Coherent bremsstrahlung in crystals as a tool for producing high energy photon beams to be used in photoproduction experiments at CERN SPS

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.

Nuclear bremsstrahlung in proton induced reactions at 190 MeV (first experiments at AGOR)

NARCIS (Netherlands)

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.

Quantitative measures of entanglement in pair-coherent states

International Nuclear Information System (INIS)

Agarwal, G S; Biswas, Asoka

2005-01-01

The pair-coherent states for a two-mode radiation field are known to belong to a family of states with non-Gaussian wavefunction. The nature of quantum entanglement between the two modes and some features of non-classicality are studied for such states. The existing criterion for inseparability are examined in the context of pair-coherent states

Wigner function and tomogram of the pair coherent state

International Nuclear Information System (INIS)

Meng, Xiang-Guo; Wang, Ji-Suo; Fan, Hong-Yi

2007-01-01

Using the entangled state representation of Wigner operator and the technique of integration within an ordered product (IWOP) of operators, the Wigner function of the pair coherent state is derived. The variations of the Wigner function with the parameters α and q in the ρ-γ phase space are discussed. The physical meaning of the Wigner function for the pair coherent state is given by virtue of its marginal distributions. The tomogram of the pair coherent state is calculated with the help of the Radon transform between the Wigner operator and the projection operator of the entangled state |η 1 ,η 2 ,τ 1 ,τ 2 >

Pair q-coherent states and their antibunching effects

International Nuclear Information System (INIS)

Wang Zhongqing; Li Junhong; An Guanglei; Chongqing Univ. of Posts and Telecommunications, Chongqing

2005-01-01

Using the properties of the q-deformed boson creation and annihilation operators and their inverse operators, two kind of q-deformed pair coherent states are introduced. Antibunching effects and correlation properties between two modes in the states are investigated. It is shown that q-deformed pair coherent states exhibit antibunching effects and the photons of the two modes are correlated. These nonclassical effects are influenced by the parameter q. These effects increase when |lnq| increases. (authors)

Coherent pair creation from beam-beam interaction

International Nuclear Information System (INIS)

Chen, Pisin.

1989-09-01

It has recently been recognized that in future linear colliders, there is a finite probability that the beamstrahlung photons will turn into e + e - pairs induced by the same beam-beam field, and this would potentially cause background problems. In this paper, we first review the probability of such a coherent pair creation process. It is seen that the constraint on the beamstrahlung parameter, Υ, is tight of these coherent pairs to be totally suppressed. We then point out that there exists a minimum energy for the pair-created particles, which scales as ∼1/5Υ. When combining this condition with the deflection angle for the low-energy particles, the constraint on the allowable Υ value is much relaxed. Finally, we calculate the effective cross section for producing the weak bosons by the low-energy e + e - pairs. It is shown that these cross sections are substantial for Υ > 1. We suggest that this effect can help to autoscan the particle spectrum in the high energy frontier. 10 refs., 2 figs

Improvement of gamma-ray Sn transport calculations including coherent and incoherent scatterings and secondary sources of bremsstrahlung and fluorescence: Determination of gamma-ray buildup factors

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

An effective potential for electron-nucleus scattering in neutrino-pair bremsstrahlung in neutron star crust

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)

Coherent lepton pair production in hadronic heavy ion collisions

Science.gov (United States)

Zha, W.; Ruan, L.; Tang, Z.; Xu, Z.; Yang, S.

2018-06-01

Recently, significant enhancements of e+e- pair production at very low transverse momentum (pT < 0.15 GeV/c) were observed by the STAR collaboration in peripheral hadronic A+A collisions. This excesses can not be described by the QGP thermal radiation and ρ in-medium broadening calculations. This is a sign of coherent photon-photon interactions, which were conventionally studied only in ultra-peripheral collisions. In this article, we present calculations of lepton pair (e+e- and μ+μ-) production from coherent photon-photon interactions in hadronic A+A collisions at RHIC and LHC energies within the STAR and ALICE acceptance.

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.

Heisenberg-limited interferometry with pair coherent states and parity measurements

International Nuclear Information System (INIS)

Gerry, Christopher C.; Mimih, Jihane

2010-01-01

After reviewing parity-measurement-based interferometry with twin Fock states, which allows for supersensitivity (Heisenberg limited) and super-resolution, we consider interferometry with two different superpositions of twin Fock states, namely, two-mode squeezed vacuum states and pair coherent states. This study is motivated by the experimental challenge of producing twin Fock states on opposite sides of a beam splitter. We find that input two-mode squeezed states, while allowing for Heisenberg-limited sensitivity, do not yield super-resolutions, whereas both are possible with input pair coherent states.

Entanglement between total intensity and polarization for pairs of coherent states

Science.gov (United States)

Sanchidrián-Vaca, Carlos; Luis, Alfredo

2018-04-01

We examine entanglement between number and polarization, or number and relative phase, in pair coherent states and two-mode squeezed vacuum via linear entropy and covariance criteria. We consider the embedding of the two-mode Hilbert space in a larger space to get a well-defined factorization of the number-phase variables. This can be regarded as a kind of protoentanglement that can be extracted and converted into real particle entanglement via feasible experimental procedures. In particular this reveals interesting entanglement properties of pairs of coherent states.

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

Sequential Coherence in Sentence Pairs Enhances Imagery during Comprehension: An Individual Differences Study.

Directory of Open Access Journals (Sweden)

Carol Madden-Lombardi

Full Text Available The present study investigates how sequential coherence in sentence pairs (events in sequence vs. unrelated events affects the perceived ability to form a mental image of the sentences for both auditory and visual presentations. In addition, we investigated how the ease of event imagery affected online comprehension (word reading times in the case of sequentially coherent and incoherent sentence pairs. Two groups of comprehenders were identified based on their self-reported ability to form vivid mental images of described events. Imageability ratings were higher and faster for pairs of sentences that described events in coherent sequences rather than non-sequential events, especially for high imagers. Furthermore, reading times on individual words suggested different comprehension patterns with respect to sequence coherence for the two groups of imagers, with high imagers activating richer mental images earlier than low imagers. The present results offer a novel link between research on imagery and discourse coherence, with specific contributions to our understanding of comprehension patterns for high and low imagers.

Pairing versus phase coherence of doped holes in distinct quantum spin backgrounds

Science.gov (United States)

Zhu, Zheng; Sheng, D. N.; Weng, Zheng-Yu

2018-03-01

We examine the pairing structure of holes injected into two distinct spin backgrounds: a short-range antiferromagnetic phase versus a symmetry protected topological phase. Based on density matrix renormalization group (DMRG) simulation, we find that although there is a strong binding between two holes in both phases, phase fluctuations can significantly influence the pair-pair correlation depending on the spin-spin correlation in the background. Here the phase fluctuation is identified as an intrinsic string operator nonlocally controlled by the spins. We show that while the pairing amplitude is generally large, the coherent Cooper pairing can be substantially weakened by the phase fluctuation in the symmetry-protected topological phase, in contrast to the short-range antiferromagnetic phase. It provides an example of a non-BCS mechanism for pairing, in which the paring phase coherence is determined by the underlying spin state self-consistently, bearing an interesting resemblance to the pseudogap physics in the cuprate.

Scintillating fiber array for tagging post-bremsstrahlung electrons

Science.gov (United States)

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.

Coherent and non-coherent double diffractive production of QQ-bar-pairs in collisions of heavy ions at high energies

International Nuclear Information System (INIS)

Agababyan, N.M.; Galoyan, A.S.; Enkovskij, L.L.; Zarubin, P.I.; Malakhov, A.I.; Melkumov, G.L.; Chatrchyan, S.A.

1999-01-01

The double coherent and non-coherent diffractive production of heavy quark-antiquark pairs (QQ-bar) in heavy ion scattering at high energies (LHC) is considered. The total and differential cross sections of these processes with the formation of cc-bar and bb-bar pairs in pp, CaCa and PbPb collisions are evaluated. The contribution of the considered mechanisms is a few per cent of the number of heavy quark-antiquark pairs obtained in the processes of hard (QCD) scattering, and it will be taken into account in the registration of c, b quarks or, for instance, in the study of the heavy quarkonia suppression effect in Quark-Gluon Plasma, in the search got intermediate mass Higgs bosons and so on. It is shown that the cross section of the coherently scattering process is great enough. This makes it suitable for studying collective effects in nuclear interactions at high energies. An example of such effects is given: large values of the invariant mass of a QQ-bar pair, M QQ-bar ≥ 100 GeV, in association with a large rapidity gap between diffractive jets Δη >5 [ru

Coherent and non-coherent double diffractive production of QQ-bar - pairs in collisions of heavy ions at high energies

International Nuclear Information System (INIS)

Agababyan, N.M.; Chatrchyan, S.A.; Galoyan, A.S.; Malakhov, A.I.; Melkumov, G.L.; Zarubin, P.I.; Jenkovszky, L.L.

1998-01-01

The double coherent and non-coherent diffractive production of heavy quark-antiquark pair (QQ-bar) in heavy ion scattering at high energies (LHC) is considered. The total and differential cross sections of these processes with the formation of cc bar and bb bar pairs in pp, CaCa and PbPb collisions are evaluated. The contribution of the considered mechanisms is a few per cent of the number of heavy quark-antiquark pairs obtained in the processes of hard (QCD) scattering, and it will be taken into account in the registration of c, b quarks or, for instance, in the study of the heavy quarkonia suppression effects in quark-gluon plasma, in the search for intermediate mass Higgs bosons and so on. It is shown that the cross section of the coherent scattering process is great enough. This makes it suitable for studying collective effects in nuclear interactions at high energies. An example of such effects is given: large values of the invariant mass of a QQ- bar pair, M QQb ar ≥ 100 GeV, in association with a large rapidity gap between diffractive jets Δη>5

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.)

Proton-proton bremsstrahlung

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

Pion-proton bremsstrahlung

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

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)

Pairing-bag excitations in small-coherence-length superconductors

International Nuclear Information System (INIS)

Bishop, A.R.; Lomdahl, P.S.; Schrieffer, J.R.; Trugman, S.A.

1988-01-01

Localized baglike solutions in the pairing theory of superconductivity are studied. Starting from the Bogoliubov--de Gennes equations on a two-dimensional square lattice for half-filled negative-U Hubbard model, cigar- and star-shaped bags are numerically obtained, inside of which the order parameter is reduced, self-consistently trapping an added quasiparticle. These nonlinear excitations are important when the coherence length is small as for the new high-temperature superconductors. Several experimental consequences are discussed

Coherence and pairing in a doped Mott insulator: application to the cuprates.

Science.gov (United States)

Senthil, T; Lee, Patrick A

2009-08-14

The issues of single particle coherence and its interplay with singlet pairing are studied within the slave boson gauge theory of a doped Mott insulator. Prior work by one of us [T. Senthil, Phys. Rev. B 78, 045109 (2008)10.1103/PhysRevB.78.045109] showed that the coherence scale below which Landau quasiparticles emerge is parametrically lower than that identified in the slave boson mean field theory. Here we study the resulting new non-Fermi liquid intermediate temperature regime characterized by a single particle scattering rate that is linear in temperature (T). In the presence of a d-wave pair amplitude, this leads to a pseudogap state with T-dependent Fermi arcs near the nodal direction. Implications for understanding the cuprates are discussed.

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

Bremsstrahlung-induced highly penetrating probes for nondestructive assay and defect analysis

CERN Document Server

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...

The elementary process of Bremsstrahlung

CERN Document Server

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

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

Soft electromagnetic bremsstrahlung in inelastic hadronic collisions at high and intermediate energies

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

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

A second order QCD effect. quark-quark bremsstrahlung contribution to transverse momentum of lepton pairs

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)

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.

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

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.

Enhanced coherence within the theta band between pairs of brains engaging in experienced versus naïve Reiki procedures.

Science.gov (United States)

Ventura, Anabela Carraca; Persinger, Michael A

2014-08-01

The study objective was to discern whether the coherence between brain activities of the "patient" and practitioner differ between Reiki experts and novices. If the physical process associated with Reiki involves "convergence" between the practitioner and subject, then this congruence should be evident in time-dependent shared power within specific and meaningful frequency electroencephalographic bands. Simultaneous quantitative electroencephalogram measures (19 channels) were recorded from 9 pairs of subjects when 1 of the pairs was an experienced Reiki practitioner or had just been shown the procedure. Pairs recorded their experiences and images. The "practitioner" and "patient" pairs were measured within a quiet, comfortable acoustic chamber. Real-time correlations and coherence between pairs of brains for power (μV(2)·Hz(-1)) within the various frequency bands over the 10-min sessions were recorded and analyzed for each pair. Descriptors of experiences were analyzed for word meanings. Only the coherence within the theta range increased over time between the brains of the Reiki pairs relative to the Sham pairs, particularly over the left hemisphere. The pleasantness-unpleasantness rating for the words employed to describe experiences written after the experiment were more congruent for the Reiki pairs compared to the reference pairs. The increased synchronization of the cerebral activity of the participant and the practitioner during proximal therapies involving touch such as Reiki may be an important component of any subsequent beneficial effects.

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

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.)

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

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.

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

Revisiting Bremsstrahlung emission associated with Light Dark Matter annihilations

CERN Document Server

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...

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)

On the possibility of a quantum bremsstrahlung induced self-modulation of a relativistic beam channeling in crystals

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

Enhancing the performance of the measurement-device-independent quantum key distribution with heralded pair-coherent sources

Energy Technology Data Exchange (ETDEWEB)

Zhu, Feng; Zhang, Chun-Hui; Liu, Ai-Ping [Institute of Signal Processing Transmission, Nanjing University of Posts and Telecommunications, Nanjing 210003 (China); Key Lab of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunications, Ministry of Education, Nanjing 210003 (China); Wang, Qin, E-mail: qinw@njupt.edu.cn [Institute of Signal Processing Transmission, Nanjing University of Posts and Telecommunications, Nanjing 210003 (China); Key Lab of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunications, Ministry of Education, Nanjing 210003 (China); Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026 (China)

2016-04-01

In this paper, we propose to implement the heralded pair-coherent source into the measurement-device-independent quantum key distribution. By comparing its performance with other existing schemes, we demonstrate that our new scheme can overcome many shortcomings existing in current schemes, and show excellent behavior in the quantum key distribution. Moreover, even when taking the statistical fluctuation into account, we can still obtain quite high key generation rate at very long transmission distance by using our new scheme. - Highlights: • Implement the heralded pair-coherent source into the measurement-device-independent quantum key distribution. • Overcome many shortcomings existing in current schemes and show excellent behavior. • Obtain quite high key generation rate even when taking statistical fluctuation into account.

Wigner function for the generalized excited pair coherent state

International Nuclear Information System (INIS)

Meng Xiangguo; Wang Jisuo; Liang Baolong; Li Hongqi

2008-01-01

This paper introduces the generalized excited pair coherent state (GEPCS). Using the entangled state |η> representation of Wigner operator, it obtains the Wigner function for the GEPCS. In the ρ-γ phase space, the variations of the Wigner function distributions with the parameters q, α, k and l are discussed. The tomogram of the GEPCS is calculated with the help of the Radon transform between the Wigner operator and the projection operator of the entangled state |η 1 , η 2 , τ 1 , τ 2 >. The entangled states |η> and η 1 , η 2 , τ 1 , τ 2 > provide two good representative space for studying the Wigner functions and tomograms of various two-mode correlated quantum states

Experimental evidence of the spatial coherence moiré and the filtering of classes of radiator pairs.

Science.gov (United States)

Castaneda, Roman; Usuga-Castaneda, Mario; Herrera-Ramírez, Jorge

2007-08-01

Evidence of the physical existence of the spatial coherence moiré is obtained by confronting numerical results with experimental results of spatially partial interference. Although it was performed for two particular cases, the results reveal a general behavior of the optical fields in any state of spatial coherence. Moreover, the study of the spatial coherence moiré deals with a new type of filtering, named filtering of classes of radiator pairs, which allows changing the power spectrum at the observation plane by modulating the complex degree of spatial coherence, without altering the power distribution at the aperture plane or introducing conventional spatial filters. This new procedure can optimize some technological applications of actual interest, as the beam shaping for instance.

Results on the Coherent Interaction of High Energy Electrons and Photons in Oriented Single Crystals

CERN Document Server

Apyan, A.; Badelek, B.; Ballestrero, S.; Biino, C.; Birol, I.; Cenci, P.; Connell, S.H.; Eichblatt, S.; Fonseca, T.; Freund, A.; Gorini, B.; Groess, R.; Ispirian, K.; Ketel, T.J.; Kononets, Yu.V.; Lopez, A.; Mangiarotti, A.; van Rens, B.; Sellschop, J.P.F.; Shieh, M.; Sona, P.; Strakhovenko, V.; Uggerhoj, E.; Uggerhj, Ulrik Ingerslev; Unel, G.; Velasco, M.; Vilakazi, Z.Z.; Wessely, O.; Kononets, Yu.V.

2005-01-01

The CERN-NA-59 experiment examined a wide range of electromagnetic processes for multi-GeV electrons and photons interacting with oriented single crystals. The various types of crystals and their orientations were used for producing photon beams and for converting and measuring their polarisation. The radiation emitted by 178 GeV unpolarised electrons incident on a 1.5 cm thick Si crystal oriented in the Coherent Bremsstrahlung (CB) and the String-of-Strings (SOS) modes was used to obtain multi-GeV linearly polarised photon beams. A new crystal polarimetry technique was established for measuring the linear polarisation of the photon beam. The polarimeter is based on the dependence of the Coherent Pair Production (CPP) cross section in oriented single crystals on the direction of the photon polarisation with respect to the crystal plane. Both a 1 mm thick single crystal of Germanium and a 4 mm thick multi-tile set of synthetic Diamond crystals were used as analyzers of the linear polarisation. A birefringence ...

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

Measurement of Coherent Emission and Linear Polarization of Photons by Electrons in the Strong Fields of Aligned Crystals

CERN Document Server

Apyan, A.; Badelek, B.; Ballestrero, S.; Biino, C.; Birol, I.; Cenci, P.; Connell, S.H.; Eichblatt, S.; Fonseca, T.; Freund, A.; Gorini, B.; Groess, R.; Ispirian, K.; Ketel, T.J.; Kononets, Yu.V.; Lopez, A.; Mangiarotti, A.; van Rens, B.; Sellschop, J.P.F.; Shieh, M.; Sona, P.; Strakhovenko, V.; Uggerhoj, E.; Uggerhj, Ulrik Ingerslev; Unel, G.; Velasco, M.; Vilakazi, Z.Z.; Wessely, O.; Kononets, Yu.V.

2004-01-01

We present new results regarding the features of high energy photon emission by an electron beam of 178 GeV penetrating a 1.5 cm thick single Si crystal aligned at the Strings-Of-Strings (SOS) orientation. This concerns a special case of coherent bremsstrahlung where the electron interacts with the strong fields of successive atomic strings in a plane and for which the largest enhancement of the highest energy photons is expected. The polarization of the resulting photon beam was measured by the asymmetry of electron-positron pair production in an aligned diamond crystal analyzer. By the selection of a single pair the energy and the polarization of individual photons could be measured in an the environment of multiple photons produced in the radiator crystal. Photons in the high energy region show less than 20% linear polarization at the 90% confidence level.

Modeling Relativistic Electron Precipitation Bremsstrahlung X-Ray Intensities at 10-100 km Manned Vehicle Altitudes

Science.gov (United States)

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.

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.

Production of a narrow band of 0. 511-MeV radiation by use of the PHERMEX bremsstrahlung spectrum. [Cross sections

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.

Coherent and noncoherent double diffractive production of QQ-bar pairs in heavy-ion collisions at high energies

International Nuclear Information System (INIS)

Agababyan, N.M.; Chatrchyan, S.A.; Galoyan, A.S.; Malakhov, A.I.; Melkumov, G.L.; Zarubin, P.I.; Jenkovszky, L.L.

1999-01-01

The coherent and noncoherent double diffractive production of heavy quark-antiquark pairs in ion scattering at the LHC energies has been considered. The total and differential cross sections for such processes featuring the production of cc-bar and bb-bar quark pairs in pp, CaCa, and PbPb collisions have been estimated. It has been shown that the fraction of heavy quark-antiquark pairs produced in double diffractive scattering amounts to a few percent of the number of QQ-bar pairs produced in hard QCD scattering; therefore, it is necessary to take into account such processes in detecting heavy quarks, in seeking Higgs bosons of intermediate mass, in investigating the suppression of heavy quarkonia in quark-gluon plasma, and so on. It has been demonstrated that the cross section for coherent scattering is so large that this process can be used to study collective effects in nuclei at high energies. Large values of the quark-antiquark invariant mass, M QQ-bar > or approx. 100 GeV, in association with a large rapidity gap between diffractive jets, Δη>5, exemplify manifestations of such nuclear interactions

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

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.)

The Radical Pair Mechanism and the Avian Chemical Compass: Quantum Coherence and Entanglement

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yiteng [Purdue Univ., West Lafayette, IN (United States); Kais, Sabre [Purdue Univ., West Lafayette, IN (United States); Berman, Gennady Petrovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-02-02

We review the spin radical pair mechanism which is a promising explanation of avian navigation. This mechanism is based on the dependence of product yields on 1) the hyperfine interaction involving electron spins and neighboring nuclear spins and 2) the intensity and orientation of the geomagnetic field. One surprising result is that even at ambient conditions quantum entanglement of electron spins can play an important role in avian magnetoreception. This review describes the general scheme of chemical reactions involving radical pairs generated from singlet and triplet precursors; the spin dynamics of the radical pairs; and the magnetic field dependence of product yields caused by the radical pair mechanism. The main part of the review includes a description of the chemical compass in birds. We review: the general properties of the avian compass; the basic scheme of the radical pair mechanism; the reaction kinetics in cryptochrome; quantum coherence and entanglement in the avian compass; and the effects of noise. We believe that the quantum avian compass can play an important role in avian navigation and can also provide the foundation for a new generation of sensitive and selective magnetic-sensing nano-devices.

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

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))

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

Coherent polarization radiation of relativistic electrons in crystals

International Nuclear Information System (INIS)

Morokhovskii, V.L.

2014-01-01

A brief narration about the history of those heated arguments and discussions around the nature of so-called parametric X-radiation, which were concluded by the recognition of the discovery the phenomenon of coherent polarization bremsstrahlung of relativistic charged particles in crystals. Some important information and comments, which stay over of notice of specialists till now are reported.

Coherent chemical kinetics as quantum walks. II. Radical-pair reactions in Arabidopsis thaliana

Science.gov (United States)

Chia, A.; Górecka, A.; Kurzyński, P.; Paterek, T.; Kaszlikowski, D.

2016-03-01

We apply the quantum-walk approach proposed in the preceding paper [A. Chia et al., preceding paper, Phys. Rev. E 93, 032407 (2016), 10.1103/PhysRevE.93.032407] to a radical-pair reaction where realistic estimates for the intermediate transition rates are available. The well-known average hitting time from quantum walks can be adopted as a measure of how quickly the reaction occurs and we calculate this for varying degrees of dephasing in the radical pair. The time for the radical pair to react to a product is found to be independent of the amount of dephasing introduced, even in the limit of no dephasing where the transient population dynamics exhibits strong coherent oscillations. This can be seen to arise from the existence of a rate-limiting step in the reaction and we argue that in such examples, a purely classical model based on rate equations can be used for estimating the time scale of the reaction but not necessarily its population dynamics.

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

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.

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)

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

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.

Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung

CERN Document Server

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

Science.gov (United States)

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.

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.

Science.gov (United States)

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.

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

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.

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.

The Cherenkov Bremsstrahlung

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

Coherent Cooper pair tunneling in systems of Josephson junctions: effects of quasiparticle tunneling and of the electromagnetic environment

NARCIS (Netherlands)

Maassen van den Brink, A.; Odintsov, A.A.; Bobbert, P.A.; Schön, G.

1991-01-01

Small capacitance tunnel junctions show single electron effects and, in the superconducting state, the coherent tunneling of Cooper pairs. We study these effects in a system of two Josephson junctions, driven by a voltage source with a finite impedance. Novel features show up in theI–V

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,

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.

Electron and bremsstrahlung penetration and dose calculation

Science.gov (United States)

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.

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...

Representations of coherent states in non-orthogonal bases

International Nuclear Information System (INIS)

Ali, S Twareque; Roknizadeh, R; Tavassoly, M K

2004-01-01

Starting with the canonical coherent states, we demonstrate that all the so-called nonlinear coherent states, used in the physical literature, as well as large classes of other generalized coherent states, can be obtained by changes of bases in the underlying Hilbert space. This observation leads to an interesting duality between pairs of generalized coherent states, bringing into play a Gelfand triple of (rigged) Hilbert spaces. Moreover, it is shown that in each dual pair of families of nonlinear coherent states, at least one family is related to a (generally) non-unitary projective representation of the Weyl-Heisenberg group, which can then be thought of as characterizing the dual pair

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

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

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

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 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.)

Teleportation of Entangled States through Divorce of Entangled Pair Mediated by a Weak Coherent Field in a High-Q Cavity

Institute of Scientific and Technical Information of China (English)

W. B. Cardosol; N. G. de Almeida

2008-01-01

We propose a scheme to partially teleport an unknown entangled atomic state. A high-Q cavity, supporting one mode of a weak coherent state, is needed to accomplish this process. By partial teleportation we mean that teleportation will occur by changing one of the partners of the entangled state to be teleported. The entangled state to be teleported is composed by one pair of particles, we called this surprising characteristic of maintaining the entanglement, even when one of the particle of the entangled pair being teleported is changed, of divorce of entangled states.

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.)

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 pair-production of positrons with low neutron background

International Nuclear Information System (INIS)

Lessner, E.

1998-01-01

Minimization of component activation is highly desirable at accelerator-based positron sources. Electrons in the 8- to 14-MeV energy range impinging on a target produce photons energetic enough to create electron-positron pairs; however, few of the photons are energetic enough to produce photoneutrons. Slow positron production by low-energy electrons impinging on a multilayer tungsten target with and without electromagnetic extraction between the layers was studied by simulation. The neutron background from 14-MeV electrons is expected to be significantly lower than that encountered with higher-energy electron beams. Numerical results are presented and some ideas for a low-activation slow-positron source are discussed

Digital coherent superposition of optical OFDM subcarrier pairs with Hermitian symmetry for phase noise mitigation.

Science.gov (United States)

Yi, Xingwen; Chen, Xuemei; Sharma, Dinesh; Li, Chao; Luo, Ming; Yang, Qi; Li, Zhaohui; Qiu, Kun

2014-06-02

Digital coherent superposition (DCS) provides an approach to combat fiber nonlinearities by trading off the spectrum efficiency. In analogy, we extend the concept of DCS to the optical OFDM subcarrier pairs with Hermitian symmetry to combat the linear and nonlinear phase noise. At the transmitter, we simply use a real-valued OFDM signal to drive a Mach-Zehnder (MZ) intensity modulator biased at the null point and the so-generated OFDM signal is Hermitian in the frequency domain. At receiver, after the conventional OFDM signal processing, we conduct DCS of the optical OFDM subcarrier pairs, which requires only conjugation and summation. We show that the inter-carrier-interference (ICI) due to phase noise can be reduced because of the Hermitain symmetry. In a simulation, this method improves the tolerance to the laser phase noise. In a nonlinear WDM transmission experiment, this method also achieves better performance under the influence of cross phase modulation (XPM).

Radiative corrections for the leptonic pair production

Energy Technology Data Exchange (ETDEWEB)

Elend, H H

1971-01-01

The one-photon bremsstrahlung correction for symmetrical lepton pair production is newly calculated. For this, from all the Feynman diagrams, the subset is picked out for this process which essentially contributes to the symmetrical case. The matrix element square value for the chosen sub-set is expressed by the Bethe-Heitler matrix element square value provided with certain kinematic factors (Huld relationship), where a) a development after the energy of the Bremsquantum, assumed to be small, is carried out and the series is cut off after the second term beyond the infrared section, b) a high-energy approximation is made. Furthermore, c) the structure of the target nucleus and of the recoil transfered to it is neglected, d) the integration on the phase space of the bremsquantitum is carried out with a peaking approximation. All these approximations are individually discussed, and the validity limits which they set for the bremsstrahlung in the result are accurately given.

Collision-induced coherence

International Nuclear Information System (INIS)

Bloembergen, N.

1985-01-01

Collision-induced coherence is based on the elimination of phase correlations between coherent Feynman-type pathways which happen to interfere destructively in the absence of damping for certain nonlinear processes. One consequence is the appearance of the extra resonances in four-wave light mixing experiments, for which the intensity increases with increasing buffer gas pressure. These resonances may occur between a pair of initially unpopulated excited states, or between a pair of initially equally populated ground states. The pair of levels may be Zeeman substrates which became degenerate in zero magnetic field. The resulting collision-enhanced Hanle resonances can lead to very sharp variations in the four-wave light mixing signal as the external magnetic field passes through zero. The theoretical description in terms of a coherence grating between Zeeman substrates is equivalent to a description in terms of a spin polarization grating obtained by collision-enhanced transverse optical pumping. The axis of quantization in the former case is taken perpendicular to the direction of the light beams; in the latter case is taken parallel to this direction

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.

Teleportation of Entangled States through Divorce of Entangled Pair Mediated by a Weak Coherent Field in a High-Q Cavity

International Nuclear Information System (INIS)

Cardoso, W. B.; Almeida, N. G. de

2008-01-01

We propose a scheme to partially teleport an unknown entangled atomic state. A high-Q cavity, supporting one mode of a weak coherent state, is needed to accomplish this process. By partial teleportation we mean that teleportation will occur by changing one of the partners of the entangled state to be teleported. The entangled state to be teleported is composed by one pair of particles, we called this surprising characteristic of maintaining the entanglement, even when one of the particle of the entangled pair being teleported is changed, of divorce of entangled states. (fundamental areas of phenomenology (including applications))

Comparison of positron emission tomography/CT and bremsstrahlung imaging following Y-90 radiation synovectomy

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.

Probing few-body systems with bremsstrahlung

NARCIS (Netherlands)

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

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.)

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

Analytical expression for the phantom generated bremsstrahlung background in high energy electron beams

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

Collimator and energy window optimization for 90Y bremsstrahlung SPECT imaging: A SIMIND Monte Carlo study

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

Probing few-body systems with bremsstrahlung

NARCIS (Netherlands)

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

NARCIS (Netherlands)

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

The role of phantom and treatment head generated bremsstrahlung in high-energy electron beam dosimetry

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

Mismatch removal via coherent spatial relations

Science.gov (United States)

Chen, Jun; Ma, Jiayi; Yang, Changcai; Tian, Jinwen

2014-07-01

We propose a method for removing mismatches from the given putative point correspondences in image pairs based on "coherent spatial relations." Under the Bayesian framework, we formulate our approach as a maximum likelihood problem and solve a coherent spatial relation between the putative point correspondences using an expectation-maximization (EM) algorithm. Our approach associates each point correspondence with a latent variable indicating it as being either an inlier or an outlier, and alternatively estimates the inlier set and recovers the coherent spatial relation. It can handle not only the case of image pairs with rigid motions but also the case of image pairs with nonrigid motions. To parameterize the coherent spatial relation, we choose two-view geometry and thin-plate spline as models for rigid and nonrigid cases, respectively. The mismatches could be successfully removed via the coherent spatial relations after the EM algorithm converges. The quantitative results on various experimental data demonstrate that our method outperforms many state-of-the-art methods, it is not affected by low initial correct match percentages, and is robust to most geometric transformations including a large viewing angle, image rotation, and affine transformation.

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)

An apparatus to study the energy and angular distributions of electron-bremsstrahlung photons from gaseous targets

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

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

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

Radical-pair based avian magnetoreception

Science.gov (United States)

Procopio, Maria; Ritz, Thorsten

2014-03-01

Behavioural experiments suggest that migratory birds possess a magnetic compass sensor able to detect the direction of the geomagnetic. One hypothesis for the basis of this remarkable sensory ability is that the coherent quantum spin dynamics of photoinduced radical pair reactions transduces directional magnetic information from the geomagnetic field into changes of reaction yields, possibly involving the photoreceptor cryptochrome in the birds retina. The suggested radical-pair based avian magnetoreception has attracted attention in the field of quantum biology as an example of a biological sensor which might exploit quantum coherences for its biological function. Investigations on such a spin-based sensor have focussed on uncovering the design features for the design of a biomimetic magnetic field sensor. We study the effects of slow fluctuations in the nuclear spin environment on the directional signal. We quantitatively evaluate the robustness of signals under fluctuations on a timescale longer than the lifetime of a radical pair, utilizing two models of radical pairs. Our results suggest design principles for building a radical-pair based compass sensor that is both robust and highly directional sensitive.

Feasibility studies of a polarized positron source based on the Bremsstrahlung of polarized electrons

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)

Comparison of different Bremsstrahlung converters and collimators for Nuclear Resonance Fluorescence setup at IFUSP

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)

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

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.

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.

'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

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.)

Electron-positron pair production in a hot accretion plasma around a massive black hole

International Nuclear Information System (INIS)

Takahara, Fumio; Kusunose, Masaaki.

1985-01-01

We investigate the electron-positron pair production in a hot accretion plasma around a supermassive black hole in connection with active galactic nuclei. Assuming that an optically thin two-temperature plasma is produced in the vicinity of the central black hole, we examine the condition for the significant pair production by comparing relevant time scales. Since the pair production is dominated by collisions between hard photons, the conditions for significant pair production depend on the production rate of hard photons. We examine the case where the unsaturated Comptonization of soft photons produces hard photons as well as that of bremsstrahlung. We show that significant pair production occurs for a moderately high accretion rate with relatively slow accretion flow as compared to the free fall velocity in both cases. Possible consequences of pair production are briefly discussed. (author)

Investigation of singularities of integral intensity of the relativistic particle bremsstrahlung radiation in a diamond crystal

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

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

Polarization Bremsstrahlung

CERN Document Server

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...

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)

On the efficiency calibration of Si(Li) detector in the low-energy region using thick-target bremsstrahlung

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%.

El Naschie's coherence on the subquantum medium

International Nuclear Information System (INIS)

Agop, M.; Ioannou, P.D.; Nica, P.; Galusca, G.; Stefan, M.

2005-01-01

In the hydrodynamic formulation of the Scale Relativity theory one shows that a stable vortices distribution of bipolaron type induces superconducting pairs by means of the quantum potential. One builds the superconducting fractal by an iterated map and demonstrates that the superconducting pairs results as projections of this fractal. Thus, usual mechanisms (as example the exchange interaction used in the bipolaron theory) are reduced to the coherence on the subquantum medium in a ε (∞) space (El Naschie's coherence)

Modeling the bremsstrahlung emission from converters

CERN Document Server

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.

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

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

Nonlinear Coherent Structures, Microbursts and Turbulence

Science.gov (United States)

Lakhina, G. S.

2015-12-01

Nonlinear waves are found everywhere, in fluids, atmosphere, laboratory, space and astrophysical plasmas. The interplay of nonlinear effects, dispersion and dissipation in the medium can lead to a variety of nonlinear waves and turbulence. Two cases of coherent nonlinear waves: chorus and electrostatic solitary waves (ESWs) and their impact on modifying the plasma medium are discussed. Chorus is a right-hand, circularly-polarized electromagnetic plane wave. Dayside chorus is a bursty emission composed of rising frequency "elements" with duration of ~0.1 to 1.0 s. Each element is composed of coherent subelements with durations of ~1 to 100 ms or more. The cyclotron resonant interaction between energetic electrons and the coherent chorus waves is studied. An expression for the pitch angle transport due to this interaction is derived considering a Gaussian distribution for the time duration of the chorus elements. The rapid pitch scattering can provide an explanation for the ionospheric microbursts of ~0.1 to 0.5 s in bremsstrahlung x-rays formed by ~10-100 keV precipitating electrons. On the other hand, the ESWs are observed in the electric field component parallel to the background magnetic field, and are usually bipolar or tripolar. Generation of coherent ESWs has been explained in terms of nonlinear fluid models of ion- and electron-acoustic solitons and double layers (DLs) based on Sagdeev pseudopotential technique. Fast Fourier transform of electron- and ion-acoustic solitons/DLs produces broadband wave spectra which can explain the properties of the electrostatic turbulence observed in the magnetosheath and plasma sheet boundary layer, and in the solar wind, respectively.

Proton-proton bremsstrahlung towards the elastic limit

Science.gov (United States)

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

Ordering states with various coherence measures

Science.gov (United States)

Yang, Long-Mei; Chen, Bin; Fei, Shao-Ming; Wang, Zhi-Xi

2018-04-01

Quantum coherence is one of the most significant theories in quantum physics. Ordering states with various coherence measures is an intriguing task in quantification theory of coherence. In this paper, we study this problem by use of four important coherence measures—the l_1 norm of coherence, the relative entropy of coherence, the geometric measure of coherence and the modified trace distance measure of coherence. We show that each pair of these measures give a different ordering of qudit states when d≥3. However, for single-qubit states, the l_1 norm of coherence and the geometric coherence provide the same ordering. We also show that the relative entropy of coherence and the geometric coherence give a different ordering for single-qubit states. Then we partially answer the open question proposed in Liu et al. (Quantum Inf Process 15:4189, 2016) whether all the coherence measures give a different ordering of states.

Comparison of the effect of soft-core potentials and Coulombic potentials on bremsstrahlung during laser matter interaction

Science.gov (United States)

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.

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.

The origins of macroscopic quantum coherence in high temperature superconductivity

International Nuclear Information System (INIS)

Turner, Philip; Nottale, Laurent

2015-01-01

Highlights: • We propose a new theoretical approach to superconductivity in p-type cuprates. • Electron pairing mechanisms in the superconducting and pseudogap phases are proposed. • A scale free network of dopants is key to macroscopic quantum coherence. - Abstract: A new, theoretical approach to macroscopic quantum coherence and superconductivity in the p-type (hole doped) cuprates is proposed. The theory includes mechanisms to account for e-pair coupling in the superconducting and pseudogap phases and their inter relations observed in these materials. Electron pair coupling in the superconducting phase is facilitated by local quantum potentials created by static dopants in a mechanism which explains experimentally observed optimal doping levels and the associated peak in critical temperature. By contrast, evidence suggests that electrons contributing to the pseudogap are predominantly coupled by fractal spin waves (fractons) induced by the fractal arrangement of dopants. On another level, the theory offers new insights into the emergence of a macroscopic quantum potential generated by a fractal distribution of dopants. This, in turn, leads to the emergence of coherent, macroscopic spin waves and a second associated macroscopic quantum potential, possibly supported by charge order. These quantum potentials play two key roles. The first involves the transition of an expected diffusive process (normally associated with Anderson localization) in fractal networks, into e-pair coherence. The second involves the facilitation of tunnelling between localized e-pairs. These combined effects lead to the merger of the super conducting and pseudo gap phases into a single coherent condensate at optimal doping. The underlying theory relating to the diffusion to quantum transition is supported by Coherent Random Lasing, which can be explained using an analogous approach. As a final step, an experimental program is outlined to validate the theory and suggests a new

Coincidence Imaging and interference with coherent Gaussian beams

Institute of Scientific and Technical Information of China (English)

CAI Yang-jian; ZHU Shi-yao

2006-01-01

we present a theoretical study of coincidence imaging and interference with coherent Gaussian beams The equations for the coincidence image formation and interference fringes are derived,from which it is clear that the imaging is due to the corresponding focusing in the two paths .The quality and visibility of the images and fringes can be high simultaneously.The nature of the coincidence imaging and interference between quantum entangled photon pairs and coherent Gaussian beams are different .The coincidence image with coherent Gaussian beams is due to intensity-intensity correspondence,a classical nature,while that with entangled photon pairs is due to the amplitude correlation a quantum nature.

Anomalous property of coherent bremsstrahlung linear polarization of relativistic electrons in a crystal

International Nuclear Information System (INIS)

Lapko, V.P.; Nasonov, N.N.; Truten', V.I.

1993-01-01

Polarization and spectral-and-angular properties of γ-radiation of the relativistic electron flux moving in a crystal under uncorrelated collisions with crystal atomic chains, are studied theoretically. Direction of linear polarization of radiation is shown to vary with energy of emitted photon. Reasons of occurrence of this effect are discussed. The results of numerical calculations demonstrating the possibility to form an intensive source of polarized γ-quanta on the basis of coherent radiation of relativistic electrons during low-angular scattering at crystal atom chains, are given

Self-induced coherence in a single pair of quantum dots

Energy Technology Data Exchange (ETDEWEB)

Sitek, Anna; Machnikowski, Pawel [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland)

2011-04-15

We study self-induced coherence (SIC) in a system composed of two coupled quantum dots (QDs). SIC consists in a coherent transfer of excitation between two systems (atoms or QDs) resulting from their collective interaction with the quantum electromagnetic vacuum. This leads to population trapping in a delocalized, optically inactive state. We focus on the effect of a difference in transition energies and coupling between the two emitters on the evolution of exciton occupation in the two QD system. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Simulation of the Focal Spot of the Accelerator Bremsstrahlung Radiation

Science.gov (United States)

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 scattering calculations for the beam stops and collimators in the APS insertion-device beamlines

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

Proton-proton bremsstrahlung in a relativistic covariant model

NARCIS (Netherlands)

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

A coherent/Compton scattering method employing an x-ray tube for measurement of trabecular bone mineral content

International Nuclear Information System (INIS)

Puumalainen, P.; Uimarihuhta, A.; Olkkonen, H.

1982-01-01

Results showed that the x-ray generator could be used as a radiation source in the coherent/Compton scattering method of measuring trabecular bone mineral content. The quasimonoenergetic x-ray beam was produced from the continuous bremsstrahlung radiation with the aid of a spectral filter. Of the two measuring arrangements that were tested, the semiconductor detector geometry appeared to give distinctly more reproducible results than the two NaI detector system. However, to improve the counting efficiency of the coherent radiation, the 'coherent' NaI detector could be replaced by a bore-through scintillation probe (bore diameter about 10mm). By placing the x-ray fluorescence target inside the bore, the yield would be considerably higher. The present method is suitable for TBMC measurements of small animal and human peripheral bones. Errors are discussed in relation to increase of bone size. (U.K.)

Pairing transition, coherence transition, and the irreversibility line in granular GdBa2Cu3O7-δ

Science.gov (United States)

Roa-Rojas, J.; Menegotto Costa, R.; Pureur, P.; Prieto, P.

2000-05-01

We report on electrical magnetoconductivity experiments near the superconducting transition of a granular sample of GdBa2Cu3O7-δ. The measurements were performed in magnetic fields ranging from 0 to 500 Oe applied parallel to the current orientation. The results show that the transition proceeds in two steps. When the temperature is decreased we first observe the pairing transition, which stabilizes superconductivity within the grains at a temperature practically coincident with the bulk critical temperature Tc. Analysis of the fluctuation contributions to the conductivity shows that the universality class for this transition is that of the three dimensional (3D)-XY model in the ordered case, with dynamic critical exponent z=3/2. Close to the zero-resistance state, the measurements reveal the occurrence of a coherence transition, where the phases of the order parameter in individual grains become long-range ordered. The critical temperature Tco for this transition is close to the point where the resistivity vanishes. A strong enlargement of the fluctuation interval preceding the coherence transition is caused by the applied magnetic field. In this region, a 3D-Gaussian regime and an asymptotic critical regime were clearly identified. The critical conductivity behavior for the coherence transition is interpreted within a 3D-XY model where disorder and frustration are relevant. The irreversibility line is determined from magnetoconductivity measurements performed according to the zero-field-cooled (ZFC) and field-cooled data collected on cooling (FCC) recipes. The locus of this line coincides with the upper temperature limit for the fluctuation region above the coherence transition. The irreversibility line is interpreted as an effect of the formation of small clusters with closed loops of Josephson-coupled grains.

Two-temperature accretion disks in pair equilibrium

International Nuclear Information System (INIS)

Kusunose, Masaaki; Takahara, Fumio.

1989-01-01

We investigate two-temperature accretion disks with electron-positron pair production, taking account of the bremsstrahlung and Comptonization of soft photons produced by the cyclotron higher harmonics. The properties of the disks are qualitatively the same as those of disks in which bremsstrahlung is the only photon source. For an accretion rate higher than a critical value, M cr , no steady solutions exist for a certain range of radial distance from a central black hole. The critical value increases only slightly with the input of soft photons; the increment is 45%, i.e., M cr ∼ 0.43 M Edd , for the viscosity parameter α = 0.1, where M Edd ≡ L Edd /c 2 = 4πGM BH m p /(σ T c) with M BH being the mass of the central black hole. Furthermore, the disks are unstable against perturbations of the proton temperature. For α ∼ 0.1, the equipartition magnetic field, and a range of accretion rates, emission spectra obey the power law with a spectral index of -0.7 to -0.6, which coincides with the observed universal X-ray spectra of Seyfert galaxies. Brief comments on the model of the γ-ray flare of Cyg X-1 are also given. (author)

Change Detection by Interferometric Coherence in Nasca Lines, Peru (1997-2004)

Science.gov (United States)

Ruescas, Ana B.; Delgado, J. Manuel; Costantini, Fabiano; Sarti, Francesco

2010-03-01

Two interferometric pairs of Synthetic Aperture Radar (SAR) images are used to generate coherence images of the Nasca Lines Pampa area. The first coherence image is based on a pair of ERS-2 SAR data from 1997 and 1999; the second one is computed from two ENVISAT-ASAR (Advanced SAR) images from 2003 and 2004. The main objective is to study the changes in the coherence values in different parts of the area. Several different decorrelation factors contributing to a loss of coherency in a radar pair can be distinguished, and these include the temporal change in the ground properties and nature between the two satellite passes. In order to do this discrimination and interpretation, some ancillary data can be used, such as optical data from the Advanced Land Observing Satellite (ALOS), and meteorological data from the Global Precipitation Climatology Center (GPCC).

High-power, photofission-inducing bremsstrahlung source for intense pulsed active detection of fissile material

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.

High-power, photofission-inducing bremsstrahlung source for intense pulsed active detection of fissile material

Science.gov (United States)

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.

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Teleportation of Entangled States through Divorce of Entangled Pair Mediated by a Weak Coherent Field in a High-Q Cavity

Science.gov (United States)

Cardoso B., W.; Almeida G. de, N.

2008-07-01

We propose a scheme to partially teleport an unknown entangled atomic state. A high-Q cavity, supporting one mode of a weak coherent state, is needed to accomplish this process. By partial teleportation we mean that teleportation will occur by changing one of the partners of the entangled state to be teleported. The entangled state to be teleported is composed by one pair of particles, we called this surprising characteristic of maintaining the entanglement, even when one of the particle of the entangled pair being teleported is changed, of divorce of entangled states.

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-.

Bremsstrahlung parameters of praseodymium-142 in different human tissues. A dosimetric perspective for 142Pr radionuclide therapy

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

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

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

Coherent photon scattering cross sections for helium near the delta resonance

International Nuclear Information System (INIS)

Delli Carpini, D.; Booth, E.C.; Miller, J.P.; Igarashi, R.; Bergstrom, J.; Caplan, H.; Doss, M.; Hallin, E.; Rangacharyulu, C.; Skopik, D.; Lucas, M.A.; Nathan, A.M.; Wells, D.P.

1991-01-01

The angular distributions for coherent photon scattering from 4 He were measured at average laboratory bremsstrahlung energies of 187, 235, and 280 MeV. The experiment was performed at the Saskatchewan Accelerator Laboratory using the new high duty factor electron beam. The scattered photons were observed with a high-resolution NaI(Tl) total absorption scintillation detector. These measurements are intended to investigate modification of the Δ properties inside the nuclear medium and the treatment of nonresonant contributions to the scattering cross sections. The results are compared to theoretical calculations in the isobar-hole model. Clear deviations from the theory are evident at all energies, especially at 187 MeV

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

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

Quasi-coherent Hecke category and Demazure descent

DEFF Research Database (Denmark)

Arkhipov, Sergey; Kanstrup, Tina

2015-01-01

Let G be a reductive algebraic group with a Borel subgroup B. We define the quasi-coherent Hecke category for the pair (G,B). For any regular Noetherian G- scheme X we construct a monoidal action of the Hecke category on the derived category of B-equivariant quasi-coherent sheaves on X. Using the...

'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.

Monitoring of energetic characteristics of electron beams during formation of high-power pulsed bremsstrahlung

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

COHeRE: Cross-Ontology Hierarchical Relation Examination for Ontology Quality Assurance.

Science.gov (United States)

Cui, Licong

Biomedical ontologies play a vital role in healthcare information management, data integration, and decision support. Ontology quality assurance (OQA) is an indispensable part of the ontology engineering cycle. Most existing OQA methods are based on the knowledge provided within the targeted ontology. This paper proposes a novel cross-ontology analysis method, Cross-Ontology Hierarchical Relation Examination (COHeRE), to detect inconsistencies and possible errors in hierarchical relations across multiple ontologies. COHeRE leverages the Unified Medical Language System (UMLS) knowledge source and the MapReduce cloud computing technique for systematic, large-scale ontology quality assurance work. COHeRE consists of three main steps with the UMLS concepts and relations as the input. First, the relations claimed in source vocabularies are filtered and aggregated for each pair of concepts. Second, inconsistent relations are detected if a concept pair is related by different types of relations in different source vocabularies. Finally, the uncovered inconsistent relations are voted according to their number of occurrences across different source vocabularies. The voting result together with the inconsistent relations serve as the output of COHeRE for possible ontological change. The highest votes provide initial suggestion on how such inconsistencies might be fixed. In UMLS, 138,987 concept pairs were found to have inconsistent relationships across multiple source vocabularies. 40 inconsistent concept pairs involving hierarchical relationships were randomly selected and manually reviewed by a human expert. 95.8% of the inconsistent relations involved in these concept pairs indeed exist in their source vocabularies rather than being introduced by mistake in the UMLS integration process. 73.7% of the concept pairs with suggested relationship were agreed by the human expert. The effectiveness of COHeRE indicates that UMLS provides a promising environment to enhance

Unconventional Cooper pairing results in a pseudogap-like phase in s-wave superconductors

International Nuclear Information System (INIS)

Springer, Daniel; Cheong, Siew Ann

2015-01-01

The impact of disorder on the superconducting (SC) pairing mechanism is the centre of much debate. Some evidence suggests a loss of phase coherence of pairs while others point towards the formation of a competing phase. In our work we show that the two perspectives may be different sides of the same coin. Using an extension of the perturbative renormalization group approach we compare the impact of different disorder-induced interactions on a SC ground state. We find that in the strongly disordered regime an interaction between paired fermions and their respective disordered environment replaces conventional Cooper pairing. For these unconventional Cooper pairs the phase coherence condition, required for the formation of a SC condensate, is not satisfied. (paper)

Soft gluon coherence at LEP

International Nuclear Information System (INIS)

Gaidot, A.

1993-01-01

After a brief overview of the experimental status on colour coherence at LEP we will focus on two recent approaches to the subject: the sub-jet multiplicities and the azimuthal correlations between pair of particles. (author)

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

Practice for dosimetry in electron and bremsstrahlung irradiation facilities for food processing. 2. ed.

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

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.

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

Polarization effects for pair creation by photon in oriented crystals at high energy

International Nuclear Information System (INIS)

Baier, V.N.; Katkov, V.M.

2006-01-01

Pair creation by a photon in an oriented crystal is considered in the frame of the quasiclassical operator method, which includes processes with polarized particles. Under some quite generic assumptions the general expression is derived for the probability of pair creation of longitudinally polarized electron (positron) by circularly polarized photon in oriented crystal. In the particular cases θ > V /m (θ is the angle of incidence, angle between the momentum of the initial photon and axis (plane) of crystal, V is the scale of a potential of axis or a plane relative to which the angle θ is defined) one has the constant field approximation and the coherent pair production theory correspondingly. Side by side with coherent process the probability of incoherent pair creation is calculated, which differs essentially from amorphous one. At high energy the pair creation in oriented crystal is strongly enhanced comparing with the amorphous medium. In the corresponding appendixes the integral polarization of positron is found in an external field and for the coherent and incoherent mechanisms

Infrared phenomena in quantum electrodynamics : II. Bremsstrahlung and compton scattering

NARCIS (Netherlands)

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

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)

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.

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.

Temperature Dependence of Quasiparticle Spectral Weight and Coherence in High Tc Superconductors

Science.gov (United States)

He, Yang; Zhang, Jessie; Hoffman, Jennifer; Hoffman Lab Team

2014-03-01

Superconductivity arises from the Cooper pairing of quasiparticles on the Fermi surface. Understanding the formation of Cooper pairs is an essential step towards unveiling the mechanism of high Tc superconductivity. We compare scanning tunneling microscope investigations of the temperature dependence of quasiparticle spectral weight and quasiparticle interference in several families of high Tc materials. We calculate the coherent spectral weight related to superconductivity, despite the coexistence of competing orders. The relation between pairing temperature and coherent spectral weight is discussed. We acknowledge support by the New York Community Trust-George Merck Fund.

Collective neutrino-pair emission due to Cooper pairing of protons in superconducting neutron stars

International Nuclear Information System (INIS)

Leinson, L.B.

2001-01-01

The neutrino emission due to formation and breaking of Cooper pairs of protons in superconducting cores of neutron stars is considered with taking into account the electromagnetic coupling of protons to ambient electrons. It is shown that collective response of electrons to the proton quantum transition contributes coherently to the complete interaction with a neutrino field and enhances the neutrino-pair production. Our calculation shows that the contribution of the vector weak current to the ννbar emissivity of protons is much larger than that calculated by different authors without taking into account the plasma effects. Partial contribution of the pairing protons to the total neutrino radiation from the neutron star core is very sensitive to the critical temperatures for the proton and neutron pairing. We show domains of these parameters where the neutrino radiation, caused by a singlet-state pairing of protons is dominating

Evaluating the therapeutic effect of 89Sr using Bremsstrahlung imaging in patients with bone metastases

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

Total bremsstrahlung spectra of thick lead compounds produced by {sup 90}Sr beta emitter in photon energy region of 10–100 keV

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.

90Y microsphere therapy: does 90Y PET/CT imaging obviate the need for 90Y Bremsstrahlung SPECT/CT imaging?

Science.gov (United States)

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.

Hard X-ray bremsstrahlung production in solar flares by high-energy proton beams

Science.gov (United States)

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.

Observation of the bremsstrahlung generation in the process of the Rayleigh endash Taylor instability development at gas puff implosion

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

Electron accelerator-based production of molybdenum-99: Bremsstrahlung and photoneutron generation from molybdenum vs. tungsten

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

Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation

OpenAIRE

Nigg, Simon E.; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L.

2014-01-01

Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the produced photon pairs can be used to violate a Bell inequality, unambiguo...

Two-temperature accretion disks with electron-positron pairs - Effects of Comptonized external soft photons

Science.gov (United States)

Kusunose, Masaaki; Takahara, Fumio

1990-01-01

The present account of the effects of soft photons from external sources on two-temperature accretion disks in electron-positron pair equilibrium solves the energy-balance equation for a given radial distribution of the input rate of soft photons, taking into account their bremsstrahlung and Comptonization. Critical rate behavior is investigated as a function of the ratio of the energy flux of incident soft photons and the energy-generation rate. As in a previous study, the existence of a critical accretion rate is established.

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

Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation

Energy Technology Data Exchange (ETDEWEB)

Nigg, Simon E.; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L. [Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland)

2015-07-01

Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the produced photon pairs can be used to violate a Bell inequality, unambiguously demonstrating the entanglement of the split Cooper pairs.

Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation

Science.gov (United States)

Nigg, Simon E.; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L.

2015-03-01

Based on the Bardeen-Cooper-Schrieffer theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the photon pairs produced can be used to violate a Bell inequality, unambiguously demonstrating the entanglement of the split Cooper pairs.

Simulation of electron, positron and Bremsstrahlung spectrum generated due to electromagnetic cascade by 2.5 GeV electron hitting lead target using FLUKA code

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)

Effects of disorder on the electron pairing

International Nuclear Information System (INIS)

Oviedo-Roa, R.; Wang, C.; Navarro, O.

1996-01-01

The electron pairing in randomly disordered lattices is studied by using an attractive Hubbard model, and by mapping the many-body problem onto a tight-binding one in a higher dimensional space, where a diagonal disorder is considered within the coherent-potential approximation. The results show an enhancement of the pair-binding energy as the self-energy difference increases in a binary alloy A x B 1-x . This fact suggests that the pairing process is highly sensitive to the one-particle localization condition. A ground-state phase diagram for on-site interaction disorder shows regions where pairing is avoided for ordered diatomic systems but not for disordered case

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...

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

Quantum coherence generating power, maximally abelian subalgebras, and Grassmannian geometry

Science.gov (United States)

Zanardi, Paolo; Campos Venuti, Lorenzo

2018-01-01

We establish a direct connection between the power of a unitary map in d-dimensions (d algebra). This set can be seen as a topologically non-trivial subset of the Grassmannian over linear operators. The natural distance over the Grassmannian induces a metric structure on Md, which quantifies the lack of commutativity between the pairs of subalgebras. Given a maximally abelian subalgebra, one can define, on physical grounds, an associated measure of quantum coherence. We show that the average quantum coherence generated by a unitary map acting on a uniform ensemble of quantum states in the algebra (the so-called coherence generating power of the map) is proportional to the distance between a pair of maximally abelian subalgebras in Md connected by the unitary transformation itself. By embedding the Grassmannian into a projective space, one can pull-back the standard Fubini-Study metric on Md and define in this way novel geometrical measures of quantum coherence generating power. We also briefly discuss the associated differential metric structures.

Coherence of Physics and Chemistry Curricula in Terms of the Electron Concept

International Nuclear Information System (INIS)

Elena, Ivanova

2016-01-01

One of the major contradictions in subject teaching is the contradiction between the unity of the world and the discrete separated generalized content of natural sciences that study natural phenomena. These are physics, chemistry, biology and more. One can eliminate the conflict if opens the content's interdisciplinary links set by the events that are studied by different disciplines. The corresponding contexts of the phenomenon content arise depending on the discipline, and they are not enough coordinated. Obviously, we need a mechanism that allows establishing interdisciplinary links in the content quickly and without losing the logic of the material and assess their coherence in academic disciplines. This article uses a quantitative method of coherence assessment elaborated by T.N. Gnitetskaya. The definition of the concept of the semantic state introduced by the authors is given in this article. The method is applied to coherence assessment of physics and chemistry textbooks. The coherence of two pairs of chemistry and physics textbooks by different authors in different combinations was calculated. The most cohered pairs of textbooks (chemistry-physics) were identified. One can recommend using the pair of textbooks for eighth grade that we offered that favors the development of holistic understandings of the world around us. (paper)

Coherence of Physics and Chemistry Curricula in Terms of the Electron Concept

Science.gov (United States)

Elena, Ivanova

2016-08-01

One of the major contradictions in subject teaching is the contradiction between the unity of the world and the discrete separated generalized content of natural sciences that study natural phenomena. These are physics, chemistry, biology and more. One can eliminate the conflict if opens the content's interdisciplinary links set by the events that are studied by different disciplines. The corresponding contexts of the phenomenon content arise depending on the discipline, and they are not enough coordinated. Obviously, we need a mechanism that allows establishing interdisciplinary links in the content quickly and without losing the logic of the material and assess their coherence in academic disciplines. This article uses a quantitative method of coherence assessment elaborated by T.N. Gnitetskaya. The definition of the concept of the semantic state introduced by the authors is given in this article. The method is applied to coherence assessment of physics and chemistry textbooks. The coherence of two pairs of chemistry and physics textbooks by different authors in different combinations was calculated. The most cohered pairs of textbooks (chemistry-physics) were identified. One can recommend using the pair of textbooks for eighth grade that we offered that favors the development of holistic understandings of the world around us.

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)

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.

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)

Bosonic Confinement and Coherence in Disordered Nanodiamond Arrays.

Science.gov (United States)

Zhang, Gufei; Samuely, Tomas; Du, Hongchu; Xu, Zheng; Liu, Liwang; Onufriienko, Oleksandr; May, Paul W; Vanacken, Johan; Szabó, Pavol; Kačmarčík, Jozef; Yuan, Haifeng; Samuely, Peter; Dunin-Borkowski, Rafal E; Hofkens, Johan; Moshchalkov, Victor V

2017-11-28

In the presence of disorder, superconductivity exhibits short-range characteristics linked to localized Cooper pairs which are responsible for anomalous phase transitions and the emergence of quantum states such as the bosonic insulating state. Complementary to well-studied homogeneously disordered superconductors, superconductor-normal hybrid arrays provide tunable realizations of the degree of granular disorder for studying anomalous quantum phase transitions. Here, we investigate the superconductor-bosonic dirty metal transition in disordered nanodiamond arrays as a function of the dispersion of intergrain spacing, which ranges from angstroms to micrometers. By monitoring the evolved superconducting gaps and diminished coherence peaks in the single-quasiparticle density of states, we link the destruction of the superconducting state and the emergence of bosonic dirty metallic state to breaking of the global phase coherence and persistence of the localized Cooper pairs. The observed resistive bosonic phase transitions are well modeled using a series-parallel circuit in the framework of bosonic confinement and coherence.

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

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

Thermal Bremsstrahlung probing nuclear multifragmentation in nucleus-nucleus collisions around the Fermi energy

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)

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

Coherent Exciton Dynamics in GaAs-Based Semiconductor Structures

Science.gov (United States)

Colocci, M.; Bogani, F.; Ceccherini, S.; Gurioli, M.

We show that a very powerful tool in the investigation of the coherent exciton dynamics in semiconductors is provided by the study of the emitted light after resonant excitation from pairs of phase-locked femtosecond pulses. Under these conditions, not only the full dynamics of the coherent transients (dephasing times, quantum beat periods, etc.) can be obtained from linear experiments, but it can also be obtained a straightforward discrimination between the coherent or incoherent character of the emission by means of spectral filtering.

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....

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

Pair production of charged Higgs scalars from electroweak gauge boson fusion

CERN Document Server

Moretti, S.

2002-01-01

We compute the contribution to charged Higgs boson pair production at the Large Hadron Collider (LHC) due to the scattering of two electroweak (EW) gauge bosons, these being in turn generated via bremsstrahlung off incoming quarks and antiquarks: $q\\bar q\\to q\\bar q V^*V^*\\to q\\bar q H^+H^-$ ($V=\\gamma,Z,W^\\pm$). We verify that the production cross section of this mode is $\\tan\\beta$ independent and show that it is smaller than that of $H^+H^-$ production via $q\\bar q$-initiated processes but generally larger than that of the loop-induced channel $gg\\to H^+H^-$.

High energy high intensity coherent photon beam for the SSC

International Nuclear Information System (INIS)

Tannenbaum, M.J.

1984-01-01

What is proposed for the 20 TeV protons hitting a fixed target is to make a tertiary electron beam similar to that which is the basis of the tagged photon beam at Fermilab. Briefly, a zero degree neutral beam is formed by sweeping out the primary proton beam and any secondary charged particles. Then the photons, from the decay of π 0 in the neutral beam, are converted to e + e - pairs in a lead converter and a high quality electron beam is formed. This beam is brought to the target area where it is converted to a photon beam by Bremsstrahlung in a radiator

Routine average effective charge calculation using visible Bremsstrahlung emission and comparison with the impurity transport code of Tore Supra

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

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.

Gamma beams generation with high intensity lasers for two photon Breit-Wheeler pair production

Science.gov (United States)

D'Humieres, Emmanuel; Ribeyre, Xavier; Jansen, Oliver; Esnault, Leo; Jequier, Sophie; Dubois, Jean-Luc; Hulin, Sebastien; Tikhonchuk, Vladimir; Arefiev, Alex; Toncian, Toma; Sentoku, Yasuhiko

2017-10-01

Linear Breit-Wheeler pair creation is the lowest threshold process in photon-photon interaction, controlling the energy release in Gamma Ray Bursts and Active Galactic Nuclei, but it has never been directly observed in the laboratory. Using numerical simulations, we demonstrate the possibility to produce collimated gamma beams with high energy conversion efficiency using high intensity lasers and innovative targets. When two of these beams collide at particular angles, our analytical calculations demonstrate a beaming effect easing the detection of the pairs in the laboratory. This effect has been confirmed in photon collision simulations using a recently developed innovative algorithm. An alternative scheme using Bremsstrahlung radiation produced by next generation high repetition rate laser systems is also being explored and the results of first optimization campaigns in this regime will be presented.

An algorithm to include the bremsstrahlung component in the determination of the absorbed dose in electron beams

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.

Thermal Bremsstrahlung probing nuclear multifragmentation in nucleus-nucleus collisions around the Fermi energy; Bremsstrahlung thermique comme sonde de la multifragmentation nucleaire dans les collisions noyau-noyau aux energies de Fermi

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)

Virtual-bremsstrahlung production in proton-proton scattering and proton-deuteron capture

NARCIS (Netherlands)

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

Pauli principle in the soft-photon approach to proton-proton bremsstrahlung

NARCIS (Netherlands)

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

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 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.

High-density EEG coherence analysis using functional units applied to mental fatigue

NARCIS (Netherlands)

Caat, Michael ten; Lorist, Monicque M.; Bezdan, Eniko; Roerdink, Jos B.T.M.; Maurits, Natasha M.

2008-01-01

Electroencephalography (EEG) coherence provides a quantitative measure of functional brain connectivity which is calculated between pairs of signals as a function of frequency. Without hypotheses, traditional coherence analysis would be cumbersome for high-density EEG which employs a large number of

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

Temporal coherence of physical, chemical and biological variables in four tropical lakes (Minas Gerais, Brazil

Directory of Open Access Journals (Sweden)

Mariana Peifer Bezerra

2017-10-01

Full Text Available Abstract Aim: The main objective of this study was to evaluate the presence of temporal coherence of limnological variables and pairs of lakes considering four tropical lakes of the Rio Doce State Park, using monthly data from the Long-Term Ecological Research Program (LTER between the years of 2004 to 2009. Methods Subsurface data (0.5 meters from the Carioca, Dom Helvécio, Gambazinho, and Jacaré Lakes were used in the analysis. We estimated the temporal coherence from the creation of time series for each of the variables. Through these series, we calculated the Pearson correlation coefficient between all pairs of lakes (N=6 and performed the average. We also analyzed the correlation between the temporal coherence found for the different pairs of lakes and two predictors of spatial patterns: proximity and exposure to climatic factors. The spatial proximity of the lake pairs was calculated in kilometers, and the exposure to climatic factors was estimated using two metrics: surface area and surface area/mean depth ratio. Results The largest temporal coherence levels were recorded for water temperature (0.97, pH (0.78, and dissolved organic carbon (DOC (0.74. The lowest levels were found for chlorophyll-a (0.25 and phytoplankton richness (-0.02. The average temporal coherence was 0.58. Different from other studies, no significant correlation was found between the synchronicity of the lake pairs and the differences in their exposure to climatic factors. Also, no relation was found with the spatial proximity. Conclusions Our results demonstrate the existence of temporal coherence in tropical lakes to compatible levels with those found in temperate regions. Our work contributes to the knowledge of how synchronicity works at different set of lakes and climatic regions.

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.

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

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

Concept of formation length in radiation theory

International Nuclear Information System (INIS)

Baier, V.N.; Katkov, V.M.

2005-01-01

The features of electromagnetic processes are considered which connected with finite size of space region in which final particles (photon, electron-positron pair) are formed. The longitudinal dimension of the region is known as the formation length. If some external agent is acting on an electron while traveling this distance the emission process can be disrupted. There are different agents: multiple scattering of projectile, polarization of a medium, action of external fields, etc. The theory of radiation under influence of the multiple scattering, the Landau-Pomeranchuk-Migdal (LPM) effect, is presented. The probability of radiation is calculated with an accuracy up to 'next to leading logarithm' and with the Coulomb corrections taken into account. The integral characteristics of bremsstrahlung are given, it is shown that the effective radiation length increases due to the LPM effect at high energy. The LPM effect for pair creation is also presented. The multiple scattering influences also on radiative corrections in a medium (and an external field too) including the anomalous magnetic moment of an electron and the polarization tensor as well as coherent scattering of a photon in a Coulomb field. The polarization of a medium alters the radiation probability in soft part of spectrum. Specific features of radiation from a target of finite thickness include: the boundary photon emission, interference effects for thin target, multi-photon radiation. The theory predictions are compared with experimental data obtained at SLAC and CERN SPS. For electron-positron colliding beams following items are discussed: the separation of coherent and incoherent mechanisms of radiation, the beam-size effect in bremsstrahlung, coherent radiation and mechanisms of electron-positron creation

Towards a coherent picture of excitonic coherence in the Fenna–Matthews–Olson complex

International Nuclear Information System (INIS)

Fidler, Andrew F; Caram, Justin R; Hayes, Dugan; Engel, Gregory S

2012-01-01

Observations of long-lived coherence between excited states in several photosynthetic antenna complexes has motivated interest in developing a more detailed understanding of the role of the protein matrix in guiding the underlying dynamics of the system. These experiments suggest that classical rate laws may not provide an adequate description of the energy transfer process and that quantum effects must be taken into account to describe the near unity transfer efficiency in these systems. Recently, it has been shown that coherences between different pairs of excitons dephase at different rates. These details should provide some insight about the underlying electronic structure of the complex and its coupling to the protein bath. Here we show that a simple model can account for the different dephasing rates as well as the most current available experimental evidence of excitonic coherences in the Fenna–Matthews–Olson complex. The differences in dephasing rates can be understood as arising largely from differences in the delocalization and shared character between the underlying electronic states. We also suggest that the anomalously low dephasing rate of the exciton 1–2 coherence is enhanced by non-secular effects. (paper)

Bremsstrahlung-Based Imaging and Assays of Radioactive, Mixed and Hazardous Waste

Science.gov (United States)

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.

Monitoring system of energy characteristics of electron beam during shaping process of power bremsstrahlung pulses

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

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

Precise Control of Molecular Dynamics with a Femtosecond Frequency Comb - A Weak Field Route to Strong Field Coherent Control

OpenAIRE

Pe'er, Avi; Shapiro, Evgeny A.; Stowe, Matthew C.; Shapiro, Moshe; Ye, Jun

2006-01-01

We present a general and highly efficient scheme for performing narrow-band Raman transitions between molecular vibrational levels using a coherent train of weak pump-dump pairs of shaped ultrashort pulses. The use of weak pulses permits an analytic description within the framework of coherent control in the perturbative regime, while coherent accumulation of many pulse pairs enables near unity transfer efficiency with a high spectral selectivity, thus forming a powerful combination of pump-d...

Linearly polarised photons at the BGO-OD experiment

Energy Technology Data Exchange (ETDEWEB)

Bella, Andreas [Physikalisches Institut, Universitaet Bonn (Germany); Collaboration: BGO-OD-Collaboration

2015-07-01

The BGO-OD experiment, located at the ELSA accelerator of the University of Bonn, aims at the study of photoproduction reactions off the nucleon. A real, energy-tagged photon beam is produced via bremsstrahlung by irradiating a thin radiator with the electron beam provided by ELSA. Linear polarisation is obtained by coherent bremsstrahlung. This requires a crystal radiator; in our case a 570 μm thick diamond is used. The production mechanism of a linearly polarised photon beam via coherent bremsstrahlung, the determination of the degree of polarisation and first results obtained with a linearly polarised photon beam are shown in this talk.

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.)

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

Kinetics of electron-positron pair plasmas using an adaptive Monte Carlo method

International Nuclear Information System (INIS)

Pilla, R.P.; Shaham, J.

1997-01-01

A new algorithm for implementing the adaptive Monte Carlo method is given. It is used to solve the Boltzmann equations that describe the time evolution of a nonequilibrium electron-positron pair plasma containing high-energy photons. These are coupled nonlinear integro-differential equations. The collision kernels for the photons as well as pairs are evaluated for Compton scattering, pair annihilation and creation, bremsstrahlung, and Coulomb collisions. They are given as multidimensional integrals which are valid for all energies. For an homogeneous and isotropic plasma with no particle escape, the equilibrium solution is expressed analytically in terms of the initial conditions. For two specific cases, for which the photon and the pair spectra are initially constant or have a power-law distribution within the given limits, the time evolution of the plasma is analyzed using the new method. The final spectra are found to be in a good agreement with the analytical solutions. The new algorithm is faster than the Monte Carlo scheme based on uniform sampling and more flexible than the numerical methods used in the past, which do not involve Monte Carlo sampling. It is also found to be very stable. Some astrophysical applications of this technique are discussed. copyright 1997 The American Astronomical Society

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.)

The effect of magnetic field strength on the time evolution of high energy bremsstrahlung radiation created by an electron cyclotron resonance ion source

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.

Physics-Based Predictions for Coherent Change Detection Using X-Band Synthetic Aperture Radar

Directory of Open Access Journals (Sweden)

Mark Preiss

2005-12-01

Full Text Available A theoretical model is developed to describe the interferometric coherency between pairs of SAR images of rough soil surfaces. The model is derived using a dyadic form for surface reflectivity in the Kirchhoff approximation. This permits the combination of Kirchhoff theory and spotlight synthetic aperture radar (SAR image formation theory. The resulting model is used to describe the interferometric coherency between pairs of SAR images of rough soil surfaces. The theoretical model is applied to SAR images formed before and after surface changes observed by a repeat-pass SAR system. The change in surface associated with a tyre track following vehicle passage is modelled and SAR coherency estimates are obtained. Predicted coherency distributions for both the change and no-change scenarios are used to estimate receiver operator curves for the detection of the changes using a high-resolution, X-band SAR system.

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)

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.

''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

Zadig: latest improvements to Bremsstrahlung treatment and in-flight annihilation scheme; Zadig: amelioration du traitement Bremsstrahlung et traitement de l'annihilation en vol

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.

Exploring coherent phenomena and energy discrimination in X-ray imaging

Energy Technology Data Exchange (ETDEWEB)

Koenig, Thomas

2011-05-04

Conventional X-ray imaging is based on the generation of photons in materials that are selected for different applications according to their densities, dimensions, and atomic numbers. The photons produced in these targets are commonly detected by measuring the integrated amount of energy released in films or digital imaging systems. This thesis aims at extending these two paradigms. First, it is shown that the use of single-crystalline, i.e. well-ordered targets, can significantly soften photon spectra created by megavoltage electrons when compared to usual targets. The reason for this is an effect called ''coherent bremsstrahlung''. It is shown that this type of radiation bears the potential of increasing the quality of megavoltage images and reducing radiation dose for image guided radiotherapy. Second, new spectroscopic pixel detectors of the Medipix2 family operated with cadmium telluride sensors are characterised and thus potential benefits and difficulties for X-ray imaging are investigated. Besides describing in detail how to calibrate these detectors, emphasis is placed on determining their energy responses, modulation transfer functions, and detective quantum efficiencies. Requirements for photon counting megavoltage imaging are discussed. The detector systems studied are finally used to perform spectral computed tomography and to illustrate the benefits of energy discrimination for coherent scatter imaging. (orig.)

Exploring coherent phenomena and energy discrimination in X-ray imaging

International Nuclear Information System (INIS)

Koenig, Thomas

2011-01-01

Conventional X-ray imaging is based on the generation of photons in materials that are selected for different applications according to their densities, dimensions, and atomic numbers. The photons produced in these targets are commonly detected by measuring the integrated amount of energy released in films or digital imaging systems. This thesis aims at extending these two paradigms. First, it is shown that the use of single-crystalline, i.e. well-ordered targets, can significantly soften photon spectra created by megavoltage electrons when compared to usual targets. The reason for this is an effect called ''coherent bremsstrahlung''. It is shown that this type of radiation bears the potential of increasing the quality of megavoltage images and reducing radiation dose for image guided radiotherapy. Second, new spectroscopic pixel detectors of the Medipix2 family operated with cadmium telluride sensors are characterised and thus potential benefits and difficulties for X-ray imaging are investigated. Besides describing in detail how to calibrate these detectors, emphasis is placed on determining their energy responses, modulation transfer functions, and detective quantum efficiencies. Requirements for photon counting megavoltage imaging are discussed. The detector systems studied are finally used to perform spectral computed tomography and to illustrate the benefits of energy discrimination for coherent scatter imaging. (orig.)

Spatial distribution of bremsstrahlung in water and water-iron by 22-MeV electron bombardment measured with activation detectors

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.)

Radiation Protection Aspects of the Linac Coherent Light Source Front End Enclosure

Energy Technology Data Exchange (ETDEWEB)

Vollaire, J.; Fasso, A.; Liu, J.C.; Mao, X.S.; Prinz, A.; Rokni, S.H.; Leitner, M.Santana; /SLAC

2010-08-26

The Front End Enclosure (FEE) of the Linac Coherent Light Source (LCLS) is a shielding housing located between the electron dump area and the first experimental hutch. The upstream part of the FEE hosts the commissioning diagnostics for the FEL beam. In the downstream part of the FEE, two sets of grazing incidence mirror and several collimators are used to direct the beam to one of the experimental stations and reduce the bremsstrahlung background and the hard component of the spontaneous radiation spectrum. This paper addresses the beam loss assumptions and radiation sources entering the FEE used for the design of the FEE shielding using the Monte-Carlo code FLUKA. The beam containment system prevents abnormal levels of radiations inside the FEE and ensures that the beam remains in its intended path is also described.

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

A collimator optimization method for quantitative imaging: application to Y-90 bremsstrahlung SPECT.

Science.gov (United States)

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

Coherence properties of spontaneous parametric down-conversion pumped by a multi-mode cw diode laser.

Science.gov (United States)

Kwon, Osung; Ra, Young-Sik; Kim, Yoon-Ho

2009-07-20

Coherence properties of the photon pair generated via spontaneous parametric down-conversion pumped by a multi-mode cw diode laser are studied with a Mach-Zehnder interferometer. Each photon of the pair enters a different input port of the interferometer and the biphoton coherence properties are studied with a two-photon detector placed at one output port. When the photon pair simultaneously enters the interferometer, periodic recurrence of the biphoton de Broglie wave packet is observed, closely resembling the coherence properties of the pump diode laser. With non-zero delays between the photons at the input ports, biphoton interference exhibits the same periodic recurrence but the wave packet shapes are shown to be dependent on both the input delay as well as the interferometer delay. These properties could be useful for building engineered entangled photon sources based on diode laser-pumped spontaneous parametric down-conversion.

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)

Coherent lattice vibrations in superconductors

International Nuclear Information System (INIS)

Kadin, Alan M.

2008-01-01

A recent analysis has shown that the pair wavefunction within the BCS theory may be represented in real-space as a spherical electronic orbital (on the scale of the coherence length ξ 0 ) coupled to a standing-wave lattice vibration with wavevector 2k F and a near-resonant phonon frequency. The present paper extends this picture to a coherent pattern of phonon standing-waves on the macroscopic scale, with electrons forming Bloch waves and an energy gap much like those in the classic band theory of crystals. These parallel planes form a diffractive waveguide permitting electron waves to traveling parallel to the planes, corresponding to lossless supercurrent. A similar picture may be extended to unconventional superconductors such as the cuprates, with an array of standing spin waves rather than phonons. Such coherent lattice vibrations should be universal indicators of the superconducting state, and should be observable below T c using X-ray and neutron diffraction techniques. Further implications of this picture are discussed

Coherent dynamics in semiconductors

DEFF Research Database (Denmark)

Hvam, Jørn Märcher

1998-01-01

enhanced in quantum confined lower-dimensional systems, where exciton and biexciton effects dominate the spectra even at room temperature. The coherent dynamics of excitons are at modest densities well described by the optical Bloch equations and a number of the dynamical effects known from atomic......Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... and molecular systems are found and studied in the exciton-biexciton system of semiconductors. At densities where strong exciton interactions, or many-body effects, become dominant, the semiconductor Bloch equations present a more rigorous treatment of the phenomena Ultrafast degenerate four-wave mixing is used...

Generation of complete coherence in Young's interference experiment with random mutually uncorrelated electromagnetic beams

NARCIS (Netherlands)

Agarwal, G. S.; Dogariu, A.; Visser, T.D.; Wolf, E.

2005-01-01

The recently developed theory that unifies the treatments of polarization and coherence of random electro-magnetic beams is applied to study field correlations in Young's interference experiment. It is found that at certain pairs of points the transmitted field is spatially fully coherent,

Coherence factors in a high-tc cuprate probed by quasi-particle scattering off vortices.

Science.gov (United States)

Hanaguri, T; Kohsaka, Y; Ono, M; Maltseva, M; Coleman, P; Yamada, I; Azuma, M; Takano, M; Ohishi, K; Takagi, H

2009-02-13

When electrons pair in a superconductor, quasi-particles develop an acute sensitivity to different types of scattering potential that is described by the appearance of coherence factors in the scattering amplitudes. Although the effects of coherence factors are well established in isotropic superconductors, they are much harder to detect in their anisotropic counterparts, such as high-superconducting-transition-temperature cuprates. We demonstrate an approach that highlights the momentum-dependent coherence factors in Ca2-xNaxCuO2Cl2. We used Fourier-transform scanning tunneling spectroscopy to reveal a magnetic-field dependence in quasi-particle scattering interference patterns that is sensitive to the sign of the anisotropic gap. This result is associated with the d-wave coherence factors and quasi-particle scattering off vortices. Our technique thus provides insights into the nature of electron pairing as well as quasi-particle scattering processes in unconventional superconductors.

Determination of the temperature of bremsstrahlung photon generated by ultraintense laser using various thickness attenuators

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.

e+e- Pair production from 10 GeV to 10 ZeV

International Nuclear Information System (INIS)

Klein, Spencer R.

2006-01-01

At very high energies, pair production (γ->e + e - ) exhibits many interesting features. The momentum transfer from the target is very small, so the reaction probes the macroscopic properties of the target, rather than individual nuclei. Interference between interactions with different atoms reduces the pair production cross section considerably below the Bethe-Heitler values. At very high energies, photonuclear interactions may outnumber pair production. In contrast, in crystals, the interaction amplitudes may add coherently, greatly increasing the cross sections. Pair production in matter-free magnetic fields is also possible. The highest energy pair production occurs at high-energy particle colliders. This article will compare pair production in these very different regimes

Y-90 SPECT ML image reconstruction with a new model for tissue-dependent bremsstrahlung production using CT information: a proof-of-concept study

Science.gov (United States)

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.

Comparison of Techniques to Reduce Bremsstrahlung Background Radiation from Monoenergetic Photon Beams

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

Classical and quantum theories of the polarization bremsstrahlung in the local electron density model

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

Continuous Variable Quantum Key Distribution Using Polarized Coherent States

Science.gov (United States)

Vidiella-Barranco, A.; Borelli, L. F. M.

We discuss a continuous variables method of quantum key distribution employing strongly polarized coherent states of light. The key encoding is performed using the variables known as Stokes parameters, rather than the field quadratures. Their quantum counterpart, the Stokes operators Ŝi (i=1,2,3), constitute a set of non-commuting operators, being the precision of simultaneous measurements of a pair of them limited by an uncertainty-like relation. Alice transmits a conveniently modulated two-mode coherent state, and Bob randomly measures one of the Stokes parameters of the incoming beam. After performing reconciliation and privacy amplification procedures, it is possible to distill a secret common key. We also consider a non-ideal situation, in which coherent states with thermal noise, instead of pure coherent states, are used for encoding.

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)

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)

Pair creation at large inherent angles

International Nuclear Information System (INIS)

Chen, P.; Tauchi, T.; Schroeder, D.V.

1992-01-01

In the next-generation linear colliders, the low-energy e + e - pairs created during the collision of high-energy e + e - beams would cause potential deleterious background problems to the detectors. At low collider energies, the pairs are made essentially by the incoherent process, where the pair is created by the interaction of beamstrahlung photons on the individual particles in the oncoming beam. This problem was first identified by Zolotarev, et al. At energies where the beamstrahlung parameter Υ lies approximately in the range 0.6 approx-lt Υ approx-lt 100, pair creation from the beamstrahlung photons is dominated by a coherent process, first noted by Chen. The seriousness of this pair creation problem lies in the transverse momenta that the pair particles carry when leaving the interaction point (IP) with large angles. Since the central issue is the transverse momentum for particles with large angles, the authors notice that there is another source for it. Namely, when the pair particles are created at low energies, the intrinsic angles of these pairs when produced may already be large. In this paper they reinvestigate the problem, following essentially the same equivalent photon approach, but with changes in specific details including the virtual photon spectrum. In addition, various assumptions are made more explicit. The formulas derived are then applied to the collider parameters designed by Palmer

Study of Diffractive Bremsstrahlung at 13 TeV LHC

CERN Document Server

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.

Powerful accelerators for bremsstrahlung and electron beams generation on the basis of inductive energy-storage elements

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.

Powerful accelerators for bremsstrahlung and electron beams generation on the basis of inductive energy-storage elements

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

A novel nuclear pyrometry for the characterization of high-energy bremsstrahlung and electrons produced in relativistic laser-plasma interactions

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.

A novel nuclear pyrometry for the characterization of high-energy bremsstrahlung and electrons produced in relativistic laser-plasma interactions

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.

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

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

Theoretical calculation on ICI reduction using digital coherent superposition of optical OFDM subcarrier pairs in the presence of laser phase noise.

Science.gov (United States)

Yi, Xingwen; Xu, Bo; Zhang, Jing; Lin, Yun; Qiu, Kun

2014-12-15

Digital coherent superposition (DCS) of optical OFDM subcarrier pairs with Hermitian symmetry can reduce the inter-carrier-interference (ICI) noise resulted from phase noise. In this paper, we show two different implementations of DCS-OFDM that have the same performance in the presence of laser phase noise. We complete the theoretical calculation on ICI reduction by using the model of pure Wiener phase noise. By Taylor expansion of the ICI, we show that the ICI power is cancelled to the second order by DCS. The fourth order term is further derived out and only decided by the ratio of laser linewidth to OFDM subcarrier symbol rate, which can greatly simplify the system design. Finally, we verify our theoretical calculations in simulations and use the analytical results to predict the system performance. DCS-OFDM is expected to be beneficial to certain optical fiber transmissions.

Determination of the parametric region in which runaway electron energy losses are dominated by bremsstrahlung radiation in tokamaks

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

New microfocus bremsstrahlung source based on betatron B-18 for high-resolution radiography and tomography

Science.gov (United States)

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.

Studies on the effect of the axial magnetic field on the x-ray bremsstrahlung in a 2.45 GHz permanent magnet microwave ion source

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

Studies on the effect of the axial magnetic field on the x-ray bremsstrahlung in a 2.45 GHz permanent magnet microwave ion source

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.

Studies on the effect of the axial magnetic field on the x-ray bremsstrahlung in a 2.45 GHz permanent magnet microwave ion source.

Science.gov (United States)

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.

Coherent control of long-distance steady-state entanglement in lossy resonator arrays

Science.gov (United States)

Angelakis, D. G.; Dai, L.; Kwek, L. C.

2010-07-01

We show that coherent control of the steady-state long-distance entanglement between pairs of cavity-atom systems in an array of lossy and driven coupled resonators is possible. The cavities are doped with atoms and are connected through waveguides, other cavities or fibers depending on the implementation. We find that the steady-state entanglement can be coherently controlled through the tuning of the phase difference between the driving fields. It can also be surprisingly high in spite of the pumps being classical fields. For some implementations where the connecting element can be a fiber, long-distance steady-state quantum correlations can be established. Furthermore, the maximal of entanglement for any pair is achieved when their corresponding direct coupling is much smaller than their individual couplings to the third party. This effect is reminiscent of the establishment of coherence between otherwise uncoupled atomic levels using classical coherent fields. We suggest a method to measure this entanglement by analyzing the correlations of the emitted photons from the array and also analyze the above results for a range of values of the system parameters, different network geometries and possible implementation technologies.

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.)

Study of 1s internal bremsstrahlung spectrum from 57Co

Science.gov (United States)

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

Transient nutation electron spin resonance spectroscopy on spin-correlated radical pairs: A theoretical analysis on hyperfine-induced nuclear modulations

Science.gov (United States)

Weber, Stefan; Kothe, Gerd; Norris, James R.

1997-04-01

The influence of anisotropic hyperfine interaction on transient nutation electron paramagnetic resonance (EPR) of light-induced spin-correlated radical pairs is studied theoretically using the density operator formalism. Analytical expressions for the time evolution of the transient EPR signal during selective microwave excitation of single transitions are derived for a model system comprised of a weakly coupled radical pair and one hyperfine-coupled nucleus with I=1/2. Zero-quantum electron coherence and single-quantum nuclear coherence are created as a result of the sudden light-induced generation of the radical pair state from a singlet-state precursor. Depending on the relative sizes of the nuclear Zeeman frequency and the secular and pseudo-secular parts of the hyperfine coupling, transitions between levels with different nuclear spin orientations are predicted to modulate the time-dependent EPR signal. These modulations are in addition to the well-known transient nutations and electron zero-quantum precessions. Our calculations provide insight into the mechanism of recent experimental observations of coherent nuclear modulations in the time-resolved EPR signals of doublets and radical pairs. Two distinct mechanisms of the modulations are presented for various microwave magnetic field strengths. The first modulation scheme arises from electron and nuclear coherences initiated by the laser excitation pulse and is "read out" by the weak microwave magnetic field. While the relative modulation depth of these oscillations with respect to the signal intensity is independent of the Rabi frequency, ω1, the frequencies of this coherence phenomenon are modulated by the effective microwave amplitude and determined by the nuclear Zeeman interaction and hyperfine coupling constants as well as the electron-electron spin exchange and dipolar interactions between the two radical pair halves. In a second mechanism the modulations are both created and detected by the microwave

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

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

Coherent triplet excitation suppresses the heading error of the avian compass

Energy Technology Data Exchange (ETDEWEB)

Katsoprinakis, G E; Dellis, A T; Kominis, I K, E-mail: ikominis@iesl.forth.g [Department of Physics, University of Crete, Heraklion 71103 (Greece); Institute of Electronic Structure and Laser, Foundation for Research and Technology, Heraklion 71110 (Greece)

2010-08-15

Radical-ion pair reactions are currently understood to underlie the biochemical magnetic compass of migratory birds. It was recently shown that radical-ion pair reactions form a rich playground for the application of quantum-information-science concepts and effects. We will show here that the intricate interplay between the quantum Zeno effect and the coherent excitation of radical-ion pairs leads to an exquisite angular sensitivity of the reaction yields. This results in a significant and previously unanticipated suppression of the avian compass heading error, opening the way to quantum engineering precision biological sensors.

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

Science.gov (United States)

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

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

Measurement of parity violation in the photodisintegration of deuterium and in the production of Bremsstrahlung on tantalum

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)

Generation of entangled coherent states for distant Bose-Einstein condensates via electromagnetically induced transparency

International Nuclear Information System (INIS)

Kuang, L.-M.; Chen Zengbing; Pan Jianwei

2007-01-01

We propose a method to generate entangled coherent states between two spatially separated atomic Bose-Einstein condensates (BECs) via the technique of electromagnetically induced transparency (EIT). Two strong coupling laser beams and two entangled probe laser beams are used to cause two distant BECs to be in EIT states and to generate an atom-photon entangled state between probe lasers and distant BECs. The two BECs are initially in unentangled product coherent states while the probe lasers are initially in an entangled state. Entangled states of two distant BECs can be created through the performance of projective measurements upon the two outgoing probe lasers under certain conditions. Concretely, we propose two protocols to show how to generate entangled coherent states of the two distant BECs. One is a single-photon scheme in which an entangled single-photon state is used as the quantum channel to generate entangled distant BECs. The other is a multiphoton scheme where an entangled coherent state of the probe lasers is used as the quantum channel. Additionally, we also obtain some atom-photon entangled states of particular interest such as entangled states between a pair of optical Bell states (or quasi-Bell-states) and a pair of atomic entangled coherent states (or quasi-Bell-states)

Electronically driven short-range lattice instability: Possible role in superconductive pairing

International Nuclear Information System (INIS)

Szasz, A.

1991-01-01

A superconducting pairing mechanism is suggested, mediating by collective and coherent cluster fluctuations in the materials. The model, based on a geometrical frustration, proposes a dynamic effect driven by a special short-range electronic instability. Experimental support for this model is discussed

Quantum correlations between each two-level system in a pair of atoms and general coherent fields

Directory of Open Access Journals (Sweden)

S. Abdel-Khalek

Full Text Available The quantitative description of the quantum correlations between each two-level system in a two-atom system and the coherent fields initially defined in a coherent state in the framework of power-law potentials (PLPCSs is considered. Specifically, we consider two atoms locally interacting with PLPCSs and take into account the different terms of interactions, the entanglement and quantum discord are studied including the time-dependent coupling and photon transition effects. Using the monogamic relation between the entanglement of formation and quantum discord in tripartite systems, we show that the control and preservation of the different kinds of quantum correlations greatly benefit from the combination of the choice of the physical quantities. Finally, we explore the link between the dynamical behavior of quantum correlations and nonclassicality of the fields with and without atomic motion effect. Keywords: Quantum correlations, Monogamic relation, Coherent states, Power-law potentials, Wehrl entropy

Characterization of network structure in stereoEEG data using consensus-based partial coherence.

Science.gov (United States)

Ter Wal, Marije; Cardellicchio, Pasquale; LoRusso, Giorgio; Pelliccia, Veronica; Avanzini, Pietro; Orban, Guy A; Tiesinga, Paul He

2018-06-06

Coherence is a widely used measure to determine the frequency-resolved functional connectivity between pairs of recording sites, but this measure is confounded by shared inputs to the pair. To remove shared inputs, the 'partial coherence' can be computed by conditioning the spectral matrices of the pair on all other recorded channels, which involves the calculation of a matrix (pseudo-) inverse. It has so far remained a challenge to use the time-resolved partial coherence to analyze intracranial recordings with a large number of recording sites. For instance, calculating the partial coherence using a pseudoinverse method produces a high number of false positives when it is applied to a large number of channels. To address this challenge, we developed a new method that randomly aggregated channels into a smaller number of effective channels on which the calculation of partial coherence was based. We obtained a 'consensus' partial coherence (cPCOH) by repeating this approach for several random aggregations of channels (permutations) and only accepting those activations in time and frequency with a high enough consensus. Using model data we show that the cPCOH method effectively filters out the effect of shared inputs and performs substantially better than the pseudo-inverse. We successfully applied the cPCOH procedure to human stereotactic EEG data and demonstrated three key advantages of this method relative to alternative procedures. First, it reduces the number of false positives relative to the pseudo-inverse method. Second, it allows for titration of the amount of false positives relative to the false negatives by adjusting the consensus threshold, thus allowing the data-analyst to prioritize one over the other to meet specific analysis demands. Third, it substantially reduced the number of identified interactions compared to coherence, providing a sparser network of connections from which clear spatial patterns emerged. These patterns can serve as a starting

Simulations of bremsstrahlung emission in ultra-intense laser interactions with foil targets

Science.gov (United States)

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.

Coherence features of the spin-aligned neutron-proton pair coupling scheme

International Nuclear Information System (INIS)

Qi, C; Blomqvist, J; Bäck, T; Cederwall, B; Johnson, A; Liotta, R J; Wyss, R

2012-01-01

The seniority scheme has been shown to be extremely useful for the classification of nuclear states in semi-magic nuclei. The neutron-proton (np) correlation breaks the seniority symmetry in a major way. As a result, the corresponding wave function is a mixture of many components with different seniority quantum numbers. In this paper, we show that the np interaction may favor a new kind of coupling in N=Z nuclei, i.e. the so-called isoscalar spin-aligned np pair mode. Shell model calculations reveal that the ground and low-lying yrast states of the N=Z nuclei 92 Pd and 96 Cd may be mainly built upon such spin-aligned np pairs, each carrying the maximum angular momentum J=9 allowed by the shell 0 g 9/2 which is dominant in this nuclear region.

Study of bremsstrahlung dose fields in radiation shield and labyrinth devices of plants with LUEH-8/5B accelerator

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

Model for bremsstrahlung emission accompanying interactions between protons and nuclei from low energies up to intermediate energies: Role of magnetic emission

Science.gov (United States)

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).

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

General individual attack on the ping-pong protocol with completely entangled pairs of qutrits

OpenAIRE

Vasiliu, E. V.

2009-01-01

The general individual (non-coherent) attack on the ping-pong protocol with completely entangled pairs of three-dimensional quantum systems (qutrits) is analyzed. The expression for amount of the eavesdropper's information as functions from probability of attack detection is derived. It is shown, that the security of the ping-pong protocol with pairs of qutrits is higher the security of the protocol with pairs of qubits. It is also shown, that with the use by legitimate users in a control mod...

Radiation safety aspects of the LINAC coherent light source

International Nuclear Information System (INIS)

Vylet, V.; Fasso, A.; Rokni, S.H.

1998-01-01

The radiation protection systems, which comprise the Personnel Protection System (PPS), Beam Containment System (BCS), and shielding, are described. The radiation sources and methods of their assessment are highlighted; these include bremsstrahlung and neutrons from electron beam losses, gas bremsstrahlung, synchrotron radiation, muons, and induced activity. By way of example, a plot of tissue dose as a function of distance from beam axis at the end of the experimental hutch is reproduced. (P.A.)

Coherence revivals in two-photon frequency combs

International Nuclear Information System (INIS)

Torres-Company, Victor; Lancis, Jesus; Lajunen, Hanna; Friberg, Ari T.

2011-01-01

We describe and theoretically analyze the self-imaging Talbot effect of entangled photon pairs in the time domain. Rich phenomena are observed in coherence propagation along dispersive media of mode-locked two-photon states with frequency entanglement exhibiting a comblike correlation function. Our results can be used to remotely transfer frequency standards through optical fiber networks with two-photon light, avoiding the requirement of dispersion compensation.

Measurement of the linear polarization of the photons in the elementary processes of bremsstrahlung production

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)

Detecting multiple moving objects in crowded environments with coherent motion regions

Science.gov (United States)

Cheriyadat, Anil M.; Radke, Richard J.

2013-06-11

Coherent motion regions extend in time as well as space, enforcing consistency in detected objects over long time periods and making the algorithm robust to noisy or short point tracks. As a result of enforcing the constraint that selected coherent motion regions contain disjoint sets of tracks defined in a three-dimensional space including a time dimension. An algorithm operates directly on raw, unconditioned low-level feature point tracks, and minimizes a global measure of the coherent motion regions. At least one discrete moving object is identified in a time series of video images based on the trajectory similarity factors, which is a measure of a maximum distance between a pair of feature point tracks.

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

Laser radiography forming bremsstrahlung radiation to image an object

Science.gov (United States)

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.

Accuracy improvement of the laplace transformation method for determination of the bremsstrahlung spectra in clinical accelerators

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

SU-E-E-08: Applications of the Quantization of Coupled Circuits in Radiation Physics (design of Klystron, Bremsstrahlung, Synchrotron)

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

Lifetime and Path Length of the Virtual Particle

International Nuclear Information System (INIS)

Lyuboshitz, V.L.; Lyuboshitz, V.V.

2005-01-01

The concepts of the lifetime and path length of a virtual particle are introduced. It is shown that, near the mass surface of the real particle, these quantities constitute a 4-vector. At very high energies, the virtual particle can propagate over considerable (even macroscopic) distances. The formulas for the lifetime and path length of an ultrarelativistic virtual electron in the process of bremsstrahlung in the Coulomb field of a nucleus are obtained. The lifetime and path length of the virtual photon at its conversion into an electron-positron pair are discussed. The connection between the path length of the virtual particle and the coherence length (formation length) is analyzed

Disoriented chiral condensates and anomalous production of pions

International Nuclear Information System (INIS)

Martinis, M.; Mikuta-Martinis, V.; Crnugelj, J.

1999-01-01

The leading-particle effect and the factorization property of the scattering amplitude in the impact parameter space are used to study semiclassical production of pions in the central region. The mechanism is related to the isospin-uniform solution of the nonlinear σ-model coupled to quark degrees of freedom. The multipion exchange potential between two quarks is derived. It is shown that the soft chiral pion Bremsstrahlung also leads to anomalously large fluctuations in the ratio of neutral to charged pion.. We show that only direct production of pions in the form of an isoscalar coherent pulse without isovector pairs can lead to large neutral-charged fluctuations. (Authors)

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

Instrumental neutron activation analysis of phosphorus in biological materials by Bremsstrahlung measurement

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)

Direct measurement of exciton valley coherence in monolayer WSe2

KAUST Repository

Hao, Kai

2016-02-29

In crystals, energy band extrema in momentum space can be identified by a valley index. The internal quantum degree of freedom associated with valley pseudospin indices can act as a useful information carrier, analogous to electronic charge or spin. Interest in valleytronics has been revived in recent years following the discovery of atomically thin materials such as graphene and transition metal dichalcogenides. However, the valley coherence time—a crucial quantity for valley pseudospin manipulation—is difficult to directly probe. In this work, we use two-dimensional coherent spectroscopy to resonantly generate and detect valley coherence of excitons (Coulomb-bound electron–hole pairs) in monolayer WSe₂ (refs ,). The imposed valley coherence persists for approximately one hundred femtoseconds. We propose that the electron–hole exchange interaction provides an important decoherence mechanism in addition to exciton population recombination. This work provides critical insight into the requirements and strategies for optical manipulation of the valley pseudospin for future valleytronics applications.

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

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.

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

Decay energy of 55Fe from its inner Bremsstrahlung spectrum

Science.gov (United States)

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.

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)

Frontal-posterior coherence and cognitive function in older adults.

Science.gov (United States)

Fleck, Jessica I; Kuti, Julia; Brown, Jessica; Mahon, Jessica R; Gayda-Chelder, Christine

2016-12-01

The reliable measurement of brain health and cognitive function is essential in mitigating the negative effects associated with cognitive decline through early and accurate diagnosis of change. The present research explored the relationship between EEG coherence for electrodes within frontal and posterior regions, as well as coherence between frontal and posterior electrodes and performance on standard neuropsychological measures of memory and executive function. EEG coherence for eyes-closed resting-state EEG activity was calculated for delta, theta, alpha, beta, and gamma frequency bands. Participants (N=66; mean age=67.15years) had their resting-state EEGs recorded and completed a neuropsychological battery that assessed memory and executive function, two cognitive domains that are significantly affected during aging. A positive relationship was observed between coherence within the frontal region and performance on measures of memory and executive function for delta and beta frequency bands. In addition, an inverse relationship was observed for coherence between frontal and posterior electrode pairs, particularly within the theta frequency band, and performance on Digit Span Sequencing, a measure of working memory. The present research supports a more substantial link between EEG coherence, rather than spectral power, and cognitive function. Continued study in this area may enable EEG to be applied broadly as a diagnostic measure of cognitive ability. Copyright © 2016 Elsevier B.V. All rights reserved.

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

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

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

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.)

A study of electron-positron pair equilibria in models of compact X- and gamma-ray sources

International Nuclear Information System (INIS)

Bjoernsson, G.

1990-01-01

Thermal electron-positron pair equilibria in two temperature models of compact x ray and gamma ray sources are studied. The pairs are assumed to be heated by Coulomb interaction with the much hotter protons and cooled by bremsstrahlung emission, Compton scattering, and annihilation. Two parameters, the proton optical depth and the compactness, characterize each equilibrium state. It is shown that a careful account of the energy balance is very important when the stability properties of the pair equilibria in a spherical plasma cloud are determined. The equilibria are found to be unstable in a very limited range of compactness and proton optical depth. This particular instability is unlikely to be the cause of the observed variability of the compact sources and implies that it is possible to build up high pair densities by a thermal mechanism in two temperature environments. The most important result considers the effects of pairs on the structure of geometrically and effectively optically thin accretion disks. A new approach for solving for the equilibrium structure of the disks is presented. In effect, the pair equilibrium states are projected into the space spanned by the disk structure parameters. This allows a direct visualization of all possible disk solutions at once. Each solution profile needs to be calculated only once and a complete disk solution is obtained by a simple radial coordinate transformation. The disk solutions are thus seen to be scale free in terms of the radial coordinate as well as in terms of the mass of the central object and the accretion rate. Two particular disk solutions are given. It is shown that including electron-positron pairs in the disk structure calculations leads to a breakdown of the thin disk assumptions and that more detailed disk modeling is required before electron-positron pairs can be self-consistently included

Gravitational bremsstrahlung in ultra-planckian collisions

CERN Document Server

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 ...

Bremsstrahlung from relativistic bare heavy ions: Nuclear and electronic contributions in amorphous and crystalline materials

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....

Qualitative comparison of bremsstrahlung X-rays and 800 MeV protons for tomography of urania fuel pellets

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.

Qualitative comparison of bremsstrahlung X-rays and 800 MeV protons for tomography of urania fuel pellets

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.

Yields of Radionuclides Created by Photonuclear Reactions on Be, C, Na, Cl, and Ge, Using Bremsstrahlung of 150-MeV Electrons

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

Accuracy evaluation of a Compton X-ray spectrometer with bremsstrahlung X-rays generated by a 6 MeV electron bunch

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.

Multiple Quantum Coherences (MQ) NMR and Entanglement Dynamics in the Mixed-Three-Spin XXX Heisenberg Model with Single-Ion Anisotropy

Science.gov (United States)

Hamid, Arian Zad

2016-12-01

We analytically investigate Multiple Quantum (MQ) NMR dynamics in a mixed-three-spin (1/2,1,1/2) system with XXX Heisenberg model at the front of an external homogeneous magnetic field B. A single-ion anisotropy property ζ is considered for the spin-1. The intensities dependence of MQ NMR coherences on their orders (zeroth and second orders) for two pairs of spins (1,1/2) and (1/2,1/2) of the favorite tripartite system are obtained. It is also investigated dynamics of the pairwise quantum entanglement for the bipartite (sub)systems (1,1/2) and (1/2,1/2) permanently coupled by, respectively, coupling constants J}1 and J}2, by means of concurrence and fidelity. Then, some straightforward comparisons are done between these quantities and the intensities of MQ NMR coherences and ultimately some interesting results are reported. We also show that the time evolution of MQ coherences based on the reduced density matrix of the pair spins (1,1/2) is closely connected with the dynamics of the pairwise entanglement. Finally, we prove that one can introduce MQ coherence of the zeroth order corresponds to the pair spins (1,1/2) as an entanglement witness at some special time intervals.

Manipulating quantum coherence of charge states in interacting double-dot Aharonov–Bohm interferometers

Science.gov (United States)

Jin, Jinshuang; Wang, Shikuan; Zhou, Jiahuan; Zhang, Wei-Min; Yan, YiJing

2018-04-01

We investigate the dynamics of charge-state coherence in a degenerate double-dot Aharonov–Bohm interferometer with finite inter-dot Coulomb interactions. The quantum coherence of the charge states is found to be sensitive to the transport setup configurations, involving both the single-electron impurity channels and the Coulomb-assisted ones. We numerically demonstrate the emergence of a complete coherence between the two charge states, with the relative phase being continuously controllable through the magnetic flux. Interestingly, a fully coherent charge qubit arises at the double-dots electron pair tunneling resonance condition, where the chemical potential of one electrode is tuned at the center between a single-electron impurity channel and the related Coulomb-assisted channel. This pure quantum state of charge qubit could be experimentally realized at the current–voltage characteristic turnover position, where differential conductance sign changes. We further elaborate the underlying mechanism for both the real-time and the stationary charge-states coherence in the double-dot systems of study.

The double copy: Bremsstrahlung and accelerating black holes

CERN Document Server

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.

Mixed optical Cherenkov–Bremsstrahlung radiation in vicinity of the Cherenkov cone from relativistic heavy ions: Unusual dependence of the angular distribution width on the radiator thickness

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.

Linearly polarised photons at the BGO-OD experiment

Energy Technology Data Exchange (ETDEWEB)

Bella, Andreas [Physikalisches Institut, Universitaet Bonn (Germany)

2016-07-01

The BGO-OD experiment, located at the ELSA accelerator of the University of Bonn studies photoproduction reactions off the nucleon. A real, energy-tagged photon beam is produced via bremsstrahlung by exposing a thin radiator to the electron beam provided by ELSA. Linear polarisation is obtained by coherent bremsstrahlung. To do this we use a 570 μm thick diamond radiator. The degree of polarisation is obtained from the bremsstrahlung spectrum. A consistency check is performed by extracting the already well measured beam asymmetry Σ in π{sup 0} photoproduction off the proton.

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.)

Monte-Carlo calculations of forward directed bremsstrahlung produced by 20 and 45 MeV electrons on tungsten

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

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.

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.

Angular distribution of thick-target bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on Ag

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.

ALOS PALSAR Winter Coherence and Summer Intensities for Large Scale Forest Monitoring in Siberia

Science.gov (United States)

Thiel, Christian; Thiel, Carolin; Santoro, Maurizio; Schmullius, Christiane

2008-11-01

In this paper summer intensity and winter coherence images are used for large scale forest monitoring. The intensities (FBD HH/HV) have been acquired during summer 2007 and feature the K&C intensity stripes [1]. The processing consisted of radiometric calibration, orthorectification, and topographic normalisation. The coherence has been estimated from interferometric pairs with 46-days repeat-pass intervals. The pairs have been acquired during the winters 2006/2007 and 2007/2008. During both winters suited weather conditions have been reported. Interferometric processing consisted of SLC co-registration at sub-pixel level, common-band filtering in range and azimuth and generation of a differential interferogram, which was used in the coherence estimation procedure based on adaptive estimation. All images were geocoded using SRTM data. The pixel size of the final SAR products is 50 m x 50 m. It could already be demonstrated, that by using PALSAR intensities and winter coherence forest and non-forest can be clearly separated [2]. By combining both data types hardly any overlap of the class signatures was detected, even though the analysis was conducted on pixel level and no speckle filter has been applied. Thus, the delineation of a forest cover mask could be executed operationally. The major hitch is the definition of a biomass threshold for regrowing forest to be distinguished as forest.

Vacuum-induced coherence in quantum dot systems

Science.gov (United States)

Sitek, Anna; Machnikowski, Paweł

2012-11-01

We present a theoretical study of vacuum-induced coherence in a pair of vertically stacked semiconductor quantum dots. The process consists in a coherent excitation transfer from a single-exciton state localized in one dot to a delocalized state in which the exciton occupation gets trapped. We study the influence of the factors characteristic of quantum dot systems (as opposed to natural atoms): energy mismatch, coupling between the single-exciton states localized in different dots, and different and nonparallel dipoles due to sub-band mixing, as well as coupling to phonons. We show that the destructive effect of the energy mismatch can be overcome by an appropriate interplay of the dipole moments and coupling between the dots which allows one to observe the trapping effect even in a structure with technologically realistic energy splitting of the order of milli-electron volts. We also analyze the impact of phonon dynamics on the occupation trapping and show that phonon effects are suppressed in a certain range of system parameters. This analysis shows that the vacuum-induced coherence effect and the associated long-living trapped excitonic population can be achieved in quantum dots.

Some advances in pairing theory

International Nuclear Information System (INIS)

Rowe, D.J.

2001-01-01

Two advances are reviewed in the application of pairing-force theory in the nuclear shell model. The first exploits a discovery that a wide range of two-nucleon interactions conserve seniority as a good quantum number. As a consequence, the eigenstates of a Hamiltonian with such an interaction belong to irreducible representations of a compact unitary-symplectic group. This makes it possible to extend the simply-solvable models with J=0 pairing forces to a much richer set of models and still obtain states uniquely classified by their seniority and angular momentum quantum numbers. Moreover, many of the low-lying energy levels of such models can be obtained algebraically; in technical terms, the models are in some cases completely solvable and in other cases partially solvable by algebraic methods. The second advance exploits the discovery that, in a coherent state representation, states of good nucleon number can be projected analytically from BCS vacuum and excited quasiparticle states. This makes it possible to perform calculations in a number-projected BCS basis without losing much of the advantage of working of the quasiparticle scheme. (Author)

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.

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)

Mixed coherent states in coupled chaotic systems: Design of secure wireless communication

Science.gov (United States)

Vigneshwaran, M.; Dana, S. K.; Padmanaban, E.

2016-12-01

A general coupling design is proposed to realize a mixed coherent (MC) state: coexistence of complete synchronization, antisynchronization, and amplitude death in different pairs of similar state variables of the coupled chaotic system. The stability of coupled system is ensured by the Lyapunov function and a scaling of each variable is also separately taken care of. When heterogeneity as a parameter mismatch is introduced in the coupled system, the coupling function facilitates to retain its coherence and displays the global stability with renewed scaling factor. Robust synchronization features facilitated by a MC state enable to design a dual modulation scheme: binary phase shift key (BPSK) and parameter mismatch shift key (PMSK), for secure data transmission. Two classes of decoders (coherent and noncoherent) are discussed, the noncoherent decoder shows better performance over the coherent decoder, mostly a noncoherent demodulator is preferred in biological implant applications. Both the modulation schemes are demonstrated numerically by using the Lorenz oscillator and the BPSK scheme is demonstrated experimentally using radio signals.

Coherent radiation spectrum measurements at KEK LUCX facility

Energy Technology Data Exchange (ETDEWEB)

Shevelev, M., E-mail: mishe@post.kek.jp [KEK: High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Aryshev, A., E-mail: alar@post.kek.jp [KEK: High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Araki, S.; Fukuda, M. [KEK: High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Karataev, P. [John Adams Institute at Royal Holloway, University of London, Egham, Surrey TW20 0EX (United Kingdom); Terunuma, N.; Urakawa, J. [KEK: High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2015-01-21

This paper demonstrates the detailed design concept, alignment, and initial testing of a Michelson interferometer for the THz spectral range. We present the first results on the measurement of a coherent transition radiation spectrum and describe the performance of a pair of ultra-fast broadband room temperature Schottky barrier diode detectors. We discuss the main criteria of interferometer beam splitter optimization, the alignment technique, the high-precision calibration and linearity check of the motion system.

Universal spectral signatures in pnictides and cuprates: the role of quasiparticle-pair coupling.

Science.gov (United States)

Sacks, William; Mauger, Alain; Noat, Yves

2017-11-08

Understanding the physical properties of a large variety of high-T c superconductors (SC), the cuprate family as well as the more recent iron-based superconductors, is still a major challenge. In particular, these materials exhibit the 'peak-dip-hump' structure in the quasiparticle density of states (DOS). The origin of this structure is explained within our pair-pair interaction (PPI) model: The non-superconducting state consists of incoherent pairs, a 'Cooper-pair glass' which, due to the PPI, undergoes a Bose-like condensation below T c to the coherent SC state. We derive the equations of motion for the quasiparticle operators showing that the DOS 'peak-dip-hump' is caused by the coupling between quasiparticles and excited pair states, or 'super-quasiparticles'. The renormalized SC gap function becomes energy-dependent and non retarded, reproducing accurately the experimental spectra of both pnictides and cuprates, despite the large difference in gap value.

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)

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

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

Optimization of the linear induction accelerator construction for maximizing the bremsstrahlung output

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.

Modeling of the electron distribution based on bremsstrahlung emission during lower hybrid current drive on PLT

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.

Modeling of the electron distribution based on bremsstrahlung emission during lower hybrid current drive on PLT

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

Identifying finite-time coherent sets from limited quantities of Lagrangian data

Energy Technology Data Exchange (ETDEWEB)

Williams, Matthew O. [Program in Applied and Computational Mathematics, Princeton University, New Jersey 08544 (United States); Rypina, Irina I. [Department of Physical Oceanography, Woods Hole Oceanographic Institute, Massachusetts 02543 (United States); Rowley, Clarence W. [Department of Mechanical and Aerospace Engineering, Princeton University, New Jersey 08544 (United States)

2015-08-15

A data-driven procedure for identifying the dominant transport barriers in a time-varying flow from limited quantities of Lagrangian data is presented. Our approach partitions state space into coherent pairs, which are sets of initial conditions chosen to minimize the number of trajectories that “leak” from one set to the other under the influence of a stochastic flow field during a pre-specified interval in time. In practice, this partition is computed by solving an optimization problem to obtain a pair of functions whose signs determine set membership. From prior experience with synthetic, “data rich” test problems, and conceptually related methods based on approximations of the Perron-Frobenius operator, we observe that the functions of interest typically appear to be smooth. We exploit this property by using the basis sets associated with spectral or “mesh-free” methods, and as a result, our approach has the potential to more accurately approximate these functions given a fixed amount of data. In practice, this could enable better approximations of the coherent pairs in problems with relatively limited quantities of Lagrangian data, which is usually the case with experimental geophysical data. We apply this method to three examples of increasing complexity: The first is the double gyre, the second is the Bickley Jet, and the third is data from numerically simulated drifters in the Sulu Sea.

Identifying finite-time coherent sets from limited quantities of Lagrangian data

International Nuclear Information System (INIS)

Williams, Matthew O.; Rypina, Irina I.; Rowley, Clarence W.

2015-01-01

A data-driven procedure for identifying the dominant transport barriers in a time-varying flow from limited quantities of Lagrangian data is presented. Our approach partitions state space into coherent pairs, which are sets of initial conditions chosen to minimize the number of trajectories that “leak” from one set to the other under the influence of a stochastic flow field during a pre-specified interval in time. In practice, this partition is computed by solving an optimization problem to obtain a pair of functions whose signs determine set membership. From prior experience with synthetic, “data rich” test problems, and conceptually related methods based on approximations of the Perron-Frobenius operator, we observe that the functions of interest typically appear to be smooth. We exploit this property by using the basis sets associated with spectral or “mesh-free” methods, and as a result, our approach has the potential to more accurately approximate these functions given a fixed amount of data. In practice, this could enable better approximations of the coherent pairs in problems with relatively limited quantities of Lagrangian data, which is usually the case with experimental geophysical data. We apply this method to three examples of increasing complexity: The first is the double gyre, the second is the Bickley Jet, and the third is data from numerically simulated drifters in the Sulu Sea

Identifying finite-time coherent sets from limited quantities of Lagrangian data.

Science.gov (United States)

Williams, Matthew O; Rypina, Irina I; Rowley, Clarence W

2015-08-01

A data-driven procedure for identifying the dominant transport barriers in a time-varying flow from limited quantities of Lagrangian data is presented. Our approach partitions state space into coherent pairs, which are sets of initial conditions chosen to minimize the number of trajectories that "leak" from one set to the other under the influence of a stochastic flow field during a pre-specified interval in time. In practice, this partition is computed by solving an optimization problem to obtain a pair of functions whose signs determine set membership. From prior experience with synthetic, "data rich" test problems, and conceptually related methods based on approximations of the Perron-Frobenius operator, we observe that the functions of interest typically appear to be smooth. We exploit this property by using the basis sets associated with spectral or "mesh-free" methods, and as a result, our approach has the potential to more accurately approximate these functions given a fixed amount of data. In practice, this could enable better approximations of the coherent pairs in problems with relatively limited quantities of Lagrangian data, which is usually the case with experimental geophysical data. We apply this method to three examples of increasing complexity: The first is the double gyre, the second is the Bickley Jet, and the third is data from numerically simulated drifters in the Sulu Sea.

SAR image effects on coherence and coherence estimation.

Energy Technology Data Exchange (ETDEWEB)

Bickel, Douglas Lloyd

2014-01-01

Radar coherence is an important concept for imaging radar systems such as synthetic aperture radar (SAR). This document quantifies some of the effects in SAR which modify the coherence. Although these effects can disrupt the coherence within a single SAR image, this report will focus on the coherence between separate images, such as for coherent change detection (CCD) processing. There have been other presentations on aspects of this material in the past. The intent of this report is to bring various issues that affect the coherence together in a single report to support radar engineers in making decisions about these matters.

Diagnostics of pre-breakdown light emission in a helium coplanar barrier discharge: the presence of neutral bremsstrahlung

Science.gov (United States)

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.

Studies of plasma breakdown and electron heating on a 14 GHz ECR ion source through measurement of plasma bremsstrahlung

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.

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

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.)

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

Diagnostics of pre-breakdown light emission in a helium coplanar barrier discharge: the presence of neutral bremsstrahlung

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

Causality analysis of alpha activities by multidimensional directed coherence; Tajigen yuko coherence ni yoru {alpha}ritsudo no ingasei kaiseki

Energy Technology Data Exchange (ETDEWEB)

Sakata, O.; Shimada, N.; Shiina, T. [University of Tsukuba, Tsukuba (Japan); Saito, Y.; Imanishi, N.

1998-07-01

Alpha activities as a basic component of EEG (electroencephalogram) are mainly observed with eye-closed and reported state, and indicates rhythmic and diffused pattern on the scalp. Therefore analysis of the relation among many sequences of alpha activities measured at different positions on the scalp is expected to be useful not only for diagnosing psychiatric but also for investigating mechanism of brain information processing by means of causality analysis that is, macroscopic estimation of flow pattern within brain. Although coherence analysis has been proposed as a method for estimating the direction and magnitude of information flow between two sequences, superposition of results for each pair of sequences can not represent true relation among the whole sequences. In this paper, we proposed the multidimensional directed coherence analysis by modifying two-channel formula in order to apply it to the analysis of multi-channel sequence of alpha activities. Results of simulation revealed that multidimensional directed coherence can indicate more quantitatively the relation among the multi-channel sequences compared with conventional two-channel formula. Moreover, the proposed method was applied to the analysis of EEG data of normal volunteer and patient. Results show the method can provide a useful diagnostic information by assessment of the signal flow pattern within brain. 16 refs., 10 figs.

Generalized quantum interference of correlated photon pairs

Science.gov (United States)

Kim, Heonoh; Lee, Sang Min; Moon, Han Seb

2015-01-01

Superposition and indistinguishablility between probability amplitudes have played an essential role in observing quantum interference effects of correlated photons. The Hong-Ou-Mandel interference and interferences of the path-entangled photon number state are of special interest in the field of quantum information technologies. However, a fully generalized two-photon quantum interferometric scheme accounting for the Hong-Ou-Mandel scheme and path-entangled photon number states has not yet been proposed. Here we report the experimental demonstrations of the generalized two-photon interferometry with both the interferometric properties of the Hong-Ou-Mandel effect and the fully unfolded version of the path-entangled photon number state using photon-pair sources, which are independently generated by spontaneous parametric down-conversion. Our experimental scheme explains two-photon interference fringes revealing single- and two-photon coherence properties in a single interferometer setup. Using the proposed interferometric measurement, it is possible to directly estimate the joint spectral intensity of a photon pair source. PMID:25951143

Neutrino-Pair Exchange Long-Range Force Between Aggregate Matter

OpenAIRE

Segarra, A.

2016-01-01

We study the long-range force arising between two neutral---of electric charge---aggregates of matter due to a neutrino-pair exchange, in the limit of zero neutrino mass. The conceptual basis for the construction of the effective potential comes from the coherent scattering amplitude at low values of t. This amplitude is obtained using the methodology of an unsubtracted dispersion relation in t at threshold for s, where (s, t) are the Lorentz invariant scattering variables. The ultraviolet be...

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.)

Linear to Circular Polarisation Conversion using Birefringent Properties of Aligned Crystals for Multi-GeV Photons

CERN Document Server

Apyan, A.; Badelek, B.; Ballestrero, S.; Biino, C.; Birol, I.; Cenci, P.; Connell, S.H.; Eichblatt, S.; Fonseca, T.; Freund, A.; Gorini, B.; Groess, R.; Ispirian, K.; Ketel, T.J.; Kononets, Yu.V.; Lopez, A.; Mangiarotti, A.; van Rens, B.; Sellschop, J.P.F.; Shieh, M.; Sona, P.; Strakhovenko, V.; Uggerhoj, E.; Uggerhj, Ulrik Ingerslev; Unel, G.; Velasco, M.; Vilakazi, Z.Z.; Wessely, O.; Kononets, Yu.V.

2003-01-01

We present the first experimental results on the use of a thick aligned Si crystal acting as a quarter wave plate to induce a degree of circular polarisation in a high energy linearly polarised photon beam. The linearly polarised photon beam is produced from coherent bremsstrahlung radiation by 178 GeV unpolarised electrons incident on an aligned Si crystal, acting as a radiator. The linear polarisation of the photon beam is characterised by measuring the asymmetry in electron-positron pair production in a Ge crystal, for different crystal orientations. The Ge crystal therefore acts as an analyser. The birefringence phenomenon, which converts the linear polarisation to circular polarisation, is observed by letting the linearly polarised photons beam pass through a thick Si quarter wave plate crystal, and then measuring the asymmetry in electron-positron pair production again for a selection of relative angles between the crystallographic planes of the radiator, analyser and quarter wave plate. The systematics...

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.

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)

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)

Tomographic bremsstrahlung imaging with yttrium-90 in the context of radioembolisation of liver tumors; Tomografische Bildgebung mit Yttrium-90-Bremsstrahlung im Rahmen der Radioembolisation von Lebertumoren

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

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

Program controlled system for measuring and monitoring the electron coherent radiation spectrum of Yerevan synchrotron

International Nuclear Information System (INIS)

Adamyan, F.V.; Vartapetyan, G.A.; Galumyan, P.I.

1980-01-01

An automatic system for measurement, processing and control of energy spectrum of polarized photons realized at the Yerevan electron synchrotron is described. For measuring energy spectra of intensive high energy photon beams a pair spectrometer is used which comprises an aluminium target-converter, an analizing magnet and 2 telescopes of scintillation counters for electron-positron pairs registration. the procedure of spectra measurement by the pair spectrometer is reduced to determining the converted e + e - pairs yield at certain values of the H field intensity of the analizing magnet. An algorithm of the data express-processing for operative monitoring of peak energy stability of electron coherent radiation spectrum is given. The spectra measurement results obtained under real experimental conditions are presented

Coherent exciton transport in dendrimers and continuous-time quantum walks

Science.gov (United States)

Mülken, Oliver; Bierbaum, Veronika; Blumen, Alexander

2006-03-01

We model coherent exciton transport in dendrimers by continuous-time quantum walks. For dendrimers up to the second generation the coherent transport shows perfect recurrences when the initial excitation starts at the central node. For larger dendrimers, the recurrence ceases to be perfect, a fact which resembles results for discrete quantum carpets. Moreover, depending on the initial excitation site, we find that the coherent transport to certain nodes of the dendrimer has a very low probability. When the initial excitation starts from the central node, the problem can be mapped onto a line which simplifies the computational effort. Furthermore, the long time average of the quantum mechanical transition probabilities between pairs of nodes shows characteristic patterns and allows us to classify the nodes into clusters with identical limiting probabilities. For the (space) average of the quantum mechanical probability to be still or to be again at the initial site, we obtain, based on the Cauchy-Schwarz inequality, a simple lower bound which depends only on the eigenvalue spectrum of the Hamiltonian.

Initial studies of Bremsstrahlung energy deposition in small-bore superconducting undulator structures in linac environments

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.

Calculation of Bremsstrahlung radiation of electrons on atoms in wide energy range of photons

CERN Document Server

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

Electron, electron-bremsstrahlung and proton depth-dose data for space-shielding applications

Science.gov (United States)

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.

Partially coherent imaging and spatial coherence wavelets

International Nuclear Information System (INIS)

Castaneda, Roman

2003-03-01

A description of spatially partially coherent imaging based on the propagation of second order spatial coherence wavelets and marginal power spectra (Wigner distribution functions) is presented. In this dynamics, the spatial coherence wavelets will be affected by the system through its elementary transfer function. The consistency of the model with the both extreme cases of full coherent and incoherent imaging was proved. In the last case we obtained the classical concept of optical transfer function as a simple integral of the elementary transfer function. Furthermore, the elementary incoherent response function was introduced as the Fourier transform of the elementary transfer function. It describes the propagation of spatial coherence wavelets form each object point to each image point through a specific point on the pupil planes. The point spread function of the system was obtained by a simple integral of the elementary incoherent response function. (author)

Development of high resolution Michelson interferometer for stable phase-locked ultrashort pulse pair generation.

Science.gov (United States)

Okada, Takumi; Komori, Kazuhiro; Goshima, Keishiro; Yamauchi, Shohgo; Morohashi, Isao; Sugaya, Takeyoshi; Ogura, Mutsuo; Tsurumachi, Noriaki

2008-10-01

We developed a high resolution Michelson interferometer with a two-frequency He-Ne laser positioning system in order to stabilize the relative phase of a pulse pair. The control resolution corresponded to a 12 as time resolution or a phase of 1.5 degrees at 900 nm. This high resolution Michelson interferometer can generate a phase-locked pulse pair either with a specific relative phase such as 0 or pi radians or with an arbitrary phase. Coherent control of an InAs self-assembled quantum dot was demonstrated using the high resolution Michelson interferometer with a microspectroscopy system.

New Frontiers in Heart Rate Variability and Social Coherence Research: Techniques, Technologies, and Implications for Improving Group Dynamics and Outcomes

Directory of Open Access Journals (Sweden)

Rollin McCraty

2017-10-01

Full Text Available Concepts embraced by the term coherence have been identified as central to fields such as quantum physics, physiology, and social science. There are different types of coherence, although the term always implies a harmonious relationship, correlations and connections between the various parts of a system. A specific measure derived from heart rate variability (HRV provides a measure of physiological coherence. Another type of coherence, social coherence, relates to the harmonious alignment between couples or pairs, family units, small groups, or larger organizations in which a network of relationships exists among individuals who share common interests and objectives. A high degree of social coherence is reflected by stable and harmonious relationships, which allows for the efficient flow and utilization of energy and communication required for optimal collective cohesion and action. Social coherence requires that group members are attuned and are emotionally connected with each other, and that the group’s emotional energy is organized and regulated by the group as a whole. A number of studies are reviewed which have explored various types of synchronization in infants, pairs and groups, indicating that feelings of cooperation, trust, compassion and increased prosocial behaviors depends largely on the establishment of a spontaneous synchronization of various physiological rhythms between individuals. This article discusses a new application using HRV monitoring in social coherence research and the importance of physiological synchronization in group developmental processes and dynamics. Building on the extensive body of research showing that providing feedback of HRV coherence level at the individual level can improve self-regulation, we suggest the following hypotheses: (1 providing feedback of individual and collective HRV coherence and the degree of heart rhythm synchronization will increase group coherence, and heart rhythm synchronization

A semi-discrete integrable multi-component coherently coupled nonlinear Schrödinger system

International Nuclear Information System (INIS)

Zhao, Hai-qiong; Yuan, Jinyun

2016-01-01

A new integrable semi-discrete version is proposed for the multi-component coherently coupled nonlinear Schrödinger equation. The integrability of the semi-discrete system is confirmed by existence of Lax pair and infinite number of conservation laws. With the aid of gauge transformations, explicit formulas for N -fold Darboux transformations are derived whereby some physically important solutions of the system are presented. Furthermore, the theory of the semi-discrete system including Lax pair, Darboux transformations, exact solutions and infinite number of conservation laws are shown for their continuous counterparts in the continuous limit. (paper)

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

Angular distributions of absorbed dose of Bremsstrahlung and secondary electrons induced by 18-, 28- and 38-MeV electron beams in thick targets.

Science.gov (United States)

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.

Non-Markovian response of ultrafast coherent electronic ring currents in chiral aromatic molecules in a condensed phase

International Nuclear Information System (INIS)

Mineo, H.; Lin, S. H.; Fujimura, Y.; Xu, J.; Xu, R. X.; Yan, Y. J.

2013-01-01

Results of a theoretical study on non-Markov response for femtosecond laser-driven coherent ring currents in chiral aromatic molecules embedded in a condensed phase are presented. Coherent ring currents are generated by coherent excitation of a pair of quasi-degenerated π-electronic excited states. The coherent electronic dynamical behaviors are strongly influenced by interactions between the electronic system and phonon bath in a condensed phase. Here, the bath correlation time is not instantaneous but should be taken to be a finite time in ultrashort time-resolved experiments. In such a case, Markov approximation breaks down. A hierarchical master equation approach for an improved semiclassical Drude dissipation model was adopted to examine the non-Markov effects on ultrafast coherent electronic ring currents of (P)-2,2 ′ -biphenol in a condensed phase. Time evolution of the coherent ring current derived in the hierarchical master equation approach was calculated and compared with those in the Drude model in the Markov approximation and in the static limit. The results show how non-Markovian behaviors in quantum beat signals of ring currents depend on the Drude bath damping constant. Effects of temperatures on ultrafast coherent electronic ring currents are also clarified

Further investigating the determination of phosphorus in plants by INAA using bremsstrahlung measurement

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)

sLORETA intracortical lagged coherence during breath counting in meditation-naïve participants

Directory of Open Access Journals (Sweden)

Patricia eMilz

2014-05-01

Full Text Available We investigated brain functional connectivity comparing no-task resting to breath counting (a meditation exercise but given as task without referring to meditation. Functional connectivity computed as EEG coherence between head-surface data suffers from localization ambiguity, reference dependence, and overestimation due to volume conduction. Lagged coherence between intracortical model sources addresses these criticisms. With this analysis approach, experienced meditators reportedly showed reduced coherence during meditation, meditation-naïve participants have not yet been investigated. 58-channel EEG from 23 healthy, right-handed, meditation-naïve males during resting [3 runs] and breath counting [2 runs] was computed into sLORETA time series of intracortical electrical activity in 19 regions of interest corresponding to the cortex underlying 19 scalp electrode sites, for each of the 8 independent EEG frequency bands covering 1.5-44 Hz. Intracortical lagged coherences and head-surface conventional coherences were computed between the 19 regions/sites. During breath counting compared to resting, paired t-tests corrected for multiple testing revealed 4 significantly lower intracortical lagged coherences, but 4 significantly higher head-surface conventional coherences. Lowered intracortical lagged coherences involved left BA 10 and right BAs 3, 10, 17, 40. In conclusion, intracortical lagged coherence can yield results that are inverted to those of head-surface conventional coherence. The lowered functional connectivity between cognitive control areas and sensory perception areas during meditation-type breath counting compared to resting conceivably reflects the attention to a bodily percept without cognitive reasoning. The reductions in functional connectivity were similar but not as widespread as the reductions reported during meditation in experienced meditators.

The Effective Coherence Length in Anisotropic Superconductors

International Nuclear Information System (INIS)

Polturak, E.; Koren, G.; Nesher, O

1999-01-01

If electrons are transmitted from a normal conductor(N) into a superconductor(S), common wisdom has it that the electrons are converted into Cooper pairs within a coherence length from the interface. This is true in conventional superconductors with an isotropic order parameter. We have established experimentally that the situation is rather different in high Tc superconductors having an anisotropic order parameter. We used epitaxial thin film S/N bilayers having different interface orientations in order to inject carriers from S into N along different directions. The distance to which these carriers penetrate were determined through their effect on the Tc of the bilayers. We found that the effective coherence length is 20A only along the a or b directions, while in other directions we find a length of 250dr20A out of plane, and an even larger value for in-plane, off high symmetry directions. These observations can be explained using the Blonder-Tinkham-Klapwijk model adapted to anisotropic superconductivity. Several implications of our results on outstanding problems with high Tc junctions will be discussed

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

A soft x-ray free electron laser (FEL) using a two-beam elliptical pill-box wake-field cavity

International Nuclear Information System (INIS)

Kim, S.H.; Chen, K.W.

1988-01-01

Stimulated bremsstrahlung in an undulating electric field in the lasing beam direction (electric wiggler) was shown to be possible from the quantum- mechanical viewpoint. Herein, this possibility is scrutinized from the viewpoint of classical electrodynamics. It is found that if stimulated bremsstrahlung in a transverse undulating magnetic field (magnetic wiggler) occurs, stimulated bremsstrahlung in the electric wiggler must also occur. We further show that a free electron laser (FEL) using a magnetic wiggler to provide a catalyzer field for stimulated bremsstrahlung cannot serve as a practical FEL operating in the soft x-ray region from both theoretical and experimental viewpoints. On the other hand, the authors demonstrate that the FEL using a traveling wake field in a two-beam elliptical pill-box cavity is well suited as a source of coherent radiation in the soft x-ray region

Effects of food web structure and resource subsidies on the patterns and mechanisms of temporal coherence in a tropical coastal lagoon: an experimental mesocosm approach

Directory of Open Access Journals (Sweden)

Luciana Silva Carneiro

Full Text Available AIM: The study of the patterns and mechanisms of temporal coherence of ecological variables among lakes has become an important area of limnology. However, no study to date has experimentally tested whether and how resource subsidies and food web configuration affect the patterns and mechanisms of temporal coherence of limnological variables. We conducted a field mesocosm experiment to test the following hypotheses: (i nutrient enrichment would reduce the temporal coherence of system variables; (ii fish predation would enhance the temporal coherence of system variables; and (iii the strength of temporal coherence decreases from physical (water transparency, to chemical (dissolved oxygen concentration [DO] to biological variables (total zooplankton biomass. METHODS: For 11 weeks, we manipulated fish presence and nutrient (N and P concentration in a 2 × 2 factorial design in sixteen within-lake enclosures installed in a tropical coastal lagoon. Coherence was estimated by pair-to-pair Pearson's moment correlations of the temporal trajectories of each response variable among enclosures of the same treatment. RESULTS: Fish presence only enhanced the temporal coherence of zooplankton biomass, whereas contrary to our expectations, nutrient addition enhanced the temporal coherence of [DO]. The strength of the individual effects of fish and nutrients on temporal coherence was affected by variable identity, but this variation did not occur in a consistent pattern across variables. However, the interactive effects of fish and nutrients on the temporal coherence of the three variables monitored were not statistically significant. CONCLUSIONS: Our results indicate that local factors, such as fish presence and nutrient availability, may affect the temporal coherence of several system variables, but these effects are better predicted by the strength of direct interactions between the local factor and the variable than by the identity of the variable itself

Coherence and interlimb force control: Effects of visual gain.

Science.gov (United States)

Kang, Nyeonju; Cauraugh, James H

2018-03-06

Neural coupling across hemispheres and homologous muscles often appears during bimanual motor control. Force coupling in a specific frequency domain may indicate specific bimanual force coordination patterns. This study investigated coherence on pairs of bimanual isometric index finger force while manipulating visual gain and task asymmetry conditions. We used two visual gain conditions (low and high gain = 8 and 512 pixels/N), and created task asymmetry by manipulating coefficient ratios imposed on the left and right index finger forces (0.4:1.6; 1:1; 1.6:0.4, respectively). Unequal coefficient ratios required different contributions from each hand to the bimanual force task resulting in force asymmetry. Fourteen healthy young adults performed bimanual isometric force control at 20% of their maximal level of the summed force of both fingers. We quantified peak coherence and relative phase angle between hands at 0-4, 4-8, and 8-12 Hz, and estimated a signal-to-noise ratio of bimanual forces. The findings revealed higher peak coherence and relative phase angle at 0-4 Hz than at 4-8 and 8-12 Hz for both visual gain conditions. Further, peak coherence and relative phase angle values at 0-4 Hz were larger at the high gain than at the low gain. At the high gain, higher peak coherence at 0-4 Hz collapsed across task asymmetry conditions significantly predicted greater signal-to-noise ratio. These findings indicate that a greater level of visual information facilitates bimanual force coupling at a specific frequency range related to sensorimotor processing. Copyright © 2018 Elsevier B.V. All rights reserved.

Measurement of {sup 27}Al(γ,2pn){sup 24}Na Reaction Cross-sections with 55 -, 60 -, 65 - MeV Bremsstrahlung Employing MCNPX Simulation

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)

Time-Resolved Magnetic Field Effects Distinguish Loose Ion Pairs from Exciplexes

Science.gov (United States)

2013-01-01

We describe the experimental investigation of time-resolved magnetic field effects in exciplex-forming organic donor–acceptor systems. In these systems, the photoexcited acceptor state is predominantly deactivated by bimolecular electron transfer reactions (yielding radical ion pairs) or by direct exciplex formation. The delayed fluorescence emitted by the exciplex is magnetosensitive if the reaction pathway involves loose radical ion pair states. This magnetic field effect results from the coherent interconversion between the electronic singlet and triplet radical ion pair states as described by the radical pair mechanism. By monitoring the changes in the exciplex luminescence intensity when applying external magnetic fields, details of the reaction mechanism can be elucidated. In this work we present results obtained with the fluorophore-quencher pair 9,10-dimethylanthracene/N,N-dimethylaniline (DMA) in solvents of systematically varied permittivity. A simple theoretical model is introduced that allows discriminating the initial state of quenching, viz., the loose ion pair and the exciplex, based on the time-resolved magnetic field effect. The approach is validated by applying it to the isotopologous fluorophore-quencher pairs pyrene/DMA and pyrene-d10/DMA. We detect that both the exciplex and the radical ion pair are formed during the initial quenching stage. Upon increasing the solvent polarity, the relative importance of the distant electron transfer quenching increases. However, even in comparably polar media, the exciplex pathway remains remarkably significant. We discuss our results in relation to recent findings on the involvement of exciplexes in photoinduced electron transfer reactions. PMID:24041160

Dosimetry and microdosimetry using LET spectrometer based on the track-etch detector: radiotherapy bremsstrahlung beam, onboard aircraft radiation field

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

Stimulated-emission pumping enabling sub-diffraction-limited spatial resolution in coherent anti-Stokes Raman scattering microscopy

NARCIS (Netherlands)

Cleff, C.; Gross, P.; Fallnich, C.; Offerhaus, Herman L.; Herek, Jennifer Lynn; Kruse, K.; Beeker, W.P.; Lee, Christopher James; Boller, Klaus J.

2013-01-01

We present a theoretical investigation of stimulated emission pumping to achieve sub-diffraction-limited spatial resolution in coherent anti-Stokes Raman scattering (CARS) microscopy. A pair of control light fields is used to prepopulate the Raman state involved in the CARS process prior to the CARS

Improved quantitative 90 Y bremsstrahlung SPECT/CT reconstruction with Monte Carlo scatter modeling.

Science.gov (United States)

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

A Single Bremsstrahlung Monitor to Measure Luminosity at LEP

CERN Multimedia

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...

The bremsstrahlung tagged photon beam in Hall B at JLab

CERN Document Server

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...

Channeling crystals for positron production

International Nuclear Information System (INIS)

Decker, F.J.

1991-05-01

Particles traversing at small angles along a single crystal axis experience a collective scattering force of many crystal atoms. The enormous fields can trap the particles along an axis or plane, called channeling. High energy electrons are attracted by the positive nuclei and therefore produce strongly enhanced so called coherent bremsstrahlung and pair production. These effects could be used in a positron production target: A single tungsten crystal is oriented to the incident electron beam within 1 mrad. At 28 GeV/c the effective radiation length is with 0.9 mm about one quarter of the amorphous material. So the target length can be shorter, which yields a higher conversion coefficient and a lower emittance of the positron beam. This makes single crystals very interesting for positron production targets. 18 refs., 2 figs

Half-integer flux quantum effect in cuprate superconductors - a probe of pairing symmetry

International Nuclear Information System (INIS)

Tsuei, C.C.; Kirtley, J.R.; Gupta, A.; Sun, J.Z.; Moler, K.A.; Wang, J.H.

1996-01-01

Based on macroscopic quantum coherence effects arising from pair tunneling and flux quantization, a series of tricrystal experiments have been designed and carried out to test the order parameter symmetry in high-T c cuprate superconductors. By using a scanning SQUID microscope, we have directly and non-invasively observed the spontaneously generated half-integer flux quantum effect in controlled-orientation tricrystal cuprate superconducting systems. The presence or absence of the half-integer flux quantum effect as a function of the tricrystal geometry allows us to prove that the order parameter symmetry in the YBCO and Tl2201 systems is consistent with that of the d x 2 -y 2 pair state. (orig.)

Time-bin entangled photon pairs from spontaneous parametric down-conversion pumped by a cw multi-mode diode laser.

Science.gov (United States)

Kwon, Osung; Park, Kwang-Kyoon; Ra, Young-Sik; Kim, Yong-Su; Kim, Yoon-Ho

2013-10-21

Generation of time-bin entangled photon pairs requires the use of the Franson interferometer which consists of two spatially separated unbalanced Mach-Zehnder interferometers through which the signal and idler photons from spontaneous parametric down-conversion (SPDC) are made to transmit individually. There have been two SPDC pumping regimes where the scheme works: the narrowband regime and the double-pulse regime. In the narrowband regime, the SPDC process is pumped by a narrowband cw laser with the coherence length much longer than the path length difference of the Franson interferometer. In the double-pulse regime, the longitudinal separation between the pulse pair is made equal to the path length difference of the Franson interferometer. In this paper, we propose another regime by which the generation of time-bin entanglement is possible and demonstrate the scheme experimentally. In our scheme, differently from the previous approaches, the SPDC process is pumped by a cw multi-mode (i.e., short coherence length) laser and makes use of the coherence revival property of such a laser. The high-visibility two-photon Franson interference demonstrates clearly that high-quality time-bin entanglement source can be developed using inexpensive cw multi-mode diode lasers for various quantum communication applications.

Many-body pairing in a two-dimensional Fermi gas

Energy Technology Data Exchange (ETDEWEB)

Neidig, Mathias

2017-05-24

This thesis reports on experiments conducted in a single layer, quasi two-dimensional, two-component ultracold Fermi gas in the strongly interacting regime. Ultracold gases can be used to simulate key aspects of more complicated systems like for example cuprates which show high-T{sub c} superconductivity. The momentum distribution of a sample of bosonic dimers in a quasi-2D square lattice geometry was measured to obtain the coherence properties. For shallow lattices, sharp peaks in the momentum distribution, indicating coherence, were observed at zero momentum as well as at positive and negative lattice momenta along each axis. For deeper lattices, heating impeded the ability to prepare a Mott-insulator. A spatially resolved radio-frequency spectroscopy was employed for a quasi-2D Fermi gas in the normal phase throughout the BEC-BCS crossover. The interaction induced energy shifts were measured in the strongly interacting region where they can be on the order of the Fermi energy and thus the local resolution is crucial. Furthermore, the onset of pairing in the strongly interacting region was measured as a function of temperature and it was shown that the fraction of free atoms decreases faster than expected from thermal non-interacting theory. At last, the pairing gap was measured using an imbalanced sample. On the BEC side it was found to be in very good agreement with two-body physics as expected. In the strongly interacting regime, however, a deviation from two-body physics indicates that here many-body effects play a role and thus further studies are required.

Influence of the electron cyclotron resonance plasma confinement on reducing the bremsstrahlung production of an electron cyclotron resonance ion source with metal-dielectric structures

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.

Towards deterministic optical quantum computation with coherently driven atomic ensembles

International Nuclear Information System (INIS)

Petrosyan, David

2005-01-01

Scalable and efficient quantum computation with photonic qubits requires (i) deterministic sources of single photons, (ii) giant nonlinearities capable of entangling pairs of photons, and (iii) reliable single-photon detectors. In addition, an optical quantum computer would need a robust reversible photon storage device. Here we discuss several related techniques, based on the coherent manipulation of atomic ensembles in the regime of electromagnetically induced transparency, that are capable of implementing all of the above prerequisites for deterministic optical quantum computation with single photons

Coherence factors beyond the BCS expressions—a derivation

International Nuclear Information System (INIS)

Gorohovsky, G; Bettelheim, E

2014-01-01

We present a derivation of a previously announced result for matrix elements between exact eigenstates of the pairing Hamiltonian. Our results, which generalize the well-known Bardeen–Cooper–Schrieffer (BCS) (Bardeen et al 1957 Phys. Rev. 108 1175; 1957 Phys. Rev. 106 162) expressions for what are known as ‘coherence factors’, are derived based on the Slavnov (1989 Theor. Math. Phys. 79 502) formula for overlaps between Bethe-ansatz states, thus making use of the known connection between the exact diagonalization of the BCS Hamiltonian, due to Richardson (1963 Phys. Lett. 3 277; 1964 Nucl. Phys. A 52 221), and the algebraic Bethe ansatz. The resulting formula has a compact form after a suitable parameterization of the energy plane. Although we apply our method here to the pairing Hamiltonian, it may be adjusted to study what is termed the ‘Sutherland limit’ (Sutherland 1995 Phys. Rev. Lett. 74 816) for exactly solvable models, namely where a macroscopic number of rapidities form a large string. (paper)

Development of a Beam Trajectory Monitoring System Using e+/e- Pair Production Events

Science.gov (United States)

Kimura, Shota; Emoto, Yusaku; Fujihara, Kento; Ito, Hiroshi; Kawai, Hideyuki; Kobayashi, Atsushi; Mizuno, Takahiro

2018-01-01

In particle therapy, it is important to monitor the Bragg-peak position. It was simulated by GEANT4 Monte Carlo Simulation Code that the distribution of secondary generated gamma rays on the carbon beam therapy and the proton beam therapy. This simulation shows that gamma rays whose energy is 10 MeV or more are intensively generated at the Bragg-peak position. We are developing the system to monitor the Bragg-peak position which can measure pair production events occurred in the detector by gamma rays from irradiation points. The momentum direction of the gamma ray can be determined by measuring passing points and energy of e+ and e- generated by pair production. This system has 5 parts. The first is the conversion part. This part consists of several layers. Each layer is composed of a La-GPS ((Gd0.75La0.24Ce0.01)2Si2O7) scintillator plate and wavelength-shifting fibre (WLSF) sheets. The scintillator plate is sandwiched between sheets, where the directions of the sheets are in orthogonally x and y directions. In this part, gamma rays are converted to e+ e- pairs and the position where the conversion occured is determined. The second is the tracking part. This part consists of 2 layers of scintillating fibre tracker. Each layer has 6 scintillating fibre sheets for x, x', u, u', v, and v'. The third is the energy measurement part. It measures the energy of e+ and e- by scintillator array and Silicon Photomultipliers. The fourth is the veto counter for bremsstrahlung gamma rays from e+ and e-. The fifth is the beam monitor. By experiment, the number of photoelectrons of La-GPS with a WLSF (B-3(300)MJ, Kuraray) sheet and scintillating fibre (SCSF-78, Kuraray) when charged particle passed was measured as 9.7 and 7.6 respectively.

Development of a Beam Trajectory Monitoring System Using e+/e− Pair Production Events

Directory of Open Access Journals (Sweden)

KIMURA Shota

2018-01-01

Full Text Available In particle therapy, it is important to monitor the Bragg-peak position. It was simulated by GEANT4 Monte Carlo Simulation Code that the distribution of secondary generated gamma rays on the carbon beam therapy and the proton beam therapy. This simulation shows that gamma rays whose energy is 10 MeV or more are intensively generated at the Bragg-peak position. We are developing the system to monitor the Bragg-peak position which can measure pair production events occurred in the detector by gamma rays from irradiation points. The momentum direction of the gamma ray can be determined by measuring passing points and energy of e+ and e− generated by pair production. This system has 5 parts. The first is the conversion part. This part consists of several layers. Each layer is composed of a La-GPS ((Gd0.75La0.24Ce0.012Si2O7 scintillator plate and wavelength-shifting fibre (WLSF sheets. The scintillator plate is sandwiched between sheets, where the directions of the sheets are in orthogonally x and y directions. In this part, gamma rays are converted to e+ e- pairs and the position where the conversion occured is determined. The second is the tracking part. This part consists of 2 layers of scintillating fibre tracker. Each layer has 6 scintillating fibre sheets for x, x’, u, u’, v, and v’. The third is the energy measurement part. It measures the energy of e+ and e− by scintillator array and Silicon Photomultipliers. The fourth is the veto counter for bremsstrahlung gamma rays from e+ and e-. The fifth is the beam monitor. By experiment, the number of photoelectrons of La-GPS with a WLSF (B-3(300MJ, Kuraray sheet and scintillating fibre (SCSF-78, Kuraray when charged particle passed was measured as 9.7 and 7.6 respectively.

One-spin asymmetries in pair production and Bremsstrahlung processes

International Nuclear Information System (INIS)

Arbuzov, A.B.; Kuraev, E.A.; Tarasov, A.V.; Merenkov, N.P.; Peresun'ko, D.Yu.

1995-01-01

Asymmetries in the interaction processes at high energies of circularly polarized photons or longitudinally polarized electrons with charged targets are considered. The derivations are shown in detail. The asymmetries are shown to be proportional to the degree of polarization of the initial particle, they do not decrease with increasing of the energy and could reach several percents for pure QED processes or tens percents in the case of a quark-antiquark jets production. Transverse to the beam direction components of the outgoing particle momenta are assumed to be large compared with the electron (quark) mass. 6 refs., 3 tabs

Cohering power of quantum operations

Energy Technology Data Exchange (ETDEWEB)

Bu, Kaifeng, E-mail: bkf@zju.edu.cn [School of Mathematical Sciences, Zhejiang University, Hangzhou 310027 (China); Kumar, Asutosh, E-mail: asukumar@hri.res.in [Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211019 (India); Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094 (India); Zhang, Lin, E-mail: linyz@zju.edu.cn [Institute of Mathematics, Hangzhou Dianzi University, Hangzhou 310018 (China); Wu, Junde, E-mail: wjd@zju.edu.cn [School of Mathematical Sciences, Zhejiang University, Hangzhou 310027 (China)

2017-05-18

Highlights: • Quantum coherence. • Cohering power: production of quantum coherence by quantum operations. • Study of cohering power and generalized cohering power, and their comparison for differentmeasures of quantum coherence. • Operational interpretation of cohering power. • Bound on cohering power of a generic quantum operation. - Abstract: Quantum coherence and entanglement, which play a crucial role in quantum information processing tasks, are usually fragile under decoherence. Therefore, the production of quantum coherence by quantum operations is important to preserve quantum correlations including entanglement. In this paper, we study cohering power–the ability of quantum operations to produce coherence. First, we provide an operational interpretation of cohering power. Then, we decompose a generic quantum operation into three basic operations, namely, unitary, appending and dismissal operations, and show that the cohering power of any quantum operation is upper bounded by the corresponding unitary operation. Furthermore, we compare cohering power and generalized cohering power of quantum operations for different measures of coherence.

Assessment of Snow Status Changes Using L-HH Temporal-Coherence Components at Mt. Dagu, China

Directory of Open Access Journals (Sweden)

Yong Wang

2015-09-01

Full Text Available Multitemporal Phased Array type L-band Synthetic Aperture Radar (PALSAR horizontally transmitted and horizontally received (HH coherence data was decomposed into temporal-coherence, spatial-coherence, and thermal noise components. The multitemporal data spanned between February and May of 2008, and consisted of two pairs of interferometric SAR (InSAR images formed by consecutive repeat passes. With the analysis of ancillary data, a snow increase process and a snow decrease process were determined. Then, the multiple temporal-coherence components were used to study the variation of thawing and freezing statuses of snow because the components can mostly reflect the temporal change of the snow that occurred between two data acquisitions. Compared with snow mapping results derived from optical images, the outcomes from the snow increase process and the snow decrease process reached an overall accuracy of 71.3% and 79.5%, respectively. Being capable of delineating not only the areas with or without snow cover but also status changes among no-snow, wet snow, and dry snow, we have developed a critical means to assess the water resource in alpine areas.

Vortex dynamics in coherently coupled Bose-Einstein condensates

Science.gov (United States)

Calderaro, Luca; Fetter, Alexander L.; Massignan, Pietro; Wittek, Peter

2017-02-01

In classical hydrodynamics with uniform density, vortices move with the local fluid velocity. This description is rewritten in terms of forces arising from the interaction with other vortices. Two such positive straight vortices experience a repulsive interaction and precess in a positive (anticlockwise) sense around their common centroid. A similar picture applies to vortices in a two-component, two-dimensional uniform Bose-Einstein condensate (BEC) coherently coupled through rf Rabi fields. Unlike the classical case, however, the rf Rabi coupling induces an attractive interaction and two such vortices with positive signs now rotate in the negative (clockwise) sense. Pairs of counter-rotating vortices are instead found to translate with uniform velocity perpendicular to the line joining their cores. This picture is extended to a single vortex in a two-component trapped BEC. Although two uniform vortex-free components experience familiar Rabi oscillations of particle-number difference, such behavior is absent for a vortex in one component because of the nonuniform vortex phase. Instead the coherent Rabi coupling induces a periodic vorticity transfer between the two components.

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

Magnetic Field Tuning and Quantum Interference in a Cooper Pair Splitter.

Science.gov (United States)

Fülöp, G; Domínguez, F; d'Hollosy, S; Baumgartner, A; Makk, P; Madsen, M H; Guzenko, V A; Nygård, J; Schönenberger, C; Levy Yeyati, A; Csonka, S

2015-11-27

Cooper pair splitting (CPS) is a process in which the electrons of the naturally occurring spin-singlet pairs in a superconductor are spatially separated using two quantum dots. Here, we investigate the evolution of the conductance correlations in an InAs CPS device in the presence of an external magnetic field. In our experiments the gate dependence of the signal that depends on both quantum dots continuously evolves from a slightly asymmetric Lorentzian to a strongly asymmetric Fano-type resonance with increasing field. These experiments can be understood in a simple three-site model, which shows that the nonlocal CPS leads to symmetric line shapes, while the local transport processes can exhibit an asymmetric shape due to quantum interference. These findings demonstrate that the electrons from a Cooper pair splitter can propagate coherently after their emission from the superconductor and how a magnetic field can be used to optimize the performance of a CPS device. In addition, the model calculations suggest that the estimate of the CPS efficiency in the experiments is a lower bound for the actual efficiency.

Coherent electron - hole state and femtosecond cooperative emission in bulk GaAs

International Nuclear Information System (INIS)

Vasil'ev, Petr P; Kan, H; Ohta, H; Hiruma, T

2002-01-01

The conditions for obtaining a collective coherent electron - hole state in semiconductors are discussed. The results of the experimental study of the regime of cooperative recombination of high-density electrons and holes (more than 3 x 10 18 cm -3 ) in bulk GaAs at room temperature are presented. It is shown that the collective pairing of electrons and holes and their condensation cause the formation of a short-living coherent electron - hole BCS-like state, which exhibits radiative recombination in the form of high-power femtosecond optical pulses. It is experimentally demonstrated that almost all of the electrons and holes available are condensed at the very bottoms of the bands and are at the cooperative state. The average lifetime of this state is measured to be of about 300 fs. The dependences of the order parameter (the energy gap of the spectrum of electrons and holes) and the Fermi energy of the coherent BCS state on the electron - hole concentration are obtained. (special issue devoted to the 80th anniversary of academician n g basov's birth)

Phase-Sensitive Coherence and the Classical-Quantum Boundary in Ghost Imaging

Science.gov (United States)

Erkmen, Baris I.; Hardy, Nicholas D.; Venkatraman, Dheera; Wong, Franco N. C.; Shapiro, Jeffrey H.

2011-01-01

The theory of partial coherence has a long and storied history in classical statistical optics. the vast majority of this work addresses fields that are statistically stationary in time, hence their complex envelopes only have phase-insensitive correlations. The quantum optics of squeezed-state generation, however, depends on nonlinear interactions producing baseband field operators with phase-insensitive and phase-sensitive correlations. Utilizing quantum light to enhance imaging has been a topic of considerable current interest, much of it involving biphotons, i.e., streams of entangled-photon pairs. Biphotons have been employed for quantum versions of optical coherence tomography, ghost imaging, holography, and lithography. However, their seemingly quantum features have been mimicked with classical-sate light, questioning wherein lies the classical-quantum boundary. We have shown, for the case of Gaussian-state light, that this boundary is intimately connected to the theory of phase-sensitive partial coherence. Here we present that theory, contrasting it with the familiar case of phase-insensitive partial coherence, and use it to elucidate the classical-quantum boundary of ghost imaging. We show, both theoretically and experimentally, that classical phase-sensitive light produces ghost imaging most closely mimicking those obtained in biphotons, and we derived the spatial resolution, image contrast, and signal-to-noise ratio of a standoff-sensing ghost imager, taking into account target-induced speckle.

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

The partial coherence modulation transfer function in testing lithography lens

Science.gov (United States)

Huang, Jiun-Woei

2018-03-01

Due to the lithography demanding high performance in projection of semiconductor mask to wafer, the lens has to be almost free in spherical and coma aberration, thus, in situ optical testing for diagnosis of lens performance has to be established to verify the performance and to provide the suggesting for further improvement of the lens, before the lens has been build and integrated with light source. The measurement of modulation transfer function of critical dimension (CD) is main performance parameter to evaluate the line width of semiconductor platform fabricating ability for the smallest line width of producing tiny integrated circuits. Although the modulation transfer function (MTF) has been popularly used to evaluation the optical system, but in lithography, the contrast of each line-pair is in one dimension or two dimensions, analytically, while the lens stand along in the test bench integrated with the light source coherent or near coherent for the small dimension near the optical diffraction limit, the MTF is not only contributed by the lens, also by illumination of platform. In the study, the partial coherence modulation transfer function (PCMTF) for testing a lithography lens is suggested by measuring MTF in the high spatial frequency of in situ lithography lens, blended with the illumination of partial and in coherent light source. PCMTF can be one of measurement to evaluate the imperfect lens of lithography lens for further improvement in lens performance.

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

Asymmetry in angular distributions of Drell-Yan dimuons produced by antiproton-tungsten interactions at 125 GeV/c and partial coherence

International Nuclear Information System (INIS)

Blazek, M.

1991-01-01

Recently published data on angular distributions of high mass dimuons produced in proton-tungsten interactions at 125 GeV/c are considered in the frame of the quantum statistical approach involving a mixture of coherent and stochastic production. The analysis leads to the conclusion that a portion of the lepton pairs is produced coherently. An accurate description of the data specifying the asymmetric angular distributions requires a non-vanishing cubic term in cosine of the polar angle and a term with treble the azimuthal angle. This can be achieved by an appropriate interplay of the parameters entering the approach which includes the partial coherency. (author). 1 tab., 19 refs

An efficient quantum mechanical method for radical pair recombination reactions.

Science.gov (United States)

Lewis, Alan M; Fay, Thomas P; Manolopoulos, David E

2016-12-28

The standard quantum mechanical expressions for the singlet and triplet survival probabilities and product yields of a radical pair recombination reaction involve a trace over the states in a combined electronic and nuclear spin Hilbert space. If this trace is evaluated deterministically, by performing a separate time-dependent wavepacket calculation for each initial state in the Hilbert space, the computational effort scales as O(Z 2 log⁡Z), where Z is the total number of nuclear spin states. Here we show that the trace can also be evaluated stochastically, by exploiting the properties of spin coherent states. This results in a computational effort of O(MZlog⁡Z), where M is the number of Monte Carlo samples needed for convergence. Example calculations on a strongly coupled radical pair with Z>10 6 show that the singlet yield can be converged to graphical accuracy using just M=200 samples, resulting in a speed up by a factor of >5000 over a standard deterministic calculation. We expect that this factor will greatly facilitate future quantum mechanical simulations of a wide variety of radical pairs of interest in chemistry and biology.

Influence of the electron cyclotron resonance plasma confinement on reducing the bremsstrahlung production of an electron cyclotron resonance ion source with metal-dielectric structures.

Science.gov (United States)

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.

Family Nurture Intervention in preterm infants alters frontal cortical functional connectivity assessed by EEG coherence.

Science.gov (United States)

Myers, M M; Grieve, P G; Stark, R I; Isler, J R; Hofer, M A; Yang, J; Ludwig, R J; Welch, M G

2015-07-01

To assess the impact of Family Nurture Intervention (FNI) on cortical function in preterm infants at term age. Family Nurture Intervention is a NICU-based intervention designed to establish emotional connection between mothers and preterm infants. Infants born at 26-34 weeks postmenstrual age (PMA) were divided into two groups, standard care (SC, N = 49) and FNI (FNI, N = 56). Infants had EEG recordings of ~one hour duration with 124 lead nets between 37 and 44 weeks PMA. Coherence was measured between all pairs of electrodes in ten frequency bands. Data were summarised both within and between 12 regions during two sleep states (active, quiet). Coherence levels were negatively correlated with PMA age in both groups. As compared to SC infants, FNI infants showed significantly lower levels of EEG coherence (1-18 Hz) largely within and between frontal regions. Coherence in FNI infants was decreased in regions where we previously found robust increases in EEG power. As coherence decreases with age, results suggest that FNI may accelerate brain maturation particularly in frontal brain regions, which have been shown in research by others to be involved in regulation of attention, cognition and emotion regulation; domains deficient in preterm infants. ©2015 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

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)

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

Continuous unitary transformation approach to pairing interactions in statistical physics

Directory of Open Access Journals (Sweden)

T.Domański

2008-06-01

Full Text Available We apply the flow equation method to the study of the fermion systems with pairing interactions which lead to the BCS instability signalled by the appearance of the off-diagonal order parameter. For this purpose we rederive the continuous Bogoliubov transformation in a fashion of renormalization group procedure where the low and high energy sectors are treated subsequently. We further generalize this procedure to the case of fermions interacting with the discrete boson mode. Andreev-type interactions are responsible for developing a gap in the excitation spectrum. However, the long-range coherence is destroyed due to strong quantum fluctuations.

Partial coherence with application to the monotonicity problem of coherence involving skew information

Science.gov (United States)

Luo, Shunlong; Sun, Yuan

2017-08-01

Quantifications of coherence are intensively studied in the context of completely decoherent operations (i.e., von Neuamnn measurements, or equivalently, orthonormal bases) in recent years. Here we investigate partial coherence (i.e., coherence in the context of partially decoherent operations such as Lüders measurements). A bona fide measure of partial coherence is introduced. As an application, we address the monotonicity problem of K -coherence (a quantifier for coherence in terms of Wigner-Yanase skew information) [Girolami, Phys. Rev. Lett. 113, 170401 (2014), 10.1103/PhysRevLett.113.170401], which is introduced to realize a measure of coherence as axiomatized by Baumgratz, Cramer, and Plenio [Phys. Rev. Lett. 113, 140401 (2014), 10.1103/PhysRevLett.113.140401]. Since K -coherence fails to meet the necessary requirement of monotonicity under incoherent operations, it is desirable to remedy this monotonicity problem. We show that if we modify the original measure by taking skew information with respect to the spectral decomposition of an observable, rather than the observable itself, as a measure of coherence, then the problem disappears, and the resultant coherence measure satisfies the monotonicity. Some concrete examples are discussed and related open issues are indicated.

Measuring coherence with entanglement concurrence

Science.gov (United States)

Qi, Xianfei; Gao, Ting; Yan, Fengli

2017-07-01

Quantum coherence is a fundamental manifestation of the quantum superposition principle. Recently, Baumgratz et al (2014 Phys. Rev. Lett. 113 140401) presented a rigorous framework to quantify coherence from the view of theory of physical resource. Here we propose a new valid quantum coherence measure which is a convex roof measure, for a quantum system of arbitrary dimension, essentially using the generalized Gell-Mann matrices. Rigorous proof shows that the proposed coherence measure, coherence concurrence, fulfills all the requirements dictated by the resource theory of quantum coherence measures. Moreover, strong links between the resource frameworks of coherence concurrence and entanglement concurrence is derived, which shows that any degree of coherence with respect to some reference basis can be converted to entanglement via incoherent operations. Our work provides a clear quantitative and operational connection between coherence and entanglement based on two kinds of concurrence. This new coherence measure, coherence concurrence, may also be beneficial to the study of quantum coherence.

Analytical pair correlations in ideal quantum gases: temperature-dependent bunching and antibunching.

Science.gov (United States)

Bosse, J; Pathak, K N; Singh, G S

2011-10-01

The fluctuation-dissipation theorem together with the exact density response spectrum for ideal quantum gases has been utilized to yield a new expression for the static structure factor, which we use to derive exact analytical expressions for the temperature-dependent pair distribution function g(r) of the ideal gases. The plots of bosonic and fermionic g(r) display "Bose pile" and "Fermi hole" typically akin to bunching and antibunching as observed experimentally for ultracold atomic gases. The behavior of spin-scaled pair correlation for fermions is almost featureless, but bosons show a rich structure including long-range correlations near T(c). The coherent state at T=0 shows no correlation at all, just like single-mode lasers. The depicted decreasing trend in correlation with decrease in temperature for T

Quantum coherent π-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

Science.gov (United States)

Mineo, Hirobumi; Fujimura, Yuichi

2015-06-01

We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.

Four-quark final state in W-pair production Case of signal and background

CERN Document Server

Ishikawa, T; Skrzypek, Maciej; Was, Zbigniew

1998-01-01

We discuss theoretical predictions for W-pair production and decay at LEP2 and higher energies in a form suitable for comparison with raw data. We present a practical framework for calculating uncertainties of predictions given by the KORALW and grc4f Monte Carlo programs. As an example we use observables in the $s\\bar s c\\bar c$ decay channel: the total four-quark (four-jet) cross section and two-quark/jet invariant-mass distribution and cross section, in the case when the other two may escape detection. Effects of QED bremsstrahlung, effective couplings, running W and Z widths, Coulomb interaction and the complete tree level set of diagrams are discussed. We also revisit the question of technical precision of the new version 1.21 of the KORALW Monte Carlo code as well as of version 1.2(26) of the grc4f one. Finally we find predictions of the two programs to have an overall physical uncertainty of 2%. As a side result we show, on the example of an $s\\bar s$ invariant mass distribution, the strong interplay o...

Multi-pair states in electron–positron pair creation

Directory of Open Access Journals (Sweden)

Anton Wöllert

2016-09-01

Full Text Available Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs.

Multi-pair states in electron–positron pair creation

Energy Technology Data Exchange (ETDEWEB)

Wöllert, Anton, E-mail: woellert@mpi-hd.mpg.de; Bauke, Heiko, E-mail: heiko.bauke@mpi-hd.mpg.de; Keitel, Christoph H.

2016-09-10

Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs.

Multi-pair states in electron–positron pair creation

International Nuclear Information System (INIS)

Wöllert, Anton; Bauke, Heiko; Keitel, Christoph H.

2016-01-01

Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs.

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.)

Measurements of Pair Production Under Channelling Conditions by 70-180 GeV Photons Incident on Single Crystals

CERN Multimedia

2002-01-01

This experiment will use the WA69 set-up to deliver a tagged photon beam in the energy range from 15~GeV to 150~GeV with a total angular spread of about @M~0.5~mrad. The incident photon direction is known to about 35~@mrad through the direction of the emitting electron. The photon beam is incident on an about 1~mm thick Ge single crystal in order to investigate pair production in single crystals. Above a certain energy threshold photons incident along crystal axis will show strongly increased pair production yi - the so-called .us Channelling Pair Production (ChPP). The produced pairs are analyzed in the @W-spectrometer. The large spread in incident photon angles offers an excellent opportunity to investigate in one single experiment the pair production in an angular region around a crystal axes and thereby compare ChPP with coherent (CPP) and incoherent (ICPP) processes. The very abrupt onset of ChPP (around threshold) will be measured and give a crucial test of the theoretical calculations. The differential...

The use of intermuscular coherence analysis as a novel approach to detect age-related changes on postural muscle synergy.

Science.gov (United States)

Degani, Adriana M; Leonard, Charles T; Danna-Dos-Santos, Alessander

2017-08-24

The overall goal of this study was to investigate potential adaptations brought about by the natural processes of aging on the coordination of postural muscles. Considering the progressive and non-homogeneous deterioration of sensorimotor and neuromuscular systems as the individual grows older, it was hypothesized that aging is associated with a reorganization of synergistic mechanisms controlling postural muscles. Therefore, the presence, distribution, and strength of correlated neural inputs to three posterior postural muscles were measured by intermuscular coherence estimations at a low frequency band (0-55Hz). Nine healthy young adults and thirteen healthy older adults performed ten trials of a perturbed task: bipedal stance while holding a five kg load for fifteen seconds. Estimates of intermuscular coherence for each pair of electromyographic signals (soleus and biceps femoris, soleus and erector spinae, and biceps femoris and erector spinae) were computed. Results revealed significantly stronger levels of synchronization of posterior muscles within 0-10Hz in seniors compared to young adults. In addition, seniors presented similar spectra of intermuscular coherence within 0-55Hz for all three muscle pairs analyzed. These findings provide valuable information regarding compensatory mechanisms adopted by older adults to control balance. The age-related reorganization of neural drive controlling posterior postural muscles revealing a stronger synchronization within 0-10Hz might be related to the faster body sway and muscle co-activation patterns usually observed in this population. Finally, this study supports the use of Intermuscular Coherence Analysis as a sensitive method to detect age-related changes in multi-muscle control. Copyright © 2017 Elsevier B.V. All rights reserved.

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)

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

Quantum coherence: Reciprocity and distribution

Energy Technology Data Exchange (ETDEWEB)

Kumar, Asutosh, E-mail: asukumar@hri.res.in [Harish-Chandra Research Institute, Allahabad-211019 (India); Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094 (India)

2017-03-18

Quantum coherence is the outcome of the superposition principle. Recently, it has been theorized as a quantum resource, and is the premise of quantum correlations in multipartite systems. It is therefore interesting to study the coherence content and its distribution in a multipartite quantum system. In this work, we show analytically as well as numerically the reciprocity between coherence and mixedness of a quantum state. We find that this trade-off is a general feature in the sense that it is true for large spectra of measures of coherence and of mixedness. We also study the distribution of coherence in multipartite systems by looking at monogamy-type relation–which we refer to as additivity relation–between coherences of different parts of the system. We show that for the Dicke states, while the normalized measures of coherence violate the additivity relation, the unnormalized ones satisfy the same. - Highlights: • Quantum coherence. • Reciprocity between quantum coherence and mixedness. • Distribution of quantum coherence in multipartite quantum systems. • Additivity relation for distribution of quantum coherence in Dicke and “X” states.

Improving slowness estimate stability and visualization using limited sensor pair correlation on seismic arrays

Science.gov (United States)

Gibbons, Steven J.; Näsholm, S. P.; Ruigrok, E.; Kværna, T.

2018-04-01

Seismic arrays enhance signal detection and parameter estimation by exploiting the time-delays between arriving signals on sensors at nearby locations. Parameter estimates can suffer due to both signal incoherence, with diminished waveform similarity between sensors, and aberration, with time-delays between coherent waveforms poorly represented by the wave-front model. Sensor-to-sensor correlation approaches to parameter estimation have an advantage over direct beamforming approaches in that individual sensor-pairs can be omitted without necessarily omitting entirely the data from each of the sensors involved. Specifically, we can omit correlations between sensors for which signal coherence in an optimal frequency band is anticipated to be poor or for which anomalous time-delays are anticipated. In practice, this usually means omitting correlations between more distant sensors. We present examples from International Monitoring System seismic arrays with poor parameter estimates resulting when classical f-k analysis is performed over the full array aperture. We demonstrate improved estimates and slowness grid displays using correlation beamforming restricted to correlations between sufficiently closely spaced sensors. This limited sensor-pair correlation (LSPC) approach has lower slowness resolution than would ideally be obtained by considering all sensor-pairs. However, this ideal estimate may be unattainable due to incoherence and/or aberration and the LSPC estimate can often exploit all channels, with the associated noise-suppression, while mitigating the complications arising from correlations between very distant sensors. The greatest need for the method is for short-period signals on large aperture arrays although we also demonstrate significant improvement for secondary regional phases on a small aperture array. LSPC can also provide a robust and flexible approach to parameter estimation on three-component seismic arrays.

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.

Coherent generation and dynamic manipulation of double stationary light pulses in a five-level double-tripod system of cold atoms

Energy Technology Data Exchange (ETDEWEB)

Bao Qianqian; Zhang Xiaohang; Gao Junyan; Zhang Yan; Cui Cuili; Wu Jinhui [College of Physics, Jilin University, Changchun 130012 (China)

2011-12-15

We study a five-level double-tripod system of cold atoms for efficiently manipulating the dynamic propagation and evolution of a quantum probe field by modulating four classical control fields. Our numerical results show that it is viable to transform the quantum probe field into a pair of two-color stationary light pulses mutually coupled through two wave packets of atomic spin coherence. The pair of stationary light pulses can be released either from the sample entrance and exit synchronously or just from the sample exit with a controlled time delay. In addition, the two-color stationary light pulses are immune to the fast decay originating from the higher-order Fourier components of atomic spin and optical coherence, and may exhibit the quantum limited beating signals with their characteristic frequency determined by detunings of the four classical control fields. These results could be explored to design novel photonic devices, such as optical routing, beam splitter, and beat generator, for manipulating a quantum light field.

Coherent generation and dynamic manipulation of double stationary light pulses in a five-level double-tripod system of cold atoms

International Nuclear Information System (INIS)

Bao Qianqian; Zhang Xiaohang; Gao Junyan; Zhang Yan; Cui Cuili; Wu Jinhui

2011-01-01

We study a five-level double-tripod system of cold atoms for efficiently manipulating the dynamic propagation and evolution of a quantum probe field by modulating four classical control fields. Our numerical results show that it is viable to transform the quantum probe field into a pair of two-color stationary light pulses mutually coupled through two wave packets of atomic spin coherence. The pair of stationary light pulses can be released either from the sample entrance and exit synchronously or just from the sample exit with a controlled time delay. In addition, the two-color stationary light pulses are immune to the fast decay originating from the higher-order Fourier components of atomic spin and optical coherence, and may exhibit the quantum limited beating signals with their characteristic frequency determined by detunings of the four classical control fields. These results could be explored to design novel photonic devices, such as optical routing, beam splitter, and beat generator, for manipulating a quantum light field.

Enhancement of coherent acoustic phonons in InGaN multiple quantum wells

Science.gov (United States)

Hafiz, Shopan D.; Zhang, Fan; Monavarian, Morteza; Avrutin, Vitaliy; Morkoç, Hadis; Özgür, Ümit

2015-03-01

Enhancement of coherent zone folded longitudinal acoustic phonon (ZFLAP) oscillations at terahertz frequencies was demonstrated in InGaN multiple quantum wells (MQWs) by using wavelength degenerate time resolved differential transmission spectroscopy. Screening of the piezoelectric field in InGaN MQWs by photogenerated carriers upon femtosecond pulse excitation gave rise to terahertz ZFLAPs, which were monitored at the Brillouin zone center in the transmission geometry. MQWs composed of 10 pairs InxGa1-xN wells and In0.03Ga0.97N barriers provided coherent phonon frequencies of 0.69-0.80 THz depending on the period of MQWs. Dependences of ZFLAP amplitude on excitation density and wavelength were also investigated. Possibility of achieving phonon cavity, incorporating a MQW placed between two AlN/GaN phonon mirrors designed to exhibit large acoustic gaps at the zone center, was also explored.

Colposcopic imaging using visible-light optical coherence tomography

Science.gov (United States)

Duan, Lian; McRaven, Michael D.; Liu, Wenzhong; Shu, Xiao; Hu, Jianmin; Sun, Cheng; Veazey, Ronald S.; Hope, Thomas J.; Zhang, Hao F.

2017-05-01

High-resolution colposcopic optical coherence tomography (OCT) provides key anatomical measures, such as thickness and minor traumatic injury of vaginal epithelium, of the female reproductive tract noninvasively. This information can be helpful in both fundamental investigations in animal models and disease screenings in humans. We present a fiber-based visible-light OCT and two probe designs for colposcopic application. One probe conducts circular scanning using a DC motor, and the other probe is capable of three-dimensional imaging over a 4.6×4.6-mm2 area using a pair of galvo scanners. Using this colposcopic vis-OCT with both probes, we acquired high-resolution images from whole isolated macaque vaginal samples and identified biopsy lesions.

Joint angle and Doppler frequency estimation of coherent targets in monostatic MIMO radar

Science.gov (United States)

Cao, Renzheng; Zhang, Xiaofei

2015-05-01

This paper discusses the problem of joint direction of arrival (DOA) and Doppler frequency estimation of coherent targets in a monostatic multiple-input multiple-output radar. In the proposed algorithm, we perform a reduced dimension (RD) transformation on the received signal first and then use forward spatial smoothing (FSS) technique to decorrelate the coherence and obtain joint estimation of DOA and Doppler frequency by exploiting the estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm. The joint estimated parameters of the proposed RD-FSS-ESPRIT are automatically paired. Compared with the conventional FSS-ESPRIT algorithm, our RD-FSS-ESPRIT algorithm has much lower complexity and better estimation performance of both DOA and frequency. The variance of the estimation error and the Cramer-Rao Bound of the DOA and frequency estimation are derived. Simulation results show the effectiveness and improvement of our algorithm.

Modulation of EMG-EMG Coherence in a Choice Stepping Task

Directory of Open Access Journals (Sweden)

Ippei Nojima

2018-02-01

Full Text Available The voluntary step execution task is a popular measure for identifying fall risks among elderly individuals in the community setting because most falls have been reported to occur during movement. However, the neurophysiological functions during this movement are not entirely understood. Here, we used electromyography (EMG to explore the relationship between EMG-EMG coherence, which reflects common oscillatory drive to motoneurons, and motor performance associated with stepping tasks: simple reaction time (SRT and choice reaction time (CRT tasks. Ten healthy elderly adults participated in the study. Participants took a single step forward in response to a visual imperative stimulus. EMG-EMG coherence was analyzed for 1000 ms before the presentation of the stimulus (stationary standing position from proximal and distal tibialis anterior (TA and soleus (SOL muscles. The main result showed that all paired EMG-EMG coherences in the alpha and beta frequency bands were greater in the SRT than the CRT task. This finding suggests that the common oscillatory drive to the motoneurons during the SRT task occurred prior to taking a step, whereas the lower value of corticospinal activity during the CRT task prior to taking a step may indicate an involvement of inhibitory activity, which is consistent with observations from our previous study (Watanabe et al., 2016. Furthermore, the beta band coherence in intramuscular TA tended to positively correlate with the number of performance errors that are associated with fall risks in the CRT task, suggesting that a reduction in the inhibitory activity may result in a decrease of stepping performance. These findings could advance the understanding of the neurophysiological features of postural adjustments in elderly individuals.

Coherent hybrid electromagnetic field imaging

Science.gov (United States)

Cooke, Bradly J [Jemez Springs, NM; Guenther, David C [Los Alamos, NM

2008-08-26

An apparatus and corresponding method for coherent hybrid electromagnetic field imaging of a target, where an energy source is used to generate a propagating electromagnetic beam, an electromagnetic beam splitting means to split the beam into two or more coherently matched beams of about equal amplitude, and where the spatial and temporal self-coherence between each two or more coherently matched beams is preserved. Two or more differential modulation means are employed to modulate each two or more coherently matched beams with a time-varying polarization, frequency, phase, and amplitude signal. An electromagnetic beam combining means is used to coherently combine said two or more coherently matched beams into a coherent electromagnetic beam. One or more electromagnetic beam controlling means are used for collimating, guiding, or focusing the coherent electromagnetic beam. One or more apertures are used for transmitting and receiving the coherent electromagnetic beam to and from the target. A receiver is used that is capable of square-law detection of the coherent electromagnetic beam. A waveform generator is used that is capable of generation and control of time-varying polarization, frequency, phase, or amplitude modulation waveforms and sequences. A means of synchronizing time varying waveform is used between the energy source and the receiver. Finally, a means of displaying the images created by the interaction of the coherent electromagnetic beam with target is employed.

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.

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.

fMRI orientation decoding in V1 does not require global maps or globally coherent orientation stimuli.

Science.gov (United States)

Alink, Arjen; Krugliak, Alexandra; Walther, Alexander; Kriegeskorte, Nikolaus

2013-01-01

The orientation of a large grating can be decoded from V1 functional magnetic resonance imaging (fMRI) data, even at low resolution (3-mm isotropic voxels). This finding has suggested that columnar-level neuronal information might be accessible to fMRI at 3T. However, orientation decodability might alternatively arise from global orientation-preference maps. Such global maps across V1 could result from bottom-up processing, if the preferences of V1 neurons were biased toward particular orientations (e.g., radial from fixation, or cardinal, i.e., vertical or horizontal). Global maps could also arise from local recurrent or top-down processing, reflecting pre-attentive perceptual grouping, attention spreading, or predictive coding of global form. Here we investigate whether fMRI orientation decoding with 2-mm voxels requires (a) globally coherent orientation stimuli and/or (b) global-scale patterns of V1 activity. We used opposite-orientation gratings (balanced about the cardinal orientations) and spirals (balanced about the radial orientation), along with novel patch-swapped variants of these stimuli. The two stimuli of a patch-swapped pair have opposite orientations everywhere (like their globally coherent parent stimuli). However, the two stimuli appear globally similar, a patchwork of opposite orientations. We find that all stimulus pairs are robustly decodable, demonstrating that fMRI orientation decoding does not require globally coherent orientation stimuli. Furthermore, decoding remained robust after spatial high-pass filtering for all stimuli, showing that fine-grained components of the fMRI patterns reflect visual orientations. Consistent with previous studies, we found evidence for global radial and vertical preference maps in V1. However, these were weak or absent for patch-swapped stimuli, suggesting that global preference maps depend on globally coherent orientations and might arise through recurrent or top-down processes related to the perception of

Scalable coherent interface

International Nuclear Information System (INIS)

Alnaes, K.; Kristiansen, E.H.; Gustavson, D.B.; James, D.V.

1990-01-01

The Scalable Coherent Interface (IEEE P1596) is establishing an interface standard for very high performance multiprocessors, supporting a cache-coherent-memory model scalable to systems with up to 64K nodes. This Scalable Coherent Interface (SCI) will supply a peak bandwidth per node of 1 GigaByte/second. The SCI standard should facilitate assembly of processor, memory, I/O and bus bridge cards from multiple vendors into massively parallel systems with throughput far above what is possible today. The SCI standard encompasses two levels of interface, a physical level and a logical level. The physical level specifies electrical, mechanical and thermal characteristics of connectors and cards that meet the standard. The logical level describes the address space, data transfer protocols, cache coherence mechanisms, synchronization primitives and error recovery. In this paper we address logical level issues such as packet formats, packet transmission, transaction handshake, flow control, and cache coherence. 11 refs., 10 figs

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

Coherent detectors

International Nuclear Information System (INIS)

Lawrence, C R; Church, S; Gaier, T; Lai, R; Ruf, C; Wollack, E

2009-01-01

Coherent systems offer significant advantages in simplicity, testability, control of systematics, and cost. Although quantum noise sets the fundamental limit to their performance at high frequencies, recent breakthroughs suggest that near-quantum-limited noise up to 150 or even 200 GHz could be realized within a few years. If the demands of component separation can be met with frequencies below 200 GHz, coherent systems will be strong competitors for a space CMB polarization mission. The rapid development of digital correlator capability now makes space interferometers with many hundreds of elements possible. Given the advantages of coherent interferometers in suppressing systematic effects, such systems deserve serious study.

Coherent detectors

Energy Technology Data Exchange (ETDEWEB)

Lawrence, C R [M/C 169-327, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Church, S [Room 324 Varian Physics Bldg, 382 Via Pueblo Mall, Stanford, CA 94305-4060 (United States); Gaier, T [M/C 168-314, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Lai, R [Northrop Grumman Corporation, Redondo Beach, CA 90278 (United States); Ruf, C [1533 Space Research Building, The University of Michigan, Ann Arbor, MI 48109-2143 (United States); Wollack, E, E-mail: charles.lawrence@jpl.nasa.go [NASA/GSFC, Code 665, Observational Cosmology Laboratory, Greenbelt, MD 20771 (United States)

2009-03-01

Coherent systems offer significant advantages in simplicity, testability, control of systematics, and cost. Although quantum noise sets the fundamental limit to their performance at high frequencies, recent breakthroughs suggest that near-quantum-limited noise up to 150 or even 200 GHz could be realized within a few years. If the demands of component separation can be met with frequencies below 200 GHz, coherent systems will be strong competitors for a space CMB polarization mission. The rapid development of digital correlator capability now makes space interferometers with many hundreds of elements possible. Given the advantages of coherent interferometers in suppressing systematic effects, such systems deserve serious study.

Operation of LIA-30 linear induction accelerator in the mode of generation of two bremsstrahlung pulses

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.

An Event Related Potentials Study of Semantic Coherence Effect during Episodic Encoding in Schizophrenia Patients

Directory of Open Access Journals (Sweden)

Lâle Battal Merlet

2018-01-01

Full Text Available The objective of this electrophysiological study was to investigate the processing of semantic coherence during encoding in relation to episodic memory processes promoted at test, in schizophrenia patients, by using the N400 paradigm. Eighteen schizophrenia patients and 15 healthy participants undertook a recognition memory task. The stimuli consisted of pairs of words either semantically related or unrelated to a given category name (context. During encoding, both groups exhibited an N400 external semantic coherence effect. Healthy controls also showed an N400 internal semantic coherence effect, but this effect was not present in patients. At test, related stimuli were accompanied by an FN400 old/new effect in both groups and by a parietal old/new effect in the control group alone. In the patient group, external semantic coherence effect was associated with FN400, while, in the control group, it was correlated to the parietal old/new effect. Our results indicate that schizophrenia patients can process the contextual information at encoding to enhance familiarity process for related stimuli at test. Therefore, cognitive rehabilitation therapies targeting the implementation of semantic encoding strategies can mobilize familiarity which in turn can overcome the recollection deficit, promoting successful episodic memory performance in schizophrenia patients.

Teleportation of a Coherent Superposition State Via a nonmaximally Entangled Coherent Xhannel

Institute of Scientific and Technical Information of China (English)

无

2002-01-01

@@ We investigate the problemm of teleportation of a superposition coherent state with nonmaximally entangled coherent channel. Two strategies are considered to complete the task. The first one uses entanglement concentration to purify the channel to a maximally entangled one. The second one teleports the state through the nonmaximally entangled coherent channel directly. We find that the probabilities of successful teleportations for the two strategies are depend on the amplitudes of the coherent states and the mean fidelity of teleportation using the first strategy is always less than that of the second strategy.

q-deformed charged fermion coherent states and SU(3) charged, Hyper-charged fermion coherent states

International Nuclear Information System (INIS)

Hao Sanru; Li Guanghua; Long Junyan

1994-01-01

By virtue of the algebra of the q-deformed fermion oscillators, the q-deformed charged fermion coherent states and SU(3) charged, hyper-charged fermion coherent states are discussed. The explicit forms of the two kinds of coherent states mentioned above are obtained by making use of the completeness of base vectors in the q-fermion Fock space. By comparing the q-deformed results with the ordinary results, it is found that the q-deformed charged fermion coherent states and SU(3) charged, hyper-charged fermion coherent states are automatically reduced to the ordinary charged fermion coherent states and SU(3) charged hyper-charged fermion coherent states if the deformed parameter q→1

State special standard for bremsstrahlung energy flux unit in the range of maximum photon energy 0.8-8.0 pJ (5-50 MeV)

International Nuclear Information System (INIS)

Yudin, M.F.; Skotnikov, V.V.; Bruj, V.N.; Tsvetkov, I.I.; Fominykh, V.I.

1976-01-01

The state special standard is described, which improves the accuracy and ensures unification and correctness of measurements of a bremsstrahlung energy flux. The size of the unit is conveyed, by means of working standards and model measuring means, to working devices measuring the energy flux over a wide range

Beam polarimetry in the CBELSA/TAPS experiment

International Nuclear Information System (INIS)

Kammer, Susanne

2010-01-01

In the identification of nucleon resonances polarization observables play an important role. For the photoproduction experiments of the CBELAS/TAPS assembly at the accelerator facility ELSA in the framework of this thesis linearly and circularly polarized were realized and prepared. Linearly polarized photons were produced on a diamond crystal under usage of the coherent bremsstrahlung. By alignment of the crystal in the bremsstrahlung coherent intensity increasements in form of pronounced edges could be generated. The number of the polarized photons lying in the increasement determines in comparison to the incoherently produced background the degree of polarization. The position of the coherent edge could be tuned by means of control distributions to an arbitrary position in the measured energy spectrum as well as the degree of polarization of the photons optimized. For the production of circularly polarized photons longitudinally polarized electrons on the bremsstrahlung target are required. The polarization transfer of the bremsstrahlung process is uniquely given by the QED, so that the degree of polarization of the photons can be determined via a measurement of the electron-beam polarization. With this goal a for the first time in the CBELSA/TAPS applied momentum-selecting Moeller polarimeter was developed and integrated in the photon-tagging facility. Via a change of the beam helicity the counting-rate asymmetry for parallely and antiparallely beam and target electrons was measured and the degree of polarization of the electrons at beam energies of 2350 MeV determined to typically above 60%. By means of dedicated test measurements and simulations the functionality of the Moeller polarimeter was checked and the relative systematic uncertainty determined to 1%. Since 2007 the Moeller polarimeter essential for the double-polarization experiments is in current operation. Finally a method was sketched, in which via the known cross-section asymmetry of the

Development of pair distribution function analysis

International Nuclear Information System (INIS)

Vondreele, R.; Billinge, S.; Kwei, G.; Lawson, A.

1996-01-01

This is the final report of a 3-year LDRD project at LANL. It has become more and more evident that structural coherence in the CuO 2 planes of high-T c superconducting materials over some intermediate length scale (nm range) is important to superconductivity. In recent years, the pair distribution function (PDF) analysis of powder diffraction data has been developed for extracting structural information on these length scales. This project sought to expand and develop this technique, use it to analyze neutron powder diffraction data, and apply it to problems. In particular, interest is in the area of high-T c superconductors, although we planned to extend the study to the closely related perovskite ferroelectric materials andother materials where the local structure affects the properties where detailed knowledge of the local and intermediate range structure is important. In addition, we planned to carry out single crystal experiments to look for diffuse scattering. This information augments the information from the PDF

Cooper Pair Writing at the LaAlO3/ SrTiO 3 Interface

Science.gov (United States)

Cen, Cheng; Bogorin, Daniela F.; Bark, Chung Wung; Folkman, Chad M.; Eom, Chang-Beom; Levy, Jeremy

2011-03-01

Superconducting semiconductors offer unique ways to exert electrostatic control over macroscopic quantum phases. The recently demonstrated nanoscale control over conductivity at the LaAl O3 / SrTi O3 interface raises the question of whether nanoscale control over superconducting phases can be realized. Here we report low-temperature magnetotransport experiments on structures defined with nanoscale precision at the LaAl O3 / SrTi O3 interface. A quantum phase transition is observed that is associated with the formation of Cooper pairs, but a finite resistance is observed at the lowest temperatures. Higher mobility interfaces exhibit larger Ginsburg-Landau coherence lengths, a stronger suppression of pairing by magnetic field as well as Shubnikov-de Haas oscillations. Cooper pair localization, spin-orbit coupling, and finite-size effects may factor into an explanation for some of the unusual properties observed. The work is supported by Department of Energy and State of Florida, NSF (DMR-0906443 and DMR-0704022), DOE (DE-FG02-06ER46327) and the Fine Foundation.

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

Topological Properties of Spatial Coherence Function

International Nuclear Information System (INIS)

Ji-Rong, Ren; Tao, Zhu; Yi-Shi, Duan

2008-01-01

The topological properties of the spatial coherence function are investigated rigorously. The phase singular structures (coherence vortices) of coherence function can be naturally deduced from the topological current, which is an abstract mathematical object studied previously. We find that coherence vortices are characterized by the Hopf index and Brouwer degree in topology. The coherence flux quantization and the linking of the closed coherence vortices are also studied from the topological properties of the spatial coherence function

Coherence and phase synchrony analyses of EEG signals in Mild Cognitive Impairment (MCI): A study of functional brain connectivity

Science.gov (United States)

Handayani, Nita; Haryanto, Freddy; Khotimah, Siti Nurul; Arif, Idam; Taruno, Warsito Purwo

2018-03-01

This paper presents an EEG study for coherence and phase synchrony in mild cognitive impairment (MCI) subjects. MCI is characterized by cognitive decline, which is an early stage of Alzheimer's disease (AD). AD is a neurodegenerative disorder with symptoms such as memory loss and cognitive impairment. EEG coherence is a statistical measure of correlation between signals from electrodes spatially separated on the scalp. The magnitude of phase synchrony is expressed in the phase locking value (PLV), a statistical measure of neuronal connectivity in the human brain. Brain signals were recorded using an Emotiv Epoc 14-channel wireless EEG at a sampling frequency of 128 Hz. In this study, we used 22 elderly subjects consisted of 10 MCI subjects and 12 healthy subjects as control group. The coherence between each electrode pair was measured for all frequency bands (delta, theta, alpha and beta). In the MCI subjects, the value of coherence and phase synchrony was generally lower than in the healthy subjects especially in the beta frequency. A decline of intrahemisphere coherence in the MCI subjects occurred in the left temporo-parietal-occipital region. The pattern of decline in MCI coherence is associated with decreased cholinergic connectivity along the path that connects the temporal, occipital, and parietal areas of the brain to the frontal area of the brain. EEG coherence and phase synchrony are able to distinguish persons who suffer AD in the early stages from healthy elderly subjects.

Automated seismic waveform location using Multichannel Coherency Migration (MCM)-I. Theory

Science.gov (United States)

Shi, Peidong; Angus, Doug; Rost, Sebastian; Nowacki, Andy; Yuan, Sanyi

2018-03-01

With the proliferation of dense seismic networks sampling the full seismic wavefield, recorded seismic data volumes are getting bigger and automated analysis tools to locate seismic events are essential. Here, we propose a novel Multichannel Coherency Migration (MCM) method to locate earthquakes in continuous seismic data and reveal the location and origin time of seismic events directly from recorded waveforms. By continuously calculating the coherency between waveforms from different receiver pairs, MCM greatly expands the available information which can be used for event location. MCM does not require phase picking or phase identification, which allows fully automated waveform analysis. By migrating the coherency between waveforms, MCM leads to improved source energy focusing. We have tested and compared MCM to other migration-based methods in noise-free and noisy synthetic data. The tests and analysis show that MCM is noise resistant and can achieve more accurate results compared with other migration-based methods. MCM is able to suppress strong interference from other seismic sources occurring at a similar time and location. It can be used with arbitrary 3D velocity models and is able to obtain reasonable location results with smooth but inaccurate velocity models. MCM exhibits excellent location performance and can be easily parallelized giving it large potential to be developed as a real-time location method for very large datasets.

Photoproduction of lepton pairs in proton-nucleus and nucleus-nucleus collisions at RHIC and LHC energies

Energy Technology Data Exchange (ETDEWEB)

Moreira, B. D.; Goncalves, V. P.; De Santana Amaral, J. T. [Universidade Federal de Pelotas, Instituto de Fisica e Matematica (Brazil)

2013-03-25

In this contribution we study coherent interactions as a probe of the nonlinear effects in the Quantum Electrodynamics (QED). In particular, we study the multiphoton effects in the production of leptons pairs for proton-nucleus and nucleus-nucleus collisions for heavy nuclei. In the proton-nucleus we assume the ultrarelativistic proton as a source of photons and estimate the photoproduction of lepton pairs on nuclei at RHIC and LHC energies considering the multiphoton effects associated to multiple rescattering of the projectile photon on the proton of the nucleus. In nucleus - nucleus colllisions we consider the two nuclei as a source of photons. As each scattering contributes with a factor {alpha}Z to the cross section, this contribution must be taken into account for heavy nuclei. We consider the Coulomb corrections to calculate themultiple scatterings and estimate the total cross section for muon and tau pair production in proton-nucleus and nucleus-nucleus collisions at RHIC and LHC energies.

Coherently combining data between detectors for all-sky semi-coherent continuous gravitational wave searches

International Nuclear Information System (INIS)

Goetz, E; Riles, K

2016-01-01

We present a method for coherently combining short data segments from gravitational-wave detectors to improve the sensitivity of semi-coherent searches for continuous gravitational waves. All-sky searches for continuous gravitational waves from unknown sources are computationally limited. The semi-coherent approach reduces the computational cost by dividing the entire observation timespan into short segments to be analyzed coherently, then combined together incoherently. Semi-coherent analyses that attempt to improve sensitivity by coherently combining data from multiple detectors face a computational challenge in accounting for uncertainties in signal parameters. In this article, we lay out a technique to meet this challenge using summed Fourier transform coefficients. Applying this technique to one all-sky search algorithm called TwoSpect, we confirm that the sensitivity of all-sky, semi-coherent searches can be improved by coherently combining the short data segments, e.g., by up to 42% over a single detector for an all-sky search. For misaligned detectors, however, this improvement requires careful attention when marginalizing over unknown polarization parameters. In addition, care must be taken in correcting for differential detector velocity due to the Earth’s rotation for high signal frequencies and widely separated detectors. (paper)

Possible antipolar pairing mechanism in high-temperature superconductors

International Nuclear Information System (INIS)

Cardwell, D.A.; Shorrocks, N.M.

1989-01-01

An antipolar pairing mechanism for free charge carriers in high-T c superconducting compounds is proposed qualitatively. This involves the establishment of a two-dimensional (2D) array of effective charge-coupling centers within the superconducting lattice via a specific phonon distortion of cation species along a nonmajor crystallographic direction. A fundamental requirement of this model is that the density of such coupling centers decreases with decreasing temperature. In the case of Y-Ba-Cu-O, it is asserted that charge carriers in a 2D oxygen band adjacent to the phonon-containing plane become localized by the resulting (local) field distortion. Cooper pairs may then form when the charge-coupling-center density falls below the charge-carrier density. Such a mechanism could be mediated by a longitudinal phonon which softens at low temperatures to produce an antipolar state, such as that incipient to an antiferroelectric distortion of the lattice (i.e., in the zero-frequency limiting case). This model, which may be investigated experimentally by low-temperature Raman spectroscopy, isotopic substitution, and x-ray diffractometry at 4.2 K, can be applied to all p-type high-T c systems. In addition, it may account for the observed lattice anisotropy and short coherence length characteristic of these materials

Spectral coherence in windturbine wakes

Energy Technology Data Exchange (ETDEWEB)

Hojstrup, J. [Riso National Lab., Roskilde (Denmark)

1996-12-31

This paper describes an experiment at a Danish wind farm to investigate the lateral and vertical coherences in the nonequilibrium turbulence of a wind turbine wake. Two meteorological masts were instrumented for measuring profiles of mean speed, turbulence, and temperature. Results are provided graphically for turbulence intensities, velocity spectra, lateral coherence, and vertical coherence. The turbulence was somewhat influenced by the wake, or possibly from aggregated wakes further upstream, even at 14.5 diameters. Lateral coherence (separation 5m) seemed to be unaffected by the wake at 7.5 diameters, but the flow was less coherent in the near wake. The wake appeared to have little influence on vertical coherence (separation 13m). Simple, conventional models for coherence appeared to be adequate descriptions for wake turbulence except for the near wake situation. 3 refs., 7 figs., 1 tab.

''Yields of Radionuclides Created by Photonuclear Reactions on Be, C, Na, C1, and Ge, Using Bremsstrahlung of 150-MeV Electrons''

Energy Technology Data Exchange (ETDEWEB)

Dickens, J.K.

2001-12-13

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: <{sigma}> for {sup 35}Cl({gamma}, n) {sup 34}Cl{sup isom}- = 4.7 mb; <{sigma}> for {sup 70}Ge({gamma}, n){sup 69}Ge = 56 mb; and <{sigma}> for {sup 76}Ge({gamma}, n){sup 75}Ge = 53 mb, where the ({gamma}, n) values are averages over the giant resonances of the stable target isotopes.

Comparison of Electroencephalography (EEG) Coherence between Major Depressive Disorder (MDD) without Comorbidity and MDD Comorbid with Internet Gaming Disorder.

Science.gov (United States)

Youh, Joohyung; Hong, Ji Sun; Han, Doug Hyun; Chung, Un Sun; Min, Kyoung Joon; Lee, Young Sik; Kim, Sun Mi

2017-07-01

Internet gaming disorder (IGD) has many comorbid psychiatric problems including major depressive disorder (MDD). In the present study, we compared the neurobiological differences between MDD without comorbidity (MDD-only) and MDD comorbid with IGD (MDD+IGD) by analyzing the quantitative electroencephalogram (QEEG) findings. We recruited 14 male MDD+IGD (mean age, 20.0 ± 5.9 years) and 15 male MDD-only (mean age, 20.3 ± 5.5 years) patients. The electroencephalography (EEG) coherences were measured using a 21-channel digital EEG system and computed to assess synchrony in the frequency ranges of alpha (7.5-12.5 Hz) and beta (12.5-35.0 Hz) between the following 12 electrode site pairs: inter-hemispheric (Fp1-Fp2, F7-F8, T3-T4, and P3-P4) and intra-hemispheric (F7-T3, F8-T4, C3-P3, C4-P4, T5-O1, T6-O2, P3-O1, and P4-O2) pairs. Differences in inter- and intra-hemispheric coherence values for the frequency bands between groups were analyzed using the independent t-test. Inter-hemispheric coherence value for the alpha band between Fp1-Fp2 electrodes was significantly lower in MDD+IGD than MDD-only patients. Intra-hemispheric coherence value for the alpha band between P3-O1 electrodes was higher in MDD+IGD than MDD-only patients. Intra-hemispheric coherence values for the beta band between F8-T4, T6-O2, and P4-O2 electrodes were higher in MDD+IGD than MDD-only patients. There appears to be an association between decreased inter-hemispheric connectivity in the frontal region and vulnerability to attention problems in the MDD+IGD group. Increased intra-hemisphere connectivity in the fronto-temporo-parieto-occipital areas may result from excessive online gaming. © 2017 The Korean Academy of Medical Sciences.

Comparison of Electroencephalography (EEG) Coherence between Major Depressive Disorder (MDD) without Comorbidity and MDD Comorbid with Internet Gaming Disorder

Science.gov (United States)

2017-01-01

Internet gaming disorder (IGD) has many comorbid psychiatric problems including major depressive disorder (MDD). In the present study, we compared the neurobiological differences between MDD without comorbidity (MDD-only) and MDD comorbid with IGD (MDD+IGD) by analyzing the quantitative electroencephalogram (QEEG) findings. We recruited 14 male MDD+IGD (mean age, 20.0 ± 5.9 years) and 15 male MDD-only (mean age, 20.3 ± 5.5 years) patients. The electroencephalography (EEG) coherences were measured using a 21-channel digital EEG system and computed to assess synchrony in the frequency ranges of alpha (7.5–12.5 Hz) and beta (12.5–35.0 Hz) between the following 12 electrode site pairs: inter-hemispheric (Fp1–Fp2, F7–F8, T3–T4, and P3–P4) and intra-hemispheric (F7–T3, F8–T4, C3–P3, C4–P4, T5–O1, T6–O2, P3–O1, and P4–O2) pairs. Differences in inter- and intra-hemispheric coherence values for the frequency bands between groups were analyzed using the independent t-test. Inter-hemispheric coherence value for the alpha band between Fp1–Fp2 electrodes was significantly lower in MDD+IGD than MDD-only patients. Intra-hemispheric coherence value for the alpha band between P3–O1 electrodes was higher in MDD+IGD than MDD-only patients. Intra-hemispheric coherence values for the beta band between F8–T4, T6–O2, and P4–O2 electrodes were higher in MDD+IGD than MDD-only patients. There appears to be an association between decreased inter-hemispheric connectivity in the frontal region and vulnerability to attention problems in the MDD+IGD group. Increased intra-hemisphere connectivity in the fronto-temporo-parieto-occipital areas may result from excessive online gaming. PMID:28581274

Doppler Broadening Analysis of Steel Specimens Using Accelerator Based In Situ Pair Production

International Nuclear Information System (INIS)

Makarashvili, V.; Wells, D. P.; Roy, A. K.

2009-01-01

Positron Annihilation Spectroscopy (PAS) techniques can be utilized as a sensitive probe of defects in materials. Studying these microscopic defects is very important for a number of industries in order to predict material failure or structural integrity. We have been developing gamma-induced pair-production techniques to produce positrons in thick samples (∼4-40 g/cm 2 , or ∼0.5-5 cm in steel). These techniques are called 'Accelerator-based Gamma-induced Positron Annihilation Spectroscopy'(AG-PAS). We have begun testing the capabilities of this technique for imaging of defect densities in thick structural materials. As a first step, a linear accelerator (LINAC) was employed to produce photon beams by stopping 15 MeV electrons in a 1 mm thick tungsten converter. The accelerator is capable of operating with 30-60 ns pulse width, up to 200 mA peak current at 1 kHz repetition rate. The highly collimated bremsstrahlung beam impinged upon our steel tensile specimens, after traveling through a 1.2 m thick concrete wall. Annihilation radiation was detected by a well-shielded and collimated high-purity germanium detector (HPGe). Conventional Doppler broadening spectrometry (DBS) was performed to determine S, W and T parameters for our samples.

Femtosecond spectroscopy in semiconductors: a key to coherences, correlations and quantum kinetics

International Nuclear Information System (INIS)

Axt, V M; Kuhn, T

2004-01-01

The application of femtosecond spectroscopy to the study of ultrafast dynamics in semiconductor materials and nanostructures is reviewed with particular emphasis on the physics that can be learned from it. Excitation with ultrashort optical pulses in general results in the creation of coherent superpositions and correlated many-particle states. The review comprises a discussion of the dynamics of this correlated many-body system during and after pulsed excitation as well as its analysis by means of refined measurements and advanced theories. After an introduction of basic concepts-such as coherence, correlation and quantum kinetics-a brief overview of the most important experimental techniques and theoretical approaches is given. The remainder of this paper is devoted to specific results selected in order to highlight how femtosecond spectroscopy gives access to the physics of coherences, correlations and quantum kinetics involving charge, spin and lattice degrees of freedom. First examples deal with the dynamics of basic laser-induced coherences that can be observed, e.g. in quantum beat spectroscopy, in coherent control measurements or in experiments using few-cycle pulses. The phenomena discussed here are basic in the sense that they can be understood to a large extent on the mean-field level of the theory. Nevertheless, already on this level it is found that semiconductors behave substantially differently from atomic systems. Subsequent sections report on the occurrence of coherences and correlations beyond the mean-field level that are mediated either by carrier-phonon or carrier-carrier interactions. The corresponding analysis gives deep insight into fundamental issues such as the energy-time uncertainty, pure dephasing in quantum dot structures, the role of two-pair or even higher correlations and the build-up of screening. Finally results are presented concerning the ultrafast dynamics of resonantly coupled excitations, where a combination of different

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)

Linear algebraic theory of partial coherence: discrete fields and measures of partial coherence.

Science.gov (United States)

Ozaktas, Haldun M; Yüksel, Serdar; Kutay, M Alper

2002-08-01

A linear algebraic theory of partial coherence is presented that allows precise mathematical definitions of concepts such as coherence and incoherence. This not only provides new perspectives and insights but also allows us to employ the conceptual and algebraic tools of linear algebra in applications. We define several scalar measures of the degree of partial coherence of an optical field that are zero for full incoherence and unity for full coherence. The mathematical definitions are related to our physical understanding of the corresponding concepts by considering them in the context of Young's experiment.

Optical Coherence and Quantum Optics

CERN Document Server

Mandel, Leonard

1995-01-01

This book presents a systematic account of optical coherence theory within the framework of classical optics, as applied to such topics as radiation from sources of different states of coherence, foundations of radiometry, effects of source coherence on the spectra of radiated fields, coherence theory of laser modes, and scattering of partially coherent light by random media. The book starts with a full mathematical introduction to the subject area and each chapter concludes with a set of exercises. The authors are renowned scientists and have made substantial contributions to many of the topi

On Longitudinal Spectral Coherence

DEFF Research Database (Denmark)

Kristensen, Leif

1979-01-01

It is demonstrated that the longitudinal spectral coherence differs significantly from the transversal spectral coherence in its dependence on displacement and frequency. An expression for the longitudinal coherence is derived and it is shown how the scale of turbulence, the displacement between ...... observation sites and the turbulence intensity influence the results. The limitations of the theory are discussed....

Store operations to maintain cache coherence

Energy Technology Data Exchange (ETDEWEB)

Evangelinos, Constantinos; Nair, Ravi; Ohmacht, Martin

2017-08-01

In one embodiment, a computer-implemented method includes encountering a store operation during a compile-time of a program, where the store operation is applicable to a memory line. It is determined, by a computer processor, that no cache coherence action is necessary for the store operation. A store-without-coherence-action instruction is generated for the store operation, responsive to determining that no cache coherence action is necessary. The store-without-coherence-action instruction specifies that the store operation is to be performed without a cache coherence action, and cache coherence is maintained upon execution of the store-without-coherence-action instruction.