Activation Cross Sectioas Induced By14MeV Neutrons And Total Cross Section Of CH₄and CD₄Induced By Cold Neutrons

Nuclear reaction is one of the most important subjects for nuclear physics, which explains the interaction process between inject particle and target nuclide. As one of the most effective tools, neutrons are used to study nuclear structure and nuclear force. Information achieved from studying nuclear reaction induced by neutrons can also exam existing nuclear theory. Nuclear data, specially, nuclear reaction cross section is very useful for development of nuclear model theory, nuclear reactor design and safety.Measurements of14MeV neutron induced nuclear reaction cross sections were reported. Data analysis process and correction factors are discussed in detail. The measurements for (n,2n),(n,p) and (n,a) cross sections induced by14MeV neutrons were performed at TD-300neutron generator in China Academy of Engineering Physics. We mainly investigated reactions which form daughter isotopes with half life about several minutes. The method we used in measurement is the activation, by which we detect the gamma rays emitted by activated isotopes with commercial HPGe detector manufactured by Ortec, the relative efficiency was68%.Neutron scattering is fundamental method for exploring structure of matter that makes our world. The low energy neutrons used in this field are usually produced from neutron source like accelerator based neutron generator and reactor source. Methane is known brightest moderator material and widely used. For instant, China Spallation Neutron Source uses liquid methane as material of one of the moderators. Neutrons collide in the moderator; meanwhile, absorption process also exists. In low energy range, the neutron capture cross section is proportional to1/v. As neutron energy decreasing, the neutron absorption gets stronger. This effect limits increasing of cold neutrons flux. Simply lowering the moderator temperature does not shift neutron spectra to lower energy. More important value is the ratio of scattering to capture cross section in low energy range. Moderator material should have large scattering cross section and small capture cross section. More cold neutrons are desired for slow neutron sources, if the scattering cross section can be modified by some method, a path for increasing colder neutrons can be opened.The total neutron cross section of solid bulk methane, confined deuterated methane and confined methane were investigated. The neutron energy ranges from0.1meV to100meV. The disorder MCM-41can affect the thermodynamic and excitation properties. if this effect is large enough, it can change the neutron scattering cross section, the inelastic scattering changes in low energy range gives new way to improve the moderator. The result shows total scattering cross sections of the bulk methane and confined methane are different. The cross section is relevant to methane temperature and neutron energy, this result may be useful for moderator design.This work was performed on LENS in CEEM, Indiana University. Neutron energy was determined by Time of Flight method. Samples were pure CH4and CD4. The disorder MCM-41is porous media with large internal surface and uniform pore size.