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Vacuum Outgassing Study of Candidate Materials for Next Generation Pulsed Power and Accelerators: Improving the Boundary Conditions for Molecular Flow Simulations

IEEE International Pulsed Power Conference

Simpson, Sean S.; Goeke, Ronald S.; Laros, James H.; Coombes, Kenneth R.; Laros, James H.; Johns, Owen J.; Leckbee, Joshua L.; Nielsen, D.S.; Sceiford, Matthew S.

Next generation pulsed power (NGPP) machines and accelerators require a better understanding of the materials used within the vacuum vessels to achieve lower base pressures (P << 10-5 Torr) and reduce the overall contaminant inventory while incorporating various dielectric materials which tend to be unfavorable for ultra-high vacuum (UHV) applications. By improving the baseline vacuum, it may be possible to delay the onset of impedance collapse, reduce current loss on multi-mega Amp devices, or improve the lifetime of thermionic cathodes, etc [3]. In this study, we examine the vacuum outgassing rate of Rexolite® (cross-linked polystyrene) and Kel-F® (polychlorotrifluoroethylene) as candidate materials for vacuum insulators [1]. These values are then incorporated into boundary conditions for molecular flow simulations using COMSOL Multiphysics® and used to predict the performance of a prototypical pulsed power system designed for 10-8 Torr operations.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

Titanium and/or Aluminum Sleeve Experiments in Fully-Reflected Water-Moderated U(4.31)O2 Fuel Rod Lattices with 2.8 cm Pitch

Laros, James H.

The US Department of Energy Nuclear Energy Research Initiative (NERI) funded the Bumup Credit Critical Experiment (BUCCX) at Sandia National Laboratories. The BUCCX was designed to investigate the effect of fission product materials on critical systems. The BUCCX assembly is a water-moderated and -reflected array of Zircaloy-clad triangular-pitched U(4.31)02 fuel elements. The original BUCCX experiments with rhodium are evaluated in LEU-COMP-THERM-079. In the experiments here, sets of up to 60 experiment titanium and aluminum sleeves with nominal outside diameter of 1 in (2.54 cm), wall thickness of 0.035 in (0.0889 cm), and length of 19.60 (49.784 cm) were fabricated. The sleeves are approximately the same length as the fueled section of the fuel elements and have an inner diameter that is 0.421 in (1.0693 cm) larger than the fuel elements. This allows for each sleeve to be centered around a fuel element between the grid plates within the array. Configurations differ by the number and location of sleeves. The seventeen BUCCX critical experiments reported here compare the effects of the titanium and aluminum sleeves on nearly critical fuel assembly arrays.

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TYPE Other Report YEAR 2019
DOIOSTI

Phase Identification of the Layered Perovskite CexSr2–xMnO4 and Application for Solar Thermochemical Water Splitting

Inorganic Chemistry

Barcellos, Debora R.; Coury, Francisco G.; Emery, Antoine; Sanders, Clay M.; Tong, Jianhua; McDaniel, Anthony H.; Wolverton, Christopher; Laros, James H.; Hayre, Ryan'

Ruddlesden–Popper (layered perovskite) phases are attracting significant interest because of their unique potential for many applications requiring mixed ionic and electronic conductivity. Here we report a new, previously undiscovered layered perovskite of composition, CexSr2–xMnO4 (x = 0.1, 0.2, and 0.3). Furthermore, we demonstrate that this new system is suitable for solar thermochemical hydrogen production (STCH). Synchrotron radiation X-ray diffraction and transmission electron microscopy are performed to characterize this new system. Density functional theory calculations of phase stability and oxygen vacancy formation energy (1.76, 2.24, and 2.66 eV/O atom, respectively with increasing Ce content) reinforce the potential of this phase for STCH application. Experimental hydrogen production results show that this materials system produces 2–3 times more hydrogen than the benchmark STCH oxide ceria at a reduction temperature of 1400 °C and an oxidation temperature of 1000 °C.

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TYPE Journal Article YEAR 2019
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A high-speed, high-performance, microfabricated comprehensive two-dimensional gas chromatograph

Lab on a Chip

Whiting, Joshua J.; Myers, Edward; Manginell, Ronald P.; Moorman, Matthew W.; Anderson, John M.; Fix, Cory S.; Washburn, Cody M.; Al StatonAl; Porter, Daniel; Graf, Darin; Wheeler, David R.; Howell, Stephen; Richards, John R.; Laros, James H.; Achyuthan, Komandoor A.; Roukes, Michael; Simonson, Robert J.

A small, consumable-free, low-power, ultra-high-speed comprehensive GC×GC system consisting of microfabricated columns, nanoelectromechanical system (NEMS) cantilever resonators for detection, and a valve-based stop-flow modulator is demonstrated. The separation of a highly polar 29-component mixture covering a boiling point range of 46 to 253 °C on a pair of microfabricated columns using a Staiger valve manifold in less than 7 seconds, and just over 4 seconds after the ensemble holdup time is demonstrated with a downstream FID. The analysis time of the second dimension was 160 ms, and peak widths in the second dimension range from 10-60 ms. A peak capacity of just over 300 was calculated for a separation of just over 6 s. Data from a continuous operation testing over 40 days and 20000 runs of the GC×GC columns with the NEMS resonators using a 4-component test set is presented. The GC×GC-NEMS resonator system generated second-dimension peak widths as narrow as 8 ms with no discernable peak distortion due to under-sampling from the detector.

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TYPE Journal Article YEAR 2019
DOIOSTIScopus
Results 1151–1175 of 2,290
Results 1151–1175 of 2,290