No Arabic abstract
Differential and angle-integrated cross sections for the $^{10}$B($n, {alpha}$)$^{7}$Li, $^{10}$B($n, {alpha}$$_{0}$)$^{7}$Li and $^{10}$B($n, {alpha}$$_{1}$)$^{7}$Li$^{*}$ reactions have been measured at CSNS Back-n white neutron source. Two enriched (90%) $^{10}$B samples 5.0 cm in diameter and ~85.0 ${mu}$g/cm$^{2}$ in thickness each with an aluminum backing were prepared, and back-to-back mounted at the sample holder. The charged particles were detected using the silicon-detector array of the Light-charged Particle Detector Array (LPDA) system. The neutron energy E$_{n}$ was determined by TOF (time-of-flight) method, and the valid ${alpha}$ events were extracted from the E$_{n}$-Amplitude two-dimensional spectrum. With 15 silicon detectors, the differential cross sections of ${alpha}$-particles were measured from 19.2{deg} to 160.8{deg}. Fitted with the Legendre polynomial series, the ($n, {alpha}$) cross sections were obtained through integration. The absolute cross sections were normalized using the standard cross sections of the $^{10}$B($n, {alpha}$)$^{7}$Li reaction in the 0.3 - 0.5 MeV neutron energy region. The measurement neutron energy range for the $^{10}$B($n, {alpha}$)$^{7}$Li reaction is 1.0 eV $le$ En < 2.5 MeV (67 energy points), and for the $^{10}$B($n, {alpha}$$_{0}$)$^{7}$Li and $^{10}$B($n, {alpha}$$_{1}$)$^{7}$Li$^{*}$ reactions is 1.0 eV $le$ En < 1.0 MeV (59 energy points). The present results have been analyzed by the resonance reaction mechanism and the level structure of the $^{11}$B compound system, and compared with existing measurements and evaluations.
Measured values of the differential cross sections for pion-nucleon charge exchange, pi- p --> pi0 n, are presented for pi- momenta of 103, 112, 120, 130, 139, 152, and 178 MeV/c. Complete angular distributions were obtained by using the Crystal Ball detector at the Alternating Gradient Synchrotron at Brookhaven National Laboratory. Statistical uncertainties of the differential cross sections vary from 3% to 6% in the backward angle region, and from 6% to about 20% in the forward region with the exception of the two most forward angles. The systematic uncertainties are estimated to be about 3% for all momenta.
We report on the measurement of the $^{7}$Be($n, p$)$^{7}$Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2) of the n_TOF facility at CERN. This reaction plays a key role in the lithium yield of the Big Bang Nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and showed a large discrepancy between each other. The measurement was performed with a Si-telescope, and a high-purity sample produced by implantation of a $^{7}$Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low-energy, relative to current evaluations, in the region of BBN interest the present results are consistent with the values inferred from the time-reversal $^{7}$Li($p, n$)$^{7}$Be reaction, thus yielding only a relatively minor improvement on the so-called Cosmological Lithium Problem (CLiP). The relevance of these results on the near-threshold neutron production in the p+$^{7}$Li reaction is also discussed.
We report on the measurement of the $^{7}$Be($n, p$)$^{7}$Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2) of the n_TOF facility at CERN. This reaction plays a key role in the lithium yield of the Big Bang Nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and showed a large discrepancy between each other. The measurement was performed with a Si-telescope, and a high-purity sample produced by implantation of a $^{7}$Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low-energy, relative to current evaluations, in the region of BBN interest the present results are consistent with the values inferred from the time-reversal $^{7}$Li($p, n$)$^{7}$Be reaction, thus yielding only a relatively minor improvement on the so-called Cosmological Lithium Problem (CLiP). The relevance of these results on the near-threshold neutron production in the p+$^{7}$Li reaction is also discussed.
The quantification of isotopes content in materials is extremely important in many research and industrial fields. Accurate determination of boron concentration is very critical in semiconductor, superconductor and steel industry, in environmental and medical applications as well as in nuclear and astrophysics research. The detection of B isotopes and of their ratio in synthetic and natural materials may be accomplished by gamma spectroscopy using the $^{10}$B(p,$alpha_1 gamma$)$^7$Be and $^{11}$B(p,$gamma$)$^{12}$C reactions at low proton energy. Here, the $^{10}$B(p,$alpha_1 gamma$)$^7$Be cross section is reported in the center of mass energy range 0.35 to 1.8 MeV. The $E_gamma$= 429 keV $gamma$ rays were detected at 45$^circ$ and 90$^circ$ using a NaI(Tl) and an HPGe detectors, respectively. In the presented energy range, previous cross sections data revealed discrepancies and normalisation issues. Existing data are compared to the new absolute measurement and discussed. The present data have been subtracted from a previous measurement of the total cross section to derive the contribution of the $alpha_0$ channel.
Differential cross sections for deuteron breakup $^{1}H(d, pp)n$ reaction were measured for a large set of 243 geometrical configurations at the beam energy of 80 MeV/nucleon. The cross section data are normalized by the luminosity factor obtained on the basis of simultaneous measurement of elastic scattering channel and the existing cross section data for this process. The results are compared to the theoretical calculations modeling nuclear interaction with and without taking into account the three-nucleon force (3NF) and Coulomb interaction. In the validated region of the phase space both the Coulomb force and 3NF play an important role in a good description of the data. There are also regions, where the improvements of description due to including 3NF are not sufficient.