.20 Mev, The Following Neutron-induced ~ (10,11) B And ~ 6li Reaction Double Differential Cross Sections Document The Establishment And ~ 5he Emission In The N + ~ (10,11) B Reaction

In this thesis, the new light nuclear reaction theoretical model based on the unifiedHauser-Feshbach and exciton model have been expounded. By using the new reactionmodel for light nuclei, the complete nuclear data for neutron induced ^10,11B and ⁶Lireactions at incident neutron energies below 20MeV have been calculated, while theneutron data libraries including the double-differential cross sections file (file-6) for ^10,11Band ⁶Li have been established. Particularly, the unstable cluster ⁵He emissions in n+^10,11Breactions has been discussed in detail with the updated level scheme and the new opticalmodel parameters.The double-differential cross section data of light nuclei are very important in thenuclear engineering design and neutron shielding design. However, the absent of thedouble-differential cross section files in international neutron evaluation libraries is a openproblem, due to lack of usable theoretical approach. The new light nuclear reactiontheoretical model could solve these problems well. This model is established to describethe pre-equilibrium emission processes from compound nucleus to the discrete levels of theresidual nuclei, since the pre-equilibrium emission processes are the dominant reactionmechanism for light nucleus reactions. The recoil effects in all nuclear reaction processesare taken into account strictly, so the energy balance is held accurately both for thesequential and unsequential reacton processes. This theoretical model conserves theangular moment and parity strictly. The spherical optical model is employed in this modelin order to obtain a set of appropriate neutron optical potential parameters, because theparticle emission rate to discrete levels needs exact transmission coefficients. Thecorrectness of the calculated results is validated through comparing the calculated datawith the measurements, so the coordinate system conversion and effects of energy-levelbroadening need to be taken into account. The double-differential cross sections files of ¹⁰B and ¹¹B are absent in CENDL. Sothe double-differential cross sections of total outgoing neutrons for n+^10,11B reactions havebeen calculated, by using the new reaction model for light nuclei, with the updated levelscheme and the new optical model parameters, which agree fairly well with themeasurements at E_n=14.2MeV. Therefore, based on the full fitting the neutron datalibraries including the double-differential cross sections file (file-6) for ¹⁰B and ¹¹B atE_n≦20MeV have been established. For n+¹¹B reactions, the file-6 has been given in theeighth release of American ENDF/B-â…¥library by using the Kalbach systematic. However,the Kalbach systematic formula is only suitable to calculate the double-differential crosssections of the continuous state emissions of the first emitted particles. For emissionprocesses from compound nucleus to the discrete levels of the residual nuclei, the smoothspectrum shape is given by using the Kalbach systematic simply, meanwhile the energybalance is not held.The double-differential cross sections for ⁶Li has been given in CENDL-3.1, but theimprovement is needed to neutron data libraries of ⁶Li with the updated level schemesrelated with the n+⁶Li reactions, such as ⁶Li, ⁵He, ⁵Li. So the double-differential crosssections of total outgoing neutrons for n+⁶Li reactions have been calculated by using theupdated LUNF code, the calculated results agree fairly well with the measurements atincident neutron energies equal 8.17MeV, 10.286MeV, 11.5MeV, 14.2MeV and 18MeV.Thus, based on the full fitting the neutron data libraries including the double-differentialcross sections file (file-6) for ⁶Li at E_n≦20MeV have been established.In the last, the contributions of the neutrons emitted from ⁵He breakup process to thetotal outgoing neutron double-differential cross sections are analyzed in detail. Thecomparisons of the double-differential cross sections of total outgoing neutrons for n+^10,11Breactions between considering ⁵He emission and without ⁵He emission are shown in thisthesis at E_n=14.2MeV for each outgoing angles, respectively. In order to analyze the contribution of 5^He emission in detail, the partial outgoing neutron energy-angular spectraat 60°are also shown in this thesis. The calculated results indicate that the neutron spectrafrom 5^He breakup process contribute to the low energy region of the total outgoing neutrondouble-differential cross sections. Once the 5^He emission is taken into account, the fittingof the double-differential measurements of total outgoing neutrons at the low energy regioncould be improved obviously.