated over the recoil energy. The effect of atomic binding is most pronounced at low energies of the incident electrons and for target atoms of high atomic numbers. The results are compared to those of previous calculations. (authors)
Decay energy of 55Fe from its inner Bremsstrahlung spectrum
Keshava, S. L.; Gopala, K.; Venkataramaiah, P.
2001-06-01
Several measurements of decay energy using the inner Bremsstrahlung spectrum (IB) due to radiative electron capture in 55Fe has been made. But the results are not uniform. Hence another attempt has been made at the same. Experimental data was obtained with a 4.445 cm. dia ' 5.08 cm thick NaI (Tl) detector. It was subjected to suitable statistical treatment and various corrections using Liden and Starfelt procedure. The corrected spectrum agrees well with the Glauber and Martin theory for 1s electron capture beyond 100 keV. From the Jauch plot, the decay energy of 232.36 +/-0.64 keV was obtained.
Study of 1s internal bremsstrahlung spectrum from 57Co
Raghavendra, M. K.; Azeez, Syed; Ramaswamy, C. R.; Umesh, T. K.; Gowda, Ramakrishna
2002-07-01
The internal bremsstrahlung contribution from the electron capture of 57Co has been measured in coincidence with K-X-ray of the residual atom. The end-point energy (EPE) is extracted from the data using the linearised Jauch plot. The transition energy obtained using the (EPE) is 842.7 keV, which is close to the value given by Audi and Wapstra. The measured intensity and shape factor from 300 to 600 keV are found to be in good agreement with the Glauber and Martin theory.
Study of 1s internal bremsstrahlung spectrum from 57Co
International Nuclear Information System (INIS)
Raghavendra, M.K.; Azeez, Syed; Ramaswamy, C.R.; Umesh, T.K.; Gowda, Ramakrishna
2002-01-01
The internal bremsstrahlung contribution from the electron capture of 57 Co has been measured in coincidence with K-X-ray of the residual atom. The end-point energy (EPE) is extracted from the data using the linearised Jauch plot. The transition energy obtained using the (EPE) is 842.7 keV, which is close to the value given by Audi and Wapstra. The measured intensity and shape factor from 300 to 600 keV are found to be in good agreement with the Glauber and Martin theory
Suppression of soft nuclear bremsstrahlung in proton-nucleus collisions
International Nuclear Information System (INIS)
Goethem, M.J. van; Bacelar, J.C.S.; Hoefman, M.; Huisman, H.; Kalantar-Nayestanaki, N.; Loehner, H.; Messchendorp, J.G.; Ostendorf, R.W.; Schadmand, S.; Siemssen, R.H.; Turrisi, R.; Volkerts, M.; Wilschut, H.W.; Aphecetche, L.; Delagrange, H.; D'Enterria, D.; Martinez, G.; Schutz, Y.; Diaz, J.; Holzmann, R.
2002-01-01
Photon energy spectra up to the kinematic limit have been measured in 190 MeV proton reactions with light and heavy nuclei to investigate the influence of the multiple-scattering process on the photon production. Relative to the predictions of models based on a quasifree production mechanism, a strong suppression of bremsstrahlung is observed in the low-energy region of the photon spectrum. We attribute this effect to the interference of photon amplitudes due to multiple scattering of nucleons in the nuclear medium
Study of Diffractive Bremsstrahlung at 13 TeV LHC
Czekierda, Sabina
2016-01-01
Feasibility studies of the diffractive bremsstrahlung measurement at the LHC at $\\sqrt s$ = 13 TeV are presented. The method considered for this measurement uses the ATLAS detector and, in particular, the Zero Degree Calorimeter and the ATLAS Forward Proton detectors. The signal and background processes were generated with GenEx and PYTHIA 8.2 generators, respectively. The obtained fiducial cross sections are 1.2 ub for the signal and 6 ub for the background. Further reduction of the background is possible by the optimisation of event selection cuts.
Application of electron and Bremsstrahlung beams for composite materials processing
International Nuclear Information System (INIS)
Zalyubovsky, I.I.; Avilov, A.M.; Popov, G.F.; Rudychev, V.G.
1998-01-01
In Kharkiv University the radiation process of obtaining composite polymer materials, CPM, with high strength properties and corrosion resistance was studied. CPM are manufactured by vacuum impregnating capillary-porous materials with synthetic monomers and oligomers or by molding granular waste and resins which are further treated by relativistic electron or Bremsstrahlung beam. Such radiation treatment yields new CPM in which capillary-porous structure acting as reinforcement is filled with polymer. The results of the applied research with industrial electron accelerator in the field of thick CPM formation are presented
Inner bremsstrahlung accompanying β-decay of 170Tm
International Nuclear Information System (INIS)
Gundu Rao, K.S.; Venkataramaiah, P.; Gopala, K.; Sanjeeviah, H.
1981-01-01
Inner bremsstrahlung accompanying non-unique first-forbidden β-decay of 170 Tm has been measured employing a magnetic deflection technique with a (4.5 x 5.1 cm) NaI(Tl) scintillation spectrometer in the energy region 200 keV to 900 keV. The raw spectrum is unfolded using the Liden and Starfelt procedure, and compared with the theories of KUB, Lewis and Ford, and Ford and Martin. The results are close to the Lewis and Ford theory over the major portion of the measured spectrum. (orig.)
Acute puerperal uterine inversion
International Nuclear Information System (INIS)
Hussain, M.; Liaquat, N.; Noorani, K.; Bhutta, S.Z; Jabeen, T.
2004-01-01
Objective: To determine the frequency, causes, clinical presentations, management and maternal mortality associated with acute puerperal inversion of the uterus. Materials and Methods: All the patients who developed acute puerperal inversion of the uterus either in or outside the JPMC were included in the study. Patients of chronic uterine inversion were not included in the present study. Abdominal and vaginal examination was done to confirm and classify inversion into first, second or third degrees. Results: 57036 deliveries and 36 acute uterine inversions occurred during the study period, so the frequency of uterine inversion was 1 in 1584 deliveries. Mismanagement of third stage of labour was responsible for uterine inversion in 75% of patients. Majority of the patients presented with shock, either hypovolemic (69%) or neurogenic (13%) in origin. Manual replacement of the uterus under general anaesthesia with 2% halothane was successfully done in 35 patients (97.5%). Abdominal hysterectomy was done in only one patient. There were three maternal deaths due to inversion. Conclusion: Proper education and training regarding placental delivery, diagnosis and management of uterine inversion must be imparted to the maternity care providers especially to traditional birth attendants and family physicians to prevent this potentially life-threatening condition. (author)
International Nuclear Information System (INIS)
Matsubara, T.C.M.; Bacchi, M.A.; De Nadai Fernandes, E.A.
2012-01-01
Phosphorus is an essential element for plants and animals, playing a fundamental role in the production of biochemical energy. Despite its relevance, phosphorus is not commonly determined by instrumental neutron activation analysis (INAA), because 32 P does not emit gamma-rays in its decay. There are alternative methods for the determination of phosphorus by INAA, such as the use of beta counting or the measurement of bremsstrahlung originated from the high energy beta particle from 32 P. Here the determination of phosphorus in plant materials by measuring the bremsstrahlung production was further investigated, to optimize an analytical protocol for minimizing interferences and overcoming the poor specificity. Eight certified reference materials of plant matrices with phosphorus ranging between 171 and 5,180 mg kg -1 were irradiated at a thermal neutron flux of 9.5 x 10 12 cm -2 s -1 and measured with a HPGe detector at decay times varying from 7 to 60 days. Phosphorus solutions added to a certified reference material at three levels were used for calibration. Counts accumulated in the baseline at four different regions of the gamma-ray spectra were tested for the determination of phosphorus, with better results for the 100 keV region. The Compton scattering contribution in the selected range was discounted using an experimental peak-to-Compton factor and the net areas of all peaks in the spectra with energies higher than 218 keV, i.e. Compton edge above 100 keV. Amongst the interferences investigated, the production of 32 P from sulfur, and the contribution of Compton scattering should be considered for producing good results. (author)
Bremsstrahlung spectra for Al, Cs, and Au atoms in high-temperature, high-density plasmas
International Nuclear Information System (INIS)
Kim, L.; Pratt, R.H.; Tseng, H.K.
1985-01-01
Results are presented from a numerical calculation for the bremsstrahlung spectrum and Gaunt factors of Al, Cs, and Au atoms in high-temperature (-T), high-density (-rho) plasmas. Plasma temperatures kT = 0.1 and 1.0 keV and plasma densities rho = rho 0 (the normal solid density) and rho = 100rho 0 are considered. This allows us to determine the generality and identify the origins of features which we had previously identified in calculations for Cs. We also now present results for the total energy loss of an electron in such a plasma. We use a relativistic multipole code which treats the bremsstrahlung process as a single-electron transition in a static screened central potential. We take for the static potential corresponding to an atom in a hot dense plasma the finite-temperature, finite-density Thomas-Fermi model. This approach corresponds to an average atom in local thermodynamic equilibrium. In comparison to isolated-neutral-atom results we observe general suppression of cross sections and a particular suppression in the tip region of the spectrum. Within this model, both superscreening and shape resonances are found in the circumstances of extreme density. At more normal densities and except for the soft-photon end, the spectrum at these energies for an atom in a hot plasma (characterized by an average degree of ionization) can be well represented by the spectrum of the corresponding isolated ion, which has a similar potential shape at the distances which characterize the process
The Schiff angular bremsstrahlung distribution from composite media
International Nuclear Information System (INIS)
Taylor, M.L.; Dalton, B.; Franich, R.D.
2012-01-01
The Schiff differential for the angular distribution of bremsstrahlung is widely employed, but calculations involving composite materials (i.e. compounds and mixtures) are often undertaken in a somewhat ad hoc fashion. In this work, we suggest an alternative approach to power-law estimates of the effective atomic number utilising Seltzer and Berger’s combined approach in order to generate single-valued effective atomic numbers applicable over a large energy range (in the worst case deviation from constancy of about 2% between 10 keV and 1 GeV). Differences with power-law estimates of Z for composites are potentially significant, particularly for low-Z media such as biological or surrogate materials as relevant within the context of medical physics. As an example, soft tissue differs by >70% and cortical bone differs by >85%, while for high-Z composites such as a tungsten–rhenium alloy the difference is of the order of 1%. Use of the normalised Schiff formula for shape only does not exhibit strong Z dependence. Consequently, in such contexts the differences are negligible – the power-law approach overestimates the magnitude by 1.05% in the case of water and underestimates it by <0.1% for the high-Z alloys. The differences in the distribution are most pronounced for small angles and where the bremsstrahlung quanta are low energy.
Bremsstrahlung of fast electrons in long air gaps
Energy Technology Data Exchange (ETDEWEB)
Oreshkin, E. V.; Barengolts, S. A. [P. N. Lebedev Physical Institute, RAS, 119991 Moscow (Russian Federation); General Physics Institute, RAS, 119991 Moscow (Russian Federation); Chaikovsky, S. A. [P. N. Lebedev Physical Institute, RAS, 119991 Moscow (Russian Federation); Institute of High Current Electronics, SB RAS, 634055 Tomsk (Russian Federation); Oginov, A. V.; Shpakov, K. V.; Bogachenkov, V. A. [P. N. Lebedev Physical Institute, RAS, 119991 Moscow (Russian Federation)
2012-01-15
The results of an experiment on discharges in long atmospheric pressure air gaps at a pulsed voltage of amplitude up to 800 kV and risetime 150-200 ns have been analyzed. In the experiment, a radiation pulse of photon energy >5 keV and duration 10-20 ns was observed. In analyzing the experimental data it was supposed that a streamer is a plasma protrusion whose surface is equipotential to the cathode surface. It has been shown that the x-ray pulse results from the switch of electrons into the mode of ''runaway'' from the head of anode-directed streamers. For the electrons injected in the electrode gap from the streamer head, conditions for their switching into the mode of continuous acceleration are realized due to the enhanced electric field at the head. The predicted maximum of the spectrum of the bremsstrahlung generated by the runaway electron beam is around 15 keV. The presence of a maximum in the bremsstrahlung spectrum is due to that the photons emitted by electrons are absorbed by atoms of the gas in which the discharge operate.
Revisiting Bremsstrahlung emission associated with Light Dark Matter annihilations
Böhm, C
2006-01-01
We compute the single bremsstrahlung emission associated with the pair annihilation of spin-0 particles into electrons and positrons, via the t-channel exchange of a heavy fermion. We compare our result with the work of Beacom et al. . Unlike what is stated in the literature, we show that the Bremsstrahlung cross section is not necessarily given by the tree-level annihilation cross section (for a generalized kinematics) times a factor related to the emission of a soft photon. Such a factorization appears only in the soft photon limit or in the approximation where the masses of the particles in the initial and final states are negligible with respect to the mass of the internal particle. However, in the latter case, we do not recover the same factor as for e^+ e- --> mu^+ mu^- gamma. Numerically the difference, in the hard photon limit, is as large as a factor 3.6. However the effect on the upper limit of the dark matter mass is not significant. Using gamma ray observations, we obtain an upper limit on the dar...
Internal bremsstrahlung spectra from 185W and 32P
International Nuclear Information System (INIS)
Babu, R.P.; Murty, K.N.; Murty, V.A.N.
1976-01-01
The internal bremsstrahlung spectra from the β decay of 185 W and 32 P were measured using a NaI(Tl) scintillation spectrometer with a standard geometrical arrangement. After making all the necessary corrections the experimental results are compared with the allowed theory of the Knipp, Uhlenbeck, and Bloch (KUB theory) and also with the Coulomb corrected theories of Lewis, Ford, and Nilsson. In the case of 185 W it is found that from 78 to 200 keV the experimental distribution is in good agreement with the KUB theory whereas beyond 200 keV and below 78 keV the experimental points are far above even the highest Coulomb corrected theoretical distribution of Nilsson. The internal bremsstrahlung from this isotope has not been previously investigated. In the case of 32 P the experimental relative intensity spectrum is compared with the KUB theory and also with the Coulomb corrected theory of Lewis and Ford. Fairly good agreement is obtained from 30 to 200 keV with the KUB theory but in the energy region from 200 to 900 keV, the experimental results deviate positively from both the KUB and Lewis and Ford theories. The experimental excess over the Lewis and Ford theory is 15% on the average
International Nuclear Information System (INIS)
Roshan, Hoda Rezaei; Mahmoudian, Babak; Gharepapagh, Esmaeil; Azarm, Ahmadreza; Pirayesh Islamian, Jalil
2016-01-01
Treatment efficacy of radioembolization using Yttrium-90 ( 90 Y) microspheres is assessed by the 90 Y bremsstrahlung single photon emission computed tomography (SPECT) imaging following radioembolization. The radioisotopic image has the potential of providing reliable activity map of 90 Y microspheres distribution. One of the main reasons of the poor image quality in 90 Y bremsstrahlung SPECT imaging is the continuous and broad energy spectrum of the related bremsstrahlung photons. Furthermore, collimator geometry plays an impressive role in the spatial resolution, sensitivity and image contrast. Due to the relatively poor quality of the 90 Y bremsstrahlung SPECT images, we intend to optimize the medium-energy (ME) parallel-hole collimator and energy window. The Siemens e.cam gamma camera equipped with a ME collimator and a voxelized phantom was simulated by the SImulating Medical Imaging Nuclear Detectors (SIMIND) program. We used the SIMIND Monte Carlo program to generate the 90 Y bremsstrahlung SPECT projection of the digital Jaszczak phantom. The phantom consist of the six hot spheres ranging from 9.5 to 31.8 mm in diameter, which are used to evaluate the image contrast. In order to assess the effect of the energy window on the image contrast, three energy windows ranging from 60 to 160 KeV, 160 to 400 KeV, and 60 to 400 KeV were set on a 90 Y bremsstrahlung spectrum. As well, the effect of the hole diameter of a ME collimator on the image contrast and bremsstrahlung spectrum were investigated. For the fixed collimator and septa thickness values (3.28 cm and 1.14 mm, respectively), a hole diameter range (2.35–3.3 mm) was chosen based on the appropriate balance between the spatial resolution and sensitivity. The optimal energy window for 90 Y bremsstrahlung SPECT imaging was extended energy window from 60 to 400 KeV. Besides, The optimal value of the hole diameter of ME collimator was obtained 3.3 mm. Geometry of the ME parallel-hole collimator and energy
Electron-electron collision effects on the bremsstrahlung emission in Lorentzian plasmas
International Nuclear Information System (INIS)
Jung, Young-Dae; Kato, Daiji
2009-01-01
Electron-electron collision effects on the electron-ion bremsstrahlung process are investigated in Lorentzian plasmas. The effective electron-ion interaction potential is obtained by including the far-field terms caused by electron-electron collisions with an effective Debye length in Lorentzian plasmas. The bremsstrahlung radiation cross section is obtained as a function of the electron energy, photon energy, collision frequency, spectral index and Debye length using the Born approximation for the initial and final states of the projectile electron. It is shown that the non-Maxwellian character suppresses the bremsstrahlung radiation cross section. It is also shown that the electron-electron collision effect enhances the bremsstrahlung emission spectrum. In addition, the bremsstrahlung radiation cross section decreases with an increase in the plasma temperature.
International Nuclear Information System (INIS)
Namatame, Hirofumi; Taniguchi, Masaki
1994-01-01
Photoelectron spectroscopy is regarded as the most powerful means since it can measure almost perfectly the occupied electron state. On the other hand, inverse photoelectron spectroscopy is the technique for measuring unoccupied electron state by using the inverse process of photoelectron spectroscopy, and in principle, the similar experiment to photoelectron spectroscopy becomes feasible. The development of the experimental technology for inverse photoelectron spectroscopy has been carried out energetically by many research groups so far. At present, the heightening of resolution of inverse photoelectron spectroscopy, the development of inverse photoelectron spectroscope in which light energy is variable and so on are carried out. But the inverse photoelectron spectroscope for vacuum ultraviolet region is not on the market. In this report, the principle of inverse photoelectron spectroscopy and the present state of the spectroscope are described, and the direction of the development hereafter is groped. As the experimental equipment, electron guns, light detectors and so on are explained. As the examples of the experiment, the inverse photoelectron spectroscopy of semimagnetic semiconductors and resonance inverse photoelectron spectroscopy are reported. (K.I.)
Study of nuclear bremsstrahlung in the model independent approach
International Nuclear Information System (INIS)
Liu, C.K.
1980-01-01
The bremsstrahlung cross section for the scattering of protons by 12 C near the 1.7-MeV resonance has been measured by the Bologna group and the Brooklyn group. In this study, we have included in our calculations the correction terms in the Feshbach-Yennie approximation and have extracted the time delay in the P- 12 C reaction from the data of the Brooklyn group. The + p process near the (1236) has been systematically studied by an experimental group at UCLA. Recently, Liou and Nutt reported a calculation using the soft-photon approximation and their results agree very well with experiment for coplanar events. We have extended their calculation to noncoplanar cases and have found that the soft-photon approximation of Liou and Nutt can describe the experimental data very well not only for coplanar cases but also for noncoplanar cases for most photon angles. In addition, we have also used the Feshbach-Yennie approximation to calculate the + p cross sections. This approximation always predicts a bump in the bremsstrahlung spectrum, although the bump may be small for some photon angles. In most cases, the predicted cross sections are in good agreement with the UCLA data. However, the data for some angles can only be described by the Feshbach-Yennie approximation, and the peak cross section is too large at some angles. We have applied the soft-photon approximation of Liou and Nutt to calculate the proton-proton bremsstrahlung (pp) cross section and have compared our results with the experimental data at 730, 157, 48 and 42 MeV. We have found that we can use the soft-photon approximation to calculate the R-type cross section without any difficulty, but we cannot use the same approximation to predict the H-type cross section without some ambiguity. We have also applied the Feshbach-Yennie approximation to the pp process at 730-MeV taking into account the principal and correction terms
Evaluation of quantitative planar 90Y bremsstrahlung whole-body imaging
International Nuclear Information System (INIS)
Minarik, D; Ljungberg, M; Gleisner, K Sjoegreen; Segars, P
2009-01-01
With high-dose administration of 90 Y labeled antibodies, it is possible to image 90 Y without an admixture of 111 In. We have earlier shown that it is possible to perform quantitative 90 Y bremsstrahlung SPECT for dosimetry purposes with reasonable accuracy. However, whole-body (WB) activity quantification with the conjugate view method is not as time consuming as SPECT and has been the method of choice for dosimetry. We have investigated the possibility of using a conjugate view method where scatter-, backscatter- and septal-penetration compensations are performed by inverse filtering and attenuation correction is performed with a WB x-ray image, for total-body and organ activity quantification of 90 Y. The method was evaluated using both Monte Carlo simulated scintillation camera images using realistic source distributions, and by an experimental phantom study. The method was evaluated in terms of image quality and accuracy of the activity quantification. The experimental phantom study was performed using the RSD torso phantom with 90 Y activity uniformly distributed in the liver insert. A GE Discovery VH/Hawkeye system was used to acquire the image. The simulation study was performed for a realistic activity distribution in the NCAT anthropomorphic phantom where 90 Y bremsstrahlung images were generated using the SIMIND MC program. Two different phantom configurations and two activity distributions were simulated. To mimic the RSD phantom experiment one simulation study was also made with 90 Y activity located only in the liver. The SIMIND program was configured to resemble a GE Discovery VH/Hawkeye system. An x-ray projector program was used to generate whole-body x-ray images from the NCAT phantom for attenuation correction in the conjugate view method. Organ activities were calculated from ROIs that exactly covered the organs. Corrections for background activity, overlapping activity and source extension in the depth direction were applied on the ROI data
Bremsstrahlung and pair production in crystals at very high energies
International Nuclear Information System (INIS)
Nikishov, A.I.
1981-01-01
The probabilities for bremsstrahlung and pair production in crystals are discussed under stringent condition when the trajectory of the high-energy electron crosses very many atoms of a crystal row (or plane). It is shown that for sufficiently long path in such conditions the probabilities are described by the formulas for these processes in a strong constant magnetic field exerting on electron the same deflection as the atom row. It turns out that for lead at energy approximately 10 12 eV the radiation length is shortened many hundred times. For greater energies the decrease of probabilities per unit length with increase of energy goes as W varies as Esup(-1/3)
The LPM effect in sequential bremsstrahlung: dimensional regularization
Energy Technology Data Exchange (ETDEWEB)
Arnold, Peter; Chang, Han-Chih [Department of Physics, University of Virginia,382 McCormick Road, Charlottesville, VA 22894-4714 (United States); Iqbal, Shahin [National Centre for Physics,Quaid-i-Azam University Campus, Islamabad, 45320 (Pakistan)
2016-10-19
The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. Of recent interest is the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD). In previous papers, we have developed methods for computing such corrections without making soft-gluon approximations. However, our methods require consistent treatment of canceling ultraviolet (UV) divergences associated with coincident emission times, even for processes with tree-level amplitudes. In this paper, we show how to use dimensional regularization to properly handle the UV contributions. We also present a simple diagnostic test that any consistent UV regularization method for this problem needs to pass.
The double copy: Bremsstrahlung and accelerating black holes
Luna, Andres; Nicholson, Isobel; O'Connell, Donal; White, Chris D
2016-01-01
Advances in our understanding of perturbation theory suggest the existence of a correspondence between classical general relativity and Yang-Mills theory. A concrete example of this correspondence, which is known as the double copy, was recently introduced for the case of stationary Kerr-Schild spacetimes. Building on this foundation, we examine the simple time-dependent case of an accelerating, radiating point source. The gravitational solution, which generalises the Schwarzschild solution, includes a non-trivial stress-energy tensor. This stress-energy tensor corresponds to a gauge theoretic current in the double copy. We interpret both of these sources as representing the radiative part of the field. Furthermore, in the simple example of Bremsstrahlung, we determine a scattering amplitude describing the radiation, maintaining the double copy throughout. Our results provide the strongest evidence yet that the classical double copy is directly related to the BCJ double copy for scattering amplitudes.
Channeling and coherent bremsstrahlung effects for relativistic positrons and electrons
International Nuclear Information System (INIS)
Walker, R.L.
1976-01-01
Channeling of positrons in single crystals of silicon was observed in transmission and scattering measurements for incident energies from 16 to 28 MeV. In addition, the spectral dependence upon crystal orientation of the forward coherent bremsstrahlung produced by beams of 28-MeV positrons and electrons incident upon a 5 μm thick single crystal of silicon was measured with a NaI photon spectrometer. Effects of channeling and perhaps of the nonvalidity of the first Born approximation were observed for beam directions near the [111] axis of the crystal, and coherent peaks near 0.5 MeV were observed for a compound interference direction, in agreement with first-order theoretical calculations. 32 fig
Decay energy of 55Fe from its inner Bremsstrahlung spectrum
International Nuclear Information System (INIS)
Keshava, S.L.; Gopala, K.; Venkataramaiah, P.
2001-01-01
Several measurements of decay energy using the inner Bremsstrahlung spectrum (IB) due to radiative electron capture in 55 Fe has been made. But the results are not uniform. Hence another attempt has been made at the same. Experimental data was obtained with a 4.445 cm dia x 5.08 cm thick NaI (Tl) detector. It was subjected to suitable statistical treatment and various corrections using Liden and Starfelt procedure. The corrected spectrum agrees well with the Glauber and Martin theory for l s electron capture beyond 100 keV. From the Jauch plot, the decay energy of 232.36±0.64 keV was obtained. (author)
The bremsstrahlung tagged photon beam in Hall B at JLab
Sober, D I; Longhi, A; Matthews, S K; O'Brien, J T; Berman, B L; Briscoe, W J; Cole, P L; Connelly, J P; Dodge, W R; Murphy, L Y; Philips, S A; Dugger, M K; Lawrence, D; Ritchie, B G; Smith, E S; Lambert, J M; Anciant, E; Audit, G; Auger, T; Marchand, C; Klusman, M; Napolitano, J; Khandaker, M A; Salgado, C W; Sarty, A J
2000-01-01
We describe the design and commissioning of the photon tagging beamline installed in experimental Hall B at the Thomas Jefferson National Accelerator Facility (JLab). This system can tag photon energies over a range from 20% to 95% of the incident electron energy, and is capable of operation with beam energies up to 6.1 GeV. A single dipole magnet is combined with a hodoscope containing two planar arrays of plastic scintillators to detect energy-degraded electrons from a thin bremsstrahlung radiator. The first layer of 384 partially overlapping small scintillators provides photon energy resolution, while the second layer of 61 larger scintillators provides the timing resolution necessary to form a coincidence with the corresponding nuclear interaction triggered by the tagged photon. The definitions of overlap channels in the first counter plane and of geometric correlation between the two planes are determined using digitized time information from the individual counters. Auxiliary beamline devices are briefl...
Nonlinear Breit–Wheeler pair creation with bremsstrahlung γ rays
Blackburn, T. G.; Marklund, M.
2018-05-01
Electron–positron pairs are produced through the Breit–Wheeler process when energetic photons traverse electromagnetic fields of sufficient strength. Here we consider a possible experimental geometry for observation of pair creation in the highly nonlinear regime, in which bremsstrahlung of an ultrarelativistic electron beam in a high-Z target is used to produce γ rays that collide with a counter-propagating laser pulse. We show how the target thickness may be chosen to optimize the yield of Breit–Wheeler positrons, and verify our analytical predictions with simulations of the cascade in the material and in the laser pulse. The electron beam energy and laser intensity required are well within the capability of today’s high-intensity laser facilities.
200-MeV bremsstrahlung tagged photon beams at Sendai
International Nuclear Information System (INIS)
Hirose, K.; Chiba, M.; Inoue, M.; Kanda, H.; Kimura, R.; Kino, K.; Kobayashi, Y.; Konno, O.; Maeda, K.; Miyase, H.; Miyamoto, A.; Ohtsuki, T.; Saito, A.; Suda, T.; Takahashi, K.; Tamae, T.; Terasaki, Y.; Terasawa, T.; Tsubota, H.; Tsuruta, T.; Utoyama, M.; Yuuki, H.; Yamaguchi, Y.; Yamazaki, H.
2006-01-01
A new beam line for photonuclear reaction experiments using tagged photons has been constructed to take advantage of the completion of the 1.2-GeV STretcher Booster (STB) ring at the Laboratory of Nuclear Science (LNS), Tohoku University. A photon tagging system was installed at the end of the new beam line. It provides bremsstrahlung tagged photon beams in an energy range from 0.2E 0 to 0.8E 0 MeV at the incident electron energy E 0 with an energy resolution of ΔE/E∼10 -2 . The tagged photon intensity I= 6 photons/s is available for typical photonuclear reaction experiments. We introduce the basic parameters of the tagged photons by showing the commissioning data
Laser radiography forming bremsstrahlung radiation to image an object
Perry, Michael D.; Sefcik, Joseph A.
2004-01-13
A method of imaging an object by generating laser pulses with a short-pulse, high-power laser. When the laser pulse strikes a conductive target, bremsstrahlung radiation is generated such that hard ballistic high-energy electrons are formed to penetrate an object. A detector on the opposite side of the object detects these electrons. Since laser pulses are used to form the hard x-rays, multiple pulses can be used to image an object in motion, such as an exploding or compressing object, by using time gated detectors. Furthermore, the laser pulses can be directed down different tubes using mirrors and filters so that each laser pulse will image a different portion of the object.
A high resolution beam profile monitor using Bremsstrahlung
International Nuclear Information System (INIS)
Norem, J.
1988-01-01
The development of efficient high energy linear colliders in the 1 TeV range requires final focus systems capable of producing beam spot sizes on the order of 1--20 nm, about three orders of magnitude smaller than those produced at the SLC. Although beam line designs exist which can, in principle, produce the required optics, the construction of quadrupoles with the size and precision required will be challenging. Field errors in these quads must be small and should be verified experimentally, which is difficult with existing technology. This paper describes a proposal to use bremsstrahlung from heavy targets to measure high energy beam profiles and positions with a resolution approaching a few nm. The method is also applicable to tests of other final focus systems (flat beams, plasma lenses) at lower energies. 6 refs., 3 figs., 1 tab
Internal Bremsstrahlung accompanying beta decay of 90 Y
International Nuclear Information System (INIS)
Elsayed, A.M.A.; Abdelhady, E.E.
1992-01-01
The internal Bremsstrahlung (IB) spectrum associated with the unique first-forbidden β decay of 9 0Y is measured employing the conventional β-stopper technique with a 5 x 5 cm NaI (T 1) scintillation spectrometer in the energy range (50-2000 keV). All the necessary corrections are made. In order to analyze the experimental data, a response matrix having the dimensions of 64 energy bins and 474 channels is constructed.with the help of the detector assembly response matrix, the true IB energy spectrum is obtained by iteratively unfolding the experimental pulse-height spectrum. The experimental results are compared with the corresponding theoretical distributions due to Knipp and Uhlenbeck and Bloch (KUB), lewis and ford (L F), and ford and martin (FM). The results show reasonable agreement with the detour theory of ford and martin.3 fig
Neutrino-antineutrino pair production by hadronic bremsstrahlung
Bacca, Sonia
2016-09-01
I will report on recent calculations of neutrino-antineutrino pair production from bremsstrahlung processes in hadronic collisions and consider temperature conditions relevant for core collapse supernovae. Earlier studies on bremsstrahlung from neutron-neutron collisions showed that the approximation used in typical supernova simulation to model this process differs by about a factor of 2 from predictions based on chiral effective field theory, where the chiral expansion of two-body forces is considered up to the next-to-next-to-next-to-leading order. When the density of neutrons is large enough this process may compete with other non-hadronic reactions in the production of neutrinos, in particular in the case of μ and τ neutrinos, which are not generated by charged-current reactions. A natural question to ask is then: what is the effect of neutrino pair production from collisions of neutrons with finite nuclei? To tackle this question, we recently have addressed the case of neutron- α collisions, given that in the P-wave channels the neutron- α scattering features a resonance near 1 MeV. We find that the resonance leads to an enhanced contribution in the neutron spin structure function at temperatures in the range of 0 . 1 - 4 MeV. For significant density fractions of α in this temperature range, this process is competitive with contributions from neutron-neutron scattering. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. This work was supported in parts by the Natural Sciences and Engineering Research Council (Grant Number SAPIN-2015-0003).
Measurements of Bremsstrahlung radiation and X-ray heat load to cryostat on SECRAL
International Nuclear Information System (INIS)
Zhao, H.Y.; Cao, Y.; Lu, W.; Zhang, W.H.; Zhao, H.W.; Zhang, X.Z.; Zhu, Y.H.; Li, X.X.; Xie, D.Z.
2012-01-01
The measurement of Bremsstrahlung radiation from ECR (Electron Cyclotron Resonance) plasma can yield certain information about the ECR heating process and the plasma confinement, and more important it can give a plausible estimate of the X-ray heat load to the cryostat of a superconducting ECR source. To better understand the additional heat load to the cryostat due to Bremsstrahlung radiation, the axial Bremsstrahlung measurements have been conducted on SECRAL (Superconducting Electron Cyclotron Resonance ion source with Advanced design in Lanzhou) with different source parameters. In addition, the heat load induced by intense X-ray or even γ-ray was estimated in terms of liquid helium consumption. The relationship between these two parameters is presented here. Thick-target Bremsstrahlung, induced by the collision of hot electrons with the wall or the source electrode, is much more intensive compared with the radiation produced in the plasma and, consequently, much more difficult to shield off. In this paper the presence of the thick-target Bremsstrahlung is correlated with the magnetic confinement configuration, specifically, the ratio of B(last) to B(ext). And possible solutions to reduce the X-ray heat load induced by Bremsstrahlung radiation are proposed and discussed. It appears that by choosing an appropriate ratio of B(last) to B(ext) the thick-target Bremsstrahlung radiation can be avoided effectively. The paper is followed by the associated poster
International Nuclear Information System (INIS)
Sorcini, B.B.; Hyoedynmaa, S.; Brahme, A.
1996-01-01
An analytical expression has been derived for the phantom generated bremsstrahlung photons in plane-parallel monoenergetic electron beams normally incident on material of any atomic number (Be, H 2 O, Al, Cu and U). The expression is suitable for the energy range from 1 to 50 MeV and it is solely based on known scattering power and radiative and collision stopping power data for the material at the incident electron energy. The depth dose distribution due to the bremsstrahlung generated by the electrons in the phantom is derived by convolving the bremsstrahlung energy fluence produced in the phantom with a simple analytical energy deposition kernel. The kernel accounts for both electrons and photons set in motion by the bremsstrahlung photons. The energy loss by the primary electrons, the build-up of the electron fluence and the generation, attenuation and absorption of bremsstrahlung photons are all taken into account in the analytical formula. The longitudinal energy deposition kernel is derived analytically and it is consistent with both the classical biexponential relation describing the photon depth dose distribution and the exponential attenuation of the primary photons. For comparison Monte Carlo calculated energy deposition distributions using ITS3 code were used. Good agreement was found between the results with the analytical expression and the Monte Carlo calculation. For tissue equivalent materials, the maximum total energy deposition differs by less than 0.2% from Monte Carlo calculated dose distributions. The result can be used to estimate the depth dependence of phantom generated bremsstrahlung in different materials in therapeutic electron beams and the bremsstrahlung production in different electron absorbers such as scattering foils, transmission monitors and photon and electron collimators. By subtracting the phantom generated bremsstrahlung from the total bremsstrahlung background the photon contamination generated in the treatment head can be
Ab initio simulation of stimulated bremsstrahlung in an intense laser field
International Nuclear Information System (INIS)
Volkova, E.A.; Popov, A.M.; Popovicheva, O.B.
1992-01-01
Numerical solution of the time-dependent Schroedinger equation for a quantum system in the field of an electromagnetic wave is used to study a one-dimensional model of stimulated bremsstrahlung (absorption or emission of photons by a field in connection with Coulomb scattering of an electron). The time dependence of the stimulated bremsstrahlung effect is analyzed for various laser radiation intensities. The process of stimulated photorecombination is examined. The results of the calculation are compared with the analytical theory of the stimulated bremsstrahlung effect. 14 refs., 6 figs
Calculation of the inverse data space via sparse inversion
Saragiotis, Christos; Doulgeris, Panagiotis C.; Verschuur, Dirk Jacob Eric
2011-01-01
The inverse data space provides a natural separation of primaries and surface-related multiples, as the surface multiples map onto the area around the origin while the primaries map elsewhere. However, the calculation of the inverse data is far from
Navrátil, Zdeněk; Morávek, Tomáš; Ráheľ, Jozef; Čech, Jan; Lalinský, Ondřej; Trunec, David
2017-05-01
Weak light emission (˜10-3 of active discharge signal; average count rate ˜ 1 photon s-1 nm-1) associated with surface charge relaxation during the dark phase of a helium diffuse coplanar barrier discharge was studied by optical emission spectroscopy, using a technique of phase-resolved single photon counting. The optical emission spectra of the dark phase contained luminescent bands of the dielectrics used (Al2O3, AlN) and spectral lines from the gas constituents (OH*, {{{N}}}2* , {{{N}}}2+* , He*, He{}2* , O*). During the charge relaxation event, a broad continuum appeared in the optical emission spectra, consisting of bremsstrahlung radiation and amplified luminescence of the dielectric barrier. The analysis presented suggests that the bremsstrahlung radiation originated from slow electrons colliding with neutral helium atoms. The fitting procedure we developed reproduced well the observed shape of the continuum. Moreover, it provided a method for the determination of electric field strength in the discharge during this particular phase. The electric field reached 1 kV cm-1 during the charge relaxation event.
International Nuclear Information System (INIS)
Watson, J.E.
1981-01-01
The observation of sharp peaks in the x-ray spectrum from 1 to 3 MeV electrons striking thin single crystals of silicon and gold is reported. These peaks were observed in the range 1 to 25 keV. The peaks are of two different origins, both direct results of the periodic nature of the target crystals. The first kind of radiation is caused by the interference of incoming and scattered electron wave functions. Because of the periodicity of the target material there is a coherence effect for certain bremsstrahlung wave vectors. This coherent bremsstrahlung, though well known at very high electron energies, has never been adequately studied at electron energies below several hundred MeV. Detailed agreement between theoretical prediction and observation in silicon is shown. The second kind of radiation is caused by electrons channeled along major crystal axes. The electrons enter certain quantized orbits as they channel and may emit photons as a consequence of transitions between the various orbits. Observations of channeling radiation for various crystal axes in silicon are presented. Both phenomena were observed in gold, the first such observation for any metallic target
Ingram, WT
2012-01-01
Inverse limits provide a powerful tool for constructing complicated spaces from simple ones. They also turn the study of a dynamical system consisting of a space and a self-map into a study of a (likely more complicated) space and a self-homeomorphism. In four chapters along with an appendix containing background material the authors develop the theory of inverse limits. The book begins with an introduction through inverse limits on [0,1] before moving to a general treatment of the subject. Special topics in continuum theory complete the book. Although it is not a book on dynamics, the influen
Precision gamma-ray polarimetry applied to studies of bremsstrahlung produced by polarized electrons
Energy Technology Data Exchange (ETDEWEB)
Kovtun, Oleksiy
2015-12-16
The thesis reports on the measurement of bremsstrahlung linear polarization produced in collisions of longitudinally and transversely polarized electrons with gold atoms. The experiment was performed at the Mainzer Microtron MAMI in the Institut fuer Kernphysik of Johannes Gutenberg-Universitaet Mainz, Germany. Spin-oriented electrons with 2.15 MeV kinetic energy collided with a thin golden target and produced bremsstrahlung. Linear polarization of the emitted photons was measured by means of Compton polarimetry applied to a segmented high-purity germanium detector. Experimental results reveal a strong correlation between the electron spin orientation and bremsstrahlung linear polarization. This indicates a dominant role of the electron spin in atomic-field bremsstrahlung and Coulomb scattering.
International Nuclear Information System (INIS)
Barber, Thomas W.; Yap, Kenneth S.K.; Cherk, Martin H.; Kalff, Victor; Powell, Anne
2013-01-01
The aim of this study is to compare the results of positron emission tomography (PET)/CT with bremsstrahlung imaging following Y-90 radiation synovectomy. All patients referred to our institution for Y-90 radiation synovectomy between July 2011 and February 2012 underwent both PET/CT and bremsstrahlung planar (±single photon emission computed tomography (SPECT) or SPECT/CT) imaging at 4 or 24 h following administration of Y-90 silicate colloid. PET image acquisition was performed for between 15 and 20min. In patients who underwent SPECT, side-by-side comparison with PET was performed and image quality/resolution scored using a five-point scale. The distribution pattern of Y-90 on PET and bremsstrahlung imaging was compared with the intra- or extra-articular location of Y-90 activity on fused PET/CT. Thirteen joints (11 knees and two ankles) were imaged with both PET/CT and planar bremsstrahlung imaging with 12 joints also imaged with bremsstrahlung SPECT. Of the 12 joints imaged with SPECT, PET image quality/resolution was superior in 11 and inferior in one. PET demonstrated a concordant distribution pattern compared with bremsstrahlung imaging in all scans, with the pattern classified as diffuse in 12 and predominantly focal in one. In all 12 diffuse scans, PET/CT confirmed the Y-90 activity to be located intra-articularly. In the one predominantly focal scan, the fused PET/CT images localised the Y-90 activity to mostly lie in the extra-articular space of the knee. PET/CT can provide superior image quality compared with bremsstrahlung imaging and may enable reliable detection of extra-articular Y-90 activity when there are focal patterns on planar bremsstrahlung imaging.
International Nuclear Information System (INIS)
Sorcini, B.B.; Hyoedynmaa, S; Brahme, A.
1995-01-01
Qualification of the bremsstrahlung photon background generated by an electron beam in a phantom is important for accurate high energy electron beam dosimetry in radiation therapy. An analytical expression has been derived for the background of phantom generated bremsstrahlung photons in plane parallel electron beams normally incident on phantoms of any atomic number between 4 and 92 (Be, C, H 2 O, Al, Cu, Ag, Pb and U). The expression can be used with fairly good accuracy in the energy range between 1 and 50 MeV. The expression is globally based on known scattering power and radiation and collision stopping power data for the phantom material at the mean energy of the incident electrons. The depth dose distribution due to the bremsstrahlung generated in the phantom is derived by folding the bremsstrahlung energy fluence with a simple analytical one-dimensional photon energy deposition kernel. The energy loss of the primary electrons and the generation, attenuation and absorption of bremsstrahlung photons are taken into account in the analytical formula. The photon energy deposition kernel is used to account for the bremsstrahlung produced at one depth that will contribute to the down stream dose. A simple analytical expression for photon energy deposition kernel is consistent with the classical analytical relation describing the photon depth dose distribution. From the surface to the practical range the photon dose increases almost linearly due to accumulation and buildup of the photon produced at different phantom layers. At depths beyond the practical range a simple exponential function can be use to describe the bremsstrahlung attenuation in the phantom. For comparison Monte Carlo calculated distributions using ITS3 Monte Carlo Code were used. Good agreement is found between the analytical expression and Monte Carlo calculation. Deviations of 5% from Monte Carlo calculated bremmstrahlung background are observed for high atomic number materials. The method can
Dose Measurements of Bremsstrahlung-Produced Neutrons at the Advanced Photon Source
International Nuclear Information System (INIS)
Job, P.K.; Pisharody, M.; Semones, E.
1998-01-01
Bremsstrahlung is generated in the storage rings of the synchrotron radiation facilities by the radiative interaction of the circulating particle beam with both the residual gas molecules and storage ring components. These bremsstrahlung photons, having an energy range of zero to the maximum energy of the particle beam, interact with beamline components like beam stops and collimators generating photoneutrons of varying energies. There are three main processes by which photoneutrons may be produced by the high energy bremsstrahlung photons: giant nuclear dipole resonance and decay (10 MeV γ γ γ > 140 MeV). The giant resonance neutrons are emitted almost isotropically and have an average energy of about 2 MeV. High energy neutrons (E > 10 MeV) emitted from the quasi-deuteron decay and intranuclear cascade are peaked in the forward direction. At the Advanced Photon Source (APS), where bremsstrahlung energy can be as high as 7 GeV, production of photoneutrons in varying yields is possible from all of the above three processes. The bremsstrahlung produced along a typical 15.38-m straight path of the insertion device (ID) beamline of the APS has been measured and analyzed in previous studies. High-Z materials constituting the beamline components, such as collimators and beam stops, can produce photoneutrons upon interaction with these bremsstrahlung photons. The 1/E nature of the bremsstrahlung spectrum and the fact that the photoneutron production cross section is comparatively larger in the energy region 10 MeV γ 3 detector, as well as a very sensitive pressurized 3 He detector, is used for neutron dose measurements. The dose equivalent rates, normalized to bremsstrahlung power, beam current, and storage ring vacuum, are measured for various targets. This report details the experimental setup,
International Nuclear Information System (INIS)
Ivaschenko, D.M.; Mordasov, N.G.; Chlenov, A.M.
2005-01-01
A method and a device for monitoring the dynamic and integrated characteristics of high-power electron and bremsstrahlung beams of the pulse accelerators are proposed. The transfer functions for various types of a target in operating conditions of the pulse accelerator UIN-10 are presented. Possibilities if the integrated diagnostics of acceleration rate of the electron beams with simultaneous testing of the bremsstrahlung parameters as a local field point beyond the converting target are shown [ru
Energy Technology Data Exchange (ETDEWEB)
Peysson, Y.; Imbeaux, F. [Association Euratom-CEA, CEA/Cadarache, Dept. de Recherches sur la Fusion Controlee (DRFC), 13 - Saint-Paul-lez-Durance (France)
1999-04-01
A new tomography dedicated to detailed studies of the fast electron Bremsstrahlung emission in the hard X-ray (HXR) energy range between 20 and 200 keV during lower hybrid (LH) current drive experiments on the TORE SUPRA tokamak [Equipe TORE SUPRA, in Proceedings of the 15. Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995), 1, AIEA-CN-60 / A1-5, p. 105] is presented. Radiation detection is performed by cadmium telluride(CdTe) semiconductors, which have most of the desirable features for a powerful diagnosing of magnetically confined hot plasmas - compact size, high X-ray stopping efficiency, fast timing characteristics, good energy resolution, no sensitivity to magnetic field, reasonable susceptibility to performance degradation from neutron/{gamma}-induced damages. This instrument is made of two independent cameras viewing a poloidal cross-section of the plasma, with respectively 21 and 38 detectors. A coarse spectrometry - 8 energy channels - is carried out for each chord, with an energy resolution of 20 keV. The spatial resolution in the core of the plasma is 4-5 cm, while the time sampling may be lowered down to of 2-4 ms. Powerful inversion techniques based on maximum entropy or regularization algorithms take fully advantage of the large number of line-integrated measurements for very robust estimates of the local HXR profiles as a function of time and photon energy. A detailed account of main characteristics and performances of the diagnostic is reported as well as preliminary results on LH current drive experiments. (authors)
International Nuclear Information System (INIS)
Peysson, Y.; Imbeaux, F.
1999-04-01
A new tomography dedicated to detailed studies of the fast electron Bremsstrahlung emission in the hard X-ray (HXR) energy range between 20 and 200 keV during lower hybrid (LH) current drive experiments on the TORE SUPRA tokamak [Equipe TORE SUPRA, in Proceedings of the 15. Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995), 1, AIEA-CN-60 / A1-5, p. 105] is presented. Radiation detection is performed by cadmium telluride (CdTe) semiconductors, which have most of the desirable features for a powerful diagnosing of magnetically confined hot plasmas - compact size, high X-ray stopping efficiency, fast timing characteristics, good energy resolution, no sensitivity to magnetic field, reasonable susceptibility to performance degradation from neutron/γ-induced damages. This instrument is made of two independent cameras viewing a poloidal cross-section of the plasma, with respectively 21 and 38 detectors. A coarse spectrometry - 8 energy channels - is carried out for each chord, with an energy resolution of 20 keV. The spatial resolution in the core of the plasma is 4-5 cm, while the time sampling may be lowered down to of 2-4 ms. Powerful inversion techniques based on maximum entropy or regularization algorithms take fully advantage of the large number of line-integrated measurements for very robust estimates of the local HXR profiles as a function of time and photon energy. A detailed account of main characteristics and performances of the diagnostic is reported as well as preliminary results on LH current drive experiments. (authors)
The effect of correction factors on internal bremsstrahlung spectrum
International Nuclear Information System (INIS)
Elias, M.M.
1985-01-01
Correction factors affecting the experimental spectrum of internal bremsstrahlung (IB) accompanying B-decay have been studied. A wide survey of previous experimental studies, show a discrepancy between experimental results and the available theories of IB production especially for heavy nuclides and forbidden B-transitions, with some agreement in bounded regions in IB spectrum. This is due to the uncertainity in evaluating correction factors and neglecting others. The experimental distributions of IB from 147 Pm, 204 Tl and 90 Y are measured by using two different crystals of NaI(Tl) scintillators (2''x2'' and 3'''x3'') with suitable geometrical arrangements designed to minimize the effect of several factors. The present study covers overlapped ranges of energy from 0.05 to 2.2 MeV to observe the effect of these factors along this wide region of energy. The experimental probabilities are compared with theories. It agrees fairly well with Lewis and Ford theory in case of 14 '7Pm, 204 Tl, and with detour transitions theory in the intermediate region of energies of IB spectrum from 90 Y. Deviation of our results from theories is less than all previous experimental work. 20 tabs.; 43 figs.; 84 refs.; 5 apps
Measuring the electron-ion ring parameters by bremsstrahlung
International Nuclear Information System (INIS)
Inkin, V.D.; Mozelev, A.A.; Sarantsev, V.P.
1982-01-01
A system is described for measuring the number of electrons and ions in the electron-ion rings of a collective heavy ion accelerator. The system operation is based on detecting gamma quanta of bremsstrahlung following the ring electron interaction with the nuclei of neutral atoms and ions at different stages of filling the ring with ions. The radiation detector is a scintillation block - a photomultiplier operating for counting with NaI(Tl) crystal sized 30x30 mm and ensuring the detection efficiency close to unity. The system apparatus is made in the CAMAC standard and rems on-line with the TRA/i miniature computer. The block-diagrams of the system and algorithm of data processing are presented. A conclusion is drawn that the results of measuring the ring parameters with the use of the diagnostics system described are in good agreement within the range of measuring errors with those obtained by means of the diagnostics system employing synchrotron radiation and induction sensors
Bremsstrahlung background and quantitation of thin biological samples
International Nuclear Information System (INIS)
Khan, K.M.
1991-02-01
An inherent feature of all electron-excited X-ray spectra is the presence of a background upon which the characteristic peaks of interest are superimposed. To extract the x-ray intensity of the characteristics lines of interest, it is necessary to subtract this background, which may be due to both specimen generated Bremsstrahlung and extraneous sources, from a measured x-ray spectrum. Some conventional methods of background subtraction will be briefly reviewed. It has been seen that these conventional methods do not give sufficiently accurate results in biological analysis where the peaks of interest are not well-separated and most of the peaks lie in the region where the background is appreciably curved. An alternative approach of background subtraction for such samples is investigated which involves modelling the background using the currently available knowledge of x-ray physics and energy dispersive detectors. This method is particularly suitable for biological samples as well as other samples having an organic matrix. 6 figs. (author)
A Single Bremsstrahlung Monitor to Measure Luminosity at LEP
2002-01-01
The luminosity, the beam divergence and the longitudinal polarization can be measured at an interaction point of LEP by dectecting the energy, the angular distribution and the circular polarization of the single bremsstrahlung photons (SB) emitted at very forward angle. The luminosity can be measured by this met than by the conventional method of detecting small angle Bhabha scattering. The bunch to bunch relative luminosity can be monitored at a few per mil level in few minutes. Absolute values of the luminosity and of the polarization can be measured with a precision of the order of 1\\%. \\\\ \\\\ The apparatus to detect SB photons consists of a low Z absorber and of an EM calorimeter made of lead and scintillating fibres. Both the total energy and the space distribution of the SB photons are measured. This apparatus has been designed and built at the Department of Physics and INFN Section of the University of Rome ``La Sapienza''. Later on, together with suitable monocrystal converters, it may be used also for...
Internal bremsstrahlung spectral shapes of 45Ca and 35S
International Nuclear Information System (INIS)
Babu, R.P.; Murty, K.N.; Murty, V.A.N.
1976-01-01
The internal bremsstrahlung spectra emitted in the beta decays of 45 Ca and 35 S were measured using a multichannel NaI(Tl) scintillation spectrometer with a standard geometrical arrangement. After making all the necessary corrections, the experimental results were compared with the allowed theory of Knipp and Uhlenbeck (Physica; 3:425 (1936)) and of Bloch (Phys. Rev.; 50:272 (1936)) (KUB theory) and also with the Coulomb-corrected theories of Lewis and Ford (Phys. Rev.; 107:756 (1957)) and of Nilsson (Ark. Fys.; 10:467 (1956)). In the case of 45 Ca, fairly good agreement with KUB theory was obtained from 30 to 155 keV and above 155 keV the experimental results were in agreement with the Lewis and Ford theory up to 210 keV, the maximum limit of the photon energy investigated. For 35 S, the experimental results are in quite good agreement with KUB theory from 25 to 45 keV, but beyond 45 keV the values are greater than the Coulomb-corrected theories due to both Lewis and Ford and to Nilsson, the experimental excess over Nilsson Coulomb-corrected theory being by factors of 1.07, 1.12 and 1.63 at energies 60, 90 and 110 keV respectively. (author)
Internal bremsstrahlung from 89Sr and 90Sr
International Nuclear Information System (INIS)
Sayibaba, T.; Narasimha Murity, K.; Rao, C.R.; Satyaprakash; Gubbi, G.K.
1987-01-01
The internal bremsstrahlung (IB) spectra emitted in the beta-decays of 89 Sr and 90 Sr were measured with a HPGe detector and a multichannel analyser along with a standard geometrical set-up. Sufficient care has been taken to avoid spurious effects. After making all the necessary corrections, the experimental results were compared with the corresponding theoretical distributions due to Knipp and Uhlenbeck and Bloch (KUB), Lewis and Ford, Nilsson, and also due to Ford and Martin (detour theory). The total IB yields of intensity and energy from each of the isotopes in the investigated energy regions are also determined and compared with the corresponding theoretical values. The present results of IB from 89 Sr are satisfactorily accounted for by the KUB theory. In the case of 90 Sr the experimental results of IB coincide with the Coulomb-corrected theoretical distibution due to Nilsson in the energy range from 60 keV to 110 keV and Beyond 110 keV, they are found to be in excess over Nilsson's theory as well as the detour theory due to Ford and Martin up to the maximum photon energy studied, namely 350 keV
Branciamore, Sergio; Di Giulio, Massimo
2012-04-01
The secondary structure of the 5S ribosomal RNA (5S rRNA) molecule shows a high degree of symmetry. In order to explain the origin of this symmetry, it has been conjectured that one half of the 5S rRNA molecule was its precursor and that an indirect duplication of this precursor created the other half and thus the current symmetry of the molecule. Here, we have subjected to an empirical test both the indirect duplication model, analysing a total of 684 5S rRNA sequences for complementarity between the two halves of the 5S rRNA, and the direct duplication model analysing in this case the similarity between the two halves of this molecule. In intra- and inter-molecule and intra- and inter-domain comparisons, we find a high statistical support to the hypothesis of a complementarity relationship between the two halves of the 5S rRNA molecule, denying vice versa the hypothesis of similarity between these halves. Therefore, these observations corroborate the indirect duplication model at the expense of the direct duplication model, as reason of the origin of the 5S rRNA molecule. More generally, we discuss and favour the hypothesis that all RNAs and proteins, which present symmetry, did so through gene duplication and not by gradualistic accumulation of few monomers or segments of molecule into a gradualistic growth process. This would be the consequence of the very high propensity that nucleic acids have to be subjected to duplications.
Directory of Open Access Journals (Sweden)
Joel Sereno
2010-01-01
Full Text Available Inverse kinematics is the process of converting a Cartesian point in space into a set of joint angles to more efficiently move the end effector of a robot to a desired orientation. This project investigates the inverse kinematics of a robotic hand with fingers under various scenarios. Assuming the parameters of a provided robot, a general equation for the end effector point was calculated and used to plot the region of space that it can reach. Further, the benefits obtained from the addition of a prismatic joint versus an extra variable angle joint were considered. The results confirmed that having more movable parts, such as prismatic points and changing angles, increases the effective reach of a robotic hand.
Contribution of 210Pb bremsstrahlung to the background of lead shielded gamma spectrometers
International Nuclear Information System (INIS)
Mrda, D.; Bikit, I.; Veskovic, M.; Forkapic, S.
2007-01-01
Lead, which is often used as a shielding material, contains 210 Pb (T 1/2 =22.3 y). The 46.54 keV γ-intensity of 210 Pb can be easily reduced by an inner lining, but the bremsstrahlung caused by the β-decay of its daughter, 210 Bi, with a maximal electron energy of 1.16 MeV, will contribute to the gamma detector background. The spectrum of this bremsstrahlung is calculated by numerically fitting the β-spectrum and integrating the Koch-Motz formula. The absorption of the bremsstrahlung in the lead and detection efficiencies for the HPGe detector are calculated by the effective solid angle algorithm, using corrections for the photopeak/Compton ratio of cross-sections in Ge. By comparison with the measured background spectrum, it is shown that, for the lead with 25 Bq/kg of 210 Pb up to 500 keV of gamma spectrum, the bremsstrahlung contribution to the background is about 20% for our surface-based detector system. Also, we compared our calculations with a Monte Carlo simulation of another detector system with a shield containing 1 Bq/kg of 210 Pb and found that our analytical method gives a value of roughly two times higher than the Monte Carlo one for the total bremsstrahlung contribution. The quality of the analytical semi-empirical method is proved by the reasonable agreement with the experimental results published
International Nuclear Information System (INIS)
Lopez, P.N; Corrales, Y.; Manso Guevara, M.V; Martins, M.N.
2007-01-01
Nuclear Resonance Fluorescence (NRF) setup will install in the new electron accelerator, which is in final stage of installation at the Physics Institute of Sao Paulo University (IFUSP). The Bremsstrahlung facility and the setup for photon scattering should be designed such that the background radiation caused by scattering photons and the production of neutrons is minimized. In this order the Monte Carlo simulation studies show the best options for the different elements of the NRF setup, and how to link these elements to the particularities of the irradiation room. In the present stage the simulations has been included the studies of different Bremsstrahlung converters and collimators. Several materials (Ta, W, Au, Nb, Cu) for Bremsstrahlung converters were studied. Detailed analyses of intensity as well as the opening angles of Bremsstrahlung radiation were carried out, for different converter thickness. For the collimator two materials (Cu and Pb) were studied in the simulations. Several opening angles and thickness (40 - 100 cm) were studied. The Bremsstrahlung beam collimation for different energy bins, and the photon scattering from the collimator ,were used as quality parameters of the collimators. (Author)
International Nuclear Information System (INIS)
Zhang Daping; Lou Cen; Chen Liang; Yu Linliang; Huang Huacheng
2003-01-01
Objective: To evaluate the therapeutic effect of 89 Sr (a pure beta emitter) using Bremsstrahlung imaging in patients with multiple bone metastases. Methods: 89 Sr Bremsstrahlung imaging was performed 1-2 weeks after injection in 14 patients with bone metastases, using GE Camstar 3200 SPECT equipped with a medium-energy collimator. To improve resolution of imaging, authors selected suitable energy level and wide window width (a 95-100% energy window around 100 KeV). Results: Abnormal uptake was seen in all and was consistent with the results of 99m Tc-MDP imaging. According to this result, authors can realize localization, retention and metabolism of 89 Sr in body. Conclusion: Bremsstrahlung imaging is useful for clinical observation and estimating the curative effect and prognosis in pure beta emitter therapy such as 89 Sr. In addition, it can be helpful in determining dose of 89 Sr if a repeated therapy is needed
Bremsstrahlung emission probability in the {alpha} decay of {sup 210}Po
Energy Technology Data Exchange (ETDEWEB)
Boie, Hans-Hermann
2009-06-03
A high-statistics measurement of bremsstrahlung emitted in the {alpha} decay of {sup 210}Po has been performed. The measured differential emission probabilities, which could be followed up to {gamma}-energies of {proportional_to} 500 keV, allow for the first time for a serious test of various model calculations of the bremsstrahlung accompanied {alpha} decay. It is shown that corrections to the {alpha}-{gamma} angular correlation due to the interference between the electric dipole and quadrupole amplitudes and due to the relativistic character of the process have to be taken into account. With the experimentally derived angular correlation the measured energydifferential bremsstrahlung emission probabilities show excellent agreement with the fully quantum mechanical calculation. (orig.)
International Nuclear Information System (INIS)
2002-01-01
This practice describes dosimetric procedures to be followed in facility characterization, process qualification, and routine processing for electron beam and bremsstrahlung irradiation facilities for food processing to ensure that product receives an acceptable range of absorbed doses. Other procedures related to facility characterization, process qualification, and routine product processing that may influence and be used to monitor absorbed dose in the product are also discussed. Information about effective or regulatory dose limits for food products is not within the scope of this practice (see ASTM Guides F 1355 and F 1356). The electron energy range covered in this practice is from 0.3 MeV to 10 MeV. Such electrons can be generated in continuous or pulse modes. The maximum electron energy of bremsstrahlung facilities covered in this practice is 10 MeV. A photon beam can be generated by inserting a bremsstrahlung converter in the electron beam path (See ISO/ASTM Practice 51608
Proton-proton and neutron-proton bremsstrahlung in the potential model
International Nuclear Information System (INIS)
Herrmann, V.
1993-11-01
The nucleon-nucleon (NN) bremsstrahlung reaction is studied in the framework of a potential model. We investigate and explain the behavior of the most important corrections to the purely non-relativistic model considering only the external current; i.e. we include the relativistic spin correction, the one-body rescattering contribution and the Coulomb-effect, where it is needed. The important contribution of the two-body or meson-exchange current is treated in the soft-photon-approximation. In addition to the usual coplanar NNγ cross section we also study non-coplanar cross sections and spin observables like the analyzing power and spin correlation coefficients. It is shown that the behavior of the relativistic spin correction is governed by the 1 S 0 partial-wave state, is almost energy independent and reduces the NNγ cross section by roughly 20 - 30%. The one-body rescattering contribution enhances the ppγ cross section for the geometry of the last TRIUMF experiment by about 20% and thus almost compensates the effect of the relativistic spin corrections. The effects of each part of the NN interaction on the ppγ observables is studied in the coplanar geometry. We find that these effects depend on the proton scattering angles as well as on the considered observable. However, the tensor component of the NN interaction is important in all geometries. The comparison of different NN potential models yields that the NNγ reaction is not able to discriminate these potentials in their off-shell behavior, although the corresponding T-matrices deviate from each other off the energy shell. It is concluded that the occuring differences originate already from deviations on the energy shell or from the fact that the approximations made in the calculations for the two-body current are not of the same quality for all NN potential models. (orig.)
International Nuclear Information System (INIS)
Job, P.K.; Haeffner, D.R.; Shu, D.
1994-12-01
Bremsstrahlung is produced in the APS storage ring by the interaction of positrons with the residual gas molecules in the vacuum chamber of the storage ring. The bremsstrahlung production causes a serious challenge in shielding the insertion-device beamlines because the entire straight section (15 meters) is in the line of sight of the beamline. The radiation emerges in a narrow cone tangential to the beam path with the characteristic emission angle 1/γ, where γ is E/mc 2 which is the ratio of the kinetic energy to the rest mass for the positrons. This high-energy gamma radiation has an approximate 1/E spectrum with the maximum energy extending up to the particle energy (7 GeV for the APS). Bremsstrahlung, being high-energy photons, produces an electromagnetic shower when it encounters the beamline elements. A beamline element not thick enough to fully contain an electromagnetic shower can cause considerable scatter of the high-energy bremsstrahlung radiation. The low-energy component of the bremsstrahlung can also be scattered and create high dose rates in the first-optical and white-beam enclosures. The fully developed electromagnetic shower will have a photon spectrum almost independent of the material. The electromagnetic showers in the high-Z materials can also produce photoneutrons. This note reports the summary of EGS4 calculations performed on bremsstrahlung scattering from different beamline components in a typical APS insertion-device beamline. The related recommendations for shielding are also given. The shielding criterion adopted is a total dose rate of 2.5μSv/h (0.25 mrem/h) at 30 cm from the shield
International Nuclear Information System (INIS)
Rueckl, R.
1978-01-01
Electromagnetic bremsstrahlung in hadronic collisions was studied extensively at low and intermediate energies. It was found that the infrared divergent term of the cross section describes the data well up to surprisingly large photon energies. Using essentially the same soft photon approximation, production of low mass-low energy electron pairs via internal conversion of soft virtual bremsstrahlung accompanying the production of charged hadrons in hadron-hadron collisions at very high and intermediate energies. The resulting electron yields explain, at least in part, the direct electrons with small transverse momenta seen at the ISR, and are in no contradiction to the rates observed at LAMPF
International Nuclear Information System (INIS)
Guirlet, R.; Mattioli, M.; DeMichelis, C.; Hess, W.; Pecquet, A.L.
1995-01-01
Effective charge measurements and calculations are presented for the Tore Supra, using visible Bremsstrahlung diagnostics. The measurements, are presented together with a reliability test of the results are discussed, by means of an impurity transport code simulating all available experimental data (XUV line spectroscopy, soft X-ray emission and Bremsstrahlung). (author) 5 refs.; 10 figs
Energy Technology Data Exchange (ETDEWEB)
Stevens, J.E.; von Goeler, S.; Bernabei, S.; Bitter, M.; Chu, T.K.; Efthimion, P.; Fisch, N.; Hooke, W.; Hosea, J.; Jobes, F.
1985-03-01
Lower hybrid current drive requires the generation of a high energy electron tail anisotropic in velocity. Measurements of bremsstrahlung emission produced by this tail are compared with the calculated emission from reasonable model distributions. The physical basis and the sensitivity of this modeling process are described and the plasma properties of current driven discharges which can be derived from the model are discussed.
Virtual-bremsstrahlung production in proton-proton scattering and proton-deuteron capture
Messchendorp, Johannes Gerhardus
1999-01-01
The well-known coupling of the photon with the nucleon together with the fact that photons (or any electromagnetic (e.m.) probe) interact only relatively weakly with nucleons, make bremsstrahlung production an ideal tool to study details of the nucleon-nucleon interaction. In this thesis dilepton
Experimental results on 2-30 keV bremsstrahlung from thick and thin targets
Energy Technology Data Exchange (ETDEWEB)
Shanker, R. [Atomic Physics Laboratory, Physics Department, Banaras Hindu University, Varanasi 221005 (India)]. E-mail: rshanker@bhu.ac.in
2006-10-15
The recent experimental investigations on electron bremsstrahlung produced from impact of 2-30 keV electrons with thick solid and thin gaseous targets are reviewed. The theoretical models describing the energy and angular distributions of bremsstrahlung photons are discussed with their brief outlines and formulations to explain the experimental data. The results on thick target bremsstrahlung (TTB) spectra produced by keV electrons have suggested that there is a need to develop a comprehensive theory for accounting the solid state effects. It is further noted that the prediction of the modified KKD formula gives a reasonable agreement with the TTB data, whereas a semi-empirical formula gives a better fit to the data for thick targets. The available experimental data for dependence of double differential cross-sections of emitted photons on impact energy and their emission angles for gaseous atoms and molecules exhibit a good agreement with the theoretical calculations of Kissel et al., [1983. Shape functions for atomic-field bremsstrahlung from electrons of kinetic energy 1-500 keV on selected neutral atoms 1
International Nuclear Information System (INIS)
Bleier, W.
1983-01-01
The polarization of the photons in the elementary processes of the electron-nucleus and electron-electron bremsstrahlung was measured. Electrons with an energy of 300 keV were scattered by copper, gold and carbon target. The polarization in the different processes was measured by using different coincidence methods. (BEF)
Lepton-pair production by bremsstrahlung in central relativistic heavy ion collisions
International Nuclear Information System (INIS)
Lippert, T.; Becker, U.; Gruen, N.; Scheid, W.; Soff, G.
1988-03-01
We study the production of lepton-pairs by classical bremsstrahlung in central relativistic heavy-ion collisions. For the stopping of the nuclei we assume a simple model of point charges and a deceleration time. Pair creation probabilities are calculated in first order perturbation theory. (orig.)
International Nuclear Information System (INIS)
Lee, R.N.; Milstein, A.I.; Strakhovenko, V.M.; Schwartz, O.Ya.
2006-01-01
The Coulomb corrections (CC) to the processes of bremsstrahlung and pair production are investigated. The next-to-leading term in the high-energy asymptotics is found. This term becomes very essential in the region of intermediate energies. The influence of screening for CC is small for differential cross section, spectrum, and the total cross section of pair production. The same is true for the spectrum of bremsstrahlung, but not for the differential cross section, where the influence of screening can be very large. The corresponding screening corrections as well as the modification of the differential cross section of bremsstrahlung are found. A comparison of our results for the total cross section of pair production with the experimental data available is performed. This comparison has justified our analytical results and allowed to elaborate a simple ansatz for the next-to-leading correction. The influence of the electron beam shape on CC for bremsstrahlung is investigated. It turns out that the differential cross section is very sensitive to this shape
''Atomic'' Bremsstrahlung or polarizational radiation in collision of many-electron ions
International Nuclear Information System (INIS)
Amusia, M.Ya.; Solov'yov, A.V.
1991-01-01
In this work the so-called ''Atomic'' bremsstrahlung (AB) or polarizational radiation, created in collisions of atoms or ions, is discussed. This kind of radiation arises due to the polarization of the electron shell of colliding particles. It is created by the structured projectiles and targets if the constituents are electrically charged. 6 refs, 2 figs
Pauli principle in the soft-photon approach to proton-proton bremsstrahlung
Liou, MK; Timmermans, R; Gibson, BF
1996-01-01
A relativistic and manifestly gauge-invariant soft-photon amplitude, which is consistent with the soft-photon theorem and satisfies the Pauli principle, is derived for the proton-proton bremsstrahlung process. This soft-photon amplitude is the first two-u-two-t special amplitude to satisfy all
International Nuclear Information System (INIS)
Stevens, J.E.; von Goeler, S.; Bernabei, S.
1985-03-01
Lower hybrid current drive requires the generation of a high energy electron tail anisotropic in velocity. Measurements of bremsstrahlung emission produced by this tail are compared with the calculated emission from reasonable model distributions. The physical basis and the sensitivity of this modeling process are described and the plasma properties of current driven discharges which can be derived from the model are discussed
Neutron-proton bremsstrahlung studies using the white neutron source at the LAMPF/WNR
International Nuclear Information System (INIS)
Wender, S.A.; Nelson, R.O.; Schillaci, M.E.; Blann, M.
1990-01-01
Nucleon-nucleon bremsstrahlung is a few-body radiative process that provides insight into several areas of nuclear physics. It is one of the simplest systems for studying the off-shell behavior of the nucleon-nucleon potential. The physics involved in neutron-proton bremsstrahlung (NPB) is significantly different from that of proton-proton bremsstrahlung (PPB). In particular, NPB cross sections are much larger than PPB cross sections because NPB allows E1 radiation, and the contribution to the cross section from the meson exchange currents has been calculated to be as large as the contributions from external radiation. To date there have been essentially four NPB experiments. These measurements have covered only a small part of the available phase space. A major experimental problem in performing these measurements has been the lack of a suitable intense, high-energy neutron beam. We are planning a measurement of the NPB cross section using the white neutron source at the WNR target area at the LAMPF accelerator. We plant to implement the experiment in three phases. In this first state, we shall measure inclusive hard-photon production using a multi-element gamma-ray telescope that is insensitive to neutrons. In the second phase, we shall measure the bremsstrahlung gamma-rays in coincidence with recoil protons. In the last phase, we shall detect the scattered neutrons in coincidence with the recoil protons and gamma rays. 8 refs., 6 figs
Multi-Regge amplitudes for bremsstrahlung in e+e- backward scattering
International Nuclear Information System (INIS)
Ermolaev, B.I.; Lipatov, L.N.
1988-01-01
Using the method of factorization, equations are obtained for the inelastic on-shell amplitudes describing the asymptotic behavior of e + e - backward scattering with emission of bremsstrahlung photons in the doubly logarithmic approximation. Explicit expressions are found for these amplitudes in the case in which the photons are emitted with multi-Regge kinematics
Directory of Open Access Journals (Sweden)
J. C. Zier
2014-06-01
Full Text Available Intense pulsed active detection (IPAD is a promising technique for detecting fissile material to prevent the proliferation of special nuclear materials. With IPAD, fissions are induced in a brief, intense radiation burst and the resulting gamma ray or neutron signals are acquired during a short period of elevated signal-to-noise ratio. The 8 MV, 200 kA Mercury pulsed-power generator at the Naval Research Laboratory coupled to a high-power vacuum diode produces an intense 30 ns bremsstrahlung beam to study this approach. The work presented here reports on Mercury experiments designed to maximize the photofission yield in a depleted-uranium (DU object in the bremsstrahlung far field by varying the anode-cathode (AK diode gap spacing and by adding an inner-diameter-reducing insert in the outer conductor wall. An extensive suite of diagnostics was fielded to measure the bremsstrahlung beam and DU fission yield as functions of diode geometry. Delayed fission neutrons from the DU proved to be a valuable diagnostic for measuring bremsstrahlung photons above 5 MeV. The measurements are in broad agreement with particle-in-cell and Monte Carlo simulations of electron dynamics and radiation transport. These show that with increasing AK gap, electron losses to the insert and outer conductor wall increase and that the electron angles impacting the bremsstrahlung converter approach normal incidence. The diode conditions for maximum fission yield occur when the gap is large enough to produce electron angles close to normal, yet small enough to limit electron losses.
Zier, J. C.; Mosher, D.; Allen, R. J.; Commisso, R. J.; Cooperstein, G.; Hinshelwood, D. D.; Jackson, S. L.; Murphy, D. P.; Ottinger, P. F.; Richardson, A. S.; Schumer, J. W.; Swanekamp, S. B.; Weber, B. V.
2014-06-01
Intense pulsed active detection (IPAD) is a promising technique for detecting fissile material to prevent the proliferation of special nuclear materials. With IPAD, fissions are induced in a brief, intense radiation burst and the resulting gamma ray or neutron signals are acquired during a short period of elevated signal-to-noise ratio. The 8 MV, 200 kA Mercury pulsed-power generator at the Naval Research Laboratory coupled to a high-power vacuum diode produces an intense 30 ns bremsstrahlung beam to study this approach. The work presented here reports on Mercury experiments designed to maximize the photofission yield in a depleted-uranium (DU) object in the bremsstrahlung far field by varying the anode-cathode (AK) diode gap spacing and by adding an inner-diameter-reducing insert in the outer conductor wall. An extensive suite of diagnostics was fielded to measure the bremsstrahlung beam and DU fission yield as functions of diode geometry. Delayed fission neutrons from the DU proved to be a valuable diagnostic for measuring bremsstrahlung photons above 5 MeV. The measurements are in broad agreement with particle-in-cell and Monte Carlo simulations of electron dynamics and radiation transport. These show that with increasing AK gap, electron losses to the insert and outer conductor wall increase and that the electron angles impacting the bremsstrahlung converter approach normal incidence. The diode conditions for maximum fission yield occur when the gap is large enough to produce electron angles close to normal, yet small enough to limit electron losses.
International Nuclear Information System (INIS)
Yadav, Namita; Bhatt, Pragya; Singh, Raj; Singh, B.K.; Quarles, C.A.; Shanker, R.
2014-01-01
An apparatus is developed to measure the energy- and angular distributions of bremsstrahlung generated from collisions of energetic electrons with isolated atoms and molecules. A considerable reduction of thick target bremsstrahlung (TTB) background produced by scattered electrons from the chamber wall is achieved. Details of the experimental setup with regard to design of its components, experimental technique, data acquisition and analysis etc. are given and discussed. The reliability and performance of the setup are demonstrated by obtaining some test results on angular- and energy distributions of bremsstrahlung produced in collisions of 4.0 keV electrons with free argon atoms. These results are compared with the theoretical predictions of the ordinary- and the polarization bremsstrahlung emissions. In this comparison, the experimental data for energy distributions of BS photons are found to be in reasonable agreement while they are found to have noticeable differences in shape of angular distributions. - Highlights: • Experimental setup is developed to study DDCS of electron-bremsstrahlung from gaseous targets. • TTB from scattering chamber's wall is reduced appreciably by using a teflon cylinder. • Shape of DDCS of bremsstrahlung compared with the theories shows a satisfactory match. • Angular distributions of bremsstrahlung show anisotropy but still affected by TTB background photons
Effective source size, yield and beam profile from multi-layered bremsstrahlung targets
International Nuclear Information System (INIS)
Svensson, R.; Brahme, A.
1996-01-01
Modern conformal radiotherapy benefits from heterogeneous dose delivery using scanned narrow bremsstrahlung beams of high energy in combination with dynamic double focused multi-leaf collimation and purging magnets. When using a purging magnet to remove electrons and positrons the target space is limited and unorthodox thin multi-layered targets are needed. A computational technique has therefore been developed to determine the forward yield and the angular distributions of the bremsstrahlung beam as well as the size and location of the effective and the virtual photon point source for arbitrary multi-layer bremsstrahlung targets. The Gaussian approximation of the diffusion equation for the electrons has been used and convolved with the bremsstrahlung production process. For electrons with arbitrary emittance impinging on targets of any multi-layer and atomic number combination, the model is well applicable, at least for energies in the range 1-100 MeV. The intrinsic bremsstrahlung photon profile has been determined accurately by deconvolving the electron multiple scattering process from thin experimental beryllium target profiles. For electron pencil beams incident on a target of high density and atomic number such as tungsten, the size of the effective photon source stays at around a tenth of a millimetre. The effective photon source for low-Z materials such as Be, C and Al is located at depths from 3-7 mm in the target, decreasing with increasing atomic number. The effective photon source at off-axis positions then moves out considerably from the central axis, which should be considered when aligning collimators. For high-Z materials such as tungsten, the location of the effective photon source is at a few tenths of a millimetre deep. The virtual photon point source is located only a few tenths of a millimetre upstream of the effective photon source both for high- and low-Z materials. For 50 MeV electrons incident on multi-layered full range targets the radial
New knowledge about the bremsstrahlung image of strontium-89 with the scintillation camera
International Nuclear Information System (INIS)
Narita, Hiroto; Hirase, Kiyoshi; Uchiyama, Mayuki; Fukushi, Masahiro
2012-01-01
Strontium-89 ( 89 Sr) chloride has been used to treat metastases in bone. A method to visualize the distribution of 89 Sr chloride with a scintillation camera was developed in 1996. Studies using bremsstrahlung imaging have shown that 89 Sr accumulates in bone and that the bremsstrahlung generated from biological tissue surrounding bone does not exceed 30 keV. However, it was not clear how low-energy bremsstrahlung from bone can produce peak energy levels of around 75 keV. We speculate that a different (unidentified) factor is involved. The energy spectrum of an 89 Sr source was acquired with a scintillation camera with or without a low-to-medium-energy general-purpose collimator. The energy window was set at 20-650 keV for 4 windows. A 50-mm thick acrylic block was placed between the scintillation camera and the 89 Sr source to exclude the effects of bremsstrahlung. The energy spectrum of 89 Sr covered with lead was acquired using the scintillation camera without a collimator. With the collimator the energy spectrum curve was similar to that without the 50 mm of acrylic. The energy spectrum curve showed peaks at about 75, 170, and 520 keV. Without the collimator the energy spectrum showed a similar curve but no peak at 75 keV peak. The curve was similar to that obtained with the scintillation camera and the collimator; however, the curve obtained when the 89 Sr source had been placed in a lead container was similar to that obtained when the source was unshielded, and the collimator was not attached to the scintillation camera. If bremsstrahlung of 89 Sr produces an image, a low-energy spectrum region should decrease when acrylic is placed between the 89 Sr source and the scintillation camera. However, similar curves were obtained both with the acrylic in place and without the acrylic. Therefore, we believe that the radiation detected by the scintillation camera was not bremsstrahlung due to the beta rays of 89 Sr. Most 89 Sr preparations are contaminated by 85 Sr
International Nuclear Information System (INIS)
Baksht, R.B.; Fedunin, A.V.; Labetsky, A.Y.; Rousskich, A.G.; Shishlov, A.V.
1997-01-01
The electron magnetohydrodynamic model predicts the appearance of anode endash cathode voltage in the process of Rayleigh endash Taylor instability development during gas puff implosions. The appearance of the anode endash cathode voltage should be accompanied by the accelerated electron flow and the generation of the bremsstrahlung radiation. Experiments with neon and krypton gas puffs were performed on the GIT-4 [S. P. Bugaev, et al., Plasma Sci. 18, 115 (1990)] generator (1.6 MA, 120 ns) to observe the bremsstrahlung radiation during the gas puff implosion. Two spikes of the bremsstrahlung radiation were observed in the experiments. The first spike is connected with the gas breakdown; the second one is connected with the final stage of the implosion. The development of the RT instabilities does not initiate the bremsstrahlung radiation, therefore, the absence of anode endash cathode voltage is demonstrated. copyright 1997 American Institute of Physics
Energy Technology Data Exchange (ETDEWEB)
Tsechanski, A. [Ben-Gurion University of the Negev, Department of Nuclear Engineering, P.O. Box 653, Beer-Sheva 84105 (Israel); Bielajew, A.F. [Department of Nuclear Engineering and Radiological Sciences, The University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States); Archambault, J.P.; Mainegra-Hing, E. [National Research Council of Canada, Ionizing Radiation Standards Laboratory, Ottawa, ON K1A 0R6 (Canada)
2016-01-01
A new “one-stage” approach for production of {sup 99}Mo and other radioisotopes by means of an electron linear accelerator is described. It is based on using a molybdenum target both as a bremsstrahlung converter and as a radioisotope producing target for the production of {sup 99}Mo via the photoneutron reaction {sup 100}Mo(γ,n){sup 99}Mo. Bremsstrahlung characteristics, such as bremsstrahlung efficiency, angular distribution, and energy deposition for molybdenum targets were obtained by means of the EGSnrc Monte Carlo simulation code system. As a result of our simulations, it is concluded that a 60 MeV electron beam incident on a thick Mo target will have greater bremsstrahlung efficiency than the same thickness (in units of r{sub 0}) W target, for target thickness z > 1.84r{sub 0}, where r{sub 0} is the electron range. A 50 MeV electron beam incident on a Mo target will result in greater bremsstrahlung efficiency than the same thickness W target (in units of r{sub 0}) for target thickness case: z ⩾ 2.0r{sub 0}. It is shown for the one-stage approach with thicknesses of (1.84–2.0)r{sub 0}, that the {sup 99}Mo-production bremsstrahlung efficiency of a molybdenum target is greater by ∼100% at 30 MeV and by ∼70% at 60 MeV compared to the values for tungsten of the same thickness (in units of the appropriate r{sub 0}) in the traditional two-stage approach (W converter and separate {sup 99}Mo producing target). This advantage of the one-stage approach arises from the fact that the bremsstrahlung produced is attenuated only once from attenuation in the molybdenum converter/target. In the traditional, two-stage approach, the bremsstrahlung generated in the W-converter/target is attenuated both in the converter in the {sup 99}Mo-producing molybdenum target. The photoneutron production yield of molybdenum and tantalum (as a substitute for tungsten) target was calculated by means of the MCNP5 transport code. On the basis of these data, the specific activity
Impact of internal bremsstrahlung on the detection of γ rays from neutralinos
International Nuclear Information System (INIS)
Cannoni, M.; Gomez, M. E.; Sanchez-Conde, M. A.; Prada, F.; Panella, O.
2010-01-01
We present a detailed study of the effect of internal bremsstrahlung photons in the context of the minimal supersymmetric standard models and their impact on γ-ray dark matter annihilation searches. We find that, although this effect has to be included for the correct evaluation of fluxes of high energy photons from neutralino annihilation, its contribution is relevant only in models and at energies where the lines contribution is dominant over the secondary photons. Therefore, we find that the most optimistic supersymmetric scenarios for dark matter detection do not change significantly when including the internal bremsstrahlung. As an example, we review the γ-ray dark matter detection prospects of the Draco dwarf spheroidal galaxy for the MAGIC stereoscopic system and the CTA project. Though the flux of high energy photons is enhanced by an order of magnitude in some regions of the parameter space, the expected fluxes are still much below the sensitivity of the instruments.
Bremsstrahlung from Relativistic Heavy Ions in a Fixed Target Experiment at the LHC
International Nuclear Information System (INIS)
Mikkelsen, Rune E.; Uggerhøj, Ulrik I.; Sørensen, Allan H.
2015-01-01
We calculate the emission of bremsstrahlung from lead and argon ions in ultraperipheral collisions in a fixed target experiment (AFTER) that uses the LHC beams. With nuclear charges of Ze equal to 82e and 18e, respectively, these ions are accelerated to energies of 7 Tev × Z. The bremsstrahlung peaks around ≈100 GeV and the spectrum exposes the nuclear structure of the incoming ion. The peak structure is significantly different from the flat power spectrum pertaining to a point charge. Photons are predominantly emitted within an angle of 1/γ to the direction of ion propagation. Our calculations are based on the Weizsäcker-Williams method of virtual quanta with application of existing experimental data on photonuclear interactions.
International Nuclear Information System (INIS)
Astapenko, V.A.; Bureeva, L.A.; Lisitsa, V.S.
2000-01-01
Classical and quantum theories of polarization bremsstrahlung in a statistical (Thomas-Fermi) potential of complex atoms and ions are developed. The basic assumptions of the theories correspond to the approximations employed earlier in classical and quantum calculations of ordinary bremsstrahlung in a static potential. This makes it possible to study on a unified basis the contribution of both channels in the radiation taking account of their interference. The classical model makes it possible to obtain simple universal formulas for the spectral characteristics of the radiation. The theory is applied to electrons with moderate energies, which are characteristic for plasma applications, specifically, radiation from electrons on the argon-like ion KII at frequencies close to its ionization potential. The computational results show the importance of taking account of the polarization channel of the radiation for plasma with heavy ions
Rychkov, M. M.; Kaplin, V. V.; Malikov, E. L.; Smolyanskiy, V. A.; Stepanov, I. B.; Lutsenko, A. S.; Gentsel'man, V.; Vas'kovskiy, I. K.
2018-01-01
New microfocus source of hard bremsstrahlung (photon energy > 1 MeV), based on the betatron B-18 with a narrow Ta target inside, for high-resolution radiography and tomography is presented. The first studies of the source demonstrate its possibilities for practical applications to detect the microdefects in products made from heavy materials and to control gaps in joints of parts of composite structures of engineering facilities. The radiography method was used to investigate a compound object consisting of four vertically arranged steel bars between which surfaces were exposed gaps of 10 μm in width. The radiographic image of the object, obtained with a magnification of 2.4, illustrates the good sensitivity of detecting the gaps between adjacent bars, due to the small width of the linear focus of the bremsstrahlung source.
Experimental and analytical study of the bremsstrahlung radiation production at low energies
International Nuclear Information System (INIS)
Moran, P.; Gonzales, L.; Delgado, V.; Lopez, A.; Vano, E.
1986-01-01
The bremsstrahlung photon beam from an X-ray tube with chromium anode has been studied, for an electron energy of 60 Kev. In the experimental step, a new measurement method has been developed. This is based on the detection and measurement of the fluorescence produced when the photons from the tube impinge on targets which are used as calibrated flux monitors. The composition and physical characteristics of the targets are well-known. In the steps of experimental data treatment, an analytical study of the theoretical models describing thick target bremsstrahlung yield is performed. A factorization which accounts for the elemental physical processes is obtained, employing simple mathematical functions. The characteristic parameters found in the numerical fit process lead to results in good agreement with the experimental observations from other authors and predict theoretical exposure values in perfect agreement with the exposures measured for X-ray beams generated in several operating conditions. (author)
International Nuclear Information System (INIS)
Hasegawa, Shuichi; Takashima, Ryuta; Todoriki, Masaru; Kikkawa, Satoshi; Soda, Keita; Takano, Kei; Oishi, Yuji; Nayuki, Takuya; Fujii, Takashi; Nemoto, Koshichi
2011-01-01
We evaluate the simplified method using the Lambert-Beer law to measure the temperature of bremsstrahlung photon generated by an ultraintense laser. Analytical values are compared to the results of the Monte Carlo calculation of GEANT4 and they agreed very well on the condition of the appropriate distance between the attenuator and the detector. We performed the experiment to measure the temperature of bremsstrahlung x-ray emitted from a metal target irradiated by a Ti:sapphire laser with 76 mJ, 72 fs, 2.2 x 10 18 W/cm 2 . For a Cu target of 30 μm thick, the photon temperature was reasonably determined to be 0.18 MeV, which is in good agreement with previous studies.
Study on the feasibilities of nondestructive testing based on bremsstrahlung albedo
International Nuclear Information System (INIS)
Zhalsaraev, B.Zh.; Meshcheryakov, R.P.
1980-01-01
Presented are the results of experimental studies of the characteristics of gamma radiation reflected from homogeneous and laminated targets irradiated by 15 MeV betatron bremsstrahlung. Considered are the possibilities of simultaneous testing of thickness and of effective atomic number of materials, identification of heterogeneity of their structure, determination of the parameters of the media which are concealed by the layers of light substances of considerable thickness. The results obtained testify the usability of bremsstrahlung backscattering for contactless or remote control and differentiation of various media and objects, for the analysis and prospecting of surface ore manifestation and for processing control at the concentrating mills as well. The efficiency of the above method is underlined
International Nuclear Information System (INIS)
Mordasov, N.G.; Ulimov, V.N.; Bryksin, V.A.; Shiyan, V.D.
2005-01-01
One proposes a procedure and a device to monitor dynamic and integral characteristics of electron power beams of high-current pulsed accelerators (HCPA) operating under Bremsstrahlung radiation mode. One obtained static and dynamic transfer characteristics for various types of heterogenous targets-converters under operation of UIN-10 HCPA with up to 4 MeV energy electrons, up to 60 kA current and 6 x 10 -8 -2 x 10 -6 s pulse efficient duration. One demonstrated the capabilities of the complex diagnostics of acceleration of electron beams by HCPA with simultaneous determination of parameters of the Bremsstrahlung radiation at the local point of the field behind the target-converter [ru
Energy Technology Data Exchange (ETDEWEB)
Klevenhagen, S C [The Royal London Hospital, London (United Kingdom). Medical Physics Dept.
1996-08-01
Currently used dosimetry protocols for absolute dose determination of electron beams from accelerators in radiation therapy do not account for the effect of the bremsstrahlung contamination of the beam. This results in slightly erroneous doses calculated from ionization chamber measurements. In this report the deviation is calculated and an improved algorithm, which accounts for the effect of the bremsstrahlung component of the beam, is suggested. (author). 14 refs, 2 figs, 1 tab.
Energy Technology Data Exchange (ETDEWEB)
Menard, St
2006-07-01
Multigroup cross-section for the 3-dimensional Monte-Carlo transport code DIANE are produced by the ZADIG code. Although DIANE does not transport the electrons and positrons, the production of Bremsstrahlung photons induced by the electrons and positrons during their slowing down is taken into account in the ZADIG code because the electron-gamma cascade is an important process in high energy gamma ray transport. ZADIG does not distinguish positrons from electrons except for the positron annihilation. However, the user can turn on this direction. This report presents the latest improvements to the Bremsstrahlung model of ZADIG and to the positron annihilation algorithm implemented in the code. Positrons can annihilate either in flight or at rest in the latest release of ZADIG. As MCNP does not take into account the annihilation in flight, results of ZADIG-DIANE calculations are compared to the results of GEANT-4 in order to validate the annihilation scheme of ZADIG. The results with annihilation divided by the results without present similar trends between 0.6 and 10 MeV for the 2 codes (GEANT-4 and ZADIG-DIANE), in other words an influence of 5%, so the annihilation scheme programmed in ZADIG appears to be satisfying and can be considered as validated.
Polarimetry of coherent bremsstrahlung by analysis of the photon energy spectrum
International Nuclear Information System (INIS)
Darbinyan, S.; Hakobyan, H.; Jones, R.; Sirunyan, A.; Vartapetian, H.
2005-01-01
A method of coherent bremsstrahlung (CB) polarimetry based on the analysis of the shape of the photon energy spectrum is presented. The influence of a number of uncertainty sources, including the choice of atomic form-factors, has been analyzed. For a CB source consisting of a diamond radiator and multi-GeV electrons, an absolute accuracy of polarimetry at the level of 0.01-0.02 is attainable
One-loop corrections to the process e+e-→tt including hard bremsstrahlung
International Nuclear Information System (INIS)
Fleischer, J.; Riemann, T.; Werthenbach, A.; Leike, A.
2002-03-01
Radiative corrections to the process e + e - → t anti t are calculated in one-loop approximation of the Standard Model. There exist results from several groups. This talk provides further comparisons of the complete electroweak contributions, including hard bremsstrahlung. The excellent final agreement of the different groups allows to continue by working on a code for an event generator for TESLA and an extension to e + e - → 6 fermions. (orig.)
International Nuclear Information System (INIS)
Bajo, S.; Wyttenbach, A.
1986-12-01
The determination of phosphorus in biological materials by instrumental neutron activation via the reaction 31 P (n,γ) 32 P is described. The Bremsstrahlung produced by 32 P is measured in a well-type NaI(Tl) detector. The samples are measured within the polyethylene irradiation container with no changes between irradiation and measurement. The sources of error were studied and the proposed method was applied to the determination of phosphorus in ten internationally certified materials. (author)
Internal Bremsstrahlung spectrum of 204TI in the X-ray region
International Nuclear Information System (INIS)
Raghavendra, M.K.; Ramaswamy, C.R.
2001-01-01
The internal Bremsstrahlung spectrum from 204 TI has been measured, using magnetic deflector method, in the X-ray region. The corrected spectral intensity is compared with the Coulomb-corrected KUB theory in the energy region of 10 to 30 keV. The good agreement between experiment and theory in this energy region, suggests that 'detour effects' are negligible in the low energy region. (author)
Photoactivation of the p-nucleus 92Mo at the bremsstrahlung measurement place of ELBE
International Nuclear Information System (INIS)
Erhard, Martin Andreas
2010-01-01
By the high intensity of the bremsstrahlung of up to 20 MeV to 10 9 MeV -1 cm -2 s -1 in the energy range up to 20 MeV in the framework of this thesis for the first time not only the (γ,n), but also the (γ,p) reactions could be studied on 92 Mo at astrophysically relevant energies.
Energy Technology Data Exchange (ETDEWEB)
Döpp, A., E-mail: andreas.doepp@polytechnique.edu [LOA, ENSTA ParisTech, CNRS, École polytechnique, Université Paris-Saclay, 828 bd des Maréchaux, 91762 Palaiseau Cedex (France); Centro de Laseres Pulsados, Parque Cientfico, 37185 Villamayor, Salamanca (Spain); Guillaume, E.; Thaury, C.; Lifschitz, A. [LOA, ENSTA ParisTech, CNRS, École polytechnique, Université Paris-Saclay, 828 bd des Maréchaux, 91762 Palaiseau Cedex (France); Sylla, F. [SourceLAB SAS, 86 rue de Paris, 91400 Orsay (France); Goddet, J-P.; Tafzi, A.; Iaquanello, G.; Lefrou, T.; Rousseau, P. [LOA, ENSTA ParisTech, CNRS, École polytechnique, Université Paris-Saclay, 828 bd des Maréchaux, 91762 Palaiseau Cedex (France); Conejero, E.; Ruiz, C. [Departamento de Física Aplicada, Universidad de Salamanca, Plaza de laMerced s/n, 37008 Salamanca (Spain); Ta Phuoc, K.; Malka, V. [LOA, ENSTA ParisTech, CNRS, École polytechnique, Université Paris-Saclay, 828 bd des Maréchaux, 91762 Palaiseau Cedex (France)
2016-09-11
Laser wakefield acceleration permits the generation of ultra-short, high-brightness relativistic electron beams on a millimeter scale. While those features are of interest for many applications, the source remains constraint by the poor stability of the electron injection process. Here we present results on injection and acceleration of electrons in pure nitrogen and argon. We observe stable, continuous ionization-induced injection of electrons into the wakefield for laser powers exceeding a threshold of 7 TW. The beam charge scales approximately with the laser energy and is limited by beam loading. For 40 TW laser pulses we measure a maximum charge of almost 1 nC per shot, originating mostly from electrons of less than 10 MeV energy. The relatively low energy, the high charge and its stability make this source well-suited for applications such as non-destructive testing. Hence, we demonstrate the production of energetic radiation via bremsstrahlung conversion at 1 Hz repetition rate. In accordance with GEANT4 Monte-Carlo simulations, we measure a γ-ray source size of less than 100 μm for a 0.5 mm tantalum converter placed at 2 mm from the accelerator exit. Furthermore we present radiographs of image quality indicators.
Energy Technology Data Exchange (ETDEWEB)
An, Z. E-mail: anzhu@scu.edu.cn; Liu, M.T
2002-10-01
In this paper, the efficiency calibration of a Si(Li) detector in the low-energy region down to 0.58 keV has been performed using thick-carbon-target bremsstrahlung by 19 keV electron impact. The shape of the efficiency calibration curve was determined from the thick-carbon-target bremsstrahlung spectrum, and the absolute value for the efficiency calibration was obtained from the use of {sup 241}Am radioactive standard source. The modified Wentzel's formula for thick-target bremsstrahlung was employed and it was also compared with the most recently developed theoretical model based upon the doubly differential cross-sections for bremsstrahlung of Kissel, Quarles and Pratt. In the present calculation of theoretical bremsstrahlung, the self-absorption correction and the convolution of detector's response function with the bremsstrahlung spectrum have simultaneously been taken into account. The accuracy for the efficiency calibration in the low-energy region with the method described here was estimated to be about 6%. Moreover, the self-absorption correction calculation based upon the prescription of Wolters et al. has also been presented as an analytical factor with the accuracy of {approx}1%.
Pandit, Rishi R.; Becker, Valerie R.; Barrington, Kasey; Thurston, Jeremy; Ramunno, Lora; Ackad, Edward
2018-04-01
An intense, short laser pulse incident on rare-gas clusters can produce nano-plasmas containing energetic electrons. As these electrons undergo scattering, from both phonons and ions, they emit bremsstrahlung radiation. Here, we compare a theory of bremsstrahlung emission appropriate for the interaction of intense lasers with matter using soft-core potentials and Coulombic potentials. A new scaling for the radiation cross-section and the radiated power via bremsstrahlung is derived for a soft-core potential (which depends on the potential depth) and compared with the Coulomb potential. Calculations using the new scaling are performed for electrons in vacuum ultraviolet, infrared and mid-infrared laser pulses. The radiation cross-section and the radiation power via bremsstrahlung are found to increase rapidly with increases in the potential depth of up to around 200 eV and then become mostly saturated for larger depths while remaining constant for the Coulomb potential. In both cases, the radiation cross-section and the radiation power of bremsstrahlung decrease with increases in the laser wavelength. The ratio of the scattering amplitude for the soft-core potential and that for the Coulombic potential decreases exponentially with an increase in momentum transfer. The bremsstrahlung emission by electrons in plasmas may provide a broadband light source for diagnostics.
Hard X-ray bremsstrahlung production in solar flares by high-energy proton beams
Emslie, A. G.; Brown, J. C.
1985-01-01
The possibility that solar hard X-ray bremsstrahlung is produced by acceleration of stationary electrons by fast-moving protons, rather than vice versa, as commonly assumed, was investigated. It was found that a beam of protons which involves 1836 times fewer particles, each having an energy 1836 times greater than that of the electrons in the equivalent electron beam model, has exactly the same bremsstrahlung yield for a given target, i.e., the mechanism has an energetic efficiency equal to that of conventional bremsstrahlung models. Allowance for the different degrees of target ionization appropriate to the two models (for conventional flare geometries) makes the proton beam model more efficient than the electron beam model, by a factor of order three. The model places less stringent constraints than a conventional electron beam model on the flare energy release mechanism. It is also consistent with observed X-ray burst spectra, intensities, and directivities. The altitude distribution of hard X-rays predicted by the model agrees with observations only if nonvertical injection of the protons is assumed. The model is inconsistent with gamma-ray data in terms of conventional modeling.
Application of split field technique with 42 MeV betatron bremsstrahlung
Energy Technology Data Exchange (ETDEWEB)
Spurny, V; Caha, A; Krystof, V; Ott, O [Vyzkumny Ustav Klinicke a Experimentalni Onkologie, Brno (Czechoslovakia)
1977-03-01
The split field technique of external irradiation in oncology is described. A 120x28x79 mm lead shielding block was manufactured for a bremsstrahlung radiation with 42 MeV maximum energy. The block was secured to a holder whose design corresponded to tube holders. The block shielding capacity was tested by phantom measurements at a focal depth of 130 mm and at a distance of the block from the phantom surface of 990 mm. For the 42 MeV bremsstrahlung the reduction was found to be 15% of the focal dose in the 20x20 cm/sup 2/ field in the focal depth at a distance of 1200 mm from the bremsstrahlung focus. Dose distribution was established by using two opposite fields in combination as well as by the courses of the maximum and the relative doses in variation with the female patient's antero-posterior diameter. The results show that the split field technique permits a short adjustment time, is simple and reproducible. As against cobalt application, the beam characteristics permit reducing the integral dose.
High-resolution x-ray spectroscopy of coherent bremsstrahlung fine structure
International Nuclear Information System (INIS)
Lund, M.W.
1989-01-01
The aim of this research was to provide experimental evidence for fine structure due to umklapp by distinct reciprocal lattice vectors in coherent bremsstrahlung spectra. The spontaneous emission of photons by relativistic electrons transversing thin crystals is made possible by recoil of the crystal, which absorbs momentum in multiples of ℎG where G is a reciprocal lattice vector. Previous work in the MeV-GeV beam energy range used detectors whose energy resolution was greater than 10%. By fitting a Johann wavelength dispersive spectrometer to a transmission electron microscope the author obtained coherent bremsstrahlung spectra of very high quality with energy resolution of 1%. Important to this result were also the fine angular collimation, small energy width of the electron beam in the microscope, and the accurate control of crystal orientation possible in a modern goniometer stage. The theory of the design of bent crystal x-ray spectrometers is extended to include effects of defocus and aberrations. The theory for diffraction from a stationary three dimensional grating due to a dipole radiator moving at relativistic speeds is derived as well as several other broadening mechanisms stemming from experimental variables. This dissertation provides the first experimental observations and corresponding theoretical background for the fine structure of coherent bremsstrahlung due to umklapp by different G-vectors in the same reciprocal lattice plane
Inverse problems of geophysics
International Nuclear Information System (INIS)
Yanovskaya, T.B.
2003-07-01
This report gives an overview and the mathematical formulation of geophysical inverse problems. General principles of statistical estimation are explained. The maximum likelihood and least square fit methods, the Backus-Gilbert method and general approaches for solving inverse problems are discussed. General formulations of linearized inverse problems, singular value decomposition and properties of pseudo-inverse solutions are given
Reverse Universal Resolving Algorithm and inverse driving
DEFF Research Database (Denmark)
Pécseli, Thomas
2012-01-01
Inverse interpretation is a semantics based, non-standard interpretation of programs. Given a program and a value, an inverse interpreter finds all or one of the inputs, that would yield the given value as output with normal forward evaluation. The Reverse Universal Resolving Algorithm is a new...... variant of the Universal Resolving Algorithm for inverse interpretation. The new variant outperforms the original algorithm in several cases, e.g., when unpacking a list using inverse interpretation of a pack program. It uses inverse driving as its main technique, which has not been described in detail...... before. Inverse driving may find application with, e.g., supercompilation, thus suggesting a new kind of program inverter....
International Nuclear Information System (INIS)
Bakht, M.K.; Jabal-Ameli, H.; Ahmadi, S.J.; Sadeghi, M.; Sadjadi, S.; Tenreiro, Claudio
2012-01-01
Praseodymium-142 [T 1/2 =19.12 h, E β -=2.162 MeV (96.3%), E γ =1575 keV (3.7%)] is one of the 141 Pr radioisotopes. Many studies have been attempted to assess the significance of usage 142 Pr in radionuclide therapy. In many studies, the dosimetric parameters of 142 Pr sources were calculated by modeling 142 Pr sources in the water phantom and scoring the energy deposited around it. However, the medical dosimetry calculations in water phantom consider Bremsstrahlung production, raising the question: ''How important is to simulate human tissues instead of using water phantom?'' This study answers these questions by estimation of 142 Pr Bremsstrahlung parameters. The Bremsstrahlung parameters of 142 Pr as therapeutic beta nuclides in different human tissues (adipose, blood, brain, breast, cell nucleus, eye lens, gastrointestinal tract, heart, kidney, liver, lung deflated, lymph, muscle, ovary, pancreas, cartilage, red marrow, spongiosa, yellow marrow, skin, spleen, testis, thyroid and different skeleton bones) were calculated by extending the national council for radiation protection model. The specific Bremsstrahlung constant (Γ Br ), probability of energy loss by beta during Bremsstrahlung emission (P Br ) and Bremsstrahlung activity (A release ) Br were estimated. It should be mentioned that Monte Carlo simulation was used for estimation of 142 Pr Bremsstrahlung activity based on the element compositions of different human tissues and the calculated exposures from the anthropomorphic phantoms. Γ Br for yellow marrow was smallest amount (1.1962 x 10 -3 C/kg-cm 2 /MBq-h) compared to the other tissues and highest for cortical bone (2.4764 x 10 -3 C/kg-cm 2 /MBq-h), and, overall, Γ Br for skeletal tissues were greater than other tissues. In addition, Γ Br breast was 1.8261 x 10 -3 C/kg-cm 2 /MBq-h which was greater than sacrum and spongiosa bones. Moreover, according to (A release ) Br of 142 Pr, the patients receiving 142 Pr do not have to be hospitalized for
International Nuclear Information System (INIS)
Johnson, M; McNabb, D
2006-01-01
An important applied technology is a tunable mono-energetic photon source [1]. These sources are made of relativistic electron accelerators coupled to low-energy lasers, which produce high-energy, mono-energetic-rays. One challenge associated with systems such as this is a continuum of bremsstrahlung background created when an electron beam passes through an aperture of some sort and the electron bunch or its halo impinges on the aperture pictured in figure 1. For instance, in the current T-REX [1] design for the interaction point between the laser- and electron-beam, the electron-beam passes through the center of a mirror used to reflect the laser. There is a potential with this design that bremsstrahlung radiation may be produced at the edges of the mirror openings and contaminate the mono-energetic photon beam. Certain applications [2] may be sensitive to this contamination. To reduce the bremsstrahlung contaminate a collimator (thickness ∼24in. (calculated from XCOM database [3]) to attenuate by a factor of 10 -3 the 112MeV photons expected in the T-REX demonstration [1]) is situated between the aperture and target. To maximize the brightness of the photon-beam, the collimator opening must be no less than the size of the photon-beam spot size expected to be about 1mm. This fixes the collimator opening. a priori the aperture size must be greater than the collimator opening and is a function distance between the aperture and collimator. In this paper we focus on two approaches to estimate the aperture size, given a collimator and a target whose sizes and distances from the aperture are given. In the next section we will discuss these approaches
The stonehenge technique: a new method of crystal alignment for coherent bremsstrahlung experiments
Livingston, Kenneth
2005-08-01
In the coherent bremsstrahlung technique a thin diamond crystal oriented correctly in an electron beam can produce photons with a high degree of linear polarization.1 The crystal is mounted on a goniometer to control its orientation and it is necessary to measure the angular offsets a) between the crystal axes and the goniometer axes and b) between the goniometer and the electron beam axis. A method for measuring these offsets and aligning the crystal was developed by Lohman et al, and has been used successfully in Mainz.2 However, recent attempts to investigate new crystals have shown that this approach has limitations which become more serious at higher beam energies where more accurate setting of the crystal angles, which scale with l/Ebeam, is required. (Eg. the recent installation of coherent bremsstrahlung facility at Jlab, with Ebeam = 6 GeV ) This paper describes a new, more general alignment technique, which overcomes these limitations. The technique is based on scans where the horizontal and vertical rotation axes of the goniometer are adjusted in a series of steps to make the normal to the crystal describe a cone of a given angle. For each step in the scan, the photon energy spectrum is measured using a tagging spectrometer, and the offsets between the electron beam and the crystal lattice are inferred from the resulting 2D plot. Using this method, it is possible to align the crystal with the beam quickly, and hence to set any desired orientation of the crystal relative to the beam. This is essential for any experiment requiring linearly polarized photons produced via coherent bremsstrahlung, and is also required for a systematic study of the channeling radiation produced by the electron beam incident on the crystal.
Secondary bremsstrahlung and the energy-conservation aspects of kerma in photon-irradiated media.
Kumar, Sudhir; Nahum, Alan E
2016-02-07
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
Measurements of bremsstrahlung spectra of Lanzhou ECR Ion Source No. 3 (LECR3)
International Nuclear Information System (INIS)
Zhao, H.Y.; Zhao, H.W.; Ma, X.W.; Zhang, S.F.; Feng, W.T.; Zhu, X.L.; Zhang, Z.M.; He, W.; Sun, L.T.; Feng, Y.C.; Cao, Y.; Li, J.Y.; Li, X.X.; Wang, H.; Ma, B.H.
2006-01-01
In order to diagnose the electron cyclotron resonance (ECR) plasma, electron bremsstrahlung spectra were measured by a HPGe detector on Lanzhou ECR Ion Source No. 3 at IMP. The ion source was operated with argon under various working conditions, including different microwave power, mixing gas, extraction high voltage (HV), and so on. Some of the measured spectra are presented in this article. The dependence of energetic electron population on mixing gas and extraction HV is also described. Additionally, we are looking forward to further measurements on SECRAL (Superconducting ECR Ion Source with Advanced design at Lanzhou)
Monte Carlo 20 and 45 MeV Bremsstrahlung and dose-reduction calculations
Energy Technology Data Exchange (ETDEWEB)
Goosman, D.R.
1984-08-14
The SANDYL electron-photon coupled Monte Carlo code has been compared with previously published experimental bremsstrahlung data at 20.9 MeV electron energy. The code was then used to calculate forward-directed spectra, angular distributions and dose-reduction factors for three practical configurations. These are: 20 MeV electrons incident on 1 mm of W + 59 mm of Be, 45 MeV electrons of 1 mm of W and 45 MeV electrons on 1 mm of W + 147 mm of Be. The application of these results to flash radiography is discussed. 7 references, 12 figures, 1 table.
Monte Carlo 20 and 45 MeV Bremsstrahlung and dose-reduction calculations
International Nuclear Information System (INIS)
Goosman, D.R.
1984-01-01
The SANDYL electron-photon coupled Monte Carlo code has been compared with previously published experimental bremsstrahlung data at 20.9 MeV electron energy. The code was then used to calculate forward-directed spectra, angular distributions and dose-reduction factors for three practical configurations. These are: 20 MeV electrons incident on 1 mm of W + 59 mm of Be, 45 MeV electrons of 1 mm of W and 45 MeV electrons on 1 mm of W + 147 mm of Be. The application of these results to flash radiography is discussed. 7 references, 12 figures, 1 table
Spectral tomographic analysis of Bremsstrahlung X-rays generated in a laser-produced plasma
Czech Academy of Sciences Publication Activity Database
Rhee, Y.-J.; Nam, S. M.; Peebles, W.; Sawada, H.; Wei, M.; Vaisseau, X.; Sasaki, T.; Giuffrida, Lorenzo; Hulin, S.; Vauzour, B.; Santos, J.J.; Batani, D.; McLean, H. S.; Patel, P. K.; Li, Y.; Yuan, D. W.; Zhang, K.; Zhong, J. Y.; Fu, C. B.; Hua, N.; Li, K.; Zhang, Y.; Zhu, J. Q.; Kim, I. J.; Jeon, J. H.; Jeong, T.M.; Choi, I.W.; Lee, H. W.; Sung, J.H.; Lee, S.K.; Nam, C.H.
2016-01-01
Roč. 34, č. 4 (2016), s. 645-654 ISSN 0263-0346 R&D Projects: GA MŠk LQ1606; GA MŠk EF15_008/0000162 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : Bremsstrahlung X-ray * filter stack spectrometer * laser-produced plasma Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.420, year: 2016
Fast measurement of luminosity at LEP by detecting the single bremsstrahlung photons
International Nuclear Information System (INIS)
Bini, C.; De Zorzi, G.; Diambrini Palazzi, G.; Di Cosimo, G.; Di Domenico, A.; Gauzzi, P.; Zanello, D.
1991-01-01
Luminosity and beam angular divergence have been measured at LEP with a fast monitor based on the single bremsstrahlung process e + e - → e + e - γ. The photons emitted at the interaction point 1 are detected by an electromagnetic calorimeter: both the photon energy and the impact point are measured. The beam angular divergence and the luminosity are determined in few minutes with a statistical error of 1%. With the present experimental layout the systematic error is of few percent; it would be reduced by performing the measurement on an experimental interaction point. (orig.)
Cooling effect in emissions of 103mRh excited by bremsstrahlung
International Nuclear Information System (INIS)
Cheng, Y; Xia, B; Chen, C P
2009-01-01
Nonlinear characteristic emissions of Kα, Kβ and γ with a significant triplet splitting at room temperature are observed from the long-lived nuclear state of 103m Rh excited by bremsstrahlung irradiation. A pronounced phase-transition-like narrowing of the emission profiles occurs immediately after the sample is cooled down to 77 K. The room temperature profiles reappear again abruptly and almost reversibly as the temperature drifts freely back to approximately the ice point after the filling with liquid nitrogen is stopped. These emission properties at 300 K and at low temperature may indicate that the 103m Rh nuclei are in collective states.
Energy Technology Data Exchange (ETDEWEB)
Zinchenko, V F; Tulisov, E V; Chlenov, A M; Shiyan, V D [Research Institute of Scientific Instruments, Turaevo-Lytkarino (Russian Federation)
1997-12-31
The results of experimental and theoretical optimization of the linear induction accelerator (LIA) design are presented. The major aim of the investigations was to maximize the bremsstrahlung output near the target face. The work was carried out in two stages: l) modernization of the injector module and 2) focusing of the relativistic electron beam (REB) produced at the exit of the accelerating system (AS) in the increasing axial magnetic field. In addition, the methods of diagnostics of angular and energetic parameters of REB based on measurements of radiation dose fields behind the target are described. (author). 2 figs., 4 refs.
Experimental study of the electron-atom Bremsstrahlung emission in an argon plasma jet
International Nuclear Information System (INIS)
Ranson, P.; Vallee, O.; Chapelle, J.
1977-01-01
Electron-neutral atom bremsstrahlung is studied between 0.4 μm and 5 μm in a decaying argon plasma jet; in visible and infra-red range, some discrepancies appear between experimental results and theoretical calculations of different authors (Geltman, Stallcop). In the infra-red, the discrepancy can be partly explained because theoretical elastic cross sections are higher than experimental values in the vicinity of the Ramsauer minimum. In the visible range, a very small amount of fast electrons due to superelastic and recombination collisions explain the observed discrepancy [fr
Calculation of Bremsstrahlung radiation of electrons on atoms in wide energy range of photons
Romanikhin, V P
2002-01-01
The complete spectra of the Bremsstrahlung radiation on the krypton atoms within the range of the photon energies of 10-25000 eV and lanthanum near the potential of the 4d-shell ionization is carried out. The atoms summarized polarizability is calculated on the basis of the simple semiclassical approximation of the local electron density and experimental data on the photoabsorption. The comparison with the calculational results is carried out through the method of distorted partial waves (PDWA) for Kr and with the experimental data on La
Energy Technology Data Exchange (ETDEWEB)
Bossamykin, V S; Gerasimov, A I; Gordeev, V S; Grishin, A V; Gritsina, V P; Tarasov, A D; Fedotkin, A S; Lazarev, S A; Averchenkov, A Ya [All-Russian Scientific Research Institute of Experimental Physics, Sarov (Russian Federation)
1997-12-31
The operating mode was studied of the LIA-30 linear induction accelerator ({approx} 40 MeV, {approx} 100 kA, {approx} 30 ns) with the generation of two bremsstrahlung pulses separated by a specified time interval from 0 to 5 {mu}s. In the accelerating channel an additional tube cathode was installed, and a synchronization system for two accelerating module groups triggering the formation and acceleration, at different initial times, of two annular electron beams with different outer diameters was changed. The energy limit of each beam electron acceleration can be controlled, and the energy sum limit is {<=} 540 MeV. (author). 2 tabs., 2 figs.
Light meson production and pp-bremsstrahlung at the COSY time-of-flight spectrometer
International Nuclear Information System (INIS)
Kuhlmann, E.; Brand, H.; Brand, S.; Cloth, P.; Dahmen, M.; Drueke, V.; Eyrich, W.; Filges, D.; Freiesleben, H.; Fritsche, A.; Kilian, K.; Kirsch, M.; Koch, H.; Kraft, R.A.; Krug, J.; Lange, S.; Machner, H.; Matthaey, H.; Michel, P.; Mirz, R.; Moeller, K.; Morsch, H.P.; Naumann, B.; Naumann, L.; Oelert, W.; Parsch, A.; Paul, N.; Ringe, P.; Roderburg, E.; Roehrich, K.; Roeser, A.; Rogge, M.; Schmidt, G.; Schmidt, M.; Schult, O.; Sefzick, T.; Steinke, M.; Stinzing, F.; Stratmann, R.; Turek, P.; Werding, R.; Wirth, S.
1993-01-01
Experiments on light meson production and pp-bremsstrahlung as planned for the initial stage at COSY are discussed. Special emphasis will be placed on near-threshold behaviour where due to kinematics all particles are forced into a rather narrow cone around the beam axis. A specially designed charged particle detector system will be used which not only covers the complete forward hemisphere of 2π in the laboratory system but additionally shows maximum resolution in the extreme forward direction with only moderate cuts in the minimally required energy of all ejectiles. (orig.)
Angular distribution of the bremsstrahlung emission during lower-hybrid current drive on PLT
International Nuclear Information System (INIS)
von Goeler, S.; Stevens, J.; Bernabei, S.
1985-06-01
The bremsstrahlung emission from the PLT tokamak during lower-hybrid current drive has been measured as a function of angle between the magnetic field and the emission direction. The emission is peaked strongly in the forward direction, indicating a strong anisotropy of the electron-velocity distribution. The data demonstrate the existence of a nearly flat tail of the velocity distribution, which extends out to approximately 500 keV and which is interpreted as the plateau created by Landau damping of the lower-hybrid waves
Internal bremsstrahlung accompanying non-unique second-forbidden β-decay of 36Cl
International Nuclear Information System (INIS)
Basha, A.M.; Khalil, E.I.; Hussein, M.; Ragab, H.S.; El-Konsol, S.
1991-01-01
The inner Bremsstrahlung spectrum (I.B.) associated with the non-unique second forbidden β-transition of 36 Cl was measured using a single channel NaI (Tl) scintillation spectrometer. After making all the necessary corrections, the experimental results were compared with the corresponding theoretical distributions due to the KUB, Lewis and Ford, Nilsson, Ford and Martin and Chang and Falkoff. Also a comparison with those calculated according to Nilsson theory after applying the shape correction factor (M. KUB) was done. The measured spectrum is found to show fairly good agreement with M. KUB theory and is found to deviate thereafter from all five theories. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Cremer, T.; Tatchyn, R. [Stanford Univ., CA (United States)
1995-12-31
One of the more promising technologies for developing minimal-length insertion devices for linac-driven, single-pass Free Electron Lasers (FELs) operating in the x-ray range is based on the use of superconducting (SC) materials. In recent FEL simulations, for example, a bifilar helical SC device with a 2 cm period and 1.8 T field was found to require a 30 m saturation length for operation at 1.5{Angstrom} on a 15 GeV linac, more than 40% shorter than an alternative hybrid/permanent magnet (hybrid/PM) undulator. AT the same time, however, SC technology is known to present characteristic difficulties for insertion device design, both in engineering detail and in operation. Perhaps the most critical problem, as observed, e.g., by Madey and co-workers in their initial FEL experiments, was the frequent quenching induced by scattered electrons upstream of their (bifilar) device. Postulating that this quenching was precipitated by directly-scattered or bremsstrahlung-induced particle energy deposited into the SC material or into material contiguous with it, the importance of numerical and experimental characterizations of this phenomenon for linac-based, user-facility SC undulator design becomes evident. In this paper we discuss selected prior experimental results and report on initial EGS4 code studies of scattered and bremsstrahlung induced particle energy deposition into SC structures with geometries comparable to a small-bore bifilar helical undulator.
A study of LPM suppression of bremsstrahlung at 25 GeV
International Nuclear Information System (INIS)
Anthony, P.; Becker-Szendy, R.; Bosted, P.
1993-03-01
We are making an accurate measurement of the LPM suppression of bremsstrahlung with 25 GeV electrons. By using a 120 pulses per second beam, a precise BGO calorimeter, and spectrometer to tag the outgoing electrons, we are able to make an accurate measurement of the bremsstrahlung photons in the 0-400 MeV region, where the Bethe Heitler and LPM predictions differ. We are taking data with targets made of carbon, uranium, tungsten and iron, with thicknesses in the 2% to 6% X 0 range. In addition, we are taking data with two very thin gold targets. The latter have thicknesses that are comparable to or less than the LPM formation zone length, and so should not exhibit LPM suppression. We are also studying photons of a few MeV in energy, to test the closely related longitudinal density effect predicted by Ter-Mikaelian in which very low energy photon emission is suppressed due to dielectric effects of the medium
Bremsstrahlung emission coefficient of a plasma in a uniform magnetic field
International Nuclear Information System (INIS)
Pangborn, R.J.
1976-01-01
The leading (electron-ion, dipole) contribution to the bremsstrahlung spectrum of a Maxwellian plasma in a constant, uniform magnetic field is calculated. The plasma is assumed infinite and fully ionized. A simpler, more direct derivation of Kirchoff's Law for anisotropic media is presented. The plasma dispersion relation is then found using previously obtained expressions for the conductivity tensor (accurate to first order in collisional effects). From the dispersion the collisional damping, assumed small, is obtained and by means of Kirchoff's Law an expression for the bremsstrahlung emission coefficient is written. No terms of order (kappa 2 lambda 2 0 ) or higher are included. For wave frequencies large compared with the plasma and electron cyclotron frequencies (ω 2 much greater than ω 2 rho, ω 2 much greater than Ω 3 ) an expansion of the exact result is given accurate to fourth order in Ω/ω and ω rho/ω. The result is found to disagree with previous high frequency expressions. Analysis of the exact expression reveals that for certain frequencies and directions of propagation the emission spectrum exhibits a resonance quality. The results are presented in such fashion that for various magnetic field strengths the frequency of the resonant emission at arbitrary angle relative to the field is easily obtained. These phenomena arise due to the influence of the magnetic fieldon the dielectric properties of the plasma and not because of its effect on the binary collision process. A physical explanation of the results is presented
Simultaneous investigation of parent electrons and bremsstrahlung x rays by rocket-borne detectors
International Nuclear Information System (INIS)
Vij, K.K.; Venkatesan, D.; Sheldon, W.R.; Kern, J.W.; Benbrook, J.R.; Whalen, B.A.
1975-01-01
Simultaneous measurements of the energy spectrum of precipitating electrons and the resulting bremsstrahlung X ray spectrum were carried out during an auroral event on March 3, 1971, at the Churchill Research Range, Manitoba, Canada. The electron data were obtained with detectors on a Black Brant VB sounding rocket (275-km apogee), while the X ray flux was measured by an instrument package that was boosted to 60 km on an Arcas rocket. The X ray package was deployed on a parachute at apogee to provide a slow descent through the atmosphere. Thick target bremsstrahlung theory is used to calculate the X ray flux produced by the incident electrons, and a Monte Carlo method is used to predict the X ray spectrum at various altitudes appropriate for comparison with the measured X ray data. Satisfactory agreement between theory and experiment is obtained, and the value of the constant in the thick target theory has been estimated to be (2plus-or-minus0.5) times10 -5
Simultaneous investigation of parent electrons and bremsstrahlung x rays by Rocket--Borne detectors
International Nuclear Information System (INIS)
Vij, K.K.; Venkatesan, D.; Sheldon, W.R.; Kern, J.W.; Benbrook, J.R.; Whalen, B.A.
1975-01-01
Simultaneous measurements of the energy spectrum of precipitating electrons and the resulting bremsstrahlung X ray spectrum were carried out during an auroral event on March 3, 1971, at the Churchill Research Range, Manitoba, Canada. The electron data were obtained with detectors on a Black Brant VB sounding rocket (275-km apogee), while the X ray flux was measured by an instrument package that was boosted to 60 km on an Arcas rocket. The X ray package was deployed on a parachute apogee to provide a slow descent through the atmosphere. Thick target bremsstrahlung theory is used to calculate the X ray flux produced by the incident electrons, and a Monte Carlo method is used to predict the X ray spectrum at various altitudes appropriate for comparison with the measured X ray data. Satisfactory agreement between theory and experiment is obtained, and the value of the constant in the thick target theory has been estimated to be (2plus-or-minus0.5) times10 -5 . (auth)
'Atomic Bremsstrahlung': Retrospectives, current status and perspectives
Energy Technology Data Exchange (ETDEWEB)
Amusia, M.Ya. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel) and Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation)]. E-mail: Amusia@vms.huji.ac.il
2006-10-15
We describe here the 'Atomic bremsstrahlung' (AB)-emission of continuous spectrum electromagnetic radiation, which is generated in collisions of particles that have internal deformable structure that includes positively and negatively charged constituents. The deformation of one or both colliding partners induces multiple, mainly dipole, time-dependent electrical moments that become a source of radiation. The history of AB invention is presented and its unusual in comparison to ordinary bremsstrahlung (OB) properties, are discussed. As examples, fast electron atom, non-relativistic and relativistic collisions are considered. Attention is given to ion-atom and atom-atom collisions. Specifics of 'elastic' and 'inelastic' (i.e. radiation accompanied by destruction of collision partners) AB will be mentioned. Attention will be given to possible manifestation of AB in nature and in some exotic systems, for instance scattering of electrons upon muonic hydrogen. Some cooperative effects connected to AB will be considered. New classical schemes similar to AB will be presented.
Bremsstrahlung-induced highly penetrating probes for nondestructive assay and defect analysis
Selim, F A; Harmon, J F; Kwofie, J; Spaulding, R; Erickson, G; Roney, T
2002-01-01
Nondestructive assay and defect analysis probes based on bremsstrahlung-induced processes have been developed to identify elements and probe defects in large volume samples. Bremsstrahlung beams from (electron accelerators) with end-point energies both above and below neutron emission threshold have been used. Below neutron emission threshold these beams (from 6 MeV small pulsed linacs), which exhibit high penetration, create positrons via pair production inside the material and produce X-ray fluorescence (XRF) radiation. Chemical assays of heavy elements in thick samples up to 10 g/cm sup 2 thick are provided by energy dispersive XRF measurements. The pair-produced positrons annihilate within the material, thereby emitting 511 keV gamma radiation. Doppler broadening spectroscopy of the 511 keV radiation can be performed to characterize the material and measure defects in samples of any desired thickness. This technique has successfully measured induced strain due to tensile stress in steel samples of 0.64 cm...
NN wave function at small distances and hard bremsstrahlung in the process pp→ppγ
International Nuclear Information System (INIS)
Neudatchin, V. G.; Khokhlov, N. A.; Shirokov, A. M.; Knyr, V. A.
1997-01-01
Various possibilities of studying the NN wave function at small distances--and in particular, quark degrees of freedom in the NN system--are discussed. It is shown that there is such a possibility at moderate energies--namely, hard bremsstrahlung in the process pp→ppγ at proton-beam energies in the range 350-450 MeV permits distinguishing between the pp wave function with nodes in S and P waves that corresponds to the Moscow potential of NN interaction from functions obtained with repulsive-core mesonic potentials. In the regions where photon energies in the c.m.s. are maximal (forward and backward photon emission angles in the laboratory frame), the pp→ppγ cross section calculated with the Moscow potential has maxima at which it is approximately five times larger than the analogous cross section calculated with repulsive-core mesonic potentials. The coordinate-representation formalism of the theory of bremsstrahlung is expounded
Simulations of bremsstrahlung emission in ultra-intense laser interactions with foil targets
Vyskočil, Jiří; Klimo, Ondřej; Weber, Stefan
2018-05-01
Bremsstrahlung emission from interactions of short ultra-intense laser pulses with solid foils is studied using particle-in-cell (PIC) simulations. A module for simulating bremsstrahlung has been implemented in the PIC loop to self-consistently account for the dynamics of the laser–plasma interaction, plasma expansion, and the emission of gamma ray photons. This module made it possible to study emission from thin targets, where refluxing of hot electrons plays an important role. It is shown that the angular distribution of the emitted photons exhibits a four-directional structure with the angle of emission decreasing with the increase of the width of the target. Additionally, a collimated forward flash consisting of high energy photons has been identified in thin targets. The conversion efficiency of the energy of the laser pulse to the energy of the gamma rays rises with both the driving pulse intensity, and the thickness of the target. The amount of gamma rays also increases with the atomic number of the target material, despite a lower absorption of the driving laser pulse. The angular spectrum of the emitted gamma rays is directly related to the increase of hot electron divergence during their refluxing and its measurement can be used in experiments to study this process.
Possibilities for a neutron-proton bremsstrahlung experiment at WNR/LAMPF
International Nuclear Information System (INIS)
Wender, S.A.; Nelson, R.O.; Laymon, C.M.; Schillaci, M.; Gibson, B.F.
1990-01-01
The high energy and high intensity of the continuous energy (white) neutron source at the WNR target area of the Los Alamos Meson Physics Facility (LAMPF) may make possible a direct measurement of the neutron-proton bremsstrahlung (NPB) cross section. Several recent papers have discussed the operation of the WNR white neutron source in detail so we will just include a short description of the relevant properties of the source in this article. Next the authors will describe one possible method of measuring the NPB cross section which is based on two calorimetric detectors that measure the energies of the scattered neutrons and the recoil protons. Although there are many other possible experimental approaches and geometries, such as measuring the bremsstrahlung gamma ray directly with a multi-element possibilities in this paper. There are several advantages in using a white neutron source for this type of measurement. First, a wide range of incident neutron energies may be covered. In the case of the WNR, the energy range is from below 50 MeV to over 400 MeV which is above the pion production threshold. Second, all incident neutron energies are measure simultaneously. 6 refs., 5 figs
Practice for dosimetry in an X-ray (bremsstrahlung) facility for radiation processing. 2. ed.
International Nuclear Information System (INIS)
2002-01-01
This practice covers dosimetric procedures to be followed in facility characterization, process qualification, and routine processing using X rays (bremsstrahlung) to ensure that the entire product has been treated within an acceptable range of absorbed doses. Other procedures related to facility characterization, process qualification, and routine processing that may influence absorbed dose in the product are also discussed. The establishment of effective or regulatory dose and X-ray energy limits are not within the scope of this practice. In contrast to monoenergetic gamma rays, the bremsstrahlung energy spectrum extends from low values up to the maximum energy of the electrons incident on the X-ray target (see Section 5 and Annex A1). Dosimetry is only one component of a total quality assurance program for an irradiation facility. Other controls besides dosimetry may be required for specific applications such as medical device sterilization and food preservation. For the irradiation of food and the radiation sterilization of health care products, other specific ISO standards exist. For food irradiation, see ISO/ASTM Practice 51431. For the radiation sterilization of health care products, see ISO 11137:1995. In those areas covered by ISO 11137, that standard takes precedence
Electron bremsstrahlung in collisions of 223 MeV/u He-like uranium ions with gaseous targets
Energy Technology Data Exchange (ETDEWEB)
Ludziejewski, T.; Beyer, H.; Bosch, F.; Brinzanescu, O.; Franzke, B.; Kozhuharov, C.; Liesen, D.; Menzel, G.; Meier, J.; Mokler, P.H.; Reich, H.; Steck, M.; Stenner, L. [Gesellschaft fuer Schwerionenforschung, D-64220 Darmstadt (Germany); Stoehlker, Th. [University of Frankfurt, D-60486 Frankfurt (Germany); Gesellschaft fuer Schwerionenforschung, D-64220 Darmstadt (Germany); Keller, S. [University of Frankfurt, D-60054 Frankfurt (Germany); Dunford, R.W. [Argonne National Laboratory, Argonne, IL 60439 (United States); Livingston, A.E. [University of Notre Dame, Indiana 4556 (United States); Rymuza, P. [Institute for Nuclear Studies, 05-400 Swierk (Poland); Stachura, Z. [Institute of Nuclear Physics, 31-342 Cracow (Poland); Swiat, P.; Warczak, A. [Jagiellonian University, 30-059 Cracow (Poland)
1998-06-14
The bremsstrahlung process in the domain of strong Coulomb fields has been investigated for N{sub 2} and Ar target electrons colliding with He-like uranium ions at 223 MeV/u. The differential cross sections for bremsstrahlung were measured at laboratory observation angles of 48 deg., 90 deg., and 132 deg. Substantial discrepancies were found between the experimental cross sections and the first-order Born approximation calculations. The reported data provide a new testing ground for non-perturbative treatment of the coupling between radiation and matter in the presence of strong fields. (author)
Electron bremsstrahlung in collisions of 223 MeV/u He-like uranium ions with gaseous targets
International Nuclear Information System (INIS)
Ludziejewski, T.; Beyer, H.; Bosch, F.; Brinzanescu, O.; Franzke, B.; Kozhuharov, C.; Liesen, D.; Menzel, G.; Meier, J.; Mokler, P.H.; Reich, H.; Steck, M.; Stenner, L.; Stoehlker, T.; Keller, S.; Dunford, R.W.; Livingston, A.E.; Rymuza, P.; Stachura, Z.; Swiat, P.; Warczak, A.
1997-09-01
The bremsstrahlung process in the domain of strong Coulomb fields has been investigated for N 2 and Ar target electrons colliding with He-like uranium ions at 223 MeV/u. The doubly differential cross sections for bremsstrahlung were measured at the laboratory observation angles of 48 , 90 , and 132 . Substantial discrepancies were found between the experimental cross secions and the first order Born approximation calculations. The reported data provide a new testing ground for non-perturbative treatment of the coupling between radiation and matter in the presence of strong fields. (orig.)
Electron bremsstrahlung in collisions of 223 MeV/u He-like uranium ions with gaseous targets
Energy Technology Data Exchange (ETDEWEB)
Ludziejewski, T.; Beyer, H.; Bosch, F.; Brinzanescu, O.; Franzke, B.; Kozhuharov, C.; Liesen, D.; Menzel, G.; Meier, J.; Mokler, P.H.; Reich, H.; Steck, M.; Stenner, L. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Stoehlker, T. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany)]|[Frankfurt Univ. (Germany); Keller, S. [Frankfurt Univ. (Germany); Dunford, R.W. [Argonne National Lab., IL (United States); Livingston, A.E. [Notre Dame Univ., IN (United States); Rymuza, P. [Institute for Nuclear Studies, Swierk (Poland); Stachura, Z. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Swiat, P.; Warczak, A. [Jagiellonian Univ., Krakow (Poland)
1997-09-01
The bremsstrahlung process in the domain of strong Coulomb fields has been investigated for N{sub 2} and Ar target electrons colliding with He-like uranium ions at 223 MeV/u. The doubly differential cross sections for bremsstrahlung were measured at the laboratory observation angles of 48 , 90 , and 132 . Substantial discrepancies were found between the experimental cross secions and the first order Born approximation calculations. The reported data provide a new testing ground for non-perturbative treatment of the coupling between radiation and matter in the presence of strong fields. (orig.) 35 refs.
International Nuclear Information System (INIS)
Vikulin, A.A.; Vanyushkin, B.M.; Garnyk, D.V.; Kon'kov, N.G.; Terent'ev, B.M.
1980-01-01
Measurement results of exposure dose rate (EDR) of radiation in fields of bremsstrahlung of radiation plants with LUEh-8/5B linear accelerator of electrons by means of DRG2-03 dose meter, intended for operative measuring EDR in high intense fields of γ-radiation of powerful radioisotopic plants, are presented. Dose meter design is described. Measurements of bremsstrahlung EDR have been carried out in the chamber of plant irradiation for radiation sterilizing medical items, as well as in the chamber of VNIIRT experimental plant. RUP-1 device has been used for measuring radiation EDR in a labyrinth behind 1.8 m thick shoulder by concrete [ru
Electroweak one-loop corrections for e+e- annihilation into t anti t including hard bremsstrahlung
International Nuclear Information System (INIS)
Fleischer, J.; Leike, A.; Riemann, T.; Werthenbach, A.
2003-01-01
We present the complete electroweak one-loop corrections to top-pair production at a linear e + e - collider in the continuum region. Besides weak and photonic virtual corrections, real hard bremsstrahlung with simple realistic kinematical cuts is included. For the bremsstrahlung we advocate a semi-analytical approach with a high numerical accuracy. The virtual corrections are parameterized through six independent form factors, suitable for Monte Carlo implementation. Alternatively, our numerical package Topfit, a stand-alone code, can be utilized for the calculation of both differential and integrated cross sections as well as forward-backward asymmetries. (orig.)
Estimation of Electron Dose Delivered by a 0.4 MeV Accelerator from Bremsstrahlung Dose Measurements
DEFF Research Database (Denmark)
Karadjov, A. G.; Hansen, Jørgen-Walther
1980-01-01
Determination of a 0.4 MeV electron dose from a bremsstrahlung dose measurement using a converter-detector system is considered. The detector used is a Frickle dosimeter, and the converters are aluminum, copper and lead foils. Optimal converter thickness is ascertained experimentally for each mat...... materials within a Z-range of 13–82. A linear relation is found between bremsstrahlung dose and electron dose ranging from 2 to 20 Mrad. Finally the effect of converter area on detector response is studied....
Inverse semigroups the theory of partial symmetries
Lawson, Mark V
1998-01-01
Symmetry is one of the most important organising principles in the natural sciences. The mathematical theory of symmetry has long been associated with group theory, but it is a basic premise of this book that there are aspects of symmetry which are more faithfully represented by a generalization of groups called inverse semigroups. The theory of inverse semigroups is described from its origins in the foundations of differential geometry through to its most recent applications in combinatorial group theory, and the theory tilings.
Energy Technology Data Exchange (ETDEWEB)
Grosser, Oliver Stephan
2013-04-12
Establish tomographic Bremsstrahlung SPECT imaging (BSPECT) for the clinical validation of Selective Internal Radiotherapy (SIRT) with Yttrium-90 ({sup 90}Y) labelled microspheres. Various energy ranges (75 ± 3.8 keV; 135 ± 6.8 keV; 167 ± 8.4 keV) and the summation window were studied to see if they were suitable for BSPECT. To this end, clinically available reconstruction techniques were analysed for their suitability for BSPECT. The tomographic examinations were performed on a cylindrical phantom filled with spheres of different diameters d = [28; 35; 40; 50; 60] mm in a non-active waterfilled background. The spheres were filled with identical {sup 90}Y activity concentration (AC). Measurements were conducted at AC = [14.58; 5.20; 1.98; 0.66] MBq/cm{sup 3}. The BSPECT were reconstructed with filtered back-projection (FBP), a 2D Ordered-Subset Expectation Maximisation Algorithm (2D-OSEM) and a 3D Geometric Mean Algorithm (3D-GMA). Evaluation was made visually and on the basis of objective performance parameters such as contrast, signal-to-noise ratio (SNR) and image noise. While the 75 keV ± 3.8 keV window was identified as suitable for the BSPECT, limitations were revealed as to use of different implementations of the Point Spread Function (PSF). It was found for all reconstruction techniques that, at a given sphere diameter, there existed a linear relationship between the AC in the spheres and the reconstructed pulse rate per volume element. The recovery effect was verified for small spheres. The iterative techniques were found to be suitable for the BSPECT at all AC. At low AC, the 3D-GMA exhibited the least noise and the highest SNR. The FBP turned out to be entirely inappropriate for the BSPECT. The narrow energy window in which the bremsstrahlung interferes with the characteristic X-radiation of lead can be used for BSPECT. In this approach, the tomographic data reconstructed with different algorithms exhibited a varying image quality, with the iterative
International Nuclear Information System (INIS)
Sahani, P.K.; Dev, Vipin; Haridas, G.; Thakkar, K.K.; Singh, Gurnam; Sarkar, P.K.; Sharma, D.N.
2009-01-01
INDUS-2 is a high energy electron accelerator facility where electrons are accelerated in circular ring up to maximum energy 2.5 GeV, to generate synchrotron radiation. During normal operation of the machine a fraction of these electrons is lost, which interact with the accelerator structures and components like vacuum chamber and residual gases in the cavity and hence generates significant amount of Bremsstrahlung radiation. The Bremsstrahlung radiation is highly dependent on the incident electron energy, target material and its thickness. The Bremsstrahlung radiation dominates the radiation environment in such electron storage rings. Because of its broad spectrum extending up to incident electron energy and pulsed nature, it is very difficult to segregate the Bremsstrahlung component from the mixed field environment in accelerators. With the help of FLUKA Monte Carlo code, Bremsstrahlung spectrum generated from 2.5 GeV electron on bombardment of high Z lead target is simulated. To study the variation in Bremsstrahlung spectrum on target thickness, lead targets of 3, 6, 9, 12, 15, 18 mm thickness was used. The energy spectrum of emerging electron and positron is also simulated. The study suggests that as the target thickness increases, the emergent Bremsstrahlung photon fluence increases. With increase in the target thickness Bremsstrahlung photons in the spectrum dominate the low energy part and degrade in high energy part. The electron and positron spectra also extend up to incident electron energy. (author)
An application of sparse inversion on the calculation of the inverse data space of geophysical data
Saragiotis, Christos
2011-07-01
Multiple reflections as observed in seismic reflection measurements often hide arrivals from the deeper target reflectors and need to be removed. The inverse data space provides a natural separation of primaries and surface-related multiples, as the surface multiples map onto the area around the origin while the primaries map elsewhere. However, the calculation of the inverse data is far from trivial as theory requires infinite time and offset recording. Furthermore regularization issues arise during inversion. We perform the inversion by minimizing the least-squares norm of the misfit function and by constraining the 1 norm of the solution, being the inverse data space. In this way a sparse inversion approach is obtained. We show results on field data with an application to surface multiple removal. © 2011 IEEE.
Energy Technology Data Exchange (ETDEWEB)
Sharma, Suhansar Jit [Department of Physics, B.B.S.B Polytechnic, Fatehgarh Sahib, Punjab (India); Singh, Tajinder, E-mail: tajindersingh2k9@gmail.com [Department of Physics, Mata Gujri College, Fatehgarh Sahib, Punjab (India); Singh, Doordarshi [Department of Mechanical Engineering, B.B.S.B Engineering College, Fatehgarh Sahib, Punjab (India); Singh, Amrit [Department of Physics, Baba Ajay Singh Khalsa College, Gurdas Nangal, Gurdaspur, Punjab (India); Dhaliwal, A.S. [Department of Physics, Sant Longowal Institute of Engineering & Technology, Longowal (Sangrur), Punjab (India)
2017-06-15
Highlights: • Total bremsstrahlung spectra in thick targets of Pb compounds by {sup 90}Sr in energy range 10–100 keV. • Experimental results show better agreement with the model which includes PB in SA up to 30 keV. • At higher photon energy region 30–100 keV the model which describes OB is more accurate. • Experimental results show positive deviations from the entire models at higher energy end spectrum. - Abstract: The total bremsstrahlung spectra in the thick targets of lead acetate trihydrate (Pb(CH{sub 3}COO){sub 2}·3H{sub 2}O), lead nitrate Pb(NO{sub 3}){sub 2} and lead chloride (PbCl{sub 2}) produced by {sup 90}Sr beta particles have been investigated in the photon energy region of 10–100 keV. The experimental bremsstrahlung spectra have been compared with the theoretical models Elwert corrected (non relativistic) Bethe Heitler theory, modified Elwert factor (relativistic) Bethe Heitler theory for ordinary bremsstrahlung and modified Elwert factor (relativistic) Bethe Heitler theory which includes polarization bremsstrahlung in the stripped atom approximation. The experimental results show better agreement with theoretical model that includes polarization bremsstrahlung in stripped approximation in the photon energy region below 30 keV. However, at higher photon energy region 30–100 keV, the theoretical model which describes ordinary bremsstrahlung is more accurate to describe the experimental bremsstrahlung spectra. The experimental results show positive deviations from the entire theoretical models at higher energy end of the spectrum. The results indicate that polarization bremsstrahlung plays important role in the formation of total bremsstrahlung spectra in lead compounds produced by continuous beta particles at low photon energy region of 10–30 keV.
Czech Academy of Sciences Publication Activity Database
Navrátil, Z.; Morávek, T.; Ráhel’, J.; Čech, J.; Lalinský, Ondřej; Trunec, D.
2017-01-01
Roč. 26, č. 5 (2017), s. 1-10, č. článku 055025. ISSN 0963-0252 Institutional support: RVO:68081731 Keywords : dielectric barrier discharge * helium * single photon counting * bremsstrahlung * electric field * backward discharge * surface charge Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.302, year: 2016
Electron, electron-bremsstrahlung and proton depth-dose data for space-shielding applications
Seltzer, S. M.
1979-01-01
A data set has been developed, consisting of depth-dose distributions for omni-directional electron and proton fluxes incident on aluminum shields. The principal new feature of this work is the accurate treatment, based on detailed Monte Carlo calculations, of the electron-produced bremsstrahlung component. Results covering the energy region of interest in space-shielding calculations have been obtained for the absorbed dose (a) as a function of depth in a semi-infinite medium, (b) at the edge of slab shields, and (c) at the center of a solid sphere. The dose to a thin tissue-equivalent detector was obtained as well as that in aluminum. Various results and comparisons with other work are given.
Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung
Energy Technology Data Exchange (ETDEWEB)
Mehtar-Tani, Yacine [Institute of Nuclear Theory, University of Washington,Seattle, WA 98195-1550 (United States); Tywoniuk, Konrad [Theoretical Physics Department, CERN,1211 Geneva 23 (Switzerland)
2017-04-21
We argue that contemporary jet substructure techniques might facilitate a more direct measurement of hard medium-induced gluon bremsstrahlung in heavy-ion collisions, and focus specifically on the “soft drop declustering” procedure that singles out the two leading jet substructures. Assuming coherent jet energy loss, we find an enhancement of the distribution of the energy fractions shared by the two substructures at small subjet energy caused by hard medium-induced gluon radiation. Departures from this approximation are discussed, in particular, the effects of colour decoherence and the contamination of the grooming procedure by soft background. Finally, we propose a complementary observable, that is the ratio of the two-pronged probability in Pb-Pb to proton-proton collisions and discuss its sensitivity to various energy loss mechanisms.
Bremsstrahlung spectra from thick-target electron beams with noncollisional energy losses
International Nuclear Information System (INIS)
Brown, J.C.; MacKinnon, A.L.
1985-01-01
We consider what can be learned from the bremsstrahlung radiation of fast electrons in a thick target, generalized to include electron energy losses additional to collisions. We show that the observed photon spectrum can, in principle, be inverted to yield an integral functional of the electron spectrum and the effective energy loss rate. In the light of this result, there seems no reason to suppose, in the absence of a priori information to the contrary, that the photon spectrum is symptomatic more of the fast electron distribution than of the energy loss processes. In cases where the electron injection spectrum is known on independent observational or theoretical grounds, it is possible to infer an effective, ''phenomenological'' energy loss function. In the more general case, however, fullest possible modeling of the physical situation and comparison of the resulting spectrum with observations is all that can be attempted
Simulations of Beam Optics and Bremsstrahlung for High Intensity and Brightness Channeling Radiation
Energy Technology Data Exchange (ETDEWEB)
Hyun, J. [Sokendai, Tsukuba; Piot, P. [NIU, DeKalb; Sen, T. [Fermilab
2018-04-12
This paper presents X-ray spectra of channeling radiation expected at the FAST (Fermi Accelerator Science and Technology) facility in Fermilab. Our purpose is to produce high brightness quasi-monochromatic X-rays in an energy range from 40 keV to 110 keV. We will use a diamond crystal and low emittance electrons with an energy of around 43 MeV. The quality of emitted X-rays depends on parameters of the electron beam at the crystal. We present simulations of the beam optics for high brightness and high yield operations for a range of bunch charges. We estimate the X-ray spectra including bremsstrahlung background. We discuss how the electron beam distributions after the diamond crystal are affected by channeling. We discuss an X-ray detector system to avoid pile-up effects during high charge operations.
Calculation of gas Bremsstrahlung power from straight sections of storage ring at SSRF
International Nuclear Information System (INIS)
Hua Zhengdong; Xu Xunjiang; Fang Keming; Xu Jiaqiang
2008-01-01
The Shanghai Synchrotron Radiation Facility (SSRF) is a third-generation synchrotron radiation light source with 3.5 GeV in energy, which is composed of the linear accelerator, the booster and the storage ring. The storage ring provides 16 standard straight sections of 6.5 m and 4 long straight sections of 12 meters. Gas Bremsstrahlung (GB) produced by the interaction of the stored beam with the residual gas molecules in straight section, which is so intense and has a very small angular that the GB spectra, the GB power and the GB power distribution should be known. The characters of GB are studied by means of Fluka Monte Carlo code. Our result shows agreement with those obtained by the experiential formulae. (authors)
Polarization bremsstrahlung of a hydrogen-like ion in a single crystal
International Nuclear Information System (INIS)
Astapenko, V. A.
2009-01-01
Polarization bremsstrahlung (PB) that arises when a fast hydrogen-like ion is scattered in a single crystal is investigated theoretically. Four types of the process are analyzed that are caused by virtual excitation of electrons of the target and of the incident particle (IP), as well as by a coherent and incoherent interaction between the IP and the single crystal. The spectral, angular, and velocity (of the IP) characteristics of PB are calculated with regard to the spectral function of a photodetector. Optimal observation conditions and regions in which different types of PB are dominant are determined, and the dependence of these regions on the charge of the IP nucleus and of the target atoms is revealed
Energy Technology Data Exchange (ETDEWEB)
Tashenov, Stanislav [Royal Institute of Technology, Stockholm (Sweden); Stockholm University (Sweden); Physikalisches Institut, Universitaet Heidelberg (Germany); Baeck, Torbjoern; Cederwall, Bo; Khaplanov, Anton; Schaessburger, Kai-Uwe [Royal Institute of Technology, Stockholm (Sweden); Barday, Roman; Enders, Joachim; Poltoratska, Yuliya [Institut fuer Kernphysik, Technische Universitaet, Darmstadt (Germany); Surzhykov, Andrey [Physikalisches Institut, Universitaet Heidelberg (Germany); GSI, Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany)
2011-07-01
Linear polarization of the photons emitted in the process of the atomic field electron bremsstrahlung has been studied at the newly developed 100 keV polarized electron source of TU Darmstadt. A correlation between the initial orientation of the electron spin and the degree and the angle of photon linear polarization has been measured for the first time. For this purpose a hard x-ray Compton polarimeter consisting of a segmented high purity germanium detector and an external passive photon scattering target have been applied. Linear polarization sensitive Compton and Rayleigh photon scattering distributions have been sampled by the segmented detector. The observed polarization correlation reveals a precession of the electron spin as it moves in the field of the nucleus. The full-relativistic calculations for the case of radiative recombination into a Rydberg series limit have been corroborated by the measurement. The results of this experiment suggest a new method for electron beam polarimetry.
X-ray generation from Bremsstrahlung effect using stainless steel target
International Nuclear Information System (INIS)
Siti Aiasah Hashim; Shari Jahar; Leo Kee Wah; Muhammad Zahidee Taat
2004-01-01
X-ray radiation is produced when high energy electron interacts with metals. This process is known as Bremsstrahlung. In commercial electron beam irradiator, this process may be utilized to serve irradiation of thick products with lower dose requirement such disinfestation of fruits, delaying ripening and medical product sterilization. Initial experiment was carried out to measure the amount of x-ray radiation produced by using a simple converter. In this experiment, the target material is the stainless steel beam shutter that is normally used to protect the window. The maximum energy for the Eps 3000 is 3 MeV and was used generate the x-ray radiation. The dose was measure using CTA film and analyzed using UV spectrophotometer. The results obtained showed that sufficient amount of x-ray dose can be generated for low dose irradiation by using this simple set up. (Author)
International Nuclear Information System (INIS)
Avakyan, R.O.; Armaganyan, A.A.; Arutyunyan, L.G.; Iskandaryan, A.G.; Taroyan, S.P.
1981-01-01
The results are given of the theoretical processing of experimental data on the investigation of orientational dependences of integral intensity of coherent bremsstrahlung radiation (CBR) of superfast electrons in a diamond crystal. It is shown that in the case of ''point effect'' right up to the electrons incident angle, which is 0.1 mrad with respect to the crystallographic plane, the CBR theory gives a good description of experimental data. In the case of ''row effect'', in order to account for the divergence between the theory and experiment at small incident angles of electrons with respect to the crystallographic axis, it is assumed that the multiple scattering angle has an orientational dependence. By fitting the theoretical curve to experimental points the dependences are obtained of the multiple scattering angle change on the crystal orientation with respect to the electron beam
BPS Wilson loops and Bremsstrahlung function in ABJ(M): a two loop analysis
Energy Technology Data Exchange (ETDEWEB)
Bianchi, Marco S. [Institut für Physik, Humboldt-Universität zu Berlin,Newtonstraße 15, 12489 Berlin (Germany); Griguolo, Luca [Dipartimento di Fisica e Scienze della Terra, Università di Parmaand INFN Gruppo Collegato di Parma,Viale G.P. Usberti 7/A, 43100 Parma (Italy); Leoni, Matias [Physics Department, FCEyN-UBA & IFIBA-CONICETCiudad Universitaria, Pabellón I, 1428, Buenos Aires (Argentina); Penati, Silvia [Dipartimento di Fisica, Università di Milano-Bicoccaand INFN, Sezione di Milano-Bicocca,Piazza della Scienza 3, I-20126 Milano (Italy); Seminara, Domenico [Dipartimento di Fisica, Università di Firenzeand INFN Sezione di Firenze,via G. Sansone 1, 50019 Sesto Fiorentino (Italy)
2014-06-19
We study a family of circular BPS Wilson loops in N=6 super Chern-Simons-matter theories, generalizing the usual 1/2-BPS circle. The scalar and fermionic couplings depend on two deformation parameters and these operators can be considered as the ABJ(M) counterpart of the DGRT latitudes defined in N=4 SYM. We perform a complete two-loop analysis of their vacuum expectation value, discuss the appearance of framing-like phases and propose a general relation with cohomologically equivalent bosonic operators. We make an all-loop proposal for computing the Bremsstrahlung function associated to the 1/2-BPS cusp in terms of these generalized Wilson loops. When applied to our two-loop result it reproduces the known expression. Finally, we comment on the generalization of this proposal to the bosonic 1/6-BPS case.
Sterilization of health care products by 5 MeV bremsstrahlung (X ray)
International Nuclear Information System (INIS)
Sato, Yoshishige; Takahashi, Thoru; Saito, Toshio; Sato, Toshio; Takehisa, Masaaki
1993-01-01
Radiation sensitivities of B. pumilis and B. subtilis spores were examined to bremsstrahlung of 5 MeV EB and Cobalt-60 γ rays in order to confirm the effects of radiation and dose rate. Biological indicators were irradiated with the X rays in the dose rate range of 4.7-47 kGy/h. D-value of B. pumilis spores was 1.4-1.5 kGy, and that of B. subtilis was 1.1-1.3 kGy. The D-values of B. pumilus and B. subtilis have very small dose rate dependences to X ray, and the D-values are similar to those of γ rays. Dose distribution by X-ray and γ irradiation was measured for cartons containing 32 unit dialyzers. The D max. /D min. of the X-ray irradiation (1.2) was smaller than that of γ ray (1.3). (author)
New exclusion limits for dark gauge forces from proton Bremsstrahlung in beam-dump data
Energy Technology Data Exchange (ETDEWEB)
Bluemlein, Johannes [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Brunner, Juergen [Aix-Marseille Univ. CNRS/IN2P3 (France). CPPM
2013-11-15
We re-analyze published proton beam dump data taken at the U70 accelerator at IHEP Serpukhov with the {nu}-calorimeter I experiment in 1989 to set mass-coupling limits for dark gauge forces. The corresponding data have been used for axion and light Higgs particle searches before. More recently, limits on dark gauge forces have been derived from this data set, considering a dark photon production from {pi}{sup 0}-decay. Here we determine extended mass and coupling exclusion bounds for dark gauge bosons ranging to masses m{sub {gamma}'} of 624 MeV at admixture parameters {epsilon}{approx_equal}10{sup -6} considering high-energy Bremsstrahlung of the U-boson of the initial proton beam and different detection mechanisms.
Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung
Mehtar-Tani, Yacine
2017-04-21
We argue that contemporary jet substructure techniques might facilitate a more direct measurement of hard medium-induced gluon bremsstrahlung in heavy-ion collisions, and focus specifically on the "soft drop declustering" procedure that singles out the two leading jet substructures. Assuming coherent jet energy loss, we find an enhancement of the distribution of the energy fractions shared by the two substructures at small subjet energy caused by hard medium-induced gluon radiation. Departures from this approximation are discussed, in particular, the effects of colour decoherence and the contamination of the grooming procedure by soft background. Finally, we propose a complementary observable, that is the ratio of the two-pronged probability in Pb-Pb to proton-proton collisions and discuss its sensitivity to various energy loss mechanisms.
Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung
Mehtar-Tani, Yacine; Tywoniuk, Konrad
2017-04-01
We argue that contemporary jet substructure techniques might facilitate a more direct measurement of hard medium-induced gluon bremsstrahlung in heavy-ion collisions, and focus specifically on the "soft drop declustering" procedure that singles out the two leading jet substructures. Assuming coherent jet energy loss, we find an enhancement of the distribution of the energy fractions shared by the two substructures at small subjet energy caused by hard medium-induced gluon radiation. Departures from this approximation are discussed, in particular, the effects of colour decoherence and the contamination of the grooming procedure by soft background. Finally, we propose a complementary observable, that is the ratio of the two-pronged probability in Pb-Pb to proton-proton collisions and discuss its sensitivity to various energy loss mechanisms.
Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung
International Nuclear Information System (INIS)
Mehtar-Tani, Yacine; Tywoniuk, Konrad
2017-01-01
We argue that contemporary jet substructure techniques might facilitate a more direct measurement of hard medium-induced gluon bremsstrahlung in heavy-ion collisions, and focus specifically on the “soft drop declustering” procedure that singles out the two leading jet substructures. Assuming coherent jet energy loss, we find an enhancement of the distribution of the energy fractions shared by the two substructures at small subjet energy caused by hard medium-induced gluon radiation. Departures from this approximation are discussed, in particular, the effects of colour decoherence and the contamination of the grooming procedure by soft background. Finally, we propose a complementary observable, that is the ratio of the two-pronged probability in Pb-Pb to proton-proton collisions and discuss its sensitivity to various energy loss mechanisms.
Studies on inner bremsstrahlung from a few β-emitting isotopes
International Nuclear Information System (INIS)
Keshava, S.L.; Gopala, K.; Venkataramaiah, P.
2000-01-01
Past experimental studies on the inner bremsstrahlung (IB) emission from the forbidden β transitions have shown marked deviations from the theoretical calculations of Lewis and Ford, Ford and Martin, Chang and Falkoff, Madansky and Gebhardt. In this paper we have re-analysed the data of IB emissions from four β-emitting isotopes, namely 89 Sr, 141 Ce, 111 Ag and 99 Tc, whose transitions are classified as forbidden. The raw experimental data already available in the literature are critically examined in the light of relevant statistics in order to arrive at meaningful conclusions. The unfolding of the IB spectra was done following the step-by-step procedure of Liden and Starfelt. The results obtained were different from those reported in the literature. (author)
Inverse logarithmic potential problem
Cherednichenko, V G
1996-01-01
The Inverse and Ill-Posed Problems Series is a series of monographs publishing postgraduate level information on inverse and ill-posed problems for an international readership of professional scientists and researchers. The series aims to publish works which involve both theory and applications in, e.g., physics, medicine, geophysics, acoustics, electrodynamics, tomography, and ecology.
Inverse Kinematics using Quaternions
DEFF Research Database (Denmark)
Henriksen, Knud; Erleben, Kenny; Engell-Nørregård, Morten
In this project I describe the status of inverse kinematics research, with the focus firmly on the methods that solve the core problem. An overview of the different methods are presented Three common methods used in inverse kinematics computation have been chosen as subject for closer inspection....
Convex blind image deconvolution with inverse filtering
Lv, Xiao-Guang; Li, Fang; Zeng, Tieyong
2018-03-01
Blind image deconvolution is the process of estimating both the original image and the blur kernel from the degraded image with only partial or no information about degradation and the imaging system. It is a bilinear ill-posed inverse problem corresponding to the direct problem of convolution. Regularization methods are used to handle the ill-posedness of blind deconvolution and get meaningful solutions. In this paper, we investigate a convex regularized inverse filtering method for blind deconvolution of images. We assume that the support region of the blur object is known, as has been done in a few existing works. By studying the inverse filters of signal and image restoration problems, we observe the oscillation structure of the inverse filters. Inspired by the oscillation structure of the inverse filters, we propose to use the star norm to regularize the inverse filter. Meanwhile, we use the total variation to regularize the resulting image obtained by convolving the inverse filter with the degraded image. The proposed minimization model is shown to be convex. We employ the first-order primal-dual method for the solution of the proposed minimization model. Numerical examples for blind image restoration are given to show that the proposed method outperforms some existing methods in terms of peak signal-to-noise ratio (PSNR), structural similarity (SSIM), visual quality and time consumption.
Original Researc Original Research
African Journals Online (AJOL)
RAGHAVENDRA
Practices. Problems. Supervision. Primary School. *Corresponding Author: Asrat Dagnew. E-mail: asratboza@yahoo.com tructional support. The relevant and ... vision is one of indispensable system pment. Supervision is a system of that directly concerned on the aff members in a school or other. Original Research ...
Original Research Original Research
African Journals Online (AJOL)
RAGHAVENDRA
language in social interaction( Anto et al., 2012; Tessema et al., 2012). While such ..... 10 items on a five-point Likert scale originally developed by Benard et al. (2007). ..... self-confidence, and hold down their anxiety levels. In this study ...
Inverse problems in the Bayesian framework
International Nuclear Information System (INIS)
Calvetti, Daniela; Somersalo, Erkki; Kaipio, Jari P
2014-01-01
The history of Bayesian methods dates back to the original works of Reverend Thomas Bayes and Pierre-Simon Laplace: the former laid down some of the basic principles on inverse probability in his classic article ‘An essay towards solving a problem in the doctrine of chances’ that was read posthumously in the Royal Society in 1763. Laplace, on the other hand, in his ‘Memoirs on inverse probability’ of 1774 developed the idea of updating beliefs and wrote down the celebrated Bayes’ formula in the form we know today. Although not identified yet as a framework for investigating inverse problems, Laplace used the formalism very much in the spirit it is used today in the context of inverse problems, e.g., in his study of the distribution of comets. With the evolution of computational tools, Bayesian methods have become increasingly popular in all fields of human knowledge in which conclusions need to be drawn based on incomplete and noisy data. Needless to say, inverse problems, almost by definition, fall into this category. Systematic work for developing a Bayesian inverse problem framework can arguably be traced back to the 1980s, (the original first edition being published by Elsevier in 1987), although articles on Bayesian methodology applied to inverse problems, in particular in geophysics, had appeared much earlier. Today, as testified by the articles in this special issue, the Bayesian methodology as a framework for considering inverse problems has gained a lot of popularity, and it has integrated very successfully with many traditional inverse problems ideas and techniques, providing novel ways to interpret and implement traditional procedures in numerical analysis, computational statistics, signal analysis and data assimilation. The range of applications where the Bayesian framework has been fundamental goes from geophysics, engineering and imaging to astronomy, life sciences and economy, and continues to grow. There is no question that Bayesian
Identification of polymorphic inversions from genotypes
Directory of Open Access Journals (Sweden)
Cáceres Alejandro
2012-02-01
Full Text Available Abstract Background Polymorphic inversions are a source of genetic variability with a direct impact on recombination frequencies. Given the difficulty of their experimental study, computational methods have been developed to infer their existence in a large number of individuals using genome-wide data of nucleotide variation. Methods based on haplotype tagging of known inversions attempt to classify individuals as having a normal or inverted allele. Other methods that measure differences between linkage disequilibrium attempt to identify regions with inversions but unable to classify subjects accurately, an essential requirement for association studies. Results We present a novel method to both identify polymorphic inversions from genome-wide genotype data and classify individuals as containing a normal or inverted allele. Our method, a generalization of a published method for haplotype data 1, utilizes linkage between groups of SNPs to partition a set of individuals into normal and inverted subpopulations. We employ a sliding window scan to identify regions likely to have an inversion, and accumulation of evidence from neighboring SNPs is used to accurately determine the inversion status of each subject. Further, our approach detects inversions directly from genotype data, thus increasing its usability to current genome-wide association studies (GWAS. Conclusions We demonstrate the accuracy of our method to detect inversions and classify individuals on principled-simulated genotypes, produced by the evolution of an inversion event within a coalescent model 2. We applied our method to real genotype data from HapMap Phase III to characterize the inversion status of two known inversions within the regions 17q21 and 8p23 across 1184 individuals. Finally, we scan the full genomes of the European Origin (CEU and Yoruba (YRI HapMap samples. We find population-based evidence for 9 out of 15 well-established autosomic inversions, and for 52 regions
International Nuclear Information System (INIS)
Burkhard, N.R.
1979-01-01
The gravity inversion code applies stabilized linear inverse theory to determine the topography of a subsurface density anomaly from Bouguer gravity data. The gravity inversion program consists of four source codes: SEARCH, TREND, INVERT, and AVERAGE. TREND and INVERT are used iteratively to converge on a solution. SEARCH forms the input gravity data files for Nevada Test Site data. AVERAGE performs a covariance analysis on the solution. This document describes the necessary input files and the proper operation of the code. 2 figures, 2 tables
Sharp spatially constrained inversion
DEFF Research Database (Denmark)
Vignoli, Giulio G.; Fiandaca, Gianluca G.; Christiansen, Anders Vest C A.V.C.
2013-01-01
We present sharp reconstruction of multi-layer models using a spatially constrained inversion with minimum gradient support regularization. In particular, its application to airborne electromagnetic data is discussed. Airborne surveys produce extremely large datasets, traditionally inverted...... by using smoothly varying 1D models. Smoothness is a result of the regularization constraints applied to address the inversion ill-posedness. The standard Occam-type regularized multi-layer inversion produces results where boundaries between layers are smeared. The sharp regularization overcomes...... inversions are compared against classical smooth results and available boreholes. With the focusing approach, the obtained blocky results agree with the underlying geology and allow for easier interpretation by the end-user....
International Nuclear Information System (INIS)
Rosenwald, J.-C.
2008-01-01
The lecture addressed the following topics: Optimizing radiotherapy dose distribution; IMRT contributes to optimization of energy deposition; Inverse vs direct planning; Main steps of IMRT; Background of inverse planning; General principle of inverse planning; The 3 main components of IMRT inverse planning; The simplest cost function (deviation from prescribed dose); The driving variable : the beamlet intensity; Minimizing a 'cost function' (or 'objective function') - the walker (or skier) analogy; Application to IMRT optimization (the gradient method); The gradient method - discussion; The simulated annealing method; The optimization criteria - discussion; Hard and soft constraints; Dose volume constraints; Typical user interface for definition of optimization criteria; Biological constraints (Equivalent Uniform Dose); The result of the optimization process; Semi-automatic solutions for IMRT; Generalisation of the optimization problem; Driving and driven variables used in RT optimization; Towards multi-criteria optimization; and Conclusions for the optimization phase. (P.A.)
Improved quantitative 90 Y bremsstrahlung SPECT/CT reconstruction with Monte Carlo scatter modeling.
Dewaraja, Yuni K; Chun, Se Young; Srinivasa, Ravi N; Kaza, Ravi K; Cuneo, Kyle C; Majdalany, Bill S; Novelli, Paula M; Ljungberg, Michael; Fessler, Jeffrey A
2017-12-01
In 90 Y microsphere radioembolization (RE), accurate post-therapy imaging-based dosimetry is important for establishing absorbed dose versus outcome relationships for developing future treatment planning strategies. Additionally, accurately assessing microsphere distributions is important because of concerns for unexpected activity deposition outside the liver. Quantitative 90 Y imaging by either SPECT or PET is challenging. In 90 Y SPECT model based methods are necessary for scatter correction because energy window-based methods are not feasible with the continuous bremsstrahlung energy spectrum. The objective of this work was to implement and evaluate a scatter estimation method for accurate 90 Y bremsstrahlung SPECT/CT imaging. Since a fully Monte Carlo (MC) approach to 90 Y SPECT reconstruction is computationally very demanding, in the present study the scatter estimate generated by a MC simulator was combined with an analytical projector in the 3D OS-EM reconstruction model. A single window (105 to 195-keV) was used for both the acquisition and the projector modeling. A liver/lung torso phantom with intrahepatic lesions and low-uptake extrahepatic objects was imaged to evaluate SPECT/CT reconstruction without and with scatter correction. Clinical application was demonstrated by applying the reconstruction approach to five patients treated with RE to determine lesion and normal liver activity concentrations using a (liver) relative calibration. There was convergence of the scatter estimate after just two updates, greatly reducing computational requirements. In the phantom study, compared with reconstruction without scatter correction, with MC scatter modeling there was substantial improvement in activity recovery in intrahepatic lesions (from > 55% to > 86%), normal liver (from 113% to 104%), and lungs (from 227% to 104%) with only a small degradation in noise (13% vs. 17%). Similarly, with scatter modeling contrast improved substantially both visually and in
Practical reconstruction protocol for quantitative 90Y bremsstrahlung SPECT/CT
International Nuclear Information System (INIS)
Siman, W.; Mikell, J. K.; Kappadath, S. C.
2016-01-01
Purpose: To develop a practical background compensation (BC) technique to improve quantitative 90 Y-bremsstrahlung single-photon emission computed tomography (SPECT)/computed tomography (CT) using a commercially available imaging system. Methods: All images were acquired using medium-energy collimation in six energy windows (EWs), ranging from 70 to 410 keV. The EWs were determined based on the signal-to-background ratio in planar images of an acrylic phantom of different thicknesses (2–16 cm) positioned below a 90 Y source and set at different distances (15–35 cm) from a gamma camera. The authors adapted the widely used EW-based scatter-correction technique by modeling the BC as scaled images. The BC EW was determined empirically in SPECT/CT studies using an IEC phantom based on the sphere activity recovery and residual activity in the cold lung insert. The scaling factor was calculated from 20 clinical planar 90 Y images. Reconstruction parameters were optimized in the same SPECT images for improved image quantification and contrast. A count-to-activity calibration factor was calculated from 30 clinical 90 Y images. Results: The authors found that the most appropriate imaging EW range was 90–125 keV. BC was modeled as 0.53× images in the EW of 310–410 keV. The background-compensated clinical images had higher image contrast than uncompensated images. The maximum deviation of their SPECT calibration in clinical studies was lowest (<10%) for SPECT with attenuation correction (AC) and SPECT with AC + BC. Using the proposed SPECT-with-AC + BC reconstruction protocol, the authors found that the recovery coefficient of a 37-mm sphere (in a 10-mm volume of interest) increased from 39% to 90% and that the residual activity in the lung insert decreased from 44% to 14% over that of SPECT images with AC alone. Conclusions: The proposed EW-based BC model was developed for 90 Y bremsstrahlung imaging. SPECT with AC + BC gave improved lesion detectability and activity
Practical reconstruction protocol for quantitative {sup 90}Y bremsstrahlung SPECT/CT
Energy Technology Data Exchange (ETDEWEB)
Siman, W.; Mikell, J. K.; Kappadath, S. C., E-mail: skappadath@mdanderson.org [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030 (United States)
2016-09-15
Purpose: To develop a practical background compensation (BC) technique to improve quantitative {sup 90}Y-bremsstrahlung single-photon emission computed tomography (SPECT)/computed tomography (CT) using a commercially available imaging system. Methods: All images were acquired using medium-energy collimation in six energy windows (EWs), ranging from 70 to 410 keV. The EWs were determined based on the signal-to-background ratio in planar images of an acrylic phantom of different thicknesses (2–16 cm) positioned below a {sup 90}Y source and set at different distances (15–35 cm) from a gamma camera. The authors adapted the widely used EW-based scatter-correction technique by modeling the BC as scaled images. The BC EW was determined empirically in SPECT/CT studies using an IEC phantom based on the sphere activity recovery and residual activity in the cold lung insert. The scaling factor was calculated from 20 clinical planar {sup 90}Y images. Reconstruction parameters were optimized in the same SPECT images for improved image quantification and contrast. A count-to-activity calibration factor was calculated from 30 clinical {sup 90}Y images. Results: The authors found that the most appropriate imaging EW range was 90–125 keV. BC was modeled as 0.53× images in the EW of 310–410 keV. The background-compensated clinical images had higher image contrast than uncompensated images. The maximum deviation of their SPECT calibration in clinical studies was lowest (<10%) for SPECT with attenuation correction (AC) and SPECT with AC + BC. Using the proposed SPECT-with-AC + BC reconstruction protocol, the authors found that the recovery coefficient of a 37-mm sphere (in a 10-mm volume of interest) increased from 39% to 90% and that the residual activity in the lung insert decreased from 44% to 14% over that of SPECT images with AC alone. Conclusions: The proposed EW-based BC model was developed for {sup 90}Y bremsstrahlung imaging. SPECT with AC + BC gave improved lesion
Benchmarking of Monte Carlo simulation of bremsstrahlung from thick targets at radiotherapy energies
International Nuclear Information System (INIS)
Faddegon, Bruce A.; Asai, Makoto; Perl, Joseph; Ross, Carl; Sempau, Josep; Tinslay, Jane; Salvat, Francesc
2008-01-01
Several Monte Carlo systems were benchmarked against published measurements of bremsstrahlung yield from thick targets for 10-30 MV beams. The quantity measured was photon fluence at 1 m per unit energy per incident electron (spectra), and total photon fluence, integrated over energy, per incident electron (photon yield). Results were reported at 10-30 MV on the beam axis for Al and Pb targets and at 15 MV at angles out to 90 degree sign for Be, Al, and Pb targets. Beam energy was revised with improved accuracy of 0.5% using an improved energy calibration of the accelerator. Recently released versions of the Monte Carlo systems EGSNRC, GEANT4, and PENELOPE were benchmarked against the published measurements using the revised beam energies. Monte Carlo simulation was capable of calculation of photon yield in the experimental geometry to 5% out to 30 degree sign , 10% at wider angles, and photon spectra to 10% at intermediate photon energies, 15% at lower energies. Accuracy of measured photon yield from 0 to 30 degree sign was 5%, 1 s.d., increasing to 7% for the larger angles. EGSNRC and PENELOPE results were within 2 s.d. of the measured photon yield at all beam energies and angles, GEANT4 within 3 s.d. Photon yield at nonzero angles for angles covering conventional field sizes used in radiotherapy (out to 10 degree sign ), measured with an accuracy of 3%, was calculated within 1 s.d. of measurement for EGSNRC, 2 s.d. for PENELOPE and GEANT4. Calculated spectra closely matched measurement at photon energies over 5 MeV. Photon spectra near 5 MeV were underestimated by as much as 10% by all three codes. The photon spectra below 2-3 MeV for the Be and Al targets and small angles were overestimated by up to 15% when using EGSNRC and PENELOPE, 20% with GEANT4. EGSNRC results with the NIST option for the bremsstrahlung cross section were preferred over the alternative cross section available in EGSNRC and over EGS4. GEANT4 results calculated with the ''low energy
Benchmarking of Monte Carlo simulation of bremsstrahlung from thick targets at radiotherapy energies
Energy Technology Data Exchange (ETDEWEB)
Faddegon, Bruce A.; Asai, Makoto; Perl, Joseph; Ross, Carl; Sempau, Josep; Tinslay, Jane; Salvat, Francesc [Department of Radiation Oncology, University of California at San Francisco, San Francisco, California 94143 (United States); Stanford Linear Accelerator Center, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); National Research Council Canada, Institute for National Measurement Standards, 1200 Montreal Road, Building M-36, Ottawa, Ontario K1A 0R6 (Canada); Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya and Centro de Investigacion Biomedica en Red en Bioingenieria, Biomateriales y Nanomedicina (CIBER-BBN), Diagonal 647, 08028 Barcelona (Spain); Stanford Linear Accelerator Center, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Facultat de Fisica (ECM), Universitat de Barcelona, Societat Catalana de Fisica (IEC), Diagonal 647, 08028 Barcelona (Spain)
2008-10-15
Several Monte Carlo systems were benchmarked against published measurements of bremsstrahlung yield from thick targets for 10-30 MV beams. The quantity measured was photon fluence at 1 m per unit energy per incident electron (spectra), and total photon fluence, integrated over energy, per incident electron (photon yield). Results were reported at 10-30 MV on the beam axis for Al and Pb targets and at 15 MV at angles out to 90 degree sign for Be, Al, and Pb targets. Beam energy was revised with improved accuracy of 0.5% using an improved energy calibration of the accelerator. Recently released versions of the Monte Carlo systems EGSNRC, GEANT4, and PENELOPE were benchmarked against the published measurements using the revised beam energies. Monte Carlo simulation was capable of calculation of photon yield in the experimental geometry to 5% out to 30 degree sign , 10% at wider angles, and photon spectra to 10% at intermediate photon energies, 15% at lower energies. Accuracy of measured photon yield from 0 to 30 degree sign was 5%, 1 s.d., increasing to 7% for the larger angles. EGSNRC and PENELOPE results were within 2 s.d. of the measured photon yield at all beam energies and angles, GEANT4 within 3 s.d. Photon yield at nonzero angles for angles covering conventional field sizes used in radiotherapy (out to 10 degree sign ), measured with an accuracy of 3%, was calculated within 1 s.d. of measurement for EGSNRC, 2 s.d. for PENELOPE and GEANT4. Calculated spectra closely matched measurement at photon energies over 5 MeV. Photon spectra near 5 MeV were underestimated by as much as 10% by all three codes. The photon spectra below 2-3 MeV for the Be and Al targets and small angles were overestimated by up to 15% when using EGSNRC and PENELOPE, 20% with GEANT4. EGSNRC results with the NIST option for the bremsstrahlung cross section were preferred over the alternative cross section available in EGSNRC and over EGS4. GEANT4 results calculated with the &apos
International Nuclear Information System (INIS)
Earle, E.D.; McDonald, A.B.; Kidner, S.H.; Clifford, E.T.H.; Hill, J.J.; Keech, G.H.; Chupp, T.E.; Schneider, M.B.
1987-01-01
The circular polarization dependent component of the total cross section for photodisintegration of deuterium has been measured to be (2.7±2.8) x 10 -6 for Bremsstrahlung with an end point of 4.1 MeV and (7.7±5.3) x 10 -6 for an end point of 3.2 MeV. The helicity dependent component of the total cross section for the production of Bremsstrahlung on tantalum by longitudinally polarized electrons has been measured to be (0.63±0.70) x 10 -6 for an electron energy of 4.1 MeV and (3.1±1.5) x 10 -6 at 3.2 MeV. All measurements are in agreement with theoretical predictions for these processes. (author)
Energy Technology Data Exchange (ETDEWEB)
Diyankov, V S; Kovalev, V P; Kormilitsin, A I; Lavrentev, B N [All-Russian Research Institute of Technical Physics, Snezhinsk (Russian Federation)
1997-12-31
The report summarizes RFNC-VNIITF activities from 1963 till 1995, devoted to the development of pulsed electron accelerators on the basis of inductive energy storage with electroexplosive wires. These accelerators are called IGUR. The activities resulted in the development of a series of generators of powerful radiation being cheap and easy in manufacturing and servicing. The accelerators achieved the following maximum parameters: diode voltage up to 6 MV, diode current up to 80 kA, current of the extracted electron beam 30 kA, density of the extracted electron beam energy 500 J/cm{sup 2}, bremsstrahlung dose 250000 Rads, and bremsstrahlung dose rate 10{sup 13} Rads/sec. (author). 3 tabs., 5 figs., 7 refs.
International Nuclear Information System (INIS)
Vysotskij, V.I.; Vorontsov, V.I.; Kuz'min, R.N.
1987-01-01
Physical predictions and quantitative estimations of a new physical effect - the phenomenon of quantum bremsstrahlung induced selfmodulation of a fast beam channeling in the crystals are considered and carried out. The occurrence of induced self-modulation results from nonstationary interference of proper waves of a channeled particle in the range of mutual coherence and with account of difference of selective bremsstrahlung losses of these waves. The modulation frequency for superrelativistic particles is shown to lie within the range from soft X-ray to hard gamma range. It proceeds from the estimations that modulation at these frequencies is preserved within the limits of macroscopically large ranges after the crystal attaining several meters. The maximum frequency of modulation for nonrelativistic heavy particles (protons) corresponds to the optical range
Energy Technology Data Exchange (ETDEWEB)
Morris, C. L.; Bourke, M.; Byler, D. D.; Chen, C. F.; Hogan, G.; Hunter, J. F.; Kwiatkowski, K.; Mariam, F. G.; McClellan, K. J.; Merrill, F.; Morley, D. J.; Saunders, A. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2013-02-15
We present an assessment of x-rays and proton tomography as tools for studying the time dependence of the development of damage in fuel rods. We also show data taken with existing facilities at Los Alamos National Laboratory that support this assessment. Data on surrogate fuel rods have been taken using the 800 MeV proton radiography (pRad) facility at the Los Alamos Neutron Science Center (LANSCE), and with a 450 keV bremsstrahlung X-ray tomography facility. The proton radiography pRad facility at LANSCE can provide good position resolution (<70 {mu}m has been demonstrate, 20 {mu}m seems feasible with minor changes) for tomography on activated fuel rods. Bremsstrahlung x-rays may be able to provide better than 100 {mu}m resolution but further development of sources, collimation, and detectors is necessary for x-rays to deal with the background radiation for tomography of activated fuel rods.
International Nuclear Information System (INIS)
Morris, C. L.; Bourke, M.; Byler, D. D.; Chen, C. F.; Hogan, G.; Hunter, J. F.; Kwiatkowski, K.; Mariam, F. G.; McClellan, K. J.; Merrill, F.; Morley, D. J.; Saunders, A.
2013-01-01
We present an assessment of x-rays and proton tomography as tools for studying the time dependence of the development of damage in fuel rods. We also show data taken with existing facilities at Los Alamos National Laboratory that support this assessment. Data on surrogate fuel rods have been taken using the 800 MeV proton radiography (pRad) facility at the Los Alamos Neutron Science Center (LANSCE), and with a 450 keV bremsstrahlung X-ray tomography facility. The proton radiography pRad facility at LANSCE can provide good position resolution (<70 μm has been demonstrate, 20 μm seems feasible with minor changes) for tomography on activated fuel rods. Bremsstrahlung x-rays may be able to provide better than 100 μm resolution but further development of sources, collimation, and detectors is necessary for x-rays to deal with the background radiation for tomography of activated fuel rods.
Energy Technology Data Exchange (ETDEWEB)
Ropponen, T; Machicoane, G; Leitner, D [National Superconducting Cyclotron Laboratory, MSU, East Lansing, MI 48824 (United States); Tarvainen, O; Toivanen, V; Koivisto, H; Kalvas, T; Peura, P; Jones, P [University of Jyvaeskylae, Department of Physics, PO Box 35 (YFL), 40500 Jyvaeskylae (Finland); Izotov, I; Skalyga, V; Zorin, V [Institute of Applied Physics, RAS, 46 Ulyanov St., 603950 Nizhny Novgorod (Russian Federation); Noland, J, E-mail: tommi.ropponen@gmail.com, E-mail: olli.tarvainen@jyu.fi [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)
2011-10-15
Temporal evolution of plasma bremsstrahlung emitted by a 14 GHz electron cyclotron resonance ion source (ECRIS) operated in pulsed mode is presented in the energy range 1.5-400 keV with 100 {mu}s resolution. Such a high temporal resolution together with this energy range has never been measured before with an ECRIS. Data are presented as a function of microwave power, neutral gas pressure, magnetic field configuration and seed electron density. The saturation time of the bremsstrahlung count rate is almost independent of the photon energy up to 100 keV and exhibits similar characteristics with the neutral gas balance. The average photon energy during the plasma breakdown is significantly higher than that during the steady state and depends strongly on the density of seed electrons. The results are consistent with a theoretical model describing the evolution of the electron energy distribution function during the preglow transient.
International Nuclear Information System (INIS)
Diyankov, V.S.; Kovalev, V.P.; Kormilitsin, A.I.; Lavrentev, B.N.
1996-01-01
The report summarizes RFNC-VNIITF activities from 1963 till 1995, devoted to the development of pulsed electron accelerators on the basis of inductive energy storage with electroexplosive wires. These accelerators are called IGUR. The activities resulted in the development of a series of generators of powerful radiation being cheap and easy in manufacturing and servicing. The accelerators achieved the following maximum parameters: diode voltage up to 6 MV, diode current up to 80 kA, current of the extracted electron beam 30 kA, density of the extracted electron beam energy 500 J/cm 2 , bremsstrahlung dose 250000 Rads, and bremsstrahlung dose rate 10 13 Rads/sec. (author). 3 tabs., 5 figs., 7 refs
Czech Academy of Sciences Publication Activity Database
Jadrníčková, Iva; Spurný, František
2006-01-01
Roč. 41, č. 4 (2006), s. 421-429 ISSN 0033-8451 R&D Projects: GA ČR GA202/04/0795; GA ČR(CZ) GD202/05/H031 Institutional research plan: CEZ:AV0Z10480505 Keywords : linear energy transfer * bremsstrahlung beam * onboard aircraft Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders
Energy Technology Data Exchange (ETDEWEB)
Ulmer, W
2015-06-15
Purpose: During the past decade the quantization of coupled/forced electromagnetic circuits with or without Ohm’s resistance has gained the subject of some fundamental studies, since even problems of quantum electrodynamics can be solved in an elegant manner, e.g. the creation of quantized electromagnetic fields. In this communication, we shall use these principles to describe optimization procedures in the design of klystrons, synchrotron irradiation and high energy bremsstrahlung. Methods: The base is the Hamiltonian of an electromagnetic circuit and the extension to coupled circuits, which allow the study of symmetries and perturbed symmetries in a very apparent way (SU2, SU3, SU4). The introduction resistance and forced oscillators for the emission and absorption in such coupled systems provides characteristic resonance conditions, and atomic orbitals can be described by that. The extension to virtual orbitals leads to creation of bremsstrahlung, if the incident electron (velocity v nearly c) is described by a current, which is associated with its inductivitance and the virtual orbital to the charge distribution (capacitance). Coupled systems with forced oscillators can be used to amplify drastically the resonance frequencies to describe klystrons and synchrotron radiation. Results: The cross-section formula for bremsstrahlung given by the propagator method of Feynman can readily be derived. The design of klystrons and synchrotrons inclusive the radiation outcome can be described and optimized by the determination of the mutual magnetic couplings between the oscillators induced by the currents. Conclusions: The presented methods of quantization of circuits inclusive resistance provide rather a straightforward way to understand complex technical processes such as creation of bremsstrahlung or creation of radiation by klystrons and synchrotrons. They can either be used for optimization procedures and, last but not least, for pedagogical purposes with regard to
International Nuclear Information System (INIS)
Kroon, John J.; Becker, Peter A.
2014-01-01
Accreting black hole sources show a wide variety of rapid time variability, including the manifestation of time lags during X-ray transients, in which a delay (phase shift) is observed between the Fourier components of the hard and soft spectra. Despite a large body of observational evidence for time lags, no fundamental physical explanation for the origin of this phenomenon has been presented. We develop a new theoretical model for the production of X-ray time lags based on an exact analytical solution for the Fourier transform describing the diffusion and Comptonization of seed photons propagating through a spherical corona. The resulting Green's function can be convolved with any source distribution to compute the associated Fourier transform and time lags, hence allowing us to explore a wide variety of injection scenarios. We show that thermal Comptonization is able to self-consistently explain both the X-ray time lags and the steady-state (quiescent) X-ray spectrum observed in the low-hard state of Cyg X-1. The reprocessing of bremsstrahlung seed photons produces X-ray time lags that diminish with increasing Fourier frequency, in agreement with the observations for a wide range of sources
International Nuclear Information System (INIS)
Fernandez-Gomez, I.; Martin-Solis, J. R.; Sanchez, R.
2007-01-01
It has been recently argued that, at sufficiently large parallel electric fields, bremsstrahlung radiation can greatly reduce the maximum energy that runaway electrons can gain in tokamaks [M. Bakhtiari et al., Phys. Plasmas 12, 102503 (2005)]. In this contribution, the work of these authors is extended to show that the region where bremsstrahlung radiation dominate runaway energy losses is however more restricted than reported by them. Expressions will be provided for the limits of this region within the parameter space spanned by the background density and parallel electric field, as a function of the rest of the plasma parameters. It will be shown that the background density has to be above a certain critical value and that the parallel electric field must lie within a range of values, below and above which synchrotron radiation dominate the runaway energy losses. Finally, it will be demonstrated that typical disruption parameters lie within this region and, as a result, bremsstrahlung losses still play an important role in controlling the runaway energy
Hydramite II screening tests of potential bremsstrahlung converter debris shield materials
International Nuclear Information System (INIS)
Reedy, E.D. Jr.; Hedemann, M.A.; Stark, M.A.
1986-03-01
Results of a brief test series aimed at screening a number of potential bremsstrahlung converter debris shield materials are reported. These tests were run on Sandia National Laboratories' Hydramite II accelerator using a diode configuration which produces a pinched electron beam. The materials tested include: (1) laminated Kevlar 49/polyester and E-glass/polyester composites, (2) a low density laminated Kevlar 49 composite, and (3) two types of through-the-thickness reinforced Kevlar 49 composites. As expected, tests using laminated Kevlar 49/polyester shields showed that shield permanent set (i.e., permanent deflection) increased with increasing tantalum conversion foil thickness and decreased with increasing shield thickness. The through-the-thickness reinforced composites developed localized, but severe, back surface damage. The laminated composites displayed little back surface damage, although extensive internal matrix cracking and ply delaminations were generated. Roughly the same degree of permanent set was produced in shields made from the low density Kevlar 49 composite and the Kevlar 49/polyester. The E-glass reinforced shields exhibited relatively low levels of permanent set
Bremsstrahlung-Based Imaging and Assays of Radioactive, Mixed and Hazardous Waste
Kwofie, J.; Wells, D. P.; Selim, F. A.; Harmon, F.; Duttagupta, S. P.; Jones, J. L.; White, T.; Roney, T.
2003-08-01
A new nondestructive accelerator based x-ray fluorescence (AXRF) approach has been developed to identify heavy metals in large-volume samples. Such samples are an important part of the process and waste streams of U.S Department of Energy sites, as well as other industries such as mining and milling. Distributions of heavy metal impurities in these process and waste samples can range from homogeneous to highly inhomogeneous, and non-destructive assays and imaging that can address both are urgently needed. Our approach is based on using high-energy, pulsed bremsstrahlung beams (3-6.5 MeV) from small electron accelerators to produce K-shell atomic fluorescence x-rays. In addition we exploit pair-production, Compton scattering and x-ray transmission measurements from these beams to probe locations of high density and high atomic number. The excellent penetrability of these beams allows assays and images for soil-like samples at least 15 g/cm2 thick, with elemental impurities of atomic number greater than approximately 50. Fluorescence yield of a variety of targets was measured as a function of impurity atomic number, impurity homogeneity, and sample thickness. We report on actual and potential detection limits of heavy metal impurities in a soil matrix for a variety of samples, and on the potential for imaging, using AXRF and these related probes.
Laser-assisted collisions: The Kroll-Watson formula and bremsstrahlung theory
International Nuclear Information System (INIS)
Geltman, S.
1996-01-01
Recent measurements on CO 2 -laser-assisted electron-atom collisions have shown large inconsistencies with the Kroll-Watson formula for small-angle scattering. We have carried out a detailed study to compare the predictions of Kroll-Watson theory (for both single and multimode fields) with those of conventional perturbation theory for stimulated free-free transitions. It is found that for E 0 /2ω 2 <1, where perturbation theory is valid, there are large differences with the Kroll-Watson theory. Comparisons of experimental variations with respect to scattering angle and electron energy show much better agreement with perturbation theory than with Kroll-Watson theory. A study of the angular variations in perturbation theory shows that use of the open-quote open-quote outgoing close-quote close-quote wave final state gives much better agreement with experiment than does the open-quote open-quote ingoing close-quote close-quote wave final state, which is different from the choice made in early bremsstrahlung theory. copyright 1996 The American Physical Society
International Nuclear Information System (INIS)
Chaichian, M.; Hayashi, M.; Honkaranta, T.
1980-01-01
We consider in QCD the second order, in gluon-quark coupling constant, contribution of the quark-quark scatte-ring (bremsstrahlung) to the transverse momentum distribution of muon pairs produced in proton-proton collisions. In certain kinematical regions accesible to experimental tests, this contribution is quite large in comparison with the first order calculations. This happens for a specific choice of scale violating structure functions which fit the deep inelastic data. Thus the first order QCD calcula-tion alone is not conclusive in trying to fit the data -one must necessarily check the effect of the second order quark-quark scattering as compared with the first order quark-gluon and the quark-antiquark scattering. This remark concerns also the case when in the first order diagrams the effect of primordial transverse momentum of partons is included as well as the case when the first order is replaced by DDT type of formulae. Mass regularization and different prescriptions for the constant term in q → g + q vertex are considered. Results are presented for the energies √s=6.5, 27, 63, 800 GeV and are compared with experiment. Implications of these results for the detection of W +- -mesons via psub(T) distribution of their decay products μ +- in proton-proton collisions are mentioned. (author)
Reconstruction of extensive air showers using the MIDAS molecular Bremsstrahlung detector
International Nuclear Information System (INIS)
Castro, Andre Ramos de; Bonifazi, Carla; Santos, Edivaldo Moura; Soares, Elvis do Amaral; Mello Neto, Joao Ramos Torres de; Almeida, Rogerio Menezes de
2011-01-01
Full text: The weakly ionized plasma created in the atmosphere after the passage of an Extensive Air Shower (EAS) gives rise to the emission of continuous radiation known as Molecular Bremsstrahlung Radiation (MBR) as free electrons scatter off neutral nitrogen (and less frequently oxygen) molecules. The isotropic and unpolarized nature of MBR rises the possibility of an EAS detection similar to that using fluorescence telescopes to capture the ultraviolet light emitted by the ionized nitrogen molecules. The MBR emission, however, falls into the centimeter wavelength range, requiring the use of radio/microwave antennas instead of optical telescopes. In order to test the feasibility of the technique, the MIDAS (Microwave Detection of Air Showers) Collaboration has built a prototype detector where a parabolical reflector illuminates a multi-pixel camera of commercial TV satellite C-band (3.4-4.2 GHz) feeds. This work addresses the geometrical reconstruction of EAS induced by Ultra High Energy Cosmic Rays (UHECR) using the MIDAS detector. The reconstruction chain is similar to that currently applied to the Auger Fluorescence detector events. We have simulated the shower MBR emission assuming two different scenarios: coherent and incoherent emission, i.e., radiation intensity scaling quadratically and linearly with the energy of the primary particle. The MIDAS prototype detector's response is then simulated. Finally, given the simulated events in real data format, we reconstruct the shower's arrival direction, including direction uncertainties and estimate the expected rate of observed events. (author)
International Nuclear Information System (INIS)
Dumas, J.
2011-09-01
The nuclear and high-energy physics communities have shown a growing interest in the availability of high current, highly-polarized positron beams. A sufficiently energetic polarized photon or lepton incident on a target may generate, via Bremsstrahlung and pair creation within a solid target foil, electron-positron pairs that should carry some fraction of the initial polarization. Recent advances in high current (> 1 mA) spin polarized electron sources at Jefferson Lab offer the perspective of creating polarized positrons from a low energy electron beam. This thesis discusses polarization transfer from electrons to positrons in the perspective of the design optimization of a polarized positron source. The PEPPo experiment, aiming at a measurement of the positron polarization from a low energy (< 10 MeV) highly spin polarized electron beam is discussed. A successful demonstration of this technique would provide an alternative scheme for the production of low energy polarized positrons and useful information for the optimization of the design of polarized positron sources in the sub-GeV energy range. (author)
DEFF Research Database (Denmark)
Mosegaard, Klaus
2012-01-01
For non-linear inverse problems, the mathematical structure of the mapping from model parameters to data is usually unknown or partly unknown. Absence of information about the mathematical structure of this function prevents us from presenting an analytical solution, so our solution depends on our......-heuristics are inefficient for large-scale, non-linear inverse problems, and that the 'no-free-lunch' theorem holds. We discuss typical objections to the relevance of this theorem. A consequence of the no-free-lunch theorem is that algorithms adapted to the mathematical structure of the problem perform more efficiently than...... pure meta-heuristics. We study problem-adapted inversion algorithms that exploit the knowledge of the smoothness of the misfit function of the problem. Optimal sampling strategies exist for such problems, but many of these problems remain hard. © 2012 Springer-Verlag....
Inverse scale space decomposition
DEFF Research Database (Denmark)
Schmidt, Marie Foged; Benning, Martin; Schönlieb, Carola-Bibiane
2018-01-01
We investigate the inverse scale space flow as a decomposition method for decomposing data into generalised singular vectors. We show that the inverse scale space flow, based on convex and even and positively one-homogeneous regularisation functionals, can decompose data represented...... by the application of a forward operator to a linear combination of generalised singular vectors into its individual singular vectors. We verify that for this decomposition to hold true, two additional conditions on the singular vectors are sufficient: orthogonality in the data space and inclusion of partial sums...... of the subgradients of the singular vectors in the subdifferential of the regularisation functional at zero. We also address the converse question of when the inverse scale space flow returns a generalised singular vector given that the initial data is arbitrary (and therefore not necessarily in the range...
Generalized inverses theory and computations
Wang, Guorong; Qiao, Sanzheng
2018-01-01
This book begins with the fundamentals of the generalized inverses, then moves to more advanced topics. It presents a theoretical study of the generalization of Cramer's rule, determinant representations of the generalized inverses, reverse order law of the generalized inverses of a matrix product, structures of the generalized inverses of structured matrices, parallel computation of the generalized inverses, perturbation analysis of the generalized inverses, an algorithmic study of the computational methods for the full-rank factorization of a generalized inverse, generalized singular value decomposition, imbedding method, finite method, generalized inverses of polynomial matrices, and generalized inverses of linear operators. This book is intended for researchers, postdocs, and graduate students in the area of the generalized inverses with an undergraduate-level understanding of linear algebra.
Some results on inverse scattering
International Nuclear Information System (INIS)
Ramm, A.G.
2008-01-01
A review of some of the author's results in the area of inverse scattering is given. The following topics are discussed: (1) Property C and applications, (2) Stable inversion of fixed-energy 3D scattering data and its error estimate, (3) Inverse scattering with 'incomplete' data, (4) Inverse scattering for inhomogeneous Schroedinger equation, (5) Krein's inverse scattering method, (6) Invertibility of the steps in Gel'fand-Levitan, Marchenko, and Krein inversion methods, (7) The Newton-Sabatier and Cox-Thompson procedures are not inversion methods, (8) Resonances: existence, location, perturbation theory, (9) Born inversion as an ill-posed problem, (10) Inverse obstacle scattering with fixed-frequency data, (11) Inverse scattering with data at a fixed energy and a fixed incident direction, (12) Creating materials with a desired refraction coefficient and wave-focusing properties. (author)
Zade, Anand A; Rangarajan, Venkatesh; Purandare, Nilendu C; Shah, Sneha A; Agrawal, Archi R; Kulkarni, Suyash S; Shetty, Nitin
2013-11-01
Transarterial radioembolization using Y microspheres is a novel therapeutic option for inoperable hepatic malignancies. As these spheres are radiolucent, real-time assessment of their distribution during the infusion process under fluoroscopic guidance is not possible. Bremsstrahlung radiations arising from 90Y have conventionally been used for imaging its biodistribution. Recent studies have proved that sources of 90Y also emit positrons, which can further be used for PET/computed tomography (CT) imaging. This study aimed to assess the feasibility of 90Y PET/CT imaging in evaluating microsphere distributions and to compare its findings with those of Bremsstrahlung imaging. Thirty-five sessions of 90Y microsphere transarterial radioembolization were performed on 30 patients with hepatic malignancies. 90Y PET/CT imaging was performed within 3 h of therapy. Bremsstrahlung imaging was also performed for each patient. The imaging findings were compared for concordance in the distribution of microspheres. Exact one-to-one correspondence between 90Y PET/CT imaging and 90Y Bremsstrahlung imaging was observed in 97.14% of cases (i.e. in 34/35 cases). Discordance was observed only in one case in which 90Y PET/CT imaging resolved the microsphere uptake in the inferior vena cava tumor thrombus, which was, however, not visualized on Bremsstrahlung imaging. There is good concordance in the imaging findings of 90Y PET/CT and 90Y Bremsstrahlung imaging. 90Y PET/CT imaging scores over the conventionally used Bremsstrahlung imaging in terms of better resolution, ease of technique, and comparable image acquisition time. This makes it a preferred imaging modality for assessment of the distribution of 90Y microspheres.
Inversion assuming weak scattering
DEFF Research Database (Denmark)
Xenaki, Angeliki; Gerstoft, Peter; Mosegaard, Klaus
2013-01-01
due to the complex nature of the field. A method based on linear inversion is employed to infer information about the statistical properties of the scattering field from the obtained cross-spectral matrix. A synthetic example based on an active high-frequency sonar demonstrates that the proposed...
Population Genomics of Inversion Polymorphisms in Drosophila melanogaster
Corbett-Detig, Russell B.; Hartl, Daniel L.
2012-01-01
Chromosomal inversions have been an enduring interest of population geneticists since their discovery in Drosophila melanogaster. Numerous lines of evidence suggest powerful selective pressures govern the distributions of polymorphic inversions, and these observations have spurred the development of many explanatory models. However, due to a paucity of nucleotide data, little progress has been made towards investigating selective hypotheses or towards inferring the genealogical histories of inversions, which can inform models of inversion evolution and suggest selective mechanisms. Here, we utilize population genomic data to address persisting gaps in our knowledge of D. melanogaster's inversions. We develop a method, termed Reference-Assisted Reassembly, to assemble unbiased, highly accurate sequences near inversion breakpoints, which we use to estimate the age and the geographic origins of polymorphic inversions. We find that inversions are young, and most are African in origin, which is consistent with the demography of the species. The data suggest that inversions interact with polymorphism not only in breakpoint regions but also chromosome-wide. Inversions remain differentiated at low levels from standard haplotypes even in regions that are distant from breakpoints. Although genetic exchange appears fairly extensive, we identify numerous regions that are qualitatively consistent with selective hypotheses. Finally, we show that In(1)Be, which we estimate to be ∼60 years old (95% CI 5.9 to 372.8 years), has likely achieved high frequency via sex-ratio segregation distortion in males. With deeper sampling, it will be possible to build on our inferences of inversion histories to rigorously test selective models—particularly those that postulate that inversions achieve a selective advantage through the maintenance of co-adapted allele complexes. PMID:23284285
Bayesian seismic AVO inversion
Energy Technology Data Exchange (ETDEWEB)
Buland, Arild
2002-07-01
A new linearized AVO inversion technique is developed in a Bayesian framework. The objective is to obtain posterior distributions for P-wave velocity, S-wave velocity and density. Distributions for other elastic parameters can also be assessed, for example acoustic impedance, shear impedance and P-wave to S-wave velocity ratio. The inversion algorithm is based on the convolutional model and a linearized weak contrast approximation of the Zoeppritz equation. The solution is represented by a Gaussian posterior distribution with explicit expressions for the posterior expectation and covariance, hence exact prediction intervals for the inverted parameters can be computed under the specified model. The explicit analytical form of the posterior distribution provides a computationally fast inversion method. Tests on synthetic data show that all inverted parameters were almost perfectly retrieved when the noise approached zero. With realistic noise levels, acoustic impedance was the best determined parameter, while the inversion provided practically no information about the density. The inversion algorithm has also been tested on a real 3-D dataset from the Sleipner Field. The results show good agreement with well logs but the uncertainty is high. The stochastic model includes uncertainties of both the elastic parameters, the wavelet and the seismic and well log data. The posterior distribution is explored by Markov chain Monte Carlo simulation using the Gibbs sampler algorithm. The inversion algorithm has been tested on a seismic line from the Heidrun Field with two wells located on the line. The uncertainty of the estimated wavelet is low. In the Heidrun examples the effect of including uncertainty of the wavelet and the noise level was marginal with respect to the AVO inversion results. We have developed a 3-D linearized AVO inversion method with spatially coupled model parameters where the objective is to obtain posterior distributions for P-wave velocity, S
Black-hole bremsstrahlung and the efficiency of mass-energy radiative transfer
International Nuclear Information System (INIS)
Oliveira, H. P. de; Soares, I. Damiao; Tonini, E. V.
2008-01-01
We present results from numerical evolution of a boosted black hole, perturbed nonlinearly by an axisymmetric distribution of matter in the realm of Robinson-Trautman spacetimes. Characteristic initial data for the system were constructed and the Robinson-Trautmann equation was integrated for these data using a numerical code based on the Galerkin-collocation method. The emission of gravitational waves by the system is typical of bremsstrahlung at early times, a consequence of the deceleration of the black hole as it interacts with the perturbation; part of the perturbation is radiated away and another part is absorbed into the hole. The angular pattern evolves to the quadrupole form for later times. The final configuration is a black hole in motion with larger (Bondi) rest mass and smaller boost parameter. The efficiency Δ of mass-energy extraction by gravitational wave emission was also computed. The relation of Δ to the mass of the remnant black hole satisfies a nonextensive thermostatistics distribution with entropic index q≅1/2. The result extends analytical evaluations based on the linearized theory of gravitational wave emission. For each initial boost parameter, there always exists a (large) value of the perturbation parameter A 0 for which the momentum of the remnant black hole has opposite sign to that of the unperturbed black hole, due to the strong deceleration during the process of gravitational wave emission. The temporal wave form is that of an initial burst and we evaluate that for a large range of A 0 the process corresponds to a high power output in the initial dominant pulse.
International Nuclear Information System (INIS)
Brown, V.R.
1990-01-01
Nucleon-nucleon bremsstrahlung, NNγ, is a fundamental process, which involves the strong and electromagnetic fields acting simultaneously. Since the electromagnetic interaction is well known, NNγ provides a calculable tool for comparing off-energy-shell effects from different two-nucleon potentials compared to experiment and also provides a simple testing ground, which is sensitive to meson-exchange-current contributions that are so important in electronuclear physics. Historically, experimental studies have focused on ppγ, with only a few measurements of npγ. The present workshop was organized primarily to investigate the interest in, the value of, and the feasibility of doing an npγ experiment using the neutron white source at LANL. An increasing amount of US nuclear physics dollars are being spent on electronuclear physics. npγ is a fundamental process with large meson-exchange currents. In the npγ calculations of Brown and Franklin, the meson-exchange contributions increase the cross section by a factor of roughly two and later the angular distribution of the emitted photon dramatically. The details of these calculated effects have never been verified experimentally, but the proper quantum-mechanical inclusion of meson-exchange contributions, using the methods of brown and Franklin, has proved to be essential in understanding the heavy-ion results. The understanding of the importance of such terms is extremely important inelectronuclear processes, such as are presently under investigation or being planned at Bates, SLAC, and CEBAF. Just one example is in the electrodisintegration of the deuteron, where meson-exchange contributions must be included properly before any conclusions about nuclear models, such as QCD versus meson-exchange potentials can be made
Inverse kinematic-based robot control
Wolovich, W. A.; Flueckiger, K. F.
1987-01-01
A fundamental problem which must be resolved in virtually all non-trivial robotic operations is the well-known inverse kinematic question. More specifically, most of the tasks which robots are called upon to perform are specified in Cartesian (x,y,z) space, such as simple tracking along one or more straight line paths or following a specified surfacer with compliant force sensors and/or visual feedback. In all cases, control is actually implemented through coordinated motion of the various links which comprise the manipulator; i.e., in link space. As a consequence, the control computer of every sophisticated anthropomorphic robot must contain provisions for solving the inverse kinematic problem which, in the case of simple, non-redundant position control, involves the determination of the first three link angles, theta sub 1, theta sub 2, and theta sub 3, which produce a desired wrist origin position P sub xw, P sub yw, and P sub zw at the end of link 3 relative to some fixed base frame. Researchers outline a new inverse kinematic solution and demonstrate its potential via some recent computer simulations. They also compare it to current inverse kinematic methods and outline some of the remaining problems which will be addressed in order to render it fully operational. Also discussed are a number of practical consequences of this technique beyond its obvious use in solving the inverse kinematic question.
Radon concentration inversions in the troposphere
International Nuclear Information System (INIS)
Pereira, E.B.
1987-07-01
Vertical concentrations of radon in the lower troposphere were obtained in Southern Brazil up to 7Km high and have shown unexpected inverted profiles. The presence of low pressure center systems southwest to the flight path suggested that inversions might have been originated by a vertical transport mechanism based on the large scale circulation of developing synoptic systems. A simple friction-driven circulation model was contructed and the transport equation was solved. (author) [pt
Energy Technology Data Exchange (ETDEWEB)
Ropponen, T. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, FI-40014 (Finland)], E-mail: tommi.ropponen@phys.jyu.fi; Tarvainen, O. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Jones, P.; Peura, P.; Kalvas, T. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, FI-40014 (Finland); Suominen, P. [Prizztech Ltd/Magnet Technology Centre, Tiedepuisto 4, FI-28600 Pori (Finland); Koivisto, H.; Arje, J. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, FI-40014 (Finland)
2009-03-11
An electron cyclotron resonance (ECR) ion source is one of the most used ion source types for high charge state heavy ion production. In ECR plasma the electrons are heated by radio frequency microwaves in order to provide ionization of neutral gases. As a consequence, ECR heating also generates very high electron energies (up to MeV region) which can produce a vast amount of bremsstrahlung radiation causing problems with radiation shielding and heating superconducting cryostat of an ECR ion source. To gain information about the time evolution of the electron energies in ECR plasma radial bremsstrahlung measurements were performed. JYFL 14 GHz ECR ion source was operated in pulsed mode and time evolution measurements were done with different axial magnetic field strengths with oxygen and argon plasmas. Bremsstrahlung data were analyzed with a time interval of 2 ms yielding information at unprecedented detail about the time evolution of high energy bremsstrahlung radiation from an ECR ion source. It was observed, for example, that reaching the steady state phase of the plasma bremsstrahlung requires several hundred milliseconds and the steady state time can be different with different gases.
Forensic analysis of explosions: Inverse calculation of the charge mass
Voort, M.M. van der; Wees, R.M.M. van; Brouwer, S.D.; Jagt-Deutekom, M.J. van der; Verreault, J.
2015-01-01
Forensic analysis of explosions consists of determining the point of origin, the explosive substance involved, and the charge mass. Within the EU fP7 project Hyperion, TNO developed the Inverse Explosion Analysis (TNO-IEA) tool to estïmate the charge mass and point of origin based on observed damage
Electrochemically driven emulsion inversion
Johans, Christoffer; Kontturi, Kyösti
2007-09-01
It is shown that emulsions stabilized by ionic surfactants can be inverted by controlling the electrical potential across the oil-water interface. The potential dependent partitioning of sodium dodecyl sulfate (SDS) was studied by cyclic voltammetry at the 1,2-dichlorobenzene|water interface. In the emulsion the potential control was achieved by using a potential-determining salt. The inversion of a 1,2-dichlorobenzene-in-water (O/W) emulsion stabilized by SDS was followed by conductometry as a function of added tetrapropylammonium chloride. A sudden drop in conductivity was observed, indicating the change of the continuous phase from water to 1,2-dichlorobenzene, i.e. a water-in-1,2-dichlorobenzene emulsion was formed. The inversion potential is well in accordance with that predicted by the hydrophilic-lipophilic deviation if the interfacial potential is appropriately accounted for.
On the calibration process of film dosimetry: OLS inverse regression versus WLS inverse prediction
International Nuclear Information System (INIS)
Crop, F; Thierens, H; Rompaye, B Van; Paelinck, L; Vakaet, L; Wagter, C De
2008-01-01
The purpose of this study was both putting forward a statistically correct model for film calibration and the optimization of this process. A reliable calibration is needed in order to perform accurate reference dosimetry with radiographic (Gafchromic) film. Sometimes, an ordinary least squares simple linear (in the parameters) regression is applied to the dose-optical-density (OD) curve with the dose as a function of OD (inverse regression) or sometimes OD as a function of dose (inverse prediction). The application of a simple linear regression fit is an invalid method because heteroscedasticity of the data is not taken into account. This could lead to erroneous results originating from the calibration process itself and thus to a lower accuracy. In this work, we compare the ordinary least squares (OLS) inverse regression method with the correct weighted least squares (WLS) inverse prediction method to create calibration curves. We found that the OLS inverse regression method could lead to a prediction bias of up to 7.3 cGy at 300 cGy and total prediction errors of 3% or more for Gafchromic EBT film. Application of the WLS inverse prediction method resulted in a maximum prediction bias of 1.4 cGy and total prediction errors below 2% in a 0-400 cGy range. We developed a Monte-Carlo-based process to optimize calibrations, depending on the needs of the experiment. This type of thorough analysis can lead to a higher accuracy for film dosimetry
DEFF Research Database (Denmark)
Gale, A.S.; Surlyk, Finn; Anderskouv, Kresten
2013-01-01
Evidence from regional stratigraphical patterns in Santonian−Campanian chalk is used to infer the presence of a very broad channel system (5 km across) with a depth of at least 50 m, running NNW−SSE across the eastern Isle of Wight; only the western part of the channel wall and fill is exposed. W......−Campanian chalks in the eastern Isle of Wight, involving penecontemporaneous tectonic inversion of the underlying basement structure, are rejected....
Reactivity in inverse micelles
International Nuclear Information System (INIS)
Brochette, Pascal
1987-01-01
This research thesis reports the study of the use of micro-emulsions of water in oil as reaction support. Only the 'inverse micelles' domain of the ternary mixing (water/AOT/isooctane) has been studied. The main addressed issues have been: the micro-emulsion disturbance in presence of reactants, the determination of reactant distribution and the resulting kinetic theory, the effect of the interface on electron transfer reactions, and finally protein solubilization [fr
Production of a narrow band of 0.511-MeV radiation by use of the PHERMEX bremsstrahlung spectrum
International Nuclear Information System (INIS)
Stroscio, M.A.
1976-06-01
The pair production cross section is numerically integrated over a typical PHERMEX bremsstrahlung spectrum to obtain the probability of pair production in a target of nuclear charge Z, and density rho. The pair production cross section used herein is only approximate in that it neglects screening, neglects the Coulomb field for the emerging pair (first Born approximation), and neglects pair production by atomic electrons. In spite of these approximations, an order-of-magnitude estimate of the amount of 0.511-MeV radiation produced by a typical pulse is still given
International Nuclear Information System (INIS)
Jadrnickova, I.; Spurny, F.
2006-01-01
The spectrometer of linear energy transfer (Let) based on the chemically etched poly-allyl-diglycol-carbonate (P.A.D.C.) track-etch detector was developed several years ago in our institute. This Let spectrometer enables determining Let of particles approximately from 10 to 700 keV/μm. From the Let spectra, dose characteristics can be calculated. The contribution presents the Let spectra and other dosimetric characteristics obtained onboard a commercial aircraft during more than 6 months long exposure and in the 18 MV radiotherapy Bremsstrahlung beam. (authors)
International Nuclear Information System (INIS)
Tsovbun, V.I.
1977-01-01
Computer calculations have been performed to extend the data available on energy and angular distribution of the 10 MeV electron bremsrahlung into a higher angle region. The ETRAN-16D program developed by R.G.Berger for calculation of electron-photon cascades passing through matter using computers IBM-360 and UNIVAC-1108 was modified to operate with the CDC-6500 computer. A brief summary of the program is provided. An angular distribution of the bremsstrahlung dose absorbed in the air has been also calculated. The results extended into the 90-180 deg region can be used to calculate the biological shield of electron accelerators
Energy Technology Data Exchange (ETDEWEB)
Rohrmoser, Benjamin Paul
2016-11-10
In order to minimize pseudo activity whilst storage of radioactive waste packages it is required to determine the nuclide inventory as precisely as possible. The in Gamma spectra contained parts of bremsstrahlung can be used to identify and quantify certain beta nuclides. For this an analytical method has been developed. This was mainly tested with beta-emitter Sr-90 and Tm-170, as well as commonly present gamma-emitters in laboratory scale and actual 200 liter waste packages. As a result, non-destructive determination of radioactive wastes can be conducted more precisely.
Internal bremsstrahlung spectra of the allowed. beta. emitters /sup 32/P, /sup 35/S and /sup 45/Ca
Energy Technology Data Exchange (ETDEWEB)
Powar, M S; Singh, M [Punjabi Univ., Patiala (India). Dept. of Physics
1976-01-01
A study of Coulomb field effects in internal bremsstrahlung (IB) has been undertaken by measuring the IB spectra for the allowed beta emitters /sup 32/P, /sup 35/S and /sup 45/Ca in the photon energy intervals of 50 to 1600 keV, 25 to 150 keV and 30 to 240 keV respectively. The experimental results show increasing positive departures from the KUB and Coulomb-corrected theories of Lewis and Ford, and Nilsson, with decreasing beta end-point energy. In the case of /sup 35/S the experimental results are 40 % higher than the more exact theory of Struzynski and Pollock for this isotope.
International Nuclear Information System (INIS)
Steinhauer, L.C.; Romea, R.D.; Kimura, W.D.
1997-01-01
A new method for laser acceleration is proposed based upon the inverse process of transition radiation. The laser beam intersects an electron-beam traveling between two thin foils. The principle of this acceleration method is explored in terms of its classical and quantum bases and its inverse process. A closely related concept based on the inverse of diffraction radiation is also presented: this concept has the significant advantage that apertures are used to allow free passage of the electron beam. These concepts can produce net acceleration because they do not satisfy the conditions in which the Lawson-Woodward theorem applies (no net acceleration in an unbounded vacuum). Finally, practical aspects such as damage limits at optics are employed to find an optimized set of parameters. For reasonable assumptions an acceleration gradient of 200 MeV/m requiring a laser power of less than 1 GW is projected. An interesting approach to multi-staging the acceleration sections is also presented. copyright 1997 American Institute of Physics
Intersections, ideals, and inversion
International Nuclear Information System (INIS)
Vasco, D.W.
1998-01-01
Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly one dimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons
Intersections, ideals, and inversion
Energy Technology Data Exchange (ETDEWEB)
Vasco, D.W.
1998-10-01
Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly onedimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons.
Testing earthquake source inversion methodologies
Page, Morgan T.; Mai, Paul Martin; Schorlemmer, Danijel
2011-01-01
Source Inversion Validation Workshop; Palm Springs, California, 11-12 September 2010; Nowadays earthquake source inversions are routinely performed after large earthquakes and represent a key connection between recorded seismic and geodetic data
Test of Compton camera components for prompt gamma imaging at the ELBE bremsstrahlung beam
Hueso-González, F.; Golnik, C.; Berthel, M.; Dreyer, A.; Enghardt, W.; Fiedler, F.; Heidel, K.; Kormoll, T.; Rohling, H.; Schöne, S.; Schwengner, R.; Wagner, A.; Pausch, G.
2014-05-01
In the context of ion beam therapy, particle range verification is a major challenge for the quality assurance of the treatment. One approach is the measurement of the prompt gamma rays resulting from the tissue irradiation. A Compton camera based on several position sensitive gamma ray detectors, together with an imaging algorithm, is expected to reconstruct the prompt gamma ray emission density map, which is correlated with the dose distribution. At OncoRay and Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a Compton camera setup is being developed consisting of two scatter planes: two CdZnTe (CZT) cross strip detectors, and an absorber consisting of one Lu2SiO5 (LSO) block detector. The data acquisition is based on VME electronics and handled by software developed on the ROOT framework. The setup has been tested at the linear electron accelerator ELBE at HZDR, which is used in this experiment to produce bunched bremsstrahlung photons with up to 12.5 MeV energy and a repetition rate of 13 MHz. Their spectrum has similarities with the shape expected from prompt gamma rays in the clinical environment, and the flux is also bunched with the accelerator frequency. The charge sharing effect of the CZT detector is studied qualitatively for different energy ranges. The LSO detector pixel discrimination resolution is analyzed and it shows a trend to improve for high energy depositions. The time correlation between the pulsed prompt photons and the measured detector signals, to be used for background suppression, exhibits a time resolution of 3 ns FWHM for the CZT detector and of 2 ns for the LSO detector. A time walk correction and pixel-wise calibration is applied for the LSO detector, whose resolution improves up to 630 ps. In conclusion, the detector setup is suitable for time-resolved background suppression in pulsed clinical particle accelerators. Ongoing tasks are the quantitative comparison with simulations and the test of imaging algorithms. Experiments at proton
Test of Compton camera components for prompt gamma imaging at the ELBE bremsstrahlung beam
International Nuclear Information System (INIS)
Hueso-González, F; Golnik, C; Berthel, M; Dreyer, A; Enghardt, W; Kormoll, T; Rohling, H; Pausch, G; Fiedler, F; Heidel, K; Schöne, S; Schwengner, R; Wagner, A
2014-01-01
In the context of ion beam therapy, particle range verification is a major challenge for the quality assurance of the treatment. One approach is the measurement of the prompt gamma rays resulting from the tissue irradiation. A Compton camera based on several position sensitive gamma ray detectors, together with an imaging algorithm, is expected to reconstruct the prompt gamma ray emission density map, which is correlated with the dose distribution. At OncoRay and Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a Compton camera setup is being developed consisting of two scatter planes: two CdZnTe (CZT) cross strip detectors, and an absorber consisting of one Lu 2 SiO 5 (LSO) block detector. The data acquisition is based on VME electronics and handled by software developed on the ROOT framework. The setup has been tested at the linear electron accelerator ELBE at HZDR, which is used in this experiment to produce bunched bremsstrahlung photons with up to 12.5 MeV energy and a repetition rate of 13 MHz. Their spectrum has similarities with the shape expected from prompt gamma rays in the clinical environment, and the flux is also bunched with the accelerator frequency. The charge sharing effect of the CZT detector is studied qualitatively for different energy ranges. The LSO detector pixel discrimination resolution is analyzed and it shows a trend to improve for high energy depositions. The time correlation between the pulsed prompt photons and the measured detector signals, to be used for background suppression, exhibits a time resolution of 3 ns FWHM for the CZT detector and of 2 ns for the LSO detector. A time walk correction and pixel-wise calibration is applied for the LSO detector, whose resolution improves up to 630 ps. In conclusion, the detector setup is suitable for time-resolved background suppression in pulsed clinical particle accelerators. Ongoing tasks are the quantitative comparison with simulations and the test of imaging algorithms. Experiments at proton
International Nuclear Information System (INIS)
Kumar, Narender; Rodrigues, G.; Lakshmy, P. S.; Mathur, Y.; Ahuja, R.; Kanjilal, D.; Baskaran, R.
2014-01-01
A compact microwave ion source has been designed and developed for operation at a frequency of 2.45 GHz. The axial magnetic field is based on two permanent magnet rings, operating in the “off-resonance” mode and is tunable by moving the permanent magnets. In order to understand the electron energy distribution function, x-ray bremsstrahlung has been measured in the axial direction. Simulation studies on the x-ray bremsstrahlung have been carried out to compare with the experimental results. The effect of the axial magnetic field with respect to the microwave launching position and the position of the extraction electrode on the x-ray bremsstrahlung have been studied
Energy Technology Data Exchange (ETDEWEB)
Kumar, Narender; Rodrigues, G., E-mail: gerosro@gmail.com; Lakshmy, P. S.; Mathur, Y.; Ahuja, R.; Kanjilal, D. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi (India); Baskaran, R. [Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu (India)
2014-02-15
A compact microwave ion source has been designed and developed for operation at a frequency of 2.45 GHz. The axial magnetic field is based on two permanent magnet rings, operating in the “off-resonance” mode and is tunable by moving the permanent magnets. In order to understand the electron energy distribution function, x-ray bremsstrahlung has been measured in the axial direction. Simulation studies on the x-ray bremsstrahlung have been carried out to compare with the experimental results. The effect of the axial magnetic field with respect to the microwave launching position and the position of the extraction electrode on the x-ray bremsstrahlung have been studied.
Kumar, Narender; Rodrigues, G; Lakshmy, P S; Baskaran, R; Mathur, Y; Ahuja, R; Kanjilal, D
2014-02-01
A compact microwave ion source has been designed and developed for operation at a frequency of 2.45 GHz. The axial magnetic field is based on two permanent magnet rings, operating in the "off-resonance" mode and is tunable by moving the permanent magnets. In order to understand the electron energy distribution function, x-ray bremsstrahlung has been measured in the axial direction. Simulation studies on the x-ray bremsstrahlung have been carried out to compare with the experimental results. The effect of the axial magnetic field with respect to the microwave launching position and the position of the extraction electrode on the x-ray bremsstrahlung have been studied.
Energy Technology Data Exchange (ETDEWEB)
Bilokon, H; D' Ettorre Piazzoli, B; Mannocchi, G [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati); Bologna, G; Picchi, P [Turin Univ. (Italy). Ist. di Fisica Generale; Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati); Celani, F; Falcioni, R [Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati
1983-01-01
We recall the properties of coherent bremsstrahlung of high energy electrons in single crystals and show that a suitably oriented diamond crystal can produce a high energy bremsstrahlung beam whose quasimonochromatic spectral composition may be exploited for increasing the production rate in a photoproduction experiment at hundreds of GeV. A careful analysis of the required angular resolutions is performed. It turns out that the standard deviation of the electron beam angular divergence in one plane should be less than 0.3 mrad, for a beam energy of 150 GeV. The standard deviation in the perpendicular plane is not critical. In this situation the photoproduction rate in a typical case is increased by a factor of about 3 with respect to the conventional bremsstrahlung beam.
Lim, Hongki; Fessler, Jeffrey A.; Wilderman, Scott J.; Brooks, Allen F.; Dewaraja, Yuni K.
2018-06-01
While the yield of positrons used in Y-90 PET is independent of tissue media, Y-90 SPECT imaging is complicated by the tissue dependence of bremsstrahlung photon generation. The probability of bremsstrahlung production is proportional to the square of the atomic number of the medium. Hence, the same amount of activity in different tissue regions of the body will produce different numbers of bremsstrahlung photons. Existing reconstruction methods disregard this tissue-dependency, potentially impacting both qualitative and quantitative imaging of heterogeneous regions of the body such as bone with marrow cavities. In this proof-of-concept study, we propose a new maximum-likelihood method that incorporates bremsstrahlung generation probabilities into the system matrix, enabling images of the desired Y-90 distribution to be reconstructed instead of the ‘bremsstrahlung distribution’ that is obtained with existing methods. The tissue-dependent probabilities are generated by Monte Carlo simulation while bone volume fractions for each SPECT voxel are obtained from co-registered CT. First, we demonstrate the tissue dependency in a SPECT/CT imaging experiment with Y-90 in bone equivalent solution and water. Visually, the proposed reconstruction approach better matched the true image and the Y-90 PET image than the standard bremsstrahlung reconstruction approach. An XCAT phantom simulation including bone and marrow regions also demonstrated better agreement with the true image using the proposed reconstruction method. Quantitatively, compared with the standard reconstruction, the new method improved estimation of the liquid bone:water activity concentration ratio by 40% in the SPECT measurement and the cortical bone:marrow activity concentration ratio by 58% in the XCAT simulation.
Dose calculations using MARS for Bremsstrahlung beam stops and collimators in APS beamline stations.
Energy Technology Data Exchange (ETDEWEB)
Dooling, J.; Accelerator Systems Division (APS)
2010-11-01
The Monte Carlo radiation transport code MARS is used to model the generation of gas bremsstrahlung (GB) radiation from 7-GeV electrons which scatter from residual gas atoms in undulator straight sections within the Advanced Photon Source (APS) storage ring. Additionally, MARS is employed to model the interactions of the GB radiation with components along the x-ray beamlines and then determine the expected radiation dose-rates that result. In this manner, MARS can be used to assess the adequacy of existing shielding or the specifications for new shielding when required. The GB radiation generated in the 'thin-target' of an ID straight section will consist only of photons in a 1/E-distribution up to the full energy of the stored electron beam. Using this analytical model, the predicted GB power for a typical APS 15.38-m insertion device (ID) straight section is 4.59 x 10{sup -7} W/nTorr/mA, assuming a background gas composed of air (Z{sub eff} = 7.31) at room temperature (293K). The total GB power provides a useful benchmark for comparisons between analytical and numerical approaches. We find good agreement between MARS and analytical estimates for total GB power. The extended straight section 'target' creates a radial profile of GB, which is highly peaked centered on the electron beam. The GB distribution reflects the size of the electron beam that creates the radiation. Optimizing the performance of MARS in terms of CPU time per incident trajectory requires the use of a relatively short, high-density gas target (air); in this report, the target density is {rho}L = 2.89 x 10{sup -2} g/cm{sup 2} over a length of 24 cm. MARS results are compared with the contact dose levels reported in TB-20, which used EGS4 for radiation transport simulations. Maximum dose-rates in 1 cc of tissue phantom form the initial basis for comparison. MARS and EGS4 results are approximately the same for maximum 1-cc dose-rates and attenuation in the photon
International Nuclear Information System (INIS)
Goosman, D.R.
1983-01-01
The SANDYL Monte-Carlo code has been used to calculate the Bremsstrahlung photon production from beams of parallel electrons incident upon three target geometries. These are 20 MeV electrons onto 1 mm of tungsten + 59 mm of Be, which simulates the operating parameters of the FXR electron accelerator at LLNL Bldg. 801, 45 MeV electrons onto 1 mm of tungsten, and finally 45 MeV electrons onto 1 mm of tungsten and 147 mm of Be. The latter two situations simulate possible future modifications to the FXR accelerator. Graphs of the spectral shape of the Bremsstrahlung photons emitted with angles between 0 0 and 1 0 to the electron direction, the angular distribution of photon-MeV, and the dose reduction curves for each of the three geometries are given. The latter dose reduction curves allow one to calculate forward-directed photon fluxes in real-life situations where the electron beam has non-zero angular divergence
International Nuclear Information System (INIS)
Dickens, J.K.
2001-01-01
The bremsstrahlung created by 150-MeV electrons impinging on a tantalum radiator was used to study photonuclear reactions on samples containing Be, C, Na, Cl and Ge. For Ge fifteen radioisotopes, ranging in half life between 2.6 min and 271 days, and in mass between 65 and 75, were obtained in sufficient amount to determine their yields quantitatively using known decay gamma-rays. Special equipment is described which was developed to create the bremsstrahlung using a beam-sharing mode, while minimizing the neutron flux on the sample. Relative production rates were determined. These were analyzed to provide absolute average cross sections for production of three reactions
Introduction to Schroedinger inverse scattering
International Nuclear Information System (INIS)
Roberts, T.M.
1991-01-01
Schroedinger inverse scattering uses scattering coefficients and bound state data to compute underlying potentials. Inverse scattering has been studied extensively for isolated potentials q(x), which tend to zero as vertical strokexvertical stroke→∞. Inverse scattering for isolated impurities in backgrounds p(x) that are periodic, are Heaviside steps, are constant for x>0 and periodic for x<0, or that tend to zero as x→∞ and tend to ∞ as x→-∞, have also been studied. This paper identifies literature for the five inverse problems just mentioned, and for four other inverse problems. Heaviside-step backgrounds are discussed at length. (orig.)
Inverse scattering with supersymmetric quantum mechanics
International Nuclear Information System (INIS)
Baye, Daniel; Sparenberg, Jean-Marc
2004-01-01
The application of supersymmetric quantum mechanics to the inverse scattering problem is reviewed. The main difference with standard treatments of the inverse problem lies in the simple and natural extension to potentials with singularities at the origin and with a Coulomb behaviour at infinity. The most general form of potentials which are phase-equivalent to a given potential is discussed. The use of singular potentials allows adding or removing states from the bound spectrum without contradicting the Levinson theorem. Physical applications of phase-equivalent potentials in nuclear reactions and in three-body systems are described. Derivation of a potential from the phase shift at fixed orbital momentum can also be performed with the supersymmetric inversion by using a Bargmann-type approximation of the scattering matrix or phase shift. A unique singular potential without bound states can be obtained from any phase shift. A limited number of bound states depending on the singularity can then be added. This inversion procedure is illustrated with nucleon-nucleon scattering
Inverse Faraday Effect Revisited
Mendonça, J. T.; Ali, S.; Davies, J. R.
2010-11-01
The inverse Faraday effect is usually associated with circularly polarized laser beams. However, it was recently shown that it can also occur for linearly polarized radiation [1]. The quasi-static axial magnetic field by a laser beam propagating in plasma can be calculated by considering both the spin and the orbital angular momenta of the laser pulse. A net spin is present when the radiation is circularly polarized and a net orbital angular momentum is present if there is any deviation from perfect rotational symmetry. This orbital angular momentum has recently been discussed in the plasma context [2], and can give an additional contribution to the axial magnetic field, thus enhancing or reducing the inverse Faraday effect. As a result, this effect that is usually attributed to circular polarization can also be excited by linearly polarized radiation, if the incident laser propagates in a Laguerre-Gauss mode carrying a finite amount of orbital angular momentum.[4pt] [1] S. ALi, J.R. Davies and J.T. Mendonca, Phys. Rev. Lett., 105, 035001 (2010).[0pt] [2] J. T. Mendonca, B. Thidé, and H. Then, Phys. Rev. Lett. 102, 185005 (2009).
Holtzman, Alexander
2009-01-01
Humorist Josh Billings quipped, "About the most originality that any writer can hope to achieve honestly is to steal with good judgment." Billings was harsh in his view of originality, but his critique reveals a tension faced by students every time they write a history paper. Research is the essence of any history paper. Especially in high school,…
Inverse compton light source: a compact design proposal
Energy Technology Data Exchange (ETDEWEB)
Deitrick, Kirsten Elizabeth [Old Dominion Univ., Norfolk, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2017-05-01
In the last decade, there has been an increasing demand for a compact Inverse Compton Light Source (ICLS) which is capable of producing high-quality X-rays by colliding an electron beam and a high-quality laser. It is only in recent years when both SRF and laser technology have advanced enough that compact sources can approach the quality found at large installations such as the Advanced Photon Source at Argonne National Laboratory. Previously, X-ray sources were either high flux and brilliance at a large facility or many orders of magnitude lesser when produced by a bremsstrahlung source. A recent compact source was constructed by Lyncean Technologies using a storage ring to produce the electron beam used to scatter the incident laser beam. By instead using a linear accelerator system for the electron beam, a significant increase in X-ray beam quality is possible, though even subsequent designs also featuring a storage ring offer improvement. Preceding the linear accelerator with an SRF reentrant gun allows for an extremely small transverse emittance, increasing the brilliance of the resulting X-ray source. In order to achieve sufficiently small emittances, optimization was done regarding both the geometry of the gun and the initial electron bunch distribution produced off the cathode. Using double-spoke SRF cavities to comprise the linear accelerator allows for an electron beam of reasonable size to be focused at the interaction point, while preserving the low emittance that was generated by the gun. An aggressive final focusing section following the electron beam's exit from the accelerator produces the small spot size at the interaction point which results in an X-ray beam of high flux and brilliance. Taking all of these advancements together, a world class compact X-ray source has been designed. It is anticipated that this source would far outperform the conventional bremsstrahlung and many other compact ICLSs, while coming closer to performing at the
Directory of Open Access Journals (Sweden)
Markus Spiliotis
Full Text Available Inverse fusion PCR cloning (IFPC is an easy, PCR based three-step cloning method that allows the seamless and directional insertion of PCR products into virtually all plasmids, this with a free choice of the insertion site. The PCR-derived inserts contain a vector-complementary 5'-end that allows a fusion with the vector by an overlap extension PCR, and the resulting amplified insert-vector fusions are then circularized by ligation prior transformation. A minimal amount of starting material is needed and experimental steps are reduced. Untreated circular plasmid, or alternatively bacteria containing the plasmid, can be used as templates for the insertion, and clean-up of the insert fragment is not urgently required. The whole cloning procedure can be performed within a minimal hands-on time and results in the generation of hundreds to ten-thousands of positive colonies, with a minimal background.
International Nuclear Information System (INIS)
Hicks, H.R.; Dory, R.A.; Holmes, J.A.
1983-01-01
We illustrate in some detail a 2D inverse-equilibrium solver that was constructed to analyze tokamak configurations and stellarators (the latter in the context of the average method). To ensure that the method is suitable not only to determine equilibria, but also to provide appropriately represented data for existing stability codes, it is important to be able to control the Jacobian, tilde J is identical to delta(R,Z)/delta(rho, theta). The form chosen is tilde J = J 0 (rho)R/sup l/rho where rho is a flux surface label, and l is an integer. The initial implementation is for a fixed conducting-wall boundary, but the technique can be extended to a free-boundary model
International Nuclear Information System (INIS)
Nakamura, Takashi; Nishimoto, Takanao; Hirayama, Hideo.
1977-01-01
The spatial distributions of bremsstrahlung in water (1 m thick) and water (60 cm thick)-iron (6.3 cm thick) bombarded by 22-MeV electrons were measured by using a new activation method which we developed. These informations are useful for studying shielding, residual activity and radiation damage of accelerator and target materials. From the measured activities, the bremsstrahlung spectra in water were evaluated with the LYRA and the SAND-II unfolding codes. The evaluated spectra were in good agreement with the analytical calculation by the DIBRE code, except for the higher energy ends. The longitudinal and the lateral distributions of bremsstrahlung flux in water were obtained by integrating the evaluated spectra above 8 MeV. The agreement of the experimental and the calculated flux distributions was very good except for a large angle to beam direction. The total photon number crossing a plane normal to the beam axis attenuates exponentially along the axial depth. The iso-flux contour of bremsstrahlung flux was given by interpolating the flux distribution curves. Only the saturated activities of gold detectors were obtained for water-iron in good experimental accuracy. The spatial distribution of gold saturated activities in water-iron clearly shows the attenuating effect due to strong absorption in iron. (auth.)
Maydanyuk, Sergei P.
2012-07-01
A model of the bremsstrahlung emission which accompanies proton decay and collisions of protons off nuclei in the low- to intermediate-energy region has been developed. This model includes spin formalism, a potential approach for describing the interaction between protons and nuclei, and an emission that includes a component of the magnetic emission (defined on the basis of the Pauli equation). For the problem of bremsstrahlung during proton decay the role of magnetic emission is studied by using such a model. For the 146Tm nucleus the following has been studied: (1) How much does the magnetic emission change the full bremsstrahlung spectrum? (2) At which angle is the magnetic emission the most intensive relative to the electric emission? (3) Is there some spatial region where the magnetic emission increases strongly relative to the electric emission? (4) How intensive is the magnetic emission in the tunneling region? (5) Which is the maximal probability? Which value does it equal to at the zero-energy limit of the emitted photons? It is demonstrated that the model is able to describe well enough experimental data of bremsstrahlung emission which accompanies collisions of protons off 9C, 64Cu, and 107Ag nuclei at an incident energy of Tlab=72 MeV (at a photon energy up to 60 MeV) and off 9Be, 12C, and 208Pb nuclei at an incident energy of Tlab=140 MeV (at a photon energy up to 120 MeV).
Transmuted Generalized Inverse Weibull Distribution
Merovci, Faton; Elbatal, Ibrahim; Ahmed, Alaa
2013-01-01
A generalization of the generalized inverse Weibull distribution so-called transmuted generalized inverse Weibull dis- tribution is proposed and studied. We will use the quadratic rank transmutation map (QRTM) in order to generate a flexible family of probability distributions taking generalized inverse Weibull distribution as the base value distribution by introducing a new parameter that would offer more distributional flexibility. Various structural properties including explicit expression...
African Journals Online (AJOL)
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Original Article. Prevalence of Gall Bladder Stones among Type 2 Diabetic ... Increasing age, female gender, overweight, familial history of the disease and type 2 diabetes mellitus is all associated ... GBS development in diabetics. An Italian ...
African Journals Online (AJOL)
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UDS Publishers Limited All Right Reserved 2026-6294. ORIGINAL ... Reproductive development and function in human and other ... sulting solution was filtered and left to stand for three days to ..... male rat brain and pituitary. Brain Res 164,.
DEFF Research Database (Denmark)
Schmidt, Christina Haandbæk
Original pedagogues Distention between competences and originality By Christina Haandbæk Schmidt, ph. d. student Aarhus University, Denmark This presentation concerns a Ph.D. project (Sept. 2012 –Sept. 2015) about pedagogues in day care facilities and their struggles to develop and retain...... shall argue that it is necessary for the pedagogues to know how they are constituted by the regimes of power on one side and on the other side are forced to create themselves. This knowledge could transform pedagogues into what I suggest calling ‘original pedagogues’, who have an authentic, ethic...... and professional autonomy in exercising judgment concerning pedagogical situations. To understand how pedagogues can struggle the distention between being competent and being original the project draws on both Michel Foucault and Charles Taylor as two incompatible theories on modern identity. The study...
Inverse feasibility problems of the inverse maximum flow problems
Indian Academy of Sciences (India)
199–209. c Indian Academy of Sciences. Inverse feasibility problems of the inverse maximum flow problems. ADRIAN DEACONU. ∗ and ELEONOR CIUREA. Department of Mathematics and Computer Science, Faculty of Mathematics and Informatics, Transilvania University of Brasov, Brasov, Iuliu Maniu st. 50,. Romania.
International Nuclear Information System (INIS)
Ballard, W.P.; Lorence, L.J. Jr.; Snowden, D.P.; Van Lint, V.A.J.; Beale, E.S.
1987-01-01
This work compares a carefully designed experiment to measure photoemission with the predictions of three different codes (CEPXS/ONETRAN, TIGERP, and TIGER) for the complex bremsstrahlung spectra typical of very intense pulsed power x-ray generators. The Monte Carlo codes TIGER and TIGERP can calculate the net photon-induced electron emission but accurate results may require that statistical error be minimized. CEPXS/ONETRAN is a new deterministic coupled electron/photon transport code that is faster than Monte Carlo and is not subject to statistical error. The comparison of net yields is a sensitive test of the relative accuracy and efficiency of these various codes. The authors find that all of the codes substantially agree with the experiments for the forward net yields. However, for reverse net yields from high-Z materials, the codes overpredict relative to measurements
Energy Technology Data Exchange (ETDEWEB)
Rassow, J; Eipper, H H; Krause, K [Essen Univ. (Gesamthochschule) (Germany, F.R.). Abt. fuer Klinische Strahlenphysik; Staedtisches Krankenhaus Koeln-Merheim (Germany, F.R.). Roentgeninstitut und Strahlenklinik)
1977-05-01
The constancy of the radiation quality of therapeutically employed particle accelerators has to be checked at weekly intervals. Any change in radiation quality may have considerable therapeutic effects owing to its influence on dose distribution. It is recommended that measurements be made instead of, or in addition to, the axial reference-point measurement at 5 and 15 cm depth in the phantom, at 5 cm depth in the beam axis and at a reference-point about 1 cm within the geometric edge of the field, for checking the constancy of the radiation quality of bremsstrahlung. Only then, if routine checks carried out for the axial and the lateral reference-point dose ratios do not show any deviations greater than e.g. +-2 %, radiation quality is deemed to have remained sufficiently constant for radiotherapeutical applications.
Lemos, N.; Albert, F.; Shaw, J. L.; Papp, D.; Polanek, R.; King, P.; Milder, A. L.; Marsh, K. A.; Pak, A.; Pollock, B. B.; Hegelich, B. M.; Moody, J. D.; Park, J.; Tommasini, R.; Williams, G. J.; Chen, Hui; Joshi, C.
2018-05-01
An x-ray source generated by an electron beam produced using a Self-Modulated Laser Wakefield Accelerator (SM-LWFA) is explored for use in high energy density science facilities. By colliding the electron beam, with a maximum energy of 380 MeV, total charge of >10 nC and a divergence of 64 × 100 mrad, from a SM-LWFA driven by a 1 ps 120 J laser, into a high-Z foil, an x/gamma-ray source was generated. A broadband bremsstrahlung energy spectrum with temperatures ranging from 0.8 to 2 MeV was measured with an almost 2 orders of magnitude flux increase when compared with other schemes using LWFA. GEANT4 simulations were done to calculate the source size and divergence.
International Nuclear Information System (INIS)
Ofengeim, D D; Kaminker, A D; Yakovlev, D G
2015-01-01
We derive an analytic approximation for the emissivity of neutrino-pair bremsstrahlung (NPB) due to scattering of electrons by atomic nuclei in a neutron star (NS) crust of any realistic composition. The emissivity is expressed through generalized Coulomb logarithm by introducing an effective potential of electron-nucleus scattering. In addition, we study the conditions at which NPB in the crust is affected by strong magnetic fields and outline the main effects of the fields on neutrino emission in NSs. The results can be used for modelling of many phenomena in NSs, such as cooling of young isolated NSs, thermal relaxation of accreting NSs with overheated crust in soft X-ray transients and evolution of magnetars. (paper)
Fission of intermediate mass nuclei by bremsstrahlung photons in the energy range 0.8-1.8 GeV
International Nuclear Information System (INIS)
Lima, D.A. de.
1983-01-01
The fission of intermediate mass nuclei in the Al-Ta internal induced by bremsstrahlung photons of maximum energies between 0,8 to 1,8 GeV is studied. Thin targets of Nd and Sm and dense targets of Al,Ti,Co,Zr,Nb,Ag,In and Ta are utilized, and all the aspects related with the fission fragment absorption by the targets themselves are considered. The samples are exposed in th 2,5 GeV Electron Synchrotron at Bonn University. Muscovite mica, CR-39 and makrofol are used as fission fragments detectors. Fission cross sections and nuclear fissionabilities of the studied elements are estimated. (L.C.) [pt
International Nuclear Information System (INIS)
Yu Haijun; Zhu Jun; Chen Nan; Xie Yutong; Jiang Xiaoguo; Jian Cheng
2010-01-01
Positive ions released from x-ray converter target impacted by electron beam of millimeter spot size can be trapped and accelerated in the incident beam's potential well. As the ions move upstream, the beam will be pinched first and then defocused at the target. Four Faraday cups are used to collect backstreaming ions produced at the bremsstrahlung converter target in Dragon-I linear induction accelerator (LIA). Experimental and theoretical results show that the backstreaming positive ions density and velocity are about 10 21 /m 3 and 2-3 mm/μs, respectively. The theoretical and experimental results of electron beam envelope with ions and without ions are also presented. The discussions show that the backstreaming positive ions will not affect the electron beam focusing and envelope radius in Dragon-I LIA.
International Nuclear Information System (INIS)
Miller, G.A.; Sorensen, L.B.
1997-01-01
Quantum electrodynamics (QED) is used to derive the differential cross sections measured in the three new experimental internal source ensemble x-ray holographies: bremsstrahlung (BXH), fluorescence (XFH), and multiple-energy (MEXH) x-ray holography. The polarization dependence of the BXH cross section is also obtained. For BXH, we study analytically and numerically the possible effects of the virtual photons and electrons which enter QED calculations in summing over the intermediate states. For the low photon and electron energies used in the current experiments, we show that the virtual intermediate states produce only very small effects. This is because the uncertainty principle limits the distance that the virtual particles can propagate to be much shorter than the separation between the regions of high electron density in the adjacent atoms. We also find that using the asymptotic form of the scattering wave function causes about a 5 10% error for near forward scattering. copyright 1997 The American Physical Society
A microwave inverse Cerenkov Accelerator (MICA)
International Nuclear Information System (INIS)
Hirshfield, Jay L.
1999-01-01
The objective of this Phase II SBIR research program was to complete the final design originated during Phase I for a prototype Microwave Inverse Cerenkov Accelerator (MICA), to fabricate the-prototype MICA, and to test its performance as an electron accelerator. This report contains details of the design, predictions of accelerator performance, results of cold tests on the MICA structure, and details of the installation of MICA on the Yale Beam Physics Laboratory 6-MeV beamline. Discussion of future work is also included
Stimulated bremsstrahlung of soft x-ray in a longitudinal undulating electric field
International Nuclear Information System (INIS)
Kim, S.H.
1991-01-01
It is shown that a high-energy electron beam injected into a longitudinal undulating electric field (electric undulator) in the field direction can emit a laser light in the field direction through both stimulated and unstimulated free-electron two-quantum Stark emission. Based on the momentum and energy conservation laws and the time-reversal invariance of the transition probability, a new quantum kinetic equation for the net energy transfer from an electron to the laser wave is derived. By using this equation, the photon concept, and the transition probability calculated by the Dirac equation, the gain spectrum and wavelength of the free-electron laser using the electric undulator are derived. The gain appears to scale as the inverse of the electron beam energy and the cube of the wavelength of the electric undulator
Reconstruction of bremsstrahlung spectra from attenuation data using generalized simulated annealing
International Nuclear Information System (INIS)
Menin, O.H.; Martinez, A.S.; Costa, A.M.
2016-01-01
A generalized simulated annealing algorithm, combined with a suitable smoothing regularization function is used to solve the inverse problem of X-ray spectrum reconstruction from attenuation data. The approach is to set the initial acceptance and visitation temperatures and to standardize the terms of objective function to automate the algorithm to accommodate different spectra ranges. Experiments with both numerical and measured attenuation data are presented. Results show that the algorithm reconstructs spectra shapes accurately. It should be noted that in this algorithm, the regularization function was formulated to guarantee a smooth spectrum, thus, the presented technique does not apply to X-ray spectrum where characteristic radiation are present. - Highlights: • X-ray spectra reconstruction from attenuation data using generalized simulated annealing. • Algorithm employs a smoothing regularization function, and sets the initial acceptance and visitation temperatures. • Algorithmic is automated by standardizing the terms of the objective function. • Algorithm is compared with classical methods.
Face inversion increases attractiveness.
Leder, Helmut; Goller, Juergen; Forster, Michael; Schlageter, Lena; Paul, Matthew A
2017-07-01
Assessing facial attractiveness is a ubiquitous, inherent, and hard-wired phenomenon in everyday interactions. As such, it has highly adapted to the default way that faces are typically processed: viewing faces in upright orientation. By inverting faces, we can disrupt this default mode, and study how facial attractiveness is assessed. Faces, rotated at 90 (tilting to either side) and 180°, were rated on attractiveness and distinctiveness scales. For both orientations, we found that faces were rated more attractive and less distinctive than upright faces. Importantly, these effects were more pronounced for faces rated low in upright orientation, and smaller for highly attractive faces. In other words, the less attractive a face was, the more it gained in attractiveness by inversion or rotation. Based on these findings, we argue that facial attractiveness assessments might not rely on the presence of attractive facial characteristics, but on the absence of distinctive, unattractive characteristics. These unattractive characteristics are potentially weighed against an individual, attractive prototype in assessing facial attractiveness. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.
Inverse problem in hydrogeology
Carrera, Jesús; Alcolea, Andrés; Medina, Agustín; Hidalgo, Juan; Slooten, Luit J.
2005-03-01
The state of the groundwater inverse problem is synthesized. Emphasis is placed on aquifer characterization, where modelers have to deal with conceptual model uncertainty (notably spatial and temporal variability), scale dependence, many types of unknown parameters (transmissivity, recharge, boundary conditions, etc.), nonlinearity, and often low sensitivity of state variables (typically heads and concentrations) to aquifer properties. Because of these difficulties, calibration cannot be separated from the modeling process, as it is sometimes done in other fields. Instead, it should be viewed as one step in the process of understanding aquifer behavior. In fact, it is shown that actual parameter estimation methods do not differ from each other in the essence, though they may differ in the computational details. It is argued that there is ample room for improvement in groundwater inversion: development of user-friendly codes, accommodation of variability through geostatistics, incorporation of geological information and different types of data (temperature, occurrence and concentration of isotopes, age, etc.), proper accounting of uncertainty, etc. Despite this, even with existing codes, automatic calibration facilitates enormously the task of modeling. Therefore, it is contended that its use should become standard practice. L'état du problème inverse des eaux souterraines est synthétisé. L'accent est placé sur la caractérisation de l'aquifère, où les modélisateurs doivent jouer avec l'incertitude des modèles conceptuels (notamment la variabilité spatiale et temporelle), les facteurs d'échelle, plusieurs inconnues sur différents paramètres (transmissivité, recharge, conditions aux limites, etc.), la non linéarité, et souvent la sensibilité de plusieurs variables d'état (charges hydrauliques, concentrations) des propriétés de l'aquifère. A cause de ces difficultés, le calibrage ne peut êtreséparé du processus de modélisation, comme c'est le
Zhang, Dongliang
2013-01-01
To increase the illumination of the subsurface and to eliminate the dependency of FWI on the source wavelet, we propose multiples waveform inversion (MWI) that transforms each hydrophone into a virtual point source with a time history equal to that of the recorded data. These virtual sources are used to numerically generate downgoing wavefields that are correlated with the backprojected surface-related multiples to give the migration image. Since the recorded data are treated as the virtual sources, knowledge of the source wavelet is not required, and the subsurface illumination is greatly enhanced because the entire free surface acts as an extended source compared to the radiation pattern of a traditional point source. Numerical tests on the Marmousi2 model show that the convergence rate and the spatial resolution of MWI is, respectively, faster and more accurate then FWI. The potential pitfall with this method is that the multiples undergo more than one roundtrip to the surface, which increases attenuation and reduces spatial resolution. This can lead to less resolved tomograms compared to conventional FWI. The possible solution is to combine both FWI and MWI in inverting for the subsurface velocity distribution.
An interpretation of signature inversion
International Nuclear Information System (INIS)
Onishi, Naoki; Tajima, Naoki
1988-01-01
An interpretation in terms of the cranking model is presented to explain why signature inversion occurs for positive γ of the axially asymmetric deformation parameter and emerges into specific orbitals. By introducing a continuous variable, the eigenvalue equation can be reduced to a one dimensional Schroedinger equation by means of which one can easily understand the cause of signature inversion. (author)
Inverse problems for Maxwell's equations
Romanov, V G
1994-01-01
The Inverse and Ill-Posed Problems Series is a series of monographs publishing postgraduate level information on inverse and ill-posed problems for an international readership of professional scientists and researchers. The series aims to publish works which involve both theory and applications in, e.g., physics, medicine, geophysics, acoustics, electrodynamics, tomography, and ecology.
Algebraic properties of generalized inverses
Cvetković‐Ilić, Dragana S
2017-01-01
This book addresses selected topics in the theory of generalized inverses. Following a discussion of the “reverse order law” problem and certain problems involving completions of operator matrices, it subsequently presents a specific approach to solving the problem of the reverse order law for {1} -generalized inverses. Particular emphasis is placed on the existence of Drazin invertible completions of an upper triangular operator matrix; on the invertibility and different types of generalized invertibility of a linear combination of operators on Hilbert spaces and Banach algebra elements; on the problem of finding representations of the Drazin inverse of a 2x2 block matrix; and on selected additive results and algebraic properties for the Drazin inverse. In addition to the clarity of its content, the book discusses the relevant open problems for each topic discussed. Comments on the latest references on generalized inverses are also included. Accordingly, the book will be useful for graduate students, Ph...
Walrand, Stephan; Hesse, Michel; Jamar, François; Lhommel, Renaud
2018-04-01
Our literature survey revealed a physical effect unknown to the nuclear medicine community, i.e. internal bremsstrahlung emission, and also the existence of long energy resolution tails in crystal scintillation. None of these effects has ever been modelled in PET Monte Carlo (MC) simulations. This study investigates whether these two effects could be at the origin of two unexplained observations in 90Y imaging by PET: the increasing tails in the radial profile of true coincidences, and the presence of spurious extrahepatic counts post radioembolization in non-TOF PET and their absence in TOF PET. These spurious extrahepatic counts hamper the microsphere delivery check in liver radioembolization. An acquisition of a 32P vial was performed on a GSO PET system. This is the ideal setup to study the impact of bremsstrahlung x-rays on the true coincidence rate when no positron emission and no crystal radioactivity are present. A MC simulation of the acquisition was performed using Gate-Geant4. MC simulations of non-TOF PET and TOF-PET imaging of a synthetic 90Y human liver radioembolization phantom were also performed. Internal bremsstrahlung and long energy resolution tails inclusion in MC simulations quantitatively predict the increasing tails in the radial profile. In addition, internal bremsstrahlung explains the discrepancy previously observed in bremsstrahlung SPECT between the measure of the 90Y bremsstrahlung spectrum and its simulation with Gate-Geant4. However the spurious extrahepatic counts in non-TOF PET mainly result from the failure of conventional random correction methods in such low count rate studies and poor robustness versus emission-transmission inconsistency. A novel proposed random correction method succeeds in cleaning the spurious extrahepatic counts in non-TOF PET. Two physical effects not considered up to now in nuclear medicine were identified to be at the origin of the unusual 90Y true coincidences radial profile. TOF reconstruction removing
African Journals Online (AJOL)
ORIGINAL ARTICLES. Illnesses of Herod the Great. Francois P Retief, Johan F G Cilliers. Herod the Great, ldumean by birth, was king ofthe Jews from 40 to 4 BC. An able statesman, builder and warrior, he ruthlessly stamped out all perceived opposition to his rule. His last decade was characterised by vicious strife within ...
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ORIGINAL ARTICLES. OCCUPATIONAL EXPOSURE OF. INTERNS TO BLOOD IN AN AREA. OF HIGH HIV SEROPREVALENCE. A S Karstaedt, L Pantanowitz. Objective. To determine the epidemiology of work-related exposure to blood among interns. Design. Interns were invited to complete anonymously a questionnaire ...
African Journals Online (AJOL)
ORIGINAL ARTICLES. References. 1. McCarthy D, Amos A, Zimmet P. The rising global burden of diabetes and its complications: estimates and projections to the year 2010. Diabet Med 1997; 14: suppl 5, Sl-585. 2. Zgibor JC, Songer TJ, Kelsey SF, et al. The association of diabetes specialist care with health care practices ...
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ORIGINAL ARTICLES. Cost to patients of obtaining treatment for HIV/AIDS in. South Africa. Sydney Rosen, Mpefe Ketlhapile, Ian Sanne, Mary Bachman DeSilva. Background. South Africa is providing antiretroviral (ARV) drugs for HIV I AIDS free of charge in order to increase access for poorer patients and promote ...
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ORIGINAL ARTICLES could be chosen to link to action policy decisions. In the. Integrated Management of Childhood Illness (IMCI) programme, such a screening test would also remind the health provider to prescribe an iron tonic and to emphasise the importance of a balanced diet. A potential disadvantage of copper ...
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Arab Journal of Nephrology and Transplantation. 2013 Sep;6(3):153-60. Original Article. AJNT. Abstract. Introduction: Dense Deposit Disease (DDD) is a devastating renal disease that leads to renal failure within. 10 years of diagnosis in about half of affected patients. In this study, we evaluated the relative prevalence and.
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One of the concerns among mothers for delivery is labor pain. There are various ... Journal of Medical and Biomedical Sciences (2017) 6(2): 11-16. © UDS Publishers ... ORIGINAL ARTICLE ..... effective than a placebo during the first stage of.
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Pezhman Kharazm
treatment in 32 patients who were admitted in Shohada-E-Tajrish hospital with final diagnosis of AMI from March 1996 to March 2002. ... of the patient and diagnostic studies and early surgical or non surgical intervention is the most ... operative diagnosis of etiology was based on presence of pulse at the origin of mesenteric.
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ORIGINAL ARTICLES. References. 1. UNAIDS. Report on the Global HTV/AIDS Epidemic. Geneva: June 2000. 2. Connor E..\\1, Sperling RS, Gelber R. et al. Reduction of maternal-infant transmission of human immunodeficiency virus type 1 with zidovu dine treatment. N Eng! J Med 1994; 331:1173-1180. 3. Undegren ML ...
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A facility based comparative cross-sectional study ... Health care delivery should consider the desire for children by men and .... Socio-Demographic Characteristics of the .... For substitution, children are an important part of marriage, current child needs sibling, original desires .... does not, the only way to avoid the risk of.
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source of blood supply whilst in developed countries VNRDs are the major source. This study de- termined and ... UDS Publishers Limited All Right Reserved 2026-6294. ORIGINAL ..... ferral rate of females in comparison to males as pre- .... nors at blood bank of a medical college,. Australia. Med J Armed Forces 61: 131- 4.
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alternatives to conventional care (homoeopathy, chiropractic, acupuncture, etc.), and also recognise the groundswell of interest in and support for inclusion of benefits for services provided by traditional healers. The transition from the original, relatively restricted approach which was concerned with established, mainstream.
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hefere
Original contributions ... Results suggest that there is a significant positive ... psychological abuse, including economic abuse, intimidation, harassment, stalking, damage ... or maintaining the structure and function of the African home (Alio et al., 2011; Jewkes,. Levin ... Revictimisation occurs due to emotional violence and.
DEFF Research Database (Denmark)
Sørensen, Tim Flohr
2013-01-01
of similarity by looking at artefactual similarity as the results of prototyping and as a production of simulacra. In this light, the concept of copying turns out to be more than simply a matter of trying to imitate an exotic or prestigious original, and it fundamentally raises the question how different a copy...
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there are racial and gender differences in the knowledge and awareness of HPV among Guyanese. The study aimed to ... UDS Publishers Limited All Right Reserved 2026-6294. ORIGINAL ... shown that, about 80.0% of women contracted HPV infection before ... 2010), age of initial sexual contact, and lack of symp- toms for ...
International Nuclear Information System (INIS)
Kimura, W.D.
1993-01-01
The final report describes work performed to investigate inverse Cherenkov acceleration (ICA) as a promising method for laser particle acceleration. In particular, an improved configuration of ICA is being tested in a experiment presently underway on the Accelerator Test Facility (ATF). In the experiment, the high peak power (∼ 10 GW) linearly polarized ATF CO 2 laser beam is converted to a radially polarized beam. This is beam is focused with an axicon at the Cherenkov angle onto the ATF 50-MeV e-beam inside a hydrogen gas cell, where the gas acts as the phase matching medium of the interaction. An energy gain of ∼12 MeV is predicted assuming a delivered laser peak power of 5 GW. The experiment is divided into two phases. The Phase I experiments, which were completed in the spring of 1992, were conducted before the ATF e-beam was available and involved several successful tests of the optical systems. Phase II experiments are with the e-beam and laser beam, and are still in progress. The ATF demonstrated delivery of the e-beam to the experiment in Dec. 1992. A preliminary ''debugging'' run with the e-beam and laser beam occurred in May 1993. This revealed the need for some experimental modifications, which have been implemented. The second run is tentatively scheduled for October or November 1993. In parallel to the experimental efforts has been ongoing theoretical work to support the experiment and investigate improvement and/or offshoots. One exciting offshoot has been theoretical work showing that free-space laser acceleration of electrons is possible using a radially-polarized, axicon-focused laser beam, but without any phase-matching gas. The Monte Carlo code used to model the ICA process has been upgraded and expanded to handle different types of laser beam input profiles
Unfolding in particle physics: A window on solving inverse problems
International Nuclear Information System (INIS)
Spano, F.
2013-01-01
Unfolding is the ensemble of techniques aimed at resolving inverse, ill-posed problems. A pedagogical introduction to the origin and main problems related to unfolding is presented and used as the the stepping stone towards the illustration of some of the most common techniques that are currently used in particle physics experiments. (authors)
Theory of net analyte signal vectors in inverse regression
DEFF Research Database (Denmark)
Bro, R.; Andersen, Charlotte Møller
2003-01-01
The. net analyte signal and the net analyte signal vector are useful measures in building and optimizing multivariate calibration models. In this paper a theory for their use in inverse regression is developed. The theory of net analyte signal was originally derived from classical least squares...
A Generalization of the Spherical Inversion
Ramírez, José L.; Rubiano, Gustavo N.
2017-01-01
In the present article, we introduce a generalization of the spherical inversion. In particular, we define an inversion with respect to an ellipsoid, and prove several properties of this new transformation. The inversion in an ellipsoid is the generalization of the elliptic inversion to the three-dimensional space. We also study the inverse images…
Statistical perspectives on inverse problems
DEFF Research Database (Denmark)
Andersen, Kim Emil
of the interior of an object from electrical boundary measurements. One part of this thesis concerns statistical approaches for solving, possibly non-linear, inverse problems. Thus inverse problems are recasted in a form suitable for statistical inference. In particular, a Bayesian approach for regularisation...... problem is given in terms of probability distributions. Posterior inference is obtained by Markov chain Monte Carlo methods and new, powerful simulation techniques based on e.g. coupled Markov chains and simulated tempering is developed to improve the computational efficiency of the overall simulation......Inverse problems arise in many scientific disciplines and pertain to situations where inference is to be made about a particular phenomenon from indirect measurements. A typical example, arising in diffusion tomography, is the inverse boundary value problem for non-invasive reconstruction...
Size Estimates in Inverse Problems
Di Cristo, Michele
2014-01-01
Detection of inclusions or obstacles inside a body by boundary measurements is an inverse problems very useful in practical applications. When only finite numbers of measurements are available, we try to detect some information on the embedded
Wave-equation dispersion inversion
Li, Jing; Feng, Zongcai; Schuster, Gerard T.
2016-01-01
We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained
Testing earthquake source inversion methodologies
Page, Morgan T.
2011-01-01
Source Inversion Validation Workshop; Palm Springs, California, 11-12 September 2010; Nowadays earthquake source inversions are routinely performed after large earthquakes and represent a key connection between recorded seismic and geodetic data and the complex rupture process at depth. The resulting earthquake source models quantify the spatiotemporal evolution of ruptures. They are also used to provide a rapid assessment of the severity of an earthquake and to estimate losses. However, because of uncertainties in the data, assumed fault geometry and velocity structure, and chosen rupture parameterization, it is not clear which features of these source models are robust. Improved understanding of the uncertainty and reliability of earthquake source inversions will allow the scientific community to use the robust features of kinematic inversions to more thoroughly investigate the complexity of the rupture process and to better constrain other earthquakerelated computations, such as ground motion simulations and static stress change calculations.
Parameter estimation and inverse problems
Aster, Richard C; Thurber, Clifford H
2005-01-01
Parameter Estimation and Inverse Problems primarily serves as a textbook for advanced undergraduate and introductory graduate courses. Class notes have been developed and reside on the World Wide Web for faciliting use and feedback by teaching colleagues. The authors'' treatment promotes an understanding of fundamental and practical issus associated with parameter fitting and inverse problems including basic theory of inverse problems, statistical issues, computational issues, and an understanding of how to analyze the success and limitations of solutions to these probles. The text is also a practical resource for general students and professional researchers, where techniques and concepts can be readily picked up on a chapter-by-chapter basis.Parameter Estimation and Inverse Problems is structured around a course at New Mexico Tech and is designed to be accessible to typical graduate students in the physical sciences who may not have an extensive mathematical background. It is accompanied by a Web site that...
Inversion Therapy: Can It Relieve Back Pain?
Inversion therapy: Can it relieve back pain? Does inversion therapy relieve back pain? Is it safe? Answers from Edward R. Laskowski, M.D. Inversion therapy doesn't provide lasting relief from back ...
Thermal measurements and inverse techniques
Orlande, Helcio RB; Maillet, Denis; Cotta, Renato M
2011-01-01
With its uncommon presentation of instructional material regarding mathematical modeling, measurements, and solution of inverse problems, Thermal Measurements and Inverse Techniques is a one-stop reference for those dealing with various aspects of heat transfer. Progress in mathematical modeling of complex industrial and environmental systems has enabled numerical simulations of most physical phenomena. In addition, recent advances in thermal instrumentation and heat transfer modeling have improved experimental procedures and indirect measurements for heat transfer research of both natural phe
Computation of inverse magnetic cascades
International Nuclear Information System (INIS)
Montgomery, D.
1981-10-01
Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed
Energy Technology Data Exchange (ETDEWEB)
Shin, S. G.; Kye, Y.; Cho, M. H. [POSTECH, Pohang (Korea, Republic of); Namkung, W. [Pohang Accelerator Laboratory, Pohang (Korea, Republic of); KIm, G. N.; Kim, K. [Kyungpook National Univ., Daegu (Korea, Republic of); Lee, M. W.; Kang, Y. R. [Dongnam Inst. Of Radiological and Medical Science, Busan (Korea, Republic of)
2014-05-15
Aluminum is used for monitoring the photon flux. The photon flux during the activation can be measured by substituting the {sup 27}Al(γ,2pn){sup 24}Na reaction cross-section induced by bremsstrahlung to reactivity equation. Therefore, if this cross-section is more accurate, gamma-ray flux can be measure more accurately. In this work, the {sup 27}Al(γ,2pn){sup 24}Na reaction cross-sections induced by 55 - 65 MeV bremsstrahlung were measured by activation technique at the Pohang Neutron Facility (PNF) which has produced the nuclear data using Time-Of-Flight method and activation technique. In order to get the photon flux, MCNPX was used. These measurement values were compared with the data of Meyer et al (1968)
Schachter, L; Stiebing, K E; Dobrescu, S
2009-01-01
The influence of metal-dielectric (MD) layers (MD structures) inserted into the plasma chamber of an electron cyclotron resonance ion source (ECRIS) onto the production of electron bremsstrahlung radiation has been studied in a series of dedicated experiments at the 14 GHz ECRIS of the Institut für Kernphysik der Universität Frankfurt. The IKF-ECRIS was equipped with a MD liner, covering the inner walls of the plasma chamber, and a MD electrode, covering the plasma-facing side of the extraction electrode. On the basis of similar extracted currents of highly charged ions, significantly reduced yields of bremsstrahlung radiation for the "MD source" as compared to the standard (stainless steel) source have been measured and can be explained by the significantly better plasma confinement in a MD source as compared to an "all stainless steel" ECRIS.
International Nuclear Information System (INIS)
Schachter, L.; Dobrescu, S.; Stiebing, K. E.
2009-01-01
The influence of metal-dielectric (MD) layers (MD structures) inserted into the plasma chamber of an electron cyclotron resonance ion source (ECRIS) onto the production of electron bremsstrahlung radiation has been studied in a series of dedicated experiments at the 14 GHz ECRIS of the Institut fuer Kernphysik der Universitaet Frankfurt. The IKF-ECRIS was equipped with a MD liner, covering the inner walls of the plasma chamber, and a MD electrode, covering the plasma-facing side of the extraction electrode. On the basis of similar extracted currents of highly charged ions, significantly reduced yields of bremsstrahlung radiation for the 'MD source' as compared to the standard (stainless steel) source have been measured and can be explained by the significantly better plasma confinement in a MD source as compared to an ''all stainless steel'' ECRIS.
EDITORIAL: Inverse Problems in Engineering
West, Robert M.; Lesnic, Daniel
2007-01-01
Presented here are 11 noteworthy papers selected from the Fifth International Conference on Inverse Problems in Engineering: Theory and Practice held in Cambridge, UK during 11-15 July 2005. The papers have been peer-reviewed to the usual high standards of this journal and the contributions of reviewers are much appreciated. The conference featured a good balance of the fundamental mathematical concepts of inverse problems with a diverse range of important and interesting applications, which are represented here by the selected papers. Aspects of finite-element modelling and the performance of inverse algorithms are investigated by Autrique et al and Leduc et al. Statistical aspects are considered by Emery et al and Watzenig et al with regard to Bayesian parameter estimation and inversion using particle filters. Electrostatic applications are demonstrated by van Berkel and Lionheart and also Nakatani et al. Contributions to the applications of electrical techniques and specifically electrical tomographies are provided by Wakatsuki and Kagawa, Kim et al and Kortschak et al. Aspects of inversion in optical tomography are investigated by Wright et al and Douiri et al. The authors are representative of the worldwide interest in inverse problems relating to engineering applications and their efforts in producing these excellent papers will be appreciated by many readers of this journal.
Energy Technology Data Exchange (ETDEWEB)
Erhard, Martin Andreas
2010-02-26
By the high intensity of the bremsstrahlung of up to 20 MeV to 10{sup 9} MeV{sup -1}cm{sup -2}s{sup -1} in the energy range up to 20 MeV in the framework of this thesis for the first time not only the ({gamma},n), but also the ({gamma},p) reactions could be studied on {sup 92}Mo at astrophysically relevant energies.
Inverse Schroedinger equation and the exact wave function
International Nuclear Information System (INIS)
Nakatsuji, Hiroshi
2002-01-01
Using the inverse of the Hamiltonian, we introduce the inverse Schroedinger equation (ISE) that is equivalent to the ordinary Schroedinger equation (SE). The ISE has the variational principle and the H-square group of equations as the SE has. When we use a positive Hamiltonian, shifting the energy origin, the inverse energy becomes monotonic and we further have the inverse Ritz variational principle and cross-H-square equations. The concepts of the SE and the ISE are combined to generalize the theory for calculating the exact wave function that is a common eigenfunction of the SE and ISE. The Krylov sequence is extended to include the inverse Hamiltonian, and the complete Krylov sequence is introduced. The iterative configuration interaction (ICI) theory is generalized to cover both the SE and ISE concepts and four different computational methods of calculating the exact wave function are presented in both analytical and matrix representations. The exact wave-function theory based on the inverse Hamiltonian can be applied to systems that have singularities in the Hamiltonian. The generalized ICI theory is applied to the hydrogen atom, giving the exact solution without any singularity problem
Directory of Open Access Journals (Sweden)
Ashok Natarajan
2012-04-01
Full Text Available History that comes to us as a chronology of events is really a collective existence that is evolving through several stages to develop Individuality in all members of the society. The human community, nation states, linguistic groups, local castes and classes, and families are the intermediate stages in development of the Individual. The social process moves through phases of survival, growth, development and evolution. In the process it organizes the consciousness of its members at successive levels from social external manners, formed behavior, value-based character and personality to culminate in the development of Individuality. Through this process, society evolves from physicality to Mentality. The power of accomplishment in society and its members develops progressively through stages of skill, capacity, talent, and ability. Original thinking is made possible by the prior development of thinking that organizes facts into information. The immediate result of the last world war was a shift in reliance from physical force and action to mental conception and mental activity on a global scale. At such times no problem need defy solution, if only humanity recognizes the occasion for thinking and Original Thinking. The apparently insoluble problems we confront are an opportunity to formulate a comprehensive theory of social evolution. The immediate possibility is to devise complete solutions to all existing problems, if only we use the right method of thought development.
Takada, Masashi; Kosako, Kazuaki; Oishi, Koji; Nakamura, Takashi; Sato, Kouichi; Kamiyama, Takashi; Kiyanagi, Yoshiaki
2013-03-01
Angular distributions of absorbed dose of Bremsstrahlung photons and secondary electrons at a wide range of emission angles from 0 to 135°, were experimentally obtained using an ion chamber with a 0.6 cm(3) air volume covered with or without a build-up cap. The Bremsstrahlung photons and electrons were produced by 18-, 28- and 38-MeV electron beams bombarding tungsten, copper, aluminium and carbon targets. The absorbed doses were also calculated from simulated photon and electron energy spectra by multiplying simulated response functions of the ion chambers, simulated with the MCNPX code. Calculated-to-experimental (C/E) dose ratios obtained are from 0.70 to 1.57 for high-Z targets of W and Cu, from 15 to 135° and the C/E range from 0.6 to 1.4 at 0°; however, the values of C/E for low-Z targets of Al and C are from 0.5 to 1.8 from 0 to 135°. Angular distributions at the forward angles decrease with increasing angles; on the other hand, the angular distributions at the backward angles depend on the target species. The dependences of absorbed doses on electron energy and target thickness were compared between the measured and simulated results. The attenuation profiles of absorbed doses of Bremsstrahlung beams at 0, 30 and 135° were also measured.
Energy Technology Data Exchange (ETDEWEB)
Gonzales, D.; Cavness, B.; Williams, S. [Department of Physics, Angelo State University, San Angelo, Texas 76909 (United States)
2011-11-15
Experimental results are presented comparing the intensities of the bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on a thick Ag target, measured at forward angles in the range of 0 degree sign to 55 degree sign . When the data are corrected for attenuation due to photon absorption within the target, the results indicate that the detected radiation is distributed anisotropically only at photon energies k that are approximately equal to the initial energy of the incident electrons E{sub 0}. The results of our experiments suggest that, as k/E{sub 0}{yields} 0, the detected radiation essentially becomes isotropic due primarily to the scattering of electrons within the target. A comparison to the theory of Kissel et al.[At. Data Nucl. Data Tables 28, 381 (1983)] suggests that the angular distribution of bremsstrahlung emitted by electrons incident on thick targets is similar to the angular distribution of bremsstrahlung emitted by electrons incident on free-atom targets only when k/E{sub 0}{approx_equal} 1. The experimental data also are in approximate agreement with the angular distribution predictions of the Monte Carlo program penelope.
Energy Technology Data Exchange (ETDEWEB)
Kojima, Sadaoki, E-mail: kojima-s@ile.osaka-u.ac.jp; Arikawa, Yasunobu; Zhang, Zhe; Ikenouchi, Takahito; Morace, Alessio; Nagai, Takahiro; Abe, Yuki; Sakata, Shouhei; Inoue, Hiroaki; Utsugi, Masaru; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Fujioka, Shinsuke; Azechi, Hiroshi [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Nishimura, Yasuhiko; Togawa, Hiromi [Toyota Technical Development Corporation, 1-21 Imae, Hanamoto-cho, Toyota, Aichi 470-0334 (Japan); Ozaki, Tetsuo [National Institute for Fusion Science, 322-6 Oroshicho, Toki, Gifu 509-5292 (Japan); Kato, Ryukou [The Institute of Science and Industrial Research, Osaka University, 2-6 Yamada-oka, Suita, Osaka (Japan)
2014-11-15
A Compton-scattering-based X-ray spectrometer is developed to obtain the energy distribution of fast electrons produced by intense laser and matter interactions. Bremsstrahlung X-rays generated by fast electrons in a material are used to measure fast electrons’ energy distribution in matter. In the Compton X-ray spectrometer, X-rays are converted into recoil electrons by Compton scattering in a converter made from fused silica glass, and a magnet-based electron energy analyzer is used to measure the energy distribution of the electrons that recoil in the direction of the incident X-rays. The spectrum of the incident X-rays is reconstructed from the energy distribution of the recoil electrons. The accuracy of this spectrometer is evaluated using a quasi-monoenergetic 6 MeV electron bunch that emanates from a linear accelerator. An electron bunch is injected into a 1.5 mm thick tungsten plate to produce bremsstrahlung X-rays. The spectrum of these bremsstrahlung X-rays is obtained in the range from 1 to 9 MeV. The energy of the electrons in the bunch is estimated using a Monte Carlo simulation of particle-matter interactions. The result shows that the spectrometer's energy accuracy is ±0.5 MeV for 6.0 MeV electrons.
International Nuclear Information System (INIS)
Guenther, M. M.; Sonnabend, K.; Harres, K.; Roth, M.; Brambrink, E.; Vogt, K.; Bagnoud, V.
2011-01-01
We present a novel nuclear activation-based method for the investigation of high-energy bremsstrahlung produced by electrons above 7 MeV generated by a high-power laser. The main component is a novel high-density activation target that is a pseudo alloy of several selected isotopes with different photo-disintegration reaction thresholds. The gamma spectrum emitted by the activated targets is used for the reconstruction of the bremsstrahlung spectrum using an analysis method based on Penfold and Leiss. This nuclear activation-based technique allows for the determination of the number of bremsstrahlung photons per energy bin in a wide range energy without any anticipated fit procedures. Furthermore, the analysis method also allows for the determination of the absolute yield, the energy distribution, and the temperature of high-energy electrons at the relativistic laser-plasma interaction region. The pyrometry is sensitive to energies above 7 MeV only, i.e., this diagnostic is insensitive to any low-energy processes.
Energy Technology Data Exchange (ETDEWEB)
Guenther, M. M.; Sonnabend, K.; Harres, K.; Roth, M. [Institut fuer Kernphysik, Schlossgartenstr. 9, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); Brambrink, E. [Laboratoire pour l' Utilisation des Lasers Intenses, UMR 7605 CNRS-CEA-Ecole Polytechnique-Universite Paris VI, F-91128 Palaiseau (France); Vogt, K.; Bagnoud, V. [GSI - Helmholtzzentrum fuer Schwerionenforschung GmbH, Planckstr. 1, D-64291 Darmstadt (Germany)
2011-08-15
We present a novel nuclear activation-based method for the investigation of high-energy bremsstrahlung produced by electrons above 7 MeV generated by a high-power laser. The main component is a novel high-density activation target that is a pseudo alloy of several selected isotopes with different photo-disintegration reaction thresholds. The gamma spectrum emitted by the activated targets is used for the reconstruction of the bremsstrahlung spectrum using an analysis method based on Penfold and Leiss. This nuclear activation-based technique allows for the determination of the number of bremsstrahlung photons per energy bin in a wide range energy without any anticipated fit procedures. Furthermore, the analysis method also allows for the determination of the absolute yield, the energy distribution, and the temperature of high-energy electrons at the relativistic laser-plasma interaction region. The pyrometry is sensitive to energies above 7 MeV only, i.e., this diagnostic is insensitive to any low-energy processes.
International Nuclear Information System (INIS)
Takacs, S.; Hermanne, A.
2001-01-01
unsealed pure β - -emitting isotopes are applied. The 3 H, 35 S, 32 P and 33 P are widely used for DNA sequencing studies. Also large amount of 3 H and 14 C are used in organic compound synthesis resulting in long-lived low-level radioactive waste. The β - -particles can be detected by beta counter but it is not applicable in the case of closed waste packages, since the β - - particles loss their energy quickly and they are not capable to escape from the sealed waste package. The emitted β - -particles have continuous energy spectrum and no direct gamma radiation follow the decay. The only means of detection of these β - -particles is through the Bremsstrahlung radiation produced while the particle slows down. The cross section of the Bremsstrahlung generation process depends on the initial energy of the slowing down β - - particles and is proportional to the atomic density n and the average Z 2 of the waste matrix. The probability of this process is much lower than that of the ionisation process for beta particles but it is still high enough to produce measurable amounts of photons. We studied the 35 S and 32 P pure β - -emitter sources in sealed waste packages. The continuous nature of the Bremsstrahlung radiation prevents us using the 'full-energy photo peak area' method. Instead a Region of Interest (ROI) was defined. Unlike for the full-energy photo peak method where the detector efficiency is calculated in the function of energy, for pure β - - emitters an optimised ROI was defined in the spectrum and a special efficiency, eps*beta(E) was determined. The used geometry and the nature of the waste matrix requires time consuming efficiency calibrations of the detector system to be able to establish an efficiency - (matrix density, geometry, matrix composition, activity distribution) function. We studied experimentally the possible deviations of the eps*beta(E) function in case of non uniform activity distribution in order to be able to model the associated error
International Nuclear Information System (INIS)
Ballard, W.P.; Lorence, L.J. Jr.; Snowden, D.P.; van Lint, V.A.J.; Beale, E.S.
1987-01-01
This work compares a carefully designed experiment with the predictions of four different codes (CEPXS/ONETRAN, TIGERP, TIGER and QUICKE2) for the complex bremsstrahlung spectra typical of very intense pulsed power x-ray generators. Accurate calculation of net photon-induced electron emission yields at material interfaces using Monte Carlo codes can be particularly difficult if the forward and reverse partial yields are of similar magnitudes. In such a circumstance, the statistical error in the Monte Carlo solution (TIGER or TIGERP) must be kept to a minimum to accurately resolve the difference. CEPXS/ONETRAN is a new deterministic coupled electron/photon transport code that is faster than Monte Carlo and is not subject to statistical error. QUICKE2 evaluates an analytical approximation and is also much less expensive to run than the Monte Carlo codes. The comparison of net yields is a sensitive test of the relative accuracy and efficiency of these various codes. We find that all of the codes except QUICKE2 substantially agree with the experiments for the forward net yields. Howver, for reverse net yields from high-Z materials, all the codes overpredict relative to measurements
International Nuclear Information System (INIS)
Gupta, B.L.
2000-01-01
Our laboratory maintains standards for high doses in India. The glutamine powder dosimeter (spectrophotometric readout) is used for this purpose. Present studies show that 20 mg of unirradiated/irradiated glutamine dissolved in freshly prepared 10 ml of aerated aqueous acidic FX solution containing 2 x 10 -3 mol dm -3 ferrous ammonium sulphate and 10 -4 mol dm -3 xylenol orange in 0.033 mol dm -3 sulphuric acid is suitable for the dosimetry in the dose range of 0.1-100 kGy. Normally no corrections are required for the post-irradiation fading of the irradiated glutamine. The response of glutamine dosimeter is independent of irradiation temperature in the range of about 23-30 deg. C and at other temperatures, a correction is necessary. The dose intercomparison results for photon, electron and bremsstrahlung radiations show that glutamine can be used as a reference standard dosimeter. The use of flat polyethylene bags containing glutamine powder has proved very successful for electron dosimetry of wide energies. Several other amino acids like alanine, valine and threonine can also be used to cover wide range of doses using spectrophotometric readout method. (author)
Energy Technology Data Exchange (ETDEWEB)
Habibi, M.; Oloumi, M.; Hosseinkhani, H.; Magidi, S. [Plasma and Fusion Research School, Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of)
2015-10-15
A highly nonlinear parabolic partial differential equation that models the electron heat transfer process in laser inertial fusion has been solved numerically. The strong temperature dependence of the electron thermal conductivity and heat loss term (Bremsstrahlung emission) makes this a highly nonlinear process. In this case, an efficient numerical method is developed for the energy transport mechanism from the region of energy deposition into the ablation surface by a combination of the Crank-Nicolson scheme and the Newton-Raphson method. The quantitative behavior of the electron temperature and the comparison between analytic and numerical solutions are also investigated. For more clarification, the accuracy and conservation of energy in the computations are tested. The numerical results can be used to evaluate the nonlinear electron heat conduction, considering the released energy of the laser pulse at the Deuterium-Tritium (DT) targets and preheating by heat conduction ahead of a compression shock in the inertial confinement fusion (ICF) approach. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
International Nuclear Information System (INIS)
Yong, G.-C.; Li Baoan; Chen Liewen
2008-01-01
Hard photons from neutron-proton bremsstrahlung in intermediate energy heavy-ion reactions are examined as a potential probe of the nuclear symmetry energy within a transport model. Effects of the symmetry energy on the yields and spectra of hard photons are found to be generally smaller than those due to the currently existing uncertainties of both the in-medium nucleon-nucleon cross sections and the photon production probability in the elementary process pn→pnγ. Very interestingly, nevertheless, the ratio of hard photon spectra R 1/2 (γ) from two reactions using isotopes of the same element is not only approximately independent of these uncertainties but also quite sensitive to the symmetry energy. For the head-on reactions of 132 Sn + 124 Sn and 112 Sn + 112 Sn at E beam /A=50 MeV, for example, the R 1/2 (γ) displays a rise up to 15% when the symmetry energy is reduced by about 20% at ρ=1.3ρ 0 which is the maximum density reached in these reactions
Three-dimensional inversion of multisource array electromagnetic data
Tartaras, Efthimios
Three-dimensional (3-D) inversion is increasingly important for the correct interpretation of geophysical data sets in complex environments. To this effect, several approximate solutions have been developed that allow the construction of relatively fast inversion schemes. One such method that is fast and provides satisfactory accuracy is the quasi-linear (QL) approximation. It has, however, the drawback that it is source-dependent and, therefore, impractical in situations where multiple transmitters in different positions are employed. I have, therefore, developed a localized form of the QL approximation that is source-independent. This so-called localized quasi-linear (LQL) approximation can have a scalar, a diagonal, or a full tensor form. Numerical examples of its comparison with the full integral equation solution, the Born approximation, and the original QL approximation are given. The objective behind developing this approximation is to use it in a fast 3-D inversion scheme appropriate for multisource array data such as those collected in airborne surveys, cross-well logging, and other similar geophysical applications. I have developed such an inversion scheme using the scalar and diagonal LQL approximation. It reduces the original nonlinear inverse electromagnetic (EM) problem to three linear inverse problems. The first of these problems is solved using a weighted regularized linear conjugate gradient method, whereas the last two are solved in the least squares sense. The algorithm I developed provides the option of obtaining either smooth or focused inversion images. I have applied the 3-D LQL inversion to synthetic 3-D EM data that simulate a helicopter-borne survey over different earth models. The results demonstrate the stability and efficiency of the method and show that the LQL approximation can be a practical solution to the problem of 3-D inversion of multisource array frequency-domain EM data. I have also applied the method to helicopter-borne EM
International Nuclear Information System (INIS)
Devred, A.
1990-03-01
In this paper, I shall discuss the quench origins. I shall first establish a method of classification and introduce the notions of conductor-limited and energy-deposited quenches. Next the paper will be devoted to the study of conductor-limited quenches, and I shall introduce the notions of plateau and of fraction of short sample. Also the paper will be devoted to the study of energy-deposited quenches, and I shall introduce the notions of training and of minimum energy deposit; I shall then review the possible causes of energy release. Lastly, I shall introduce the notion of operating margin, and I shall indicate how to optimize the operating margin in order to limit the risk of premature quenching. 112 refs., 14 figs
Papaceit, Montserrat; Segarra, Carmen; Aguadé, Montserrat
2013-01-01
Drosophila subobscura is a paleartic species of the obscura group with a rich chromosomal polymorphism. To further our understanding on the origin of inversions and on how they regain variation, we have identified and sequenced the two breakpoints of a polymorphic inversion of D. subobscura--inversion 3 of the O chromosome--in a population sample. The breakpoints could be identified as two rather short fragments (∼300 bp and 60 bp long) with no similarity to any known transposable element family or repetitive sequence. The presence of the ∼300-bp fragment at the two breakpoints of inverted chromosomes implies its duplication, an indication of the inversion origin via staggered double-strand breaks. Present results and previous findings support that the mode of origin of inversions is neither related to the inversion age nor species-group specific. The breakpoint regions do not consistently exhibit the lower level of variation within and stronger genetic differentiation between arrangements than more internal regions that would be expected, even in moderately small inversions, if gene conversion were greatly restricted at inversion breakpoints. Comparison of the proximal breakpoint region in species of the obscura group shows that this breakpoint lies in a small high-turnover fragment within a long collinear region (∼300 kb). © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.
Inverse source problems in elastodynamics
Bao, Gang; Hu, Guanghui; Kian, Yavar; Yin, Tao
2018-04-01
We are concerned with time-dependent inverse source problems in elastodynamics. The source term is supposed to be the product of a spatial function and a temporal function with compact support. We present frequency-domain and time-domain approaches to show uniqueness in determining the spatial function from wave fields on a large sphere over a finite time interval. The stability estimate of the temporal function from the data of one receiver and the uniqueness result using partial boundary data are proved. Our arguments rely heavily on the use of the Fourier transform, which motivates inversion schemes that can be easily implemented. A Landweber iterative algorithm for recovering the spatial function and a non-iterative inversion scheme based on the uniqueness proof for recovering the temporal function are proposed. Numerical examples are demonstrated in both two and three dimensions.
Inversion of the star transform
International Nuclear Information System (INIS)
Zhao, Fan; Schotland, John C; Markel, Vadim A
2014-01-01
We define the star transform as a generalization of the broken ray transform introduced by us in previous work. The advantages of using the star transform include the possibility to reconstruct the absorption and the scattering coefficients of the medium separately and simultaneously (from the same data) and the possibility to utilize scattered radiation which, in the case of conventional x-ray tomography, is discarded. In this paper, we derive the star transform from physical principles, discuss its mathematical properties and analyze numerical stability of inversion. In particular, it is shown that stable inversion of the star transform can be obtained only for configurations involving odd number of rays. Several computationally-efficient inversion algorithms are derived and tested numerically. (paper)
Inverse comptonization vs. thermal synchrotron
International Nuclear Information System (INIS)
Fenimore, E.E.; Klebesadel, R.W.; Laros, J.G.
1983-01-01
There are currently two radiation mechanisms being considered for gamma-ray bursts: thermal synchrotron and inverse comptonization. They are mutually exclusive since thermal synchrotron requires a magnetic field of approx. 10 12 Gauss whereas inverse comptonization cannot produce a monotonic spectrum if the field is larger than 10 11 and is too inefficient relative to thermal synchrotron unless the field is less than 10 9 Gauss. Neither mechanism can explain completely the observed characteristics of gamma-ray bursts. However, we conclude that thermal synchrotron is more consistent with the observations if the sources are approx. 40 kpc away whereas inverse comptonization is more consistent if they are approx. 300 pc away. Unfortunately, the source distance is still not known and, thus, the radiation mechanism is still uncertain
Optimization for nonlinear inverse problem
International Nuclear Information System (INIS)
Boyadzhiev, G.; Brandmayr, E.; Pinat, T.; Panza, G.F.
2007-06-01
The nonlinear inversion of geophysical data in general does not yield a unique solution, but a single model, representing the investigated field, is preferred for an easy geological interpretation of the observations. The analyzed region is constituted by a number of sub-regions where the multi-valued nonlinear inversion is applied, which leads to a multi-valued solution. Therefore, combining the values of the solution in each sub-region, many acceptable models are obtained for the entire region and this complicates the geological interpretation of geophysical investigations. In this paper are presented new methodologies, capable to select one model, among all acceptable ones, that satisfies different criteria of smoothness in the explored space of solutions. In this work we focus on the non-linear inversion of surface waves dispersion curves, which gives structural models of shear-wave velocity versus depth, but the basic concepts have a general validity. (author)
Some Phenomena on Negative Inversion Constructions
Sung, Tae-Soo
2013-01-01
We examine the characteristics of NDI (negative degree inversion) and its relation with other inversion phenomena such as SVI (subject-verb inversion) and SAI (subject-auxiliary inversion). The negative element in the NDI construction may be" not," a negative adverbial, or a negative verb. In this respect, NDI has similar licensing…
An Entropic Estimator for Linear Inverse Problems
Directory of Open Access Journals (Sweden)
Amos Golan
2012-05-01
Full Text Available In this paper we examine an Information-Theoretic method for solving noisy linear inverse estimation problems which encompasses under a single framework a whole class of estimation methods. Under this framework, the prior information about the unknown parameters (when such information exists, and constraints on the parameters can be incorporated in the statement of the problem. The method builds on the basics of the maximum entropy principle and consists of transforming the original problem into an estimation of a probability density on an appropriate space naturally associated with the statement of the problem. This estimation method is generic in the sense that it provides a framework for analyzing non-normal models, it is easy to implement and is suitable for all types of inverse problems such as small and or ill-conditioned, noisy data. First order approximation, large sample properties and convergence in distribution are developed as well. Analytical examples, statistics for model comparisons and evaluations, that are inherent to this method, are discussed and complemented with explicit examples.
New RADIOM algorithm using inverse EOS
Busquet, Michel; Sokolov, Igor; Klapisch, Marcel
2012-10-01
The RADIOM model, [1-2], allows one to implement non-LTE atomic physics with a very low extra CPU cost. Although originally heuristic, RADIOM has been physically justified [3] and some accounting for auto-ionization has been included [2]. RADIOM defines an ionization temperature Tz derived from electronic density and actual electronic temperature Te. LTE databases are then queried for properties at Tz and NLTE values are derived from them. Some hydro-codes (like FAST at NRL, Ramis' MULTI, or the CRASH code at U.Mich) use inverse EOS starting from the total internal energy Etot and returning the temperature. In the NLTE case, inverse EOS requires to solve implicit relations between Te, Tz, and Etot. We shall describe these relations and an efficient solver successively implemented in some of our codes. [4pt] [1] M. Busquet, Radiation dependent ionization model for laser-created plasmas, Ph. Fluids B 5, 4191 (1993).[0pt] [2] M. Busquet, D. Colombant, M. Klapisch, D. Fyfe, J. Gardner. Improvements to the RADIOM non-LTE model, HEDP 5, 270 (2009).[0pt] [3] M.Busquet, Onset of pseudo-thermal equilibrium within configurations and super-configurations, JQSRT 99, 131 (2006)
Inverse Magnetoresistance in Polymer Spin Valves.
Ding, Shuaishuai; Tian, Yuan; Li, Yang; Mi, Wenbo; Dong, Huanli; Zhang, Xiaotao; Hu, Wenping; Zhu, Daoben
2017-05-10
In this work, both negative and positive magnetoresistance (MR) in solution-processed regioregular poly(3-hexylthiophene) (RR-P3HT) is observed in organic spin valves (OSVs) with vertical La 2/3 Sr 1/3 MnO 3 (LSMO)/P3HT/AlO x /Co configuration. The ferromagnetic (FM) LSMO electrode with near-atomic flatness is fabricated by a DC facing-target magnetron sputtering method. This research is focused on the origin of the MR inversion. Two types of devices are investigated in details: One with Co penetration shows a negative MR of 0.2%, while the other well-defined device with a nonlinear behavior has a positive MR of 15.6%. The MR measurements in LSMO/AlO x /Co and LSMO/Co junctions are carried to exclude the interference of insulating layer and two FM electrodes themselves. By examining the Co thicknesses and their corresponding magnetic hysteresis loops, a spin-dependent hybrid-interface-state model by Co penetration is induced to explain the MR sign inversion. These results proven by density functional theory (DFT) calculations may shed light on the controllable interfacial properties in designing novel OSV devices.
The Inverse of Banded Matrices
2013-01-01
indexed entries all zeros. In this paper, generalizing a method of Mallik (1999) [5], we give the LU factorization and the inverse of the matrix Br,n (if it...r ≤ i ≤ r, 1 ≤ j ≤ r, with the remaining un-indexed entries all zeros. In this paper generalizing a method of Mallik (1999) [5...matrices and applications to piecewise cubic approximation, J. Comput. Appl. Math. 8 (4) (1982) 285–288. [5] R.K. Mallik , The inverse of a lower
Size Estimates in Inverse Problems
Di Cristo, Michele
2014-01-06
Detection of inclusions or obstacles inside a body by boundary measurements is an inverse problems very useful in practical applications. When only finite numbers of measurements are available, we try to detect some information on the embedded object such as its size. In this talk we review some recent results on several inverse problems. The idea is to provide constructive upper and lower estimates of the area/volume of the unknown defect in terms of a quantity related to the work that can be expressed with the available boundary data.
-Dimensional Fractional Lagrange's Inversion Theorem
Directory of Open Access Journals (Sweden)
F. A. Abd El-Salam
2013-01-01
Full Text Available Using Riemann-Liouville fractional differential operator, a fractional extension of the Lagrange inversion theorem and related formulas are developed. The required basic definitions, lemmas, and theorems in the fractional calculus are presented. A fractional form of Lagrange's expansion for one implicitly defined independent variable is obtained. Then, a fractional version of Lagrange's expansion in more than one unknown function is generalized. For extending the treatment in higher dimensions, some relevant vectors and tensors definitions and notations are presented. A fractional Taylor expansion of a function of -dimensional polyadics is derived. A fractional -dimensional Lagrange inversion theorem is proved.
Darwin's "strange inversion of reasoning".
Dennett, Daniel
2009-06-16
Darwin's theory of evolution by natural selection unifies the world of physics with the world of meaning and purpose by proposing a deeply counterintuitive "inversion of reasoning" (according to a 19th century critic): "to make a perfect and beautiful machine, it is not requisite to know how to make it" [MacKenzie RB (1868) (Nisbet & Co., London)]. Turing proposed a similar inversion: to be a perfect and beautiful computing machine, it is not requisite to know what arithmetic is. Together, these ideas help to explain how we human intelligences came to be able to discern the reasons for all of the adaptations of life, including our own.
Inverse transport theory and applications
International Nuclear Information System (INIS)
Bal, Guillaume
2009-01-01
Inverse transport consists of reconstructing the optical properties of a domain from measurements performed at the domain's boundary. This review concerns several types of measurements: time-dependent, time-independent, angularly resolved and angularly averaged measurements. We review recent results on the reconstruction of the optical parameters from such measurements and the stability of such reconstructions. Inverse transport finds applications e.g. in medical imaging (optical tomography, optical molecular imaging) and in geophysical imaging (remote sensing in the Earth's atmosphere). (topical review)
Inverse Interval Matrix: A Survey
Czech Academy of Sciences Publication Activity Database
Rohn, Jiří; Farhadsefat, R.
2011-01-01
Roč. 22, - (2011), s. 704-719 E-ISSN 1081-3810 R&D Projects: GA ČR GA201/09/1957; GA ČR GC201/08/J020 Institutional research plan: CEZ:AV0Z10300504 Keywords : interval matrix * inverse interval matrix * NP-hardness * enclosure * unit midpoint * inverse sign stability * nonnegative invertibility * absolute value equation * algorithm Subject RIV: BA - General Mathematics Impact factor: 0.808, year: 2010 http://www.math.technion.ac.il/iic/ ela / ela -articles/articles/vol22_pp704-719.pdf
Fourier rebinning algorithm for inverse geometry CT.
Mazin, Samuel R; Pele, Norbert J
2008-11-01
Inverse geometry computed tomography (IGCT) is a new type of volumetric CT geometry that employs a large array of x-ray sources opposite a smaller detector array. Volumetric coverage and high isotropic resolution produce very large data sets and therefore require a computationally efficient three-dimensional reconstruction algorithm. The purpose of this work was to adapt and evaluate a fast algorithm based on Defrise's Fourier rebinning (FORE), originally developed for positron emission tomography. The results were compared with the average of FDK reconstructions from each source row. The FORE algorithm is an order of magnitude faster than the FDK-type method for the case of 11 source rows. In the center of the field-of-view both algorithms exhibited the same resolution and noise performance. FORE exhibited some resolution loss (and less noise) in the periphery of the field-of-view. FORE appears to be a fast and reasonably accurate reconstruction method for IGCT.
Forward and inverse kinematics of double universal joint robot wrists
Williams, Robert L., II
1991-01-01
A robot wrist consisting of two universal joints can eliminate the wrist singularity problem found on many individual robots. Forward and inverse position and velocity kinematics are presented for such a wrist having three degrees of freedom. Denavit-Hartenberg parameters are derived to find the transforms required for the kinematic equations. The Omni-Wrist, a commercial double universal joint robot wrist, is studied in detail. There are four levels of kinematic parameters identified for this wrist; three forward and three inverse maps are presented for both position and velocity. These equations relate the hand coordinate frame to the wrist base frame. They are sufficient for control of the wrist standing alone. When the wrist is attached to a manipulator arm; the offset between the two universal joints complicates the solution of the overall kinematics problem. All wrist coordinate frame origins are not coincident, which prevents decoupling of position and orientation for manipulator inverse kinematics.
SDG multiple fault diagnosis by real-time inverse inference
International Nuclear Information System (INIS)
Zhang Zhaoqian; Wu Chongguang; Zhang Beike; Xia Tao; Li Anfeng
2005-01-01
In the past 20 years, one of the qualitative simulation technologies, signed directed graph (SDG) has been widely applied in the field of chemical fault diagnosis. However, the assumption of single fault origin was usually used by many former researchers. As a result, this will lead to the problem of combinatorial explosion and has limited SDG to the realistic application on the real process. This is mainly because that most of the former researchers used forward inference engine in the commercial expert system software to carry out the inverse diagnosis inference on the SDG model which violates the internal principle of diagnosis mechanism. In this paper, we present a new SDG multiple faults diagnosis method by real-time inverse inference. This is a method of multiple faults diagnosis from the genuine significance and the inference engine use inverse mechanism. At last, we give an example of 65t/h furnace diagnosis system to demonstrate its applicability and efficiency
SDG multiple fault diagnosis by real-time inverse inference
Energy Technology Data Exchange (ETDEWEB)
Zhang Zhaoqian; Wu Chongguang; Zhang Beike; Xia Tao; Li Anfeng
2005-02-01
In the past 20 years, one of the qualitative simulation technologies, signed directed graph (SDG) has been widely applied in the field of chemical fault diagnosis. However, the assumption of single fault origin was usually used by many former researchers. As a result, this will lead to the problem of combinatorial explosion and has limited SDG to the realistic application on the real process. This is mainly because that most of the former researchers used forward inference engine in the commercial expert system software to carry out the inverse diagnosis inference on the SDG model which violates the internal principle of diagnosis mechanism. In this paper, we present a new SDG multiple faults diagnosis method by real-time inverse inference. This is a method of multiple faults diagnosis from the genuine significance and the inference engine use inverse mechanism. At last, we give an example of 65t/h furnace diagnosis system to demonstrate its applicability and efficiency.
Directory of Open Access Journals (Sweden)
Duo Zhang
2014-07-01
Full Text Available Vehicle active safety control is attracting ever increasing attention in the attempt to improve the stability and the maneuverability of electric vehicles. In this paper, a neural network combined inverse (NNCI controller is proposed, incorporating the merits of left-inversion and right-inversion. As the left-inversion soft-sensor can estimate the sideslip angle, while the right-inversion is utilized to decouple control. Then, the proposed NNCI controller not only linearizes and decouples the original nonlinear system, but also directly obtains immeasurable state feedback in constructing the right-inversion. Hence, the proposed controller is very practical in engineering applications. The proposed system is co-simulated based on the vehicle simulation package CarSim in connection with Matlab/Simulink. The results verify the effectiveness of the proposed control strategy.
Origin of the cosmic x-ray background
International Nuclear Information System (INIS)
Margon, B.
1983-01-01
Since 1962, it has been known that every part of the sky emits a uniform glow of x-rays. After two decades of intense study the origin of this diffuse x-ray background is still a subject of controversy. The near perfect isotropy of the x-ray background is clearly a vital clue to its origin. A second clue to the origin of the x-ray background arises from the fact that it is x-radiation tha is generated, rather than some longer wavelength radiation. Two hypotheses of the origin of this x-ray background are discussed. One hypothesis is that the x-ray background can be attributed to bremsstrahlung from a hot intergalactic medium. The second hypothesis is that the x-ray background originates from a large number of quasars. Because there is no estimate independent of the intensity of the x-ray background of how much hot intergalactic medium exists (if any), there is a real possibility that both sources contribute to the observed x-rays. (SC)
Superconductivity in Pb inverse opal
International Nuclear Information System (INIS)
Aliev, Ali E.; Lee, Sergey B.; Zakhidov, Anvar A.; Baughman, Ray H.
2007-01-01
Type-II superconducting behavior was observed in highly periodic three-dimensional lead inverse opal prepared by infiltration of melted Pb in blue (D = 160 nm), green (D = 220 nm) and red (D = 300 nm) opals and followed by the extraction of the SiO 2 spheres by chemical etching. The onset of a broad phase transition (ΔT = 0.3 K) was shifted from T c = 7.196 K for bulk Pb to T c = 7.325 K. The upper critical field H c2 (3150 Oe) measured from high-field hysteresis loops exceeds the critical field for bulk lead (803 Oe) fourfold. Two well resolved peaks observed in the hysteresis loops were ascribed to flux penetration into the cylindrical void space that can be found in inverse opal structure and into the periodic structure of Pb nanoparticles. The red inverse opal shows pronounced oscillations of magnetic moment in the mixed state at low temperatures, T 0.9T c has been observed for all of the samples studied. The magnetic field periodicity of resistivity modulation is in good agreement with the lattice parameter of the inverse opal structure. We attribute the failure to observe pronounced modulation in magneto-resistive measurement to difficulties in the precision orientation of the sample along the magnetic field
Inverse problem of solar oscillations
International Nuclear Information System (INIS)
Sekii, T.; Shibahashi, H.
1987-01-01
The authors present some preliminary results of numerical simulation to infer the sound velocity distribution in the solar interior from the oscillation data of the Sun as the inverse problem. They analyze the acoustic potential itself by taking account of some factors other than the sound velocity, and infer the sound velocity distribution in the deep interior of the Sun
Wave-equation dispersion inversion
Li, Jing
2016-12-08
We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.
Orengo, D J; Puerma, E; Papaceit, M; Segarra, C; Aguadé, M
2015-06-01
Genome sequence comparison across the Drosophila genus revealed that some fixed inversion breakpoints had been multiply reused at this long timescale. Cytological studies of Drosophila inversion polymorphism had previously shown that, also at this shorter timescale, some breakpoints had been multiply reused. The paucity of molecularly characterized polymorphic inversion breakpoints has so far precluded contrasting whether cytologically shared breakpoints of these relatively young inversions are actually reused at the molecular level. The E chromosome of Drosophila subobscura stands out because it presents several inversion complexes. This is the case of the E1+2+9+3 arrangement that originated from the ancestral Est arrangement through the sequential accumulation of four inversions (E1, E2, E9 and E3) sharing some breakpoints. We recently identified the breakpoints of inversions E1 and E2, which allowed establishing reuse at the molecular level of the cytologically shared breakpoint of these inversions. Here, we identified and sequenced the breakpoints of inversions E9 and E3, because they share breakpoints at sections 58D and 64C with those of inversions E1 and E2. This has allowed establishing that E9 and E3 originated through the staggered-break mechanism. Most importantly, sequence comparison has revealed the multiple reuse at the molecular level of the proximal breakpoint (section 58D), which would have been used at least by inversions E2, E9 and E3. In contrast, the distal breakpoint (section 64C) might have been only reused once by inversions E1 and E2, because the distal E3 breakpoint is displaced >70 kb from the other breakpoint limits.
Workflows for Full Waveform Inversions
Boehm, Christian; Krischer, Lion; Afanasiev, Michael; van Driel, Martin; May, Dave A.; Rietmann, Max; Fichtner, Andreas
2017-04-01
Despite many theoretical advances and the increasing availability of high-performance computing clusters, full seismic waveform inversions still face considerable challenges regarding data and workflow management. While the community has access to solvers which can harness modern heterogeneous computing architectures, the computational bottleneck has fallen to these often manpower-bounded issues that need to be overcome to facilitate further progress. Modern inversions involve huge amounts of data and require a tight integration between numerical PDE solvers, data acquisition and processing systems, nonlinear optimization libraries, and job orchestration frameworks. To this end we created a set of libraries and applications revolving around Salvus (http://salvus.io), a novel software package designed to solve large-scale full waveform inverse problems. This presentation focuses on solving passive source seismic full waveform inversions from local to global scales with Salvus. We discuss (i) design choices for the aforementioned components required for full waveform modeling and inversion, (ii) their implementation in the Salvus framework, and (iii) how it is all tied together by a usable workflow system. We combine state-of-the-art algorithms ranging from high-order finite-element solutions of the wave equation to quasi-Newton optimization algorithms using trust-region methods that can handle inexact derivatives. All is steered by an automated interactive graph-based workflow framework capable of orchestrating all necessary pieces. This naturally facilitates the creation of new Earth models and hopefully sparks new scientific insights. Additionally, and even more importantly, it enhances reproducibility and reliability of the final results.
Directory of Open Access Journals (Sweden)
Cristina Aguado
2014-03-01
Full Text Available In recent years different types of structural variants (SVs have been discovered in the human genome and their functional impact has become increasingly clear. Inversions, however, are poorly characterized and more difficult to study, especially those mediated by inverted repeats or segmental duplications. Here, we describe the results of a simple and fast inverse PCR (iPCR protocol for high-throughput genotyping of a wide variety of inversions using a small amount of DNA. In particular, we analyzed 22 inversions predicted in humans ranging from 5.1 kb to 226 kb and mediated by inverted repeat sequences of 1.6-24 kb. First, we validated 17 of the 22 inversions in a panel of nine HapMap individuals from different populations, and we genotyped them in 68 additional individuals of European origin, with correct genetic transmission in ∼ 12 mother-father-child trios. Global inversion minor allele frequency varied between 1% and 49% and inversion genotypes were consistent with Hardy-Weinberg equilibrium. By analyzing the nucleotide variation and the haplotypes in these regions, we found that only four inversions have linked tag-SNPs and that in many cases there are multiple shared SNPs between standard and inverted chromosomes, suggesting an unexpected high degree of inversion recurrence during human evolution. iPCR was also used to check 16 of these inversions in four chimpanzees and two gorillas, and 10 showed both orientations either within or between species, providing additional support for their multiple origin. Finally, we have identified several inversions that include genes in the inverted or breakpoint regions, and at least one disrupts a potential coding gene. Thus, these results represent a significant advance in our understanding of inversion polymorphism in human populations and challenge the common view of a single origin of inversions, with important implications for inversion analysis in SNP-based studies.
Repar, Jelena; Warnecke, Tobias
2017-08-01
Inversions are a major contributor to structural genome evolution in prokaryotes. Here, using a novel alignment-based method, we systematically compare 1,651 bacterial and 98 archaeal genomes to show that inversion landscapes are frequently biased toward (symmetric) inversions around the origin-terminus axis. However, symmetric inversion bias is not a universal feature of prokaryotic genome evolution but varies considerably across clades. At the extremes, inversion landscapes in Bacillus-Clostridium and Actinobacteria are dominated by symmetric inversions, while there is little or no systematic bias favoring symmetric rearrangements in archaea with a single origin of replication. Within clades, we find strong but clade-specific relationships between symmetric inversion bias and different features of adaptive genome architecture, including the distance of essential genes to the origin of replication and the preferential localization of genes on the leading strand. We suggest that heterogeneous selection pressures have converged to produce similar patterns of structural genome evolution across prokaryotes. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
A structured approach to forensic study of explosions: The TNO Inverse Explosion Analysis tool
Voort, M.M. van der; Wees, R.M.M. van; Brouwer, S.D.; Jagt-Deutekom, M.J. van der; Verreault, J.
2015-01-01
Forensic analysis of explosions consists of determining the point of origin, the explosive substance involved, and the charge mass. Within the EU FP7 project Hyperion, TNO developed the Inverse Explosion Analysis (TNO-IEA) tool to estimate the charge mass and point of origin based on observed damage
Energy Technology Data Exchange (ETDEWEB)
Stroscio, M.A.
1976-06-01
The pair production cross section is numerically integrated over a typical PHERMEX bremsstrahlung spectrum to obtain the probability of pair production in a target of nuclear charge Z, and density rho. The pair production cross section used herein is only approximate in that it neglects screening, neglects the Coulomb field for the emerging pair (first Born approximation), and neglects pair production by atomic electrons. In spite of these approximations, an order-of-magnitude estimate of the amount of 0.511-MeV radiation produced by a typical pulse is still given.
Energy Technology Data Exchange (ETDEWEB)
Tickner, James, E-mail: james.tickner@csiro.a [CSIRO Process Science and Engineering, PMB 5, Menai, NSW 2234 (Australia); Bencardino, Raffaele; Roach, Greg [CSIRO Process Science and Engineering, PMB 5, Menai, NSW 2234 (Australia)
2010-01-15
Activation yields have been measured for (gamma,n) reactions of the elements Ru, Rh, Pd, Ir and Pt. Metallic foils of natural isotopic composition were irradiated using Bremsstrahlung radiation produced from an electron linear accelerator operated with electron beam energies in the range 11-14 MeV. Activation products, including both unstable ground states and metastates were measured using a high-purity germanium detector. Cross-sections were estimated from the yield data by assuming a simple two-parameter model for the shape of the cross-section with energy.
International Nuclear Information System (INIS)
Tickner, James; Bencardino, Raffaele; Roach, Greg
2010-01-01
Activation yields have been measured for (γ,n) reactions of the elements Ru, Rh, Pd, Ir and Pt. Metallic foils of natural isotopic composition were irradiated using Bremsstrahlung radiation produced from an electron linear accelerator operated with electron beam energies in the range 11-14 MeV. Activation products, including both unstable ground states and metastates were measured using a high-purity germanium detector. Cross-sections were estimated from the yield data by assuming a simple two-parameter model for the shape of the cross-section with energy.
Inverse photon-photon processes
International Nuclear Information System (INIS)
Carimalo, C.; Crozon, M.; Kesler, P.; Parisi, J.
1981-12-01
We here consider inverse photon-photon processes, i.e. AB → γγX (where A, B are hadrons, in particular protons or antiprotons), at high energies. As regards the production of a γγ continuum, we show that, under specific conditions the study of such processes might provide some information on the subprocess gg γγ, involving a quark box. It is also suggested to use those processes in order to systematically look for heavy C = + structures (quarkonium states, gluonia, etc.) showing up in the γγ channel. Inverse photon-photon processes might thus become a new and fertile area of investigation in high-energy physics, provided the difficult problem of discriminating between direct photons and indirect ones can be handled in a satisfactory way
Hedland, D. A.; Degonia, P. K.
1974-01-01
The RAE-1 spacecraft inversion performed October 31, 1972 is described based upon the in-orbit dynamical data in conjunction with results obtained from previously developed computer simulation models. The computer simulations used are predictive of the satellite dynamics, including boom flexing, and are applicable during boom deployment and retraction, inter-phase coast periods, and post-deployment operations. Attitude data, as well as boom tip data, were analyzed in order to obtain a detailed description of the dynamical behavior of the spacecraft during and after the inversion. Runs were made using the computer model and the results were analyzed and compared with the real time data. Close agreement between the actual recorded spacecraft attitude and the computer simulation results was obtained.
Inverse problem in nuclear physics
International Nuclear Information System (INIS)
Zakhariev, B.N.
1976-01-01
The method of reconstruction of interaction from the scattering data is formulated in the frame of the R-matrix theory in which the potential is determined by position of resonance Esub(lambda) and their reduced widths γ 2 lambda. In finite difference approximation for the Schroedinger equation this new approach allows to make the logics of the inverse problem IP more clear. A possibility of applications of IP formalism to various nuclear systems is discussed. (author)
Elastic reflection waveform inversion with variable density
Li, Yuanyuan; Li, Zhenchun; Alkhalifah, Tariq Ali; Guo, Qiang
2017-01-01
Elastic full waveform inversion (FWI) provides a better description of the subsurface than those given by the acoustic assumption. However it suffers from a more serious cycle skipping problem compared with the latter. Reflection waveform inversion
Photospallation reactions of 133Cs and 139La by 100 MeV- and 200 MeV bremsstrahlungs
International Nuclear Information System (INIS)
Sakamoto, K.; Toramoto, H.; Hamajima, Y.; Okada, K.; Dohniwa, M.
1984-01-01
Spallation yields relative to the 196 Au yield from 197 Au(γ,n) of 26 to 46 nuclides of Sb, Te, I, Xe, Cs and/or Ba and La from 133 Cs and 139 La targets irradiated with bremsstrahlungs of end energies of 100 MeV and 200 MeV were radiochemically determined. The isomeric yield ratios for 132 La and 131 Ba from the ( 139 La + 100 MeV-γ), 132 La, 131 Ba, 121 Te and 119 Te from the ( 139 La + 200 MeV-γ, and 120 I, 121 Te and 119 Te from the ( 133 Cs +- 200 MeV-γ) were also determined. The isotopic yields from the (γ,yn) reactions decrease exponentially with increase of y up to 5, and show no dependence on energy and targets studied, indicating that the reactions of a few neutron emissions occur at energies lower than 100 MeV. When the product yields from the (γ,xpyn) reactions were plotted against (x + y) for each x (isotopic distribution), a regular variation of the Gaussian distributions, typical of nuclear spallation, was observed. Isobaric mass distributions and charge dispersions were deduced to extract characteristic features of these reactions. The isobaric distributions due only to photons of 100 MeV to 200 MeV, which were obtained by subtracting the 100 MeV-yields from the 200 MeV-yields, are very close to a symmetric one peaking at about 8 amu from the target masses. Nuclear charges are also dispersed symmetrically, with most probable N/Zsub(p) of about 1.3 replaced by about 1 amu to the neutron-deficient side from the beta stability valley in all the cases studied. Parameters included in Rudstam's semi-empirical formula were examined by comparing with the observed yield curves. The P values of 0.45 and 0.65, chosen for a better fit to the 200 MeV data on 133 Cs and 139 La, respectively, were larger than the predictions reported in the literature. The magic number effects of 139 La may explain the target-differences in mass distributions. (orig.)
On a complete topological inverse polycyclic monoid
Directory of Open Access Journals (Sweden)
S. O. Bardyla
2016-12-01
Full Text Available We give sufficient conditions when a topological inverse $\\lambda$-polycyclic monoid $P_{\\lambda}$ is absolutely $H$-closed in the class of topological inverse semigroups. For every infinite cardinal $\\lambda$ we construct the coarsest semigroup inverse topology $\\tau_{mi}$ on $P_\\lambda$ and give an example of a topological inverse monoid $S$ which contains the polycyclic monoid $P_2$ as a dense discrete subsemigroup.
Inversion: A Most Useful Kind of Transformation.
Dubrovsky, Vladimir
1992-01-01
The transformation assigning to every point its inverse with respect to a circle with given radius and center is called an inversion. Discusses inversion with respect to points, circles, angles, distances, space, and the parallel postulate. Exercises related to these topics are included. (MDH)
Probabilistic Geoacoustic Inversion in Complex Environments
2015-09-30
Probabilistic Geoacoustic Inversion in Complex Environments Jan Dettmer School of Earth and Ocean Sciences, University of Victoria, Victoria BC...long-range inversion methods can fail to provide sufficient resolution. For proper quantitative examination of variability, parameter uncertainty must...project aims to advance probabilistic geoacoustic inversion methods for complex ocean environments for a range of geoacoustic data types. The work is
Jha, Ashish Kumar A; Zade, Anand A; Rangarajan, Venkatesh; Purandare, Nilendu; Shah, Sneha A; Agrawal, Archi; Kulkarni, Suyash S; Shetty, Nitin
2012-05-01
(99m)Tc macroaggregate albumin (MAA) scintigraphy is routinely used to estimate the hepatopulmonary shunt (HPS) of (90)Y microspheres because of their comparable average particle sizes (20-30 µm). However, the MAA particle size can vary from 10 to 90 µm. Therefore, HPS computed from (99m)Tc MAA scintigraphy may not accurately represent the HPS of (90)Y microspheres. In view of this, the present study was undertaken to investigate the accuracy of (99m)Tc MAA scintigraphy in estimating the HPS of (90)Y microspheres. Nineteen sessions of transarterial radioembolization using (90)Y therasphere were carried out in 17 patients for hepatic malignancies (both primary and secondary). For each session of therapy, a pretherapeutic (99m)Tc MAA scintigraphy and post-therapeutic (90)Y Bremsstrahlung scintigraphy were performed. The HPSs obtained from these images were compared. The mean HPS fractions calculated from the pretherapeutic (99m)Tc MAA study and the post-therapeutic (90)Y Bremsstrahlung images were 4.77 ± 2.81 and 4.52 ± 2.5%, respectively. The coefficient of correlation (r) was 0.96. (99m)Tc MAA scintigraphy accurately predicts the HPS of (90)Y microspheres.
Lebed', A. A.; Padusenko, E. A.; Roshchupkin, S. P.; Dubov, V. V.
2018-04-01
Electron-nucleus bremsstrahlung in the field of two moderately strong pulsed laser waves in the case of incommensurate frequencies is theoretically studied under resonant conditions. The process is studied in detail in a special kinematic region, where stimulated processes with correlated emission and absorption of photons of the first and second waves become predominant (parametric interference effect). The availability of this region is caused by interference of the first and second laser waves. The correspondence between the emission angle and the final-electron energy is established in this interference kinematic. In this case, the cross-sectional properties are determined by the multiphoton quantum interference parameter, which is proportional to the product of intensities of the first and second waves. The resonant differential cross section of electron-nucleus spontaneous bremsstrahlung with simultaneous registration of both emission angles of the spontaneous photon and the scattered electron can exceed by four or five orders of magnitude the corresponding cross section in the absence of an external field. It was shown for nonrelativistic electrons that the resonant cross section of the studied process in the field of two pulsed laser waves within the interference region in two order of magnitude may exceed corresponding cross sections at other scattering kinematics. The obtained results may be experimentally verified, for example, by scientific facilities at sources of pulsed laser radiation (such as SLAC, FAIR, XFEL, ELI).
International Nuclear Information System (INIS)
Kitsos, S.; Diop, C.M.; Assad, A.; Nimal, J.C.; Ridoux, P.
1996-01-01
Improvements of gamma-ray transport calculations in S n codes aim at taking into account the bound-electron effect of Compton scattering (incoherent), coherent scattering (Rayleigh), and secondary sources of bremsstrahlung and fluorescence. A computation scheme was developed to take into account these phenomena by modifying the angular and energy transfer matrices, and no modification in the transport code has been made. The incoherent and coherent scatterings as well as the fluorescence sources can be strictly treated by the transfer matrix change. For bremsstrahlung sources, this is possible if one can neglect the charged particles path as they pass through the matter (electrons and positrons) and is applicable for the energy range of interest for us (below 10 MeV). These improvements have been reported on the kernel attenuation codes by the calculation of new buildup factors. The gamma-ray buildup factors have been carried out for 25 natural elements up to 30 mean free paths in the energy range between 15 keV and 10 MeV
Inversion of self-potential anomalies caused by 2D inclined sheets using neural networks
International Nuclear Information System (INIS)
El-Kaliouby, Hesham M; Al-Garni, Mansour A
2009-01-01
The modular neural network (MNN) inversion method has been used for inversion of self-potential (SP) data anomalies caused by 2D inclined sheets of infinite horizontal extent. The analysed parameters are the depth (h), the half-width (a), the inclination (α), the zero distance from the origin (x o ) and the polarization amplitude (k). The MNN inversion has been first tested on a synthetic example and then applied to two field examples from the Surda area of Rakha mines, India, and Kalava fault zone, India. The effect of random noise has been studied, and the technique showed satisfactory results. The inversion results show good agreement with the measured field data compared with other inversion techniques in use
Inverse Compton gamma-rays from pulsars
International Nuclear Information System (INIS)
Morini, M.
1983-01-01
A model is proposed for pulsar optical and gamma-ray emission where relativistic electrons beams: (i) scatter the blackbody photons from the polar cap surface giving inverse Compton gamma-rays and (ii) produce synchrotron optical photons in the light cylinder region which are then inverse Compton scattered giving other gamma-rays. The model is applied to the Vela pulsar, explaining the first gamma-ray pulse by inverse Compton scattering of synchrotron photons near the light cylinder and the second gamma-ray pulse partly by inverse Compton scattering of synchrotron photons and partly by inverse Compton scattering of the thermal blackbody photons near the star surface. (author)
Point-source inversion techniques
Langston, Charles A.; Barker, Jeffrey S.; Pavlin, Gregory B.
1982-11-01
A variety of approaches for obtaining source parameters from waveform data using moment-tensor or dislocation point source models have been investigated and applied to long-period body and surface waves from several earthquakes. Generalized inversion techniques have been applied to data for long-period teleseismic body waves to obtain the orientation, time function and depth of the 1978 Thessaloniki, Greece, event, of the 1971 San Fernando event, and of several events associated with the 1963 induced seismicity sequence at Kariba, Africa. The generalized inversion technique and a systematic grid testing technique have also been used to place meaningful constraints on mechanisms determined from very sparse data sets; a single station with high-quality three-component waveform data is often sufficient to discriminate faulting type (e.g., strike-slip, etc.). Sparse data sets for several recent California earthquakes, for a small regional event associated with the Koyna, India, reservoir, and for several events at the Kariba reservoir have been investigated in this way. Although linearized inversion techniques using the moment-tensor model are often robust, even for sparse data sets, there are instances where the simplifying assumption of a single point source is inadequate to model the data successfully. Numerical experiments utilizing synthetic data and actual data for the 1971 San Fernando earthquake graphically demonstrate that severe problems may be encountered if source finiteness effects are ignored. These techniques are generally applicable to on-line processing of high-quality digital data, but source complexity and inadequacy of the assumed Green's functions are major problems which are yet to be fully addressed.
Inversion of GPS meteorology data
Directory of Open Access Journals (Sweden)
K. Hocke
Full Text Available The GPS meteorology (GPS/MET experiment, led by the Universities Corporation for Atmospheric Research (UCAR, consists of a GPS receiver aboard a low earth orbit (LEO satellite which was launched on 3 April 1995. During a radio occultation the LEO satellite rises or sets relative to one of the 24 GPS satellites at the Earth's horizon. Thereby the atmospheric layers are successively sounded by radio waves which propagate from the GPS satellite to the LEO satellite. From the observed phase path increases, which are due to refraction of the radio waves by the ionosphere and the neutral atmosphere, the atmospheric parameter refractivity, density, pressure and temperature are calculated with high accuracy and resolution (0.5–1.5 km. In the present study, practical aspects of the GPS/MET data analysis are discussed. The retrieval is based on the Abelian integral inversion of the atmospheric bending angle profile into the refractivity index profile. The problem of the upper boundary condition of the Abelian integral is described by examples. The statistical optimization approach which is applied to the data above 40 km and the use of topside bending angle profiles from model atmospheres stabilize the inversion. The retrieved temperature profiles are compared with corresponding profiles which have already been calculated by scientists of UCAR and Jet Propulsion Laboratory (JPL, using Abelian integral inversion too. The comparison shows that in some cases large differences occur (5 K and more. This is probably due to different treatment of the upper boundary condition, data runaways and noise. Several temperature profiles with wavelike structures at tropospheric and stratospheric heights are shown. While the periodic structures at upper stratospheric heights could be caused by residual errors of the ionospheric correction method, the periodic temperature fluctuations at heights below 30 km are most likely caused by atmospheric waves (vertically
A nonlinear approach of elastic reflection waveform inversion
Guo, Qiang
2016-09-06
Elastic full waveform inversion (EFWI) embodies the original intention of waveform inversion at its inception as it is a better representation of the mostly solid Earth. However, compared with the acoustic P-wave assumption, EFWI for P- and S-wave velocities using multi-component data admitted mixed results. Full waveform inversion (FWI) is a highly nonlinear problem and this nonlinearity only increases under the elastic assumption. Reflection waveform inversion (RWI) can mitigate the nonlinearity by relying on transmissions from reflections focused on inverting low wavenumber components of the model. In our elastic endeavor, we split the P- and S-wave velocities into low wavenumber and perturbation components and propose a nonlinear approach to invert for both of them. The new optimization problem is built on an objective function that depends on both background and perturbation models. We utilize an equivalent stress source based on the model perturbation to generate reflection instead of demigrating from an image, which is applied in conventional RWI. Application on a slice of an ocean-bottom data shows that our method can efficiently update the low wavenumber parts of the model, but more so, obtain perturbations that can be added to the low wavenumbers for a high resolution output.
A nonlinear approach of elastic reflection waveform inversion
Guo, Qiang; Alkhalifah, Tariq Ali
2016-01-01
Elastic full waveform inversion (EFWI) embodies the original intention of waveform inversion at its inception as it is a better representation of the mostly solid Earth. However, compared with the acoustic P-wave assumption, EFWI for P- and S-wave velocities using multi-component data admitted mixed results. Full waveform inversion (FWI) is a highly nonlinear problem and this nonlinearity only increases under the elastic assumption. Reflection waveform inversion (RWI) can mitigate the nonlinearity by relying on transmissions from reflections focused on inverting low wavenumber components of the model. In our elastic endeavor, we split the P- and S-wave velocities into low wavenumber and perturbation components and propose a nonlinear approach to invert for both of them. The new optimization problem is built on an objective function that depends on both background and perturbation models. We utilize an equivalent stress source based on the model perturbation to generate reflection instead of demigrating from an image, which is applied in conventional RWI. Application on a slice of an ocean-bottom data shows that our method can efficiently update the low wavenumber parts of the model, but more so, obtain perturbations that can be added to the low wavenumbers for a high resolution output.
Energy Technology Data Exchange (ETDEWEB)
Renard, F.
2003-01-01
The goal of seismic inversion is to recover an Earth model that best fits some observed data. To reach that goal, we have to minimize an objective function that measures the amplitude of the misfits according to a norm to be chosen in data space. In general, the used norm is the L2 norm. Unfortunately, such a norm is not adapted to data corrupted by correlated noise: the noise is in that case inverted as signal and the inversion results are unacceptable. The goal of this thesis is to obtain satisfactory results to the inverse problem in that situation. For this purpose, we study two inverse problems: reflection tomography and waveform inversion. In reflection tomography, we propose a new formulation of the continuum inverse problem which relies on a H1 norm in data space. This allows us to account for the correlated nature of the noise that corrupts the kinematic information. However, this norm does not give more satisfactory results than the ones obtained with the classical formalism. This is why, for sake of simplicity, we recommend to use this classical formalism. Then we try to understand how to properly sample the kinematic information so as to obtain an accurate approximation of the continuum inverse problem. In waveform inversion, we propose to directly invert data corrupted by some correlated noise. A first idea consists in rejecting the noise in the residues. In that goal, we can use a semi-norm to formulate the inverse problem. This technique gives very good results, except when the data are corrupted by random noise. Thus we propose a second method which consists in retrieving, by solving an inverse problem, the signal and the noise whose sum best fits the data. This technique gives very satisfactory results, even if some random noise pollutes the data, and is moreover solved, thanks to an original algorithm, in a very efficient way. (author)
ANNIT - An Efficient Inversion Algorithm based on Prediction Principles
Růžek, B.; Kolář, P.
2009-04-01
Solution of inverse problems represents meaningful job in geophysics. The amount of data is continuously increasing, methods of modeling are being improved and the computer facilities are also advancing great technical progress. Therefore the development of new and efficient algorithms and computer codes for both forward and inverse modeling is still up to date. ANNIT is contributing to this stream since it is a tool for efficient solution of a set of non-linear equations. Typical geophysical problems are based on parametric approach. The system is characterized by a vector of parameters p, the response of the system is characterized by a vector of data d. The forward problem is usually represented by unique mapping F(p)=d. The inverse problem is much more complex and the inverse mapping p=G(d) is available in an analytical or closed form only exceptionally and generally it may not exist at all. Technically, both forward and inverse mapping F and G are sets of non-linear equations. ANNIT solves such situation as follows: (i) joint subspaces {pD, pM} of original data and model spaces D, M, resp. are searched for, within which the forward mapping F is sufficiently smooth that the inverse mapping G does exist, (ii) numerical approximation of G in subspaces {pD, pM} is found, (iii) candidate solution is predicted by using this numerical approximation. ANNIT is working in an iterative way in cycles. The subspaces {pD, pM} are searched for by generating suitable populations of individuals (models) covering data and model spaces. The approximation of the inverse mapping is made by using three methods: (a) linear regression, (b) Radial Basis Function Network technique, (c) linear prediction (also known as "Kriging"). The ANNIT algorithm has built in also an archive of already evaluated models. Archive models are re-used in a suitable way and thus the number of forward evaluations is minimized. ANNIT is now implemented both in MATLAB and SCILAB. Numerical tests show good
Semi-local inversion of the geodesic ray transform in the hyperbolic plane
International Nuclear Information System (INIS)
Courdurier, Matias; Saez, Mariel
2013-01-01
The inversion of the ray transform on the hyperbolic plane has applications in geophysical exploration and in medical imaging techniques (such as electrical impedance tomography). The geodesic ray transform has been studied in more general geometries and including attenuation, but all of the available inversion formulas require knowledge of the ray transform for all the geodesics. In this paper we present a different inversion formula for the ray transform on the hyperbolic plane, which has the advantage of only requiring knowledge of the ray transform in a reduced family of geodesics. The required family of geodesics is directly related to the set where the original function is to be recovered. (paper)
Park, Kiwan
2017-12-01
In our conventional understanding, large-scale magnetic fields are thought to originate from an inverse cascade in the presence of magnetic helicity, differential rotation or a magneto-rotational instability. However, as recent simulations have given strong indications that an inverse cascade (transfer) may occur even in the absence of magnetic helicity, the physical origin of this inverse cascade is still not fully understood. We here present two simulations of freely decaying helical and non-helical magnetohydrodynamic (MHD) turbulence. We verified the inverse transfer of helical and non-helical magnetic fields in both cases, but we found the underlying physical principles to be fundamentally different. In the former case, the helical magnetic component leads to an inverse cascade of magnetic energy. We derived a semi-analytic formula for the evolution of large-scale magnetic field using α coefficient and compared it with the simulation data. But in the latter case, the α effect, including other conventional dynamo theories, is not suitable to describe the inverse transfer of non-helical magnetic energy. To obtain a better understanding of the physics at work here, we introduced a 'field structure model' based on the magnetic induction equation in the presence of inhomogeneities. This model illustrates how the curl of the electromotive force leads to the build up of a large-scale magnetic field without the requirement of magnetic helicity. And we applied a quasi-normal approximation to the inverse transfer of magnetic energy.
Inverse problems in systems biology
International Nuclear Information System (INIS)
Engl, Heinz W; Lu, James; Müller, Stefan; Flamm, Christoph; Schuster, Peter; Kügler, Philipp
2009-01-01
Systems biology is a new discipline built upon the premise that an understanding of how cells and organisms carry out their functions cannot be gained by looking at cellular components in isolation. Instead, consideration of the interplay between the parts of systems is indispensable for analyzing, modeling, and predicting systems' behavior. Studying biological processes under this premise, systems biology combines experimental techniques and computational methods in order to construct predictive models. Both in building and utilizing models of biological systems, inverse problems arise at several occasions, for example, (i) when experimental time series and steady state data are used to construct biochemical reaction networks, (ii) when model parameters are identified that capture underlying mechanisms or (iii) when desired qualitative behavior such as bistability or limit cycle oscillations is engineered by proper choices of parameter combinations. In this paper we review principles of the modeling process in systems biology and illustrate the ill-posedness and regularization of parameter identification problems in that context. Furthermore, we discuss the methodology of qualitative inverse problems and demonstrate how sparsity enforcing regularization allows the determination of key reaction mechanisms underlying the qualitative behavior. (topical review)
The seismic reflection inverse problem
International Nuclear Information System (INIS)
Symes, W W
2009-01-01
The seismic reflection method seeks to extract maps of the Earth's sedimentary crust from transient near-surface recording of echoes, stimulated by explosions or other controlled sound sources positioned near the surface. Reasonably accurate models of seismic energy propagation take the form of hyperbolic systems of partial differential equations, in which the coefficients represent the spatial distribution of various mechanical characteristics of rock (density, stiffness, etc). Thus the fundamental problem of reflection seismology is an inverse problem in partial differential equations: to find the coefficients (or at least some of their properties) of a linear hyperbolic system, given the values of a family of solutions in some part of their domains. The exploration geophysics community has developed various methods for estimating the Earth's structure from seismic data and is also well aware of the inverse point of view. This article reviews mathematical developments in this subject over the last 25 years, to show how the mathematics has both illuminated innovations of practitioners and led to new directions in practice. Two themes naturally emerge: the importance of single scattering dominance and compensation for spectral incompleteness by spatial redundancy. (topical review)
Inversion theory and conformal mapping
Blair, David E
2000-01-01
It is rarely taught in an undergraduate or even graduate curriculum that the only conformal maps in Euclidean space of dimension greater than two are those generated by similarities and inversions in spheres. This is in stark contrast to the wealth of conformal maps in the plane. The principal aim of this text is to give a treatment of this paucity of conformal maps in higher dimensions. The exposition includes both an analytic proof in general dimension and a differential-geometric proof in dimension three. For completeness, enough complex analysis is developed to prove the abundance of conformal maps in the plane. In addition, the book develops inversion theory as a subject, along with the auxiliary theme of circle-preserving maps. A particular feature is the inclusion of a paper by Carath�odory with the remarkable result that any circle-preserving transformation is necessarily a M�bius transformation, not even the continuity of the transformation is assumed. The text is at the level of advanced undergr...
LHC Report: 2 inverse femtobarns!
Mike Lamont for the LHC Team
2011-01-01
The LHC is enjoying a confluence of twos. This morning (Friday 5 August) we passed 2 inverse femtobarns delivered in 2011; the peak luminosity is now just over 2 x1033 cm-2s-1; and recently fill 2000 was in for nearly 22 hours and delivered around 90 inverse picobarns, almost twice 2010's total. In order to increase the luminosity we can increase of number of bunches, increase the number of particles per bunch, or decrease the transverse beam size at the interaction point. The beam size can be tackled in two ways: either reduce the size of the injected bunches or squeeze harder with the quadrupole magnets situated on either side of the experiments. Having increased the number of bunches to 1380, the maximum possible with a 50 ns bunch spacing, a one day meeting in Crozet decided to explore the other possibilities. The size of the beams coming from the injectors has been reduced to the minimum possible. This has brought an increase in the peak luminosity of about 50% and the 2 x 1033 cm...
Inverse design of multicomponent assemblies
Piñeros, William D.; Lindquist, Beth A.; Jadrich, Ryan B.; Truskett, Thomas M.
2018-03-01
Inverse design can be a useful strategy for discovering interactions that drive particles to spontaneously self-assemble into a desired structure. Here, we extend an inverse design methodology—relative entropy optimization—to determine isotropic interactions that promote assembly of targeted multicomponent phases, and we apply this extension to design interactions for a variety of binary crystals ranging from compact triangular and square architectures to highly open structures with dodecagonal and octadecagonal motifs. We compare the resulting optimized (self- and cross) interactions for the binary assemblies to those obtained from optimization of analogous single-component systems. This comparison reveals that self-interactions act as a "primer" to position particles at approximately correct coordination shell distances, while cross interactions act as the "binder" that refines and locks the system into the desired configuration. For simpler binary targets, it is possible to successfully design self-assembling systems while restricting one of these interaction types to be a hard-core-like potential. However, optimization of both self- and cross interaction types appears necessary to design for assembly of more complex or open structures.