Review of Scientific Instruments最新文献

Transient absorption (TA) is the most prominent method to observe relaxation dynamics in the toolbox of ultrafast spectroscopy. Within the framework of time-dependent perturbation theory, TA is a third-order technique as it relies on two interactions with the pump and one with the probe field. Since the advent of ultrafast TA, researchers have struggled to limit or better quantify the contributions of higher orders, such as the fifth order, as they will emerge along the same phase matching direction as the desired third order. Intensity cycling is a recently demonstrated experimental approach to isolate third from higher order signals. It requires transient absorption spectra at a minimum of three different intensities. This is experimentally challenging as the conditions for these three experiments need to be as similar as possible for a meaningful comparison. We present a solution to this problem based on a Sagnac-interferometer. Our design allows for shot-to-shot variations of pump pulse intensities. An entire intensity cycling dataset with 290 delay times for three different pump excitation densities is recorded within 30 min. We demonstrate the feasibility of our setup on a cyanine dye in solution.

The determination of low-Z elements (Z < 17), such as Na, Mg, Al, Si, S, and P, in trace amounts is crucial in various fields ranging from semiconductors to biological sciences. Similarly, the detection of medium-Z elements, such as Mo, Ru, Pd, Ag, Cd, and Sn, is vital for the pharmaceutical industry and other energy-sector-related applications. Synchrotron-based total reflection X-ray fluorescence (TXRF) is a well-known analytical technique for the detection of elements at trace and ultratrace levels. We present here the commissioning results of a newly developed, vacuum-compatible TXRF system designed for the detection of low-Z and medium-Z elements at the microprobe X-ray fluorescence beamline (BL-16) of the Indus-2 synchrotron facility. The achieved detection limits for Na, Mg, Al, Si, P, and S at an excitation X-ray energy of 6 keV were found to be in the range of ∼2 μg to 15 ng. However, in the case of medium-Z elements, analyzed using their Lα peaks, the detection limits were found to be in the range of ∼19 ng (Mo) to 5 ng (Sn). Relative sensitivity (Sj) with respect to Sc was also determined and further validated by analyzing an ICP multi-element standard IV. To employ it for a real application, the concentration of various low-Z elements present in coconut water was determined. The results obtained demonstrate that the newly commissioned TXRF setup has relatively enhanced elemental detection capabilities at the BL-16 beamline, enabling reliable analysis of both low-Z and medium-Z elements along with other elements.

Neutron coded imaging is a powerful tool for diagnosing the shape and size of the thermonuclear reaction zone in inertial confinement fusion, but achieving high-fidelity reconstruction under near-field conditions remains a challenging, ill-posed inverse problem. In this paper, we propose a novel Fitness-Guided Adaptive Genetic Algorithm (FGAGA) for near-field neutron coded imaging reconstruction. FGAGA employs a fitness-guided adaptive selection operation to dynamically switch between two selection strategies to balance exploration and exploitation, where strategy 1 utilizes parallel processing and strategy 2 utilizes serial processing. The Fitness-Guided Hybrid Crossover Operation and Fitness-Guided Adaptive Mutation Operation (FGAMO) enable the algorithm to accelerate convergence while preserving population diversity. FGAMO further classifies pixels into internal pixels and boundary pixels and designs corresponding neighborhood mutation rules for each category. The algorithm also employs an Isolated Pixel Treatment Operation to suppress the generation of isolated pixels. Reconstructed results demonstrate that FGAGA successfully achieves high-precision continuous grayscale reconstruction of near-field neutron sources under challenging low neutron yields, thereby overcoming the limitation of traditional heuristic algorithms that are restricted to binary reconstruction. Furthermore, the FGAGA shows superior performance compared to established deterministic algorithms. For a near-real neutron radiation source, the FGAGA yields a 2.27 dB gain in PSNR and a 0.12 increase in SSIM over SART with TV.

Temperature measurements are essential in laboratory and industrial applications. We demonstrate a contactless magneto-optical measurement scheme that directly relates magnetization loop shape to temperature. The scheme relies on the characteristic temperature-dependent loop shapes associated with domain wall motion, domain wall nucleation, and annihilation. The magnetization response characteristics are defined by the harmonics of the magnetic field responses, where temperature can be derived from the ratio of the frequency components of the magnetization reversal for a given modulation field amplitude. This enables the temperature to be determined independently of the signal amplitude, eliminating the need for recurring calibrations. Multiple harmonic ratios can be combined for a more unambiguous and robust determination of physical quantities. The temperature measurement method is demonstrated in magneto-optically active iron garnet films. The shown scheme is extendable to the measurements of other quantities, e.g., magnetic field strength and electric current sensing capabilities as well as enabling mechanical stress sensing, empowering further and multi-functional sensor applications. Other magnetic materials, which exhibit temperature-dependent magnetization reversal properties and magneto-optical measurements based on the magneto-optical Kerr effect or detection schemes, are also compatible with the proposed measurement scheme.

Acoustic pyrometry (AP) is a reliable technique designed for high-quality reconstruction of temperature fields, whereas most existing AP reconstruction methods have been developed for use in thermally uniform environments. The AP technique is inherently limited in circumstances characterized by extremely high temperature gradients over limited areas. This limitation manifests as hotspot localization failures and a large normalized root mean square error (NRMSE) of more than 8.3%. Subsequently, an acousto-optic coupled method was proposed, in which the optic luminous flame information was introduced as an additional constraint to the improved acoustic pyrometry. Quantitative reconstruction results demonstrate that the proposed method overcomes the limitations of AP in high gradient flame regions, achieving an NRMSE of less than 5% and reducing errors by over 60% in comparison with the improved AP method. The proposed acousto-optic coupled method offers a novel solution for temperature field diagnostics in complex combustion environments, with strong implications for industrial furnace monitoring.

To address the challenge of detecting weak magnetic anomaly signals in low signal-to-noise ratio conditions, this paper proposes a novel method that integrates Principal Component Analysis (PCA) with Cascaded Bi-stable Stochastic Resonance (CB-SR), referred to as PCA-SR. The proposed approach leverages PCA to extract the principal components of the target signal while suppressing background noise. In addition, the CB-SR system enhances detection performance through the inter-well transition characteristics. Simulation and experimental results validate the effectiveness of PCA-SR. Compared to classical PCA and Stochastic Resonance (SR) methods, PCA-SR demonstrates superior detection performance and an extended detection range.

High-power microwave with pulse durations of tens of nanoseconds cannot effectively go through PIN limiters, due to the conductivity modulation effect of the PIN diodes. This article proposed a method of utilizing ultra-short electromagnetic pulses (EMPs) to go through the PIN limiter with a low attenuation. Due to its short pulse duration (1 ns or less), it can directly go through the limiter and inject into the low noise amplifier before the limiter responds. The influence of different frequencies and phases of ultra-short EMPs on the PIN limiters attenuation is experimentally investigated. Experimental results indicate that ultra-short mono-frequency EMPs with frequencies from 2 to 5 GHz can go through the PIN limiter with the lowest attenuation to 0.64 dB at 2 GHz. Ultra-short pulses generated by frequency-modulated pulse compression with a bandwidth ranging from 1 to 3 GHz also show a low attenuation after going through the PIN limiter. The lowest attenuation is 1.5 dB at a frequency range of 2.182-5.182 GHz. Experimental results verified the feasibility of the proposed method.

We describe a 88Sr+ ion trap apparatus with the capability to produce high-quality 408 nm photons aimed at distributed quantum computing and networking applications. This instrument confines ion chains using a surface electrode trap with a two-dimensional magneto-optical trap as an atomic source. Several laser systems spanning 400-1100 nm are used to achieve high-fidelity state preparation and readout. Photons are produced via the decay of an exited state, which is accessed using a custom 408 nm laser system that produces 150 ps optical pulses using non-linear photonics. We demonstrate single-photon production through a Hanbury Brown-Twiss measurement for one to six ions.

We present a high-repetition-rate laser-induced fluorescence (LIF) instrument operating at 10 kHz for measuring reaction kinetics of species that dissociate to produce LIF-detectable products. The technique employs a tunable dye laser to excite OH radicals with fluorescence detected by a photomultiplier tube, providing 100 μs temporal resolution. The high repetition rate enables rapid accumulation of thousands of laser shots, achieving high sensitivity and excellent signal-to-noise ratios. We demonstrate this proxy detection approach by monitoring Criegee intermediates (CIs) through their unimolecular decomposition to OH radicals, where the OH temporal profile directly reflects CI decay kinetics. The method is validated using the well-characterized syn-CH3CHOO + SO2 reaction in a flow reactor, yielding rate coefficients consistent with literature values. This technique extends conventional LIF measurements to species that are not directly detectable but produce LIF-active fragments upon decomposition, offering a sensitive, time-resolved approach for studying reactive intermediates with applications in atmospheric and combustion chemistry.

Solid-state thermoelectric cooling is a promising solution for localized thermal management. Accurate evaluation of the cooling performance is essential for optimization and design of high-performance thermoelectric coolers. However, conventional methods fail to capture performance under actual operating conditions. This article examines the measurement uncertainties in key performance metrics, e.g., cooling temperature difference, cooling power, and coefficient of performance, in the context of the heat-flow method. The results highlight that reliable measurements depend critically on both the quality of the thermal interface and the establishment of steady-state conditions. Moreover, the thermal inhomogeneity and radiative heat exchange issues have also been emphasized, and strategies to mitigate them have been discussed. In addition, a practical reference of the coefficient of performance equal to 0.5 at maximum cooling power has been proposed.