Utah Aurora - May 10/11 2024

The far-UV (FUV) reflectance of the state-of-the-art, broadband UV/optical/IR mirrors of XeF2-passivated LiF on Al (Al + XeLiF) is promising for future space telescope missions. To reach their potential, dependable cleaning procedures and storage methods for such reflective surfaces need to be developed. First Contact™ polymer (FCP) formulations have proven to be a reliable method for cleaning conventional mirror surfaces coated with oxides or bare metal and for protecting them in storage. We report here on studies of the cleaning and storage of Al + XeLiF samples using customized FCP formulations designed by Photonic Cleaning Technologies. Cleaning of such mirrors is demanding since fluoride coatings are softer than oxides and can be moisture sensitive. Any damage that marks the overcoat can lead to catastrophic loss of FUV reflectance due to surface roughening and formation of aluminum oxide, which is FUV opaque. We discovered that one formulation could be successfully applied to and removed from Al + XeLiF coatings multiple times. The coatings retained low roughness, minimal aluminum oxide thickness, and high far-UV reflectance. Another of the four FCP formulations successfully cleaned the Al + XeLiF coatings several times. Variable-angle, spectroscopic ellipsometry, tapping-mode atomic force microscopy, x-ray photoelectron spectroscopy, and FUV reflectance allowed us to observe any changes in reflectance and surface roughness, the formation of aluminum oxide, and damage to coating integrity. From the studies of the range of FCP-fluoride interactions, we noted that too much polymer-to-surface adhesion or exposure to trace water in the polymer can result in coating damage.

In this Sound Perspectives essay, I summarize potential impacts of rocket noise and suggest that the Acoustical Society of America (ASA), with its interdisciplinary expertise in acoustics and vibration, is uniquely positioned to help address these growing challenges. 

The search for new useful molecular ferroelectrics is a non-trivial problem. We present the application of an automated symmetry-searching method (FERROSCOPE) to the Cambridge Structural Database (CSD) in order to identify polar structures with a closely-related non-polar phase. Such structures have the possibility of undergoing a polarization-switching phase transition thus forming a ferroelectric-paraelectric pair. FERROSCOPE successfully identifies this relationship in 84% of a curated list of 156 known molecular ferroelectrics from the literature and identifies an additional 17 000 potentially ferroelectric compounds in the CSD. Our analysis shows that the method identifies CSD structures which have potentially been described in incorrect space groups, extending previous analyses. We describe experimental case studies which reveal phase transitions in two polar systems predicted to have related non-polar phases.

Understanding and harnessing X-ray quantum effects could open new, to our knowledge, frontiers in imaging and quantum optics. In this study, we measured the process of X-ray parametric down-conversion, where a single high-energy X-ray photon splits into two lower-energy photons. Using the SACLA X-ray free electron laser in Japan at 9.83 keV, we found clear evidence that pairs of photons were produced along the energy-angle relationship that conserved both energy and momentum, as predicted for down-conversion, and consistent with quantum entanglement of X-ray photons. By matching specific photon pairs for energy and momentum conservation, we observe a signal rate of 1250 pairs per hour, confirming that correlated photon pairs can be generated and observed in the absence of explicit time correlations. Our results show that with further refinement, the number of entangled photons produced per laser pulse could increase by an order of magnitude. This paves the way for demonstrating quantum-enhanced X-ray imaging, and confirmation of X-ray photon entanglement.

A unique circuit technique utilizing the active quasi-circulator (AQC) for impedance measurement is presented. Overcoming limitations of size, frequency, and sensitivity, the technique enables sensitive MHz impedance measurements for wearable applications. The AQC measures the impedance of the device-under-test (DUT) at MHz excitation frequencies through nulling the output at the DUT match point while offering enhanced sensitivity. A circuit analysis presents the theory of operation and models the AQC to extract the DUT impedance. Fabricated in a 180-nm CMOS process, the circuit occupies an active area of 0.012 mm2 and demonstrates impedance measurement at excitation frequencies up to 25 MHz. The proposed circuit is attractive for measuring living tissues that exhibit strong bioimpedance response at MHz frequencies.

Galaxies with polar structures (of which polar-ring galaxies (PRGs) are a prominent subclass) contain components that are kinematically decoupled and highly inclined relative to the major axis of the host galaxy. Modern deep optical surveys provide a powerful means of detecting low surface brightness (LSB) features around galaxies, which offers critical insights into the formation and evolution of galaxies with polar structures. UGC 10043 is an edge-on galaxy that is notable for its prominent bulge, which extends orthogonally to the disk plane. In addition, the galaxy displays a well-defined integral-shaped disk warp and multiple dust features crossing the bulge along the minor galaxy axis. We present new deep optical photometry of UGC 10043 down to μ_g = 29.5 mag arcsec⁻² and perform a detailed analysis of its LSB and polar structures. The observations reveal a stellar stream aligned along the polar axis, alongside other signatures of tidal interaction, including a flat, tilted LSB envelope that extends toward the neighboring galaxy MCG +04-37-035, with which UGC 10043 is connected by an HI bridge. Our results suggest that the polar component of UGC 10043 comprises an older, triaxial polar bulge and a younger, forming polar structure that likely originates from the ongoing disruption of a dwarf satellite galaxy. It also simultaneously participates in active interaction with MCG +04-37-035.