Scintillation characteristics of the EJ-299-02H scintillator.

A study of the dead layer thickness and quenching factor of a plastic scintillator for use in ultracold neutron (UCN) experiments is described. Alpha spectroscopy was used to determine the thickness of a thin surface dead layer to be 630 ± 110 nm. The relative light outputs from the decay of 241Am and Compton scattering of electrons were used to extract Birks' law coefficient, yielding a kB value of 0.087 ± 0.003 mm/MeV, consistent with some previous reports for other polystyrene-based scintillators. The results from these measurements are incorporated into the simulation to show that an energy threshold of (∼9 keV) can be achieved for the UCNProBe experiment. This low threshold enables high beta particle detection efficiency and the indirect measurement of UCN. The ability to make the scintillator deuterated, accompanied by its relatively thin dead layer, gives rise to unique applications in a wide range of UCN experiments, where it can be used to trap UCN and detect charged particles in situ.

Simulation and validation studies of a large drift tube muon tracker.

Cosmic ray muons are massive, charged particles created from high energy cosmic rays colliding with atomic nuclei in Earth's atmosphere. Because of their high momenta and weak interaction, these muons can penetrate through large thicknesses of dense material before being absorbed, making them ideal for nondestructive imaging of objects composed of high-Z elements. A Giant Muon Tracker with two horizontal 8 × 6 in.2 and two vertical 6 × 6 in.2 modules of drift tubes was used to measure muon tracks passing through samples placed inside the detector volume. The experimental results were used to validate a Monte Carlo simulation of the Giant Muon Tracker. The imaging results of simulated samples were reconstructed and compared with those from the experiment, which showed excellent agreement.

Improved Neutron Lifetime Measurement with UCNτ.

We report an improved measurement of the free neutron lifetime τ_{n} using the UCNτ apparatus at the Los Alamos Neutron Science Center. We count a total of approximately 38×10^{6} surviving ultracold neutrons (UCNs) after storing in UCNτ's magnetogravitational trap over two data acquisition campaigns in 2017 and 2018. We extract τ_{n} from three blinded, independent analyses by both pairing long and short storage time runs to find a set of replicate τ_{n} measurements and by performing a global likelihood fit to all data while self-consistently incorporating the ß-decay lifetime. Both techniques achieve consistent results and find a value τ_{n}=877.75±0.28_{stat}+0.22/-0.16_{syst} s. With this sensitivity, neutron lifetime experiments now directly address the impact of recent refinements in our understanding of the standard model for neutron decay.

Ultracold neutron properties of the Eljen-299-02D deuterated scintillator.

In this paper, we report studies of the Fermi potential and loss per bounce of ultracold neutrons (UCNs) on a deuterated scintillator (Eljen-299-02D). These UCN properties of the scintillator enable its use in a wide variety of applications in fundamental neutron research.

Application of muon tomography to fuel cask monitoring.

Long-term monitoring of spent fuel stored in dry cask storage is currently achieved through the use of seals and surveillance. Muon tomography can provide direct imaging that may be useful in cases where what is known as Continuity of Knowledge (CoK) has been lost using the former methods. Over the past several years, a team from Los Alamos National Laboratory has been studying the use of muon scattering and stopping to examine spent fuel in dry cask storage. Data taken on a partially loaded Westinghouse MC-10 fuel cask have demonstrated that muon scattering radiography can detect missing fuel assemblies. A model, validated by this data, shows that tomographic reconstructions of the fuel can be obtained in relatively short exposures. Model fitting algorithms have been developed for dealing with datasets with limited angular that appear to work well. Here we show that muon tomography can provide a fingerprint of a loaded fuel cask, because of its sensitivity to both the density and atomic charge of the spent fuel, and that it is sensitive to many diversion scenarios.This article is part of the Theo Murphy meeting issue 'Cosmic-ray muography'.

Search for the Neutron Decay n→X+γ, Where X is a Dark Matter Particle.

Fornal and Grinstein recently proposed that the discrepancy between two different methods of neutron lifetime measurements, the beam and bottle methods, can be explained by a previously unobserved dark matter decay mode, n→X+γ. We perform a search for this decay mode over the allowed range of energies of the monoenergetic γ ray for X to be dark matter. A Compton-suppressed high-purity germanium detector is used to identify γ rays from neutron decay in a nickel-phosphorous-coated stainless-steel bottle. A combination of Monte Carlo and radioactive source calibrations is used to determine the absolute efficiency for detecting γ rays arising from the dark matter decay mode. We exclude the possibility of a sufficiently strong branch to explain the lifetime discrepancy with 97% confidence.

Measurement of the neutron lifetime using a magneto-gravitational trap and in situ detection.

The precise value of the mean neutron lifetime, τn, plays an important role in nuclear and particle physics and cosmology. It is used to predict the ratio of protons to helium atoms in the primordial universe and to search for physics beyond the Standard Model of particle physics. We eliminated loss mechanisms present in previous trap experiments by levitating polarized ultracold neutrons above the surface of an asymmetric storage trap using a repulsive magnetic field gradient so that the stored neutrons do not interact with material trap walls. As a result of this approach and the use of an in situ neutron detector, the lifetime reported here [877.7 ± 0.7 (stat) +0.4/-0.2 (sys) seconds] does not require corrections larger than the quoted uncertainties.

A new method for measuring the neutron lifetime using an in situ neutron detector.

In this paper, we describe a new method for measuring surviving neutrons in neutron lifetime measurements using bottled ultracold neutrons (UCN), which provides better characterization of systematic uncertainties and enables higher precision than previous measurement techniques. An active detector that can be lowered into the trap has been used to measure the neutron distribution as a function of height and measure the influence of marginally trapped UCN on the neutron lifetime measurement. In addition, measurements have demonstrated phase-space evolution and its effect on the lifetime measurement.

Evaluation of raw pork as a commercially manufactured diet option for zoo-managed African wildcats (Felis silvestris lybica).

Second to beef, pork is a major protein source produced in the US. Properly sourced and handled pork could be utilized as a protein option for zoo-managed carnivores. Concerns of high levels of microbial populations in raw meat diets are common. The objectives of this study were to determine apparent total tract macronutrient and energy digestibility and fecal scores from cats fed a commercially manufactured raw pork-based diet compared with commercially available raw carnivore diets formulated with either horse or beef and evaluate typical microbial population variation among the diets. Dietary treatments consisted of 4 raw meat-based diets: Horse, Beef, Pork, and beef/horse Blend. All diets were highly digestible, especially fat digestibility (98.6 to 99.7%) in which there were no statistical differences among diets. Digestibility of organic matter (OM) was greater (P = 0.05) when cats consumed the Blend diet (97.2%) compared to the Pork diet (93.1%). Fecal scores ranged from 1.6 to 2.6 (on a 5-point scale), with Beef (2.6) being greater than (P = 0.01) Horse (1.6) and (P = 0.02) Pork (1.9). E. coli counts ranged from 110 to 10,000 cfu/g; total coliforms: 150 to 28,000 cfu/g; yeast: 20 to 4,000 cfu/g; mold count: not detectable to 10 cfu/g; and aerobic plate count: 23,000 to 26,000,000 cfu/g. Staphylococcus aureus was not detected in any of the diets. Salmonella was presumptive positive in the Pork and Blend diet, and was negative in the other 2 diets. In conclusion, commercially manufactured diets have varying microbial counts. All diets, including the raw pork-based diet were well utilized by exotic small cats and can be included among dietary options for managed felids.

A study of CR-39 plastic charged-particle detector replacement by consumer imaging sensors.

Consumer imaging sensors (CIS) are examined for real-time charged-particle detection and CR-39 plastic detector replacement. Removing cover glass from CIS is hard if not impossible, in particular for the latest inexpensive webcam models. We show that $10-class CIS are sensitive to MeV and higher energy protons and α-particles by using a 90Sr ß-source with its cover glass in place. Indirect, real-time, high-resolution detection is also feasible when combining CIS with a ZnS:Ag phosphor screen and optics. Noise reduction in CIS is nevertheless important for the indirect approach.

Influence of pork and pork by-products on macronutrient and energy digestibility and palatability in large exotic felids.

Two experiments were conducted to evaluate digestibility and palatability of a new commercial pork-based raw diet for zoo-managed felids. Currently 2 protein sources (beef or horse) comprise the majority of commercial raw meat diet formulations for exotic carnivores in zoological institutions. Pork-based diets have traditionally not been widely utilized and thus nutrient digestibility of pork has not been adequately evaluated in exotic carnivores. The objectives of this study were 1) to determine if a pork-based diet had similar apparent total tract macronutrient digestibility and fecal scores as standard zoo carnivore diets formulated with either horse or beef, in large exotic felids and 2) evaluate palatability of pork for use in zoos. Ten exotic felids were used including cheetahs (; 3), jaguars (; = 3), leopards (; 2), puma (; 1), and Bengal tiger (; 1). Dietary treatments consisted of 4 raw meat diets: 1 horse-based (Horse), 2 beef-based (B1, B2), and 1 pork-based diet (Pork). Fecal scores also were evaluated (1 = hard to 5 = watery/liquid). This randomized crossover design study consisted of 4 periods, each 10 d for treatment adaptation followed by 4 d of sample collection. Dry matter and crude protein apparent digestibility values were greater ( < 0.05) in felids fed Pork (88.0 and 95.7%) compared with felids fed Horse (83.6 and 92.7%) and B2 (85.6 and 93.1%). Apparent organic matter digestibility was greater ( < 0.05) in felids fed Pork (90.8%) than felids fed Horse (88.5%). Apparent fat digestibility values were high across all treatments but were greater ( < 0.05) in felids fed Pork (98.5%) compared with felids fed B1 (95.5%) or B2 (96.5%). Gross energy digestibility values were greater in felids fed Pork (92.4%) compared with B1 (90.2%). Average fecal scores were 2.30, 2.94, 3.42, and 3.54 for Horse, Pork, B1 and B2, respectively; and were different ( < 0.05) between treatments with exception of B1 and B2 that did not differ. Felids approached the pork diet first in 65.6% of observations and tasted the pork diet first in 71.9% of observations, compared with a beef-based raw diet. Based on results, the evaluated pork-based diet had similar apparent total tract macronutrient digestibility and palatability compared with standard zoo carnivore formulations. In conclusion, pork-based diets could be included among dietary options for large zoo felids.

High order magnetic optics for high dynamic range proton radiography at a kinetic energy of 800 MeV.

Flash radiography with 800 MeV kinetic energy protons at Los Alamos National Laboratory is an important experimental tool for investigations of dynamic material behavior driven by high explosives or pulsed power. The extraction of quantitative information about density fields in a dynamic experiment from proton generated images requires a high fidelity model of the proton imaging process. It is shown that accurate calculations of the transmission through the magnetic lens system require terms beyond second order for protons far from the tune energy. The approach used integrates the correlated multiple Coulomb scattering distribution simultaneously over the collimator and the image plane. Comparison with a series of static calibration images demonstrates the model's accurate reproduction of both the transmission and blur over a wide range of tune energies in an inverse identity lens that consists of four quadrupole electromagnets.

Apparent total tract energy and macronutrient digestibility of one- to three-day-old, adult ground, extruded, and canned chicken-based diets in domestic cats (Felis silvestris catus).

There has been a recent increase in the popularity of feeding unconventional diets, including whole prey diets, to domestic cats (Felis silvestris catus). Data are needed that allow animal caretakers to choose and formulate diets that meet the nutritional requirements of their cats. Our objective was to evaluate the effects of feeding 1- to 3-d-old whole chicks (WHO), ground adult chicken product (GRO), a chicken-based canned diet (CAN), and a chicken-based extruded diet (EXT) on apparent total tract energy and macronutrient digestibility, N balance, and blood metabolites of domestic cats (n = 11). Macronutrient, energy, and moisture concentrations of diets varied greatly (e.g., CP: 35 to 72% DM); however, cats fed all diets maintained BW and N balance. In general, cats fed WHO had lower nutrient digestibility than those fed CAN and EXT. Cats fed GRO had greater nutrient digestibility than cats fed commercial diets. For example, apparent OM and GE digestibility coefficients were greater (P ≤ 0.05) for cats fed CAN (86 and 88%, respectively), EXT (88 and 88%), and GRO (94 and 95%) compared with those fed WHO (83 and 83%) and greater (P ≤ 0.05) for cats fed GRO compared with those fed CAN and EXT. Many blood metabolites were modified by diet, but most remained within reference ranges for domestic cats. Serum cholesterol was elevated above the reference range for all treatments and greater (P ≤ 0.05) for cats fed WHO compared with those fed CAN, EXT, and GRO. Serum creatinine concentrations were above the reference range for all treatments and greater (P ≤ 0.05) for cats fed GRO compared with those fed CAN or WHO. These data indicate that the whole prey tested herein maintained short-term health and are adequately digestible for use in companion animal diets. Research is needed to determine the global and long-term health implications of feeding whole or ground diets to domestic cats, which may be different in terms of macronutrient, energy, and moisture profiles and nutrient digestibility.

Influence of dietary fiber type and amount on energy and nutrient digestibility, fecal characteristics, and fecal fermentative end-product concentrations in captive exotic felids fed a raw beef-based diet.

Little nutritional or metabolic information has been collected from captive exotic cats fed raw diets. In particular, fiber types and concentrations for use in raw meat-based diets for captive exotic felids have not been well studied. Our objective was to evaluate the effects of fiber type and concentration on apparent total tract energy and macronutrient digestibility, fecal characteristics, and fecal fermentative end-products in captive exotic felids. Four animals of each captive exotic species (jaguar (Panthera onca), cheetah (Acinonyz jubatus), Malayan tiger (Panthera tigris corbetti), and Siberian tiger (Panthera tigris altaica) were randomized in four 4 × 4 Latin square designs (1 Latin square per species) to 1 of the 4 raw beef-based dietary treatments (94.7 to 96.7% beef trimmings): 2 or 4% cellulose or 2 or 4% beet pulp. Felid species, fiber type, and fiber concentration all impacted digestibility and fecal fermentative end-products. Inclusion of beet pulp increased (P ≤ 0.05) fecal short-chain fatty acids and fecal output in all cats. Inclusion of 2 and 4% cellulose, and 4% beet pulp increased (P ≤ 0.05) fecal bulk and diluted fecal branched-chain fatty acid concentrations compared with 2% beet pulp. Apparent total tract DM, OM, fat, and GE digestibility coefficients decreased (P ≤ 0.05) linearly with BW of cats. Additionally, fecal moisture, fecal score, and concentrations of fermentative end-products increased (P ≤ 0.05) with BW. Although the response of many outcomes was dependent on cat size, in general, beet pulp increased wet fecal weight, fecal scores, and fecal metabolites, and reduced fecal pH. Cellulose generally reduced DM and OM digestibility, but increased dry fecal weight and fecal percent DM. Although beet pulp and cellulose fibers were tested individually in this study, these data indicate that the optimum fiber type and concentration for inclusion in captive exotic felid diets is likely a combination of fermentable and nonfermentable fibers, with the optimal fiber blend being dependent on species. Smaller cats, such as cheetahs and jaguars, tolerated fermentable fibers, whereas larger cats, such as Malayan and Siberian tigers, appeared to require more insoluble fibers that limit fermentation and provide fecal bulk. Further research is required to test whether these trends hold true when fed in combination.

Qualitative comparison of bremsstrahlung X-rays and 800 MeV protons for tomography of urania fuel pellets.

We present an assessment of x-rays and proton tomography as tools for studying the time dependence of the development of damage in fuel rods. We also show data taken with existing facilities at Los Alamos National Laboratory that support this assessment. Data on surrogate fuel rods have been taken using the 800 MeV proton radiography (pRad) facility at the Los Alamos Neutron Science Center (LANSCE), and with a 450 keV bremsstrahlung X-ray tomography facility. The proton radiography pRad facility at LANSCE can provide good position resolution (<70 µm has been demonstrate, 20 µm seems feasible with minor changes) for tomography on activated fuel rods. Bremsstrahlung x-rays may be able to provide better than 100 µm resolution but further development of sources, collimation, and detectors is necessary for x-rays to deal with the background radiation for tomography of activated fuel rods.

Charged particle radiography.

New applications of charged particle radiography have been developed over the past two decades that extend the range of radiographic techniques providing high-speed sequences of radiographs of thicker objects with higher effective dose than can be obtained with conventional radiographic techniques. In this paper, we review the motivation and the development of flash radiography and in particular, charged particle radiography.

Performance of the Los Alamos National Laboratory spallation-driven solid-deuterium ultra-cold neutron source.

In this paper, we describe the performance of the Los Alamos spallation-driven solid-deuterium ultra-cold neutron (UCN) source. Measurements of the cold neutron flux, the very low energy neutron production rate, and the UCN rates and density at the exit from the biological shield are presented and compared to Monte Carlo predictions. The cold neutron rates compare well with predictions from the Monte Carlo code MCNPX and the UCN rates agree with our custom UCN Monte Carlo code. The source is shown to perform as modeled. The maximum delivered UCN density at the exit from the biological shield is 52(9) UCN/cc with a solid deuterium volume of ~1500 cm(3).

Evaluation of four raw meat diets using domestic cats, captive exotic felids, and cecectomized roosters.

Our objective was to evaluate raw meat diets for captive exotic and domestic carnivores containing traditional and alternative raw meat sources, specifically, beef trimmings, bison trimmings, elk muscle meat, and horse trimmings. We aimed to examine diet composition and protein quality; apparent total tract energy and macronutrient digestibility in domestic cats, African wildcats, jaguars, and Malayan tigers; and ME and fecal fermentative end-products in domestic cats. Because of variation in the meat sources, dietary proximate, AA, and long-chain fatty acid composition were variable. Our analyses indicated that all diets had essential fatty acid deficiencies, and the elk diet (i.e., trimmed muscle meat) was deficient in total fat. Standardized AA digestibilities measured using the cecectomized rooster assay were high (>87%). Using the NRC minimum requirements for the growth of kittens, the first limiting AA of all diets was the combined requirement of Met and Cys (AA score: 81 to 95; protein digestibility corrected AA score: 75 to 90). All diets were highly digestible (88 to 89% OM digestibility). There was no effect of diet or felid species on DM (85 to 87%), OM, and GE (90 to 91%) digestibilities. Apparent CP digestibility was greater (P≤0.05) in cats fed elk (97%) compared with those fed bison (96%), and greater (P≤0.05) in wildcats (97%) and domestic cats (97%) compared with tigers (95%). The diet and species interaction (P≤0.05) was observed for apparent fat digestibility. In domestic cats, the fresh fecal pH and proportions of acetate and butyrate were altered (P≤0.05) due to diet. Diet also affected (P≤0.05) fresh fecal concentrations of total branched-chain fatty acids, valerate, and Lactobacillus genus. In conclusion, although the raw meat diets were highly digestible, because of variation in raw meat sources the nutrient composition of the diets was variable. Thus, compositional analysis of raw meat sources is necessary for proper diet formulation. The types of meat commonly used in raw meat diets may be deficient in total fat (trimmed muscle meat) and essential fatty acids (trimmings and muscle meats). Additionally, differences in raw meat source nutrient composition and digestibility affect the beneficial and putrefactive fermentative end-products found in feces.