Experiments on the Sandia Z pulsed-power accelerator have demonstrated the ability to produce warm dense matter (WDM) states with unprecedented uniformity, duration, and size, which are ideal for investigations of fundamental WDM properties. For the first time, space-resolved x-ray Thomson scattering (XRTS) spectra from shocked carbon foams were recorded on Z. The large (> 20 MA) electrical current produced by Z was used to launch Al flyer plates up to 25 km/s. The impact of the flyer plate on a CH 2 foam target produced a shocked state with an estimated pressure of 0.75 Mbar, density of 0.52 g/cm 3 , and temperature of 4.3 eV. Both unshocked and shocked portions of the foam target were probed with 6.2 keV x-rays produced by focusing the Z-Beamlet laser onto a nearby Mn foil. The data is composed of three spatially distinct spectra that were simultaneously captured with a single spectrometer with high spectral (4.8 eV) and spatial (190 m) resolutions. Detailed spectral information from three target locations is provided simultaneously: the incident x-ray source, the scattered signal from unshocked foam, and the scattered signal from shocked foam.
Imploding wire arrays on the 20 MA Z generator have recently provided some of the most powerful and energetic laboratory sources of multi-keV photons, including ∼375 kJ of Al K-shell emission (hν ∼ 1–2 keV), ∼80 kJ of stainless steel K-shell emission (hν ∼ 5–9 keV) and a kJ-level of Mo K-shell emission (hν ∼ 17 keV). While the global implosion dynamics of these different wire arrays are very similar, the physical process that dominates the emission from these x-ray sources fall into three broad categories. Al wire arrays produce a column of plasma with densities up to ∼3 × 1021 ions/cm3, where opacity inhibits the escape of K-shell photons. Significant structure from instabilities can reduce the density and increase the surface area, therefore increase the K-shell emission. In contrast, stainless steel wire arrays operate in a regime where achieving a high pinch temperature (achieved by thermalizing a high implosion kinetic energy) is critical and, while opacity is present, it has less impact on the pinch emissivity. At higher photon energies, line emission associated with inner shell ionization due to energetic electrons becomes important.
As the number of air passengers with disabilities is expected to increase in the coming decades, the significance of airport wayfinding accessibility has been recognized by airport stakeholders. Emerging assistive technologies have been used to accommodate passengers’ wayfinding needs; however, because of non-standard practices and the complexity of terminal designs, the literature only provides general guidance on improving airport wayfinding accessibility. There is a need for detailed analysis of quantitative traveler performance measures to evaluate airport wayfinding accessibility. This research is the first use of a wheelchair simulator to compare airport wayfinding signage with a mobile wayfinding application. A virtual model of the St. Louis Lambert International Airport main terminal was replicated using as-built computer-aided-design files. A federated simulation architecture was used to integrate the wheelchair simulator with a mobile wayfinding application. Wheelchair simulator experiments were conducted by analyzing twenty-four wheelchair users’ performance measures and eye tracking data. Although the mobile wayfinding application did not significantly reduce total travel time (–23.8 s) and deviation ratio (–3%), it reduced wheelchair users’ reliance on wayfinding signs by decreasing total glance frequency (–23.3 times) and total glance duration (–26.7 s) and helped to reduce travel anxiety in wheelchair users. The potential benefits of a mobile wayfinding application include improving traveler levels of service, reducing airport operating costs, and enhancing non-airline revenue. Overall, this study showed that, with the use of a wheelchair simulator, passenger performance could be captured and analyzed for evaluating the effectiveness of airport wayfinding accessibility and emerging assistive technologies.
Gas targets are often used at accelerator facilities. A design of
high-pressure gas cells that are suitable for hydrogen and helium isotopes at
relatively high electron beam currents is presented. In particular, we consider
rare gas targets, $^3$H$_2$ and $^3$He. In the design, heat transfer and
mechanical integrity of the target cell are emphasized. ANSYS 12 was used for
the thermo-mechanical studies of the target cell. Since the ultimate goal in
this study was to design a gas target for use at the Jefferson Laboratory
(JLab), particular attention is given to the typical operating conditions found
there. It is demonstrated that an aluminum alloy cell can meet the required
design goals
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