scholarly journals Systematic study of the de-excitation of neutron-rich nuclei produced in different fission reactions

2021 ◽  
Vol 256 ◽  
pp. 00012
Author(s):  
Andreas Oberstedt ◽  
Angélique Gatera ◽  
Alf Göök ◽  
Matthieu Lebois ◽  
Stephan Oberstedt ◽  
...  
Keyword(s):  
Energy Release ◽  
Systematic Study ◽  
Time Window ◽  
Spectral Characteristics ◽  
Average Energy ◽  
Average Multiplicity ◽  
Fast Neutrons ◽  
Fission Reactions ◽  
Timing Resolution ◽  
Prompt Fission

In this paper we present results from two recent studies, both related to the emission of prompt fission γ rays. Firstly, we have analyzed data from the reaction 235U(n, f) induced by fast neutrons of average energy E̅n = 1.7 MeV. The deduced spectral characteristics are an average multiplicity M̅γ = 7.11 ± 0.44 γ rays per fission and an average total γ-ray energy release in fission E̅γ,tot = 5.51 ± 0.46 MeV, corresponding to an average γ-ray energy ɛ̅γ = 0.77 ± 0.08 MeV. Secondly, we have addressed – and answered – the question how those characteristics in general depend on the width of the chosen prompt time window and the timing resolution, determined by the employed detectors and electronics. The conclusion is that once this is known, it is possible to compare results from different experiments in a more meaningful way.

scholarly journals Prompt fission gamma-ray emission spectral data for 239Pu(n,f) using fast directional neutrons from the LICORNE neutron source

2018 ◽  
Vol 169 ◽  
pp. 00018 ◽  
Author(s):  
L. Qi ◽  
J.N. Wilson ◽  
M. Lebois ◽  
A. Al-Adili ◽  
A. Chatillon ◽  
...  
Keyword(s):  
Neutron Source ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Average Energy ◽  
Fast Neutrons ◽  
Complementary Information ◽  
Total Energy Release ◽  
The Mean ◽  
Induced Fission ◽  
Prompt Fission

Prompt fission gamma-ray spectra (PFGS) have been measured for the 239Pu(n,f) reaction using fast neutrons at Ēn=1.81 MeV produced by the LICORNE directional neutron source. The setup makes use of LaBr3 scintillation detectors and PARIS phoswich detectors to measure the emitted prompt fission gamma rays (PFG). The mean multiplicity, average total energy release per fission and average energy of photons are extracted from the unfolded PFGS. These new measurements provide complementary information to other recent work on thermal neutron induced fission of 239Pu and spontaneous fission of 252Cf.

scholarly journals Effect of the Characteristic Size and Content of Graphene on the Crack Propagation Path of Alumina/Graphene Composite Ceramics

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 611
Author(s):  
Benshuai Chen ◽  
Guangchun Xiao ◽  
Mingdong Yi ◽  
Jingjie Zhang ◽  
Tingting Zhou ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Volume Content ◽  
Phase Interface ◽  
Average Energy ◽  
Characteristic Size ◽  
Composite Ceramics ◽  
Graphene Composite

In this paper, the Voronoimosaic model and the cohesive element method were used to simulate crack propagation in the microstructure of alumina/graphene composite ceramic tool materials. The effects of graphene characteristic size and volume content on the crack propagation behavior of microstructure model of alumina/graphene composite ceramics under different interfacial bonding strength were studied. When the phase interface is weak, the average energy release rate is the highest as the short diameter of graphene is 10–50 nm and the long diameter is 1600–2000 nm. When the phase interface is strong, the average energy release rate is the highest as the short diameter of graphene is 50–100 nm and the long diameter is 800–1200 nm. When the volume content of graphene is 0.50 vol.%, the average energy release rate reaches the maximum. When the velocity load is 0.005 m s−1, the simulation result is convergent. It is proven that the simulation results are in good agreement with the experimental phenomena.

scholarly journals Systematic Study of Anomalous Fragment Anisotropies in Near-and Sub-barrier Fusion-fission Reactions

2002 ◽  
Vol 3 (1) ◽  
pp. 99-101 ◽  
Author(s):  
H. Q. Zhang ◽  
Z. H. Liu ◽  
J. C. Xu ◽  
M. Ruan ◽  
C. J. Lin ◽  
...  
Keyword(s):  
Systematic Study ◽  
Fission Reactions

On the Energy Release Rate of Elliptical Cracks in Anisotropic Elastic Media

2003 ◽  
Vol 19 (1) ◽  
pp. 233-239
Author(s):  
Yibin Xue ◽  
Jianmin Qu
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Crack Opening Displacement ◽  
Release Rate ◽  
Crack Opening ◽  
Average Energy ◽  
Local Energy ◽  
Opening Displacement ◽  
Work Done ◽  
Elliptical Cracks

ABSTRACTThis brief note discusses some issues related to the calculation of energy release rate for elliptical cracks in anisotropic solids. By using the Stroh formalism, analytical expressions of the energy release rate are obtained for elliptical cracks in an unbounded anisotropic solid. Because of material anisotropy and geometric asymmetry of the crack, the local energy release rate varies along the crack front. The average energy release rate can be obtained by integrating the local energy release rate over the entire crack front. On the other hand, the total work done by the crack-surface traction on the entire crack opening displacement can be easily evaluated once the crack opening displacement is known. It is shown that the average energy release rate is equal to the rate of change per unit crack area increment of the work done by the external load on the crack opening displacement.

Integral measurement of spectrum-averaged cross sections of a few threshold reactions induced by fast neutrons of a TRIGA reactor: comparison with integrated data from excitation functions given in various data libraries

2020 ◽  
Vol 108 (7) ◽  
pp. 511-516
Author(s):  
Md. Shuza Uddin ◽  
K. A. Rafee ◽  
S. M. Hossain ◽  
R. Khan ◽  
S. M. Qaim
Keyword(s):  
Excitation Function ◽  
Cross Sections ◽  
Fast Neutrons ◽  
Integral Test ◽  
Triga Reactor ◽  
Fission Spectrum ◽  
Data Libraries ◽  
First Time ◽  
Prompt Fission ◽  
Fast Neutron Spectrum

AbstractIntegral cross sections of the reactions 24Mg(n,p)24Na, 27Al(n,p)27Mg, 27Al(n,α)24Na, 58Ni(n,d + np)57Co and 60Ni(n,p)60Co were measured for the first time using the fast neutron spectrum of a TRIGA reactor extending from 0.5 to 20 MeV. The values obtained in this work were comparable with the recommended values for a pure 235U prompt fission spectrum. The measured integral value was utilized for integral test of excitation function of each reaction given in some data libraries, namely ENDF/B-VIII.0, TENDL-2017, IRDFF-1.05 and ROSFOND-2010. The integral measurements are generally consistent with the integrated values within 5 %, except for a few cases, e. g. the reaction 60Ni(n,p)60Co, where the data libraries appear to need improvement.

Detection of Combined n/γ Fission Signatures Induced by an Epithermal Neutron Source

2017 ◽  
Vol 3 (3) ◽  
Author(s):  
A. Ocherashvili ◽  
T. Bogucarska ◽  
A. Beck ◽  
G. Heger ◽  
M. Mosconi ◽  
...  
Keyword(s):  
Neutron Source ◽  
Proper Time ◽  
Pulse Shape Discrimination ◽  
Fast Neutrons ◽  
Nuclear Materials ◽  
Test Assembly ◽  
Fission Neutrons ◽  
Pulsed Neutron ◽  
Prompt Fission ◽  
Multiple Detectors

In this paper, a method is presented for the detection of special nuclear materials (SNMs) in shielded containers, which is both sensitive and applicable under field conditions. The method uses an external pulsed neutron source to induce fission in SNM and subsequent detection of the fast prompt fission neutrons. The detectors surrounding the container under investigation are liquid scintillation detectors able to distinguish gamma rays from fast neutrons by means of pulse shape discrimination method (PSD). One advantage of these detectors, besides the ability for PSD analysis, is that the analog signal from a detection event is of very short duration (typically few tens of nanoseconds). This allows the use of very short coincidence gates for the detection of the prompt fission neutrons in multiple detectors, while benefiting from a low background coincidence rate, yielding a low detection limit. Another principle advantage of this method derives from the fact that the external neutron source is pulsed. By proper time gating, the interrogation can be conducted by epithermal source neutrons only. These neutrons do not appear in the fast neutron signal following the PSD analysis, thus providing a fundamental method for separating the interrogating source neutrons from the sample response in the form of fast fission neutrons. This paper describes laboratory tests with a configuration of eight detectors in the Pulsed Neutron Interrogation Test Assembly (PUNITA). Both the photon and neutron signature for induced fission is observed, and the methods used to isolate these signatures are described and demonstrated.

scholarly journals Is Resting-State EEG Longitudinally Associated With Recovery of Clinical Neurological Impairments Early Poststroke? A Prospective Cohort Study

2020 ◽  
Vol 34 (5) ◽  
pp. 389-402 ◽  
Author(s):  
Mique Saes ◽  
Sarah B. Zandvliet ◽  
Aukje S. Andringa ◽  
Andreas Daffertshofer ◽  
Jos W. R. Twisk ◽  
...  
Keyword(s):  
Upper Limb ◽  
Resting State ◽  
Time Course ◽  
Time Window ◽  
Spectral Characteristics ◽  
Motor Recovery ◽  
National Institutes Of Health ◽  
Cortical Activation ◽  
Clinical Measures ◽  
The Brain

Background. The time course of cortical activation and its relation with clinical measures may elucidate mechanisms underlying spontaneous neurobiological recovery after stroke. Objective. We aimed to investigate (1) the time course of cortical activation as revealed by EEG-based spectral characteristics during awake rest and (2) the development of these spectral characteristics in relation to global neurological and upper-limb motor recovery in the first 6 months poststroke. Methods. Resting-state EEG was measured serially in 41 patients after a first-ever ischemic stroke, within 3 and at 5, 12, and 26 weeks poststroke. We computed the brain symmetry index (BSI) and directional BSI (BSIdir) over different frequency bands (1-25 Hz, delta, theta) and delta/alpha ratio (DAR). The National Institutes of Health Stroke Scale (NIHSS) and Fugl-Meyer motor assessment of the upper extremity (FM-UE) were determined as clinical reflections of spontaneous neurobiological recovery. Longitudinal changes in spectral characteristics and within- and between-subject associations with NIHSS and FM-UE were analyzed with linear mixed models. Results. Spectral characteristics showed a gradual normalization over time, within and beyond 12 weeks poststroke. Significant within- and between-subject associations with NIHSS were found for DAR of the affected hemisphere (DARAH) and BSIdirdelta. BSIdirdelta also demonstrated significant within- and between-subject associations with FM-UE. Conclusions. Changes in spectral characteristics are not restricted to the time window of recovery of clinical neurological impairments. The present study suggests that decreasing DARAH and BSIdirdelta reflect improvement of global neurological impairments, whereas BSIdirdelta was also specifically associated with upper-limb motor recovery early poststroke.

Systematic study of rapidity dispersion parameter in high energy nucleus–nucleus interactions

2014 ◽  
Vol 23 (03) ◽  
pp. 1450012 ◽  
Author(s):  
Swarnapratim Bhattacharyya ◽  
Maria Haiduc ◽  
Alina Tania Neagu ◽  
Elena Firu
Keyword(s):  
Experimental Data ◽  
Monte Carlo ◽  
Systematic Study ◽  
Nuclear Emulsion ◽  
Quantitative Measure ◽  
High Energy ◽  
Average Multiplicity ◽  
Experimental Results ◽  
Dispersion Parameter ◽  
Parameter Values

A systematic study of rapidity dispersion parameter as a quantitative measure of clustering of particles has been carried out in the interactions of 16 O , 28 Si and 32 S projectiles at 4.5 A GeV/c with heavy ( AgBr ) and light (CNO) groups of targets present in the nuclear emulsion. For all the interactions, the total ensemble of events has been divided into four overlapping multiplicity classes depending on the number of shower particles. For all the interactions and for each multiplicity class, the rapidity dispersion parameter values indicate the occurrence of clusterization during the multiparticle production at Dubna energy. The measured rapidity dispersion parameter values are found to decrease with the increase of average multiplicity for all the interactions. The dependence of rapidity dispersion parameter on the average multiplicity can be successfully described by a relation D(η) = a + b〈ns〉 + c〈ns〉2. The experimental results have been compared with the results obtained from the analysis of Monte Carlo simulated (MC-RAND) events. MC-RAND events show weaker clusterization among the pions in comparison to the experimental data.

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