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Peculiar nuclear structures of two colliding nuclei such has clustering, neutron halo/skin or very low breakup thresholds can affect the reaction dynamics below the Coulomb barrier and this may also have astrophysical consequences. In order to have a better understanding of this topic, in the last decade, several experiments were performed. A typical experimental challenge of such studies is the need to measure excitation functions below the Coulomb barrier, having a strong energy dependence, with rather large beam energy dispersions inside the target. This may easily lead to ambiguities in associating the measured cross section with a proper beam energy. In this paper a discussion on this topic is reported and a new technique to deal with the above problem will be proposed. [ABSTRACT FROM AUTHOR]

Elastic scattering angular distributions and heavy residue production cross sections have been measured at different energies around the Coulomb barrier for the systems 6,7Li+64Zn. Optical model fits of the elastic angular distributions were performed using a renormalized double folding potential and absence of usual threshold anomaly in the optical potential was found. Excitation functions for heavy residue production have been measured using an activation technique. Comparison of the data with the results of different calculations show that complete fusion is the dominant reaction mechanism above the barrier, whereas the heavy residue yield below the barrier is mainly due to incomplete fusion and transfer. [ABSTRACT FROM AUTHOR]

The study of reaction mechanisms in collisions induced by halo and/or weakly bound nuclei around the barrier has recently been the subject of many theoretical and experimental papers. Here we discuss our recent results concerning the study of the systems 13N+9Be and 6He+64Zn. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The characteristics of a new multidetector based on the use of Monolithic Silicon Telescopes are presented. Using suitable ion implantation techniques, the ΔE and residual energy stages of the telescopes have been integrated on a single Si chip, obtaining a typical thickness for the ΔE stage of the order of 2μm. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The cross section of 8Li(α,n)11B is very important for the study of primordial nucleosinthesys models. In this paper we report on the production of a 8Li beam via the 7Li(d,p)8Li reaction at the Laboratori Nazionali del Sud. Also, a novel experimental technique for measuring the reaction 8Li(α,n)11B at energies of astrophysical interest has been implemented and tested. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Different aspects of the formation and decay of [sup 24]Mg in the collision [sup 13]N+[sup 11]B have been studied using a large solid angle and highly segmented Silicon strip detector. Results concerning the fusion cross section, the 6 α decay of [sup 24]Mg and the GDR gamma ray emission are discussed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In astrophysics, the abundance of 26Al is essential for understanding nucleosynthesis in the Milky Way and Galactic core-collapse supernovae rates. Detection methods involve γ-ray lines and comparing 26Mg overabundance with the common Mg isotope in meteorites. Therefore, stable isotopes 27Al and 24Mg play a crucial role and the MgAl cycle affecting aluminum and magnesium production has to be carefully studied. Recent surveys reveal complexities in stellar populations whose understanding may also benefit from better constraining the closure of the MgAl cycle. The 27Al(p, α)24Mg fusion reaction, a key 27Al destruction channel, is central to these scenarios. Due to uncertainties, the Trojan Horse Method is applied, allowing high-precision spectroscopy on the compound nucleus 28Si. It reveals crucial fusion cross section information in the astrophysically relevant energy range. The indirect measurement by means of the 2H(27Al,α24Mg)n process made it possible to assess the contribution of the 84.3 keV resonance and to set upper limits on nearby resonances. This study evaluates the THM recommended rate's impact on intermediate-mass asymptotic giant branch stars, showing a notable increase in surface aluminum abundance at lower masses due to fusion cross section modification, while 24Mg remains largely unaffected. [ABSTRACT FROM AUTHOR]

There are evidences that the 15C nucleus has an extended neutron distribution or a "neutron halo", but this situation is far from clear. If 15C has 1n-halo, the scattering dynamics should be affected and the angular distribution of the elastic channels should be sensitive to coupling effects due to the halo configuration. The objetive of this study is to understand the role of the halo in 15C by investigating its dynamical response in intense electric fields at energies close to the Coulomb barrier. For this purpose experiment IS619 was conducted performing the 15C + 208Pb elastic scattering reaction at HIE-ISOLDE, CERN. The beam energy was 4.37 MeV/u, which is very close to the Coulomb barrier of the system. The experimental setup used was the global detection system GLORIA, a six silicon telescopes array enable to measure the energy and angular distributions of the scattered particles. During the experiment, the 12C+208Pb scattering at 4.37 MeV/u was measured for calibration. The results of the 12C+208Pb measurement were used to fine-tune the geometry of the experimental setup and it is presented in this contribution. [ABSTRACT FROM AUTHOR]

12C +12 C is the main reaction during core and shell carbon burning in massive stars, however, at temperatures higher than 109K when most of the carbon is depleted and its abundance is lower than 16O, the 12C +16 O fusion can also become relevant. Moreover, 12C +16 O reaction can ignite also in the scenario of explosive carbon burning. The astrophysical energy region of interest thus ranges from 3 to 7.2 MeV in the center-of-mass frame. There are various measurements of the cross-section available in the literature, however, they all stop around 4 MeV, making extrapolation necessary at lower energies. To try to solve this uncertainty and corroborate direct measurement the Trojan Horse Method was applied to three-body processes 16O(14N, α24Mg)2H and 16O(14N, p27Al)2H to study the 16O(12C, α)24Mg and 16O(12C, p)27Al reactions. [ABSTRACT FROM AUTHOR]

The p - p-chain reaction 3He(α, γ)7Be can sensitively influence the prediction of the 7Be and 8B neutrino fluxes. Despite its importance, the knowledge of its reaction cross section at energies of the core of the Sun (15 keV 30 keV) is limited and the accuracy far from the desired 3% level. In the present paper the indirect measurement of the external capture contribution using the asymptotic normalization coefficient (ANC) technique is reported. The angular distributions of deuterons emitted in the 6Li(3He,d)7Be α-transfer reactions were measured and the ANCs extracted from the scaling of distorted-wave Born approximation (DWBA) and coupled-channel (CC) calculations. Then, the astrophysical S-factor for the 3He(α, γ)7Be reaction was calculated assuming E1 direct capture and the zero energy value turned out to be 0.534 0.025 keVb. Both our experimental and theoretical approaches were benchmarked through the analysis of the 6Li(p,γ)7Be astrophysical factor, with interesting astrophysical applications to the understanding of the primordial lithium problem. In particular, the present work disfavors the occurrence of a claimed 200 keV resonance in the astrophysical factor. [ABSTRACT FROM AUTHOR]

The carbon-burning process in massive stars mainly occurs via the 12C +12 C. However, at temperatures higher than 109K and considering the increased abundance of 16O produced during the later stages of the heliumburning,the 12C+16O fusion can also become relevant. Moreover, 12C+16O also plays a role in the scenario of explosive carbon burning. Thus, the astrophysical energy region of interest ranges from 3 to 7.2 MeV in the center-of-mass frame. However, the various measurements of the cross-section available in the literature stop around 4 MeV, making extrapolation necessary. To solve this uncertainty and corroborate direct measurement we applied the Trojan Horse Method to three-body processes 16O(14N, α24Mg)2H and 16O(14N, p27Al)2H to study the 12C(16O, α)24Mg and 12C(16O, p)27Al reactions in their entire energy region of astrophysical interest. In this contribution, after briefly describing the method used, the experiment and the preliminary phases of the data analysis will be presented and discussed. [ABSTRACT FROM AUTHOR]

Astrophysical reactions involving radioactive isotopes (RI) often play an important role in high-temperature stellar environments. The experimental studies on the reaction rates for those are still limited mainly due to the technical difficulties in producing high-quality RI beams. A direct measurement of those reactions would be still challenging in many cases, however, we can make a reliable evaluation of the reaction rates by an indirect method or by studying the resonance prorerties. Here we ntroduce recent examples of experimental studies on such RI-involving astrophysical reactions, performed at Center for Nuclear Study, the University of Tokyo, using the low-energy RI beam separator CRIB. One is for the neutron-induced destruction reactions of 7Be in the Big-Bang nucleosynthesis, and the other is the study on the 22Mg(α, p) reaction relevant in X-ray bursts, which was performed with the resonant scattering method from the inverse reaction channel. [ABSTRACT FROM AUTHOR]

The experimental elastic scattering angular distributions of the collisions involving the weakly bound nuclei 6,7Li and the halo nucleus 6He on the same 64Zn target at several energies around the Coulomb barrier were measured at the Laboratori Nazionali del Sud (LNS, Italy), and the Cyclotron Research Center, Louvain La Neuve (Belgium), respectively. The experimental elastic scattering angular distributions of the 6,7Li + 64Zn systems have been analyzed within the continuum-discretized coupled-channels method, while the 6He + 64Zn data have been compared with both continuum-discretized coupled-channels and coupled-reaction-channels calculations. [ABSTRACT FROM AUTHOR]

The reaction dynamics of collisions involving halo or weakly bound nuclei, at energies around the Coulomb barrier, can be strongly affected by the structure of such nuclei. Very strong entrance channel effects have been observed on various reaction pocess such as, elastic scattering, fusion and direct reactions when comparing collision induced by the 6He and 11Be halo nuclei with the ones induced by their cores 4He and 10Be. Collisions induced by the stable weakly bound nuclei 6Li, 7Li show also some peculiarities in comparison to the ones induced by well bound nuclei; coupling with the break-up channel is in fact very important in reproducing low energy data. In this contribution an overview of our present understanding of the discussed topic will be given along with the discussion of some new preliminary results. [ABSTRACT FROM AUTHOR]

The experimental elastic scattering angular distributions for the weakly bound nuclei 6,7Li and for the halo nucleus 6He on the same 64Zn target at several energies around the Coulomb barrier were measured at the Laboratori Nazionali del Sud (LNS, Italy) and at the Cyclotron Research Center, Louvain La Neuve (Belgium), respectively. The measured elastic scattering angular distributions of these three systems at the same center of mass energy have been compared. The experimental data of the 6,7Li+ 64Zn systems have been analyzed within the CDCC method, while the 6He+64Zn data have been compared with both both CDCC and CRC calculations. [ABSTRACT FROM AUTHOR]

In this contribution, results of experiments performed with the three Beryllium isotopes 9,10,11Be on a medium mass 64Zn target, at a center of mass energy of ≈1.4 the Coulomb barrier, will be discussed. Elastic scattering angular distributions have been measured for the 9,10Be reactions. In the 11Be case the quasielastic scattering angular distribution was obtained. In the halo nucleus case, the angular distribution exhibit a non-Fresnel-type pattern with a strong damping of the Coulomb-nuclear interference peak. Moreover, it is found that the total reaction cross-section for the halo nucleus induced collision is more than double the ones extracted in the collisions induced by the non-halo Beryllium isotopes. A large contribution to the total-reaction cross-section in the 11Be case could be attributed to transfer and/or break-up events. [ABSTRACT FROM AUTHOR]

Experimental studies on astrophysical reactions involving radioactive isotopes (RI) often accompany technical challenges. Studies on such nuclear reactions have been conducted at the low-energy RI beam separator CRIB, operated by Center for Nuclear Study, the University of Tokyo. We discuss two cases of astrophysical reaction studies at CRIB; one is for the 7Be+n reactions which may affect the primordial 7Li abundance in the Big-Bang nucleosynthesis, and the other is for the 22Mg(α, p) reaction relevantin X-raybursts. [ABSTRACT FROM AUTHOR]

New fusion data for the 4He+64Zn system at sub-barrier energies are measured to cover the same energy region of previous measurements for 6He+64Zn. Aim of the experiment was to compare the fusion excitation functions for the two system to investigate on the effects of the 6He neutron-halo structure on the fusion reaction mechanism at energies around the Coulomb barrier. The fusion cross section was measured by using an activation technique. Comparing the two systems, we observe an enhancement of the fusion cross section in the reaction induced by 6He, at and below the Coulomb barrier. [ABSTRACT FROM AUTHOR]

Owing the presence of the Coulomb barrier at astrophysically relevant kinetic energies, it is very difficult, or sometimes impossible to measure astrophysical reaction rates in laboratory. To overcome the problems related to the use of extrapolation procedure, the Trojan Horse Method (THM) has been applied extensively for the last 25 years to measure nuclear reaction cross sections of astrophysical interest. Although it has been mainly applied for charged particle-induced reactions, recently the THM has been found to have also a relevant role for neutron-induced ones. Here, the basic principle and a review of the main application of the Trojan Horse Method are presented, following a step-by-step description of the results concerning the study of the 17O(n,α)14C reaction. [ABSTRACT FROM AUTHOR]

The cosmological 7Li problem has been one of the big issues left in the standard Big-Bang nucleosynthesis (BBN) model. In order to determine the radiogenic 7Li abundance by the BBN, it is important to know the production and the destruction rate of 7Be rather than 7Li itself. We performed indirect measurements of the relevant neutron-induced reactions 7Be(n; p)7Li and 7Be(n; α)4He simultaneously by the Trojan Horse Method (THM) via the three-body reactions 7Be(d;7Lip)¹H and 7Be(d; αα)¹H. A 7Be radioactive-isotope (RI) beam at 3.16 MeV/u was produced at Center-for-Nuclear-Study RI Beam (CRIB) separator. The Qvalue spectra shows the evidence of the three-body channels of interest. We confirmed that the THM was applicable to the present measurements by the momentum distributions of the spectator proton. Preliminary excitation functions are roughly consistent with the previous studies, moreover providing new data in the BBN energy range, and suggesting that new information about the 7Be(n; p1)7Li* contribution may be obtained by carrying out a further data analysis. [ABSTRACT FROM AUTHOR]

The cosmological 7Li problem has been one of the big issues left in the standard Big-Bang nucleosynthesis (BBN) model. In order to determine the radiogenic 7Li abundance by the BBN, it is important to know the production and the destruction rate of 7Be rather than 7Li itself. We performed indirect measurements of the relevant neutron-induced reactions 7Be(n, p) 7Li and 7Be(n, α)4He simultaneously by the Trojan Horse Method (THM) via the three-body reactions 7Be(d, 7Lip)¹H and 7Be(d, αα)¹H. A 7Be radioactive-isotope (RI) beam at 3.16 MeV/u was produced at Center-for-Nuclear-Study RI Beam (CRIB) separator. The Q-value spectra shows the evidence of the three-body channels of interest. We confirmed that the THM was applicable to the present measurements by the momentum distributions of the spectator proton. Preliminary excitation functions are roughly consistent with the previous studies, moreover providing new data in the BBN energy range, and suggesting that new information about the 7Be(n, p1)7Li* contribution may be obtained by carrying out a further data analysis. [ABSTRACT FROM AUTHOR]

The abundance of 19F in the universe is strictly related to standard and extra-mixing processes taking place inside AGB-stars, that are considered to be the most important sites for its production. Nevertheless the way in which it is destroyed is far from being well understood. For this reason we studied the 19F(α,p)22Ne reaction, that is supposed to be the main destruction channel in the Helium-rich part of the star. In this experiment, the reaction has been studied in the energy range of relevance for astrophysics (0÷1 MeV) via the Trojan Horse Method (THM), using the three-body reaction 6Li(19F,p22Ne)d. [ABSTRACT FROM AUTHOR]

In this work the effects of the segmentation of the electrodes of Double Sided Silicon Strip Detectors (DSSSDs) are investigated. In order to characterize the response of the DSSSDs we perform a first experiment by using tandem beams of different energies directly sent on the detector and a second experiment by mean of a proton microbeam. Results show that the effective width of the inter-strip region and the efficiency for full energy detection, varies with both detected energy and bias voltage. The experimental results are qualitatively reproduced by a simplified model based on the Shockley-Ramo-Gunn framework. [ABSTRACT FROM AUTHOR]

The 16O+16O fusion reaction is important in terms of the explosive oxygen burning process during late evolution stage of massive stars as well as understanding of the mechanism of low-energy heavy-ion fusion reactions. We aim to determine the excitation function for the most major exit channels, α+28Si and p+31P, toward stellar energies indirectly by the Trojan Horse Method via the 16O(20Ne, α28Si)α and 16O(20Ne,p31P)α three-body reactions. We report preliminary results involving reaction identification, and determination of the momentum distribution of α-16O intercluster motion in the projectile 20Ne nucleus. [ABSTRACT FROM AUTHOR]

Due to their high selectivity, transfer and sequential decay reactions are powerful tools for studies of both single particle (nucleon) and cluster states in light nuclei. Their use is particularly simple for investigations of α-particle clustering (because a-particle has Jπ=0+, which simplifies spin and parity assignments to observed cluster states), but they are also easily applicable to other types of clustering. Recent results on clustering in neutron-rich isotopes of beryllium, boron and carbon obtained measuring the 10B+10B reactions (at 50 and 72 MeV) are presented. The highly efficient and segmented detector systems used, built from 4 Double Sided Silicon Strip Detectors (DSSSD) allowed detection of double and multiple coincidences and, in that way, studies of states populated in transfer reactions, as well as their sequential decay. [ABSTRACT FROM AUTHOR]

For measuring fusion excitation functions, the activation technique with a stack of targets offers the considerable advantage that several reaction energies may be simultaneously measured by using one beam energy. However, its main drawback is the degradation of the beam quality as it passes through the stack due to statistical nature of energy loss processes and any non-uniformity of the stacked targets. If not taken properly into account, this degradation can lead to a wrong determination of the fusion excitation function. In this contribution some results of the investigation of this problem are reported. [ABSTRACT FROM AUTHOR]

The use of the stacked target technique to measure fusion cross-sections of reactions induced by low intensity radioactive beams offers considerable advantages since several reaction energies may be simultaneously measured. The main disadvantage of the method is the degradation of the beam quality as it passes through the stack due to statistical nature of energy loss processes and any non-uniformity of the stacked targets. This degradation can lead to ambiguities of associating effective beam energies to reaction product yields for the targets within the stack. A detailed investigation of these ambiguities has been performed and some of the obtained results are presented. [ABSTRACT FROM AUTHOR]