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The 14C(n, γ)15C reaction plays an important role in inhomogeneous big bang models. In Timofeyuk et al. [ Phys. Rev. Lett. 96 162501 (2006)] it was shown that the 14C(n, γ)15C radiative capture at astrophysically relevant energies is a peripheral reaction, i.e., the overall normalization of its cross section is determined by the asymptotic normalization coefficient (ANC) for 15C→14C+n. Here we present new measurements of the 14C(d, p)15C differential cross sections at deuteron incident energy of 17.06 MeV and the analysis to determine the ANCs for neutron removal from the ground and first excited states of 15C. The results are compared with previous estimations. [ABSTRACT FROM AUTHOR]

Abstract: An activation experiment on the Eurofer-97 low activation steel was performed to provide the database for validating activation cross-section data in the energy range relevant for the International Fusion Material Irradiation Facility (IFMIF). An IFMIF-like white neutron field extending up to energy of 32MeV was produced at the isochronous cyclotron U-120M of the Nuclear Physics Institute (NPI) Řež, by bombarding a flowing heavy water target with a 37MeV proton beam. The induced gamma radioactivity for 22 product radio-nuclides was determined by gamma ray spectrometry at different cooling time intervals using calibrated HPGe detectors. Activation calculations were performed with the ALARA inventory code using the activations cross-sections from the Intermediate Energy Activation File IEAF-2001. The neutron spectrum at sample sport was combined from one measured at large distance and calculated by MCNPX for energies below the detector threshold. The comparison of calculated and measured induced activities reveals reasonable agreement for half of the detected radio-nuclides and large discrepancies for the other ones. The analysis of the dominant reactions indicates the need for updating the relevant cross-sections in the IEAF-2001 data library. [Copyright &y& Elsevier]

The differential cross section of elastic and inelastic scattering of 3He ions on the 13C nucleus has been measured at an energy of 37.9 MeV. By fitting the shape of the measured angular distribution of the elastic scattering the parameters of the optical model have been found. These parameters have been used for the DWBA calculations of angular distributions corresponding to excitations of the 13C levels 3.09(1/2+) MeV, 3.68(3/2−) MeV, 3.85(5/2+) MeV, 7.55(5/2−) MeV, 8.84(1/2−) MeV and 11.85(7/2+) MeV. Several sets of transition densities calculated with different effective nucleon-nucleon interactions and six different M3Y interactions between a projectile and target nucleon have been tested. Analysis of the inelastic scattering of 135 MeV protons on 13C is also presented, which enabled us to obtain additional information about the tested structure models. [ABSTRACT FROM AUTHOR]

Abstract: An assessment of the activation caused by deuteron and proton beam losses in the accelerating components and by the full beam current in the beam dump during the International Fusion Material Irradiation Facility (IFMIF) prototype accelerator testing period was performed. The losses along the acceleration line were calculated by the Monte Carlo codes PARTMTEQM and PARMILA. The activation analysis was performed by the European Activation System EASY-2007 recently upgraded to include charge particle-induced reactions. The deuteron and proton activation cross-sections from this library for the dominant reactions were validated against experimental data demonstrating an acceptable uncertainty. The transport of the decaying gamma-rays and the calculation of the radiation dose rate on the external surfaces of the accelerator tank and beam dump have been performed by the MCNP-5 code. The results show that activation induced by the deuteron and proton beam losses in the accelerating components are below the legal transport and hands-on limits. This is also proved to be the case for the proposed design of the beam dump employing the tungsten as ions stopper to accommodate 1.2MW beam power. [Copyright &y& Elsevier]

Abstract: This work proposes to use the activation foil method for the neutron spectrum determination in the IFMIF facility. Suitable elements were selected to this end with dosimetry reactions having thresholds and effective cross sections covering the whole IFMIF energy range up to 55MeV. The available evaluated nuclear data libraries and experimental data were carefully screened to select appropriate dosimetry cross sections with uncertainties as low as possible. For the determination of the neutron spectra from the induced γ-activities the unfolding code SAND-II was applied after having it modified for the use of the selected dosimetry cross sections above 20MeV. This approach was tested by measuring the white neutron spectrum at the cyclotron of Nuclear Physics Institute (Řež), where neutrons up to 35MeV energy were generated by a 37MeV proton beam impinging on a heavy water target. The paper concludes with recommendations for the procedure for determining the neutron energy differential flux in the IFMIF test cell with respect to the size of the dosimetry foils, the irradiation time and the expected induced activities. [Copyright &y& Elsevier]

The 13C(p, γ)14N radiative capture reaction is analyzed within the R-matrix approach with the aim to determine the astrophysical S factor. The low-energy astrophysical S factor has important contributions from both resonant and nonresonant captures. The contribution of the nonresonant component of the transition to a particular 14N bound state is expressed in terms of the asymptotic normalization coefficient (ANC). The experimental ANCs induced from the 13C(14N, 13C)14N and 13C(3He, d)14N reactions are used in the analysis. The fits of the calculated S factors to the experimental data are sensitive to the ANC values and are used to test the extracted ANCs. It is found that the ANCs determined from the transfer reactions provide the best fit for transitions to all the states in 14N, except for the third excited state. The obtained astrophysical factor, S(0)=7.6±1.1 keV b, is in excellent agreement with published values. [Copyright &y& Elsevier]

The indirect method of determining astrophysical nuclear reaction rates is discussed. The overall normalization of the astrophysical S-factor for such reactions may be determined from one quantity, the asymptotic normalization coefficient of the overlap function of the bound state wave functions for the initial and final channels. These coefficients can be found also from peripheral transfer reactions whose amplitudes are determined by the same overlap function as the amplitudes of the corresponding astrophysical radiative capture processes. The experimental test of this approach and the last results of S17 measurements are presented. [ABSTRACT FROM AUTHOR]

Angular distributions of protons, deuterons, tritons and alpha particles emitted in the d + 9Be reaction at Elab = 19.5 and 35.0 MeV have been measured. The elastic scattering channel is analysed in the framework of both the optical model and the coupled-channel approach. The interaction potential of the d + 9Be system is calculated in the framework of the Double-Folding model using the α + α + n three-body wave function of the 9Be nucleus. The (d, p) and (d, t) one-nucleon-transfer reactions are analysed within the coupled-reaction-channel approach. The spectroscopic amplitudes for the different nuclear cluster configurations are calculated. Differential cross sections for the reaction channel 9Be()7Li are calculated including all possible reaction mechanisms within the coupled-reaction-channel method. Corresponding contributions to the cross sections are analysed. [ABSTRACT FROM AUTHOR]

The influence of the mechanisms of nuclear reactions on the population of isomeric states 44mSc (6+), 196mAu (12-), 198mAu (12-), 195mHg (13/2+), 197mHg (13/2+), 198mTl (7+), 196mTl (7+) obtained in reactions induced by beams of weakly bound and radioactive nuclei 3He, 6Li, 6He are studied. In direct reactions involving cluster transfer, the isomeric ratio is lower than in reactions, where fusion with evaporation of nucleons occurs. In the case of charge exchange reactions with beams of weakly bound nuclei, the isomeric ratios change only slightly. If the reaction Q-value is positive, neutron transfer is observed with high probability in interactions of all weakly bound nuclei with both light and heavy stable target nuclei. Cross sections and their isomeric ratios differ for nucleon stripping and pickup channels owing to the difference in population of excited single-particle and collective states. [ABSTRACT FROM AUTHOR]

We have measured the differential cross-sections for the elastic as well as inelastic scattering populating the 2.43 MeV (5 / 2 −) excited state in 9 Be using 3 He beams at energies of 30, 40 and 47 MeV on a 9 Be target. The experimental results for the elastic scattering were analyzed within the framework of the optical model using the Woods–Saxon and double-folding potentials. The theoretical calculations for the concerned excited states were performed using the coupled-channel method. The optimal deformation parameters for the excited states of 9 Be nucleus were extracted. [ABSTRACT FROM AUTHOR]

The 10B(p,α0)7Be bare nucleus astrophysical S(E) factor has been measured for the first time at energies from about 100 keV down to about 5 keV by means of the Trojan Horse method (THM). In this energy region, the S(E) factor is strongly dominated by the 8.699 MeV 11C level (Jπ = 5/2+), producing an s-wave resonance centered at about 10 keV in the entrance channel. Up to now, only the high-energy tail of this resonance has been measured, while the low-energy trend is extrapolated from the available direct data. The THM has been apphed to the quasifree ²H(10B,α0 7Be)n reaction induced at a boron-beam energy of 24.5 MeV. An accurate analysis leads to the determination of the 10B(p,α0)7Be S(E) factor and of the corresponding electron screening potential Ue, thus giving for the first time an independent evaluation of it. [ABSTRACT FROM AUTHOR]

In the last decades, the Trojan Horse method (THM) has played a crucial role for the measurement of several particle (both neutron and charged one) induced cross sections for reactions of astrophysical interest. To better understand its cornerstones and its applications to physical cases, many tests were performed to verify all its properties and the possible future perspectives. The Trojan Horse nucleus invariance proves the relatively simple approach allowed by the pole approximation and sheds light in the involved reaction mechanisms. Here we shortly review the complete work for the binary H(d,p)H, Li(d, α)He, Li(p, α)He, Li(p, α)He reactions, by using the quasi free reactions after break-ups of different nuclides. Results are compared assuming the Li and He break-up in the case of the d(d,p)t, Li(d, α)He reactions and considering the H and He break-up for Li(p, α)He, Li(p, α)He reactions. These results, regardless of the Trojan Horse particle or the break-up scheme, confirms the applicability of the standard description of the THM and suggests the independence of binary indirect cross section on the chosen Trojan Horse nuclei for a whole spectra of different cases. This gives a strong basis for the understanding of the quasi-free mechanism which is the foundation on which the THM lies. [ABSTRACT FROM AUTHOR]

The cross sections of the 2H(d,p)3H and 2H(d,n)3He reactions have been measured via the Trojan Horse method applied to the quasi-free 2H(3He,p3H)1H and 2H(3He,n3He)1H processes at 18 MeV off the proton in 3He. For the first time, the bare nucleus S(E) factors have been determined from 1.5 MeV, across the relevant region for standard Big Bang nucleosynthesis, down to the thermal energies of deuterium burning in the pre-main-sequence (PMS) phase of stellar evolution, as well as of future fusion reactors. Both the energy dependence and the absolute value of the S(E) factors deviate by more than 15% from the available direct data and existing fitting curves, with substantial variations in the electron screening by more than 50%. As a consequence, the reaction rates for astrophysics experience relevant changes, with a maximum increase of up to 20% at the temperatures of the PMS phase. From a recent primordial abundance sensitivity study, it turns out that the 2H(d,n)3He reaction is quite influential on 7Li, and the present change in the reaction rate leads to a decrease in its abundance by up to 10%. The present reaction rates have also been included in an updated version of the FRANEC evolutionary code to analyze their influence on the central deuterium abundance in PMS stars with different masses. The largest variation of about 10%-15% pertains to young stars (⩽1 Myr) with masses ⩾1 M☼. [ABSTRACT FROM AUTHOR]

The 14C + n ↔ l5C system has been used as a test case in the evaluation of a new method to determine spectroscopic factors that uses the asymptotic normalization coefficient (ANC). The method proved to be unsuccessful for this case. As part of this experimental program, the ANCs for the 15C ground state and first excited state were determined using a heavy-ion neutron transfer reaction as well as the inverse kinematics (d,p) reaction, measured at the Texas A&M Cyclotron Institute. The values C²id5/2 = 1.88 ± 0.18 fm 1 for the ground state and C²id5/2 = 4.25 ± 0.38 × 10-3 fm-1 for the first excited state (Eexc = 740 keV) were obtained. The ANCs were used to evaluate the astrophysical direct neutron capture rate on 14C, which was then compared with the most recent direct measurement and found to be in good agreement. A study of the 15C SF via its mirror nucleus 15F and a new insight into deuteron stripping theory are also presented. [ABSTRACT FROM AUTHOR]

The reaction 17O(n, α)14C was studied at energies from Ec,m = 0 to Ec,m = 350 keV by using the quasifree deuteron breakup in the three-body reaction 17O + d -> α + 14C + p, which extended the Trojan Horse indirect method (THM) to neutron-induced reactions. It is found that the 18O excited state at E* = 8.125 ± 0.002 MeV, observed in THM experiments, is absent in the direct measurement because of its high centrifugal barrier. The angular distributions of the populated resonances have been measured by using this method. The results unambiguously indicate the ability of the THM to overcome the centrifugal barrier suppression effect and to pick out the contribution of the bare nuclear interaction [ABSTRACT FROM AUTHOR]

Abstract: The bare nucleus factors for the and reactions have been measured for the first time via the Trojan Horse Method off the proton in 3He 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 factors deviate by more than 15% from available direct data with new values of for and for . 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. [Copyright &y& Elsevier]

The Trojan horse nucleus invariance for the binary reaction cross section extracted from the Trojan horse reaction was tested using the quasifree ³He(6Li(α,α)H and ³He(7Li,αα)²H reactions. The cross sections for the 6Li(d,α)4He and 7Li(p,α)4He binary processes were extracted in the framework of the plane wave approximation. They are compared with direct behaviors as well as with cross sections extracted from previous indirect investigations of the same binary reactions using deuteron as the Trojan horse nucleus instead of ³He. The very good agreement confirms the applicability of the plane wave approximation which suggests the independence of the binary indirect cross section on the chosen Trojan horse nucleus, at least for the investigated cases. [ABSTRACT FROM AUTHOR]

We address two important indirect techniques, the asymptotic normalization coefficient (ANC) and the Trojan Horse (TH) methods. We discuss the application of the ANC technique to determine the astrophysical factor for the 13C(α, n)16O reaction which is one of the neutron generators for the s processes in AGB stars. The TH method is a unique indirect technique allowing one to measure astrophysical S factors for rearrangement reactions down to astrophysically relevant energies. We derive equations connecting the cross sections for the binary direct and resonant reactions determined from the indirect TH reactions to direct cross sections measurements. [Copyright &y& Elsevier]

The Trojan Horse Method (THM) was applied to the 3He+ 7Li interaction in order to investigate the quasi-free 7Li(p,α)4He reaction. The three-body experiment was performed at 33 MeV corresponding to a 7Li-p relative energy ranging from 50keV to 7MeV. The extracted 7Li(p,α)4He quasi-free cross-section was compared with the behavior of direct data, as well as with the result of a previous THM investigation on the 7Li(p,α)4He reaction off the neutron in 2H. 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. [ABSTRACT FROM AUTHOR]

Owing to the presence of the Coulomb barrier at astrophysically relevant kinetic energies it is very difficult, or sometimes impossible, to measure astrophysical reaction rates in the laboratory. That is why different indirect techniques are being used along with direct measurements. Here we address two important indirect techniques, the asymptotic normalization coefficient (ANC) and the Trojan Horse (TH) methods. We discuss the application of the ANC technique for calculation of the astrophysical processes in the presence of subthreshold bound states, in particular, two different mechanisms are discussed: direct capture to the subthreshold state and capture to the low-lying bound states through the subthreshold state, which plays the role of the subthreshold resonance. The ANC technique can also be used to determine the interference sign of the resonant and nonresonant (direct) terms of the reaction amplitude. The TH method is unique indirect technique allowing one to measure astrophysical rearrangement reactions down to astrophysically relevant energies. We explain why there is no Coulomb barrier in the sub-process amplitudes extracted from the TH reaction. The expressions for the TH amplitude for direct and resonant cases are presented. [ABSTRACT FROM AUTHOR]

The H(d,p)H and H(d,n)He reactions have been indirectly studied by means of the Trojan Horse Method applied to the quasi-free H(He, pH)H H(He, nHe)H reaction at 18 MeV of beam energy. This is the first experiment where the spectator (here H) has been detected in coincidence with the charged participant, avoiding the limitations of standard neutron detectors. The d − d relative energy has been measured from 1.5 MeV down to 2 keV, at center of mass angles from 40° to 170°. Indirect angular distributions are compared with the direct behaviour in the overlapping regions. [ABSTRACT FROM AUTHOR]

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 He (n,p) 3 H reaction after a detailed study of the 2 H ( 3 He ,pt)H three-body process. Data extracted from the present measurement are compared with other published sets. [ABSTRACT FROM AUTHOR]

Abstract: Direct measurements in the last decades have highlighted a new problem related to the lowering of the Coulomb barrier between the interacting nuclei due to the presence of the “electron screening” in the laboratory measurements. It was systematically observed that the presence of the electronic cloud around the interacting ions in measurements of nuclear reactions cross sections at astrophysical energies gives rise to an enhancement of the astrophysical S(E)-factor as lower and lower energies are explored [H. Assenbaum, K. Langanke, C. Rolfs, Z. Phys. 327 (1987) 461]. Moreover, at present such an effect is not well understood as the value of the potential for screening extracted from these measurements is higher than the upper limit of theoretical predictions (adiabatic limit). On the other hand, the electron screening potential in laboratory measurement is different from that occurring in stellar plasmas thus the quantity of interest in astrophysics is the so-called “bare nucleus cross section”. This quantity can only be extrapolated in direct measurements. These are the reasons that led to a considerable growth on interest in indirect measurement techniques and in particular the Trojan Horse Method (THM) [G. Baur, Phys. Lett. B 178, (1986) 135; S. Cherubini et al. Ap. J. 457, (1996) 855] Results concerning the bare nucleus cross sections measurements will be shown in several cases of astrophysical interest. In those cases the screening potential evaluated by means of the THM will be compared with the adiabatic limit and results arising from extrapolation in direct measurements. [Copyright &y& Elsevier]