Total Scattering Cross-Section

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Numerical Total Scattering Cross Section from Reverberating Electromagnetic Experiments

Numerical Total Scattering Cross Section from Reverberating Electromagnetic Experiments

may need to gather simplicity of MSRC test processes with an accurate idea of incidence and polarization of fields. In this context, different methods and tools have been extensively used to compute the total scattering cross section (TSCS) of various objects [5]. Historically, related to the definition of the radar cross section (RCS), these measurements (experimental and/or numerical) were led in free-space for an object located in the far-field area (relatively to the frequency of the illuminating wave) [6]. In this letter, we adapt and extend an alternative methodology [7] which uses a reverberation chamber (RC) to compute the TSCS of various objects. We put the focus on the numerical setup (RC modeling: losses, sources, probes, targets and post-treatment) needed to compute the TSCS. The validity and an illustration of the method are finally given by comparing results from traditional calculation of TSCS in free-space simulations with ones obtained from simulations in reverberating environment.

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Scattering Cross Section of a Meta-Sphere

Scattering Cross Section of a Meta-Sphere

the meta-sphere and its surrounding medium. This concept has been used in the solution of uniform homogeneous (right-handed) dielectric spheres [11, 12]. Based on such work, the total scattering cross section due to N meta-spheres in a medium is defined to be

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Neutron Nucleus Total Elastic Scattering

Neutron Nucleus Total Elastic Scattering

Using an exact and complete Yukawa Potential Energy (YPE), the neutron-triton and neutron-he- lium elastic total scattering cross section is estimated and extrapolated to zero energy. The esti- mated value agrees pretty well with the experimental value and the procedure can be extended to any neutron-nucleus total scattering. The results are extended to the case of 4 He, 7 Li, 9 Be and 27 Al

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Approximate Electromagnetic Cloaking of a Dielectric Sphere Using Homogeneous Isotropic Multi Layered Materials

Approximate Electromagnetic Cloaking of a Dielectric Sphere Using Homogeneous Isotropic Multi Layered Materials

In cloaking, a body is hidden from detection by surrounding it by a coating consisting of an unusual anisotropic non- homogeneous material. The permittivity and permeability of such a cloak are determined by the coordinate transforma- tion of compressing a hidden body into a point or a line. The radially-dependent spherical cloaking shell can be ap- proximately discretized into many homogeneous anisotropic layers; each anisotropic layer can be replaced by a pair of equivalent isotropic sub-layers, where the effective medium approximation is used to find the parameters of these two equivalent sub-layers. In this work, the scattering properties of cloaked dielectric sphere is investigated using a combi- nation of approximate cloaking, where the dielectric sphere is transformed into a small sphere rather than to a point, together with discretizing the cloaking material using pairs of homogeneous isotropic sub-layers. The back-scattering normalized radar cross section, the scattering patterns are studied and the total scattering cross section against the fre- quency for different number of layers and transformed radius.

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The Optical Properties of Spiky Gold Nanoshells

The Optical Properties of Spiky Gold Nanoshells

The contribution of each type of mode mixing is shown in Figure 6.12B. Inter- estingly, the residual function shown in Figure 6.12A shows both constructive and destructive interferences. Despite the fact that the quadrupoles themselves scatter very weakly and are dark modes (as shown in Figure 6.11), they produce about half of the interference effects observed in the total scattering cross section. The dipole-dipole and quadrupole-dipole mode mixing together produce a total scattering cross section change of just under 20% of the total cross section, while the dipole- quadrupole and quadrupole-quadrupole modes produce almost no change at all. From Eq. 6.3.6, changes to the scattered dipole are magnified by the squaring operation due to the existing scattered dipole, while the quadrupole modes are not. This al- lows the quadrupole modes to couple with the bright far-field scattering mode and therefore be observed in the far-field as interferences. This effect is similar to the Fano resonances observed in previous studies [86, 118, 72]. However, we note that the complexity of this structure requires the full T-matrix solution to explain the interferences observed here and a simple coupling between one electric quadrupole and one electric dipole is not enough to fully explain the extent and complexity of the effect. When observed at a different orientation, the apparent coupling strength may vary between the dipole-dipole and quadrupole-dipole modes (both bright), and dipole-quadrupole (dark) modes. This is due to the heterogeneous nature of these nanoshells.

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Role of Anomalous Quark-Gluon Chromomagnetic Interaction in Hadron Physics

Role of Anomalous Quark-Gluon Chromomagnetic Interaction in Hadron Physics

The gluon distribution in nucleon is one of the central quantities in particle physics which deter- mines the high energy cross section values of the huge amount of important processes. In spite of the tremendous achievements in the last years in the measurement of this distribution, full understanding of the dynamics of gluons inside hadrons is absent so far (see reviews [1, 2]). In the Regge theory the behaviour of the gluon distribution function at small Bjorken x is controlled by the contribution coming from the Pomeron exchange which may have so-called ”soft” and ”hard” parts [3]. Usually, the hard Pomeron is associated with the perturbative BFKL regime [4] and the soft part is assumed to be originated from nonperturbative QCD dynamics [5]. Nonperturbative e ff ects arise from the com- plex structure of QCD vacuum. The instantons are one of the well studied topological fluctuations of vacuum gluon fields which might be responsible for many nonperturbative phenomena observed in particle physics (see reviews [6, 7]). Their possible importance in the structure of the Pomeron and gluon distribution was considered in quite di ff erent approaches [8], [9], [10], [11],[7] for the di ff erent approximations to the complicated quark-gluon dynamics in instanton vacuum. In particular, it was shown [12] that instantons lead to the appearance of anomalous chromomagnetic quark-gluon interac- tion (ACQGI). It was demonstrated that this new type of quark-gluon interaction might be responsible for the observed large single-spin asymmetries in various high energy reactions [12, 13]. Furthermore, it gives a large contribution to the high energy quark-quark scattering cross section [14]. The first es- timation of the effect of ACQGI on nucleon gluon distribution was made in [8] and small x behavior g(x) ∝ 1/x corresponding to soft Pomeron was found. It was clear from that study that anomalous chromomagnetic interaction should also play an important role in the structure of Pomeron. Indeed, recently the model for soft Pomeron based on this interaction has been suggested [7].

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Measurement of the total cross section from elastic scattering in pp collisions at root s=8 TeV with the ATLAS detector

Measurement of the total cross section from elastic scattering in pp collisions at root s=8 TeV with the ATLAS detector

Events are required to pass the trigger conditions for elastic-scattering events and have a reconstructed track in all four detectors of an arm in the golden topology. The fiducial volume is defined by cuts on the vertical coordinate of the reconstructed track, which is required to be at least 90 µm from the detector edge near the beam and at least 1 mm away from the shadow of the beam screen, in each of the four detectors. 3 The values of cuts are chosen to obtain good agreement between data and simulation in the position distri- butions. The back-to-back topology of elastic events is further exploited to clean the sample by imposing cuts on the left-right acollinearity. The di ff erence between the absolute value of the vertical coordinate at the A- and C-side is requested to be below 3 mm. For the horizontal coordinate the correlation of the A- and C-sides is used. Events are selected inside an ellipse with half-axis values of 3.5σ of the resolution determined by simulation, as illustrated in Figure 1(a). Elastic events are concentrated inside a narrow ellipse with negative slope, whereas the beam-halo background appears in broad uncorrelated bands. The most efficient selection against background is obtained from the correlation between the position in the horizontal plane and the local angle between two stations, where events on either side are again required to be inside an ellipse of 3.5σ width. From an initial sample of 4.2 million elastic candidates, 3.8 million

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Poincaré Invariant Three-Body Scattering at Intermediate Energies

Poincaré Invariant Three-Body Scattering at Intermediate Energies

It is obvious that, especially for energies below 300 MeV, the contribution of rescattering terms is huge. However, for extracting the size of relativistic effect, it is more use- ful to consider the relative difference between the rela- tivistic and non-relativistic calculations. In first order, there is essentially no effect in the total elastic cross section, which is consistent with the observation that the relativistic two-body t-matrix is constructed to be phase-shift equiva- lent to the non-relativistic one. The same comparison with fully converged Faddeev calculations indicates that rela- tivistic effects in the three-body problem increase the total cross section for elastic scattering with increasing energy, whereas it is slightly reduced in the total breakup cross section.

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A stochastic method to propagate uncertainties along large cores deterministic calculations

A stochastic method to propagate uncertainties along large cores deterministic calculations

Abstract. Deterministic uncertainty propagation methods are certainly powerful and time-sparing but their access to uncertainties related to the power map remains difficult due to a lack of numerical convergence. On the contrary, stochastic methods do not face such an issue and they enable a more rigorous access to uncertainty related to the PFNS. Our method combines an innovative transport calculation chain and a stochastic way of propagating uncertainties on nuclear data: first, our calculation scheme consists in the calculation of assembly self-shielded cross sections and a pin-by-pin flux calculation on the whole core. Validation was done and the required CPU time is suitable to allow numerous calculations. Then, we sample nuclear cross sections with consistent probability distribution functions with a correlated optimized Latin Hypercube Sampling. Finally, we deduce the power map uncertainties from the study of the output response functions. We performed our study on the system described in the framework of the OECD/NEA Expert Group in Uncertainty Analysis in Modelling. Results show the 238 U

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Study on neutron scattering in light water

Study on neutron scattering in light water

Abstract. It is presented a method to produce covariance matrices of the light water total cross section from thermal scattering laws of the JEFF-3.1.1 nuclear data library and CAB model. The generalized least square method was used to fit the LEAPR module parameters of the processing tool NJOY with light water experimental transmission measurements at 293.6K with CONRAD code. The marginalization technique was applied to account for systematic uncertainties.

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Sum Rules for Parallel Plate Waveguides: Experimental Results and Theory

Sum Rules for Parallel Plate Waveguides: Experimental Results and Theory

The results show that the entire spectrum interaction between the electromag- netic eld and the periodic structure in a parallel plate waveguide is proportional to the static polarizability that can be found from a parallel plate capacitor, regard- less of shape and resonant behavior. This simple approach provides physical insight into the total cross section integrated over the bandwidth of any scatterer. The method is applicable for frequency selective structures [18], metamaterials [5, 23], and electromagnetic band gap structures [29].

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The calculation and evaluation for n+54,56,57,58Fe reactions

The calculation and evaluation for n+54,56,57,58Fe reactions

The UNF [17] code is used at incident neutron energies below 20 MeV. The MEND code is used up to 200 MeV. The angular momentum and parity dependent exciton model is used in UNF code, other models are the same as MEND [18] code. The parameters of the level densities and pair correction are taken from RIPL [19], and adjusted by fitting the experimental data of some channel reaction cross sections.

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Quantemol Electron Collisions (QEC): an enhanced expert system for performing electron molecule collision calculations using the R-matrix method

Quantemol Electron Collisions (QEC): an enhanced expert system for performing electron molecule collision calculations using the R-matrix method

Abstract: Collisions of low energy electrons with molecules are important for understanding many aspects of the environment and technologies. Understanding the processes that occur in these types of collisions can give insights into plasma etching processes, edge effects in fusion plasmas, radiation damage to biological tissues and more. A radical update of the previous expert system for computing observables relevant to these processes, Quantemol-N, is presented. The new Quantemol Electron Collision (QEC) expert system simplifyies the user experience, improving reliability and implements new features. The QEC GUI interfaces the Molpro quantum chemistry package for molecular target setups and to the sophisticated UKRmol+ codes to generate accurate and reliable cross-sections. These include elastic cross-sections, super elastic cross-sections between excited states, electron impact dissociation, scattering reaction rates, dissociative electron attachment, differential cross-sections, momentum transfer cross-sections, ionization cross sections and high energy electron scattering cross-sections. With this new interface we will be implementing dissociative recombination estimations, vibrational excitations for neutrals and ions, and effective core potentials in the near future.

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Scattering of Light by the Metal-Coated Dielectric Nanocylinders with Angular Periodicity

Scattering of Light by the Metal-Coated Dielectric Nanocylinders with Angular Periodicity

periodically distributed along layered cylindrical surfaces. Formulation of boundary-value problem for the configuration composed of the PEC rods is quite different from that of the metallic rods in the optical region. In this regard, this manuscript is devoted to the investigation of the light scattering by metal- coated dielectric nanocylinders periodically distributed along the cylindrical surface. Authors believe that these studies could find practical application in the analyses of optical ring resonators [21, 22], cylindrical THz waveguides [23–25] and Plasmonic Crystals having cylindrical configuration. The rigorous formulation proposed in the manuscript uses T-matrix of a circular scatterer in isolation [26, 27] and it is taking into account all cylindrical Floquet modes and their interactions through the scattering between the nanocylinders periodically distributed along a circular ring [20, 28, 29]. It could be considered as the main advantage of the proposed formulation. Another advantage is that the method can be easily applied to various configurations of the layered cylindrical structures (Plasmonic Crystals) with different types and locations of the excitation sources. Our method is also applicable to the analyses of electromagnetic scattering by the multi-layer-coated nanocylinders. The extension is straightforward. We may replace the expression of the T-matrix of the coated nanocylinder by the T-matrix of the multi-layer-coated nanocylinder, which can be easily obtained using the recursive relation for the reflection and transmission coefficients of cylindrical waves at multilayered cylindrical surfaces. We have already conducted the preliminary studies about electromagnetic scattering on the multi-layer- coated nanocylinders.

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Backscattering Analysis for Snow Remote Sensing Model with Higher Order of Surface-Volume Scattering

Backscattering Analysis for Snow Remote Sensing Model with Higher Order of Surface-Volume Scattering

It is essential to develop a reliable theoretical model to study the medium where multiple surface scattering and second order surface-volume scattering may be important, to better understand these effects. In a previous work [7], a backscattering model for an electrically dense medium was developed. It was modeled as a layer of a discrete inhomogeneous medium, where randomly distributed ice spherical scatterers are embedded in homogeneous medium in the layer. This layer is bounded on the top and bottom by irregular surface boundaries. Above the layer is air, and below the layer can be a homogenous half space where this can be used to represent earth ground layer beneath the snow or a very thick layer of sea ice beneath the snow layer with high attenuation rate of wave penetration. For ice shelf, this can be a very thick layer of compacted snow on top of the ocean. The spherical scatterer is modelled as a Mie scatterer characterized by Mie scattering. This medium is considered electrically dense where the spacing between the scatterers is comparable to the wavelength [6]. The modified phase matrix for Mie scatterers based on the dense medium phase and amplitude correction theory (DM-PACT) [4] were taken into account to consider the close spacing effects of the scatterers. Radiative transfer theory [3] was used to calculate the backscattering coefficient of this medium. The radiative transfer equation was solved iteratively up to the second order. Three major scattering mechanisms were derived based on [9], which are direct surface scattering, surface-volume scattering and volume scattering. IEM was used to calculate the top and bottom rough surfaces. However, the IEM used in [7] accounts for single scattering only, and this requires further improvement by also considering multiple surface scattering.

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Thermal Neutron Scattering in Graphite

Thermal Neutron Scattering in Graphite

In this work, investigation of thermal neutron scattering in graphite as a function of temperature was performed. The fundamental input for the calculation of thermal neutron scattering cross sections, i.e., the phonon frequency distribution and/or the dispersion relations, was generated using a modern approach that is based on quantum mechanical electronic structure (ab initio) simulations combined with a lattice dynamics direct method supercell approach. The calculations were performed using the VASP and PHONON codes. The VASP calculations used the local density approximation, and the projector augmented-wave pseudopotential. A supercell of 144 atoms was used; and the integration over the Brillouin zone was confined to a 3×3×4 k-mesh generated by the Monkhorst-Pack scheme. A plane-wave basis set with an energy cutoff of 500 eV was applied. The corresponding dispersion relations, heat capacity, and phonon frequency distribution show excellent agreement with experimental data.

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Constrained two-stream algorithm for calculating aerosol light absorption coefficient from the Particle Soot Absorption Photometer

Constrained two-stream algorithm for calculating aerosol light absorption coefficient from the Particle Soot Absorption Photometer

Abstract. We present a new correction scheme for filter- based absorption photometers based on a constrained two- stream (CTS) radiative transfer model and experimental cal- ibrations. The two-stream model was initialized using ex- perimentally accessible optical parameters of the filter. Ex- perimental calibrations were taken from the literature and from dedicated experiments for the present manuscript. Un- certainties in the model and calibration experiments are dis- cussed and uncertainties for retrieval of absorption coeffi- cients are derived. For single-scattering albedos lower than 0.8, the new CTS method and also other correction schemes suffer from the uncertainty in calibration experiments, with an uncertainty of about 20 % in the absorption coefficient. For high single-scattering albedos, the CTS correction signif- icantly reduces errors. At a single-scattering albedo of about 0.98 the error can be reduced to 30 %, whereas errors using the Bond correction (Bond et al., 1999) are up to 100 %. The correction scheme was tested using data from an indepen- dent experiment. The tests confirm the modeled performance of the correction scheme when comparing the CTS method to other established correction methods.

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(n,xn γ) reaction cross section measurements for (n,xn) reaction studies

(n,xn γ) reaction cross section measurements for (n,xn) reaction studies

With the GRAPhEME set-up we provide (n,xn γ ) cross section as accurate as possible. Several analy- ses are still in progress and the covariance matrix determination of our data sets will also be conducted. All this work is performed with the collaboration of our theoretician and evaluator colleagues. In the near future, this kind of measurement on a more active target, 233 U, will be carried out. The knowledge

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Photoproduction models for total cross section and shower development

Photoproduction models for total cross section and shower development

single gluon emission, regularized in the infrared. The extension to infrared gluons is crucial for this model and requires an ansatz as to the coupling of very soft gluons to the emitting quarks, which the model introduces through a singularity parameter 1 / 2 < p < 1 [14]. The physical content of this model can be summarized as follows: i) the rise is obtained from low-x parton-parton collision, ii) the taming of the rise is obtained from the Fourier transform in impact parameter space of the resummation of all soft gluons emitted in the parton-parton collisions. The expression for the impact parameter distribution when the two hadrons collide describes the acollinearity introduced by soft gluon emission which reduces the cross-section from mini-jets. The expression is energy dependent through the parameter q max , which embeds the

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Measurement of the total cross section from elastic scattering in pp collisions at √s=8 TeV with the ATLAS detector

Measurement of the total cross section from elastic scattering in pp collisions at √s=8 TeV with the ATLAS detector

tion) and 241 m (outer station) on either side of the ATLAS in- teraction point (IP). Each station houses two vertically moveable scintillating fibre detectors which are inserted in RPs and posi- tioned close to the beam for data taking. Each detector consists of 10 modules of scintillating fibres with 64 fibres on both the front and back sides of a titanium support plate. The fibres are ar- ranged orthogonally in a u–v-geometry at ± 45 ◦ with respect to the y-axis. 1 The spatial resolution of the detectors is about 35 μm. Elastic scattering events are recorded in two independent arms of the spectrometer. Arm 1 consists of two upper detectors at the left side and two lower detectors at the right side, and arm 2 consists inversely of two lower detectors at the left and two upper detec- tors at the right side. Events with reconstructed tracks in all four detectors of an arm are referred to as “golden” events [1]. The de- tectors are supplemented with trigger counters consisting of plain scintillator tiles. The detector geometry is illustrated in Fig. 1 of Ref. [1]. All scintillation signals are detected by photomultipliers coupled to a compact assembly of front-end electronics including the MAROC chip [15,16] for signal amplification and discrimina- tion. The entire experimental setup is depicted in Fig. 2 of Ref. [1]. 3. Experimental method

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