S. Tudisco

The Trojan Horse Method in nuclear astrophysics

Abstract The basic features of the Trojan Horse Method are discussed together with a review of recent applications, aimed to extract the bare astrophysical S(E)-factor for several two-body processes. In this framework information on electron screening potential U e was obtained from the comparison with direct experiments.

Pulse shape discrimination of charged particles with a silicon strip detector

Abstract A simple and effective pulse shape discrimination technique is applied to a silicon strip detector array. Excellent charge identification from H up to the Ni projectile has been obtained and isotope separation up to N has also been observed. The method we systematically studied is essentially based on a suitable setting of the constant fraction discriminators, and its main advantage is that no additional electronic modules are needed compared to the ones used in the standard TOF technique.

Indirect measurement of the 18O(p, α)15N reaction rate through the THM

A preliminary indirect investigation of the 18O(p, α)15N reaction via the THM is discussed, focusing on the extraction of the resonance parameters of the 656 keV resonance (corresponding to the state at Ex = 8.65 MeV in 19F), which gives strong contribution both at low and high temperatures, being quite broad. Even though a non-negligible discrepancy is found, both as regards the strength and the energy of the resonance, no change in the reaction rate is apparent in the astrophysically relevant temperature range.

TRASMA, a detector for γ-charged particle coincidences

Abstract An apparatus for detecting light and heavy fragments, in coincidence with γ-rays is described. Its use is foreseen for studying heavy ion complete and incomplete fusion reactions at low and intermediate energy. The ΔE-E and TOF techniques are used for charged particle identification at small angles using a combination of Si strip detectors and CsI(Tl) crystals. The γ-ray detection is performed by using a coverage of 9 clusters, each consisting of 7 BaF2 crystals, similar to the TAPS configuration, resulting in a large solid angle and a high granularity. We report on recent results about the charged particle discrimination and the time and energy resolution for the whole detector. Initial tests were performed using 12C, 19F and 28Si beams accelerated by the 15 MV tandem of the Laboratorio Nazionale del Sud in Catania.

The Trojan horse method in nuclear astrophysics: Recent results

Difficulties in cross-section measurements at very low energies, when charged particles are involved, led to the development of some indirect methods. The Trojan horse method (THM) allows us to bypass the Coulomb effects and has been successfully applied to several reactions of astrophysical interest. A brief review of the THM applications is reported together with some of the most recent results.

Indirect measurement of 17O(p,α)14N cross section at ultra-low energies

The indirect measurement of 17O(p,?)14N cross section was performed by means of the Trojan Horse Method. This approach allowed to investigate the ultra-low energy range (Ec.m. = 0?300 keV) relevant for several astrophysics environments, where two resonant levels of 18F at ERc.m. = 65 keV and ERc.m. = 183 keV play a significant role in the reaction rate determination.

Trojan Horse Method: Recent Experiments

The Trojan Horse Method allows for the measurements of cross sections in nuclear reactions between charged particles at astrophysical energies. The basic features of the method are discussed and recent applications are presented.

Study of the 10B(p,α)7Be Reaction through the Indirect Trojan Horse Method

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 10 B ( p ,α) 7 Be reaction has been studied by means of the Trojan Horse Method. The Trojan Horse Method was thus applied to the 10 B ( d ,α 7 Be ) n reaction, studied at 24 MeV. The obtained results will be discussed.

Improved Results on Extraction of 11B(p, α0)8Be and 10B(p, α)7Be S(E)‐Factor Through the Trojan Horse Method

In this work the analysis of the 10B(23p, α)7Be and 11B(p, α)8Be reactions, studied via the indirect Trojan Horse Method (THM), is discussed. In the astrophysical context of light nuclei LiBeB depletion, the above mentioned reactions are the main responsible for the destruction of boron in the stellar interior. The THM application allows their investigation in the astrophysically relevant energy region, around the Gamow Peak (≈10 keV), overcoming the problems due to the presence of the Coulomb barrier and electron screening effect. The experimental procedure and the preliminary results are shown.

First measurement of the 18O(p,α)15N cross section at astrophysical energies

The 18O(p,α)15N reaction rate has been deduced by means of the Trojan horse method. For the first time the contribution of the 20 keV resonance has been directly evaluated, giving a value about 35% larger than the one in the literature. Moreover, the present approach has allowed to improve the accuracy by a factor 8.5, as it is based on the measured strength instead of spectroscopic measurements. The contribution of the 90 keV resonance has been also determined, which turned out to be of negligible importance to astrophysics.