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Reactions with Helium and Lithium Nuclei

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The Study of Nuclear Interaction of He-3,4,6 and Li-6 Ions Beams at the Energy Region of 2-15 MeVA

Tech Area / Field

  • PHY-ANU/Atomic and Nuclear Physics/Physics

Status
3 Approved without Funding

Registration date
18.10.2002

Leading Institute
National Nuclear Center of the Republic of Kazakstan / Institute of Nuclear Physics, Kazakstan, Almaty

Collaborators

  • Grand Accélérateur National d'Ions Lourds, France, Caen\nInstitute of Physical and Chemical Research (RIKEN), Japan, Saitama, Wako

Project summary

An intensive use of radioactive beams during the last 20 years led to revealing of a number of unusual properties of the light exotic nuclei, i.e. nuclei remote from the line of b-stability. On the basis of cross-sectional analysis of interaction Не, Li, Be isotopes at the energy 790 MeV/nucleon both within the empirical approach and the Glauber one it was concluded that there is a considerable extension of neutron density in neutron-rich isotopes of these nuclei what enables us to advance a hypothesis about possible existence of a so-called "neutron halo" in some of them. Further investigations have showed that the situation with neutron halo can be realized in nuclei 6He, 11Li, 11Be.

A weak energetic dependence of the total cross section in reaction 6Не+28Si, which contradicts to existing theoretical predictions, was discovered in the experiments at average energies of 6,8Не ions. Considerable increase in the 6Не+28Si cross section at energies 15-17 MeV/nucleon has been observed in our experiments.

Experimental data with neutron-rich helium and lithium isotopes were received for limited nuclei-targets especially in low-energy range (below 10 MeV/nucleon) of ions 6Не and 6Li. Theoretical calculations forecast а cross section growth of fusion reactions in under-barrier energy range because of a large mean-squire radius of these (A=6) exotic nuclei or more wide distribution of neutron or proton density. On the other hand, the nuclei structure with halo is closely connected with small binding energy of external nucleon that facilitates the break up cross sections of these nuclei to be large when interact with target nuclei. Nowadays in LNR JINR (Dubna, Russian Federation) the DRIBS-project is in progress. In the framework of this project it is supposed to obtain an intensive beam (109 particles/sec) of 6,8He ions with energy up to 12-14 MeV/nucleon and energy resolution 300 KeV what opens further possibilities for experiments in scantily investigated energy range. The corresponding cross section measurements of elastic, quasi-elastic processes and total absorption cross sections in the same energy diapason can be fulfilled with 4He ions on isochronous cyclotron of Institute of Nuclear Physics of National Nuclear Center of the Republic of Kazakhstan (INP NNC RK). There are just few inpidual complex investigations to the present time.

In connection with the above-stated Institute of Nuclear Physics NNC RK (Almaty, Kazakhstan) and the Laboratory of Nuclear Reactions JINR (Dubna, Russian Federation) propose to carry out a number of experiments to study of energy dependence of total reaction cross sections and angular distributions of differential sections of elastic and quasi-elastic reaction channels of 3,4,6He and 6Li ions with nuclei 1,2Н, 3,4Не, 6,7Li, 12С, 28Si, 90Zr as well as to carry out the experimental investigations of influence of neutron-rich 6He isotopes for estimations of probabilities of fusion-fission in reactions with heavy nuclei 238U, 208Pb and processes with neutron transfer in highly inelastic interactions.

Project goal is experimental and theoretical investigation of energy dependence of cross sections for elastic and inelastic interactions of 3,4,6He and 6Li ions with light and heavy nuclei in the weakly investigated energy diapason of 2-15 MeV/nucleon.

Expected results.

– New systematic experimental data about total cross sections and angular distributions of differential sections of elastic and inelastic scattering of 3,4,6He and 6Li ions at nuclei isotopes 1,2Н, 3,4Не, 6,7Li, 12С, 28Si, 90Zr in weakly investigated energy diapason 2-15 MeV/nucleon.


– New experimental data on excitation functions in reactions of fusion and fission owing to 4,6He ions at heavy nuclei 238U, 208Pb and processes with neutron transfer in highly inelastic interactions.
– New data about structure of investigated nuclei including nuclei in the vicinity of nuclear stability border (neutron-rich nuclei).
– New data about mechanisms of nuclear interaction of exotic nuclei.

Scope of Work.

The Project works are to include the following stages:

1. Adaptation and development of apparatus-methodical complex on the basis of measuring-calculating systems of INP NNC RK and LNR JINR.


2. Development of optimal acceleration regimes for 3,4,6He and 6Li at accelerating facilities of INP NNC RK and LNR JINR to get ion beams of necessary intensity and stability.
3. Optimization of the measurement method of total reaction cross sections with helium and lithium nuclides.
4. Production of nuclear targets with optimal on thickness and homogeneity parameters from the isotopes 1,2Н, 3,4Не, 6,7Li, 12С, 28Si, 90Zr, 208Pb, 238U.
5. Measurements at comparable conditions of differential sections of elastic and inelastic scattering of nuclides 3,4,6He and 6Li on the isotopes 1,2Н, 3,4Не, 6,7Li 12С, 28Si, 90Zr, 208Pb, 238U.
6. Measurement of total reaction cross sections of interaction of 3,4,6Не, 6Li ions with nuclei 1,2Н, 3,4Не, 6,7Li, 12С, 28Si, 90Zr, 208Pb, 238U in the energy range 2-15 MeV/nucleon.
7. Measurement of excitation function in reactions of fusion and fission owing to 4,6He ions on heavy nuclei 238U, 208Pb and processes with neutron transfer in highly inelastic interactions.
8. Theoretical analysis of the experimental results on the basis phenomenological and semi-microscopical models (optical model, method of coupled channels and distorted waves, method of double folding).

Due to fundamental character of the proposed investigations, it seems fruitful to involve nuclear scientists from CIS previously participated in nuclear weapon development in ex-USSR. In this aspect it is principal to utilize scientific and technical potential of INP NNC RK (Almaty) and LNR JINR (Dubna).

Scientific and technical staff involved in this project is highly qualified and experienced in the field of acceleration techniques, modern methods of automated nuclear-physical experiments, investigations of nuclear reactions with heavy ions and theoretical analysis of experimental results.

The Project completely meets the ISTC goals and objectives:

– this is a fundamental (experimental and theoretical) research, directed to expansion of modern conceptions about exotic neutron-rich nuclei;


– the project results will promote stabilization and make better international collaboration of the Kazakhstan institute with the international intergovernmental organization of JINR (Dubna, Russian Federation) involving collaborating support of the institutes RIKEN (Japan) and GANIL (France) what in future can lead to organization of international scientific laboratory in INP NNC RK (Almaty, Kazakhstan);
– the project encourages involving into the international scientific collaboration the Kazakhstan scientists and engineers previously involved into nuclear weapon tests.


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The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.

 

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