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; Kononets, Y V; López, A; Mangiarotti, A; Sellschop, J P Friedel; Shieh, M; Sona, P; Strakhovenko, V M; Uggerhøj, U; Uggerhøj, Erik; Van Rens, B; Velasco, M; Vilakazi, Z Z; Wessely, O; Ünel, G; Kononets, Yu V
2008-01-01
The processes of coherent bremsstrahlung (CB) and coherent pair production (CPP) based on aligned crystal targets have been studied in the energy range 20-170 GeV. The experimental arrangement allowed these phenomena as well as their polarization dependence to be evaluated under conditions where single-photon cross-sections could be measured. This proved very important as the theoretical description of CB and CPP is an area of active theoretical debate and development. The theoretical approach used in this paper predicts both the cross sections and polarization observables very well for the experimental conditions investigated, indicating that the understanding of CB and CPP is reliable up to energies of 170 GeV. A birefringence effect in CPP was studied and it was demonstrated this enabled new technologies for high energy photon beam optics, such as polarimeters (for both linear and circular polarization) and phase plates. We also present new results regarding the features of coherent high energy photon emis...
Coherent bremsstrahlung at colliding beams
Energy Technology Data Exchange (ETDEWEB)
Ginzburg, I.F. (Inst. of Mathematics, Novosibirsk (Russia)); Kotkin, G.L.; Serbo, V.G. (Novosibirsk State Univ. (Russia)); Polityko, S.I. (Irkutsk State Univ. (Russia))
1992-07-30
We consider a new type of radiation at colliders with short bunches - coherent bremsstrahlung (CBS). CBS can be treated as radiation of the first bunch particles caused by the collective electromagnetic field of the short second bunch. A general method for the calculation of this CBS is presented. The number of CBS photons per single collision is dN{sub {gamma}}{approx equal}N{sub 0}dE{sub {gamma}}/E{sub {gamma}} in the energy range E{sub {gamma}}
Coherence effects in nuclear bremsstrahlung
Lohner, H
2002-01-01
The production of nuclear bremsstrahlung (Egamma > 30 MeV) has been studied in heavy-ion collisions, as well as proton and alpha-particle collisions with nuclei. In heavy-ion reactions the measured photon spectra show an exponential shape dominated by the incoherent sum of photons produced in first-
Goniometer Control System for Coherent Bremsstrahlung Production
Acousta, V. M.
2002-08-01
A system for the generation of a high-intensity, quasi-monochromatic photon beam is discussed. The theory behind coherent bremsstrahlung photon beam production is analyzed and developed. The mechanics of a goniometer control system are presented. The software developed for remote control of the goniometer is also discussed. Finally, the results from various performance measurements are included.
Coherent bremsstrahlung at the HERA collider
Energy Technology Data Exchange (ETDEWEB)
Ginzberg, I.F. (Inst. of Mathematics, Novosibirsk (Russian Federation)); Kotkin, G.L. (Novosibirsk State Univ. (Russian Federation)); Polityko, S.I. (Irkutsk State Univ. (Russian Federation)); Serbo, V.G. (Irkutsk State Univ. (Russian Federation))
1993-12-01
We consider a new type of radiation at colliders with short bunches - coherent bremsstrahlung (CBS) which is the radiation of the first bunch particles caused by the collective electromagnetic field of the second bunch. The number of CBS photons for a single collision is dN[sub y][approx]N[sub 0]dE[sub y]/E[sub y] in the energy range E[sub y]< or [approx]E[sub c]=4y[sub 1][sup 2]hc/l[sub 2]. Here y[sub 1]=E[sub 1]/m[sub 1]c[sup 2]; l[sub 2] is the length of the opposing (second) bunch and N[sub 0] is proportional to N[sub 1]N[sub 2][sup 2] where N[sub j] is the j-th bunch population. For the HERA collider N[sub 0]=14, E[sub c]=73 eV in the case when photons are emitted by protons and N[sub 0]=6.10[sup 7], E[sub c]=24 keV - when photons are emitted by electrons. Unusual properties of such a coherent bremsstrahlung and the possibility to use CBS for fast beam steering and for luminosity optimization are discussed. (orig.)
Coherent bremsstrahlung used for digital subtraction angiography
Überall, Herbert
2007-05-01
Digital subtraction angiography (DSA), also known as Dichromography, using synchrotron radiation beams has been developed at Stanford University (R. Hofstadter) and was subsequently taken over at the Brookhaven Synchrotron and later at Hamburg (HASYLAB) [see, e.g., W.R. Dix, Physik in unserer Zeit. 30 (1999) 160]. The imaging of coronary arteries is carried out with an iodine-based contrast agent which need not be injected into the heart. The radiation must be monochromatized and is applied above and below the K-edge of iodine (33.16 keV), with a subsequent digital subtraction of the two images. Monochromatization of the synchrotron radiation causes a loss of intensity of 10 -3. We propose instead the use of coherent bremsstrahlung [see, e.g., A.W. Saenz and H. Uberall, Phys. Rev. B25 (1982) 448] which is inherently monochromatic, furnishing a flux of 10 12 photon/sec. This requires a 10-20 MeV electron linac which can be obtained by many larger hospitals, eliminating the scheduling problems present at synchrotrons. The large, broad incoherent bremsstrahlung background underlying the monochromatic spike would lead to inadmissible overexposure of the patient. This problem can be solved with the use of Kumakhov's capillary optics [see e.g., S.B.Dabagov, Physics-Uspekhi 46 (2003) 1053]: the low-energy spiked radiation can be deflected towards the patient, while the higher energy incoherent background continues forward, avoiding the patient who is placed several meters from the source.
Bremsstrahlung Pair Production In Relativistic Heavy Ion Collision
Meier, H; Hencken, K.; Trautmann, D.; Baur, G.
1997-01-01
We calculate production of electron- and muon-pairs by the bremsstrahlung process in hadron collisions and compare it with the dominant two-photon process. Results for the total cross section are given for proton-proton and heavy-ion collisions at energies of the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC).
Axial coherent bremsstrahlung of type A in a diamond crystal
International Nuclear Information System (INIS)
Axial coherent bremsstrahlung of type A (ACBA) has not been intensively investigated either theoretically or experimentally. Making use of the many-beam (two-dimensional quantum treatment) formalism for transversely bound electrons moving through crystal lattices, we have computed ACBA spectra for 17 MeV electrons passing through a 10 μm thick diamond (C) crystal. We found that the momentum transfer occurs in the plane perpendicular to the axis of interest. Only momentum transfers along the scan direction (electron transverse momentum direction) result in a photon emission in the forward direction. Two different scans have shown that the energies of the coherent bremsstrahlung peaks depend strongly on the direction of the electron transverse momentum. We also present a comparison of the first order Born approximation and the many-beam formalism
Neutrino-pair bremsstrahlung in a neutron star crust
Ofengeim, D D; Yakovlev, D G
2014-01-01
Based on the formalism by Kaminker et al. (Astron. Astrophys. 343 (1999) 1009) we derive an analytic approximation for neutrino-pair bremsstrahlung emissivity due to scattering of electrons by atomic nuclei in the neutron star crust of any realistic composition. The emissivity is expressed through generalized Coulomb logarithm which we fit by introducing an effective potential of electron-nucleus scattering. In addition, we study the conditions at which the neutrino bremsstrahlung in the crust is affected by strong magnetic fields. The results can be applied for modelling of many phenomena in neutron stars, such as thermal relaxation in young isolated neutron stars and in accreting neutron stars with overheated crust in soft X-ray transients.
Angular Distribution of Photons in Coherent Bremsstrahlung in Deformed Crystals
Parazian, V V
2010-01-01
We investigate the angular distribution of photons in the coherent bremsstrahlung process by high-energy electrons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The case is considered in detail when the electron enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for SiO2 single crystal and Moliere parameterization of the screened atomic potentials in the case of the deformation field generated by the acoustic wave of S -type.
Pairing versus quarteting coherence length
Delion, Doru S
2015-01-01
We systematically analyse the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have in all considered cases a long range character inside the nucleus and decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in continuum is investigated. Strong shell effects are evidenced, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar...
EXPERIMENTAL SET UP TO MEASURE COHERENT BREMSSTRAHLUNG AND BEAM PROFILES IN RHIC.
Energy Technology Data Exchange (ETDEWEB)
TRBOJEVIC,D.; GASNER,D.; MACKAY,W.; MCINTYRE,G.; PEGGS,S.; TEPIKIAN,S.; SERBO,V.; KOTKIN,G.
2002-06-03
A proposal for an experiment to detect and measure with an array infrared detector either the infrared radiation from the beam-beam coherent bremsstrahlung or from the synchrotron light from the edge effect of large DX RHIC magnet is described. Predictions for the 100 GeV/nucleon gold and 250 GeV proton signals from both bremsstrahlung and synchtrotron radiation magnet edge effect are shown.
Monte Carlo simulation and analytical calculation of coherent Bremsstrahlung and its polarisation
Energy Technology Data Exchange (ETDEWEB)
Natter, F.A.; Grabmayr, P. E-mail: grabmayr@uni-tuebingen.de; Hehl, T.; Owens, R.O.; Wunderlich, S
2003-12-01
Spectral distributions for coherent and incoherent Bremsstrahlung produced by electrons on thin diamond radiators are calculated accurately by a Monte Carlo procedure. Realistic descriptions of the electron beam and the physical processes within the radiator have been implemented. Results are compared to measured data. A faster calculation at only a slight loss of precision is possible using analytical expressions which can be derived after simplifying assumptions.
Chiral baryon in the coherent pair approximation
Aly, T S T
1999-01-01
We revisit the work of K. Goeke, M. Harvey, F. Grümmer, and J. N. Urbano (Phys. Rev. {\\bf D37}, 754 (1988)) who considered a chiral model for the nucleon based on the linear sigma model with scalar-isoscalar scalar-isovector mesons coupled to quarks and solved using the coherent-pair approximation. In this way the quantum pion field can be treated in a non-perturbative fashion. In this work we review this model and the coherent pair approximation correcting several errors in the earlier work. We minimize the expectation value of the chiral hamiltonian in the ansatz coherent-pair ground state configuration and solve the resulting equations for nucleon quantum numbers. We calculate the canonical set of nucleon observables and compare with the Hedgehog model and experiment. Using the corrected equations yield slightly different values for nucleon observables but do not correct the large virial deviation in the $\\pi$-nucleon coupling. Our results therefore do not significantly alter the conclusions of Goeke, et ...
Planar and axial coherent bremsstrahlung of type A from a 17-MeV electron beam in a diamond crystal
International Nuclear Information System (INIS)
Making use of the many-beam (one- and two-dimensional quantum treatment) formalism for transversely bound electrons moving through crystal lattices, we have computed planar and axial coherent bremsstrahlung (type A) spectra for 17-MeV electrons passing through a 10-μm thick diamond (C) crystal. We found that in the planar case the momentum transfer occurs in the direction perpendicular to the plane and results in a photon emission in the forward direction (electron-beam direction). In the axial case, the momentum transfer occurs in the plane perpendicular to the axis of interest. Only momentum transfers along the scan direction (electron transverse momentum direction) result in a photon emission in the forward direction. Two different scans have shown that the energies of the coherent bremsstrahlung peaks depend strongly on the direction of the electron transverse momentum but the intensities of the strongest peaks do not show any considerable change
Coherent bremsstrahlung and a new possibility to monitor collisions of beams at colliders
Energy Technology Data Exchange (ETDEWEB)
Kotkin, G.L. [Novosibirskij Gosudarstvennyj Univ. (Russian Federation); Serbo, V.G. [Novosibirskij Gosudarstvennyj Univ. (Russian Federation)
1996-09-21
We consider the coherent bremsstrahlung (CBS) at colliders with short bunches. CBS is radiation of particles of one bunch in the collective electromagnetic field of the oncoming bunch. It seems that CBS can be a potential tool for fast control over collisions and for measuring beam parameters. The bunch length {sigma}{sub z} can be found from the critical energy of the CBS spectrum E{sub c}{proportional_to}1/{sigma}{sub z}; the transverse bunch size {sigma} {sub perpendicular} {sub to} is related to the photon rate dN{sub {gamma}}{proportional_to}1/{sigma} {sub perpendicular} {sub to} {sup 2}. A specific dependence of dN{sub {gamma}} on the impact parameter between the beams allows for a fast control over the beam displacement. We present the main characteristics of CBS calculated for B and {phi} factories, LHC (in the p-p and Pb-Pb modes), RHIC, VEPP-2M and VEPP-4M. (orig.).
Energy Technology Data Exchange (ETDEWEB)
Walker, R. L.
1976-03-22
Channeling of positrons in single crystals of silicon was observed in transmission and scattering measurements for incident energies from 16 to 28 MeV. In addition, the spectral dependence upon crystal orientation of the forward coherent bremsstrahlung produced by beams of 28-MeV positrons and electrons incident upon a 5 ..mu..m thick single crystal of silicon was measured with a NaI photon spectrometer. Effects of channeling and perhaps of the nonvalidity of the first Born approximation were observed for beam directions near the (111) axis of the crystal, and coherent peaks near 0.5 MeV were observed for a compound interference direction, in agreement with first-order theoretical calculations. 32 fig.
Fischer, Tobias
2016-01-01
In this article the neutrino-pair production from nucleon-nucleon (NN) bremsstrahlung is explored via medium-modifications of the strong interactions at the level of the one-pion exchange approximation. It governs the bulk part of the NN interaction at low densities relevant for the neutrino physics in core-collapse supernova studies. The resulting medium modified one-pion exchange rate for the neutrino-pair processes is implemented in simulations of core collapse supernovae in order to study the impact on the neutrino signal emitted from the deleptonization of the nascent proto-neutron star. Consequences for the nucleosynthesis of heavy elements of the material ejected from the PNS surface are discussed.
Coherent Pion Pairs from Heavy-Ion Collisions
Pratt, Scott; Haglin, Kevin
1996-01-01
The degree to which a nucleus can act as a source for coherent pion pairs is investigated for intermediate-energy heavy-ion collisions. Creation through both isovector and isoscalar channels is considered. Two experimental signals are proposed for evidence of two-pion coherent production, two-pion enhancement and the focusing of outgoing pions along the beam axis.
The LPM effect in sequential bremsstrahlung 2: factorization
Arnold, Peter; Iqbal, Shahin
2016-01-01
The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. In this paper, we continue analysis of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-gluon approximations. In particular, this paper analyzes the subtle problem of how to precisely separate overlapping double splitting (e.g.\\ overlapping double bremsstrahlung) from the case of consecutive, independent bremsstrahlung (which is the case that would be implemented in a Monte Carlo simulation based solely on single splitting rates). As an example of the method, we consider the rate of real double gluon bremsstrahlung from an initial gluon with various simplifying assumptions (thick media; $\\hat q$ approximation; large $N_c$; and neglect for the mome...
Coherent pair production in deformed crystals with a complex base
Mkrtchyan, A R; Saharian, A A
2006-01-01
We investigate the coherent electron-positron pair creation by high-energy photons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The conditions are specified under which the influence of the deformation is considerable. The case is considered in detail when the photon enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for $\\mathrm{SiO}_{2}$ single crystal and Moliere parametrization of the screened atomic potentials in the case of the deformation field generated by the acoustic wave of $S$ type. In dependence of the parameters, the presence of deformation can either enhance or reduce the pair creation cross-section. This can be used to control the parameters of the positron sources for storage rings and colliders.
Energy Technology Data Exchange (ETDEWEB)
Kotkin, G.L.; Polityko, S.I.; Serbo, V.G.
1985-09-01
For high energies of colliding e/sup +/e/sup -/, ep, and ..gamma..e beams in processes of bremsstrahlung and production of e/sup +/e/sup -/ pairs, an important role is played by impact parameters much greater than the transverse dimensions of the beams. This leads to a decrease of the number of observed events in comparison with the standard calculations. Exact formulas and a number of convenient approximate formulas are obtained for the number of events in an arbitrary reaction with allowance for the finite dimensions of the beams. Concrete calculations are given for production of e/sup +/e/sup -/ pairs.The deviations from the standard calculations for e/sup +/e/sup -/ collisions under the conditions of LEP, SLC, and VLEPP are 1, 4, and 15%, respectively, and for ..gamma..e collisions under the conditions of SLC and VLEPP they are 20 and 35%, respectively.
The LPM effect in sequential bremsstrahlung
Arnold, Peter
2015-01-01
The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. We analyze the case when the coherence lengths of two consecutive splitting processes overlap, which is important for understanding corrections to standard treatments of the LPM effect in QCD. Previous authors have analyzed this problem in the case of overlapping double bremsstrahlung where at least one of the bremsstrahlung gluons is soft. Here we show how to generalize to include the case where both splittings are hard. A number of techniques must be developed, and so in this paper we simplify by (i) restricting attention to a subset of the interference effects, which we call the "crossed" diagrams, and (ii) working in the large-$N_c$ limit. We first develop some general formulas that could in principle be implemented numerically (with substantial difficulty). To make more analytic progress...
The LPM effect in sequential bremsstrahlung: 4-gluon vertices
Arnold, Peter; Iqbal, Shahin
2016-01-01
The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. In this paper, we continue study of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-gluon approximations. In particular, this paper completes the calculation of the rate for real double gluon bremsstrahlung from an initial gluon with various simplifying assumptions (thick media; $\\hat q$ approximation; and large $N_c$) by now including processes involving 4-gluon vertices.
Pantel, R
2011-11-01
In this paper, during dopant analysis of silicon devices, we have observed a phenomenon generally neglected in EDX analysis: the coherent Bremsstrahlung (CB). We discussed the reason why and came to the conclusion that the analytical TEM used for these experiments presents a configuration and performances, which makes this equipment very sensitive to the CB effect. This is due to large collection solid angle and high counting rate of the four silicon drift EDX detectors (SDD), a high brightness electron source providing large probe current and moreover a geometry favorable to on axis crystal observations. We analyzed silicon devices containing Si [110] and Si [100] crystal areas at different energies (80-120-200keV). We also observed relaxed SiGe (27 and 40at% of Ge). The CB effect, whose intensity is maximum near zone axis beam alignment, manifests as characteristic broad peaks present in the X-ray spectrum background. The peak energies are predicted by a simple formula deduced for the CB models found in the literature and that we present simply. We evaluate also the CB peak intensities and discuss the importance of this effect on the detection and quantification traces of impurities. The CB peaks also give information on the analyzed crystal structure (measurement of the periodicity along the zone axis) and allow, in every particular experiment or system, to determine the median take off angle of the EDX detectors. PMID:21946001
International Nuclear Information System (INIS)
In this paper, during dopant analysis of silicon devices, we have observed a phenomenon generally neglected in EDX analysis: the coherent Bremsstrahlung (CB). We discussed the reason why and came to the conclusion that the analytical TEM used for these experiments presents a configuration and performances, which makes this equipment very sensitive to the CB effect. This is due to large collection solid angle and high counting rate of the four silicon drift EDX detectors (SDD), a high brightness electron source providing large probe current and moreover a geometry favorable to on axis crystal observations. We analyzed silicon devices containing Si [110] and Si [100] crystal areas at different energies (80–120–200 keV). We also observed relaxed SiGe (27 and 40 at% of Ge). The CB effect, whose intensity is maximum near zone axis beam alignment, manifests as characteristic broad peaks present in the X-ray spectrum background. The peak energies are predicted by a simple formula deduced for the CB models found in the literature and that we present simply. We evaluate also the CB peak intensities and discuss the importance of this effect on the detection and quantification traces of impurities. The CB peaks also give information on the analyzed crystal structure (measurement of the periodicity along the zone axis) and allow, in every particular experiment or system, to determine the median take off angle of the EDX detectors. -- Highlights: ► STEM EDX dopant distribution analysis (As and P) in Si devices is carried out. ► High brightness electron source and four EDX Silicon Drift detectors are used. ► The obtained signal dynamics (four decades) allows detection down to 0.01 at%. ► During silicon axis analysis coherent Bremmsstrahlung is observed. ► This effect is studied at different energies and Si crystal orientations.
Nuclear spin pair coherence in diamond for atomic scale magnetometry
Zhao, Nan; Hu, Jian-Liang; Ho, Sai-Wah; Wen, Tsz-Kai; Liu, R. B.
2010-01-01
The nitrogen-vacancy (NV) centre, as a promising candidate solid state system of quantum information processing, its electron spin coherence is influenced by the magnetic field fluctuations due to the local environment. In pure diamonds, the environment consists of hundreds of C-13 nuclear spins randomly spreading in several nanometers range forming a spin bath. Controlling and prolonging the electron spin coherence under the influence of spin bath are challenging tasks for the quantum inform...
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...
Generation of Pair Coherent States in Two-dimensional Trapped Ion
Institute of Scientific and Technical Information of China (English)
WANG Kai-Ge; S Maniscalco; A Napoli2, A Messina
2001-01-01
We consider a two-dimensional (2D) trapped ion model in which two laser beams drive the corresponding vibrational motions and are carrier resonant with the two-level of the ion. Due to the coherent superposition of two sub-Rabi oscillations involved in the bimodal vibrations, the Rabi frequency degeneration and offset may occur in this model. This provides the possibility of generating the pair coherent state in the 2D trapped ion.
Institute of Scientific and Technical Information of China (English)
S. Salimi; A. Mohammadzadet
2011-01-01
Pair coherent state, is a state of a two-mode radiation field that is known as a state with non-gaussian wave function. In this paper, study on the pair coherent state, we notice that with superposition of two first terms of this states, one two-qubits formed. Because of the importance of two-qubits in theory of quantum entanglement, with two different measures with the title of concurrence and D-concurrence, we have studied the amount of entanglement and discussed its details. At the end, we describe these measures for pair coherent states as a function of the amplitude of the SU（2） coherent states.
THREE-DIMENSIONAL PAIRING OF COHERENT STRUCTURES IN A PLANE MIXING LAYER
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The three-dimensional (3D) pairing process of coherent structures in a plane mixing layer was simulated numerically with the pseudo-spectral method. The behaviors of spanwise cup-shaped vortices, streamwise rib-shaped vortices and quadrupoles were obtained in terms of their iso-surfaces. The results show that three-dimensional structures are strongly influenced by the initial ampiitude of the 3D disturbance, and that in most cases the local pairing finishes in a roughly two-dimensional manner. In pairing region, the streamwise vortices are chaotic after pairing due to the breakdown of the engulfed ribs and especially the subsequent breakdown of the quadrupoles. The surviving ribs extend to the top (or bottom) of the paired vortices under the stretch of them. In addition, it is revealed that three dimensional vortices pairing can enhance the mixing of fluid. Finally, some patterns of numerical flow visualization are presented by computing the passive scalar.
The Radical Pair Mechanism and the Avian Chemical Compass: Quantum Coherence and Entanglement
Zhang, Yiteng; Kais, Sabre
2015-01-01
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 o...
The LPM effect in sequential bremsstrahlung: dimensional regularization
Arnold, Peter; Iqbal, Shahin
2016-01-01
The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. Of recent interest is the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD). In previous papers, we have developed methods for computing such corrections without making soft-gluon approximations. However, our methods require consistent treatment of canceling ultraviolet (UV) divergences associated with coincident emission times, even for processes with tree-level amplitudes. In this paper, we show how to use dimensional regularization to properly handle the UV contributions. We also present a simple diagnostic test that any consistent UV regularization method for this problem needs to pass.
Coherent combs of anti-matter from nonlinear electron-positron pair creation
Krajewska, K
2014-01-01
Electron-positron pair creation in collisions of a modulated laser pulse with a high-energy photon (nonlinear Breit-Wheeler process) is studied by means of strong-field quantum electrodynamics. It is shown that the driving pulse modulations lead to appearance of comb structures in the energy spectra of produced positrons (electrons). It is demonstrated that these combs result from a coherent enhancement of probability amplitudes of pair creation from different modulations of the laser pulse. Thus, resembling the Young-double slit experiment for anti-matter (matter) waves.
Coherent chemical kinetics as quantum walks. I. Reaction operators for radical pairs
Chia, A.; Tan, K. C.; Pawela, Ł.; Kurzyński, P.; Paterek, T.; Kaszlikowski, D.
2016-03-01
Classical chemical kinetics uses rate-equation models to describe how a reaction proceeds in time. Such models are sufficient for describing state transitions in a reaction where coherences between different states do not arise, in other words, a reaction that contains only incoherent transitions. A prominent example of a reaction containing coherent transitions is the radical-pair model. The kinetics of such reactions is defined by the so-called reaction operator that determines the radical-pair state as a function of intermediate transition rates. We argue that the well-known concept of quantum walks from quantum information theory is a natural and apt framework for describing multisite chemical reactions. By composing Kraus maps that act only on two sites at a time, we show how the quantum-walk formalism can be applied to derive a reaction operator for the standard avian radical-pair reaction. Our reaction operator predicts the same recombination dephasing rate as the conventional Haberkorn model, which is consistent with recent experiments [K. Maeda et al., J. Chem. Phys. 139, 234309 (2013), 10.1063/1.4844355], in contrast to previous work by Jones and Hore [J. A. Jones and P. J. Hore, Chem. Phys. Lett. 488, 90 (2010), 10.1016/j.cplett.2010.01.063]. The standard radical-pair reaction has conventionally been described by either a normalized density operator incorporating both the radical pair and reaction products or a trace-decreasing density operator that considers only the radical pair. We demonstrate a density operator that is both normalized and refers only to radical-pair states. Generalizations to include additional dephasing processes and an arbitrary number of sites are also discussed.
Quantitative study of coherent pairing modes with two neutron transfer: Sn-isotopes
Potel, G; Barranco, F; Vigezzi, E; Broglia, R A
2012-01-01
Pairing rotations and pairing vibrations are collective modes associated with a field, the pair field, which changes the number of particles by two. Consequently, they can be studied at profit with the help of two-particle transfer reactions on superfluid and in normal nuclei, respectively. The advent of exotic beams has opened, for the first time, the possibility to carry out such studies in medium heavy nuclei, within the same isotopic chain. In the case studied in the present paper that of the Sn-isotopes (essentially from closed (Z=N=50) to closed (Z=50,N=82) shells). The static and dynamic off-diagonal, long range order phase coherence in gauge space displayed by pairing rotations and vibrations respectively, leads to coherent states which behave almost classically. Consequently, these modes are amenable to an accurate nuclear structure description in terms of simple models containing the right physics, in particular BCS plus QRPA and HF mean field plus RPA respectively. The associated two- nucleon trans...
Measurement device-independent quantum key distribution with heralded pair coherent state
Chen, Dong; Shang-Hong, Zhao; Lei, Shi
2016-10-01
The original measurement device-independent quantum key distribution is reviewed, and a modified protocol using heralded pair coherent state (HPCS) is proposed to overcome the quantum bit error rate associated with the dark count rate of the detectors in long-distance quantum key distribution. Our simulation indicates that the secure transmission distance can be improved evidently with HPCS owing to the lower probability of vacuum events when compared with weak coherent source scenario, while the secure key rate can be increased with HPCS due to the higher probability of single-photon events when compared with heralded single-photon source scenario. Furthermore, we apply the finite key analysis to the decoy state MDI-QKD with HPCS and obtain a practical key rate.
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.
Angular distribution of positrons in coherent pair production in deformed crystals
Parazian, V V
2008-01-01
We investigate the angular distribution of positrons in the coherent process electron-positron pair creation process by high-energy photons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The case is considered in detail when the photon enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for ${\\mathrm{SiO}}_{2}$ single crystal and Moliere parameterization of the screened atomic potentials in the case of the deformation field generated by the acoustic wave of S -type.
Angular distribution of positrons in coherent pair production in deformed crystals.
Parazian, V V
2009-05-01
We investigate the angular distribution of positrons in the coherent process electron-positron pair creation process by high-energy photons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross section is derived for an arbitrary deformation field. The case is considered in detail when the photon enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for SiO(2) and diamond single crystals and Moliere parameterization of the screened atomic potentials in the case of the deformation field generated by an acoustic wave of S-type.
Bremsstrahlung in $\\alpha$ Decay
Takigawa, N; Hagino, K; Ono, A; Brink, D M
1999-01-01
A quantum mechanical analysis of the bremsstrahlung in $\\alpha$ decay of $^{210}$Po is performed in close reference to a semiclassical theory. We clarify the contribution from the tunneling, mixed, outside barrier regions and from the wall of the inner potential well to the final spectral distribution, and discuss their interplay. We also comment on the validity of semiclassical calculations, and the possibility to eliminate the ambiguity in the nuclear potential between the alpha particle and daughter nucleus using the bremsstrahlung spectrum.
Runaway electrons and Bremsstrahlung
Helander, Per
2016-09-01
If an electric field is applied to a plasma, it causes ‘runaway’ acceleration of some electrons—a phenomenon that has been known for almost a century. A paper by Embréus et al (2016 New J. Phys. 18 093023) calculates how the emission of Bremsstrahlung affects the upper end of the energy spectrum of these electrons, and finds that it is important to carefully account for finite energy of the emitted photons.
Simulation of Bremsstrahlung production
Energy Technology Data Exchange (ETDEWEB)
Patau, J.P.; Malbert, M.; Terrissol, M. (Centre de Physique Atomique, Toulouse (France))
1981-10-01
Electron slowing down and related phenomena are often greatly affected by bremsstrahlung production. Each creation of photon is individually simulated on the basis of a cross-section pack advised by Koch and Motz with corrections in the high energy frequency limit region. An accurate and fast sampling method is described. Its applicability covers a range between 50 keV and 80 MeV for target atoms whose atomic number is from 5 up to 90.
Sarunic, Marinko V.; Han, Shuo; Wu, Jigang; Yaqoob, Zahid; Humayun, Mark; Yang, Changhuei
2007-02-01
Vitrectomy (removal of the vitreous humor) is an ophthalmic surgery required as a precursor to several posterior chamber procedures. Vitrectomy is commonly performed using an endoscopic vitreous cutter and fiber based light delivery for observation through a surgical microscope. Cross-sectional visualization of the retina and remnant vitreous layers during surgery using an external optical coherence tomography (OCT) scanner is impractical due to deformation in the shape of the eye and the cornea. We present a forward imaging probe with 820 μm outer diameter (21 gauge needle) for cross-sectional endoscopic OCT imaging during ophthalmic surgeries. The Paired-Angle-Rotating Scanner (PARS) OCT probe is based on angle polished gradient index (GRIN) lenses which are rotated about the optical axis. The scan pattern is determined by the angle between the GRIN lenses and the relative angular velocity. Endoscopic placement of the PARS-OCT probe tip near the retinal surface permits use of a longer wavelength light, in particular 1310 nm, which would otherwise suffer significant attenuation traversing the vitreous humor. The prototype endoscopic PARS-OCT probe is coupled to a commercially available 1310 nm swept laser source, and uses commercial software for data acquisition, processing, and display of retinal images in real time at an A-scan rate of 16 kHz. We present an analysis of aberrations due to off axis use of GRIN lenses and measure the scan pattern of the PARS probe. Images acquired on an ex vivo porcine retina are presented, motivating development of the endoscopic PARS-OCT probe for clinical evaluation.
Polarization bremsstrahlung in α decay
International Nuclear Information System (INIS)
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
Coherent Control of Resonant Two-Photon Transitions by Counter-Propagating Ultrashort Pulse Pairs
Lee, Woojun; Kim, Kyungtae; Ahn, Jaewook
2015-01-01
We describe optimized coherent control methods for two-photon transitions in atoms of a ladder-type three-state energy configuration. Our approach is based on the spatial coherent control scheme which utilizes counter-propagating ultrashort laser pulses to produce complex excitation patterns in an extended space. Since coherent control requires constructive interference of constituent transition pathways, applying it to an atomic transition with a specific energy configuration requires specially designed laser pulses. Here, we show, in an experimental demonstration, that the two-photon transition with an intermediate resonant energy state can be coherently controlled and retrieved out from the resonance-induced background, when phase-flipping of the laser spectrum near the resonant intermediate transition is used. A simple reason for this behavior is the fact that the transition amplitude function (to be added to give an overall two-photon transition) changes its sign at the intermediate resonant frequency, t...
Vector dark matter annihilation with internal bremsstrahlung
Bambhaniya, Gulab; Kumar, Jason; Marfatia, Danny; Nayak, Alekha C.; Tomar, Gaurav
2016-01-01
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 st...
Bremsstrahlung signatures of dark matter annihilation in the Sun
Fukushima, Keita; Kumar, Jason; Marfatia, Danny
2012-01-01
The nonrelativistic annihilation of Majorana dark matter in the Sun to a pair of light fermions is chirality-suppressed. Annihilation to 3-body final states $\\ell^+f^-V$, where $V=W,Z,\\gamma$, and $\\ell$ and $f$ are light fermions (that may be the same), becomes dominant since bremsstrahlung relaxes the chirality suppression. We evaluate the neutrino spectra at the source, including spin and helicity dependent effects, and assess the detectability of each significant bremsstrahlung channel at IceCube/DeepCore. We also show how to combine the sensitivities to the dark matter-nucleon scattering cross section in individual channels, since typically several channels contribute in models.
Revisiting Bremsstrahlung emission associated with Light Dark Matter annihilations
Boehm, C; Uwer, P.
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 factoriza...
Coherence features of the spin-aligned neutron-proton pair coupling scheme
Qi, C; 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 contribution 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 mainly be built upon such spin-aligned $np$ pairs each carrying the maximum angular momentum $J = 9$ allowed by the shell $0g_{9/2}$ which is dominant in this nuclear region.
International Nuclear Information System (INIS)
A full quantum microscopic theory is developed to analyze a biexciton radiative cascade coupled to bulk acoustic phonons in a quantum dot. By considering the phonon sub-system in coherent state representation a new approach is proposed for investigating the phonon effects. Via this approach it is possible to obtain an exact analytical result for the phonon kernel in this system. This approach is introduced in the context of an example: the process of generating polarization-entangled photon pairs from the biexciton cascade in a quantum dot. We calculate the exact density matrix (using quantum state tomography) of photons and their concurrence. We show that the exchange interaction and temperature have remarkable effects on the degree of entanglement of the emitted photons. The approach introduced provides an exact analytical result for finite discrete electron states interacting with phonons. (paper)
Vector dark matter annihilation with internal bremsstrahlung
Bambhaniya, Gulab; Marfatia, Danny; Nayak, Alekha C; Tomar, Gaurav
2016-01-01
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.
Neutrino signals from electroweak bremsstrahlung in solar WIMP annihilation
Energy Technology Data Exchange (ETDEWEB)
Bell, Nicole F.; Brennan, Amelia J.; Jacques, Thomas D., E-mail: n.bell@unimelb.edu.au, E-mail: a.brennan@pgrad.unimelb.edu.au, E-mail: thomas.jacques@asu.edu [ARC Centre of Excellence for Particle Physics at the Terascale, School of Physics, The University of Melbourne, Victoria 3010 (Australia)
2012-10-01
Bremsstrahlung of W and Z gauge bosons, or photons, can be an important dark matter annihilation channel. In many popular models in which the annihilation to a pair of light fermions is helicity suppressed, these bremsstrahlung processes can lift the suppression and thus become the dominant annihilation channels. The resulting dark matter annihilation products contain a large, energetic, neutrino component. We consider solar WIMP annihilation in the case where electroweak bremsstrahlung dominates, and calculate the resulting neutrino spectra. The flux consists of primary neutrinos produced in processes such as χχ→ν-bar νZ and χχ→ν-bar lW, and secondary neutrinos produced via the decays of gauge bosons and charged leptons. After dealing with the neutrino propagation and flavour evolution in the Sun, we consider the prospects for detection in neutrino experiments on Earth. We compare our signal with that for annihilation to W{sup +}W{sup −}, and show that, for a given annihilation rate, the bremsstrahlung annihilation channel produces a larger signal by a factor of a few.
Ultrahigh-intensity inverse bremsstrahlung
Kostyukov, I. Yu.; Rax, J.-M.
1999-01-01
We study inverse bremsstrahlung in the ultrahigh intensity relativistic regime. The fully relativistic ultrahigh intensity absorption (emission) coefficient is derived for an arbitrary scattering potential and small-angle scattering. We find that in the Coulomb field case this absorption (emission) coefficient can be calculated as a function of the quiver energy, drift momentum, and impact parameter in two complementary regimes: (i) for remote collisions when the impact parameter is larger than the amplitude of the quiver motion, and (ii) for instantaneous collisions when the scattering time is shorter than the period of the wave. Both circular and linear polarizations are considered, and this study reveals that in this relativistic regime inverse bremsstrahlung absorption can be viewed as a harmonic Compton resonance heating of the laser-driven electron by the virtual photon of the ion Coulomb field. The relativistic modification of Marcuse's effect [Bell Syst. Tech. J. 41, 1557 (1962)] are also discussed, and relations with previous nonrelativistic results are elucidated.
International Nuclear Information System (INIS)
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))
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.
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.
Diffractive Bremsstrahlung in Hadronic Collisions
Directory of Open Access Journals (Sweden)
Roman Pasechnik
2015-01-01
Full Text Available Production of heavy photons (Drell-Yan, gauge bosons, Higgs bosons, and heavy flavors, which is treated within the QCD parton model as a result of hard parton-parton collision, can be considered a bremsstrahlung process in the target rest frame. In this review, we discuss the basic features of the diffractive channels of these processes in the framework of color dipole approach. The main observation is a dramatic breakdown of diffractive QCD factorisation due to the interplay between soft and hard interactions, which dominates these processes. This observation is crucial for phenomenological studies of diffractive reactions in high energy hadronic collisions.
Diffractive bremsstrahlung in hadronic collisions
Pasechnik, Roman; Potashnikova, Irina
2015-01-01
Production of heavy photons (Drell-Yan), gauge bosons, Higgs bosons, heavy flavors, which is treated within the QCD parton model as a result of hard parton-parton collision, can be considered as a bremsstrahlung process in the target rest frame. In this review, we discuss the basic features of the diffractive channels of these processes in the framework of color dipole approach. The main observation is a dramatic breakdown of diffractive QCD factorisation due to the interplay between soft and hard interactions, which dominates these processes. This observation is crucial for phenomenological studies of diffractive reactions in high-energy hadronic collisions.
Polarizational bremsstrahlung in non-relativistic collision
Korol, A V
2004-01-01
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.
Yim, Sin Hyuk; Cho, D
2010-02-01
We produced a pair of coherent laser beams with a 3-GHz frequency difference by optically phase locking two modes from a single, multimode extended-cavity diode laser. This method is complementary to either a direct modulation or an optical phase locking of two independent lasers. A large differential frequency shift between the two modes of the laser allows efficient phase locking. We developed a simple theory to account for the large differential frequency shift. Allan deviation of the beat frequency when the two modes are phase-locked drops as an inverse of the measurement time and it reaches 10(-14) when the time is 1 h. Coherent population trapping spectroscopy of Rb atoms using the phase-locked beams resulted in a spectrum as narrow as that of the case using direct modulation by a stable frequency synthesizer.
Bremsstrahlung from Electrons and Positrons in Peripheral Relativistic Heavy Ion Collisions
Hencken, Kai; Trautmann, Dirk; Baur, Gerhard
1999-01-01
We study the spectrum of the bremsstrahlung photons coming from the electrons and positrons, which are produced in the strong electromagnetic fields present in peripheral relativistic heavy ion collisions. We compare different approaches, making use of the exact pair production cross section in heavy ion collisions as well as the double equivalent photon approximation.
Relativistic Non-Thermal Bremsstrahlung Radiation
Zeković, Vladimir; Dobardzić, Aleksandra; Pavlović, Marko
2013-01-01
By applying a method of virtual quanta we derive formulae for relativistic non-thermal bremsstrahlung radiation from relativistic electrons as well as from protons and heavier particles with power-law momentum distribution $N(p)dp = k p^{-q} dp.$ We show that emission which originates from an electron scattering on an ion, represents the most significant component of relativistic non-thermal bremsstrahlung. Radiation from an ion scattering on electron, known as inverse bremsstrahlung, is shown to be negligible in overall non-thermal bremsstrahlung emission. These results arise from theory refinement, where we introduce the dependence of relativistic kinetic energy of an incident particle, upon the energy of scattered photon. In part, it is also a consequence of a different mass of particles and relativistic effects.
Impact of Nucleon-Nucleon Bremsstrahlung Rates Beyond One-Pion Exchange
Bartl, Alexander; Janka, Hans-Thomas; Schwenk, Achim
2016-01-01
Neutrino-pair production and annihilation through nucleon-nucleon bremsstrahlung is included in current supernova simulations by rates that are based on the one-pion-exchange approximation. Here we explore the consequences of bremsstrahlung rates based on a modern nuclear interactions for proto-neutron star cooling and the corresponding neutrino emission. We find that despite a reduction of the bremsstrahlung emission by a factor of 2-5 in the neutrinospheric region, models with the improved treatment exhibit only $\\lesssim$5% changes of the neutrino luminosities and an increase of $\\lesssim$0.7 MeV of the average energies of the radiated neutrino spectra, with the largest effects for the antineutrinos of all flavors and at late times. Overall, the proto-neutron star cooling evolution is slowed down modestly by $\\lesssim$0.5-1 s.
Spectra and rates of bremsstrahlung neutrino emission in stars
Guo, Gang; Qian, Yong-Zhong
2016-08-01
We calculate the energy-differential rate for neutrino emission from electron-nucleus bremsstrahlung in stellar interiors taking into account the effects of electron screening and ionic correlations. We compare the energy-differential and the net rates, as well as the average ν¯e and ν¯x(x =μ ,τ ) energies, for this process with those for e± pair annihilation, plasmon decay, and photoneutrino emission over a wide range of temperature and density. We also compare our updated energy loss rates for the above thermal neutrino emission processes with the fitting formulas widely used in stellar evolution models and determine the temperature and density domain in which each process dominates. We discuss the implications of our results for detection of ν¯e from massive stars during their presupernova evolution and find that pair annihilation makes the predominant contribution to the signal from the thermal emission processes.
Polarization of thermal bremsstrahlung emission due to electron pressure anisotropy
Komarov, S; Churazov, E; Schekochihin, A
2016-01-01
Astrophysical plasmas are typically magnetized, with the Larmor radii of the charged particles many orders of magnitude smaller than their collisional mean free paths. The fundamental properties of such plasmas, e.g., conduction and viscosity, may depend on the instabilities driven by the anisotropy of the particle distribution functions and operating at scales comparable to the Larmor scales. We discuss a possibility that the pressure anisotropy of thermal electrons could produce polarization of thermal bremsstrahlung emission. In particular, we consider coherent large-scale motions in galaxy clusters to estimate the level of anisotropy driven by stretching of the magnetic-field lines by plasma flow and by heat fluxes associated with thermal gradients. Our estimate of the degree of polarization is $\\sim 0.1 \\%$ at energies $\\gtrsim kT$. While this value is too low for the forthcoming generation of X-ray polarimeters, it is potentially an important proxy for the processes taking place at extremely small scale...
Anomalous fluorescence line intensity in megavoltage bremsstrahlung
Pereira, Nino; Litz, Marc; Merkel, George; Schumer, Joseph; Seely, John; Carroll, Jeff
2009-11-01
A Cauchois transmission crystal spectrometer intended for laser plasma diagnostics has measured an anomalous ratio between the fluorescence lines in megavoltage bremsstrahlung. When observed in reflection, Kα1 fluorescence is twice as strong as the Kβ line, as is usual. However, in forward-directed bremsstrahlung from a 2 MV end point linear accelerator with a tungsten converter, the Kα1 and Kβ fluorescence are approximately equal. The anomalous fluorescence line ratio, unity, reflects the large amount of fluorescence generated on the side of the converter where the electrons enter, and the differential attenuation of the fluorescence photons as they pass through the converter to opposite side. Understanding of fluorescence in megavoltage bremsstrahlung is relevant to the explanation of anomalous line ratios in spectra produced by high-energy electrons generated by intense femtosecond laser irradiation.
Radiative Corrections to High Energy Lepton Bremsstrahlung on Heavy Nuclei
Arbuzov, A B
2008-01-01
One-loop radiative corrections to the leptonic tensor in high energy bremsstrahlung on heavy nuclei are calculated. Virtual and real photon radiation is taken into account. Double bremsstrahlung is simulated by means of Monte Carlo. Numerical results are presented for the case of muon bremsstrahlung in conditions of the COMPASS experiment at CERN.
Bremsstrahlung from relativistic heavy ions in matter
DEFF Research Database (Denmark)
Sørensen, Allan Hvidkjær
2010-01-01
MeV for a lead ion (γ≡E/Mc2 is the Lorentz factor of the projectile of energy E and mass M). The maximum exceeds the bremsstrahlung from a hypothetical structureless, pointlike particle of the same charge and mass as the incoming nucleus, but rapid depletion follows on the high-energy side of the peak...
Modeling the bremsstrahlung emission from converters
Mirea, M; Clapier, F; Hassaïne, M; Ibrahim, F; Müller, A C; Pauwels, N; Proust, J; Verney, D; Antoni, R; Bourgeois, L; Kandri-Rody, S
2001-01-01
The bremsstrahlung angular and energy theoretical distributions delivered from W and UCx thick converters are reported. This study is focussed on initial kinetic energies of the electron beam included in the range 30-60 MeV, suitable for the production of large radiative yields able to induce the $^{238}$U fission. These results offer the possibility to evaluate the required shielding for a neutron rich nuclei source.
Bremsstrahlung Radiation At a Vacuum Bubble Wall
Lee, Jae-Weon; Lee, Chul H; Jang, Ji-ho
2007-01-01
When charged particles collide with a vacuum bubble, they can radiate strong electromagnetic waves due to rapid deceleration. Owing to the energy loss of the particles by this bremsstrahlung radiation, there is a non-negligible damping pressure acting on the bubble wall even when thermal equilibrium is maintained. In the non-relativistic region, this pressure is proportional to the velocity of the wall and could have influenced the bubble dynamics in the early universe.
Radiative corrections to pion-nucleus bremsstrahlung
Kaiser, N.(Physik Department T39, Technische Universität München, Garching, D-85747, Germany); Friedrich, J. M.
2008-01-01
We calculate the one-photon loop radiative corrections to virtual pion Compton scattering $\\pi^- \\gamma^* \\to \\pi^- \\gamma$, that subprocess which determines in the one-photon exchange approximation the pion-nucleus bremsstrahlung reaction $\\pi^- Z\\to \\pi^- Z \\gamma$. Ultraviolet and infrared divergencies of the loop integrals are both treated by dimensional regularization. Analytical expressions for the ${\\cal O}(\\alpha)$ corrections to the virtual Compton scattering amplitudes, $A(s,u,Q)$ a...
Cottet, Audrey; Kontos, Takis; Yeyati, Alfredo Levy
2011-01-01
We suggest a way to characterize the coherence of the split Cooper pairs emitted by a double-quantum-dot based Cooper pair splitter (CPS), by studying the radiative response of such a CPS inside a microwave cavity. The coherence of the split pairs manifests in a strongly nonmonotonic variation of the emitted radiation as a function of the parameters controlling the coupling of the CPS to the cavity. The idea to probe the coherence of the electronic states using the tools of Cavity Quantum Ele...
Thermal Bremsstrahlung Radiation in a Two-Temperature Plasma
Luo, Bin; Zhang, S. Nan
2002-01-01
In the normal one-temperature plasma the motion of ions is usually neglected when calculating the Bremsstrahlung radiation of the plasma. Here we calculate the Bremsstrahlung radiation of a two-temperature plasma by taking into account of the motion of ions. Our results show that the total radiation power is always lower if the motion of ions is considered. We also apply the two-temperature Bremsstrahlung radiation mechanism for an analytical Advection-Dominated Accretion Flow (ADAF) model; w...
Bremsstrahlung-induced highly penetrating probes for nondestructive assay and defect analysis
Selim, F. A.; Wells, D. P.; Harmon, J. F.; Kwofie, J.; Spaulding, R.; Erickson, G.; Roney, T.
2002-12-01
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 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 thick. Bremsstrahlung beams above neutron emission threshold, from a 20 MeV pulsed electron linac, have also been used to produce residual nuclei in excited states via photonuclear reactions allowing the detection of heavy elements via their characteristic γ-rays. This can be developed into a technique to trace some heavy metals in large rocks and soils for environmental applications.
Thermal Bremsstrahlung Radiation in a Two-Temperature Plasma
Institute of Scientific and Technical Information of China (English)
Bin Luo; Shuang-Nan Zhang
2004-01-01
In normal one-temperature plasma the motion of ions is usually neglected when calculating the Bremsstrahlung radiation of the plasma.We calculate the Bremsstrahlung radiation of a two-temperature plasma by taking into account of the motion of ions.Our results show that the total radiation power is always lower if the motion of ions is considered.We also apply the two-temperature Bremsstrahlung radiation mechanism for an analytical Advection-Dominated Accretion Flow(ADAF)model:we find the two-temperature correction to the total Bremsstrahlung radiation for ADAF is negligible.
Internal bremsstrahlung spectrum of 139Ce
International Nuclear Information System (INIS)
The internal bremsstrahlung spectrum which accompanies the electron capture decay of 139Ce to the first excited state of 139La has been measured in coincidence with the nuclear gamma ray which deexcites that state. The measured intensity above 42 keV is found to be (1.070±0.024) times that predicted by the recent calculations of Suriacute c et al. The QEC value is found to be 264.6±2.0 keV. copyright 1996 The American Physical Society
Polarization of thermal bremsstrahlung emission due to electron pressure anisotropy
Komarov, S. V.; Khabibullin, I. I.; Churazov, E. M.; Schekochihin, A. A.
2016-09-01
Astrophysical plasmas are typically magnetized, with the Larmor radii of the charged particles many orders of magnitude smaller than their collisional mean free paths. The fundamental properties of such plasmas, e.g. conduction and viscosity, may depend on the instabilities driven by the anisotropy of the particle distribution functions and operating at scales comparable to the Larmor scales. We discuss a possibility that the pressure anisotropy of thermal electrons could produce polarization of thermal bremsstrahlung emission. In particular, we consider coherent large-scale motions in galaxy clusters to estimate the level of anisotropy driven by stretching of the magnetic-field lines by plasma flow and by heat fluxes associated with thermal gradients. Our estimate of the degree of polarization is ˜0.1 per cent at energies ≳kT. While this value is too low for the forthcoming generation of X-ray polarimeters, it is potentially an important proxy for the processes taking place at extremely small scales, which are impossible to resolve spatially. The absence of the effect at the predicted level may set a lower limit on the electron collisionality in the ICM. At the same time, the small value of the effect implies that it does not preclude the use of clusters as (unpolarized) calibration sources for X-ray polarimeters at this level of accuracy.
Radiative corrections to pion-nucleus bremsstrahlung
Kaiser, N
2008-01-01
We calculate the one-photon loop radiative corrections to virtual pion Compton scattering $\\pi^- \\gamma^* \\to \\pi^- \\gamma$, that subprocess which determines in the one-photon exchange approximation the pion-nucleus bremsstrahlung reaction $\\pi^- Z\\to \\pi^- Z \\gamma$. Ultraviolet and infrared divergencies of the loop integrals are both treated by dimensional regularization. Analytical expressions for the ${\\cal O}(\\alpha)$ corrections to the virtual Compton scattering amplitudes, $A(s,u,Q)$ and $B(s,u,Q)$, are derived with their full dependence on the (small) photon virtuality $Q$ from 9 classes of contributing one-loop diagrams. Infrared finiteness of these virtual radiative corrections is achieved (in the standard way) by including soft photon radiation below an energy cut-off $\\lambda$. In the region of low $\\pi^- \\gamma$ center-of-mass energies, where the pion-nucleus bremsstrahlung process is used to extract the pion electric and magnetic polarizabilities, we find radiative corrections up to about -3% fo...
Bremsstrahlung spectra from atoms and ions at low relativistic energies
International Nuclear Information System (INIS)
Analytic expressions for bremsstrahlung spectra from neutral atoms and ions, including the polarizational bremsstrahlung contribution in a stripped atom approximation, are developed for electron scattering at energies of 10-2000 keV. A modified Elwert factor and a simple higher Born correction are used for the Coulomb spectrum, with ordinary bremsstrahlung screening effects in ions and atoms adequately characterized in the non-relativistic Born approximation. In parallel with the development of this analytic description, new numerical results are obtained for ordinary bremsstrahlung from ions and from bare nuclei, appreciably extending the available data set which can be used to study dependences on element, ionicity, energy and the fraction of incident energy radiated. The accuracy of predictions with the analytic expressions is then determined by comparison with the full numerical relativistic partial-wave results for ordinary bremsstrahlung and with non-relativistic numerical results in the Born approximation or in partial waves for the polarizational amplitude. (author)
On the formation of bremsstrahlung in an absorptive QED/QCD medium
Bluhm, Marcus; Gousset, Thierry; Aichelin, Joerg
2012-01-01
The radiative energy loss of a relativistic charge in a dense, absorptive medium can be affected significantly by damping phenomena. The effect is more pronounced for large energies of the charge and/or large damping of the radiation. This can be understood in terms of a competition between the formation time of bremsstrahlung and a damping time scale. Discussing this competition in detail for the absorptive QED and QCD medium, we identify the regions in energy and parameter space, in which either coherence or damping effects are of major importance for the radiation spectrum. We show that damping mechanisms lead to a stronger suppression of the spectrum than coherence effects. This might be visible experimentally in correlations between hadrons at large momenta.
Dynamical model for Pion-Nucleon Bremsstrahlung
Mariano, A V
2000-01-01
A dynamical model based on effective Lagrangians is proposed to describe the bremsstrahlung reaction $ \\pi N \\to \\pi N \\gamma$ at low energies. The $\\Delta(1232)$ degrees of freedom are incorporated in a way consistent with both, electromagnetic gauge invariance and invariance under contact transformations. The model also includes the initial and final state rescattering of hadrons via a T-matrix with off-shell effects. The $\\pi N \\gamma$ differential cross sections are calculated using three different T-matrix models and the results are compared with the soft photon approximation, and with experimental data. The aim of this analysis is to test the off-shell behavior of the different T-matrices under consideration.
Internal bremsstrahlung endpoint energy of 54Mn
International Nuclear Information System (INIS)
For 54Mn there is a discrepancy between the QEC obtained from the endpoint energy of the internal bremsstrahlung (IB) spectrum which accompanies the electron capture decay (QEC=1353±8 keV) and that obtained from the accepted mass differences (QEC=1377±1 keV). This Q value is needed to deduce the partial-half life of the astrophysically interesting β- decay of 54Mn from the recently measured β+ partial half-life. To resolve this discrepancy, we have remeasured the endpoint energy of the IB spectrum, by recording coincidences between the IB and the 835-keV γ ray, both detected in Compton-suppressed Ge detectors. The QEC we deduce is 1379±8 keV, in agreement with the accepted mass differences. (c) 2000 The American Physical Society
Coulomb correction calculations of pp Bremsstrahlung
International Nuclear Information System (INIS)
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
Effect of bremsstrahlung radiation emission on fast electrons in plasmas
Embréus, O.; Stahl, A.; Fülöp, T.
2016-09-01
Bremsstrahlung radiation emission is an important energy loss mechanism for energetic electrons in plasmas. In this paper we investigate the effect of spontaneous bremsstrahlung emission on the momentum-space structure of the electron distribution, fully accounting for the emission of finite-energy photons by modeling the bremsstrahlung interactions with a Boltzmann collision operator. We find that electrons accelerated by electric fields can reach significantly higher energies than predicted by the commonly used radiative stopping-power model. Furthermore, we show that the emission of soft photons can contribute significantly to the dynamics of electrons with an anisotropic distribution by causing pitch-angle scattering at a rate that increases with energy.
International Nuclear Information System (INIS)
Full text : In the paper, there were calculated cross sections of photoproduction of lepton pair in crystal environment with due account for spin states of electron, positron and photon in the case of screening. All calculations indicated that proposed new screening method makes considerable impact on both cross sections of non-elastic radiation processes and polarization characteristics of reactions. The development and improvement of the accelerators used to form high-energy electron beams and the possibility of applying polarized beams stimulate further theoretical and experimental study of the interaction between fast particles and matter. Passage of fast charged leptons e and and high-energy photons through matter is accompanied by various electromagnetic phenomena, such as bremsstrahlung, photoproduction of leptonic pairs, channeling of charged particles, Cherenkov and transition radiation, etc. The characteristics of electromagnetic processes with participation of high-energy particles depend strongly on the medium structure and should significantly differ for ordered (crystalline) and disordered media. When fast particles interact with nuclei in crystals, diffraction amplification of the bremsstrahlung and pair photoproduction cross sections arises due to the coherent effects. There are various methods of screening nuclear field, and the most commonly used method is Schiff method.
Bremsstrahlung spectra produced by kilovolt electron impact on thick targets
International Nuclear Information System (INIS)
Measurements of bremsstrahlung spectra generated by 5-25 keV electron impact on thick targets of aluminium, titanium, zirconium, molybdenum and tungsten are reported. The experimental data are compared with the simulation results of X-ray spectra obtained from the general-purpose Monte Carlo code PENELOPE, which implements accurate cross-sections for ordinary bremsstrahlung emission but disregards polarization bremsstrahlung. The agreement between the experimental and simulation results is satisfactory. This is in contrast with a recent study in which large discrepancies were observed between experimental and Monte Carlo simulation results. Our results provide evidence for the reliability of the combined choices of the interaction cross-sections and of the simulation algorithms implemented in PENELOPE for bremsstrahlung emission.
Feasibility Studies of the Diffractive Bremsstrahlung Measurement at the LHC
J.J. Chwastowski; Czekierda, S.; Kycia, R.; Staszewski, R.(The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Kraków, Poland); Turnau, J.; Trzebiński, M
2016-01-01
Feasibility studies of an observation of the exclusive diffractive bremsstrahlung in proton-proton scattering at the LHC are reported. A simplified approach to the photon and the scattered proton energy reconstruction is used. The background influence is discussed.
Calculation of the collimated bremsstrahlung flux from thin radiators
International Nuclear Information System (INIS)
A method is outlined for calculating the absolute flux of a bremsstrahlung beam created by passing an electron beam through thin radiators. Multiple scattering of the electron beam in the radiator and collimation of the bremsstrahlung flux are considered in this calculation. Separate measurements determine that this calculations has an absolute accuracy of 2.8% for an endpoint energy range from 120 to 360 MeV for a total radiator thickness of less than 0.012 radiation lengths. (orig.)
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.
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-induced highly penetrating probes for nondestructive assay and defect analysis
Selim, F A; Harmon, J F; Kwofie, J; Spaulding, R; Erickson, G; Roney, T
2002-01-01
Nondestructive assay and defect analysis probes based on bremsstrahlung-induced processes have been developed to identify elements and probe defects in large volume samples. Bremsstrahlung beams from (electron accelerators) with end-point energies both above and below neutron emission threshold have been used. Below neutron emission threshold these beams (from 6 MeV small pulsed linacs), which exhibit high penetration, create positrons via pair production inside the material and produce X-ray fluorescence (XRF) radiation. Chemical assays of heavy elements in thick samples up to 10 g/cm sup 2 thick are provided by energy dispersive XRF measurements. The pair-produced positrons annihilate within the material, thereby emitting 511 keV gamma radiation. Doppler broadening spectroscopy of the 511 keV radiation can be performed to characterize the material and measure defects in samples of any desired thickness. This technique has successfully measured induced strain due to tensile stress in steel samples of 0.64 cm...
Sum rules for the polarization correlations in photoionization and bremsstrahlung
Pratt, R. H.; Müller, R. A.; Surzhykov, A.
2016-05-01
The polarization correlations in doubly differential cross sections are investigated for photoionization and ordinary bremsstrahlung. These correlations describe the polarization transfer between incident light and ejected photoelectrons as well as between an incoming electron beam and bremsstrahlung light, respectively. They are characterized by a set of seven real parameters Ci j. We show that the squares of these parameters are connected by simple "sum rules." These sum rules can be applied for both one-electron systems and also for atoms, if the latter are described within the independent particle approximation. In particular, they are exact in their simplest form (i) for the photoionization of K -, LI ,I I-, and MI ,I I-atomic shells, as well as (ii) for bremsstrahlung in which the electron is scattered into s1 /2 or p1 /2 states, as in the tip (bremsstrahlung) region. Detailed calculations are performed to verify the derived identities and to discuss their possible applications for the analysis of modern photoionization and bremsstrahlung experiments. In particular, we argue that the sum rules may help to determine the entire set of (significant) polarization correlations in the case when not all Ci j are available for experimental observation.
Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung
Mehtar-Tani, Yacine
2016-01-01
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.
Elastic photonuclear cross sections for bremsstrahlung from relativistic ions
Mikkelsen, R. E.; Sørensen, A H; Uggerhøj, U. I.
2015-01-01
In this paper, we provide a procedure to calculate the bremsstrahlung spectrum for virtually any relativistic bare ion with charge 6$e$ or beyond, $Z\\ge 6$, in ultraperipheral collisions with target nuclei. We apply the Weizs\\"{a}cker-Williams method of virtual quanta to model the effect of the distribution of nuclear constituents on the interaction of the ion with the radiation target. This leads to a bremsstrahlung spectrum peaking at $2\\gamma$ times the energy of the giant dipole resonance...
Effect of bremsstrahlung radiation emission on fast electrons in plasmas
Embréus, Ola; Fülöp, Tünde
2016-01-01
Bremsstrahlung radiation emission is an important energy loss mechanism for energetic electrons in plasmas. In this paper we investigate the effect of spontaneous bremsstrahlung emission on the momentum-space structure of the electron distribution, fully accounting for the emission of finite-energy photons. We find that electrons accelerated by electric fields can reach significantly higher energies than what is expected from energy-loss considerations. Furthermore, we show that the emission of soft photons can contribute significantly to the dynamics of electrons with an anisotropic distribution.
Coherence vortices of partially coherent beams in the far field
Institute of Scientific and Technical Information of China (English)
Liu Pu-Sheng; Lü Bai-da
2007-01-01
Based on the propagation law of cross-spectral density function, studied in this paper are the coherence vortices of partially coherent, quasi-monochromatic singular beams with Gaussian envelope and Schell-model correlator in the far field, where our main attention is paid to the evolution of far-field coherence vortices into intensity vortices of fully coherent beams. The results show that, although there are usually no zeros of intensity in partially coherent beams with Gaussian envelope and Schell-model correlator, zeros of spectral degree of coherence exist. The coherence vortices of spectral degree of coherence depend on the relative coherence length, mode index and positions of pairs of points.If a point and mode index are kept fixed, the position of coherence vortices changes with the increase of the relative coherence length. For the low coherent case there is a circular phase dislocation. In the coherent limit coherence vortices become intensity vortices of fully coherent Laguerre-Gaussian beams.
Electron-electron bremsstrahlung emission and the inference of electron flux spectra in solar flares
Kontar, E. P.; Emslie, A. G.; Massone, A. M.; Piana, M.; Brown, J.C.; Prato, M.
2007-01-01
Although both electron-ion and electron-electron bremsstrahlung contribute to the hard X-ray emission from solar flares, the latter is normally ignored. Such an omission is not justified at electron (and photon) energies above $\\sim 300$ keV, and inclusion of the additional electron-electron bremsstrahlung in general makes the electron spectrum required to produce a given hard X-ray spectrum steeper at high energies. Unlike electron-ion bremsstrahlung, electron-electron bremsstrahlung cannot ...
Neutrino-pair emission in a strong magnetic field
van Dalen, ENE; Dieperink, AEL; Sedrakian, A; Timmermans, RGE
2000-01-01
We study the neutrino emissivity of strongly magnetized neutron stars due to the charged and neutral current couplings of neutrinos to baryons in strong magnetic fields. The leading order neutral current process is the one-body neutrino-pair bremsstrahlung, which does not have an analogue in the zer
A detector for use in high energy bremsstrahlung shielding studies
International Nuclear Information System (INIS)
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 104 to 105 times that of the P2 ion chamber
Spectra and rates of bremsstrahlung neutrino emission in stars
Guo, Gang
2016-01-01
We calculate the energy-differential rate for neutrino emission from electron-nucleus bremsstrahlung in stellar interiors taking into account the effects of electron screening and ionic correlations. We compare the energy-differential and the net rates, as well as the average $\\bar{\
Constructing the nuclear caloric curve from thermal bremsstrahlung
Ortega, R
2004-01-01
The behavior of the emission of thermal bremsstrahlung with the reaction centrality has been studied in Xe-121 + Sn-nat reactions at 50A MeV. A thermal hard photon component is present along the measured impact parameter range (0.1 less than or equal to b/b(max) less than or equal to 0.6) showing th
Infrared phenomena in quantum electrodynamics : II. Bremsstrahlung and compton scattering
Haeringen, W. van
1960-01-01
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
Feasibility Studies of Exclusive Diffractive Bremsstrahlung Measurement at RHIC Energies
Chwastowski, Janusz; Cyz, Antoni; Fulek, Łukasz; Kycia, Radosław; Pawlik, Bogdan; Sikora, Rafał; Turnau, Jacek
2015-01-01
Feasibility studies of an observation of the exclusive diffractive bremsstrahlung at RHIC at $\\sqrt{s} = 200$~GeV and at $\\sqrt{s} = 500$~GeV are reported. A simplified approach to the photon and the scattered proton energy reconstruction is used. Influence of possible backgrounds is discussed.
Exact Bremsstrahlung Function in N=2 Superconformal Field Theories.
Fiol, Bartomeu; Gerchkovitz, Efrat; Komargodski, Zohar
2016-02-26
We propose an exact formula for the energy radiated by an accelerating quark in N=2 superconformal theories in four dimensions. This formula reproduces the known bremsstrahlung function for N=4 theories and provides a prediction for all the perturbative and instanton corrections in N=2 theories. We perform a perturbative check of our proposal up to three loops. PMID:26967407
Observation of the Muon Inner Bremsstrahlung at LEP1
Abdallah, J; Adam, W; Adzic, P; Albrecht, T; Alemany-Fernandez, R; Allmendinger, T; Allport, P P; Amaldi, U; Amapane, N; Amato, S; Anashkin, E; Andreazza, A; Andringa, S; Anjos, N; Antilogus, P; Apel, W D; Arnoud, Y; Ask, S; Åsman, B; Augustin, J E; Augustinus, A; Baillon, P; Ballestrero, A; Bambade, P; Barbier, R; Bardin, D; Barker, G J; Baroncelli, A; Battaglia, M; Baubillier, M; Becks, K H; Begalli, M; Behrmann, A; Ben-Haim, E; Benekos, N; Benvenuti, A; Bérat, C; Berggren, M; Bertrand, D; Besançon, M; Besson, N; Bloch, D; Blom, M; Bluj, M; Bonesini, M; Boonekamp, M; Booth, P S L; Borisov, G; Botner, O; Bouquet, B; Bowcock, T J V; Boyko, I; Bracko, M; Brenner, R; Brodet, E; Brückman, P; Brunet, J M; Buschbeck, B; Buschmann, P; Calvi, M; Camporesi, T; Canale, V; Carena, F; Castro, N; Cavallo, F; Chapkin, M; Charpentier, P; Checchia, P; Chierici, R; Shlyapnikov, P; Chudoba, J; Chung, S U; Cieslik, K; Collins, P; Contri, R; Cosme, G; Cossutti, F; Costa, M J; Crennell, D J; Cuevas-Maestro, J; D'Hondt, J; Da Silva, T; Da Silva, W; Della Ricca, G; De Angelis, A; de Boer, Wim; De Clercq, C; De Lotto, B; De Maria, N; De Min, A; De Paula, L; Di Ciaccio, L; Di Simone, A; Doroba, K; Drees, J; Eigen, G; Ekelöf, T J C; Ellert, M; Elsing, M; Espirito-Santo, M C; Fanourakis, G K; Fassouliotis, D; Feindt, M; Fernández, J; Ferrer, A; Ferro, F; Flagmeyer, U; Föth, H; Fokitis, E; Fulda-Quenzer, F; Fuster, J; Gandelman, M; García, C; Gavillet, P; Gazis, E; Gokieli, R; Golob, B; Gómez-Ceballos, G; Gonçalves, P; Graziani, E; Grosdidier, G; Grzelak, K; Guy, J; Haag, C; Hallgren, A; Hamacher, K; Hamilton, K; Haug, S; Hauler, F; Hedberg, V; Hennecke, M; Herr, H; Hoffman, J; Holmgren, S O; Holt, P J; Houlden, M A; Jackson, J N; Jarlskog, G; Jarry, P; Jeans, D; Johansson, E K; Jonsson, P; Joram, C; Jungermann, L; Kapusta, F; Katsanevas, S; Kokkinias, P; Leinonen, L; Katsoufis, E; Kernel, G; Kersevan, B P; Krumshtein, Z; Lesiak, T; Kerzel, U; Liebig, W; King, B T; Lamsa, J; Liko, D; Kjaer, N J; Leder, G; Kluit, P; Kourkoumelis, C; Leitner, R; Kuznetsov, O; Kucharczyk, M; Ledroit, F; Lopes, J H; Lemonne, J; Lepeltier, V; Lipniacka, A; López, J M; Loukas, D; Lutz, P; Lyons, L; MacNaughton, J; Malek, A; Maltezos, S; Mandl, F; Marco, J; Marco, R; Maréchal, B; Margoni, M; Marin, J C; Mariotti, C; Markou, A; Martínez-Rivero, C; Masik, J; Mastroyiannopoulos, N; Matorras, F; Matteuzzi, C; Mazzucato, F; Mazzucato, M; McNulty, R; Meroni, C; Migliore, E; Mitaroff, W A; Mjörnmark, U; Moa, T; Moch, M; Mönig, K; Monge, R; Montenegro, J; Moraes, D; Moreno, S; Morettini, P; Müller, U; Münich, K; Mulders, M; Mundim, L; Murray, W; Muryn, B; Myatt, G; Myklebust, T; Paganoni, M; Nassiakou, M; Paiano, S; Navarria, F; Nawrocki, K; Nicolaidou, R; Nikolenko, M; Ouraou, A; Parkes, C; Oblakowska-Mucha, A; Oyanguren, A; Obraztsov, V F; Olshevski, A; Palacios, J P; Onofre, A; Palka, H; Orava, R; Österberg, K; Pape, L; Papadopoulou, T D; Parodi, F; Parzefall, U; Passeri, A; Passon, O; Peralta, L; Perepelitsa, V; Perrotta, A; Petrolini, A; Piedra, J; Pieri, L; Pierre, F; Pimenta, M; Piotto, E; Podobnik, T; Poireau, V; Pol, M E; Polok, G; Pozdnyakov, V; Pukhaeva, N; Pullia, A; Rames, J; Read, A; Rebecchi, P; Rehn, J; Reid, D; Reinhardt, R; Renton, P B; Richard, F; Rídky, J; Rivero, M; Rodríguez, D; Romero, A; Ronchese, P; Roudeau, P; Rovelli, T; Ruhlmann-Kleider, V; Ryabtchikov, D; Sadovskii, A; Salmi, L; Salt, J; Sander, C; Savoy-Navarro, A; Schwickerath, U; Sekulin, R; Siebel, M; Sisakian, A; Smadja, G; Smirnova, O; Sokolov, A; Sopczak, A; Sosnowski, R; Spassoff, Tz; Stanitzki, M; Stocchi, A; Strauss, J; Stugu, B; Szczekowski, M; Szeptycka, M; Szumlak, T; Tabarelli de Fatis, T; Tegenfeldt, F; Timmermans, J; Tkatchev, L; Tobin, M; Todorovova, S; Tomé, B; Tonazzo, A; Tortosa, P; Travnicek, P; Treille, D; Tristram, G; Trochimczuk, M; Troncon, C; Turluer, M L; Tyapkin, I A; Tyapkin, P; Tzamarias, S; Uvarov, V; Valenti, G; van Dam, P; Van Eldik, J; Van Remortel, N; Van Vulpen, I; Vegni, G; Veloso, F; Venus, W; Verdier, P; Verzi, V; Vilanova, D; Vitale, L; Vrba, V; Wahlen, H; Washbrook, A J; Weiser, C; Wicke, D; Wickens, J; Wilkinson, G; Winter, M; Witek, M; Yushchenko, O; Zalewska-Bak, A; Zalewski, P; Zavrtanik, D; Zhuravlov, V; Zimin, N I; Zintchenko, A; Zupan, M
2008-01-01
Muon bremsstrahlung photons converted in front of the DELPHI main tracker (TPC) in dimuon events at LEP1 were studied in two photon kinematic ranges: 0.2 < E_gamma <= 1 GeV and transverse momentum with respect to the parent muon p_T < 40 MeV/c, and 1 < E_gamma <= 10 GeV and p_T < 80 MeV/c . A good agreement of the observed photon rate with predictions from QED for the muon inner bremsstrahlung was found, contrary to the anomalous soft photon excess that has been observed recently in hadronic Z^0 decays. The obtained ratios of the observed signal to the predicted level of the muon bremsstrahlung are 1.06 +/- 0.12 +/- 0.07 in the photon energy range 0.2 < E_gamma <= 1 GeV and 1.04 +/- 0.09 +/- 0.12 in the photon energy range 1 < E_gamma <= 10 GeV. The bremsstrahlung dead cone is observed for the first time in the direct photon production at LEP.
Spatial representation of coherence.
von Hecker, Ulrich; Hahn, Ulrike; Rollings, Jasmine
2016-07-01
Four experiments examined spatial correlates of the experience of coherence, that is, the extent to which propositions "fit together." Experiment 1 demonstrates for Heiderian triads (i.e., sets of liking/disliking relations between 3 fictitious persons) that name pairs from balanced triads, such as 2 friends commonly disliking a third person (high coherence) are seen as closer to each other in physical space as compared to name pairs from unbalanced triads, such as 2 persons disliking each other and having a common friend (low coherence). This pattern of results is conceptually replicated in 2 further experiments for categorical syllogisms. Two terms in conclusions from valid syllogisms (high coherence) were seen as spatially closer to each other than when 2 terms came from invalid syllogisms (low coherence). In the final 2 experiments, similar closeness effects are demonstrated for word pairs from scenarios that "made sense" in terms of causal connectedness (latent causality) as opposed to word pairs from scenarios perceived as causally unconnected. These findings are discussed in the context of spatial binding theories, applied psychology, and embodied cognition in general, and their methodological implications are highlighted. (PsycINFO Database Record PMID:27175899
Catalytic coherence transformations
Bu, Kaifeng; Singh, Uttam; Wu, Junde
2016-04-01
Catalytic coherence transformations allow the otherwise impossible state transformations using only incoherent operations with the aid of an auxiliary system with finite coherence that is not being consumed in any way. Here we find the necessary and sufficient conditions for the deterministic and stochastic catalytic coherence transformations between a pair of pure quantum states. In particular, we show that the simultaneous decrease of a family of Rényi entropies of the diagonal parts of the states under consideration is a necessary and sufficient condition for the deterministic catalytic coherence transformations. Similarly, for stochastic catalytic coherence transformations we find the necessary and sufficient conditions for achieving a higher optimal probability of conversion. We thus completely characterize the coherence transformations among pure quantum states under incoherent operations. We give numerous examples to elaborate our results. We also explore the possibility of the same system acting as a catalyst for itself and find that indeed self-catalysis is possible. Further, for the cases where no catalytic coherence transformation is possible we provide entanglement-assisted coherence transformations and find the necessary and sufficient conditions for such transformations.
Reconstruction of 12 MV bremsstrahlung spectra from measured transmission data
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
Transmission data for 12 MV bremsstrahlung beams produced by the process for continuous-pulsed 12 MV electrons coming from a linear accelerator hitting a 1.2mm thick plane tantalum target have been acquired with a combination of iron and Telfon attenuators. Two solid state dosimeters with LiF-TLD material surrounded Telfon were used as detectors. It has been checked that the experimental system achieves reasonably narrow-beam geometry by Monte Carlo simulations. From these transmission data, the original energy photon spectrum has been reconstructed using the iterative least-squares technique and compared with the spectrum calculated with Monte Carlo code system EGSnrc. The comparison shows that the numerical technique for analysis of transmission data can represent 12 MV bremsstrahlung spectrum acceptably well. The purpose of our work is to provide an effective way to reconstruct an unknown photon spectrum with high energy component and prove the correctness of this way.
Bremsstrahlung during $\\alpha$-decay: quantum multipolar model
Maydanyuk, Sergei P
2008-01-01
In this paper the improved multipolar model of bremsstrahlung accompanied the $\\alpha$-decay is presented. The angular formalism of calculations of the matrix elements, being enough complicated component of the model, is stated in details. A new definition of the angular (differential) probability of the photon emission in the $\\alpha$-decay is proposed where direction of motion of the $\\alpha$-particle outside (with its tunneling inside barrier) is defined on the basis of angular distribution of its spacial wave function. In such approach, the model gives values of the angular probability of the photons emission in absolute scale, without its normalization on experimental data. Effectiveness of the proposed definition and accuracy of the spectra calculations of the bremsstrahlung spectra are analyzed in their comparison with experimental data for the $^{210}{\\rm Po}$, $^{214}{\\rm Po}$, $^{226}{\\rm Ra}$ and $^{244}{\\rm Cm}$ nuclei, and for some other nuclei predictions are performed (in absolute scale). With ...
Cross sections for bremsstrahlung production and electron-impact ionization
International Nuclear Information System (INIS)
Electron transport codes require extensive information on the cross sections that govern electron interactions with the atoms that make up the medium. These processes include bremsstrahlung production in the atomic field, excitation and ionization of atomic electrons, and elastic scattering by screened atomic nuclei. These fundamental processes are of basic interest in many fields, but their inclusion in general purpose Monte Carlo transport codes imposes the requirement that reasonably accurate cross-section data be available over a very wide range of energies and for virtually any material. In this chapter, the author discusses two of these processes: bremsstrahlung production and electron-impact ionization. Both of these interactions result in the production of secondary radiations that can be important in radiation transport calculations
Feasibility studies of the diffractive bremsstrahlung measurement at the LHC
Energy Technology Data Exchange (ETDEWEB)
Chwastowski, Janusz J.; Czekierda, Sabina; Staszewski, Rafal; Turnau, Jacek; Trzebinski, Maciej [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow (Poland); Kycia, Radoslaw [Cracow University of Technology, Faculty of Physics, Mathematics and Computer Science, Cracow (Poland)
2016-06-15
Feasibility studies of an observation of the exclusive diffractive bremsstrahlung in proton-proton scattering at the centre of mass energy 13 TeV at the LHC are reported. These studies aim at the dedicated data taking periods with low instantaneous luminosity delivered by the LHC where the pile-up interactions can be neglected. A simplified approach to the photon and the scattered proton energy reconstruction is used. The background influence is discussed. (orig.)
Bremsstrahlung of Fast Charged Particles on Clusters in a Wide Spectral Range
International Nuclear Information System (INIS)
Within the framework of the first Born approximation and a simple model of the structural factor, the bremsstrahlung of fast charged particles on polyatomic clusters is calculated and analyzed with regard to the polarization mechanism in a wide spectral range including a domain of high frequencies. The role of cooperative phenomena in the static and polarization channels of bremsstrahlung is investigated. It is established that these phenomena, being negligible for static bremsstrahlung, substantially influence the polarization bremsstrahlung. It is shown that the constructive interference between the contributions of the atoms of a cluster to the polarization bremsstrahlung substantially increases its intensity and changes its dependence on the basic parameters of the problem compared with the case of bremsstrahlung on an isolated atom
Bremsstrahlung of fast charged particles when scattering on clusters in wide spectral range
International Nuclear Information System (INIS)
Within the framework of the first Born approximation and a simple model of the structural factor, the bremsstrahlung of fast charged particles on polyatomic clusters is calculated and analyzed with regard to the polarization mechanism in a wide spectral range including a domain of high frequencies. The role of cooperative phenomena in the static and polarization channels of bremsstrahlung is investigated. It is established that these phenomena, being negligible for static bremsstrahlung, substantially influence the polarization bremsstrahlung. It is shown that the constructive interference between the contributions of the atoms of a cluster to the polarization bremsstrahlung substantially increases its intensity and changes its dependence on the basic parameters of the problem compared with the case of bremsstrahlung on an isolated atom
Energy Technology Data Exchange (ETDEWEB)
Kim, Young Chul; Kim, Wun Hwan; Um, Soon Ho; Seo, Yeon Seok; Park, Eun Kyung; Oh, Sun Young; Han, You Mie [Korea Univ. Anam Hospital, Seoul (Korea, Republic of); Choe, Jae Gol [Hallym Univ. Hangang Secred Heart Hospital, Seoul (Korea, Republic of)
2011-03-15
Y 90 resin microsphere radioembolization is used to treat inoperable hepatic tumors. After injection of Y 90 resin microsphere, the only method to visualize the distribution of Y 90 is the scintigraphic imaging of bremsstrahlung radiation. The purpose of this study was to evaluate the characteristics and usefulness of bremsstrahlung imaging in Y 90 resin microsphere treatment. Twenty patients (22 administrations) underwent intra arterial Y 90 resin microsphere treatment. For pretreatment planning, images of Tc 99m albumin macroag gregate (MAA) arterial injection and hepatic contrast angiography were obtained. Post treatment bremsstrahlung images were taken and compared with pre treatment images. The extrahepatic activity was evaluated on bremsstrahlung images. To correlate the size and vascularity of the tumors with tumor visualization on bremsstrahlung images, the individual tumors were grouped according to visualization on each image and compared with one another by size and tumor to normal ratio. All post therapeutic bremsstrahlung images showed similar contours of the liver with pre treatment angiography. No extrahepatic activity was seen in all cases. The visualized tumors on bremsstrahlung images were significantly larger than the non visualized tumors on bremsstrahlung images were significantly higher than those of the non visualized tumors. Bremsstrahlung images after intra arterial Y 90 resin microsphere treatment are useful in evaluating the intrahepatic distribution of radioisotope and detecting possible extrahepatic activity.
Ji, Y.; Han, H.; Lee, H.
2014-12-01
Analysis of the surface properties of Antarctica is very important to study the change of environment and climate in the polar region. Synthetic aperture radar (SAR) has been widely used to study Antarctic surface properties because it is independent of sun altitude and atmospheric conditions. Interferometric SAR (InSAR) observes surface topography and deformation, by calculating the phase differences between two or more SAR images obtained over same area. InSAR technique can be used for height mapping in stable areas with a few meter accuracy. However, the InSAR-derived height map can have errors if the phase differences due to surface deformation or change of the scattering center by microwave penetration into snow are misinterpreted as the elevation. In this study, we generated the height maps around Terra Nova Bay in East Antarctica from 13 COSMO-SkyMed one-day tandem InSAR pairs obtained from December 2010 to January 2012. By analyzing the height maps averaged over the 13 interferograms and its standard deviation (STD) map, we could classify the surface types into glacier, mountains and basin areas covered with snow. The mountain areas showed very small STD because its surface property is unchanged with time, except for the small STD values caused by the errors from the unwrapping processing, satellite orbit or atmospheric phase distortion. Over the basin areas, however, the STD of the height was much larger than the mountain area due to the variation of scattering center either from the change in surface property such as snowfall and sublimation or by the surface displacement of snow mass that are too slow. A year-long constant motion of such slow-creeping snow body was positively identified by its linear relationship between the misinterpreted elevation and the baseline perpendicular component of InSAR pair. Analysis of time-series coherence maps and amplitude maps have also contributed to clarify the surface properties and its changes due to various
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.
Formation of bremsstrahlung in an absorptive QED/QCD medium
Bluhm, Marcus; Gossiaux, Pol Bernard; Gousset, Thierry; Aichelin, Joerg
2012-01-01
The radiative energy loss of a relativistic charge in a dense, absorptive medium can be affected significantly by damping phenomena. The effect is more pronounced for large energies of the charge and/or large damping of the radiation. This can be understood in terms of a competition between the formation time of bremsstrahlung and a damping time scale. We discuss this competition in detail for the absorptive QED and QCD medium, focusing on the case in which the mass of the charge is large com...
Generation of Long-Lived Isomeric States via Bremsstrahlung Irradiation
Cheng, Y; Tang, C; Liu, Y; Jin, Q; Cheng, Yao; Xia, Bing; Tang, Chuanxiang; Liu, Yinong; Jin, Qingxiu
2006-01-01
A method to generate long-lived isomeric states effectively for Mossbauer applications is reported. We demonstrate that this method is better and easier to provide highly sensitive Mossbauer effect of long-lived isomers (>1ms) such as 103Rh. Excitation of (gamma,gamma) process by synchrotron radiation is painful due mainly to their limited linewidth. Instead,(gamma,gamma') process of bremsstrahlung excitation is applied to create these long-lived isomers. Isomers of 45Sc, 107Ag, 109Ag, and 103Rh have been generated from this method. Among them, 103Rh is the only one that we have obtained the gravitational effect at room temperature.
Diffraction structures in high-energy electron–nucleus bremsstrahlung
Energy Technology Data Exchange (ETDEWEB)
Jakubassa-Amundsen, D.H.
2013-10-30
The emission of hard bremsstrahlung during the collision of relativistic spin-polarized electrons with inert spin 0 and spin 1/2 nuclei is calculated within the weak-potential approximation. Diffraction structures in the polarization correlations between the beam electron and the emitted photon are predicted for collision energies in the region 50–120 MeV if the photon is emitted at backward angles. The dynamical recoil plays a dominant role concerning the location and the shape of the structures. The target nuclei {sup 19}F, {sup 64}Zn and {sup 89}Y are investigated.
Raman Scattering in Coherently Prepared Atomic System
Institute of Scientific and Technical Information of China (English)
LIN Fu-Cheng(林福成); Yongjoo Rhee; Jonghoon Yi; Hyunmin Park
2001-01-01
Atoms in the coherent superposition state prepared by a pulse pair are used as a novel optical memory material where a single interrogation pulse will produce a new pulse pair preserving the relative amplitudes and phases of the preparing pulse pair. Such a coherent superposition state can also be specially tailored along the propagation path to generate Raman scattering in a relatively short distance with very high efficiency.
Molecular bremsstrahlung radiation at GHz frequencies in air
Al Samarai, Imen; Bérat, Corinne; Deligny, Olivier; Letessier-Selvon, Antoine; Montanet, François; Settimo, Mariangela; Stassi, Patrick
2016-03-01
A detection technique for ultra-high-energy cosmic rays, complementary to the fluorescence technique, would be the use of the molecular bremsstrahlung radiation emitted by low-energy ionization electrons left after the passage of the showers in the atmosphere. In this article, a detailed estimate of the spectral intensity of photons at ground level originating from this radiation is presented. The spectral intensity expected from the passage of the high-energy electrons of the cascade is also estimated. The absorption of the photons in the plasma of electrons and neutral molecules is shown to be negligible. The obtained spectral intensity is shown to be 2 ×1 0-21 W cm-2 GHz-1 at 10 km from the shower core for a vertical shower induced by a proton of 1 017.5 eV . In addition, a recent measurement of bremsstrahlung radiation in air at gigahertz frequencies from a beam of electrons produced at 95 keV by an electron gun is also discussed and reasonably reproduced by the model.
Molecular Bremsstrahlung Radiation at GHz Frequencies in Air
Samarai, I Al; Deligny, O; Letessier-Selvon, A; Montanet, F; Settimo, M; Stassi, P
2016-01-01
A detection technique for ultra-high energy cosmic rays, complementary to the fluorescence technique, would be the use of the molecular Bremsstrahlung radiation emitted by low-energy ionization electrons left after the passage of the showers in the atmosphere. In this article, a detailed estimate of the spectral intensity of photons at ground level originating from this radiation is presented. The spectral intensity expected from the passage of the high-energy electrons of the cascade is also estimated. The absorption of the photons in the plasma of electrons/neutral molecules is shown to be negligible. The obtained spectral intensity is shown to be $2\\times10^{-21} $W cm$^{-2}$ GHz$^{-1}$ at 10 km from the shower core for a vertical shower induced by a proton of $10^{17.5}$ eV. In addition, a recent measurement of Bremsstrahlung radiation in air at gigahertz frequencies from a beam of electrons produced at 95 keV by an electron gun is also discussed and reasonably reproduced by the model.
Koehn, Christoph
2012-01-01
Within thunderstorms electrons can gain energies of up to hundred(s) of MeV. These electrons can create X-rays and gamma-rays as Bremsstrahlung when they collide with air molecules. Here we calculate the distribution of angles between incident electrons and emitted photons as a function of electron and photon energy. We derive these doubly differential cross-sections by integrating analytically over the triply differential cross-sections derived by Bethe and Heitler; this is appropriate for light atoms like nitrogen and oxygen and for electron energies between 1 keV and 1 GeV. We also discuss some simplifying limit cases, and we derive some simple approximation for the most probable scattering angle. We also provide cross sections for the production of electron positron pairs from energetic photons when they interact with air molecules. This process is related to the Bremsstrahlung process by some physical symmetry. Therefore the results above can be transferred to predictions on the angles between incident p...
Measurement of absorbed dose by 7-GeV bremsstrahlung in a PMMA phantom
Job, P K; Semones, E
1999-01-01
High-energy electron storage rings generate energetic bremsstrahlung photons through radiative interaction of the particle beam with the residual gas molecules and other components inside the storage ring. At synchrotron radiation facilities, where beamlines are channeled out of the storage ring, a continuous bremsstrahlung spectrum, with a maximum energy of the stored particle beam, will be present. At the advanced photon source (APS), where the stored beam energy is 7 GeV, bremsstrahlung generated in the straight sections of the insertion device beamlines, which are a total of 15.38 m in length, can be significant. The contribution from each bremsstrahlung interaction adds up to produce a narrow mono-directional bremsstrahlung beam that comes down through the insertion device beamlines. The resulting absorbed dose distributions by this radiation in a 300 mmx300 mmx300 mm tissue substitute cube phantom were measured with LiF:Mg,Ti (TLD-700) thermoluminescent dosemeters. The normalized absorbed dose, in a cro...
Search of gamma-rays Bremsstrahlung mirror reflection
International Nuclear Information System (INIS)
Full text: Total external reflection of soft X-rays is widely used in many X-ray optic systems. At the same time in the wavelength range of gamma rays the corresponding total external reflection on macroscopic smooth surface hasn't been surely verified yet. Samarkand microtron MT-22S with 330 meter flying distance was used for a search experiment of detecting gamma-ray total external reflection. Measured slip angles (i.e. angles between incident ray and reflector surface) are negligible and don't exceed tens of micro-radian. And it is a complicated problem to get required characteristics of collimating, reflecting and detecting gamma rays. The experimental setup was described earlier. Here we report experimental results of very small-angle Bremsstrahlung scattering only in comparison with results of computer simulation by Monte-Carlo method. It is continuous energy spectrum of Bremsstrahlung gamma rays (described by Shift formula) that is the first characteristic property of the experiment. And it is air in the way of gamma rays that is the second one. Continuous energy spectrum provides a use of some range of reflector inclinations (but bounded above) that satisfy the conditions of the total reflection for a corresponding part of gamma ray beam. As for air it absorbs gamma rays on their long way to detectors lowering the ratio of searching effect to background. Horizontal belt type Bremsstrahlung beam was collimated for the experiment. So the beam's horizontal acceptance was relatively wide (∼ 34 mrad). A collimator with gap heights of 100, 50 and 20 μ limited the beam in vertical that results in beam vertical divergences of 125, 62 and 25 μrad, correspondingly. The gap height of 100 μ used for positioning procedure, and the ones of 50 and 20 μ used for measurements. No separate peak of reflected gamma rays was observed at the experiment. However when vertical profiles measured at the reflector inclinations of 0 and 40 μrad are compared one can see gamma
Vacuum Cherenkov radiation and bremsstrahlung from disformal couplings
van de Bruck, Carsten; Burrage, Clare; Morrice, Jack
2016-08-01
The simplest way to modify gravity is to extend the gravitational sector to include an additional scalar degree of freedom. The most general metric that can be built in such a theory includes disformal terms, so that standard model fields move on a metric which is the sum of the space time metric and a tensor constructed from first derivatives of the scalar. In such a theory gravitational waves and photons can propagate at different speeds, and these can in turn be different from the maximum speed limit for matter particles. In this work we show that disformal couplings can cause charged particles to emit Cherenkov radiation and bremsstrahlung apparently in vacuum, depending on the background evolution of the scalar field. We discuss the implications of this for observations of cosmic rays, and the constraints that arise for models of dark energy with disformal couplings.
Vacuum Cherenkov radiation and bremsstrahlung from disformal couplings
van de Bruck, Carsten; Morrice, Jack
2016-01-01
The simplest way to modify gravity is to extend the gravitational sector to include an additional scalar degree of freedom. The most general metric that can be built in such a theory includes disformal terms, so that standard model fields move on a metric which is the sum of the space time metric and a tensor constructed from first derivatives of the scalar. In such a theory gravitational waves and photons can propagate at different speeds, and these can in turn be different from the maximum speed limit for matter particles. In this work we show that disformal couplings can cause charged particles to emit Cherenkov radiation and bremsstrahlung apparently in vacuum, depending on the background evolution of the scalar field. We discuss the implications of this for observations of cosmic rays, and the constraints that arise for models of dark energy with disformal couplings.
Internal bremsstrahlung endpoint energy of {sup 54}Mn
Energy Technology Data Exchange (ETDEWEB)
Hindi, M. M. [Physics Department, Tennessee Technological University, Cookeville, Tennessee 38505 (United States); Larimer, R.-M. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Norman, E. B. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Rech, G. A. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
2000-05-01
For {sup 54}Mn there is a discrepancy between the Q{sub EC} obtained from the endpoint energy of the internal bremsstrahlung (IB) spectrum which accompanies the electron capture decay (Q{sub EC}=1353{+-}8 keV) and that obtained from the accepted mass differences (Q{sub EC}=1377{+-}1 keV). This Q value is needed to deduce the partial-half life of the astrophysically interesting {beta}{sup -} decay of {sup 54}Mn from the recently measured {beta}{sup +} partial half-life. To resolve this discrepancy, we have remeasured the endpoint energy of the IB spectrum, by recording coincidences between the IB and the 835-keV {gamma} ray, both detected in Compton-suppressed Ge detectors. The Q{sub EC} we deduce is 1379{+-}8 keV, in agreement with the accepted mass differences. (c) 2000 The American Physical Society.
Decay energy of 55Fe from its inner Bremsstrahlung spectrum
Indian Academy of Sciences (India)
S L Keshava; K Gopala; P Venkataramaiah
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.
Nucleon-Nucleon Bremsstrahlung emission of massive Axion
Giannotti, M
2005-01-01
We consider the problem of axion production by bremsstrahlung emission in a nuclear medium. The usual assumption of a massless axion is replaced by more general hypotheses, so that we can describe the emission process for axions with mass up to a few MeV. We point out that in certain physical situations the contribution from non-zero mass is non-negligible. In particular, in the mechanism for the production of Gamma Ray Bursts via emission of heavy axions the axion mass m_a ~ 1MeV is comparable with the temperature of the nuclear medium and thus can not be disregarded. Looking at our results we find, in fact, a fairly considerable reduction of the axion luminosity in that mechanism.
The double copy: Bremsstrahlung and accelerating black holes
Luna, Andres; Nicholson, Isobel; O'Connell, Donal; White, Chris D
2016-01-01
Advances in our understanding of perturbation theory suggest the existence of a correspondence between classical general relativity and Yang-Mills theory. A concrete example of this correspondence, which is known as the double copy, was recently introduced for the case of stationary Kerr-Schild spacetimes. Building on this foundation, we examine the simple time-dependent case of an accelerating, radiating point source. The gravitational solution, which generalises the Schwarzschild solution, includes a non-trivial stress-energy tensor. This stress-energy tensor corresponds to a gauge theoretic current in the double copy. We interpret both of these sources as representing the radiative part of the field. Furthermore, in the simple example of Bremsstrahlung, we determine a scattering amplitude describing the radiation, maintaining the double copy throughout. Our results provide the strongest evidence yet that the classical double copy is directly related to the BCJ double copy for scattering amplitudes.
The double copy: Bremsstrahlung and accelerating black holes
Luna, Andrés; Monteiro, Ricardo; Nicholso, Isobel; O'Connell, Donal; White, Chris D.
2016-06-01
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 intro-duced 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.
Vircator in regime of x-ray Bremsstrahlung
International Nuclear Information System (INIS)
The power vircator with multi-flight electrons cross optical thin anode foil power pulses generation of X-ray radiation created and operated in first. The vircator realized on the base of direct action electron accelerator with supplies of inductive energy storage with plasma switch of current. In paper results of 2-D self-consistent calculations of electron beam dynamics in vircator camera and determined spectra of arise UHF-radiation. The results of first experiments on vircator X-ray Bremsstrahlung for thin (10 mkm, Ta) and thick (100 mkm, Ta) anode foils are presented. The dose of X-ray radiation for thin foil (Eγ > 30 keV) in 8 greater than dose received for thick anode, middle photon energy reduced from 80 keV to 30 keV
Rhodium M(o)ssbauer Effect Generated by Bremsstrahlung Excitation
Institute of Scientific and Technical Information of China (English)
CHENG Yao; XIA Bing; LIU Yi-Nong; JIN Qing-Xiu
2005-01-01
@@ A method for effectively generating long-lived Mossbauer photons and methods for proving the associated Mossbauer effects are reported. For the first time, we observed resonant propagation and resonant absorption of 40-keV Mossbauer photons emitted from 103Rh through (γ,γ′) process excited by bremsstrahlung. This is a new efficient way to generate long-lived isomer (＞ 1 ms) for Mossbauer spectroscopy with sufficient brilliance.An abnormally large ratio of resonant absorption between horizontal and vertical directions indicates horizontal trapping of Mossbauer photons and anisotropic Mossbauer emission, which can be attributed to gravitational effect on the 103Rh Mossbauer isomer with extremely narrow 10-19 eV linewidth.
Koehn, Christoph; Chanrion, Olivier; Neubert, Torsten
2016-04-01
Streamers, the beginning stages of electric discharges, evolve differently depending on their polarity and on the ambient gas composition. One of the well-known supporting mechanisms is "UVphotoionization" where, in air, excited nitrogen emits a UV photon subsequently ionizing oxygen. In pure nitrogen, however, this mechanism is suppressed because of the lack of oxygen; hence this mechanism strongly depends on the ambient gas medium. In this paper we introduce Bremsstrahlung induced photoionization: In the ambient electric field,electrons gain energy and produce Bremsstrahlung photons through the collision with the ambient gas molecules; similarly to "UV-photoionization", the Bremsstrahlung photons ionize the gas molecules and, as such, create electron populations detached from the initial electron patch. For the study of this process we implemented the electron-nucleus Bremsstrahlung process as well as the photoionization by individual photons into an already existing 2.5 D Monte Carlo particle code for the simulation of streamers. We initiated plasma patches of electrons and ions with varying initial electron energies and peak densities in different ambient fields in air and pure nitrogen. We will compare the temporal evolution of the electron densities as well as of the electric field with and without modelling Bremsstrahlung. In air we will test the influence of Bremsstrahlung induced photoionization against "UV-photoionization". We will show that the influence of Bremsstrahlung is negligible in air, but plays a significant role in pure nitrogen at standard temperature and pressure.
Maydanyuk, Sergei P
2016-01-01
In this paper a role of many-nucleon dynamics in formation of the compound $^{5}{\\rm Li}$ nucleus in the scattering of protons off $\\alpha$-particles at the proton incident energies up to 20 MeV is investigated. We propose a bremsstrahlung model allowing to extract information about probabilities of formation of such nucleus on the basis of analysis of experimental cross-sections of the bremsstrahlung photons. In order to realize this approach, the model includes elements of microscopic theory and also probabilities of formation of the short-lived compound nucleus. Results of calculations of the bremsstrahlung spectra are in good agreement with the experimental cross-sections.
External bremsstrahlung spectra excited by 204Tl β particles in thick targets
Powar, M. S.; Ahmad, Salim; Singh, M.
1980-06-01
Spectral distributions of bremsstrahlung produced by 204Tl β particles in thick targets of Perspex, aluminum, copper, tin, and lead have been measured in a sandwich geometry. The contributions of internal bremsstrahlung produced along with the β particles have been determined by magnetic field deflection as well as the Z=O extrapolation method. Experimental results agree with Bethe-Heitler Born-approximation theory, corrected for Coulomb-field effects for low- and medium-Z targets, but show 25% positive deviation for high-Z targets. Again it is found that the bremsstrahlung produced in low-Z targets like Perspex is comparable with internal bremsstrahlung, and the corrections for its contribution to measurements by earlier workers can lead to large uncertainties.
International Nuclear Information System (INIS)
Gold-198 (βmax= 0.96 MeV (98.6%), γmax= 0.412 MeV (95.5%) and T1/2 = 2.7 days) is a well-known therapeutic beta emitter in the field of nuclear medicine, and is being used for the treatment of many different cancers. In the present study, the Bremsstrahlung exposure induced by 198Au in different human tissues, DNA and RNA has been calculated. The specific Bremsstrahlung constant (ΓBr), Probability of energy loss by beta during Bremsstrahlung emission (PBr) and Bremsstrahlung activity (Arelease)Br were estimated. We strongly recommend these parameters should be considered in absorbed dose calculations of radionuclide therapy via 198Au. (orig.)
Effects of electron temperature and density on ion-dust bremsstrahlung
Jung, Young-Dae; MURAKAMI, Izumi
2009-01-01
The effects of electron temperature and density on the ion-dust grain bremsstrahlung process industy plasmas are studied. The ion-dust bremsstrahlung radiation cross section is obtained as afunction of the dust charge, dust radius, Debye length, collision energy, radiation energy, electrondensity, and electron temperature by using the Born approximation. It is shown that the ion-dustbremsstrahlung radiation cross section decreases with an increase in the electron density in dustyplasmas. It i...
International Nuclear Information System (INIS)
Neutron energy spectra in carbon, nitrogen and oxygen were calculated for various bremsstrahlung end-point energies and, from these, tissue spectra were calculated using the tissue equivalent molecular formula C5H40O18N. The method involves folding the known bremsstrahlung spectrum shape with the cross section for each possible decay mode in each element which leads to neutron production. The partial photoneutron cross sections used have been derived from published data
Screening Effects on Nonrelativistic Bremsstrahlung in the Scattering of Electrons by Neutral Atoms
Jung, Young-Dae; Lee, Kun-Sang
1995-01-01
Atomic screening effects on nonrelativistic electron-atom bremsstrahlung radiation are investigated using a simple analytic solution of the Thomas-Fermi model for many-electron atoms. The Born approximation is assumed for the initial and final states of the projectile electron. The results show that the screening effect is important in the soft radiation region and is decreasing with increasing radiation. These results help provide correct information about the behavior of bound electrons in the target atom in bremsstrahlung processes.
Dose assessment of Bremsstrahlung induced by beta isotopes of Uranium-238 series in human tissues
International Nuclear Information System (INIS)
In the natural Uranium-238 decay series, pure beta isotopes such as 234Th, 234Pa, 214Pb, 214Bi, 210Pb and 210Bi are released. These beta isotopes having maximum beta energies and it induces the Bremsstrahlung radiation. The Bremsstrahlung component of these beta isotopes has been traditionally ignored in dosimetry calculations. This may be due to a lack of available methods for including this component in the calculations or to the belief that the contribution of this component is negligible compared to that of other emissions. The resulting hazard of Bremsstrahlung radiation may therefore be some of concern, at least theoretically, and should be systematically evaluated. In the present investigation, it has been estimated that the Bremsstrahlung dose of beta isotopes of Uranium-238 series such as 234Th, 234Pa, 214Pb, 214Bi, 210Pb and 210Bi in various body organs (Adrenals, Brain, Breasts, Gallbladder Wall, LLI Wall, Small Intestine, Stomach, ULI Wall, Heart Wall, Kidneys, Liver, Lungs, Muscle, Ovaries, Pancreas, Red Marrow, Bone Surfaces, Skin, Spleen, Testes, Thymus, Thyroid, Urine Bladder Wall, Uterus, Fetus, Placenta and Total Body). We have considered bone and muscle is target organs. These estimated values shows that the Bremsstrahlung radiation absorbed dose contribution from an organ to itself is very small compared to that from the beta source, but contribution to other organs is not always negligible. Hence the component of Bremsstrahlung dose to total dose should be considered in the environmental radioactivity dose calculations. (author)
Studies of some isomeric yield ratios produced with bremsstrahlung
Kolev, D
1998-01-01
The experimental isomeric ratios for sup 5 sup 2 sup m sup , sup g Mn, sup 8 sup 6 sup m sup , sup g Y, sup 8 sup 7 sup m sup , sup g Y, sup 8 sup 9 sup m sup , sup g Zr, sup 1 sup 1 sup 0 sup m sup , sup g In, sup 1 sup 1 sup 1 sup m sup , sup g In, sup 1 sup 1 sup 2 sup m sup , sup g In, sup 1 sup 5 sup 2 sup m sup 1 sup , sup g Pm, sup 1 sup 5 sup 2 sup m sup 2 sup , sup m sup 1 Eu, sup 1 sup 6 sup 2 sup m sup , sup g Ho, sup 1 sup 6 sup 4 sup m sup , sup g Ho and sup 1 sup 7 sup 8 sup m sup , sup g Lu measured by the activation technique from different targets in (gamma, xnp) reactions (x<=3) at the bremsstrahlung end-point energy of 43 MeV are presented. The predictions of calculations performed by means of compound nucleus particle evaporation and final gamma-deexcitation were critically discussed. The importance of inclusion in the calculations of nonequilibrium particle emission and an adequate gamma-decay mode of isomeric nuclei was considered for some of the reactions investigated.
Development of bremsstrahlung detection type tritium gas monitoring system, (1)
International Nuclear Information System (INIS)
A tritium monitoring system by means of bremsstrahlung detecting was developed. A prototype system consisted of a sampling cylinder, a gas circulating apparatus, an NaI(T1) detector, an amplifier and a multichannel analyzer. The sizes of sampling cylinders used 208 mm phi x 290; 170; 70 mmH, 133 mm phi x 292; 172; 72 mmH and 55 mm phi x 294; 174; 74 mmH, respectively. The sensitivity of prototype system was from 12 to 57 cps/μCi.cm-3, depending on the size of sampling cylinder and an efficiency of NaI(T1) detector. When pulses due to breamsstrahlungs with energy from 4 to 17 keV were counted, the minimum detectable concentration of the prototype tritium monitoring system was obtained to be 5.2 x 10-3 μCi/cm3. It was evaluated that the detectable range of concentration was from 1 x 10-2 to 1 x 103 μCi/cm3. (author)
Bremsstrahlung in carbon thick targets by proton incidence
International Nuclear Information System (INIS)
The subtraction of the continuum from an X-ray spectrum emitted by proton bombardment is usually carried out by means of a mathematical fitting. The purpose of the present work is to develop an analytical function to model the continuous spectrum generated in a PIXE experiment for different incident beam energies in carbon thick targets. With this purpose, PIXE spectra of a carbon bulk sample were measured in an ion accelerator. The proton beam energies were varied between 0.7 MeV and 2 MeV and the X-rays generated were collected by an energy dispersive spectrometer. The spectra analysis was performed taking into account the main effects underlying the production of the continuous spectrum. Nevertheless, for the cases considered here, it was found that the atomic bremsstrahlung is the most important and other contributions were neglected. The experimental spectra from carbon thick targets were corrected by self-absorption and detector efficiency. The results show that the spectral shape corresponding to thick targets corrected by these effects is similar to the functional behavior presented by thin targets
A Single Bremsstrahlung Monitor to Measure Luminosity at LEP
2002-01-01
The luminosity, the beam divergence and the longitudinal polarization can be measured at an interaction point of LEP by dectecting the energy, the angular distribution and the circular polarization of the single bremsstrahlung photons (SB) emitted at very forward angle. The luminosity can be measured by this met than by the conventional method of detecting small angle Bhabha scattering. The bunch to bunch relative luminosity can be monitored at a few per mil level in few minutes. Absolute values of the luminosity and of the polarization can be measured with a precision of the order of 1\\%. \\\\ \\\\ The apparatus to detect SB photons consists of a low Z absorber and of an EM calorimeter made of lead and scintillating fibres. Both the total energy and the space distribution of the SB photons are measured. This apparatus has been designed and built at the Department of Physics and INFN Section of the University of Rome ``La Sapienza''. Later on, together with suitable monocrystal converters, it may be used also for...
International Nuclear Information System (INIS)
Application of the 'photon fluence scaling theorem' allows the ionization chamber to be placed at points in media where the photon fluence is the same, hence eliminating problems with energy response. The theorem is applicable to Compton scattered photons. For photon energies greater than 1.02 MeV, pair production alters the photon fluence in such a way as to invalidate the scaling theorem. In this report the effect of pair production is examined, so that a correction may be applied to the photon fluence scaling theorem. This correction extends application of the theorem for bremsstrahlung spectra up to at least 25 MeV peak energy. 10 refs., 4 tabs., 1 fig
Weber, G; Surzhykov, A; Yasuda, M; Yerokhin, V A; Stöhlker, Th
2012-01-01
We present a Monte Carlo code dedicated to the simulation of bremsstrahlung arising in collisions of polarized electrons with thin target foils. The program consists of an electron transport algorithm taking into account elastic electron-nucleus scattering and inelastic collisions with target electrons as well as a treatment of polarized-electron bremsstrahlung emission. Good agreement is found between the predictions of the electron transport code and data stemming from other simulation programs and experiments. In addition, we present first results from the bremsstrahlung simulation which indicate a significant decrease in the degree of linear polarization of bremsstrahlung even for the thinnest gold targets considered.
Electroencephalograpic coherence
Directory of Open Access Journals (Sweden)
Simon Brežan
2004-08-01
Full Text Available Different brain areas process various aspects of information in parallel as well as segregated way. It is not known, how is this information integrated into a unitary percept or action. The binding problem is one of the key problems in understanding brain function. Synchronized oscillatory activity of neurons is one possible mechanism of the functional integration of different communicating brain areas. The binding has been well-studied in the visual system, but it could also serve as a mechanism in visuomotor integration or functional coupling present with other brain processes and behavioural modes (perception, complex motor behaviour, selective attention, learning, working memory, etc.. Interregional synchronization of the electroencephalographic (EEG signal can be determined by EEG coherence analysis. In the article we present a research example of coherence changes in a visuomotor task. During this task, coherence between visual and motor brain areas increased. This might reflect functional coupling between those areas, but it could also be influenced by other cognitive processes (e.g. selective attention. Coherence analysis is suitable for studying integrative brain function. Because it measures only one of the possible mechanisms of integration, it offers promise especially when combined with other electrophysiological and functional imaging methods.
Coherence and Sense of Coherence
DEFF Research Database (Denmark)
Dau, Susanne
2014-01-01
Constraints in the implementation of models of blended learning can be explained by several causes, but in this paper, it is illustrated that lack of sense of coherence is a major factor of these constraints along with the referential whole of the perceived learning environments. The question...... of coherence is both related to conditional matters as learning environments, structure, clarity and linkage but also preconditioned matters and prerequisites among participants related to experiences and convenience. It is stressed that this calls for continuous assessment and reflections upon these terms...... and conditions if the student shall be able acquire the necessary competencies....
Gas bremsstrahlung studies for medium energy electron storage rings using FLUKA Monte Carlo code
Sahani, Prasanta Kumar; Haridas, G.; Sinha, Anil K.; Hannurkar, P. R.
2016-02-01
Gas bremsstrahlung is generated due to the interaction of the stored electron beam with residual gas molecules of the vacuum chamber in a storage ring. As the opening angle of the bremsstrahlung is very small, the scoring area used in Monte Carlo simulation plays a dominant role in evaluating the absorbed dose. In the present work gas bremsstrahlung angular distribution and absorbed dose for the energies ranging from 1 to 5 GeV electron storage rings are studied using the Monte Carlo code, FLUKA. From the study, an empirical formula for gas bremsstrahlung dose estimation was deduced. The results were compared with the data obtained from reported experimental values. The results obtained from simulations are found to be in very good agreement with the reported experimental data. The results obtained are applied in estimating the gas bremsstrahlung dose for 2.5 GeV synchrotron radiation source, Indus-2 at Raja Ramanna Centre for Advanced Technology, India. The paper discusses the details of the simulation and the results obtained.
Can a many-nucleon structure be visible in bremsstrahlung emission during $\\alpha$ decay?
Maydanyuk, Sergei P; Zou, Li-Ping
2015-01-01
We analyze if the nucleon structure of the $\\alpha$ decaying nucleus can be visible in the experimental bremsstrahlung spectra of the emitted photons which accompany such a decay. We develop a new formalism of the bremsstrahlung model taking into account distribution of nucleons in the $\\alpha$ decaying nuclear system. We conclude the following: (1) After inclusion of the nucleon structure into the model the calculated bremsstrahlung spectrum is changed very slowly for a majority of the $\\alpha$ decaying nuclei. However, we have observed that visible changes really exist for the $^{106}{\\rm Te}$ nucleus ($Q_{\\alpha}=4.29$ MeV, $T_{1/2}$=70 mks) even for the energy of the emitted photons up to 1 MeV. This nucleus is a good candidate for future experimental study of this task. (2) Inclusion of the nucleon structure into the model increases the bremsstrahlung probability of the emitted photons. (3) We find the following tendencies for obtaining the nuclei, which have bremsstrahlung spectra more sensitive to the ...
Z-dependence of thick-target bremsstrahlung produced by monoenergetic low-energy electrons
Czarnecki, S.; Short, A.; Williams, S.
2016-07-01
The dependence of thick-target bremsstrahlung emitted by low-energy beams of monoenergetic electrons on the atomic number of the target material has been investigated experimentally for incident electron energies of 4.25 keV and 5.00 keV using thick aluminum, copper, silver, tungsten, and gold targets. Experimental data suggest that the intensity of the thick-target bremsstrahlung emitted is more strongly dependent on the atomic number of the target material for photons with energies that are approximately equal to the energy of the incident electrons than at lower energies, and also that the dependence of thick-target bremsstrahlung on the atomic number of the target material is stronger for incident electrons of higher energies than for incident electrons of lower energies. The results of the experiments are compared to the results of simulations performed using the PENELOPE program (which is commonly used in medical physics) and to thin-target bremsstrahlung theory, as well. Comparisons suggest that the experimental dependence of thick-target bremsstrahlung on the atomic number of the target material may be slightly stronger than the results of the PENELOPE code suggest.
Coherence, Pseudo-Coherence, and Non-Coherence.
Enkvist, Nils Erik
Analysis of the factors that make a text coherent or non-coherent suggests that total coherence requires cohesion not only on the textual surface but on the semantic level as well. Syntactic evidence of non-coherence includes lack of formal agreement blocking a potential cross-reference, anaphoric and cataphoric references that do not follow their…
Korman, Simon; Avidan, Shai
2016-06-01
Coherency Sensitive Hashing (CSH) extends Locality Sensitivity Hashing (LSH) and PatchMatch to quickly find matching patches between two images. LSH relies on hashing, which maps similar patches to the same bin, in order to find matching patches. PatchMatch, on the other hand, relies on the observation that images are coherent, to propagate good matches to their neighbors in the image plane, using random patch assignment to seed the initial matching. CSH relies on hashing to seed the initial patch matching and on image coherence to propagate good matches. In addition, hashing lets it propagate information between patches with similar appearance (i.e., map to the same bin). This way, information is propagated much faster because it can use similarity in appearance space or neighborhood in the image plane. As a result, CSH is at least three to four times faster than PatchMatch and more accurate, especially in textured regions, where reconstruction artifacts are most noticeable to the human eye. We verified CSH on a new, large scale, data set of 133 image pairs and experimented on several extensions, including: k nearest neighbor search, the addition of rotation and matching three dimensional patches in videos. PMID:26372204
Coherence and Sense of Coherence
DEFF Research Database (Denmark)
Dau, Susanne
2014-01-01
of coherence is both related to conditional matters as learning environments, structure, clarity and linkage but also preconditioned matters and prerequisites among participants related to experiences and convenience. It is stressed that this calls for continuous assessment and reflections upon these terms...... and conditions if the student shall be able acquire the necessary competencies....
Anomalous inverse bremsstrahlung heating of laser-driven plasmas
Kundu, Mrityunjay
2016-05-01
Absorption of laser light in plasma via electron-ion collision (inverse bremsstrahlung) is known to decrease with the laser intensity as I 0 -3/2 or with the electron temperature as T e -3/2 where Coulomb logarithm ln Λ = 0.5ln(1 + k 2 min/k 2 max) in the expression of electron-ion collision frequency v ei is assumed to be independent of ponderomotive velocity v 0 = E0/ω which is unjustified. Here k -1 min = v th/max(ω, ω p), and k -1 max = Z/v 2 th are maximum and minimum cut-off distances of the colliding electron from the ion, v th = √T e is its thermal velocity, ω, ω p are laser and plasma frequency. Earlier with a total velocity v = (v 2 0 + v 2 th)1/2 dependent ln Λ(v) it was reported that v ei and corresponding fractional laser absorption (α) initially increases with increasing intensity, reaches a maximum value, and then fall according to the conventional I 0 -3/2 scaling. This anomalous increase in v ei and α may be objected due to an artifact introduced in ln Λ(v) through k-1 min ∝ v. Here we show similar anomalous increase of v ei and α versus I 0 (in the low temperature and under-dense density regime) with quantum and classical kinetic models of v ei without using ln Λ, but a proper choice of the total velocity dependent inverse cut-off length kmax -1 ∝ v 2 (in classical case) or kmax ∝ v (in quantum case). For a given I 0 15 eV, anomalous growth of vei and a disappear. The total velocity dependent k max in kinetic models, as proposed here, may explain anomalous increase of a with I 0 measured in some earlier laser-plasma experiments. This work may be important to understand collisional absorption in the under-dense pre-plasma region due to low intensity pre-pulses and amplified spontaneous emission (ASE) pedestal in the context of laser induced inertial confinement fusion.
Galloway, R K; MacKinnon, A L; Brown, J C
2010-01-01
Most theoretical descriptions of the production of solar flare bremsstrahlung radiation assume the collision of dilute accelerated particles with a cold, dense target plasma, neglecting interactions of the fast particles with each other. This is inadequate for situations where collisions with this background plasma are not completely dominant, as may be the case in, for example, low-density coronal sources. We aim to formulate a model of a self-interacting, entirely fast electron population in the absence of a dense background plasma, to investigate its implications for observed bremsstrahlung spectra and the flare energy budget. We derive approximate expressions for the time-dependent distribution function of the fast electrons using a Fokker-Planck approach. We use these expressions to generate synthetic bremsstrahlung X-ray spectra as would be seen from a corresponding coronal source. We find that our model qualitatively reproduces the observed behaviour of some flares. As the flare progresses, the model's...
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.)
Electron spectroscopy at the high-energy endpoint of electron-nucleus bremsstrahlung
Energy Technology Data Exchange (ETDEWEB)
Hillenbrand, Pierre-Michel [GSI Darmstadt (Germany); Univ. Giessen (Germany); Hagmann, Siegbert [GSI Darmstadt (Germany); Univ. Frankfurt (Germany); Banas, Dariusz [Univ. Kielce (Poland); Brandau, Carsten [Extreme Matter Institute Darmstadt (Germany); Univ. Giessen (Germany); Doerner, Reinhard [Univ. Frankfurt (Germany); De Filippo, Enrico [INFN Catania (Italy); Gumberidze, Alexandre [Extreme Matter Institute Darmstadt (Germany); Guo, Dalong [IMP Lanzhou (China); Univ. Beijing (China); Jakubassa-Amundsen, Doris [Univ. Muenchen (Germany); Lestinsky, Michael; Spillmann, Uwe [GSI Darmstadt (Germany); Litvinov, Yuri [GSI Darmstadt (Germany); Univ. Heidelberg (Germany); Mueller, Alfred; Schippers, Stefan [Univ. Giessen (Germany); Rothard, Hermann [CIRIL GANIL Caen (France); Surzhykov, Andrey [Helmholtz-Institut Jena (Germany); Trotsenko, Sergey [GSI Darmstadt (Germany); Helmholtz-Institut Jena (Germany); Voitkiv, Alexander [MPI-K Heidelberg (Germany); Yerokhin, Vladimir [Petersburg State Univ. (Russian Federation); Stoehlker, Thomas [GSI Darmstadt (Germany); Helmholtz-Institut Jena (Germany); Univ. Jena (Germany)
2014-07-01
The high-energy endpoint of electron-nucleus bremsstrahlung has been studied in inverse kinematics: For collisions U{sup 88+}+N{sub 2} → U{sup 88+}+[N{sub 2}{sup +}]{sup *} + e{sup -} + γ the energy distribution of electrons scattered under θ{sub e}{sup lab} = 0 {sup circle} with v{sub e} ∼ v{sub proj} was measured coincident with the bremsstrahlung photons emitted under various angles θ{sub γ}{sup lab}. The triple-differential cross sections provide a stringent test for the fully relativistic theory of electron-nucleus bremsstrahlung. Furthermore the studied process, also termed radiative electron capture to continuum RECC, was compared to the competing processes of non-radiative electron capture to continuum ECC and the electron loss to continuum ELC.
ELBA, Bremsstrahlung Dose from Isotropic Electron Flux on Plane Al Shield
International Nuclear Information System (INIS)
1 - Description of problem or function: ELBA takes an incident isotropic electron flux with a given differential energy spectrum and calculates the dose rate received from Bremsstrahlung produced in a plane aluminium shield placed in front of the receiver. There is an option to also calculate the electron dose rate from the same source. 2 - Method of solution: The electron differential spectrum as a function of depth is inferred by assuming that electrons travel straight ahead and that distance travelled and energy are related by a range-energy relationship. The electron dose rate at a given depth is calculated by integrating, over energy and direction, the product of the electron flux, the stopping power, and the appropriate flux- to-dose rate conversion factor. The Bremsstrahlung source is assumed to be plane and isotropic at a given depth. This source is defined as the integral over energy and direction of the product of photon energy, the differential Bremsstrahlung spectrum from electrons of a given energy, and the electron flux differential spectrum. The differential Bremsstrahlung spectrum is derived from the Born approximation cross section multiplied by a correction factor. The Bremsstrahlung dose rate is obtained by integrating, over photon energy and slab volume, the product of the Bremsstrahlung source, photon energy flux-to-dose rate conversion factor, buildup factor, and attenuation kernel. The buildup factor assumed is a plane isotropic buildup factor generate by Monte Carlo calculations. The integrations are performed by evaluating the integrand at the midpoint of each integration step, multiplying by the step width, and summing the result. The incident electron spectrum, dose rate conversion factors, and range formula coefficients are input by the user. The buildup factor information is contained in three Data statements in subroutine BURP. 3 - Restrictions on the complexity of the problem: There are limitations on the dimensions of certain arrays
Evaluation of bremsstrahlung contribution to photon transport in coupled photon-electron problems
Fernández, Jorge E.; Scot, Viviana; Di Giulio, Eugenio; Salvat, Francesc
2015-11-01
The most accurate description of the radiation field in x-ray spectrometry requires the modeling of coupled photon-electron transport. Compton scattering and the photoelectric effect actually produce electrons as secondary particles which contribute to the photon field through conversion mechanisms like bremsstrahlung (which produces a continuous photon energy spectrum) and inner-shell impact ionization (ISII) (which gives characteristic lines). The solution of the coupled problem is time consuming because the electrons interact continuously and therefore, the number of electron collisions to be considered is always very high. This complex problem is frequently simplified by neglecting the contributions of the secondary electrons. Recent works (Fernández et al., 2013; Fernández et al., 2014) have shown the possibility to include a separately computed coupled photon-electron contribution like ISII in a photon calculation for improving such a crude approximation while preserving the speed of the pure photon transport model. By means of a similar approach and the Monte Carlo code PENELOPE (coupled photon-electron Monte Carlo), the bremsstrahlung contribution is characterized in this work. The angular distribution of the photons due to bremsstrahlung can be safely considered as isotropic, with the point of emission located at the same place of the photon collision. A new photon kernel describing the bremsstrahlung contribution is introduced: it can be included in photon transport codes (deterministic or Monte Carlo) with a minimal effort. A data library to describe the energy dependence of the bremsstrahlung emission has been generated for all elements Z=1-92 in the energy range 1-150 keV. The bremsstrahlung energy distribution for an arbitrary energy is obtained by interpolating in the database. A comparison between a PENELOPE direct simulation and the interpolated distribution using the data base shows an almost perfect agreement. The use of the data base increases
Complete gluon bremsstrahlung corrections to the process b -> s l+ l-
Asatryan, H. H.; Asatrian, H. M.; Greub, C.; M. Walker
2002-01-01
In a recent paper, we presented the calculation of the order (alpha_s) virtual corrections to b->s l+ l- and of those bremsstrahlung terms which are needed to cancel the infrared divergences. In the present paper we work out the remaining order(alpha_s) bremsstrahlung corrections to b->s l+ l- which do not suffer from infrared and collinear singularities. These new contributions turn out to be small numerically. In addition, we also investigate the impact of the definition of the charm quark ...
Complete gluon bremsstrahlung corrections to the process b -> s l+ l-
Asatryan, H H; Greub, Christoph; Walker, M
2002-01-01
In a recent paper, we presented the calculation of the order (alpha_s) virtual corrections to b->s l+ l- and of those bremsstrahlung terms which are needed to cancel the infrared divergences. In the present paper we work out the remaining order(alpha_s) bremsstrahlung corrections to b->s l+ l- which do not suffer from infrared and collinear singularities. These new contributions turn out to be small numerically. In addition, we also investigate the impact of the definition of the charm quark mass on the numerical results.
Nuclear structure effects in high-energy bremsstrahlung from spin-0 and spin-1/2 nuclei
Energy Technology Data Exchange (ETDEWEB)
Jakubassa-Amundsen, Doris [University of Munich (Germany)
2014-07-01
Bremsstrahlung from relativistic spin-polarized electrons colliding with inert nuclei is calculated by taking into account the nuclear form factors and the kinematical recoil. For the spin-1/2 nuclei additional contributions from the anomalous magnetic moment and the dynamical recoil are considered. Electron bremsstrahlung is described with the help of semirelativistic wavefunctions while nuclear bremsstrahlung, when present, is treated within the Born approximation. The triply differential bremsstrahlung cross section is integrated over the electron scattering angle to study the polarization correlations between the beam electron and the emitted photon. Results are shown for 20-120 MeV electrons colliding with protons, 19F, 64Zn and 89Y. It is also attempted to explain the background in electron spectra from nuclear excitation in terms of bremsstrahlung. As an example the 180 degree spectrum from exciting the giant M2 resonance in 90Zr by 42.7 MeV electrons is analyzed.
Pairing Learners in Pair Work Activity
Storch, Neomy; Aldosari, Ali
2013-01-01
Although pair work is advocated by major theories of second language (L2) learning and research findings suggest that pair work facilitates L2 learning, what is unclear is how to best pair students in L2 classes of mixed L2 proficiency. This study investigated the nature of pair work in an English as a Foreign Language (EFL) class in a college in…
Virtual-bremsstrahlung production in proton-proton scattering and proton-deuteron capture
Messchendorp, Johannes Gerhardus
1999-01-01
The well-known coupling of the photon with the nucleon together with the fact that photons (or any electromagnetic (e.m.) probe) interact only relatively weakly with nucleons, make bremsstrahlung production an ideal tool to study details of the nucleon-nucleon interaction. In this thesis dilepton pr
EFFECTS OF MESON-DECAY DIAGRAMS IN PROTON-PROTON BREMSSTRAHLUNG
DEJONG, F; NAKAYAMA, K
1995-01-01
We investigate the effect of meson-decay diagrams on the proton-proton bremsstrahlung process. We explicitly include short-range correlations by calculating single- and double-scattering diagrams using an NN T-matrix interaction. We find that in general these diagrams interfere destructively with th
Absolute intensity of internal bremsstrahlung from the electron capture decay of 125I
International Nuclear Information System (INIS)
The absolute intensity of the internal bremsstrahlung spectrum accompanying the electron capture decay of 125I has been measured and compared to the recent calculation of Suric et al. The measured intensity above the 1s end point is found to be (86±10)% of the calculated intensity
THE BREMSSTRAHLUNG ISOCHROMAT SPECTRA OF D(0) TRANSITION-METAL OXIDES
SORIANO, L; ABBATE, M; ALDERS, D; SANZ, JM
1994-01-01
We present and discuss the bremsstrahlung isochromat spectra (BIS) of four d0 transition-metal oxides, namely ZrO2, HfO2, Nb2O5, and Ta2O5. The spectra are related to the density of unoccupied states in the conduction band. They give directly the magnitude of the crystal-field splitting and the disp
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....
Strong linear polarization of bremsstrahlung emissivity in photospheres of magnetic white dwarfs
Energy Technology Data Exchange (ETDEWEB)
Bubukina, I I; Koryagin, S A, E-mail: koryagin@appl.sci-nnov.r [Institute of Applied Physics of the Russian Academy of Sciences, 46 Uljanova str., Nizhny Novgorod 603950 (Russian Federation)
2009-06-01
We discuss the strong linear polarization and the appreciable decrease of the bremsstrahlung emissivity at frequencies below the electron cyclotron frequency (infrared wave band) in the photospheres of the isolated magnetic white dwarfs. In the photospheres of strongly magnetized white dwarfs (B > 10{sup 7} G, T approx 10{sup 4} K), the electron's Larmor radius becomes smaller than the characteristic impact parameter of close Coulomb collisions in a non-magnetized plasma. Thus, the cyclotron period of the electron becomes smaller than the duration of all distant collisions and of most close collisions. The magnetic field effectively 'freezes' the electron motion in the plane transverse to the magnetic field lines. The resulting motion is nearly one-dimensional and parallel to the magnetic field, inducing a strong linear polarization of the bremsstrahlung emission. Being attached to a magnetic field line, an electron cannot approach an ion as closely as it does in the case in which the magnetic field is absent. Thus, the bremsstrahlung emissivity appreciably decreases. We analytically compute an approximation to the spectrum of the strongly linear polarized bremsstrahlung emissivity at the frequencies below the electron cyclotron frequency.
Experimental bremsstrahlung yields for MeV proton bombardment of beryllium and carbon
Energy Technology Data Exchange (ETDEWEB)
Cohen, David D. [Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 (Australia)], E-mail: dcz@ansto.gov.au; Stelcer, Eduard; Siegele, Rainer; Ionescu, Mihail; Prior, Michael [Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 (Australia)
2008-04-15
Experimental bremsstrahlung yields for 2, 3 and 4 MeV protons on thin beryllium and carbon targets have been measured. The yields have been corrected for detector efficiency, self-absorption in the target and fitted to 9th order polynomials over the X-ray energy range 1-10 keV for easy comparison with theoretical calculations.
Bright-dark incoherently coupled soliton pairs composed of spatially incoherent solitons
Institute of Scientific and Technical Information of China (English)
Jielong Shi; Yuanyuan Chen; Qi Wang
2005-01-01
It is shown that bright-dark incoherently coupled soliton pairs can exist in photorefractive (PR) crystals under steady-state conditions, each soliton constituent of which is spatially incoherent. The characteristics of bright-dark incoherently coupled soliton pairs are studied by the coherent density approach and the intensity expressions of soliton pairs are obtained. The propagation properties of coherent components of each constituent in a soliton pair are also discussed in detail.
Institute of Scientific and Technical Information of China (English)
何明烈; 戢焕奇
2008-01-01
Based on the investigation of the origin and definition of topic as well as the classification of textual coherence, this paper ana-lyzes the function of topic to non-coherence, imphcit coherence and explicit coherence, and concludes that topic relevance is the primary cri-terion for textual coherence.
Pair Creation at Large Inherent Angles
Energy Technology Data Exchange (ETDEWEB)
Chen, P.; Tauchi, T.; Schroeder, D.V.; /SLAC
2007-04-25
In the next-generation linear colliders, the low-energy e{sup +}e{sup -} pairs created during the collision of high-energy e{sup +}e{sup -} 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[1]. At energies where the beamstrahlung parameter {Upsilon} lies approximately in the range 0.6 {approx}< {Upsilon} {approx}< 100, pair creation from the beamstrahlung photons is dominated by a coherent process, first noted by Chen[2]. 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. One source of transverse momentum is from the kick by the field of the oncoming beam which results in an outcoming angle {theta} {proportional_to} 1/{radical}x, where x is the fractional energy of the particle relative to the initial beam particle energy[2,3]. As was shown in Ref. 131, there in fact exists an energy threshold for the coherent pairs, where x{sub th} {approx}> 1/2{Upsilon}. Thus within a tolerable exiting angle, there exists an upper limit for {Upsilon} where all coherent pairs would leave the detector through the exhaust port[4]. A somewhat different analysis has been done by Schroeder[5]. In the next generation of linear colliders, as it occurs, the coherent pairs can be exponentially suppressed[2] by properly choosing the {Upsilon}({approx}< 0.6). When this is achieved, the incoherent pairs becomes dominant. Since the central issue is the transverse momentum for particles with large angles, we 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. This issue was
Revealing Hidden Coherence in Partially Coherent Light
Svozilík, Jiří; Peřina, Jan; Torres, Juan P
2015-01-01
The coherence of a system can be ultimately related to the nature of its correlations with the surroundings (outside world). The system can be, for instance, the polarization of a photon, which forms part of a polarization-entangled two-photon state, or the spatial shape of a coherent beam, where each spatial mode bears different polarizations. Whereas a local unitary transformation of the system do not affect its coherence, global unitary transformations modifying both the system and its surroundings can enhance its coherence transforming mutual correlations into coherence. The question naturally arises of what is the best measure that quantifies the correlations that can be turned into coherence, and how much coherence can be extracted. We answer both questions, and illustrate its application for some typical simple systems, with the aim at illuminating the general concept of enhancing coherence by modifying correlations.
Jakubassa-Amundsen, D H
2016-01-01
Inspired by the work of Pratt and coworkers on a sum rule for the polarization correlations in electron bremsstrahlung when the outgoing electron is not observed, we derive the corresponding sum rule for the elementary process of bremsstrahlung. This sum rule is valid for arbitrary electron wavefunctions provided the electron is emitted in the reaction plane. The numerical evaluation of this sum rule within the Dirac partial-wave theory for bare inert spin-zero nuclei and collision energies in the range of 1-10 MeV reveals violations for high nuclear charge. Such violations serve as a measure of the inaccuracies in the bremsstrahlung calculations.
Wave "Coherency" and Implications for Wave-Particle Interactions
Tsurutani, Bruce; Singh Lakhina, Gurbax; Bhanu, Remya; Lee, Lou-Chuang
2016-07-01
Wave "coherency" was introduced in 2009 by Tsurutani et al. (JGR, doi:10.1029/2008JA013353, 2009) to describe the waves detected in the ~10 to 100 ms duration subelements which are the fundamental components of ~0.1 to 0.5 s chorus "elements". In this talk we will show examples of what we mean by coherency, quasi-coherency and incoherency for a variety of magnetospheric plasma waves. We will show how to measure coherency/quasicoherency quantitatively for electromagnetic whistler mode chorus, electromagnetic ion cyclotron (EMIC) waves, plasmaspheric hiss and linearly polarized magnetosonic waves. If plasma waves are coherent, their interactions with resonant particles will be substantially different. Specific examples will be used to show that the pitch angle scattering rates for energetic charged particles is roughly 3 orders of magnitude faster than the Kennel-Petschek diffusion (which assumes incoherent waves) rate. We feel that this mechanism is the only one that can explain ~ 0.1- 0.5 s bremsstrahlung x-ray microbursts.
Asher, D. J.; Clube, S. V. M.; Napier, W. M.; Steel, D. I.
We review the theoretical and observational evidence that, on timescales relevant to mankind, the prime collision hazard is posed by temporally correlated impacts (coherent catastrophism, Δt ˜ 10 2-10 4 yr) rather than random ones (stochastic catastrophism, Δt ˜ 10 5-10 8 yr). The mechanism whereby coherent incursions into and through the terrestrial atmosphere occur is described as being the result of giant cometary bodies arriving in orbits with perihelia in the inner solar system. Hierarchical fragmentation of such large (100 km-plus) bodies — due to thermal stresses near perihelion, collisions in the asteroid belt, or passages through the Jovian Roche radius — results in numerous ˜kilometre-sized objects being left in short-period orbits, and appearing in telescopic searches as Apollo-type asteroids. Many more smaller objects, in the 10-100 metre size range and only recently observed, by the Spacewatch team, are expected to be in replenished clusters in particular orbits as a result of continuing disintegrations of large, differentiated, cometary objects. Gravitational perturbations by Jupiter bring these clusters around to have a node at 1 AU in a cyclic fashion, leading to impacts at certain times of year every few years during active periods lasting a few centuries, such periods being separated by intervals of a few millennia. Furthermore, fragmentations within the hierarchy result in significant bombardment commensurabilities ( Δt ˜ 10-10 2 yr) during active periods occurring at random intervals ( Δt ˜ 10 2-10 3 yr). It appears that the Earth has been subject to such impacts since the break-up of such a comet ˜2×10 4 years ago; currently we are not passing through a high-risk epoch, although some phenomena originating in the products of this break-up have been observed in the 20th century. This most recent hierarchical disintegration, associated with four well-known meteor showers and termed the Taurid Complex, is now recognized as resulting
Measurement of gas Bremsstrahlung at the Pohang Light Source by using a CeF3 scintillator
International Nuclear Information System (INIS)
We have measured the gas Bremsstrahlung photon energy from the 2.5-GeV electron storage ring at the Pohang Light Source (PLS). Gas Bremsstrahlung was generated in the straight section of the beam-diagnosis beamline 1C1 with an effective length of 5.3 m. We present the measurement results for the Bremsstrahlung photon energy spectrum and the photon flux, which were obtained by using a CeF3 calorimeter. The calorimeter consisted of nine CeF3 blocks, each being 3.3 x 3.3 x 33 cm3, stacked into a 3 x 3 array. The Bremsstrahlung photon flux above 40 MeV was measured to be 218 s-1 at an electron beam current of 180 mA.
Pair production in classical Stueckelberg-Horwitz-Piron electrodynamics
Land, Martin
2016-01-01
In this paper we calculate pair production from bremsstrahlung as a classical effect in Stueckelberg-Horwitz-Piron electrodynamics. In this framework, worldlines are traced out dynamically through the evolution of events $x^\\mu(\\tau)$ parameterized by a chronological time $\\tau$ that is independent of the spacetime coordinates. These events, defined in an unconstrained 8D phase space, interact through five $\\tau$-dependent gauge fields induced by the event evolution. The resulting theory differs in its underlying mechanics from conventional electromagnetism, but coincides with Maxwell theory in an equilibrium limit. In particular, the total mass-energy-momentum of particles and fields is conserved, but the mass-shell constraint is lifted from individual interacting events, so that the standard Feynman-Stueckelberg interpretation of pair creation/annihilation is implemented in classical mechanics.
Roshan, Hoda Rezaei; Mahmoudian, Babak; Gharepapagh, Esmaeil; Azarm, Ahmadreza; Islamian, Jalil Pirayesh
2016-02-01
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 31.8mm 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 (2.35-3.3mm) 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 3.3mm. Geometry of the ME parallel-hole collimator and energy
Krychowiak, M.; König, R.; Klinger, T.; Fischer, R.
2004-11-01
At the stellarator Wendelstein 7-AS (W7-AS) a spectrally resolving two channel system for the measurement of line-of-sight averaged Zeff values has been tested in preparation for its planned installation as a multichannel Zeff-profile measurement system on the stellarator Wendelstein 7-X (W7-X) which is presently under construction. The measurement is performed using the bremsstrahlung intensity in the wavelength region of ultraviolet to near infrared. The spectrally resolved measurement allows to eliminate signal contamination by line radiation. For statistical data analysis a procedure based on Bayesian probability theory has been developed. With this method it is possible to estimate the bremsstrahlung background in the measured signal and its error without the necessity to fit the spectral lines. For evaluation of the random error in Zeff the signal noise has been investigated. Furthermore, the linearity and behavior of the charge-coupled device detector at saturation has been analyzed.
Experimental and analytical study of the bremsstrahlung radiation production at low energies
International Nuclear Information System (INIS)
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)
Tsechanski, A.; Bielajew, A. F.; Archambault, J. P.; Mainegra-Hing, E.
2016-01-01
A new "one-stage" approach for production of 99Mo 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 99Mo via the photoneutron reaction 100Mo(γ,n)99Mo. 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 r0) W target, for target thickness z > 1.84r0, where r0 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 r0) for target thickness case: z ⩾ 2.0r0. It is shown for the one-stage approach with thicknesses of (1.84-2.0)r0, that the 99Mo-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 r0) in the traditional two-stage approach (W converter and separate 99Mo 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 99Mo-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 for the one-stage approach of three enriched 100Mo-targets of a 2 cm diameter and
Effect of Degenerated Particles on Internal Bremsstrahlung of Majorana Dark Matter
Okada, Hiroshi
2014-01-01
Gamma-ray generated by annihilation or decay of dark matter can be its smoking gun signature. In particular, gamma-ray coming from internal bremsstrahlung of dark matter is promising since it can be a leading emission of sharp gamma-ray. However if thermal production of Majorana dark matter is considered, the derived cross section for internal bremsstrahlung becomes too small to be observed by future gamma-ray experiments. We consider a framework to achieve an enhancement of the cross section by taking into account degenerated particles with dark matter. We find that the enhancement of about order one is possible without conflict with the dark matter relic density. Due to the enhancement, it would be tested by the future experiments such as GAMMA-400 and CTA.
International Nuclear Information System (INIS)
A method is described for determining an effective, depth dose consistent bremsstrahlung spectra for high-energy photon beams using depth dose curves measured in water. A simple, analytical model with three parameters, together with the nominal accelerating potential is used to characterise the bremsstrahlung spectra. The model is used to compute weights for depth dose curves from monoenergetic photons. These monoenergetic depth doses, calculated with the convolution method from Monte Carlo generated point spread functions (PSF), are added to yield the pure photon depth dose distribution. The parameters of the analytical spectrum model are determined using an iterative technique to minimise the difference between calculated and measured depth dose curves. The influence from contaminant electrons is determined from the difference between the calculated and the measured depth dose. (author)
International Nuclear Information System (INIS)
An indigenous setup for studying the process of atomic-field Bremsstrahlung produced from the interaction of keV electrons with a solid or a gaseous target has been developed and described. The setup consists of a high-vacuum scattering chamber, a home-built keV electron gun with a replaceable tungsten filament cathode, an isolated floating high-voltage control unit, signal processing electronic modules and a data-acquisition system comprising of an IBM PC/XT 4-K multichannel analyser. The performance of the setup has been tested and used for accumulating data for Bremsstrahlung spectra from 7.0 keV electrons incident on thin Ag and Au targets. These spectra have been analyzed and discussed in light of the semiclassical and the quantum calculations. The agreement between experiment and theory is found to be satisfactory within the experimental uncertainty of the measurements. (author). 10 refs., 5 figs., 1 tab
Investigation of the partner-potentials from supersymmetric quantum mechanics by bremsstrahlung
International Nuclear Information System (INIS)
With the explicit example of α + α scattering we emphasize the incompleteness of using just the on-shell properties in any inversion procedure. A deep, energy-independent and angular-momentum-independent effective local potential is constructed to reproduce the phase shifts from a single-configuration microscopic resonating-group method (RGM) calculation for α + α scattering up to E = 16 MeV. From this we derive its phase-shift-equivalent shallow supersymmetric partner-potentials by eliminating the bound states which are unphysical due to the Pauli principle. These deep and shallow potentials are used to calculate bremsstrahlung emission in α + α collision and compared with the results from RGM as a means to investigate their wave functions. While the bremsstrahlung cross sections from RGM and the deep potential resemble each other, those of the shallow potentials are distinctly different. (orig.)
Coherent analysis of quantum optical sideband modes
Huntington, E H; Robilliard, C; Ralph, T C
2005-01-01
We demonstrate a device that allows for the coherent analysis of a pair of optical frequency sidebands in an arbitrary basis. We show that our device is quantum noise limited and hence applications for this scheme may be found in discrete and continuous variable optical quantum information experiments.
Energy Technology Data Exchange (ETDEWEB)
Yu, S.-W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tobin, J. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chung, B. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2011-01-01
A new system for spin resolved photoelectron spectroscopy and bremsstrahlung isochromat spectroscopy has been built and commissioned at Lawrence Livermore National Laboratory for the investigation of the electronic structure of the actinides.Actinide materials are very toxic and radioactive and therefore cannot be brought to most general user facilities for spectroscopic studies. The technical details of the new system and preliminary data obtained therein will be presented and discussed.
Self-absorption correction factor for a sample excited by the bremsstrahlung radiation
Mandal, A C; Mitra, D; Sarkar, M; Bhattacharya, D P
2002-01-01
A method of calculating the self-absorption correction factor for fluorescent X-rays from a sample excited by the bremsstrahlung has been described. As a typical example, the correction factors for K subalpha of Si and Cu for different tube voltages have been calculated. Polynomial fit of the correction factor against the tube voltage in the range 10-100 kV has been given for both the elements.
The internal bremsstrahlung accompanying the β-dacay from 185W
International Nuclear Information System (INIS)
The internal bremsstrahlung (IB) spectrum accompanying the β-decay from 185W radionuclide has been measured. The obtained spectrum was analyzed into its constituting gamma lines taking into account all the proper corrections. The analyzed spectrum was compared with those theoretically calculated. The experimental results for the IB probability were found to be in good agreement with theoretical calculations especially with the shape corrected modified KUB theory of Nilsson up to 357.7 keV. (author)
Singh, Amrit; Dhaliwal, A S
2016-09-01
In the present paper, the formation of bremsstrahlung spectra by ordinary bremsstrahlung (OB) and polarization bremsstrahlung (PB) in metallic targets by (35)S beta particles has been investigated in the photon energy region of 1-100keV. From the experimental measurements and the theoretical results obtained from Elwert corrected (non-relativistic) Bethe Heitler (EBH) theory, modified Elwert factor (relativistic) (FmodBH) theories for OB and Avdonina and Pratt (FmodBH+PB) theory for total bremsstrahlung (BS) having the contribution of PB into OB, it has been found that the contribution of PB into BS in a target is limited to a low energy region only and also varies with the atomic number of target material. The FmodBH+PB theory is in agreement with the experimental results in low energy regions of the target, whereas at high energy region FmodBH is found to give better agreement. Further, the present experimental results indicate that the screening effects in the Coulombic bremsstrahlung process cannot be neglected in the high energy region, and the multiple scattering and secondary electron emissions effects in thick target are required to be taken into account in describing the bremsstrahlung process. PMID:27400163
Studies on Neutron, Photon (Bremsstrahlung and Proton Induced Fission of Actinides and Pre-Actinides
Directory of Open Access Journals (Sweden)
H. Naik
2015-08-01
Full Text Available We present the yields of various fission products determined in the reactor neutron, 3.7-18.1 MeV quasi-mono energetic neutron, 8-80 MeV bremsstrahlung and 20-45 MeV proton induced fission of 232Th and 238U using radiochemical and off-line beta or gamma ray counting. The yields of the fission products in the bremsstrahlung induced fission natPb and 209Bi with 50- 70 MeV and 2.5 GeV based on off-line gamma ray spectrometric technique were also presented. From the yields of fission products, the mass chains yields were obtained using charge distribution correction. From the mass yield distribution, the peak-to-valley (P/V ratio was obtained. The role of excitation energy on the peak-to-valley ratio and fine structure such as effect of shell closure proximity and even-odd effect of mass yield distribution were examined. The higher yields of the fission products around A=133-134, 138-140 and 143-144 and their complementary products explained from the nuclear structure effect and role of standard I and II mode of asymmetric fission. In the neutron, photon (bremsstrahlung and proton induced fission, the asymmetric mass distribution for actinides (Th, U and symmetric distribution for pre-actinides (Pb, Bi were explained from different type of potential fission barrier
International Nuclear Information System (INIS)
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 (Eγ > 30 MeV) emitted in nucleus-nucleus collisions. Photon and charged-particle production in four different heavy-ion reactions (Ar36 + Au197, Ag107, Ni58, C12 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)
Dose calculation and measurement for bremsstrahlung at BL18U beamline of SSRF
International Nuclear Information System (INIS)
Background: Gas bremsstrahlung is one of the most important radiation sources that needs to be taken into consideration for shielding design of beamlines at the third generation synchrotron radiation light source. Shanghai Synchrotron Radiation Facility (SSRF) is one of the third generation synchrotron radiation light source in the world. The Protein Micro-crystallography Beamline (BL18U) is one of the commissioning beamlines and is a representative insertion device beamline at SSRF. Purpose: Estimation of radiation dose induced by scattering bremsstrahlung and photoneutrons at BL18U. Methods: Dose rate distribution induced by scattering bremsstrahlung and photoneutrons at BL18U are performed by Monte Carlo simulation code FLUKA. The radiation dose was analyzed with the variation of slits size, beam current at storage ring and the vacuum. Dose rate of photons and photoneutrons at the outside of the optical enclosure of BL18U were measured by using high sensitivity photon and neutron monitors. Results: The measurement results show that the reliability of the simulation. Conclusion: The simulation and measurement methods presented in this study can be applied to evaluate the dose rate level of other beamline stations at SSRF, and provide references to the shielding design for the following beamlines at SSRF in the near future. (authors)
Optimal design of Anger camera for bremsstrahlung imaging: Monte Carlo evaluation.
Directory of Open Access Journals (Sweden)
Stephan eWalrand
2014-06-01
Full Text Available A conventional Anger camera is not adapted to bremsstrahlung imaging and, as a result, even using a reduced energy acquisition window, geometric x-rays represent less than 15% of the recorded events. This increases noise, limits the contrast, and reduces the quantification accuracy.Monte Carlo simulations of energy spectra showed that a camera based on a 30mm-thick BGO crystal and equipped with a high energy pinhole collimator is well adapted to bremsstrahlung imaging. The total scatter contamination is reduced by a factor ten versus a conventional NaI camera equipped with a high energy parallel hole collimator enabling acquisition using an extended energy window ranging from 50 to 350 keV. By using the recorded event energy in the reconstruction method, shorter acquisition time and reduced orbit range will be usable allowing the design of a simplified mobile gantry. This is more convenient for use in a busy catheterization room. After injecting a safe activity, a fast SPECT could be performed without moving the catheter tip in order to assess the liver dosimetry and estimate the additional safe activity that could still be injected.Further long running time Monte Carlo simulations of realistic acquisitions will allow assessing the quantification capability of such system. Simultaneously, a dedicated bremsstrahlung prototype camera reusing PMT-BGO blocks coming from a retired PET system is currently under design for further evaluation.
Verdoolaege, G.; Von Hellermann, M. G.; Jaspers, R.; Ichir, M. M.; Van Oost, G.
2006-11-01
The validation of diagnostic date from a nuclear fusion experiment is an important issue. The concept of an Integrated Data Analysis (IDA) allows the consistent estimation of plasma parameters from heterogeneous data sets. Here, the determination of the ion effective charge (Zeff) is considered. Several diagnostic methods exist for the determination of Zeff, but the results are in general not in agreement. In this work, the problem of Zeff estimation on the TEXTOR tokamak is approached from the perspective of IDA, in the framework of Bayesian probability theory. The ultimate goal is the estimation of a full Zeff profile that is consistent both with measured bremsstrahlung emissivities, as well as individual impurity spectral line intensities obtained from Charge Exchange Recombination Spectroscopy (CXRS). We present an overview of the various uncertainties that enter the calculation of a Zeff profile from bremsstrahlung date on the one hand, and line intensity data on the other hand. We discuss a simple linear and nonlinear Bayesian model permitting the estimation of a central value for Zeff and the electron density ne on TEXTOR from bremsstrahlung emissivity measurements in the visible, and carbon densities derived from CXRS. Both the central Zeff and ne are sampled using an MCMC algorithm. An outlook is given towards possible model improvements.
Photoelectric converters with quantum coherence
Su, Shan-He; Sun, Chang-Pu; Li, Sheng-Wen; Chen, Jin-Can
2016-05-01
Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nanosized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency ηCA. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We show that, by adopting a pair of suitable degenerate states, quantum coherences induced by the couplings of QDs to sunlight and fermion baths can coexist steadily in nanoelectronic systems. Our analysis indicates that the efficiency at maximum power is no longer limited to ηCA through manipulation of carefully controlled quantum coherences.
Photoelectric converters with quantum coherence.
Su, Shan-He; Sun, Chang-Pu; Li, Sheng-Wen; Chen, Jin-Can
2016-05-01
Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nanosized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency η_{CA}. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We show that, by adopting a pair of suitable degenerate states, quantum coherences induced by the couplings of QDs to sunlight and fermion baths can coexist steadily in nanoelectronic systems. Our analysis indicates that the efficiency at maximum power is no longer limited to η_{CA} through manipulation of carefully controlled quantum coherences.
Powered Tate Pairing Computation
Kang, Bo Gyeong; Park, Je Hong
In this letter, we provide a simple proof of bilinearity for the eta pairing. Based on it, we show an efficient method to compute the powered Tate pairing as well. Although efficiency of our method is equivalent to that of the Tate pairing on the eta pairing approach, but ours is more general in principle.
Robustness of quantum critical pairing against disorder
Kang, Jian; Fernandes, Rafael M.
2016-06-01
The remarkable robustness of high-temperature superconductors against disorder remains a controversial obstacle towards the elucidation of their pairing state. Indeed, experiments report a weak suppression rate of the transition temperature Tc with disorder, significantly smaller than the universal value predicted by extensions of the conventional theory of dirty superconductors. However, in many high-Tc compounds, superconductivity appears near a putative magnetic quantum critical point, suggesting that quantum fluctuations, which suppress coherent electronic spectral weight, may also promote unconventional pairing. Here we investigate theoretically the impact of disorder on such a quantum critical pairing state, considering the coupling of impurities both to the low-energy electronic states and to the pairing interaction itself. We find a significant reduction in the suppression rate of Tc with disorder near the magnetic quantum critical point, shedding new light on the nature of unconventional superconductivity in correlated materials.
Generation of photon pairs using polarization-dependent two-photon absorption
Nakanishi, T; Kitano, M
2003-01-01
We propose a new method for generating photon pairs from coherent light using polarization-dependent two-photon absorption. We study the photon statistics of two orthogonally polarized modes by solving a master equation, and show that when we prepare a coherent state in one polarization mode, photon pairs are created in the other mode. The photon pairs have the same frequency as that of the incident light.
Superconductivity by means of the subquantum medium coherence
Agop, M.; Ioannou, P. D.; Nica, P.
2005-06-01
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. Then, usual mechanisms (as, for example, the exchange interaction used in the bipolaron theory) are reduced to the coherence on the subquantum medium, the superconducting pairs resulting as a one-dimensional projection of a fractal. The temperature dependences of the superconducting parameters (coherence length, critical speed, pair breaking time, carriers concentration, penetration depth, critical field, critical current) and the concordance with the experimental data and other theories are analyzed.
Entanglement Swapping of Pair Coherent States with Phase Decoherence
Institute of Scientific and Technical Information of China (English)
Taishi Okita; Toshiyuki Takagi
2009-01-01
We study the relation between the magnetic field structure and the induced electric-current distribution based on a cylindrical model composed of a uniform electrically conductive medium. When the time-varying magnetic fields are axisymmetrically applied in the axial direction of the model, the electric fields are induced around the central axis in accordance with Faradays law. We examine the eddy-current distributions generated by loop-coils with various geometries carrying an alternating electric current. It is shown that the radial structure of the induced fields can significantly be controlled by the loop coil geometry, which will be suitable for practical use especially in magnetic nerve stimulation on bioelectromagnetics, if we appropriately place the exciting coil with optimum geometry.
Partially coherent imaging and spatial coherence wavelets
Castaneda, R
2003-01-01
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.
International Nuclear Information System (INIS)
We present in this paper the influence of a synergistic radiation effect of both bremsstrahlung photons with maximum energy of 60 MeV and intense laser radiation (up to 60 KW cm−2) on the structural properties of carbon nanotubes (CNTs). The defect formation (damage) in CNTs under separate irradiations of 60 MeV bremsstrahlung photon or intense laser and their combined irradiations has been investigated by Raman spectroscopy. The experimental results show that (i) our obtained natural CNTs are multi-walled carbon nanotubes (MWCNTs) with a large number of structural defects, which are non-nanotube carbon impurities; (ii) the MWCNTs were not damaged by the irradiations of an intense laser and a bremsstrahlung photon beam with low electron fluency and the irradiation even leads to more purification/ordering; (iii) the reversible modification in non-irradiated and 60 MeV bremsstrahlung photon irradiated MWCNTs with variation of laser power density (LPD) have been received; (iv) the influence on the structural properties of MWCNTs induced by the combined irradiation was greater than the separate irradiation of a 60 MeV bremsstrahlung photon or intense laser radiation. The result also demonstrates that micro-Raman spectroscopy is a valuable, fast and non-destructive tool for the investigation of purification/ordering of CNTs
Energy Technology Data Exchange (ETDEWEB)
Tarvainen, Ollie [Los Alamos National Laboratory; Ropponen, Tommi [JYFL; Jones, Peter [JYFL; Kalvas, Taneli [JYFL
2008-01-01
Electron cyclotron resonance ion sources (ECRIS) are used to produce high charge state heavy ion beams for the use of nuclear and materials science, for instance. The most powerful ECR ion sources today are superconducting. One of the problems with superconducting ECR ion sources is the use of high radio frequency (RF) power which results in bremsstrahlung radiation adding an extra heat load to the cryostat. In order to understand the electron heating process and timescales in the ECR plasma, time evolution measurement of ECR bremsstrahlung was carried out. In the measurements JYFL 14 GHz ECRIS was operated in a pulsed mode and bremsstrahlung data from several hundred RF pulses was recorded. Time evolution of ion production was also studied and compared to one of the electron heating theories. To analyze the measurement data at C++ program was developed. Endpoint energies of the bremsstrahlung spectra as a function of axial magnetic field strength, pressure and RF power are presented and ion production timescales obtained from the measurements are compared to bremsstrahlung emission timescales and one of the stochastic heating theories.
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...
Spontaneous Pair Creation Revisited
Pickl, P
2006-01-01
Recently the so called Spontaneous Pair Creation of electron positron pairs in a strong external field has been rigorously established. We give here the heuristic core of the proof, since the results differ from those given in earlier works.
On the bremsstrahlung background correction to the high-energy Compton spectroscopy
Indian Academy of Sciences (India)
S Mathur; B L Ahuja
2005-07-01
A methodology for bremsstrahlung (BS) background correction to extract a true Compton profile in high-energy Compton scattering experiments is presented. The BS background profiles for Hg, computed within the Born approximation, are estimated for different values of incident energy. It is seen for the first time that the BS background contribution in high-energy Compton profile experiments like those employing third generation synchrotron radiation sources comes out to be significant and non-linear. Further, it is found that the incorporation of BS correction in data reduction of such an experiment performed on Hg at 662 keV energy helps in reconciliation of theory and experiment.
Pion mass effects on axion emission from neutron stars through NN bremsstrahlung processes
International Nuclear Information System (INIS)
The rates of axion emission by nucleon-nucleon bremsstrahlung are calculated with the inclusion of the full momentum contribution from a nuclear one pion exchange (OPE) potential. The contributions of the neutron-neutron (nn), proton-proton ( pp) and neutron-proton (np) processes in both the non-degenerate and degenerate limits are explicitly given. We find that the finite-momentum corrections to the emissivities are quantitatively significant for the non-degenerate regime and temperature-dependent, and should affect the existing axion mass bounds. The trend of these nuclear effects is to diminish the emissivities.
Emerging Hawking-Like Radiation from Gravitational Bremsstrahlung Beyond the Planck Scale
Ciafaloni, Marcello; Colferai, Dimitri; Veneziano, Gabriele
2015-10-01
We argue that, as a consequence of the graviton's spin-2, its bremsstrahlung in trans-Planckian-energy (E ≫MP ) gravitational scattering at small deflection angle can be nicely expressed in terms of helicity-transformation phases and their transfer within the scattering process. The resulting spectrum exhibits deeply sub-Planckian characteristic energies of order MP2/E ≪MP (reminiscent of Hawking radiation), a suppressed fragmentation region, and a reduced rapidity plateau, in broad agreement with recent classical estimates.
Emerging Hawking-Like Radiation from Gravitational Bremsstrahlung Beyond the Planck Scale
Ciafaloni, Marcello; Veneziano, Gabriele
2015-01-01
We argue that, as a consequence of the graviton's spin-2, its bremsstrahlung in trans-planckian-energy ($E\\gg M_P$) gravitational scattering at small deflection angle can be nicely expressed in terms of helicity-transformation phases and their transfer within the scattering process. The resulting spectrum exhibits deeply sub-planckian characteristic energies of order $M_P^2/E \\ll M_P$ (reminiscent of Hawking radiation), a suppressed fragmentation region, and a reduced rapidity plateau, in broad agreement with recent classical estimates.
Monte Carlo 20 and 45 MeV Bremsstrahlung and dose-reduction calculations
International Nuclear Information System (INIS)
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
Interference Peak in the Spectrum of Bremsstrahlung on Two Amorphous Targets
Bondarenco, M V
2014-01-01
We investigate the interference pattern in the spectrum of non-dipole bremsstrahlung on two amorphous foils. Apart from suppression at lowest $\\omega$, the spectrum exhibits an enhancement adjacent to it. In classical electrodynamics, the net effect of suppression and enhancement proves to be zero. We study the location and the origin of the spectral features, comparing predictions of full Moli\\`ere averaging with those of the Gaussian averaging with Coulomb corrections to the rms multiple scattering angle. Comparison with experimental data, and with previous theoretical predictions is presented.
Angular distribution of the bremsstrahlung emission during lower-hybrid current drive on PLT
International Nuclear Information System (INIS)
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
International Nuclear Information System (INIS)
Inverse bremsstrahlung absorption of the pump laser beam in a backward Raman amplifier over the round-trip light transit time through the subcritical density plasma can more than double the electron temperature of the plasma and produce time-varying axial temperature gradients. The resulting increased Landau damping of the plasma wave and detuning of the resonance can act to stabilize the pump against unwanted amplification of Langmuir noise without disrupting nonlinear amplification of the femtosecond seed pulse. Because the heating rate increases with the charge state Z, only low-Z plasmas (hydrogen, helium, or helium-hydrogen mixtures) will maintain a low enough temperature for efficient operation
Virtual- and bremsstrahlung corrections to b -> d l+ l- in the standard model
Asatrian, H. M.; Bieri, K.; Greub, C.; M. Walker
2003-01-01
We present the calculation of the virtual- and bremsstrahlung corrections of O(alpha_s) to the matrix elements . This is the missing piece in the NNLL results for various observables associated with the process B-> X_d l+ l-, like the branching ratio, the CP-rate asymmetry and the forward-backward asymmetry. This paper is an extension of analogous calculations done by some of us for the process B-> X_s l+ l-. As the contributions of the diagrams induced by the operators O_1^u and O_2^u with a...
High-power vircator in the regime of warm bremsstrahlung X-ray pulses generation
International Nuclear Information System (INIS)
The article presents the results of 2D self-consistent calculations of electron beam dynamics in vircator cell alongside with the resulting spectra of the accompanying microwave radiation. Also presented are the results of 1D calculations of electron beam dynamics with consideration for dissipation at the anode foil alongside with the resulting spectra of X-ray radiation. Being presented are the results of the first experiments aimed at investigation of bremsstrahlung X-ray radiation of the vircator for thin (10 μm, Ta) and thick (100 μm, Ta) anode foil
The development of a high power bremsstrahlung radiator for the production of monochromatic X-rays
International Nuclear Information System (INIS)
An experimental setup for the production of monochromatic X-ray beams tunable in the energy region between 75 KeV and 700 KeV was built at our facility. The concept is based on monochromatization of a broad energy bremsstrahlung spectrum by Laue diffraction on a curved single crystal and by selection of the desired energy with an appropriate slit system, 10.45 meters behind the crystal. The bremsstrahlung spectrum is created when accelerated electrons from a high power 20 kW linac lose energy in a radiator. In this study, the radiator has been optimized for the creation of a bremsstrahlung spectrum suitable for monochromatization with a crystal. Monte-Carlo Simulations (using the BEAM-EGS4 code) of electrons incident with different energies on a radiator with varying composition (aluminum, carbon and tantalum) and thickness were carried out. Furthermore a study of the thermal properties of these materials when being exposed to a high power electron beam was done. This lead to the remarkable conclusion that a thin radiator composed of a low Z material should be used. This result is quite surprising as usually a high Z material is used for efficient transformation of charged particle energy to bremsstrahlung photons. A low Z radiator however will create a less divergent photon beam, leading to more photons on the effective surface area of the crystal. A set of radiators was designed to have an optimal configuration for different monochromatic beams needed. Because only a small fraction of the electrons are stopped in these thin radiators, a cleaning magnet and a beamstop need to be inserted in the setup. Due to the high power of the electron beam on the one hand and its divergency after traversing the radiator on the other, a special magnet system had to be designed to remove the electrons from the photon beam. This was done by means of Monte-Carlo simulations and a ray tracing program. Finally it was estimated that, when using this new setup, the intensity of the
Coherent Theta^+ and Lambda(1520) photoproduction off the deuteron
Titov, A I; Daté, S; Ohashi, Y
2005-01-01
We analyze an effect of the coherent $\\Theta^+\\Lambda(1520)$ photoproduction in $\\gamma D$ interaction near the threshold. We demonstrate that the coherence effect becomes manifest in a comparison of the $nK^+$ invariant mass distribution when the $pK^-$ invariant equals the $\\Lambda(1520)$ mass. Our model calculations indicate a sizeable contribution of resonant and non-resonant background processes in the $\\gamma D\\to np K^+K^-$ reaction which generally exceed the contribution of the coherent resonant channel. However, we find that the coherent $\\Theta^+\\Lambda(1520)$ photoproduction is enhanced relative to the background processes in the forward hemisphere of the $pK^-$ pair photoproduction. Moreover, the coherence effect does not depend on the $\\Theta^+$ photoproduction amplitude and is defined by the probabilities of the $\\Lambda(1520)$ photoproduction and the $\\Theta^+\\to NK$ transition. Therefore, this coherence effect may be used as an independent method for studying the mechanism of $\\Theta^+$ produc...
Directory of Open Access Journals (Sweden)
Hui Xue
2016-04-01
Full Text Available Neutron-proton bremsstrahlung in intermediate energy nucleus–nucleus collisions is proposed as a possible probe to study the high-momentum component in nucleon momentum distribution of finite nucleus. Based on the Boltzmann–Uehling–Uhlenbeck (BUU transport model, the effects of high-momentum component on the production of bremsstrahlung photons in the reaction of C12+12C collisions at different incident beam energies are studied. It is found that the high-momentum component increases the high-energy bremsstrahlung photon production remarkably. Furthermore, the ratio of photon production at different incident beam energies is suggested as a potential observable to probe the high-momentum component in nucleon momentum distribution of finite nucleus.
Narrowband Photon Pair Source for Quantum Networks
Monteiro, F; Sanguinetti, B; Zbinden, H; Thew, R T
2013-01-01
We demonstrate a compact photon pair source based on a periodically poled lithium niobate nonlinear crystal in a cavity. The cavity parameters are chosen such that the emitted photon pair modes can be matched in the region of telecom ultra dense wavelength division multiplexing (U-DWDM) channel spacings. This approach provides efficient, low-loss, mode selection that is compatible with standard telecommunication networks. Photons with a coherence time of 8.6 ns (116 MHz) are produced and their purity is demonstrated. A source brightness of 134 pairs(s.mW.MHz)$^{-1}$ is reported. The high level of purity and compatibility with standard telecom networks is of great importance for complex quantum communication networks.
International Nuclear Information System (INIS)
Radiation hazard at synchrotron radiation (SR) beam lines of Indus-2 Synchrotron Radiation Source (SRS) consists of synchrotron radiation (SR) and Bremsstrahlung radiation (BR). These hazards were quantified experimentally in Lithography beam line (BL-07) of Indus-2 SRS. Measurement was performed during the initial trial operation of the beam line. Transmission of SR through the beam line was optimized by providing bump to the electron beam, prior to the measurement. Thin window ion chamber was used for the SR measurement in the direct beam. Ion current obtained is converted to exposure rate using a calibration factor obtained w.r.t. 60Co source. Copper absorber of 6 mm thick was used for eliminating SR contribution during BR dose measurement. The exposure rates obtained are 3.83E05 R/h-mA and 0.042 R/h-mA for SR and BR respectively. Energy of Bremsstrahlung radiation was also experimentally evaluated using attenuation technique. Details of these measurement and results are presented in this paper. (author)
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.
Photoactivation of the p-nucleus {sup 92}Mo with bremsstrahlung at ELBE
Energy Technology Data Exchange (ETDEWEB)
Erhard, M; Grosse, E; Junghans, A R; Klug, J; Nair, C; Rusev, G; Schilling, K D; Schwengner, R; Wagner, A, E-mail: erhard@pd.infn.i [Institut f. Strahlenphysik, Forschungszentrum Dresden-Rossendorf, 01314 Dresden (Germany)
2010-01-01
In nuclear network calculations especially the p-nucleus {sup 92}Mo is frequently underproduced. Since experimental data of the photodisintegration of {sup 92}Mo so far do not exist, it was necessary to measure the reaction yields with the photoactivation method using the brems-strahlung facility ELBE at FZ Dresden-Rossendorf. Also the reaction {sup 100}Mo({gamma},n) could be tested while irradiating Mo samples of natural composition. The photon fluence was measured with nuclear resonance fluorescence (NRF) of strong and well-known transitions in {sup 11}B. As a normalization standard the photoactivation reaction {sup 197}Au({gamma},n) was used. For the 65 s half-life of {sup 91m}Mo a fast pneumatic delivery was used. The photoactivation yields of the ({gamma},p) and ({gamma},n) reactions are compared to yield integrals of the bremsstrahlung spectral shape folded with the cross sections derived from Hauser-Feshbach nuclear model calculations using the TALYS program and cross sections from earlier experiments.
Photoactivation of the p-nucleus 92Mo with bremsstrahlung at ELBE
Erhard, M.; Grosse, E.; Junghans, A. R.; Klug, J.; Nair, C.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.
2010-01-01
In nuclear network calculations especially the p-nucleus 92Mo is frequently underproduced. Since experimental data of the photodisintegration of 92Mo so far do not exist, it was necessary to measure the reaction yields with the photoactivation method using the brems-strahlung facility ELBE at FZ Dresden-Rossendorf. Also the reaction 100Mo(γ,n) could be tested while irradiating Mo samples of natural composition. The photon fluence was measured with nuclear resonance fluorescence (NRF) of strong and well-known transitions in 11B. As a normalization standard the photoactivation reaction 197Au(γ,n) was used. For the 65 s half-life of 91mMo a fast pneumatic delivery was used. The photoactivation yields of the (γ,p) and (γ,n) reactions are compared to yield integrals of the bremsstrahlung spectral shape folded with the cross sections derived from Hauser-Feshbach nuclear model calculations using the TALYS program and cross sections from earlier experiments.
Effect of degenerate particles on internal bremsstrahlung of Majorana dark matter
Okada, Hiroshi; Toma, Takashi
2015-11-01
Gamma-rays induced by annihilation or decay of dark matter can be its smoking gun signature. In particular, gamma-rays generated by internal bremsstrahlung of Majorana and real scalar dark matter is promising since it can be a leading emission of sharp gamma-rays. However in the case of Majorana dark matter, its cross section for internal bremsstrahlung cannot be large enough to be observed by future gamma-ray experiments if the observed relic density is assumed to be thermally produced. In this paper, we introduce some degenerate particles with Majorana dark matter, and show they lead enhancement of the cross section. As a result, increase of about one order of magnitude for the cross section is possible without conflict with the observed relic density, and it would be tested by the future gamma-ray experiments such as GAMMA-400 and Cherenkov Telescope Array (CTA). In addition, the constraints of perturbativity, positron observation by the AMS experiment and direct search for dark matter are discussed.
Bremsstrahlung from nuclear scattering at low energy near a resonance. Final report
International Nuclear Information System (INIS)
The understanding of almost all low-energy reaction processes depends upon a distorted wave Born approximation (DWBA) analysis. DWBA procedures, in turn, depend crucially upon a correct optical model description of the projectile-target elastic scattering process. An assumption that the potential is local together with measurements of the elastic scattering data at all energies (0 -infinity) would completely determine that potential, including its off-shell or short-range properties. However, one does not have the luxury of knowing the elastic scattering phase shifts for all energies nor are we so naive as to believe that the potential is completely local. Thus, an alternative approach is called for. The present proposal describes a program to contribute to the general understanding of nuclear reactions by determining as many of the off-shell properties of the proton-nucleus interaction as possible through the study of the proton-nucleus bremsstrahlung process. We seek to establish the limits of validity of a model independent analysis of these reactions in the neighborhood of a resonance or a breakup threshold, and to utilize the differences between this analysis and the data to elucidate those off-shell constraints which any valid proton-nucleus model interaction must satisfy. The bremsstrahlung process provides a method for determining the off-shell properties of the proton-nucleus potential, and the Brooklyn College program offers a unique opportunity to measure these crucial aspects of the low energy proton-nucleus interaction. 18 references
Limits for an inverse bremsstrahlung origin of the diffuse Galactic soft gamma-ray emission
DEFF Research Database (Denmark)
Pohl, M.
1998-01-01
RXTE, GINGA, and OSSE observations have revealed an intense low-energy gamma-ray continuum emission from the Galactic plane, which is commonly interpreted as evidence for the possible existence of a strong flux of low-energy cosmic ray electrons. In this Paper I discuss the scenario of a hadronic...... 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...
A high-power vircator operating as an X-ray bremsstrahlung generator
International Nuclear Information System (INIS)
A vircator capable of generating high-power X-ray pulses due to the multiple transitions of electrons through a thin anode foil transparent to X radiation has been created and put into operation for the first time. The vircator is created on the basis of a direct-action electron accelerator supplied from an inductive energy storage operating with a plasma opening switch. Self-consistent two-dimensional simulations of the electron beam dynamics in the vircator chamber are performed, and the spectra of the generated microwave radiation are determined. Self-consistent one-dimensional simulations of the beam dynamics with allowance for electron scattering in the foil were also carried out, and the X-ray bremsstrahlung spectra were measured. Results are presented from the first experiments on the generation of X-ray bremsstrahlung in vircators with thin (10 μm) and thick (100 μm) tantalum anode foils. For a thin foil, the X-ray (Eγ > 30 keV) dose is eight times as high as that for a thick foil and the average photon energy is 30 keV (against 80 keV for a thick foil)
Shimony-Wolf states and hidden coherences in classical light
Eberly, J. H.
2015-10-01
The classical theory of polarisation coherence is briefly summarised and then extended. The extension is motivated by the recognition that the traditional theory of two-point coherence provides only what we identify as 'diagonal' correlation functions and their associated two-point coherence matrices. It is pointed out that a wider focus is possible when taking account of the three-sector vector space underlying all two-point coherences in classical optics. This reveals the possibility of observing a new type of 'off-diagonal' correlations that arise when the correlation functions under investigation are associated with points in two distinct vector spaces, pairs of points that are not analogous to the pairs of space points or time points that underlie traditional measures of spatial and temporal coherence. Quantum theory has experience with correlations engaging such 'cross-sector' coherences, for example in tests of Bell inequalities, and the quantum formulations are shown to be easily adopted by classical theory without incorporating quantum features in the optical signals. The familiar theory of classical coherence that is associated with the pioneering work of Emil Wolf is extended in conformance with three criteria advanced by Abner Shimony to obtain formulas for correlation functions and for the Bell measure ? of coherence. Values of ? greater than the standard upper limit ? are predicted for certain classical Shimony-Wolf fields, indicating strong cross-sector coherence, but only when standard measures of coherence such as degree of polarisation ? are minimised. Experimental results confirming the predictions for cross-sector coherence are exhibited.
Spin polarization transfer by the radical pair mechanism
Energy Technology Data Exchange (ETDEWEB)
Zarea, Mehdi, E-mail: m-zarea@northwestern.edu; Ratner, Mark A.; Wasielewski, Michael R. [Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113 (United States)
2015-08-07
In a three-site representation, we study a spin polarization transfer from radical pair spins to a nearby electron or nuclear spin. The quantum dynamics of the radical pair spins is governed by a constant exchange interaction between the radical pair spins which have different Zeeman frequencies. Radical pair spins can recombine to the singlet ground state or to lower energy triplet states. It is then shown that the coherent dynamics of the radical pair induces spin polarization on the nearby third spin in the presence of a magnetic field. The spin polarization transfer depends on the difference between Zeeman frequencies, the singlet and triplet recombination rates, and on the exchange and dipole-dipole interactions between the different spins. In particular, the sign of the polarization depends on the exchange coupling between radical pair spins and also on the difference between singlet and triplet recombination rate constants.
On -Coherent Endomorphism Rings
Indian Academy of Sciences (India)
Li-Xin Mao
2008-11-01
A ring is called right -coherent if every principal right ideal is finitely presented. Let $M_R$ be a right -module. We study the -coherence of the endomorphism ring of $M_R$. It is shown that is a right -coherent ring if and only if every endomorphism of $M_R$ has a pseudokernel in add $M_R; S$ is a left -coherent ring if and only if every endomorphism of $M_R$ has a pseudocokernel in add $M_R$. Some applications are given.
Application Coherency Manager Project
National Aeronautics and Space Administration — This proposal describes an Application Coherency Manager that implements and manages the interdependencies of simulation, data, and platform information. It will...
Eesley, G L
1981-01-01
Coherent Raman Spectroscopy provides a unified and general account of the fundamental aspects of nonlinear Raman spectroscopy, also known as coherent Raman spectroscopy. The theoretical basis from which coherent Raman spectroscopy developed is described, along with its applications, utility, and implementation as well as advantages and disadvantages. Experimental data which typifies each technique is presented. This book is comprised of four chapters and opens with an overview of nonlinear optics and coherent Raman spectroscopy, followed by a discussion on nonlinear transfer function of matter
Atomic Coherent Trapping and Properties of Trapped Atom
Institute of Scientific and Technical Information of China (English)
YANG Guo-Jian; XIA Li-Xin; XIE Min
2006-01-01
Based on the theory of velocity-selective coherent population trapping, we investigate an atom-laser system where a pair of counterpropagating laser fields interact with a three-level atom. The influence of the parametric condition on the properties of the system such as velocity at which the atom is selected to be trapped, time needed for finishing the coherent trapping process, and possible electromagnetically induced transparency of an altrocold atomic medium,etc., is studied.
Secondary bremsstrahlung and the energy-conservation aspects of kerma in photon-irradiated media
Kumar, Sudhir; Nahum, Alan E.
2016-02-01
Kerma, collision kerma and absorbed dose in media irradiated by megavoltage photons are analysed with respect to energy conservation. The user-code DOSRZnrc was employed to compute absorbed dose D, kerma K and a special form of kerma, K ncpt, obtained by setting the charged-particle transport energy cut-off very high, thereby preventing the generation of ‘secondary bremsstrahlung’ along the charged-particle paths. The user-code FLURZnrc was employed to compute photon fluence, differential in energy, from which collision kerma, K col and K were derived. The ratios K/D, K ncpt/D and K col/D have thereby been determined over a very large volumes of water, aluminium and copper irradiated by broad, parallel beams of 0.1 to 25 MeV monoenergetic photons, and 6, 10 and 15 MV ‘clinical’ radiotherapy qualities. Concerning depth-dependence, the ‘area under the kerma, K, curve’ exceeded that under the dose curve, demonstrating that kerma does not conserve energy when computed over a large volume. This is due to the ‘double counting’ of the energy of the secondary bremsstrahlung photons, this energy being (implicitly) included in the kerma ‘liberated’ in the irradiated medium, at the same time as this secondary bremsstrahlung is included in the photon fluence which gives rise to kerma elsewhere in the medium. For 25 MeV photons this ‘violation’ amounts to 8.6%, 14.2% and 25.5% in large volumes of water, aluminium and copper respectively but only 0.6% for a ‘clinical’ 6 MV beam in water. By contrast, K col/D and K ncpt/D, also computed over very large phantoms of the same three media, for the same beam qualities, are equal to unity within (very low) statistical uncertainties, demonstrating that collision kerma and the special type of kerma, K ncpt, do conserve energy over a large volume. A comparison of photon fluence spectra for the 25 MeV beam at a depth of ≈51 g cm-2 for both very high and very low charged-particle transport cut
Ordering states with coherence measures
Liu, C. L.; Yu, Xiao-Dong; Xu, G. F.; Tong, D. M.
2016-07-01
The quantification of quantum coherence has attracted a growing attention, and based on various physical contexts, several coherence measures have been put forward. An interesting question is whether these coherence measures give the same ordering when they are used to quantify the coherence of quantum states. In this paper, we consider the two well-known coherence measures, the l_1 norm of coherence and the relative entropy of coherence, to show that there are the states for which the two measures give a different ordering. Our analysis can be extended to other coherence measures, and as an illustration of the extension we further consider the formation of coherence to show that the l_1 norm of coherence and the formation of coherence, as well as the relative entropy of coherence and the coherence of formation, do not give the same ordering too.
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...
The origins of macroscopic quantum coherence in high temperature superconductivity
Energy Technology Data Exchange (ETDEWEB)
Turner, Philip, E-mail: ph.turner@napier.ac.uk [Edinburgh Napier University, 10 Colinton Road, Edinburgh EH10 5DT (United Kingdom); Nottale, Laurent, E-mail: laurent.nottale@obspm.fr [CNRS, LUTH, Observatoire de Paris-Meudon, 5 Place Janssen, 92190 Meudon (France)
2015-08-15
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
Secure pairing with biometrics
Buhan, I.R.; Boom, B.J.; Doumen, J.M.; Hartel, P.H.; Veldhuis, R.N.J.
2009-01-01
Secure pairing enables two devices that share no prior context with each other to agree upon a security association, which they can use to protect their subsequent communication. Secure pairing offers guarantees of the association partner identity and it should be resistant to eavesdropping and to a
Statistically normalized coherent change detection for synthetic aperture sonar imagery
G-Michael, Tesfaye; Tucker, J. D.; Roberts, Rodney G.
2016-05-01
Coherent Change Detection (CCD) is a process of highlighting an area of activity in scenes (seafloor) under survey and generated from pairs of synthetic aperture sonar (SAS) images of approximately the same location observed at two different time instances. The problem of CCD and subsequent anomaly feature extraction/detection is complicated due to several factors such as the presence of random speckle pattern in the images, changing environmental conditions, and platform instabilities. These complications make the detection of weak target activities even more difficult. Typically, the degree of similarity between two images measured at each pixel locations is the coherence between the complex pixel values in the two images. Higher coherence indicates little change in the scene represented by the pixel and lower coherence indicates change activity in the scene. Such coherence estimation scheme based on the pixel intensity correlation is an ad-hoc procedure where the effectiveness of the change detection is determined by the choice of threshold which can lead to high false alarm rates. In this paper, we propose a novel approach for anomalous change pattern detection using the statistical normalized coherence and multi-pass coherent processing. This method may be used to mitigate shadows by reducing the false alarms resulting in the coherent map due to speckles and shadows. Test results of the proposed methods on a data set of SAS images will be presented, illustrating the effectiveness of the normalized coherence in terms statistics from multi-pass survey of the same scene.
Nazaryan, T A; Hakobyan, A A; Adibekyan, V Zh; Kunth, D; Mamon, G A; Turatto, M; Aramyan, L S
2013-01-01
We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies. SN types are not correlated with the luminosity ratio of host and neighbor galaxies in pairs. The orientation of SNe with respect to the preferred direction toward neighbor galaxy is found to be isotropic and independent of kinematical properties of the galaxy pair.
Thick-target external-bremsstrahlung spectra of 147Pm and 35S β rays
Dhaliwal, A. S.; Powar, M. S.; Singh, M.
1993-08-01
External-bremsstrahlung spectra excited by soft β particles of 147Pm (Emaxβ=225 keV) and 35S (Emaxβ=167 keV) in targets of Al, Cu, Sn, and Pb have been studied. The experimental and theoretical results are compared in terms of the number of photons of energy k per m0c2 per unit photon yield to exclude the uncertainty in the source strength measurement and overcome the inherent inadequacy of the normalization procedure used by earlier workers. The results of present measurements for medium- and high-Z elements show better agreement with the theory of Tseng and Pratt [Phys. Rev. A 3, 1714 (1976)] than with Elwert's corrections [Ann. Phys. (N.Y.) 34, 78 (1939)] to the Bethe-Heitler theory [Proc. R. Soc. London Ser. A 14, 83 (1934)], particularly at the higher-energy ends. However, for low-Z elements, both theories are found to be adequate.
Fermi LAT Search for Internal Bremsstrahlung Signatures from Dark Matter Annihilation
Bringmann, Torsten; Ibarra, Alejandro; Vogl, Stefan; Weniger, Christoph
2012-01-01
A commonly encountered obstacle in indirect searches for galactic dark matter is how to disentangle possible signals from astrophysical backgrounds. Given that such signals are most likely subdominant, the search for pronounced spectral features plays a key role for indirect detection experiments; monochromatic gamma-ray lines or similar features related to internal bremsstrahlung, in particular, provide smoking gun signatures. We perform a dedicated search for the latter in the data taken by the Fermi gamma-ray space telescope during its first 43 months. To this end, we use a new adaptive procedure to select optimal target regions that takes into account both standard and contracted dark matter profiles. The behaviour of our statistical method is tested by a bootstrap analysis of the full sky data and found to reproduce the theoretical expectations very well. The limits on the dark matter annihilation cross-section that we derive are stronger than what can be obtained from the observation of dwarf galaxies a...
Aranha, R F; Soares, I Damião; Tonini, E V
2008-01-01
We examine the efficiency of gravitational bremsstrahlung production in the process of head-on collision of two boosted Schwarzschild black holes. We constructed initial data for the characteristic initial value problem in Robinson-Trautman spacetimes, that represent two instantaneously stationary Schwarzschild black holes in motion towards each other with the same velocity. The Robinson-Trautman equation was integrated for these initial data using a numerical code based on the Galerkin method. The final resulting configuration is a boosted black hole with Bondi mass greater than the sum of the individual mass of each initial black hole. Two relevant aspects of the process are presented. The first relates the efficiency $\\Delta$ of the energy extraction by gravitational wave emission to the mass of the final black hole. This relation is fitted by a distribution function of non-extensive thermostatistics with entropic parameter $q \\simeq 1/2$; the result extends and validates analysis based on the linearized t...
International Nuclear Information System (INIS)
Following Wilson's suggestion of electron acceleration by the electric fields in thunderclouds, a number of experiments were attempted to investigate whether or not energetic electrons and bremsstrahlung X-rays were generated by thunderstorm electric fields or lightning discharge processes. In recent years, enhanced radiation at high altitude has been detected in experiments using scintillation detectors on a jet and an artificial satellite, demonstrating that radiation is indeed associated with lightning activities. However there are few experimental reports of detection near the ground since Whitmire's investigation using thermoluminescent dosimeters (TLDs) in 1979. In winter, many thunderstorms occur on the west coast of Japan, and it has been suggested that gamma-ray dose may increase occasionally during winter thunderstorms. Recently, a gamma-ray dose enhancement which might be caused by the lightning activity was measured by TLDs and environmental radiation monitors around the site of the fast breeder reactor 'Monju', a nuclear power plant facing the Japan Sea. (author)
Jeffrey, Natasha
2011-01-01
This paper aims to study the polarization of hard X-ray (HXR) sources in the solar atmosphere, including Compton backscattering of photons in the photosphere (the albedo effect) and the spatial distribution of polarization across the source. HXR photon polarization and spectra produced via electron-ion bremsstrahlung are calculated from electron distributions typical for solar flares. Compton scattering and photoelectric absorption are then modelled using Monte Carlo simulations of photon transport in the photosphere. Polarization maps across HXR sources (primary and albedo components) for each of the modelled electron distributions are calculated at various source locations from the solar centre to the limb. We show that Compton scattering produces a distinct polarization variation across the albedo patch at peak albedo energies of 20-50 keV for all anisotropies modelled. The results show that there are distinct spatial polarization changes in both the radial and perpendicular to radial directions across the...
Search for a 17 keV neutrino in the internal bremsstrahlung spectrum of 125I
International Nuclear Information System (INIS)
We have searched for evidence of the emission of a 17 keV neutrino in the internal bremsstrahlung (IB) spectrum accompanying the electron capture decay of 125I. The IB spectrum, recorded in a planar Ge detector, has 1.2x106 counts per keV at 17 keV below the 2p end point. We set an upper limit of 0.4% for the admixture of a 17 keV neutrino, at the 90% confidence level, and exclude a 0.8% admixture at the 99.6% confidence level. The QEC value is found to be 185.77±0.06 keV. We also find that the recent calculations of Suric et al., which employ relativistic self-consistent-field atomic wave functions, reproduce the shape and relative intensity of IB partial spectra within a few percent
Study of the inner Bremsstrahlung following the electron-capture decay of 193 Pt
International Nuclear Information System (INIS)
We are measuring the inner Bremsstrahlung (I B) photons emitted in some of the electron-capture decays of 193 Pt. The source was prepared with highly pure metal Pt. It was irradiated with neutron for 52 days and let to cool down for eight months. The remaining activities were due to 193 Ptg (half-life 50 yr) and 192 Ir (half-life 74 d), the latter coming from (n, γ) reactions on a small content of Ir. We have used a radiochemistry method to reduce the Ir content of the source. The resulting Pt compound will be dissolved in a plastic scintillator disk. Most of the 192 Ir decays are β- and their signal in the plastic will be used as a veto for the I B-photon detector. We have performed simulations of the efficiency and absorption effects in the detection geometry. (author)
The interference effect of laser-assisted bremsstrahlung emission in Coulumb fields of two nuclei
Li, Ankang; Ren, Na; Wang, Pingxiao; Zhu, Wenjun; Li, Xiaoya; Hoehn, Ross; Kais, S
2013-01-01
In this paper, the spontaneous bremsstrahlung emission from an electron scattered by two fixed nuclei in an intense laser field is investigated in details based upon the Volkov state and the Dirac-Volkov propagator. It has been found that the fundamental harmonic spectrum from the electron radiation exhibits distinctive fringes, which is dependent not only upon the internucleus distance and orientation, but also upon the initial energy of the electron and the laser intensity. By analyzing the differential cross section, we are able to explain these effects in terms of interference among the electron scattering by the nuclei. These results could have promising applications in probing the atomic or molecular dressed potentials in intense laser fields.
Bremsstrahlung x ray spectra of Jupiter and Saturn: Predictions for future planetary spacecraft
International Nuclear Information System (INIS)
Calculations of X ray spectra due to bremsstrahlung from precipitating auroral electrons at Jupiter and Saturn are presented. The model assumes that a field-aligned potential drop accelerates a primary beam of electrons into the atmosphere where a population of secondary electrons having a power law energy dependence is generated. The spectrum at Jupiter is normalized to the soft X ray observations of Metzger et al (1983) at the low-energy end and constrained at the high-energy end by UV auroral energy requirements. The spectrum at Saturn is constructed by analogy to the Jovian case allowing for variation of the beam energy, energy flux, and scale size of the Saturnian aurora. The resulting indicate that a significant flux of X rays is emanating from both planets which may serve as a basis for conducting planetary X ray astronomy as part of future spacecraft missions to the planets
42 MeV bremsstrahlung spectrum analysis by a photoactivation method
Energy Technology Data Exchange (ETDEWEB)
Calzado, A.; Vano, E.; Delgado, V.; Gonzalez, L. (Universidad Complutense de Madrid (Spain). Catedra de Fisica Medica; Junta de Energia Nuclear, Madrid (Spain). Inst. de Estudios Nucleares)
1984-08-01
The evaluation of 42 MeV, bremsstrahlung spectra from a clinical betatron by using the photoactivation method is described. Photonuclear reactions, mainly of the (..gamma.., n) type, are used as activation detectors. After measurements of photon-induced activities from residual nuclei are performed, the spectral distribution of photons is evaluated by solving the unfolding problem. The latter is carried out through the use of two independent methods, orthonormal expansion and Monte Carlo. In both cases prior conditions to the solution are imposed. Spectra evaluated by both methods and making use of two different size flattening filters are presented. An empirical method to estimate the 'effective' thickness of the Pt target is described.
Study on the dose distribution of 8-MeV bremsstrahlung in mantle field techniques
International Nuclear Information System (INIS)
The dose distribution within the patient was studied with 8-MeV bremsstrahlung from a linear accelerator during mantle field irradiation using molded shielding blocks. Doses and dose distributions in the different layers of a modified Alderson phantom were measured by means of film dosimetry and related to the dose in the central ray beam at the middle of the body. Dose distribution within unshielded regions perpendicular to the central ray beam generally being relatively homogeneous, the highest relative doses, amounting to ca. 115%, are found in the region of the mandibular angle and in the supraclavicular region; the dose to superficial lymph nodes at the supraclavicular region reaches 100% of the dose in the central ray beam. As a cause for these important doses near the surface of the body are discussed the extension of mantle fields as well as the increased exit dose of the opposed field and the oblique incidence of radiation. (orig.)
Studies on inner bremsstrahlung from a few β-emitting isotopes
International Nuclear Information System (INIS)
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 89Sr, 141Ce, 111Ag and 99Tc, 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)
Determination of the anomalous scattering factors of high-Z atoms using bremsstrahlung radiation
International Nuclear Information System (INIS)
The anomalous scattering factors (f' and f'') of tungsten, gold and lead atoms have been determined using external bremsstrahlung (EB) photons. The EB photons are produced by the interaction of a beta particle from a beta source with a nickel target. These photons are allowed to pass through thin targets of tungsten, gold and lead. The transmitted photons have been measured by using a GMX-type HPGe detector coupled to an 8K multichannel analyser. The transmitted spectra show a sharp decrease in intensity at the K shell binding energies of the target atoms. The regions around the decreased portion have been used to determine the anomalous scattering factors. The experimentally measured values are compared with the available theoretical values.
Determination of the anomalous scattering factors of high-Z atoms using bremsstrahlung radiation
Energy Technology Data Exchange (ETDEWEB)
Hosur, Savita B; Naik, L R; Badiger, N M [Department of Physics, Karnatak University, Dharwad 580003 (India)], E-mail: nagappa123@yahoo.co.in
2009-02-14
The anomalous scattering factors (f' and f'') of tungsten, gold and lead atoms have been determined using external bremsstrahlung (EB) photons. The EB photons are produced by the interaction of a beta particle from a beta source with a nickel target. These photons are allowed to pass through thin targets of tungsten, gold and lead. The transmitted photons have been measured by using a GMX-type HPGe detector coupled to an 8K multichannel analyser. The transmitted spectra show a sharp decrease in intensity at the K shell binding energies of the target atoms. The regions around the decreased portion have been used to determine the anomalous scattering factors. The experimentally measured values are compared with the available theoretical values.
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.
Pair plasma in pulsar magnetospheres
International Nuclear Information System (INIS)
The main features of radiation received from pulsars imply that they are neutron stars which contain an extremely intense magnetic field and emit coherently in the radio domain. Most recent studies attribute the origin of the coherence to plasma instabilities arising in pulsar magnetospheres; they mainly concern the linear, or the nonlinear, character of the involved unstable waves. We briefly introduce radio pulsars and specify physical conditions in pulsar emission regions: geometrical properties, magnetic field, pair creation processes and repartition of relativistic charged particles. We point to the main ingredients of the linear theory, extensively explored since the 1970s: (i) a dispersion relation specific to the pulsar case; (ii) the characteristics of the waves able to propagate in relativistic pulsar plasmas; (iii) the different ways in which a two-humped distribution of particles may arise in a pulsar magnetosphere and favour the development of a two-stream instability. We sum up recent improvements of the linear theory: (i) the determination of a 'coupling function' responsible for high values of the wave field components and electromagnetic energy available; (ii) the obtention of new dispersion relations for actually anisotropic pulsar plasmas with relativistic motions and temperatures; (iii) the interaction between a plasma and a beam, both with relativistic motions and temperatures; (iv) the interpretation of observed 'coral' and 'conal' features, associated with the presence of boundaries and curved magnetic field lines in the emission region; (v) the detailed topology of the magnetic field in the different parts of the emission region and its relation to models recently proposed to interpret drifting subpulses observed from PSR 0943+10, showing 20 sub-beams of emission. We relate the nonlinear evolution of the two-stream instability and development of strong turbulence in relativistic pulsar plasmas to the emergence of relativistic solitons, able
García-Patrón, Raúl; Pirandola, Stefano; Lloyd, Seth; Shapiro, Jeffrey H.
2008-01-01
In this letter we define a family of entanglement distribution protocols assisted by feedback classical communication that gives an operational interpretation to reverse coherent information, i.e., the symmetric counterpart of the well known coherent information. This lead to the definition of a new entanglement distribution capacity that exceeds the unassisted capacity for some interesting channels.
García-Patrón, Raúl; Pirandola, Stefano; Lloyd, Seth; Shapiro, Jeffrey H.
2009-05-01
In this Letter we define a family of entanglement distribution protocols assisted by feedback classical communication that gives an operational interpretation to reverse coherent information, i.e., the symmetric counterpart of the well-known coherent information. This leads to the definition of a new entanglement distribution capacity that exceeds the unassisted capacity for some interesting channels.
Understanding Causal Coherence Relations
Mulder, G.
2008-01-01
The research reported in this dissertation focuses on the cognitive processes and representations involved in understanding causal coherence relations in text. Coherence relations are the meaning relations between the information units in the text, such as Cause-Consequence. These relations can be m
DEFF Research Database (Denmark)
Jensen, Jesper Bevensee; Rodes, Roberto; Caballero Jambrina, Antonio;
2014-01-01
We present a review of research performed in the area of coherent access technologies employing vertical cavity surface emitting lasers (VCSELs). Experimental demonstrations of optical transmission over a passive fiber link with coherent detection using VCSEL local oscillators and directly modula...
DEFF Research Database (Denmark)
Jensen, Jesper Bevensee; Rodes, Roberto; Cheng, Ning;
2015-01-01
Recent advances and research on coherent technologies for access networks are discussed and put into context of user demands and standardization work.......Recent advances and research on coherent technologies for access networks are discussed and put into context of user demands and standardization work....
Zheng, Yanping
2009-01-01
In the thesis a coherent text is defined as a continuity of senses of the outcome of combining concepts and relations into a network composed of knowledge space centered around main topics. And the author maintains that in order to obtain the coherence of a target language text from a source text during the process of translation, a translator can…
Relating Sentinel-1 Interferometric Coherence to Mowing Events on Grasslands
Directory of Open Access Journals (Sweden)
Tanel Tamm
2016-09-01
Full Text Available In this study, the interferometric coherence calculated from 12-day Sentinel-1 image pairs was analysed in relation to mowing events on agricultural grasslands. Results showed that after a mowing event, median VH (vertical transmit, horizontal receive and VV (vertical transmit, vertical receive polarisation coherence values were statistically significantly higher than those from before the event. The shorter the time interval after the mowing event and the first interferometric acquisition, the higher the coherence. The coherence tended to stay higher, even 24 to 36 days after a mowing event. Precipitation caused the coherence to decrease, impeding the detection of a mowing event. Given the three analysed acquisition geometries, it was concluded that afternoon acquisitions and steeper incidence angles were more useful in the context of this study. In the case of morning acquisitions, dew might have caused a decrease of coherence for mowed and unmowed grasslands. Additionally, an increase of coherence after a mowing event was not evident during the rapid growth phase, due to the 12-day separation between the interferometric acquisitions. In future studies, six-day pairs utilising Sentinel-1A and 1B acquisitions should be considered.
Energy Technology Data Exchange (ETDEWEB)
Singh, Amrit; Dhaliwal, A. S., E-mail: dhaliwalas@hotmail.com [Department of Physics, Sant Longowal Institute of Engineering and Technology, Longowal(Sangrur) -148106, Punjab (India)
2015-08-28
Bremsstrahlung spectra in thick targets of Mo and Pt, produced by beta emitter {sup 90}Sr (end point energy = 546 keV) have been studied in the photon energy range of 1-100 keV. The experimentally measured bremsstrahlung spectra measured with Si(Li) detector were compared with the theoretical spectral distributions calculated from Elwert corrected (non relativistic) Bethe-Heitler [EBH] theory, modified Elwert factor (relativistic) Bethe-Heitler (F{sub mod}BH) theory for ordinary bremsstrahlung (OB) and the modified Elwert factor (relativistic) Bethe-Heitler (F{sub mod}BH+PB) theory, which includes the polarization bremsstrahlung (PB) into total bremsstrahlung (BS). The present results indicate the correctness of F{sub mod}BH+PB theory in the low energy region, where the contributions of PB into BS are dominant, which is described in terms of stripped atom (SA) approximation. But at the middle and higher energy region of the bremsstrahlung spectrum, where the contribution of PB is negligible, the F{sub mod}BH theory is more close to the experimental results. Hence, it is clear that the production of PB in the low energy region, due to the dynamic response of the target atom suppresses the production of bremsstrahlung at higher energy ends.
Singh, Amrit; Dhaliwal, A. S.
2015-08-01
Bremsstrahlung spectra in thick targets of Mo and Pt, produced by beta emitter 90Sr (end point energy = 546 keV) have been studied in the photon energy range of 1-100 keV. The experimentally measured bremsstrahlung spectra measured with Si(Li) detector were compared with the theoretical spectral distributions calculated from Elwert corrected (non relativistic) Bethe-Heitler [EBH] theory, modified Elwert factor (relativistic) Bethe-Heitler (FmodBH) theory for ordinary bremsstrahlung (OB) and the modified Elwert factor (relativistic) Bethe-Heitler (FmodBH+PB) theory, which includes the polarization bremsstrahlung (PB) into total bremsstrahlung (BS). The present results indicate the correctness of FmodBH+PB theory in the low energy region, where the contributions of PB into BS are dominant, which is described in terms of stripped atom (SA) approximation. But at the middle and higher energy region of the bremsstrahlung spectrum, where the contribution of PB is negligible, the FmodBH theory is more close to the experimental results. Hence, it is clear that the production of PB in the low energy region, due to the dynamic response of the target atom suppresses the production of bremsstrahlung at higher energy ends.
Partially coherent ultrafast spectrography
Bourassin-Bouchet, C.; Couprie, M.-E.
2015-01-01
Modern ultrafast metrology relies on the postulate that the pulse to be measured is fully coherent, that is, that it can be completely described by its spectrum and spectral phase. However, synthesizing fully coherent pulses is not always possible in practice, especially in the domain of emerging ultrashort X-ray sources where temporal metrology is strongly needed. Here we demonstrate how frequency-resolved optical gating (FROG), the first and one of the most widespread techniques for pulse characterization, can be adapted to measure partially coherent pulses even down to the attosecond timescale. No modification of experimental apparatuses is required; only the processing of the measurement changes. To do so, we take our inspiration from other branches of physics where partial coherence is routinely dealt with, such as quantum optics and coherent diffractive imaging. This will have important and immediate applications, such as enabling the measurement of X-ray free-electron laser pulses despite timing jitter. PMID:25744080
Electron pairing without superconductivity
Levy, Jeremy
Strontium titanate (SrTiO3) is the first and best known superconducting semiconductor. It exhibits an extremely low carrier density threshold for superconductivity, and possesses a phase diagram similar to that of high-temperature superconductors--two factors that suggest an unconventional pairing mechanism. Despite sustained interest for 50 years, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. Here we perform transport experiments with nanowire-based single-electron transistors at the interface between SrTiO3 and a thin layer of lanthanum aluminate, LaAlO3. Electrostatic gating reveals a series of two-electron conductance resonances--paired electron states--that bifurcate above a critical pairing field Bp of about 1-4 tesla, an order of magnitude larger than the superconducting critical magnetic field. For magnetic fields below Bp, these resonances are insensitive to the applied magnetic field; for fields in excess of Bp, the resonances exhibit a linear Zeeman-like energy splitting. Electron pairing is stable at temperatures as high as 900 millikelvin, well above the superconducting transition temperature (about 300 millikelvin). These experiments demonstrate the existence of a robust electronic phase in which electrons pair without forming a superconducting state. Key experimental signatures are captured by a model involving an attractive Hubbard interaction that describes real-space electron pairing as a precursor to superconductivity. Support from AFOSR, ONR, ARO, NSF, DOE and NSSEFF is gratefully acknowledged.
Quantum coherence and sensitivity of avian magnetoreception
Bandyopadhyay, Jayendra N; Kaszlikowski, Dagomir
2012-01-01
Migratory birds and other species have the ability to navigate by sensing the geomagnetic field. Recent experiments indicate that the essential process in the navigation takes place in bird's eye and uses chemical reaction involving molecular ions with unpaired electron spins (radical pair). Sensing is achieved via geomagnetic-dependent dynamics of the spins of the unpaired electrons. Here we utilize the results of all behavioral experiments conducted on European Robins to argue that the average life-time of the radical pair is of the order of a microsecond and therefore agrees with experimental estimations of this parameter for cryptochrome --- a pigment believed to form the radical pairs. We also found a reasonable parameter regime where sensitivity of the avian compass is enhanced by environmental noise, showing that long coherence time is not required for navigation and may even spoil it.
Waveguide-based OPO source of entangled photon pairs
International Nuclear Information System (INIS)
In this paper, we present a compact source of narrow-band energy-time-entangled photon pairs in the telecom regime based on a Ti-indiffused periodically poled lithium niobate (PPLN) waveguide resonator, i.e. a waveguide with end-face dielectric multi-layer mirrors. This is a monolithic doubly resonant optical parametric oscillator (OPO) far below threshold, which generates photon pairs by spontaneous parametric down-conversion (SPDC) at around 1560 nm with a 117 MHz (0.91 pm)-bandwidth. A coherence time of 2.7 ns is estimated by a time correlation measurement and a high quality of the entangled states is confirmed by a Bell-type experiment. Since highly coherent energy-time-entangled photon pairs in the telecom regime are suitable for long distance transmission and manipulation, this source is well suited to the requirements of quantum communication.
Photon and neutrino-pair emission from circulating quantum ions
Yoshimura, M
2015-01-01
The recent proposal of photon and neutrino pair beam is extensively investigated. Production rates, both differential and total, of single photon, two-photon and neutrino-pair emitted from quantum ions in circular motion are calculated for any velocity of ion. This part is an extension of our previous results at highest energies to lower energies of circulating ions, and helps much to identify the new process at a low energy ion ring. We clarify how to utilize the circulating ion for a new source of coherent neutrino beam despite of much stronger background photons. Once one verifies that the coherence is maintained in the initial phases of time evolution after laser irradiation, large background photon emission rates are not an obstacle against utilizing the extracted neutrino pair beam.
Schwinger pair production with ultracold atoms
Kasper, V.; Hebenstreit, F.; Oberthaler, M. K.; Berges, J.
2016-09-01
We consider a system of ultracold atoms in an optical lattice as a quantum simulator for electron-positron pair production in quantum electrodynamics (QED). For a setup in one spatial dimension, we investigate the nonequilibrium phenomenon of pair production including the backreaction leading to plasma oscillations. Unlike previous investigations on quantum link models, we focus on the infinite-dimensional Hilbert space of QED and show that it may be well approximated by experiments employing Bose-Einstein condensates interacting with fermionic atoms. Numerical calculations based on functional integral techniques give a unique access to the physical parameters required to realize QED phenomena in a cold atom experiment. In particular, we use our approach to consider quantum link models in a yet unexplored parameter regime and give bounds for their ability to capture essential features of the physics. The results suggest a paradigmatic change towards realizations using coherent many-body states for quantum simulations of high-energy particle physics phenomena.
DEFF Research Database (Denmark)
Dalgas, Karina Märcher
2015-01-01
Since 2000, thousands of young Filipino migrants have come to Denmark as au pairs. Officially, they are there to “broaden their cultural horizons” by living temporarily with a Danish host family, but they also conduct domestic labor in exchange for food and money, which allows them to send...... ethnographic component of the dissertation consists of four articles, all emphasizing the au pairs’ agency by viewing their migration as a dynamic personal and social experience. Arguing that Filipina au pairs tend to be understood primarily from the perspective of their precarious situation as domestic...... of their Danish host families. Based on their migratory status as au pairs, these young migrants must therefore negotiate the different moral and contractual rights and obligations that characterize the local and transnational family ties in which they are engaged. This study of Filipina au pair migration through...
Schlueter-Kuck, Kristy L
2016-01-01
We present a frame-invariant method for detecting coherent structures from Lagrangian flow trajectories that can be sparse in number, as is the case in many fluid mechanics applications of practical interest. The method, based on principles used in graph coloring and spectral graph drawing algorithms, examines a measure of the kinematic dissimilarity of all pairs of fluid trajectories, either measured experimentally, e.g. using particle tracking velocimetry; or numerically, by advecting fluid particles in the Eulerian velocity field. Coherence is assigned to groups of particles whose kinematics remain similar throughout the time interval for which trajectory data is available, regardless of their physical proximity to one another. Through the use of several analytical and experimental validation cases, this algorithm is shown to robustly detect coherent structures using significantly less flow data than is required by existing spectral graph theory methods.
DEFF Research Database (Denmark)
Andersen, Anne Bendix; Frederiksen, Kirsten; Beedholm, Kirsten;
2016-01-01
of coherence in treatment and patient pathways. The aim of our study is to explore the role of health care providers in furthering coherence. Our ambition is to identify areas for improvement or change of collaborative practice between health care providers in municipalities, hospitals and general practice...... initiatives in health care. The present study will generate new, valuable insight into the areas of cross-sectorial health care collaboration. Our findings may facilitate change in current practice and improve the quality and coherence in patient pathways of EPCD. The findings of this study will be useful...
Institute of Scientific and Technical Information of China (English)
Michael Thomas
2005-01-01
@@ What makes a coherent EFL curriculum? How can curriculum planners avoid a mismatch between policy and pragmatics to produce an effective decision-making process? In The Second Language Curriculum, Johnson describes the coherent curriculum as one in which decision outcomes from the various stages of development are mutually consistent and complementary,and learning outcomes reflect curriculum aims.The achievement of coherence is said to depend crucially in most educational contexts upon the formalisation of decision-making processes and products. This formalisation facilitates consensus among those involved and is a prerequisite for effective evaluation and subsequent renewal (1994: xiii)
High-density EEG coherence analysis using functional units applied to mental fatigue
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
Bromley, Thomas R; Adesso, Gerardo
2014-01-01
We analyse under which dynamical conditions the coherence of an open quantum system is totally unaffected by noise. For a single qubit, specific measures of coherence are found to freeze under different conditions, with no general agreement between them. Conversely, for an N-qubit system with even N, we identify universal conditions in terms of initial states and local incoherent channels such that all bona fide distance-based coherence monotones are left invariant during the entire evolution. This finding also provides an insightful physical interpretation for the freezing phenomenon of quantum correlations beyond entanglement. We further obtain analytical results for distance-based measures of coherence in two-qubit states with maximally mixed marginals.
... Cardiac Magnetic Resonance Imaging (MRI and MRA) Computed Tomography (CT) Scan Diagnostic Tests and Procedures Echocardiography Electrocardiogram ... Ultrasound Nuclear Stress Test Nuclear Ventriculography Positron Emission Tomography (PET) Stress ... Optical Coherence Tomography | ...
Coherence in Industrial Transformation
DEFF Research Database (Denmark)
Jørgensen, Ulrik; Lauridsen, Erik Hagelskjær
2003-01-01
The notion of coherence is used to illustrate the general finding, that the impact of environmental management systems and environmental policy is highly dependent of the context and interrelatedness of the systems, procedures and regimes established in society....
Streltsov, Alexander
2015-01-01
The basis of any quantum resource theory are free states and free operations, these are states and operations which can be created or performed at no cost. In the resource theory of quantum coherence free states are states which are diagonal in a fixed reference basis. This choice is natural in many experimental scenarios where the reference basis is singled out by the unavoidable decoherence. The corresponding free operations are called incoherent, they can be implemented as a generalized measurement which does not create any coherence. However, a general quantum operation admits different experimental realizations, and a quantum operation which seems incoherent in one experimental realization might create coherence in another. Starting from this observation, we propose the framework of genuine quantum coherence. This approach is based on a simple principle: we demand that a genuinely incoherent operation preserves all incoherent states. This simple condition automatically guarantees that the operation is in...
A Numerical Study of On-Axis Dose Rate from Ta and W Bremsstrahlung Converter Targets
International Nuclear Information System (INIS)
The bremsstrahlung converter target in radiographic accelerators is not, in general, considered a high-technology piece of equipment. In its essential form it is merely a solid plate of high-Z metal, usually tungsten (W) or tantalum (Ta); electrons go in, X-rays come out [1]. However, there are some important factors to keep in mind for this kind of target system. One is a constraint on the target itself: the proper thickness of material. Too little material reduces the probability that an electron will have a significant nuclear collision before exiting the plate. Too much material has a number of effects: small-angle scattering will occur to such an extent that bremsstrahlung photons will not be pointed in the forward direction. Electrons which small-angle scatter away and then back to the forward direction will have moved to larger radii as they traverse the target, increasing the effective source size. Electrons ''backscattered'' from the target --primaries or secondaries ejected from the upstream surface after sufficient angular scatter--exert a defocusing force on the incoming beam due to increased space charge at fixed (or even slightly reduced) current. Finally, a sufficiently thick target will begin to self-attenuate the X-ray photons produced in the upstream portion of the plate. A second constraint is obvious but is harder to accommodate when designing a radiographic accelerator system. The angular distribution of the incoming electron beam will change the forward dose. Just as electrons which have undergone small-angle scatter will no longer produce forward dose, electrons which have large angles before they ever enter the target cannot produce forward dose. Accurate prediction of dose requires incorporating the effect of the initial angle of the electron coming into the target material. The further step of controlling the angular distribution--which means keeping it as close to zero as possible--is difficult since it tends to drive important beam
Partially coherent ultrafast spectrography
Bourassin-Bouchet, C.; Couprie, M.-E.
2015-01-01
Modern ultrafast metrology relies on the postulate that the pulse to be measured is fully coherent, that is, that it can be completely described by its spectrum and spectral phase. However, synthesizing fully coherent pulses is not always possible in practice, especially in the domain of emerging ultrashort X-ray sources where temporal metrology is strongly needed. Here we demonstrate how frequency-resolved optical gating (FROG), the first and one of the most widespread techniques for pulse c...
Spohn, Wolfgang
1999-01-01
The paper proposes two principles of coherence (thus taking up work started in Spohn (1991) "A Reason for Explanation: Explanations Provide Stable Reasons"). The latter indeed serves as a weak, but precise explication of the notion of coherence as it is used in the current epistemological discussion. After discussing their epistemological setting, the paper considers four ways of establishing these principles. They may be inferred neither from enumerative induction, nor from the nature of pro...
Chapman, H. N.; Bajt, S.; Barty, A.; Benner, W. H.; Bogan, M. J.; Boutet, S.; Cavalleri, A.; Duesterer, S.; Frank, M.; Hajdu, J.; Hau-Riege, S. P.; Iwan, B.; Marchesini, S.; Sakdinawat, A.; Sokolowski-Tinten, K.; Seibert, M. M.; Timneanu, N.; Treusch, R.; Woods, B. W.
2009-09-01
We have carried out high-resolution single-pulse coherent diffractive imaging at the FLASH free-electron laser. The intense focused FEL pulse gives a high-resolution low-noise coherent diffraction pattern of an object before that object turns into a plasma and explodes. In particular we are developing imaging of biological specimens beyond conventional radiation damage resolution limits, developing imaging of ultrafast processes, and testing methods to characterize and perform single-particle imaging.
A J Seeds; Fice, M. J.; Balakier, K; M Natrella; Mitrofanov, O.; Pepper, M.; Renaud, C.C.; M. Lamponi; M Chtioui; Van Dijk, F.; Aeppli, G.; A G Davies; Dean, P.; Linfield, E
2013-01-01
We present a review of recent developments in THz coherent systems based on photonic local oscillators. We show that such techniques can enable the creation of highly coherent, thus highly sensitive, systems for frequencies ranging from 100 GHz to 5 THz, within an energy efficient integrated platform. We suggest that such systems could enable the THz spectrum to realize its full applications potential. To demonstrate how photonics-enabled THz systems can be realized, we review the performance...
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)
International Nuclear Information System (INIS)
Full text: The aim of investigations was the study of spectral and relaxation characteristics of radiation induced emission in the FSHA-800 type quartz-polymer optical fibres (OF) which are used as active media of Cherenkov's detectors in the CMS experiment (CERN). The part of OF with the length L turned in to ring of 5 cm of diameter was placed right of the way of a bunch of Bremsstrahlung gamma - rays. At the same time this OF was used for transportation of induced light which has been detected by EPP 2000C model Miniature Fiber Optic Spectrometer. The emission kinetics was measured by TDS 3032 model TEKTRONIX digital storage oscilloscope. Tungstate target plate being irradiated by electrons beam of MT-22C model microthrone (frequency of 400 Hz at a current of 7 μA) was as Bremsstrahlung gamma irradiation source (average energy of 7 MeV). For changing of irradiating dose rate the sample investigated was placed at the different distance from the target. The results of investigations The emission spectra are characterized by several bands with the maximum at 370, 420, 470, 520 and 670 nm. The transformation of the spectra take place for the different length of irradiating (L) of OF. The dose dependence of the observed emission depends on the irradiating length too. For the small value of L (0.5 m) the increasing of irradiation dose result in increasing of emission intensity. In the case of large L (5 m) we have opposite effect. The emission decay kinetics are characterized by (i) fast (time constant τ<1 μs) and slow (II) components (time constant τ- a few μs). The both spectra were measured at the irradiating dose of D=0.36 Mrad. The given curves are corrected on spectral sensitivity of the equipment. The nature of observed emission and its peculiarities are discussed in terms of existing models of radiation defect formation in the quartz glass. The influence of induced absorption on emission spectra transformation is considered. The authors express the
Benchmarking of Monte Carlo simulation of bremsstrahlung from thick targets at radiotherapy energies
Energy Technology Data Exchange (ETDEWEB)
Faddegon, Bruce A.; Asai, Makoto; Perl, Joseph; Ross, Carl; Sempau, Josep; Tinslay, Jane; Salvat, Francesc [Department of Radiation Oncology, University of California at San Francisco, San Francisco, California 94143 (United States); Stanford Linear Accelerator Center, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); National Research Council Canada, Institute for National Measurement Standards, 1200 Montreal Road, Building M-36, Ottawa, Ontario K1A 0R6 (Canada); Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya and Centro de Investigacion Biomedica en Red en Bioingenieria, Biomateriales y Nanomedicina (CIBER-BBN), Diagonal 647, 08028 Barcelona (Spain); Stanford Linear Accelerator Center, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Facultat de Fisica (ECM), Universitat de Barcelona, Societat Catalana de Fisica (IEC), Diagonal 647, 08028 Barcelona (Spain)
2008-10-15
Several Monte Carlo systems were benchmarked against published measurements of bremsstrahlung yield from thick targets for 10-30 MV beams. The quantity measured was photon fluence at 1 m per unit energy per incident electron (spectra), and total photon fluence, integrated over energy, per incident electron (photon yield). Results were reported at 10-30 MV on the beam axis for Al and Pb targets and at 15 MV at angles out to 90 degree sign for Be, Al, and Pb targets. Beam energy was revised with improved accuracy of 0.5% using an improved energy calibration of the accelerator. Recently released versions of the Monte Carlo systems EGSNRC, GEANT4, and PENELOPE were benchmarked against the published measurements using the revised beam energies. Monte Carlo simulation was capable of calculation of photon yield in the experimental geometry to 5% out to 30 degree sign , 10% at wider angles, and photon spectra to 10% at intermediate photon energies, 15% at lower energies. Accuracy of measured photon yield from 0 to 30 degree sign was 5%, 1 s.d., increasing to 7% for the larger angles. EGSNRC and PENELOPE results were within 2 s.d. of the measured photon yield at all beam energies and angles, GEANT4 within 3 s.d. Photon yield at nonzero angles for angles covering conventional field sizes used in radiotherapy (out to 10 degree sign ), measured with an accuracy of 3%, was calculated within 1 s.d. of measurement for EGSNRC, 2 s.d. for PENELOPE and GEANT4. Calculated spectra closely matched measurement at photon energies over 5 MeV. Photon spectra near 5 MeV were underestimated by as much as 10% by all three codes. The photon spectra below 2-3 MeV for the Be and Al targets and small angles were overestimated by up to 15% when using EGSNRC and PENELOPE, 20% with GEANT4. EGSNRC results with the NIST option for the bremsstrahlung cross section were preferred over the alternative cross section available in EGSNRC and over EGS4. GEANT4 results calculated with the &apos
International Nuclear Information System (INIS)
The BioXAS beamlines consist of an undulator beamline followed by two wiggler beamlines sharing the same insertion device. To contain gas bremsstrahlung in the primary optical enclosure (POE), three tungsten blocks are placed, one of which is common to all the three beamlines. A radiation shielding study is carried out for primary and secondary gas bremsstrahlung of the BioXAS beamlines. Dose rates behind the back wall, side wall and the top of the roof are obtained by calculating energy depositions in a water phantom, which surrounds the POE. Discussion is made regarding the adequacy of radiation shielding for the BioXAS beamlines, which will be built in the near future at the Canadian Light Source.
Entanglement and Coherence in Quantum State Merging.
Streltsov, A; Chitambar, E; Rana, S; Bera, M N; Winter, A; Lewenstein, M
2016-06-17
Understanding the resource consumption in distributed scenarios is one of the main goals of quantum information theory. A prominent example for such a scenario is the task of quantum state merging, where two parties aim to merge their tripartite quantum state parts. In standard quantum state merging, entanglement is considered to be an expensive resource, while local quantum operations can be performed at no additional cost. However, recent developments show that some local operations could be more expensive than others: it is reasonable to distinguish between local incoherent operations and local operations which can create coherence. This idea leads us to the task of incoherent quantum state merging, where one of the parties has free access to local incoherent operations only. In this case the resources of the process are quantified by pairs of entanglement and coherence. Here, we develop tools for studying this process and apply them to several relevant scenarios. While quantum state merging can lead to a gain of entanglement, our results imply that no merging procedure can gain entanglement and coherence at the same time. We also provide a general lower bound on the entanglement-coherence sum and show that the bound is tight for all pure states. Our results also lead to an incoherent version of Schumacher compression: in this case the compression rate is equal to the von Neumann entropy of the diagonal elements of the corresponding quantum state.
International Nuclear Information System (INIS)
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
Nazaryan, T A; Hakobyan, A A; Adibekyan, V Zh; Kunth, D; Mamon, G A; Turatto, M; Aramyan, L S
2013-01-01
We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are consistent with previous results compiled with the larger sample. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies.
Al Samarai, Imen; Deligny, Olivier; Rosado, Jaime
2016-10-01
A small contribution of molecular Bremsstrahlung radiation to the air-fluorescence yield in the UV range is estimated based on an approach previously developed in the framework of the radio-detection of showers in the gigahertz frequency range. First, this approach is shown to provide an estimate of the main contribution of the fluorescence yield due to the de-excitation of the C 3Πu electronic level of nitrogen molecules to the B 3Πg one amounting to Y[ 337 ] =(6.05 ± 1.50) MeV-1 at 800 hPa pressure and 293 K temperature conditions, which compares well to previous dedicated works and to experimental results. Then, under the same pressure and temperature conditions, the fluorescence yield induced by molecular Bremsstrahlung radiation is found to be Y[330-400]MBR = 0.10 MeV-1 in the wavelength range of interest for the air-fluorescence detectors used to detect extensive air showers induced in the atmosphere by ultra-high energy cosmic rays. This means that out of ≃175 photons with wavelength between 330 and 400 nm detected by fluorescence detectors, one of them has been produced by molecular Bremsstrahlung radiation. Although small, this contribution is not negligible in regards to the total budget of systematic uncertainties when considering the absolute energy scale of fluorescence detectors.
Crossover from BCS superconductivity to superfluidity of local pairs
International Nuclear Information System (INIS)
We review some recent results concerning crossover from cooperative Cooper pairing to independent bound states formation and their superfluidity, and a possible relevance of the crossover behavior to the anomalous properties of short-coherence length superconductors. Using the extended Hubbard model with on-site attraction (EHM), we analyze the behavior of collective modes, thermodynamic and electromagnetic properties versus the coupling strength and electron concentration. The normal state properties of the 2D attractive Hubbard model obtained with the conserving, self-consistent T-matrix approach, are presented. These studies also indicate possible deviations from conventional Fermi-liquid behavior, above Tc, in 2D short coherence length superconductors. (orig.)
Hybrid quantum repeater using bright coherent light.
van Loock, P; Ladd, T D; Sanaka, K; Yamaguchi, F; Nemoto, Kae; Munro, W J; Yamamoto, Y
2006-06-23
We describe a quantum repeater protocol for long-distance quantum communication. In this scheme, entanglement is created between qubits at intermediate stations of the channel by using a weak dispersive light-matter interaction and distributing the outgoing bright coherent-light pulses among the stations. Noisy entangled pairs of electronic spin are then prepared with high success probability via homodyne detection and postselection. The local gates for entanglement purification and swapping are deterministic and measurement-free, based upon the same coherent-light resources and weak interactions as for the initial entanglement distribution. Finally, the entanglement is stored in a nuclear-spin-based quantum memory. With our system, qubit-communication rates approaching 100 Hz over 1280 km with fidelities near 99% are possible for reasonable local gate errors.
Attention alters the appearance of motion coherence.
Liu, Taosheng; Fuller, Stuart; Carrasco, Marisa
2006-12-01
Selective attention enhances visual information processing, as measured by behavioral performance and neural activity. However, little is known about its effects on subjective experience. Here, we investigated the effect of transient (exogenous) attention on the appearance of visual motion, using a psychophysical procedure that directly measures appearance and controls for response bias. Observers viewed pairs of moving dot patterns and reported the motion direction of the more coherent pattern. Directing attention (via a peripheral precue) to a stimulus location increased its perceived coherence level and improved performance on a direction discrimination task. In a control experiment, we ruled out response bias by lengthening the time interval between the cue and the stimuli, so that the effect of transient attention could no longer be exerted. Our results are consistent with those of neurophysiological studies showing that attention modulates motion processing and provide evidence of a subjective perceptual correlate of attention, with a concomitant effect on performance.
Quantum-coherent mixtures of causal relations
MacLean, Jean-Philippe W; Spekkens, Robert W; Resch, Kevin J
2016-01-01
Understanding the causal influences that hold among the parts of a system is critical both to explaining that system's natural behaviour and to controlling it through targeted interventions. In a quantum world, understanding causal relations is equally important, but the set of possibilities is far richer. The two basic ways in which a pair of time-ordered quantum systems may be causally related are by a cause-effect mechanism or by a common cause acting on both. Here, we show that it is possible to have a coherent mixture of these two possibilities. We realize such a nonclassical causal relation in a quantum optics experiment and derive a set of criteria for witnessing the coherence based on a quantum version of Berkson's paradox. The interplay of causality and quantum theory lies at the heart of challenging foundational puzzles, such as Bell's theorem and the search for quantum gravity, but could also provide a resource for novel quantum technologies.
Entanglement and coherence in quantum state merging
Streltsov, A; Rana, S; Bera, M N; Winter, A; Lewenstein, M
2016-01-01
Understanding the resource consumption in distributed scenarios is one of the main goals of quantum information theory. A prominent example for such a scenario is the task of quantum state merging where two parties aim to merge their parts of a tripartite quantum state. In standard quantum state merging, entanglement is considered as an expensive resource, while local quantum operations can be performed at no additional cost. However, recent developments show that some local operations could be more expensive than others: it is reasonable to distinguish between local incoherent operations and local operations which can create coherence. This idea leads us to the task of incoherent quantum state merging, where one of the parties has free access to local incoherent operations only. In this case the resources of the process are quantified by pairs of entanglement and coherence. Here, we develop tools for studying this process, and apply them to several relevant scenarios. While quantum state merging can lead to ...
Stimulated coherent transition radiation
International Nuclear Information System (INIS)
Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed
Hydramite II screening tests of potential bremsstrahlung converter debris shield materials
International Nuclear Information System (INIS)
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
Electron spectroscopy in the fundamental process of electron-nucleus bremsstrahlung
International Nuclear Information System (INIS)
Within the scope of this thesis the fundamental process of electron-nucleus bremsstrahlung was studied in inverse kinematics at the Experimental Storage Ring ESR at GSI. For the system U88+ + N2 at 90 MeV/u it was shown, that by using inverse kinematics coincidence measurements between the scattered electron and the emitted photon can be performed for the case, in which the incoming electron transfers almost all of its kinetic energy onto the emitted photon. The sensitivity to the fundamental process could be achieved by measuring triple differential cross sections as a function of the emission angle of the photon and the scattered electron as well as the energy of the scattered electron. The optics of the magnetic electron spectrometer used were thoroughly revised and optimized to the experimental requirements. Analyzing different coincidences in this collision system, it was possible to determine the contributions to the electron distribution arising from radiative electron capture to the projectile continuum, nonradiative electron capture to the projectile continuum, and electron loss to the projectile continuum. The experimental results of each of these processes were compared to theoretical calculations. The electron spectra for the radiative and the nonradiative electron capture to continuum clearly reproduce the opposite asymmetry predicted by theory. Furthermore electron spectra for collisions of U28+ with different gases were measured.
Search for 17-keV neutrinos in the internal bremsstrahlung spectrum of 125I
International Nuclear Information System (INIS)
We have conducted an experiment to search for the signature of a 17-keV neutrino in the internal bremsstrahlung (IB) spectrum of 125I. Gamma rays from a ∼ 100 mCi 125I point source were counted in a planar HPGe detector which is 16 mm in diameter and 10 mm in depth and which has a resolution of 560 eV at 122 keV. The source was counted for 61 d and the background for 17 d. At the start of the counting period the count rate was 650 s-1; the number of counts 17 keV below the 2p endpoint is 106 per keV. Data in the energy interval 120-150.5 keV were fitted with a theoretical spectrum calculated using nonrelativistic Hartree-Fock atomic wavefunctions. The preliminary fits reject the hypothesis of a 0.8% 17-keV neutrino at a confidence level of ≥ 98%. We are in the process of reanalyzing the data using recent relativistic theoretical shapes
Hidden Photon Compton and Bremsstrahlung in White Dwarf Anomalous Cooling and Luminosity Functions
Chang, Chia-Feng
2016-01-01
We computed the contribution of the Compton and Bremsstrahlung processes with a hidden light $U(1)_D$ neutral boson $\\gamma_D$ to the white dwarf G117-B15A anomalous cooling rate, as well as the white dwarf luminosity functions (WDLF). We demonstrated that for a light mass of hidden photon ($m_{\\gamma_D} \\ll$ a few keV), compatible results are obtained for the recent Sloan Digital Sky Survey and the SuperCOSMOS Sky Survey observation, but the stringent limits would be imposed on the kinetic mixing $\\epsilon$. We performed $\\chi^2$-tests to acquire a quantitative assessment on the WDLF data in the context of our model, computed under the assumption of different kinetic mixing $\\epsilon$, the age of the oldest computed stars $T_D$, and a constant star formation rate $\\psi$. Then taken together, the WDLF analysis of 2$\\sigma$ confidence interval $\\epsilon = \\left( 0.37^{+0.35}_{-0.37}\\right) \\times 10^{-14}$ is barely consistent with the cooling rate analysis at 2$\\sigma$ regime $\\epsilon = \\left( 0.97^{+0.35}_{...
Study of the inner Bremsstrahlung following the electron-capture decay of {sup 193} Pt
Energy Technology Data Exchange (ETDEWEB)
Chavez, J.Y.Z.; Cruz, M.T.F. da; Martins, M.N.; Santos, R.T. dos [Sao Paulo Univ., SP (Brazil). Inst. de Fisica; Zamboni, C.B.; Hamada, M.M.; Camargo, S.P. de; Medeiros, J.A.G. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil); Hindi, M.M. [Tennessee Technological Univ., Cookeville, TN (United States). Dept. of Physics
1997-12-31
We are measuring the inner Bremsstrahlung (I B) photons emitted in some of the electron-capture decays of {sup 193} Pt. The source was prepared with highly pure metal Pt. It was irradiated with neutron for 52 days and let to cool down for eight months. The remaining activities were due to {sup 193} Pt{sup g} (half-life 50 yr) and {sup 192} Ir (half-life 74 d), the latter coming from (n, {gamma}) reactions on a small content of Ir. We have used a radiochemistry method to reduce the Ir content of the source. The resulting Pt compound will be dissolved in a plastic scintillator disk. Most of the {sup 192} Ir decays are {beta}{sup -} and their signal in the plastic will be used as a veto for the I B-photon detector. We have performed simulations of the efficiency and absorption effects in the detection geometry. (author) 6 refs., 1 fig.; juan at if.usp.br; czamboni at net.ipen.br; hindi at hindi.physics.tntech.edu
The bremsstrahlung tagged photon beam in Hall B at the Jefferson Laboratory
International Nuclear Information System (INIS)
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 briefly described, and performance results to date under real operating conditions are presented. The entire photon-tagging system has met or exceeded its design goals
Virtual- and bremsstrahlung corrections to b -> d l+ l- in the standard model
Asatrian, H M; Greub, C; Walker, M
2003-01-01
We present the calculation of the virtual- and bremsstrahlung corrections of O(alpha_s) to the matrix elements . This is the missing piece in the NNLL results for various observables associated with the process B-> X_d l+ l-, like the branching ratio, the CP-rate asymmetry and the forward-backward asymmetry. This paper is an extension of analogous calculations done by some of us for the process B-> X_s l+ l-. As the contributions of the diagrams induced by the operators O_1^u and O_2^u with a u-quark running in the quark loop are strongly CKM suppressed, they were omitted in the analysis of B->X_s l+ l-. This is no longer possible for B-> X_d l+ l-, as the corresponding contributions are not suppressed. The main new work therefore consists of calculating the O(alpha_s) corrections to . In this paper we restrict ourselves to the range 0.05 X_d l+ l- as expansions in the small parameters s/m_b^2, z = m_c^2/m_b^2 and s/(4 m_c^2). In the phenomenological analysis at the end of the paper we discuss the impact of ...
Davidson, M P
2003-01-01
The mathematical expression for the electromagnetic current of a quantum particle describes an extended charge in the sense that it is non-vanishing over the volume of the wave packet or the Schroedinger wave for the particle. In the hydrodynamic model this charge current and associated density are interpreted as a physical reality. Coupling such a current to a classical electromagnetic field in the soft photon limit then results in a theory for radiation. It is shown that this predicts that bremsstrahlung is sometimes greatly suppressed when the force acting on the particle is due to a classical potential field and when the volume over which the force is active is small compared to the volume of the particle's wave packet. Solving the same problem using conventional quantum radiation theory gives a different result. Therefore it is possible to test this effect experimentally and either confirm or rule out a hydrodynamic model for Schroedinger wave mechanics. An experiment is proposed to make such a test. It ...
X-rays from Proton Bremsstrahlung: Evidence from Fusion Reactors and Its Implication in Astrophysics
Luo, Nie
2009-01-01
In a fusion reactor, a proton and a neutron generated in previous reactions may again fuse with each other. Or they can in turn fuse with or be captured by an un-reacted deuteron. The average center-of-mass (COM) energy for such reaction is around 10 keV in a typical fusion reactor, but could be as low as 1 keV. At this low COM energy, the reacting nucleons are in an s-wave state in terms of their relative angular momentum. The single-gamma radiation process is thus strongly suppressed due to conservation laws. Instead the gamma ray released is likely to be accompanied by x-ray photons from a nuclear bremsstrahlung process. The x-ray thus generated has a continuous spectrum and peaks around a few hundred eV to a few keV. The average photon energy and spectrum properties of such a process are calculated with a semiclassical approach. The results give a peak near 1.1 keV for the proton-deuteron fusion and a power-to-the-minus-second law in the spectrum's high-energy limit. An analysis of some prior tokamak disc...
A consistent meson-field-theoretical description of pp-bremsstrahlung
Eden, J A
1996-01-01
A parameter-free and relativistic extension of the RuhrPot meson-baryon model is used to define the dominant isoscalar meson-exchange currents. We compute pp-bremsstrahlung observables below the \\pi-production threshold using a relativistic hadronic current density that includes impulse, wave function re-orthonormalization, meson-recoil, \\bar{{\\rm N}}N creation and annihilation, \\rho\\pi\\gamma + \\omega\\pi\\gamma + \\rho\\eta\\gamma + \\omega\\eta\\gamma vector-meson decay and N\\Delta\\gamma(\\pi,\\rho) exchange currents. We obtain a good description of the available data. The N\\Delta\\gamma(\\pi) current is shown to dominate the large two-body contributions and closed-form expressions for various non-relativistic approximations are analyzed. An experimental sensitivity to the admixture of pseudo-scalar and pseudo-vector admixture of the NN\\pi interaction is demonstrated. We examine the Lorentz invariance of the NN\\rightleftharpoonsNN t-matrices and show a dominantly pseudo-vector NN\\pi coupling renders impulse approximati...
Phase and coherence analysis of VHF scintillation over Christmas Island
Shume, E. B.; Mannucci, A. J.; Caton, R.
2014-03-01
This short paper presents phase and coherence data from the cross-wavelet transform applied on longitudinally separated very high frequency (VHF) equatorial ionospheric scintillation observations over Christmas Island. The phase and coherence analyses were employed on a pair of scintillation observations, namely, the east-looking and west-looking VHF scintillation monitors at Christmas Island. Our analysis includes 3 years of peak season scintillation data from 2008, 2009 (low solar activity), and 2011 (moderate solar activity). In statistically significant and high spectral coherence regions of the cross-wavelet transform, scintillation observations from the east-looking monitor lead those from the west-looking monitor by about 20 to 60 (40 ± 20) min (most frequent lead times). Using several years (seasons and solar cycle) of lead (or lag) and coherence information of the cross-wavelet transform, we envisage construction of a probability model for forecasting scintillation in the nighttime equatorial ionosphere.
Direct measurement of exciton valley coherence in monolayer WSe2
Hao, Kai; Moody, Galan; Wu, Fengcheng; Dass, Chandriker Kavir; Xu, Lixiang; Chen, Chang-Hsiao; Sun, Liuyang; Li, Ming-Yang; Li, Lain-Jong; MacDonald, Allan H.; Li, Xiaoqin
2016-07-01
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.
DEFF Research Database (Denmark)
Rodríguez, J. Tinguaro; Franco de los Ríos, Camilo; Gómez, Daniel;
2015-01-01
In this paper we want to stress the relevance of paired fuzzy sets, as already proposed in previous works of the authors, as a family of fuzzy sets that offers a unifying view for different models based upon the opposition of two fuzzy sets, simply allowing the existence of different types...
Hadronic lepton pair production
International Nuclear Information System (INIS)
The author describes a beam dump experiment at the CERN SPS for the study of μ pair production by π+-, K+-, and p(anti p) beams on a copper target at 39.5 GeV/c. The dependence of the cross sections from various parameters is discussed. (HSI)
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.
Multi-pair states in electron-positron pair creation
Wöllert, Anton; Bauke, Heiko; Keitel, Christoph H.
2016-09-01
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.
Treutlein, P; Steinmetz, T; Hänsch, T W; Reichel, J; Treutlein, Philipp; Hommelhoff, Peter; Steinmetz, Tilo; H\\"ansch, Theodor W.; Reichel, Jakob
2003-01-01
We report the coherent manipulation of internal states of neutral atoms in a magnetic microchip trap. Coherence lifetimes exceeding 1 s are observed with atoms at distances of $4-130 \\mu$m from the microchip surface. The coherence lifetime in the microtrap is independent of atom-surface distance and agrees well with the results of similar measurements in macroscopic magnetic traps. Due to the absence of surface-induced decoherence, a miniaturized atomic clock with a relative stability in the $10^{-13}$ range can be realized. For applications in quantum information processing, we propose to use microwave near-fields in the proximity of chip wires to create potentials that depend on the internal state of the atoms.
Maintaining Web Cache Coherency
Directory of Open Access Journals (Sweden)
2000-01-01
Full Text Available Document coherency is a challenging problem for Web caching. Once the documents are cached throughout the Internet, it is often difficult to keep them coherent with the origin document without generating a new traffic that could increase the traffic on the international backbone and overload the popular servers. Several solutions have been proposed to solve this problem, among them two categories have been widely discussed: the strong document coherency and the weak document coherency. The cost and the efficiency of the two categories are still a controversial issue, while in some studies the strong coherency is far too expensive to be used in the Web context, in other studies it could be maintained at a low cost. The accuracy of these analysis is depending very much on how the document updating process is approximated. In this study, we compare some of the coherence methods proposed for Web caching. Among other points, we study the side effects of these methods on the Internet traffic. The ultimate goal is to study the cache behavior under several conditions, which will cover some of the factors that play an important role in the Web cache performance evaluation and quantify their impact on the simulation accuracy. The results presented in this study show indeed some differences in the outcome of the simulation of a Web cache depending on the workload being used, and the probability distribution used to approximate updates on the cached documents. Each experiment shows two case studies that outline the impact of the considered parameter on the performance of the cache.
Ferraro, Pietro; Zalevsky, Zeev
2011-01-01
This book deals with the latest achievements in the field of optical coherent microscopy. While many other books exist on microscopy and imaging, this book provides a unique resource dedicated solely to this subject. Similarly, many books describe applications of holography, interferometry and speckle to metrology but do not focus on their use for microscopy. The coherent light microscopy reference provided here does not focus on the experimental mechanics of such techniques but instead is meant to provide a users manual to illustrate the strengths and capabilities of developing techniques. Th
Coherent states measurement entropy
Kwapien, J; Zyczkowski, K; Kwapien, Jaroslaw; Slomczynski, Wojciech; Zyczkowski, Karol
1996-01-01
Coherent states (CS) quantum entropy can be split into two components. The dynamical entropy is linked with the dynamical properties of a quantum system. The measurement entropy, which tends to zero in the semiclassical limit, describes the unpredictability induced by the process of a quantum approximate measurement. We study the CS--measurement entropy for spin coherent states defined on the sphere discussing different methods dealing with the time limit n \\to \\infty. In particular we propose an effective technique of computing the entropy by iterated function systems. The dependence of CS--measurement entropy on the character of the partition of the phase space is analysed.
Pair fireball precursors of neutron star mergers
Metzger, Brian D.; Zivancev, Charles
2016-10-01
If at least one neutron star (NS) is magnetized in a binary NS merger, then the orbital motion of the conducting companion during the final inspiral induces a strong voltage and current along the magnetic field lines connecting the NSs. If a modest fraction η of the extracted electromagnetic power extracted accelerates relativistic particles, the resulting gamma-ray emission a compact volume will result in the formation of an electron-positron pair fireball. Applying a steady-state pair wind model, we quantify the detectability of the precursor fireball with gamma-ray satellites. For η ˜ 1 the gamma-ray detection horizon of Dmax ≈ 10(Bd/1014 G)3/4 Mpc is much closer than the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo horizon of 200 Mpc, unless the NS surface magnetic field strength is very large, B_d ≲ 10^{15} G. Given the quasi-isotropic nature of the emission, mergers with weaker NS fields could contribute a nearby population of short gamma-ray bursts. Power not dissipated close to the binary is carried to infinity along the open field lines by a large-scale Poynting flux. Reconnection within this outflow, well outside of the pair photosphere, provides a potential site for non-thermal emission, such as a coherent millisecond radio burst.
Coherence Constraints and the Last Hidden Optical Coherence
Qian, Xiao-Feng; Vamivakas, A Nick; Eberly, Joseph H
2016-01-01
We have discovered a new domain of optical coherence, and show that it is the third and last member of a previously unreported fundamental triad of coherences. These are unified by our derivation of a parallel triad of coherence constraints that take the form of complementarity relations. We have been able to enter this new coherence domain experimentally and we describe the novel tomographic approach devised for that purpose.
Jeffrey, N. L. S.; Kontar, E. P.
2011-12-01
Aims: We study the polarization of hard X-ray (HXR) sources in the solar atmosphere, including Compton backscattering of photons in the photosphere (the albedo effect) and the spatial distribution of polarization across the source. Methods: HXR photon polarization and spectra produced via electron-ion bremsstrahlung emission are calculated from various electron distributions typical for solar flares. Compton scattering and photoelectric absorption are then modelled using Monte Carlo simulations of photon transport in the photosphere to study the observed (primary and albedo) sources. Polarization maps across HXR sources (primary and albedo components) for each of the modelled electron distributions are calculated at various source locations from the solar centre to the limb. Results: We show that Compton scattering produces a distinct polarization variation across the albedo patch at peak albedo energies of 20-50 keV for all anisotropies modelled. The results show that there are distinct spatial polarization changes in both the radial and perpendicular to radial directions across the extent of the HXR source at a given disk location. In the radial direction, the polarization magnitude and direction at specific positions along the HXR source will either increase or decrease with increased photon distribution directivity towards the photosphere. We also show how high electron cutoff energies influence the direction of polarization at above ~100 keV. Conclusions: Spatially resolved HXR polarization measurements can provide important information about the directivity and energetics of the electron distribution. Our results indicate the preferred angular resolution of polarization measurements required to distinguish between the scattered and primary components. We also show how spatially resolved polarization measurements could be used to probe the emission pattern of an HXR source, using both the magnitude and the direction of the polarization.
Energy Technology Data Exchange (ETDEWEB)
Peysson, Y.; Imbeaux, F. [Association Euratom-CEA, CEA/Cadarache, Dept. de Recherches sur la Fusion Controlee (DRFC), 13 - Saint-Paul-lez-Durance (France)
1999-04-01
A new tomography dedicated to detailed studies of the fast electron Bremsstrahlung emission in the hard X-ray (HXR) energy range between 20 and 200 keV during lower hybrid (LH) current drive experiments on the TORE SUPRA tokamak [Equipe TORE SUPRA, in Proceedings of the 15. Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995), 1, AIEA-CN-60 / A1-5, p. 105] is presented. Radiation detection is performed by cadmium telluride(CdTe) semiconductors, which have most of the desirable features for a powerful diagnosing of magnetically confined hot plasmas - compact size, high X-ray stopping efficiency, fast timing characteristics, good energy resolution, no sensitivity to magnetic field, reasonable susceptibility to performance degradation from neutron/{gamma}-induced damages. This instrument is made of two independent cameras viewing a poloidal cross-section of the plasma, with respectively 21 and 38 detectors. A coarse spectrometry - 8 energy channels - is carried out for each chord, with an energy resolution of 20 keV. The spatial resolution in the core of the plasma is 4-5 cm, while the time sampling may be lowered down to of 2-4 ms. Powerful inversion techniques based on maximum entropy or regularization algorithms take fully advantage of the large number of line-integrated measurements for very robust estimates of the local HXR profiles as a function of time and photon energy. A detailed account of main characteristics and performances of the diagnostic is reported as well as preliminary results on LH current drive experiments. (authors)
Deformation of coherent structures
Fledderus, E.R.; Groesen, van E.
1996-01-01
In this review we investigate the mathematical description of the distortion of clearly recognisable structures in phenomenological physics. The coherent structures we will explicitly deal with are surface waves on a layer of fluid, kink transitions in magnetic material, plane vortices, swirling flo
DEFF Research Database (Denmark)
Andersen, Anne Bendix; Frederiksen, Kirsten; Beedholm, Kirsten;
2016-01-01
During the past decade, politicians and health care providers have strived to create a coherent health care system across primary and secondary health care systems in Denmark. Nevertheless, elderly patients with chronic diseases (EPCD) continue to report experiences of poor-quality care and lack ...
Hobson, R. Peter
2014-01-01
There is a growing body of opinion that we should view autism as fractionable into different, largely independent sets of clinical features. The alternative view is that autism is a coherent syndrome in which principal features of the disorder stand in intimate developmental relationship with each other. Studies of congenitally blind children…
Measuring a coherent superposition
Vitanov, N V; Unanyan, R G; Bergmann, K
1999-01-01
We propose a simple method for measuring the populations and the relative phase in a coherent superposition of two atomic states. The method is based on coupling the two states to a third common (excited) state by means of two laser pulses, and measuring the total fluorescence from the third state for several choices of the excitation pulses.
Coherent detection spectroscopy
Bueren, H.G. van
1969-01-01
Various methods of optical spectroscopy are compared, with special emphasis on resolution and acceptance of the systems. It is shown that coherent detection with a laser as a local oscillator has important advantages for specific applications in astronomical spectroscopy and interferometry, especial
Coherence in multilevel systems
International Nuclear Information System (INIS)
Mathematical descriptions of an excited state multilevel system are developed to include progressively the effects of coherent coupling, feeding, decay and relaxation, and the expressions are illustrated with several pulse coherence experiments utilizing zero field optically detected magnetic resonance of excited triplet states. A new method is described in which the time development of the coherent components in a multilevel system is monitored by using an observable that can measure only relative populations between the levels. The method is illustrated. By treating a coherently driven excited state system as two levels in contact with a population reservoir, exact expressions are obtained for both transient and steady-state behavior in the presence of transverse and spin lattice relaxation, constant incoherent pumping, spontaneous emission between the two levels, and also decay back into the reservoir. The general mathematical development is applied specifically to zero field microwave phosphorescence double resonance. Experimental methods and apparatus are discussed in detail and results of optically detected transient mutations, spin echoes, and Fourier transform spectroscopy are presented. (26 figs, 220 refs)
Dental Optical Coherence Tomography
Kun-Feng Lin; Jui-che Tsai; Ching-Cheng Chuang; Shyh-Yuan Lee; Yi-Ching Ho; Yao-Sheng Hsieh; Chia-Wei Sun
2013-01-01
This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons between OCT and other clinical oral diagnostic methods are also discussed.
Coherent states in quantum mechanics
Rodrigues, R D L; Fernandes, D
2001-01-01
We present a review work on the coherent states is non-relativistic quantum mechanics analysing the quantum oscillators in the coherent states. The coherent states obtained via a displacement operator that act on the wave function of ground state of the oscillator and the connection with Quantum Optics which were implemented by Glauber have also been considered. A possible generalization to the construction of new coherent states it is point out.
Coherent states in quantum mechanics
International Nuclear Information System (INIS)
We present a review work on the coherent states is non-relativistic quantum mechanics analysing the quantum oscillators in the coherent states. The coherent states obtained via a displacement operator that act on the wave function of ground state of the oscillator and the connection with Quantum Optics which were implemented by Glauber have also been considered. A possible generalization to the construction of new coherent states it is point out. (author)
Operational Resource Theory of Coherence.
Winter, Andreas; Yang, Dong
2016-03-25
We establish an operational theory of coherence (or of superposition) in quantum systems, by focusing on the optimal rate of performance of certain tasks. Namely, we introduce the two basic concepts-"coherence distillation" and "coherence cost"-in the processing quantum states under so-called incoherent operations [Baumgratz, Cramer, and Plenio, Phys. Rev. Lett. 113, 140401 (2014)]. We, then, show that, in the asymptotic limit of many copies of a state, both are given by simple single-letter formulas: the distillable coherence is given by the relative entropy of coherence (in other words, we give the relative entropy of coherence its operational interpretation), and the coherence cost by the coherence of formation, which is an optimization over convex decompositions of the state. An immediate corollary is that there exists no bound coherent state in the sense that one would need to consume coherence to create the state, but no coherence could be distilled from it. Further, we demonstrate that the coherence theory is generically an irreversible theory by a simple criterion that completely characterizes all reversible states. PMID:27058063
Coherent hybrid electromagnetic field imaging
Cooke, Bradly J.; Guenther, David C.
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.
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 action we define the Demazure Descent Data on the latter category and prove that the Descent category is equivalent to the derived category of G-equivariant sheaves on X....
Disruption, beamstrahlung, and beamstrahlung pair creation
Energy Technology Data Exchange (ETDEWEB)
Chen, P.
1988-12-01
The two major effects from the interaction of e/sup /minus//e/sup +/ beams---beamstrahlung and disruption---are reviewed, with emphasis on flat beam collisions. For the disruption effects we discuss the luminosity enhancement factor, the maximum and rms disruption angles, and the ''kink instability''. All the results are obtained from computer simulations, and scaling laws based on these are deduced whenever possible. For the beamstrahlung effects, we concentrate only on the final electron energy spectrum and the deflection angle associated with low energy particles. In addition to the generic studies on the beam-beam effects, we also list the relevant beam-beam parameters obtained from simulations on two sample designs: the TLC and the ILC. As an addendum, the newly discovered phenomenon of coherent beamstrahlung pair creation, together with the incoherent process, are discussed. 18 refs., 15 figs., 1 tab.
Scott, R H H; Perez, F; Streeter, M J V; Davies, J R; Schlenvoigt, H -P; Santos, J J; Hulin, S; Lancaster, K L; Baton, S D; Rose, S J; Norreys, P A
2013-01-01
A photon detector suitable for the measurement of bremsstrahlung spectra generated in relativistically-intense laser-solid interactions is described. The Monte Carlo techniques used to back-out the fast electron spectrum and laser energy absorbed into fast electrons are detailed. A relativistically-intense laser-solid experiment using frequency doubled laser light is used to demonstrate the effective operation of the detector. The experimental data was interpreted using the 3-spatial-dimension Monte Carlo code MCNPX (Pelowitz 2008), and the fast electron temperature found to be 125 keV.
Abgrall, N; Avignone, F T; Barabash, A S; Bertrand, F E; Boswell, M; Brudanin, V; Busch, M; Caldwell, A S; Chan, Y-D; Christofferson, C D; Combs, D C; Cooper, R J; Creswick, R J; Detwiler, J A; Doe, P J; Efremenko, Yu; Egorov, V; Elliott, S R; Fast, J E; Finnerty, P; Giovanetti, G K; Goett, J; Green, M P; Gruszko, J; Guiseppe, V E; Gusev, K; Hegai, A; Henning, R; Hoppe, E W; Howard, S; Howe, M A; Keeter, K J; Kidd, M F; Knecht, A; Kochetov, O; Konovalov, S I; Kouzes, R T; LaFerriere, B D; Leon, J; Leviner, L E; Loach, J C; MacMullin, J; MacMullin, S; Marino, M G; Martin, R D; Mertens, S; Orrell, J L; O'Shaughnessy, C; Overman, N R; Phillips, D G; Poon, A W P; Pushkin, K; Radford, D C; Robertson, R G H; Ronquest, M C; Schubert, A G; Shanks, B; Shirchenko, M; Snavely, K J; Snyder, N; Steele, D; Suriano, A M; Thompson, J; Timkin, V; Varner, R L; Vasilyev, S; Vetter, K; Vorren, K; White, B R; Wilkerson, J F; Xu, W; Yakushev, E; Young, A R; Yu, C H; Yumatov, V
2014-01-01
A low-background, high-purity germanium detector has been used to search for evidence of low-energy, bremsstrahlung-generated solar axions. An upper bound of $1.36\\times 10^{-11}$ $(95\\% CL)$ is placed on the direct coupling of DFSZ model axions to electrons. The prospects for the sensitivity of the Majorana Demonstrator array of point-contact germanium detectors to solar axions are discussed in the context of the model-independent annual modulation due to the seasonal variation of the earth-sun distance.
International Nuclear Information System (INIS)
Inverse bremsstrahlung absorption of the pump laser beam in a backward Raman amplifier over the round-trip light transit time through the sub-critical density plasma can more than double the electron temperature of the plasma and produce time-varying axial temperature gradients. The resulting increased Landau damping of the plasma wave and detuning of the resonance can act to stabilize the pump against unwanted amplification of Langmuir noise without disrupting nonlinear amplification of the femtosecond seed pulse. Because the heating rate increases with the charge state Z, only low-Z plasmas (hydrogen, helium, or helium-hydrogen mixtures) will maintain a low enough temperature for efficient operation
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.
Monte-Carlo method simulation of the Bremsstrahlung mirror reflection experiment
International Nuclear Information System (INIS)
Full text: To detect gamma-ray mirror reflection on macroscopic smooth surface a search experiment at microtron MT-22S with 330 meter flying distance is in progress. Measured slip angles (i.e. angles between incident ray and reflector surface) don't exceed tens of micro-radian. Under such angles an effect of the reflection could be easily veiled due to negative background conditions. That is why the process needed to be simulated by Monte-Carlo method as accurate as possible and corresponding computer program was developed. A first operating mode of the MT-22S generates 13 MeV electrons that are incident on a Bremsstrahlung target. So energies of gamma-rays were simulated to be in the range of 0.01†12.5 MeV and be distributed by known Shift formula. When any gamma-quantum was incident on the reflector it resulted in following two cases. If its slip angle was more than the critical one, gamma-quantum was to be absorbed by the reflector and the program started to simulate next event. In the other case the program replaced incident gamma-quantum trajectory parameters by the reflected ones. The gamma-quantum trajectory behind the reflector was traced till its detector. Any gamma-quantum that got the detector was to be registered. As any simulated gamma-quantum was of random energy the critical slip angle of every simulated event was evaluated by the following formula: αcrit = eh/E √ZNAρ/πAm. Table values of the absorption coefficients were used for random simulation of gamma-quanta absorption in the air. And it was assumed that any gamma-quantum interaction with air resulted in its disappearance. Dependence of different flying distances (120 and 330 m), gap heights (10, 20 and 50 μ) of the gap collimator and inclinations (20 and 40 μrad) of the reflector's plane on detected gamma-quanta energy distribution and vertical angle one was studied with a help of the developed program
Test of Compton camera components for prompt gamma imaging at the ELBE bremsstrahlung beam
Hueso-González, F.; Golnik, C.; Berthel, M.; Dreyer, A.; Enghardt, W.; Fiedler, F.; Heidel, K.; Kormoll, T.; Rohling, H.; Schöne, S.; Schwengner, R.; Wagner, A.; Pausch, G.
2014-05-01
In the context of ion beam therapy, particle range verification is a major challenge for the quality assurance of the treatment. One approach is the measurement of the prompt gamma rays resulting from the tissue irradiation. A Compton camera based on several position sensitive gamma ray detectors, together with an imaging algorithm, is expected to reconstruct the prompt gamma ray emission density map, which is correlated with the dose distribution. At OncoRay and Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a Compton camera setup is being developed consisting of two scatter planes: two CdZnTe (CZT) cross strip detectors, and an absorber consisting of one Lu2SiO5 (LSO) block detector. The data acquisition is based on VME electronics and handled by software developed on the ROOT framework. The setup has been tested at the linear electron accelerator ELBE at HZDR, which is used in this experiment to produce bunched bremsstrahlung photons with up to 12.5 MeV energy and a repetition rate of 13 MHz. Their spectrum has similarities with the shape expected from prompt gamma rays in the clinical environment, and the flux is also bunched with the accelerator frequency. The charge sharing effect of the CZT detector is studied qualitatively for different energy ranges. The LSO detector pixel discrimination resolution is analyzed and it shows a trend to improve for high energy depositions. The time correlation between the pulsed prompt photons and the measured detector signals, to be used for background suppression, exhibits a time resolution of 3 ns FWHM for the CZT detector and of 2 ns for the LSO detector. A time walk correction and pixel-wise calibration is applied for the LSO detector, whose resolution improves up to 630 ps. In conclusion, the detector setup is suitable for time-resolved background suppression in pulsed clinical particle accelerators. Ongoing tasks are the quantitative comparison with simulations and the test of imaging algorithms. Experiments at proton
Maydanyuk, Sergei P
2012-01-01
A new model of the bremsstrahlung emission which accompanies proton decay and collisions of protons off nuclei in the energy region from the lowest up to intermediate, has been developed. This model includes spin formalism, potential approach for description of interaction between protons and nuclei, and operator of emission includes component of the magnetic emission (defined on the basis of Pauli equation). In the problem of the bremsstrahlung during the proton decay in the first time a role of the magnetic emission is studied using such a model. For the studied $^{146}{\\rm Tm}$ nucleus it has been studied the following: (1) How much does the magnetic emission change the full bremsstrahlung spectrum? (2) At which angle is the magnetic emission the most intensive relatively electric one? (3) Is there some space region where the magnetic emission increases strongly relatively electric one? (4) How intensive is the magnetic emission in the tunneling region? (5) Which values has the probability at its maximum a...
Photoproduction of $\\pi^0$-pairs off protons and off neutrons
Dieterle, M; Ahrens, J; Annand, J R M; Arends, H J; Bantawa, K; Bartolome, P A; Beck, R; Bekrenev, V; Berghäuser, H; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Costanza, S; Demissie, B; Downie, E J; Drexler, P; Fil'kov, L V; Fix, A; Garni, S; Glazier, D I; Hamilton, D; Heid, E; Hornidge, D; Howdle, D; Huber, G M; Jahn, O; Jude, T C; Käser, A; Kashevarov, V L; Keshelashvili, I; Kondratiev, R; Korolija, M; Krusche, B; Lisin, V; Livingston, K; MacGregor, I J D; Maghrbi, Y; Mancell, J; Manley, D M; Marinides, Z; McGeorge, J C; McNicoll, E; Mekterovic, D; Metag, V; Micanovic, S; Middleton, D G; Mushkarenkov, A; Nikolaev, A; Novotny, R; Ostrick, M; Otte, P; Oussena, B; Pedroni, P; Pheron, F; Polonski, A; Prakhov, S; Robinson, J; Rostomyan, T; Schumann, S; Sikora, M H; Sober, D I; Starostin, A; Strub, Th; Supek, I; Thiel, M; Thomas, A; Unverzagt, M; Walford, N K; Watts, D P; Werthmüller, D; Witthauer, L
2015-01-01
Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of $\\pi^0\\pi^0$ pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557~MeV, which produced bremsstrahlung in thin radiator foils. The tagged photon beam covered energies up to 1400~MeV. The data from the free proton target are in good agreement with previous measurements and were only used to test the analysis procedures. The results for differential cross sections (angular distributions and invariant-mass distributions) for free and quasi-free protons are almost identical in shape, but differ in absolute magnitude up to 15\\%. Thus, moderate final-state interaction effects are present. The data for quasi-free neutrons are similar to the proton data in the second resonance r...
Symmetric, coherent, Choquet capacities
Kadane, Joseph B.; Wasserman, Larry
1996-01-01
Choquet capacities are a generalization of probability measures that arise in robustness, decision theory and game theory. Many capacities that arise in robustness are symmetric or can be transformed into symmetric capacities. We characterize the extreme points of the set of upper distribution functions corresponding to coherent, symmetric Choquet capacities on [0, 1]. We also show that the set of 2-alternating capacities is a simplex and we give a Choquet representation of this set.
Bidirectional coherent classical communication
Harrow, Aram W.; Leung, Debbie W.
2005-01-01
A unitary interaction coupling two parties enables quantum or classical communication in both the forward and backward directions. Each communication capacity can be thought of as a tradeoff between the achievable rates of specific types of forward and backward communication. Our first result shows that for any bipartite unitary gate, bidirectional coherent classical communication is no more difficult than bidirectional classical communication — they have the same achievable rate regions. ...
Interleaved optical coherence tomography.
Lee, Hee Yoon; Sudkamp, Helge; Marvdashti, Tahereh; Ellerbee, Audrey K
2013-11-01
We present a novel and cost-effective technique--interleaved optical coherence tomography (iOCT)--to enhance the imaging speed of swept source OCT systems by acquiring data from multiple lateral positions simultaneously during a single wavelength sweep, using a single detector and a virtually imaged phase array (VIPA) as a multi-band demultiplexer. This technique uses spectral encoding to convert coherence length into higher imaging speed; the speed enhancement factor is independent of the source speed or center wavelength, and the effective A-scan rate scales linearly with sweep speed. The optical configuration requires only a change in the sample arm of a traditional OCT system and preserves the axial resolution and fall-off characteristic of a traditional SS-OCT using the same light source. Using 10 kHz, 20 kHz and 100 kHz sources we provide a first demonstration of image speed enhancement factors of up to 12, 6 and 10, respectively, which yield effective A-scan rates of 120 kHz, 120 kHz and 1 MHz for B-scan imaging, with a sensitivity of up to 82.5 dB. We also show that iOCT can image faster dynamics than traditional OCT B-scan imaging and is capable of 3D biological imaging. The iOCT concept suggests a new route to high-speed OCT imaging for laser developers: that is, by focusing on improving the coherence length and linewidth of existing and emerging sources. Hence, iOCT is a nice complement to ongoing research and commercial efforts to enable faster imaging through development of lasers with faster sweep rates, and offers new hope for existing sources with slow sweep rates and potential for enhancement of coherence length to compete with faster sources to achieve high-speed OCT. PMID:24216876
Diffractive charged meson pair production
Lehmann-Dronke, B; Schäfer, S; Stein, E; Schäfer, A
1999-01-01
We investigate the possibility to measure the nonforward gluon distribution function by means of diffractively produced charged pion and kaon pairs in polarized lepton nucleon scattering. The resulting cross sections are sizable and are dominated by the gluonic contribution. We find large spin asymmetries, both for pion pairs and for kaon pairs.
Physiological aspects of paired stimulation
Meijler, F.L.; Durrer, D.
1965-01-01
In this paper some physiological and clinical aspects of paired stimulation are discussed. I) The augmenting effect of paired stimulation on rnyocardial contractility is due to potentiation (increase in speed of restitution) and fusion of two contractions. 2) While using paired stimulation the oxyg
Energy Technology Data Exchange (ETDEWEB)
Litvinenko,V.
2009-05-04
Cooling intense high-energy hadron beams remains a major challenge in modern accelerator physics. Synchrotron radiation is still too feeble, while the efficiency of two other cooling methods, stochastic and electron, falls rapidly either at high bunch intensities (i.e. stochastic of protons) or at high energies (e-cooling). In this talk a specific scheme of a unique cooling technique, Coherent Electron Cooling, will be discussed. The idea of coherent electron cooling using electron beam instabilities was suggested by Derbenev in the early 1980s, but the scheme presented in this talk, with cooling times under an hour for 7 TeV protons in the LHC, would be possible only with present-day accelerator technology. This talk will discuss the principles and the main limitations of the Coherent Electron Cooling process. The talk will describe the main system components, based on a high-gain free electron laser driven by an energy recovery linac, and will present some numerical examples for ions and protons in RHIC and the LHC and for electron-hadron options for these colliders. BNL plans a demonstration of the idea in the near future.
International Nuclear Information System (INIS)
The Coherent Laser Vision System (CLVS) is being developed to provide precision real-time 3D world views to support site characterization and robotic operations and during facilities Decontamination and Decommissioning. Autonomous or semiautonomous robotic operations requires an accurate, up-to-date 3D world view. Existing technologies for real-time 3D imaging, such as AM laser radar, have limited accuracy at significant ranges and have variability in range estimates caused by lighting or surface shading. Recent advances in fiber optic component technology and digital processing components have enabled the development of a new 3D vision system based upon a fiber optic FMCW coherent laser radar. The approach includes a compact scanner with no-moving parts capable of randomly addressing all pixels. The system maintains the immunity to lighting and surface shading conditions which is characteristic to coherent laser radar. The random pixel addressability allows concentration of scanning and processing on the active areas of a scene, as is done by the human eye-brain system
Energy Technology Data Exchange (ETDEWEB)
Sebastion, R.L. [Coleman Research Corp., Springfield, VA (United States)
1995-10-01
The Coherent Laser Vision System (CLVS) is being developed to provide precision real-time 3D world views to support site characterization and robotic operations and during facilities Decontamination and Decommissioning. Autonomous or semiautonomous robotic operations requires an accurate, up-to-date 3D world view. Existing technologies for real-time 3D imaging, such as AM laser radar, have limited accuracy at significant ranges and have variability in range estimates caused by lighting or surface shading. Recent advances in fiber optic component technology and digital processing components have enabled the development of a new 3D vision system based upon a fiber optic FMCW coherent laser radar. The approach includes a compact scanner with no-moving parts capable of randomly addressing all pixels. The system maintains the immunity to lighting and surface shading conditions which is characteristic to coherent laser radar. The random pixel addressability allows concentration of scanning and processing on the active areas of a scene, as is done by the human eye-brain system.
Institute of Scientific and Technical Information of China (English)
De Xu ZHOU
2009-01-01
Assume that S is an almost excellent extension of R. Using functors Hom R(S,-) and -(×)R S, we establish some connections between classes of modules (L)R and (L)S, cotorsion pairs ((A)R, (A)R)and ((A)S, (B)S). If (L)S is a T-extension or (and) H-extension of (L)R, we show that (L)S is a (resp., monomorphic, epimorphic, special) preenveloping class if and only if so is (L)R. If (S, S) is a TH-extension of ((A)R,(B)R), we obtain that ((A)S,(B)S) is complete (resp., of finite type, of cofinite type, hereditary, perfect, n-tilting) if and only if so is ((A)R,(B)R).
International Nuclear Information System (INIS)
A many-body approach to hadron structure is presented, in which we consider two parton species: spin-0 (b-partons), and spin-1/2 (f-partons). We extend a boson and a fermion pairing scheme for the b-, and f-partons respectively, into a Yang-Mills gauge theory. The main feature of this theory is that the gauge field is not identified with the usual gluon field variable in QCD. We study the confinement problem of the hadron constituents, and obtain, for low temperatures, partons that are confined by energy gaps. As the critical temperatures for the corresponding phase transitions are approached, the energy gap gradually disappears, and confinement is lost. The theory goes beyond the non-relativistic harmonic oscillator quark model, in the sense of giving physical reasons why a non-relativistic approximation is adequate in describing the internal dynamics of hadron structure. (author)
Calibration of airborne SAR interferograms using multisquint-processed image pairs
Prats, Pau; Mallorqui, Jordi J.; Reigber, Andreas; Broquetas, Antoni
2004-01-01
This paper presents two different approaches to detect and correct phase errors appearing in interferometric airborne SAR sensors due to the lack of precision in the navigation system. The first one is intended for interferometric pairs with high coherence, and the second one for low coherent ones. Both techniques are based on a multisquint processing approach, i.e., by processing the same image pairs with different squint angles we can combine the information of different interferograms to obtain the desired phase correction. Airborne single- and repeat-pass interferometric data from the Deutsches Zentrum fur Luft- und Raumfahrt (DLR) Experimental airborne SAR is used to validate the method.
Dose calculations using MARS for Bremsstrahlung beam stops and collimators in APS beamline stations.
Energy Technology Data Exchange (ETDEWEB)
Dooling, J.; Accelerator Systems Division (APS)
2010-11-01
The Monte Carlo radiation transport code MARS is used to model the generation of gas bremsstrahlung (GB) radiation from 7-GeV electrons which scatter from residual gas atoms in undulator straight sections within the Advanced Photon Source (APS) storage ring. Additionally, MARS is employed to model the interactions of the GB radiation with components along the x-ray beamlines and then determine the expected radiation dose-rates that result. In this manner, MARS can be used to assess the adequacy of existing shielding or the specifications for new shielding when required. The GB radiation generated in the 'thin-target' of an ID straight section will consist only of photons in a 1/E-distribution up to the full energy of the stored electron beam. Using this analytical model, the predicted GB power for a typical APS 15.38-m insertion device (ID) straight section is 4.59 x 10{sup -7} W/nTorr/mA, assuming a background gas composed of air (Z{sub eff} = 7.31) at room temperature (293K). The total GB power provides a useful benchmark for comparisons between analytical and numerical approaches. We find good agreement between MARS and analytical estimates for total GB power. The extended straight section 'target' creates a radial profile of GB, which is highly peaked centered on the electron beam. The GB distribution reflects the size of the electron beam that creates the radiation. Optimizing the performance of MARS in terms of CPU time per incident trajectory requires the use of a relatively short, high-density gas target (air); in this report, the target density is {rho}L = 2.89 x 10{sup -2} g/cm{sup 2} over a length of 24 cm. MARS results are compared with the contact dose levels reported in TB-20, which used EGS4 for radiation transport simulations. Maximum dose-rates in 1 cc of tissue phantom form the initial basis for comparison. MARS and EGS4 results are approximately the same for maximum 1-cc dose-rates and attenuation in the photon
International Nuclear Information System (INIS)
Inertial confinement fusion is being studied on the Z facility at Sandia National Laboratories. Z is a large z-pinch machine which can provide 20 MA of current to z-pinch loads producing ∼1.8 MJ of soft x rays in less than 10 ns. Within the pinch region, decelerated electrons produce a strong source of bremsstrahlung radiation which varies from shot to shot. Additionally, a variety of inertial confinement fusion targets may produce fusion neutrons, the intensity and distribution of which depend on the temperature and density of the pinch. In this article, we describe the computer modeling behind the shielding design of a simple time-resolved, one-dimensional imaging array. This diagnostic will provide a time history for both the bremsstrahlung and neutron production as a function of height in the target. Calculations show that by building an array of scintillator fibers separated by long, thin tungsten collimator plates, a sampling rate of 0.254 mm at the target can be achieved. The corresponding channel-to-channel discrimination for such a design is shown to be better than 1000 ampersand as;1 for <4 MeV photons and 100 ampersand as;1 for 2.45 MeV neutrons. By coupling scintillator fibers to a fiber-optic streak camera system, the system time response is expected to be dominated by the scintillator response (∼1.2 ns). copyright 1999 American Institute of Physics
Attenuation of bremsstrahlung from 90Sr-90Y, 147Pm and 204Tl in thick target compounds
Manjunatha, H. C.
2014-11-01
The external bremsstrahlung (EB) produced by beta particles such as from 90Sr-90Y, 147Pm and 204Tl in PbCl2, PbF2, Pb(NO3)2 and CdO were measured using NaI(Tl) crystal. The beta stopper technique is employed to measure the integral intensities above 100 keV energy in different absorber thicknesses. Attenuation of the external bremsstrahlung, excited by 90Sr-90Y, 147Pm and 204Tl beta-emitters in the same compounds has also been studied. The measured attenuation parameter is not constant with absorber thickness and it increases with increasing Zmod of the absorber. Whereas, the mass attenuation coefficient of gamma rays of equivalent energy is independent of the absorber thickness. This confirms that the attenuation of EB in an absorber does not conform to a single exponential law, unlike the absorption of monoenergetic gamma rays. Rather it may be a combination of a large number of exponential terms.
International Nuclear Information System (INIS)
The energy spectra of secondary neutrons produced when bremsstrahlung of end-point energy in the range 10-30 MeV is incident on oxygen, carbon and nitrogen have been calculated. Photonuclear reactions of the type (γ,n) and (γ,pn) have been included. The respective contributions of various nuclear reactions have been adjusted using the published values of experimentally determined cross-sections, or branching ratios, where these are available. Where no such information exists in the literature, the values have been empirically estimated. Agreement has been obtained between the calculated photoneutron spectra from C, N and O at various energies and the available experimentally-measured spectra. The photoneutron spectra from C,N and O have been combined in the right proportion (C5H40O18N) to compute the spectra of secondary neutrons from tissue irradiated with bremsstrahlung of end-point energy from 10-30 MeV. Mean neutron energies and kerma factors for these spectra have been calculated. (author)
Samarai, I Al; Rosado, J
2016-01-01
A small contribution of molecular Bremsstrahlung radiation to the air-fluorescence yield in the UV range is estimated based on an approach previously developed in the framework of the radio-detection of showers in the gigahertz frequency range. First, this approach is shown to provide an estimate of the main contribution of the fluorescence yield due to the de-excitation of the C $^3\\Pi_{\\mathrm{u}}$ electronic level of nitrogen molecules to the B $^3\\Pi_{\\mathrm{g}}$ one amounting to $Y_{[337]}=(6.05\\pm 1.50)~$ MeV$^{-1}$ at 800 hPa pressure and 293 K temperature conditions, which compares well to previous dedicated works and to experimental results. Then, under the same pressure and temperature conditions, the fluorescence yield induced by molecular Bremsstrahlung radiation is found to be $Y_{[330-400]}^{\\mathrm{MBR}}=0.10~$ MeV$^{-1}$ in the wavelength range of interest for the air-fluorescence detectors used to detect extensive air showers induced in the atmosphere by ultra-high energy cosmic rays. This m...
Quantum Dynamics of Radical-Ion-Pair Reactions
Kominis, I K
2010-01-01
Radical-ion-pair reactions were recently shown to represent a rich biophysical laboratory for the application of quantum measurement theory methods and concepts, casting doubt on the validity of the theoretical treatment of these reactions and the results thereof that has been at the core of spin chemistry for several decades now. The ensued scientific debate, although exciting, is plagued with several misconceptions. We will here provide a comprehensive treatment of the quantum dynamics of radical-ion-pair reactions, generalizing our recent work and elaborating on the analogy with the double-slit experiment having partial "which-path" information. This analogy directly leads to the general treatment of radical-ion pair reactions covering the whole range between the two extremes, that of perfect singlet-triplet coherence and that of complete incoherence.
Energy Technology Data Exchange (ETDEWEB)
Medenwaldt, R.; Moeller, S.P.; Soerensen, A.H.; Uggerhoej, E. (Aarhus Univ. (Denmark). Inst. for Synchrotron Radiation); Elsener, K. (European Organization for Nuclear Research, Geneva (Switzerland)); Hage-Ali, M.; Siffert, P.; Stoquert, J. (Strasbourg-1 Univ., 67 (France). Centre de Recherches Nucleaires); Sona, P. (Florence Univ. (Italy). Dipt. di Fisica Istituto Nazionale di Fisica Nucleare, Florence (Italy))
1991-05-09
Along planar directions in both Si and C single crystals the radiation yields from 150GeV electrons are enhanced 40 times or more and the data present the first use of C crystals in the multi-hundred GeV region. For channeled electrons in Si the experimental results agree with calculations using the constant field approximation (CFA). Increasing incident angles reduce rapidly soft photon yields as expected from first order corrections to CFA. The first Born approximation only describes experimental results for large incident angles to planes. (orig.).
Medenwaldt, R.; Møller, S. P.; Sørensen, A. H.; Uggerhøj, E.; Elsener, K.; Hage-Ali, M.; Siffert, P.; Stoquert, J.; Sona, P.
1991-05-01
Along planar directions in both Si and C single crystals the radiation yields from 150 GeV electrons are enhanced 40 times or more and the data present the first use of C crystals in the multi-hundred GeV region. For channeled electrons in Si the experimental results agree with calculations using the constant field approximation (CFA). Increasing incident angles reduce rapidly soft photon yields as expected from first order corrections to CFA. The first born approximation only describes experimental results for large incident angles to planes.
Multiple origins of asteroid pairs
Jacobson, Seth A.
2016-01-01
Rotationally fissioned asteroids produce unbound asteroid pairs that have very similar heliocentric orbits. Backward integration of their current heliocentric orbits provides an age of closest proximity that can be used to date the rotational fission event. Most asteroid pairs follow a predicted theoretical relationship between the primary spin period and the mass ratio of the two pair members that is a direct consequence of the YORP-induced rotational fission hypothesis. If the progenitor asteroid has strength, asteroid pairs may have higher mass ratios or faster rotating primaries. However, the process of secondary fission leaves the originally predicted trend unaltered. We also describe the characteristics of pair members produced by four alternative routes from a rotational fission event to an asteroid pair. Unlike direct formation from the event itself, the age of closest proximity of these pairs cannot generally be used to date the rotational fission event since considerable time may have passed.
Holographic microscopy in low coherence
Chmelík, Radim; Petráček, Jiří; Slabá, Michala; Kollárová, Věra; Slabý, Tomáš; Čolláková, Jana; Komrska, Jiří; Dostál, Zbyněk.; Veselý, Pavel
2016-03-01
Low coherence of the illumination substantially improves the quality of holographic and quantitative phase imaging (QPI) by elimination of the coherence noise and various artefacts and by improving the lateral resolution compared to the coherent holographic microscopy. Attributes of coherence-controlled holographic microscope (CCHM) designed and built as an off-axis holographic system allowing QPI within the range from complete coherent to incoherent illumination confirmed these expected advantages. Low coherence illumination also furnishes the coherence gating which constraints imaging of some spatial frequencies of an object axially thus forming an optical section in the wide sense. In this way the depth discrimination capability of the microscope is introduced at the price of restricting the axial interval of possible numerical refocusing. We describe theoretically these effects for the whole range of illumination coherence. We also show that the axial refocusing constraints can be overcome using advanced mode of imaging based on mutual lateral shift of reference and object image fields in CCHM. Lowering the spatial coherence of illumination means increasing its numerical aperture. We study how this change of the illumination geometry influences 3D objects QPI and especially the interpretation of live cells QPI in terms of the dry mass density measurement. In this way a strong dependence of the imaging process on the light coherence is demonstrated. The theoretical calculations and numerical simulations are supported by experimental data including a chance of time-lapse watching of live cells even in optically turbid milieu.
Propagation of some coherent and partially coherent laser beams
Cai, Yangjian
2006-01-01
In this thesis, we investigate the propagation of some coherent and partially coherent laser beams, including a dark hollow beam (DHB), an elliptical Gaussian beam (EGB), a flat-topped beam and a twisted anisotropic Gaussian Schell-model (TAGSM) beam, through a paraxial optical system or a turbulent atmosphere. Several theoretical models are proposed to describe a DHB of circular or non-circular symmetry. Approximate analytical formulas for a DHB and a partially coherent TAGSM beam propagatin...
2000-01-01
Honolulu, on the island of Oahu, is a large and growing urban area. This stereoscopic image pair, combining a Landsat image with topography measured by the Shuttle Radar Topography Mission (SRTM), shows how topography controls the urban pattern. This color image can be viewed in 3-D by viewing the left image with the right eye and the right image with the left eye (cross-eyed viewing), or by downloading and printing the image pair, and viewing them with a stereoscope.Features of interest in this scene include Diamond Head (an extinct volcano near the bottom of the image), Waikiki Beach (just above Diamond Head), the Punchbowl National Cemetary (another extinct volcano, near the image center), downtown Honolulu and Honolulu harbor (image left-center), and offshore reef patterns. The slopes of the Koolau mountain range are seen in the right half of the image. Clouds commonly hang above ridges and peaks of the Hawaiian Islands, but in this synthesized stereo rendition appear draped directly on the mountains. The clouds are actually about 1000 meters (3300 feet) above sea level.This stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with a Landsat 7 Thematic Mapper image collected at the same time as the SRTM flight. The topography data were used to create two differing perspectives, one for each eye. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions. The United States Geological Survey's Earth Resources Observations Systems (EROS) Data Center, Sioux Falls, South Dakota, provided the Landsat data.The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission was designed to collect three-dimensional measurements of the Earth
Pairing interactions and vanishing pairing correlations in hot nuclei
Energy Technology Data Exchange (ETDEWEB)
Khan, E.; Giai, Nguyen Van [Institut de Physique Nucleaire, Universite Paris-Sud, IN2P3-CNRS, 91406 Orsay Cedex (France); Sandulescu, N. [Institut de Physique Nucleaire, Universite Paris-Sud, IN2P3-CNRS, 91406 Orsay Cedex (France); Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest (Romania)
2007-03-15
Finite temperature Hartree-Fock-Bogoliubov calculations are performed in Sn isotopes using Skyrme and zero-range, density-dependent pairing interactions. For both stable and very neutron- rich nuclei the critical temperature at which pairing correlations vanish is independent of the volume/surface nature of the pairing interaction. The value of the critical temperature follows approximately the empirical rule T{sub c} {approx_equal} 0.5 {delta}{sub T=0} for all the calculated isotopes, showing that the critical temperature could be deduced from the pairing gap at zero temperature. On the other hand, the pairing gap at temperatures just below T{sub c} is strongly sensitive to the volume/surface nature of the pairing interaction. (authors)
Stereo Pair, Pasadena, California
2000-01-01
This stereoscopic image pair is a perspective view that shows the western part of the city of Pasadena, California, looking north toward the San Gabriel Mountains. Portions of the cities of Altadena and La Canada Flintridge are also shown. The cluster of large buildings left of center, at the base of the mountains, is the Jet Propulsion Laboratory. This image shows the power of combining data from different sources to create planning tools to study problems that affect large urban areas. In addition to the well-known earthquake hazards, Southern California is affected by a natural cycle of fire and mudflows. Data shown in this image can be used to predict both how wildfires spread over the terrain and how mudflows are channeled down the canyons.The image was created from three datasets: the Shuttle Radar Topography Mission (SRTM) supplied the elevation, U. S. Geological Survey digital aerial photography provided the image detail, and the Landsat Thematic Mapper provided the color. The United States Geological Survey's Earth Resources Observations Systems (EROS) Data Center, Sioux Falls, South Dakota, provided the Landsat data and the aerial photography. The image can be viewed in 3-D by viewing the left image with the right eye and the right image with the left eye (cross-eyed viewing), or by downloading and printing the image pair, and viewing them with a stereoscope.The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an additional C-band imaging antenna and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA
Topological Properties of Spatial Coherence Function
Institute of Scientific and Technical Information of China (English)
REN Ji-Rong; ZHU Tao; DUAN Yi-Shi
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.
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.
Volitional Control of Neuromagnetic Coherence
Directory of Open Access Journals (Sweden)
Matthew D Sacchet
2012-12-01
Full Text Available Coherence of neural activity between circumscribed brain regions has been implicated as an indicator of intracerebral communication in various cognitive processes. While neural activity can be volitionally controlled with neurofeedback, the volitional control of coherence has not yet been explored. Learned volitional control of coherence could elucidate mechanisms of associations between cortical areas and its cognitive correlates and may have clinical implications. Neural coherence may also provide a signal for brain-computer interfaces (BCI. In the present study we used the Weighted Overlapping Segment Averaging (WOSA method to assess coherence between bilateral magnetoencephalograph (MEG sensors during voluntary digit movement as a basis for BCI control. Participants controlled an onscreen cursor, with a success rate of 124 of 180 (68.9%, sign-test p < 0.001 and 84 out of 100 (84%, sign-test p < 0.001. The present findings suggest that neural coherence may be volitionally controlled and may have specific behavioral correlates.
Quantum Coherence as a Resource
Streltsov, Alexander; Plenio, Martin B
2016-01-01
The coherent superposition of states, in combination with energy quantization, represents one of the most fundamental features that mark the departure of quantum mechanics from the classical realm. Quantum coherence in many-body systems embodies the essence of entanglement and is an essential ingredient for a plethora of physical phenomena in quantum optics, quantum information, solid state physics, and nanoscale thermodynamics. In recent years, research on the presence and functional role of quantum coherence in biological systems has also attracted a considerable interest. Despite the fundamental importance of quantum coherence, the development of a rigorous theory of quantum coherence as a physical resource has only been initiated recently. In this Colloquium we discuss and review the development of this rapidly growing research field that encompasses the characterization, quantification, manipulation, dynamical evolution, and operational application of quantum coherence.
Objective Eulerian coherent structures
Serra, Mattia; Haller, George
2016-05-01
We define objective Eulerian Coherent Structures (OECSs) in two-dimensional, non-autonomous dynamical systems as the instantaneously most influential material curves. Specifically, OECSs are stationary curves of the averaged instantaneous material stretching-rate or material shearing-rate functionals. From these objective (frame-invariant) variational principles, we obtain explicit differential equations for hyperbolic, elliptic, and parabolic OECSs. As an illustration, we compute OECSs in an unsteady ocean velocity data set. In comparison to structures suggested by other common Eulerian diagnostic tools, we find OECSs to be the correct short-term cores of observed trajectory deformation patterns.
Objective Eulerian Coherent Structures
Serra, M
2015-01-01
We define objective Eulerian Coherent Structures (OECSs) in two-dimensional, non-autonomous dynamical systems as instantaneously most influential material curves. Specifically, OECSs are stationary curves of the averaged instantaneous material stretching-rate or material shearing-rate functionals. From these objective (frame-invariant) variational principles, we obtain explicit differential equations for hyperbolic, elliptic and parabolic OECSs. As illustration, we compute OECSs in an unsteady ocean velocity data set. In comparison to structures suggested by other common Eulerian diagnostic tools, we find OECSs to be the correct short-term cores of observed trajectory deformation patterns.
Diffraction coherence in optics
Françon, M; Green, L L
2013-01-01
Diffraction: Coherence in Optics presents a detailed account of the course on Fraunhofer diffraction phenomena, studied at the Faculty of Science in Paris. The publication first elaborates on Huygens' principle and diffraction phenomena for a monochromatic point source and diffraction by an aperture of simple form. Discussions focus on diffraction at infinity and at a finite distance, simplified expressions for the field, calculation of the path difference, diffraction by a rectangular aperture, narrow slit, and circular aperture, and distribution of luminous flux in the airy spot. The book th
Coherent white light amplification
Jovanovic, Igor; Barty, Christopher P.
2004-05-25
A system for coherent simultaneous amplification of a broad spectral range of light that includes an optical parametric amplifier and a source of a seed pulse is described. A first angular dispersive element is operatively connected to the source of a seed pulse. A first imaging telescope is operatively connected to the first angular dispersive element and operatively connected to the optical parametric amplifier. A source of a pump pulse is operatively connected to the optical parametric amplifier. A second imaging telescope is operatively connected to the optical parametric amplifier and a second angular dispersive element is operatively connected to the second imaging telescope.
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...... 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...
Brignon, Arnaud
2013-01-01
Recently, the improvement of diode pumping in solid state lasers and the development of double clad fiber lasers have allowed to maintain excellent laser beam quality with single mode fibers. However, the fiber output power if often limited below a power damage threshold. Coherent laser beam combining (CLBC) brings a solution to these limitations by identifying the most efficient architectures and allowing for excellent spectral and spatial quality. This knowledge will become critical for the design of the next generation high-power lasers and is of major interest to many industrial, environme
Ionica, Sorina
2011-01-01
Isogeny volcanoes are graphs whose vertices are elliptic curves and whose edges are $\\ell$-isogenies. Algorithms allowing to travel on these graphs were developed by Kohel in his thesis (1996) and later on, by Fouquet and Morain (2001). However, up to now, no method was known, to predict, before taking a step on the volcano, the direction of this step. Hence, in Kohel's and Fouquet-Morain algorithms, many steps are taken before choosing the right direction. In particular, ascending or horizontal isogenies are usually found using a trial-and-error approach. In this paper, we propose an alternative method that efficiently finds all points $P$ of order $\\ell$ such that the subgroup generated by $P$ is the kernel of an horizontal or an ascending isogeny. In many cases, our method is faster than previous methods. This is an extended version of a paper published in the proceedings of ANTS 2010. In addition, we treat the case of 2-isogeny volcanoes and we derive from the group structure of the curve and the pairing ...
Quantum correlation via quantum coherence
Yu, Chang-shui; Zhang, Yang; Zhao, Haiqing
2014-01-01
Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition--------quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes ...
Review of Entangled Coherent States
Sanders, Barry C
2011-01-01
We review entangled coherent state research since its first implicit use in 1967 to the present. Entangled coherent states are important to quantum superselection principles, quantum information processing, quantum optics, and mathematical physics. Despite their inherent fragility they have produced in a conditional propagating-wave quantum optics realization. Fundamentally the states are intriguing because they are entanglements of the coherent states, which are in a sense the most classical of all states of a dynamical system.
On Nonlinear Bosonic Coherent States
Genovese, Marco; Rasetti, Mario
2009-01-01
Nonlinear coherent states are an interesting resource for quantum technologies. Here we investigate some critical features of the single-boson nonlinear coherent states, which are theoretically constructed as eigenstates of the annihilation operator and experimentally realized as stationary states of a trapped laser-driven ion. We show that the coherence and the minimum-uncertainty properties of such states are broken for values of the Lamb-Dicke parameter corresponding to the roots of the Laguerre polynomials, which enter their explicit expression. The case of the multiboson nonlinear coherent states is also discussed.
Coherence in monoidal track categories
Guiraud, Yves
2010-01-01
We introduce homotopical methods based on rewriting on higher-dimensional categories to prove coherence results in categories with an algebraic structure. We express the coherence problem for (symmetric) monoidal categories as an asphericity problem for a track category and use rewriting methods on polygraphs to solve it. The setting is generalized to more general coherence problems, seen as 3-dimensional word problems in a track category. We prove general results that, in the case of braided monoidal categories, yield the coherence theorem for braided monoidal categories.
Chadzitaskos, G; Tolar, J
2011-01-01
We present a possible construction of coherent states on the unit circle as configuration space. In our approach the phase space is the product Z x S^1. Because of the duality of canonical coordinates and momenta, i.e. the angular variable and the integers, this formulation can also be interpreted as coherent states over an infinite periodic chain. For the construction we use the analogy with our quantization over a finite periodic chain where the phase space was Z_M x Z_M. Properties of the coherent states constructed in this way are studied and the coherent states are shown to satisfy the resolution of unity.
Superposition Coherent States and Their Properties%叠加相干态及其性质
Institute of Scientific and Technical Information of China (English)
董传华
2000-01-01
Special kinds of generalized superposition states, superposition coherent states, are studied in this paper. These states can be produced by superposing a pair of coherent states |α>and |α>.Their quantum statistical properties, the fluctuations of field and squeezing have been discussed in detail. These properties are dependent on superposition phase. We also describe the squeezing regions in phase space for these states.
Multiple origins of asteroid pairs
Jacobson, Seth A
2015-01-01
Rotationally fissioned asteroids produce unbound daughter asteroids that have very similar heliocentric orbits. Backward integration of their current heliocentric orbits provides an age of closest proximity that can be used to date the rotational fission event. Most asteroid pairs follow a predicted theoretical relationship between the primary spin period and the mass ratio of the two pair members that is a direct consequence of the YORP-induced rotational fission hypothesis. If the progenitor asteroid has strength, asteroid pairs may have high mass ratios with possibly fast rotating primaries. However, secondary fission leaves the originally predicted trend unaltered. We also describe the characteristics of pair members produced by four alternative routes from a rotational fission event to an asteroid pair. Unlike direct formation from the event itself, the age of closest proximity of these pairs cannot generally be used to date the rotational fission event since considerable time may have passed.
International Nuclear Information System (INIS)
We describe recent efforts to study Cooper pairs in atomic nuclei. We consider a self-consistent Hartree Fock mean field for the even Sm isotopes and compare results based on three treatments of pairing correlations: a BCS treatment, a number-projected BCS treatment and an exact treatment using the Richardson Ansatz. Significant differences are seen in the pairing correlation energies. Furthermore, because it does not average over the properties of the fermion pairs, the Richardson solution permits a more meaningful definition of the Cooper wave function and of the fraction of pairs that are collective. Our results confirm that only a few pairs near the Fermi surface in realistic atomic nuclei are collective. (Author)
Energy Technology Data Exchange (ETDEWEB)
Pittel, S. [Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, 19716 Delaware (United States); Dussel, G. G. [Departamento de Fisica J.J. Giambiagi, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Dukelsky, J.; Sarriguren, P. [Instituto de Estructura de la Materia, CSIC, Serrano 123, 28006 Madrid (Spain)
2008-12-15
We describe recent efforts to study Cooper pairs in atomic nuclei. We consider a self-consistent Hartree Fock mean field for the even Sm isotopes and compare results based on three treatments of pairing correlations: a BCS treatment, a number-projected BCS treatment and an exact treatment using the Richardson Ansatz. Significant differences are seen in the pairing correlation energies. Furthermore, because it does not average over the properties of the fermion pairs, the Richardson solution permits a more meaningful definition of the Cooper wave function and of the fraction of pairs that are collective. Our results confirm that only a few pairs near the Fermi surface in realistic atomic nuclei are collective. (Author)
Aflatouni, Firooz; Abiri, Behrooz; Rekhi, Angad; Hajimiri, Ali
2015-02-23
An integrated silicon nanophotonic coherent imager (NCI), with a 4 × 4 array of coherent pixels is reported. In the proposed NCI, on-chip optical processing determines the intensity and depth of each point on the imaged object based on the instantaneous phase and amplitude of the optical wave incident on each pixel. The NCI operates based on a modified time-domain frequency modulated continuous wave (FMCW) ranging scheme, where concurrent time-domain measurements of both period and the zero-crossing time of each electrical output of the nanophotonic chip allows the NCI to overcome the traditional resolution limits of frequency domain detection. The detection of both intensity and relative delay enables applications such as high-resolution 3D reflective and transmissive imaging as well as index contrast imaging. We demonstrate 3D imaging with 15μm depth resolution and 50μm lateral resolution (limited by the pixel spacing) at up to 0.5-meter range. The reported NCI is also capable of detecting a 1% equivalent refractive index contrast at 1mm thickness. PMID:25836545
Combescure, Monique; Robert, Didier
2012-06-01
The aim of this paper is to give a self-contained and unified presentation of a fermionic coherent state theory with the necessary mathematical details, discussing their definition, properties and some applications. After defining Grassmann algebras, it is possible to get a classical analog for the fermionic degrees of freedom in a quantum system. Following the basic work of Berezin (1966 The Method of Second Quantization (New York: Academic); 1987 Introduction to Superanalysis (Dordrecht: Reidel Publishing Company)), we show that we can compute with Grassmann numbers as we do with complex numbers: derivation, integration, Fourier transform. After that we show that we have quantization formulas for fermionic observables. In particular, there exists a Moyal product formula. As an application, we consider explicit computations for propagators with quadratic Hamiltonians in annihilation and creation operators. We prove a Mehler formula for the propagator and Mehlig-Wilkinson-type formulas for the covariant and contravariant symbols of ‘metaplectic’ transformations for fermionic states. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’.
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).
Langer, S. H.; Petrosian, V.
1976-01-01
The spectrum, directivity and state of polarization is presented of the bremsstrahlung radiation expected from a beam of high energy electrons spiraling along radial magnetic field lines toward the photosphere. The results are used for calculation of the characteristics of the reflected plus direct flux.
Dussel, G G; Dukelsky, J; Sarriguren, P
2007-01-01
We consider the development of Cooper pairs in a self-consistent Hartree Fock mean field for the even Sm isotopes. Results are presented at the level of a BCS treatment, a number-projected BCS treatment and an exact treatment using the Richardson ansatz. While projected BCS captures much of the pairing correlation energy that is absent from BCS, it still misses a sizable correlation energy, typically of order $1 MeV$. Furthermore, because it does not average over the properties of the fermion pairs, the exact Richardson solution permits a more meaningful definition of the Cooper wave function and of the fraction of pairs that are collective.
Controversies in kidney paired donation.
Gentry, Sommer E; Montgomery, Robert A; Segev, Dorry L
2012-07-01
Kidney paired donation represented 10% of living kidney donation in the United States in 2011. National registries around the world and several separate registries in the United States arrange paired donations, although with significant variations in their practices. Concerns about ethical considerations, clinical advisability, and the quantitative effectiveness of these approaches in paired donation result in these variations. For instance, although donor travel can be burdensome and might discourage paired donation, it was nearly universal until convincing analysis showed that living donor kidneys can sustain many hours of cold ischemia time without adverse consequences. Opinions also differ about whether the last donor in a chain of paired donation transplants initiated by a nondirected donor should donate immediately to someone on the deceased donor wait-list (a domino or closed chain) or should be asked to wait some length of time and donate to start another sequence of paired donations later (an open chain); some argue that asking the donor to donate later may be coercive, and others focus on balancing the probability that the waiting donor withdraws versus the number of additional transplants if the chain can be continued. Other controversies in paired donation include simultaneous versus nonsimultaneous donor operations, whether to enroll compatible pairs, and interactions with desensitization protocols. Efforts to expand public awareness of and participation in paired donation are needed to generate more transplant opportunities. PMID:22732046
Uzdin, Raam
2016-08-01
Collective behavior, where a set of elements interact and generate effects that are beyond the reach of the individual noninteracting elements, is always of great interest in physics. Quantum collective effects that have no classical analog are even more intriguing. In this work, we show how to construct collective quantum heat machines and explore their performance boosts with respect to regular machines. Without interactions between the machines, the individual units operate in a stochastic, nonquantum manner. The construction of the collective machine becomes possible by introducing two simple quantum operations: coherence extraction and coherence injection. Together, these operations can harvest coherence from one engine and use it to boost the performance of a slightly different engine. For weakly driven engines, we show that the collective work output scales quadratically with the number of engines rather than linearly. Eventually, the boost saturates and then becomes linear. Nevertheless, even in saturation, work is still significantly boosted compared to individual operation. To study the reversibility of the collective machine, we introduce the "entropy-pollution" measure. It is shown that there is a regime where the collective machine is N times more reversible while producing N times more work, compared to the individual operation of N units. Moreover, the collective machine can even be more reversible than the most reversible unit in the collective. This high level of reversibility becomes possible due to a special symbiotic mechanism between engine pairs.
Selective preparation of the maximum coherent superposition state in four-level atoms
Institute of Scientific and Technical Information of China (English)
Li Deng; Yueping Niu; Shangqing Gong
2011-01-01
We demonstrate that the maximum coherent superposition state can be selectively prepared using a sequence of pulse pairs in lambda-type atomic systems, with the final level as a doublet. In each pair, the Stocks pulse comes before the pump pulse, with their back edges overlapping. Numerical results indicate that by tuning the interval of the adjacent pulse pairs, the selective maximum coherent superposition state preparation between the initial and one of the final levels can be achieved. The phenomenon is caused by the accumulative property of the pulse sequence.%The coherent superposition state in atoms or molecules plays a crucial role in quantum physics.It has applications in many areas such as electromagnetically induced transparency[1-5],quantum information[6-8] and control of chemical reaction[9-11].Many schemes can prepare the coherent superposition state.For instance,the fractional stimulated Raman adiabatic passage(F-STIRAP) [12] and the coherent population trapping[13] can obtain the maximum coherent superposition state of the two lower levels in lambda-type atoms.Our group also proposed several schemes to achieve this goal,such as the methods based on the STIRAP[14,15] and the pulse train method[16].
Quantum repeater based on cavity QED evolutions and coherent light
Gonţa, Denis; van Loock, Peter
2016-05-01
In the framework of cavity QED, we propose a quantum repeater scheme that uses coherent light and chains of atoms coupled to optical cavities. In contrast to conventional repeater schemes, in our scheme there is no need for an explicit use of two-qubit quantum logical gates by exploiting solely the cavity QED evolution. In our previous work (Gonta and van Loock in Phys Rev A 88:052308, 2013), we already proposed a quantum repeater in which the entanglement between two neighboring repeater nodes was distributed using controlled displacements of input coherent light, while the produced low-fidelity entangled pairs were purified using ancillary (four-partite) entangled states. In the present work, the entanglement distribution is realized using a sequence of controlled phase shifts and displacements of input coherent light. Compared to previous coherent-state-based distribution schemes for two-qubit entanglement, our scheme here relies only upon a simple discrimination of two coherent states with opposite signs, which can be performed in a quantum mechanically optimal fashion via a beam splitter and two on-off detectors. For the entanglement purification, we employ a method that avoids the use of extra entangled ancilla states. Our repeater scheme exhibits reasonable fidelities and repeater rates providing an attractive platform for long-distance quantum communication.
Tan, S.; Tsang, L.; Xu, X.; Ding, K. H.
2015-12-01
In this paper we describe partial coherent model and fully coherent snowpack scattering model based on numerical simulation of Maxwell's equation. In medium characterization, we derive the correlation functions from the pair distribution functions of sticky spheres and multiple-size spheres used in QCA. We show that both the Percus-Yevick pair functions and the bicontinuous model have tails in the correlation functions that are distinctly different from the traditional exponential correlation functions. The methodologies of using ground measurements of grain size distributions and correlation functions to obtain model parameters are addressed. The DMRT theory has been extended to model the backscattering enhancement. We developed the methodology of cyclical corrections beyond first order to all orders of multiple scattering. This enables the physical modeling of combined active and passive microwave remote sensing of snow over the same scene. The bicontinuous /DMRT is applied to compare with data acquired in the NoSREx campaign, and the model results are validated against coincidental active and passive measurements using the same set of physical parameters of snow in all frequency and polarization channels. The DMRT is a partially coherent approach that one accounts for the coherent wave interaction only within few wavelengths as represented by phase matrix. However, the phase information of field is lost in propagating the specific intensity via RT and this hinders the use of DMRT in coherent synthetic aperture radar (SAR) analysis, including InSAR, PolInSAR and Tomo-SAR. One can alternatively calculate the scattering matrix of the terrestrial snowpack above ground by solving the volume integral equations directly with half space Green's function. The scattering matrix of the snowpack is computed for each realization giving rise to the speckle statistics. The resulting bistatic scattering automatically includes the backscattering enhancement effects. Tomograms of
A novel technique to achieve atomic macro-coherence as a tool to determine the nature of neutrinos
Boyero García, R.; Carpentier, A. V.; Gómez-Cadenas, J. J.; Peralta Conde, A.
2016-10-01
The photon spectrum in macro-coherent atomic deexcitation via radiative emission of neutrino pairs has been proposed as a sensitive probe of the neutrino mass spectrum, capable of competing with conventional neutrino experiments. In this paper, we revisit this intriguing possibility, presenting an alternative method for inducing large coherence in a target based on adiabatic techniques. More concretely, we propose the use of a modified version of coherent population return (CPR), namely two-photon CPR, that turns out to be extremely robust with respect to the experimental parameters and capable of inducing a coherence close to 100 % in the target.
Second-Scale Nuclear Spin Coherence Time of Trapped Ultracold $^{23}$Na$^{40}$K Molecules
Park, Jee Woo; Loh, Huanqian; Will, Sebastian A; Zwierlein, Martin W
2016-01-01
Coherence, the stability of the relative phase between quantum states, lies at the heart of quantum mechanics. Applications such as precision measurement, interferometry, and quantum computation are enabled by physical systems that have quantum states with robust coherence. With the creation of molecular ensembles at sub-$\\mu$K temperatures, diatomic molecules have become a novel system under full quantum control. Here, we report on the observation of stable coherence between a pair of nuclear spin states of ultracold fermionic NaK molecules in the singlet rovibrational ground state. Employing microwave fields, we perform Ramsey spectroscopy and observe coherence times on the scale of one second. This work opens the door for the exploration of single molecules as a versatile quantum memory. Switchable long-range interactions between dipolar molecules can further enable two-qubit gates, allowing quantum storage and processing in the same physical system. Within the observed coherence time, $10^4$ one- and two-...
Production of isotopes and isomers with irradiation of Z = 47–50 targets by 23-MeV bremsstrahlung
Energy Technology Data Exchange (ETDEWEB)
Karamian, S. A., E-mail: karamian@nrmail.jinr.ru [Joint Institute for Nuclear Research (Russian Federation); Carroll, J. J. [US Army Research Laboratory (United States); Aksenov, N. V.; Albin, Yu. A.; Belov, A. G.; Bozhikov, G. A.; Dmitriev, S. N.; Starodub, G. Ya. [Joint Institute for Nuclear Research (Russian Federation)
2015-09-15
The irradiations of Ag to Sn targets by bremsstrahlung generated with 23-MeV electron beams are performed at the MT-25 microtron. Gamma spectra of the induced activities have been measured and the yields of all detected radionuclides and isomers are carefully measured and analyzed. A regular dependence of yields versus changed reaction threshold is confirmed. Many isomers are detected and the suppression of the production probability is observed with growing product spin. Special peculiarities for the isomer-to-ground state ratios were deduced for the {sup 106m}Ag, {sup 108m}Ag, {sup 113m}In, {sup 115m}In, and {sup 123m}Sn isomers. The production of such nuclides as {sup 108m}Ag, {sup 115m}In, {sup 117g}In, and {sup 113m}Cd is of interest for applications, especially when economic methods are available.
Higher-order corrections to electron-nucleus bremsstrahlung cross sections above a few MeV
Mangiarotti, A.; Martins, M. N.
2016-08-01
Despite the fact that the first calculations of nuclear bremsstrahlung cross sections were performed for relativistic electrons more than 80 years ago by Sauter, Bethe and Heitler, and Racah, a fully satisfactory solution to this problem is still missing up to the present day. Numerical approaches are impractical for electrons with energies above a few MeV because they require a prohibitively large number of partial waves. Analytic formulae need to describe simultaneously and accurately the interaction with the Coulomb field of the nucleus and the screening effect of the atomic electrons. In the present paper, a state-of-the-art analytic calculation will be discussed. In particular, higher-order corrections to the interaction with the Coulomb field of the nucleus, a subject seldom tackled in the past, are included and compared extensively with published data. The emerged difficulties will be highlighted, but unfortunately they can be overcome only with future large coordinated theoretical and experimental efforts.
Energy Technology Data Exchange (ETDEWEB)
Hosur, S.B.; Naika, L.R.; Badiger, N.M. [Department of Studies in PhysicsKarnatak University, Dharwad - 580003 (India)
2011-04-15
Low energy external Bremsstrahlung (EB) photons were used to estimate the K shell photoelectric parameters; the K shell photoelectric cross section at the K edge, the K shell binding energy, the K shell jump ratio, the K shell jump factors, the Davisson-Kirchner ratio and the K shell oscillator strength for dysprosium (Dy), ytterbium (Yb) and tungsten (W) atoms. The EB photons are produced in the nickel (Ni) target by using the beta particles from a weak beta source of {sup 90}Sr-{sup 90}Y. These photons are made to fall on these elemental targets of our interest and the transmitted spectrum is measured using GMX 10P HPGe detector coupled to an 8K multichannel analyzer. The sharp decrease at the K edge in the measured spectrum is used to determine the K shell photoelectric parameters of these elements. The experimental results are in good agreement with the theoretical values. (authors)
International Nuclear Information System (INIS)
Low energy external Bremsstrahlung (EB) photons were used to estimate the K shell photoelectric parameters; the K shell photoelectric cross section at the K edge, the K shell binding energy, the K shell jump ratio, the K shell jump factors, the Davisson-Kirchner ratio and the K shell oscillator strength for dysprosium (Dy), ytterbium (Yb) and tungsten (W) atoms. The EB photons are produced in the nickel (Ni) target by using the beta particles from a weak beta source of 90Sr-90Y. These photons are made to fall on these elemental targets of our interest and the transmitted spectrum is measured using GMX 10P HPGe detector coupled to an 8K multichannel analyzer. The sharp decrease at the K edge in the measured spectrum is used to determine the K shell photoelectric parameters of these elements. The experimental results are in good agreement with the theoretical values. (authors)
Observation of planar three-jet events in e+e- annihilation and evidence for gluon bremsstrahlung
International Nuclear Information System (INIS)
Topological distributions of charged and neutral hadrons from the reaction e+e%YI multihadrons are studied at √s of about 30 GeV. An excess of planar events is observed at a rate which cannot be explained by statistical fluctuations in the two-jet process. The planar events, mostly consisting of a slim jet on one side and a broader jet on the other, are shown actually to possess three-jet structure by demonstrating that the broader jet itself consists of two collinear jets in its own rest system. Detailed agreement between data and predictions is obtained if the process e+e- → q anti q g is taken into account. This strongly suggests gluon bremsstrahlung as the origin of the planar three-jet events. The data are consistent with a strong coupling constant αs (q2) of about 0.17. (orig.) 891 HSI/orig. 892 RDG
Robustness of a coherence vortex.
Alves, Cleberson R; Jesus-Silva, Alcenisio J; Fonseca, Eduardo J S
2016-09-20
We study, experimentally and theoretically, the behavior of a coherence vortex after its transmission through obstacles. Notably, we find that such a vortex survives and preserves its effective topological charge. Despite suffering changes on the modulus of the coherence function, these changes disappear during propagation.
Quantum coherence of steered states
Hu, Xueyuan; Milne, Antony; Zhang, Boyang; Fan, Heng
2016-01-01
Lying at the heart of quantum mechanics, coherence has recently been studied as a key resource in quantum information theory. Quantum steering, a fundamental notion originally considered by Schödinger, has also recently received much attention. When Alice and Bob share a correlated quantum system, Alice can perform a local measurement to ‘steer’ Bob’s reduced state. We introduce the maximal steered coherence as a measure describing the extent to which steering can remotely create coherence; more precisely, we find the maximal coherence of Bob’s steered state in the eigenbasis of his original reduced state, where maximization is performed over all positive-operator valued measurements for Alice. We prove that maximal steered coherence vanishes for quantum-classical states whilst reaching a maximum for pure entangled states with full Schmidt rank. Although invariant under local unitary operations, maximal steered coherence may be increased when Bob performs a channel. For a two-qubit state we find that Bob’s channel can increase maximal steered coherence if and only if it is neither unital nor semi-classical, which coincides with the condition for increasing discord. Our results show that the power of steering for coherence generation, though related to discord, is distinct from existing measures of quantum correlation.
Dynamics of generalized coherent states
De Martino, S; Illuminati, F; De Martino, S; De Siena, S; Illuminati, F
1995-01-01
We show that generalized coherent states follow Schr\\"{o}dinger dynamics in time-dependent potentials. The normalized wave-packets follow a classical evolution without spreading; in turn, the Schr\\"{o}dinger potential depends on the state through the classical trajectory. This feedback mechanism with continuous dynamical re-adjustement allows the packets to remain coherent indefinetely.
Dymanics of Generalized Coherent States
Martino, S; De Siena, S.; Illuminati, F.
1995-01-01
We show that generalized coherent states follow Schr\\"{o}dinger dynamics in time-dependent potentials. The normalized wave-packets follow a classical evolution without spreading; in turn, the Schr\\"{o}dinger potential depends on the state through the classical trajectory. This feedback mechanism with continuous dynamical re-adjustement allows the packets to remain coherent indefinetely.
Directory of Open Access Journals (Sweden)
Mattijs Elschot
Full Text Available BACKGROUND: After yttrium-90 ((90Y microsphere radioembolization (RE, evaluation of extrahepatic activity and liver dosimetry is typically performed on (90Y Bremsstrahlung SPECT images. Since these images demonstrate a low quantitative accuracy, (90Y PET has been suggested as an alternative. The aim of this study is to quantitatively compare SPECT and state-of-the-art PET on the ability to detect small accumulations of (90Y and on the accuracy of liver dosimetry. METHODOLOGY/PRINCIPAL FINDINGS: SPECT/CT and PET/CT phantom data were acquired using several acquisition and reconstruction protocols, including resolution recovery and Time-Of-Flight (TOF PET. Image contrast and noise were compared using a torso-shaped phantom containing six hot spheres of various sizes. The ability to detect extra- and intrahepatic accumulations of activity was tested by quantitative evaluation of the visibility and unique detectability of the phantom hot spheres. Image-based dose estimates of the phantom were compared to the true dose. For clinical illustration, the SPECT and PET-based estimated liver dose distributions of five RE patients were compared. At equal noise level, PET showed higher contrast recovery coefficients than SPECT. The highest contrast recovery coefficients were obtained with TOF PET reconstruction including resolution recovery. All six spheres were consistently visible on SPECT and PET images, but PET was able to uniquely detect smaller spheres than SPECT. TOF PET-based estimates of the dose in the phantom spheres were more accurate than SPECT-based dose estimates, with underestimations ranging from 45% (10-mm sphere to 11% (37-mm sphere for PET, and 75% to 58% for SPECT, respectively. The differences between TOF PET and SPECT dose-estimates were supported by the patient data. CONCLUSIONS/SIGNIFICANCE: In this study we quantitatively demonstrated that the image quality of state-of-the-art PET is superior over Bremsstrahlung SPECT for the
Teramoto, Hiroko; Akimoto, Takayoshi; Shiota, Hiroshi; Kamei, Satoshi
2016-01-01
Objective. To assess the relation between executive dysfunction (ED) in Parkinson's disease (PD) and resting state functional connectivity evaluated using electroencephalography (EEG) coherence. Methods. Sixty-eight nondemented sporadic PD patients were assessed using the Behavioural Assessment of the Dysexecutive Syndrome (BADS) to evaluate executive function. EEG coherence in the left frontoparietal electrode pair (F3-P3) and the right frontoparietal electrode pair (F4-P4) was analyzed in the alpha and theta range. The BADS scores were compared across the coherence groups, and the multiple logistic regression analysis was performed to assess the contribution of confounders. Results. The standardized BADS score was significantly lower in the low F3-P3 coherence group in the alpha range (Mann-Whitney U test, p = 0.032), though there was no difference between F4-P4 coherence group in the alpha range, F3-P3, and F4-P4 coherence groups in the theta range and the standardized BADS score. The multiple logistic regression analysis revealed the significant relation between the F3-P3 coherence group in alpha range and age-controlled standardized BADS score (p = 0.039, 95% CI = 1.002–1.062). Conclusion. The decrease in resting state functional connectivity between the frontal and parietal cortices especially in the left side is related to ED in PD. PMID:27433473
Assessment Strategies for Pair Programming
Hahn, Jan Hendrik; Mentz, Elsa; Meyer, Lukas
2009-01-01
Although pair programming has proved its usefulness in teaching and learning programming skills, it is difficult to assess the individual roles and abilities of students whilst programming in pairs. (Note that within this manuscript, the term assessment refers to evaluating individual student performance.) Assessing only the outcomes of a pair…
PERIODIC COMPLEMENTARY BINARY SEQUENCE PAIRS
Institute of Scientific and Technical Information of China (English)
XuChengqian; ZhaoXiaoqun
2002-01-01
A new set of binary sequences-Periodic Complementary Binary Sequence Pair (PCSP)is proposed .A new class of block design-Difference Family Pair (DFP)is also proposed .The relationship between PCSP and DFP,the properties and exising conditions of PCSP and the recursive constructions for PCSP are given.
PERIODIC COMPLEMENTARY BINARY SEQUENCE PAIRS
Institute of Scientific and Technical Information of China (English)
Xu Chengqian; Zhao Xiaoqun
2002-01-01
A new set of binary sequences-Periodic Complementary Binary Sequence Pair (PCSP) is proposed. A new class of block design-Difference Family Pair (DFP) is also proposed.The relationship between PCSP and DFP, the properties and existing conditions of PCSP and the recursive constructions for PCSP are given.
Singh, Amrit; Dhaliwal, A. S.
2016-02-01
Total bremsstrahlung (BS) spectra in thick targets of Al, Ti, Sn and Pb produced by beta emitter 90Sr (End point energy=546 keV) are studied in the photon energy range of 1-100 keV. The experimentally measured BS spectra are compared with the theoretical spectral distributions calculated from Elwert corrected (non relativistic) Bethe-Heitler [EBH] theory, modified Elwert factor (relativistic) Bethe-Heitler [Fmod BH] theory for ordinary bremsstrahlung (OB) and the Avdonina and Pratt [Fmod BH+PB] theory, which include the contribution of polarization bremsstrahlung (PB) into OB. The present results are indicating the correctness of Fmod BH+PB theory in the low energy region, where PB dominates into the BS, but at the middle and higher photon energy region of the bremsstrahlung spectrum, the Fmod BH theory is more close to the experimental results. The description of the bremsstrahlung process in stripped atom (SA) approximation, which indicates the suppression of the bremsstrahlung at higher energy ends due to the production of PB in the low energy region, needs further considerations. Hence, the present measurements for BS for different target materials indicates that the considerations of the screening effects along with other secondary effects during the interaction of incident electrons with the target nuclei are important while describing the production of bremsstrahlung, particularly for the higher energy regions.
Coherent imaging without phases
Moscoso, Miguel; Papanicolaou, George
2015-01-01
In this paper we consider narrow band, active array imaging of weak localized scatterers when only the intensities are recorded at an array with N transducers. We consider that the medium is homogeneous and, hence, wave propagation is fully coherent. This work is an extension of our previous paper, where we showed that using linear combinations of intensity-only measurements imaging of localized scatterers can be carried out efficiently using MUSIC or sparsity promoting optimization. Here we show the same strategy can be accomplished with only 3N-2 illuminations, therefore reducing enormously the data acquisition process. Furthermore, we show that in the paraxial regime one can form the images by using six illuminations only. In particular, this paraxial regime includes Fresnel and Fraunhofer diffraction. The key point of this work is that if one controls the illuminations, imaging with intensity-only can be easily reduced to a imaging with phases and, therefore, one can apply standard imaging techniques. Det...
DEFF Research Database (Denmark)
Andersen, Anne Bendix; Frederiksen, Kirsten; Beedholm, Kirsten;
2016-01-01
Background During the past decade, politicians and healthcare providers have strived to create a coherent healthcare system across primary and secondary healthcare sectors in Denmark. Nevertheless, elderly patients with chronic diseases (EPCD) continue to report experiences of poor-quality care...... to an acute care ward to discharge and later in meetings with healthcare providers in general practice, outpatient clinics, home care and physiotherapy. Furthermore, field observations were conducted in general practice, home care and rehabilitation settings. Research design An explorative design based...... on an interactionistic approach was used. As a consequence, the focus of data collection is the production of meaning happening between human beings in social interaction in the field of cross-sectorial collaboration. Research questions The research questions reflect the interactionistic approach as they concentrate...
Quantum information and coherence
Öhberg, Patrik
2014-01-01
This book offers an introduction to ten key topics in quantum information science and quantum coherent phenomena, aimed at graduate-student level. The chapters cover some of the most recent developments in this dynamic research field where theoretical and experimental physics, combined with computer science, provide a fascinating arena for groundbreaking new concepts in information processing. The book addresses both the theoretical and experimental aspects of the subject, and clearly demonstrates how progress in experimental techniques has stimulated a great deal of theoretical effort and vice versa. Experiments are shifting from simply preparing and measuring quantum states to controlling and manipulating them, and the book outlines how the first real applications, notably quantum key distribution for secure communication, are starting to emerge. The chapters cover quantum retrodiction, ultracold quantum gases in optical lattices, optomechanics, quantum algorithms, quantum key distribution, quantum cont...
Coherent Scatter Imaging Measurements
Ur Rehman, Mahboob
In conventional radiography, anatomical information of the patients can be obtained, distinguishing different tissue types, e.g. bone and soft tissue. However, it is difficult to obtain appreciable contrast between two different types of soft tissues. Instead, coherent x-ray scattering can be utilized to obtain images which can differentiate between normal and cancerous cells of breast. An x-ray system using a conventional source and simple slot apertures was tested. Materials with scatter signatures that mimic breast cancer were buried in layers of fat of increasing thickness and imaged. The result showed that the contrast and signal to noise ratio (SNR) remained high even with added fat layers and short scan times.
Ultrabroadband coherent supercontinuum frequency comb
Energy Technology Data Exchange (ETDEWEB)
Ruehl, Axel; McKay, Hugh; Thomas, Brian; Dong, Liang; Fermann, Martin E.; Hartl, Ingmar [IMRA America Inc., 1044 Woodridge Avenue, Ann Arbor, Michigan 48105 (United States); Martin, Michael J.; Cossel, Kevin C.; Chen Lisheng; Benko, Craig; Ye Jun [JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, 440 UCB, Boulder, Colorado 80309 (United States); Dudley, John M. [Institute FEMTO-ST, CNRS-University of Franche-Comte UMR 6174, Besancon (France)
2011-07-15
We present detailed studies of the coherence properties of an ultrabroadband supercontinuum, enabled by a comprehensive approach involving continuous-wave laser sources to independently probe both the amplitude and phase noise quadratures across the entire spectrum. The continuum coherently spans more than 1.5 octaves, supporting Hz-level comparison of ultrastable lasers at 698 nm and 1.54 {mu}m. We present a complete numerical simulation of the accumulated comb coherence in the limit of many pulses, in contrast to the single-pulse level, with systematic experimental verification. The experiment and numerical simulations reveal the presence of quantum-seeded broadband amplitude noise without phase coherence degradation, including the discovery of a dependence of the supercontinuum coherence on the fiber fractional Raman gain.
Coherence and correspondence in medicine
Directory of Open Access Journals (Sweden)
Thomas G. Tape
2009-03-01
Full Text Available Many controversies in medical science can be framed as tension between a coherence approach (which seeks logic and explanation and a correspondence approach (which emphasizes empirical correctness. In many instances, a coherence-based theory leads to an understanding of disease that is not supported by empirical evidence. Physicians and patients alike tend to favor the coherence approach even in the face of strong, contradictory correspondence evidence. Examples include the management of atrial fibrillation, treatment of acute bronchitis, and the use of Vitamin E to prevent heart disease. Despite the frequent occurrence of controversy stemming from coherence-correspondence conflicts, medical professionals are generally unaware of these terms and the philosophical traditions that underlie them. Learning about the coherence-correspondence distinction and using the best of both approaches could not only help reconcile controversy but also lead to striking advances in medical science.
Bennis, Driss
2010-01-01
This paper unifies several generalizations of coherent rings in one notion. Namely, we introduce $n$-$\\mathscr{X}$-coherent rings, where $\\mathscr{X}$ is a class of modules and $n$ is a positive integer, as those rings for which the subclass $\\mathscr{X}_n$ of $n$-presented modules of $\\mathscr{X}$ is not empty, and every module in $\\mathscr{X}_n$ is $n+1$-presented. Then, for each particular class $\\mathscr{X}$ of modules, we find correspondent relative coherent rings. Our main aim is to show that the well-known Chase's, Cheatham and Stone's, Enochs', and Stenstrom's characterizations of coherent rings hold true for any $n$-$\\mathscr{X}$-coherent rings.
Experimental evidence of coherent transport.
Flores-Olmedo, E; Martínez-Argüello, A M; Martínez-Mares, M; Báez, G; Franco-Villafañe, J A; Méndez-Sánchez, R A
2016-01-01
Coherent transport phenomena are difficult to observe due to several sources of decoherence. For instance, in the electronic transport through quantum devices the thermal smearing and dephasing, the latter induced by inelastic scattering by phonons or impurities, destroy phase coherence. In other wave systems, the temperature and dephasing may not destroy the coherence and can then be used to observe the underlying wave behaviour of the coherent phenomena. Here, we observe coherent transmission of mechanical waves through a two-dimensional elastic Sinai billiard with two waveguides. The flexural-wave transmission, performed by non-contact means, shows the quantization when a new mode becomes open. These measurements agree with the theoretical predictions of the simplest model highlighting the universal character of the transmission fluctuations. PMID:27121226
Integrated coherent matter wave circuits
International Nuclear Information System (INIS)
An integrated coherent matter wave circuit is a single device, analogous to an integrated optical circuit, in which coherent de Broglie waves are created and then launched into waveguides where they can be switched, divided, recombined, and detected as they propagate. Applications of such circuits include guided atom interferometers, atomtronic circuits, and precisely controlled delivery of atoms. We report experiments demonstrating integrated circuits for guided coherent matter waves. The circuit elements are created with the painted potential technique, a form of time-averaged optical dipole potential in which a rapidly moving, tightly focused laser beam exerts forces on atoms through their electric polarizability. Moreover, the source of coherent matter waves is a Bose-Einstein condensate (BEC). Finally, we launch BECs into painted waveguides that guide them around bends and form switches, phase coherent beamsplitters, and closed circuits. These are the basic elements that are needed to engineer arbitrarily complex matter wave circuitry
Highly efficient Cooper pair splitting with carbon nanotube quantum dots
Energy Technology Data Exchange (ETDEWEB)
Schindele, Jens; Baumgartner, Andreas; Schoenenberger, Christian [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)
2012-07-01
An elegant idea for the creation of entangled electrons in a solid-state device is to split spin-singlet Cooper pairs by coupling a superconductor to two parallel quantum dots (QDs) in a Y-junction geometry. Such Cooper pair splitting (CPS) was successfully detected in recent transport experiments on devices based on InAs nanowires and Carbon nanotubes (CNTs). Here we present experiments on a CNT based Cooper pair splitter device with low inter-dot tunnel coupling. We find an unprecedented splitting efficiency, often much larger than 50%, the upper limit in devices with large inter-dot coupling. Such CPS rates allow us to investigate this effect as a function of a variety of external parameters. In addition, we discuss Fano line-shapes as a feature of our QD resonances. A high CPS efficiency is a prerequisite for Bell state measurements, a clear way of proving that Cooper pairs can be extracted coherently and lead to spatially separated entangled electron pairs.
Energy Technology Data Exchange (ETDEWEB)
Shirbisheh, Vahid, E-mail: shirbisheh@gmail.com
2012-06-15
As the first step towards developing noncommutative geometry over Hecke C{sup Asterisk-Operator }-algebras, we study property (RD) (Rapid Decay) for Hecke pairs. When the subgroup H in a Hecke pair (G, H) is finite, we show that the Hecke pair (G, H) has (RD) if and only if G has (RD). This provides us with a family of examples of Hecke pairs with property (RD). We also adapt Paul Jolissant's works in Jolissaint (J K-Theory 2:723-735, 1989; Trans Amer Math Soc 317(1):167-196, 1990) to the setting of Hecke C{sup Asterisk-Operator }-algebras and show that when a Hecke pair (G, H) has property (RD), the algebra of rapidly decreasing functions on the set of double cosets is closed under holomorphic functional calculus of the associated (reduced) Hecke C{sup Asterisk-Operator }-algebra. Hence they have the same K{sub 0}-groups.
Shirbisheh, Vahid
2012-06-01
As the first step towards developing noncommutative geometry over Hecke C ∗-algebras, we study property (RD) (Rapid Decay) for Hecke pairs. When the subgroup H in a Hecke pair ( G, H) is finite, we show that the Hecke pair ( G, H) has (RD) if and only if G has (RD). This provides us with a family of examples of Hecke pairs with property (RD). We also adapt Paul Jolissant's works in Jolissaint (J K-Theory 2:723-735, 1989; Trans Amer Math Soc 317(1):167-196, 1990) to the setting of Hecke C ∗-algebras and show that when a Hecke pair ( G, H) has property (RD), the algebra of rapidly decreasing functions on the set of double cosets is closed under holomorphic functional calculus of the associated (reduced) Hecke C ∗-algebra. Hence they have the same K 0-groups.
Entanglement and Sources of Magnetic Anisotropy in Radical Pair-Based Avian Magnetoreceptors
Hogben, Hannah J; Hore, P J
2012-01-01
One of the principal models of magnetic sensing in migratory birds rests on the quantum spin-dynamics of transient radical pairs created photochemically in ocular cryptochrome proteins. We consider here the role of electron spin entanglement and coherence in determining the sensitivity of a radical pair-based geomagnetic compass and the origins of the directional response. It emerges that the anisotropy of radical pairs formed from spin-polarized molecular triplets could form the basis of a more sensitive compass sensor than one founded on the conventional hyper?ne-anisotropy model. This property offers new and more flexible opportunities for the design of biologically inspired magnetic compass sensors.
Pairing correlations in exotic nuclei
Sagawa, H
2012-01-01
The BCS and HFB theories which can accommodate the pairing correlations in the ground states of atomic nuclei are presented. As an application of the pairing theories, we investigate the spatial extension of weakly bound Ne and C isotopes by taking into account the pairing correlation with the Hartree-Fock-Bogoliubov (HFB) method and a 3-body model, respectively. We show that the odd-even staggering in the reaction cross sections of $^{30,31,32}$Ne and $^{14,15,16}$C are successfully reproduced, and thus the staggering can be attributed to the unique role of pairing correlations in nuclei far from the stability line. A correlation between a one-neutron separation energy and the anti-halo effect is demonstrated for $s$- and p-waves using the HFB wave functions. We also propose effective density-dependent pairing interactions which reproduce both the neutron-neutron ($nn$) scattering length at zero density and the neutron pairing gap in uniform matter. Then, we apply these interactions to study pairing gaps in ...
Accumulation of Raman gain between closely spaced pulse pairs.
Marshall, L R; Piper, J A
1990-12-01
The short-pulse conversion efficiency of stimulated Raman scattering in Pb vapor is increased from 15% to 35% by using a novel technique that employs a closely spaced pair of pump pulses. The second pulse scatters off the coherent excitation induced in the medium by the first pulse, with a resultant enhancement in efficiency. To our knowledge these results give the first observation of such long-lived cooperative phenomena in stimulated Raman scattering. We have also observed this phenomenon in H(2) and show that this technique is readily applicable to other Raman-active media. PMID:19771085
Auñón, Juan Miguel; Nieto-Vesperinas, Manuel
2014-01-01
We present a theory and computation method of radiation pressure from partially coherent light by establishing a coherent mode representation of the radiation forces. This is illustrated with the near field emitted from a Gaussian Schell model source, mechanically acting on a single cylinder with magnetodielectric behavior, or on a photonic molecule constituted by a pair of such cylinders. Thus after studying the force produced by a single particle, we address the effects of the spatial coherence on the bonding and anti-bonding states of two particles. The coherence length manifests the critical limitation of the contribution of evanescent modes to the scattered fields, and hence to the nature and strength of the electromagnetic fores, even when electric and/or magnetic partial wave resonances are excited.
Coherence Properties of the LCLS
Energy Technology Data Exchange (ETDEWEB)
Ocko, Samuel
2010-08-25
The LINAC Coherent Light Source (LCLS), an X-Ray free-electron laser(FEL) based on the self amplified spontaneous emission principle, has recently come on-line. For many users it is desirable to have an idea of the level of transverse coherence of the X-Ray beam produced. In this paper, we analyze the output of GENESIS simulations of electrons traveling through the FEL. We first test the validity of an approach that ignores the details of how the beam was produced, and instead, by assuming a Gaussian-Schell model of transverse coherence, predicts the level of transverse coherence simply through looking at the beam radius at several longitudinal slices. We then develop a Markov chain Monte Carlo approach to calculating the degree of transverse coherence, which offers a {approx}100-fold speedup compared to the brute-force algorithm previously in use. We find the beam highly coherent. Using a similar Markov chain Monte Carlo approach, we estimate the reasonability of assuming the beam to have a Gaussian-Schell model of transverse coherence, with inconclusive results.
Pairing Correlations at High Spins
Ma, Hai-Liang; Dong, Bao-Guo; Zhang, Yan; Fan, Ping; Yuan, Da-Qing; Zhu, Shen-Yun; Zhang, Huan-Qiao; Petrache, C. M.; Ragnarsson, I.; Carlsson, B. G.
The pairing correcting energies at high spins in 161Lu and 138Nd are studied by comparing the results of the cranked-Nilsson-Strutinsky (CNS) and cranked-Nilsson-Strutinsky-Bogoliubov (CNSB) models. It is concluded that the Coriolis effect rather than the rotational alignment effect plays a major role in the reduction of the pairing correlations in the high spin region. Then we proposed an average pairing correction method which not only better reproduces the experimental data comparing with the CNS model but also enables a clean-cut tracing of the configurations thus the full-spin-range discussion on the various rotating bands.
Coherent Matterwave Emission from an Atomtronic Transistor
Straatsma, Cameron; Anderson, Dana
2016-05-01
We investigate matterwave emission from a triple-well ``transistor'' atomic potential consisting of a ``source'' well treated as a reservoir having fixed chemical potential and temperature, a narrow ``gate'' well, and a ``drain'' well coupled to the vacuum. The ground state of the gate well is occupied by a Bose-Einstein condensate having large chemical potential along with the first excited state of the potential. These lower states are coupled to the two highest lying bound states lying near the top of the barriers separating the gate from the other two wells. We show that the energy level separations of the two lower states and the two upper states can be made degenerate by design of the Gaussian barrier widths and separation. When degenerate, the two pairs of states are strongly coupled by phonon exchange. We seek a self-consistent solution for the coupling between the high-lying states and the ground state pair, which occurs due to stimulated absorption and emission of phonons. In steady-state, coupling of the upper states leads to matter wave emission such that the emission of the two states is mutually coherent. The output from the transistor is thus an intensity-modulated matterwave whose frequency is approximately equal to the ground-state trap frequency.
International workshop on phase retrieval and coherent scattering. Coherence 2005
Energy Technology Data Exchange (ETDEWEB)
Nugent, K.A.; Fienup, J.R.; Van Dyck, D.; Van Aert, S.; Weitkamp, T.; Diaz, A.; Pfeiffer, F.; Cloetens, P.; Stampanoni, M.; Bunk, O.; David, C.; Bronnikov, A.V.; Shen, Q.; Xiao, X.; Gureyev, T.E.; Nesterets, Ya.I.; Paganin, D.M.; Wilkins, S.W.; Mokso, R.; Cloetens, P.; Ludwig, W.; Hignette, O.; Maire, E.; Faulkner, H.M.L.; Rodenburg, J.M.; Wu, X.; Liu, H.; Grubel, G.; Ludwig, K.F.; Livet, F.; Bley, F.; Simon, J.P.; Caudron, R.; Le Bolloc' h, D.; Moussaid, A.; Gutt, C.; Sprung, M.; Madsen, A.; Tolan, M.; Sinha, S.K.; Scheffold, F.; Schurtenberger, P.; Robert, A.; Madsen, A.; Falus, P.; Borthwick, M.A.; Mochrie, S.G.J.; Livet, F.; Sutton, M.D.; Ehrburger-Dolle, F.; Bley, F.; Geissler, E.; Sikharulidze, I.; Jeu, W.H. de; Lurio, L.B.; Hu, X.; Jiao, X.; Jiang, Z.; Lurio, L.B.; Hu, X.; Jiao, X.; Jiang, Z.; Naryanan, S.; Sinha, S.K.; Lal, J.; Naryanan, S.; Sinha, S.K.; Lal, J.; Robinson, I.K.; Chapman, H.N.; Barty, A.; Beetz, T.; Cui, C.; Hajdu, J.; Hau-Riege, S.P.; He, H.; Stadler, L.M.; Sepiol, B.; Harder, R.; Robinson, I.K.; Zontone, F.; Vogl, G.; Howells, M.; London, R.; Marchesini, S.; Shapiro, D.; Spence, J.C.H.; Weierstall, U.; Eisebitt, S.; Shapiro, D.; Lima, E.; Elser, V.; Howells, M.R.; Huang, X.; Jacobsen, C.; Kirz, J.; Miao, H.; Neiman, A.; Sayre, D.; Thibault, P.; Vartanyants, I.A.; Robinson, I.K.; Onken, J.D.; Pfeifer, M.A.; Williams, G.J.; Pfeiffer, F.; Metzger, H.; Zhong, Z.; Bauer, G.; Nishino, Y.; Miao, J.; Kohmura, Y.; Yamamoto, M.; Takahashi, Y.; Koike, K.; Ebisuzaki, T.; Ishikawa, T.; Spence, J.C.H.; Doak, B
2005-07-01
The contributions of the participants have been organized into 3 topics: 1) phase retrieval methods, 2) X-ray photon correlation spectroscopy, and 3) coherent diffraction imaging. This document gathers the abstracts of the presentations and of the posters.
International workshop on phase retrieval and coherent scattering. Coherence 2005
International Nuclear Information System (INIS)
The contributions of the participants have been organized into 3 topics: 1) phase retrieval methods, 2) X-ray photon correlation spectroscopy, and 3) coherent diffraction imaging. This document gathers the abstracts of the presentations and of the posters
Optical coherent control in semiconductors
DEFF Research Database (Denmark)
Østergaard, John Erland; Vadim, Lyssenko; Hvam, Jørn Märcher
2001-01-01
The developments with coherent control (CC) techniques in optical spectroscopy have recently demonstrated population control and coherence manipulations when the induced optical phase is explored with phase-locked laser pulses. These and other developments have been guiding the new research field...... of quantum control including the recent applications to semiconductors and nanostructures. We study the influence of inhomogeneous broadening in semiconductors on CC results. Photoluminescence (PL) and the coherent emission in four-wave mixing (FWM) is recorded after resonant excitation with phase-locked...
Second harmonic optical coherence tomography
Jiang, Y; Wang, Y; Chen, Z; Jiang, Yi; Tomov, Ivan; Wang, Yimin; Chen, Zhongping
2004-01-01
Second harmonic optical coherence tomography, which uses coherence gating of second-order nonlinear optical response of biological tissues for imaging, is described and demonstrated. Femtosecond laser pulses were used to excite second harmonic waves from collagen harvested from rat tail tendon and a reference nonlinear crystal. Second harmonic interference fringe signals were detected and used for image construction. Because of the strong dependence of second harmonic generation on molecular and tissue structures, this technique offers contrast and resolution enhancement to conventional optical coherence tomography.
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)
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.)
Quantum Zeno Effect Underpinning the Radical-Ion-Pair Mechanism of Avian Magnetoreception
Kominis, I K
2008-01-01
The intricate biochemical processes underlying avian magnetoreception, the sensory ability of migratory birds to navigate using earths magnetic field, have been narrowed down to spin-dependent recombination of radical-ion pairs to be found in avian species retinal proteins. The avian magnetic field detection is governed by the interplay between magnetic interactions of the radicals unpaired electrons and the radicals recombination dynamics. Critical to this mechanism is the long lifetime of the radical-pair spin coherence, so that the weak geomagnetic field will have a chance to signal its presence. It is here shown that a fundamental quantum phenomenon, the quantum Zeno effect, is at the basis of the radical-ion-pair magnetoreception mechanism. The quantum Zeno effect naturally leads to long spin coherence lifetimes, without any constraints on the systems physical parameters, ensuring the robustness of this sensory mechanism. Basic experimental observations regarding avian magnetic sensitivity are seamlessly...
An explanation of trans-ionospheric pulse pairs
Wu, H -C
2016-01-01
Trans-ionospheric pulse pairs are the most powerful natural radio signals on the Earth and associated with lightning. They have been discovered for two decades by satellites, but their origin still remains elusive. Here we attribute these radio signals to relativistic electrons produced by cloud-to-ground lightning. When these electrons strike the ground, radio bursts are emitted towards space in a narrow cone. This model naturally explains the interval, duration, polarization, coherence and bimodal feature of the pulse pairs. Based on electron parameters inferred from x-ray observation of lightning, the calculated signal intensity agrees with the measurement of satellites. Our results are useful to develop global warning system of storms and hurricane based on GPS satellites.
Transient quantum coherent response to a partially coherent radiation field
Energy Technology Data Exchange (ETDEWEB)
Sadeq, Zaheen S.; Brumer, Paul, E-mail: pbrumer@chem.utoronto.ca [Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)
2014-02-21
The response of an arbitrary closed quantum system to a partially coherent electric field is investigated, with a focus on the transient coherences in the system. As a model we examine, both perturbatively and numerically, the coherences induced in a three level V system. Both rapid turn-on and pulsed turn-on effects are investigated. The effect of a long and incoherent pulse is also considered, demonstrating that during the pulse the system shows a coherent response which reduces after the pulse is over. Both the pulsed scenario and the thermally broadened CW case approach a mixed state in the long time limit, with rates dictated by the adjacent level spacings and the coherence time of the light, and via a mechanism that is distinctly different from traditional decoherence. These two excitation scenarios are also explored for a minimal “toy” model of the electronic levels in pigment protein complex PC645 by both a collisionally broadened CW laser and by a noisy pulse, where unexpectedly long transient coherence times are observed and explained. The significance of environmentally induced decoherence is noted.
COHeRE: Cross-Ontology Hierarchical Relation Examination for Ontology Quality Assurance.
Cui, Licong
2015-01-01
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
Pairing mechanisms for binary stars
Kouwenhoven, M B N; Goodwin, S P; Zwart, S F Portegies; Kaper, L; 10.1002/asna.200811061
2008-01-01
Knowledge of the binary population in stellar groupings provides important information about the outcome of the star forming process in different environments. Binarity is also a key ingredient in stellar population studies and is a prerequisite to calibrate the binary evolution channels. In these proceedings we present an overview of several commonly used methods to pair individual stars into binary systems, which we refer to as the pairing function. Many pairing functions are frequently used by observers and computational astronomers, either for the mathematical convenience, or because they roughly describe the expected outcome of the star forming process. We discuss the consequences of each pairing function for the interpretation of observations and numerical simulations. The binary fraction and mass ratio distribution generally depend strongly on the selection of the range in primary spectral type in a sample. These quantities, when derived from a binary survey with a mass-limited sample of target stars, ...
Kramers Pairs in configuration interaction
DEFF Research Database (Denmark)
Avery, John Scales; Avery, James Emil
2003-01-01
The theory of symmetry-preserving Kramers pair creation operators is reviewed and formulas for applying these operators to configuration interaction calculations are derived. A new and more general type of symmetry-preserving pair creation operator is proposed and shown to commute with the total ...... spin operator and with all of the symmetry operations which leave the core Hamiltonian of a many-electron system invariant. The theory is extended to cases where orthonormality of orbitals of different configurations cannot be assumed.......The theory of symmetry-preserving Kramers pair creation operators is reviewed and formulas for applying these operators to configuration interaction calculations are derived. A new and more general type of symmetry-preserving pair creation operator is proposed and shown to commute with the total...
Kramers Pairs in Configuration Interaction
DEFF Research Database (Denmark)
Avery, John Scales; Avery, James Emil
2003-01-01
The theory of symmetry-preserving Kramers pair creation operators is reviewed and formulas for applying these operators to configuration interaction calculations are derived. A new and more general type of symmetry-preserving pair creation operator is proposed and shown to commute with the total ...... spin operator and with all of the symmetry operations which leave the core Hamiltonian of a many-electron system invariant. The theory is extended to cases where orthonormality of orbitals of different configurations cannot be assumed.......The theory of symmetry-preserving Kramers pair creation operators is reviewed and formulas for applying these operators to configuration interaction calculations are derived. A new and more general type of symmetry-preserving pair creation operator is proposed and shown to commute with the total...
[Optical coherence tomography].
von Braunmühl, T
2015-07-01
Optical coherence tomography (OCT) was introduced in the 1990s in dermatology and is nowadays established as a noninvasive high-resolution technique for the in vivo evaluation of the skin. To date several studies have been successfully demonstrated the application of OCT for various dermatological questions. The main indication for OCT in the daily practice is the noninvasive diagnosis of nonmelanoma skin cancer such as actinic keratosis and basal cell carcinoma. OCT has also been shown to be a valuable tool in treatment monitoring and evaluation of therapeutic success of noninvasive treatment strategies like topical immune modulators or photodynamic treatment. Other potential applications for OCT include inflammatory diseases, microbial or parasitic infestations of the skin, e.g. scabies mites or onychomycosis. In recent years high-definition OCT devices have been developed that can potentially be used for the evaluation of melanocytic lesions and, due to the higher resolution, for the visualization of intrafollicular demodex mites. Furthermore different commercially available devices offer-in addition to the cross-sectional images-a fast-generated horizontal (en face) imaging mode. With respect to resolution and penetration depth the OCT technique is taking a middle position in comparison to other noninvasive imaging devices in dermatology such as sonography and reflectance confocal microscopy. PMID:25809459
Pair programming: more than just working together in pairs.
Directory of Open Access Journals (Sweden)
Elsa Mentz
2012-03-01
Full Text Available Pair programming originated in the industry where focus is placed on the development of a programme at the most costand time-effective manner, and within the parameters of quality. In this context, a specific programming code is not developed individually; rather, two people work together in order to ensure a higher quality programming code and to motivate each other to work at a faster pace. The problem with this approach was that novice programmers lacked the social skills to work in pairs as they had not been exposed to this sufficiently at tertiary level. The demand of the industry, especially in terms of programmers needing to be able to programme together, led to the incorporation of pair programming at tertiary level in the late nineties. The pedagogical principles on which any teaching-learning strategy should be built were, however, largely overlooked during this process. This article firstly looks into the semantic and ontological differences between co-operative and collaborative learning and secondly argues that pair programming, within the context of a social constructivist approach to teaching and learning, can be seen as a co-operative teaching-learning strategy. Pair programming is more than just allowing two students to work together on a programming task. The more structured way, in which pair programming needs to be implemented, concur with the principles of co-operative learning. The article concludes that the correct pedagogical application of pair programming as a co-operative teaching-learning strategy in tertiary education will result in improved learning capital.
Counting pairs of faint galaxies
Woods, D; Richer, H B; Woods, David; Fahlman, Gregory G; Richer, Harvey B
1995-01-01
The number of close pairs of galaxies observed to faint magnitude limits, when compared to nearby samples, determines the interaction or merger rate as a function of redshift. The prevalence of mergers at intermediate redshifts is fundamental to understanding how galaxies evolve and the relative population of galaxy types. Mergers have been used to explain the excess of galaxies in faint blue counts above the numbers expected from no-evolution models. Using deep CFHT (I\\leq24) imaging of a ``blank'' field we find a pair fraction which is consistent with the galaxies in our sample being randomly distributed with no significant excess of ``physical'' close pairs. This is contrary to the pair fraction of 34\\%\\pm9\\% found by Burkey {\\it et al.} for similar magnitude limits and using an identical approach to the pair analysis. Various reasons for this discrepancy are discussed. Colors and morphologies of our close pairs are consistent with the bulk of them being random superpositions although, as indicators of int...
Energy Technology Data Exchange (ETDEWEB)
Docaj, A. [Physics Department, Texas Tech University, Lubbock, TX 79409-1051 (United States); Estreicher, S.K., E-mail: Stefan.Estreicher@ttu.edu [Physics Department, Texas Tech University, Lubbock, TX 79409-1051 (United States)
2012-08-01
Carbon impurities in Si are common in floating-zone and cast-Si materials. The simplest and most discussed carbon complex is the interstitial-substitutional C{sub i}C{sub s} pair, which readily forms when self-interstitials are present in the material. This pair has three possible configurations, each of which is electrically active. The less common C{sub s}C{sub s} pair has been studied in irradiated material but has also recently been seen in as-grown C-rich cast-Si, which is commonly used to fabricate solar cells. The third pair consists of two interstitial C atoms: C{sub i}C{sub i}. Although its formation probability is low for several reasons, the C{sub i}C{sub i} pair is very stable and electrically inactive. In this contribution, we report preliminary results of first-principles calculations of these three C pairs in Si. The structures, binding energies, vibrational spectra, and electrical activity are predicted.
Coherence of Physics and Chemistry Curricula in Terms of the Electron Concept
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.
Coherence matrix of plasmonic beams
DEFF Research Database (Denmark)
Novitsky, Andrey; Lavrinenko, Andrei
2013-01-01
We consider monochromatic electromagnetic beams of surface plasmon-polaritons created at interfaces between dielectric media and metals. We theoretically study non-coherent superpositions of elementary surface waves and discuss their spectral degree of polarization, Stokes parameters, and the for...... of the spectral coherence matrix. We compare the polarization properties of the surface plasmonspolaritons as three-dimensional and two-dimensional fields concluding that the latter is superior....
Diffusion Processes and Coherent States
Martino, S; De Siena, S.; Illuminati, F.; Vitiello, G.
1994-01-01
It is shown that stochastic processes of diffusion type possess, in all generality, a structure of uncertainty relations and of coherent and squeezed states. This fact is used to obtain, via Nelson stochastic formulation of quantum mechanics, the harmonic-oscillator coherent and squeezed states. The method allows to derive new minimum uncertainty states in time-dependent oscillator potentials and for the Caldirola-Kanai model of quantum damped oscillator.
Pseudo-Fermionic Coherent States
Cherbal, Omar; Drir, Mahrez
2009-01-01
We have generalized the fermionic coherent states to pseudo-fermion oscillator system. The system of coherent states constructed consist of two subsets, which are bi-normalized and bi-overcomplete. The two subsets are built up as eigenstates of two annihilation operators $b$ and $\\tilde{b} = \\eta b \\eta^{-1}$ of respectively $H$ and $H^+$ where $\\eta$ is the Hermitian and invertible operator that ensures the pseudo-Hermiticity of the Hamiltonian $H = \\eta^{-1} H^+ \\eta$
Qin, Zhiyuan; Tao, Rumao; Zhou, Pu; Xu, Xiaojun; Liu, Zejin
2013-11-20
Based on partially coherent Bessel-Gaussian beams (BGBs), the coherence evolution of the partially coherent beams carrying optical vortices in non-Kolmogorov turbulence is investigated in detail. The analytical formulas for the spatial coherence length of partially coherent BGBs with optical vortices in non-Kolmogorov turbulence have been derived by using the combination of a coherence superposition approximation of decentered Gaussian beams and the extended Huygens-Fresnel principle. The influences of beam and turbulence parameters on spatial coherence are investigated by numerical examples. Numerical results reveal that the coherence of the partially coherent laser beam with vortices is independent of the optical vortices, and the spatial correlation length of the beams does not decrease monotonically during propagation in non-Kolmogorov turbulence. Within a certain propagation distance, the coherence of the partially coherent beam will improve, and the improvement of the coherence of the partially coherent beams is closely related to the beam and turbulence parameters.
Energy Technology Data Exchange (ETDEWEB)
Rong Xing; Ghaly, Michael; Frey, Eric C. [Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21287-0859 (United States)
2013-06-15
Purpose: In yttrium-90 ({sup 90}Y) microsphere brachytherapy (radioembolization) of unresectable liver cancer, posttherapy {sup 90}Y bremsstrahlung single photon emission computed tomography (SPECT) has been used to document the distribution of microspheres in the patient and to help predict potential side effects. The energy window used during projection acquisition can have a significant effect on image quality. Thus, using an optimal energy window is desirable. However, there has been great variability in the choice of energy window due to the continuous and broad energy distribution of {sup 90}Y bremsstrahlung photons. The area under the receiver operating characteristic curve (AUC) for the ideal observer (IO) is a widely used figure of merit (FOM) for optimizing the imaging system for detection tasks. The IO implicitly assumes a perfect model of the image formation process. However, for {sup 90}Y bremsstrahlung SPECT there can be substantial model-mismatch (i.e., difference between the actual image formation process and the model of it assumed in reconstruction), and the amount of the model-mismatch depends on the energy window. It is thus important to account for the degradation of the observer performance due to model-mismatch in the optimization of the energy window. The purpose of this paper is to optimize the energy window for {sup 90}Y bremsstrahlung SPECT for a detection task while taking into account the effects of the model-mismatch. Methods: An observer, termed the ideal observer with model-mismatch (IO-MM), has been proposed previously to account for the effects of the model-mismatch on IO performance. In this work, the AUC for the IO-MM was used as the FOM for the optimization. To provide a clinically realistic object model and imaging simulation, the authors used a background-known-statistically and signal-known-statistically task. The background was modeled as multiple compartments in the liver with activity parameters independently following a
International Nuclear Information System (INIS)
Purpose: In yttrium-90 (90Y) microsphere brachytherapy (radioembolization) of unresectable liver cancer, posttherapy 90Y bremsstrahlung single photon emission computed tomography (SPECT) has been used to document the distribution of microspheres in the patient and to help predict potential side effects. The energy window used during projection acquisition can have a significant effect on image quality. Thus, using an optimal energy window is desirable. However, there has been great variability in the choice of energy window due to the continuous and broad energy distribution of 90Y bremsstrahlung photons. The area under the receiver operating characteristic curve (AUC) for the ideal observer (IO) is a widely used figure of merit (FOM) for optimizing the imaging system for detection tasks. The IO implicitly assumes a perfect model of the image formation process. However, for 90Y bremsstrahlung SPECT there can be substantial model-mismatch (i.e., difference between the actual image formation process and the model of it assumed in reconstruction), and the amount of the model-mismatch depends on the energy window. It is thus important to account for the degradation of the observer performance due to model-mismatch in the optimization of the energy window. The purpose of this paper is to optimize the energy window for 90Y bremsstrahlung SPECT for a detection task while taking into account the effects of the model-mismatch. Methods: An observer, termed the ideal observer with model-mismatch (IO-MM), has been proposed previously to account for the effects of the model-mismatch on IO performance. In this work, the AUC for the IO-MM was used as the FOM for the optimization. To provide a clinically realistic object model and imaging simulation, the authors used a background-known-statistically and signal-known-statistically task. The background was modeled as multiple compartments in the liver with activity parameters independently following a Gaussian distribution; the
Directory of Open Access Journals (Sweden)
Pier Alberto Testoni
2007-01-01
Full Text Available Optical coherence tomography (OCT is an optical imaging modality that performs high-resolution, cross-sectional, subsurface tomographic imaging of the microstructure of tissues. The physical principle of OCT is similar to that of B-mode ultrasound imaging, except that it uses infrared light waves rather than acoustic waves. The in vivo resolution is 10–25 times better (about 10 µm than with high-frequency ultrasound imaging, but the depth of penetration is limited to 1–3 mm, depending on tissue structure, depth of focus of the probe used, and pressure applied to the tissue surface. In the last decade, OCT technology has evolved from an experimental laboratory tool to a new diagnostic imaging modality with a wide spectrum of clinical applications in medical practice, including the gastrointestinal tract and pancreatico-biliary ductal system. OCT imaging from the gastrointestinal tract can be done in humans by using narrow-diameter, catheter-based probes that can be inserted through the accessory channel of either a conventional front-view endoscope, for investigating the epithelial structure of the gastrointestinal tract, or a side-view endoscope, inside a standard transparent ERCP (endoscopic retrograde cholangiopancreatography catheter, for investigating the pancreatico-biliary ductal system. The esophagus and esophagogastric junction have been the most widely investigated organs so far; more recently, duodenum, colon, and the pancreatico-biliary ductal system have also been extensively investigated. OCT imaging of the gastrointestinal wall structure is characterized by a multiple-layer architecture that permits an accurate evaluation of the mucosa, lamina propria, muscularis mucosae, and part of the submucosa. The technique may therefore be used to identify preneoplastic conditions of the gastrointestinal tract, such as Barrett's epithelium and dysplasia, and evaluate the depth of penetration of early-stage neoplastic lesions. OCT imaging
Energy Technology Data Exchange (ETDEWEB)
Juste, B.; Miro, R.; Verdu, G.; Diez, S.; Campayo, J. M.
2010-07-01
Determining the spectral distribution of the emitted photon medical linear accelerator (linac) used in radiotherapy treatment is extremely important for performing dosimetry calculations as to accurately calculate the therapeutic dose distributions. Since directly measure the spectrum is very complicated, this paper presents an indirect technique to accurately calculate the spectra of Bremsstrahlung photons emitted by linacs.
Energy Technology Data Exchange (ETDEWEB)
Erhard, Martin Andreas
2010-02-26
By the high intensity of the bremsstrahlung of up to 20 MeV to 10{sup 9} MeV{sup -1}cm{sup -2}s{sup -1} in the energy range up to 20 MeV in the framework of this thesis for the first time not only the ({gamma},n), but also the ({gamma},p) reactions could be studied on {sup 92}Mo at astrophysically relevant energies.
Coherent communication with continuous quantum variables
International Nuclear Information System (INIS)
The coherent bit (cobit) channel is a resource intermediate between classical and quantum communication. It produces coherent versions of teleportation and superdense coding. We extend the cobit channel to continuous variables by providing a definition of the coherent nat (conat) channel. We construct several coherent protocols that use both a position-quadrature and a momentum-quadrature conat channel with finite squeezing. Finally, we show that the quality of squeezing diminishes through successive compositions of coherent teleportation and superdense coding
Coherent states and applications in mathematical physics
Combescure, Monique
2012-01-01
This book presents the various types of coherent states introduced and studied in the physics and mathematics literature and describes their properties together with application to quantum physics problems. It is intended to serve as a compendium on coherent states and their applications for physicists and mathematicians, stretching from the basic mathematical structures of generalized coherent states in the sense of Perelomov via the semiclassical evolution of coherent states to various specific examples of coherent states (hydrogen atom, quantum oscillator, ...).
Bracket states for communication protocols with coherent states
Allevi, Alessia; Olivares, Stefano; Bondani, Maria
2014-05-01
We present the generation and characterization of the class of bracket states, namely phase-sensitive mixtures of coherent states exhibiting symmetry properties in the phase-space description. A bracket state can be seen as the statistical ensemble arriving at a receiver in a typical coherent-state-based communication channel. We show that when a bracket state is mixed at a beam splitter with a local oscillator, both the emerging beams exhibit a Fano factor larger than 1 and dependent on the relative phase between the input state and the local oscillator. We discuss the possibility to exploit this dependence to monitor the phase difference for the enhancement of the performances of a simple communication scheme based on direct detection. Our experimental setup involves linear optical elements and a pair of photon-number-resolving detectors operated in the mesoscopic photon-number domain.
Quantum memory receiver for superadditive communication using binary coherent states
Klimek, Aleksandra; Wasilewski, Wojciech; Banaszek, Konrad
2015-01-01
We propose a simple architecture based on multimode quantum memories for collective readout of classical information keyed using a pair coherent states, exemplified by the well-known binary phase shift keying format. Such a configuration enables demonstration of the superadditivity effect in classical communication over quantum channels, where the transmission rate becomes enhanced through joint detection applied to multiple channel uses. The proposed scheme relies on the recently introduced idea to prepare Hadamard sequences of input symbols that are mapped by a linear optical transformation onto the pulse position modulation format [Guha, S. {\\em Phys. Rev. Lett.}\\ {\\bf 2011}, {\\em 106}, 240502]. We analyze two versions of readout based on direct detection and an optional Dolinar receiver which implements the minimum-error measurement for individual detection of a binary coherent state alphabet.
Pair extended coupled cluster doubles
Henderson, Thomas M; Scuseria, Gustavo E
2015-01-01
The accurate and efficient description of strongly correlated systems remains an important challenge for computational methods. Doubly occupied configuration interaction (DOCI), in which all electrons are paired and no correlations which break these pairs are permitted, can in many cases provide an accurate account of strong correlations, albeit at combinatorial computational cost. Recently, there has been significant interest in a method we refer to as pair coupled cluster doubles (pCCD), a variant of coupled cluster doubles in which the electrons are paired. This is simply because pCCD provides energies nearly identical to those of DOCI, but at mean-field computational cost (disregarding the cost of the two-electron integral transformation). Here, we introduce the more complete pair extended coupled cluster doubles (pECCD) approach which, like pCCD, has mean-field cost and reproduces DOCI energetically. We show that unlike pCCD, pECCD also reproduces the DOCI wave function with high accuracy. Moreoever, pEC...
Coherence measurements and coherent diffractive imaging at FLASH
Energy Technology Data Exchange (ETDEWEB)
Vartanyants, I A; Mancuso, A P; Singer, A; Yefanov, O M; Gulden, J, E-mail: ivan.vartaniants@desy.d [Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg (Germany)
2010-10-14
We present an overview of recent experiments performed at the free-electron laser (FEL) FLASH at DESY in Hamburg. Experiments were focused on coherence measurements and coherent x-ray diffractive imaging (CXDI) of periodic and non-periodic biological samples. Young's double slit experiment was performed at FLASH to measure its coherence properties at a fundamental wavelength of 13.7 nm. Additionally, a uniformly redundant array was used to measure the coherence properties of the third harmonic (2.7 nm) of an 8 nm fundamental wavelength at FLASH. Coherent imaging of a two-dimensional (2D) finite crystal structure using a single pulse train of FLASH radiation was demonstrated. We show that the structure is reconstructed to the detector-limited resolution of 220 nm, given an adequate signal to noise ratio. We have also employed CXDI in a non-destructive regime to compare the images of a biological sample using single, femtosecond pulses of FLASH radiation. We have verified that images reconstructed using CXDI are similar for statistically different FEL pulses. We have also demonstrated Fourier transform holography of the same biological sample and present diffraction data measured at the third harmonic of FLASH, reaching into the water window.
Döpp, A; Thaury, C; Lifschitz, A; Sylla, F; Goddet, J-P; Tafzi, A; Iaquanello, G; Lefrou, T; Rousseau, P; Conejero, E; Ruiz, C; Phuoc, K Ta; Malka, V
2016-01-01
Laser wakefield acceleration permits the generation of ultra-short, high-brightness relativistic electron beams on a millimeter scale. While those features are of interest for many applications, the source remains constraint by the poor stability of the electron injection process. Here we present results on injection and acceleration of electrons in pure nitrogen and argon. We observe stable, continuous ionization-induced injection of electrons into the wakefield for laser powers exceeding a threshold of 7 TW. The beam charge scales approximately linear with the laser energy and is limited by beam loading. For 40 TW laser pulses we measure a maximum charge of almost 1 nC per shot, originating mostly from electrons of less than 10 MeV energy. The relatively low energy, the high charge and its stability make this source well-suited for applications such as non-destructive testing. Hence, we demonstrate the production of energetic radiation via bremsstrahlung conversion at 1 Hz repetition rate. In accordance wit...
Döpp, A.; Guillaume, E.; Thaury, C.; Lifschitz, A.; Sylla, F.; Goddet, J.-P.; Tafzi, A.; Iaquanello, G.; Lefrou, T.; Rousseau, P.; Conejero, E.; Ruiz, C.; Ta Phuoc, K.; Malka, V.
2016-09-01
Laser wakefield acceleration permits the generation of ultra-short, high-brightness relativistic electron beams on a millimeter scale. While those features are of interest for many applications, the source remains constraint by the poor stability of the electron injection process. Here we present results on injection and acceleration of electrons in pure nitrogen and argon. We observe stable, continuous ionization-induced injection of electrons into the wakefield for laser powers exceeding a threshold of 7 TW. The beam charge scales approximately with the laser energy and is limited by beam loading. For 40 TW laser pulses we measure a maximum charge of almost 1 nC per shot, originating mostly from electrons of less than 10 MeV energy. The relatively low energy, the high charge and its stability make this source well-suited for applications such as non-destructive testing. Hence, we demonstrate the production of energetic radiation via bremsstrahlung conversion at 1 Hz repetition rate. In accordance with GEANT4 Monte-Carlo simulations, we measure a γ-ray source size of less than 100 μm for a 0.5 mm tantalum converter placed at 2 mm from the accelerator exit. Furthermore we present radiographs of image quality indicators.
Energy Technology Data Exchange (ETDEWEB)
Sivakumaran, V.; Joshi, H. C.; Singh, R. K.; Kumar, Ajai, E-mail: ajai@ipr.res.in [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat 382428 (India)
2014-06-15
The early stage of formation of lithium plasma in a collinear—double pulse laser ablation mode has been studied using optical time of flight (OTOF) spectroscopy as a function of inter-pulse delay time, the distance from the target surface and the fluence of the ablation lasers. The experimental TOF measurements were carried out for lithium neutral (670.8 nm and 610.3 nm), and ionic (548.4 nm and 478.8 nm) lines. These experimental observations have been compared with that for single pulse laser ablation mode. It is found that depending on the fluence and laser pulse shape of the first pre-ablation laser and the second main ablation laser, the plasma plume formation and its characteristic features can be described in terms of plume-plume or laser-plume interaction processes. Moreover, the enhancement in the intensity of Li neutral and ionic lines is observed when the laser-plume interaction is the dominant process. Here, we see the evidence of the role of inverse Bremsstrahlung absorption process in the initial stage of formation of lithium plasma in this case.
International Nuclear Information System (INIS)
Hard photons from neutron-proton bremsstrahlung in intermediate energy heavy-ion reactions are examined as a potential probe of the nuclear symmetry energy within a transport model. Effects of the symmetry energy on the yields and spectra of hard photons are found to be generally smaller than those due to the currently existing uncertainties of both the in-medium nucleon-nucleon cross sections and the photon production probability in the elementary process pn→pnγ. Very interestingly, nevertheless, the ratio of hard photon spectra R1/2(γ) from two reactions using isotopes of the same element is not only approximately independent of these uncertainties but also quite sensitive to the symmetry energy. For the head-on reactions of 132Sn + 124Sn and 112Sn + 112Sn at Ebeam/A=50 MeV, for example, the R1/2(γ) displays a rise up to 15% when the symmetry energy is reduced by about 20% at ρ=1.3ρ0 which is the maximum density reached in these reactions
Dolmatov, V K; Cooper, M B; Hunter, M E
2015-01-01
Electron elastic-scattering phase shifts and cross sections along with the differential and total cross sections and polarization of low-frequency bremsstrahlung upon low-energy electron collision with endohedral fullerenes $A$@C$_{60}$ are theoretically scrutinized versus the nature, size and spin of the encapsulated atom $A$. The case-study-atoms $A$ are N, Ar, Cr, Mn, Mo, Tc, Xe, Ba, and Eu. They are thoughtfully picked out of different rows of the periodic table. The study is performed in the framework of a model static approximation. There, both the encapsulated atom $A$ and C$_{60}$ cage are regarded as non-polarizable targets. The C$_{60}$ cage is modeled by an attractive spherical annular potential well. The study provides the most complete initial understanding of how the processes of interest might evolve upon electron collision with various $A$@C$_{60}$. Calculated results identify the most interesting and/or useful future measurements or more rigorous calculations of an electron+$A$@C$_{60}$ colli...
Energy Technology Data Exchange (ETDEWEB)
Habibi, M.; Oloumi, M.; Hosseinkhani, H.; Magidi, S. [Plasma and Fusion Research School, Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of)
2015-10-15
A highly nonlinear parabolic partial differential equation that models the electron heat transfer process in laser inertial fusion has been solved numerically. The strong temperature dependence of the electron thermal conductivity and heat loss term (Bremsstrahlung emission) makes this a highly nonlinear process. In this case, an efficient numerical method is developed for the energy transport mechanism from the region of energy deposition into the ablation surface by a combination of the Crank-Nicolson scheme and the Newton-Raphson method. The quantitative behavior of the electron temperature and the comparison between analytic and numerical solutions are also investigated. For more clarification, the accuracy and conservation of energy in the computations are tested. The numerical results can be used to evaluate the nonlinear electron heat conduction, considering the released energy of the laser pulse at the Deuterium-Tritium (DT) targets and preheating by heat conduction ahead of a compression shock in the inertial confinement fusion (ICF) approach. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Asatov, U T
2002-01-01
In the present work the characteristics of backward (90 sup d eg
Nuclear Scissors Mode with Pairing
Balbutsev, E B; Urban, M; Vinyes, X
2007-01-01
The coupled dynamics of the scissors mode and isovector giant quadrupole resonance are studied using a generalized Wigner function moments method taking into account the pair correlations. Equations of motion for angular momentum, quadrupole moment and other relevant collective variables are derived on the basis of the time dependent Hartree-Fock-Bogoliubov equations. Analytical expressions for energy centroids and transitions probabilities are found for the harmonic oscillator model with the quadrupole-quadrupole residual interaction and monopole pairing force. Deformation dependences of energies and $B(M1)$ values are correctly reproduced. The inclusion of pair correlations leads to a drastic improvement in the description of qualitative and quantitative characteristics of the scissors mode.
Pairing effects in nuclear dynamic
Lacroix, Denis; Scamps, Guillaume; Tanimura, Yusuke
2016-05-01
In recent years, efforts have been made to account for super-fluidity in time-dependent mean-field description of nuclear dynamic [1-5]. Inclusion of pairing is important to achieve a realistic description of static properties of nuclei. Here,we show that pairing can also affect the nuclear motion. State of the art TDHF approach can describe from small to large amplitude collective motion as well as the collision between nuclei. Very recently, this microscopic approach has been improved to include pairing either in the BCS or HFB framework. Recent applications of the 3D TDHF + BCS (TDHF+BCS) model introduced in [4] will be presented. The role of super-fluidity on collective motion [6, 7], on one- and two-particle transfer [8] and on fission [9, 10] will be illustrated.
Vector bright solitons associated with positive coherent coupling via Darboux transformation.
Lü, Xing; Ling, Liming
2015-12-01
Describing coherently coupled and orthogonally polarized waveguide modes in the Kerr medium, vector bright solitons associated with positive coherent coupling are studied in this paper. Some conserved quantities and infinitely many conservation laws are computed, and the existence of Lax pair indicates the integrability of the two-coupled nonlinear Schrödinger system with positive coherent coupling. Performing the iterative algorithm of Darboux transformation, we present formulas of one-, two-, and even N-soliton solutions. With appropriate choices of the phase parameters, collision mechanisms of vector bright solitons (of single-hump, double-hump, or flat-top profiles) are displayed, which show the elastic collision under the combined influences of group velocity dispersion, self-phase modulation, cross-phase modulation, and positive coherent coupling. PMID:26723142
Harvesting, Coupling, and Control of Single-Exciton Coherences in Photonic Waveguide Antennas.
Mermillod, Q; Jakubczyk, T; Delmonte, V; Delga, A; Peinke, E; Gérard, J-M; Claudon, J; Kasprzak, J
2016-04-22
We perform coherent nonlinear spectroscopy of individual excitons strongly confined in single InAs quantum dots (QDs). The retrieval of their intrinsically weak four-wave mixing (FWM) response is enabled by a one-dimensional dielectric waveguide antenna. Compared to a similar QD embedded in bulk media, the FWM detection sensitivity is enhanced by up to 4 orders of magnitude, over a broad operation bandwidth. Three-beam FWM is employed to investigate coherence and population dynamics within individual QD transitions. We retrieve their homogenous dephasing in a presence of low-frequency spectral wandering. Two-dimensional FWM reveals off-resonant Förster coupling between a pair of distinct QDs embedded in the antenna. We also detect a higher order QD nonlinearity (six-wave mixing) and use it to coherently control the FWM transient. Waveguide antennas enable us to conceive multicolor coherent manipulation schemes of individual emitters.
Ai, Qing; Jin, Bih-Yaw; Cheng, Yuan-Chung
2013-01-01
Elucidating quantum coherence effects and geometrical factors for efficient energy transfer in photosynthesis has the potential to uncover non-classical design principles for advanced organic materials. We study energy transfer in a linear light-harvesting model to reveal that dimerized geometries with strong electronic coherences within donor and acceptor pairs exhibit significantly improved efficiency, which is in marked contrast to predictions of the classical F\\"orster theory. We reveal that energy tuning due to coherent delocalization of photoexcitations is mainly responsible for the efficiency optimization. This coherence-assisted energy-tuning mechanism also explains the energetics and chlorophyll arrangements in the widely-studied Fenna-Matthews-Olson complex. We argue that a clustered network with rapid energy relaxation among donors and resonant energy transfer from donor to acceptor states provides a basic formula for constructing efficient light-harvesting systems, and the general principles revea...
Exlusive charmed meson pair production
Berezhnoy, A V
2004-01-01
The experimental data of BELLE Collaboration on the exclusive charmed meson pair production in the process of monophotonic $e^+e^-$-annihilation ($e^+e^-\\to \\gamma^* \\to D\\bar D$) has been studied. It has been shown that these data is described satisfactorily in the frame work of constituent quark model. Our studies have demonstrated that the central production process $e^+e^-\\to e^+e^-\\gamma\\gamma \\to e^+e^-D\\bar D +X$ and the process of monophotonic $e^+e^-$-annihilation yield comparable numbers of the charmed meson pairs.
Instantons in lepton pair production
Energy Technology Data Exchange (ETDEWEB)
Brandenburg, A.; Ringwald, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Utermann, A. [Vrije Univ., Amsterdam (Netherlands). Dept. of Physics and Astronomy
2006-05-15
We consider QCD instanton-induced contributions to lepton pair production in hadron-hadron collisions. We relate these contributions to those known from deep inelastic scattering and demonstrate that they can be calculated reliably for sufficiently large momentum transfer. We observe that the instanton contribution to the angular distribution of the lepton pairs at finite momentum transfer strongly violates the Lam-Tung relation - a relation between coefficient functions of the angular distribution which is valid within the framework of ordinary perturbation theory. The drastic violation of this relation, as seen in experimental data, might be related to such instanton-induced effects. (Orig.)
DEFF Research Database (Denmark)
Wang, W.; Duan, Z.H.; Hanson, Steen Grüner;
2006-01-01
By controlling the irradiance of an extended quasimonochromatic, spatially incoherent source, an optical field is generated that exhibits spatial coherence with phase singularities, called coherence vortices. A simple optical geometry for direct visualization of coherence vortices is proposed, and...
Coherent states on Hilbert modules
International Nuclear Information System (INIS)
We generalize the concept of coherent states, traditionally defined as special families of vectors on Hilbert spaces, to Hilbert modules. We show that Hilbert modules over C*-algebras are the natural settings for a generalization of coherent states defined on Hilbert spaces. We consider those Hilbert C*-modules which have a natural left action from another C*-algebra, say A. The coherent states are well defined in this case and they behave well with respect to the left action by A. Certain classical objects like the Cuntz algebra are related to specific examples of coherent states. Finally we show that coherent states on modules give rise to a completely positive definite kernel between two C*-algebras, in complete analogy to the Hilbert space situation. Related to this, there is a dilation result for positive operator-valued measures, in the sense of Naimark. A number of examples are worked out to illustrate the theory. Some possible physical applications are also mentioned.
Coherent Lensless imaging with Ultra-Broadband Light Sources
Directory of Open Access Journals (Sweden)
Eikema K. S. E.
2013-03-01
Full Text Available We demonstrate a method for efficient lensless imaging using ultra-broadband light sources. By using a pair of time-delayed, coherent pulses in a Fourier-transform scheme, spectrally resolved diffraction patterns are obtained throughout the entire spectrum of the incident light source. We perform a proof-of-principle experiment using an octave-spanning visible light source, and obtain images of a holographic test sample with near-diffraction limited resolution. Our approach provides a promising route towards efficient high-resolution imaging using table-top high-harmonic soft-X-ray sources.
Channels that do not generate coherence
Hu, Xueyuan
2016-07-01
We define the non-coherence-generating channel as the completely positive trace-preserving map which does not generate quantum coherence from an incoherent state. The incoherent operations are the strict subset of the non-coherence-generating channels. Although the relative entropy of coherence is monotonically decreasing under the non-coherence-generating channels, we prove that the coherence of formation may increase under such channels. Interestingly, by building a mathematical relation between the coherence of formation and the entanglement of formation, we show that the coherence of formation of a single-qubit state is never increased by a non-coherence-generating channel. This leads to the superadditivity property for the coherence increasing power of quantum channels, namely, while two channels cannot increase coherence individually, they may increase the quantum coherence of a composed system. Further, we derive the general form of the rank-2 non-coherence-generating qubit channels. Our results contribute to the resource theory of quantum coherence.
Coherent neocortical 40-Hz oscillations are not present during REM sleep.
Castro, Santiago; Falconi, Atilio; Chase, Michael H; Torterolo, Pablo
2013-04-01
During cognitive processes there are extensive interactions between various regions of the cerebral cortex. Oscillations in the gamma frequency band (≈40 Hz) of the electroencephalogram (EEG) are involved in the binding of spatially separated but temporally correlated neural events, which results in a unified perceptual experience. The extent of these interactions can be examined by means of a mathematical algorithm called 'coherence', which reflects the 'strength' of functional interactions between cortical areas. The present study was conducted to analyse EEG coherence in the gamma frequency band of the cat during alert wakefulness (AW), quiet wakefulness (QW), non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. Cats were implanted with electrodes in the frontal, parietal and occipital cortices to monitor EEG activity. Coherence values within the gamma frequency (30-100 Hz) from pairs of EEG recordings were analysed. A large increase in coherence occurred between all cortical regions in the 30-45 Hz frequency band during AW compared with the other behavioral states. As the animal transitioned from AW to QW and from QW to NREM sleep, coherence decreased to a moderate level. Remarkably, there was practically no EEG coherence in the entire gamma band spectrum (30-100 Hz) during REM sleep. We conclude that functional interactions between cortical areas are radically different during sleep compared with wakefulness. The virtual absence of gamma frequency coherence during REM sleep may underlie the unique cognitive processing that occurs during dreams, which is principally a REM sleep-related phenomenon. PMID:23406153
Coherent transport through interacting quantum dots
Energy Technology Data Exchange (ETDEWEB)
Hiltscher, Bastian
2012-10-05
the linear-conductance regime. The second work deals with the ratio of coherent processes in transport through quantum dots. To this end, a quantum dot is embedded in one of the arms of an Aharonov-Bohm interferometer. In former theoretical as well as experimental works it has been observed that an important source of decoherence are cotunneling processes that flip the dot's spin. In order to elucidate the role of spin in more detail, we assume one of the leads to be ferromagnetic and the other one to be normal. The main motivations of our work are the two questions: (1) What fraction of the total current through a single-level quantum dot weakly coupled to the electrodes is coherent? (2) How and under which circumstances can this fraction be extracted from a current measurement in an Aharonov-Bohm setup? The measurable quantity in such an experiment is the magnetic-flux dependent ratio of the total current. It turns out that the answers of the two questions strongly depend on the dot level position, the polarization of the ferromagnet, and the transport direction. Especially the flux-dependent and the coherent ratios are not necessarily the same. The main motivation of the third work is to identify crossed Andreev reflection in quantum dots, that is, a Cooper pair splits into two single electrons, which are transferred into different quantum dots in one coherent process. We consider a setup, where two quantum dots are tunnel coupled to the same superconductor and each dot is additionally coupled to a normal conductor. In previous works a bias voltage has been applied between the superconductor and the normal conductors. Then, three processes sustain transport. Beside crossed Andreev reflection also local Andreev reflection, where both electrons of the Cooper pair tunnel into the same dot, and single-particle tunneling occur. This complicates the identification of crossed Andreev reflection. Therefore, we propose the transport mechanism of adiabatic pumping in
DEFF Research Database (Denmark)
Christensen, Ole; Goh, Say Song
2012-01-01
is needed. The purpose of the present paper is to provide constructions of dual pairs of frames in the setting of the Hilbert space of periodic functions L2(0,2π). The frames constructed are given explicitly as trigonometric polynomials, which allows for an efficient calculation of the coefficients...
Electron pair creation by photons
Holtwijk, Theodoor
1960-01-01
In our experiment on the creation of electron pairs a 5 MeV betatron was used as radiation source and a cloud chamber (with magnetic field) was used as detection instrument. The experimental arrangement is described in section 2.1. The cloud chamber was of the overcompression type so that the recove
Calculation of two Belyi pairs
Dremov, V. A.
2008-01-01
We calculate two Belyi pairs using the properties of Mulase-Penkava differential. Details are provided including accurate construction of coordinates, variables and equations. The calculation is a part of the work which results in a catalogue arXiv:0710.2658
Paired Reading: Psycholinguistics in Practice.
Barrett, James Martin
1987-01-01
Contends that children need to learn phonic skills, not necessarily through early direct teaching, but through reading experience. Suggests using Paired Reading, which is validated by psycholinguistic reading theory and provides opportunities to learn to read from context and use innate syntactic and semantic knowledge. (SKC)