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Roberts, S.

Publications and source records attributed to Roberts, S..

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Performance of the wavelength-shifting fiber upgrade for the Mu2e cosmic-ray veto detector

The Cosmic-Ray Veto detector for the muon-to-electron conversion experiment at Fermilab consists of four plastic scintillating counter layers read out by silicon photo-multipliers through embedded wavelength-shifting fibers. In order to increase the light yield in the most critical regions of the Cosmic-Ray Veto detector for improved background rejection, a 1.8 mm diameter fiber is being used in many of the detector's critical modules instead of the previously planned 1.4 mm diameter fiber. This paper reports the testing procedure and light properties of thirty-four 1.8 mm fiber spools, with measurements performed using a custom-built scanner. We compare these new results with previously published data from the 1.4 mm diameter fiber used for regions of the cosmic-ray veto where the increased light yield is not required. In addition, measurements of fiber aging were performed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Diffusion energy barrier of Au on Bi 2 Se 3 : theory and experiment

The stability and diffusion of ultra-thin thermally deposited Au films on Bi 2 Se 3 was studied using scanning tunneling microscopy and density functional theory calculations. The Au/Bi 2 Se 3 interface is of interest as gold is predicted to provide excellent electrical contact while maintaining the spin-polarized characteristics of the electronic states in Bi 2 Se 3 that make the material attractive for spintronic applications. When deposited at room temperature, Au 10 covers the surface with tightly packed islands of nanometer scale dimension. The surface morphology is stable up to 400K. At this annealing temperature, Au atoms have sufficient energy to diffuse across the surface and aggregate into larger nanostructures. At 550K, the Bi 2 Se 3 surface is only sparsely covered, and the Au has formed clusters with length scales 5-10 times larger than the original islands formed at room temperature. Comparison of the experiment and first principle calculation lead to the conclusion that the diffusion energy barrier for Au on Bi 2 Se 3 is as high as 0.47 eV, 15 which is much larger than diffusion barriers on other van der Waals materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Collaborative, Nondestructive Analysis of Contaminated Soil

This report summarizes a joint nondestructive analysis exercise that LLNL, LANL, and COMENA discussed through a collaborative meeting in July 2017. This work was performed as one part of a collaboration with Algeria under Action Sheet 7: “Technical Cooperation and Assistance in Nuclear Forensics”. The primary intent of this exercise was for US and Algerian participants to jointly share results of nondestructive analyses (NDA) of a contaminated soil sample provided by the Algerians and to discuss key observations and analytical approaches. While the two samples were analyzed blind at LLNL and LANL, the soil samples were revealed after the exercise to have a common origin, and to have originated as an IAEA soil sample (IAEA-326, Bojanowski et al., 2001) provided to COMENA as part of a previous exercise. Comparative analysis revealed common findings between the laboratories, and also emphasized the need for standardized operating procedures to improve inter-comparability and confidence in conclusions. Recommended handling practices in the presence of sample heterogeneities were also discussed. This exercise provided an opportunity to demonstrate nuclear forensics analytical capabilities at COMENA, LANL, and LLNL, and identified areas that could benefit from future technical exchanges. Plans were made for a follow-on joint exercise in 2018, involving destructive analyses of the CUP-2 uranium ore concentrate standard.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2017

The Analysis of Sulfur-35 as a Young Groundwater Tracer at E-Tunnel, Rainier Mesa, Nevada National Security Site

Analysis of the relatively short-lived radionuclide sulfur-35 (t 1/2 = 87 days) provides useful insight into groundwater discharge from E-Tunnel at the Nevada National Security Site (NNSS). Discharge rates at E-Tunnel vary with precipitation, potentially as the result of short or fast flowpaths between recharge and discharge. The presence of sulfur-35 in groundwater would indicate a significant component of young (< 2-year-old) groundwater. We collected two large volume (20 L) samples of discharge water in November 2016. The samples were sent to Lawrence Livermore National Laboratory (LLNL), where they were processed and analyzed by Liquid Scintillation Counting (LSC). Sulfur-35 was not detected in either the sample or field duplicate, a finding consistent with E-Tunnel discharge containing no significant component of groundwater with age less than six months.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Experimental results of beryllium exposed to intense high energy proton beam pulses

Beryllium is extensively used in various accelerator beam lines and target facilities as a material for beam windows, and to a lesser extent, as secondary particle production targets. With increasing beam intensities of future accelerator facilities, it is critical to understand the response of beryllium under extreme conditions to reliably operate these components as well as avoid compromising particle production efficiency by limiting beam parameters. As a result, an exploratory experiment at CERN’s HiRadMat facility was carried out to take advantage of the test facility’s tunable high intensity proton beam to probe and investigate the damage mechanisms of several beryllium grades. The test matrix consisted of multiple arrays of thin discs of varying thicknesses as well as cylinders, each exposed to increasing beam intensities. This paper outlines the experimental measurements, as well as findings from Post-Irradiation-Examination (PIE) work where different imaging techniques were used to analyze and compare surface evolution and microstructural response of the test matrix specimens.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

TaC Studios New Construction Test House

As part of the NAHB Research Center Industry Partnership, Southface partnered with TaC Studios, an Atlanta based architecture firm specializing in residential and light commercial design, on the construction of a new test home in Atlanta, GA in the mixed humid climate zone. This home will serve as a model home for the builder partner and addresses Building America energy savings targets through the planning and implementation of a design package will serve as a basis of design for the builder partner's future homes. As a BA test house, this home will be evaluated to detail whole house energy use, end use loads, and HVAC and hot water efficiency.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

TaC Studios New Construction Test House

As part of the NAHB Research Center Industry Partnership, Southface partnered with TaC Studios, an Atlanta based architecture firm specializing in residential and light commercial design, on the construction of a new test home in Atlanta, GA, in the mixed humid climate zone. This home will serve as a model home for the builder partner and addresses Building America energy savings targets through the planning and implementation of a design package will serve as a basis of design for the builder partner’s future homes. As a BA test house, this home will be evaluated to detail whole house energy use, end use loads, and HVAC and hot water efficiency.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗