Analysis of209Bi and238U photofission cross section in the quasi-deuteron region of photonuclear absorption

Tavares, O. A. P.; Terranova, Maria Letizia

doi:10.1007/bf01289817

Cited by 23 publications

(42 citation statements)

References 43 publications

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“…A fourth possibility there exists clearly of obtaining residual nuclei, namely, escaping of both the neutron and proton simultaneously from the nucleus. In this case, however, no excitation energy is left to the residual nucleus, with the consequence of null chance for fission from this residual [14]. Let τ n and τ p denote, respectively, the probabilities of escaping for neutron and proton from the nucleus (without suffering for any secondary interaction), i.e., the nuclear transparencies to neutron (τ n ) and proton (τ p ).…”

Section: Nuclear Excitation and Fission Probabilitymentioning

confidence: 99%

“…Nuclear transparencies depend essentially upon neutron and proton kinetic energies in their final states [12,14]. For photons in the energy range 60-130 MeV interacting with actinides, it is found that for almost ∼ 80% of cases excited residual nuclei are formed (E * 1 ≈ E * 2 ≈ E γ /2, hence, highly fissionable residuals), and the third mode of formation is the predominant one.…”

Section: Nuclear Excitation and Fission Probabilitymentioning

confidence: 99%

“…The experimental data from such photonuclear reactions (cross section measurements and fission probability) have been generally interpreted on the basis of a current nuclear photoreaction model for intermediate-(30 E γ 140 MeV) and high-(E 140 MeV) energy photons [2,[11][12][13][14]. In brief, during the first reaction step, the incoming photon interacts with a neutron-proton pair (E γ 500 MeV) and/or individual nucleons (E γ 140 MeV), where pions and baryon resonances, and recoiling nucleons initiate a rapid (∼ 10 −23 s) intranuclear cascade process which produces a residual, excited nucleus.…”

Section: Introductionmentioning

confidence: 99%

“…The aim of the present work is to perform an analysis of the nuclear fissility data obtained from such measurements in a semiempirical and systematic way by making use of the two-step photoreaction model [12,14]. The study will cover the range 60-130 MeV, where nuclear photoabsorption has been described by the interaction of the incident photon with neutronproton pairs (quasi-deuterons), as described for the first time by Levinger [15,16].…”

Section: Introductionmentioning

confidence: 99%

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Fissility of actinide nuclei by 60-130 MeV photons

Morcelle¹,

Tavares²

2006

Braz. J. Phys.

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Nuclear fissilities obtained from recent photofission reaction cross section measurements carried out at Saskatchewan Accelerator Laboratory (Saskatoon, Canada) in the energy range 60-130 MeV for 232 Th, 233 U, 235 U, 238 U, and 237 Np nuclei have been analysed in a systematic way. To this aim, a semiempirical approach has been developed based on the quasi-deuteron nuclear photoabsorption model followed by the process of competition between neutron evaporation and fission for the excited nucleus. The study reproduces satisfactorily well the increasing trend of nuclear fissility with parameter Z 2 /A.

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Section: Nuclear Excitation and Fission Probabilitymentioning

confidence: 99%

Section: Nuclear Excitation and Fission Probabilitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fissility of actinide nuclei by 60-130 MeV photons

Morcelle¹,

Tavares²

2006

Braz. J. Phys.

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“…The routine calculation of the probability-values for the neutron emission (n), proton emission (p), alpha-particle emission (α), and fission (f ) modes has been already detailed in [5][6][7]. For the level-density parameter of the residual nucleus after neutron evaporation, a n , we adopted the expression…”

mentioning

confidence: 99%

New approach to nuclear photofission reactions above 0.15 GeV

Tavares¹,

Duarte²,

Deppman

et al. 2004

Braz. J. Phys.

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A simple approach to evaluate nuclear photofissilities at energies above the pion photoproduction threshold has been developed. It is based on the current, two-step model for intermediate-energy photonuclear reactions, i.e. a photon-induced intranuclear cascade followed by a fission-evaporation competition process for the excited, post-cascade residual nucleus. The calculation method (semiempirical by nature) shows that fissility (i.e., total fission probability) is governed by two basic quantities, namely, the first-chance fission probability for the average cascade residual, and a parameter which defines an evaporative sequence of residuals in which the average, equivalent chance-fission probabilities of nuclides belonging to the same generation are located. The nat Pb photofissility data measured recently in the range ∼ 0.2 − 3.8 GeV at the Thomas Jefferson Laboratory could be explained very satisfactorily by the present approach.The simultaneous photofission cross section measurements carried out very recently at the Thomas Jefferson Laboratory on a number of actinide target nuclei and natural lead using tagged photons in the range ∼0.2-3.8 GeV and PPAD-detectors for detection of fission fragments [1,2] made possible to extract important conclusions about the nuclear photoabsorption and fissility of these nuclei. Among others, i) the 237 Np photofissility is very close to unity in the whole energy interval, thus indicating that its photofission cross section is almost completely equal to the total photoabsorption cross section, and ii) the photofissility for all other actinide nuclei (uranium isotopes and thorium) is less than unity, therefore their photofission cross section does not represent the photoabsorption cross section for these nuclei. Very recently, results of a detailed and refined description of photofission reactions in heavy nuclei covering a large photon energy range ( ∼0.07−4.0 GeV) became also available [3]. Since photofissility data for actinide targets have been already analysed to some detail [2-4], we decided in the present work to focus attention on the newest photofissility data of nat Pb reported in [1,2]. Photofissility data will be here analysed in the framework of a phenomenological, semi-empirical way, aiming to obtain average calculated fissility values from an approach which has been developed for the first time in describing intermediate-energy photofission reactions in the entire energy range of ∼0.2−3.8 GeV covered by the measured photofission cross section data. Monte Carlo calculations are, at present, the main tool to describe quantitatively both the cascade and fission-evaporation competition processes, as well as to obtain the total fission probabilities (i.e., fissility values) for a number of photofission reaction cases. However, for cases where the target nucleus is expected to have very low fissility-values (pre-actinide, intermediate-mass, and less massive nuclei), the available codes may reveal themselves very time-consuming in obtaining a calculated fissility-cur...

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