As a preliminary step towards measurements of the C-12 + (12) C reactions at astrophysical energies, we investigate the behaviour of targets under beam bombardment, specifically the quantitative relation between hydrogen and deuterium content of different carbon targets and target temperature. Experiments have taken place at the CIRCE accelerator in Caserta, Italy and preliminary results are presented here.

C-12(C-12; alpha)Ne-20 and C-12(C-12;p)Na-23 are the most important reactions during the carbon burning phase in stars. Direct measurements at the relevant astrophysical energy (E=1.5 +/- 0.3MeV) are very challenging because of the extremely small cross sections involved and of the high beam-induced background originating from impurities in the targets. In addition, persistent resonant structures at low energies are not well understood and make the extrapolation of the cross section from high energy data very uncertain. As a preliminary step towards the measurements of the C-12(C-12;alpha)Ne-20 and C-12(C-12;p)Na-23 reactions we intend to investigate the behaviour of targets under beam bombardment, specifically the quantitative measurement of hydrogen and deuterium content of highly pure stable carbon targets in relation to target temperature. Experiments are taking place at the CIRCE accelerator in Caserta, Italy and preliminary results are presented here.

Summary 7Be is a key radionuclide for investigation of several astrophysical processes and phenomena. In addition, it is used as a tracer in wear measurements. It is produced in considerable amounts in the cooling water (D2O) of the Spallation Induced Neutron Source (SINQ) facility at PSI by spallation reactions on 16O with the generated fast neutrons. A shielded ion-exchange filter containing 100 mL of the mixed-bed ion exchanger LEWATIT was installed as a bypass for the cooling water into the cooling loop of SINQ for three months. The collected activity of 7Be was in the range of several hundred GBq. Further, the 7Be was separated and purified in a hot-cell remotely-controlled using a separation system installed. With the exception of 10Be, radioactive byproducts can be neglected, so that this cooling water could serve as an ideal source for highly active 7Be-samples. The facility is capable of producing 7Be with activities up to 1 TBq per year. The 7Be sample preparation is described in detail and the possible uses are discussed. In particular some preliminary results of 7Be ion beam production are presented.

Stellar models show an exceptional sensitivity on the cross section of 12C(α,γ)16O and a precision of about 10% is required to provide adequate constraints on stellar evolution. A measurement at the astrophysical energy, E0≈300 keV, is unfeasible due to the extremely low cross section. Furthermore, the extrapolation of existing high-energy data is complicated by a complex reaction scheme. Besides direct measurements of 12C(α,γ)16O, the β-delayed α-decay of 16N and 12C + 4He elastic scattering provide additional information for the relevant 16O levels. In this Letter we present a new R-matrix analysis, where systematic uncertainties of the included data sets, in particular the absolute normalization, were treated in the fitting procedure. The data were selected according to rigorous criteria in order to reduce uncontrolled systematic effects and, finally, a Monte Carlo approach was used to evaluate the uncertainty at astrophysical energy. The resulting S factor, S(300)=161±19stat−2sys+8 keVb, is, for the first time, close to the required precision.

The reaction $^{17}$O$(p,\gamma)^{18}$F influences hydrogen-burning nucleosynthesis in several stellar sites, such as red giants, asymptotic giant branch (AGB) stars, massive stars and classical novae. In the relevant temperature range for these environments ($T_{9}=0.01-0.4), the main contributions to the rate of this reaction are the direct capture process, two low lying narrow resonances ($E_{r}=65.1$ and 183 keV) and the low-energy tails of two broad resonances ($E_{r}=557$ and 677 keV). Previous measurements and calculations give contradictory results for the direct capture contribution which in turn increases the uncertainty of the reaction rate. In addition, very few published cross section data exist for the high energy region that might affect the interpretation of the direct capture and the contributions of the broad resonances in the lower energy range. This work aims to address these issues. The reaction cross section was measured in a wide proton energy range ($E_{c.m.}=345$ - 1700 keV) and at several angles ($\theta_{lab}=0^{\circ},45^{\circ},90^{\circ},135^{\circ}$). The observed primary $\gamma$-transitions were used as input in an $R$-matrix code in order to obtain the contribution of the direct capture and the two broad resonances to the low-energy region. The extrapolated S-factor from the present data is in good agreement with the existing literature data in the low-energy region. A new reaction rate was calculated from the combined results of this work and literature S-factor determinations. Resonance strengths and branchings are reported for several $^{18}$F states. We were able to extrapolate the astrophysical S-factor of the reaction $^{17}$O$(p,\gamma)^{18}$F at low energies from cross section data taken at higher energies. No significant changes in the nucleosynthesis are expected from the newly calculated reaction rate.

We report here on the direct generation of a CN− ion beam for the production of a N ion beam to be used in nuclear astrophysics measurements. The procedure relies on the production of CN− ion beam with a SNICS source starting from several appropriate substrates containing CN− triple bond. Several of the investigated substrates showed a higher beam intensity with respect to the common N beam production from a cathode of BN plus graphite. Best results in terms of analyzed beam intensity were observed with K3Fe(CN)6 and KSCN cathodes. Use of the latter compound is particularly appealing because of the easy availability of mass-15 enriched molecule.

The radiative capture reaction C-12(alpha, gamma)O-16 has been investigated in the energy range E = 3.3 to 4.5 MeV. This experiment focused in particular on the cascade transition to the 0(+) state at E-x= 6.05 MeV in O-16 and was performed by detecting the capture gamma-rays with a Nal detector array at the windowless He-4 gas target of the recoil mass separator ERNA in coincidence with the O-16 ejectiles. The 6.05 MeV transition has been considered recently as a component accounting for up to 15% of the C-12(alpha, gamma)O-16 total cross section at astrophysical energies. The arrangement of the detector array yielded additional information on the gamma-ray multipolarity, i.e. the ratio sigma(E2)/sigma(E1), and it was found that the 6.05 MeV transition is entirely E2 in the studied energy range. The results for this transition are analyzed in an R-matrix formalism and extrapolated to the relevant Gamow energy of stellar helium burning. E-0 similar or equal to 300 key. In contrast to a previous analysis, the present extrapolation suggests a negligible contribution from this amplitude, S-6.05(300) < 1 keV b. Additional data for cascade transitions to excited states at E-x = 6.13, 6.92, and 7.12 MeV, respectively, as well as to the ground state were obtained and the corresponding S factors in the studied energy range are given. (C) 2011 Elsevier B.V. All rights reserved.

The set of fusion reactions C-12 + C-12 play a critical role in several astrophysical processes. In a recent experiment, the fusion reactions C-12 + C-12 have been studied at E-CM = 2.10 to 4.75 MeV by gamma-ray spectroscopy using a C target of ultra-low hydrogen contamination. The deduced astrophysical (S) over tilde (E) factor exhibits previously unknown resonances at E <= 3.0 MeV, in particular a strong and narrow resonance at E = 2.14 MeV, the high-energy tail of the Gamow peak. Current extrapolations of the reaction rate, which assume that the astrophysical (S) over tilde (E) factor varies smoothly with energy within the Gamow window, are thus subject to significant uncertainty.

The reaction He-3(alpha, gamma)Be-7 plays a key role for the understanding of the production of Li-7 in Big Bang nucleosynthesis as well as for the high energy component of the solar neutrino spectrum. The uncertainty in its absolute cross-section arises from systematic differences of the available data sets. In various experiments the cross-section was measured by the detection of the prompt gamma-rays or by the off-line observation of the gamma-rays following the Be-7 electron capture; in a few cases both observations were carried out.We report on a new approach based on the use of the recoil separator ERNA (European Recoil separator for Nuclear Astrophysics) to detect directly the Be-7 recoils as well as the prompt gamma-rays in coincidence with the recoils. We present technical details of the experimental setup, such as a recirculating He-3 gas target, a TOF-E end detector, and a Nal detector array. In addition, the measurement of the separator acceptance is discussed and compared to the expected recoil emittance. The feasibility of the approach is demonstrated by sample spectra, indicating cross-section determinations of He-3(alpha, beta)Be-7 in the energy range E-cm = 0.7-3.3 MeV with high precision and accuracy. (C) 2008 Elsevier B.V. All rights reserved.

We report on a new lifetime measurement of the E-x = 6792 keV state in O-15 via the Doppler-shift attenuation method at the E = 259 keV resonance in the reaction N-14(p, gamma)O-15. This subthreshold state is of particular importance for the determination of the ground state astrophysical S factor of N-14(p, gamma)O-15 at stellar energies. The measurement technique has been significantly improved over that used in previous work. The conclusion of a finite lifetime drawn there cannot be confirmed with the present data. In addition, the lifetimes of the two states at E-x = 5181 and 6172 keV have been measured with the same technique in order to verify the experimental method. We observe an attenuation factor F(tau) > 0.98 for the E-x = 6172 and 6792 keV states, respectively, corresponding tau < 0.77 fs. The attenuation factor for the E-x = 5181 keV state results in F(tau) = 0.78 +/- 0.02 corresponding to tau = 8.4 +/- 1.0 fs, which is in excellent agreement with literature.

For the beta(-)-decay of Au-198 in a Au metallic environment the half-life was observed to be longer by 0.4 +/- 0.7% at room temperature (T = 293K) and by 4.0 +/- 0.7% when the metal was cooled to T = 12 K, both compared to the literature value of T (1/2) = 2.6943 +/- 0.0008d.