Utah Aurora - May 10/11 2024

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.

Though some LHC searches for new physics exceed the TeV scale, there may be discoveries waiting to be made at much lower masses. We outline a simple quirk model, motivated by models that address the hierarchy problem through neutral naturalness, in which new electroweakly charged states with masses as low as 100 GeV have not yet been probed by the LHC. We also describe a novel search strategy which is complementary to current search methods. In particular, we show its potential to discover natural quirks over regions of parameter space that present methods will leave unexplored, even after the LHC’s high-luminosity run.

We fit archival near-IR spectra of ∼300 brown dwarfs with atmosphere models from the Sonora and Phoenix groups. Using the parameters of the best-fit models as estimates for the physical properties of the brown dwarfs in our sample, we have performed a survey of how brown dwarf atmospheres evolve with spectral type and temperature. We present the fit results and observed trends. We find that clouds have a more significant impact on near-IR spectra than disequilibrium chemistry, and that silicate clouds influence the near-IR spectrum through the late T types. We note where current atmosphere models are able to replicate the data and where the models and data conflict. We also categorize objects with similar spectral morphologies into families and discuss possible causes for their unique spectral traits. We identify two spectral families with morphologies that are likely indicative of binarity.

We describe efforts to develop broadband mirror coatings with high performance that will extend from the far-ultraviolet (FUV) to infrared wavelengths. Our team at the Goddard Space Flight Center has developed a reactive physical vapor deposition (rPVD) process that combines a fluorination with a XeF2 gas (which grants a thin AlF3 layer) in between the Al and the metal-fluoride protection layer (either LiF or MgF2) that are done with the conventional PVD process. This recently developed rPVD process produces protected Al mirrors coatings with an improved average FUV reflectance between 10% and 15% higher (when compared with conventionally prepared samples). We have termed these coatings as XeLiF when the dielectric overcoat is LiF or XeMgF2 when the dielectric overcoat is MgF2. The XeLiF-coated Al mirrors meet current goals for advanced broadband mirrors in the FUV (R>70% at 103 nm and R>80 above 110 nm), whereas the XeMgF2 provides R>80% above 115 nm. The IR/Vis/UV reflectance for either XeLiF or XeMgF2 mirrors is similar to the theoretical reflectance of bare aluminum at wavelengths >200 nm. In addition, long-term lifetime testings of XeLiF mirrors indicate the rPVD process produces more environmentally stable coatings, where a XeLiF sample showed a degradation in the average FUV reflectance of around 1% to 2% when stored in a relative humidity of 40% over a period of 3.5 years. These results are a remarkable improvement when compared with conventionally prepared Al+LiF samples that would degrade their FUV reflectance in a matter of weeks or months when exposed to those kinds of relative humidity levels. Surface topographies on several XeLiF samples with varying Al and LiF thicknesses have been measured with an atomic force microscope (AFM). The root mean square (RMS) roughness (σ) values derived from these AFM results have ranged between 0.6 and 0.9 nm. For comparison, samples without the Xe process start off by having an RMS roughness that is 30% larger than samples treated with the XeF2 gas. We have also determined that these roughness values are showing a slight increase, ranging between 0.9 and 1.0 nm, when samples are exposed to room temperature and relative humidity as high as 50% over one week. Both of these key performance parameters (environmental stability in reflectance and smoothness of ≤1 nm) are key considerations for using the XeLiF coating in the primary and secondary mirrors of the Habitable Worlds Observatory (HWO). We also show evidence that the rPVD coating process is compatible with deposition on Si-based gratings. It is known that XeF2 vapor is a strong Si etchant, thus the demonstration that the native SiO2 layer on Si test samples is sufficient to protect the groove profile of E-beam-ruled Si gratings from degradation is an important and significant finding.