Session W12: Advances in Detectors and Their Electronics

Harnessing excitons at the nanoscale - photoelectrical sensing and quantification

Excitons, quasiparticles formed by the binding of an electron and a hole through electrostatic attraction, hold promise in the realms of quantum light confinement and optoelectronic sensing. Atomically thin transition metal dichalcogenides (TMDs) provide a highly versatile platform for hosting and manipulating excitons, given their robust Coulomb interactions and exceptional sensitivity to dielectric environment. In this talk, we introduce a photoelectrical sensing technique, termed optically coupled microwave impedance microscopy (OC-MIM). OC-MIM enables the sensitive probing of exciton polarons and their Rydberg states at the nanoscale, unveiling their potential as localized quantum sensors. By utilizing this technique, we explore the interplay between excitons and material properties at the nanoscale, including carrier density, in-plane electric field, and dielectric screening. Furthermore, we employ a neural network algorithm to enable automated data analysis and quantitative extraction of nanoscale electrical information. Our findings establish an invaluable sensing platform and readout mechanism, enhancing the understanding of exciton excitations and their applications in the quantum realm.   

Time-resolved THz-TDS Nanoscopy for Probing Carrier Dynamics with Femtosecond Temporal and Nanometer Spatial Resolution

By combining THz-TDS based scattering near-field optical microscopy (THz s-SNOM) with VIS/NIR ultrafast pump-probe spectroscopy we enable probing of dynamic material properties with femtosecond temporal and 20nm spatial resolution. We demonstrate s-SNOM based ultra-fast pump-probe THz-TDS imaging and spectroscopy as well as time-resolved THz near-field transient measurements at extreme sub-wavelength scale sample structures. As a representative material system, we study the spatial heterogeneity of photoexcited carriers in a silicon based semiconductor device and a micron-sized MoS₂ crystal. For the latter, near-field THz transients reveal thickness/layer dependent decay dynamics and lifetimes in the picosecond range.   

An array structure testing the micron-scale Yukawa Gravity

Exploring the specific manifestation of short-range gravity is an important experimental way to study dark matter and dark energy at laboratory scale. Existing techniques have achieved high accuracy at micron scale and above, however, for micron scale or smaller, existing experimental schemes still face the challenge that the large Newtonian gravitational background limits the accuracy of the measurements. We have found an array structure that achieves the goal of eliminating the Newtonian gravitational background at a certain frequency by nesting two sets of period structures, which in turn significantly improves the accuracy of non-Newtonian gravity measurements. Considering the available experimental parameters, this method is expected to achieve an improvement of six orders of magnitude in the parameter space near lambda=10um. As a result, by employing a novel fluid levitation method, our experiments outperform previous magnetic levitation methods and are highly promising to fill the gap in high-precision experiments at the 10um scale. Our proposed method allows further improvement of the accuracy through the integration of components.   

Transition-Edge-Sensor utilizing the Magnetic Superconducting Transition

We present experimental results from a Transition-Edge-Sensor (TES) based on the magnetic superconducting transition. For the devices reported here, the change in magnetic flux from a microscale disk of electrodeposited tin may be detected by a planar pickup coil consisting of a niobium thin film. We present experimental data revealing the magnetic superconducting transition that is the basis for the principle of transduction between temperature and magnetic flux. The prototype magnetic TES devices may ultimately be utilized for microscale magnetometry or microcalorimetry. We present experimental data without and with a source of ionizing radiation as an experimental demonstration applicable to microcalorimetry.   

Development of a circular polarized microwave cavity and microwave Hall effect measurements

 A microwave cavity has been used for electron spin/ferromagnetic resonance and surface impedance measurements in condensed matter physics. More recently, it has also been a powerful tool in qubit control and the study of cavity quantum electrodynamics (cavity QED).

 In this study, we have developed the high-Q microwave dielectric cavity, which can generate circularly polarized eigenmodes. It can maintain a high-Q value even in a high magnetic field, and the circular dichroism allows us to evaluate the conductivity susceptibility and impedance tensor, including the off-diagonal term. In this talk, we will present our developed cavity and the results of Hall effect measurements in the microwave region by surface impedance tensor measurements.   

Improving equivalent circuit models of interdigitated capacitors

Interdigitated capacitors are nearly ubiquitous circuits found in everything from telecommunications components to superconducting quantum computers. When the guided wavelength becomes comparable to the length of the interdigitation in the capacitor, common lumped-element models fail to describe how the impedance changes as a function of frequency. This failure limits the frequency range where one can accurately predict the performance of interdigitated capacitors and extract material properties. Here, we develop a multi-mode distributed theory for interdigitated capacitors and quantify the trade-offs between a lumped-element and distributed approach. To test our model, we measured interdigitated capacitors fabricated on (LaAlO₃)_0.3(Sr₂TaAlO₆)_0.7 substrate and interdigitated capacitors with same geometry fabricated on a BaSrTiO₃ thin film.   

Robust Heat Flux Sensors for Power Plant Extreme Environments

Direct heat flux measurements in extreme environments are valuable for the optimal performance of combustion systems, particularly when thermocouple- and optics-based diagnostics are inadequate. We report on the development of a robust heat flux sensor using the Transverse Seebeck Effect (TSE). Elicited through intentional misalignment of anisotropic single crystals with respect to the direction of heat flow, the TSE can generate an electric field perpendicular to the applied heat flux and can facilitate rugged devices with less complex constructions. In this work, we detail the design and characterization of an extreme environment-tailored heat flux sensor leveraging the Seebeck coefficient tensor anisotropy and high melting point of Rhenium single crystals. Experimental characterization of the sensor demonstrated its linear response to heat flux and that the transduction mechanism is based on the TSE. Through independent modulation of the sensor package temperature and incident heat flux, we obtain temperature-dependent calibration data consistent with a model that incorporates the impact of the surrounding package on the heat flow through the transducers.   

Comparison of Neutron Transport Concepts for the Single-Crystal Neutron Diffractometer PIONEER at the Second Target Station of the Spallation Neutron Source

PIONEER is a single-crystal neutron diffractometer for measuring tiny volume single-crystals and epitaxial films at the Second Target Station (STS), Spallation Neutron Source. To take advantage of the high source brilliance and the advancements in neutron optics, we have performed Monte-Carlo ray tracing simulations and geometry optimizations for multiple neutron transport concepts, including Montel mirrors, curved guides using a bender, and straight and kinked beamlines using elliptical guides. Our priorities include signal-to-background ratio and operational reliability and flexibility. The optimization metrics count for high brilliance transfer, high spatial and angular beam homogeneity within the phase-space region of interest (ROI), and low flux outside the ROI. We found that the straight beamline delivers the best performance, with the brightest beam but with more flux outside the spatial ROI. Montel mirrors deliver fewer neutrons outside the ROI but at a high cost of thermal neutron flux. The bender and kink options deliver less bright and less uniform beams. Our studies also show that the straight beamline displays a moderate flux loss to engineering imperfections, including mirror waviness and misalignment. Further optimization on the straight beamline has identified effective solutions for beam size and divergence control using slit packages.   

Monte-Carlo ray-tracing studies of multiplexed prismatic graphite analyzers for the MANTA implementation at the High Flux Isotope Reactor

Condensed matter physics was revolutionized when the Nobel prize-winning triple-axis spectrometer was invented in 1956. The latest development in triple-axis spectrometry is the use of a multiplexing analyzer system, seen at other laboratories such as the Swiss Neutron Source's instrument CAMEA [2]. Oak Ridge National Laboratory aims to utilize this technology to create the latest development in triple-axis spectrometry known as the Multi-Analyzer Neutron Triple Axis (MANTA) to be installed at the High Flux Isotope Reactor. While studying MANTA's performance using the Monte-Carlo ray-tracing program McStas, we developed the Positionally-Calibrated Prismatic Analysis (PCPA) technique, which makes full use of the prismatic concept [3] by accounting for statistical variations in neutron energy per pixel along a position-sensitive detector. Now we are looking at potential modifications of the CAMEA design that are optimized to the PCPA technique. Through this approach, MANTA aims to become a top-of-the-line instrument in neutron spectroscopy. [1] A. Desai, T. J. Williams, A. Aczel, G. Sala, G. E. Granroth, M. Mourigal, "Monte-Carlo ray-tracing studies of multiplexed prismatic graphite analyzers for the MANTA implementation at the High Flux Isotope Reactor" (In preparation) [2] F. Groitl, D. Graf, J. O. Birk, M. Markó, M. Bartkowiak, U. Filges, C. Niedermayer, C. Rüegg, H. M. Rønnow "CAMEA – a Novel Multiplexing Analyzer for Neutron Spectroscopy" Review of Scientific Instruments (2016) [3] J. O. Birk, M. Markó, P. G. Freeman, J. Jacobsen, R. L. Hansen, N. B. Christensen, C. Niedermayer, M. Månsson, H. M. Rønnow, and K. Lefmann, "Prismatic analyser concept for neutron spectrometers," Review of Scientific Instruments   

Scheimpflug LIDAR for Power Plant Monitoring

To optimize the efficiency of power plants, real-time information about the local operating conditions is supremely important. As the environment inside the boilers is hardly appropriate for traditional measuring techniques, alternative methods are useful to measure the parameters like temperature and species concentration. In such conditions, the Scheimpflug-Light Detection and Ranging (S-LIDAR) technique, which requires special condition of detection configuration, can be a good alternative. In this work, the S-LIDAR system was developed for measurement inside the furnace operated in simulated conditions of power plants. A green laser operating at 532 nm wavelength was used as a continuous light source and was focused into the tube furnace. Scattered light coming back from the gas species inside the furnace was collected to infer the information about the conditions inside the furnace.   

Progress in Fission Fragment Rocket Engine Development and Alpha Particle Detection in Ultrahigh Magnetic Fields

We present an innovative design of an alpha particle detection system operating in high magnetic fields over large cross-sections. Our primary focus revolves around enhancing nuclear rocket designs and empirically evaluating its operational efficiency through experiments and simulations. This experiment provides a platform to evaluate confinement and thrust within a future fission fragment rocket engine (FFRE). This study utilized the naturally occurring radio-isotope Th-232 with extremely low specific activity (10^-7 Ci/g) in the form of ThO₂ as a source of alpha particles as a surrogate for fission fragments. The source is located within a cylindrical vacuum chamber and is held within a powerful 3-Tesla magnetic field, effectively confining the flight path of the emitted alpha particles. Additionally, we present the results from a study of attenuation ratio of alpha particle numbers due to aerogel sheet using a CR39 method and an Am-241 source. By simulating, measuring, and analyzing the emitted alpha particle flux, we gain valuable information about the distribution and escape potential of fission fragments in future FFRE designs. More generally, this work provides a powerful new method to analyze ion fluxes and nuclear reaction fragmentation in a variety of experimental designs.    

Gas Pore Formation in Powder Bed Fusion

Additive manufacturing (AM) of metal materials based on powder bed fusion technology is widely used now in many industries. A known limitation of this type of manufacturing is the formation of gas pores in bulk material arising from stochastic events related to molten metal fluid instabilities of a vapor depression. Here we present a combined X-ray imaging and infrared pyrometry study of pore formation in repeated adjacent tracks, and quantify the correlations of pore positions and sizes for a common material (Aluminum 6061) of interest in AM as a function of its laser processing conditions. We find in both cases that an existing pore in one track often catalyzes the formation of another pore in a consecutive track at the distance of closest approach. In a raster scan strategy commonly used to construct bulk material, this phenomenon has the result of forming perforations, or lines of pores transverse to the scanning direction in a rastered patch. If controlled, this effect can be eliminated to improve the yield strength of the build, or exploited to create programmable failures for specific purposes.

 

Distribution A. Approved for public release: distribution unlimited. (AFRL-2023-5001). Date Approved 10-10-2023.