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Precise neutron inelastic and charged particle reaction cross sections as a tool for a better understanding of nuclear reaction mechanisms
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Acronym: NP_INEL
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
Partners:
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 [1]. 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 [2]. 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.
[1] A. Negret et al., Phys. Rev. C 88, 034604 (2013).
[2] 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. (2019-12-31)
RESULTS [Project Activity Report]
PUBLISHED ARTICLES
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