Analysis of the Johns Hopkins Neutron Background Measurements

This report addresses the analysis of the Johns Hopkins neutron background measurements

Rain-Induced Increase in Background Radiation Detected by Radiation Portal Monitors

A complete understanding of both the steady state and transient background measured by Radiation Portal Monitors (RPMs) is essential to predictable system performance, as well as maximization of detection sensitivity. To facilitate this understanding, a test bed for the study of natural background in RPMs has been established at the Oak Ridge National Laboratory. This work was performed in support of the Second Line of Defense Program's mission to detect the illicit movement of nuclear material. In the present work, transient increases in gamma ray counting rates in RPMs due to rain are investigated. The increase in background activity associated with rain, which has been well documented in the field of environmental radioactivity, originates from the atmospheric deposition of two radioactive daughters of radon-222, namely lead-214 and bismuth-214 (henceforth {sup 222}Rn, {sup 214}Pb and {sup 214}Bi). In this study, rainfall rates recorded by a co-located weather station are compared with RPM count rates and High Purity Germanium spectra. The data verifies these radionuclides are responsible for the dominant transient natural background fluctuations in RPMs. Effects on system performance and potential mitigation strategies are discussed

Fast-, Light-Cured Scintillating Plastic for 3D-Printing Applications

Additive manufacturing techniques enable a wide range of possibilities for novel radiation detectors spanning simple to highly complex geometries, multi-material composites, and metamaterials that are either impossible or cost prohibitive to produce using conventional methods. The present work identifies a set of promising formulations of photocurable scintillator resins capable of neutron-gamma pulse shape discrimination (PSD) to support the additive manufacturing of fast neutron detectors. The development of these resins utilizes a step-by-step, trial-and-error approach to identify different monomer and cross-linker combinations that meet the requirements for 3D printing followed by a 2-level factorial parameter study to optimize the radiation detection performance, including light yield, PSD, optical clarity, and hardness. The formulations resulted in hard, clear, PSD-capable plastic scintillators that were cured solid within 10 s using 405 nm light. The best-performing scintillator produced a light yield 83% of EJ-276 and a PSD figure of merit equaling 1.28 at 450–550 keVee

ADVANCED NEUTRON GENERATOR FOR SNM IMAGING

Report about the Advanced Neutron Generator for SNM Imaging

T=1 states in Rb74 and their Kr74 analogs

Charge symmetry breaking effects that perturb analog symmetry between nuclei are usually small but are important in extracting reliable Fermi matrix elements from "superallowed" β decays and testing conserved vector current theory, especially for the heavier cases. We have used the Ca40(Ar36, pn)Rb74 and Ca40(Ca40,αpn)Rb74 reactions at 108, 123 and 160 MeV, respectively, to populate Rb74 and determine the analog distortion through comparison of T=1 states in Rb74 with their corresponding Kr74 levels. We have traced the analogs of the Kr74 ground-state band in Rb74 to a candidate spin J=8 state and determined the Coulomb energy differences. They are small and positive and increase smoothly with spin. New T=0 states were found that better delineate the deformed band structure and clarify the steps in deexcitation from high spin. A new T=0 band was found. No evidence was found for γ decay to or from a low-lying Jπ=0+ state in Rb74 despite a careful search

alpha-decay of excited states in 11C and 11B

Studies of the 16O(9Be,alpha7Be)14C and 7Li(9Be,alpha7Li)5He reactions at E{beam}=70 MeV have been performed using resonant particle spectroscopy techniques. The 11C excited states decaying into alpha+7Be(gs) are observed at 8.65, 9.85, 10.7 and 12.1 MeV as well as possible states at 12.6 and 13.4 MeV. This result is the first observation of alpha-decay for excited states above 9 MeV. The alpha+7Li(gs) decay of 11B excited states at 9.2, 10.3, 10.55, 11.2, (11.4), 11.8, 12.5,(13.0), 13.1, (14.0), 14.35, (17.4) and (18.6) MeV is observed. The decay processes are used to indicate the possible three-centre 2alpha+3He(3H) cluster structure of observed states. Two rotational bands corresponding to very deformed structures are suggested for the positive-parity states. Excitations of some observed T=1/2 resonances coincide with the energies of T=3/2 states which are the isobaric analogs of the lowest 11Be states. Some of these states may have mixed isospin.Comment: accepted for publication in Nuclear Physics

Manganese Superoxide Dismutase: Guardian of the Powerhouse

The mitochondrion is vital for many metabolic pathways in the cell, contributing all or important constituent enzymes for diverse functions such as β-oxidation of fatty acids, the urea cycle, the citric acid cycle, and ATP synthesis. The mitochondrion is also a major site of reactive oxygen species (ROS) production in the cell. Aberrant production of mitochondrial ROS can have dramatic effects on cellular function, in part, due to oxidative modification of key metabolic proteins localized in the mitochondrion. The cell is equipped with myriad antioxidant enzyme systems to combat deleterious ROS production in mitochondria, with the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD) acting as the chief ROS scavenging enzyme in the cell. Factors that affect the expression and/or the activity of MnSOD, resulting in diminished antioxidant capacity of the cell, can have extraordinary consequences on the overall health of the cell by altering mitochondrial metabolic function, leading to the development and progression of numerous diseases. A better understanding of the mechanisms by which MnSOD protects cells from the harmful effects of overproduction of ROS, in particular, the effects of ROS on mitochondrial metabolic enzymes, may contribute to the development of novel treatments for various diseases in which ROS are an important component

High spin states in (72,73)krypton and exit channel selection using neutron coindicidence with gammasphere

Spectroscopic investigations of the N = Z system, 72Kr and N = Z + 1 system 73Kr were performed using the national γ-ray facility Gammasphere. The systems were populated via the 2p2 n and 2pn channels of the 36Ar + 40Ca reaction at a nominal Ar beam energy of 145 MeV. An array of 15 liquid scintillation neutron detectors was installed in Gammasphere for the purpose of exit channel selection. The present work represents the first use of Gammasphere in conjunction with an array of neutron detectors and the first use of Gammasphere with complex trigger conditions. The investigations yielded improved spectroscopic data as well as the design of an optimum array for use with Gammasphere. The high spin data in 72Kr and 73Kr were considerably extended. The data were compared with the predictions of pairing and deformation self-consistent total Routhian surface calculations. The nonobservation of a backbend in 72Kr, and the anomolously large alignment in the (π, α) = (+, +1/2) band in 73Kr are not understood either in the context of the current calculations or the heavier isotopes 74,76Kr mid 75,77Kr. Despite the improved data on 72Kr and 73Kr, no hard spectroscopic evidence regarding the shape of either isotope was obtained. An improved measurement of the lifetime of the isomeric (9/2+) state in 73Kr was possible by means of a backed target measurement

High spin states in (72,73)krypton and exit channel selection using neutron coindicidence with gammasphere

Spectroscopic investigations of the N = Z system, 72Kr and N = Z + 1 system 73Kr were performed using the national γ-ray facility Gammasphere. The systems were populated via the 2p2 n and 2pn channels of the 36Ar + 40Ca reaction at a nominal Ar beam energy of 145 MeV. An array of 15 liquid scintillation neutron detectors was installed in Gammasphere for the purpose of exit channel selection. The present work represents the first use of Gammasphere in conjunction with an array of neutron detectors and the first use of Gammasphere with complex trigger conditions. The investigations yielded improved spectroscopic data as well as the design of an optimum array for use with Gammasphere. The high spin data in 72Kr and 73Kr were considerably extended. The data were compared with the predictions of pairing and deformation self-consistent total Routhian surface calculations. The nonobservation of a backbend in 72Kr, and the anomolously large alignment in the (π, α) = (+, +1/2) band in 73Kr are not understood either in the context of the current calculations or the heavier isotopes 74,76Kr mid 75,77Kr. Despite the improved data on 72Kr and 73Kr, no hard spectroscopic evidence regarding the shape of either isotope was obtained. An improved measurement of the lifetime of the isomeric (9/2+) state in 73Kr was possible by means of a backed target measurement

Passive and Active Fast-Neutron Imaging in Support of Advanced Fuel Cycle Initiative Safeguards Campaign

Results from safeguards-related passive and active coded-aperture fast-neutron imaging measurements of plutonium and highly enriched uranium (HEU) material configurations performed at Idaho National Laboratory s Zero Power Physics Reactor facility are presented. The imaging measurements indicate that it is feasible to use fast neutron imaging in a variety of safeguards-related tasks, such as monitoring storage, evaluating holdup deposits in situ, or identifying individual leached hulls still containing fuel. The present work also presents the first demonstration of imaging of differential die away fast neutrons