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To study the cosmic ray muon tomographic imaging of high-Z material with Micromegas-based tracking system. A high-spatial-resolution tracking system was set up with the micro-mesh gaseous structure (Micromegas) detectors in order to study the muon tomographic imaging technique. Six layers of 90 mm × 90 mm one-dimensional readout Micromegas were used to construct a tracking system. The imaging test using some metallic bars was performed with cosmic ray muons. A two-dimensional imaging of the test object was presented with a newly proposed ratio algorithm. The result of this work shows that the ratio algorithm is well performed.

The $^{2}\mathrm{H}(d,p)^{3}\mathrm{H}$ bare nucleus astrophysical $S(E)$ factor has been measured indirectly at energies from about 500 keV down to several keV by means of the Trojan-horse method applied to the $^{2}\mathrm{H}(^{6}\mathrm{Li},pt)^{4}\mathrm{He}$ quasifree reaction induced at 11 MeV. The obtained results are compared with direct data as well as with previous indirect investigation of the same binary reactions. It shows that the precision of $S(E)$ data in the low-energy range extracted via the same Trojan-horse nucleus [$^{6}\mathrm{Li}=(d\ensuremath{\bigoplus}\ensuremath{\alpha})$] increases while the incident energy of the virtual binary process approaches the zero-quasi-free-energy point. The very good agreement between data extracted from different Trojan-horse nuclei $[^{6}\mathrm{Li}=(d\ensuremath{\bigoplus}\ensuremath{\alpha})$ vs $^{3}\mathrm{He}=(d\ensuremath{\bigoplus}p)]$ gives a strong updated test for the independence of the binary indirect cross section on the chosen Trojan-horse nucleus at low energies.

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.

The Coulomb barrier and electron screening cause difficulties in directly measuring nuclear reaction cross sections of charged particles in astrophysical energies. The Trojan-horse method has been introduced to solve the difficulties as a powerful indirect tool. In order to understand experimental spectra better, Geant4 is employed to simulate the method for the first time. Validity and reliability of the simulation are examined by comparing the experimental data with simulated results. The Geant4 simulation can give useful information to understand the experimental spectra better in data analysis and is beneficial to the design for future related experiments., Comment: 4 pages, 5 figures

The low-energy bare-nucleus cross section for ${}^{9}\mathrm{Be}(p,\ensuremath{\alpha}){}^{6}\mathrm{Li}$ has been extracted by means of the Trojan horse method (THM) applied to the ${}^{2}\mathrm{H}({}^{9}\mathrm{Be}$, $\ensuremath{\alpha},{}^{6}\mathrm{Li})n$ reaction at a beam energy of $^{9}\mathrm{Be}$ of 22.35 MeV. For the first time, we assume an intermediate process, ${}^{9}\mathrm{Be}+{}^{2}\mathrm{H}\ensuremath{\rightarrow}{}^{9}\mathrm{Be}+p+n$, and considered this process as one criterion of the quasifree condition. Accordingly, sequential decay processes were eliminated. The derived astrophysical $S(E)$ factor for the two-body process ${}^{9}\mathrm{Be}(p,\ensuremath{\alpha}){}^{6}\mathrm{Li}$ is compared with that obtained from direct experiments. We have found good agreement between the two results, leading to an improved determination of the $S(E)$ with $S(0)=21.0\ifmmode\pm\else\textpm\fi{}0.8$ MeV b. Furthermore, the electron screening potential energy ${U}_{e}=676\ifmmode\pm\else\textpm\fi{}86$ eV has also been extracted in a model-independent way by comparing the direct and THM data. The value is significantly higher than that predicted by current theoretical models, whereas it is lower than $\mathit{Ue}\ensuremath{\simeq}830$ eV, which was extracted from direct measurements with inclusion of the ${E}_{\mathrm{c}.\mathrm{m}.}=\ensuremath{-}23$ keV subthreshold resonance.

A new measurement of the 11B(p,?0)8Be has been performed applying the Trojan horse method (THM) to the 2H(11B,?80Be)n quasi-free reaction induced at a laboratory energy of 27 MeV. The astrophysical S(E) factor has been extracted from ?600 keV down to zero energy by means of an improved data analysis technique and it has been compared with direct data available in the literature. The range investigated here overlaps with the energy region of the light element LiBeB stellar burning and with that of future aneutronic fusion power plants using the 11B+p fuel cycle. The new investigation described here confirms the preliminary results obtained in the recent TH works. The origin of the discrepancy between the direct estimate of the 11B(p,?0)8Be S(E)-factor at zero energy and that from a previous THM investigation is quantitatively corroborated. The results obtained here support, within the experimental uncertainties, the low-energy S(E)-factor extrapolation and the value of the electron screening potential deduced from direct measurements.

The identification of the quasifree mechanism is very important in the application of the Trojan horse method (THM). We present here a new phenomenological approach for selecting quasifree events in Trojan horse experiments. This approach is based on the assumption that an intermediate break-up process exists. Under certain conditions, the break-up can be considered as quasifree and events can be selected from nonnegative real number solutions of energy and momentum conservation equations. We use experimental data of Wen Q G et al (2008 Phys. Rev. C 78 035805) to preliminarily test the validity of this approach in the THM.

Owing the presence of the Coulomb barrier at astrophysically relevant energies, it is very difficult, or sometimes impossible to measure reaction rates for charged particle induced reactions. Moreover due to the presence of the electron screening effect in direct measurements, the relevant nuclear input for astrophysics, i.e. the bare nucleus S(E)-faetor, can hardly be extracted. This is why different indirect techniques are being used along with direct measurements. The THM is an unique: indirect technique which allows one to measure reactions cross sections of astrophysical interest down the thermal energies typical of the different scenarios. The basic principle and a review of the main applications of the Trojan Horse Method are given. The applications aiming at the extraction of the bare Sb(E) astrophysical factor and electron screening potentials Ue for several two body processes are discussed.