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Precise neutron inelastic and charged particle reaction cross sections as a tool for a better understanding of nuclear reaction mechanisms
Contracting Authority: Executive Agency for Higher Education, Research, Development and Innovation Funding (UEFISCDI)
Number / Date of the contract: 197/2017 / 2017-08-09
PN III, Program 4 - Fundamental research
Project Manager: Alexandru Negret
Starting date / finishing date: 2017-08-09 / 2019-12-31
Project value: 763500 RON
Abstract: The present project aims to make a significant step forward in the field of neutron
cross section data. The field is directly linked with the most important
technological applications of nuclear physics: energetics, medicine, safety and is
therefore the main research area of several large scale recent European FP7 projects
like ANDES and CHANDA. Our approach is based on the most advanced currently
available experimental techniques and incorporates an important theoretical
component. By combining our experimental investigation with the latest theoretical
calculations we pursue a two-folded goal: we wish to clarify essential aspects of
nuclear reaction mechanisms but also to generate highly precise data required by the
development of the next generation of nuclear applications and facilities.
Therefore, the first goal of our project is to determine very precisely the cross
sections for the neutron and proton inelastic scattering on structural materials.
Based on our previous experience and using two of the best available experimental
setups, the measurements we wish to perform will have an unprecedented precision in
term of cross section uncertainty and incident particle energy resolution.
The novelty and the exploratory character of our proposal comes mostly from the
intended attempt to generate neutron-induced cross sections based on charged
particle induced reaction cross sections. Generally, the neutron cross section
measurements suffer from the fact that neutrons cannot be accelerated and therefore
neutron beams can only be made based on collimation. On the other hand, intense
charged particle beams can be created with any desired energy using electro-magnetic
accelerating and focusing techniques. It would be therefore very interesting if a
profound understanding of the reaction mechanisms would allow us to infer the cross
sections of neutron induced reactions from those of charged particle induced
reactions. We are well experienced in both types of experiments and we performed
extensive measurements during the last decade both at the GELINA neutron source
operated by EC-JRC Geel and at the 9 MV Tandem accelerator of IFIN-HH. Therefore, we
are well equipped for using a unitary, consistent approach in order to investigate
the two types of reactions and to compare the results.
Of course, the idea of generating neutron cross sections by exploiting the
possibilities offered by charged particle beams is not completely new. The so-called
surrogate technique uses high-energy charged particles to excite a nucleus through a
direct reaction. The subsequent fission or the gamma decay of the excited nucleus
can be related, using certain theoretical assumptions, with the fission or capture
cross sections induced by neutrons. Unfortunately the technique can only be applied
to fission and neutron capture processes and depends on the theoretical assumptions.
In a recent study we investigated a slightly different approach: we tried to employ
the Bohr hypothesis in comparing the gamma-production cross sections for the
25Mg(a,ng)28Si and the 28Si(n,n'g)28Si . We concluded that the main reason for
the differences between the two cases is due to the total angular momentum
distribution in the compound nucleus. Starting from this conclusion we wish now to
investigate another option: based on the similarity between the neutron and the
proton (isospin symmetry) we wish to compare the production cross sections for gamma
transitions excited through neutron and proton inelastic scattering reactions. In
order to minimize the differences, the first attempt will be made on the N=Z nucleus
24Mg, by performing a 24Mg(p,p'g)24Mg reaction and the results will be compared with
those already available for 24Mg(n,n'g)24Mg . In this situation the two targets
are the same, the projectiles and the outgoing particles are similar (except of
course for the Coulomb component of the interaction) and the reaction proceeds
through compound mirror nuclei having a similar structure. Further, we wish also to
make an attempt to compare the neutron and proton inelastic scattering processes on
a N?Z nucleus 58Ni and check the differences from the first case. For this purpose
we will have to perform two experiments, one at EC-JRC Geel [58Ni(n,n'g)58Ni] and
one at IFIN-HH [58Ni(p,p'g)58Ni].
To conclude, we emphasize that these three experiments and the interplay and
comparisons among them should allow us to gain significant knowledge in the field of
nuclear reactions while providing very precise and valuable data for applications.
We should be able to make a step forward towards the possibility of inferring
neutron inelastic cross sections from charged particle induced reaction studies.
This is indeed an ambitious purpose, but based on our previous experience and on the
fact that we will make use of the best experimental facilities available, we believe
that a significant advance in this direction is within our reach.
 A. Negret et al., Phys. Rev. C 88, 034604 (2013).
 A. Olacel et al., Phys. Rev. C 90, 034603 (2014).
Objectives: The main goal behind this investigation is to study
the possibility to generate neutron cross sections based on charged particle
reaction data. Our investigation is driven by the increased need of very precise
reaction data of importance for the development of the future nuclear applications
and facilities. Therefore we wish to produce high quality, very reliable data while
attempting a better understanding of the profound mechanisms of nuclear reactions.
THE STAGES OF THE PROJECT AND DELIVERY DATES
1. Preparation of the 24Mg(p,p'g) and the 58Ni(n,n'g) experiments (2017-12-31)
2. Data taking for the 24Mg(p,p'g) and the 58Ni(n,n'g) experiments (2018-12-31)
3. Preparation and data taking for the 58Ni(p,p'g) experiment. Final
data analysis and dissemination.
RESULTS [Project Activity Report]
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