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, ) reaction is investigated at the energies typical of the primordial nucleosynthesis by means of the Trojan Horse Method applied to the 2H(7Be, )p quasi-free reaction. The 7Be(n, )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.
Carbon burning powers scenarios that influence the fate of stars, such as the late evolutionary stages of massive stars 1 (exceeding eight solar masses) and superbursts from accreting neutron ...stars2,3. It proceeds through the 12C + 12C fusion reactions that produce an alpha particle and neon-20 or a proton and sodium-23-that is, 12C(12C, α)20Ne and 12C(12C, p)23Na-at temperatures greater than 0.4 × 109 kelvin, corresponding to astrophysical energies exceeding a megaelectronvolt, at which such nuclear reactions are more likely to occur in stars. The cross-sections 4 for those carbon fusion reactions (probabilities that are required to calculate the rate of the reactions) have hitherto not been measured at the Gamow peaks 4 below 2 megaelectronvolts because of exponential suppression arising from the Coulomb barrier. The reference rate 5 at temperatures below 1.2 × 109 kelvin relies on extrapolations that ignore the effects of possible low-lying resonances. Here we report the measurement of the 12C(12C, α0,1)20Ne and 12C(12C, p0,1)23Na reaction rates (where the subscripts 0 and 1 stand for the ground and first excited states of 20Ne and 23Na, respectively) at centre-of-mass energies from 2.7 to 0.8 megaelectronvolts using the Trojan Horse method6,7 and the deuteron in 14N. The cross-sections deduced exhibit several resonances that are responsible for very large increases of the reaction rate at relevant temperatures. In particular, around 5 × 108 kelvin, the reaction rate is boosted to more than 25 times larger than the reference value 5 . This finding may have implications such as lowering the temperatures and densities 8 required for the ignition of carbon burning in massive stars and decreasing the superburst ignition depth in accreting neutron stars to reconcile observations with theoretical models 3 .
•The device shows promising qualities as control system for 2-D relative dosimetry thanks to its characteristics.•Experimental results demonstrate that the accuracy of the system is very close to the ...existing dosimetric devices.•At 100 MeV proton energy, the agreement between our system and the EBT3 is within 6% for all the investigated parameters.•The use of the device can be obviously extended to other ion beams, where the lateral penumbras are expected to be sharper.
The main purpose of this work is the inter-comparison between different devices devoted to the transversal dose profile recostruction for daily QA tests in proton therapy.
The results obtained with the EBT3 radiochromic films, used as a reference, and other common quality control devices, have been compared with those obtained with a beam profiling system developed at the “Laboratori Nazionali del Sud” of Italian Institute for Nuclear Physics (INFN-LNS, Catania, Italy). It consists of a plastic scintillator screen (thickness 1 mm), mounted perpendicularly to the beam axis and coupled with a highly sensitive CCD detector in a light-tight box.
The tests, carried out both at the INFN-LNS and Trento Proton Therapy Center facilities, show, in general, a good agreement between the different detectors. The beam profiling system, in particular, appears to be a promising quality control device for 2-D relative dosimetry, because of its linear response in a dose rate range useful for proton therapy treatments, its high spatial resolution and its short acquisition and processing time.
In equation (1) of this Letter, the closing bracket was missing; in Extended Data Fig. 1 and the accompanying legend, 'Φ(pd)' should have been 'Φ2(pd)', and in the Methods the text "Odd J assignments ...are uncertain by ±1." has been added. These errors have all been corrected online.
In this work we present the response of a new large volume 4H Silicon Carbide (SiC) detector to 14 MeV neutrons. The device has an active thickness of 100μm (obtained by epitaxial growing) and an ...active area of 25 mm2. Tests were conducted at the ENEA-Frascati Neutron Generator facility by using 14.1 MeV neutrons. The SiC detector performance was compared to that of Single-Crystal Diamond (SCD) detectors. The SiC response function was successfully measured and revealed a very complex structure due to the presence in the detector of both Silicon and Carbon atoms. Nevertheless, the flexibility in the SiC manufacturing and the new achievements in terms of relatively large areas (up 1x1 cm2) and a wide range of thicknesses makes them an interesting alternative to diamond detectors in environments where limited space and high neutron fluxes are an issue, i.e. modern neutron cameras or in-vessel tokamak measurements for the new generation fusion machines such as ITER. The absence of instabilities during neutron irradiation and the capability to withstand high neutron fluences and to follow the neutron yield suggest a straightforward use of these detectors as a neutron diagnostics.
With the introduction of the Trojan Horse Method, nuclear cross sections between charged particles at astrophysical energies can now be measured. Here the basic features of the method are recalled ...together with recent results relevant for Nuclear Astrophysics. New applications in connection with plasma physics and industrial energy production are discussed.
The {sup 13}C(α, n){sup 16}O reaction is the neutron source for the main component of the s-process, responsible for the production of most of the nuclei in the mass range 90 ∼< A ∼< 208. This ...reaction takes place inside the helium-burning shell of asymptotic giant branch stars, at temperatures ∼< 10{sup 8} K, corresponding to an energy interval where the {sup 13}C(α, n){sup 16}O reaction is effective in the range of 140-230 keV. In this regime, the astrophysical S(E)-factor is dominated by the –3 keV sub-threshold resonance due to the 6.356 MeV level in {sup 17}O, giving rise to a steep increase in the S-factor. Its contribution is still controversial as extrapolations, e.g., through the R-matrix and indirect techniques such as the asymptotic normalization coefficient (ANC), yield inconsistent results. The discrepancy amounts to a factor of three or more precisely at astrophysical energies. To provide a more accurate S-factor at these energies, we have applied the Trojan horse method (THM) to the {sup 13}C({sup 6}Li, n {sup 16}O)d quasi-free reaction. The ANC for the 6.356 MeV level has been deduced through the THM as well as the n-partial width, allowing us to attain unprecedented accuracy for the {sup 13}C(α, n){sup 16}O astrophysical factor. A larger ANC for the 6.356 MeV level is measured with respect to the ones in the literature, (C-tilde{sub α{sup 1}{sup 3}C}{sup 17O(1/2+)2} = 7.7 ± 0.3{sub stat} {sub -1.5}{sup +1.}|6 norm fm{sup –1}, yet in agreement with the preliminary result given in our preceding letter, indicating an increase of the {sup 13}C(α, n){sup 16}O reaction rate below about 8 × 10{sup 7} K if compared with the recommended values. At ∼10{sup 8} K, our reaction rate agrees with most of the results in the literature and the accuracy is greatly enhanced thanks to this innovative approach.
A study of the response of three ΔE-E telescopes to fragments produced in nuclear interactions at 40AMeV is presented. All the employed telescopes feature silicon carbide (SiC) detectors for at least ...one detection stage. Two identification methods have been used and their performance discussed: the ΔE-E technique and the Pulse Shape Analysis technique (for identification of nuclear fragments stopped in a single SiC layer). Identification capabilities similar to those obtained with the best available silicon detectors have been found for the SiC detector prototypes studied in this work.
This work aim to prepare a program of studies on nuclear physics and astrophysics, which will be conducted at the new ELI-NP Laser facility, which actually is under construction in Bucharest, ...Romania. For the arguments treated, such activity has required also a multidisciplinary approach and knowledge in the fields of nuclear physics, astrophysics, laser and plasma physics join with also some competences on solid state physics related to the radiation detection. A part of this work has concerned to the experimental test, which have been performed in several laboratories and in order to study and increase the level of knowledge on the different parts of the project. In particular have been performed studies on the laser matter interaction at the ILIL laboratory of Pisa Italy and at the LENS laboratory in Catania, where (by using different experimental set-ups) has been investigated some key points concerning the production of the plasma stream. Test has been performed on several target configurations in terms of: composition, structure and size. All the work has been devoted to optimize the conditions of target in order to have the best performance on the production yields and on energies distribution of the inner plasma ions. A parallel activity has been performed in order to study the two main detectors, which will constitute the full detections system, which will be installed at the ELI-NP facility.
The (19)F(p, alpha)(16)O reaction is an important fluorine destruction channel in the proton-rich outer layers of asymptotic giant branch (AGB) stars and it might also play a role in ...hydrogen-deficient post-AGB star nucleosynthesis. So far, available direct measurements do not reach the energy region of astrophysical interest (E(cm) less than or similar to 300 keV), because of the hindrance effect of the Coulomb barrier. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution to the (2)H((19)F, alpha(16)O)n and the (19)F((3)He, alpha(16)O)d reactions. The TH measurement of the alpha(0) channel shows the presence of resonant structures not observed before, which cause an increase of the reaction rate at astrophysical temperatures up to a factor of 1.7, with potential consequences for stellar nucleosynthesis.
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