Review of Scientific Instruments最新文献

In this paper, an experimental setup for successful generation of single micro blood droplets is reported and preliminary investigations on the formation of micro droplets and micro droplet impact dynamics are presented. An optimal operating range is identified for the stable generation of single blood droplet in the droplet-on-demand (DoD) mode. By raising the local relative humidity around the tip of the piezoelectric dispensing nozzle, a single blood droplet can be generated in the DoD mode without clogging for a long operation time. The influence of pulse width on the generation of micro blood droplets has been studied and an optimal operation region for generating single micro blood droplet has also been identified. The surface wettability is found to affect the maximum spread factor and post-impact oscillation of an impacting micro blood droplet. The influence of the surface wettability becomes weaker with an increasing Weber number, We. The variation of the maximum spread factor for a millimeter-sized blood droplet follows a trend similar to that for a micro blood droplet on silicon and Teflon surfaces (advancing contact angle θa > 90°) but not on the glass surface (θa < 90°). Micro bloodstains on the glass surface exhibit zonal characteristics similar to the macro-sized bloodstains. The blood cells can be clearly identified in the central part of the micro bloodstain. The bloodstain on the Plain Woven fabric surface basically stays on the top of a yarn without saturating too much space within it due to the tiny amount of the micro blood droplet and the comparable size of the yarn.

Scanning Tunneling Microscopy (STM)-induced luminescence is a powerful, advanced experimental method to study electroluminescence on the atomic scale. However, obtaining high and reliable count rates has proven to be difficult in the past. Here, we present a self-built STM operating under ultrahigh vacuum and at temperatures below 10 K to address this issue. The setup achieves an outstanding detection efficiency, which is about an order of magnitude higher compared to similar instruments, and count rates of up to 6 × 106 cps at 1 nA from Ag/Ag(111) surface plasmon polariton decay have been observed. This experimentally obtained value translates to a conversion factor in the order of 10-3 photons per tunneling electron. The increased count rate results from the use of a large parabolic mirror, which collects about 65% of the emitted light, together with a robust focusing procedure and the implementation of free-beam optics. Furthermore, the STM is equipped with high frequency compatible cabling with a verified bandwidth of at least 16 GHz for the entire setup, which enables rise times well below the nanosecond range for electrical signals directly in the tunneling junction. The combination of high luminescence detection efficiency and high time resolution allows us to electrically drive individual molecules and study their excitonic behavior in the picosecond range. In addition, the high efficiency simplifies time-consuming experiments, such as spectrally resolved 3D photon maps, and offers the opportunity to study very sensitive emitters that have not been accessible so far.

We present a 1 T deep high-critical-temperature (high-Tc) superconducting magnetic trap with magnetic field transients reaching 2000 T/s, spatial gradients of ∼0.3 T/mm, and arbitrarily tunable time evolution of the trapping field intensity for durations up to several minutes. In addition, our trap driver electronic circuit allows independent operation of the two superconducting coils with only a single high-current power supply and two cryogenic leads. By implementing the possibility to change polarity of the current pulse in one of the trap coils, we enable a compact design that facilitates the loading sequence of a high-gradient magnetic quadrupole trap.

Diagnostic methods play a critical role in understanding the properties of fast particle beams, which is essential for experimentally validating theoretical studies in laser-plasma interactions. Two-screen magnetic spectrometers are commonly used to simultaneously measure both the energy and angular electron distributions. In a magnetic field, electrons are deflected according to their energy, resulting in light signals detected by a scintillator. However, the analysis of the obtained data often involves solving complex multi-parameter problems, which typically require heuristic approaches and manual intervention. In this work, we propose a method for reconstructing the electron distribution using a deep neural network. Unlike existing methods, the proposed approach enables the automatic and simultaneous reconstruction of both the energy and angular electron distribution. Since the labeled experimental data are unavailable, synthetic data generated through numerical simulations, combined with data augmentation techniques, are used for training the neural network. The neural network achieved a cosine similarity of 0.79 between experimental data and data obtained through numerical simulation based on the predicted distribution.

Oxyfuel combustion of zero-carbon fuels offers a promising pathway to carbon-neutral energy and propulsion systems but requires robust laboratory-scale flat-flame burners for fundamental research. This study introduces a laboratory-scale multi-element diffusion burner fabricated via additive manufacturing of 316L stainless steel, featuring an integrated micro-channel architecture for leak-free micro-mixing of fuel and oxidizer and structural fins for enhanced thermal resilience. The burner demonstrates superior flame stability and versatility across a wide range of conditions. These include CH4/NH3/H2 fuel blends with arbitrary compositions, wide global equivalence ratios (0.2-4.0 for CH4/H2 and 0.2-1.6 for NH3), O2 fraction in oxidizer up to 100%, and power loads varying by several orders of magnitude. In situ N2 spontaneous Raman scattering thermometry reveals uniform temperature distributions in CH4/NH3/H2-O2 flames, with post-flame temperatures up to 3000 K, while OH planar laser-induced fluorescence imaging confirms homogeneous radical distributions, stable flame anchoring, and well-defined reaction zones across varied operation regimes. These properties establish the burner as a reliable platform for investigating the kinetics of zero-carbon fuel combustion while also providing a quasi-one-dimensional, high-temperature environment for heterogeneous combustion studies.

A new analysis method has been developed for measurements of broadband, low-amplitude turbulent electron temperature fluctuations in fusion plasmas using individual radiometer channels of a correlation electron cyclotron emission diagnostic. This method takes advantage of differences in the correlation time of thermal noise compared to the correlation time of plasma fluctuations in fusion reactors. The validation of this single-channel method is demonstrated using comparisons with the standard dual-channel radiometer spectral decorrelation method for measurements of turbulent electron temperature fluctuations in the core and edge of low confinement (L), improved confinement (I), and high confinement (H)-mode plasmas at the ASDEX Upgrade tokamak.

A large-diameter, double-diaphragm, single-pulse converging shock tube crafted for kinetic studies of high-pressure reactions is described. A three-dimensional converging structure connecting the driven section and the test section was designed, which reduced the inner diameter of the shock tube gradually from 210 to 105 mm, effectively enhancing the shock intensity, meanwhile maintaining a stable pressure region following the reflected shock wave. A novel disk-shape dumper plate was proposed to replace the conventional dump tank, enabling the suppression of secondary temperature rise induced by the re-reflection of the reflected shock wave. A switchable test section was designed to adapt to substituted tubes of conventional constant-diameter shock tube (CDST) and a novel converging shock tube (CST). The conventional CDST was primarily for testing the effects of large diameter characteristics as well as performing validation or control experiments for CST. The CST facility was validated by single-pulse functionality, shock wave repeatability, and capability to generate high Mach numbers. The characterized pressure profiles showed that the large-diameter configuration was able to generate nearly ideal pressure curves, and the three-dimensional converging structure notably promoted the shock intensity without disturbing the flow field. Extensive repeatability experiments were conducted in both CST and CDST with single- and double-diaphragm configurations, and reliability experiments for high-pressure ignition delay time were performed. The results indicated that both the CST and CDST were exceptionally reliable in generating strong shock waves and mitigating additional shock wave pulses, making them useful equipment for advanced high-pressure kinetic studies.

We demonstrate a straightforward optoelectronic fiber alignment technique for superconducting nanowire single-photon detectors (SNSPDs), which exploits the temperature-dependent resistance of a nanowire under optical absorption. The target nanowire is illuminated via the fiber, and the local absorption of light heats the wire, causing a change in its resistivity. Scanning the fiber over the nanowire, the change in its resistivity is monitored by lock-in amplifier, mapping the spatial photothermal response correlated with absorption and coupling efficiency. The maximum of the response corresponds to optimal fiber-SNSPD alignment. This method allows for aligning the fiber to the center of the meander with sub-micron precision. The response is robust to variations in the angle and height of the fiber, providing an alternative or complement to fiber-to-chip alignment methods based on the back-reflection or transmission measurement.

Combinatorial sputtering is a physical vapor deposition method that enables the high-throughput synthesis of compositionally varied thin films. Using this technique, the effects of stoichiometry on specific properties of alloy thin films with analog composition gradients can be mapped using high-throughput characterization. To obtain specific stoichiometries, such as those desired for an equiatomic, intermetallic, or doped compounds, the sputter power of each target must be simultaneously tuned to optimize the deposition rate of each component. This optimization problem increases in complexity with the number of components, which commonly leads to iterative guess-and-check processing and can limit the intrinsic high-throughput advantages of this synthesis method. To circumvent this challenge, this work introduces a composition optimization procedure that enables the facile synthesis of sputtered combinatorial films with targeted compositions. This procedure leverages the expeditious mapping of composition using wavelength dispersive x-ray fluorescence and is capable of optimizing processing for an arbitrary number of components. As a demonstration, this method is leveraged to sputter a combinatorial CrvFewMoxNbyTaz film with an equiatomic composition near the wafer center.

Micro-hemispherical resonator gyroscopes (μHRGs) have attracted significant attention in high-end fields such as inertial navigation, aerospace, unmanned aerial vehicles, military equipment, and deep space exploration due to their high precision, low noise, long-term stability, low power consumption, impact resistance, and potential for miniaturization. However, traditional PI control algorithms fail to meet μHRGs' stringent requirements for high bandwidth, low noise, and long-term stability. To address this, an optimized PI closed-loop control system is proposed in this paper. The system implements adaptive tuning of the proportional and integral gain parameters on a Field-Programmable Gate Array (FPGA) platform, enhancing μHRGs' bandwidth from a minimum of 1.5 Hz to over 8 Hz. Additionally, alternating pseudo-rotation modulation effectively eliminates the zero bias caused by the circumferential inhomogeneity of μHRGs. Experimental results validate the reliability and effectiveness of the proposed adaptive PI algorithm.