J. D. T. Arruda-Neto

The CRISP package for intermediate- and high-energy photonuclear reactions

The two-step process that characterizes the intermediate- and high-energy photonuclear reactions (between 40 MeV and 4 GeV) has been successfully described by Monte Carlo calculations. Recently, a new class of codes capable to perform those calculations according to a more realistic method has been developed, improving the possibilities for simulating the reactions in more details. In this work we present the CRISP package (standing for Rio–Sao Paulo Collaboration), which is a coupling of the multi collisional Monte Carlo (MCMC) and the Monte Carlo for evaporation–fission (MCEF) codes. The first one describes the intranuclear cascade process, while the second one is dedicated to the evaporation/fission competition step. Both codes have already shown to be useful for calculating several features of different nuclear reactions. The CRISP code, coupling these two software, represents a good tool to describe the complex characteristics of the nuclear reactions, and opens the opportunity for applications in quite different fields, such as studies of hadron physics inside the nucleus, specific nuclear reactions, spallation and/or fission processes initiated by different probes and many others.

In Vitro Effects of Gamma Radiation from 60Co and 137Cs on Plasmid DNA

The effects of gamma radiation from 60Co and 137Cs on DNA in aqueous solution are studied experimentally. Using an improved plasmid purification protocol and improved electrophoretic gel analysis techniques provided results with relatively small uncertainties. The results are compared with both theoretical and experimental results. In particular, the results obtained here are discussed in the light of recent discussion on supposed differences of the effects induced by gamma radiation from 60Co and 137Cs. We find that the effects of both types of gamma radiation are similar.

Tagged bremsstrahlung polarization: A Monte-Carlo approach

Abstract We present a Monte-Carlo approach for the determination of the degree of polarization of tagged bremsstrahlung. Our method allows the evaluation of the Bethe-Heitler expression in the photon-oriented reference system, while defining the photon and electron collimators in the spectrometer coordinate system. This avoids the need to perform fourfold integrals of complicated and bulky expressions. We reproduced the published calculations and measurements, and studied the polarization behavior as a function of several parameters in different geometric conditions.

Radiation interaction with DNA

We developed a model to describe the radiation-DNA interaction in water solution. The model is based on some important aspects of the Bethe Theory for the ionizing process, and on the assumption that the direct interaction between the incident particle and the DNA molecule is negligible in comparison with the indirect effect. This assumption can always be true under controlled conditions. The results show that the number of damages induced by radiation depends on the accumulated dose, on parameters related only to the medium properties, and on the DNA structure, but not on the incident particle. A few applications of the model are discussed, and results are successfully compared with experimental data. New experiments are proposed.

Disintegration of the deuteron by linearly polarized photons at low energies

Abstract The cross section and the Σ -asymmetry of the reaction d (γ → ,p) were measured in the energy interval E γ = 5–10 MeV. Cross sections dσ and dσ ⊥ were derived from the measured quantities dσ 0 and Σ -asymmetry. The results are compared with theoretical calculations available for this energy region.

The CRISP Code for Nuclear Reactions

The CRISP package performs the intranuclear cascade process and the evaporation/fission competition resulting in a code that represents a good tool to describe complexes characteristics of the nuclear reactions, and opens the opportunity for applications in different fields, such as medical physics, photonuclear reactions, spallation or fission process initiated by different probes and in Accelerator Driven Systems, where precise description of energetic and angular neutron distribution, neutron multiplicity and spallation products information are needed. In the CRISP model, was included the time‐sequence characteristics of the MCMC code and the evaporation/fission competition process model of the MCEF. Also, includes improvements in the code, as the excitation of nucleonic resonances heavier than Delta; the initial nuclear ground state construction according to the Fermi model and Pauli principle; and a more realistic Pauli blocking mechanism. Some consequences of the improvements performed in the code w...

Photoneutron multiplicities of preactinide nuclei at energies above the pion threshold

Abstract The average photoneutron muliplicities ν of Au, Ta and 182 W were deduced from their previously measured excitation energies E x , from 160 to 250 MeV. A combined analysis of these data and those measured at Saclay up to 140 MeV allowed the extraction of information on E x at the “pure evaporation” and quasideuteron energy regions. A theoretical approach for the study of ν above 140 MeV, which incorporates photopion reabsorption processes by two-body, was proposed, allowing a tentative delineation of the pion mean free path in the nucleus.

Developement of crisp package for spallation reaction studies and its utilization in ADS (Accelerator Driven System)

The progress of nuclear physics had allowed a better understanding of nuclear structure and reaction mechanisms, but also enables important applications of nuclear energy in our modern way of life. We can point out those ones related to power generation from nuclear reactors, providing an almost inexhaustive power source due to the huge quantities of nuclear fuel existent in our planet, which guaranties its utilization for thousands of years. The main interest is the so-called Hybrid Reactors (ADS - Accelerator Driven System), in which the reactor has a sub critical core and the chain reaction is sustained by an external source that comes from spallation reactions induced by high energy protons (about 1 GeV) from an accelerator, producing a large number of secondary particles (mainly neutrons). For those applications, precise knowledge about nuclear structure and nuclear reaction characteristics is needed.

Quasi-free 238U(e,e′f) cross section in macroscopic–microscopic approach

We present the result of a theoretical study of inclusive quasi-free electrofission of 238U. The off-shell cross sections for the quasi-free reaction stage have been calculated within the Plane Wave Impulse Approximation (PWIA) using a macroscopic–microscopic description of the proton and neutron single particle momentum distributions. Electron wave function distortion corrections were included using the effective momentum approximation. The fissility for the proton single hole excited states of the residual nucleus 237Pa was calculated both with and without contributions of the pre-equilibrium emission of the particles. The fissility of the 237,238U residual nuclei was calculated within the compound nucleus model. Final state interaction correction to the fissility was calculated using a pure imaginary optical potential. The (e,e′f) cross sections, thus obtained, were compared with available experimental data.We present the result of a theoretical study of inclusive quasi free electrofission of

Quasifree electrofission of238U

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