Double-differential cross sections for light charged particle production (up to A=4) were measured in 96 MeV neutron-induced reactions, at the TSL Laboratory Cyclotron in Uppsala (Sweden). Measurements for three targets, Fe, Pb, and U, were performed using two independent devices, SCANDAL and MEDLEY. The data were recorded with low-energy thresholds and for a wide angular range (20°–160°). The normalization procedure used to extract the cross sections is based on the np elastic scattering reaction that we measured and for which we present experimental results. A good control of the systematic uncertainties affecting the results is achieved. Calculations using the exciton model are reported. Two different theoretical approaches proposed to improve its predictive power regarding the complex particle emission are tested. The capabilities of each approach is illustrated by comparison with the 96 MeV data that we measured, and with other experimental results available in the literature.
The differential cross sections and vector analyzing powers for nd elastic scattering at E-n=248 MeV were measured for 10 degrees-180 degrees in the center-of-mass (c.m.) system. To cover the wide angular range, the experiments were performed separately by using two different setups for forward and backward angles. The data are compared with theoretical results based on Faddeev calculations with realistic nucleon-nucleon (NN) forces such as AV18, CD Bonn, and Nijmegen I and II, and their combinations with the three-nucleon forces (3NFs), such as Tucson-Melbourne 99 (TM99), Urbana IX, and the coupled-channel potential with Delta-isobar excitation. Large discrepancies are found between the experimental cross sections and theory with only 2N forces for theta(c.m.)>90 degrees. The inclusion of 3NFs brings the theoretical cross sections closer to the data but only partially explains this discrepancy. For the analyzing power, no significant improvement is found when 3NFs are included. Relativistic corrections are shown to be small for both the cross sections and the analyzing powers at this energy. For the cross sections, these effects are mostly seen in the very backward angles. Compared with the pd cross section data, quite significant differences are observed at all scattering angles that cannot be explained only by the Coulomb interaction, which is usually significant at small angles.
Recently, many new applications of fast neutrons are emerging or under development, like dose effects due to cosmic ray neutrons for airplane crew, fast neutron cancer therapy, studies of electronics failure induced by cosmic ray neutrons and accelerator-driven incineration of nuclear waste and energy production technologies. In radiation treatment, the kerma (Kinetic energy release in matter) coefficient, which describes the average energy transferred from neutrons to charged particles, is widely used. The kerma coefficient can be calculated from microscopic nuclear data. Nuclear data above 20 MeV are rather scarce, and more complete nuclear data libraries are needed in order to improve the understanding of the processes occurring on a cellular level. About half the dose in human tissue due to fast neutrons comes from proton recoils in neutronproton (np) scattering, 10-15% from nuclear recoils due to elastic and inelastic neutron scattering and the remaining 35-40% from neutron-induced emission of light ions. Experimental data on elastic and inelastic neutron scattering at 96 MeV from C-12 and O-16 have been obtained recently at The Svedberg Laboratory in Uppsala, Sweden. These data are shown to be relevant for the determination of nuclear recoil kerma coefficients from elastic and inelastic neutron scattering at intermediate energies.
In fast neutron cancer therapy, similar to 50% of the cell damage is caused by recoil protons from neutron-proton (np) scattering. In the intermediate energy region, there is a need for unambiguous np scattering data with good precision in both the shape of the angular distribution and the absolute normalisation. The normalisation techniques have been reviewed for np scattering measurements as well as recent experimental results, particularly the data obtained at The Svedberg Laboratory at 96 and 162 MeV. In addition, to what extent systematic uncertainties in the np differential cross section might affect the determination of proton recoil kerma coefficients is investigated.
Double-differential cross-sections for light-ion production (up to A = 4) induced by 96 MeV neutrons have been measured for Fe, Pb and U. The experiments have been performed at The Svedberg Laboratory in Uppsala, using two independent devices, MEDLEY and SCANDAL. The recorded data cover a wide angular range (20 degrees-160 degrees) with low energy thresholds. The data have been normalised to obtain cross-sections using up elastic scattering events. The latter have been recorded with the same setup, and results for this measurement are reported. The work was performed within the HINDAS collaboration with the primary aim of improving the database for three of the most important nuclei for incineration of nuclear waste with accelerator-driven systems. The obtained cross-section data are of particular interest for the understanding of the so-called pre-equilibrium stage in a nuclear reaction and will be compared with model calculations.
Double-differential cross sections for light-ion (p, d, t, 3He, and α) production in silicon, induced by 96 MeV neutrons, are reported. Energy spectra are measured at eight laboratory angles from 20° to 160° in steps of 20°. Procedures for data taking and data reduction are presented. Deduced energy-differential, angle-differential, and production cross sections are reported. Experimental cross sections are compared to theoretical reaction model calculations and experimental data in the literature.
In recent years, an increasing number of applications involving fast neutrons have been developed or are under consideration, e.g. radiation treatment of cancer, neutron dosimetry at commercial aircraft altitudes, soft-error effects in computer memories, accelerator-driven transmutation of nuclear waste and energy production and determination of the response of neutron detectors. Data on light-ion production in tight nuclei such as carbon, nitrogen and oxygen are particularly important in calculations of dose distributions in human tissue for radiation therapy at neutron beams, and for dosimetry of high-energy neutrons produced by high-energy cosmic radiation interacting with nuclei (nitrogen and oxygen) in the atmosphere. When studying neutron dose effects, it is especially important to consider carbon and oxygen, since they are, by weight, the most abundant elements in human tissue. Preliminary experimental double-differential cross sections of inclusive light-ion (p, d, t, He-3 and alpha) production in carbon induced by 96-MeV neutrons have been presented. Energy spectra were measured at eight laboratory angles: 20, 40, 60, 80, 100, 120, 140 and 160 degrees. Measurements were performed at The Svedberg Laboratory (TSL), Uppsala, using the dedicated MEDLEY experimental setup. The authors have earlier reported experimental double-differential cross sections of inclusive light-ion production in oxygen. In this paper, the deduced kerma coefficients for oxygen has been presented and compared with reaction model calculations.
A liquid scintillation detector aimed for neutron energy and fluence measurements in the energy region below 20 MeV has been calibrated using monoenergetic and white spectrum neutron fields. Careful measurements of the proton light output function and the response matrix have been performed allowing for the application of unfolding techniques using existing codes. The response matrix is used to characterize monoenergetic neutron fields produced by the T(d,n) reaction at low deuteron energies.