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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.

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.

In the environment of a hot plasma, as achieved in stellar explosions, capture and photodisintegration reactions proceeding on excited states in the nucleus can considerably contribute to the astrophysical reaction rate. Such reaction rates including the excited-state contribution are obtained from theoretical calculations as the direct experimental determination of these astrophysical rates is currently unfeasible. In the present study, ($\gamma$,p) and ($\gamma$,$\alpha$) reactions in the mass and energy range relevant to the astrophysical $p$ process are considered and the feasibility of measuring them with the ELISSA detector system at the future Variable Energy $\gamma$-ray (VEGA) facility at ELI-NP is investigated. The simulation results reveal that, for the ($\gamma$,p) reaction on twelve targets of $^{29}$Si, $^{56}$Fe, $^{74}$Se, $^{84}$Sr, $^{91}$Zr, $^{96,98}$Ru, $^{102}$Pd, $^{106}$Cd, and $^{115, 117, 119}$Sn, and the ($\gamma$,$\alpha$) reaction on five targets of $^{50}$V, $^{87}$Sr, $^{123,125}$Te, and $^{149}$Sm, the yields of the reaction channels with the transitions to the excited states in the residual nucleus are relevant and even dominant. It is further found that for each considered reaction, the total yields of the charged-particle $X$ may be dominantly contributed from one, two or three ($\gamma$,$X_{i}$) channels within a specific, narrow energy range of the incident $\gamma$-beam. Furthermore, the energy spectra of the ($\gamma$,$X_{i}$) channels with $0\leq i\leq 10$ are simulated for each considered reaction, with the incident $\gamma$-beam energies in the respective energy range as derived before. It becomes evident that measurements of the photon-induced reactions with charged-particle emissions considered in this work are feasible with the VEGA+ELISSA system and will provide knowledge useful for nuclear astrophysics., Comment: 11 figures, 17 pages

The abundance of 26Al carries a special role in astrophysics, since it probes active nucleosynthesis in the Milky Way and constrains the Galactic core-collapse supernovae rate. It is estimated through the detection of the 1809 keV γ-line and from the superabundance of 26Mg in comparison with the most abundant Mg isotope (A = 24) in meteorites. For this reason, high precision is necessary also in the investigation of the stable 27Al and 24Mg isotopes. Moreover, these nuclei enter the so-called MgAl cycle, playing an important role in the production of Al and Mg. Recently, high-resolution stellar surveys have shown that the Mg–Al anticorrelation in red-giant stars in globular clusters may hide the existence of multiple stellar populations, and that the relative abundances of Mg isotopes may not be correlated with Al. The common thread running through these astrophysical scenarios is the 27Al(p,α)24Mg reaction, which is the main 27Al destruction channel and directly correlates its abundance with the 24Mg one. Since available reaction rates show large uncertainties owing to the vanishingly small cross section at astrophysical energies, we have applied the Trojan Horse Method to deduce the reaction rate with no need of extrapolation. The indirect measurement made it possible to assess the contribution of the 84 keV resonance and to lower upper limits on the strength of nearby resonances. In intermediate-mass AGB stars experiencing hot bottom burning, a sizeable increase in surface aluminum abundance is observed at the lowest masses, while 24Mg is essentially unaffected by the change in the reaction rate.

The $$^{27}\hbox {Al}(\hbox {p},\alpha )^{24}\hbox {Mg}$$ 27 Al ( p , α ) 24 Mg reaction, which drives the destruction of $$^{27}$$ 27 Al and the production of $$^{24}\hbox {Mg}$$ 24 Mg in stellar hydrogen burning, has been investigated via the Trojan Horse Method (THM), by measuring the $$^2\hbox {H}(^{27}\hbox {Al},\alpha ^{24}\hbox {Mg})\hbox {n}$$ 2 H ( 27 Al , α 24 Mg ) n three-body reaction. The experiment covered a broad energy range ($$E_\mathrm{c.m.}\le \,1.5\,\hbox {MeV}$$ E c . m . ≤ 1.5 MeV ), aiming to investigate those of interest for astrophysics. The results confirm the THM as a valuable technique for the experimental study of fusion reactions at very low energies and suggest the presence of a rich pattern of resonances in the energy region close to the Gamow window of stellar hydrogen burning (70–120 keV), with potential impact on astrophysics. To estimate such an impact a second run of the experiment is needed, since the background due the three-body reaction hampered to collect enough data to resolve the resonant structures and extract the reaction rate.

Background: The Li 6 ( p , γ ) Be 7 cross section influences a variety of astrophysical scenarios, including big-bang and stellar nucleosynthesis. In recent years, conflicting results of direct measurements have been published, reporting contradictory low-energy trends. Purpose: To shed light on the contradiction between the existing data sets, the reaction was studied using the asymptotic normalization coefficient (ANC) technique which was up-to-now never used for this reaction. Methods: To derive the ANC, the Li 6 ( He 3 , d ) Be 7 transfer reaction, studied at the Department of Physics and Astronomy of the University of Catania and at the John. D. Fox Superconducting Accelerator Laboratory at Florida State University, was re-analyzed, focusing on the proton transfer mechanism [the α transfer process is discussed by Kiss et al. [Phys. Lett. B 807, 135606 (2020)]. The energy of the He 3 beam impinging on a Li 6 target was E lab = 3 MeV and E lab = 5 MeV. The yield of the emitted deuterons was measured with high precision by using silicon Δ E - E telescopes. Results: From the DWBA analysis of the angular distributions of the emitted deuterons populating the ground ( E * = 0.0 MeV; 3 2 − ) and the first excited ( E * = 0.429 MeV ; 1 2 − ) states of Be 7 , the ANCs for the Li 6 + p → Be 7 system were deduced. Furthermore, the recently measured Li 6 ( p , γ ) Be 7 reaction cross sections [Piatti , Phys. Rev. C 102, 052802 (2020)] were also analyzed within this theoretical framework. Excellent agreement was found between ANC values derived indirectly and those determined from the direct data, which strengthens the conclusion of the present work. The astrophysical S factor—at energies characterizing the Sun—for the Li 6 ( p , γ ) Be 7 reaction was calculated using the weighted mean of the experimentally derived ANC values. Conclusions: The result of the present comprehensive study supports the extrapolation of Piatti [Phys. Rev. C 102, 052802 (2020)], Dong [J. Phys. G Nucl. Partic. 44, 045201 (2017)], and Gnech and Marcucci [Nucl. Phys. A 987, 1 (2019)], and thus disfavors the conclusions drawn by He [Phys. Lett. B 725, 287 (2013)] and Xu [Nucl. Phys. A 918, 61 (2013)].

The neutron capture reaction $$^{10}$$ B(n, $$\alpha $$ ) $$^{7}$$ Li has been investigated via the Trojan Horse Method from 0 to 1 MeV. The $$\alpha _{0}$$ and $$\alpha _{1}$$ channels, corresponding to $$^{7}$$ Li in its g.s. and 1st excited level respectively, have been analyzed and cross sections have been measured for the two reaction channels. Angular distributions for the $$^{11}$$ B energy levels in the explored range have been extracted and compared with literature, while the J $$^{\pi }$$ of the level at $$E_{11B}=11.450$$ MeV (4 keV before the $$\alpha $$ emission threshold) has been clearly determined for the first time.

The $^{26}\mathrm{Si}(p,\ensuremath{\gamma})^{27}\mathrm{P}$ reaction might be relevant in understanding the $^{26}\mathrm{Si}$ depletion and $^{26}\mathrm{Al}$ production in stars. The asymptotic normalization coefficients (ANC) for the $^{26}\mathrm{Si}(p,\ensuremath{\gamma})^{27}\mathrm{P}$ reaction were extracted earlier from the reanalysis of $^{26}\mathrm{Mg}(d,p)^{27}\mathrm{Mg}$ and $^{26}\mathrm{Mg}(t,d)^{27}\mathrm{Mg}$ reactions, in which the deduced ANC's show significant discrepancies. In this work, a dedicated ($d,p$) measurement is presented: the ANC for the $^{27}\mathrm{Mg}\ensuremath{\rightarrow}\phantom{\rule{0.16em}{0ex}}^{26}\mathrm{Mg}+n$ virtual decay is deduced from the $^{26}\mathrm{Mg}(d,p)^{27}\mathrm{Mg}$ reaction populating the ground and the first excited state of $^{27}\mathrm{Mg}$ using the distorted wave Born approximation (DWBA). The charge symmetry properties for mirror nuclei have been used to calculate the ANC for the direct capture $^{26}\mathrm{Si}+p\ensuremath{\rightarrow}\phantom{\rule{0.16em}{0ex}}^{27}\mathrm{P}$ populating the ground state of $^{27}\mathrm{P}$. By means of the same formalism, the ${\mathrm{\ensuremath{\Gamma}}}_{p}$ width for the first excited state has also been deduced. The reaction rate is also updated using recent values for the ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}/{\mathrm{\ensuremath{\Gamma}}}_{p}$ ratio measured by [Sun et al., Phys. Rev. C 99, 064312 (2019); Sun et al., Phys. Lett. B 802, 135213 (2020)].

For the first time in an application to nuclear astrophysics, a process induced by the unstable $$^5$$ He = ( $$^4$$ He-n) nucleus, the $$^3$$ He+ $$^5$$ He $$\rightarrow $$ 2 $$\alpha $$ reaction, has been studied through the Trojan Horse Method (THM). For that purpose, the quasi-free (QF) contribution of the $$^9$$ Be( $$^3$$ He, $$\alpha \alpha $$ ) $$^4$$ He reaction was selected at $$E_{^{3}\text{ He }}=4$$ MeV incident energy. The reaction was studied in a kinematically complete experiment following a recent publication (Spitaleri et al. in Eur Phys J A 56:18, 2020), where for the quasi free contribution the momentum distribution between $$\alpha $$ and $$^5$$ He particle cluster in the $$^9$$ Be nucleus in the ground state have been extracted. The angular distribution of the QF $$^3$$ He+ $$^5$$ He $$\rightarrow $$ 2 $$\alpha $$ reaction was measured at $$\theta _{cm}$$ = 78 $$^{\circ }$$ –115 $$^{\circ }$$ . The energy dependence of the differential cross section of the $$^3$$ He+ $$^5$$ He $$ \rightarrow $$ 2 $$\alpha $$ virtual reaction was extracted in the energy range $$E_{cm}$$ = 0–650 keV. The total cross section obtained from the Trojan-horse method was normalized to absolute cross sections from a theoretical calculation in the energy range $$E_{cm}$$ =300–620 keV.

Nuclear reactions play a key role in the framework of the Big Bang Nucleosynthesis. A network of 12 principal reactions has been identified as the main path that drove the elemental nucleosynthesis in the first 20 min of the history of the Universe. Among them an important role is played by neutron-induced reactions, which, from an experimental point of view, are usually a difficult task to be measured directly. Nevertheless big efforts in the last decades have led to a better understanding of their role in the primordial nucleosynthesis network. In this work we apply the Trojan Horse Method to extract the cross section at astrophysical energies for the $$^3\text {He}$$ (n,p) $$^3\text {H}$$ reaction after a detailed study of the $$^2\hbox {H}$$ ( $$^3\text {He}$$ ,pt)H three-body process. Data extracted from the present measurement are compared with other published sets.

The $^{7}\mathrm{Li}(\ensuremath{\gamma},t)^{4}\mathrm{He}$ ground state cross section was measured for the first time using monoenergetic $\ensuremath{\gamma}$ rays with energies between 4.4 and 10 MeV at the High Intensity Gamma-ray Source. The reaction is important for the primordial Li problem and for testing our understanding of the mirror $\ensuremath{\alpha}$-capture reactions $^{3}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})^{7}\mathrm{Li}$ and $^{3}\mathrm{He}(\ensuremath{\alpha},\ensuremath{\gamma})^{7}\mathrm{Be}$. Although over the last 30 years most measurements of the $^{3}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})^{7}\mathrm{Li}$ reaction have concentrated in an energy range below ${E}_{\ensuremath{\gamma}}=3.65$ MeV, measurements at higher energies could potentially restrict the extrapolation to astrophysically important energies. The experimental arrangement for measuring the $^{7}\mathrm{Li}(\ensuremath{\gamma},t)^{4}\mathrm{He}$ reaction included a large-area silicon detector array and several beam characterization instruments. The experimental astrophysical $S$ factor of $^{3}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})$ calculated from the present data was fitted using the $R$-matrix formalism. The results are in disagreement with previous experimental measurements in the same energy range but the extrapolated $S$ factor agrees with the potential model calculation and lower energy experimental data.

We discuss experimentally and theoretically neutron production from the laser driven explosion of gas clusters prepared near the liquid-gas critical point. We let deuterated methane that was prepared very close to its critical temperature and pressure expand through a conical nozzle to create clusters, and then irradiated those clusters with a high intensity pulse from the Texas Petawatt Laser. After ionization, the clusters explode producing energetic ions, some of which fuse with resultant neutron emission. We show that the critical fluctuations present in the nozzle before the expansion influence the dynamics of neutron production. Neutron production near the critical point follows a power law, which is a signature of a second order phase transition and it is consistent with the Fisher model. This result might be relevant for energy production from fusion reactions.

A new study of the quasi-free contribution to the $$^3\hbox {He}+\,^9\hbox {Be}\rightarrow 3\alpha $$ reaction (Q value = 19.004 MeV) at low $${E}_{^3{{\mathrm{He}}}}$$ energy is presented. The reaction was studied in a kinematically complete experiment at beam energy of 4 MeV. To clarify the presence of the quasi-free mechanism, the $$^4{\hbox {He}}$$–$$^5\hbox {He}$$ momentum distribution of the $$^9\hbox {Be}$$ ground state was extracted. Standard tests were also carried out to confirm the presence of the quasi-free contribution and are reported in this work. The full width at half maximum of the $$^4\hbox {He}$$–$$^5\hbox {He}$$ inter-cluster momentum distribution inside $$^9\hbox {Be}$$ was measured with improved accuracy, by adopting several different approaches that all led to consistent results. These preliminary investigations on the reaction mechanism are fundamental for future studies employing the Trojan Horse Method, with the $$^5\hbox {He}$$ unbound nucleus as a virtual projectile.

Neutron induced reactions are fundamental for the nucleosynthesis of elements in the universe. Indeed, to correctly study the reactions involved in the well-known s-process in stars, which produce about half of the elements beyond the iron peak, it is mandatory to know the neutron abundance available in those stars. The 17O(n, a)14C reaction is one of the so-called “neutron poisons” for the pro- cess and it could play an important role in the balance of the neutron abundance. The reaction is therefore investigated in the energy range of astrophysical inter- est between 0 and 350 keV in the center of mass by applying the Trojan Horse Method to the three body reaction 2H(17O, a14C)H.

In the network of reactions present in the Big Bang nucleosynthesis, the 3He(n, p)3H has an important role which impacts the final 7Li abundance. The Trojan Horse Method (THM) has been applied to the 3He(d, pt)H reaction in order to extract the astrophysical S(E)-factor of the 3He(n, p)3H in the Gamow energy range. The experiment will be described in the present work together with the first preliminary results.

Abundance of 19F exceeds by far the predicted one. This problem represents one of the unanswered questions of stellar modelling. A source of large uncertainties at relevant energies are the 19F(p, α)16O and 19F(α, p)22Ne reactions. Although the lowest energy point from direct experiments are at about ∼660 keV, the astrophysical relevant energy region is only known by R-Matrix calculations. In this work we apply the Trojan Horse Method (THM) to the appropriate quasi-free three-body reactions. The THM application allowed us to study the sub-Coulomb energy region and to get the corresponding S(E)-factor values, thus allowing for a detailed evaluation of its astrophysical impact.

The detection of the neutrinos produced in the p − p chain and in the CNO cycle can be used to test the Standard Solar Model. The 3He( α , γ )7Be reaction is the first reaction of the 2nd and 3rd branch of the p − p chain, therefore, the uncertainty of its cross section sensitively influences the prediction of the 7Be and 8B neutrino fluxes. Despite its importance and the large number of experimental and theoretical works devoted to this reaction, the knowledge on the reaction cross section at energies characterizing the core of the Sun (15 keV - 30 keV) is limited and further experimental efforts are needed to reach the desired (≈ 3%) accuracy. The precise knowledge on the external capture contribution to the 3He( α , γ )7Be reaction cross section is crucial for the theoretical description of the reaction mechanism. In the present work the indirect measurement of this external capture contribution using the Asymptotic Normalization Coefficient (ANC) technique is reported. To extract the ANC, the angular distributions of deuterons emitted in the 6Li(3He,d)7Be α-transfer reaction were measured with high precision at E H 3 e = 3.0 MeV and E H 3 e = 5.0 MeV. The ANCs were then extracted from comparison of DWBA calculations to the measured data and the zero energy astrophysical S-factor for 3He( α , γ )7Be reaction was found to be 0.534 ± 0.025 keVb.

The use of the Trojan Horse Method (THM) appears as one of the most suitable tools for investigating nuclear processes of interest for astrophysics. THM has been demonstrated to be useful for exploring different nuclear reactions intervening both in stellar and primordial nucleosynthesis as well. Some recent results will be here discussed together with a brief discussion of the fundamental theoretical description. General details about the recently studied 7Be(n,α)4He reaction will be given.

Two analysis methods for $$\textit{Z}_\mathrm{eff}$$ evaluation were explored using both experimental and simulated gamma-ray attenuation data. Using particle-capture reactions on composite targets to generate multi-monoenergetic gamma rays between 1 and 12 MeV, we demonstrate the advantage of using neural networks for effective Z evaluation of shielded materials in single-pixel measurements. Furthermore, we extend the analysis to 2D processing of transmission radiography and by using Geant4-simulated data we prove the superiority of artificial neural networks in terms of image quality and material discrimination against classical methods.

Second-order processes in physics is a research topic focusing attention from several fields worldwide including, for example, non-linear quantum electrodynamics with high-power lasers, neutrinoless double-β decay, and stimulated atomic two-photon transitions. For the electromagnetic nuclear interaction, the observation of the competitive double-γ decay from 137mBa has opened up the nuclear structure field for detailed investigation of second-order processes through the manifestation of off-diagonal nuclear polarisability. Here, we confirm this observation with an 8.7σ significance, and an improved value on the double-photon versus single-photon branching ratio as 2.62 × 10−6(30). Our results, however, contradict the conclusions from the original experiment, where the decay was interpreted to be dominated by a quadrupole-quadrupole component. Here, we find a substantial enhancement in the energy distribution consistent with a dominating octupole-dipole character and a rather small quadrupole-quadrupole component in the decay, hindered due to an evolution of the internal nuclear structure. The implied strongly hindered double-photon branching in 137mBa opens up the possibility of the double-photon branching as a feasible tool for nuclear-structure studies on off-diagonal polarisability in nuclei where this hindrance is not present., Second order effects can play an important role in highlighting nuclear structure properties. Here, the authors show how the second-order nuclear transitions in the form of double-gamma decay in 137Ba help understanding atomic nuclei.

Compton γ -ray sources have been in operation for over 30 years with new facilities being under construction or proposed. The gamma beam system under implementation at the Extreme Light Infrastructure - Nuclear Physics facility in Romania will deliver brilliant γ -ray beams with energies up to 19.5 MeV. Several instruments for measuring the parameters of the γ -ray beam are under development at ELI-NP. One of these instruments based on a High Purity Germanium detector is routinely used for beam energy measurements at other facilities. Here we investigate the use of a High Purity Germanium detector to continuously monitor the intensity of the ELI-NP gamma beam by measuring the inelastic scattering of photons. This method relies on both experimental and simulated data and it has been successfully tested during a recent experiment at the High Intensity γ -ray Source facility.

In the network of reactions present in the Big Bang nucleosynthesis, the 3He(n, p)3H reaction has an important role which impacts the final 7Li abundance. The Trojan Horse Method (THM) has been applied to the 3He(d, pt)H reaction in order to extract the astrophysical S(E)-factor of the 3He(n, p)3H reaction in the Gamow energy range. The experiment will be described in the present work together with the first preliminary results.

An experiment was performed by means of Trojan Horse Method (THM) at the LNS Tandem in Catania. The investigation of the relevant 19F(p,α)16O two-body reaction was performed by selecting the quasi free (QF) contribution of the 19F(2H,α16O)n three-body reaction, using the deuteron target as TH nucleus. The aim of this measurement is to obtain the 19F(p,α)16O cross section. The experimental set-up and the calibration of the detectors will be presented.

In AGB environment, Fluorine and Sodium production and destruction pathways are still not completely understood: their abundances are therefore still matter of debate. \(^{19}\mathrm {F}\) (only stable isotope of fluorine) abundance is strongly related to standard and extra-mixing processestype typical of the interior AGB-stars. Furthermore, the destruction channels for this element are far from being well understood. About \(^{23}\)Na, its presence in Globular Clusters along with the well-known anticorrelation with oxygen, underline that this element has been produced in previous generations of stars: in particular, intermediate-mass AGB stars are one of the possible candidates for its production. For this reason we studied the \(^{19}\mathrm {F}\)(\(\alpha \),p)\(^{22}\mathrm {Ne}\) and \(^{23}\mathrm{Na}(\mathrm{p},\alpha )^{20}\)Ne reactions in the energy range of relevance for astrophysics via the Trojan Horse Method (THM), using the three-body reactions \(^{6}\mathrm {Li}\)(\(^{19}\mathrm {F}\), p\(^{22}\mathrm {Ne}\))d and \(^{23}\mathrm {Na}\) (d, pn)\(^{20}\mathrm {Ne}\).

Here we report on the characterization of one of the large-volume LaBr$_{3}$:Ce detectors for the ELIGANT project at ELI-NP. The main focus of this work is the response function for high-energy $\gamma$ rays of such detectors. In particular, we compare a selection of unfolding methods to resolve small structures in $\gamma$-ray spectra with high-energies. Three methods have been compared using $\gamma$-ray spectra with energies up to 12 MeV obtained in an experiment at the 3 MV Tandetron\texttrademark\ facility at IFIN-HH. The results show that the iterative unfolding approach gives the best qualitative reproduction of the emitted $\gamma$-ray spectrum. Furthermore, the correlation fluctuations in high-energy regime from the iterative method are two orders of magnitude smaller than when using the matrix inversion approach with second derivative regularization. In addition, the iterative method is computationally faster as it does not contain large matrix inversions. The matrix inversion method does, however, give more consistent results over the full energy range and in the low-statistics limit. Our conclusion is that the performance of the iterative approach makes it well suitable for semi-online analysis of experimental data. These results will be important, both for experiments with the ELIGANT setup, and for on-line diagnostics of the energy spread of the $\gamma$-ray beam which is under implementation at ELI-NP., Comment: 12 pages, 6 figures, 1 table

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.

The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, under construction in Magurele near Bucharest in Romania, will provide high-intensity and high-resolution gamma ray beams that can be used to address hotly debated problems in nuclear astrophysics. For this purpose, a silicon strip detector array (named ELISSA) will be realized in a common effort by ELI-NP and Laboratori Nazionali del Sud (INFN-LNS), in order to measure excitation functions and angular distributions over a wide energy and angular range. An experimental campaign is ongoing in order to test the feasibility of the future study at ELI-NP. With this aim, an experiment has been approved at INFN-LNS in order to measure the \(^{19}\)F(p,\(\alpha _{\pi }\))\(^{16}\)O reaction at astrophysical energies using a prototype of the ELISSA array. Moreover, an exploratory experiment to measure the \(^{7}\)Li(\(\gamma \),\(^{3}\)H)\(^{4}\)He reaction has been performed at High Intensity Gamma Source (HI\(\gamma \)S). The good preliminary results of our tests and simulations allows us to conclude that the ELISSA detector will be very suitable for nuclear astrophysics experiments with the upcoming gamma ray beam at the ELI-NP facility.

The \(^{19}\)F(p,\(\alpha \))\(^{16}\)O reaction is an important channel of fluorine destruction in H-rich environments as the outer layers of Asymptotic Giant Branch (AGB) stars. Measurements of the \(^{19}\)F(p,\(\alpha _0\))\(^{16}\)O reaction via the Trojan Horse Method (THM) have shown the presence of resonant structures not observed before. As a consequence, the reaction rate at astrophysical temperatures (about \(10^{7}\)–\(10^{8}\) K) exceeds up to a factor 1.7 the one previously adopted. Here we present the result of an experiment in which THM was used to extract the Quasi-Free (QF) contribution of the \(^{2}\)H(\(^{19}\)F,\(\alpha \) \(^{16}\)O)n reaction to the \(^{19}\)F(p,\(\alpha _1\))\(^{16}\)O channel, corresponding to the population of the first excited state of the \(^{16}\)O. Three resonances in the E\(_{cm}\) energy region below about 500 keV have been observed. This result hints to an enhancement of the \(^{19}\)F(p,\(\alpha \))\(^{16}\)O destruction rate, with respect to what presently predicted.

In the framework of the experimental campaign of the ($ p,\alpha$) and ($ n,\alpha$) reactions cross sections measurement involving the 10, 11B isotopes, different ($ n,\alpha$) cross section measurements have been performed at ultra-low energy. In this work, the 10B(n,$ \alpha$)7Li reaction was investigated through the Trojan Horse Method, by means of the Quasi-Free (QF) 2H(10B,$ \alpha^{7}$Li)1H reaction at 30 MeV of beam energy. As in the standard THM approach, the measurement has been performed in inverse kinematics using a 10B beam. The excitation function of the 10B(n,$ \alpha$)7Li reaction has been measured at a center-of-mass energy between 0 and 700 keV. The data were compared with the existing experimental ones. Even if the energy resolution of the present experiment did not allow a separation between the channels ($ n,\alpha_0$) and ($ n,\alpha_1$) the low energy cross section and the angular distribution are presented, pointing out once more the ability of the method in studying neutron induced reactions using deuteron as source of virtual neutrons.

Studying interactions of radioactive ions with neutrons is particularly demanding and has been performed only in a few cases. Some of these interactions are crucial in several astrophysical contexts. In the present work, the case of the 7Be destruction induced by the (n, α) reaction is investigated at the energies typical of the primordial nucleosynthesis by means of the Trojan Horse Method applied to the 2H(7Be, αα)p quasi-free reaction. The 7Be(n, α)4He cross-section has been measured in a single experiment from ∼2 MeV down to cosmological energies. The corresponding deduced reaction rate has been adopted to evaluate the impact on big bang nucleosynthesis and on the lithium problem., This work has been partially supported by the Italian Ministry of the University under grant RBFR082838 and "LNS-Astrofisica Nucleare (fondi premiali)." J.M. and G.D'A. acknowledge MEYS, under the project SPIRAL2-CZ, EF16-013/0001679. C.A.B. acknowledges support from the U.S. NSF grant No 1415656 and the U.S. DOE grant No. DE-FG02-08ER41533. S.H. acknowledges "JSPS KAKENHI (grant No. 15K17631)."

The cosmologically relevant \(^7\)Be(n,\(\alpha \))\(^4\)He has been matter of recent studies aimed at contributing to the long-standing Li-problem. Here a brief description of the twin THM investigations will be shown and the main results discussed.

The Trojan Horse Method has been applied to many neutron-induced reactions using the deuteron as a virtual source of neutrons, to explore wide energy regions of interest for astrophysics and applied physics and to investigate the suppression of the centrifugal barrier, that is one of the key advantages of this Method. The neutron-induced experimental campaign has already concerned 17O(n, α)14C, 6Li(n,α)3H, 7Be(n,p)7Li, 7Be(n,α)4He, 18F(n,α)15O and 14N(n,p)14C, and very recently 25Mg(n,α)22Ne and 27Al(n,p)27Mg, while others are planned to be measured soon, thus influencing different astrophysical scenarios. Particular attention is dedicated to a new measurement regarding the 10B(n,α)7Li reaction, aimed to disentangle the 7Li ground state contribution from its first excited state to the cross section.

The Trojan Horse Method is an indirect technique to measure nuclear reactions of astrophysical relevance at the energies of interest, free of Coulomb suppression and electron screening effects. Its basic features in the framework of the theory of direct reactions will be discussed and the physics case of the 12C+12C fusion will be addressed.

The \(^{12}\)C(\(^{12}\)C,\(\alpha _{0,1}\))\(^{20}\)Ne and \(^{12}\)C(\(^{12}\)C,\(p_{0,1}\))\(^{23}\)Na reactions, which determine carbon burning in stars, have been measured from E\(_{c.m.}\) = 2.7 MeV down to 0.8 MeV via the Trojan Horse Method off the deuteron in \(^{14}\)N. This range of energies is relevant for several astrophysical scenarios, from superburst ignition to hydrostatic burning. The measured astrophysical S(E) factors reveal several resonances, which are responsible for a very large increase of the reaction rate at the relevant temperatures.

The 10B(p,$\alpha_{1}$)7Be reaction has been studied for the first time via the Trojan Horse Method (THM) applied to the 2H(10B,$\alpha$7Be)n quasi-free three-body process. The present experiment allowed for a clear separation between $ \alpha_{0}$ and $\alpha_{1}$ channels thanks to the improved energy resolution with respect to previous THM studies of the 2H(10B,$\alpha$7Be)n reaction. The extracted half-off-energy-shell cross section was found to be characterized by several structures attributable to the population of 11C. In particular, six resonances have been observed at 10.086, 10.352, 10.525, 10.686, 10.841 and 10.976 MeV 11C excitation energy.

In equation (1) of this Letter, the closing bracket was missing; in Extended Data Fig. 1 and the accompanying legend, 'Φ(p