Review of Scientific Instruments最新文献

Semiconductors as silicon carbide are used for particle-here fast neutrons-detection because of their wide bandgap and efficiency with thermal and radiation resistance. The behavior of SiC diodes is better documented in harsh environments, but there is a lack of knowledge regarding their industrial integration. To reach a higher technology readiness level, the present work proposes for the detector conception an assembly made by Additive Manufacturing and sealed with Field Assisted Sintering Technologies. The design relies on a coaxial shape of insulating parts in alumina made by using the digital layer process and electrodes, core, and shell made of copper alloys using the layer powder bed fusion process. The overall shape of the parts is conical, which allows for self-centering, locking, and pressure of the electrode on the SiC diode. The electrodes are designed with an origami-type structure, which allows for controlled deformation and ensures electrical continuity. The housing is sealed using transient liquid phase bonding of borosilicate glass applied by screen printing. After sealing, detectors were investigated with x-ray tomography and electrical behavior. Finally, the detector was exposed to a fast neutron flux and successfully detected it.

The accurate determination of thermal conductivity κ(T) in bulk materials at room temperature and above is crucial for evaluating their compatibility for specific applications. The 3ω technique is an established methodology for studying the thermal conductivity of thin films, becoming particularly suitable in the case of bulk specimens for T ≳ 300 K, where standard stationary techniques require significant corrections for radiative losses. Although this method has been employed in several works, it remains not widely adopted because its implementation demands considerable sophistication, including experiment design, thin film deposition techniques, and choices of the geometry of the current/heat transducer, electronics, and analytical treatment of the signals. Based on a critical review of the technique's key technical aspects, this work provides practical support for a rapid and user-friendly implementation, from the design phase through to execution and analysis. We release a Python-based graphical user interface that supports a quantitative estimation of the investigated temperature profiles based on the geometrical parameters (width/length) of the deposited transducer (heater/thermometer metal line) before an experiment, guaranteeing an optimal design of the experimental conditions for each given material under scrutiny.

Helium metastable species play a critical role in sustaining radio-frequency-driven micro-atmospheric pressure plasma jets through Penning ionization and in the generation of reactive oxygen and nitrogen species. Their densities are typically measured using tunable diode laser absorption spectroscopy (TDLAS). Most spatially resolved TDLAS approaches rely on mechanical scanning of a narrow laser beam across the plasma, which is time-consuming and limits spatial resolution. In this study, we present an advanced two-dimensional (2D) TDLAS method that enables direct spatial mapping of helium metastable densities without the need for mechanical scanning. A rotating optical diffuser is employed to suppress speckle interference and generate uniform illumination across the plasma region. The absorption profile is captured using a short-wavelength infrared camera equipped with a telecentric lens, achieving high spatial resolution (∼10 μm) across the entire field of view. This approach significantly enhances both data quality and acquisition speed. The improved 2D TDLAS system is applied to measure helium metastable densities in plasma jets with structured electrodes driven by different tailored voltage waveforms. The results show very good qualitative agreement with fluid simulations and previously reported experimental data.

We report a home-built femtosecond laser frequency comb-based continuous scanning Fourier transform spectrometer (FC-FTS) for the spectroscopy of gas phase molecules at a spectral resolution of 0.06 cm-1 working in a tunable wavelength range from 2900 nm (3450 cm-1) to 4600 nm (2174 cm-1). The FC-FTS employs a homemade broadband mid-infrared femtosecond laser frequency comb (FC) and a narrow linewidth He:Ne laser as a reference source for sampling the dependence of the interferogram signals on the optical path differences (OPDs). Both real-time correction and OPD resampling are achieved via precise zero-crossing analysis of the He:Ne reference laser interference signal, processed by customer-developed software to effectively compensate for mechanical perturbations. Software-based bandpass filtering, autobalancing, and etalon suppression of the OPD interferogram can improve the signal-to-noise ratio of the molecular spectra by nearly two orders of magnitude in a single sampling experiment. Both hardware and software frameworks have been presented, respectively. We also report the absorption spectra of four molecular species (acetylene, carbonyl sulfide, methane, and water) using the FC-FTS system, validating its utility for molecular fingerprinting. The concentration of each molecular species has been determined through spectral fitting analysis, wherein the experimentally measured absorption spectra are matched to the simulated spectra derived from the high-resolution transmission molecular absorption database. The developed diagnostic system achieves high-resolution, multispecies quantification, enabling precise identification of trace components in complex molecular systems.

To develop a feasible methodology to observe the dynamics of element-specific electronic structures, collective excitations, and lattice structures, we are going to implement a time-resolved resonant electron energy-loss spectroscopy (TR-rEELS), which is expected to pave the way for exploring unconventional phenomena in quantum materials. Before the implementation, to determine the optimal parameters of the probe electron beam and to verify the feasibility of this methodology, we evaluated the profile and the space-charge effect of the pulsed electron beam with a kinetic energy less than 2 keV based on both simulation and experiment. By controlling the initial electron beam parameters, we realized an energy width less than 2 eV with a calculated temporal width of ∼30 ps, enabling the time-resolved measurement, while maintaining a sufficient signal-to-noise ratio, and, thus, showed the feasibility of TR-rEELS. An experimental demonstration result of TR-EELS using this apparatus is also introduced.

Ultrashort laser platforms equipped with in situ, in-operando diagnostics are pivotal for advancing the frontiers of modern laser-based engineering. Aligned with this objective, we developed the LP3-ASUR platform, which combines moderate (∼1013 W/cm2) and high-intensity laser beamlines (∼1017-2.5 × 1019 W/cm2), enabling pump-probe arrangements with modular (optical/x-ray) time-resolved diagnostics. We demonstrate high-repetition rate (100 Hz), high-brilliance, hard Kα x-ray sources induced by laser-plasma interaction. Favorably, they can be synchronized with optical pump and probe laser pulses and are jitter-free with respect to them thanks to the multi-beamline, low- and high-peak power architecture of the laser platform. For x-ray analysis and imaging, these characteristics enable a high signal-to-noise ratio and minimize the need for long accumulation times, allowing for addressing demanding scientific cases. Building such a platform encompassed efforts of research and development involving the laser system, the x-ray conversion targetry, and the formatting of x-ray source characteristics under various operation conditions. To have robust and stable x-ray tools with pulsed, well-defined characteristics, the x-ray targetry is operated in front-face geometry with a massive laser-x-ray converter material. In such a configuration, a hard Kα x-ray source delivering peak performances of 109 photons/sr/shot at the repetition-rate of 100 Hz with a few-hundred femtosecond duration is routinely obtained and implemented in flexible pump-probe analytical experiments and x-ray imaging protocols operated in air. Finally, two descriptive measurements highlight the platform's ability to perform cutting-edge diagnostics, opening the door for innovative imaging and improved understanding of electron and lattice dynamics in solid materials exposed to external laser irradiation.

High-pressure conditions in the megapascal range are critical in industrial material synthesis, food science, and biospheric Earth science. However, in situ measurements for analyzing material behavior under such conditions remains challenging because of the difficulty of precise pressure-temperature control and high-Q-range data acquisition. To overcome these limitations, we developed a compact high-pressure cell for synchrotron x-ray diffraction, enabling crystal structural analysis at pressures up to 400 MPa and temperatures up to 180°C. The cell provides a wide downstream aperture angle of 72°, substantially larger than those of conventional cells, and is optimized for wide-angle diffraction necessary for crystallographic studies. Using water as the pressure medium, the system allows fine pressure adjustments in 0.1 MPa increments via a manual pump, while a pressure transducer enables real-time monitoring without the need for pressure markers. Temperature is controlled with cartridge heaters and monitored by a thermocouple positioned near the sample. Validation experiments using compressibility, phase transitions, and freezing point determination helped confirm the high accuracy of the results, with the absolute errors in the pressure and temperature being below 10 MPa and 1.5°C, respectively. A Rietveld refinement of NaCl diffraction data at 400 MPa yielded low R-factors, confirming the reliability of the cell for crystal structural analysis. Powdered samples were sealed in polyimide tubes or tapes, facilitating rapid and disposable sample exchange while accommodating soluble, hygroscopic, deliquescent, or anaerobic materials. The cell can support hydrostatic and uniaxial compressions by selecting the sample packing method, offering versatility in a single apparatus.

Controlled nucleation and growth of thin films and nanostructured surfaces is one of the fundamental challenges and intriguing aspects of nanomaterials for researchers and manufacturers. The unique properties exploited in the application of nanomaterials rely on controlling the mechanism underlying their synthesis, i.e., the nucleation and growth. Several approaches have been adopted for controlled synthesis of nanomaterials. Herein, we report on the design and building of a pressure controlled vacuum chamber to process thin films under controlled pressure/temperature using xenon flashlamp photonic curing. We built a UV-vis pressure-controlled chamber (PCC) and demonstrated the processing of thin films at pressures varying from 1 to 3.5 atm in different gas environments ranging from inert to reactive gases. Our results showed that the processing of thin films under controlled pressure changes the nano-morphology of thin film growth. The successful implementation of the PCC for photothermal processing of thin films makes it a promising route to control the nucleation and growth of nanomaterials under various conditions for large scale-controlled synthesis of nanomaterials.

This paper presents new type of dual mode sensor for dielectric characterization. The design uses the even mode of the resonator for measuring the dielectric constant of a sample under test. For the odd mode, two identification (ID) transmission lines are loaded such that we obtain four ID combinations (00, 01, 10, and 11). By proper design procedure, the even mode resonances are insensitive to the ID resonator loading, whereas the odd mode resonances are insensitive to the sample characteristics. The dielectric constant and loss tangent are successfully measured with this sensor.