The Fundamental Neutron Physics Facilities at NIST

The program in fundamental neutron physics at the National Institute of Standards and Technology (NIST) began nearly two decades ago. The Neutron Interactions and Dosimetry Group currently maintains four neutron beam lines dedicated to studies of fundamental neutron interactions. The neutrons are provided by the NIST Center for Neutron Research, a national user facility for studies that include condensed matter physics, materials science, nuclear chemistry, and biological science. The beam lines for fundamental physics experiments include a high-intensity polychromatic beam, a 0.496 nm monochromatic beam, a 0.89 nm monochromatic beam, and a neutron interferometer and optics facility. This paper discusses some of the parameters of the beam lines along with brief presentations of some of the experiments performed at the facilities.     

Operating conditions of batteries in off-grid renewable energy systems

Operating conditions in off-grid renewable energy systems (RES) vary significantly in different applications and locations. To describe RES and the operating conditions of their components it is useful to define categories of similar operating conditions. Categories can also be used for lifetime considerations of RES components, for making recommendations and for analysing the properties and performance of a RES and its components. Categories support system designers and an economic analysis. This paper describes the process and the results of creating RES categories of similar operating conditions for batteries. Categories are defined in such a way that batteries belonging to the same category are subjected to similar operating conditions and a similar combination of stress factors. The results provide a comprehensive overview of battery operating conditions in existing off-grid renewable energy systems. This work is part of the EU research project Benchmarking.¹     

Disk-shaped packed bed micro-reactor for butane-to-syngas processing

A novel disk-shaped packed bed micro-reactor containing Rh/ceria/zirconia nanoparticles is investigated with respect to catalytic butane-to-syngas processing at moderate temperatures of 550 °C. The main goal of this study is the development of an efficient butane processor which can be integrated into a micro solid oxide fuel cell system due to its small size, easily packaged geometry in layered microdevices, high compactness, low pressure drop, and low reaction temperature. It is shown that Rh/ceria/zirconia has an excellent long-term stability and achieves very high C₄H₁₀ conversion and syngas selectivity, considering the relatively low operating temperature. The yields of H₂ and CO can be increased up to 71% and 57%, respectively, by optimizing operational parameters such as the C/O ratio and the total inlet flow rate. The introduced disk-shaped packed bed reactor shows significant advantages in catalytic behavior, at a 6.5 times lower pressure drop compared to an equivalent tubular packed bed reactor. This increased catalytic performance is pursued extensively by investigating possible reaction pathways in three regions of the radial-flow reactor, leading to the significant discovery of a threefold pathway of syngas production on a single catalyst. To this end, it is shown that the excellent selectivities to H₂ and CO for high flow rates are due to the combination of partial oxidation, steam reforming, and dry reforming of C₄H₁₀, indicating one direct and two indirect reaction paths.     

Elasticity of nanocrystalline kyanite at high pressure and temperature from ultrasonic and synchrotron X-ray techniques

Material properties, such as elasticity data at wide-ranging conditions of pressure and temperature, attract increasing attention for material and earth sciences. In particular, polycrystalline ceramics for next-generation photonic applications are nowadays fabricated by advanced syntheses techniques operating under elevated pressures and temperatures. Herein, the elastic properties of a synthetic transparent and reinforced aluminosilicate nanoceramic composed of triclinic kyanite with minor amounts of trigonal α-alumina crystals are investigated using in situ synchrotron X-ray diffraction and ultrasonic techniques at high-pressure (up to 11 GPa) and high-temperature (300-1500 K) conditions. This not only enables the determination of the equation of state (EoS) parameters by applying the pressure-volume-temperature (P-V-T) data to the high-temperature Birch-Murnaghan EoS but also yields the elastic moduli together with their P and T derivatives from the fit of the compressional and shear wave velocities to a finite strain EoS: K_S0,300 = 186(2) GPa, K′_S0,300 = 7.2(6), (∂K_S0,300/∂T)_P = −0.023(2) GPa K⁻¹, G_0,300 = 125(1) GPa G′_0,300 = 2.3(2), (∂G_0,300/∂T)_P = −0.017(1) GPa K⁻¹. On the basis of our acquired results, we propose to predict the elastic moduli of aluminosilicate ceramics by a linear function of the ratio of AlO₆ octahedra and SiO₄ tetrahedra within the constituting phases.     

Packaging effects on the sensing performance of RTDs on an AlN substrate of a wafer heater

Journal of Mechanical Science and Technology - This study investigates packaging effects on the sensing performance of resistance temperature detectors (RTDs) on an AlN substrate of a wafer heater....     

Bridging the scales: A conceptual model for coordinated expansion of renewable power generation,transmission and storage

To analyze the challenge of large-scale integration of renewables during the next decades, we present a conceptual power system model that bridges the gap between long term investment allocation and short-term system operation decisions. It integrates dynamic investments in generation, transmission and storage capacities as well as short-term variability and spatial distribution of supply and demand in a single intertemporal optimization framework. Large-scale grid topology, power flow distributions and storage requirements are determined endogenously. Results obtained with a three region model application indicate that adequate and timely investments in transmission and storage capacities are of great importance. Delaying these investments, which are less costly than investments in generation capacities, leads to system-wide indirect effects, such as non-optimal siting of renewable generation capacities, decreasing generation shares of renewables, increasing residual emissions and hence higher overall costs.