Search results for "Neutron cross section"
showing 10 items of 39 documents
Developments for neutron-induced fission at IGISOL-4
2016
At the IGISOL-4 facility, neutron-rich, medium mass nuclei have usually been produced via charged particle-induced fission of natural uranium and thorium. Neutron-induced fission is expected to have a higher production cross section of the most neutron-rich species. Development of a neutron source along with a new ion guide continues to be one of the major goals since the commissioning of IGISOL-4. Neutron intensities at di↵erent angles from a beryllium neutron source have been measured in an on-line experiment with a 30 MeV proton beam. Recently, the new ion guide coupled to the neutron source has been tested as well. Details of the neutron source and ion guide design together with prelimi…
Relevance of β-delayed neutron data for reactor, nuclear physics and astrophysics applications
2023
Initially, yields (or abundances) and branching ratios of β-delayed neutrons (βdn) from fission products (Pn-values) have had their main importance in nuclear reactor control. At that time, the six-group mathematical approximation of the time-dependence of βdn-data in terms of the so-called "Keepin groups" was generally accepted. Later, with the development of high-resolution neutron spectroscopy, βdn data have provided important information on nuclear-structure properties at intermediate excitation energy in nuclei far from stability, as well as in nuclear astrophysics. In this paper, I will present some examples of the βdn-studies performed by the Kernchemie Mainz group during the past th…
Measurement of the 241Am neutron capture cross section at the n-TOF facility at CERN
2016
New neutron cross section measurements of minor actinides have been performed recently in order to reduce the uncertainties in the evaluated data, which is important for the design of advanced nuclear reactors and, in particular, for determining their performance in the transmutation of nuclear waste. We have measured the 241 Am(n,γ) cross section at the n TOF facility between 0.2 eV and 10 keV with a BaF2 Total Absorption Calorimeter, and the analysis of the measurement has been recently concluded. Our results are in reasonable agreement below 20 eV with the ones published by C. Lampoudis et al. in 2013, who reported a 22% larger capture cross section up to 110 eV compared to experimental …
Two-neutron removal reactions for very neutron-rich nuclei
1992
Abstract The two-neutron removal reactions of beams of 11 Li, 14 Be and 8 He upon Be, Ni and Au targets were studied at 30 MeV/u. The cross sections and the neutron forward angular distributions were measured; they correlate strongly with the two-neutron separation energy of the projectile. Even though the coverage of the neutron detectors was limited, a rough neutron-neutron distribution could be extracted. A simplified interpretation of the data is presented.
Overlappingβdecay and resonance neutron spectroscopy of levels inKr87
1983
Energy levels in $^{87}\mathrm{Kr}$ have been studied, with special emphasis on the unbound region, using two different methods. The first method comprises neutron capture and transmission measurements on an enriched gas target of $^{86}\mathrm{Kr}$ using neutron time-of-flight techniques. In this way, neutron widths were determined for 39 resonances below 400 keV and capture areas for 14 resonances below 90 keV. The second method is a decay study of 56-s $^{87}\mathrm{Br}$ in which a level scheme for $^{87}\mathrm{Kr}$ has been established that shows 126 levels in the bound and 12 levels in the unbound region. A detailed comparison amongst the neutron resonance, the $\ensuremath{\gamma}$-r…
The 236U neutron capture cross-section measured at the n TOF CERN facility
2016
International audience; The $^{236}$U isotope plays an important role in nuclear systems, both for future and currently operating ones. The actual knowledge of the capture reaction of this isotope is satisfactory in the thermal region, but it is considered insufficient for Fast Reactor and ADS applications. For this reason the $^{236} \text{U}(n, \gamma)$ reaction cross-section has been measured for the first time in the whole energy region from thermal energy up to 1 MeV at the n_TOF facility with two different detection systems: an array of C$_6$D$_6$ detectors, employing the total energy deposited method, and a 4$\pi$ total absorption calorimeter (TAC), made of 40 BaF$_2$ crystals. The t…
New measurement of the 242Pu(n,γ) cross section at n-TOF-EAR1 for MOX fuels: Preliminary results in the RRR
2016
The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with 238U to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. The use of MOX fuels in thermal and fast reactors requires accurate capture and fission cross sections. For the particular case of 242Pu, the previous neutron capture cross section measurements were made in the 70’s, providing an uncertainty of about 35% in the keV region. In this context, the Nuclear Energy Agency recommends in its “High Priority Request List” and its report WPEC-26 that the capture cross section of 242Pu…
Neutron capture cross section measurement ofU238at the CERN n_TOF facility in the energy region from 1 eV to 700 keV
2017
The aim of this work is to provide a precise and accurate measurement of the U238(n,γ) reaction cross section in the energy region from 1 eV to 700 keV. This reaction is of fundamental importance for the design calculations of nuclear reactors, governing the behavior of the reactor core. In particular, fast reactors, which are experiencing a growing interest for their ability to burn radioactive waste, operate in the high energy region of the neutron spectrum. In this energy region most recent evaluations disagree due to inconsistencies in the existing measurements of up to 15%. In addition, the assessment of nuclear data uncertainty performed for innovative reactor systems shows that the u…
New Beta-delayed Neutron Measurements in the Light-mass Fission Group
2014
A new accurate determination of beta-delayed neutron emission probabilities from nuclei in the low mass region of the light fission group has been performed. The measurements were carried out using the BELEN 4π neutron counter at the IGISOL-JYFL mass separator in combination with a Penning trap. The new results significantly improve the uncertainties of neutron emission probabilities for {sup 91}Br, {sup 86}As, {sup 85}As, and {sup 85}Ge nuclei.
Characterization and First Test of an i-TED Prototype at CERN n_TOF
2018
International audience; Neutron capture cross section measurements are of fundamental importance for the study of the slow process of neutron capture, so called s-process. This mechanism is responsible for the formation of most elements heavier than iron in the Universe. To this aim, installations and detectors have been developed, as total energy radiation C$_{6}$ D$_{6}$ detectors. However, these detectors can not distinguish between true capture gamma rays from the sample under study and neutron induced gamma rays produced in the surroundings of the setup. To improve this situation, we propose (Domingo Pardo in Nucl Instr Meth Phys Res A 825:78–86, 2016, [1]) the use of the Compton princ…