scholarly journals First results of the 230Th(n,f) cross section measurements at the CERN n_TOF facility

2020 ◽  
Vol 239 ◽  
pp. 05004
Author(s):  
V. Michalopoulou ◽  
A. Stamatopoulos ◽  
R. Vlastou ◽  
M. Kokkoris ◽  
A. Tsinganis ◽  
...  
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Fuel Cycle ◽  
Fission Cross Section ◽  
Reaction Cross ◽  
Rare Isotope ◽  
Fuel Cycles ◽  
Broad Energy Range ◽  
Nuclear Systems

The study of neutron-induced reactions on actinides is of considerable importance for the design of advanced nuclear systems and alternative fuel cycles. Specifically, 230Th is produced from the α-decay of 234U as a byproduct of the 232Th/233U fuel cycle, thus the accurate knowledge of its fission cross section is strongly required. However, few experimental datasets exist in literature with large deviations among them, covering the energy range between 0.2 to 25 MeV. In addition, the study of the 230Th(n,f) cross-section is of great interest in the research on the fission process related to the structure of the fission barriers. Previous measurements have revealed a large resonance at En=715 keV and additional fine structures, but with high discrepancies among the cross-section values of these measurements. This contribution presents preliminary results of the 230Th(n,f) cross-section measurements at the CERN n_TOF facility. The high purity targets of the natural, but very rare isotope 230Th, were produced at JRC-Geel in Belgium. The measurements were performed at both experimental areas (EAR-1 and EAR-2) of the n_TOF facility, covering a very broad energy range from thermal up to at least 100 MeV. The experimental setup was based on Micromegas detectors with the 235U(n,f) and 238U(n,f) reaction cross-sections used as reference.

scholarly journals Chemical Reaction Kinematics

1968 ◽  
Vol 23 (12) ◽  
pp. 2080-2083 ◽  
Author(s):  
D. Hyatt ◽  
K. Lacmann
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Mass Spectrometer ◽  
Cross Sections ◽  
Impulse Approximation ◽  
Reaction Cross ◽  
Molecule Reaction ◽  
Polarization Theory ◽  
Reaction Cross Sections

A Bendix time of flight mass spectrometer has been modified to enable the determination of some ion-molecule reaction cross sections in the energy range 1 — 100 eV.In the reactions studiedX+ + D2 → XD++Dwhere X may be Ar, N2 or CO, the results obtained agree with the predictions of the polarization theory in the range below 10 eV despite the fact that no intermediate complex is formed at these energies. Between about 10—50 eV where spectator stripping occurs the cross section follows an approximate E-l dependence. Above these energies the results are consistent with a transition to a region in which knock-on processes predominate and where an impulse approximation treatment would be valid.

scholarly journals Measurement of the 237Np(n,f) cross section with the FIC detector at the CERN n_TOF facility

2019 ◽  
Vol 22 ◽  
pp. 20
Author(s):  
M. Diakaki ◽  
Et al. For the nTOF Collaboration
Keyword(s):  
Energy Range ◽  
Phenomenological Models ◽  
Cross Section ◽  
Cross Sections ◽  
High Accuracy ◽  
Reaction Cross ◽  
Neutron Energy Range ◽  
Ionisation Chamber ◽  
Accuracy Data ◽  
Reaction Cross Sections

The cross section of the 237Np(n,f) reaction has been experimentally determined at the n_TOF facility at CERN, in the neutron energy range 100 keV – 10 MeV, relative to the standard 235U(n,f) and 238U(n,f) reaction cross sections with use of a Fast Ionisation Chamber. The reproduction of the high accuracy data obtained from this experiment was attempted within the Hauser-Feshbach formalism and phenomenological models with use of the code EMPIRE 3.2.

scholarly journals Study of the neutron-induced fission cross section of 237Np at CERN's n_TOF facility over a wide energy range

2020 ◽  
Vol 239 ◽  
pp. 05006
Author(s):  
A. Stamatopoulos ◽  
A. Tsinganis ◽  
M. Diakaki ◽  
N. Colonna ◽  
M. Kokkoris ◽  
...  
Keyword(s):  
Experimental Data ◽  
Energy Range ◽  
Cross Section ◽  
Fuel Cycle ◽  
Fission Cross Section ◽  
Nuclear Model ◽  
Wide Energy Range ◽  
Model Parameters ◽  
Wide Range ◽  
Induced Fission

Neutron-induced fission cross sections of isotopes involved in the nuclear fuel cycle are vital for the design and safe operation of advanced nuclear systems. Such experimental data can also provide additional constraints for the adjustment of nuclear model parameters used in the evaluation process, resulting in the further development of fission models. In the present work, the 237Np(n,f) cross section was studied at the EAR2 vertical beam-line at CERN's n_TOF facility, over a wide range of neutron energies, from meV to MeV, using the time-of-flight technique and a set-up based on Micromegas detectors, in an attempt to provide accurate experimental data. Preliminary results in the 200 keV – 14 MeV neutron energy range as well as the experimental procedure, including a description of the facility and the data handling and analysis, will be presented.

scholarly journals Preparation and characterization of 10B targets at JRC-Geel

2020 ◽  
Vol 229 ◽  
pp. 03005
Author(s):  
David Vanleeuw ◽  
Jan Heyse ◽  
Goedele Sibbens ◽  
Mariavittoria Zampella
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Time Of Flight ◽  
Fission Cross Section ◽  
Nuclear Data ◽  
Areal Density ◽  
Reaction Cross ◽  
Neutron Time

Measurements of neutron-induced cross sections to generate nuclear data are a core activity of the JRC-Directorate G Standards for Nuclear Safety, Security and Safeguards unit in Geel. Thin 10B layers are of great importance in this activity as they are used to measure the absolute neutron flux in the beam using the standard 10B(n,α)7Li reaction cross-section as a reference. After a period of reduced activity and in line with a renewed interest for nuclear data, the demand for high quality 10B targets increased. In this paper we describe the design and features of a new e-beam evaporator specifically customized for the preparation of boron targets as replacement of the old dysfunctional equipment. Several 10B targets of varying thicknesses were prepared and characterized as part of the factory acceptance tests and implementation in the JRC-Geel target preparation laboratory. Differential substitution weighing was applied for mass determination and in order to calibrate the thickness monitor. Comparative time-of-flight measurements relative to 10B and 235U standard targets were conducted at the GELINA neutron time-of-flight facility at the JRC-Geel site as second methodology for the determination of 10B areal density. The morphology of the layers was assessed by means of Scanning Electron Microscopy (SEM). The determination of impurities was realized by means of Energy Dispersive X-ray (EDX). Finally, two boron targets were prepared in the frame of the measurement of the neutron induced fission cross-section of 230Th at the n_TOF neutron time-of-flight facility at CERN.

scholarly journals Covariance generation for the prompt neutron multiplicity of 239Pu including the (n,γf) process

2020 ◽  
Vol 239 ◽  
pp. 12002
Author(s):  
Esther Leal-Cidoncha ◽  
Gilles Noguere ◽  
Olivier Bouland ◽  
Olivier Serot
Keyword(s):  
Covariance Matrix ◽  
Cross Section ◽  
Cross Sections ◽  
Matrix Theory ◽  
Fission Cross Section ◽  
Reaction Cross ◽  
Partial Width ◽  
R Matrix ◽  
Reaction Cross Sections

Fission cross section of 239Pu can be seen as a sum of the “immediate" fission and “two-step" (n,γf) reactions. In the Resolved Resonance Range of the reaction cross sections, the contribution of the (n,γf) process has an impact on the determination of the partial widths magnitude involved in the Reich-Moore approximation of the R-matrix theory. The present work aims to investigate this impact by using the CONRAD code and the partial width Γγf for the (n,γf) reaction calculated by Lynn et al. [1]. A special attention will be paid to the covariance matrix obtained on νp.

scholarly journals Preliminary results on the study of 237Np(n,f) at n_TOF/EAR2 in energies related to nuclear waste transmutation

2020 ◽  
Vol 27 ◽  
pp. 18
Author(s):  
Athanasios Stamatopoulos ◽  
And The n_TOF Collaboration
Keyword(s):  
Cross Section ◽  
Fuel Cycle ◽  
Evaluation Process ◽  
Fission Cross Section ◽  
Nuclear Model ◽  
Model Parameters ◽  
Preliminary Results ◽  
Wide Range ◽  
Nuclear Systems ◽  
Induced Fission

The accurate knowledge of neutron-induced fission cross sections of isotopes involved in the nuclear fuel cycle is essential for the optimum design and safe operation of next generation nuclear systems. Such experimental data can additionally provide constraints for the adjustment of nuclear model parameters used in the evaluation process, resulting in a further understanding of the nuclear fission process. In this respect measurements of the 237Np(n,f) cross section have been performed at the n_TOF facility at CERN in the horizontal 185 m flight-path (EAR1) which were discrepant by 7% in the MeV region. The neutron-induced fission cross section of 237Np(n,f) was recently restudied at the EAR2 19.5 m vertical beam-line at CERN’s n_TOF facility, over a wide range of neutron energies, from 100 keV up to 15 MeV, using the time-of-flight technique and a modern set-up based on Micromegas detectors. This study was performed in an attempt to resolve the aforementioned discrepancies and to provide accurate data of a reaction that is frequently used as reference in measurements related to feasibility and design studies of advanced nuclear systems. Preliminary results with a high statistical accuracy that resolve the discrepancies will be presented along with a brief discussion concerning the facility and the analysis.

scholarly journals Neutron induced fission cross-section of 240Pu(n,f): first results from n_TOF (CERN) Experimental Area II

2019 ◽  
Vol 23 ◽  
pp. 22
Author(s):  
A. Tsinganis ◽  
A. Stamatopoulos ◽  
N. Colonna ◽  
R. Vlastou ◽  
P. Schillebeeckx ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Fission Cross Section ◽  
Incident Neutron ◽  
Present Measurement ◽  
Experimental Area ◽  
Nuclear Systems ◽  
First Results ◽  
And Performance ◽  
Accelerator Driven Systems

The accurate knowledge of neutron cross-sections of a variety of plutonium isotopes and other minor actinides, such as neptunium, americium and curium, is crucial for feasibility and performance studies of advanced nuclear systems (Generation-IV reactors, Accelerator Driven Systems). In this context, the 240Pu(n,f) cross-section was measured with the time-of-flight technique at the CERN n_TOF facility at incident neutron energies ranging from thermal to several MeV. The present measurement is the first to have been performed at n_TOF's newly commissioned Experimental Area II (EAR-2), which is located at the end of an 18m neutron beam-line and features a neutron fluence that is 25-30 times higher with respect to the existing 185m flight-path (EAR-1), as well as stronger suppression of sample-induced backgrounds, due to the shorter times-of-flight involved. Preliminary results are presented.

scholarly journals The 240Pu(n,f) cross section measurement at the new experimental area at CERN's n_TOF facility

2019 ◽  
Vol 24 ◽  
pp. 139
Author(s):  
A. Stamatopoulos ◽  
For the NTOF Collaboration
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Fuel Cycle ◽  
Evaluation Process ◽  
Nuclear Fission ◽  
Nuclear Model ◽  
Model Parameters ◽  
Experimental Area ◽  
Wide Range ◽  
Nuclear Systems

The accurate knowledge of the neutron-induced fission cross-sections of actinides and other isotopes involved in the nuclear fuel cycle are essential for the design of advanced nuclear systems. These experimental data can also provide feedback for the adjustment of nuclear model parameters used in the evaluation process, resulting in further developments of nuclear fission models. In the present work, the 240Pu(n,f) cross-section was measured at CERN's n_TOF facility over a wide range of neutron energies, from a few meV to several MeV, using the time-of-flight technique and a set-up based on MicroMegas detectors. This measurement was the first experiment to be performed in n_TOF's new experimental area (EAR-2), which offers a significantly higher neutron flux compared to the existing experimental area. Preliminary results as well as the experimental procedure, including a brief description of the facility, the sample mounting, the read-out process and the data handling and analysis, are presented.

CROSS SECTIONS OF (p, xn) REACTIONS IN THE ISOTOPE OF LEAD AND BISMUTH

1956 ◽  
Vol 34 (8) ◽  
pp. 745-766 ◽  
Author(s):  
R. E. Bell ◽  
H. M. Skarsgard
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Compound Nucleus ◽  
Cross Sections ◽  
Proton Energy ◽  
Neutron Cross Section ◽  
Smooth Curve ◽  
Nucleon Nucleon ◽  
Reaction Cross ◽  
Total Reaction Cross Section

Measurements have been made by the activation method of cross sections of (p, xn) reactions in Bi209, Pb206, Pb207, and Pb208. The present results cover x = 3 to 7 in Bi209, 2 to 6 in Pb206, 2 to 4 in Pb207, and 3 and 4 in Pb208, over a total proton energy range from 12 to 85 Mev. The absolute accuracy is about 15%. Each cross section plotted as a function of proton energy rises above its threshold to a peak whose height is of the order of one barn, and then falls again to a low and fairly constant value. The results from x = 3 to 7 are consistent with a compound nucleus plus prompt nucleon–nucleon cascade model using reasonable nuclear parameters, but the experimental (p, 2n) cross section appears to be almost double the value so predicted. Since (p, xn) reactions are dominant in the energy range 10 to 40 Mev., their sum approximates the total reaction cross section; the experimental sum fluctuates around the smooth curve computed for the compound nucleus model with r0 = 1.3 × 10−13 cm. The fluctuations are similar to, but more marked than, those in the total neutron cross section of heavy elements in the same energy range. A more detailed theoretical discussion of these results is given by Jackson in the paper immediately following.

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