Review of Scientific Instruments最新文献

Hard x-rays generated by bremsstrahlung from low-energy electrons have a wide distribution of emission angles, which inherently limits radiation utilization efficiency. This study proposes a Compton-scattering-based augmentation technique that increases utilization efficiency by partially scattering laterally escaping photons into the detection region and reducing their average energy. The augmentation characteristics of various Compton scattering layer (CSL) materials and geometries were analyzed theoretically, validated numerically, and used to establish a practical selection method for CSL design. A graphite CSL tailored for a cylindrical virtual-cathode reflex triode array was developed and experimentally tested. The experimental data show a 13.9% increase in radiation utilization efficiency-consistent with the 13.5% predicted by simulation-and a 28.4% increase in uniform-dose area.

We present a custom sample holder system (SHS) enabling high-fidelity reflectance and transmittance ([R, T]) measurements of small (3-7 mm) diamond samples using dual-beam spectrophotometry. Through precision alignment, standard reference material-based correction strategies, and aperture-induced distortion cancellation, the SHS achieves sub-percent absolute photometric accuracy, allowing direct inversion of [R, T] for optical constants [n, k] via a Newton-Raphson (N-R) method. This process eliminates reliance on curve-fitting, instead using branch topology-physical (p-) and mathematical (m-) branch crossings-to extract thickness, roughness, and vertical non-uniformity from fringe behavior. Applied to boron-doped diamond (BDD) homoepitaxial films, the method reduces thickness variance by over 3× compared to mass-gain measurements and reveals carrier density gradients in thin layers consistent with secondary ion mass spectroscopy (SIMS). Notably, ripple-like discontinuities in [n, k]-often dismissed as artifacts-are shown to encode real growth physics. This enables optical retrieval of effective hole mass (∼0.48 m0), carrier lifetime, and depth-dependent doping profiles non-destructively and with nanoscale sensitivity. Beyond diamond, this approach reframes spectrophotometry not as a passive measurement but as an epistemic filter: a falsification engine that tests the adequacy of optical models. Inversion-aware metrology thus enables new modes of structural verification, diagnostic clarity, and growth-process insight across small-scale and high-optical density material systems.

In situ x-ray mirror surface figure metrology under vacuum and high heat loads is essential for monitoring deformations and enabling adaptive corrections. This study introduces a high-precision vacuum metrology system based on a pentaprism long trace profiler, designed to monitor clamping and thermal deformations while enabling adaptive wavefront corrections. The pentaprism and scanning stage are vacuum-internal, with an external detector to minimize window errors. Two different optical configurations were studied: the Internal Optical Path with External Detector (IOP-ED) configuration and the external optical head configuration. Vacuum evaluations improved to sub-0.1 μrad RMS slope repeatability, yielding 0.23 μrad RMS systematic errors for the IOP-ED configuration, with a scan range of 150 mm on a flat mirror at a vacuum level of 200 Pa. Future enhancements include full-vacuum integration to eliminate residual instabilities.

The 3ω technique is a prominent thermal conductivity measurement methodology for thin films, substrates, nanowires, and thermal boundary conductance. The extraction of the thermal conductivity typically relies on measuring the thermal response across a wide range of frequencies and determining the slope within acceptable limiting conditions, which can be a time-consuming process prone to error from the amplification of noise when taking the derivative of discrete temperature data to determine thermal conductivity. Here, we develop and demonstrate a frequency-modulated 3ω method (FM-3ω) with which we directly measure the derivative of the 3ω signal by varying the center frequency ω, eliminating the need to postprocess the data, thereby reducing the time to take such measurements from hours to minutes. Our modulation approach is a frequency modulation method in which the frequency ω of the excitation current is sinusoidally varied over time. We show that our new method produces results with similar accuracy to the traditional method on bulk sapphire and borofloat 33 samples, and we further explore the limitations of modulation depth and center frequency on the results. We find that thermal conductivity measurements from the FM-3ω method agree well with thermal conductivities extracted through linear fits to temperature data over similar frequency windows of the traditional method. Our method provides a new strategy using frequency modulation and tandem demodulation to directly measure the derivative of temperature, thus contributing to the advancement of thermal transport sciences by increasing the ease and pace of measuring the thermal conductivity of thin films and multilayer structures.

In order to meet the demand for current measurement in industrial production, this study presents a novel high-sensitivity fiber-optic current sensor and conducts experimental verification. The current sensing measurement is achieved using a Fabry-Perot interferometer (FPI) manufactured directly on a thin copper rod. Two single-mode fibers, observed and aligned by a charge coupled device imaging system, are glued onto the surface of the thin copper rod to form a FPI. When the copper rod is powered on, abundant heat is generated and then the copper rod expands, directly changing the length of the FPI cavity. This variation changes the optical path length of the FPI, enabling the indirect measurement of current. The experiment shows that the current square sensitivity of a single FPI can reach 568 ± 10 pm/A2. To further enhance the sensitivity, we used the FPI as a sensing interferometer to fabricate the Vernier effect sensor S1. The experiments found that the current square sensitivity of S1 is 4.7 ± 0.1 nm/A2, which is 8.5 times higher than the sensitivity of a single sensing FPI. Owing to the direct fabrication of the F-P cavity on a copper rod with excellent electrical and thermal conductivity, the sensor is particularly easy to fabricate, robust, and highly sensitive, offering an extremely simple solution for measuring current.

Enhancing the operability of next-generation combustion devices with emerging fuels at near-limit conditions requires the development of innovative ignition strategies. To address this need, a new modular plasma-coupled rapid compression machine (PRCM) featuring a mono-piston, single-stroke configuration was developed to support auto-ignition, conventional spark-ignition, and non-equilibrium plasma-assisted ignition studies within a single experimental platform. The PRCM attains end-of-compression pressures up to 70 bar and temperatures up to 1200 K, enabling systematic investigation of ignition phenomenon and the effects of non-equilibrium plasmas on fuel reactivity at regimes inaccessible to previous platforms. A high-voltage pulse generator delivers up to 20 kV pulses at repetition rates up to 100 kHz, producing kilohertz repetitive nanosecond pulsed (KRNP) discharges at elevated pressures in the combustion chamber. Integrated diagnostics include high-speed pressure transducers and optical access to enable time-resolved measurements of ignition delay, burn rate, and kernel and plasma morphology to probe for plasma-combustion coupling. Initial benchmarking with methane and n-butane mixtures demonstrated good agreement with auto-ignition data from the literature, validating the PRCM's functionality and measurement fidelity. Preliminary KRNP studies at 10 bar revealed a nearly 20% increase in burn rate compared to conventional spark ignition for n-butane, highlighting the efficacy of pulsed plasma in enhancing fuel reactivity and ignition kernels. This novel experimental facility offers a versatile, high-fidelity platform for investigating the fundamental processes by which non-equilibrium plasmas initiate, control, and accelerate combustion. These insights are expected to guide the design of optimized plasma-based ignition strategies for advanced air-breathing propulsion and power systems.

Diamond anvil cells are commonly used at synchrotron x-ray diffraction beamlines to study structural and thermoelastic properties of materials at high pressures. In a radial geometry, where the x-ray probe is oriented perpendicular to the axis of force, the deformation and strength of materials can be measured in situ. Because the anelastic and failure properties of materials depend strongly on temperature, many applications would benefit from the ability to measure high pressure radial diffraction in elevated and accurately controlled thermal environments. Previous work to introduce high temperature to radial diamond anvil cells has been largely limited to laser heating, with relatively scant efforts to resistively heat the sample. Here, we report a relatively straightforward adaptation of a simple wire coil heater, with in situ high-temperature radial diffraction performed on tungsten carbide up to 573 K at beamline 12.2.2 of the Advanced Light Source. The results demonstrate that the differential stress supported by WC decreases with increasing temperature: the differential stress on the basal (001) and pyramidal (101) planes decreased 6.6% and 5.5%, respectively, while the (100) plane only saw a 2.7% decrease, in agreement with previous studies.

A novel flip-coil measurement system has been developed for the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory. This paper describes the design, implementation, and commissioning of the new measurement bench, highlighting its key features, including improved mechanical stability, advanced data acquisition, and enhanced reproducibility. The system enables precise characterization of field integrals and multipole components, ensuring the optimal performance of Insertion Devices (IDs) before installation in the NSLS-II storage ring. The flip-coil system incorporates an innovative approach to minimize mechanical and electrical errors, which significantly improves the reproducibility of measurements. In addition, the system features a state-of-the-art data acquisition system that enables real-time monitoring and analysis, further enhancing the efficiency and accuracy of the measurement process. Preliminary tests have demonstrated that the new system meets the stringent requirements for magnetic field characterization of advanced insertion devices, making it an essential tool for future ID commissioning and quality assurance at NSLS-II.

Maintaining optimal x-ray beam quality in accelerator-based light-sources requires mirrors with exceptional shape and surface precision. In practice, mirrors are often mounted in diverse orientations-such as in Kirkpatrick-Baez systems-where gravitational and mechanical effects may differ significantly from upward-facing metrology configurations. In this study, we use optical ray tracing to investigate alternative metrology geometries suitable for measuring side-facing and downward-facing mirrors. We propose a modified profilometry approach for use with the European Synchrotron Radiation Facility long trace profiler, in which beam folding optics are integrated beneath the scanning head to redirect the measurement beam. The approach combines a detailed optical model of the instrument implemented using ray-tracing, enabling accurate evaluation of the impact of motion-induced errors under realistic acquisition conditions. For downward-facing configurations, a promising solution was found experimentally, then characterized, and investigated with an analysis of the impact of alignment tolerance. While preliminary insights are provided for the side-facing setup, all proposed configurations exhibited sensitivity to motion errors of the scanning head, highlighting challenges for robust implementation.

Compliant-mechanism-based precision positioning stages are widely employed in micro/nano manipulation applications. However, cross-coupling motions are major sources of positioning errors, particularly in multi-axis, multi-stage systems. Here, we develop a visual sensing-based compliant dual-stage nano-manipulator driven by piezoelectric actuators for decoupled motion control. It comprises a XY stage for lateral motion and a Z stage for axial motion, both designed using symmetrical four-bar flexure mechanisms. The load-displacement relationships of both stages were analyzed theoretically and their dimensions were optimized according to a maximum-stiffness criterion. A visual sensing-based position measurement and closed-loop control system was implemented to enable real-time motion compensation. Experimental results demonstrate good decoupling performance, with cross-coupling errors below 0.4% and 0.7% for the XY and Z stages, respectively. These errors can be further compensated in real time via visual servo control. The system capability was demonstrated by fabricating a micro-droplet array through droplet sliding on a hydrophobic surface.