[Formula: see text]Al is an important radionuclide for research on stellar nucleosynthesis in the Galaxy and the environment of the early solar system. Computational simulations involving the production and destruction of [Formula: see text]Al in stellar nucleosynthesis and supernovae rely on accurate nuclear reaction network data. Some of the destruction channels via neutron-induced reactions for [Formula: see text]Al either have no measured data or discrepancies in the measured data. The Low Energy (n,Z) instrument at the Los Alamos National Laboratory can perform these measurements on neutron-induced charged-particle reactions; however, a thin and uniform target is required. Such a target can be manufactured via molecular plating, but this process needs to be optimized. This study was able to determine a procedure that allows for the production of an Al target on a 1 [Formula: see text]m thick Ti foil with a >70% yield. Adding a small amount of Ce in the initial plating solution and increasing the drying time resulted in a thin, uniform, and physically stable Al target.

Neutron-induced reactions on 35Cl have recently been measured and analyzed in a Hauser-Feshbach framework at Los Alamos National Laboratory. Particular focus has been applied to the “fast” energy range above 100 keV, where these reactions become important for applications like CLYC (Cs2LiYCl6:Ce) detector characterization and the development of molten chloride fast reactors. However, challenges to applying a purely statistical analysis to this mass range have presented themselves in the form of cross section fluctuations and deviations due to low-mass structure. In this paper, these challenges and their current solutions will be highlighted, as well as preliminary extensions of the analysis to neighboring isotopes and future plans to extend the measurements down to thermal energies.

High quality nuclear reaction data for radionuclides is lacking, which can be best rectified by performing direct measurements of neutron-induced reactions on the target nuclei of interest. Two instruments at the Los Alamos Neutron Science Center, the Low Energy (n,Z) (LENZ) instrument and the Device for Indirect Capture Experiments on Radionuclides (DICER), can perform such measurements on radioactive targets. This manuscript covers the target requirements for such experiments and provides examples of how defects in the targets manifests in the measured data.

This paper provides a template of expected uncertainties and correlations for measurements of neutron-induced capture and charged-particle production cross sections. Measurements performed in-beam include total absorption spectroscopy, total energy detection,γ-ray spectroscopy, and direct charged-particle detection. Offline measurements include activation analysis and accelerator mass spectrometry. The information needed for proper use of the datasets in resonance region and high energy region evaluations is described, and recommended uncertainties are provided when specific values are not available for a dataset.

The characterization of fission-driven nuclear systems primarily relies on calculations of neutron-induced chain reactions, and these calculations require evaluated nuclear data as input. Calculation accuracy heavily depends on input nuclear data evaluation accuracy, and thus high precision on the experimental input to the nuclear data evaluation is essential for fundamental quantities like the energy spectrum of neutrons emitted from neutron-induced fission (i.e., the prompt fission neutron spectrum, PFNS). Despite decades of measurement efforts, prior to the measurements described in this work there were only three literature data sets for the U-235(n, f) PFNS at incident neutron energies above 1.0 MeV considered reliable for inclusion in nuclear data evaluations and no reliable data sets above 3.0 MeV incident neutron energy. In this work we report on new measurements of the U-235(n, f) PFNS spanning a grid of 1.0-20.0 MeV in incident neutron energy and 0.0110.0 MeV in outgoing (PFNS) neutron energy. These measurements were carried out at the Weapons Neutron Research facility at the Los Alamos Neutron Science Center and used a multifoil parallel-plate avalanche counter target with both a Li-glass and a liquid scintillator detector array in separate experiments to span the quoted outgoing neutron energy ranges. The PFNS results are shown in terms of the energy spectra themselves as well as the average PFNS energy ((E)) and ratios of (E) at forward and backward angles. The results are compared with literature data and selected nuclear data evaluations. Generally, the data agree with the ENDF/B-VIII.0 evaluation below 5.0-MeV incident neutron energy and more closely with the JEFF-3.3 evaluation above 5.0 MeV, though no evaluations considered for comparison in this work agree with the data across all of the incident and outgoing neutron energies shown, especially in regions where the third-chance fission process becomes available. Additionally, we show a ratio of the present PFNS results for U-235(n, f) with a recent and highly correlated experiment to measure the Pu-239(n, f) PFNS at the same experimental facility and with nearly identical equipment and analysis procedures. Many observations reported in this work are the first of their kind and represent significant advancements for knowledge of the U-235(n, f) PFNS.

Nuclear reaction data for neutron induced reactions on unstable nuclei are critical for a wide range of applications spanning studies of nuclear astrophysics, nuclear reactor designs, and radiochemistry diagnostics. However, nuclear data evaluations of the reaction cross sections are largely based on calculations due to the difficulty in performing this class of measurements and the resulting lack of experimental data. For neutron induced charged particle reactions at fast neutron energies, at the MeV scale, these cross section predictions are predominately driven by statistical Hauser-Feshbach calculations. In this work, we present partial and total Ni-59(n, p) and Ni-59(n, alpha) cross sections, measured directly with a radioactive Ni-59 target, and compare the results to the present nuclear data evaluations. In addition, the results from this work are compared to a recent study of the (59) Ni(n, xp) reaction cross section that was performed via an indirect surrogate ratio method. The expected energy trend of the cross section, based on the current work, is inconsistent with that of the surrogate work. This calls into question the reliability of that application of the surrogate ratio method and highlights the need for direct measurements on unstable nuclei, when feasible.

Nuclear reaction data for neutron induced reactions on unstable nuclei are critical for a wide range of applications spanning studies of nuclear astrophysics, nuclear reactor designs, and radiochemistry diagnostics. However, nuclear data evaluations of the reaction cross sections are largely based on calculations due to the difficulty in performing this class of measurements and the resulting lack of experimental data. For neutron induced charged particle reactions at fast neutron energies, at the MeV scale, these cross section predictions are predominately driven by statistical Hauser-Feshbach calculations. In this work, we present partial and total $^{59}\mathrm{Ni}(n,p)$ and $^{59}\mathrm{Ni}(n,\ensuremath{\alpha})$ cross sections, measured directly with a radioactive $^{59}\mathrm{Ni}$ target, and compare the results to the present nuclear data evaluations. In addition, the results from this work are compared to a recent study of the $^{59}\mathrm{Ni}(n,xp)$ reaction cross section that was performed via an indirect surrogate ratio method. The expected energy trend of the cross section, based on the current work, is inconsistent with that of the surrogate work. This calls into question the reliability of that application of the surrogate ratio method and highlights the need for direct measurements on unstable nuclei, when feasible.

Prompt fission neutron spectrum (PFNS) evaluations use provide nuclear data for the PFNS across a wide range of incident and outgoing neutron energies. However, experimental data underlying the evaluation are sparse, inconsistent, and incomplete with respect to the desired incident and outgoing energy coverage. As such, evaluations sometimes predict features of the PFNS, such those relating to multi-chance fission and pre-equilibrium pre-fission neutron emission, without any experimental validation. The Chi-Nu experiment at Los Alamos National Laboratory has recently obtained high-precision results for the 239Pu and 235U PFNS which, for the first time in both cases, have shed light on multi-chance fission and pre-equilibrium contributions to the observed fission neutron spectrum. In addition to providing the first experimental data on some of these fission properties, the angular coverage of the Chi-Nu experiment allows for the extraction of angular distributions of pre-equilibrium pre-fission neutrons. PFNS results of multi-chance fission and pre-equilibrium pre-fission neutron emission are discussed in this proceedings in terms of the observed neutron spectrum and the average PFNS energies.

Recent development on neutron-induced charged particle reaction measurements can provide high-quality double differential cross sections at Los Alamos Neutron Science Center. With newly measured cross section data, we found lacking nuclear outputs for neutron-induced charged particle reactions in the latest ENDF/B-VIII.0 library, when compared with Monte Carlo simulations. This paper presents how we improved the missing angular distributions and energy spectra for these reactions and the validation of our new evaluations with the measurements performed with the LENZ instrument at LANSCE. The impact of this additional evaluation is demonstrated by comparing the MCNP simulations with the LENZ experimental data.

The lack of experimental data on the $^{35}\mathrm{Cl}(n,p)^{35}\mathrm{S}$ reaction above 100 keV has led to nuclear data evaluations that are relatively unconstrained at fast neutron energies. As a result, efforts to explore, develop, and potentially certify next generation reactor designs that incorporate chloride salts as a coolant material have been hindered. In this paper, we report partial cross section data for the $^{35}\mathrm{Cl}(n,p)^{35}\mathrm{S}$ and $^{35}\mathrm{Cl}(n,\ensuremath{\alpha})^{32}\mathrm{P}$ reactions at incident neutron energies between 0.6 MeV and 6 MeV. The measurement was performed using the pulsed beam of neutrons at the unmoderated WNR spallation neutron source at the Los Alamos Neutron Science Center, with the outgoing charged particles detected by the LENZ experimental setup, consisting of annular silicon detectors. Nonstatistical fluctuations in the $^{35}\mathrm{Cl}(n,{p}_{0})$ cross section were observed up to around 3 MeV, and the magnitude of the cross section was systematically lower than all available data evaluations at energies above 1 MeV. Modifications to the ENDF/B-VIII.0 data evaluation are suggested to better reproduce the energy averaged experimental data.

We report the current results of a large effort to accurately measure the Prompt Fission Neutron Spectra (PFNS) for neutron-induced fission of 235U and 239Pu for incident neutrons with energies from 1 to 20 MeV. The Chi-Nu experiment at the Los Alamos Neutron Science Center used an unmoderated, white spectrum of neutrons to induce fission in actinide samples that were placed inside a parallel plate avalanche counter to provide a fast fission signal. A double time-of-flight technique was used to determine the incoming and outgoing neutron energies. Two neutron detector arrays, one with 54 liquid scintillators and another with 22 lithium glass detectors, were used to detect the outgoing neutrons and measure the PFNS distributions over a wide range in outgoing neutron energy, from below 100 keV to 10 MeV. Extensive Monte Carlo modeling was used to understand the experiment response and extract the PFNS. Systematic errors and uncertainties in the method have been examined and quantified. A summary of these results for incoming energies from 1 to 5 MeV is presented here.

The total kinetic energy (TKE) release in fission is an important observable, constituting over 80% of the energy released in fission ( $$\hbox {E}_{f} \approx 200~\hbox {MeV}$$ ). While the TKE release in the $$^{239}\hbox {Pu}$$ (n,f) reaction was previously measured up to 50 MeV incident neutron energy ( $$\hbox {E}_{n}$$ ), there were features in TKE release at the highest values of $$\hbox {E}_{n}$$ that were puzzling. There was a marked flattening of TKE release from $$\hbox {E}_{n} = 30$$ to 50 MeV, in disagreement with the clearly decreasing TKE observed from $$\hbox {E}_{n} = 0.5$$ to 30 MeV. To verify and clarify this trend, TKE measurements at higher values of $$\hbox {E}_n$$ were made. We present absolute measurements of TKE release in $$^{239}\hbox {Pu}$$ (n,f) from $$\hbox {E}_{n} = 2.4$$ to 100 MeV. We used silicon PIN detectors to measure the fragment energies and deduce mass-yield curves using the 2E-method. We also discuss fission asymmetry and the relationships between approximate fission fragment mass and distortion.

Mycoplasma pneumoniae is a main pathogen causing community-acquired pneumonia in children and young adults. Since the emergence of macrolide-resistant M. pneumoniae in the early 2000s in Japan, it has been increasingly reported worldwide as a growing problem in treatment for children. With increasing macrolide-resistant M. pneumoniae and limited data regarding its characterization and molecular analysis, we investigated the dominant M. pneumoniae strains during the recent outbreak in South Korea, and evaluated if there was an association between a specific type and macrolide resistance. Between October 2014 and December 2016 in South Korea, 249 respiratory specimens obtained from patients with confirmed M. pneumoniae pneumonia were genotyped the P1 adhesin gene, and the mutations associated with resistance (A2063G and A2064G) were tested by sequencing the targeted domain V regions of the 23S ribosomal RNA gene. Results revealed that M. pneumoniae type 1 were predominant, which was strongly associated with macrolide-resistance during the whole study period. This is the first study assessing whether M. pneumoniae subtype is related to macrolide resistance during the outbreak of M. pneumoniae.