Theresa Elizabeth Cutler

Uncertainties of the Yn Parameters of the Hage-Cifarelli Formalism

One method for determining the physical parameters of a multiplying system is summarized by Cifarelli [1]. In this methodology the single, double and triple rates are determined from what is commonly referred to as Feynman histograms. This paper will examine two methods for estimating the uncertainty in the parameters used in inferring these rates. These methods will be compared with simulated data in order to determine which one best approximates the sample uncertainty.

Neutron Imaging at LANSCE—From Cold to Ultrafast

In recent years, neutron radiography and tomography have been applied at different beam lines at Los Alamos Neutron Science Center (LANSCE), covering a very wide neutron energy range. The field of energy-resolved neutron imaging with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as quantitative density measurements, was pioneered at the Target 1 (Lujan center), Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutrons and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR) facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns), time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.

Development and Characterization of a High-Energy Neutron Time-of-Flight Imaging System

Los Alamos National Laboratory has developed a prototype of a high-energy neutron time-of-flight imaging system for the nondestructive evaluation of dense, massive, and/or high atomic number objects. High-energy neutrons provide the penetrating power, and thus the high dynamic range necessary to image internal features and defects of such objects. The addition of the time gating capability allows for scatter rejection when paired with a pulsed monoenergetic beam, or neutron energy selection when paired with a pulsed broad-spectrum neutron source. The Time Gating to Reject Scatter and Select Energy system was tested at the Los Alamos Neutron Science Center’s weapons nuclear research facility, a spallation neutron source, to provide proof of concept measurements and to characterize the instrument response. This paper will show results of several objects imaged during this run cycle. In addition, results from system performance metrics, such as the modulation transfer function and the detective quantum efficiency measured as a function of neutron energy, characterize the current system performance and inform the next generation of neutron imaging instrument.

Uncertainties in the Standard Moments, the Derivation of the Y1 to Y8 parameters, and the Derivation of w1 to w8 for Feynman Histograms

Momentum is a neutron multiplicity analysis software package that calculates a variety of parameters associated with Feynman histograms. While most of these parameters are documented in Cifarelli and Smith-Nelson, there are some parameters which are not. Most prominent of these are the uncertainties in the standard moments, and this paper will explicitly document these parameters. This paper will also document the higher-order Yn parameters and their associated ωn functions because they may be useful for future applications. The generation of what is referred to as Feynman histograms is not explained here.

Pictures from VIP Tour During CNEC and CVT Measurements 2016

Below are pictures from the VIP tour on July 13, 2016 at the DAF and Sedan Crater. The tour occurred during the CNEC and CVT Year Two measurements.

Pictures from Year Two CNEC and CVT Measurements

Below are all of the pictures for the CNEC and CVT measurements performed at the DAF in July 2016. In total there are 165 pictures. The photos on pages 2-105 were taken during the first week of measurements and the photos on pages 106-165 were taken during the second week of measurements. Many photos are applicable to both sets, which is why it is best to keep the entire set together. For most configurations, a description of the configuration was written on a white board; photos of the measurement setup were taken, then a photo of the white board was taken. For example, the pictures on pages 6-19 (which precede a white board picture on page 20) are of the configuration with Rocky Flats Shells 1-2 surrounded by 4 AmLi sources, which is listed on the white board picture on page 20. In some cases, the white board picture precedes the configuration pictures.