Angular distribution of 238U photofission fragments for 12 different mono-energetic γ-rays

doi:10.1016/0375-9474(69)91013-6

Nuclear Physics A

Volume 123, Issue 3, 27 January 1969, Pages 664-672

https://doi.org/10.1016/0375-9474(69)91013-6 Get rights and content

Abstract

Mono-energetic γ-rays of 12 different energies in the energy range 5.4–9 MeV have been used to irradiate ²³⁸U. The results of measurements of angular distributions of photofission fragments are reported and discussed. An analysis assuming penetration barrier function has been performed, and energies of the K-levels have been obtained as well as other nuclear parameters.

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Cited by (12)

Observation of uranium photo-fission by 16N decay gamma rays from water activated by D-T fusion neutrons
2000, Fusion Engineering and Design
Citation Excerpt :
Photo-fission cross sections for 234U, 235U, and 238U were obtained from the Photo-Nuclear Data Library in the EXFOR Library System [28,29] and from a compilation assembled at Lawrence Livermore National Laboratory and provided to us by Warshaw [30]. Extensive experimental data have been reported for the photo-fission of 238U [9,10,15,31,35–52]. The cross-section values obtained from the literature for gamma-ray energies around 6 and 7 MeV are listed in Table 5.
Radioactive ¹⁶N is generated in pure water (H₂O) which has been exposed to D-T fusion neutrons with energies near 14 MeV. The principal neutron-activation reaction is ¹⁶O(n,p) ¹⁶N. Decay by β emission (100%) of the 7.13±0.02 s ¹⁶N activity is accompanied by production of energetic gamma rays (most of them with energies>6 MeV) that are associated with the prompt radiative de-excitation of various elevated energy levels of ¹⁶O populated through the process ¹⁶N(β-) ¹⁶O. The dominant gamma-ray emission branch energies (intensities) are 6.129 MeV (67.0±0.6%) and 7.115 MeV (4.9±0.4%). A particular given intensity refers to the percent of ¹⁶N decays that produce the indicated gamma ray. Both photons possess energies that are above the photo-fission threshold for the naturally occurring isotopes of uranium, namely, ²³⁴U, ²³⁵U, and ²³⁸U. This paper reports on an experiment that demonstrated ¹⁶N decay gamma-ray induced photo-fission in a commercial fission detector that contained 0.14 g of depleted uranium (predominantly ²³⁸U with a small trace of ²³⁵U). This detector was placed near a tubing system containing circulating water that had been activated by neutron bombardment as it passed near to the target of an intense D-T fusion neutron generator. The fission detector was situated in a shielded location remote from the source of primary D-T neutrons. Other possible mechanisms leading to the generation of the observed detector events were considered. Among these were natural background radiation (e.g., cosmic rays), delayed neutrons from the decay of ¹⁷N and ¹⁸N also produced in water by D-T neutrons, secondary neutrons from (γ,n) reactions in materials near the detector, and electronic noise or pulse pileup. All of these alternative possibilities were ultimately rejected as significant contributors to the experimental detector counts by a detailed examination of the pertinent nuclear data and by specific measurements carried out in the present study. Photo-fission of ²³⁸U remained as the predominant source of the recorded fission-detector events after elimination of these other possibilities as significant contributors of observed counts. The anticipated photo-fission yield was calculated based on consideration of the experimental setup, tabulated cross sections, and other pertinent nuclear data. This analysis yielded results which were found to be consistent with the present experimental observations to within the combined — rather large — uncertainties. This outcome further supports the conclusion that photo-fission events were indeed observed in this experiment. Some engineering implications of this investigation, and potential applications for the observed phenomenon in contemporary nuclear fusion technology, are also discussed.
Photofission cross sections of 238U and 235U from 5.0 MeV to 8.0 MeV
1973, Nuclear Physics, Section A
Cross sections extracted from measured yield curves are reported for photofission of ²³⁸U and ²³⁵U. Surface barrier detectors were used to measure the fission yields from metal foil targets of ²³⁸U (enriched to 99.97%) and ²³⁵U (enriched to 97.68%) for maximum photon energies stepped from 5.0 MeV to 8.0 MeV in 0.1 MeV increments. The photons were obtained by Compton scattering γ-rays produced by neutron capture in a nickel plate near the core of the 5 MW Ames Laboratory Research Reactor. An unfolding procedure was used to extract the smoothed cross sections from the measured yield curves. In the ²³⁸U(γ, f) cross section, prominent structure is observed at 6.2 MeV and 7.6 MeV with hints of structure at 5.5 MeV and 7.0 MeV. The ²³⁵U(γ, f) cross section shows pronounced structure at 5.9 MeV, 6.6 MeV and 7.5 MeV with a hint of structure at 5.4 MeV. These cross sections are compared to previous photofission measurements and are discussed in the framework of Bohr's “fission channel” theory.
Angular distributions of 238U photofission fragments
1971, Nuclear Physics, Section A
Angular distributions of fragments from the photofission of ²³⁸U were measured for discrete excitation energies in the range 5.6–9 MeV. Monoenergetic γ-rays from radiative neutron capture were used to produce the excitation and solid-state particle-track recorders were used as fragment detectors. From the measured angular distributions, the barrier heights and curvatures for three low-energy fission channels in the transition state nucleus were deduced.
80 years of experimental photo-fission research
2024, European Physical Journal A
238 u fission near the threshold
2020, Problems of Atomic Science and Technology
Prompt neutron polarization asymmetries in photofission of Th 232, U 233,235,238, Np 237, and Pu 239,240
2014, Physical Review C - Nuclear Physics

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^☆: This work was done under the auspices of the Euratom/CNEN-INFN n. 002-63-11 MPAI contract.

^††: Present address: Istituto di Fisica dell’Universitá Messina.

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Nuclear Physics A

Abstract

References (12)

Nucl. Phys.

Phys. Lett.

Phys. Lett.

Nucl. Phys.

Cited by (12)

Observation of uranium photo-fission by <sup>16</sup>N decay gamma rays from water activated by D-T fusion neutrons

Photofission cross sections of <sup>238</sup>U and <sup>235</sup>U from 5.0 MeV to 8.0 MeV

Angular distributions of <sup>238</sup>U photofission fragments

80 years of experimental photo-fission research

238 u fission near the threshold

Prompt neutron polarization asymmetries in photofission of Th 232, U 233,235,238, Np 237, and Pu 239,240

Angular distribution of 238U photofission fragments for 12 different mono-energetic γ-rays☆

Abstract

Nucl. Phys.

Phys. Lett.

Phys. Lett.

Nucl. Phys.

Angular distribution of ²³⁸U photofission fragments for 12 different mono-energetic γ-rays☆