Characterization of the New Neutron Line at CERN-n_TOF and Study of the Neutron-induced Fission of 237Np PDF Download
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Author: Yonghao Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The neutron time-of-flight (n_TOF)facility at CERN is a unique worldwide pulsedneutron source to measure the nuclear data over thewidest energy range with two beam lines currentlyexploited. One is horizontal with a ~185 metersflight path, sending neutrons to experimental area-1(EAR-1). The second one is a new line sendingneutrons vertically to experimental area-2 (EAR-2)with a ~20 meters flight path.The first part of this PhD work is dedicated to thecharacterization of the beam (flux, geometricalprofile, energy spectrum) of the new EAR-2 neutronbeam, of the utmost importance for the experimentalproposals and analyses. An experiment was carriedout at EAR-2, based on PPAC detectors looking atfission of 235U, and the beam profile and neutronflux have been obtained for the entire availableenergy range (from thermal to 200 MeV).The second part of the thesis aims to study theneutron-induced fission of 237Np. 237Np isabundantly produced in present nuclear reactor andis one of the major long-lived components ofnuclear waste which can be considered as apotential target of incineration in fast neutronreactors. Consequently its neutron-induced fissioncross section has been measured at differentfacilities. However, significant discrepancies existbetween different experiments. Especially, therecent one performed at n_TOF in 2010 is about 6%higher by comparison to the evaluation data basedon previous experiments. Therefore an experimenthas been performed at n_TOF EAR-1 to measure itsfission cross section, in a configuration allowing anaccurate control of the detection efficiency, aimingto give a definite answer to the puzzle. In this work,we found that the efficiencies for different targetelements are different, even though they havesimilar thickness, reflecting the conditions ofelectrodeposition. After application of thisefficiency correction in the energy range from 1 to 5MeV, the newly extracted fission cross section is 2-3% lower compared with our previous measurementin 2010, however they are 3-4% higher than the.
Author: Yonghao Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The neutron time-of-flight (n_TOF)facility at CERN is a unique worldwide pulsedneutron source to measure the nuclear data over thewidest energy range with two beam lines currentlyexploited. One is horizontal with a ~185 metersflight path, sending neutrons to experimental area-1(EAR-1). The second one is a new line sendingneutrons vertically to experimental area-2 (EAR-2)with a ~20 meters flight path.The first part of this PhD work is dedicated to thecharacterization of the beam (flux, geometricalprofile, energy spectrum) of the new EAR-2 neutronbeam, of the utmost importance for the experimentalproposals and analyses. An experiment was carriedout at EAR-2, based on PPAC detectors looking atfission of 235U, and the beam profile and neutronflux have been obtained for the entire availableenergy range (from thermal to 200 MeV).The second part of the thesis aims to study theneutron-induced fission of 237Np. 237Np isabundantly produced in present nuclear reactor andis one of the major long-lived components ofnuclear waste which can be considered as apotential target of incineration in fast neutronreactors. Consequently its neutron-induced fissioncross section has been measured at differentfacilities. However, significant discrepancies existbetween different experiments. Especially, therecent one performed at n_TOF in 2010 is about 6%higher by comparison to the evaluation data basedon previous experiments. Therefore an experimenthas been performed at n_TOF EAR-1 to measure itsfission cross section, in a configuration allowing anaccurate control of the detection efficiency, aimingto give a definite answer to the puzzle. In this work,we found that the efficiencies for different targetelements are different, even though they havesimilar thickness, reflecting the conditions ofelectrodeposition. After application of thisefficiency correction in the energy range from 1 to 5MeV, the newly extracted fission cross section is 2-3% lower compared with our previous measurementin 2010, however they are 3-4% higher than the.
Author: Hans G. Börner
Publisher: World Scientific
ISBN: 9814273082
Category : Science
Languages : en
Pages : 284
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Book Description
The reactor-based laboratory at the Institut Laue-Langevin is recognized as the world's most productive and reliable source of slow neutrons for the study of low energy particle and nuclear physics. The book highlights the impact of about 600 very diverse publications about work performed in these fields during the past more than 30 years of reactor operation at this institute. On one hand neutrons are used as a tool to generate nuclei in excited states for studying their structure and decay, in particular fission. Uniquely sensitive experiments can tell us a great deal about the symmetry characteristics of nuclei and their fission properties. On the other hand, studies with slow neutrons as the object of investigation are complementary to studies at huge particle accelerators. Experiments carried out at the ILL contribute to elucidate basic questions about the building blocks of the Universe by analyzing very precisely subtle neutron properties.
Author: Hans G Borner
Publisher: World Scientific
ISBN: 9814468002
Category : Science
Languages : en
Pages : 284
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Book Description
The reactor-based laboratory at the Institut Laue-Langevin is recognized as the world's most productive and reliable source of slow neutrons for the study of low energy particle and nuclear physics. The book highlights the impact of about 600 very diverse publications about work performed in these fields during the past more than 30 years of reactor operation at this institute. On one hand neutrons are used as a tool to generate nuclei in excited states for studying their structure and decay, in particular fission. Uniquely sensitive experiments can tell us a great deal about the symmetry characteristics of nuclei and their fission properties. On the other hand, studies with slow neutrons as the object of investigation are complementary to studies at huge particle accelerators. Experiments carried out at the ILL contribute to elucidate basic questions about the building blocks of the Universe by analyzing very precisely subtle neutron properties.
Author: Nikolay Kornilov
Publisher: Springer
ISBN: 3319071335
Category : Science
Languages : en
Pages : 135
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Book Description
Although the fission of heavy nuclei was discovered over 75 years ago, many problems and questions still remain to be addressed and answered. The reader will be presented with an old, but persistent problem of this field: The contradiction between Prompt Fission Neutron (PFN) spectra measured with differential (microscopic) experiments and integral (macroscopic and benchmark) experiments (the Micro-Macro problem). The difference in average energy is rather small ~3% but it is stable and we cannot explain the difference due to experimental uncertainties. Can we measure the PFN spectrum with high accuracy? How may we compare results of different experiments to provide better accuracy? Are our traditional theoretical models correct? What can be done to solve the Micro-Macro problem in future? These questions are discussed in this monograph for the reader. The current work will be of interest to graduate students and researchers, particularly those working in nuclear and neutron physics.
Author: Joseph H Hamilton
Publisher: World Scientific
ISBN: 9814525448
Category : Science
Languages : en
Pages : 746
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Book Description
These proceedings are the fifth in the series of International Conferences covering fission and properties of neutron-rich nuclei, which are at the forefront of nuclear research. The time interval of 5 years between each conference allows for significant new results to be achieved. Recently, world leaders in theory and experiments in research and the development of new facilities for research presented their latest results in areas such as synthesis of superheavy elements, new facilities for and recent results with radioactive ion beams, structure of neutron-rich nuclei, nuclear fission process, fission yields and nuclear astrophysics. This book is a major source of the latest research in these areas and plans for the future. The conference brought together a unique group of over 100 speakers including leaders from the major nuclear laboratories in Canada, China, France, Finland, Germany, Italy, Japan, Russia, Switerzland and the US along with leading research scientists from around the world.
Author: Massimo Barbagallo
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The study of neutron-induced reactions is of high relevance in a wide variety of fields, ranging from stellar nucleosynthesis and fundamental nuclear physics to applications of nuclear technology. In nuclear energy, high accuracy neutron data are needed for the development of Generation IV fast reactors and accelerator driven systems, these last aimed specifically at nuclear waste incineration, as well as for research on innovative fuel cycles. In this context, a high luminosity Neutron Time Of Flight facility, n_TOF, is operating at CERN since more than a decade, with the aim of providing new, high accuracy and high resolution neutron cross-sections. Thanks to the features of the neutron beam, a rich experimental program relevant to nuclear technology has been carried out so far. The program will be further expanded in the near future, thanks in particular to a new high-flux experimental area, now under construction.
Author: Manbir Singh Kathuria
Publisher:
ISBN:
Category :
Languages : en
Pages : 82
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Book Description
Author: S. B. Borzakov
Publisher:
ISBN:
Category :
Languages : en
Pages : 16
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Book Description
Author: Frank Gunsing
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Neutron-induced reaction cross sections are important for a wide variety of research fields ranging from the study of nuclear level densities, nucleosynthesis to applications of nuclear technology like design, and criticality and safety assessment of existing and future nuclear reactors, radiation dosimetry, medical applications, nuclear waste transmutation, accelerator-driven systems and fuel cycle investigations. Simulations and calculations of nuclear technology applications largely rely on evaluated nuclear data libraries. The evaluations in these libraries are based both on experimental data and theoretical models. CERN's neutron time-of-flight facility n_TOF has produced a considerable amount of experimental data since it has become fully operational with the start of its scientific measurement programme in 2001. While for a long period a single measurement station (EAR1) located at 185 m from the neutron production target was available, the construction of a second beam line at 20 m (EAR2) in 2014 has substantially increased the measurement capabilities of the facility. An outline of the experimental nuclear data activities at n_TOF will be presented.
Author: Valery I. Zagrebaev
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The present limits of the upper part of the nuclear map are rather close to the beta stability line while the unexplored area of heavy neutron rich nuclides (also those located along the neutron closed shell N = 126 to the right hand side of the stability line) is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleogenesis. For elements with Z > 100 only neutron deficient isotopes (located to the left of the stability line) have been synthesized so far. The “north-east” area of the nuclear map can be reached neither in fusion-fission reactions nor in fragmentation processes widely used nowadays for the production of new nuclei. Multi-nucleon transfer processes in near barrier collisions of heavy ions seem to be the only reaction mechanism allowing us to produce and explore neutron rich heavy nuclei including those located at the superheavy island of stability. Neutron capture process can be also considered as an alternative method for the production of long-lived neutron rich superheavy nuclei. Strong neutron fluxes might be provided by nuclear reactors and nuclear explosions in laboratory frame and by supernova explosions in nature.
