scholarly journals How to produce accurate inelastic cross sections from an indirect measurement method?

2018 ◽  
Vol 4 ◽  
pp. 23
Author(s):  
Maëlle Kerveno ◽  
Greg Henning ◽  
Catalin Borcea ◽  
Philippe Dessagne ◽  
Marc Dupuis ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Power Distribution ◽  
Nuclear Reactor ◽  
Indirect Measurement ◽  
Neutron Energy Spectrum ◽  
Slowing Down ◽  
Reactor Cores ◽  
Experimental Difficulty

Inelastic reactions ((n,xn) for x ≥ 1) play a key role in reactor cores as they influence the slowing down of the neutrons. A reactor neutron energy spectrum depends thus on this process which is in strong competition with elastic scattering and fission; a nice example is the case of 238U. Inelastic scattering (x = 1) impacts keff and radial power distribution in the nuclear reactor. For several years, it has been shown that the knowledge of the inelastic cross sections in nuclear databases is not good enough to accurately simulate reactor cores and a strong demand for new measurements has emerged with very tight objectives (only a few percent) for the uncertainties on the cross section. To bypass the well-known experimental difficulty to detect neutrons, the prompt γ-ray spectroscopy method is a powerful but indirect way to obtain inelastic cross sections. Our collaboration has used this method for more than ten years and have produced a lot of (n,n′γ) cross sections for nuclei from 7Li to 238U. In this article, we will first discuss the issues of the prompt γ-ray spectroscopy regarding the control of all the uncertainties involved in the (n,n′γ) cross section estimation. Secondly, we will focus on the role of theoretical modeling which, in certain cases, is crucial to reach the objectives of a few percent uncertainty on the (n,n′) cross sections.

Oxygen K near edge structures studied with multiple scattering calculations

1988 ◽  
Vol 46 ◽  
pp. 504-505
Author(s):  
Xudong Weng ◽  
Peter Rez
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Partial Cross Section ◽  
Energy Window ◽  
Edge Structure ◽  
Fine Structures ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
Quantitative Chemical

In electron energy loss spectroscopy, quantitative chemical microanalysis is performed by comparison of the intensity under a specific inner shell edge with the corresponding partial cross section. There are two commonly used models for calculations of atomic partial cross sections, the hydrogenic model and the Hartree-Slater model. Partial cross sections could also be measured from standards of known compositions. These partial cross sections are complicated by variations in the edge shapes, such as the near edge structure (ELNES) and extended fine structures (ELEXFS). The role of these solid state effects in the partial cross sections, and the transferability of the partial cross sections from material to material, has yet to be fully explored. In this work, we consider the oxygen K edge in several oxides as oxygen is present in many materials. Since the energy window of interest is in the range of 20-100 eV, we limit ourselves to the near edge structures.

scholarly journals NONLINEAR ANALYSIS OF STATICALLY INDETERMINATE WOODEN STRUCTURES AND OPTIMIZATION OF CROSS SECTION DIMENSIONS OF DOME RIBS

2018 ◽  
Vol 14 (4) ◽  
pp. 130-139 ◽  
Author(s):  
Konstantin P. Pyatikrestovsky ◽  
Boris S. Sokolov
Keyword(s):  
Nonlinear Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Frame Analysis ◽  
Significant Part ◽  
Design Recommendations ◽  
Longitudinal Ribs ◽  
Non Linear ◽  
Wooden Structures

The analysis of the behaviour of natural structures of laminated wood domes and the numerous preliminary calculations have shown the possibility of saving materials by reducing the height of cross sections of meridional ribs. This is especially effective when you include in design of skins, performing a role of building shell, the collaboration with frame elements (annular and longitudinal ribs). Multiple static indeterminacy of such structure allows its non-linear work and the redistribution of forces under nonuniform loads. At the same ime, the skin carries a significant part of the forces appearing in the shell and the ribs are underloaded. The tress-strain states of all elements are investigated. For the frame analysis the calculation is performed by the method of integral module that allows controlling strength resistance of a structure at any moment of its operation. The design recommendations for section dimensions of a shell are developed.

scholarly journals EXTRACTION OF RESONANCE PARAMETERS AND ROLE OF THE FINAL STATE INTERACTIONS

2014 ◽  
Vol 26 ◽  
pp. 1460082 ◽  
Author(s):  
IGOR I. STRAKOVSKY ◽  
WILLIAM J. BRISCOE ◽  
ALEXANDER E. KUDRYAVTSEV ◽  
VLADIMIR E. TARASOV
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Impulse Approximation ◽  
Pion Photoproduction ◽  
Final State ◽  
The World ◽  
Final State Interactions ◽  
Watson’S Theorem ◽  
Photoproduction Data

We present an overview of the SAID group effort to analyze new γn → π-p cross sections vs. the world database to get new multipoles and determine neutron electromagnetic couplings. The differential cross section for the processes γn → π-p was extracted from new measurements at CLAS and MAMI-B accounting for Fermi motion effects in the impulse approximation (IA) as well as NN- and πN-FSI effects beyond the IA. We evaluated results of several pion photoproduction analyses and compared πN PWA results as a constraint for analyses of pion photoproduction data (Watson's theorem).

MEASURING CAPTURE CROSS SECTIONS FOR HEAVY-ELEMENT PRODUCTION

2004 ◽  
Vol 13 (01) ◽  
pp. 293-300
Author(s):  
NEIL ROWLEY ◽  
NABILA GRAR
Keyword(s):  
Cross Section ◽  
Compound Nucleus ◽  
Cross Sections ◽  
Reaction Path ◽  
Superheavy Element ◽  
Evaporation Residue ◽  
Capture Cross ◽  
Total Capture ◽  
Capture Cross Sections

The creation of the nucleus of a superheavy element follows an extremely complex reaction path starting with the crossing of an external potential barrier (or distribution of barriers). This is followed by the evolution towards an equilibrated compound nucleus, which takes place in competition with pre-compound-nucleus fission (quasi-fission). Once formed the equilibrated compound nucleus must still survive against true fusion to yield a relatively long-lived evaporation residue. Much of this path is poorly understood, though recently, progress has been made on the role of the entrance-channel in quasi-fission. This will be briefly reported and a method proposed to measure the total capture cross section for such systems directly.

COLLISIONS OF LONG-LIVED EXCITED IONS OF OXYGEN AND NITROGEN

1964 ◽  
Vol 42 (11) ◽  
pp. 2086-2101 ◽  
Author(s):  
William McGowan ◽  
Larkin Kerwin
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ion Beam ◽  
Collision Induced Dissociation ◽  
Ion Molecule Reactions ◽  
Collision Region ◽  
Mean Lifetime ◽  
New States ◽  
Product Ions

The role of some excited ions in laboratory ion–molecule reactions has been investigated, and their possible importance in the upper atmosphere considered. The mass spectrometer techniques of Aston banding and of comparing I.P. curves of parent and product ions have been applied to studies of collision-induced dissociation and charge exchange of oxygen and nitrogen in their parent gas. In every case studied, cross sections depended markedly upon the presence in the ion beam of ions in metastable or long-lived radiative states. In order that an ion reach the collision region, it had to have a mean lifetime greater than 3 μsec.The a 4Πu and b 4Σg excited states of O2+ were identified in the collision[Formula: see text]Higher states of O2+, which have not as yet been identified spectroscopically, were found in the collision[Formula: see text]The thresholds of these new states are 23.9, 27.9, 31.3, and 34.1 eV with an uncertainty ±0.2 eV. From the collision-induced dissociation of N2+, the A 2Πu and the [Formula: see text] states have been identified. Also, the reported transfer of the ν = 3 level of the B [Formula: see text] to the ν = 14 level of the A 2Πu was found.The cross section for 10/01 charged exchange of N2+ in N2 exhibited a marked decrease as excited-state ions diluted the beam. The 10/01 collisions of N+ in N2 and O+ in O2 exhibited an increase in cross section as metastables were added to the parent ion beam. The 10/20 reaction of O2+ in O2 was also observed to depend on excited O2+ ions.

The Generation of Few-Group Constants for Fast Reactor Analysis

2016 ◽  
Author(s):  
Xianan Du ◽  
Liangzhi Cao ◽  
Youqi Zheng
Keyword(s):  
Monte Carlo ◽  
Cross Section ◽  
Cross Sections ◽  
Fast Reactor ◽  
Monte Carlo Calculation ◽  
Anisotropic Scattering ◽  
Slowing Down ◽  
Nodal Method ◽  
Reactor Calculation ◽  
Broad Energy

A way to generate the few-group cross sections for fast reactor calculation is presented in this paper. It is based on the three steps computational scheme. In the first step, the ultrafine method is used to solve the slowing down equation based on the ultrafine group cross section generated by NJOY. Optional 0D or 1D calculation is used to collapse energy group into broad energy groups. In the second step, the 2D RZ calculation using SN method is performed to obtain the space dependent neutron spectra to collapse broad energy groups into few groups. The anisotropic scattering is well handled by the direct SN calculation. Finally, the full core calculation is performed by using the 3D SN nodal method. The results are compared with continuous energy Monte-Carlo calculation. Both the cross section generated in the first step and the final keff in the last step are compared. The results match well between the three steps calculation and Monte-Carlo calculation.

scholarly journals Taming the Energy Rise of the Total Proton-Proton Cross-Section

Universe ◽  
2019 ◽  
Vol 5 (5) ◽  
pp. 106 ◽  
Author(s):  
Sergey Ostapchenko ◽  
Marcus Bleicher
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Strong Increase ◽  
Momentum Fraction ◽  
Proton Proton ◽  
High Energies ◽  
Model Predictions ◽  
Potential Impact ◽  
Very High

Steep rise of parton densities in the limit of small parton momentum fraction x poses a challenge for describing the observed energy-dependence of the total and inelastic proton-proton cross sections σ p p tot / inel : considering a realistic parton spatial distribution, one obtains a too-strong increase of σ p p tot / inel in the limit of very high energies. We discuss various mechanisms which allow one to tame such a rise, paying special attention to the role of parton-parton correlations. In addition, we investigate a potential impact on model predictions for σ p p tot, related to dynamical higher twist corrections to parton-production processes.

UNDERSTANDING THE NATURE OF PROTON–AIR CROSS-SECTIONS AT VERY HIGH ENERGIES AND THE IMPLICATIONS

2001 ◽  
Vol 16 (37) ◽  
pp. 2387-2397 ◽  
Author(s):  
BHASKAR DE ◽  
S. BHATTACHARYYA ◽  
P. GUPTAROY
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Cross Section Data ◽  
Section Data ◽  
High Energies ◽  
Production Models ◽  
Simulation Based ◽  
Effective Role ◽  
Very High

The purpose of this paper is to focus on the possible effective role of two relatively less-known models in analyzing comprehensively the very up-to-date data on proton–air inelastic cross-sections at high and ultra high energies. The standard versions of all the familiar simulation-based multiparticle production models, which nowadays normally claim front-ranking positions, address on the contrary, only a small part of the cross-section data for a very limited or sectional range of energy values. Against this background, the relevance and impact of the present study have finally been highlighted.

scholarly journals Role of an Electron Screened Mott - Schwinger Interaction in the Elastic Scattering of Neutrons

1996 ◽  
Vol 49 (3) ◽  
pp. 633 ◽  
Author(s):  
N Alexander ◽  
K Amos
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Scattering Amplitude ◽  
Nuclear Interaction ◽  
Electron Cloud ◽  
Scattering Cross Section ◽  
Scattering Cross ◽  
Total Scattering Cross Section ◽  
Scattered Neutrons

The Mott–Schwinger potential arising from the interaction of the magnetic moment of a neutron incident upon the (electric) field of a nucleus has a profound effect upon the cross sections for scattering. The purely nuclear interaction (hadronic plus Mott–Schwinger) leads to a divergence in the spin–flip scattering amplitude at 0° scattering and thus to a divergent total scattering cross section. We demonstrate that the screening of this interaction caused by the atomic electron cloud essentially compensates that divergence so that the scattering cross-section values, to be used for example in reactor moderation calculations, are effectively those given by calculations made without consideration of any Mott–Schwinger potential. However, the forward scattered neutrons remain strongly polarised as a result of the (complete) Mott–Schwinger interaction.

scholarly journals The Role of Bedload Transport in the Development of a Proglacial River Alluvial Fan (Case Study: Scott River, Southwest Svalbard)

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 173
Author(s):  
Waldemar Kociuba
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
River Mouth ◽  
Active Role ◽  
Bedload Transport ◽  
Alluvial Fan ◽  
Surface Erosion ◽  
The Individual ◽  
Active Channel

This study, which was conducted between 2010 and 2013, presents the results of direct, continuous measurements of the bedload transport rate at the mouth section of the Scott River catchment (NW part of Wedel-Jarlsberg Land, Svalbard). In four consecutive melt seasons, the bedload flux was analyzed at two cross-sections located in the lower reaches of the gravel-bed proglacial river. The transported bedload was measured using two sets of River Bedload Traps (RBTs). Over the course of 130 simultaneous measurement days, a total of 930 bedload samples were collected. During this period, the river discharged about 1.32 t of bedload through cross-section I (XS I), located at the foot of the alluvial fan, and 0.99 t through cross-section II (XS II), located at the river mouth running into the fjord. A comparison of the bedload flux showed a distinctive disproportion between cross-sections. Specifically, the average daily bedload flux QB was 130 kg day−1 (XS I) and 81 kg day−1 (XS II) at the individual cross-profiles. The lower bedload fluxes that were recorded at specified periods in XS II, which closed the catchment at the river mouth from the alluvial cone, indicated an active role of aggradation processes. Approximately 40% of all transported bedload was stored at the alluvial fan, mostly in the active channel zone. However, comparative Geomorphic Change Detection (GCD) analyses of the alluvial fan, which were performed over the period between August 2010 and August 2013, indicated a general lowering of the surface (erosion). It can be assumed that the melt season’s average flows in the active channel zone led to a greater deposition of bedload particles than what was discharged with high intensity during floods (especially the bankfull stage, effectively reshaping the whole surface of the alluvial fan). This study documents that the intensity of bedload flux was determined by the frequency of floods. Notably, the highest daily rates recorded in successive seasons accounted for 12–30% of the total bedload flux. Lastly, the multi-seasonal analysis showed a high spatio-temporal variability of the bedload transport rates, which resulted in changes not only in the channel but also on the entire surface of the alluvial fan morphology during floods.

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