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Fission product yields (FPY) are one of the most fundamental quantities that can be measured for a fissioning nucleus and are important for basic and applied nuclear physics. Recent measurements using mono-energetic and pulsed neutron beams generated using Triangle Universities Nuclear Laboratory’s tandem accelerator and employing a dual fission chamber setup have produced self-consistent, high-precision data critical for testing fission models for the neutron-induced fission of 235,238U and 239Pu between neutron energies of 0.5 to 15.0 MeV. These data have elucidated a low-energy dependence of FPY for several fission products using irradiations of varying lengths and neutron energies. This paper will discuss new measurements just beginning utilizing a RApid Belt-driven Irradiated Target Transfer System (RABITTS) to measure shorterlived fission products and the time dependence of fission yields, expanding the measurements from cumulative towards independent fission yields. The uniqueness of these FPY data and the impact on the development of fission theory will be discussed.

The cross section for the 169Tm(n,3n) 167Tm reaction was measured from 17 to 22 MeV using quasimonoenergetic neutrons produced by the ²H(d,n) ³He reaction. This energy range was studied to resolve the discrepancy between previous (n,3n) cross-section measurements. In addition, the absolute γ -ray branching ratios following the electron-capture decay of 167Tm were measured. These results provide more reliable nuclear data for an important diagnostic that is used at the National Ignition Facility to estimate the yield of reaction-in-flight neutrons produced via the inertial-confinement-fusion plasma in deuterium-tritium capsules. [ABSTRACT FROM AUTHOR]

Using the activation technique, the cross section for the reaction 181Ta(n,2n)180Tag was measured from 8 to 15 MeV in small energy steps to resolve inconsistencies in the existing database. The 93.4 keV γ ray from the decay of the 180Tag ground state was recorded with a high-purity germanium (HPGe) detector. The monitor reactions 27Al(n,α)24Na and 197Au(n,2n)196Au were used for neutron fluence determination. The ENDF VII.1 and TENDL 2011 evaluations are in considerable disagreement with the present data, which in turn agree very well with the majority of the existing data in the 14 MeV energy region. A detailed analysis using the code talys was performed to describe the present data and to predict the (n,2n) cross section to the isomeric state of 180Ta. [ABSTRACT FROM AUTHOR]

At the National Ignition Facility, experiments are being performed to measure charged-particle stopping powers in the previously unexplored warm dense plasma regime. These measurements are done using reaction-in-flight (RIF) neutrons from an inertial confinement fusion system. RIF neutrons are produced with a continuum of energies up to 30 MeV. By making activation measurements utilizing threshold reactions for neutrons in the energy range of 15 < En < 30 MeV, the number of RIF neutrons can be determined and from this the stopping power of the deuterium and tritium ions that produced the RIF neutrons can be inferred. Currently, the 169Tm(n,3n) 167Tm reaction has been used. However, in an effort to provide a secondary complimentary measurement, efforts are underway to make use of the 209Bi(n,4n) 206Bi reaction, with a threshold of 22.5 MeV. The cross sections were measured at the 10 MV tandem Van De Graaff accelerator at the Triangle Universities Nuclear Laboratory with quasimonoenergetic neutrons between 23.5 and 30.5 MeV, where few previous measurements have been made. Cross-section data are compared to calculations and other available measurements. [ABSTRACT FROM AUTHOR]

The 86Kr(n,y)87Kr neutron-capture cross section was measured at 11 energies between 0.37 and 14.8 MeV. Cross-section data for the 86Kr(n,2n)85Krm reaction were obtained at 9 energies between 10.9 and 14.8 MeV. The data are important for testing calculations used to predict the. v-process cross section in the unmeasured energy range above 1 MeV for the 86Kr(n,2n)87 reaction, and to check on the consistency of parameters used in TALYS calculations for the 86Kr(n,2n)85Krm+g cross section. The two data sets could also be used as a nuclear physics based diagnostic tool for studying properties of the deuterium-tritium plasma created in inertial confinement fusion reactions at the National Ignition Facility at Lawrence Livermore National Laboratory. [ABSTRACT FROM AUTHOR]

Using dual-fission chambers each loaded with a thick (200-400-mg/cm²) actinide target of 235,238U or 239Pu and two thin (~10-100-μg/cm²) reference foils of the same actinide, the cumulative yields of fission products ranging from 92Sr to 147Nd have been measured at En = 8.9MeV. The ²H(d,n)³He reaction provided the quasimonoenergetic neutron beam. The experimental setup and methods used to determine the fission product yield (FPY) are described, and results for typically eight high-yield fission products are presented. Our FPYs for 235U(n,f), 238U(n,f), and 239Pu(n,f) at 8.9 MeV are compared with the existing data below 8 MeV from Glendenin et al. [Phys. Rev. C 24, 2600 (1981)], Nagy et al. [Phys. Rev. C 17, 163 (1978)], Gindler et al. [Phys. Rev. C 27, 2058 (1983)], and those of Mac Innes et al. [Nucl. Data Sheets 112, 3135 (2011)] and Laurec et al. [Nucl. Data Sheets 111, 2965 (2010)] at 14.5 and 14.7 MeV, respectively. This comparison indicates a negative slope for the energy dependence of most fission product yields obtained from 235U and 239Pu, whereas for 238U the slope issue remains unsettled. [ABSTRACT FROM AUTHOR]

Measurements of the neutron radiative-capture cross section of 124Xe have been performed for the first time for neutron energies above 100 keV. In addition, data for the 124Xe(n,2n)123Xe reaction cross section have been obtained from threshold to 14.8 MeV to cover the entire energy range of interest, while previous data existed only at around 14 MeV. The results of these measurements provide the basis for an alternative and sensitive diagnostic tool for investigating properties of the inertia! confinement fusion plasma in deuterium-tritium (DT) capsules at the National Ignition Facility located at Lawrence Livermore National Laboratory. Here, areal density pR (density x radius) of the fuel, burn asymmetry, and fuel-ablator mix are of special interest. The 124Xe(n,γ)125Xe reaction probes the down-scattered neutrons, while the 124Xe(n,2n)123Xe reaction provides a measure of the 14 MeV direct neutrons. [ABSTRACT FROM AUTHOR]

The cross section of the reaction 136Xe(n,2n)135Xe to both the ground state and the 526.6 keV isomeric states of 135Xe was measured between 9.0 and 14.9 MeV. These data are important to guide evaluations and theoretical calculations aimed at estimating the importance of neutron-induced background effects in searches for neutrinoless double-β decay of 136Xe. [ABSTRACT FROM AUTHOR]

The activation technique was used to measure the cross section for the reaction 40Ar(n,p)40Cl in 0.5 MeV energy steps in the neutron energy range between 9 and 15 MeV. These data are important for estimating background contributions in neutrinoless double-beta decay and dark matter searches, as well as in argon-based large neutrino detectors. The data are compared to evaluations and theoretical predictions. [ABSTRACT FROM AUTHOR]

The magnetic dipole strength in the energy region of the spin-flip resonance is investigated in 128Xe and 134Xe using quasimonoenergetic and linearly polarized γ-ray beams at the High-Intensity γ-Ray Source facility in Durham, North Carolina, USA. Absorption cross sections were deduced for the magnetic and electric and dipole strength distributions separately for various intervals of excitation energy, including the strength of states in the unresolved quasicontinuum. The magnetic dipole strength distributions show structures resembling a resonance in the spin-flip region around an excitation energy of 8 MeV. The electric dipole strength distributions obtained from the present experiments are in agreement with the ones deduced from an earlier experiment using broad-band bremsstrahlung instead of a quasimonoenergetic beam. The experimental magnetic and electric dipole strength distributions are compared with phenomenological approximations and with predictions of a quasiparticle random phase approximation in a deformed basis. [ABSTRACT FROM AUTHOR]

Two samples, one of natural iridium and the other of enriched 193 Ir, were irradiated with a monoenergetic neutron beam of energy 6.0 MeV at the Triangle Universities Nuclear Laboratory. The product of the 193 Ir [Formula: see text] Ir reaction was determined by means of measuring X-rays following electron conversion of the isomeric state at 80.2 keV in 193 Ir. The cross section for inelastic neutron scattering is reported disagreeing with the literature data., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)