MeV Incident Proton Energy Research Articles

Determinations of fission cross-sections and fission yields from proton induced fission reactions of 232Th, 233,235,236,238U, 237Np and 239Pu

In this work, the proton induced fission reaction cross-sections and fission yields are calculated for some actinides [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] using the fission barrier models of the TALYS 1.95 code. Cross-sections and fission yield calculations are carried out up to 100 MeV incident proton energies. The calculation results are compared with the available experimental data in the EXFOR library. In addition, a relative variance analysis of fission barrier models was done to determine the fission barrier model whose results best matched with the experimental results. Among the fission barrier models, the best agreement with the experimental data is obtained from the rotating-finite-range fission barrier model calculation for the [Formula: see text] reaction of the studied nuclei having the atomic mass number larger than 230. On the other hand, fission barrier heights for the studied reactions are determined using the same models.

Impact of Be7 breakup on the Li7(p,n) neutron spectrum

The formation of continuum neutron distribution in $^{7}\mathrm{Li}(p,n)$ has been identified as due to the coupling of the $^{7}\mathrm{Be}$ breakup levels to the final state of the reaction. The continuum neutron spectra produced by the $^{7}\mathrm{Li}(p,n)$ reaction has been estimated by measuring the double differential cross sections for continuum and resonant breakup of $^{7}\mathrm{Be}$, through the $^{7}\mathrm{Li}(p,n)^{7}\mathrm{Be}^{*}$ reaction at 21 MeV of proton energy. The breakup contributions from continuum and $5/{2}^{\ensuremath{-}}$, $7/{2}^{\ensuremath{-}}$ states of $^{7}\mathrm{Be}$ have been identified. The measured double differential cross sections have been reproduced through continuum-discretized coupled channel-coupled reaction channel calculations. The cross sections were projected to neutron spectrum using the Monte Carlo approach and validated using experimentally measured $^{3}\mathrm{He}$ gated neutron spectra. $^{7}\mathrm{Li}(p,n)$ neutron spectrum at 20 MeV incident proton energy measured by McNaughton et al. [Nucl. Instrum. Methods 130, 555 (1975)] has been reproduced by adapting estimated model parameters for the reaction.

MO-A-213AB-06: Validation of Nuclear Reaction Models to Simulate Proton Therapy Range Verification Using Prompt Gamma-Rays.

The impact of nuclear reaction model differences on simulation of prompt gamma-ray imaging for proton therapy range verification was assessed. Four nuclear reaction models were used to simulate gamma emission in proton beams, and were validated against experimental cross-sections. Proton-induced nuclear reactions on carbon, oxygen, nitrogen and calcium were investigated with the Monte Carlo toolkits GEANT4 9.5 and MCNPX 2.7, and the dedicated nuclear reaction codes TALYS 1.4 and EMPIRE 3.1. Absolute cross-sections of discrete prompt gamma lines and the total gamma production were obtained for the 1-200 MeV incident proton energy range. They were compared to 34 discrete line measurements reported in literature. Using these cross-sections, we analyzed the gamma production along the path of proton beams passing through various tissues. The differences in absolute discrete line cross-sections as predicted by the models ranged from almost zero to an order of magnitude, depending on the gamma line and incident proton energy. Overall, the dedicated nuclear reaction codes provided a better fit to most experimental excitation functions. For a 150 MeV proton beam stopping in soft tissue, these differences amount to a variation by a factor of 4 of the gamma emission around the Bragg peak location. The maximum of gamma production near the end of proton range differed by 7 mm, and the change of the 50% emission fall-off position was 4 mm. There is a clear need for improvement of nuclear reaction models to accurately simulate proton range verification using prompt gamma-rays. Current simulation codes show large uncertainties in both the total gamma yield and the correlation of gamma emission with the proton Bragg peak. GEANT4 and MCNPX in particular appear to have limited predictive power.

Nuclear model calculations on the production of 125,123Xe and 133,131,129,128Ba radioisotopes

In this study, production rates of 125,123Xe and 133,131,129,128Ba medical isotopes produced by 127I(p, 3n)125Xe, 127I(p, 5n)123Xe, 133Cs(p, n)133mg Ba, 133Cs(p, 3n)131mg Ba, 133Cs(p, 5n)129Ba, and 133Cs(p, 6n)128Ba reactions have been investigated up to 100 MeV incident proton energy. The preequilibrium calculations involve the hybrid model, the geometry-dependent hybrid model and the cascade exciton model. The calculated results are compared with the experimental data taken from the literature.

Homologous states in 139,140pr via the 139,140pr reactions

In order to study the spectator role of the f7/2 unpaired neutron outside the N = 82 closed shell in 143Nd, the 142,143Nd(p,α)139,140Pr reactions have been measured in high resolution experiments at 23.5 MeV incident proton energy from the Munich MP Tandem accelerator, using the Stern-Gerlach type polarized hydrogen ion source and the Q3D magnetic spectrograph. Multiplets of states of 140Pr, homologous to the low-lying states of 139Pr have been identified in Jπ

Fission properties of actinide nuclei from proton-induced fission at 26.5 and 62.9 MeV incident proton energies

Fission properties of proton-induced fission on {sup 232}Th, {sup 237}Np, {sup 238}U, {sup 239}Pu, and {sup 241}Am targets, measured at the Louvain-la-Neuve cyclotron facility at proton energies of 26.5 and 62.9 MeV, are compared with the predictions of the state-of-the-art nuclear reaction code talys. The code couples the multimodal random neck-rupture model with the pre-equilibrium exciton and statistical models to predict fission fragment mass yields, pre- and post-scission neutron multiplicities, and total fission cross sections in a consistent approach. The sensitivity of the calculations to the input parameters of the code and possible improvements are discussed in detail.

Calculation of direct-semidirect radiative proton capture with Skyrme-Hartree-Fock-BCS model

We calculate the direct-semidirect (DSD) radiative proton capture cross section on 112 Sn, 63 Cu, and 209 Bi in the microscopic Hartree-Fock-BCS approach using the Skyrme interaction. Compared to the compound process, the DSD process becomes dominant in the proton capture reaction above ten and several MeV incident proton energies. We compare several particle-vibration coupling forms, which is sensitive to the semidirect cross section.

Investigation of neutron skin effect with density dependence by using a new calculation method for initial exciton numbers on pre-equilibrium reactions

In this study, we investigated the pre-equilibrium effect by using a new evaluated geometry-dependent hybrid model and a neutron skin effect with density dependence for the 204,206,207Pb(p, xn) reaction at 25.5 MeV incident proton energy. We calculated the initial exciton numbers obtained from the modified Skyrme force based on fitting the fission barriers of heavy deformed nuclei (SKM*) and SLy4 for proton induced reaction on target nuclei 204,206,207Pb. We calculated, by using a new calculation method, the initial neutron and proton exciton numbers for 204,206,207Pb from the neutron and proton density and we investigated the shell effect by using an effective nucleon–nucleon interaction with Skyrme force. We also compared the geometry-dependent hybrid model (GDH), newly evaluated with the initial exciton number calculations of the neutron emission spectra of the 204,206,207Pb(p, xn) reaction, with the values reported in the literature at 25.5 MeV incident proton energy. The obtained results were investigated and compared with the pre-equilibrium calculations and experimental results.

New calculations of cyclotron production cross sections of some positron emitting radioisotopes in proton induced reactions

In this study, new calculations on the excitation functions of 13C(p,n)13N, 14N(p,a)11C, 15N(p,n)15O, 16O(p,a)13N, 18O(p,n)18F, 62Ni(p,n)62Cu, 68Zn(p,n)68Ga and 72Ge(p,n)72 As reactions have been carried out in the 5–40 MeV incident proton energy range. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve hybrid model, geometry dependent hybrid model, the cascade exciton model and full exciton model. Equilibrium effects were calculated according to Weisskopf-Ewing model. The calculated results have been compared with experimental data taken from literature.

Energy dependence of the three-nucleon analyzing power puzzle

We report on the energy dependence of the three-nucleon analyzing power puzzle in proton–deuteron elastic scattering. It was found that the relative difference between calculations and data remains nearly constant at the 25% level up to about 25 MeV incident proton energy. Above this energy the relative difference decreases, approaching zero near 40 MeV.

Study of activation cross sections of proton induced reactions on erbium for practical applications

Excitation functions of the natEr(p,x) 163,166,167,168,170Tm and natEr(p,x) cum161Er reactions were measured experimentally from the respective threshold up to 36 MeV incident proton energy and in the range of 60–70 MeV. The cross sections were measured with activation method using the stacked foil irradiation technique. A theoretical interpretation of contributing reactions based on results of the ALICE-IPPE code was done. From our experimental cross section data integral production yields were calculated which were compared to the experimental integral yield data reported in the literature.

New calculation method for initial exciton numbers on nucleon induced pre-equilibrium reactions

In this study, we investigate the pre-equilibrium effect by using new evaluated geometry dependent hybrid model for the {sup 208}Pb (p,xn) reaction at 25.5 and 62.9 MeV incident proton energies. We also suggest that the initial neutron and proton exciton numbers for the nucleon induced precompound reactions be calculated from the neutron and proton density by using an effective nucleon-nucleon interaction with Skyrme force. We calculate the initial exciton numbers obtained from SKM* and SLy4 for a proton induced reaction on target nuclei {sup 208}Pb. The obtained results have been investigated and compared with the pre-equilibrium calculations and experimental results.

OBSERVATION OF η→π+π-e+e- DECAY WITH WASA AT CELSIUS

We present preliminary results on the observation of the η→π+π-e+e- decay in the CELSIUS/WASA experiment. The η mesons were produced from proton-proton interactions at 1360 MeV incident proton energy.

Parity violation in proton-proton scattering at 221 MeV

pp elastic scattering at 221.3 MeV incident proton energy. This comprehensive paper includes details of the corrections, some of magnitude comparable to Az itself, required to arrive at the final result. The largest correction was for the effects of first moments of transverse polarization. The addition of the result, Az = (0.84 ± 0.29(stat.) ± 0.17(syst.)) × 10 7 , to the ~ pp parity violation experimental data base greatly improves the experimental constraints on the weak meson-nucleon coupling constants h pp and h pp , and also has implications for the interpretation of electron parity violation experiments.

Polarization transfer measurements for the13C(p→,n→)13Nreaction at 197 MeV and empirical isovector spin-longitudinal response for the(1/2)g.s.−→(1/2)1+transition

We present differential cross sections and complete sets of polarization-transfer coefficients, ${D}_{\mathrm{ij}},$ obtained in the ${}^{13}\mathrm{C}(\stackrel{\ensuremath{\rightarrow}}{p},\stackrel{\ensuremath{\rightarrow}}{n}{)}^{13}\mathrm{N}$ reaction studied at 197 MeV incident proton energy and laboratory angles between $0\ifmmode^\circ\else\textdegree\fi{}$ and $33\ifmmode^\circ\else\textdegree\fi{}.$ These complete sets of polarization observables are used to obtain spin-longitudinal and spin-transverse components for transitions to the ground state, to the first, and to the unresolved second and third excited states in ${}^{13}\mathrm{N}$ at 2.36 MeV and $(3.50+3.55) \mathrm{MeV},$ respectively. The results are used to obtain the two $\ensuremath{\Delta}{J}^{\ensuremath{\pi}}$ contributions for the ground and first excited state transitions and are compared with corresponding distorted-wave impulse approximation (DWIA) calculations. In particular, empirical angular distribution values for the unique spin-longitudinal $\ensuremath{\Delta}{J=0}^{\ensuremath{-}}$ transition to the first excited state in ${}^{13}\mathrm{N}$ are obtained and compared with DWIA calculations.

Spin Transfer Measurements in $(\vec{p},\vec{n})$ Reactions

The measurement of complete sets of spin transfer coefficients in nuclear transitions, induced via charge-exchange (\((\vec p, \vec n)\)) reactions at intermediate energies, is a unique form of separating the spin-dependent and spin-independent contributions to the differential cross section. The two components of the spin-dependent contribution, the spin-longitudinal and spin-transverse components may equally be separated. This is extremely important in cases where the target nuclei has a non-integer ground state spin. In this study and as an example of the above, we present differential cross section and complete set of polarization transfer coefficients obtained in the (\(^{13} C(\vec p, \vec n)\)) 13N reaction studied at angles between 0° and 33° and at 197 MeV incident proton energy. Polarization transfer coefficients are used to obtain the fraction of the Gamow-Teller (GT) component in the mirror ground state transition, which is a combination of the spin-independent Fermi (F) and spin-dependent GT components. Data are also presented for the transition to the first excited state in 13N at 2.34 MeV. This is a (1/2)− → (1/2)+ transition and the cross section is an incoherent admixture of ΔJ π = 1− and ΔJ π = 0− components. The complete set of polarization transfer coefficients are used to obtain differential cross section data for both components. The empirical results are compared with Distorted Wave Impulse Approximation calculations, DWIA.

Zero degree polarization transfer measurements for the13C(p→,n→)13Nreaction at 197 MeV and empirical Gamow-Teller strength distribution

In this paper, we present differential cross sections and complete sets of polarization transfer coefficients, ${D}_{\mathrm{ij}},$ obtained in the ${}^{13}\mathrm{C}(\stackrel{\ensuremath{\rightarrow}}{p},\stackrel{\ensuremath{\rightarrow}}{n}{)}^{13}\mathrm{N}$ reaction studied at zero degree and at 197 MeV incident proton energy. The complete set of polarization observables is used to obtain the Fermi and Gamow-Teller (GT) cross section contributions in the ground state transition, which are then used to deduce GT transition strengths. The sum of the GT strength up to 20 MeV of excitation is compared with shell model calculations. In the region between 20 to 46 MeV of excitation, the differential cross section has been separated in spin and nonspin components.

Measurement of Gamow-Teller strength for127Ias a solar neutrino detector

Gamow-Teller transition strengths obtained in the ${}^{127}\mathrm{I}{(p,n)}^{127}\mathrm{Xe}$ reaction studied at 94, 159, and 197 MeV incident proton energies are presented, and used to evaluate the efficiency of ${}^{127}\mathrm{I}$ as a solar neutrino detector. Excitation of the ${J}^{\ensuremath{\pi}}{=(3/2)}^{+}$ first excited state at ${E}_{x}=0.125 \mathrm{MeV}$ in ${}^{127}\mathrm{Xe},$ sensitive to ${}^{7}\mathrm{Be}$ solar neutrinos, is evaluated. The sum of Gamow-Teller strength up to particle emission threshold and up to 20 MeV excitation energy are also reported. This paper also provides a new measurement of the Coulomb displacement energy $\ensuremath{\Delta}{E}_{c},$ the excitation energy of the isobaric analog state, and the centroid of the Gamow-Teller resonance in ${}^{127}\mathrm{Xe}.$

New precompound decay model: Angular distributions

A new Monte Carlo precompound decay model is used to calculate double-differential spectra using an approach based on conservation of linear momentum between an incident nucleon and the three quasiparticles activated in the collisions of the equilibration process. The angular distribution theory is presented as it is applied to the individual three-exciton cascades of the precompound model. The importance of multiple precompound decay beyond two nucleons per nucleus is illustrated for ${}^{90}$Zr$(p,xn)$ reactions for incident protons up to 256 MeV. These components are shown to be important for extending the useful range of the precompound approach to energies beyond 80 MeV. The contribution to nucleon spectra due to hole conversion processes is illustrated. We compare results of the formulation described with experimental angular distributions for ${}^{90}$Zr$(p,xn)$ reactions at incident energies of 45, 80, and 160 MeV, and for the ${}^{90}$Zr$(p,xp)$ reactions at incident energies of 80, 160, and 200 MeV. Additionally, ${}^{208}$Pb$(p,xn)$ spectra at 7.5\ifmmode^\circ\else\textdegree\fi{}, 30\ifmmode^\circ\else\textdegree\fi{}, 60\ifmmode^\circ\else\textdegree\fi{}, 120\ifmmode^\circ\else\textdegree\fi{}, and 150\ifmmode^\circ\else\textdegree\fi{} are compared with two experimental data sets for 256 MeV incident proton energy, and ${}^{90}$Zr$(p,xn)$ spectra at the same five angles are compared with predicted results for 256 MeV incident protons. At 256 MeV incident proton energy, the higher energy emission spectra are seriously overpredicted at 60\ifmmode^\circ\else\textdegree\fi{}. All other results are reproduced quite well, including back-angle yields. The quasielastic peak measured at 7.5\ifmmode^\circ\else\textdegree\fi{} at 256 MeV incident proton energy is shown to be in quite reasonable agreement with experimental results.

Analysis of isotope yields and excitation functions for fissile and non-fissile nuclei with CEF and HMS-ALICE codes

The CEF and ALICE nuclear reaction codes are benchmarked via comparisons with activation yields for proton-induced reactions in the range of 50 MeV to 1.8 GeV with targets of 58,62Ni, 209Bi, 232Th, and 238U. The CEF code results are presented over the entire energy range, whereas results for the ALICE code are given only up to 480 MeV incident proton energy. Different targets have been irradiated in different energy intervals. The codes are generally succesful in reproducing the experimental yields and yield patterns. For the ALICE code, we find an underestimation of multiple charged particle emission in heavy elements.