Intranuclear cascade model for a comprehensive description of spallation reaction data

This thesis presents a complete set of proton-impact ionization cross section data of DNA constituents determined at the Physikalisch-Technische Bundesanstalt (PTB). The cross section data describe the probabilities for the ionization of gas-phase tetrahydrofuran, pyrimidine and trimethyl phosphate that are structural analogues to the base, sugar, and phosphate residue of the DNA, respectively. Total, single-differential and double-differential ionization cross sections were determined, whereby the differential description refers to the energy or angular dependence of electron emission. Double-differential cross sections were measured for impact energies between 75 keV and 3000 keV over an angular range between 15бу and 150бу in 15бу intervals. Both single-differential and total ionization cross sections were derived by integration of the measured double-differential cross sections. The measurements of double-differential cross sections were carried out using a crossed-beam arrangement in a high-vacuum chamber. The proton beam, which perpendicularly crosses an effusive gas jet target of DNA constituents inside the chamber, was generated either by the 3.75 MV Van de Graaff accelerator of the PTB ion accelerator facility (PIAF) or a newly developed 155 kV ion accelerator. In the measurement a newly constructed electron spectrometer was used to detect the secondary electrons produced by proton collisions with the target molecules. The energy of the secondary electrons was selected by a hemispherical electron energy analyzer, which was mounted on a turntable to allow the spectrometer to rotate around the axis of the gas jet. Hence, the energy spectra could be recorded at defined observation angles with respect to the proton beam. These spectra were converted into absolute cross section values via a normalization procedure based on previously published absolute electron-impact cross section data.

We present an intranuclear cascade (INC) model which includes the dynamics of the cascade particles and uses in-medium $\mathit{NN}$ elastic cross sections. Our model is still based on the impulse approximation and does not have the complexity of other sophisticated nuclear models. Nevertheless, its results of angle-energy distributions of emitted nucleons in continuum are in good agreement with experimental data for nucleon induced reactions from low intermediate energy to high energy, between 14 MeV and 1.6 GeV, and for light to heavy target nuclei. Comparisons with results of Bertini's INC model and of a previous version of our INC model show the clear contribution of the combined effects of better dynamics and the in-medium $\mathit{NN}$ cross sections. From our results, we conclude that our INC model effectively includes the preequilibrium emission.

A new reaction model for light nuclei is proposed to analyze the measured data, especially for the double-differential cross sections. In this paper the calculation with this model is employed to analyze measurements of the total outgoing neutron double-differential cross sections for n+11B reactions at En = 14.2 MeV. The representation of the double-differential cross sections of the second emitted particles is given in detail. The calculation results indicate that the recoil effect in light nuclear reaction is essentially important. The reaction channels are discussed in detail.

Two features, a slow slope and a sharp drop, in neutron induced total nonelastic cross-sections are analyzed within the framework of an intra-nuclear cascade (INC) model. First, to reproduce the slow slope from 100MeV to 10 MeV, the original INC is generalized in two points; a method to construct the ground state of the target nucleus, and a method of taking the effective two body cross-sections between two nucleons. Secondly, to analyze the origin of the sharp drop from 10MeV to nearly 1 MeV, the INC is extended to include quantum effects which are originated from the existence of the discrete states in the nuclear potential. It is shown that this extension leads to the sharp drops in the very low energy below around 10MeV. It is concluded that the INC model can be extended to explain the sharp drops in addition to the slow slope in neutron induced nonelastic cross-sections in the energy region from 100MeV down to 1 MeV.

The nuclear incoherent π 0 photoproduction cross section from 12C is evaluated at forward angles in the 4.0 to 6.0 GeV energy range using the multicollisional intranuclear cascade model MCMC. The model incorporates some improvements in comparison with previous versions associated with the momentum distribution (MD) for light nuclei - extracted from the available (e,e ′p) data - as well as the evaluation of the shadowing effects during the photo-nucleus interaction. The final results of the single and double differential cross sections at forward angles are very sensitive to the MD parameterizations due to the Pauli principle, which largely suppresses the cross sections for low momentum transfer. The attenuation of the nuclear cross section due to pion - nucleus final state interactions is approximately 40% (without nuclear shadowing), which is in nice agreement with the predictions from the Glauber model. The single and double π 0 differential cross sections are presented for possible applications for the interpretation of the inelastic background in the PrimEx experiment at the Jefferson Laboratory. © 2007 American Institute of Physics.

Some test calculations were carried out to demonstrate the usefulness of double-differen-tial cross sections for neutron transport calculations including anisotropic scattering. A transport code system NITRAN was applied for the purpose. In NITRAN, the anisotropy of elastic and inelastic scattering can be treated in a general form by double-differential total neutron-emission cross sections, which are generated from single-differential and/or original double-differential cross section data base.The test calculations were performed for neutron flux spectra in aluminum and lead slabs, and also f, or tritium production rates in a natural lithium sphere. Since the treat-ment free from collision kinematics is possible by using the double-differential cross sections in the Sn calculations, the discretization of secondary neutron energy distribution becomes independent of the segmentation of angular distribution. A significant improvement due to this independence can be seen in calculating the anisotropy of general inelastic scatter-ing and the extreme anisotropy of elastic scattering by heavy nuclei. For precise aniso-tropic transport calculations, it is therefore concluded that the nuclear data of double-dif-ferential type are more suitable than those of single-differential type.

We present a theoretical study of the ionization of nitrogen atom by a singly charged sodium ion using the classical trajectory Monte Carlo method. Although we suffer from a lack of cross section data of this collision system, the knowledge of the basic cross sections is essential in fusion science, because this reaction has potential applications in the diagnostic of magnetically confined fusion plasmas. In our investigations, the Na+–N collision system is reduced to a three-body problem. The interaction between the collision partners is described by the Garvey-type model potential. The results of our study provide insight into the dynamics of singly charged sodium–nitrogen interactions. The total cross sections are presented in the impact energy range between 10 keV and 10 MeV and compared them with the available experimental data. The single and double differential cross sections are presented at 30, 40, 50 and 60 keV energies related to the energies of the plasma diagnostic used in the nuclear fusion.

Measurement of fusion cross sections for the $^{6,7}\mathrm{Li}$ $+$ $^{24}\mathrm{Mg}$ reactions by the characteristic $\ensuremath{\gamma}$-ray method has been done at energies from below to well above the respective Coulomb barriers. The fusion cross sections obtained from these $\ensuremath{\gamma}$-ray cross sections for the two systems are found to agree well with the total reaction cross sections at low energies. The relatively large difference between total cross sections and measured fusion cross sections at higher energies is consistent with the fact that other channels, in particular breakup, open up with an increase of bombarding energy. The breakup channel, however, appears not to have any influence on fusion cross sections. The critical angular momenta (${l}_{\mathrm{cr}}$) deduced from the fusion cross sections are found to have an energy dependence similar to other Li-induced reactions.

We have developed a low threshold detector consisting of Bragg curve counter (BCC), two siliconsurface barrier detectors (SSDs) and BGO scintillator to obtain experimental double-differential cross section (DDX) data for low energy proton production. Since the BCC offers advantage of self particle identification capability and a few μm-thick entrance window, protons produced by nuclear reactions down to 1 MeV have been identified. The capability of the detector is demonstrated in measurements using 70-MeV protons. Measured spectra are compared with calculation results of intra-nuclear cascade (INC) plus evaporation models and nuclear data library.

Absolute double differential cross sections (DDCS) of secondary electrons emitted in ionization of O2 by fast electrons have been measured for different emission angles. Theoretical calculations of atomic DDCS were obtained using the first Born approximation with an asymptotic charge of Z T = 1. The measured molecular DDCS were divided by twice the theoretical atomic DDCS to detect the presence of interference effects which was the aim of the experiment. The experimental to theoretical DDCS ratios showed clear signature of first order interference oscillation for all emission angles. The ratios were fitted by a first order Cohen-Fano type model. The variation of the oscillation amplitudes as a function of the electron emission angle showed a parabolic behaviour which goes through a minimum at 90°. The single differential and total ionization cross sections have also been deduced, besides the KLL Auger cross sections. In order to make a comparative study, we have discussed these results along with our recent experimental data obtained for N2 molecule.

To be able to calculate the nucleon-nucleon and nucleon-nucleus total reaction cross sections with precision is very important for studies of basic nuclear properties, e.g. nuclear structure. This is also of importance for particle and heavy ion transport calculations since in all particle and heavy ion transport codes, the probability function that a projectile particle will collide within a certain distance x in the matter depends on the total reaction cross sections. This will also scale the calculated partial fragmentation cross sections. It is therefore crucial that accurate total reaction cross section models are used in the transport calculations. In this paper, different models for calculating nucleon-nucleus and nucleus-nucleus total reaction cross sections are compared.1,2

Cross section measurements for the 9Be+9Be System at subbarrier energies

Absolute double differential cross sections (DDCS) of low-energy electron emission from water molecule were measured upon collisions with 250-keV protons for emission angles between 30--150 degrees. The electrons having energies between 1 and 600 eV were detected by using hemispherical electrostatic analyzer. The single differential (SDCS) and total cross section (TCS) were calculated by integrating the DDCS and SDCS, respectively. The measured DDCS, SDCS, and TCS were compared with the classical trajectory Monte Carlo (CTMC) model, using a dynamical approach in which a time-dependent screening is considered. The continuum-distorted-wave eikonal-initial state (CDW-EIS) theoretical model has also been used to explain the energy and angular distribution data. The angular distribution of the DDCS are very well reproduced by the CTMC approach. The TCS calculated by the CTMC model matches better with the measured values as compared to the CDW-EIS estimation. The forward-backward angular asymmetry parameter was also estimated to test the validity of the state-of-the-art theoretical models used. Finally the recently developed CDW-EIS calculations considering a residual target dynamic charge (DC-CDW-EIS) is shown to provide an improved agreement with the experiments compared to the CDW-EIS. The present data and interpretation should provide inputs towards energy loss calculations required for the radiobiology involved in the hadron therapy of cancer.

Comparisons are made among results of calculations for intermediate-energy nucleon-nucleus scattering for C12, O16, Ca40, Zr90, and Pb208, by use of optical potentials obtained from global Dirac phenomenology and from a microscopic Schrdinger model. Differential cross sections and spin observables for scattering from the set of five nuclei at 65 and 200 MeV have been studied to assess the relative merits of each approach. Total reaction cross sections from proton-nucleus and total cross sections from neutron-nucleus scattering have been evaluated and compared with data for those five targets in the energy range 20-800 MeV. The methods of analyses give results that compare well with experimental data in those energy regimes for which the procedures are suited. 2005 The American Physical Society.

A phenomenological formula for in-medium nucleon-nucleon cross section is presented, in which nuclear matter density and incident energy dependencies are included. This formula is used to study total nuclear reaction cross section based on Coulomb-modified Glauber model. The calculated results can reproduce experimental total reaction cross section induced by the stable nuclei and the exotic nuclei over a wide energy range.