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The Asymptotic Normalization Coefficient (ANC) method has proven to be useful in retrieving the direct part of the radiative capture cross section for a number of reactions of astrophysical interest. In this work, the study of the 26Si(p, γ)27P reaction, studied via the ANC in its extension for mirror nuclei will be discussed. [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 12C(12C,α0,1)20Ne and 12C(12C,p0,1)23Na reactions have been measured from Ec.m.=2.7 MeV down to 0.8 MeV via the Trojan Horse Method o the deuteron in 14N. This range of energies is relevant in astrophysical scenarios, from superburst ignition to explosive stellar carbon burning. The deduced astrophysical S(E) factors exhibit several resonances that are responsible for a very large increase of the reaction rate at the relevant temperatures. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method (THM) has been applied extensively for the last 25 years to measure nuclear reaction cross sections of interest for astrophysics. Although it has been mainly applied for charged particle-induced reactions, recently it has been found to have also a relevant role for neutron-induced reactions. Here, some advantages of THM will be discussed and the preliminary results of the cosmological relevant 7Be(n,α)4He cross section measurement are discussed. [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]

The 10B(p,α0)7Be reaction cross section has been measured in an wide energy range from 2.2 MeV down to 3 keV in a single experiment applying THM. Optimized experimental set-up ensured good energy resolution leading to a good separation of α0 and α1 contributions to the cross section coming from the 7Be ground and first excited state, respectively [ABSTRACT FROM AUTHOR]

The 12C(14N,α20Ne)²H and 12C(14N,p23Na)²H reactions have been measured at a 14N beam energy of 30.0 MeV. The experiment aims to explore 24Mg excited states that can be populated in the quasi-free reaction off the deuteron in 14N. In particular, the 24Mg excitation region explored in the measurement plays a key role in stellar carbon burning whose cross section is obtained by extrapolating high-energy fusion data. From preliminary results, α and proton channels are clearly identified. In particular, ground and first excited states of 20Ne and 23Na play a major role. [ABSTRACT FROM AUTHOR]

In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the Trojan Horse Method by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature. [ABSTRACT FROM AUTHOR]

A measurement of the 12C(14N,α20Ne)²H and 12C(14N,p23Na)²H reactions has been performed at a 14N beam energy of 30.0 MeV. The experiment aims to explore the extent to which contributing 24Mg excited states can be populated in the quasi-free reaction off the deuteron in 14N. In particular, the 24Mg excitation region explored in the measurement plays a key role in stellar carbon burning whose cross section is commonly determined by extrapolating high-energy fusion data. From preliminary results, α and proton channels are clearly identified. In particular, ground and first excited states of 20Ne and 23Na play a major role. [ABSTRACT FROM AUTHOR]

In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of protoninduced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the THM by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. Two measurements will be described and the experimental THM cross sections will be shown for both experiments. [ABSTRACT FROM AUTHOR]

Burning reaction S(E)-factor determinations are among the key ingredients for stellar models when one has to deal with energy generation evaluation and the genesis of the elements at stellar conditions. To by pass the still present uncertainties in extrapolating low-energies values, S(E)-factor measurements for charged-particle induced reactions involving light elements have been made available by devote Trojan Horse Method (THM) experiments. The recent results are here discussed together with their impact in astrophysics. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of the 17O(p,α)14N and 18O(p,α) 15N fusion reactions and to extract the strengths of the resonances that more contribute to the reaction rates at astrophysical energies. Moreover, the strength of the 65 keV resonance in the 17O(p,α) 14N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the 17O + p radiative capture channel. Since, proton-induced fusion reactions on 17O and 18O belong to the CNO cycle network for H-burning in stars, the new estimates of the cross sections have been introduced into calculations of Asymptotic giant branch (AGB) star nucleosynthesis to determine their impact on astrophysical environments. Results of nucleosynthesis calculations have been compared with geochemical analysis of "presolar" grains. These solids form in the cold and dusty envelopes that surround AGB stars and once that have been ejected by stellar winds, come to us as inclusions in meteorites providing invaluable benchmarks and constraints for our knowledge of fusion reactions in astrophysical environments. [ABSTRACT FROM AUTHOR]

Boron abundances in stellar atmospheres, as well as berillium and lithium ones, can give useful hints for non-standard transport processes discrimination in stars. They can also be relevant for understanding several astrophysical processes (e.g. primordial nucleosynthesis and spallation reactions in ISM). A comprehensive study of Li Be B abundances can therefore confirm or not the presence of non-standard mixing processes in stellar envelopes. For this reason nuclear processes producing or depleting boron isotope abundance need to be studied at astrophysical energies. The 10B(p,α)7Be reaction has been studied by means of the Trojan Horse Method. The Trojan Horse Method was thus applied to the 10B(d,α 7Be)n reaction, studied at 24 MeV. The obtained results will be discussed. [ABSTRACT FROM AUTHOR]

Presolar grains form in the cold and dusty envelopes of Asymptotic Giant Branch (AGB) stars. These solides, once that have been ejected by stellar winds, come to us as inclusions in meteorites providing invaluable benchmarks and constraints for our knowledge of low temeperature H-burning in stars. The Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of the 17O(p,α)14N and 18O(p,α)15N reactions. Moreover, the strength of the 65 keV resonance in the 17O(p,α)14N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the 17O + p radiative capture channel. The new estimates of the reaction rates have been introduced into calculations of AGB star nucleosynthesis and the results have been compared with geochemical analysis of "presolar" grains to determine their impact on astrophysical environments. [ABSTRACT FROM AUTHOR]

The 17O(p,α)14N reaction is of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RG), asymptotic giant branch (AGB) stars, massive stars and classical novae. We report on the indirect study of the 17O(p,α)14N reaction via the Trojan Horse Method by applying the approach recently developed for extracting the resonance strength of the narrow resonance at Ec.m.R = 65 keV (EX =5.673 MeV). The strength of the 65 keV resonance in the 17O(p,α)14N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the 17O + p radiative capture channel. [ABSTRACT FROM AUTHOR]

Experimental nuclear astrophysics aims at determining the reaction rates for astrophysically relevant reactions at their Gamow energies. For charged-particle induced reactions, the access to these energies is usually hindered, in direct measurements, by the presence of the Coulomb barrier between the interacting particles or by electron screening effects, which make hard the determination of the bare-nucleus S(E)-factor of interest for astrophysical codes. The use of the Trojan Horse Method (THM) appears as one of the most suitable tools for investigating nuclear processes of interest for astrophysics. Here, in view of the recent TH measurements, the main destruction channels for deuterium (²H), for the two lithium 6,7Li isotopes, for the 9Be and the one for the two boron 10,11B isotopes will be discussed. [ABSTRACT FROM AUTHOR]

The rates for the 17O(p,a)14N, 17O(p,?)18F and 18O(p,a)15N reactions deduced trough the Trojan Horse Method (THM) have been introduced into a state-of-the-art asymptotic giant branch (AGB) models for proton-capture nucleosynthesis and cool bottom process. The predicted abundances have been compared with isotopic compositions provided by geochemical analysis of presolar grains. As a result, an improved agreement is found between the models and the isotopic mix of oxide grains of AGB origins, whose composition is the signature of low-temperature proton-capture nucleosynthesis. [ABSTRACT FROM AUTHOR]

The neutron capture rate 18O(n,? )19O is important for analysis of nucleosynthesis in inhomogeneous Big Bang models and also for models of processes in massive red giant stars and AGB stars. Angular distributions of the 18O(d,p)19O reaction were measured at a deuteron energy of 16.3 MeV in NPI in Řež, Czech Republic, with the aim to determine Asymptotic Normalization Coefficients which can then be used for indirect determination of the direct contribution to the 18O(n,? )19O process. In the experiment, the gas target with 18O isotope of high purity 99.9 % was used thus eliminating any contaminating reactions. Reaction products were measured by the set of 8 ?E -E telescopes consisting of thin and thick silicon surface-barrier detectors. Angular distributions of proton transfers corresponding to 6 levels of 19O up to the 4.1093 MeV excitation energy were determined. The analysis of angular distributions in the angular range from 6 to 64 degree including also the angular distribution of elastically scattered deuterons was carried out by means of ECIS and DWUCK codes. From the determined ANCs the direct contribution to the radiative capture 18O(n,? )19O was deduced and compared with existing direct measurements. [ABSTRACT FROM AUTHOR]

The role of oxygen in astrophysics is related to different problems as novae nucleosynthesis and gamma-ray astronomy. In particular, owing to the still present uncertainties on its rate, the 17O(p,α)14N is one of the most important reaction to be studied in order to get more information about the fate of oxygen in different astrophysical scenarios. [ABSTRACT FROM AUTHOR]

The 2H(3He,p3H)1H and 2H(3He,n3He)1H processes have been measured in quasi free kinematics to investigate for the first time the 2H(d,p)3H and 2H(d,n)3He reactions by means of the Trojan Horse Method. The 3He+d experiment was performed at 18 MeV, corresponding the a d-d energy range from 1.5 MeV down to 2 keV. This range overlaps with the relevant region for Standard Big Bang Nucleosynthesis as well as with the thermal energies of future fusion reactors and deuterium burning in the Pre Main Sequence phase of stellar evolution. This is the first pioneering experiment in quasi free regime where the charged spectator is detected. Both the energy dependence and the absolute value of the bare nucleus S(E) factors have been extracted for the first time. They deviate by more than 15% from available direct data with new S(0) values of 57.4±1.8 MeVb for 3H+p and 60.1±1.9 MeVb for 3He+n. None of the existing fitting curves is able to provide the correct slope of the new data in the full range, thus calling for a revision of the theoretical description. This has consequences in the calculation of the reaction rates with more than a 25% increase at the temperatures of future fusion reactors. [ABSTRACT FROM AUTHOR]

Nuclear clusters play a key role in the Trojan Horse Method for Nuclear Astrophysics studies. The Trojan Horse Method is an indirect technique to determine the astrophysical S(E) factor at ultra-low energies, free of Coulomb suppression and electron screening effect. Clustering makes it possible to use a few-body approach to derive a simple relationship between the measured 2 → 3 cross section and that of the 2 → 2 cross section of interest for astrophysics. The basic features of the Trojan Horse Method will be discussed and some recent results will be presented. [ABSTRACT FROM AUTHOR]

A single crystal diamond detector was exposed to the quasi mono-energetic neutron fields in the energy range from 7 MeV to 20.5 MeV produced by the Van de Graaff neutron generator of the EC-JRC-IRMM. Pulse Height Spectra (PHS) of the neutron interaction with the diamond (carbon) were recorded in order to derive the experimental response function of this detector to neutrons in view of its use as a compact fast neutron spectrometer. Several peaks produced by outgoing charged particles produced when neutrons interact with carbon were identified using the reaction Q-values. The corresponding nuclear reactions, such as (n,α), (n,p), (n,d) for different excitation states were identified in the PHS. The analysis of the peaks allows the derivation of some neutron reaction cross sections in carbon. The results are presented in this paper together with the associated uncertainties. [ABSTRACT FROM AUTHOR]

The 18O(p,α)15N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as 19F, 18O and 15N. In this work, a high accuracy 18O(p,α)15N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2+ resonance. Since Γ∼100-300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T∼0.5 109 K based over our new improved determination of its resonance parameters. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method (THM) was applied to the 3He+6Li interaction in order to investigate the quasi-free 6Li(d,α)4He reaction. The experiment was performed at 17 MeV at the Cyclotron Institute of the Czech Academy of Science. The extracted 6Li(d,α)4He quasi-free cross-section was compared with the behavior of direct data. A good agreement between data sets shows up throughout the energy range investigated, providing a very important validity test of the pole approximation for the THM above the Coulomb barrier. [ABSTRACT FROM AUTHOR]

We present here an important test of the main feature of the Trojan Horse Method (THM), namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. This is done by measuring the THM p-p elastic scattering via the p+d→p+p+n reaction at 4.7 and 5 MeV, corresponding to a p-p relative energy ranging from 80 to 670 keV. In contrast to the on-energy-shell (OES) case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum due to the suppression of the Coulomb amplitude. This is confirmed by the half-off-energy shell (HOES) calculations and strengthened by the agreement with the calculated OES nuclear cross sections. [ABSTRACT FROM AUTHOR]

In order to understand primordial and stellar nucleosynthesis, we have studied 2H(d,p)3H reaction at 0.4 MeV down to astrophysical energies. Knowledge of its S-factor is interesting also to plan reactions for fusion reactors to produce energy. The 2H(d,p)H reaction has been studied through the Trojan Horse Method applied to the three-body reaction 2H(He,pt)H, at beam energy of 17 MeV. Once selection of protons and tritons detected in coincidence and the selection of quasi-free events, the obtained S-factor is compared with direct measurements. Such data are in agreement with the direct ones and a pole invariance test has been obtained comparing the present results with another 2H(d,p)3H THM measurements, where a different spectator particle was employed. [ABSTRACT FROM AUTHOR]

In order to understand primordial and stellar nucleosynthesis, we have studied 2H(d,p)3H reaction at 0, 4 MeV down to astrophysical energies. Knowledge of this S-factor is interesting also to plan reactions for fusion reactors to produce energy. 2H(d,p)3H has been studied through the Trojan Horse Method applied to the three-body reaction 2H(3He,pt)H, at a beam energy of 17 MeV. Once protons and tritons are detected in coincidence and the quasi-free events are selected, the obtained S-factor has been compared with direct reactions results. Such data are in agreement with the direct ones, and a pole invariance test has been obtained comparing the present result with another 2H(d,p)3H THM one, performed with a different spectator particle (see fig. 1). [ABSTRACT FROM AUTHOR]

We present here an important test of the main feature of the Trojan Horse Method (THM), namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. This is done by measuring the THM p—p elastic scattering via the p+d→p+p+n reaction at 4.7 and 5 MeV, corresponding to a p—p relative energy ranging from 80 to 670 keV. In contrast to the on-energy-shell (OES) case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum due to the suppression of the Coulomb amplitude. This is confirmed by the half-off-energy shell (HOES) calculations and strengthened by the agreement with the calculated OES nuclear cross sections. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method (THM) is an unique indirect technique allowing to measure astrophysical rearrangement reactions down to astrophysical relevant energies. The basic principle and a review of the recent applications of the Trojan Horse Method are presented. The applications aiming to the extraction of the bare astrophysical Sb(E) for some two-body processes are discussed. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method has been recently applied to the study of reactions involved in fluorine nucleosynthesis inside AGB stars. Fluorine abundance is important since it allows to constrain mixing models from the comparison of the observed fluorine abundances with the ones predicted by models. Anyway direct measurements of the cross section do not extend down to the Gamow peak, which is the astrophysically relevant energy region. In particular the study focuses on the 15N(p,α)12C and the 18O(p,α)15N reactions which can influence fluorine yield as they are part of 19F production/destruction network. [ABSTRACT FROM AUTHOR]

Light elements lithium, beryllium and boron (LiBeB) were used in the last years as 'possible probe' for a deeper understanding of some extra-mixing phenomena occurring in young Main-Sequence stars. They are mainly destroyed by (p,α) reactions and cross section measurements for such channels are then needed. The Trojan Horse Method (THM) allows one to extract the astrophysical S(E)-factor without the experience of tunneling through the Coulomb barrier. In this work a résumé of the recent results about the 11B(p,α0)8Be and 10B(p,α)7Be reactions is shown. [ABSTRACT FROM AUTHOR]

The THM has been applied to the study of reactions involved in the fluorine production in AGB stars with the aim of extending these measurements down to the Gamow peak. Fluorine abundance is important since it allows to constrain mixing models from the comparison of the observed fluorine abundances with the ones predicted by models. In particular the study focuses on the 15N(p,α)12C and the 18O(p,α)15N reactions which can influence fluorine yield as they are part of 19F production (and destruction) network. [ABSTRACT FROM AUTHOR]

The astrophysically relevant 7Li+p→α+α reaction was investigated via the THM by selecting the quasi-free contribution to the measured 3He+7Li→α+α+d three-body process. This investigation is mainly aimed at testing the validity of the pole approximation in the THM against the bound structure of the Trojan-horse nucleus. The three-body experiment was performed at 33 MeV, corresponding to a 7Li-p relative energy ranging from 0.2 to 7 MeV. The quasi-free 7Li+p cross-section was compared with the free reaction cross-section as well as with indirect data from a previous THM experiment. The good agreement between data sets throughout the energy range investigated provided a very important validity test of the pole approximation for the THM. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]