Engineering topics
Publications and source records attributed to Barry, D..
This presentation covers the validation and evaluation uses of quasi-differential high-energy scattering data. This lecture covers motivation behind this work. The lecture then touches on quasi-differential for evaluation, quasi-differential for covariance, and quasi-differential for validation. The presentation concludes with a summary.
This presentation begins with the motivation for performing 181 Ta and 19 F high energy quasi-differential and neutron emission measurements. It then provides a discussion of significant pulse digitization upgrade. The Quasi-Differential methodology and importance for validating nuclear data are provided. Preliminary results from 181 Ta and 19 F are displayed. The presentation concludes with a discussion and future studies.
This presentation touches on fast neutron evaluations for advanced lead systems. This lecture covers project goals to evaluate lead (Pb) isotopes with a focus on improving predictive capabilities of fast systems. Additionally, the project sets out to benchmark available critical and shielding experiments with sensitivity to Pb and utilize RPI Quasi-Differential Scattering experiment for scattering reactions. This project will perform Resolved Resonance Region (RRR) and fast region evaluations for natural Pb isotopes with differential data on EXchange FORmat for experimental numerical nuclear reaction data (EXFOR) and ultimately will submit evaluations to the ENDF/B-VIII.1 library.
This presentation discusses the experimental, simulation, and nuclear data methods that were validated for the RPI γ-Multiplicity Detector. When the neutron capture γ-cascade data is well-known, the γ-emission spectra can be accurately calculated using the modified simulation tools. The RPI γ-Multiplicity Detector system is now ready for analysis and recommendations for isotopes with deficiencies in γ-ray data. The presentation also discusses future work which includes developing a method for analyzing and adjusting nuclear data for 59 Co, 55 Mn and other measured isotopes including 181 Ta. Additionally, future work includes comparing experimental γ-emission spectra with MCNP-6.2/DICEBOX simulations for 238 U and 235 U. In summation, new capture and transmission measurements for 54 Fe will help improve resonance parameter evaluation. Neutron capture gamma cascade spectra and yields were measured in the resolved resonance region and compared to evaluations. In addition, the pulsed neutron die-away method was developed as a tool to provide data for validation of TSLs.
A new sub-thermal neutron transmission capability at RPI LINAC has been used to validate Be (metal). NNL transmission measurements validated NCSU Be and Be+Sd TSLs for ENDF/B-VIII.1 and showed improvements WRT ENDF/B-VII.1 and ENDF/B-VIII.0. Amplitude differences highlighted the importance of sample characterization. Additional measurement is in progress for CY2022. PNDA is being developed as an alternative to critical experiment validation.
This presentation covers how a new sub-thermal neutron transmission capability at RPI LINAC is now in use to help validate TSL evaluations. Additionally, NNL has contributed multiple material evaluations to ENDF/B-VIII.1. Lastly, this presentation covers new methods to improve TSL physics and accuracy are being formulated.
In order to improve on current prompt fission neutron spectrum measurements, a gamma multiplicity tagging method was developed at the Rensselaer Polytechnic Institute Gearttner Linear Accelerator Center. This method involves using a coincidence requirement on an array of BaF 2 gamma detectors to determine the timing of a fission event. This allows for much larger fission samples to be used due to the higher penetrability of gammas compared to fission fragments. Additionally, since the method relies on gammas as opposed to fission fragments, the effects of the low level discriminator, used in fission chambers to eliminate alpha events, are not seen. A 252 Cf fission chamber was constructed in order to determine the viability of this method as well as the efficiency when compared to a fission chamber. The implemented multiple gamma tagging method was found to accurately reproduce the prompt fission neutron spectrum for the spontaneous fission of 252 Cf and to detect 30% of fission events.
Accurate nuclear data are important in several aspects of nuclear engineering, such as reactor simulations, nonproliferation, and criticality safety. One of the nuclear data measurements that requires reduced uncertainties in its related cross-sections is neutron capture. The neutron capture cross-sections have particular deficiencies in the incident neutron energy range from 1 keV to 1 MeV. This is due to the predominance of scattering reactions in this energy region. In order to provide more accurate measurements in this energy region, a new experimental setup has been designed and created at Rensselaer Polytechnic Institute (RPI). This experiment utilizes several C{sub 6}D{sub 6} detectors in a low mass system to minimize the effects of neutron scattering on the experiment. In order to determine the capture yield for the measurements, several additional factors need to be known about the neutron beam including the energy dependence of the neutron flux incident on the sample. A detector made from a thin piece of EJ-204 plastic scintillator was designed to measure the neutron flux, as a function of incident neutron energy, during the capture measurements. (authors)
A new array of four C6D6 detectors has been developed at the Rensselaer Polytechnic Institute Gaerttner LINAC center for the purposes of measuring neutron capture cross sections in the keV resonance region with low sensitivity to scattered neutrons. The new detection apparatus incorporates low-mass, low cross-section materials to reduce neutron sensitivity, and uses digital data acquisition equipment to enable saving of the full waveform output of each detector module for offline analysis. Capture yields are determined by applying the total energy method and pulse height weighting technique during the analysis of the saved data. Measurements have been performed on samples of iron and tantalum using the new system, with results consistent with existing data libraries. (authors)
Accurate isotopic molybdenum nuclear data are important because molybdenum can exist in nuclear reactor components including fuel, cladding, or as a high yield fission product. High-resolution time-of-flight neutron transmission measurements on highly enriched isotopic metallic samples of 95 Mo, 96 Mo, 98 Mo, and 100 Mo were performed in the resonance energy range from 1 to 620 keV. The measurements were taken with the newly developed modular 6 Li-glass transmission detector positioned at the 100-m experimental flight station. For the unresolved energy region (URR), new comprehensive methods of analysis were developed and validated in order to obtain accurate neutron total cross-section data from the measurement by correcting for background and transmission enhancement effects. Average parameters and fits to the total cross section for 95 Mo were obtained using the Hauser-Feshbach statistical model code FITACS, which is currently incorporated into the SAMMY code. Moreover, fits to the experimental data deviate from the current evaluated nuclear data file/B-VII.1 isotopic Mo evaluations by several percent in the URR.
A summary is presented for 130 galaxies observed with the Herschel Photodetector Array Camera and Spectrometer instrument to measure fluxes for the [C II] 158 μm emission line. Sources cover a wide range of active galactic nucleus to starburst classifications, as derived from polycyclic aromatic hydrocarbon strength measured with the Spitzer Infrared Spectrograph. Redshifts from [C II] and line to continuum strengths (equivalent width (EW) of [C II]) are given for the full sample, which includes 18 new [C II] flux measures. Calibration of L([C II)]) as a star formation rate (SFR) indicator is determined by comparing [C II] luminosities with mid-infrared [Ne II] and [Ne III] emission line luminosities; this gives the same result as determining SFR using bolometric luminosities of reradiating dust from starbursts: log SFR = log L([C II)]) – 7.0, for SFR in M{sub ☉} yr{sup –1} and L([C II]) in L{sub ☉}. We conclude that L([C II]) can be used to measure SFR in any source to a precision of ∼50%, even if total source luminosities are dominated by an active galactic nucleus (AGN) component. The line to continuum ratio at 158 μm, EW([C II]), is not significantly greater for starbursts (median EW([C II]) = 1.0 μm) compared to composites and AGNs (median EW([C II]) = 0.7 μm), showing that the far-infrared continuum at 158 μm scales with [C II] regardless of classification. This indicates that the continuum at 158 μm also arises primarily from the starburst component within any source, giving log SFR = log νL{sub ν}(158 μm) – 42.8 for SFR in M{sub ☉} yr{sup –1} and νL{sub ν}(158 μm) in erg s{sup –1}.